A METHOD FOR APPLYING A PRIMER, IN PARTICULAR A PRIMER FOR UV COATING SYSTEMS, ON THE SURFACE OF AN ELECTRICALLY CONDUCTIVE SUBSTRATE
20190134665 ยท 2019-05-09
Assignee
Inventors
Cpc classification
B05D3/064
PERFORMING OPERATIONS; TRANSPORTING
International classification
Abstract
The invention relates to a method for applying a primer, in particular a primer for UV coating systems, on an electrically conductive substrate, in particular a metal surface, comprising the steps of the treatment of the surface with process plasma providing an activated surface, and subsequently contacting of the plasma treated surface with a primer. The invention further relates to a pretreated surface comprising an electrically conductive substrate and a layer of a primer, which form an activated treatment surface for the treatment with a color characterized in that the activated surface is stable for at least several hours and a printed surface, in particular a printed surface comprising an electrically conductive substrate, a layer of a primer and a printed color layer, characterized in that the printed color layer is stable after immersion in water for more than 48 hours.
Claims
1. A method for applying a primer, in particular a primer for UV coating systems, on the surface of an anodized aluminium surface, comprising the steps of a. treatment of the surface with a process plasma providing an activated surface, wherein the treatment of the surface with said process plasma occurs under a process pressure lower than the atmospheric pressure, and subsequently b. contacting of the plasma treated surface with said primer.
2. The method according to claim 1, wherein the treatment of the surface with said process plasma occurs under a process pressure between 0.05 to 1 mbar.
3. The method according to claim 1, wherein the treatment of the surface with said process plasma occurs under a process pressure between 0.2 to 0.5 mbar, wherein particularly the process pressure is 0.3 mbar.
4. (canceled)
5. The method according to claim 1, wherein the process plasma comprises hydrogen gas, in particular pure hydrogen gas or a mixture of hydrogen gas and at least one inert gas, more particularly a mixture of hydrogen gas and at least one inert gas.
6. The method according to claim 5, wherein the process plasma comprises hydrogen gas in the range of 5% to 60% and at least one inert gas in the range of 95% to 40%, in particular hydrogen gas in the range of 10% to 40% and at least one inert gas in the range of 90% to 60%, more particularly hydrogen gas in the range of 15% to 25% and at least one inert gas in the range of 85% to 75%.
7. The method according to claim 5, wherein the at least one inert gas is selected from the group comprising nitrogen, helium, neon, argon, krypton, xenon or a mixture thereof, in particular from nitrogen and argon or a mixture thereof, more particularly the at least one inert gas is argon.
8. The method according to claim 1, wherein the primer is a monomer, in particular a volatile monomer, providing a monomer or polymer layer, wherein more particularly the monomer is a monomer suitable for graft-copolymerization.
9. The method according claim 8, wherein the primer is selected from the group of a C.sub.1-C.sub.8 alkene, C.sub.1-C.sub.8 alkine, C.sub.1-C.sub.8 carboxylic acid, C.sub.1-C.sub.8 diamine, a C.sub.1-C.sub.8 diole, R.sub.1CN, R.sub.1COOH, R.sub.1COOR.sub.2, or R.sub.1COO-L-Si(OR.sub.3).sub.3, with R.sub.1 being a C.sub.1-C.sub.8 alkene, C.sub.1-C.sub.8 alkenylaryl or C.sub.1-C.sub.8 alkine, in particular a C.sub.1-C.sub.8 alkene, R.sub.2 being a C.sub.1-C.sub.8 alkyl, in particular a C.sub.1 alkyl, R.sub.3 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, and L being a C.sub.1-C.sub.6 alkyl, in particular a C.sub.1-C.sub.4 alkyl, wherein in particular the primer is selected from the group of a C.sub.1-C.sub.4 alkene, C.sub.1-C.sub.4 alkine, C.sub.1-C.sub.4 carboxylic acid, C.sub.1-C.sub.4 diamine, a C.sub.1-C.sub.4 diole, R.sub.1CN, R.sub.1COOH, R.sub.1COOR.sub.2, or R.sub.1COO-L-Si(OR.sub.3).sub.3, with R.sub.1 being a C.sub.1-C.sub.4 alkene, C.sub.1-C.sub.4 alkenylaryl or C.sub.1-C.sub.4 alkine, in particular a C.sub.1-C.sub.4 alkene, R.sub.2 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, R.sub.3 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, and L being a C.sub.1-C.sub.6 alkyl, in particular a C.sub.1-C.sub.4 alkyl, wherein more particularly the primer is selected from R.sub.1COOH or R.sub.1COO-L-Si(OR.sub.3).sub.3, with Ri being a C.sub.1-C.sub.4 alkene, C.sub.1-C.sub.4 alkenylaryl or C.sub.1-C.sub.4 alkine, in particular a C.sub.1-C.sub.4 alkene, R.sub.3 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, and L being a C.sub.1-C.sub.6 alkyl, in particular a C.sub.1-C.sub.4 alkyl.
10. The method according to claim 8any one of the previous claims, wherein the primer is selected from the group of a C.sub.1-C.sub.8 alkene, R.sub.1CN, R.sub.1COOH, R.sub.1COOR.sub.2, or R.sub.1COOLSi(OR.sub.3).sub.3, with R.sub.1 being a C.sub.1-C.sub.8 alkene, C.sub.1-C.sub.8 alkenylaryl or C.sub.1-C.sub.8 alkine, in particular a C.sub.1-C.sub.8 alkene, R.sub.2 being a C.sub.1-C.sub.8 alkyl, in particular a C.sub.1 alkyl, R.sub.3 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, and L being a C.sub.1-C.sub.6 alkyl, in particular a C.sub.1-C.sub.4 alkyl, wherein in particular the primer is selected from the group of a C.sub.1-C.sub.4 alkene, R.sub.1CN, R.sub.1COOH, R.sub.1COOR.sub.2, or R.sub.1COO-L-Si(OR.sub.3).sub.3 with R.sub.1 being a C.sub.1-C.sub.4 alkene, C.sub.1-C.sub.4 alkenylaryl or C.sub.1-C.sub.4 alkine, in particular a C.sub.1-C.sub.4 alkene, R.sub.2 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, R.sub.3 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, and L being a C.sub.1-C.sub.6 alkyl, in particular a C.sub.1-C.sub.4 alkyl, wherein more particularly the primer is selected from R.sub.1COOH or R.sub.1COO-L-Si(OR.sub.3).sub.3, with R.sub.1 being a C.sub.1-C.sub.4 alkene, C.sub.1-C.sub.4 alkenylaryl or C.sub.1-C.sub.4 alkine, in particular a C.sub.1-C.sub.4 alkene, R.sub.3 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, and L being a C.sub.1-C.sub.6 alkyl, in particular a C.sub.1-C.sub.4 alkyl.
11. The method according to claim 8, wherein the primer is selected from the group of acrylonitrile, butadiene, styrene, methyl 2-methylpropenoate, prop-2-enoic acid, methyl-propenoate, ethyl-propenoate, butyl prop-2-enoate, 2-hydroxyethyl 2-methylprop-2-enoate, or 3-trimethoxysilylpropylmethacrylate, in particular from prop-2-enoic acid or 3-trimethoxysilylpropylmethacrylate, more particularly from 3-trimethoxysilylpropylmethacrylate.
12. The method according to claim 8, wherein the primer is R.sub.1COO-L-Si(OR.sub.3).sub.3, with R.sub.1 being a C.sub.1-C.sub.4 alkene, C.sub.1-C.sub.4 alkenylaryl or C.sub.1-C.sub.4 alkine, in particular a C.sub.1-C.sub.4 alkene, R.sub.3 being a C.sub.1-C.sub.4 alkyl, in particular a C.sub.1 alkyl, and L being a C.sub.1-C.sub.6 alkyl, in particular a C.sub.1-C.sub.4 alkyl.
13. The method according to claim 12, wherein said primer is mixed with a carboxylic acid, particularly acetic acid and/or an alcohol, particularly isopropyl alcohol, prior to or during contacting said plasma treated surface with said primer, in particular prior to contacting said plasma treated surface with said primer.
14. The method according to claim 1, wherein the contacting of the plasma treated surface with the primer occurs under a process pressure lower than the atmospheric pressure, in particular between 0.1 mbar to 0.3 bar, more particularly the process pressure is around 0.2 bar, in particular wherein the primer is a volatile monomer.
15. The method according to claim 14, wherein the contacting of the plasma treated surface with the primer occurs under a process pressure between 0.05 to 1 mbar.
16. The method according to claim 1, wherein after the contacting of the plasma treated surface with the primer, a color, in particular an UV color, is applied on the primer, in particular on the monomer or polymer layer.
17. The method according to claim 16, wherein the application of the color is achieved by a printing method.
18. A pretreated surface, in particular a pretreated surface obtainable by a method according to claim 1, comprising an anodized aluminium substrate, and a layer of a primer, which form an activated treatment surface for the application of color, in particular UV color, characterized in that the activated surface is stable for at least several hours.
19. A printed surface, in particular a printed surface obtainable by a method according to claim 1, comprising an anodized aluminium surface, a layer of a primer and a printed color layer, in particular a printed UV color layer, characterized in that the printed color layer is stable after immersion in water for more than 48 hours.
20. The method according to claim 6, wherein the at least one inert gas is selected from the group comprising nitrogen, helium, neon, argon, krypton, xenon or a mixture thereof, in particular from nitrogen and argon or a mixture thereof, more particularly the at least one inert gas is argon.
Description
SHORT DESCRIPTION OF THE FIGURES
[0143]
[0144]
[0145]
[0146]
[0147]
[0148] In the figures, an aluminium plate can be seen, which was first pre-treated according to the invention or with the flame pyrolysis and then printed. After printing, it was machined on a CNC machining centre, with the application of a large amount of coolant (here ethanol). The words test test test . . . and the horizontal bars were engraved and were not provided by the application of the printed color layer. Milled (engraved) elements comprise especially at the edges extreme demands on the adhesion.
EXAMPLES
Method of the Invention
[0149] A plasma system PAC357Spot 2.5KW of the company plasma technology GmbH (Herrenberg/Gultstein Germany) was used.
[0150] First Step (Pre-Preparation Step):
[0151] The protective film of anodized aluminium plate was removed and the anodized aluminium plate was put into the plasma system without further cleaningthus there is no time delay for the drying of the cleaner.
[0152] Second Step (H.sub.2 Plasma Process):
[0153] The surface is cleaned and activated by the low pressure plasma comprising H.sub.2 and other gases. The process conditions can be found below:
[0154] Initiation pressure: 0.5 mbar
[0155] Process pressure: 0.3 mbar
[0156] Process time: 5 minutes or longer
[0157] Gas: hydrogen argon mixture Arcal Plasma 62 of Air Liquide Deutschland GmbH
[0158] Third Step (Polymerization/Layer Formation):
[0159] A primer is applied to the surface in form a monomer or polymer layer under low pressure.
[0160] The process conditions can be found below:
[0161] Initiation pressure: 0.1 mbar
[0162] Process pressure: 0.2 bar
[0163] Acrylic acid polymerization/layer formation process
[0164] Process time: 5 minutes or longer
[0165] Acrylic acid used: acrylic acid (stabilized with hydroquinone monomethyl ether) for synthesis (CAS No.: 79-10-7)
[0166] Fourth Step (Printing):
[0167] The plate is removed from the plasma system and subsequently printed with IJC255 ink by a Canon Oc Arizona UV printer system.
[0168] If necessary, the plate is swept with a commercially available hand brushthe monomer or polymer layer of the invention endures these mechanical contacts.
[0169] Fifth Step (Cutting):
[0170] If necessary, the anodized aluminium plate is cut to the appropriate form with high feed rates and speeds. As a coolant ethanol is used.
[0171] Sixth Step (Cleaning):
[0172] If necessary, the anodized aluminium plate is cleaned with n-butyl acetate-based detergents.
[0173] Manual Flame Pyrolysis Flamprico:
[0174] The protective film is peeled off from the aluminium plate and the aluminium plate is then cleaned. A specific, scratch free microfiber cloth (non-woven), which can only be used once, and the Flamprico Cleaner, a highly flammable liquid which causes severe eye irritation and may cause drowsiness and dizziness, have to be used. Solvent resistant protective gloves and a tight-fitting safety goggles must be worn and sufficient ventilation has to be provided.
[0175] The flame treatment step is applied after drying of the cleaner. It is of utmost importance that the cleaner has dried to 100%, otherwise it might catch fire with the flame pyrolysis.
[0176] Furthermore, precautions have to be taken if the provided flame pyrolysis Flamprico gas comprising silane is used. Since the gas is an extremely flammable gas, in particular an electrostatic charge in the environment must be prevented, which is quite laborious. The flaming must be done manually in such a way that the same amount of silane is applied per unit area. Not enough silane reduces the adhesion, excess silane produces white, veil-like impurities in the aluminium, which cannot be removed with conventional cleaning agents and sponges. When these impurities occur, the process has to be repeated with a new aluminium plate. After the flame treatment is finished, Flamprico 2030 primer must be applied in a timely manner. The primer is applied by a spray gun under safety measures (gloves, goggles and a protective mask with solvent filter). It is carried out under sufficient ventilation. Since liquid and vapour are highly flammable, it is important that the aluminium surface is cooled before the primer is applied. For the process, it is important that the surface is still hot when applying the primer. If too much primer is applied, the plates have to dry for up to 24 hours before they can be processed further otherwise the adhesion is very poor. If too little primer is used the adhesion is also poor. This process is also determined by the manual application of the primer.
[0177] After the two-step process is finished, the UV ink adheres very well to the surface of the anodized material. As a test method, special test panels were milled after printing on CNC machining centres. The extreme stress by the rotating cutters and the use of coolant (ethanol) are a burden on the coating. Test panels produced with a flame pyrolysis process showed that 25% to 33% of the printing plates comprised after the milling unsightly discoloration or the print is chipped. All of the test panels produced according to the method of the invention showed no discoloration or chipping after the milling.
[0178] Furthermore, the print is resistant to the interaction with ethanol (bath, one hour) and against wiping with n-butyl acetate of.
[0179] The print will separate if test panels produced with the flame pyrolysis method are placed into cold tap water for 24 to 48 hours. Test panels produced according to the method of the invention showed no separationeven after 504 hours water. This is particularly important for use on outdoor signs.
[0180] Furthermore, the plasma pretreatment time can be 16-18 days, without losing a significant part of adhesion, when the primer is applied by this time. Thereafter, the print is no longer optimal (about 10% loose color after milling).
[0181] Additionally, the method of the invention comprises only very few steps and consumes a very low amount of material, which significantly reduces the production time and cost.
[0182] For example a 50 litre and 200 bar gas bottle (Arcal plasma 62) and one litre of acrylic acid allows for two months continuous printing. The material cost per-treatment is therefore extremely low.