FI124379B - Coating of the piece - Google Patents

Description

SECTION COATING Explanation 5 Technology

The invention relates to the coating of bodies, wherein the mixture applied to the surface of the body is cured by UV irradiation. The invention relates to a method and a device in which an inert gas is introduced into the surface of a body during irradiation.

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Technology background

UV curing compositions can be used for coating or gluing the pieces. The mixture is then applied to the surface of the body, which is then drawn by irradiation. The mixture contains a photoinitiator which, upon exposure to radiation, activates and initiates a curing reaction. Radiation curable coatings are used especially when good chemical and abrasion resistance is desired.

Oxygen generally inhibits the curing reaction, which is why curing is often carried out in an inert gas phase. For example, nitrogen, carbon dioxide, argon or helium can be used as the inert gas. One way is to insert the piece into a chamber filled with an inert gas and to cure there. However, this is not always the case

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o 00 25 o x Methods have also been proposed for conducting the surface of a body to be irradiated.

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flow of inert gas. For example, EP 1 804 243 A2 discloses a g method for curing web-like material. In the method, the web of material r-- g is passed under a web-wide irradiation device. At the same time, the front

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30 an inert gas between the irradiation device and the web and is sucked away from the rear edge of the irradiation device. The arrangement provides a laminar flow of inert gas to the surface of the web.

General description of the invention

A method and apparatus for coating a body according to the independent claims have now been invented and for their use in particular for coating a body having recesses or bumps on the surface.

According to the invention, the article is conveyed under an irradiation apparatus, wherein the mixture fed to the article is cured by irradiation. The device has means for introducing an inert gas heavier than oxygen to the surface of the body and then means for applying another inert gas to the surface of the body. A gas heavier than oxygen effectively displaces oxygen from the surface of the body, even when it has recesses. The second gas may then be more appropriate, for example cheaper or easier to use or as little as possible to hinder irradiation.

Heavy gas remains well in the recesses despite the turbulence caused by the surface shapes. Thus, the oxygen concentration in the wells is lower than the high-20 stump, where turbulence facilitates the mixing of the inert gas with oxygen. After all, the recesses are further away from the radiation source, whereby the amount of radiation in the recesses is correspondingly smaller. Thus, the invention also promotes uniform curing ·

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m o d > 25 Typically, the curable mixture contains monomers, oligomers, or polymer-x, which are polymerized by a radical reaction or a cationic mechanism. The mixture then contains a photoinitiator which is activated by UV radiation and initiates the reaction.

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g is. The application mixture may be, for example, UV curing varnish, tinted varnish or paint.

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Thanks to the invention, a lower radiation dose or faster curing can be used.

In the process according to the invention, the cure of the mixture can be accelerated by increasing the temperature of the mixture applied to the body, thereby increasing the reaction rate. Under acidic conditions this cannot be done, as the number of oxidation reactions would be adversely increased as the temperature increases. The mixture may be heated, for example, by heating an inert gas introduced to the surface, in particular a first inert gas. Another option to heat the mixture is to apply IR-10 radiation to it just before the piece goes under the irradiator. The desired temperature may be, for example, 20-50 ° C, such as 30-40 ° C. Heating particularly improves the deep curing of the mixture, i.e. the curing of the inner part.

The device of the invention preferably has means on the sides of the conveyor to prevent leakage of inert gas. Preferably, the means have a lateral flow shield attached to the irradiation device which fits snugly against the conveyor edge.

The invention is suitable, for example, for coating coated articles and upholstery materials and furniture such as doors, door frames, window frames, furniture components and panels. Unless conduction of the first gas is necessary, such as when the surface of the body is flat (such as floor coverings, flat panels and furniture), the supply of the first gas can be switched off.

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m cp ώ 25 The first gas may be, in particular, carbon dioxide and the second gas, for example, o x nitrogen, argon or helium, especially nitrogen. Nitrogen of sufficient purity can be

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preferably prepared in situ by removing oxygen from the air by membrane filtration.

m co o § Mercury arc lamps have been used to provide UV radiation since ancient times.

The energy consumption of these lamps is very high and the temperature is also very high (typically about 800 ° C). A significant part of the energy goes to waste heat 4, which causes problems when the coating and substrate become uncontrolled. Mercury arc lamps also produce ozone in the presence of oxygen. Ozone removal and your cooling require a large amount of air.

5 Nowadays, semiconductor emitters, especially fluorescent diodes (LEDs), which have a much lower energy consumption than conventional arc lamps, can be used to provide UV light. The temperature of the emitters is low (typically up to about 70 ° C), whereby irradiation is also easier to arrange. As with arc lamps, there is no ozone level. The life of the emitters is also very long (typically about 10,000 hours) compared to arc lamps (which typically have about 2,000 hours). The output of the emitters will also remain constant throughout their life. In addition, the emitter does not spend much on ignition and shutdown (such as arc lamps), which can further reduce energy consumption without shortening the service life. When the amount of heat radiation is low, it is also possible to freely use materials that are harmful to heat radiation. The power of such emitters is quite low, which is why they have been formed into larger units, especially so-called. panels with hundreds or even thousands of issuers. For example, the above-mentioned EP 1 804 243 A2 and WO 2006/072071 A2 describe such a radiation technique in greater detail.

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BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are part of the written description of the invention and are related to the detailed description of some embodiments of the invention set forth below. In the drawings, FIG. 1 shows an irradiation device for carrying out the invention.

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x si, fig. 2 shows height adjustment and sealing of the irradiation apparatus; 3 shows another irradiation device.

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Detailed description of some embodiments of the invention

The device according to Fig. 1 has a carpet conveyor 1, and above it is a irradiation device 2.1 with a UV LED unit 3 which is rich in fluorescent diodes. The curable composition is dispensed onto the body 5 to be coated, after which the body is conveyed under the irradiation apparatus and irradiated to cure the composition.

The irradiation device 2.1 first includes carbon dioxide guiding means 5.1 for dispensing carbon dioxide onto the surface of section 4 below the irradiation device. Because carbon dioxide is heavier than oxygen, it effectively displaces oxygen from the surface of the body 10 even when the surface has recesses. Prior to the UV LED unit 3, there are still nitrogen conducting means 6.1 for introducing nitrogen into the surface of the object below the UV LED unit for the most uniform, preferably laminar flow. As the flow remains laminar, nitrogen escape will be reduced and oxygen may be present above the nitrogen layer without interfering with the curing reaction. Nitrogen is supplied to the surface 15 obliquely in the direction of travel. The region in which the inertia and the irradiation take place is marked with an oval.

Preferably, the carbon dioxide delivery means 5.1 also includes a heating device for heating the gas supplied to the surface of the body.

The irradiation device 2.1 has a sealed housing 7.1 with its side edges sealed against the conveyor 1. The irradiation device is adjustable (e.g., up to 200 mm). The irradiation device is set at exactly the height δ ™ that allows the piece to pass underneath. This minimizes the escape of the inert gas.

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o 2 Fig. 2 shows the height adjustment and the edge sealing of the irradiation device 2.1. The equipment

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^ 25 has a vertical threaded rod 8 on each side secured by a threaded fit to a lateral extending rod 9 in the irradiation device. tightly against the conveyor edge.

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Also, the irradiation device 2.2 of Fig. 3 has, before the UV LED unit 3, carbon dioxide conducting means 5.2 and nitrogen conducting means 6.2. Here, the carbon conducting means is housed in its own sealed housing 7.2 'and the nitrogen conducting means and the UV LED unit housed in its own housing 7.2 ".

The distance of the object 4 to be irradiated is preferably 2 - 3 mm from the LEDs 3 of the UV LED unit 3.

It is good to equip the UV LED units 3 with cooling, preferably by water circulation. In this way, the curing conditions remain as stable as possible.

Preferably, the apparatuses have an autopilot which shuts down the UV LED units 3, cooling and inertia when the curing zone has not been cured for a period of time.

It is advantageous to connect a conveyor 1 with a limit switch, for example an optical, which stops the conveyor if the incoming body is too large. The conveyor speed required depends on the amount of radiation needed. The speed is typically 4-20 m / min.

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Claims (10)

A method for coating a body (4), comprising: - dispensing a UV curable mixture onto the body of the body, - transporting the body under an irradiation device (2.1; 2.2) in which an inert gas is introduced into the body 5 and irradiated by UV to that - in the irradiation apparatus (2.1; 2.2), an inert gas heavier than oxygen is first introduced into the surface of the body and then a second inert gas is introduced into the surface and the body is irradiated with UV radiation. The method of claim 1, wherein the UV radiation is formed by semiconductor emitters. 15 The method of claim 2, wherein the UV radiation is formed by fluorescent diodes. The process of any one of claims 1-3, wherein the inert gas, which is heavier than oxygen, is carbon dioxide. The process of any one of claims 1-4, wherein the second inert gas is ° nitrogen. i m o i oo ° 25 A method according to any one of claims 1 to 5, wherein the surface of the body has X £ recesses or bumps. m oo A method according to any one of claims 1 to 6, wherein the mixture fed to the body is heated prior to irradiation, preferably by means of an inert gas. 30 Apparatus for curing a UV curable composition dispensed on the surface of a body (4) by irradiation comprising: - a conveyor (1), - a radiation apparatus (2.1; 2.2) above the conveyor having inert gas conducting means and a UV source (3). ), characterized in that - the irradiation device (2.1, 2.2) has means for conducting an inert gas heavier than oxygen (5.1; 5.2), and then means for conducting another inert gas (6.1; 6.2). 10 The device of claim 8, comprising means (10) for preventing inert gas from leaking from the side of the conveyor. Use of a device according to claim 8 or 9 for curing the coating 15 of a body having recesses or protrusions on its surface. 't δ c \ j m o CO o X cc CL 1 ^ m oo o o o c \ j