DE2949710A1 - Crosslinking process for paints - uses protective layer of water pref. containing surface-active ingredient - Google Patents

Abstract

The process is for the cross-linking of synthetic points, applied to a carrier material, using ionizing radiation, esp. electron beams. The paint is covered by a protective layer, which prevents any breaks in the cross-linkage process due to reaction of the paint with oxygen. Before and/or during the process, water is applied/generated on the paint surface, to act as protective layer. The water is destilled, or de-ionized in some other way. It may contain one or more surface active materials.

Description

DR. JOACHIM STEFFENS on / m-in

/ yy / Iu

DIPLOMA CHEMIST UN PATENT ADVOCATE MOZARTSIRASSE 24 D-8032 LOCHHAM / MONCHEN

TELEPHONE {089) 87 25 51 TELEX: 529 830 steff d

IHK SIGN:

my reference: Physik-i4 December 10, 1979 p

Polymer-Physik GmbH & Co. KG 2844 Leraförde

Process for crosslinking plastic-based paints applied to carrier materials

The present invention relates to a method for crosslinking paints applied to carrier materials Plastic base by means of ionizing rays, especially electron beams.

Process for curing or crosslinking coating materials plastic-based with the help of ionizing rays, e.g. electron beams are gaining more and more Significance, since solvent-free systems are used as paints and for drying that take place at room temperature expires, relatively little energy has to be expended. The cross-linked layers have very good physical properties on, such as high abrasion resistance, solvent resistance etc. devices that matter today too

13G025 / 0Ö89

Roll work are characterized by high production output with little space requirement.

In electron beam hardening, a Hot cathode triggered, accelerated and in a deflection system by applying the accelerating high voltage fanned out. After the electrons have passed through a thin metal foil, they can act on the object. Since X-rays are generated when the electrons are slowed down, the electron accelerator as well as the inlet and outlet are in the system is shielded with lead sheet.

It is perceived as disturbing that the lacquer layer is covered with an oxygen-free gas at the point of hardening must to exclude oxygen molecules. This is necessary because the radicals generated in the paint by the ionizing radiation react faster with the oxygen in the air than with unsaturated carbon-carbon bonds. The reaction Atmospheric oxygen with radicals results in a stable connection, i.e. at this point there is no chain extension, there is only a low level of crosslinking with a relatively low level Molecular weight of the polymer on the surface. The surface is then not scratch-resistant. It can be a very thin one Film to be wiped off with solvent.

With the systems for electron beam hardening of surfaces that exist today, the object is usually equipped with a so-called protective gas covered. For this purpose, mainly purified nitrogen or a stoichiometric combustion gas, which is free of oxygen is used.

Such methods are technically complex and costly in the case of flat parts such as panels, doors and material still acceptable from roll to roll, especially - especially in the case of web-shaped material - through suitable constructions of the inertization space considerable amounts of Inerting gas can be saved.

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However, this does not work if deformed individual parts are painted and to be hardened by electron irradiation. Here is an enormous amount of inerting devices and Inert gas quantities necessary to get the irradiation room completely free of oxygen.

In order to solve this problem, a known UV curing method is used a wax is added to the paint material, which after the paint has been applied to the Material washes out to the surface, creating an inhibiting protective layer. The wax must then be polished off. This method is unsatisfactory because it counteracts fast throughput rates.

The object of the invention is therefore to provide a method which has the disadvantages outlined above does not have.

This object is achieved in that the protective layer used is water, which is preferably a surface-active one Has added funds.

The invention thus relates to a method for crosslinking VQn on paints applied to carrier materials Plastic base by means of ionizing rays, especially electron beams, in the presence of one on the paint surface located protective layer, which terminates the crosslinking reaction by reacting the paint with oxygen prevented, which is characterized in that before and / or during crosslinking on the paint surface Applies or generates water as a protective layer.

According to the invention, preference is given to using distilled or otherwise deionized water, in particular those that contain one or more surface-active agents The surface-active agents used with preference include surfactants, such as those commercially available from the trademarks, which are protected by trademarks, Spüli, Motiv and

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Agepon are available.

The surface-active agents are added to the water, especially in the case of crosslinking with electron beams, otherwise the water would not evenly wet the surface in the form of a fine film and the water layer would be too thick due to their surface tension on differently curved surfaces, so that the Electron beam, which is limited in its range, could not penetrate this layer and thus the the underlying lacquer layer would not crosslink.

When electron beam hardening is in the smallest of spaces within Within a fraction of a second, the lacquer layer is crosslinked, i.e. the water can mechanically immediately after the irradiation process wiped off or blown off by air or a stream of warm air without damaging the paint layer.

Another possibility is to mix something relaxed with the paint distilled water, which is due to the different density of water and varnish before cross-linking to the Penetrates the surface and thus prevents the paint from coming into contact with oxygen during the irradiation process.

Another possibility is that you can paint the surface so strongly hypothermic that a film of water is formed by condensation of water contained in the air.

The advantages achieved with the method according to the invention are obvious. There are particular

(a) Saving of inert gas

(b) faster throughput of the object, since the purging time of the inerting space with inert gas is not waited for must be, and

(c) more problem-free inerting of lacquer surfaces to be crosslinked of deformed parts.

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-y-t.

The following example explains the invention without restricting it thereto. _#

example

Primed sample panels are coated with a pigmented ESII lacquer, for example Viedopol from Hermann Wiederhold GmbH., KiI-den / Rhld., In a layer thickness of 40 g / m 2 in a spray booth by spraying on.
Then the undried paint film is applied with a

Spray a covering layer of approx. 10 g / m 2 of distilled water, which was relaxed by adding 0.1 - 1% of a surfactant, such as, for example, rinsing agent.

The curing of the paint film takes place with an electron gun system ESK 150 from Polymer-Physik Tübingen with a Accelerating voltage of 150-180 keV, with a radiation dose of 5 Mrad, which occurs at a feed rate of Object is applied at a speed of 50 m / min. The water on the surface is wiped off. The surface qualities of the coating do not differ from the same coating, which was cured under inert gas.

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Claims (3)

Claims 1. Method for crosslinking on carrier materials plastic-based paints applied by means of ionizing rays, in particular electron beams, in the presence of a protective layer on the paint surface, which is a break-off the crosslinking reaction is prevented by reacting the paint with oxygen, characterized in that that before and / or during the crosslinking on the paint surface water as a protective layer applies or generates. 2. The method according to claim 1, characterized in that that the water used is distilled or otherwise deionized water. 3. The method according to claim 1 and 2, characterized in that water is used, the one or more contains surfactants. 130025/0089 ORIGINAL INSPECTED