Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-07-11
2003-10-21
Lorengo, J. A. (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272200, C156S230000, C156S240000, C156S247000, C156S277000, C156S289000, C427S146000, C427S147000, C427S148000, C427S299000, C427S372200, C428S195100, C428S202000, C428S914000, C008S468000, C008S471000
Reexamination Certificate
active
06635142
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for the preparation of a decorated substrate comprising the steps of:
submitting the substrate to a treatment to prepare its surface for the application of a coating,
applying a coating to the surface of the substrate in one or more cycles,
covering the surface of the substrate with a sheet comprising a decoration which is to be transferred to said surface, and
heating the substrate and the sheet comprising the decoration to effect the transfer of the decoration from the sheet onto the substrate.
Such a process is known from patent application WO 96/29208, which is directed to a process and the relevant apparatus for making decorated, extruded, profiled elements. However, in this publication very little information is given on the material used to coat the surface of the substrate.
In U.S. Pat. No. 3,907,974 curable decorating systems for glass or metal containers using a heat transfer decoration are disclosed. This patent is mainly concerned with the heat transfer decoration itself, i.e. a sheet comprising the decoration. Such a decoration can be built up of multiple layers comprising a clear lacquer, a binder, a hardener, solvents, dyes, etc. Before the decoration is applied to it, the substrate is treated with a silane adhesion promoter. Before application of the decoration, the substrate is heated to a temperature of 65 to 120° C. After transfer of the decoration, the decorated substrate is heat cured for 10-20 minutes at 95-150° C. and optionally cured further for 10-20 minutes at 175-230° C.
In view of the comparatively high temperatures used in the curing of the decorated substrate over a relatively long time, this technique is not suitable for the decoration of heat sensitive substrates like wood, wood-containing materials, or (shaped) plastic materials which are susceptible to heat.
In EP 60 107 a process for transfer printing is disclosed in which a substrate (a continuous length of strip) is coated with a thermosetting material, e.g., an alkyd, polyester, polyurethane or epoxy paint. Immediately after curing at a temperature between 190 and 250° C. the substrate is brought into contact with a continuous strip of printed material. At a temperature between 180-280° C. the printing ink is transferred to the strip by sublimation.
In view of the relatively high temperature applied to the substrate during the curing of the coating, the process disclosed in this publication is not suitable for the decoration of heat sensitive substrates either.
In EP 14 901 a process for transfer printing of a heat sensitive substrate is disclosed. In this process, the substrate is heated to a temperature above 220° C., which makes this process also not suited for the decoration of a heat sensitive substrate.
In JP 58-162374 a process is disclosed for transferring a dye to PVC mouldings by using a UV-curable resin.
In WO 98/08694 a process is disclosed for decorating metal, plastic or the like materials. In this publication very little information is given on the material used to coat the surface of the substrate.
SUMMARY OF THE INVENTION
The process according to the present invention provides a process for the decoration of heat sensitive substrates. By using this process, the decoration on the substrates can be very detailed and bright colours can be used without the danger of colour diffusion. The thus decorated substrate is very durable and shows excellent weather and outdoor resistance. The technique is also applicable for heat resistant substrates.
In comparison with the processes known in the art, the process according to the present invention comprises the following additional steps, viz. that the coating is cured using electromagnetic radiation having a wavelength shorter than 400 nm, until a coating is obtained which has a T
g
between 50 and 130° C. and a scar resistance at 200° C. of at least 3N and wherein the temperature during the transfer of the decoration into the coating is from 180 to 220° C.
DETAILED DESCRIPTION OF THE INVENTION
Within the framework of the present invention, a heat sensitive substrate is a substrate that shows deformation, structural changes, discolouration, or other thermal damage when heated for a prolonged time to a temperature above 200° C.
Several apparatus can be used as a source of electromagnetic radiation with a wavelength shorter than 400 nm. In view of their availability and ease of incorporation into a production process, UV lamps or an apparatus generating an electron beam are preferred.
It was found that for a proper transfer of the decoration from the sheet onto the coated substrate, the T
g
and the hardness of the coating at the temperature at which the transfer of the decoration takes place are of the utmost importance.
If the T
g
is too low, i.e. below 50° C., the coating will be too soft at the transfer temperature in the range of 180 to 220° C. This will hamper the release of the sheet from the substrate after the transfer of the decoration, due to the softening of the coated surface.
If the T
g
is too high, i.e. above 130° C., the coating will be too brittle, causing easy damaging of the substrate in normal use and, for some substrates, poor adhesion between the coating and the surface.
In view of the optimum results obtained in the heat transfer of a decoration, preference is given to a coating that is cured until it has a T
g
between 80 and 110° C.
Further, the hardness of the coating at the temperature at which the decoration is transferred onto the substrate is important. If the hardness is too low, the release of the sheet from the substrate after the transfer of the decoration will be hampered. If the hardness is too high, an incomplete transfer of the decoration will be observed (or a longer time is needed for the complete transfer of the decoration) and also the adhesion between the coating and the surface will be lower.
A reliable measure of the hardness of the coating at the temperature at which the decoration is transferred onto the substrate is the scar resistance of the cured coating at 200° C. For a quick release of the sheet from the substrate, the scar resistance should be at least 3N, preferably at least 8N, more in particular at least 11N. The upper limit for the scar resistance is given by the time needed for the complete transfer of the decoration. This maximum time depends, int. al., on the thermal stability of the substrate. In general, it can be said that the scar resistance should be less than 30N in order to have the transfer of the decoration onto the substrate achieved in a reasonable period of time when the temperature during the transfer of the decoration into the coating is from 180 to 220° C.
Before a decoration is transferred onto it, the substrate is coated. The coating used in the process according to the present invention is one that can be cured by using electromagnetic radiation with a wavelength shorter than 400 nm, e.g., a coating that can be cured using UV light or electron beam radiation.
Before or during curing, the coating can be heated to accelerate the curing. However, this is not compulsory. Above all, during curing the temperature should not be so high as to have a negative impact on the properties of the substrate.
In particular for heat sensitive substrates, the manner of heating the substrate is important. For these substrates, IR heating is particularly useful. Using IR heating makes it possible to have only the sheet containing the decoration and the surface layer of the coated substrate reach the temperature in the range of 180-220° C. necessary for the transfer by sublimation of the decoration.
In a preferred embodiment of the present process, the coating is fully cured before the decoration is transferred onto the substrate.
For the process according to the present invention, in principle all coating compositions can be used, provided that
the adhesion to the substrate is sufficient,
the coating can be cured using electromagnetic radiation with a wavelength shorter than 400 nm, and
the coating can be cur
Rossini Tullio
Stula Vladimir
Akzo Nobel N.V.
Lorengo J. A.
Parker Lainie E.
Vickrey David H.
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