Coating processes – Direct application of electrical – magnetic – wave – or... – Polymerization of coating utilizing direct application of...
Patent
1995-02-21
1996-06-25
Pianalto, Bernard
Coating processes
Direct application of electrical, magnetic, wave, or...
Polymerization of coating utilizing direct application of...
1562735, 1562755, 427264, 427270, 427278, 427359, 427369, 4273855, 427393, 427397, 427408, 427494, 427504, 427551, 427552, C08F 246
Patent
active
055298125
DESCRIPTION:
BRIEF SUMMARY
The subject invention concerns a method of electron-beam curing varnish that is applied on boards having a decorative surface. The method consists of curing a final (and possibly single) layer of varnish in a two-step procedure with an intermediate pressing step. The curing in the first EB-curing apparatus is intentionally incomplete (to 60-95%) in order to allow the technique chosen for the pressing step to shape the surface of the varnish as desired.
Different surface finish effects (varnish texture and gloss intensity) could be obtained by using differently configured press plates and also by varying the force of the pressure applied. Immediately following the pressing step curing to 100% is effected in the second EB-curing apparatus. The technique is particularly well suited for the manufacture of decorative board material that need to meet exceptionally high requirements as to abrasion resistance, scratch resistance and impact resistance.
High-pressure laminate is a decorative surfacing material that is appreciated for its excellent properties such as e.g. abrasion resistance, impact resistance, scratch resistance, appearance, light resistance, resistance to burns.
The manufacture of high-pressure laminates is effected by bonding together a number of phenol or melamine resin impregnated paper sheets by subjecting them to high pressures and high temperatures. The resulting product is an organic material with inherent stress, which consequently reacts strongly to changes in temperature and the contents of humidity in the air. Even chipboard having a thickness of 40 mm need to be provided with some kind of backing material in order to counter-act the stress exerted by the high-pressure laminate.
In case of thinner applications the stress counter-action is even harder to achieve. A particularly demanding application in this respect is laminated flooring materials having a thickness of 7 mm. In addition, the requirements on abrasion resistance are higher in this case, a problem which is solved by providing the laminates with overlay (an abrasive-resistant coating of cellulose material which is impregnated with melamine and which becomes transparent in the lamination process), reinforced by aluminium oxide particles. The higher the amount of aluminium oxide, the higher the abrasion resistance. However, the amount of aluminium oxide also affects the transparency of the material, and it imparts a greyish appearance to the material which detracts from the aesthetic design of the product. In addition, the aluminium particles have an abrasive effect on the tools in the application stage with resulting increase of the costs in this stage and lower productivity. The following description will show the limitations occurring when high-pressure laminates are to be used in positions where extremely high abrasive resistance is required.
Attempts have been made to replace the expensive high-pressure laminates by other decorative surfacing materials but either the impact resistance or the abrasion resistance has been found to be too low or else both these characteristics have deteriorated to an unacceptable degree. Also the resistance to burns is often lost when the high-pressure laminate is replaced by alternative surfacing materials.
The technique of using electron-beam cured varnish has been known for about 15 years. So far, the technique has been put to practical use in a very limited number of applications. In all, five applications are mentioned in the article `Decorative particle board surfaces via the UV/EB curing process--15 years of success` in the publication Betagamma, No. 2/88, which is an international periodical on electron and gamma radiation, St. Gallen, Switzerland. It appears that the technique can be used only on flat surfaces and in addition it requires large-series production of articles for which the properties of electron-beam cured varnish are appreciated.
An article in No. 6/89 in the German trade journal I-Lacke, Lacke, written by Wilhelm Baulmann, lCI Lacke Farben, Hilden, Germany makes it irr
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