Heat-sensitive material coated with powder paint

Details Heat-sensitive material coated with powder paint Heat-sensitive material coated with powder paint

1998-04-01

2001-10-02

Copenheaver, Blaine (Department: 1773)

Stock material or miscellaneous articles

Composite

Of epoxy ether

C428S481000, C427S195000, C427S317000, C427S325000, C427S386000, C427S397000, C427S421100, C427S475000, C427S553000, C427S557000

Reexamination Certificate

active

06296939

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to coating heat-sensitive materials, preferably wood, with a powder paint.
BACKGROUND OF THE INVENTION
Today's orientation towards technologies that protect the environment is distinguished by ever more stringent regulations governing the maintenance of air purity. For this reason, attempts are made to use these technologies when coating wood and wood based products. Up to the present time, powder-paint technology has not played any significant role when substrates of this kind are being coated at an industrial scale. Reviews of this subject matter can be found in the following publications: Alfred Krüger, Magdeburg, Josef Heinskill, Brunswick “Möglichkeiten der Pulverbeschich-tung von Holz und Holzwerkstoffen,” [Possibilities for Powder-coating, Wood and Wood Products],
DFO Tagungsbericht
[DFO Conference Proceedings], 1994; Istvan Radoczy, Tigerwerk A-Wels “Das Wood-Dual Verfahren zur MDF-Veredelung,” [The Wood-Dual Process for MDF Processing],
I
-
Lack, March
1995, pp. 96-98; Danilo Malavolti “Polveri nella verniciatura del legno e deli plastici?” [Powders for Finishing Wood and Plastics?,“
La Revista del Colore/Verniciatura Industriale
[Industrial Colours and Finishes Review], No. 281, September 1991, pp. 277-278, Simon Peter Höldmoser, Hali Büromöbel, A-Eferding “Pulverbeschichtung von MDF Platten in der Praxis,” [Powder Coating of MDF Panels in Practice], JOT Seminarunterlagen [JOT Seminar Papers], Munich, January 1995; G. Sauerbrey, “Holzbeschichtung im Aufbruch,” [Wood Coating Flourishing], Report of Powder Meeting, 1991, in CC Hamburg, Vinzenz Verlag, Hannover (Abb. TB Pulver 91); Anon. “Powder coating of wood and woodbased materials,”
DTI Surface Coating Technology,
August, 1993; Leonardo Zelaschi “Novita dal mondo dei vernicianti e della verniciatura,” [New from the world of finishes and finishing],
La Revista del Colore/Verniciatura Industriale
[Industrial Colours and Finishes Review], No. 241, May, 1998, pp. 165-166.
The difficulties that have been encountered up to the present can be attributed to a number of technical causes. Wood is a natural, non-homogeneous and hygroscopic material. Its properties and features are formed by a number of factors that influence it during its growth and when it is being processed. As an organic material, it is constantly being affected by the environment as it is being processed and used.
The substances that make up wood, including moisture that is contained in it, play a decisive role. As the moisture content of wood changes, not only does it volume change—with anistropy exacerbating existing anatomical problems—its electrical conductivity and its behaviour when wet also change.
Different rates of swelling and shrinkage in materials and coatings, which change as tile moisture content changes, impose enormous mechanical stresses on the bonding systems and lead to premature failures at critical points. The constituent substances of the wood migrate to the surface and can result in pronounced colour changes and uncontrolled chemical reactions with the substances used in the coatings.
Problems encountered when powder-coating wood and wood based products are caused by the migration of volatile substances such as water, resins, waxes and terpenes from the substrate; this migration is brought about by the high temperatures that are required in order to form a film from the powder paint. These volatile components result in bubbles being included in the film These, in their turn, degrade the chemical stability of the film, its mechanical properties, and the appearance of the surface of the paint. The lowest possible melt and polymerization temperature is required at the lowest possible viscosity of the molten powder paint in order to reduce off-gassing of the substrate, and in order to encourage de-aeration of the melt. But limits are imposed on these requirements with respect to the shelf life and amenability to processing of powder paints. The exacting demands of the furniture industry for flawless and homogeneous surfaces constitute another challenge to the performance of powder paints of this kind.
For all of the above reasons, it is impossible to simply transfer the technological conditions for powder paint that proved themselves when used such paints are applied to metallic surfaces.
For this reason, I. Radoczy,
I
-
Lack
3/95, 63rd year, pp. 96 et seq. proposes using a symbiosis of powder paint and water-based paint. The author proposes a formulation for a water paint that has been adapted for wood, and which is used to wet the substrate. Using this water paint causes the powder paint to adhere to the wood substrate. However, a disadvantage with this procedure is that the advantages of the totally emission-free dry powder paint are not exploited. For this reason, there is still a need to use powder paints without the addition of water-based paints.
For this reason, it is the task of the present invention to make available a layered material consisting of a substrate that is of heat-sensitive material, preferably wood, and a powder paint coat that is applied thereto, which simultaneously ensures the minimal formation of bubbles and optimization of its flow and polymerization characteristics.
SUMMARY OF THE INVENTION
Most surprisingly, according to the present invention, it has been possible to solve this problem by a layered material that can be obtained by:
a) heating the substrate by microwave radiation;
b) application of a powder paint to the surface of the substrate, preferably by electrostatic spraying;
c) heating the powder paint to sintering temperature;
d) subsequent hardening of the paint coat
DETAILED DESCRIPTION OF THE INVENTION
All heat-sensitive materials can be used as substrates for the coating; examples of these are solid woods, as well as hard-fibre and medium-density panels (MDF). In particular, according to the present invention, it is possible to use materials that are used in the furniture industry. In particular, the layered material according to the present invention is intended to replace the furniture surfaces used in the past by an emission-free system.
It is preferred that the powder paints used according to the present invention contain epoxy resins, carboxypolyesters, catalysts, secondary substances and, if necessary, secondary agents, and additives typically associated with powders, and agents to enhance their frangibility.
In general, the epoxy resins based on bisphenol A and bisphenol F have a functionality of 2 and the epoxydized novolack resins have a functionality of greater than 2. Especially preferred in the powder paints according to the present invention are novolac resins with a mean functionality in the range from 2.4 to 2.8, and with an equivalent epoxy weight in the range from 600 to 850. In the case of the epoxydized novolac resins, some of the phenolic hydroxyl groups can be etherified with alkyl or similar groups. Epoxydized groups are introduced into the molecule by conversion of the phenolic hydroxyl groups with epichlorhydrides. When this is done, the so-called epoxydized novolac is formed starting with the novolacs. The epoxydized novolacs are structurally related to bisphenol-A resins. Epoxydizing novolac resins can be manufactured by epoxydized novolacs that consist, for example, of three to four phenol nuclei that are connected to each other by methylene bridges. Alkyl-substituted phenols that have been converted with formaldehyde can be used as novolac resins.
The products that are a commercially available under such names as Araldit, Grilesta, or Epikote are suitable epoxy resins.
The epoxy resins that are used in the powder paints (Component A) according to the present invention are solid epoxy resins with an equivalent epoxy weight from 300 to 5500, preferably 800 to 3000. Aromatic, aliphatic and/or cycloaliphatic epoxy resins are suitable. It is preferred that aromatic epoxy resins based on bisphenol-A

Affiliated with

Also associated with

Rating

Heat-sensitive material coated with powder paint does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Heat-sensitive material coated with powder paint, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat-sensitive material coated with powder paint will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2581581