EP1055524A1

EP1055524A1 - Process for decorating metals

Info

Publication number: EP1055524A1
Application number: EP00106868A
Authority: EP
Inventors: Paolo Michele Rinaldi
Original assignee: Comital SpA
Current assignee: Comital SpA
Priority date: 1999-04-07
Filing date: 2000-03-30
Publication date: 2000-11-29
Anticipated expiration: 2020-03-30
Also published as: EP1055524B1; DE60011185D1; ES2218020T3; ITBA990012A1; ATE268269T1; IT1307891B1; DE60011185T2

Abstract

A process for the decoration of metals, metal alloys, in the form of extruded profiles, sheets and metal articles in general, that utilizes the transfer system.

The process allows the decoration, with one only treatment, of metal extruded profiles on the four faces, independently on the shape of the profile, using suction and compressed air. The new process causes transfer to be quicker and provides an optimum result with respect to the quality of the final product. After the preliminary steps of pickling and painting, obtained by using colorless paints, the profile is wrapped up in a paper bag bearing on the surface the color and the pattern to be transferred. Air is removed from this bag. To correct paper adhesion to the support, compressed air is utilized and lastly heating.

Only compressed air is utilized for sheet decoration.

Description

The decoration of surfaces by the transfer system, independently on their being fabrics or metals in the general meaning of the word, is already known in the art.
These applications are still carried out with various techniques, all of which require for the polymerization of the inks on the surfaces to be decorated, the presence of pressure and heat.
Object of the invention is the decoration of metals, metal alloys, in the form of extruded profiles, sheets and objects from metal in general.
The process utilizes the already known transfer system.
The novelty lies in the decoration of sheets and profiles extruded on all the faces by one only treatment, independently on the shape of the section, utilizing at the same time suction and compressed air.
The new system allows to make the transfer process quicker, and to obtain an optimal result with regard to the quality of the end product.
The surface to be decorated is submitted to the traditional pickling treatments, to prepare it for painting and to allow a better adhesion of the paint film onto the metal surface.
The base paint or primer utilized is colorless, and the chromatic colors as well as the pattern of the decoration are transferred by the transfer system.
This process is innovating in that the systems used still today include the coloring of the surface with priming colors whereon the pattern is transferred through transfer.
This allows to obtain a range of colors that is markedly more various, with shades of colors and color-matching that are still unthinkable on metal surfaces; in fact, the color range of inks is much more various and more easily realizable, compared to the color range of powder paints.
As mentioned above, the process utilizes suction and compressed air.
Two processes shall be distinguished, the first one for the decoration of extruded profiles, the second one for the decoration of sheets.
The process utilized for the decoration of extruded profiles requires the utilization of suction and compressed air.
As said above, this system allows the decoration on all the faces of the profile, whatever the shape of the section, with one only process.
After the pickling process and the painting with transparent paints, the extruded profile is wrapped up in the support (transfer) which is constituted by particularly smooth paper bearing on its surface the colors and the pattern to be transferred.
As specified above, the paper employed shall have a particularly smooth surface obtained by a mechanical finishing, and a weight in grams of 30 g/m².
By gluing means, the paper is closed around the profile on three sides, so as to form a bag open on the head side.
The gluing performed is perfectly tight, and suction shall be from the open side, to remove air from the bag, causing at the same time the paper to adhere to the surface of the metal extruded profile.
Suction shall take place gradually, in order to allow a perfect adhesion of paper to the profile in the longitudinal direction, avoiding therefore the formation of folds and flaps.
The final suction value shall be contained and not exceed the ceiling of 150 mm of Hg column.
In the presence of high temperatures, paper shows a slight expansion, that facilitates a better adhesion on the metal surface.
The adhesion of paper to the profile, obtained by suction, causes pleats and air pockets in the central region of the extruded profile, which pockets, because of the length of the profiles (about 6,5 m), cannot be eliminated by simple suction.
In these central regions of the extruded profiles, adhesion is ensured through the pressure of a cloth (cotton jacquard fabric) treated with proofing systems to ensure air-tightness.
Said cloth is constantly kept under pressure with compressed air.
During transfer, this cloth, kept under pressure on the profiles, removes the air pockets that have formed in the central regions, allowing a better adhesion of paper to the surface of the profile.
The process utilized for the decoration of sheets needs only the use of compressed air.
Sheets shall be covered on a face by paper whereon, on reaching the transfer temperature, the aforementioned jacquard cloth will exercise the pressure desired to ensure the pressure of paper on the support to be decorated.
The pressure exercised by the cloth will ensure the perfect adhesion of paper to the sheet support, allowing a transfer without bleeds and distorsions of the colors and patterns to be transferred to the sheet surface.
The last step of the process lies in bringing the profiles to the transfer temperature of from 160 to 210°C for a period of 15-16 seconds, necessary for the transfer and crystallization of monomers for the perfect polymerization of the inks on the profile.
In order to reach the temperature necessary for the polymerization process, the profiles are placed in a tunnel-oven of the ventilated type fed by a fumes-air heating system, and a particular ventilation system.
The transfer of the profiles in the inside of the tunnel is obtained with the help of longitudinal or transversal translation trolleys, provided with a rigid top bearing the profiles and sheets.
The heating system is obtained by a fumes-air exchanger having a special conformation.
Air laps at the same speed all the exchange surface, assuring the passage all over the surface of the exchanger, avoiding also the formation of vortexes that lead unavoidably to the formation of air stagnation in large regions.
Ventilation in the inside of the oven is ensured by two centrifugal fans located downstream of the exchanger.
The particular system utilized for ventilation allows the formation of fluid threads as linear as possible, so as to ensure a uniformity of temperatures throughout the length of the tunnel.
When all the system is steadily running, monitoring the different temperatures, the maximum difference that may be find in the inside of the tunnel is of 2°C.

Claims

A process for the decoration of metals, metal alloys, in the form of extruded profiles, sheets and metal articles, through the utilization of the transfer system, including the following treatments:

pickling of the surface according to commonly used traditional systems;

painting of the surface with perfectly transparent powder paints;

utilization for the transfer of paper caused to be smooth by means of mechanical finishing processes, with a weight in grams of 30 g/m², bearing both the colors necessary for the decoration and the pattern to be transferred.
A system to prepare metal profiles for decoration, by means of transfer including:

formation of a bag around the profile, constituted by the paper mentioned under claim 1, closed on three sides and open on the transversal side;

gluing of the bag on the three sides wit perfectly tight gluing methods, utilizing adhesive paper or glues;

suction on the short side of the bag left open, so as to cause the removal of air and the ensuing adhesion of paper on all the faces of the profile.
A decoration of all the faces of the metal profiles, including:

suction on the short side of the bag, left open, so as to cause the removal of air and the ensuing adhesion of paper on all the faces of the profile;

the suction value shall not exceed 150 mm of the Hg column.
Utilization of compressed air, comprising:

pressure of a cloth from jacquard cotton fabric, inflated to a pressure of 1 Atm, that shall press the profile throughout the length thereof;

the cloth is treated with systems that impart it air-tightness, and is constantly kept in the inside of the tunnel oven.
A method for decorating metal sheets that includes the following preparation steps:

covering of one of the faces of the sheets with the paper of claim 1;

utilization of compressed air;

the cloth from jacquard fabric of claim 4, such as to exercise a constant and uniform pressure on all the surface of the sheet to be decorated.