FR2774156A1 - Accelerated drying of inks, varnishes and paints for water based and flammable bases - Google Patents

Abstract

The accelerated drying is obtained by use of infrared radiation accompanied by air cooling of the surface using a stream of air at very low temperature. The drier head has a central chamber housing an infrared emitter (2) and two side chambers (6) into which compressed air is injected (8,9) to cool as it expands. Air is drawn upward over the infrared element to extract it (4) from the head.

Description

 The present invention relates to a device intended for accelerating the drying of printing inks and varnishes, and more particularly the water-based inks and varnishes used in flexography and the fatty inks and aqueous varnishes used in offset as well as paints not comprising no components liable to ignite on contact with a heat source.

 The drying of such inks, varnishes or paints is traditionally carried out by means of short infrared emitters in front of which the previously printed or painted support scrolls, these emitters having the characteristic of emitting, in addition to infrared radiation, a large quantity heat. Although it may include a heat extractor, the high temperature prevailing around such devices is harmful to certain printed or painted substrates sensitive to heat, such as plastic films, which may prohibit the use of this technique in the most difficult cases. more critical, represented in particular by very thin films.

The device according to the invention overcomes this drawback
It indeed comprises, according to a first characteristic, a device making it possible to bring into contact with the previously printed material and in the immediate vicinity of the infrared emitter, a large volume of air at very low temperature, which can be much less than zero degrees Celsius. This air at very low temperature is produced by any suitable means, in particular by using the adiabatic expansion effect of the air.

 According to a second characteristic, an extraction of cold air is also created in the immediate vicinity of the emitter, so as to cool the emitter. The volume of extracted air is greater than the volume of air supplied so as to create a zone of depression near the substrate to be dried, this depression preventing the propagation of residual heat around the device.

 According to a particular embodiment, the device which is the subject of the present invention may include: - a first element of suitable shape serving as support for a long, medium or short infrared emitter and ensuring the focusing of the infrared radiation on the printed or painted substrate and kept close to the substrate.

- two elements symmetrically attached to the first, intended to channel the flow of cold air and ensure its distribution in the most uniform way on the printed substrate.

- cold air generators based on the principle of adiabatic air expansion and capable of producing a sufficient volume of air at a very low temperature.

- an air extraction system which can be provided by a turbine and whose extraction volume is greater than the volume of cold air supplied.

- a protective cover allowing thermal insulation of the entire device for the faces that can be accessed by operators.

 Depending on the amount of energy required for drying the inks or paints and in the case of finding the highest running speed of the substrate, several devices as described above can be combined.

 The attached drawing illustrates in section the device.

 With reference to this drawing, a profile (1) of length adapted to the dimension of the substrate to be dried, closed at its two ends and open at its base, receives an infrared emitter fixed by its ends. The upper part of the profile is pierced with one or more orifices (3) allowing, using a turbine (4) and an exhaust duct (5) to extract the air contained in the profile ( 1).

The profiles (6), of identical length to the profile (1) and also closed at their ends diffuse, over their entire length, through the opening (7) the cold air produced by the generators (8) operating according to the principle of the adiabatic expansion of the compressed air arriving through the orifices (9)
A cover (10), containing a thermal insulator (11) ensures the safety of the operators in the face of the heating produced by the release of heat from the transmitter (2) on the upper part of the profile (1).

 The assembly is kept at the smallest distance (D) from the substrate (12) to be dried. The volume of air extracted by the turbine (4) being greater than the volume of air produced by the generators (8) there is created in the area (13) an air depression preventing the heat generated by the infrared emitter. red to spread beyond the device.

Claims (3)

 1) Device accelerating the drying of varnishes and water-based inks used in flexographic printing, fatty inks and water-based varnishes used in offset printing, paints having no constituents liable to ignite on contact with 'a heat source, by using infrared radiation characterized in that it comprises an air generation system (8) whose temperature can be less than zero degrees Celsius by using the adiabatic expansion effect of air in order to reduce the temperature prevailing inside the profile (1) due to the presence of the infrared emitter (2).  2) Device according to claim (1) characterized in that the presence of air at very low temperature from the generators (8) allows, by reducing the heat in the vicinity of the emitter (2) to position the device at closer to the substrate carrying the ink, varnish or paint whose drying must be accelerated, even in the presence of substrates sensitive to heat.  3) Device according to claim 2 characterized in that an extraction system (4) of the air present in the profile (1), of extraction capacity greater than the volume of cold air produced by the generators (8 ) creates a vacuum zone (13) preventing the propagation of heat outside the enclosure of the profile (1).