Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
  • B05D3/0209—Multistage baking
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
  • B05D3/0254—After-treatment
  • B05D3/0263—After-treatment with IR heaters

Definitions

• the present invention relates to a method of light-curing a coating on at least one surface of a substrate, in which the coating applied to the substrate is subjected to at least a first exposure by infrared radiation of short or medium wavelength .
• the coatings concerned are for example paints, varnishes, plastic coatings in the form of powder and or solution.
• It also relates to an installation for implementing the method comprising at least one frame, at least a first coating exposure zone provided with short or medium infrared radiation generators.
• the invention also relates to a product consisting of a substrate covered on at least one of its surfaces with at least one polymerized coating.
• infrared rays having respectively their maximum emission peak less than 1, 4 microns and between 1, 4 and 3 microns.
• ultra violet generators are used associated with coatings comprising photo-initiators which capture the energy of the radiations, transmit it to oligomers also contained in the coating in order to initiate the polymerization chain reaction of the coating.
• photoinitiators thus allow photopolymerization at low temperature.
• the thickness of the coating must be limited.
• these specific coatings have a high cost and make the process expensive to implement.
• the method described in publication WO-01/62401 consists in powder coating automobile body parts, in which the polymerization of a lacquer is carried out, obtained from pigments suspended in water , by heat only or by heat combined with actinic radiation.
• the method described in publication WO-01/64794 consists in obtaining the polymerization of the paint by means of near infrared radiation and of ultra violet radiation and / or of electronic radiation applied successively or simultaneously by preheating the paint by means of near infrared radiation. then by polymerizing it by means of ultra violet rays. This process therefore requires the use of specific paints and resins, sensitive to ultra violet radiation and of a high cost.
• the purpose of the present invention is to overcome the drawbacks mentioned above by providing a method of photopolymerization of a layer of paint applied to a substrate and an installation for the implementation of this method, simple, economical, allowing considerably reducing the polymerization time, treating substrates having complex shapes, treating successive series of substrates having different shapes and considerably improving the quality of the painted substrates obtained.
• This object is achieved by the process specified in the preamble and characterized in that the coating is subjected to at least a second exposure by infrared radiation of respectively medium or short wavelength, the short and medium infrared radiation coming from generators. short and medium infrared rays arranged on the side of the surface of the substrate.
• the first exposure is preferably carried out by infrared radiation of short wavelength and the second exposure is made by infrared radiation of medium wavelength.
• each exposure is modulated in power and / or in time as a function of the instantaneous temperature of the coating.
• said sunstrokes can be carried out simultaneously or successively so that the duration of each sunstroke is less than thirty seconds and preferably less than five seconds. It is also possible to carry out at least one additional insolation by means of medium infrared radiation.
• the substrate is displaced along a predetermined trajectory relative to the generators of short and / or medium infrared radiation and / or the generators of short or medium infrared radiation relative to the substrate.
• a set of exposure sequences is carried out, each sequence comprising at least the first and second exposure.
• fast infrared radiation generators having a low thermal inertia and reaction times on emission or extinction of less than one second, short infrared radiation having a wavelength of the emission peak. between 0.4 and 1.4 micrometers and preferably substantially equal to 1 micrometer and the medium infrared radiation having the wavelength of the emission peak between 1.4 and 3 micrometers and preferably substantially equal to 1, 7 micrometers.
• ultraviolet radiation can be used in combination with said short and medium infrared radiation.
• This object is also achieved by the installation as defined in the preamble and characterized in that it comprises at least a second exposure zone provided with respectively medium or short infrared radiation generators, the short and medium infrared radiation generators being arranged on the side of the surface of the substrate.
• the first insolation zone is provided with short infrared radiation generators and the second insolation zone with medium infrared radiation generators.
• the installation advantageously comprises at least one generator of complementary medium infrared radiation.
• the generators of short or medium infrared radiation are adjustable in power and / or in time as a function of the instantaneous temperature of said coating and arranged so that the exposure zones are at least partially superimposed.
• the installation preferably comprises means of transport arranged to move, along a predetermined path, the substrate relative to the generators of short and / or medium infrared radiation and / or the generators of short and / or medium infrared radiation relative to the substrate .
• the short and / or medium infrared radiation generators are advantageously arranged in groups each comprising at least one short infrared radiation generator and at least one medium infrared radiation generator.
• the short and / or medium infrared radiation generators are mounted movable in translation relative to the chassis and associated with drive means arranged to modify the exposure distance between the generators of short and / or medium infrared radiation and the surface of the substrate.
• the short and / or medium infrared radiation generators are arranged on each side of the substrate to insulate it on its two opposite surfaces.
• the short and / or medium infrared radiation generators are preferably mounted on at least one gantry suspended from the chassis and carried by at least one carriage movable in translation in at least one guide rail secured to the chassis, the drive means comprising at less an actuator and a transmission between the actuator and the carriage.
• the exposure means can also be mounted mobile in rotation relative to the chassis around axes and associated with pivoting means arranged to modify the exposure angle on said surface to be treated of the substrate by rotating the radiation generators. short and / or medium infrared simultaneously or independently.
• each generator of short and / or medium infrared radiation is housed in a cassette coupled to the pivoting means, the cassettes being mounted adjacent to the gantry.
• Each cassette advantageously comprises a substantially cylindrical tubular body provided with at least one reflector in front of which is placed at least one emitting tube forming a generator of short and / or medium infrared radiation.
• the cassette can be hollow so that it can be traversed by a cooling air circuit.
• the exposure means may include generators of ultraviolet radiation used in combination with said generators of short and medium infrared radiation.
• the installation comprises at least one auxiliary generator of short and / or medium infrared radiation disposed at a lateral end of at least one of the insolation zones defined by the preceding short and medium infrared radiation generators , the auxiliary generator can also be coupled to pivoting means.
• This installation is advantageously supplemented by at least one computerized management unit arranged to automatically control the short and medium infrared radiation generators, drive and pivoting means according to the shape and dimensions of the substrate as well as the thickness. and the nature of the layer of paint to be polymerized.
• FIG. 1 schematically represents an installation for implementing the method according to the prior art
• FIG. 2 schematically represents an installation for implementing the method according to the invention
• FIG. 3 is an overall view of an installation according to the invention.
• FIG. 4 schematically represents one side of the insolation means of the installation of FIG. 3 according to the arrows IV-IV,
• FIG. 5 schematically represents a section along the arrows V-V of the installation of FIG. 3,
• FIG. 6 is an enlarged section of a cassette equipped with an infrared radiation generator forming said insolation means of FIG. 4, and
• FIGS. 7A-B are partial views respectively from above, from the side and from the front of the insolation means of FIG. 4.
• FIG. 1 schematically illustrates an installation 10 according to the prior art which comprises a single cassette 11 of infrared radiation generators with a predetermined wavelength either short or medium. These infrared radiation are applied for a long time to the surface to be treated of a substrate 13 previously covered with a powder or solution coating, such as for example polyester type paints, a varnish, a coating of synthetic materials or any other similar coating containing polymerizing oligomers. This process takes a long time to implement. In addition, due to adjustment difficulties, the final result is a poor quality coating that is not sufficiently polymerized or overheated with blistering and having reduced hardness and life. Illustration of the invention:
• the installation 20 comprises a single cassette 21 provided with generators of infrared radiation of different wavelengths, for example generators of short infrared radiation 22a and generators of medium infrared radiation 22b.
• These short and medium infrared 22a and 22b generators are preferably of the fast type and have reaction times on emission and extinction of less than one second.
• Short infrared radiation can have a wavelength of the emission peak at least between 0.4 and 1.4 micrometers and preferably substantially equal to 1 micrometer and medium infrared radiation can have a wavelength of the peak emission at least between 1, 4 and 3 micrometers and preferably substantially equal to 1, 7 micrometers.
• the generators of short infrared radiation 22a and medium 22b are arranged in the cassette 21 in an alternative manner, which makes it possible to obtain rapid sequential insolation of the surface of a substrate 23 which continuously scrolls past the short infrared radiation generators 22a and medium 22b.
• the short and medium infrared rays are applied to the surface to be treated of the substrate 23, this surface having previously been coated with a layer of paint, for example powder, solution or suspension, of the polyester or similar type, which contains oligomers polymerizing respectively under the effect of short or medium infrared radiation.
• a layer of paint for example powder, solution or suspension, of the polyester or similar type, which contains oligomers polymerizing respectively under the effect of short or medium infrared radiation.
• the interface between the coating and the substrate 23 is heated as a priority and the temperature in the thickness of the coating is gradually raised to its surface.
• the treatment durations go from 8-10 minutes according to the prior art to 1-3 minutes with the method of the invention, the duration of each exposure being less than thirty seconds and preferably less than five seconds.
• the BUCHHOLZ hardnesses of the coating obtained go from 80-90 to 110 with the process of the invention.
• the substrate 23 is usually in motion and passes under the cassette 21 of the short and medium 22a and 22b radiation generators.
• These radiation generators have been described with reference to FIG. 2 as being generators of short infrared radiation 22a and medium 22b. They may also include generators of ultraviolet radiation and / or generators of long infrared radiation. All combinations are possible depending on the nature of the coatings and the nature of the substrates 23 and the surface to be treated. This surface can be made of metal, wood, synthetic materials, composite materials, a combination of these materials or any other similar material.
• the substrate 23 can undergo known preparatory physical and / or chemical treatments such as, for example, pickling, degreasing, shot blasting, sandblasting, preheating, etc. which facilitate and improve the application of the paint layer and its polymerization by infrared radiation. Best way to realize the invention:
• FIGS 3 to 7 illustrate a preferred embodiment of an installation 200 according to the invention.
• This installation 200 is an infrared radiation oven comprising in particular a chassis 210, insolation zones A1, A2 delimited by short and medium infrared radiation generators 22a and 22b, the insolation zones being at least in superimposed parts.
• the installation 200 also includes means 230 for transporting a substrate 23 arranged to move it along a predetermined path through said insolation zone A.
• This installation 200 is characterized by the fact that it is suspended.
• the chassis 210 is formed of guide rails 211 fixed for example to the ceiling so as to carry the short infrared radiation generators 22a and 22b which are in the form of two panels 220a, 220b suspended vertically from side and other from the median plane B of the installation 200 (cf. fig. 3) and corresponding to the trajectory of the substrate 23.
• the substrate 23 is also suspended vertically from a transport rail 231 fixed for example to the ceiling in the plane B
• the short and medium infrared 22a and 22b generators are mounted movable in translation along an axis C perpendicular to plane B (cf. FIG. 3) so as to adapt the insolation distance to the shape of the substrate. 23 to be processed.
• Each panel 220a 220b is formed, with reference to FIG. 4, of a set of cassettes 221 arranged in an adjacent manner and extending substantially vertically, that is to say in a direction substantially perpendicular to the direction of travel of the substrate. 23, so as to irradiate the faces of the substrate 23 over their entire height.
• these panels 220a, 220b are completed by auxiliary cassettes 222 arranged in the upper part and in the lower part on either side of the set of cassettes 221, and extending longitudinally, ie -to say in a direction substantially parallel to the direction of travel of the substrate 23, so as to irradiate the upper and lower fields of the substrate 23.
• Each cassette 221 comprises, in the example shown, a series of generators of infrared radiation of the same wavelength, either short 22a or medium 22b, for example four aligned generators.
• the cassettes 221 of different wavelengths alternate in the direction of travel of the substrate 23.
• each cassette can include infrared generators of different wavelengths.
• the first cassette 221 comprises generators of short infrared radiation 22a (short IR) and the two following cassettes 221 of the generators of medium infrared radiation 22b (medium IR).
• This group of three cassettes 221 is reproduced three times in the same order, each panel 220a, 220b comprising a total of twelve cassettes 221.
• each group of three cassettes 221 defines a sequence of sunstrokes: exposure by short infrared rays followed by two exposures by medium infrared rays, this sequence of exposures repeating successively and rapidly on the substrate 23 during scrolling.
• Other arrangements can also be envisaged in order to define other repetitive sunshine sequences.
• the auxiliary cassettes 222 comprise from left to right: a generator of short infrared radiation 22a (short IR), two generators of medium infrared radiation 22b (medium IR) and a generator of infrared radiation short 22a (short IR).
• These panels 220a, 220b are mounted movable in translation along an axis C substantially perpendicular to the plane B (cf. FIG. 3) and associated with drive means 240 making it possible to adapt the insolation distance between the generators of short infrared radiation 22a and means 22b and the substrate 23 in the form of the substrate 23 to be treated.
• the C axis can have any other suitable orientation.
• the cassettes 221, 222 forming each panel 220a, 220b are mounted on a gantry 241 suspended from said chassis 210.
• This gantry 241 is carried by carriages 242 movable in translation in the guide rails 211.
• the drive means 240 include in the example shown an actuating member in the form of a crank 243 controlling the movement of the carriages 242 by a chain and pinion transmission 244.
• actuating member in the form of a crank 243 controlling the movement of the carriages 242 by a chain and pinion transmission 244.
• this is only one example among all known mechanisms such as systems pinions / racks, pulleys / belts, etc., which can be controlled manually or automatically by motors or jacks.
• the drive means 240 of the two panels 220a, 220b can be coupled to move them simultaneously and in the opposite direction. They can also be independent.
• the width of the exposure zone A can be adapted to the shape of the substrate 23, detected before entering the oven, for example by means of a scanner.
• the panels 220a, 220b are brought closer together, while for a larger substrate 23, the panels 220a, 220b are spaced apart as a function of the greater width of the substrate 23.
• the exposure distance is generally between 2 cm and 150 cm, this insolation distance being in particular linked to the flux emitted by the generators of short infrared radiation 22a and means 22b and to the relative speed of movement of the substrate 23 relative to the generators of short infrared radiation 22a and means 22b.
• each short infrared radiation generator 22a or means 22b can be secured to a mobile carriage, independently with respect to the other carriages carrying the other short infrared radiation generators 22a or means 22b.
• the installation may include several independent fixed or mobile gantries.
• the exposure distance can be constant or variable and adapted during exposure.
• the substrate is fixed and the exposure panels are movable along a predetermined path.
• each cassette 221, 222 comprises, in the example shown, a substantially cylindrical tubular body 223 provided with a longitudinal opening closed by a parabolic reflector 224 in front of which is placed an emitting tube 225 of infrared radiation.
• the reflector 224 is mounted in the body 223 by means of a profile 226 which fits into a peripheral groove of the reflector 224 and is fixed to the body 223 by screwing, riveting, welding, or any other equivalent means.
• the reflector 224 and the emitter tube 225 form said generators of infrared radiation 22a, 22b.
• This reflector 224 can be completed by fins 227 placed at the front of the emitter tube 225 and having the function of creating an air mattress in front of this emitter tube 225 to protect it from the solvents released by the layer of paint during its polymerization. .
• each cassette 221, 222 being hollow allows air to circulate therein to evacuate the calories released by the emitter tubes 225 and avoid the risks of overheating and breakage of the tubes.
• the installation 200 comprises air circuits 260 provided with fans 261 which blow fresh air inside the cassettes 221, 222 by conduits 262 and regulating valves 263.
• installation 220 includes air extractors (not shown) in the upper part to evacuate the ambient hot air mixed with the solvents released by paint during polymerization and avoid the risk of explosion. This air extraction takes place symmetrically inside the oven to preserve its balance.
• the insolation means 220 are also movable in rotation.
• each cassette 221, 222 is mounted mobile in rotation on the gantry 241 and is associated with orientation means 250 arranged to adapt the exposure angle to the substrate 23 to be treated.
• the cassettes 221 are movable around an axis D substantially perpendicular to the direction of travel of the substrate 23 and the cassettes 222 are mobile around an axis E substantially parallel to the direction of travel of the substrate 23.
• the rotation of these cassettes 222 can be carried out manually by a simple handle or automatically by a motor or a jack.
• FIGS. 7A and B illustrate an embodiment of the orientation means 250 in which all the cassettes 221 of the same panel 220a or 220b are connected together by a system of rods 251 controlled by an actuating member in the form of a lever 252.
• a system of rods 251 controlled by an actuating member in the form of a lever 252.
• this is only one example among all the known mechanisms such as pinion / rack and pinion systems, pinions / chains, gear train, etc., which can be controlled manually or automatically by motors or cylinders. It is also possible to envisage controlling the rotation of the cassettes 221 individually, for example by means of stepping motors which can be easily programmed.
• the cassettes 221 being cylindrical can advantageously be arranged against one another while remaining movable with respect to each other. Being adjacent, they prevent infrared radiation from passing between them, which would have the consequence of heating the outer walls of the furnace, resulting in significant energy losses and a significant drop in efficiency.
• This installation 200 is supplemented by a programmable computerized management unit arranged to manage and control the operating parameters of the oven (scrolling of the substrate 23, cooling and air extraction circuits, etc.) and to automatically control the means of sunshine 220 and the drive means 240 and pivoting 250 depending in particular on the shape and dimensions of the substrate 23 as well as the thickness and the nature of the layer of paint to be polymerized.
• This installation 200 makes it possible to polymerize the paint layer on the substrate 23 whether it is independently applied to one of its faces or to its two opposite faces by selecting one of the panels or the two panels 220a, 220b of the insulating means 220.
• the particular construction of the installation 220 as described makes it possible to obtain a very compact oven, not requiring insulation, with variable geometry according to the shape of the substrate 23 to be treated and, consequently, very flexible allowing rapid change of series.
• the insolation means 220 as described can be individually controlled in power and / or in time, which makes it possible to obtain great flexibility and optimal quality of treatment.
• its suspended design makes it easier to clean floors, especially when installed in clean rooms with tiled floors.
• This installation 200 allows the implementation of the photopolymerization method according to the invention of a layer of paint applied to at least one surface of a moving substrate 23.
• This method consists in subjecting the paint layer to at least two exposures by infrared radiation of different wavelengths coming from two independent infrared radiation generators arranged successively relative to the direction of travel of the substrate 23, the first being a generator of short infrared radiation 22a and the second a generator of medium infrared radiation 22b, these generators being both arranged on the side of the surface to be treated.
• the short infrared radiation generator 22a is arranged to pass through the layer of paint and primarily heat the interface between the surface of the substrate and the paint layer at a temperature between 100 and 300 ° C and preferably substantially close to 190 ° C depending on the type of coating used. While the medium infrared radiation generator 22b is in spectral agreement with the paint to be polymerized, so as to penetrate inside the layer of paint and gradually raise its temperature from the interface to its outer face to reach an outside temperature between 50 and 90 ° C and preferably substantially close to 60 ° C.
• the infrared radiation generators 22a, 22b are arranged on each side of the substrate 23.
• this photopolymerization process can be implemented by other installations than that described.
• the sunshine means 220 are not necessarily suspended.
• the substrate 23 is not necessarily suspended.
• the drive means 240 and the transport means 230 must then guide the insulating panels 220a, 220b and the substrate 23 respectively in the upper part and in the lower part.
• the surface to be treated can be made of metal, wood, synthetic or composite materials, a combination of these materials or any other similar material.

Landscapes

• Application Of Or Painting With Fluid Materials (AREA)
• Coating Apparatus (AREA)
• Paints Or Removers (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=27772039

Family Applications (1)

Country Status (6)

Families Citing this family (7)

Family Cites Families (13)

• 2003
  • 2003-03-06 EP EP03725272A patent/EP1485213A2/de not_active Withdrawn
  • 2003-03-06 WO PCT/FR2003/000733 patent/WO2003074199A2/fr not_active Ceased
  • 2003-03-06 US US10/506,667 patent/US20050163937A1/en not_active Abandoned
  • 2003-03-06 JP JP2003572700A patent/JP2005526592A/ja active Pending
  • 2003-03-06 AU AU2003227819A patent/AU2003227819A1/en not_active Abandoned
  • 2003-03-06 CA CA002477665A patent/CA2477665A1/fr not_active Abandoned

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events