WO2008055926A1 - Procédé d'application de revêtement liquide sur un substrat - Google Patents

Procédé d'application de revêtement liquide sur un substrat Download PDF

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Publication number
WO2008055926A1
WO2008055926A1 PCT/EP2007/061997 EP2007061997W WO2008055926A1 WO 2008055926 A1 WO2008055926 A1 WO 2008055926A1 EP 2007061997 W EP2007061997 W EP 2007061997W WO 2008055926 A1 WO2008055926 A1 WO 2008055926A1
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WO
WIPO (PCT)
Prior art keywords
electroheat
substrate
susceptible material
primer
resin
Prior art date
Application number
PCT/EP2007/061997
Other languages
English (en)
Inventor
Kevin Jeffrey Kittle
Nigel Ivor Edward Shewring
Klaas Jan Hendrik Kruithof
Original Assignee
Akzo Nobel Coatings International B.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Akzo Nobel Coatings International B.V. filed Critical Akzo Nobel Coatings International B.V.
Publication of WO2008055926A1 publication Critical patent/WO2008055926A1/fr

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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
    • B05D3/0254—After-treatment
    • B05D3/029—After-treatment with microwaves
    • 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
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/50—Multilayers
    • B05D7/52—Two layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
    • B29C37/0025—Applying surface layers, e.g. coatings, decorative layers, printed layers, to articles during shaping, e.g. in-mould printing
    • B29C37/0028—In-mould coating, e.g. by introducing the coating material into the mould after forming the article
    • B29C2037/0035—In-mould coating, e.g. by introducing the coating material into the mould after forming the article the coating being applied as liquid, gel, paste or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
    • B29C37/0025—Applying surface layers, e.g. coatings, decorative layers, printed layers, to articles during shaping, e.g. in-mould printing
    • B29C37/0028—In-mould coating, e.g. by introducing the coating material into the mould after forming the article
    • B29C37/0032—In-mould coating, e.g. by introducing the coating material into the mould after forming the article the coating being applied upon the mould surface before introducing the moulding compound, e.g. applying a gelcoat

Definitions

  • the present invention pertains to a process for coating a substrate with a liquid coating. It also pertains to coated substrates that may be obtained using the process.
  • a liquid coating composition is a coating composition in the form of a liquid.
  • Thermosetting liquid coating compositions generally comprise a resin having functional groups and a curing agent capable of reacting with the functional groups of the resin. They are applied onto the substrate, e.g. via brushing, dipping, electrostatic spraying, or air assisted spraying.
  • the substrate provided with the coating is subjected to a heating step to cause and/or accelerate curing wherein the resin and the curing agent react to form a crossl inked polymer network.
  • liquid coating compositions are known in the art.
  • the coating layer is cured on the substrate by the application of heat (the process of stoving).
  • the curing times and temperatures are interdependent in accordance with the composition formulation that is used, and will vary between 10 seconds at a temperature of the order of 28O 0 C to 40 minutes at a temperature of the order of 40 to 80 0 C.
  • the disadvantage of this curing process is that for a fast curing process high temperatures are required, while not all substrates can withstand such high temperatures.
  • the coated substrate is led through an oven, which means that not only the coating layer, but also the substrate and the air surrounding it are heated and subsequently cooled. Even if this does not affect the substrate, unnecessary heating and cooling of substrate and air is an inefficient use of energy.
  • radiant energy such as infra-red (IR) or ultraviolet (UV) in the curing of liquid coatings is also known.
  • UV curing of liquid coatings requires the presence of a photoinitiator, the properties of which should be carefully matched to those of the resin, the curing agent, and the other components of the liquid coating composition, such as the pigment.
  • a photoinitiator the properties of which should be carefully matched to those of the resin, the curing agent, and the other components of the liquid coating composition, such as the pigment.
  • curing liquid coatings with UV light can cut the cure time significantly.
  • pigmented UV formulations can be difficult to cure all the way down through to the substrate, in particular when a higher layer thickness is to be cured.
  • IR curing of liquid coatings may be attractive, because less energy is wasted in heating the substrate or the air surrounding it. Further, the coating layer is heated from the outside going in, which means that temperature-sensitive substrates are exposed to less heat than in conventional curing using an oven.
  • IR curing IR waves with a variety of wavelengths are used, where some will heat the liquid coating to effect flowing and curing, but others will be absorbed by the substrate and heat that, or will be absorbed by the air, making for an inefficient use of energy.
  • Curing resins using microwave irradiation is also known in the art.
  • DE 3511654 describes a resin containing microwave susceptors which is cured using microwaves, the susceptors being heated by catching the waves and initiating the curing reaction.
  • US 5,234,760 describes coating a heat-sensitive substrate with a powder coating followed by film-formation of the coating through electromagnetic radiation.
  • the substrate should be at most very slightly excitable by microwaves.
  • the coating is based on a microwave-excitable polymer. In both references, the coating has to be specifically adapted to be suitable for microwave curing. In US 5,234,760 the coating has to be based on a specific type of polymer, which will lead to increased costs.
  • DE 3511654 an electroheat-susceptible material is to be added to a conventional polymer resin. This will necessitate reformulation and testing of the resin composition to ensure that its properties are not affected.
  • US 4585699 describes a method consisting in depositing a coating to be treated on a first face of a dielectric support, depositing a layer of electrically conductive material on an opposite face of the support, and applying microwave energy to the assembly. Curing of the coating layer requires heat transfer through the substrate. For heat sensitive substrates, this method is not suitable.
  • microwave curing of liquid coatings is still attractive for a number of reasons.
  • the application of microwaves results in very fast, virtually instantaneous heating of the liquid coating, as a result of which curing conditions are obtained very quickly.
  • the process can be carried out in a controlled manner, where undesired heating of the substrate is prevented.
  • fewer substances are microwave absorbers. Therefore, the energy put into the process will be used more efficiently, because there is less absorbance which does not contribute to the curing of the liquid coating.
  • the present invention pertains to a process for coating a substrate comprising the steps of o providing a substrate the outer layer of which comprises an electroheat- susceptible material o applying a liquid coating composition onto the face of the substrate comprising the electroheat-susceptible material, and o curing the liquid coating composition using electroheating.
  • electroheating refers to heating using radiation with a frequency of 10 MHz to 3 GHz.
  • Radiation with a frequency of 10 MHz to 100 MHz will be indicated as radio frequency, or RF, radiation, while radiation with a frequency of 100 MHz to 3 GHz will be indicated as microwave radiation.
  • the allocated radio frequencies are 13.56 MHz ⁇ 6.68 kHz, 27.12 MHz ⁇ 160.0OkHz, and 40.68 MHz ⁇ 20.00 kHz.
  • the allocated microwave frequencies are 915 MHz ⁇ 13 MHz, 2450 MHz ⁇ 50 MHz, 5800 MHz ⁇ 75 MHz, and 24125 MHz ⁇ 125 MHz.
  • Ionic conduction primarily takes place in the RF range. In this mechanism, the application of an electromagnetic field leads to oscillation of ions with the oscillation of the field. If there is any electrical resistance in the conductor, then this ionic movement will generate heat. In the microwave range there is the combined use of ionic conduction and dielectric heating, with dielectric heating being the main mechanism. In dielectric heating, molecules with a dipolar or magnetic nature will oscillate with the oscillation of the electromagnetic field, resulting in heating.
  • the process according to the invention starts out from a substrate the outer layer of which comprises an electroheat-susceptible material.
  • An electroheat-susceptible material is defined as a material which absorbs radiation with a frequency in the electroheating range and converts it to heat.
  • Suitable conductive materials include carbon black, graphites, metals, such as aluminium, conductive oxides like indium tin oxide, fluorine-doped tin oxides, etc.
  • Suitable magnetic materials include ferrites. Mixtures of various materials may also be used, e.g., a mixture of a conductive and a magnetic material.
  • the electroheat-susceptible material is primarily susceptible to microwave radiation. This will further be indicated as a microwave- susceptible material. In another embodiment the electroheat-susceptible material is primarily susceptible to radio frequency radiation. This will further be indicated as an RF-susceptible material.
  • conductive materials including those listed above, are microwave- susceptible materials, while magnetic materials, including those listed above, are RF-susceptible materials.
  • a substrate the outer layer of which comprises an electroheat-susceptible material can be obtained by contacting the substrate with a primer comprising an electroheat-susceptible material. This contacting can be carried out in various ways.
  • a substrate is coated with a primer comprising an electroheat-susceptible material.
  • the primer can be liquid or solid (determined at application temperature).
  • Liquid primers can be applied in any manner known in the art for the application of liquid coating materials, e.g., using brushes, sprays, rollers, dip coating, curtain coating, etc. Solid primers are in particulate form. They may be applied to the substrate via a powder spraying process.
  • an electrostatic application process whether in the form of an electrostatic fluidised bed or in the form of an electrostatic spraying process, may be used.
  • electrostatic bed applications also for non-conductive substrates and less- conductive substrates, reference is made to WO 99/30838, WO02/098577, WO 2004/052558, and WO 2004/052557.
  • the contacting of the substrate with the primer is carried out during the moulding process of the substrate. More in particular, in this embodiment the contacting with a primer is performed by coating the inside of a mould with a layer of a primer, filling the mould with a curable resin that will form the substrate, curing the resin, and releasing the substrate the outer layer of which comprises an electroheat-susceptible material from the mould. In this embodiment the primer will be solid.
  • the primer prefferably contains a resin in addition to the electroheat- susceptible material.
  • the presence of a resin increases the adhesion of the electroheat-susceptible material to the substrate. It can also increase the adhesion of the liquid coating composition to the substrate.
  • An additional advantage of the presence of a resin in the primer is that it can act as a heat dispersant. It will help the distribution of heat through the entire coating layer, resulting in less risk of the formation of hot spots.
  • a substrate the outer layer of which comprises an electroheat-susceptible material is provided by coating a substrate with a primer comprising a curable resin and an electroheat-susceptible material, and curing the primer partially or fully to help fix the electroheat-susceptible material to the substrate.
  • a substrate the outer layer of which comprises an electroheat-susceptible material is provided by coating the inside of a mould with a layer of primer, curing the primer partially or fully to help fix the electroheat-susceptible material to the mould, filling the mould with a curable resin that will form the substrate, curing the resin, and releasing the substrate the outer layer of which comprises an electroheat-susceptible material from the mould.
  • the electroheat-susceptible material is generally present in the primer in an amount of 100 to 2 wt.%, calculated on the total of electroheat-susceptible material and resin present in the primer. If the resin is added to obtain one or more of the advantageous effects described above, it is preferably added in an amount of at least 10% of the total of electroheat-susceptible material and resin, more preferably at least 20%. The addition of very little electroheat-susceptible material may result in insufficient curing efficiency of the liquid coating composition to be cured. Accordingly, it may be preferred for the electroheat- susceptible material to make up at least 10% by weight of the total of resin and electroheat-susceptible material.
  • the resin used therein will be a solid resin.
  • the primer may comprise resin particles mixed with particles of an electroheat- susceptible material, but it is also possible for the primer to comprise particles containing both resin and electroheat-susceptible material. Accordingly, the primer may be obtained by mixing particles of a resin with particles of an electroheat-susceptible material, by mixing particles of a resin with particles of an electroheat-susceptible material followed by a step to bond the particles of the electroheat-susceptible material to the resin particles, or by mixing the electroheat-susceptible material with the resin in liquid form and then converting the mixture into particles, e.g. by solidifying the mixture and grinding.
  • suitable resins include the resins for powder coating compositions which a skilled person is well aware of.
  • the coating primer comprises a conventional powder coating composition to which an electroheat-susceptible material has been added, for example by dry-blending it with the existing powder coating composition, by bonding it to the existing powder coating composition, or by adding it to the powder coating composition at some stage during its manufacture, which results in the incorporation of the electroheat-susceptible material into the particles of the powder coating composition.
  • the electroheat-susceptible material can be added to the powder coating before extrusion.
  • the nature of the resin can be selected to be compatible with the resin that will become the substrate.
  • the solid primer is to be applied to the mould, it generally has a particle size of 1 -300 microns, preferably 10-200 microns. Preferably, 95% by volume is below 120 microns. In some embodiments it may be attractive for 95% of the particles to be below 50 microns, or even below 20 microns. When a large percentage of small particles is present, it may be attractive to include a dry-flow improvement additive in the primer. These compounds are known in the art of powder coatings manufacture.
  • the solid primer If the solid primer is to be applied to a substrate, it will generally have a particle size of 1 -200 microns; preferably at least 95% by volume of the particles have a diameter of at most 120 microns. Again, in some embodiments it may be attractive for 95% of the particles to be below 50 microns, or even below 20 microns. Again, when a large percentage of small particles is present, it may be attractive to include a dry-flow improvement additive in the primer.
  • the primer is liquid, it generally contains a liquid carrier, which may be water- based or solvent based.
  • a liquid carrier which may be water- based or solvent based.
  • the use of water-based carriers is preferred for environmental reasons.
  • the resin that may be used in a liquid primer may be in the form of dispersed particles. Solute resins may also be used.
  • the resin is a resin selected from the resins suitable for use in liquid coatings. In an aqueous primer this would result in a resin dispersion.
  • Liquid primer layers are dried in a conventional manner. For example, they may be dried at room temperature, at increased temperature using hot air, subjected to microwave irradiation, or using IR. IR may be preferred for the reasons given above. It is well within the scope of the skilled person to formulate appropriate liquid primers, e.g., by adding electroheat-susceptible particles to conventional liquid primer formulations.
  • the amount of electroheat-susceptible material available on the surface of the substrate should be an effective amount to allow electroheat curing of the liquid coating composition. Determination of the effective amount is well within the scope of the skilled person using conventional trial and error in accordance with the following guidelines.
  • the use of larger amounts of electroheat-susceptible material will lead to increased curing speed, but too much electroheat- susceptible material will take curing out of control, possibly resulting in damage to heat-sensitive substrates.
  • the addition of a conductive electroheat- susceptible material can also serve to increase the surface conductivity of the substrate, which in turn results in an improved addition of liquid coating via an electrostatic process, thus resulting in a more even and consistent liquid coating layer.
  • the amount of electroheat-susceptible material present on the substrate generally is between 0.5 gram/m 2 and 100 gram/m 2 , preferably between 1 gram/m 2 and 10 gram/m 2 .
  • the thickness of the primer layer (after drying/curing) generally is between 10 and 200 microns.
  • the thickness When the primer is applied by coating the substrate, the thickness generally is between 10 and 100 microns, preferably between 15 and 80 microns.
  • the thickness When the primer is applied to the mould, the thickness generally is between 20 and 300 microns, preferably between 50 and 200 microns.
  • the primer can be applied in one or more layers.
  • the primer layer may be thinner, e.g., in the range of 1 -50 microns, more in particular 1 -10 microns.
  • the particle size of the electroheat-susceptible material should be adapted to the desired thickness of the primer layer. If the primer layer is relatively thick, e.g., for mould curing, an electroheat-susceptible material with a larger particle size may be used. If the primer layer is thinner, the size of the electroheat- susceptible material should be reduced correspondingly. If the particle size of the electroheat-susceptible material is too large, the finished properties of the coating will be undesirable.
  • the particles of the electroheat-susceptible material generally have a d(v,90) of 30 microns or less, preferably 10 microns or less. The d(v,90) generally is at least 0.5 microns.
  • the d(v,x) indicates for a stated particle size (d) the percentage (x) of the total volume of particles lying below the stated particle size; the percentage (100-x) of the total area lies at or above the stated size.
  • d(v,90) 7 microns indicates that 90% of the particles (the percentage calculated on the particle volume) are below 7 microns and 10% are above this size.
  • Particle sizes are measurable by laser diffraction techniques, for example by the Malvern Mastersizer, and unless indicated otherwise, the sizes quoted are as measured by the Mastersizer 2000, refractive index 1.45, absorption index 0.01.
  • the primer can contain other components conventional in the art of coatings manufacture, such as stabilisers, thickeners, dispersing aids, wetting agents, adhesion promotors, etc.
  • the primer may or may not contain pigments. In some cases, the addition of pigment to the primer may be attractive, especially in systems where the electroheat-susceptible material does not possess a strong colour. Pigmentation then facilitates visual identification of the areas of a substrate to which the primer has been applied.
  • the electroheat-susceptible material is embedded in the substrate. This provides increased adhesion of the liquid coating layer to the substrate. Embedding the electroheat-susceptible material in the substrate surface can be achieved in various ways.
  • a first method is by incorporating the electroheat- susceptible material into the surface of a plastic substrate during the moulding process of the substrate, via the method described above.
  • a further method is by coating a substrate having a heat-deformable outer layer with a primer comprising an electroheat-susceptible material, and then heating the primer layer. This will result in the particles of the electroheat-susceptible material becoming embedded in the substrate.
  • the primer in this embodiment it is attractive for the primer to contain a heat-curable resin in an amount of 10-90% by weight, calculated on the total of resin and primer.
  • the heat-curable resin will cure during the heating performed to embed the electroheat-susceptible material in the substrate and will contribute to fixing the electroheat-susceptible material in the substrate.
  • a material is considered embedded in another material if at least 50% by number of the particles meet the requirement that at least 25% of their largest cross-sectional diameter in the direction perpendicular to the substrate surface is embedded in the substrate.
  • MDF medium-density fibre-board
  • the surface of MDF boards is smooth and has a low porosity. When they are provided with a liquid coating, a smooth surface will thus easily be obtained.
  • the edges of MDF are relatively porous and rough. Conventional application of a liquid coating to the edges will result in adsorption of the molten liquid coating resin into the pores, which will result in an irregular coating on the surface of the edges. This effect is aggravated by the rough fibres on the MDF edges, which tend to rise in the direction perpendicular to the edge.
  • an MDF substrate is treated with a primer comprising an electroheat-susceptible material and 30- 90% of a resin, calculated on the total of electroheat-susceptible material and resin, the resin will block the pores of the MDF edges so that the resin of the subsequently provided liquid coating composition will not sink into the pores. Additionally, any protruding fibres formed during application of the primer can be sanded off after drying the primer, resulting in a smooth, non-porous surface which is very suitable for the application of liquid coatings.
  • a liquid coating composition is applied to the substrate the outer layer of which comprises an electroheat-susceptible material.
  • Methods for applying liquid coating compositions to substrates are well known in the art.
  • the liquid coating composition can be applied by methods which are conventional for the application of liquid paints, e.g., using brushes, sprays, rollers, dip coating, curtain coating, etc.
  • the coated substrate is subjected to electroheat radiation to cure the liquid coating composition.
  • electroheating refers to heating using radiation with a frequency of 10 MHz to 3 GHz. Radiation with a frequency of 10 MHz to 100 MHz will be indicated as radio frequency, or RF, radiation, while radiation with a frequency of 100 MHz to 3 GHz will be indicated as microwave radiation. In commercial practice specific wavelengths have been allocated for the purposes of heating. For the United States, the allocated radio frequencies are 13.56 MHz ⁇ 6.68 kHz, 27.12 MHz ⁇ 160.0OkHz, and 40.68 MHz ⁇ 20.00 kHz.
  • the allocated microwave frequencies are 915 MHz ⁇ 13 MHz, 2450 MHz ⁇ 50 MHz, 5800 MHz ⁇ 75 MHz, and 24125 MHz ⁇ 125 MHz. In other countries or regions, different frequencies may have been allocated for heating; in particular, outside of the United States frequencies of 433.92 MHz, 896 MHz, and 2375 MHz have been allocated. In a preferred embodiment of the present invention, the process is carried out using radiation with a frequency allocated for heating in the country where the process is carried out.
  • the curing time will generally be between 0.5 seconds and 40 minutes, in particular between 10 seconds and 30 minutes.
  • the energy added will generally be between 10 W and 4 kW.
  • the energy levels may be varied during the curing process. For example, in one embodiment the curing is started with a high energy pulse, followed by a number of lower energy pulses to keep the coating heated for as long as is necessary to ensure curing.
  • the selected frequency will be matched with the nature of the electroheat-susceptible material. If the electroheat- susceptible material is primarily susceptible to RF radiation, curing will be carried out with RF radiation at an RF frequency. Alternatively, if the electroheat-susceptible material is primarily susceptible to microwave radiation, curing will be carried out using microwave radiation at a microwave frequency. If the electroheat-susceptible material is susceptible to both RF and microwave radiation, frequencies in either range may be used.
  • a non-conductive substrate is defined as a substrate with a surface resistance of more than 10 ⁇ 11 ohms/square
  • a poorly conductive substrate is a substrate with a surface resistance of 10 ⁇ 3 ohms/square to 10 ⁇ 11 ohms/square
  • a conductive substrate is a substrate with a surface resistance of less than 10 ⁇ 3 ohms/square. The surface resistance is determined in accordance with
  • Suitable non-conductive substrates and poorly conductive substrates include medium density fibre-board (MDF), wood, wood products, plastics materials, plastics materials including electrically conductive additives, polyamide, and highly insulating plastics materials, for example, polycarbonate.
  • MDF medium density fibre-board
  • wood wood products
  • plastics materials plastics materials including electrically conductive additives
  • polyamide polyamide
  • highly insulating plastics materials for example, polycarbonate.
  • plastic substrates are used which are suitable for interior and exterior applications in the automotive industry, such as airbag covers, bumpers, fascias, fenders, wing mirrors, door panels, panel hoods, panel roofs, and panel trunk lids.
  • An MDF substrate may have a surface resistance of the order of between 10 ⁇ 3 ohms/square and 10 ⁇ 11 ohms/square depending on its moisture content, where a higher moisture content will lead to a lower surface resistance.
  • Wood and wood products may be expected to have a surface resistance of the order of between 10 ⁇ 3 ohms/square and 10 ⁇ 11 ohms/square depending on the type of wood and its moisture content.
  • Plastics materials including electrically conductive additives and various plastics materials without electrically conductive additives may have a surface resistance of the order of between 10 ⁇ 3 and 10 ⁇ 11 ohms/square, depending on the material and, where included, the additive or additives.
  • Highly insulating plastics materials including, for example, polyamide and polycarbonate, may be expected to have a surface resistance of the order of above 10 ⁇ 11 ohms/square. If so desired, the substrate provided with the electroheat-susceptible material is chemically or mechanically cleaned using methods known to the skilled person prior to application of the liquid coating. If the electroheat-susceptible material is applied to the substrate using a primer, it may be advantageous to perform a chemical or physical cleaning step before application of the primer.
  • the substrate may be washed or sanded before use.
  • Other types of pre-treatment known in the art of liquid coating application may also be applied.
  • the substrate contains moisture, like MDF or wood, it may be desired to preheat the substrate to reduce the moisture content before applying the liquid coating composition, as the presence of moisture may cause problems during curing of the liquid coating composition.
  • moisture-containing substrates it may be attractive to use RF-cuhng, because while moisture is sensitive to microwave radiation, causing heating of the substrate, RF radiation is less specific.
  • the substrate is a heat-sensitive substrate.
  • a first liquid coating composition is a base coat composition comprising colour and/or effect imparting pigments
  • a second clear liquid coating composition is applied on top of the base coat composition.
  • a further advantage of the process according to the invention is that as the electroheat-susceptible material is not incorporated into the liquid coating composition, the process can be used with all conventional heat-curable liquid coating compositions.
  • Heat-curable liquid coating compositions are well-known in the art.
  • Suitable liquid coating compositions comprise one or more film-forming resins and a curing agent.
  • the resin acts as a binder, having the capability of wetting pigments and providing cohesive strength between pigment particles and of wetting or binding to the substrate, and after application to the substrate flows in the curing process to form a homogeneous film.
  • suitable film-forming resins include polyesters, polyurethanes, polyacrylates, epoxy resins, and mixtures thereof.
  • Suitable functional groups present in the film-forming resin are hydroxyl groups, thiol groups, amino groups, epoxide groups, alkoxysilane groups, and activated C-H groups, such as malonates or acetoacetates, and mixtures thereof.
  • suitable counter reactive groups present in the crosslinker are isocyanate groups, which optionally may be blocked, ethehfied amino groups, such as etherified melamine formaldehyde resins, carboxylic acid groups, and Michael acceptor groups, such as acryloyl groups.
  • Suitable combinations of mutually counter reactive functional groups are well known in the art. The combination of hydroxyl-functional resins with isocyanate crosslinkers may be specifically mentioned.
  • liquid coating composition conventional additives for coatings may be present.
  • additives include stabilizers, flow additives, fillers, UV-absorbers, catalyst blocking agents, pigments (colour pigments, metallics and/or pearls), wax, defoamers, surfactants, and wetting agents.
  • the liquid coating composition may be water borne or solvent borne.
  • Solvent borne compositions may include any solvent known in the art, i.e. aliphatic and/or aromatic hydrocarbons.
  • Examples include toluene, xylene, butyl acetate, ethyl acetate, acetone, methyl isobutyl ketone, methyl isoamyl ketone, methyl ethyl ketone, ether, ether alcohol, ether ester, hexylglycol, butoxyethanol, 1 -methoxy- propanol-2, 1-ethoxy-propanol-2, 1-propoxy-propanol-2, 1-butoxy-propanol-2, 1 - isobutoxy-propanol-2, dipropylene glycol monomethyl ether; methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, ethylene glycol, diethylene glycol, dimethyl dipropylene glycol, diacetone alcohol, methylether of diacetone alcohol, ethoxy ethyl propionate, or a mixture of any of these. Water
  • the liquid coating composition comprises less than 780 g/l of volatile organic solvent based on the total composition, more preferably less than 420 g/l, most preferably less than 250 g/l.
  • the present invention also pertains to substrates provided with a layer of a primer containing an electroheat-susceptible material and a layer of a liquid coating composition.
  • a layer of a primer containing an electroheat-susceptible material and a layer of a liquid coating composition.
  • a plastic substrate is coated with a primer containing an electroheat-susceptible material in combination with a resin.
  • the electroheat-susceptible material comprises 30-90 wt.% of the total of electroheat-susceptible material and resin.
  • the resin is a solid powder coating resin, which is dispersed in an aqueous primer.
  • the primer is applied via a conventional application process for liquid paint.
  • the primer layer is allowed to dry.
  • a liquid coating composition is applied onto the substrate, e.g., via a spraying process.
  • the coated substrate is treated with intermittent bursts of microwave radiation to allow curing of the liquid coating composition.
  • the plastic substrate coated with the primer is heated to a temperature sufficient to soften the substrate surface.
  • the temperature is sufficiently high to allow the electroheat-susceptible material to become embedded in the substrate surface.
  • the heating also results in the curing of the resin in the primer, which helps to fix the electroheat-susceptible material to the substrate.
  • the substrate surface is treated to remove loose material and the liquid coating composition is applied and cured as described above.
  • an MDF substrate is coated with a primer containing an electroheat-susceptible material in combination with a resin.
  • the electroheat-susceptible material comprises 10-40 wt.% of the total of electroheat-susceptible material and resin.
  • the resin is a solid powder coating resin as described above, which is dispersed in an aqueous primer.
  • the primer is applied via a conventional application process for liquid paint.
  • the primer layer is allowed to dry. To ensure that a sufficient amount of electroheat- susceptible material is applied, more than one primer layer may be applied.
  • the substrate Upon drying of the primer layer(s), the substrate is treated to remove surface irregularities, e.g., by sanding.
  • a liquid coating composition is applied onto the substrate, e.g., via an air assisted spraying process.
  • the coated substrate is treated with intermittent bursts of microwave radiation to allow curing of the liquid coating composition.
  • a mould is treated with a solid primer composition containing an electroheat-susceptible material in combination with a resin.
  • the electroheat-susceptible material comprises 10-40 wt. % of the total of electroheat-susceptible material and resin.
  • the resin is selected to be compatible with the resin that will make up the substrate.
  • the primer is added to the mould in a conventional manner, e.g., via an electrostatic spray gun where the primer is in the form of a powder, or via a wet paint spray gun where this is not the case.
  • the mould is heated to ensure sufficient curing of the resin to ensure adherence of the primer to the mould surface during addition of the liquid substrate resin.
  • the liquid substrate resin is added to the mould, and the mould is heated to cure the substrate resin.
  • the substrate provided with a surface layer comprising an electroheat-susceptible material is released from the mould.
  • the electroheat-susceptible material is embedded in the substrate surface.
  • a liquid coating composition is applied onto the substrate, e.g., via an air assisted spraying process.
  • the coated substrate is treated with intermittent bursts of microwave radiation to allow curing of the liquid coating composition.

Landscapes

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

Abstract

La présente invention concerne un procédé d'application d'un revêtement sur un substrat, lequel procédé consiste à disposer d'un substrat dont la couche extérieure comprend un matériau sensible à l'électrothermie, à appliquer une composition de revêtement liquide sur la face du substrat comprenant le matériau sensible à l'électrothermie, puis à faire durcir la composition de revêtement liquide au moyen d'un rayonnement électrothermique.
PCT/EP2007/061997 2006-11-09 2007-11-07 Procédé d'application de revêtement liquide sur un substrat WO2008055926A1 (fr)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
EP06123770.7 2006-11-09
EP06123770 2006-11-09
EP06125113.8 2006-11-30
EP06125113 2006-11-30
US87367906P 2006-12-07 2006-12-07
US87363606P 2006-12-07 2006-12-07
US60/873,679 2006-12-07
US60/873,636 2006-12-07

Publications (1)

Publication Number Publication Date
WO2008055926A1 true WO2008055926A1 (fr) 2008-05-15

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Application Number Title Priority Date Filing Date
PCT/EP2007/061997 WO2008055926A1 (fr) 2006-11-09 2007-11-07 Procédé d'application de revêtement liquide sur un substrat

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Country Link
WO (1) WO2008055926A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITVI20090025A1 (it) * 2009-02-12 2010-08-13 Viv Internat S P A Linea e metodo per il trattamento superficiale di oggetti allungati
WO2014008993A1 (fr) * 2012-07-12 2014-01-16 Tata Steel Uk Limited Durcissement de revêtements multicouche par micro-ondes

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5234760A (en) * 1989-03-31 1993-08-10 Elf Atochem, S.A. Composite material comprising a substrate and a polymeric based coating and process for the manufacture thereof
DE19622921A1 (de) * 1996-06-07 1997-12-11 Basf Lacke & Farben Mit Pulverlack beschichteter wärmeempfindlicher Werkstoff
EP1172192A2 (fr) * 2000-07-11 2002-01-16 Nippon Liner Co., Ltd. Méthode de réticulation rapide de résines époxy, et méthode d'absorption d'ondes électromagnétiques à travers les résines époxy réticulées obtenues par ladite méthode de réticulation
EP1541641A1 (fr) * 2003-12-05 2005-06-15 Rohm And Haas Company Revêtements en poudre réticulés par induction pour substrats thermosensibles

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5234760A (en) * 1989-03-31 1993-08-10 Elf Atochem, S.A. Composite material comprising a substrate and a polymeric based coating and process for the manufacture thereof
DE19622921A1 (de) * 1996-06-07 1997-12-11 Basf Lacke & Farben Mit Pulverlack beschichteter wärmeempfindlicher Werkstoff
EP1172192A2 (fr) * 2000-07-11 2002-01-16 Nippon Liner Co., Ltd. Méthode de réticulation rapide de résines époxy, et méthode d'absorption d'ondes électromagnétiques à travers les résines époxy réticulées obtenues par ladite méthode de réticulation
EP1541641A1 (fr) * 2003-12-05 2005-06-15 Rohm And Haas Company Revêtements en poudre réticulés par induction pour substrats thermosensibles

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITVI20090025A1 (it) * 2009-02-12 2010-08-13 Viv Internat S P A Linea e metodo per il trattamento superficiale di oggetti allungati
EP2218996A1 (fr) * 2009-02-12 2010-08-18 V.I.V. International S.p.A. Système et procédé pour la peinture et le séchage des objets allongés
WO2014008993A1 (fr) * 2012-07-12 2014-01-16 Tata Steel Uk Limited Durcissement de revêtements multicouche par micro-ondes
US9636705B2 (en) 2012-07-12 2017-05-02 Tata Steel Uk Limited Microwave curing of multi-layer coatings

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