WO1998008614A9

WO1998008614A9 - Polymer coating by means of hot gases

Info

Publication number: WO1998008614A9
Application number: PCT/US1997/015193
Authority: WO
Filing date: 1997-08-28
Publication date: 1998-06-04

Abstract

An improved method and apparatus for applying a plastic powder material (34) to a substrate (36) includes heating a noncombusting gas and discharging the gas as well as powdered plastic material (34) into a nozzle or fitting (22). The plastic powder (34) is thereby heated to a fluid state and applied by entrainment in the gas stream onto a substrate (36). The coating (35) is subsequently solidified and, if appropriate, cured to properly coat the substrate (36).

Description

POLYMER COATING BY MEANS OF HOT GASES

BACKGROUND OF THE INVENTION

This invention relates to an improved method for coating substrates, and, more particularly, a method for coating a substrate by means of a two-step process involving; first, entraining thermoplastic or thermoset plastic powder in a non-combusting, gas stream while heating the powder and directing the liquified powder onto the substrate; and, second, subsequently cooling, setting or solidifying of the liquified powder material applied to the substrate. Additional curing or processing of the coating may be effected in situ. Additionally, apparatus for effecting liquification, application and solidification of the plastic powder is disclosed.

The volatile organic compound content of paint formulations is increasingly the subject of various federal and state regulations in the United States and throughout the world, which limit or preclude the use of formulations containing such compounds. Such regulations now exist because dispersal or evaporation of volatile organic compounds into the atmosphere has been identified as one potential cause of air pollution and degradation of the atmosphere. One solution to this problem has been to eliminate or significantly lower the quantitative amount of volatile organic compounds in such formulations. Utilization of water based paints and coatings is another solution to this problem.

A disadvantage associated with low volatile organic compound materials as well as water based materials is their poor or limited performance as a coating material on substrates. Moreover, alternative coating techniques such as electrostatic deposition processes require significant capital expenditures and potentially hazardous application processes as well as curing processes in ovens. Further, the size of items which may be coated utilizing such technology is limited. Another drawback is that such techniques are not field portable.

Thus, a need has developed to provide an improved methodology and apparatus for coating materials on substrates regardless of the size, configuration and location of the substrate using means or methods and apparatus which eliminate or greatly limit the evaporation or dispersal into the atmosphere of volatile organic compounds, while at the same time providing a coating which is rugged, long lasting and economical. SUMMARY OF THE INVENTION

In a principal aspect, the present invention comprises a method for applying powdered plastic to a substrate and apparatus for performing the method of applying various powdered plastic materials to a substrate as a coating. The method includes injecting plastic powder material into a non-combusting, gas stream and heating the powder to thereby simultaneously melt and forcefully direct the liquified plastic powder droplets onto a substrate where it adheres. A solidification mechanism such as cooling then takes place, and a further curing mechanism such as heating, exposure to ultraviolet light or other curing means may then occur. By use of heated gases or other heating means, the coating materials can be entrained and applied in an appropriate manner, set and then cured, if necessary, after application. The methodology as well as the apparatus are useful in the application of coatings onto a variety of substrates, including wood, metal, plastic, paper, concrete and other materials.

Thus, it is an object of the present invention to provide an improved method for coating materials on substrates. It is a further object of the invention to provide an improved method for coating materials on substrates utilizing a two-step process, the first step involving heating of a powdered plastic material to a liquid or fluid phase and ejection of that material via a non-combusting gas onto the substrate to form a coating. Subsequently, as a second step, the coating on the substrate is cooled, set or hardened. Optionally, the coating may then be cured or treated further to enhance the protective character of the coating.

Yet another object of the invention is to provide an apparatus for ejecting plastic powder material onto a substrate while simultaneously heating the plastic powder material sufficiently so that it will melt or fluidize and adhere to the substrate as a coating.

Yet a further object of the invention is to provide a field portable means for applying plastic materials as a coating onto substrates or articles that cannot be easily brought into a shop for coating.

Yet a further object of the invention is to provide an inexpensive, rugged and repeatable method for applying plastic materials as a coating onto substrates of various size and configuration. Yet a further object of the invention is to provide a device and method for applying a plastic powder material onto a substrate by a method which does not vaporize the powder, which does provide generally uniform heating of the powder to the liquid phase as it coats the substrate, which does not degrade the powder material, and which is environmentally safe.

Another object and advantage of the invention is associated with circumstances where open flames pose a hazard, such as when coating the surface of pipelines in which volatile materials are transported. The ability to coat such pipelines or repair corrosion protective coatings without exposing the coating to an open flame or interrupting pipeline service is thus an object and advantage of the invention.

As a further object, the method and apparatus of the invention may be used in a household environment as a replacement for painting because the coatings may be applied without the hazard of open flames. Another object of the method and apparatus of the invention is to provide the ability to apply a plastic coating in conjunction with elements such as decorative additives, biocides, pigments, insecticides, etc., utilizing a process wherein the temperature of the application process will not affect the desired properties of such additives.

Another object is to provide a coating method and apparatus having reduced transportation costs, since unlike paints, water and/or solvents are not necessary, thus the weight and bulk associated with such liquid coatings is significantly reduced.

A further object of the invention is to eliminate direct exposure of the plastic powder or substrate to combustion or flame as part of the coating process and to enable simultaneous coating of multiple surfaces comprised of different materials. Another object of the invention is to provide a methodology by which a substrate or object can be coated in a continuous manner. That is, with the subject matter of the invention, a coating hood or enclosure can be provided wherein the object to be coated is maintained within a heated region where the ambient temperature in the region is sufficient to melt or liquify the powder as it is ejected into a non-combusting gas stream and directed onto an object passing through the region or maintained in the region. Thereafter, the object may be transported or passed into a second hood, furnace or region for cooling, setting or, if necessary, curing.

Another object of the invention is to provide a method and apparatus whereby powdered plastic material may be applied to a substrate having a three-dimensional configuration or shape and wherein the application method comprises utilization of a heating mechanism such as a resistive wire that conforms to the general shape of the substrate. Gases passed through or over the resistive elements are appropriately heated and powder material is selectively liquified and propelled to form a uniform coating on an item. These and other objects, advantages and features of the invention will be set forth in the detailed description which follows. -

BRIEF DESCRIPTION OF THE DRAWING In the detailed description as follows, reference will be made to the drawing comprised of the following figures:

FIGURE 1 is a schematic view of the construction and method of operation of the apparatus of the present invention;

FIGURE 2 is a schematic view depicting an experimental arrangement for controlled practice of the invention;

FIGURE 3 is a schematic view depicting a further test setup to practice the invention; FIGURE 4 is a schematic view of an alternative apparatus to practice the invention. FIGURE 5 is another schematic view depicting apparatus to practice the invention; and FIGURE 6 is a schematic cross-sectional view of a Coanda effect nozzle applicator used in the practice of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Very generally, the present invention includes a process for coating plastic material onto a substrate by way of introducing the powdered material into a stream of non-combusting gas, entraining the powdered material in the gas stream, the gas stream and material being heated to liquefy the powdered material, followed by directing the entrained liquefied, powdered material onto the substrate by directing the gas stream toward the substrate, coating the substrate with the material, and setting the material on the substrate as a solid phase adhered to the substrate. The powdered material in general is a cross-linkable polymeric system having a melting point of less than about 150 C in its uncured state and is typically a polyester polymer, an epoxy polymer, a polyurethane polymer, an acrylic polymer or mixtures thereof. Most preferably, the step of setting the material includes crosslinking the polymeric system substantially contemporaneously with the step of coating the substrate.

Briefly, the subject matter of the invention utilizes characteristics of thermoplastic and thermoset plastic powders that melt at temperatures significantly less than their decomposition temperatures, for example, yet which, for certain thermoset materials, when properly applied to a surface or substrate, can, in some cases, survive temperatures up to 400°C. Existing technologies utilize combustion or flame techniques to apply such coatings. For example, Glass and DePay in the Fourth National Thermal Spray Conference Proceedings Report, at pages 345- 351, entitled "Protective Thermoplastic Powder Coating Specifically Designed Adhesive Polymer," disclose devices and methods for application of plastic in powder form to a substrate using a flame spray gun.

The method and apparatus of the present invention provides a different, but straightforward, distinct and safe method for application of such materials as a coating onto a substrate. That is, air and other gases may be heated by a variety of methodologies including precombustion or electrical resistance heating. The plastic powder is then entrained in the heated gas, liquified and applied to the substrate by directing the gas flow and entrained particles at the substrate. Alternatively, heat can be transferred by convective, conductive or radiant means to gas entrained powder to liquify the powder. The gas stream is then directed at the substrate being coated.

In this manner, thermoset powders of a desired particle size (e.g., in the range of 20 to 150 microns) may be injected into a gas stream and heated so that the powder becomes melted and remains substantially liquid until it reaches a substrate surface upon which it is to be placed as a coating. The initial melting temperature of the plastic powder is dependent upon the material and can be determined by fhermochemical or other methods. When utilizing heated, non-combusting gas, the appropriate increase in gas temperature above the melting point of the plastic powder injected in the gas is therefore determined by factors such as the thermal mass, i.e. size and volume of the particle, the rate of heat transfer to the particle, which is dependent at least in part on the gas involved, the residence time of the particle in the heat transfer area, and the composition of the powder.

By adopting such a methodology, disadvantages associated with injection of particles into flames and/or plasmas are avoided. That is, the temperatures of the particles in prior art methodologies are much higher than the melting temperature of the material comprising the particle and, therefore, a portion of the material may become vaporized or charred. By contrast, with the method of the present invention, heating of the plastic powder takes place at a lower temperature and is much more uniform than with the described prior art. Note however, prior art heating protocols can be used to heat a non-combusting or uncombusted gas which is then used to entrain, melt and carry the plastic powder material.

The method of the invention works with thermoset materials which, after liquifying and applying, cool and set, and may, if necessary, be cured by a variety of methods including infrared, ultraviolet, microwave or controlled heating methods. The method of the invention also applies to thermoplastic materials which are entrained and heated to a molten state and applied onto a surface. They then cool or are exposed to a second or controlled cooling stage where they harden on the substrate. In other words, the method and apparatus of the invention contemplate a first step of entraining and liquifying powdered plastic material followed by a second step (upon application of the liquified material to a substrate) of converting the material to a solid phase. Such thermally processed powder materials require spraying at or above their melting points, yet it is appropriate to avoid exposure to temperatures significantly above the melting point. In some circumstances, it may be appropriate to reheat the substrate coating as an additional step to smooth the coating on the substrate. Again, by using the apparatus and methodology of the present invention, a reheating step may be utilized followed by a resetting and, if necessary, further curing step. The separate or additional curing step implies change in the physical character of the coating in the solid phase due to heat, radiation, chemical action or other means.

FIGURE 1 therefore discloses, in schematic form, one embodiment of the invention. Specifically, a hot air blower or gun 10 includes an electric coil 12, to heat air flowing through the gun 10. A motor 14 operates a fan or propeller 16 to move the air through the gun 10. An adjustable power supply 18 controls the energy to the coil 12 and thus controls the heat input to the air flowing through the hot air gun 10. The hot air gun 10 may, for example, be in the form of a hair dryer or hot air paint removal gun, appropriately modified to practice the invention. The motor 14 operates to move or effect discharge of heated air from the front or outlet 20 of the gun 10.

Attached to the outlet 20 of the gun 10 is a fitting or discharge nozzle 22 having a passage 24 with an inlet 26 and an outlet 28. Thus, hot air discharging from gun 10 will flow into nozzle 22 via inlet 26 through passage 24 and out of the outlet 28. Liquified or melted particles of plastic powder 34 entrained in the heated air flow will simultaneously be discharged from nozzle 22. The nozzle 22 thus is attached to a mechanism which feeds plastic powder 34 in the solid phase into the passage 24 at or near inlet 26 to be liquified or changed to the liquid state. The plastic material or powder 34 is maintained in a storage bin 30 and is fed from that bin 30 through a hose or discharge line 32 by means of a feeder, such as a screw feed mechanism or other transport mechanism. The hose 32 directs the powder 34 into or near the inlet 26 of the nozzle or fitting 22. The inlet 26 is positioned so that the powder 34 is injected into passage 22 in a manner which permits optimal residence time for melting or liquification. The heated, noncombusting gas, which is typically air, thus entrains plastic powder 34. The powdered plastic material 34 is heated and substantially melted, or liquified and directed onto a substrate 36 by the air flow from outlet 28 of nozzle 22. Upon engaging the substrate 36, the powder 34 will coat the substrate 36.

Of course, the gun 10 may be directed or moved over the surface of the substrate 36 to effect a coating over the total surface of the substrate 36 and into all of the depressions and projections of the substrate 36. The powder 34 is thus applied as a coating 35 and must be post- processed or changed into the solid phase on the substrate 36. The post-processing operation may, in the case of thermoplastics for example, be effected solely by cooling due to removal of the gun 10 or due to unheated air discharge from the gun 10. Also for thermosets an additional curing step may be effected by further heating associated with the air discharge from gun 10. For example, a valve in the powder hose 32 may be closed and cool air or hot air may thus be applied to the coated substrate 36 to effect curing my means of ambient or heated air application. Alternative methods of curing of the coating material include application of infrared light, ultraviolet light or other curative materials or methods depending upon the material which has been deposited on the substrate 36. For example, the powder 34 may be a blend of materials which, when liquified, will mix and form a composite coating. Two guns may be used to simultaneously apply the liquified constituents of an epoxy with the mixing being effected as the materials are applied to the substrate 36.

Thus, at least the material that forms the coating is a plastic material taken from the group of plastics including the following thermoset and thermoplastic materials: acrylics, alkyds, allyl phthlates, epoxies, melamine, melamine/phenolics, phenolics, unsaturated polyesters, vinyl esters, polyimides, silicones, fluorosihcones, ureas, polyurethanes, ABS, ABS alloys, acetal, acrylic copolymers, acrylonitrile copolymers, cellulosics, fluoropolymers, ionomers, liquid crystal polymers, nylons, nylon alloys, polyamide-imide, polyarylate, polybutylene, polyarylsufone, polycarbonate, polycarbonate alloys, polyestercarbonate, thermoplastic polyesters (such as PET, PBT, PCT, PCTA, PCTG, and PETC), ethylene acrylic acid and copolymers, polyaryletherketone, polyetheretherketone, polyetherketone, polyetherimide, polyethersulfone, polyethylenes, ethylene vinyl alcohol, other ethylene copolymers, polymethylpentene, polyphenylene ether/oxide (PPE/PPO) based resins, polyphenylene sulfide, polyphthalamide, polypropylene, polypropylene alloys, polystyrene, styrene-acrylonitrile copolymers, styrene-maleic anhydride copolymers, styrene-butadine copolymers, other styrenic copolymers, polysulfone, polysulfone alloys, polyurethane thermoplastics, polyvinyl chloride and its alloys and blends, and chlorinated polyvinyl chloride. Basically, any polymeric material that can be melted can be applied as a coating using the process of this invention.

One of the factors affecting practice of this technology is associated with the variability of powder composition and size. To illustrate how these variables can be addressed, a review of the procedures used in examples of the practice of the invention is set forth: A commercial 1500 watt hot-air gun 68 (Figure 2), with variable power (rheostat controlled), was mounted in a fixture 70. A 1/8" internal diameter copper tube 71 was mounted onto a ring stand 72. One end 73 of the copper tube was attached to a commercially available powder feed device (not shown) commonly used in the thermal-spray industry. The other end 74 of the tube was placed radially extending from the centerline 75 of the exhaust from the hot-air gun 68. Powder 76 was injected from the copper tube 71 into the hot-air stream perpendicular to the axis 75 of gas exhaust. The original point of injection of powder 76 was several inches from the face of the hot- air gun. The injection points were varied, in a direction along the axis 75 toward and away from the face of the hot-air gun (as depicted in phantom by way of example), until the powder 68 melted upon being entrained. If the powder melted more than 2" from the face of the gun, the power to the gun was reduced. This was done to minimize fixturing. Next it was necessary to find, an optimun angle of injection of the powder. This angle was varied (from the perpendicular 90° to 0°) until all the molten droplets remained co-axial with the hot-air stream (Figure 3). Thus, for a given powder, the power level, axial distance, and angle of injection were determined. A "nozzle" was developed that maintained the geometrical orientation of the powder injection, and it was fabricated and affixed to the gun 68. Finally, fine tuning to account for the effects of the nozzle were performed.

Many variations and permutations of the gun 10, 68 as well as the method are possible. For example, air which is a non-combustible gas is preferable as a carrier and heating medium, but other gases may be utilized, including high heat capacity gases such as hydrocarbons like methane, ethane, propane; halocarbons such as methyl chloride; freons, water vapor and carbon dioxide; inert gases such as nitrogen argon and helium; and reactive gases such as ammonia, silane, and water vapor; basic gases and acidic gases. The temperature of the air discharged from the gun 10 is typically greater than 100°C and in the range, of 100°C to 500°C, although variations in the temperature may be needed and may be effected by variations in the motor speed, fan blade size, power to the coil and the size of the coil and many other factors.

Additionally, the rate of powder 34, 76 feed through the line 32, 71 may be varied. The size and configuration of the nozzle 22 may be varied. The powder feed rate may be steady or variable based on power consumption and other parameters such as described. The length of the passage through the nozzle 22, the size and shape of the inlet 26 and outlet 28 of the nozzle 22 may be varied. The number and arrangement of powder hoses 32 may be varied. That is, hoses 32 may be arranged radially around the inlet 26 of the nozzle 22. The material that is fed into the nozzle 22 may be mixed within the nozzle 22 during the heating operation. That is, more than one powder hose 32 may be provided to provide a mix of powders utilized for coating the substrate. Also, the substrate may be preheated by application of heated, non-combusting gas. In the commercial hot-air gun utilized in experiments, an electrical heating element is powered by an alternating current (ac) power supply, typically 120V ac. A fan forces ambient air through the heating elements to heat the air and then propel the heated air from the nozzle. However, the heating element need not be powered by ac. Direct current power is easily available from batteries, generators, fuel cells or even automotive cigarette lighter sockets. Also, a fan is not necessary since the gas to be heated can be supplied from pressurized systems (i.e. compressed gas cylinders).

Also, when a fan is employed, the shaft for the fan can be made hollow, allowing axial feed of the powder, thereby requiring less energy to be consumed in the process. For example, at Figure 4, a powder port 80 is in line with an axial ring of ceramic material 82. A heating element 84 is wound on ceramic 82 and powder flows through a hollow shaft 86. A gas is flowed through the heating elements by a fan 88, or from a separate gas source 87 (Figure 5). The powder is then melted at point 90 and transported to a substrate. A ceramic 82 is used to provide both electrical isolation and a thermal barrier to prevent the polymer powder from melting until point 90. A nozzle can be added to allow for modified heating of the powder. For example, a two-piece nozzle 92 and 94 would allow modification of nozzle length. Perforations of nozzle piece 92 would allow modification of the time at temperature of the powders.

Experiments were conducted using a series of polymers which were deposited on a variety of substrates as shown in Table 1. Table 1 lists the polymers, the coating conditions, and substrates. TABLE 1 MATERIALS AND COATING PROCESS PARAMETERS

An additional device, depicted in Figure 6, utilizes a Coanda effect nozzle 50. Hot gas is directed through a circumferential passage 52 surrounding the nozzle interior. This gas stream is then fed through a ring nozzle 54 and follows the Coanda profile wall 56 to a nozzle outlet 58. Powdered coating material is drawn through inlet 60, suspended in a cool or heated gas, by the low pressure at the center of the nozzle 50 induced by the Coanda effect. The heated powder and gases then exit the nozzle 50 through outlet 58 directed at the article or substrate to be coated. This design is particularly resistant to powder accumulation on the interior of the nozzle 50 because of the continuous gas flow attached to the inner wall 56 by the Coanda effect even though the relative pressure at the inner wall 56 is less than that at the interior or center of the nozzle 50.

A variation of this device utilizes a modified nozzle 50 by addition of a radiant heating device 62 surrounding the inner wall 56 of the nozzle 50 to melt the powder. Another variation would utilize multiple Coanda effect nozzles connected in series to achieve the desired residence time and heating of powder particles. Moreover, multiple nozzles would allow spraying multiple powders resulting in continuous or discretely graded coatings. Such multiple nozzles could also be used to inject components into the coatings, which are non-reactive with the coating material. Such other components or additives may include pigment, pestitcides, metal flakes, corrosion inhibitors, insecticides, solid lubricant, herbacides, fungicides, biocides, germacides, fluxes and other materials.

Various constructions may be utilized to introduce hot, non-combusting gas. For example, the hot gases can be by-products of a combustion process. Also, the powder injection system may be altered. For example, the apparatus may include a central throughbore or shaft associated with the fan motor as described above. The plastic powder may then be introduced through the hollow shaft to the interior of the nozzle as described above. Additionally, the powder may be entrained in the air prior to heating of the air or gas. Thus coils may surround the gas entrained powder to thereby effect liquification or melting. For example, the heating coil may be positioned around or circumferentially surrounding the nozzle 22. There are many combinations' and permutations of the apparatus which may be utilized to practice the invention and the method may be altered to accommodate each of these apparatus variations. Thus, the invention is to be limited only by the following claims and their equivalents.

Claims

CLAIMSWhat is claimed is:

1. A process for application of powdered, plastic material onto a substrate comprising the steps of: introducing the powdered material into a stream of non-combusting gas; entraining the powdered material in the gas stream, said gas stream and material being heated to liquefy the powdered material; directing the entrained liquified, powdered material onto the substrate by directing the gas stream toward the substrate; coating the substrate with the material; and setting the material on the substrate as a solid phase adhered to the substrate.

2. A process as set forth in Claims 1 , 14 or 15 including the additional step of curing the solid phase material coating on the substrate.

3. A process as set forth in Claims 1, 14 or 15 wherein the gas is a non-combusting gas taken from the group consisting of air, water vapor, carbon monoxide, carbon dioxide, nitrogen, argon, basic gases, acidic gases, hydrocarbons, halocarbons, ammonia silane and mixtures thereof.

4. A process as set forth in Claims 1, 14 or 15 wherein the gas is air.

5. A process as set forth in Claims 1, 14 or 15 wherein the gas is air and the powdered material is a plastic taken from the group consisting of ethylene acrylic acid copolymers, polyethylene terephalate, polyethylene, polyphenylene oxide, polycarbonate, polystyrene, polyphenylene sulfide, polyethylene terephalate copolyester, and acryloid.

6. The process of Claim 2 wherein the step of curing includes the step of applying radiation, heat, acoustical energy, a gas, a liquid or combinations thereof to the solid phase material coating the substrate.

7. A process as set forth in Claim 1 wherein the powdered material is a plastic material taken from the group of thermosets consisting of acrylics, alkyds, allyl phthlates, epoxies, melamine, melamine-phenolics, phenolics, unsaturated polyesters, vinyl esters, polyimides, silicones, fluorosihcones, ureas and polyurethanes; and from the group of thermoplastics consisting of thermosets, acrylonitrile butadine-styrene (ABS), ABS alloys, acetal, acrylic copolymers, acrylonitrile copolymers, cellulosics, fluoropolymers, ionomers, liquid crystal polymers, nylons, nylon alloys, polyamide-imide, polyarylate, polybutylene, polyarylsufone, polycarbonate, polycarbonate alloys, polyestercarbonate, thermoplastic polyesters, ethylene acrylic acid, copolymers polyaryletherketone, polyetheretherketone, polyetherketone, polyetherimide, poly ethers ulfone, polyethylenes, ethylene vinyl alcohol, ethylene copolymers, polymethylpentene, polyphenylene ether/oxide based resins, polyphenylene sulfide, polyphthalamide, polypropylene, polypropylene alloys, polystyrene, styrene-acrylonitrile copolymers, styrene-maleic anhydride copolymers, styrene-butadine copolymers, styrenic copolymers, polysulfone, polysulfone alloys, polyurethane thermoplastics, polyvinyl chloride, polyvinyl chloride alloys, polyvinyl chloride blends, chlorinated polyvinyl chloride, preceramic polymers, and mixtures thereof.

8. The process of Claims 1, 14 or 15 wherein the powdered material is a thermoset plastic material.

9. The process of Claims 1, 14 or 15 wherein the powdered material is a thermoplastic material.

10. The process of Claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 14 or 15 including the additional step of introducing an additive taken from the group consisting of pesticides, insecticides, herbacides, fungicides, biocides, germacides, fluxes, pigments, metal flakes, corrosion inhibitors, solid lubricants, and mixtures thereof.

11. The process of Claims 1, 2, 3, 4, 5, 6, 7, 14 or 15 including the additional step of introducing an additive which is non-reactive with the powdered material.

12. A process as set forth in Claims 1, 14 or 15 wherein the powdered material is liquified by heated gas having a temperature in the range of about 100°C to 500°C.

13. A product made by the process of any of the Claims 1 through 12, 14 or 15.

14. A process for the application of a coating of plastic material on a substrate comprising the steps of: providing a powder of plastic material; providing a nozzle having an inlet, an outlet and a through passage for heated, noncombusting gas and further having a powdered plastic material injection port into the passage; directing non-combusting gas into the inlet; directing powdered plastic material through the injection port; liquifying the powdered material by the heated, non-combusting gas as it is entrained in the non-combusting gas in the nozzle; directing the outlet of the passage toward the substrate whereby the liquified, powder material is transported onto the substrate and thereby coats the substrate; and setting the liquified material on the substrate.

15. A process for the application of a coating of plastic material on a substrate comprising the steps of: providing a powder of plastic material; providing a nozzle having an inlet, an outlet and a through passage for non-combusting gas and further having a powdered plastic material injection port into the passage; directing non-combusting gas into the through passage from the inlet; directing powdered plastic material into the through passage through the injection port; liquifying the powdered material by heating as it is entrained in the non-combusting gas in the nozzle; directing the outlet of the passage toward the substrate whereby the liquified powdered material is transported onto the substrate and coats the substrate; and setting the liquified material on the substrate.

16. The process of Claim 1 or 15 wherein the powdered plastic material is heated by radiation, conduction, convection or combinations thereof

17. An assembly for applying a plastic coating onto a substrate comprising, in combination: a powdered plastic material -source; a discharge nozzle having a through passage with an inlet and an outlet and an injection port into the nozzle; a non-combusting gas source for injecting gas into the passage through the inlet for discharge through the outlet; metering means for directing a metered amount of powdered plastic into said passage as said gas flows therethrough, and means for heating the gas and material that flows in the nozzle from the outlet to liquify the material for an application onto a substrate.

18. The apparatus of Claim 17 wherein the nozzle is configured to provide a coanda effect around the internal circumferential wall of the nozzle thereby maintaining a relatively lower pressure region adjacent said wall and a higher pressure region within the nozzle for entraining powder material.

19. The apparatus of Claim 17 wherein the metering means comprises a low-pressure region in the nozzle at the center thereof between side walls and wherein a gas source comprises gas fed into the nozzle around the periphery of the walls.

20. The process of any of the Claims 1 through 12 and 14 through 16, including the further step of charging the liquified plastic material and grounding the substrate to enhance the application process.

21. A process for application of powdered, plastic material onto a substrate comprising the steps of: introducing the powdered material into a stream of non-comubsting gas; entraining the powdered material in the gas stream, said gas stream and material being heated to liquefy the powdered material; directing the entrained liquefied, powdered material onto the substrate by directing the gas stream toward the substrate; coating the substrate with the material; and setting the material on the substrate as a solid phase; wherein the powdered material is a cross-linkable polymeric system having a melting point of less than about 150°C in its uncured state and including a polyester polymer, an epoxy polymer, a polyurethane polymer, an acrylic polymer or mixtures thereof; and wherein further said step of setting the material includes crosslinking the polymeric system substantially contemporaneously with said step of coating the substrate.

22. A method of providing a cured coating to a substrate comprising the steps of:

(a) entraining a curable powder composition into a hot gaseous stream at a temperature sufficient to melt said powder composition to form a liquefied material;

(b) applying said stream to said substrate to form a liquefied curable coating thereon; and

(c) curing said liquefied curable coating on the surface of said substrate.

23. The method according to claim 22, wherein the temperature of said hot gaseous stream is operable to induce cross-linking of said composition substantially immediately upon application to said substrate.

24. The method according to claim 22, wherein said curable powder composition is a radiation-curable powder composition.

25. The method according to claim 24, wherein said step of curing said liquefied curable coating comprises exposing said coating to a radiation beam operable to effect at least a partial cure of said coating substantially simultaneously with said step of applying said coating to said substrate.

26. The method according to claim 22, wherein said substrate is an architectural structure.

27. A method ofproviding a cured coating to a substrate comprising:

(a) entraining a curable powder composition into a hot gaseous stream, said powder composition comprising at least one base resin, the temperature of said hot gaseous stream being at least twice that of the melting temperature of said powder composition such that the hot gaseous stream is operable to melt the powder composition;

(b) applying said stream to said substrate to form a liquefied curable coating thereon; and (c) curing said liquefied curable coating.

28. The method according to claim 27, wherein said base resin comprises an acrylic resin.

29. The method according to claim 22, wherein said substrate is a polymer substrate.

30. The method according to claim 28, wherein said substrate is a thermoplastic substrate.

31. The method according to claim 28, wherein said substrate is an elastomer substrate.