AU2006205090A1 - Powder thermal spray compositions - Google Patents

Description

WO 2006/076341 PCT/US2006/000787 POWDER THERMAL SPRAY COMPOSITIONS CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to United States Provisional Application Serial No. 60/642,831 filed January 10, 2005, which is herein incorporated by reference. FIELD OF THE INVENTION The present invention is directed to thermal spray compositions, and particularly to powder thermal spray compositions that can be applied to clean uncoated surfaces. BACKGROUND TO THE INVENTION Thermal spray compositions come in powder form and can be applied to a surface by thermal spraying. The term "thermal spraying" refers to process in which a coating material feedstock, thermal spray composition, is heated and propelled as individual droplets or particles onto the surface of a substrate. The coating material is heated by the applicator (e.g., a thermal spray gun) by using combustible gas, plasma flame or electric hot air to heat and melt the plastic particles into droplets, which are propelled out of the spray gun by compressed gas. When the coating material particles strike the substrate they flatten, flow and melt into adjacent particles to form a continuous film. It is this film that coats the surface It is well appreciated in the art that different types of thermal spray compositions are available on the market today which can be used to coat various surfaces such as metal, paper, wood, plastic, concrete and the like. However, these compositions often require that the surface to be coated be primed with special primers and/or coated with a 1 WO 2006/076341 PCT/US2006/000787 bonding material prior to thermal spraying the surface. These primers/coatings are most often in liquid form and are applied by simple spreading of the material onto a substrate to be coated. This additional step not only results in increased cost, but also often prevents the surface to be coated from being thermally sprayed "on-site". In other words, instead of the surface to be coated being thermally sprayed in a single step, as in the present invention, multiple steps are required. This increases labor costs as well as material cost. In some instances, the surface/object to be coated must be brought back to a workshop to be pre-coated with a primer and/or bonding coat since the effectiveness of the thermal spray is directly related to how well the primer and/or bonding coat is applied. In addition, many of the primers and/or bonding coating materials available on the market are either in liquid or emulsion form. These liquid compositions contain solvents that slowly evaporate from the coating once it is applied. If a coated surface is thermally sprayed before the primer and/or bond coat fully cures, which is often the case, the solvent will evaporate and eventually cause mini-pores in the coating. These mini-pores, often described as pitting, compromise the integrity of the thermal coating. In addition, using these liquid primers/bond coating materials often result in the production of High Volatile Organic Compounds (HVOC) and may require increased ventilation. Powder thermal sprays that do not require liquid primers, on the other hand, contain no solvent to evaporate and therefore do not emit HVOCs and/or result in pitting of the surface. Therefore, in view of the foregoing, what is needed in the market place today is a powder thermal spray composition that can be applied to a surface in a single spraying. In other words, a powder thermal spray composition that can be effectively sprayed on a 2 WO 2006/076341 PCT/US2006/000787 surface without first having to prime and/or apply bond coating to the surface. Such a thermal spray composition must also have all of the aforementioned attributes so that it can be applied on-site and does not need to be brought back to a workshop to apply a special primer and/or bonding coat. One object of the present invention is to provide a powder thermal spray composition that can be applied to a surface in a single spraying. In other words, a powder thermal spray that can be applied to a clean, non-coated surface. Another object of the invention is to provide a powder thermal spray phosphorescent composition that can be applied to a surface in a single spraying and causes the surface to glows in the dark. Still another object of the invention is to provide a powder thermal spray anti microbial composition that can be applied to a surface in a single spraying and retards microbial growth on any surface it is applied. Still yet another object of the invention is to provide a zinc plastic composition that can be applied to steel surfaces so as to prevent corrosion and prepare the steel to more readily accept additional coatings. The zinc plastic thermal spray compositions can be applied on site quickly and relatively easily. The present invention has the aforementioned characteristics as well as others and overcomes the shortcomings of the prior art discussed above. The present invention is further described in the sections below. 3 WO 2006/076341 PCT/US2006/000787 SUMMARY OF THE INVENTION The present invention relates to a powder thermal spray composition comprising at least one thermoset material and at least one thermoplastic material. The powder thermal spray composition can be applied to a clean, non-coated surface in a single application. The present invention also relates to a powder thermal spray composition comprising at least one phosphorescent composition that can be applied to a clean, non coated surface so that it glows in the dark. The present invention also relates to a thermal spray of the present invention further comprising anti-microbial additives so as to prevent anti-microbial growth on the surface to which it is applied. Finally, the present invention relates to a powder thermal spray zinc plastic composition that can be used to coat steel surfaces so as to prevent corrosion and prepare the steel surface for subsequent coating materials. As stated above, one clear advantage of the powder thermal sprays of the present invention over thermal sprays available on the market is that the thermal spray compositions of the present invention can be applied directly to clean, non-coated surfaces and therefore reduces labor and materials costs. In addition, no HVOC are produced since the composition is in powder form. The embodiments of the present invention are further described in the Detailed Description section of this application that directly follows. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder thermoset/thermoplastic composition having improved properties such as greater impact resistance, exceptionally high 4 WO 2006/076341 PCT/US2006/000787 adhesion properties, extensive flexibility, increased thickness application without cracking, the ability to cure at room temperature, no ultra violet degradation, no water penetration, no loss in salt spray resistance, and the ability to provide an architectural finish without using a primer. One embodiment of the present invention is directed to a powder thermal spray composition comprising at least one thermoset material and at least one thermoplastic material. The thermoset material can be present in amounts up to 50 weight percent and the thermoplastic material can be present in amounts up to 90 weight percent. Unexpectedly, the resulting powder thermal spray composition possesses better physical properties than when the thermoset and/or thermoplastic are applied individually. The thermoset material of the powder thermal spray of the present invention can be selected from the group consisting essentially of Triglycidyl isocyanurate (TGIC) Polyester, Epoxies, Urethane polyesters, polyester alloys and mixtures thereof. The thermoplastic material of the powder thermal spray of the present invention can be selected from the group consisting of co-polyamide materials containing various percentages of Nylon 6, Nylon 66 and Nylon 12, amines and amides. The thermoplastic most preferably used is Platamid@ H2513TA copolyamide (available from Arkema, Inc. Philadelphia, PA) and the polyether amide most preferably used is Pebax @ MX 1205 BLACK ES (available from Arkema, Inc. Philadelphia, PA). In one embodiment of the present invention, the powder thermal spray composition comprises up to about 90 weight percent TGIC polyester and up to about 50 weight percent co-polyamide, preferably Platamid@ H2513TA copolyamide, wherein the 5 WO 2006/076341 PCT/US2006/000787 average diameter size is less than about 200 microns, preferably less than about 100 microns. As stated above, the thermoplastic composition of the present invention may be a copolyamide of at least two polymers selected from the group consisting essentially of Nylon 6, Nylon 66, Nylon 12, amines and amides. In the alternative, a single polyamide having the same or similar properties of the aforementioned listed compounds may also be used. Different weight percentages and various combinations of these polyamides compounds can be used to customize a particular thermal spray and these variations are considered to be part of the invention. The thermal spray composition comprising modified polyamides and thermoset resins of the present invention is a multiphase thermal spray and bonds readably to most surfaces. In other words, the thermal spray compositions bond readably to aluminum, fiberglass, masonry, plastic, and wood by griping deep into surface imperfections as the thermal spray flows and wets the surface to form a smooth and continuous film. This thermal spray composition is useful as a one step coating that can be applied directly to the substrate for both interior and long term exterior exposure. As mentioned above, no primer or bond coating is necessary. However, when using the thermal spray of the present invention to coat steel surfaces exposed to the exterior environment for long periods of time, the steel should be coated prior to applying the thermal spray of the present invention in order to prolong the life span of the thermal coat. Preferably, the zinc plastic composition of the present invention, further described below, should be used to coat the steel prior to applying the thermal spray of the invention. Although this adds 6 WO 2006/076341 PCT/US2006/000787 additional cost when coating steel, the effectiveness of the primer to prevent corrosion of the steel more than makes up for the additional expense. Since all of the powder thermal sprays of the present invention grip deep into the imperfections of the surface to which it is applied, increasing the imperfections of the surface to which it is applied enhances the adhesion of the thermal spray coating. One way to increase these imperfections of a surface is to first degrease the surface followed by grit blasting. Degreasing makes the imperfections already on the surface more available for bonding by removing greasy deposits from these imperfections as well as eliminating any adverse chemicals that might interfere with the chemical bonding of the thermal spray of the invention. The grit blasting, on the other hand, increases the imperfections of the surface to be treated allowing the thermal spray to adhere deep into the imperfections of the surface. Grit blasting at 0.3 Mpa (40 psi) using fine steel and/or alumina grit (0.2 to 0.5 mm) is recommended. In the alternative any other sort of surface roughing can be used. Another embodiment of the present invention is directed to epoxy base powder thermal spray compositions. The embodiments of the present invention that contain epoxy or an epoxy base compounds as the thermoset material of the thermal spray may also bond to surfaces such as aluminum, fiberglass, masonry, plastic, paper and wood by griping deep into surface imperfections of the surface as the thermal spray flows and wets the surface to form a smooth and continuous film. This thermal spray coating has a very high resistance to moisture and is designed for immersion applications. The chemistry of this composition allows for chemical bonding with thermally sprayed top coatings 7 WO 2006/076341 PCT/US2006/000787 available from most if not all of the major thermoplastic and thermoset plastic groups available on the market today. The epoxy based thermal spray compositions of the present invention are designed to replace fuse bond epoxies, two component liquid epoxies, liquid urethanes as well as other liquid primers currently used to treat surfaces for subsequent application of a functional coating. In other words, the epoxy based compositions of the present invention can be used to coat clean, non-coated surfaces (surfaces without primer) in which it will be used as the main coating or, in the alternative, can be used as a base coat for subsequent applications of functional top coatings that would normally not adhere to the surface without a primer. As with the other embodiments of the present invention described above, degreasing the surface and grit blasting the surface to increase the available imperfections in the surface enhances the adhesion of the thermal spray. In addition, the surface can be heated to about 1 00F to about 200F and the temperature of the substrate held at the preheated temperature while indexing so as to effectively cause plastic stream melting (i.e. wetting the surface) on impact. If the object to be coated is small enough the complete object can be heated prior and during coating. If a large surface is being coated, only the portion of the surface being coated at any given time needs to heated. Electric, hot air or flame sources can be used to pre-heat and maintain the temperature of the surface to be coated. In another embodiment of the invention, the thermal spray further comprises at least one type of phosphorescent particle. In other words, at least one type of phosphorescent particle can be added to the base thermal spray composition containing at 8 WO 2006/076341 PCT/US2006/000787 least one thermoset material and at least one thermoplastic material. The phosphorescent green pigment containing thermal spray composition can be used to make products and/or surfaces "glow in the dark." As with the thermal sprays described above, it bonds readably to most surfaces and can be used for both indoor and outdoor applications. No primer liquid or bond coating is required. For thin coatings less than 0.010 inches, a white coating can be used first to enhance the "glow in the dark" properties of the spray. Degreasing, preheating and grit blasting the surface enhances the adhesion of the thermal spray to the imperfections in the surface and/or product to which it is applied. Depending on the thickness, once activated with light, the glow in the dark properties can last up to about 12 hours. The phosphorescent thermal spray of the invention combines the properties of the basic thermal spray compositions of the invention with the "glow in the dark" properties associated with phosphorescent compounds. Although many different applications are conceivable for the phosphorescent thermal spray of the present invention, coating stairways and other passages ways with the thermal spray is of particular interest. Coating areas like these with the phosphorescent thermal spray not only protects the surfaces from wear and provides additional traction but also adds the safety feature of illuminating the stairway and/or passage way in case of a power failure. In other words, in an emergency situation where the stairways of an office building must be used to evacuate the building and power to the building has been lost, the luminescence of the coated stairs will allow the evacuating population to exit the building safely. The present invention also relates to zinc containing plastic thermal spray compositions that can be used to pre-treat hard to coat surfaces such as steel before being 9 WO 2006/076341 PCT/US2006/000787 coated. As mentioned above, the thermal sprays of the present invention normally do not require coating of the surface with a primer and/or a bond coating except when the thermal spray is being applied to steel, especially if the steel will be exposed to exterior conditions for long periods of time. Under these circumstances, it is recommended that the exterior steel surface be coated with the zinc plastic thermal spray composition of the present invention prior to applying additional coatings to the steel surface. The zinc plastic thermal spray composition of the present invention comprises about 20 weight percent to about 50 weight percent zinc epoxy powder, about 30 weight percent to about 50 weight percent zinc powder having an average particle diameter of about 1 micron to about 60 microns, and about 10 weight percent to about 30 weight percent polyether amide. The plastic used in the thermal sprays may be an epoxy based thermal spray. The epoxies used can be the same as the epoxies listed above for the other thennal sprays of the invention. In addition to epoxies, polyether amides are also applicable here. In a preferred embodiment of the invention, the thermal spray zinc plastic composition comprises about 20 weight percent to about 50 weight percent zinc epoxy powder, about 30 weight percent to about 50 weight percent zinc powder having an average particle diameter of about 1 micron to about 60 microns, and the co-polyamide used is about 10 weight percent to about 30 weight percent Pebax @. It is understood that additional additives such as UV filters, preservatives, pigmentation, anti-microbial compounds and the like can also be added to the thermal spray compositions and are considered to be part of the claimed invention. In particular, Agion@ (available from Agion, Inc. Rhode Island), silver ion powder, tricylostranes 10 WO 2006/076341 PCT/US2006/000787 and/or Microbane@ (available from Microbane, Inc. located in North Carolina) can be added to the thermal spray compositions of the present invention to bestow anti-microbial attributes on a substrate once the composition is thermally applied to a substrate. Various types of thermal spray guns can be used to apply the thermal sprays of the present invention. Thermal spray guns typically use mixtures of oxygen-fuel gas, air fuel gas, air-liquid fuel, oxygen-liquid fuel, and plasma and/or electric hot air as a heat medium to melt and propel the individual droplets to a prepared substrate. Thermal spray devices fall within general classification of equipment: (1) wire combustion, (2) powder combustion, (3) plasma-powder, (4) high velocity oxygen-fuel gas-powder, (5) high velocity oxygen-fuel gas-wire, (6) high velocity air-liquid fuel-powder, (7) high velocity oxygen-liquid fuel-powder, (8) detonation gun powder, and (9) water cannon plasma. In general, thermal spray devices use wire combustion, powder combustion, plasma combustion or electric arc combustion. In the wire combustion process a combustion heat source is initiated and feed stock material in wire or rod form is driven into the heat medium where a compressed air stream concentrates the heat source about the axially fed feed stock whereby it is melted atomized and propelled to the substrate for deposition of the coating. In the powder combustion process a combustion heat source is initiated and feed stock material in powder form is introduced axially or tangentially to the propagated flame. The feedstock powder material is delivered by means of a powder feeder or gun mounted hopper. In the plasma powder system a heat source is generate by passing an inert gas between the gap formed by an electrode and nozzle which are at an electrical potential. 11 WO 2006/076341 PCT/US2006/000787 A high voltage, high frequency, low amperage are is struck which bridges the gap between the electrode and nozzle. This small amperage are partially ionizes the inert gas and generates a conductive path for the low voltage, high amperage potential to complete a circuit. The inert gas is thereby totally disassociated expands and exits the nozzle bore at high velocity. During the recombination of the disassociated gas heat is generated which is used to melt the feedstock material powder injected into the plasma flame tangentially. The velocity of the flame propels the feedstock material powder onto a substrate. Although any of the above thermal spray processes can technically be used to apply the thermal compositions of the present invention, a powder combustion thermal spray process is preferred. In particular, a powder combustion thermal spray process using the thermal spray system described in co-pending United States Patent Application No.10/909,115 that is incorporated herein in its entirety by reference is most preferred. The thermal spray compositions of the present invention can be produced using standard blending techniques including cladding. Cladding, a well-known process, involves agglomerating two or more powder materials together using a binder so that they do not separate during spraying. As mentioned above, the powder thermal sprays of the present invention provide unexpected favourable physical properties when applied to clean uncoated substrates. For example, Table 1 below lists the physical properties of XT600 which is a powder thermal spray composition of the present invention comprising about 66 weight percent TGIC polyester and about 34 weigh percent Platamid@ 2513TA co-polyamide available from Arkema, Inc. Philadelphia, PA. The thermal spray composition was tested by a 12 WO 2006/076341 PCT/US2006/000787 commercial laboratory using standard testing and measuring procedures from the American Society of Testing and Materials (ASTM). The standard testing and measuring procedure used for each category is listed in column number 2 of Table 1 by ASTM number. These procedures can be identified and obtained from the American Society of Testing and Materials using the numbers listed in Table 1 and are herein incorporated by reference. The results obtained from the tensile adhesion tape test, the impact resistance test, the Taber abrasion resistance test, the pencil hardness and flexibility mandrel test either meet or exceed commercially acceptable values for thermal sprays applied to surfaces that were either primed and/or bond coated. The fact that the XT600 values were obtained without first coating the surface (tensile adhesion tape test done with and without primer on steel) is an added benefit and is an inventive aspect of the present invention. Table 1 is set forth below. 13 WO 2006/076341 PCT/US2006/000787 TABLE 1 PHYSICAL PROPERTIES TEST METHOD USED RESULTS TESTED Tensile Adhesion Tape Test ASTM D3359 4A on scale of OA to 5A for direct spraying of XT600 to steel, and atop XT725 (Zn bond coat). Impact Resistance ASTM D2794 30 inch pounds, no cracking observed. Taber abrasion Resistance ASTM D4060 50 mg loss, 1000 cycles, 1000g load. Pencil Hardness ASTM D3363 3H on a scale of HB to HHHH. Flexibility Mandrel ASTM D522 Coating thickness 0.012 inches exceeded upper limit for flexibility for this test, elongation is greater than 5.3 %. While the above description contains many specifics, these specifies should not be construed as limitations of the invention, but merely as exemplifications of preferred embodiments thereof. Those skilled in the art will envision many other embodiments within the scope and spirit of the invention as defined by the claims appended hereto. 14

Claims (22)

1. A powder thermal spray composition comprising: up to about 90 weight percent of at least one thermoset material and up to about 50 weight percent of at least one thermoplastic material.

2. The thermal spray composition according to Claim I wherein the thermoset material is selected from a group consisting essentially of triglycidyl isocyanurate (TGIC) polyesters, epoxies, urethane polyesters, polyester alloys, and mixtures thereof.

3. The thermal spray composition according to Claim 2 wherein the thermoplastic material is a co-polyamide.

4. The thermal spray composition according to Claim 3 wherein the co-polyamide composition comprises at least two polymers selected from the group consisting essentially of Nylon 6, Nylon 66, Nylon 12, amines and amides.

5. The thermal spray composition according to Claim 2 comprising up to about 90 weight percent TGIC and up to about 50 weight percent co-polyamide.

6. The thermal spray composition according to Claim 5 wherein the average particle diameter is less than about 200 microns. 15 WO 2006/076341 PCT/US2006/000787

7. The thermal spray composition according to Claim 6 wherein the average particle diameter is less than about 100 microns.

8. A phosphorescent composition comprising at least one type of phosphorescent material; at least one thermoplastic material; and at least one thermoset material.

9. The phosphorescent composition according to Claim 8 wherein the at least one thermoplastic material is a co-polyamide.

10. The phosphorescent composition according to Claim 9 wherein the co-polyamide composition comprises at least two compounds selected from the group consisting essentially of Nylon 6, Nylon 66, Nylon 12, amines and amides.

11. The phosphorescent composition according to Claim 8 wherein the co-polyamide is a polyether amide.

12. The phosphorescent composition according to Claim 8 wherein the thermoset is selected from a group consisting essentially of triglycidyl isocyanurate (TGIC) polyester, epoxy, urethane polyester, and a polyester alloy. 16 WO 2006/076341 PCT/US2006/000787

13. The phosphorescent composition according to Claim 12 comprising up to about 90 weight percent of phosphorescent material, up to about 70 weight percent TGIC polyester and up to about 30 weight percent co-polyamide.

14. The phosphorescent composition according to Claim 13 wherein said phosphorescent composition comprises up to about 50 weight percent of phosphorescent material having an average particle diameter less than about 55 microns.

15. The thermal spray composition according to Claim 2 wherein said thermal spray composition comprises up to about 65 weight percent epoxy and up to about 50 weight percent polyether amide.

16. The thermal spray composition according to Claim 2 wherein said thermal spray composition comprises about 10 weight percent to about 70 weight percent poly ether amide.

17. The thermal spray composition according to Claim 15 wherein the average diameter is less than about 200 microns.

18. The thermal spray composition according to Claim 17 wherein the average diameter is less than about 100 microns. 17 WO 2006/076341 PCT/US2006/000787

19. A thermal spray zinc primer composition comprising: about 20 weight percent to about 50 weight percent zinc epoxy powder; about 30 weight percent to about 50 weight percent zinc powder having an average particle diameter of about 1 micron to about 60 microns, and about 10 weight percent to about 30 weight percent co-polyamide.

20. A thermal spray zinc primer composition comprising: about 20 weight percent to about 50 weight percent zinc epoxy powder; about 30 weight percent to about 50 weight percent zinc powder having an average particle diameter of about 1 micron to about 60 microns, and about 10 weight percent to about 30 weight percent polyether amide.

21. A thermal spray composition according to Claim 1 further comprising at least one anti-microbial additive.

22. The thermal spray composition according to Claim 21 wherein the anti-microbial comprises silver ion powder, tricyclostranes, and mixtures thereof. 18