MXPA06009062A - Novel powder coloring system - Google Patents

Abstract

In one aspect, a method for coloring powders is provided. The method includes mixing a base powder and a stable colorant dispersion. In another aspect, a colored powder composition having a core particle and at least a partial shell about the core particle is provided.

Description

NEW POWDER COLORING SYSTEM FIELD OF THE INVENTION This invention relates to powder compositions and methods for their manufacture and use. BACKGROUND OF THE INVENTION Powder coatings are an alternative to traditional liquid-based coatings and paints. Liquid-based systems are clearly easy to inking and coloring to produce a desired color. However, this has not been generally true for dust-based systems, due to the manufacturing process as well as the powder application process. Powder coatings are generally manufactured in a multi-step process. Various ingredients, which may include resins, curing agents, pigments, additives, and fillers, are mixed dry to form a premix. This premix is then fed to an extruder, which uses a combination of heat, pressure and shear to melt and mix the ingredients perfectly. As the ingredients are mixed together in molten form during the extrusion process, various pigment colors can be mixed together to produce a uniform color. The extrudate is cooled and then crushed into a powder. Depending on the end use of the desired coating, the grinding conditions are typically adjusted to achieve a mean particle size of the powder of about 25 to 150 microns. The final powder can then be applied to an article by various means, including the use of fluidized beds and spray or spray applicators. More commonly, an electrostatic spraying process is used, wherein the particles are electrostatically charged and sprayed onto an article that has been grounded so that the dust particles are attracted to and hung onto the article. After the coating, the article is heated. This heating step causes the powder particles to melt and flow together to coat the article. Optionally, continuous or additional heating can be used to cure the coating. Other alternatives such as UV cure of the coating have been discovered and can be used. One feature and limitation of powder coatings that is different from liquid paints is that when powder coatings of two different colors are mixed together, the resulting finish typically has a mottled appearance instead of being uniform in color. For example, if a white powder coating is mixed with or contaminated with a black powder coating and then applied, the final coating will have a black and white mottled appearance, instead of having a uniform gray finish. This characteristic of powder coatings has important implications in the economics of powder coating manufacturing, since each powder composition must be separated from other powder compositions. However, it is difficult to change quickly and inexpensively from one color of powder coating composition to another. The change of the compositions requires complete separation of the product from one colored batch to the next at all stages of manufacture. In the extruder, this typically requires a complete purge of the equipment, and then feeding the next composition until it is stabilized. This takes time and results in waste products. In the shredder, the complete shredding system must be cleaned. This typically requires major disassembly and cleaning of all the crushing equipment and associated ducts, and then reassembly, which is a commitment of intense time and labor. Failure to completely clean the equipment will result in the second powder color composition having flecks or spots of the first composition in it. The cleaning process to change the production from one color to another, it is particularly burdensome in the production of small batches of special colors. For small batches, it is common for the cleaning process to take more time and labor than was required to extrude and crush the batch. A related problem occurs when a customer requests a custom colored powder coating. If the initially produced color does not conform to the required color, then it must be fed back into the extruder with pigment or additional material. This requires that the entire process, including cleaning, be repeated. Alternatively, the batch can be discarded and a run of a completely new batch can be obtained to obtain the appropriate color match. For all these reasons, it is difficult, time consuming, and it is expensive to produce small amounts of any particular powder coating color. It is highly preferred to produce large quantities of the same color, with minimal changes. However, due to the full advantages of powder coatings, there is an increasing acceptance of powder coatings. This in turn has led to an increased demand for a wider variety of colors for a growing suite of applications. BRIEF DESCRIPTION OF THE INVENTION In one aspect, the invention allows the rapid and inexpensive creation of an almost endless variety of powder coating compositions. This is achieved by making it possible to mix the color and other desired additives in a powder. An additional benefit is that this allows different steps of the process to be carried out more efficiently and effectively. Another benefit is that the number of intermediate materials can be reduced to a minimum while maximizing the set of available finished products. This provides an efficient manufacturing process that minimizes the costs associated with inventory and cleaning. In yet another aspect, a method is provided that includes the provision of at least one base powder, providing at least one stable coloring dispersion, and mixing the base powder (s) and the dye dispersion (s) to form a colored mixture. In a preferred embodiment, the treatment of the mixture produces a free flowing colored powder. Yet another aspect of the invention is a method that includes the provision of at least one base powder, and the provision of at least one color dispersion, wherein each dispersion includes: at least one of a pigment and a dye, a carrier, and a auxiliary dispersion; or a coloring solution, which includes a colorant and a carrier; and mixing the base powder (s) and the coloring dispersion (s) to form a colored mixture. Yet another aspect of the invention is a method that includes the provision of at least one powder, which provides at least one stable dye dispersion, wherein the dye dispersion includes at least one of a dye and a dye in a carrier, and mixing the dye base and the coloring dispersion to form a colored mixture, wherein the mixture includes a film-forming polymer. Yet another aspect of the invention is a powder coating method that includes the provision of at least one base powder, the provision of at least one stable coloring dispersion, the mixing of the base powder (s) and the stable coloring dispersion (s). , to form a colored powder, treating the mixture to form a free-flowing colored powder, applying the colored powder to a substrate, and heating the colored powder to form a powder coating on the substrate. Yet another aspect of the invention is a composition that includes a core particle, and at least one shell or partial shell around the core particle, wherein the shell includes a dye or a pigment particle and a dispersion aid. The details of one or more embodiments and aspects of the invention are described below. Other characteristics, objects and advantages of the invention will be apparent from the description and the claims. DETAILED DESCRIPTION OF THE INVENTION In one aspect, a method is provided that includes the provision of at least one base powder, the provision of at least one stable dye dispersion, and the mixing of the base powder and the dye dispersion (s). to form a colored mixture. In a preferred embodiment, the treatment of the mixture produces a free flowing colored powder. Suitable base powders for use generally include at least one polymeric binder. These may also optionally include one or more colorants, and optionally include one or more other additives. These ingredients are combined and mixed before being fed into an extruder. Suitable polymeric binders generally include a film-forming resin and optionally a curing agent for the resin. The binder can be selected from any resin or resin combination that provides the desired film properties. Suitable examples of polymeric binders include thermosetting and / or thermoplastic materials, and may be made with epoxy, polyester, polyurethane, polyamide, acrylic, polyvinyl chloride, nylon, fluoropolymer, silicone, other resins, or combinations thereof. Examples of preferred binders include the following: polyester resins with carboxyl functional group, cured with epoxide functional group compounds such as triglycidyl isocyanurate (TGIC), polyester resins with carboxyl functional group cured with polymeric epoxy resins, polyester resins with carboxyl functional group cured with hydroxyalkyl amides, polyester resins with hydroxyl functional group cured with block isocyanates or uretdiones, epoxy resins cured with amines such as dicyandiamide, epoxy resins cured with phenolic functional group resins, epoxy resins cured with healers with carboxyl functional group , acrylic resins with carboxyl functional group cured with epoxy polymeric resins, acrylic resins with hydroxyl functional group cured with block isocyanates or uretdiones, unsaturated resins that are cured through reactions with free radicals, and silicone resins utili either as the binder alone or in combination with organic resins. The optional curing reaction can be thermally induced, or by exposure to radiation (for example UV, UV-Vis, visible light, IR, near IR and E beam). The final base powder can be clear or colored, translucent or opaque. The light base powders do not have added dyes, and are useful for dark colors and for metallic or pearl finishes. Dyes and pigments can be used as colorants. The colored base powders contain a sufficient amount of pigments or dyes to induce a certain degree of opacity, and are useful for colors in which a substantial portion of the required pigmentation is already included in the base powder. While a wide variety of dry pigments can be used for the pigmented base powder, the most common and widely used is white titanium dioxide. The base powder may optionally include other additives. These other additives can improve the application of the powder coating, the melting and / or curing of that coating, or the operation or appearance of the final coating. Examples of optional additives that may be useful in the base powder include: curing catalysts, antioxidants, color stabilizers, slip and wear additives, UV absorbers, hindered amine light stabilizers, photoinitiators, conductivity additives. , tribocarga additives, anticorrosion additives, fillers, inert pigments, texture agents, degassing additives, flow control agents, thixotropes, and edge coverage additives. The polymeric binder is dry blended together with any optional additives, and then it is typically fed through an extruder. The resulting extrudate is then ground to form a powder. Other methods can also be used. For example, an alternative method uses a binder that is soluble in liquid carbon dioxide. In that method, the dry ingredients are mixed into the liquid carbon dioxide and then sprayed to form the base powder particles. The resulting powder is at a size that can be effectively used by the application process. Practically, particles smaller than 10 micrometers in size are very difficult to apply effectively using conventional electrostatic spraying methods. For smooth finishes, particles up to 150 micrometers in size, with an average particle size of 45 micrometers, are preferred. For texturized finishes, particles up to 300 micrometers in size are preferred, with an average particle size of 60 micrometers. Suitable base powders can be processed, or alternatively can be obtained from various suppliers including Valspar, Akzo Nobel, Rohm &; Haas, Sherwin Williams and H.B. Fuller. Dye dispersions include pigment dispersions, dye solutions and combinations thereof. Suitable dye dispersions include a solid dye, a dye solution, a dye solution with a dispersion aid, pigments in a dispersion aid in solid form, a pigment and a dispersion aid in a carrier, and a pigment and a dye, and a dispersion aid in a carrier. In dry form, most pigments are highly agglomerated, consisting of clumps of primary particles that are bound together by physical forces. In order to create a stable pigment dispersion, the dry pigment is typically combined with a dispersion aid and a carrier. Mechanical energy is then applied to the mixture in order to overcome the forces that agglomerate the pigment agglomerates with each other. The resulting stable pigment dispersion would then consist of individual pigment particles that are encapsulated within the dispersion aid, suspended in the carrier medium. These pigment particles are ideally reduced in this way to their primary particle size, as opposed to the highly agglomerated state of the crude dry pigment. Various organic or inorganic pigments can be used. Suitable pigments include titanium dioxide, carbon black, red iron oxide, yellow iron oxide, natural sienna, phthalocyanine blue, phthalocyanine green, naphthol red, toluidine red, various organic yellows, carbazole violet and quinacridones . Essentially, any colored pigment having utility for use in powders in dry form, could also be considered for use in a coloring dispersion. A representative list of pigments used in commercially available dye dispersions can be found in the product literature describing the Covon101 Dyes sold by Degussa. The average pigment particle size is suitably from about 0.01 to 4.0 microns, and preferably from about 0.04 to 1.0 microns. Organic pigments typically have an average particle size of less than 0.3 microns. The titanium dioxide pigments generally have an average particle size of 0.3 to 0.5 micrometers. The iron oxide pigments typically have an average particle size of 0.2 to 0.6 microns. The carbon black has an average particle size of about 0.07 microns, while the phthalocyanine blue typically has an average particle size of about 0.05 microns. Alternatively, the dye dispersion may include a dye in a carrier instead of a pigment dispersion. A dye is a colored matter that is soluble in carrier liquid, and therefore dissolved in the carrier. Suitable colorants can be purchased from various suppliers including Sandoz and Ciba Specialty Chemicals. In addition, the colorant dispersion may include some combination of pigments, colorants and dispersion aids.

Suitable carriers for use in the present invention include, for example, water, organic solvents or combinations thereof. In preferred embodiments, the carrier is selected to prevent or minimize undesirable melting or softening of the base powder components. Some examples of suitable carriers include water, aliphatic solvents such as mineral spirits, VM &P, hexane, heptane and octane naphtha. The preferred carrier liquid includes water, and water is most preferred. An aqueous carrier is preferred for ease of handling, reduced flammability and exposure problems for workers, and reduced impact on the environment. Suitable pigment dispersions preferably include a dispersion aid. This dispersion aid can be selected from any material that maintains the stability of the dispersion for a long time. Suitable dispersion aids include one or more resins, polymers, monomers, oligomers or surfers. The dispersion aid is typically a surfactant or soluble polymer in the carrier, which maintains the stability of the dispersion. Some useful dispersion aids include sodium lauryl sulfate, acrylic amines, acrylic carboxylates, acrylic polymers, alkylphenol ethoxylates, and alkylphenol propoxylates. The coloring solutions may also include a dispersion aid. The dye used in the stable dye dispersion can be selected from pigments, dyes or combinations thereof. The coloring dispersion can also have any hue or color. This can be clear, transparent, translucent or opaque. The dispersion can be a liquid, suspension, gel, paste or solid, although liquids are generally preferred for ease of measurement or handling. The colorant dispersion can be made before mixing with the base powder, or can be purchased from a variety of commercial suppliers. The pigments in pre-dispersed solid form are available from Sun Chemical under the tradename of Surpass Specialty Paint Flush1 * 11, Ciba Specialty Chemicals under the tradename Microlean-UA101, and others. The solid predispersing pigments can also be mixed with a suitable carrier and used as a liquid dye dispersion. Suitable commercially available liquid pigment dispersions are available from various suppliers including The Valspar Corporation (through its subsidiary EPS / CCA) under the trade designation Novacolor1111, and DeGussa Corp., under the trade designation Covon ™ or Aquatrend1111. A dye dispersion in the form of paste is available from Penn Color under the trade name Aquacolor1111. Suitable liquid color dispersions include about 4 to 80% by weight of pigments, 3 to 30% by weight of the dispersion aid, with the remainder being the carrier. Preferably, the dispersion includes 5 to 70% by weight of pigments, 5 to 25% by weight of the dispersion assistant, with the remainder being the carrier. More preferably, the dispersion includes 5 to 70% by weight of pigments, 7 to 22% by weight of auxiliary dispersion, with the remainder being the carrier. The colorant dispersion is essentially stable since the pigment or the colorant is uniformly dispersed throughout its length. Settling occurs at a very slow rate such that the dispersion remains essentially homogeneous for extended periods of time, preferably at least 4 hours, and more preferably 24 hours or more. The dye dispersion prevents the agglomeration of the pigment particles, and there is no irreversible settling or coagulation of the particles over periods as long as six months and preferably up to one year or more. After this extended period of storage, the coloring dispersion can be gently mixed, shaken or gently shaken to restore dispersion to a uniform consistency. A characteristic resulting from the coloring dispersion is the reproducible coloring force. This stability increases the dispersion to be premixed and assorted either by weight or volume. This feature allows reliable and reproducible standards to be prepared for use in computerized color matching, and results in consistently colored, predictable powder compositions. A predictable amount of pigment can be introduced into the process by using a measurable volume of the dye dispersion. Alternatively, the dispersion can be measured in weight, or by any other system such as the use of time and flow velocity, or any other static measuring system or process. Optionally, other additives may be used in the present invention. As discussed above, these optional additives can be added before extrusion and be part of the base powder, or can be added after extrusion. Suitable additives for the post-extrusion addition include materials that would not work well if they were added before extrusion, materials that could cause additional wear on the extrusion equipment, or other additives. Additionally, the optional additives include materials that are feasible to add during the extrusion process, but which are found desirable to add later. The additives can be added alone or in combination with other additives to provide a desired effect on the powder finish or the powder composition.

These and other additives may improve powder application, melting and / or curing, or performance or final appearance. Examples of optional additives that may be useful include: curing catalysts, antioxidants, color stabilizers, anti-wear slip additives, UV absorbers, hindered amine light stabilizers, photoinitiators, conductivity additives, tribocharger additives, additives anti-corrosion, fillers, inert pigments, texture agents, degassing additives, flow control agents, thixotropes and edge coverage additives. Other preferred additives for incorporation in this step include metallic effect pigments, such as dried aluminum flakes, pearlescent pigments, micas and bronze pigments. The most preferred grades of aluminum and bronze pigments for incorporation by this process include grades that are highly surface-treated, including grades specifically designed for use in powder coatings or aqueous liquid coating applications. Some suppliers of these materials include MD-Both and Eckart. Other preferred additives include performance additives such as rubberizers, friction reducers and microcapsules. In addition, the additive could be an abrasive, a catalyst, a heat-sensitive material, or one that helps create a final porous coating. Also, the additives to improve the wetting of the base powder can be added. One or more base powders, one or more coloring dispersions, and any optional additives are mixed. Additional liquid of any suitable type can also be added during mixing. If used, this additional liquid is preferably water. The mixing can be carried out by any available mechanical mixer or by manual mixing. Some examples of possible mixers include Henschel mixers, Mixaco mixers, and horizontal axis mixers. Preferred mixers could include those that are more easily cleaned. A changeable can mixer style, or mixed in the effective shipping container, is most preferred. The mixing step is preferably performed at less than 40 ° C, and even more preferably at less than 30 ° C, and under mild conditions. Because a dye dispersion is used, heat and high shear are neither necessary nor desired in the mixing. The coloring dispersion, any optional additives and the base powders must be mixed together to produce a sufficiently uniform mixture. Typically, the components are stirred together in a Henschel mixer or mixer for less than 1 minute to provide the required mixing. Ideally, notwithstanding the particular mixing device used, the mixing time and revolutions per minute should be chosen such that there is only minimal change in particle size. The purpose of the mixing step is to coat the base powder particles with the colorant, not to cause significant changes in particle size. The resulting mixture can have a variety of appearances. This can remain in a mainly solid form, having the consistency of wet sand, or it can be a thick suspension, or it can even be liquid. The physical form of the product at the time of mixing will be largely determined by the proportions of colorant, carrier, additional liquid added and the base powders used. After mixing, the carrier can be removed from the powder. The desired final product is a free flowing powder. The elimination of the carrier includes the change of the state of the carrier, the reaction of the carrier, the evaporation of the carrier, or other methods. Preferably, the powder is dried. As the mixing, drying will generally take place under mild conditions, and at a temperature preferably below 40 ° C, and even more preferably at less than 30 ° C. In all cases, drying must occur well below the softening point of the base powder. The softening point of the base powder is the point at which the surface of the powder particles are heated to the point where the particles become sticky and adherent. In one embodiment, the material may be allowed to dry in an open container. More preferably, the material will be dispersed, or otherwise more fully exposed for drying. Optionally, dry air or other gas can be blown through the material to accelerate the drying process. Alternatively, a certain level of vacuum can be used to accelerate the drying process. In yet another embodiment, drying is achieved by means of a fluidized bed. The use of fluidizing air to accelerate the drying process can be done either in a separate process vessel or in the mixing vessel. In yet another embodiment, the mixing and drying steps can be performed in a disposable garbage container. In general, the more humid the intermediate mixture is, the longer it will take to dry it. As the material dries, it becomes freer flow. A discussion on free flow capacity and a general definition can be found in Powder Coating Institute Technical Brief # 24. If agglomeration is present after carrier removal, sieving, grinding, ball milling, air blowers, stirring or other methods can eliminate lumps. Preferably, sieving will be used. The sieve to be used will have a desired mesh or pore size depending on the desired powder attributes. Typically, for smooth finishes, the screen will have a mesh size between about 75 microns and about 150 microns. The larger the mesh sizes, such as up to 300 micrometers, may be preferred for some textured finishes. When a sieve is used, the dry material will be passed through the sieve, which will prevent any clumps of material from passing over the final product. These can be lumps of soft material, not completely dry, or hard lumps of particles. Sifting allows the process to continue without requiring that the entire mixture be uniformly dried, and also helps to maintain a consistent final product. The screening also makes it possible for the drying step to be optimized from a process perspective. An illustrative method of the present invention is to select one or more base powders and one or more stable coloring dispersions. The stable coloring dispersion is added to the base powders by emptying, spraying or any manual, mechanical or automatic means. Other optional additives can be added. These can be emptied, sprayed, or added by any manual, mechanical or automatic means. These optional additives can be combined with the base powder before or after the addition of the coloring dispersion, or they can be premixed with the colorant before the addition of the coloring dispersion. Additional liquid, which may or may not be the same as a carrier used for stable dye dispersion, may also be added. For example, a small amount of water can be added to improve mixing. This can be emptied, sprayed or added by any manual, mechanical or automatic means. The base powder plus any additions are mixed or allowed to distribute evenly. In certain embodiments, mixing may occur at the same time any additives are added, which may avoid the need for additional or separate mixing and will provide the required level of uniformity to the mixture. After mixing, the material can be dried, and can be passed through a screen. In a preferred embodiment, the stable dye dispersion includes a pigment and a dispersion aid. In such dispersion, the dispersion aid surrounds the pigment particles, which prevents the pigment particles from coalescing. In typical formulations, after the stable colorant dispersion is mixed with the base powder, there are many more pigment particles than the base powder particles. As the carrier is removed, the surrounded pigment particles have a tendency to couple to the base powder particles. Since many pigment particles adhere to each particle of base powder, it begins to form at least a partial layer, more preferably, a substantially complete layer of dye on the surface of the core particle. This forms a shell-like structure or complete or partial shell (although it is recognized that the "shell-shaped shell" will not necessarily be a continuous shell, but may be a discontinuous layer of discrete particles or islands of colored particles) . While not wishing to be bound by any theory, the currently available evidence indicates that once the dye dispersion is added to the base powder, the dyes in the dye dispersion form a coating layer on the surface of the base powder particles. It is believed that the other components in the coloring dispersion loosely associate the pigment particles with the base powder particles. Currently available evidence indicates that the number of pigment particles typically associated with each core base particle varies depending on the size of the base particle, the size of the pigment / dye particle, and the amount of pigment / dye used. This can be seen in the following table, which uses a base particle size of 32 micrometers in diameter for calculations.

The completed powder can then be applied to a substrate using any conventional method, including spraying, electrostatic spraying, fluidized beds and the like. After application of the powder, the substrate is heated to a temperature sufficient to cause the powder particles to melt and flow. Various sources of heating may be used, including convective heating, infrared heating, induction heating, or a combination thereof. Optionally, the powder can be applied to a preheated substrate. Then, the coating is optionally cured, and such cure can occur via continuous heating, subsequent heating, or residual heat in the substrate. In another embodiment of the invention, if a powder coating base curable by radiation is selected, the powder can be melted by a relatively short or low temperature heating cycle, and then it can be exposed to radiation to initiate the healing process. . An example of this embodiment is a UV curable powder. Other examples of radiation healing include the use of UV-Vis, visible light, near IR, IR and electron beam. Preferably, the coated substrate is uniformly colored and has desirable physical and mechanical properties. The thickness of the final film coating depends on the desired application of the substrate and the selected additives. Typically, the final film coating will have a final thickness of 25 to 200 microns. Another feature of the present invention is that less dye may be necessary to produce the same color in the final film coating. This may vary depending on the colorant used, but typically about 25% less colorant is required than if the colorant will blend perfectly with the film-forming resin, such as occurs in the extruder. It is anticipated that this process can better distribute the colorant than the mixing that occurs in the extruder. Additionally, in the present invention, the colorant is on the surface of the particles, instead of being all along the powder particles. This allows the same amount of dye on the surface of the final film coating with less dye to be added. Illustratively, when a very thin cut is made through the final film coating and the exposed cut is examined under a microscope, the dye appears to be distributed at the interface of the coalesced base powder. The following examples are offered to help understand the present invention, and are not considered to be limiting of the scope thereof. Unless stated otherwise, all parts and percentages are by weight. EXAMPLES Several materials cited in the following examples were evaluated by the tests common in the industry. These test results were obtained from the manufacturer's literature. The Equivalent Weight of Epoxide measures the molecular weight per epoxide group. The acid value measures the mg of potassium hydroxide that reacts per g of resin. Example 1 Preparation of hybrid white base powder The above ingredients were combined and mixed dry in a Reos mixer for 20 seconds, then extruded through a Werner-Pfleiderer ZS-30 extruder. The cooled extruded was combined with 0.2% by weight of dry flow agent C Aluminum Oxide of Degussa, then ground on an air sorting mill (laboratory model of Powder Process Systems). Aluminum Oxide C was added to help the free-flowing properties of the finished powder. The resulting powder was then sieved through a Sweco sieve of 230-T mesh. The particle size of the powder was measured on a Malvern Mastersizer 2000 laser particle size analyzer, and it was found to have a mean particle size (d (0.5)) of 30.4 microns. A panel of the product after electrostatic spraying and baking (20 minutes at 190 ° C) gave gloss readings of 96 (at an angle of 60 degrees) and 74 (at an angle of 20 degrees). Example 2 Preparation of hybrid clear base powder The above ingredients were processed as described in Example 1. The average particle size of the resulting powder was found to be 29.7 micrometers. Example 3 Preparation of the white base powder of thermosettable polyester The above ingredients were processed as described in Example 1. The average particle size of the resulting powder was found to be 32.8 microns. The panels of the product, after electrostatic spraying and baking for 20 minutes at 190 ° C, had luster readings of 96 (geometry at 60 degrees) and 82 (geometry at 20 degrees). Example 4 Preparation of hybrid white powder The above ingredients were combined and mixed dry in a Reos mixer for 20 seconds, then extruded through a Werner-Pfleiderer ZSK-30 extruder. The cooled extrudate was combined with 0.15% Degussa Aluminum Oxide C and crushed over a Micropul Bantam mill, and then sieved through a 145 mesh screen. The average particle size of the resulting powder was found to be of 43 micrometers. Example 5 Gray Powder 100.0 g of hybrid white base powder (Example 1) were charged to a small pharmaceutical mixing mill, model DM-6. This device comprises a stainless steel bowl approximately 11.4 cm in diameter and 5 cm deep, with a removable screw cap. A simple rotating mixing blade is mounted near the bottom of the pan. The rotational speed of the blade is 4800 rpm. Inside a separate container were added 2.0 g of Degussa Covon 832-0001 White Dye Dispersion, 1.5 g of Degussa Covon Black Dye Dispersion 832-9901, and 10.0 g of distilled water. The dye dispersion mixture was manually premixed with a small spatula until it was a uniform gray color. The dye dispersion mixture was added to the mixer containing the hybrid white powder and mixed by two separate 10 second cycles. After removing the lid, it was apparent that some of the unmixed white product was caught in the threads of the bowl and on the surface of the lid. The lid and the threads were cleaned by rubbing, then the product was mixed for an additional 20 seconds. The product appeared uniform in color with the naked eye, and was a cohesive, non-free-flowing powder. The consistency of the product at this point resembled fresh brown sugar. The product was discharged from the mixer and left to dry overnight in an open container at room temperature (21 ° C). The product was then sieved through a 170 mesh screen. The resulting product was a free flowing powder, similar in material handling characteristics to the initial, original white base powder. The product was electrostatically sprayed on a 0.051 cm (0.020 inch) thick cold rolled steel substrate. The product showed good spray or spray characteristics. After curing for 10 minutes at 204 ° C, the panel had a luster of 88 (at an angle of 60 degrees) and 48 (at an angle of 20 degrees). The chlorine was not uniform to the naked eye, and had white flecks and black flecks. Example 6 Gray powder 75.0 g of hybrid white base powder (Example 1) were charged to the mixer described in Example 5. Within a separate vessel was added 4.0 g of Degussa Covon 832-0001 White Color Dispersion, 0.3 g of Black Dye Dispersion. Degussa Covon 832-9901, and 10.0 g of distilled water. The dye dispersion mixture was manually premixed with a small spatula until it was a uniform gray color. The dye dispersion mixture was added to the mixer containing the hybrid white powder and mixed for 20 seconds. The lid was removed and the lid and the threads were scraped to free them from an unmixed product, then the mixing process was repeated for an additional cycle of 20 seconds. The product was allowed to cool briefly, and then mixed for two additional cycles of 10 seconds. The product appeared uniform in color with the naked eye, and was a moist cohesive solid, which resembled brown sugar in consistency. The product was discharged from the mixer and allowed to dry for three days in an open container at room temperature (21 ° C). After drying, the product was sieved through a 170 mesh screen. The resulting product was a free flowing powder, similar in material handling characteristics to the original initial white base. After spraying and curing, the color was rated as very uniform to the naked eye. The luster was 69 (at an angle of 60 degrees) and 22 (at an angle of 20 degrees). Example 7 Gray-colored powders The general procedure described in Example 6 was followed for Example 7, except that the mixing time was four separate cycles of 10 seconds, and the drying time before sieving was overnight (a 21 ° C). In the following diagram, VG = very good, G = good, F = regular, P = poor. The quantities used (parts by weight) are listed below.

In order to determine the effect, if any, of the dyes on the corrosion resistance, the samples of the hybrid white base (Example 1) and the gray powder (Example 7 run 5) were applied to Bonderite panels 1000 and subjected to the salt spray test (ASTM B117, test duration 1000 hours) and moisture test (ASTM D2247, test duration 1000 hours). The results were rated according to ASTM D714 and ASTM D1654. After 1000 hours of salt spray: Qualifications of Example 1: ampoules = 10, rust = 10, and run = 1.5 mm. Qualifications of Example 7 run 5: ampoules = 8 (little), rust = 9, and run = 1 .7 mm. After 1000 hours of humidity: Grades of Example 1: ampoules = 10, and rust = 10. Qualifications of Example 7 run 5: ampoules = 10, and rust = 10. These results of the corrosion resistance test indicate that the addition of the colorant has only a minor effect on the corrosion resistance of the coating. Example 8 Gray powder (low intensity mixing) 75.0 g of hybrid white base powder (Example 1) were charged to a 1 liter polyethylene laboratory vessel, which was adjusted to an electric Cole-Parmer model 4554 electric mixer -10, eguipated with a propeller of three blades of 6.35 cm in diameter. In a separate container, 4.0 g of White Dye Dispersion Degussa Covon 832-0001, 0.3 g of Degussa Covon Black Dye Dispersion 832-9901, and 4.0 g of distilled water. The dye mixture was stirred until a uniform gray color was obtained. The white base powder was stirred at a propellant speed of 250 RPM, and the colorant dispersion was added under agitation. The dye initially appeared to settle on the bottom of the container, and it was noted that there were certain dead spots around the edges of the container, where relatively poor agitation was obtained. These dead spots were agitated periodically with the hand with a spatula pegueña. After approximately five minutes of agitation, the color of the product was a visually uniform gray. The dry flow properties of the product at this time were relatively poor. The product was a moderately cohesive, moist solid. The product was allowed to dry at room temperature (21 ° C) in the open container for approximately four hours. At that time, the fluidity of the powder had improved. The product was then transferred to a fluidized bed and aerated with dry air for approximately five minutes, then sieved through a 170 mesh screen, electrostatically sprayed on 0.051 cm (0.020 inch) cold rolled steel and baked for 20 minutes at 190 ° C. The color uniformity of the panel was rated as good. With the naked eye examination, the colored specks were not easily apparent. Using a manual amplification glass, lighter motes with a darker color matrix were visible. The luster was 71 (at an angle of 60 degrees) and 21 (at an angle of 20 degrees). These results show that low intensity mixing is a viable technique for mixing the colorant. Example 9 Gray powder (reduced time of the mixing cycle) 75.0 g of the white hybrid base powder (Example 1) were charged to the mixer described in Example 5. A premixed dye dispersion contained 4.0 g of the Dispersion White Color Degussa Covon 832-0001, 0.4 g of the Dispersion Black Dye Degussa Covon 832-9901, and 4.0 g of distilled water was added. The surface temperature of the powder was measured with an optical pyrometer before mixing, and found to be 21 ° C. The mixer was run for 5 seconds, then the lid was removed and the temperature of the contents was measured again. After 5 seconds of mixing time, the surface temperature of the contents remained at 21 ° C. The product was discharged from the mixer and left to dry overnight in an open container. After sifting (170 mesh), the product was sprayed and cured for 20 minutes at 190 ° C. The resulting panel had good color uniformity, since no visible spots could be detected. The luster of the panel was 70 (at an angle of 60 degrees) and 21 (at an angle of 20 degrees). EXAMPLE 10 Effect of mixing cycle time and temperature The measurement of the temperature described in Example 9 was repeated using a mixing time of 10 seconds, and a temperature rise from 21 ° C of initial surface temperature was measured. up to 24 ° C after mixing. The measurement was repeated using a mixing time of 20 seconds, and a temperature rise from 20 ° C of initial surface temperature to 32 ° C after mixing was measured. The powder of this example is formulated to withstand storage temperatures of 35 ° C or higher for periods of several days without significant sintering. Accordingly, it is believed that exposure of the powder to the relatively low temperatures and short times employed in these mixing cycles may not cause significant irreversible agglomeration effects.

Example 11 Evaluation of alternative coloring dispersions In this Example, alternative aqueous coloring dispersions were evaluated. The following examples were prepared using the same mixer and the same general technique as described in Example 5, mixing for 5 seconds, cleaning the lid and threads, then mixing for 7 additional seconds. The resulting mixture was dried overnight at 20-23 ° C. The following powders were prepared (all weights in grams): These data indicate that EPS / CCA coloring dispersions are able to give reasonably high gloss at moderate dose levels, but produce significant reduction in luster when used at relatively high dosage levels in a straight black. Additionally, pill flow tests were conducted in Examples 2, 11-4 and 11-5. The pill flow is a measure of the ability of the powder to flow outward during the heating / melting stage, and is described in and run according to ASTM Standard Test Method D4242-02 for Flow in Slant Plate for Dust Powders. Thermo-hardening coating. The comparison of the results shows that sample 11-4 had an increased pill flow over the base powder, while sample 11-5 had a decreased pill flow. The specific results were: Example 2 (hybrid clear base) = 25 mm Example 11-4 = 42 mm Example 11-5 = 16 mm Example 12 Black powder For comparison with Examples 11-4 and 11-5, a sample using Black Color Dispersion Degussa Covon was prepared using techniques similar to the example 11. The quantities of the material are as follows: Clear Base Hybrid (Example 2) 75.0 g, Black coloring dispersion Degussa Covon 832-9901 5.6 g, distilled water 10.0 g. The resulting gloss readings were 41 (at an angle of 60 degrees) and 7 (at an angle of 20 degrees). The pill flow was 16 mm. The effect of the dye on the resistance to sintering of the product was determined by placing the samples of Example 1 and Example 12 in an oven at 40 ° C for three days. Both Examples 1 and 12 were free flowing powders without visible agglomeration, cake formation, or sintering after exposure to the test conditions. The comparison of the results of Examples 2, 11 and 12 suggest that Black Degussa Covon and Black EPS / CCA Dispersions cause both reduction in the powder melt flow, as indicated by the decrease in pill flow values versus the untreated base. In contrast, the addition of the Penncolor dispersion increased the pill flow, but also gave a somewhat poorer color uniformity when added to the white base. Example 13 Various additional colored powders The same mixing conditions described in Example 11 were used to prepare the following additional powders.

Example 14 Various additional colored powders The mixing conditions as described in Example 11 were used to prepare the following additional powders.

A sample of Run Example 14 was dispersed with a spatula on a cold-rolled steel panel, on a gel plate heated at 180 ° C. The melt was stirred with the spatula, and the panel was then cooled. It was observed that the color obtained by stirring the product was much lighter than the color obtained from a panel that had been electrostatically sprayed and cured in the oven. This result suggests that a given shade of color can be achieved by using less colored pigment, by adding dye to the surface of the powder than would be required if the dyes were completely mixed in molten form with the resin base. EXAMPLE 15 Additional Colors Using the Clear Base Using the mixing conditions described in Example 11, the following colors were produced. In table 15, the appearance ratings for straight (non-metallic) shadow finishes refer to color uniformity, and appearance ratings for metallic and pearl finishes refer to overall overall aesthetic appearance.

Example 16 Powder colored using dye 100 g of distilled water were heated to 80 ° C and 1.6 g of black water soluble dye Transfast # 3280 (sold by Homestead Finishing Products, Cleveland, Ohio) was added with magnetic stirring. The solution was stirred until the dye was visually dissolved. After cooling to 21 ° C, the dye solution was added to the base powder using the same mixer and procedure as described in Example 11. The amounts of the materials used are as follows (all weights are in grams).

Example 17 Use of solid pigment dispersions To a mixture of 45.0 g of VM &P naphtha and 5.0 g of isopropanol was added 2.0 g of the Pigment Dispersion 649GP49 Sun Pigments. Sun Pigments 649GP49 is described as a pre-dispersed solid pigment concentrate, comprising 60% phthalo blue pigment and 40% Laropal A81 aldehyde resin. The mixture was stirred until it appeared to be visually free of undissolved solids. A portion of 11.7 g of this mixture was added to 100 g of the white powder (Example 4). The resulting mixture was stirred in a fume extraction hood using a laboratory agitation motor, equipped with a propeller stirrer. The product was left to dry overnight in a smoke hood. After drying, it was observed that the product contained many hard lumps that were somewhat difficult to break with manual stirring with a spatula. The product was sieved (170 mesh), sprayed and baked 20 minutes at 190 ° C. The appearance of the resulting panels was rated as regular, with traces of motes visible to the naked eye. Example 18 Evaluation of alternative aqueous pigment dispersions In Example 18, two commercially available aqueous pigment dispersions (from the Degussa 870 series and from the Degussa 895 series) were compared to the Covon 832 series dispersions (used in the previous examples). ). The comparison was made using a TGIC polyester base powder (Example 3). The mixing device described in Example 5 was used to process the following samples. The mixing time was 5 seconds, followed by cleaning of the lid and the thread, followed by an additional mixing time of 5 seconds. The drying time was overnight at 20 ° C. The dried product was sieved (170 mesh), sprayed and baked 20 minutes at 10 ° C. The amounts of the ingredients are as follows (all weights are in grams): Particularly notorious is the improved result of the luster at 20 degrees, obtained from dispersions 870 and 895 compared to the 832 series. Especially notorious is that this improvement in luster was obtained without sacrificing color uniformity. Samples of the powders of Examples 3, 18-1, 18-2 and 18-3 were subjected to the sintering resistance test as previously described in Example 12. After three days at 40 ° C, the Examples 18-1 and 18-2 were both poorly sintered in a simple lump that did not break easily, while Examples 3 and 18-3 were both free flowing powders without agglomeration or cake formation. These results of resistance to sintering for Examples 18-1 and 18-2 show that these powders may require extra care in transport and storage. In addition, these results taken together also show that a mixture of the coloring dispersions can be more effective in obtaining optimum performance characteristics in the powders. It is anticipated that a mixture of the coloring dispersions could provide good luster results and good sintering results. Example 19 Use of the improved mixing process A Reos mixer equipped with variable speed drive capacity was used to mix the color dispersions with powder bases. The Reos mixer comprises containers of portable and interchangeable mixes that are adjusted to a motor-driven propulsion unit. The clearances obtained between the propellant and the bottom and sides of the container are sufficiently airtight to provide good mixing of the solids. The portable containers and the mixing propellant are relatively easy to clean between batches. The variable speed control also allows the selection of rotational speed of the propeller for the process to be optimized. A second batch of hybrid white base powder was prepared using the same techniques and type as described in Example 1. Although identical in each of the other known aspects to the first batch of the powder described in Example 1, it was found that the second batch has a mean particle size (d (0.5)) of 28.4 micrometers. 53.3 g of White Dye Dispersion Degussa Covon 832-0001, 5.3 g of Degussa Covon Black Dispersion Covon 832-9901, and 67.0 g of distilled water were combined and shaken with a spatula until a visually uniform color was obtained. This dye dispersion was added to 1000 g of hybrid white base powder (second batch of the formula of Example 1, as described above) in a Reos mixing vessel. The initial surface temperature of the mixture was 20 ° C (as measured by an optical pyrometer). The mixture was stirred using a propeller speed of 800 RPM for 20 seconds. The immediate surface temperature of the product after mixing was measured as 23 ° C. The product under the propellant and the sides of the mixing vessel was scraped with a spatula. The mixing vessel and the contents were replaced on the mixer, and the surface temperature was found to be 21 ° C. The product was mixed for an additional cycle of 20 seconds at 800 RPM. The surface temperature of the product after mixing was 23 ° C. The product was allowed to dry in an open mixing vessel overnight. After sieving (170 mesh), the product was found to have a mean particle size (d (0.5)) of 31.0 microns. The powder was then sprayed and baked 20 minutes at 190 ° C. The resulting panels were rated as very good for uniformity of appearance, with no visible spots of color, and only minimal specks visible with manual amplification. The luster of the panels was 73 (at an angle of 60 degrees) and 23 (at an angle of 20 degrees). Example 20 Processing in a disposable seizure container 1000.0 g of the white base powder (Example 3) was charged to a small disposable fiberglass drum, manufactured by Grief Brothers. 15.0 g of the White Pigment Dispersion Degussa Covon 832-0001, 1.6 g of Black Pigment Dispersion Degussa Covon 832-9901, and 50.0 g of distilled water were combined and pre-mixed. This dye dispersion was added to the powder described above and the resulting mixture of the components was mixed on the Reos mixer described in Example 19. After a mixing cycle of 20 seconds at 800 RPM agitator speed, the walls and the bottom of the container were scraped manually with a spatula, and then the container was mixed for an additional 20 seconds at 800 RPM. The walls and the bottom of the container were scraped again, and an additional mixing cycle of 20 seconds at 800 RPM was carried out. The resulting product was allowed to dry overnight in the disposable shipping container, discovered at 20 ° C, and stored for future use. Example 21 Use of the flattening pigment dispersion 15.0 g of Modaflow AQ-3025 (from UCB Surface Specialties) and 185.0 g of distilled water were agitated with a laboratory powder air stirrer equipped with a 75 mm stirring blade diameter. 500 g of the Minex 4 pigment (from Indusmin) were then added with stirring. The mixture was stirred at maximum speed until a Hegman calibrator reading of # 4- # 5 was obtained. The Modaflow-Minex blend was emptied into a sealable plastic container for later use. 2.5 grams of the coloring dispersion 832-0501 of Degussa Covon 2B Red Calcium, 0.1 g of the Degussa Covon 832-8801 Carbazole Violet Dispersion, 2.0 g of Powdall 3400 aluminum flakes (from MD Both) and 3.0 g of distilled water were combined and pre-mixed until they were uniform in appearance. The premixed dye dispersion was added to 75.0 g of the hybrid clear base (from Example 5) in the mixer. After processing as described in Example 11, the resulting panels had good metallic appearance and luster of 65 (at an angle of 60 degrees) and 20 (at an angle of 20 degrees). A second dye premix was prepared from 2.5 g of the color dispersion 832-0501 of Red Calcium 2B of Degussa Covon, 0.1 g of Carbazole Violet Dye Dispersion of Degussa Covon 832-8801, 2.0 g of Powdall aluminum flake 3400 (from MD Both), 5.0 g of Modaflow-Minex mixture described above in this example, and 5.0 g of distilled water. After processing as described above, the resulting panels had luster 55 (at an angle of 60 degrees) and 15 (at an angle of 20 degrees). The appearance was good with respect to the metallic appearance, but suffered from significant seeds on the surface. The Modaflow-Minex mixture described above was stirred with a spatula, and it was noted that a significant amount of hard settling of the pigment was present at the bottom of the container. This settlement suggests that the stability of this pigment dispersion may be inadequate, and that an alternative dispersion aid is necessary.

Example 22 Evaluation of the alternative aqueous pigment dispersions Using the mixing device and the mixing times described in Example 18, two additional samples were prepared from the aqueous pigment dispersions supplied by Sun Chemical Corporation. The drying time was 3 days at 20 ° C. The dried product was sieved (170 mesh), sprayed and baked 20 minutes at 190 ° C. The amounts of the ingredients are as follows (all weights in grams): Samples of the powder coatings were subjected to the sintering resistance test as previously described in Example 18. After 3 days at 40 ° C, Examples 22-1 and 22-2 were free flowing powders without agglomeration or cake formation. Having thus described the preferred embodiments of the present invention, those skilled in the art will readily appreciate that the teachings found herein may be applied to other embodiments within the scope of the appended claims. The complete description of all patents, patent documents and publications are incorporated herein by reference, as if they were incorporated individually. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Claims (36)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A method, characterized in that it comprises: the provision of at least one base powder; the provision of at least one stable dye dispersion including a liquid carrier, a dye and a dispersion aid; and mixing the base powder (s) and the coloring dispersion (s) to form a colored mixture.
2. 2. The method of compliance with the claim 1, characterized in that the dye comprises at least one of a pigment or a dye.
3. 3. The method of compliance with the claim 2, characterized by further comprising: removing or changing the state of a sufficient amount of the liquid carrier to form a free-flowing powder. .
4. The method according to claim 1, characterized in that it further comprises: the treatment of the colored mixture to form a free flowing powder.
5. 5. The method according to claim 1, characterized in that the powder base and the coloring dispersion are mixed at a temperature below about 40 ° C.
6. 6. The method according to claim 1, characterized in that the base powder and the coloring dispersion are mixed for approximately 1 minute.
7. 7. The method of compliance with the claim 2, characterized in that the liquid carrier comprises water, an organic solvent, or a combination thereof.
8. 8. The method of compliance with the claim 7, characterized in that the liquid carrier is water.
9. The method according to claim 1, characterized in that the stable dye dispersion comprises a dispersion auxiliary selected from the group consisting of surfactants, monomers, polymers, and oligomers.
10. The method according to claim 9, characterized in that the dispersion aid is soluble in the liquid carrier.
11. 11. The method according to the claim I, characterized in that the base powder comprises a polymeric binder.
12. 12. The method in accordance with the claim II, characterized in that the base powder further comprises a curing agent.
13. 13. The method according to claim 1, characterized in that the stable dye dispersion comprises pigments with an average particle size of about 0.01 to about 4 microns in diameter.
14. The method according to claim 13, characterized in that the stable dye dispersion comprises pigments with an average particle size of about 0.05 to about 1 micrometer in diameter.
15. 15. The method according to claim 1, characterized in that the base powder comprises particles with an average particle size of about 2 to about 100 microns in diameter.
16. 16. The method of compliance with the claim 15, characterized in that the base powder comprises particles with an average particle size of about 10 to about 60 microns in diameter.
17. 17. A method, characterized in that it comprises: the provision of at least one base powder; the provision of at least one stable dye dispersion, wherein each dispersion comprises one of: (a) at least one of a pigment or a dye; a liquid carrier; and an auxiliary of dispersion; or (b) a coloring solution, comprising a colorant and a liquid carrier; and mixing the base powder (s) and the stable coloring dispersion (s) to form a colored mixture.
18. 18. The method of compliance with the claim 17, characterized in that it further comprises: the treatment of the colored mixture to form a free-flowing powder.
19. 19. The method according to claim 17, characterized in that the base powder and the stable coloring dispersion are mixed at a temperature below about 40 ° C.
20. 20. The method according to claim 17, characterized in that the liquid carrier comprises water, an organic solvent or a combination thereof.
21. The method according to claim 17, characterized in that the dispersion aid is soluble in the liquid carrier and is selected from the group consisting of surfactants, monomers, polymers and oligomers.
22. 22. A method, characterized in that it comprises: the provision of at least one powder; the provision of at least one stable dye dispersion, wherein the dye dispersion comprises a liquid carrier, an auxiliary of the dispersion and at least one of a dye or pigment; and mixing the base powder and the coloring dispersion to form a colored mixture, wherein the mixture comprises a film-forming polymer.
23. 23. The method according to claim 22, characterized in that it further comprises: the treatment of the colored mixture to form a free-flowing powder.
24. 24. The method according to claim 22, characterized in that the powder and stable coloring dispersion are mixed at a temperature below about 40 ° C.
25. 25. The method according to claim 22, characterized in that the liquid carrier comprises water, an organic solvent or a combination thereof.
26. 26. The method of compliance with the claim 22, characterized in that the dispersion aid is soluble in the liquid carrier, and is selected from the group consisting of surfactants, monomers, polymers and oligomers.
27. 27. A powder coating method, characterized in that it comprises: the provision of at least one base powder; the provision of at least one stable dye dispersion including a liquid carrier, a dye and a dispersion aid; mixing the base powder (s) and the stable coloring dispersion (s) to form a colored mixture; treating the colored mixture to form a free-flowing colored powder; the application of the colored powder to a substrate; and heating the colored powder to form a powder coating on the substrate.
28. 28. The method according to claim 27, characterized in that the base powder comprises a polymeric binder.
29. 29. The method according to claim 27, characterized in that the dye comprises at least one of a pigment or a dye in the liquid carrier, and wherein the liquid carrier comprises water.
30. 30. The method of compliance with the claim 27, characterized in that the base powder and the stable coloring dispersion are mixed at a temperature below about 40 ° C.
31. 31. The method according to claim 27, characterized in that the dispersion aid is soluble in the liquid carrier and is selected from the group consisting of surfactants, monomers, polymers and oligomers.
32. 32. A composition, characterized in that it comprises: a core particle; and at least one cover or partial shell around the core particle, wherein the shell comprises one of: (a) a colorant; or (b) a pigment particle and a dispersion aid.
33. 33. The composition according to claim 32, characterized in that the dispersion aid is selected from the group consisting of surfactants, monomers, polymers, oligomers and combinations thereof.
34. 34. The composition according to claim 32, characterized in that the pigment particles have an average particle size of about 0.04 to about 1.0 micrometer in diameter.
35. 35. The composition according to claim 32, characterized in that the core particle has a particle size of at least 10 micrometers in diameter.
36. 36. The composition according to claim 32, characterized in that it is in the form of a free flowing powder.