MXPA00006937A - Powder coating composition - Google Patents

Abstract

A composition suitable for use in a powder coating process comprising a powdered polymer composition and a metal oxide based fluidization enhancer, or a metal oxide based flatting agent.

Description

COMPOSITION OF POWDER COATING BACKGROUND OF THE INVENTION (1) Field of the Invention This invention relates to powder coating compositions and particularly to powder coating compositions having improved fluidization properties as a result of the inclusion of a small amount of a metal oxide fluidization improver. in the composition This invention is also a powder coating composition that includes a small amount of a novel metal oxide brightness reducing agent. (2) Description of the Technique Polymer-based powder coatings are solid particulate compositions which are generally applied to substrates to give the substrate a durable, resistant surface coating Powder coatings are applied to substrates by electrostatic, corona processes or powder spray in which powder coating particles are electrostatically charged to the spray can and the substrate is grounded or charged in an opposite manner. The applied powder coating is then heated to melt and fuse the particles in a continuous coating and to cure the resulting coating. Powder coating particles that do not adhere to the substrate can be recovered for re-use. The powder coating compositions are generally free of added solvents and, in particular, do not use organic solvents and are therefore non-contaminating. Powder coating compositions generally comprise a resin that forms a solid film, usually with one or more coloring agents. such as pigments They usually thermoset, incorporating, for example, a film-forming polymer and a corresponding curing agent (which itself can be another film-forming polymer). The powder coating compositions are generally prepared by intimately mixing the ingredients, for example, in an extruder, at a temperature above the softening temperature of the film-forming polymers but below a temperature at which significant polymerization would occur. The extrudate is usually rolled into a flat sheet and the size is reduced, for example, by grinding, to the desired particle size. The particle size distribution required for most commercial electrostatic spray devices is between 10 and 20 microns, with an average particle size in the range of 15 to 75 microns, and preferably 25-50 microns. Examples of powder polymer coating compositions are described in U.S. Pat. Nos. 5,461,089, 5,470,893, 5,614,323 and 5,229,460. Powder polymers cure to a glossy finish. In some applications, however, the reduction in gloss is desirable. The reduction in gloss is typically achieved in powder coatings by adding large inert particles known as "texturizing agents" to the compositions. The texturizing agents are encapsulated in the cured polymer film and are large enough to give the final finish a rough appearance. Examples of large inert texturing agents include fibers, pigments, micas and abrasives, such as those described in U.S. Pat. No. 5,470,893. Powdered polymer coating compositions are also difficult to fluidize and maintain a free flow during distribution, application and use due to the tendency of powdered polymer coatings to sediment, compact, and agglomerate during storage, reconstitution and driving. The problem with fluidization it becomes more predominant when the particle size of the polymer powder composition decreases. Traditionally it has been typical to use precipitated or gelled silicas as free flowing additives, particularly for powder coatings of larger particle sizes. It is believed that precipitated silicas and gelled silicas increase the free flow of powdered polymer compositions due to their ability to absorb moisture in the form of water vapor or liquid, which minimizes the binding of liquid and liquid bridges -liquid between the powdered polymer particles. However, with smaller polymer powder particles it becomes a norm, the need for additives that absorb moisture and / or improve the performance of the polymer powder. Although the existing powder coating compositions are satisfactory in many aspects, there is nevertheless a need for powdered polymer coating compositions that produce a low gloss finish. An object of the present invention is, therefore, to provide a low-gloss powder coating composition. There is also a need for novel fluidization improver compositions that can be combined with powdered polymer compositions, and especially with powdered polymer compositions with a small particle size to improve the performance of the polymer powder.

BRIEF DESCRIPTION OF THE INVENTION This invention is a powder coating composition that includes at least one solid, a particulate fluidization enhancer that improves the performance of the pulverized polymer. This invention is also a powder coating composition that includes a fluidization improver which reduces the gloss of the cured polymer film. Furthermore, this invention is a powder coating composition that includes a gloss reducing agent that releases gas during the curing step to reduce the gloss of a cured polymer film layer. Yet another aspect of the invention is a polymer composition that cures to give a thin uniform finish. In one embodiment, this invention is a powder coating composition. The powder coating composition comprises at least one pulverized polymer, and at least one metal oxide having a average particle size of less than about 25 microns In another embodiment, this invention is a powder coating composition. The composition comprises from about 99.5 to about 99.9% pulverized polymer, and from about 0.1 to about 0.5% by weight of a fuming silica having an average particle size of less than 10 microns which has been modified with hexamethylenediysplassane. In yet another embodiment, this invention is a powder coating composition that includes at least one pulverized polymer and the non-deamonised product of the mixture of particles of at least one metal oxide and hexamethyldisilasan.

DESCRIPTION OF THE FIGURES Figures 1-8 are evaluations of Scanning Electron Microscopy (EEM) of two powder coatings each of which has been combined with: (1) no additive, ie, virgin material; (2) Composition 1 - is a fumed silica with a surface area of 120 m2 / g that has not been subjected to crushing; (3) Composition 2 - a fumed silica partially treated with dimethyldichlorosilane having a surface area of 120 m / g that has not undergone crushing; and (4) Composition 3 - a reaction product milled to fuming silica jet having a surface area of 200 m2 / g and about 5.0% by weight of HMDZ and 4.0% by weight of water, where the fuming silica has a size of average particle of approximately 10 microns. In the Figures: Figure 1 is a photograph of MEE of a virgin polyester powdered polymer manufactured by Tiger-Drylac®; Figure 2 is a photograph of MEE of a powdered polyester polymer described in Figure 1 coated with Composition 1; Figure 3 is a photograph of MEE of a powdered polyester polymer described in Figure 1 coated with Composition 2, Figure 4 is a photograph of MEE of a pulverized polymer of polyester described in Figure 1 coated with Composition 3, Figure 5 is a photograph of MEE of a mixture of virgin polyester hybrid powdered polymer and epoxy manufactured by Tiger-Drylac; Figure 6 is a photograph of MEE of the virgin hybrid powdered polymer described in Figure 5 which has been coated with Composition 1; Figure 7 is a photograph of MEE of the virgin hybrid powdered polymer described in Figure 5 which has been coated with Composition 2; and Figure 8 is an MEE photograph of the virgin hybrid powdered polymer described in Figure 5 which has been coated with Composition 3. Figures 1 and 5 show uncoated virgin powdered polymers. Figures 2, 3, 6, and 7 each show that the distribution of agglomerated non-comminuted fuming silica through a powder coating with a conventional particle size. { 30-40 microns psd) is only somewhat uniform, with a tendency to observe as silica concentrates in an area and larger distribution areas insufficient In contrast, Figures 4 and 8 show that a fuzzy silica fluidization enhancer of reduced size it is able to distribute evenly over the entire surface of the polymer particle thus promoting the fluidization of the polymer powder even at very low loading levels.

DESCRIPTION OF CURRENT MODALITY The present invention relates to powder coating compositions that include a novel fluidization improver, a reducing agent of the novel brightness or both. The fluidization improvers useful in the composition of this invention promote the efficient fluidization of pulverized polymers of all particle sizes. The novel brightness reducing agent reduces the brightness of cured films prepared using pulverized polymer coating compositions. The powder coating composition of this invention includes at least one polymer powder. Powdered polymers useful in the composition of this invention include any spray polymers that are useful in electrostatic spray coating techniques. Non-limiting examples of useful pulverized polymers include, but are not limited to, carboxy-functional polyester reams, functional acrylic resins, epoxides, polyurethanes, polyolefms, PTFE, nylons, copolymers, and mixtures thereof. In addition, examples of powder coating compositions are described in U.S. Patent Nos. 5,461,089, 5,229,460 and 4,122,060, each of which is incorporated herein by reference.

The powder coating compositions of this invention will include from about 90.0 to about 99.9% by weight of at least one pulverized polymer, and preferably from about 98. 0 to about 99 95% by weight of a polymer powder. The term "pulverized polymer" as used herein refers to a single powdered polymer, to mixtures of pulverized polymers, to copolymers, and to pulverized polymers that include, additives, which are useful in powder coating compositions. The additives that can be incorporated in the "powdered polymer" include, for example, we propose only, additives that reduce trapped air or volatile compounds, catalysts to promote the polymerization reaction, stabilizers, pigments and dyes. Each of these "powdered polymers" are also commonly known as powder coatings and powder coating formulations. Although it is possible to cure or crosslink the pulverized polymer composition without the use of a catalyst, it is usually desirable to employ a catalyst to assist the crosslinking reaction. Both the fluidization-improving agents and the gloss reducers useful in the pulverized coating compositions of this invention include particulate metal oxides. The metal oxides which are useful in the present invention are selected from the group of silica, alumina, seria, germania, titania, circoma, zinc oxide and mixtures thereof. The Useful metal oxides can be found in nature, or they can be manufactured. In addition, metal oxides can be a mixed or co-produced product that contains two or more types of metal oxides. The metal oxide can be produced using techniques known to those skilled in the art. For example, the production of fuming metal oxide is a well-documented process which involves the hydrolysis of a suitable feed vapor (such as silicon tetrachloride for fuming silica) into a hydrogen and oxygen flame. the combustion process, the size of which is varied through the parameters of the process. These molten particles, commonly known as primary particles, fuse with others, experiencing collisions at their contact points to form chain-like, branched, three-dimensional particles. Preferably, the metal oxides are precipitated, evaporated, co-punched, or co-evaporated or gel-processed materials, for example, aerogels, silica gels, xerogels, and the like.

It is considered that the formation of metal oxide particles is irreversible as a result of the fusion between the primary particles. During cooling and harvesting, the particles experience additional collisions that can result in some mechanical entanglement to form agglomerates. It is thought that these agglomerates are held loosely together by van der Waals forces and can be reversed, ie de-agglomerated, with appropriate dispersion in suitable media. The manufacture of gel-based metal oxide materials, for example aerogels, xerogels, hydrogels and other gels, is well known to those skilled in the art and can be effected using conventional techniques, for example, US Patent No. 3,652,214 of Aboutboul. et al., U.S. Patent No. 5,270,027 to Balducci, et al., U.S. Patent No. 2,188,007 to Kistler, and as described in the article by Heley, et al., entitled "Fine Density Silica Powders Prepared by Supercic Drying of Silicon Tetrachloride Derived Gels ", Journal of Non-Crystalline Solids, 186, 30-36 (1995), the descriptions of which are incorporated herein by reference in their entirety. The size of the primary spherical particles comprising the metal oxide particles determines the surface area. The surface area of the metal oxides can be measured by the adsorption method of nitrogen from S. Brunauer, P.H. Emmet, and I. Teller, J. Am. Chemical Society, Volume 60, Pages 309 (1938) and commonly known as BET. Typically the BET values for the metal oxides range from 40 m2 / g to approximately 1000 m2 / g, preferably from 50 m2 / g to approximately 400 m2 / g. Although many commercially available metal oxides are suitable for use as the inert carrier according to this invention, it is preferred that the metal oxide be silica. The silica used should have a surface area of about 25 m2 / g to about 400 m2 / g and preferably about 150 m2 / g to about 350 m2 / g. In particular, fumed silica CAB-O-SIL® having a surface area of between about 50 m2 / g to about 350 m2 / g, available from Cab-O-Sil Division of Cabot Corporation, Tuscola, IL, is a silica preferred If the metal oxides used as fluidization improvers are manufactured as aggregates, the aggregate metal oxides are preferably at least partially reduced in size which means that the average particle size of the metal oxide is reduced by minus 25% as a result of a crushing process. It is preferred more that the useful metal oxide has an average particle size which is reduced by trituration by at least 50%. In addition, the fluidization improver may consist of particles at least partially reduced in size from a single metal oxide compound or may be a partial mixture of several metal oxide compounds. The fluidization enhancer of metal should also have an average particle size that is significantly less than the particle size of the polymer powder. Significantly smaller, it means that the particle size should be less than or equal to one sixth of the average particle size of the pulverized polymer on average, and preferably less than or equal to one tenth of the size. Preferred metal oxide particles useful as fluidization improvers are preferably manufactured so that they have an average particle size of less than about 25 microns. It is preferred that the average particle size of the metal oxide fluidization improver be about 15 microns or less and more preferably less than about 1.0 microns. The term "particle" as used in the term of average particle size refers to primary particles of metal oxides, aggregates of metal oxide particles, and agglomerates of aggregates of metal oxides. The term "metal particle size" refers not to the size of a single particle but to the weighted average of a sample of multiple particles analyzed using a Microtrac X-100 manufactured by Leeds S Northrup Co., St. Petesburg, Florida A most preferred fluidization improver is a fumed silica of at least partially reduced, treated size. Fuming silica particles are typically agglomerated from two or more fumed silica aggregates, some of which are very large. Therefore, size reduction via grinding removes the very large agglomerates and significantly reduces the average particle size of the resulting fuming silica. Metal oxide particles useful as fluidization improvers can, if necessary, be reduced in size by a crushing method known in the art, including methods such as grinding or milling that are employed to produce fuming silica of reduced size. The metal oxide particles can be subjected to trituration using conventional size reduction techniques to reduce and narrow the average particle size of the metal oxide. He Suitable equipment includes, for example, ball mills, grinders, jet mill, pin mills, and the like. It is more preferred that the fuming silica agglomerates be milled in a jet mill to produce a fuming silica of reduced size. When incorporated into a polymer powder composition, the metal oxide fluidization improver reduces the compressibility and increases the apparent bulk density of the resulting powder coating composition, thereby ensuring excellent fluidization and fluidity during life. The ability of powdered polymer compositions that include a fluidization improver to flow freely and predictably has a positive impact on the sufficiency of the transfer of the first path of the resulting powder polymer composition. In addition, the fluidization enhancer promotes the uniform application of the resulting powder polymer composition to a substrate. The role of the fluidization improver of this invention is to modify the flow characteristics of the material of the polymer powder compositions. which is important, this is only partially understood. What is understood, however, is the final result - the composition of the oxidation fluidization improver of The small metal of this invention has a positive influence on the particle-particle interactions of the polymer powder and makes its additions to the advantageous high-performance powder coating formulations. Only a very small amount of the fluidization-enhancer is needed to uniformly coat each pulverized polymer particle-to improve the fluidization of a pulverized polymer. The pulverized coating compositions of this invention will include from about 0.01 to about 3.0% by weight of a metal oxide fluidization improver. More preferably, the polymer powder composition of this invention will include from about 0.05 to about 1.0% by weight, and more preferably from about 0.05 to about 0.5% by weight of the metal oxide fluidization improver. The metal oxide particles useful as fluidization improvers may be unmodified or modified before being combined with a pulverized polymer. The modifying agent can be any compound that is useful in improving the oxidation of metal oxide. The type of agent treated and the level of treatment will vary depending on the sought-after characteristics such as the reduction of hydrophobicity or brightness. Useful modifying agents include, for example, modifying hydrophobic treatment agents such as organopolysiloxanes, organo-xyloxanes, organosiloxanes, organosilanes, halogen-organopolysiloxanes, halogen-organosiloxanes, halogenorga-silanes, such as dimethyldichlorosilane, trimethyl-oxyoctylsilane, hexamethyldisilazane and polymethylsiloxane. The modification of the aggregate of o > Gone metal can be achieved by dry or wet techniques that are well known in the art. For example, a dry treatment method may include stirring or mixing the metal oxide and the modifying agent in a fluid bed reactor. Alternatively, a wet treatment method may include dispersing the metal oxide in a solvent for forming a suspension of metal oxide, and adding the modifying agent to the suspension to thereby modify the surface of the metal oxide with the modifying agent. In addition, a modified metal oxide can be prepared using a batch or continuous process, where the dry metal oxide is in contact with a liquid modifying agent or in the form of steam with sufficient mixing. In another method, the modified metal oxide is maintained for a period of time at a temperature sufficient to modifying the surface properties of the metal oxide and thereby making the hydrophobic modified metal oxide Typically, a temperature range of about 25 ° C to about 200 ° C for a time period of 30 minutes to about 16 hours or More suitable Examples of metal oxide modifying methods are described in U.S. Patent Nos. 5,133,030, 4,307,023, 4,054,689 each of which are incorporated herein by reference The metal oxide fluidization enhancer useful in the compositions of this invention they preferably include a volatilizable modifying agent. The volatilizable modifying agent can be any composition which is capable of being combined by a metal oxide at standard temperatures and pressures and which is at least partially volatilized to form a gas or a vapor when the metal oxide is heated to a temperature above room temperature Steam released reduces the gloss of the cured pulverized polymer Examples of useful volatilizable modifiers are water, ammonia, volatilizable hydrocarbons, gases such as CO, He, and Ar, and compounds that decompose upon heating and / or after the addition of moisture to release gaseous reaction products A more preferred volatilizable modifying agent is hexamethyldisilazane. The volatilizable modifying agent is applied to the metal oxide particles of this invention by methods described above. The optional volatilizable modifying agent should be present in the metal oxide fluidization improver in an amount sufficient to obtain the reduction in brightness of the desired cured polymer. The metal oxide, therefore, will be the product of the reaction of a combined metal oxide with from about 0.05 to about 40.0% by weight of a volatilizable modifier, and preferably combined with from about 0.2 to about 10%. by weight of a volatilizable modifying agent using one of the methods described above. A most preferred fluidization improver composition is fuming silica reduced in size that has been modified with hexamethyldisilazane. It has been found that metal oxide particles are not useful in gloss reducing agents. In this way another separate embodiment of this invention is a pulverized polymer composition that includes a gloss reducing agent which is a product of the reaction of the metal oxide particles, preferably fuming silica and hexamethyldisilazane which has not been deamonised. The metal oxide particles useful in the gloss reducing agent may comprise any of the metal oxides described above. When hexamethyldisilazane is combined with metal oxide particles, such as fumed silica particles, hexamethyldisilazane reacts with the metal oxide in a form that causes the silane portion of hexamethyldisilazane to bind to the metal oxide and release ammonia as a byproduct. of the reaction. At least a portion of the ammonia byproduct remains associated with the metal oxide particles where they remain until the metal oxide particles are heated to a temperature above room temperature, such as at the curing temperatures of the polymer powder. Alternatively, the ammonia byproduct can be released from the metal oxide particle by exposing the surface of the metal oxide particle to water, which releases the ammonia from the metal oxide particle. comprises the reaction product of a metal oxide and hexamethyldisilazane is heated before being combined with a pulverized polymer, much of the ammonia associated with the particle will volatilize to give a reduction of the "de-ammoniated" brightness. A Reducing agent of the deamoneous gloss is less useful than a non-deamonate gloss reducing agent. The preferred brightness reducing agent of this invention comprises the non-stripped reaction product of metal oxide particles and hexamethyldisilazane which has not been treated at a temperature greater than 50 ° C. Such reaction products of the metal oxide particle / hexamethyldisilazane are defined herein as "non-deamped". The preferred gloss reducing agent of this invention, the product of the reaction of the metal oxide particles and hexamethyldisilazane, is preferably the non-deamonised product of the combination of about 0 1 to about 40% by weight of hexamethyldisilazane with from about 60% by weight to about 99 9% by weight. weight of particulate metal oxide. The magnitude of the brightness reduction achieved using the gloss reducing agents of this invention will vary depending on the amount of hexamethyldisilazane associated with the metal oxide particles and the amount by weight of the gloss reducer. incorporated in the polymer powder composition. In addition, the amount of brightness reduction depends on the polymer powder used. Acceptable brightness leaching results are obtained when the powder coating compositions of this invention include from about 0.1 to about 50% by weight of a gloss reducing agent. More preferably, the powder coating compositions will include from about 0.2 to about 2.0% by weight of a gloss reducing agent. The average particle size d «= the metal oxides used in the gloss reducing agent is not critical. It is important, however, that the average particle size of the metal oxide particles is not too large to cause opaqueness due to their size. Therefore, the average particle size of the metal oxide particles used in the agent The brightness reducer should be equal to or smaller in size than the average particle size of the pulverized polymer. More preferably, the average particle size of the corresponding metal oxide particles is less than about 25 microns and preferably less than about 15 microns.

The polymer powder compositions of this invention that include a gloss reducing agent or a fluidization improver can be prepared by several different methods. In one method, the pulverized polymer can be combined with finely divided particulates of a gloss reducing agent or with a fluidization enhancer, or both, to give a powdered polymer composition of this invention. Alternatively, the gloss reducing agent or the fluidization improver may be combined with pieces of polymer after which the powder / pieces mixture is ground to give a heterogeneous, sprayed coating composition comprising the polymer powder and additive. After the grinding step, the resulting pulverized polymer composition can, if desired or required, be screened to remove particles having a particle size greater than a particular value. If, for example, a powder coating product is required, the powdered polymer particles having a particle size greater than about 120 microns are preferably removed. The particle size of the pulverized polymer will depend on the application, but typically the pulverized polymer will have a fluctuating particle size of about 10 to about 90 microns, more preferably about 10 to about 65 microns and more preferably about 10 to about 40 microns. It is preferred that the compounds of this invention are prepared by combining a gloss reducing agent or an enhancer. fluidizing with pieces of polymer and subsequently crushing the mixture in a pulverized polymer composition. The compositions of this invention can be applied to a conductive metal surface by any method known in the art for applying a sprayed polymer composition to a metal surface, for example, using an electrostatic spray apparatus, an ionization chamber, an fluidized bed, or a tpboelectric coating apparatus. The preferred method is a corona spray in which a voltage is applied to the spray gun. The composition can be applied in one step or in several steps to provide a variable polymer powder thickness depending on the desired end use of the coated article. After application of the powder coating composition of this invention to a conductive surface, the coated surface is heated to a sufficient temperature to cure the polymer powder in a coherent coating layer. The curing temperature will vary depending on the type of pulverized polymer used in the composition. Curing temperatures can range from about 100 ° C to as high as about 800 ° C. The powder coated surface should be exposed to curing temperatures for a sufficient time to cure the powder particles in a uniform, substantially continuous coating. Typically, a curing time of about 1 to about 10 minutes or more is necessary to convert the pulverized particles into a substantially continuous uniform coating. It is preferred that the powder coating compositions of this invention be applied to a conductive surface, and subsequently cured to give a cured polymer coating of from about 0 8 (20.32 μm) to about 4 0 mils (101.6 μm) and from preferably from about 0.8 (20.32 μm) to 1.5 mil (38.1 μm). Although the present invention has been described by means of specific embodiments, it will be understood that modifications can be made without departing from the spirit of the invention. It is considered that the scope of invention is not limited by the description of the invention set forth in the specification and the examples, but according to what is defined by the claims EXAMPLE 1 This example describes the method used here to determine the average particle size of the metal oxide shields using a Honeywell Microtrac X-100. To determine the average particle size of the sample, a mixture 1 to 9 was used. Triton X-11 DIH2O (deionized water) to make dispersions of the treated silica sample The deionized water was heated and stirred to facilitate the Triton X-100 solution. 20 ml of the Triton X-100 / DI solution was placed in the solution. a beaker when it was used to dissipate the treated silica and 50 ml of DIH0 solution was placed in a beaker and used to dissipate the untreated silica. 0 5 grams of silica was added to the appropriate beaker and mixed on a stir plate until dispersed in a solution. When the treated silica was being dispersed, 30 ml of DIH2O was added to the sample to bring it to a total volume of the sample. 50 ml Once the sample dispersions were prepared, the samples were added to the the Microtrac X-100 from Honey ell and analyzed to determine the average particle size.

EXAMPLE 2 This example describes the basic method for preparing fuming silica modified with HMDZ. 500 grams of silica was added to a large plastic bag in three or four increments. After each silica increase, an appropriate amount of water was added to give a final desired amount. After all the water is added, the bag is sealed and manually stirred for several minutes. The silica will then either settle overnight. The silica-water mixture was then transferred to another plastic bag in three increments. After each increment was added to the bag, 1/3 of the amount of hexamethyldisilazane was added to the mixture. After all the silica was transferred and the hexamethyldisilazane added, the bag was sealed and manually stirred for several minutes. This mixture was then left to rest overnight. The silica modified with HMDZ used in Examples 3A, 3B and 3H, below, was prepared using 4% by weight of water and 8% of hexamethyldisilazane in the above method. The fumed silicas modified with HMDZ used in Examples 3C, 3F and 3G, are prepared using 8% by weight of water and 10% by weight of hexamethyldisilazane in the above method.

EXAMPLE 3 This example describes the methods for incorporating additives, including fuming silica containing the gloss reducing agents of this invention into commercial polymer powder coating compositions and then curing the powders. Powder coatings and fuming silica were mixed via a double-shell mixer equipped with an enrichment bar. The double-shell mixer was a four-quarter LB-3699 model, made by Patterson-Kelly of East Stroudsburg, PA. The powder-silica coating mixture was applied to a shredded conductor substrate, by means of an IPS Versa-Spray II controller from Nordson (Amhurst, OH) and a hand-held powder spray gun. The coated conductive substrate was baked at 392 ° F (200 ° C) in an Economy class "A" batch oven by Blue M, made by Blue M of Blue Island, IL. The brightness measurements were made using a micro-TRI-gloss reflectometer made by BYK Gardner of Geretsped, Germany. The angle of incidence of the light was 60 degrees. The thickness of the film was generally determined between 1.5 and 2 thousandths of an inch (38.1 and 50.5 μm). Baseline gloss measurements were taken for two powdered polyester compositions for comparison purposes. The polyesters used were manufactured by Tiger-Drylac, Inc, of Austria. The polyesters used and the brightness measurements are as follows: for the TGIC polyester 39/80040 the brightness measurement is 55 with a smooth glossy finish and low orange peel. With the Polyester 39/80010 TGIC, the brightness measurement was 85 with a smooth shiny finish and light orange peel.

Example 3A 0.5% by weight of a gloss reducing agent consisting of fuming silica containing non-demamonted HMDZ having a surface area of 200 m2 / g was combined with 99.5% by weight of Polyester 39/80040 TGIC according to the method described in Example 1 and brightness was evaluated. The resulting measured brightness of 30 corresponds to a brightness reduction of 54.5% compared to the virgin powdered polymer. The finish was medium orange peel with a light texture. The non-demamonised silica brightness reducing agent used in this example was produced by reacting the fumed silica with hexamethyldisilazane according to that described in Example 2.

Example 3B 1.0% by weight of the non-demamused gloss reducing agent prepared according to the method described in Example 3A was combined with 99.0% by weight of Polyester 39/80040 TGIC according to the method described in this example and was evaluated to determine the brightness. The brightness measurement was 0.5, representing a brightness reduction of 99.5% compared to the virgin material. The finished one had a textupzada appearance.

Example 3C The non-deamped gloss reducing agent prepared according to the method of Example 3A was deammonium by transferring the non-desamous silica into a shallow vessel of appropriate size and covered with an aluminum foil. Slots were made in the sheet to allow the gases to escape. The container was placed in an oven with air circulation and heated overnight at 125 C. Once the vessel was removed and cooled, the silica was collected. 1.0% by weight of the fuming silica treated with the resulting deamonated HMDZ was combined with 99.0% by weight of Polyester 39/80040 TGIC according to the method described in Example 3 and evaluated to determine brightness. The resulting gloss measured only 9.1 representing a significant increase in brightness compared to the non-deamped gloss reducing agent.

Example 3D 1.0% by weight of powdered polymer additive consisting of untreated, untreated hydrophilic fuming silica having a surface area of 200 m2 / g and an average size of about 30 microns was combined with 99.0% by weight of Polyester 39/80040 TGIC according to the method described in Example 1 and evaluated to determine brightness. The brightness measurement was 30, representing a reduction of 54.5%. The finish had a very rough surface of poor quality due to the presence of silica particles on the surface.

Example 3E This example used the same pulverized polymer compositions as in Example 3D except that the fumed silica was dried overnight at 110 ° C to remove any volatile compounds, and then tested immediately. This silica exhibited a 0.8% weight loss at drying. The measurement of The resulting brightness was 54.5%, representing a reduction of 0.1%. It is believed that the reason for the significant decrease in brightness of Example 3D is due to the removal of the water from the silica M5 before using this Example. The finish had a very rough surface of poor quality due to the presence of silica particles on the surface.

Example 3F The deamonating gloss reducing agent used in Example 3C was exposed to an environment saturated with ammonia overnight by placing 100 grams of gloss reducing agent in a closed container. 0.5% by weight of the gloss reducing agent post-treated with ammonia was combined with 99.5% Polyester 39/80040 TGIC. The resulting brightness measurement was 38.8, representing a reduction of 54.3% compared to the virgin material. When 1.0% by weight of gloss reducing agent post-treated with ammonia was combined with 99.0% by weight of Polyester 39/80010 TGIC, the resulting gloss was 1.0, representing a brightness reduction of 98.8% of the brightness of the virgin material. When 1.0% by weight of silica treated with ammonia was combined with 99.0% by weight of Polyester 39/80010 TGIC, the The resulting brightness measurement was 1.0, representing a brightness reduction of 98 8%.

Example 3G The deamonated fuming silica prepared according to Example 3C was combined with Polyester 39/80010 TGIC (0.5 wt% to 99.5 wt%). The resulting brightness measurement was 42, representing a reduction of 50.1%. When a mixture of 1.0% by weight / 99.0% by weight was prepared and cured, the resulting brightness measurement was 3.7%, representing a reduction of 85.0%. The finish had a rough surface with a medium to strong orange peel.

Example 3H The non-desamomated silica prepared according to Example 3A was combined with Polyester 39/80010 TGIC (1.0 wt% to 99.0 wt%). The measurement of the brightness of the resulting cured polymer was 5.0, representing a reduction of 99 4%. The finished one had an opaque textured appearance.

EXAMPLE 4 Fuming silica treated with non-desamominated HMDZ from Example 4A was combined with several powdered polymers to evaluate the gloss levels resulting from cured polymers. The cured polymers were combined with a gloss reducing agent, applied, cured and evaluated according to the method set forth in Example 3. The gloss results are reported in Table 1, below.

Table 1 Table 1 (continued) The results show a significant reduction in gloss as a result of the incorporation of an opaque agent consisting of a non-deamoneous mixture of fuming silica with HMDZ in a wide variety of powdered polymers.

EXAMPLE 5 To evaluate the utility of using very small metal oxide particles as the best fluidizing ions in powdered polymer coatings, we evaluate the fluidization efficiency of powdered polymer compositions including fluidization improvers in a simulation of A Production Environment This Example evaluated the stability of the fluidization improver comprising additive over time with respect to breakage during operation, transfer efficiency and mechanical distress requirements.

In each case, a control material without any fluidization improver was included in the evaluations to provide a reference value. The control powder was the pulverized polymer of Polyester 39/80040 TGIC manufactured by Tiger-Drylac, Inc. The fluidization improver used was HMDZ modified jet-milled fumed silica having an average particle size of about 10 microns. The fumed silica was modified with HMDZ before the jet milling according to that described in Example 3A, above. The powdered polymer that included the fluidization improver consisted of 99.0% by weight of powdered polymer and 1.0% by weight of fluidization improver. The powders were sprayed with a Nordson® Versa-Spray II 4 mm flat spray nozzle and a Versa-Spray II powder pack. The spray gun was operated at 100 KV at 10 inches distance (25.4 cm) from the barrel. The powder was extracted from a hopper with a capacity of 25 pounds (11.35 kg). The spray gun removed the powder from the hopper and sprayed the powder back into the hopper. The friction results of the two tests are shown in Tables 2 to 3, below: TABLE 2 The considerable improvement in the stability of the product (minimum reduction in the average particle size and the consistent ratio of particles oversized and undersized) demonstrates the reduction in impact melting that results from the uniform distribution of fumed silicas as they act as a dry lubricant or glide (maintaining interparticle distance) and facilitates the mechanical transfer characteristics of the material. Reduced abrasion during handling, transfer and application minimizes changes in performance characteristics observed in properly modified powder coatings. The relative uniformity of the particle size distribution over the extended recovery and recycling also indicates an ability to spray material at a significantly higher percentage of recovery from dust to virgin powder without the traditional loss of appearance, performance of the application, load characteristics and surface uniformity. In addition, the significant reduction in the generation of fines, filter clogging and other associated mechanical complications that are created are minimized.

EXAMPLE 6 This example evaluates the ability of a fluidization improver of this invention to improve the fluidization efficiency of a variety of commercial powder coating chemicals. Each tested powder coating composition was prepared by combining 0.25% by weight of the HMDZ modified fumed silica fluidization improver described in Example 3A, above, with 99.75% by weight of the pulverized polymer identified in Table 4, below. The compositions were evaluated by placing the composition in a standard fluidizing basket and measuring the reduction in air pressure required to double the height of the powder coating in the basket. Compositions prepared using some pulverized polymers combining 0-25% by weight of non-jet fumed silica having a surface area of 200 m2 / g were reported for comparison purposes.

TABLE 4 (Continuation Table 4) With each pulverized polymer, the addition of a very small amount of fluidization improver significantly improved the efficiency of fluidization. It is noted that in relation to this date, the best method known to the applicant to carry Practices the aforementioned invention, is the conventional for the manufacture of the objects to which it refers.

Claims (2)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property. A powder coating composition, characterized in that it comprises: at least one pulverized polymer; and a metal oxide having an average particle size of at least about 25 microns. 2. The powder coating composition according to claim 1, characterized in that the metal oxide has an average particle size of less than about 15 microns. 3. The powder coating composition according to claim 1, characterized in that the metal oxide is selected from the group including silica, alumina, dinner, germania, titania, zirconia, zinc oxide and mixtures thereof. 4. The powder coating composition according to claim 3, characterized in that the metal oxide is fuming silica. 5. The powder coating composition according to claim 1, characterized in that the metal oxide is present in the composition in a fluctuating amount from about 0.05 to about 3% by weight. 6. The powder coating composition according to claim 1, characterized in that the metal oxide is present in the composition in a fluctuating amount of from about 0.1 to about 0.5% by weight. The powder coating composition according to claim 1, characterized in that the metal oxide includes at least one modifying agent. The powder coating composition according to claim 7, characterized in that the modifying agent is selected from light hydrocarbons, ammonia, water, gases and mixtures thereof 9. The powder coating composition according to claim 1 , characterized in that the metal oxide is treated with a hydrophobic agent. 10. The powder coating composition according to claim 9, characterized in that the hydrophobic agent is selected from the group consisting of: organopolysiloxanes, organosiloxanes, organosiloxanes, organosilanes, halogenorgano-polysiloxanes, halogenorganosiloxanes, halogenorganosilazanes, halogenorganosilanes, and mixtures thereof. 11. The powder coating composition according to claim 10, characterized in that the hydrophobic agent is a dimethyldichlorosilane, trimethoxy octylsilane, hexamethyldisilazane, polydimethylsiloxane and mixtures thereof. 12. A powder coating composition, characterized in that it comprises: from about 99.5% to about 99.9% by weight and at least one pulverized polymer; and from about 0.1 to about 0.5% by weight of the product of the reaction of fuming silica and hexamethyldisilazane having a particle size of less than 10 microns. 13. A powder coating composition according to claim 12, characterized in that the fuming silica further includes a volatilizable agent. 14. A powder coating composition characterized in that it comprises: at least one pulverized polymer; Y the non-deamonised reaction product of at least one metal oxide and hexamethyldisilazane. 15. The powder coating composition according to claim 14, characterized in that the metal oxide has a BET surface area between about 50 m2 / g and about 400 m2 / g. 16. The powder coating composition according to claim 14, characterized in that the metal oxide has an average particle size of between about 0.05 μm to about 200 μm. 17. The powder coating composition according to claim 14, characterized in that the metal oxide is selected from the group including alumina, dinner, germam, silica, titania, zirconia, zinc oxide and mixtures thereof. 18. The powder coating composition according to claim 17, characterized in that the metal oxide is silica. 19. The powder coating composition according to claim 18, characterized in that the silica is fuming silica. The powder coating composition according to claim 14, characterized in that the metal oxide is reacted with about 0.5 to about 40.0% by weight of hexamethyldisilazane. 21. The powder coating composition according to claim 14, characterized in that the non-deamped reaction product of at least one metal oxide and hexamethyldisilazane is present in the composition in an amount ranging from about 0-1 to about 2.0%. in weigh. 22. The powder coating composition according to claim 14, characterized in that the nondemored reaction product of at least one metal oxide and hexamethyldisilazane is present in the composition in an amount ranging from about 0.5 to about 1.0% by weight. 23. A powder coating composition, characterized in that it comprises: from about 98 to about 99 9 weight percent of at least one pulverized polymer; and from about 0 1 to about
2. 2. 0 weight percent of an opacifying agent which is the deamped reaction product of about 80.0 to about 99.9 weight percent fuming silica and about 0.1 to about 20.0 weight percent hexamethyldisilazane.