HK1127509B

HK1127509B - Aqueous dispersions of polymer-enclosed particles, related coating compositions and coated substrates

Info

Publication number: HK1127509B
Application number: HK09105196.2A
Authority: HK
Inventors: J．M．费伦茨; W．D．波尔克; D．L．费勒
Original assignee: Ppg工业俄亥俄公司
Priority date: 2006-01-20
Filing date: 2007-01-10
Publication date: 2013-03-08

Description

Aqueous dispersions of polymer-enclosed particles, related coating compositions and coated substrates

Cross Reference to Related Applications

This application is a continuation-in-part of U.S. patent application serial No. 10/876,031 entitled "aqueous dispersion of particles with nanoparticle phase and coating composition comprising the same," which claims priority to U.S. provisional application serial No. 60/482,167 filed 24/6/2003, both of which are incorporated herein by reference. This application is also filed 3/25/2004 and is entitled "method of preparing powder coating compositions incorporating hardstock to incorporate additives and/or provide dynamic color control"; U.S. patent application serial No. 10/809,595, entitled "thermal polymerization extrusion process for preparing powder coating compositions," filed 3/25/2004; and part of U.S. patent application serial No. 10/809,639, entitled "apparatus for preparing thermosetting powder coating compositions with dynamic control including low pressure injection system," filed on 25/3 of 2004, each of which is incorporated herein by reference.

Technical Field

The present invention relates, inter alia, to aqueous dispersions of polymer-enclosed particles, e.g., nanoparticles, methods of making the aqueous dispersions, polymerizable polymers useful in the methods, powder coating compositions formed from the aqueous dispersions, and substrates at least partially coated with the compositions.

Background

Coating compositions, such as powder coating compositions, typically include colorants and/or filler particles to impart color and/or properties in the resulting coating. Pigment particles tend to have a strong affinity for each other and, unless separated, tend to clump together to form agglomerates. Thus, these agglomerates are typically dispersed in a resinous grind vehicle and optionally a dispersant by grinding or milling using high shear techniques to break up the agglomerates. If nano-sized pigment particles are desired, further grinding is typically required to obtain the desired particle size.

Pigments and fillers are generally composed of solid crystalline particles having a diameter of about 0.02 to 2 microns (i.e., 20 to 2000 nanometers). Agglomeration is a serious problem for nano-sized particulate pigments and filler materials (e.g., carbon black), particularly because these nanoparticles have a relatively large surface area. Thus, acceptable dispersion of these nanoparticles often requires an excessive amount of resinous grind vehicle and/or dispersant to effect de-agglomeration and prevent subsequent re-agglomeration of the nanoparticles.

However, the presence of such high levels of resinous grind vehicle and dispersant in the final coating composition can be detrimental to the resulting coating. For example, high dispersant content is known to contribute to the water sensitivity of the resulting coating. Also, some resinous grind vehicles, such as acrylic grind vehicles, may negatively impact coating properties such as chip resistance and flexibility.

Powder coating compositions for coating various types of substrates are generally required. Such coating compositions can greatly reduce or even eliminate the use of organic solvents commonly used in liquid coating compositions. When the powder coating composition is cured by heating, little if any volatile material is released into the surrounding environment. This is a significant advantage over liquid coating compositions in which organic solvents are volatilized into the surrounding atmosphere when the coating composition is cured by heating.

It would also be desirable to provide an aqueous dispersion of resin-enclosed particles in which re-agglomeration of the particles is minimized and which may be suitable for use in preparing powder coating compositions.

Disclosure of Invention

In certain aspects, the present invention relates to aqueous dispersions comprising polymer-enclosed particles, wherein the polymer-enclosed particles comprise particles enclosed by a brittle polymer. The invention also relates to a powder coating composition comprising the polymer-enclosed particles, a substrate at least partially coated with the powder coating composition, and a substrate at least partially coated with a multi-layer composite coating wherein at least one coating layer is deposited from the powder coating composition.

In other aspects, the invention relates to a method of making an aqueous dispersion of polymer-enclosed particles. The method comprises the following steps: (1) providing a mixture of: (a) particles, (b) a polymerizable ethylenically unsaturated monomer, and (c) a water-dispersible polymerizable dispersant, and (2) polymerizing the ethylenically unsaturated monomer and the polymerizable dispersant to form polymer-enclosed particles comprising a water-dispersible polymer.

In other aspects, the invention relates to methods of making polymer-encapsulated particles. The method comprises the following steps: (1) providing a mixture of: (a) particles, (b) a polymerizable ethylenically unsaturated monomer, and (c) a water-dispersible polymerizable dispersant; (2) polymerizing an ethylenically unsaturated monomer and a polymerizable dispersant to form an aqueous dispersion comprising polymer-enclosed particles comprising a water-dispersible brittle polymer; (3) removing water from the aqueous dispersion to form a solid material comprising polymer-enclosed particles; and (4) breaking the solid material.

In other aspects, the invention relates to a method of preparing a powder coating composition comprising: (1) introducing into an extruder components comprising: (a) an aqueous dispersion of particles of the polymeric peak, and (b) a dry material; (2) blending (a) and (b) in an extruder; (3) devolatilizing the blend to form an extrudate; (3) cooling the extrudate, and (4) grinding the extrudate to the desired particle size.

In still other aspects, the present invention relates to a method of increasing the chroma of a powder coating composition. These methods include including a plurality of polymer-encapsulated nanoparticles having a maximum haze (haze) of 10% in a powder coating composition.

In still other aspects, the present invention relates to a method of matching the color of preselected protective and decorative coatings deposited from a liquid coating composition. These methods include: (a) determining the visible color of the preselected coating by measuring the absorbance or reflectance of the preselected coating; and (b) preparing a powder coating composition comprising a plurality of polymer-encapsulated nanoparticles having a maximum haze of 10%, wherein a coating deposited from the powder coating composition matches the visible color of the preselected coating.

The invention also relates to water dispersible polymerizable polyester polyurethanes comprising terminal ethylenically unsaturated groups. The polyurethane is prepared from reactants comprising: (a) a polyisocyanate, (b) a polyester polyol, (c) a polyamine, (d) a material having an ethylenically unsaturated group and an active hydrogen group, and (e) a material having an acid functional group or anhydride and an active hydrogen group.

Detailed Description

For the purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variations found in their respective testing measurements.

Also, it will be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, all sub-ranges having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

In this application, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. In addition, in this application, the use of "or" means "and/or" unless specifically stated otherwise, although "and/or" may be explicitly used in certain instances.

As previously mentioned, certain embodiments of the present invention are directed to aqueous dispersions of polymer-enclosed particles. The term "dispersion" as used herein refers to a two-phase system in which one phase comprises finely divided particles distributed throughout a second phase which is a continuous phase. The dispersion of the present invention is an oil-in-water emulsion in which the aqueous medium provides the continuous phase of the dispersion in which the polymer-enclosed particles are suspended as the organic phase.

The terms "aqueous," "aqueous phase," "aqueous medium," and the like, as used herein, refer to a medium consisting of water alone or comprising primarily water in combination with another material, such as an inert organic solvent. In certain embodiments, the amount of organic solvent present in the aqueous dispersions of the present invention is less than 20 weight percent, such as less than 10 weight percent, or in some cases less than 5 weight percent, or in still other cases less than 2 weight percent, with weight percent based on the total weight of the dispersion. Non-limiting examples of suitable organic solvents are propylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monobutyl ether, n-butanol, benzyl alcohol, and mineral spirits.

The term "polymer-encapsulated particles" as used herein refers to particles that are at least partially encapsulated by a polymer, i.e., confined within a polymer to an extent sufficient to physically separate the particles from each other in an aqueous dispersion, thereby preventing significant agglomeration of the particles. Of course, it will be understood that the dispersions of the present invention may also include particles that are not polymer-encapsulated particles.

In certain embodiments, the particles encapsulated by the polymer in the aqueous dispersion of the present invention comprise nanoparticles. The term "nanoparticles" as used herein refers to particles having an average particle size of less than 1 micron. In certain embodiments, the nanoparticles used in the present invention have an average particle size of 300 nanometers or less, such as 200 nanometers or less, or in some cases 100 nanometers or less. Thus, in certain embodiments, the aqueous dispersions of the present invention comprise nanoparticles that are polymer-encapsulated and, therefore, do not significantly agglomerate.

For the purposes of the present invention, the average particle size can be measured according to known laser light scattering techniques. For example, the average particle size can be measured using a Horiba model LA900 laser diffraction particle size instrument that uses a helium-neon laser at a wavelength of 633nm to measure the size of the particles and assumes that the particles have a spherical shape, i.e., "particle size" refers to the smallest sphere that will completely encapsulate the particle. The average particle size can also be determined by visually examining an electron micrograph of a transmission electron microscope ("TEM") image of a representative sample of particles, measuring the diameter of the particles in the image, and calculating the average primary particle size of the measured particles based on the magnification of the TEM image. One of ordinary skill in the art will understand how to prepare the TEM image and determine the primary particle size based on magnification. The primary particle size of a particle refers to the smallest diameter sphere that will completely encapsulate the particle. The term "primary particle size" as used herein refers to the size of an individual particle.

The shape (or morphology) of the particles may vary. For example, spherical morphologies (e.g., solid beads, microbeads, or hollow spheres), as well as cubic, platelet, or needle-shaped (elongated or fibrous) particles can generally be used. In addition, the particles may have an internal structure that is hollow, porous, or non-porous, or a combination of any of the foregoing, such as a hollow center with porous or solid walls. For more information on suitable particle characteristics, see H.Katz et al (eds.), Handbook of fillers and Plastics (1987) pages 9-10.

Depending on the desired properties and characteristics of the resulting dispersion and/or coating composition of the invention (e.g., coating hardness, scratch resistance, stability, or color), mixtures of one or more particles having different average particle sizes may be used.

The particles, e.g., nanoparticles, present in the aqueous dispersions of the present invention can be formed from polymeric and/or non-polymeric inorganic materials, polymeric and/or non-polymeric organic materials, composite materials, and mixtures of any of the foregoing. As used herein, "formed from" means open-ended, i.e., "comprising," claim language. Thus, a composition or substance "formed from a list of listed components" is intended to mean a composition that includes at least these listed components and that may further include other non-listed components during the formation of the composition. In addition, the term "polymer" as used herein is meant to include oligomers and includes, without limitation, homopolymers and copolymers.

The term "polymeric inorganic material" as used herein refers to a polymeric material having backbone repeat units based on elements other than carbon. In addition, the term "polymeric organic material" as used herein refers to synthetic polymeric materials, semi-synthetic polymeric materials, and natural polymeric materials, all of which have a carbon-based backbone repeating unit.

The term "organic material" as used herein refers to a carbon-containing compound in which carbon is typically associated with itself and hydrogen and is also typically associated with other elements, and does not include binary compounds such as carbon oxides, carbides, carbon disulfide, and the like; ternary compounds such as metal cyanides, metal carbonyls, phosgene, carbonyl sulfide, and the like; and carbon-containing ionic compounds such as metal carbonates, e.g., calcium carbonate and sodium carbonate.

The term "inorganic material" as used herein refers to any material that is not an organic material.

The term "composite material" as used herein refers to a combination of two or more different materials. Particles formed from composite materials typically have a hardness at their surface that is different from the hardness of the interior of the particle below its surface. More particularly, the surface of the particle may be modified in any manner known in the art including, but not limited to, chemically or physically altering its surface characteristics using techniques known in the art.

For example, the particles may be formed from a primary material that is coated, or encapsulated with one or more secondary materials to form a composite particle having a softer surface. In certain embodiments, particles formed from composite materials may be formed from a primary material that is coated, or encapsulated with a different form of primary material. For more information on particles that can be used in the present invention, see g.wypych, Handbook of Fillers, 2 nd edition (1999), pages 15-202.

As noted above, the particles useful in the present invention may comprise any inorganic material known in the art. Suitable particles may be formed from ceramic materials, metallic materials, and mixtures of any of the foregoing. Non-limiting examples of such ceramic materials can include metal oxides, mixed metal oxides, metal nitrides, metal carbides, metal sulfides, metal silicates, metal borides, metal carbonates, and mixtures of any of the foregoing. One specific non-limiting example of a metal nitride is boron nitride; one specific non-limiting example of a metal oxide is zinc oxide; non-limiting examples of suitable mixed metal oxides are aluminosilicates and magnesium silicates; non-limiting examples of suitable metal sulfides are molybdenum disulfide, tantalum disulfide, tungsten disulfide, and zinc sulfide; non-limiting examples of metal silicates are aluminosilicates and magnesium silicates, such as vermiculite.

In certain embodiments of the invention, the particles comprise an inorganic material selected from the group consisting of: aluminum, barium, bismuth, boron, cadmium, calcium, cesium, cobalt, copper, iron, lanthanum, magnesium, manganese, molybdenum, nitrogen, oxygen, phosphorus, selenium, silicon, silver, sulfur, tin, titanium, tungsten, vanadium, yttrium, zinc, and zirconium, including oxides thereof, nitrides thereof, phosphides thereof, phosphates thereof, selenides thereof, sulfides thereof, sulfates thereof, and mixtures thereof. Suitable non-limiting examples of the foregoing inorganic particles include aluminum oxide, silicon dioxide, titanium oxide, cesium oxide, zirconium oxide, bismuth oxide, magnesium oxide, iron oxide, aluminum silicate, boron carbide, nitrogen-doped titanium oxide, and cadmium selenide.

The particles may comprise a core of, for example: substantially a single inorganic oxide such as silica in colloidal, calcined or amorphous form, alumina or colloidal alumina, titania, iron oxide, cesium oxide, yttrium oxide, colloidal yttrium oxide, zirconia such as colloidal or amorphous zirconia, and mixtures of any of the foregoing; or an inorganic oxide having another inorganic oxide deposited thereon.

Non-polymeric inorganic materials useful in forming particles for use in the present invention may include inorganic materials selected from the group consisting of graphite, metals, oxides, carbides, nitrides, borides, sulfides, silicates, carbonates, sulfates, and hydroxides. A non-limiting example of a useful inorganic oxide is zinc oxide. Non-limiting examples of suitable inorganic sulfides include molybdenum disulfide, tantalum disulfide, tungsten disulfide, and zinc sulfide. Non-limiting examples of useful inorganic silicates include aluminosilicates and magnesium silicates such as vermiculite. Non-limiting examples of suitable metals include molybdenum, platinum, palladium, nickel, aluminum, copper, gold, silver, alloys, and mixtures of any of the foregoing.

In certain embodiments, the particles may be selected from the group consisting of calcined silica, amorphous silica, colloidal silica, alumina, colloidal alumina, titania, iron oxide, cesium oxide, yttrium oxide, colloidal yttrium oxide, zirconium oxide, colloidal zirconium oxide, and mixtures of any of the foregoing. In certain embodiments, the particles comprise colloidal silica. As noted above, these materials may be surface treated or untreated. Other useful particles include, for example, the surface modified silicas described in U.S. Pat. No.5,853,809 at column 6, line 51 to column 8, line 43, which is incorporated herein by reference.

Alternatively, the particles may be formed from a primary material that is coated, or encapsulated with one or more secondary materials to form a composite material having a harder surface. Alternatively, the particles may be formed from a primary material that is coated, clad or encapsulated with a different form of primary material to form a composite material having a harder surface.

In one example and not limiting to the invention, inorganic particles formed from inorganic materials such as silicon carbide or aluminum nitride may be coated with silica, carbonate or nanoclay to form useful composite particles. In another non-limiting example, silane coupling agents with alkyl side chains can interact with the surface of inorganic particles formed from inorganic oxides to provide useful composite particles having a "softer" surface. Other examples include coating, encapsulating, or coating particles formed of non-polymeric or polymeric materials with different non-polymeric or polymeric materials. A specific non-limiting example of such a composite particle is DUALITE^TMA synthetic polymeric particle coated with calcium carbonate commercially available from Pierce and stevens Corporation of Buffalo, NY.

In certain embodiments, the particles used in the present invention have a layered structure. Particles with a layered structure are composed of sheets or slabs of hexagonally arranged atoms with strong bonds within the sheets and weak van der waals bonds between the sheets, which provide low shear strength between the sheets. A non-limiting example of a layered structure is a rheologically crystalline structure. Inorganic solid particles having a layered fullerene (i.e., planocopheral) structure may also be used in the present invention.

Non-limiting examples of suitable materials having a layered structure include boron nitride, graphite, metal dichalcogenides, mica, talc, gypsum, kaolin, calcite, cadmium iodide, silver sulfide, and mixtures thereof. Suitable metal dichalcogenides include molybdenum disulfide, molybdenum diselenide, tantalum disulfide, tantalum diselenide, tungsten disulfide, tungsten diselenide, and mixtures thereof.

The particles may be formed from a non-polymeric organic material. Non-limiting examples of non-polymeric organic materials that can be used in the present invention include, but are not limited to, stearates (e.g., zinc stearate and aluminum stearate), diamond, carbon black, and stearamide.

The particles used in the present invention may be formed from inorganic polymeric materials. Non-limiting examples of useful inorganic polymeric materials include polyphosphazenes, polysilanes, polysiloxanes, polygeremanes, polymeric sulfur, polymeric selenium, silicones, and mixtures of any of the foregoing. A specific non-limiting example of a particle formed of an inorganic polymeric material suitable for use in the present invention is Tospearl, which is a particle formed of a cross-linked silicone and is commercially available from Toshiba Silicones Company, ltd.

The particles may be formed from synthetic inorganic polymeric materials. Non-limiting examples of suitable inorganic polymeric materials include, but are not limited to, thermoset materials and thermoplastic materials. Non-limiting examples of suitable thermoplastic materials include thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polycarbonates, polyolefins such as polyethylene, polypropylene, and polyisobutylene, acrylic polymers such as copolymers of styrene and acrylic monomers and methacrylate-containing polymers, polyamides, thermoplastic polyurethanes, vinyl polymers, and mixtures of any of the foregoing.

Non-limiting examples of suitable thermoset materials include thermoset polyesters, vinyl esters, epoxy materials, phenolic resins, aminoplasts, thermoset polyurethanes, and mixtures of any of the foregoing. A specific non-limiting example of a synthetic polymeric particle formed from an epoxy material is an epoxy microgel particle.

The particles may also be hollow particles formed from materials selected from polymeric and non-polymeric inorganic materials, polymeric and non-polymeric organic materials, composite materials, and mixtures of any of the foregoing. Non-limiting examples of suitable materials from which the hollow particles may be formed are described above.

In certain embodiments, the particles used in the present invention comprise organic pigments such AS azo compounds (monoazo, disazo, β -naphthol, naphthol AS salt type azo pigment lakes, benzimidazolone, disazo condensates, isoindolinones, isoindolines), and polycyclic (phthalocyanine, quinacridone, perylene, perinone, diketopyrrolopyrrole, thioindigo, anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine, triarylcarbonium, quinophthalone (quinophtalone)) pigments, and mixtures of any of the foregoing. In certain embodiments, the organic material is selected from perylenes, quinacridones, phthalocyanines, isoindolines, dioxazines (i.e., triphendioxazines), 1, 4-diketopyrrolopyrroles, anthrapyrimidines, anthanthrones, flavanthrones, indanthrones, perinones, pyranthrones, thioindigo, 4 '-diamino-1, 1' -dianthraquinonyl, and substituted derivatives thereof and mixtures thereof.

Perylene dyes used in the practice of the present invention may be unsubstituted or substituted. The substituted perylene may be substituted, for example, on the imide nitrogen atom, and the substituents may include alkyl groups of 1 to 10 carbon atoms, alkoxy groups of 1 to 10 carbon atoms, and halogens (e.g., chlorine), or combinations thereof. The substituted perylene may contain more than one of any of the substituents. Preference is given to the diimides and dianhydrides of perylene-3, 4,9, 10-tetracarboxylic acid. Crude perylene may be prepared by methods known in the art.

Phthalocyanine dyes, especially metal phthalocyanines, can be used. Although copper phthalocyanine is more readily available, other metal-containing phthalocyanine dyes, such as those based on zinc, cobalt, iron, nickel and some other metals, can also be used. Metal-free phthalocyanines are also suitable. The phthalocyanine pigment can be unsubstituted or partially substituted, for example, with one or more alkyl groups (having 1-10 carbon atoms), alkoxy groups (having 1-10 carbon atoms), halogens such as chlorine, or other substituents typical of phthalocyanine pigments. The phthalocyanine may be prepared by any of several methods known in the art. They are generally prepared by reacting phthalic anhydride, phthalonitrile or derivatives thereof with a metal donor, a nitrogen donor (for example urea or phthalonitrile itself) and optionally a catalyst, preferably in an organic solvent.

Quinacridone pigments used herein include unsubstituted or substituted quinacridones (e.g., having one or more alkyl, alkoxy, halogen such as chlorine, or other typical substituents of quinacridone pigments) and are suitable for use in the practice of the present invention. Quinacridone pigments can be prepared by any of several methods known in the art, but are preferably prepared by thermally ring-closing various 2, 5-dianilinophenedicarboxylic acid precursors in the presence of polyphosphoric acid.

Isoindoline pigments, which may optionally be substituted symmetrically or asymmetrically, also suitable for use in the practice of the present invention, can be prepared by methods known in the art. Suitable isoindoline pigment-pigment yellow 139 is a symmetric adduct of iminoisoindoline and barbituric acid precursors. Dioxazine pigments (i.e., triphendioxazines) are also suitable organic pigments and may be prepared by methods known in the art.

Mixtures of any of the foregoing inorganic particles and/or organic particles may also be used.

The particles useful in the aqueous dispersions of the present invention may include color-imparting particles. By the term "color-imparting particles" is meant particles that absorb significantly more of some wavelengths of visible light, i.e. wavelengths of 400-700nm, than other wavelengths of the visible light region.

The above particles may be formed into nanoparticles, if desired. In certain embodiments, the nanoparticles are formed in situ during the formation of the aqueous dispersion of polymer-enclosed particles as described in more detail below. However, in other embodiments, the nanoparticles are formed prior to their incorporation into the aqueous dispersion. In these embodiments, the nanoparticles may be formed by any of a number of various methods known in the art. For example, nanoparticles may be prepared by pulverizing and classifying a dried particulate material. For example, bulk pigments such as any of the inorganic or organic pigments described above may be milled with milling media having a particle size of less than 0.5 millimeters (mm), or less than 0.3mm, or less than 0.1 mm. The pigment particles are typically milled to a nanometer particle size in a high energy mill in one or more solvents (water, organic solvents, or a mixture of the two), optionally in the presence of a polymeric milling carrier. If desired, the dispersant may include, for example (if in an organic solvent), SOLSPERSE available from Lubrizol Corporation32000 or 32500, or (if in water) SOLSPERSE also available from Lubrizol Corporation27000. Other suitable methods of preparing nanoparticles include crystallization, precipitation, gas phase condensation, and chemical attrition (i.e., partial dissolution).

In certain embodiments, the color-imparting particles used in the polymer encapsulation of the present invention comprise, for example, a polymer selected from the group consisting of acrylic polymers, polyurethane polymers, polyester polymers, polyether polymers, silicon-based polymers, copolymers thereof, and mixtures thereof. These polymers may be prepared by any suitable method known to those skilled in the art to which the present invention pertains. Suitable polymers include those disclosed in the following patent applications: U.S. patent application Ser. No. 10/876,031, [0061] - [0076] -the cited portion of which is incorporated herein by reference, and U.S. patent application publication No. 2005/0287348A1, [0042] - [0044] -the cited portion of which is incorporated herein by reference.

However, as noted in other embodiments, the aqueous dispersions of the present invention comprise particles encapsulated by a friable polymer. The term "brittle polymer" as used herein refers to a polymer that readily crumbles under ambient conditions. That is, when the liquid material is removed from the dispersion, the resulting solid material is readily broken into small fragments or pieces, such as would be suitable as a dry feed to an extruder to produce a powder coating composition. On the other hand, when the liquid material is removed from the dispersion, the film-forming polymer will form a self-supporting continuous film on at least the horizontal surface of the substrate. The term "ambient conditions" as used herein refers to ambient conditions, which are typically about 1 atmosphere, 50% relative humidity and 25 ℃.

In certain embodiments of the present invention, the brittle polymer comprises the reaction product of (i) a polymerizable polyester polyurethane and (ii) an ethylenically unsaturated monomer. The term "polymerizable polyester polyurethane" as used herein refers to polymers that: which comprises a plurality of ester unitsAnd a plurality of urethane unitsHaving functional groups capable of polymerizing to form larger polymers, and wherein R¹Is an alkyl, cycloalkyl or oxyalkyl moiety, R²Is an alkyl or cycloalkyl moiety, and R³Is an alkyl, cycloalkyl, aralkyl or aromatic moiety. In certain embodiments, the polymerizable polyester polyurethane comprises a polyester polyurethane having terminal ethylenic unsaturation. The phrase "terminal ethylenic unsaturation" as used herein means that at least some of the terminals of the polyester polyurethane comprise a functional group containing ethylenic unsaturation. Such polyester polyurethanes may also, but need not necessarily, include internal ethylenic unsaturation. Thus, in some casesIn an embodiment, the aqueous dispersion of the present invention comprises a polymerizable polyester polyurethane having terminal ethylenic unsaturation prepared from reactants comprising: (a) a polyisocyanate, (b) a polyester polyol, and (c) a material containing an ethylenically unsaturated group and an active hydrogen group. In certain embodiments, the polymerizable polyester polyurethane used in the aqueous dispersion of the present invention is formed from reactants further comprising: (d) a polyamine and/or (e) a material comprising an acid functional group or anhydride and a functional group that reacts with an isocyanate or hydroxyl group. The term "active hydrogen group" as used herein refers to a functional group that reacts with isocyanate as determined by the Zerewitnoff test as described in juournal OF THE AMERICAN chemistry nature, volume 49, page 3181 (1927).

Suitable polyisocyanates for use in preparing the polymerizable polyester polyurethane include aliphatic, cycloaliphatic, araliphatic and/or aromatic isocyanates, and mixtures thereof.

Examples of useful aliphatic and cycloaliphatic polyisocyanates include: 4, 4-methylenebisdicyclohexyldiisocyanate (hydrogenated MDI), Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), methylenebis (cyclohexyl isocyanate), trimethylhexamethylene diisocyanate (TMDI), m-tetramethylxylylene diisocyanate (TMXDI), and cyclohexylene diisocyanate (hydrogenated XDI). Other aliphatic polyisocyanates include isocyanurates of IPDI and HDI.

Examples of suitable aromatic polyisocyanates include: tolylene Diisocyanate (TDI) (i.e., 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, or a mixture thereof), diphenylmethane-4, 4-diisocyanate (MDI), naphthalene-1, 5-diisocyanate (NDI), 3-dimethyl-4, 4-biphenyldiisocyanate (TODI), crude TDI (i.e., a mixture of TDI and its oligomers), polymethylene polyphenyl polyisocyanate, crude MDI (i.e., a mixture of MDI and its oligomers), Xylylene Diisocyanate (XDI), and phenylene diisocyanate.

Polyisocyanate derivatives prepared from hexamethylene diisocyanate, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane ("IPDI"), including the isocyanurate thereof, and/or 4, 4' -bis (isocyanatocyclohexyl) methane are suitable.

In certain embodiments, the amount of polyisocyanate used to prepare the polymerizable polyester polyurethane is from 20 to 70 weight percent, such as from 30 to 60 weight percent or in some cases from 40 to 50 weight percent, with weight percent being based on the total weight of resin solids used to prepare the polymerizable polyester polyurethane.

Polyester polyols suitable for use in preparing polymerizable polyester polyurethanes can be prepared by any suitable method, for example using an unsaturated dicarboxylic acid or anhydride thereof (or a combination of acid and anhydride) and a polyol, or by ring opening of caprolactone, such as epsilon caprolactone. Such polyester polyols of various molecular weights are commercially available. Aliphatic dicarboxylic acids suitable for use in preparing the polyesters include those containing from 4 to 14, such as from 6 to 10 inclusive, carbon atoms. Examples of such dicarboxylic acids include: succinic, glutaric, adipic, pimelic, suberic, azelaic and sebacic acids. The corresponding anhydrides may also be used. Generally, adipic acid and azelaic acid are used.

Polyols useful in preparing polyester polyols suitable for use in preparing the polymerizable polyester polyurethanes used in certain embodiments of the present invention include, without limitation, aliphatic alcohols containing at least 2 hydroxyl groups, such as linear diols containing from 2 to 15, such as from 4 to 8 inclusive, carbon atoms. In certain embodiments, the diol contains a hydroxyl group at a terminal position. Non-limiting examples of such polyols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1, 3-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 2-dimethylpropanediol, 1, 5-hexanediol, 1, 7-heptanediol, 1, 8-octanediol, 1, 10-decanediol, and mixtures of these polyols.

In certain embodiments, the polyester polyols are prepared by reacting a dicarboxylic acid (or anhydride thereof) with a polyol in the presence of an esterification catalyst, such as an organotin catalyst. The amount of acid and alcohol used will vary and depend on the desired molecular weight of the polyester. The hydroxyl-terminated polyester is obtained by using an excess of alcohol, thereby obtaining a linear chain containing predominantly terminal hydroxyl groups. Examples of polyesters include: poly (1, 4-butylene adipate), poly (1, 4-butylene succinate), poly (1, 4-butylene glutarate), poly (1, 4-butylene pimelate), poly (1, 4-butylene suberate), poly (1, 4-butylene azelate), poly (1, 4-butylene sebacate), and poly (epsilon-caprolactone). In certain embodiments, the polyester polyol used to prepare the brittle polymerizable polyester polyurethane used in the aqueous dispersions of the present invention has a weight average molecular weight of 500-.

In certain embodiments, the amount of polyester polyol used to prepare the polymerizable polyester polyurethane included in certain embodiments of the present invention is from 10 to 60 weight percent, such as from 20 to 50 weight percent or in some cases from 30 to 40 weight percent, with weight percent based on the total weight of resin solids used to prepare the polymerizable polyester polyurethane.

As noted, the polymerizable polyester polyurethane present in certain embodiments of the aqueous dispersions of the present invention is formed from a material comprising ethylenically unsaturated groups and active hydrogen groups. Suitable ethylenically unsaturated groups include, for example, acrylates, methacrylates, allyl urethanes, and allyl carbonates. The acrylate and methacrylate functional groups may be represented by the formula CH₂＝C(R₁) -C (O) O-represents, wherein R₁Is hydrogen or methyl. The allyl carbamate and the carbonate may each be represented by the formula CH₂＝CH-CH₂-NH-C (O) O-and CH₂＝CH-CH₂-O- (O) O-represents.

In certain embodiments, the ethylenically unsaturated group and active hydrogen group-containing material used to prepare the polymerizable polyester polyurethane comprises a hydroxyalkyl (meth) acrylate. Suitable hydroxyalkyl (meth) acrylates include those having from 1 to 18 carbon atoms in the alkyl group, which alkyl group is substituted or unsubstituted. Specific non-limiting examples of such materials include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, hexane-1, 6-diol mono (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and mixtures thereof. The term "(meth) acrylate" as used herein is intended to include both acrylates and methacrylates.

In certain embodiments, the amount of material comprising ethylenically unsaturated groups and active hydrogen groups used to prepare the polymerizable polyester polyurethane is from 1 to 12 weight percent, such as from 2 to 8 weight percent or in some cases from 4 to 6 weight percent, with weight percent being based on the total weight of resin solids used to prepare the polymerizable polyester polyurethane.

As previously noted, in certain embodiments, the polymerizable polyester polyurethane present in certain embodiments of the aqueous dispersions of the present invention is formed from a polyamine. Useful polyamines include, but are not limited to, primary or secondary diamines or polyamines in which the groups attached to the nitrogen atoms can be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic-substituted aliphatic, aliphatic-substituted aromatic, and heterocyclic. Exemplary suitable aliphatic and cycloaliphatic diamines include 1, 2-ethylenediamine, 1, 2-propylenediamine, 1, 8-octanediamine, isophoronediamine, propane-2, 2-cyclohexylamine, and the like. Exemplary suitable aromatic diamines include phenylenediamine and tolylenediamine, such as o-phenylenediamine and p-phenylenediamine. These and other suitable polyamines are described in detail in U.S. Pat. No.4,046,729 at column 6, line 61-column 7, line 26, the incorporated by reference herein.

In certain embodiments, the amount of polyamine used to prepare the polymerizable polyester polyurethane is from 0.5 to 5 weight percent, such as from 1 to 4 weight percent or, in some cases, from 2 to 3 weight percent, with weight percent being based on the total weight of resin solids used to prepare the polymerizable polyester polyurethane.

As previously noted, in certain embodiments, the polymerizable polyester polyurethane present in certain embodiments of the aqueous dispersions of the present invention is formed from a material comprising an acid functional group or anhydride and a functional group that reacts with the isocyanate or hydroxyl groups of the other components from which the polyurethane material is formed. Useful acid-functional materials include compounds having the following structure:

X-Y-Z

wherein X is OH, SH, NH₂Or NHR, and R includes alkyl, aryl, cycloalkyl, substituted alkyl, substituted aryl, and substituted cycloalkyl, and mixtures thereof; y comprises alkyl, aryl, cycloalkyl, substituted alkyl, substituted aryl and substituted cycloalkyl, and mixtures thereof; and Z comprises OSO₃H、COOH、OPO₃H₂、SO₂OH, POOH and PO₃H₂And mixtures thereof.

Examples of suitable acid functional materials include hydroxypentanoic acid, 3-hydroxybutyric acid, D, L-tropic acid, D, L-hydroxymalonic acid, D, L-malic acid, citric acid, thioglycolic acid, glycolic acid, amino acids, 12-hydroxystearic acid, dimethylolpropionic acid, mercaptopropionic acid, mercaptobutyric acid, mercaptosuccinic acid, and mixtures thereof.

Useful anhydrides include aliphatic, cycloaliphatic, olefinic, cyclic olefinic and aromatic anhydrides. Substituted aliphatic and aromatic anhydrides are also useful as long as the substituents do not adversely affect the reactivity of the anhydride or the properties of the resulting polyurethane. Examples of the substituent include chlorine, alkyl and alkoxy. Examples of anhydrides include succinic anhydride, methylsuccinic anhydride, dodecenylsuccinic anhydride, octadecenylsuccinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, alkyl hexahydrophthalic anhydrides such as methylhexahydrophthalic anhydride, tetrachlorophthalic anhydride, endo-methylenetetrahydrophthalic anhydride, trimesic anhydride, chlorendic anhydride, itaconic anhydride, citraconic anhydride, maleic anhydride, and mixtures thereof.

In certain embodiments, the acid functional material or anhydride provides a polymerizable polyester polyurethane having anionic ionizable groups that can be ionized for dissolving the polymer in water. Thus, in certain embodiments, the invention resides inThe polymerizable polyester polyurethane in certain embodiments of the aqueous dispersion is water dispersible. The term "water-dispersible" as used herein means that the material can be dispersed in water without the aid or use of a surfactant. The term "ionizable" as used herein refers to a group that is capable of becoming ionic, i.e., capable of dissociating into ions or becoming charged. The acid may be neutralized with a base to form a carboxylate group. Examples of anionic groups include-OSO₃ ^-、-COO^-、-OPO₃ ^-、-SO₂O、-POO^-And PO₃ ^-。

In certain embodiments, the amount of material comprising acid functional groups or anhydrides and functional groups reactive with isocyanate or hydroxyl groups used to prepare the polymerizable polyester polyurethane is from 5 to 20 weight percent, such as from 7 to 15 weight percent or in some cases from 8 to 12 weight percent, the weight percent being based on the total weight of resin solids used to prepare the polymerizable polyester polyurethane.

As noted, in certain embodiments, the acid groups may be neutralized with a base. The degree of neutralization can be from about 0.6 to about 1.1, such as from 0.4 to 0.9 or in some cases from 0.8 to 1.0, of the total theoretical neutralization equivalents. Suitable neutralizing agents include inorganic and organic bases such as sodium hydroxide, potassium hydroxide, ammonia, amines, alcohol amines having at least one primary, secondary or tertiary amino group and at least one hydroxyl group. Suitable amines include alkanolamines such as monoethanolamine, diethanolamine, dimethylaminoethanol, diisopropanolamine and the like.

The polymerizable polyester polyurethane used in certain embodiments of the aqueous dispersions of the present invention may be formed by combining the above components in any suitable arrangement. For example, polymerizable polyester polyurethanes can be prepared by solution polymerization techniques understood by those skilled in the art to which the present invention pertains.

As will be apparent from the foregoing description, the polymerizable polyester polyurethane present in certain embodiments of the present invention may be nonionic, anionic or cationic. In certain embodiments, the polymerizable polyester polyurethane will have a weight average molecular weight of less than 150,000g/mol, such as 10,000-100,000g/mol, or in some cases 40,000-80,000 g/mol. The molecular weight of the polyurethanes and other polymeric materials used in the practice of the present invention is measured by gel permeation chromatography using polystyrene standards.

As will be apparent from the foregoing description, the present invention also relates to a water-dispersible polymerizable polyester polyurethane comprising terminal ethylenically unsaturated groups and formed from components comprising: (a) a polyisocyanate, (b) a polyester polyol, (c) a polyamine, (d) a material having an ethylenically unsaturated group and an active hydrogen group, and (e) a material having an acid functional group and an active hydrogen group. In certain embodiments, the present invention relates to a water dispersible polymerizable polyester polyurethane comprising terminal ethylenically unsaturated groups formed from components comprising: (a) a polyisocyanate present in an amount of 20 to 70 wt%, (b) a polyester polyol present in an amount of 10 to 60 wt%, (c) a polyamine present in an amount of 0.5 to 5 wt%, (d) a material having ethylenically unsaturated groups and active hydrogen groups present in an amount of 1 to 12 wt%, and (e) a material having acid functional groups or anhydrides and active hydrogen groups present in an amount of 5 to 20 wt%.

As previously noted, in certain embodiments of the aqueous dispersions of the present invention, a friable polymer is present comprising the reaction product of (i) a polymerizable polyester polyurethane, such as described above, and (ii) an ethylenically unsaturated monomer. Suitable ethylenically unsaturated monomers include any polymerizable ethylenically unsaturated monomer, including vinyl monomers known in the art. Non-limiting examples of useful ethylenically unsaturated carboxylic acid functional group containing monomers include (meth) acrylic acid, beta-carboxy ethyl acrylate, acryloxypropionic acid, crotonic acid, fumaric acid, monoalkyl esters of fumaric acid, maleic acid, monoalkyl esters of maleic acid, itaconic acid, monoalkyl esters of itaconic acid, and mixtures thereof. As used herein, "(meth) acrylic" and terms derived therefrom are intended to include both acrylic and methacrylic.

Non-limiting examples of other useful ethylenically unsaturated monomers that do not contain a carboxylic acid functional group include alkyl esters of (meth) acrylic acid, such as ethyl (meth) acrylate, methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, isobornyl (meth) acrylate, lauryl (meth) acrylate, and ethylene glycol di (meth) acrylate; vinyl aromatics such as styrene and vinyl toluene; (meth) acrylamides such as N-butoxymethylacrylamide; acrylonitrile; dialkyl esters of maleic and fumaric acids; vinyl and vinylidene halides; vinyl acetate; a vinyl ether; allyl ether; allyl alcohol; derivatives thereof and mixtures thereof.

Ethylenically unsaturated monomers can also include ethylenically unsaturated beta-hydroxy ester functional monomers, such as those resulting from the reaction of ethylenically unsaturated acid functional monomers, e.g., monocarboxylic acids such as acrylic acid, and epoxides that do not precipitate during free radical initiated polymerization, with unsaturated acid monomers. Examples of such epoxides are glycidyl ethers and esters. Suitable glycidyl ethers include glycidyl ethers of alcohols and phenols such as butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl ether, and the like.

In certain embodiments, the polymerizable polyester polyurethane and ethylenically unsaturated monomer are polymerized in a ratio of 95: 5-30: 70, e.g. 90: 10-40: 60 or in some cases 80: 20-60: 40 parts by weight are present in the aqueous dispersion of the invention.

Aqueous dispersions comprising the polymer-enclosed particles of the present invention can be prepared by any of a variety of methods, whether or not they comprise a brittle polymer. For example, in certain embodiments, the aqueous dispersions of the present invention are prepared by a process comprising: (A) providing (i) particles, (ii) one or more polymerizable ethylenically unsaturated monomers in an aqueous medium; and/or (iii) a mixture of one or more polymerizable unsaturated monomers and one or more polymers; and/or (iv) a mixture of one or more polymers, and then subjecting the mixture to high stress shear conditions in the presence of an aqueous medium.

These methods are described in detail in U.S. patent application Ser. No. 10/876,031, [0054] - [0090], which is incorporated herein by reference, and U.S. published patent application No. 2005/0287348, [0036] - [0050], the incorporated sections of which are incorporated herein by reference.

However, in other embodiments, the aqueous dispersions of the present invention are prepared by a process comprising: (1) providing a mixture of (i) particles, (ii) a polymerizable ethylenically unsaturated monomer, and (iii) a water-dispersible polymerizable dispersant in an aqueous medium, and (2) polymerizing the ethylenically unsaturated monomer and the polymerizable dispersant to form polymer-enclosed particles comprising a water-dispersible polymer. In these embodiments, the polymerizable dispersant can include any polymerizable material that is water dispersible and when polymerized with ethylenically unsaturated monomers produces polymer-enclosed particles comprising a water dispersible polymer, in some cases a water dispersible brittle polymer. In certain embodiments, the polymerizable dispersant comprises the aforementioned water-dispersible polymerizable polyester polyurethane having terminal ethylenic unsaturation.

In these embodiments, the water-dispersible polymerizable dispersant is capable of dispersing itself and other materials, including ethylenically unsaturated monomers, in an aqueous medium without the need for surfactants and/or high shear conditions. Thus, the foregoing method of preparing an aqueous dispersion of polymer-enclosed particles is particularly suitable for situations where: wherein the use of high stress shear conditions as described in U.S. patent application Ser. Nos. 10/876,031, [0081] - [0084] and U.S. published patent application Ser. No. 2005/0287348, [0046] is not desirable or feasible. Thus, in certain embodiments, the aqueous dispersions of the present invention are prepared by a process that does not include the step of subjecting the mixture of particles, polymerizable ethylenically unsaturated monomer, and water-dispersible polymerizable dispersant to high stress shear conditions.

In addition, the aforementioned inventive process enables the nanoparticles to be formed in situ without the need to form the nanoparticles prior to preparation of the aqueous dispersion. In these methods, particles having an average particle size of 1 micron or greater can form nanoparticles after mixing with the ethylenically unsaturated monomer and the water-dispersible polymerizable dispersant in an aqueous medium (i.e., nanoparticles are formed in situ). In certain embodiments, the nanoparticles are formed by subjecting an aqueous medium to comminution conditions. For example, the particles may be milled with milling media having a particle size of less than 0.5 millimeters, or less than 0.3 millimeters, or in some cases less than 0.1 millimeters. In these embodiments, the particles may be milled to nanoparticle size in a high energy mill in the presence of an aqueous medium, a polymerizable ethylenically unsaturated monomer, and a water-dispersible polymerizable dispersant. Additional dispersants, such as SOLSPERSE 27000 available from Avecia, Inc, may be used if desired.

As noted, the foregoing method of preparing the aqueous dispersion of the present invention comprises the step of free-radically polymerizing an ethylenically unsaturated monomer and a polymerizable dispersant to form polymeric encapsulated particles comprising a water dispersible polymer. In certain embodiments, at least a portion of the polymerization is conducted during the formation of the nanoparticles, if applicable. Free radical initiators may also be used. Water and oil soluble initiators may be used.

Non-limiting examples of suitable water-soluble initiators include ammonium peroxodisulfate, potassium peroxodisulfate, and hydrogen peroxide. Non-limiting examples of oil-soluble initiators include t-butyl hydroperoxide, dilauryl peroxide, and 2, 2' -azobis (isobutyronitrile). In many cases, the reaction is carried out at a temperature of from 20 to 80 ℃. The polymerization can be carried out in a batch or continuous process. The length of time required to effect polymerization may be, for example, from 10 minutes to 6 hours, so long as the time is sufficient to form a polymer in situ from the one or more ethylenically unsaturated monomers.

Once the polymerization process is complete, the resulting product is a stable dispersion of polymer-encapsulated particles in an aqueous medium that may contain some organic solvent. Some or all of the organic solvent may be removed by distillation under reduced pressure at a temperature of, for example, less than 40 ℃. The term "stable dispersion" or "stable dispersion" as used herein means that the polymer-enclosed particles neither settle out of the aqueous medium nor coagulate and flocculate when left to stand.

In certain embodiments, the polymer-enclosed particles are present in the aqueous dispersion of the present invention in an amount of at least 10 wt%, or in an amount of from 10 to 80 wt%, or in an amount of from 25 to 50 wt%, or in an amount of from 25 to 40 wt%, the weight percent being based on the weight of all solids present in the dispersion.

In certain embodiments, the dispersed polymer-enclosed particles have a maximum turbidity of 10%, or in some cases a maximum turbidity of 5%, or in still other cases a maximum turbidity of 1%, or in other embodiments a maximum turbidity of 0.5%. As used herein, "haze" is measured by ASTM D1003.

The haze values of the polymer-encapsulated particles described herein are measured by: these dispersions diluted in a solvent such as butyl acetate are first of all provided with particles such as nanoparticles dispersed in a liquid such as water, organic solvents and/or dispersants as described herein, and then measured using a Byk-Gardner TCS (The Color Sphere) instrument having a pore path length of 500 microns. Since% turbidity of a liquid sample is concentration dependent, the% turbidity as used herein is reported at a transmission of about 15% to about 20% at the wavelength of maximum absorbance. Relatively large particles can achieve acceptable haze when the refractive index difference between the particle and the surrounding medium is low. Conversely, for smaller particles, a larger refractive index difference between the particle and the surrounding medium may provide acceptable haze.

In the aforementioned process of the present invention, the polymer encapsulated particles are formed when the ethylenically unsaturated monomer reacts with the polymerizable dispersant, which, as previously mentioned, the present inventors believe results in a phase barrier that physically prevents the particles, particularly the nanoparticles, from reagglomerating in the aqueous dispersion. Thus, the aforementioned inventive process results in an aqueous dispersion of particles, e.g., nanoparticles, wherein re-agglomeration of the nanoparticles is minimized or avoided altogether.

In certain embodiments, the present invention relates to methods of making polymer-encapsulated particles. These methods include a method of making an aqueous dispersion of polymer-enclosed particles as previously described, wherein the polymer-enclosed particles comprise a brittle polymer and further comprising (1) removing water from the aqueous dispersion to form a solid material comprising the polymer-enclosed particles, and (2) breaking the solid material. In these embodiments, the water may be removed from the aqueous dispersion by any suitable drying method, for example, by using a drum dryer, a roller dryer, a spray dryer, or the like. Furthermore, the solid material may be broken up by any suitable technique, for example by using a hammer mill or the like. After crushing, the resulting granules may be further processed, for example by sieving in a classifier, before packaging.

The invention also relates to powder coating compositions formed from aqueous dispersions of polymer-enclosed particles. The term "powder coating composition" as used herein refers to a composition suitable for preparing a coating embedded in solid particulate form rather than liquid form. In certain embodiments of the powder coating compositions of the present invention, the polymer-enclosed particles comprise nanoparticles.

In addition to the polymer-enclosed particles, the powder coating composition of the present invention may comprise a particulate film-forming resin. Suitable film-forming resins include, for example, epoxy resins such as epoxy-containing acrylic polymers or polyglycidyl ethers of polyhydric alcohols, and suitable curing agents for epoxy resins such as polyfunctional carboxylic acid group-containing materials or dicyanamides. Examples of curable particulate resin materials are described in re-issued U.S. patent No. re32,261 and U.S. patent No.4,804,581, which are incorporated herein by reference. Examples of other suitable particulate film-forming resins are carboxylic acid functional resins such as carboxylic acid functional polyesters and acrylic polymers, and suitable curing agents for these materials such as triglycidyl isocyanurate and β -hydroxyalkylamide curing agents as described in U.S. Pat. No.4,801,680 and U.S. Pat. No.4,988,767, which are incorporated herein by reference.

In certain embodiments, the powder coating compositions of the present invention comprise from 50 to 90 weight percent, such as from 60 to 80 weight percent, of the particulate film-forming resin, based on the total weight of the powder coating composition. In certain embodiments, the powder coating compositions of the present invention comprise from 0.1 to 50 weight percent, such as from 1 to 20 weight percent, of the polymer-enclosed particles, based on the total weight of the powder coating composition.

The powder coating composition of the present invention may optionally include other materials such as other pigments, fillers, light stabilizers, flow modifiers, explosion suppressants and antioxidants. Suitable pigments include, for example, titanium dioxide, ultramarine blue, phthalocyanine green, carbon black, graphite fibrils, black iron oxide, chromium green oxide, yellow ferrites, and quintored (quindo red).

An explosion-proof agent may be added to the composition to allow any volatile materials to escape from the film during baking. Benzoin is a generally preferred explosion suppressant and is typically present in an amount of 0.5 to 3.0 wt% based on the total weight of the powder coating composition when used.

In certain embodiments, the powder coating compositions of the present invention include fumed silica or the like to reduce caking of the powder during storage. An example of a fumed silica is sold under the trademark CAB-O-SIL by Cabot corporation. The fumed silica is present in an amount of 0.1 to 1 weight percent based on the total weight of the powder coating formulation.

The invention also relates to a process for preparing the powder coating composition. In certain embodiments where the polymer-enclosed particles comprise a brittle polymer, the polymer-enclosed particles and other coating components are all embedded in a dry granular form, blended together, and then melt blended in an extruder. However, in other embodiments, such as those in which an aqueous dispersion of polymer-enclosed particles that do not include a brittle polymer is used, the powder coating composition of the present invention is prepared by a process comprising the steps of: (1) introducing into an extruder the powder coating composition components comprising: (a) an aqueous dispersion of polymer-enclosed particles, and (b) a dry material; (2) blending (a) and (b) in an extruder; (3) devolatilizing the blend to form an extrudate; (4) cooling the extrudate, and (5) grinding the extrudate to the desired particle size. The term "devolatilization" as used herein refers to the removal of volatile materials, including water and organic solvents. In certain embodiments, such powder coating compositions are prepared by the methods described in U.S. patent application publication nos. 2005/0212159a 1; 2005/0213423A 1; and/or 2005/0212171A1, the relevant disclosures of which are incorporated herein by reference.

In the methods of the present invention, the dry material may include the particulate film-forming resin described previously, as well as any other composition additives. The dry materials may be first blended in a high shear mixer, such as a planetary mixer. In certain embodiments, the dry material and the aqueous dispersion of the present invention are then blended in an extruder at a temperature of from 80 ℃ to 150 ℃. The extrudate is then cooled and comminuted into a particulate blend.

The powder coating compositions of the present invention may be applied to a variety of substrates, including metal substrates such as aluminum and steel substrates. Powder coating compositions are generally applied by spraying, and in the case of metal substrates by electrostatic spraying, or by using a fluidized bed. The powder coating compositions of the present invention may be applied in one sweep or in several passes to provide a film having a thickness of about 1 to 10 mils (25 to 250 micrometers), typically about 2 to 4 mils (50 to 100 micrometers) after curing. In many cases, after application of the powder coating composition, the coated substrate is heated to a temperature sufficient to cure the coating, typically to a temperature of 250 ° F to 500 ° F (121.1 ℃ to 260.0 ℃) for 1 to 60 minutes, for example 300 ° F to 400 ° F (148.9 ℃ to 204.4 ℃) for 15 to 30 minutes.

Thus, the present invention also relates to substrates, such as metal substrates, which are at least partially coated with a coating deposited from the powder coating composition of the present invention.

The powder coating compositions of the present invention may be used to form a monocoat, such as a monocoat, a clear topcoat or a basecoat, or both, in a two-layer system; or as one or more layers of a multi-layer system, including a clear top coat composition, a colorant layer, and/or a basecoat composition, and/or a basecoat layer, including, for example, an electrodeposited basecoat layer and/or a primer-surfacer layer.

The invention also relates to a substrate at least partially coated with a multi-layer composite coating, wherein at least one coating layer is deposited from the composition. For example, in certain embodiments, the powder coating compositions of the present invention comprise a basecoat layer in a multilayer composite coating comprising a basecoat layer and a topcoat layer. Thus, in these embodiments, at least one topcoat layer may be applied over the basecoat layer after the powder coating composition of the present invention is applied and cured. As is well known in the art, the topcoat may be deposited, for example, from a powder coating composition, an organic solvent-based coating composition, or a water-based coating composition. The film-forming composition of the top coat may be any composition useful in coating applications, including, for example, film-forming compositions comprising resinous binders selected from acrylic polymers, polyesters, including alkyds, and polyurethanes. The topcoat compositions can be applied by any conventional coating technique such as brushing, spraying, dipping or flow coating, but they are most commonly applied by spraying. Common spray techniques and equipment for air spraying, airless spraying and electrostatic spraying in a manual or automatic way may be used.

In certain embodiments, the present invention relates to a reflective surface at least partially coated with a color-imparting non-hiding coating deposited from a powder coating composition comprising a plurality of polymer-encapsulated nanoparticles having a maximum haze of 10%. In certain embodiments, a clear coat layer can be deposited over at least a portion of the color-imparting non-hiding coating layer.

The term "reflective surface" as used herein refers to a surface comprising a reflective material having a total reflectivity of at least 30%, for example at least 40%. "Total reflectance" herein refers to the proportion of reflected light from an object relative to incident light impinging on the object in the visible spectrum integrated at all viewing angles. The "visible spectrum" refers herein to the portion of the electromagnetic spectrum having wavelengths of 400-700 nm. "viewing angle" herein refers to the angle between the detected ray and normal to the surface at the point of incidence. The reflectance values described herein can be measured, for example, by using a Minolta spectrophotometer CM-3600d according to the instructions provided by the manufacturer.

In certain embodiments, the reflective surface comprises a substrate such as, inter alia, polished aluminum, cold rolled steel, chrome plated metal, or vacuum deposited metal on plastic. In other embodiments, the reflective surface can comprise a pre-coated surface, which can, for example, comprise a reflective coating deposited from a coating composition, such as, inter alia, a silver metal basecoat, a non-ferrous metal basecoat, a mica-containing basecoat, or a white basecoat.

These reflective coatings can be deposited from film-forming compositions that can, for example, include any of the film-forming resins typically used in protective coating compositions. For example, the film-forming composition of the reflective coating may comprise a resinous binder and one or more pigments to act as colorants. Useful resinous binders include, but are not limited to, acrylic polymers, polyesters, including alkyds, and polyurethanes. The resinous binder used in the reflective coating composition may, for example, be embedded in a powder coating composition, an organic solvent-based coating composition, or a water-based coating composition.

As mentioned, the reflective coating composition may contain pigments as colorants. Suitable pigments for use in the reflective coating composition include, for example, metallic pigments including aluminum flakes, copper or bronze flakes, and metal oxide coated mica; non-metallic colored pigments such as titanium dioxide, iron oxide, chromium oxide, lead chromate, and carbon black; and organic pigments such as phthalocyanine blue and phthalocyanine green.

The reflective coating composition can be applied to the substrate by any conventional coating technique such as brushing, spraying, dipping or flow coating, among others. Common spray techniques and equipment for air spraying, airless spraying and electrostatic spraying in a manual or automatic way may be used. The film thickness of the primer layer formed on the substrate during application of the primer layer to the substrate is typically from 0.1 to 5 mils (2.5 to 127 mm), or from 0.1 to 2 mils (2.5 to 50.8 mm).

After the reflective coating film is formed on the substrate, the reflective coating may be cured or optionally subjected to a drying step in which the solvent is driven out of the primed film by a heating or air drying stage prior to application of a subsequent coating composition. Suitable drying conditions will depend on the particular undercoating composition, and if the composition is waterborne one condition is ambient humidity, but in general a drying time of 1 to 15 minutes at a temperature of 75 to 200F (21 to 93℃) will be sufficient.

The reflective surface of the present invention is at least partially coated with a color-imparting non-hiding coating layer deposited from the powder coating composition of the present invention. The term "non-hiding coating" as used herein refers to a coating in which the surface underlying the coating is visible when deposited on the surface. In certain embodiments of the invention, the surface underlying the non-hiding coating layer is visible when the non-hiding layer is applied at a dry film thickness of 0.5 to 5.0 mils (12.7 to 127 microns). One way to evaluate non-hiding is by measuring opacity. As used herein, "opacity" refers to the degree to which a material obscures a substrate.

"percent opacity" herein refers to the ratio of the reflectance of a dried coating film on a black substrate of 5% or less reflectance to the reflectance of the same coating film that is also coated and dried on a substrate of 85% reflectance. The percent opacity of the dry paint film will depend on the dry film thickness of the paint and the concentration of color-imparting particles. In certain embodiments of the present invention, the color-imparting non-hiding coating layer has a percent opacity of no more than 90%, such as no more than 50%, at a dry film thickness of one (1) mil (about 25 microns).

In certain embodiments of the reflective surfaces of the present invention, a clear coating is deposited over at least a portion of the color-imparting non-hiding coating. The clear coat layer can be deposited from a composition comprising any typical film-forming resin, and can be applied over the color-imparting non-hiding layer to impart additional depth and/or protective properties to the underlying surface. The resinous binder for the clearcoat can be embedded as a powder coating composition, an organic solvent-based coating composition, or a water-based coating composition. Optional components suitable for inclusion in the clear coating composition include those well known in the art for formulating surface coatings, such as those materials described previously. The clear coating composition can be applied to the substrate by any conventional coating technique such as, inter alia, brushing, spraying, dipping, or flow coating.

In certain embodiments, coatings deposited from the powder coating compositions of the present invention exhibit "richer" color than similar powder coating compositions that do not include a plurality of polymer-encapsulated nanoparticles having a maximum haze of 10%, such as those described above. Accordingly, the present invention relates to a method of increasing the color richness of a coating deposited from a powder coating composition. These methods include including a plurality of polymer-encapsulated nanoparticles having a maximum haze of 10% in a powder coating composition. The term "color richness" as used herein refers to the L values in the CIELAB color system described in U.S. patent No.5,792,559, column 1, lines 34-64, the incorporated by reference herein, wherein lower L values correspond to higher degrees of color richness. For the purposes of the present invention, color measurements at various angles can be made using an X-RITE spectrophotometer, such as the MA68I multiangle spectrophotometer commercially available from X-RITE Instruments, Inc.

The present invention also relates to a method of matching the color of preselected protective and decorative coatings deposited from a liquid coating composition. The inventors have found that unlike prior art powder coating compositions, the powder coating compositions of the present invention are capable of producing coatings that exhibit color properties similar to coatings deposited from liquid coating compositions. Thus, the powder coating compositions of the present invention can be used for color matching of coatings deposited from liquid coating compositions. These methods include: (a) determining a visible color of the preselected coating by measuring an absorbance or reflectance of the preselected coating; and (b) preparing a powder coating composition comprising a plurality of polymer-enclosed nanoparticles having a maximum haze of 10%, wherein a coating deposited from the powder coating composition matches the visible color of the preselected coating. In these methods, a spectrophotometer (as described above) is used to measure the absorbance or reflectance of a preselected coating and a profile of absorbance or reflectance is made across a range of wavelengths corresponding to the visible spectrum. This curve is referred to as the visible absorption or reflection spectrum. A powder coating composition comprising a plurality of polymer-enclosed nanoparticles having a maximum haze of 10% is prepared such that a coating deposited from the powder coating composition has a visible absorption or reflection spectrum that closely matches a preselected coating.

The following examples illustrate the invention and are not to be construed as limiting the invention to their details. All parts and percentages in the examples, as well as throughout the specification, are by weight unless otherwise indicated.

Examples

Example 1

Polyurethane dispersions

This example describes the preparation of a polyurethane dispersion that was subsequently used to form the polyurethane/nanopigment dispersions of examples 2-4. The polyurethane dispersion is prepared from a mixture of the following components in the stated proportions:

components	Weight (g)
		Feed I
Poly (neopentyl glycol adipate)¹	780.0
		Dimethylolpropionic acid (DMPA)	280.7
Triethylamine	127.1
		Butylated hydroxytoluene	2.5
Phosphorous acid triphenyl ester	2.5
		Feed II
Hydroxyethyl methacrylate (HEMA)	116.7
		Methacrylic acid butyl ester	791.2
Feed III
		Methylene bis (4-cyclohexyl isocyanate)	1175.1
Feed IV
		Methacrylic acid butyl ester	57.5
Feeding V
		Deionized water	4734.8
Ethylene diamine	49.2
		Dimethylethanolamine	40.6
Feed VI
		Methacrylic acid butyl ester	50

¹Poly (neopentyl glycol adipate) having a number average molecular weight of 1000.

The polyurethane dispersion was prepared in a four-necked round bottom flask equipped with an electronic thermometer, mechanical stirrer, condenser and heating mantle. Charge I was stirred in a flask at a temperature of 90 ℃ for 5 minutes. Charge II was added and the mixture was cooled to 60 ℃. Feed III was added over 10 minutes. Charge IV was added and the resulting mixture was gradually heated to 90 ℃ over 45 minutes and then held at 90 ℃ for 3 hours. Feed V was stirred in a separate flask and heated to 80 ℃. 3000.0g of the reaction product of feeds I, II, III and IV are added to feed V over 30 minutes. Charge VI was added and the resulting mixture was cooled to room temperature. The final product was a translucent emulsion having an acid number of 12.1, a Brookfield viscosity of 872 cps (spindle #3 at 30 rpm), a pH of 7.75 and a non-volatile content of 29.4% measured at 110 ℃ for 1 hour.

Example 2

Polyurethane/nanopigment dispersions

This example describes nano-sized PB 15: preparation of 3 phthalocyanine blue pigment dispersion. The dispersion is prepared from the following mixture of components in the proportions indicated:

components	Weight (g)
		Feed I
Polyurethane Dispersion of example 1	4772.7
		Deionized water	2304.5
Hydroquinone Methyl Ether (MEHQ)	1.36
		PB 15: 3 pigments²	700.0
Shellsol OMS(Shell Chemical Co.)	86.4
		Feed II
Deionized water	71.5
		Tert-butyl hydroperoxide (70% aqueous solution)	5.8
Feed III
		Deionized water	337.2
Ferrous ammonium sulfate	0.13
		Sodium metabisulfite	8.18

²Commercially available from BASF Corp.

The components were mixed using a 4.5 inch Cowles blade connected to an air motor. The mixture was then mixed in a1 liter mill chamber with a solvent containing 353mL1.2-1.7mm ZirconoxA Premier Mill PSM-11 basket Mill of grinding media was predispersed at 1000fpm mixing blade and 960rpm pump speed for 1.25 hours and then recirculated through a pump containing 500mL of 0.3mm ZirconoxAdvantis V15 Drais Mill for grinding media. The mixture was milled at 1400rpm with a pump setting of 19rpm for a total time of 15 hours. The progress of the abrasion was monitored by visual inspection of the transparency change of the sample films taken on the black and white Leneta papers. Charge II was added and the resulting mixture was stirred for 5 minutes. Charge III was added in two aliquots over 5 minutes. The final product was a cyan (blue) liquid with a Brookfield viscosity of 356 cps (spindle #3 at 30 rpm), a pH of 7.29 and a non-volatile content of 28.9% measured at 110 ℃ for 1 hour.

Example 3

Polyurethane/nanopigment dispersions

This example describes the preparation of nano-sized PR122 quinacridone magenta pigment dispersions. The dispersion is prepared from the following mixture of components in the proportions indicated:

components	Weight (g)
		Feed I
Polyurethane Dispersion of example 1	4772.7
		Deionized water	2304.5
Hydroquinone Methyl Ether (MEHQ)	1.36
		PR122 pigment³	700.0
Shellsol OMS(Shell Chemical Co.)	86.4
		Feed II
Deionized water	71.5
		Tert-butyl hydroperoxide (70% aqueous solution)	5.8
Feed III
		Deionized water	337.2
Ferrous ammonium sulfate	0.13
		Sodium metabisulfite	8.18

³Commercially available from Sun Chemical.

The components were mixed using a 4.5 inch Cowles blade connected to an air motor. The mixture was then mixed in a1 liter mill chamber with a solvent containing 353mL1.2-1.7mm ZirconoxA Premier Mill PSM-11 basket Mill of grinding media was predispersed at 1000fpm mixing blade and 960rpm pump speed for 1.5 hours and then recirculated through a pump containing 500mL of 0.3mm ZirconoxAdvantis V15 Drais Mill for grinding media. The mixture was milled at 1260fpm with a pump setting of 19rpm for a total time of 15 hours. The progress of the abrasion was monitored by visual inspection of the transparency change of the sample films taken on the black and white Leneta papers. Charge II was added and the resulting mixture was stirred for 5 minutes. Charge III was added in two aliquots over 5 minutes. The final product was a magenta liquid with a Brookfield viscosity of 28.1 cps (spindle #3 at 30 rpm), a pH of 7.61 and a non-volatile content of 28.2% measured at 110 ℃ for 1 hour.

Example 4

Polyurethane/nanopigment dispersions

This example describes the preparation of a nano-sized PY128 disazo yellow pigment dispersion. The dispersion is prepared from the following mixture of components in the proportions indicated:

components	Weight (g)
		Feed I
Polyurethane Dispersion of example 1	4872.7
		Deionized water	2204.5
Hydroquinone Methyl Ether (MEHQ)	1.36
		PY128 pigment⁴	700.0
Shellsol OMS(Shell Chemical Co.)	86.4
		Feed II
Deionized water	71.5
		Tert-butyl hydroperoxide (70% aqueous solution)	5.8
Feed III
		Deionized water	337.2
Ferrous ammonium sulfate	0.13
		Sodium metabisulfite	8.18

⁴Commercially available from CIBA.

The components were mixed using a 4.5 inch Cowles blade connected to an air motor. The mixture was then mixed in a1 liter mill chamber with a solvent containing 353mL1.2-1.7mm ZirconoxA Premier Mill PSM-11 basket Mill of grinding media was predispersed at 1000fpm mixing blade and 960rpm pump speed for 4.7 hours and then recirculated through a pump containing 500mL of 0.3mm ZirconoxAdvantis V15 Drais Mill for grinding media. The mixture was milled at 1400rpm with a pump setting of 19rpm for a total time of 18 hours. The progress of the abrasion was monitored by visual inspection of the transparency change of the sample films taken on the black and white Leneta papers. Charge II was added and the resulting mixture was stirred for 5 minutes. Charge III was added in two aliquots over 5 minutes. The final product was a yellow liquid with a Brookfield viscosity of 48.1 cps (spindle #3 at 30 rpm), a pH of 7.40 and a non-volatile content of 29.4% measured at 110 ℃ for 1 hour.

Example 5

Cylinder dried nanopigment dispersions

This example describes the conversion of the liquid polyurethane/nanopigment dispersion of example 3 into a dry material suitable for mechanical grinding into a powdery raw material for subsequent use in the preparation of a powder coating composition. The dispersion described above in example 3 was dried using a Bufolvak6 "x 8" dual cylinder dryer setup with a 10 mil gap and a 240 ° F cylinder temperature rotating at 2.9 rpm. The resulting material formed a ribbon-like sheet that was easily broken into large powders with a nonvolatile content of 96.0% measured at 110 ℃ for 1 hour.

Example 6

Polyurethane dispersions

This example describes the preparation of polyurethane dispersions which are subsequently used to form the corresponding polyurethane/nanopigment dispersions of examples 7-9 and 13. The polyurethane dispersion is prepared from a mixture of the following components in the stated proportions:

components	Weight (g)
		Feed I
Poly (cyclobutaxanes)⁵	355.6
		Dimethylolpropionic acid (DMPA)	119.2
Triethylamine	54.0
		Butylated hydroxytoluene	2.2
Phosphorous acid triphenyl ester	1.1
		Feed II
Hydroxyethyl methacrylate (HEMA)	27.8
		Methacrylic acid butyl ester	48.4
Acrylic acid butyl ester	319.2
		Feed III
Methylene bis (4-cyclohexyl isocyanate)	558.9
		Feed IV
Methacrylic acid butyl ester	55.6
		Feeding V
Deionized water	2086.3
		Diethanolamine (DEA)	20.2
Ethylene diamine	26.9
		Dimethylethanolamine	19.7
Feed VI
		Methacrylic acid butyl ester	50.0

⁵Poly (butylene oxide) having a number average molecular weight of 1000.

The polyurethane dispersion was prepared in a four-necked round bottom flask equipped with an electronic thermometer, mechanical stirrer, condenser and heating mantle. Charge I was stirred in the flask for 5 minutes at a temperature of 125 ℃. Charge II was added and the mixture was cooled to 70 ℃. Feed III was added over 10 minutes. Charge IV was added and the resulting mixture was gradually heated to 90 ℃ over 90 minutes and then held at 90 ℃ for 1 hour. Feed V was stirred in a separate flask and heated to 60 ℃. 1387.8g of the reaction product of feeds I, II, III and IV were added to feed V over 10 minutes. Charge VI was added and the resulting mixture was cooled to room temperature. The final product was a translucent emulsion having an acid number of 12.5, a Brookfield viscosity of 3710 cps (spindle #5 at 60 rpm), a pH of 7.6 and a non-volatile content of 29.4% measured at 110 ℃ for 1 hour.

Example 7

Polyurethane/nanopigment dispersions

components	Weight (g)
		Feed I
Polyurethane Dispersion of example 6	7271.0
		Deionized water	3293.1
Hydroquinone Methyl Ether (MEHQ)	2.0
		PB 15: 3 pigments	1079.5
Shellsol OMS(Shell Chemical Co.)	131.5
		Feed II
Deionized water	102.4
		Tert-butyl hydroperoxide (70% aqueous solution)	12.3
Feed III
		Deionized water	512.1
Ferrous ammonium sulfate	0.15
		Sodium metabisulfite	12.3

The components were mixed for 2.5 hours using a Ross rotor/stator mixer model HSM-100L and then recirculated through a mill containing 500mL of 0.3mm Zirconox in a1 liter grinding chamberAdvantis V15 Drais Mill for grinding media. The mixture was milled at 1400rpm for a total time of 19.0 hours. The progress of the abrasion was monitored by visual inspection of the transparency change of the sample films taken on the black and white Leneta papers. Charge II was added and the resulting mixture was cooled to 11 deg.CStirred for 5 minutes. Charge III was added in two aliquots over 5 minutes. The temperature of the mixture was increased to 13 ℃. The final product was a blue colored liquid with a Brookfield viscosity of 26 cps (spindle #1 at 60 rpm), a pH of 7.2 and a non-volatile content of 30.0% measured at 110 ℃ for 1 hour.

Example 8

Polyurethane/nanopigment dispersions

components	Weight (g)
		Feed I
Polyurethane Dispersion of example 6	7271.0
		Deionized water	3293.1
Hydroquinone Methyl Ether (MEHQ)	2.0
		PR122 pigment	1079.5
Shellsol OMS(Shell Chemical Co.)	131.5
		Feed II
Deionized water	102.4
		Tert-butyl hydroperoxide (70% aqueous solution)	12.3
Feed III
		Deionized water	512.1
Ferrous ammonium sulfate	0.15
		Sodium metabisulfite	12.3

The components were mixed for 4 hours using a Ross rotor/stator mixer model HSM-100L and then recirculated through a mill containing 500mL of 0.3mm Zirconox in a1 liter grinding chamberAdvantis V15 Drais Mill for grinding media. The mixture was milled at 1400rpm for a total time of 23 hours. The progress of the abrasion was monitored by visual inspection of the transparency change of the sample films taken on the black and white Leneta papers. Charge II was added and the resulting mixture was stirred at 24 ℃ for 5 minutes. Charge III was added in two aliquots over 5 minutes. The temperature of the mixture was increased to 26 ℃. The final product was a magenta liquid with a Brookfield viscosity of 27 cps (spindle #1 at 60 rpm), a pH of 7.4 and a non-volatile content of 29.3% measured at 110 ℃ for 1 hour.

Example 9

Polyurethane/nanopigment dispersions

components	Weight (g)
		Feed I
Polyurethane Dispersion of example 6	7271.0
		Deionized water	3293.1
Hydroquinone Methyl Ether (MEHQ)	2.0
		PY128 pigment	1079.5
Shellsol OMS(Shell Chemical Co.)	131.5
		Feed II
Deionized water	102.4
		Tert-butyl hydroperoxide (70% aqueous solution)	12.3
Feed III
		Deionized water	512.1
Ferrous ammonium sulfate	0.15
		Sodium metabisulfite	12.3

The components were mixed for 5.5 hours using a Ross rotor/stator mixer model HSM-100L and then recirculated through a mill containing 500mL of 0.3mm Zirconox in a1 liter grinding chamberAdvantis V15 Drais Mill for grinding media. The mixture was milled at 1400rpm for a total time of 23 hours. The progress of the abrasion was monitored by visual inspection of the transparency change of the sample films taken on the black and white Leneta papers. Charge II was added and the resulting mixture was stirred for 5 minutes. Charge III was added in two aliquots over 5 minutes. The final product was a yellow liquid with a Brookfield viscosity of 53 cps (spindle #1 at 60 rpm), a pH of 7.3 and a non-volatile content of 28.8% measured at 110 ℃ for 1 hour.

Example 10

Preparation of powder coating composition intermediates

This example describes the preparation of a core formulation of the dry material used to prepare the powder coating compositions of the subsequent examples. The core formulation is prepared from the following mixture of components in the proportions described:

components	Composition (I)	Parts by weight
			1	Uralac P880 resin⁶	81.136
2	Primid XL552⁷	11.064
			3	Resin flow PL 200A⁸	1
4	Benzoinum⁹	0.7
			5	Irganox 1076¹⁰	1.2
6	Flow additive	1.3
			7	Tinuvin 144¹¹	1
8	Tinuvin 900¹¹	2
			9	Transparent zinc oxide¹²	0.5
10	Aluminum oxide C¹³	0.01

⁶Commercially available from DSM Resins

⁷Commercially available from EMS

⁸Commercially available from Estron Chemical

⁹Commercially available from GCA Chemical

¹⁰From Clariant is commercially available

¹¹Commercially available from CIBA

¹²Commercially available from Bayer Chemical

¹³Commercially available from Palmer Supplies

Components 1-9 were pre-mixed in a Henschel blender at 1000RPM for 1 minute. The mixture was then extruded through a Coperion W & P30mm co-rotating twin screw extruder at 340RPM screw speed and 30-40% average torque. As described in U.S. published patent application 2005/0213423; 2005/0212159A1 and 2005/0212171A1, the extruders were equipped with a low pressure injection system and 5 separate temperature control zones. These 5 independent temperature control zones were controlled at the following temperatures: zone 1: 60 ℃; zone 2: 120 ℃; zone 3: 130 ℃; zone 4: 120 ℃; zone 5: at 100 ℃. The extrudate is cooled and ground in a mechanical grinding system to a particle size of about 28-30 microns. Oversized particles are removed and component 10 is added.

Example 11

Preparation of powder coating compositions

Various powder coating compositions were prepared from the powder coating composition intermediate of example 10 with the polyurethane/nanopigment dispersions of examples 2-4 and 7-9 and various mixtures of those dispersions (weight ratio 90: 10 to 10: 90). Each powder coating composition was prepared as described in U.S. published patent application 2005/0213423; 2005/0212159A1 and 2005/0212171A1 were prepared using a Coperion W & P30mm co-rotating twin screw extruder equipped with a low pressure injection system and 5 independent temperature control zones and the conditions described in example 10. The powder coating composition intermediate of example 10 was fed into the extruder at a rate of 280 g/min and the pigment dispersion was fed into the extruder at a rate of 105 g/min via a low pressure injection system. Zone 4 is equipped with a devolatilization port for volatile vapor removal. The extrudate is cooled and ground in a mechanical grinding system to a particle size of about 28-30 microns.

Example 12

Color matching method

This example describes the improved ability of the powder coating compositions of the present invention to match the color of a colored coating deposited from a liquid coating composition. In this example, a colored violet/magenta coating deposited from a liquid coating composition is the standard. Color data measured by the MA68I multi-angle spectrophotometer at various viewing angles are shown in table 1. Powder coating a represents the best color match, which can be achieved using powder coating compositions containing only standard pigments. Powder coating B represents the best color match that can be achieved using powder coating compositions comprising the combination of nanopigment dispersions of examples 2-4 and 7-9.

TABLE 1

Powder coating A

Angle of rotation	L	a	b	C	h
						15	9.2	-14.6	8.53	-15.6	6.53
25	6.27	-7.94	5.68	-8.46	4.86
						45	8.19	5.16	5.71	5.35	5.53
75	10.03	17.53	6.73	18.34	4.05
						110	10.69	22	7.24	22.97	2.95

Powder coating B

Angle of rotation	L	a	b	C	h
						15	-9.58	-9.21	-1.6	-8.57	-3.72
25	-5.59	-5.98	-3.27	-5.13	-4.49
						45	0.25	0.09	-5.75	1.06	-5.66
75	1.75	5.86	-5.54	6.43	-4.86
						110	1.84	6.02	-4.26	6.32	-3.8

In this example, a positive trend in the "C" value was observed, thereby indicating a better color match to the standard at face angles (15 and 25). When measuring the drop angle (45, 75, 110), the negative trend indicates a deeper and more desirable colorimetric shift. In the case of the above sample, their values are reduced for all three angles relative to the original powder match, thereby moving closer to the standard.

Example 13

Polyurethane/nanopigment dispersions

This example describes the preparation of nano-sized PR-179 perylene red pigment dispersions. The dispersion is prepared from the following mixture of components in the proportions indicated:

components	Weight (g)
		Polyurethane Dispersion of example 6	6272.3
Deionized water	4545.6
		PR179 pigment¹⁴	1818.2
Shellsol OMS(Shell Chemical Co.)	218.2

¹⁴Commercially available from Sun Chemical

The components were mixed and recycled through a mill containing 500mL of 0.3mmZirconox in a1 liter grinding chamberAdvantis V15 Drais Mill for grinding media. The mixture was milled at a maximum of 1350rpm for a total time of 42.75 hours. The final product was a red liquid with a nonvolatile content of 39.4% measured at 110 ℃ for 1 hour.

Example 14

In this example, two powder coating compositions were prepared using the components and methods described in example 10. For example 14a, 3 parts by weight of a commercially available PR179 pigment from Sun Chemical was included in the composition of example 10. For example 14b, 3 parts by weight of a polyurethane/nanopigment dispersion were included in the composition of example 10. The powder coating compositions of examples 14a and 14b were electrostatically coated onto 4 "x 12" electrocoated panels. The panel is cured at a suitable elevated temperature and cooled to ambient temperature. Color data were measured at various viewing angles by a MA68I multi-angle spectrophotometer. The results are shown in table 1 and reported as the difference between example 14b compared to example 14 a.

Angle of rotation	L	a	b	C	h
						15	-1.76	-3.2	-2.64	-4.08	-0.77
25	-3	-5.02	-4.05	-6.33	-1.21
						45	-4.05	-8.41	-5.9	-10.2	-1.23
75	-4.5	-10.17	-6.52	-12.06	-0.65
						110	-4.59	-10.85	-6.68	-12.74	-0.18

In this example, a decrease in the "L" value indicates an increase in the color richness and the degree of development.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A powder coating composition formed from an aqueous dispersion comprising polymer-enclosed particles, wherein the polymer-enclosed particles comprise particles enclosed by a brittle polymer, wherein the brittle polymer comprises the reaction product of (1) a water-dispersible polymerizable dispersant and (2) a polymerizable ethylenically unsaturated monomer.

2. The powder coating composition of claim 1, wherein the particles comprise nanoparticles.

3. The powder coating composition of claim 2, wherein the nanoparticles comprise inorganic nanoparticles.

4. The powder coating composition of claim 3, wherein the nanoparticles comprise inorganic nanoparticles selected from the group consisting of: colloidal silica, fumed silica, amorphous silica, alumina, colloidal alumina, titania, iron oxide, cesium oxide, yttrium oxide, colloidal zirconium oxide, amorphous zirconium oxide, and mixtures thereof.

5. The powder coating composition of claim 3, wherein the inorganic nanoparticles comprise mixed metal oxides.

6. The powder coating composition of claim 2, wherein the nanoparticles have a maximum haze of 10%.

7. The powder coating composition of claim 2, wherein the nanoparticles comprise organic nanoparticles.

8. The powder coating composition of claim 7, wherein the organic nanoparticles comprise an organic pigment selected from the group consisting of:

perylene, quinacridone, phthalocyanine, isoindoline, dioxazine, 1, 4-diketopyrrolopyrrole, anthrapyrimidine, anthanthrone, flavanthrone, indanthrone, perinone, pyranthrone, thioindigo, 4 '-diamino-1, 1' -dianthraquinonyl, azo compounds, and mixtures thereof.

9. An aqueous dispersion comprising polymer-enclosed particles, wherein the polymer-enclosed particles comprise particles enclosed by a brittle polymer, wherein the brittle polymer comprises the reaction product of (i) a polymerizable polyester polyurethane and (ii) an ethylenically unsaturated monomer.

10. The aqueous dispersion of claim 9, wherein the polymerizable polyester polyurethane comprises a polyester polyurethane having terminal ethylenic unsaturation.

11. The aqueous dispersion of claim 10, wherein the polyester polyurethane having terminal ethylenic unsaturation is prepared from reactants comprising:

(a) a polyisocyanate;

(b) a polyester polyol; and

(c) a material comprising an ethylenically unsaturated group and an active hydrogen group.

12. The aqueous dispersion of claim 11, wherein the polyester polyurethane having terminal ethylenic unsaturation is prepared from reactants further comprising:

(d) a polyamine; and

(e) a material comprising an acid functional group or anhydride and a functional group that reacts with an isocyanate group or a hydroxyl group.

13. The aqueous dispersion of claim 9, wherein the polymerizable polyester polyurethane is water dispersible.

14. The aqueous dispersion of claim 9 wherein the polymerizable polyester polyurethane has a weight average molecular weight of 40,000-80,000 g/mol.

15. A substrate at least partially coated with a coating deposited from the powder coating composition of claim 1.

16. The substrate of claim 15, wherein the substrate comprises a metal substrate.

17. A multilayer composite coating wherein at least one coating layer is deposited from the powder coating composition of claim 1.

18. A method of preparing a powder coating composition comprising:

(1) introducing into an extruder components comprising:

(a) an aqueous dispersion comprising polymer-enclosed particles, wherein the polymer-enclosed particles comprise particles enclosed by a friable polymer, wherein the friable polymer comprises the reaction product of (1) a water-dispersible polymerizable dispersant and (2) a polymerizable ethylenically unsaturated monomer, and

(b) drying the material;

(2) blending (a) and (b) in an extruder;

(3) devolatilizing the blend to form an extrudate;

(4) cooling the extrudate, and

(5) the extrudate is milled to the desired particle size.

19. A method of making an aqueous dispersion of polymer-enclosed particles comprising:

(1) providing a mixture of:

(a) the particles are selected from the group consisting of,

(b) an ethylenically unsaturated monomer, and

(c) a water-dispersible polymerizable dispersant comprising a polymerizable polyester polyurethane, and

(2) polymerizing an ethylenically unsaturated monomer and a polymerizable dispersant to form polymer-enclosed particles comprising a water-dispersible polymer,

wherein the method does not include the step of subjecting the mixture to high stress shear conditions.

20. The method of claim 19, wherein the particles form nanoparticles after step (1).

21. The method of claim 19, wherein the polymerizable polyester polyurethane has a weight average molecular weight of 40,000-80,000 g/mol.

22. A powder coating composition formed from the aqueous dispersion prepared by the process of claim 19.

23. A reflective surface at least partially coated with a color-imparting non-hiding coating layer deposited from a powder coating composition comprising a plurality of polymer-encapsulated nanoparticles having a maximum haze of 10%, the polymer-encapsulated nanoparticles comprising nanoparticles encapsulated by a brittle polymer, wherein the brittle polymer comprises the reaction product of (1) a water-dispersible polymerizable dispersant and (2) a polymerizable ethylenically unsaturated monomer.