Fall 2002 Vol. 4, No. 2

U.S. Patents

Electrostatic Powder Coating of Electrically Nonconducting Substrates
U.S. Patent 6,270,853
Issued: August 7, 2001
Inventors: Brown, Larry W., et al
Assigned to: Raytheon Company

A powder coating method includes applying an antistatic material to the surface of an electrically nonconducting substrate. The antistatic material is preferably a fatty amine salt and is applied by spraying. A flow of electrostatically charged powder particles is directed toward the substrate to form a powder coating on the substrate, and the powder coating is thereafter cured.

Powder Coating Compositions and Methods
U.S. Patent 6,270,855
Issued: August 7, 2001
Inventors: Jung, Rolf, et al
Assigned to: The Valspar Corporation

Powder coating compositions for metal substrates, a method of powder coating a metal substrate, and a metal article are disclosed. The powder coating composition is a thermoplastic material and comprises (a) a first polyester having a weight average molecular weight of about 10,000 to about 80,000 and a Tg of greater than 45ºC. to about 100ºC., (b) a second polyester having a weight average molecular weight of about 10,000 to about 70,000 and Tg of about minus 10ºC to about 45ºC, and optionally, (c) a modifying resin, such as an epoxy resin having an epoxy equivalent weight of about 500 to about 15,000, wherein the Tg of the first and second polyesters differ by about 5ºC to about 60ºC. The powder coating composition is applied to a metal substrate to provide a composition film having a thickness of about 1 to about 200 microns.

Powder Coating Compositions Containing Functional Polysiloxanes
U.S. Patent 6,274,672
Issued: August 14, 2001
Inventors: Ambrose, Ronald R., et al
Assigned to: PPG Industries Inc.

Improved powder coating compositions containing novel polysiloxanes having various reactive functional groups are disclosed. The compositions are particularly useful as thermosetting powder coating compositions where they provide excellent filiform corrosion resistance.

Powder Coating Compositions and Coated Substrates With Multilayered Coatings
U.S. Patent 6,277,917
Issued: August 21, 2001
Inventors: Jurgetz, Anton, et al
Assigned to: PPG Industries Inc.

Curable powder clear coating compositions and a coated substrate with multilayered coatings have as the predominant film-forming polymer in the coating at least one epoxy acrylic copolymer in an amount from 60 to 99.99% by weight and 10 to 40% by weight of a polycarboxylic acid crosslinking agent. The percentages by weight are based on solids of the curable coating composition. A blend of epoxy acrylic copolymers has one polymer which is the single epoxy acrylic copolymer and another polymer of the blend having a lower Tg and higher epoxy content.

Fluidized Bed Powder Coating Process Utilizing Tribostatic Charging
U.S. Patent 6,280,798
Issued: August 28, 2001
Inventors: Ring, John, et al
Assigned to: International Coatings Limited

A process for forming a coating on a conductive substrate, which comprises establishing a fluidized bed of a powder coating composition, in which the mechanism for particle charging is tribostatic charging, immersing the substrate wholly or partly within the said fluidized bed, applying a voltage to the substrate for at least part of the period of immersion, whereby particles of the powder coating composition adhere to the substrate, withdrawing the substrate from the fluidized bed and forming the adherent particles into a continuous coating over at least part of the substrate. The process enables the coating of substrate areas which, because of the Faraday cage effect, are inaccessible in conventional electrostatic coating processes, and also enables the formation of thinner coatings than are obtainable by conventional fluidized-bed processes. Preheating of the substrate is not required.

Unsaturated Polyesterurethane Acrylates as Binders for Powder Coatings
U.S. Patent 6,284,321
Issued: September 4, 2001
Inventors: Brindoepke, Gerhard, et al
Assigned to: Solutia Germany GmbH & Co. KG

Binders for powder coatings are disclosed that contain solid, unsaturated polyesterurethane (meth) acrylates having a melting temperature of from 35 to 180ºC.

Stable Powder Coating Compositions Which Produce Consistent Finishes
U.S. Patent 6,294,619
Issued: September 25, 2001
Inventors: Chasser, Anthony M., et al.
Assigned to: PPG Industries Inc.

The invention provides powder coatings that consistently produce durable finishes when cured and are stable when uncured. These powder coatings of the invention include novel film-forming systems. The novel film-forming system, in turn, includes a polymer component and a crosslinker component. In one embodiment, the polymer component is novel and, in another embodiment, both the polymer and crosslinker components are novel. The novel polymer component includes a novel polyester polyol. This novel polyester polyol includes the reaction product of a cycloaliphatic component and a polyfunctional isocyanurate component. The novel crosslinker component which can be used when practicing certain embodiments of this invention includes a novel, polyfunctional isocyanate compound which is at least partially blocked with at least one of the following: a polyhydroxy aromatic compound or a mixture of a polyhydroxy aromatic compound and a hydroxy-functional ester compound.

Powder Coating Crosslinking Agents Containing Uretdione Groups and Free Isocyanate
U.S. Patent 6,297,343
Issued: October 2, 2001
Inventors: Lars; Hans-Josef, et al.
Assigned to: Bayer Aktiengesellschaft

The present invention relates to polyaddition compounds, which are solid below 40ºC and liquid above 125ºC and are prepared by the reaction of an isocyanate component containing uretdione groups with a polyol containing ester and/or carbonate groups. The present invention also relates to a process for the preparation of these polyaddition compounds to two-component polyurethane powder coating compositions containing the polyaddition compounds as the crosslinking agent and isocyanate-reactive compounds as the binder.

Resin Composition for Powder Coating
U.S. Patent 6,303,706
Issued: October 16, 2001
Inventors: Miyake; Satoru, et al.
Assigned to: Nissan Chemical Industries Ltd.

A resin composition for powder coating, which comprises (A) a carboxyl group-containing resin, (B) tris (beta-methylglycidyl) isocyanurate as a ring opening polymerization inhibitor, and at least one compound selected from the group consisting of amines and onium salts.

Process for the Preparation of Powder Coating Composition
U.S. Patent 6,309,572
Issued: October 30, 2001
Inventors: Isozaki, Tsuyoshi, et al.
Assigned to: Mitsubishi Gas Chemical Company Inc.

A process for the preparation of a powder coating composition, wherein 5 to 90% by weight of at least one monomeric compound selected from glycidyl group-containing unsaturated compounds and methylglycidyl group-containing unsaturated compounds is copolymerized with 95 to 10% by weight of an ethylenically unsaturated monomer in methanol to obtain a resin solution. The resin solution is spraydried to obtain a powdery resin. Alternatively, the resin solution is fed to an extruder having a die and a plurality of vent ports and extruded through the die, while removing volatile matters through the vent ports, to obtain extrudates. The extrudates are pulverized to obtain a powdery resin.

Burnish Resistant Powder Coating Compositions
U.S. Patent 6,310,139
Issued: October 30, 2001
Inventors: Demain, Eric, et al
Assigned to: Reichhold Inc.

The present invention provides a low-gloss powder coating composition comprising a polyester having hydroxyl and carboxyl groups and glycidyl-containing acrylic copolymer, the copolymer having a Tg less than about 55ºC. and a number average molecular weight greater than about 8000.

Powder Coating of Epoxy-Acrylic Resin, Polycarboxylic Acid, Crosslinked Particles and Liquid Resin.
U.S. Patent 6,313,221
Issued: November 6, 2001
Inventors: Yabuta, Masami, et al
Assigned to: Nippon Paint Co. Ltd.

A thermosetting powder coating composition prepared by a wet process, which contains a mixture comprising (a) an epoxy-containing acrylic resin, (b) a polycarboxylic acid compound curing agent, (c) fine crosslinked resin particles and/or (d) a resin that exists in the liquid form at room temperature.

Aminoplast-Based Crosslinkers and Powder Coating Compositions Containing Such Crosslinkers
U.S. Patent 6,316,109
Issued: November 13, 2001
Inventors: Ambrose, Ronald R. et al
Assigned to: PPG Industries Inc.

A crosslinking agent having reactive benzoxazine groups is provided. The crosslinking agent is the ungelled reaction product of a polyhydric aromatic compound and an aminotriazine compound having one or less nonalkylated NH bond per triazine ring. The crosslinking agent is essentially free of hydroxyl functionality and has a glass transition temperature of at least 10ºC. Additionally provided is a method for preparing the crosslinking agent. Also provided is a curable powder coating composition including a solid particulate, film-forming mixture of a polymer having functional groups reactive with benzoxazine groups and the crosslinking agent. Further provided is a multilayer composite coating composition having a basecoat layer deposited from a film-forming basecoating composition and a topcoat layer deposited from the curable powder coating composition. Coated substrates are also provided.

Powder Coatings Employing Silyl Carbamates
U.S. Patent 6,319,311
Issued: November 20, 2001
Inventors: Katz, Lawrence E., et al.
Assigned to: OSI Specialties Inc.

Powder coating formulations which include as a component thereof a silyl carbamate. The silanes are useful as crosslinkers and/or adhesion promoters.

Method for Powder Coating the Surface of Heat Sensitive Objects
U.S. Patent 6,319,562
Issued: November 20, 2001
Inventors: Arverus, H.ang.kan, et al
Assigned to: Triline AB (SE)

Method and plant for powder coating the surfaces of objects with polymeric powder having a melting and softening temperature near 100ºC, said polymeric powder includes a polymer curable under the influence of electromagnetic radiation, the method including a first step in which the objects to be coated are prepared to retain powder charged with static electricity, a second step in which the objects are sprayed with powder charged with static electricity, a third step in which the objects are heated to a surface temperature of about 100ºC, thereby melting the powder retained on the surfaces by being exposed to the objects to infrared radiation and heated air, and a fourth step in which the objects are radiated by electromagnetic radiation for initiating of curing of the powder.

Powder Coating for Packaging Containers
U.S. Patent 6,322,900
Issued: November 27, 2001
Inventors: Kiriazis, Leonidas
Assigned to: PPG Industries Inc.

The present invention relates to a powder coating for application to packaging containers, the powder coating comprising A) at least one thermoplastic, B) if desired, at least one thermoset, preferably an epoxy resin having an epoxy equivalent weight of from 400 to 3000, C) if desired, pigments, fillers, catalysts, typical powder coating additives. The powder coating has a particle-size distribution such that at least 90% by mass of the powder coating particles have a size of between 1 and 120 microns, the maximum size of the powder coating particles is 150 microns, and the mean size of the powder coating particles is between 1 and 60, preferably from 1 to 30 microns.

Powder Coating Composition and Method
U.S. Patent 6,325,846
Issued: December 4, 2001
Inventors: Bagala, Joseph Michael, et al
Assigned to: Engelhard Corp.

A laminar pigment which has an aluminum or an aluminum-cerium oxide coating combined with a hydrolyzed silane coupling agent treated surface is used as a pigment for a powder coating composition. By combining the pigment with a powdery film-forming polymer, a film-forming composition which can be applied by electrostatic coating is produced.

European Patents

Blocked Polyisocyanates With Built-in HALS-Stabilizer
Granted: May 10, 2000
EP0839845
Assigned to: Degussa-Huls Aktiengesellschaft

A transparent or pigmented PUR powder coating, having a) 100 parts of OH-containing resin, b) 10 to 90 parts of a polyisocyanate blocked with a 2,2,6,6-tetramethyl-substitued HALS-compound bearing one di-ethanolamine-substituent, and at least one flow agent in an amount of 0.5 to 5 parts by weight, with an OH/NCO-ratio of 2 to 0.5.

Modified Polyester Resin/Organic Peroxide Systems for Powder Coatings
Granted: August 23, 2000
EP0891383
Assigned to: E.I. Du Pont

De Nemours and Company
Modified polyester resin/peroxide systems for powder coatings comprising a) 55 to 60 wt% of a polyester resin which originates from the reaction of polycarboxylic acids or anhydrides with polyhydroxylated alcohols, including unsaturated compound(s) selected from (meth)acrylic acid, unsaturated polycarboxylic acid, their esters or their anhydrides, allyl compounds and dicyclopentadiene, with molecular weights of between 2k and 15k and the degree of branching being between 2 and 4; b) 0.5 to 3 wt% of an organic peroxide with a minimum curing temperature of between 140 and 190ºC.

Powder Coating
Granted: November 8, 2000
EP0846034
Assigned to: Dupont Powder
Coatings Scandinavia AB

Powder for use in a melt coating process at temperatures below 100ºC, which is curable by electromagnetic radiation, especially ultraviolet radiation.

Self-Adhesive Compositions with Improved Tracking Resistance for Coating Metal Substrates
Granted: January 31, 2001
EP0821039
Assigned to: Atofina

Precipitated calcium carbonate, uncoated, with a BET surface of between 7 and 12 sqm/g and a free flow specific weight of between 130 and 180 g/l as an anti-creepage additive for a metal-covered powder coating.

Inhibition of Bacterial Growth
Granted: July 18, 2001
EP0904323
Assigned to: Biocote Limited

A powder coating composition containing 0.1 to 20 wt% of a biocide said biocide being uniformly incorporated into the powder by means of a melt mixing method.

Use of Cyclic Oligosaccharides or Polysaccharides as Charge Control Agents
Granted: October 10, 2001
EP0687959
Assigned to: Clarient Gmb H

A powder or powder coating comprising a polyester or acrylic resin comprising epoxide, carboxyl or hydroxide groups, and 0.01 to 50 wt% of at least one cyclically linked oligosaccharide having a polymerization degree of 6 to 80; each glucose unit bearing at least one substituent selected from methylhalogenide, methanol or methoxymethyl, methoxytriphenylmethane, methoxytrimethylsilane, methoxysulfonate, carboxyl or carboxymethylester.

Linear Epoxy Functional Polyester Resins
Granted: October 17, 2001
EP0720997
Assigned to: Resolution
Research Nederland B.V.

A powder coating composition comprising a linear polyester resin obtainable by reaction of a) at least one cycloaliphatic carboxylic acid compound, b) at least one cyclohexane compound, c) at least one hydroxyl substituted carboxylic acid compound, and d) a secondary cycloaliphatic carboxylic acid compound. The reaction is performed at a temperature between 120 and 230ºC, the reaction product further being reacted with epihalohydrin in the presence of base until the carboxyl groups have disappeared.

Heat-Curable Powder Coating
Granted: April 3, 2002
EP0776949
Assigned to: Ems-Inventa AG

Process for preparing powder coatings based on acrylate copolymers containing glycidyl ether, characterized in that a hydroxyl functional acrylate copolymer is prepared by free radical polymerization of a monomer mixture consisting of (meth)acrylate esters and up to 90 wt% of vinylaromatic compounds, with the proviso that the polymer has an OH number of from 10 to 400 mg KOH/g, and is reacted with epihaloalkanes into an acrylate copolymer containing glycidyl ether; and said polymer is extruded conjointly with an acid component selected from (cyclo)aliphatic polybasic acid and/or its anhydride, an amorphous or semicrystalline carboxy functional polyester resin and/or a carboxy functional acrylic resin; and optionally additional pigments, fillers and/or additives processed to give a powder coating.

Method for Producing a Powder Coating Composition
Granted: April 3, 2002
EP1042412
Assigned to: E.I. Du Pont
De Nemours and Company

Process for the production of a polyester-based powder coating composition by a) joint or separate heating of 99-40 wt% of polyester (precursor) and 1 to 60 wt% of pigment(s) to a temperature of 120 to 200ºC with application of shear forces so that the melting temperature of the polyester (forming precursors) is at least reached and condensation reaction takes place until a polyester is obtained; cooling the dispersion to the temperature range from 60 to 140ºC and adding a crosslinking agent.

Smooth Thin Film Powder Coating
Granted: March 6, 2002
EP0720999
Assigned to: Morton International Inc.

A coating powder consisting essentially of generally spherical hollow particles wherein at least 96 Vol% of said particles having a size below 20 æm, the median particle size is from 6 to 7 æm.

Powder Coating for Eggshell Coatings
Granted: April 17, 2002
EP0744421
Assigned to: Bayer AG

Powder coating comprising A) a binder component having an OH number of 25 to 200, B) a polyaddition compound based on uretdione formed from (cyclo)aliphatic diisocyanates, C) a component solid below 40 degrees C and liquid above 160ºC, characterized that it is either a dicarboxylic acid or anhydrides thereof, a hydroxycarboxylic acid, and D) a component reactive to carboxyl and/or carboxylic anhydride groups.