WO2014099580A1 - Powder coating composition - Google Patents
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- WO2014099580A1 WO2014099580A1 PCT/US2013/074578 US2013074578W WO2014099580A1 WO 2014099580 A1 WO2014099580 A1 WO 2014099580A1 US 2013074578 W US2013074578 W US 2013074578W WO 2014099580 A1 WO2014099580 A1 WO 2014099580A1
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- coating composition
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/67—Unsaturated compounds having active hydrogen
- C08G18/671—Unsaturated compounds having only one group containing active hydrogen
- C08G18/672—Esters of acrylic or alkyl acrylic acid having only one group containing active hydrogen
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/30—Low-molecular-weight compounds
- C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
- C08G18/3203—Polyhydroxy compounds
- C08G18/3206—Polyhydroxy compounds aliphatic
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/30—Low-molecular-weight compounds
- C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
- C08G18/3203—Polyhydroxy compounds
- C08G18/3212—Polyhydroxy compounds containing cycloaliphatic groups
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
- C08G18/72—Polyisocyanates or polyisothiocyanates
- C08G18/73—Polyisocyanates or polyisothiocyanates acyclic
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
- C08G18/81—Unsaturated isocyanates or isothiocyanates
- C08G18/8141—Unsaturated isocyanates or isothiocyanates masked
- C08G18/815—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen
- C08G18/8158—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen with unsaturated compounds having only one group containing active hydrogen
- C08G18/8175—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen with unsaturated compounds having only one group containing active hydrogen with esters of acrylic or alkylacrylic acid having only one group containing active hydrogen
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
- C09D175/04—Polyurethanes
- C09D175/14—Polyurethanes having carbon-to-carbon unsaturated bonds
- C09D175/16—Polyurethanes having carbon-to-carbon unsaturated bonds having terminal carbon-to-carbon unsaturated bonds
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/03—Powdery paints
- C09D5/033—Powdery paints characterised by the additives
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G2150/00—Compositions for coatings
- C08G2150/20—Compositions for powder coatings
Definitions
- the technical field refers to a powder coating composition useful for the preparation of coatings with anti-graffiti properties.
- polyurethane resins are known to the person skilled in the art; in particular, they may be produced by reacting polyol(s) with polyisocyanate(s).
- Coatings with anti-graffiti properties can also be based on powder coating compositions comprising a mixture of polyester binder resins having different hydroxyl numbers and number-average molar masses (Mn), see for example EP-A 2214917.
- WO 2007059133 discloses a powder coating composition containing hydrophobic agents such as functional alkyl silanes, alkyl siloxanes, fluorine alkyl silanes and fluorine alkyl siloxanes, and perfluorinated hydro carbons.
- EP-A 772 514 describes surfaces having specific structure consisting of elevations and depths with specific distances, the elevations are made of hydrophobic polymers providing a self-cleaning surface.
- WO 02/064266 describes coatings providing a particle-based surface structure wherein the particles have an average diameter lower 100 nm, and wherein the coating is at least partially hydrophobic.
- the self-cleaning ability of the coatings of prior art often is not stable during the time of exposure of the coated surface to weather.
- the exemplary embodiments herein relate to a powder coating composition
- a powder coating composition comprising:
- the powder coating composition according to the invention based on the at least such polyurethane resin provides coatings with highly improved anti-graffity properties, and can be used to provide additionally a stable self-cleaning effect of the coatings.
- the various embodiments refer to a powder coating composition
- a powder coating composition comprising as component A) about 30 to about 99.5 wt%, based on the total weight of the powder coating composition, of at least one polyurethane resin as binder resin which is produced from an isocyanate component and an alcohol component comprising at least one ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane, providing the powder coating composition a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition.
- the powder coating composition comprises as component A) about 50 to about 99.5 wt%, more preferably about 80 to about 99.5 wt%, of the at least one polyurethane resin, the wt% based on the total weight of the powder coating composition, particularly in case the powder coating composition of the invention is cured by high energy radiation, for example, ultra violet (UV) irradiation.
- high energy radiation for example, ultra violet (UV) irradiation.
- the powder coating composition bcomprises as component A) about 30 to about 90 wt%, more preferably about 50 to about 80 wt%, of the at least one polyurethane resin, the wt% based on the total weight of the powder coating composition, particularly in case the powder coating composition of the invention is cured by thermal energy.
- the at least one polyurethane resin contemplated herein can be selected from the group consisting of amorphous, crystalline and/or semi-crystalline polyurethane resins.
- the at least one polyurethane resin is selected from the group consisting of crystalline and/or semi-crystalline polyurethane resins.
- Amorphous substances can be defined by glass transition temperatures (Tg), and crystalline and/or semi-crystalline substances can be defined by melting temperatures (Tm).
- Tg is the glass transition temperature of the solid component(s) measured by means of differential scanning calorimetry (DSC) according to ISO 1 1357-2 standard.
- Tm is the melting temperature of the solid component(s) measured by means of DSC at heating rates of 10 K/min according to DIN 53765-B-10 standard.
- the melting temperature is not in general a sharp melting point, but instead the upper end of melting range with a breadth, as known by a skilled person.
- the at least one polyurethane resin contemplated herein may have a number-average molar mass (Mn) in the range of, for example, about 500 to about 15000, preferably about 1000 to about 12000.
- the number-average molar mass (Mn) stated herein is the number average molar mass determined or to be determined by gel permeation chromatography (GPC; divinylbenzene-cross-linked polystyrene as the immobile phase,
- polystyrene standards determined according to ISO 13885-1 standard.
- the at least one polyurethane resin may be non-functional, or may have functional groups such as hydroxyl, carboxyl, alkoxy, (meth)acryl, blocked
- the polyurethane resin carries functional groups.
- the functional groups can be incorporated by reactions as known in the art.
- (meth)acryloyl groups can be introduced by transesterifying hydroxy functional polyurethane resin with alkyl esters of (meth)acrylic acid;
- esterifying hydroxy functional polyurethane resin with (meth)acrylic acid reacting hydroxyl functional polyurethane resin with isocyanate-functional (meth)acrylates or reacting carboxy functional polyurethane resin with epoxy-functional (meth)acrylates, reacting isocyanate functional polyurethane resin with hydroxyalkyl (meth)acrylates.
- the hydroxyl groups may be introduced using measures known to the person skilled in the art, for example, by reacting isocyanate groups still present in the
- (meth)acryloyl is respectively intended to mean acryloyl and/or methacryloyl.
- (meth)acryl is respectively intendedo to mean acryl and/or methacryl.
- the at least one polyurethane resin contemplated herein may have a hydroxyl number in the range of, fobr example, about 30 to about 150 milligrams (mg) KOH/g resin, preferably about 30 to about 120 mg KOH/g resin.
- the carboxyl functional polyurethane resin contemplated herein may have an acid number in the range of, for example, about 30 to about 150 mg KOH/g resin, preferably about 30 to about 120 mg KOH/g resin.
- the at least one polyurethane resin may have a number of blocked isocyanate groups, calculated as latent NCO-content in a range of about 5 to about 15, preferably about 5 to about 10.
- the latent NCO-content stated herein is the grams of free isocyanate groups NCO (NCO calculated with molecular mass 42) after deblocking, per 100g resin.
- the isocyanate groups are incorporated in blocked form. Blocking may proceed as known in the art with conventional agents, e.g., with monoalcohols, glycol ethers, ketoximes, lactams, malonic acid esters, acetoacetic acid esters, for example, ethylene glycol monobutyl ether, butanone oxime, phenol, ethyl
- hydroxyl number as used herein is defined as the number of mg of potassium hydroxide (KOH) which is equal to the number of mg acetic acid for acetalizing of 1 g of the resin, determined according to DIN 53240 standard.
- acid number as used herein is defined as the mg of potassium hydroxide required to neutralise the acid groups of the polyester, described in DIN EN ISO 21 14 standard.
- the isocyanate component for the production of the polyurethane resin contemplated herein comprises isocyanate(s) as known by a skilled person as such for the production of polyurethanes.
- diisocyanates such as 1 ,6-hexane diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, the isomeric diphenylmethandiisocyanates, dicyclohexylmethane diisocyanate and cyclohexane diisocyanate, but also polyisocyanates derived from these
- diisocyanates like for example, uretidione or isocyanurate type polyisocyanates produced by di- or trimerization of these diisocyanates or polyisocyanates produced by reaction of these diisocyanates with water and containing biuret groups or urethane group containing polyisocyanates produced by reaction of these diisocyanates with polyols.
- Preferred examples of the isocyanate component are isophorone diisocyanate, 1 ,6-hexane diisocyanate and dicyclohexylmethane diisocyanate.
- the alcohol component for the production of the polyurethane resin contemplated herein comprises the at least one ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane in a content providing the powder coating composition contemplated herein a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, preferably about 0.2 to about 4 wt%, the wt% based on the total weight of the powder coating composition.
- the silicon content of the powder coating composition is provided by the content of the at least one polyurethane resin in the powder coating composition and particularly by the amount of the at least one ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane used for the preparation of the polyurethane resin
- the ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane can be a linear ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane, for example, linear ⁇ , ⁇ - dihydroxyalkylpolydimethylsiloxane having a hydroxyl number in the range of, for example, about 30 to about 150, preferably about 35 to about 120, providing a calculated hydroxy equivalent weight of about 375 to about 1900, preferably about 470 to about 1600.
- the alkyl residue can be, for example, C1 to C6 alkyl group.
- the alcohol component for the production of the polyurethane resin contemplated herein further comprises alcohols which are diols or polyols in the form of low molar mass compounds defined by empirical and structural formula and/or oligomeric or polymeric polyols with number-average molar masses of, for example, up to 800, for example, corresponding hydroxyl-fu notional polyethers, hydroxyl- functional polyesters and/or hydroxyl-functional polycarbonates.
- Examples of such low molar mass diols are ethylene glycol, the isomeric propane- and butanediols, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,10-decanediol, 1 ,12- dodecanediol, 1 ,4-cyclohexanedimethanol, hydrogenated bisphenol A, dimer fatty alcohol, neopentyl glycol, butylethylpropanediol, the isomeric cyclohexanediols, the isomeric cyclohexanedimethanols, tricyclodecanedimethanol.
- polyols are polyols with more than two hydroxyl groups such as glycerol, trimethylolpropane, trimethylolethane and pentaerythrite.
- Preferred examples of such further diols and polyols are trimethylolpropane and glycerol.
- polyurethane resin contemplated herein in such a manner providing the powder coating composition contemplated herein a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition.
- a perfluoroalkyl alcohol can be used in the production of the at least one polyurethane resin, resulting in a fluoro-modified polyurethane resin based on the isocyanate component, the alcohol component comprising the at least one ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane and the perfluoroalkyl alcohol, providing a fluorine content (calculated as elementary fluorine with molecular mass 19) of the powder coating composition contemplated herein in the range of about 0.1 to about 3 wt%, preferably about 0.1 to about 2 wt%, the wt% based on the total weight of the powder coating composition.
- the fluorine content of the powder coating composition is provided by the content of the fluoro-modified polyurethane resin in the powder coating composition and particularly by the amount of the perfluoroalkyl alcohol used for the production of the fluoro-modified
- the perfluoroalkyl alcohol can be a perfluoroalkyl containing polymeric polyol and/or a perfluoroalkyl containing monoalcohol.
- the fluorine-containing polyether polyol has a fluorine content provided by its -OCH 2 C n F 2n+ i groups in the range of, for example, about 24 to about 40 wt%, and it may have a number-average molar mass (Mn) in the range of, for example, about 470 to about 5000.
- the fluorine-containing monoalcohol has a fluorine content provided by its F-(CF 2 ) n - groups in the range of, for example, about 65 to about 70 wt%, and it may have a number-average molar mass (Mn)in the range of, for example, about 416to about 528.
- F-(CF 2 ) n - groups in the range of, for example, about 65 to about 70 wt%, and it may have a number-average molar mass (Mn)in the range of, for example, about 416to about 528.
- Mn number-average molar mass
- Examples of commercially available products are POLYFOXTM 636 (Omnova Solutions), POLYFOXTM 656 (Omnova Solutions) and ZONYL® BA-types (DuPont).
- the person skilled in the art selects the nature and proportion of the isocyanate component and the polyol component comprising the ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane and the perfluoroalkyl alcohol for the production of the fluoro-modified polyurethane resin in such a manner providing the powder coating composition contemplated herein a fluorine content (calculated as elementary fluorine with molecular mass 19) in a range of about 0.1 to about 3 wt%, the wt% based on the total weight of the powder coating composition.
- a fluorine content (calculated as elementary fluorine with molecular mass 19) in a range of about 0.1 to about 3 wt%, the wt% based on the total weight of the powder coating composition.
- the isocyanate component and the polyol component comprising the at least one ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane, and, if desired, the perfluoroalkyl alcohol, can be reacted with one another in substance or in the presence of a solvent and/or water.
- solvent means an organic solvent or mixture of organic solvents, as known in the art.
- solvent may be used, in general, for example, in an amount of 0 to about 50 wt%, the wt% based on the total amount of the polyurethane resin solution which, however, makes it necessary to remove the solvent from the resulted resin.
- the production of the polyurethane resin contemplated herein is carried out without solvent and without subsequent purification operations.
- the reactants may all be reacted together simultaneously or in two or more synthesis stages. When the synthesis is performed in multiple stages, the reactants may be added in the most varied order, for example, also in succession or in alternating manner.
- the polyol component may be divided into two or more partial amounts, for example, or into the individual polyols, for example, such that the isocyanate component is reacted first with a portion of the polyol component, e.g. ⁇ , ⁇ -hydroxy organo functional polydimethylsiloxane, and finally with the remaining proportion of the polyol component.
- the isocyanate component may also be divided into two or more partial amounts, for example, such that the polyols are reacted first with a portion of the isocyanate component and finally with the remaining proportion of the isocyanate component. That means, that the individual reactants may be added in their entirety or in two or more portions.
- the reaction is exothermic and proceeds at a temperature above the melting temperature of the reaction mixture.
- the reaction temperature is, for example, about 60 to about 140°C.
- the rate of addition or quantity of reactants added is accordingly determined on the basis of the degree of exothermy and the liquid (molten) reaction mixture may be maintained within the desired temperature range by heating or cooling.
- solid polyurethane resin is obtained.
- the polyurethane resin assumes the form of a mixture exhibiting a molar mass distribution.
- the polyurethane resin does not, however, require working up and may be used directly as a powder coating binder resin.
- the resulted polyurethane resin may be used in the powder coating composition contemplated herein as binder resin in combination with, as component B), 0 to about 70 wt%, preferably 0 to about 60%, based on the total weight of the powder coating composition, of at least one co-binder resin to cross-link (cure) with one another.
- Examples of the at least one co-binder resin of component B) are binders known as such in the art of paints and coatings by a skilled person which are different from the polyurethane resin of component A) and which are able to crosslink with the polyurethane resin of component A).
- Examples are compounds curable by free-radical polymerization of olefinic double bonds, such as unsaturated polyesters, and/or resins based on polyesters, polyurethanes, phenolic resins, polyester epoxy resins, epoxy resins and/or (meth)acrylic copolymer resins such as glycidyl functionalized (meth) acrylic copolymers, polymer hybrid resins derived from these classes of resin binders, with a number-average molar mass (Mn) in the range of, for example, about 500 to about 10000.
- Mn number-average molar mass
- Examples are also compounds containing amino, amido groups, for example hydroxyl alkylamide compounds, further, dimerized isocyanates (uretidiones), triglycidyl isocyanurate (TGIC);
- polyglycidyl ethers based on diethylene glycol.
- the powder coating composition contemplated herein comprises at least one pigment, filler and/or coating additive known at a skilled person in a range of about 0.5 to about 60 wt%, preferably about 1 to about 60 wt%, based on the total weight of the powder coating composition.
- the pigments can be transparent pigments, color-imparting and/or special effect-imparting pigments and/or fillers (extenders), for example, corresponding a pigment plus filler : resin ratio by weight in the range from about 0:1 to about 2: 1 .
- inorganic or organic color-imparting pigments are titanium dioxide, iron oxide pigments, carbon black, azo pigments, phthalocyanine pigments, quinacridone or pyrrolopyrrole pigments.
- special effect-imparting pigments are metal pigments, for example, made from aluminum, copper or other metals; interference pigments, such as, for example, metal oxide coated metal pigments, for example, titanium dioxide coated or mixed oxide coated aluminum, coated mica, such as, for example, titanium dioxide coated mica.
- Examples of usable fillers are silicon dioxide, aluminum silicate, barium sulfate, calcium carbonate and talcum.
- Coating additives are, for example, inhibitors, catalysts, levelling agents, degassing agents, wetting agents, anticratering agents, initiators, antioxidants and light stabilizers.
- the coating additives are used in conventional amounts known to the person skilled in the art.
- the powder coating composition consists of
- the wt% based on the total weight of the powder coating composition.
- the components of the powder coating composition are mixed, extruded and ground by conventional techniques employed in the powder coatings art familiar to a person of ordinary skill in the art. Typically, all of the components of the present powder coating formulation are added to a mixing container and mixed together. The blended mixture is then melt blended, for example, in a melt extruder. Also, components can be melt blended with the molten polyurethane resin. The melt blended, for example extruded, composition is then cooled and broken down and ground to a powder. The ground powder is subsequently screened to achieve the desired particle size, for example, an average particle size (mean particle diameter) of about 20 to about 200 ⁇ , determined by means of laser diffraction.
- an average particle size mean particle diameter
- a predetermined amount of a component of the powder coating components be added, for example, to the further components of the composition, and then premixed.
- the premix can then be extruded, cooled, and thereafter pulverized and classified.
- the powder coating composition may also be prepared by spraying from supercritical solutions, NAD "non-aqueous dispersion” processes or ultrasonic standing wave atomization process.
- specific components of the powder coating composition may be processed with the finished powder coating particles after extrusion and grinding by a "bonding" process using an impact fusion.
- the specific components may be mixed with the powder coating particles.
- the individual powder coating particles are treated to softening their surface so that the components adhere to them and are homogeneously bonded with the surface of the powder coating particles.
- the softening of the powder particles' surface may be done by heat treating the particles to a temperature, e.g., about 40 to about 100°C, dependent from the melt behaviour of the powder particles.
- a temperature e.g., about 40 to about 100°C
- the powder coating composition contemplated herein can be readily applied to metallic and non-metallic substrates, in a dry-film thickness of about 10 to about 300 ⁇ , preferably about 20 to about 100 ⁇ , particularly from about 10 to about 50 ⁇ for thin film coatings.
- the powder coating composition can be used to coat metallic substrates including, but not limited to, steel, brass, aluminum, chrome, and mixtures thereof, and also to other substrates including, for example, heat-sensitive substrates, such as, substrates based on wood, plastics and paper, and other substrates based, for example, on glass and ceramics.
- the surface of the substrate may be subjected to a mechanical treatment, such as, blasting followed by, in case of metal substrates, acid rinsing, or cleaning followed by chemical treatment.
- the powder coating composition contemplated herein may be applied by, e.g., electrostatic spraying, electrostatic brushing, thermal or flame spraying, fluidized bed coating methods, flocking, tribostatic spray application and the like, also coil coating techniques, all of which are known to those skilled in the art.
- the substrate Prior to applying the powder coating composition contemplated herein the substrate may be grounded but not pre-heated, so that the substrate is at an ambient temperature of about about 25°C.
- the substrate to be coated may be pre-heated before the application of the powder coating composition, and then either heated after the application of the powder composition or not.
- gas is commonly used for various heating steps, but other methods, e.g., microwaves, infrared (IR), near infrared (NIR) and/or ultra violet (UV) irradiation are also known.
- the pre-heating can be to a temperature ranging from about 60 to about 260°C using means familiar to a person of ordinary skill in the art.
- the powder coating composition of the invention can be applied directly on the substrate surface as a primer coating or on a layer of a primer which can be a liquid or a powder based primer.
- the powder coating composition can also be applied as a coating layer of a multilayer coating system based on liquid or powder coats, for example, as clear coat layer applied onto a color-imparting and/or special effect-imparting base coat layer or as pigmented one-layer coat applied onto a prior coating.
- the powder After being applied, the powder can be melted by exposing by convective, gas and/or radiant heating, e.g., IR and/or NIR irradiation, as known in the art, to temperatures of, e.g. about 100°C to about 300°C, preferably, about 120°C to about 200°C, object temperature in each case, for, e.g., about 2 to about 20 minutes in case of pre-heated substrates, and, for example, about 4 to about 30 minutes in case of non-pre-heated substrates.
- convective, gas and/or radiant heating e.g., IR and/or NIR irradiation
- the applied and melted powder can be cured by thermal energy.
- the coating layer may, for example, be exposed to convective, gas and/or radiant heating, e.g., infra-red (IR) and/or near infra-red (NIR) irradiation, as known in the art, to temperatures of, e.g., about 100 to about 300°C, preferably of about 120 to about 230°C for convective thermal curing and preferably about 200 to about 280°C for radiation heating processes (object temperature in each case).
- IR infra-red
- NIR near infra-red
- Dual curing means a curing method of the powder coating composition where the applied powder coating composition can be cured, e.g., both by high energy radiation such as, e.g. ultra violet (UV) irradiation, and by thermal curing methods known by a skilled person as described above.
- high energy radiation such as, e.g. ultra violet (UV) irradiation
- thermal curing methods known by a skilled person as described above.
- UV (ultraviolet) radiation or electron beam radiation may be used as high- energy radiation. UV-radiation is the preferred high-energy radiation. Irradiation may proceed continuously or discontinuously.
- thermally curable powder coating compositions may contain thermally cleavable free-radical initiators
- the powder coating compositions curable by UV irradiation contain photoinitiators.
- the initiators can be used, for example, in amounts of about 0.1 to about 7 wt%, preferably of about 0.5 to about 5 wt%, based on the total powder coating composition.
- the initiators may be used individually or in combination.
- thermally cleavable free-radical initiators are azo compounds, peroxide compounds and C-C-cleaving initiators, as known by a person skilled in the art.
- photoinitiators are benzoin and derivatives thereof, acetophenone, benzophenone, thioxanthone and derivatives thereof, anthraquinone, 1 - benzoylcyclohexanol, organophosphorus compounds as known by a person skilled in the art.
- the self-cleaning properties of the coatings provided by the powder coating composition contemplated herein can be determined by testing the initial self- cleaning ability of a coating layer on a panel by applying Leverkusen standard dirt 09 LD-40 (commercially available from wfk-Cleaning Technology Institute, Krefeld, Germany) on the horizontally positioned coated panel, using a sieve, to the horizontally positioned panel. Then, 10 ml of water droplets are placed on the unsoiled area of the coated panel. The unsoiled end of the panel is slowly and continuously raised from the horizontal position to a more vertical position, and the angle at which the water droplets begin to move is recorded.
- Leverkusen standard dirt 09 LD-40 commercially available from wfk-Cleaning Technology Institute, Krefeld, Germany
- the mixture is heated to 60 °C, and 19.4 wt% of hydroxyethylacrylate is dosed in such a way that a temperature of 80 °C is not exceeded.
- the mixture is kept at 80 °C till the target NCO-value is reached.
- the molten resin is filled off and cooled down.
- HDI 1 ,6-hexandiisocyanate
- the powder clear coats are applied with a film thickness of 80 ⁇ onto steel panels, molten for 10 min at 140 °C (oven temperature) and after that irradiated with UV-light with an intensity of 500 mW/cm2 and a UV-dose of 800 mJ/cm2.
- the self-cleanability of a coating layer over time are determined by the following method.
- Leverkusen standard dirt 09 LD- 40 commercially available from wfk institute Krefeld, Germany
- self-cleanability data comprising the initial self-cleanability and self-cleanability after 500, 1000 and 2000 hours of artificial weathering are obtained and a trend can be estimated, if or to what extent the self-cleanability of the coating layer reduces over time when exposed to the weather.
- the coated panel is sprayed with a commercial black spray-can lacquer. After the lacquer had dried, an adhesive strip was stuck on the surface. If the spray- can lacquer layer was also removed when the strip was torn-off the desired unsticking-property was achieved (rating satisfactory), whereas when the spray-can lacquer remained on the panel the test result was unsatisfactory.
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Abstract
A powder coating composition includes: A) about 30 to about 99.5 wt% of a polyurethane resin as binder resin which is produced from an isocyanate component and an alcohol component comprising a α,ω-hydroxy organo functional polydimethylsiloxane, providing the powder coating composition a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition, B) 0 to about 70 wt% of a co-binder (cross-linking agent, hardener), and C) about 0.5 to about 60 wt% of a pigment, filler and/or coating additive, the wt% based on the total weight of the powder coating composition. The powder coating composition provides coatings with highly improved anti-graffity properties and can be used to provide additionally a stable self-cleaning effect of the coatings.
Description
POWDER COATING COMPOSITION
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional Application No. 61/738,054, filed December 17, 2012.
TECHNICAL FIELD
[0002] The technical field refers to a powder coating composition useful for the preparation of coatings with anti-graffiti properties.
BACKGROUND
[0003] The production of polyurethane resins is known to the person skilled in the art; in particular, they may be produced by reacting polyol(s) with polyisocyanate(s).
[0004] Undesired graffiti on buildings and vehicles produced by spraying cannot be eliminated in most cases simply by washing; usually the graffiti-bearing walls and substrates have to be repainted, which is laborious and expensive.
[0005] Attempts have been made to prepare protective coatings providing a low surface tension and, therefore, dirt-repellent properties. Examples are formulations comprising fluorine containing polymers, see US 4929666, and formulations comprising polysiloxane compounds as described in DE-A 2610 372 and US 5426151 . Problems arising with these systems are the incompatibility of components in the coating formulation or insufficient anti-graffiti protection for a long time period.
[0006] Coatings with anti-graffiti properties can also be based on powder coating compositions comprising a mixture of polyester binder resins having different hydroxyl numbers and number-average molar masses (Mn), see for example EP-A 2214917.
[0007] Easy-to-clean powder coating compositions are known providing coatings having a self-cleaning effect. For example, WO 2007059133 discloses a powder coating composition containing hydrophobic agents such as functional alkyl silanes, alkyl siloxanes, fluorine alkyl silanes and fluorine alkyl siloxanes, and perfluorinated hydro carbons. EP-A 772 514 describes surfaces having specific structure consisting of elevations and depths with specific distances, the elevations are made of
hydrophobic polymers providing a self-cleaning surface. WO 02/064266 describes coatings providing a particle-based surface structure wherein the particles have an average diameter lower 100 nm, and wherein the coating is at least partially hydrophobic. Unfortunately, the self-cleaning ability of the coatings of prior art often is not stable during the time of exposure of the coated surface to weather.
[0008] Accordingly, it is desirable to provide a powder coating composition having anti-graffity properties. In addition, it desirable to provide powder coating
compositions with stable self-cleaning effects. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.
SUMMARY
[0009] The exemplary embodiments herein relate to a powder coating composition comprising:
A) about 30 to about 99.5 wt% of at least one polyurethane resin as binder resin which is produced from an isocyanate component and an alcohol component comprising at least one α,ω-hydroxy organo functional polydimethylsiloxane, providing the powder coating composition a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition,
B) 0 to about 70 wt% of at least one co-binder (cross-linking agent, hardener), and
C) about 0.5 to about 60 wt% of at least one pigment, filler and/or coating additive,
[00010] the wt% based on the total weight of the powder coating composition.
[00011] The powder coating composition according to the invention based on the at least such polyurethane resin provides coatings with highly improved anti-graffity properties, and can be used to provide additionally a stable self-cleaning effect of the coatings.
DETAILED DESCRIPTION
[00012] The following detailed description is merely exemplary in nature and is not intended to limit the embodiments herein or the application and uses thereof.
Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
[00013] The features and advantages of the present invention will be more readily understood, by those of ordinary skill in the art, from reading the following detailed description. It is to be appreciated that those certain features of the invention which are, for clarity, described above and below in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. In addition, references in the singular may also include the plural (for example, "a" and "an" may refer to one, or one or more) unless the context specifically states otherwise.
[00014] The disclosure of value ranges is intended as a continuous range of values including every value between the minimum and maximum values.
[00015] The various embodiments refer to a powder coating composition comprising as component A) about 30 to about 99.5 wt%, based on the total weight of the powder coating composition, of at least one polyurethane resin as binder resin which is produced from an isocyanate component and an alcohol component comprising at least one α,ω-hydroxy organo functional polydimethylsiloxane, providing the powder coating composition a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition.
[00016] Preferably, the powder coating composition comprises as component A) about 50 to about 99.5 wt%, more preferably about 80 to about 99.5 wt%, of the at least one polyurethane resin, the wt% based on the total weight of the powder coating composition, particularly in case the powder coating composition of the invention is cured by high energy radiation, for example, ultra violet (UV) irradiation.
[00017] Preferably, the powder coating composition bcomprises as component A) about 30 to about 90 wt%, more preferably about 50 to about 80 wt%, of the at least
one polyurethane resin, the wt% based on the total weight of the powder coating composition, particularly in case the powder coating composition of the invention is cured by thermal energy.
[00018] The at least one polyurethane resin contemplated herein can be selected from the group consisting of amorphous, crystalline and/or semi-crystalline polyurethane resins. Preferably, the at least one polyurethane resin is selected from the group consisting of crystalline and/or semi-crystalline polyurethane resins.
[00019] The terms amorphous, crystalline and semi-crystalline stated herein are known by a skilled person. Amorphous substances can be defined by glass transition temperatures (Tg), and crystalline and/or semi-crystalline substances can be defined by melting temperatures (Tm). The term Tg is the glass transition temperature of the solid component(s) measured by means of differential scanning calorimetry (DSC) according to ISO 1 1357-2 standard. The term Tm is the melting temperature of the solid component(s) measured by means of DSC at heating rates of 10 K/min according to DIN 53765-B-10 standard. The melting temperature is not in general a sharp melting point, but instead the upper end of melting range with a breadth, as known by a skilled person.
[00020] The at least one polyurethane resin contemplated herein may have a number-average molar mass (Mn) in the range of, for example, about 500 to about 15000, preferably about 1000 to about 12000.
[00021] The number-average molar mass (Mn) stated herein is the number average molar mass determined or to be determined by gel permeation chromatography (GPC; divinylbenzene-cross-linked polystyrene as the immobile phase,
tetrahydrofuran as the liquid phase, polystyrene standards) determined according to ISO 13885-1 standard.
[00022] The at least one polyurethane resin may be non-functional, or may have functional groups such as hydroxyl, carboxyl, alkoxy, (meth)acryl, blocked
isocyanate groups and/or may have free-radically polymerizable olefinic double bonds in the form of (meth)acryloyl within its resin structure. Preferably, the polyurethane resin carries functional groups.
[00023] The functional groups can be incorporated by reactions as known in the art.
[00024] For example, (meth)acryloyl groups can be introduced by transesterifying hydroxy functional polyurethane resin with alkyl esters of (meth)acrylic acid;
esterifying hydroxy functional polyurethane resin with (meth)acrylic acid; reacting hydroxyl functional polyurethane resin with isocyanate-functional (meth)acrylates or reacting carboxy functional polyurethane resin with epoxy-functional (meth)acrylates, reacting isocyanate functional polyurethane resin with hydroxyalkyl (meth)acrylates. The hydroxyl groups may be introduced using measures known to the person skilled in the art, for example, by reacting isocyanate groups still present in the
polyurethane resin with polyols.
[00025] The term (meth)acryloyl is respectively intended to mean acryloyl and/or methacryloyl.
[00026] The term (meth)acryl is respectively intendedo to mean acryl and/or methacryl.
[00027] For example, the at least one polyurethane resin contemplated herein may have a hydroxyl number in the range of, fobr example, about 30 to about 150 milligrams (mg) KOH/g resin, preferably about 30 to about 120 mg KOH/g resin. The carboxyl functional polyurethane resin contemplated herein may have an acid number in the range of, for example, about 30 to about 150 mg KOH/g resin, preferably about 30 to about 120 mg KOH/g resin. Further, the at least one polyurethane resin may have a number of blocked isocyanate groups, calculated as latent NCO-content in a range of about 5 to about 15, preferably about 5 to about 10.
[00028] The latent NCO-content stated herein is the grams of free isocyanate groups NCO (NCO calculated with molecular mass 42) after deblocking, per 100g resin.
[00029] The isocyanate groups are incorporated in blocked form. Blocking may proceed as known in the art with conventional agents, e.g., with monoalcohols, glycol ethers, ketoximes, lactams, malonic acid esters, acetoacetic acid esters, for example, ethylene glycol monobutyl ether, butanone oxime, phenol, ethyl
acetoacetate, dimethylpyrazole or caprolactam.
[00030] The term hydroxyl number as used herein is defined as the number of mg of potassium hydroxide (KOH) which is equal to the number of mg acetic acid for acetalizing of 1 g of the resin, determined according to DIN 53240 standard.
[00031] The term acid number as used herein is defined as the mg of potassium hydroxide required to neutralise the acid groups of the polyester, described in DIN EN ISO 21 14 standard.
[00032] The person skilled in the art selects the nature and proportion of the components of the polyurethane resin contemplated herein in such a manner providing the polyurethane resin the functional groups as described above.
[00033] The isocyanate component for the production of the polyurethane resin contemplated herein comprises isocyanate(s) as known by a skilled person as such for the production of polyurethanes. Examples are diisocyanates such as 1 ,6-hexane diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, the isomeric diphenylmethandiisocyanates, dicyclohexylmethane diisocyanate and cyclohexane diisocyanate, but also polyisocyanates derived from these
diisocyanates, like for example, uretidione or isocyanurate type polyisocyanates produced by di- or trimerization of these diisocyanates or polyisocyanates produced by reaction of these diisocyanates with water and containing biuret groups or urethane group containing polyisocyanates produced by reaction of these diisocyanates with polyols.
[00034] Preferred examples of the isocyanate component are isophorone diisocyanate, 1 ,6-hexane diisocyanate and dicyclohexylmethane diisocyanate.
[00035] The alcohol component for the production of the polyurethane resin contemplated herein comprises the at least one α,ω-hydroxy organo functional polydimethylsiloxane in a content providing the powder coating composition contemplated herein a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, preferably about 0.2 to about 4 wt%, the wt% based on the total weight of the powder coating composition. The silicon content of the powder coating composition is provided by the content of the at least one polyurethane resin in the powder coating composition and particularly by the amount of the at least one α,ω-hydroxy organo functional polydimethylsiloxane used for the preparation of the polyurethane resin
contemplated herein.
[00036] The α,ω-hydroxy organo functional polydimethylsiloxane can be a linear α,ω-hydroxy organo functional polydimethylsiloxane, for example, linear α,ω-
dihydroxyalkylpolydimethylsiloxane having a hydroxyl number in the range of, for example, about 30 to about 150, preferably about 35 to about 120, providing a calculated hydroxy equivalent weight of about 375 to about 1900, preferably about 470 to about 1600. The alkyl residue can be, for example, C1 to C6 alkyl group.
[00037] An example of a commercially available product is TEGOMER® H-Si 231 1 (Evonic Ind.)
[00038] The alcohol component for the production of the polyurethane resin contemplated herein further comprises alcohols which are diols or polyols in the form of low molar mass compounds defined by empirical and structural formula and/or oligomeric or polymeric polyols with number-average molar masses of, for example, up to 800, for example, corresponding hydroxyl-fu notional polyethers, hydroxyl- functional polyesters and/or hydroxyl-functional polycarbonates.
[00039] Examples of such low molar mass diols are ethylene glycol, the isomeric propane- and butanediols, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,10-decanediol, 1 ,12- dodecanediol, 1 ,4-cyclohexanedimethanol, hydrogenated bisphenol A, dimer fatty alcohol, neopentyl glycol, butylethylpropanediol, the isomeric cyclohexanediols, the isomeric cyclohexanedimethanols, tricyclodecanedimethanol.
[00040] Examples of polyols are polyols with more than two hydroxyl groups such as glycerol, trimethylolpropane, trimethylolethane and pentaerythrite.
[00041] Preferred examples of such further diols and polyols are trimethylolpropane and glycerol.
[00042] The person skilled in the art selects the nature and proportion of the isocyanate component and the alcohol component comprising at least one α,ω- hydroxy organo functional polydimethylsiloxane for the production of the
polyurethane resin contemplated herein in such a manner providing the powder coating composition contemplated herein a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition.
[00043] Further, additionally a perfluoroalkyl alcohol can be used in the production of the at least one polyurethane resin, resulting in a fluoro-modified polyurethane resin based on the isocyanate component, the alcohol component comprising the at least one α,ω-hydroxy organo functional polydimethylsiloxane and the perfluoroalkyl
alcohol, providing a fluorine content (calculated as elementary fluorine with molecular mass 19) of the powder coating composition contemplated herein in the range of about 0.1 to about 3 wt%, preferably about 0.1 to about 2 wt%, the wt% based on the total weight of the powder coating composition. The fluorine content of the powder coating composition is provided by the content of the fluoro-modified polyurethane resin in the powder coating composition and particularly by the amount of the perfluoroalkyl alcohol used for the production of the fluoro-modified
polyurethane resin.
[00044] The perfluoroalkyl alcohol can be a perfluoroalkyl containing polymeric polyol and/or a perfluoroalkyl containing monoalcohol. The perfluoroalkyl containing polymeric polyol can be an aliphatic and/or cycloaliphatic polyether polyol having - OCH2CnF2n+i groups with n = 1 or 2, and it can be prepared from a polyether polyol wherein a number of the hydroxyl groups have been etherified with an alcohol of the formula CnF2n+iCH2OH with n = 1 or 2, and wherein two or more hydroxyl groups are unetherified free hydroxyl groups in the molecule. The fluorine-containing polyether polyol has a fluorine content provided by its -OCH2CnF2n+i groups in the range of, for example, about 24 to about 40 wt%, and it may have a number-average molar mass (Mn) in the range of, for example, about 470 to about 5000. The perfluoroalkyl containing monoalkohol can be a perfluoroalkyl ethanol of the formula F-(CF2)n- CH2CH2OH with n = 2-8, for example, perfluorobutyl ethanol, perfluorohexyl ethanol and/or perfluorooctyl ethanol. The fluorine-containing monoalcohol has a fluorine content provided by its F-(CF2)n- groups in the range of, for example, about 65 to about 70 wt%, and it may have a number-average molar mass (Mn)in the range of, for example, about 416to about 528. Examples of commercially available products are POLYFOXTM 636 (Omnova Solutions), POLYFOXTM 656 (Omnova Solutions) and ZONYL® BA-types (DuPont).
[00045] The person skilled in the art selects the nature and proportion of the isocyanate component and the polyol component comprising the α,ω-hydroxy organo functional polydimethylsiloxane and the perfluoroalkyl alcohol for the production of the fluoro-modified polyurethane resin in such a manner providing the powder coating composition contemplated herein a fluorine content (calculated as
elementary fluorine with molecular mass 19) in a range of about 0.1 to about 3 wt%, the wt% based on the total weight of the powder coating composition.
[00046] In the process for the production of the polyurethane resin contemplated herein the isocyanate component and the polyol component comprising the at least one α,ω-hydroxy organo functional polydimethylsiloxane, and, if desired, the perfluoroalkyl alcohol, can be reacted with one another in substance or in the presence of a solvent and/or water.
[00047] The term solvent as used herein means an organic solvent or mixture of organic solvents, as known in the art. In the process for the production of the polyurethane resin, solvent may be used, in general, for example, in an amount of 0 to about 50 wt%, the wt% based on the total amount of the polyurethane resin solution which, however, makes it necessary to remove the solvent from the resulted resin. Preferably, the production of the polyurethane resin contemplated herein is carried out without solvent and without subsequent purification operations.
[00048] The reactants may all be reacted together simultaneously or in two or more synthesis stages. When the synthesis is performed in multiple stages, the reactants may be added in the most varied order, for example, also in succession or in alternating manner. The polyol component may be divided into two or more partial amounts, for example, or into the individual polyols, for example, such that the isocyanate component is reacted first with a portion of the polyol component, e.g. α,ω-hydroxy organo functional polydimethylsiloxane, and finally with the remaining proportion of the polyol component. Equally, however, the isocyanate component may also be divided into two or more partial amounts, for example, such that the polyols are reacted first with a portion of the isocyanate component and finally with the remaining proportion of the isocyanate component. That means, that the individual reactants may be added in their entirety or in two or more portions.
[00049] The reaction is exothermic and proceeds at a temperature above the melting temperature of the reaction mixture. The reaction temperature is, for example, about 60 to about 140°C. The rate of addition or quantity of reactants added is accordingly determined on the basis of the degree of exothermy and the liquid (molten) reaction mixture may be maintained within the desired temperature range by heating or cooling.
[00050] Once the reaction is complete and the reaction mixture has cooled, solid polyurethane resin is obtained. The polyurethane resin assumes the form of a mixture exhibiting a molar mass distribution. The polyurethane resin does not, however, require working up and may be used directly as a powder coating binder resin.
[00051] The resulted polyurethane resin may be used in the powder coating composition contemplated herein as binder resin in combination with, as component B), 0 to about 70 wt%, preferably 0 to about 60%, based on the total weight of the powder coating composition, of at least one co-binder resin to cross-link (cure) with one another.
[00052] Examples of the at least one co-binder resin of component B) are binders known as such in the art of paints and coatings by a skilled person which are different from the polyurethane resin of component A) and which are able to crosslink with the polyurethane resin of component A). Examples are compounds curable by free-radical polymerization of olefinic double bonds, such as unsaturated polyesters, and/or resins based on polyesters, polyurethanes, phenolic resins, polyester epoxy resins, epoxy resins and/or (meth)acrylic copolymer resins such as glycidyl functionalized (meth) acrylic copolymers, polymer hybrid resins derived from these classes of resin binders, with a number-average molar mass (Mn) in the range of, for example, about 500 to about 10000. Examples are also compounds containing amino, amido groups, for example hydroxyl alkylamide compounds, further, dimerized isocyanates (uretidiones), triglycidyl isocyanurate (TGIC);
polyglycidyl ethers based on diethylene glycol.
[00053] The powder coating composition contemplated herein comprises at least one pigment, filler and/or coating additive known at a skilled person in a range of about 0.5 to about 60 wt%, preferably about 1 to about 60 wt%, based on the total weight of the powder coating composition.
[00054] The pigments can be transparent pigments, color-imparting and/or special effect-imparting pigments and/or fillers (extenders), for example, corresponding a pigment plus filler : resin ratio by weight in the range from about 0:1 to about 2: 1 . Examples of inorganic or organic color-imparting pigments are titanium dioxide, iron oxide pigments, carbon black, azo pigments, phthalocyanine pigments, quinacridone
or pyrrolopyrrole pigments. Examples of special effect-imparting pigments are metal pigments, for example, made from aluminum, copper or other metals; interference pigments, such as, for example, metal oxide coated metal pigments, for example, titanium dioxide coated or mixed oxide coated aluminum, coated mica, such as, for example, titanium dioxide coated mica.
[00055] Examples of usable fillers are silicon dioxide, aluminum silicate, barium sulfate, calcium carbonate and talcum.
[00056] Coating additives are, for example, inhibitors, catalysts, levelling agents, degassing agents, wetting agents, anticratering agents, initiators, antioxidants and light stabilizers. The coating additives are used in conventional amounts known to the person skilled in the art.
[00057] Preferably, the powder coating composition consists of
A) about 30 to about 99.5 wt% of at least one polyurethane resin as binder resin which is produced from an isocyanate component and an alcohol component comprising at least one α,ω-hydroxy organo functional polydimethylsiloxane, providing the powder coating composition a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition,
B) 0 to about 70 wt% of at least one co-binder (cross-linking agent, hardener), and
C) about 0.5 to about 60 wt% of at least one pigment, filler and/or coating additive,
the wt% based on the total weight of the powder coating composition.
[00058] The components of the powder coating composition are mixed, extruded and ground by conventional techniques employed in the powder coatings art familiar to a person of ordinary skill in the art. Typically, all of the components of the present powder coating formulation are added to a mixing container and mixed together. The blended mixture is then melt blended, for example, in a melt extruder. Also, components can be melt blended with the molten polyurethane resin. The melt blended, for example extruded, composition is then cooled and broken down and ground to a powder. The ground powder is subsequently screened to achieve the
desired particle size, for example, an average particle size (mean particle diameter) of about 20 to about 200 μιη, determined by means of laser diffraction.
[00059] It is possible that a predetermined amount of a component of the powder coating components be added, for example, to the further components of the composition, and then premixed. The premix can then be extruded, cooled, and thereafter pulverized and classified.
[00060] The powder coating composition may also be prepared by spraying from supercritical solutions, NAD "non-aqueous dispersion" processes or ultrasonic standing wave atomization process.
[00061] Furthermore, specific components of the powder coating composition, for example, coating additives, pigment, fillers, may be processed with the finished powder coating particles after extrusion and grinding by a "bonding" process using an impact fusion. For this purpose, the specific components may be mixed with the powder coating particles. During blending, the individual powder coating particles are treated to softening their surface so that the components adhere to them and are homogeneously bonded with the surface of the powder coating particles. The softening of the powder particles' surface may be done by heat treating the particles to a temperature, e.g., about 40 to about 100°C, dependent from the melt behaviour of the powder particles. After cooling the mixture the desired particle size of the resulted particles may be proceed by a sieving process.
[00062] The powder coating composition contemplated herein can be readily applied to metallic and non-metallic substrates, in a dry-film thickness of about 10 to about 300 μιη, preferably about 20 to about 100 μιη, particularly from about 10 to about 50 μιη for thin film coatings.
[00063] The powder coating composition can be used to coat metallic substrates including, but not limited to, steel, brass, aluminum, chrome, and mixtures thereof, and also to other substrates including, for example, heat-sensitive substrates, such as, substrates based on wood, plastics and paper, and other substrates based, for example, on glass and ceramics.
[00064] Depending upon the requirements placed upon the coated substrate, the surface of the substrate may be subjected to a mechanical treatment, such as,
blasting followed by, in case of metal substrates, acid rinsing, or cleaning followed by chemical treatment.
[00065] The powder coating composition contemplated herein may be applied by, e.g., electrostatic spraying, electrostatic brushing, thermal or flame spraying, fluidized bed coating methods, flocking, tribostatic spray application and the like, also coil coating techniques, all of which are known to those skilled in the art.
[00066] Prior to applying the powder coating composition contemplated herein the substrate may be grounded but not pre-heated, so that the substrate is at an ambient temperature of about about 25°C.
[00067] In certain applications, the substrate to be coated may be pre-heated before the application of the powder coating composition, and then either heated after the application of the powder composition or not. For example, gas is commonly used for various heating steps, but other methods, e.g., microwaves, infrared (IR), near infrared (NIR) and/or ultra violet (UV) irradiation are also known. The pre-heating can be to a temperature ranging from about 60 to about 260°C using means familiar to a person of ordinary skill in the art.
[00068] The powder coating composition of the invention can be applied directly on the substrate surface as a primer coating or on a layer of a primer which can be a liquid or a powder based primer. The powder coating composition can also be applied as a coating layer of a multilayer coating system based on liquid or powder coats, for example, as clear coat layer applied onto a color-imparting and/or special effect-imparting base coat layer or as pigmented one-layer coat applied onto a prior coating.
[00069] After being applied, the powder can be melted by exposing by convective, gas and/or radiant heating, e.g., IR and/or NIR irradiation, as known in the art, to temperatures of, e.g. about 100°C to about 300°C, preferably, about 120°C to about 200°C, object temperature in each case, for, e.g., about 2 to about 20 minutes in case of pre-heated substrates, and, for example, about 4 to about 30 minutes in case of non-pre-heated substrates.
[00070] The applied and melted powder can be cured by thermal energy. The coating layer may, for example, be exposed to convective, gas and/or radiant heating, e.g., infra-red (IR) and/or near infra-red (NIR) irradiation, as known in the
art, to temperatures of, e.g., about 100 to about 300°C, preferably of about 120 to about 230°C for convective thermal curing and preferably about 200 to about 280°C for radiation heating processes (object temperature in each case).
[00071] If the powder coating composition contemplated herein is used together with unsaturated resins and, optionally photo-initiators, dual curing may also be used. Dual curing means a curing method of the powder coating composition where the applied powder coating composition can be cured, e.g., both by high energy radiation such as, e.g. ultra violet (UV) irradiation, and by thermal curing methods known by a skilled person as described above.
[00072] UV (ultraviolet) radiation or electron beam radiation may be used as high- energy radiation. UV-radiation is the preferred high-energy radiation. Irradiation may proceed continuously or discontinuously.
[00073] While thermally curable powder coating compositions may contain thermally cleavable free-radical initiators, the powder coating compositions curable by UV irradiation contain photoinitiators. The initiators can be used, for example, in amounts of about 0.1 to about 7 wt%, preferably of about 0.5 to about 5 wt%, based on the total powder coating composition. The initiators may be used individually or in combination.
[00074] Examples of thermally cleavable free-radical initiators are azo compounds, peroxide compounds and C-C-cleaving initiators, as known by a person skilled in the art. Examples of photoinitiators are benzoin and derivatives thereof, acetophenone, benzophenone, thioxanthone and derivatives thereof, anthraquinone, 1 - benzoylcyclohexanol, organophosphorus compounds as known by a person skilled in the art.
[00075] The self-cleaning properties of the coatings provided by the powder coating composition contemplated herein can be determined by testing the initial self- cleaning ability of a coating layer on a panel by applying Leverkusen standard dirt 09 LD-40 (commercially available from wfk-Cleaning Technology Institute, Krefeld, Germany) on the horizontally positioned coated panel, using a sieve, to the horizontally positioned panel. Then, 10 ml of water droplets are placed on the unsoiled area of the coated panel. The unsoiled end of the panel is slowly and continuously raised from the horizontal position to a more vertical position, and the
angle at which the water droplets begin to move is recorded. After the water droplets have reached the bottom end of the panel it is visually rated how much dirt the water droplets have removed from the surface. The coated panel is then carefully cleaned to remove any remaining dirt, and is subjected to artificial weathering conditions (1000h CAM 180 artficial weathering test). The artificially weathered panel is then subjected to the same self-cleaning ability test as described above, and this is repeated again. Finally, a trend can be estimated, if or to what extent the self- cleaning ability reduces over time.
[00076] The following examples illustrate the invention.
Examples
[00077] Example 1
[00078] Preparation of a polyurethane resin as contemplated herein
[00079] In a 2l-four neck glass reactor equipped with stirrer, thermo couple and column 42.1 wt% of 1 ,6-Hexandiisocyanate (HDI) are mixed with 0.3 wt% of methylhydrochinone and 0.01 wt% dibutyltindilaurate. The mixture is heated to 60 °C, and 19.4 wt% of hydroxyethylacrylate is dosed in such a way that a temperature of 80 °C is not exceeded. The mixture is kept at 80 °C till the target NCO-value is reached. After having reached the target NCO-content 20.0 wt% of hydrogenated Bisphenol A, 3.9% of TEGOMER® H-Si 231 1 (commercially available from Tego, a part of Evonik Industries AG) and 14.2 w% of 1 ,10-Dekandiol are added one after the other in such a way that a temperature of 120°C is not exceeded. The
temperature is kept at 120°C till no NCO-value is detectable. The molten resin is filled off and cooled down.
Example 2
[00080] Preparation of a polyurethane resin according to prior art
[00081] In a 2l-four neck glass reactor equipped with stirrer, thermo couple and column 43.7 wt% of 1 ,6-hexandiisocyanate (HDI) are mixed with 0.3 w% of methylhydrochinone and 0.01 wt% dibutyltindilaurate. The mixture is heated to 60 °C and 20.1 w% of hydroxyethylacrylate is dosed in such a way that a temperature of 80 °C is not exceeded. The mixture is kept at 80 °C till the target NCO-value is reached. After having reached the target NCO-content 20.8 wt% of hydrogenated Bisphenol A
and 15.1 wt% of 1 ,10-Dekandiol are added one after the other in such a way that a temperature of 120°C is not exceeded. The temperature is kept at 120°C till no NCO- value is detectable. The molten resin is filled off and cooled down.
Example 3
[00082] Preparation of powder coating compositions, application and test results
[00083] Via premixing and extrusion of a crushed mixture of 96.5 wt% of the polyurethane resin of Example 1 , 1 wt% of IRGACURE® 2959 (Photoinitiator from Ciba), 0.5 wt% of POWDERMATE® 486 CFL (flow additive from Troy Chemical Company), 1 wt% of TINUVIN® 144 (HALS-Light stabilizer from Ciba) and 1 wt% of TINUVIN® 405 (UV-Absorber from Ciba) a powder clear coat is prepared according to standard powder manufacturing process of cooling, breaking, milling and sieving.
[00084] The same preparation is done to prepare a powder clear coat based on the polyurethane resin of Example 2.
[00085] The powder clear coats are applied with a film thickness of 80 μιη onto steel panels, molten for 10 min at 140 °C (oven temperature) and after that irradiated with UV-light with an intensity of 500 mW/cm2 and a UV-dose of 800 mJ/cm2.
[00086] The self-cleanability of a coating layer over time are determined by the following method. First, the initial self-cleanability of a panel provided with the coating layer to be tested is determined by applying Leverkusen standard dirt 09 LD- 40 (commercially available from wfk institute Krefeld, Germany) to all but a 4 centimeter portion of one end of the horizontally positioned panel. Dirt application is performed making use of a sieve. Three 25μΙ drops of deionized water are placed on the unsoiled area of the coated panel. The unsoiled end of the panel is slowly and continuously raised from the horizontal position to a 30° angle causing the water drops to move through the soiled area. After 5 minutes the position of the water drops is recorded and it is visually rated how much dirt the water drops on their move downwards have removed from the surface. The coated panel is then carefully cleaned to remove any remaining dirt and it is thereafter subjected to artificial weathering conditions (500 hours according to SAE J2527, CAM 180 artificial weathering test). Then the self-cleanability test is repeated followed by further cycles of artificial weathering and self-cleanability testing. Finally, self-cleanability data comprising the initial self-cleanability and self-cleanability after 500, 1000 and 2000
hours of artificial weathering are obtained and a trend can be estimated, if or to what extent the self-cleanability of the coating layer reduces over time when exposed to the weather.
[00087] The anti-graffiti-properties are tested in the following manner:
[00088] The coated panel is sprayed with a commercial black spray-can lacquer. After the lacquer had dried, an adhesive strip was stuck on the surface. If the spray- can lacquer layer was also removed when the strip was torn-off the desired unsticking-property was achieved (rating satisfactory), whereas when the spray-can lacquer remained on the panel the test result was unsatisfactory.
Test Results:
Table 1 :
* visual rating
** Chemical resistance test:The panel is placed on a heating plate at 65°C. Over a time
period of 30min droplets of 50μΙ of 36% sulfuric acid are placed on the clear coat
surface in intervals of 1 min. Rating: destruction of the film after x min (0-30).
*** how much dirt is removed by the self cleaning ability test described
above
**** removal of spray-can lacquer according to test described above
[00089] While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.
Claims
1 . A powder coating composition comprising:
A) about 30 to about 99.5 wt% of at least one polyurethane resin as binder resin which is produced from an isocyanate component and an alcohol component comprising at least one α,ω-hydroxy organo functional
polydimethylsiloxane, providing the powder coating composition a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition,
B) 0 to about 70 wt% of at least one co-binder (cross-linking agent, hardener), and
C) about 0.5 to about 60 wt% of at least one pigment, filler and/or coating additive,
the wt% based on the total weight of the powder coating composition.
2. The composition according to claim 1 wherein the silicon content (calculated as elementary silicon with molecular mass 28) is in a range of about 0.2 to about 4 wt%, the wt% based on the total weight of the powder coating
composition.
3. The composition according to claim 1 wherein the α,ω-hydroxy organo functional polydimethylsiloxane is a linear α,ω-dihydroxyalkylpolydimethylsiloxane having a hydroxyl number in the range of about 30 to about 150 providing a calculated hydroxy equivalent weight of about 375 to about 1900.
4. The composition according to claim 3 wherein the linear α,ω- dihydroxyalkylpolydimethylsiloxane has a C1 to C6 alkyl group as alkyl residue.
5. The composition according to claim 1 wherein the polyurethane resin of component A) is in a range of about 50 to about 99.5 wt%, the wt% based on the total weight of the powder coating composition.
6. The composition according to claim 1 wherein the polyurethane resin of component A) is in a range of about 30 to about 90 wt%, the wt% based on the total weight of the powder coating composition.
7. A process for the preparation of a powder coating composition, the powder coating composition comprising:
A) about 30 to about 99.5 wt% of at least one polyurethane resin as binder resin which is produced from an isocyanate component and an alcohol component comprising at least one α,ω-hydroxy organo functional
polydimethylsiloxane, providing the powder coating composition a silicon content (calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition,
B) 0 to about 70 wt% of at least one co-binder (cross-linking agent, hardener), and
C) about 0.5 to about 60 wt% of at least one pigment, filler and/or coating additive,
8. the wt% based on the total weight of the powder coating composition, wherein the at least one polyurethane resin is produced by reacting the isocyanate component and the alcohol component comprising the at least one α,ω-hydroxy organo functional polydimethylsiloxane with one another in substance or in the presence of a solvent and/or water.
9. A substrate coated with a powder coating composition, the powder coating composition comprising:
A) about 30 to about 99.5 wt% of at least one polyurethane resin as binder resin which is produced from an isocyanate component and an alcohol component comprising at least one α,ω-hydroxy organo functional
polydimethylsiloxane, providing the powder coating composition a silicon content
(calculated as elementary silicon with molecular mass 28) in a range of about 0.2 to about 5 wt%, the wt% based on the total weight of the powder coating composition,
B) 0 to about 70 wt% of at least one co-binder (cross-linking agent, hardener), and
C) about 0.5 to about 60 wt% of at least one pigment, filler and/or coating additive,
the wt% based on the total weight of the powder coating composition.
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US201261738054P | 2012-12-17 | 2012-12-17 | |
US61/738,054 | 2012-12-17 |
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WO2014099580A1 true WO2014099580A1 (en) | 2014-06-26 |
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PCT/US2013/074578 WO2014099580A1 (en) | 2012-12-17 | 2013-12-12 | Powder coating composition |
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CN112159621A (en) * | 2020-09-24 | 2021-01-01 | 浙江华彩新材料有限公司 | High-hardness easy-to-clean powder coating and preparation method thereof |
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US6187863B1 (en) * | 1997-08-01 | 2001-02-13 | Ppg Industries Ohio, Inc. | Curable compositions based on functional polysiloxanes |
DE102004058069A1 (en) * | 2004-12-01 | 2006-06-08 | Basf Ag | Scratch-resistant radiation-curable coatings |
US20070112164A1 (en) * | 2005-11-17 | 2007-05-17 | Bayer Materialscience Llc | Low surface energy, ethylenically unsaturated polyisocyanate addition compounds and their use in coating compositions |
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2013
- 2013-12-12 WO PCT/US2013/074578 patent/WO2014099580A1/en active Application Filing
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US6187863B1 (en) * | 1997-08-01 | 2001-02-13 | Ppg Industries Ohio, Inc. | Curable compositions based on functional polysiloxanes |
DE102004058069A1 (en) * | 2004-12-01 | 2006-06-08 | Basf Ag | Scratch-resistant radiation-curable coatings |
US20070112164A1 (en) * | 2005-11-17 | 2007-05-17 | Bayer Materialscience Llc | Low surface energy, ethylenically unsaturated polyisocyanate addition compounds and their use in coating compositions |
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CN112159621A (en) * | 2020-09-24 | 2021-01-01 | 浙江华彩新材料有限公司 | High-hardness easy-to-clean powder coating and preparation method thereof |
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