HK1145090B - Coating compositions exhibiting corrosion resistance properties and methods of coil coating - Google Patents

Description

Coating composition exhibiting corrosion resistance and coil coating method

Technical Field

The present invention relates to a coating composition showing corrosion resistance properties and a process for coil coating (coilling) a metal strip (metal strip).

Background

Coatings are often applied to metal coils (strip or long sheet) such as coils of galvanized steel or aluminum by using roll coating of counter rolls. Since the processing of the metal does not take place until after the coating has been applied, the coating must have excellent mechanical integrity, e.g., flexibility. Coated coils are frequently used in the construction industry for the production of ceiling and wall elements, doors, pipe insulation (piping), roller blinds (roller shutters) or window profiles, building side and roof panels, in the automotive industry for the production of panels for trailer or truck bodies, in the domestic field for the production of shaped parts (profile elements) for washing machines, dishwashers, refrigerators and ranges (ranges), etc.

In many cases, a "primer" coating is applied to the coil to protect the metal substrate from corrosion. The primer layer is often applied directly to the bare or pretreated metal substrate. In some cases, particularly where a primer layer is to be applied over a bare metal substrate, the primer layer is deposited from a composition comprising a substance that enhances the adhesion of the primer layer to the substrate, for example an acid, such as phosphoric acid.

Historically, corrosion resistant "primer" coatings have utilized chromium compounds and/or other heavy metals such as lead to achieve the desired level of corrosion resistance and adhesion to subsequently applied coatings. However, the use of chromium and/or other heavy metals results in the generation of waste streams, which can raise environmental concerns and disposal issues.

Recently, efforts have been made to reduce or eliminate the use of chromium and/or other heavy metals. As a result, coating compositions have been developed that contain other substances added to inhibit corrosion. These include, for example, zinc phosphate, iron phosphate, zinc molybdate, calcium molybdate particles, and the like.

In addition, since solvents, particularly organic solvents, can be expensive, hazardous, and environmentally unfriendly, coatings that are substantially free of solvents are often desired. The presence of significant amounts of organic solvents may be particularly undesirable for health and environmental reasons. Coatings containing water or organic solvents can also be inefficient and expensive because these diluents typically evaporate from the coating before curing is complete.

It would be desirable to provide coating compositions that are substantially free of chromium and/or other heavy metals, and substantially free of organic solvents, wherein the compositions are capable of exhibiting advantageous corrosion resistance properties. In addition, it would be desirable to provide such coating compositions suitable for application by roll coating in coil coating (coil coating) applications, wherein the resulting coating must be flexible.

Summary of The Invention

In certain aspects, the present invention relates to a coating composition comprising: (a) a non-chromium corrosion resistant filler; and (b) a radiation curable film forming binder comprising an unsaturated monomer containing a nitrogen containing cyclic structure and one ethylenically unsaturated double bond. These coating compositions are substantially solvent-free, have high shear ICI viscosity at 50 ℃ of no greater than 550cps, and are capable of producing coatings exhibiting advantageous corrosion resistance properties.

In a further aspect, the invention relates to a method of coil coating a metal strip. These methods include: (a) rolling a primer composition on the strip, the primer composition comprising (1) a non-chrome corrosion resistant filler; and (2) a radiation curable film forming binder comprising an unsaturated monomer containing a nitrogen containing cyclic structure and one ethylenically unsaturated double bond; (b) curing the primer composition by exposing the composition to actinic radiation to form a primer coating exhibiting advantageous corrosion resistance properties; and (c) depositing a top coat composition over at least a portion of the primer coating.

The invention also relates to the relevant coated substrates.

Detailed description of embodiments of the invention

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

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

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

As previously mentioned, certain embodiments of the present invention are directed to coating compositions comprising a film-forming binder. The term "film-forming binder" as used herein refers to a binder capable of forming a self-supporting continuous film on at least a horizontal surface of a substrate when any diluent or carrier present in the composition is removed or when cured at ambient or elevated temperature. The term "binder" as used herein refers to a continuous mass having dispersed therein a particulate material, such as the non-chromium corrosion-resistant filler (which is described below).

In certain embodiments, the film-forming binder is radiation curable, i.e., it is capable of curing when exposed to actinic radiation. "actinic radiation" is light having wavelengths of electromagnetic radiation ranging from gamma rays to ultraviolet ("UV") light, through the visible range, and into the infrared range. Actinic radiation that may be used to cure certain coating compositions of the present invention typically has an electromagnetic radiation wavelength of 100-. Examples of suitable ultraviolet light sources include mercury arcs, carbon arcs, low, medium or high pressure mercury lamps, swirl-flow plasma arcs, and ultraviolet light emitting diodes. The preferred ultraviolet light-emitting lamp is a medium pressure mercury vapor lamp having an output of 200- ­ 600 watts per inch (79-237 watts per centimeter) along the length of the tube. For example, a 5 micron thick wet film of a 100% solids (described below) coating composition of the present invention can be cured through its entire thickness to a tack-free state when exposed to actinic radiation by passing the film under 2-4 medium pressure mercury vapor lamps at a rate of 20-1000 feet per minute (6-300 meters per minute) with UVA energy exposure of 200-1000 mJ/cm.

Substances that are curable upon exposure to actinic radiation include compounds having radiation curable functional groups, such as unsaturated groups, including vinyl groups, vinyl ether groups, epoxy groups, maleimide groups, fumarate groups, and combinations of the foregoing. In certain embodiments, the radiation curable groups are curable upon exposure to ultraviolet radiation and may include, for example, acrylate groups, maleimides, fumarates, and vinyl ethers. Suitable vinyl species include those having unsaturated ester and vinyl ether groups.

In certain embodiments, the radiation curable film-forming binder present in the compositions of the present invention comprises a soft urethane (meth) acrylate polymer. The term "(meth) acrylate" as used herein is meant to include both acrylates and methacrylates. The term "urethane (meth) acrylate polymer" as used herein refers to a polymer having (meth) acrylate functional groups and containing urethane linkages. As will be appreciated, the above-described polymers may be prepared, for example, by reacting a polyisocyanate, a polyol, and a (meth) acrylate having hydroxyl groups, such as described in U.S. Pat. No. 4 column 4 lines 4-49 of 6,899,927, the cited portion of which is incorporated herein by reference.

The term "flexible urethane (meth) acrylate polymer" as used herein refers to a flexible urethane (meth) acrylate polymer that is the reaction product of a polyisocyanate and a polyol having a relatively small number of functional groups per molecule, often two functional groups per molecule. In many cases, the soft urethane (meth) acrylate polymer is a difunctional aliphatic urethane (meth) acrylate polymer in which, for example, a (meth) acrylate group is present at each end of the urethane polymer. In some cases, the molecular weight of the above polymer is 3,000. Another example of a "soft type urethane (meth) acrylate polymer" is described in U.S. patent 6,899,927, column 4, line 50 to column 5, line 3.

In certain embodiments, the soft urethane (meth) acrylate polymer is present in the coating composition of the present invention in an amount of at least 10 weight percent, such as at least 20 weight percent, with the weight percent being based on the total weight of the composition. In certain embodiments, the soft urethane (meth) acrylate polymer is present in the coating composition of the present invention in an amount of no greater than 50 weight percent, such as no greater than 40 weight percent, with the weight percent being based on the total weight of the composition. The amount of the soft type urethane (meth) acrylate polymer in the composition of the present invention may range between any combination of the recited values, inclusive.

As previously mentioned, the radiation curable film-forming binder present in the coating composition of the present invention comprises an unsaturated monomer containing a nitrogen containing cyclic structure and one ethylenically unsaturated double bond, examples of which include N-vinyl pyrrolidone having the chemical structure described in U.S. Pat. No. 5,166,186, column 3, lines 43-49, the cited portion of which is incorporated herein by reference; and (meth) acryloyl morpholine having the chemical structure described in U.S. patent 4,886,840, column 2, lines 25-30, the cited portion of which is incorporated herein by reference; and mixtures thereof. In certain embodiments, the (meth) acryloyl morpholine comprises acryloyl morpholine ("ACMO").

In certain embodiments, the unsaturated monomer containing a nitrogen-containing cyclic structure and one ethylenically unsaturated double bond is present in the coating composition of the present invention in an amount of at least 1 weight percent, such as at least 5 weight percent, with the weight percent being based on the total weight of the composition. In certain embodiments, the unsaturated monomer containing a nitrogen-containing cyclic structure and one ethylenically unsaturated double bond is present in the coating composition of the present invention in an amount of no greater than 30 weight percent, such as no greater than 15 weight percent, with the weight percent being based on the total weight of the composition. The amount of the unsaturated monomer containing a nitrogen-containing cyclic structure and one ethylenically unsaturated double bond in the composition of the present invention can range between any combination of the recited values, inclusive.

In certain embodiments, the radiation-curable film-forming binder present in the coating compositions of the present invention comprises a monofunctional (meth) acrylate monomer and/or polymer that is different from the aforementioned unsaturated monomer containing a nitrogen-containing cyclic structure and one ethylenically unsaturated double bond. The term "monofunctional (meth) acrylate monomer and/or polymer" as used herein includes monomers and polymers that contain one (meth) acrylate group.

Examples of monofunctional (meth) acrylate monomers suitable for use in the present invention include esters of acrylic acid and methacrylic acid such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, neopentyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, isohexyl (meth) acrylate, n-heptyl (meth) acrylate, isoheptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, methyl methacrylate, ethyl methacrylate, n-butyl (meth) acrylate, neopentyl (meth) acrylate, undecyl (meth) acrylate, isoundecyl (meth) acrylate, dodecyl (meth) acrylate, isododecyl (meth) acrylate, tridecyl (meth) acrylate, isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate, and mixtures thereof.

In certain embodiments, the monofunctional (meth) acrylate monomer and/or polymer is present in the coating composition of the present invention in an amount of at least 10 weight percent, such as at least 20 weight percent, with the weight percent being based on the total weight of the composition. In certain embodiments, the monofunctional (meth) acrylate monomer and/or polymer is present in the coating composition of the present invention in an amount of no greater than 70 weight percent, such as no greater than 60 weight percent, with the weight percent being based on the total weight of the composition. The amount of monofunctional (meth) acrylate monomer and/or polymer in the compositions of the present invention can range between any combination of the recited values, inclusive.

In certain embodiments, the radiation curable coating compositions of the present invention may further comprise multifunctional (meth) acrylate monomers and/or polymers, such as difunctional, trifunctional, tetrafunctional, and/or higher functional (meth) acrylates.

In certain embodiments, the film-forming binder is present in the coating compositions of the present invention in an amount of greater than 30 weight percent, such as from 40 to 90 weight percent, and in some cases from 50 to 90 weight percent, with the weight percentages being based on the total weight of the coating composition. The amount of film-forming binder in the compositions of the present invention can range between any combination of the recited values, inclusive.

In certain embodiments, the coating compositions of the present invention comprise a non-chrome corrosion resistant filler. Suitable non-chrome corrosion resistant fillers include, but are not limited to, zinc phosphates such as zinc orthophosphate, zinc metaborate, barium metaborate monohydrate, calcium ion exchanged silica, colloidal silica, synthetic amorphous silica, and molybdates such as calcium molybdateZinc molybdate, barium molybdate, strontium molybdate, and mixtures thereof. Suitable calcium ion exchanged silicas are available from w.r.grace&As ofAC3 and/orC303, obtaining the product. Suitable amorphous silicas are available from w.r.gra ce&Co, under the trade nameAnd (4) obtaining the product. Suitable zinc phosphates are commercially available from Heubach as HEUCOPHOS ZP-10.

In certain embodiments of the present invention, the weight ratio of the aforementioned non-chromium corrosion inhibiting filler to the radiation curable film-forming binder in the coating composition of the present invention is from 0.05 to 0.5: 1, such as from 0.1 to 0.45: 1. The weight ratio of the non-chromium corrosion inhibiting filler to the organic film-forming binder in the coating composition of the present invention can range between any combination of the recited values, inclusive.

In certain embodiments, the coating compositions of the present invention further comprise additional fillers, such as calcium carbonate; magnesium carbonate; metal oxides such as oxides of aluminum (alumina), antimony, iron, magnesium, molybdenum, silicon (silica), titanium and/or zirconium; mica; talc; kaolin; clay; diatomaceous earth; asbestos; montmorillonite; bentonite; graphite; pumice powder; perlite; barite; quartz sand; silicon carbide; boron fibers; boron nitride; dolomite; a hollow ball; glass; aluminum hydroxide; barium sulfate; calcite; calcium sulfate; calcium sulfite; calcium silicate; potassium titanate; molybdenum sulfide; polyethylene fibers; polyester fibers and aramid fibers.

In certain embodiments, the coating composition is substantially free, or in some cases completely free, of chromium containing species, i.e., contains less than about 2 wt% chromium containing species (expressed as CrO)₃) Less than about 0.05 wt% chromium containing species, or about 0.00001 wt%, or in some cases no chromium containing species. Chromium-containing substanceExamples of the material include chromic acid, chromium trioxide, chromic anhydride, dichromate such as ammonium dichromate, sodium dichromate, potassium dichromate, and calcium chromate. In another embodiment, the composition of the present invention is free of zeolite.

In certain embodiments, the coating compositions of the present invention are embodied as liquid coating compositions (substantially 100% solids coatings) that are substantially solvent-free and non-aqueous. As used herein, the term "substantially 100% solids" means that the composition is substantially free of volatile organic solvents ("VOCs"), has substantially zero VOC emissions, and is substantially free of water. In certain embodiments, the substantially 100% solids coating of the present invention comprises less than 5% VOC and water by weight of the coating composition, in some cases less than 2% by weight of the coating composition, in other some cases less than 1% by weight of the coating composition, and in other some cases VOC and water are not present in the coating composition at all.

In certain embodiments, the coating composition of the present invention is embodied as a metal substrate primer coating composition. The term "primer coating composition" as used herein refers to a coating composition as follows: from this composition, a primer (undercoating) can be deposited on a substrate in order to prepare a surface for application of a protective or decorative coating system. Metal substrates that can be coated with the above compositions include, for example, substrates comprising steel (including, inter alia, electro-galvanized steel, cold rolled steel, hot dip galvanized steel), aluminum alloys, zinc-aluminum alloy coated steel, and aluminized steel.

The metal substrate primer coating composition of the present invention may be applied to bare metal. By "bare" is meant a feedstock that has not been treated with any pretreatment composition, such as a conventional phosphating bath (phosphatingbath), heavy metal rinse, and the like. In addition, the bare metal substrate coated with the primer coating composition of the invention may be a cut edge of the substrate which is otherwise treated and/or coated on the remainder of its surface.

Prior to application of the primer coating composition of the present invention, the metal substrate to be coated may first be cleaned to remove grease, dirt, or other foreign matter. Conventional cleaning procedures and materials may be employed. These materials may include, for example, weak base or strong base cleaners such as those commercially available as Parco-Cleaner 338, available from Henkel. Water washing may be performed after and/or before applying these cleaners.

The metal surface may then be washed, for example with water, and dried. Next, in certain embodiments, the metal surface may be contacted with a metal substrate pretreatment composition, such as a phosphate and/or titanium based pretreatment, and the like, prior to contact with the coating composition of the present invention.

Certain embodiments of the present invention, particularly the metal substrate primer coating compositions, relate to coating compositions comprising an adhesion promoting component. The term "adhesion promoting component" as used herein refers to any substance included in the composition to improve the adhesion of the coating composition to the metal substrate.

In certain embodiments, the adhesion-promoting component itself is a radiation-curable compound, as is typically the case with (meth) acrylates containing acid groups, for example as171 modified phosphates available from Cytec, and a mixture of methacrylated mono-and diphosphates available as Polysurf HPm from ADD aptchemics.

In certain embodiments of the invention, the adhesion promoting component comprises a free acid. The term "free acid" as used herein is meant to include organic and/or inorganic acids included as separate components of the compositions of the present invention, as opposed to any acid that may be present in the composition that may be used to form a polymer. In certain embodiments, the free acid comprised within the coating composition of the present invention is selected from tannic acid, gallic acid, phosphoric acid, phosphorous acid, citric acid, malonic acid, derivatives thereof, or mixtures thereof. Suitable derivatives include esters, amides and/or metal complexes of the acids.

In certain embodiments, the free acid comprises an organic acid, such as tannic acid, i.e., tannin. Tannins are extracted from various plants and trees, and can be classified according to their chemical properties into (a) hydrolyzable tannins, (b) condensed tannins, and (c) mixed tannins containing hydrolyzable tannins and condensed tannins. Tannins useful in the present invention include those containing tannin extracts from naturally occurring plants and trees, and are commonly referred to as plant tannins. Suitable plant tannins include natural, ordinary or hot water-soluble condensed plant tannins, such as quebracho, mimosa, mangrove, spruce, hemlock, gaiben, wattle, catechu, uranday, tea tree, larch, myrobalan, chestnut trees, spruce, valonia, sumac, cinchona, oak, and the like. These plant tannins are not pure chemical compounds of known structure, but contain many components, including phenolic moieties such as catechol, pyrogallol, and the like, which condense into complex polymeric structures.

In certain embodiments, the free acid comprises a phosphoric acid, such as 100% orthophosphoric acid, superphosphoric acid, or an aqueous solution thereof, such as a 70-90% phosphoric acid solution.

Other suitable adhesion promoting components in addition to or instead of these free acids are organophosphates and organophosphonates. Suitable organophosphates and organophosphonates include U.S. patent 6,440,580, column 3, line 24-column 6, line 22; 5,294,265 column 1, line 53-column 2, line 55 and 5,306,526 column 2, line 15-column 3, line 8, the citations of which are incorporated herein by reference. Metal phosphate adhesion promoting components may also be used. Suitable metal phosphates include, for example, zinc phosphate, iron phosphate, manganese phosphate, calcium phosphate, magnesium phosphate, cobalt phosphate, zinc iron phosphate, zinc manganese phosphate, zinc calcium phosphate, including those described in U.S. patents 4,941,930, 5,238,506, and 5,653,790.

In certain embodiments, the adhesion promoting component comprises a phosphated (phosphated) epoxy resin. The resin may include the reaction product of one or more epoxy-functional materials and one or more phosphorus-containing materials. Non-limiting examples of such materials suitable for use in the present invention are disclosed in U.S. patent 6,159,549, column 3, lines 19-62, the cited portion of which is incorporated herein by reference, and U.S. patent 7,147,897, column 2, line 13-column 4, line 5, the cited portion of which is incorporated herein by reference.

In certain embodiments, the adhesion promoting component is present in the coating composition of the present invention in an amount of from 0.05 to 20 weight percent, such as from 3 to 15 weight percent, with the weight percentages being based on the total weight of the composition.

In certain embodiments, the coating compositions of the present invention may also comprise additional optional ingredients, such as those well known in the art of formulating surface coatings. The optional ingredients may include, for example, surfactants, flow control agents, thixotropic agents, anti-gassing agents, antioxidants, light stabilizers, UV absorbers and other conventional adjuvants. Any of the above additives known in the art may be used without compatibility issues.

In certain embodiments, particularly when the coating compositions of the present invention are to be cured by UV radiation, these compositions further comprise a photoinitiator. As will be appreciated by those skilled in the art, a photoinitiator absorbs radiation during the curing process and converts it into chemical energy that can be used for polymerization. Photoinitiators are classified into two broad categories based on mode of action, either or both of which may be used in the compositions of the present invention. Cleavage type photoinitiators include acetophenones, alpha-aminoalkylphenones, benzoin ethers, benzoyl oximes, acyl phosphine oxides, and diacyl phosphine oxides, and mixtures thereof. The extraction type photoinitiators include benzophenone, michael ketone, thioxanthone, anthraquinone, camphorquinone, fluorone, coumarone, and mixtures thereof.

Specific non-limiting examples of photoinitiators that may be used in certain embodiments of the coating compositions of the present invention include benzil, benzoin methyl ether, benzoin isobutyl ether benzophenol (benzoin isobutenyl ether benzophenon), acetophenone, benzophenone, 4, 4 ' -dichlorobenzophenone, 4, 4 ' -bis (N, N ' -dimethylamino) benzophenone, diethoxyacetophenone, fluoroketones, such as the H-Nu series of initiators available from Spectra Group Ltd., 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-isopropyl thioxanthone, alpha-aminoalkylphenyl ketones, such as 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone, acylphosphine oxides, such as 2, 6-dimethylbenzoyldiphenylphosphine oxide, 2, 4, 6-trimethylbenzoyldiphenylphosphine oxide, bis (2, 4, 6-trimethylbenzoyl) phenylphosphine oxide, 2, 6-dichlorobenzoyldiphenylphosphine oxide and 2, 6-dimethoxybenzoyldiphenylphosphine oxide, bisacylphosphine oxides, such as bis (2, 6-dimethoxybenzoyl) -2, 4, 4-trimethylpentylphosphine oxide, bis (2, 6-dimethylbenzoyl) -2, 4, 4-trimethylpentylphosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -2, 4, 4-trimethylpentylphosphine oxide and bis (2, 6-dichlorobenzoyl) -2, 4, 4-trimethylpentylphosphine oxide, and mixtures thereof.

In certain embodiments, the coating compositions of the present invention comprise from 0.01 to 15 wt% photoinitiator, or in certain embodiments from 0.01 to 10 wt%, or in yet other embodiments from 0.01 to 5 wt% photoinitiator, based on the total weight of the coating composition. The amount of photoinitiator present in the coating composition can range between any combination of these values, inclusive.

In certain embodiments, the compositions of the present invention comprise a colorant. The term "colorant" as used herein refers to any substance that imparts color and/or other opacity and/or other visual effect to the composition. The colorant may be added to the coating in any suitable form, such as discrete particles, dispersions, solutions, and/or flakes. A single colorant or a mixture of two or more colorants can be used in the coating of the present invention.

Examples of colorants include pigments, dyes, and tints, such as those used in the coatings industry and/or listed in the Dry Color Manufacturers Association (DCMA), as well as special effect compositions. The colorant may comprise, for example, a finely divided solid powder that is insoluble but wettable under the conditions of use. The colorant may be organic or inorganic and may be aggregated or non-aggregated. The colorants can be incorporated into the coating by utilizing a grind vehicle, such as an acrylic grind vehicle, the use of which is well known to those skilled in the art.

Examples of pigments and/or pigment compositions include, but are not limited to, carbazole dioxazine crude pigment, azo, monoazo, disazo, naphthol AS, salts (lakes), benzimidazolone, condensation, metal complexes, isoindolinone, isoindoline and polycyclic phthalocyanine, quinacridone, perylene, perinone, diketopyrrolopyrrole, thioindigo, anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine, triarylcarbonium, quinophthalone pigments, diketopyrrolopyrrole red ("DPPBO red"), titanium dioxide, carbon black, and mixtures thereof. The terms "pigment" and "colored filler" may be used interchangeably.

Examples of dyes include, but are not limited to, those that are solvent and/or aqueous based such as phthalocyangreen or phthalocyanblue, iron oxide, bismuth vanadate, anthraquinone, perylene, aluminum, and quinacridone.

Examples of tints include, but are not limited to, pigments dispersed in an aqueous-based or water-miscible vehicle such as AQUA-CHEM 896 commercially available from Degussa, inc. and CHAR ISMA COLORANTS and maxi interior COLORANTS commercially available from Accurate Dispersions division of Eastman Chemical, inc.

As noted above, the colorant can be in the form of a dispersion, including but not limited to in the form of a nanoparticle dispersion. Nanoparticle dispersions can include one or more highly dispersed nanoparticle colorants and/or colorant particles that produce a desired visible color and/or opacity and/or visual effect. The nanoparticle dispersion may include a colorant such as a pigment or dye having a particle size of less than 150nm, such as less than 70nm or less than 30 nm. Nanoparticles can be produced by milling raw organic or inorganic pigments with grinding media having a particle size of less than 0.5 mm. Examples of nanoparticle dispersions and their methods of manufacture are described in U.S. Pat. No.6,875,800B 2, incorporated herein by reference. Nanoparticle dispersions can also be produced by crystallization, precipitation, gas phase condensation, and chemical attrition (i.e., partial dissolution). To minimize re-aggregation of the nanoparticles in the coating, a dispersion of resin-coated nanoparticles may be used. As used herein, a "dispersion of resin-coated nanoparticles" refers to a continuous phase in which are dispersed discrete "composite particles" comprising nanoparticles and a resin coating on the nanoparticles. Examples of dispersions of resin-coated nanoparticles and methods for their manufacture are described in U.S. patent application publication 2005-0287348a1, filed 24.6.2004, U.S. provisional application 60/482,167, filed 24.6.2003, and U.S. patent application 11/337,062, filed 20.1.2006, which are also incorporated herein by reference.

Examples of special effect compositions that may be used in the compositions of the present invention include pigments and/or compositions that produce one or more appearance effects such as reflectance, pearlescence, metallic sheen, phosphorescence, fluorescence, photochromism, photosensitivity, thermochromism, goniochromism (goniochromism), and/or color change. Additional special effect compositions may provide other perceptible properties such as opacity or texture. In one non-limiting embodiment, the special effect composition can produce a color shift such that the color of the coating changes when the coating is viewed at different angles. Examples of color effect compositions are described in U.S. Pat. No.6,894,086, which is incorporated herein by reference. Additional color effect compositions can include transparent coated mica and/or synthetic mica, coated silica, coated alumina, transparent liquid crystal pigments, liquid crystal coatings, and/or any composition in which interference is caused by refractive index differences within the material and not due to refractive index differences between the surface of the material and the air.

In general, the colorant can be present in any amount sufficient to impart the desired visual and/or color effect. The colorant may comprise 1 to 65 weight percent, such as 3 to 40 weight percent or 5 to 35 weight percent of the composition of the present invention, wherein weight percent is based on the total weight of the composition of the present invention.

The coating compositions of the present invention may be prepared by any suitable technique, including those described in the examples herein. The coating components can be mixed using, for example, a stirred tank, dissolver (including in-line dissolvers), ball mill, agitator mill, static mixer, and the like. If appropriate, preparation is carried out with the exclusion of actinic radiation in order to prevent damage to the actinic radiation-curable coating of the invention. During the preparation, the individual components of the mixtures according to the invention can be mixed in separately. Alternatively, the mixtures of the invention can be prepared separately and mixed with the other ingredients.

In certain embodiments, the coating compositions of the present invention are suitable for deposition by roll coating in a metal coil coating operation. Coil coating starts from a metal sheet in the form of a coil. In certain embodiments, the metal sheet of the coil has a thickness of 200 μm to 2 mm.

In a coil coating operation, the metal coil passes through the coil coating line at a speed appropriate to the application and curing properties of the coating used, as will be understood by those skilled in the art. The speed can thus vary very widely from one coating process to another. In certain embodiments, the line speed (line speed) is from 10 to 200, such as from 12 to 150, from 16 to 120, or from 20 to 100 m/min.

The coating of the present invention may be applied in any desired manner; for example by spraying, flow coating or roll coating. Of these application techniques, roll coating can be particularly advantageous and is therefore often used. Each application step in the roll coating may be performed using two or more rolls. To be particularly suitable for roll-coating applications, it is desirable that the coating compositions of the present invention have a high shear (ICI) viscosity at 50 ℃ of no greater than 550cps, and in some cases no greater than 500 cps. For the purposes of the present invention, ICI viscosity is determined using a cone/plate viscometer according to the standard test method for high shear viscosity (ASTM test method D4287-00).

In roll coating, a rotating uptake roll (pickup roll) is immersed in the reservoir of the coating material according to the invention and thus takes up the coating material to be applied. The coating material is transferred to a rotating fountain roll (application roll) by a liquid pick-up roll directly or via at least one transfer roll (transfer roll). The coating is transferred from the rotating applicator roll to the web by means of co-or counter-contact transfer. Alternatively, the coating of the present invention may be pumped directly into the gap or nip (nip) between two rolls, which is known to those skilled in the art as nip feed.

In roll coating, the peripheral speeds of the uptake roll and the feed roll can vary greatly from one coating process to another. The peripheral speed of the feed roll is often 110-125% of the web speed (coilspeed), and the peripheral speed of the uptake roll is often 20-40% of the web speed.

In certain embodiments, the coating compositions of the present invention are applied so as to produce a cured coating having a dry film thickness of greater than 2.2 μm, such as from 4 to 12 μm, in some cases from 5 to 10 μm, in some cases from 5 to 9.5 μm, and in other cases from 6 to 9 μm.

The application methods described above can be used together with the coatings with which the protective coatings (overcoats) are applied to the coatings of the invention, except when they are powder coatings or electrocoat coatings, for which the usual and known special application methods are used, such as electrostatic powder spraying in the case of low-speed rolls or powder cloud chamber processes in the case of high-speed rolls, and cathodic electrodeposition coating.

If two or more coating materials are applied during the coil coating operation, this is carried out on a suitably configured production line, in which two or more application stations and, if appropriate, curing stations are arranged in series. Alternatively, after the first coating material, i.e., the coating material of the present invention, is applied and cured, the coated coil is wound up again and then provided with the second, third, etc. coating material on one or both sides thereof on a second, third, etc. coil coating line.

After the coated rolls are prepared, they may be wound and then further processed elsewhere; alternatively, they may be further processed as they come directly from the coil coating operation. For example, they may be laminated with plastics or provided with a removable protective film. After cutting into suitably sized portions, they may be shaped. Examples of suitable forming methods include pressing and deep drawing.

It has surprisingly been found that by maintaining the weight ratio of the non-chromium corrosion inhibiting filler to the radiation curable film forming binder at a level of not more than 0.5: 1 in accordance with the present invention, a substantially solvent-free coating composition having an ICI viscosity (specified above) at 50 ℃ of not more than 550cps can be prepared, which is particularly suitable for roll-coating applications, and, despite the relatively small ratios described above, the coating composition of the present invention is still capable of exhibiting advantageous corrosion resistance properties. Furthermore, no chromate pre-treatment of the metal coil is required in order to obtain the desired corrosion protection.

The term "corrosion resistance" as used herein means corrosion resistance as measured on a metal substrate using the test described in ASTM B117 (salt spray test). In this test, the coated substrate was scribed with a knife to expose the bare metal substrate. The scribed substrate was placed in a test chamber where a continuous spray of saline solution was applied to the substrate. The laboratory was kept at a constant temperature. The coated substrate is exposed to the salt spray environment for a specified period of time, such as 250, 500, or 1000 hours. After exposure, the coated substrates were removed from the laboratory and evaluated for corrosion along the scribe line. Corrosion is measured by "scribe creep," which is defined as the total distance of corrosion measured in millimeters across a scribe line. When it is stated that the coating composition of the present invention "exhibits advantageous corrosion resistance" it is meant that a metal substrate, such as a steel substrate (including hot dip galvanized steel), coated with the coating composition of the present invention exhibits a scribe creep of no more than 2mm after 250 hours of testing in a salt spray environment in accordance with ASTM B117.

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

Examples

The coating compositions were prepared using the components and weights (in grams) shown in table 1. Coatings were prepared by adding components 1-9 to a suitable vessel under agitation with a cowles blade for about 30 minutes to achieve a 5Hegman fineness. Next, components 10-12 were added while stirring and allowed to mix for 10 minutes. After mixing the coating is ready for application.

TABLE 1

Number of component	Substance(s)	Example 1	Example 2	Example 3	Example 4	Example 5
							1	100% solids difunctional aliphatic urethane acrylate resin1	23.9	26.4	23.9	26.4	26.4
2	SR531 (Cyclic trimethylolpropane formaldehydeacrylate)2	29.3	32.3	23.1	25.4	26.4
							3	ACMO3	-	-	6.2	6.9	6.9
4	PolySurf HPm4	4.2	4.7	4.2	4.2	4.7
							5	Shieldex C3035	24.9	24.1	24.9	19.8	24.1
6	Heuscophos ZP-106	6.2	-	6.2	4.3	-
							7	Bayferrox 3910 (yellow iron oxide)7	0.2	0.3	0.2	0.3	0.3
8	Special Black #58	0.1	0.1	0.1	0.1	0.1
							9	Tioxide R-HD29	6.2	6.9	6.2	6.9	6.9
10	Darocure 117310	2.1	2.4	2.1	2.4	2.4
							11	Irgacure 81910	0.5	0.6	0.5	0.6	0.6
12	Benzophenones as fungicides11	2.2	2.5	2.2	2.5	2.5
	Pigment/binder	0.6	0.45	0.6	0.45	0.45
								ICI viscosity (centipoise) at 50 deg.C	680	500	750	520	500

¹Available from Sartomer, Cytec, or BASF.

²Available from Sartomer.

³Commercially available from Rahn.

⁴Available from ADD APT Chemicals.

⁵Available from Grace.

⁶Commercially available from Heubach.

⁷Commercially available from Lanxess.

⁸Available from Degussa.

⁹Available from Huntsman.

¹⁰Commercially available from Ciba.

¹¹Available from Cognis.

Test substrate preparation

The compositions of table 1 were applied on top of the alkali cleaned HDG steel using a wire wound film applicator. The composition was applied at a dry film thickness of about 0.2 mils (5.08 μm) and cured with a Fusion 600 watt/inch H lamp. The energy and intensity output is 263mJ/cm²UVA and 1281mW/cm²UVA (measured with EIT UV Power Puck). Subsequently, the coil was topcoated with a wire-wound draw-down film applicator (Durastar, available from PPG Industries) at a dry film thickness of about 0.75 mils (19 μm)^TMHP 7000) was applied over the primer and cured in a gas fired oven at 450 ° F peak metal temperature for 30 seconds.

Salt spray results

Salt spray panels were prepared by cutting the panels to about 4 inches wide and 5 inches long. The left and right edges are cut with metal shear. The surface of the plate was scored in the middle with vertical and horizontal scores about 1.5 inches long and spaced about 0.5 inches apart. This was achieved with a tungsten tipped tool (tungsten tipool) and extended down just through the organic coating.

Salt spray resistance was tested as described in ASTM B117. After 250 hours, the panels were removed from the salt spray test. Immediately after the salt spray, the panels were washed with hot water, scored and trimmed with wooden scrapers to remove salt buildup, and then towel dried. The panels were then taped with Scotch 610 tape to remove the foamed coating.

The panels were evaluated for surface blistering, cut edge creep (cut edge creep) and scribe creep. Surface blistering was measured according to ASTM D714-87. The cut edge value is reported as the average of the maximum creep on the left and right cut edges in millimeters. Scribe creep values are reported as the average of the maximum creep (from scribe to creep) in millimeters on the vertical and horizontal scribes. The results are depicted in table 2, with lower values indicating better corrosion resistance results.

TABLE 2

HDG steel base material	Example 1	Example 2	Example 3	Example 4	Example 5
						Surface foaming	Is free of	Is free of	Is free of	Is free of	Is free of
Edge cutting	5.5	3.5	6.0	5.0	4
						Marking off	5.0	5.0	0.5	1.75	0.0

It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Such variations are to be considered as included in the following claims, unless these claims by their language expressly state otherwise. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims (13)

1. A coating composition comprising:

(a) a non-chromium corrosion resistant filler; and

(b) a radiation curable film-forming binder comprising an unsaturated monomer containing a nitrogen containing cyclic structure and one ethylenically unsaturated double bond, the unsaturated monomer containing a nitrogen containing cyclic structure and one ethylenically unsaturated double bond being present in an amount of at least 1 wt% and not more than 15 wt%, based on the total weight of the composition, wherein,

the coating composition contains less than 5% by weight of the coating composition of a volatile organic solvent and water, and

the coating composition has a high shear ICI viscosity of no greater than 550cps at 50 ℃, and

when the weight ratio of (a) to (B) in the coating composition is no greater than 0.5: 1, the metal substrate having the coating composition exhibits a scribe creep of no greater than 2mm after 250 hours testing in a salt spray environment according to ASTM B117.

2. The coating composition of claim 1, wherein the radiation curable film-forming binder further comprises a soft urethane (meth) acrylate polymer.

3. The coating composition of claim 2, wherein the soft urethane (meth) acrylate polymer is present in the coating composition in an amount of at least 10 wt%, based on the total weight of the composition.

4. The coating composition of claim 1, wherein the unsaturated monomer containing a nitrogen-containing cyclic structure and one ethylenically unsaturated double bond comprises (meth) acryloyl morpholine.

5. The coating composition of claim 1, wherein the non-chromium corrosion resistant filler comprises calcium ion-exchanged silica.

6. The coating composition of claim 1, wherein the coating composition comprises an adhesion promoting component comprising a radiation curable compound.

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

8. The metal substrate of claim 7, wherein the metal substrate is in the form of a coil.

9. A method of coil coating a metal strip comprising:

(a) roll coating the coating composition of claim 1 on said strip,

(b) curing the coating composition by exposing the composition to actinic radiation to form a primer coating exhibiting advantageous corrosion resistance properties, and

(c) depositing a top coat composition over at least a portion of the primer coating.

10. The method of claim 9, wherein the radiation curable film-forming binder further comprises a soft urethane (meth) acrylate polymer.

11. The method of claim 9, wherein the unsaturated monomer containing a nitrogen-containing cyclic structure and one ethylenically unsaturated double bond comprises (meth) acryloyl morpholine.

12. The method of claim 9, wherein the non-chromium corrosion resistant filler comprises calcium ion-exchanged silica.

13. A metal coil coated by the method of claim 9.