Application improvement for acid resistant waterborne acrylic coating
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-02
- Publication Date
- 2026-08-13
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Figure US2026013452_13082026_PF_FP_ABST
Abstract
Description
Patent P02738-USP-WO APPLICATION IMPROVEMENT FOR ACID RESISTANT WATERBORNE ACRYLIC COATINGBACKGROUND OF THE IN VENTION
[0001] Polymer coating compositions are routinely applied to substrates, especially metal substrates. Such coatings are used for a variety of reasons, including, for example, to protect the substrate from degradation because of exposure to the environment, to harsh chemicals, and the like, to beautify the substrate (e.g., to provide color, brightness, etc,), and / or to reflect light, among many other reasons.
[0002] Many such polymer coating compositions are applied on a variety of substrates that are subsequently formed into finished articles, including articles used in infrastructure and transportation, such as rail cars, for example In general, for a coating composition or system to be used as an exterior coating, the composition or system must demonstrate optimal or even superior formability', chemical resistance, long-term outdoor weathering, durability1, and improved wear resistance. The coating must also maintain a suitable aesthetic appearance (gloss, color, and the like) over prolonged periods of exposure to exterior conditions, including sunlight, humidity, rain, harsh chemicals, and the like.
[0003] Rail cars are often used to transport highly corrosive liquids such as concentrated acids. These liquids can drip down the side of the rail car and damage the exterior surface. To prevent or mitigate this damage, acid-resistant coatings are applied to the exterior surfaces of rail cars. These coatings are typically one- or two-component coatings applied to the exterior surface of rails cars and include a high filler load to make the coating resistant to acid.Adhesive stencils, i.e. self-adhesive decals, which may be composed of vinyl or another material that can adhere permanently to substrate, are then applied over the acid-resistant coating to mark or label the rail cars. However, conventional acid-resistant coatings of this type have poor adhesion to such stencils and over time, the stencils tend to delaminate.
[0004] The risk of stencil delamination significantly increases production time as the application shops must either 1) apply a coat of a separate product over the (cured) existing acid-resistant product; or 2) further prepare the surface of the cured acid-resistant coating by means of sanding, scrubbing, solvent wiping, or other means of enhancing or altering the surface of the cured coating. This adds both time and expense for the customer. Moreover, a delamination of adhesive stencils can result in fines from the governmental authorities.
[0005] Accordingly, there is a continuing need for waterborne coating compositions for application to the exterior surface of a rail car that has optimal acid resistance and also demonstrates optimal adhesion to stencils such that no additional surface preparation is required before affixing the stencil.BRIEF DESCRIPTION OF THE FIGURES
[0006] FIG. 1 is a photographic representation of a stencil adhesion test on metal panels coated with a commercially available coating as well as the waterborne coating composition described herein.SUMMARY
[0007] The present invention provides a coating system for metal substrates. The coating system demonstrates optimal acid resistance and adhesion and may be applied to a variety of metal substrates, including the exterior of rail cars, by various methods, including by spray application. Methods of making the coating composition and for coating substrates or articles with the described coating system are also provided.
[0008] In one embodiment, the present description provides an acid-resistant waterborne coating composition. The composition includes a polymeric binder resin component derived from at least one ethylenically unsaturated monomer along with at least carbonaceous filler material and at least one inert filler material. The described coating composition is applied to at least an exterior surface of a rail car and cured. An adhesive stencil can be applied to the cured coating without needing to prepare the surface prior to applying the stencil.
[0009] In another embodiment, a coating system is described. The system includes a substrate and an acid-resistant waterborne coating composition applied and cured on the substrate, along with an adhesive stencil applied over the cured coating without needing to prepare the surface prior to applying the stencil. The composition includes a polymeric binder resin component derived from at least one ethylenically unsaturated monomer along with at least carbonaceous filler matenal and at least one inert filler material.
[0010] In yet another embodiment, a method is provided. The method includes steps of providing a substrate and applying an acid-resistant waterborne coating composition on thesubstrate. The applied substrate is then dried to obtain a cured coating on the substrate. An adhesive stencil is applied over the cured coating without needing to prepare the surface prior to applying the stencil. The composition includes a polymeric binder resin component derived from at least one ethylenically unsaturated monomer along with at least carbonaceous filler material and at least one inert filler material.
[0011] The above summary of the present invention is not intended to describe each disclosed embodiment or even / implementation of the present invention. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which can be used in various combinations. In each instance, the recited list senes only as a representative group and should not be interpreted as an exclusive list.
[0012] The details of one or more embodiments of the invention are set for in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.SELECTED DEFINITIONS
[0013] Unless otherwise specified, the following terms as used herein have the meanings as provided below.
[0014] The term “component” refers to any compound that includes a particular feature or structure. Examples of components include compounds, monomers, oligomers, polymers, resins, and organic groups contained there.
[0015] The term “double bond” is non-limiting and refers to any type of double bond between any suitable atoms (e.g., C, O, N. etc ).
[0016] The term “triple bond” is non-limiting and refers to any type of triple bond between any suitable atoms.
[0017] The term “substantially free” of a particular compound or component means that the compositions described herein contain less than 5 percent by weight (based on the total weight of the composition) of the particular compound or component. The term “essentially free” of a particular component or compound means that the compositions described herein contain less than 2 parts by weight (based on the to tal weight of the composition) of the particular component or compound. The term “completely free” of a particular mobile compound means that the compositions of the present invention contain less than 1 part byweight (based on the total weight of the composition) of the particular component or compound.
[0018] The term "‘crosslinker” refers to a molecule capable of forming a covalent linkage between poly mers or between two different regions of the same polymer.
[0019] The term “self-crosslinking,” when used in the context of a self-crosslinking polymer, refers to the capacity of a polymer to enter into a crosslinking reaction with itself and / or another molecule of the polymer, in the absence of an external crosslinker, to form a covalent linkage therebetween Typically, this crosslinking reaction occurs through reaction of complimentary reactive functional groups present on the self-crosslinking polymer itself or two separate molecules of the self-crosslinking polymer.
[0020] Tire term “water-dispersible” in the context of a water-dispersible polymer means that the polymer can be mixed into water (or an aqueous earner) to form a stable mixture. For example, a stable mixture will not separate into immiscible layers over a period of at least 2 weeks when stored at 49°C (120°F), or when physical force (such as vibration, for example) is applied. The term “water-dispersible” is intended to include the term “water-soluble.” In other words, by definition, a water-soluble polymer is also considered to be a water-dispersible polymer As used herein, the term "‘waterborne”' refers to a coating composition including a water-dispersible or water-soluble polymer.
[0021] Ihe term “dispersion” in the context of a dispersible polymer refers to the mixture of a dispersible polymer and a carrier. The term “dispersion” is intended to include the term “solution.”
[0022] The term “thermoplastic” refers to a material that melts and changes shape when sufficiently heated and hardens when sufficiently cooled. Such materials are typically capable of undergoing repeated melting and hardening without exhibiting appreciable chemical change. In contrast, a “thermoset” refers to a material that is crosslinked and does not “melt.”
[0023] The term “stencil,” as used herein, refers to self-adhesive decals that may be composed of vinyl or another material and are adhered permanently to substrate surfaces. As used herein, the term may refer to decals attached to the exterior of rail cars. The term “stencil” is used interchangeably with “adhesive stencil” or “decal” herein.
[0024] Unless otherwise indicated, a reference to a “(meth)acrylate” compound (where “meth” is bracketed) is meant to include both acrylate and methacrylate compounds.
[0025] Unless otherwise indicated, “molecular w eight” refers to number average molecular weight (Mn). Molecular weight (both number average and weight average (Mw)) are determined by standard methods knoyvn to those of skill in the art. Unless otherwiseindicated, the method used to determine molecular weight is size exclusion chromatography (SEC), more specifically, gel permeation chromatography (GPC).
[0026] The term “particle size,” as used herein, refers to the mean or average particle size based on particle size distribution (D50), where D50 is the median diameter or the medium value of the particle size distribution, i.e., the value of the particle diameter at 50% in the cumulative distribution. For example, a D50 particle size of 2.0 pm means that 50% of the particles in a given sample are larger than 2.0 pm and 50% are smaller than 2,0 pm. Unless otherwise indicated, the particle size discussed herein is determined by methods known to those of skill in the art, specifically by dy namic light scattering (DLS) analysis.
[0027] Except as otherwise indicated, the term “weight percent” or “wt%” refers to the concentration of a component or composition based on the total weight of the composition, expressed as a percentage. Except as otherwise indicated, the term “parts by weight” refers to the concentration of a component or composition based on the total weight of the composition.
[0028] The term “on,” when used in the context of a coating applied on a surface or substrate, includes both coatings applied directly or indirectly to the surface or substrate. Thus, for example, a coating applied to a primer layer overlying a substrate constitutes a coating applied on the substrate.
[0029] Unless otherwise indicated, the term “poly mer” includes both homopoly mers and copolymers (i.e., polymers of two or more different monomers).
[0030] The term “comprises” and variations thereof do not have a limiting meaning where these terms appear in the description and claims.
[0031] The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.
[0032] As used herein, “a,” “an,” “’the,” “at least one,” and “’one or more” are used interchangeably. Thus, for example, a coating composition that comprises “an” additive can be interpreted to mean that the coating composition includes “one or more” additives.
[0033] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes I, 1,5, 2. 2.75, 3, 3,80, 4, 5, etc.).Furthermore, disclosure of a range includes disclosure of all subranges included within the broader range (e.g.. 1 to 5 discloses 1 to 4, 1.5 to 4.5, 1 to 2, etc.).DETAILED DESCRIPTION
[0034] The present description provides an acid-resistant waterborne coating composition. In an aspect, the coating system includes a polymeric binder resin component, at least carbonaceous filler material, and at least one inert filler material. The coating composition provides acid resistance and adhesion when applied to a substrate, particularly metal substrates that form the exterior of rail cars.
[0035] In an embodiment, the present description provides an acid-resistant waterborne coating system that includes a polymeric binder resin component. The polymeric binder resin component is a thermoplastic material or component. As used herein, the term “■thermoplastic” means polymeric material that will melt upon exposure to sufficient heat to form a flowable liquid and will return to a solidified state upon sufficient cooling. Further, some embodiments of a thermoplastic resin useful in the practice of the present invention may be amorphous, crystalline or semicrystalline. Illustrative resins used in the first resin component include acyclic, cyclic, branched, linear, aliphatic, or aromatic resins.Thermoplastic resins desirably have a minimum film-forming temperature (MFFT) that is below 65°C, preferably below 45°C. more preferably below 25°C. It is also desirable that such resins desirably har e a minimum film forming temperature that is greater than -50°C, preferably greater than -25°C, more preferably greater than 0°C. Suitable thermoplastic polymers include, but are not limited to, polymers derived from one or more ethylenically unsaturated monomers including, for example, (meth)acrylic resins, polyolefins (e.g., polyethylenes, polypropylenes, polybutylenes, and any combinations thereof), polyamides (e.g., nylon), polyurethanes, polyesters (e.g., polyethylene terephthalate), and the like, as well as any combinations thereof These thermoplastic polymers can be in the form of powder, fluff, flake, prill, or pellet made from freshl -produced polymer, polymer regrind, post¬ consumer waste, or post-industrial waste. For the coating composition described herein, polymers derived (meth)aciylic acid are particularly preferred.
[0036] In some embodiments, the present description provides an acid-resistant waterborne coating system that includes a polymeric binder resin component. In an aspect, the polymer binder resin component is a self-crosslinking polymer, i.e. a polymer capable of entering into a crosslinking reaction with itself and / or another molecule of the polymer, in the absence of an external crosslinker.
[0037] The coating composition described herein may be a one-component or two- component coating, in a preferred embodiment, the coating composition described herein a waterborne one-component acrylic coating.
[0038] In exemplar}' embodiments, a suitable polymeric binder resin component is a copolymer derived from reactants including (a) optionally at least one aromatic reactant including pendant free radically poly merizable functionality, (b) al least one free radically polymerizable reactant hat ing pendant acid functionality (or a salt or ester thereof): and (c) optionally at least one other copolymerizable reactant with free radically polymerizable functionality. Such reactants often are monomers, oligomers, and / or resins.
[0039] Examples of reactant (a) include, without limitation, styrene, alpha-methyl styrene, t-butyl styrene, 1,3-diisopropenylbenzene, 2,4,6-trimethylstyrene, 2, 4-dimethyl styrene, 2,4-diphenyl-4-methyl-l -pentene, 2,5-dimethylstyrene, 2-vmylnaphthalene. 3 -methyl styrene. 4-benzyloxy-3-methoxystyrene, 9-vinylanthracene, a,2-dimethylstyrene, combinations of these, and the like. These may be substituted or unsubstituted. Illustrative embodiments of the resin include preferably from about 10 to 70 parts by weight of reactant(s) (a) per 100 parts by weight of the total reactants used to form the resin.
[0040] Examples of reactant (b) include, without limitation, unsaturated or other free radically polymerizable acids. In many embodiments, reactant (b) is provided by one or more carboxylic acids or anhydrides thereof having one or more acid groups. Examples include, without limitation, (meth)aciylic acid, sorbic acid, maleic anhydride, maleic acid, crotonic acid, itaconic acid, palmitoleic acid, oleic acid, linoleic acid, arachidonic acid, benzoic acid, fumaric acid, combinations of these, and the like. Illustrative embodiments of the resin include preferably from about 2 to 20 parts by weight of reactant(s) (b) per 100 parts by weight of the total reactants used to form the resin. Preferably, the acid functionality is atypically high in that the one or more acid functional reactants incorporated into the res n are at least 3 w eight percent, at least 4 w-eight percent, at least 5 weight percent, and up to 10, 15, or 20 weight percent of total w eight of all reactants used to make the resin.
[0041] Examples of reactant (c) include, w ithout limitation, vinyl esters, vinyl ethers, lactams such as N-vinyl-2-pyrrolidone, (meth)acrylamide. N-substituted (meth)aciylamide. octyl (meth)acrylate, nonylphenol ethoxylate (meth)acrylate, isononyl (meth)acrylate, 1,6- hexanediol (meth)acrylate, isobomyl (meth)acrylate, 2-(2-ethoxy ethoxy )ethyl (meth)acrylate, 2 ethylhexyl (meth)acrylate, lauryl (meth)acrylate, beta-carboxyethyl (meth)aciylate. butyl (meth)aciylate: isobutyl (meth)acrylate, cycloaliphatic epoxide, alpha-epoxide. 2-hydroxy ethyl (meth)acrylate, (meth)acrylonitrile, maleic anhydride, itaconic acid, isodecyl(meth)acrylate, dodecyl (meth)acrylate, n-butyl (meth)aciylate, methyl (meth)aciyfate, hexyl (meth)acrylate. (meth)acrylic acid, N-vinylcaprolactam. stearyl (meth)acrylate. hydroxy functional caprolactone ester (meth)acrylate, octodecyl (meth)acrylate, isooctyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxypropyl (meth)aciylate, hydroxyisopropyl (meth)acrylate, hydroxy butyl (meth)acrylate, hydroxyisobutyl (meth)aci late, tetrahydrofurfuryl (meth)acrylate, combinations of these, and the like. Illustrative embodiments of the resin include preferably from about 10 to 80 parts by weight of reactant(s) (c) per 100 parts by weight of the total reactants used to form the resin.
[0042] The polymeric binder resin components useful in the composition described herein may be polymerized from the constituent reactants using a variety of suitable polymerization techniques that are currently known or hereafter developed. Suitable such techniques are as described in U. S. Pat. Pub. No. 2007 / 0110981 Al (dated 17 May 2010), for example.
[0043] The amount of the polymeric binder resin component in the coating composition described herein may be selected from a wide range. Generally, if the amount of resin component is too low, then it may% be difficult to form a film, more difficult to form a film that has sufficient adhesion to the substrate, the film may have insufficient corrosion or acid resistance or other performance, and / or the like. If too much is used, then it may be harder to formulate a pigmented system or it may be more difficult to make a material that can be applied to the substrate. Balancing such concerns, the coating composition described herein preferably includes from about 10% to 70% by weight, more preferably about 15% to 50% by weight, and even more preferably about 20% to 40% by weight of the polymeric binder resin component, based on the total weight of the coating composition.
[0044] The molecular weight(s) of the one or more resins of the polymeric binder resin component independently may van7over a wide range. If the molecular weight is too low, then the coating may not be durable enough or may not be resistant to acid attack. If too high, then the coating may not be easy to apply at sufficient solids level. Balancing such concerns, the number average molecular weight desirably is in the range from about 5000 to 75,000. more preferably about 10,000 to 50,000, more preferably from about 10.000 to 20,000; and the weight average molecular weight desirably is in the range from about 8,000 to 150,000, more preferably about 20,000 to 80,000, more preferably about 35,000 to 55,000. As used herein, molecular weight refers to the number average molecular weight (Mn) unless otherwise expressly noted.
[0045] In an embodiment, the present description provides an acid-resistant waterborne coating system that includes a polymeric binder resin component and at least one carbonaceous filler material. As used herein, the term '‘carbonaceous filler’’ refers to a material that includes at least 50% by weight of elemental carbon, preferably at least 75% by¬ weight of elemental carbon, more preferably- at least 90% by weight of elemental carbon. A particularly preferred carbonaceous filler contains or consists of elemental carbon in an amount of 99% by weight or more.
[0046] Preferably, the carbonaceous filler used in the composition described herein is selected from carbon nanotubes, carbon, graphite, graphene, and carbon black. Graphite is particularly preferred. Suitable forms of graphite include, without limitation, commercially available graphite such as natural graphite, graphite F516, and the like. Graphite may be in any suitable form including particles, sheets, flakes, and the like.
[0047] In certain embodiments, the carbonaceous filler used in the composition described herein has particle size (D50) of preferably about 10 to 500 pm, more preferably about 20 to 400 pm, and even more preferably about 50 to 300 pm.
[0048] The coating composition described herein includes a sufficient amount of the carbonaceous filler to be effective in a film of the composition. In certain embodiments, the carbonaceous filler is present in an amount of preferably about 1% to 40% by weight, more preferably about 5% to 25% by weight, and even more preferably about 10% to 20% by weight, based on the total weight of the composition. By’ ‘'total weight of the composition’" is meant the total weight of the liquid coating composition, including components such as water and other volatiles in the composition. The weight percentages provided herein do not represent the composition of the cured film, but rather the entire wet weight of the coating composition prior to drying.
[0049] In an embodiment, the present descnption provides an acid-resistant waterborne coating system that includes a polymeric binder resin component and at least one inert filler material. By “inert filler"’ is meant materials such as extenders, pigments, or other additives included in a coating composition to further improve corrosion protection, adhesion, chemical resistance, and / or provide optimal permeability' through the coating once applied on a substrate. Additionally, these inert fillers may be used as thickeners, to help reduce foaming and to help improve application of the coating composition.
[0050] Without being bound to theory / , it is believed that specific properties of the inert filler, including oil absorptivity’, surface area, surface energy, particle shape, particle size, aspectratio, porosity, surface treatment, ion effects and the like, may contribute to the acid resistance, adhesion, or other characteristics of the coating.
[0051] Suitable inert fillers for use with the coating composition described herein include, without limitation, insoluble compounds of one or more of metals, or combinations or mixtures of these, and the like. Insoluble compounds include sulfates, hydroxides, carbides, nitrides, oxides, oxynitrides, oxycarbides, silicates, and / or carbonates. Specific embodiments of such fillers include talc. CaCO3, BaSO4, aluminum silicate, aluminum hydroxide, mica, silica (as glass beads or glass flake, for example), wollastonite, china clay, chlorite, dolomite, mixtures or combinations of the above, and the like. BaSO4, CaCO3, dolomite and wollastonite are preferred. In an aspect, the coating composition may include a mixture of two or more inert fillers. In a preferred aspect, the inert filler used with the coating composition described herein is silica in the form of glass beads, glass sphere, glass flake, or combinations or mixtures thereof, with glass flake particularly preferred. Any commercially available form of the inert filler is suitable for use in the composition described herein.
[0052] In certain embodiments, the inert filler used in the composition described herein is a flake, plate-like, lamellar, and / or platy matenal having an approximate aspect ratio of preferably about 20:1 to 200:1, more preferably about 10:1 to 100:1, and even more preferably about 5:1 to 50:1. In a preferred aspect, the inert filler used in the composition described herein is glass flake with an aspect ratio of about 45:5.
[0053] In certain embodiments, the inert filler used in the composition described herein is a granular or spherical matenal and has particle size (D50) of preferably about 50 to 500 pm, more preferably about 100 to 400 pm, and even more preferably about 200 to 300 pm. In a preferred aspect, the inert filler used in the composition described herein is glass bead with a D50 particle size of preferably about 1 to 100 pm, more preferably about 5 to 50 pm.
[0054] Tire coating composition described herein includes a sufficient amount of the inert filler to be effective in a film of the composition. In certain embodiments, the inert filler is present in an amount of preferably about 1% to 40% by weight, more preferably about 5% to 25% by weight, and even more preferably about 10% to 20% by weight, based on the total w eight of the composition. By "‘total w eight of the composition” is meant the total w eight of the liquid coating composition, including components such as w-ater and other volatiles in the composition. The weight percentages provided herein do not represent the composition of the cured film, but rather the entire wet weight of the coating composition prior to drying.
[0055] Rail cars are used to transport a wide variety' of materials and substances, including as tank cars for highly corrosive liquids such as concentrated sulfuric acid, for example. Whenthe tank cars are filled with the liquid material to be transported, or even sometimes during use, the liquid material tends to drip down the exterior of the tank car. If the liquid material is highly corrosive, such as an acid, for example, the acid drip can cause damage to the paint or coating on the exterior of the tank car as well as potentially to the metal substrate underneath. Conventionally, to protect against such damage, rail cars often have acid-resistant coatings applied. These coatings include a filler material, typically graphite at high loading or concentration to make the coating resistant to acid,
[0056] Rail cars often have adhesive stencils applied as labels or markings on the exterior. These stencils are typically self-adhering and are applied over any acid-resistant coating or paint that has already been applied to the rail car exterior. Unfortunately, the high graphite load in these acid-resistant coatings leaves unbound graphite dust at the surface of the cured coating, which can lead to delamination of the stencil. Therefore, the graphite dust must then be sanded or scrubbed away or, in the alternative, the acid-resistant coating must be coated over with another product to allow the stencils to adhere properly to the coating surface. The need for surface preparation before applying the stencils causes significant delays and increased expense for the customer. If'when a delamination of adhesive stencils does occur, the customer may be subject to significant government fines as well.
[0057] Surprisingly, and in contravention of current knowledge in the industry, the coating composition described herein is acid resistant and provides optimal adhesion for stencils without the need to sand away the coating or apply an additional coating before attaching the adhesive stencils. Without limiting to theory, it is believed that significantly reducing the carbonaceous filler (e.g., graphite) load and including a small amount of an inert filler (e.g., glass flake) helps improve the adhesion of the stencil to the coating such that no additional surface preparation or enhancement is required to prevent delamination of the stencil. As a result, significant gains in productivity and cost are seen with the coating composition described herein.
[0058] Accordingly, in an embodiment, the present description provides methods for obtaining a coated surface, substrate, or article that is resistant to acid and to which an adhesive stencil can be applied without prior surface treatment. In some embodiments, the method described herein include steps of providing a substrate including, without limitation, a metal substrate forming at least part of the exterior surface of a rail car. The coating composition described herein is then applied to the substrate and dried or cured to form a cured coating on the substrate. An adhesive stencil can then be applied directly over the cured coating, without having to enhance, alter, or prepare the surface before applying the stencil.[0059 J The coating composition described herein may be used to coat or paint a wide variety of substrates. In an aspect, the substrate is made of metal, metal alloy, metal-containing composite, intermetal compositions, and mixtures or combinations thereof. Preferably, the metal substrate forms at least part of freight containers, motor vehicle components, aircraft components, trucks, rail cars, guard rails, tunnels, pipes, marine components, machinery components, laminates, equipment components, appliances, packaging, or combinations thereof. In a preferred aspect, the substrate forms at least part of the exterior surface of a rail car.
[0060] The coating composition described herein may be applied to the substrate by any method known to the those of skill in the art, including, for example, by brushing, spraying, spin coating, roll coating, curtain coating, dipping, gravure coating, and / or the like.
[0061] The coating composition described herein may be applied to the substrate in a wide range of film thicknesses. In illustrative embodiments, the applied coating has a thickness in the range from about 15 micrometers to about 200 micrometers, preferably about 15 micrometers to about 100 micrometers, more preferably about 30 micrometers to about 50 micrometers. One or more additional coats of the coating composition can be applied if desired.
[0062] A wide variety of other additional ingredients optionally may be included in the coating composition described herein, if desired. Examples of these include one or more defoaming aids, grinding aids, wetting agents, surfactants, coalescing aids, processing aids, skid resistance agents, abrasion resistance agents, conductive agents, antistatic agents, coloring agents, anticorrosion aids, thickeners, sag resistant agents, plasticizers, antioxidants, ultraviolet stabilizers, biocides, fungicides, fillers, combinations of these, and the like. These can be used in accordance with conventional practices currently known or hereafter developed.
[0063] After application to the metal substrate, the coating composition described herein is typically cured or dried at room temperature, with the coating typically dry or partially cured within two hours and fully cured within seven days. These coatings are waterborne and dry or cure by evaporation of water from the coating before or during film formation. High humidity, poor air circulation, and low temperatures complicate evaporation of water from the coating and can significantly hinder the drying or curing process. Accordingly, drying or curing in a heated temperature environment is sometimes preferred, with the drying temperatures chosen according to humidity conditions and desired performance.EXAMPLES
[0064] The invention is illustrated by the following examples. It is to be understood that the particular examples, materials, amounts, and procedures are to be interpreted broadly in accordance with the scope and spirit of the inventions as set forth herein. Unless otherwise indicated, all parts and percentages are by weight and all molecular weights are weight average molecular weight. Unless otherwise specified, all chemicals used are commercially available from, for example. Sigma-Aldrich, St. Louis, Missouri.TEST METHODS
[0065] Unless indicated otherwise, the following test methods were utilized in the Examples that follow.A. Acid Drip Test
[0066] The acid drip test can be used to determine a cured coating or coating system's resistance to acid. The test is performed by exposing a cured coating applied on a test panel to acid. A small amount of acid at particular concentrations (e.g., 10% HCl, 10% H2SO4, etc.) is dripped on to the coating for a given period of time (e.g., 4 hours) The coating is then visually observed at various time periods after the exposure (e.g., immediately after exposure, 7 days after exposure, etc. ), for signs of coating failure (such as delamination of the coating and / or exposure of the substrate), discoloration, and / or swelling as a result of acid exposure.Example 1. Preparation of Coating Composition and Acid Drip Testing
[0067] Test samples of a waterborne aciylic composition as described herein #2 to #6 were prepared as shown in Table 1A for acid drip testing. A commercially available product known to have high graphite fill was also prepared (Sample #1) and tested in the same way. Drawdowns of each sample were applied to metal test panels and subjected to acid drip testing. Coating characteristics following exposure to acid are shown in Table IB.Table 1A, Test SamplesSample Composition Graphite (wt%) Glass Flake (wt%) NVM NVV (Commercial) WB Acrylic High Fill - UNK UNK? WB Acrylic 16 - 48.97 42.01 3 WB Acrylic - 16 49.50 42.01 4 WB Acrylic 5.6 4.5 44.88 39.68 5 WB Acrylic 4.5 4.5 44.11 39.286 (Inventive) WB Acrylic 7.6 15.4 53.20 44.24Table 1B, Characteristics of coating after acid testingSample # Swelling Coating Failure Immediate 7 Days Immediate 7 Days 1 Slight Minimal Failed Failed 2 Slight Minimal No failure No failure 3 Slight Minimal No failure No failure 4 Significant Slight Failed Failed 5 Significant Significant Failed Failed6 Minimal No swelling No failure No failureExample 2. Stencil Adhesion Testing
[0068] Test samples of a waterborne acrylic composition as described herein (Sample #6 from Example 1) were prepared and applied to test panels and cured. A strip of adhesive stencil material was then applied to the cured coating and pulled off. A commercially available product known to have high graphite fill was also prepared (Sample #1) and tested in the same way. As seen in Figure 1, the strip applied to the commercial coating pulled off easily, suggesting poor adhesion to the coating. In contrast, the strip applied to the coating as described herein did not pull off easily. Significant effort was required to remove the strip, and it deformed in the process This indicates strong adhesion to the cured coating.
[0069] The complete disclosure of all patents, patent applications, and publications, and electronically available material cited herein are incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to theexact details shown and described, for variations obvious to one skilled in the art will be included within the invention defined by the claims. The invention illustratively disclosed herein suitably may be practiced, in some embodiments, in the absence of any element which is not specifically disclosed herein.
Claims
WHAT IS CLAIMED IS:
1. An acid-resistant waterborne coating composition, comprising:a polymeric binder resin component derived from at least one ethylenically unsaturated monomer;at least one carbonaceous filler material; andat least one inert filler material.wherein the coating composition is applied to at least an exterior surface of a rail car, and wherein an adhesive stencil can be applied to a cured coating derived from the composition without needing to prepare the surface prior to applying the stencil.
2. A coating system, comprising:a substrate;an acid-resistant waterborne coating composition applied and cured on the substrate, said composition comprisinga polymeric binder resin component derived from at least one ethylenically unsaturated monomer;at least one carbonaceous filler material; andat least one inert filler material; andan adhesive stencil applied over the cured coating without needing to prepare the surface prior to applying the stencil.3 A method, comprising:providing a substrate;applying an acid-resistant waterborne coating composition on the substrate, said composition comprisinga polymeric binder resin component derived from at least one ethylenically unsaturated monomer;at least one carbonaceous filler material; andat least one inert filler material;drying the applied coating composition to obtain a cured coating on the substrate; andapplying an adhesive stencil over the cured coating without needing to prepare the surface prior to applying the stench.
4. The composition, system, or method of any of the above claims, wherein the polymeric binder resin component is derived from polymerization of at least one ethylenically unsaturated monomer selected from alkyl and alkoxy (meth)acrylates, vinyl esters of saturated carboxylic acids, monoolefins, conjugated dienes, with one or more monomers comprising styrene, methyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, vinyl acetate, acrylonitrile, vinyl chloride, or mixtures or combinations thereof.
5. The composition, system, or method of any of the above claims, wherein the carbonaceous material is selected from carbon black, graphite, or carbon fiber.
6. The composition, system, or method of any of the above claims, wherein the carbonaceous material is graphite.
7. The composition, system, or method of any of the above claims, wherein the carbonaceous material has particle size (D50) of about 20 to 400 gm,8. The composition, system, or method of any of the above claims, wherein the carbonaceous material has particle size (D50) of about 50 to 300 gm.
9. Ihe composition, system, or method of any of the above claims, wherein the carbonaceous material is present in an amount of about 5% to 25% by weight, based on the total weight of the composition.
10. The composition, system, or method of any of the above claims, wherein the carbonaceous material is present in an amount of about 10% to 20% by weight, based on the total weight of the composition.
11. The composition, system, or method of any of the above claims, wherein the inert filler material is selected from talc, CaCO3, BaSO4. aluminum silicate, aluminum hydroxide, mica, silica, wollastonite, china clay, chlorite, dolomite, or mixtures or combinations thereof.
12. The composition, system, or method of any of the above claims, wherein the inert filler material is silica in the form of glass beads, glass sphere, glass flake, or combinations thereof.
13. The composition, system, or method of any of the above claims, wherein the inert filler material is glass flake.
14. The composition, system, or method of any of the above claims, wherein the inert filler material has particle size (D50) of about 100 to 400 um.
15. The composition, system, or method of any of the above claims, wherein the inert filler material has particle size (D50) of about 200 to 300 pm.
16. The composition, system, or method of any of the above claims, wherein the inert filler material is present is an amount of about 5% to 25% by weight, based on the total weight of the composition.
17. The composition, system, or method of any of the above claims, wherein the inert filler material is present in an amount of about 10% to 20% by weight, based on the total weight of the composition.
18. The system, or method of any of the above claims, wherein the substrate is selected from metals, metal alloys, intermetallic compositions, metal-containing composites, or combinations thereof.
19. The system, or method of any of the above claims, wherein the substrate forms at least part of freight containers, motor vehicle components, aircraft components, trucks, rail cars guard rails, tunnels, pipes, marine components, machinery components, laminates, equipment components, appliances, packaging, or combinations thereof.
20. The system or method of any of the above claims, wherein the substrate forms at least part of an exterior surface of a rail car.