PVDF dispersion composition

Abstract

The present invention relates to a PVDF solvent dispersion composition containing polyvinylidene fluoride (PVDF), which composition is substantially free of fluorine-containing surfactants and contains a low level of dispersant. PVDF may be used to prepare tough, chemical resistant coatings, especially on metal substrates, including as coil coatings or architectural coatings. In the embodiments disclosed herein, the PVDF coating composition comprises a solvent, such as diisobutyl ketone (DIBK), which promotes the composition to have advantageous viscosity and rheology even in the absence of fluorine-containing surfactants and conventional solvents, such as isophorone.

Description

Cross Reference to Related Applications

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 498,592, filed April 27, 2023, the disclosure of which is incorporated herein by reference in its entirety. BACKGROUND

[0002] Fluoropolymer resins are used to make high performance coatings. Among fluoropolymers, polyvinylidene fluoride (“PVDF”) is often preferred because of its dispersibility in common solvents and acrylic resins allows formulation into stable solvent dispersions that can be formulated into liquid paints for application by various methods known in the art, including, for example, reverse roll coating in coil lines. Such coatings are particularly advantageous for application to metal substrates, such as aluminum, hot-dipped galvanized steel, and zinc-aluminum alloys on steel, which must maintain excellent appearance and substrate protection for long periods of time. Suitable PVDF dispersion-type coatings are described, for example, in U.S. Patent No. 7,399,533.

[0003] To successfully apply a smooth and defect-free coating on a coil line, for example, the viscosity and solids content of the liquid coating must be carefully controlled. Conventionally, perfluoro and polyfluoroalkyl substances or surfactants are used to prepare fluoropolymer resins, but environmental concerns and regulatory changes have led suppliers to stop using fluorosurfactants in the manufacture of fluoropolymers, resulting in changes in coating formulation viscosity and rheology. Therefore, fluoropolymer coating formulations must be changed to maintain the desired properties, including optimal viscosity and rheology.

[0004] Typically, solvents and / or dispersants are used to control the viscosity and rheology of the coating formulation while maintaining coating performance and characteristics. Suitable solvents include, for example, isophorone, glycol ethers, glycol ether acetates, and the like. In particular, isophorone is often used in liquid coating formulations, but isophorone can pose health and environmental hazards and, therefore, the use of isophorone can be reduced or even eliminated. However, in the absence of solvents such as isophorone, coating formulations can exhibit increased viscosity, poor thermal stability, and other suboptimal characteristics.

[0005] Therefore, there remains a need to develop PVDF dispersions or coatings that are substantially free of fluorosurfactants but use environmentally friendly solvents and provide optimal viscosity and rheology control as well as optimal performance characteristics. SUMMARY

[0006] Various embodiments of the present invention provide PVDF-containing coating compositions that are substantially free of fluorosurfactants and thus minimize environmental concerns associated with fluorosurfactant use. The coating compositions can be applied by various conventional methods and provide, upon curing, elastic, corrosion-resistant cured films.

[0007] Various embodiments herein provide PVDF coating compositions that have a relatively long pot life for storage and transport and / or exhibit high physical strength and excellent chemical resistance upon curing. In the embodiments disclosed herein, the PVDF coating compositions include a solvent, such as but not limited to diisobutyl ketone (DIBK), that helps control the viscosity and rheology of the coating in the absence of fluorosurfactants and conventional solvents such as isophorone.

[0008] Accordingly, embodiments of the present application describe a coating composition having a dispersed fluoropolymer resin, the composition comprising: at least about 30 wt% of a PVDF polymer, based on resin solids, and at least one organic solvent including a non-aromatic ester, a non-aromatic ketone, or a mixture thereof.

[0009] Embodiments of the present application describe a composite material constituting a metal substrate having at least one surface comprising a PVDF-based film, the PVDF-based film being formed by a process comprising: coating at least one surface with the coating composition according to any one of the preceding claims to form a coated metal substrate; and heating the coated metal substrate.

[0010] Embodiments of the present application describe a coating composition having a dispersed PVDF resin, the coating composition comprising: at least about 30 wt% of a PVDF, based on total resin solids; and an organic solvent including an organic solvent having a HSP polarity delta P < 6 and a hydrogen bonding component delta H < 10 between 0 wt% and 20 wt%, based on the weight of the total composition.

[0011] “Embodiments of the present application describe a coating composition comprising: at least about 50 wt% of a PVDF, based on resin solids; a first organic solvent selected from the group consisting of: DIBK, DAA (diacetone alcohol), DB (diethylene glycol butyl ether), DPM (dipropylene glycol methyl ether), Aro 150 (Aromatic 150), EA Ac (ethyl acetoacetate), TMB (trimethylbenzene), EB Ac (ethylene glycol butyl ether acetate), PM Ac (propylene glycol methyl ether acetate), and mixtures thereof; and a second organic solvent including isophorone, xylene, toluene, or mixtures thereof.”

[0012] The advantages and features of the present disclosure are particularly pointed out and distinctly claimed in the claims attached to this disclosure and form a part of this disclosure. However, for a better understanding of the present disclosure, reference should be made to the examples and the descriptive content, which form a part of this disclosure, wherein embodiments of the present disclosure are illustrated and described. BRIEF DESCRIPTION OF DRAWINGS

[0013] Non-limiting and incomplete examples are described with reference to the following figures.

[0014] Figure 1 Rheology profiles (shear increase) of exemplary compositions of the present disclosure are depicted.

[0015] Figure 2A Viscosities of exemplary compositions of the present disclosure measured with a Brookfield viscometer at 10 rpm are depicted.

[0016] Figure 2B Viscosities of exemplary compositions of the present disclosure measured with a Brookfield viscometer at 100 rpm are depicted.

[0017] Figure 2C Thixotropy indices (also referred to as thix indices) of exemplary compositions of the present disclosure are depicted.

[0018] Figure 3 Effect of DIBK on viscosity of exemplary PVDF formulations is depicted. DETAILED DESCRIPTION

[0019] Various embodiments of the present disclosure relate to a solvent-based composition or dispersion coating containing polyvinylidene fluoride ("PVDF"). The described compositions or dispersion coatings can be used to produce tough, chemical resistant coatings, especially on metal substrates, including use as coil coatings, architectural coatings, and the like. The various embodiments described herein provide compositions containing significantly higher fluoropolymer and / or total solids loading than conventional fluoropolymer coating compositions, using PVDF to form stable formulations that are substantially free of fluorosurfactants, which can enable higher line speeds of application, thereby increasing productivity. In some examples, the compositions disclosed herein can produce robust coatings with high temperature cure, and solvents with high boiling points can reduce film defects, such as blistering, in the coatings. The PVDF coating compositions described herein use solvents, such as but not limited to diisobutyl ketone (DIBK), which help control the viscosity and rheology of the coating in the absence of fluorosurfactants and conventional solvents such as isophorone, while providing optimal performance characteristics and enhancing the action of other additives and dispersants. The coating compositions can be applied by various conventional methods and provide elastic, corrosion resistant cured films upon heating. In particular, the various embodiments herein provide polyvinylidene fluoride (polyvinylidene difluoride, "PVDF") coating compositions that have a relatively long pot life for storage and transport, and exhibit high physical strength and excellent chemical resistance when cured.

[0020] Aspects of the present disclosure relate to a coating composition comprising a fluoropolymer resin dispersed in an organic solvent in the absence of fluorosurfactants and conventional solvents such as isophorone. The fluoropolymer resin generally includes a polyvinylidene fluoride-based polymer, and preferably includes PVDF. In one aspect, the solvent used to disperse the fluoropolymer resin component is a non-aromatic ester or ketone, preferably diisobutyl ketone (DIBK). The composition generally further comprises pigments and polymeric additives designed to improve the hardness and / or adhesion of the resulting cured film, for example a combination of a thermoplastic acrylic polymer or a hydroxy-functional polymer and a curing agent. Depending on the desired properties of the final cured film, the composition can include other additives, such as matting agents for reducing gloss or additives for improving mar resistance. In some examples, the PVDF can be dispersed in an acrylic resin solution prepared in DIBK.

[0021] Aspects of the present disclosure also provide a method of coating a metal substrate to provide a cured vinylidene fluoride-based polymer film on at least one surface of the substrate. The method includes applying a coating composition to a surface of a metal substrate to form a film, for example by roll coating or spraying the coating composition onto the substrate surface. The coated metal substrate is then heated so that the coating cures to form a tough cured film adhered to the substrate surface. The coated metal substrate is cured by heating the vinylidene fluoride-based resin film to a temperature sufficient to cause the fluoropolymer resin to coalesce.

[0022] Another aspect of the present disclosure provides a method of classifying various solvents in a coil coating formulation. This classification helps to identify the best solvents for a given paint or liquid coating system.

[0023] Selected definitions

[0024] The term "fluoropolymer" means any polymer having at least one monomer in its chain selected from compounds containing a vinyl group capable of opening for polymerization, and the polymer contains at least one fluorine atom, at least one fluoroalkyl group, or at least one fluoroalkoxy group directly attached to this vinyl group. Examples of fluorine-containing monomers include, but are not limited to, fluoroethylene; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(l,3-dioxolane); perfluoro(2,2-dimethyl-l,3-dioxolane) (PDD). Preferred fluoropolymers are homopolymers and copolymers of vinylidene fluoride. Particularly preferred fluoropolymers are homopolymers of vinylidene fluoride.

[0025] As used herein, the term "PVDF" refers to polyvinylidene fluoride or vinylidene fluoride. The PVDF can be a homopolymer, copolymer, terpolymer, or a blend of a PVDF homopolymer or copolymer with one or more other polymers that are compatible with the PVDF (co)polymer. PVDF copolymers and terpolymers of the present disclosure are those in which the vinylidene fluoride units comprise greater than 40% of the total weight of all monomer units in the polymer and more preferably greater than 70% of the total weight of these units. Copolymers, terpolymers, and higher polymers of vinylidene fluoride can be prepared by reacting vinylidene fluoride with one or more monomers selected from the group consisting of one or more of fluoroethylene, trifluoroethylene, tetrafluoroethylene, partially or fully fluorinated alpha-olefins such as 3,3,3-trifluoro-l-propene, 1,2,3,3,3-pentafluoropropene, 3,3,3,4,4-pentafluoro-l-butene, and hexafluoropropene, partially fluorinated olefin hexafluoroisobutene, perfluorinated vinyl ether such as perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoro-n-propyl vinyl ether, and perfluoro-2-propyloxypropyl vinyl ether, fluorinated dioxole such as perfluoro(l,3-dioxole) and perfluoro(2,2-dimethyl-l,3-dioxole), allyl, partially fluorinated allyl, or fluorinated allyl monomers such as 2-hydroxyethyl allyl ether or 3-allyloxypropanediol, and ethylene or propylene. In certain aspects of the present disclosure, the PVDF has a Mw of about 150,000 to about 500,000. More preferably, the PVDF has a molecular weight (Mw) of about 350,000 to about 450,000, a molecular weight per mole number (Mw / Mn) ratio of about 3.5 to about 5.0, and / or a melting point of about 150°C to 170°C. One example of a commercially available PVDF particularly suitable for use in the compositions of the present disclosure is Kynar ® 500.

[0026] The term "substantially free" can refer to any component that is absent or largely absent from a composition of the present disclosure. When referring to "substantially free," the component is not intentionally added to the composition of the present disclosure. The use of the term "substantially free" of a component allows for trace amounts of the component to be included in the composition of the present disclosure as they are present in another component. However, it is recognized that when a composition is referred to as "substantially free" of a component, only trace or minor amounts of the component will be allowed. Further, if a composition is referred to as "substantially free" of a component, if the component is present in trace or minor amounts, it is understood that it does not affect the effectiveness of the composition. It is understood that if an ingredient is not expressly included herein or is not stated herein as possibly included, the composition of the present disclosure can be substantially free of that ingredient. Likewise, the express inclusion of an ingredient allows for the express exclusion of that ingredient, allowing the composition to be substantially free of the expressly stated ingredient.

[0027] As used herein, the terms "free of fluoro surfactant" and "substantially free of fluoro surfactant" means less than 0.1 wt% fluoro surfactant.

[0028] The methods, systems, and compositions of the present disclosure can comprise, consist essentially of, or consist of the components and ingredients of the present disclosure, as well as other ingredients described herein. As used herein, "consisting essentially of" means that the methods and compositions can include additional steps, components or ingredients, but only if the additional steps, components or ingredients do not materially alter the basic and novel characteristics of the claimed methods and compositions.

[0029] As used herein, "percent by weight," "wt.-%," "percent by weight," "% by weight," and variations thereof refer to the concentration of a substance that is the weight of that substance divided by the total weight of a composition, multiplied by 100. It should be appreciated that "percent," "%" and the like are intended to be synonymous with "percent by weight," "wt.-%," and the like, as used herein.

[0030] As used herein, "g" means gram; "L" means liter; "mg" means milligram (10"3gram); "mL" means milliliter (10"3liter); "cm" means centimeter (10"2meter); micrometer means 10"6meter; "mm" means millimeter (10"3meter); "inch" is used as a unit of length and one inch is equal to about 2.54 cm; "centipoise" or "cPs" or "cP" is used as a unit of viscosity and 1 cP = 10"3Pa-s = 1 mPa-s. The temperature units used herein are degrees Celsius (°C).

[0031] The term "about" is used in connection with a value to include normal variations that would be expected by persons of ordinary skill in the art in making a measurement, and is understood to have the same meaning as "approximately" and to cover typical error limits, such as ±10% of the stated value. The term "about" also covers amounts that differ due to different equilibration conditions of the compositions resulting from the particular initial compositions. Whether modified by the term "about" or not, the claims include equivalents.

[0032] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing "a compound" includes having two or more compounds the same or different from each other. It should also be noted that the term "or" is generally employed in its sense including "and / or" unless the content clearly dictates otherwise.

[0033] For the sake of brevity and conciseness in the description herein, any range of values stated recited herein contemplates all values within the range and the range should be understood to support the claim of any sub-range recited as being a range of real values within the particular range discussed. By way of illustrative example, a disclosure in the description herein of a range from 1 to 5 should be considered to support a statement of any range from the following: 1-5; 1-4; 1-3; 1-2; 2-5; 2-4; 2-3; 3-5; 3-4; and 4-5.

[0034] Aspects of the coating composition of the present disclosure include a fluoropolymer dispersion, i.e., a dispersion of fluoropolymer resin particles in an organic solvent, such as a non-aromatic ketone or ester. Generally, the present composition includes at least about 30 wt%, preferably at least about 35 wt%, and more preferably about 40 wt% - 50 wt% of PVDF polymer resin (based on the total dry film weight of the coating composition). In some examples, the present composition includes 47 wt% of PVDF polymer resin (based on the total dry film weight of the coating composition). In some cases, the PVDF polymer can constitute up to about 70 wt% to 95 wt% of the resin solids. Aspects of the coating composition of the present disclosure include a fluoropolymer dispersion, i.e., a dispersion of fluoropolymer resin particles in an organic solvent, such as a non-aromatic ketone or ester. Aspects of the coating composition of the present disclosure can include an acrylic resin.

[0035] Generally, the present composition includes at least about 10 wt% - 80 wt%, preferably at least about 20 wt% - 70 wt%, and more preferably about 25 wt% - 60 wt% of non-volatile material (“NVM” or “resin solids”) (based on the total wet weight of the coating composition). The PVDF polymer generally constitutes at least about 30 wt%, preferably at least about 35 wt%, and more preferably about 40 wt% - 50 wt% of the NVM (based on the total wet weight of the coating composition).

[0036] The fluoropolymer resin-based compositions of the present application can also include a dispersant. While not limiting the present application, it is believed that the role of the dispersant is to maintain spacing between the fluoropolymer particles, thereby acting as a dispersing aid. Dispersants commonly used to formulate pigment dispersions have been found to be suitable for use in the compositions of the present application. Dispersants generally contain functional groups that can be adsorbed onto the surface of the pigment or fluoropolymer particles. Compounds that contain a polar group (e.g., an amino group) on one end and a portion that is soluble in the continuous phase of the solvent (hydrophobic tail) on the other end are suitable for use as dispersants. Generally, the compositions of the present application include from about 0.005 wt% to about 5.0 wt% and preferably from about 0.01 wt% to about 3.0 wt% of a dispersant. When the compositions include relatively high NVM (e.g., at least about 55 wt%) and PVDF (e.g., at least about 35 wt%) loadings, from about 0.5 wt% to about 3.0 wt% of a dispersant is generally employed. When the compositions are clear coatings having a total NVM content of from about 35 wt% to 70 wt% and a PVDF content of from about 30 wt% - 60 wt%, lower levels of dispersant (e.g., 0.01 wt% to 2 wt%) are generally employed. In some examples, the compositions of the present application include 2 wt% of a dispersant. In some examples, the compositions of the present application include from about 2 wt% to about 4 wt% of a dispersant. In some examples, the compositions of the present application include from about 3 wt% to about 5 wt% of a dispersant. In some examples, the compositions of the present application include from about 0.01 wt% to about 4 wt% of a dispersant.

[0037] A particularly suitable class of dispersants for use in the compositions of the present application are referred to herein as "hyperdispersants." As used herein, the term "hyperdispersant" refers to a dispersant that allows the preparation of stable dispersions containing at least about 90 wt% PVDF (based on NVM) at PVDF loadings of about 35 wt% or more when included in a solvent-based formulation at up to about 3 wt%. Examples of suitable hyperdispersants include polymeric dispersants having one or more amino groups covalently bonded to the polymer. Hyperdispersants are generally employed at relatively low levels (e.g., 0.01 wt% to 0.5 wt%) in formulations containing from about 25 wt% to about 35 wt% PVDF. From about 0.1 wt% to about 3.0 wt% of a hyperdispersant is generally employed when the formulation includes greater than about 40 wt% PVDF.

[0038] In certain embodiments, preferred dispersants are phosphonic acids (and salts thereof) and some natural polymers or synthetic polymers. The polymeric dispersants can have different polymer structures, including linear, comb / branched, star, and dendritic (including dendrimers and highly branched polymers). Useful natural polymers include, but are not limited to, proteins such as gelatin, gelatin, casein, and albumin; naturally occurring rubbers such as gum arabic and gum tragacanth; glucosides such as saponin; alginic acid and alginic acid derivatives such as propylene glycol alginate; and cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, and ethyl hydroxy cellulose; wool and silk, and synthetic polymers.

[0039] In other embodiments, the dispersants can contain one or more amino groups covalently bonded to the polymer backbone or to the side chains of the polymer. Examples of suitable polymeric dispersants include alkoxylated amines and polymeric polyester / polyamine condensates. Suitable alkoxylated amines include alkoxylated amino alcohols such as Solsperse ® 20000 (available from Zeneca, Inc.) and alkoxylated alkyl amines such as Tetronic ® 150R1 (available from BASF). Tetronic ® 150R1 (herein "T150R1" or "T150") is a polymer formed by the reaction of 1,2-ethanediamine with propylene oxide and ethylene oxide. This latter type of polymer is generally referred to herein as a "polymeric alkoxylated ethylenediamine." Examples of suitable polymeric polyester / polyamine condensates are commercially available under the trade name Solsperse ® 27000, 28000, 36600, and 24000 SC from Lubrizol, Inc.

[0040] Alternatively, the amine groups can be attached to the polymer as amine salts of carboxylic acid groups. Examples of such amine salt-containing dispersants include alkylol ammonium salts of acidic polyesters (e.g., Disperbyk ® -180; available from BYK-Chemie, USA, Wallingford, Conn.); salts of unsaturated polyamine amides and higher molecular weight acidic esters such as Antiterra ® U80 (BYK-Chemie, USA). Another type of dispersant that can be used in the present compositions is a partial amide of a higher molecular weight unsaturated polycarboxylic acid such as Disperplast ® I (available from BYK-Chemie, USA) and salts of long chain polyamine amides and polar acidic esters such as Disperbyk® 101). Other dispersants still include high molecular weight polyester / polyurethane block copolymers (such as Disperbyk® from Byk-Chemie ® 163 and Disperbyk® 165 from Byk-Chemie ® Nuosperse® from Elementis Specialties ® 9850). All of the above dispersants can be used as provided and incorporated into the fluoropolymer dispersion.

[0041] Aspects of embodiments of the present disclosure relate to PVDF coating compositions that are free or substantially free of fluorinated anionic dispersants. Fluorinated anionic dispersants are another class of superdispersants, commonly referred to as fluorosurfactants. In certain aspects, the embodiments described herein are substantially free or even completely free of fluorosurfactants.

[0042] Traditionally, PVDF coatings free of fluorosurfactants were not possible in certain colors, including white. The significantly higher pigment load required for white coating compositions resulted in high initial viscosity (Zahn #4), which led to poor hot box stability (+10 seconds Zahn #4). Alternative methods to reduce viscosity included increasing the level of non-fluorosurfactants, which was limited due to subsequent changes in color development / appearance and the appearance of haze in the coating. Other methods included increasing the level of solvent, which reduced the solids of the formulation (to achieve the desired film thickness target, the application line speed needed to be reduced), and also increased the volatile organic compound (“VOC”) concentration. Traditionally, a variety of organic solvents could be used to formulate the fluoropolymer dispersion of the present invention, including, for example, but not limited to, solvents such as isophorone. The organic solvents typically act as a latent solvent for the fluoropolymer; that is, the fluoropolymer is substantially insoluble and dispersible in the solvent at room temperature, but when the composition is heated, it solvates or dissolves in the solvent. Some of these traditional solvents caused additional problems when included in the composition.

[0043] Surprisingly, Applicants have discovered that the compositions of the present disclosure have reduced dispersion viscosity as compared to traditional PVDF dispersions in organic solvents in the absence of fluorine-containing surfactants. The compositions of the present disclosure are particularly advantageous because they allow for increased PVDF resin solids content (or NVM content), which reduces dispersion VOC levels, while preventing blistering and supporting application at higher line speeds. Applicants have surprisingly discovered that the use of non-aromatic aliphatic esters or ketones, such as diisobutyl ketone (“DIBK”), for example, allows for 100% fluorine-free surfactant PVDF coatings, while maintaining color, viscosity and rheology profiles (flow / more stable viscosity) and performance, including providing batch-to-batch consistency, without introducing additional issues (e.g., fogging or blistering). Without being limited by theory, the presence of non-aromatic aliphatic ester or ketone solvents, such as DIBK, enables the reduction of the initial viscosity and thixotropic index of the coating to target ranges, which generally results in improved stability of the PVDF coating composition during heat aging (hot box stability). In particular, in white coatings, for example, higher concentrations of DIBK in combination with a dispersing or wetting additive (e.g., BYK 2117) results in a substantial reduction in viscosity, which can enable higher solid products within current viscosity specifications. As shown in Table 1 below, the viscosity of the coating composition is improved by the presence of the combination of non-aromatic ester or ketone solvent and dispersing or wetting additive. Figures 1-3

[0044] In some examples, the amount of solvent used and / or the type of solvent / co-solvent can depend at least in part on the intended method of application of the composition (e.g., spray or coil coating). In some examples, solvents exhibiting relatively low boiling points can be less suitable for coil coating applications because they can evaporate more quickly and can result in blistering. However, even in such coil coating applications, solvents exhibiting relatively low boiling points can be effectively used as co-solvents with at least one other solvent without resulting in negative effects.

[0045] ​The solvent typically comprises from about 10 wt% to about 50 wt% and preferably from about 25 wt% to about 40 wt% of the composition. In preferred embodiments of the present disclosure useful for coil coating applications, the composition has a solvent component comprising at least 10 wt% to 30 wt% (based on total solvent) of a solvent having a boiling point between about 200°C to about 300°C, and at least 10 wt% to 25 wt% of a non-aromatic ketone solvent having from about 6 to about 30 carbon atoms; more preferably from about 9 to about 20 carbon atoms. In some preferred embodiments of the present disclosure useful for coil coating applications, the composition has a solvent component comprising at least 10 wt% to 30 wt% (based on total solvent) of the solvent isophorone and at least 10 wt% to 25 wt% of DIBK. Applicants have surprisingly found that higher concentrations of DIBK in combination with a dispersing or wetting additive, such as BYK-2117, for example, results in a substantial reduction in viscosity for certain coatings (e.g., white coatings) having high pigment loadings, which can enable higher solid product within current viscosity specifications. Applicants have also found that the presence of DIBK in the composition allows for more selection in dispersant type and efficacy at lower levels. Further, the presence of DIBK in these compositions results in less foaming on-line during coil coating applications, for example, relative to compositions using conventional solvents, such as acetate solvents.

[0046] In other preferred embodiments of the present disclosure useful for coil coating applications, the composition has a solvent component comprising at least 10 wt% to 30 wt% (based on total solvent) of a solvent having a boiling point between about 200°C to about 300°C and at least 10 wt% to 25 wt% of a polyol diester, such as triethylene glycol bis(2-ethylhexanoate) (“TEG-EH”) and esterified ethers, such as esters of glycol monoethers, such as propylene glycol methyl ether acetate (“PMA” or “PM acetate”) or dipropylene glycol methyl ether acetate (“DPMA” or “DPM acetate”). In another embodiment of the present disclosure useful for coil coating applications, the composition has a solvent component comprising at least 10 wt% to 30 wt% (based on total solvent) of a solvent having a boiling point between about 200°C to about 300°C and at least 10 wt% to 25 wt% of a diester of a branched aliphatic diol, and more preferably a butyric acid diester of a branched octanediol, such as 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (“TXIB”). Other preferred compositions comprise a solvent component consisting essentially of DIBK, PM acetate, DB acetate, DPM acetate, toluene, xylene, or mixtures thereof.

[0047] Hansen solubility parameters ("HSP") have proven to be a powerful practical way to understand solubility, dispersion, diffusion, chromatography, and the like. Accordingly, in certain embodiments, a method of selecting the best solvent for dispersing a fluoropolymer resin for web coating is provided herein. In certain embodiments, three HSP parameters are utilized to select solvents: δD, for dispersion (van der Waals); δP, for polarity (related to dipole moment); and δH, for hydrogen bonding. For reference, the HSP values for solvents used in embodiments of the present disclosure are provided in Table 1. In certain aspects, the compositions of the present disclosure contain organic solvents with HSP polarity δP < 4 and hydrogen bonding component δH < 6. In certain aspects, the compositions of the present disclosure contain organic solvents with HSP polarity δP < 8 and hydrogen bonding component δH < 9. In certain aspects, the compositions of the present disclosure contain organic solvents with HSP polarity δP < 12 and hydrogen bonding component δH < 15.

[0048] The following Table 1 includes the predicted Hansen solubility parameters for various solvents. These values were collected from the database HSPiP version 5.3.06 (Hansen Solubility Parameters in Practice). The HSPiP database includes solubility parameters. The software of the HSPiP database allows for the classification of solvents relative to a target. To generate the data in the following table, the target was selected to be DIBK, and the HSPiP database software was used to identify potential alternative solvents that can have similar behavior to DIBK based on their similar solubility parameters. To generate the data in Table 1, a small radius in the space around DIBK was selected.

[0049] The data in Table 1 predicts that the lowest viscosity can be obtained with solvents having Hansen solubility parameters in the range of δP < 6 and δH < 10 (most preferred). Acceptable coating viscosity and storage stability can be obtained with solvents using Hansen solubility parameters in the range of δP < 9 and δH < 7. Once δH increases to values higher than 8, it becomes more difficult to obtain stable viscosity even if δP is low (δP > 6). In some examples, these solvents can be suitable for use as co-solvents.

[0050] The data in Table 1 predicts that solvents with RED < 1 (relative energy difference) are predicted to behave similarly to DIBK and act favorably. As evidenced by the data in Example 1, solvents with RED > 1, such as those with RED > 2, can still achieve desirable viscosity results compared to DIBK. Accordingly, based on these solubility parameter characteristics and experimental data, other solvents can be proposed as alternatives to DIBK.

[0051] Table 1 : Hansen Solubility Parameters of Exemplary Solvents

[0052] High solids coating compositions of the type disclosed herein include at least about 70 wt% and preferably at least about 85 wt% (based on total resin) of a vinylidene fluoride based polymer such as PVDF, which can be used to form a coil coating having a significantly higher thickness than can be achieved with conventional PVDF coating without forming bubbles. For example, tinted embodiments of the present compositions include a substantial portion (based on total solvent) of a solvent having a boiling point between about 180°C to about 300°C, which allows for the formation of a coil coating having a dry film thickness ("DFT") that exceeds twice the DFT that can be achieved using conventional 70% PVDF coating compositions.

[0053] In some cases, it can be preferable to include an amount of solvent in addition to DIBK, for example, a solvent that does not completely volatilize under baking conditions, such as isophorone, which can be used to form a dry film on a substrate. In such cases, the residual solvent remaining in the fluorine containing polymer based dry film can act as a plasticizer. For other applications, it can be preferable to select a solvent that substantially completely volatilizes under the baking conditions employed. Preferably, the solvent has a boiling point of about 170°C to about 400°C and more preferably about 200°C to about 350°C. Preferably, such compositions include about 60 wt% - 80 wt% total solids and about 35 wt% to about 50 wt% of a PVDF polymer.

[0054] Other examples of suitable solvents that can be present, to some extent, as part of the solvent portion of the compositions of the present application include phthalates such as butyl benzyl phthalate, TXIB (trimethyl pentylidene isobutyrate) and dialkyl phthalates (e.g., di(2-ethylhexyl) phthalate, dimethyl phthalate and dioctyl phthalate); aromatic compounds such as toluene and xylene; ketones such as isophorone; aliphatic dibasic esters such as dioctyl azelate, diisodecyl adipate and di(2-ethylhexyl) sebacate; phosphate esters such as trioctyl phosphate and 2-ethylhexyl diphenyl phosphate; epoxy plasticizers such as epoxidized soybean oil, epoxidized tall oil fatty acid 2-ethylhexyl ester and other conventional polyester solvents commonly used as plasticizers. Embodiments of the present application intended for use as clear coatings typically include alkyl-substituted benzenes, phthalates, glycol monoethers, glycol esters and / or monoesters of alkyleneoxy ethers. Examples of suitable organic solvents that can be used to formulate the compositions of the present application in clear form include toluene, xylene, dimethyl phthalate, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, butyl cellosolve, n-butanol and mixtures thereof.

[0055] To improve the hardness and adhesion of the resulting cured film, the compositions of the present application can include a hydroxyl functional polymer, such as a hydroxyl acrylate polymer. Those coating compositions containing a hydroxyl functional polymer typically also include a curing agent, such as an aminoplast resin.

[0056] Hydroxyl functional polymers are numerous and are generally solvent soluble copolymers containing from about 1% to about 25% by weight of a hydroxyl functional monomer of a monoethylenic monomer. The hydroxyl functional group is typically the only reactive group in the copolymer, although a small amount of carboxylic acid functionality is permissible, but not necessary. Preferably, the hydroxyl monomer content is from 2% to 10% by weight of the monomer mixture.

[0057] A variety of hydroxyl functional monomers can be used, but it is preferred to use a hydroxyalkyl ester of a mono carboxylic acid such as acrylic or methacrylic acid. The alkyl group envisioned is primarily those containing 1-4 carbon atoms and is illustrated by methyl ethyl, propyl or butyl, however esters of alcohols having up to 12 carbons can also be used. Preferred hydroxyl functional monomers include 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate. Hydroxyalkyl ethers, such as the hydroxyethyl ether of an alkyl alcohol are also useful.

[0058] Hydroxyl functional copolymers can be prepared by free radical polymerization of a mixture of monoethylenically unsaturated monomers including hydroxyalkyl acrylate or methacrylate in the desired proportions; or hydroxyethyl acrylate or methacrylate. Other monomers are preferably acrylic and methacrylic esters of alcohols containing from 1 to 6 carbon atoms and preferably 1 or 2 carbon atoms. Most preferably, the non-hydroxyl monomers include at least about 50% of methyl methacrylate, n-butyl methacrylate and / or ethyl acrylate. Small amounts, e.g., about 1 to 2% by weight, of a carboxylic acid, such as acrylic or methacrylic acid, can also be included in the monomer mixture. The hydroxyl copolymers are preferably used in amounts of from about 1 to about 15% by weight and more preferably from about 2 to about 10% by weight of the composition. In some examples, other suitable unsaturated monomers can be included.

[0059] In some examples, a thermoplastic resin can be included in the composition (e.g., a thermoplastic resin having a relatively low molecular weight). Such a thermoplastic resin can comprise from about 0 to 50% by weight and preferably 0 to 10% by weight of the total resin solids present in the composition. When DIBK is used as a solvent to synthesize these acrylic resins, the DIBK content is increased in the coating formulations made therefrom, providing a pathway to high solids PVDF coating formulations with the desired properties described above.

[0060] The aminoplast resin is typically added to the composition in sufficient amount to cure the hydroxyl functional polymer. The weight ratio of the hydroxyl functional polymer to the aminoplast resin is typically from about 2: 1 to about 10: 1 and preferably from about 3: 1 to about 6: 1. The aminoplast resin is based on the addition product of an aldehyde, preferably formaldehyde, with a substance bearing amino or amido groups. Examples of suitable aminoplast resins include condensation products obtained from the reaction of an alcohol and formaldehyde with melamine, urea or benzoguanamine. These condensation products can be monomeric or polymeric. Other condensation products of amines and amides can also be employed, such as triazines, diazines, triazoles, guanidines, guanamines, and aldehyde condensates of alkyl- and aryl-substituted melamines. Some examples of such compounds are N,N'-dimethylurea, benzourea, dicyandiamide, formoguanamine, acetoguanamine, glycoluril, melonamide, 2-chloro-4,6-diamino-l,3,5-triazine, 6-methyl-2,4-diamino-l,3,5-triazine, 3,5-diaminotriazole, triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine, 3,4,6-tris(ethylamino)-l,3,5-triazine, and the like. While the aldehyde employed most commonly is formaldehyde, other similar condensation products can be prepared from other aldehydes, such as acetaldehyde, crotonaldehyde, propyl aldehyde, benzaldehyde, furfural, glyoxal, and the like.

[0061] A preferred aminoplast curing agent is simply a formaldehyde condensate with an amine, preferably melamine, to provide a thermally hardening hydroxymethyl functional resin. While many aminoplast resins, such as urea formaldehyde condensates and benzoguanamine formaldehyde condensates, are widely applicable, preferably the aminoplast resin is a polyalkoxymethyl melamine resin in which the alkoxyl groups contain 1 to 4 carbon atoms. Suitable melamine-formaldehyde condensates are well known and are readily available commercially and are typically etherified with lower alcohols for use in organic solvent solutions. An example of a suitable aminoplast curing agent includes an etherified melamine-formaldehyde condensate as an organic solvent solution (e.g., poly-methoxymethyl melamine available from Cytec, such as Cymel 303). The aminoplast resin is typically present at 0.1 to 10 weight percent of the total resin solids, and preferably, in an amount of 0.2 to 3.0 weight percent of the total resin solids.

[0062] While aminoplast resins are preferred for curing the hydroxyl functional copolymer, any curing agent that reacts with the hydroxyl functionality can also be used, such as a phenolic resin or a blocked polyisocyanate. Suitable blocked isocyanate curing agents include isophorone diisocyanate blocked with methyl ethyl ketoxime or 2,4-toluene diisocyanate blocked with octanol. Such blocked isocyanate curing agents are well known and these agents effect curing by forming urethane groups with the hydroxyl functionality on the coating composition when baking causes the blocked isocyanate groups to dissociate and become active.

[0063] When the present composition is used to form a clear coating, the formulation will typically include a thermoplastic resin, such as a thermoplastic acrylic polymer. Thermoplastic acrylic resins are typically polymeric ester derivatives of acrylic and methacrylic acids. These esters are formed by the reaction of acrylic or methacrylic acid with suitable alcohols, for example, methanol, ethanol, propanol, butanol, and 2-ethylhexanol. Generally, the larger the alcohol portion of the ester, the softer and more flexible the resulting resin. Methacrylic esters tend to form harder films than the corresponding acrylic esters. Monomers, such as styrene, vinyl toluene, vinyl chloride, and vinylidene chloride, can also be reacted with the acrylic and methacrylic esters to produce thermoplastic resins with superior properties. A particularly suitable resin is a copolymer of methyl methacrylate and ethyl acrylate having a Mw of between about 50,000 and about 150,000.

[0064] The present composition can be clear (essentially no color) where it is designed to be used as a protective topcoat. However, more typically, the coating composition includes pigments. The pigment loading will depend on many factors, including the desired opacity, color, and chemical resistance. A typical pigmented form of the present composition includes about 5 to about 25 weight percent and preferably about 10 to about 20 weight percent of one or more pigments.

[0065] Conventional additives, including surfactants, antioxidants, ultraviolet light absorbers and stabilizers, rheology control agents, coalescing agents, and the like, can also be added to the coating compositions of the present application. For example, to prevent yellowing and / or degradation during the baking process, the coating compositions of the present application can include an antioxidant such as Irgonox 1010 (available from Ciba-Geigy). Matting agents such as DeGussa product OK-412 or silica (e.g., Syloid 7000 available from W. R. Grace) can be added to reduce the 60° gloss reading to within the desired range. Additives such as waxes (e.g., Polymekon wax or Paxwax) or micronized PTFE can be added to improve surface lubricity and thus improve scratch resistance.

[0066] The coating compositions of the present disclosure can be prepared by conventional methods. For example, the coating compositions can be prepared by blending the various components using a high speed disperser and milling equipment such as a small media mill.

[0067] The coating compositions can be applied using any of a variety of standard application methods, for example, brushing, bar coating, slot coating, roll coating, or spraying. The viscosity required will vary depending on the particular end use, the desired dry film thickness, and the application method of the coating. For example, when the coating composition is applied by a web coating process (e.g., by reverse roll coating), the composition preferably includes at least about 40 wt% and more preferably from about 55 wt% to about 80 wt% total solids, and generally has a viscosity of from about 40 seconds to about 120 seconds and preferably from about 60 seconds to about 120 seconds (#2 Zahn.). In some examples, the composition includes from about 40 wt% to about 45 wt% total solids and has a viscosity of from about 20 seconds to about 40 seconds (#4 Zahn) and from about 500 seconds to about 1500 seconds (10 rpm, Brookfield #4 spindle). In some examples, the composition includes from about 45 wt% to about 55 wt% total solids and has a viscosity of from about 20 seconds to about 40 seconds (#4 Zahn) and from about 700 seconds to about 1300 seconds (10 rpm, Brookfield #4 spindle). In some examples, the composition includes from about 40 wt% to about 55 wt% total solids and has a viscosity of from about 20 seconds to about 40 seconds (#4 Zahn) and from about 500 seconds to about 1500 seconds (10 rpm, Brookfield #4 spindle). The coating compositions applied via a web coating process more preferably have a viscosity of from about 80 seconds to about 105 seconds (#2 Zahn.) and include from about 35 wt% to about 50 wt% PVDF polymer (based on total composition weight).

[0068] Roll coating of this type of composition allows for the formation of a wet film thickness of 0.5 mil to 5 mil, or in some examples 0.5 mil to 10 mil. Roll coating, including but not limited to roll coating of this type of composition, allows for the formation of a wet film thickness of 0.2 mil to 2 mil, or in some examples 0.2 mil to 6 mil or 0.7 mil to 6 mil. In other embodiments, the composition preferably contains at least about 50% by weight, and more preferably about 55% by weight to about 80% by weight, of total solids, and typically has a viscosity of 900 Pa·s to 5000 Pa·s (10 rpm, Brookfield #4 rotor), preferably less than 4000 Pa·s (10 rpm, Brookfield #4 rotor), more preferably less than 2000 Pa·s (10 rpm, Brookfield #4 rotor), and more preferably less than 1000 Pa·s (10 rpm, Brookfield #4 rotor). In other embodiments, the composition preferably comprises at least about 50% by weight, and more preferably about 55% by weight to about 80% by weight, total solids, and typically has a viscosity of 400 Pa·s to 1500 Pa·s (100 rpm, Brookfield #4 rotor), preferably less than 1500 Pa·s (100 rpm, Brookfield #4 rotor), more preferably less than 1000 Pa·s (100 rpm, Brookfield #4 rotor), and even more preferably less than 500 Pa·s (100 rpm, Brookfield #4 rotor). When the composition of the present invention is used as a topcoat (e.g., a coating over a primer), the composition is typically applied with a wet film thickness of 1 to 3 mils and produces a cured dry film thickness of about 0.2 to 1.0 mils, and the total dry film thickness of a multi-coat system is about 0.9 to 2.3 mils.

[0069] In the case of utilizing spray application, pigmented versions of the present compositions preferably comprise at least about 50% by weight total solids, and typically have a viscosity of about 25 seconds to about 60 seconds (#2 Zahn). In the case of using the present compositions to form clear coatings, total solids contents of 35% to 45% by weight and PVDF contents of at least about 30% by weight are common. Such composition coatings can be used to make spray coatings (e.g., via electrostatic spray) having a wet film thickness of about 2 mils to about 4 mils and a dry film thickness of about 1.0 mils to about 2.0 mils. In the case of using the compositions to form clear topcoats, spray application is typically performed to yield coatings having a wet film thickness of about 1 mil to 2 mils and a dry film thickness of about 0.3 mils to 0.7 mils. In some cases, the present compositions can be diluted with a suitable reducing solvent (e.g., xylene, butyl carbitol, or a combination thereof) prior to spray application. The particular reducing solvent employed depends on a variety of factors, including line conditions and the desired or specified DFT.

[0070] The dispersion coatings of the present disclosure can be applied to a substrate by means known in the art, including but not limited to brushing, bar coating, roll coating, inkjet application, and spraying. The coatings can be applied to one or more sides of the substrate. The substrate is typically metallic, including but not limited to aluminum, hot-dipped galvanized steel, and zinc-aluminum alloys on steel. Two or more coats of the dispersion coating can be added, and the metal can be physically or chemically primed prior to coating. In a preferred aspect, the coating compositions described herein are applied using coil coating as known in the art, including, for example, by a reverse roll coating process. After application of the fluoropolymer dispersion coating, the substrate is heated to cure the coating and form a tough film.

[0071] Prior to application of the present coating compositions, the metal surface to be coated with a fluoropolymer- or acrylic-based primer coating can be coated with a primer containing PVDF, such as a primer based on a blend of PVDF and a hydroxy-functional acrylic copolymer. A variety of conventional fluoropolymer- and acrylic-based primers are known to those skilled in the art. Examples of suitable primers that can be applied to a metal surface prior to the present compositions are disclosed in U.S. Patent No. 4,684,677, the disclosure of which is incorporated herein by reference. Other suitable primers include those based on commercially available acrylic emulsions, such as AC-1822 (available from Rohm & Hass), UCAR ® 452 and UCAR ® 455 (available from Union Carbide Corp.), Joncryl ® 537 (available from S.C. Johnson), and Sequabond ®TR7830 (available from Sequa Chemicals, Chester, S.C.).

[0072] In the case of coating large roll thin gauge metal, it is advantageous to apply the coating composition via a roll coating process such as reverse roll coating. When coating using this process, the coated metal substrate is typically cured by heating at a temperature of about 200°C to 300°C for about 10 seconds to about 50 seconds. If a spray process is used, the resulting film is typically cured by heating at a temperature of about 210°C to about 270°C for about 10 minutes to about 15 minutes. The bake temperature is not critical, but must be high enough to coalesce the fluoropolymer particles in the dispersion with the acrylic resin into a continuous film.

[0073] In certain aspects, the present compositions are generally suitable for use in roll coating and spray processes (e.g., total solids content of about 30 wt% to about 70 wt%). However, if desired, the compositions can be diluted prior to application by the addition of solvent. For spray processes, additional solvents such as xylene, toluene, methyl ethyl ketone, or 2-butoxyethanol, etc. can be added to reduce the resin solids content of the composition. The desired viscosity will vary depending on the spray equipment and atmospheric conditions. When applied via a spray process, the pigmented versions of the present compositions generally have a viscosity of 20-60 (#2 Zahn) and a total solids content of about 50 wt% to about 70 wt% (about 35 wt% to about 50 wt% total resin solids). The clear versions of the present coating compositions generally have similar viscosities and contain about 30 wt% to about 45 wt% total resin solids content. Typically, the clear versions are diluted to some extent with an organic solvent prior to the spray process (e.g., by adding 1 to 2 parts butyl carbitol per 10 parts of the clear coating composition).

[0074] The bake temperature is not critical, but must be high enough to coalesce the fluoropolymer particles (e.g., PVDF particles) present in the dispersion into a continuous film. A temperature of at least about 210°C for about 10 minutes is generally sufficient for this purpose. This temperature is more than sufficient to cure any hydroxyl functional polymers present, providing enhanced solvent resistance and improved hardness. In roll coating processes, the oven dwell temperature is typically no more than about 30 seconds, and oven temperatures as high as 300°C to 400°C can be used. PVDF-based films are preferably cured by baking for a dwell time of about 0.25 minutes to 1.0 minutes, such that the metal substrate reaches a peak metal temperature of 225°C to 260°C.

[0075] Examples

[0076] Example 1

[0077] A composition of a PVDF coating without fluorosurfactant was prepared according to the following recipe, where solvent X is solvent:

[0078] Table 2: Composition of PVDF Coatings Without Fluorosurfactant NVM VOC Isophorone Solvent X 58.53% 41.47% 21.47% 0%-20%

[0079] Figure 1 Rheology profiles (shear increase) of exemplary compositions where different solvents are utilized are depicted.

[0080] Viscosities of various formulations are reported in Table 3 below and Figures 2A-2C . Figure 2A Viscosities of exemplary compositions measured with a Brookfield viscometer at 10 rpm are depicted. Figure 2A The data included in Table 4 include viscosities measured before being put into a hot box, after one week in a hot box at 110 °F, after two weeks in a hot box at 110 °F, and after four weeks in a hot box at 110 °F. Figure 2B Viscosities of exemplary compositions measured with a Brookfield viscometer at 100 rpm are depicted. Figure 2B The data included in Table 5 include viscosities measured before being put into a hot box, after one week in a hot box at 110 °F, and after two weeks in a hot box at 110 °F. Figure 2C Thixotropic indices (also referred to as thix indices) of exemplary compositions of the present disclosure are depicted, where the thix index represents the ratio of the viscosity measured at 10 rpm to the viscosity measured at 100 rpm. Figure 2C The data included in Table 6 include viscosities measured before being put into a hot box, after one week in a hot box at 110 °F, after two weeks in a hot box at 110 °F, and after four weeks in a hot box at 110 °F.

[0081] Testing was performed at room temperature about one week after initial formulation.

[0082] Table 3: Viscosity of Test Formulations

[0083] Conditions for testing include: utilizing a Brookfield #4 spindle; stirring for 5 minutes before testing is performed; and testing at room temperature.

[0084] As can be seen, the viscosity of the formulation containing the mixture of isophorone with DIBK, PM Ac, TMB, and EB Ac is improved relative to the formulation containing isophorone alone. As Figure 3As shown, increasing the amount of DIBK in the formulation decreases the high shear viscosity. In the formulation containing 40 wt% PVDF in isophorone. Further, the combination of BYK-2117 and DIBK achieves high Ti02formulations.

[0085] Example 2

[0086] Four coating compositions were prepared according to the following formulations of Table 4. Compositions 1 and 2 contain PVDF in PM Acetate (as solvent) as the resin component, and isophorone, etc. as the solvent component. Composition 1 contains only Solsperse 20k as the dispersant. Composition 2 contains Solsperse 20k and Tetronic ® 150R1 (referred to herein as “T150R1” or “T150”) as the dispersant.

[0087] Compositions 3 and 4 contain PVDF in DIBK (as solvent) as the resin component, and the solvents used do not contain isophorone (DIBK solvent). Composition 3 includes Solsperse 20k and Solsperse 75K in a 2: 1 weight ratio as the dispersant. Composition 4 includes Solsperse 20k and Solsperse 75K in a 2: 1 weight ratio and T150 as the dispersant.

[0088] The PVDF contained in the four compositions of Example 2 was 20C7001 Arkema PVDF. 20C7001 Arkema is a PFOA-free PVDF material from Arkema, batch number 21C7001.

[0089] The viscosity tests were conducted at room temperature for about one week after initial formulation. Test conditions for testing with a Brookfield #4 spindle included stirring for five (5) minutes prior to testing, and testing at room temperature. Test conditions for testing with a Zahn #4 cup included stirring for five (5) minutes prior to testing, and testing at room temperature.

[0090] Compositions 3 and 4 both do not contain fluorosurfactant and PFOA, and contain acrylic resins synthesized in DIBK.

[0091] Table 4: Composition of PVDF Coatings

[0092] Compositions with higher solids content (Composition 3 and Composition 4) exhibited higher NVV (non-volatile volume) (and NVM) values (e.g., as shown in Table 4 above, Composition 4 was able to achieve 48.43% NVV as compared to 42.44% NVV of Composition 2) as compared to Composition 1 and Composition 2.

[0093] Compositions 3 and 4, which included DIBK in the solvent, also exhibited lower viscosity (as shown in Table 4 above) as compared to Composition 1 and Composition 2.

[0094] While only illustrative embodiments of the present disclosure have been described in detail herein, those skilled in the art will readily appreciate that many modifications are possible in the inventive technology without materially departing from the novel teachings and advantages of the subject technology. Accordingly, all such modifications are intended to be included within the scope of the present disclosure as defined in the following claims.

[0095] While specific uses of the technology have been described and illustrated in detail, the technology disclosed can be used in a variety of environments according to many examples of the technology. The discussion above is not intended to indicate that the technology disclosed is suitable only for use in the environments shown and described above.

[0096] In the case of operations of the disclosed processes, those operations are described for the purpose of illustrating the technology of the invention and are not intended to limit the disclosure to a particular sequence of operations. For example, the operations can be performed in different sequences, two or more operations can be performed concurrently, additional operations can be performed, and disclosed operations can be excluded, all without departing from the disclosure. Further, each operation can be implemented via one or more sub-operations. The disclosed processes can be repeated.

[0097] Although specific aspects were described herein, the scope of aspects of the technology is not limited to those specific aspects. One skilled in the art will recognize other aspects or improvements subsumed by the technology. Therefore, the specific structure, acts, or operations are disclosed as illustrative aspects. The scope of the technology is defined by the following claims and any equivalents therein. Examples of the disclosure can be described according to the following aspects.

[0098] Aspect 1. A coating composition having a dispersed fluorine-containing polymer resin, the composition comprising: i) at least about 30 wt% of a PVDF polymer based on resin solids; ii) at least one organic solvent, the organic solvent comprising a non-aromatic ester, a non-aromatic ketone, or a mixture thereof.

[0099] Aspect 2. The coating composition of Aspect 1, the coating composition comprising at least about 85 wt% of a PVDF based on resin solids.

[0100] Aspect 3. The coating composition of aspects 1-2, wherein the at least one organic solvent is di-isobutyl ketone (DIBK).

[0101] Aspect 4. The coating composition of aspects 1-3, wherein the organic solvent comprises between 1 wt% and 60 wt% of the non-aromatic ester or non-aromatic ketone.

[0102] Aspect 5. The coating composition of aspects 1-3, wherein the organic solvent comprises between 1 wt% and 20 wt% of a non-aromatic ester or non-aromatic ketone having a boiling point less than 200 °C.

[0103] Aspect 6. The coating composition of aspects 1-5, wherein the non-aromatic ester comprises a chain alkane diester having 10 to 30 carbon atoms.

[0104] Aspect 7. The coating composition of aspects 1-5, wherein the non-aromatic ketone comprises a C6 to C12 branched or unbranched aliphatic ketone.

[0105] Aspect 8. The coating composition of aspect 7, wherein the non-aromatic ketone further comprises isophorone, di-isobutyl ketone, and mixtures thereof.

[0106] Aspect 9. The coating composition of any of the preceding aspects, wherein the organic solvent further comprises toluene, xylene, or mixtures thereof.

[0107] Aspect 10. The coating composition of any of the preceding aspects, wherein the coating composition further comprises about 0.01 wt% to about 3.0 wt% of a hyperdispersant.

[0108] Aspect 11. The coating composition of aspect 10, wherein the hyperdispersant is selected from the group consisting of an alkoxylated amino alcohol, a polymeric alkoxylated ethylene diamine, or mixtures thereof.

[0109] Aspect 12. The coating composition of any of the preceding aspects, wherein the composition is substantially free of a fluorosurfactant.

[0110] Aspect 13. The coating composition of any of the preceding aspects, wherein the composition comprises (i) at least about 50 wt% of a PVDF polymer based on the total amount of resin solids and (ii) at least about 30 wt% of the organic solvent having a boiling point greater than 200 °C.

[0111] Aspect 14. The coating composition of any of the preceding aspects, further comprising an inorganic pigment; wherein the coating composition has a #2 Zahn viscosity of about 25 seconds to about 60 seconds.

[0112] Aspect 15. The coating composition of any of the preceding aspects, wherein the PVDF- based polymer comprises a PVDF having a Mw of about 350,000 to about 450,000, a Mw / Mn ratio of about 3.5 to about 5.0, and a melting point of about 150°C to 170°C.

[0113] Aspect 16. The coating composition of any of the preceding aspects, wherein the composition further comprises a hydroxyl functional polymer and an aminoplast resin.

[0114] Aspect 17. A composite material comprising a metal substrate having at least one surface comprising a PVDF-based film, the PVDF-based film formed by a process comprising: coating at least one surface with the coating composition of any of the preceding aspects to form a coated metal substrate; and heating the coated metal substrate.

[0115] Aspect 18. A coating composition having a dispersed PVDF resin, the coating composition comprising: i) at least about 30 wt% of PVDF based on total resin solids; and ii) an organic solvent comprising between 0 wt% and 20 wt% of an organic solvent having a HSP polarity delta P < 6 and a hydrogen bonding component delta H < 10 based on the weight of the total composition.

[0116] Aspect 19. The coating composition of aspect 18, comprising 30 wt% isophorone.

[0117] Aspect 20. The coating composition of aspects 18-19, comprising at least about 85 wt% of polyvinylidene fluoride based on resin solids.

[0118] Aspect 21. The coating composition of aspects 18-20, wherein the coating composition is substantially free of fluorosurfactant.

[0119] Aspect 22. The coating composition of aspects 18-21, wherein the coating composition further comprises an inorganic pigment.

[0120] Aspect 23. The coating composition of aspect 22, further comprising: iv) a hyperdispersant comprising an alkoxylated amino alcohol, a polymeric alkoxylated ethylene diamine, or a mixture thereof; and v) about 5 wt% to about 15 wt% of a thermoplastic acrylic polymer based on resin solids.

[0121] Aspect 24. A coating composition comprising: i) at least about 50 wt% of PVDF based on resin solids; ii) a first organic solvent selected from the group consisting of DIBK (diisobutyl ketone), DAA (diacetone alcohol), DB (diethylene glycol butyl ether), DPM (dipropylene glycol methyl ether), Aro 150 (Aromatic 150), EA Ac (ethyl acetoacetate), TMB (trimethylbenzene), EB Ac (ethylene glycol butyl ether acetate), PM Ac (propylene glycol methyl ether acetate), and mixtures thereof; and iii) a second organic solvent comprising isophorone, xylene, toluene, or mixtures thereof.

[0122] Aspect 25. The coating composition of aspect 24, wherein the coating composition further comprises a polymer dispersant that is free of fluorosurfactant.

[0123] Aspect 26. The coating composition of any of the preceding aspects, wherein the composition comprises at least about 50 wt% total solids.

Claims

1. A coating composition having a dispersed fluoropolymer resin, said composition comprising: i) Based on a PVDF polymer with at least about 30% by weight of resin solids; ii) at least one organic solvent, said organic solvent including non-aromatic esters, non-aromatic ketones or mixtures thereof.

2. The coating composition according to claim 1, wherein the coating composition comprises at least about 85% by weight of PVDF based on resin solids.

3. The coating composition according to claims 1 to 2, wherein the at least one organic solvent is di-isobutyl ketone (DIBK).

4. The coating composition according to claims 1 to 3, wherein the organic solvent comprises between 1% by weight and 60% by weight of the non-aromatic ester or non-aromatic ketone.

5. The coating composition according to claims 1 to 3, wherein the organic solvent comprises a non-aromatic ester or non-aromatic ketone with a boiling point of less than 200°C, between 1% and 20% by weight.

6. The coating composition according to claims 1 to 5, wherein the non-aromatic ester comprises an alkyl diol diester having 10 to 30 carbon atoms.

7. The coating composition according to claims 1 to 5, wherein the non-aromatic ketone comprises a C6 to C12 branched or unbranched aliphatic ketone.

8. The coating composition according to claim 7, wherein the non-aromatic ketone further comprises isophorone, di-isobutyl ketone, and mixtures thereof.

9. The coating composition according to any one of the preceding claims, wherein the organic solvent further comprises toluene, xylene, or a mixture thereof.

10. The coating composition according to any one of the preceding claims, wherein the coating composition further comprises about 0.01% by weight to about 3.0% by weight of a superdispersant.

11. The coating composition according to claim 10, wherein the superdispersant is selected from the group consisting of alkoxylated amino alcohols, polymeric alkoxylated ethylenediamines, or mixtures thereof.

12. The coating composition according to any one of the preceding claims, wherein the composition is substantially free of fluorinated surfactants.

13. The coating composition according to any one of the preceding claims, wherein the composition comprises (i) at least about 50% by weight of a PVDF polymer based on the total amount of resin solids and (ii) at least about 30% by weight of the organic solvent having a boiling point greater than 200°C.

14. The coating composition according to any one of the preceding claims, wherein the coating composition further comprises an inorganic pigment; wherein the coating composition has a #2 Zahn viscosity of about 25 seconds to about 60 seconds.

15. The coating composition according to any one of the preceding claims, wherein the PVDF-based polymer comprises PVDF having a Mw of about 350,000 to about 450,000, a Mw / Mn ratio of about 3.5 to about 5.0, and a melting point of about 150°C to 170°C.

16. The coating composition according to any one of the preceding claims, wherein the composition further comprises a hydroxyl-functionalized polymer and an amino plastic resin.

17. A composite material comprising a metal substrate having at least one surface including a PVDF-based film, the PVDF-based film being formed by a method comprising: The coating composition according to any one of the preceding claims is used to coat at least one surface to form a coated metal substrate; and The coated metal substrate is heated.

18. A coating composition having a dispersed PVDF resin, the coating composition comprising: i) Based on at least about 30% by weight of PVDF in total resin solids; and ii) Organic solvents, including organic solvents with HSP polarity δP ≤ 6 and hydrogen bonding component δH ≤ 10 based on the weight of the total composition between 0% and 20% by weight.

19. The coating composition according to claim 18, wherein the coating composition comprises 30% by weight of isophorone.

20. The coating composition according to claims 18 to 19, wherein the coating composition comprises at least about 85% by weight of polyvinylidene fluoride based on resin solids.

21. The coating composition according to claims 18 to 20, wherein the coating composition is substantially free of fluorinated surfactants.

22. The coating composition according to claims 18 to 21, wherein the coating composition further comprises inorganic pigments.

23. The coating composition according to claim 22, further comprising: iv) Superdispersants, said superdispersants comprising alkoxylated amino alcohols, polymeric alkoxylated ethylenediamines, or mixtures thereof; and v) Based on about 5% to about 15% by weight of a thermoplastic acrylic polymer in resin solids.

24. A coating composition comprising: i) Based on at least about 50% by weight of PVDF in resin solids; ii) A first organic solvent, selected from the group consisting of: DIBK (diisobutyl ketone), DAA (diacetone alcohol), DB (diethylene glycol butyl ether), DPM (dipropylene glycol methyl ether), Aro 150 (Aromatic 150), EA Ac (ethyl acetoacetate), TMB (trimethylbenzene), EB Ac (ethylene glycol butyl ether acetate), PM Ac (propylene glycol methyl ether acetate), and mixtures thereof; and iii) A second organic solvent, comprising isophorone, xylene, toluene, or mixtures thereof.

25. The coating composition of claim 24, wherein the coating composition further comprises a polymeric dispersant free of fluorinated surfactants.

26. The coating composition according to any one of the preceding claims, wherein the composition comprises at least about 50% by weight of total solids.

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