Aqueous coating composition

Abstract

An aqueous coating composition is provided comprising an acrylic modified fluoropolymer comprising a fluoropolymer moiety and an acrylic moiety and a dihydrazide, and optionally an additional polymer and optionally a pigment, the additional polymer being not part of the acrylic modified fluoropolymer. The acrylic modified fluoropolymer composition comprises DAAM monomeric units, preferably the aqueous coating composition comprises greater than 50% by weight of polymer based on the total solids content of the aqueous coating composition.

Description

TECHNICAL FIELD

[0001] The present invention relates to an aqueous coating composition comprising i) an acrylic modified polymer containing a diacetone acrylamide "DAAM" functional group and ii) a dihydrazide which crosslinks upon drying. These coatings are useful as exterior coatings. BACKGROUND

[0002] Fluorine-containing paints are used as weatherable paints for the exterior and interior of buildings and structures. Fluorine-containing paints are typically dispersed in organic solvents, but the use of organic solvents is problematic in terms of safety and environmental protection. Aqueous coatings are more environmentally friendly than solvent-borne coatings, but are not preferred for protective coating applications because of their inferior water resistance (as surfactants are required to stabilize the water dispersion). For protective coatings, a crosslinked protective coating is preferred because it enhances hardness, chemical resistance, but the crosslinking reaction can also leave surfactants and other hydrophilic species in the coating film, reducing water resistance. Non-isocyanate crosslinking methods are particularly preferred for worker health and safety, and are more preferred if they provide the convenience of "one pack" or at least have a very long potlife (days to weeks). The ketone-hydrazide reaction is such a room temperature crosslinking reaction, and the crosslinking reaction is driven by water loss (such as physical drying of the coating).

[0003] We have found that PVDF-acrylic hybrids for crosslinking with dihydrazides, in which the acrylic portion contains ketone functionality, especially DAAM, provide stable one-component (1 pack) compositions for coating applications.

[0004] Japanese patent JPH09165490A discloses acrylic modified fluoropolymers, AAEM is a monomer used in the acrylic portion of the acrylic modified fluoropolymer in its examples. There is no teaching of diacetone acrylamide in the acrylic modified fluoropolymer.

[0005] WO2017 / 091408 discloses an aqueous, fluoropolymer hybrid composition for coatings that maintains excellent mechanical properties in coatings, paints, caulks and adhesives, while also having excellent weatherability. There is no teaching of diacetone or dihydrazide. SUMMARY

[0006] An aqueous coating composition comprising:

[0007] i) an acrylic modified fluoropolymer composition comprising a fluoropolymer portion and an acrylic portion, and

[0008] ii) a dihydrazide, and

[0009] iii) optionally an additional polymer that is not part of the acrylic modified fluoropolymer,

[0010] wherein the acrylic modified fluoropolymer composition ("AMF") comprises at least 1 weight percent of DAAM monomer units and less than 15 weight percent, based on the total acrylic monomer units in the acrylic modified fluoropolymer. The molar ratio of dihydrazide to DAAM functional groups is 0.02 to 0.5.

[0011] Preferably, the waterborne coating composition comprises a pigment.

[0012] Preferably, the waterborne coating composition comprises greater than 50 weight percent of polymer, based on the total solids content of the waterborne coating composition.

[0013] The acrylic portion of the AMF generally includes acrylic and / or methacrylic monomer units. The amount of diacetone acrylamide "DAAM" in the acrylic portion of the AMF is greater than 1% and less than 20 weight percent, preferably less than 15 weight percent. The total amount of DAAM is based on the cumulative total of all acrylic polymers in the AMF.

[0014] Preferably, the acrylic portion of the AMF comprises at least one monomer having an acid functional group, such as acrylic acid or methacrylic acid or other monomers having an acid functional group.

[0015] The waterborne coating composition dries once applied to a substrate. The DAAM and hydrazide crosslink during drying. The waterborne coating composition is stable and does not crosslink prior to drying.

[0016] The present invention provides a coating on a substrate, provided by drying the waterborne coating composition on the substrate. The dried coating comprising the AMF polymer has DAAM-dihydrazide crosslinks.

[0017] The coating of the present invention is intended for use as an architectural coating or a protective coating, such as a weather resistant coating.

[0018] Aspects of the present invention

[0019] Aspect 1. A waterborne coating composition comprising

[0020] i) an acrylic modified fluoropolymer comprising a fluoropolymer portion and an acrylic portion

[0021] ii) a dihydrazide, and

[0022] iii) optionally an additional polymer that is not part of the acrylic modified fluoropolymer,

[0023] wherein the acrylic modified fluoropolymer composition comprises at least 1 wt% of DAAM and up to 20 wt%, based on total acrylic monomer units in the acrylic modified fluoropolymer composition.

[0024] Aspect 2. The aqueous coating composition of Aspect 1, wherein the aqueous coating composition comprises greater than 50 wt% of the polymer, based on total solids content in the aqueous coating composition.

[0025] Aspect 3. The aqueous coating composition of Aspect 1 or 2, wherein the acrylic portion further comprises an acrylic or methacrylic monomer having an acid functional group.

[0026] Aspect 4. The aqueous coating composition of any one or more of the preceding Aspects, wherein the acrylic portion of the acrylic modified fluoropolymer further comprises 0.01 to 10% of (meth)acrylic acid, based on total acrylic monomer units in the acrylic modified fluoropolymer composition.

[0027] Aspect 5. The aqueous coating composition of any one or more of the preceding Aspects, wherein the molar ratio of dihydrazide to DAAM is between 0.02 and 0.5.

[0028] Aspect 6. The aqueous coating composition of any one or more of the preceding Aspects, wherein the aqueous coating composition further comprises a pigment.

[0029] Aspect 7. The aqueous coating composition of any one or more of the preceding Aspects, wherein the aqueous coating composition further comprises an acrylic polymer separate from the acrylic modified fluoropolymer.

[0030] Aspect 8. The aqueous coating composition of any one or more of the preceding Aspects, wherein the additional polymer that is not part of the acrylic modified fluoropolymer is selected from the group consisting of acrylic and / or vinyl based, polyurethane, polyester, melamine resin, or epoxy resins polymers and copolymers.

[0031] Aspect 9. The aqueous coating composition of any one or more of the preceding Aspects, wherein the additional polymer that is not part of the acrylic modified fluoropolymer comprises at least one of an acrylic latex, a polyvinyl acetate (PVA) latex, a styrene / butadiene latex, a vinyl latex, or a vinyl acrylic latex.

[0032] Aspect 10. The aqueous coating composition of any one or more of the preceding aspects, wherein the fluoropolymer moiety comprises 50 to 100 weight percent of vinylidene fluoride units, and 0 to 50 weight percent of monomer units copolymerizable with vinylidene fluoride, based on the weight of the fluoropolymer moiety, preferably the fluoropolymer moiety comprises 50 to 100 weight percent of vinylidene fluoride units.

[0033] Aspect 11. The aqueous coating composition of any one or more of the preceding aspects, wherein the fluoropolymer moiety comprises 3 to 30 weight percent of hexafluoropropylene units, based on the total weight of the fluoropolymer moiety.

[0034] Aspect 12. The aqueous coating composition of any one or more of the preceding aspects, wherein the fluoropolymer moiety comprises a polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the total weight percent of hexafluoropropylene monomer units in the acrylic modified fluoropolymer is 5 to 20%, preferably 10 to 20 weight percent, based on the weight of the acrylic modified fluoropolymer.

[0035] Aspect 13. The aqueous coating composition of any one or more of the preceding aspects, wherein the total weight percent of acrylic monomer units in the acrylic modified fluoropolymer is 10 to 50 weight percent, preferably the total weight percent of acrylic monomer units in the acrylic modified fluoropolymer is 15 to 40 weight percent.

[0036] Aspect 14. The aqueous coating composition of any one or more of the preceding aspects, wherein the acrylic modified fluoropolymer comprises 3 to 100 weight percent of the total polymer in the aqueous coating composition.

[0037] Aspect 15. The aqueous coating composition of any one or more of the preceding aspects, further comprising UV stabilizers, pH adjusters, colorants, dyes, water soluble resins, rheology control additives and thickening agents, pigments and pigment extenders, and fillers.

[0038] Aspect 16. A method of coating a substrate comprising providing a substrate, providing a coating composition of any one or more of the preceding aspects, applying the coating composition to the substrate, drying the coating composition on the substrate to form a coated substrate.

[0039] Aspect 17. A coated substrate comprising a substrate coated on at least one surface with an aqueous coating composition of any one or more of aspects 1-15, and wherein the coating composition is dried to form a coated substrate.

[0040] Aspect 18. The coated substrate of aspect 17, wherein the substrate is selected from the group consisting of primed or unprimed metal, wood, glass, plastic, and composite.

[0041] Aspect 19. The coated substrate of aspect 18, wherein the coating is an exterior coating selected from the group consisting of architectural coatings, marine coatings, and protective coatings.

[0042] Aspect 20. Use of the aqueous coating composition of any one or more of aspects 1 to 15 in an exterior construction. DETAILED DESCRIPTION

[0043] In this specification, the embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended that the application be construed as including alternative embodiments and equivalents. For example, it will be clear that all preferred features described herein with respect to one embodiment can be applied to other embodiments. For the sake of completeness, reference is made to the attached drawings.

[0044] In this application, all references listed are incorporated by reference. Unless otherwise indicated, all percentages in the compositions are in weight percent.

[0045] Crystallinity and melting temperature were determined by DSC as described in ASTM D3418 with a heating rate of 10 °C / min. Melt viscosity was determined according to ASTM D3835 at 230 °C in kilopoise @ 100 seconds -1

[0046] Unless otherwise indicated, the term "polymer" refers to both homopolymers and copolymers. "Copolymer" is used to mean a polymer having two or more different monomeric units. For example, as used herein, unless otherwise specifically indicated, "PVDF" and "polyvinylidene fluoride" are used to mean both homopolymers and copolymers. The polymers can be homogenous, heterogeneous, and can have a gradient distribution of comonomer units.

[0047] Crosslinkable means that the acrylic portion of the acrylic modified fluoropolymer has functional groups in the monomers that can crosslink or contains a crosslinking agent.

[0048] Acrylic modified fluoropolymer composition means a composition in which acrylics have polymerized in the presence of a fluoropolymer seed. Such hybrid compositions have been described in U.S. patents and applications, such as US 5349003, US 6680357, and US 2011 / 0118403.

[0049] ​Unless otherwise indicated, acrylics include both acrylic monomers and methacrylic monomers. Unless otherwise specified, acrylic polymers refer to polymers having acrylic monomer units and / or methacrylic monomer units.

[0050] "DAAM" refers to diacetone acrylamide.

[0051] Stable means that the composition performs in double rub testing no more than 10% worse after one month in an oven at 50°C compared to a freshly prepared composition.

[0052] The present invention provides a stable aqueous coating composition comprising a crosslinkable acrylic modified fluoropolymer and a dihydrazide.

[0053] According to the present invention, there is provided an aqueous coating composition comprising an acrylic modified fluoropolymer having DAAM monomer units, a dihydrazide, and optionally a pigment. The molar ratio of dihydrazide to DAAM functionality is from 0.02 to 0.5.

[0054] The aqueous coating composition comprises greater than 50 wt% polymer based on total solids content. Polymer in this context refers to the sum of the AMF plus any optional additional polymer that is not part of the acrylic modified fluoropolymer.

[0055] The acrylic modified fluoropolymer "AMF" comprises a seed fluoropolymer and an acrylic polymer, wherein the acrylic monomer composition is polymerized in the presence of the seed fluoropolymer ("acrylic polymerization") to produce the acrylic modified fluoropolymer.

[0056] The weight percent of the fluoropolymer seed (preferably a vinylidene fluoride polymer) in the AMF is at least 50%, preferably greater than 60 wt% of the AMF.

[0057] Seed fluoropolymer

[0058] The fluoropolymer used as a seed for the acrylic polymerization in the present invention is formed primarily from fluoromonomers. The term "fluoromonomer" or the expression "fluorinated monomer" refers to a polymerizable olefin containing at least one fluorine atom, fluoroalkyl group, or fluoroalkoxy group attached to the double bond in the olefin that undergoes polymerization. The term "fluoropolymer" refers to a polymer formed from the polymerization of at least one fluoromonomer, including homopolymers, copolymers, which are thermoplastic in nature, i.e., they are capable of forming useful articles by flowing when heated, for example, in molding and extrusion processes. The fluoropolymer preferably contains at least 50 wt%, preferably at least 70 wt% of one or more fluoromonomers.

[0059] The vinylidene fluoride copolymer comprises a polymer copolymerized from vinylidene fluoride monomers and at least one other monomer, the monomer composition selected to contain at least 50 weight percent, preferably at least 70 weight percent, of vinylidene fluoride monomer units. The fluoropolymer used in the present invention can be prepared by methods known in the art, for example, by emulsion, suspension, solution, or supercritical CO2 polymerization processes. Preferably, the fluoropolymer is formed by an emulsion process. The process is free of fluorinated surfactants. By fluoropolymer seed free of fluorinated surfactants is meant that no fluorinated surfactants are used in any part of the emulsion polymerization process.

[0060] The vinylidene fluoride polymer is in an aqueous dispersion that can be produced by any conventional fluoropolymer emulsion polymerization process, provided that the fluoropolymer particle size is maintained below 900 nm, more preferably below 700 nm.

[0061] Fluoropolymer emulsion polymerization processes are known in the literature, for example, U.S. Patent No. 3,051,677, U.S. Patent No. 3,178,399, U.S. Patent No. 3,475,396, U.S. Patent No. 3,857,827, U.S. Patent No. 6,187,885, U.S. Patent No. 6,586,547, U.S. Patent No. 6,841,616, U.S. Patent No. 7,122,610, and U.S. Patent No. 8,338,518, as specific examples. Preferably, the fluoropolymer dispersion is synthesized using a free radical initiation process. Chain transfer agents, buffers, stain resistants, and other additives commonly used in fluoropolymer emulsion processes can be present.

[0062] Fluorine-containing monomers that can be used in the practice of the present invention include, for example, vinylidene fluoride (VDF), tetrafluoroethylene (TFE), trifluoroethylene (VF3), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), fluoroethylene (VF), hexafluoroisobutene, perfluorobutyl ethylene (PFBE), pentafluoropropylene, 2,3,3,3-tetrafluoropropene (HFO-1234yf), 2-chloro-1-1-difluoroethylene (R-1122), 3,3,3-trifluoro-1-propene, 2-fluoromethyl-3,3,3-trifluoropropene, fluorinated vinyl ethers, fluorinated allyl ethers, non-fluorinated allyl ethers, fluorinated dioxoles, and combinations thereof.

[0063] Preferably, the fluorine-containing polymer seed is a vinylidene fluoride polymer obtained by emulsion polymerization. Such aqueous vinylidene fluoride polymer dispersions can be prepared by traditional emulsion polymerization methods, such as by emulsion polymerization of the initial monomers in an aqueous medium in the presence of a polymerization initiator, which process is known in the art. Specific examples of vinylidene fluoride polymers obtained by emulsion polymerization include vinylidene homopolymers and copolymers of (1) vinylidene fluoride with (2) fluorine-containing ethylenically unsaturated compounds [such as tetrafluoroethylene (TFE), trifluoroethylene (VF3), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), fluoroethylene (VF), hexafluoroisobutylene, perfluorobutyl ethylene (PFBE), pentafluoropropylene, 2,3,3,3-tetrafluoropropene (HFO-1234yf), 2-chloro-1-1-difluoroethylene (R-1122), 3,3,3-trifluoro-1-propene, 2-fluoromethyl-3,3,3-trifluoropropene, fluorinated vinyl ethers, fluorinated allyl ethers, non-fluorinated allyl ethers, fluorinated dioxoles, perfluoropropenoic acid], fluorine-free ethylenically unsaturated compounds (such as cyclohexyl vinyl ether, hydroxyethyl vinyl ether, and the like), fluorine-free diene compounds (such as butadiene, isoprene, chlorobutadiene), which can all be copolymerized with vinylidene fluoride.

[0064] Particularly preferred fluorine-containing polymers are homopolymers of VDF, and copolymers of VDF with HFP, TFE or CTFE, comprising from about 50 to about 99 weight percent VDF, more preferably from about 70 to about 99 weight percent VDF. A particularly preferred copolymer is a copolymer of VDF with HFP, wherein the weight percent of VDF in the copolymer is from 50 to 99 weight percent, preferably from 65 to 95 weight percent, based on the total monomers in the copolymer. In one preferred embodiment of the VDF / HFP copolymer, the weight percent of HFP is from 5 to 30%, preferably from 8 to 25%, based on the total monomers in the polymer.

[0065] The fluorine-containing polymer preferably has a high molecular weight. As used herein, high molecular weight means a melt viscosity greater than 1.0 kilopoise, preferably greater than 5 kilopoise, more preferably greater than 10 kilopoise, as determined at 230 ℃ and 100 seconds -1 under ASTM method D-3835.

[0066] The fluoropolymer seed can be functionalized by copolymerization with 0.1 to 25 weight percent, preferably 0.1 to 10 weight percent, of at least one functionalized comonomer, based on the total weight of the fluoropolymer seed. The copolymerization can add one or more functionalized comonomers to the backbone of the fluoropolymer, or it can be added by a grafting process. The fluoropolymer seed can also be functionalized by polymerization using 0.1 to 25 weight percent of one or more low molecular weight polymer functionalized chain transfer agents. Low molecular weight means that the polymer has a degree of polymerization of less than or equal to 1,000, preferably less than 800. The low molecular weight functionalized chain transfer agent is a polymer or oligomer having two or more monomer units, preferably three or more monomer units, such as polyacrylic acid. The residual polymer chain transfer agent can provide functional groups to the fluoropolymer. The fluoropolymer seed can have both functionalized comonomers and residual functionalized polymer chain transfer agents. As used herein, functionalized polymer chain transfer agent means a low molecular weight polymer chain transfer agent containing one or more different functional groups, such as acid functional groups. Some examples of useful functionalized comonomers include phospho(meth)acrylate, (meth)acrylic acid, and hydroxy functionalized (meth)acrylic acid comonomers.

[0067] Acrylic moieties

[0068] The AMF polymer contains acrylic moieties. The acrylic moieties comprise one or more acrylic polymers. The acrylic moieties of the AMF polymer comprise diketone acrylamide ("DMMA") units in at least one acrylic polymer comprising the acrylic moieties. The acrylic moieties are obtained by emulsion polymerization of a monomer mixture containing at least one monomer selected from the group consisting of alkyl acrylates having alkyl groups of 1 to 18 carbon atoms, alkyl methacrylates having alkyl groups of 1 to 18 carbon atoms, and ethylenically unsaturated compounds which can be polymerized with the alkyl acrylates and alkyl methacrylates in the presence of a fluoropolymer seed in an aqueous medium, preferably the fluoropolymer is a vinylidene fluoride polymer. The acrylic moieties contain at least 1 weight percent of DAAM monomer units and up to 20 weight percent, based on the total acrylic monomer units in the acrylic modified fluoropolymer composition.

[0069] The alkyl group of the alkyl acrylate having 1 to 18 carbon atoms includes, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, isopentyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate. Among them, the alkyl acrylate whose alkyl group has 1 to 8 carbon atoms is preferred, and the alkyl acrylate whose alkyl group has 1 to 5 carbon atoms is more preferred. The alkyl group of the alkyl methacrylate having 1 to 18 carbon atoms includes, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, lauryl methacrylate. Among them, the alkyl methacrylate whose alkyl group has 1 to 8 carbon atoms is preferred, and the alkyl methacrylate whose alkyl group has 1 to 5 carbon atoms is more preferred. These compounds (alkyl acrylate and alkyl methacrylate) can be used alone or two or more kinds can be used in mixture. The acrylate and / or methacrylate monomer unit after polymerization preferably should account for 50 or more by weight% of the total monomer unit, and more preferably, should account for 70 or more by weight% of the acrylic modified fluoropolymer.

[0070] The ethylenically unsaturated compound that can be copolymerized with the alkyl acrylate and alkyl methacrylate can optionally be a functional group-containing monomer that can be copolymerized with the alkyl acrylate and alkyl methacrylate. The copolymerizable ethylenically unsaturated compound is typically used in an amount less than 29 weight percent, based on the acrylic portion of the modified fluoropolymer. Functional group-containing monomers include, for example: α,β-unsaturated carboxylic acids (such as acrylic acid, methacrylic acid, fumaric acid, crotonic acid, itaconic acid, vinyl phosphonic acid, and sulfonic acid); vinyl ester compounds (such as vinyl acetate and the like); amide compounds (such as acrylamide, methacrylamide, N-methyl acrylamide, N-methyl methacrylamide, N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N,N-dialkyl acrylamide, N,N-dialkyl methacrylamide); acrylates (such as 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, fluoroalkyl acrylate); methacrylates (such as dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate); allyl glycidyl ether compounds (such as allyl glycidyl ether); hydroxyl-containing monomers (such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, diethylene glycol ethyl ether acrylate, polyethylene glycol acrylate and methacrylate, polypropylene glycol acrylate and methacrylate); allyl ether methacrylate; acetoacetoxyethyl methacrylate; vinyl acetate; epoxy-containing monomers (such as glycidyl acrylate and methacrylate); cyclic substituent-containing monomers (such as cyclohexyl acrylate, tetrahydrofurfuryl acrylate and methacrylate, isobornyl acrylate); silanol-containing monomers; fluoroalkyl acrylate and methacrylate; acrylonitrile and methacrylonitrile. The functional group-containing monomer units can have more than one functional unit as part of their composition, examples of which are polyol acrylates and methacrylates, including diol diacrylates, diol dimethacrylates, triol triacrylates and triol trimethacrylates, and tetrol tetraacrylates, with representative compounds being 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, 1,3-propanediol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and pentaerythritol tetraacrylate.Among them, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, N- hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, 2-hydroxyethyl acrylate, 2- hydroxyethyl methacrylate, and allyl glycidyl ether are preferred. These ethylenically unsaturated compounds can be used alone or two or more kinds can be mixed.

[0071] When both the alkyl acrylate and the alkyl methacrylate are used, the ratio of the two esters is not critical and can be varied as desired for the properties of the resulting fluoropolymer. Provided that a major portion of the monomers (meaning greater than 50% by weight of the acrylic portion) must be selected from the group consisting of acrylates and methacrylates, and DAAM must be incorporated into the acrylic portion.

[0072] Emulsion polymerization

[0073] The acrylic modified fluoropolymer composition can be obtained by emulsion polymerization of 5 to 100 parts by weight, particularly preferably 5 to 95, preferably 20 to 90 parts by weight of the above acrylic monomers in the presence of 100 parts by weight of the above vinylidene fluoride polymer particles ("fluoropolymer seed") in an aqueous medium. The emulsion polymerization can be carried out using conventional emulsion polymerization conditions. Emulsion polymerization processes are known in the art. Generally, elements of a conventional seeded emulsion polymerization can include monomers, initiators, surfactants, chain transfer agents, pH adjusters, and chelating agents, some or all of which can be added to the seed latex to affect further polymerization. The temperature range commonly used is from 20 to 150°C. The reaction is usually intended to run at atmospheric pressure, but the pressure can be raised and venting can be required, usually less than 3 or 4 atmospheres. The reaction is usually run in an inert atmosphere, for example under nitrogen. The emulsion polymerization seeded with the fluoropolymer seed, preferably vinylidene fluoride polymer particles, can be carried out according to known methods, for example, a method in which the entire amount of monomers is fed to the reaction system at once in the presence of the fluoropolymer seed, preferably vinylidene fluoride polymer; a method in which a part of the monomers is fed and allowed to react, after which the remaining monomers are continuously or batchwise fed; a method in which the entire amount of monomers is continuously added, or a method in which the fluoropolymer seed is continuously or batchwise added while the monomers are allowed to react. Different acrylic monomer mixtures can be polymerized in turn around the fluoropolymer seed.

[0074] The fluoropolymer seed, preferably a vinylidene fluoride polymer, can be added to the polymerization system in any state, so long as it is dispersed in the aqueous medium in particulate form. Since vinylidene fluoride polymers are typically provided as aqueous dispersions, it is convenient to use the produced aqueous dispersion as the fluoropolymer seed. The fluoropolymer seed, preferably a vinylidene fluoride polymer, particle diameter can vary depending on the diameter of the polymer particles present in the target aqueous dispersion of the polymer, but is typically in the range of 50-900 nm. In a preferred embodiment, the diameter of the polymer particles is preferably 50 nm-700 nm.

[0075] The acrylic portion of the AMF is made of acrylic polymers made by sequential polymerization of monomers on the fluoropolymer seed. The acrylic portion of the AMF can be only one acrylic polymer or can be two or more acrylic polymers. The acrylic polymers are typically acrylic copolymers. Some of the monomer units of the acrylic polymers can optionally contain functional groups. As described herein, the weight percent of functional monomers refers to the weight percent of monomers having functional groups. Typically, the sequential polymerization of monomers on the fluoropolymer seed uses different monomer compositions, thereby forming different acrylic polymers that make up the acrylic portion of the AMF. For example, a first monomer composition can include methyl methacrylate, butyl acrylate, and DAAM, a second monomer composition (different from the first monomer composition) can include methyl methacrylate, butyl acrylate, DAAM, and methacrylic acid. The first monomer composition can be polymerized on the fluoropolymer seed, followed by a second polymerization of the second monomer composition, thereby resulting in two acrylic polymers that make up the acrylic portion of the AMF.

[0076] Crosslinking agent

[0077] The acrylic modified fluoropolymer resin is crosslinkable. The acrylic portion is crosslinked using a dihydrazide.

[0078] The hydrazide derivative has at least two hydrazide residues. Aliphatic carboxylic dihydrazides having 2 to 10 carbon atoms can be used. The most common dihydrazides include adipic acid dihydrazide (ADH), sebacic acid dihydrazide (SDH), malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, valine dihydrazide (VDH), isophthalic acid dihydrazide (IDH). Carbonic acid polyhydrazides, such as carbonic acid dihydrazide, can also be used. Other hydrazide derivatives that can be used include dihydrazine-triazine, thiohydrazide, N,N'-diaminogliadin, hydrazine-pyridine derivatives, bis-thiosemicarbazide, alkylene bis-acrylamide dihydrazine, examples of which include hydrazine alkanes, aromatic dihydrazides, or monoethylenically unsaturated dicarboxylic acid dihydrazides. Aliphatic carboxylic dihydrazides having 2 to 10 carbon atoms are preferred, with adipic acid dihydrazide being most preferred.

[0079] The present application remains stable without the use of heavy metal ions. Heavy metals include copper, zinc, iron, chromium, manganese, lead, vanadium, cobalt, and / or nickel.

[0080] The aqueous coating composition can include additional polymers that are not part of the acrylic modified fluoropolymer. Additional polymers include latex-based binders such as acrylic and / or vinyl based polymers and copolymers, acrylic latex, polyvinyl acetate (PVA) latex, styrene / butadiene latex, vinyl latex, ethylene acrylic acid latex, polyurethanes, polyesters, melamine resins, epoxy resins, and / or oils with other suitable monomeric species.

[0081] Coalescing solvent can optionally be added to the formulation. The latex formulation typically has low VOC, less than 100 g / liter, preferably less than 50 g / liter, as defined in EPA Method 24.

[0082] The coating composition can contain additives commonly used in coatings including, but not limited to, pH adjusters, UV stabilizers, foam control agents, wetting agents, pigments, pigment extenders, fillers, dyes, flatting and texturing agents, pigment enhancers, emulsifiers, surfactants, dispersants, curing agents, coalescing agents, wetting agents, biocides, thickening agents, rheology modifiers, plasticizers, waxes, antioxidants, antifoams, anti-settling agents, anti- skinning agents, corrosion inhibitors, dehydrators, anti-gassing agents, dispersion aids, drying agents, antistatic additives, flash corrosion inhibitors, floating and flooding additives, in-can and in-film preservatives, biocidal additives, optical brighteners, odor control agents, water soluble resins, and other agents used in the art.

[0083] Pigments include colored pigments and opacifying pigments. Pigment volume concentration is used in amounts less than 40 volume %, or less than 20 volume %, based on the dry components of the coating composition. Pigment volume concentration = pigment volume / total solid volume.

[0084] Colored pigments are finely ground natural or synthetic insoluble particles that are added to paint and coating compositions to impart color. Pigments refer to a class of organic or inorganic substances that do not dissolve in water or in the medium of use, but which, by virtue of a high degree of dispersion, impart color to the coloring matter. Pigments used in coatings are well known in the art. Non-limiting examples of pigments include anatine, brookite, cadmium yellow, cadmium red, cadmium green, orange cobalt, cobalt blue, cerulean blue, aureolin, cobalt yellow, copper pigments, azurite, Han purple, Han blue, Egyptian blue, malachite, Paris green, phthalocyanine blue BN, phthalocyanine green G, verdigris, viridian, iron oxide pigments, blood red, caput mortuum, red oxide, red ochre, Venetian red, Prussian blue, clay pigments, yellow ochre, raw sienna, burnt sienna, raw umber, burnt umber, marine pigments (e.g., ultramarine and ultramarine green), and zinc pigments (e.g., zinc white and zinc ferrite).

[0085] Opacifying pigments reflect light rays to make the coating opaque or less transparent. They prevent the transmission of light and provide the desired brightness and whiteness to the final product. The most commonly used are titanium dioxide (Ti02), barium sulfate, zinc oxide, calcium carbonate, talc, nepheline syenite, and combinations thereof. The most commonly used and preferred is Ti02. Extenders can also be added to the formulation. Suitable examples of extenders include precipitated calcium carbonate, directly mined calcium carbonate, clean grade calcium magnesium carbonate (dolomite), clean grade calcined pulverized clay (aluminosilicate), and clean purified magnesium silicate.

[0086] Coalescents - Coalescents can be an important component of water-based latex or latex coating compositions. The purpose of the coalescent in these compositions is to aid in the formation of a continuous film from the discrete polymer particles present in the latex when the coating is dried after application to a substrate. The role of the coalescent is to soften the polymer particles so that they fuse into a tough, continuous film. Commonly used coalescents include ester alcohols, ethers of esters and glycols, esters, alcohols, amides, and polymers.

[0087] MFFT is the minimum temperature at which a binder or composition forms a continuous film. MFFT can be measured according to ASTM D 2354-10 (2012) on a gradient temperature bar. An example of a suitable gradient temperature bar is a Rhopoint Minimum Film Forming Temperature Bar (MFFT), which is a standalone benchtop instrument available from Paul Gardner, Inc. Generally, the coating compositions of the present application can be applied to a substrate at a temperature above the MFFT of the composition. For example, a modified coating composition having an MFFT of 5°C can be applied to a substrate and dried at an ambient temperature of 5°C or greater. It should be understood that both binders and compositions can have their own MFFT values. In certain embodiments, the AMF of the present application can exhibit an MFFT of about 25°C or less, in certain embodiments, about 15°C or less, in certain embodiments, about 5°C or less, and in certain embodiments, about 2°C or less.

[0088] To improve the availability, in certain embodiments, the MFFT of the coating composition can be reduced by adding a suitable coalescent to the coating composition. Such coalescents are typically selected from slow evaporating solvents having a high boiling point, by which is meant from about 160°C to about 240°C. Non-limiting examples of suitable coalescents can include dipropylene glycol methyl ether, dipropylene glycol methyl ether acetate, dipropylene glycol n-butyl ether, ethylene glycol n-butyl ether, Texanol® ester alcohol [Eastman Chemical Co.], and dipropylene glycol dimethyl ether. In certain embodiments, the coalescent can comprise about 2% or less of the total weight of the coating composition (including water), about 1.7% or less, or about 1.5% or less, of the total weight of the coating composition. However, it should be understood that the minimum amount of coalescent necessary to achieve a suitable MFFT can be desirable to allow for faster drying times and to ensure that the VOC of the coating composition remains below any applicable limits.

[0089] A plasticizer can also be added to reduce the MFFT. However, plasticizers are generally distinguished from coalescents in that plasticizers have a higher boiling point, for example, a boiling point of about 250°C or greater.

[0090] Preferably, the MFFT of the coating composition is less than 25°C.

[0091] The waterborne coating compositions of the present application are useful as coatings on architectural substrates, including but not limited to wood, metal, plastic, and composite materials. The waterborne coating compositions of the present application can be used in architectural coatings.

[0092] The aqueous coating composition can be used for field-applied protective coatings of structures or objects made of typical building materials, such as wood, plastic, composite, cementitious substrates, stone or metal, for example, as a polymeric binder for high-weatherability topcoats on steel structures, such as bridges, storage tanks or water towers, or for factory-applied coatings on steel pipes. In some cases, as is well known in the protective coating industry, in order to improve adhesion and system corrosion protection performance, it can not be applied directly on the substrate, but on a primer layer or multiple layers of primer and intermediate coatings. For example, it can be used in tinted topcoat formulations applied in field-applied protective coatings on steel substrates on epoxy, polyamide, acrylic or alkyd primers, where the selected pigments bring both decorative and protective properties to the coating.

[0093] The coating can be applied in the field without additional heating, or it can be applied in a factory, optionally with heating to speed up the rate of water removal and to fully develop its performance.

[0094] In this specification, the embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended that the embodiments can be carried out in various ways without departing from the inventive concept. For example, it will be appreciated that all preferred features described herein apply to all aspects of the invention described herein.

[0095] Examples

[0096] Test Methods and Definitions

[0097] The glass transition temperature was calculated from accepted differential scanning calorimetry measurements using the Fox equation described in T.G. Fox Bull. Am. Phys. Soc. 1, 123 (1956).

[0098] MMA refers to methyl methacrylate. BA refers to butyl acrylate. DAAM refers to diacetone acrylamide. MAA refers to methacrylic acid. The monomer ratios in the examples are by weight.

[0099] The solids content of a latex sample weighing at least 1 gram was determined gravimetrically. The solids weight percent was measured using a drying temperature of 125°C, with an end point indicated by an average weight loss of 1 mg in 50 seconds.

[0100] Example 1 (Resin 1): Preparation of an acrylic-modified fluoropolymer composition with diacetone acrylamide (DAAM)

[0101] A polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer latex was used as seed and an emulsion polymerization process was used to synthesize a latex comprising an acrylic modified fluoropolymer composition. To a 2 liter reactor was added 1400 g PVDF-HFP copolymer latex seed and 100 g deionized water. The reactor was purged with argon / nitrogen and then a low flow rate argon / nitrogen purge was maintained during the reaction. The reactor was stirred at 160 rpm while a monomer mixture (mass ratio 36.5 MAA / 9.5 BA / 4.0 DAAM) 120.0 g was fed to the reactor over 30 minutes. During this time, an initiator solution [1.7 g VAZO-67 dissolved in 17.0 g TPM (tripropylene glycol methyl ether)] was also added. The reactor was then stirred at room temperature for 30 minutes and then heated to 75 °C. The reactor was held at 75 °C for 30 minutes. Then a monomer mixture (34.3 MAA / 9.8 BA / 4.0 DAAM / 1.9 MAA) 120.0 g was fed to the reactor over 60 minutes. The reactor was held at 75 °C for an additional 10 minutes. As the reactor cooled to room temperature, a chase catalyst and activator (t-butyl hydroperoxide / sodium metabisulfite) solution was fed to the reactor over 30 minutes. When the reactor temperature was below 50 °C, a neutralizer (NH4OH) and a biocide (Proxel BZ Plus) were added. At 30 °C, the stirring was stopped and the reactor was drained. The resulting latex was measured for solids content (47.8%), pH (8.3), and particle size (178 nm).

[0102] Example 2 (Resin 2): Acrylic Modified Fluoropolymer Composition Prepared with Diacetone Acrylamide (DAAM)

[0103] A polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer latex was used as seed and an emulsion polymerization process was used to synthesize a latex comprising an acrylic modified fluoropolymer composition. To a 2 liter reactor was added 1400 g PVDF-HFP copolymer latex seed and 100 g deionized water. The reactor was purged with argon / nitrogen and then a low flow argon / nitrogen purge was maintained during the reaction. The reactor was agitated at 160 rpm while a monomer mixture (mass ratio of 26.1 MAA / 19.9 BA / 4.0 DAAM) 120.0 g was fed to the reactor over 30 minutes. During this time, an initiator solution [1.7 g VAZO-67 dissolved in 17.0 g TPM (tripropylene glycol methyl ether)] was also added. The reactor was then agitated at room temperature for 30 minutes and then heated to 75 °C. The reactor was held at 75 °C for 30 minutes. Then a monomer mixture (23.6 MAA / 20.6 BA / 4.0 DAAM / 1.8 MAA) 120.0 g was fed to the reactor over 60 minutes. The reactor was held at 75 °C for an additional 10 minutes. As the reactor cooled to room temperature, a chase catalyst and activator (t-butyl hydroperoxide / sodium metabisulfite) solution was fed to the reactor over 30 minutes. When the reactor temperature was below 50 °C, a neutralizer (NH4OH) and a biocide (Proxel BZ Plus) were added. The agitation was stopped and the reactor was drained at 30 °C. The resulting latex was measured for solids content (47.8%), pH (8.3), and particle size (178 nm).

[0104] Comparative Example 1 (Resin 3): Acetoacetoxyethyl methacrylate (AAEM) was used to prepare an acrylic modified fluoropolymer composition

[0105] A polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer latex was used as seed and an emulsion polymerization process was used to synthesize a latex comprising an acrylic modified fluoropolymer composition. To a 2 liter reactor was added 1400 g PVDF-HFP copolymer latex seed and 100 g deionized water. The reactor was purged with argon / nitrogen and then a low flow argon / nitrogen purge was maintained during the reaction. The reactor was stirred at 160 rpm while a monomer mixture (mass ratio 36.5 MAA / 9.5 BA / 4.0 AAEM) 120.0 g was fed to the reactor over 30 minutes. During this time, an initiator solution [1.7 g VAZO-67 dissolved in 17.0 g TPM (tripropylene glycol methyl ether)] was also added. The reactor was then allowed to stir at room temperature for 30 minutes and then heated to 75 °C. The reactor was held at 75 °C for 30 minutes. Then a monomer mixture (34.3 MAA / 9.9 BA / 4.0 AAEM / 1.8 MAA) 120.0 g was fed to the reactor over 60 minutes. The reactor was held at 75 °C for an additional 10 minutes. As the reactor cooled to room temperature, a chase catalyst and activator (t-butyl hydroperoxide / sodium metabisulfite) solution was fed to the reactor over 30 minutes. When the reactor temperature was below 50 °C, a neutralizer (NH4OH) and a biocide (Proxel BZ Plus) were added. The stirring was stopped and the reactor was drained at 30 °C. The resulting latex was measured to have a solids content (47.7%), a pH of 8.1, and a particle size (175 nm).

[0106] Comparative Example 2 (Resin 4): Preparation of an acrylic modified fluoropolymer composition

[0107] A polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer latex was used as a seed and an emulsion polymerization process was used to synthesize a latex comprising an acrylic modified fluoropolymer composition. To a 2 liter reactor was added 1400 g of PVDF-HFP copolymer latex seed and 100 g of deionized water. The reactor was purged with argon / nitrogen and then a low flow rate argon / nitrogen purge was maintained during the reaction. The reactor was stirred at 160 rpm while a monomer mixture of 120.0 g (mass ratio of 40 MMA / 10 BA) was fed to the reactor over 30 minutes. During this time, an initiator solution [1.7 g VAZO-67 dissolved in 17.0 g TPM (tripropylene glycol methyl ether)] was also added. The reactor was then stirred at room temperature for 30 minutes and then heated to 75 °C. The reactor was held at 75 °C for 30 minutes. A monomer mixture of 120.0 g (37.4 MMA / 10.2 BA / 2.4 MAA) was then fed to the reactor over 60 minutes. The reactor was held at 75 °C for an additional 10 minutes. As the reactor cooled to room temperature, a chase catalyst and activator (t-butyl hydroperoxide / sodium metabisulfite) solution was fed to the reactor over 30 minutes. When the reactor temperature was below 50 °C, a neutralizer (NH4OH) and a biocide (Proxel BZ Plus) were added. At 30 °C, the stirring was stopped and the reactor was drained. The resulting latex was measured for solids content (44%), pH (8.0), and particle size (185 nm).

[0108] The resins from Example 1, Example 3 followed the same synthesis path and used the same PVDF-HFP copolymer latex seed. The difference between Example 1 and Example 3 was the type of functionalized monomer with a ketone functional group, resin 1 was diacetone acrylamide (DAAM) and resin 3 was acryloyloxyethyl acetoacetate (AAEM).

[0109] Preparation of Gray Paints

[0110] Each of the gray paints (A, B, C, and D) was made from the ingredient mixtures in Table 2 below. In contrast, A and C both used resin 1, but A used freshly prepared resin 1 and C used heat aged resin 1 containing adipic acid dihydrazide. In contrast, B and D both used resin 3, but B used freshly prepared resin 3 and D used heat aged resin 3 containing adipic acid dihydrazide. The heat aged resin containing adipic acid dihydrazide was prepared by first mixing the adipic acid dihydrazide with the resin and then placing the mixture in a sealed glass jar which was subsequently placed in an oven at 50 °C for 4 weeks. After the 4 weeks in the oven at 50 °C, the heat aged resin mixture was combined with the other ingredients in the formulation for C and D.

[0111] Table 1. Gray paint.

[0112]

[0113] 1 Adipic dihydrazide, purchased from Millipore Sigma.

[0114] 2 Desiccant, purchased from BYK-Chemie (Wesel, Germany).

[0115] 3 Dowanol DPM, dipropylene glycol methyl ether, purchased from Dow Chemical.

[0116] 4 Deionized water (56.0 grams), Tamol 165A (5.1 grams, purchased from Dow Chemical), ammonia (0.3 grams, 28% concentration), Surfynol AD-01 (1.1 grams, purchased from Evonik), Shepherd black 30C965 (52.0 grams), and R-960 Ti02 (191.0 grams, purchased from Kemira) were mixed and milled into a dispersion having a Hegman number of 7 or greater.

[0117] The paint was applied to a chromized aluminum substrate (AL-412, purchased from Q-lab) using an 8-mil gap BYK box applicator. The applied film was dried and cured for 10 days at ambient temperature prior to solvent resistance testing.

[0118] The following procedure was used to perform solvent resistance testing on each of the cured paint compositions:

[0119] 1. Place the test panel on a flat table or other suitable flat, solid surface.

[0120] 2. Secure a piece of felt to the ball end of a one-pound weight hammer. The felt should be securely fastened in place using rubber bands.

[0121] 3. Soak the felt with the solvent appropriate for the material being tested [methyl ethyl ketone (MEK) was used in this test] and re-soak the felt with solvent after every 50 double rubs.

[0122] 4. Immediately rub the soaked felt back and forth over the test area for a distance of about 4-6 inches.

[0123] 5. Do not apply any downward or upward pressure on the handle of the hammer. The weight of the hammer controls the downward pressure.

[0124] 6. Continue this back and forth motion, counting as one “double rub” for each complete forward and backward motion, until the center of the rub strip exposes bare substrate.

[0125] 7. Record the test result as the number of double rubs required to expose bare substrate in the center of the rub strip.

[0126] 8. After each individual sample test, the felt must be removed and replaced with a new piece of felt.

[0127] Paints A through E were applied to PVC (polyvinyl chloride) substrates using a BYK square applicator with an 8 mil gap. The coated films were flash air dried at room temperature for 10 minutes, followed by a 30 minute cure at 50 °C, prior to the Detergent Resistance Test. The Detergent Resistance Test is based on AAMA 2605-13.

[0128] The results of the solvent resistance test (MEK double rub) and the Detergent Resistance Test are shown in Table 2.

[0129] Table 2. Solvent resistance (MEK double rub) of cured panels made from paints A, B, C, and D.

[0130]

[0131] It is noted that the AAEM (aged D) containing AMF composition exhibited a pink color after aging. The DAAM (aged C) containing AMF composition did not exhibit any color change during the aging process.

[0132] The panels made from paint A and paint C had similar solvent resistance, but there was a significant difference in solvent resistance between the panels made from paint B and paint D. This result indicates that resin 1 with DAAM functionality has good thermal aging stability, while resin 2 with AAEM functionality has poor aging stability. The poor stability is also consistent with the color change before and after the hot room stability test.

[0133] Comparison A and C shows that the aging of the composition does not affect the solvent resistance when DAAM is used in the acrylic modified fluoropolymer. Comparison B and D shows that the aging of the composition does affect the solvent resistance when AAEM is used in the acrylic modified fluoropolymer. The solvent resistance of the composition using AAEM is severely reduced with aging, exhibiting a decrease in MEK double rubs from 100 for the fresh polymer to 15 for the aged polymer.

[0134] In the solvent resistance test, the PVC panels coated with paint E (not crosslinked) severely blistered and failed the test, while the PVC panels coated with paints A and C (containing DAAM) passed the Detergent Resistance Test. The PVC panels coated with paints B and D (containing AAEM) failed the Detergent Resistance Test.

[0135] DAAM is stable and provides resistance to solvents, thus passing the detergent resistance test. Stable means that the composition performs in double rub test no more than 10% different after one month in an oven at 50°C compared to the freshly prepared composition.

[0136] Clear Varnish Formulation:

[0137] About 65-75 g of neutralized latex [100% acrylic and acrylic fluoropolymer dispersion latex (with PVDF seed)] (35 g resin solids) was mixed with Texanol® ester alcohol (coalescent, 0.7 g), BYK-346 (wetting agent, 0.5 gram) and water (to get 40% volume solids) to get clear varnish. These clear varnishes were draw down with a 6 mil doctor blade on Leneta opacity test cards to measure their dry film properties. (ASTM D4062-11 "Standard Test Method for Determining Leveling of Coatings Using Drawdown" was used). The clear varnishes were cured for at least 12 hours at 25°C / 50% relative humidity or 5°C. Then the gloss was measured. The dirt pick up resistance was measured after 1 week of curing under ambient conditions (25°C / 50% RH).

[0138] Dirt pick up resistance was measured using an aqueous slurry consisting of hydrophobic carbon black (Birla Raven 22) and BYK 346 as wetting agent. The slurry was applied to the dry coating at room temperature for 4 hours, then rinsed gently with cold water and a paper towel. The test was performed after the film was dried comparing the dirted and non-dirted parts of the coating. The lower the value indicates better dirt pick up resistance.

[0139] Acrylic 1 is a commercially available acrylic latex with a minimum film formation temperature (MFFT) of 15°C and a solid weight % of 58%.

[0140] Table 3

[0141]

[0142] These examples show that acrylic modified fluoropolymers containing DAAM have higher gloss at room temperature and do not crack when cured at low temperature while maintaining similar dirt pick up resistance.​

Claims

1. An aqueous coating composition comprising i) an acrylic modified fluoropolymer comprising a fluoropolymer portion and an acrylic portion ii) a dihydrazide, and iii) optionally an additional polymer that is not part of the acrylic modified fluoropolymer, wherein the acrylic modified fluoropolymer composition comprises at least 1 wt% of DAAM and at most 20 wt% based on total acrylic monomer units in the acrylic modified fluoropolymer composition.

2. The aqueous coating composition of claim 1, wherein the aqueous coating composition comprises greater than 50 wt% of polymer based on total solids content in the aqueous coating composition.

3. The aqueous coating composition of claim 1, wherein the acrylic portion further comprises an acrylic or methacrylic monomer having an acid functional group.

4. The aqueous coating composition of claim 1, wherein the acrylic portion of the acrylic modified fluoropolymer further comprises 0.01 to 10% of (meth)acrylic acid based on total acrylic monomer units in the acrylic modified fluoropolymer composition.

5. The aqueous coating composition of claim 1, wherein the molar ratio of dihydrazide to DAAM is between 0.02 and 0.

5.

6. The aqueous coating composition of claim 1, wherein the aqueous coating composition further comprises a pigment.

7. The aqueous coating composition of any one or more of claims 1 to 6, wherein the aqueous coating composition further comprises an acrylic polymer separate from the acrylic modified fluoropolymer.

8. The aqueous coating composition of claim 1, wherein the additional polymer that is not part of the acrylic modified fluoropolymer is selected from the group consisting of acrylic, vinyl, polyurethane, polyester, melamine resin or epoxy based polymers and copolymers.

9. The aqueous coating composition of any one or more of claims 1 to 6, wherein the additional polymer that is not part of the acrylic modified fluoropolymer comprises at least one of an acrylic latex, a polyvinyl acetate (PVA) latex, a styrene / butadiene latex, a vinyl latex or a vinyl acrylic latex.

10. The aqueous coating composition of any one or more of claims 1 to 6, wherein the fluoropolymer portion comprises 50 to 100 wt% of vinylidene fluoride units based on the weight of the fluoropolymer portion, and 0 to 50 wt% of monomer units copolymerizable with vinylidene fluoride, preferably the fluoropolymer portion comprises 50 to 100 wt% of vinylidene fluoride units.

11. The aqueous coating composition of any one or more of claims 1 to 6, wherein the fluoropolymer portion comprises 3 to 30 wt% of hexafluoropropylene units based on the total weight of the fluoropolymer portion.

12. The aqueous coating composition of any one or more of claims 1 to 6, wherein the fluoropolymer portion comprises a polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the total weight percent of hexafluoropropylene monomer units in the acrylic modified fluoropolymer is from 5 to 20%, preferably from 10 to 20% by weight based on the weight of the acrylic modified fluoropolymer.

13. The aqueous coating composition of any one or more of claims 1 to 6, wherein the total weight percent of acrylic monomer units in the acrylic modified fluoropolymer is from 10 to 50% by weight, preferably the total weight percent of acrylic monomer units in the acrylic modified fluoropolymer is from 15 to 40% by weight.

14. The aqueous coating composition of any one or more of claims 1 to 6, wherein the acrylic modified fluoropolymer comprises from 3 to 100% by weight of the total polymer in the aqueous coating composition.

15. The aqueous coating composition of any one or more of claims 1 to 6, further comprising UV stabilizers, pH adjusters, colorants, dyes, water soluble resins, rheology control additives and thickeners, pigments and pigment extenders, and fillers.

16. A method of coating a substrate comprising providing a substrate, providing a coating composition of any one or more of the preceding claims, applying the coating composition to the substrate, drying the coating composition on the substrate to form a coated substrate.

17. A coated substrate comprising a substrate coated on at least one surface with an aqueous coating composition of any one or more of claims 1-15, and wherein the coating composition is dried to form a coated substrate.

18. The coated substrate of claim 17, wherein the substrate is selected from the group consisting of primed or unprimed metals, wood, glass, plastics, and composites.

19. The coated substrate of claim 18, wherein the coating is an exterior coating selected from the group consisting of architectural coatings, marine coatings, and protective coatings.

20. Use of the aqueous coating composition of any one or more of claims 1 to 15 in an exterior construction.

21. An aqueous coating composition comprising i) an acrylic modified fluoropolymer comprising a fluoropolymer portion and an acrylic portion ii) a dihydrazide, and iii) an additional polymer that is not part of the acrylic modified fluoropolymer, and iv) a pigment, wherein the acrylic modified fluoropolymer composition comprises DAAM monomer units, wherein the aqueous coating composition comprises greater than 50% by weight of polymer based on the total solids content of the aqueous coating composition, wherein the acrylic portion further comprises an acrylic or methacrylic monomer having an acid functional group, and wherein the molar ratio of dihydrazide and DAAM is between 0.02 and 0.

5.

22. The aqueous coating composition of claim 21, wherein the acrylic portion of the acrylic-modified fluoropolymer further comprises 0.01 to 10% of (meth)acrylic acid, based on total acrylic monomer units in the acrylic-modified fluoropolymer composition.

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