WO2011006065A2

WO2011006065A2 - Aqueous fluoropolymer coating composition and coated articles made using such composition

Info

Publication number: WO2011006065A2
Application number: PCT/US2010/041522
Authority: WO
Inventors: Cheng Chen; Chao Yu Han; Naiyong Jing; Zhigang Yu; Zai-Ming Qiu
Original assignee: 3M Innovative Properties Company
Priority date: 2009-07-10
Filing date: 2010-07-09
Publication date: 2011-01-13
Also published as: WO2011006065A3; CN101948647B; CN101948647A

Abstract

There is provided an aqueous fluoropolymer coating composition and a coated article made using this composition.

Description

AQUEOUS FLUOROPOLYMER COATING COMPOSITION AND COATED ARTICLES MADE USING SUCH COMPOSITION

The present disclosure relates to an aqueous fluoropolymer coating composition. The present disclosure also relates to coated articles made using this composition as a coating on various metal substrates.

SUMMARY

In one aspect, the present disclosure provides an aqueous fluoropolymer coating composition including a substantial amount of water, a fluoropolymer, a base, and at least one functional additive selected from at least one hydrophilic aldhehyde, at least one hydroxyaromatic compound, and combinations thereof, where the hydroxyaromatic compound comprises at least one hydroxy group bonded directly to an aromatic carbon.

In another embodiments, the aqueous fluoropolymer coating composition comprises a perfluoropolymer with tertiary carbon.

In some embodiments, the aqueous fluoropolymer coating composition includes a co-solvent. In some embodiments, the aqueous fluoropolymer coating composition includes a film former.

In still another aspect of the present disclosure, there is provided a coated article including a substrate, and a first layer derivable from an aqueous fluoropolymer coating comprising a substantial amount of water, a fluoroplastic, a base, and at least one functional additive selected from at least one hydrophilic aldhehyde, at least one hydroxyaromatic compound, and combinations thereof, where the hydroxyaromatic compound comprises at least one hydroxy group bonded directly to an aromatic carbon.

In still another aspect of the present disclosure, there is provided a coated article including a substrate, and a second fluoropolymer layer on the top of the first primer layer derivable from an aqueous fluoropolymer coating comprising a substantial amount of water, a fluoroplastic, a base, and at least one functional additive selected from at least one hydrophilic aldhehyde, at least one hydroxyaromatic compound, and combinations thereof, where the hydroxyaromatic compound comprises at least one hydroxy group bonded directly to an aromatic carbon. In some embodiments, the substrate is aluminum. In some embodiments, the substrate is stainless steel.

The above summary of the present disclosure is not intended to describe each embodiment of the present invention. The details of one or more embodiments of the invention are also set forth in the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.

DETAILED DESCRIPTION

As used herein the terms "a", "an", and "the" are used interchangeably and mean one or more; and "and/or" is used to indicate one or both stated cases may occur, for example A and/or B includes, (A and B) and (A or B). Also herein, recitation of ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.). Also herein, recitation of "at least one" includes all numbers of one and greater (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least

50, at least 100, etc.).

Fluoropolymers, for example, polytetrafluoroethylene (PTFE),

tetrafluoroethylene (TFE) and perfluoroalkoxyvinylether copolymer (PFA),

poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-alt- ethylene) (ETFE), terpolymer of tetrafluoroethylene/hexafluoropropylen/vinylidene fluroride (THV), are capable of forming pinhole-free films and are widely used as coating materials. In use, these fluoropolymers exhibit a wide range of outstanding properties, including high-temperature stability, excellent chemical resistance, low water sorption, and low dielectric constant. Due to strong chemical bonding between the carbon and fluorine atoms in these fluoropolymers, they also exhibit other properties, for example, low refractive index and very low surface energy. As a result coatings having a fluoropolymer surface (or fluoropolymeric coatings) repel contaminants and are easy to clean. Therefore, fluoropolymeric coatings act as a barrier and are widely used for anti- stick applications in the paint, varnish and adhesives industries or corrosion protection in industrial equipments. Although fluoropolymers can be used in coating compositions, application of fluoropolymeric coatings can be difficult relative to other types of coatings. The general cause of these difficulties is that most fluoropolymers are not soluble under standard coating conditions, and thus cannot be formulated like traditional soluble resins. Thus, these fluoropolymers are applied to substrates using other means, including electrostatic application of powder coating compositions or liquid dispersions, which can be stabilized with a surfactant in water or based on organic liquids. The characteristic low surface energy and resulting poor adhesion of fluoropolymeric coatings to other materials have created numerous technical challenges because they do not stick to other materials, especially dissimilar materials, with any practical degree of bond strength. For instance, adhesion of fluoropolymeric coating, especially stable perfluoropolymer coating, to metals and semiconductors has been a constant challenge in the electronics and microelectronics packaging industries. These harsh application conditions prevent the use of

fluoropolymeric coatings on many substrates.

Efforts have been made to overcome these limitations of fluoropolymers as coatings. Two methods are commonly used to improve the bonding of fluoropolymeric coatings to substrates, in particular to metal substrates. One method involves activating the surface of the fluoropolymeric coating by chemical etching of the surface with an etchant, for example, alkali metal vapor, alkali metal hydroxides, alkaline earth metals, "tetra-etch" solutions, and aromatic radical dianions. Depending on the types of chemical etchants used, various extents of defluorination and the incorporation of new functional groups are observed, which are effective in promoting the adhesion of the fluoropolymeric coating to the metal substrate.

Despite their effectiveness in activating and re-functionalizing the surface of the fluoropolymeric coatings, the treatments of chemical etchants have several drawbacks.

One drawback is that it can be difficult to monitor and control the depth profile of the etching and, hence, the modification of the surface of the fluoropolymeric coating. The bulk properties of the fluoropolymers are usually affected by the chemical etchants during surface modification. Another drawback is that chemical treatments using reactive etchants are often accompanied by undesirable environmental problems. Another method commonly used to improve the bonding of fluoropolymeric coatings to metal substrates involves using high temperature resistant thermoplastics (HTRP), for example, polyamide amide, polyarylene sulfide and polyether sulfone, as adhesion promoters of fluoropolymers. In addition, liquid crystal polymers have been included in HTRP groupings, and they also exhibit some adhesion to metal in the neat state. Such adhesion is much less than exhibited by the recognized HTRP adhesion promoters. These coatings generally include two fluoropolymeric coating layers, including a specially formulated aqueous fluoropolymer coating composition and a top layer. The aqueous fluoropolymer coating compositions for these systems typically include a heat resistant organic binder resin and one or more fluoropolymer resin.

Known aqueous fluoropolymer coating compositions based on HTRP generally include organic solvents or contain epoxy compounds in order to obtain good dispersion and stability of the HTRP compositions in aqueous media. Many of the organic solvents used in these aqueous fluoropolymer coating compositions are subject to regulatory restrictions because of potential health risks associated with organic solvents. As such, it is desirable to eliminate use of these organic solvents in aqueous fluoropolymer coating compositions.

Aqueous fluoropolymer coating compositions provide a variety of advantages over existing aqueous fluoropolymer coating compositions that contain organic solvents, including cost effectiveness, lower impact on the environment, low levels of volatile organic carbons, and ease in processing. Liquid aqueous fluoropolymer coating compositions are often preferential because they are lower in cost and provide higher efficiency when used under powder top coatings.

Although organic solvents are used in aqueous fluoropolymer coating compositions, these types of compositions are still subject to problems with coagulation and precipitation when stored for a long time. In addition, existing aqueous fluoropolymer coating compositions are generally only suitable for use on certain substrates. It is desirable to develop an aqueous fluoropolymer coating composition that is useful on a variety of substrates and substantially free of organic solvents.

The present disclosure provides aqueous fluoropolymer coating compositions that are substantially free of organic solvents. The term "substantially free" as used herein means less than 10 wt% of organic solvent. The presently disclosed aqueous

fluoropolymer coating compositions include a substantial amount of water. The term "substantial amount" as used herein means greater than 50 wt% of water based on the total weight of the aqueous fluoropolymer coating composition. In one embodiment, the aqueous fluoropolymer coating composition includes at least one functional additive selected from at least one of a hydroxyaromatic compound, at least one of an aliphatic aldehyde compound, and combinations thereof. The aqueous fluoropolymer coating composition also includes at least one basic compound. In one embodiment, these compositions include at least one aqueous fluoropolymer dispersion combined with at least one functional additive. The individual functional additive or combination of functional additives is selected based on the type of substrate to be coated and/or the type of fluoropolymer dispersion mixed therewith.

Fluoropolymers useful in the presently disclosed aqueous fluoropolymer dispersion include one or more interpolymerized units derived from at least two principal monomers. Examples of suitable candidates for the principal monomer(s) include perfluoroolefms (e.g., tetrafluoroethylene (TFE) and hexafluoropropylene (HFP)), perfluorovinyl ethers (e.g., perfluoroalkyl vinyl ethers and perfluoroalkoxy vinyl ethers), perfluorovinyl ethers and hydrogen-containing monomers such as olefins (e.g., ethylene, propylene, and the like) and vinylidene fluoride (VDF). Such fluoropolymers include, for example, fluoroelastomers and semi-crystalline fluoroplastics or combinations.

In some embodiments, the fluoropolymers are selected from perfluoropolymers with tertiary carbon. As used herein the term "tertiary carbon" means a carbon atom having three other carbon atoms bonded thereto. The tertiary carbon in perfluoropolymers is derived from, such as the copolymerization of HFP and perfluorovinyl ethers.

Those skilled in the art are capable of selecting specific interpolymerized units at appropriate amounts to form an elastomeric polymer. Thus, the appropriate level of interpolymerized units is based on mole percent and is selected to achieve an elastomeric, polymeric composition.

In one embodiment, the aqueous fluoropolymer coating composition comprises one aqueous fluoropolymer dispersion or a mixture of fluoropolymer dispersions in combination with at least one hydroxyaromatic compound and at least one aliphatic aldehyde. The hydroxyaromatic compounds useful in the present disclosure include at least one hydroxy group bonded directly to an aromatic carbon. For example,

hydroxyaromatic compounds useful in the present disclosure include 2-napthol, phloroglucin, bisphenol A, catechol, hydroquinol, resorcinol, 2-fluorophenol, and the like. In some embodiments, two or more hydroxyaromatic compounds are included in the presently disclosed aqueous fluoropolymer coating composition.

In some embodiments, the hydroxyaromatic compounds include at least one hydroxy group bonded directly to an aromatic carbon. In some embodiments, the hydroxyaromatic compounds are poly(hydroxyaromatic) compounds, such as polyphenols. In some embodiment, the hydroxyaromatic compounds include at least one additional polar group or water soluble functional group. As used herein the term "polar group" means any group in which the distribution of electrons is uneven enabling it to take part in electrostatic interactions, such as -C(=O)- and -SO₂-. As used herein the term "water soluble functional group" means a hydrophilic group that when included in a compound results in improved solubility in water, such as -CO₂H, -O- and -S-. In some

embodiment, the hydroxyaromatic compounds include at least one additional electron- donating group. As used herein, the term "electron-donating group" means a functional group that releases electrons into a reaction center and as such stabilizes electron deficient carbocations. Examples of electron-donating groups include but are not limited to alkyl groups, ether group, alcohol groups, and amino groups. In some embodiment, the hydroxyaromatic compounds include at least one basic group, such as an amine group. Following are some exemplary hydroxyaromatic compounds that are useful in the present disclosure.

Aliphatic aldehydes useful in the present disclosure are hydrophilic aldehydes, such as, for example, glutaraldehydes, glyoxals, terephthaldehydes, napthaldehydes, furfurals, and the like. In some embodiments, the hydrophilic aldehydes include materials that are converted to aldehydes in-situ under conditions of heat and/or base. In some embodiments, the hydrophilic aldehydes are multifunctional, such as, for example, 2- hydroxy- 1-napthaldehyde. The term "multifunctional" as used herein means molecules having at least two functional groups, such as, for example two aldehyde functional groups, one aldehyde functional group and one hydroxy 1 functional group, and the like. In some embodiments two or more aliphatic aldehydes are included in the presently disclosed aqueous fluoropolymer coating composition.

Bases useful in the present disclosure include organic and inorganic bases. For example, bases useful in the present disclosure may include diaminobenzene,

diaminoethane, diethanolamine, diethylenetriamine, phenylenediamine, calcium hydroxides, polyethyleneimide, polyetheramines, potassium hydroxides, triethylamine, triethanolamine, and the like. In some embodiments, the organic amine may include hydroxyaromatic group, such as aminophenol derivatives and 4-(4-aminophenoxy)phenol.

In some embodiments, the fluoropolymer coating composition includes a co- solvent. Exemplary co-solvents include ethanol, ethylene glycol, and the like. In some embodiments, the aqueous fluoropolymer coating composition includes a film former. Exemplary film formers include acrylic copolymers, such as urethane acrylic copolymer, anionic acrylic copolymer, or polyurethane. Film formers are used to improve the appearance of a coating created using the fluoropolymer coating composition. Exemplary film formers include anionic acrylic copolymers (such as an anionic acrylic copolymer available under the trade designation "NeoCryl A-I lOl" commercially available from DSM LTD., Netherlands) and aromatic urethane acrylic copolymer (such as an aromatic urethane acrylic copolymer available under the trade designation "NeoPac E-180" commercially available from DSM LTD., Netherlands). In some embodiments, at least two film formers may be used, such as for example, NeoCryl A-I lOl and NeoPac E-180 mixed in volume rations ranging from 1 :5 to 3:5. The total weight percent of film former based on the total weight of the aqueous fluoropolymer coating composition may range from about 15 wt% to about 35 wt%.

In some embodiments, the fluoropolymer coating composition includes water- born nanoparticles. Exemplary water-born nanoparticles include nanoparticle metal oxides, such as those commercially available under the trade designation "Ludox AM-30" from W. R. Grace & Co, Columbia, Maryland.

In some embodiments, the fluoropolymer coating composition includes one or more additional additives. These additional additives include pigments, antifoam agents, wetting agents, dispersants, thickeners, leveling agents and the like. In some

embodiments, the fluoropolymer coating composition includes at least 50 wt% water, no more than 30 wt% fluoropolymer, less than 1 wt% of an aliphatic aldehyde, lwt% or less of a hydroxyaromatic compound, less than 2 wt% of a base, and up to 16 wt% of additional additives.

Antifoam agents useful in the present disclosure include, for example, those available under the trade designations "DynolTM HOD" from Air Products LTD. US, and "BYK-093", BYK LTD., Netherlands. In some embodiments, more than one antifoam agent may be used in the aqueous fluoropolymer coating composition. The total amount of antifoam agent based on the total weight of the aqueous fluoropolymer coating composition may range from about 0.2 wt% to about 0.8 wt%. Wetting agents useful in the present disclosure include, for example, those available under the trade designations "DynolTM 104BC", "DynolTM S440", and "DynolTM D604" from Air Products LTD., US. The total amount of wetting agents based on the total weight of the aqueous fluoropolymer coating composition may range from about 0.3 wt% to about 0.8 wt%. Silicone surface additives useful in the present disclosure include polydimethylsiloxane, such as polydimethylsiloxane available under the trade designation "Dow Corning 51" from Dow Corning LTD. US, and poly ether modified polydimethylsiloxane, such as that available under the trade designations "BYK-302" and "BYK-333" from BYK Co., Germany. Leveling agents useful in the present disclosure include any compounds that can be added to an electroplating solution that change the mechanism of the plating to produce a metal deposit smoother than the original substrate, such as those commercially available under the trade designation "Surfynol 440" from Air Products Co., Allentown, Pennsylvania.

In some exemplary embodiments, up to 9 wt% ethylene alcohol may be used to dissolve the hydroxyaromatic compound before adding it to the fluoropolymer coating composition. In some exemplary embodiments, up to 2 wt% pigment is added to the fluoropolymer coating composition, such as carbon black (commercially available from Clariant Co., Charlotte, NC under trade designation "Colanyl Black N131"). In some exemplary embodiments up to 7 wt% of a film former is added to the fluoropolymer coating composition, such as aromatic urethane acrylic copolymer (commercially available in 33% solid by weight from DSM Co. Netherland under the trade designation

"NeoPac E- 180"). In some exemplary embodiments up to 1 wt% of additional additives are added to the fluoropolymer coating composition, such as additional pigments, antifoam agents, wetting agents, dispersants, thickeners, and the like.

The present disclosure also provides the use of these aqueous fluoropolymer coating compositions to coat a substrate. These compositions provide excellent bonding of fluoropolymers, and specifically perfluoroplastics, to various metal substrates. Exemplary substrates include various metals, such as aluminum, stainless steel, carbon steel, nickel coated steel, galvanized steel, iron, and the like. The surface of the substrate to be coated may or may not be prepared before being coated using any of a variety of techniques, including cleaning, hardening, etching, and the like. Once the substrate is ready to be coated, a first layer of the aqueous fluoropolymer coating composition is coated on the substrate. The first layer is coated to a thickness of less than 0.06 mm (2.4 mil).

In some embodiments, a second layer is coated on the first layer. In some embodiments, the second layer includes a fluoroplastic. Exemplary fluoroplastics include homopolymers and blends of polymers, such as PFA, TFE, perfluoro(alkylvinylether), and the like. In some embodiments, a third layer is coated on the second layer. Additional layers may be coated on the aforementioned layers according to the desired use of a coated article made according to this technique. One of skill in the art appreciates that various materials and thicknesses of materials can be used in these coated articles.

In some embodiments, traditional spraying and dipping methods, which are especially suitable for the application of ultrathin coatings, can be used to provide a first layer of the fluoropolymer coating composition without requiring additional layers. A coating of this first layer of fluoropolymer coating composition may provide excellent interfacial adhesion between the coating and different metal substrates. It may also exhibit low tape release and good oil phobic ability and be scratch resistant. Use of the first layer of fluoropolymer coating composition can also improve the anticorrosion of substrates, especially for the corrosion of acids and alkali.

After further optional adjustments of additives and compositions the

fluoropolymer coating composition can be directly used on smooth metallic surfaces by spraying or dipping methods. A non-stick coating with excellent adhesion strength can be achieved after thermal treatment of the coated smooth metallic surfaces. For example, the fluoropolymer coating composition may be applied to metallic scissors (e.g. those available under the trade designation "Scotch", commercially available from 3M

Company, St.Paul, MN) resulting in excellent appearance, oil resistant, adhesive, anti- corrosion and non-stick properties. In addition to application to scissors, a first layer of the fluoropolymer coating composition may also be applied to other metallic substrates and articles including stainless steel, aluminum and iron for household, garden, hospital and industrial applications. For example, fluoropolymer coating compositions according to the present disclosure are useful as thermally stable and durable non-stick coatings for use in printed circuit boards. Another exemplary use for fluoropolymer coating compositions according to the present invention includes non-stick, easy cleaning and anti-corrosion coatings for die cutters, optionally used in combination with optically clear adhesives.

The following specific, but non-limiting, examples will serve to illustrate the invention. In these examples, all amounts are expressed in parts by weight, or parts by weight per one hundred parts by weight of rubber (phr). The monomer composition ratio was measured by ¹H/ ¹⁹F cross-integration NMR analysis.

Examples

These examples are merely for illustrative purposes only and are not meant to be limiting on the scope of the appended claims. All parts, percentages, ratios, and the like in the examples are by weight, unless noted otherwise. All materials used were available from Shanghai Aibi Chemistry Preparation Co. LTD, unless otherwise noted.

Table of Materials

Formulations

In example 1, a FEP6300RG dispersion (15g, 75 wt %) and a PFA6990RG dispersion (4g, 20 wt %) were weighed and then mixed with 2-naphthol (0.8grams, 10% solids in ethylene glycol, 4 wt. %) and diaminoethane (0.2 grams, 1 wt. %). After shaking, the resulting solution was available as a liquid aqueous fluoropolymer coating

composition. Examples 2-34 and comparative examples CE1-CE4 were prepared as described in Example 1 except the materials and ratios were varied as shown in Tables 1 and 2. The resulting dispersions were then primer coated on panels followed by top coating as described under "Peel Test Preparation". Peel testing was performed as described under "Peel Testing" and results are recorded in Tables 1 and 2. As the formulations were not optimized for dispersion stability all examples and comparative example dispersions (except example 34) were coated on panels within 24 hours after the dispersions were made.

To improve dispersion stability the simple process above was modified as exemplified below. 24 grams 1 ,2-diaminoethane (DAE) was mixed with 300 grams water, and then 120 grams 2-naphthol /ethylene glycol solution (10% solids by wt) was added into the stirring amine solution. Then, 7 grams glyoxal/water solution (40 % in water) was added and blended for 30 minutes. The resulting solution was blended with a mixture of FEP6300RG/PFA6900RG dispersions (480 grams/120 grams). After blending for 1 hour, 32 grams aqueous of 40 wt% by solids of a carbon black pigment was added

(commercially available from Clariant Co., Charlotte, NC under trade designation

"Colanyl Black N131"). Then, 250 grams aromatic urethane acrylic copolymer

(commercially available in 33% solid by weight from DSM Co. Netherland under the trade designation "NeoPac E-180") as a film former and other additives, including 8 grams of an antifoam agent, such as an antifoam commercially available from Air Products Co.,

US under the trade designation "Surfynol DFl 10D" and 4.2 grams of an additional antifoam agent commercially available from BYK Co., Germany under the trade designation "BYK-093", 8 grams of a wetting agent, such as a wetting agent commercially available from Air Products Co., US under the trade designation "Dynol 604 Surfactant" and 6 grams of a wetting agent, such as a wetting agent commercially available from Air Products Co., US under the trade designation "Surfynol 440", and 4.2 grams of a wetting agent, such as a wetting agent commercially available from BYK Co., Germany under the trade designation "BYKETOL-WS", and 8.5 grams of a thickener commercially available from Cognis Co., Germany under the trade designation "DSX-3291" were added and mixed until a uniform solution was obtained. The peel strengths after aqueous

fluoropolymer coating compositions coat and PFA topcoat on aluminum and stainless steel grit blasted substrates were >1.41 N/mm and 0.93 N/mm after boiling for 24 hours, respectively. Comparative Example CE5

To 10 g TF-5035R PTFE dispersion were added in order with mixing: 5 g water, 0.4 g DAE, 1.8 g BPA solution (10% in ethylene glycol), 0.2 g DDS solution (10% in ethylene glycol) and 0.25 g GLA solution (50% in water).

Example 49

A first solution of 12 g 2-napthol (2 -N) was dissolved in 108 g ethylene glycol with stirring. A second solution of 24 g diaminoethane (DAE) was dissolved in 300 g deionized water. The first solution was slowly added to the second solution with stirring. A third solution of 7.5 g of 40% glyoxal (GLY) was added to the mixture of the first and second solution. 36 g of the mixture of the first, second and third solutions was then added to 100 g of an aqueous fluoroplastic solution of 80 g PFA 6900GZ and 20 g FEP X6300. This mixture was then further diluted with 60 g deionized water and the top red oil layer was removed before coating.

Example 50

Example 49 was repeated except 4-4'sulfonyldipheol (SFD) was used instead of 2- napthol (2 -N) and the final mixture was not diluted with 60 g deionized water. Example 51

Example 50 was repeated and the final mixture was diluted with 60 g deionized water.

Example 52

A first solution of 12 g bis-phenol A (BP) was dissolved in 108 g ethylene glycol with stirring. A second solution of 24 g diaminoethane (DAE) was dissolved in 300 g deionized water. The first solution was slowly added to the second solution with stirring. A third solution of 7.5 g of 40% glutaraldehyde (GLA) was added to the mixture of the first and second solution. 36 g of the mixture of the first, second and third solutions was then added to 100 g of an aqueous fluoroplastic solution (50% solids) of FEP X6300. This mixture was then further diluted with 60 g deionized water and the top red oil layer was removed before coating. Example 53

Example 52 was repeated except 4,4-bis(4-hydroxyphenyl) valeric acid (BHVA) was used instead of BP. Example 54

To 10 g of FEP 6300GZ dispersion was added in order with mixing: 5 g water, 0.4 g DAE, 2 g BHVA solution (10% in ethylene glycol) and 0.25 g GLA solution (50% in water). Examples 55-57

Example 54 was repeated but with the substitituted hydroxyaromatics as indicated in Table 6.

Example 58

Example 54 was repeated except with FKM-DS2600 dispersion, a hexafluoroproylene (HFP)/vinylidene fluoride(VDF) amorphous fluoropolymer (i.e. curable fluoroelastomer) replacing the FEP fluoroplastic.

Example 59

Example 58 was repeated with SFD replacing the BHVA.

Example 60

100 g of a 28.35% solids 1 :9 PFE:FEP fluoropolymer mixture was prepared by diluting 8.34g PFE-B (2.835g solid) with deionized water to a total of 56.Og and then mixing this 56.0 g solution with 44.Og FEP-6300GZ (25.52g solid). 12 g TDP dissolved in 108g ethylene glycol was added slowly with stirring to 24g ethylenediamine dissolved in 276g deionized water in a 1 liter jar to give a clear solution. To this clear solution was added 7.5g of a 40% solution of glyoxal to form 427.5 g (9.12% solids by weight) of a clear and transparent light pink solution. 20 g of this light pink solution was added with stirring to the fluoropolymer mixture to give a clear and transparent coating solution. Example 61

Example 60 was repeated except the 8.34 g PFE-B was replaced with 9.45 g PFE-A (2.935 g solids). Example 62

The release performance of examples 49, 51, 60 and 61 was tested for an application involving multilayer printed circuit boards (PCB's). Commonly several layers of PCB's are placed over one another and fused together with an adhesive such as those

commercially available under the trade designation "Prepreg" from bonding sheets such as a bisphenol A based epoxy resin and E-glass woven glass fiber filament. In this example a 1" x 1" bonding sheet (commercially available under the trade designation "PCL-FR- 370HR" from the Isola Group, Chandler, AZ) made using "Prepeg" was placed between 2 coated steel plates. The samples were pressed under pressure of 350 psi at 180 ⁰C for 70 min. The pressing was repeated 3 times with fresh epoxy for examples 49 and 51 and 10 times for examples 60 and 61. After cooling to room temperature the top plates were removed from the laminated adhesive without any stickiness. The surface of the coated plates also appeared unchanged.

Peel Test Sample Preparation

Stainless steel (A3, thickness 1.55 mm (0.06 in), 2.54 x 15.2 cm (1x6 in) or aluminum panels (1060, thickness 1.78 mm (0.07 in), 2.54 x 15.2 cm (1x6 in) were directly purchased and subsequently wiped twice with isopropanol and dried at room temperature until the solvent completely volatilized. Unless otherwise noted each strip was grit blasted to roughen the surface using 60-80 mesh aluminum oxide and 552 kPa (80 psi) air pressure. Unless otherwise stated, the top layer is made from PFA 6503 C powder. In a typical experiment, the cleaned strips were rinsed over 4 inches of one end of each strip with the aqueous fluoropolymer coating compositions. This provided an area where the coating would not adhere to the strips (no aqueous fluoropolymer coating

compositions) to create a tab for the peel test. The coated strips were dried at room temperature for 10-15 minutes. The PFA powders were electrostatically powder coated on the surface of the dried aqueous fluoropolymer coating compositions coated substrates using a Nordson SureCoat (Nordson Corporation, Amherst, Ohio) at 70 volts and 15OkPA airflow until a total thickness of about 70-90 microns was obtained. The coated strips were then baked in an air circulating oven at 400⁰C for 10 minutes and then cooled to room temperature. In some cases the ETFE powders were used as a top layer. The samples coated with the ETFE powders were thermally treated at 300⁰C for 10 minutes.

Metal Strip Peel Test

The coated metal strips were immersed in boiling water for 24 hours. After cooling to room temperature the residual water on the samples was removed with filter paper and the edges of each strip were scraped with a sharp blade to remove any coating that may have accumulated at the edges. According to ASTM D3330 (180 peel) the peel strength was measured by testing the samples using an INSTRON Model 5565 Tester (available from Instron Corp., Canton, MA) equipped with a floating roller peel test fixture at a crosshead speed of 30 cm/min (12 in/min). The peel strength was calculated over 5 to 20 mm (0.20 to 0.80 in.) extension using an integrated average and reported in units of N/mm (lbf/inch width) as an average of two samples. When the samples broke within the materials without separating the layers at the bonding interface, the peak value was used instead of the average number. The symbol ">" in peel strength means that the top layer was broken within the materials without separating the layers at the bonding interface or part of the top layer was broken in the process of the peeling.

Table 1

# = aluminum strips were not grit blasted; *=topcoat was ETFE; ND=No data; NO BOND=no bond was observed after boiling water exposure.

Table 2

# = aluminum strips were not grit blasted; ND=no data; NO BOND=no bond was observed after boiling water exposure. Contact Angle Measurement

Contact angle measurements were taken using a video-based contact angle meter, such as a meter available under the trade designation "KRUSS DSA 100" (Drop Shape Analysis System, Germany) at ambient temperature. The average value was obtained by measuring more than five different positions for the same sample. The volume of water droplet was set to be 10 μL. In order to measure oil resistant properties of the coatings, edible vegetable oil, such as a blend of olive and sunflower seed oil, was used as medium instead of water. These results are summarized in Tables 4 and 5 below.

Adhesion Strength Test

Coated samples were immersed in boiling water for 24 hours. After cooling to ambient temperature, the residual water on the samples was removed with filter paper. A Crosshatch pattern of 1 mm was made in the coated samples by using a knife. Adhesive tape, such as tape available under the trade designation "3M 610" (3M Company, St. Paul, MN) was applied as firmly as possible onto the cut lines and pulled vertically. After the tape was applied and pulled 10 times, the appearance of the cut lines was evaluated according to DIN EN ISO 2409 (0~5 levels are used to evaluate the adhesion of the coating, where 0 is the best level of adhesion and 5 is the worst level of adhesion). These results are summarized in Table 3 below.

Tape Release Test

Tape such as that available under the trade designation "3M 2525" (3M Company, St. Paul, MN) was adhered to coated samples and further pressed with a 2 pound roller. Tape release was then tested according to ASTM D3330 (180 degree peel) using an Imass SP-2000 Slip-Peel Tester (IMASS, Inc, Accord, MA) at a crosshead speed of 304.8 mm/min. These results are summarized in Tables 4 and 5 below. Formulations for First Layer of Aqueous Coating Composition on Metal Substrate

In Example 35, an FEP6300RG dispersion (15g, 75 wt %) and a PFA 6900RG dispersion (4g, 20 wt%) were weighed, and then mixed with 2-naphthol (0.4g, solid content, 10% in ethylene glycol; 2 wt %), glyoxal (0.4g, 40% in water; 2 wt%), and DAE (0.2g, 1 wt%). The resulting solution was coated on metal plates at 380⁰C for 10 min.

Examples 36-39 were prepared as described in Example 35 except that the compounding materials and ratios were varied as shown in the Table 3.

In Example 40, a THV dispersion (19g, 95 wt %) was weighed and then mixed with 2-naphthol (0.4g, solid content = 10% in ethylene glycol; 2 wt%), glyoxal (0.4g, 40% in water; 2 wt%), and DAE (0.2g, 1 wt%). The resulting solution was coated on metal plates at 200⁰C for 10 min. Examples 41-43 were prepared as described in Example 40 except that the compounding materials and ratios were varied as shown in the Table 3.

First Aqueous Coating Composition Layer Plate Metal Plate Coating and Cure

Commercial smooth stainless steel (SS) and aluminum plates (A3, 0.06" (1.54 mm) thick, 4"x6" (2.54 x 15.2 cm)) were directly purchased, wiped with acetone twice and dried at room temperature until the solvent completely volatilized. The clean metal plates were then coated without further treatments. Aqueous fluoropolymer coating

compositions with the formulations designated in Table 3 were coated on the metal plates with a coated bar, such as that available under the trade designation "GAROCO" from Paul N. GARDNER Company, Inc., Florida. The resulting coatings were dried at room temperature and then cured in an oven. Specifically, Examples 35-39 were cured at 300⁰C for 10 minutes and Examples 40-43 were cured at 200⁰C for 10 minutes. Unless otherwise noted, the metal was SS and the thickness of the wet coatings on the plates was 12.7 μm (0.5 mil) in wet weight. Adhesion of the first layer of aqueous coating composition to the metal plates was measured according to the procedures set forth in the section above entitled Adhesion Strength Test. The results are summarized in Table 3 below. Table 3

First Aqueous Coating Composition Layer Scissors Coating and Cure

All of scissor blades were coated by using dipping method. The coating/dipping process was carried out using a layer building device, such as a device available under the trade designation "KSV Layer Builder" from KSV Instruments LTD., Finland. The scissor blades were firmly fixed on a clip and then dipped into the aqueous coating compositions disclosed in Examples 35 and 36 in Table 3 above at a rate of 10 cm/min under the control of a computer. After immersion in the aqueous coating composition for 1 min, the scissor blades were raised. The coated blades were dried at room temperature and cured at 300⁰C for 10 min.

Examples 44-46 were prepared by mixing 100 grams of the aqueous fluoropolymer coating composition based on Example 35 in Table 3 above with 0.2g of an antifoam agent commercially available under the trade designation "Dynol HOD" from Air Products LTD. US, 0.4g of a first wetting agent commercially available under the trade designation "Dynol S440" from Air Products LTD. US, and 0.2g of a second wetting agent commercially available under the trade designation "Dynol 104BC" from Air Products LTD. US . This mixture was mixed for 30 minutes at ambient conditions. The resulting mixture was used as an aqueous coating composition to coat scissors blades.

The Examples were dip coated and cured onto acetone degreased scissor blades, such as scissor blades available under the trade designations "8" 3M Scotch PRECISION" and "3M Scotch TITANIUM" from 3M Company, St. Paul, MN, using the dip coating procedure described above. Contact angles were measured according the section above entitled Contact Angle Measurement and are shown in Table 4. The coated scissors were tested according to the section above entitled Adhesion Strength Test and the results are summarized in Table 4 below. In addition, even after thermal treatment for 10 minutes at 300⁰C, the first layer of the aqueous fluoropolymer coating composition was transparent, or did not alter the look of the surface of the scissors to the naked eye.

Comparative Examples CE5, CE6 and CE7 were the same type of scissor blades as those used in Examples 44-48 but they were not coated with the aqueous fluoropolymer coating composition. Contact angles were measured according the section above entitled Contact Angle Measurement and are shown in Tables 4 and 5. These comparative examples were tested according to the section above entitled Adhesion Strength Test, with the results summarized in Tables 4 and 5.

Table 4

One Layer Scissors Blade Coating and Cure

Examples 47 and 48 were prepared by mixing 100 grams of the aqueous fluoropolymer coating composition based on Example 36 in Table 3 above with 0.2g of an antifoam agent commercially available under the trade designation "Dynol HOD" from Air Products LTD. US, 0.4g of a first wetting agent commercially available under the trade designation "Dynol S440" from Air Products LTD. US, and 0.2g of a second wetting agent commercially available under the trade designation "Dynol 104BC" from Air Products LTD. US . This mixture was mixed for 30 minutes at ambient conditions. The resulting mixture was used as an aqueous coating composition to coat scissors blades.

The Examples were dip coated and cured onto acetone degreased scissor blades, such as scissor blades available under the trade designations "8" 3M Scotch PRECISION" and "3M Scotch TITANIUM" from 3M Company, St. Paul, MN, using the dip coating procedure described above in the section entitled First Aqueous Coating Composition Layer Plate Coating and Cure. Contact angles were measured according the section above entitled Contact Angle Measurement and the results are shown in Table 5 below. The coated scissors were tested according to the section above entitled Adhesion Strength Test and the results are shown in Table 5 below. In addition, even after thermal treatment for 10 minutes at 300⁰C, the first layer of the aqueous fluoropolymer coating composition was transparent, or did not alter the look of the surface of the scissors to the naked eye.

Table 5

Corrosion Resistance

Two scissor blades, commercially available under the trade designation "Scotch

PRECISION", were half coated with a composition according to that disclosed as

Example 36 in Table 3 above while the other half was left uncoated. One of the half coated scissor blades was immersed in a boiling solution of sodium chloride (5 wt %) for

24 hours. The other half coated scissor blade was immersed in boiling oxalic acid (30 wt %) for 3 minutes and then placed in a boiling solution of sodium hydroxide (40 wt %) for 3 minutes. After both tests, clear rust traces were observed with the naked eye on the uncoated half of the scissor blade side without coating while the coated side did not exhibit such traces of rust.

Coating Procedures for Examples 49-61 and Comparative Example 5

Clean 4x4 inch stainless steel or aluminum plates were dip coated in the solutions or dispersions. The dipping process used for all examples was carried out with a KSV Layer Builder (KSV Instruments LTD, Finland). The metal plates were firmly fixed on a clip and the clip-plate assembly was descended into the aqueous mixture at a rate of 107 cm/min (except examples 49-53 and 60-61 which was 90 cm/min) under the control of a computer. After immersion for 30 seconds the clip-plate assembly was ascended at the same rate (except examples 49-53 and 60-61 which were ascended at a rate of

19cm/min) and the coated plates were dried at room temperature and then fully cured at

300⁰C for 15 minutes. For examples 49-53 and 60-61 the coated metal was dried in an oven at 100⁰C for 10 minutes. For examples 49-53 the coated metal was then fully cured at 38O⁰C for 20 minutes and for examples 60-61 the coated metal was fully cured at 32O⁰C for 20 minutes. Comparative example CE5 and examples 54-57 were further

electrostatically powder top coated with "PFA 6503C" as per the "Peel Test Sample

Preparation" except that the final powder coated metal strips were immersed in boiling water for 3 days (40 hours for comparative example 5). After cooling to room temperature the residual water on the samples was removed with filter paper and the edges of each strip were scraped with a sharp blade to remove any coating that may have accumulated at the edges of the specimens.

Table 7

NA=not applicable or not done

1 : stainless steel and galvanized steel

1 : % transmittance was done with a "HAZE-GARD DUAL AT-4727" (BYK-Gardner

GmBH, Germany). Results are expressed as the mean of 3 independent experiments with deionized water used as a control. Numbers in parentheses are standard deviation.

The transparency of the water (96.4%) was used to calibrate the final %T (% transmission) of the solutions.

2: "cal"=calibrated based on the water

3 : PTFE primer/PFA powder coated sample immersed only 40 hours in boiling water vs 3 days for other samples

Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention.

Claims

What is claimed is:

1. An aqueous fluoropolymer coating composition comprising:

(a) a substantial amount of water;

(b) a fluoropolymer;

(c) a base; and

(d) at least one functional additive selected from at least one hydrophilic aldehyde, at least one hydroxyaromatic compound, and combinations thereof,

wherein the hydroxyaromatic compound comprises at least one hydroxy group bonded directly to an aromatic carbon.

2. The aqueous fluoropolymer coating composition of claim 1 is a perfluoropolymer comprising tertiary carbon.

3. The aqueous fluoropolymer coating composition of claim 1 wherein the fluoropolymer is selected from FEP, ETFE, PFA, THV, PVDF, PFE, PTFE and combinations thereof.

4. The aqueous fluoropolymer coating composition in any of the preceding claims wherein the base is selected from organic amine.

5. The organic amine of claim 4 is selected from diaminoethane, diaminopropane, phenylendiamine diethanolamine, diethylenetriamine, polyethyleneimine,

N(CH₂CH₂NH₂)_S, and combinations thereof.

6. The aqueous fluoropolymer coating composition in any of the preceding claims wherein the hydrophilic aldehyde is selected from glyoxal, glutaraldehyde, 2-hydroxy-l- napthaldehyde, terephthaldehyde, furfural, and combinations thereof.

7. The aqueous fluoropolymer coating composition any of the preceding claims wherein the hydroxyaromatic compound is selected from polyphenol compounds.

8. The hydroxyaromatic compounds of any preceding claims further comprise water soluble group.

9. The hydroxyaromatic compounds of any preceding claims further comprise electron- donating group.

10. The aqueous fluoropolymer coating composition any of the preceding claims wherein the hydroxyaromatic compound is selected from 2-napthol, 2-fluorophenol, resorcinol, hydroquinol, phloroglucin, bisphenol A, catechol, 4,4'-Sulfonyldiphenol, ,4-bis(4- hydroxyphenyl)-valeric acid, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl thioether, 4,4'-dihydroxydiphenyl ketone, HOPh-CEt(OH)-CEt(OH)-PhOH and combinations thereof.

11. The aqueous fluoropolymer coating composition any of the preceding claims further comprising a co-solvent.

12. The aqueous fluoropolymer coating composition any of the preceding claims further comprising a film former.

13. The aqueous fluoropolymer coating composition any of the preceding claims further comprising water-born nanoparticle metal oxide.

14. The aqueous fluoropolymer coating composition any of the preceding claims further comprising a leveling agent.

15. The aqueous fluoropolymer coating composition any of the preceding claims wherein the fluoropolymer is selected from at least one of a fluoroelastomer, a fluoroplastic, and combinations thereof.

16. A coated article comprising:

(a) a substrate; and

(b) a first layer derivable from an aqueous fluoropolymer coating composition comprising a substantial amount of water, a fluoropolymer, a base, and at least one functional additive selected from at least one hydrophilic aldehyde, at least one hydroxyaromatic compound, and combinations thereof,

17. The coated article of claim 16 wherein the substrate is metal.

18. The coated article of any of claims 16 and 17 further comprising a second layer comprising a fluoropolymer.

19. The second layer of claim 18 is selected from perfluoropolymers.

20. The coated article of any of claims 16 to 19 wherein the fluoropolymer of the first layer is a copolymer of TFE and a perfluoroolefm and the fluoropolymer of the second layer is fluoroplastic.

21. The coated article of claim 20 wherein the fluoroplastic of the first layer is a blend of two copolymers, wherein a first copolymer comprises TFE and a perfluoroolefm and a second copolymer comprises TFE and a perfluoro(alkylvinylether).

22. The coated article of any of claims 16 to 21 wherein the fluoropolymer of the second layer is fluoroelastomer.

23. The coated article of any of claims 16 to 22 wherein the first layer has a wet thickness of less than 0.06 mm (2.4 mil).

24. The coated article of any of claims 16 to 23 wherein the substrate is stainless steel or aluminum.

25. The coated article of claim 16 wherein the substrate is stainless steel, and further wherein a peel strength between the substrate and a combination of the first layer and second layer is greater than 0.12 N/mm.

26. The coated article of claim 16 wherein the substrate is aluminum, and further wherein a peel strength between the substrate and a combination of the first layer and second layer is greater than 0.50 N/mm.

27. The coated article of any of the preceding claims wherein the base is selected from diaminoethane, 1.3-diaminopropane, phenylendiamine diethanolamine,

diethylenetriamine, polyethyleneimine, N(CH₂CH₂NH₂)S and combinations thereof.

28. The coated article of any of the preceding claims wherein the hydrophilic aldehyde is selected from glyoxal, glutaraldehyde, 2-hydroxy-l-napthaldehyde, terephthaldehyde, furfural, and combinations thereof.

29. The coated article of any of the preceding claims wherein the hydroxyaromatic compound is selected from 2-napthol, 2-fluorophenol, resorcinol, hydroquinol, phloroglucin, bisphenol A, catechol, 4,4'-sulfonyldiphenol, ,4-bis(4-hydroxyphenyl)- valeric acid, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl thioether, 4,4'- dihydroxydiphenyl ketone, HOPh-CEt(OH)-CEt(OH)-PhOH, and combinations thereof.

30. The coated article of any of the preceding claims wherein the fluoropolymer is selected from at least one of a perfluoroelastomer, a fluoroplastic, and combinations thereof.