WO2008103593A1

WO2008103593A1 - Powder coating fluoropolymer compositions with deprotectable aromatic materials

Info

Publication number: WO2008103593A1
Application number: PCT/US2008/053944
Authority: WO
Inventors: Blake E. Chandler; Gregg D. Dahlke; Naiyong Jing; Zhigang Yu
Original assignee: 3M Innovative Properties Company
Priority date: 2007-02-19
Filing date: 2008-02-14
Publication date: 2008-08-28

Abstract

Described are compositions comprising a) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof; b) a base; c) a fluoroplastic; and optionally, d) a phase transfer catalyst. Also described are multi-layer articles comprising a substrate and a first layer. The first layer may comprise i) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof; ii) a base; iii) a fluoroplastic; and, optionally, iv) a phase transfer catalyst. Also provided are methods of making coatable compositions, and methods of bonding compositions to substrates.

Description

POWDER COATING FLUOROPOLYMER COMPOSITIONS WITH DEPROTECTABLE AROMATIC MATERIALS

Summary The present invention relates to a powder coating fluoropolymer composition comprising an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof; a base; a fluoroplastic; and optionally a phase transfer catalyst. In one aspect, the present invention relates to a composition comprising an aromatic material wherein the aromatic material is selected from a polythiol aromatic compound or resin; a hydroxythiophenol compound or resin; a catechol novolak resin; a catechol cresol novolak resin; a polyhydroxy aromatic resin or compound comprising at least one aromatic ring having at least one hydroxyl group attached directly to the aromatic ring; or a combination thereof. The composition may further comprise a base, a fluoroplastic, and optionally a phase transfer catalyst.

In another aspect, the present invention relates to a composition comprising an aromatic material wherein the aromatic material is selected from an aromatic material having exactly one protected hydroxyl group, wherein the aromatic material is free of thiol groups (protected or unprotected), and wherein the hydroxyl group is bonded to an aromatic carbon. The composition may further comprise a base, a fluoroplastic, and optionally a phase transfer catalyst.

In a further aspect, the present invention relates to a composition comprising an aromatic material wherein the aromatic material is selected from (i) an aromatic compound; (ii) an aromatic resin; (iii) a heteroaromatic compound; and (iv) a heteroaromatic resin, wherein the aromatic material has at least one protected amine group bonded to an aromatic or heteroaromatic ring. The composition may further comprise a base, a fluoroplastic, and optionally a phase transfer catalyst.

Detailed Description The present description relates to derivatives of protected aromatic phenols, amines, and nitrogen-containing aromatic materials, which may be combined with a base and optionally a phase transfer catalyst. In some embodiments, such compositions promote efficient adhesion of fluoroplastics to substrates, in particular metallic substrates. The compositions described herein may be applied to substrates, for instance, by solvent-free conditions such as powder coating.

In some embodiments, aromatic materials having protected moieties display a capability to bond fluoroplastics to substrates (especially metal substrates) at conditions normally employed for fluoroplastic powder coating procedures. In particular embodiments, no surface roughening treatments are required to yield such bonding.

The aromatic material has a protected polar group covalently bonded thereto. Upon deprotection, the protected polar group forms a polar group having a hydrogen atom bonded to an N, O, or S atom. Examples of polar groups having a hydrogen atom covalently bonded to an N, O, or S atom include -SH, -OH, -NH₂, -NHR, RNR', wherein each R and R independently represents H or an optionally substituted alkyl, aryl, alkaryl, or aralkyl group. In some embodiments, R and R may form a cyclic structure that includes a N atom. In certain embodiments, that cyclic structure may be an aromatic ring. Of course there are many additional polar groups that have a hydrogen atom covalently bonded to an N, O, or S atom that may also be used. Salts (e.g., alkali metal salts, alkaline earth salts) of such polar groups may be readily obtained, for example, by reaction with a suitable base.

The protected polar groups may comprise, for example, protected hydroxyl groups, protected amine groups, protected thiol groups, and combinations thereof. The aromatic material may be prepared by any suitable method such as, for example, by protecting polar groups on a corresponding aromatic material. Typically, polar groups having one or more hydrogen atoms bonded to an N, O, or S atom may be converted to a protected form by reaction with a suitable reagent that reacts with (i.e., protects) the polar group and converts it to a form without hydrogen atoms bonded to an N, O, or S atom, or a salt thereof. Subsequent deprotection regenerates the original polar group. Methods for protecting polar groups having one or more hydrogen atoms bonded to an N, O, or S atom, and deprotecting the corresponding protected polar groups, are widely known and are described, for example, by P.J. Kocienski in "Protecting Groups", 3rd ed., Stuttgart: Thieme, 2004 and by T.W. Greene and P.G.M. Wuts in "Protective Groups in Organic Synthesis", 2nd ed., New York: Wiley-Interscience, 1991.

Examples of compounds having protected hydroxyl groups include: ethers such as, for example, tert-butyl ethers, isopropyl ethers, benzyl ethers, p-methoxyben/y! ethers, 3 ,4-di-mcthoxy benzyl ethers, trityl ethers, allyl ethers, phenyl ethers, benzyl ethers, alkoxyraethyl ethers, raethoxy methyl ethers, 2-raethoxyethoxymethyl ethers, bcnzyloxymethyl ethers, p-methoxybcnzyloxymethyl ethers, silyl ethers (e.g., triracthylsilyl ethers, triethylsilvl ethers, tcrt-bulyldimetbvlsilyl ethers, tert- bulyldiphenylsilyl ethers, triisopropylsilyi ethers, diethylisopropylsilyl ethers, thcxyldiniethylsilyl ethers, triphcnylsilyl ethers, di-tcrt-butyimcthylsilyl ethers, and 2- (trimεthylsilyl)ethoxymethyl ethers), and methylthiomethyl ethers; and acetals or hemiacetals such as, for example, tetraliydropyranyl ethers; esters such as. for example, acetate esters, benzoate esters, pivalate esters, methoxyaceiate esters, fluoroaeetaie esters, chloroacetate esters, phosphate esters and levulinate esters; and carbonates such as, for example, benzyl carbonates, p-nitroben/yl carbonates, tert-butyi carbonates, 2,2,2- trichlorocthyl carbonates, 2-(trimethyisilyl)cthyl carbonates, and allyl carbonates. Useful protecting groups for hydroxyl groups include, for example, t-butoxycarbonyloxy, t- butylcarbamato, and trialkylsiloxy groups. t-Butyl derivatives (e.g., t-butyl esters, t-butyl carbonates) are particularly useful in many cases as they generate a gaseous byproduct

(isobutylene) that may typically be readily removed.

Examples of compounds having protected diol groups (or poly hydroxy groups generally) include 0,0-acetals such as, for example, isopropylidene acetals, cyclopentylidcnc acetals, cyclohexylidene acetals, arylmethylenc acetals, methylene acetals, and dipbenylmethylcne acetals; 1.2-diaceta3s such as, for example, cyclohcxane- 1.2-diacetals and butane -2, 3-diacetaLs; and silylene derivatives such as, for example, 1.1 ,3,3-tetraisopiOpyldisiloxanylidcnc derivatives.

Examples of compounds having protected thiol groups include: thioethers such as, for example, tcrt-butyl thioethers. benzyl and substituted benzyl thioethers (e.g., trityl thioethers); 2-(trimethylsilyl)ethyl thioethers; 2-cyanoethyl thioethers; 9-fluorenylmethyl thioethers; and thiocarbonate derivatives.

Examples of compounds having protected amine groups include: imides and amides, such as, for example, phthaloyl and tctrachlorophthaloyl imides, and dithiasuccinyl imides, and fluoroamides, such as for example, trifluoroacclamidcs; carbamates such as, for example, methyl carbamates, ethyl carbamates, tert-butyl carbamates, benzyl carbamates, allyl carbamates, 9-fluorenylmcthyl carbamates, 2- (trimethylsilyl)ethyl carbamates, and 2,2,2-trichloroethyl carbamates; sulfonyl derivatives such as, for example, aryl sulfonamides (e.g., p-tolueπesulfonamidcs); N-sulfenyl derivatives; N₅O-acctals such as, for example, metboxymelbv famines; tria/inanones such as, for example, l,3-dimethy!-l,3,5-triazinan-2-αne; N-silyl derivatives such as, for example. N-trirnethylsilylatnine derivatives, 2.2₅5,5.-tctrametbvl-l-aza-2,5- disilacyclopentane derivatives; and inline and enamine derivatives such as, for example,

N-bisfmethylthio)mcthyleneimine and N-diphenylmcthyleneamine. In some embodiments, the amine in the amine group is non-hindered, i.e., the amine functional group is not surrounded by a crowded steric environment.

In some embodiments, the aromatic material may be a resin. As used herein, the term "resin" is a polymer or oligomer whereas a "compound" is not a polymer or oligomer. For example, an aromatic material with too few or no repeating units typical of a polymer or oligomer is a "compound". Resins may be prepared by polymerizing or oligomerizing one or more polymerizable monomers wherein at least one of the monomers has a protected polar group. There are many readily apparent synthetic methods of making polymerizable monomers having one or more protected polar groups such as those as described hereinabove. For example, a moiety having one or more protected polar groups may be attached to a polymerizable moiety. This technique is particularly useful for monomers wherein the polar group is incompatible with the polymerizable moiety. In another exemplary method, the polar group(s) of a polar group-containing polymerizable monomer (e.g., 2-hydroxyethyl (meth)acrylate) may be directly protected.

Examples of free-radically polymerizable monomers that have at least one protected polar group include: free-radically polymerizable monomers having protected carboxyl groups such as, for example, t-butyl or trialkylsilyl esters and tetrahydropyranyl esters of (meth)acrylic acid; free-radically polymerizable monomers having protected hydroxyl groups such as, for example, vinyl trifluoroacetate and silyl ethers, t-alkyl ethers, t-butyl carbonates, and t-butyl or alkoxyalkyl ethers of hydroxyalkyl (meth)acrylates; free- radically polymerizable monomers having protected amino groups such as, for example, t- butylcarbamatopropyl (meth)acrylate and N-vinyl-t-butyl carbamate; free-radically polymerizable monomers having protected amido groups such as, for example, N₅N- bis(trimethylsilyl)(meth)acrylamide, N-alkyl-N-trimethylsilyl(meth)acrylamides, and related compounds; and free-radically polymerizable monomers having protected sulfhydryl groups such as, for example, include silyl thioethers, t-alkyl thioethers, and alkoxyalkyl thioethers derived from mercaptoalkyl (meth)acrylates.

Examples of anionically polymerizable monomers that have at least one protected polar group include: anionically polymerizable monomers having protected carboxyl groups such as, for example, t-butyl esters, trialkylsilyl esters, and tetrahydropyranyl esters of (meth)acrylic acid; anionically polymerizable monomers having protected hydroxyl groups, such as, for example, silyl ethers, t-alkyl ethers, and alkoxyalkyl ethers of hydroxyalkyl (meth)acrylates; anionically polymerizable monomers having protected amino groups such as, for example, t-butylcarbamatoalkyl (meth)acrylates and N-vinyl-t- butyl carbamate; anionically polymerizable monomers having protected amido groups such as, for example, N,N-bis(trialkylsilyl)(meth)acrylamides, N-alkyl-N-trialkylsilyl- (meth)acrylamides, and related compounds; and anionically polymerizable monomers having protected sulfhydryl groups such as, for example, silyl thioethers, t-alkyl thioethers, and alkoxyalkyl thioethers of sulfhydrylalkyl (meth)acrylates. Examples of cationically polymerizable monomers that have at least one protected polar group include: cationically polymerizable monomers having protected hydroxyl groups such as, for example, t-butyl, trialkylsilyl, and tetrahydropyranyl vinyl ethers; vinyl esters (e.g., vinyl benzoate); vinylene carbonate; and alkyl vinyl carbonates. Examples of cationically polymerizable monomers having protected sulfhydryl groups include: t-butyl, trialkylsilyl, and tetrahydropyranyl vinyl thioethers, vinyl thioesters (e.g., vinyl thiobenzoates), and alkyl vinyl thiocarbonates.

The resin aromatic material may typically be prepared by polymerizing monomers comprising one or more monomers comprising a protected moiety. The resin aromatic material may also be prepared by protecting pendant groups on a resin such as, for example, a resin having one or more pendant groups with a hydrogen atom bonded to an

N, S, or O atom or a salt thereof.

Monomers comprising a protected moiety may be homopolymerized or copolymerized with one or more additional monomers, including additional monomers further comprising a protected moiety. Suitable polymerization methods include, for example, cationic, anionic, free radical, metathesis, and condensation polymerization methods, and combinations thereof. In many of these polymerization techniques inclusion of amine, hydroxy, or thiol group- containing monomers can lead to undesirable side reactions such as, for example, Michael addition, chain transfer, and/or termination. For example, in the case of anionic polymerization, it can be difficult or impossible to polymerize or copolymerize monomers having one or more hydrogen atoms bonded to an N, O, or S atom, since the polymerization is typically quenched by abstraction of the proton by the initiator and/or growing polymer.

Additional methods and equipment for making deprotectable resin aromatic materials are described in, for example, U.S. Pat. Appl. Publ. No. 2004/0024130 Al (Nelson et al.). For example, the deprotectable resin aromatic material may be synthesized in processes that are carried out in batch or semi-batch reactors; continuous stirred tank reactors; tubular reactors; stirred tubular reactors; plug flow reactors; temperature controlled stirred tubular reactors as described, for example, in U.S. Pat. App. Publ. Nos. 2004/0024130 Al and 2003/0035756 Al (Nelson et al.); static mixers; continuous loop reactors; extruders; shrouded extruders as described, for example, in U.S. Pat. No. 5,814,278 (Maistrovich et al.); and pouched reactors as described in PCT Publ. WO

96/07522 (Hamer et al.) and U.S. Pat. No. 5,902,654 (Davidson et al.). Polymerizations may take place in bulk, solution, suspension, emulsion, and/or in an ionic or supercritical fluid. Specific methods of making resin aromatic materials include atom transfer radical polymerization, reversible addition- fragmentation chain transfer polymerization, and nitroxyl or nitroxide (stable free radical or persistent radical) mediated polymerization.

Typically, the resin aromatic material should be melt-processible, although this is not a requirement. For example, if the resin aromatic material is soluble in a solvent, then the components may be combined in that solvent. The resin aromatic material may have any form such as, for example, a linear or branched homopolymer, random copolymer, tapered or gradient copolymer, or block copolymer (e.g., diblock and triblock copolymers), including linear, comb, ladder, and star forms thereof, as long as it is not covalently crosslinked to form a three-dimensional polymeric network that is neither melt- processable nor solvent-soluble.

The resin aromatic material may be free of hydrogen atoms covalently bonded to a heteroatom (e.g., N, S, O), however the resin aromatic material may contain hydrogen atoms that are covalently bonded to a heteroatom. Removing a protecting group (i.e., "deprotection") according to the present description includes, for example, base catalyzed deprotection and/or thermolysis of one or more protected polar groups.

Generally, the greater the degree of deprotection, the greater will be the number of polar groups having N-H, O-H, and/or S-H bonds on an at least partially deprotected aromatic material, which in turn typically tends to increase the rate and/or degree of fluoropolymer bonding to a substrate. The rate and/or extent of bonding of a fluoropolymer to a substrate (e.g., a metallic substrate) may also be influenced by variables such as the presence of solvent, temperature of heating a multi-layer composition comprising a first layer and a substrate, the chemical nature and/or concentration of the components in a first layer, (e.g., aromatic material, fluoropolymer, base, substrate and/or optional phase transfer catalyst), amount of time spent heating the multi-layer composition, and thickness of the layers in a multi-layer composition.

In some embodiments, the aromatic material is selected from an aromatic material wherein the aromatic material is selected from a polythiol aromatic compound or resin; a hydroxythiophenol compound or resin; a catechol novolak resin; a catechol cresol novolak resin; a polyhydroxy aromatic resin or compound comprising at least one aromatic ring having at least one hydroxyl group attached directly to the aromatic ring; or a combination thereof. In some embodiments, aromatic materials are preparable from, for instance, polyhydroxy aromatic compounds having at least one aromatic ring, which ring has at least one hydroxyl group attached directly to it and at least one hydroxyl group is capable of forming a phenolate salt. In one aspect, the polyhydroxy aromatic compounds comprise at least one aromatic ring having a plurality of hydroxyl groups attached directly to the aromatic ring. Examples of suitable polyhydroxy aromatic compounds include resorcinol, pyrogallol, phloroglucinol, catechol, 1,5-dihyrdroxynaphthalene, and 4,4'- dihyroxybiphenyl, hydroquinone, or a combination thereof.

In further embodiments, aromatic materials are preparable from polythiol aromatic materials, and hydroxythiophenol aromatic materials. An example of a suitable polythiol aromatic material is benzene- 1,4-dithiol. An example of a suitable hydroxythiophenol compound is 4-mercaptophenol. In yet further embodiments, aromatic materials are preparable from a resin. For example, useful are polyhydroxy aromatic resins that comprise at least one aromatic ring having at least one hydroxyl group attached directly to the aromatic ring, and in certain embodiments at least one aromatic ring has at least two hydroxyl groups attached directly to the aromatic ring. Also useful are polythiol aromatic resins, hydroxythiophenol resins, phenolic resins (e.g., those available under the trade name designation DURITE from Borden Chemical Company), catechol novolak resin, and/or catechol cresol novolak resin, along with combinations of these materials.

In other embodiments, the aromatic material is selected from an aromatic material having exactly one hydroxyl group, wherein the aromatic material is free of thiol groups, and wherein the hydroxyl group is bonded to an aromatic carbon.

In some embodiments, aromatic materials are preparable from mono-hydroxy aromatic materials having at least one aromatic ring wherein the aromatic material is free of thiol groups. The hydroxyl group of the mono-hydroxy aromatic material is bonded to an aromatic carbon atom. In some embodiments, the aromatic material is a mono-cyclic aromatic compound such as phenol or a substituted phenol. In other embodiments, the aromatic material is a poly-cyclic aromatic compound such as naphthol or a substituted naphthol.

Particular examples of mono-hydroxy aromatic materials from which the aromatic materials are preparable include pentafluorophenol, nitrophenol, fluorophenol, naphthol, methoxynaphthol, fluorenol, or a combination thereof. It is understood that the aromatic groups contemplated by the present application may be substituted by any groups known to organic chemistry, including, for instance, a hydrogen atom, an alkyl group (e.g., having from 1 to 10 carbon atoms), an alkylene group (e.g., having from 1 to 10 carbon atoms), an aryl group (e.g., having from 5 to 20 carbon atoms), an alkaryl group (e.g., having from 6 to 25 carbon atoms), a nitro group, a cyano group, an acyl group, an Ar- S(O)- group wherein Ar is an aromatic group, an Ar-S(O)2~ group wherein Ar is an aromatic group, an Ar2-P(O)- group wherein Ar is an aromatic group, a halogen atom, and any combination thereof. In some particular embodiments, the mono-hydroxy aromatic materials from which the aromatic material is preparable has a structure of the general formula:

wherein Rl, R2, R3, R4, and R5 are each independently selected from a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an alkylene group having 1 to 10 carbon atoms wherein the alkylene group forms an alkylene fused ring with a group in the ortho position, an alkenylene group having 1 to 10 carbon atoms wherein the alkenylene group forms an alkenylene fused ring with a group in the ortho position, an aryl group having 5 to 20 carbon atoms, an alkaryl group having 6 to 25 carbon atoms, a nitro group, a cyano group, an acyl group, an Ar-S(O)- group wherein Ar is an aromatic group, an Ar-S(O)2~ group wherein Ar is an aromatic group, an A^P(O)- group wherein Ar is an aromatic group, and a halogen atom. In particular embodiments, at least one of Rl to R5 is an aryl group or an alkaryl group. It is understood throughout that the alkyl, alkaryl, alkylene, and alkenylene groups described as aromatic substituents may be non-fluorinated, partially fluorinated, or perfluorinated. Further, the alkyl, alkaryl, alkylene, and alkenylene groups described as aromatic substituents may be linear or branched. In certain embodiments, it may be desirable to either increase or decrease the acidity of the hydroxyl group attached to the aromatic ring in precursor from which the aromatic material is preparable. One having ordinary skill in the art recognizes the ability to increase the acidity of the hydroxyl group by adding electron- withdrawing substituents to the aromatic ring, as well as the ability to decrease the acidity of the hydroxyl group by adding electron-donating substituents to the aromatic ring. Such effects are described, for instance, in "Perspectives on Structure and Mechanism in Organic Chemistry", Carroll, Brooks/Cole, Pacific Grove (1998) (particularly pages 366-86, discussing substituent effects and linear free energy relationships).

Examples of precursor materials that can be used to prepare aromatic materials as described herein, wherein at least one of Rl to R5 is selected from an alkylene group having 1 to 10 carbon atoms wherein the alkylene group forms an alkylene fused ring with a group in the ortho position, include those having a carbon backbone such as:

Examples of aromatic materials wherein at least one of Rl to R5 is selected from an alkenylene group having 1 to 10 carbon atoms wherein the alkenylene group forms an alkenylene fused ring with a group in the ortho position include those having a carbon backbone such as:

In some embodiments, the alkenylene-fused ring is an aromatic ring, such as when the alkenylene fused ring forms a naphthyl ring. Indeed, particular embodiments of precursor materials include mono-hydroxy naphthalene and substituted mono-hydroxy naphthalene.

In yet another embodiment, the aromatic material is selected from an aromatic compound, an aromatic resin, a heteroaromatic compound, and a heteroaromatic resin. The aromatic compounds and aromatic resins may have at least one aromatic ring, which at least one aromatic ring has at least one protected amine group bonded to the aromatic ring.

Appropriate protected amine groups include, for example, protected primary amines and protected secondary amines.

In some embodiments, the precursor material from which the aromatic material is preparable may comprise two or more amine groups. The two or more amine groups may, for instance, be arranged as substituents on the same aromatic ring, there may be one aromatic amine and one aliphatic amine, there may be one amine group arranged as a substituent on one aromatic ring and a second amine group arranged as a substituent on a second aromatic ring, and the like. Those having ordinary skill in the art are capable of preparing such embodiments by synthetic methods well known in the art. In some embodiments wherein the aromatic material is selected from an aromatic compound or aromatic resin, the precursor material from which the deprotectable aromatic material is preparable comprises at least one aromatic ring selected from a phenyl ring, a naphthyl ring, a phenanthryl ring, an anthracyl ring, and combinations thereof. As distinguished in the present description, an aromatic compound or resin differs from a heteroaromatic compound or resin in that all of the aromatic rings in an aromatic material have only carbon atoms in the aromatic ring. Heteroaromatic compounds and resins, as that term is used in the present description, indicates that at least one of the aromatic rings present in the material comprises carbon atoms and at least one of nitrogen, sulfur, or oxygen.

In particular embodiments, the aromatic ring or rings present in an aromatic resin or an aromatic compound is selected from a biphenyl group, a phenanthryl group, an anthracyl group, an oxy biphenyl group, a binaphthyl group, a tolyl group, and combinations thereof. Examples of such embodiments include, for instance, 3,3'- diaminobenzidine; 9,10-diaminophenanthrene; 1,8-diaminonaphthalene; 1,1'- binaphthalene-2,2'-diamine; 2,3-diaminotoluene; 1-naphthylamine; l-amino-8-naphthol-2- sulfonic acid; 2-aminoanthracene; and combinations thereof.

In further embodiments, it may be desirable to either increase or decrease the acidity of the amine group attached to the aromatic ring in the precursor material.

Accordingly, some embodiments of the present description include those wherein at least one aromatic ring has a substituent other than a protected amine group and other than hydrogen. Such substituents may be selected from an alkyl group, a fluorinated alkyl group (including a perfluorinated alkyl group), a halogen atom, a hydroxyl group, an alkoxy group, a fluorinated alkoxy group (including a perfluorinated alkoxy group), a nitrile group, a nitro group, an aromatic group, a fluorinated aromatic group, an alkyl- aromatic group, a fluorinated alkyl-aromatic (including a perfluorinated(alkyl) aromatic, alkyl perfluorinated(aromatic), and perfluorinated (alkyl-aromatic) groups), an acyl group, a carboxyl group, a sulfonic acid group, and combinations thereof. In further embodiments, the aromatic material may be selected from a heteroaromatic compound and a heteroaromatic resin. The heteroaromatic compound or heteroaromatic resin may further have at least one protected amine group bonded to a heteroaromatic ring. In some particular embodiments, the protected aromatic material comprises two or more amine groups, at least one of which is protected. Further, the heteroaromatic compound or heteroaromatic resin may have at least one heteroaromatic ring having two or more amine groups, at least one of which is protected, bonded directly to the heteroaromatic ring. By "bonded directly", as used herein, it is meant that a substituent is covalently bonded to a ring atom of an aromatic or heteroaromatic ring.

Further, the heteroaromatic compounds or heteroaromatic resins described herein may have a heteroaromatic ring that contains a nitrogen atom, a sulfur atom, an oxygen atom, or some combination thereof, along with one or more carbon atoms. Particular examples of such heteroaromatic rings include, for instance, 1,10-phenanthroline; thiazole; benzimidazole; benzothiazole; imidazole; cyanuric acid; pyrimidine; benzotriazole; pyrazine; pyridine; and combinations thereof. Particular embodiments of heteroaromatic compounds or heteroaromatic reins include 2-aminobenzimidazole; 5-amino-l,10- phenanthroline; 2-aminobenzothiazole; 7-aminobenzothiazole; 2-aminothiazole; 2-amino-

4,6-dimethylpyrimidine; 2,3-diaminopyridine; and combinations thereof.

The heteroaromatic compounds and heteroaromatic resins may have at least one heteroaromatic ring, which at least one heteroaromatic ring has at least one protected amine group bonded to the aromatic ring. In further embodiments of the heteroaromatic compounds and heteroaromatic resins, it may be desirable to either increase or decrease the acidity of the deprotected amine group attached to the heteroaromatic ring in the precursor material.

Accordingly, some embodiments of the present invention include those wherein at least one heteroaromatic ring has a substituent other than the protected amine group and other than hydrogen. Such substituents may be selected from an alkyl group, a fluorinated alkyl group (including a perfluorinated alkyl group), a halogen atom, a hydroxyl group, an alkoxy group, a fluorinated alkoxy group (including a perfluorinated alkoxy group), a nitrile group, a nitro group, an aromatic group, a fluorinated aromatic group, an alkyl- aromatic group, a fluorinated alkyl-aromatic (including a perfluorinated(alkyl) aromatic, alkyl perfluorinated(aromatic), and perfluorinated (alkyl-aromatic) groups), an acyl group, a carboxyl group, a sulfonic acid group, and combinations thereof.

In particular embodiments of the heteroaromatic compounds and heteroaromatic resins, it is understood that, while a heteroaromatic group is present, there may be other aromatic groups present that are not heteroaromatic. In yet further embodiments, the aromatic material may be selected from heteroaromatic compounds and heteroaromatic resins wherein the aromatic material has a nitrogen atom in a heteroaromatic ring. In such embodiments, the aromatic material may further comprise at least one protected amine group bonded directly to the heteroaromatic ring. Further embodiments include heteroaromatic compounds or resins with at least two protected amine groups bonded directly to the heteroaromatic ring.

In other embodiments, the heteroaromatic ring may further comprise so-called heteroatoms other than nitrogen (e.g., sulfur and/or oxygen) in addition to at least one carbon atom. Such heteroaromatic rings include, for instance, 1,10-phenanthroline; thiazole; benzimidazole; benzothiazole; imidazole; cyanuric acid; pyrimidine; benzotriazole; pyrazine; pyridine; and combinations thereof. Particular aromatic materials include 1,10-phenanthroline; 2-aminobenzimidazole; 5 -amino- 1,10-phenanthroline; 2- aminobenzothiazole; 7-aminobenzothiazole; 2-aminothiazole; 2-amino-4,6- dimethylpyrimidine; 2,3-diaminopyridine; 2-phenylimidazole; cyanuric acid; benzotriazole, 2,3-pyrazinedicarboxamide; and combinations thereof.

In yet further embodiments, the aromatic materials are protected phenolic polymers. Phenolic polymers are those obtained by the polymerization or oligomerization of phenol with formaldehyde. The polymerization reaction occurs under either acidic or basic conditions. The strong base-catalyzed polymerization yields mixtures, referred to as resoles, resole prepolymers, or resole phenolics. Phenol-formaldehyde prepolymers, also referred to as novolacs, are obtained by using a ratio of formaldehyde to phenol of 0.75:1 to 0.85:1, sometimes lower. Since the reaction system is limited by formaldehyde, low molecular weight polymers can be formed and generally a much narrower range of products is formed compared to reactions yielding resoles. Although unsubstituted phenol is commonly used, various substituted phenols such as cresol (ortho, meta, para), para- butylphenol, recorcinol, and bisphenol-A may used for certain applications. Some use is also made of aldehydes other than formaldehyde, such as acetaldehyde, glyoxal, and 2- furaldehyde.

The preparation of aromatic materials as described herein may be achieved by methods familiar to those of ordinary skill in the art. These methods include, for instance, those described in Organic Synthesis, 2nd ed., Fuhrhop and Penzlin, VCH, Weinheim (1994); Some Modern Methods of Organic Synthesis, 3rd ed., Carruthers, University Press, Cambridge (1993); and March's Advanced Organic Chemistry: Reactions, Mechanism and Structure, 5th ed., Smith and March, John Wiley & Sons, (2001) (particularly chapters 11 and 13). In some embodiments, the present invention demonstrates that compositions comprising (a) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof; (b) a base; (c) a fluoroplastic; and optionally (d) a phase transfer catalyst may give excellent adhesion to a substrate, in particular, to metal substrates. In yet further embodiments, a boiling water test was used to show that the interlayer adhesion remained strong after exposure to several hours, e.g., after 24 hours. Surprisingly, the aromatic material, in some embodiments, aids with the adherence of fluoroplastics, and in particular perfluoroplastics, to metal surfaces. Fluoroplastics included in the present description include partially and perfluorinated fluoroplastics. Fluoroplastics include, for instance, those having interpolymerized units of one or more fluorinated or perfluorinated monomers such as tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), vinylidene fluoride (VDF), fluorovinyl ethers, perfluorovinyl ethers, as well as combinations of one or more of these. Fluoroplastics may further include copolymers comprising one or more of the fluorinated or perfluorinated monomers in combination with one or more non-fluorinated comonomer such as ethylene, propylene, and other lower olefins (e.g., C2-C9 containing alpha-olefins).

In other embodiments, polytetrafluoroethylene (PTFE) can be the fluoroplastic according to the present description. When PTFE is used, it may be used as a blend with another fluoropolymer and may also contain a fluoropolymer filler (in the blend or in the PTFE only).

More specifically, useful fluoroplastics also include those commercially available under the designations THV (described as a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride), FEP (a copolymer of tetrafluoroethylene and hexafluoropropylene), PFA (a copolymer of tetrafluoroethylene and perfluorovinyl ether), HTE (a copolymer of tetrafluoroethylene, hexafluoropropylene, and ethylene), ETFE (a copolymer of tetrafluoroethylene and ethylene), ECTFE (a copolymer of chlorotrifluoroethylene and ethylene), PVF (polyvinyl fluoride), PVDF (polyvinylidene fluoride), as well as combinations and blends of one or more of these fluoroplastics.

Any of the aforementioned fluoropolymers may further contain interpolymerized units of additional monomers, e.g., copolymers of TFE, HFP, VDF, ethylene, or a perfluorovinyl ether such as perfluoro(alkyl vinyl) ether (PAVE) and/or a perfluoro(alkoxy vinyl) ether (PAOVE). Combinations of two or more fluoroplastics may also be used. In some embodiments, fluoroplastics such as THV and/or ETFE and/or HTE are preferred. In addition to a fluoroplastic and an aromatic material as described above, the description also provides a base. Useful bases include oxides and/or hydroxides of magnesium, calcium, and other materials, as well as amines. In one aspect of the present invention, the base has a pKb below about 8, below about 6, below about 4, below about 2, around 0, or even below 0.6. The aromatic material and/or base described are generally present in small amounts relative to the weight of the fluoroplastic. For example, the amount of aromatic material and/or base (combined or individually) is generally below about 25 weight percent (wt %), below about 30 wt%; below about 20 wt%, or even below 15 wt% of the overall composition (the aromatic material, base, phase transfer catalyst, if any, and fluoropolymer, but not including the substrate when used). In another aspect, the aromatic material and/or base (combined or individually) are generally above about 0.1 wt%, above 0.5 wt%, or even above 1 wt% of the overall composition.

In some embodiments, a phase transfer catalyst (PTC) may be used in the compositions described herein. Such materials are known in the art and include, for instance, triphenylbenzylphosphonium salts, tributylalkylphosphonium salts, tetraphenylphosphonium salts, tetrabutylphosphonium salts, tributylbenzylammonium salts, tetrabutylammonium salts, tetrapropylammonium salts, tetrakis(2- hydroxyethyl)ammonium salts, tetramethylammonium salts, tetraalkylarsonium salts, tetraarylarsonium salts, and triarylsulfonium salts. Also contemplated are multi-valent onium salts. That is, salts that are multi-valent cations having two or more sites of positive charge. The salts described include, for instance, halide salts such as bromide, chloride, and iodide salts. Also contemplated herein are crown-ether containing phase transfer catalysts.

The PTC may be used in amounts below about 20 wt%, below about 15 wt%, below about 10 wt%, below about 5 wt%, or even below about 2 wt%, based on the total weight of the salt former compound, the aromatic material, PTC, and the fluoropolymer (but not including the weight of the substrate when used). In another aspect, the PTC may be used in amounts above 0.1 wt%, above 0.3 wt%, or even above 0.5 wt% based on the total weight of the salt former compound, the aromatic material, PTC, and the fluoropolymer. In some embodiments, it has been found that adjusting the amount of phase transfer catalyst can reduce the amount of bubbling observed in coatings as described herein. That is, some of the coatings described herein, when heated with a substrate, form bubbles. By adjusting the amount of phase transfer catalyst, the amount of bubbling can be reduced. For instance, in some embodiments, increasing the amount of phase transfer catalyst may reduce the amount of bubbling observed.

The compositions described herein may also include additives incorporated therein. Additives include, but are not limited to, inert fillers, anti-oxidants, stabilizers, pigments, reinforcing agents, lubricants, flow additives, other polymers, and the like. Yet further additives include metals and metal oxides such as, for instance, chromium oxide, chromium, zinc oxide, copper oxide, copper, nickel, titanium, stainless steel, aluminum, titanium dioxide, tin oxide, iron, iron oxide, and the like. Such metals may serve, for instance, as abrasion-resistant fillers or as compatibilizers. Also included herein are polymeric additives such as polyphenylene sulfide resin, epoxy resins, polyether sulfones, polyamide imide, polyetherether ketones, and combinations thereof. Other abrasion- resistant fillers include, for example, ceramics, high temperature and/or abrasion-resistant polymers, and the like. Further additives include those capable of imparting desirable coating properties such as increased hardness, abrasion resistance, electrical and thermal conductivity, and color. Flow additives are, generally, materials known to improve wetting and flow of polymer compositions (including low molecular weight materials, oligomers, polymers, and combinations thereof). Flow additives may, for instance, be selected from low viscosity materials and materials that are not compatible with the fluoropolymer (e.g., hydrocarbon polymers such as polyacrylates). In some embodiments, the compositions are substantially free of polymers other than the fluoroplastic or combination of fluoroplastics described above. That is, the compositions may include less than 25 wt% of a polymer additive, less than 10 wt%, less than 5% of a polymer additive, or even no polymer additive. In another aspect, the present description provides a composition comprising a reaction product of a) a fluoroplastic, b) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof, c) a base, and optionally d) a phase transfer catalyst. In yet a further aspect, the present description provides an article comprising a coating, the coating comprising a reaction product of a) a fluoroplastic, b) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof, c) a base, and optionally d) a phase transfer catalyst.

In other aspects, the present description provides layered articles that comprise a coating. In some embodiments, the coating comprises a) a fluoroplastic, b) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof, c) a base, and optionally d) a phase transfer catalyst. In other embodiments, the coating comprises a reaction product of a) a fluoroplastic, b) a an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof, c) a base, and optionally d) a phase transfer catalyst.

In yet further embodiments, the layered articles comprise a substrate comprising a substantially organic material or a substantially inorganic material. The substantially organic material may optionally be essentially free of a phenolate or thiolate salt. The layered article further has a first layer comprising a reaction product of a) a fluoroplastic, b) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof, c) a base, and optionally d) a phase transfer catalyst. In such layered articles, each of (i) the aromatic material and (ii) the base is, independently, present at the interface between the substrate and the remainder of the first layer, present in the fluoroplastic, or both. In some embodiments, the first layer is bonded to the substrate. In some embodiments, the layer of the layered articles that comprises a fluoroplastic is substantially free of fluoroelastomer. That is, the layer that comprises the fluoroplastic contains less than about 10% by weight of fluoroelastomer, less than 5% by weight, less than 1% by weight, less than 0.5% by weight, or even no fluoroelastomer. Substantially inorganic substrates can be, for example, glass, ceramic, metal, iron, stainless steel, steel, aluminum, copper, nickel, and alloys and combinations thereof. In certain embodiments, the substrate is selected from metal substrates. Other suitable substrates include fluoropolymers, nylon, and the like.

The substrate shape is not particularly limited. For example, the substrate can be the surface of a fiber, a flake, a particle, or combinations thereof. Specific examples include metallic sheeting in the form of ductwork such as is useful in exhaust ducts for chemical or semiconductor operations.

In some embodiments, layered articles may further comprise a second layer adjacent to the first layer. The second layer may comprise a fluoropolymer. Further, a third layer may optionally be present, which may also comprise a fluoropolymer. The optional second and third layers may further comprise a mixture of two or more fluoropolymers.

The layered articles of the present invention provide bonding, as measured by peel strength testing, described below, between the substrate and the fluoroplastic. For example, at 22-25⁰C, after baking the samples, the compositions described herein bond to various substrates. In some embodiments, the layered articles maintain desirable peel strengths after various exposure conditions of increasing severity and duration to boiling water. For example, in several embodiments, the layered articles provide high or very high peel strength even after boiling water exposure for 1 hour, for 5 hours, for 15 hours, or even for 24 hours. The multi-layered articles may exhibit peel strengths, optionally after boiling water exposure, of at least 0.7, at least 0.9, at least 1.8, at least 2.6, at least 3.5, or even at least 4.3 N/mm.

In another aspect, the present description provides a method of providing a fluoropolymer coating composition comprising providing a composition comprising a) a fluoroplastic, b) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof, c) a base, and optionally d) a phase transfer catalyst. The fluoroplastic may be provided in granular or powder form. The method further comprises heating the composition to a temperature above the melting point of the aromatic material and mixing the composition. In some embodiments, the aromatic material is a liquid at 25⁰C at 1 atmosphere of pressure. In other embodiments, the aromatic material may be dissolved in a solvent and the method may further comprise mixing the solvent containing the aromatic material with the fluoroplastic before heating the composition. In another aspect, the present description provides a method of providing a fluoropolymer coated surface. The method comprises providing a substrate (optionally selected from an inorganic material), applying a composition to the substrate, and bonding the composition to the substrate to give a bonded composition. Bonding the composition may comprise fusing the composition to the substrate. The composition applied to the substrate comprises a) a fluoroplastic, b) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof, c) a base, and optionally d) a phase transfer catalyst. Each of the aromatic material and the base is, independently, present at the interface between the substrate and the remainder of the first layer, present within the fluoroplastic, or both. The composition may optionally be provided as the fluoroplastic having a coating, wherein the coating comprises one or more of b) the aromatic material, c) the base, and optionally d) the phase transfer catalyst.

In further embodiments, the method may comprise bonding a second layer to the bonded composition, the second layer comprising a fluoropolymer.

In certain embodiments, the applying of the composition to the substrate comprises a method selected from, for example, electrostatic powder coating, co-extruding the composition and the substrate, and applying the composition to the substrate as a film, sheet, or molded part. In other embodiments, at least one of the aromatic material, optional phase transfer catalyst, and base may be applied to the substrate to form a primer layer before applying the remainder of the composition as described herein.

Various embodiments of the present invention are useful in chemical storage tanks, exhaust duct coatings, biomedical devices, electronic materials, cookware and bakeware, and architectural coatings, to name a few applications. In further embodiments, the aromatic materials described herein provide an advantage over the corresponding precursor materials in that the precursor materials may be subject to oxidation in air. Such reactivity may decrease the shelf- life and storage capability of compositions comprising precursor materials. Furthermore, some precursor materials may have compatibility issues with fluoroplastic powder matrixes and as a result may not be uniformly dispersed in a given fluoropolymer system. The aromatic materials may, in some embodiments, overcome some or all of these shortcomings noticed in some precursor materials. Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.

EXAMPLES

In the descriptions below, percent means percent by weight unless otherwise described in context. Unless otherwise stated, materials were available from Aldrich Chemicals, Milwaukee, WI.

Example 1

CH₂Cl₂ (63.7g) and 2-naphthol (5g) were placed into a 500 mL flask and triethylamine (4.2g Reagent, 99.5%) was added. After the 2-naphthol was completely dissolved, N-(trimethylsilyl)-acetamide (5.5g) was added and the solution was heated to reflux gently for 8 hours under a N₂ atmosphere. After the 8 hours the reaction solution was poured into ice water, the organic CH₂Cl₂ phase was separated, and the water phase was washed 3 times with 20 to 3OmL CH₂Cl₂. The collected CH₂Cl₂ phase was washed with 25OmL deionized water 3 times to remove any remaining unreacted starting materials. The combined CH₂Cl₂ solution was dried with anhydrous magnesium sulfate overnight. The dried CH₂Cl₂ solution was filtered to remove magnesium sulfate and the solution was subjected to vacuum rotary evaporation to remove CH₂Cl₂. A solid was obtained with 80% yield. The solid was sampled and analyzed by ¹H NMR. The ¹H NMR spectrum was consistent with the desired product.

Example 2 Tetrahydrofuran (THF/80 mL) and 2-naphthol (10 g) were placed into a 250 mL flask and a sodium methoxide-methanol solution (25wt%, 14.9g) was added. After addition the reaction became dark blue. To the solution was added allyl bromide (9g) and the reaction solution was heated to reflux gently for 20 hours under a N₂ atmosphere. After the 20 hours the reaction solution was poured into ice water, the organic THF phase was separated, and the water phase was washed 3 times with 3OmL CH₂Cl₂. The collected CH₂Cl₂ phase was then washed with 10OmL deionized water 3 times to remove any unreacted starting materials. The combined CH₂Cl₂ solution was dried with anhydrous magnesium sulfate overnight. The dried CH₂Cl₂ solution was filtered to remove magnesium sulfate and the solution was subjected to vacuum rotary evaporation to remove CH₂Cl₂. A liquid was obtained with 85% yield. The solid was sampled and analyzed by ¹H NMR. The ¹H NMR spectrum was consistent with the desired product.

Example 3

CH₂Cl₂ (101.2g) and 2-naphthol (1Og) were placed into a 500 mL flask and triethylamine (8.4g Reagent, 99.5% purity) was added. After the 2-naphthol was completely dissolved, trifluoroacetic anhydride (20.7g) was slowly added through a dropping funnel. After addition, the reaction solution was heated to reflux gently for 20 hours under a N₂ atmosphere. After the 20 hours the reaction solution was poured into ice water, the organic CH₂Cl₂ phase was separated, and the water phase was washed 3 times with 3OmL CH₂Cl₂. The separated CH₂Cl₂ phase was washed 4 times to remove any unreacted starting materials (2x 25OmL deionized water, Ix 10OmL K₂Cθ3 in deionized water solution and Ix 10OmL deionized water). The combined CH₂Cl₂ solution was dried with anhydrous magnesium sulfate overnight. The dried CH₂Cl₂ solution was filtered to remove magnesium sulfate and the solution was subjected to vacuum rotary evaporation to remove CH₂Cl₂. A yellow solid was obtained with 80% yield. The solid was sampled and analyzed by ¹H NMR. The ¹H NMR spectrum was consistent with the desired product.

Example 4

CH₂Cl₂ (67.8g) and 2-naphthol (1Og) were placed into a 500 mL flask and triethylamine (8.5g Reagent, 99.5% purity) was added. After the 2-naphthol was completely dissolved, acetyl chloride in CH₂Cl₂ solution (7.4g acetyl chloride dissolved in 14g CH₂Cl₂) was slowly added to the 2-naphthol through a dropping funnel. An exothermic reaction occurred immediately and the reaction solution was cooled with an ice-water bath. Finally, the reaction solution was heated to reflux gently for 20 hours under a N₂ atmosphere. After the 20 hours the reaction solution was poured into ice water, the organic (CH₂Cl₂) phase was separated, and the water phase was washed 3 times with 20 to 3OmL CH₂Cl₂. Then all the collected CH₂Cl₂ phase was washed 4 times to remove any unreacted starting materials (2x 25OmL deionized water, Ix 10OmL K₂Cθ₃ in deionized water solution and Ix 10OmL deionized water). The combined CH₂Cl₂ solution was dried with anhydrous magnesium sulfate overnight. The dried CH₂Cl₂ solution was filtered to remove magnesium sulfate and the solution was subjected to vacuum rotary evaporation to remove CH₂Cl₂. A yellow solid was obtained with a 90% yield. The solid was sampled and analyzed by ¹H NMR. The ¹H NMR spectrum was consistent with the desired product.

Example 5

Toluene (48.5 g) and 2-naphthol (7.2 g) were placed into a 500 mL flask and triethylamine (6.25g Reagent, 99.5%) was added. After the 2-naphthol was completely dissolved, an isopropyl chloroformate in toluene solution (6OmL, 1 molar) was added through a dropping funnel. After addition the reaction solution was heated to a gentle reflux overnight under a N₂ atmosphere. The reaction solution was poured into ice water, the organic toluene phase was separated and the water phase was washed 3 times with 3OmL CH₂Cl₂. Then all the collected CH₂Cl₂ phase was washed with deionized water 3 times to remove any unreacted starting materials. The combined CH₂Cl₂ solution was dried with anhydrous magnesium sulfate overnight. The dried CH₂Cl₂ solution was filtered to remove magnesium sulfate and the solution was subjected to vacuum rotary evaporation to remove CH₂Cl₂. A solid was obtained with 90% yield. The solid was sampled and analyzed by ¹H NMR. The ¹H NMR spectrum was consistent with the desired product.

CH₂Cl₂ (10OmL) and bisphenol-AF (10.0g, 4,4'- hexafluoroisopropylidene)dipheonl, DuPont, Wilmington, DE) were placed into a 500 mL flask and 3,4-dihydro-2H-pyran (12g) and toluenesulfonic acid (O.lg) were added. After addition, the reaction solution was stirred and heated to reflux gently overnight. After the overnight reflux the reaction solution was poured into ice water, the organic CH₂Cl₂ phase was separated and the water phase was washed 3 times with 3OmL CH₂Cl₂. The collected CH₂Cl₂ phase was then washed with deionized water 3 times to remove any unreacted starting materials. The combined CH₂Cl₂ solution was dried with anhydrous magnesium sulfate overnight. The dried CH₂Cl₂ solution was filtered to remove magnesium sulfate and the solution was subjected to vacuum rotary evaporation to remove CH₂Cl₂. A solid was obtained with 95% yield. The solid was sampled and analyzed by ¹H NMR. The ¹H NMR spectrum was consistent with the desired product.

Preparation of Primers

2-Naphthyl acetate (1.Og) (Example 4) was added to 0.5g of tetraphenylphosphonium chloride (TPPCl) in a small vial. 1.5 grams of methanol was added and the vial was heated until the TPPCl and the 2-naphthyl acetate were dissolved into a solution containing no solids. Then 37.5g of PFA 6503 A EPC (available from Dyneon LLC, Oakdale, MN) was dry blended with 1 gram of Ca(OH)₂. The solution containing the TPPCl and the 2-naphthyl acetate was added to the PFA/Ca(OH)₂ and blended for 1 minute in a Minimill (available from BelArt Products, Pequannock, NJ). When properly mixed the PFA powder particles are uniformly coated with the added ingredients. Other primers were made similarly using the same 37.5:1 :1 :0.5 ratio of PFA:protected aromatic: TPPCl: Ca(OH)₂.

Peel Sample Preparation and Testing

Three strips each of stainless steel (400 series) and aluminum (panels 1x6x0.05 inch, 2.54x 15.2x0.127 cm) were degreased by immersing the strips in a heated alkaline solution [75 g of Oakite Cleaner 164 (available from Oakite Products, Berkeley Heights, NJ) per liter of water] maintained at 180°F (82°C) for 10 minutes. The strips were then rinsed several times with distilled water and dried in an air-circulating oven at 160°F

(71⁰C) for 10 minutes. Each strip was grit blasted to roughen the surface using 60 mesh alumina grit and 100 psi (552 kPa) air pressure. Any residual dust was removed with an air gun. The strips were placed on a /4x6x6 inch, (0.635x15.2x15.2 cm) plate of mild steel and brushed with a thin layer of PFA 6503B EPC powder (available from Dyneon, Oakdale, MN) over 2 inches (5 cm) of one end of each strip. This provided an area where the coating would not adhere to the metal to create a tab for the peel test. The strips were then electrostatically powder coated with the primer using a Nordson SureCoat (Nordson Corp., Westlake, Ohio), at 70 volts, 150 kPa airflow until no bare metal was visible. The strips were then baked in an air-circulating oven at 750°F (400°C) for 15 minutes. Upon removal of the strips from the oven, the strips were immediately electro-statically powder- coated with PFA fluoropolymer topcoat at 70 volts, 150 kPa airflow and then placed back into the oven for an additional 15 minutes. A second layer of topcoat was applied and baked to achieve a coating thickness of 20 to 30 mils (508 to 762 cm). After the samples were cooled, 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. The specimens were immersed in boiling water for 24 hours. After removal from the water, the samples were allowed to cool to room temperature, and the peel strength was measured by testing the samples using an tensile tester sold under the trade designation "INSTRON" (Instron, Norwood, MA) equipped with a floating roller peel test fixture at a crosshead speed of 6 in/min (15 cm/min) and peeling to 3.75 inches (9.5 cm) extension per ASTM D3167. The peel strength was calculated over 1 to 3 inches (2.54 to 7.62 μm) extension using an integrated average and reported as an average of three samples. In cases where the tab breaks the average is taken for an area before the break. This area average is less than the peak force.

The employed bonding agents are listed in Table 1 below. Formulation, preparation and thermal bonding was in each case done the same except for substituting the various bonding agents as indicated in Table 1.

Table 1

NT=not tested

Claims

What is claimed is:

1. A composition comprising: a) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof; b) a base; c) a fluoroplastic; and optionally, d) a phase transfer catalyst.

2. The composition of claim 1 wherein the aromatic material is selected from an aromatic material comprising at least two protected polythiol groups; an aromatic material comprising a protected hydroxy group and a protected thiol group; an aromatic material comprising a catechol novolak resin having at least one protected hydroxyl group; an aromatic material comprising at least two protected hydroxyl groups further comprising at least one aromatic ring having at least one protected hydroxyl group attached directly to the aromatic ring; and combinations thereof.

3. The composition of claim 1 wherein the aromatic material is selected from an aromatic material having exactly one protected hydroxyl group, wherein the aromatic material is free of thiol groups, and wherein the protected hydroxyl group is bonded to an aromatic carbon.

4. The composition of claim 1 wherein the aromatic material is selected from (i) an aromatic compound; (ii) an aromatic resin; (iii) a heteroaromatic compound; and (iv) a heteroaromatic resin, wherein the aromatic material has at least one protected amine group bonded to an aromatic or heteroaromatic ring.

5. The composition of claim 4 wherein the amine is a non-hindered amine.

6. The composition of claim 1 further comprising a phase transfer catalyst.

7. A multi-layer article comprising: a) a substrate; and b) a first layer, wherein the first layer comprises i) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof; ii) a base; iii) a fluoroplastic; and, optionally, iv) a phase transfer catalyst.

8. The multi-layer article of claim 7, wherein the first layer further comprises a phase transfer catalyst.

9. A method comprising: a) providing a coating composition, the composition comprising i) a fluoroplastic; ii) an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof; iii) a base; and, optionally, iv) a phase transfer catalyst b) heating the composition to a temperature above the melting point of the aromatic material; and c) mixing the composition.

10. The method of claim 9 wherein the fluoroplastic is a powder.

11. The method of claim 9 wherein the coating composition further comprises a phase transfer catalyst.

12. The method of claim 9 wherein the aromatic material is a liquid at 25⁰C at 1 atmosphere of pressure.

13. The method of claim 9 further comprising dissolving the aromatic material in a solvent and mixing the solvent-containing aromatic material with the fluoroplastic before heating the composition.

14. A method comprising: a) providing a substrate; b) applying a composition to the substrate; and c) bonding the composition to the substrate to give a bonded composition wherein the composition comprises a fluoroplastic; an aromatic material having at least one protected moiety selected from a protected hydroxyl group, a protected amine group, a protected thiol group, and combinations thereof; a base; and, optionally, a phase transfer catalyst; and further wherein each of the aromatic material and the base is, independently, present at the interface between the substrate and the remainder of the first layer, present within the fluoroplastic, or both.

15. The method of claim 14 wherein the fluoroplastic is coated with one or more of the aromatic material and the base.

16. The method of claim 14 wherein the composition further comprises a phase transfer catalyst.

17. The method of claim 14 wherein applying is selected from electrostatic powder coating, co-extruding the composition and the substrate, and applying the composition to the substrate as a film, sheet, or molded part.

18. The method of claim 16 wherein at least one of the aromatic material, phase transfer catalyst, or base is applied to the substrate to form a primer layer before applying the remainder of the composition.

19. A chemical storage tank comprising a coating having a composition according to claim 1.

20. An exhaust duct coating having a composition according to claim 1.