WO2009015281A2

WO2009015281A2 - Epoxy and hydroxy-functional acrylic resins for use in coating applications

Info

Publication number: WO2009015281A2
Application number: PCT/US2008/071040
Authority: WO
Inventors: Timothy A. Pincikowski; Timothy Klots; David Trumbo; Gary Deeter
Original assignee: BASF Corp
Current assignee: BASF Corp
Priority date: 2007-07-25
Filing date: 2008-07-24
Publication date: 2009-01-29
Anticipated expiration: 2010-01-25
Also published as: WO2009015281A3

Abstract

Polymers having dual functionalities, where one functionality imparts the polymer with the ability to crosslink with a crosslinking agent and the other functionality imparts at least one beneficial property to the polymer. In one embodiment, the two functionalities are epoxy and hydroxy-functionalities.

Description

Atty. Dkt. No.: 018894-0275

EPOXY AND HYDROXY-FUNCTIONAL ACRYLIC RESINS FOR USE IN COATING APPLICATIONS

FIELD OF THE INVENTION

[0001] The present invention relates to polymers containing more than one functional groups, to coatings containing these polymers, and to methods for making the same. In particular, the present invention relates to epoxy and hydroxy- functional polymers, to coatings containing the polymers, and to methods for making the same.

BACKGROUND

[0002] Polymers containing more than one functional group are known. These polymers find use in a variety of applications including coatings based on polymers containing functional groups. To a large extent, such coatings utilize only one functional group present in the polymer for providing for crosslinking reactions or other desired properties. Specifically, polymers having both epoxy and hydroxy functional groups are known. However, cured coatings made from these polymers suffer from significant drawbacks, such as poor adhesion to metal substrates and/or discoloration (e.g., blushing) when cured with certain crosslinking agents, such as polyamines. Thus, a need exists for a coating composition comprising an epoxy and hydroxy-functionalized polymer and an appropriate crosslinking agent that provides good adherence to metal substrates and/or improved appearance after curing.

SUMMARY

[0003] This invention generally relates to polymers having dual functionalities. In such polymers, one functionality imparts the polymer with the ability to crosslink with a crosslinking agent, and the other functionality imparts at least one beneficial property to the polymer. In one embodiment, the two functionalities are epoxy and hydroxy-groups. The polymers are well-suited for use in coating applications. Compared to similar polymers having only epoxy-functional groups, the present polymers provide coatings that may Atty. Dkt. No.: 018894-0275

exhibit one or more of the following benefits: improved appearance (e.g., reduced blushing), improved reactivity, improved adhesion to substrates (particularly metals such as chromium substrates), corrosion resistance, thermal shock resistance and longer pot life.

[0004] The polymers are prepared from at least one epoxy-functional acrylic monomer and at least one hydroxy-functional acrylic monomer. Optionally, the polymers also include one or more non-functional acrylate or methacrylate monomers and/or one or more non-functional styrenic monomers.

[0005] In another embodiment, the two functionalities are hydroxyl and carboxylic acid groups. The polymers are well suited for use in coating applications. Compared to similar polymers containing only hydroxyl-functional groups, the present polymers provide coatings that may exhibit one or more of the following benefits: improved reactivity, improved adhesion to substrates (particularly hard to adhere substrates such as chromium and plastic substrates), and improved dispersion of pigments and other additives.

[0006] In yet another embodiment, the two functionalities are at least one selected from a surfactant-like moiety and the other is selected from epoxy, hydroxyl, carboxylic acid or other functional groups. Compared to polymers containing epoxy, hydroxyl, carboxylic acid or other functional groups, the dual functional polymers may exhibit one or more of the following benefits: improved ability to disperse pigments, colorants and other additives used in coatings, and improved resistance properties and durability over compositions having conventional surfactants.

[0007] The polymers containing epoxy and hydroxyl functional groups may be made by continuously charging a monomer feed containing at least one epoxy-functional acrylic monomer, at least one hydroxy-functional acrylic monomer, and any additional optional monomers and/or polymerization initiators into a reactor and maintaining the monomer mixture at an effective temperature for an effective period of time to cause polymerization of the monomers into the polymer. Similarly, polymers containing hydroxyl and carboxylic acid functional groups may be made by continuously charging a monomer feed containing at least one carboxylic acid functional acrylic monomer, at least one hydroxy-functional acrylic Atty. Dkt. No.: 018894-0275

monomer, and any additional optional monomers and/or polymerization initiators into a reactor and maintaining the monomer mixture at an effective temperature for an effective period of time to cause polymerization of the monomers into the polymer.

[0008] Polymers containing at least one surfactant-like moiety and at least one functional group selected from epoxy, hydroxyl, carboxylic acid or other functional groups may also be made by continuously charging a monomer feed containing at least one acrylic monomer containing a surfactant-like moiety and at least one acrylic monomer containing a functional group selected from epoxy, hydroxyl, carboxylic acid or other functional groups.

[0009] The dual functional polymers can also be prepared via polymerization processes disclosed in US patents 7,230,048; 6,255,403, 6,346,590, 6,355,727, 6,605,681, 6,689,853, and 6,858,678.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The preferred exemplary embodiment of the invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements and:

[0011] FIG. 1 is a plot of Konig hardness (swings) versus bake temperature for three coating compositions in accordance with the present invention.

DETAILED DESCRIPTION

[0012] The present invention provides polymers having dual functionalities, wherein one functionality imparts the polymer with the ability to crosslink with a crosslinking agent and the other functionality imparts at least one beneficial property to the polymer. In one embodiment, the two functionalities are epoxy and hydroxy-functionalities. In another embodiment, the two functionalities are carboxylic acid and hydroxyl functionalities. Benefits that may be imparted to the polymers by the functional groups include, but are not limited to, improved appearance (e.g., reduced blushing in coatings made from the Atty. Dkt. No.: 018894-0275

polymers), improved reactivity, improved adhesion to substrates, corrosion resistance and thermal shock resistance. The polymers are well-suited for use in coating applications.

[0013] In one embodiment, the polymers are polymerized from at least one epoxy- functional acrylic monomer and at least one hydroxy-functional acrylic monomer. In addition, the polymer optionally may be polymerized from at least one non-functional acrylate or methacrylate monomer and/or at least one non-functional styrenic monomer. For the purposes of this disclosure, a non-functional monomer is a monomer that does not include a cross-linkable functional epoxy group, or any functional group that could chemically react with an epoxy group.

[0014] In another embodiment, the polymers are polymerized from at least one carboxylic acid functional acrylic monomer and at least one hydroxyl functional acrylic monomer. In addition, the polymer optionally may be polymerized from at least one nonfunctional acrylate or methacrylate monomer and/or at least one non-functional styrenic monomer. For the purposes of this disclosure, a non-functional monomer is a monomer that does not include a crosslinkable functional group such as carboxylic acid, hydroxyl and epoxy functional groups.

[0015] In yet another embodiment, the polymers are polymerized from at least one acrylic monomer containing a surfactant-like moiety and at least one acrylic monomer containing a functional group selected from epoxy, hydroxyl, carboxylic acid or other functional groups. Examples of surfactant-like moieties include both hydrophobic and hydrophilic groups. Hydrophobic groups include alkyl or aromatic alkyl groups containing 12 or more carbon atoms. For example, the alkyl or aromatic alkyl groups may contain from 12 to 36 carbon atoms, in some embodiments, and from 12 to 22 carbon atoms, in other embodiments. Hydrophilic groups include polyethers such as poly(ethylene oxide) as well as block and random copolymers of ethylene oxide.

[0016] Examples of epoxy-functional acrylic monomers which may be polymerized to provide the present polymers include both acrylates and methacrylates. Examples of the epoxy-functional acrylic monomers include, but are not limited to, those containing 1,2- Atty. Dkt. No.: 018894-0275

epoxy groups such as glycidyl acrylate and glycidyl methacrylate. One of the preferred epoxy-functional acrylic monomers is glycidyl methacrylate.

[0017] Examples of hydroxy-functional acrylic monomers which may be polymerized to provide the present polymers also include both acrylates and methacrylates. Examples of these monomers include, but are not limited to, those containing one or more hydroxy groups such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2,3- hydroxypropyl acrylate, 2,3-hydroxypropyl methacrylate, 2,4- hydroxybutyl acrylate and 2,4-hydroxybutyl methacrylate. When hydroxy-functional acrylic monomers are utilized, the preferred epoxy-functional acrylic monomer is glycidyl methacrylate.

[0018] Examples of carboxylic acid functional acrylic monomers which may be polymerized to provide polymers of present invention include both acrylate and methacrylates. Examples of these monomers include, but are not limited to, acrylic acid, methacrylic acid, crotonic acid, fumaric acid, and other such acids known to those of skill in the art.

[0019] Examples of non-functional acrylate and methacrylate monomers that optionally may be polymerized to provide the present polymers include, but are not limited to, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, s- butyl acrylate, i-butyl acrylate, t-butyl acrylate, n-amyl acrylate, i-amyl acrylate, isobornyl acrylate, n-hexyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n- decyl acrylate, methylcyclohexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, n-propyl methacrylate, n- butyl methacrylate, i-propyl methacrylate, i-butyl methacrylate, n-amyl methacrylate, n- hexyl methacrylate, i-amyl methacrylate, s-butyl-methacrylate, t-butyl methacrylate, 2- ethylbutyl methacrylate, methylcyclohexyl methacrylate, cinnamyl methacrylate, crotyl methacrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, 2-ethoxyethyl methacrylate, and isobornyl methacrylate. The preferred non-functional acrylate and nonfunctional methacrylate monomers are butyl acrylate, butyl methacrylate, methyl Atty. Dkt. No.: 018894-0275

methacrylate, iso-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobomyl acrylate, isobornyl methacrylate and combinations thereof.

[0020] In preferred processes of the present invention, the monomer feed from which the polymers are made will comprise at least two different non-functional acrylate or non-functional methacrylate monomers, and in a still more preferred embodiment, the monomer feed for the continuous reaction will comprise at least three different nonfunctional methacrylate monomers. In some processes of the present invention, at least two non-functional methacrylate monomers and one non-functional acrylate monomer is fed into the continuous reaction mixture. In still another process of the present invention, the monomer feed will comprise at least one non-functional acrylate and one non-functional methacrylate.

[0021] The polymeric product of the present invention also may optionally include one or more non- functional styrenic monomers. Styrenic monomers for use in the present invention include, but are not limited to, styrene, α-methylstyrene, p-methylstyrene, t-butylstyrene, o-chlorostyrene, and mixtures of these species. Preferred styrenic monomers for use in the process include styrene and α-methyl-styrene.

[0022] The dual functionality polymers provided herein may be made by methods known in the art. Suitable methods are described in U.S. Patent No. 6,552,144, the entire disclosure of which is incorporated herein by reference. In one illustrative embodiment of these methods, the polymers are made as follows. At least one epoxy-functional acrylic monomer, at least one hydroxy- functional acrylic monomer, and any additional optional monomers are continuously charged into a reactor. A free radical polymerization initiator may also be added to the reactor. In one embodiment, the monomer feed may be free of any other monomers or compounds which include functional groups other than the epoxy and hydroxyl functional groups. The monomer mixture may be maintained in the reactor at an effective temperature for an effective period of time to cause polymerization of the monomers and produce a polymer that is desirably, but not necessarily, free, or substantially free, of gel particles. Atty. Dkt. No.: 018894-0275

[0023] In one embodiment of the present invention, the epoxy-fiinctional acrylic monomer(s) are present in the monomer feed in amounts ranging from about 5% to 50% by weight, in another embodiment about 10% to about 40% by weight, based on the total weight of the polymerizable monomers in the feed.

[0024] The hydroxy-functional acrylic monomer(s) are desirably present, for example, in the monomer feed in amounts ranging from about 2% to about 50% by weight, based on the total weight of the polymerizable monomers in the feed.

[0025] The epoxy-functional and hydroxy-functional acrylic monomer(s) may be, for example, present in the monomer feed in a combined amount from about 20% to about 60% by weight, with the epoxy-functional acrylic monomers comprising at least 50% by weight of the combined epoxy-functional and hydroxy-functional acrylic monomer(s).

[0026] The monomer feed may also comprise, for example, from about 5% to about

60% of at least one non- functional acrylate or methacrylate monomer and/or non-functional styrenic monomer by weight based on the total weight of polymerizable monomers in the feed.

[0027] The term "by weight" as used herein is hereby defined as the total weight of the entire class of the particular monomer(s) used, for example, if multiple epoxy-functional acrylic monomers are utilized, the preferred total weight of all such monomers may be, for example, from about 15% to about 60% by weight based on the total weight of the polymerizable monomers in the feed. AU ranges recited herein include all combinations and subcombinations included with that range's limits; therefore, a range from about "15% to about 60%" would include ranges from about 15% to about 45%, from about 30% to about 47%, etc. A range of "up to 85%" would include up to 80%, up to 50%, up to 24%, etc.

[0028] The process may optionally, but not necessarily, use one or more free radical polymerization initiators. Initiators suitable for carrying out the process are typically compounds which decompose thermally into radicals in a first order reaction, although this is not a critical factor. Suitable initiators preferably have half-life periods in the radical Atty. Dkt. No.: 018894-0275

decomposition process of about 1 hour at temperatures greater or equal to 90⁰C and more preferably 10 hours at temperatures greater or equal to 100⁰C. Others with about 10 hour half-lives at temperatures significantly lower than 100⁰C may also be used. Suitable initiators are, for example, aliphatic azo compounds such as 1-t-amylazo-l- cyanocyclohexane, azo-bis-isobutyronitrile and 1-t-butylazo-cyanocyclohexane, 2,2'-azo- bis-(2-methyl)butyronitrile and peroxides and hydroperoxides, such as t-butylperoctoate, t- butyl perbenzoate, dicumyl peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, di-t-amyl peroxide and the like. Additionally, di-peroxide initiators may be used alone or in combination with other initiators. Such di-peroxide initiators include, but are not limited to, 1 ,4-bis-(t-butyl peroxycarbo)cyclohexane, 1 ,2-di(t-butyl peroxy)cyclohexane, and 2,5-di(t-butyl peroxy)-3-hexyne, and other similar initiators well known in the art. The preferred initiators are di-t-butyl peroxide and di-t-amyl peroxide.

[0029] The initiator is preferably added with the monomers. The initiators may be added in any appropriate amount, but preferably the total initiators are added in an amount of about 0.0005 to about 0.06 moles initiator(s) per mole of monomers in the feed. For this purpose initiator may be either admixed with the monomer feed or added to the process as a separate feed.

[0030] An inert solvent may also be fed into the reactor. This solvent may be fed into the reactor together with the monomers, or in a separate feed. The solvent may be any solvent well known in the art that preferably does not react with the epoxy-functionality on the epoxy-functional acrylic monomer(s) or the hydroxy- functionality on the hydroxy- functional acrylic monomers at the high temperatures of the continuous process described herein. The proper selection of solvent may decrease the gel particle formation during the continuous, high temperature reaction. Suitable solvents include, but are not limited to, xylene, toluene, ethyl-benzene, Aromatic- lOOθ, Aromatic 150θ, Aromatic 200θ (all Aromatics available from Exxon), acetone, methylethyl ketone, methyl amyl ketone, methyl-isobutyl ketone, N-methyl pyrrolidinone, and combinations thereof. When used, the solvents are present in any amount desired, taking into account reactor conditions and Atty. Dkt. No.: 018894-0275

monomer feed. In one embodiment, one or more solvents are present in an amount of up to 40% by weight, based on the total weight of the polymerizable monomers.

[0031] By way of illustration only, the temperature during the polymerization of the monomers may range from about 16O⁰C to about 27O⁰C, preferably about 17O⁰C to about 25O⁰C, and more preferably from about 17O⁰C to about 232⁰C. The residence time in the reactor may be less than one hour, with a preferred average residence time for the monomers of less than 15 minutes.

[0032] The process may be conducted using any type of reactor or combination of reactors well-known in the art, in a continuous configuration. Such reactors include, but are not limited to, continuous stirred tank reactors ("CSTRs"), tube reactors, loop reactors, extruder reactors, or any reactor or combination of reactors suitable for continuous operation.

[0033] Optionally, some of the epoxy and/or hydroxy groups on the resulting polymer may be modified with acrylic acid to provide a polymer having pendant vinyl groups. This modification provides a UV-curable polymer that may be particularly useful in various coating applications. This modification may be carried out by heating the dual functional polymer-containing epoxy and hydroxyl groups with acrylic acid at a temperature suitable for reaction. Optically, a catalyst may be added to promote reaction of the dual functional polymer with acrylic acid. It may be desirable to add an inhibitor during this reaction in order to prevent premature polymerization of the pendant acrylic functionality.

[0034] The resulting polymers may have a variety of physical and chemical properties, depending upon the nature and relative amounts of monomers employed. However, in some illustrative embodiments, the polymers desirably have an epoxy equivalent weight of at least about 200 and/or a hydroxy equivalent weight of at least about 300. This includes polymers having an epoxy equivalent weight of at least about 500 and/or a hydroxy equivalent weight of at least about 800. By way of illustration only, some of the polymers provided herein will have an epoxy equivalent weight of about 200 to about 1000 and/or a hydroxy equivalent weight of about 300 to about 1200. Epoxy and hydroxyl Atty. Dkt. No.: 018894-0275

equivalent weight of polymers represents the weight of a polymer containing one equivalent of epoxy and hydroxyl groups, respectively.

[0035] In some illustrative embodiments the polymers may have a number average molecular weight (Mn) of about 1,200 to about 10,000, a weight average molecular weight (Mw) of about 2,200 to about 50,000 and/or a z-average molecular weight of about 6,000 to about 200,000. However, the present polymers are not limited to those falling within these molecular weight ranges.

[0036] In another embodiment, polymers useful in the present invention can be made by a continuous polymerization process described in US patent 7,230,048. This comprises continuously charging into a first reaction zone at least one functional monomer and maintaining an effective temperature in the first reaction zone for an effective period of time to cause polymerization of the monomers to produce a first polymeric product having at least one functional group. The first polymeric product is then continuously, directly charged into a second reaction zone together with at least one modifier reactant having a functional group that is complementary to the functional group of the first polymeric product. An effective temperature is maintained in the second reaction zone for an effective period of time such that at least a portion of the modifier reactant reacts with at least one of the functional groups of the first polymeric product to produce a second polymeric product which incorporates at least a portion of the modifier reactant, such that the second polymeric product contains at least two functional groups.

[0037] Polymers may be made by a continuous polymerization and condensation processes disclosed in US patents 6,255,403; 6,346,590 and 6,689,853. Such processes include continuously charging into at least one primary reactor, at least one radically- polymerizable monomer having a radically polymerizable group and also having at least one condensation reactive functionality; and at least one modifying agent having more than one functional group capable of reacting with the condensation reactive functionality on the radically-polymerizable monomer. The process also includes maintaining an effective temperature in the primary reactor sufficient to cause polymerization of the monomer and to Atty. Dkt. No.: 018894-0275

allow at least a portion of the condensation reactive functionality to react with one of the functional group of the modifying agent such that a first polymeric product is produced which incorporates at least some of the modifying agent.

[0038] The polymers may be prepared by a continuous polymerization and esterifϊcation process such as that disclosed in US patents 6,355,727 and 6,858,678. According to this process polymers of present invention are made by a continuous bulk polymerization and esterifϊcation process including charging continuously into a reaction zone at least one ethylenically unsaturated acid-functional monomer and at least one alkanol having the formula ROH, where R is a linear or branched chain alkyl moiety, or combinations thereof, having greater than 11 carbon atoms. The process also includes maintaining a flow rate through the reaction zone sufficient to provide an average residence time of the monomers in the reaction zone of less than 60 minutes and maintaining a temperature in the reaction zone sufficient to produce a polymeric product.

[0039] The polymeric products of the present invention have a wide range of industrial uses, most notably, in pigmented and clear coatings, of both liquid and powder design. The powder and liquid coatings may be created by methods well known in the art, for example, as described in United States Patent No. 5,256,452, the entire disclosure of which is hereby incorporated by reference. The coatings may be applied to a wide variety of substrates using techniques known in the art. For example, the coatings may be applied to metal substrates, polymer substrates and glass substrates.

[0040] Methods of making powder coatings are well known in the art, and those of the present invention are generally prepared in accordance with those methods. Generally, the powder coatings of the present invention comprise one or more polymers of the present invention, one or more crosslinking agents, one or more catalysts, and one or more flow modifying agents. The powder coatings of the present invention also may optionally include one or more degassing agents, one or more antioxidants and/or one or more UV stabilizers.

[0041] Similarly, methods of making liquid coatings are well known in the art and those of the present invention are generally prepared in accordance with such methods. The Atty. Dkt. No.: 018894-0275

liquid coatings also may optionally include one or more flow modifying agents, one or more antioxidants and/or one or more UV stabilizers described above in connection with the powder coatings. Similar compounds may be utilized in preparing the liquid coatings as in the powder coatings.

[0042] Many types of crosslinking agents can be used with coatings. The selection of a particular crosslinking agent will depend on the type of functional groups present in polymeric products made according to this invention. Examples of crosslinking agents suitable for use in the present coatings include, but are not limited to, epoxies, isocyanates, amino resins, amines, thiols, acids and anhydrides.

[0043] Isocyanate crosslinking agents may be particularly well-suited for use in coating applications based on polymeric compositions containing epoxy and hydroxyl functional groups because they provide crosslinked resins with improved adhesion to metal substrates, including substrates, such as chrome, to which many polymer coatings adhere poorly. In such resins, it is believed that the pendant hydroxy groups on the polymers provide crosslinking sites, while the pendant epoxy groups on the polymers provide affinity for the substrates. Coatings made from such resins may be characterized by good thermal shock resistance. Alternatively, polyamines, and diamines in particular, may be used as crosslinking agents in the present coatings based on polymeric compositions containing epoxy and hydroxyl functional groups. Specific examples of suitable polyamine crosslinking agents include, but are not limited to, those containing at least two nitrogen atoms per molecule and at least two and preferably at least three active hydrogens attached to nitrogen atoms per molecule. Useful amines include aliphatic, araliphatic, aromatic, cycloaliphatic, and heterocyclic di- and polyamines. Examples of polyamines can be found in U.S. Patent No. 5,508,324. Such examples include, but are not limited to polyethylene polyamines (ethylene diamine, diethylene triamine, triethylene tetramine, pentaethylene hexamine and the like), 1 ,2-propylene diamine, 1,3 -propylene diamine, 1 ,4-butanediamine, 1,5-pentanediamine, 1,3-pentanediamine, 1 ,6-hexanediamine, 3,3,5-trimethyl-l,6- hexanediamine, 3,5,5-trimethyl-l,6-hexane-diamine, 2-methyl- 1,5-pentanediamine, bis-(3- aminopropyl)amine, N,N'-bis-(3 -amino-propyl)- 1 ,2-ethanediamine, N-(3-amino-propyl)- Atty. Dkt. No.: 018894-0275

1 ,2-ethanediamine, 1 ,2-diamino-cyclohexane, 1,3-diaminocyclohexane, 1,4- diaminocyclohexane, aminoethylpiperazine, the poly(alkylene oxide) diamines and triamines (such as for example Jeffamine.RTM. D-230, Jeffamine D-400, Jeffamine D- 2000, Jeffamine D-4000, Jeffamine T-403, Jeffamine EDR- 148, Jeffamine EDR-192, Jeffamine C-346, Jeffamine ED-600, Jeffamine ED-900, and Jeffamine ED-2001), meta- xylylene diamine, phenylene diamine, 4,4'-diaminodiphenyl methane, toluene diamine, isophorone diamine, 3,3'-dimethyl-4,4'-diaminodicyclohexyl methane, 4,4'- diaminodicyclohexyl methane, 2,4'-diaminodicyclohexyl methane, the mixture of methylene bridged poly(cyclohexylaromatic)amines (also known as MBPCAA) described in U.S. Pat. No. 5,280,091, and polyaminoamides. Mixtures of the above amines may also be employed.

[0044] The use of polyamine crosslinking agents eliminates the need for isocyanates and, in combination with the present epoxy and hydroxy-functional polymers, may provide a blush-free or blush-resistant coating. Blushing, a common problem in amine-cured epoxy resins, occurs during ambient temperature curing and is attributed to the absorption of carbon dioxide and water from the atmosphere, which leads to carbonation and results in surface oiliness and/or a whitish appearance.

[0045] Catalysts suitable for use in the isocyanate crosslinked coatings may be those well known in the art which include, but are not limited to, inorganic alkaline salts which include tetrabutyl ammonium acetate, tetrabutyl ammonium hydroxide; phosphonium compounds such as ethyltriphenylphosphonium acetate, tetrabutyl-phosphonium bromide; organometallic salts such as stannous octoate, zirconium ocotate; and other organic compounds including tertiary amines, such as N,N-dimethyldodecylamine, dimethylaniline, secondary amines, such as piperidine, and phosphines such as triphenyl phosphine. Specific examples of catalysts are tertiary amines such as Armeen DM-12D9, a N'N-dimethyl amine catalyst available from AKZO Chemical. Notably, if an isocyanate crosslinking agent is used, dibutyltindilaurate is a preferred catalyst, because this combination has been found to provide the resin with increased pot life. Photoinitiators, including UV and cationic photoinitiators may also be used in the coatings. Example 3, below, illustrates the advantages that may be achieved by employing cationic photoinitiators. Atty. Dkt. No.: 018894-0275

[0046] Flow modifying agents suitable for use in the coatings may be those well known in the art which include, but are not limited to, polyacrylates such as ρoly(butylacrylate), ρoly(ethylhexylacrylate) and mixtures thereof; and polyamides. Preferred flow modifying agents are polyacrylates.

[0047] Degassing agents suitable for use in the coatings may be those well known in the art which include benzoin which is the preferred degassing agent.

[0048] UV stabilizers suitable for use in the coatings may be those well known in the art which include, but are not limited to hindered amines and benzotriazoles. Preferred UV stabilizers are benzotriazoles.

[0049] Antioxidants suitable for use in the coatings may be those well known in the art which include, but are not limited to, hindered phenolics.

[0050] The invention will be further described by reference to the following examples which are presented for the purpose of illustration only and are not intended to limit the scope of the invention. Unless otherwise indicated, all parts are by weight.

EXAMPLES

Example 1 : Production of an Epoxy/Hydroxy-Functional Polymer

[0051] Epoxy/Hydroxy-Functional Polymers were made as follows: A reaction mixture of monomers, solvent and initiator was continuously supplied to a reactor comprising a continuous stirred tank reactor (CSTR) maintained at a constant temperature. Reaction zone mass and feed mass flow rate were controlled to provide a constant average residence time within the 10 to 15 minute range in the CSTR. The reaction temperature of the CSTR was maintained constant within the range of 175°C to 232°C. The reaction product was continuously pumped to a devolatization zone, and the polymeric product from the devolatization zone was continuously collected and later analyzed for molecular weight averages (Mn, Mw and Mz) and mass balance composition from which its epoxy equivalent weight (EEW) and hydroxyl equivalent weight (OHEEW) was computed. Table 1 shows Atty. Dkt. No.: 018894-0275

the amount of each monomer, solvent, and initiator in the monomer feed. Table 2 shows the polymerization temperature and some relevant characteristics for each polymer.

Table 1. Monomer Feeds

Table 2. Polymer Characteristics

Example 2: Production of Coatings

[0052] Coatings were formed on various metal substrates using a coating formulation comprising the first polymer in table 2 of Example 1, a polyamine crosslinking agent and a variety of catalysts. The polyamine crosslinking agent was a polyether triamine sold by Hunstman Corp. under the tradename Jeffamine T-403 ("T-403") and having the following structure: Atty. Dkt. No.: 018894-0275

[0053] The crosslinked polymer achieved adequate hardness in 15 minutes with a cure of temperature of ~110⁰C. A Cure at 80⁰C will also work, provided a sufficient ambient cure is allowed so that the polymer achieves full crosslinking and hardness. The fastest catalyst studied was salicylic acid.

[0054J The ratio of polymer to crosslinking agent in the coating composition was chosen to provide a 1 : 1 epoxy : NH equivalence. An epoxy equivalent weight of 500 g was used for the polymer and 81 g was used for the NH equivalent weight for the T-403. The catalysts investigated were salicylic acid (SA), p-toluene sulfonic acid (pTSA), and the combination of pTSA and Acc-399. Acc-399 is a promoter package from Huntsman Corp. containing about 60 % triethanolamine, 30 % aminoethyl piperazine (AEP), and 10 % piperazine (P). The experimental formulations used in this study are shown in Table 3, and include calculated solids, catalyst part per hundred (pHR), and effective catalyst molar ratios. N-butyl actate (nBAc), n-butanol, isopropanol (IPA) and mixtures thereof were used as solvents in the coating compositions. All formulations were given the additional accelerant of ~ 3.5 per hundred parts resin (pHR) nonylphenol. The T-403 amine, with a molecular weight of- 490 g, should not bake out of the coatings under any of the processing conditions employed in these studies.

[0055J Coatings were cast using a 4 mil gate applicator (Gardner Co.) over various metal substrates. At the solids concentrations in the coating formulations in Table 5, this provides about 1.2 mils dry film thickness (DFT). A bake study was conducted for coatings applied to bare iron (Fe) panels (B-1000), which were then cured for 30 minutes at 80, 100, Atty. Dkt. No.: 018894-0275

120, and 140 ⁰C, Additional panels were coated and studied for ambient hardness development. Draw down films were also cast over white-basecoated aluminum (Al) panels at 4 mil gate for preparation in a weathering study. Panels were removed from the oven after 30 minutes and brought to the constant temperature humidity room (CTHR) maintained at 77°F, 50% relative humidity (RH) and allowed to equilibrate for 30 minutes.

Table 3.

[0056] Formulation 1 had an effective molar ratio (acid:amine) of 0.145 and a solids content of about 60% by weight. The fractions of polymer and solvent (nBAc) in the initial polymer solution used to make the coating composition of formulation 1 were 0.6 and 0.4, respectively. The fractions of catalyst and solvent (n-butanol) in the catalyst solution used to make the coating composition of formulation 1 were 0.2 and 0.8, respectively. Formulation 2 had an effective molar ratio (acid: amine) of 0.185 and a solids content of Atty. Dkt. No.: 018894-0275

about 62% by weight. The fractions of polymer and solvent (nBAc) in the initial polymer solution used to make the coating composition of formulation 2 were 0.6 and 0.4, respectively. The fractions of catalyst and solvent (IPA) in the catalyst solution used to make the coating composition of formulation 2 were 0.4 and 0.6, respectively. Formulation 3 had an effective molar ratio (acid:amine) of 0.147 and a solids content of about 63% by weight. The fractions of polymer and solvent (nBAc) in the initial polymer solution used to make the coating composition of formulation 3 were 0.6 and 0.4, respectively. The fractions of catalyst and solvent (IPA) in the catalyst solution used to make the coating composition of formulation 3 were 0.4 and 0.6, respectively.

[0057] Table 4 summarizes the Konig data obtained for the three coating compositions shown in Table 3, including measurements taken immediately and measurements taken at day four. FIG. 1 is a plot of Konig hardness (swings) versus bake temperature for the three formulations used here.

Table 4.

Atty. Dkt. No.: 018894-0275

[0058] The results show that, using a modestly high level of SA, near or full cure using the T-403 amine in a bake system after 30 minutes at 100 ⁰C, or in -20 minutes at 105⁰C can be achieved. Curing is slower with pTSA, but the K-cure 1040 (King Industries, 40 % pTSA in IPA) is convenient to use. A cure using pTSA at 9O⁰C is expected to be comparable to a cure using SA at 80⁰C. The pTSA tended to give the poorest looking films, with some cratering and other defects observed. However, this could be due to the use of IPA as well as the pTSA. Finally, it is noted that films baked at 8O⁰C initially may be under-cured, but continue to cure post-bake under ambient conditions (Table 4).

[0059] The data presented here show that various catalyst packages can be used to achieve baked cure for a GMA resin with a slower reacting amine in the 100-110 ⁰C range.

Example 3 : Dual Functional Carboxylic Acid/Hydroxy Reactive Acrylic Polymer.

[0060] hi this example, the first polymeric product produced in the first reaction zone is a hydroxy functional polymer, which is directly charged into the second reaction zone with succinic anhydride to obtain a dual functional carboxylic acid/hydroxy reactive acrylic polymer. A reaction mixture including 31.15% St, 31.15% HEMA, 26.7% EHA, 10% MAK, and 1% DTBP was continuously supplied to a reactor comprising an agitated reaction zone maintained at a constant temperature. Reaction zone mass and feed mass flow rate were controlled to provide a constant average residence time within the 10 to 15 minute range in the agitated reaction zone. The reaction temperature of the agitated reaction zone was maintained constant at different settings within the range of 175⁰C to 232⁰C. The first polymeric product was continuously pumped to a devolatization zone, and then a reactor train. The continuous in-line post-modification in the reactor train was performed by addition of calculated amount of SAH to first polymeric product at 12O⁰C for an average residence time of 20 minutes. Properties of the first polymeric product and the reactive acrylic polymer are given below in Table 5. Atty. Dkt. No.: 018894-0275

Table 5

[0061] The resulting reactive polymers with controlled level of dual carboxylic acid and hydroxy functionalities were obtained in quantitative yield. Such reactive acrylic polyol polymers with high acid number are useful in preparing automotive coatings, industrial maintenance, and powder coatings. Such polymers can be cured with crosslinkers such as amino resins, polyisocyanates, epoxy resins, etc. Crosslinking takes place with one of the two types of functional groups. The other functional group is able to provide additional benefits to the coatings such as increased reactivity, etc.

Example 4: Polymer Containing Carboxylic Acid and Surfactant Like Functional Groups.

[0062] A monomer mixture was prepared by mixing monomers in a weight ratio of

28.4 parts styrene, 33.8 parts acrylic acid, and 37.8 parts α-methylstyrene monomers. A reaction mixture of the monomer mixture and varying weight percentages of PLURONIC® P84, a polymeric modifying agent that is a block copolymer of ethylene oxide and propylene oxide and is available from BASF Corporation, was continuously passed through a 500 mL continuous stirred tank reactor (CSTR) maintained at a constant temperature. The polymeric modifying agent had a M_n of 4200 and an average functionality of two hydroxyl condensation reactive groups on each chain. Reaction zone level and feed flow rate were Atty. Dkt. No.: 018894-0275

adjusted to provide a residence time of 12 or 24 minutes. The temperature of the reaction zone was maintained at 282⁰C. The reaction product was continuously collected and later analyzed for molecular weight averages (M_n, M_w and M_z) and acid number which indicates the level of functional carboxylic groups present on the polymer chains.

[0063] The resulting polymer is useful in preparing automotive coatings, industrial maintenance, and powder coatings. Additional benefits are obtained due to the presence of a surfactant-like functional group in the polymer. The polymer of this example contains non-ionic surfactant-like groups and is therefore amphoteric in character. This property provides benefits such as improved dispersibility and stabilization to coatings formulated from these polymers.

Example 5: Polymers Containing Carboxylic Acid and Hydrophobic Groups.

[0064] This polymer was prepared by the bulk polymerization and esterification process. The reaction components utilized, reactor feeds and resin composition are summarized in Table 6. The polymerization reaction conditions included about 15 minute reactor residence time and a reaction temperature of about 254⁰C. The resultant resin had a molecular weight (M_w) of about 1,800 daltons and an acid number of 237. Analysis of the polymeric product and process indicated that about 95.2 percent of the alkanol had been incorporated into the polymer.

Table 6

formalized reactor feed was calculated by assuming that initiator was not present in the feed. Atty. Dkt. No.: 018894-0275

[0065] This polymer has both ionic and hydrophobic groups and is useful in preparing automotive coatings, industrial maintenance, and powder coatings.. It provides benefits such as improved dispersibility and stability when used as a binder in coatings and inks.

[0066] It is understood that the invention is not confined to the particular formulations and arrangements of parts herein illustrated and described, but embraces all such modified forms thereof as come within the scope of the following claims.

Claims

Atty. Dkt. No.: 018894-0275WHAT IS CLAIMED IS:

1. A coating composition comprising: a polymer comprising: a epoxy-fiinctional acrylic monomer which has been polymerized into the polymer; and a hydroxy-functional acrylic or methacrylic monomer which has been polymerized into the polymer; and a crosslinking agent selected from the group consisting of epoxy, isocyanate, amino, amine and anhydride functional resins.

2. The coating composition of Claim 1 , wherein a coating made from the coating composition is free of blushing.

3. The coating composition of Claim 1 , wherein a coating made from the coating composition adheres to a substrate.

4. The coating composition of Claim 3, wherein the substrate is a metal substrate.

5. The coating composition of Claim 4, wherein the metal substrate is a chromium substrate.

6. The coating composition of Claim 1 , wherein the epoxy-functional acrylic monomer is glycidyl acrylate, glycidyl methacrylate, or a mixture thereof.

7. The coating composition of Claim 1 , wherein the hydroxy-functional acrylic or methacrylic monomer is 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2,3- hydroxypropyl acrylate, 2,3-hydroxypropyl methacrylate, 2,4- hydroxybutyl acrylate, 2,4-hydroxybutyl methacrylates, or a mixture of any two or more thereof.

8. The coating composition of Claim 1 , wherein the polymer has an EEW of at least 200 and an OHEW of at least 300. Atty. Dkt. No.: 018894-0275

9. The coating composition of Claim 1, wherein the polymer further comprises a monomer polymerized into the polymer selected from methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, s-butyl acrylate, i-butyl acrylate, t-butyl acrylate, n-amyl acrylate, i-amyl acrylate, isobornyl acrylate, n-hexyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-decyl acrylate, methylcyclohexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-propyl methacrylate, i-butyl methacrylate, n- amyl methacrylate, n-hexyl methacrylate, i-amyl methacrylate, s-butyl-methacrylate, t-butyl methacrylate, 2-ethylbutyl methacrylate, methylcyclohexyl methacrylate, cinnamyl methacrylate, crotyl methacrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, 2-ethoxyethyl methacrylate, isobornyl methacrylates, or a mixture of any two or more thereof.

10. The coating composition of Claim 1 , wherein the crosslinking agent is a polyamine crosslinking agent selected from ethylene diamine, diethylene triamine, triethylene tetramine, pentaethylene hexamine, 1 ,2-propylene diamine, 1,3 -propylene diamine, 1 ,4-butanediamine, 1,5-pentanediamine, 1 ,3-pentanediamine, 1,6-hexanediamine, 3,3,5-trimethyl-l ,6-hexanediamine, 3,5,5-trimethyl-l ,6-hexane-diamine, 2-methyl- 1 ,5-pentanediamine, bis-(3-aminopropyl)amine, N,N'-bis-(3 -amino-propyl)- 1 ,2- ethanediamine, N-(3 -amino-propyl)- 1 ,2-ethanediamine, 1 ,2-diamino-cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, aminoethylpiperazine, the poly(alkylene oxide) diamines and triamines (such as for example Jeffamine.RTM. D-230, Jeffamine D-400, Jeffamine D-2000, Jeffamine D-4000, Jeffamine T-403, Jeffamine EDR-148, Jeffamine EDR-192, Jeffamine C-346, Jeffamine ED-600, Jeffamine ED-900, and Jeffamine ED-2001), meta-xylylene diamine, phenylene diamine, 4,4'-diaminodiphenyl methane, toluene diamine, isophorone diamine, 3,3'- dimethyl-4,4'-diaminodicyclohexyl methane, 4,4'-diaminodicyclohexyl methane, 2,4'-diaminodicyclohexyl methane, a mixture of methylene bridged Atty. Dkt. No.: 018894-0275

poly(cyclohexylaromatic)amines, polyaminoamides, and mixtures of any two or more thereof.

11. A coating composition comprising: a polymer comprising: a carboxylic acid-functional acrylic monomer which has been polymerized into the polymer; and a hydroxy-functional acrylic or methacrylic monomer which has been polymerized into the polymer; and a crosslinking agent selected from the group consisting of epoxy, isocyanate, amino and anhydride functional resins.

12. The coating composition of Claim 11, wherein a coating made from the coating composition adheres to a substrate.

13. The coating composition of Claim 12, wherein the substrate is a metal substrate or a plastic substrate.

14. The coating composition of Claim 13, wherein the metal substrate is a chromium substrate.

15. The coating composition of Claim 11, wherein the carboxylic acid-functional acrylic monomer is acrylic acid, methacrylic acid, crotonic acid, fumaric acid, or a mixture of any two more thereof.

16. The coating composition of Claim 11 , wherein the hydroxy-functional acrylic or methacrylic monomer is 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2,3- hydroxypropyl acrylate, 2,3-hydroxypropyl methacrylate, 2,4- hydroxybutyl acrylate, 2,4-hydroxybutyl methacrylates, or a mixture of any two or more thereof.

17. A coating composition comprising: a polymer comprising: Atty. Dkt. No.: 018894-0275

a first monomer with a surfactant moiety which has been polymerized into the polymer; and a second monomer which has been polymerized into the polymer wherein the second monomer has at least one moiety selected from epoxy, hydroxyl, and carboxylic acid; and a crosslinking agent selected from the group consisting of epoxy, isocyanate, amino, amine and anhydride functional resins.

18. The coating composition of Claim 17, wherein the surfactant moiety of the first monomer is a polyethylene glycol or polypropylene glycol moiety.

19. The coating composition of Claim 17, wherein the second monomer is glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2,3-hydroxypropyl acrylate, 2,3-hydroxypropyl methacrylate, 2,4- hydroxybutyl acrylate, 2,4-hydroxybutyl methacrylates, acrylic acid, methacrylic acid, crotonic acid, fumaric acid, or a mixture of any two more thereof.