Title of Invention

"AN AMINOPLAST BASED CROSSLINKING AGENT, METHOD OF PREPARATION THEREOF AND A CURABLE POWDER COATING COMPOSITION CONTAINING SAID CROSSLINKING AGENT"

Abstract The present invention provides an aminoplast based crosslinking agent having reactive benzoxazine groups comprising the ungelled reaction product of the following reactants: (a) at least one mono-hydroxy aromatic compound having the following structure (I): wherein R1 represents a monovalent hydrocarbon group, COOR5 where R5 represents H or a monovalent hydrocarbon group, NO2, halogen or XR4, where X represents O or S and R4 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms; R3, R3', R2 and R2' can be the same or different and each independently represents a substituent selected from H, a monovalent hydrocarbon group, COOR5, NO2, halogen and XR4, provided that at least one of R3 and R3' is H; or when R3' is non-hydrogen substituted and R3' is H, RI and R2 taken together, R1 and R2' taken together, or R2 and R3 taken together represent fused aliphatic or aromatic ring structures, or when R3' is non-hydrogen substituted and R3 is H, R1 and R2 taken together, RI and R2' taken together, or R2' and R3' taken together represent fused aliphatic or aromatic ring structures; and (b) at least one aminotriazine compound having one or less non-alkylated NH group, present in a molar ratio of reactant (a) to reactant (b) ranging from 1.0 to 3.0: 1.0, provided that where reactant (a) is a single ring monohydroxy aromatic compound, the molar ratio of reactant (a) to reactant (b) ranges from 1.0 to less than 1.8:1.0 and from greater than 2.2 to 3.0:1.0, wherein said crosslinking agent is essentially free of hydroxyl functionality and has a glass transition temperature of at least 40°C. The invention also relates to a method of preparation of said crosslinking agent and to a curable powder coating composition containing the crosslinking agent.
Full Text FIELD OF THE INVENTION
The present invention relates to amino-plast based crosslinking agents, to method of preparation of such compositions and to curable powder coating compositions containing such amino-plast based crosslinking agents.
The present invention relates to crosslinkers based on aminoplast resins and mono-hydroxy aromatic compounds, to a method for preparing such crosslinking agents and to curable powder coating compositions containing such crosslinkers.
BACKGROUND OF THE INVENTION
In recent years, powder coatings have become increasingly popular because these coatings are inherently low in volatile organic content ("VOC"), which significantly reduces emissions of volatile organic compounds into the atmosphere during application and curing processes.
Hydroxyl, carboxyl, carbamate and/or epoxy functional resins, such as acrylic and polyester resins having relatively high glass transition temperatures ("Tg"), are commonly used as main film-forming polymers for these coatings. The relatively high Tg of such acrylic polymer systems provides powder coatings having good storage stability. However, when exposed to the extreme temperatures which can be encountered during shipping and/or storage in many geographic areas, even better powder coating stability is desired.
Aminoplast resins are well known in the art as low cost crosslinking agents for hydroxyl, carboxyl and/or carbamate functional polymers in conventional liquid coating compositions. Common aminoplast resins are based on condensation products of formaldehyde with an amino- or amido-group carrying substance. Condensation products obtained from the reaction of alcohols and formaldehyde with melamine, urea or benzoguanamine are most commonly used in liquid coating compositions where they provide enhanced coating properties such as exterior durability, chemical resistance and mar resistance. Such aminoplast resins typically are in liquid form and,
as such, generally are not suitable for use in curable powder coating compositions.
The alkoxylated aldehyde condensates of glycoluril, which are solid products, are the aminoplast resins most commonly employed as crosslinking agents in powder coating compositions. Although in solid form, these materials nonetheless can depress the Tg of the powder coating composition significantly, even when combined with high Tg film-forming polymers such as the acrylic polymers described above. Such a depression in Tg also can result in poor powder stability.
Moreover, the use of conventional aminoplast resins in curable powder coating compositions can result in the phenomenon commonly referred to as "gassing*. "Gassing" occurs as a result of vaporization of the alcohol generated in the thermally induced aminoplast crosslinking reaction. The alcohol vapor is driven off through the coating film upon heating and, as the viscosity of the coating increases during the curing process, pinholes or craters are formed as gases escape through coating surface.
U.S. Patent Nos. 3,904,623,4,189,421 and 4,217,377 disclose a solid, non-gelled low molecular weight addition reaction product and a method for preparing the reaction product. The addition reaction product is suitable for use as a crosslinking agent in powder coating compositions when combined with polymers having various reactive functional groups. The crosslinking agent is the reaction product of 1.8 to 2.2 moles of a monohydroxy-, single-ring aromatic compound, for example phenol, and 1 0 mole of an aikoxymethyl aminotriazine compound, such as hexakis (methoxymethyl) aminotriazine.
U.S. Patent No. 4,393,181 discloses solid, adducts prepared from aminotriazine compounds and a large excess of polyhydric phenols. The adducts, due to their phenolic functionality, are useful as crosslinking agents for epoxy resins in powder coating compositions when used in conjunction with a curing agent accelerator such as an imidazole or benzimidazole.
U.S. Patent No. 3.759,864 discloses heat-fusible powder coating compositions comprising a crossiinker prepared by pre-reacting a thermosetting polyester resin and a suitable conventional aminoplast crosslinking lesin such as a condensation product of an aldehyde with meiamine, urea or benzoguanamine.
U.S. Patent No. 5,302,462 discloses a similar process for preparing a partially cured powder coating crossiinker. The crossiinker is prepared by partially reacting a less than stoichiometric amount of methoxymethyl aminotriazine with a linear, hydroxyl-terminated polyester.
U.S. Patent No. 3,980,732 discloses a process for preparing a curable powder resin composition having a sintering temperature above 40°C. The method comprises partially reacting a methylolamino compound with an aliphatic alcohol and an aliphatic diamide to produce an aminoplast condensate with a Tc ranging from -10°C to 100°C and blending the aminoplast condensate with an acrylic or polyester resin having a glass transition temperature ranging from 60°C to 100°C.
U.S. Patent No. 4,185,045 discloses a powder coating composition comprising a solid crosslinking agent having a softening point ranging from 50°C to 120°C and prepared by heating 40 to 75% by weight of an acrylic polyol and 60 to 25% by weight of an alkoxyaminotriazine at 50° to 120°, and a base resin having a softening point ranging from 60°C to 130°C.
U.S. Patent No. 4,230,829 discloses a solid crosslinking agent having a softening point of 50°C to 120°C and prepared by heating 40 to 70% by weight cf a polyester polyol and 60 to 30% by weight of an aikoxyaminotriazine.
While the above-described prior art aminoplast-based crossiinkers for powder coating compositions provide some improvement in "gassing" and powder stability over their liquid aminoplast counterparts, the powder coating compositions containing these crossiinkers can, nonetheless, exhibit some of the aforementioned deficiencies. In addition, most of the crossiinkers disclosed in the prior art are high molecular weight, partially cured and,

hence, unstable mixtures. Further, the crosslinkers described in U,S. Patent Nos. 3,904,623, 4,189;421. and 4.217,377 contain a significant amount of unreacted phenol impurity, which significantly limit their use in the powder coatings industry.
Thus, there remains a need for an aminoplast crosslinking agent suitable for use in curable powder coating compositions which provides a storage stable powder composition having the desirable coating properties usually associated with arninoplast-based liquid coatings without causing coating surface defects due to "gassing".
SUMMARY OF THE INVENTION In accordance with the present invention, provided is a crosslinking agent having reactive benzoxazine groups comprising the ungelled reaction product of (a) at (east one mono-hydroxy aromatic compound having the following structure (I):
(Formula Removed)
wherein R1 represents a monovalent hydrocarbon group, COOR5 where R5 represents H or a monovalent hydrocarbon group NO2, halogen or X R4, where X represents 0 or S and RA represents a monovalent hydrocarbon group having 1 to 8 carbon atoms; R5, R3', R2 and R2' can be the same or different and each independently represents a substituent selected from H, a monovalent hydrocarbon group, COOR5, N02. halogen and XR4. provided that at least one of R3 and R3' is H; or, when R3 is other than H (i.e., "non-hydrogen substituted") and R3" is H, R1 and R2 taken together, R1 and R2' taken together, or R2 taken together with the non-hydrogen substituted R3
represent fused aliphatic or aromatic ring structures; or, when R3' is non-hydrogen substituted and R3 is H, R, and R2 taken together, R1 and R2' taken together, or R2' taken together with the non-hydrogen substituted R3' represent fused aliphatic or aromatic ring structures, and (b) at least one aminotriazine compound having one or less non-alkylated NH group. Reactants (a) and (b) are present in a molar ratio of reactant (a) to reactant (b) ranging from 1.0 to 3.0: 1.0, provided that where reactant (a) is a single ring monohydroxy aromatic compound, the moiar ratio of reacfant (a) to reactant (b) ranges from 1.0 to 1 8:1.0 and from 2.2 to 3.0:1.0, wherein the crosslinking agent is essentialfy free of hycroxyl functionality and has a glass transition temperature of at least 25°C.
The present invention is further directed to a method for preparing the above-described crosslinking agent. The method comprises the steps of (1) combining (a) at least one mono-hydroxy aromatic compound having the structure (I) where R1, R2, R2', R3 and R3' are as described above for that structure and (b) at least one aminotriaine compound having one or less non-alkylated NH group, in a molar ratio of (a) to (b) ranging from 1 0 to 3.0: 1.0, provided that where reactant (a) is a single ring monohydroxy aromatic compound, the molar ratio of reactant (a) to reactant (b) ranges from 1.0 to 1.8:1.0 and from 2.2 to 3.0:1.0, to form a reaction admixture; (2) heating the reaction admixture of step (1) to a temperature ranging from 90°C to 135°C; and (3) maintaining the temperature achieved in step (2) for a time sufficient to produce an ungelled reaction product having a glass transition temperature of at least 25°C which is essentially free of hydroxy! functionality as determined by infrared spectroscopy.
The present invention is also directed to a eurabie powder coating composition comprising a solid particulate, film-forming mixture of (A) a polymer having functional groups reactive with benzoxazine groups, the polymer having a glass transition temperature of at least 30°C; and (B) the previously described crosslinking agent.
Multilayer composite coating compositions are also provided. The multilayer composite coating composition comprises a base coat deposited from a film-forming composition and a topcoat over the base coat. The topcoat is deposited from the curable powder coating composition described above.
The present invention further provides coated substrates,
DETAILED DESCRIPTION OF THE INVENTION
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.
As mentioned above, the crosslinking agent of the present invention comprises the ungelled reaction product of (a) at least one mono-hydroxy aromatic compound having the structure (I) as described above, and (b) at least one aminotriazine compound having one or less non-alkylated NH group (described in detail below).
By "ungeiled" is meant that the reaction product can be dissolved.in a suitable solvent or resin and has an intrinsic viscosity when so dissolved. The intrinsic viscosity of the reaction product is an indication of its molecular weight. A gelied reaction product, on the other hand, since it is of essentially infinitely high molecular weight, will have an intrinsic viscosity too high to measure. Moreover, the reaction product can be melted, solidified and remelted.
The substituent group R, represents a monovalent hydrocarbon, COOR5 where R5 represents H or a monovalent hydrocarbon group, NO2, halogen or XR4, where X represents O or S and R4 represents a monovalent hydrocarbon group, preferably having 1 to 8 carbon atoms.
By "monovalent hydrocarbon group" is meant an organic group containing essentially carbon and hydrogen. The hydrocarbon groups may be aliphatic, aromatic, cyclic or acyclic and may contain from 1 to 24 (in the case of aromatic from 3 to 24} carbon atoms. Optionally, the hydrocarbon groups can be hetsroatomic hydrocarbon groups, that is, the hydrocarbon groups can be substituted with heteroatoms, typically oxygen or nitrogen. Non-limiting examples of such monovalent hydrocarbon groups include alkyl, alkoxyl, aryl, alkylaryl cr aikoxyaryl groups.
By "alkyl" is meant acyclic or cyclic alkyl croups having a carbon chain length of from C1 to C35. By "alkoxyl" is meant an alkyl group containing at least one oxygen atom, such as an ether oxygen, and having a carbon chain length of from C2 to C25, preferably of from C2 to C8. By alkylaryl is meant an acyclic alkyl group having a carbon chain length of from C2to C25and containing at least one aryl group, preferably phenyl. The aryl group(s) may
optionally be substituted. Suitable substituent groups can include hydroxyl, benzyl, catboxylic acid and aliphatic groups.
The substituent groups R3, R3, R2 and R2' can be the same or different and each independently represents a substituent selected from H, monovalent hydrocarbon groups, COOR5 where R5 represents H or a monovalent hydrocarbon group, NO2, halogen and XR4 where X represents 0 or S and R4 represents a monovalent hydrocarbon g'oup, preferably having 1 to 8 carbon atoms, provided that at least one of R3 and R3' s H. in a preferred embodiment of the present invention. R3 and R3' both represent H. In another preferred embodiment of the present invention, R, is an aryi group and R2, R2', R3 and R3' are the same or different and each independently represents H. monovalent hydrocarbon groups, COOR5 where R5 represents H or a monovalent hydrocarbon group, NOj, halogen and XR4 where X represents O or S and R4 represents a monovalent hydrocarbon group, preferably having 1 to 8 carbon atoms, provided that at least one of R3 and R3' is H.
Non-limiting examples cf mono-hydroxy aromatic compounds suitable for use as reactant (a) in the present invention include p-cresol, 4-methoxyphenol. 4-tert-butyl phenol, 4-nitrophenoi, 4-fluorophenol, 2-phenyl phenol, 4-phenyl phenol, 1-naphthol, and 2-naphthcl The preferred mono-hydroxy aromatic compound comprises 4-phenyl phenol.
Afternatively. when R3 represents a substituent other than H (i.e.. is "non-hydrogen substituted") and R3' is H, R1 and R2 taken together, R1 and R2 taken together, or R2 taken together with the non-hydrogen substituted R3 represent fused aliphatic or aromatic ring structures, or when R3' is non-hydrogen substituted and R3 is H, R1 and R2 taken together, R1 and R2' taken together, or R2 taken together with the non-hydrogen substituted R3' represent fused aliphatic or aromatic ring structures
In one preferred embodiment of the present invention, R1 represents an electron-withorawing group selected from aryl, atkylaryl, alkoxy. COOH, NO2 and halogen
As previously mentioned, the crosslinking agent of the present invention comprises the reaction product of at least one mono-hydroxy aromatic compound as reactant (a) (as described above) and, as reactant (b), at least one amhotriazine compound having one or less non-alkylated NH group. The aminotriazine compound (b) which has one or less non-alkylated NH bond per triazine ring can include aminoplast resins such as alkoxyalkyl derivatives of melamine, benzoguanimine, acetoguanamine. formoguanamine, spiroguanamine and the like. In a preferred embodiment of the present invention, the aminotriazine compound (b) comprises a (methoxymethyl) aminotriazine compound, for example, (methoxymethyl) melamine.
Aminoplast resins are based on the condensation products of formaldehyde, with an amino- or amido-group carrying substance. Condensation products obtained from the reaction of alcohols and formaldehyde with melamine, urea or benzoguanamine are most common and preferred herein. However, condensation products of other amines and amides can also be employed, for example, aldehyde condensates of triazines, diazines, triazoies, guanadines, guanamines and alkyl- and aryl-substituted derivatives of such compounds, including alkyl-and aryl-substituted ureas and alkyl- and aryl-substituted melamines. Some examples of such compounds are N.N'-dimethyl urea, benzcurea, dicyandiamide, formaguanamine, acetcguanamme, glycoluril. ammeline, 2-chloro-4,6-diamino-1,3,5-triazine, 6-methy!-2,4-diamir.o-1,3,5-triazine 3,5-diammotriazole, triaminopyrimidine, 2-mercapto-4.6-diaminopyrimidine and 3,4,6-tris(eihylamino)-1,3,5 triazine.
While the aldehyde employed is most often formaldehyde, other similar condensation products can be made from other aldehydes, for example acetaldehyde, crotonaidehyde, acrolein, benzaldehyde, furfural and glyoxal.
The aminoplast resins preferably contain methylol or other alkylol groups, and in most instances, at least a portion of these alkylol groups are etherified by a reaction with an alcohol. Any monohydric alcohol can be employed for this purpose, including such alcohols as methanol, ethanol, prcpanol, butanol, pentanol, hexanol, heptanoi and others, as well as, benzyl
alcohol and other aromatic alcohols, cyclic alcohols such as cyclohexanol, monoethers of glycols, and halogen-substituted or other substituted alcohols, such as 3-chloropropanol and butoxyethanol. Commonly employed aminoplast resins are substantially alkylated with methanol or butanol.
Preferred aminoplast resins for use as the aminotriazine compound (B) in the preparation of the crosslinking agent of the present invention are the highly alkylated, low imino aminoplast resins which have a degree of polymerization ("DP") of less than 1.5. Generally, the number average degree of polymerization Is defined as the average number of structural units per polymer chain (see George Odian, Principles of Polymerization, John Wiley & Sons (1991)), For purposes of the present invention, a DP of 1.0 would indicate a complete monomeric triazine structure, while a DP of 2.0 indicates two triazine rings joined by a methylene or methylene-oxy bridge. It should be understood that the OP values reported herein and in the claims represent average DP values as determined by gel permeation chromatography data.
Preferred aminotriazine compounds include modified melamine-formaldehyde resin, for example RESIMENE® CE-7103 commercially available from Solatia, Inc. and CYMEL® 300; ethylated-methylated benzoguanimine-formaldehyde resin, for example CYMEL® 1123; and methylated-butylated melamine-formaldehyde resin, for example CYMEL® 1135, both of which are commercially available from Cytec Industries, Inc.
The present invention is also directed to a method for preparing the above-described crosslinking agent The mono-hydroxy aromatic compound (a) and the aminotriazine compound (b) generally are combined in a suitably equipped reaction vessel, typically with a suitable solvent and an appropriate strong acid as catalyst. Any suitable solvent can be used, with aromatic solvents being preferred. Non-limiting examples of suitable aromatic solvents include xylene, toluene, and mixtures thereof. Non-limiting examples of strong acids suitable for use as a catalyst include, but are not limited to, para-toluene sulfonic acid and dodecyl benzene sulfonic acid. Normal condensation techniques as are well-known in the art can be used.
The reaction admixture is heated to a temperature ranging from 90°C to 135°C, preferably from 100°C to 120°C, and held at that temperature for a period sufficient to obtain an ungelled product having a Tg of at least 25°C. The reaction is terminated when the end point (i.e., the disappearance of the OH signal) is detected by infrared spectroscopy.
It should be understood that the molar ratio of reactant (a) to reactant (b) can range from 1.0 to 4.0: 1.0, more preferably from 1 to 3:1.0 with the proviso that where reactant (a) is a single ring monohydroxy aromatic compound, the molar ratio of reactant (a) to reactant (b) ranges from 1 0 to 1.8:1.0 and from 2.2 to 3.0:1.0. Also, it should be noted that for purposes of the present invention, the theoretical molecular weight of the monomerjc aminotriazine compound (that is, where DP=1) is used to calculate the "molar ratio".
Depending on the molar ratio, the resulting crosslinkers may contain different amounts cf residual aminotriazine functionality. For example, in practice, one mole of mono-hydroxy aromatic compound (a) typically consumes two mcies of reactive functionality of the aminotriazine compound (b).The above-described reaction typically results in a crosslinking agent having both reactve aminotriazine groups and benzoxazine groups. Theoretically, at a molar ratio of reactant (a) to reactant (b) of 3.0:1.0, all of the aminotriazine functionality will be consumed. A higher ratio of reactant (a) to reactant (b) typically :s not desired because it can result in a crosslinking agent having residual OH functionality.
Preferably, in the preparation of the crosslinking agent of the present invention the monc-hydroxy aromatic compound (a) and the aminotriazine compound (b) are combired in a molar ratio such that the mono-hydroxy aromatic compound (a) is in excess. This results in a stable crosslinking agent which is essentially fiee of hydroxy! functionality. The reaction is monitored for the disappearance of hydroxyl functionality relative to an internal standard via infrared spectroscopy (i.e., the hydroxy! signal is compared to the signal of a structure which will remain essentially unchanged as the reaction proceeds to completion, for example, the C-H stretch signal).
The mechanism for the benzoxazine ring formation includes an electrophilic aromatic substitution followed by O-alkylation, which is assisted by the formation of the benzoxazine ring structure. It should be understood that formation of the benzoxazine ring structure at the ortho-postion is preferable because such a reaction at the para-position can result in an undesirable increase in molecular weight and, ultimately, gellation of the reaction.
To prevent gellation, the substituent groups on the mono-hydroxy aromatic ring should be such that the first aromatic substitution occurs at the position ortho to the phenolic OH group and the remaining positions are deactivated or blocked with respect to further electrophilic substitution reaction, or at least made to react slower than the subsequent O-alkylation reaction. To ensure that the remaining positions on the ring are deactivated with respect to further electrophilic substitution, the substituent group R1 preferably represents an electron-withdrawing group.
By "electron-withdrawing group" is meant herein a substituent group which is capable of withdrawing electrons from the aromatic ring, destabilizing charge and thereby substantially deactivating all remaining positions of the aromatic ring to further electrophilic substitution. In a preferred embodiment of the present invention, the substituent R1 represents an electron-withdrawing group selected from aryl, alkylaryl, alkoxy, COOH, NO2 and halogen. The benzoxazine structures formed in the syntheses described above can be confirmed by NMR spectroscopy data.
By way of example, the reaction of a monomeric hexa(methoxymethyl) melamine with monohydroxy aromatic compound, for example, phenol, is represented structurally below.
(Formula Removed)
The reaction product depicted above is the theoretical product resulting from tine above-described condensation reaction where the molar ratio of reactant (a) to reactant (b) is 3:1. This theoretical reaction product would contain only reactive benzoxazine groups. As mentioned above, in practice, however, the reaction typicaiiy results in a crosslinking agent having both reactive aminotriazine groups and benzoxazine groups.
The crosslinking agent of the present invention typically has a glass transition temperature of at least 25°C, preferably at least 30°C, more preferably at least 35°C, and even more preferably at least 40°C. Also, the crosshnking agent typically has a glass transition temperature less than 100°C, preferably less than 85°C, more preferably less than 75°C, and even more preferably less than 70°C. The glass transition temperature of the crosslinking agent can range between any combination of these values, inclusive of the recited values. The Tg of the crosslinking agent can be measured experimentally using differential scanning calorimetry (rate of heating 10°C per minute, T9 taken at the first inflection point) Unless otherwise indicated, the stated Tg as used herein refers to the measured Tg.
The present invention is also directed to curable powder coating compositions comprising (A) a polymer having functional groups reactive with
benzoxazine groups (as well as aminotriazine groups) and having a glass transition temperature of at least 30°C, and (B) the crossllnking agent described above. Curable powder coatings are particulate compositions that are solid and free flowing at ambient room temperature. As mentioned above, the curable powder coating compositions of the present inventor comprise, as a first component (A), at least one reactive functional group-containing polymer having a glass transition temperature of at least 30°C, e.g., a hydroxyl and/or an epoxide functional acrylic polymer, and as a second component (B). the cross/inking agent described above. The components (A) and (B) of the curable powder coating composition may each independently comprise one or more functional species, and are each present in amounts sufficient to provide cured coatings having a desirable combination of physical properties, e.g., smoothness, optical clarity, scratch resistance, solvent resistance and hardness.
As used herein, the term "reactive" refers to a functional group that forms a covalent bond with another functional group under suitable reaction conditions.
As used herein, the term "cure" as used in connection with a composition, e.g., "a curable composition," shall mean that any crosslinkable components of the composition are at ieast partially crosslinked. In certain embodiments of the present invention, the crosslink density of the crosslinkable components, i.e., the degree of crosslinkmg, ranges from 5% to 100% of complete crosslinking. In other embodiments, the crosslink density ranges from 35% to 35% of full crosslinking. In other embodiments, the crosslink density ranges from 50% to 85% of full crosslinking. One skilled in the art will understand that the presence and degree of crosslinking, i.e., the crosslink density, can be determined by a variety cf methods, such as dynamic mechanical thermal analysis (DMTA) using a Polymer Laboratories MK III DMTA analyzer conducted under nitrogen. This method determines the glass transition temperature and crosslink density of free films of coatings
or polymers. These physical properties of a cured material are related to the structure of the crosslinked network
According to this method, the length, width, and thickness of a sample to be analyzed are first measured, the sample is tightly mounted to the Polymer Laboratories MK III apparatus, and the dimensional measurements are entered into the apparatus. A thermal scan is run at a heating rate of 3°C/min, a frequency of 1 Hz, a strain of 120%, and a static force of 0.01N, and sample measurements occur every two seconds. The mode of deformation, glass transition temperature, and crosslink density of the sample can. be determined according to this method. Higher crosslink density valves indicate a higher degree cf crosslinking in the coating.
Also, as used herein, the term "polymer" is meant to refer to oligomers and both homopolymers and copolymers. Unless stated otherwise, as used m the specification and the claims, molecular weights are number average molecular weights for polymeric materials indicated as "Mn" and obtained by gel permeation chromatography using a polystyrene standard in an art-recognized manner.
The polymer (A) can be any of a variety of polymers having arr.inopiast-reactive functional groups as are well known in the art, so long as the Ts of the polymer is sufficiently high to permit the formation of a stable, solid particulate composition. The Tc of the polymer (A) typically is at least 30°C. preferably at least 40°C, more preferably at least 50°C. The T9 of the polymer (A) also typically is less than 130°C, preferably less than 100°C, more preferably less than 8C°C. The T9 of tne functional group-containing polymer (A) can range between any combination of these values inclusive of the recited values.
Non-limiting examples of polymers having alkoxyalkyl aminotriazine and/cr benzoxazine-reactive functional groups useful in the curable powder coating compositions of the invention as the polymer (A) include those selected from the group consisting of acrylic, polyester, polyurethane, polyepoxide and polyether polymers. The polymer (A) can comprise a wide
variety of alkoxyalkyl aminotriazine and /or benzoxazine-reactive functional groups, for example hydroxyl, carboxyl, anhydride, epoxy, thiol, phenolic, amine and/or amide functional groups. The polymer (A) preferably comprises alkoxyalkyl aminotriazine/benzoxazine-reactive functional groups selected the group consisting of hydroxyl, epoxy, carboxyl and/or carbamate functional groups, with hydroxyl and/or carbamate functional groups being preferred.
In one embodiment of the present invention, the polymer (A) comprises hydroxyl and/or carbamate functional groups Hydroxyl and/or carbamate functional group-containing acrylic polymers and/or polyester polymers are preferred. In another embodiment of the invention, the polymer (A) comprises epoxy and/or hydroxyl functional groups.
Suitable functional group-containing acn/lic polymers include copolymers prepared from one or more alkyl esters of acrylic acid or methacrylic acid and, optionally, one or more other polymerizable ethylenically unsaturated monomers. Suitable alkyl esters of acrylic or methacrylic acid include methyl (meth)acrylate, ethy! (rneth)acry(ate, butyl (meth)acryiate. As used herein, by "(meth)acryiate" and like terms is meant both methacrylates and acrylates. Ethylenically unsaturated carboxylic acid functional monomers, for examp e acrylic ac;u and/or methacrylic acid, can also be used when a carboxylic acid functional acrylic polymer is desired. Amide functional acrylic polymers can be formed by polymerizing ethylenically unsaturated acrylamide monomers, such as N-butoxymethyl acrylamide and N-butoxyethy! acrylamide with ether po'ymerizable ethylenically unsaturated monomers. Non-limiting examples of suitable other polymerizable ethylenically unsaturated monomers include vinyl aromatic compounds, such as styrene and vinyl toluene; nitrites, such as acrylonitrile and methacry'.onitrile; vinyl and vinylidene halides, such as vinyl chloride and vinylidene fluoride and vinyl esters, such as vinyl acetate.
In one embodiment, the acrylic polymers contain hydroxyl functionality which can be incorporated into the acrylic polymer through the use of hydroxyl functional monomers such as hydroxyethyl (meth)acrylate and
hydroxypropyl (meth)acryiate which may be copoiymerized with the other acryiic monomers mentioned above.
The acrylic polymer can be prepared from ethylenically unsaturated, beta-hydroxy ester functional monomers. Such monomers are derived from the reaction of an ethylenical!/ unsaturated acid functional monomer, such as monocarboxyiic acids, for example, acrylic acid, and an epoxy compound which dues not j:art:cipace in the free radical initiated polymerization with the unsaturated acid monomer. Examples of such epoxy compounds are glycidyl ethers and esiers. Suitable glycidyl ethers include glycidyl ethers of alcohols and pher.o's, such as butyl glycidyl ether octyi glycidyl ether, phenyl glycidyl ether and the i:ke. Suitable giycidvl esters irclude those which are commercially ava.lable from Shell Chemical Company under the tradename CARDURA® E; and from Exxon Chemical Company under the tradename
GLYDEXX®-10.
Alternatively, the beta-hydroxy ester functional monomers are prepared from an ethylenically unsaturated, epoxy functional monomer, for example giycidyl methacrlate and allyl clycdyl ethe", and a saturated carboxyi:c acid such as s saturatec monocarboxylic acid, for example, isostearic acid.
The hydroxy group-rontairinc acybc polymers useful in the compositions of the present invention typically have anydroxyl value ranging ion 5 to 150 prefergoly from 10 to 100. ana mors preferably from 20 to 150
The acrylic polymer is typicaly prepared by solution pciymenzalicn techniques the pressuere of suitable initiators such as organic peroxides or azo compound, tor example, benzoyl oeroxide or N,N-azobisusobutytrotnis The polymerization can. be carried out :n an organic solution ;in. vrnicle the monomers are solube by techniques conventional \r the art.
Pendent and.or terminal Carbamate functional groups can be incorporated into the acrylic polymer by copolymerizing the acrylic monomer v/itn a carbamate functional vinyl monomer, such as a carbamate functional
aikyl ester of methacrylic acid. These carbamate functional alkyl esters are prepared by reacting, for example, a hydroxyalkyl carbamate, such as the reaction product of ammonia and ethylene carbonate or propylene carbonate, with methacrylic anhydride. Other carbamate functional vinyl monomers can include the reaction product of hydroxyethyl methacrylate. isophorone diisocyanate and hydroxypropyl carbamate. Still other carbamate functional vinyl monomers may be used, such as the reaction product of isocyanic acid (HNCO) with a hydroxy! functional acrylic or methacrylic monomer such as hydroxyethyl acrylate, and those carbamate functional vinyl monomers described in U.S. Patent No. 3,479,328
As is preferred, carbamate groups can also be incorporated into the acrylic polymer by a "transcarbamoylation" reaction in which a hydroxyl functional acrylic polymer is reacted with a low molecular weight carbamate derived from an alcohoi or a glycol ether. The carbamate groups exchange with the hydroxyl groups yielding the carbamate functional acrylic polymer and the original alcohol or glycol ether.
The low molecular weight carbamate functional material derived from an alcohol or glycol ether is first prepared by reacting the alcohol or glycol ether with urea in the presence of a catalyst such as butyl stannoic acid. Suitable alcohols include lower molecular weight aliphatic, cycloaliphatic and aromatic alcohols such as methanol, ethancl, propanol, butanol, cyclohexanol, 2-e,.nyihexanoi and 3-methyloutano!. Suitable glycol etners include ethylene glycol methyl ether and propylene glycol methyl ether. Propylene glycol methyl ether is preferred.
Also hydroxyl functional acrylic polymers can be reacted with isocyanic acid yielding pendent carbamate groups. Note that the production of isocyanic acid is disclosed in U.S. Patent No. 4,364,913. Likewise, hydroxyl functional acrylic polymers can be reacted with urea to give an acrylic polymer with pendent carbamate groups
Epoxide functional acrylic polymers are typically prepared by polymerizing one or more epoxide functional ethylenically unsaturated
monomers, e.g., glycidyl (meth)acrylate and ailyl glycidyl ether more ethylenicaily unsaturated monomers that are free of e i functionality, e.g., methyl (meth)acryJate, isobornyl (meth)au.. (meth)acrylate and styrene. Examples of epoxide functional ethylei.. unsaturated monomers that may be used in the preparation of epoxide functional acrylic polymers include, but are not limited to, glycidyl (meth)acrylate, 3,4-epoxycyclohexyImethyl (meth)acrylate, 2-(3,4-epoxycyclchexyl)ethy! (meth)acrylate and aliyl glycidyl ether. Examples of ethylenicaily unsaturated monomers that are free cf epoxide functionality include those described above as well as those described in U.S. Patent 5,407,707 at column 2, lines 17 through 56, which disclosure is incorporated herein by reference. In one embodiment of the present invention, the epoxide functional acrylic polymer is prepared from a majority of (meth)acrylate monomers.
The functional group-containing acryiic polymer typically has a Mn ranging frcm 500 to 30,000 and preferably from 1000 to 5000. If carbamate functions!, the acrylic polymer typically has a calculated carbamate equivalent weight typically within the range cf 15 to 150, and oreferably less than 50, Dased on equivalents of reactive carbamate groups.
Non-limiting examples of functional group-containing polyester polymers suitable for use as the polymer (A) in the curable powder coating compositions of the present invention car-, include imear or branched polyesters having hydroxy!, carboxyl and/or carbanate functionality. Such polyeste' polymers are generally prepared by the oolyesterification of a polycarboxylic acid or anhydride thereof with polyois and/or an epoxide using tecnniques known to these skilled in the art. Usually, the pclycarboxylic acids and polyois are aliphatic or aromatic dibasic acids and diols. Transesterification of polycarboxylic acid esters using conventional techniques is also possible.
The polyois which usually are employed in making the polyester (or the polyurethane polymer, as described below) include alkylene glycols, such as
ethylene glycol and other diols, such as neopentyl glycol, hydrogenated Bisphenol A, cyclohexanediol, butyl ethyl propane diol, trimethyl pentane diol, cyclohexanedimethanol, caprolactonediol, for example, the reaction product of epsilon-caprolactone and ethylene glycol, hydroxy-alkylated bisphenols, polyether glycols, for example, poly(oxytetramethylene) glycol and the like. Polyols of higher functionality may also be used. Examples include trimethylolpropane, trimethylolethane, pentaerythritol, tris-hydroxyethylisocyanurate and the like. Branched polyols, such as trimethylolpropane, are preferred for use in the preparation of the polyester.
The acid component used to prepare the polyester polymer can include, primanly, monomeric carboxylic acids or anhydrides thereof having 2 to 18 carbon atoms per molecule. Among the acids which are useful are cycloaliphatic acids and anhydrides, such as phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, 1,3-cyclohexane d;carboxylic acid and 1,4-cydohexane dicarboxytic acid. Other suitable acids include adipic acid, azelaic acid, sebacic acid, rnaieic add, glutaric acid, decanoic diacid, dodecanoic diacid and other dicarboxyiic acids of various types. The polyester may include minor amounts of monobasic acids such as benzoic acid, stearic acid, acetic acid and oleic acic. Also, there may be employed higher ca'bcxylic acds, such as trimeliitic acid and tricarballylic acid. Where adds are referred to above, it is understood that arhydrides thereof which exist may be used in place of the ac;d. Also, lower alkyl esters of diacids such as dimethyl glutarate and dimethyl terephthalate can be used. Because it is readily available and low in cost, terephthaiic acid is preferred.
Pendent and/or terminal carbamate functional groups may be incorporated into the polyester by first forming a hydroxyalkyl carbamate which can be reacted with the polyacids and polyols used in forming the polyester. The hydroxyalkyl carbamate is. condensed with acid functionality on the polyester yielding carbamate functionality. Carbamate functional groups may also be incorporated into the polyester by reacting a hydroxyl
functional polyester with a low molecular weight carbamate functional material via a transcarbamoylation process similar to the one described above in connection with the incorporation of carbamate groups into the acrylic polymers or by reacting isocyanic acid with a hydroxy! functional polyester.
Epoxide functional polyesters can be prepared by art-recognized methods, which typically include first preparing a hydroxy functional polyester that is then reacted with epichlorohydrin. Polyesters having hydroxy functionality may be prepared by art-recognized methods, which include reacting carboxylic acids (and/or esters thereof) having acid (or ester) functionalities of at least 2, and polyols having hydroxy functionalities of at least 2. As is known to those of ordinary skill in the art, the molar equivalents ratio of carboxylic acid groups to hydroxy groups of the reactants is selected such that the resulting polyester has hydroxy functionality and the desired molecular weight.
The functional group-containing polyester polymer typically has a Mn ranging from 500 to 30,000, preferably about 1000 to 5000. If carbamate functional, the poiyester polymer typically has a calculated carbamate equivalent weight within the range of 15 to 150, preferably 20 to 75, based on equivalents of reactive pendent or terminal carbamate groups.
Non-limiting examples of suitable polyurethane polymers having pendent and/or terminal hydroxy! and/or carbamate functional groups include the polymeric reaction products of polyols which are prepared by reacting the polyester polyols or aorylic polyols, such as those mentioned above, with a polyisocyanate such that the OH/NCO equivalent ratio is greater than 1:1 such that free hydroxyl groups are present in the product. Such reactions emproy typical conditois for urethane formation, for example, temperatures of 60°C to 90°C and up to ambient pressure, as known to those skilled in the art.
The organic polyisocyanates which can be used to prepare the functional group-containing polyurethane polymer include aliphatic or aromatic polyisocyanates or a mixture of the two. Diisocyanates are
preferred, although higher polyisocyanates can be used in place of or in combination with diisocyanates.
Examples of suitable aromatic diisocyanates include 4,4'-diphenylmethane diisocyanate and toluene diisocyanate. Examples of suitable aliphatic diisocyanates incluae straight chain aliphatic diisocyanates, such as 1,6-hexamethylene diisocyanate and trimethyl hexamethylene. Also, cycloaliphatic diisocyanates canbe employed. Examples include isophorone diisocyanate, tetramethy! xylene ocyanate and 4,4'-methylene-bis-(cyclohexyl isocyanate). Examples of suitable higher polyisocyanates include 1,2,4-benzene triisocyanate and poiymethylene polypheny! isocyanate.
Terminal and/or pendent carbamate functional groups can be incorporated into the polyurethene by reacting a poiyisocyanate with a polyester pclyoi containing the terminal/pendent carbamate groups. Alternatively, carbamate functional groups can be incorporated ink the polyurethane by reacting a poiyisocyanate with a polyester polyol and a hydroxyalkyi carbamate or isocyanic acid as separate reactants. Carbamate functional groups can also be incorporated into the polyurethane by reacting a hydroxy) functional polyurethane with a low molecular weight carbamate functional material via a transcarbamoy'ation process similar to the one described above :n connection with the incorporation of carbamate groups into the acrylic polymer.
The hydroxyl and/or carbamate functional group-containing polyurethane polymers typic have a Mn ranging from 500 to 20,000, preferably from 1900 to 5000 If carbamate functional the polyurethane polymer typically has a carbamate equivalent weight witnin the range of 15 to 150, preferably 20 to 75, based on equivalents of reactive pendent or terminal carbamate groups.
Although generally noi preferred, for some applications it may be desirable to employ a functional group-containing polyether polymer in the curable powder coating compositions of the present invention. Suitable hydroxy! and/or carbamate functional polyether polymers can be prepared by
reacting a polyether polyol with urea under reaction conditions well known to those skilled in the art- More preferably, the polyether polymer is prepared by a transcarbamoylation reaction similar to the reaction described above in connection with the incorporation of carbamate groups into the acrylic polymers.
Examples of polyether polyols are polyalkylene ether polyols which include those having the following structural formulae (II) and (III):
(Formula Removed)
where the substituent R1 is hydrogen or lower alky! containing from 1 to 5 carbon atoms including mixed substituents, n is tyoically from 2 to 5, and m is from 8 to 10C or higher Note that the hydroxy', groups, as shown in structures (!l) and (III) above, are terminal to the molecules. Included are po'y(oxytetramethylene) glycols, poly(oxytetraethyiene) glycols, poly(oxy-1,2-propylene) gr/co!s and poiy(oxy-l,2-butylene) glycols.
Aiso useful are polyether polyols formed from oxyalkylation of various poiyols, for example, dots, such as ethylene glycol. ". ,6-hexanediol, Bispheno! A and the like, or other higher polyols, such as trimethylolpropane, pentaerythritol and the like. Polyols of higher functionality which can be utilized as indicated can be made, for instance, by oxyalkylation of compounds, such as sucrose or sorbitol. One commonly utilized oxyalkylation method is reaction of a polyol with an alkylene oxide, for example, propylene or ethylene oxide, in the presence of a conventional
acidic or basic catalyst as known to those skilled in the art. Typical oxyalkylation reaction condftions may be employed. Preferred pofyethers include those sold under the names TERATHANE® and TERACOL®, available from E. I. du Pont de Nemours and Company, inc. and POLYMEG®, available from Q O Chemicals, Inc., a subsidiary of Great Lakes Chemical Corp.
Epoxide functional pofyethers can be prepared from a hydroxy functional monomer, e.g., s diol, and an epoxide functional monomer, and/or a monomer having both hydroxy and epoxide functionality. Suitable epoxide functional polyethers include, but are not limited to, those based on 4,4'-isopropyiidenediphenol (Bispheno! A), a specific example of which is EPON® RESIN 2002 available commercially from Shell Chemicals.
Suitable functional group-containing polyether polymers typically have a number average mciecular weight (Mn) ranging from 500 to 30,000 and preferably from 1000 to 5000 if carbamate functional, the polyether polymers have a carbamate equivalent weight of within tne range of 15 to 150, preferably 25 to 75, based on equivalents of reactive pendent and/or terminal carbamate croups and the solids of the polyether polymer.
it shouid be understood that the preferred carbamate functional group-coniaining poiymers typically contain residual hydroxy) functional groups wnich provide aouitional crossiinking sites. Preferably, the caroarnate/nydrcxy! functional group-containing polymer (A) has a residual hydroxyl value ranging from 0.5 to 10, more prefreably from 1 to 10, and even more preferably from 2 to 10 (rr.g KOh per gram.'.
Tne functional group-ccntaining polymer (A) typically is present in the curable powder coating compositions of tne present invention in an amount ranging from at ieast 5 percent by weight; preferably at least 20 percent by weight, more preferably at least 30 percent by weight, and even more preferably at least 40 percent by weight based on the total weight of the film-forming composition. The functional group-containing polymer (A) also typically is present in the curabie powder coating compositions of the present invention in an amount less than 90 percent by weight, preferably less than
85 percent by weight, more preferably less than 80 percent by weight, and even more preferably less than 70 percent by weight based on the total weight of the curable powder coating composition. The amount of the functional group-containing polymer (A) present in the powder coating compositions of the present invention can range between any combination of these values inclusive of the recited values.
As mentioned above, the powder coating compositions of the present invention further comprise, as component (B), the crosslinking agent described above. The crosslinking agent (B) typically is present in the powder coating compositions of the present invention in an amount ranging from at least 5 percent by weight, preferably at least 10 percent by weight, more preferably at least 15 percent by weight, and even more preferably at least 20 percent by weight based on the total weight of the powder coating composition The crosslinking agent (B) also typically is present in the powder coating compositions of the present invention in an amount less than 90 percent by weight, preferably less than 70 percent by weight, more preferably less than 50 percent by weight, and even more preferably less than 25 percent by weight based on the total weight of the powder coating composition. The amount of the crosslinking agent (B) present m the powder coating compositions of the present invention can range between any combination of these values inclusive of the recited values
It desired, the curabie powder coating compositions of the present invention also can incude an adjuvant curing agent which is different from the crosslinking agent (B) The adjuvant curing agent can be any compound having functional croups reactive with the funciionai groups of the polymer (A) described above. Non-limiting examples of suitable adjuvant curing agents include, for example, blocked isocyanates, tnarine compounds, glycoluril resins, and mixtures thereof.
The blocked isocyanates suitable for use as the adjuvant curing agent in the powder coating compositions of the invention are known compounds and can be obtained from commercial sources or may be prepared according
to published procedures. Upon being heated to cure the curable powder coating compositions, the isocyanates are unblocked and the isocyanate groups become available to react with the functional groups of the polymer
(A).
Any suitable aiiphatic, cycloaliphatic or aromatic alkyl monoalcohol known to those skilled in the art can be used as a blocking agent for the isocyanate. Other suitable blocking agents include oximes and lactams. Non-limiting examples of suitable blocked isocyanate curing agents include these based on isophorone diisocyanate blocked with C-caprolactam; toluene 2,4-toiuene diisocyanate blocked with C-caprolactam; or phenol-blocked hexamethylene diisocyanate. The blocked isocyanates mentioned immediately above are described in detail in U.S. Patent No. 4,988,793 at column 3, lines 1 to 36. Preferred blocked isocyanate curing agents include BF-1530. which is the reaction product of epsilon- caprolactam blocked T1890, a trimerized :sophorone diisocyanate ("IPDI") with an isocyanate equivalent weight of 280, and BF-1540, a uretidione of IPDI with an isocyanate equivalent weight of 280, all of which are available from Creanova of Somerset, NJ.
Conventional aminoplast crosslinkers can be used as the adjuvant curing agent provided that the Tg of the coating is not lowered to an undesirable extent. A particularly preferred class of arrinoplast resins include aldehyde condensates of clycoluril, such as those described above. Glycoluril resins suitable for use as the adjuvant curing agent in the curable powder coating compositions of the invention include POVVDERLINK® 1174 commercially available from Cytec Industries, Inc. of Stamford, Connecticut.
When employed, the adjuvant curing agent typically is present in the curable powder coating compositions of the present invention in an amount ranging from 0.5 to 20 percent by weight, and preferably from 1 to 15 percent by weight based on the total weight of the curable powder coating composition.
Also suitable for use as an adjuvant curing agent In the curable powder coating compositions of the present invention are triazine compounds, such as the tricarbamoyl triazine compounds described in detail in U.S. Patent No. 5,084,541. When used, the triazine curing agent is typically present in the powder coating composition of the present invention in an amount ranging up to about 20 percent by weight, and preferably from about 1 to 20 percent by weight, percent by weight based on the total weight of the powder coating composition.
Mixtures of the above-described curing agents also can be used advantageously.
Also, it should be understood that for purposes of the present invention, the curable powder coating compositions which contain epoxy group-containing polymers typically also include an epoxide-reactive curing (i.e., crosslinking) agent, preferably an acid functional curing agent, in addition to the crosslinking agent (B). A secondary hydroxyl group can be generated upon reaction of each epoxy functional group with a functional group cf the epoxide-reactive curing agent. These secondary hydroxyl groups are then available for subsequent reaction with the aminoplast-based crosslinking agent (B)
Epoxide-reactive curing agents which can be used in curable powder coating compositions comprising an epoxide functional polymer can have functional groups selected from the group consisting of hydroxyl, thiol, primary amines, secondary amines, acia (e.g. carboxylic acid) and mixtures thereof. Useful epoxide reactive curing agents having amine functionality include, for example, diayandiamide and substituted dicyandiamides, Preferably, the epoxide reactive curing agent has carboxylic acid groups. In one embodiment of the present invention, the epoxide reactive crosslinking agent has carboxylic acid functionality and is substantially crystalline. By "crystalline" is meant that the co-reactant contains at least some crystalline domains, and correspondingly may contain some amorphous domains. While not necessary, it is preferred that the epoxide reactive
crosslinking agent have a melt viscosity less than that of the epoxy functional polymer (i.e., at the same temperature). As used herein and in the claims, by "epoxide reactive crosslinking agent" is meant that the epoxide reactive crosslinking agent has at least two functional groups that are reactive with epoxide functionality.
Preferably, the epoxide reactive crosslinking agent is a carboxylic acid functional curing agent, which contains from 4 to 20 carbon atoms. Examples of carboxylic acid functional crosslinking agents useful in the present invention include, but are not limited to, dodecanedioic acid, azelaic acid, adipic acid, 1,6-hexanedioicacid, succinic acid, pimelicacid, sebasic acid, maleic acid, citric acid, itaconic acid, aconitic acid and mixtures thereof.
Other suitable carboxylic acid functional curing agents include those represented by the following general formula (IV),
(Formula Removed)
in general formula (IV), R is the residue of a poiyol, E is a divalent linking group having from 1 to 10 carbon atoms, and n is an integer of from 2 to 10. Examples of polyois from which R of general formula (IV) may be derived include, but are not limited to, ethylene glycol, di(ethylene glycol), trimethylolethane, trimethylolpropane, pentaerytftrito!. di-trimethylolpropane, di-pentaerythritol and mixtures thereof. Divalent linking groups from which E may be selected include, but are not limited to, methylene, ethylene, propylene, isopropylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene. decylene, cyclohexyiene, e.g., 1,2-cyclohexylene, substituted cyclohexyiene, e g , 4-methyl-1,2-cyc!ohexylene, phenylene, e.g., 1,2-phenylene, and substituted phenylene, e.g., 4-methyl-1,2-phsnylene and 4-carboxylic acid-1,2-phenylene. The divalent linking group E is preferably aliphatic.
The curing agent represented by general formula (IV) is typically prepared from a polyol and a dibasic acid or cyclic anhydride. For example, trimethylol propane and hexahydro-4-methylphthalic anhydride are reacted together in a molar ratio of 1:3 respectively, to form a carboxylic acid functional curing agent. This particular curing agent can be described with reference to gerera! formula (IV) as follows, R is the residue of trimethylol propane, E is the divalent linking group 4-methyl-1,2-cyclohexyIene, and n is 3. Carboxylic acid functional curing agents described herein with reference to general formula (IV) also are meant to include any unreacted starting materials and/or co-products, e.g., oligomeric species, resulting from their preparation and contained therein.
Curable powder coating compositions comprising an epoxide functional polymer and an epoxide reactive curing agent can also include one or more cure catalysts as are well known in the art for catalyzing the reaction between the reactive functional groups of the crosslinking agent and the epoxide groups of the polymer Examples of cure catalysts for use with acid functional crosslinking agents include tertiary amines, e.g., methyl dicocoamine, and tin compounds, e.g., triphenyl tin hydroxide. When employed, the curing catalyst is typically present in the curable powder coating composition in an amount of less than 5 percent by weight, e.g., from 0.25 oercent by weight :o 2.0 percent by weight, based on total weight of the composition.
Curable powder coating compositions comprising epoxide functional polymers and epoxide reactive curing agents typically have present therein epoxide functional polymer in an amount ranging from 2 percent to 50 percent by weight; based on total weight of the composition, e.g., from 70 percent to 85 percent by weight, based on total weight of the composition. The epoxide reactive curing agent is typically present in the curable powder coating composition in an amount corresponding to the balance of these recited ranges, i.e., 5 to 40, particularly 15 to 30, percent by weight The equivalent rat;o of epoxide equivalents in the epoxide functional polymer to the
equivalents of reactive functional groups in the curing agent is typically from 0.5:1 to 2:1. e.g., from 0.8:1 to 1.5:1.
Curable powder coating compositions of the present invention comprising an epoxide functional polymer as reactant (A) and an epoxide reactive curing agent typically contain the crosslinking agent (B) in an amount ranging from 2 to 50 weight percent, preferably from 3 to 40 weight percent and more preferably from 5 to 20 weight percent based on total weight of the powder coating composition.
The curable powder coating compositions of the present invention can further include additives as are commonly known in the art. Typical additives include benzoin, used to reduce entrapped air or volatiles; flow aids or flow control agents which aid in the formation of a smooth and/or glossy surface, for example, MODAFLOW® available from Monsanto Chemical Co., waxes such as MICROWAX® C available from Hoechst, fillers such as calcium carbonate, barium sulfate and the like; colorants, such as pigments (e.g., carbon black or Shepard Black pigments) and dyes; UV light stabilizers such as T1NUVIN® 123 or TINUVIN® 900 available from Cytec Industries, Inc. and catalysts to promote the various crosslinking reactions.
ouch additives are typicaliy present in the curable powder coating compositions of the present invention in an amount ranging from 5 to 50 weight percent based on total weight of the powder coating composition.
The curable powder coating compositions of the invention are typically prepared by blending the functional group-containing polymer (A) and the crosslinking agent (B), along with any adjuvants, additives and catalyst, if employed, for approximately 1 minute in a Henschel blade blender. The powder is trier, extruded through a Baker-Perkins twin screw extruder at a temperature ranging from 70°F to 13C°F (21.1°C to 54.4°C). The finished powder then can be classified to an appropriate particle size, typically between 20 and 200 microns, in a cyclone grinder/sifter.
The curable powder coating compositions of the invention can be applied to a variety of substrates including metallic substrates, for example,
aluminum and steel substrates, and non-metallic substrates, for example, thermoplastic or thermoset composite substrates. The curable powder coating compositions are typically applied by spraying, and in the case of a metal substrate, by electrostatic spraying which is preferred, or by the use of a fluidized bed. The powder coating can be applied in a single sweep or in several passes to provide a film having a thickness after cure of from about 1 to 10 mils (25 to 250 micrometers), usually about 2 to 4 mils (50 to 100 micrometers).
Generally, after application of the curable powder coating composition, the powder coated substrate is heated to a temperature sufficient to cure the coating, typically to a temperature ranging from 250°F to 500°F (121.1°C to 260.0°C) for 1 to 60 minutes, and preferably from 300°F to 400°F (148.9°C to 204.4°C) for 15 to 30 minutes.
The curable powder coating composition can be applied as a primer or primer surfacer, or as a topcoat, for example, a "monocoat". The curable powder coating composition of the invention also can be advantageously employed as a topcoat in a multi-component composite coating composition. Such a multi-component composite coating composition generally comprises a basecoat deposited from a film-forming composition and a topcoat applied over the base coat, the topcoat being deposited from the curable powder coating composition of the present invention as described above. In a preferred embodiment, the multi-component composite coating composition is a color-plus-clear system where the basecoat is deposited from a pigmented film-forming coating composition and the topcoat is deposited from a curable powder coating composition which is substantial pigrnent-free, i.e., a clear coat.
The film-forming composition from which the basecoat is deposited can be any of the compositions useful in coatings applications for example, in automotive applications where color-plus-clear systems are most often used. A fiim-forming composition conventionally comprises a resinous binder and a
pigment to serve as a colorant Particularly useful resinous binders include acrylic polymers, polyesters including alkyds, and polyurethanes.
The resinous binders for the base coat can be organic solvent-based materials, such as those described in U.S. Patent No. 4,220,679. Water-based coating compositions, such as those described in U.S. Patent Nos. 4,403,003; 4,147,679; and 5,071,904, also can be used as the base coat composition.
As mentioned above, the base coat compositions also contain pigments of various types as colorants. Suitable metallic pigments include aluminum flake, bronze flake, copper flake and the like. Other examples of suitable pigments include mica, iron oxides, lead oxides, carbon black, titanium dioxide, talc, as well as a variety of color pigments.
Optional ingredients for the base coat film-fcrming compositions include those which are well known in the art of surface coatings and include surfactants, flow control agents, thixotropic agents, fillers, anti-gassing agents, organic co-solvents, catalysts and ether suitable adjuvants.
The base coat film-forming compositions can be applied to the substrate by any of the conventional coating techniques, such as brushing, spraying, dipping cr flowing, but they are most often spray-applied. The usual spray techniqjes and equipment for air spraying, airless spraying and electrostatic spraying can be used.
The base coat film-forming compositions are typically applied to the substrate such thai a cured base coat having a film thickness ranging from 0.5 to 4 mils (12.5 to 100 micrometers) is formed thereon.
After forming a film of the base coat on the substrate, the base coat can be cured or alternatively given a drying step in which solvent, i.e., organic solvent and/or water, is driven off by heating or an air drying step before application of the clear coat, Suitable drying conditions will depend on the particular base coat film-forming composition and on the ambient humidity with certain water-based compositions. In general, a drying time ranging from 1 to 15 minutes at a temperature of 75°F to 200°F (21°C to 93°C) is adequate.
The curable powder topcoating composition can be applied over at least a portion of the base coat by any of the methods of application described above. As discussed above, the clear coat can be applied to a cured or a dried base coat before the base coat has been cured. In the latter case, the clear coat and the base coat are cured simultaneously.
illustrating the invention are the following examples which are not to be considered as limiting the invention to their details. Unless otherwise indicated, all parts and percentages in the following examples, as well as throughout the specification, are by weight.
EXAMPLES
Examples A through C describe the preparation of benzoxazine group containing erosslinking agents of the present invention. Examples 1 through 5 describe the preparation of curable powder coating compositions.
POWDER CROSSLINKING AGENTS EXAMPLE A
The following ingredients v/ere added to a suitable reaction vessel
equipped with thermometer, a mechanical stirrer, nitrogen inlet, and means
for removing the methanol by-product: 480.0 parts of Cymel®300; 340.4 parts
of 4-pheny! phenol; 351.7 parts of xylene; and 0.3 part of p-toluenesulfonic
acid. The mixture was heated to a temperature of approximately 80 °C and
held at that temperature for 20 m'nutes until the mixture was homogenous.
The reaction mixture was further heated to a temperature of 120 °C and
maintained at that temperature as the condensation reaction by-product,
methanol, was removed from the system. The reaction was monitored for the
disappearance of hydroxy! functionality by infrared spectroscopy and was
terminated when the end point was detected. Thereafter, the mixture was
concentrated at a temperature ranging from 100°C to 130 °C in vacuo at a
pressure of 3 to 50 mm Hg to remove the xylene solvent. The reaction
product thus obtained was a pale yellow solid having a softening temperature
of 65°C. The benzoxazine ring structure formed in this product was confirmed by NMR spectroscopy.
EXAMPLE B
The following ingredients were added to a suitable reaction vessel equipped with a thermometer, a mechanical stirrer, nitrogen inlet, and means for removing the condensation reaction by-product (methanol): 480.0 parts of Cymel® 300; 300.0 parts of 4-tert-buryl phenol; 334.4 parts of xylene; and 0.3 part of p-toluenesulfonic acid. The mixture was heated to 80 °C and held at that temperature for 20 minutes until the reaction mixture was homogenous. At that time the reaction mixture was further heated to a temperature of 120 °C and was maintained at that temperature as the methanol by-product was removed from the system. The reaction was monitored for the disappearance of hydroxy! functionality by infrared spectroscopy terminated when the end point was detected. Thereafter, the mixture was concentrated at a temperature of 1005C to 130 °C in vacuo at a pressure of 3 to50 mm Hg to remove the xylene solvent. The reaction product thus obtained was a pale yeilow solid having a softening temperature of 75 °C. The benzoxazine ring structure formed in this reaction product was confirmed by NMR spectroscopy.
EXAMPLE C
The following ingredients were added to a suitable reaction vessel equipped with a thermometer, a mechanical stirrer, nitrogen inlet, and means for removing the condensation reaction by-product (methanol): 480.0 parts of Cymel® 300; 288.3 parts of 2-naphthol; 329.4 parts of xylene; and 0.3 part of p-toluenesulfonic acid. The mixture was heated to a temperature of 80 °C and held at that temperature for.20 minutes until the mixture was homogenous. The reaction mixture was further heated to a temperature 120 °C and maintained at that temperature as the methanol by-product was removed from the system. The reaction was monitored for the disappearance of hydroxy! functionality by infrared spectroscopy and was terminated when the end point is detected Thereafter, the reaction mixture was concentrated at a temperature ranging from 100°C to 130 °C in vacuo at a pressure of 3 to 50 mm Hg to remove the xylene solvent The reaction product thus obtained was a pale yellow solid having a softening temperature of 44 °C. The benzoxazine ring structure formed in this product was confirmed by NMR spectroscopy.
CURABLE POWDER COATING COMPOSITIONS EXAMPLES 1 through 5
Corrparative Example 1 describes the preparation of a conventional powder coating composition, based on an epoxy functional acrylic resin and an acid functional polyester crosslinking agent. Comparative Example 2 describes the preparation of an analogous powder coating composition which further includes a conventional glycoluril crosslinking agent, POWDERLINK® 1174 available from Cytec Industries, Inc., (for crosslinking with the secondary hydroxy' groups generated upon reaction of the epoxy and acid groups). Example 3 describes the preparation of powder coating composition of the present invention which includes the crosslinking agent of Example A as a replacement for the glycoluril crosslinking agent in Comparative Example
2. mparative Example 4 describes the preparation of a powder coating composition based upon a hydroxyl functional polyester resin and a conventional glycoluril crosslinking agent. Example 5 describes the preparation of the analogous powder coating composition of the present invention containing the crosslinking agent of Example A as a replacement for the glycoluril crosslinking agent in Comparative Example 4. The powder coating compositions were prepared from a mixture of the following ingredients:
(Table Removed)
* A hydroxyl funtional palyester resin commercially available from UCB.
* An acid functional poiyeserriosin having an acid number of approximately 33, ;omrie:cial|y available
from McWhorther Technologies, 'nc
* Epoxy functional acrylic resin prepared from 50% gyadyl methacrylate, 35% methylrnethacrylate, 10%
butyl methacrylate, 5% styrene. t$:ng l-s.n/l peracetatc as initiator
* Acrylic flow add tive available from Monsanto Co
* Srearamide wax commmercally aveilable from Hoechst. Inc.
* R706 co-time rcially available from E I Dypont be Nemours and Company.
Each of the above-described powder coating compositions was prepared as follows. For each of the powder coating compositions of Examples 1 through 5, all of the listed components were blended for 10 seconds at 3500 rpm in a PRISM blender. The powders were then fed through a 19 millimeter, twin screw extruder available from b&p Process

Equipment and Systems, by way of an ACCU-RATE auger feeder. The resulting chip was classified to a median particle size of approximately 40 microns.
Each of the powder coating compositions thus prepared were applied by electrostatic spray using a Nordson Versa-Spray II, corona-type spray gun to B1000 P60 DIW steel test panels (available from ACT Laboratories, Inc.) to a targeted cured film thickness of 2.0 to 3.0 mils (50 to 75 micrometers). Two panel sets were prepared wherein the coating compositions were cured at two different cure temperatures. One panel set was cured at 320°F (160°C) for 20 minutes, and another set was cured at 380°F (193.3°C) for 20 minutes.
TESTING PROCEDURES:
The powder storage stability of each powder coating composition was evaluated by storing a 20g sample of each powder coating composition at a temperature of 40°C for a 24 hour period. The stability of the powder was determined upon visual inspection. Powder stability results are reported from best to worst as follows: excellent, good, slightly cakey, cakey, slightly clumpy, clumpy, fused and sintered.
The propensity of the coating composition to "gas" upon curing was tested by increasing the cured film thickness of the powder coating on a test panel until surface defects (i.e., pinholes) formed due to the escape of gases through the coating surface during the cure process. Values reported represent the maximum film thickness achieved just prior to the development of the pinholes in the coating surface.
Chemical resistance was evaluated by double rubs using methyl ethyl ketone. Results reported are the extent of film surface marring or softening in the area contacted with the methyl ethyl ketone after 200 double rubs.
Flexibility and impact resistance (both direct and reverse impact) was evaluated using a Gardner Impact Tester in accordance with ASTM-D-2794.
Two sets of test panels were prepared. Test results are reported in the following Table 1 for the set of test panels coated with each of the powder
(coating compositions of Examples 1 through 5 which were cured at 380°F (193.3°C) for 30 minutes. Test results for an analogous set of coated test panels which were cured at 320°F (160°C) for 30 minutes are reported below in the following Table 2.
TABLE 1
(Table Removed)

TABLE 2
(Table Removed)
The data presented in Tables 1 and 2 above illustrate that the crosslinking agent of Example A provides powder coating compositions having improved impact resistance and enhanced powder stability over those compositions containing a conventional glycoluril crosslinking agent.






We claim:
1. An aminoplast based crosslinking agent having reactive benzoxazine groups comprising the
ungelled reaction product of the following reactants:
(a) at least one mono-hydroxy aromatic compound having the following structure (I):
(Formula Removed)
wherein R1 represents a monovalent hydrocarbon group, COOR5 where R5 represents H or a
monovalent hydrocarbon group, NO2, halogen or XR4, where X represents O or S and R4 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms; R3, R3', R2 and R2' can be the same or different and each independently represents a substituent selected from H, a monovalent hydrocarbon group, COOR5, NO2, halogen and XR4, provided that at least one of R3 and R3' is H; or when R3' is non-hydrogen substituted and R3 ' is H, R1 and R2 taken together, R1 and R2' taken together, or R2 and R3 taken together represent fused aliphatic or aromatic ring structures, or when R3' is non-hydrogen substituted and R3 is H, R1 and R2 taken together, R1 and R2' taken together, or R2' and R3' taken together represent fused aliphatic or aromatic ring structures; and
(b) at least one aminotriazine compound having one or less non-alkylated NH group,
present in a molar ratio of reactant (a) to reactant (b) ranging from 1.0 to 3.0: 1.0, provided that
where reactant (a) is a single ring monohydroxy aromatic compound, the molar ratio of reactant
(a) to reactant (b) ranges from 1.0 to less than 1.8:1.0 and from greater than 2.2 to 3.0:1.0,
wherein said crosslinking agent is essentially free of hydroxyl functionality and has a glass
transition temperature of at least 40°C.
2. A crosslinking agent as claimed in claim 1, wherein R1 represents an electron-withdrawing group selected from aryl, alkylaryl, alkoxyl, COOH, NO2 and halogen.
3. A crosslinking agent as claimed in claim 1 or 2, wherein the molar ratio of reactant (a) to reactant (b) ranges from 1.0 to less than 1.8:1.0.
4. A crosslinking agent as claimed in any preceding claim wherein both R3 and R3' are H.
5. A crosslinking agent as claimed in any one of claims 1 to 3, wherein R1 is an aryl group and R2, R2', R3 and R3' are the same or different and each independently represents H, alkyl or aryl, or a heteroatomic monovalent hydrocarbon group, provided that at least one of R3 and R3' is H.
6. A crosslinking agent as claimed in claim 1 or 5, wherein reactant (a) comprises a mono-hydroxy aromatic compound selected from p-cresol, 4-methoxyphenon, 4-tert-butyl phenol, 4-nitrophenol, 4-fluorophenol, 2-phenyl phenol, 4-phenyl phenol, 1-naphthol, and 2-naphthol.
7. A crosslinking agent as claimed in claim 1 or 5 wherein reactant (a) comprises 4-phenyl phenol.
8. A crosslinking agent as claimed in any preceding claim wherein aminotriazine compound (b) comprises an (alkoxyalkyl) aminotriazine compound.
9. A method for forming an aminoplast based crosslinking agent as claimed in any preceding claim comprising the following steps:
(1) combining the following reactants:
(a) at least one mono-hydroxy aromatic compound having the following structure (I):
(Formula Removed)
wherein R1 represents a monovalent hydrocarbon group, COOR5 where R5 represents H or a monovalent hydrocarbon group, NO2, halogen or XR4, where X represents O or S and R4 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms; R3, R3', R2 and R2' can be the same or different and each independently represents a substituent selected from H, a monovalent hydrocarbon group, COOR5, NO2, halogen and XR4, provided that at least one of R3 and R3' is H; or when R3 is non-hydrogen substituted and R3' is H, R1 and R2 taken together, R1 and R2' taken together, or R2 and R3 taken together represent fused aliphatic or aromatic ring structures, or when R3' is non-hydrogen substituted and R3 is H, R1 and R2 taken together, R1 and R2, taken together, or R2' and R3' taken together represent fused aliphatic or aromatic ring structures; and
(b) at least one aminotriazine compound having one or less non-alkylated NH group,
in a molar ratio of (a) to (b) ranging from 1.0 to 3.0:1.0, provided that where reactant (a) is a
single ring monohydroxy aromatic compound, the molar ratio of reactant (a) to reactant (b)
ranges from 1.0 to less than 1.8:1.0 and from greater than 2.2 to 3.0:1.0, to form a reaction
admixture;
(2) heating the reaction admixture of step (1) to a temperature ranging from 90°C to
135°C; and
(3) maintaining the temperature achieved in step (2) for a time sufficient such as herein described to produce an ungelled reaction product having a glass transition temperature of at least 40°C which is essentially free of hydroxyl functionality as determined by infrared spectroscopy.
10. A method as claimed in claim 9, wherein R1 represents an electron-withdrawing group selected from aryl, alkylaryl, alkoxyl, COOH, NO2 and halogen.
11. A method as claimed in claim 9 or 10, wherein R3 and R3' are both H.
12. A method as claimed in claim 9 or 10, wherein R1 is an aryl group and R2, R2', R3 and R3' are the same or different and each independently represents H, alkyl or aryl, or a heteroatomic monovalent hydrocarbon group, provided that at least one of R3 and R3' is H.
13. A method as claimed in claim 9, wherein reactant (a) comprises a mono-hydroxy aromatic compound selected from p-cresol, 4-methoxyphenol, 4-tert-butyl phenol, 4-nitrophenol, 4-fluorophenol, 2-phenyl phenol, 4-phenyl phenol, 1-naphthol, and 2-naphthol.
14. A method as claimed in claim 9, wherein reactant (a) comprises 4-phenyl phenol.
15. A method as claimed in any one of claims 9 to 14, wherein the aminotriazine compound (b) comprises an (alkoxyalkyl) aminotriazine compound.
16. A method as claimed in claim 15, wherein the aminotriazine compound (b) comprises (methoxymethyl) aminotriazine.
17. A curable powder coating composition comprising a solid particulate, film - forming
mixture of the following components:
(A) a polymer having functional groups reactive with benzoxazine groups, said polymer having a glass transition temperature of at least 30°C; and
(B) a cross linking agent having reactive benzoxazine groups comprising the ungelled reaction product of the following reactants:
(1) at least one mono-hydroxy aromatic compound having the following structure (I):
(Formula Removed)
wherein Ri represents a monovalent hydrocarbon group, COOR5 where R5 represents H or a
monovalent hydrocarbon group, NO2, halogen or XR4, where X represents 0 or S and R4 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms; R3, R3', R2 and R2' can
be the same or different and each independently represents a substituent selected from H, a monovalent hydrocarbon group, COOR5, NO2, halogen and XR4, provided that at least one of R3 and R3' is H; or when R3' is non-hydrogen substituted and R3' is H, R1 and R2 taken together, R1 and R2' taken together, or R2 and R3 taken together represent fused aliphatic or aromatic ring structures, or when R3' is non-hydrogen substituted and R3 is H, R1 and R2 taken together, R1 and R2' taken together, or R2' and R3' taken together represent fused aliphatic or aromatic ring structures; and
(b) at least one aminotriazine compound having one or less non-alkylated NH group, present in a molar ratio of reactant (a) to reactant (b) ranging from 1.0 to 3.0: 1.0, provided that where reactant (a) is a single ring monohydroxy aromatic compound, the molar ratio of reactant (a) to reactant (b) ranges from 1.0 to less than 1.8:1.0 and from greater than 2.2 to 3.0:1.0, wherein said crosslinking agent is essentially free of hydroxyl functionality and has a glass transition temperature of at least 40°C.
18. A curable powder coating composition as claimed in claim 17 wherein the polymer (A) is selected from the group consisting of acrylic, polyester, polyurethane, polyepoxide and polyether polymers and any mixtures thereof.
19. A curable powder coating composition as claimed in claim 17, wherein the polymer (A) comprises functional groups selected from the group consisting of hydroxyl, primary and secondary amine, carbamate, amide, thiol, phenolic, carboxyl and epoxy functional groups and mixtures thereof.
20. A curable powder coating composition as claimed in any one claims 17 to 19, wherein the polymer (A) is present in an amount ranging from 5 to 90 percent by weight based on total weight of the composition.
21. A curable powder coating composition as claimed in claim 17, wherein R1 represents an electron-withdrawing group selected from aryl, alkylaryl, alkoxyl, COOH, NO2 and halogen.
22. A curable powder coating composition as claimed in claim 17, wherein R3 and R3' are both H.
23. A curable powder coating composition as claimed in claim 17, wherein Ri is an aryl group and R2, R2', R3 and R3' are the same or different and each independently represents H, alkyl or aryl, or a heteroatomic monovalent hydrocarbon group, provided that at least one of R3 and R3' isH.
24. A curable powder coating composition as claimed in claim 23, wherein R1 comprises a phenyl group.
25. A curable powder coating composition as claimed in claim 17, wherein reactant (1)
comprises a mono-hydroxy aromatic compound selected from p-cresol, 4-methoxyphenol, 4-
tert-butyl phenol, 4-nitrophenol, 4-fluorophenol, 2-phenyl phenol, 4-phenyl phenol, 1-naphthol, and 2-naphthol.
26. A curable powder coating composition as claimed in claim 17, wherein the aminotriazine compound (2) comprises an (alkoxyalkyl) aminotriazine compound.
27. A curable powder coating composition as claimed in claim 26, wherein the aminotriazine compound (2) comprises (methoxymethyl) aminotriazine.
28. A curable powder coating composition as claimed in claim 17, wherein the crosslinking agent (B) is present in an amount ranging from 5 to 90 weight percent based on total weight of the powder coating composition.
29. A curable powder coating composition as claimed in claim 17, wherein the polymer (A) comprises hydroxyl and/or epoxy functional groups.
30. A curable powder coating composition as claimed in claim 17, wherein, if desired, a second crosslinking agent having carboxylic acid functional groups is present.


Documents:

324-delnp-2003-abstract.pdf

324-delnp-2003-assignment.pdf

324-delnp-2003-claims.pdf

324-delnp-2003-complete specification(as files).pdf

324-delnp-2003-complete specification(granted).pdf

324-delnp-2003-correspondence-others.pdf

324-delnp-2003-correspondence-po.pdf

324-delnp-2003-description (complete).pdf

324-delnp-2003-form-1.pdf

324-delnp-2003-form-18.pdf

324-delnp-2003-form-2.pdf

324-delnp-2003-form-3.pdf

324-delnp-2003-form-4.pdf

324-delnp-2003-form-5.pdf

324-delnp-2003-gpa.pdf

324-delnp-2003-pct-210.pdf

324-delnp-2003-pct-304.pdf

324-delnp-2003-pct-408.pdf

324-delnp-2003-pct-409.pdf

324-delnp-2003-pct-416.pdf

324-delnp-2003-petition-137.pdf

324-delnp-2003-petition-138.pdf

abstract.jpg


Patent Number 240756
Indian Patent Application Number 324/DELNP/2003
PG Journal Number 23/2010
Publication Date 04-Jun-2010
Grant Date 28-May-2010
Date of Filing 07-Mar-2003
Name of Patentee PPG INDUSTRIES OHIO, INC
Applicant Address 3800 WEST 143RD STREET, CLEVELAND, OH 44111, U.S.A.
Inventors:
# Inventor's Name Inventor's Address
1 AMBROSE, RONALD, R 6307 HAMPTON STREET, PITTSBURGH, PA 15206, U.S.A.
2 CHASSER, ANTHONY, M 1409 PERNLEGE DRIVE, ALLISON PARK, PA 15101, USA.
3 HU, SHENGKUI 304-B, GLEN DOUGLAS DRIVE, GLENSHAW, PA 15116, USA.
4 SCHNEIDER, JOHN, R 306 LAURELWOOD DRIVE, GLENSHAW, PA 15116, USA.
5 SMITH, JACKIE, L 5501 ORCHARD HILL DRIVE, APARTMENT 514, GIBSONIA, PA 15044, USA.
PCT International Classification Number C08K 5/00
PCT International Application Number PCT/US01/28921
PCT International Filing date 2001-09-14
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 09/666,175 2000-09-21 U.S.A.