Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2002-04-10
2003-04-22
Woodward, Ana (Department: 1711)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C427S386000, C427S387000, C428S423100, C428S447000, C524S500000, C524S504000, C524S506000, C524S507000, C524S513000
Reexamination Certificate
active
06551713
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a curable coating composition particularly useful as a topcoat in multi-layered coating systems.
Basecoat-clearcoat systems have found wide acceptance in the past decade as automotive finishes. Continuing effort has been directed to such coating systems to improve the overall appearance, the clarity of the topcoat, and the resistance to deterioration. Further effort has been directed to the development of coating compositions having low volatile organic content (VOC). A continuing need exists for coating formulations which provide outstanding performance characteristics after application, and particularly mar-resistance and resistance to environmental etching. Heretofore, mar-resistant coatings were attained by softening the coating, which depreciates other performance characteristics. The instant invention overcomes this problem.
SUMMARY OF THE INVENTION
This invention concerns a curable coating composition of a binder in an organic solvent, the composition having a volatile organic content not exceeding about 0.4 kilograms per liter, comprising:
i) a binder selected from a linear or branched cycloaliphatic moiety-containing oligomer or blend of oligomers with a weight average molecular weight not exceeding about 3,000, a polydispersity not exceeding about 1.5 and functionality A or A plus B; and
ii) an optional oligomeric crosslinker or blend of crosslinkers with a weight average molecular weight not exceeding about 3,000 and functionality C or C plus D;
components i and ii reacting at cure to form a three-dimensional network having chains of substantially uniform, controllable molecular weight between crosslinks.
Preferred functionalities in oligomeric components i and ii are as follows:
COMPONENT (i)
COMPONENT (ii)
A = hydroxyl
C = isocyanate
A = hydroxyl
C = melamine
A = anhydride
C = epoxy
A = anhydride
C = epoxy; D = hydroxyl
A = acid
C = epoxy
A = acid; B = hydroxyl
C = epoxy; D = melamine
A = epoxy
C = isocyanate
A = epoxy; B = hydroxyl
C = isocyanate
A = aldimine
C = isocyanate
A = aldimine; B = hydroxyl
C = isocyanate
A = ketimine
C = isocyanate
A = ketimine; B = hydroxyl
C = isocyanate
A = silane
C = silane
A = silane; B = hydroxyl
C = melamine
A = silane; B = hydroxyl
C = isocyanate
A = silane; B = epoxy
C = acid; D = melamine
The compositions of this invention, comprising (i) when (i) is self-crosslinking, or, (i) plus (ii), may also contain up to a total of about 300% based on the total binder of a noncyclic oligomer and/or an acrylic polymer and/or a dispersed macromolecular polymer as described in more detail hereafter. This invention also concerns a method for coating a substrate comprising applying the disclosed composition thereto and curing the composition; as well as a substrate coated with the composition. The term “isocyanate(s)” employed herein includes blocked isocyanate(s) as well.
DETAILS OF THE INVENTION
The compositions of this invention form structured polymer networks of high hardness and excellent mar resistance. The functionality of these oligomers is predictably (nonrandomly) located versus polymers in which functionality is randomly distributed and whose polydispersities generally exceed 2.0. By “polydispersity” is meant weight average molecular weight divided by number average molecular weight, both measured by gel permeation chromotography. In compositions of this invention, molecular weight between crosslinks can be controlled to form more uniformn networks minimizing short, embrittling lengths and long, softening lengths; minimizing soluble non-functional materials in the network and maximizing the toughness of the films (energy to break). These systems develop open networks with high molecular weight between crosslinks, vs. polymeric systems, at relatively high Tg's.
The Tg of these systems can be controlled to give a maximum balance of mar, hardness, durability, and etch. In measuring Tg of crosslinked films made from compositions of this invention using dynamic mechanical analysis, the Tg regime is characterized by a steep slope versus a gradual slope for a random system based on polymers. The reactivity of these systems is such that complete reaction is attainable to minimize hydrophilic groups. These systems are typically baked at 120° to 141° C. (250° to 285° F.), but can be cured at lower temperatures through the use of more reactive groups and catalysis.
Representative of the functionalized oligomers that can be employed as component i or ii are the following:
Acid Oligomers: The reaction product of multifunctional alcohols such as pentaerythritol, hexanediol, trimethylol propane, and the like, with cyclic monomeric anhydrides such as hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and the like.
Hydroxyl Oligomers: The above acid oligomers further reacted with monofunctional epoxies such as butylene oxide, propylene oxide, and the like.
Anhydride Oligomers: The above acid oligomers further reacted with ketene.
Silane Oligomers: The above hydroxyl oligomers further reacted with isocyanato propyl trimethoxy silane.
Epoxy Oligomers: The diglycidyl ester of cyclohexane dicarboxylic acid, such as AralditeÓ CY −184 from Ciba Geigy, and cycloaliphatic epoxies, such as ERLÓ-4221, and the like from Union Carbide.
Isocyanate Oligomers: The isocyanurate trimer of hexamethylene diisocyanate, DESMODURÓ 3300 from Bayer or Tolonate HDTa from Rhone-Poulenc, and the isocyanurate trimer of isophorone diisocyanate, and the like.
Aldimine Oligomers: The reaction product of isobutyraldehyde with diamines such as isophorone diamine, and the like.
Ketimine Oligomers: The reaction product of methyl isobutyl ketone with diamines such as isophorone diamine.
Melamine Oligomers: Commercially available melamines such as CYMELÓ 1168 from Cytec Industries, and the like.
AB-Funtionalized Oligomers: Acidchydroxyl functional oligomers made by further reacting the above acid oligomers with 50%, based on equivalents, of monofunctional epoxy such as butylene oxide or blends of the hydroxyl and acid oligomers mentioned above or any other blend depicted above.
CD-Functionalized Crosslinkers: Epoxylhydroxyl functional crosslinkers such as the polyglycidyl ether of Sorbitol DCE-358Ó from Dixie Chemical or blends of the hydroxyl oligomers and epoxy crosslinkers mentioned above or any other blend as depicted above.
The compositions of this invention may additionally contain up to 30% by weight of binder of a noncyclic oligomer, i.e., one that is linear or aromatic. Such noncyclic oligomers can include, for instance, succinic anhydride- or phthalic anhydride-derived moieites in the “Acid Oligomers” such as described above.
Preferred oligomers (i) have weight average molecular weight not exceeding about 3,000 with a polydispersity not exceeding about 1.5; more preferred oligomers have molecular weight not exceeding about 2,500 and polydispersity not exceeding about 1.4; most preferred oligomers have molecular weight not exceeding about 2,200, and polydisperity not exceeding about 1.25. The compositions of this invention can comprise 100% by weight of component (i) when (i) is a self-crosslinker. More typically, compositions will comprise 20-80 weight percent of (i), preferably 30 to 70 weight percent and more preferably 40 to 60 weight percent, with the balance being (ii).
The present coating composition can further comprise a functional amount of catalyst, generally about 0.1 to 5 weight percent, based on the weight of solids in the formulation. A wide variety of catalysts can be used, such as dibutyl tin dilaurate for isocyanate based reactions, tertiary amines such as triethylenediamine or phosphonium based catalysts for epoxy reaction and sulfonic acids, such as dodecylbenzene sulfonic acid for
Barsotti Robert John
Hazan Isidor
Neff Bruce Lyle
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
Woodward Ana
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