Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-01-06
1998-05-12
Sellers, Robert E.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525438, C08L 5100, C08L 6300, C08L 6702
Patent
active
057506191
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a curable coating composition particularly useful as a top coat in multi-layered coating systems.
Base coat-clear coat 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 top coat, and the resistance to deterioration. Further effort has been directed to the development of coating compositions having low volatile organic content (VOC).
Previous efforts at improving the etch resistance and durability of coatings had suggested the use of anhydride resins having pendant non-cyclic anhydride moieties in combination with resins that react with the polyanhydride resins to cure under curing conditions. However, a continuing need exists for coating formulations which can be sprayed at low VOC and which exhibit outstanding performance characteristics after application, and particularly resistance to environmental etching.
SUMMARY OF THE INVENTION
The present invention provides a sprayable coating composition which can be easily applied at high solids and exhibits outstanding appearance and durability after application and ease of maintenance.
Specifically, the instant invention provides a curable coating composition comprising organic solvent and binder, the binder comprising contains (1) a central moiety, and (2) on average, more than one pendant, non-cyclic anhydride moiety bonded to each central moiety; molecular weight of less than about 1500; resin having grafted thereto, acrylic backbone and at least about 3% ethylenically unsaturated monomers containing epoxy functionality, each of which is soluble in organic solvent and has one end grafted to the core, the stabilized acrylic resin being substantially free from non-polymerizable linear polymer; and of equivalents of epoxy to anhydride is about from 0.5 to 1.8.
DETAILED DESCRIPTION OF THE INVENTION
Anhydride resins which can be used in the present invention include those having a molecular weight of less than about 3000 having a central moiety and more than one pendant, non-cyclic anhydride moiety bonded to each central moiety. The anhydride is asymmetrical, and preferably contains a moiety represented by the following formula: ##STR1## wherein (CM) is a central moiety, (R.sup.1) is an organic moiety, and n is a number of pendant anhydride groups that averages greater than one.
The central moiety can be a simple organic moiety, such as an aliphatic, cycloaliphatic or aromatic moiety, with a plurality of anhydride groups bonded to it. Alternatively, it can contain a plurality of repeating units which are bonded to one or more pendant anhydride groups. Examples of suitable non- polymeric central moieties are those derived from multifunctional alcohols such as pentaerythritol, trimethylolpropane and neopentyl glycol. The multifunctional alcohols are reacted with cyclic, monomeric anhydride such as methyl hexahydrophthalic anhydride to give a multifunctional acid containing moiety. The resulting product is then reacted with ketene to form the linear pendant anhydride.
The central moiety is linked to more than one non-cyclic anhydride moiety, on average. It is preferably linked to at least about 2 non-cyclic anhydride groups on average and more preferably to at least about 3 non-cyclic anhydride groups on average. The anhydride equivalent weight (formula weight per anhydride group) is preferably at least about 200 and preferably no more than about 1000.
Each anhydride moiety is typically terminated by an organic group, which is preferably aliphatic and more preferably alkyl. It preferably contains no more than about 6 carbon atoms, more preferably no more than about 4 carbon atoms, and most preferably methyl.
The oligomeric anhydride can optionally contain a polyvalent organic moiety (A) that is linked to a plurality of anhydride groups by a plurality of pendant linking groups (LG), as illustrated in the following formula: ##STR2## wherein R.sup.1 is an organic
REFERENCES:
patent: 4746714 (1988-05-01), Spinelli et al.
patent: 5010140 (1991-04-01), Antonelli et al.
patent: 5428082 (1995-06-01), Gould et al.
patent: 5633330 (1997-05-01), Gould et al.
Barsotti Robert John
Scopazzi Christopher
E. I. Du Pont de Nemours and Company
Sellers Robert E.
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