Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-08-13
1999-11-16
Dawson, Robert
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
428418, C08K 320, C08L 6302
Patent
active
059859563
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to a coating composition comprising acid group-containing oligomer, a polymer containing epoxy and silane functionality and an acrylic polymer component containing an ethylenically unsaturated monomeric element.
2. Description of the Prior Art
A problem with present coating compositions for certain metal substrates including those employed for automobiles and trucks, or parts thereof, is that durability is not as good as desired. An important aspect of durability is environmental resistance. The present invention offers a high quality finish exhibiting superior environmental resistance. Another problem with epoxy-containing systems has been that, due to limited pot life, they have been used as a two-package system, which packages are conventionally mixed shortly before use. The present composition is a one-package system characterized by good package stability and excellent crack resistance in use.
SUMMARY OF THE INVENTION
This invention pertas to a stable, crack-resistant, one-package coating composition with a volatile organic content of less tand or equal to 4.2 pounds per gallon comprising a volatile organic solvent and a binder, the binder comprising (by weight of binder): and a weight average molecular weight of no more than about 2,000; functionality and a weight average molecular weight between 1,500 and 50,000 comprising about 0.5 to 1.7 equivalents of epoxy per equivalent of acid in (i), the silane being at least 2 percent by weight of the binder; and
(iii) 3 to 40 percent of an acrylic component comprising a core of acrylic polymer and, grafted thereto, a plurality of substantially linear stabilizer components; component (iii) containing at least about 2 percent of ethylenically unsaturated monomer with finctionality capable of reacting with (i), (ii), or both (i) and (ii); the core being substantially insoluble and the stabilizer components being soluble in the solvent.
The composition can also be pigmented to form a colored finish, although the composition is especially useful as a clearcoat.
Preferred component (i) is the reaction product of methylhexahydrophthalic anhydride and pentaerythritol. Preferred component (ii) comprises polymerized units, in addition to glycidyl methacxylate and methacryloxypropyltrimethoxy silane, selected from at least one member of the group alkyl methacrylate, alkylacrylate and styrene, wherein the alkyl moiety contains 1 to 8 carbon atoms. Preferred component (iii) contains finctional monomer selected from at least one member of the group hydroxyethylacrylate, hydroxypropyl acrylate, glycidyl methacrylate and glycidyl acrylate.
DETAILS OF THE INVENTION
The coating composition of this invention has a solids content of between 40% to 80% binder, based on the weight of the binder/solvent composition. Preferably, the binder will comprise at least about 50% by weight of the composition.
Contemplated as usefui oligomeric compounds are the reaction products of an acid anhydride such as hexahydrophthalic anhydride, or methylhexahydrophthic anhydride, or a succinic anhydride which can be substituted for example with a C.sub.1 -C.sub.8 alkyl group, with a dihydroxyl finctional or polyhydroxyl functional compound such as pentaerythritol or ethylene glycol. A preferred half ester is the reaction product of methylhexahydrophthalic anhydride and pentaerythritol. Other hydroxy finctional compounds are trimethylolpropane, ditrimethyol propane, cyclohexane dimethanol, and hydrogenated bisphenol A.
Other compounds containing the requisite acid finctionality can be used such as glutaric acid and the like provided the volatility is such that they remain in the film during the curing process and can react in. The acid oligomer can have hydroxyl functionality, for example the reaction product of a 3:1 molar ratio of methylhexylhydrophthalic anhydride and pentraexthritol.
The epoxy- and silane-containing polymer can be made by the copolymerization of an ethylenically unsaturated epoxy-containing mono
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Barsotti Robert John
Lee Ying Kao
Lewin Laura Ann
Aylward D.
Costello James A.
Dawson Robert
Deshmukh Sudhir G.
E. I. Du Pont de Nemours and Company
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