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| Aqueous dispersions of olefin copolymers |
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| Hot melt adhesive pellet comprising continuous coating of pelletizing aid |
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| Water tree resistant insulating composition |
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| Masonry weep hole insert |
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| Pre-expanded particles of polypropylene resin and inmolded foamed article using the same |
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| Carboxylated polymer composition |
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| Photoimageable elements |
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Powder coating compositions and method
| Details |
Inventors: Jung, Rolf; Schmid, Christian;
Assignee: The Valspar Corporation (Minneapolis, MN)
Primary Examiner: Short; Patricia A.
Assistant Examiner:
Attorney, Agent or Firm: Marshall, Gerstein & Borun
Powder coating compositions for metal substrates, a method of powder coating a metal substrate, and a metal article are disclosed. The powder coating composition is a thermoplastic material and comprises: (a) a first polyester having a weight average molecular weight of about 10,000 to about 80,000 and a Tg of greater than 45.degree. C. to about 100.degree. C., (b) a second polyester having a weight average molecular weight of about 10,000 to about 70,000 and a Tg of about -10.degree. C. to about 45.degree. C., and optionally, (c) a modifying resin, such as an epoxy resin having an epoxy equivalent weight of about 500 to about 15,000, wherein the Tg of the first and second polyesters differ by about 5.degree. C. to about 60.degree. C. The powder coating composition is applied to a metal substrate to provide a composition film having a thickness of about 1 to about 200 microns. |
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A powder coating composition of the present invention, after application to a metal substrate, provides an applied coating composition that effectively inhibits the corrosion of metal substrates, such as, but not limited to, aluminum, iron, steel and copper.
An applied coating composition also demonstrates excellent adhesion to the metal substrate, excellent chemical resistance and scratch resistance, and excellent flexibility.
An applied coating composition does not impart a taste to foods or beverages that contact the applied coating composition.
In general, a present powder coating composition comprises: (a) a first polyester having an M.
sub.
w of about 10,000 to about 80,000 and a Tg of greater than 45.
degree.
C.
to about 100.
degree.
C.
, and (b) a second polyester having an M.
sub.
w of about 10,000 to about 70,000 and a Tg of about -5.
degree.
C.
to about 45.
degree.
C.
The first polyester has Tg that is about 5.
degree.
C.
to about 60.
degree.
C.
greater than the Tg of the second polyester.
The powder-coating composition is a solid and is free of organic solvents.
A powder coating composition optionally can further include: (c) a modifying resin, such as an epoxy or phenoxy resin having an EEW of about 500 to about 15,000 and/or (d) a filler and/or (e) a flow control agent.
In addition, a present powder coating composition can include optional ingredients that improve the esthetics of the composition, that facilitate manufacture and/or application of the composition, or that improve a functional property of the composition.
The individual composition ingredients are described in more detail below.
(a) Polyesters In accordance with an important feature of the present invention, a powder coating composition includes a first thermoplastic polyester and a second thermoplastic polyester in a total amount of about 50% to about 100%, by total weight of the composition.
Preferably, a powder composition includes about 55% to about 90%, by total weight of the composition, of the first and second polyesters
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Adhesives and Rubbers 
