Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-04-20
2001-08-14
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S163000, C521S164000, C521S167000
Reexamination Certificate
active
06274639
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to sprayable polyurethane compositions and to methods for coating surfaces with such compositions. In particular, the polyurethane coating of the invention is low density, durable, and has a thickness greater than that achievable with previous polyurethane coatings
2. Description of the Related Art
A durable, low density, thick, high build rate coating with low volatile organic compound (VOC) emissions has been desired as a protective coating for many years. Attempts at producing a coating having those characteristics has resulted in compromising one or several of the desired properties. When low density coatings are fabricated they tend to have low toughness or abrasion resistance. Furthermore, most low density coatings require a significant amount of organic solvent to carry the coating during spraying applications, which contributes significantly to the problem of VOC emissions. Thick coatings tend to be spongy or brittle and applying that type of coating to a vertical surface is a slow and tedious process due to slumping problems or curing/out gassing times required. The majority of low VOC coatings available at the present time are only acceptable for thin coating applications (less than 20 mils dry film thickness), or have an exceedingly long dry time between applications which prohibits the successful fabrication of high build rate and/or thick coatings.
These and other material and process problems associated with thick, durable, low density coatings necessitated the development of a low VOC coating that could be applied by a conventional spraying method.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore a general object of the present invention to provide an improved durable, low density, thick, high build rate polyurethane coating. The polyurethane coating preferably also has low VOC emissions.
It is a more specific object of the present invention to provide a durable, low density, high build polyurethane coating which is capable of having a thickness greater than 0.100 inches when applied during a single application.
It is another object of the invention to provide a durable, low density, high build polyurethane coating which is capable of having a thickness greater than 0.030 inches when applied during a single application to a vertical surface.
It is yet another object of the present invention to provide a method for producing a durable, low density, high build polyurethane coating comprising:
(a) mixing at least one polyol and at least one polyisocyanate so as to provide a uniform mixture in which the polyol and polyisocyanate have not substantially reacted to form a urethane and which has sufficiently low viscosity such that the mixture is capable of being sprayed,
(b) introducing a catalytically effective amount of at least one polyurethane catalyst, and
(c) spraying the mixture onto a substrate so as to form a polyurethane coating thereon.
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Dowell Douglas R.
Foreman James E.
Isler Bobby G.
Burns Doane , Swecker, Mathis LLP
Lockheed Martin Corporation
Pezzuto Helen L.
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