Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-10-19
2004-09-28
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S459000, C525S504000, C528S061000, C428S423100, C427S421100, C427S426000
Reexamination Certificate
active
06797789
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the preparation and application of polyurea elastomeric coating/lining systems, and more particularly to a phenolic/polyurea co-polymer system for applications requiring extreme chemical resistance and performance.
Many different types of materials are used to build the engineering structures and vehicles found in our lives today. Most of these materials must be protected from environmental elements of one form or another. For instance, steel needs to be protected from moisture and oxygen to prevent corrosion. Likewise, wood needs to be protected from moisture to prevent rotting. Concrete should be protected from corrosion due to chlorides, other salts, and corrosive air. Further, moisture penetration can lead to spalling of concrete from freeze-thaw cycling.
During the last decade, environmental sensitivity has spawned the need for secondary containment around hazardous chemical storage tanks and processing equipment. Spray polyurea coating systems have become one of the major candidates for secondary containment use. They are used extensively to provide the monolithic impervious membrane to contain spilled and fugitive chemicals caused by leakage or accident.
In addition to the secondary containment of chemicals, surfaces, such as concrete floors, are frequently coated to control dust and dirt that are associated with the substrate when it is not coated. Further, it is often desirable to color code surfaces for pedestrian or worker safety. For instance, roadways have crosswalk striping, and safety railings are often orange or yellow. Identifying danger with a colored coating, and providing barriers to entry or exit are typical of this type of marking.
Many surfaces are coated simply for aesthetic purposes. Even if surfaces need not be protected from the elements, architectural designers commonly specify coatings or other decor to render the completed item artistically pleasing. The color combinations, patterns and decorations they specify are chosen with purpose and careful consideration to have the desired effect.
Paint and coating systems used for these purposes have proliferated over the decades, and polyurea spray elastomeric coating/lining technology has found a place in many of these application areas. Variations of the polyurea technology have allowed for UV color stability, abrasion resistance, easier processing conditions and improved substrate adhesion. U.S. Pat. No. 5,162,388 to Primeaux, II (1992) discloses Aliphatic Polyurea Elastomers comprising an (A) component and a (B) component. The (A) component includes an aliphatic isocyanate, while the (B) component includes an amine-terminated polyoxylalkylene polyol and certain specific cycloaliphatic diamine chain extenders. Primeaux, II (1992) represents one example of a polyurea elastomer system, and in particular, teaches a polyurea elastomer system with good flexibility and ultraviolet stability. U.S. Pat. No. 5,504,181 to Primeaux, II (1996) discloses Aliphatic Spray Polyurea Elastomers comprising an (A) component including an aliphatic isocyanate, and a (B) component including an amine-terminated polyoxyalkylene polyol, and an amine-terminated aliphatic chain extender. The elastomer of Primeaux, II (1996) must be prepared by impingement mixing the isocyanate preparation with the amine-terminated polyether. An additional example of a polyurea elastomer system is found in U.S. Pat. No. 5,480,955, also to Primeaux, II (1996), which teaches additional Aliphatic Spray Polyurea Elastomers. In that reference, the aliphatic spray polyurea elastomer disclosed comprises an (A) component which includes an aliphatic isocyanate, and a (B) component which includes (1) a primary amine-terminated polyoxyalkylene polyol with a molecular weight of at least about 2000, and (2) a specific primary amine-terminated chain extender. A Method of Preparing an Aliphatic Polyurea Spray Elastomer System is disclosed in another patent to Primeaux, II: U.S. Pat. No. 6,013,755. That reference teaches the preparation of a resin blend which is reacted with an isocyanate under conditions effective to form a polyurea elastomer.
The references disclosed herein teach effective methods and materials for coating and protecting a wide variety of substrates. Engineers, however, are always searching for improvements upon earlier inventions, as well as entirely new ones. Two primary deficiencies highly limit the use of polyurea systems in highly chemical/corrosive environments, and in immersion service. The main drawback to the polyurea technology in very corrosive applications is that the resistance to strong acid and base systems, as well as solvents, is very poor. Generally, resistance to crude or heavy fractions of petroleum is excellent, but the ability to withstand the presence of medium to light petroleum fractions is very poor. Solvent resistance also tends to be very selective and highly limited. While the current polyurea technology will withstand relatively low concentrations of acidic and basic solution, exposure to medium to high concentrations tends to result in extreme deterioration and failure in a very short time.
Additionally, the relatively higher moisture vapor permeation through the coating system allows for its delamination from certain substrates in immersion/lining applications. This problem is common in steel tank lining applications where you have a temperature gradient from inside the tank to the outside. In other words, the liquid inside the tank is heated and the ambient temperature outside the tank is relatively cooler. This results in a moisture drive through the coating/lining system and causes a phenomenon referred to as “Cold Wall Effect.”
The present invention is directed to one or more of the problems or shortcomings associated with the prior art.
SUMMARY OF THE INVENTION
The present invention address one or more of the deficiencies noted above with respect to the current polyurea spray elastomer coating/lining technology. This invention will markedly improve the performance of the polyurea elastomer coating/lining technology with regard to both moisture vapor transmission and chemical resistance.
A primary aspect of the present invention is the reacting of phenolic resins, blended into the resin blend component, with polyisocyanates in the polyurea formulation. The incorporation of the phenolic resins into the polyurea backbone will increase cross-link density of the cured polymer, resulting in a reduction of the moisture vapor transmission compared to non-phenolic containing polyurea system.
Phenolics are also known for their chemical resistance, and it is therefore expected that the inclusion of phenolic resins will enhance the chemical resistance of cured systems. Phenolics are also known for high temperature resistance, making another benefit of phenolic inclusion an increased elevated temperature resistance over non-phenolic systems. Phenolics are also known for their superior adhesion characteristics compared to other materials. The use of phenolic resins in the polyurea technology will tend to improve adhesion to the various substrates that are coated/lined, and give significant performance advantages over the current polyurea elastomer coating/lining technology.
To complement the above, specialized epoxy resins may be incorporated to form an Interpenetrating Polymer Network, further enhancing the target properties of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention relates to the preparation and application of plural component, phenolic/polyurea co-polymer coating systems that exhibit significantly improved chemical resistance as compared to conventional polyurea elastomer coating systems. The present systems include the reaction product of two components to produce a phenolic/polyurea co-polymer elastomeric coating system. In the preferred embodiment, the first, (a), component comprises an isocyanate, and preferably includes an isocyanate quasi-prepolymer of an isocyanate and an active hydrogen
Davis Thomas E.
Primeaux, II Dudley J.
Bissett Melanie
Dinnin & Dunn P.C.
Seidleck James J.
Visuron Technologies, Inc.
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