Compositions – Preservative agents – Anti-corrosion
Reexamination Certificate
1998-11-12
2001-05-29
Warden, Jill (Department: 1743)
Compositions
Preservative agents
Anti-corrosion
C252S387000, C252S389100, C252S601000, C252S602000, C252S606000, C252S607000, C252S608000
Reexamination Certificate
active
06238594
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an intumescent material, and, in particular, to a intumescent material that can be applied as a caulking, coating or film, which includes a liquid carrier with a corrosion inhibitor, expandable particulate graphite, and a filler, if desired, and the method of making such an intumescent material.
Intumescent materials, which are commonly used as fire stopping barriers, typically include a liquid coating, caulking or film forming carrier, expandable graphite, and a filler. These materials, applied as caulking, coatings, films, etc., form passive fire protection systems which remain inactive until subjected to heat and temperatures such as those encountered from the flames of a fire. When these passive fire protection systems are subjected to heat and temperatures, such as those encountered in a fire, these intumescent materials react, grow and expand forming a char (many times the original thickness of the caulking, coating or film applied) to insulate the surface to which the material is applied, e.g. the surface of structural steel in a building, from the damaging effects of the heat generated by the fire.
Typically, the expandable graphite, used in these materials, is prepared from particulate, naturally occurring crystalline flake graphite or crystalline lump graphite, that has been acid treated to make the graphite intumescent. It is believed that the treatment of the crystalline flake graphite or crystalline lump graphite with concentrated sulfuric acid in the presence of an oxidizing agent, such as nitric acid, forms the compound graphite sulfate which exfoliates and expands upon heating.
While these materials can be quite effective as fire barriers, the acidic properties of the expandable graphite in these materials causes these materials to be corrosive to steel, stainless steel, copper, aluminum, galvanized steel and other metals or metal alloys, such as those commonly used in the construction industry. Thus, in applications, where these intumescent materials come in contact with metal components, e.g. girders and other structural members of buildings and the like, the use of these intumescent materials can cause corrosion problems or require the application of primers or other protective coatings to the metal components prior to the application of the intumescent material thereby increasing both labor and material costs.
SUMMARY OF THE INVENTION
The present invention provides a solution to the metal corrosion problems encountered with previous intumescent materials by providing an intumescent material, containing expandable particulate graphite, which is non-acidic (has a pH greater than 7.0) and contains a corrosion inhibitor so that the corrosion of metals by the intumescent material is greatly reduced or eliminated.
The intumescent material of the present invention includes a liquid carrier (such as but not limited to a caulking, coating or film forming material), expandable particulate graphite (preferably washed to remove residual acid or acid components), a corrosion inhibitor, and, if desired, one or more fillers. The intumescent material has a pH greater than 7.0, preferably, between about 7.5 and about 10.0, and most preferably between about 8.0 and about 8.5, to reduce the corrosive properties of the intumescent material with respect to most commonly used metals, such as those used in the construction industry, except aluminum, and to provide a chemically conducive environment for the corrosion inhibitor to form a protective layer on the metal to which the intumescent material is applied to prevent or greatly reduce corrosion on all commonly used metals including aluminum.
The preferred method of making the intumescent material includes washing the expandable particulate graphite with water to remove residual acid or acid components from the expandable particulate graphite and increase the pH of the expandable particulate graphite to about 7.0. The expandable particulate graphite is then added to a liquid carrier, such as a caulking, coating or film forming carrier, containing a corrosion inhibitor and, in most embodiments, a filler, to form the intumescent material of the present invention. As mentioned above, the intumescent material of the present invention (the liquid carrier with the expandable particulate graphite, the corrosion inhibitor and filler, if used) has a pH greater than 7.0, preferably between about 7.5 and about 10.0 and most preferably, between about 8.0 and about 8.5, to reduce the corrosive properties of the intumescent material and to provide a chemically conducive environment for the corrosion inhibitor to form a protective corrosion inhibiting layer on a metal to which the intumescent material is applied to prevent or greatly reduce corrosion. If the pH of the liquid carrier, to which the expandable particulate graphite is to be added, is not within the ranges set forth above, a pH enhancer (basic material) can be added directly to the carrier or applied to the washed expandable particulate graphite, prior to introducing the expandable particulate graphite into the carrier, to bring the intumescent material of the present invention within the required pH range.
REFERENCES:
patent: Re. 34951 (1995-05-01), Slosberg et al.
patent: 1137373 (1915-04-01), Aylsworth
patent: 3574644 (1971-04-01), Olstowski et al.
patent: 3642531 (1972-02-01), Peterson
patent: 3945962 (1976-03-01), Clark
patent: 4043950 (1977-08-01), Wilmsen et al.
patent: 4176071 (1979-11-01), Crouch
patent: 4179535 (1979-12-01), Kalbskopf et al.
patent: 4191675 (1980-03-01), Inagaki et al.
patent: 4222926 (1980-09-01), Mizuno et al.
patent: 4273879 (1981-06-01), Langer et al.
patent: 4284550 (1981-08-01), Mizuno et al.
patent: 4563491 (1986-01-01), Comune
patent: 4689256 (1987-08-01), Slosberg et al.
patent: 4729853 (1988-03-01), Von Bonin
patent: 4992481 (1991-02-01), Von Bonin et al.
patent: 5057367 (1991-10-01), Morii et al.
patent: 5076969 (1991-12-01), Fox
patent: 5132054 (1992-07-01), Stahl
patent: 5175197 (1992-12-01), Gestner et al.
patent: 5232976 (1993-08-01), Horacek et al.
patent: 5338349 (1994-08-01), Farrar
patent: 5498466 (1996-03-01), Navarro et al.
Bright Edward A.
Duquette David J.
Hamilton Robert D.
Johnson Walter A.
Shumate Monroe W.
Cross LaToya
Lister John D.
Passive Fire Protection Partners
Warden Jill
LandOfFree
Intumescent material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Intumescent material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Intumescent material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2471215