Stock material or miscellaneous articles – Web or sheet containing structurally defined element or...
Reexamination Certificate
1999-07-20
2001-10-30
Cole, Elizabeth M. (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
C428S920000, C428S921000, C252S605000, C252S607000, C252S610000, C427S202000, C427S426000, C427S427000
Reexamination Certificate
active
06309740
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to spray-applicable cementitious fireproofing, and in particular to a coating system and method relative to the use of a spray-applicable primary cementitious fireproofing coating and the use of an overlying secondary coating formed using an aqueous dispersion of delaminated vermiculite platelets.
BACKGROUND OF THE INVENTION
It is well known to spray-apply fireproofing slurries to metal structural members and other building surfaces to provide a heat resistant coating thereon. Spray-applied, hydratable, cementitious fireproofing compositions are disclosed, for example, in U.S. Pat. No. 4,751,024 of Shu et al.; and U.S. Pat. No. 4,904,503 of Hilton et al.; U.S. Pat. No. 5,034,160 of Kindt et al.; and U.S. Pat. No. 5,340,612 of Perito, which are owned by the common assignee hereof and incorporated herein by reference. These fireproofing compositions teach the use of lightweight aggregates, such as shredded polystyrene particles, to obtain concentrations favorable for pumping the fireproofing composition through hoses, sometimes to great heights, to nozzles from which the fireproofing is sprayed onto a substrate surface using compressed air. Moreover, the fireproofing compositions provide non-segregating, uniform slurries displaying desired levels of adhesion to steel substrates and excellent fire protection. The density of the slurry compositions containing concentrations of lightweight aggregate is sufficiently low after application to ensure that the coating stays in place before and after setting. Thus, “fall off” of the applied composition due to inadequate adherence of mechanical and structural disturbance is minimized or eliminated. One of the unavoidable features of spray-applying cementitious fireproofing, however, is the need for achieving certain coating thicknesses. Such coating thicknesses are needed to meet fireproofing standards, and are attained, for the most part, through successive spray passes over the substrate surface. For example, U.S. Pat. No. 5,340,612 of Perito disclosed a sprayable fireproofing composition that provided a quick setting time such that multiple coatings of the slurry could be applied within the same working day. Nevertheless, there remains a concern that using multiple coatings to achieve minimal thicknesses sufficient for attaining fireproofing protection is time-consuming and labor-intensive.
The present invention pertains to the surprising discovery that the fireproofing performance of conventional spray-applicable cementitious fireproofing may be considerably enhanced using a secondary, overlying layer formed from an aqueous dispersion of delaminated vermiculite platelets. In other words, the present inventors envision that it is possible to use a relatively thinner coating of cementitious fireproofing without substantially sacrificing fireproofing efficacy. The ability to apply the fireproofing in a relatively thinner coating will conserve labor and energy, and expenses and time at the application site.
The present invention also does not need to rely upon lightweight or heavy aggregate, which may be optional, and thus provides the ability to use even thinner wet pass coatings that afford a savings in time and labor.
SUMMARY OF THE INVENTION
The present invention provides an improved hydratable cementitious fireproofing coating system and method by which a “thickness savings” can be realized without sacrificing substantial fireproofing efficacy. This is achieved by providing a relatively thin, overlying secondary coating formed from an aqueous dispersion of delaminated vermiculite platelets, placed on top of a primary coating layer formed from a hydratable cementitious fireproofing composition of the kind now conventionally used.
The present inventors have surprisingly found that this laminar coating arrangement can lead to a decrease in the thickness of the fireproofing coating normally required to achieve a given fireproofing performance level. The ability of the present invention to employ thinner spray-applied coating layers of primary fireproofing will conserve effort, time, labor, and expense, because the spray-application will require fewer passes during spray-application to attain minimum coating thickness. It is surmised by the inventors that the secondary vermiculite coating helps to contribute moisture barrier properties, such that the loss of inherent moisture from the cementitious fireproofing is slowed during exposure to fire or flames, while at the same time acts to transfer or deflect heat away from the underylying cementitious fireproofing composition. Thus, the ability to use relatively thinner cementitious fireproofing layers can translate into lower cumulative labor and time required for successive spray passes across the substrate surface to be protected.
A coating system for providing fireproofing protection to a substrate, comprising: (A) an hydratable cementitious fireproofing composition; and (B) a composition of delaminated vermiculite platelets. These components would be contained in separate containers but could be sold as part of a package, wherein the components are sold in pre-measured amounts suitable for application at a project site. Preferably, the fireproofing composition is spray-applied using an injected accelerator, as known in the fireproofing art (and the accelerator could be sold in its separate container), and the vermiculite coating layer is preferably spray-applied during or after the spraying of the fireproofing composition, as an aqueous dispersion, preferably using a separate spray nozzle.
An exemplary method of the invention thus comprises spray-applying onto a substrate surface a primary coating comprising a cementitious fireproofing composition, preferably using an injected accelerator; and, during this spray-application of the primary fireproofing coating or subsequent thereto, spray-applying over the coated substrate surface a secondary, overlying coating comprising an aqueous dispersion of delaminated vermiculite platelets. Thus, for example, the inventors envision that the operator of the spray equipment can mount a second nozzle (for spray-applying the vermiculite dispersion coating) adjacent to a first nozzel (for spray-applying the primary cementitious fireproofing coating), such that the dispersion can be quickly applied over substrate surface areas over which the first nozzle has just applied the fireproofing. Alternatively, the vermiculite dispersion coating may be spray-applied subsequent to the fireproofing-coated substrate surface using a second spray nozzle, or applied using some other conventional technique.
It is believed that the secondary overlying vermiculite coating can be applied either when the fireproofing coating is still wet or moist, or after the fireproofing has dried or substantially cured.
Further features and advantages of the invention are described in detail hereinafter.
REFERENCES:
patent: 4366203 (1982-12-01), Briggs
patent: 4366204 (1982-12-01), Briggs
patent: 4425465 (1984-01-01), Paget et al.
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patent: 4780147 (1988-10-01), Ou et al.
patent: 4904503 (1990-02-01), Hilton et al.
patent: 5034160 (1991-07-01), Kindt et al.
patent: 5102464 (1992-04-01), Ou
patent: 5116537 (1992-05-01), Yang et al.
patent: 5244740 (1993-09-01), Ou et al.
patent: 5330843 (1994-07-01), Ou et al.
patent: 5340612 (1994-08-01), Perito et al.
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Cirignano Paul
Shu Larry S.
Baker William L.
Cole Elizabeth M.
Leon Craig K.
W. R. Grace & Co.,-Conn.
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