Compositions: coating or plastic – Coating or plastic compositions – Alkali metal silicate containing
Reexamination Certificate
2000-05-08
2002-06-25
Marcheschi, Michael (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Alkali metal silicate containing
C106S602000, C106S603000, C106S605000, C106S618000, C106S624000, C106S632000, C106S634000, C106S122000, C106S628000, C106S637000, C106S406000, C106S407000, C106S482000, C264S041000, C264S042000, C264S045100, C264S045300, C264S050000, C501S080000, C501S084000
Reexamination Certificate
active
06409817
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to fine-celled rigid foams for retention of liquids having improved thermal insulation and fire retardant properties.
BACKGROUND OF THE INVENTION
The present invention constitutes an improvement over the fine-celled foam composition and method of U.S. Pat. No. 5,714,000 in that it has improved retention of liquids by absorption/adsorption which improves the thermal insulation and fire retardant properties of the fine-celled foam.
The stated uses for the fine-celled foam composition of U.S. Pat. No. 5,714,000 are for retention of liquids for floral, agricultural, nursery, horticulture use, such as for cut flowers, plant propagation mediums and growth cubes, soil conditioners, mulches, microwave and sound attenuation, filtration and liquid purification, industrial waste water containment and absorption, mediums for bioremediation, as a fire stop in hollow walled vessels and the like. The foam composition has from about 16 to 19 percent water hydrate (chemically bound water) and carbon particles diffused throughout the foam retain water. After the wet foam is dispensed into molds or receptacles, it is allowed to set in place for a period of 24 to 48 hours to allow excess liquid drainage and curing reaction; and then the damp foam is removed from the molds and placed in a leaching facility for removal of unwanted byproducts, such as sodium fluoride, any excess reactants, tall oil residue, and the like.
U.S. Pat. Nos. 5,081,761 and 5,695,089 describe and illustrate the use of cementitious, curable insulating materials as fire proofing material in the interstitial space or gap between two walls of a double wall tank.
U.S. Pat. No. 5,595,089 discloses a tank cavity filled with an insulating material comprised of perlite, cement, an air entrainment agent and water. The properties are described as: wet density from 28 to 40 pounds per cubic foot; compressive strength of about 25 to 150 psi; porosity of about 40 to 80 percent by volume. The porosity is sufficient to allow liquid and vapors to migrate through the insulation to monitoring points and also to an emergency vent port without over pressurization within the space. This insulating material contains chemically bound water hydrate in amounts sufficient to keep the temperature of the inner storage tank at an acceptable low level during an external fire. Such insulation, however, is relatively heavy, adding considerable weight when used in double wall tanks, overhead canopies, structures, and walls having cavities and the like.
U.S. Pat. Nos. 3,741,898 and 3,856,539 produce silica foam products without the inclusion of any substantial amounts of fillers or reinforcements. “Substantial amounts” of fillers or reinforcements were stated to be an amount in excess of about 10 percent on a dry basis or about 3 percent by weight of the alkali metal silicate (commercial sodium silicate) raw material on a wet basis. These foam products were produced for use as spray applied structural and insulation materials on walls, ceilings, and other relatively flat surfaces. The products were not commercially acceptable due to the long curing time (polymerization period) required to achieve sufficient rigidity, thereby, preventing flowing and sagging. The damp foam in this “uncured state” flowed and sagged from the surfaces leaving bare or thin spots of uneven coverage.
The terms “silica” and “silicate” have been used interchangeably in the trade. In the foregoing patents, a silica foam product from sodium silicate solution was defined as not having over a substantial amount of filler (10 percent) or reinforcement materials. In the present invention, considerably in excess of 10 percent “filler,” such as activated carbon, absorbents/adsorbents are present; and the caustic silicate solution derived from caustic digestion of rice hull ash has about ½ percent by weight of metals.
Adsorption, which is often confused with absorption, refers to the adhering of molecules of gases or liquids to the surfaces of porous solids. Adsorption is a physical process that occurs when liquids, gases, or suspended matters adhere to the external surfaces, or the internal pore surfaces, of an adsorbent media such as activated carbon. Absorption is the process in which one substance penetrates into the body of another substance or fills the pores in a solid, usually through capillary action. An example is the absorption of water in the cellular structure of fine-celled foam. In the present invention the improved retention of liquids results from the fine-celled foam absorption acting synergistically with the adsorption capabilities of the fillers and activated carbon components of the foam composition. Therefore, for convenience, the combined term absorption/adsorption is used throughout the specification.
It would be highly desirable to provide a method for producing a relatively light weight, fine-celled, rigid foam composition which has improved thermal insulation and fire retardant properties.
It is also highly desirable to provide a method of producing a foam composition in which absorbent/adsorbent fillers are added in such a manner that they do not disrupt the fine-celled feature and integrity of the final foam product thereby resulting in sufficient porosity and compressive strength for use in double walled tanks and hollow canopies, building panels, profiles, and the like.
SUMMARY OF THE INVENTION
The present invention is directed to such a process and a relatively light weight foam product which has improved thermal insulation and fire retardant properties. The resulting foam is inorganic, non-cementitious, non-combustible, non-toxic, non-shrinking, non-degradable, non-corrosive on steel, resistant to acids, alkalis and oil, heat absorbing, with low thermal conductivity. The addition of absorbent/adsorbent fillers is performed in such a manner that they do not disrupt the fine-celled features and integrity of the final foam product. This results in sufficient porosity and compressive strength for use as insulation or fire retardant in double walled tanks and hollow canopies, building panels, profiles, and the like.
The foam is comprised of inorganic compounds including: Amorphous precipitated silica from a sodium silicate solution produced by caustic digestion of rice hull ash obtained by thermal pyrolysis of rice hulls; activated carbon from the thermal pyrolysis of rice hulls; sodium fluoride produced by the curing reaction; inorganic absorbent/adsorbent fillers such as calcite or ground limestone (CaCO
3
), bentonitic clay, rice hull ash, ground particles of floral and horticultural foam scraps; chemically bound water (hydrate); and absorbed/adsorbed water and surface tension depressant, such as distilled tall oil.
The foam contains no cementitious materials including Portland cement, aluminous cement, or other cements.
The foam is non-combustible in that it will not burn or support combustion.
The foam is non-toxic with no toxic vapors or gases liberated upon heating.
The foam does not shrink during the curing process; therefore, the volume occupied is essentially constant. Also, the material is thermally isotropic which means it does not expand when heated. The foam matrix is isotropic since it has the same mechanical and physical properties in all directions.
The foam is non-degradable due to the stable nature of the inorganic compounds which are not biodegradable or chemically reactive.
The foam is non-corrosive on steel because the pH of the resulting mixture is in the 9.0 to 9.5 range which results in passavation of steel surfaces.
The foam is chemically inert when exposed to acids, alkalis, and oil solutions.
The foam has relatively high heat absorbing capability due to its specific heat capacity. The heat capacity is defined as the amount of heat, Joules or calories (BTU), required to raise the temperature of 1 kg (1 lb.) by 1° C. (1° F.) at constant pressure. The foam product heat capacity is about 1.4 to 1.5 times greater than that of the typical perlite-cement insulating materials.
The therm
Agritec, Inc.
Marcheschi Michael
Weiler James F.
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