Patent Application
20090078918
The present invention relates generally to the manufacturing field, and more particularly, relates to a method and structures including fire retardant spheres for implementing enhanced fire protection.
Today various solutions are used to control fire and the associated thermal energy to prevent damage or loss of life.
Typical fire-extinguishing foams are termed aqueous film forming foam (AFFF) and consist of perfluorinated surfactants synthesized from perflourooctyl sulfonate (PFOS). PFOS is environmentally persistent and bioaccumulative and has come under intense scrutiny. Suitable replacements are also fluorinated surfactants and may also be deemed environmentally unacceptable.
A need exists for a new solution to control and abate potentially dangerous situations from getting out of control, or at least controlling the situation long enough to save life and property that allows for broad applications, such as, within fabric, foam, plywood, firewalls, gas tanks, enclosures and shields that are integrated into various products, such as, electronic equipment, housing materials, furniture, ash trays, mattresses, tanks, automobile floors and firewalls.
Principal aspects of the present invention are to provide a method and structures including fire retardant spheres for implementing enhanced fire protection. Other important aspects of the present invention are to provide such method and structures including fire retardant spheres for implementing enhanced fire protection substantially without negative effect and that overcome many of the disadvantages of prior art arrangements.
In brief, a method and fire retardant structures including fire retardant spheres are provided for implementing enhanced fire protection. A selected fire retardant material is encapsulated in microspheres. The microspheres have a melting temperature. The fire retardant structure is formed of the microspheres encapsulating the fire retardant material and included in an article being produced. In response to a thermal fire event, the microspheres rupture or decompose releasing the encapsulated material to provide fire suppression.
In accordance with a preferred embodiment of the invention, a fire retardant structure alternatively is formed of second microspheres having predefined expansion characteristics. A layer of the second microspheres is disposed between two layers of an article being produced. In response to a thermal fire event, the microspheres expand to fill the space between the layers, providing fire suppression.
In accordance with features of the invention, the selected fire retardant material includes a selected biodegradable flame arresting material. The selected fire retardant material can include a thermally degradable material for forming an inert blanketing gas. Also a combination of a selected biodegradable flame arresting material and a thermally degradable material for forming an inert blanketing gas are respectively encapsulated in microspheres used to form the structures of the invention.
In accordance with features of the invention, the fire retardant structure forms a sheet integrated into a fabric, foam, plywood, firewall, gas tank, enclosure, shield of a particular article of manufacture.
The present invention together with the above and other objects and advantages may best be understood from the following detailed description of the preferred embodiments of the invention illustrated in the drawings, wherein:
In accordance with features of the invention, an effective method is provided for implementing enhanced fire protection. Microspheres with a set melting temperature encapsulate a selected fire retardant material. Then at a given temperature the microspheres burst, and the fire retardant material is released.
In accordance with features of the invention, a fire retardant structure alternatively is formed of second microspheres having predefined expansion characteristics. A layer of the second microspheres is disposed between two layers of a structure. In response to a thermal fire event, the microspheres expand to fill the space between the layers, providing fire suppression.
In accordance with features of the invention, the fire retardant microspheres form structures, such as sheets, that advantageously are integrated into fabric, foam, plywood, firewalls, gas tanks, enclosures, shields, and the like. Many different laminated structures can be created. The microspheres are designed to burst or decompose at a given temperature whereby the fire retardant material is released to suppress a fire. This fire suppression action can either stop or abate the fire to prevent harm to individuals and effectively provide additional time to escape.
In accordance with features of the invention, the fire retardant material is a selected environmentally suitable material, and typical fire-extinguishing foams are not used to create the fire retardant microspheres of the invention. Thus, aqueous film forming foam (AFFF) consisting of perfluorinated surfactants synthesized from perflourooctyl sulfonate (PFOS) and other fluorinated surfactants that are environmentally persistent and bioaccumulative generally are unacceptable.
In accordance with features of the invention, the fire retardant microspheres form structures that are integrated into many products. Some product examples are housing materials, fabrics, furniture, ashtrays, mattresses, tanks, automobile floors, firewalls, and the like. The fire retardant microspheres form structures that advantageously are used to protect electronic equipment. Potential military applications are ships, submarines, airplanes, tanks, hummers, and the like.
In accordance with features of the invention, blowing agents are encapsulated that trigger at predetermined temperatures and decompose to various gases, such as nitrogen. As another embodiment of the invention, the microspheres merely encapsulate the blowing agent. As the temperature rises, the blowing agent decomposes to form a gas, such as nitrogen and carbon dioxide, both of which would extinguish a fire, which due to the huge increase in volume while going from a solid to a gas, ruptures the shell and extinguishes the fire.
Having reference now to the drawings, in
A selected one or more first fire extinguishing materials are encapsulated within respective first spheres or first shells; or second microspheres having predefined thermal expansion characteristics are encapsulated, as indicated at a block 100. The first spheres or first shells encapsulating the first selected fire extinguishing materials are first microspheres with a set melting temperature. A selected product or an article of manufacture is produced including a structure formed by one or a combination of the first encapsulated materials; or a layer of the second microspheres are provided between two layers of the article being produced, as indicated at a block 102. The encapsulated materials, for example, form a sheet that is integrated into the product, such as, a fabric, a foam, a firewall, a shield, an enclosure, and the like, at block 102.
In use, when a fire event occurs as indicated at a block 104, then the first fire suppressant microspheres or shells decompose or rupture; or the second microspheres expand, as indicated at a block 106. The encapsulated fire extinguishing material or compounds are released; or expanding and filling the space between the two layers with the expanded second microspheres is provided responsive to the thermal event, as indicated at a block 108 for implementing suppression of the fire as indicated at a block 110.
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A selected fire extinguishing material encapsulated at block 100 includes, for example, but is not limited to a selected one of the following fire extinguishing/flame arresting materials including:
FE-36 (Dupont trademark; HFC-236fa);
FE-25 (pentafluoroethane);
FE-227 (HFC-227ea);
Aluminium hydroxide;
Magnesium hydroxide and various hydrates;
Organobromines and organochlorines;
Phosphorus, in the form of organophosphates, halogenated phosphorus compounds, and red phosphorus;
Antimony trioxide;
Boron compounds, mainly as borates;
Tetrakis(hydroxymethyl) phosphonium salts;
Chlorinated paraffins;
Tri-o-cresyl phosphate;
Tris(2,3-dibromopropyl) phosphate (TRIS);
Bis(2,3-dibromopropyl) phosphate;
Tris(1-aziridinyl)-phosphine oxide (TEPA).
A selected fire extinguishing material encapsulated at block 100 includes, for example, thermally degradable material for forming an inert blanketing gas. The microspheres advantageously encapsulate commercially available products that thermally decompose to form gaseous products at predefined trigger temperatures.
Such thermally degradable materials for forming an inert blanketing gas include various compounds, such as, plastic foaming agents such as azo compounds, for example, azodicarbonamide blowing agents, and sulfonyl hydrazides, for example, one or more of the sulfonylhydrazide compounds sold commercially under the tradename “Celogen” by Chemura Corporation, located in Middlebury, Conn.
Azo compounds decompose at specific trigger temperatures to form nitrogen gas plus other non-oxidizing gaseous products. In general, any compound that thermally decomposes to gaseous products, with the stipulation that the gaseous product be non-oxidizing, at a desired trigger temperature is suitable as the flame arresting material. For example, calcium oxalate decomposes by loss of water (as steam) at elevated temperature and hence is a suitable fire extinguishing agent.
In accordance with features of the invention, microspheres, such as a type of microspheres manufactured and sold by Akzo Nobel Company under the mark EXPANCEL may be used for the second microspheres. EXPANCEL® microspheres consist of a small amount of a hydrocarbon gas encapsulated by a gas-tight thermoplastic shell. When the microspheres are heated, the thermoplastic shell softens and the hydrocarbon inside the shell increases its pressure. This results in a dramatic expansion of the spheres (typically from 10 μm to 40 μm diameter). The EXPANCEL® microspheres are available with expansion temperatures in the range of 80-190 C. The temperature of expansion onset as well as the temperature at which the maximum expansion is obtained depends on the heating rate. EXPANCEL® microspheres can withstand thousands of cycles of loading/unloading without collapsing or breaking and can be used in contact with many chemicals, including solvents, without any negative effects on expansion or other thermomechanical properties.
It should be understood that all of the above are non-limiting examples; various other materials that serve as suitable fire extinguishing compounds are known to those skilled in the art and could also be encapsulated without deviating from the scope of the invention.
Various known techniques to encapsulate materials within microspheres are known to those skilled in the art. The selected one or more fire extinguishing materials are encapsulated within respective microspheres with a set melting temperature, or predefined thermal expansion characteristics, at block 100, using techniques known to those skilled in the art, forming microcapsules.
Prior art techniques include those whereby the microcapsule is manufactured from gelatin via a simple precipitation process, for example, as disclosed in U.S. Pat. No. 2,183,053 issued Dec. 12, 1939 to Taylor, or a more complex precipitation process such as those generally described in U.S. Pat. Nos. 2,800,457 and 2,800,458 issued Jul. 23, 1957 to Green et al.
More generally, microcapsules may also be formed by two well-known processes: complex coacervation and interfacial polymerization. Complex coacervation is conducted in aqueous media and is used to encapsulate water insoluble liquids. Gelatin and gum arabic (both natural products) are the two major raw materials used in the manufacture of microcapsule shells. In this case, the gelatin is dissolved in warm water and the water-insoluble substance to be encapsulated is dispersed therein. Gum arabic and water are added, the pH adjusted to approximately 4.0, and a complex coacervate of gelatin and gum arabic is formed surrounding the water-insoluble material. The gelatin is subsequently crosslinked, typically with an aldehyde such as formaldehyde or gluteraldehyde. Various other crosslinkers are known, including polyfunctional carbodiimides, anhydrides, and aziridines.
Interfacial polymerization involves the reaction of various monomers at the interface between two immiscible liquid phases to form a polymer film that encapsulates the dispersed phase. The monomers diffuse together and rapidly polymerize at the interface of the two phases. The degree of polymerization can be controlled by monomer reactivity, concentration, composition of either phase, and temperature. Microcapsules produced in this fashion may have shell walls comprised of polyamides, polyureas, polyurethanes, and polyesters, for example, as disclosed in U.S. Pat. No. 3,516,941 issued Jun. 23, 1970 to Matson; U.S. Pat. No. 3,860,565 issued Jan. 14, 1975 to Barber, Jr., U.S. Pat. No. 4,056,610 issued Nov. 1, 1977 to Barber Jr. et al., and U.S. Pat. No. 4,756,906 issued Jul. 12, 1988 to Sweeny. Post-crosslinking of the shell wall of these microcapsules with polyfunctional aziridines reduces porosity and improves structural integrity.
U.S. Pat. No. 3,516,941, issued Jun. 23, 1970 to Matson, teaches a process for the fabrication of microcapsules on the order of 5-25 microns. The process consists of the following steps. An aqueous insoluble fill material is dispersed into the precondensate prepared via dissoultion of a water soluble, low MW urea-aldehyde precondensate comprising predominantly low MW reaction products of urea and formaldehyde (e.g., dimethylol urea) with a solids content of approximately 3-30 wt % of the aqueous precondensate. The resultant dispersion is maintained at a temperature of 10 C-50 C while the pH is adjusted to 1.0-3.5 by acid addition to initiate polymerization of the precondensate. The solution is rapidly agitated at 20 C-90 C for a time interval of at least one hour whereupon an aqueous slurry of water insoluble microcapsules with a urea-formaldehyde shell is formed.
U.S. Pat. No. 5,401,505, issued Mar. 28, 1995 to Duell et al., teaches the fabrication of microcapsules from polyfunctional aziridines. In this case, the shell wall is prepared via interfacial polymerization of a polyfunctional aziridine with at least one other polyfunctional coreactant selected from the class consisting of polyacid halides, polycarboxylic acids, polyamines, polyhydroxyl-containing compounds, polythiol-containing compounds, polyisocyanates, polyisothiocyanates, and mixtures thereof. The use of polyfunctional aziridines presents a number of advantages over the prior art. For example, polyfunctional aziridines readily react via interfacial polymerization with a wide variety of other organic polyfunctional groups in both aqueous and water-insoluble media. This breadth of reactivity with other functional groups enables the fabrication of microcapsules with shell walls covering a range of porosities, solubility characteristics, and mechanical and structural properties.
Any of the above-described techniques can be used to encapsulate the selected fire retardant material. The method described in U.S. Pat. No. 5,401,505 affords the greatest latitude in structural properties, and producing microcapsules that can be stored as discrete materials.
While the present invention has been described with reference to the details of the embodiments of the invention shown in the drawing, these details are not intended to limit the scope of the invention as claimed in the appended claims.
