Gel-coated materials with increased flame retardancy

Details Gel-coated materials with increased flame retardancy Gel-coated materials with increased flame retardancy

1999-01-22

2001-03-06

Morris, Terrel (Department: 1771)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Composite having voids in a component

C428S317900, C428S319900, C428S327000, C427S223000, C427S227000, C156S307500, C442S136000

Reexamination Certificate

active

06197415

ABSTRACT:

The invention relates to gel-coated materials suitable for use in applications in which flame retardancy is a highly desired characteristic, and methods for fabricating such materials.
BACKGROUND OF THE INVENTION
Materials desirably made fire resistant include polymeric materials, both natural and synthetic, woven and nonwoven fabrics, fibers, matting and batting. From a chemical structure perspective, low flammability can be achieved by introducing ring structures, and side groups which are not readily oxidized. For example, aromatic polyimides show excellent fire resistance, but are too costly for routine use.
A more common approach is to introduce one or more fire-retardant constituents to an inherently flammable material, such as in the case of a flammable polymer. The additive can be a fire-retardant monomer which is copolymerized to some degree with the inherently flammable monomer. Alternatively, the additive can be an unreactive material which is coated onto the material post-production, or molded or extruded with a polymeric material in a physical blend. The inherently flammable material could also be reactively treated with a fire-retardant additive after polymer production, as in the chlorination of polymers such as polyethylene.
Compounds which have found use as fire-retardants include inorganic compounds such as antimony compounds, including antimony trioxide, antimony pentoxide, and sodium antimonate. Boron compounds such as zinc borate, boric acid and sodium borate. Alumina trihydrate and molybdenum oxides are also useful inorganic compounds.
Halogenated compounds have also been used, including decabromodiphenyl oxide, chlorendic acid, tetrabromophthalic anhydride, and similarly halogenated compounds. These halogenated compounds, especially chlorinated compounds, are often combined with the above-mentioned inorganic compounds, especially antimony-, iron-, cobalt-, nickel-, molybdenum-, and other metal-containing compounds, to produce synergistic fire-retarding effects.
SUMMARY OF THE INVENTION
The invention uses gel coatings on base materials to greatly increase the fire retardance of such materials. The gel coatings can be produced through sol-gel processing of foamed materials. The gel coating provides a degree of physical and flame protection for the materials thus produced. The oxidative resistance of such materials is improved as well. The coating is believed to minimize oxygen contact with the material. This can result in reduced incidence of oxidation from atmospheric oxygen for the materials, or any components contained within the materials, for example, reduced flammability for flammable contents, or reduced chemical oxidation for atmospheric oxidation-sensitive contents. The contents which can be included in the gel-coated materials include phase change materials in various forms.
The invention further provides a method for providing a gel coating on a material by a sol-gel process.
The invention provides flame-retardancy without altering the physical processing of the material, while undesirable alteration is commonly the case when inert halogen-containing additives are added. The gel-coated materials of the invention possess excellent light stability, in contrast to many halogen-based and phosphorus-based flame-retardant materials. The thermal stability of the gel-coated materials of the invention is at least as high as the untreated material; this is often not the case for halogen-based flame-retardant materials, which can produce corrosive hydrogen halides upon exposure to heat. The density of the gel-coated materials of the invention is lower than that of halogen-containing fire-retardant materials. The invention provides a gel-coated material having permanent fire-retardant properties.
The gel-coated materials of the invention are noncombustible, maintain their integrity upon exposure to flame, and seal the material completely from fire. The gel coatings are easily applied, and can easily be modified, with, for example, coloring agents. The gel coatings are repeatedly washable with commonly available solvents, and the fire-retardancy is retained upon such repeated washing.
The gel-coated materials of the invention possess excellent hydrolytic and chemical resistance, whereas phosphorus-containing flame-retardant materials generally do not.
Base materials generally described are adapted to be placed within articles of clothing including footwear and various articles of protective clothing designed for environments of extreme temperature and hazard from fire. According to the invention, a base material such as a foamed polymer, fiber, woven or nonwoven fabric, batting or matting is coated with a gel coating. The gel coating can also provide increased resistance to chemical reactants such as acids, bases and other chemicals that can damage or dissolve foamed materials. Such materials are ideal in protective clothing, for example, fire fighting suits. Gel-coated foamed materials are suitable for flame-resistant cushions used in aircraft, automobiles, furniture and other cushioned articles. Fabrics, matting and batting are other applications for which the invention is suited.
The gel-coated materials of the invention can also contain heat control agents, such as those which store latent heat. Such heat control agents include phase change materials, which can be integral to the base materials or gel coatings of the invention.
For the purposes of this specification, metal oxides, and metal alkoxides also include those materials which are calcinable (or otherwise oxidizible) to metal oxides, and metal alkoxides, as described below. For the purposes of this specification, calcination includes oxidation processes in general.
A flammable base material can be inherently flammable, or can become flammable upon the introduction of flammable materials in the interior or exterior of the base material.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions will control. In addition, the materials, methods and examples are illustrative only and not intended to be limiting.
DETAILED DESCRIPTION
The gel-coated materials of the invention feature base materials coated with a gel, specifically a gel produced by sol-gel processing. The gel coating provides flame-, physical- and chemical-resistances to the coated material, resulting in enhanced performances in critical applications. The materials which are coated with a gel can be fabrics, fibers, matting, batting or polymeric materials.
Useful polymeric materials can be foamed polymeric materials, for example, foam insulation layers of footwear or garments.
The burning of polymeric materials is highly influenced by the density of materials in general. Most unexpanded plastic polymers have densities commonly in the range of at least 0.7 g/cm
3
and at most 1.5 g/cm
3
. On the other hand, foamed polymeric materials have densities of about 0.03 g/cm
3
, so that only a few percent (typically less than 5%) of the total volume of these foams is solid polymer. The presence of so much gas in the structure of a foamed polymer influences the burning characteristics greatly.
The exposure of a large surface area to the oxygen present in air results in an increased rate of burning. On the other hand, since the amount of potentially flammable material per unit volume is relatively small, the heat Available for flame propagation per unit area is relatively low. Also, for thermoplastic foams such as polystyrene foam, rapid melting results from the heat of flames. This causes the foam to recede rapidly from the f

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