Compositions – Fire retarding – Intumescent
Reexamination Certificate
1999-03-31
2001-03-27
Wallenhorst, Maureen M. (Department: 1743)
Compositions
Fire retarding
Intumescent
C252S602000, C162S159000
Reexamination Certificate
active
06207085
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a composition which, when subjected to heat, expands to form heat-insulating barriers. The composition comprises expandable graphite, a fire retardant, resinous emulsion and optionally an intumescent inorganic filler. In addition, the composition may contain a surfactant as well as a defoamer. The invention further relates to a fire retardant heat-insulating barrier consisting of a flexible substrate onto which is coated the stated composition. Such barriers have particular application as a fire stop seal for door frame assemblies.
BACKGROUND OF THE INVENTION
Fire retardant, fire proofing, and even fire stopping materials and their method of production and use have been disclosed in the prior art. For example, U.S. Pat. No. 5,462,699 discloses a fire retardant composition to be applied to materials such as building materials and corrugated board materials. By using silica or silicate, water, and a surfactant, the composition of this patent may provide a fire retardant coating. This composition, however, does not offer desired intumescent qualities. Such properties are specifically desired for the sealing of door frames as well as in the wrapping of pipes.
Additionally, the production and use of intumescent compounds has been described in the prior art. For example EPO 0 256 967 discloses a process for the production of moldings by extrusion or injection molding of a mixture that contains polyvinyl chloride and a mixture of polyhydric alcohol, a polyamide compound, and a phosphate at temperatures of 140° C. or less. Unfortunately, this patent required the use of a polyvinyl chloride resin.
Additionally, EPO 0 302 987 disclosed the production of a thermoplastic mixture containing expandable graphite, a non-polyvinyl chloride polymer, and two of the following group consisting of phosphates, polyamide compounds, and polyhydric compounds at temperatures of 150° C. or less. This disclosure only teaches the formation of a thermoplastic mixture and requires either a polyamide compound or a polyhydric alcohol.
U.S. Pat. No. 5,094,780 discloses the use of expandable graphite in fire retardant intumescent moldings wherein the graphite containing materials are heated in molds to temperatures between 150° C. and 350° C. More suitable means for producing fire retardant materials and less expensive fire retardant compositions are desired.
SUMMARY OF THE INVENTION
The present invention overcomes the difficulties of the prior art by providing a composition which, when subjected to heat, expands to form a heat-insulating barrier. The composition contains an expandable graphite and a fire retardant, optionally with an inorganic intumescent filler, all of which is admixed with a resinous emulsion. The composition of the invention may be produced at room temperature.
The invention further relates to molding strips for providing fire-retardant barriers to doorways and pipes. Such strips may optionally include a flexible substrate. The substrate may be wax paper, mineral wool, artificial fiber ribbons such as tetrahydrofuran fibers and aromatic amide fibers, polyethylene film, polypropylene film, polyurethane film or a polyester film. Onto the substrate is extruded, at room temperature, the resinous emulsion composition. The resulting fire stopping intumescent strips may be applied to door frames. In addition, the molding strips of the invention may be used to enclose pipes or other points of vulnerability in order to aid in the prevention of penetration of fire and/or smoke by intumescing and sealing off available pathways.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The composition of the invention expands upon an exposure to heat, thereby creating a seal in the spread of fire and/or smoke. The composition consists of a resinous emulsion into which is admixed an expandable graphite and a fire retardant agent. In an alternative embodiment, an inorganic intumescent filler may be used in conjunction with the fire retarding agent.
Examples of emulsions for use in the invention are acrylic emulsions, polyvinyl acetate emulsions, silicone emulsions, and styrene butadiene emulsions. In one embodiment of the invention, a resinous aqueous emulsion of a polyvinyl acetate may be used. In addition to aqueous emulsions, the resinous emulsion for use in the composition of the invention may consist of emulsions of polymers within an organic solvent, such as hydrocarbons, like xylene and toluene. In addition, keto alcohols or similar co-solvents can be used. In a preferred embodiment, diacetone alcohol co-solvent is used in combination with water. In such instances, between about 0.5 to about 10 weight percent, preferably less than one weight percent of the composition prior to extrusion is co-solvent.
The composition of the invention (prior to extrusion) contains about 15 to about 90, preferably between about 25 to 90, most preferably between about 30 to about 60, weight percent of resinous emulsion.
Suitable styrene-butadiene polymers may be characterized as those polymers having from about 99 to about 65, preferably 99 to 80, weight percent of a C
8
-C
12
vinyl or vinylidene aromatic monomer and the remainder being butadiene. The styrenic moiety can be optionally substituted with a C
1
-C
4
alkyl or hydroxy alkyl radical or a chlorine or bromine atom.
Such polymers may further comprise one or more copolymerizable monomers containing a functional group. When present, the functional monomers are present in an amount from about 0.5 to about 6 weight percent. The functional monomers may be selected from the group consisting of (1) one or more C
3
-C
6
ethylenically unsaturated carboxylic acids; (2) one or more amides of C
3
-C
6
ethylenically unsaturated carboxylic acids, which amide may be substituted or unsubstituted at the nitrogen atom by a C
1
-C
4
alkyl or hydroxy alkyl radical; (3) one or more C
3
-C
6
ethylenically unsaturated aldehydes; and (4) one or more C
1
-C
6
alkyl or hydroxy alkyl esters of C
3
-C
6
ethylenically unsaturated carboxylic acids. Suitable C
8
-C
12
vinyl aromatic monomers include styrene, alpha methyl styrene and chlorostyrene. Part of the aromatic monomer may be replaced by small amounts of an alkenyl nitrile such as acrylonitrile. Suitable conjugated diolefins include the aliphatic diolefins such as 1,3-butadiene, isoprene and their chlorinated homologues. Up to about half, preferably less than about 20 percent of the conjugated diolefin may be replaced with an ester of acrylic or methacrylic acid; or a vinyl ester of a saturated carboxylic acid. Suitable esters are those of acrylic or methacrylic acid such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxy ethyl methacrylate and the higher branched esters such as ethyl hexyl acrylate and ethyl hexyl methacrylate. Suitable vinyl esters include vinyl acetate.
The resin within the emulsion of the composition of the invention may further include commercially available acrylic resins such as those derived from acrylic acid, methacrylic acid, itaconic acid, fumaric acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, ethyl hexyl methacrylate, ethyl hexyl acrylate, acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide and/or acrolein.
The acrylate type polymers may further be characterized as polymers consisting of from about 60 to 99.5, preferably from about 85 to about 94.5 weight percent of a C
1
-C
8
alkyl or hydroxy alkyl ester of acrylic and methacrylic acid, from about 10 to 40, preferably from about 5 to 15 weight percent of one or more monomers selected from the group consisting of C
8
-C
12
vinyl or vinylidene aromatic monomers, which may be unsubstituted or substituted by a C
1
-C
4
alkyl radical or a chlorine, or bromine atom, and a C
3
-C
6
alkenyl nitriles and acrylic and methacrylic acid. The acrylate polymers may optionally further contain from about 0.5 to 10, preferably less than 5 weight percent, of a functional monomer other than a C
1-
Cross LaToya I.
Locke Liddell & Sapp LLP
The Rectorseal Corporation
Wallenhorst Maureen M.
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