Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2001-09-27
2002-10-29
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S408000, C428S391000, C428S396000, C428S447000, C428S688000, C156S307100, C156S307300, C156S311000, C156S312000
Reexamination Certificate
active
06472067
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to non-flammable, polymeric siloxane resins comprising atoms of silicon, hydrogen, carbon and oxygen, and more particularly, to siloxane resins useful with reinforcing fibers to make cured non-flammable fire-resistant panels having a density ranging from about 1 to 3 g/cc. and a limited oxygen index (LOI) above 30. The preferred siloxane polymer resins are characterized as having lower alkyl groups e.g. 1 to 12 carbons attached to the silicon atoms. These viscous polymeric siloxane resins function as an adhesive for the non-flammable reinforcing fibers, such as glass fiber (fiberglass), alumina fiber, silica fiber, carbon fibers and the like to form strong non-flammable composites at relative low temperatures and pressures. The cured siloxane-fiber composites can be formed into various materials e.g. panels which are non-flammable and therefore particularly useful as a fire barrier in manufacturing building materials and the like.
The need for lightweight, high strength, cost competitive parts by the aircraft, automotive, building and other industries has led to a demand for improved strength to weight ratio materials such as matrix composites. Polymeric matrix composites are known to have weight savings of at least 20% over their metal counterparts as well as having much lower operational and maintenance costs. Composites of fibers continue to find applications in futuristic and exotic demanding systems. Composites made with polymeric resins and reinforced with various fibers e.g. fiberglass, carbon or organic fibers possess high-specific strength modulus and low coefficient of thermal expansion, thus making these composites very attractive for space, transportation, construction and household applications. In the field of polymers, it is known to use glass and carbon fibers to reinforce resin materials; see U.S. Pat. Nos. 4,856,146 and 4,857,385. Currently, polymeric resins used in preparing fibrous composites are primarily epoxy, phenolic, bismaleimide, polyester or polyimide resins. However, these polymeric resins have low limited-oxygen indices (LOI) and therefore are highly flammable in air. The development of non-flammable polymeric siloxane resins with a high limited-oxygen index (LOI), as taught by this invention, solves the flammability problem
Previously, silicon-based polymeric materials were developed for instantly repairing damaged Space Shuttle tiles (U.S. Pat. No. 5,985,433). This particular silicon-based polymeric material, after curing, does not easily burn when exposed to flame. The novel silicon-based polymeric resins of this invention, however, provides non-flammable fibrous composites having densities ranging from about 1 to 3 g/cc. and a high limited-oxygen index which means these composites are particularly useful for building materials e.g. panels and for designing future transportation vehicles, such as aircraft, boats, automobiles and the like. As an added terrestrial benefit, these non-flammable siloxane composites could dramatically reduce fatalities during a fire from smoke and flames, if building interiors were protected by panels of this non-flammable composite. If these non-burning light-weight composites were installed in the interiors of buildings, they would be a life saving devise.
2. Description of the Prior Art
In general, polymeric matrix composites are fiber-reinforced thermosetting or thermoplastic resin composites. However, all of the organic thermosetting resins, and most of the thermoplastic resins are flammable organic polymers; see Advanced Composites, edited by I. K. Partridge, Elsevier Applied Science, NY1989. It has been reported that both PEEK and PPS are fire-resistant thermoplastics composites. (Briggs, P. J. Leach, D. C., & Carlile, D. R., Mechanical and fire properties of aromatic polymer composites, and Proc. 3
rd
European Symposium on Spacecraft Materials in Space Environment, Noordwik Netherlands, Oct. 1-4, 1985; ESA-SP-232, November 1985) (Shue, R. S., Fire safety testing of PPS thermoplastic composites). Unfortunately, all of these materials require high processing at temperatures greater than 300° C.
SUMMARY OF THE INVENTION
This invention relates to ambient or low-temperature processing, of non-flammable and low-cost fibrous siloxane polymeric composites. The composites comprise at least one fiber reinforced silicon-based polymeric matrix. The reinforcing fibers include, for example, fiberglass, carbon fibers, aluminalsilicalboria fibers and the like. The silicon-based polymers comprise silicon, carbon, hydrogen and oxygen and are derived from the polymerization reaction of organodialkoxy silanes, organotrialkoxy silanes and tetraalkoxy silanes. More particularly, this invention relates to non-flammable fire-resistant composites derived from silicon-based polymeric resins reinforced with known fibers such as fiberglass or carbon fiber and the like. The silicon-based polymers comprise resins derived from the reaction of at least one dialkoxy and one or more trialkoxy/tetraalkoxy sitanes with water (such as di- and tri-/tetra-functional silanes) to form viscous siloxane resins.
The preferred di- and tri-tetra-functional silicon alkoxides have di- and tri-/tetra-oxygen functionality wherein the silicon alkoxide has two and three/four Si—O bonds, respectively. The silanes particularly useful in the practice of this invention include a combination of silanes with tri-/tetra- and di- oxygen functionality of the general formula RSi(R
I
O)
3
/Si(R
I
O)
4
and RR
III
—Si—(OR
II
)
2
wherein R
I
and R
II
are the same or different and represent alkyl hydrocarbon groups e.g. radicals of 1-12 carbons wherein R and R
III
are different or the same hydrocarbon groups as R
I
and R
II
. The groups R and R
III
can be the same or different hydrocarbon groups of 1 to 12 carbons and include the alkyl, aryl, alkaryl, and aralkyl groups. One of the R and R
III
can be hydrogen. The hydrocarbon groups i.e. (—CH) contain carbon and hydrogen and include the straight or branched chains, and saturated or unsaturated groups of 1 to 12 carbons. In general, the number of carbon atoms in the hydrocarbon groups range from 1-12, and preferably from 1-8 and more preferably from 1-2.
A process of preparing non-flammable high-tensile strength, cured fibrous-siloxane composites having a density ranging from about 1 to 3 g/cc. and a limited oxygen index above 30 which comprises:
(a) polymerizing in an aqueous medium about 50 to 95 parts by weight of at least one trialkoxysilane, about 5.0 to 50 parts by weight of at least one dialkoxysilane, and 0 to 10 parts by weight of at least one tetraalkoxysilane to obtain liquid polyalkylsiloxane resins,
(b) impregnating fibrous materials with an effective amount of said siloxane resins to obtain fibrous-siloxane prepregs,
(c) drying said fibrous-siloxane prepregs, and
(d) subsequently subjecting at least two plies of said fibrous-siloxane prepregs to pressures ranging from about 25 psi to 700 psi at temperatures ranging from about 50° to 300° C. to obtain said non-flammable cured fibrous-siloxane composites.
It is therefore an object of this invention to provide a process of preparing non-flammable, fibrous siloxane composites having densities ranging from 1 to 3 g/cc., high-temperature characteristics, light-weight, high-tensile strength and capable of being formed into various shapes.
It is another object of this invention to provide cured fibrous composites having densities ranging from about 1 to 3 g/cc. and limited oxygen index above 30. These siloxane resins are derived from the polymerization reaction of different alkoxy silanes including a combination of one or more dialkoxy silanes and tri-/tetra-alkoxy silanes, which are useful in preparing fire-resistance panels, having high-temperature characteristics, lightweight and high-tensile strength.
These and other objects of the invention will become apparent from a further and more detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
This invention rela
Chen Timothy S.
Hsu Ming-Ta S.
Dixon Merrick
HC Chem Research and Service Corp.
Tura James V.
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