Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1999-06-03
2002-06-11
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S032000, C528S014000, C556S430000, C556S478000
Reexamination Certificate
active
06403750
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the invention is to the continuous manufacturer of fiber reinforced high temperature ceramic composites for use in military, commercial and industrial applications.
The synthesis of polycarbosilane from the pyrolytic condensation reaction of polydimethylsilane obtained from the reaction of dichlorodimethylsilane with an alkali metal, such as sodium. In the latter approach, polydimethylsilane can be prepared by Würtz type coupling of dichlorodimethylsilane with sodium in toluene. The direct pyrolysis of polydimethylsilane, a viscous thermoplastic resin, at high temperature gives SiC in a ceramic yield of about 30%-40%. By thermally cross-linking the polydimethylsilane into an infusible rigid thermoset polymer, which is insoluble in any common solvents, the subsequent pyrolysis yield is on the order of 88%-93%. This thermolysis was accomplished by refluxing the polydimethyl-silane to in excess of 350° C.
Numerous embodiments of pre-ceramic polymers with improved yields of the ceramic have been described in U.S. Pat. No. 5,138,080, U.S. Pat. No. 5,091,271, U.S. Pat. No. 5,051,215 and U.S. Pat. No. 5,707,471. The fundamental chemistry contained in these embodiments is specific to the process employed and mainly leaves the pre-ceramic polymer in a thermoplastic state. Embodiments that employ catalytic or photo induced crosslinking do not satisfy the high ceramic yield, purity, and fluidity in combination with low temperature crosslinking ability necessary for producing large densified ceramic structures in a single step continuous process.
U.S. Pat. No. 5,138,080 teaches a novel polysilamethylenosilane polymers which has polysilane-polycarbosilane skeleton which can be prepared in one-step reaction from mixtures of chlorosilaalkanes and organochloro silanes with alkali metals in one of appropriate solvents or in combination of solvents thereof. Such polysilamethyleno silane polymers are soluble and thermoplastic and can be pyrolyzed to obtain improved yields of silicon carbide at atmospheric pressure.
U.S. Pat. No. 5,091,271 teaches a shaped silicon carbide-based ceramic article which has a mechanical strength which is produced at a high efficiency by a process including the step of forming an organic silicone polymer, for example, polycarbosilastyrene copolymer, into a predetermined shape, for example, a filament or film; doping the shaped polymer with a doping material consisting of at least one type of halogen, for example, bromine or iodine, in an amount of 0.01% to 150% based on the weight of the shaped polymer, to render the shaped polymer infusible; and pyrolyzing the infusible shaped polymer into a shaped SiC-based ceramic article at a temperature of 800° C. to 1400° C. in an inert gas atmosphere, optionally the halogen-doped shaped polymer being treated with a basic material, for example, ammonia, before the pyrolyzing step, to make the filament uniformly infusible.
U.S. Pat. No. 5,300,605 teaches poly(I-hydro-I-R-1-silapent-3-ene) homopolymers and copolymers which contain silane segments with reactive silicon-hydride bonds and contain hydrocarbon segments with cis and trans carbon-carbon double bonds.
U.S. Pat. No. 5,171,810 teaches random or block copolymers with (I-hydro-I-I-sila-cis-pent-3-ene), poly(I-hydro-I-R-3,4 benzo-I-sila pent-3-ene) and disubstituted I-silapent-3-ene repeating units of the general formula ##STRI## where R is hydrogen, an alkyl radical containing from one to four carbon atoms or phenyl, R.sup.1 is hydrogen, an alkyl radical containing from one to four carbon atoms, phenyl or a halogen and R.sup.2 is hydrogen, or R.sup.1 and R.sup.2 are combined to form a phenyl ring, are prepared by the anionic ring opening polymerization of silacyclopent-3-enes or 2-silaindans with an organometallic base and cation coordinating ligand catalyst system or a metathesis ring opening catalyst system.
U.S. Pat. No. 5,169,916 Poly(I-hydro-I-R-I-sila-cis-pent-3-ene) and poly(I-hydro-I-R-3,4 benzo-I-sila pent-3-ene) polymers which has repeating units of the general formula polycarbosilane containing at least two tbd.SiH groups per molecule via intimately contacting such fusible polycarbosilane with an effective hardening amount of the vapors of sulfur.
U.S. Pat. No. 5,064,915 teaches insoluble poly-carbosilanes, readily pyrolyzed into silicon carbide ceramic materials such as SiC fibers, are produced by hardening a fusible polycarbosilane containing at least two tbd.SiH groups per molecule via intimately contacting such fusible polycarbosilane with an effective hardening amount of the vapors of sulfur.
U.S. Pat. No. 5,049,529 teaches carbon nitride ceramic materials which are produced by hardening a fusible polycarbosilane containing at least two tbd.SiH groups per molecule by intimately contacting such fusible polycarbosilane with an effective hardening amount of the vapors of sulfur, next, heat treating the infusible polycarbosilane which results under an ammonia atmosphere to such extent as to introduce nitrogen into the infusible polycarbosilane without completely removing the carbon therefrom and then heat treating the nitrogenated polycarbosilane in a vacuum or in an inert atmosphere to such extent as to essentially completely convert it into a ceramic silicon carbon nitride.
U.S. Pat. No. 5,051,215 teaches a rapid method of infusibilizing pre-ceramic polymers which includes treatment of the polymers with gaseous nitrogen dioxide. The infusibilized polymers may be pyrolyzed to temperatures in excess of about 800° C. to yield ceramic materials with low oxygen content and, thus, good thermal stability. The methods are especially useful for the production of ceramic fibers and, more specifically, to the on-line production of ceramic fibers.
U.S. Pat. No. 5,028,571 teaches silicon nitride ceramic materials which are produced by hardening a fusible polycarbosilane containing at least two dbd.SiH groups per molecule by intimately contacting such fusible polycarbo-silane with an effective hardening amount of the vapors of sulfur and then pyrolyzing the infusible polycarbosilane which results under an ammonia atmosphere.
U.S. Pat. No. 4,847,027 teaches a method for the preparation of ceramic materials or articles by the pyrolysis of pre-ceramic polymers wherein the pre-ceramic polymers are rendered infusible prior to pyrolysis by exposure to gaseous nitric oxide. Ceramic materials with low oxygen content, excellent physical properties, and good thermal stability can be obtained by the practice of this process. This method is especially suited for the preparation of ceramic fibers.
U.S. Pat. No. 5,714,025 teaches a method for preparing a ceramic-forming pre-preg tape which includes the steps of dispersing in water a ceramic-forming powder and a fiber, flocculating the dispersion by adding a cationic wet strength resin and an anionic polymer, dewatering the flocculated dispersion to form a sheet, wet pressing and drying the sheet, and coating or impregnating the sheet with an adhesive selected from the group consisting of a polymeric ceramic precursor, and a dispersion of an organic binder and the materials used to form the sheet. The tape can be used to form laminates, which are fired to consolidate the tapes to a ceramic.
U.S. Pat. No. 5,707,471 teaches a method for preparing fiber reinforced ceramic matrix composites which includes the steps of coating refractory fibers, forming the coated fibers into the desired curing the coated fibers to form a pre-preg, heating the pre-preg to form a composite and heating the composite in an oxidizing shape, environment to form an in situ sealant oxide coating on the composite. The refractory fibers have a interfacial coating thereon with a curable pre-ceramic polymer which has a char containing greater than about 50% sealant oxide atoms. The resultant composites have good oxidation resistance at high temperature as well as good strength and toughness.
U.S. Pat. No. 5,512,351 teaches a new pre-preg material which has good tack drape properties and feasible out-time. The pre-pr
Kratsch Kenneth M.
Pope Edward J. A.
Johansen W. Edward
Moore Margaret G.
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