Polysilan-Polycarbosilane mit reduziertem Chlorgehalt auf Basis von Methylchlorpolysilanen sowie daraus hergestellte Spinnmassen und keramische Formkoerper

(A1) Die Erfindung betrifft ein Verfahren zur Herstellung von unschmelzbaren, in indifferenten Loesemitteln loeslichen Polysilan-Polycarbosilan-Copolymeren, umfassend die Schritte - Bereitstellen des Produkts einer Disproportionierung eines oder eines Gemischs mehrerer Methylchlordisilane der Zusammensetzung Si2MenCl6-n, worin n = 1-4 ist, wobei die Disproportionierung mit einer Lewis-Base als Katalysator erfolgte, wobei dieses Produkt ein chlorhaltiges, Kohlenwasserstoffgruppen enthaltendes Roh-Polysilan/Oligosilan ist, und - thermisches Nachvernetzen des Roh-Polysilans/Oligosilans zu einem Polysilan-Polycarbosilan-Copolymer, dadurch gekennzeichnet, dass der Chlorgehalt des Polysilan-Polycarbosilan-Copolymers dadurch gesenkt wird, dass das Roh-Polysilan/Oligosilan oder das Polysilan-Polycarbosilan-Copolymer mit einem Substitutionsmittel umgesetzt wird, durch welches darin gebundenes Chlor durch einen chlorfreien Substituenten ersetzt wird. Unter Einsatz dieses Verfahrens lassen sich Gruenfasern und sauerstoffarme/-freie Keramikfasern mit einem sehr geringen Chlorgehalt herstellen.

DE 102008064372 A1 UPAB: 20100714 NOVELTY - Preparing infusible polysilane-polycarbosilane copolymer, which is soluble in indifferent solvents, comprises: (a) providing the disproportionation product of/a mixture of several methylchloro disilane (I), where the disproportionation is carried out with Lewis base as catalyst, and the product is chlorine-, and hydrocarbon group-containing raw polysilane/oligosilane; and (b) thermally crosslinking the raw polysilane/oligosilane to the polysilane-polycarbosilane copolymer, where the chlorine content of the polysilane-polycarbosilane copolymer is reduced. DETAILED DESCRIPTION - Preparing infusible polysilane-polycarbosilane copolymer, which is soluble in indifferent solvents, comprises: (a) providing the disproportionation product of/a mixture of several methylchloro disilane of formula (Si2MenCl6-n) (I) (where n is 1-4), where the disproportionation is carried out with Lewis base as catalyst, and the product is chlorine-, and hydrocarbon group-containing raw polysilane/oligosilane; and (b) thermally crosslinking the raw polysilane/oligosilane to the polysilane-polycarbosilane copolymer, where the chlorine content of the polysilane-polycarbosilane copolymer is reduced and the raw polysilane/oligosilane or the polysilane-polycarbosilane copolymer is reacted with a substitution agent by which the chlorine bound to it is replaced with chlorine-free substituents. INDEPENDENT CLAIMS are included for: (1) preparing green fibers comprising the steps (a) and (b) as above per se, (c) dissolving the polysilane-polycarbosilane copolymer in indifferent solvents, and (d) spinning (preferably by dry spinning process) the dissolved polysilane-polycarbosilane copolymer to green fibers; (2) preparing ceramic fibers (having low-oxygen content) with a composition close to silicon carbide comprising preparing the green fibers as above per se and pyrolysing the dried green fibers under inert gas atmosphere or reducing atmosphere; (3) the ceramic fibers, having low-oxygen content, a composition close to silicon carbide, fiber diameter of 5-50 mu m, tensile strength of above 500 MPa and elasticity module of above 120 GPa, prepared by the method as above per se; and (4) a method for constructing ceramic matrices comprising the steps (a)-(c) and using the dissolved polysilane-polycarbosilane copolymer for constructing the ceramic matrix by liquid phase infiltration. USE - The infusible polysilane-polycarbosilane copolymer is useful for preparing green fibers that are useful for preparing ceramic fibers having low-oxygen content. The ceramic fibers are useful as reinforcing elements in ceramic matrix composites (all claimed). The polysilane-polycarbosilane copolymer is useful for preparing spinning masses and ceramic molded body. ADVANTAGE - The method is inexpensive and allows for high degree of crosslinking of the starting materials. The reduced chlorine content avoids the susceptibility to corrosion.