Aramid fibrils

Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Staple length fiber

Reexamination Certificate

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C428S357000, C428S395000, C264S140000, C264S142000, C264S183000, C162S157100, C162S157300

Reexamination Certificate

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07629047

ABSTRACT:
Aramid fibrils having in the wet phase a Canadian Standard Freeness (CSF) value less than 100 ml, after drying a specific surface area (SSA) less than 7 m2/g, and a weight weighted length for particles having a length >250 μm (WL 0.25) less than 1.2 mm, are described. A method of preparing the fibrils includes the steps (a) polymerizing an aromatic diamine and an aromatic dicarboxylic acid halide to an aramid polymer, in a mixture of N-methylpyrrolidone or dimethylacetamide and calcium chloride or lithium chloride to obtain a dope wherein the polymer is dissolved in the mixture and the polymer concentration is 2 to 6 wt. %, (b) converting the dope to fibrils by using a jet spin nozzle under a gas stream, and (c) coagulating the fibrils using a coagulation jet.

REFERENCES:
patent: 4963298 (1990-10-01), Allen et al.
patent: 5028372 (1991-07-01), Brierre et al.
patent: 5202184 (1993-04-01), Brierre et al.
patent: 5296286 (1994-03-01), Allen et al.
patent: 5442003 (1995-08-01), Takahashi et al.
patent: 6942757 (2005-09-01), Iwama et al.
patent: 0 348 996 (1990-01-01), None
patent: 0 381 206 (1990-08-01), None

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