| 摘要 |
Flame-retardant, high temperature-resistant polyimide fibres of the general formula <IMAGE> in which n is an integer greater than 1, A is a tetravalent aromatic group and R represents at least one divalent aromatic group, which polyimide fibres are heat-treated in the unstretched state and on heating to a temperature of 400 DEG C have a shrinkage of at most 14%. The polyimide fibres according to the invention are prepared by first spinning raw fibres from a solution of the corresponding polyimide in an aprotic organic solvent by the dry-spinning method, which solution optionally contains additives, washing the resulting raw fibres with water to remove solvents, drying the washed raw fibres, subjecting them to a heat treatment at a temperature between 315 DEG C and 450 DEG C, cooling and optionally crimping and cutting to give staple fibres, it being essential that the heated raw fibres are heat-treated and cooled in the unstretched state. |
