MULTI-STAGE DRAWING METHOD FOR POROUS FIBER FORMING Russian patent published in 2021 - IPC D04H1/49 

FIELD: chemical fibers.

SUBSTANCE: method for forming porous fibers is provided. The fibers are formed from a thermoplastic composition containing a continuous phase that contains a matrix polymer and a nano-inclusion additive that at least partially incompatible with the matrix polymer, so that it becomes dispersed in the continuous phase as discrete nanoscale phase domains. The method includes passing a bundle of fibers through a multi-stage drawing system that includes at least a first fluid drawing stage and a second fluid drawing stage. At the first drawing stage, the first fluid medium having the first temperature is used, and at the second drawing stage, the second fluid medium having the second temperature is used. Both the first and second temperature are lower than the melting point of the matrix polymer, and the first temperature is higher than the second temperature, with the first temperature ranging from 20°C to 90°C, and the second temperature is from -10°C to 20°C. A higher first temperature can heat the fibers to the optimal temperature for drawing, at which pores can still form, essentially without breaking. A lower second temperature, however, can ensure that the fibers become more rigid, thus reducing the likelihood of deformation.

EFFECT: improved technique for obtaining porous fibers is proposed.

23 cl, 2 tbl, 4 ex, 7 dwg