Abstract:

Objective Poly(propylene terephthalate) (PTT) is widely used for its excellent all-round properties, especially in the field of apparel. However, its poor fiber dyeability limits its application in fibers. Currently commonly used disperse dyes have the disadvantages of poor environmental friendliness, incomplete chromatography, high cost, and so on. Compared with disperse dyes, cationic dyes have the advantages of environmental friendliness, complete chromatography, bright color and low cost. Therefore, studying cationic dyeable PTT fibers is of great significance.

Method Cationic dyeable poly(propylene terephthalate)(CDPTT) is prepared by adding sodium malonyl isophthalate-5-sulfonate to the polymerization process of PTT. Using PTT and CDPTT as raw materials, PTT and CDPTT pre-oriented yarn (POY) were prepared by high-speed melt spinning. In order to investigate the comprehensive performance of CDPTT, the influences of spinning temperature, spinning speed, and draw multiplier on the spinnability, orientation, crystallization, mechanical properties, and boiling water shrinkage were studied. Meanwhile, the dyeing properties of CDPTT fibers were investigated using cationic red and cationic blue.

Results The results showed that since the melting point of CDPTT slices was lower than that of PTT slices, the temperature of CDPTT slices was appropriately lowered in all zones of the spinning process screw, and they had good spinnability at 255 ℃. With the increase of spinning speed, the crystallinity and breaking strength of the fiber increased, and the elongation at break decreased. This can be explained by the fact that faster the spinning speed is associated to larger the nozzle stretching ratio, and hence the macromolecular chain can be better stretched under the action of spinning stress. When the spinning speed was 3 500 m/min, the crystallinity of CDPTT fiber was 19.19%, the breaking strength was 2.54 cN/dtex, and the elongation at break was 18.41%. With the increase of drafting ratio, the orientation and crystallinity of CDPTT fiber demonstrated increases, and the boiling water shrinkage became decreases, because the drafting is conducive to the further arrangement of macromolecules in the direction of the fiber axis, and the molecular chain is further oriented and arranged, and the crystallization occurs. When the drafting ratio was 2.3, the orientation of CDPTT fiber was 40.89%, the crystallinity was 21.01%, the breaking strength was 3.45 cN/dtex, the elongation at break was 20.41%, and the boiling water shrinkage was 17.08%. CDPTT fiber had good cationic dyeing performance under conditons low temperature and normal pressure, and the dyeing rate and K/S value of the fiber showed a tendency to increase firstly and then decrease as the temperature was raised, and the change of dyeing rate and K/S value tended to be flat as the dye dosage was raised. The dyeing rate and K/S value of the two cationic dyes reached the maximum value at 100 ℃, which were 98.45% and 99.68%, 32.57 and 34.18, respectively, and the color fastness to soap washing of the CDPTT fibers after dyeing was above level 4, which was in line with the requirements of the color fastness to soap washing for apparel fabrics.

Conclusion CDPTT fibers prepared by high-speed melt spinning had a strength up to 3.45 cN/dtex, an elongation at break up to 20.41%, an orientation of 40.89%, a crystallinity of 21.01% and a boiling water shrinkage of 17.08%. Due to the addition of sodium malonyl isophthalate-5-sulfonate, the regularity of the original structure of the fiber was destroyed, which caused the mechanical properties, crystallinity and orientation of CDPTT fiber decreased compared with those of PTT fiber. Through the study of the dyeing performance of CDPTT and PTT fiber, the addition of dyeing groups significantly improved the dyeing properties of the fiber with cationic dyes, so that the dyeing rate of CDPTT fiber and the K/S value of CDPTT fiber were significantly improved, with the color fastness to soap washing reaching above grade 4. The prepared CDPTT fiber has good comprehensive performance, which broadens its application prospect in the field of fiber and textile.

Key words: poly(propylene terephthalate), cationic dye dyeable, spining, mechanical property, dyeing property, pre-oriented yarn