Preparation Of Super-soft And Highly Moisture-absorbent Modified Pet Fibers And Investigation Of Their Dyeing Properties

Polyethylene terephthalate（PET）fiber is widely used in industrial,home textile and garment fields.It has excellent mechanical properties,stable thermal and chemical properties,and strong wrinkle resistance and shape retention in clothes,but due to the regular arrangement of its internal macromolecular chains and the lack of hydrophilic groups,the softness and moisture absorption of its fabrics are poor,resulting in poor wearing comfort.In addition,PET fibers are often dyed with dispersed dyes at high temperatures and high pressure,which not only requires high dyeing equipment but also consumes a lot of energy and causes serious water pollution,which is not in line with the green concept advocated by the state,so it is of great practical significance to improve the softness and moisture absorption of PET fibers while having room temperature and atmospheric pressure dyeing.In this paper,2 series of polyamide esters,fibers and fabrics were prepared by amide-modified polyester copolymerization and melt spinning,and the spinnability of polyamide esters was studied to characterize the mechanical properties,moisture absorption and softness of the fibers,and their dyeing properties were systematically analyzed to get the best dyeing process.The softness and dyeing of the fabrics were characterized,which in turn provided the reference for the industrial application of modified PET fibers.The main research contents are as follows:1.2 series of modified PET containing different molar fractions（3%,6%,9%and 12%）were prepared by melt copolymerization of glutaric diamine adipate（PA56 salt）and its derivative p-adipic acid glutaric diamide（APA56）with ethylene terephthalate（BHET）.T_m,glass transition temperature（T_g）and crystallinity(X_dsc)of the modified PET decreased with increasing molar fraction of the modified monomers,with more decrease in APA56-modified PET than PA56-salt-modified PET,which facilitated the ambient temperature and pressure dyeing of the fibers.The thermal weight loss apparatus（TGA）test shows that the starting decomposition temperature of modified PET is higher than370℃,which is higher than the spinning temperature and can meet the demand of subsequent spinning processing.The melt index test shows that the thermal fluidity of the modified PET increases with the increase of the molar fraction of the modified monomer,and the characteristic viscosity of the modified PET chips is 0.7～0.77 d L/g,with the molecular weight distribution less than 2.4,which can basically meet the spinning requirements.2.2 series of modified PET fibers with different drafting multiples were prepared by melt spinning,compared with PET fibers,the orientation,crystallinity and fracture strength of modified PET fibers were reduced and decreased with the increase of the molar fraction of modified monomer,while the softness and moisture absorption of the fibers were significantly improved,with the molar fraction of modified monomer ranging from 3%to 12%,PA56 salt and APA56 modified The relative flexural stiffness of PET fiber was reduced by 18%～71%and40%～88%,and the moisture regain rate was increased by 39%～200%and 53%～213%,respectively,and the softness and moisture absorption of APA56 was better than that of PA56 salt modified PET fiber.When the molar fraction of the modified monomer is 6%and above,the fiber breaking strength is above 2.0 c N/dtex and the elongation at break is about 30%,which retains certain mechanical properties.the bending stiffness（B）and bending hysteresis moment（2HB）of the knitted fabric woven by APA56-6 are lower than those of conventional PET knitted fabric,which has excellent softness and deformation regain the ability.3.The dyeing performance of modified PET fibers was investigated by using acid dyes and dispersing dyes.When acid dyes were used to dye modified PET fibers,the dyeing rate and K/S value were significantly improved compared with conventional PET,but they were not higher than 35%and were not suitable for dyeing modified PET fibers.The disperse dyeing experiments showed that the modified PET fibers could be dyed at low temperature under normal pressure,and the optimal dyeing process was obtained by process optimization:PA56-6 dyeing process:dyeing temperature 100℃,pH=5,bath ratio 1:20,holding time40 min;APA56-6 dyeing process:dyeing temperature 90℃,pH=5,bath ratio 1:40,holding time 40 min.The knitted fabrics dyed by the optimal process showed good color fastness up to grade 5 for soaping and grade4-5 for rubbing.