The present invention addresses the problem of suitably suppressing fluffing during a spinning process. This method for producing a treatment agent for synthetic fibers, wherein the boron content in the nonvolatile content of the treatment agent for synthetic fibers as detected by ICP emission spectrometry is 200 ppm or less, comprises: an addition step wherein a (poly)oxyalkylene derivative is produced by adding an alkylene oxide to an alcohol in the presence of a catalyst that has a boron atom in each molecule; and a removal step wherein the catalyst is removed so that the boron content in the nonvolatile content of the treatment agent for synthetic fibers as detected by ICP emission spectrometry becomes 200 ppm or less.

A lightweight heat-preserving fiber and a preparation method thereof are provided, wherein the fiber is prepared by measuring, composite spinneret's extruding, cooling, oiling, drawing, heat setting and winding a polyester melt. The composite spinneret has a hollow spinning hole and a circular spinning hole. The ratio of the micropore length of hollow spinning hole to circular spinning hole equals to the ratio of the equivalent diameter of hollow spinning hole to circular spinning hole multiplies the coefficient K, and the equivalent diameter is the ratio of the cross-sectional area to the circumference of the cross-section, the coefficient K ranges from 0.97 to 1.03. The oil agent contains a crown ether, and the content of the crown ether ranges from 67.30 to 85.58 wt %. The thermal conductivity of a knitted fabric having a basis weight of 100 g/m.sup.2 prepared by lightweight heat-preserving fiber is no larger than 0.150 W/m.Math.K.

A lightweight heat-preserving fiber and a preparation method thereof are provided, wherein the fiber is prepared by measuring, composite spinneret's extruding, cooling, oiling, drawing, heat setting and winding a polyester melt. The composite spinneret has a hollow spinning hole and a circular spinning hole. The ratio of the micropore length of hollow spinning hole to circular spinning hole equals to the ratio of the equivalent diameter of hollow spinning hole to circular spinning hole multiplies the coefficient K, and the equivalent diameter is the ratio of the cross-sectional area to the circumference of the cross-section, the coefficient K ranges from 0.97 to 1.03. The oil agent contains a crown ether, and the content of the crown ether ranges from 67.30 to 85.58 wt %. The thermal conductivity of a knitted fabric having a basis weight of 100 g/m.sup.2 prepared by lightweight heat-preserving fiber is no larger than 0.150 W/m.Math.K.

A high-strength polyamide 610 multifilament has a sulfuric acid relative viscosity of 3.0 to 3.7 and a drying strength of more than 9.2 cN/dtex and within 11.0 cN/dtex, having a total fineness of 100 to 2,500 dtex and a single fiber fineness of 1.5 to 40 detex and a birefringence Δn of 50.0 x 10.sup.-3 or more.

A thermal-moisture comfortable polyester FDY for summer use and a preparation method thereof are provided. The FDY is made of matting agents dispersed polyester via the steps of spinning melt metering, extruding via the compositional spinneret, cooling, oiling, drawing, heat setting and winding. The woven fabrics manufactured with the FDY possess a wicking height and an evaporation rate of larger than or equal to 135 mm and 0.22 g/h, respectively. The compositional spinneret is simultaneously provided with cruciform orifices and circular orifices, and the length ratio of cruciform orifice to circular orifice is equal to the product of their equivalent diameter ratio and a coefficient K, here equivalent diameter is the ratio of orifice cross-section area to its circumference and K ranges from 0.97 to 1.03, and the oiling involves the oiling agent containing 67.30-85.58 wt % of crown ether.

A thermal-moisture comfortable polyester FDY for summer use and a preparation method thereof are provided. The FDY is made of matting agents dispersed polyester via the steps of spinning melt metering, extruding via the compositional spinneret, cooling, oiling, drawing, heat setting and winding. The woven fabrics manufactured with the FDY possess a wicking height and an evaporation rate of larger than or equal to 135 mm and 0.22 g/h, respectively. The compositional spinneret is simultaneously provided with cruciform orifices and circular orifices, and the length ratio of cruciform orifice to circular orifice is equal to the product of their equivalent diameter ratio and a coefficient K, here equivalent diameter is the ratio of orifice cross-section area to its circumference and K ranges from 0.97 to 1.03, and the oiling involves the oiling agent containing 67.30-85.58 wt % of crown ether.

An ultrafine fiber printing system contains a moving deck having a nozzle seat that disposed on the moving deck. A pipe is installed in the nozzle seat and a nozzle is disposed at the bottom end of the pipe. The upper portion and the lower portion of the pipe are combined with a heat dissipating unit and heater respectively. The top end of the pipe is connected to a feed tube having an outer end being connected with a thread squeezer. A printing platform is disposed around the moving deck. The nozzle is connected to a static electricity supply and the fiber carrier is grounded. An electric field is formed between the nozzle and the fiber carrier. The droplets exported from the nozzle are stretched into ultrafine fibers to form a patterned fabric or product.

A type of polyester yarn for an industrial sewing thread and preparing method thereof are provided. The preparing method is composed of a viscosity enhancing by a solid state polycondensation and a melt spinning for a modified polyester, and the modified polyester is a product of esterification and polycondensation of evenly mixed terephthalic acid, ethylene glycol, tert-butyl branched dicarboxylic acid, trimethylsilyl branched diol and a doped Sb.sub.2O.sub.3 powder, wherein the tert-butyl branched dicarboxylic acid is selected from the group consisting of 5-tert-butyl-1,3-benzoic acid, 2-tert-butyl-1,6-hexanedioic acid, 3-tert-butyl-1,6-hexanedioic acid and 2,5-di-tert-butyl-1,6-hexanedioic acid. Moreover, the modified polyester is dispersed with a doped ZrO.sub.2 powder. An obtained fiber has an intrinsic viscosity drop of 23-28% when stored at 25° C. and R.H. 65% for 60 months.

A type of polyester yarn for an industrial sewing thread and preparing method thereof are provided. The preparing method is composed of a viscosity enhancing by a solid state polycondensation and a melt spinning for a modified polyester, and the modified polyester is a product of esterification and polycondensation of evenly mixed terephthalic acid, ethylene glycol, tert-butyl branched dicarboxylic acid, trimethylsilyl branched diol and a doped Sb.sub.2O.sub.3 powder, wherein the tert-butyl branched dicarboxylic acid is selected from the group consisting of 5-tert-butyl-1,3-benzoic acid, 2-tert-butyl-1,6-hexanedioic acid, 3-tert-butyl-1,6-hexanedioic acid and 2,5-di-tert-butyl-1,6-hexanedioic acid. Moreover, the modified polyester is dispersed with a doped ZrO.sub.2 powder. An obtained fiber has an intrinsic viscosity drop of 23-28% when stored at 25° C. and R.H. 65% for 60 months.

A process for forming a splittable fiber having the steps of providing a multicomponent fiber; or a multicomponent staple fiber, providing a finish material, and at least partially coating the multicomponent fiber with the finish material to form a splittable fiber. The multicomponent fiber; or a multicomponent staple fiber, contains a first thermoplastic segment comprising polymer component A and a second thermoplastic segment comprising polymer component B. The finish material has an evaporation point of less than about 160° C. A process for forming a nonwoven fabric, a split multicomponent fiber, a split multicomponent fiber with a durable charge, a nonwoven fabric, and a filter and/or a spun yarn formed by the fibers herein is also described.