Patent ID: 8648166

Claim:
A process for producing antimony-free polyethylene terephthalate fiber, excellent in no yellowish look, comprising the steps of: (a) producing an inorganic Ti—Mg polycondensation catalyst synthesized by chemical precipitation and satisfied requirements of containing titanium element ranging from 1 to 20 wt %, being made in form of titanium dioxide (TiO 2 ) covered on magnesium hydroxide (Mg(OH) 2 ) to obtain a molar ratio of titanium to magnesium ranging from 0.005 to 1 and having an particle size between 0.1 to 1.0 μm; wherein the organic Ti—Mg catalyst is produced by the steps of: (a1) allowing an aqueous MgCl 2 solution and an aqueous NaOH solution to react at 170° C. for about 30 minutes, and afterward, filtering and washing the reactant to obtain Mg(OH) 2 aqueous slurry; and (a2) mixing an aqueous TiCl 4 solution and an aqueous NaOH solution, adding the mixed solution into the Mg(OH) 2 aqueous slurry drop by drop, ripening the resultant slurry for one hour to make TiO 2 cover Mg(OH) 2 particles, filtering the slurry, and washing, dehydrating as well as comminuting the filtered solid, thereby obtaining the inorganic Ti—Mg catalyst in the form of particles; (b) producing an antimony-free polyethylene terephthalate (PET) in the absence of an antimony catalyst and a phosphorus stabilizer, comprising the steps of: (i) undergoing a first-stage direct esterification reaction in a reactor to obtain a reaction mixture by reacting purified terephthalic acid with ethylene glycol; (ii) after step (i) being completed, based on the total reaction mixture weight, adding the following additives into the reactor at same time: (1) the inorganic Ti—Mg catalyst made of step (a) in an amount of ranging from 30 to 150 ppm, wherein the inorganic Ti—Mg catalyst containing titanium element 2 to 10 ppm; (2) a blue dye in an amount of ranging from 1 to 5 ppm; (3) a red dye in an amount of ranging from 1 to 3 ppm and (4) titanium dioxide (TiO 2 ) in an amount of ranging from 0 to 4 wt %; and (iii) undergoing a second-stage polycondensation to obtain a polyethylene terephthalate (PET) resin, containing polyethylene terephthalate (PET), blue dye, red dye and titanium dioxide (TiO 2 ) with intrinsic viscosity ranging from 0.5 to 0.7 dl/g; and (c) by a melt spinning process to obtain a glossiness of PET polyester fiber excellent in no yellowish color produced from the polyethylene terephthalate (PET) resin of step (b).