Study On The Cationic Dyeable Polyester Added With SIPA

In this paper, the accumulates which were found in the pipeline during the industrialproduction process of CDP(cationic dyeable polyester) were analyzed. The ingredient, reasons andpreliminary solutions of accumulates were explored. The third monomer SIPE (sodium3,5-dicarbohydroxyethyl benzene sulfonate) or SIPA (5-sulfoisophthalic acid sodium salt) wasadded in the synthesis of CDP. Moreover, thermal performance, kinetics of the esterification andthermal degradation, intrinsic viscosity decrease were studied and compared.The composition of accumulates was analyzed by infrared spectroscopy and X-ray energyspectroscopy. Results showed that the accumulates contain polar groups sodium and a large numberof Sb compounds.CDP was synthesized with a new modifier SIPA. The effects of the quantity of SIPA on theesterification kinetics were studied. The results showed that with the content increase of SIPA, theesterification reaction time was shortened and the reaction activation energy decreased, theoptimum esterification conditions were [SIPA(1.5%)+PTA(98.5%)]:EG=1:1.5。The intrinsic viscosity of CDP were all lower than PET. With the increase of SIPE and SIPAcontent, the intrinsic viscosity of the copolyester was gradually decreased. The Tg of thecopolyester added with SIPE had no obvious change, but Tcc was on the rise, Tm was in decline.After adding SIPA, the copolyesters’ Tg was decreased, there was no cold crystallization peak. Themelting peak was not obvious gradually in heating DSC curves.The thermal weight loss activation energy of pure PET was significantly higher than that of thecopolyester. The thermal weight loss activation energy of the copolyesters added with SIPE wereobviously higher than that of copolyesters added with SIPA. With the increase of the content ofSIPE, the thermal weght loss activation energy had no obvious change. However, with increase ofthe content of SIPE, the thermal weght loss activation energy was decreasing.At last, the intrinsic viscosity reduction of the two kinds of copolyesters was studied. It has shown that with the increase of the content of SIPE or SIPA, the intrinsic viscosity decrease rateconstant was on the rise. It was found that with the extension of heat-treatment time the intrinsicviscosity decrease obviously. Moreover, the intrinsic viscosity decrease was more severely in the airthan that in the vacuum. For the same content of the two different modifiers of SIPE and SIPA, theintrinsic viscosity decrease rate constant was quite similar.