Synthesis Of Regenerated Cationic-dyeable PET By Using Glycolysis Products Of Waste PET

The increasing consumption of poly?ethylene terephthalate??PET?products generates a great amount of solid non-biodegradable waste,which could not only pollute the environment but also lay great burden on oil resources,thus,recycling of PET waste has draw more and more attention all over the world recently.Mechanical way has been largely used in recycling post-consumer PET bottles,however,effective method which could deal with low-purity waste PET products,especially for waste fabrics,has not been developed yet.Chemical recycling,undoubtedly,is the most prospective way to solve these problems discussed above and realize a circle use of waste PET.Among all of the chemical methods,glycolysis becomes outstanding for its mild reaction condition,relatively simple process and industrial applicability.In this paper,waste PET fibers was glycolyzed with ethylene glycol and glycolysis products were used in polymerization of regenerated PET/CDP,which could contribute to waste PET recycling in commercial application.In the first part,conversion of PET and yield of bis?hydroxyethyl?terephthalate?BHET?were measured for evaluation the efficiency of glycolysis reaction.Investigation of parameters,such as EG/PET weight ratio,amount of Zn?Ac?₂?catalyst?,reaction time and temperature,on glycolysis reaction were carried out in a round-bottom three-necked flask.The results showed that,with EG/PET weight ratio at 3,0.2%of catalyst,reaction temperature at 196?for 1 h,PET was almost totally depolymerized and 80%of BHET yield was obtained.Regenerated PET were synthesized in a batch polymerization reactor using purified BHET and compound glycolysis products,respectively.The thermal properties,structure information,molecular weight as well as some regular indexes,such as DEG content,end carboxyl content,yellowness index?b value?of regenerated PET were tested and compared with that of virgin PET.DSC and TGA tests showed that thermal properties of regenerated and virgin PET were similar,NMR and intrinsic viscosity tests proved the same structure and molecular weight.Regenerated PET derived from compound glycolysis products has higher DEG content,carboxyl end group as well as yellowness than virgin PET,and those indexes of regenerated PET derived from purified BHET are similar to virgin PET.Based on synthesis of regenerated PET derived from compound glycolysis products,cationic-dyeable PET?CDP?was produced through adding dyeable modifying agent.Tested by HPLC,SIPE-EG solution with high ester exchange rate was prepared previously by controlling of reaction time and temperature.0%?1.5%?3.0%mole ratio of SIPE was added into reactor before polycondensation reaction started to produce CDP.DSC,TGA and intrinsic viscosity tests indicated that with SIPE content increasing,melting point,molecular weight of CDP decreased while the crystallization temperature increased,thermal stability,DEG content,end carboxyl content and yellowness were not affected by SIPE.Rheological property test indentfied regenerated CDP as pseudoplastic fluid,and their viscous activation energy decreased with SIPE content increasing.Dyeable test verified that PET modified with SIPE has excellent dyeability.