Synthesis And Application Performances Of Novel Titanium Catalysts For PET Polycondensation

Polyesters refers to the polymers obtained by the polycondensation of polybasic acids and polyols,of which the largest productive kind is poly ethylene terephthalate(PET).The polycondensation of PET requires catalysts,and more than 80%of the catalyst market share in the industry is occupied by antimony catalyst currently.Nowadays,with the awareness of environmental protection winning support among people,traditional antimony-based catalysts have been unable to meet the needs of ecological health due to intrinsic defects of heavy metal.Therefore,the development of new environmentally friendly catalysts for polyester is imperative and the key to make polyester industry ecological and environmental friendly.However,as a country owning 70%of world's polyester capacity,China has been lagging behind developed countries like Germany and Japan in the development of new catalysts used for polyester.In particular,non-antimony catalysts rely heavily on imports,which greatly limits the development of China's polyester industry.Therefore,the design and synthesis of new heavy-metal-free catalysts for polyester with proprietary intellectual property rights is of great significance to the sustainable development of China's polyester industry.Based on this requirement,we first explored a new,simple and easy synthesis route of titanium glycolate(Ti(EG)2)which possess excellent catalytic activity and hydrolysis resistance.Then we systematically investigated the influences of polyester synthesis process,including esterification reaction conditions,adding method,adding stage and content of Ti(EG)2,and stabilizers and delusterant Ti02,on the catalytic activity of Ti(EG)2.Moreover,relevant impact mechanisms were proposed and confirmed in this work.Based on the research findings of Ti(EG)2,a series of new titanium catalysts with good catalytic activity,selectivity and universality were designed and synthesized through the introduction of ether chain into the chelate ring of Ti(EG)2.The influence of the ether chain on the solubility,catalytic activity and selectivity of the catalyst,and the properties of polyester product was systematically studied to obtain the internal relation between molecular structure and catalytic performance of the catalyst,thereby provides the theoretical basis for the design and practical application of new catalysts uesd for polyester.The main contents and conclusions obtained are as follows:1.The synthesis route of Ti(EG)2 based on tetrabutyl titanate was optimized.The optimized synthesis method possesses the advantage of low reaction temperature(40?),short reaction time(4h)and no catalyst,which greatly reduces energy consumption and simplifies the purification process.With the increase of the temperature,the solubility of Ti(EG)2 in glycol significantly enhanced,and the decrease of the temperature does not cause the separation of dissolved Ti(EG)2 from the solution.This characteristic is extremely beneficial to the application of catalyst,because this implies that fluctuations of the temperature will not affect the stability of sizing agents.2.We explored the influences of the adding method,adding stage and content of Ti(EG)2,and the esterification reaction conditions,stabilizers and delusterant Ti02 on polycondensation time and the performance of PET.We have proposed and confirmed relevant impact mechanisms,which indicates the direction for the design and modification of subsequent catalysts.It is beneficial for improvement of the performance of the catalyst to introduce intramolecular coordination bonds into catalyst molecules,increase the solubility and reduce the precipitation of the catalyst on the surface of Ti02.3.To introduce intramolecular coordinate bond and increase solubility of the catalyst,Ti(EG)3Na2 was synthesized,and its solubility in EG and catalytic activity were investigated.The results show that the catalytic activity of Ti(EG)3Na2 for PET polycondensation is reduced,but the catalytic activity of Ti(EG)3Na2 for thermal degradation is not significantly inhibited.Therefore,Ti(EG)3Na2 is not suitable for bright PET,but its excellent solubility makes it applicable for semi-dull PET.4.TiEG2E1 and TiEG2E2 were designed and synthesized through introducing ether chains into the chelating ring.The solubility and catalytic activity of the two catalysts were explored.The results show that the introduction of ether chain greatly improves catalyst solubility,which is far better than Ti(EG)2.The steric hindrance and intramolecular coordination of ether chain are key factors in regulating catalytic activity and selectivity.In the presence of the stabilizer trimethyl phosphate,TiEG2E1 and TiEG2E2 exhibit excellent catalytic performance for the polycondensation of bright PET,The b value of PET product is reduced to about 2.0.For semi-dull PET preparation catalyzed by TiEG2E2,the polycondensation time is only prolonged by 31 minutes compared with bright PET,and the b value of PET product is up to 3.1,which demonstrates that delusterant Ti02 has minor influence on PET polycondensation.TiEG2E1 and TiEG2E2 exhibit excellent performance for polyester polycondensation and have broad application prospects in polyester production industry.