Catalytic Synthesis And Application Of Citrate Esters

Polyvinyl chloride(PVC)polymeric materials are widely used in the field of industry andagriculture and human life. As the largest amount[]of plastic additives, the demand forplasticizers[]continues to increase. As phthalate esters raise enormous[]concerns aboutecosystems[]and human health. Citrate ester has been[]favored in[]plastics industry[]withexcellent performance[]and environmental characteristics. Because of the small molecularweight, the majority varieties of citrates such as TBC and ATBC have small[]migrationresistance, large[]volatile, and are easy to be[]extracted by solvent when added to the polymerproducts, which result in reducing durability of product.The purpose of this study is the concept of green chemistry, in order to improve thedisadvantages of citrate, by optimizing the esterification process, a series of excellent citratesplasticizers were synthesized, and applied[]in PVC resin.A heterogeneous catalyst(pTSA/C) using in this study is made of P-toluenesulfonic[]acidsupported on activated[]carbon. The tri(2-propyl heptyl) citrate[]plasticizer(TPHC) andTribenzyl citrate[]plasticizer(TBnC) were synthesized by[]2-propylheptanol(2-PH), benzylalcohol(BnOH), and citric acid[]via esterification reaction[]respectively, with cyclohexane aswater-carrying agent. The optimized reaction conditions for the synthesis of the twoplasticizers were obtained after the investigation for the amount of water-carrying agent, theamount of catalyst, reaction[]temperature, the reaction time, the[]stuff ration. The mainproperties of citrate plasticizer were determined by the[]acid value, the density, the viscosity,the chroma and[]the heating loss, after the products was purified and used by IR, NMR, andMS to[]characterize their structure.The results show that the[]optimized synthesis conditions of TPHC[]plasticizers are asfollows:55%pTSA/C as[]catalyst,m(catalyst)=2%m (Citric acid), m(cyclohexane)=8%-10%m(Citric acid and2-PH), n(2-PH):n(Citric acid)=3.7:1.0, reaction[]time6h in less[]than140℃.The optimized synthesis conditions of TBnC plasticizers[]are as follows:55%pTSA/C ascatalyst,[]m(catalyst)=3%m[(Citric acid), m(cyclohexane)=8%-10%m(Citric acid and BnOH),n(BnOH):n(Citric acid)=3.9:1.0, reaction[]time8h in less than150℃.The[]study developed themathematical model that[]described the kinetics of esterification.Kinetic[]and thermodynamicsparameters were[]estimated by fitting[]experimental data using[]the linear fit method.The way of synthesizing[]a series of mixed esters[]2-PH butyl citrate[]plasticizers andBenzyl butyl[]citrate plasticizers[]are as follows: take the different[]amounts of citric acid[]and2-PH or BnOH via esterification reaction[]after a period of time,[]then added different[]amountsof butanol into the System[]respectively.[]Determined the acid number, density, chroma of theproducts after purified. The application performance[]of citrate plasticizers including the[]compatibility with PVC,mechanical properties, heating[]loss, migration loss, extraction[]loss and thermal stability weretested. The results shows that[]with the increase content[]of long chain ester[]in the mixed esters,the compatibility[]with PVC of2-PH butyl[]mixed citrate is reduced slightly and the heatingloss,[]migration loss[]and extraction loss decreased,[]the thermal stability[]was increasedobviously; compared with TBC,[]heating loss of PVC resin24h in[]120℃decreased from25%to6%, migration loss of PVC resin[]48h in120℃decreased from30%to17%and50%weight loss temperature of modified PVC was increased from280℃to307℃.The compatibility with PVC, heating loss, migration loss[]extraction loss and thermalstability of Benzyl butyl[]mixed citrate were increased[]correspondingly as the increase contentof Benzyl esters. Compared with[]TBC, the significant changes[]are extraction loss, whichdecreased[]from29.8%,25.1%,24.5%to2.5%,0.2%,1.4%, when immersed in[]ethanol,cyclohexane,[]petroleum ether24h respectively.