Research On Crystallization Processes Of Tris-(2,4-ditertbutylphenyl)-phosphite

Tris-(2,4-ditertbutylphenyl)-phosphite(TDP)is one kind of auxiliary antioxidant and used in the anti-aging process of polymer materials.At present,the TDP products sold in the market have small and uneven crystal size,irregular crystal habit and uneven properties.In this paper,the crystallization process of TDP is studied systematically and the specific works and results are shown as follows:Firstly,the thermodynamic properties of TDP are studied.In this paper,the solubility data of TDP in acetone,ethyl acetate,methyl acetate,the sethyl formate,isopropyl acetate,butyl acetate,cyclohexane,n-hexane,n-heptane,octane and isooctane are measured.The Modified Apelblat equation,λh equation and NRTL equation are involved to correlate the solubility data.In addition,the thermodynamic functions of dissolving process of TDP,such as dissolving enthalpy and dissolving entropy,are estimated by using Modified van ’t Hoff equation.Results show that the TDP solubility has a large change with temperature increasing,and it is more apparent in solvents with stronger polarity,which is appropriate for cooling crystallization process.Then,the dynamic data of TDP crystallization process is studied.By conducting the TDP continuous crystallization experiments under different conditions,crystal nucleation and growth rate of TDP can be obtained based on MSMPR model.Furthermore,the crystal nucleation and growth rate equations can be obtained by using nonlinear least squares fitting to the empirical models.The results show to get bigger TDP crystals,the crystallization temperature should be decreased,part of the crystal should be removed,stirring rate should be reduced appropriately and supersaturation should be maintained at a proper level.Finally,based on the above research,the optimization of crystallization process for TDP is studied.The cooling rate,stirring rate,initial concentration of cooling process and the solvent and anti-solvent system,the quantity and adding rate of anti-solvent,temperature,stirring speed of anti-solvent crystallization have been investigated systematically to optimize the TDP manufacture process.The modified products exhibit larger crystal size and evenly size distribution,higher yield,which are superior to the other domestic products.No similar reports have been published in literature up to date.