Synthesis and Processes of Liquid Polycarbonate Diol
To obtain an efficient synthesis process for polycarbonate diol(PCDL),this study used 1,4-butanediol(BDO),1,6-hexanediol(HDO)and dimethyl carbonate(DMC)as raw materials and tetrabutyl titanate(TBOT)as a catalyst to prepare a copolycarbonate diol(PCDL-BH)by a transesterification method.The effects of the catalyst dosages,reaction temperatures,and reaction time on the synthesis of PCDL-BH were studied.The products were characterized by proton nuclear magnetic spectroscopy(1H NMR),Fourier infrared spectroscopy(FTIR),gel permeation chromatography(GPC),differential scanning calorimetry(DSC)and determination of hydroxyl value and viscosity.The experiment results show that when the catalyst dosage is between 0.04％and 0.08％of the diol mass,the number-average molecular weight((M)n,hydroxyl value)calculated from hydroxyl value tests of PCDL-BH increases with the increase content of catalyst dosage.When the catalyst content exceeds 0.08％of the diol mass,increasing the catalyst dosage has little effect on(M)n,hydroxyl value of PCDL-BH.As the atmospheric reaction temperature(120～150 ℃)and decompression reaction temperature(170～200 ℃)increase,the Mn,hydroxyl value of PCDL-BH gradually increases.With the decompression reaction time increases from 1 h to 3 h,the(M)n,hydroxyl value of PCDL-BH significantly increases.Under the conditions of TBOT content accounting for 0.08％of the diol mass,atmospheric reaction temperature at 150 ℃,decompression reaction temperature at 200 ℃,and decompression reaction time for 2 h,the hydroxy-terminated liquid PCDL-BH with a(M)n,hydroxyl value of about 2 000 is efficiently prepared.The glass transition temperature(Tg)of PCDL-BH is-71.5 ℃,which could be used to prepare flexible polyurethane and polyurethane elastomers.
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