| Acetate propionate cellulose (CAP) was synthesized from natural cellulose through esterification. It was widely used to prepare the coating, film and so on. Although CAP has been industrial produced in USA and Germany, CAP has not been industrial produced in China and the studies on synthesis of CAP were seldom reported. In this thesis, the synthesis of CAP by heterogeneous and homogeneous esterification reactions was investigated, with emphasis on the influences of reaction conditions on the substitution degree and viscosity of CAP products.Firstly, CAP was synthesized through the heterogeneous reaction. In this way, the cellulose is activated by acid at first, and then added with anhydride as the ester agent, sulfuric acid as the catalyst and acid as a dispersion medium. During the acid activation process, the crystallinity degree of cellulose is decreased, and the activation time and temperature had significant effect on the crystallinity. After 2h activation at 40-60 ℃, the crystallinity was decreased to about 50%. When the activation temperature is above 60 ℃, the polymerization degree (DP) of cellulose was significantly decreased. The optimized acid activation technology was obtained as follows: activation temperature 60 ℃, activation time 2h, amount of acid is 8 times to that of cellulose. The acid activation of cellulose is a physical swelling process, with no chemical reaction except of degradation.In the CAP synthesis under heterogeneous condition, the substitution degree of acetyl and propionyl were increased as the reaction temperature and time increased, while the viscosity of CAP was decreased. The optimized technology was obtained as follows: reaction temperature 60℃, reaction time 2h, amount of sulfuric acid 1% and amount of anhydride 300-400% excess to the targeted DS. The crystallinity, Tg and the thermal stability of CAP decreased as the substitution degree increased has.Secondly, CAP was prepared by homogeneous reaction using LiCl/DMAc as the solvent. It was found that the solubility of cotton increased with the increase of LiCl in solvent, dissolving temperature and time. Cellulose activated by water is disslovedfor 1% in 10wt% LiCl/DMAc by heated in 150°C for 2h,and then stirred for 16h in room temperature, and 3% could be dissolved by heated in 150°C for 6h and stirred for 48h in room temperature. 8-12% cellulose could dissolve in LiCl/DMAc with 10% concentration as cellulose activated by 20wt% NaOH.Cellulose in LiCl/DAMc solution was esterified through different technological routes. It was found that only CAP with low substitution degree could be prepared by one-step esterification without catalyst. The reaction time was longer than 24h at temperature of 60~80°C and the usage of anhydride 400-500% excess to the targeted DS. Esterification using sulfuric acid catalyst was active. CAP with greater substitution degree could be obtained after reaction at 60-80 "C and anhydride 100-150% excess to targeted DS for 4~6h. Pyridine is not a very activate catalyst for esterification. CAP with greater substitution degree could be obtained after reaction at 80°C the 300-400% excess anhydride is used to get the targeted DS for 12h. The sulfuric acid catalyst is more effective in homogeneous than in heterogeneous. CAP with high DS and high viscosity could be synthesized by using less anhydride in homogeneous process.
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