Synthesis Of Cellulose Acetate Butyrate And Polit Scaling Up

Cellulose acetate butyrate is a mixed cellulose fatty acid ester.It shows excellent resistance against moisture and ultraviolet light.Therefore,CAB can be widely used to prepare leather brightener,wood paint,automobile paint,motorcycle paint,etcAlthough CAB has been commercialized for a long history,CAB products manufacutured in China are still inferior to the products from international market in quality.The shortcomings of domestic CAB products are mainly lower viscosity,poor colourity and unstable product quality.As a relust,Almost all of the CAB products used in Chian have to depend on international market so far.In this dissertation,the synethsis process of CAB was reinvestigated schematically using refined cotton linters both in bench scale and in pilot scale.Appropriate synthesis process condtions are determined.Based on the optimization of the process parameters,two kinds of qualified CAB(CAB-381-2 and CAB-551-0.2)were successfully prepared.It was found that species of activating reagent,activation temperature and activation time were the predominant factors that significantly affect the specific viscosity of the prepared CAB products.High esterification temperature and long reaction time can lead to the cellulose degradation and thus significantly reduce the viscosity of CAB as well.When butyric acid was used as reaction media in the synthesis of CAB-381-2,it was observed the esterification reaction rate was very low since the reactivity of butyric anhydride is much lower than that of acetic anhydride.On the other hand,the competitive effect among butyric acid,butyric anhydride and acetic anhydride also can be considered as a reason to this result.Moreover,long reaction time could result in the serious degradation of the cellulose chain and thus low specific viscosity the prepared CAB product.Although high molar ratio of acetic anhydride/butyric anhydride can accelerate the reaction and afford qualified specific viscosity(>1.1),the butyryl content is below 36%.Acetone was also tested as the reaction media given a fact that it is an excellent solvent for CAB.However,acetone led to dark brown reaction mixture.When dichloroethane was used as the solvent,the prepared CAB products were qualified in the specific viscosity but unqualified in the butyryl content.Based on the above results,blended solvent was chosen in the synthsis of CAB381-2.Perchloric acid is an effective catalyst for the reaction of cellulose esterification.In the presence of perchloric acid and blended solvent,high specific viscosity of CAB could be easily gotten.The optimal reaction condition for CAB-381-2 is:13.4 g refined cotton linter of M1000 is activated for 1.3?1.5 h at 10?15? using 18.0 g glacial acetic acid as activating agent.And then the acvitaed cotton linter is subjected to esterification at 0-30? for 8-9 h with mechanistic stirring.The reaction media is composed of 80.0 g blended solvent,0.6 g sulfuric acid,37.0 g butyl anhydride and 10.5 g acetic anhydride.After esterification reaction,the reaction mixture is treated futher by hydrolysis,neutralization,decoloration,filtering,settling out,and drying.The optimal reaction had been validated experimentally in pilot scale.The experimental result showed that qualified CAB-381-2 product can be produced.The optimal reaction condition for CAB-551-0.2 is:45.0 g refined cotton linter of M1000 is activated for 1.5 h at 30? using 50.0 g glacial acetic acid as activating agent.And then the acvitaed cotton linter is subjected to esterification at 10?40? for 5-6 h with mechanistic stirring.The reaction media is composed of 1.0 g sulfuric acid,180?190 g butyl anhydride.After esterification reaction,the reaction mixture is treated futher by hydrolysis,neutralization,decoloration,filtering,settling out,and drying.The optimal reaction had been validated experimentally in pilot scale.The experimental result showed that qualified CAB-551-0.2 product can be produced.