Study On The Particle Size Control And Fluidity Of Medicial Microcrystalline Cellulose

Microcrystalline cellulose(MCC)is a functional cellulose product obtained by hydrolyzing natural cellulose.It is used as a tablet binder,disintegrant and excipient in the pharmaceutical industry because of its good properties,such as high degree of crystallinity,good fluidity,adhesiveness,water swelling and easy deformability.However,the domestically-made medicinal MCCs had some problems of poor morphological manipulation and fluidity.The law of influence of particle size and morphology of MCC on fluidity was not yet clear.In this work,we mainly focused on the particle size manipulation of MCC by changing the raw material and manufacture process,and analyzed the impact of MCC particle size,distribution and morphology on the fluidity of MCC.First of all,comparing the domestic MCC with imported MCC,we found that the differences between the same type of domestic and imported MCC were not very big in terms of chemical structure,crystal structure and thermal stability.However,the fluidity and crystallinity of domestic MCC were lower than that of imported MCC.Besides,by comparing different types of imported MCC,it was concluded that the morphology of the particles was the key factor affecting the fluidity of powder when the particle size and distribution were almost the same.The more the spherical particles,the better the fluidity of MCC powder.Secondly,comparing the influence of raw material types and the acid hydrolysis process on the properties of MCC.The results showed that the optimal acid hydrolysis process conditions for the preparation of MCC from the dissolving pulp of Masson pine were 4.0 mol/L HCl,75 ? of the reaction temperature,1:16 of the solid-liquid ratio and 60 minutes of the reaction time.In the process of acid hydrolysis,the particle size of MCC became smaller and the distribution became uniform with the increase of acid concentration and reaction temperature.Compared with MCC of Eucalyptus,masson pine MCC had a larger particle size,better fluidity,better thermal stability and higher crystallinity.It was further proved that softwood was better than hardwood when MCC was prepared under the same conditions.At the same time,the eucalyptus MCC and Masson MCC conformed to the requirements of Pharmacopoeia of the People's Republic of China and could be used as pharmaceutical excipients.Then,the effects of drying methods and grinding processes on the particle size,morphology,fluidity and crystallinity of MCC were explored.When the milling time increased,the size of MCC obtained from blasting and infrared drying decreased firstly and then increased.Because secondary particles could easily be formed between the MCC particles when the time of ball milling was too long.The morphology of MCC changed from a short rod to a sphere one,and the fluidity became better with an increase of balling time.At the same time,the crystal structure of MCC changed,the crystallinity value was significantly reduced and the thermal stability was decreased.The air inlet temperature of spray drying had little effect on particle size,fluidity,moisture content and thermal stability of MCC powder.The crystal structure did not changed,and the morphology was short rod like.Finally,fractal dimension method and response surface method were adopted to quantitatively characterize the influence of MCC morphology and different particle size contents on the fluidity of MCC.The fractal dimension and mobility of MCC were negatively correlated with each other.That was,when the fractal dimension was larger,the angle of repose was larger and the fluidity of the powder was worse.Calculating the average circularity of MCC powders,it was found that when the average circularity was larger,the angle of repose was smaller and the fluidity was better.There existed a variable relationship between particle diameter and shape factor.With the increased of particle diameter,the degree of circularity and compaction gradually decreased,and the elongation increased and the roughness did not change very much.The relationship between the angle of repose and the particle of different sizes was obtained by response surface methodology and the results were highly fitted quadratic regression.In summary,by changing the raw material type,hydrolysis process,drying and grinding methods,it is possible to achieve the control of the particle size of the MCC and the improvement of its fluidity and crystallinity.At the same time,the fluidity of MCC was related to its particle size distribution and particle morphology.That was,when the MCC particle size distribution was narrow and the shape was more spherical,the fluidity was better.However,MCCs with different particle size distributions and morphology were aimed at different applications.The study also provided some guidance for the preparation of medicinal MCC.