Studies On The Preparation And Application Of Cross-linked CMS

It is studied in this thesis how to prepare corss-linked carboxymethyl starch.Carboxymethylstarch's properties and applications in clay suspension and inner wall dope are also researched inthis paper.The single drum dryer's operation condition were studied. By single factor experiments, theeffects of the varieties of factors on the degree of substituent(DS), reaction efficiency(RE),viscidity, water-holding ability , and water keeping of CMS are studied, including the degree ofneutralisation , proportion of acid and alkali, basification temperature , basification time ,etherify temperature, etherify time and so on. Based on those, the perpendicular experiments areused to optimize the technology. The optimum condition is as follows, starch slurry 25%(d.b),M_AGU:M_{chloroactic acid}:M_NaOH=1:0.2:0.4, basification temperature 35℃ , etherify temperature 60℃ ,etherify time 2h. The DS of ether in the product is about 0.138. CMS paste is relatively instable,while corss-linking bond will make it more stable in the heating and shearing. POCl₃ andepichlorohydrin as corss-link reagent. The DS of Cross-linked CMS prepared is about 0.138.The Cross-linked CMS paste is shear-thinning which belong to Pseudoplastic Liquid. It'spaste viscidity increase with the increase in the thickness of pieces of CMS, but decrease whenthe thickness arrive a certain value. The viscidity decrease the increase in the dimension of theCMS pieces. The smaller is the easier agglomeration of it is . Cross-link reagent make two ormore starch molecule "bridge" together and form a 3D net structure. This will increase theviscosity stability of the paste and dry pieces of the carboxymethyl tapioca starch. Moreover itcan improve the water sorption of the product. The fluid liquid characters of samples were studied.The structure of sampels is researched. Infra-red spectrometris shows chloroactic acidlinked to Tapioca starch by aether bond . The intensity of the flexing-oscillation peak in3000³700cm^-1 become weak due to hydroxyl bond stretching. The result of micrograph revealthat reaction and drying demolished the starch granule and form the pieces with hole.Cross-linked CMS will be with better stability of paste and tighter structure of pieces than CMS.Molecular weight analysis shows that corss-link reagent make up the destruction of alkali andhigh tempreture. DSC analysis shows that the cross-linking of CMS results the increase in glasstransition temperature, which is good for storage stability.The applications of samples in clay suspension and inner wall dope are investigated at last.When CMS is used as suspension reagent, the optimum content is 0.15%(w/w,DS=0.138).Whencross-linked CMS is used as felt reagent inner wall dope, the optimum formula is : 1% ofcross-linked CMS (epichlorohydrin 0.02% (v/w), DS=0.136) , 21% of cement , ms_{cale calciumcarbonate}:m_{quartz grit}=1:1. The dope up to par and had better character than the contrast.