| Starch is an important part of biomass resources, which has wide array of sources, biodegradable, renewable and other fine features. Currently, the starch has been widely used in papermaking, food, textile, petroleum and other industries. However, the scope of application of native starch is limited greatly by its structure and lack of performance, such as cold water insoluble, easy to aging, or the starch paste solution instable under mechanically stirred and acid conditions. Therefore, the native starch is modified to meet the needs of industrial production by physical, chemical or enzymatic treatment method, which has important research value and significance.In this paper, cationic waxy corn starch was prepared from waxy corn starch with 2,3-epoxypropyl trimethyl ammonium chloride(ETMAC) as a cationic etherifying reagent under laboratory conditions. The low and high degree of substitution of cationic waxy corn starch were prepared with wet and dry method, respectfully. They were also applied to secondary fibers. Firstly, the low degree of substitution of cationic waxy corn starch(LDSCWS) was prepared by wet process. Investigating the influence of different factors on the degree of substitution and reaction efficiency of LDSCWS by univariate control act. LDSCWS was then applied into newsprint waste paper pulp as a paper reinforcer, and the result was compared with that of cationic tapioca starch and cationic corn starch. HDSCWS was prepared by a dry process and its structure was also analyzed and characterized. The performance of LDSCWS and HDSCWS were compared and they were mixed used in newsprint waste paper pulp at a certain percentage. The physical properties of samples like functional group, crystalline texture, thermostability and microstructure were detected and analyzed by FT-IR, XRD, TG-DTG, SEM and any other detection means.The experimental results showed that: in the process of preparing LDSCWS, the optimum reaction conditions were: the system water content was 75%, the mass ratio of ETMAC and starch was 1:10, the reaction temperature is 50 ℃, the reaction time was 7h, the mass ratio of sodium hydroxide and ETMAC is 3:10, the order of addition was the starch sample, swelling inhibitor, sodium hydroxide, ETMAC. Compared to other types of cationic starch, LDSCWS was more cost-efficient in newsprint waste paper pulp applications. Cationization reaction occurred at the surface of waxy corn starch granules, and the amorphous region of starch granules increased after the cationization reaction. In the process of preparing HDSCWS, the molar ratio between starch and ETMAC was 1.2: 1, the molar ratio between sodium hydroxide and starch was 1: 1, storage temperature was 40 ℃, the reaction efficiency of the process stabilized at 75% to 80%. The cationisation reaction occurred not only in the surface of starch granules but also in the interior of the particles. Compared with the native starch, the apparent viscosity of cationic waxy corn starch was higher and the shear stability was lower. The apparent viscosity of native and cationic waxy corn starch both decreased with increasing shear rate. While LDSCWS and HDSCWS mixed use in newsprint waste paper pulp, the optimum amount of cationic starch was 5kg / t and the best ratio was H / L = 1: 4(w/w). |
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