The New Technology Research Of Multiple-modified Starch By Semi-dry Method With Microwave Heating Treatment

The modified starch is abundant, cheap, stable, easy-to-use, can be modified and degraded chemically etc. In the refined papermaking chemistry, starch and modified starch take 80~90%(by weight). Therefore, in our papermaking industry, the modified starch has great potential, its application can bring huge economic and social benefits. Now, our papermaking industry is facing serious situation of pollution, and timber insufficiency, moreover, the additives of quality grade paper rely on import mainly. We need urgently to develop the additive that suits the national conditions of our country, that is fit for grass pulp, waste paper pulp, neutral glue, recyled pulp. In Modified Starch Technology Exchange Meeting of year 2000, experts suggested that we should take the modified starch as a major project of refined chemical industry, and optimize the technology of amphoteric starch and multiple-modified starch. This paper focuses on the optimization of multiple-modified starch, and conducts series of experiments. With cassava starch as the raw material, we apply the semi-dry processing method, heating with the microwave. Through starch ester reaction, and then ether reaction, a new kind of multiple-modified starch is developed, which is proved a kind of effective paper strengthen agent by application experiment. At the same time, we have adopted the multivariate nonlinear equation to simulate the process of multiple-modified starch. The purpose of this paper is to develop and optimize the theory of modified starch technology . The main findings are summarized as follows: 1.Applying the theory that the microwave heating can speed up chemical reaction, the advanced semi-dry processing method, it can shorten the reaction time greatly. Adopting the semi-dry technology, it is important to control the water content. This technology has lower requirement on equipment, and it's later course of washing produces less sewages, so as to reduce the environmental pollution. 2.Discussing the influence of microwave heating on the starch modification process, the microwave heating can speed up the chemical reaction, and at the same time, save energy. In the second chapter, through series of experiments, we adopted low frequency microwave, intermitted heating scheme, to avoid the problem of starch scorch, and to raise the production rate by 2~3 times. 3.Analyzing the principle of starch ester and ether reaction, we have combined the two ester reactions one, so that through one ester reaction, and then ether reaction, into a kind of multiple-modified starch that includes 3 kinds of modified groups—positive ion group, negative ion group, neutral group. This scheme can simplify the process, and shorten the reaction 15~20 times than the ordinary dry thermal reaction. 4.Since the major index that affects the application of multiple-modified starch is positive ion group replace degree, we need to raise the efficiency of ether reaction. It is critical to control soda reagent quantity. Through application orthogonal experiment analysis, we have determined the optimal parameter of ester and ether reaction, which is the foundation of establishing the technology model of the multiple-modified starch process. 5.Applying the papermaking wet chemistry theory of potential, electric charge, ionization as well as wadding congeal theoretical etc. In the paper pulp, the starch can enhance the strength of paper fiber, which has close relation withthe electric charge on it. Because paper fiber usually carries negative charge, and attract the positive ion group of the multiple-modified starch, the negative group of the starch will expell the other negative ion in the paper pulp, the neutral group not only have the function of adhesion, strengthen, but also prevent the positive and the negative group electrostatic combination. Besides, the starch has balance of electric charge, when starch recycled in paper pulp, it will not break the balance of electric charge, so that the paper machine can be ensured in good operation state. Therefore, in papermaking course, it will not affect the Zeta potential of paper pulp by whatever amount of quantity. 6.Applying the multiple-modified starch in papermaking process, detecting the influence on the starch to paper physical property, it has risen the tension index, tear-apart index, and burst index of paper. 7.We made the tension index as function, analyzed the relation between the replace degree of the starch and tension index of paper, through regression analysis, found regression equation of the positive ion group replace degree of the starch, Y=5E+0.6x4+7463.4x3-30170x2+1028.6x-6.7628; the negative ion group replace degree regression equation Y=1E+10x4-1E+0.9x3+3E+0.7x2-440497x+2149.2; the neutral group replace degree regression equation Y=2E+10x4-1E+ 0.9x3+3E+0.7x2-350894x+1426.8, all the regression confidence R2=1. 8.Establishing the multivariate nonlinear regression equation model to simulate the technology of multiple-modified starch firstly, we have applied software such as Matlab and Excel to handle test data.We have established the...