| In the paper industry, internal sizing and surface sizing are the main methods to improve the function of anti-water and paper surface. Reducing or even avoiding internal sizing will help white water cycling. So improving the function of surface sizing agent to make the paper meet the need of the print industry is an urgency topic.This paper discussed the craft condition of enzyme converted starch by modifying tapioca original starch with a-amylase and got the enzyme converted starch with high solid content (25%) and low viscosity. At the same time the effect on surface sizing was measured and the reaction mechanism of enzyme converted starch was discussed. The detail results are following:1,The best craft condition of enzyme converted starch shows: substrate concentration is 25%, keep temperature at 45℃for 12mins, and pH 7.0. At this best condition the viscosity of starch paste is 13mPa.s. It need not buffer solution to adjust pH during the reaction of enzyme Conversion. Directly using the distilled water can decrease the cost obviously.2,The studing of the surface sizing effect about the starch paste viscosity and solid content shows: To the newspaper be tested, the best sizing result are the compatible viscosity of enzyme converted starch paste was about 10mPa.s and the compatible solid content was 25%.3,Compared the sizability among enzyme converted starch, original tapioca starch and oxidized starch. The result shows the effect of enzyme converted starch is better than the others. Comparing the original paper, when paper treated with enzyme converted starch, water absorption has deceased 19.65%, the surface strength has improved fourfold, the anti-piece index number has raised 50.7%, and the folding endurance has improved about threefold.4,Researched the reaction mechanism of enzyme converted starch. Different degradation degree enzyme converted starch were got by changing dosage of amylase. Using Colorimetry to measure reducing sugar content, Gel Permeation Chromatography (GPC) to measure the distribution of molecular weight, and scan electricity mirror to observe the surface appearance of enzyme converted starch. The studing shows that the degradation process of starch is uneven, and the molecular weight of the products distribute unevenly. But in a certain degree the starch degradation degree can be controlled. GPC is an effective way to monitor the degree of starch hydrolysis reaction.5,Using the enzyme converted starch to replace oxidized starch in surface sizing can improve resin content and decrease the consume of dry steam. Only calculated the latex content it can save 45yuan per ton. |
