| The increasing shortage of petroleum energy, alternative energy is becoming more and more urgent the search for oil. With the development of biochemical technology, the products prepared by corn starch from a single ethanol become diversified. Corn starch industry development faster and faster, the level of industrialization was increasingly high, which due to the increasingly serious energy crisis. After the polyol with higher economic value added was extracted, some residues cannot be used. The purpose of this paper is based on the performance of these residues, using these polyols residue for preparing a composite adhesive with stable property and meets the national standard. The significance of this paper is shown as follows,(a) Utilization of biomass polyol developed a green biological adhesive with little pollution to the environment.(b) Using renewable bio-polyols prepared adhesive, to replace petroleum products used in traditional industries, so as to get rid of the dependence on petroleum products,(c) A great amount of polyols residues form corn production of bio-polyols is effectively utilized. In this study, these polyols residues had good use, which improve the economic value added of downstream products, extend the industrial of corn industry, promote the healthy development of boil-polyol alcohol industry, and improve the comprehensive economic benefits of corn production of polyols industry.Bio-polyol residues had small molecular weight and better water-soluble, it cannot be directly used as adhesive, and need for chemical blending modified. The oxidized starch with high carboxyl content was use as chain extender for small molecule alcohol, and as a role of filling, thereby reduces the permeability of the polyol residues. Emulsified isocyanate was use to improve waterproof of Polyol adhesives.In the oxidized starch preparation, preparation of high carboxyl content of oxidized starch with hydrogen peroxide, sodium hypochlorite, potassium permanganate three oxidation agent. Through test the carboxyl group content, viscosity thermodynamic properties (TGA, DSC), XRD and other performance index of the sample, analyze the effect of pH, temperature, acidification, amount of oxidant on oxidized starch prepared. Draw the following conclusions:Preparation of oxidized starch with hydrogen peroxide, oxidized starch had high degree of oxidation when prepared in alkaline environment; the optimum pH value is9. Hydrogen peroxide is more active in high temperature environment, the preparation of oxidized starch with high degree of oxidation, the optimum temperature is45℃. The degree of oxidation was increasing with oxidant dosage increased, hydrogen peroxide in rate of0.57%in the optimal preparation conditions.Preparation of oxidized starch with sodium hypochlorite, products had high degree of oxidation in alkalescent environment, the best preparation condition at pH9. The high or low temperature was unfavorable to the oxidation of sodium hypochlorite on starch, the best preparation temperature is50℃. The more the amount of sodium hypochlorite, the greater the degree of oxidation starch. The utilization rate of sodium hypochlorite is1.57%under the optimal preparation conditions.Preparation of oxidized starch with potassium permanganate, products had high degree of oxidation when activation pH value of the first phase selection11. Temperature too high or too low are not conducive to oxidation starch by potassium permanganate, the best preparation temperature is40℃.Acidification quality had great effect on the second stage oxidation, the deep degree of oxidation for starch when acidification quality was11%to dry starch. The utilization rate of potassium permanganate was50.28%under the optimum preparation conditions.Comparing three kinds of oxidant with equivalent oxidizing power, the oxidation ability of sodium hypochlorite was strongest; hydrogen peroxide was weakest, Potassium permanganate in the middle.Sodium hypochlorite had the deepest degree of oxidation on starch, can break the crystal shell of starch, and penetrate into the internal of starch granules. Potassium permanganate can also break the crystalline structure of starch, corrosion of starch crystalline shell, which make uneven for starch shell. Hydrogen peroxide was only oxidize the free amylose and amylopectin of starch, cannot damage the crystal structure of starch, it has little effect on the crystalline structure of starch granules.Then the emulsifiable isocyanate was modified with two hydrophilic modifiers (A, B). The optimum molar ratio of NCO/OH, the amount of emulsifier and stabilizer was analysis from the aspect of the application period of emulsion. The optimum conditions of prepare emulsion with hydrophilic modifier A was that the molar ratio of NCO/OH was160:1, emulsifier dosage was2%and addition amount of stabilizer is0.3%. For hydrophilic modifier B, the optimum conditions for the preparation of emulsion was that80:1of NCO/OH molar ratio,1%of emulsifier dosage and1%of the addition amount of stabilizer. Two kinds of modifiers were modified with DMPA, the results show that introducing an amount of1%DMPA to the system of hydrophilic modifier A can improve the application period of emulsion, reaching152.9min. The system of hydrophilic modifier B was not suitable for the introduction of DMPA.Finally, preparing oxidized starch with high carboxyl content and emulsifiable isocyanate prepolymer with a long period. Then mixed oxidized starch, emulsified isocyanate and bio-polyol for prepared adhesive. The best ratio of biological composite adhesive was that biological polyol residues was40%of the total, for emulsified isocyanate was23%, and9% for oxidized starch. The strength of the adhesive was1.105MPa. |
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