Continuous Preparation Of Granular Superabsorbent Polymer In Tubular Reactor

Super absorbent polymer (SAP) is a kind of macromolecule polymer which can absorb a large number of water or aqueous liquid. Currently the technique of continuous preparation of SAP in industry is mature and high-yield. But many of them need the additional step of grinding by which we can obtain the product with a good distribution of size but terrible shape. Wang Xu.et al has designed a new way which can prepare the granular superabsorbent polymer by one step successfully and the product of this method is irregular and can absorb pure water as much as 731 times of its own weight. But the disadvantage of this method is the main synthetic process being taken place in a reaction still and the reaction of the reactive solution from the reaction still to the extrusion granulation unit haven’t finished yet so transferring a great number of this solution will lead a difference of their reactive time and this can result in the difference of the performance of the product. In this paper, we tried to improve the Wang Xu’s method to prevent the difference of property by using the tubular reactor. The solution flowed in this tube in succession so the factors which can affect the reaction, such as reactive time, were the same and the performance of the products was uniform. We have prepared the granular konjac superabsorbent polymer in tubular reactor continuously. At the same time, we used some methods to characterize its microstructure and its performance in agroforestry production. Through the above research, the conclusions were as follow:(1) Through using a tubular reactor to instead the reaction still, the problem which the factors affecting the reaction, such as reactive time, were different and the performance of the products was nonuniform can be solved. The results of experiment design show that the bibulous granule is capable of absorbing pure water 411 g/g when the mass ratio of cross linker and initiator to KGM is 0.29 and 0.45, respectively. The inner diameter of the tubular reactor is 4 mm meanwhile the length of the reactor is 36 m (reactive time is 25 min). The reactor is heated to 78℃. The pressure offered by the pressure injection device is 0.7 MPa. The continuous phase is polyethylene glycol-600(PEG-600). The temperature of the continuous phase is 80℃.(2) To solve the problem that some of the granules adhered with each other when the continuous phase was less, we took the following measures. In one way, we used other organic solvents as the continuous phase. In the other way, we mixed the PEG-600 with some substances to serve as the continuous phase. Through doing the research, we found out some continuous phases that can be used in the preparation the SAP.(3) The picture of fourier infrared transform indicated that the N, N-methylene bis-acrylamid had been crosslinked with amide bond. The picture of scanning electron microscope indicated that the KSAP particles prepared by tubular reactor were as regular as the ones produced in the reaction still. The result of differential scanning calorimeter indicated that KSAP was synthesized by konjac glucomannan and sodium acrylate. The analysis of TG showed that most of the total mass is water, in which the free water is about 70% and others is bound water.(4) Though the experiment was carried out to test the affection of pH, inorganic salts types, salt dissolve degrees, fertilizer type on the absorption rate, KSAP was not suited for using in the strong acid and alkaline soils. However, it had a good performance in other conditions. The KSAP had a good reusability, too. In the retention water test, we have indicated that the effect of KSAP was significantly.