| PVA collodion is prepared by acetalization reaction of polyvinyl alcohol and formaldehyde, and is widely used as a cleaning, adsorption and filter material. A large number of waste PVA collodion are generated during it’s manufacturing process. Traditional treatment methods for waste PVA collodion, such as direct incineration or landfill, are not environmentally friendly, and resulte in a waste of resources. In recent years, the recycling of waste PVA collodion has gradually attracted great attentions. Therefore, study of the recycling and reusing of waste PVA collodion has important practical significance.This study is aming to develop a novel technology for the reusing of waste PVA collodion under the request of Suqian Jiahe Plastic Metal Products Co., Ltd.. We planned to hydrolyze waste PVA collodion to raw PVA material, and then make new PVA collodion using the hydrolysis products. The effects of reaction conditions on the hydrolysis behavior of the waste PVA collodion were studied, and the hydrolyzate a nd it’s solution were characterized by means of viscosity, magnetic resonance(NMR) and contact angle test. The hydrolyzate of waste collodion was mixed with the new PVA marerial, and then the regenerate PVA collodion was prepared. The effects of technological conditions for preparing PVA collodion on the water absorption, softening time and tensile strength of the regenerate collodion were studied. On the basis of laboratory results, we also conducted experiments in the workshop.(1)The optimum conditions for hydrolyzing waste PVA collodion were determined. The hydrochloric acid solution dissolved reagent W was used as solution medium for the hydrolysis of waste PVA collodion. The optimum hydrolysis condition were determined as: temperature 90 ℃; time 40min; mass ratio of waste PVA collodion and reagent W 1:2; solid-liquid ratio 1:15; concentration of HC l 6.2wt%. Under these conditions, the waste collodion was fully hydrolyzed, and the hydrolysis products were able to be reused.(2)The technological conditions for the manufacturing of PVA collodion using the hydrolysis products were studied. In laboratory experiments, the amount of formaldehyde and curing temperature were optimized to be 4.45wt% and 66℃ respectively. In the amplificatio n experiments, we mainly focused on adjustmenting the acetal degree of PVA collodion to optimize the regeneration process. The 120- fold scale-up experiments for laboratory results was conducted using one-step program, and the amount of formaldehyde and cur ing temperature were optimized to be 4.20wt% and 60℃ respectively. In this condition, the rate of qualified and first-class of recycled products were both more than 95%. On this basis, the process had been adjusted to improve the efficiency of recycling wa ste PVA collodion. The waste collodion treatment capacity of the adjusted process increased about 2- fold compared to the original one, while it’s experimental results was consistent with that of the 120-fold amplification experiments. In the 2400 times large scale- up experiments, the amount of formaldehyde after optimization increased to 4.52wt%, while the curing temperature and hydrolysis time remained the same. The resultant rate of qualified recycling products was more than 95%, and the rate of first-class products was not less than 50%.Compared with the existing technology, our method of recycling waste PVA collodion is easy to operate, and will not increase the cost of raw materials and lower production efficiency. Currently, the regeneration process is basically stable, and can easily consume a large number of waste PVA collodion generated in the manufacturing process. Therefore, our method of recycling the waste PVA colllodion is a good solution to solve the environmental problems, and also reduces production costs. |
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