Research On Novel Synthesis Technology Of Curing Agents For Foundry No-bake Furan Resin

Due to the advantages of high sand mold strength, great dimensional accuracy, fast curing rate, high efficiency, low production costs, low labor intensity, perfectly conforms to the requirements of modern casting technology, no-bake furan resin sand molding process has been widely used in production, and considered to be the main process of foundry industry in the future. At the same time, curing agent for no-bake furan resin, the quality of which is an important guarantee for the development of no-bake furan resin sand molding, is a decisive factor to the performance of furan resin sand.In this investigation, a series of casting furan resin curing agents, xylene sulfonic acid and methyl hydrogen sulfate as the main active ingredient, were synthesized via concentrated sulfuric acid liquid phase sulfonating method. Besides, lots of researches on curing mechanism of no-bake furan resin, characteristics and using technology of curing agents have been done. The conclusions are as following:(1) Compared with the synthesis of similar products in the market, this series of curing agents get advantages of low synthesis temperature(the sulphonation temperature was dropped from about 120℃to 80℃), short reaction time(the sulphonation time was cutted from 8h to 4h).(2) Combination of sulfonation and esterification was achieved in this synthesis. So, there are both xylene sulfonate and dimethyl sulfate in these curing agents. It turned out that sand molds hardened by this series of products got higher initial strength and final strength. Besides, this series of curing agents illustrated better moisture resistance, and met producing demands with less dosage under varieties of environmental conditions.(3) The active ingredients in this series of products are confirmed as aryl sulfonic acid, sulfonate and dimethyl sulfate by infrared spectroscopy, which means that reactions during the synthesis process occurred in the manner envisaged. The synthesis process was divided into two parts, sulfonation and esterification. How synthesis factors affected the reaction was figured out by analyzing the infrared spectra.(4) In reference to related literatures, based on the results of experiments and SEM images, the curing mechanism of no-baking furan resin was discussed, including the role curing agents played in the curing process and how to measure the properties of curing agents.(5) To compare with the synthesis of similar products in the market, experiments on using life time and curing rate of molding sand mixed with different curing agents were done. Hardening coefficient K was introduced into this thesis to investigate the hardening properties of curing agents comprehensively. The results showed that our productions had better performances.(6) Relationship between acidities of curing agents and hardening coefficient K was discussed. It appeared that K decreased with the increase of acidity. Besides, it was proved that temperature influenced the curing rate of molding sand deeper than humidity, which indicated the choice of curing agent should be firstly based on temperature to determine appropriate type of curing agents and then adjust the dosage of them according to humidity condition. At last, proper range of temperature and humidity conditions for this series of curing agents and the process for synthetically using them were summarized.