Preparation Of The Modified Animal Glue Binder For Foundry And Study On The Gas-Cured Mechanism

With the increased awareness of environmental protection requirements, a non-toxic, non-polluting, low-cost foundry binder is an urgent requirement. Animal glue is a water soluble binder which is non-toxic,pollution-free and biodegradable. The animal glue has some advantages, such as extensive sources, low cost, pollution-free and so on, and has a spacious prospect in application. When the animal glue was directly used as a binder for foundry,a poor result could get , so it needs to be modified. In this paper, the ordinary animal bone glue was modified by a modification and a new binder for foundry, which was liquid at room temperature, cured by CO₂ was prepared with a higher bonding strength.First, the appropriate decomposition process was determined through the tests. A alkaline catalyst has the feature of rapid decomposition speed. NaOH was chosen as catalyst and the optimum addition amount of NaOH is 4% of animal glue content, the temperature of alkaline decomposition process was 50℃, the period of time was 30 min.Next, the grafting polymerization and esterification crosslinking methods were applied to modify the animal glue, which made the core sands of animal glue have higher strength cured by gas. Through lots of experiments, glycerin, dextrin and ethanol were chosen as modifiers finally, and an orthogonal experiment was done to determine the best proportion of them and the process parameters for the preparation of the animal glue binder. The best technology of new modified animal glue binder agent is : m (glycerin) : m (dextrin): m (ethanol):m (animal glue) = 9:10:9:100, water-animal glue ratio is 4:5, modification temperature is 75℃and modification time is 90min. By the infrared spectrum, the new modified animal glue binder was characterized and the results showed that the modified animal glue had been modified by a grafting copolymerization and an esterification reaction.Through the tests, the way of cured by CO₂ for the new modified animal glue binder was adopted and Ca (OH)2 in powder was used as a cure-promoter. The addition of new animal binder is 3.5% to sand the addition of Ca (OH)2 is 1.25%. A good flow of CO₂ is 0.7m3·h-1, a good period of time for blowing CO₂ is 60s and the mixing time of sand is 150 s. The original strength of the binder is above 0.8 MPa and its final strength is 6.0 MPa. By scanning electron microscope, the feature of bonding bridge was analyzed, and the gas-cured mechanism was analyzed in theory.At last, tests on the performance of new modified animal glue binder sand were done, such as the serviceable time, gas evolution, storage capacity and collapsibility of core. Through the tests, it was found that the sand has a low gas evolution, a good storage capacity and a low residual strength of high temperature. Through economic analysis, compared to the triethylamine cold box binder, which has widely application in the market, the new type of animal glue binder has an economic advantage, and which provides a new way in development of binder for foundry.