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HWAHAK KONGHAK,
Vol.41, No.1, 51-57, 2003
Vol.41, No.1, 51-57, 2003
금속분말 사출성형공정 중 초임계 CO2를 이용한 탈지공정에서 공용매 효과
Effects of Cosolvent on Supercritical CO2 Debinding in Metal Injection Molding Process
초임계상태에서 공용매의 첨가는 용매의 밀도와 성질을 변화시켜 용해력을 증진시키게 된다. 이러한 이유로 초임계 유체를 이용한 추출공정에서 추출효율을 높이기 위해 공용매를 첨가하는 방법을 많이 사용한다. 본 연구에서는 급속분말사출성형공정 중 초임계 CO2를 이용한 탈지 공정에서 공용매 첨가가 탈지시간에 미치는 영향을 고찰하였다. 공용매로는 methanol, 1-butanol, n-hexane, dichloromethane을 사용하였다. Paraffin wax가 주결합제인 시편의 경우 348.15 K, 25 MPa의 조건에서 5 wt%, n-hexane을 첨가하면 순수 초임계 CO2만을 이용하여 탈지할 때보다 탈지속도가 2배 이상 증가하였고, 압력과 공용매의 농도 증가에 따라 탈지시간을 더욱 단축시킬 수 있었다. 또한 탈지속도를 Fick의 diffusion model에 적용시켜 계산한 결과 실험값과 잘 일치하는 것을 확인하였고, 이를 이용하여 paraffin wax의 확산도를 구할 수 있었다.
In this study, we have investigated the effect of cosolvents on supercritical CO2 debinding in metal injection molding(MIM) process. We used methanol, 1-butanol, n-hexane, and dichloromethane as cosolvents. In paraffin wax based system, the debinding rate was enhanced when non-polar or midium-polar cosolvents such as n-hexane or dichloromethane was added into supercritical CO2, while it was decreased when polar cosolvents such as methanol or 1-butanol was added. For example, the debinding rate was enhanced more than two times by adding 5wt% of n-hexane into supercritical CO2 under 348.2 K, 25 MPa in paraffin wax based system. It was also found that the debinding rate was much more enhanced with increasing concentration of n-hexane or dichloromethane in paraffin wax based system and increasing system pressure. The kinetics of debinding were investigated using the Fick’s diffusion model and they showed good agreement with experimental data. By using this model, the diffusivities of paraffin wax into supercritical solvent could be evaluated in each experimental conditions.
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