Development of Debindering Process of Molded New Ceramics Using Supercritical Fluid

将超临界流体（SCF）萃取技术应用于新型成型陶瓷的脱除工艺，取得了以下结果：对新型成型陶瓷进行粘结剂提取实验，寻找适合于SCF脱胶的粘结剂组分。结果发现，低熔点温度的石蜡适合作为低分子量粘结剂组分，低熔点温度和低玻璃化转变温度的热塑性树脂适合作为高分子量粘结剂组分。此外，与传统的热分解法相比，SCF法可大大缩短脱墨时间。为进一步缩短脱渣时间，减少所需SCF的用量，采用活性炭联用的方法进行了SCF脱渣实验。因此，在没有SCF流过萃取池的情况下，获得了高提取率，因为被萃取的粘合剂在活性炭上的吸附使SCF相中的粘合剂浓度保持在很小的值。萃取率的结果通过一个只考虑黏合剂组分在绿体中的扩散作为传质阻力的模型进行关联。用菲克扩散方程可以很好地将脱胶速率与绿体中粘结剂组分的浓度分布相关联。对脱脂后的试样进行了烧结和抗弯强度测试。SCF萃取法脱泥后烧结产物的抗弯强度与常规脱泥法脱泥的抗弯强度相当。

In this work, supercritical fluid (SCF) extraction technique was applied to the debindering process of molded new ceramics, and following results were obtained :1. Binder extraction experiments were carried out from molded new ceramics to search the binder components which were suitable for the SCF debindering. As a result, it was found that paraffin waxes with a low melting point temperature were suitable as low-molecular weight binder components, and thermoplastic resins with a low melting point temperature and a low glass transition temperature were suitable as high-molecular weight ones. In addition, the debindering process time could be reduced to a great extent by the SCF debindering compared with that by conventional thermal decomposition method.2. SCF debindering experiments were carried out by joint use of activated carbon to reduce the debindering process time further and to cut down the quantity of needed SCF. As a result, high extraction yields were obtained without flowing SCF through the extraction cell since binder concentrations in the SCF phase were maintained at small values due to the adsorption of extracted binders on the activated carbon.3. The results of extraction yields were correlated by a model which considers only diffusion of the binder components in the green body as a mass transfer resistance. The debindering rates and the concentration distributions of the binder components in the green body could be satisfactorily correlated by Fick's diffusion equation.4. The debindered samples were sintered and tested for bending strength. The bending strength of the sintered products which were debindered by the SCF extraction method was as high as that of those produced by the conventional method.