Development of Debindering Process of Molded New Ceramics Using Supercritical Fluid

本文将超临界流体萃取技术应用于新型陶瓷模塑脱粘工艺中，取得了以下结果：1.对模塑新陶瓷进行了粘结剂萃取实验，寻找适合超临界流体脱粘的粘结剂组分。结果表明，低熔点温度的石蜡适合作为低分子粘结剂，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相对分子质量的粘结剂。此外，与传统的热分解方法相比，超临界流体脱脂可以大大缩短脱脂过程时间。为了进一步缩短脱粘时间，减少所需超临界流体的用量，进行了联合使用活性碳的超临界流体脱粘试验。结果是，由于提取的粘结剂在活性碳上的吸附，使得超临界流体相中的粘结剂浓度保持在较小的值，因此在没有超临界流体流过萃取池的情况下，获得了高的萃取率。萃取率的结果通过一个模型进行关联，该模型仅将粘结剂组分在坯体中的扩散视为传质阻力。脱粘速率与粘结剂组分在坯体中的浓度分布可以用Fick扩散方程进行较好的关联。对脱粘样品进行烧结，并测试其抗弯强度。用超临界流体萃取法脱粘的烧结体的抗弯强度与传统方法脱粘的烧结体的抗弯强度相当。

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.