聚硅氧烷消泡剂的失活和再生机理

Mechanism of deactivation and reactivation of polysiloxane antifoamers

介绍了聚硅氧烷消泡剂失活和再生的现象,分析了失活过程中消泡剂分散体粒径大小和分布,泡沫体系的表面张力、接触角、硅油铺展层的厚度以及泡沫膜的结构和状态,结果表明:硅油组成的改变、硅油和疏水二氧化硅微粒的分离、消泡剂分散体粒径的变小、铺展油层的消失和白色絮凝物的出现导致消泡剂失活,其中二氧化硅硅粒-硅油的分离和泡沫膜上硅油铺展油层的消失是主要因素。失活的消泡剂中加入硅油,消泡活性可再次恢复,这主要是由于消泡剂分散体粒子中的硅油-二氧化硅硅粒比例达到最佳的状态并在泡沫膜上又形成了新的具有消泡活性的硅油铺展油层。

<Abstrcat>The phenomena about the deactivation and reactivation of polysiloxane antifoamers,as well as the particle size and distribution of the antifoam dispersion,surface tension of the foam system,contact angle,the thickness of the spreading out layer of silicone oil,and the structure and profile of the foam film in the deactivation process were presented.The deactivation can be resulted in by change of the composition of the silicone oil,separation of the silicone oil and the hydrophobic silica particulate,reduction of the particle size of the antifoaming agent dispersion,the elimination of the spreading out silicone oil and the formation of the white flocculates.Among the above mentioned causes,the separation of the silica (particles) and the silicone oil as well as the elimination of the spreading out silicone oil are the main causes.The addition of (silicone) oil into the deactivated antifoaming agent the antifoaming activity can be resumed.It can be explained by the achieving of optimal ratio of silicone oil to the silica particulate in the antifoam dispersion particles and formation of new silicone oil spreading out layer that has the antifoaming activity.