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On the Relation between Natural and Enforced Syneresis of Acidic Precipitated Silica

机译：酸性沉淀二氧化硅的自然脱水收缩与强迫脱水收缩之间的关系

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Silica in industrial production processes is precipitated by mixing an acid and an inorganic precursor. In this aqueous solution, silica particles form due to a polymerization reaction and agglomeration and, finally, build a gel. Thereafter, the reaction continues, and the gel network shrinks with the expulsion of the enclosed pore liquid. This slow process is known as “natural syneresis” and strongly affects the product properties, such as the agglomerate size, specific surface or porosity of the silica produced. In order to investigate the influence of process parameters, such as temperature, pH or ionic strength, on the shrinkage in shorter time-scales, we propose an acceleration of this process and define it as “enforced syneresis”. The acceleration is performed by applying a mechanical external force to the gel by means of a plunger and measuring the shrinkage behavior under these conditions. Thereby, the conceptual idea is the prediction of the shrinkage due to natural syneresis based on the results of enforced syneresis. We are now able to predict the natural syneresis behavior from enforced syneresis data by the development of a correlative model. Using this prediction model, we can show the influence of temperature on the maximum shrinkage and on its rate in a significantly shorter time of about 12 h instead of several days.
机译：工业生产过程中的二氧化硅是通过混合酸和无机前体来沉淀的。在该水溶液中，由于聚合反应和附聚而形成二氧化硅颗粒，并最终形成凝胶。此后，反应继续进行，并且凝胶网络随着被包封的孔隙液体的排出而收缩。这种缓慢的过程称为“自然脱水收缩”，并且会严重影响产品性能，例如附聚物的尺寸，比表面积或所生产二氧化硅的孔隙率。为了研究工艺参数（例如温度，pH或离子强度）在较短时间尺度上对收缩率的影响，我们建议加快该过程，并将其定义为“强制脱水收缩”。通过用柱塞向凝胶施加机械外力并在这些条件下测量收缩行为来进行加速。因此，概念上的想法是基于强制脱水收缩的结果来预测由于自然脱水收缩引起的收缩。现在，我们可以通过开发相关模型来根据强制性脱水收缩数据预测自然脱水收缩行为。使用此预测模型，我们可以在大约12小时（而不是几天）的明显较短时间内显示温度对最大收缩率及其速率的影响。

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