Four kinds of modification processes and characteristics of nano-calcium carbonate
干法改性是指在干燥的环境下，密闭设备中高速旋转叶桨将团聚的纳米碳酸钙打散，同时滴加改性剂，借助机械作用力使改性剂包覆在纳米碳酸钙表面。
Dry modification means that in a dry environment, the agglomerated nano-calcium carbonate is dispersed by high-speed rotating blades in the closed equipment, and the modifier is added at the same time, so that the modifier is coated on the surface of nano-calcium carbonate by mechanical force.
该工艺简单高效，无污染物释放和废液产出，适合规模化改性，在工业界广泛应用。但是这种方法改性后的产品往往不能均匀和完全包覆涂层，易出现部分包覆现象。
The process is simple and efficient, without pollutant release and waste liquid output, suitable for large-scale modification, and widely used in industry. However, the products modified by this method often can not uniformly and completely cover the coating, and are prone to partial coating.
2、湿法改性 Wet modification
湿法改性是将纳米碳酸钙悬浮液在搅拌的条件下加入一定量改性剂，控制搅拌速度、温度和时间，然后过滤、烘干、分散得到改性纳米碳酸钙。
Wet modification is to add a certain amount of modifier to the nano-calcium carbonate suspension under stirring conditions, control the stirring speed, temperature and time, and then filter, dry and disperse to obtain modified nano-calcium carbonate.
该工艺的改性效果好，但是投资相对大，需要对废液进行处理，因此一般企业不愿意接受，难以规模化地推广应用。
The modification effect of this process is good, but the investment is relatively large, and the waste liquid needs to be treated. Therefore, general enterprises are unwilling to accept it, and it is difficult to promote and apply it on a large scale.
3、原位改性 in-situ modification
原位改性是将纳米碳酸钙制备及其表面改性两个步骤在原位同步完成，直接向合成纳米碳酸钙的反应体系中加入改性剂，使纳米碳酸钙刚生成时就被改性剂包覆，有效地抑制了碳酸钙的生长和团聚，使碳酸钙具有良好的分散性。此外，通过使用不同改性剂或对工艺条件加以控制，所制备的纳米碳酸钙的晶型晶貌以及粒径大小均有所不同。
In-situ modification is the simultaneous completion of the two steps of the preparation and surface modification of nano-calcium carbonate in situ. The modifier is directly added to the reaction system for the synthesis of nano-calcium carbonate, so that the nano-calcium carbonate is coated by the modifier when it is just generated, effectively inhibiting the growth and aggregation of calcium carbonate, and making the calcium carbonate have good dispersion. In addition, the crystal morphology and particle size of the prepared nano-calcium carbonate are different by using different modifiers or controlling the process conditions.
该工艺代表纳米碳酸钙改性发展的新趋势，但是当前处于基础研究阶段，距离投产还需时日。
This process represents a new trend in the development of nano-calcium carbonate modification, but it is still in the basic research stage and it will take time before it is put into production.
4、复合改性 Composite modification
当前复合改性成为该领域最新尝试，具体方法是将常用改性工艺复合使用以达到协同增效作用，研究证明复合改性效果很好。颜干才等先用硬脂酸钠对纳米碳酸钙进行湿法改性，之后又增加一道干法改性工艺，然后填充到硅酮密封胶中，发现复合改性得到的样品能更有效提高密封胶的储存稳定性和浸水粘结性能。
At present, composite modification has become the latest attempt in this field. The specific method is to combine common modification processes to achieve synergy. Research has proved that the composite modification effect is very good. Yan Gancai and others first modified nano-calcium carbonate with sodium stearate by wet method, then added a dry method modification process, and then filled it into silicone sealant. It was found that the sample obtained by composite modification can more effectively improve the storage stability and water-immersion adhesion of the sealant.
