博客

The surface modification of powders is largely achieved through the action of 表面改性剂s on the powder surface. 因此, 表面改性剂的配方（品种）, dosage and usage) has an important influence on the modification effect of the powder surface and the application performance of the modified product.

表面改性剂的配方具有很强的针对性, 这是, 它具有“一钥匙开一锁”的特点。, 其中主要包括品种的选择, 剂量和用法的确定.

1. 表面改性剂的筛选

The main considerations for selecting 表面改性剂 varieties are the properties of 粉状原料, 产品的用途或应用领域, 还有过程等因素, 价格与环保.

(1)粉体原料性能

粉体原料的性质主要是酸性, 碱度, 表面结构和官能团, 吸附和化学反应特性, 等. Surface modifiers that can react che云母lly or che云母lly adsorb with the surface of 粉末粒子 should be selected as much as possible, because physical adsorption is easy to desorb under strong stirring or extrusion during subsequent application. 例如, 硅酸矿物的表面，如石英, 长石, 云母, and kaolin can bond with silane coupling agents to form a relatively strong che云母l adsorption; however, silane coupling agents generally cannot che云母lly react or che云母lly adsorb with carbonate alkaline minerals, while titanate and 铝酸盐 coupling agents can che云母lly adsorb with carbonate alkaline minerals under certain conditions and to a certain extent. 因此, silane coupling agents are generally not suitable for use as 表面改性剂s for carbonate alkaline mineral powders, 如轻质碳酸钙和重质碳酸钙.

(2)产品使用

产品的使用是选择表面改性剂时最重要的考虑因素. Different application fields have different technical requirements for the application performance of powders, 如表面润湿性, 可分散性, pH值, 遮盖力, 耐气候性, 光泽, 抗菌性能, 防紫外线, 等. 这就是为什么要根据其用途选择表面改性剂的原因之一. 例如, 用于各种塑料的无机粉末（填料或颜料）, 橡胶, 粘合剂, 油性或溶剂型涂料需要良好的表面亲脂性, 这是, 与有机高分子基材有良好的亲和性或相容性, which requires the selection of 表面改性剂s that can make the inorganic powder surface hydrophobic and oleophilic; inorganic pigments used in ceramic blanks are not only required to have good 可分散性 in the dry state, but also require good affinity with inorganic blanks and be able to be evenly dispersed in the blanks; 表面改性剂s for inorganic powders (fillers or pigments) used in water-based paints or coatings require good 可分散性, 改性粉体在水相中的沉降稳定性和相容性. The selection of inorganic 表面改性剂s is mainly based on the functional requirements of the powder material in the application field. 例如, 使二氧化钛具有良好的耐候性和化学稳定性, 表面涂覆（膜）应采用SiO2和Al2O3, 并使白色云母颜料具有良好的珠光效果, 表面涂覆（膜）应使用TiO2. 同时，不同的应用系统具有不同的组件. 选择表面修饰剂时, the compatibility and compatibility with the components of the application system must also be considered to avoid the failure of other components in the system due to the 表面改性剂.

(3)修改过程

改性过程也是选择表面改性剂的重要考虑因素之一, 比如温度, 压力和环境因素. 所有的有机表面改性剂在一定温度下都会分解. 例如, 硅烷偶联剂的沸点根据类型在100 ~ 310℃之间变化. 因此, the decomposition 温度 or boiling point of the selected 表面改性剂 is preferably higher than the processing 温度 during application.

目前，表面改性工艺主要采用干法和湿法两种方法. 对于干燥过程, 不需要考虑其水溶性, 但是对于湿法, 必须考虑表面改性剂的水溶性, because only when it is soluble in water can it fully 联系 and react with the 粉末粒子 in a wet environment. 例如, 硬脂酸 can be used for dry surface modification of 碳酸钙粉 (either directly or after dissolving in an organic solvent). 然而, 湿式表面改性, 如果直接添加硬脂酸, it is not only difficult to achieve the expected surface modification effect (mainly physical adsorption), 而且利用率也很低. 过滤后表面改性剂损失严重, 滤液中有机物排放超标. 其他类型的有机表面改性剂也有类似的情况. 因此, 不能直接溶于水但必须在潮湿环境中使用的表面改性剂, 它们必须皂化, 预先氨化或乳化的，使它们能溶解和分散在水溶液中.

(4)价格和环境因素

最后，表面改性剂的选择还应考虑价格和环境因素. On the premise of meeting the application performance requirements or optimizing the application performance, 尽量使用较便宜的表面改性剂，以降低表面改性的成本. 同时要注意选择不污染环境的表面改性剂.

2. 表面改性剂的用量

从理论上讲, 在颗粒表面实现单层吸附所需的用量为最佳用量, which is related to the specific surface area of ​​the powder raw material and the cross-sectional area of ​​the 表面改性剂 molecule, 但这个用量不一定是达到100%覆盖时表面改性剂的用量. 用于无机表面涂层改性, 不同的涂覆速率和涂覆层厚度会表现出不同的特性, 比如颜色, 光泽, 等. 因此, the actual optimal dosage should be determined through modification tests and application performance tests. This is because the dosage of the 表面改性剂 is not only related to the dispersion of the 表面改性剂 during surface modification and the uniformity of coating, but also to the specific requirements of the application system for the surface properties and technical indicators of the 粉状原料.

湿法改性, the actual coating amount of the 表面改性剂 on the powder surface is not necessarily equal to the dosage of the 表面改性剂, because there is always a part of the 表面改性剂 that fails to react with the 粉末粒子 and is lost during filtration. 因此, 实际用量应大于实现单层吸附所需的用量.

3. 表面改性剂的使用方法

The method of using 表面改性剂s is one of the important components of the 表面改性剂 formula and has an important impact on the surface modification effect of powders. A good method of use can improve the dispersion degree of 表面改性剂s and the surface modification effect of powders. 正相反, improper method of use may increase the amount of 表面改性剂s used and the modification effect cannot achieve the expected purpose.

使用表面改性剂的方法包括制备, 使用两种以上表面改性剂时的分散和添加方法以及添加顺序.

(1)准备工作

表面改性剂的制备方法取决于表面改性剂的类型, 改造工艺和改造设备. 不同的表面改性剂需要不同的制备方法. 例如，对于硅烷偶联剂，硅烷醇粘合到粉末的表面. 因此, 达到良好的改性效果（化学吸附）, 加入前最好先水解. 使用前需稀释溶解的其他有机表面改性剂, 比如钛酸盐, 铝酸盐, 硬脂酸, 等.，相应的有机溶剂如无水乙醇、甲苯、乙醚、丙酮等. 是否应用于稀释和溶解. 用于有机表面改性剂，如硬脂酸、钛酸盐、铝酸盐等. 不直接溶于水的，用于湿改性工艺, 它们应该被皂化, 预先氨化或乳化成为可溶于水的产品.

(2)加法法

The best way to add 表面改性剂s is to make the 表面改性剂s and powders 联系 evenly and fully to achieve a high degree of dispersion of the 表面改性剂s and uniform coating of the 表面改性剂s on the particle surface. 因此, 最好采用连续喷涂或滴（加）法，与给粉速度挂钩. 当然, 只有连续粉末表面改性剂才能实现表面改性剂的连续添加.

无机表面改性剂的制备方法比较特殊, 需要考虑溶液pH等多种因素, 浓度, 温度, 和添加剂. 例如, 当二氧化钛被涂在白云母表面时, 硫酸钛或四氯化钛必须事先水解.

（三）加药顺序

当使用两种以上表面改性剂处理粉末时, 加入药物的顺序对最终的表面改性效果也有一定的影响. 确定表面改性剂添加顺序时, we must first analyze the role of each of the two 表面改性剂s and the mode of action on the powder surface (whether it is mainly physical adsorption or che云母l adsorption). 一般来说, 首先加入起主要作用且以化学吸附为主的表面改性剂, 而后加入以物理吸附为主、起次要作用的表面改性剂.

例如, 当偶联剂和硬脂酸混合时, 一般来说, 应先加入偶联剂，后加入硬脂酸, because the main purpose of adding 硬脂酸 is to enhance the hydrophobicity and lipophilicity of the powder and reduce the amount of coupling agent and the cost of the modification operation.