介绍 -The first steps in the pigment dispersion process are wetting 和 separation of the pigment. 然而，如果颜料分散不稳定， 絮凝1 (图. 1、2)会有结果. 絮凝 is a result of pigment 粒子 being attracted to each other to form loose aggregates that can be redispersed under mild shear.
当颜料颗粒相互强烈吸引时，粘结剂或 聚集 粒子的概率. 团聚体 (chemically bound pigment aggregates that are encapsulated by resin or wetting agent) cannot be readily redispersed. 絮凝 在油漆上应用低剪切能逆转吗. 絮凝 会对颜色的显现、光泽和遮盖有不利影响吗.
获得颜料稳定的两个主要机制是 空间 和 负责. 负责排斥, particle surfaces with like 负责s repel each other (more applicable to 水传播的 systems, 无花果. 4) w在这里as 空间 stabilization is a more common mechanism in solvent born 油漆s (无花果. 5). 适当稳定的颜料分散剂可以防止絮凝和结块.
Pigment dispersion in aqueous media uses the same principles as inorganic solvent media: that is, 合适的润湿, 颜料分散与稳定. 然而, the 表面张力 of water 和 high polarity makes it more problematic in wetting low polarity pigments. 在许多情况下, 水与颜料表面强烈地相互作用, 使颜料表面的分散剂不稳定. 确保颜料分散均匀稳定(消除颜料) 絮凝 除一种颜料外的其他颜料). 第三, the use of suitable wetting agents/表面活性剂s help to ameliorate differences in polarity 和 表面张力 色素之间的关系 色素不稳定.
氧化铁等无机颜料, 二氧化钛, 碳酸钙, 氧化锌, 和二氧化硅, 碳酸钙 和 barium sulfate 和 many other 填料 pigments have a very polar surface. 然而，仅用水通常不能充分湿润颜料表面. 因此，他们需要一个 表面活性剂 湿润和稳定分散.
也有许多颜料厂家供应 表面处理颜料 帮助颜料稳定. Many manufacturers modify the surface of organic pigment to increase polarity by adding a layer of inorganic oxide to improve pigment wetting.
颜料稳定化的讨论不可能不考虑其作用 色素沉淀 随着时间的推移. These factors all influence the degree of 色素沉淀 和 resistance to hard settling:
- 颜料分散的质量
- 颜料颗粒大小
- 吸油
- 形状
- 分布
- 色素密度
- 油漆粘度
A more complete discussion of the impact of each of these parameters on pigment hard settling 和 stability would require several articles to adequately describe. 然而, 无花果ure 6 provides a simplified relationship of pigment 和 油漆 parameters to 色素沉淀.
最后, the use of an appropriate thixotrope helps to build sufficient viscosity 和 a 净work structure that discourages pigment hard settling. A suitable thixotrope can improve resistance to hard settling by a few different mechanisms.
- 通过增加低剪切粘度来提高抗硬沉降能力
- Forms an association with the pigment to decrease the effective density of the settled pigment layer.
然而, one must be sure that t在这里 is acceptable compatibility between the thixotropic 和 dispersant. Thixotropes commonly used to promote soft settling include clays treated with quaternary ammonium compounds to provide higher organophilicity for solvent born 涂料. 凹凸棒石粘土可用于水性和溶剂型涂料, as the needle like clay 粒子 associate to increase viscosity that easily breaks down under shear. Other polymeric thickeners can be effective by increasing viscosity 和 by promoting readily redispersible soft settling, 如:
- 细粒二氧化硅
- 蓖麻油衍生物
- 基本的磺酸钙
- 胶态硅酸铝
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Ron Lewarchik，文章作者 & 十大靠谱彩票平台总裁
作为一个特约作家, 罗恩在涂料工业中撰写与配方有关的文章. 他还担任勘探者材料搜索引擎的顾问, advising on issues related to optimization 和 organization materials within the database.
