Development of Tribocharging Powder Coating System for Top-Coating of Automobile Bodies

粉末涂料被认为是一种不含挥发性有机化合物的技术。采用以有机材料为主的电荷控制剂(CCA)对粉末涂料进行摩擦充电，形成高质量、高转移效率的涂层。本文首先考察了CCA对粉末涂料摩擦荷电的影响。为此，将CCA引入到聚合物层中，并用串联法测量了聚合物包覆铁氧体粉末的摩擦荷电特性。不含CCA的苯丙聚合物片材对铁氧体粉末略带负电荷。在聚合物中加入正的CCA后，铁氧体粉末的负摩擦电荷增加，负的CCA位移是铁氧体粉末正方向的摩擦荷电。然后，将CCA加入到带摩擦荷电的喷枪中，考察了涂层粉末摩擦荷电的变化。可以肯定的是，涂层粉末的摩擦荷电是由CCA控制的，但大多数有机CCA在较低的温度下容易分解，这限制了CCA在粉末喷枪中的实际应用，因为喷枪通常是通过模压制造的。如果用金属氧化物粉末代替有机CCA，就可以解决CCA的分解问题。然而，金属氧化物的电荷控制力弱于通常的有机CCA。总之，CCA在粉末涂料中的应用改善了涂层粉末的摩擦荷电，从而改善了涂层的性能。

Powder coating is known as a technique, which is free from volatile organic compounds. Brushing-up of powder coating technique has been tried by using charge control agent(CCA), most of which are organic materials, to tribocharging powder coating to form coating layers with high quality with high transfer efficiency in this studyFirst, effects of CCA on tribocharging of coating powders was examined. For that purpose, CCA was incorporated into a polymer layer, and tribocharging characteristics of a ferrite powder with polymer coating by the polymer was measured by cascade method. The CCA free styrene-acrylic polymer sheet tribocharges the ferrite powder slightly negatively. When a positive CCA is incorporated into the polymer, the negative tribocharge of the ferrite powder increases, and a negative CCA shifis the tribocharging of the ferrile powder in the positve direction.Next, CCA was incorporated into a triobcharging power spray gun, and change in the tribocharging of coating powders was examined. It could be confirmed that the tribocharging of coating powders was controlled by CCA.However, most organic CCAs decompose easily at relatively low temperature, which limits practical application of CCA to powder spray gun, because spray guns are usually fabricated by modlding.If we use metal oxide powders instead of organic CCAs, we can clear the problem of decomposition of CCAs. Unfortunately, however, charge control power of metal oxides are weaker than usual organic CCAs.In conclusiron, application of CCA to powder coating improves the tribocharging of coating powders, bringing about improvement of coated layers.