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。本研究尝试了粉末涂料刷涂技术，采用电荷控制剂（CCA）（大部分为有机材料）对粉末涂料进行摩擦起电，以形成高质量、高转移效率的涂层。首先，考察了CCA对涂料粉末摩擦起电的影响。为此，将CCA掺入聚合物层中，并通过级联法测量具有聚合物涂层的铁氧体粉末的摩擦带电特性。不含 CCA 的苯乙烯-丙烯酸聚合物片材对铁氧体粉末产生轻微的负摩擦电荷。当聚合物中掺入正的CCA时，铁氧体粉末的负摩擦电荷增加，而负的CCA则使铁氧体粉末的摩擦起电向正方向移动。接下来，将CCA掺入摩擦带电动力喷枪中，检查涂料粉末的摩擦带电的变化。可以证实涂料粉末的摩擦起电是由CCA控制的。然而，大多数有机CCA在相对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。如果我们使用金属氧化物粉末代替有机CCA，我们可以解决CCA分解的问题。然而不幸的是，金属氧化物的电荷控制能力比通常的有机CCA弱。总之，CCA应用于粉末涂料改善了涂料粉末的摩擦带电，从而改善了涂层。

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.