彩涂板背面漆面起什么作用，哪些涂料可以做底背面漆

彩涂板对背漆的要求不高，但与底漆相比，对耐候性和柔韧性仍有一定的要求。后漆涂在线圈背面，主要保护线圈，提供外观和耐久性。要求漆膜具有良好的耐腐蚀性、耐划伤性、附着力和可加工性，但无装饰性和室外耐久性要求。

彩涂板常用的背涂料有三种：环氧型、醇酸型和聚酯型。由于前两种材料的耐久性差，目前还没有得到广泛的应用。目前，大多数是氨基聚酯型。聚酯后涂层的成分与面漆基本相同。
目前，彩色涂覆板的大部分背面涂层直接涂覆在预处理的基材上，通常没有底漆，或在5UM底漆之后，可以涂覆背面涂层。背胶可根据其结构和用途分为三类。
（1）防腐性能要求高。基材的背涂结构为底漆和背漆。此时的背胶主要起到保护作用，并且可以与同一品种的面漆配套使用，但性能要求低于面漆，只要耐划伤性、附着力和加工性满足要求。氨基醇酸树脂可广泛用作背光涂料的成膜树脂，如大豆油改性短油醇酸树脂和三聚氰胺树脂背胶。
（2） 彩涂板背面不涂底漆，只涂一道背漆。此时，它起着底漆和后涂层的双重作用。除了抗划伤性、附着力和后涂层的可加工性外，还必须具有良好的耐腐蚀性。成膜物质一般可用于环氧氨基、环氧聚酯和聚酯聚氨酯等。为了改善背漆的防腐性能，除了着色颜料外，还应在涂料中添加防腐蚀颜料。

（3）当预涂覆金属线圈主要用于制备泡沫夹芯板时，背衬涂料还必须适应夹芯板的制造工艺，除了对底漆或基材要求良好的附着力和机械性能之外。例如，直接注入发泡工艺要求背衬涂料与泡沫材料具有良好的粘合性；泡沫芯板粘合工艺；所需的背衬涂料与所用粘合剂相匹配。成膜材料通常可用于环氧聚酯或聚酯聚氨酯。为了保证在生产中缠绕后的夹层材料具有足够的粘附性和抗粘连性，不使用助剂和表面滑动促进剂来减少背胶中漆膜的表面张力，并且应使用漆膜本身的硬度来防止卷绕粘附。

The requirement of color coated board for back paint is not high, but compared with primer, it still has certain requirements of weatherability and flexibility. The back paint is applied on the back of the coil, which mainly protects the coil and provides the appearance and durability. It is required that the paint film has good corrosion resistance, scratch imitation resistance, adhesion resistance and processability, but no decorative and outdoor durability requirements.
There are three kinds of common back coatings for color coated panels: epoxy type, alkyd type and polyester type. Because of the poor durability of the first two, they are not widely used now. At present, most of them are amino-polyester type. The composition of polyester backcoat is basically the same as that of topcoat.
At present, most of the back coatings of color coated boards are directly coated on the pretreated substrates, usually without primer, or after 5um primer, back coatings can be applied. Back paints can be classified into three categories according to their construction and use.
(1) The anticorrosion performance is required to be high. The structure of the back coating of the substrate is primer and back paint. Back paints at this time mainly play a protective role and can be used with the same variety of topcoat, but the performance requirements are lower than topcoat, as long as scratch resistance, adhesion resistance and processability meet the requirements. Amino alkyd resins can be generally used as film-forming resins for back paints, such as soybean oil modified short oil alkyd resins and melamine resin back paints.
(2) No primer is applied on the back of the color-coated board, only one back paint is applied. At this time, it plays a dual role of primer and backcoat. In addition to scratch resistance, adhesion resistance and processability of backcoat, it must also have good corrosion resistance. Film-forming substances can be generally used in epoxy amino, epoxy-polyester and polyester-polyurethane, etc. In order to improve the anticorrosive property of back paint, besides coloring pigments, anticorrosive pigments should be added to the paint.
(3) when the pre coated metal coils are mainly used to prepare foam sandwich panels, the backing paint must also be adapted to the manufacturing process of the sandwich panels in addition to requiring good adhesion and mechanical properties to primers or substrates. For example, the direct injection foaming process requires the backing paint to have good adhesion to the foamed material; the foam core board bonding process; the required backing paint is matched with the adhesive used. Film-forming materials can be generally used in epoxy-polyester or polyester-polyurethane. In order to ensure enough adhesion to sandwich material and anti-adhesion after winding in production, no auxiliaries and surface sliding enhancers can be used to reduce the surface tension of paint film in backcoat, and the hardness of paint film itself should be used to prevent winding adhesion.