采用扫描电镜和图像分析表征帘式涂布涂层中的孔隙结构和粘土取向

造纸行业对高速帘式涂布非常感兴趣,因为帘式涂布可以不使用与网接触的机械计量设备而达到生产高涂布量的涂布纸和纸板的目的。该具有计量功能的涂布工艺避免了很多在计量过程中与高剪切相关的问题和由此带来的缺陷。而且,帘式涂布可以形成覆盖率良好且均匀的涂层。尽管越来越多工厂使用帘式涂布工艺,但对帘式涂布形成涂层的结构特征的研究却很少。在此次研究中,我们将会分析商业化生产的帘涂牛卡纸和纸板的涂层结构,并使用横截面图像分析技术来表征涂层结构。对帘式涂布纸的结构参数如孔隙尺寸分布、颗粒取向以及涂层厚度的均匀性进行了评价,并与传统的刮刀涂布和膜涂布纸进行了对比。结果表明,帘式涂布形成的涂层结构具有更松厚且更多孔等优点。粘土粒子在帘式涂层中分布更均匀,这也表明了帘式涂布具有良好的涂布覆盖率以及涂层厚度均匀性。

Characterization of the pore structure and clay orientation in curtain coating layers using SEM and image analysis

High-speed curtain coating technology is of interest to the paper industry because it can be used to coat paper and paperboard with high-solids colors without using a mechanical metering device that contacts the running web. This pre-metered coating process avoids the numerous problems, and consequently defects, associated with high shear conditions during metering. Moreover, curtain coating provides excellent coverage and uniform coating. Despite the growing use of this application process, however, very little research has been reported on the structural characteristics of curtain coating layers. In this study, we analyzed the coating structure of commercially produced curtain coated linerboards and papers. Coating structure was characterized using a cross section image analysis technique. Structural parameters of curtain coated papers, such as pore size distribution, particle orientation, and evenness of coating thickness, were evaluated and compared with traditional blade coated papers and iflm coated papers. Results showed that curtain coating provides a bulkier and more porous structure. Clay particles were aligned more randomly in curtain coating layers, which also showed good coating coverage and uniform coating thickness.