【作者】 黄俊；

【导师】 杨仁党；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2010， 硕士

【摘要】 近年来,随着我国经济结构的调整发展,商品包装领域对涂布白板纸的需求在数量和质量上也大大提高了。国内的生产厂家在完成了向刮刀涂布工艺转化的过程之后,希望能研制合适的涂料来满足生产和市场的要求,以最低的成本获取最大的市场和经济效益,所以在制备刮刀涂布涂料时必须朝着“高浓低粘”的方向进行,即涂料液浓度要求为60 %以上,同时具有剪切稀化的流变性,在较高剪切速度下有较低的粘度。流变助剂在涂料配方中起着改善涂料流变性能的作用,而涂料流变性是影响涂布加工纸质量的重要因素之一。本论文以造纸涂料的流变助剂为主要研究对象,全面分析并比较了流变助剂羧甲基纤维素(CMC)、氧化淀粉、丙烯酸碱润胀乳液(L255)和聚乙烯醇PVA对涂料流变性及涂层表面性能的影响。经实验研究发现,CMC和L255对典型工厂涂布配方的流变调节作用影响是明显的,中低剪切表观粘度都能在剪切速率范围内下降两个数量级左右,但L255对涂料的粘度增加作用要强些,因此可以用较低量的L255便达到与较高用量CMC相似的效果。用拟合公式对四种流变助剂的各流变曲线进行拟合,中低剪切条件下涂料呈现明显的剪切稀化特性,用Cross模型进行拟合,在高剪切条件下,用H-B模型进行拟合,但是四种流变助剂的涂料在超过一定的剪切速率后粘度有程度不一的增加现象,尤其是淀粉和PVA的涂料剪切增稠最为明显,它们更多时候是作为辅助胶黏剂而非良好的流变助剂使用。涂料的线性粘弹区都在3%以内,在此区域内进行频率扫描,L255的粘弹模量与PVA的接近,淀粉的模量最低。随着频率的增加,弹性模量呈现先上升后稳定的趋势,而粘性模量则相反变化,并且涂料的相位角都没有超过15°,涂料的弹性特性要强于粘性特性。用SEM和AFM等分析手段,对涂层表面结构的表征以及涂层表面性能进行了分析,添加流变助剂后,在高倍放大状态下可以看到涂层颜料粒子的堆积状态,涂层存在着大小不一的空隙,CMC和L255能赋予涂层较好的光泽度和平滑度,但是淀粉和PVA则能保证涂料有较好的油墨吸收性和较高的拉毛强度。因此,在高浓涂料中,若是以GCC和高岭土为主要颜料,则要控制流变助剂的用量,添加量不能太高以免引起流动性能的恶化,同时根据对涂层表面性能的不同要求,选择合适的流变助剂及其用量,调整涂料配方。更多还原

【Abstract】 Recently, with the rapid development of economy, the high quality requirements to coated white paper and paperboard are increased dramatically in package decorating field. Manufactures wish to seek suitable chemicals with better quality to prepare coating colour so that they can meet customers’desiration and also obtain market and economic profits, just after they had completed the adjustments of coating process. So, the key point is how to adjust the coating formulation wih high concentration and low viscosity. That’s to say, concentration surpass 60% and has perfect shear-shinning characteristic. The function of rheological agnets in the process of coating colour formulations is improving rheological characteristics,which is one of the important factors work on the quality of coated paper.In this research, some normal used agents including CMC、PVA、Starch and L255 are discussed comprehensively. The coating colors were prepared by adding different rheological angents and changed their dosage separately, coating layer physical properties, surface layer structure characterization and rheological performance were investigated. The effects of rhological agents on rheological properties of paper coating colors were studied with an attempt to offer technological and theoretical support for this field of research.The relationship between viscosity and shear rate was researched by AR550 rheometer, which also could help denifite the linear viscoelasticity zone of coating colours. The results showed that the coating colour has markedly shear-thinning performance in low-medium shear condition ,also Cross equation could be used to fit the curves.Which need to be noticed was that L255 had more intense effects than CMC, just added into typical formula, while H-B model is appropriate for overfitting the relationship between high-shear viscosity and shear rate, but unlike with low shear curves, beyond a certain shear rate, all coating formulations contained with these four style rheological agents, there is shear-thickening. Especailly Starch and PVA have negative effects on the coating operation. L255 can make coating web have similar viscoelastic properties, while starch has the lowest modulus in spite of its highest doasage. The storage modulus is increased firstly then tend to gently with increasing frequency,which is contrast to shear loss modulus.There are no phase angles exceed 15°,which indicate that the elastic character of the color is more pronounced than the viscous character.According to related national standards ,combined the surface layer characteristics by SEM and AFM with coating layer performance analysis,we can see the stacking among compositions clearly in high magnification, pigments interlaced with each other and voids exist. For CMC and L255, they can provide better smoothness and gloss, while Starch and PVA can obtain preferable IGT and ink absorbancy.更多还原