表面施胶水性聚氨酯对箱纸板耐折性能的影响及作用机理

通过表面施胶不同特性（非离子型和阳离子型）的水性聚氨酯（WPU），研究了WPU施胶对箱纸板耐折性能的影响及作用机理。结果表明，WPU成膜性能、纸张结构和施胶工艺，对箱纸板耐折性能均有显著影响。非离子型的WPU-A膜强韧，拉伸强度达7.11 MPa；阳离子型的WPU-B膜中软易黏，拉伸强度很低。对于含水量低的纸张，在同等实验条件下，成膜柔韧、拉伸强度高的WPU施胶，有利于提高箱纸板的耐折性能。纸张结构越疏松，WPU施胶对其耐折度的提升幅度越大，且对于结构紧实的纸张，WPU膜强度与纸张强度显示出协同作用。对比4种不同施胶工艺所得箱纸板，干燥后双面施胶箱纸板的耐折性能提升效果最佳。

Effect and Mechanism of Waterborne Polyurethane on the Folding Endurance of Liner Board by Surface Sizing

The effects and mechanisms of waterborne polyurethane （WPU） with different charactristics （non-ionic and cationic） surface sizing on the folding endurance of liner board were studied. The results showed that the WPU film-forming properties， paper structure， and sizing process had a significant impact on the folding endurance of liner board. The non-ionic WPU-A film was highly elastic and resilient， with a tensile strength of 7.11 MPa， while the cationic WPU-B film was soft and sticky， with low tensile strength. For paper with low water content， under the same experimental conditions， sizing by WPU with high flexibility and tensile strength was beneficial to improve the folding resistance of liner board. The greater the enhancement of folding endurance by WPU sizing for the looser the paper structure， and the WPU film strength and paper strength showed synergistic effects for tightly structured paper. Comparing the liner board made by four different sizing processes， the best folding endurance improvement was achieved by the double-sided sizing liner board after drying.