摘要
本研究以高透气、高强度的长纤维薄页纸为基材,利用纤维素纳米纤丝(CNF)和烷基烯酮二聚物(AKD)乳液涂布制备一种高强度、高透光、柔软的高阻隔长纤维薄页纸。比较了CNF、羧甲基化改性纤维素纳米纤丝(C-CNF)、AKD等对涂布后纸张的抗张强度、透气度、水蒸气透过率、表面疏水性能等的影响。结果表明,C-CNF较CNF表现出更优异的性能,当涂布液浓度为1.0%(涂布量1.6 g/
关键词
随着现代运输以及物流行业的发展,日用商品的数量激增,促使包装材料逐渐朝着环保、轻量、多功能化方向发
纤维素纳米纤丝(CNF)是将天然植物纤维通过机械或化学加工处理成粒径为纳米级(1~100 nm)的纤维素纤丝。作为一种绿色生物质材料,CNF具备可降解、资源丰富、纸基相容性高等优
目前,提高CNF干燥后的柔韧性、均匀度以及疏水效果的方法主要是通过添加增塑剂或复合其他高分子物质等方式来完成,也有通过接枝改性来提高CNF疏水性或结合强度。Mousavi等
据报
原料:漂白硫酸盐针叶木浆(SBKP,15°SR);烷基烯酮二聚物(AKD)乳液(固含量1%,实验室自制);异丙醇、一氯乙酸、乙醇、NaOH、甲醇(均为分析纯,国药集团化学有限公司);长纤维薄页纸(19.5 g/
仪器:AFA-Ⅳ自动涂布机,广东东莞仪器有限公司;AH-PILOT 2015高压均质机,加拿大安拓思纳米技术有限公司;DHG-9140A电热恒温鼓风干燥箱,上海景鸿实验设备涌现公司;Bruker Vertex70傅里叶变换红外光谱仪,布鲁克科技有限公司;JEM 2100透射电子显微镜,日本电子珠式会社;Gurley 4320N透气度仪,美国格利精密仪器公司;JGW-300B接触角测定仪,承德市科承试验机有限公司;HT-101SC-1电子拉力试验机,东莞市宏拓仪器有限公司;马尔文Zeta电位和纳米粒径测定仪,英国马尔文帕纳科公司;Hitachi S-4800场发射扫描电子显微镜,日本。
取30 g SBKP(绝干浆)分散在去离子水中,使用乙醇进行洗涤、过滤;再用10 g氯乙酸和500 mL异丙醇的溶液浸渍浆料30 min;然后将浆料加入装有16.2 g NaOH的500 mL甲醇和2 L异丙醇的混合溶液中,持续羧基化反应1 h。反应后用去离子水洗涤30 min并过滤排出纤维。最后使用高压均质机对改性前后的纤维以及未改性纤维分别进行均质,在2%浆浓和1.65 MPa的操作压力下实现完全的均质,得到CNF及C-CNF。
以150 mm×200 mm的长纤维薄页纸原纸为基纸,分别将CNF与C-CNF按照涂布液浓度0.1%、0.5%、1.0%、2.0%,采用自动涂布机以单面涂布的方式进行涂布,涂布速度1.5 cm/s。然后在105℃的鼓风干燥箱中干燥20 min,取出纸张并以相同涂布速度在涂布纸上进行AKD乳液涂布(固含量1%),再次干燥20 min后即得到CNF、C-CNF涂布纸。
采用透气度仪,按GB/T 22819—2008对涂布纸的阻隔空气性能进行测试。在压力127 Pa条件下,测试空气流过单位面积的试样所需要的时间,每种样品测试不少于3次,结果取平均值。透气度按照
(1) |
式中,P为样品透气度,μm/(Pa·s);Q为纸张在127 Pa压力下的透气量,c
按照GB1037—88的杯式法进行测试。称取适量粒径为2 mm的无水CaCl2颗粒,在(200±2)℃的烘箱中干燥2 h以上。冷却后,将1 g CaC12放入洁净的50 mL离心管中并于底部铺平。利用涂布纸张分别对离心管进行密封,在分析天平上称量质量。随后每24 h称量1次,直至离心管的整体质量基本稳定;通过每种涂层的3个样品分别计算水蒸气透过率(WVP),各纸张分别测试3次,结果取平均值。WVP按照
(2) |
式中,Δm为CaCl2的质量变化量,g;d为涂层厚度,m;A为涂布纸在离心管口的覆盖面积,

图1 CNF与C-CNF的FT-IR图
在CNF、C-CNF不同涂布液浓度涂布后,涂布量检测结果见

图3 不同涂布液浓度下的纸张抗张强度

图4 不同涂布液浓度下的纸张透气度

图5 不同涂布液浓度下的纸张水蒸气透过率

图6 不同涂布液浓度下的纸张接触角
将CNF与C-CNF进行多次涂布,
对不同涂布次数的纸张抗张指数进行检测,结果见

图11 涂布前后纸张的SEM图
本研究通过对纤维素纳米纤丝(CNF)进行羧甲基化学改性制得C-CNF,再配合AKD乳液涂布于长纤维薄页纸表面,制备一种高强度、高透光、高阻隔长纤维薄页纸。对涂布液浓度、涂布次数对纸张疏水性、阻隔性及透明度等性能的影响进行探讨。
3.1 红外光谱分析表明,CNF内部结构发生变化,完成了羧甲基基团的接枝。透射电子显微镜观察发现,CNF形貌变化、平均长度降低,生成大量纳米级细小纤维呈交缠网络状分布,也证明了羧甲基改性的完整进行。
3.2 CNF和C-CNF涂布纸的性能检测表明,C-CNF涂层具有更高的抗张强度、空气阻隔性,其涂布液浓度1.0%(涂布量1.6 g/
3.3 多次涂布对于提高纸张的空气阻隔性能有一定效果,但通过多次涂布来提高纸张力学性能及疏水的作用十分有限。
3.4 C-CNF涂布纸的表面SEM分析表明,C-CNF涂布对AKD分子具有留着作用,其更加致密的纤维网络结构进一步减小的纸张孔隙,从而得到良好的疏水性、阻隔性和柔韧性。
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