The Twenty-First Century Paper Grocery Bag

针对加拿大计划加入其他国家禁止或限制使用一次性塑料的计划，拟议工作的总体目标是重新设计牛皮纸食品袋，以取代聚乙烯(PE)袋，为我们的森林产品行业提供新的市场，同时改善对环境的影响。材料科学的挑战是巨大的。最重要的是对水的敏感性。我们父母用的纸袋湿了就没用了。加拿大北方针叶木硫酸盐纸浆(NSK)是世界上最坚固的木浆纤维之一，但由NSK制成的湿纸很弱，因为纸结构中的纤维连接在暴露在水中时会自发剥离。在过去的一个世纪里，化学工业开发了湿强度粘合剂，将纤维-纤维接头粘合在一起，使它们更耐水。咖啡滤纸和墙纸是湿增强纸的日常例子。不幸的是，这些产品不能回收，失去了用纸取代塑料的绿色优势。这个回收问题的根源很容易解释。回收中的一个关键操作是再制浆步骤，在该步骤中，纸张与水混合，以释放单独的纸浆纤维。防止湿纸中的湿纤维-纤维接头断裂的特性，也抑制了纤维在再浆过程中的释放。这项拟议工作的目标是开发新的纸张湿强度粘合剂化学物质，以提供坚固的湿纸或干纸，同时完全可回收。方法是在粘合剂接头中建立不稳定的连接，在回收过程中，可以通过暴露于温和的裂解剂，如还原剂或蛋白酶酶来裂解这些连接。理想情况下，新的粘合剂应该是廉价的，基于可持续的原料，并涉及绿色化学转化。我们建议的解决方案涉及纸浆纤维，这些纤维已经在纸浆厂进行了修改，以与新的粘合剂配合使用。尽管加拿大永远不会成为纸袋的主要出口国，但我们是市场纸浆的主要出口国。世界上最好的纸袋可以用加拿大的特种纸浆制造。为加拿大一种重要资源的绿色转型开发新技术，是培训年轻的加拿大研究人员改善环境，同时为经济做出贡献的绝佳机会。

In response to Canada's plans to join other countries by banning or restricting the use of single-use plastics, the overall goal of the proposed work is to re-engineer the brown paper grocery bag to replace polyethylene (PE) bags, offering new markets for our forest products industries while improving environmental impacts. The material science challenges are significant. Foremost is water sensitivity. The paper bags our parents used were useless when wet. Canadian northern softwood kraft pulps (NSK) are among the strongest wood pulp fibers in the world, however wet paper made from NSK is weak because fiber-fiber joints in the paper structure spontaneously delaminate upon exposure to water. Over the last century the chemical industry has developed wet-strength adhesives that glue together fiber-fiber joints making them more water resistant. Coffee filters and wall paper are everyday examples of wet-strengthened papers. Unfortunately, such products are not recyclable, losing the green advantages of replacing plastics with paper. The origin of this recycling problem is easy to explain. A critical operation in recycling is the repulping step, where paper is mixed with water to release individual pulp fibers. The characteristics that prevent wet fiber-fiber joints in wet paper from breaking, also inhibit the release of fibers during repulping. The objective of the proposed work is to develop new paper wet-strength adhesive chemistries to give strong wet or dry paper, while being completely recyclable. The approach is to build labile linkages in the adhesive joints that can be cleaved during recycling by exposure to a mild cleavage agent such as reducing agents or protease enzymes. Ideally, the new adhesives should be inexpensive, based on sustainable feedstocks, and involve green chemical transformations. Our proposed solutions involve pulp fibers that have been modified in the pulp mill to work with the new adhesives. Whereas Canada will never be a major exporter of paper bags, we are a major exporter of market pulps. The best paper bags around the world could be manufactured with Canadian specialty pulps. The development of new technologies for the green transformation of an important Canadian resource is a wonderful opportunity for training young Canadian researchers to improve the environment while contributing to the economy.