The Twenty-First Century Paper Grocery Bag

为了响应加拿大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购物袋以取代聚乙烯（PE）袋，为我们的森林产品行业提供新市场，同时改善环境影响。材料科学的挑战是巨大的。首先是水的敏感性。我们父母用的纸袋湿了就没用了。 加拿大北方软木硫酸盐浆（NSK）是世界上最强的木浆纤维之一，然而由NSK制成的湿纸是脆弱的，因为纸结构中的纤维-纤维接头在暴露于水时自发地分层。在上个世纪，化学工业已经开发出湿强度粘合剂，将纤维与纤维之间的接头粘合在一起，使其更具防水性。咖啡滤纸和墙纸是湿强化纸的日常例子。不幸的是，这类产品不可回收，失去了用纸替代塑料的绿色优势。这个回收问题的起源很容易解释。回收过程中的一个关键操作是再制浆步骤，其中纸张与水混合以释放单个纸浆纤维。防止湿纸中的湿纤维-纤维接头断裂的特性也抑制了再制浆过程中纤维的释放。 拟议工作的目标是开发新的纸张湿强度粘合剂化学品，以提供强大的湿或干纸，同时完全可回收利用。该方法是在粘合接头中建立不稳定的连接，其可以在回收过程中通过暴露于温和的裂解剂如还原剂或蛋白酶而裂解。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。 我们提出的解决方案涉及在纸浆厂经过改性以与新粘合剂配合使用的纸浆纤维。虽然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。 为加拿大重要资源的绿色转化开发新技术是培训加拿大年轻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.