The Twenty-First Century Paper Grocery Bag

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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.