Research progress, application status and prospects of paper-based packaging materials
The application history of packaging materials can be traced back to the early days of human civilization and is a vital part of the packaging industry. With the increasing environmental pollution and the increasing awareness of people’s environmental protection, low-carbon, environmental protection and energy saving have become the focus of global attention. The green R&D and application of packaging materials have also become a hot spot of people’s attention. In recent years, related research and industrialization The application is developing rapidly. On January 19, 2020, my country's National Development and Reform Commission and the Ministry of Ecology and Environment issued the "Opinions on Further Strengthening the Treatment of Plastic Pollution" (hereinafter referred to as the "Opinions"), which was called the new version of the "Plastic Restriction Order" by the industry. This article systematically discusses the research progress and application status of paper-based packaging materials from the perspective of the new opportunities and challenges faced by the packaging industry and the paper industry under the new version of the “plastic restriction order”, especially the recent developments in paper-based packaging materials. The research and application of hot materials-paper-based composite packaging materials and pulp molded packaging materials provide research directions and ideas for expanding the application fields of paper-based packaging materials and developing innovative technologies and industrialization of functional paper-based packaging materials.
1. Overview of paper-based packaging materials
Paper-based Packaging Material (Paper-based Packaging Material) refers to a class of natural plant fiber-based materials used for packaging purposes. Paper-based materials are the most familiar, earliest-used, and most widely used green environmental protection materials. Currently, paper-based materials widely used in the packaging field include traditional packaging paper and cardboard materials, new functional paper-based packaging materials, and paper-based composite packaging. Materials and pulp molding packaging materials, etc. In recent years, with the rapid development of emerging businesses such as e-commerce, express delivery, and food delivery, and the country’s construction and encouragement of rural logistics, the pollution caused by plastic packaging products has received more and more attention. "The importance and urgency of ", this has brought new opportunities for the development of the paper-based packaging materials industry. But at the same time, due to the limitations of the inherent properties of natural plant fiber materials, paper-based packaging materials have encountered new challenges in the process of replacing plastic packaging materials.
In the traditional pulping and papermaking industry, paper-based materials are given the ability to resist liquid penetration and diffusion through the treatment of sizing in the pulp or on the surface. With the gradual expansion of paper-based materials in the packaging industry, traditional sizing technology has long been unable to meet the performance requirements of paper-based materials in certain fields. According to the requirements of the packaged products on packaging materials, such as the cushioning performance, surface performance, barrier performance of paper-based packaging materials, etc., researching different processing techniques and technologies to improve and enrich the performance of paper-based materials to meet the needs of different fields has become paper Trends in the functionalization of basic packaging materials.
2. Research and application progress of paper-based composite packaging materials
Paper-based composite packaging material refers to the use of packaging paper or cardboard as the base material, and other materials and the paper base material are formed into a multifunctional composite packaging material through a certain processing technology. Paper-based composite packaging materials are based on various material properties, complementing each other's strengths, and make full use of the excellent barrier, heat preservation, antibacterial properties of metal materials, polymer materials and other substrates, as well as the ecological and environmental protection properties of natural plant fibers. They generally include paper-based layers, Functional layer and heat seal layer. According to the type and category of composite technology and auxiliary materials, paper-based composite packaging materials can be divided into paper/plastic/aluminum composite packaging materials and paper/polymer composite packaging materials.
Paper/plastic/aluminum composite packaging materials emerged around 1980. With the introduction of packaging equipment, their domestic applications have developed rapidly. However, due to the wide variety of raw and auxiliary materials used in paper/plastic/aluminum composite packaging materials, it is difficult and costly to recycle. Most of the waste paper/plastic/aluminum composite packaging materials are treated as worthless waste. Cause waste of resources and environmental pollution. Based on the pressure of environmental protection and resource conservation, people began to reconsider the paper/plastic/aluminum composite packaging technology from the source of materials to the impact of the entire process of processing and molding and disposal on the environment.
Paper/polymer composite packaging material is a type of composite material that combines paper-based materials with different properties and polymer materials through a certain process. The types of polymers used in paper/polymer composite packaging materials can be divided into two categories according to environmental performance: non-biodegradable plastics and biodegradable polymers (paper-based biopolymer composite packaging materials). The research of paper-based biopolymer composite packaging materials focuses on the performance modification and type expansion of biopolymers, the performance improvement and optimization of packaging materials based on the needs of packaging content, the research of coating composite technology, paper-based materials and biopolymerization The interface compatibility of the material coating, etc. Polylactic acid (PLA) is a new type of aliphatic polyester biopolymer with the most promising applications. However, the current polylactic acid paper-based composite materials have insufficient durability and barrier properties, and the cost is higher than that of traditional plastic coated paper-based composite materials. When used as packaging materials, they will still encounter this or that. Practical problems, there are still many problems that need to be overcome in order to realize the real industrial application.
3. New paper-based packaging materials: pulp molded products
The pulp molding industry originated in Europe in the 1930s. The molding technology was first applied to the plastics industry as a molding processing technology. By combining with papermaking technology, a three-dimensional papermaking technology using natural plant fiber materials was derived— -Pulp molding. Pulp molded products have the characteristics of non-standard, small batch, and small quantity, which brings great challenges to the development and use of pulp molded products production equipment. In the sixty to seventy years of development of pulp molded products, the focus of related research work has also shifted from how to reduce production costs and expand the scope of product application to a deeper level of pulp fiber raw material performance optimization, research and development of additives, pulp and its molds. The measurement of the physical and chemical characteristic parameters of plastic products, the research and development of special molding equipment, the structural design of pulp molded products, and the optimization of production and processing parameters.
Pulp molded packaging products have always had problems such as insufficient apparent smoothness and easy chipping. The research on the surface properties of pulp molded products at home and abroad is still in the initial stage, and the research on improving the surface properties of products from the aspects of raw materials, additives, surface treatment technology, etc. has just started. Due to the late development of the pulp molding industry, there are few and simple researches on its special barrier properties. However, because the main raw material of pulp molding products is pulp fibers of various properties, which are natural fiber cellulose-based materials, Relevant research can be based on the progress of natural fiber cellulose-based materials in terms of resistance to liquid water and fluid penetration, gas diffusion, and grease impregnation, in terms of barrier mechanism, barrier technology, barrier additives, etc.
Pulp molded products have been developed in our country for more than 30 years. Especially with the help of the "plastic limit" decree, it has become more and more widely recognized and used in the fields of environmental protection industrial product packaging and disposable environmental protection tableware. However, pulp molded products Some of the common technical problems of the pulp molding industry still need to be solved by research and development, such as mold making, surface modification technology of pulp molded products, slurry preparation research, high energy consumption in the production process, and lack of uniform industry standards, etc., which require upstream and downstream of the pulp molding industry The industry chain researches and solves key problems together. With the widespread application of molded pulp products in the field of high value-added packaging, how to integrate smart packaging technology into the production process of molded pulp packaging materials, and apply nanomaterials or high-strength fiber materials to the production of pulp fiber raw materials Pulp molding packaging materials with special properties are an important research direction and development trend of the industry in the future.
Paper-based packaging materials are an important material for the cross-conciliation of the two pillar industries of the national economy-the paper industry and the packaging industry. In recent years, the types of finished paper-based packaging materials have become more and more diverse based on the expansion of application fields. For example, in the field of food delivery, disposable plastic tableware and packaging have caused increasing environmental pressure. In order to support the construction of a green supply chain in the food delivery industry, the "Green Mountain Project Special Fund" jointly initiated by the China Environmental Protection Foundation and Meituan Waimai set up a "Recommended Paper Delivery Packaging Directory and Innovative Product Incubation Project" to help paper packaging products be sold in takeaway The promotion and use of the field. With the continuous extension of the application scenarios of paper-based packaging materials, the pressure of environmental protection and resource-saving economy, and the increasing requirements of people for packaging materials, more and more challenges are presented to paper-based packaging materials. Generally speaking, under the impetus of my country's new version of "plastic restriction order" at the beginning of 2020, the paper-based packaging industry has not only ushered in new development opportunities, but also faced new challenges. Paper-based packaging materials should increase innovation, develop mature alternatives that are equivalent to or close to the widely used non-degradable plastic products in terms of performance and cost, and launch functional products that meet market needs.