Green Packaging: The Only Way to Plastic Packaging

The harm caused by plastic packaging waste has aroused widespread concern in the society. How to strengthen the scientific management and use of plastics, recycle plastics, recycle and use waste plastics as much as possible, and gradually develop and apply degradable plastics are urgent tasks.

Recycling recycling

For plastic packaging, such as film food packaging bags, shopping bags, garbage bags, beverage bottles, fast food boxes, etc. due to the short life cycle, the amount of waste is more worth paying attention. Among them, polyester films and polyester bottles are the most widely used varieties. Discarded polyester films and polyester bottles can be recycled, reused, and reused in two ways.

1. Physical method: After the clean PET waste film or waste PET bottle is crushed, it is granulated through an extrusion granulation equipment into a regeneration slice and used directly in a new material. Physical methods Re-granulated PET chips have no change in chemical structure but only a slight reduction in molecular weight and do not affect use. The twin-screw extruder and the compression-densifying and extruding granulator are the equipments used for recycling granulation. The characteristics of these two recycling granulation equipments are that they need not be dried before processing and they can be fed directly with clean crushed materials. The extruder melt-plasticized, vacuum exhaust through the exhaust port, the melt through the porous die can create a regular shape, uniform size PET particles, and the viscosity is reduced, can be recycled. Similarly, side scraps such as BOPP, CPP, and PE films can also be reused after regranulation using the above method. This saves resources and protects the environment.

2. Chemical methods: Still using polyester as an example, alcoholysis can be used. Because polyester is based on PTA and EG as the main raw material, the polymer obtained by esterification and polycondensation reaction. Because the polycondensation reaction is a reversible reaction, under certain conditions, the PET edge waste can use the alcoholysis method to recover the clean PET crushed material, and use methanol or triethylene glycol to depolymerize the PET into monomers or partial depolymerization under the action of a basic catalyst. The oligomers are then repolymerized with the monomers or oligomers into PET resin for reuse in packaging materials or for the manufacture of polyester staple fibers.

Development of degradable plastics

Degradable plastic refers to a kind of plastic whose chemical structure changes, long-chain macromolecules are destroyed, and the molecular weight degrades to low-molecules in a certain time and under a specific environment. The biodegradable plastic packaging material not only has the functions and characteristics of traditional plastics, but also can be decomposed and reduced in the natural environment through the action of ultraviolet light in sunlight or microorganisms in soil and water after the service life is completed, and finally be non-toxic. The form re-enters the ecological environment.

There are currently three types of degradable plastics, which are biodegradable plastics, photodegradable plastics and light/biodegradable plastics. Biodegradable plastic is one of the most promising ones. At present, the world's biodegradable plastics are mainly made of aliphatic polyester or aliphatic polyester mixed starch. Aliphatic polyesters mainly include polycaprolactone (PCL), polybutylene (PBS) and its copolymers, polylactic acid (PLA) produced from renewable resources, and polyhydroxybutyric acid produced by microorganisms ( PHB) etc.

Of particular interest lately is the use of polylactic acid to make biodegradable plastics. Polylactic acid is a macromolecule material that is produced through production of lactic acid products through modern biotechnology in important agricultural economic crops (corn, etc.) and then undergoes special polymerization reactions. It is also called corn plastic. Nature Works Inc. of the United States has developed a "two-step method" of corn plastics. Its strength and plasticity have basically reached the level of chemical plastics. The company plans to use the opportunity of the 2008 Beijing Olympic Games to cooperate with Chinese companies to accelerate the promotion and application of corn plastics in the Chinese market. In addition, NEC Corporation of Japan developed bio-degradable plastics for electronic applications. The material contains polylactic acid and 20% natural fibers called Kenaf. This new material is used for electronic product packaging, that is, encapsulating silicon chips.

In China, biodegradable plastics have also been greatly developed. It is understood that Harbin Wei Lida Company has signed a contract with German Wood Company to introduce advanced polylactic acid production technology. By 2007, the project will produce 10,000 tons of polylactic acid annually. This year, Shanghai Tongjieliang Biomaterials Co., Ltd. will formally produce "corn plastics" in Shanghai, and it is expected that the annual output will be more than 1,000 tons.

In short, vigorously develop and promote the use of biodegradable plastics, and the development of green packaging is the only way for plastic packaging.

Jiangyin Jinzhongda New Material Co., Ltd. Feng Shuming
Source: Jiagong Machine Grid