- Developing pollution-free technology by using supercritical fluids -


As demands for environmentally friendly industries have been increasing, the plastic industry, known as a polluter generating noxious chemicals, is developing pollution-free technology using supercritical fluids.


Supercritical fluids are materials obtained by increasing the temperature and pressure of fluid/gas over the critical point. The process facilitates the melting of plastic. The resulting product is used as a solvent in the plastic industry, and is harmless to humans and to the environment.


The most common procedure uses a supercritical fluid of carbon dioxide as a solvent. The fluid is harmless to humans and to the environment. After obtaining the chemical reaction needed or the product shape required by melting plastic, carbon dioxide can be restored to its original gaseous state by lowering the pressure or temperature. By alternating noxious organic solvents through this procedure, an environmentally friendly chemical procedure can be developed.


Technologies related to plastic industry using supercritical fluids can be divided into three areas.

1.
Reaction media technology, where supercritical fluid is used as the solvent in chemical reactions necessary for synthesizing, dissolving and enhancing plastic.

2.
Restoration and separation technology, such as recycling waste plastics, separating noxious & foreign materials, and purifying plastic

3.
Plastic processing technology, such as manufacturing microcellular foam, particle & high-functional complex, and high-efficiency injection molding


There were only 3~4 patent applications a year related to supercritical fluids before 1995. Between 1996~2001, the number was 8~11 a year. Between 2002~2004, an increasing trend reveals 13~20 annual applications. The interesting point is that although there were almost no applications made by domestic applicants until 1997, the number of domestic applications has increased rapidly since 1997. This trend shows the increased interest towards environmentally friendly technology by the domestic plastic industry.


Prior to 1995, patent applications were focused on the use of plastic, such as coating and spraying plastic materials using supercritical fluids. Recent patent applications are more focused on polymerization, separation and processing technology related to high-functionality and recycling of plastic products. Patents applications after 1995 can be broken down by 33 reaction media technologies (35%), 18 restoration and separation technologies (19%) and 39 processing technologies (42%). Especially, patent applications are being filed for manufacturing plastic particles measured in nanometer units using supercritical fluids as reaction solvents, dissolving waste plastic using supercritical fluids, separating foreign materials to restore plastic, and manufacturing microcellular foamed plastic with outstanding solidity using supercritical fluid as plastic solvents instead of noxious chemical blowing agents. .



In this time when companies recognize their social obligations to protect the environment, the development of pollution-free technology using supercritical fluids in the plastic industry has great potential, not only from an industrial aspect, but also from social aspects. By replacing noxious materials, such as organic solvents, with environmentally friendly solvents, companies create high-functional products, and technology related to supercritical fluid accomplishes both goals of environment protection and industrial development. By leading environmentally friendly plastic technology globally, and by continuously developing related technologies, the domestic plastic industry is positioned to create new value-added opportunities.