Green Packaging: Environmental Issues in PVC (I)

Abstract: Polyvinyl chloride (PVC) has been widely used in industrial and daily life products. The harm of PVC to the environment and human health has always been one of the focuses of debate. This article analyzes in detail the various environmental issues during the life cycle of PVC, and proposes some measures to reduce the impact on the environment. 

Keywords: 〖HTK〗 PVC Environmental Impact Countermeasures Recommendation

1 Introduction

The European Commission has made a comprehensive analysis of the impact of PVC on the environment and human health. It is recommended in the "Discarded Vehicle Indicators"; the European Commission will study the environmental issues of waste PVC, and rethink its policies based on research results. In the proposal, The committee will propose recommendations for the use of PVC, including on automobiles, based on this work. 

In the recent decades, PVC has been the focus of debate. The impact of PVC on human health and the environment, from scientific, technical and economic analysis, there are different views. Many EU member states have adopted methods to study the special issues of the PVC life cycle. These methods are not uniform, and some of them may have problems that are constrained by internal market mechanisms. The comprehensive approach is necessary to analyze the life cycle of PVC and adopt appropriate methods to ensure a high degree of protection of human health and the environment and to adapt the internal market mechanism functions. 

The two goals of this document are: Firstly, on the basis of science, analyze various environmental issues during the PVC life cycle, including the impact on human health. Second, from the point of view of sustainable development, take some measures to reduce these impacts. 

2 PVC industry and its products

2.1 PVC material and its application

Polyvinyl chloride (PVC) is a polymeric material (or resin) that is made up of multiple superpositions of monomeric vinyl chloride (VCM) of the formula CH2-CHCI. In addition to chlorine, PVC has the same structure as polyethylene, with chlorine accounting for 57% of pure polymer resin in PVC, and 35% of chlorine comes from electrodialysis of potassium chloral. 

Pure PVC is a granular material, high mechanical hardness, very good climate change, waterproof, anti-chemical properties and is an electrical insulating material. However, heat and light are relatively unstable, heating and ultraviolet light cause the loss of chlorine in hydrogen chloride (HCL), which can be avoided by adding stabilizers, which are usually made of metal salts such as lead, antimony, calcium, cadmium, or organotin. Compound composition. 

The mechanical properties of PVC can be changed by mixing low molecular weight compounds in the polymer matrix. Addition of this so-called plasticizer makes various materials have important variable properties, making PVC have a wide range of uses. This plastic material is an organic salt, mainly phthalates and oxalates. The main applications are rigid PVC (2/3 of total usage) and flexible PVC (1/3 of total usage).

The following table shows the percentage of PVC used in Europe. The life cycle range of PVC is used as a structural material. From several months up to 50 years, PVC is mainly used in construction industry in Europe, accounting for 57% of the total usage. Long service life.
2.2 Production Process of PVC and PVC Compounds

PVC began production in the 30's and was produced and used in large quantities in the 50s and 60s. 

Today, the world produces 20 million tons of PVC per year, and in the year 1965 it was 3 million tons, which is equivalent to 1/5 of the total plastic production. Therefore, PVC is the most important synthetic material. Its products are mainly in the United States, Western Europe and Asia, Western Europe. Production in 1998 was 5.5 million tons (approximately 26% of world production). The average growth rate of PVC products in recent years was 2-10%, which varies from region to region (high in Asia and low in Europe). Different (particles are highly flexible and low). Due to changes in supply and demand and changes in raw material prices, the price of PVC is constantly changing. 

PVC mainly has two production processes, VCM's suspension polymer (80%) and emulsified polymer (10%):

Production of VCM from ethylene and chlorine, or ethylene and hydrogen chloride is a closed industrial production process. Emissions of chlorine, ethylene, dechlorinated ethylene, HCL, VCM, and chlorine by-products include dioxins, which can be released into the work environment and external environment. In air and water, some of these chemicals are substances that must be strictly controlled. Some technical guidelines have been applied to the PVC and VCM production processes. In other sectors of the chemical industry, technology has been established over the years to improve production processes to produce VCM and suspended particulate PVC, and the Convention for the Protection of the Marine Environment of the Northeast Pacific Ocean (OSPAR) has been established. ) Some emission limits were set in the resolution. As early as 1995, the European PVC Producers (ECVM) Association signed a voluntary commitment. Before the end of 1998, the industrial sectors of VCM and PVC production had to strictly limit the emission of some chemical substances and implement it through an independent audit. Through the audit, it is shown that: 88% of the standards have been met, and ECVM has stated that it complies with all standards as much as possible, except for the licensing of VCM and PVC products. ECVM signed a contract on the production of emulsified PVC in 1998 and strictly controlled the discharge of VCM into air and water, as well as the content of VCM in the final polymer. Although these companies have already complied with current national and local regulations or requirements, they have not complied with strict voluntary restrictions. It is stipulated that they will be completed in 2003 and external confirmation will be implemented in 2004. 

The original PVC must be added with some additives called PVC compounds before being processed into the final product. PVC is a thermoplastic material, that is, many shapes can be formed by melting by heating. After cooling, the material shows its original characteristics. Using this principle, a large number of different methods are used to promote the conversion of PVC, such as extrusion, wheel pressing, injecting and sanding, blow molding, rotating forming, heat removal and blown film. 

During the synthesis and further conversion, the release of some harmful substances exposes the workers. The synthesis of PVC powder and additives (in the form of powder or liquid) is usually carried out in closed equipment. Workers are exposed only when they are synthesized in the mixer. This can be reduced or eliminated in accordance with EU Directive 98/24/EC on preventing workers from exposure to chemical agents at work. 

The overheating of PVC during the formation and cooling conversion by heating has the risk of emission of some degradable compounds, among which HCL is the most important one. However, the total amount is very small and has only a very low negative effect on the environment. Discharge of VCM monomer during conversion is also considered to be very small. Emissions of stabilizers and plasticizers are also rarely followed by appropriate methods. 

In general, work protection measures are taken to comply with the current regulations on worker health and environmental protection. 

(to be continued)