Direct use of waste PVC

Polyvinyl chloride (PVC) products are many, according to the plasticization or not can be divided into two categories of hard and soft. Hard PVC products are produced with lower molecular weight PVC plus 15% impact modifier and 3% processing aids, while higher molecular weight PVC is difficult to process and can be processed into soft products by adding plasticizers. Both contain 5% stabilizers.

Waste PVC plastic products mainly have the following two sources.

(1) Wastes such as scraps, wastes, and waste generated during plastic molding processing are relatively clean and uniform in composition. They can be re-pelletized by a simple recycling method, added to a new material in a certain proportion, and replaced with some new materials to be reshaped. .

(2) Discarded products in daily life and industrial applications

Due to the large amount of additives contained in PVC plastics, there are many kinds of such wastes, the components are not uniform, and the performance is greatly affected by the external environment. At the same time, other wastes are mixed, and the recycling process is relatively complicated. Generally, the following methods are used for recycling.

1 First, separate and remove the mixed non-PVC products.

2 Because PVC products are divided into hard and soft materials, they should be recycled separately according to the type of product, and be pretreated by screening, cleaning and drying to remove impurities.

PVC products add a lot of additives in the processing to ensure the performance of the products. During the process of use, PVC resin and these additives will change due to external conditions. Therefore, prior to the PVC waste recycling process, it is necessary to first understand the molecular weight (or viscosity), the double bond structure, the remaining additives and the content of PVC in the waste products, and then determine the types of additives to be added according to the requirements of the recycled products. The amount can be, for example, an appropriate amount of tribasic lead sulfate that has a strong ability to absorb HCl and a high thermal stability, a dibasic lead phosphite having strong anti-oxidation and ultraviolet absorption ability, and a methyl group having a light stabilizing effect. Benzoyl hydrazide and other heat stabilizers to meet the requirements of recycled products.

Direct use of waste PVC:

First, PVC bottle:

Since no plasticizer is added, hard PVC products can be recycled, but only PVC bottles have a market value for recycling. In mid-1995 bottle-grade PVC pellets cost more than 75 cents per pound, while other crystal grade PVCs are less than 40 cents per pound, so recycled transparent PVC bottles are then used for bottle grade pellets for non-food products. Use is very attractive. Other hard durable products cannot be reclaimed as blow moldable due to their higher molecular weight than bottle grade PVC

Bottle grades, which have low market prices, are difficult to withstand recycling costs and are therefore unattractive. In addition, these durable hard products generally contain pigments that can only be recycled for use in dark products.

Second, PVC doors and windows:

. The use of PVC doors and windows started in the former Federal Republic of Germany in the 1950s and 1960s. Due to its unique energy-saving, moisture-proof, sound-insulating, heat-insulating, and anti-corrosion properties, it gradually replaced steel and wooden doors and windows and was quickly promoted in Europe. The country has formulated the corresponding PVC doors and windows standards and supporting standards, forming a complete system of PVC doors and windows.

After introducing two types of PVC door and window production technology and equipment from Europe and the United States in the 1980s and 1990s, China’s production scale has been continuously expanded. There are 2,100 PVC door and window production lines with a production capacity of approximately 1 million tons. By 2005, the market share of plastic doors and windows in the national building doors and windows market will exceed 25%, of which the market share of the heating area will reach over 50%, and the market share of other areas and buildings that implement the building energy conservation design standards shall not be less than 35%. The actual output is 800,000-900,000 tons. By 2010, the plastic doors and windows will occupy more than 30% of the market for building doors and windows across the country. The actual output and usage will exceed 1.4 million tons. Since the service life of PVC windows and doors is as long as 40 to 50 years, but only about 1% of windows and doors have been used for more than 30 years, the amount of used PVC windows and doors that can be obtained is limited. Most of them are generated during building renewal and demolition.

There are few doors and windows that have been scrapped beyond their useful life. This situation makes the current recycling technology of waste PVC doors and windows immature, and there are almost no factories specializing in the recovery of PVC plastic doors and windows. However, according to a recent report, Beijing New Building Materials Factory has planned to cooperate with Japanese companies to produce waste plastic PVC and wood powder blended plastic products.

There are three main sources of discarded PVC door and window materials: 1) waste in production; 2) scraps generated during the cutting of scraps and doors and windows; and 3) waste generated during the replacement of old doors and windows.

After the PVC doors and windows wastes are collected, sorted, removed glass and metal, cleaned and crushed, they can be used together with new materials to produce regenerated door and window profiles through a co-extrusion process. The core of this type of door and window profile is made of recycled material, the surface layer is made of new material, and the core layer and surface layer are fused together to form an inseparable whole. The mass ratio of the two parts is 2:1, which means that the recycled material accounts for 2/3. The surface layer made of 100% new material can ensure sufficient lightfastness, weatherability and aesthetics, and there is no difference between the doors and windows obtained after installation and the doors and windows completely made of new materials.

Source: China Plastics Industry Network