Production residues: these arise mostly in the form of off-cuts, in the factory or plant, as the product is made. For many years such valuable `waste' has been recycled as a matter of good housekeeping and only a small proportion needs to be disposed of as waste to landfill or by combustion.
Installation waste: this results from sold products, such as flooring, cables and pipes, being cut to size during installation. In recent years, the PVC industry has become active in organising collection systems and in recycling these `waste' products back into new products.
Post-consumer waste: products which have fulfilled their service life and end up in waste streams from different domestic and industry sectors.
Incineration with Energy Recovery
Oil used in PVC production can be utilised at least twice, making positive use of its high heat value, through incineration with energy recovery. Incorporating PVC consumer products at the end of their useful life in controlled municipal incinerators reduces the need for additional fuel and reduces the amount of PVC going to landfill. A number of independent studies have demonstrated that PVC in addition to the natural presence of chlorine in waste, does not increase the generation of potentially harmful emissions. Modern incinerators are operated to the highest standards and equipped with pollution control equipment that minimises the release of emissions to the environment.
Vinyloop is a process of recovering PVC plastic from composite materials through dissolution and precipitation.
The technical process of Vinyloop can be described fairly simply; it includes only 6 main steps. To begin the cycle, composite waste is collected and brought to the plant. Much of the material is preprocessed but some of this step takes place in the factory. Some operations that may be performed are, “a cleaning step (washing, etc.) reducing the size for fast dissolution (by cutting, grinding, milling, etc.) and a homogenization step.”
After pre-treatment, the material is sent to a dissolution chamber where the solvent, methyl ethyl ketone, dissolves the PVC and its additives. While these factors are dissolved or suspended, the insoluble materials of the original composite remain out of solution and can thus be removed in subsequent steps.
The separation of the insoluble materials occurs in the next tank. There are many techniques to filter the solid from the solution such as, “centrifuging, decanting, or cycloning,”, the particular method used is mandated by each individual situation. “After separation, the secondary material is: washed with pure hot solvent to eliminate virtually all of the dissolved PVC compound, stripped with steam to recover all the solvent, then discharged.”1 In this way all material is removed from the PVC. This is a very important step to yield pure PVC material for reuse.
The next stage in the process is the precipitation of the dissolved PVC. At the onset of this stage, it is possible to integrate more additives into the dissolved PVC to achieve a variety of characteristics. At the Ferrara Plant, a plasticizer is added to the PVC in order to generate a more flexible and less brittle product. Steam is then injected into the solution, evaporating the solvent completely, leaving an aqueous slurry of PVC and additives. The unwanted material from the composite as well as the solvent are thus removed. The evaporated solvent condenses in its original chamber, ready to dissolve another batch of composite material. This closed loop cycle has an effective retention rate of 99.9%, rendering the solvent a technical nutrient in this process.
The final stage in the Vinyloop is the drying phase. The aqueous solution of PVC is dried and the effluent water filtered to remove impurities. The dry R-PVC forms pellets (a significant occurrence due to that form’s ease of use in the plastics industry). Dry pellets are easy to package and ship out to be molded into other products. Many times these pellets can comprise 100% of the material for a new product, but when not, any percentage of R-PVC can be added to virgin PVC in product formation.
APPLICATION OF PROCESS
The Vinyloop process was developed by Solvay SA’s
The materials suited to the Vinyloop process are composites, such as PVC coated wire, coated fabrics, flooring, or automotive products. While in the past it was not possible or feasible to separate plastic from other materials in composites such as these, the Vinyloop process allows for such separation through its dissolution and precipitation system. It allows for the retention of the PVC’s original character by preserving its stabilizers, plasticizers, colorizers, etc. This elicits a 100% direct reuse of R-PVC produced by Vinyloop.
HOW USEFUL IS IT TO PLASTIC INDUSTRY?
Vinyloop is one of few processes which can effectively separate PVC from a composite material. It is also a recycler of post consumer waste. This is therefore a significant diverter of plastic from the waste stream. While other cruder plastic recycling processes cannot reclaim a pure form of PVC from a material, leading to subsequent lifescycles of lower quality, Vinyloop yields a very pure product which is of comparable quality to virgin material.
Further research will determine the viability of these ideas concerning the Vinyloop process, specifically the test of whether the R-PVC can be reintegrated into the composite products it originated from and be continually processed by Vinyloop at the end of each of its lifecycles.