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PVC- or Vinyl Recycling has historically been difficult to perfect on the industrial scale. But within the last decade several viable methods for recycling or upcycling PVC plastic have been developed.

One of the several new methods of PVC recycling is Vinyloop.

Contents

Vinyloop

Vinyloop is a process of recovering PVC plastic from composite materials through dissolution and precipitation.

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Application

The Vinyloop process was developed by Solvay SA’s R&D Center in Brussels in the late 1990s. Since then, a research plant, as well as two industrial scale plants, one in Ferrara, Italy and another in China, Japan, have been built to implement the Vinyloop process. The Ferrara Plant’s tests in 2002-2003 have proven the system viable on a large scale. Vinyloop’s R-PVC (Reconstituted PVC) can be produced at a lower cost than the equivalent virgin plastic.

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.

Process

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.) increasing surface area to speed up dissolution (by cutting, grinding, milling, etc.) and a homogenization step.”[1]

After pre-treatment, the materials are 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.

Importance to Plastics 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. This characteristic suggests that, in the terminology of William McDonough and Michael Braungart in their book Cradle to Cradle, Vinyloop is an upcycling process, yielding R-PVC as a technical nutrient.

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.

Sustainability

In these ways, PVC recycling may become a virtually sustainable industry in the near future. An important characteristic that makes the Vinyloop process sustainable is its dissolution solvent recovery process. Instead of using a solvent which is spent and becomes waste after each use, Vinyloop integrates a step of solvent recovery in which 99.9% of the solvent is recovered and reused for each cycle. Again this component to the system is a technical nutrient which stays within the system rather than degrading in quality and becoming waste. Additionally, the natural formation of R-PVC microgranules makes the transition to processing the plastic's next life very easy.

Problems/Questions

Before a stamp of sustainability can be put on the Vinyloop process, several questions must be answered. The first concerns the treatment of the aqueous effluent which comes from the drying of the aqueous PVC solution. This effluent could potentially contain harmful chemical additives. The question regarding the management of this effluent must be answered to help complete the picture of the Vinyloop process. Less than perfect filtration should be cause for concern.

Another point of concern is the use of secondary additives to adapt the PVC to a new use, or to make it usable at all in a second lifecycle. More detailed information is needed concerning the necessity for these additives, as well as the effect the eventual accumulation of additives may have on the PVC. Whether or not this step in the process could limit the number of lifecycles a 'vinylooped' PVC product is embodied with is an important question whose answer could affect its level of sustainability.

Another major issue is that this process targeted to recycle plasticized/flexible PVC only, from wires, coatings, etc. Plasticized PVC softens/flows with much lower viscosity at much lower temperature than rigid uPVC, and therefore suffers from much less insoluble crosslinking and thermal breakdown than rigid uPVC. However, the bulk of the PVC consumed in the world is not plasticized/flexible PVC, but rigid uPVC (construction siding, window frames, etc.). Therefore this process still leaves the bulk of the PVC recycling problem unsolved. Complete thermal depolymerization/pyrolysis to polyacetylenic char and HCl, and char gasification similar to wood/coal gasification into fuel might be able to tackle any PVC material, flexible or rigid. The major question remains the fate of dioxin and similar chlorinated byproduct contamination.

See also

Sources

  • Machine Design. Cleveland: Jun 5, 2003. vol. 75, Iss. 11; pg. 79 . Abstract
  • Chemical Week. v 164 n 10 Mar 6 2002. . Intro to Vinyloop
  • Plastics Technology. v 47 n 8 August 2001. p 58-61. New methods in PVC recycling
  • Shinkokankyosoryushon Shinko Kankyo Soryushon Giho (KOBELCO Eco-Solutions Engineering Report) , 2005 , VOL.1,NO.2 , PAGE.14-20 , FIG.6, TBL.7, REF.2 . Vinyloop Japan
  • Solvay S.a., Brussels, Bel Proc Int Symp Feedstock Recycl Plast , 2002 , VOL.2nd , PAGE.76-79 , FIG.3. Vinyloop Japan
  • http://www.Vinyloop.com Solvay Site
  • http://www.chemicals-technology.com/projects/ferrara/ Article on Ferrara Plant

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