Recycling polyolefins

AA Adewole, MD Wolkowicz. Processabihty-Morphology-Properties Relationship in Compounding Polyolefinic Recycled Plastics. Proc. 51st SPE ANTEC. 1993, p. 39. 

For illustrative purposes, to demonstrate the state of polyolefin recycling in 1992, the life of 200 kg of virgin HOPE bottle resin is studied. The assumptions are that 10% of the resin is used in milk bottles, which is a homopolymer product, 8% is used in motor oil bottles, a difficult to clean product, and the remainder is used in other consumer bottles. A macroscopic perspective suggests that consumer products use about 5% post consumer recycled material and motor oil bottles about 25%. Some products would use more and some none at all. This does not take post industrial or internal scrap levels into consideration in terms of reclaimed content. It can be concluded that, at the current levels of recycling, a large fraction of the polyolefin molecules will be exposed to at most 4 thermal and shearing cycles. 

Recycling of HDPE. Polyolefins, including HDPE, are the second most widely recycled thermoplastic materials after PET (110). A significant fraction of articles made from HDPE (mostly bottles, containers, and film) are collected from consumers, sorted, cleaned, and reprocessed (110—113). Processing of post-consumer HDPE includes the same operations as those used for virgin resins blow mol ding, injection molding, and extmsion. 

These models are usually overall plant or corporation oriented and are geared toward running the business. If utilities are included, they are probably keyed to production levels of operating units or, in the case of the polyolefin plant, a characteristic set of utilities is charged against each unit of each specialty product. Often, recycle streams within segments of the operation are not pertinent and not included. 

Dow ABS Nylon 6/6 Polycarbonate Polyethylene, HDPE, LDPE, LLDPE, ULDPE Polypropylene HPPP, CPPP Polystyrene HIPS, GPPS, Recycled, Advanced Styrenic Resin SAN Polyurethane Elastomers Polyolefin Plastomer PC/ABS Crystalline Polymer ABS/TPU... 

Macromolecular Symposia Vol.135, Dec. 1998, p. 175-82 NEW CHEMICAL RECYCLING METHODOLOGIES HYDROUS PYROLYSIS TO RECOVER MONOMERS FROM POLYOLEFINS Audisio G Bertini F Beltrame P L Bergamasco L Castelli A... 

The Parak process for the recycling of polyolefins and the production of raw materials for the production of paraffin waxes, is described. The process is claimed to provide a link between mechanical and feedstock recycling, employing elements of feedstock recycling, e.g. melting and cracking. The main product obtained is paraffin wax, which can be used for coatings for cardboard and paper, and corrosion protection. 

The use of pyrolysis for the recycling of mixed plastics is discussed and it is shown that fluidised bed pyrolysis is particularly advantageous. It is demonstrated that 25 to 45% of product gas with a high heating value and 30 to 50% of an oil rich in aromatics can be recovered. The oil is found to be comparable with that of a mixture of light benzene and bituminous coal tar. Up to 60% of ethylene and propylene can be produced by using mixed polyolefins as feedstock. It is suggested that, under appropriate conditions, the pyrolysis process could be successful commercially. 23 refs. 

Details are given of a visit by RECOUP to BP Chemical s feedstock recycling demonstration unit in Sunbury. The feedstock recycling technology has been developed by a consortium of companies, and will enable polyolefin rich plastic waste from domestic and commercial sources to be vapourised and then condensed to form a hydrocarbon wax. This can then be used to feed existing petrochemical crackers to produce polymers indistinguishable from virgin material, it is claimed. 

Davos, 7th-10th April 1992, p.3/2-1 - 3/2-12. 8(13) TERTIARY RECYCLING OF POLYOLEFINS Meszaros M Amoco Chemical Co. 

Recycling plastics back to hydrocarbons (tertiary recycling) may offer significant promise. Three different options currently being evaluated for the tertiary recycling of polyolefins - refinery recycling, pyrolysis and depolymerisation - are discussed. 

Okamato et al. [110] developed a new mbber recycling technology to produce a polyolefin TPE-based on EPDM waste and PP. Pine mbber powder can also be obtained from the sanding process of... 

Traditionally carpet tile backings have been made from bitumen, PVC or polyurethane. There are problems with the environmental impact of these materials and they are difficult to recycle. Shaw industries developed their EcoWorx carpet tile backing using a polyolefin resin. This has superior environmental profile to PVC and is easier to recycle than bitumen and the cross-linked polyurethane backings. EcoWorx has lower toxicity, better adhesion and good dimensional stability. It is easy to recycle and can be separated from any fibre type used in the carpet tile. It works particularly well with nylon-6 fibres. EcoWorx tiles contain 40% recycled content and Shaw have established a collection and return scheme to close the loop. 

Karlsson, S. Recycled Polyolefins. Material Properties and Means for Quality Determination. Vol. 169, pp. 201-229. 

To override any effect that particulate impurities or polyolefin contamination would have in modifying the crystallization behaviour of recycled PET. 

Chtourou, H., Riedl, B. and Ait-Kadi, A. (1992). Reinforcement of recycled polyolefins with wood fibres. Journal of Reinforced Plastic and Composites, 11, 372-394. 

The origin of defects causing discoloration in polyolefin pellets can be identified using light and electron microscopy. For example, PE pellets from an in-plant recycle re-pelletlzing process contained pellets that were off color and had black specks, as shown In Fig. 11.6(a). One of these defects was isolated using the cross sectioning technique, as shown in Fig. 11.6(b). The cross section revealed an intense reddish particle that caused the discoloration of the pellet. 

Shaw selected a combination of polyolefin resins as the base polymer of choice for its substitute, EcoWorx . Due to the low toxicity of its feedstocks, superior adhesion properties, dimensional stability, and its ability to be recycled, EcoWorx meets all of the design criteria necessary to satisfy the needs of the marketplace from a performance, health, and environmental standpoint. Research also indicated that the post-consumer carpet tile had a positive economic value at the end of its useful life. The cost of collection, transportation, elutriation, and return to manufacturing processes is less than the cost of using virgin raw materials. This is a truly recyclable (or Cradle to Cradle) product and is a good example of how substitution through innovation can make economic as well as environmental sense. ... 

There have been more efforts to use blends such as Nova Chemicals Arcel (an ethylene styrene interpolymer in bead form) to create a more durable foam than EPS. EPP can be moulded into complex shapes, with the steam bonding of the beads (291). These packaging foams compete with polyolefin film products such as Jiffy foam (bubblewrap) and macrobubbles made by heat sealing 150 mm lengths of tubular LDPE film. As it is difficult or costly to recycle such foam products, in some countries there is a move towards biodegradable starch foams and moulded paperboard. 

RECYCLING TECHNOLOGY FOR LAMINATES COMPOSED OF THERMOPLASTIC POLYOLEFIN ELASTOMER AND CROSSLINKED POLYPROPYLENE FOAM... 

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