Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Composite article making
Reexamination Certificate
1999-04-26
2001-05-08
Foelak, Morton (Department: 1711)
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Composite article making
C264S126000, C264S122000, C264S912000, C264S917000, C521S054000
Reexamination Certificate
active
06228295
ABSTRACT:
The present invention concerns a new material composition where the main constituent is recycled vulcanised rubber and a process for producing this material.
THE BACKGROUND TO THE INVENTION
Worn out tyres are associated with special problems, both regarding recycling and disposal on waste disposal/landfill sites. In addition to containing a rubber matrix comprising natural and/or synthetic rubber, modern tires also contain carbon black, plastisizers, cross-linkers, anti-oxidants, anti-ozone agents and other performance-improving additives plus metal or fibre reinforcement.
In addition to taking up a great deal of space on waste disposal sites, the dumping of tires causes several other problems as well. The shape of the tires causes it to slowly but surely migrate up to the surface of the disposal site and thereby greatly disrupt the degradation process. Tires also have a long life as they are manufactured to resist both thermal and biological degradation as well as mechanical wear. Furthermore, tires resist ultraviolet radiation, ozone and other oxidants, as well as water and ice. Fires in a used tires depot are especially problematic as they have proven to be very difficult to extinguish. In addition, the fire releases toxic substances both in the smoke and in the water used to extinguish the blaze.
Problems also occur when tires are used as a source of combustion, among other reasons, because of their content of sulphur but also because they contain metals and chemicals.
As no one has so far succeeded in developing a large scale method for devulcanising recycled rubber, this is difficult to use to any great extent in the production of new tires. At present, no more than 2% of old rubber is used in new tires. The problem can be partially overcome by modifying the surface of the rubber particles. Surface modification of rubber particles from ground down tires is a technique that means that the very outer layer of the rubber particles is modified to allow improved adhesion when combined with other materials, e.g. other elastomers. The technique involves exposing the rubber particles to a powerful reactive gas, e.g. fluorine. It is, therefore, not without its problems.
The reuse of rubber from tires has so far been focused on relatively uncomplicated applications, such as blasting mats, mixing in asphalt or in the production of low vibration flooring. Sheared fragments of rubber or rubber granulate can even be used as such, for purposes as improving soil, filling material for building work, e.g. road construction for recreation or trotting tracks, etc. Mixing in with compost has also been suggested. The problem of leaching of metals and poly-aromatic hydrocarbons that can be taken up by the biosystem is nevertheless associated with these applications.
Bearing in mind this background, there is thus a need for new, functional and beneficial materials with a high content of recycled vulcanised rubber.
THE PRIOR ART
According to U.S. Pat. No. 5,157,082 (EP 649 871), one can produce a thermoplastic composition that comprises particles of vulcanised rubber and a polyolefine resin with an addition of a functionalised olefine polymer. Polyolefine resins are, for example, polyethene, polypropene, polybutadiene, polybutylene, polyisoprene or mixtures thereof, preferably polyethene. The functionalised olefine polymer is a co-polymer of at least one olefine comprising hydrated butadiene or isoprene or one or more ethylenically unsaturated organic monomers. To produce useful products with this composition in practice, the mixture must be processed under high pressure. The description mentions process steps such as extruding and compression moulding. These are associated with high costs for mechanical equipment and dies due to the high pressures required. As a consequence, large series are needed if manufacturing is to be profitable.
Also the production of elastic insulating material comprising a large number of separate cavities by using constant shape or expandable microspheres is known, for example via WO 87/06245 and WO 96/11226. According to WO 87/06245, the procedure also requires that the mixture is subjected to a considerable external pressure by compression moulding or similar processing. The microspheres used in that mixture must, therefore have a sufficiently high crush strength. WO 96/11226 concerns a thermoplastic material mixed together with expandable microspheres. The foam material can, after extrusion, be reheated and shaped, for example to make an orthopaedic immobilising element or similar. Other production methods referred to include compression moulding and injection moulding.
EP 692 516 describes a procedure and a material that allows the involvement of waste and recycled material from the production of the same. The possibility of including recycled vulcanised rubber in similar mixtures is not mentioned. In fact, such a measure would be alien to the skilled person, since it is well-known that vulcanised rubber has poor adhesion characteristics and that the mixing of rubber adversely affects the melt characteristics of thermoplastics. In addition, it has been shown that thermoplastics that have been mixed with rubber cannot be fused together with a completely satisfactory result.
SUMMARY OF THE INVENTION
Surprisingly, it has now been shown to be possible to produce a material that uses recycled rubber as its main component without any process step that involves high pressure, be it compression moulding or extrusion.
REFERENCES:
patent: 3615972 (1971-10-01), Morehouse et al.
patent: 5234757 (1993-08-01), Wong
Foelak Morton
John Lezdey & Assoc
Rolf Innovations Corp.
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