Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1992-05-26
1994-10-25
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525239, 525240, 524413, C08K 308, C08L 2304, C08L 2706, C08L 900
Patent
active
053590074
DESCRIPTION:
BRIEF SUMMARY
The present invention is related to a new method for obtaining a thermoplastic rubber, using as main products the devulcanized rubber or rubbers of little vulcanizing, along with a thermoplastic.
The thermoplastic rubber is already known, since the last century, under the names of gutta-percha, balata ou chicle. It is a form of TRANS 1-4 polyisoprene, obtained from the latex of one sapotacea, differing of the natural rubber, wich is the form of CIS 1-4 polyisoprene. The gutta-percha is a hard, low elongation, low water permeability and high dieletric resistance product. It has been used for many years in the coating of electric cables, namely submarine cables, golf balls, heat-sealing adhesives, chewing gums, varnishes, etc, along with a various applications in dental treatment.
With the devellopment of the synthetic polymers, appeared the TRANS-polyisoprene and the TRANS-polybutadiene with characteristics approaching those of the natural polymers.
They can be vulcanized, resulting in a product more or less crystalline wich keeps the deformation at ambient temperature, being recoverable by heating. They are reinforced with carbon black, acquiring exelent abrasion resistance, thus being applied in heels, soles, pavements, gaskets, sponges, golf balls, battery cases, etc. New kinds of polymers were also develloped, now no more in the TRANS 1-4 form, like the by-products of the POLYURETHANES, POLYESTERS, STIRENICS and OLEFININCS. The most used are the STIRENIC thermoplastic rubbers, followed by the OLEFINICS and POLYESTERS. The polyurethanes, due to their high cost, are used only in very rare and specific cases.
The main use of thermoplastic rubbers is in the manufacture of heels and soles, gaining back a large slice of the market that has been absorbed by the polyvinyl chloride (PVC). As is of general knowledge, the processing of plastic is much more economic than the processing of the conventional rubber, since it is not necessary to vulcanize the plastic and the process burrs may be used anew, with the same characteristics of the original product. The rubber in its natural state is composed of different products, wich are blended, homogenized, allowed to rest for 24 hours, pre-molded, vulcanized and, finally, burred. The burrs and vulcanization left-overs are not ready re-usable, and they have to be reclaimed. The vulcanization transforms the rubber blend from a plastic state into an elastic state, and it does not return to the plastic state, as is the case of plastics, by means of mere heating. Only in rare cases, when the thermoplastic is cured, its burrs cannot be re-used by mere heating. It is necessary to uncure them, a process akin to devulcanization.
Thus, the main application of the thermoplastic rubber, after blending, is to be processed, without the need to vulcanize it, and left-overs and the burrs may return to the initial process.
Although there are many kinds of thermoplastic rubbers with applications in industry, the price factor keeps some restrictions to their use, chiefly because of the difficulties that thermoplastics show on being blended with pigments that would mantain or enhance their characteristics.
The inventor develloped a simple method for the manufacturing of thermoplastic rubber wich fulfills not only the product quality requirement, but also the economic one, that is, producing it from a plentyful and problematic raw material, wich is the already vulcanized rubber artifact, like tires, leftovers or surplus of pre-vulcanized moldings, transtorming it, blended with thermoplastics, in a kind of thermoplastic rubber with characteristics adequated for being used in a rubber artifact.
The already vulcanized rubber artifact undergoes a devulcanization process, physical, chemical or physico-chemical, being transformed into a regular and uniform batch, known as Regenerated Rubber, Reclaimed Rubber. Devulcanized Rubber or Devulcanized Rubber "Masterbatch". This devulcanized rubber is heated to the plastic melting point and blended with it. The batch thus obtained is homogenized, its cr
REFERENCES:
patent: 4257925 (1981-03-01), Freegard
patent: 4400488 (1983-08-01), Lal et al.
patent: 5010122 (1991-04-01), Koski
Clark W. R. H.
Relastomer S/A
Seidleck James J.
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