Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-01-25
2004-06-01
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S113000, C524S210000, C524S251000
Reexamination Certificate
active
06743836
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for predispersing additives used in a compounding process. More particularly, the present invention relates to methods for predispersing additives, particularly ground elastomers which are used as compounding ingredients for many applications, especially for the production of rubber or plastic materials such as tires.
2. Description of the Related Art
In recycling and reusing rubber materials, it is generally known to decrease the size of such rubber materials to small ground rubber particles (i.e., particles of irregular outline that pass through a minus 80 mesh or through a minus 50-mesh or finer). Such particles can be chemically more reactive and mechanically easier to dissolve into various mixes.
A variety of rubber products (e.g., natural rubber, synthetic rubber, vulcanized rubber, automotive tire scrap, etc.) may be reduced to ground rubber particles. Known methods for producing rubber of a decreased size include cryogenic cracking of the rubber. Other known methods include the milling of the rubber between horizontal grinding stones in a horizontal grinding mill. Such milling techniques have been developed in the flour, paper pulp industry and the paint pigment compounding industries. Such milling techniques include grinding the rubber between opposed milling wheels, such that one wheel is fixed and the other wheel rotates relative to the fixed wheel. Such known milling techniques include pressing the two wheels against a rubber slurry, such that the rubber is ground to a fine state (i.e., powder). The final powder product can then used as an ingredient in compounding applications. For example, the fine powder can be used as an additive to compounding components for the formation of tire rubber, as an additive in the compounding of asphalt, and the like.
The use of powder additives such as ground rubber or other powder ingredients in compounding processes often times poses a handling problem. For example, the powder must be weighed and added in stoichiometric ratios to the compounding process. Due to the small particle size of the powder, the powder will readily disperse in air or under the slightest pressure such that measurement of exact and precise quantities is difficult, if not impossible. This phenomenon is true not just for ground elastomeric material, but for any powder or liquid compounding ingredient that is added in precise quantities.
For example, it is disclosed in U.S. Pat. No. 5,758,961 to Deal et al., the disclosure of which is incorporated herein by reference, that in mixing rubber, the dosaging of the different front base components must be very precise. This precise dosaging does not raise any particular problem when one proceeds by successive batches, that is to say, in batchwise processes. On the other hand, when it is a question of proposing continuous mixing, it is indispensable to be able to effect the necessary dosaging of the different ingredients continuously. Furthermore, in the case of powdered products, in addition to the difficulty of dosaging, there is the difficulty of transporting the products, particularly downstream of the dosaging.
Generally, dosaging units deposit the necessary ingredients at regular intervals on a belt conveyor which feeds the mixing unit or units proper. A recent attempt to make the mixing of rubber continuous is described in an article published in the “European Rubber Journal” for March, 1987, entitled: “A Tale of Continuous Development”, incorporated herein by reference in its entirety. This continuous mixing process, already proposed in the prior art, effects the dosaging of components by weighing and then effects the introduction of different components into apparatus which effect a premixing, this being done at different places in the mixing chain. This, therefore, makes it necessary to install numerous separate apparatus, each carrying out a very precise function-weighing, conveying, premixing. It is only then that the different components can be introduced by gravity into feed wells, for instance in a mixer of the type described in patent application EP 0 490 056 which is very difficult, and creates the handling problems discussed above.
Accordingly, it would be desirable to have a process for adding compounding ingredients, especially for compounding of rubber or elastomeric virgin compositions, that makes addition of fine particles (or even liquids) more precise and reduces handling problems at least to some extent.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a method for predispersing a first compounding ingredient of a downstream compounding process in a second liquid compounding ingredient of said downstream compounding process which is capable of solubilizing and/or dispersing the compounding ingredient therein and then using the now predispersed first and second ingredients in the downstream compounding process. In a particularly preferred embodiment, the first compounding ingredient is a powder, in particular ground rubber or a ground elastomer and the second compounding ingredient is an aromatic oil or ester. This method can optionally comprise converting an elastomer to a decreased size in a grinding apparatus using a size reduction operation and soaking the elastomer in the second compounding ingredient during the size reduction operation. The instant process can optionally include decreasing the size of an elastomer in a grinding apparatus to form a fine particle having a particle size of −50 mesh or −80 mesh, and then introducing the fine particle into a compounding process wherein the fine particle is mixed with an aromatic oil or ester at a predetermined stoichiometric ratio at a point upstream from (that is, at a point before) a mixer used in the compounding process.
In accordance with the present invention, there is also provided a predispersed particle. The particle includes an elastomer which has been predispersed in a solvent such as an aromatic oil or ester.
Additional objects, features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects, features and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The size of an elastomer (e.g., natural rubber, synthetic rubber, recycled rubbers containing polyethylene and/or polypropylene, vulcanized rubber, carbon black, waste from tire production, various polymers, various plastics, thermoplastic elastomers, thermoplastic vulcanates, polyethylene plastics, etc.) may be decreased using a variety of mechanisms. According to an exemplary embodiment, the elastomer is predispersed in a fluid that is capable of dispersing and/or solubilizing the elastomer and is a fluid that will be mixed with the elastomer in a downstream process. In particular, pre-swelling of vulcanized rubber with an oil normally used as part of a tire rubber (or other rubber) composition, enhances the dispensability/solubility of the vulcanized ground scrap into the host compound. Oils or esters of specific compositions can be used as plasticizers (softeners) for rubber and the oil/ester has to be an excellent solvent for the vulcanized rubber, otherwise the oil/ester would ooze out of the vulcanized composition. One of skill in the art would be capable of selecting appropriate oils or esters for a particular elastomer or ground particle. The swelling of the scrap rubber by the oil and/or ester can be enhanced by many different means, such as by heating, adding a surfactant to the oil and/or ester to enhance its ability to swell the vulcanized rubber quickly, by further reducing the particle size of the elastomer to expose more surface area and enhance the swelling process, and/or by grinding the rubber in the presence of an oil and/or este
Deeb Victor M.
Rouse Michael W.
Connolly Bove & Lodge & Hutz LLP
Lipman Bernard
R&D Technology, Inc.
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