Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Utility Patent
1999-06-15
2001-01-02
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S080000, C524S525000
Utility Patent
active
06169128
ABSTRACT:
TECHNICAL FIELD
This invention relates to a process for manufacturing products from discarded rubber and plastic materials.
BACKGROUND ART
One environmental problem that has existed for decades, and continues to exist without a viable resolution, is the inability to discard rubber tires in a manner which is not environmentally detrimental. Due to the volume of discarded tires, landfills often refuse to accept these products and consumers and the tire industry have developed no viable solution for resolving this difficulty.
It is presently estimated that over two billion discarded tires exist in the United States with about 300,000,000 tires being discarded annually. Presently, any viable use for discarded tires raises serious environmental issues or has such a limited commercial feasibility that no significant impact on the problem is realized.
Various attempts have been proposed for re-claiming vulcanized rubber over the last several decades. However, these proposals typically attempt to de-vulcanize the rubber in order to obtain a processable rubber. However, this technology typically requires the taking of particular vulcanized rubber and removing fibers therefrom. Then, the resulting product is treated with combinations of chemicals, steam heat and/or considerable mechanical working to reduce molecular weight and thereby enable the resultant material to be processed and re-vulcanized as a conventional rubber product. The reclaimed rubber produced by this process is typically blended with virgin rubber or used directly, depending on the particular techniques used and the end product to be made.
The use of particular vulcanized rubber as an ingredient in thermoplastic compounds is very limited. Although several proposals have been made, these prior art proposals typically suffer from the primary disadvantage that the process is extremely costly due to the de-vulcanization expenses and the limited utility of the resulting product.
In spite of these prior art efforts, a need continues to exist for a processable composition of vulcanized rubber and thermoplastic materials which exhibit excellent overall toughness, strength, and wearability and flexibility. Furthermore, a need exists for a plastic/rubber composition which can be processed in a relatively simple and economical manner without requiring de-vulcanization the particulate rubber.
One prior art teaching in this field is found in U.S. Pat. No. 5,010,122 wherein a process is taught for combining rubber particulate and thermoplastic material with a coupling agent to achieve a final usable resulting composition. However, the composition and process taught in this prior art patent has achieved only limited success, since the process has been difficult and costly to carry out.
Therefore, it is a principal object of the present invention to provide a plastic/rubber composition having utility in producing high quality non-rubber thermoplastic products as well as crossed linked products and rubber products.
Another object of the present invention is to provide plastic/rubber compositions having the characteristic features described above which incorporate excellent physical properties.
Another object to the present invention is to provide plastic/rubber compositions having the characteristic features described above which is capable of being produced in a relatively simple and economical process.
Other and more specific objects will in part be obvious it will in part appear hereinafter.
SUMMARY OF THE INVENTION
By employing the present invention, all of the difficulties and drawbacks found in the prior art are eliminated and an easily employed process is achieved which is capable of producing products which are highly flexible, possess greater elasticity, wearability, and longevity. In addition, the processing drawbacks encountered by employing the teaching of U.S. Pat. No. 5,010,122 are completely overcome and totally eliminated by the present invention.
In accordance with the present invention, compositions of vulcanized rubber and thermoplastic polymers, particularly those of the olefinic branch, are intermixed with a bonding agent to produce a processable compound having a combination of unique and unexpected properties. Such products manufactured from these compounds have been found to exhibit excellent processability, overall toughness, strength, flexibility, wearability, and elasticity. It is believed that the ingredients act synergistically to impart a resulting compound with superior strength, as compared to the base thermoplastic material, while also possessing the wide variety of the other attributes detailed above.
In accordance with the present invention, the desired composition is realized by combining rubber particulate, thermoplastic material, and a bonding agent as detailed herein. Preferably, the bonding agent comprises between about 1% and 12% by weight of the weight of the rubber particulate and thermoplastic material. In addition, the rubber particulate and the thermoplastic material are present in a weight ratio ranging between about 1:9 and 9:1.
The rubber particulate preferably comprises one or more selected from the group consisting of natural rubber, synthetic polymers and copolymers of rubber and blends thereof. The thermoplastic material preferably comprises one or more selected from the group consisting of olefins, copolymers of olefins, homopolymers of olefins and blends thereof. In particular, such thermoplastic materials may be selected from the group consisting of polyethylene, polypropylene, ionomers, polybutylene, and ethylene vinyl acetate.
In the present invention, a unique bonding agent is employed to attain the desired final composition using a process which is easily achieved. This unique bonding agent comprises a combination of ethylene co-polymers, ethylene-octane and acrylic acid. By employing this bonding agent with the rubber particular and thermoplastic material in a quantity ranging between about 1% and 12% by weight of the weight of the rubber particulate and thermoplastic material, all of the prior art drawbacks are eliminated and a unique, desirable, highly useful composition is produced.
In the preferred process for attaining the desired resulting composition of the present invention, vulcanized rubber is first ground into small particles or particulates. The rubber particulate is then mixed with the thermoplastic material in a mixer at a sheer rate less than that which causes de-vulcanization of the rubber and at a relatively low pressure to reduce the creation of a thermal history. Preferably, mixing is carried out at a temperature near the mid-point of the base polymer's established melt range.
During the mixing of these two ingredients, the bonding agent is blended into the mixture. The resulting composition is then processed in any desired manner for achieving the final product for which the composition is to be employed. Examples of various processing steps include pelletizing the composition by feeding it through a die face and then packaging the resulting pelletized product for shipment to processors. Alternatively, the mixture can feed the thermoplastic composition directly into final processing equipment, such as sheet extruders, profile extruders, injection molding machines, and the like.
REFERENCES:
patent: 5010122 (1991-04-01), Koski
Nutter Nathan M.
Poly-Typlax Technology Div. of R.W. Technology, Inc.
Stoltz Melvin I.
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