Solid material comminution or disintegration – Processes – Plural successive comminuting operations
Reexamination Certificate
2001-04-25
2004-04-20
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
Plural successive comminuting operations
C241S159000, C241S260100
Reexamination Certificate
active
06722593
ABSTRACT:
The present invention relates to a method for processing waste elastomeric material to recover the material and optionally to de the elastomeric material so as to recover materials such as carbon and volatile hydrocarbon products. The method of the invention is particularly suitable for recovering materials from vehicle tires.
BACKGROUND OF THE INVENTION
The present invention will be described with particular reference to the treatment of used vehicle tires, however it will be appreciated that the methods and apparatus described herein may also be suitable for the treatment of other articles containing elastomeric materials, such as conveyor belts, and no limitation is intended thereby.
Vehicle tires are typically formed from synthetic and natural rubber materials together with carbon black, plasticizers together with steel reinforcing wires, metal beads at the inner diameter of the tire and fibers formed from nylon or polyester.
Used vehicle tires are commonly disposed of by dumping to landfill. However, dumps of old tires are undesirable for environmental reasons. They take up large amount of space and can be a fire hazard. Also, in view of the costs of manufacture of rubber it would be desirable to be able to recycle the rubber in used tires. Methods which have been proposed to dispose of used tires include simply slicing the tires to reduce the large volume of tire dumps. Used tires may also be ground to produce rubber crumb which may be used in the production of rubber flooring, roads, sports surfaces and other rubber products. Typically, the steel wires and beads are magnetically separated from the crumb during granulation and the fiber separated by flotation systems. Generally, the tires are subjected to an initial slicing or shredding step with the steel and fiber intact. Slicing and shredding of the steel requires additional energy and leads to high wear and tear on slicing and shredding blades.
Another approach has been to carbonize the tires to produce breakdown the rubber to products such as carbon black and fuel oil. Generally, the tires are carbonized whole and the steel is separated afterwards. A disadvantage of heating whole tires is that the carbon and fuel oil, end products can be contaminated by wire and breakdown products of the fibers.
Separation of rubber from reinforcement materials in vehicle tires may be facilitated by first softening the rubber with a solvent followed by subjecting the tire to shear conditions to separate the rubber from the reinforcing materials. However a disadvantage of softening the rubber with solvents is that large volumes of solvents are required. This adds to costs together with the associated health, safety and environmental hazards associated with handling and ultimately disposing of large amounts of solvents. An example of such a process has been described in U.S. Pat. No. 5,316,224 in which material from waste tires was soaked in vats containing solvent for between about 5 to about 6 hours.
Attempts have also been made to reclaim carbon and volatile products from waste rubber by heating the rubber in the absence of oxygen to high temperatures in a microwave. A disadvantage of this process is that although rubber absorbs microwave energy it is a poor conductor. This results in uneven heating of the rubber. This uneven heating can have an adverse effect on the quality of the final product as it may be contaminated by combustion products or products resulting from incomplete carbonization.
It is therefore an object of the present invention to provide a method and apparatus for recovering an elastomeric material from an article containing that material or to provide the public with a useful or commercial choice.
According to a first broad from of the invention, there is provided a method of recovering elastomeric material from an article containing the material, the method including softening the elastomeric material by contacting the article with a fluid comprising an oil in admixture with solvents to soften the elastomeric material and subjecting the softened material to a shearing force to recover the elastomeric material.
Articles containing such elastomeric material suitably include vehicle tires, conveyor belts, rubberized fabrics, and elastomeric materials reinforced with metal, wires, filaments and the like.
The article containing the elastomeric material may be required to be precut or shredded to a processable size. Thus, vehicle tires are debeaded and sliced or coarsely shredded by any conventional shredding apparatus.
Suitable elastomeric materials include those capable of being softened by absorbing liquids into the elastomeric material. These materials may include synthetic or natural rubbers, modified rubbers, vulcanized rubbers, neoprenes, isoprenes, compositions of natural or synthetic rubbers, homopolymers or copolymers of conjugated diene hydrocarbons, homopolymers or copolymers or chloroprene, carboxylated rubbers, halogeneated rubbers, silicones, ABS elastomers, EP and EPT rubbers, cross-linked, graft, block or interpenetrating elastomers.
Suitably, the solvent is selected from hydrocarbons, nitrohydrocarbons, alcohols, ethers, ketones, esters, glycols and glycol ethers, cycloalkyl alcohols, esters and ketones, chlorinated hydrocarbons, cyclic ethers and aldehydes and mixtures thereof.
Preferred solvents in these classes include benzene, toluene, xylene, tetrohydronaphthalene, decahydronaphtalene, dipentene, petroleum liquids, naphtha liquids, nitropropane, methyl alcohol, ethyl alcohol, N-propyl alcohol, N-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, amyl alcohol, benzyl alcohol, diacetone, diethyl ether, diisopropyl ether, acetone, methyl isobutyl ketone, methyl acetate, ethyl acetate, N-butyl acetate, amyl acetate, hexyl acetate, amyl formate, ethyl lactate, butyl glycollate, methyl benzoate, butyl stearate, dimethylphthalate, dibutylphthalate, dibutylsebacate, methylabietate, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol ethyl ether acetate, ethylene glycol monobutyl ether, ethylene glycol ethyl ether acetate, ethylene glycol monobutyl ether, diethylene glycol, diethylene glycol monoethyl ether, propylene glycol, cyclohexanol, cyclohexanol acetate, cyclohexanone, methyl cyclohexanone, methylene dichloride, chloroform, carbon tetrachloride, dichloroethane, perchloroethane, dichloroethylene, trichloroethylene, perchloroethylene, mono chlorobenzene, dichloroethylether, 1,1,2,-trichlorotrifluroethane, dioxane and furfural.
Preferred solvents include toluene and xylene used alone or in mixture with each other or with other liquids. Other preferred liquids include Shellsol A, Shellsol 1021 and water. The preferred liquids may be mixed with inert liquids of high boiling point such as halogenated hydrocarbons.
Small proportions (5-11%) of inert hydrocarbons such as trichloroethylene, 1,1,1-trichloroethylene or carbon tetrachloride may also be added.
The solvent may also include waste solvents from industries such as the automotive and paint industries. It has been surprisingly found that impurities in these waste solvents does not adversely affect the ability of the liquid mixture to soften the elastomeric materials. Typical waste solvents include a mixture of aromatic solvents such as toluene, xylene and benzene.
The oil may include any suitable oil or mixture thereof. Suitable oils include engine oil, grease, coal oil, fuel oil, paraffin oil, mineral oil and oils derived from plants or animals. An especially preferred oil is that obtained as a product of destructive distillation of an elastomeric material or as a byproduct of carbonization of the tires. Typically such an oil, comprises limonene, other saturated hydrocarbons and aromatic compounds.
Typically the fluid mixture comprises between about 50 to about 90vol % oil and preferably between about 60 to about 80vol %.
In the method of the invention, the article containing the elastomeric material is contacted with the fluid for a time sufficient to soften the material. The material is typically
Kotab Dominic M.
Rosenbaum Mark
Silicon Valley IP Group PC
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