HK1135999B - Devulcanized rubber and methods - Google Patents

Description

Devulcanized rubber and method

[ technical field ] A method for producing a semiconductor device

The present invention relates generally to compositions and methods for devulcanizing rubber.

[ background of the invention ]

The recovery of used or discarded tires and other rubber products that are almost always cured or vulcanized by devulcanization has proven to be a very challenging problem. This problem can be attributed to the fact that: vulcanization crosslinks the polymer in the rubber or elastomer with sulfur. The resulting crosslinked rubber or elastomer is thermoset, preventing it from melting or recombining into other products like thermoplastic polymers or metals.

There is an increasing need for used or discarded tires and other rubber products to be recycled in uncured or devulcanized form. Fossil fuels (e.g., petroleum, natural gas, and coal) are raw materials for the manufacture of various synthetic rubbers and elastomers. It is also an energy source for the manufacture and transportation of natural rubber.

Various devulcanization processes have been devised to recover or reclaim rubber from used or discarded tires and other rubber products containing cured or vulcanized rubber or elastomers. If a large scale devulcanization process can be performed at relatively low cost without rubber degradation, the reclaimed rubber can be co-cured or co-vulcanized with virgin rubber to make new tires and other rubber products. However, no desulfurization process has proven commercially viable on a large scale to date. This is due to the fact that: each of the desulfurization processes invented to date are prohibitively expensive to construct and operate; furthermore, each process is very difficult to scale up and control and/or difficult to recover and purify high quality devulcanized rubber with minimal degradation for one or more of the following reasons: (1) operating at very high pressures; (2) operating at extremely high temperatures; (3) subjected to extreme shear forces; (4) the use of expensive containers and mechanical devices, such as extruders and high speed rollers; (5) the need to supply a specific form of energy, such as ultrasound and microwave radiation; (6) subjected to a mixture or composition of two or more reagents, catalysts and/or cocatalysts, which are often highly toxic; (7) even for partial devulcanization of cured rubber or elastomers, unusually long times are required; and (8) only the surface of the recovered rubber crumb can be devulcanized. The typical or well-known devulcanization processes invented to date, all of which have one or more of these 8 major drawbacks, are summarized below.

U.S. Pat. No. 4,104,205 discloses a process for devulcanizing polar group-containing sulfur-cured elastomers. This method applies a controlled dose of microwave energy between 915MHz and 2450MHz and between 41 and 177 watt-hours per pound that is sufficient to break substantially all carbon-sulfur and sulfur-sulfur bonds, but insufficient to break a significant amount of carbon-carbon bonds.

U.S. Pat. No. 5,284,625 discloses a process for continuously applying ultrasonic radiation to a vulcanized elastomer or rubber to crack carbon-sulfur, sulfur-sulfur and, if desired, carbon-carbon bonds in the vulcanized elastomer. Cured (i.e., vulcanized) elastomers or rubbers are reported to be cleavable by the application of a level of ultrasonic amplitude, optionally in the presence of pressure and heat. By this method, the rubber is softened, thereby enabling it to be reprocessed and reshaped in a manner similar to previously uncured rubber or elastomers.

U.S. Pat. No. 5,602,186 discloses a method of devulcanizing cured rubber by devulcanization. The method comprises the following steps: (1) contacting the rubber vulcanizate with a solvent and an alkali metal to form a reaction mixture; (2) heating the reaction mixture in the absence of oxygen with mixing to a temperature sufficient to react the alkali metal with the sulfur in the vulcanizate; and (3) maintaining the temperature below the temperature at which thermal cracking of the rubber occurs, thereby devulcanizing the vulcanizate. The patent indicates that it is preferable to control the temperature below about 300 c or below the temperature at which thermal cracking of the rubber is initiated.

U.S. Pat. No. 5,891,926 discloses a process for devulcanizing cured rubber into devulcanized rubber that can be remixed and resolidified into a suitable rubber product and recovering the devulcanized rubber from the cured rubber. The method comprises the following steps: (1) at least about 3.4 x 10⁶Heating the cured rubber to a temperature in the range of about 150 ℃ to about 300 ℃ in 2-butanol under a pressure of pascals (34.0atm) to devulcanize the cured rubber into a devulcanized rubber to produce a mixture of solid cured rubber, solid reclaimed rubber, and a reclaimed rubber 2-butanol solution; (2) removing the devulcanized rubber solution from the solid cured rubber and the solid devulcanized rubber; (3) cooling the 2-butanol solution of devulcanized rubber to a temperature of less than about 100 ℃; and (4) separating the devulcanized rubber from the 2-butanol.

U.S. Pat. No. 6,380,269 discloses a process for surface devulcanizing reclaimed rubber crumb into surface reclaimed devulcanized rubber crumb suitable for remixing and resolidification into high performance rubber products. The method comprises the following steps: (1) in the presence of 2-butanol at least about 3.4X 10⁶Heating the devulcanized rubber crumb to a temperature in the range of from about 150 ℃ to about 300 ℃ at a pressure of pascals (34.0atm) to devulcanize the surface of the rubber crumb, thereby producing a 2-butanol slurry of surface devulcanized reclaimed rubber crumb, wherein the reclaimed rubber crumb has a particle size in the range of from about 325 mesh to about 20 mesh; and (2) separating the surface devulcanized reclaimed rubber crumb from the 2-butanol.

U.S. patent No. 6,416,705 discloses a method and apparatus for devulcanizing cured or crosslinked elastomers or various rubbers by: (1) subdividing the rubber or elastomer into a small particle form; (2) confining the elastomer particles under an intense force as in a screw extruder or the like; and (3) imparting ultrasonic energy to the still confined particles to effect desulfurization. Energy is input into the confined particle in a direction perpendicular to the axis of advancement of the confined particle and a source of energy is partially reflected off the apparatus and back into the processing region for maximum energy utilization. In certain cases, the reflection of energy is achieved by opposing, powered ultrasonic horns that provide in-phase resonance. In another embodiment, oppositely oriented resonance-tuned ultrasonic horns are used, wherein not all of the ultrasonic horns are powered, the remainder being passive or unpowered reflecting ultrasonic horns that tune the resonant frequency to the resonant frequency of the powered ultrasonic horn. In one device, the pair of ultrasonic horns resonate in phase due to a delay line interposed between the two power sources. In other forms, the mass of the passive ultrasonic horn is balanced with the mass of the active ultrasonic horn to achieve in-phase tuning that maximizes energy reflection.

U.S. patent No. 6,479,558 discloses a method for selectively breaking chemical bonds of vulcanized solid particles, such as vulcanized crumb rubber, by biological treatment with a thermophilic microorganism selected from natural isolates of hot sulfur springs and the resulting products. The biological treatment of crumb rubber provides treated crumb rubber that is more suitable for use in new rubber formulations. Thus, greater loading levels and sizes of treated crumb rubber can be used in the new rubber mixtures.

U.S. Pat. No. 6,541,526 discloses mechanical/chemical methods and compositions for devulcanizing cured rubber that maintain macromolecules and render sulfur passive for later re-vulcanization. The method comprises the following steps: (1) shredding and grinding the used rubber; (2) removing metal bits from the shredded and ground rubber; and (3) adding the modifying composition while the shredded waste rubber particles are poured between two rollers that further grind the particles. The modified composition is a mixture of: a proton donor that selectively cleaves sulfur bonds and renders sulfur inactive; a metal oxide; organic acids that establish new bonds between macromolecules for later revulcanization; inhibitors that prevent the reattachment of sulfur groups to each other before the proton donor attaches itself to sulfur; and a friction agent for preventing the waste rubber from sliding between the rollers. The particles are subjected to at least ten sets of rollers.

U.S. patent No. 6,590,042 discloses a process for reclaiming sulfur cured (i.e., vulcanized) rubber by: (1) combining finely ground waste vulcanized rubber in a special twin-screw extruder capable of providing strong shearing force and mixing on time; (2) adding a regenerant to the extruder; and (3) masticating the rubber crumb and the regenerant in the extruder until the rubber crumb is devulcanized. This patent also discloses a unique composition of rejuvenating agents, which preferably include the following compounds: accelerators, N-tert-butyl-2-benzothiazole sulfonamide (TBBS), Zinc Mercaptobenzothiazole (ZMBT), 2-Mercaptobenzothiazole (MBT) and tetramethylthiuram monosulfide (TMTM); activators, zinc oxide and stearic acid; and zinc sulfates of fatty acids. The reclaimed rubber is suitable for manufacturing high-grade rubber products without adding an adhesive or is suitable for being combined with newly-made rubber compounds to manufacture high-specification rubber products.

U.S. Pat. No. 6,831,109 discloses a process for providing a modifier for devulcanizing cured elastomers and particularly vulcanized rubbers. The modifier contains a first chemical that is further processed and forms an organic cation and an amine; and the modifier further contains a second chemical as a co-catalyst for dissociating the first chemical. The cocatalyst contains a functional group that constitutes an acceptor for the amine.

U.S. Pat. No. 6,924,319 discloses a process for devulcanizing comminuted crumb rubber of rubber particles, the sulfur bridges on which are broken and activated for revulcanization. The method comprises the following steps: (1) treating the rubber particles to expand the rubber structure at the surface of the particles; and (2) mixing the treated rubber particles with a devulcanizing agent that mechanically and chemically reduces the rubber particles in a combination of heating and cooling mixers. The rubber particles and devulcanization formulation were heated to a temperature of 105-150 ℃ and immediately cooled thereafter. The devulcanizing compound is prepared by mixing the devulcanizing product with a vulcanizing and binding agent so as to uniformly coat the rubber particles therewith. The devulcanization compound may also be prepared by blending vulcanizing agents (such as accelerators, activators, coagents, binders, oxygen radical donors and scavengers) to coat the expanded rubber particles in layers.

Us patent 6,992,116 discloses a process, the invention of which is based on the unexpected finding that: the surface of the reclaimed rubber crumb particles may be prepared by treating the particles in the presence of 2-butanol at a rate of at least about 3.4X 10⁶Desulfurizing the agglomerate particles by heating the agglomerate particles to a temperature of at least about 150 ℃ at a pressure of pascals (34.0 atm). It is also based on the following unexpected findings: the surface devulcanized rubber crumb particles having a particle size in the range of about 325 mesh to about 20 mesh may be remixed and resolidified into high performance rubber products such as tires, hoses and power transmission belts. This patent more specifically discloses a method of surface devulcanizing reclaimed rubber crumb suitable for remixing and resolidifying to surface devulcanized reclaimed rubber crumb of high performance rubber products. The method comprises the following steps: (1) in the presence of 2-butanol at least about 3.4X 10⁶Heating the reclaimed rubber crumb to a temperature in the range of from about 150 ℃ to about 300 ℃ at a pressure of pascals (34.0atm) to devulcanize the surface of the rubber crumb, thereby producing a 2-butanol slurry of surface devulcanized reclaimed rubber crumb, wherein the reclaimed rubber crumb has a particle size in the range of from about 325 mesh to about 20 mesh; and (2) separating the surface devulcanized reclaimed rubber crumb from the 2-butanol.

[ summary of the invention ]

One aspect of the invention provides a method of devulcanizing rubber wherein a portion of the vulcanized rubber is contacted with a turpentine liquid in a reaction mixture in the absence of an alkali metal.

According to one aspect of the invention, the turpentine liquid is any one or more liquids selected from the group consisting of: natural turpentine, synthetic turpentine, pine oil, alpha-pinene, beta-pinene, alpha-pinoresinol, beta-pinoresinol, 3-carene, anethole, dipentene (p-mentha-1, 8-diene), terpene resin, nopol (nopol), pinane, camphene, p-isopropyltoluene, anisaldehyde, 2-pinane hydroperoxide, 3, 7-dimethyl-1, 6-octadiene, isobornyl acetate, terpene glycol hydrate, ocimene (ocimene), 2-pinanol, dihydromyrcenol, isoborneol, alpha-pinoresinol, alloocimene, alloocimenol, geraniol, 2-methoxy-2, 6-dimethyl-7, 8-epoxyoctane, camphor, p-menthe-8-ol, alpha-terpinyl acetate, Citral, citronellol, 7-methoxydihydrocitronellal, 10-camphorsulfonic acid, p-menthene, p-menth-8-yl acetate, citronellal, 7-hydroxydihydrocitronellal, menthol, menthone, polymers thereof, and mixtures thereof.

According to a preferred aspect of the invention, the turpentine liquid is any one or more liquids selected from the group consisting of: natural turpentine, synthetic turpentine, pine oil, alpha-pinene, beta-pinene, gamma-pinoresinol, beta-pinoresinol, polymers thereof, and mixtures thereof.

According to an aspect of the invention, any size of vulcanized rubber that facilitates contact with turpentine liquid may be provided. The rubber may be provided in the form of a block, one or more pieces, or a block, such as a large section or block of an automobile or truck tire. The rubber may comprise a complete device or article, such as a complete tire or sheet. According to a preferred aspect of the present invention, a vulcanizate is provided in the form of a vulcanizate crumb. According to a preferred aspect of the present invention, the rubber crumb has an average particle size of about 0.074 millimeters to about 50 millimeters.

According to an aspect of the invention, the turpentine liquid further comprises a solvent. According to a preferred aspect of the present invention, the solvent is selected from the group consisting of lower fatty alcohols, lower alkanes and mixtures thereof. According to a preferred aspect, the solvent is selected from the group consisting of ethanol, propanol, butanol, heptane and mixtures thereof.

According to one aspect of the invention, the rubber is contacted with the turpentine liquid at a temperature of about 10 ℃ to about 180 ℃. Preferably, the rubber is contacted with the turpentine liquid at a temperature below 180 ℃. More preferably, the rubber is contacted with the turpentine liquid at a temperature below 100 ℃.

According to another aspect of the invention, the rubber and turpentine liquid is at about 4X 10⁴Pascal to about 4 x 10⁵Contact under pressure of pascal. According to one aspect, the method is performed at a pressure of about 0.4 atmospheres to about 4 atmospheres.

According to one aspect of the invention, the method further comprises providing a reaction vessel in which the vulcanized rubber is contacted with the turpentine liquid. According to one aspect, a stirring member is provided, whereby the vulcanized rubber and the turpentine liquid contained in the reaction vessel are mixed and stirred.

According to one aspect, vulcanized rubber and turpentine liquid are incubated in a holding tank to extend the contact time. According to another aspect, the degree of vulcanization is controlled by the length of time the rubber is in contact with the turpentine liquid and/or the temperature of the mixture of rubber and turpentine liquid.

According to one aspect, the vulcanized rubber is contacted with a heterogeneous liquid comprising a turpentine liquid and water.

According to one aspect, the vulcanized rubber is contacted with a turpentine liquid in the presence of an energy input selected from the group consisting of: thermal energy at pressures in excess of 4 atmospheres at temperatures in excess of about 250 ℃, microwave energy, ultrasonic energy, mechanical shear forces, and mixtures thereof.

According to one aspect, a devulcanization catalyst is provided to the mixture of rubber and turpentine liquid.

According to one aspect, the reaction mixture is supplemented by the addition of a compound selected from the group consisting of: carbon dioxide, metal oxides, sulfur radical inhibitors, N-tert-butyl-2-benzothiazolesulfenamides (TBBS), Zinc Mercaptobenzothiazoles (ZMBT), 2-Mercaptobenzothiazoles (MBT), tetramethylthiuram monosulfide (TMTM), and mixtures thereof.

According to one aspect, thermophilic microorganisms are included in the reaction mixture.

Other aspects and advantages of this invention will become readily apparent to those skilled in this art from the following detailed description, wherein it is shown and described preferred embodiments of this invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.

[ detailed description ] embodiments

Non-limiting representative known turpentine oils that may be suitable for use in accordance with the present invention are disclosed in Ullmann's encyclopedia of Industrial Chemistry, sixth full revision, volume 37, page 565 (2003) and may include natural turpentine, synthetic turpentine, pine oil, alpha-pinene, beta-pinene, alpha-pinoresinol, beta-pinoresinol, 3-carene, anethole, dipentene (p-mentha-1, 8-diene), terpene resins, nopol, pinane, camphene, p-isopropyltoluene, anisaldehyde, 2-pinane hydroperoxide, 3, 7-dimethyl-1, 6-octadiene, isobornyl acetate, terpineol hydrate, ocimene, 2-pinanol, dihydromyrcenol, isoborneol, alpha-pinoresinol, ocimene alcohol, allol, alcohol, alpha-pinoresinol, alcohol, or allol 2-methoxy-2, 6-dimethyl-7, 8-epoxyoctane, camphor, p-menth-8-ol, alpha-terpinyl acetate, citral, citronellol, 7-methoxy dihydrocitronellal, 10-camphorsulfonic acid, p-menthene, p-menth-8-yl acetate, citronellal, 7-hydroxy dihydrocitronellal, menthol, menthone, polymers thereof, and mixtures thereof.

In a preferred embodiment of the invention, the selected sweetening agent is alpha-pinoresinol, natural turpentine, synthetic turpentine or pine oil, the latter three being rich in alpha-pinoresinol. Most preferably, the devulcanizing agent is alpha-pinoresinol.

Preferably, devulcanization of the cured (vulcanized) rubber or elastomer is carried out at a temperature in the range of about 10 ℃ to about 180 ℃. Most preferably, the desulfurization temperature is in the range of about 60 ℃ to about 140 ℃. The pressure at which the desulfurization is carried out is generally about 4.0X 10⁴Pascal (0.4atm or 5.9 lbs/in)²) To about 4.0X 10⁵Pascal (4.0atm or 74 lbs/in)²) Within the range of (1). Generally most preferably at about 8.0X 10⁴Pascal (0.8atm or 2 lbs/in)²) To about 2.0X 10⁵Pascal (2.0atm or 30 lbs/in)²) The method is performed at a pressure within a range. It is generally preferred that the devulcanized cured or vulcanized rubber or elastomer in the form of a bed of cured rubber or elastomer particles or pieces having a size in the range of about 0.074mm (200 mesh) to about 50mm is impregnated with one or more of the devulcanizing agents in a vessel (reactor) containing the one or more of the devulcanizing agents; most preferably, the size of the crumb particles or bits of cured (vulcanized) rubber or elastomer is in the range of about 0.297mm (50 mesh) to about 10 mm. It is generally preferred that the bed of agglomerated particles or pieces of cured (vulcanized) rubber or elastomer is agitated by passing the devulcanizing agent in liquid form through the bed of agglomerated particles or by steaming the agent. Preferably, the duration of the devulcanization is within about 1 minute to about 60 minutes. The cured (vulcanized) rubber or elastomer is partially or fully devulcanized; the degree of desulfurization can be achieved by controlling the desulfurization conditions, such as temperature and pressure, and the duration of desulfurization, and/or adjusting the type, relative amount, and concentration of the individual desulfurization reagents in the desulfurization vessel (reactor).

The most effective devulcanizing agent that has been claimed to be useful up to now for curing (vulcanizing) rubber or elastomers is 2-butanol. However, it is well known that large-scale commercial devulcanization of cured (vulcanized) rubber or elastomers requires large amounts of 2-butanol. A more recently invented desulfurization process that attempts to reduce the amount of 2-butanol required is described in U.S. Pat. No. 6,992,116. In this invention, 2-butanol is supplemented with another reagent, carbon dioxide, at a concentration of at least about 3.4X 10⁶Maintaining the sulfidation temperature in the range of about 150 ℃ to about 300 ℃ at a pressure of pascals (34.0atm) can achieve a reduction of 50% or more in the need for 2-butanol.

The present invention is based on the following totally unexpected findings: the family of devulcanizing agents, including natural and/or synthetic pinorenols, pinenes, and turpentines containing pinorenols, pinenes, and/or polymers thereof, are very effective in devulcanizing cured (vulcanized) rubber or elastomers. With all other known desulphurizationsThese agents (including 2-butanol and/or polymers thereof, as well as various solutions or mixtures of these agents with other compounds) are "green" (i.e., less toxic) and relatively inexpensive. It has been found that any of the devulcanizing agents penetrates or diffuses at an appreciable rate into the particles or pieces of cured (vulcanized) rubber or elastomer, thus causing the particles or pieces to expand and remain significantly and permanently expanded even under milder conditions (e.g., atmospheric temperature and pressure) than those required for the recent inventions relating to devulcanizing cured (vulcanized) rubber or elastomer. Scrap tire pieces having dimensions of about 30mm by 10mm and about 60mm by 20mm were observed in alpha-pinoresinol, one of the newly discovered devulcanizing agents of the present invention, at about 70 ℃ and slightly below 1.01 x 10⁵Pascal (1.0atm or 14.8 lbs/in)²) Becomes tearable with hand after heating for about 4 hours under pressure. The pieces thereafter turned into pasty masses after being left in the reagent alpha-pinoresinol for about 2 weeks. When analyzed by a separate qualification laboratory, the product was found to have a total sulfur content of 0.03 wt%. All of the above observations and results taken together indicate that the recovered used tire pieces that have undergone significant sulfur curing or vulcanization are essentially completely desulfurized. It can be readily estimated or inferred that if any finite size small pieces or particles of cured (vulcanized) rubber or elastomer, such as rubber components of a typical passenger car tire having dimensions of about 260mm wide, about 660mm outer diameter and about 410mm inner diameter, are subjected to moderate temperatures of between about 50 and 120 ℃ and at about 1.01 x 10⁵Pascal (1.0atm or 14.8 lbs/in)²) Is stored with one or more of the desulfurization reagents for a period of about one week to 6 weeks, then it may be at least partially or even fully desulfurized. Further, crumb particles from recycled cured (vulcanized) rubber from used tires having a size in the range of about 100 mesh (0.15mm) to about 10 mesh (2mm) are substantially fully devulcanized in about 12 minutes at the same pressure but at moderate to high temperatures (e.g., about 150 ℃). In practice, the density of the cured (vulcanized) rubber crumb particles is reduced from about 1.05 to about 0.90. The value of 1.05 is the weight average density of the rubber component close to a typical passenger car tire comprising cured SBR, natural rubber, carbon black and inorganic filler. In the uncured or desulphurised state of the catalyst,it is about 0.90. In addition, the approximate density of some types of synthetic rubbers is also known. It is worth noting that at least about 3.4X 10 is required at 150 deg.C⁶The lowest temperature reported by a recent comparative invention of pascal (34.0atm) pressure (U.S. patent No. 6,992,116). It is known to the fact that temperatures in excess of about 300 ℃ will induce depolymerization, thereby producing low molecular weight (i.e., low quality) devulcanized rubber. It is apparent that under mild conditions, any of the newly disclosed devulcanizing agents of the present invention will produce a devulcanized rubber that substantially retains the original microstructure of the rubber; which will allow it to maintain a relatively high molecular weight. Thus, any of the desulfurization agents of the present invention primarily cleave sulfur-sulfur bonds and/or carbon-sulfur bonds, but not carbon-carbon bonds. Thus, the devulcanized reclaimed rubber can be used in the same type of application as the virgin rubber or virgin rubber.

By utilizing any of the devulcanization reagents and methods of the present invention, cured (vulcanized) rubber or elastomers can be devulcanized with simple techniques without the need for high pressure vessels (reactors), microwaves, ultrasound, catalysts or other agents such as alkali metals or carbon dioxide.

The present invention more specifically discloses a family of desulfurization reagents including natural and/or synthetic pinoresinol, pinene, turpentine containing pinoresinol, pinene and/or polymers thereof, and various homogeneous solutions or heterogeneous mixtures of these compounds with other compounds. The invention also specifically discloses a set of methods for devulcanizing cured (vulcanized) rubber or elastomers with any of the devulcanizing agents into fully devulcanized, partially devulcanized or surface devulcanized rubber or elastomers that can be remixed and resolidified into useful rubber products. The method comprises cooling or heating the cured (vulcanized) rubber or elastomer to a temperature in the range of from about 5 ℃ to about 250 ℃ and at a temperature of at least about 1.01 x 10⁴Pascal (0.1atm) to about 1.01X 10⁶Pressure in the range of pascals (10.0 atm).

Examples

Example 1

In this example, alpha-pinoresinol is a devulcanizing agent used to cure (vulcanize) cuboid pieces of passenger car tires. Typical passenger car tires nominally contain about 35 wt% Styrene Butadiene Rubber (SBR) and about 18 wt% Natural Rubber (NR); the balance comprising carbon black, filler and sulfur. The dimensions of the rectangular parallelepiped blocks of the cured passenger vehicle tire were about 60mm by 20 mm. Initially, a small block weighing about 38 grams and about 400 grams of desulfurization reagent were charged into a vessel having a diameter of about 58mm and a volume of 250 ml. At a temperature of about 70 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) The desulfurization operation (experiment) was carried out at a pressure of (1) for about 240 minutes; this pressure was maintained in all experiments due to the altitude of the location where the desulfurization operation (experiment) was conducted. The small pieces absorbed about 36% of the desulfurization reagent at the end of the experiment and became tearable with hand, thereby indicating that the bonds in the sulfur crosslinks were essentially completely broken.

Example 2

This example is essentially the same as example 1, except that the cured (cured) passenger car tire desulfurized has cuboid platelet sizes of about 30mm by 10 mm. Initially, a small block weighing about 18 grams and about 400 grams of the desulfurization reagent were loaded into a vessel having a diameter of about 58mm and a volume of about 250 ml. At a temperature of about 70 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) The desulfurization operation (experiment) was carried out at a pressure of (1) for about 240 minutes. When left in a container at about 25 ℃ for 14 days with the reagents, the pieces turned into a paste-like mass. In addition, the total sulfur content of the pellets was analyzed by a separate identification laboratory to be about 0.03 wt%. It shows essentially complete breaking of the sulfur crosslinks in the cured (vulcanized) passenger tire nubs: the sulfur content of the cured passenger tire was nominally about 1.24 wt%.

Example 3

In this example, as in examples 1 and 2, α -pinoresinol is the devulcanizing agent; however, cured (vulcanized) passenger car tires are in the form of pelletized particles. As illustrated in examples 1 and 2, passenger vehicle tires nominally contain about 35 weight percent styrene butadiene rubber (R) ((R))SBR) and about 18 wt% Natural Rubber (NR); the balance comprising carbon black, filler and sulfur. The size of the aggregate particles is in the range of about 100 mesh (0.15mm) to about 10 mesh (2 mm). Initially, about 5 grams of the pellet and about 15 grams of desulfurization reagent were loaded into a test tube having a diameter of about 16mm and a length of about 125 mm. These pellet particles form a bed at the bottom of the tube. Slightly below 1.01X 10at 5 temperatures of about 16, 45, 65, 96 and 150 deg.C⁵Pascal (1.0atm or 14.7 lbs/in)²) A series of desulfurization operations (experiments) were carried out at the pressure of (1). At each temperature, the degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. Bed expansion ratios at 4 time increments of about 30, 60, 120 and 240 minutes: about 1.0, 1.05, 1.08 and 1.38 at 16 deg.C, respectively; about 1.0, 1.09, 1.20, and 1.47, respectively, at 45 ℃; about 1.16, 1.35, 1.44 and 1.46, respectively, at 65 ℃; and about 1.36, 1.60, 1.68, and 1.68, respectively, at 96 ℃. The bed expansion ratios at 150 ℃ at time increments of about 5, 12, 18 and 24 minutes were about 1.44, 1.88, 2.13 and 2.25, respectively. Note that the bed height expansion ratio is initially defined as 1.

The degree of devulcanization was evaluated at temperatures of about 16, 45, 65 and 96 ℃ from the previously described pre-established relationship between bed expansion ratio and density of devulcanized cured (vulcanized) rubber measured at 4 time increments of about 30, 60, 120 and 240 minutes. Degree of conversion: about 0, 15, 24 and 87 percent at 16 deg.C, respectively; about 0, 23, 46 and 89 percent (%) at 45 ℃ respectively; about 69, 94, 97 and 100 percent (%) at 65 ℃, respectively; about 69, 94, 97 and 100 percent (%) at 96 ℃. The degree of conversion was estimated at 150 ℃, also as previously described, at 4 time increments of about 5, 12, 18 and 24 minutes; which are about 54, 83, 94 and 99 percent, respectively.

The results suggest that the extent or range of devulcanization of cured (vulcanized) rubber or elastomers is easily varied by manipulating the temperature and duration of the devulcanization operation with the devulcanizing agent alpha-pinorenol. All of the partially or fully devulcanized, cured passenger vehicle tire crumb particles remain expanded even after at least two days of treatment with little to no change in expansion ratio. This observation indicates that the swelling of the crumb particles is not simply due to the physical swelling caused by penetration of the devulcanizing agent alpha-pinorenol into the crumb particles; in other words, it is indeed desulfurized. This observation is further confirmed by the fact that: the desulfurization reagent, which was originally completely transparent, became darker and opaque as the treatment time progressed; the higher the temperature, the faster the color change rate. This is due to the outflow of carbon black and filler from the pores of the agglomerate particles; as is clearly revealed by microscopic observation, the size and number of the pores expand with time.

Example 4

In this example, a mixture of alpha-pinoresinol and n-butanol (1-butanol) that formed a homogeneous solution was the desulfurization reagent. The final devulcanized cured (vulcanized) passenger car tire was in the form of pelletized particles as in example 3. Initially, about 5 grams of the pellet and about 15 grams of desulfurization reagent (a homogeneous solution comprising α -pinoresinol and 1-butanol) were loaded into a test tube having a diameter of about 16mm and a length of about 125 mm. These pellet particles form a bed at the bottom of the tube. At about 65 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) A series of desulfurization operations at a pressure of (1); wherein the concentration of the desulfurization reagent (solution) has a water average of about 1.01X 10⁵Pascal (10atm or 14.7 lbs/in)²) To about 20, 40, 60, 80, and 100 weight percent (wt%) 1-butanol (or, equivalently, about 80, 60, 40, 20, and 0 wt% alpha-pinoresinol). The degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. Bed expansion ratios at 5 time increments of about 20, 40, 60, 80 and 120 minutes: about 1.36, 1.40, 1.42, and 1.42 at 20 wt%, respectively; about 1.31, 1.37, 1.39, and 1.39 at 40 wt%, respectively; about 1.20, 1.24 and 1.24 at 60 wt%, respectively; about 1.15, 1.17 and 1.17 at 80 wt%, respectively; and at 100 wt% (which indicates pure 1-butanol) are about 1.16, and 1.16, respectively. Note that the bed height expansion ratio is initially defined as 1.

The degree of devulcanization was estimated as previously described from a pre-established relationship between bed expansion ratio and density of devulcanized cured (vulcanized) rubber measured at 5 time increments of about 20, 40, 60, 80 and 120 minutes. The desulfurization degree: about 85, 94 and 94 percent (%) at 20 wt%, respectively; about 76, 87, 91 and 91 percent (%) at 40 wt%, respectively; and at 60 wt% is about 54, 62 and 62 percent (%) respectively. The slight bed expansion observed at 1-butanol concentrations in excess of about 60 wt% can be generally attributed to the well-known physical expansion of cured (vulcanized) rubber induced by permeation of relatively small molecular size organic solvents such as butanol, propanol, and hexane.

The results suggest that cured (vulcanized) rubber or elastomers can be readily devulcanized to varying degrees with the devulcanizing agent (a homogeneous solution comprising alpha-pinorenol and 1-butanol) by varying the concentration of the agent and the duration of the devulcanizing operation. As long as the concentration of 1-butanol is less than about 80 wt% (or equivalently, the alpha-pinoresinol concentration is greater than about 20 wt%), the partially or nearly fully devulcanized cured (cured) passenger car tire crumb particles remain expanded without a significant change in expansion ratio even after at least two days of processing. This observation indicates that the swelling of the aggregate particles is not simply due to the physical swelling caused by the infiltration of the desulfurization agent into the aggregate particles; in other words, it is indeed desulfurized. This observation is further confirmed by the fact that: the color of the desulfurization reagent, which was originally transparent, becomes deeper and less transparent as desulfurization progresses. This is due to the outflow of carbon black and filler from the pores of the agglomerate particles.

The data obtained indicates that the higher the concentration of 1-butanol, the slower the desulfurization rate and the lower the maximum desulfurization degree or range that can be achieved, as long as the desulfurization reagent contains less than about 60 wt% 1-butanol. However, it is not necessarily disadvantageous, especially when only surface or partial desulfurization is to be achieved. The addition of 1-butanol to alpha-pinoresinol will make it easy to adjust the degree of desulfurization by reducing the desulfurization rate; enhancing the possibility of minimizing the consumption and/or cost of desulfurization reagents; the physical properties of the desulfurization reagent are altered to facilitate desulfurization.

Example 5

This example is similar to example 4; however, a homogeneous solution of alpha-pinoresinol and propanol, rather than alpha-pinoresinol and 1-butanol, is the desulfurization reagent. The final devulcanized cured (vulcanized) passenger car tire was in the form of pelletized particles as in examples 3 and 4. At about 65 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) A series of desulfurization operations were performed using the desulfurization reagent (solution) by varying the concentration level of the desulfurization reagent (solution) to about 20, 30, and 40 weight percent (wt%) propanol (or, equivalently, about 80, 70, and 60 wt% alpha-pinoresinol). The degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. Bed expansion ratios at 4 time increments of about 20, 60, 100 and 800 minutes: about 1.08, 1.24, 1.29 and 1.42 at 20 wt%, respectively; about 1.09, 1.17, 1.26, and 1.34 at 30 wt%, respectively; and at about 40 wt% are about 1.02, 1.07, 1.13, and 1.15, respectively.

As previously described, the degree of devulcanization was estimated from a pre-established relationship between bed expansion ratio and density from devulcanized cured (vulcanized) rubber measured at 4 time increments of about 20, 60, 100 and 800 minutes. The desulfurization degree: at 20 wt%, about 24, 62, 72 and 94 percent (%); about 26, 46, 66 and 81 percent (%) at 30 wt%, respectively; and about 6, 21, 37 and 42 percent (%) at 40 wt%, respectively. The relatively slight bed expansion observed when propanol concentrations exceed about 40% can be generally attributed to the well-known physical expansion of cured (vulcanized) rubber.

The data obtained indicate that the higher the propanol concentration, the slower the desulfurization rate and the lower the maximum desulfurization degree or range that can be achieved, as long as the desulfurization reagent contains less than 40 wt% propanol. Comparison of the data in this example with those of example 4 shows that the effect of the inert component (1-butanol in example 4 and propanol in this example) in the desulfurization reagent as a homogeneous solution is similar in nature but substantially different in amount on the rate and extent of desulfurization. It provides additional degrees of freedom to optimize the devulcanization operation to suit its purpose (which may be surface, partially or fully devulcanized), the tire type, the size and shape of the cured (vulcanized) rubber or elastomer to be devulcanized, and the prevailing price of the components in the devulcanizing agent. Furthermore, it seems quite reasonable to include two or more soluble components in the desulfurization reagent in the form of a homogeneous solution.

Example 6

In this example, a homogeneous solution of alpha-pinoresinol and isopropanol was used as the desulfurization reagent. The final devulcanized cured (vulcanized) passenger car tire was in the form of pelletized particles as in examples 4 and 5. At about 65 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) By varying the concentration level of the desulfurization reagent (solution) to about 20, 30, and 40 weight percent (wt%) isopropanol (or, equivalently, about 80, 70, and 60 wt% alpha-pinoresinol). Bed expansion ratios at 4 time increments of about 20, 60, 100 and 800 minutes: about 1.04, 1.15, 1.17, and 1.17 at 20 wt%, respectively; about 1.06, 1.16 and 1.16 at 30 wt%, respectively; and at 40 wt% are about 1.06, 1.18 and 1.18, respectively.

The degree of devulcanization was again estimated as previously described from a pre-established relationship between bed expansion ratio and density of devulcanized cured (vulcanized) rubber measured at 4 time increments of about 20, 60, 100 and 800 minutes. The desulfurization degree: at 20 wt%, about 12, 42, 46 and 46 percent (%); about 18, 44 and 44 (%), respectively, at 30 wt%; and about 18, 48 and 48 percent (%) at 40 wt%, respectively.

The data obtained show that the desulfurization rate and the maximum degree or range of desulfurization achievable show relatively little variation when the concentration of isopropanol in the desulfurization reagent is between about 20 wt.% and about 40 wt.%. It is substantially different from the trend obtained from the data in examples 4 and 5.

Example 7

This example is similar to example 4; a homogeneous solution of alpha-pinoresinol and heptane, but not alpha-pinoresinol and isopropanol, is the desulfurization reagent. At about 65 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) A series of desulfurization operations were performed with the desulfurization reagent (solution) by varying the concentration level of the desulfurization reagent (solution) to about 20, 30, and 40 weight percent (wt%) heptane (or, equivalently, about 80, 70, and 60 wt% alpha-pinoresinol). Bed expansion ratios at 4 time increments of about 20, 60, 100 and 800 minutes: about 1.17, 1.28, and 1.28 at 10 wt%, respectively; about 1.08, 1.23, 1.29 and 1.29 at 20 wt%, respectively; about 1.13, 1.19, 1.25 and 1.25 at 30 wt%, respectively; and at 40 wt% are about 1.15, 1.18, 1.24 and 1.24, respectively.

The degree of devulcanization was estimated as previously described from a pre-established relationship between bed expansion ratio and density from devulcanized cured (vulcanized) rubber measured at 4 time increments of about 20, 60, 100 and 800 minutes. The desulfurization degree: about 46, 71 and 71 percent (%) at 10 wt%, respectively; about 24, 60, 72 and 72 percent (%) at 20 wt%, respectively; about 37, 48, 64 and 64 percent (%) at 30 wt%, respectively; and about 42, 48, 62 and 62 percent (%) at 40 wt%, respectively.

The data also shows that the higher the heptane concentration, the slower the desulfurization rate (except at an early stage) and the lower the maximum desulfurization degree or range that can be achieved, as long as the desulfurization reagent contains less than about 40 wt% heptane.

Comparison of the data in this example with those of examples 4 and 5 again shows that the effect of the inert components in the desulfurization reagent on the rate and extent of desulfurization obtained in this example is somewhat similar in nature but substantially different in amount to those of examples 4 and 5.

Example 8

This example is almost identical in every respect to example 4, but a homogeneous solution of α -pinoresinol with 2-butanol instead of 1-butanol was used as desulfurization reagent.

It is clear that 2-butanol is considered one, if not the most effective, of the desulfurization agents in some patents (e.g., as outlined in paragraph [0014 ]). However, it requires stringent conditions in terms of pressure and temperature and some auxiliary reagents and/or catalysts to exhibit its effectiveness.

Initially, about 5 grams of the pellet and about 15 grams of the desulfurization reagent (a homogeneous solution containing α -pinoresinol and 2-butanol) were loaded into a test tube having a diameter of about 16mm and a length of about 125 mm. These pellet particles form a bed at the bottom of the tube. At about 65 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.71 bs/in)²) A series of desulfurization operations (experiments) were carried out at the pressure of (1). Bed expansion ratios at 5 time increments of about 20, 40, 60, 80 and 120 minutes: about 1.24, 1.29, 1.34 and 1.34 at 20 wt%, respectively; about 1.24, 1.29, 1.33, and 1.33 at 40 wt%, respectively; and at 60 wt% are about 1.12, 1.23 and 1.23, respectively. The corresponding desulfurization degree: about 62, 72, 81 and 81 percent (%) at 20 wt%, respectively; about 62, 72, 79 and 79 (%), respectively, at 40 wt%; and at 60 wt% are about 46, 92, 94 and 94 (%), respectively. The slight bed expansion observed at 2-butanol concentrations in excess of about 60 wt% can be generally attributed to the well-known physical expansion of the relatively small molecular size organic solvent permeation-induced cured (vulcanized) rubber.

Comparison of the results of this example with those of examples 4 to 7, particularly those of example 4, shows that at any given concentration, solutions comprising alpha-pinoresinol and 2-butanol are similarly effective in devulcanizing cured rubber as solutions comprising alpha-pinoresinol and 1-butanol. Furthermore, the degree of reduction in the effectiveness of α -pinoresinol in devulcanizing cured rubber is about the same when diluted with 1-butanol, 2-butanol, propanol, isopropanol and heptane.

Example 9

This example is similar to examples 4 to 8 in almost all respects, including devulcanized vulcanized (vulcanized) rubber crumb particles. A unique feature is that the inert component solvent in the desulfurization reagent is ethanol, which is one of the most commonly available organic solvents. At about 65 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) Some devulcanization operations (experiments) were performed at pressures to determine if the effect of adding ethanol was similar to those of adding any of the other solvents used in examples 4-8, i.e. 1-butanol, propanol, isopropanol, heptane and 2-butanol. The results indicate that this is true; when the concentration of ethanol in the desulfurization reagent is less than about 70 wt.%, the degree of desulfurization achievable is in the range of about 20 percent (%) for about 20 minutes of desulfurization (treatment) time to about 50 percent (%) for about 100 minutes of desulfurization (treatment) time.

Example 10

In this example, the devulcanizing agent is a heterogeneous mixture of alpha-pinoresinol and water rather than a homogeneous solution of alpha-pinoresinol and an organic solvent. The final devulcanized cured (vulcanized) passenger car tire was in the form of pelletized particles as in examples 4 and 9. At about 96 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) A series of desulfurization operations (experiments) were performed with the desulfurization reagent (mixture) by varying the weight fraction of the desulfurization reagent (mixture) in the mixture to about 20, 30, and 40 weight percent (wt%) water (or, equivalently, about 80, 70, and 60 wt% alpha-pinoresinol). The degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. Bed expansion ratios at 4 time increments of about 20, 40, 60 and 80 minutes: about 1.35, 1.46 and 1.46 at 20 wt%, respectively; about 1.33, 1.49 and 1.49 at 30 wt%, respectively; and at about 40 wt% are about 1.34, 1.47, and 1.47, respectively. The corresponding desulfurization degree: about 62, 75 and 75 percent (%) at 20 wt%, respectively; about 59, 79 and 79 (%), respectively, at 30 wt%; and at 40 wt% are about 61, 76 and 76 (%), respectively.

The data obtained show that the desulfurization rate and the maximum degree of desulfurization achievable show relatively minimal changes when the weight fraction of water in the desulfurization reagent that is a heterogeneous mixture is between about 20 wt.% and about 40 wt.%. It is substantially different from the trend of the data obtained in examples 4 and 5 and similar to the trend of the data of example 6. However, the initial desulfurization rates recorded in this example were much greater than those recorded in example 6. This result can be attributed to the effect of vigorous mechanical agitation of the reagents and the aggregate particles by boiling water bubbles.

Example 11

This example is similar to example 3 in many respects including devulcanized cured (vulcanized) rubber crumb particles. The unique characteristic is that the desulfurizing agent is natural turpentine rather than alpha-pinoresinol, and the desulfurizing agent can be widely obtained. The desulfurization operation was performed at only one temperature level of about 96 deg.c instead of 5 temperature levels (experiment). As in example 3, the pressure was maintained slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²). The degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. Bed expansion ratios at 4 time increments of about 20, 40, 60 and 80 minutes were about 1.29, 1.56, 1.60 and 1.62, respectively; the corresponding degrees of conversion are about 54, 86, 90 and 91 percent (%), respectively.

Comparison of the data obtained with those from example 3 shows that natural turpentine containing alpha-pinoresinol is only slightly less efficient than alpha-pinoresinol for devulcanizing cured rubber. Notably, as disclosed in examples 4 to 10, alpha-pinoresinol is substantially more effective as a desulfurization agent than any other agent that is a solution or mixture containing alpha-pinoresinol.

Example 12

This example is similar to example 11. The unique feature is that the desulfurization reagent is synthetic turpentine (which is also widely available) rather than natural turpentine. At two temperatures of about 96 and 150 DEG CTwo desulfurization operations (experiments) were performed horizontally. The pressure was kept slightly below 1.01X 10at both temperatures⁵Pascal (1.0atm or 14.7 lbs/in)²). At each temperature, the degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. The bed expansion ratios at about 96 ℃ at 4 time increments of about 20, 40, 60 and 80 minutes were about 1.46, 1.48 and 1.48, respectively. The corresponding degrees of conversion were about 75, 78 and 78 (%), respectively. The bed expansion ratios at about 150 ℃ in 6 time increments of about 2, 5,8, 11, 14 and 24 minutes were about 1.35, 1.60, 1.75, 1.95, 2.03 and 2.03, respectively. The corresponding degrees of conversion are about 46, 67, 76, 87, 90 and 90 (%) percent, respectively.

Comparison of the data obtained with those from example 3 using alpha-pinoresinol as the reagent shows that synthetic turpentine enriched in alpha-pinoresinol is slightly less efficient than alpha-pinoresinol as a desulfurization reagent at about 96 ℃, but it is nearly equally effective at about 150 ℃. Furthermore, comparison of the data from this example with the previous examples suggests that synthetic turpentine is slightly less efficient than natural turpentine as a desulfurization reagent at about 96 ℃. However, it is noteworthy that natural turpentine begins to boil at about 150 ℃ and therefore cannot be operated continuously at the above pressures.

Example 13

In this example, pellets of cured (vulcanized) rubber are devulcanized with natural turpentine and synthetic turpentine in parallel. At a temperature level of only about 65 ℃ and slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²) The desulfurization operation (experiment) was carried out at the pressure of (1). The degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. Bed expansion ratios at 4 time increments of about 20, 40, 60 and 80 minutes, about 1.28, 1.37, 1.51 and 1.54 for natural turpentine, respectively; and about 1.28, 1.38, 1.43 and 1.43 for synthetic turpentine, respectively. The corresponding conversion degree for natural turpentine is about 70 percent, 86 percent and 100 percent respectivelyAnd 100 (%); and about 70, 88, 96 and 96 percent (%) for synthetic turpentine, respectively.

Comparison of the data obtained with those from example 3 shows that at about 65 ℃, alpha-pinoresinol, natural turpentine and synthetic turpentine are nearly equally effective as desulfurization agents.

Example 14

In this example, both synthetic turpentine and α -pinoresinol were used as desulfurizing agents for desulfurizing aggregate particles of cured (vulcanized) isoprene rubber having a size in the range of 6 to 10 mesh. The desulfurization operation (experiment) was carried out at only one temperature of about 96 ℃. Maintaining the pressure slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²). The degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. The bed expansion ratios at 4 time increments of about 20, 40, 60 and 80 minutes were about 1.23, 1.32, 1.45 and 1.49 for the synthetic turpentine, and about 1.33, 1.42, 1.49 and 1.49 for alpha-pinoresinol, respectively. The corresponding conversion degrees were about 44, 58, 74 and 79 (%) for the synthesized turpentine, and about 59, 71, 79 and 79 (%) for alpha-pinoresinol, respectively.

Comparison of the two sets of data obtained shows that, especially in the early stages at a temperature of about 96 ℃, synthetic turpentine rich in α -pinoresinol is only slightly less efficient than α -pinoresinol for devulcanizing cured isoprene rubber. Comparison of the results of this example with those of example 3 reveals that the cured isoprene is less susceptible to devulcanization by alpha-pinorenol than the SBR-rich cured passenger car tires. Notably, as disclosed in examples 4 to 10, alpha-pinoresinol is substantially more effective as a desulfurization agent than any other agent that is a solution or mixture containing alpha-pinoresinol.

Example 15

In this example, synthetic turpentine and alpha-pinoresinol were used both to make the size in the range of 6 to 10 meshThe desulfurizing agent for desulfurizing granular particles of the cured (vulcanized) SBR rubber in the inner part. The desulfurization operation (experiment) was carried out at only one temperature of about 96 ℃. Maintaining the pressure slightly below 1.01X 10⁵Pascal (1.0atm or 14.7 lbs/in)²). The degree of bed expansion is calculated and recorded from the ratio between the bed height at any time increment and the original bed height. The bed expansion ratios at 4 time increments of about 20, 40, 60 and 80 minutes were about 1.46, 1.54 and 1.54 for the synthetic turpentine, and about 1.60, 1.64 and 1.64 for alpha-pinoresinol, respectively. The corresponding degrees of conversion are about 75, 85 and 85 (%) for the synthetic turpentine, and about 90, 93 and 93 (%) for alpha-pinoresinol, respectively.

Comparison of the two sets of data obtained shows that synthetic turpentine rich in α -pinoresinol is only slightly less efficient than α -pinoresinol for devulcanizing cured SBR rubber at a temperature of about 96 ℃. Comparison of the results of this example with those of example 3 reveals that cured SBR is nearly equally susceptible to devulcanization with alpha-pinorenol as compared to SBR-rich cured passenger tire.

Thus, it will be appreciated by those skilled in the art that the present invention is capable of providing compositions and methods suitable for devulcanizing rubber. Moreover, it is to be understood that the forms of the invention shown and described are to be taken as the presently preferred embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in each and every process step with the benefit of the present disclosure. It is intended that the following claims be interpreted to embrace all such modifications and changes and, accordingly, the specification and drawings to be regarded in an illustrative rather than a restrictive sense. Furthermore, it is intended that the appended claims be construed to include alternative embodiments.

Claims (24)

1. Use of a turpentine liquid as a devulcanizing agent in the absence of alkali metals for devulcanizing vulcanized rubber.

2. The use of claim 1, wherein the turpentine liquid is selected from the group consisting of:

natural turpentine, synthetic turpentine, pine oil, alpha-pinene, beta-pinene, alpha-pinoresinol, beta-pinoresinol, 3-carene, anethole, dipentene, terpene resins, nopol, pinane, camphene, p-isopropyltoluene, anisaldehyde, 2-pinane hydroperoxide, 3, 7-dimethyl-1, 6-octadiene, isobornyl acetate, hydroterpineol, ocimene, 2-pinanol, dihydromyrcenol, isoborneol, gamma-pinoresinol, alloocimene, alloocimenol, geraniol, 2-methoxy-2, 6-dimethyl-7, 8-epoxyoctane, camphor, p-mentha-8-ol, alpha-terpinyl acetate, citral, citronellol, 7-methoxy dihydrocitronellal, and the like, 10-camphorsulfonic acid, p-menthene, p-menth-8-yl acetate, citronellal, 7-hydroxydihydrocitronellal, menthol, menthone, polymers thereof, and mixtures thereof.

3. The use of claim 1, wherein the turpentine liquid is selected from the group consisting of: natural turpentine, synthetic turpentine, pine oil, alpha-pinene, beta-pinene, alpha-pinoresinol, beta-pinoresinol, polymers thereof, and mixtures thereof.

4. The use according to claim 1, wherein the vulcanized rubber is provided in the form of: at least one whole vulcanized rubber article, vulcanized rubber block, vulcanized rubber section, vulcanized rubber pellet, vulcanized rubber sheet, or a composite or mixture thereof.

5. The use according to claim 4, wherein the vulcanized rubber is in the form of rubber crumb.

6. The use according to claim 5, wherein the rubber crumb has an average particle size of from 0.074mm to 50 mm.

7. The use of claim 1, wherein said turpentine liquid further comprises a solvent or a liquid immiscible with the turpentine liquid.

8. The use of claim 7, wherein the solvent is selected from the group consisting of lower fatty alcohols, lower alkanes and mixtures thereof.

9. The use of claim 8, wherein the solvent is selected from the group consisting of ethanol, propanol, butanol, heptane, and mixtures thereof.

10. The use of claim 8, wherein said liquid immiscible with said turpentine liquid further comprises water.

11. Use according to claim 10, wherein the water is boiling water.

12. The use of claim 1, wherein the rubber is contacted with the turpentine liquid at a temperature of 10 ℃ to 180 ℃.

13. The use of claim 1, wherein said rubber and said turpentine liquid are present at 4 x 10⁴Pascal to 4 x 10⁵Contact under pascal pressure.

14. The use of claim 1, further comprising:

providing a reaction vessel, and contacting the vulcanized rubber with the turpentine liquid in the reaction vessel;

providing a means for agitating said vulcanized rubber and said turpentine liquid in said reaction vessel; and

stirring the rubber and the turpentine liquid.

15. The use of claim 1, further comprising incubating said vulcanized rubber with said turpentine liquid in a holding tank.

16. The use of claim 14, wherein the vulcanized rubber is contacted with the turpentine liquid for a period of time to induce a predetermined degree of devulcanization.

17. The use of claim 1, wherein said rubber is contacted with said turpentine liquid at a temperature of less than 180 ℃.

18. The use of claim 1, wherein said rubber is contacted with said turpentine liquid at a temperature of less than 100 ℃.

19. The use of claim 1, further comprising providing microwave energy, providing ultrasonic energy, providing mechanical shear force, or subjecting a reaction mixture of said vulcanized rubber and said turpentine liquid to a combination thereof.

20. The use of claim 19, wherein the microwave energy, ultrasonic energy, mechanical shear force, or a combination thereof is provided to the reaction mixture prior to the devulcanization.

21. The use of claim 19, wherein the microwave energy, ultrasonic energy, mechanical shear force, or a combination thereof is provided to the reaction mixture after the desulfurization.

22. The use of claim 1, further comprising providing a devulcanization catalyst to a reaction mixture of said vulcanized rubber and said turpentine liquid during contact of said vulcanized rubber with said turpentine liquid.

23. The use of claim 1, further comprising providing a compound selected from the group consisting of carbon dioxide, metal oxides, sulfur radical inhibitors, N-tert-butyl-2-benzothiazolesulfenamides, zinc mercaptobenzothiazoles, 2-mercaptobenzothiazoles, tetramethylthiuram monosulfide, and mixtures thereof, to a reaction mixture of said vulcanized rubber and said turpentine liquid during contact of said vulcanized rubber with said turpentine liquid.

24. The use of claim 1, further comprising providing a thermophilic microorganism to a reaction mixture of said vulcanized rubber and said turpentine liquid during contact of said vulcanized rubber with said turpentine liquid.