WO1995004640A1

WO1995004640A1 - Method for recycling tires

Info

Publication number: WO1995004640A1
Application number: PCT/CA1994/000416
Authority: WO
Inventors: William Forlippa
Original assignee: MOVETECH Inc
Current assignee: MOVETECH Inc
Priority date: 1993-08-05
Filing date: 1994-08-04
Publication date: 1995-02-16
Anticipated expiration: 1997-02-04
Also published as: AU7379394A

Abstract

A process for the separation of metal from a rubber tire, which comprises: a) cutting the tire into two pieces; b) pressing the pieces between rollers to devulcanize the rubber; c) subjecting the devulcanized rubber to a magnetic field while holding the devulcanized rubber stationary to draw the larger metal inclusion pieces from the rubber; and d) grinding the rubber into pieces for recycling the same; and an apparatus for treating vulcanized rubber.

Description

METHOD FOR RECYCLING TIRES

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for recycling tires and, more particularly, to a method for removing steel wires from rubber material by compressing split tires to devulcanize them prior to removing the metal inclusion therein.

BACKGROUND OF THE frJVENTION

Reclaiming processes for the recovery of rubber, metal content and tire cord have been known; however, such processes have attempted to grind the tire and then salvage the metal and cord therefrom. The pieces of rubber containing retained metal or cord therein were then discarded while the recoverable material was recycled.

Without such reclaiming processes, the accumulation of whole used tires creates significant societal problems. The storage of used tires in dumps creates a hazard to underground water systems since toxic materials may leach from the tires into the ground water. The storage of used tires also creates fire hazards. In addition, the burning of tires, either accidentally or as an energy source, creates air pollution and noxious odors. Tire dumps also create an eyesore which reduce property values and diminish the natural beauty of the environment.

In order to alleviate the problems associated with the accumulation of used tires, many local governments have begun programs for purchasing used tires and using the tires in children recreation areas. However, there is still a need for improved ways of disposing of used tires in which the components which make up the tire can be recovered and reused to make new tires or other articles.

Various attempts have been made to enable tires to be ground into pieces for reuse. Exemplary processes include some of the following.

SUBSTITUTE SHEET U.S. Patent Number 3,384,309 to James E.F. Marshall relates to a process for the separation of metal from rubber or similar compositions and, more particularly, to the reclamation of rubber from scrap tires having wire plies. Pieces of scrap tire are passed through a cracking plant and converted to crumbs. The crumbs are separated by size by a shaker and crumbs that are contaminated by heavy pieces of wire are removed by a magnetic drum separator and discarded. No steel wire is removed from the rubber prior to crumb formation and the crumbs are exposed to only one magnetic separator.

In U.S. Patent Number 4,090,670 to Bennett, rubber is recovered for reuse, e.g. , from scrap pneumatic tires by briefly raising the surface of the tire to a high temperature and then rasping the heat-treated surface. The surface of the rubber is preferably raised to a temperature in the range of 2000° to 3000°C for a period of less than 0.5 seconds. A machine is provided which accepts pieces of vulcanized material and progressively reduces them to heat-treated particles by repetitively heating a surface of each piece and attacking it with a rasping tool.

In U.S. Patent Number 4,607,796 to Enikolopov et al. , a method is provided wherein the source material (rubber or vulcanization products) is pulverized in an extruder wherein it is first compressed by a force of 0.2 to 0.7 MPa, then subjected simultaneously to a pressure ranging from 0.2 to 50 MPa and a shear force ranging from 0.03 to 5 N/mm² while heating the material to a temperature ranging from 80° to 250°C and then cooling said material to a temperature ranging from 15° to 60°C. The source materials can be used rubber goods, such as used tires and rejects of the tire industry, footwear and industrial rubber production. This method does not address the removal of steel or textile supports.

Japanese Patent Number 5-4011 - 184 discloses a method for recovering rubber powder from scrap tires. The tires are crushed and then exposed to a primary magnetic separator. The remaining substances are exposed to a secondary magnetic separator and the iron-containing rubber particles are introduced to a cracking means

SUBSTITUTE SHEET to separate the iron components and the adhered substances; and again supplying the substances to the primary magnetic separator.

U.S. Patent Number 4,025,990 (Norris G. Lovette, Jr.) discloses a process wherein scrap tires, containing magnetic components and non-magnetic rubber and cord components, are cooled in a cryogenic freezer to the embrittlement temperature, comminuted in a comminution device and passed through a series of screening and density classification operations, followed by magnetic material separation and further cryogenic size reduction to produce a rubber crumb product having a particle size of about 1/20 inch or less.

U.S. Patent Number 4, 113, 186 (George William Smith) discloses a system for treating rubber tires which reduces the tires to a particulate agglomeration wherein cord and rubber matter therein can be separated. A further treating of those rubber particles reduces them to screen size. The system requires the steps of: (a) initially debeading the tire; (b) cutting the tire into chunks; (c) regulating the quantity of chunks as they pass through the system; (d) grinding the tire in a high intensity mixer; (e) passing the grind to a hammer mill to loosen the rubber and the cord from one another; and (f) separating the rubber particles to a size of about 30 to 100 mesh as a final product. Oversized pieces of rubber discharged from the separator near the end of the system would be returned to the high intensity mixer.

U.S. Patent Number 4,134,556 (Ehrlich et al.) describes a tire shredder in which multiple cutting discs are fixed in spaced-apart positions on each of two side- by-side counter-rotating shafts so that peripheral portions of the discs on each shaft extend into the spaces between discs on the opposite shaft. Each disc has a smooth cylindrical peripheral surface which meets opposed sidewalls at sharp continuous cutting edges. Material shredded by the discs falls out onto a slowly rotating screening drum encircling the disc assembly. The smallest shredded pieces pass through the drum onto a discharge conveyor.

SUBSTITUTE SHEET U.S. Patent Number 4,405,090 to Wakeem describes an apparatus which includes a conveyor which carries the tires through a cutting mechanism in the form of a pair of transverse saw blades and a single longitudinal saw blade. The saw blades cut each tire into four pieces which are fed down an inclined chute against the abrasive surface of a grinding wheel. The tire pieces are ground by the wheel into small particles of rubber and steel which are separated from one another by a magnetic conveyor.

U.S. Patent Number 4,714,201 to Rouse et al. discloses an apparatus and method for use in reducing discarded pneumatic tires. The apparatus includes a series of machines which successively shear and granulate the tires into smaller and smaller pieces. In one embodiment, two successive rotary shear machines are followed by a granulator. The pieces are sorted before being sent to the granulator and oversize pieces are sent a second time through the two shears. In another embodiment of the invention, a single rotary shear apparatus is followed by a pair of granulators which successively reduce the size of pieces of material to progressively smaller sizes.

Materials are fed to the rotary shears and granulators by conveyors whose speeds are controlled by varying the frequency of alternating current electric power supplied to electric monitors driving the conveyors, with the frequency being controlled in responses to sensing the load on the shears and granulators, so that the shears and granulators are operated at or near their maximum capacity.

U.S. Patent Number 4,726,530 to Miller discloses a continuous process for reclaiming rubber, steel and fiber products from tires wherein the tires and tire material flow on conveyors throughout the various steps of the process, including steps of shredding a flow of whole tires into pieces in a shear-type shredder, and screening the flow of tire pieces by size into a first flow containing pieces of at least as large as a specific size, and a second flow containing pieces under a specified size. Reshredding and rescreening the pieces of the first flow is performed until they are smaller than the specified size. Granulating the pieces of the second flow occurs in a first granulator wherein the pieces remain in the granulator until they are reduced

SUBSTITUTE SHEET below a second specified size. Fiber materials are vacuumed from the flow of granulated material within an air separator after granulation and steel and steel- containing rubber pieces are removed from the flow of material via a magnetic separator after the fiber materials have been removed.

U.S. Patent Number 4,813,614 (Moore et al.) discloses a process wherein scrap tires are subjected to low temperatures that are approximately the temperature of crystallization of the components thereof. The product at this lowered temperature is then crushed sufficiently to cause the components thereof to release sufficiently to be subsequently separated according to material. The separation steps can include subjecting the crushed material to magnetic or electrostatic fields, air flows caused by either pressurized air or vacuums, and mechanical separation with vibratory screens and rakes. The materials of the original product are sufficient separated to enable them to be recycled into a reusable product.

U.S. Patent Number 5,024,386 to Alvin L. Morris discloses a method and apparatus for shredding tires, comprising the steps of: debeading the tire; cutting it diametrically into segments; and then spreading the sidewalls apart while flattening each segment and feeding the segment into a shredding cutter causing the shredding of the tire while the segment is held in flattened condition. The resulting crumbs are then granulated and the granulated particles are passed over magnetic separator drums.

Finally, U.S. Patent Number 4,840,316 (Barclay) discloses an apparatus for removing the rubber from the crown portion of a tire having a rotatably driven rasp and a linearly displaceable capture roller. The capture roller is moved from a load position distant the rasp to an engagement position closely adjacent the rasp. First and second tensioning rollers are biased to pinch a tire between each of the tensioning rollers and the capture roller. In forcing a captive tire into the area between the tensioning rollers, the capture roller presents to the rasp a work surface which is

SUBSTITUTE SHEET highly stressed. Traction-enhancement rollers further deform the tire by increasing the wrap angle around each of the tensioning rollers.

Despite the prior efforts toward recycling tires discussed above, there remains a need for new methods of recycling used tires, e.g. , recycling tires in which more of the rubber from each tire is recovered and the resulting rubber product has fewer steel contaminants. There is also a need for a process for efficiently recycling the components of used tires and for processes which generate less waste.

There is also a need for improved processes for the removal of steel from tires. It is particularly desirable that the steel wire recovered from used tires have a low rubber content in order to both reduce the waste of rubber and to reduce pollution emitted from steel recovery furnaces. There is also a need for rubber powders which can be used to prepare articles that contain rubber.

SUMMARY OF THE INVENTION

The present invention relates to a novel process for recovering reusable material from steel-containing rubber articles, especially used tires. It has been discovered that by magnetically removing steel wires from heated, devulcanized tire scrap prior to granulation of the tire scrap, a rubber powder having a very low iron content can be recovered. The use of the term "tire scrap" in the present invention relates to whole or ungranulated portions of used or defective tires as well as other rubber products having metal inclusion pieces in the rubber. The rubber powder that is recovered by the process of the present invention has a lower steel content than processes which granulate steel-containing used tires, without first removing some of the steel reinforcing wires from the used tires. Another aspect of the present invention is that steel, having relatively little rubber contamination, can be recovered from used tires. The objectives of the present invention are achieved without requiring the rubber articles to be cooled below their crystallization temperatures.

SUBSTITUTE SHEET One embodiment of the present invention for recycling components of tires comprises the following steps: cutting the tire into two pieces; pressing the pieces between rollers to devulcanize the rubber; subjecting the devulcanized rubber to a magnetic field while holding the devulcanized rubber stationary to draw the larger metal inclusion pieces from the rubber; and grinding the rubber into pieces to be recycled.

Another embodiment of the invention involves a process for the extraction of steel from vulcanized rubber. The process comprises the step of heating an ungranulated, steel-containing rubber article and applying a magnetic field to the ungranulated, steel-containing rubber article, said magnetic field having sufficient strength to remove at least a portion of the steel contained in the rubber article.

A further embodiment of the invention involves a process for recovering rubber and metal content from tires by debeading the tires; devulcanizing the tires by compressing the tires between rollers; removing steel wire, with a magnetic separator, from the compressed material; grinding the material that results from the previous step into pieces; passing said pieces by a magnetic separator to remove additional steel wire; grinding the pieces that result from the previous step into particles having a mean size of at least about 50 mesh U.S. standard size; and separating flock cord from the rubber particles and recovering the rubber product.

An additional embodiment involves a process for the separation of components in tire scrap. This process comprises the step of heating the tire scrap while compressing the tire to devulcanize the tire prior to applying a magnetic field to the tire to remove metal content from the tire.

An apparatus for separating components present in tires is also embodied in the present invention. This apparatus comprises a cracker mill and a magnetic separator positioned such that said magnetic separator is able to remove steel wires

SUBSTITUTE SHEET having a length of above 2 cm to about 40 cm from the tires which have been processed by said cracker mill.

A particularly preferred embodiment involves a rubber powder which is produced by the processes of the invention.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a process flowsheet illustrating a preferred embodiment of the invention for reclaiming rubber, metal content and flock from whole tires.

DETAILED DESCRIPTION OF THE INVENTION

In its broadest aspects, the present invention involves a process for the extraction of steel from vulcanized rubber by devulcanizing the rubber by passing the rubber through a mill while heating and then applying a magnetic field to said ungranulated, steel-containing rubber article. The magnetic field has sufficient strength to remove at least a portion of the steel wire contained in the rubber article. Preferably the process entails the separation of components from tire scrap by heating the tires while compressing the tires to devulcanize them prior to applying a magnetic field to die tire to remove metal content from the tire. The term "components" used herein refers to rubber, steel wire and tire cord that can be removed from the tire and either recycled or discarded as waste. The steel wires that are removed will have varied lengths depending on the step in the process when they are removed. Wire pieces removed during early processing will have lengths of about 2 cm to about 40 cm, whereas wire removed after the rubber has been ground into pieces will have pieces of at least about 50 mesh and sizes that coincide with the rubber pieces themselves. A distinct advantage of the present invention is the removal of as much of the longer wire as possible before the rubber is ground into pieces. In this fashion, the amount of small pieces of wire embedded in the rubber is significantly reduced, thus aiding in increasing the amount of rubber that can be recycled.

SUBSTITUTE SHEET A particularly preferred process for recycling the components of tires involves cutting the tires into two pieces of approximately equal size; pressing the pieces between rollers to devulcanize the rubber; subjecting the devulcanized rubber to a magnetic field while holding the devulcanized rubber stationary to draw the larger metal inclusion pieces from the rubber; and grinding the rubber into pieces to be recycled. Preferably the tires are cut into a pair of arcuate or vertical pieces of approximately equal size. In this manner, the tires are able to be readily debeaded to remove the inside rims and compressed within a roller mill, such as a cracker mill which employs smooth steel rollers to destroy the vulcanization/memory ofthe rubber tire. This process also creates heat while compressing the tire which also aids in the devulcanization process. Excess heat, however, should be avoided. Once the rubber is compressed, the wire inclusions are brought to the surface of the rubber which can then be readily removed by conventional procedures. One preferred procedure involves passing the rubber sheet between, over and/or under a magnetic field of low or high intensity depending on the amount of wire being exposed. Larger exposure surfaces require lower intensities when passing through the first mill than would subsequent runs using additional cracker mills.

When removing the longer length wire from the rubber, it is preferable to hold the rubber in a firm or stationary manner to enable it to be drawn from the rubber without being broken into smaller pieces which will be removed later in the process.

After passing the rubber through the cracker mills, tires of different rubber consistency and color are blended together into a single solid mass which is then ground into smaller pieces. Grinding may be done by conventional means such as in a refiner mill which receives the rubber sheet which passes between corrugated rollers to produce the desired piece size. Sizes of at least about 50 mesh, U.S. standard size, have been found useable in the process of the invention. Once ground, the pieces are passed once more through a magnetic separator to further remove steel inclusion pieces from the rubber particles. This procedure may be repeated several times to ultimately prepare a metal-free rubber product that can be readily recycled.

SUBSTITUTE SHEET In another process, the tires are preferably first debeaded and then further processed by devulcanizing the tires by compressing the tires between rollers; removing steel wire with a magnetic separator from the compressed material; grinding the material that results into pieces; passing said pieces through another magnetic separator; grinding the pieces that result into particles having a mean size of at least about 50 mesh U.S. standard size; and separating flock cord from the rubber particles by subjecting the mass to an air classifier and recovering the rubber product. Conventional air classifiers are used for this purpose since they enable the removal of flock cord without contaminating the fine rubber pieces that are passed to a bagger device for storage or shipment for reuse. The flock can then also be conveniently bailed and reused.

The apparatus used in the present invention comprises a cracker mill and a magnetic separator positioned such that said magnetic separator is able to remove steel wires having a length of about 2 cm to about 40 cm from the tires which have been processed by the cracker mill. Preferably, the apparatus further comprises means for introducing debeaded tires into the cracker mill and means for continuously conveying the output from said cracker mill to a grinding means. Additionally, the apparatus further comprises a tire splitter which splits the tires which are then passed to the cracker mill; a primary refiner mill which receives the devulcanized rubber from the cracker mill; a second magnetic separator; a fine grinder to grind the milled rubber into small pieces; and an air classifier capable of removing cord from rubber particles and recovering the rubber pieces.

The rubber powder which is produced by the process of the invention can be recycled for use with natural rubber to produce shoe soles, new tires and other rubber products. The amount of material that can be used in such products will depend on various factors, such as end product desired, structural integrity of the product and intended use. Amounts of about 2% to 25% have been found effective in a variety of applications, including fillers for asphalt and concrete.

SUBSTITUTE SHEET Narious preferred embodiments ofthe present invention are described in detail below.

The invention will now be described in connection with the accompanying drawing wherein like reference numerals have been used to designate like parts.

In general, the process begins by loading whole tires 2 and splitting them in half in tire splitter 4. The whole tires are loaded in a vertical position onto a side and bottom moving conveyor. This type of conveyor ensures that the tires are somewhat forced into the cutting blade. The conveyor is operated by an electric motor (not shown). While the length of this conveyor can vary greatly, a preferred conveyor is about 15 feet long or long enough to hold at least five (5) tires on the conveying belt.

As the tire 2 is moved into the cutting position, an upper and lower drive belt center the tire past the blade 6. The drive belts ensure a straight center cut made vertically (i.e. , parallel) to the tread. Typically, the drive belts are centered for a 14- inch tire. The upper belt will run substantially higher than center on 13-inch tires and very close to center on 15-inch tires. The distance between the top upper edge of the bottom belt and the lower edge of the top belt is approximately six inches, even though this is not a critical feature. The bottom conveyor continues from the point of loading up to the point of the cutting blade.

The cutting blade may be any suitable cutting blade, such as a band saw type. The blade may rotate constantly at a high speed or be activated when receiving each tire. The teeth of the saw can be very fine and may create some residue during the cutting process. The dust that is created by the blade is a mixture of steel shavings and tire tread rubber. This mixture may be conveniently collected below the cutting blade and disposed of in a routine manner. When a sufficient amount of this mixture is collected, it is passed through a magnetic separator where the steel is removed and the rubber sent on for further processing.

SUBSTITUTE SHEET When the cutting of tire 2 is complete, tire 2 falls onto conveyor 8 which leads to the debeading operation. Typically, the tire splitter 4 has the capacity to handle 1,200 to 1,600 vehicle tires per hour, including automobile, truck and bus tires. Multiple tire splitters or larger capacity devices can be used if higher capacity is desirable.

Conveyor 8, such as an electric-powered conveyor, transfers the split tires from tire splitter 4 to debeader 10. The size of conveyor 8 can vary but is about 3.5 feet wide and about 10 feet long. The conveyor may be optionally equipped with steel rollers along the sides to ensure that no jam-ups occur.

The debeader 10 has the capacity to handle up to 15-inch passenger tires, but may be readily modified to handle more or less tires. An attached sensor means (not shown) senses an awaiting tire and initiates the debeader' s roller conveyor to position the tire under tearing and holding rings. Another sensor determines the diameter of the tire and sets the tearing ring to a preset diameter, depending on tire size, i.e. , 13- , 14- or 15-inch tire. The holding ring ensures that the tire does not move while the tearing ring is extracting the bead from the tire.

The debeader 10 is optionally hydraulically operated and controlled movements are determined by sensors or other conventional means. The purpose of the holding ring is to secure the tire while the tire is being debeaded. A hydraulically powered tearing ring (not shown) then typically tears the bead away from the tire. The tearing ring may be a conventional device such as one comprising five piercing 2" ends which are followed by push-bars. As the piercing ends are pushed through the tires at the outer bead area, the bead is torn away from the carcass of the tire. The removed bead, which has only minimal rubber attached, is then put aside for further disposal. The debeader then resets for the next tire. Conventional debeaders typically have capacity to handle 2,600 tires per hour, which can be used herein.

SUBSTITUTE SHEET A second conveyor 12 then transfers the debeaded tire to primary cracker mill 14. The cracker mill 14 may have a variable length (typically about 90" long) and powered by electric motors. The rubber is meshed together as it passes through the rolls of the mill, which are preferably smooth steel rollers.

The rubber in tires is generally referred to as vulcanized rubber. Basically, this means that the tire rubber is in a memorized state. Vulcanization of rubber decreases its solubility in solvents and this property frequently is used as a qualitative measure of cure. Vulcanization by sulfur accounts for practically all the commercial products; however, peroxide types of curing systems may be used, especially for some of the synthetic rubber. The treads of most passenger cars consist mainly of styrene-butadiene synthetic rubber. The primary cracker mill 14 removes the memory from the tire or devulcanizes the rubber by masticating and heating the rubber.

At the outlet of the primary cracker mill 14, the rubber from separate tires is only partially mixed and is conveyed by conveyor 16 to an optional secondary cracker mill 18.

The -conveyor 16 that transfers the stock material from the primary cracker 14 to the secondary cracker 18 may be about 12" wide to several feet wide and is powered by an electric motor (not shown). Knives affixed to the primary cracker mill 14 ensure that the width of the stock remains consistent, preferably about 10" wide. The stock from the conveyor 16 is fed directly into the secondary mill 18.

The secondary mill 18 can be identical to the primary mill 14, both being conventional pieces of equipment. The mills' function is to further mix the rubber in order to make the blend of rubber from different tires more consistent. The smooth steel rollers on this mill are placed closer together than the rolls on the primary mill in order to ensure a proper blend.

SUBSTITUTE SHEET The white side wall, black side wall and the tread are all made from different formulas of rubbers and chemicals. The above-described process of mixing tires at two different stages will ensure that all of the formulas are mixed uniformly and consistently together. The properties of the rubber powder which result from the process of the present invention may thus be controlled by the addition of suitable rubber materials into the primary cracker.

The rubber is heated by the physical action of the rollers on the rubber in the primary and secondary crackers. Additional, i. e. , non-frictional, heat may be utilized in the process of the present invention to further devulcanize the rubber.

The rubber exiting from the cracker mill is in the form of a devulcanized sheet of rubber and is then treated to remove metal tread or wire inclusive pieces in the rubber. As discussed above, the steel from the bead was removed at an earlier stage in the process and, therefore, the only steel that remains in the rubber is the steel that was in the tread. The steel length in the tread is directly proportional to the width of the tire and steel wire in the tread typically varies from about 2 cm to about 40 cm. Before the stock is stripped off the secondary mill, a magnetic separator 21, which is located directly above the blending stock, draws out steel wire which is located near the outer surface of the stock. The steel that is collected by magnetic separator 21 is put aside to a separate bin to be recycled. The magnetic separator has an electromagnetic roller which may have a low intensity magnetic field or high intensity magnetic field depending on the thickness of the rubber exiting the cracker mill.

The rubber stock is then conveyed by conveyor 20, which may be the same type of conveyor as that which is used between the primary and secondary cracker mills and is preferably 30" wide. The rubber stock is preferably fed directly into the top of the refiner mill 22, which breaks the rubber up into pieces.

SUBSTITUTE SHEET Refiner mill 22 is very similar to cracker mills 14 and 18; the major difference being that instead of having smooth steel rollers, the refiner mill has corrugated rollers 24. The refiner mill 22 may be quite long, e.g. , 42" long, and powered by an electric motor (not shown). The incoming stock will be ground by offset corrugated rollers 24 and, unlike the cracker mills, instead of stock coming back up over the top of the roller, the stock will fall to conveyor 26 below. The pieces •f rubber that fall to conveyor 26 will be about eight mesh in size (U.S. standard size).

The particles, having sizes of about eight mesh, are then passed through another optional magnetic separator 28. The magnetic separator 28 is similar to magnetic separator 21 previously described and extracts additional metal inclusion pieces within the rubber particles.

Conveyor 26 is preferably situated under the primary refiner mill 22 and is about 60" wide, with rungs running across the width every 12 inches. The purpose of the rungs is to ensure that the stock material is transferred to the secondary refiner mill 30. This conveyer will be between 12 to 15 feet in length.

The particles of stock material are then loaded from conveyor 26 into the top of an optional secondary refiner mill 30. The rollers and the corrugation of the rolls in secondary refiner mill 30 are closer than that of the primary refiner mill in order to produce finer particle size material.

The finer particles which fall from the secondary refiner mill 30 pass by magnetic separator 32, similar in construction to those described previously, which continues the process of removing metal fine inclusions from the particles.

The rubber particles are then passed into a fine grinder using a vibrating conveyor 34 which may be 24" wide and powered by an electric motor (not shown). The conveyor vibrates in order to level the load of rubber particles so that they may drop consistently into fine grinder 36. The particles on the vibrator conveyor are

SUBSTITUTE SHEET generally about 10 to 20 mesh in size and are transferred through a funnel (not shown) at the end of the vibrating conveyor 34 into the top of a circular grinder. The fine grinder 36, which is a conventional piece of equipment, is totally enclosed and designed for grinding the rubber. The unit is equipped with a size classifier and is designed not to allow anything larger than about 50 mesh to exit.

The greater than 50 mesh rubber then falls from the bottom of the fine grinder 26 and passes over another magnetic separator 38 of the same or different type as previously described. At this point, very little metal is left in the rubber and the rubber can be recycled and used for its intrinsic purposes without fear of metal contamination of products produced therefrom.

The fine mesh rubber is optionally stored or passed to air classifier 40 to separate heavy objects from light objects. Fifty mesh rubber particles fall from the fine grinder 36 into the top of air classifier 40. The air classifier 40 separates cord

(flock) from the rubber particles. The flock is put aside in a separate bin 42 to be bailed.

The rubber product then drops directly from air classifier 40 into the opening of pneumatic conveyor 44 which then transfers the rubber to storage tank 46 directly above the weight bagger 48. One thousand pound sacks, or sacks of other convenient size, are then placed in position on the weight scale. A sliding door on the storage tank is opened to release the exact amount of rubber, such as 1,000 pounds, into the sack and then the door shuts. The full sack is removed and another sack is positioned to receive more rubber particles.

The metal and steel products removed during the process are eventually collected in collectors 50 and used as metal scrap. The small particles of rubber can be used as fill-in asphalt and rubber products without being melted down or naturally separated from new rubber. Levels of about 1% to about 10%, and preferably about

SUBSTITUTE SHEET 3% to about 6%, have been found acceptable for most commercial applications when used with non-recycled material.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.

SUBSTITUTE SHEET

Claims

WHAT IS CLAIMED IS;

1. A process for recycling the components of tires which comprises: a) cutting the tires into two pieces of approximately equal size; b) pressing the pieces between rollers to devulcanize the rubber; c) subjecting the devulcanized rubber to a magnetic field while holding the devulcanized rubber stationary to draw the larger metal inclusion pieces from the rubber; and d) grinding the rubber into pieces to be recycled.

2. The process of claim 1 wherein the tires are cut into a pair of arcuate pieces to approximately equal size.

3. The process of claim 1 wherein a low intensity magnetic field is used to draw the wire from the rubber.

4. The process of claim 1 wherein a high intensity magnetic field is used to draw the wire from the rubber.

5. The process of claim 1 where the pieces are heated while being pressed between the rollers.

6. The process of claim 5 wherein the rollers are smooth steel rollers.

7. The process of claim 1 wherein the process of pressing the rubber and drawing the metal inclusion pieces from the rubber is repeated.

8. The process of claim 1 wherein after the tires are cut into pieces, the inside rims of the tires are debeaded before being pressed.

SUBSTITUTE SHEET

9. The process of claim 1 wherein the pieces obtained after grinding the rubber are passed through a magnetic separator to remove small metal inclusion pieces from the rubber.

10. The process of claim 9 wherein the pieces are ground to a mesh size of at least about 50 mesh U.S. Standard size and stored for further use.

11. A process for the extraction of steel from vulcanized rubber, comprising the step of heating an ungranulated, steel-containing rubber article and applying a magnetic field to said ungranulated, steel-containing rubber article, said magnetic field having sufficient strength to remove at least a portion of said steel contained in said rubber article.

12. A process for recovering rubber and metal content from tires, said process comprising the steps of: a) debeading the tires; b) devulcanizing the tires by compressing the tires between rollers; c) removing steel wire, with a magnetic separator, from the compressed material; d) grinding the material that results from step c) into pieces; e) removing further steel wire by passing said pieces by a magnetic separator; f) grinding the pieces that result from step e) into particles having a mean size of at least about 50 mesh U.S. standard size; and g) separating flock cord from the rubber particles and recovering the rubber product.

13. The process of claim 1 wherein said tires comprise automobile, truck and bus rubber tires.

SUBSTITUTE SHEET

14. The process of claim 1 wherein prior to said debeading step, whole tires are split vertically in half to produce arcuate pieces of approximately equal size.

15. The process of claim 14 wherein the devulcanizing step comprises a first step wherein debeaded tires are passed through a primary cracker mill; and a second step wherein the resulting material is stripped off a roller at the outlet of said primary cracker mill and then conveyed to a second cracker mill to form a sheet of devulcanized rubber.

16. The process of claim 1 wherein the magnetic separator of step c) comprises an electromagnetic roller positioned at a distance above said rolled material which is heated and wherein said distance is effective for removing metal inclusion pieces from said heated material.

17. The process of claim 16 wherein the tires are heated as they pass through the rollers.

18. The process of claim 1 wherein the steel wires removed from the tires have a length of between about 2 cm to about 40 cm.

19. A process for the separation of components in tire scrap comprising the step of heating said tire while compressing the tire to devulcanize the tire prior to applying a magnetic field to the tire to remove metal content from the tire.

20. The process of claim 19 wherein said components are selected from the group consisting of rubber, steel wire and tire cord.

21. The process of claim 19 wherein steel wires, having a length of about 2 cm to about 40 cm, are removed from said tire.

SUBSTITUTE SHEET

22. An apparatus for separating components present in tires, said apparatus comprising a cracker mill and a magnetic separator positioned such that said magnetic separator is able to remove steel wires having a length of about 2 cm to about 40 cm from the tires which have been processed by said cracker mill.

23. The apparatus of claim 22 further comprising means for introducing debeaded tires into said cracker mill and means for continuously conveying the output from said cracker mill to a grinding means.

24. The apparatus of claim 22 further comprising a tire splitter which splits the tires which are then passed to the cracker mill; a primary refiner mill which receives the devulcanized rubber from the cracker mill; a second magnetic separator; a fine grinder to grind the milled rubber into small pieces; and an air classifier capable of removing cord from rubber particles and recovering the rubber pieces.

25. A rubber powder which is produced by the process of claim 1.

SUBSTITUTE SHEET