CA1116576A

CA1116576A - Reclaiming elastomeric material as a particulate product

Info

Publication number: CA1116576A
Application number: CA000300866A
Authority: CA
Inventors: John G. Dobozy; Neville W. Halley; John L. Campbell
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-04-12
Filing date: 1978-04-11
Publication date: 1982-01-19
Also published as: BE865859A; DK159578A; IL54453A0; IE780714L; NL7803846A; IT1108016B; FR2387261A1; NZ186863A; SE7804112L; GB1595810A; IE46770B1; GR64793B; ES468696A1; FI781073A; JPS53134081A; PH14210A; ZA781891B; IL54453A; DE2815122A1; IT7867783A0

Abstract

ABSTRACT OF THE DISCLOSURE
A method of reclaiming elastomeric material from scrap material which may include reinforcing fibres to produce a particular product by chemical treatment of the scrap material in a solvent which softens the elastomeric material to a stage where the material can be disintegrated into the particulate produce by stages of grinding or mincing, and drying the product. The particulate product may be used with unvulcanized rubber for moulding articles.

Description

~11 iJA ~ L' ~' The present lnventlon relates -to a method for reclaiming elastomeric material from scrap containing such material and in particular rubber tires. The method involves the breaking down of pieces of softened elas-tomeric material into particles of smaller size. In addition the invention relates to apparatus suitable for use in the method.
There is a major world wide problem in the disposal of large amounts of some types of elastomeric materials, and in particular used motor vehicle tires. Many suggestions have been put forward to overcome this problem, one example of which is the formation of artificial sea reefs for breeding fish. Such artificial sea reefs are formed by dumping used motor vehicle tires under the sea in predetermined locations.
A further example is the con-trolled burning of waste rubber in furnaces.
Many elastomeric materials are relatively expensive, and therefore it is desirable that used elastomeric materials and surplus elastomeric materials such as off-cuts, trimmings and the like, be broken down into small size particles in order that they may be reused. Accordingly, it would be advantag20us to have a method of recovering from scrap elastomeric materials in the form of particles of small size which are capable of being recycled to produce new and valuable products.
According to one aspect of the present invention, there is provided a method for the continuous treatment of rubber tires comprising the step of:
(a) soaking said tires in a suitable organic solvent;
(b) disintegrating the soaked tires into particles of constituent elements -thereof, including particles of rubber, in the presence of water;

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(c~ separating the particles of rubber from the particles of other constituent elements;
(d) disintegrating the rubber particles to a particle size of between 20 and 100 mesh BSS, and (e) drying the rubber particles obtained in step (d) above.
The presen-t invention also provides a method for the continuous treatment of steel belted rubber tires comprising the steps of:
(a) soaking said tires in an organic solvent;
(b~ disintegrating the soaked tires into particles of rubber, steel cord, textile cord and fabric (e.g. of appproximately 5 mm. in diameter) in the presence of water;
(c) separating the particles of rubber and steel cord from the particles of textile cord and fabric;
(d) separating the rubber particles from the steel particles;
(e) disintegrating the rubber particles to a particle size of between 20 to 100 mesh BSS; and -(f) drying the rubber particles obtained in step (e) above.
The present invention further provides a method for the continuous treatment of textile relnforced rubber tires comprising the steps of:
(a) soaking said tires in an organic solvent;
(b) disintegrating the soaked tires into particles of rubber, textile cord and fabric in the presence of water;
(c) separating the particles of rubber from the particles of textile cord and fabric;

(d) disintegrating the rubber particles to a particle size of between 20 to 100 mesh BSS; and (e) drying the rubber particles obtained in step (d) above.
According to another aspect the present invention provides apparatus for the c~ntinuous treatment of rubber tires including:
- a vessel for soaking said tires in a suitable organic solvent;

- first disintegration means wherein the soaked tires are disintegrated into particles of constituent elements thereof, including particles of rubber;

- means for in-troducing water into the first disintegrating means;

- means for transferring the soaked tires to the first disintegrating means;

- separating means for separating the particles of rubber from the particles of other cons-tituent elements;

- means for transferring the disintegrated mat~rial from the first disintegrating means to the separating means;

- second disintegrating means for disintegrating the rubber particles to a particle size of between 20 to 100 mesh BSS;

- means for transferring the rubber particles from the separating means to the second disintegrating means; and - drying means for drying the disintegrated material from the second disintegrating means.

~ he present invention also provides apparatus for the continuous treatment of steel belted tires including:

- a vessel for soaking said tires in a suitable organic solvent;

- first disintegrating means wherein the soaked tires are - 3a -disintegrated into particles of rubber, s-teel cord, textile cord and fabric (e.a. o~ a~proxu~tely 5 m~. in diame-ter);

means for introducing water into -tlle first disintegrating means;

means for transferring the soaked tires ~rom the vessel to the first disintegra-ting means;

first separating means for separating the particles of rubber and steel from the particles of textile cord and fabric;

means for transferring the ground material from the first disintegrating means to the first separating means;

second separating means for separating the rubber particles from the steel particles;

means for transferring the rubber and steel particles from the first separatin~ means to the second separating means;

second disintegrating means for disintegrating the rubber par-ticles to a particle size of between 20 to 100 mesh BSS;

means for transferring the rubber particles from the second separating means to the second disintegrating means; and drying means for drying the disintegrating material from the disintegrating means.
The present invention further provides apparatus for the continuous treatment of textile reinforced rubber tires including:

a vessel for soaking said tires in a suitable organic solvent;

first disintegrating means wherein the soaked tires are disin-tegrated into particles of rubber, textile cord and fabric;

means for introducing water into the first disintegrating means;
- 3b -- means for transferrlng the soakecl-tires -to the first disintegrating means;

- separating means for separating the particles of rubber from the particles of textile cord and fabric;

- means for transferring the disintegrated material from the first disintegrating means to the separating means;

- second disintegrating means for disintegra-ting the rubber particlcs to a particle sizc oE bctwccn ~0 to 100 mesll BSS;

- means for transferring the rubber particles from -the separating means to -the second disintegrating means;
and - drying means for drying the disintegrated material from the second disin-tegrating means.

Solvents suitable for use in the invention must be capable of softening the elastomeric material and at the same time rendering it friable so that it can be ground or other-- 3c -wise disi.ntegrated to a sllitahle particle size by convent-ional equlpmentO
Snitable solvents may be selected from the following class:-hydrocarbons, nitrohydrocarbons, alcohols, ethers, ketones, esters, glycols and glycol ethers, cycloalkyl alcohols, esters and ke-tones, chlorinated hydrocarbons, cyclic ethers and aldehydes, and mixture., of any two or more o-f these.
p:referred solvents in these classes are as follows:-~IYDROCARBONS

Benzene Toluene Xylene Tetrahydronaphthalene Decahydronaphthalene Dipentene (Lirnonene) VM and P Naphtha, Petroleum NITROALKANES
Nitropropane ALCOHOLS

Methyl alcohol Ethyl alcohol N-propyl alcohol N-butyl alcohol Isobutyl alcohol Sec-butyl alcohol Amyl alcohol Benzyl alcohol Di aJ ` etone alcohol ETHERS

Die-thyl ether Diisopropyl ether KETONES

Acetone Methyl isobu-tyl ketone _~_ ~6~i76 . RSTERS
_ Methyl acetate E-thyl acetate N-butyl acetate Amyl acetate Hexyl acetate Amyl ~ormate Ethyl lac-tate Butyl glycollate Methyl benzoate Bu-tyl stearate Dimenthyl phthalate Dibutyl phthalate Dibutyl sebacate ~e-thyl abieta-te GLYCOLS
Ethylene glycol Ethylene glycol monome-thyl ether Ethylene glycol monoethyl ether Ethylene glycol ebhyl e-ther acetate Ethylene glycol monobutyl ether Diethylene gly~ol Diethylene glycol monoethyl ether Propylene glycol CYCLOALKYL CO~IPOUNDS
Cyclohexanol Cyclohexanol acetate Cyclohexanone Methyl cyclohexanone CHLORO-COMPOUNDg Methylene dichloride Chloroform Carbon tetrachloride Dichloroethane Tetrachloroethane Perchloroethane Dichloraethylene Trichloroethylene Perchloroethylene ~ono chlorobenzene Dichloroethyl ether 1,1,2-Trichlorotri~luoroethane CYCLIC ETHERS, etc.
Dioxane Fur~ural Specifically pre~erred solvents are toluene and xylene, used alone or in mixture with each other or with other solvents. The commercial solvent EPOSOLVE ~0 i'7~ii (manuf`ac-tured hy Shell) is an example o-~ mixe~l solvent containing 66~ toluene.
Since toluene has a boi.ling poin-t oE 110C and xylene approximately 1~0C, both these liquids are very volatile at room temperatures. Bo-th also have low flash poin CS . In order to reduce the hazards of working with these solven-ts, they ( and other flammable solvents) may be mixed with an additional solvent component which is non-inflammable or raises the boiling point of the liquid mixture or bothO l~nown solvents suitable Eor this purpose include the halogenated hydrocarbons, such as methylene chloride, ethylene chloride, trichloroethylene, perchloro-me-thane, :L,l,l~trichloroethane or carbon tetrachloride plus ASA 3 antistatic additiveO
One advantage o:E both toluene and xylene is that they both can be produced from coal. Thus as the price o:E
oil as a chemical ~Eeeds-tock is expected to rise rapidly in -Euture years, the cost o-E toluene and xylene should remain relatively stable.
The process whereby the elastomeric material is softened is not very sensitive to temperature and may be conveniently carried out at room temperature or any other temperature between the freezing and boiling point of the solvent. The ac-tual temperature will be determined by convenience and nature of the elastomeric material to be softened.
For example with natural and synthetic rubbers, the desirable maximum temperature of the soaking liquid will depend upon the specific maximum working temperature 3Q of the rubber concerned. For those rubbers which have a high maximum working temperature, the tempera-ture of the v -6-'7~

soaking liquid may be very much higher than that able to be used with those ruhbers having a relatively low maximum wor~ing temperature. For rubhers having a relatively low maximum working temperature, a soal,ing liquid o~ excessively high temperature tends -to cause the rubber to so~ten less e~sily. Ilowever, in general, -the higher the temperature of the soaking liquid, the grea-ter the speed with which the elastomeric material softens.
A typical rubber sample obtained from a motor vehicle tyre, prior to any chemical treatment has a Shore Hardness (Shore A2 Durometer) of approximately 60. After soaking for 5 to 6 hours in toluene at room temperature the Shore Hardness o-f the sample was reduced to approximately 10. At this hardness the rubber sample was friable and easily hroken, even by hand, into pieces and had lost the natural strength o-f the rubber. Such small pieces when dried, however, have a Shore Hardness which is substantially the same as, or only slightly less than, the Shore Hardlless of the original material. Typically a Shore Hardness of 58 for an original Shore Hardness o~ 60 is experienced~
The other properties of the reclaimed rubber remain essentially unchanged and may be used to replace up to 85/g o-f virgin rubber in the manufacture of car tyres and other vulcanized rubber products.
The soaking time required for the pieces of elasto-meric material depend in large part upon the size of the pieces and most pieces which are able to be easily handled (e.g. typical dimension 300 mm) show substantial softening after approximately three hours. For a soaking time in excess of eight hours, no substantial improvement in the degree of o softeniny .is achieved. I~ the pieces are soaked for prolonged periods, of -the order of several weeks, a de-ter-ioration of the quali-ty of the small rubber particles eventually obtained begins to become apparent.
A g.iven quan-tity oE solvent within a tank may be used to soak a large number of batches of pieces of elasto-meric material. Naturally as each batch is removed from the tank some of the solvent adheres to and is absorbed by the elastomeric material. As a result -the volume of solvent in the tank is thus progressively reduced and therefore may need to be augmented from time to time. In addi-tion, the solvent in the tank gradually loses efficiency and therefore, as the number of batches soaked by a given quantity of solvent increases, more soaking -time is required to get the same degree of softening.
As a result, when the rate of action of the solvent - becomes unacceptably low, the solvent must be replaced.
However, the used solvent need not be discarded since it is quite suitable for use for other purposes or may be repurified for further use.
The presen-t invention also provides, as indicated above~ an apparatus for carrying out the method of the invention.
The :Lnvention in its various aspects is discussed in more detail, by reference to the specifically preferred embodllllent o~ the apparatus depicted in the accompanying drawing.

_ ~ _ 'lllc clrawillg ls a diagrammatic rcprcsentatioll oE
a pilot procluction ulant for procluc-incJ crumbed rubber from both natural and systhetic rubber pieces such as motor vehieles tires, rubber off cuts and trimmings, and other sueh sources of non-usable rubber. Such relatively large rubber pieees are placed in a soaking tank 1 whieh eontains toluene, xylene or other suitable solvent or mixture of solvents, together wi-th boiling and/or flash point raising additives if required. ~ore than one tank may be used if continuous or semi-continuous opera-tion of the subsequent stages is required.
The scrap rubber is eonveyed from a receiving hopper (not shown) into the tank 1, whieh is provided with means (not shown) for agi-tating the eontents of the tank and removing the serap from the tan]c after soaking.
Whole motor vehiele tires may be used as sueh, but it is preferable that sueh tires be eut in-to pieees having a maximum dimension of approxima-tely 12 inehes (300mm) sinee this assists in handling -the pieees. After a non-eritieal time, of the order of 2 to 8 hours, the rubber iseonsiderably softened and the serap is eonveyed (by means not shown in detail) to the first stage grinder 2.
The grinder 2 is of eonventional form and is adjusted to produee partieles of about 3/16 ineh (5mm) diameter.

6t~7~

If necessary at this s-tage, water may be introdueed into the grinder 2 via line 3 from a tank 22 which is described hereinaf-ter. The function of the water is to assist in the grinding or mincing operation and to push the particles of rubber created within the grinder 2 through the grinder and prevent them lodging within the in-terior of the grinder. In addition, the water keeps down the heat generated through the breaking up of the sof-tened rubber.
The efficiency of the grinder 2 in breaking up -the scrap may be reduced in the absence of any water.
From the grinder 2, the ground material, whieh comprises rubber, steel cord, textile cord and fabrie from the tires (plus water if added) passes on -to a vibrating screen 4 which allows the particles of rubber and steel to pass through but retains textile cord and fabric. The - latter is vibrated and/or washed off the screen and passes (line 5) to a storage silo 7.
The rubber and steel cord particles with added water from tank 22 pass into a magnetic separator 8 which separates the steel partieles (at 90) for collection and disposal. 'l'hc rub~cr p.lrticlcs collcct in a sulllL) 9 Erom which they are pumped, with water, to the second grinder 11, where the particles are further ground -to a particle size of from 20 to 100 mesh BSS preEerably 50 to 80 mesh BSS.
A dcwatering scrccll 12 se~para~cs ~hc ~ar~iclcs ~rom the water. The water passes back along line 13 to the sump 9, WllilC~

. j ~6~7~

the particles pass -to a rotary dryer 1~l for final drying.
Some of the air stream eMerging -from the dryer 14 (which contains water and solvent vapour) is passed through a heater 16 for recycle to the dryer via line 17. The remai.nder of the air stream is passed to a condenser 18 where solvent and water are condensed out and pass into a separating tank 19.
The dried particulate produc-t emerging from the dryer 14 is passed to storage in another silo 21.
From the separator 19 the water is returned to the feeder tank 22, while the solvent is passed to a solvent feeder tank 230 The solvent tank 23 also collects used solvent from the soaking tank 1~ "Clean" solvent, i.e.
solven-t which has only a relatively small solids content is tapped off tank 1 at a point 2~ some distance above the bottom 26 of the tank 1 and passes directly into the tank 23 "Dirty" solvent, which has a relatively high content of sollds is tapped off at the bottom 26 of tank 1 and passes through a settling tank 27 before reaching tank 23.
From tank 23 the solvent passes through a filter 28 to a solvent holding tank 29 from which it is recycled to the soaking tank 1~
It is convenient to maintain a moisture content of approximately 7~0 in the produc-t since this ensures a rubber powder with convenient properties and al.lows -for some further drying during transport.
There is an approximately 20% reduction in the particle size of the product as it is dried. A mini~num particle size o~ about 50 mesh is preferred in order -to maintain a free flowing product, since below this size, there is a ten(lency ~or the r)artlcLes to coa~ulate or adhere one ~o another.
The foregolng describes only some embodim~nts of the present invention and various modifications may be made thereto without departing from the spirit of the present invention.
For example the mincers or grinders 2 and 11 could be replaced by apparatus which produces cutting, abrading, crushing, milling, shearing, chopping or tearing actions or any combination of these.
Experiments have shown that the particulate produce is particularly suitable for producing carbon, and in particular, carbon suitable for purification processes.
The particula-te product is burnt in a closed low-oxygen atmo.sphere burner to produce carbon powder. The conditions under which the par-ticulate produce is burnt depends on the form of carbon product desired, the main factors varied being the oxygen conten-t in -the burner and the mesh size of the particulate product.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for the continuous treatment of rubber tires including:
- a vessel for soaking said tires in a suitable organic solvent;

- first disintegration means wherein the soaked tires are disintegrated into particles of constituent elements thereof, including particles of rubber;

- means for introducing water into the first disintegrating means;

- means for transferring the soaked tires to the first disintegrating means;

- separating means for separating the particles of rubber from the particles of other constituent elements;

- means for transferring the disintegrated material from the first disintegrating means to the separating means;

- second disintegrating means for disintegrating the rubber particles to a particle size of between 20 to 100 mesh BSS:

- means for transferring the rubber particles from the separating means to the second disintegrating means; and - drying means for drying the disintegrated material from the second disintegrating means.

2. Apparatus for the continuous treatment of steel belted rubber tires including:

- a vessel for soaking said tires in a suitable organic solvent;

- first disintegrating means wherein -the soaked tires are disintegrated into particles of rubber, steel cord, textile cord and fabric;

- means for introducing water into the first disintegrating means;

- means for transferring the soaked tires from the vessel to the first disintegrating means;

- first separating means for separating the particles of rubber and steel from the particles of textile cord and fabric;

- means for transferring the ground material from the first disintegrating means to the first separating means;

- second separating means for separating the rubber particles from the steel particles;

- means for transferring the rubber and steel particles from the first separating means to the second separating means;

- second disintegrating means for disintegrating the rubber particles to a particle size of between 20 to 100 mesh BSS:

- means for transferring the rubber particles from the second separating means to the second disintegrating means; and - drying means for drying the disintegrated material from the second disintegrating means.

3. Apparatus for the continuous treatment of textile reinforced rubber tires including:

- a vessel for soaking said tires in a suitable organic solvent;

- first disintegrating means wherein the soaked tires are disintegrated into particles of rubber, textile cord and fabric;

- means for introducing water into the first disintegrating means;

- means for transferring the soaked tires -to the first disintegrating means;

- separating means for separating the particles of rubber from the particles of textile cord and fabric;

- means for transferring the disintegrated material from the first disintegrating means to the separating means;

- second disintegrating means for disintegrating the rubber particles to a particle size of between 20 to 100 mesh BSS;

- means for transferring the rubber from the separating means to the second disintegrating means; and - drying means for drying the disintegrated material from the second disintegrating means.

4. Apparatus as claimed in claim 2 or 3 wherein there is provided means for recovering solvent and, if present, water from the drying means and recycling same.

5. Apparatus as claimed in claim 2 or 3 wherein second separating means is magnetic separating means.

6. Apparatus as claimed in claim 3 for use with belted tires wherein:

- the separating means separates the particles of rubber and belt cords from the particles of textile cord and fabric, and further including:

- second separating means for separating the particles of rubber from the belt cords.

7. A method for the continuous treatment of rubber tires comprising the steps of:

(a) soaking said tires in a suitable organic solvent;
(b) disintegrating the soaked tires into particles of constituent elements thereof, including particles of rubber, in the presence of water;
(c) separating the particles of rubber from the particles of other constituent elements;

(d) disintegrating the rubber particles to a particle size of between 20 and 100 mesh BSS; and (e) drying the rubber particles obtained in step (d) above.

8. A method for the continuous treatment of steel belted rubber tires comprising the steps of:

(a) soaking said tires in an organic solvent (b) disintegrating the soaked tires into particles of rubber, steel cord, textile cord and fabric in the presence of water;
(c) separating the particles of rubber and steel cord from the particles of textile cord and fabric;
(d) separating the rubber particles from the steel particles;
(e) disintegrating the rubber particles to a particle size of between 20 to 100 mesh BSS: and (f) drying the rubber particles obtained in step (e) above.

9. A method for the continuous treatment of textile reinforced rubber tires comprising the steps of:

(a) soaking said tires in an organic solvent;
(b) disintegrating the soaked tires into particles of rubber, textile cord and fabric in the presence of water;
(c) separating the particles of rubber from the particles of textile cord and fabric;
(d) disintegrating the rubber particles to a particle size of between 20 to 100 mesh BSS; and (e) drying the rubber particles obtained in step (d) above.

10. The method as claimed in claim 8 or 9 wherein solvent and water are recovered after drying and are recycled.

11. The method as claimed in claim 8 wherein rubber particles are separated from steel particles magneti-cally.

12. The method as claimed in claim 9 for use with belted tires wherein:

- the particles of rubber and the belt cords are separated from the particles of textile cord and fabric, and the particles of rubber are separated from the belt cords.

13. A method as claimed in claim 8 or 9, wherein said suitable solvent is selected from the class consisting of:

- hydrocarbons; nitrohydrocarbons; alcohols; ethers;
ketones; esters; glycol and glycol ethers;
cycloalkyl alcohols, esters and ketones;
chlorinated hydrocarbons; cyclic ethers and aldehydes, and mixtures of any two or more of these.

14. A method as claimed in claim 8 or 9, wherein said suitable solvent is selected from toluene, xylene and mixturesthereof.

15. A method as claimed in claim 8 wherein said suitable solvent is an inflammable liquid and includes an additional, non-inflammable component to raise its flash point.

16. A method as claimed in claim 15 wherein said additional component is a chlorinated hydrocarbon.

17. A method as claimed in claim 9 wherein said suitable solvent is an inflammable liquid and includes an additional, non-inflammable component to raise its flash point.

18. A method as claimed in claim 17 wherein said additional component is a chlorinated hydrocarbon.

19. A method as claimed in claim 8 or 9 wherein the said soaking step is carried out at a temperature below the boiling point of said solvent.

20. A method as claimed in claim 8 or 9 wherein the tires are contacted with said solvent for a period of from about 2 to 8 hours at ambient temperature.

21. A method as claimed in claim 8 or 9 wherein the product has a particle size in the range of from 50 to 80 BSS mesh.

22. A method as claimed in anyone of claims 7, 8 and 9 wherein rubber particles are disintegrated to a particle size of between 20 to 100 mesh BSS in the presence of water.

23. Apparatus as claimed in anyone of claims 1, 2 and 3 wherein there is provided means for introducing water into the second disintegrating means.