GB1595810A

GB1595810A - Reclaiming elastomeric material as a particulate product

Info

Publication number: GB1595810A
Application number: GB13069/78A
Authority: GB
Original assignee: DEBOZY J G
Current assignee: DEBOZY J G
Priority date: 1977-04-12
Filing date: 1978-04-04
Publication date: 1981-08-19
Also published as: FR2387261A1; IE46770B1; JPS53134081A; NZ186863A; CA1116576A; IL54453A0; IT1108016B; DK159578A; BE865859A; DE2815122A1; ZA781891B; ES468696A1; IT7867783A0; NL7803846A; IE780714L; FI781073A; IL54453A; PH14210A; SE7804112L; GR64793B

Description

(54) RECLAIMING ELASTOMERIC MATERIAL AS A PARTICULATE PRODUCT (71) We, JOHN GEZA DOBOZY, of 9, Dunbarton Avenue, Sorrento, Queensland 4217, Australia, NEVILLE WILLIAM HALLEY, of 131, Muir Street, Labrador, Queensland 4215, Australia, and JOHN LANCELOT CAMPBELL, of 26, Collins Street, Surfers Heights, Queensland 4217, Australia, all Australian citizens, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a method for reclaiming elastomeric material from scrap containing such material and in particular rubber tyres. The method involves the breaking down of pieces of softened elastomeric material into particulates 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 tyres. 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 tyres under the sea in predetermined locations. A further example is the controlled 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 recovered and subjected to treatment processes which render the recovered materials suitable for reuse. Patents Nos. 505 156, 584 667 and 622 576 disclose known rubber reclaiming processes. The object of the present invention is to provide an improved method of recovering from scrap tyres 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 we provide a method for the continuous treatment of steel belted tyres com prising the steps of: (a) soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; (b) disintegrating the soaked tyres into particles of rubber, steel cord, textile cord and fabric of approximately 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).

According to another aspect of the invention we provide a method for the treatment of textile reinforced tyres comprising the steps of: (a) soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; (b) disintegrating the soaked tyres into particles of rubber, textile cord and fabric of approximately 5 mm diameter 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).

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 otherwise disintegrated to a suitable particle size by conventional equipment.

Suitable solvents may be selected from the following class: hydrocarbons, nitrohydrocarbons, alcohols, ethers, ketones, esters, glycols and glycol ethers, cycloalkyl alcohols, ester and ketones, chlorinatedhydrocarbons, cyclic ethers and aldehydes, and mixtures of any two or more of these.

Preferred solvents in these classes are as follows: HYDROCARBONS Benzene Toluene Xylene Tetrahydronaphthalene Decahydronaphthalene Dipentene (Limonene) 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 Diacetone alcohol ETHERS Diethyl ether Diisopropyl ether KETONES Acetone Methyl isobutyl ketone ESTERS Methyl acetate Ethyl acetate N-butyl acetate Amyl acetate Hexyl acetate Amyl formate Ethyl lactate Butyl glycollate Methyl benzoate Butyl stearate Dimethyl phthalate Dibutyl phthalate Dibutyl sebacate Methyl abietate GL YCOLS Ethylene glycol Ethylene glycol monomethyl ether Ethylene glycol monoethyl ether Ethylene glycol ether acetate Ethylene glycol monobutyl ether Diethylene glycol Diethylene glycol monoethyl ether Propylene glycol CYCLOALK YL COMPOUNDS Cyclohexanol Cyclohexanol acetate Cyclohexanone Methyl cyclohexanone CHLORO-COMPOUNDS Methylene dichloride Chloroform Carbon tetrachloride Dichlorethane Tetrachloroethane Perchloreoethane Dichloroethylene Trichloroethylene Perchloroethylene Mono chlorobenzene Dichloroethyl ether 1,1 ,2-Trichlorotrifluoroethane CYCLICETHERS,ete Dioxane Furfural Specifically preferred solvents are toluene and xylene, used alone or in mixture with each other or with other solvents. The commercial solvent EPOSOLVE 70 (manufactured by Shell) is an example of mixed solvent containing 66% toluene.

Since toluene has a boiling point of 110"C and xylene approximately 1400C, both these liquids are very volatile at room temperatures.

Both also have low flash points. In order to reduce the hazards of working with these solvents, 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 both. Known solvents suitable for this purpose include the halogenated hydrocarbons, such as methylene chloride, ethylene chloride, trichloroethylene, perchloromethan, 1,1,1-trichloroethane or carbon tetrachioride plus ASA 3 antistatic additive.

One advantage of both toluene and xylene is that they both can be produced from coal.

Thus as the price of oil as a chemical feedstock is expected to rise rapidly in future years, the cost of 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 actual 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 of the rubber concerned. For those rubbers which have a high maximum working temperature, the temperature of the soaking liquid may be very much higher than that able to be used with those rubbers having a relatively low maximum working temperature. For rubbers having a relatively low maximum working temperature, a soaking liquid of excessively high temperature tends to cause the rubber to soften less easily.

However, in general, the higher the temperature of the soaking liquid, the greater 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 of the sample was reduced to approximately 10. At this hardness the rubber sample was friable and easilybroken, even by hand, into pieces and had lost the natural strength of 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 Hardness of the original material. Typically a Shore Hardness of 58 for an original Shore Hardness of 60 is experienced.

The other properties of the reclaimed rubber remain essentially unchanged and may be used to replace up to 85% of virgin rubber in the manufacture of car tyres and other vulcanized rubber products.

The soaking time required for the pieces of elastomeric 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 softening is achieved. If the pieces are soaked for prolonged periods, of the order of several weeks, a deterioration of the quality of the small rubber particles eventually obtained begins to become apparent.

A given quantity of solvent within a tank may be used to soak a large number of batches of pieces of elastomeric 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 addition, 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.

According to a further aspect of the present invention we provide apparatus for the continuous treatment of steel belted tyres including: to soften the elastomeric material therein a vessel for soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; first disintegrating means wherein the soaked tyres are disintegrated into particles of rubber, steel cord, textile cord and fabric of approximately 5 mm. in diameter; means for introducing water into the first disintegrating means; means for transferring the soaked tyres 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 disintegrated 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.

According to yet another aspect of the present invention we provide apparatus for the treatment of tyres including: a vessel for soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; first disintegrating means wherein the soaked tyres are disintegrated into particles of rubber, textile cord and fabric of approximately 5 mm. diameter; means for introducing water into the first disintegrating means; means for transferring the soaked tyres 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 particles from the second separating means to the second disintegrating means; and drying means for drying the disintegrated material from the second disintegrating means.

According to yet another aspect of the present invention we provide apparatus for the treatment of tyres including: a vessel for soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; first disintegrating means wherein the soaked tyres are disintegrated into particles of rubber, textile cord and fabric of approximately 5 mm. diameter; means for introducing water into the first disintegrating means; means for transferring the soaked tyres 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 disintegratint 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.

The invention in its various aspects is discussed in more detail, by reference to the specifically preferred embodiment of the apparatus depicted in the accompanying drawing.

The drawing is a diagrammatic representation of a pilot production plant for producing crumbed rubber from both natural and synthetic rubber pieces, in particular motor vehicle tyres. Such relatively large rubber pieces are placed in a soaking tank 1 which contains toluene, xylene or other suitable solvent or mixture of solvents, together with boiling and/ or flash point raising additives if required. More than one tank may be used if continuous or semi-continuous operation of the subsequent stages is required.

The scrap rubber is conveyed from a receiving hopper (not shown) into the tank 1, which is provided with means (not shown) for agitating the contents of the tank and removing the scrap from the tank after soaking.

Whole motor vehicle tyres may be used as such, but it is preferable that such tyres be cut into pieces having a maximum dimension of approximately 12 inches (300 mm) since this assists in handling the pieces. After a noncritical time, of the order of 2 to 8 hours, the rubber is considerably softened and the scrap is conveyed (by means not shown in detail) to the first stage grinder 2.

The grinder 2 is of conventional form and is adjusted to produce particles of about 3/16 inch (5 mm) diameter.

At this stage, water is introduced into the grinder 2 via line 3 from a tank 22 which is described hereinafter. 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 interior of the grinder. In addition, the water keeps down the heat generated through the breaking up of the softened 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, which comprises rubber, steel cord, textile cord and fabric from the tyres (plus the added water) 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 particles (at 90) for collection and disposal. The rubber particles collect in a sump 9 from 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 preferably 50 to 80 mesh BSS. A dewatering screen 12 separates the particles from the water. The water passes back along line 13 to the sump 9, while the particles pass to a rotary dryer 14 for final drying. Some of the air stream emerging from the drying 14 (which contains water and solvent vapour) is passed through a heater 16 for recycle to the dryer via line 17.The remainder 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 product 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 23. The solvent tank 23 also collects used solvent from the soaking tank 1. "Clean" solvent, i.e. solvent which has only a relatively small solids content is tapped off tank 1 at a point 24 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 solids is tapped off at the bottom 26 of tank I 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% in the product since this ensures a rubber powder with convenient properties and allows for some further drying during transport.

There is an approximately 20% reduction in the particle size of the product as it is dried.

A minimum particle size of about 50 mesh is preferred in order to maintain a free flowing product, since below this size, there is a tendency for the particles to coagulate or adhere one to another.

The foregoing describes only some embodiments of the present invention and various modifications may be made thereto without departing from the scope of the present invention as defined in the appended claims.

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 product is particularly suitable for producing carbon, and in particular, carbon suitable for purification processes. The particulate product is burnt in a closed low-oxygen atmosphere burner to produce carbon powder.

The conditions under which the particulate produce is burnt depends on the form of carbon product desired, the main factors varied being the oxygen content in the burner and the mesh size of the particulate Product.

WHAT WE CLAIM IS: 1. Apparatus for the continuous treatment of steel belted tyres including: a vessel for soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; first disintegrating means wherein the soaked tyres are disintegrated into particles of rubber, steel cord, textile cord and fabric of approximately 5 mm. in diameter; means for introducing water into the first disintegrating means; means for transferring the soaked tyres 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 disintegrated 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.

2. Apparatus for the treatment of textile reinforced tyres including: a vessel for soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; first disintegrating means wherein the soaked tyres are disintegrated into particles of rubber, textile cord and fabric of approximately 5 mm.

diameter; means for introducing water into the first disintegrating means; means for transferring the soaked tyres 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 particles from the separating means to the second disintegrating means; and drying means for drying the disintegrated material.

3. Apparatus as claimed in Claim 1 or 2 wherein there is provided means for recovering solvent and water from the drying means and recycling same.

4. Apparatus as claimed in Claim 1 wherein second separating means is magnetic separating means.

5. Apparatus as claimed in Claim 2 for use with belted tyres 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.

6. A method for continuous treatment of steel belted tyres comprising the steps of: (a) soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; (b) disintegrating the soaked tyres into particles of rubber, steel cord, textile cord and fabric of approximatley 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).

7. A method for the treatment of textile reinforced tyres comprising the stpes of: (a) soaking said tyres in an organic solvent to soften the elastomeric material therein and render it more friable; (b) disintegrating the soaked tyres into particles of rubber, textile cord and fabric of approximately 5 mm. diameter 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).

8. The method as claimed in Claim 6 or 7 wherein the solvent and water are recovered after drying and are re-cycled.

9. The method as claimed in Claim 6 wherein the rubber particles are separated from the steel particles magnetically.

10. The method as claimed in Claim 7 for use with belted tyres 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.

11. The product obtained by the method of

Claims

Claim 6 or 7.

12. Apparatus for the treatment of rubber tyres, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

13. A method for the treatment of rubber tyres, substantially as hereinbefore described with reference to the accompanying drawings.