AU2002322876A1

AU2002322876A1 - Process for regeneration of rubber from scrap

Info

Publication number: AU2002322876A1
Application number: AU2002322876A
Authority: AU
Inventors: Roland Fulford; Daniel Martin; El Hadi Zaddi
Original assignee: Fulford Group Inc
Current assignee: Fulford Group Inc
Priority date: 2001-08-08
Filing date: 2002-08-08
Publication date: 2003-06-19
Anticipated expiration: 2022-08-08

Description

PROCESS FOR REGENERATION OF RUBBER FROM SCRAP

BACKGROUND OF THE INVENTION

1. Field of the Invention The present invention relates to improvements in the field of recycled rubber. More particularly, the invention relates to a process for converting a rubber from scrap to a regenerated rubber.

2. Description of the Prior Art

Recycling of elastomers in general and more particularly recycling of rubber constitute a major concern from a social and environmental view. As little progress in the production of high quality rubber products derived from vulcanized rubber has failed to meet the quality required by the industry, the current situation calls for the development of new technologies, to show the ability to expand a very demanding market by producing a larger number of high quality and competitive products derived form scrap rubber. This can be achieved if the recycled elastomer or rubber is processed with the same conventional processing methods as for virgin elastomer or rubber.

There are several major markets in use today for the recycling of elastomers from scrap, rubber from scarp, tire derived fuel, punched or stamped products from tire carcasses, mats and many low end applications using bonding technologies of the rubber particles. However, those issues that deal with reclaimed rubber derived from some chemical treatment of vulcanized rubber hold a promising alternative to a durable solutions. Various patented methods are claiming a successful chemical partial devulcanization of scrap rubber using a chemical treatment that involves thermal, mechanical energy or other form of energy such as ultra sonic. Devulcanization is defined as a reverse reaction of the sulfur carbon bonding. Unfortunately, large-scale commercial applications of those methods are prohibited either from an economical point of view or in regard to the poor properties of the products obtained from the processes proposed. SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a process for converting an elastomer from scrap to a regenerated elastomer. It is another object of the present invention to provide a regenerated elastomer having properties similar to a corresponding virgin elastomer.

According to a first aspect of the invention, there is provided a process for converting an elastomer from scrap to a regenerated elastomer which comprises the steps of: a) introducing the elastomer from scrap into a vessel equipped with agitating means, the elastomer from scrap being in a powder form; b) agitating and heating the elastomer from scrap, limiting the heating of the elastomer from scrap to a temperature below the temperature where the elastomer begins to degrade; c) introducing an oil into the vessel and admixing together the elastomer from scrap and the oil; and d) cooling down the so formed regenerated elastomer, whereby the regenerated elastomer has properties similar to a corresponding virgin elastomer.

The term "elastomer" as used herein refers to a crosslinked polymer having a structure forming a network where the chains of the polymer are joined together. This term is used as a broader term than rubber since in many cases rubbers can also comprise other additives such as filling agents and vulcanizing agents.

According to a second aspect of the invention, there is provided a regenerated elastomer obtained via the process described in the first aspect of the invention or in any of its preferred embodiments. Applicant has found quite surprisingly that by agitating and heating an elastomer from scrap prior to admixing it with a preheated oil, it is possible to convert the elastomer from scrap to a regenerated elastomer and avoid its degradation. Also, the applicant has found that by using such a process, the obtained regenerated elastomer is an expanded and soft powder which is non-sticky and non-masticated or unmasticated. The regenerated elastomer does not soil hands by touch and has a characteristic velvet touch. Furthermore, the regenerated elastomer has properties similar to a corresponding virgin elastomer. During experiments, it was demonstrated that the regenerated elastomer is compatible with the corresponding virgin elastomer and it has a similar polymer content. Thus, in elastomer compounds, the regenerated elastomer could replace a portion of the virgin elastomer normally used without affecting the properties of the compound.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment of the process according to the first aspect of the invention, the vessel can be a vessel of the double boiler type. Preferably, the boiler comprises a mixing chamber and a heating chamber. Agitating means preferably comprises a rotor having at least one blade mounted on a central shaft. The agitation of the elastomer from scrap can be brought by rotating the rotor to generate shearing forces. Preferably, the rotor is rotated at a revolution comprised between 150 and 1200 rpm and more preferably comprised between 160 and 200 rpm. The elastomer from scrap can be converted to the regenerated elastomer in a period of time comprised between 30 seconds and 20 minutes, preferably comprised between 5 minutes and 15 minutes and more preferably of about 10 minutes. In another preferred embodiment of the process according to the first aspect of the invention, the vessel is preferably a mixer and more preferably a thermokinetic mixer. The elastomer from scrap can be heated from the heat generated through thermokinetic energy produced by the agitation. The agitating means preferably comprises a rotor having at least one blade mounted on a central shaft. The agitation of the elastomer from scrap can be brought by rotating the rotor to generate shearing forces. The rotor can be rotated at a revolution comprised between 1500 and 3000 rpm and preferably comprised between 1800 and 2000 rpm. The elastomer from scrap can be converted to the regenerated elastomer in a period of time comprised between 30 seconds and 5 minutes, preferably comprised between 45 seconds and 3 minutes and more preferably of about 1 minute.

Vessel

In the process according to the first aspect of the invention, the vessel can be equipped with a temperature control device comprising a heating system. The temperature control device can further comprise a cooling system. Additional steps

According to the first aspect of the invention, the process can further comprise after step (b) and prior to step (c): b') stopping the agitation and the agitation is started again in step (c), after the introduction of the oil into the vessel. The process can also further comprise after step (c) and prior to step (d): c') ejecting the regenerated elastomer from the vessel. Temperature

In the process according to the first aspect of the invention, the elastomer form scrap is preferably heated at a temperature t} comprised between 50 and 200 °C, _t more preferably comprised between 140 and 170 ° C and even more preferably at about 160 °C. Particle size

In the process according to the first aspect of the invention, the powder can have a particle size of about 15 to about 200 mesh, preferably of about 20 to about 120 mesh and more preferably of about 80 to 100 mesh. The powder can also be constituted by at least 90 % of particles having a size of at least 15 mesh and preferably of at least 30 mesh. The powder can further be constituted by at least 99 % of particles having a size of at least 15 mesh and preferably of at least 30 mesh.

Agitation

In the process according to the first aspect of the invention, the agitation is preferably carried out to avoid having stagnant particles of the elastomer in the vessel. The agitation can alsb be carried out to evenly heat the elastomer from scrap and therefore prevent its degradation. The agitation can be maintained during step (c) and preferably, also during step (d).

Oil

In the process according to the first aspect of the invention, the weight ratio, oil / elastomer from scrap, can be comprised between 0.03 and 0.2, preferably comprised between 0.04 and 0.14 and more preferably comprised between 0.05 and 0.09. The oil is preferably preheated prior to admixing and preferably at a temperature t₂ being higher or equal to ti. The temperature t₂ can also have a value comprised between t and ti+60 °C and preferably comprised between tχ+10 and tι+40 °C. The oil can be selected from the group consisting of synthetic oil, vegetable oil and mixtures thereof. The oil is preferably synthetic oil and more preferably selected from the group consisting of aromatic oil, naphtenic oil, paraffinic oil and mixtures thereof. When use is made of a paraffinic oil, the elastomer from scrap is preferably an ethylene propylene diene monomer rubber (EPDM). When use is made of an aromatic oil or a naphthenic oil, the elastomer from scrap is preferably a styrene butadiene rubber (SBR). Cooling

In the process according to the first aspect of the invention, in step (d), the regenerated elastomer can be kept in continuous motion in order to avoid degradation. Step (d) is preferably carried out using a screw type cooling device which preferably comprises a temperature control device. In step (d), the regenerated elastomer is preferably cooled down to a temperature below 120°C and more preferably to a temperature comprised between 90 and 120°C, to prevent its degradation.

Experimental conditions of the process

The process according to the first aspect of the invention can be carried out in the presence of air. The process can also be carried out under an inert gas atmosphere and the inert gas is preferably argon or nitrogen. Preferably, the gas atmosphere is substantially free of oxygen. Preferably, the risks of a potential side reaction such as oxidation are reduced.

Mass recovered

In the process according to the first aspect of the invention, the quantity of regenerated elastomer obtained at the end of the process corresponds to a value comprised between 97.0 and 99.9% and preferably comprised between 98.5 and 99.5% of the combined weight of the elastomer from scrap and the oil introduced into the vessel.

Mastication

In the process according to the first aspect of the invention, preferably, no mastication of the elastomer from scrap or of the regenerated elastomer occurs.

Rubber

The elastomer from scrap, in the process according to the first aspect of the invention, is preferably a rubber from scrap.

Regenerated Elastomer In the second aspect of the invention, the regenerated elastomer is preferably in a powder form and more preferably the regenerated elastomer has an aspect of expanded powder. Preferably, the regenerated elastomer is an unmasticated elastomer. It also preferably does not retain moisture. The regenerated elastomer can have a velvet touch and is preferably non-sticky. Preferably, The regenerated elastomer does not soil hands by touch. The regenerated elastomer preferably comprises a quantity of oil comprised between 3 and 14 % by weight, the oil being encapsulated into the regenerated elastomer. More preferably, the quantity of said oil is comprised between 5 and 8 % by weight. Also, the regenerated elastomer preferably does not retain moisture. The regenerated elastomer can exhibit all the required characteristics needed for processing by using the methods of mixing, molding, extrusion and calendering, commonly used in the rubber industry. The regenerated elastomer can be effective in the composition of a product selected from the group consisting of gasket, hose and roofing. Also, the regenerated elastomer can be effective in the composition of hoses and car tires.

The regenerated elastomer is preferably a regenerated rubber. The regenerated rubber can have a polymer content comprised between 10 and 40% by weight and preferably comprised between 25 and 35% by weight.

Utilisation of the regenerated elastomer

The regenerated elastomer according to the second aspect of the invention can be used in the rubber industry. Preferably, the regenerated elastomer is, previously to its use in the rubber industry, prepared by a process selected from the group consisting of mixing, molding, extrusion, and calendering. The regenerated elastomer can be added with additives commonly used in the preparation of native rubber, previously to its use in the rubber industry. The regenerated elastomer can also be used in the composition of a product of the automobile industry. The composition preferably comprises between 1 and 40% by weight and more preferably between 25 and 35% by weight of said regenerated elastomer. It is also possible to use the regenerated elastomer in the fabrication of a hose, a gasket or a seal. The hose, the gasket or the seal preferably comprise between 1 and 40% by weight and more preferably between 25 and 35% by weight of said regenerated elastomer. The elastomer is preferably a rubber.

Experimental section

The following non-limiting protocols and compounds illustrate the invention. General procedures

The Applicant has prepared regenerated rubber according to two main procedures, Protocol A and B. Prior to treating the rubber from scrap according to any one of these two protocols, all the undesired components contained in the powder (steel, fibers, general dirt) have been removed. The experimental conditions investigated in the present work are in accordance with the definitions given in the claims.

Protocol A

A weighted quantity of scrap rubber from scrap tires in the form of a granulated powder, having a given size of 80, 100 or 120 mesh, was introduced into a vessel of the double boiler type having a volume of 8 US gallons. The vessel is equipped with agitation means comprising a rotor having three blades mounted on a central shaft and capable of generating shearing forces. The rotor blades were adequately designed and the agitation is carried out to avoid having stagnant particles of rubber in the vessel. Thus, all rubber powder was uniformly subjected to the combination of the thermal and mechanical energies. The rotor speed was set based on the quantity, type and granulometry of the rubber powder introduced into the vessel and at a sufficient level to generate shearing forces. The powder was heated for 5 minutes until it reached a temperature comprised between 140°C and 160°C. A tight control of the temperature was necessary during the process in order to prevent any damage to the powder in the form of degradation. When all the particles have reached the required temperature, a hot oil (aromatic oil, naphtenic oil or paraffinic oil ) having a temperature of about 190 to 200°C was added in a weight ratio, oil / rubber from scrap, comprised between 0.05 and 0.12. The ratio depends on the nature and the granulometry of the powder as well as on the type of oil selected and its temperature. The mixture was kept under agitation for a period of time of about 5 minutes to allow the completion of the reaction. The regenerated rubber was ejected of the vessel and cooled down. It is preferable to keep the regenerated rubber in continuous motion while cooling, in order to avoid degradation of the regenerated rubber. The regenerated rubber was, in some cases, cooled down using a screw type cooling device. The obtained regenerated rubber was slightly expanded, not oily, unmasticated, and non-sticky or non-tacky. It also had a characteristic velvet touch. Protocol B

A weighted quantity of scrap rubber from scrap tires in the form of a granulated powder, having a given size of 80, 100 or 120 mesh, was introduced into a vessel of the thermokinetic mixer type having a volume of 1 litter. The mixer is equipped with a temperature control system comprising a cooling jacket and with agitation means comprising a rotor having blades mounted on a central shaft and capable of generating high shearing forces. The thermokinetic energy generated by the agitation produce heat and the elastomer from scrap is thereby heated. The rotor blades were adequately designed and the agitation is carried out to avoid having stagnant particles of rubber in the vessel. Thus, all rubber powder was uniformly subjected to the combination of the thermal and mechanical energies. The rotor speed was set based on the quantity, type and granulometry of the rubber powder introduced into the vessel and at a sufficient level to generate high shearing forces. The powder was vigorously agitated for 30 seconds until it reached a temperature comprised between 140°C and 160°C. A tight control of the temperature was necessary during the process in order to prevent any damage to the powder in the form of degradation. When all the particles^' have reached the required temperature, a hot oil (aromatic oil, naphtenic oil or paraffinic oil ) having a temperature of about 190 to 200°C was added in a weight ratio, oil / rubber from scrap, comprised between 0.05 and 0.12. The ratio depends on the nature and the granulometry of the powder as well as on the type of oil selected and its temperature. The mixture was kept under agitation for a period of time of about 30 seconds to allow the completion of the reaction. The regenerated rubber was ejected of the vessel and cooled down. It is preferable to keep the regenerated rubber in continuous motion while cooling, in order to avoid degradation of the regenerated rubber. The regenerated rubber was, in some cases, cooled down using a screw type cooling device. The obtained regenerated rubber was slightly expanded, not oily, unmasticated, and non-sticky or non-tacky. It also had a characteristic velvet touch.

Chemical and physical properties of the regenerated rubber Laboratory tests revealed the presence of small amounts of free sulfur in the process of regenerating rubber that establishes that devulcanization has effectively taken place during the reaction using the process according to the present invention. The tests conducted for testing the recycling ability of the rubbery mass obtained according to the process of the invention consist of using the following formulation: regenerated rubber 100 phr zinc oxide 4 phr stearic acid 2 phr

Delac^® S lphr

With no sulfur added into the compound, a rheometer test carried out with a ViscoGraph from TechPro at a temperature of 150 °C, shows the typical curve of vulcanization. This is the evidence that some amount of free sulfur has effectively been released during the chemical treatment of the rubber particles. The devulcanization has involved the breakage of the C-S and S-S bonds that link the different rubber molecules. The devulcanization process is believed to be facilitated by the swelling action of the oil added into the rubber particles. In addition, breakage of the main backbone chains at some locations is also believed to take place as the green strength and the mechanical properties of the regenerated mass are poorer than those of a virgin rubber of the same type as evidenced by tensile, elongation and tear properties.

Other tests have been performed to determine the quantity of oil lost during the process according to the first aspect of the invention. The weight of the reactants, rubber from scrap + oil, has been compared to the weight of the final product, the regenerated rubber, when using Protocol A. In a first experiment, a Goodyear 80 mesh EPDM from scarp was heated during 5 minutes until it reached the temperature of 152°C. Then a Shellflex oil at 199 °C was added in a weight ratio, oil / elastomer from scrap, of 0.08. The mixing time was 5 minutes. At the end of the process, the regenerated EPDM was obtained indicating a potential lost of oil of 0.6% by weight.

In a second experiment, a ROUSE 120 mesh EPDM from scarp was heated during 5 minutes until it reached the temperature of 153 °C. Then a Shellflex oil at 200

°C was added in a weight ratio, oil / elastomer from scrap, of 0.08. The mixing time was 5 minutes. At the end of the process, the regenerated EPDM was obtained indicating a potential lost of oil of 0.9 % by weight. In a third experiment, a SIMCO 100 mesh EPDM from scarp was heated during 5 minutes until it reached the temperature of 160 °C. Then a Shellflex oil at 200 °C was added in a weight ratio, oil / elastomer from scrap, of 0.08. The mixing time was 5 minutes. At the end of the process, the regenerated EPDM was obtained indicating a potential lost of oil of 1.3 % by weight.

Physical characterisation and analysis of compounds comprising regenerated rubber

The processing abilities and the mechanical properties have been evaluated by designing compounds based on the regenerated rubber. Basic compounds comprising regenerated rubber and virgin rubber at various proportions have been designed as shown below in Table 1. The regenerated SBR has been obtained according to Protocol A using

80 mesh SBR from scrap and Shellflex oil as starting material.

Table 1. Composition of Compounds 1 to 4 comprising virgin SBR and regenerated SBR.

The mixing operations for compounds 1 to 4 were carried out in a 5-liter Banbury mixer. All ingredients were added in the order listed above on a one-stage basis.

The mechanical properties of the cured compounds were evaluated with a tensile testing machine. Dumbbell shaped samples were die cut out of compression molded sheets. The curing conditions in the compression press were 10 minutes at .180 °C. The tensile properties and tear resistance were measured and compared to those of a compound based on virgin SBR rubber. The results are displayed in Table 2 for compounds containing 25, 50, 75 and 100 phr of regenerated rubber. Table 2. Mechanical properties of Compounds 1 to 4.

Further investigation on the effect of the parameters listed below on the mechanical properties of the regenerated rubber based compounds were evaluated. The results are listed in tables 3.1 to 3.3.

Compounds 5 and 6 are both compounds comprising virgin SBR and regenerated SBR. The Compound 5 comprises 25% by weight of regenerated SBR and compound 6 comprises 30% by weight of regenerated SBR. The regenerated SBR has been obtained according to Protocol A using 80 mesh SBR form scrap and Shellflex oil as starting material. Tables 4 to 6 illustrate results obtained with these compounds during several tests.

Table 4. Rheometer 191 C test for Compounds 5 and 6

According to the following tables, Compounds 5 and 6 are acceptable for use in hose construction. No difficulties were encountered when applying Compounds 5 and 6 on a mandrel. The hose tube and cover surfaces appeared smooth and not granulated. The processing of Compound 5 on the mill and calender was achieved with success. The compounds were not sticky and they did not break down in crumbs. The surface of these compounds was smooth and showed no evidence of surface defects. The surface was similar to standard product.

Compounds 7, 8 and 9 are compounds comprising virgin EPDM and regenerated EPDM. Compound 7 comprises 20% by weight of regenerated EPDM, Compound 8 comprises 30% by weight of regenerated EPDM and Compound 9 comprises 40% by weight of regenerated EPDM. The regenerated EPDM has been obtained according to Protocol A using 80 mesh EPDM form scrap and Sunpar 2280 oil as starting material. Tables 7 to 9 illustrate results obtained with these compounds during several tests.

Table 7. Rheometer 191 C test for Compounds 7, 8, and 9

According to the following tables, Compounds 7, 8 and 9 are acceptable for use in hose construction. No difficulties were encountered when applying these compounds on a mandrel. The hose tube and cover surfaces appeared smooth and not granulated. The processing of Compound 8 on the calender was achieved with success, it showed good tack on rolls, a smooth surface and it accepts anti-tack-dust. The surface of these compounds was smooth and showed no evidence of surface defects.

Tests have also been made in order to verify if it was necessary to add sulfur and accelerators to EPDM compounds comprising virgin EPDM and regenerated EPDM. The regenerated EPDM has been obtained according to Protocol A using 80 mesh EPDM form scrap and Sunpar 2280 oil as starting material. Compounds 10 to 21 are EPDM compounds comprising from 2.4 to 6.7% by weight of regenerated EPDM rubber and having a polymer content (EPDM) varying from 10 to 30% by weight. Compounds 10, 11, 16 and 17 comprise about 2.4 % by weight of regenerated EPDM and have a polymer content of about 10% by weight. Compounds 12, 13, 14, 18, 19 and 20 comprise about 4.8 % by weight of regenerated EPDM and have a polymer content of about 20% by weight. Compounds 15 and 21 comprise about 6.7% by weight of regenerated EPDM and have a polymer content of about 30% by weight. Compounds 10 to 15 have been prepared using 100 mesh regenerated EPDM and Compounds 16 to 21 have been prepared using 120 mesh regenerated EPDM. The results of these tests are showed in Tables 10 to 15. Cont represents a compound comprising virgin EPDM only and having a polymer content of about 23 % by weight.

Virgin EPDM rubber compound was banded on a 20 cm X 50 cm two-roll laboratory mill and the regenerated rubber was mixed in to it. Total milling time was about 10 minutes. The virgin material was passed through the mill 10 times with the gap narrowing after each two passes then banded and the regenerated material added. When the regenerated material was dispensed additional sulfur or curatives was added at this point. When all was dispersed the rubber was then pigged and passed through the mill 10 times sheeting it out on the last pass at approximately 100 thou in thickness.

Rheometer traces were obtained on an ODR at 150 °C, test plaques cured to (t₈₀+ 5 minutes at 150 C). After 24 hours specimens were die cut and tested using an Instron tensile tester. Table 10. Composition of Compounds 10 to 15 comprising 100 mesh regenerated EPDM

Table 11. Rheometer data at 150 °C for Compounds 10 to 15

Table 13. Composition of Compounds 16 to 21 comprising 120 mesh regenerated EPDM

Table 14. Rheometer data at 150 °C for Compounds 16 to 21

Table 15. Vulcanizate properties for Compounds 16 to 21 cured at 150 °C

From Tables 10 to 12, it can be seen that when the polymer content was about 10% by weight (Compound 10) there was little change in viscosity, a slight drop in maximum torque and a slower cure rate. There was however a reduction in scorch safety. When additional sulfur was added, the maximum torque increased, cure rate and scorch safety decreased (Compound 11).

With the additional of the regenerated rubber itself, Compound 10, the hardness increased slightly; modulus, tensile strength and resistance to tearing increased while the elongation decreased but was still acceptable. Upon the addition of sulfur, in Compound 11, hardness and modulus increased further and tensile changed little, elongation decreased further, which then became less than the desired value and tear decreased. The scorch time decreased further as did the cure rate but in all cases was slower than the virgin compound.

Increasing the polymer content to 20% by weight (Compound 12) the viscosity and maximum torque increased, scorch safety decreased and cure rate slowed (Compound 12 vs 10). The differences in property values were minor except hardness. However the elongation became marginally lower than desired but tear strength remained good. Additional sulfur produced only minor changes except for elongation and tear strength (Compound 13 vs. 12 ). Adding sulfur and accelerator produced minor changes (Compound 14 vs. 13 ) except tear became higher again. Compound 14 also had the highest viscosity and rheometer torque. Increasing the level to 30% by weight (Compound 15) did little except reduce elongation and increase hardness. The elongation is now well below the desired level.

In Tables 13 to 15, the trends of, both rheological and physical properties, are more or less the same as the results of Tables 10 to 12 although the scorch time did not decrease as much and cure time was a little faster. Property values were quite similar. Modulus was slightly lower and elongation higher.

In view of the results of Tables 10 to 15, it does not appear overly necessary to add additional sulfur and accelerator to the compounds comprising virgin EPDM and regenerated EPDM. When adding these components, there is a reduction in scorch safety and elongation. Also with nothing else added but the regenerated material, the property values appear to be sufficient. The difference between nothing added and additional curatives is not all that large. In the presence of regenerated 120 mesh material, the properties appear to be slightly better than the 100 mesh material i.e. elongation and tear are better. The regenerated EPDM mixed well into the virgin EPDM and sheeted out well. Upon curing, the surface of regenerated EPDM is shiny and did not differ from the virgin.

Compounds 22 and 23 are SBR rubbers comprising virgin SBR and regenerated SBR. Compound A, used as a reference, comprises 173.89 phr of a virgin SBR. Compound 22 comprises 173.89 phr of a virgin SBR, 45 phr of a regenerated SBR and 10 phr of carbon black. Compound 23 comprises 173.89 phr of a virgin SBR, 45 phr of a regenerated SBR and 20 phr of carbon black. The regenerated SBR has been obtained using the process according to the Protocol A. The regenerated SBR has been obtained using 80 mesh SBR from scrap and naphtenic oil. The tests made on these compounds are illustrated in Table 16 .

Table 16. Tests of Compounds 22 and 23

The cure properties for Compound 22 are very similar to Compound A Compound 22 even seems to cure slightly faster but with the same scorch safety. At lower temperatures the cure differences are amplified. At 166 °C Compound 22's Tc (80) is 5.41 minutes where Compound A's is around 7.5 minutes. Compound 22's viscosity is very interesting and should process well at the extruder. The physical properties demonstrated that Compound 22 should perform as well as a virgin SBR since it has similar properties than SBR. During experiments, it was demonstrated that the regenerated elastomer is compatible with the corresponding virgin elastomer and it has a similar polymer value. Thus, in elastomer compounds, the regenerated elastomer could replace a portion of the virgin elastomer normally used without affecting the properties of the compound. Finally, it proves the efficiency of the process according to the first aspect of the invention.

Claims

CLAIMS:

1. A process for converting an elastomer from scrap to a regenerated elastomer which comprises the steps of: a) introducing the elastomer from scrap into a vessel equipped with agitating means, said elastomer from scrap being in a powder form; b) agitating and heating said elastomer from scrap, limiting the heating of said elastomer from scrap to a temperature below the temperature where the elastomer begins to degrade; c) introducing an oil into said vessel and admixing together the elastomer from scrap and the oil; and d) cooling down the so formed regenerated elastomer, whereby the regenerated elastomer has properties similar to a corresponding virgin elastomer.

2. A process according to claim 1, wherein said vessel is equipped with a temperature control device comprising a heating system.

3. A process according to claim 2, wherein said temperature control device further comprises a cooling system.

4. A process according to any one of claims 1 to 3, wherein said agitating means comprises a rotor having at least one blade mounted on a central shaft.

5. A process according to claim 4, wherein the agitation of said elastomer from scrap is brought by rotating said rotor to generate shearing forces.

6. A process according to any one of claims 1 to 5, wherein the rotor is rotated at a revolution comprised between 150 and 1200 rpm.

7. A process according to claim 6, wherein the rotor is rotated at a revolution comprised between 160 and 200 rpm.

8. A process according to any one of claims 1 to 7, wherein said elastomer from scrap is converted to said regenerated elastomer in a period of time comprised between 30 seconds and 20 minutes.

9. A process according to claim 8, wherein said period of time is comprised between 5 minutes and 15 minutes.

10. A process according to claim 9, wherein said period of time is about 10 minutes.

11. A process according to any one of claims 1 to 10, wherein the vessel is a vessel of the double boiler type.

12. A process according to claim 11, wherein said boiler comprises a mixing chamber and a heating chamber.

13. A process according to any one of claims 1 to 3, wherein said elastomer from scrap is heated from the heat generated through thermokinetic energy produced by the agitation.

14. A process according to claim 13, wherein said agitating means comprise a rotor having at least one blade mounted in a central shaft.

15. A process according to claim 14, wherein the agitation of said elastomer from scrap is brought by rotating said rotor to generate shearing forces.

16. A process according to claim 14 or 15, wherein the rotor is rotated at a revolution comprised between 1500 and 3000 rpm.

17. A process according to claim 16, wherein the rotor is rotated at a revolution comprised between 1800 and 2000 rpm.

18. A process according to any one of claims 13 to 17, wherein said vessel is a mixer.

19. A process according to claim 18, wherein said mixer is a thermokinetic mixer

20. A process according to any one of claims 13 to 19, wherein said elastomer from scrap is converted to said regenerated elastomer in a period of time comprised between 30 seconds and 5 minutes.

21. A process according to claim 20, wherein said period of time is comprised between 45 seconds and 3 minutes.

22. A process according to claim 21, wherein said period of time is about 1 minute.

23. A process according to any one of claims 1 to 22, wherein said elastomer form scrap is heated at a temperature ti comprised between 50 and 200 °C.

24. A process according to claim 23, wherein said temperature t is comprised between 140 and 170 °C.

25. A process according to claim 24, wherein said temperature t] is about 160 ° C.

26. A process according to any one of claims 1 to 25, wherein said powder has a particle size of about 15 to about 200 mesh.

27. A process according to claim 26, wherein said particle size is about 20 to about 120 mesh.

28. A process according to claim 27, wherein said particle size is about 80 to 100 mesh.

29. A process according to any one of claims 1 to 25, wherein the powder is constituted by at least 90 % of particles having a size of at least 15 mesh.

30. A process according to claim 29, wherein said particles have a size of at least 30 mesh.

31. A process according to any one of claims 1 to 25, wherein the powder is constituted by at least 99 % of particles having a size of at least 15 mesh.

32. A process according to claim 31, wherein said particles have a size of at least 30 mesh.

33. A process according to any one of claims 1 to 32, wherein said agitation is carried out to avoid having stagnant particles of said elastomer in the vessel.

34. A process according to any one of claims 1 to 33, wherein said agitation is carried out to evenly heat the elastomer from scrap and therefore prevent its degradation.

35. A process according to any one of claims 1 to 34, wherein said process has a weight ratio, oil / elastomer from scrap, comprised between 0.03 and 0.2.

36. A process according to claim 35, wherein said ratio is comprised between 0.04 and 0.14.

37. A process according to claim 36, wherein said ratio is comprised between 0.05 and 0.09.

38. A process according to any one of claims 1 to 37, wherein said oil is preheated prior to admixing.

39. A process according to any one of claims 23 to 25 wherein said oil is preheated, prior to admixing, at a temperature t₂ being higher or equal to ti.

40. A process according to claim 39, wherein the temperature t₂ has a value comprised between ti and ti+60 °C.

41. A process according to claim 40, wherein the temperature t₂ has a value comprised between tι+10 and tι+40 °C.

42. A process according to any one of claims 1 to 41, wherein said oil is selected from the group consisting of synthetic oil, vegetable oil and mixtures thereof.

43. A process according to claim 42, wherein said oil is synthetic oil.

44. A process according to claim 43, wherein said synthetic oil is selected from the group consisting of aromatic oil, naphtenic oil, paraffinic oil and mixtures thereof.

45. A process according to claim 44, wherein said synthetic oil is paraffinic oil.

46. A process according to claim 45, wherein said elastomer from scrap is an ethylene propylene diene monomer rubber

47. A process according to claim 44, wherein said synthetic oil is aromatic oil or naphthenic oil.

48. A process according to claim 47, wherein said elastomer from scrap is a styrene butadiene rubber.

49. A process according to any one of claims 1 to 48, wherein said agitation is maintained during step (c).

50. A process according to any one of claims 1 to 48, wherein said agitation is maintained during steps (c) and (d).

51. A process according to any one of claims 1 to 48, wherein said process further comprises after step (b) and prior to step (c): b') stopping said agitation and said agitation is started again in step (c), after the introduction of the oil into said vessel.

52. A process according to any one of claims 1 to 51, wherein in step (d), the regenerated elastomer is kept in continuous motion in order to avoid degradation.

53. A process according to any one of claims 1 to 52, wherein said process further comprises after step (c) and prior to step (d): c') ejecting said regenerated elastomer from said vessel.

54. A process according to claim 53, wherein step (d) is carried out using a screw type cooling device.

55. A process according to claim 54, wherein said screw type cooling device comprises a temperature control device.

56. A process according to any one of claims 1 to 55, wherein in step (d), said regenerated elastomer is cooled down to a temperature below 120°C to prevent its degradation.

57. A process according to claim 56, wherein said temperature is comprised between 90 and 120°C.

58. A process according to any one of claims 1 to 57, wherein said process is carried out in the presence of air.

59. A process according to any one of claims 1 to 57, wherein said process is carried out under an inert gas atmosphere.

60. A process according to claim 59, wherein said inert gas atmosphere is substantially free of oxygen.

61. A process according to claim 59 or 60, wherein said inert gas is argon or nitrogen.

62. A process according to any one of claims 59 to 61, wherein risks of a potential side reaction are reduced.

63. A process according to claim 62, wherein said side reaction is oxidation.

64. A process according to any one of claims 1 to 63, wherein no mastication of said elastomer from scrap occurs.

65. A process according to any one of claims 1 to 64, wherein no mastication of said regenerated elastomer occurs.

66. A process according to any one of claims 1 to 65, wherein the quantity of regenerated elastomer obtained at the end of said process corresponds to a value comprised between 97.0 and 99.9% of the combined weight of said elastomer from scrap and said oil introduced into the vessel.

67. A process according to claim 66, wherein said value is comprised between 98.5 and 99.5 % of the combined weight of said elastomer from scrap and said oil introduced into the vessel.

68. A process according to any one of claims 1 to 45, 47 and 49 to 67, wherein the elastomer from scrap is a rubber from scrap and the regenerated elastomer is a regenerated rubber.

69. A regenerated elastomer obtained by a process as defined in any one of claims 1 to 35 and 38 to 68.

70. A regenerated elastomer according to claim 69, wherein said regenerated elastomer is in a powder form.

71. A regenerated elastomer according to claim 70, wherein said regenerated elastomer has an aspect of expanded powder.

72. A regenerated elastomer according to claim 70 or 71, wherein said regenerated elastomer comprises a quantity of said oil comprised between 3 and 14 % by weight, the oil being encapsulated into said powder.

73. A regenerated elastomer according to claim 72, wherein the quantity of said oil is comprised between 5 and 8 % by weight.

74. A regenerated elastomer according to any one of claims 69 to 73, wherein said regenerated elastomer has a velvet touch and is non-sticky.

75. A regenerated elastomer according to any one of claims 69 to 74, wherein said regenerated elastomer does not retain moisture.

76. A regenerated elastomer according to any one of claims 69 to 75, wherein said regenerated elastomer does not soil hands by touch.

77. A regenerated elastomer according to any one of claims 69 to 76, wherein said regenerated elastomer is an unmasticated elastomer.

78. A regenerated elastomer according to any one of claims 69 to 77, wherein said regenerated elastomer exhibits all the required characteristics needed for processing by using the methods of mixing, molding, extrusion and calendering, commonly used in the rubber industry.

79. A regenerated elastomer obtained by a process as defined in claim 46, wherein said regenerated elastomer is effective in the composition of a product selected from the group consisting of gasket, hose and roofing.

80. A regenerated elastomer obtained by a process as defined in claim 48, wherein said regenerated elastomer is effective in the composition of hoses and car tires.

81. A regenerated rubber obtained by a process as defined in claim 68, wherein said rubber has a polymer content comprised between 10 and 40% by weight.

82. A regenerated rubber according to claim 81, wherein the polymer content is comprised between 25 and 35% by weight.

83. Use of the regenerated elastomer according to any one of claims 69 to 78 in the rubber industry.

84. Use according to claim 83, wherein the regenerated elastomer is, previously to its use in the rubber industry, prepared by a process selected from the group consisting of mixing, molding, extrusion, and calendering.

85. Use according to claim 83 or 84, wherein the regenerated elastomer is added with additives commonly used in the preparation of native rubber, previously to its use in the rubber industry.

86. Use of the regenerated elastomer according to any one of claims 69 to 78 in the composition of a product of the automobile industry.

87. Use according to claim 86, wherein said composition comprises between 1 and 40% by weight of said regenerated elastomer.

88. Use according to claim 87, wherein said composition comprises between 25 and 35% by weight of said regenerated elastomer.

89. Use of the regenerated elastomer according to any one of claims 69 to 78 in the fabrication of a hose.

90. Use according to claim 89, wherein said hose comprises between 1 and 40% by weight of said regenerated elastomer.

91. Use according to claim 90, wherein said hose comprises between 25 and 35% by weight of said regenerated elastomer.

92. Use of the regenerated elastomer according to any one of claims 69 to 78 in the fabrication of a gasket or a seal.

93. Use according to claim 92, wherein said gasket comprises between 1 and 40% by weight of said regenerated elastomer.

94. Use according to claim 93, wherein said gasket comprises between 25 and 35% by weight of said regenerated elastomer.

95. Use according to claim 92, wherein said seal comprises between 1 and 40% by weight of said regenerated elastomer.

96. Use according to claim 95, wherein said seal comprises between 25 and 35% by weight of said regenerated elastomer.