Method to reduce pah content in rubber vulcanizates

Abstract

The present invention provides methods for reducing the content of polycyclic aromatic hydrocarbons in rubber powder, the method comprising extraction of rubber powder with a supercritical extraction solvent containing carbon dioxide, and / or subjecting the rubber powder to elevated temperature and reduced pressure conditions. The present invention further provides rubber powder obtainable by the methods of the invention, as well as consumer goods manufactured using the rubber powder of the invention.

Description

Method to reduce PAH content in rubber vulcanizatesDescription1. Technical filed of the invention

[0001] The present invention relates to methods for the removal of toxic organics from rubber goods, more particularly from rubber vulcanizate and even more particularly from recycled rubber vulcanizate.

[0002] Polycyclic aromatic hydrocarbons (PAH) are regulated toxics substances and are classified as carcinogenic.

[0003] PAH contained in tyre rubber originate primarily from the carbon black and the processing oil used in the rubber formulation (Hoyer et al., Materials 2022, 15(19), 7017).

[0004] The presence of PAH in tire-derived recycled material prevents their use in certain applications such as consumer goods and is therefore a limitation to the efficient recycling of end-of-life tires.2. State of the art

[0005] US 4 138471 A describes a process for reducing the polycyclic aromatic hydrocarbon content of carbon black. The amount of PAH is reduced by heat treating the carbon black in a fluidized bed at temperature comprised 1150 - 1850 °F for 5 to 165 minutes. This method decreases the PAH content on the surface of a carbon black.

[0006] Gutierrez-Urbano et al. described a method for the removal of PAHs) in conventional drinking water treatment processes. The technology uses KMnO4, FeCL and NaCIO and can yield removal efficiency over 90% for certain molecules. This process, however, is a liquidbased method (Gutierrez-Urbano et o / ., J. Contam. Hydrol. 2021, 243, 103888).

[0007] Satouh et al. reported a process of adsorption of polycyclic aromatic hydrocarbons by natural, synthetic, and modified clays. Adsorption percentages close to 100% were observed in liquid solid extraction (Satouh et al., Environments 2021, 8(11), 124).

[0008] Mokhatri et al. disclosed the removal of polycyclic aromatic hydrocarbons from contaminated sewage sludge using advanced oxidation process using hydrogen peroxide and sodium persulfate. PAH removal reaches levels superior to 90% upon treatment time of 10 to 20 days (Mokhtari et al., Desalination Water Treat. 2021, 213, 311).

[0009] Arouca etal. disclosed a method using white light-photolysis as an advanced oxidation process for removing PAHs contained in fabrics. Photolysis proved high removal rates of thePAH without degradation the structure of the fabric using process time from 1 to 15 days (Arouca et al., Int. J. Environ. Res. Public Health 2022, 19, 10054).

[0010] Nwinyi et al. reported the degradation of polynuclear aromatic hydrocarbons by bacteria as a technology for biorestoration of former industrial site soil by microbial communities. The authors demonstrated metabolic capacity of Pseudomonas plecoglossicida strain and Pseudomonas sp. on pyrene at a multi weeks time scale (Nwinyi et al., Braz. J. Microbiol. 2016, 47(3), 551).[Oil] Letellier and coworkers studied polycyclic aromatic hydrocarbons extraction from sediments by focused microwave-assisted extraction. The authors claimed a process with extraction time as short as 10 min, limited need of solvent and nearly quantitative extraction recovery rates (Letellier et al., Org. Geochem. 199, 30(11), 1353).

[0012] Librando et al. described the supercritical fluid extraction of polycyclic aromatic hydrocarbons from marine sediments and soil samples. The extractions were carried out at 50 and 80 °C, at a pressure varying from 230 to 600 bar and using CO2 in the supercritical phase and the effect of three organic modifiers (methanol, n-hexane and toluene), added at 5% / vol, at the same temperature and pressure conditions, were then considered. The recovery yield for PAHs from the spiked soil sample was measured and found to be greater than 90% (Librando et al., Chemosphere 2044, 54(8), 1189).

[0013] Zhang etal. reported supercritical CO2 Extraction of PAHs from Contaminated Soil. The authors investigated the effect of pressure, temperature, and modifier solvent on extraction efficiency. Under the optimum conditions (30 MPa, 120°C, methanol as modifier), the recoveries for PAHs from the sample was found to be greater than 90% (Zhang et al., J. Liq. Chromatogr. Relat. Technol. 2008, 31, 695).

[0014] Alassali et al. assessed the supercritical CO2 extraction as a method for plastic waste decontamination. The extraction was conducted at 300 bar, applying temperatures from 70 to 90 °C (Alassali et al., Polymers 2020, 12(6), 1347).

[0015] Wenclawiak et al. Reported the supercritical fluid extraction of polycyclic aromatic hydrocarbons from native soil and fly ash with pure and modified carbon dioxide and dimethylether (Wenclawiak et al., FreseniusJ. Anal. Chem. 1997, 357, 1128).3. Problem solved by the invention

[0016] Having regard to the state of the art summarized above, there remains a need for an efficient, fast, scalable, and economic process to remove the PAH contained in solids, especially in recycled materials.

[0017] The method described herein addresses this need and is particularly suited for the treatment of rubber powder obtained from end-of-life tyres.4. Summary of the invention

[0018] Every year in the world, over one billion tires reach the end of their service life. The recycling and re-use of the tire derived materials is hampered in some applications by their content of toxic substances, especially PAH.

[0019] The invention described herein provides methods for decreasing the PAH content of rubber goods, more particularly from rubber vulcanizate and even more particularly from recycled rubber vulcanizate. It pertains to methods especially suitable to treat end-of-life tires and / or used tires derived materials, as specified in the appended claims. In further aspects, the present invention provides rubber powder that is obtainable by the methods of the present invention, as well as consumer goods containing such rubber powder or being manufactured from such rubber powder.5. Figures description

[0020] Figure 1: PAH content of recycled rubber powder as a function of supercritical CO2 process treatment condition (data extracted from example 1).

[0021] Figure 2: PAH content of recycled rubber powder as a function of vacuum process treatment condition (data extracted from example 5).

[0022] Figure 3: PAH content of recycled rubber powder before and after vacuum treatment (data extracted from example 3 and example 4).6. Detailed description of the invention Definitions

[0023] In the context of the present application, the term "recycled rubber" is meant to describe vulcanized rubber product obtained from post-consumer or post-industrial applications. It is thus used synonymously with "recycled vulcanizate" refers to a vulcanized rubber product obtained from post-consumer or post-industrial applications.

[0024] In the context of the present application, the term "polycyclic aromatic hydrocarbon (PAH)" refers to as a class of organic compounds containing two or more fused aromatic rings. Example PAH comprised, but are not limited to: Benzo[a]pyrene, Benzo[e]pyrene, Benzo[a]anthracene, Benzo[b]fluoranthene, Benzo[j]fluoranthene, Benzo[k]fluoranthene, Chrysene, Dibenzo[a,h]anthracene, Benzo[g,h,i]perylene, lndeno[l,2,3-cd]pyrene, Acenaphthylene, Acenaphthene, Fluorene, Phenanthrene, Pyrene, Anthracene, Fluoranthene and their derivatives. The term "method for reducing the content of polycyclic aromatic hydrocarbons" is thus meant to characterize a method in which the content of at least one substance belonging to the class of polycyclic aromatic hydrocarbons is reduced. Preferably, this term is meant to characterize a method in which the content of at least one of the substances listed above is reduced. Of course, reductions in the content of two, three or more of PAH substances are also meant to be encompassed.

[0025] In the context of the present application, the term "rubber powder" describes particles of vulcanized rubber obtained by size reduction of a vulcanized rubber material. Any vulcanized rubber material obtained from any rubber source can be used, including in particular recycled rubber material derived from end-of-life tire and / or used tires. The size of the rubber particle composing the rubber powder is typically inferior to 1 mm, wherein said rubber particle size indication means that 80% or more, preferably 90% or more, and more preferably 100% of the particles fall below 1 mm and wherein said rubber particle size isderived from the cumulative particle size distribution graph obtained by rubber powder granulometry relying on the Ro-tap sieve test method according to ASTM D5644-18.

[0026] In the context of the present invention, the term "used tire” is meant to characterize any tire, such as including passenger car, truck, airplane, agricultural, 2-wheel and off-road tires, that has been used for running a car for 10 km, preferably 100 km, more preferably 1000 km, or more. The term "end-of-life tire” is meant to characterize used tires that have been put out of service since they can no longer be used for their original purpose, typically because they no longer satisfy safety requirements. For instance, in Germany the profile must have a minimum depth of the profile of 1.6 mm, so that in one embodiment tires with a profile depth of less than 1.6 mm are to be considered as end-of-life tires or used ties. According to another embodiment, end-of-life tires are all tires that can be found in tire disposal sites. According to another embodiment, new tires failing to comply with manufacturers and / or agencies quality and safety requirements are considered as end-of-life tires and may also be used in accordance with the present invention.

[0027] In the context of the present application, the term "supercritical" is meant to characterize conditions wherein pressure and temperature are above the respective values of the critical point of the substance of interest. For pure CO2, the critical point is at 7.375 MPa (73.75 bar) and 304.13 K. Supercritical CO2 therefore requires a pressure > 7.375 MPa and a temperature > 304.13 K. In case of solvent mixtures, if the critical point is not known, it can be determined in an iterative manner by repeatedly crossing the liquid-vapor phase transition (by increasing temperature and temperature in an alternating manner) until the phase boundary between liquid and vapor disappears. Alternatively, the critical point may be computed, for instance by a computation method as described in "Reliable Computation of Mixture Critical Points" by Stradi et al., AIChE J. 2001, 47(1), 212, or the alternative computation methods described in the literature cited in this publication.

[0028] In the context of the present application, the term "average particle size" is meant to characterize the weight average as determined by the Ro-tap sieve test method as per ASTM D 5644-18 on the basis of the cumulative particle size distribution curve.

[0029] In the context of the present invention, the term "manufactured from" is meant to characterize goods and especially consumer goods that are obtainable by using the specified rubber powder as a raw material, for instance in a process involving steps of combining the rubber powder with further materials such as matrix materials, shaping the material and / or subjecting the shaped material to a curing or related treatment. The manufacturing process may or may not change the identity of the rubber powder, for instance by binding of the rubber powder surface to a surrounding matrix material.

[0030] In the context of the present application, the term "comprising" is meant to introduce an open list, such that further unmentioned members are not excluded. However, the use of "comprising" is intended to specifically characterize also the scenario, wherein no further unmentioned members are present. In other words, a disclosure of "comprising" is to be understood as a disclosure of "consisting of" as one distinct option.

[0031] In the context of the present invention, the reference to a feature being a "preferred" feature is meant to indicate that it is preferred to combine this feature with other preferred features of the invention. It is intended by the inventors, and should therefore be understood by the reader, that all such combinations of preferred features with other preferred features are directly and unambiguously disclosed.

[0032] In the context of the present application, multiple limitations are to be considered in a cumulative manner.Rubber powder materials

[0033] The present invention permits to reduce the PAH content of rubber powder of any type or origin. According to preferred embodiments, the rubber powder is recycled rubber powder, such as rubber powder obtained from used tires or end-of-life tires. Such rubber powders can be obtained by separating a rubber material from a rubber source and subjecting the rubber material to particle size reduction. The method of particle size reduction can be selected from ambient grinding, cryogenic grinding, or waterjet grinding.

[0034] The methods of the invention can be implemented using rubber powder derived from any vulcanized rubber material ( / .e. rubber vulcanizate). Of course, from a practical point of view, it only makes sense to use rubber materials that contain a detectable amount of PAH, for instance due to the additional presence of carbon black or any compound ingredient that may contain those elements as trace and / or impurities. Regarding the chemical identity of the rubber, there is no particular restriction of type and chemical composition that can be used. That is, the method of the present invention can be implemented using any natural or synthetic rubber as well as any mixture thereof. Typical synthetic rubbers include for instance S-SBR and E-SBR, EPDM rubber, BR, HR, NBR, polyisoprene, neoprene in any mixing ratio. The additional presence of further additives, such as carbon black fillers, silica fillers, process oils, plasticizers, process aids, anti-degradant, zinc oxide, stearic acid, sulfur, accelerators and the like, is not harmful for practicing the present invention.

[0035] Recycled rubber powders can be obtained from various rubber sources of rubber such as tires, hoses, shoe soles, gaskets, conveyor belts, general rubber goods, and preferably tires such as used tires and / or end-of-life tires. These can be passenger tires, truck tires, off the road tyres, light truck tyres, trailer tyres or bicycle tyres. There is no particular restriction to a particular part of the tire. The tire tread can be advantageously used, but other parts such as the sidewalls may also be used.

[0036] The recycled rubber powders can be obtained by separation of the rubber part, followed by subjecting the rubber material to one or more of various particle size reduction procedures, such as ambient grinding (Tire Waste and Recycling, 1stEdition, 2021), cryogenic grinding (Yerezhep et al., Polymers 2021, 13(15), 2494), and / or waterjet grinding (Wang et al., J. Polym. Eng 2017, 37(3), 211 & Zefeng et al., J. Polym. Eng 2018, 38(1), 51). The same particle size reduction methods may also be used when producing rubber powder from vulcanized virgin rubber as a rubber source.

[0037] In ambient grinding, rubber materials from isolated parts or entire tyres are micronized using a multiple-stage blades-mediated grinding,

[0038] In cryogenic milling, tire chips are frozen in liquid nitrogen and then size-reduced with a hammer mill or a similar technique.

[0039] In the waterjet process, ultra-high-pressure water is used to micronize tire rubber from targeted areas of the tire.

[0040] The production method used for the fabrication of recycled rubber powders greatly affects their properties and morphology.

[0041] Recycled rubber powders are known to the skilled person to the art and can be classified and characterized by using, for instance, the following standard of the ASTM International:• ASTM D5603-19a Standard Classification for Rubber Compounding Materials— Recycled Vulcanizate Rubber• ASTM D5644-18 Standard Test Method for Rubber Compounding Materials— Determination of Particle Size Distribution of Recycled Vulcanizate Particulate Rubber

[0042] The rubber powder is preferably provided in pure form. It may be provided in dried form even though remaining solvent (e.g. residual water from the waterjet process described above) is not harmful. There is no particular limitation on the particle sizes and particle size distribution of the rubber powder. It is however preferred that rubber powder with an average particle size ranging from 0.001 mm to 1mm and more preferably from 0.01 mm to 0.8mm is used. Supercritical CO2 extraction treatment

[0043] In a preferred embodiment, PAH can be removed from rubber powder using supercritical CO2 extraction process.

[0044] The supercritical CO2 extraction process comprises the steps of(i) providing rubber powder;(ii) contacting the rubber powder with extraction solvent; and(iii) removing the extraction solvent.

[0045] The extraction solvent contains supercritical CO2. A co-solvent may also be present.

[0046] For the process, when contacting the extraction solvent with the rubber powder, the application of a pressure in the range of 74 to 600 bar, preferably 100 to 500 bar and even more preferably 200 to 500 bar is advantageous.

[0047] For the process, when contacting the extraction solvent with the rubber powder, the application of temperature in the range of 31 to 180°C, preferably 40 to 150°C and even more preferably 60°C to 100°C is advantageous.

[0048] The person skilled in the art will select a combination of pressure and temperature ensuring that the CO2 is in its supercritical state. The temperature and pressure ranges specified above are particularly suitable for using pure CO2 as the extraction solvent. When using a co-solvent, the process is carried out at a temperature above the respective critical temperature and at a pressure above the respective critical pressure of the solvent mixture of interest. In preferred embodiments, the temperature is 10°C or more, more preferably 30°C or more above the respective critical temperature and 150° or less, more preferably 70°C or less above the respective critical temperature; and the pressure is 25 bar or more, more preferably 525 bar or more above the respective critical pressure and 425 bar or less, more preferably 425 bar or less above the respective critical pressure.

[0049] The process time is preferably 0.1 to 24h, more preferably 0.5 to 12h and even more preferably 0.5 to 6h. Highly preferred is also a process time of 1 to 12h, 2 to lOh or 3 to 8h.

[0050] In a preferred embodiment, in combination with any of the above or below embodiments, a co-solvent is used in combination with CO2 for the extraction process. Said co-solvents are known to the skilled person in the art and include, but are not limited to linear or branched alkanes such as linear or branched C1-10 alkanes (such as n-hexane); unsubstituted or substituted aromatic hydrocarbon (the aromatic ring typically having 6 or 10 carbon atoms and the substituent typically being 1, 2 or 3 Ci-w alkane groups, such as benzene or toluene); linear or branched aliphatic alcohols such as linear or branched CMO alcohols (such as methanol, ethanol, 1-propanol, 2-propanol, 2-ethyl hexanol, n-butanol, 2-butanol, n-pentanol, 2-methyl-2-butanol or 1-Dodecanol); linear or branched organic acids such as such as C2-20 aliphatic monocarboxylic acids (such as acetic acid, hexanoic acid, octanoic acid, decanoic acid,pentanoic acid or heptanoic acid); linear or branched ketone (such as acetone); linear, branched or cyclic aldehydes such as aldehydes carrying a linear, branched or cyclic Cno group, wherein the cyclic group may be homocyclic or heterocyclic, and also saturated, unsaturated or aromatic (such as furan-2-carbaldehyde), linear or branched amines such as linear or branched amine compounds carrying 1, 2 or 3 CMO linear or branched alkyl groups at the nitrogen atom (such as trioctylamine, or 2-propylamine), organophosphorus compounds such as phosphine oxide compounds carrying 1, 2 or 3 linear or branched Ci-io alkanes (such as trioctylphosphine oxide); halogenated hydrocarbon (the hydrocarbon typically having 1 to 3 carbon atoms and the halogen being typically selected from F, Cl, or Br, wherein any number between 1 and the maximum possible number of halogen atoms may be present, such as chloroform); cyanide compounds (wherein the cyanide group is typically bonded to a hydrocarbon group having 1 to 3 carbon atoms, such as acetonitrile); water and / or mixtures thereof.

[0051] In a preferred embodiment, in combination with any of the above or below embodiments, a co-solvent is present at a level of 0.01 to 50 parts by weight (pbw), preferably 0.1 to 40 pbw and even more preferably 1 to 30 pbw with respect to 100 pbw of the carbon dioxide.

[0052] The extraction process is preferably carried out in a supercritical fluid extractor device comprising at least, a high-pressure resistant extraction vessel, one or more separators, one or more condensers and one or more working tanks. Hence, the rubber powder is preferably provided in one of these devices when carrying out the above-mentioned first step.

[0053] The process can be carried out batch-wise or in semi-continuous manner, typical batch reactor sizes may range from 1 to 10 000 liters, preferably from 100 to 5000 liters.

[0054] Supercritical fluid extraction process is known to the skilled person in the art (Supercritical Fluid Extraction, 2ndEdition, 1994). Briefly, the process first requires subjecting the extraction fluid (as for instance CO2) to temperature and pressure condition such as it reaches its supercritical state. Next the supercritical fluid is passed through an extraction vessel containing the rubber material and it diffuses throughout the solid and dissolves the PAH. The supercritical fluid is then swept to a separator where a pressure decrease yields a solidification of the extracted organics and a separation of the extraction fluid. The latter can subsequently be either re-compressed and recirculate in the system or discharged. acuum treatment

[0055] In a preferred embodiment, PAH can be removed from rubber powder by subjecting said powder to the combined action of heat and vacuum. This treatment thus comprises the steps of providing rubber powder, followed by subjecting the rubber powder to heat and vacuum conditions.

[0056] The rubber powder to be used for this treatment can be the same as described above with respect to the supercritical CO2 extraction process.

[0057] For the process, the application of a vacuum with pressure in the range of 0.001 to 100 mbar, preferably 0.01 to 75 mbar and even more preferably 0.1 to 50 mbar is advantageous, especially preferably 0.1 to 40 mbar, 0.1 to 30 mbar or even 0.1 to 20 mbar, such as 5 mbar, 10 mbar or 15 mbar.

[0058] For the process, the application of temperature in the range of 80 to 180°C, preferably 100 to 160°C and even more preferably 130°C to 160°C is advantageous.

[0059] The process time is preferably 0.5 to 120h, preferably 1 to 60h and even more preferably 1 to 24h. In another preferred embodiment, the process time is selected from thefollowing ranges: 4 to 150h, 6 to 120h, 8 to llOh, 12 to lOOh, 4 to lOOh, 6 to 80h, 8 to 60h, 12 to 40h, 4 to 50h, 6 to 40h, 8 to 30h, 12 to 20h, 1 to 4h, 2 to 4h, 1 to 6h, 2 to 6h, 1 to 8h, 2 to 8h, 1 to 12h, 2 to 12h and / or any ranges resulting from a combination of one of the above lower limits with any of the above upper limits.

[0060] The skilled person in the art is familiar with the degradation temperature of tire rubber and will select processing conditions under which the bulk materials is not negatively affected by the treatment condition. For typical tire rubber, this means that processing condition should remain below 250°C and more preferably below 200°C, depending on the chemical composition of the rubber compound.

[0061] The rubber material to be treated is typically provided in the form of rubber powder e.g., as described above in relation to the rubber material to be used in the supercritical CO2 extraction process.

[0062] In some embodiments, the process is carried out (i) at a pressure of 0.1 to 50 mbar over a time period of 4 to lOOh, (ii) at a pressure of 0.1 to 40 mbar over a time period of 6 to 80h, (iii) at a pressure of 0.1 to 30 mbar over a time period of 8 to 60h, (iv) at a pressure of 0.1 to 20 mbar over a time period of 12 to 40h, (v) at a pressure of 0.1 to 20 mbar over a time period of 4 to 50h, (vi) at a pressure of 0.1 to 20 mbar over a time period of 6 to 40h, (vii) at a pressure of 0.1 to 20 mbar over a time period of 8 to 30h. For all the embodiments in this paragraph, the temperature is not particularly limited and can for instance be selected within the range of 50°C to 200°C.

[0063] In some embodiments, the process is carried out (i) at a temperature of 50 to 200°C over a time period of 4 to lOOh, (ii) at a temperature of 60 to 180°C over a time period of 6 to 80h, (iii) at a temperature of 80 to 160°C over a time period of 8 to 60h, (iv) at a temperature of 100 to 160 °C over a time period of 12 to 40h, (v) at a temperature of 120 to 160°C over a time period of 4 to 50h, (vi) at a temperature of 140 to 160°C over a time period of 6 to 40h, (vii) at a temperature of 140 to 160°C over a time period of 8 to 30h. For all the embodiments in this paragraph, the pressure is not particularly limited and can for instance be selected within the range of 0.1 to 50 mbar.

[0064] The treatment can be applied static or by agitating the bulk materials using for instance, paddle vacuum drier, conical vacuum drier, screw vacuum drier or ribbon vacuum drier. Combined treatment

[0065] The supercritical CO2 extraction process of the invention may be suitably combined with the vacuum treatment process of the invention.

[0066] According to one aspect of this embodiment, the supercritical CO2 extraction process of the invention may be carried out first and the obtained rubber powder may subsequently be subjected to the vacuum treatment process of the invention.

[0067] According to another aspect of this embodiment, the vacuum treatment process of the invention may be carried out first and the obtained rubber powder may subsequently be subjected to the supercritical CO2 extraction process of the invention. Rubber powder

[0068] Another embodiment of the invention relates to the rubber powder that can be obtained by the methods of the invention. That is, the rubber powder of the invention ischaracterized by the reduced PAH contents accomplished by the methods of the present invention.

[0069] For instance, in some aspects of this embodiment, the rubber powder of the invention is characterized by a content of pyrene of 18 mg / kg or less, preferably 16 mg / kg or less, more preferably 14 mg / kg or less and even more preferred 10 mg / kg or less. There is no particular lower limit to the pyrene content. It is typically 0.0 mg / kg, or 0.1 mg / kg, or 0.2 mg / kg or 0.5 mg / kg or even 1.0 mg / kg.

[0070] Further characteristic features of the rubber powder of the invention are particle morphology obtainable by ambient grinding, cryogenic grinding, and / or waterjet grinding. Yet another characteristic is an average particle size ranging from 0.001 mm to 1mm and more preferably from 0.01 mm to 0.8mm. Consumer goods

[0071] The low content of PAH makes the rubber powder of the invention particularly suitable for the manufacture of consumer goods. It is therefore another embodiment of the invention to provide consumer goods, which contain the rubber powder of the invention, or which have been manufactured using the rubber material of the invention.

[0072] Such consumer goods may include bit are not limited to tires, soles of shoes, rubber boots, elastic bands, erasers, rubber flooring, rubbery stoppers, conveyor belt, sealing materials, and rubber-containing sports equipment such as resistance bands or squash balls.

[0073] The rubber powder of the invention may be incorporated into such consumer goods or components thereof using established rubber manufacturing methods, such as mixing with other components and bringing the material into the desired shape, e.g. using established procedures like extrusion, injection molding and the like. For instance, the rubber powder may be mixed with and / or incorporated into virgin rubber or a rubber composition based on virgin rubber, followed by processing the resulting rubber powder-containing composition in a conventional manner.

[0074] The rubber powder of the invention may as well be incorporated into non-rubber- based formulations such as, thermoplastic and thermoplastic elastomer compounds, polyurethanes, concretes and mortar, and / or any combination thereof.

[0075] Before incorporating the rubber powder of the invention into compositions for manufacturing consumer goods, the rubber powder of the invention may optionally be activated e.g. by surface treatment or devulcanization. Examples

[0076] In the examples below, different recycled rubber powders with particle size below 0.4 mm produced from end-of-life tires were used.

[0077] PAH concentration was determined by gas chromatography-mass spectrometry (limit of detection 0.2mg / kg).

[0078] The result of the treatment is presented in semi-quantitative method where, "+++" means reduction by more than 75% "++" means reduction by 25 to 50%, "+" means reduction by 10-30%, and "o" means reduction of less than 25% or no representative reduction as per measurement limit of detection and variability. In the table below "n.d." stands for not detectable, i.e. concentration below the limit of detection of the measurement method, when measured prior to the process of the present invention.Example 1. Supercritical C02extractionTable 1 eAcenaphthene n.d. n.d. n.d. n.d.Acenaphthylene +++ +++ +++ +++Anthracene +++ +++ +++ +++Benzo[a]anthracene +++ +++ +++ oBenzo[e]pyrene o o o oBenzo[a]pyrene o o o oBenzo[ghi]perylene o o o oBenzofluoranthene o + o oChrysene +++ +++ +++ +++Dibenzo[a,h]anthracene n.d. n.d. n.d. n.d.Fluoranthene +++ +++ +++ ++Fluorene n.d. n.d. n.d. n.d.Indeno[l,2,3-cd]pyrene n.d. n.d. n.d. n.d.Naphthalene +++ +++ +++ +++Phenanthrene +++ +++ +++ +++Pyrene +++ +++ +++ ++Example 2. Supercritical C02extractionTable 2 eAcenaphthene n.d. n.d.Acenaphthylene ++ ++Anthracene +++ +++Benzo[a]anthracene o oBenzo[e]pyrene o oBenzo[a]pyrene o oBenzo[ghi]perylene o oBenzofluoranthene o oChrysene o oDibenzo[a,h]anthracene n.d. n.d.Fluoranthene o oFluorene +++ +++ lndeno[l,2,3-cd]pyrene n.d. n.d.Naphthalene + +Phenanthrene ++ ++Pyrene ++ +Example 3. Vacuum dryingTable 3Benzo[a] pyrene oBenzo[e] pyrene +Benzo[a]anthracene +++Benzo[b]fluoranthene +Benzo[j]fluoranthene n.d.Benzo[k]fluoranthene n.d.Chrysene ++Dibenzo[a,h]anthracene n.d.Benzo[g,h,i]perylene +++ lndeno[l,2,3-cd]pyrene +++Acenaphthylene +++Acenaphthene n.d.Fluorene n.d.Phenanthrene +++Pyrene +++Anthracene +++Fluoranthene +++Naphthalene +++Example 4. Vacuum dryingTable 4Benzo[a] pyrene oBenzo[e] pyrene oBenzo[a]anthracene +++Benzo[b]fluoranthene +Benzo[j]fluoranthene n.d.Benzo[k]fluoranthene n.d.Chrysene oDibenzo[a,h]anthracene n.d.Benzo[g,h,i]perylene +++ lndeno[l,2,3-cd]pyrene +++Acenaphthylene +++Acenaphthene n.d.Fluorene n.d.Phenanthrene +++Pyrene +++Anthracene +++Fluoranthene +++Naphthalene +++Example 5. Vacuum dryingTable 5Benzo[a] pyrene o o + o +Benzo[e] pyrene o o o o oBenzo[a]anthracene + + + o +Benzo[b]fluoranthene o o o o oBenzo[j]fluoranthene +++ +++ +++ +++ +Benzo[k]fluoranthene +++ +++ +++ +++ n.d.Chrysene o o + o +Dibenzo[a,h]anthracene n.d. n.d. n.d. n.d. n.d.Benzo[g,h,i]perylene o o o o o lndeno[l,2,3-cd]pyrene o o o o oAcenaphthylene + ++ ++ + +Acenaphthene n.d. n.d. n.d. n.d. n.d.Fluorene n.d. n.d. n.d. n.d. n.d.Phenanthrene + ++ + + +Pyrene + + + + +Anthracene +++ +++ +++ ++ +Fluoranthene + + + o +Naphthalene +++ +++ +++ o n.d.Table 6. continuedBenzo[a] pyrene o + + +++Benzo[e] pyrene o o o +++Benzo[a]anthracene + + ++ +++Benzo[b]fluoranthene o o o +++Benzo[j]fluoranthene o + + +++Benzo[k]fluoranthene n.d. n.d. n.d. n.d.Chrysene o + + +++Dibenzo[a,h]anthracene n.d. n.d. n.d. n.d.Benzo[g,h,i]perylene o o o +++ lndeno[l,2,3-cd]pyrene o o o +++Acenaphthylene +++ ++ ++ +++Acenaphthene n.d. n.d. n.d. n.d.Fluorene n.d. n.d. n.d. n.d.Phenanthrene + ++ + +++Pyrene +++ Anthracene +++ Fluoranthene +++ Naphthalene n.d. n.d. n.d. n.d.Example 6. Vacuum dryingTable 6.Benzo[a] pyrene o o o o oBenzo[e] pyrene o o o o oBenzo[a]anthracene + + + o +Benzo[b]fluoranthene o o o o oBenzo[j]fluoranthene +++ +++ +++ +++ oBenzo[k]fluoranthene +++ +++ +++ +++ oChrysene o o o o oDibenzo[a,h]anthracene n.d. n.d. n.d. n.d. n.d.Benzo[g,h,i]perylene o o o o o lndeno[l,2,3-cd]pyrene o o o o oAcenaphthylene o o o o oAcenaphthene n.d. n.d. n.d. n.d. n.d.Fluorene n.d. n.d. n.d. n.d. n.d.Phenanthrene o + + o +Pyrene o o o o oAnthracene + + + o +Fluoranthene o o o o oNaphthalene o o o o oTable 6. continued eBenzo[a] pyrene o o o +++Benzo[e] pyrene o o o +++Benzo[a]anthracene + + + +++Benzo[b]fluoranthene o o o +++Benzo[j]fluoranthene o o o +++Benzo[k]fluoranthene o o o +++Chrysene o o o +++Dibenzo[a,h]anthracene n.d. n.d. n.d. n.d.Benzo[g,h,i]perylene o o o +++ lndeno[l,2,3-cd]pyrene o o o +++Acenaphthylene o o o +++Acenaphthene n.d. n.d. n.d. n.d.Fluorene n.d. n.d. n.d. n.d.Phenanthrene o o o +++Pyrene o o o +++Anthracene + + + +++Fluoranthene o o o +++Naphthalene o o o +++

Claims

Claims1. A method for reducing the content of polycyclic aromatic hydrocarbons in rubber powder, the method comprising the steps of(i) providing rubber powder;(ii) subjecting the rubber powder to heat treatment at reduced pressure.

2. The method of claim 1, wherein step (ii) is carried out at a pressure in a range selected from 0.001 to 100 mbar, 0.01 to 75 mbar, 0.1 to 50 mbar, 0.1 to 40 mbar, 0.1 to 30 mbar, and 0.1 to 20 mbar.

3. The method of claims 1 or 2, wherein step (ii) is carried out at a temperature in the range of 80 to 180°C, preferably 100 to 160°C and even more preferably 130°C to 160°C.

4. The method of any one of claims 1 to 3, wherein step (ii) is carried out for a time period in a range selected from 0.5 to 120h, 1 to 60h, 1 to 24h, 4 to 150h, 6 to 120h, 8 to llOh, 12 to lOOh, 4 to lOOh, 6 to 80h, 8 to 60h, 12 to 40h, 4 to 50h, 6 to 40h, 8 to 30h, 12 to 20h, 1 to 4h, 2 to 4h, 1 to 6h, 2 to 6h, 1 to 8h, 2 to 8h, 1 to 12h, and 2 to 12h .

5. A method for reducing the content of polycyclic aromatic hydrocarbons in rubber powder, the method comprising the steps of(i) providing rubber powder;(ii) contacting the rubber powder with supercritical extraction solvent; and(iii) removing the extraction solvent wherein the extraction solvent contains CO2.

6. The method of claim 5, wherein step (ii) is carried out at a pressure in the range of 75 to 600 bar, preferably 100 to 500 bar and more preferably 200 to 500 bar.

7. The method of claims 5 or 6, wherein step (ii) is carried out at a temperature in the range of 31 to 180°C, preferably 40 to 150°C and more preferably 60°C to 100°C.

8. The method of any one of claims 5 to 7, wherein step (ii) is carried out for a time period in a range selected from 0.1 to 24h, 0.5 to 12h, 0.5 to 6h, 1 to 12h, 2 to lOh and 3 to 8h.

9. The method of any one of claims 5 to 8, wherein the extraction solvent contains a co-solvent that is preferably selected from the group consisting of linear or branched alkanes, linear or branchedaliphatic alcohols, organic acids, aldehydes, amines, organophosphorus compounds, halogenated hydrocarbons, cyanide compounds, water and mixtures thereof.

10. The method of claim 9, wherein the co-solvent is selected from the group consisting of n-hexane, methanol, ethanol, 2-ethyl hexanol, n-butanol, n-pentanol, 2-methyl-2-butanol, 1-Dodecanol, hexanoic acid, octanoic acid, decanoic acid, pentanoic acid, heptanoic acid, furan-2-carbaldehyde, trioctylamine, 2-propylamine, trioctylphosphine oxide, chloroform, acetonitrile, water and mixtures thereof.

11. The method of any one of claims 1 to 4, wherein the method is carried out before or after carrying out the method of any one of claims 5 to 9.

12. The method of any one of claims 1 to 11, wherein the method uses rubber powder as a starting material, which is obtained by separating a rubber material from a rubber source and subjecting the rubber material to particle size reduction, wherein the rubber source preferably comprises one or more used tires or end-of-life tires, and wherein the method of particle size reduction is selected from ambient grinding, cryogenic grinding, or waterjet grinding.

13. The method of any one of claims 1 to 12, wherein the method uses rubber powder as a starting material, which is characterized by an average particle size of from 0.1 to 0.6mm as determined according to ASTM D5644-18.

14. Rubber powder obtainable by the method of any one of claims 1 to 13.

15. Consumer good article containing or manufactured from the rubber powder of claim 14.

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