DEODORIZATION PROCESS OF VULCANIZED RUBBER GRANULATIONS RECOVERED

Abstract

The invention relates to a process for deodorizing rubber granules, comprising a drying step of said rubber granules, characterized in that the rubber granules subjected to the drying treatment comprise rubber in the vulcanized state. The invention also relates to the deodorized rubber granules obtainable by this process. The invention further relates to the process for obtaining objects made of such deodorized rubber granules, as well as the objects made of deodorized rubber granules obtainable by the process. Deodorized rubber granules are used in the manufacture of playing fields, athletic tracks, playgrounds, shoe soles, or solid casters, particularly for scooters, trolleys, Segways, or hospital beds. Figure for the abstract: none

Description

Title of the invention: METHOD FOR DEODORIZING RECOVERED VULCANIZED RUBBER GRANULATES FIELD OF INVENTION

[0001] The present invention relates to the field of articles made from deodorized rubber granules.

[0002] The invention relates to a deodorization process by steaming of vulcanized rubber granules. STATE OF THE ART

[0003] Currently, the question of recycling end-of-life tires is being raised more and more frequently. The need felt most acutely is the ability to reuse the material of the components or, in other words, to reprocess them in order to recover all or part of the material that constitutes a used tire.

[0004] When used tires are to be recycled, they are shredded. Shredding is carried out in a machine equipped with powerful rotating shredding blades capable of shredding tires of different sizes and types. The resulting shreds, or in other words, the sheared pieces of used tires, have different sizes, generally between 25 mm and 350 mm, and an average composition identical to that of the original whole tire.

[0005] In order to recover value from their constituent material, the shredded material is processed in a granulator where it is ground more finely to obtain granules. The granules come from the very fine grinding of the rubber contained in pieces of used tires, generally after the extraction of textile fibers and metal wires from the tires. The granules thus obtained have a size between 0.8 mm and 20 mm. The granules can then be ground even finer and dried to obtain rubber powder.

[0006] We seek to be able to reuse these granules or the rubber powders derived from these granules directly in new rubber objects without having to subject them to a chemical modification of functionalization or devulcanization, in particular without biological and / or chemical treatment.

[0007] Document FR 2 475 458 describes a manufacturing process by sintering of articles made from recovered rubber which consists of depositing in a mold powder mixed preferably with a vulcanizing agent, alone or in mixture with an accelerator.

[0008] Document WO2020128212 describes a sintering process for manufacturing articles from recycled rubber that eliminates the need for any binding agent. The powder particles used have a size not exceeding 800 µm.

[0009] Document WO2020128213 describes a process for manufacturing recycled rubber articles by sintering, comprising the following steps. Powder particles are mixed with solute particles. Then, a molded object is produced by sintering this mixture. A step of contacting the molded object with a solvent dissolves at least some of the solute particles, resulting in partial or total porosity of the molded object.

[0010] Among the uses of sintered objects obtained according to the processes described above, we can mention: tire bands, wheels or casters for scooters, roller skates, gyropods, etc., shoe soles, floor coverings or underlays for them, etc.

[0011] By using recycled materials, the manufacturing processes for such objects are economically and ecologically attractive.

[0012] However, in the course of their use, particularly in hot weather, such objects may generate odors.

[0013] When these objects are, for example, floor coverings for playgrounds, these odors can be bothersome to users. Description of the invention

[0014] There therefore remains a need to develop objects, particularly sintered objects, based on rubber granules comprising vulcanized rubber that emit fewer odors. The rubber granules contain volatile organic compounds trapped in the vulcanized rubber, which will evaporate slowly and contribute to the odors emitted by the object over several weeks, months, or years, depending on the size of the object.

[0015] Surprisingly, it was found that steaming the rubber granules allowed the release of volatile substances although they were trapped in the vulcanized rubber without devulcanizing the rubber granules, i.e. without breaking the bridges, i.e. the covalent bonds, between the sulfur atoms.

[0016] A process for deodorizing vulcanized rubber granules has thus been developed, comprising drying said granules. In the process according to the invention, when subjected to the drying treatment, the rubber granules comprise rubber in the vulcanized state. After the drying treatment, the rubber granules still comprise rubber in the vulcanized state.

[0017] The process of the invention makes it possible to deodorize the rubber granules while preserving their vulcanized state. The deodorized rubber granules can be used as is for the manufacture of rubber articles, in particular by sintering. Summary of the invention

[0018] The invention relates to a process for deodorizing a rubber granule comprising a step of steaming said rubber granule, characterized in that the rubber granule subjected to the steaming treatment comprises rubber in the vulcanized state.

[0019] Preferably, the rubber granules are heated during the curing step to a temperature between 55°C and 180°C, preferably between 60°C and 130°C, even more preferably between 65°C and 120°C, particularly preferably between 75°C and 110°C, for a duration between a minimum and a maximum value as indicated in the table below:

[0020] [Tables 1] Temperature Minimum Duration Maximum Duration 55°C 1.2 weeks 3 weeks 60°C 0.8 weeks 2 weeks 65°C 0.6 weeks 1.5 weeks 70°C 2.8 days 7.1 days 75°C 2.1 days 5.3 days 80°C 1.4 days 3.6 days 85°C 1.1 days 2.7 days 90°C 0.7 days 1.8 days 95°C 12.5 hours 1.3 days 100°C 8.5 hours 21.3 hours 105°C 6.4 hours 16.0 hours 110°C 4.3 hours 10.7 hours 115°C 3.2 hours 8 hours 120°C 2.1 hours 5.3 hours 125°C 1.6 hours 4 hours 130°C 1.1 hours 2.7 hours 135°C 48 minutes 120 minutes 140°C 32 minutes 80 minutes 145°C 24 minutes 60 minutes 150°C 15 minutes 40 minutes 155°C 12 minutes 30 minutes 160°C 8 minutes 20 minutes 165°C 6 minutes 15 minutes 170°C 4 minutes 10 minutes 175°C 3 minutes 7.5 minutes 180°C 2 minutes 5 minutes

[0021] Preferably, the pressure used during the curing step is between 2*104 Pa and atmospheric pressure, preferably between 3*104 Pa and 5*104 Pa.

[0022] Preferably, the rubber granules are in the form of particles whose average diameter D50 in volume is between 0.8 mm and 20 mm, preferably between 0.8 mm and 8 mm.

[0023] Preferably, the rubber granule is a rubber powder in the form of particles whose average diameter D50 in volume is between 10 pm and 800 pm, preferably between 50 pm and 200 pm.

[0024] Preferably, the emission of total volatile organic compounds by the rubber granule, after the curing step, is reduced compared to that of the rubber granule before the curing step.

[0025] Preferably, the reduction in the emission of total volatile organic compounds by the rubber granule, after the curing step, is greater than 50% by weight, preferably greater than 70% by weight.

[0026] Preferably, the process for deodorizing the rubber granules includes a preliminary step of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide said rubber granules.

[0027] The invention also relates to a deodorized rubber granule that can be obtained according to the process as described above.

[0028] The invention also relates to a method for manufacturing an object made of rubber granules comprising the following successive steps:

[0029] a.supply of a deodorized rubber granule that can be obtained according to the deodorization process as described above;

[0030] b.optionally, preparation of a composition comprising said aggregate and, for example, metallic, mineral or organic particles, said mineral or organic particles being a salt, a saccharide, a water-soluble protein or a water-soluble polymer;

[0031] c.sintering in a mold of the deodorized granulate or of the composition comprising it;

[0032] d.retrieval of the object obtained at the end of step c.

[0033] According to one embodiment, the deodorized rubber granules of step a. are prepared by carrying out the following successive steps:

[0034] al. supply of an aggregate comprising rubber in the vulcanized state;

[0035] a2. deodorization of said granule according to the deodorization process as described below- above.

[0036] Preferably, step c. directly follows the baking step applied to the granule comprising vulcanized rubber in step a2. so that said granule is introduced into the mold for shaping by sintering at a temperature above 30°C, preferably above 40°C.

[0037] Preferably, the process for manufacturing an object made of rubber granules includes a preliminary step to step al. of grinding an object made of vulcanized rubber, preferably used tires or pieces of used tires, to provide the granule comprising rubber in the vulcanized state.

[0038] The invention also relates to an object made of deodorized rubber granules that can be obtained by the process as described above.

[0039] The invention also relates to the use of the rubber granulate object as described above, for the manufacture of playing fields, athletic tracks, playgrounds, shoe soles or solid wheels, in particular wheels for scooters, trolleys, gyropods or medical beds.

[0040] Other aspects of the invention are as described below and in the claims.

[0041] Definitions

[0042] By "vulcanized rubber" is meant a crosslinked rubber with a sulfur-based crosslinking system.

[0043] By "room temperature" is meant a temperature ranging from 18°C ​​to 22°C.

[0044] The terms "granulate" and "granulates" are interchangeable. "Granulate" or "granulates" refers to tire shreds processed in a granulator where they are ground to a finer size. The granules thus obtained, having an average volume diameter D50 of between 0.8 mm and 20 mm, can then be ground further and dried to obtain rubber powder with an average volume diameter D50 of less than 800 µm. For the purposes of the present invention, "granulate" or "granulates" therefore also refers, where applicable, to the rubber powder thus obtained.

[0045] By “particles”, we mean particles which have a size, namely their average diameter D50 in volume, of a few tens of microns to a few millimeters.

[0046] The average diameter D50 of the aggregate particles is an average diameter D50 by volume and can be measured by laser diffraction particle size analysis or by sieve analysis for particles with a D50 greater than 1 mm. Particles with a diameter less than D50 represent 50% by volume of the total particle volume.

[0047] By "sintering" of rubber granules, we mean a step of shaping a predetermined quantity of granules by heating them to a temperature lower than that at which the constituent grains vulcanize, and simultaneously pressurizing this quantity of granules in the cavity of a mold. DESCRIPTION OF FIGURES

[0048] [Fig-1] represents the concentration of total volatile organic compounds, expressed in ppm (parts per million), emitted by the different vulcanized rubber granules retrieved examples before and after implementation of the deodorization process according to the invention.

[0049] [Fig.2] represents the results of the sensory evaluation of concentration Subjective assessment of odors emitted by different vulcanized rubber granules recovered from examples before and after implementation of the deodorization process according to the invention. The number of points obtained following the scoring of the trained panel is plotted on the y-axis. The figures are therefore unitless. DETAILED DESCRIPTION OF THE INVENTION

[0050] Process for deodorizing a rubber granule

[0051] The inventors have developed a process for deodorizing a rubber granule while preserving its vulcanized state.

[0052] A first object of the invention thus relates to a process for deodorizing a rubber granule comprising a step of steaming said granule, characterized in that the rubber granule subjected to the steaming treatment comprises rubber in the vulcanized state.

[0053] Rubber granules are obtained by grinding or micronizing new or previously used cured rubber compounds, for example, in tires. They are advantageously a material recycling product. They are thus advantageously obtained from grinding already vulcanized tires, whether used or new. Such a tire is chosen from among those intended to equip a two-wheeled vehicle, a passenger vehicle, or a so-called "heavy goods vehicle" (i.e., subways, buses, off-road vehicles, road transport vehicles such as trucks, tractors, trailers), or even aircraft, construction equipment, agricultural machinery, or handling equipment. The granules used are those obtained by grinding a previously detached part of the tire, for example, from a tread, sidewalls, etc., or they are obtained by grinding the entire tire.In the latter case, the granulate also advantageously undergoes a stage during which textile or metallic residues present in the tire are removed.

[0054] The rubber granules are in the form of particles.

[0055] Advantageously, the rubber granules are in the form of particles whose average diameter D50 in volume is between 0.8 mm and 20 mm, preferably between 0.8 mm and 8 mm.

[0056] Advantageously, the rubber granule is a rubber powder in the form of particles whose average diameter D50 in volume is between 10 pm and 800 pm, preferably between 50 pm and 200 pm.

[0057] Thus, the rubber granules, whether in powder form or not, are in the form of individual particles and not a paste comprising even partially vulcanized rubber.

[0058] The granules are advantageously simple rubber granules, without any further treatment. In particular, the granules have not been subjected to any chemical modification for functionalization or devulcanization. In particular, the granules have not been subjected to any modifications by biological and / or chemical treatment.

[0059] A so-called primary shredding process allows obtaining, from tires, pieces of sheared tires having different sizes (D50) generally between 25 mm and 350 mm and an average composition identical to that of the original whole tire.

[0060] A granulation step makes it possible to reduce the size of the ground material obtained after primary grinding.

[0061] Granulation comprises a first dissociation step consisting of reducing the size of the ground material to obtain a particle size sufficient to allow the separation of rubber, textile, and metallic reinforcements. Once dissociated, the materials are sorted in a second step. When the granules are smaller than 2.5 mm, the sorting step is facilitated, and it is generally possible to obtain granules free of metallic and textile residues.

[0062] The aggregates obtained generally have a size between 0.8 mm and 20 mm.

[0063] The aggregates can also be ground more finely and dried to obtain rubber powder whose particles are smaller than 800 pm.

[0064] The grinding to obtain the granules and, where appropriate, a powder of a determined size, can be carried out by different technologies.

[0065] The implementation of knife mills composed of a rotor, a stator and a grid allows, by successive grinding, the reduction of the particle size.

[0066] Crushing can be carried out using a Kahl type granulator. This type of granulator includes fins for breaking up the material to be crushed, rollers for crushing the material and forcing it through a die.

[0067] Cryogenic impact micronization technologies enable the production of small particles on rubber materials. Commercial equipment such as the Netzsch CUM150 or Alpine CW250 mills can be used. Sieving steps follow the milling process to select particles with a predetermined average size.

[0068] Advantageously, the granules have an acetone extract of between 3 and 15% by mass, more preferably in the range of 3 to 10% by mass. Also, it is preferred that the granules have a chloroform extract of between 3 and 20% by mass, more preferably in the range of 5 to 15% by mass. Preferably, the chloroform extract of the granules of rubber has a mass average molecular weight (Mw) of less than 10000 g / mol, preferably less than 8000 g / mol.

[0069] It is preferred that the ratio of chloroform extract to acetone extract, expressed as a mass percentage, be less than 1.5.

[0070] The granules are advantageously free of textile or metallic residues present in the tire. However, it is possible to consider using rubber granules that contain metallic or textile inclusions.

[0071] The granules are preferably made up of a composition based on an elastomer and a filler. They may also include all the ingredients commonly used in rubber compositions such as plasticizers, antioxidants, vulcanizing additives, etc.

[0072] Thus, the granule comprises an elastomer, preferably a diene elastomer. This elastomer preferably represents at least 30% by mass, more preferably at least 35% by mass, and even more preferably at least 45% by mass of the granule weight, a percentage determined according to ASTM E131. It is preferably selected from the group consisting of polybutadienes, polyisoprenes including natural rubber, butadiene copolymers, and isoprene copolymers. More preferably, the molar content of diene-derived motifs (conjugated dienes) present in the diene elastomer is greater than 50%, preferably between 50% and 70%.

[0073] According to a preferred embodiment of the invention, the aggregate contains between 5% and 80% by mass of filler, more preferably between 10% and 75%, and very preferably between 15% and 70%.

[0074] The term "filler" here refers to any type of filler, whether reinforcing (typically nanometric particles, and preferably with a weight average size of less than 500 nm, in particular between 20 nm and 200 nm) or non-reinforcing or inert (typically micrometric particles, and preferably with a weight average size greater than 1 µm, for example between 2 µm and 200 µm). The weight average size of nanometric particles is measured in a manner well known to those skilled in the art (for example, according to application WO2009 / 083160, paragraph 1.1). The weight average size of micrometric particles can be determined by mechanical sieving.

[0075] Examples of fillers known to those skilled in the art to be reinforcing include carbon black or an inorganic reinforcing filler such as silica or alumina in the presence of a coupling agent, or mixtures thereof.

[0076] The granules include vulcanized rubber, i.e. crosslinked rubber with a sulfur-based crosslinking system.

[0077] Reaction products or residues may also be found in the aggregate of at least one vulcanization accelerator and, optionally, of various known vulcanization activators such as zinc oxide, stearic acid or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders.

[0078] As an example of an accelerator, we can mention in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sul-fenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-ter-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-ter-butyl-2-benzothiazyl sul-fenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0079] The granules may contain all other common additives, or their reaction products or residues, that are used in a rubber composition, particularly for tires. These common additives include liquid or solid plasticizers, non-reinforcing fillers such as chalk, kaolin, and preservatives. These additives may also be found in the granules in the form of residues or derivatives, since they may have reacted during the manufacturing or crosslinking stages of the composition from which the granules are derived.

[0080] The aggregate shall also comprise at least one volatile organic compound advantageously having a molar mass of less than 130 g / mol.

[0081] The objective of the process is to reduce the emission of total volatile organic compounds by the rubber granule.

[0082] The curing step according to the deodorization process of the invention is applied to a rubber granule comprising vulcanized rubber as just described.

[0083] Advantageously, the rubber granules subjected to the oven treatment have not undergone any devulcanization step, even partial.

[0084] The drying step is carried out in any closed heat treatment device, in particular an oven, allowing the aggregate to be heated homogeneously and regularly, if necessary under a partial vacuum. Ovens with natural or forced convection, advantageously with forced convection, are preferred.

[0085] Infrared radiation heating does not allow the aggregate to be heated sufficiently homogeneously.

[0086] Microwave radiation heating is also not preferred because it is more difficult to control.

[0087] To make deodorization more effective, the granules can be set in motion within the heat treatment device. For example, the heat treatment device may include a rotating tube with blades that cause the granule particles to rise and fall repeatedly inside the tube.

[0088] The temperature within the heat treatment device is maintained at a temperature above ambient temperature and advantageously below 180°C, in order to avoid degradation of the rubber.

[0089] According to one embodiment, the temperature in the heat treatment device is between 55°C and 180°C, preferably between 60°C and 130°C, even more preferably between 65°C and 120°C, particularly preferably between 75°C and 110°C.

[0090] The temperature corresponds to the temperature measured inside the heat treatment device, using any suitable means, for example a temperature probe.

[0091] For example, in the case of a rotating device, the temperature measuring device may be in contact with the bed of moving aggregate particles inside the device.

[0092] The drying process can be carried out under vacuum, in particular under 10% to 80% partial vacuum, advantageously under 50% to 70% partial vacuum. Thus, in the device, the air pressure inside the heat treatment device advantageously varies from 20,000 Pa to 90,000 Pa, more advantageously from 30,000 Pa to 50,000 Pa.

[0093] The drying process can also be carried out under atmospheric pressure or under a light vacuum, i.e., from 0% to 10% vacuum. Thus, in the device, the air pressure inside the heat treatment device advantageously varies from 90,000 Pa to 101,325 Pa.

[0094] Advantageously, the pressure used during the curing stage is thus between 2*104 Pa and atmospheric pressure, preferably between 3*104 Pa and 5*104 Pa.

[0095] The duration of the heat treatment step depends on multiple factors such as the type of device used, the quantity of granules to be deodorized, the size of the granules to be deodorized and the temperature of the granules during treatment.

[0096] Thus, the duration of the heat treatment step can range from a few minutes, for example 5 minutes, to several weeks, for example 3 weeks.

[0097] The duration of the deodorization step depends particularly on the temperature at which the deodorization step is carried out.

[0098] The duration of the deodorization step is thus chosen to avoid the reversion of the vulcanized rubber from the granules, that is to say, to avoid degradation of the rubber. The maximum duration of the deodorization step, that is to say, not causing reversion of the rubber, can easily be determined using charts available to a person skilled in the art.

[0099] The duration of the deodorization step must also be sufficient to allow the deodorization of the rubber granules.

[0100] According to one embodiment, the rubber granules are heated during the curing step to a temperature between 55°C and 180°C, preferably between 60°C and 130°C, even more preferably between 65°C and 120°C, particularly preferably between 75°C and 110°C for a duration between a minimum value and a maximum value as indicated in the table below:

[0101] [Tables 1] Temperature Minimum Duration Maximum Duration 55°C 1.2 weeks 3 weeks 60°C 0.8 weeks 2 weeks 65°C 0.6 weeks 1.5 weeks 70°C 2.8 days 7.1 days 75°C 2.1 days 5.3 days 80°C 1.4 days 3.6 days 85°C 1.1 days 2.7 days 90°C 0.7 days 1.8 days 95°C 12.5 hours 1.3 days 100°C 8.5 hours 21.3 hours 105°C 6.4 hours 16.0 hours 110°C 4.3 hours 10.7 hours 115°C 3.2 hours 8 hours 120°C 2.1 hours 5.3 hours 125°C 1.6 hours 4 hours 130°C 1.1 hours 2.7 hours 135°C 48 minutes 120 minutes 140°C 32 minutes 80 minutes 145°C 24 minutes 60 minutes 150°C 15 minutes 40 minutes 155°C 12 minutes 30 minutes 160°C 8 minutes 20 minutes 165°C 6 minutes 15 minutes 170°C 4 minutes 10 minutes 175°C 3 minutes 7.5 minutes 180°C 2 minutes 5 minutes

[0102] The deodorization process can be a batch process consisting of loading the heat treatment device with the granules to be deodorized, applying the heat treatment as described above, and then recovering the granules. deodorized.

[0103] The deodorization process can be a process consisting of continuously feeding the heat treatment device with the granules to be deodorized. The deodorized granules are then continuously recovered from the outlet of the heat treatment device.

[0104] The deodorization process according to the invention allows the elimination of part of the volatile components (VOCs) present in the granule.

[0105] According to one embodiment, the emission of total volatile organic compounds by the rubber granule, after the curing step, is reduced compared to that of the rubber granule before the curing step.

[0106] Advantageously, the reduction in total volatile organic compound emissions after the curing step is greater than 50% by weight, preferably greater than 70% by weight.

[0107] The total volatile organic compound content emitted can be measured using an automated analyzer with a photoionization detector (PID) or with a flame ionization detector (FID). Preferably, an analyzer with a photoionization detector (PID) is used.

[0108] Advantageously, said volatile organic compounds whose content is reduced by the heat treatment step comprise at least one volatile organic compound whose molar mass is less than or equal to 130 g / mol.

[0109] Various analytical methods allow for the specific detection and quantification of these volatile organic compounds. These include gas chromatography with flame ionization detectors (FID), photo ionization detectors (PID), mass spectrometry (MS), high-performance liquid chromatography (HPLC) with UV detectors, pGC / TCD / MS coupling, or Fourier Transform Infrared (FTIR) spectroscopy.

[0110] The rubber granules used are advantageously recycled rubber granules. The process according to the invention may therefore include a preliminary step of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide the vulcanized rubber granules used according to the process.

[0111] The deodorization process makes it possible to deodorize the rubber granules while preserving their vulcanized state. The deodorized rubber granules can then be reused as is for the manufacture of objects, in particular by sintering. Deodorized rubber granules

[0112] Another object of the invention relates to a deodorized rubber granule that can be obtained according to the deodorization process as described above.

[0113] The deodorized rubber granules have the same characteristics as the granules of rubber before curing with regard to its size and composition, except for its volatile organic compound content which has been reduced.

[0114] Advantageously, the emission of total volatile organic compounds by the deodorized rubber granule is reduced by at least 50%, preferably by at least 70%, compared to that of the non-deodorized granule.

[0115] Advantageously, said volatile organic compounds whose emission is reduced by the drying step comprise at least one volatile organic compound whose molar mass is less than or equal to 130 g / mol.

[0116] The vulcanized rubber granules before implementation of the deodorization process are as described above.

[0117] Method for manufacturing an object from rubber granules

[0118] The deodorized granules as described above can then be used for the manufacture of rubber articles. The fact that they are still vulcanized allows for their direct use, without the need to add vulcanizing agents in particular.

[0119] In particular, it can be used in a sintering process, especially for powder, in the processes described in patent applications WO2020 / 128212 and WO2020 / 128213.

[0120] Thus, another object of the invention relates to a method for manufacturing an object made of rubber granules comprising the following successive steps:

[0121] a.supply of a deodorized rubber granule capable of being obtained according to the deodorization process as described above;

[0122] b.optionally, preparation of a composition comprising said aggregate and, for example, metallic, mineral or organic particles, said mineral or organic particles being a salt, a saccharide, a water-soluble protein or a water-soluble polymer;

[0123] c.sintering in a mold of the deodorized granulate or of the composition comprising it;

[0124] d.retrieval of the object obtained at the end of step c.

[0125] According to one embodiment, the deodorized rubber granules of step a. are prepared by carrying out the following successive steps:

[0126] al. supply of an aggregate comprising rubber in the vulcanized state as described above;

[0127] a2. deodorization of said granule according to the deodorization process as described below- above.

[0128] Step c. allows the object to be shaped by agglomerating rubber granule particles together.

[0129] The deodorized granule is the deodorized rubber granule that can be obtained according to the deodorization process as described above or is the The granule obtained at the end of step a2 of deodorization. The composition comprising it is the composition comprising the granule obtained at the end of step b of preparation of said composition.

[0130] Sintering is advantageously a solid-phase sintering of the granulate grains, in other words, an agglutination of the deodorized rubber granulate grains, which remain in a solid state throughout the sintering process. Heating and pressurizing the granulate creates a sintered agglomerate of granulate particles. Thus, compression creates a physical proximity of the particles, and heating promotes molecular mobility and therefore this proximity. Under the effect of temperature, molecular mobility increases and gives rise to an intermolecular interaction of the van der Waals type, which creates a resistant physical bond, or physisorption, between the molecules of the different granulate particles.

[0131] Advantageously, step c. comprises the following substeps: - cl. introduction of the aggregate into the mold; then - c2. compressing the aggregate to a predetermined nominal pressure while maintaining the mold heating at a chosen nominal temperature for a predetermined duration; then - c3. cooling the mold to a temperature lower than the working temperature for a predetermined cooling time; - c4. Opening of the mold.

[0132] Advantageously, the aggregate introduced into the mold during step cl. is subjected during step c2. to a nominal temperature between 100°C and 150°C and to a nominal pressure between 20 105 Pa and 200 105 Pa for a period of time between 2 minutes and 15 minutes.

[0133] Advantageously, the aggregate introduced into the mold during step cl. is subjected during step c2. to a nominal temperature of 120°C, to a nominal pressure of 100 105 Pa for a period of 10 minutes.

[0134] Advantageously the cooling step of the object in the mold takes place at a temperature below 50°C and preferably at room temperature.

[0135] Sintering is carried out on aggregate particles in a vulcanized state. Advantageously, the object obtained at the end of step d therefore does not need to undergo an additional annealing step.

[0136] According to one embodiment, step c. follows directly, i.e. without an intercalary step, the heat treatment step applied to the granule comprising vulcanized rubber during step a2. In this variant, the granule is introduced into the mold for shaping by sintering at a temperature above 30°C, preferably above 40°C, even more preferably above 60°C.

[0137] This embodiment saves energy because the aggregate is still The heat from the steam-heating stage is retained when the aggregate is introduced into the sintering mold. It also reduces the sintering cycle time by decreasing the time it takes for the aggregate to reach the sintering temperature. Furthermore, it ensures better temperature uniformity of the aggregate during sintering, specifically by reducing, or even eliminating, the temperature gradient between the aggregate in contact with the mold wall and the core of the aggregate mass within the sintering mold.

[0138] Step b. is an optional step for obtaining a composition comprising the deodorized granule obtained at the end of step a.

[0139] It is thus possible to include, during step b, solid particles of predetermined size, in particular metallic, mineral, or organic particles, to modify the mechanical properties, for example, the stiffness of the resulting sintered object. For example, particles of a thermoplastic material with controlled stiffness and predetermined size can be added to modify the final stiffness of the sintered object.

[0140] It is also possible to mix granulate particles with solute particles as described in document WO2020128213, the solute particles being a salt, a saccharide, a water-soluble protein, or a water-soluble polymer. The molded object obtained by sintering this mixture and recovered at the end of step e is then subjected to a solvent contact step to dissolve at least some of the solute particles and thus obtain partial or total porosity in the recovered object.

[0141] Advantageously, the rubber granules used are recycled rubber granules. The process therefore advantageously includes a preliminary step to step a1 of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide the rubber granules.

[0142] Advantageously, the granules of step a1a are a powder whose particles have an average size not exceeding 800 pm. In particular, the rubber powder has an average particle size of between 200 pm and 800 pm, and preferably of about 400 pm.

[0143] In this embodiment, advantageously, during this process, no vulcanizing additive, binder, or bonding additive is added. Thus, when prepared, the composition of step b. implemented in step c. is advantageously free of vulcanizing additives, binders, or bonding additives other than those intrinsically provided by the rubber powder.

[0144] Step c. of shaping by sintering is advantageously as described in patent applications WO2020 / 128212 and WO2020 / 128213, in particular as detailed in [Fig.1] of each of these requests.

[0145] By using powder particles with a size of less than 800 pm, the objects obtained by sintering the powder alone and recovered at the end of step d. exhibit excellent mechanical properties.

[0146] According to one embodiment, an object is produced by sintering only powder particles whose average size is less than or equal to 800 pm without the addition of vulcanizing additive or binder. Object made of deodorized rubber granules

[0147] Another object of the invention relates to an object made of deodorized rubber granules that can be obtained by the manufacturing process as described above.

[0148] Advantageously, the emission of total volatile organic compounds by the deodorized rubber granulate object is reduced by at least 50%, preferably by at least 70%, compared to that of the non-deodorized rubber granulate object.

[0149] Advantageously, said volatile organic compounds, the emission of which is reduced by the drying step, have a molar mass less than or equal to 130 g / mol. Use

[0150] Another object of the invention relates to the use of the deodorized rubber granule as described above or of the object comprising it as described above for the manufacture, for example, of playing fields, athletic tracks, playgrounds, shoe soles or solid wheels, in particular wheels for scooters, Segways, trolleys or medical beds.

[0151] The following examples are given for illustrative purposes only, but should in no way be considered as limiting the present invention. Examples

[0152] In the example below, a deodorization process according to the invention is applied to various rubber granules. The odor emission from the granules deodorized according to the process is evaluated. Aggregates used:

[0153] • powder (VL_02) of used light vehicle (LV) tires having a particle size (D50) less than 0.2mm; • Granulated (VL_3) from used light vehicle (VL) tires with a particle size (D50) less than 3mm; • powder (PL_02) of used heavy goods vehicle (HGV) tires having a particle size (D50) less than 0.2mm; • Granulated (PL_3) from used heavy goods vehicle (HGV) tires with a particle size (D50) less than 3mm.

[0154] The particle size of the aggregate, D50 average by volume, is measured by granule laser diffraction iometry using a Malvem Mastersizer type device for powders (VL_02 and PL_02) and by sieve analysis for aggregates (VL_3 and PL_3). Oven heat treatment stage:

[0155] Each type of aggregate is placed in a static oven for 11 days, at a temperature of 65°C and under a pressure of 900 mbar.

[0156] Characterization of aggregates before and after heat treatment step:

[0157] The aggregates before the oven heat treatment stage are referenced respectively VL_02, VL_3, PL_02 and PL_3 as indicated above.

[0158] After heat treatment, the corresponding aggregates are referenced respectively VL02 E. VL 3 E. PL 02 E and PL 3_E.

[0159] The aggregates are subjected to a protocol for measuring the content of volatile organic compounds (VOCs) and to a sensory evaluation test of their odor.

[0160] The study is carried out at room temperature, in a temperature-controlled room. For each type of aggregate, the experimental conditions are as follows: 1. Packaging of aggregates in Nalophan® bags: A quantity of aggregates corresponding to a volume of 300 ml of each material is placed in a Nalophan® bag, which is then filled with 40 L of nitrogen. The samples are then placed in a room with a controlled temperature (T=20± 2°C). 2. Verification of the achievement of equilibrium emission levels in the aggregates through periodic measurements of emitted VOCs. The concentration of VOCs emitted by the materials is monitored regularly until thermodynamic equilibrium is reached using a portable photoionization analyzer (RAE Systems / ppb RAE). As this instrument is calibrated with isobutene, the measured concentrations are expressed in ppm isobutene equivalent. The values ​​given below correspond to the values ​​measured at equilibrium. 3. Sensory Analyses (Odor Concentration, Acceptability, and Quality). For these sensory analyses, conducted on a panel of six trained individuals, the odorant gas to be analyzed was presented at different concentrations in the form of successive dilutions. This sensory analysis was performed using an Odile® multi-station dynamic dilution olfactometer and complies with standard NF 13725. For each dilution, each participant indicated whether or not they perceived the odor. Thus, for each individual and then for the entire panel, the odor perception threshold (odor concentration) was determined.

[0161] Results of tests measuring the VOC content of aggregates:

[0162] The concentration of VOCs emitted by the aggregates is shown in [Fig.1].

[0163] In all cases, steaming makes it possible to reduce the amount of VOCs in the aggregate.

[0164] Drying is more efficient (higher VOC reduction rate after heat treatment) when applied to a fine particle size aggregate (VL_02_E and PL_02_E powders) rather than to an aggregate made up of larger particles (VL_3_E and PL-3_E aggregates).

[0165] VOC emissions from fine particle size materials (VL_02_E and PL_02_E powders) are independent of their origin (light vehicle or heavy vehicle). Oven curing reduces their VOC content from 7.8 ppm to 2.2 ppm on average, which corresponds to a 70% reduction in VOC content.

[0166] Results of sensory analysis tests:

[0167] The results of the sensory evaluation are shown in [Fig.2].

[0168] The values ​​shown on the ordinates are relative values ​​and it is the decrease in this value after steaming (expressed as a percentage) that must be taken into account to evaluate the effectiveness of the deodorization process.

[0169] In all cases, the steam-treated aggregates exhibit a lower subjective odor level than the untreated aggregates.

Claims

Demands

1. A process for deodorizing a rubber granule comprising a drying step of said rubber granule, characterized in that the rubber granule subjected to the drying treatment comprises rubber in the vulcanized state, said rubber granule being heated during the drying step to a temperature between 55°C and 180°C, preferably between 60°C and 130°C, even more preferably between 65°C and 120°C, particularly preferably between 75°C and 110°C, for a duration between a minimum value and a maximum value as indicated in the table below: Temperature Minimum Duration Maximum Duration 55°C 1.2 weeks 3 weeks 60°C 0.8 weeks 2 weeks 65°C 0.6 weeks 1.5 weeks 70°C 2.8 days 7.1 days 75°C 2.1 days 5.3 days 80°C 1.4 days 3.6 days 85°C 1.1 days 2.7 days 90°C 0.7 days 1.8 days 95°C 12.5 hours 1.3 days 100°C 8.5 hours 21.3 hours 105°C 6.4 hours 16.0 hours 110°C 4.3 hours 10.7 hours 115°C 3.2 hours 8 hours 120°C 2.1 hours 5.3 hours 125°C 1.6 hours 4 hours 130°C 1.1 hours 2.7 hours 135°C 48 minutes 120 minutes 140°C 32 minutes 80 minutes 145°C 24 minutes 60 minutes 150°C 15 minutes 40 minutes

2.

3.

4.

5.

6.

7. 155°C 12 minutes 30 minutes 160°C 8 minutes 20 minutes 165°C 6 minutes 15 minutes 170°C 4 minutes 10 minutes 175°C 3 minutes 7.5 minutes 180°C 2 minutes 5 minutes and said rubber granules retaining their vulcanized state. Method according to the preceding claim, characterized in that the pressure used during the curing step is between 2*104 Pa and atmospheric pressure, preferably between 3*104 Pa and 5*104 Pa. A process according to any one of the preceding claims, characterized in that the rubber granules are in the form of particles whose average volume diameter D50 is between 0.8 mm and 20 mm, preferably between 0.8 mm and 8 mm. A process according to any one of claims 1 to 2 characterized in that the rubber granule is a rubber powder in the form of particles whose average diameter D50 in volume is between 10 pm and 800 pm, preferably between 50 pm and 200 pm. A method according to any one of the preceding claims, characterized in that it comprises a preliminary step of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide said rubber granules. Deodorized rubber granules obtainable according to the process of any one of the preceding claims. A method for manufacturing an object from rubber granules comprising the following successive steps: a. supplying deodorized rubber granules according to claim 6; b. Optionally, preparation of a composition comprising said aggregate and, for example, metallic, mineral or organic particles, said mineral or organic particles being a salt, a saccharide, a water-soluble protein or a water-soluble polymer; c. sintering in a mold of the deodorized granulate or the composition comprising it; d. recovery of the object obtained at the end of step c.

8. A process according to claim 7 wherein the deodorized rubber granules of step a. are prepared by carrying out the following successive steps: a1. supplying granules comprising rubber in the vulcanized state; a2. deodorizing said granules according to the process described in any one of claims 1 to 5.

9. A method according to claim 8, characterized in that step c directly follows the baking step applied to the granule comprising vulcanized rubber in step a2, so that said granule is introduced into the mold for shaping by sintering at a temperature above 30°C, preferably above 40°C.

10. A method according to claim 8 or 9, characterized in that it comprises a step prior to step a1 of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide the granule comprising rubber in the vulcanized state.

11. Object made of deodorized rubber granules which can be obtained by the process according to any one of claims 7 to 10.

12. Use of the object according to claim 11, for the manufacture of playing fields, athletic tracks, playgrounds, shoe soles or solid wheels, in particular wheels for scooters, trolleys, Segways or medical beds.

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