Method for deodorizing recovered vulcanized rubber crumb

Abstract

The invention relates to a method for deodorizing rubber crumb, the method comprising a step of steaming the rubber crumb, characterized in that the rubber crumb subjected to the steaming treatment comprises rubber in the vulcanized state. The invention also relates to deodorized rubber crumb that can be obtained according to this method. The invention also relates to a method for obtaining objects made of rubber crumb deodorized in this way and to objects made of deodorized rubber crumb that can be obtained according to the method. The deodorized rubber crumb is used for the production of playing fields, athletics tracks, play areas, soles for shoes or solid castors, in particular wheels for scooters, for trolleys, for self-balancing human transporters or for healthcare beds.

Description

[0001] PROCESS FOR DEODORIZING RECOVERED VULCANIZED RUBBER AGGREGATES

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of articles manufactured from deodorized rubber granules.

[0004] The invention relates to a method for deodorizing vulcanized rubber granules by steaming.

[0005] STATE OF THE ART

[0006] Currently, the question of recycling end-of-life tires is increasingly being asked. The need that is felt more particularly is the capacity to reuse the material of the components or, in other words, the reprocessing with a view to recovering all or part of the material that constitutes a used tire. When we want to recover used tires, we crush them. The crushing is carried out in a machine equipped with powerful rotating shredding blades capable of crushing tires of different sizes and types. The shredded material obtained, or, in other words, the pieces of sheared used tires, have different sizes generally ranging from 25 mm to 350 mm and an average composition identical to that of the original whole tire.

[0007] To recover the material they are made from, the shredded material is processed in a granulator where it is ground more finely to obtain aggregates. The aggregates come from very finely grinding the rubber contained in the pieces of used tires, generally after extraction of the textile fibers and metal wires contained in the tires. The resulting aggregates have a size between 0.8 mm and 20 mm. The aggregates can then be ground more finely and dried to obtain rubber crumb.

[0008] The aim is to be able to reuse these granules or the rubber powders produced from these granules directly in new rubber objects without having to subject them to chemical modification of functionalization or devulcanization, in particular without biological and / or chemical treatment.

[0009] Document FR 2 475 458 describes a method for manufacturing recovered rubber articles by sintering, which consists of depositing in a mold powder preferably mixed with a vulcanizing agent, alone or mixed with an accelerator. Document W02020128212 describes a method for manufacturing recovered rubber articles by sintering, which eliminates the need for any binding agent. The powder particles used have a size not exceeding 800 μm.

[0010] Document WO2020128213 describes a method for manufacturing recovered rubber articles by sintering, comprising the following steps. Powder particles are mixed with solute particles. A molded object is then produced by sintering this mixture. A step of bringing the molded object into contact with a solvent dissolves at least some of the solute particles, making it possible to obtain partial or total porosity of the molded object.

[0011] Among the uses of the sintered objects obtained according to the processes described above, we can cite: tires, wheels or casters for scooters, roller skates, Segways, etc., soles for shoes, floor coverings or underlays for these, etc.

[0012] By using recycled materials, the manufacturing processes for such objects are economically and ecologically attractive.

[0013] However, when used, especially in hot weather, such items can generate odors.

[0014] When these objects are, for example, floor coverings for playgrounds, these odors can be unpleasant for users.

[0015] STATEMENT OF THE INVENTION

[0016] There remains a need to develop objects, particularly sintered objects, made from rubber granules containing vulcanized rubber that emit less odor. Rubber granules contain volatile organic compounds trapped in the vulcanized rubber that will slowly evaporate and contribute to the odors emitted by the object over several weeks, months, or years, depending on the size of the object.

[0017] Surprisingly, it was found that curing 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.

[0018] A process for deodorizing a vulcanized rubber granulate has thus been developed, comprising steaming said granulate. In the process according to the invention, when subjected to the steaming treatment, the rubber granulate comprises rubber in the vulcanized state. At the end of the steaming treatment, the rubber granulate still comprises rubber in the vulcanized state.

[0019] The process of the invention makes it possible to deodorize the rubber granulate while retaining its vulcanized state. The rubber granulate thus deodorized can be used as such for the manufacture of rubber objects, in particular by sintering.

[0020] Summary of the invention

[0021] The subject of the invention is a method for deodorizing a rubber granulate comprising a step of steaming said rubber granulate, characterized in that the rubber granulate subjected to the steaming treatment comprises rubber in the vulcanized state, the rubber granulate being heated during the steaming step to a temperature of 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 time of between a minimum value and a maximum value as indicated in the table below:

[0022] [Table 1] and said baking step not comprising devulcanization means.

[0023] Preferably, the pressure used during the steaming stage is between 2*10 4 Pa and atmospheric pressure, preferably between 3*10 4Pa and 5*10 4 Pa.

[0024] Preferably, the rubber granulate is 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.

[0025] Preferably, the rubber granulate is a rubber powder in the form of particles whose average diameter D50 by volume is between 10 pm and 800 pm, preferably between 50 pm and 200 pm.

[0026] Preferably, the emission of total volatile organic compounds by the rubber granulate, after the baking step, is reduced compared to that of the rubber granulate before the baking step.

[0027] Preferably, the reduction in the emission of total volatile organic compounds by the rubber granulate, after the baking step, is greater than 50% by weight, preferably greater than 70% by weight.

[0028] Preferably, the process for deodorizing rubber granulate comprises a prior step of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide said rubber granulate.

[0029] The invention also relates to a deodorized rubber granulate capable of being obtained according to the process as described above.

[0030] The invention also relates to a method for manufacturing an object made of rubber granules comprising the following successive steps: a. providing a deodorized rubber granule capable of being obtained according to the deodorization method as described above; b. optionally, preparing a composition comprising said granule and, for example, metallic, mineral or organic particles, said mineral or organic particles possibly being a salt, a saccharide, a water-soluble protein or a water-soluble polymer; c. sintering in a mold the deodorized granule or the composition comprising it; d. recovering the object obtained at the end of step c.

[0031] According to one embodiment, the deodorized rubber granulate of step a. is prepared by implementing the following successive steps: a1. providing a granulate comprising rubber in the vulcanized state; a2. deodorizing said granulate according to the deodorization method as described above.

[0032] Preferably, step c. directly follows the baking step applied to the granulate comprising vulcanized rubber during step a2. so that said granulate is introduced into the mold for its shaping by sintering at a temperature above 30°C, preferably above 40°C.

[0033] Preferably, the method for manufacturing an object made of rubber granules comprises a step prior to step a1. of grinding an object made of vulcanized rubber, preferably used tires or pieces of used tires, to provide the granules comprising rubber in the vulcanized state.

[0034] The invention also relates to an object made of deodorized rubber granules capable of being obtained by the process as described above.

[0035] The invention also relates to the use of the rubber granulate object as described above, for the manufacture of playing fields, athletics tracks, playgrounds, soles for shoes or solid casters, in particular casters for scooters, trolleys, Segways or medical beds.

[0036] Other aspects of the invention are as described below and in the claims. Definitions

[0037] "Vulcanized rubber" means rubber crosslinked with a sulfur-based crosslinking system.

[0038] “Room temperature” means a temperature ranging from 18°C ​​to 22°C.

[0039] The terms "granulate" and "granulates" are interchangeable. "Granulate" or "granulates" means shredded tires processed in a granulator where they are ground more finely. The resulting aggregates generally have a volume average diameter D50 of less than 20 mm. Advantageously, the resulting aggregates have a volume average diameter D50 of between 0.8 mm and 20 mm. These aggregates can then be ground more finely and dried to obtain rubber crumb whose volume average diameter D50 is less than 800 μm. For the purposes of the present invention, "granulate" or "granulates" therefore also means, where appropriate, the resulting rubber crumb.

[0040] 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.

[0041] The mean diameter D50 of aggregate particles is a volume average diameter D50 and can be measured by laser diffraction granulometry 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.

[0042] By "sintering" rubber granules is meant a step of shaping a predetermined quantity of granules by heating to a temperature lower than that of vulcanization of the grains composing it and at the same time pressurizing this quantity of granules in the cavity of a mold.

[0043] DESCRIPTION OF FIGURES

[0044] [Fig. 1] represents the concentration of total volatile organic compounds, expressed in ppm (parts per million), emitted by the different vulcanized rubber granules recovered from the examples before and after implementation of the deodorization process according to the invention.

[0045] [Fig. 2] represents the results of the sensory evaluation of the subjective concentration of odors emitted by the different vulcanized rubber granules recovered from the 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

[0046] Process for deodorizing rubber granules

[0047] The inventors have developed a process for deodorizing rubber granules while maintaining their vulcanized state.

[0048] Rubber granules are produced by grinding or micronizing cooked rubber compositions that are new or already used for a first application, for example in tires. They are advantageously a product of material recycling. They are thus advantageously produced by grinding already vulcanized tires, whether used or new. Such a tire is chosen from tires intended to equip a two-wheeled vehicle, a passenger vehicle, or a so-called "heavy goods vehicle" (i.e. metro, bus, off-road vehicles, road transport equipment such as trucks, tractors, trailers), or even airplanes, civil engineering, agricultural, or handling equipment. The granule used is that obtained by grinding a previously detached part of the tire, for example from a tread, sidewalls, etc. or it is obtained by grinding the entire tire.In the latter case, the aggregate also advantageously undergoes a stage during which the textile or metallic residues present in the tire are removed.

[0049] Rubber granulate comes in the form of particles.

[0050] Advantageously, the rubber granulate is 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.

[0051] Advantageously, the rubber granulate is a rubber powder in the form of particles whose average diameter D50 by volume is between 10 pm and 800 pm, preferably between 50 pm and 200 pm.

[0052] Thus, the rubber granulate, whether in powder form or not, is in the form of individual particles and not a paste comprising rubber, even if partially vulcanized.

[0053] The aggregates are advantageously simple rubber shreds, without any other treatment, that is to say that the aggregates have not undergone any other treatment than grinding operations aimed at reducing their size and, where appropriate, at extracting the residues of textile and mechanical reinforcements present. In particular, the aggregates have not been subjected to a chemical modification of functionalization or devulcanization. In particular, the aggregates have not been subjected to modifications by biological and / or chemical treatment.

[0054] Primary crushing makes it possible to obtain, 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.

[0055] A granulation step reduces the size of the ground material obtained after primary grinding.

[0056] Granulation involves a first dissociation step, which involves reducing the size of the shredded material to obtain a particle size sufficient to allow the separation of rubber, textile and metal reinforcements. Once dissociated, the materials are sorted during a second step. When the aggregates are smaller than 2.5 mm, the sorting step is made easier and it is generally possible to obtain aggregates free of metal and textile residues.

[0057] The aggregates obtained generally have a size between 0.8 mm and 20 mm.

[0058] The aggregates can also be ground more finely and dried to obtain rubber crumb with particles smaller than 800 pm.

[0059] By eliminating metal and textile residues, this process makes it possible to obtain powders containing only the rubber composition.

[0060] Grinding to obtain aggregates and, where appropriate, a powder of a specific size, can be carried out using different technologies.

[0061] The use of knife mills composed of a rotor, a stator and a grid allows the particle size to be reduced by successive grinding.

[0062] Crushing can be carried out using a Kahl-type granulator. This type of granulator includes fins to break up the material to be ground, rollers to crush the material and force it through a die.

[0063] Cryogenic impact micronization technologies allow the production of small particle sizes on rubber materials. Commercial equipment such as the CUM150 mills from Netzsch or CW250 from Alpine can be used. Sieving steps follow the grinding in order to select particles with a predetermined average size. Advantageously, the granulate has an acetone extract of between 3 and 15% by mass, more preferably in a range of 3 to 10% by mass. Also, it is preferred that the granulate has a chloroform extract of between 3 and 20% by mass, more preferably in a range of 5 to 15% by mass. Preferably, the chloroform extract of the rubber granulate has a mass-average molecular weight (Mw) of less than 10,000 g / mol, preferably less than 8,000 g / mol.

[0064] It is preferred that the ratio of the chloroform extract to the acetone extract, expressed as a mass percentage, be less than 1.5.

[0065] The granulate is advantageously freed from textile or metal residues present in the tire. However, it is possible to consider using a rubber granulate which contains metal or textile inclusions.

[0066] The aggregates are preferably made of a composition based on an elastomer and a filler. They may also include all the ingredients usually used in rubber compositions such as plasticizers, antioxidants, vulcanization additives, etc.

[0067] Thus, the aggregate comprises an elastomer, preferably a diene elastomer. This elastomer preferably represents at least 30% by mass, more preferably at least 35% by mass, even more preferably at least 45% by mass of the weight of the aggregate, percentage determined according to standard ASTM E1 131. It is preferably chosen from the group consisting of polybutadienes, polyisoprenes including natural rubber, butadiene copolymers and isoprene copolymers. More preferably the molar content of units of diene origin (conjugated dienes) present in the diene elastomer is greater than 50%, preferably between 50% and 70%.

[0068] 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%.

[0069] By filler is meant here any type of filler, whether reinforcing (typically with 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 with micrometric particles, and preferably with a weight average size of greater than 1 μm, for example between 2 μm and 200 μm). The weight average size of the 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 the micrometric particles can be determined by mechanical sieving.

[0070] Examples of fillers known to those skilled in the art as reinforcing include carbon black or a reinforcing inorganic filler such as silica or alumina in the presence of a coupling agent, or mixtures thereof.

[0071] The aggregates include vulcanized rubber, i.e. rubber crosslinked with a sulfur-based crosslinking system.

[0072] The granulate may also contain reaction products or residues of at least one vulcanization accelerator and, optionally, 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.

[0073] Examples of accelerators include, but are not limited to, thiazole-type accelerators and their derivatives, sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate accelerators. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC"), and mixtures of these compounds.

[0074] The aggregate may contain all other usual additives, or their reaction products or residues, which are included in a rubber composition, particularly for tires. Among these usual additives, we can cite liquid or solid plasticizers, non-reinforcing fillers such as chalk, kaolin, and protective agents. These additives may also be found in the aggregate in the form of residue or derivative, since they may have reacted during the stages of manufacturing the composition or crosslinking the composition from which the aggregate is derived.

[0075] The aggregate will also comprise at least one volatile organic compound advantageously having a molar mass of less than 130 g / mol.

[0076] The objective of the process is to reduce the emission of total volatile organic compounds from the rubber granulate. The stoving step according to the deodorization process of the invention is applied to a rubber granulate comprising vulcanized rubber as just described.

[0077] Advantageously, the rubber granulate subjected to the steaming treatment has not undergone any devulcanization step, even partial.

[0078] A first subject of the invention thus relates to a method for deodorizing a rubber granulate comprising a step of steaming said granulate, characterized in that the rubber granulate subjected to the steaming treatment comprises rubber in the vulcanized state, the rubber granulate being heated during the steaming step to a temperature of 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 of between a minimum value and a maximum value as indicated in the table below:

[0079] [Table 1] and said baking step not comprising devulcanization means.

[0080] The drying step is carried out in any closed heat treatment device, in particular an oven, allowing the aggregate to be heated evenly and regularly, if necessary under a partial vacuum. Ovens with natural or forced convection, advantageously with forced convection, are preferred.

[0081] Infrared radiation heating does not allow the aggregate to be heated sufficiently evenly.

[0082] Microwave radiant heating is also not preferred because it is more difficult to control.

[0083] To make deodorization more effective, the aggregate may be set in motion within the heat treatment device. For example, the heat treatment device may include a rotating tube with blades to cause the aggregate particles to rise and fall, and so on, within the tube.

[0084] Advantageously, the steaming step is carried out without applying mechanical stress such as mixing or shearing to the rubber granules, causing a change in their size.

[0085] The temperature within the heat treatment device is maintained above room temperature and below 180°C, in order to avoid degradation of the rubber.

[0086] 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.

[0087] The temperature corresponds to the temperature measured inside the heat treatment device, using any suitable means, for example a temperature probe.

[0088] For example, in the case of a rotating device, the temperature measuring device may be in contact with the moving bed of aggregate particles within the device.

[0089] The baking 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.

[0090] Steaming 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.

[0091] Advantageously, the pressure used during the steaming stage is thus between 2*10 4Pa and atmospheric pressure, preferably between 3*10 4 Pa and 5*10 4 Pa.

[0092] The duration of the heat treatment step depends on multiple factors such as the type of device used, the quantity of aggregate to be deodorized, the size of the aggregate to be deodorized and the temperature of the aggregate during treatment.

[0093] 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.

[0094] The duration of the deodorization step depends particularly on the temperature at which the deodorization step is carried out.

[0095] The duration of the deodorization step is thus chosen so as to avoid the reversion of the vulcanized rubber from the granulate, that is to say so as 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 by means of charts available to those skilled in the art.

[0096] The duration of the deodorization stage must also be sufficient to allow the deodorization of the rubber granulate.

[0097] The steaming step does not include any devulcanization means. Thus, the process according to the invention makes it possible to deodorize the rubber granules while maintaining their vulcanized state.

[0098] By devulcanization means is meant any means of breaking bonds in the three-dimensional structure of vulcanized rubber, in particular SS bonds.

[0099] The means of devulcanization are well known to those skilled in the art. These include thermomechanical, mechanochemical processes and even grinding.

[0100] The implementation of thermal processes with sufficiently high temperatures can also lead to a reversion of the rubber granules. The baking step is carried out in the absence of a devulcanizing agent. Examples of devulcanizing agents or fragmenting agents include the agents disclosed in application EP3541867À1 such as hexadecyl amine (HDÀ) or diphenyldisulfide (DPDS).

[0101] Advantageously, the steaming step is carried out on the rubber granules alone, in the absence of any other component.

[0102] The steaming stage is carried out without applying mechanical stress such as mixing or shearing which induces devulcanization of the rubber of the aggregates.

[0103] The deodorization process may be a batch process consisting of loading the heat treatment device with the aggregate to be deodorized, applying the heat treatment as described above and then recovering the aggregate thus deodorized.

[0104] The deodorization process may be a process consisting of continuously feeding the heat treatment device with the aggregate to be deodorized. The aggregate thus deodorized is then continuously recovered at the outlet of the heat treatment device.

[0105] The deodorization process according to the invention allows the elimination of part of the volatile components (VOCs) present in the granulate.

[0106] According to one embodiment, the emission of total volatile organic compounds by the rubber granulate, after the baking step, is reduced compared to that of the rubber granulate before the baking step.

[0107] Advantageously, the reduction in the emission of total volatile organic compounds after the baking step is greater than 50% by weight, preferably greater than 70% by weight.

[0108] The content of total volatile organic compounds emitted can be measured using an automatic analyzer with a photoionization detector (PID) or a flame ionization detector (FID). Preferably, an analyzer with a photoionization detector (PID) is used.

[0109] 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. Different analysis methods make it possible to specifically detect these volatile organic compounds and to quantify them. 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 spectroscopy (FTIR).

[0110] The rubber granulate used is advantageously a recovered rubber granulate. The method according to the invention may therefore comprise a prior step of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide the vulcanized rubber granulate used according to the method.

[0111] The deodorization process allows the rubber granules to be deodorized while maintaining their vulcanized state. The deodorized rubber granules can be reused as is for the manufacture of objects, particularly by sintering.

[0112] Deodorized rubber granules

[0113] Another subject of the invention relates to a deodorized rubber granulate obtained according to the deodorization process as described above.

[0114] Deodorized rubber granulate has the same characteristics as pre-oiled rubber granulate in terms of size and composition, except that its volatile organic compound content has been reduced.

[0115] Advantageously, the emission of total volatile organic compounds by the deodorized rubber granulate is reduced by at least 50%, preferably by at least 70% compared to that of the non-deodorized granulate.

[0116] Advantageously, said volatile organic compounds whose emission is reduced by the baking step comprise at least one volatile organic compound whose molar mass is less than or equal to 130 g / mol.

[0117] The vulcanized rubber granulate before carrying out the deodorization process is as described above.

[0118] The deodorized rubber granulate can be obtained according to the deodorization process as described above. Process for manufacturing an object from rubber granulate

[0119] The deodorized granulate as described above can then be used for the manufacture of rubber objects. The fact that it is still vulcanized allows its direct use, without the need to add vulcanizing agents in particular.

[0120] In particular, it can be used in a sintering process, in particular for powder, in the processes described in patent applications WO2020 / 128212 and WO2020 / 128213.

[0121] Thus, another subject of the invention relates to a method for manufacturing an object made of rubber granules comprising the following successive steps: a. providing a deodorized rubber granule capable of being obtained according to the deodorization method as described above; b. optionally, preparing a composition comprising said granule and, for example, metallic, mineral or organic particles, said mineral or organic particles possibly being a salt, a saccharide, a water-soluble protein or a water-soluble polymer; c. sintering in a mold the deodorized granule or the composition comprising it; d. recovering the object obtained at the end of step c.

[0122] According to one embodiment, the deodorized rubber granulate of step a. is prepared by implementing the following successive steps: a1. providing a granulate comprising rubber in the vulcanized state as described above; a2. deodorizing said granulate according to the deodorization method as described above.

[0123] Step c. allows the object to be shaped by agglomerating rubber granule particles together.

[0124] The deodorized granulate is the deodorized rubber granulate that can be obtained according to the deodorization process as described above or is the granulate obtained at the end of step a2. of deodorization. The composition comprising it is the composition comprising the granulate obtained at the end of step b. of preparation of said composition. The sintering is advantageously a solid-phase sintering of the granulate grains, in other words, an agglutination of the deodorized rubber granulate grains that remain in the solid state throughout the sintering. The heating and pressurization of the granulate create a sintered agglomerate of granulate particles. Thus, the compression creates a physical approximation of the particles and the heating promotes molecular mobility and therefore this approximation.Under the effect of temperature, molecular mobility increases and gives rise to an intermolecular interaction of the van der Waals force type, which creates a resistant physical bond or physisorption between the molecules of the different aggregate particles.

[0125] Advantageously, step c. comprises the following sub-steps: c1. introduction of the aggregate into the mold; then

[0126] - c2. compressing the aggregate to a pre-established nominal pressure while maintaining the heating of the mold at a chosen nominal temperature for a predetermined duration; then

[0127] - c3. cooling the mold to a temperature lower than the working temperature for a predetermined cooling time;

[0128] - c4. opening the mold.

[0129] Advantageously, the aggregate introduced into the mold during step c1. is subjected during step c2. to a nominal temperature of between 100°C and 150°C and to a nominal pressure of between 20 10 5 Pa and 200 10 5 Pa for a period of time between 2 minutes and 15 minutes.

[0130] Advantageously, the aggregate introduced into the mold during step c1. is subjected during step c2. to a nominal temperature of 120°C, to a nominal pressure of 100 10 5 Pa for a period of 10 minutes.

[0131] Advantageously, the step of cooling the object in the mold takes place at a temperature below 50°C and preferably at room temperature.

[0132] 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.

[0133] According to one embodiment, step c. directly follows, i.e. without an intervening step, the heat treatment step applied to the granulate comprising vulcanized rubber during step a2. In this variant, the granulate is introduced into the mold for its shaping by sintering at a temperature above 30°C, preferably above 40°C, even more preferably above 60°C. This embodiment makes it possible to save energy because the granulate is still hot from the heat treatment step by baking when it is introduced into the sintering mold. It also makes it possible to reduce the sintering cycle time by reducing the duration of the temperature rise of the granulate to the sintering temperature.It also allows for better homogeneity of the temperature of the aggregate during sintering, in particular with a reduction, or even an absence of temperature gradient between the aggregate in contact with the wall of the mold and the core of the mass of aggregate within the sintering mold.

[0134] Step b. is an optional step for obtaining a composition comprising the deodorized granulate obtained at the end of step a.

[0135] 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 rigidity of the sintered object obtained. For example, particles of a thermoplastic material of controlled rigidity and predetermined size can be added in order to modify the final rigidity of the sintered object.

[0136] It is also possible to mix aggregate particles with solute particles as described in document WO2020128213, the solute particles being able to be 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 step of contacting with a solvent making it possible to dissolve at least a portion of the solute particles and thus to obtain partial or total porosity of the recovered object.

[0137] Advantageously, the rubber granulate used is a recovered rubber granulate. The method therefore advantageously comprises a step prior to step a1. of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide the rubber granulate.

[0138] Advantageously, the granulate of step a1., is a crumb whose particles have an average size not exceeding 800 μm. In particular, the rubber crumb has an average particle size of between 200 μm and 800 μm, and preferably approximately 400 μm. In this variant, advantageously, during this process, no vulcanization additive, binder or binding additive is added. Thus, when it is prepared, the composition of step b. implemented in step c. is advantageously free of vulcanization additive, binder or binding additive other than those provided intrinsically by the rubber crumb.

[0139] Step c. of shaping by sintering is advantageously as described in patent applications WO2020 / 128212 and WO2020 / 128213, in particular as detailed in Figure 1 of each of these applications.

[0140] 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. have excellent mechanical properties.

[0141] 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 adding a vulcanization additive or binder.

[0142] Object made of deodorized rubber granules

[0143] Another subject of the invention relates to an object made of deodorized rubber granules capable of being obtained by the manufacturing method as described above.

[0144] 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.

[0145] Advantageously, said volatile organic compounds whose emission is reduced by the baking step have a molar mass less than or equal to 130g / mol.

[0146] Use

[0147] Another subject of the invention relates to the use of the deodorized rubber granulate as described above or of the object comprising it as described above for the manufacture of, for example, playing fields, athletics tracks, playgrounds, shoe soles or solid casters, in particular casters for scooters, Segways, trolleys or medical beds.

[0148] The following examples are given for illustrative purposes, but should not in any way be considered as limiting the present invention. Examples:

[0149] In the example below, a deodorization process according to the invention is applied to different rubber granules. The odor emission from the granules deodorized according to the process is evaluated.

[0150] Aggregates used:

[0151] • powder (VL_02) from used light vehicle (VL) tires with a particle size (D50) of less than 0.2mm;

[0152] • granulate (VL_3) of used light vehicle (VL) tires with a particle size (D50) of less than 3mm;

[0153] • powder (PL_02) from used heavy goods vehicle (HGV) tires with a particle size (D50) of less than 0.2mm;

[0154] • granulate (PL_3) of used heavy goods vehicle (HGV) tires with a particle size (D50) of less than 3mm.

[0155] The size of the aggregate particles, D50 average by volume, is measured by laser diffraction granulometry using a Malvern Mastersizer type device for the powders (VL_02 and PL_02) and by sieve analysis for the aggregates (VL_3 and PL_3).

[0156] Heat treatment step in oven:

[0157] 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.

[0158] Characterization of aggregates before and after the heat treatment stage:

[0159] The aggregates before the heat treatment stage in the oven are referenced respectively VL_02, VL_3, PL_02 and PL_3 as indicated above.

[0160] After heat treatment, the corresponding aggregates are referenced respectively VL_02_E, VL_3_E, PL_02_E and PL_3_E.

[0161] 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.

[0162] 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 introduced into a Nalophan® bag subsequently filled with 40L of nitrogen. The samples are then placed in a temperature-controlled room (T=20± 2°C). 2. Verification of the achievement of aggregate emission equilibrium by periodic measurements of the emitted VOCs. The concentration of VOCs emitted by the materials is regularly monitored until thermodynamic equilibrium is reached using a portable photoionization analyzer (RAE Systems / ppb RÀE). This device being calibrated with isobutene, the measured concentrations are expressed in ppm equivalent of isobutene. The values ​​given below correspond to the values ​​measured at equilibrium.

[0163] 3. Sensory analyses (Odor concentration, Acceptability and Quality). For these sensory analyses conducted on a panel of 6 trained individuals, the odorous gas to be analyzed is presented at different concentrations in the form of successive dilutions. This sensory analysis was carried out with an Odile® multi-station dynamic dilution olfactometer and complies with the NF 13725 standard. For each dilution, each individual indicates whether they perceived the odor or not. Thus, for each individual and then for the entire panel, the perception threshold (odor concentration) of the odors could be determined.

[0164] Results of the tests to measure the VOC content of aggregates: The concentration of VOCs emitted by the aggregates is shown in Fig. 1. In all cases, steaming reduces the amount of VOCs in the aggregate. Steaming is more effective (higher VOC reduction rate after heat treatment) when applied to a fine-grained 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-grained materials (VL_02_E and PL_02_E powders) are independent of their origin (light vehicle or heavy goods vehicle). Oven treatment reduces their VOC content from 7.8 ppm to 2.2 ppm on average, which corresponds to a reduction in VOC content of 70%.

[0166] Results of sensory analysis tests:

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

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

[0169] In all cases, the aggregates after kilning have a lower subjective odor level than the untreated aggregates.

Claims

CLAIMS 1. A method for deodorizing a rubber granulate comprising a step of steaming said rubber granulate, characterized in that the rubber granulate subjected to the steaming treatment comprises rubber in the vulcanized state, said rubber granulate being heated during the steaming step to a temperature of 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 time of between a minimum value and a maximum value as indicated in the table below: and said baking step not comprising devulcanization means.

2. Method according to claim 1, characterized in that the pressure used during the steaming step is between 2*10 4 Pa and atmospheric pressure, preferably between 3*10 4Pa and 5*10 4 Pa.

3. Method according to any one of the preceding claims, characterized in that the rubber granulate is in the form of particles whose average diameter D50 by volume is between 0.8 mm and 20 mm, preferably between 0.8 mm and 8 mm.

4. Method according to any one of claims 1 to 2, characterized in that the rubber granulate is a rubber crumb in the form of particles whose average diameter D50 by volume is between 10 pm and 800 pm, preferably between 50 pm and 200 pm.

5. Method according to any one of the preceding claims, characterized in that it comprises a prior step of grinding a vulcanized rubber object, preferably used tires or pieces of used tires, to provide said rubber granulate.

6. Deodorized rubber granulate obtained according to the process of any one of the preceding claims.

7. A method of manufacturing an object made of rubber granulate comprising the following successive steps: a. providing a deodorized rubber granulate according to claim 6; b. optionally, preparing a composition comprising said granulate and, for example, metallic, mineral or organic particles, said mineral or organic particles possibly being a salt, a saccharide, a water-soluble protein or a water-soluble polymer; c. sintering in a mold the deodorized granulate or the composition comprising it; d. recovering the object obtained at the end of step c.

8. Method according to claim 7 in which the deodorized rubber granulate of step a. is prepared by carrying out the following successive steps: a1. providing a granulate comprising rubber in the vulcanized state; a2. deodorization of said aggregate according to the method described in any one of claims 1 to 6.

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

10. 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 granulate comprising rubber in the vulcanized state.

11. Object made of deodorized rubber granules capable of being 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, athletics tracks, playgrounds, soles for shoes or solid casters, in particular casters for scooters, trolleys, Segways or medical beds.

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