Preparation process of styrene-butadiene rubber containing recycled rubber powder

Abstract

A process for preparing styrene-butadiene rubber containing finely divided recycled rubber powder, the process comprising the steps of: (a) preparing a suspension containing finely divided recycled rubber powder, water, and one or more surfactants; (b) mixing the suspension obtained in step (a) with one or more styrene-butadiene latexes to obtain a styrene-butadiene latex containing finely divided recycled rubber powder; and (c) coagulating the latex obtained in step (b) to obtain a coagulated styrene-butadiene rubber containing finely divided recycled rubber powder. and (c), wherein in step (a), the particle size of the finely pulverized recycled rubber powder is in the range of 0.05 mm to 0.8 mm, preferably in the range of 0.1 mm to 0.4 mm; in step (a), the one or more surfactants are present in an amount in the range of 0.5 wt % to 3 wt %, preferably in the range of 1 wt % to 2.5 wt %, based on the total weight of the finely pulverized recycled rubber powder; and in step (a), the finely pulverized recycled rubber powder has a concentration in water in the range of 1 wt % to 50 wt %, preferably in the range of 5 wt % to 30 wt %, based on the total weight of the water. The styrene-butadiene rubber containing finely pulverized recycled rubber powder obtained by the aforementioned process, either as is or in a mixture with other rubbers, such as natural rubber (NR), polybutadiene (BR), styrene-butadiene copolymers, or mixtures thereof, can be advantageously used in vulcanizable elastomer compositions, which can then be used in various sectors, such as tires, shoe soles, brakes, conveyor belts, etc.

Description

Technical Field

[0001] The present invention relates to a process for preparing styrene-butadiene rubber containing micronized recycled rubber powder.

[0002] More specifically, the present invention relates to a process for preparing styrene-butadiene rubber containing micronized recycled rubber powder, the process comprising the following steps: (a) preparing a suspension comprising micronized recycled rubber powder, water, and one or more surfactants; (b) mixing the suspension obtained in step (a) with one or more styrene-butadiene latexes to obtain a styrene-butadiene latex containing micronized recycled rubber powder; and (c) coagulating the latex obtained in step (b) to obtain a coagulated styrene-butadiene rubber containing micronized recycled rubber powder.

Background Art

[0003] Styrene-butadiene rubber containing micronized recycled rubber powder obtained by the aforementioned process, either as such or in a mixture with other rubbers such as natural rubber (NR), polybutadiene (BR), styrene-butadiene copolymers, or mixtures thereof, can be advantageously used in vulcanizable elastomeric compositions and can then be used, for example, in various sectors such as tires, shoe soles, brakes, conveyor belts, etc.

[0004] The recycling of rubber is a sector that is attracting even more attention and is continuously developing as concerns such as environmental sustainability and circular economy are receiving increasing attention. As a result, there are a very large number of scientific papers and patents related to said recycling.

[0005] One of the most widely used methods in rubber recycling is to convert the rubber into fine powder and add the fine powder to virgin rubber by dry mechanical mixing.

[0006] For example, U.S. Patent No. 9,840,613 relates to a polymer formulation useful as a structural material for manufacturing a wide variety of goods, the polymer formulation comprising (1) about 45% to about 85% by weight of finely powdered rubber powder, (2) about 15% to about 45% by weight of metallocene polyolefin elastomer, and (3) about 1% to about 10% by weight of polyethylene grafted with maleic anhydride. The components of the aforementioned polymer formulation are dried and mixed in a twin-screw extruder.

[0007] Furthermore, it is known that rubber can be recycled using a technique called desulfurization, which aims to break down sulfur crosslinks in order to bring the polymer as close as possible to its original form.

[0008] For example, U.S. Patent No. 5,602,586 relates to a process for desulfurizing vulcanized rubber by desulfurization, the process comprising: contacting a crumb of vulcanized rubber with a solvent and an alkali metal to obtain a reaction mixture; heating the reaction mixture, in the absence of oxygen, with stirring to a temperature sufficient to react the alkali metal with sulfur present in the vulcanized rubber; and maintaining the temperature below the temperature at which thermal decomposition of the rubber occurs, thereby desulfurizing the rubber.

[0009] Further details on desulfurization technology can be found, for example, in U.S. Patent Nos. 6,541,526 and 9,527,978.

[0010] Furthermore, rubber recycling processes are known that involve the use of rubber in emulsions or solutions.

[0011] For example, Chinese Patent Application No. 101792546 relates to a process for preparing rubber powder and rubber compositions, the process comprising the following steps: mixing rubber powder, optionally containing a powder additive or sizing agent containing water or a softening oil, with rubber in an emulsion or solution, or with solid wet rubber that has not been dried beforehand, to obtain an intermediate product consisting of a rubber-rubber powder composition; and subsequently performing a liquid removal process to obtain a product consisting of a solid rubber-rubber powder composition.

[0012] Chinese Patent Application No. 102344591 relates to a process for preparing a rubber-containing composition, characterized by comprising the following steps: (1) mixing grafted or mixed recycled rubber powder with a particle size of 90 mesh (approximately 0.16 mm) to 200 mesh (0.074 mm), optionally containing powder additives or additives including water and / or softening oil, with rubber in an emulsion or solution in a closed mixer to obtain a homogeneous material, or mixing the recycled rubber powder with solid wet rubber that has not been pre-dried in a kneader to obtain a homogeneous material; and (2) dehydrating the homogeneous material obtained in step (1) by, for example, demulsification, centrifugation, pelletization, hot air fluidization, flue gas calcination, vaporization in a steam cylinder, hot extrusion, or conventional liquid removal techniques to obtain a homogeneous composition containing rubber-rubber powder. [Overview of the project] [Problems that the invention aims to solve]

[0013] However, the above process is, for example, - Deteriorating the physical and mechanical properties of the elastomer composition used. - Issues related to handling and operator health - Technical issues regarding deposits on the manufacturing lines and equipment used. It may have had drawbacks such as these.

[0014] Micronized recycled rubber powder is known to be highly water-containing. The absorption of moisture by micronized recycled rubber powder can impair both the mechanical mixing with unused rubber ("dry mixing") and the subsequent vulcanization process, potentially leading to a deterioration of the physical and mechanical properties of the final vulcanized product.

[0015] Furthermore, the use of micronized recycled rubber powder in mechanical mixing ("dry mixing") requires careful management in terms of both environmental sustainability and operator health to avoid hazards such as explosions or the dispersion of fine particles into the atmosphere, resulting in increased process costs. In addition, the use of micronized recycled rubber powder in mechanical mixing ("dry mixing") can be a major problem for inadequate equipment.

[0016] Finally, the use of micronized recycled rubber powder can cause buildup in the manufacturing lines and equipment used, which can lead to clogging, malfunctions, and increased time and process costs.

[0017] Therefore, the applicant's objective was to find a process for preparing styrene-butadiene rubber containing micronized recycled rubber powder that can overcome the above-mentioned problems. [Means for solving the problem]

[0018] The applicant has found that the aforementioned drawbacks can be overcome by a novel preparation process for styrene-butadiene rubber containing micronized recycled rubber powder, using a suspension comprising micronized recycled rubber powder of a specific size, water, and one or more surfactants present in specific amounts. The process makes it possible to obtain styrene-butadiene rubber containing micronized recycled rubber powder that can be advantageously used in vulcanizable elastomer compositions, either as is or in mixtures with other rubbers such as natural rubber (NR), polybutadiene (BR), styrene-butadiene copolymers, or mixtures thereof, and can then be used in various sectors such as tires, soles, brakes, and conveyor belts.

[0019] Therefore, the object of the present invention is a process for preparing styrene-butadiene rubber containing micronized recycled rubber powder, the process comprising the following steps: (a) preparing a suspension comprising micronized recycled rubber powder, water, and one or more surfactants; (b) mixing the suspension obtained in step (a) with one or more styrene-butadiene latexes to obtain a styrene-butadiene latex containing micronized recycled rubber powder; (c) coagulating the latex obtained in step (b) to obtain a coagulated styrene-butadiene rubber containing micronized recycled rubber powder; In step (a), the particle size of the micronized recycled rubber powder ranges from 0.05 mm to 0.8 mm, preferably from 0.1 mm to 0.4 mm; In step (a), the one or more surfactants are present in an amount ranging from 0.5 wt% to 3 wt%, preferably from 1 wt% to 2.5 wt%, based on the total weight of the recycled rubber powder; In step (a), the micronized recycled rubber powder has a concentration in water ranging from 1 wt% to 50 wt%, preferably from 5 wt% to 30 wt%, based on the total weight of the water.

Brief Description of the Drawings

[0020] [Figure 1] Figure 1 schematically shows a first embodiment of the object of the process of the present invention. [Figure 2] Figure 2 schematically shows a second embodiment of the object of the process of the present invention.

Modes for Carrying Out the Invention

[0021] In this specification and the following claims, unless otherwise specified, the definition of a numerical interval always includes the extreme values.

[0022] Furthermore, in this specification and the following claims, the term “comprising” also includes the terms “which essentially consists of” or “which consists of.”

[0023] In this specification and the following claims, the particle size of the micronized recycled rubber powder is determined in accordance with ASTM D5644-18.

[0024] In the process of the present invention, the micronized recycled rubber powder may be derived from different types of rubber products, such as waste tires (ELT) or parts of tires (e.g., treads). Therefore, the micronized recycled rubber powder may contain different types of rubber, such as natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR), as well as various types of additives, such as fillers such as carbon black and silica, sulfur, and accelerators.

[0025] Micronized recycled rubber powder can be obtained by processes known in the art. For example, micronized recycled rubber powder may be obtained in the presence of water by a cryogenic process, a mechanical milling process, or a high-pressure process. In all processes, steel components are removed by a magnetic separator and fibrous components are separated by an air classifier or other separation device. In the cryogenic process, the pulverized rubber is frozen at a cryogenic temperature and then pulverized into small particles. To mechanically reduce rubber into small particles, the mechanical milling process is generally carried out at room temperature (25°C) and uses various milling devices such as cracker mills and granulators. In the high-pressure method, rubber products, such as waste tires, are exposed to a high-pressure water jet in the presence of water to scrape off the outermost layer of the tire and generate small particles.

[0026] In the present invention, micronized recycled rubber powder obtained by any one of the processes known in the art may be used, for example, by any of the above processes.

[0027] An example of a commercially available micronized recycled rubber powder that can be advantageously used in the present invention is PolyDyne® (registered trademark) manufactured by Lehigh Technologies. 90 (0.074mm~0.4mm), Albatros rubber powder B.0 / 0.35 (d 90 <0.35mm), TyreXol® CWN 0-400 (d) manufactured by Tyre Recicling Solutions, Inc. 90 This product is known by the product name <0.33mm).

[0028] According to a preferred embodiment of the present invention, in step (a), the one or more surfactants may be selected, for example, from nonionic surfactants such as polyoxyethylene derivatives of fatty acids, alkyl polyglucosides, ethanolamides, ethoxyamides, ethoxyamines, ethoxylic acids, polyoxyethylene alkyl ethers, or mixtures thereof.

[0029] According to a further preferred embodiment of the present invention, in step (a), the one or more surfactants are, for example, salts formed by long carbon chains terminated with carboxylate or sulfonate groups [e.g., sodium lauryl sulfate (SLS), sodium lauryl ethoxysulfate (SLES)], alkylbenzene sulfonic acid (ABS), polysulfonated aromatic ethers (e.g., Dowfax® manufactured by Dow Chemical). 2A1), or mixtures thereof; sodium, potassium, lithium, or ammonium salts, preferably sodium or potassium salts, or mixtures thereof, of saturated or unsaturated fatty acids containing 6 to 22 carbon atoms in their molecule, such as caproic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, or mixtures thereof; sodium, potassium, lithium, or ammonium salts, preferably sodium or potassium salts, or mixtures thereof, of modified resin acids obtained by dimerization, disproportionation, hydrogenation, or modification of a mixture of resin acids containing abietic acid, neoabietic acid, pulsed phosphoric acid, levopimal acid, or mixtures thereof; anionic surfactants such as [for example, potassium salt derived from disproportionation of Parchem's potassium resin acid soap 80% Gresinox 578M] may be selected.

[0030] According to a further preferred embodiment of the present invention, in step (a), the one or more surfactants may be selected, for example, from cationic surfactants such as long-chain quaternary ammonium salts [e.g., benzalkonium chloride (BAC), cetyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium bromide], or mixtures thereof.

[0031] According to a further preferred embodiment of the present invention, in step (a), the one or more surfactants may be selected from amphoteric surfactants such as cocamidopropyl betaine, dodecyl betaine, lecithin, aminocarboxylic acid, or mixtures thereof, for example.

[0032] According to a further preferred embodiment of the present invention, step (a) may be performed at a temperature in the range of 20°C to 90°C, preferably in the range of 50°C to 80°C, for a time that depends on the size of the mixer and is sufficient to obtain a homogeneous suspension, preferably in the range of 2 minutes to 60 minutes, preferably in the range of 4 minutes to 40 minutes.

[0033] Step (a) may be carried out by mixing the micronized recycled rubber powder, water, and one or more surfactants in a mixer equipped with a stirring system suitable for obtaining a homogeneous suspension, i.e., a suspension in which the micronized recycled rubber powder is homogeneously dispersed over the total volume of water and surfactant. Preferably, the stirring system may consist of a mixing secondary flow impeller such as a 45° "pitch blade" type impeller, or a pure axial flow "hydrofoil" type impeller such as Lightnin's A310 3-blade propeller.

[0034] It should be noted that by performing the procedure described above, a stable, homogeneous ("opaque") suspension is obtained at the end of step (a). For the purposes of this specification, the term "stable, homogeneous suspension" means that such a suspension does not show any visible stratification, phase separation, or precipitation at room temperature (25°C) for more than 5 minutes without stirring.

[0035] In the processes of the present invention, the styrene-butadiene latex used may be obtained by processes known in the art, for example, by emulsion radical copolymerization as reported in U.S. Patent No. 4,070,324 and U.S. Patent No. 5,504,168, or in El-Aasser MS and Sudol D., “Emulsion Polymerization and Emulsion Polymers” (1997), Klein A. and Daniel ESEd., John Wiley and Sons, New York, Chapter VI, pp. 37-55.

[0036] According to a preferred embodiment of the present invention, in step (b), the one or more styrene-butadiene latex may have a styrene-butadiene polymer content in the range of 10% to 50% by weight, preferably 15% to 30% by weight, relative to the total weight of the latex, and a bound styrene content in the range of 10% to 60% by weight, preferably 20% to 50% by weight, relative to the total weight of the latex.

[0037] According to a preferred embodiment of the present invention, in step (b), the suspension obtained in step (a) may be increased in an amount such that the amount of micronized recycled rubber powder is in the range of 5% to 95% by weight, preferably 8% to 35% by weight, relative to the total weight of styrene-butadiene rubber contained in the latex.

[0038] Step (b) may also be carried out in a mixer (referred to as a “premixer”) equipped with a stirring system suitable for obtaining styrene-butadiene latex containing micronized recycled rubber powder, wherein the micronized recycled rubber powder is uniformly dispersed in the latex. Preferably, the stirring system may consist of a mixing secondary flow impeller, such as a 45° “pitch blade” type impeller, or a pure axial flow “hydro-wing” type impeller, such as a Lightnin A310 3-blade propeller.

[0039] According to embodiments of the present invention, step (b) may be carried out in a mixer (referred to as a premixer) at a temperature range of 20°C to 90°C, preferably 50°C to 80°C, for a variable time depending on the size of the mixer, sufficient to obtain styrene-butadiene latex containing micronized recycled rubber powder, wherein the powder is homogeneously dispersed in the latex, preferably for 1 to 45 minutes, preferably 5 to 15 minutes.

[0040] The mixer (referred to as the premixer) may also contain further components commonly used in emulsion radical copolymerization (e-SBR) processes for the production of styrene-butadiene rubber, such as surfactants, extender oils, and antioxidants selected from those described above. Further details regarding the emulsion radical copolymerization (e-SBR) process for styrene-butadiene rubber can be found, for example, in U.S. Patent No. 4,070,324 and U.S. Patent No. 5,504,168, or in “Emulsion Polymerization and Emulsion Polymers” (1997) by El-Aasser MS and Sudol D., Lovell P. A and El-Aasser Ed., John Wiley and Sons, New York, Chapter VI, pp. 208–234.

[0041] Alternatively, step (b) may be carried out in the same coagulation mixer (referred to as the “coagulation tank”) in which step (c) (coagulation) is performed, in which case the suspension obtained in step (a) and the styrene-butadiene latex are mixed directly in the coagulation mixer (referred to as the “coagulation tank”) [step (c1)].

[0042] Therefore, this is a further subject of the present invention, and the process is as follows: (a1) A step of preparing a suspension containing micronized recycled rubber powder, water, and one or more surfactants, (c1) The step of mixing the suspension obtained in step (a) with one or more types of styrene-butadiene latex and solidifying the whole to obtain solidified styrene-butadiene rubber containing finely powdered recycled rubber powder, In step (a1), the particle size of the micronized recycled rubber powder is in the range of 0.05 mm to 0.8 mm, preferably in the range of 0.1 mm to 0.4 mm. In step (a1), the one or more surfactants are present in an amount ranging from 0.5% to 3% by weight, preferably 1% to 2.5% by weight, relative to the total weight of the micronized recycled rubber powder. In step (a1), the concentration of the micronized recycled rubber powder in water is in the range of 1% to 50% by weight, preferably 5% to 30% by weight, relative to the total weight of the water.

[0043] If step (b) is performed in the same coagulation mixer (referred to as the "coagulation tank") in which step (c) (coagulation) is performed, that is, in the case of [step (c1)], it should be noted that the above-mentioned further components and the styrene-butadiene rubber latex may be further mixed in a mixer (referred to as the "premixer") in order to obtain a styrene-butadiene rubber latex in which the further components are homogeneously dispersed in the latex by operating under the same conditions as described above for step (b).

[0044] Step (a1) is performed by operating under the same conditions as described above for step (a).

[0045] According to a preferred embodiment of the present invention, in step (c1), the amount of styrene-butadiene polymer in the one or more styrene-butadiene latex may be in the range of 10% to 50% by weight, preferably 15% to 30% by weight, relative to the total weight of the latex, and the amount of bound styrene may be in the range of 10% to 60% by weight, preferably 20% to 50% by weight, relative to the total weight of the latex.

[0046] According to a preferred embodiment of the present invention, in step (c1), the suspension obtained in step (a1) may be enriched in such an amount that the amount of micronized recycled rubber powder is in the range of 5% to 95% by weight, preferably 8% to 35% by weight, relative to the total weight of styrene-butadiene rubber contained in the latex.

[0047] According to a preferred embodiment of the present invention, steps (c) and (c1) may be carried out in the presence of one or more coagulants selected from, for example, alkylamine-epichloridine copolymers (e.g., dimethylamine-epichlorhydrin copolymers known by the trade name Floquat® FL 2250 from NSF).

[0048] The amount of coagulant and other possible components, such as surfactants, extender oils, and antioxidants, varies depending on the amount of latex and micronized recycled rubber powder used.

[0049] According to a preferred embodiment of the present invention, steps (c) and (c1) may be carried out at a temperature in the range of 40°C to 90°C, preferably in the range of 60°C to 80°C, for a variable time depending on the size of the coagulation mixer (referred to as the “coagulation tank”), the amount of suspension obtained in step (a) or step (a1) and the amount of styrene-butadiene latex used, the temperature, and the pH, and the stirring system used, preferably in the range of 5 minutes to 120 minutes, preferably in the range of 10 minutes to 60 minutes.

[0050] According to a preferred embodiment of the present invention, steps (c) and (c1) may be performed at a pH of 5 or less, preferably in the range of 2.5 to 4.

[0051] According to a preferred embodiment of the present invention, one or more inorganic acids, such as sulfuric acid, phosphoric acid, and preferably sulfuric acid, may be added to steps (c) and (c1).

[0052] According to a preferred embodiment of the present invention, one or more organic acids may be added in an amount such that the pH is maintained at 5 or less, preferably in the range of 2.5 to 4, throughout the entire duration of step (c) and step (c1).

[0053] Steps (c) and (c1) may be carried out in a solidification mixer (referred to as a "solidification tank") equipped with an agitation system. When step (b) is carried out in the same solidification mixer (referred to as a "solidification tank") as step (c) [step (c1)], it should be noted that the agitation system is also suitable for homogeneously distributing the finely powdered recycled rubber powder in the styrene-butadiene latex. Preferably, the agitation system may consist of a mixing secondary flow impeller such as a 45° "pitch blade" type impeller, or a pure axial flow "hydro-wing" type impeller such as Lightnin's A310 3-blade impeller.

[0054] After solidification, styrene-butadiene rubber containing micronized recycled rubber powder usually exists in a crumbly state.

[0055] For example, it is preferable to neutralize the crumb by adding an aqueous solution containing one or more organic bases, such as a sodium carbonate solution, and then washing it with water. The water used for washing may be either deionized water or non-deionized water.

[0056] Preferably, the washing with water may be carried out at a temperature in the range of 35°C to 90°C, preferably in the range of 40°C to 90°C.

[0057] The styrene-butadiene rubber containing the micronized recycled rubber powder may be washed with water one or more times, for example, one to seven times, and this washing may be carried out in a batch or continuous manner, preferably in a continuous manner. Partial drying of the styrene-butadiene rubber containing the micronized recycled rubber powder may be carried out between washings.

[0058] After washing with water, the styrene-butadiene rubber containing the micronized recycled rubber powder is usually dehydrated. Dehydration may be carried out in two steps, first by mechanically treating the styrene-butadiene rubber containing the micronized recycled rubber powder, for example, using a screw device, and then by evaporation, for example, using a stove or hot plate; or it may be carried out in a single step, by directly evaporating the styrene-butadiene rubber containing the micronized recycled rubber powder, for example, using a stove or hot plate. Dehydration may be carried out at a temperature in the range of 40°C to 150°C, preferably in the range of 60°C to 120°C, for a time longer than 5 minutes, preferably in the range of 8 minutes to 45 minutes, but this time must be sufficient to obtain styrene-butadiene rubber containing the micronized recycled rubber powder in which the residual moisture content is less than 1% by weight of the total weight of the styrene-butadiene rubber.

[0059] According to a preferred embodiment of the present invention, the process may be carried out in either a batch or continuous manner, with the continuous manner being preferred.

[0060] As described above, styrene-butadiene rubber, including the micronized recycled rubber powder obtained by the aforementioned process, either in its raw state or in a mixture with other rubbers such as natural rubber (NR), polybutadiene (BR), styrene-butadiene copolymer, or mixtures thereof, may be advantageously used in vulcanizable elastomer compositions, which may then be used in various sectors such as tires, shoe soles, brakes, and conveyor belts.

[0061] For example, the styrene-butadiene rubber containing the aforementioned finely powdered recycled rubber powder may be used in a vulcanizable elastomer composition suitable for tire manufacturing, mixed with carbon black and / or silica.

[0062] Therefore, a further subject of the present invention is a vulcanizable elastomer composition comprising one or more styrene-butadiene rubbers containing the micronized recycled rubber powder obtained as described above, one or more fillers selected from carbon black, silica, or mixtures thereof, and one or more vulcanizing agents. Preferably, the fillers may be present in the vulcanizable elastomer composition in an amount ranging from 5 phr to 500 phr.

[0063] The vulcanizable elastomer composition may also contain other elastomers, such as natural rubber (NR), polybutadiene (BR), or mixtures thereof, in addition to the styrene-butadiene rubber containing the micronized recycled rubber powder.

[0064] In the present invention and the following claims, the term "phr" means parts by weight of a given component per 100 parts by weight of styrene-butadiene rubber containing present micronized recycled rubber powder and any other elastomer optionally present in the vulcanizable elastomer composition.

[0065] The vulcanizing agent may be selected, for example, from soluble or insoluble elemental sulfur, sulfur donors, or mixtures thereof.

[0066] Examples of sulfur donors include dimorpholyl disulfide (DTDM), 2-morpholino-dithiobenzothiazole (MBSS), caprolactam disulfide, dipentamethylenethuram tetrasulfide (DPTT), tetramethylthiuram disulfide (TMTD), or mixtures thereof.

[0067] When the vulcanizing agent is selected from sulfur or sulfur donors, it may also be advantageous to use other additives (e.g., accelerators) such as dithiocarbamates, thiuram, thiazoles, sulfenamides, xanthogenic salts, guanidine derivatives, caprolactams, thiourea derivatives, or mixtures thereof, in order to increase the amount of vulcanization.

[0068] In the vulcanizable elastomer composition, the sulfur and / or the sulfur donor, and any other additives present as described above, are typically present in amounts ranging from 0.05 phr to 10 phr, preferably from 0.1 phr to 8 phr.

[0069] Other components may be added to the vulcanizable elastomer composition of the present invention.

[0070] For example, inorganic or organic compounds may be added. Examples of such compounds include zinc oxide, zinc carbonate, lead oxide, saturated or unsaturated organic fatty acids or their zinc salts, polyalcohols, amino alcohols (e.g., triethanolamine), amines (e.g., dibutylamine, dicyclohexylamine, cyclohexylethylamine), polyetheramines, or mixtures thereof.

[0071] Additionally, vulcanization inhibitors such as N-cyclohexylthiophthalimide (PVI), N,N'-dinitrosopentamethylenetetramine (DNPT), phthalic anhydride (PTA), diphenylnitrosamine, or mixtures thereof may be added.

[0072] In addition to the vulcanizing agents and / or other compounds described above, the vulcanizable elastomer compositions of the present invention may also include other additives commonly used in elastomer compositions and known to those skilled in the art, such as other fillers, filler activators, ozone protectants, anti-aging agents, antioxidants, processing aids, extender oils, plasticizers, reinforcing agents, and mold release agents.

[0073] Other fillers that may be used in the present invention include, for example, barium sulfate, titanium dioxide, zinc oxide, calcium oxide, calcium carbonate, magnesium oxide, aluminum oxide, iron oxide, aluminum hydroxide, magnesium hydroxide, aluminum silicate, diatomaceous earth, talc, kaolin, bentonite, carbon nanotubes, Teflon® (preferably in powder form), silicates, or mixtures thereof. However, the total amount of filler is in the range of 5 phr to 500 phr.

[0074] Examples of filler activators that can be used in the present invention include organic silanes such as bis(triethoxysilylpropyl) polysulfide, vinyltrimethylsilane, vinyldimethoxymethylsilane, vinyltriethoxysilane, vinyltris-(2-methoxyethoxy)silane, N-cyclohexyl-3-aminopropyl-trimethoxysilane, 3-amino-propyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, isooctyltrimethoxysilane, isooctyltriethoxysilane, hexadecyltrimethoxysilane, (octadecyl)methyldimethoxysilane, or mixtures thereof. Further filler activators include surfactants such as triethanolamine, ethylene glycol, or mixtures thereof. The amount of filler activator is usually in the range of 0 phr to 10 phr.

[0075] A further subject of the present invention is the vulcanized product obtained by vulcanization of the vulcanizable elastomer composition.

[0076] The present invention will now be described in more detail with reference to embodiments, with reference to Figures 1 and 2 described below.

[0077] Figure 1 schematically illustrates a first embodiment of the process of the present invention, in which micronized recycled rubber powder (micronized powder), water, and one or more surfactants (e.g., potassium soap 80% Gresinox 578M) are supplied to a first mixer (1) equipped with a stirring system (e.g., a 45° “pitch blade” type impeller, or a 3-blade propeller A310 from Lightnin) to obtain an (“opaque”) suspension [step (a)]. Step (b) (SBR latex + micronized powder) is obtained by supplying the ("opaque") suspension obtained in step (a) to a second mixer (2) equipped with a stirring system (e.g., a 45° "pitch blade" type impeller, or a Lightnin 3-blade propeller A310), and also supplying styrene-butadiene latex (SBR latex) and any other components [e.g., surfactants, extender oils, antioxidants (other components)] to the second mixer (2) to obtain styrene-butadiene latex containing micronized recycled rubber powder. The obtained latex is supplied to a third mixer (e.g., a coagulation mixer called a "coagulation tank") equipped with an agitation system (e.g., a 45° "pitch blade" type impeller, or a Lightnin 3-blade propeller A310), and an acid (e.g., sulfuric acid) and a coagulant (e.g., Floquat FL 2250) are also supplied to the third mixer to coagulate [step (c)], the pH is neutralized (e.g., with an aqueous solution of sodium carbonate), washed with water, and the water is removed ("dehydrated") to obtain styrene-butadiene rubber (eSBR rubber + micronized powder) containing micronized recycled rubber powder.

[0078] Figure 2 schematically illustrates a second embodiment of the process of the present invention, in which micronized recycled rubber powder (micronized powder), water, and one or more surfactants (e.g., potassium soap 80% Gresinox 578M) are supplied to a first mixer (1) equipped with a stirring system (e.g., a 45° "pitch blade" type impeller, or a Lightnin 3-blade propeller A310) to obtain a ("opaque") suspension [step (a1)]. Styrene-butadiene latex (SBR latex) and any other components [e.g., surfactants, extender oils, antioxidants (further components)] are supplied to a second mixer (2) (referred to as a "premixer") equipped with a stirring system (e.g., a 45° "pitch blade" type impeller, or a Lightnin 3-blade propeller A310) to obtain styrene-butadiene latex (SBR + further components) containing the other components. The obtained latex is fed into a third mixer (e.g., a third mixer, also known as a "solidification tank") equipped with an agitation system (e.g., a 45° "pitch blade" type impeller or a Lightnin 3-blade propeller A310), and the ("opaque") suspension obtained in step (a1), an acid (e.g., sulfuric acid), and a coagulant (e.g., Floquat FL 2250) are also fed into the third mixer to solidify the whole [step (c1)], the pH is neutralized (e.g., with an aqueous solution of sodium carbonate), the mixture is washed with water, and the water is removed ("dehydrated") to obtain styrene-butadiene rubber (eSBR+ micronized powder) containing micronized recycled rubber powder. [Examples]

[0079] To better understand and implement the present invention, several illustrative and non-limiting examples of the invention are described below.

[0080] Example 1 In a first 20-liter mixer equipped with an agitation system consisting of a 45° "pitch blade" type impeller, finely ground recycled rubber powder derived from waste tires (ELT) [rubber powder B.0 / 0.35mm(d 9067.5 g of [<0.35 mm)-Albatoros], 675 mL of water, and 13.5 g of a 10 wt% aqueous solution of an anionic surfactant (potassium soap 80% Gresinox 578M-Parchem) were added, and the mixture was stirred at 310 rpm for 5 minutes at 60°C to obtain 765 g of ("opaque") suspension.

[0081] The ("opaque") suspension was transferred to a second 20-liter mixer (referred to as the "premixer") equipped with a stirring system consisting of a 45° "pitch blade" type impeller. 3.2 liters of styrene-butadiene latex (containing 21% by weight of styrene-butadiene polymer and 40% by weight of styrene, relative to the total weight of the latex), 2.7 g of antioxidant (Irganox® 1520L-Basf), 252 g of aromatic oil [RAE ("residual aromatic extract")-Clematis RL-Eni], and 25 g of a 10% by weight aqueous solution of an anionic surfactant (potassium soap 80% Gresinox 578M-Parchem) were added. The mixture was stirred at 310 rpm for 10 minutes at 60°C to obtain 4.25 liters of styrene-butadiene latex containing micronized recycled rubber powder.

[0082] In a third 70-liter mixer (for example, a coagulation mixer called a "coagulation tank") equipped with an agitation system consisting of a 45° "pitch blade" type impeller, 10 liters of deionized water were added and the temperature was raised to 70°C. Then, sulfuric acid (Aldrich) was gradually added until the pH reached 3. Subsequently, 4.25 liters of styrene-butadiene latex containing the finely powdered recycled rubber powder obtained as described above were added at a flow rate of approximately 0.7 liters / minute, along with 13.4 grams of coagulant (Floquat FL 2250-SNF). Finally, the mixture was stirred at 100 rpm for a further 30 minutes, maintaining the temperature at 70°C and pH 3, with sulfuric acid (Aldrich) added again if necessary to maintain the pH at 3 during coagulation. Subsequently, while stirring at 100 rpm, the temperature was raised to 80°C, and then sodium carbonate (Aldrich) was added to bring the pH to 6.5-7. Once the desired pH was reached, the coagulated latex was filtered to recover the styrene-butadiene rubber crumb containing the micronized recycled rubber powder, and then washed under a stream of deionized water at a temperature of approximately 70°C for 10 minutes.

[0083] After 10 minutes, the styrene-butadiene rubber crumb containing the micronized recycled rubber powder was dried in an air dryer at 100°C for 24 hours (residual moisture content: less than 1%).

[0084] Example 2 Example 2 was carried out using different amounts of components and under the same operating conditions as Example 1. Table 1 shows the amounts of various components for the production of styrene-butadiene rubber containing micronized recycled rubber powder.

[0085] [Table 1] *:Appropriate amount

[0086] Example 3 Example 3 was carried out using different amounts of components and different aromatic oils [TDAE ("Treated Distillate Aromatic Extracts")], under the same operating conditions as Example 1. Table 2 shows the amounts of various components for the production of styrene-butadiene rubber containing micronized recycled rubber powder.

[0087] [Table 2] *:Appropriate amount

[0088] Example 4 Example 4 was carried out under the same operating conditions as Example 1, but with different amounts of components, different styrene-butadiene latex (21% by weight of styrene-butadiene polymer and 23.5% by weight of styrene relative to the total weight of the latex), and without fragrance oil. Table 3 shows the amounts of various components for the production of styrene-butadiene rubber containing micronized recycled rubber powder.

[0089] [Table 3] *:Appropriate amount

[0090] Example 5 The styrene-butadiene rubber containing the micronized recycled rubber powder obtained in Examples 1 and 2 above was used to produce a tread compound.

[0091] The compound containing styrene-butadiene rubber, including the micronized recycled rubber powder obtained in Example 1, will be referred to as (A) below.

[0092] The compound containing styrene-butadiene rubber, including the micronized recycled rubber powder obtained in Example 2, will be referred to as (B) below.

[0093] The physical and mechanical properties of the above compound are as follows: (C) Styrene-butadiene rubber (Europrene® 1739-Versalis) added by dry mixing and micronized recycled rubber powder derived from waste tires (ELT) [Rubber powder B.0 / 0.35(d 90 Formulation containing <0.35mm)-Albatros (10phr) (D) Styrene-butadiene rubber (Europrene® 1739-Versalis) and finely powdered recycled rubber powder derived from waste tires (ELT) added by dry mixing [rubber powder B.0 / 0.35(d 90 Formulation containing <0.35mm)-Albatros (20 phr) The physical and mechanical properties of the two other formulations defined as follows were compared.

[0094] Preparation of formulations The formulation was prepared in a 1.6-liter Banbury-type internal mixer. The operating conditions are shown in Table 4, and the components and quantities are given in Table 5.

[0095] [Table 4] *FF: Filling rate

[0096] Next, the samples were vulcanized at 160°C in accordance with the ISO 6502-1:2018 standard.

[0097] [Table 5]

[0098] e-SBR + micronized powder: Styrene-butadiene rubber containing the micronized recycled rubber powder obtained as described above in Examples 1 and 2. Europrene(registered trademark) 1739(e-SBR): Oil-extracted styrene-butadiene rubber (TDAE-oil) obtained as an emulsion (Versalis) ELT: Rubber powder B.0 / 0.35(d 90 <0.35mm)-Albatros N220: Carbon Black Aromatic oil: TDAE ("Processed Distillate Aromatic Extract")-NORMAN 346-ORGKHIM WB220 (processing aid): Struktol Stearic acid: Sigma Aldrich TMQ (Antioxidant): 2,2,4-Trimethyl-1,2-Dihydroquinoline Polymer (Nord Chemie) Rhenogran(registered trademark) ZnO 80 (activator): Zinc oxide (Lanxess) TBBS (stimulant): N-tert-butyl-2-benzothiadylsulfenamide, Vulkacit® NZ / EGC (Lanxess) TBTD 80 (Stimulant): Tetrabutylthiuramdisfide (Sigma Aldrich)

[0099] Table 6 shows the physical and mechanical properties of the obtained vulcanized formulations and the corresponding measurement methods.

[0100] [Table 6]

[0101] According to the data reported in Table 6, it is clear that the styrene-butadiene rubber formulations containing pulverized recycled rubber powder obtained according to the process of the present invention [Formulation (A) and Formulation (B)] maintain or even improve upon the physical and mechanical properties of the styrene-butadiene rubber and recycled rubber powder formulations obtained by dry mixing [Formulation (C) and Formulation (D)]. In particular, it is noteworthy that Formulation (A) and Formulation (B) show improvements in tear resistance and abrasion volume compared to Formulation (C) and Formulation (D), respectively.

[0102] Example 6 The physical and mechanical properties of compound (B) were compared with those of compound (E) containing styrene-butadiene rubber SBR+20phr with particle sizes of 0.8-2.5 mm (Tritogran 1-P-0.8-2.5mm--Tritogom), which includes finely powdered recycled rubber powder. The rubber was obtained by the procedure described in Example 1.

[0103] Compound (E) was obtained by operating under the operating conditions reported in Example 5 (i.e., the same mixing, acceleration, and vulcanization cycles), and by operating with the same components and amounts as those reported in Table 5 for Compound (B) (i.e., 157.5 phr of e-SBR + micronized recycled rubber powder + the same phr of the aforementioned further components).

[0104] Table 7 shows the properties of the obtained vulcanized compound and the related measurement methods.

[0105] [Table 7]

[0106] The data reported in Table 7 clearly shows that the compound containing styrene-butadiene rubber and micronized recycled rubber powder obtained according to the process of the present invention [Compound (B)] exhibits improved physical and mechanical properties compared to the compound containing styrene-butadiene rubber and recycled rubber powder with larger particle sizes [Compound (E)].

Claims

1. A method for producing styrene-butadiene rubber containing micronized recycled rubber powder, The manufacturing method involves the following steps: (a) A step of preparing a suspension containing micronized recycled rubber powder, water, and one or more surfactants, (b) The step of mixing the suspension obtained in step (a) with one or more types of styrene-butadiene latex to obtain styrene-butadiene latex containing micronized recycled rubber powder, (c) The step of solidifying the latex obtained in step (b) to obtain solidified styrene-butadiene rubber containing finely powdered recycled rubber powder, In step (a), the particle size of the micronized recycled rubber powder is in the range of 0.05 mm to 0.8 mm. In step (a), the one or more surfactants are present in an amount ranging from 0.5% to 3% by weight relative to the total weight of the recycled rubber powder. A method for producing styrene-butadiene rubber, wherein in step (a), the micronized recycled rubber powder has a concentration in water of 1% to 50% by weight relative to the total weight of the water.

2. In step (a), the one or more surfactants are Nonionic surfactants such as polyoxyethylene derivatives of fatty acids, alkyl polyglucosides, ethanolamides, ethoxyamides, ethoxyamines, ethoxylic acids, polyoxyethylene alkyl ethers, or mixtures thereof, and / or Salts formed by long carbon chains terminated with carboxylate or sulfonate groups [e.g., sodium lauryl sulfate (SLS), sodium lauryl ethoxysulfate (SLES)], alkylbenzene sulfonic acid (ABS), polysulfonated aromatic ethers, or mixtures thereof; sodium, potassium, lithium, or ammonium salts of saturated or unsaturated fatty acids containing 6 to 22 carbon atoms in their molecules, such as caproic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, or mixtures thereof; sodium, potassium, lithium, or ammonium salts of modified resin acids obtained by dimerization, disproportionation, hydrogenation, or modification of mixtures of resin acids containing abietic acid, neoabietic acid, pulsed phosphoric acid, levopimal acid, or mixtures thereof, or mixtures thereof, and / or Cationic surfactants such as long-chain quaternary ammonium salts [benzalkonium chloride (BAC), cetyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium bromide, etc.], or mixtures thereof, and / or A method for producing styrene-butadiene rubber, comprising the micronized recycled rubber powder according to claim 1, selected from amphoteric surfactants such as cocamidopropyl betaine, dodecyl betaine, lecithin, aminocarboxylic acid, or mixtures thereof.

3. A method for producing styrene-butadiene rubber containing pulverized recycled rubber powder according to claim 1 or 2, wherein step (a) is performed at a temperature in the range of 20°C to 90°C for a variable time, depending on the size of the mixer, that is sufficient to obtain a homogeneous suspension.

4. A method for producing styrene-butadiene rubber, comprising the micronized recycled rubber powder according to any one of claims 1 to 3, wherein in step (b), the amount of styrene-butadiene polymer in the one or more styrene-butadiene latex is in the range of 10% to 50% by weight relative to the total weight of the latex, and the amount of bound styrene is in the range of 10% to 60% by weight relative to the total weight of the latex.

5. A method for producing styrene-butadiene containing micronized recycled rubber powder according to any one of claims 1 to 4, wherein in step (b), the suspension obtained in step (a) is added in an amount such that the amount of micronized recycled rubber powder is in the range of 5% to 95% by weight relative to the total weight of the styrene-butadiene rubber contained in the latex.

6. Step (b) is performed at a temperature in the range of 20°C to 90°C for a variable time, depending on the size of the mixer, that is sufficient to obtain styrene-butadiene latex containing micronized recycled rubber powder. A method for producing styrene-butadiene containing the micronized recycled rubber powder according to any one of claims 1 to 5, comprising homogeneously dispersing the powder in latex for a time ranging from 1 to 45 minutes.

7. (a1) A step of preparing a suspension containing micronized recycled rubber powder, water, and one or more surfactants, (c1) The suspension obtained in step (a) is mixed with one or more types of styrene-butadiene latex and the whole is coagulated to obtain coagulated styrene-butadiene rubber containing finely powdered recycled rubber powder, In step (a1), the particle size of the micronized recycled rubber powder is in the range of 0.05 mm to 0.8 mm. In step (a1), one or more surfactants are present in an amount ranging from 0.5% to 3% by weight relative to the total weight of the micronized recycled rubber powder. A method for producing styrene-butadiene rubber, wherein in step (a1), the micronized recycled rubber powder has a concentration in water of 1% to 50% by weight relative to the total weight of the water.

8. A method for producing styrene-butadiene rubber containing the micronized recycled rubber powder according to claim 7, wherein step (a1) is performed according to claim 2 or 3.

9. A method for producing styrene-butadiene rubber containing micronized recycled rubber powder according to any one of claims 1 to 8, wherein step (c) and step (c1) are carried out in the presence of one or more coagulants selected from a plurality of alkylamine-epicloridine copolymers.

10. A method for producing styrene-butadiene rubber comprising micronized recycled rubber powder according to any one of claims 1 to 9, wherein step (c) and step (c1) are performed at a temperature in the range of 40°C to 90°C for a variable time depending on the size of the coagulation mixer, the amount of the suspension obtained in step (a) or step (a1) and the styrene-butadiene latex used, the temperature and pH, and the stirring system used.

11. A method for producing styrene-butadiene rubber containing micronized recycled rubber powder according to any one of claims 1 to 10, wherein step (c) and step (c1) are performed at a pH of 5 or less.

12. A method for producing styrene-butadiene rubber containing micronized recycled rubber powder according to any one of claims 1 to 11, comprising adding one or more inorganic acids such as sulfuric acid and phosphoric acid in step (c) and step (c1), and adding one or more organic acids in an amount that maintains the pH at 5 or less throughout the entire period of step (c) and step (c1).

13. A method for producing styrene-butadiene rubber containing the micronized recycled rubber powder according to any one of claims 1 to 12, wherein the manufacturing method is carried out in a batch or continuous manner.

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