Process for producing manganese-containing precipitated silica from plant ash, precipitated silica, and its use in tire applications.

Abstract

The present invention relates to a process for producing precipitated silica from plant ash, wherein the precipitated silica contains particulate SiO2 and manganese. The plant ash is preferably used directly in the process without any pretreatment such as washing and / or incineration. The present invention further relates to precipitated silica containing particulate SiO2 and manganese (obtainable by the above process) and its use in the manufacture of filler-containing elastomer compositions, tire parts and / or tires.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority from European Patent Applications No. 23305439.4 and No. 23305440.2, both filed on 29 March 2023, and European Patent Applications No. 23185252.6 and No. 23185224.5, both filed on 13 July 2023, the entire contents of these applications are incorporated herein by reference for any purpose.

[0002] The present invention relates to a process for producing precipitated silica from plant ash. The process comprises alkaline hot immersion of the plant ash to obtain a silicate solution, the silicate solution being successively reacted with an acidifying agent to achieve SiO2 precipitation. The process is characterized in that the plant ash is subjected directly to alkaline hot immersion without any pretreatment such as washing and / or incineration. The present invention further relates to precipitated silica that can or is obtained by the process described above. The present invention further relates to the use of precipitated silica that can or is obtained by the process described above, preferably, for the manufacture of filler-filled elastomer compositions, tire parts and / or tires. [Background technology]

[0003] Silicon dioxide (SiO2), also known as silica, is a silicon compound commonly found in nature. Naturally occurring silica exists in both amorphous and crystalline forms, such as cristobalite, tridymite, and quartz, the latter being the main component of sand.

[0004] Quartz sand is frequently used for the production of silicates, particularly sodium silicate, and can be obtained, for example, by hydrothermal treatment of quartz sand with a strong base such as sodium hydroxide, or by fusing quartz sand with sodium carbonate at high temperatures of approximately 1400-1500°C.

[0005] Sodium silicate can be used as such, or as a raw material for the preparation of various inorganic materials, particularly silica gel and precipitated silica. Precipitated silica is a form of amorphous synthetic silica.

[0006] Silicates and precipitated silica are both highly versatile materials with diverse applications across a wide range of technological fields, from construction to detergents, tires, adhesives, food, and pharmaceutical industries, and their global demand is constantly increasing.

[0007] However, the above process for producing precipitated silica has a major drawback: the sand used as a raw material is replenished by rock erosion or weathering processes over geological timescales, and therefore is not a renewable resource on a human timescale.

[0008] Furthermore, the aforementioned conventional process for producing silica by sand fusion requires heating the reactants to high temperatures, thus consuming a large amount of energy.

[0009] Therefore, it is clear that there is still a need to find a process for producing precipitated silica that is not only more environmentally sustainable but also cost-effective.

[0010] Possible renewable sources include ash derived from the combustion of plants or plant parts, particularly plant ash derived from the combustion of silica-rich plants. In this regard, one particularly silica-rich biosource is ash derived from rice husks.

[0011] Rice husks are agricultural residues from the rice milling industry and are abundant in rice-producing countries. When burned, approximately 20% of the weight of the rice husks is converted into ash containing up to 97% silica by weight.

[0012] Considering the large amounts of silica contained in these ashes and their potential for essential recycling, many efforts have been made to extract silica from them, as this could represent an economically viable option for obtaining precipitated silica that can also address the problem of proper disposal of rice husks (which are waste in the milling industry, as described above).

[0013] However, one of the important aspects of using plant ashes, particularly rice husk ash (RHA), as starting materials is related to the complex nature and variable composition of said ashes, which generally contain, in addition to SiO2, other elements such as carbon, K, Mn, P, S, etc. For many applications, high purity precipitated silica is often desired, so many efforts have been made to purify said ashes in order to reduce the content of the above elements prior to alkaline leaching of the ashes.

[0014] International Publication No. WO 2019 / 168690 describes a process for the preparation of silicates from RHA. In this process, clean water is used to remove impurities contained in the ash to a level of less than 250 ppm (of S and Cl) prior to alkaline leaching of the rice husk ash in order to obtain high purity silicates.

[0015] The main drawback of this type of process is that the washing step uses a very large amount of water that could otherwise be used for other needs. This fact not only contributes to the overall cost and complexity of the process, but also has an adverse impact on the environment as it contributes to the depletion of the earth's resources.

[0016] Indian Patent Application Publication No. 2020 / 21056035 discloses a process for preparing precipitated silica from RHA, in which the RHA is incinerated (reburned) at a temperature of 900 °C to 1025 °C prior to alkaline leaching of the ash to remove moisture, carbon and other volatile substances to achieve high purity precipitated silica.

[0017] Furthermore, in this case, such ash pretreatment is energy-consuming and unfavorable from an economic and ecological perspective, which is a drawback of this process. [Overview of the Initiative] [Problems that the invention aims to solve]

[0018] Therefore, there was still a need to develop a novel process for producing precipitated silica that was easy, environmentally friendly, and cost-effective. [Means for solving the problem]

[0019] The present invention relates to a process for producing precipitated silica from plant ash, wherein the process comprises: (I) Plant ash containing SiO2 and, based on the weight of SiO2 contained in the plant ash, at least 10 ppm of manganese expressed by weight as elemental manganese, (i) SiO2 in the form of silicate anions, and (ii) manganese expressed by weight as elemental manganese, at least 10 ppm based on the weight of SiO2 contained in the silicate solution, by reacting with an alkali metal base, preferably an alkali metal hydroxide, in an aqueous reaction medium at a temperature of at least 100°C. and, (II) To achieve SiO2 precipitation and produce an aqueous slurry containing particulate SiO2 and manganese by weight, expressed as elemental manganese, at least 10 ppm based on the weight of SiO2 contained in the aqueous slurry, the silicate aqueous solution is reacted with an acidifying agent in an aqueous reaction medium having a pH greater than 7.0 for at least part of the duration of the reaction at a temperature of at least 40°C. This includes processes related to the process.

[0020] The process according to the present invention further optionally includes, prior to step (I), step (A) of burning a plant and / or plant part containing SiO2 and manganese in a weight of at least 10 ppm, expressed as elemental manganese, based on the weight of SiO2 contained in the plant and / or plant part, in order to obtain plant ash. According to one embodiment, the process according to the present invention further includes step (A).

[0021] According to one embodiment, the plant portion and / or plant, plant ash, silicate aqueous solution, and aqueous slurry further contain phosphorus in an amount expressed as elemental phosphorus, at least 10 ppm, based on the weight of the SiO2 contained in each.

[0022] The process of the present invention comprises step (A) and may not include any step (B) which includes the re-combustion of plant ash, wherein step (B) is after step (A) and before step (I).

[0023] The process of the present invention may include step (A) and may not include any step (B) which includes washing the plant ash with a liquid containing water or acidic water, wherein step (B) is after step (A) and before step (I). It may include step (A) and may not include any step (B) which includes acid leaching and / or acid wetting the plant ash, wherein step (B) is after step (A) and before step (I). It may include step (A) and may not include any step (B) which includes (i) washing the plant ash with a liquid containing water or acidic water, and (ii) acid leaching and / or acid wetting the plant ash, wherein step (B) is after step (A) and before step (I). Washing the plant ash with a liquid containing water or acidic water, acid leaching the plant ash, and acid wetting the plant ash are operations that will, in other ways generally result in the partial or complete removal of manganese and / or phosphorus (if present) from the plant ash.

[0024] In a particularly preferred embodiment, the process of the present invention comprises step (A) and does not include any step (B) of removing some or all of the manganese and / or phosphorus (if present) from the plant ash, wherein step (B) is after step (A) and before step (I).

[0025] The process of the present invention comprises step (A) and does not comprise any step (B') comprising washing the plant and / or plant parts with a liquid containing water or acidic water, wherein step (B') precedes step (A). It may comprise step (A) and not comprise any step (B') comprising acid leaching and / or acid wetting the plant and / or plant parts, wherein step (B') precedes step (A). It may comprise step (A) and not comprise any step (B') comprising at least one of (i) washing the plant and / or plant parts with a liquid containing water or acidic water, and (ii) acid leaching and / or acid wetting the plant and / or plant parts, wherein step (B') precedes step (A) and step (I). Washing plants and / or plant parts with water or a liquid containing acidic water, acid leaching plants and / or plant parts, and acid wetting plants and / or plant parts will, in other words, generally result in the partial or complete removal of manganese and / or phosphorus (if present) from plants and / or plant parts.

[0026] According to another embodiment, the process of the present invention may also not include any step (B') of removing some or all of the manganese and / or phosphorus (if present) from the plant and / or plant part, wherein step (B') precedes step (A).

[0027] In a more preferred embodiment, the process of the present invention comprises (i) step (A), (ii) any step (B) of removing some or all of the manganese and / or phosphorus (if present) from plant ash, and (iii) any step (B') of removing some or all of the manganese and / or phosphorus (if present) from plants and / or plant parts, wherein step (B) is after step (A) and before step (I), and where step (B') is before step (A).

[0028] According to another embodiment, the process of the present invention further: (III) The aqueous slurry obtained after step (II) is filtered, preferably using a filter press, to obtain a filter cake containing particulate SiO2; (IV) Optionally, wash the filter cake with a water-containing liquid; (V) A step of liquefying the filter cake into a fluid aqueous suspension containing particulate SiO2 by adding a water-containing liquid to the filter cake and optionally further subjecting the filter cake to mechanical and / or chemical treatment; (VI) To obtain precipitated silica, the fluid aqueous suspension is dried, preferably using a spray dryer. Includes.

[0029] The process of the present invention is advantageously free from any step (B'') after step (VI), which includes washing the precipitated silica with a liquid containing water or acidic water. The process of the present invention is also advantageously free from any step (B'') after step (VI), which includes acid leaching and / or acid wetting the precipitated silica. Washing the precipitated silica with a liquid containing water or acidic water, acid leaching the precipitated silica, and acid wetting the precipitated silica will, in other ways generally result in the partial or complete removal of manganese and / or phosphorus (if present) from the precipitated silica.

[0030] Preferably, the process of the present invention does not include any step (B'') after step (VI) which removes some or all of the manganese and / or phosphorus (if present) from the precipitated silica.

[0031] Furthermore, the present invention relates to precipitated silica containing particulate SiO2 and manganese by weight, expressed as elemental manganese, in a range of 10 ppm to 75 ppm based on the weight of SiO2 contained in the precipitated silica. Preferably, the precipitated silica further contains phosphorus by weight, expressed as elemental phosphorus, in at least 10 ppm based on the weight of SiO2 contained in the precipitated silica. According to a preferred embodiment, the precipitated silica is obtainable or acquired according to the process of the present invention.

[0032] Furthermore, the present invention relates to the use of precipitated silica for the manufacture of at least one tire comprising (i) a precipitated silica-filled elastomer composition, (ii) a tire portion comprising (possibly composed of) the precipitated silica-filled elastomer composition, and (iii) at least one portion comprising (possibly composed of) the precipitated silica-filled elastomer composition, wherein the precipitated silica contains particulate SiO2 and manganese by weight, expressed as elemental manganese, in a range of 10 ppm to 75 ppm based on the weight of SiO2 contained in the precipitated silica. Similarly, the present invention relates to a method for producing at least one tire comprising (i) a precipitated silica-filled elastomer composition, (ii) a tire portion comprising (possibly composed of) the precipitated silica-filled elastomer composition, and (iii) at least one portion comprising (possibly composed of) the precipitated silica-filled elastomer composition, wherein the method comprises mixing at least one elastomer with precipitated silica, wherein the precipitated silica contains particulate SiO2 and manganese by weight, expressed as elemental manganese, in the range of 10 ppm to 75 ppm based on the weight of SiO2 contained in the precipitated silica. Preferably, the precipitated silica further contains phosphorus by weight, expressed as elemental phosphorus, in at least 10 ppm based on the weight of SiO2 contained in the precipitated silica. According to a preferred embodiment, the precipitated silica is obtainable or can be obtained according to the process of the present invention.

[0033] The present invention further relates to a precipitated silica-filled elastomer composition comprising at least one elastomer and the precipitated silica, a tire portion comprising (possibly composed of) the precipitated silica-filled elastomer composition, and a tire comprising at least one portion comprising (possibly composed of) the precipitated silica-filled elastomer composition.

[0034] The present invention also relates to a vehicle including the aforementioned tire. The vehicle may be an automobile, such as a car, van, mobile home, bus, coach, truck, or construction machinery (such as a backhoe loader or dumper); or the vehicle may be a non-automobile vehicle (such as a trailer or cart).

[0035] The present invention solves the aforementioned problems of the prior art by providing a process for preparing precipitated silica from plant ash that is not only environmentally friendly but also economically advantageous. In fact, the process of the present invention does not require any pretreatment of plants, plant parts and / or plant ash, nor any posttreatment of the precipitated silica, in particular any washing step, in order to efficiently prepare precipitated silica having the desired properties. In fact, the precipitated silica obtainable or obtained by the process of the present invention can be advantageously used for the manufacture of precipitated silica-containing elastomer compositions and tires having desired properties in terms of performance and mechanical and dynamic properties. [Modes for carrying out the invention]

[0036] Before the problems of the present invention are described in detail, the following should be considered.

[0037] It should be understood that the invention is not limited to such embodiments, as the specific embodiments described may of course be modified. It should also be understood that the terminology used herein is not intended to be restrictive, as the scope of the invention will be limited only by the appended claims.

[0038] As used herein, the singular forms "a," "an," and "the" refer to both singular and plural objects unless the context clearly indicates otherwise. For example, "compound" refers to one compound or two or more compounds.

[0039] The terms “comprising,” “comprises,” and “comprised of,” as used herein, are synonymous with “including,” “includes,” or “containing,” and are comprehensive or unrestrictive, and do not exclude additional, unenumerated members, elements, or method steps. It will be fully understood that the terms “comprising,” “comprises,” and “comprised of,” as used herein, include the terms “consisting of,” “consists,” and “consists of.”

[0040] Throughout this application, the term “about” is used to indicate that a value includes the standard deviation of errors in the apparatus or method used to measure that value.

[0041] As used herein, the term "mean" refers to a numerical mean unless otherwise specified.

[0042] As used herein, the terms “weight percentage,” “weight percentage,” “weight percentage,” or “weight percentage” are used interchangeably. The same applies to the terms “volume percentage,” “volume percentage,” “volume percentage,” or “volume percentage,” or “mol percentage,” “mol%, “mol percentage,” or “mol percentage.”

[0043] As used herein, the terms “‰ by weight” or “‰ by weight” are used interchangeably to indicate a quantity in “per mille” (i.e., “per thousand”). The same applies to “‰ by volume,” “‰ by volume,” or “‰ by mole,” “‰ by mole.”

[0044] Enumerations of number ranges by endpoint include all integers, and optionally fractions, that fall within that range (for example, 1-5, when referring to the number of elements, may include 1, 2, 3, and 4; and also, when referring to measured values, may include 1.5, 2, 2.75, and 3.80). Enumerations of endpoints also include the endpoint values ​​themselves (for example, 1.0-5.0 includes both 1.0 and 5.0). Any number range enumerated herein is intended to include all partial ranges that fall within it.

[0045] In patent law, the technical term "X substantially contains no Y" is used herein in its ordinary, generally accepted sense, allowing for the possible presence of Y in X, provided that, if present, the amount of Y in X does not substantially affect the fundamental properties of X. In relation to the present invention, the fundamental properties of precipitated silica are the physical parameters determined in Table 4 and the end-use properties determined in Tables 6-8.

[0046] Another technical term in patent law, "X does not essentially contain Y," is also used herein in its ordinary sense, allowing for the possible and unavoidable presence of trace amounts of Y, such as impurities, in X, which should be avoided as much as possible.

[0047] To avoid misunderstanding, "X does not contain Y" simply means that X does not contain Y at all.

[0048] As used herein, the term “manganese” encompasses any form of manganese contained in precipitated silica, in particular at least one form of manganese selected from the group consisting of: elemental manganese, manganese on the surface of SiO2 particles, manganese inserted into SiO2 particles, manganese silicate, and manganese oxide in any oxidized state.

[0049] For the purposes of this invention, the weight of manganese is expressed as elemental manganese throughout the specification.

[0050] As used herein, the term "phosphorus" is intended to mean any form of phosphorus contained in precipitated silica, in particular: elemental phosphorus, phosphorus on the surface of SiO2 particles, phosphorus inserted into SiO2 particles, orthophosphate ions, polyphosphate ions, and phosphides, which are selected from the group consisting of these.

[0051] For the purposes of this invention, the weight of phosphorus is expressed as elemental phosphorus throughout the specification.

[0052] All references cited herein are incorporated herein by reference in their entirety. In particular, all teachings of references specifically mentioned herein are incorporated herein by reference.

[0053] Unless otherwise defined, all terms used to disclose this invention, including technical and scientific terms, have meanings that are generally understood by those skilled in the art to which this invention belongs. Further guidance provides definitions of terms to better and fully understand the teachings of this invention.

[0054] In the following sections, different alternatives, embodiments, and variations of the present invention are defined in more detail. Each of the alternatives and embodiments thus defined may be combined with any other alternatives and embodiments, and this also applies to each variation, provided that the opposite is not explicitly shown or is not explicitly contradictory when the same parameter ranges are separated. In particular, any feature shown to be preferred or advantageous may be combined with any other one or more features shown to be preferred or advantageous.

[0055] Furthermore, certain features, structures, or properties described herein may be combined in any preferred manner in one or more embodiments, as will be apparent to those skilled in the art from this disclosure. Moreover, while some embodiments described herein include some features that are included in other embodiments, but not others, combinations of features from different embodiments constitute different embodiments, meaning they fall within the scope of the invention and will be understood by those skilled in the art.

[0056] The present invention relates to a process for producing precipitated silica from plant ash, wherein the process is: (I) Reacting plant ash containing SiO2 and at least 10 ppm of manganese by weight, expressed as elemental manganese, based on the weight of SiO2 contained in the plant ash, with an alkali metal base, preferably an alkali metal hydroxide, in an aqueous reaction medium at a temperature of at least 100°C to obtain an aqueous silicate solution containing (i) SiO2 in the form of silicate anions and (ii) manganese by weight, expressed as elemental manganese, based on the weight of SiO2 contained in the silicate solution. and, (II) A step of reacting an aqueous silicate aqueous solution with an acidifying agent in an aqueous reaction medium having a pH greater than 7.0 for at least part of the time at a temperature of at least 40°C in order to achieve SiO2 precipitation and produce an aqueous slurry containing particulate SiO2 and manganese by weight, expressed as elemental manganese, at least 10 ppm based on the weight of SiO2 contained in the aqueous slurry. This refers to the process, including the following:

[0057] According to a preferred embodiment, the plant ash contains manganese in an amount expressed as elemental manganese, at least 15 ppm, at least 18 ppm, at least 20 ppm, at least 50 ppm, at least 100 ppm, or at least 200 ppm, based on the weight of SiO2 contained in the plant ash. More preferably, the plant ash contains manganese in an amount expressed as elemental manganese, at least 500 ppm, based on the weight of SiO2 contained in the plant ash. Even more preferably, the plant ash contains manganese in an amount expressed as elemental manganese, at least 1000 ppm, based on the weight of SiO2 contained in the plant ash. Most preferably, the plant ash contains manganese in an amount expressed as elemental manganese, at least 2000 ppm, based on the weight of SiO2 contained in the plant ash.

[0058] Advantageously, the plant ash contains manganese in a weight expressed as elemental manganese at a maximum of 15,000 ppm, preferably at a maximum of 12,000 ppm, more preferably at a maximum of 9,000 ppm, even more preferably at a maximum of 7,000 ppm, even more preferably at a maximum of 5,000 ppm, and most preferably at a maximum of 3,500 ppm, based on the weight of SiO2 contained in the plant ash. In some specific examples, the plant ash may contain manganese in a lower weight, for example, in a weight expressed as elemental manganese at a maximum of 2,500 ppm, at a maximum of 1,250 ppm, or at a maximum of 675 ppm, based on the weight of SiO2 contained in the plant ash.

[0059] In some embodiments, the plant ash contains manganese in a weight expressed as elemental manganese, ranging from 10 ppm to 5000 ppm, based on the weight of SiO2 contained in the plant ash.

[0060] According to a preferred embodiment of the present invention, the silicate aqueous solution contains manganese in an amount expressed as elemental manganese, at a maximum of 500 ppm, preferably at a maximum of 375 ppm, more preferably at a maximum of 250 ppm, even more preferably at a maximum of 200 ppm, even more preferably at a maximum of 150 ppm, and most preferably at a maximum of 100 ppm, based on the weight of SiO2 contained in the silicate aqueous solution.

[0061] In some specific examples, the silicate aqueous solution may contain manganese in lower amounts by weight, for example, at most 75 ppm, at most 50 ppm, at most 30 ppm, and at most 25 ppm, expressed as elemental manganese.

[0062] Furthermore, the silicate aqueous solution contains manganese by weight, expressed as elemental manganese, preferably at least 10 ppm, more preferably at least 30 ppm, and even more preferably at least 50 ppm, based on the weight of SiO2 contained in the silicate aqueous solution.

[0063] In some specific examples, the silicate aqueous solution may contain manganese in weight, expressed as elemental manganese, in the ranges of 10 ppm to 100 ppm, 10 ppm to 80 ppm, 10 ppm to 75 ppm, 15 ppm to 50 ppm, or 18 ppm to 25 ppm, based on the weight of SiO2 contained in the silicate aqueous solution.

[0064] According to embodiments of the present invention, the aqueous slurry obtained in step (II) contains manganese in the same amount as disclosed for aqueous silicate solutions.

[0065] According to embodiments of the present invention, during step (I), the plant ash is reacted with an alkali metal base at a temperature of at least 120°C, preferably at least 140°C, and more preferably at least 160°C. Furthermore, step (I) is advantageously carried out at a temperature of at most 250°C, preferably at most 220°C, and more preferably at most 200°C. Favorable results were obtained when the plant ash was reacted with the alkali metal base at a temperature in the range of 140°C to 220°C, preferably 160°C to 200°C.

[0066] Preferably, the alkali metal base is tetraalkylammonium hydroxide ((NR4 + OH - (Here, R is an alkyl chain, preferably a C1-C4 alkyl chain), selected from the group consisting of a base containing sodium or potassium, or a combination thereof. More preferably, the alkali metal base is an alkali metal hydroxide selected from sodium hydroxide or potassium.

[0067] In a particularly preferred embodiment, the process according to the present invention comprises, prior to step (I), step (A) of burning a plant and / or plant part to obtain plant ash, wherein the plant and / or plant part contains SiO2 and manganese by weight, expressed as element manganese, which is the same as disclosed above for plant ash, based on the weight of SiO2 contained in the plant and / or plant part. In other words, the plant ash is obtained from the burning of the plant and / or plant part.

[0068] Preferably, the plant and / or plant part contains manganese in a weight expressed as elemental manganese at a rate of at least 15 ppm, at least 18 ppm, at least 20 ppm, at least 50 ppm, at least 100 ppm, or at least 200 ppm, based on the weight of SiO2 contained in the plant and / or plant part. More preferably, the plant and / or plant part contains manganese in a weight expressed as elemental manganese at a rate of at least 500 ppm, based on the weight of SiO2 contained in the plant and / or plant part. Even more preferably, the plant and / or plant part contains manganese in a weight expressed as elemental manganese at a rate of at least 1000 ppm, based on the weight of SiO2 contained in the plant and / or plant part. Most preferably, the plant and / or plant part contains manganese in a weight expressed as elemental manganese at a rate of at least 2000 ppm, based on the weight of SiO2 contained in the plant and / or plant part.

[0069] Advantageously, the plant and / or plant part contains manganese in a weight expressed as elemental manganese at a maximum of 15,000 ppm, preferably at a maximum of 12,000 ppm, more preferably at a maximum of 9,000 ppm, even more preferably at a maximum of 7,000 ppm, even more preferably at a maximum of 5,000 ppm, and most preferably at a maximum of 3,500 ppm, based on the weight of SiO2 contained in the plant and / or plant part. In some specific examples, the plant and / or plant part may contain manganese in a lower weight expressed as elemental manganese at a maximum of 2,500 ppm, at a maximum of 1,250 ppm, or at a maximum of 675 ppm, based on the weight of SiO2 contained in the plant and / or plant part.

[0070] According to a particularly preferred embodiment of the present invention, the plant and / or plant part contains manganese by weight, expressed as elemental manganese, in a range of 10 ppm to 5000 ppm, preferably 15 ppm to 2500 ppm, more preferably 18 ppm to 1250 ppm, and even more preferably 18 ppm to 675 ppm, based on the weight of SiO2 contained in the plant and / or plant part.

[0071] According to embodiments of the present invention, plants and / or plant parts, plant ash, silicate aqueous solutions, and / or slurry aqueous solutions further contain phosphorus. Plants and / or plant parts may contain phosphorus in a weight expressed as elemental phosphorus at a concentration of at least 10 ppm, at least 15 ppm, or at least 20 ppm, based on the weight of SiO2 contained in the plants and / or plant parts.

[0072] Advantageously, the plant and / or plant part further contains phosphorus in a higher weight, for example, at least 500 ppm, preferably at least 1000 ppm, more preferably at least 1500 ppm, even more preferably at least 1650 ppm, at least 1700 ppm or at least 1750 ppm, based on the weight of SiO2 contained in the plant and / or plant part, expressed as elemental phosphorus.

[0073] Preferably, the plant and / or plant part contains phosphorus in a weight expressed as elemental phosphorus, at a maximum of 5000 ppm, more preferably at a maximum of 3500 ppm, even more preferably at a maximum of 2500 ppm, and most preferably at a maximum of 2000 ppm, based on the weight of SiO2 contained in the plant and / or plant part.

[0074] In some specific examples, the plant and / or plant part contains phosphorus by weight, expressed as elemental phosphorus, at a maximum of 1250 ppm or at a maximum of 675 ppm, based on the weight of SiO2 contained in the plant and / or plant part.

[0075] According to embodiments of the present invention, the plant and / or plant part contains phosphorus in a weight expressed as elemental phosphorus, in the range of 10 ppm to 5000 ppm, 15 ppm to 2500 ppm, or 20 ppm to 1250 ppm, based on the weight of SiO2 contained in the plant and / or plant part.

[0076] Similarly, the plant ash, silicate aqueous solution, and / or aqueous slurry may further contain phosphorus in an amount expressed as elemental phosphorus, at least 10 ppm, at least 15 ppm, or at least 20 ppm, based on the weight of the SiO2 contained in the plant ash, silicate aqueous solution, and / or aqueous slurry.

[0077] Advantageously, the plant ash, silicate aqueous solution, and / or aqueous slurry contain phosphorus in a higher amount by weight, for example, based on the weight of SiO2 contained in the plant ash, silicate aqueous solution, and / or aqueous slurry, at least 500 ppm, preferably at least 1000 ppm, more preferably at least 1500 ppm, even more preferably at least 1650 ppm, at least 1700 ppm, or at least 1750 ppm, expressed as elemental phosphorus. Furthermore, the silicate aqueous solution and / or aqueous slurry contain phosphorus in a weight, expressed as elemental phosphorus, even more preferably at least 2000 ppm, most preferably at least 2500 ppm, based on the weight of SiO2 contained in the silicate aqueous solution and / or aqueous slurry.

[0078] Preferably, the plant ash, silicate aqueous solution, and / or aqueous slurry contain phosphorus in a weight expressed as elemental phosphorus, at most 5000 ppm, more preferably at most 3500 ppm, and even more preferably at most 3000 ppm, based on the weight of SiO2 contained in the plant ash, silicate aqueous solution, and / or aqueous slurry. Furthermore, the plant ash contains phosphorus in a weight expressed as elemental phosphorus, even more preferably at most 2500 ppm, and most preferably at most 2000 ppm, based on the weight of SiO2 contained in the plant ash.

[0079] In some specific examples, the plant ash, silicate aqueous solution, and / or aqueous slurry contain phosphorus in a weight expressed as elemental phosphorus, at a maximum of 1250 ppm or 675 ppm, respectively, based on the weight of SiO2 contained.

[0080] According to embodiments of the present invention, the plant ash, silicate aqueous solution, and / or aqueous slurry contain phosphorus in a weight expressed as elemental phosphorus, in the range of 10 ppm to 5000 ppm, 15 ppm to 2500 ppm, or 20 ppm to 1250 ppm, based on the weight of SiO2 contained in each.

[0081] According to embodiments of the present invention, the aqueous slurry obtained in step (II) preferably contains phosphorus in the same amount as disclosed for aqueous silicate solutions.

[0082] Without wishing to be bound by a specific mechanism theory, it was found that the weight of manganese contained in plants and / or plant parts, and subsequently in the aforementioned plant ash, and, if present, phosphorus, does not adversely affect the preparation of silicate aqueous solutions and the preparation of precipitated silica, nor its properties.

[0083] Similarly, it was found that the presence of manganese and, if present, phosphorus in the silicate aqueous solution does not affect the preparation of precipitated silica or its properties.

[0084] Furthermore, for the purposes of the present invention, it has been found that the presence of manganese and, if present, phosphorus in the above-mentioned weight amounts does not adversely affect the properties of precipitated silica, and therefore it is not necessary to treat either the plants and / or plant parts or plant ash to remove the manganese and, if present, phosphorus contained therein.

[0085] Therefore, according to one embodiment, the process of the present invention may include step (A) and may not include any step (B) after step (A) and before step (I), which includes re-combusting plant ash.

[0086] According to one embodiment, the process of the present invention may include step (A) and may not include any step (B) after step (A) and before step (I), which includes washing the plant ash with a liquid containing water or acidic water.

[0087] According to one embodiment, the process of the present invention comprises step (A) and does not include any step (B) after step (A) and before step (I), which includes acid leaching and / or wetting plant ash.

[0088] Preferably, the acid leaching and / or acid wetting is carried out with an acidifying agent, more preferably with HCl, and even more preferably with a 1N or 6N HCl solution.

[0089] According to one embodiment, the acid leaching can be carried out by treating the plant ash under reflux with the acidifying agent, preferably HCl, and more preferably 1N or 6N HCl, for at least 1 hour, preferably at least 1.5 hours.

[0090] The acid wetting is preferably carried out by immersing the plant ash in the acidifying agent, preferably HCl, preferably a 1N or 6N HCl solution, for at least 1 hour, preferably at least 3 hours, and more preferably 3 to 7 hours.

[0091] According to one embodiment, the process of the present invention may include step (A), which includes (i) washing the plant ash with a liquid containing water or acidic water, and (ii) acid leaching and / or acid wetting the plant ash, but does not include any step (B) after step (A) and before step (I).

[0092] Washing plants with water or a liquid containing acidic water, acid leaching of plant ash, and acid wetting of plant ash are, in other words, operations that will generally result in the partial or complete removal of manganese and / or phosphorus, if present, from plant ash.

[0093] In a particularly preferred embodiment, the process of the present invention comprises step (A) and does not include any step (B) after step (A) and before step (I), which remove some or all of the manganese and / or phosphorus, if present, from the plant ash.

[0094] According to the present invention, step (B) in any of the above embodiments can be considered as a step of pre-treating plant ash.

[0095] According to another particularly preferred embodiment, the process of the present invention may include any step (B') prior to step (A), which includes washing the plant and / or plant parts with a liquid containing water or acidic water.

[0096] According to one embodiment, the process of the present invention may include step (A) and may not include any step (B') prior to step (A), which includes acid leaching and / or acid wetting of plants and / or plant parts.

[0097] Preferably, the acid leaching and / or acid wetting is as defined above for step (B).

[0098] According to one embodiment, the process of the present invention may include any step (B') prior to step (A), which includes (i) washing a plant and / or plant part with a liquid containing water or acidic water, and (ii) acid leaching and / or acid wetting the plant and / or plant part.

[0099] Washing plants and / or plant parts with water or a liquid containing acidic water, acid leaching plants and / or plant parts, and acid wetting plants and / or plant parts will, in other ways, generally result in the partial or complete removal of manganese and / or phosphorus, if present, from plants and / or plant parts.

[0100] In a particularly preferred embodiment, the process of the present invention comprises step (A) and does not include any step (B') of removing some or all of manganese and / or phosphorus, if present, from the plant and / or plant part. According to the present invention, step (B') can be considered a step of pre-treating the plant and / or plant part.

[0101] According to the present invention, plant ash that has not been subjected to any of the above embodiments in step (B) is considered untreated plant ash, preferably unwashed and / or unre-combusted plant ash.

[0102] Similarly, according to the present invention, any plant and / or plant part that has not been subjected to any step (B') according to any of the embodiments described above is considered to be an untreated plant and / or plant part, preferably an unwashed plant and / or part.

[0103] Without wishing to be bound by any particular theory, it was found that the process according to the present invention does not require any pretreatment of plants, plant parts, and / or plant ash to remove manganese and, if present, phosphorus contained therein. On the contrary, it was surprisingly found that the presence of manganese and / or, if present, phosphorus in the plants, plant parts, and / or plant ash does not affect the synthesis of precipitated silica, and consequently, the precipitated silica thus obtained still possesses desirable mechanical and rheological properties that are particularly advantageous for tire applications.

[0104] According to the present invention, the plant is preferably an angiosperm, more preferably a monocotyledonous plant or a eudicotyledonous plant, most preferably a plant belonging to a family selected from the group consisting of the grasses, horsetails, sedges, cucurbits, cannabaceous, palms, brassicas, and combinations thereof.

[0105] According to embodiments of the present invention, the plant is a tree. Preferably, the tree is selected from the group consisting of pine, oak, birch, elm, and combinations thereof.

[0106] Preferably, the plants belonging to the grass family are selected from the group consisting of rice, wheat, sugarcane, bamboo, oats, barley, rye, sorghum, triticalla, reed, corn, miscanthus, and combinations thereof.

[0107] Preferably, the plant belonging to the Equisetaceae family is horsetail (Equisetum arvense).

[0108] Preferably, the plant belonging to the Cyperaceae family is sedge.

[0109] Preferably, the plants belonging to the Cucurbitaceae family are selected from the group consisting of melons, watermelons, pumpkins, cucumbers, and combinations thereof.

[0110] Preferably, the plant belonging to the Cannabaceae family is cannabis.

[0111] Preferably, plants belonging to the Arecaceae family are palm trees.

[0112] Preferably, the plant belonging to the Brassicaceae family is rapeseed.

[0113] Silica-containing plants (SiO2-containing plants) are plants selected from the group consisting of rice, wheat, rapeseed, barley, bamboo, horsetail, sedge, watermelon, and combinations thereof.

[0114] Preferably, the plant part is selected from the group consisting of roots, stems, leaves, flowers, fruits, husks, rods, stalks, xylem, and combinations thereof.

[0115] According to the present invention, the plant portion may also be derived from processed plants such as straw (e.g., grain straw), bagasse (e.g., sugarcane bagasse), oil (e.g., palm oil), sawdust (e.g., wood sawdust), and / or pellets.

[0116] The plant parts are preferably selected from the group consisting of rice husks, rice straw, wheat husks, wheat straw, barley straw, barley husks, sugarcane bagasse, sugarcane leaves, bamboo stalks, bamboo leaves, corn cobs, palm oil, miscanthus stalks, miscanthus leaves, sedge leaves, watermelon fruits, woody parts of trees, and combinations thereof.

[0117] In a particularly preferred embodiment of the present invention, the plant is rice, and preferably the plant part is the husk.

[0118] According to the present invention, the combustion of plants and / or plant parts (step A above)) is carried out by conventional techniques, which involve burning plant parts and / or plants containing silica.

[0119] In one embodiment, the combustion of plants and / or plant parts is carried out at a temperature of 300 to 1500°C, preferably 500 to 1000°C. According to another embodiment, the combustion of plants and / or plant parts is carried out at a temperature above 700°C, preferably above 700°C and below 1000°C. According to yet another embodiment, the combustion of plants and / or plant parts is carried out at a maximum temperature of 700°C, preferably between 500°C and 700°C.

[0120] According to the present invention, the acidifying agent in step (II) above is preferably selected from the group consisting of mineral acids selected from the group consisting of sulfuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), phosphoric acid (H3PO4), and combinations thereof, and organic acids selected from the group consisting of acetic acid, formic acid, carbonic acid, and combinations thereof.

[0121] According to the present invention, step (II) of the above process is carried out in an aqueous reaction medium having a pH greater than 7.0 for at least a portion of the duration of the reaction, preferably for at least 25% of the duration of the reaction, more preferably for at least 28% of the duration of the reaction, and even more preferably for at least 33% of the duration of the reaction. In some embodiments, step (II) of the above process is carried out in an aqueous reaction medium having a pH greater than 7.0 for at most 66% of the duration of the reaction, preferably for at most 50% of the duration of the reaction; in some other embodiments, step (II) of the above process is carried out in an aqueous reaction medium having a pH greater than 7.0 for more than 50% of the duration of the reaction, preferably for at least 90% of the duration of the reaction, more preferably for 95% of the duration of the reaction, and even more preferably for the entire duration of the reaction.

[0122] Preferably, step (II), in which the silicate aqueous solution is reacted with the acidifying agent, is carried out at a temperature of at least 50°C, more preferably at least 60°C, even more preferably at least 75°C, and most preferably at least 80°C. Furthermore, step (II) is advantageously carried out at a temperature of at most 150°C, preferably below 100°C, and more preferably at most 95°C. Good results were obtained when step (II) was carried out at a temperature in the range of 60°C to less than 100°C. Excellent results were obtained when step (II) was carried out at a temperature in the range of 75°C to 95°C.

[0123] Preferably, the aqueous reaction medium in step (I) and / or (II) of the process of the present invention is water.

[0124] According to the present invention, this process further: (III) The aqueous slurry obtained after step (II) is filtered, preferably using a filter press, to obtain a filter cake containing particulate SiO2; (IV) Optionally, wash the filter cake with a water-containing liquid; (V) A step of liquefying the filter cake into a fluid aqueous suspension containing particulate SiO2 by adding a water-containing liquid to the filter cake; (VI) A step of drying the fluid aqueous suspension, preferably using a spray dryer, in order to obtain precipitated silica. It can include...

[0125] According to embodiments of the present invention, step (V) further comprises subjecting the filter cake to mechanical and / or chemical treatment (in addition to adding a water-containing liquid to the filter cake).

[0126] According to one embodiment, the process of the present invention does not include any step (B'') after step (VI), which includes washing the precipitated silica with a liquid containing water or acidic water.

[0127] According to one embodiment, the process of the present invention does not include any step (B'') after step (VI), which involves acid leaching and / or acid wetting of the precipitated silica.

[0128] Preferably, the acid leaching and / or acid wetting is as defined above for steps (B) and (B').

[0129] According to one embodiment, the process of the present invention does not include any step (B'') after step (VI), which includes (i) washing the precipitated silica with a liquid containing water or acidic water, and (ii) acid leaching and / or acid wetting the precipitated silica.

[0130] Washing the precipitated silica with water or a liquid containing acidic water, acid leaching the precipitated silica, and acid wetting the precipitated silica will, in other ways generally result in the partial or complete removal of manganese and / or the partial or complete removal of phosphorus, if present, from the precipitated silica.

[0131] In a particularly preferred embodiment, the process according to the present invention does not include any step (B'') after step (VI) which removes some or all of the manganese and / or some or all of the phosphorus, if present, from the precipitated silica.

[0132] According to the present invention, step (B'') can be considered as a post-treatment step for precipitated silica.

[0133] According to one embodiment, the process according to the present invention does not involve (i.e., does not include) a step of forming a xerogel.

[0134] According to the present invention, the precipitated silica obtained at the end of the above process may also contain other elements selected from the group consisting of Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Ni, Pb, S, Sb, Ti, Zn, K, Na, and combinations thereof (derived from synthesis and, in particular, from the use of untreated plant ash and untreated plants and / or plant parts).

[0135] The present invention also relates to precipitated silica containing particulate SiO2 and manganese by weight, expressed as elemental manganese, in a range of 10 ppm to 75 ppm, based on the weight of SiO2 contained in the precipitated silica. The present invention also relates to the use of said precipitated silica for the production of precipitated silica-filled elastomer compositions.

[0136] Preferably, the precipitated silica contains manganese in an amount expressed as elemental manganese, at least 10 ppm, preferably at least 15 ppm, and more preferably at least 18 ppm, based on the weight of SiO2 contained in the precipitated silica.

[0137] Preferably, the precipitated silica contains manganese in an amount expressed as elemental manganese, at a maximum of 75 ppm, preferably at a maximum of 50 ppm, more preferably at a maximum of 30 ppm, and even more preferably at a maximum of 25 ppm, based on the weight of SiO2 contained in the precipitated silica.

[0138] According to a particularly preferred embodiment of the present invention, the precipitated silica contains manganese by weight, expressed as elemental manganese, in a range of 15 ppm to 50 ppm, preferably 18 ppm to 30 ppm, and more preferably 18 ppm to 25 ppm, based on the weight of SiO2 contained in the precipitated silica.

[0139] Preferably, the precipitated silica further contains phosphorus in an amount by weight, expressed as elemental phosphorus, at least 10 ppm, preferably at least 15 ppm, more preferably at least 20 ppm, and even more preferably at least 23 ppm, based on the weight of SiO2 contained in the precipitated silica.

[0140] Preferably, the precipitated silica contains phosphorus in an amount expressed as elemental phosphorus, at a maximum of 300 ppm, more preferably at a maximum of 100 ppm, even more preferably at a maximum of 50 ppm, and even more preferably at a maximum of 30 ppm, based on the weight of SiO2 contained in the precipitated silica.

[0141] According to embodiments of the present invention, the precipitated silica contains phosphorus in a weight amount expressed as elemental phosphorus, in the range of 10 to 300 ppm, preferably 15 to 100 ppm, more preferably 20 to 50 ppm, and even more preferably 23 to 30 ppm, based on the weight of SiO2 contained in the precipitated silica.

[0142] Preferably, the precipitated silica contains particulate SiO2 in an amount of at least 90.0%, more preferably at least 93.0%, and even more preferably at least 95.0% by weight, based on the weight of the precipitated silica.

[0143] Preferably, the precipitated silica contains particulate SiO2 in an amount of at most 99.0%, preferably at most 98.0%, and more preferably at least 97.0% by weight, based on the weight of the precipitated silica.

[0144] According to embodiments of the present invention, the precipitated silica contains particulate SiO2 in an amount of 90.0% to 99.0%, preferably 93.0% to 98.0%, and more preferably 95.0% to 97.0%, based on the weight of the precipitated silica.

[0145] Preferably, the precipitate is substantially free of SiO2 particles in which the organic portion is covalently bonded via Si-C bonds; it may be essentially free of or even free of SiO2 particles in which the organic portion is covalently bonded via Si-C bonds.

[0146] Preferably, the precipitated silica is substantially free, essentially free, or even free of SiO2 particles to which the organic part is covalently bonded (whatever the covalent bond between the SiO2 particles and the organic part may be).

[0147] More preferably, the precipitated silica is different from any organically modified precipitated silica.

[0148] As used herein, the term “organically modified precipitated silica” means precipitated silica containing SiO2 particles and a substantial amount of (i) an organic compound and / or (ii) an organic moiety covalently bonded to the SiO2 particles. Organically modified precipitated silica may also contain a substantial amount of an organic compound (e.g., polyethylene glycol) that is not covalently bonded to the SiO2 particles. Organically modified precipitated silica may also contain a substantial amount of an organic moiety covalently bonded to the SiO2 particles; such organically modified precipitated silica is typically produced by a chemical reaction between an organic compound (e.g., potassium methyl siliconate) and SiO2 particles. Organically modified precipitated silica therefore contains a substantial amount of carbon, particularly in the form of an organic compound and / or an organic moiety. Organically modified precipitated silica may contain at least 0.5%, at least 0.75%, and even at least 1% carbon, based on the weight of SiO2 contained in the modified precipitated silica.

[0149] The carbon in question is the carbon contained in the aforementioned organic portion that is covalently bonded to the SiO2 particles via a Si-C bond.

[0150] In contrast, the precipitated silica may, advantageously, be substantially carbon-free, essentially carbon-free, or even carbon-free. Its carbon content, as measured by the C / S method, is advantageously in the range of 0 to less than 0.5%, preferably 0 to 4000 ppm, more preferably 0 to 3000 ppm, even more preferably 0 to 2000 ppm, and even more preferably 0 to 1000 ppm, based on the weight of SiO2 contained in the precipitated silica.

[0151] According to one embodiment, the precipitated silica is at least 165m 2 Preferably at least 180m / g 2 / g, more preferably at least 200m 2 It has a BET specific surface area of ​​1 / g. According to a preferred embodiment, the precipitated silica has a maximum surface area of ​​290m 2 Preferably a maximum of 280m / g 2 / g, more preferably 165m2 / g~280 m 2 It has a BET specific surface area in the range of / g.

[0152] According to another embodiment, the precipitated silica has a CTAB specific surface area of at least 155 m 2 / g, preferably at least 165 m 2 / g, more preferably at least 180 m 2 / g. According to a preferred embodiment, the precipitated silica has a CTAB specific surface area of at most 225 m 2 / g, preferably at most 220 m 2 / g, even more preferably 155 m 2 / g to 220 m 2 / g.

[0153] According to one embodiment, the precipitated silica has a d in the range of 20 nm to 200 nm, preferably 50 nm to 180 nm 50 . According to the present invention, the d 50 is measured by centrifugal sedimentation, preferably by centrifugal sedimentation in a disk centrifuge using a centrifugal photosedimentometer (CPS).

[0154] According to a particularly preferred embodiment, the precipitated silica can be obtained or obtained by the process according to the present invention as described above.

[0155] Without wishing to be bound by any particular theory, it has been found that manganese in plant ash is insoluble in basic media, i.e., it is present especially in one or more forms that cannot be dissolved by alkali metal bases having sodium such as NaOH. These include one or more manganese oxides or mixed oxides of manganese with other metals such as aluminum and / or iron. Therefore, it can be concluded that it would result in a lower value for the manganese content in the aqueous silicate solution than in the plant ash.

[0156] Furthermore, in the aqueous slurry obtained after step (II), a large amount of manganese is present, forming manganese ions (Mn 2+ and / or Mn 3+ It is thought that manganese ions exist in the aqueous liquid phase of the slurry in the form of ). According to embodiments of the present invention, when the aqueous slurry is filtered according to step (III) to obtain a filter cake, a large amount of such manganese ions are thus entrained in the liquid phase of the slurry, and thus the precipitated silica is separated from the filter cake obtained therefrom. For stronger reasons, if the filter cake is washed according to embodiments of the present invention, a certain amount of residual manganese that may be present in the filter cake, for example as a manganese salt, can be removed by washing. Therefore, without wishing to be bound by any particular theory, it can be concluded that the manganese content in precipitated silica may be lower than that in aqueous silicate solutions and plant ash.

[0157] In contrast to manganese, phosphorus is essentially present in plant ash in one or more forms that are highly soluble in aqueous basic media (e.g., hydrogen phosphates), and it can therefore be readily extracted with sodium-containing alkali metal bases such as NaOH.

[0158] Without wishing to be bound by any particular theory, it can be concluded that the presumably higher phosphorus content in aqueous silicate solutions than in plant ash according to embodiments of the present invention simply reflects the fact that phosphorus is extracted from plant ash in a better yield than Si, without any phosphorus formation. Particularly high phosphorus content in silicates can be achieved when an excess amount of plant ash (expressed as SiO2 content) is used compared to the amount of sodium-containing alkali metal base, such as NaOH.

[0159] The present invention also relates to a method for preparing a precipitated silica-filled elastomer composition, wherein the method comprises mixing at least one elastomer with precipitated silica as described above.

[0160] The present invention also relates to a precipitated silica-filled elastomer composition comprising at least one elastomer and precipitated silica as described above.

[0161] According to the present invention, precipitated silica is used as a reinforcing filler in the precipitated silica-filled elastomer composition.

[0162] Preferably, the at least one elastomer has at least one glass transition temperature of -150°C to +300°C, for example, -150°C to +20°C.

[0163] A notable non-limiting example of a suitable elastomer is a diene elastomer. For example, an aliphatic or aromatic monomer containing at least one unsaturated monomer, e.g., In particular, elastomers derived from ethylene, propylene, butadiene, isoprene, styrene, acrylonitrile, isobutylene or vinyl acetate, polybutyl acrylate, or mixtures thereof may be used. Functionalized elastomers, i.e., elastomers functionalized by chemical groups located along and / or at one or more of their ends (e.g., by functional groups that can react with the surface of SiO2 particles), and halogenated polymers may also be used. Examples include polyamides, ethylene homo- and copolymers, and propylene homo- and copolymers.

[0164] Examples of diene elastomers include polybutadiene (BR), polyisoprene (IRS), butadiene copolymers, isoprene copolymers, or mixtures thereof, particularly styrene / butadiene copolymers (SBRS, particularly ESBR (emulsion) or SSBR (solution)), isoprene / butadiene copolymers (BIR), isoprene / styrene copolymers (SIR), isoprene / butadiene / styrene copolymers (SBIR), ethylene / propylene / diene copolymers (EPDM), and related functionalized polymers (e.g., exhibiting pendant polar groups or polar groups at the chain ends that can interact with SiO2 chain particles).

[0165] Natural rubber (NR) and epoxidized natural rubber (ENR) are also examples.

[0166] The precipitated silica-filled elastomer composition can be vulcanized with sulfur (a vulcanized product is obtained at that time) or crosslinked with a peroxide or other crosslinking system (e.g., diamine or phenolic resin).

[0167] The precipitated silica-filled elastomer composition according to embodiments of the present invention may also contain at least one coupling agent and / or at least one coating agent and / or finally an antioxidant.

[0168] As coupling agents, "symmetrical" or "asymmetrical" silane polysulfides may be particularly used; more specifically, bis((C1-C4)alkoxyl(C1-C4)alkylsilyl(C1-C4)alkyl) polysulfides (especially disulfides, trisulfides, or tetrasulfides), such as bis(3-(trimethoxysilyl)propyl) polysulfide or bis(3-(triethoxysilyl)propyl) polysulfide, such as triethoxysilylpropyl tetrasulfide.

[0169] Monoethoxydimethylsilylpropyltetrasulfide is another example.

[0170] Silanes containing masked or free thiol functional groups may also be mentioned.

[0171] The coupling agent can be pre-grafted onto the elastomer. It can also be used in a free state or grafted onto the surface of SiO2 particles.

[0172] The coupling agent can be optionally combined with a suitable "coupling activator," that is, a compound that is mixed with the coupling agent to increase its effectiveness.

[0173] The amount of precipitated silica that can be used in the precipitated silica-filled elastomer composition can be within a fairly wide range. It typically represents 10% to 200% by weight, particularly 20% to 150% by weight, especially 20% to 80% by weight, for example, 30% to 70% by weight, of the amount of at least one elastomer. Alternatively, the weight percentage of precipitated silica of the present invention in the precipitated silica-filled elastomer composition may be 80% to 120% by weight, for example, 90% to 110% by weight, of the amount of at least one elastomer.

[0174] The precipitated silica described above can, advantageously, constitute all of the reinforcing inorganic fillers, or even all of the reinforcing fillers in the elastomer composition.

[0175] The precipitated silica described above can be optionally combined with at least one other reinforcing filler, for example, commercially available highly dispersible silicas such as Zeosil® 1165, Zeosil® 1115 MP, or Zeosil® 1085 MP precipitated silica (commercially available from Solvay); or with another inorganic reinforcing filler, such as alumina, or even organic reinforcing fillers, in particular carbon black (e.g., SiO2, optionally coated with an inorganic layer).

[0176] Preferably, the precipitated silica constitutes at least 50% by weight, and even as much as 80% by weight, of the total amount of the reinforcing filler.

[0177] This precipitated silica-filled elastomer composition can be used for the manufacture of tire parts. Therefore, another object of the present invention is the use of the above-described precipitated silica-filled elastomer composition for the manufacture of tire parts comprising (or possibly composed of) the said precipitated silica-filled elastomer composition.

[0178] The present invention also relates to a method for producing a tire portion comprising (possibly composed of) the precipitated silica-filled elastomer composition, the method comprising (i) mixing at least one elastomer with the precipitated silica to obtain the precipitated silica-filled elastomer composition, and (ii) molding the precipitated silica-filled elastomer composition thus obtained into a tire portion.

[0179] Another object of the present invention is the tire portion comprising (and possibly composed of) the precipitated silica-filled elastomer composition as described above. Preferably, the tire portion is a tire tread.

[0180] The present invention also relates to the use of the above-described precipitated silica-filled elastomer composition for the manufacture of a tire comprising (possibly composed of) at least one portion thereof (i.e., a tire portion according to the present invention).

[0181] The present invention also relates to a method for producing a tire comprising at least one portion (i.e., a tire portion according to the present invention) comprising (or possibly composed of) the above-described precipitated silica-filled elastomer composition, wherein the method comprises: (i) mixing at least one elastomer with the above-described precipitated silica to obtain the precipitated silica-filled elastomer composition; (ii) molding the thus obtained precipitated silica-filled elastomer composition into a tire portion comprising (or possibly composed of) the precipitated silica-filled elastomer composition; and (iii) assembling the thus molded tire portion comprising (or possibly composed of) the precipitated silica-filled elastomer composition with at least one tire portion other than the tire portion comprising (or possibly composed of) the precipitated silica-filled elastomer composition to obtain a tire.

[0182] The present invention also relates to a tire, which includes a tire portion comprising (possibly composed of) the precipitated silica-filled elastomer composition described above, and a vehicle, which includes the tire.

[0183] The present invention further relates to precipitated silica obtainable or obtained by the above process, and its use / method for the manufacture of a tire comprising (i) a precipitated silica-filled elastomer composition, (ii) a tire portion comprising (possibly composed of) the precipitated silica-filled elastomer composition and / or (iii) at least one portion comprising (possibly composed of) the precipitated silica-filled elastomer composition, as described in any of the above embodiments.

[0184] If any disclosure of a patent, patent application, or publication incorporated herein by reference conflicts with the description of this application to such an extent that it obscures certain terms, the description herein shall prevail.

[0185] The present invention is illustrated by the following embodiments, which are not intended to be limiting. [Examples]

[0186] Raw materials and methods All starting materials used in the examples are commercially available.

[0187] Example 1 Potentiometric titration method for measuring Rp The Titrando 808 was used to measure the weight ratio (Rp) [weight% (SiO2) / weight% (Na2O)]. This instrument consisted of a reference electrode (Ag / AgCl) in KCl 3M and a working electrode in tungsten. Each Rp value was measured twice (both positive and negative), and the presented Rp value is the average of the two measurements. 0.5 g of the sample was weighed and prepared with 30 mL of desalted water. The titration solution was a 0.1 N HCl solution. Volume V1 (mL) was measured as the equivalent volume for the titration. After weighing, 0.5 mL of the titration solution was added. Subsequently, 50 mL of KF solution (50 g / l KF solution in water / ethanol (50 / 50)) was added and the mixture was allowed to react for 3 minutes. Then, 15 mL of 0.1 N HCl solution was added. The excess HCl was titrated with 1 N NaOH solution, and volume V2 (mL) was the equivalence point of the titration. Next, Rp was calculated according to the following formula: Rp=(0.31*V1) / (1.5(15*1-V2*1)+(0.5*0.1))

[0188] Assay purity analysis for measuring SiO2 content A 1g sample was burned at 1000°C for 1 hour in a tare-covered platinum dish, cooled in a desiccator, and weighed. The resulting solid was moistened with water, and 10mL of hydrofluoric acid was added gradually. The mixture was then evaporated to dryness in a steam bath and cooled. 10mL of hydrofluoric acid and 0.5mL of sulfuric acid were slowly added until all the acid had evaporated. The sample was then burned at 1000°C, cooled in a desiccator, and weighed. The ratio of the difference between the final weight and the weight of the initially burned portion to the weight of the original sample represented the weight percentage of SiO2.

[0189] Carbon-sulfur analysis (C / S method) for measuring carbon content A 200 mg sample was analyzed using a Horiba EMIA 320-V2. Lecocel®, iron, and tin balls were used as combustion accelerators. CS26-3.19% was used to calibrate the sensor.

[0190] Possible pretreatments for precipitated silica If the precipitated silica is in a highly aggregated form such as granules, pretreatment is performed to deaggregate the granules in order to obtain a precipitated silica sample in powder form, before applying the CTAB surface area measurement method. Precipitated silica samples in the form of highly aggregated particles, particularly granular particles, were smoothly ground using a hand agate mortar and pestle, applying smooth pressure and friction by hand to cause the breakdown of aggregates and other lumps contained therein. The grinding was carried out for a sufficient duration to allow the sample to acquire a visually uniform consistency that was that of a powder; this duration was typically several tens of seconds and did not usually exceed one minute. If the precipitated silica is in the form of a powder or micropearls, such pretreatment is not necessary.

[0191] N-hexadecyl-N,N,N-trimethylammonium bromide (CTAB) method for measuring specific surface area CTAB surface area (S CTAB The values ​​were measured according to the following method derived from the standard NF ISO 5794-1, Appendix G. This method is based on the adsorption of CTAB on the "outer" surface of SiO2 particles. In this method, CTAB was adsorbed onto precipitated silica under magnetic stirring. The precipitated silica and residual CTAB solution were then separated. The excess, unadsorbed CTAB was measured by back titration with sodium bis(2-ethylhexyl) sulfosuccinate (hereinafter referred to as "AOT") using a titroprocessor, with the endpoint given by the maximum turbidity of the solution, measured using an optrode.

[0192] Device: Metrohm Optrode (wavelength: 520nm) connected to a 662 Metrohm photometer; Metrohm Titrator: Titrino DMS 716; Metrohm titration software: Tiamo. Glass beaker (2000mL); volumetric flask (2000mL); sealed glass bottles (1000 and 2000mL); disposable beaker (100mL); micropipette (500-5000μL); magnetic stirring rod with 25mm disk end for adsorption (Ref VWR 442-9431); magnetic stirring rod for titration (straight); polycarbonate centrifuge tube (at least 20mL), centrifuge (capable of 10000rpm speed); glass vial (30mL); thermobalance.

[0193] Solution preparation - Preparation of CTAB solution at 5.5 g / L (buffered at approximately pH 9.6). In a 2000 mL beaker containing approximately 1000 mL of distilled water at 25°C, 54.25 g of boric acid solution ([c]=4%), 2.60 g of KCl, and 25.8 mL (±0.1 mL) of sodium hydroxide were added. The resulting solution was stirred for 15 minutes, after which 11.0 g ± 0.01 g of CTAB powder (99.9% purity, purchased from Merck) was added. After stirring, the solution was transferred to a 2000 mL volumetric flask kept at 25°C, and the volume was increased to 2000 mL with distilled water. The solution was then transferred to a 2000 mL glass bottle and kept at a temperature not lower than 22°C to avoid CTAB crystallization (which occurs at 20°C). - Preparation of AOT solution. Approximately 1200 mL of distilled water in a 2000 mL beaker was heated to 35°C under magnetic stirring. 3.7038 g of AOT (98% purity, purchased from Aldrich) was added. The solution was then transferred to a 2000 mL volumetric flask and cooled to 25°C. The volume was increased to 2000 mL with distilled water, and the solution was transferred to two 1000 mL glass bottles, which were stored in a dark place at 25°C. All equipment and solutions were kept at 25°C throughout the analysis.

[0194] Procedures for the start and end of each experiment Experiment Start: The solution was stirred before use. The injection device was purged before use. At least 40 mL of AOT was passed through the device to ensure that the device was clean and all air bubbles were removed. Experiment complete: The injector was purged to remove the AOT solution. The optorode was cleaned and immersed in distilled water.

[0195] Measurement of Blank Factor The temporal variations in AOT and CTAB solution concentrations were corrected by measuring a ratio called the "blank factor" per day, R1 = V1 / m1. 4.9000g ± 0.0100g of 5.5g / L CTAB solution (m1) was accurately weighed into a 100mL disposable beaker. Tare was taken, and 23.0000g ± 1.0000g of distilled water (M) was added. WATER The solution was added precisely. The solution was placed on the injection device under stirring using a magnetic stirrer at 500 rpm, and the titration was started. The stirring speed must be kept strictly stable throughout the titration without generating too many bubbles. V1 is the endpoint volume of AOT solution required to titrate ml of CTAB solution. R1 measurements should be performed using at least two methods: primary and secondary. If the standard deviation of R1 = V1 / m1 exceeds 0.010, the titration should be repeated until the standard deviation is 0.010 or less. The daily ratio R1 should be calculated as the average of two or three measurements. The optorode must be washed with distilled water after every measurement and dried on absorbent paper.

[0196] CTAB adsorption on precipitated silica The water content (%H2O) of each precipitated silica sample was measured using a thermobalance (temperature: 160°C) before the adsorption step as follows: Tare the balance with aluminum cups; weigh approximately 2 g of precipitated silica, spread the powder evenly on the cups, close the balance; and record the water content. 0.0100 g of precipitated silica (m0) was accurately weighed into a 100 mL disposable beaker. Then, 50.0000 mL + 1.0000 mL of CTAB stock solution (V0) were added. The total mass was recorded. The suspension was stirred for 40 minutes ± 1 minute on a stirring plate at 450 rpm using a magnetic stirrer with a disk end. After 40 minutes, the sample was removed from the stirring plate. Next, 25–50 mL of the suspension was transferred to a centrifuge tube (volume depending on the size of the centrifuge tube), and these were centrifuged at 10,000 rpm at 25°C for 35 minutes. After centrifugation, the tube was slowly removed from the centrifuge without destabilizing the precipitated silica. 10–20 mL of the CTAB solution was transferred to a glass vial, then capped and kept at 25°C.

[0197] Titration of CTAB solution In a 100 mL disposable beaker, 4.0000 g ± 0.0100 g of CTAB solution (m2) at an unknown concentration was accurately weighed. After tare, 19.4000 g ± 1.0000 g of distilled water (M2) was added. WATER ) was added. This solution was placed on an injection device under stirring at 500 rpm, and titration with the AOT solution was started. V2 is the endpoint volume of AOT required to titrate m2 of the CTAB solution. CTAB surface area S CTAB It is calculated as follows:

number

[0198] Measurement of specific surface area BET surface area S BET The following measurements were taken according to the Brunauer-Emmett-TellerBET) method as detailed in NF ISO 5794-1, Appendix E (June 2010), with the following adjustments: the sample was pre-dried at 160°C ± 10°C; and the partial pressure P / P used for the measurement was... 0 The values ​​ranged from 0.05 to 0.2.

[0199] Measurement of particle size distribution and particle size by centrifugal sedimentation using a disk centrifuge with a centrifugal photometer (CPS). d 50 d 16 d 84 The values ​​of FWHM and Ld were measured by centrifugal sedimentation using a disk centrifuge with a centrifugal optical sedimentation velocometer, "CPS DC 24000UHR," sold by CPS Instruments. This instrument comes with operating software (operating software version 11g) supplied with the device. Instruments used: For measurement requirements, the following materials and products were used: Ultrasonic system: 1500W generator type Sonics Vibracell VC1500 / VCX1500 with 19mm probe (converter: CV154 + booster (part number: BHNVC21) + 19mm probe (part number: 630-0208)). Analytical balance with 0.1 mg accuracy (e.g., Mettler AE260); syringes: 1.0 ml and 2.0 ml with 20 ga needles; 50 ml high-profile glass beaker (SCHOTT DURAN: 38 mm diameter, 78 mm height); magnetic stirrer with 2 cm stirring bar; container for ice bath during ultrasonic treatment. Chemicals: Deionized water; 96% ethanol; 99% sucrose; dodecane, all manufactured by Merck; PVC reference standard manufactured by CPS Instrument Inc.; The peak maximum value of the reference standard used should be between 200 and 600 nm (e.g., 237 nm).

[0200] Preparation of a disk centrifuge The following parameters were determined for the measurements (see Table 1). For the calibration standard parameters, we used the PVC standard information provided by the supplier.

[0201] [Table 1]

[0202] System Configuration The measurement wavelength was set to 405 nm. The following runtime option parameters were determined (Table 2):

[0203] [Table 2]

[0204] All other software options remain as configured by the instrument manufacturer.

[0205] Preparation of a disk centrifuge Rotate the centrifugal disk at 24,000 rpm for 30 minutes. Prepare the density gradient of sucrose (CAS number 57-50-1) as follows: Prepare a 24 wt% aqueous solution of sucrose in a 50 mL beaker. Prepare an 8 wt% aqueous solution of sucrose in a 50 mL beaker. Immediately after homogenizing these two solutions separately, take samples from each solution using a 2 mL syringe and inject them into the rotating disk in the following order: Sample 1: 1.8 mL of 24 wt% solution Sample 2: 1.6 mL of 24 wt% solution + 0.2 mL of 8 wt% solution Sample 3: 1.4 mL of 24 wt% solution + 0.4 mL of 8 wt% solution Sample 4: 1.2 mL of 24 wt% solution + 0.6 mL of 8 wt% solution Sample 5: 1.0 mL of 24 wt% solution + 0.8 mL of 8 wt% solution Sample 6: 0.8 mL of 24 wt% solution + 1.0 mL of 8 wt% solution Sample 7: 0.6 mL of 24 wt% solution + 1.2 mL of 8 wt% solution Sample 8: 0.4 mL of 24 wt% solution + 1.4 mL of 8 wt% solution Sample 9: 0.2 mL of 24 wt% solution + 1.6 mL of 8 wt% solution Sample 10: 1.8 mL of 8 wt% solution.

[0206] Before each injection into the disc, add approximately 0.2 mL of air, then homogenize the two solutions in the syringe by a brief manual agitation for a few seconds, taking care not to lose any liquid.

[0207] With a total volume of 18 mL, these injections aim to create a density gradient useful for eliminating certain instabilities that may occur during the injection of the sample to be measured. To protect the density gradient from evaporation, 1 mL of dodecane is added to the rotating disk using a 2 mL syringe. The disk is then rotated at 24,000 rpm for 60 minutes before any first measurement.

[0208] Sample preparation Samples were prepared and analyzed according to the current protocol, namely: PE=3.2g / 40ml H2O- suspension was subjected to ultrasound at 1500W for 8 minutes in a refrigerated environment (ice bath), a 100μL sample was taken, the disk was rotated at 24000rpm, and the analysis time was 20-25 minutes. 3.2 g of precipitated silica was weighed into a 50 mL high-profile glass beaker (SCHOTT DURAN: 38 mm diameter, 78 mm height), and 40 mL of deionized water was added to obtain an 8 wt% suspension of precipitated silica. The suspension was stirred with a magnetic stirrer (for a minimum of 20 seconds) before placing the beaker in a crystallization dish filled with ice and cold water. The magnetic stirrer was removed, and the crystallization dish was placed under an ultrasonic probe positioned 1 cm from the bottom of the beaker. The ultrasonic probe was set to 56% of its maximum amplitude and activated for 8 minutes. At the end of the sonication, the beaker was again placed on a magnetic stirrer with a 2 cm magnetic stirring bar, which was stirred at a minimum of 500 rpm until after sampling. The ultrasonic probe should be in proper operating conditions. At least one, preferably both, of the following inspections should be performed: (i) Visual inspection of the physical integrity of the probe end (roughness depth less than 2 mm as measured with a fine caliper); (ii) Measurement of commercially available Zeosil® 1165MP precipitated silica 50 The probe should be checked to ensure it is 93nm ± 3nm. If the result is negative, a new probe should be used.

[0209] analysis Before analyzing each sample, the calibration standard was recorded. In each case, 0.1 mL of a PVC standard provided by CPS Instruments, whose characteristics were pre-entered into the software, was injected. It is important to start the measurement in the software simultaneously with this initial injection of the PVC standard. To ensure that the measurement starts simultaneously with the injection, the instrument must be checked before injecting 100 μL of the pre-sonicated sample. These injections were performed using two clean 1 mL syringes. At the end of the measurement, when the time required to settle all particles smaller than 0.02 μm (configured as 0.02 μm in the software) was reached, a ratio was obtained for each diameter class. The resulting curve is called the aggregate size distribution.

[0210] result value d 50 d 16 d 84 And Ld are based on the distribution drawn on a straight ruler. Integrating the particle size distribution function with respect to diameter makes it possible to obtain the "cumulative" distribution, i.e., the total mass of particles between the minimum diameter and the diameter of interest. d 50 : This is the diameter below and above which 50% of the population of SiO2 particles are found. 50 This is called the median size, and it is the median diameter of the precipitated silica. d 84 : This is the diameter below which 84% of the particle's total mass is measured. d 16 : This is the diameter below which 16% of the particle's total mass is measured. Ld:Equation:Ld=(d 84 -d 16 ) / d 50 It is calculated according to [the formula].

[0211] Measurement of pore volume and pore diameter by mercury (Hg) porosimetry Pore ​​volume and pore size distribution were measured using a Micromeritics AutoPore® IV 9520 porosimeter; they were calculated using the Washburn relation between a contact angle theta equal to 140° and a surface tension gamma equal to 485 dynes / cm. Each sample was dried in an oven at 200°C for 2 hours at atmospheric pressure before measurement. The starting weight of the precipitated silica placed in a Type 10 penetrometer with an accuracy of 0.001 g was selected for good reproducibility of the measurement, such that the "stem volume used," i.e., the percentage mercury (Hg) volume consumed for filling the penetrometer, was between 40% and 80%. The penetrometer was then slowly evacuated to 50 μm Hg and held at this pressure for 5 minutes. The AutoPore® apparatus was operated using software version IV 1.09. No corrections were made to the raw data. The measurement range was 3.59 kPa (0.52 psi) to 413685 kPa (60000 psi), and at least 100 measurement points were used (19 measurement points from 3.59 kPa (0.52 psi) to 193 kPa (28 psi) with a 10-second equilibrium time, and then 81 points from 1.93 kPa (0.28 psi) to 413685 kPa (60000 psi) with a 20-second equilibrium time). Where appropriate, if the gradually increasing inflation volume was greater than 0.5 mL / g, the software introduced additional measurement points. The inflation curve was smoothed by the "smooth derivative" function of the apparatus software. Log differential intrusion (mL / g) for pore diameter data was analyzed in the pore diameter range of 3.5 nm to 5 μm.

[0212] Example 1 - Precipitated silica pre-sand (comparative) A control precipitate of silica was prepared from sodium silicate obtained from sand. The properties (impurity profile and elemental composition) of the sodium silicate (S0) used for this reaction are shown in Table 3 below. The Rp value of sodium silicate was obtained by the potentiometric measurement method described above. 17 L of purified water and 0.260 kg of sodium sulfate (S0) were introduced into a 25 L stainless steel reactor. The resulting solution was heated to 92°C. The entire reaction was carried out at this temperature. 80 g / L of sulfuric acid was introduced under stirring (350 rpm, using a TT Mixel) until the pH reached 4.1. A sodium silicate solution with a weight ratio of SiO2 / Na2O equal to 3.5 and a concentration of 230 g / L, and sulfuric acid with a concentration equal to 80 g / L were simultaneously introduced into the reactor over a period of 10 minutes. During this time, the sodium silicate solution was introduced at a flow rate of 107 g / min, and the sulfuric acid was introduced at a flow rate adjusted to maintain the pH of the reaction medium at the value of 4.1. After 10 minutes, the sodium silicate flow rate was kept constant. 80 g / L sulfuric acid was replaced with sulfuric acid at a concentration of 1710 g / L over a period of 16 minutes at a flow rate that allowed the pH of the reaction medium to be maintained at 4.1. Next, the addition of sulfuric acid was stopped. Sodium silicate was introduced at a flow rate of 107 g / min as long as the pH of the reaction medium remained below 8.0. Next, the pH of the reaction medium was maintained at 8.0 for 18 minutes by the simultaneous addition of sodium silicate at a flow rate of 167 g / min and sulfuric acid at a controlled flow rate that allowed the pH to be maintained, at a concentration of 1710 g / L. Finally, at the end of this simultaneous addition, the pH of the reaction medium was adjusted to 4.0 by adding sulfuric acid at a concentration of 1710 g / L. The medium was aged at this pH for 10 minutes. The slurry obtained in this way was filtered and washed through a filter press (20% dry cake extract). Next, the resulting cake was mechanically broken up, and the resulting slurry was dried using a spray dryer. The properties of the precipitated silica (precipitated silica P0) obtained in this way are shown in Tables 3 and 4 below.

[0213] Example 2 - Pre-washed RHA with precipitated silica (comparison) A control precipitate of silica was prepared from sodium silicate obtained from washed rice husk ash (RHA) (pre-washed sodium silicate).

[0214] Initial RHA characteristics: The following characteristics were used in the use of rice husk ash (RHA): - The SiO2 concentration was measured by the ASSAY purity method described above: 88.3% by weight relative to the total sample; - Carbon content was analyzed by the C / S ratio as described above: 4.9% by weight relative to the total sample.

[0215] RHA washing: 1000 g of sulfuric acid solution at a concentration of 0.05 wt% and 50 g of RHA were introduced into a reactor under stirring. The mixture was kept under stirring and heated to 70°C for 30 minutes. After 30 minutes, the RHA and acidic water mixture were separated by Büchner filtration to concentrate the solid before dissolution.

[0216] RHA dissolution: The following reagents were introduced into a 5L stainless steel 316L autoclave reactor: - 290 g of soda solution with a concentration of 397 g / L; - 1164g of RHA, and - 2560g of desalinated water. The reaction mixture was kept agitated at 500 rpm using a TT Mixel stirrer. Next, the temperature of the mixture was raised to 160°C using a double jacket and maintained for 3 hours. Immediately after the reaction was complete, solid / liquid separation was performed by centrifugation. The centrifuged product was diluted to the desired SiO2 concentration and density. The diluted product corresponds to sodium silicate S1, which is used for the subsequent silica precipitation step as described below. The properties (elemental composition) of pre-RHA washed sodium silicate (S1) are shown in Table 3 below. The Rp of this sodium silicate was analyzed using the potentiometric measurement method described above.

[0217] Silica precipitation: 17 L of purified water and 0.260 kg of sodium sulfate S1 were introduced into a 25 L stainless steel reactor. The solution was heated to 92°C. The entire reaction was carried out at this temperature. 80 g / L of sulfuric acid was introduced under stirring (350 rpm, TT Mixel stirring) until the pH reached 4.1. A sodium silicate solution with a weight ratio of SiO2 / Na2O equal to 3.5 and a concentration of 230 g / L, and sulfuric acid with a concentration equal to 80 g / L were simultaneously introduced into the reactor over a period of 10 minutes. The sodium silicate solution was introduced at a flow rate of 107 g / min, and the sulfuric acid was introduced at a flow rate adjusted to maintain the pH of the reaction medium at 4.1. After 10 minutes, the sodium silicate flow rate was kept constant. 80 g / L sulfuric acid was replaced over 16 minutes with the introduction of 1710 g / L sulfuric acid at a flow rate that maintained the pH of the reaction medium at 4.1. Next, the addition of sulfuric acid was stopped. Sodium silicate was introduced at a flow rate of 107 g / min until the pH of the reaction medium reached 8.0. Next, the pH of the reaction medium was maintained at 8.0 for 18 minutes by the simultaneous addition of sodium silicate at a flow rate of 167 g / min and sulfuric acid at a controlled flow rate that allowed the pH to be maintained, at a concentration of 1710 g / L. Finally, at the end of this simultaneous addition, the pH of the reaction medium was adjusted to 4.0 by adding sulfuric acid at a concentration of 1710 g / L. The medium was aged at this pH for 10 minutes. The slurry obtained in this way was filtered and washed through a filter press (20% dry cake extract). Next, the resulting cake was mechanically broken up, and the resulting slurry was dried using a spray dryer. The properties of the precipitated silica (precipitated silica P1) obtained in this way are shown in Tables 3 and 4 below.

[0218] Example 3 - Precipitated silica unwashed RHA The precipitated silica according to the present invention was produced from sodium silicate (pre-RHA sodium silicate) obtained from unwashed rice husk ash (RHA).

[0219] Initial RHA characteristics: The following characteristics were used in the use of rice husk ash (RHA): - The SiO2 concentration was measured by the ASSAY purity method as described above: 88.1% by weight relative to the total sample; - Carbon content was analyzed by the C / S ratio as described above: 11% by weight relative to the total sample.

[0220] RHA dissolution: The following reagents were introduced into a 20L stainless steel 316L autoclave reactor: - 1682g of soda solution with a concentration of 397g / L; - 3700g of RHA, and - 4628g of desalinated water. The reaction mixture was kept under agitation at 800 rpm using a TT Mixel stirrer. Next, the temperature of the mixture was raised to 160°C using a double jacket and maintained for 3 hours. Immediately after the reaction was complete, solid / liquid separation was performed by centrifugation. The centrifuged product was diluted to the desired SiO2 concentration and density. The diluted product corresponds to sodium silicate S2, which is used for the subsequent silica precipitation step as described below. The properties (elemental composition) of unwashed RHA sodium silicate (S2) are shown in Table 3 below. The Rp of this sodium silicate was analyzed using the potentiometric measurement method described above.

[0221] Silica precipitation: 17 L of purified water and 0.260 kg of sodium sulfate (S2) were introduced into a 25 L stainless steel reactor. The solution was heated to 92°C. The entire reaction was carried out at this temperature. 80 g / L of sulfuric acid was introduced under stirring (350 rpm, TT Mixel stirring) until the pH reached 4.1. A sodium silicate solution with a weight ratio of SiO2 / Na2O equal to 3.5 and a concentration of 230 g / L, and sulfuric acid with a concentration equal to 80 g / L were simultaneously introduced into the reactor over a period of 10 minutes. The sodium silicate solution was introduced at a flow rate of 107 g / min, and the sulfuric acid was introduced at a flow rate adjusted to maintain the pH of the reaction medium at 4.1. After 10 minutes, the sodium silicate flow rate was kept constant. 80 g / L sulfuric acid was replaced with sulfuric acid at a concentration of 1710 g / L over a period of 16 minutes at a flow rate that allowed the pH of the reaction medium to be maintained at 4.1. Next, the addition of sulfuric acid was stopped. Sodium silicate was introduced at a flow rate of 107 g / min, as long as the pH of the reaction medium remained below 8.0. Next, the pH of the reaction medium was maintained at 8.0 for 18 minutes by the simultaneous addition of sodium silicate at a flow rate of 167 g / min and sulfuric acid at a controlled flow rate that allowed the pH to be maintained, at a concentration of 1710 g / L. Finally, at the end of this simultaneous addition, the pH of the reaction medium was adjusted to 4.0 by adding sulfuric acid at a concentration of 1710 g / L. The medium was aged at this pH for 10 minutes. The slurry obtained in this way was filtered and washed through a filter press (20% dry cake extract). Next, the resulting cake was mechanically broken up, and the resulting slurry was dried using a spray dryer. The properties of the precipitated silica (precipitated silica P2) obtained in this way are shown in Tables 3 and 4 below.

[0222] Example 4 The following table (Table 3) reports the impurity profiles and elemental compositional properties of the pre-sand sodium silicate (S0), pre-RHA washed sodium silicate (S1), and unwashed pre-RHA sodium silicate (S2) used in Examples 1-3. The impurity profiles and elemental compositional properties of the corresponding precipitated silica (P0, P1, and P2) produced by Examples 1-3 are also reported. Unless otherwise specified, the quantities in Table 3 are in ppm units. The amount in precipitated silica is based on the total weight of precipitated silica. In Table 3, the symbol * indicates that the amount in the silicate solution is based on the total weight of the silicate solution. The symbol ** indicates that the amount in the silicate solution is based on the weight of SiO2. From this table, it can be understood that the absence of the washing step primarily affects the amounts of Mn and P.

[0223]

Table 3

[0224] The properties of the precipitated silica produced according to the above Examples 1 to 3 are reported in the following table (Table 4).

[0225]

Table 4

[0226] Example 5 - Rubber Application Performance Preparation of a rubber composition suitable for the preparation of a tire or tire part: The process of preparing the rubber composition (i.e., the precipitated silica-filled elastomer composition) was carried out in three successive stages. The first and second mixing stages (non-production stages, NP1 and NP2) consisted of a thermo-mechanical operation at high temperature followed by a third mechanical stage (production stage, P3) at a temperature below 110 °C. The latter enabled the introduction of the vulcanization system. The first and second stages were carried out by means of an internal mixer from Brabender (net chamber volume 380 mL) having filling rates of 0.62 and 0.6, respectively. The initial temperature and speed of the kneader were fixed each time so as to reach a mixing drop temperature of about 140 - 170 °C. The duration of the first mixing stage was 2 - 10 minutes. After cooling of the mixture (temperature below 100 °C), the second mixing stage enabled the introduction of the vulcanization system (sulfur and accelerator). It was carried out on an open two-roll mill preheated to 50 °C.

[0227] The duration of this stage was 2 - 6 minutes. Subsequently, the final rubber composition was calendered into sheets with a thickness of 2 - 3 mm. In Table 5, the amounts of the individual components of the composition are expressed as phr (per hundred rubbers), i.e., they are based on the total amount of rubber contained in the rubber formulation (here sSBR + BR).

[0228] [Table 5]

[0229] SSBR with 21% styrene and 49% vinyl functionalization (Sprintan SLR 4602 from Synthos) BR: Arlanxeo beech CB 25 TESPT: Bis-triethoxysilylpropyl-tetrasulfide, manufactured by Evonik Si69 N330: Carbon Black TDAE (Processed Distilled Aromatic Extract) Vivatec 500 by Hansen & Rosenthal KG 6-PPD: N-(1,3-dimethylbutyl)-N-phenyl-para-phenylenediamine (Santoflex 6-PPD manufactured by Flexsys) CBS: N-Cyclohexyl-2-benzothiadyl sulfenamide (Rhenogran CBS-80 manufactured by RheinChemie) DPG: Diphenylguanidine (Rhenogran DPG-80 manufactured by RheinChemie)

[0230] The rheological properties of the uncured compound were evaluated to monitor processability. After measuring the vulcanization properties, the uncured compound was vulcanized at optimal vulcanization (T98), and its mechanical and dynamic properties were measured.

[0231] Viscosity of the uncured composition Mooney viscosity was measured at 100°C using an MV200 rheometer according to the NF ISO289 standard. After a 1-minute preheating, torque values ​​were read at 4 minutes (ML1+4-100°C). From the curve of torque variation as a function of time, the following was determined: - Minimum torque (Tmin), reflecting the viscosity of the composition at the temperature under consideration; - Maximum torque (Tmax); - Delta torque (ΔT = Tmax - Tmin) reflects the degree of crosslinking brought about by the action of the crosslinking system and, if necessary, the coupling agent; - T.90%, corresponding to the time required to reach 90% of the maximum torque; - Scorch time TS2 (the mixture hardens from TS2) that corresponds to the time required to rise 2 points above the minimum torque at the temperature under consideration, and reflects the time during which the raw mixture can be processed at this temperature without initiating vulcanization. The results obtained are shown in Table 6.

[0232] Mechanical properties of cured compositions The Shore A hardness of the cured composition was measured according to the ASTM D2240 standard (vulcanization time T98 at 160°C). The value was measured after 3 seconds. Uniaxial tensile testing was performed using an INSTRON 5564 with H2 specimens at a speed of 500 m / min, according to the NF ISO37 standard. The modulus of elasticity M100 and M300 (obtained at 100% and 300% strain, respectively) and tensile strength (TS) are expressed in MPa; elongation at fracture (EB) is expressed in %. The strengthening index (RI), defined as the ratio between the modulus of elasticity obtained at 300% strain and the modulus of elasticity obtained at 100% strain, is calculated. The measured characteristics are reported in Table 7.

[0233] Dynamic properties of cured composition Dynamic properties were measured using a viscometer (METRAVIB DMA+1000) according to ASTM D5992. Dynamic response of cured compound under strain sweeping conditions Parallelepiped specimen (cross-section 8mm) 2, with a height of 4 mm, was subjected to sinusoidal deformation by alternating two-plane shear at a temperature of 40 °C and a frequency of 10 Hz according to cycle reciprocations in the range of 0.1% to 50% for the forward cycle and 50% to 0.1% for the return cycle. The values of the maximum loss factor (Tan δmax), the shear storage modulus (G’0.1% and G*12%), and the Payne effect (G’0.1% - G50%) were recorded during the return cycle. The measured properties are reported in Table 8.

[0234] Dynamic Response of the Cured Composition under Temperature Sweep Conditions The dynamic response of the vulcanized rubber composition was measured by subjecting a parallelepiped specimen (cross-sectional area 8 mm 2 and height 7 mm) to a temperature sweep from -70 °C to 100 °C (+5 °C / min temperature increase rate) under 1% alternating two-plane shear sinusoidal deformation and at a frequency of 10 Hz. Then, the maximum loss factor (Tan δmax) was measured.

[0235] [Table 6]

[0236] [Table 7]

[0237] [Table 8]

[0238] The above results demonstrate that the rubber composition containing precipitated silica obtained by the process according to the present invention (i.e., pre-RHA unwashed) advantageously exhibits mechanical and dynamic properties similar to those of the rubber composition containing precipitated silica obtained by pre-washing rice husk ash (i.e., pre-RHA washed).

Claims

1. A process for producing precipitated silica from plant ash, wherein the process is: (I) SiO ２ And the SiO contained in the aforementioned plant ash ２ Based on the weight of (i) SiO in the form of silicate anions, plant ash containing at least 10 ppm of manganese by weight, expressed as elemental manganese. ２ (ii) SiO contained in the silicate solution ２ To obtain an aqueous silicate solution containing at least 10 ppm of manganese by weight, expressed as elemental manganese, based on the weight of the silicate, the step of reacting it with an alkali metal base, preferably an alkali metal hydroxide, in an aqueous reaction medium at a temperature of at least 100°C, and, (II) SiO ２ Achieves precipitation of particulate SiO ２ And the SiO contained in the aqueous slurry ２ To produce the aqueous slurry containing, based on the weight of, at least 10 ppm of manganese by weight, expressed as elemental manganese, the steps are to react the silicate aqueous solution with an acidifying agent in an aqueous reaction medium having a pH greater than 7.0 for at least a portion of the duration of the reaction at a temperature of at least 40°C. Includes, The process optionally further comprises, prior to step (I), burning the plant and / or plant part containing, on the basis of the weight of SiO ２ ２ and SiO ２ ２ contained in the plant and / or plant part, at least 10 ppm of manganese, expressed as elemental manganese, in an amount by weight, to obtain plant ash.

2. The process according to claim 1, The process further includes step (A), The process described above does not include any step (B) after step (A) and before step (I) that removes some or all of the manganese and, if present, some or all of the phosphorus from the plant ash. A process which does not include any step (B') prior to step (A) which removes some or all of the manganese and, if present, some or all of the phosphorus from the plant and / or part of the plant.

3. The aforementioned plant ash contains SiO ２ The process according to claim 1 or 2, wherein the material contains manganese by weight, expressed as elemental manganese, at least 500 ppm, more preferably at least 1000 ppm, and most preferably at least 2000 ppm, based on the weight of the material.

4. The aforementioned plant ash contains SiO ２ The process according to any one of claims 1 to 3, comprising manganese by weight, expressed as element manganese, at most 15,000 ppm, preferably at most 12,000 ppm, more preferably at most 9,000 ppm, even more preferably at most 7,000 ppm, even more preferably at most 5,000 ppm, and most preferably at most 3,500 ppm, based on the weight of the product.

5. The silicate aqueous solution contains SiO ２ The process according to any one of claims 1 to 4, comprising containing manganese by weight, expressed as elemental manganese, at least 10 ppm, preferably at least 30 ppm, preferably at least 50 ppm, based on the weight of the material.

6. The silicate aqueous solution contains SiO ２ The process according to any one of claims 1 to 5, comprising manganese by weight, expressed as element manganese, at most 500 ppm, preferably at most 375 ppm, more preferably at most 250 ppm, even more preferably at most 200 ppm, even more preferably at most 150 ppm, and most preferably at most 100 ppm, based on the weight of the product.

7. The aforementioned plant ash contains SiO ２ The process according to any one of claims 1 to 6, wherein the product contains phosphorus in an amount expressed as elemental phosphorus, which is at least 500 ppm, preferably at least 1000 ppm, more preferably at least 1500 ppm, even more preferably at least 1650 ppm, at least 1700 ppm, or at least 1750 ppm, based on the weight of the product.

8. The aforementioned plant ash contains SiO ２ The process according to any one of claims 1 to 7, wherein the product contains phosphorus in an amount expressed as elemental phosphorus, which is at most 5,000 ppm, preferably at most 3,500 ppm, more preferably at most 3,000 ppm, even more preferably at most 2,500 ppm, and most preferably at most 2,000 ppm, based on the weight of the product.

9. The silicate aqueous solution contains SiO ２ The process according to any one of claims 1 to 8, comprising a weight of phosphorus, expressed as elemental phosphorus, in an amount of at least 500 ppm, preferably at least 1000 ppm, more preferably at least 1500 ppm, even more preferably at least 1650 ppm, at least 1700 ppm, or at least 1750 ppm, even more preferably at least 2000 ppm, and most preferably at least 2500 ppm, based on the weight of the product.

10. The silicate aqueous solution contains SiO ２ The process according to any one of claims 1 to 9, comprising containing phosphorus by weight, expressed as elemental phosphorus, at a maximum of 5000 ppm, preferably at a maximum of 3500 ppm, and more preferably at a maximum of 3000 ppm, based on the weight of the product.

11. (III) Particulate SiO ２ To obtain a filter cake containing, preferably using a filter press, the aqueous slurry obtained after step (II) is filtered, (IV) Optionally, the step of washing the filter cake with a liquid containing water, (V) By adding a water-containing liquid to the filter cake, and optionally by further subjecting the filter cake to mechanical and / or chemical treatment, particulate SiO ２ The steps include liquefying the filter cake into a fluid aqueous suspension containing, (VI) In order to obtain the precipitated silica, preferably by drying the fluid aqueous suspension using a spray dryer, The process according to any one of claims 1 to 10, further comprising:

12. The process according to claim 11, wherein it does not include any step (B'') after step (VI) of removing some or all of the manganese and, if present, some or all of the phosphorus from the precipitated silica.

13. The precipitated silica produced in this way is a particulate SiO ２ And the SiO contained in the precipitated silica ２ The process according to any one of claims 1 to 12, comprising manganese by weight, expressed as elemental manganese in a range of 10 ppm to 75 ppm based on the weight of [the specified amount].

14. Particulate SiO ２ And the SiO contained in the precipitated silica ２ Precipitated silica containing manganese by weight, expressed as elemental manganese in a range of 10 ppm to 75 ppm, based on the weight of the silica.

15. The SiO contained in the aforementioned precipitated silica ２ The precipitated silica according to claim 14, which contains manganese by weight, expressed as elemental manganese, at least 15 ppm, preferably at least 18 ppm, based on the weight of the precipitate.

16. The SiO contained in the aforementioned precipitated silica ２ The precipitated silica according to claim 14 or 15, containing manganese by weight, expressed as elemental manganese, at a maximum of 50 ppm, preferably at a maximum of 30 ppm, and more preferably at a maximum of 25 ppm, based on the weight of the precipitated silica.

17. The SiO contained in the aforementioned precipitated silica ２ The precipitated silica according to any one of claims 14 to 16, containing phosphorus by weight, expressed as elemental phosphorus, in an amount of at least 10 ppm, preferably at least 15 ppm, more preferably at least 20 ppm, and even more preferably at least 23 ppm, based on the weight of the precipitated silica.

18. The SiO contained in the aforementioned precipitated silica ２ The precipitated silica according to any one of claims 14 to 17, containing phosphorus by weight, expressed as elemental phosphorus, in an amount of at most 300 ppm, preferably at most 100 ppm, more preferably at most 50 ppm, and even more preferably at most 30 ppm, based on the weight of the precipitated silica.

19. Use of precipitated silica according to any one of claims 14 to 18 for the manufacture of (i) a precipitated silica-filled elastomer composition, (ii) a tire portion comprising the precipitated silica-filled elastomer composition, and (iii) at least one portion comprising the precipitated silica-filled elastomer composition.

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