ENERGY-EFFICIENT SOLVENT-FREE PROCESS FOR ORGANOSILANIZATION OF SILICATE AND SILICON DIOXIDE MATERIALS

Description

[0001] The invention relates to a process for the organosilanization of silicon dioxide and / or inorganic silicates, a process for producing a rubber compound, a process for producing a vulcanizate or rubber product comprising the vulcanizate, and the use of a grinding device for energy-efficient, solvent-free organosilanization.

[0002] Furthermore, a composition comprising at least one organosilanized compound, a rubber mixture comprising a corresponding composition, a vulcanizate, manufactured or producible by vulcanization of this rubber mixture, and a rubber product comprising the corresponding vulcanizate are disclosed.

[0003] The subject matter of the invention is defined in the attached claims.

[0004] The automotive industry is among the sectors that have faced fundamental challenges since the beginning of the 21st century, while simultaneously being shaped by numerous technological innovations. Growing customer awareness of environmental aspects such as emissions profiles and resource efficiency necessitates new concepts for mobility. At the same time, the demand for improved vehicle performance characteristics and the requirements regarding driving safety are increasing. Meeting these challenges is not solely the responsibility of vehicle manufacturers. In practice, many of these aspects are significantly influenced by tire properties, making tire optimization a crucial area for innovation.

[0005] Several relevant properties of vehicle tires, such as rolling resistance and wet grip, are closely linked to the rubber composition of the tread. Therefore, much research effort focuses on optimizing the properties of the rubber composition and its additives.

[0006] Significant progress has been made in this field in recent decades. A key innovation has been the at least partial replacement of carbon black fillers with silicon-containing compounds, particularly silicon dioxide compounds such as pyrogenic silica or silicates. It has been shown that particularly favorable properties can be obtained when the silicon-containing compounds are modified on their surface by organosilanization, also known as organosilylation. This involves reacting the silicon-containing compounds with organo-oxysilyl compounds, i.e., compounds that have at least one CO-Si bond and at least one organic residue linked by a Si-C bond.During the chemical reaction, which is typically a condensation reaction, a modification with the organic residue of the organyloxysilyl compounds occurs at the interface of the silicon-containing compounds. This organic residue allows for targeted control of the compatibility of the fillers in the rubber compound and their interactions with the rubber. In many cases, it is advantageous for the organic residues to carry functional groups that can crosslink with the rubber compound during vulcanization, thereby increasing the degree of crosslinking in the vulcanizate. This principle is disclosed, for example, in DE 2536674 C3 and DE 2255577 C3.

[0007] Milling processes are known from the prior art for obtaining surface-modified substances, where the surface modification can potentially occur as a chemical and / or physical bonding of organic components to the surface of the substances. EP 1 607 448 A2, for example, discloses the production of surface-modified silica gels, where polymers are used for the modification. GB 2179268 A relates to the comminution of materials in the dry state, where, in some embodiments, surfactants can be used in addition to the materials to be comminuted. Further disclosures relating to the milling of inorganic substances can be found, for example, in EP 2 301 667 A2 and DE 69203643 T2.

[0008] In practice, organosilanization—that is, the bonding of organo-oxysilyl compounds to silicon-containing compounds—in the tire industry is usually carried out as an in-situ reaction in the mixer. This means that the components, for example, silica and a free silane with an organic residue, are only brought to reaction in the mixer and in the presence of common chemicals used in rubber compounds. However, this process is regularly considered disadvantageous because flammable and potentially harmful gases, such as ethanol, can be released, which is generally undesirable in rubber processing. Furthermore, a separate mixing step is required, which increases the time and energy expenditure for the process.In addition, the corresponding process is comparatively difficult to control, since the reaction takes place in situ in a large volume and in the presence of other substances, unwanted reaction products such as ethanol must be removed from the rubber mixture, and the degree of organosilanization, i.e., the success of the intended in situ reaction, is difficult to determine.

[0009] For this reason, the prior art involves modifying the silicon-containing compounds beforehand by organosilanization. This allows the subsequent fillers to be obtained with a well-defined degree of silanization and added to the rubber compound without the formation of volatile organic compounds in the mixer.

[0010] This upstream organosilanization is currently carried out using a wet chemical process, i.e., with the use of solvents and in a comparatively lengthy procedure. Alternatively, large-scale production can also be carried out using an overpressure process, i.e., for example, with supercritical CO₂ as a solvent (see EP 1357156 B1). The organosilanized compounds produced in this way must be separated from the liquid reaction medium after the wet chemical reaction to obtain the pure product and then dried. This requires not only elevated temperatures but also reduced pressures, which regularly results in low energy efficiency and high labor costs.

[0011] The overarching objective of the invention was to provide a process for the organosilanization of silicon dioxide and / or inorganic silicates which eliminates or at least reduces the disadvantages of the prior art described above.

[0012] In particular, it was an object of the present invention to provide a process for the organosilanization of silicon dioxide and / or inorganic silicates which makes it possible to carry out the upstream organosilanization in a particularly energy-efficient manner.

[0013] It was an object of the present invention to provide a process for the organosilanization of silicon dioxide and / or inorganic silicates that largely, preferably entirely, requires no solvents. It was also desirable that the process be fully achievable with solid starting materials.

[0014] Ideally, the specified process should be able to provide organosilanized compounds with high yield and high selectivity, in particular free from thermal decomposition products of the starting materials. It was also a requirement that the specified process should preferably provide the organosilanized compounds in a particularly high degree of purity, especially free from metallic impurities that may arise, for example, from abrasion of the equipment used.

[0015] A further objective of the present invention was that the specified process should function without the use of additional chemicals, in particular without the use of potentially harmful compounds, and should produce as little waste as possible, such as solvents or unbound silane. Accordingly, the specified process should ideally exhibit high operational reliability, require little maintenance, and necessitate as few wear parts as possible.

[0016] The inventors of the present invention have now recognized that the problems described above can be solved if the organosilanization is carried out not in a wet chemical reaction, but by a so-called reaction milling process as defined in the claims, in which the starting compounds are presented in a starting composition and the organosilanization is caused by intensive mechanical stress on the starting composition in a milling device. The inventors have recognized that particularly advantageous results can be achieved when a fluidized bed counterjet mill is used as the milling device.

[0017] The aforementioned problems are solved accordingly by a process for the organosilanization of silicon dioxide and / or inorganic silicates and corresponding further processing, as defined in the claims. Preferred embodiments of the invention are described in the dependent claims and the following descriptions.

[0018] Such features of the methods according to the invention, which are hereinafter referred to as preferred, are combined in particularly preferred embodiments with other features also referred to as preferred. Combinations of two or more of the methods hereinafter referred to as particularly preferred are therefore especially preferred. Features of preferred compositions, rubber compounds, vulcanizates, rubber products, and uses result from the features of preferred methods.

[0019] The invention relates to a process for the organosilanization of silicon dioxide and / or inorganic silicates, comprising the steps of: a) Producing or providing a starting composition comprising at least one first compound selected from the group consisting of silicon dioxide and inorganic silicates, and at least one second compound selected from the group consisting of organyloxysilylorganic compounds, and b) mechanically subjecting the starting composition in a milling device for the mechanical activation of the first and / or second compound, wherein the mechanical stress is applied in such a way that, as a result of the mechanical stress, an organosilanization of the first The connection is made through the second compound, resulting in an organosilanized compound.

[0020] InIn the process according to the invention, the starting composition is first produced or provided. This means that the starting composition is either produced in a preceding step, for example by mixing the individual components, which may have been produced separately, or is merely provided, for example by purchasing the starting composition from a supplier.

[0021] According to the invention, the starting composition comprises at least one first compound and at least one second compound. This means that the starting composition can also comprise two or more first compounds and / or two or more second compounds, which may be preferred for certain applications.

[0022] The person skilled in the art recognizes that the process according to the invention is not suitable for all silicon-containing materials. Instead, the first compound, i.e., the compounds to be organosilanized at their interface, is one comprised of inorganic compounds containing silicon oxide or Si-O-Si linkages. The first compound is therefore selected from the group consisting of silicon dioxide and inorganic silicates. The applicability of the process according to the invention is not limited, in particular, with regard to the structural modification in which the silicon oxide compounds exist. Accordingly, the process according to the invention can be carried out, in particular, for all forms of silicon dioxide, for example, amorphous silicon dioxide, such as geyserite or tektite, or crystalline silicon dioxide, such as α-quartz or tridymite.

[0023] The person skilled in the art will recognize that the process according to the invention is thus limited to non-metallic silicon compounds as the first compound. It cannot be deduced from the available experimental results whether the process according to the invention would also be applicable to silicon compounds in which the silicon has an oxidation state of 0, such as elemental silicon. However, this question may remain open here, since the functionalization of metals and metalloids concerns a different technology and the use of metallic silicon compounds in rubber compounds would not be desirable in any case. A process according to the invention is therefore preferred in which the starting composition essentially does not comprise elemental silicon.

[0024] The starting composition also includes a second compound selected from the group consisting of organo-oxysilyl compounds. For those skilled in silanization processes, this term is a precise designation for materials suitable for silanization. The prefix "organo-oxysilyl" indicates that the corresponding silicon-containing compound has at least one organic residue bonded to the central silicon atom via an oxygen atom. The prefix "-organic" clarifies that, in addition, another organic residue is directly bonded to the central silicon via a carbon atom.The person skilled in the art understands that this organic residue is intended to remain at the interface of the modified first compound in the organosilanized compound to be produced, whereas the organyloxy groups are leaving groups that can be released in the course of a condensation reaction in which Si-O-Si linkage is generated.

[0025] Although organo-oxysilyl compounds can in principle be used in which three of the four residues are directly linked to the central silicon via a carbon atom and which accordingly only have one leaving group, in practice those organo-oxysilyl compounds are particularly relevant which have three, mostly identical, leaving groups, which are mostly ethoxy groups that are released as ethanol during the reaction.

[0026] When using appropriate trialkoxy compounds, organosilyloxysilicium materials are formed during organosilanization with the alkoxysilyl compound via condensation. After the initial condensation, the alkoxysilyl components can react with up to two additional binding sites on the first compound. It is possible that all Si-O-Si links originating from the central silicon atom are formed to create the same particle, or that links between several particles of the first compound are formed via the organosilyl compounds.

[0027] An advantage of the process according to the invention is that the first and second compounds present in the initial composition are automatically mixed synergistically during mechanical stress. Nevertheless, it can be advantageous, particularly with regard to the time required for complete conversion, if the initial composition already represents a close mixture of the two compounds. Accordingly, a process according to the invention is preferred in which the first and second compounds are present in the initial composition in a substantially homogeneous mixture.

[0028] The first compound is naturally a solid, i.e., a substance that is solid under typical ambient conditions, e.g., 20 °C and 1 bar atmospheric pressure. The second compound, however, can, in principle, exist as either a solid or a liquid, depending on its chemical structure. In the case of a liquid second compound, the first compound is expediently moistened or impregnated with the second compound. From a practical standpoint, however, it is particularly efficient if the second compound is also a solid in the initial composition. Indeed, this can be seen as an advantage of the process according to the invention, since it is what enables the efficient use of initial compositions consisting solely of solids, which is particularly advantageous from a process engineering perspective with regard to process reliability.Thus, a method according to the invention is preferred, wherein the second compound is selected from the group consisting of solid and liquid, preferably solid, organyloxysilylorganic compounds and / or wherein the mass fraction of liquid and / or solid organyloxysilylorganic compounds in the starting composition is in the range of 5 to 10%, based on the mass of the starting composition or at 5 to 10 pphf, i.e. parts per hundred filler.

[0029] The starting composition can include a catalyst material that catalyzes the silanization reaction, which can be particularly advantageous for certain applications depending on the nature of the second compound. Suitable catalyst materials can be found in the prior art and selected according to the first and second compounds used. According to the inventors, such catalyst materials can be used that would also be suitable for the comparable wet chemical reaction. A preferred method according to the invention includes a catalyst material in the starting composition.

[0030] The process according to the invention is, in principle, tolerant of the presence of further additives in the starting composition. However, the inventors have found that the efficiency of the mechanochemical reaction decreases when the effective concentration of the first and second compounds in the starting composition decreases. It is assumed that this is due to a reduction in the probability of collisions between the particles of the two compounds. Accordingly, processes according to the invention are preferably characterized in which the combined mass fraction of all first and second compounds in the starting composition is greater than 60%, preferably greater than 70%, particularly preferably greater than 80%, and most preferably greater than 90%, based on the mass of the starting composition.

[0031] In the process according to the invention, the starting composition is mechanically subjected to stress in a grinding device for the purpose of mechanically activating the first and / or second compound, preferably both compounds. In the process according to the invention, the grinding device is a fluidized bed counterjet mill.

[0032] In the process according to the invention, the mechanical stress is applied in such a way that the organosilanization of the first compound by the second compound occurs as a result of the mechanical stress, i.e., is caused by the mechanical stress. A wet-chemical organosilanization, which, for example, takes place under stirring, would therefore explicitly not be an example of a reaction in which the organosilanization occurs as a result of mechanical stress. Rather, in the process according to the invention, the intensive mechanical stress on the starting composition is the cause of the chemical reaction, thereby functionally defining a minimum energy input that is sufficient to trigger the reaction of the first with the second compound.

[0033] Without wishing to be bound by this theory, the inventors assume that in grinding devices with grinding media, the friction mediated by the grinding media, as well as impacts, and in the case of eccentric vibratory mills, to a large extent also the impact stress, are primarily responsible for triggering the chemical reaction. In contrast, the triggering of the mechanochemical reaction in a fluidized bed counter-jet mill used according to the invention is presumably mainly due to the mutual collision of the particles of the first and second compounds, whereby the necessary activation energy for a chemical reaction involving bond cleavage and the formation of new chemical bonds is achieved.Without wishing to be bound to this theory, it is assumed that the energy input leads to stress on the material, resulting in lattice defects that then enable the chemical reaction, whereby it is assumed that the mechanical activation in the process according to the invention probably primarily affects the first compounds used. A process according to the invention is therefore preferred in which the mechanical activation of the first and / or second compound, preferably the first compound, is effected by friction and / or impact and / or shock.

[0034] A person skilled in the art is familiar with a fluidized bed counterjet mill for the process according to the invention and can operate it in the intended manner. In doing so, the person skilled in the art can control the mechanochemical reaction, or the energy input into the starting material, by adjusting the operating parameters of the milling device. When using a fluidized bed counterjet mill, the operating conditions include, for example, the type, number, and arrangement of the milling gas nozzles, the milling gas flow rate, the pressure of the milling gas, its properties, and the rotational speed of the air classifier used for product discharge, which also affects, among other things, the residence time of the reactant in the fluidized bed and thus the final fineness. Furthermore, the addition rate of the starting components is also among the operating parameters.

[0035] In the method according to the invention, it is not necessary to supply additional thermal energy to the system by increasing the temperature, although this may still be advantageous in certain scenarios. However, for reasons of energy efficiency, a method according to the invention is preferred in which all steps of the method are carried out at room temperature, i.e., 20 °C, or in which no energy is supplied to the system by external heating devices.

[0036] The present invention enables the organosilanization of silicon dioxide and / or inorganic silicates in a solvent-free process, advantageously allowing the use of solid starting materials. The process according to the invention is particularly energy-efficient and allows the production of organosilanized compounds with high yield and high selectivity. The process advantageously requires no additional chemicals and produces little or no waste or byproducts. Furthermore, it can be carried out using commercially available equipment and therefore exhibits a high degree of operational reliability.

[0037] Although the inventive method has proven to be very flexible in its own experiments with regard to the selection of the first and second compounds, the inventors were nevertheless able to identify a group of first and second compounds that are particularly suitable for use in the inventive method.A preferred method according to the invention is the first compound being selected from the group consisting of silica, precipitated silica gel, flint, quartz sand, flint, chert, diatomaceous earth, cristobalite, tridymite, coesite, stishovite, melanophlogite, opal, moganite, and cyclic and polycyclic silicates, wherein the first compound is preferably selected from the group consisting of silica, silica gel, cristoballite, flint, quartz sand, flint, chert, diatomaceous earth or diatomaceous earth, wherein the first compound is particularly preferably amorphous silicon dioxide, wherein the first compound can be, for example, synthetically produced or of natural origin.

[0038] A preferred method according to the invention is also one wherein the second compound has a structure of the formula (R 1< O) 3 SiR 2< wherein R1< denotes organic residues which are selected independently of one another in the three groups, preferably from the group consisting of linear or branched alkyl groups with 1 to 8 carbon atoms, more preferably from linear alkyl groups with 2 to 4 carbon atoms, wherein the three organic residues R1< are preferably identical, and wherein R2< denotes a, preferably linear, organic residue of the formula (CH2)nY, wherein n is a natural number and is preferably in the range of 1 to 10, particularly preferably in the range of 2 to 6, and wherein Y is a functional group or a structural element containing a functional group, which is preferably arranged in a terminal position, and wherein the functional group is preferably selected from the group consisting of alkenyl groups, alkynyl groups, aryl groups, silyl groups and functional groups containing at least one atom of the 3rd, 5th, 6th or 7th carbon atoms.The main group of the periodic table of chemical elements, preferably selected from the group consisting of alkenyl groups, alkynyl groups, aryl groups, silyl groups, aldehyde groups, acid groups, activated acid groups, amino groups, alcohol groups, thiol groups, and urea groups, wherein Y is preferably selected such that the functional group can react with a carbon-carbon double bond to form a bond. Although Y can be a structural element containing a functional group, as explained above, it is preferred if Y is a functional group, i.e., consists exclusively of a functional group, wherein the second compound in this case is particularly preferably selected from the group consisting of 3-(triethoxysilyl)propanethiol and 3-(triethoxysilyl)propylamine.

[0039] In accordance with the understanding of the person skilled in the art, a structural element containing a functional group may also comprise more than one of the functional groups defined above, which may be connected to each other either directly or via organic residues.

[0040] It is generally possible to use organo-oxysilyl compounds that have two or more organo-oxysilyl groups linked together by an organic residue. This can be particularly advantageous for certain applications because it allows for a higher degree of crosslinking between the first compounds or a multidentate connection of the organic residue to the first compound. In these organo-oxysilyl compounds, the structural element Y containing a functional group comprises, in addition to at least one functional group, one or more further silyl groups, which are also typically linked to the functional group via an organic residue.The corresponding second compounds can also be designed such that, for example through a subsequent reaction, a cleavage reaction can occur in the connecting organic residue, so that after bond cleavage, an organyloxysilylorganic compound leaves two organic residues at the interface of the organosilanized compounds. A preferred method according to the invention is therefore one in which the second compound has a structure of the formula (R 1< O) 3 Si-(CH 2 ) m -Z-(CH 2 ) u -Si(OR 1< ) 3, where m and u are natural numbers, which are independent of each other, preferably in the range of 1 to 10, particularly preferably in the range of 2 to 6, and where Z is a functional group or a structural element containing a functional group, as defined above for Y.In this context, methods according to the invention are particularly preferred, wherein Z comprises a disulfide group or at least a urea group, preferably two urea groups connected via an aryl group, which are preferably arranged in para-position to each other, wherein the second compound is preferably selected from the group consisting of bis[(triethoxysilyl)propyl]disulfide and 1,1'-(1,4-phenylene)bis(3-(3-(triethoxysilyl)propyl)urea).

[0041] In accordance with expert understanding, it can be advantageous to characterize the organyloxysilylorganic compounds by their ability to condense with hydroxyl groups, or more precisely, Si-OH groups, such as those regularly present on the surface of the first compounds. Accordingly, a method according to the invention is preferred, wherein the second compound is selected from the group consisting of organically substituted silanes capable of condensation with hydroxyl groups.

[0042] For certain applications, non-inventive methods are preferred, wherein the grinding device is a mill with grinding media, since such devices are already available in many plants and are usually particularly easy to operate and maintain. In such cases, the non-inventive method is typically operated as a batch process, which means that the grinding device is fed with the initial composition, whereupon the mechanical stress on the initial composition is carried out until the reaction has progressed sufficiently. A non-inventive method is preferred, wherein the grinding device is a mill with grinding media and the method is preferably operated as a batch process.

[0043] The experiments showed that when using suitable grinding devices with grinding media, reaction times of several minutes, typically 30 to 120 minutes, are required to achieve a sufficient yield of the organosilanized compound. However, these devices also regularly subject the starting material to thermal stress, which, especially during prolonged operation, can lead to the thermal decomposition of components of the starting material, an undesirable outcome. Therefore, a time window was identified that consistently achieves a particularly good compromise between silanization conversion and thermal stress. A preferred method, not according to the invention, involves the mechanical stress in step b) being applied for a time in the range of 15 to 120 minutes, preferably 30 to 60 minutes.

[0044] A disadvantage of using mills with grinding media has been found to be that, depending on the material of the mill and the grinding media, impurities can occur in the produced organosilanized compound, caused by abrasion from the mill components. To solve this problem, it is proposed to make the grinding device from a hard oxide material, such as zirconium oxide. A preferred method is therefore one not according to the invention, wherein the grinding device preferably consists of an oxide material, preferably zirconium oxide.

[0045] As a particularly advantageous alternative to the use of a mill with grinding media, the inventors have identified that a fluidized bed counterjet mill, as disclosed in principle in WO 2018 192686 A1, can be used as the grinding device according to the invention. In such grinding devices, the energy required for the reaction is provided by the repeated collision of the particles of the first and second compounds through high-pressure, intersecting fluid jets. These devices operate on the counterjet principle and have a crossing zone that forms the reaction chamber for the organosilanization.

[0046] A particular advantage of this embodiment of the process according to the invention is that the process can be operated as a continuous process using a fluidized bed jet mill, in which the first and second compounds can be continuously fed and the resulting organosilanized compounds can be continuously removed. The residence time of the individual particles of the starting material in the reaction chamber is comparatively short, so that this process is particularly energy-efficient and a first batch of product can be obtained relatively quickly. The fluidized bed jet mill can advantageously have a plurality of fluid nozzles and is typically operated with a standard process gas.

[0047] Further information on the fluidized bed jet mill can be found, for example, in Y. Wang, F. Peng, Part. Sci. Technol. 2010, 28, 566-580, Y. Wang, F. Peng, Powder Technology 2011, 214, 269-277, MX Zhang, HY Chen, CP Yan, LY Lin, Rev. Adv. Mat. Sci. 2013, 33, 77-84, X. Su, Z. Cao, Q. Li, Z. Zhang, J. Adv. Microscopy Res. 2014, 9, 54-57 and X. Su, S. Xu, T. Cai, Guangzhou Huagong 2012, 40, 101-102.

[0048] In summary, it is evident to the person skilled in the art that the process according to the invention is preferably operated as a continuous process, wherein in the grinding device a fluidized bed is preferably formed as a reaction chamber in a crossing area of ​​the jet direction of at least two nozzles together with the introduced starting composition, wherein the nozzles are preferably arranged at an angle in the range of 60° and 180° to each other.

[0049] Likewise, methods according to the invention are preferred in which the first and / or the second compound, preferably both compounds, are transported by means of a conveying device into a grinding chamber of the grinding device and reach the reaction space inside the grinding chamber in free fall.

[0050] In particular, methods according to the invention are preferred, wherein the mean residence time of the reactant in the reaction chamber of the fluidized bed counterjet mill is in the range of 1 to 60 s, preferably 5 to 40 s, particularly preferably 10 to 20 s.

[0051] Furthermore, methods according to the invention are preferred, wherein the fluidized bed counterjet mill comprises two to six, preferably two to four, nozzles. The fluidized bed counterjet mill particularly preferably comprises three nozzles arranged at an angle of 120° to each other.

[0052] Furthermore, methods according to the invention are preferred in which the fluidized bed counterjet mill is operated with a gas which is selected from the group consisting of air, nitrogen, argon, carbon dioxide, water vapor and mixtures of these gases.

[0053] Additional advantages of using a fluidized bed counterjet mill compared to other grinding devices include the fact that it operates without grinding media, which, as explained above, can lead to contamination of the organosilanic compound being produced through abrasion. Furthermore, no additional masses need to be set in motion within the grinding chamber, as is the case with a ball mill, for example, making such grinding devices particularly energy-efficient. In addition, a fluidized bed counterjet mill is generally more resource-efficient, as there is no need to replace worn balls as consumable parts.A particular advantage of this process has proven to be that the short residence time of the particles in the reaction chamber and the inherent cooling provided by the fluid flows largely prevent unwanted temperature increases during the reaction, thus effectively counteracting thermal decomposition of the components contained in the initial composition. Furthermore, it has been shown that the noise emission of fluidized bed counterjet mills during operation is typically so low that, unlike large-scale ball mills, especially eccentric vibratory mills, no enclosure is necessary for noise reduction purposes, and the process is therefore also advantageous from an occupational safety perspective.

[0054] In their own experiments, the inventors of the present invention identified operating parameters that enable a particularly good reaction result with low energy consumption when using a fluidized bed counterjet mill. Specifically, the process according to the invention requires that the fluidized bed counterjet mill be operated with flow velocities in the range of 100 to 1000 m / s and a milling gas pressure in the range of 5 to 10 bar, preferably in the range of 7 to 8 bar.

[0055] It can be considered particularly advantageous that in a process according to the invention, which is carried out using a fluidized bed counterjet mill, the reaction milling is completely autogenous, so that all the energy for product formation, including the necessary activation energy, is provided exclusively by the fluid jet. Neither an external temperature increase is required, nor does an uncontrolled temperature increase of the starting composition occur due to the milling process, which would be associated with the disadvantages described above.

[0056] The invention further relates to a method for producing a rubber mixture, comprising the steps of the method according to the invention, additionally comprising the step: c) mixing the organosilanized compound with at least one rubber to obtain the rubber mixture.

[0057] It has proven particularly advantageous that the organosilanized compounds produced by the inventive process can optionally be mixed directly, i.e., without further processing, with rubber and, optionally, other typical components of rubber compounds to obtain a rubber compound. The interaction of the organosilanized compounds with the other components of the rubber compound can be precisely controlled by the inventive process, due to the wide range of possible second compounds, i.e., indirectly, organic functionalities.

[0058] Accordingly, rubber compounds can be produced using the inventive method whose properties can be particularly efficiently tailored to the properties required for the subsequent application. Within the scope of the preferred inventive method, all typical materials known to those skilled in the art from the field of tire manufacturing are suitable as rubber, for example, natural rubber or synthetic materials such as styrene-butadiene rubber.

[0059] The invention further relates to a method for producing a vulcanizate or a rubber product comprising the corresponding vulcanizate, comprising the steps of the inventive method for producing a rubber compound, additionally comprising the step: d) Vulcanizing the rubber compound to obtain the vulcanizate, and optionally step e) processing the vulcanizate into a rubber product, in particular a vehicle pneumatic tire.

[0060] In this process, the rubber compound produced using the inventive method is vulcanized according to the method commonly used in the tire industry, for example by sulfur-based crosslinking.

[0061] In light of the foregoing, it is evident to the person skilled in the art that the present disclosure also includes a composition comprising at least one organosilanized compound, produced or producible by a process according to the invention, a rubber mixture comprising a corresponding composition, a vulcanizate produced or producible by vulcanization of this rubber mixture, and a rubber product, preferably a vehicle tire, comprising the corresponding vulcanizate.

[0062] Finally, the present invention also relates to the use of a fluidized bed counterjet mill for the energy-efficient, solvent-free organosilanization of a first compound selected from the group consisting of silicon dioxide and inorganic silicates, with a second compound selected from the group consisting of organyloxysilylorganic compounds, wherein, as a result of the mechanical stress, an organosilanization of the first compound by the second compound takes place, characterized in that the fluidized bed counterjet mill is operated with flow velocities in the range of 100 to 1000 m / s and a milling gas pressure in the range of 5 to 10 bar.

[0063] The advantages of this application, which were not previously known from the prior art, will become apparent from the above explanations.

[0064] The invention will now be explained in more detail using exemplary embodiments and comparative calculations. Calculations regarding energy consumption:

[0065] Since the process according to the invention does not require the removal of solvents from the obtained product and also does not require the use of increased temperatures and / or reduced pressures, the process according to the invention is more energy-efficient compared to the wet-chemical silanization processes known from the prior art.

[0066] However, the inventors recognized that a particularly energy-efficient design could be achieved in the inventive method if a fluidized bed counter-jet mill was used as the grinding device. For this purpose, a comparison is presented below between an exemplary eccentric vibratory mill ESM 504 (comparative example) and such a fluidized bed counter-jet mill of type AFG 630 / 1 (inventive example).

[0067] The eccentric vibratory mill, which uses 32 mm x 32 mm Cylpeps steel grinding media, has a throughput of approximately 40 kg / h in batch operation. The mixer / drive requires 27.5 kW of power, with the fine classifier requiring an additional 5.5 kW. This results in a specific energy consumption of approximately 825 kWh / t. For the fluidized bed counterjet mill, calculations are based on ISO 1217, operating at a pressure of 8 bar and a temperature of 20 °C with an airflow of 3000 m³ / h. The required compressor power is approximately 270 kW. The classifier wheel also requires approximately 11 kW. This setup enables a continuous throughput of approximately 600 kg / h, resulting in a specific energy consumption of approximately 468 kWh / t.

[0068] The above calculation using a practical example illustrates that the specific energy expenditure for the inventive method, in which a fluidized bed counterjet mill is used as a grinding device, is significantly lower than the energy expenditure required with an eccentric vibratory mill. Examples of implementation Example 1:

[0069]

[0070] In a Retsch MM400 vibrating mill, 3.751 g of silica gel and 0.343 g of 1,1'-(1,4-phenylene)bis(3-(3-(triethoxysilyl)propyl)urea), synonymous with 1,4-bis{N'-[3-(triethoxysilyl)propyl]ureido}benzene, [CAS No. 668994-10-3], are milled together for 60 minutes. Steel balls with a diameter of 9 mm are used as grinding media. After the specified grinding time, the silanization product is separated from the grinding media by sieving. Example 2:

[0071]

[0072] In a Retsch S1 centrifugal mill, 5.75 g of silica gel and 0.53 g of 1,1'-(1,4-phenylene)bis(3-(3-(triethoxysilyl)propyl)urea), synonymous with 1,4-bis{N'-[3-(triethoxysilyl)propyl]ureido}benzene, [CAS No. 668994-10-3], are milled together for 30 minutes. Steel balls with a diameter of 10 mm are used as grinding media. After the specified duration of the reaction milling process, the silanization product is separated from the grinding media by sieving. Example 3:

[0073]

[0074] In an eccentric vibratory mill (GSM sieve mill), 30.0 g of silica gel and 2.74 g of 1,1'-(1,4-phenylene)bis(3-(3-(triethoxysilyl)propyl)urea), synonymous with 1,4-bis{N'-[3-(triethoxysilyl)propyl]ureido}benzene, [CAS No. 668994-10-3], are milled together for 120 minutes. Steel or zirconium dioxide spheres with a diameter of 10 mm are used as grinding media. The material of the milling vessel is adjusted accordingly. After the specified duration of the reaction milling, the silanization product is separated from the grinding media by sieving. Example 4:

[0075]

[0076] In a PicoJet fluidized bed counterjet mill (Alpine-Hosokawa), 33.3 g of silica gel and 3.05 g of 1,1'-(1,4-phenylene)bis(3-(3-(triethoxysilyl)propyl)urea), synonymous with 1,4-bis{N'-[3-(triethoxysilyl)propyl]ureido}benzene, [CAS No. 668994-10-3], are subjected to reaction milling at a milling gas pressure of 8.5 bar and a classifier rotation speed of 60,000 rpm. The silanization product is collected in a downstream product filter during the continuous reaction. Example 5:

[0077]

[0078] In a Retsch MM400 vibrating mill, 3,751 g of silica gel and 0,270 g of bis[(triethoxysilyl)propyl]disulfide, synonym: 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane, TESPD [CAS No. 56706-10-6], are milled together for 90 minutes. Steel balls with a diameter of 9 mm are used as grinding media. After the specified duration of the reaction milling process, the silanization product is separated from the grinding media by sieving. Example 6:

[0079]

[0080] In an eccentric vibratory mill (GSM sieve mill), 30.0 g of silica gel and 2.16 g of bis[(triethoxysilyl)propyl]disulfide, synonym: 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane, TESPD [CAS No. 56706-10-6], are milled together for 120 minutes. Steel or zirconium dioxide spheres with a diameter of 10 mm are used as grinding media. The material of the milling vessel is adjusted accordingly. After the specified duration of the reaction milling, the silanization product is separated from the grinding media by sieving. Example 7:

[0081]

[0082] In a Retsch MM400 vibrating mill, 3.751 g of silica gel and 0.271 g of 3-(triethoxysilyl)propanethiol, synonymous with (3-mercaptopropyl)triethoxysilane [CAS No. 14814-09-6], are milled together for 30 minutes. Steel balls with a diameter of 9 mm are used as grinding media. After the specified grinding time, the silanization product is separated from the grinding media by sieving. Example 8:

[0083]

[0084] In a Retsch MM400 vibrating mill, 3.751 g of silica gel and 0.252 g of 3-(triethoxysilyl)propylamine, synonymous with 3-aminopropyltriethoxysilane [CAS No. 919-30-2], are milled together for 20 minutes. Steel balls with a diameter of 9 mm are used as grinding media. After the specified grinding time, the silanization product is separated from the grinding media by sieving. Example 9:

[0085]

[0086] In a Retsch MM400 vibrating mill, 3.751 g of commercially available quartz sand with a grain size of 0.075–0.090 mm and 0.270 g of bis[(triethoxysilyl)propyl]disulfide, synonym: 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane, TESPD [CAS No. 56706-10-6], are milled together for 60 minutes. Steel balls with a diameter of 12.7 mm are used as grinding media. After the specified duration of the reaction milling, the silanization product is separated from the grinding media by sieving. Example 10:

[0087]

[0088] In a Retsch S1 centrifugal mill, 11.50 g of commercially available quartz sand with a grain size of 0.09–0.20 mm and 0.82 g of bis[(triethoxysilyl)propyl]disulfide, synonym: 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane, TESPD [CAS No. 56706-10-6], are milled together for 30 minutes. Steel balls with a diameter of 10 mm are used as grinding media. After the specified duration of the reaction milling process, the silanization product is separated from the grinding media by sieving. Example 11:

[0089]

[0090] In a Retsch MM400 vibrating mill, 3.751 g of commercially available quartz sand with a grain size of 0.075–0.090 mm and 0.271 g of 3-(triethoxysilyl)propanethiol, synonymous with (3-mercaptopropyl)triethoxysilane [CAS No. 14814-09-6], are milled together for 45 minutes. Steel balls with a diameter of 12.7 mm are used as grinding media. After the specified duration of the reaction milling process, the silanization product is separated from the grinding media by sieving. Example 12:

[0091]

[0092] In a Retsch MM400 vibrating mill, 3.751 g of commercially available quartz sand with a grain size of 0.09–0.20 mm and 0.271 g of 3-(triethoxysilyl)propanethiol, synonymous with (3-mercaptopropyl)triethoxysilane [CAS No. 14814-09-6], are milled together for 45 minutes. Steel balls with a diameter of 12.7 mm are used as grinding media. After the specified duration of the reaction milling process, the silanization product is separated from the grinding media by sieving. Evaluation:

[0093] The quantitative binding of the respective organic silane to the silicon-containing starting material is demonstrated for all of the silanization products obtained in embodiments 1 to 12 by an NMR spectroscopic analysis ( 1< H-NMR, 600 MHz). Further implementation:

[0094] The silanization products obtained in embodiments 1 to 12, wherein embodiment 4 is according to the invention, were used in further tests in typical rubber mixtures (e.g. comprising natural rubber, SSBR, plasticizers, sulfur and other commonly used additives) and vulcanized with them, thereby demonstrating the basic suitability of the silanization products obtained.

Claims

1. Process for organosilanization of silicon dioxide and / or inorganic silicates, comprising the steps of: a) producing or providing a starting composition comprising at least a first compound selected from the group consisting of silicon dioxide and inorganic silicates and at least a second compound selected from the group consisting of organyloxysilylorganic compounds, and b) mechanically stressing the starting composition in a milling apparatus for mechanical activation of the first and / or second compound, wherein the mechanical stressing is carried out such that the mechanical stressing results in organosilanization of the first compound by the second compound, to obtain an organosilanized compound, wherein the milling apparatus is a fluidized-bed opposed-jet mill, characterized in that the fluidized-bed opposed-jet mill is operated with flow velocities in the range from 100 to 1000 m / s and a milling gas pressure in the range from 5 to 10 bar.

2. Process according to Claim 1, wherein the first compound is selected from the group consisting of silica, precipitated silica gel, silex, silica sand, flintstone, chert, kieselguhr, diatomaceous earth, cristobalite, tridymite, coesite, stishovite, melanophlogite, opal, moganite, and cyclic and polycyclic silicates, wherein the first compound is preferably selected from the group consisting of silica, silica gel, cristobalite, silex, silica sand, flintstone, chert, kieselguhr or diatomaceous earth, wherein the first compound is more preferably an amorphous silicon dioxide.

3. Process according to either of Claims 1 and 2, wherein the second compound has a structure of formula (R1O)3SiR2, wherein R1 denotes organic radicals selected independently of one another, preferably from the group consisting of linear or branched alkyl groups having 1 to 8 carbon atoms, preferably of linear alkyl groups having 2 to 4 carbon atoms, wherein the three organic radicals are preferably identical, and wherein R2 denotes a preferably linear organic radical of formula (CH2)nY, wherein n is a natural number and is preferably in the range from 1 to 10, more preferably in the range from 2 to 6, and wherein Y is a functional group or a structural element containing a functional group which is preferably arranged in the terminal position and wherein the functional group is preferably selected from the group consisting of alkenyl groups, alkynyl groups, aryl groups, silyl groups and functional groups containing at least one atom of main group 3, 5, 6 or 7 of the Periodic Table of the Chemical Elements, preferably selected from the group consisting of alkenyl groups, alkynyl groups, aryl groups, silyl groups, aldehyde groups, acid groups, activated acid groups, amino groups, alcohol groups, thiol groups and urea groups.

4. Process according to any of Claims 1 to 3, wherein the process is operated as a continuous process, wherein a fluidized bed is configured as a reaction space in the milling apparatus preferably in a region of intersection in the jet direction of at least two nozzles together with the introduced starting composition, wherein the nozzles are arranged preferably at an angle in the range of 60° and 180° to one another.

5. Process according to Claim 4, wherein the fluidized-bed opposed-jet mill is operated with a milling gas pressure in the range from 7 to 8 bar.

6. Process according to either of Claims 4 and 5, wherein the first and / or the second compound, preferably both compounds, are transported by means of a conveying device into a milling chamber of the milling apparatus and reach the reaction space in the interior of the milling chamber in free fall.

7. Process for producing a rubber mixture, comprising the steps of the process according to any of Claims 1 to 6, additionally comprising the step of: c) mixing the organosilanized compound with at least one rubber to obtain the rubber mixture.

8. Process for producing a vulcanizate or rubber product comprising the vulcanizate, comprising the steps of the process according to Claim 7, additionally comprising the step of: d) vulcanizing the rubber mixture to obtain the vulcanizate and optionally the step of e) processing the vulcanizate to give a rubber product, in particular a pneumatic vehicle tyre.

9. Use of a fluidized-bed opposed-jet mill for energy-efficient, solvent-free organosilanization of a first compound selected from the group consisting of silicon dioxide and inorganic silicates, with a second compound selected from the group consisting of organyloxysilylorganic compounds, wherein the mechanical stressing results in organosilanization of the first compound by the second compound, characterized in that the fluidized-bed opposed-jet mill is operated with flow velocities in the range from 100 to 1000 m / s and a milling gas pressure in the range from 5 to 10 bar.