RU2786563C1 - Method for obtaining compounds for tires and tires including them - Google Patents

Abstract

FIELD: automotive industry.

SUBSTANCE: present invention relates to a compound represented by formula (II): CB-O-ROS-GC-Zn (II). In formula (II), CB is a white filler selected from the group consisting of silica and silicates in the form of fibers, flakes or granules, O is one or more oxygen bridges, ROS is an organosilane moiety containing at least one a straight or branched alkyl chain having 1-6 carbon atoms bonded to a silicon atom, GC is one or more coordination groups chelated with zinc in ionic form, and Zn is zinc in ionic form coordinated by coordination groups, where the coordination GC groups are linear, branched or cyclic alkyl chains having 1-6 carbon atoms and containing one or more heteroatoms inside or at the end of the alkyl chain. Also proposed are a method for producing a compound of formula (II), a vulcanizable elastomeric compound and a method for producing it, a tire element containing a vulcanizable elastomeric compound, and a tire for vehicle wheels.

EFFECT: invention leads to an improvement in the effectiveness of activating fillers in the production of tire compounds, in order to reduce their amount used for vulcanization, and, accordingly, the load in the form of pollutants on the environment as a result of the release of zinc, and at the same time maintain or possibly improve technological conditions. process and properties of final elastomeric compounds.

16 cl, 9 dwg, 21 tbl, 5 ex

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to a process for the preparation of zinc reduced elastomeric tire compounds, characterized by the incorporation of specific modified fillers which can promote vulcanization.

BACKGROUND OF THE INVENTION

In the tire industry, vulcanization is a method commonly used to improve the mechanical properties of natural rubber or unsaturated polymers, a method that results in a change in the hardness, elasticity, hysteresis of the material at different temperatures and, as a result, the behavior of the tire on wet surfaces, as well as its friction and abrasive wear during use.

Over the years, various additives have been proposed as vulcanization activators and accelerators to improve the vulcanization process.

In general, with these additives it is desirable to increase the degree and uniformity of crosslinking while reducing the energy and time required to complete the reaction.

The main vulcanization activators that can increase the efficiency of the process are inorganic compounds such as metal oxides and hydroxides, eg ZnO, MgO, Ca(OH) ₂ .

Among the various activators, zinc oxide ZnO is considered the most effective and is still used today in many vulcanization processes. This activator is used in combination with weak organic acids (eg stearic acid) which promote its activity in rubber.

Some studies - see, for example, Y. Ikeda, et al., Dinuclear bridging bidentate zinc/stearate complex in sulfur cross-linking of rubber , Macromolecules 48 (2015) 462-475) - have suggested that Zn ^{2 +} , produced by the interaction of ZnO with stearic acid, interact with accelerator and sulfur molecules to form organometallic complexes, which will act as more effective sulphurizing agents. The ability of Zn ²⁺ to form these complexes is a key element of the vulcanization process and is highly dependent on the dispersion of ZnO within the polymer matrix, which in turn depends on both the particle size and the crystal structure of the zinc oxide.

Typically, in vulcanization processes for tire rubbers, microcrystalline ZnO is used as an activator, which, however, is not readily dispersed in the polymer matrix and reacts only partially with other vulcanizing agents.

The poor dispersibility and low reactivity of microcrystalline zinc oxide in the elastomeric compound inevitably leads to the introduction of an excessive dose of it relative to the amount actually required for crosslinking.

During tire use, especially due to tread abrasion on asphalt, the zinc present in the compounds is partially released.

Therefore, for environmental reasons, efforts have been made to reduce the amount of zinc in compounds for many years.

For example, attempts have been made to use finer ZnO (nanosized particles), but dispersion has still been difficult due to the formation of aggregates within the polymer matrix, effectively eliminating the size advantage over microcrystalline zinc oxide.

On the other hand, the use of compounds consisting of nanoparticles of zinc oxide directly bonded to nanoparticles of silicon dioxide, compounds having a dual function - the function of a filler and vulcanization activators (hereinafter generally referred to as activating fillers or specifically ZnO/SiO ₂ ) proved to be advantageous (see A. Susanna et al. ZnO nanoparticles anchored to silica filler. A curing accelerator for isoprene rubber composites , Chemical Engineering Journal 275 (2015) 245-252) and A. Susanna et al., Catalytic effect of ZnO anchored silica nanoparticles on rubber vulcanization and cross-link formation , European Polymer Journal 93 (2017) 63-74).

SUMMARY OF THE INVENTION

The Applicant has conducted research to further improve the performance of the activating fillers described above in the preparation of tire compounds, with the aim of further reducing the amount used for vulcanization and thus the environmental pollutant load due to the release of zinc, and together in order to maintain or possibly improve the process conditions, yield and, above all, the properties of the final elastomeric compounds.

Surprisingly, the applicant found that zinc in ionic form can be associated with white filler particles, for example, silica nanoparticles, through a coupling agent containing reactive groups capable of binding to the surface of the white filler, in particular, capable of forming oxygen bridges, and coordination groups capable of chelating zinc in ionic form.

The binding agent can thus be schematically represented by the following formula (I):

GR-ROS-GC (I)

where GR is one or more reactive groups that can bind to the surface of the white filler through the formation of oxygen bridges (-O-), ROS is an organosilane residue, and GC is one or more coordination groups.

In addition, the material obtained by the applicant can thus be schematically represented by the following formula (II),

CB-O-ROS-GC-Zn (II)

where the reactive GR groups reacted with the surface of the white filler (CB) to form oxygen bridges (-O-) with the organosilane residue (ROS), and subsequently the GC coordination groups chelate zinc in ionic form (Zn).

The applicant has surprisingly found that such materials provide various advantages when used in the vulcanization processes of compounds used in the manufacture of tires.

Advantageously, the use of such materials makes the zinc in ionic form readily available, thus more rapidly and more effectively complexing the accelerator and sulfur molecules, which therefore act as more effective sulphurizing agents.

In fact, the greater availability and effectiveness of these materials allows the use of smaller amounts of zinc than those used with conventional zinc-based materials, and allows the use of fatty acids such as, for example, stearic acid to be completely eliminated.

The Applicant observed that the use of such materials provides, with the use of lower mixing temperatures due to the absence of the need for silanes, the full advantage in both the structural integrity of the materials and the cost of obtaining the elastomeric compound to be cured.

In addition, the applicant noted that such materials provide shorter vulcanization times as well as better mechanical properties of the resulting vulcanized materials. An additional advantage noted by the applicant is the reduction or elimination of the phenomenon of zinc release from the tire during use, since the zinc remains bound to the surface of the white filler without being able to move (migrate) towards the surface of the tire, with obvious advantages in terms of protection. environment.

The first aspect of the present invention is thus a compound represented by the following formula (II):

CB-O-ROS-GC-Zn (II)

where CB is a white filler, O is one or more oxygen bridges, ROS is an organosilane residue, GC is one or more ionic zinc chelate coordination groups, and Zn is ionic zinc coordinated by coordination groups where said GC coordination groups are linear, branched or cyclic alkyl chains containing one or more heteroatoms inside or at the end of the alkyl chain.

The second aspect of the present invention is represented by a method for preparing a compound according to the first aspect of the present invention, wherein said method comprises at least:

provision of white filler (CB)

providing a binding agent having the following formula (I):

GR-ROS-GC (I)

where GR is one or more reactive groups capable of forming oxygen bridges with the surface of said white filler, ROS is an organosilane residue, and GC is one or more coordination groups,

providing a zinc compound (Zn ²⁺ )

reacting between the white filler (CB) and one or more reactive groups (GR) of said compound of formula (I) to form oxygen bridges (-O-) between said white filler and said organosilane residue (ROS), and

carrying out a reaction between one or more coordination groups (GC) of said compound of formula (I) and a zinc compound to form a chelate, and

isolation of the resulting compound of formula (II) CB-O-ROS-GC-Zn.

A third aspect of the present invention is a process for preparing a vulcanizable elastomeric tire compound, said process comprising at least:

a step of mixing (1) at least one elastomeric polymer and at least one elastomeric compound additive, excluding a curing agent, to obtain a non-vulcanizable elastomeric compound;

a step of mixing (2) a non-vulcanizable elastomeric compound and at least one curing agent to form a curable elastomeric compound, and

the step of unloading the vulcanizable elastomeric compound,

wherein the compound according to the first aspect of the invention is added in at least one of said mixing steps (1) and (2).

The fourth aspect of the present invention is a vulcanizable elastomeric compound obtained according to the method of the third aspect of the present invention.

The fifth aspect of the present invention is a tire element containing the vulcanizable compound according to the fifth aspect of the present invention or the vulcanized compound obtained by vulcanization thereof.

The sixth aspect of the present invention is a tire for vehicle wheels including the element according to the fifth aspect of the present invention.

DEFINITIONS

For purposes of describing the present invention and forming the following claims, the term "phr" (parts per 100 parts of rubber) means parts by weight of a given component of the elastomeric composition per 100 parts by weight of the diene elastomeric polymer.

Unless otherwise indicated, all percentages are expressed as percentages by weight.

As used herein, the term "elastomeric polymer" or "rubber" or "elastomer" means a natural or synthetic polymer which, after vulcanization at room temperature, can be re-stretched to at least double its original length and which, after When the tensile load is removed, it returns substantially instantaneously with force to approximately its original length (according to the terminology of ASTM D1566-11 relating to Rubber).

In the description of the present invention, the term "reinforcing filler" refers to a reinforcing material commonly used in the art to improve the mechanical properties of tire rubbers, preferably selected from the group consisting of carbon black, commonly used silica, such as silica from precipitated sand. with strong acids, preferably amorphous, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibers and mixtures thereof.

In the description of the present invention, the term "white filler" refers to a reinforcing material commonly used in the art from among the commonly used silica and silicates in the form of fibers, thin plates or granules, such as sepiolite, palygorskite, also called attapulgite, montmorillonite, alloisite and the like, possibly modified by acid treatment and/or derivatized. Typically, white fillers have surface hydroxyl groups.

In the description of the present invention, the term "reactive group" allows you to specify a group that can react with the surface hydroxyl groups of the white filler and form an oxygen bridge (-O-) upon elimination of water or alcohol, usually a hydroxyl group (-OH) or an alkoxy group ( -OR), where R is a straight or branched alkyl chain having 1-6 carbon atoms.

In the description of the present invention, the term "organosilane residue" means a residue containing at least one linear or branched alkyl chain having 1-6 carbon atoms associated with a silicon atom.

In the description of the present invention, the term "coordination group" indicates a functional group containing an atom capable of forming a coordination bond with a zinc ion (Zn ²⁺ ), such as, for example, nitrogen, oxygen or sulfur.

In the description of the present invention, the term "zinc compound" means a compound selected from ZnO, Zn(OH) ₂ , and organic or inorganic salts of Zn ²⁺ .

In the description of the present invention, the term "elastomeric compound" refers to a product obtained by mixing and optionally heating at least one elastomeric polymer with at least one of the additives commonly used in the preparation of tire compounds.

In the description of the present invention, the term "unvulcanizable elastomeric compound" means a product obtained by blending at least one elastomeric polymer with at least one of the additives commonly used in the preparation of tire compounds, excluding vulcanizing agents. The non-vulcanizable elastomeric compound may also be referred to as a phased elastomeric compound (1).

In the description of the present invention, the term "vulcanizable elastomer compound" means a ready-to-vulcanize elastomeric compound in which all additives are included, including vulcanization additives. The vulcanizable elastomeric compound may also be referred to as a phased elastomeric compound (2).

In the description of the present invention, the term "cured elastomer compound" means a material obtained by vulcanizing a vulcanizable elastomer compound.

In the description of the present invention, the term "mixing step (1)" indicates a step in the process for producing an elastomeric compound, in which one or more additives can be included by mixing and possibly heating, with the exception of vulcanization additives, which are served in step (2).

In the description of the present invention, the term "mixing step (2)" indicates a subsequent step in the process of obtaining an elastomeric compound, in which curing additives and, preferably, curing accelerators and/or retarders, are introduced and mixed into the material, at a controlled temperature, usually at mixing temperature below 160ºС.

The mixing step (1) is also referred to as the "non-productive step" because the compound components are fed into the mixing device, with the exception of the components responsible for crosslinking (eg, sulfur and accelerators).

The mixing step (2) is instead referred to as the production step. At this stage, the elastomeric compound obtained in step (1) and curing additives capable of promoting and/or controlling crosslinking are fed into the mixing device to provide a curable elastomeric compound.

In the description of the present invention, the term "green" is generally used to refer to a material, compound, composition, element or tire that has not yet been vulcanized.

DETAILED DESCRIPTION OF THE INVENTION

The process for preparing the compound of formula (II) according to the invention will be illustrated in detail below.

This method is characterized by one or more of the following preferred aspects, considered alone or in combination with each other, specifically when using a binding agent having the following formula (I):

GR-ROS-GC (I)

where GR is one or more reactive groups, ROS is an organosilane residue, and GC is one or more coordination groups.

The method of the present invention includes at least:

provision of white filler (CB)

providing a binding agent having the following formula (I):

GR-ROS-GC (I)

where GR is one or more reactive groups, ROS is an organosilane residue, and GC is one or more coordination groups,

providing a zinc compound (Zn ²⁺ )

reacting between the white filler (CB) and one or more reactive groups (GR) of said compound of formula (I) to form oxygen bridges between said white filler and said reactive groups (GR), and

carrying out a reaction between one or more coordination groups (GC) of said compound of formula (I) and a zinc compound to form a chelate, and

isolation of the resulting compound of formula (II) CB-O-ROS-GC-Zn.

The white filler may be any conventional white reinforcing filler that has hydroxyl groups on the surface.

The white filler is preferably selected from commonly used silicas and silicates, in the form of fibers, flakes or granules, such as bentonite, nontronite, beidellite, wolkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, palygorskite, also called attapulgite, montmorillonite, alloisite and the like, optionally modified by acid treatment and/or derivatized, and mixtures thereof, more preferably it is silica.

Silica can vary in shape, specific surface area and size.

Examples of silica are pyrogenic silica, precipitated amorphous silica, wet silica (hydrated silicic acid), or mixtures thereof.

Examples of suitable commercial silicas are precipitated silica Rhodia Zeosil MP1165 (BET specific surface area 160 m ² /g), Ultrasil VN3 GR (BET specific surface area 180 m ² /g) and Zeosil 1115 MP (specific surface area BET 180 m 2 /g). BET 95-120 m ² /g).

Preferably, the silica has a specific surface area (BET) of at least 120 m ² /g, more preferably at least 140 m ² /g.

Preferably, the silica has a specific surface area (BET) of less than 220 m ² /g, more preferably less than or equal to 180 m ² /g.

Useful examples of compounds represented by formula (I) include alkoxysilanes functionalized with one or more heteroatom-containing functional groups, where the alkoxy groups are reactive GR groups that can bind to a white filler, and the heteroatom-containing functional groups are GC coordination groups. capable of forming a coordination bond with the zinc ion. Preferred examples of GR reactive groups include alkoxy groups having 1-4 carbon atoms, namely methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, and tert-butoxy groups.

Preferred examples of GC coordination groups include functional groups represented by the formula -C _n H _2n -XC _m H _2m -Y, where n and m, the same or different from each other, denote an integer from 1 to 6 inclusive; Y and X, the same or different from each other, represent a group selected from a mercapto group and an amino group.

Useful examples of compounds represented by formula (I) are represented by the following general formula (Ia):

(R) ₃ Si-C _n H _2n -XC _m H _2m -Y (Ia)

where the R groups, identical or different from each other, are selected from alkyl groups or alkoxy groups having 1-4 carbon atoms, provided that at least one of the R groups is an alkoxy group; n and m, identical or different from each other, mean an integer from 1 to 6 inclusive; Y and X, the same or different from each other, represent a group selected from a mercapto group and an amino group.

The compounds used in the present invention and represented by formula (Ia) include (3-aminopropyl)triethoxysilane (APTES), N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (also known as N-[3-(trimethoxysilyl)propyl ]ethylenediamine (EDTMS)), N-(2-aminoethyl)-3-aminopropyl-triethoxysilane, N-(2-aminoethyl)-3-aminopropyl-methyl-dimethoxysilane, 3-aminopropylmethyl-diethoxysilane, 3-ureidopropyl-trimethoxysilane, 3 -ureidopropyltriethoxysilane, N-cyclohexyl(aminomethyl)methyldiethoxysilane, N-cyclohexyl(aminomethyl)triethoxysilane, N-cyclohexyl-3-aminopropyltrimethoxysilane, 3-(2-aminomethylamino)propyltriethoxysilane, N-(n-butyl)- 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-(2-(2-aminoethylamino)ethylamino)propyl- trimethoxysilane, N-(n-butyl)-3-aminopropyltriethoxysilane, N,N-diethylaminopropyltrimethoxysilane, N,N-dimethylaminopropyltrimethoxysilane, butylaminomethyltriethox silane, N-cyclohexyl(aminomethyl)trimethoxysilane, 2-aminoethylaminomethyltriethoxysilane, diethylaminomethyltriethoxysilane, (3-mercaptopropyl)triethoxysilane and (3-mercaptopropyl)trimethoxysilane.

Preferred compounds represented by formula (Ia) are (3-mercaptopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane (APTES), (3-aminopropyl)trimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (also known as N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDTMS)), and N-(2-aminoethyl)-3-aminopropyltriethoxysilane.

The zinc compound may be Zn, Zn(OH) ₂ , and organic or inorganic salts of Zn ²⁺ such as zinc nitrate, zinc sulfate, zinc chloride, zinc bromide and zinc acetate.

The reaction step between the white filler and the coupling agent is carried out with heating in the solvent phase, first by dispersing the white filler in a suitable solvent and then by adding the coupling agent, allowing it to react until the reaction is completed.

The solvent used for the reaction is preferably selected from the group of non-polar solvents such as hexane, cyclohexane, benzene and toluene.

Optionally, the white filler is first activated by dispersion in a basic aqueous solution such as, for example, sodium hydroxide solution. Activation of the white filler is carried out at room temperature, ranging from 20° to 30°C, for a period of at least 1 hour, more preferably at least 3 hours, and even more preferably at least 6 hours. The activation period is preferably less than 48 hours, more preferably less than 36 hours. Preferably, the activation period is in the range between 12 and 24 hours. The white excipient thus activated is isolated by a commonly used separation method (filtration, centrifugation, and the like) and then subjected to lyophilization.

The reaction between the white filler and the binding agent is carried out preferably at a temperature above 40°C, more preferably above 60°C, and even more preferably above 80°C. The reaction temperature is preferably below 200°C, more preferably below 180°C, and even more preferably below 160°C.

The reaction between the white filler and the coupling agent is carried out preferably at the reflux temperature of the reaction mixture in a vessel under reflux for a period of at least 1 hour, more preferably at least 3 hours, and even more preferably at least 6 hours. The reaction period is preferably less than 48 hours, more preferably less than 36 hours. Preferably, the reaction period is in the range between 12 and 24 hours.

The reaction product, represented by a functionalized white filler, is isolated/separated by a commonly used separation method (filtration, centrifugation, and the like) and then dried at temperatures from 60°C to 100°C.

The functionalized white excipient, which may be represented by the formula CB-O-ROS-GC, is then reacted with a zinc compound to obtain a chelate represented by formula (II).

The reaction is carried out with heating in the solvent phase, first by dispersing the functionalized white filler (CB-O-ROS-GC) in a suitable solvent and then by adding a zinc compound, allowing it to react until the reaction is complete.

The solvent used for the reaction is preferably selected from the group of polar protic solvents such as ethanol, methanol and isopropanol.

The reaction is carried out preferably at a temperature above 40°C, more preferably above 60°C, and even more preferably above 80°C. The reaction temperature is preferably below 200°C, more preferably below 180°C, and even more preferably below 160°C.

The reaction is carried out preferably at the reflux temperature of the reaction mixture for a period of at least 10 minutes, more preferably at least 30 minutes, and even more preferably at least 1 hour. The reaction period is preferably less than 12 hours, more preferably less than 6 hours. Advantageously, the reaction period is in the range between 2 and 4 hours.

The reaction product represented by the formula (II) according to the present invention is isolated by a commonly used separation method (filtration, centrifugation, and the like) and then dried at a temperature of 60°C to 100°C.

The method for producing a vulcanizable elastomeric tire compound according to the invention will be illustrated in detail below.

This method is characterized by one or more of the following preferred aspects, considered alone or in combination with each other, specifically when using the compound represented by the following formula (II):

CB-O-ROS-GC-Zn (II)

where CB is a white filler, O is one or more oxygen bridges, ROS is an organosilane moiety, GC is one or more ionic zinc chelate coordination groups, and Zn is ionic zinc coordinated to coordination groups, where said GC coordination groups are linear, branched or cyclic alkyl chains containing one or more heteroatoms inside or at the end of the alkyl chain.

The method of the present invention may be a continuous process, however, it is preferably an interrupted process (batch).

The process of the present invention, when batchwise, can be carried out in one or more mixers, preferably in one mixer.

The process according to the invention includes the step of mixing (step 1) at least one diene elastomeric polymer and at least one elastomeric compound additive which is not a curing agent.

The at least one additive for elastomeric compounds that is mixed with at least one diene elastomeric polymer in the mixing step (1) may be, for example, a compound of formula (II) of the present invention, a reinforcing filler, an antioxidant, a wax , plasticizer and the like.

Generally, in the mixing step (1), no vulcanizing agent is added, and preferably not even vulcanization accelerator or retardant agents are added.

In the method of the present invention, in the mixing step (1), the compound of formula (II) of the present invention may be fed, all in whole or in part.

Preferably, the compound of formula (II) according to the present invention is served entirely in step (1).

In step (1), mixing is carried out at mixing temperatures, typically between 70° and 160° C., and for a period of time typically from 2 to 20 minutes.

Before proceeding to step (2), it may be advantageous to carry out the step of unloading and/or curing the unvulcanizable elastomeric compound to ensure that any reactions are completed.

Preferably, the compound of step (1) is discharged before proceeding to step (2). In the subsequent step (2), at least one curing agent is added. Optionally, at least one vulcanization accelerator agent, at least one vulcanization retarder agent can be added in step (2) and, if not yet fully introduced into the mixing step (1), then the compound of formula (II ) according to the present invention.

In step (2) of the process of the present invention, the mixing temperature is maintained generally below 160°C, preferably at 140°C, more preferably at 120°C, to avoid any undesirable phenomenon of premature crosslinking.

Typically, in step (2), mixing can be carried out at mixing temperatures between 70° and 155° C. and for 2 to 10 minutes.

At the end of step (2), the method of the present invention includes the step of discharging the vulcanizable elastomeric compound, which is intended to be sent to subsequent conventional manufacturing steps for the production of tires and their components.

In one or more steps of the process of the present invention, other additives commonly used in the preparation of tire compounds may be added, selected according to the particular application for which the composition is intended. For example, the following additives may be added: antioxidant agents, plasticizers, adhesives, antiozonant agents, resin modifying agents, or mixtures thereof.

In the method of the present invention, at least one diene elastomeric polymer may be selected from diene elastomeric polymers commonly used in sulfur curable elastomeric compositions that are particularly suitable for making tires, i.e., from among elastomeric polymers or unsaturated chain copolymers, having a glass transition temperature (Tg) usually below 20°C, preferably in the range from 0°C to -110°C.

Preferably, the diene elastomeric polymer has a weight average molecular weight (Mw) above 80,000 g/mol.

These polymers or copolymers may be of natural origin or may be prepared using solution polymerization, emulsion polymerization or gas-phase polymerization of one or more conjugated diolefins, optionally mixed with at least one comonomer selected from monovinylarenes and/or polar comonomers, in an amount not exceeding 60% by weight.

Conjugated diolefins generally contain 4 to 12, preferably 4 to 8 carbon atoms and may be selected, for example, from the group consisting of: 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1, 3-pentadiene. 1,3-hexadiene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene and mixtures thereof. 1,3-Butadiene and isoprene are particularly preferred.

Monovinylarenes, which may optionally be used as comonomers, generally contain 8 to 20, preferably 8 to 12 carbon atoms and may be selected, for example, from: styrene; 1-vinylnaphthalene; 2-vinylnaphthalene; various alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl styrene derivatives such as, for example, α-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-para- tolyl-styrene, 4-(4-phenylbutyl)styrene, and mixtures thereof. Styrene is particularly preferred.

Polar comonomers, which may optionally be used, may be selected, for example, from: vinylpyridine, vinylquinoline, acrylic acid and alkylacrylic acid esters, nitriles, or mixtures thereof, such as, for example, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile and their mixtures.

Preferably, the diene elastomeric polymer that can be used in the present invention can be selected from, for example, cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (particularly polybutadiene with a high content of 1,4-cis), optionally halogenated isoprene/isobutene copolymers, 1,3-butadiene/acrylonitrile copolymers, styrene/1,3-butadiene copolymers, styrene/isoprene/1,3-butadiene copolymers, styrene/1 ,3-butadiene/acrylonitrile copolymers, and mixtures thereof.

The above curable elastomeric compound may optionally comprise an elastomeric polymer of one or more monoolefins with an olefin comonomer or derivatives thereof. The mono-olefins may be selected from ethylene and α-olefins, typically having 3 to 12 carbon atoms, such as, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and mixtures thereof. The following are preferred: copolymers selected from ethylene and an α-olefin, optionally with a diene; isobutene homopolymers or copolymers thereof with small amounts of a diene, which are optionally at least partially halogenated. The diene that may be present typically contains 4 to 20 carbon atoms and is preferably selected from: 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5- methylene-2-norbornene, vinylnorbornene and mixtures thereof. Of these, the following are particularly preferred: ethylene/propylene (EPR) copolymers or ethylene/propylene/diene (EPDM) copolymers; polyisobutene; butyl rubber; halobutyl rubbers, in particular chlorobutyl or bromobutyl rubbers; or mixtures thereof.

A diene elastomeric polymer or an elastomeric polymer functionalized by reaction with suitable chain terminators or coupling agents may also be used. In particular, diene elastomeric polymers obtained by anionic polymerization in the presence of an organometallic initiator (in particular an organolithium initiator) can be functionalized by reacting residual organometallic groups derived from the initiator with suitable chain terminators or coupling agents, such as, for example, , imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes or aryloxysilanes.

In the process of the present invention for preparing a vulcanizable elastomeric compound, at least one elastomeric polymer may include one or more of the diene elastomeric polymers as defined above in a mixture that may be advantageously subjected to a 'chewing' step (steps 1-0 ) to achieve better mixing.

In the method of the present invention, the amount of at least one elastomeric polymer or mixture of two or more elastomeric polymers as defined above is used is only 100 parts per 100 parts of rubber (phr).

In the method of the present invention, the at least one curing agent is preferably selected from sulfur or alternatively sulfur-containing molecules (sulfur donors) such as, for example, caprolactam disulfide (CLD), bis(trialkoxysilyl)propyl]polysulfides, dithiophosphates, phosphorylpolysulfide ( SDT) and mixtures thereof.

Preferably, the curing agent is sulfur, preferably selected from (i) soluble sulfur (crystalline sulfur), (ii) insoluble sulfur (polymeric sulfur), (iii) oil-dispersed sulfur, and mixtures thereof.

Commercially available examples of suitable vulcanizing agents include 65% sulfur known under the trade name Rhenogran from Lanxess, 67% sulfur known under the trade name Crystex OT33 from Eastman, 95% sulfur known under the trade name Solvay SchwefelKC, rhombic crystalline sulfur, known under the trade name Sulfur (1% oil and 0.3% silica) from Zolfindustria.

The curing agent may be present in the vulcanizable elastomeric compound in a total amount, typically 0.1 to 15 phr, preferably 0.5 to 10 phr, even more preferably 1 to 7 phr.

The elastomeric compound of the present invention may contain one or more curing agents as defined above in admixture.

In the method of the present invention, the vulcanizing agent is preferably used together with auxiliary additives such as vulcanization accelerators and/or retarders known to those skilled in the art.

In the method of the present invention, the vulcanization accelerator agent is preferably selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulfenamides, sulfenimides, thiurams, amines, xanthates and mixtures thereof.

Preferably, the accelerator agent is selected from N-cyclohexyl-2-benzothiazole-sulfenamide (CBS), N-tert-butyl-2-benzothiazole-sulfenamide (TBBS) and mixtures thereof.

A commercially available example of a suitable accelerator agent is N-cyclohexyl-2-bezothiazole-sulfenamide Vulkacit® (CBS or CZ) marketed by Lanxess.

The accelerator agent may be present in the vulcanizable elastomeric compound in a total amount typically in the range of 0.05 phr to 10 phr, preferably 0.1 phr to 5 phr.

The elastomeric compound of the present invention may contain one or more accelerator agents as defined above in admixture.

In the method of the present invention, the vulcanization retarding agent may be selected from, for example, urea, phthalic anhydride, N-nitrosodiphenylamine N-cyclohexylthiophthalimide (CTP or PVI), and mixtures thereof.

A commercially available example of a suitable retarding agent is N-cyclohexylthiophthalimide VULKALENT G from Lanxess.

The retarder agent may be present in the curable elastomeric compound in an amount typically in the range of 0.05 phr to 2 phr.

The elastomeric compound of the present invention may contain one or more retarder agents as defined above in admixture.

Preferably, in the process of the present invention, preferably in the mixing step (1), one or more optional additives, such as, for example, at least one reinforcing filler, at least one antioxidant agent, at least one wax and at least one plasticizer.

In the method of the present invention, the reinforcing filler is selected from carbon black, commonly used silica such as silica from sand precipitated with strong acids, preferably amorphous, hydrotalcite, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates , kaolin, silicate fibers and mixtures thereof.

Preferably, the additional reinforcing filler is selected from carbon black, commonly used silica, silicate fibers and mixtures thereof, preferably it is silicon dioxide.

The carbon black may be selected from standard tire grade carbon blacks, or having a surface area of at least 20 m ² /g, more preferably greater than 50 m ² /g (measured according to ASTM D6556-16).

A commercially available example of a suitable reinforcing filler is Zeosil 1165MP silica from Solvay Rhodia.

Commercially available examples of carbon black are N375 or N234 marketed by Birla Group (India) or Cabot Corporation.

The reinforcing filler may be present in the vulcanizable elastomeric compound in an amount typically in the range of 0 phr to 120 phr, preferably 3 phr to 80 phr.

In one embodiment, the reinforcing filler may be absent, in which case the reinforcing function is performed by the compound of formula (II) according to the present invention.

For some applications, the elastomeric compound obtained according to the method of the present invention may contain at least 1 phr, more preferably at least 2 phr, more preferably at least 3 or 4 phr carbon black, which advantageously protects elastomer against aging caused by ultraviolet radiation.

The elastomeric compound of the present invention may contain one or more reinforcing fillers as defined above in a mixture.

In the method of the present invention, phenylenediamine, diphenylamine, dihydroquinoline, phenol, benzimidazole, hydroquinone and their derivatives, optionally in admixture, can be used as an antioxidant.

In the method of the present invention, the antioxidant agent is preferably selected from N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethyl-butyl)-n'-phenyl-p-phenylenediamine (6PPD ), N, N'-bis-(1,4-dimethyl-pentyl)-p-phenylenediamine (77PD), N, N'-bis-(1-ethyl-3-methyl-pentyl)-p-phenylenediamine (DOPD ), N, N'-bis-(1,4-dimethyl-pentyl)-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine (DPPD), N, N'-ditolyl-p-phenylenediamine (DTPD) , N, N'-di-beta-naphthyl-p-phenylenediamine (DNPD), N, N'-bis(1-methylheptyl)-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine ( 44PD), N-phenyl-N-cyclohexyl-p-phenylenediamine, N-phenyl-N'-1-methylheptyl-p-phenylenediamine and the like, and mixtures thereof, preferably N-(1,3-dimethyl- butyl)-N'-phenyl-para-phenylenediamine (6PPD).

An example of a commercially available suitable antioxidant agent is 6PPD from Solutia/Eastman.

The antioxidant agent may be present in the vulcanizable elastomeric compound in a total amount typically in the range of 0 phr to 20 phr, preferably 0.5 phr to 10 phr.

In the method of the present invention, the wax may be, for example, a petroleum wax or a mixture of paraffins.

Examples of commercially available suitable waxes are Repsol's N-paraffin mixture and Antilux® 654 microcrystalline wax from Rhein Chemie.

The wax may be present in the vulcanizable elastomeric compound in an aggregate amount typically in the range of 0 phr to 20 phr, preferably 0.5 phr to 10 phr.

In the method of the present invention, in order to further improve the processing characteristics, the elastomeric compound may be mixed with at least one plasticizing agent, usually selected from mineral oils, vegetable oils, synthetic oils, low molecular weight polymers and mixtures thereof, such as, for example, aromatic oil, naphthenic oil, phthalates, soybean oil and mixtures thereof. The amount of plasticizer is generally in the range from 0 phr to 70 phr, preferably from 5 phr to 30 phr. Preferably, the plasticizing agent is added during the 1-0 polymer 'chewing' step, if any.

The fourth aspect of the present invention is a vulcanizable elastomeric compound obtained according to the method of the third aspect of the present invention.

Preferably, the vulcanizable elastomer compound of the invention contains less than 4 phr zinc, more preferably less than 3 phr, even more preferably less than 2 phr zinc, with the consequent environmental benefit of lower zinc release compared to conventional elastomer compounds.

Preferably, the vulcanizable elastomeric compound according to the invention contains zinc in an amount of less than 4 phr, more preferably less than 3 phr, even more preferably less than 2 phr.

In the elastomeric compound of the invention, zinc is present in ionic form as Zn ²⁺ coordinated to form the compound represented by formula (II) of the present invention, but not in the form of metallic zinc (Znº).

The amount of zinc in the compound can be determined, for example, by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) spectrometry, which is described in the experimental part.

The vulcanizable elastomeric compound of the present invention may be incorporated into one or more tire elements.

Due to the presence of at least one vulcanizing agent, the vulcanizable compound can be vulcanized in accordance with known methods.

By using the compound represented by the formula (II) of the present invention as an activator, a complete and uniform dispersion of zinc is obtained, with undoubted advantages in the subsequent vulcanization reaction of the elastomeric compound, such as more pronounced and more uniform crosslinking, the absence of aggregates of unreacted zinc oxide, and in the properties of the vulcanized compound regarding static and dynamic mechanical properties, as well as the greater reactivity of the green compound. This particular reactivity results from reduced crosslinking times and/or from obtaining a higher maximum torque (MH). The compound of the present invention also exhibits static modulus values (~0.1 and ~0.5) corresponding to reference values from opposing materials, predicting good resiliency of the compound, which in turn predicts good tire handling. Finally, the compound of the present invention has a high hysteresis at low temperatures (10°C and 23°C), which predicts good wet and dry braking performance without significantly affecting high speed performance.

Thanks to the method of the present invention, it is possible to reduce the amount of zinc added to the compounds, with important environmental benefits, without compromising or even improving their performance compared to comparable commonly used compounds.

According to the fifth aspect of the invention, the elastomeric compound of the present invention is applied to tire components such as tread, underlayer, anti-abrasion elongation, sidewall, bead reinforcement, mini-sidewall, bottom liner, rubber layers, filler cord and sheet, more preferably in the tread, in the underlayer and in the sidewall. Preferably, the tire element according to the invention consists of a vulcanizable compound according to the invention (green element) or a vulcanized compound obtained by vulcanizing it (vulcanized element).

A sixth aspect of the present invention is a tire for vehicle wheels including at least one of the elements mentioned above.

Preferably, a tire for vehicle wheels according to the invention includes at least one tire element, which consists of a vulcanizable elastomeric compound (green element) according to the second aspect of the invention or a vulcanized elastomeric compound obtained by vulcanization thereof.

In one embodiment, a tire for vehicles according to the present invention includes at least

a carcass structure comprising at least a carcass layer having opposite side edges associated with a respective bead structure;

possibly a pair of sidewalls attached to the side surfaces of the carcass structure, respectively, in an axially outward position;

possibly a belt structure attached in a radially outward position relative to the carcass structure;

a tire tread band applied in a radially outward position to said carcass structure or, if present, to said belt structure;

- possibly a layer of elastomeric material, called underlayer, applied in a radially internal position relative to said running belt;

wherein at least one element selected from said pair of sidewalls, said underlayer and said running belt comprises or preferably consists of an elastomeric compound according to the present invention.

An embodiment according to the present invention relates to a tire for high performance vehicles (HP, SUV and UHP), where at least one element, preferably selected from the underlayer, sidewall and running belt, includes, or preferably consists of an elastomeric compound according to the invention.

An embodiment according to the present invention relates to a tire for heavy vehicles, where at least one element, preferably selected from the underlayer, the sidewall and the running belt, comprises, or preferably consists of an elastomeric compound according to the invention.

The tire according to the invention may be a tire for two-, three- or four-wheeled vehicles.

In one embodiment, the tire according to the invention is a tire for bicycle wheels. A tire for bicycle wheels typically includes a carcass structure enveloping a pair of bead cores on the beads and a running belt disposed at a radially outward position relative to the carcass structure.

The carcass structure is designed to withstand the internal air pressure of the tire and support the weight of the bike and rider. It includes one or more carcass plies, each containing a plurality of suitably oriented reinforcing cords. In the case of multiple carcass layers, they are angled relative to each other to form a crossed structure.

Bead cores are designed to reliably secure the tire to the wheel rim.

At the radially inward position of the carcass structure, an air chamber into which compressed air is pumped can be provided.

The tire according to the invention may be intended for use in summer or winter periods or for all seasons.

The tire according to the present invention can be manufactured in accordance with a method that includes:

- the composition of the elements of the green tire, at least one forming cylinder;

- shaping, molding and vulcanization of the tire;

where the composition of at least one of the elements of the green bus includes:

- production of at least one green element containing, or preferably consisting of a vulcanizable elastomeric compound according to the invention.

DESCRIPTION OF THE DRAWINGS

Figure 1 shows a radial semi-profile of a tire for vehicle wheels according to the invention.

Figure 2 shows the FTIR ATR spectrum for two silica samples functionalized with a coupling agent described in Example 1.

Figure 3 shows the TGA spectrum for four samples of silica functionalized with a coupling agent described in example 1.

Figure 4 shows the TGA spectrum for the SiO ₂ reference sample as described in Example 1.

Figure 5 shows the NMR spectrum in the solid state for a reference sample of silicon dioxide (SiO ₂ ) and for two samples of silica functionalized with a coupling agent described in example 1.

Figure 6 shows the NMR spectrum for a sample of silica functionalized with a coupling agent, and the NMR spectrum for the same sample after chelation with zinc, which is described in example 1.

Figure 7 shows spectra obtained from XPS (X-ray Photo Emission Spectroscopy) analysis of a silica sample functionalized with a zinc-chelated coupling agent as described in Example 1.

Figure 8 shows the FTIR ATR spectrum for a sample of silica functionalized with a coupling agent and for a reference sample of pure silica (SiO ₂ ), which are described in example 4.

Figure 9 shows the TGA spectrum for a sample of silica functionalized with a coupling agent and for a reference sample of pure silica (SiO ₂ ), which are described in example 4.

In particular, Figure 1 shows a radial half-profile of a tire for vehicle wheels containing a vulcanized elastomeric compound obtained by vulcanizing an elastomeric compound obtained according to the method of the invention.

In Figure 1, "a" indicates the axial direction and "X" indicates the radial direction, specifically X-X indicates the contour line of the equatorial plane. For simplicity, Figure 1 shows only a part of the tire, where the remaining part not shown is identical and is located symmetrically about the "X-X" equatorial plane.

The tire 100 for four-wheeled vehicles includes at least one carcass structure comprising at least one carcass ply 101 having rim bands with respectively opposite ends engaged with respective annular anchoring structures 102, referred to as bead cores. , possibly related to the filler cord of bot 104.

The framework layer 101 is optionally made from an elastomeric compound.

The area of the tire, including the bead core 102 and filler cord 104, forms the bead structure 103 for attaching the tire to a respective support (fixing) rim, which is not shown.

The carcass structure is typically of the radial type, that is, the reinforcing elements of at least one carcass ply 101 lie on planes containing the tire's rotational axes and substantially perpendicular to the tire's equatorial plane. Said reinforcement elements generally consist of textile cords such as viscose, nylon, polyester (eg polyethylene naphthalate, PEN). Each bead structure is connected to the carcass structure by folding back the opposite side edges of at least one carcass layer 101 around the annular anchoring structure 102 to form so-called carcass rim strips 101a, which are shown in Figure 1.

In one embodiment, bonding between the carcass structure and the bead structure can be provided by a second carcass layer (not shown in Figure 1) applied at an axially outward position relative to the first carcass layer.

An anti-abrasive tape 105, optionally made from an elastomeric compound, is placed at the outer position of each bead structure 103.

The carcass structure is associated with a breaker structure 106 including one or more breaker plies 106a, 106b placed in radial lamination with respect to each other and with respect to a carcass layer having typically textile and/or metal cords for reinforcement embedded within the vulcanized elastomeric compound layer.

Such reinforcement cords may have a crossed orientation with respect to the circumferential direction of the tire 100. By "circumferential" is meant a direction generally facing the direction of rotation of the tire.

At least one layer of zero-degree reinforcement 106c, commonly referred to as a "0° breaker", may be applied at a radially outward outermost position to the breaker layers 106a, 106b, which typically includes a plurality of elongated elements for reinforcements, usually metal or textile cords, oriented in a substantially circular direction, respectively forming an angle of several degrees (such as an angle of from about 0° to 6°) relative to a direction parallel to the equatorial plane of the tire, and coated with a vulcanized elastomeric compound.

A running belt 109 of a vulcanized elastomeric compound is applied in a radially outward position to the breaker structure 106.

In addition, respective sidewalls 108 of the vulcanized elastomer compound are applied at an axially outward position to the side surfaces of the carcass structure, where they each start from one of the side edges of the tread 109 in the respective bead structure 103.

In a radially outward position, the running belt 109 has a rolling surface 109a designed to come into contact with the ground. Circular grooves that are connected by transverse recesses (not shown in Figure 1) for the purpose of establishing a plurality of blocks of various shapes and sizes distributed over the rolling surface 109a are typically made on this surface 109a, which for simplicity is displayed as smooth in Figure 1.

An underlayer 111 of vulcanized elastomeric compound may be located between the breaker structure 106 and the running belt 109.

A tape consisting of an elastomeric compound 110, commonly referred to as a "mini-sidewall", of vulcanized elastomeric compound, may optionally be provided in the bonding area between the sidewalls 108 and the running belt 109, where this mini-sidewall is usually produced by co-extrusion with the running belt 109 and thereby improving the mechanical interaction between the running belt 109 and the sidewalls 108. Preferably, the end portion of the sidewall 108 directly covers the side edge of the running belt 109.

In the case of tubeless tyres, a rubber layer 112, commonly referred to as a "sealing layer", which provides impermeability to air pumped into the tire, can also be provided at a radially inward position relative to the carcass layer 101.

The rigidity of the tire sidewall 108 can be improved by providing the bead structure 103 with a reinforcement layer 120, commonly referred to as "reinforcing tape" or additional tape-like insertion.

The reinforcing tape 120 is a reinforcing layer that is wound around the respective bead core 102 and filler cord 104 to at least partially encircle them, where said reinforcing layer is placed between at least one carcass layer 101 and the bead structure 103. Typically, the reinforcing tape is in contact with said at least one carcass layer 101 and said bead structure 103.

Reinforcement tape 120 typically includes a plurality of textile cords embedded in a layer of vulcanized elastomeric compound.

The bead structure 103 may include an additional protective layer, which is commonly known as bead tape 121 or protective tape, and which has the function of reinforcing the rigidity and integrity of the bead structure 103.

The bead tape 121 typically comprises a plurality of cords embedded in a rubber layer of a vulcanized elastomeric compound. Such cords are typically made from textile materials (such as aramid or viscose) or metallic materials (such as steel cords).

A layer or sheet of elastomeric compound may be placed between the breaker structure and the carcass structure. The layer may have a uniform thickness. Alternatively, the layer may have a variable thickness in the axial direction. For example, the layer may be thicker towards its axially outer edges relative to the central (crown) zone.

Advantageously, the layer or sheet may extend over a surface substantially corresponding to the elongation surface of said breaker structure.

In a preferred embodiment, a layer or sheet of elastomeric compound as described above may be placed between said breaker structure and said running belt, where said additional layer or sheet preferably extends over a surface substantially corresponding to the extension surface of said breaker structure.

The elastomeric compound of the present invention may advantageously be included in one or more tire elements selected from a breaker structure, a carcass structure, a running belt, an underlayer, a sidewall, a mini-sidewall, a sidewall liner, a bead, a reinforcing tape, a bead tape, a sheet, and an anti- abrasive tape, preferably embedded, at least in the sidewalls and/or in the underlayer.

According to one embodiment not shown, the tire may be a motorcycle tire, which is typically a tire having a straight section showing a large camber of the tread profile.

In one embodiment, not shown, the tire may be a bicycle tire.

In one embodiment, not shown, the tire may be a heavy vehicle wheel tire such as trucks, buses, trailers, vans, and typically vehicles where the tire is subjected to a high load. Preferably, such a tire is capable of being mounted on wheel rims having a diameter equal to or greater than 17.5 inches for directional or trailer wheels.

A description of some preparative examples according to the invention and comparative examples, given only to illustrate the invention and not limit its scope, is set forth below.

EXPERIMENTAL PART

ANALYSIS METHODS

Functionalization of white filler

The functionalization of the white filler is confirmed by ATR-FTIR, TGA, CHNS, BET and NMR analysis in the solid state.

ATR-FTIR analysis was carried out on a Perkin Elmer Spectrum 100 instrument (4 cm ^-1 resolution spectra, 650 to 400 cm ^-1 region, 32 scans).

Thermogravimetric analysis (TGA) was carried out on a TGA/DCS1 STARe SYSTEM (Mettler Toledo) with constant air flow (50 ml min ^-1 ). The method used involves applying a temperature ramp with 10°C min ^-1 heating, starting from an initial temperature of 30°C up to a final temperature of 1000°C. Also add two 15-minute isotherms at 150°C and 1000°C. Measurements are carried out in aluminum crucibles with a volume of 75 µl.

CHNS analysis is performed on an Elementar VarioMICRO analyzer with CHNS configuration. The measurement uncertainty is stated at the level of 0.1%. Measurements are normalized with respect to the sulfanilamide standard. The combustion column is at 1150°C while the recovery column is at 850°C.

BET analysis is performed using Micromeritics Tristar II porosity and surface area analysis equipment.

Solid state NMR analysis is carried out on a Bruker 400WB spectrometer operating at a proton frequency of 400.13 MHz. Magic angle spinning (MAS) NMR spectra are obtained using single pulse (SP) and cross polarization (CP) experiments. The following experimental conditions apply to establish the ²⁹ Si frequency: 79.48 MHz, π̟/4-pulse 2 µs, decoupling duration 6.3 µs, recycle delay: 150 s, 3k scans; for CP measurements: contact time 5ms, 2k scans with 4µs ̟π/2-pulse. For ¹³ C frequency measurements: 100.52 MHz, CP, ̟π/2-pulse, contact time 2ms, decoupling time 6.3 µs, recycle delay 4s, 2k scans. ¹ H: single pulse with seq. π/2 pulse 5µs, recycle delay: 20 s, 32 scans. Samples are placed in 4 mm zirconia rotors rotating at 7 kHz (10 kHz for proton) under airflow conditions.

Determination of zinc content

Zinc content can be measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) spectrometry on an ICP Parallel Plasma Spectrometer (model TJA IRIS II; excitation source: 27.12 MHz RF oscillator with variable output power up to 1750 W).

XPS analysis was performed on a Perkin Elmer Φ 5600-ci spectrometer using a non-monochromatic Al-Mg double anode source. Samples are placed in steel sample holders and injected directly into the closed high energy system in the analytical chamber of the instrument. The analysis zone is 800 µm in diameter, and the operating pressure is less than 10 ^-9 mbar.

Spectroscopic analysis in the UV-visible region of the spectrum is carried out using a Perkin Elmer UV Lambda 900 spectrometer on powder samples, in the wavelength range from 800 to 200 nm, with an accuracy of 0.08 nm.

Rheometric Analysis Using a Punch Viscometer (MDR) (according to ISO 6502): Alpha Technologies rheometer type MDR2000 is used. The tests are carried out at 151°C for 30 minutes or at 170°C for 10 minutes, at an oscillation frequency of 1.66 Hz (100 oscillations per minute) and an oscillation amplitude of ± 0.5°, with the measurement of the value of the minimum torque (ML ), maximum torque (MH), the time required to increase the torque by one or two units (TS1 and TS2), and the time required to reach different percentages (5, 30, 50, 60, 90, 95 and 100 %) relative to the value of the maximum torque (MH).

Properties of vulcanized materials

The elastomeric materials obtained as described in the previous examples are vulcanized to obtain samples on which analytical studies and evaluation of dynamic mechanical properties are carried out. Unless otherwise indicated, the vulcanization is carried out in a mold, in a hydraulic press at 170° C. and at a pressure of 200 bar for approximately 10 minutes.

Static modulus of elasticity : static mechanical properties are measured at 23°C according to ISO 37:2005. In particular, tensile modulus at various elongation levels (10%, 50%, 100% and 300%, referred to in the following order as CA0.1, CA0.5, CA1 and CA3) is measured on samples of cured elastomeric compositions.

Dynamic modulus of elasticity : dynamic mechanical properties are measured using an Instron dynamic compression and tensile device in the following manner. A sample of vulcanized elastomeric cylindrical compositions (length=25 mm; diameter=18 mm) preloaded in compression up to 25% longitudinal strain relative to the original length and maintained at a given temperature (10°C, 23°C or 100°C ) during the test, subjected to a dynamic sinusoidal tension with an amplitude of ± 3,5% relative to the length of the sample with preload, at a frequency of 1 Hz, 10 Hz and 100 Hz.

Dynamic mechanical properties are expressed in terms of dynamic modulus of elasticity (E'), dynamic viscosity modulus (E") and tan delta (loss factor). The tan delta value is calculated as the ratio between the dynamic modulus of viscosity (E") and the dynamic modulus of elasticity (E').

EXAMPLE 1

Obtaining functionalized silicon dioxide

Materials used

Precipitated silica Rhodia Zeosil MP1165 (BET specific surface area 160 m ² /g) manufactured by Rhodia;

Coupling agent (APTES): (3-aminopropyl)triethoxysilane H ₂ N(CH ₂ ) ₃ Si(OC ₂ H ₅ ) ₃ (99%) manufactured by Sigma Aldrich;

Zinc nitrate hexahydrate Zn(NO ₃ ) ₂ ⋅6H ₂ O (99%) manufactured by Alfa Aesar;

Toluene (99%) manufactured by Alfa Aesar;

Anhydrous ethanol EtOH (99.9%) manufactured by Scharlau.

The preparation is a two-step process where first the silica is functionalized with a coupling agent and after isolation, the anhydrous powder is reacted with a zinc precursor (zinc nitrate hexahydrate) to achieve zinc binding by chelate formation with GC coordination groups.

First stage

In a 50 ml flask, 1 g of SiO ₂ powder is dispersed with stirring in 25 ml of toluene for ten minutes at 120°C. Then, an adequate amount of (3-aminopropyl)triethoxysilane is added to the dispersion, and the reaction mixture is maintained at 120° C. for 24 hours (reflux condition) with stirring. After cooling, the reaction product is recovered by centrifugation (9000 revolutions per minute (rpm), 10 minutes), washed twice with fresh toluene and dried in an oven at 80° C. overnight.

Various amounts of APTES are tested, as shown in the following Table 1, which are used to obtain samples with different zinc contents. The amount of silane is chosen based on the number of hydroxyl groups on the silica surface, adjusting for the molar ratios between hydroxyl groups and silane.

TABLE 1

Sample APTES (ml) APTES/OH ratio SiO ₂ -APTES-1 0.132 1:6.25 SiO ₂ -APTES-2 0.274 1:3 SiO ₂ -APTES-3 0.394 1:2 SiO ₂ -APTES-4 0.788 1:1

Second stage

1 g of the functionalized silica obtained in the first step (SiO ₂ -APTES) is dispersed in 50 ml of ethanol with stirring for 20 minutes at 100° C. to obtain a homogeneous suspension. Thereafter, an adequate amount of zinc precursor (Zn(NO ₃ ) ₂ ⋅H ₂ O) is added and the reaction is carried out for 2 hours. After cooling, the powder is separated by centrifugation (9000 rpm, 10 minutes) and washed twice with fresh ethanol. The powder is dried at 80° C. overnight. For each preformed functionalized silica (SiO ₂ -APTES-1, SiO ₂ -APTES-2, SiO ₂ -APTES-3, SiO ₂ -APTES-4), a constant Zn/APTES molar ratio of 0.7 is used. This amount is chosen taking into account that, under these experimental conditions, the maximum amount of zinc that can bind to SiO ₂ -APTES corresponds to a Zn/APTES molar ratio of 0.5. A slight excess of zinc relative to the stoichiometric value is used in order to reliably ensure the reproducibility of the synthesis as such.

Preparation of functionalized sepiolite

In the case of sepiolite, an activation step is added to the process described above to improve the surface reactivity of the sepiolite and increase its reactivity. Before functionalizing the sepiolite with APTES (first step of the previous method), the sepiolite is washed in an alkaline solution as follows.

1 g of Sepiolite is dispersed in 50 ml of 0.03M NaOH solution and kept under stirring at room temperature for 24 hours. The sepiolite is recovered by centrifugation (9000 rpm, 30 minutes) and washed with fresh water until neutral pH (pH=7) is obtained in the wash solution. The powder is dried using a lyophilization method. After this treatment, similar steps of functionalization with silane (APTES) and reaction with a zinc precursor are carried out.

Determination of the characteristics of the obtained materials

Figure 2 shows the FTIR ATR spectrum obtained for SiO ₂ -APTES-1 and SiO ₂ -APTES-3 materials. In SiO ₂ -APTES samples, one can always see two peaks at 2864 and 2932 cm ^-1 , which are attributed to the symmetric and asymmetric stretching of the CH ₂ groups, which is characteristic of the propyl chains of the APTES molecules. The intensity of these two peaks is strongly dependent on the amount of APTES involved in the reaction, as shown in Figure 2. This observation provides the first indication that the reaction proceeds in proportion to the amount of APTES used in the reaction itself.

In addition, from a comparison of the spectra for SiO ₂ -APTES and pure silicon dioxide (SiO ₂ ), not shown in Figure 2, a peak shift at 958 cm ^-1 is noted, which is attributed to the stretching of the Si-OH bond in hydroxyl groups on the surface of silicon dioxide , to higher wave numbers. The peak becomes the shoulder of the main peak at 1068 cm ^-1 due to the formation of the Si-O-Si bond, after the reaction of partial replacement of the hydroxyl groups of silicon dioxide with other molecules, which confirms the reaction between the APTES molecules and the surface of silicon dioxide.

Figure 3 shows the TGA spectrum obtained for the materials SiO ₂ -APTES-1, SiO ₂ -APTES-2, SiO ₂ -APTES-3 and SiO ₂ -APTES-4, while Figure 4 shows the TGA spectrum obtained for the SiO reference sample ₂ .

The following Table 2 shows the total weight loss after treatment at 150° to 1000°C.

TABLE 2

Sample % weight loss
150-1000°C _SiO2 4.102 SiO ₂ -APTES-1 7.087 SiO ₂ -APTES-2 8.023 SiO ₂ -APTES-3 10.366 SiO ₂ -APTES-4 10.458

TGA analysis allows you to check and confirm the effective functionalization of silica after reaction with APTES. This is possible because the mass loss in the range between 150°C and 1000°C is due to the presence of organic material on the silica surface: when comparing the TGA spectra for the SiO ₂ -APTES samples and for the reference SiO ₂ sample, an increase in mass loss associated with with these samples, which confirms the presence of organic material due to the functionalization reaction.

This weight loss increases with the amount of silane used, as expected, except in the case where sample 3 and sample 4 are compared. In the latter, despite the use of double the amount of silane, a percentage weight loss is recorded, which is exactly the same as the result for sample 3. This is believed to be due to the fact that, starting from sample 3, the silica reaches the surface saturation condition, whereby no silane molecule is able to further bond to the silica surface completely covered with APTES molecules.

The following Table 3 also shows the degree of surface coverage (expressed as a percentage by weight) and the surface density of the APTES molecules (expressed in molecules/nm ² ).

TABLE 3

Sample Coverage
surface (% by mass) n. molecules APTES /nm ² Reaction Yield (%) SiO ₂ -APTES-1 3.2 2.3 99 SiO ₂ -APTES-2 6.2 4.4 95 SiO ₂ -APTES-3 7.6 5.2 76 SiO ₂ -APTES-4 7.8 5.3 41

The values shown in Table 3 are obtained based on the following formulas (1) and (2):

(1)

(one)

where n _R is the number of moles of APTES, Δw _150-1000°C is the weight loss recorded in the range of 150-1000°C, n _OH is the number of surface hydroxyl groups of silica (determined by TGA analysis performed on pure silica), w _{SiO2 (1000°C)} is the weight of silica measured at 1000°C, MW _H2O is the molecular weight of water, MW _R is the molecular weight of the APTES residue, N _A is the Avogadro number, MW _SiO2 is the molecular weight of silica (60 g *mol ^-1 ) and S _BET is the surface area of silicon dioxide (160 m ² /g).

The data in Table 3 demonstrate that the number of APTES molecules on silica can be suitably changed from 2 to 6 molecules/nm ² , corresponding to a surface coverage of 3 to 8% by weight, at high reaction yields (>80%). Above 8% by mass, the yield of the reaction decreases significantly, which reveals that this value corresponds to the mass value at which the silica surface can be considered saturated.

The following Table 4 compares the nitrogen percentage values calculated using the data obtained from the TGA analysis with the nitrogen percentage values obtained using the CHNS analysis data.

TABLE 4

Sample N% (TGA) N% (CHNS) SiO ₂ -APTES-1 0.75 0.90 SiO ₂ -APTES-2 1.45 1.38 SiO ₂ -APTES-3 1.78 1.51 SiO ₂ -APTES-4 1.84 2.01

Taking into account the experimental error, the N% values are completely comparable, which provides additional confirmation of the formation of a bond between APTES and silica.

Table 5 below shows BET surface area values for pure silica (SiO ₂ ) and for two samples of SiO ₂ -APTES-1 and SiO ₂ -APTES-3.

TABLE 5

Sample BET (m ² /g) _SiO2 160 SiO ₂ _APTES_1 107 SiO ₂ _APTES_3 107

For functionalized samples, a decrease in the surface area value is observed due to the presence of APTES molecules on the surface, which partially close the pores and micropores of the silica particles, reducing the measured value of the total surface area.

Figure 5 illustrates the solid state NMR spectrum for pure silica (SiO ₂ ) and for two samples of SiO ₂ -APTES-1 and SiO ₂ -APTES-3. This spectrum shows that the functionalized samples have the same spectrum as pure silica, with the addition of T1 and T2 peaks due to the presence of APTES bound to the silica surface.

It is noted that the value of T-units increases with the percentage of functionalization, while the ratio Q3/Q4 decreases significantly from pure silica to functionalized silica, suggesting a decrease in Si-OH surface groups after functionalization. It is also noted that the T2/T3 ratio decreases as the amount of APTES increases, suggesting that the APTES molecules seem to bind to silica via two or three bonds per molecule. Finally, when comparing the T/Q ratio, a semi-quantitative analysis is obtained, which shows that the APTES signals increase proportionally with increasing nominal concentration.

The following Table 6 shows the results of the analysis c ICP, in particular, the amount of zinc actually bound on two samples of SiO ₂ -APTES-2-Zn and SiO ₂ -APTES-3-Zn, using different amounts of zinc, calculated based on the molar ratio between silane molecules in the original sample and zinc molecules.

TABLE 6

Sample n(Zn)/n(APTES) %wt Zn (nominal) %wt Zn (actual) SiO ₂ -APTES-2-Zn ½ 2.2 2.2±0.2 one 4.4 2 8.8 SiO ₂ -APTES-3-Zn ½ 3.4 3.1±0.2 one 6.8 2 11.3

The data in Table 6 clearly shows that the amount of zinc present in the final sample does not depend on the amount of zinc precursor chosen, but rather on the amount of silane previously bound to the silica. When using largely excess amounts of zinc nitrate, the final percentage by weight remains unchanged. In addition, the Zn:APTES ratio is always 1:2 for each SiO ₂ -APTES sample. This result provides primary data on the binding of zinc as a single site to two APTES molecules via an amino group, where the other two free positions around the zinc are likely to be occupied by anions present under the conditions of this synthesis, such as OH groups or NO ₃ groups.

Additional experimental confirmation of the presence of a bond between zinc and amino groups is obtained by examining the NMR spectra. Figure 6 shows the spectrum of the original sample of SiO ₂ -APTES-3 and the spectrum of the final sample of SiO ₂ -APTES-3-Zn. Band 1, present at 1.9 ppm (ppm), which is attributed to the NH ₂ groups, disappears after their interaction with zinc, and instead a broader band 2 appears at 7.3 ppm, exactly due to the interaction of amino groups with a zinc precursor . The information obtained from this analysis confirms the amine-zinc interaction based on the formation of zinc complexes on the silica surface.

Figure 7 shows the spectra obtained from the XPS analysis, which reveal the photoemission region of the N1S signal for a sample of SiO ₂ -APTES-Zn.

Figure 7 shows that the registered nitrogen signal consists of two main components, one organic (relating to the amino group of the ligand) and one inorganic (derived from the nitrate group). As a result of normalization, it is possible to set the percentage of the two components and, accordingly, determine the quantitative relationships between the various elements.

Of particular interest are the NH/Zn and Zn/NO ₃ ratios shown in the following Table 7.

TABLE 7

Sample NH/Zn Zn/ _NO3 SiO ₂ -APTES-3-Zn 1.7 1.5

The value of the ratio NH/Zn, which is approximately equal to 2, in accordance with expectations within the experimental error, confirms the coordination of each zinc atom with two APTES molecules via amino groups.

In addition, the value of the Zn/NO ₃ ratio confirms that at least one of the other two free zinc positions is occupied by NO ₃ groups resulting from the synthesis of zinc nitrate. Thus, it is confirmed that zinc is an isolated center coordinated to only two amino groups, and actually has two free positions, in which there are mobile ligands, such as the NO ₃ group, which is easily replaced in subsequent reactions by other molecules.

Finally, UV-visible spectroscopic analysis confirms the absence of the characteristic zinc oxide absorption band present around 370 nm, thereby confirming the complete absence of zinc oxide on the silica surface and in the system as a whole.

A sample of SiO ₂ -APTES-3-Zn is subjected to a similar analysis after a model vulcanization reaction, using a standard compound, carried out in TME (2,3-dimethyl-2-butene) at 120 ° C, in the presence of CBS (N-cyclohexyl-2-benzothiazole -sulfenamide) and sulfur, with an optimum vulcanization time of 20 minutes.

The NMR spectrum of the sample after vulcanization appeared to be in complete agreement with the spectrum of the sample before the reaction, where a broad band at 7.3 ppm is still visible, due to the interaction between zinc and amino groups, which was discussed in relation to Figure 6.

The NH/Zn and Zn/NO ₃ ratio values obtained from the XPS analysis data and shown in the following Table 7bis confirm that the NH/Zn ratio remains nearly constant after the model vulcanization reaction in TME, indicating no release of zinc from the vulcanized material, while they show an increase in the Zn/NO ₃ ratio, indicating a decrease in the NO ₃ groups associated with the zinc centers after the reaction.

TABLE 7bis

SiO ₂ -APTES-3-Zn sample NH/Zn Zn/ _NO3 Pre-vulcanization 1.7 1.5 Post-vulcanization 1.5 2.3

In view of the results thus obtained, it is thus demonstrated that the zinc centers, although actively involved in the vulcanization reaction as activators, remain stable and associated with the silane molecules present on the silica surface. In addition, the participation of the zinc center in the reaction is additionally demonstrated by the reduction of nitrate groups coordinated with zinc after the reaction, which shows, on the one hand, the weakness of these bonds relative to the bond with the amino group and, on the other hand, the possible interaction of zinc with other chemical agents involved in reaction.

EXAMPLE 2

Obtaining an elastomeric compound

The following Table 8 shows the compositions of a reference compound (R1) containing silica (43 phr (parts per 100 parts of rubber)) and zinc oxide (corresponding to 1.49 phr Zn ²⁺ ) added separately, and a compound according to the present invention (I1 ), which introduced 49.4 phr SiO ₂ -APTES-3-Zn, obtained as described in example 1, corresponding to 1.49 phr Zn ²⁺ , 3.42 phr APTES, 0.96 phr nitrate, 0, 54 phr hydroxyl groups (-OH) and 43 phr silica.

TABLE 8

Component R1 I1 Stage 1 IR 100 100 Silica 43.0 - SiO ₂ -APTES-3-Zn - 49.4 Silane 3.44 - Stearic acid 2 - 6PPD 2 2 ZnO 1.85 - Stage 2 CBS 1.6 1.6 Sulfur (67%) 3 3

IR: high cis synthetic polyisoprene (min. 96%) obtained by solution polymerization with a Ziegler/Natta catalyst; Supplier NIZHNEKAMSKNEFTECHIM EXPORT;

Silica: ZEOSIL 1115 MP (BET specific surface area 95-120 m ² /g, white microgranules obtained by precipitation from sodium silicate solutions with sulfuric acid. It does not contain crystalline silica. Supplier SOLVAY RHODIA OPERATIONS

Stearic Acid: Supplier TEMIX OLEO SRL

6PPD: N-(1,3-dimethylbutyl)-N`-phenyl-p-phenylenediamine, Supplier: SOLUTIA/EASTMAN

ZnO(80): zinc oxide 80%, polymer binder and dispersant 20%, Supplier LANXESS ADD

Silane: TESPD Bis-(3-triethoxy-silyl-propyl)disulfide Supplier JINGZHOU JIANGHAN FINE CHEM

CBS: N-cyclohexyl-2-benzothiazylsulfenamide, <1% cyclohexylamine content, Supplier DUSLO

Sulfur: Crystex OT33 amorphous sulfur, insoluble in CS ₂ and in toluene. Treated with 33% hydrotreated heavy naphthenic distillate (mixture of hydrocarbons), Supplier EASTMAN.

All components, with the exception of sulfur and accelerator (CBS) are mixed together in an internal mixer (model Pomini PL 1.6) for approximately 5 minutes (1st stage). As soon as the temperature reaches 145+5°C, the elastomeric mixture is discharged. Sulfur and accelerator (CBS) are then added and mixing is carried out in an open roller mixer (2nd stage).

Using the compounds of Table 8, samples were prepared and rheometrically measured with a punch viscometer (MDR).

The results are summarized in the following Table 9.

TABLE 9

R1 I1 Δ I1 relative to R1 (%) MH 22.2 28.8 +30 t50 2.05 0.52 -75 t100 4.40 2.50 -43

The results of Table 9 show greater reactivity and greater maximum torque (MH) for the compound of the invention (I1) compared to the reference compound.

EXAMPLE 3

Obtaining an elastomeric compound

The following Table 10 shows the compositions of the reference compound (R2) containing silica (43 phr) and zinc oxide (corresponding to 1.49 phr Zn ²⁺ ) added separately, of the reference compound R3 containing silica (43 phr), zinc oxide (corresponding to 1.49 phr Zn ²⁺ ) and APTES silane (3.56 phr) added separately, and the compound of the present invention (I2) in which 49.4 phr SiO ₂ -APTES-3-Zn was introduced, obtained so, as described in example 1, equal to 1.49 phr Zn ²⁺ , 3.42 phr APTES, 0.96 phr nitrate, 0.54 phr hydroxyl groups (-OH) and 43 phr silica.

TABLE 10

Component R2 R3 I2 Stage 1 IR 100 100 100 Soot 15.00 15.00 15.00 Silica 43.0 43.0 - SiO ₂ -APTES-3-Zn - - 49.4 APTES - 3.56 - Silane 3.44 - - Stearic acid 2.0 2.0 2.0 ZnO 1.85 1.85 - 6PPD 3.0 3.0 3.0 Wax 1.0 1.0 1.0 Stage 2 DCBS 1.8 1.8 1.8 PVI 0.4 0.4 0.4 Sulfur (67%) 3.0 3.0 3.0

IR: Synthetic high cis polyisoprene (min. 96%) obtained by solution polymerization with a Ziegler/Natta catalyst; Supplier NIZHNEKAMSKNEFTECHIM EXPORT;

Carbon Black: N375 Carbon Black, Supplier CABOT

Silica: ZEOSIL 1115 MP (BET specific surface area 95-120 m ² /g, white microgranules obtained by precipitation from sodium silicate solutions with sulfuric acid. It does not contain crystalline silica. Supplier SOLVAY RHODIA OPERATIONS

APTES: (3-aminopropyl)triethoxysilane (99%) Supplier Sigma Aldrich

Silane: TESPT Bis-(3-triethoxy-silyl-propyl)-tetrasulfide Supplier Evonik

Stearic Acid: Supplier TEMIX OLEO SRL

ZnO(80): zinc oxide 80%, polymer binder and dispersant 20%, Supplier LANXESS ADD

6PPD: N-(1,3-dimethylbutyl)-N`-phenyl-p-phenylenediamine, Supplier: SOLUTIA/EASTMAN

Wax: RIOWAX BN01, mixture of n- and iso-paraffins, Supplier: SER

DCBS: N,N'-dicyclohexyl-2-benzothiazylsulfenamide, <1% cyclohexylamine, Supplier LANXESS ADD

PVI: N-cyclohexyl-thiophthalimide, Supplier of Solutia

Sulfur: Crystex OT33 amorphous sulfur, insoluble in CS ₂ and in toluene. Treated with 33% hydrotreated heavy naphthenic distillate (mixture of hydrocarbons), Supplier EASTMAN.

All components except sulfur, moderator (PVI) and accelerator (CBS) are mixed together in an internal mixer (model Pomini PL 1.6) for approximately 5 minutes (1st stage). As soon as the temperature reaches 145+5°C, the elastomeric mixture is discharged. Sulfur, retarder (PVI) and accelerator (CBS) are then added and mixed in an open roller mixer (2nd stage).

Using the compounds of Table 10, specimens were made, on which rheometric measurements were made using MDR (30 minutes at 151°C and 10 minutes at 170°C) and measurement of static and dynamic mechanical properties after curing for 30 minutes at 151°C.

The results are summarized in the following Tables 11-13.

TABLE 11

MDR 30 minutes at 151°C R2 R3 I2 Δ R3 relative to R2 (%) Δ I2 vs. R2 (%) Δ I2 relative to R3 (%) MH[daN/m) 28.06 30.86 40.95 9.98 45.94 32.70 TS1[min] 0.79 0.68 0.52 -13.92 -34.18 -23.53 TS2[min] 2.52 0.97 0.82 -61.51 -67.46 -15.46 T05[min] 1.08 0.74 0.75 -31.48 -30.56 1.35 T30[min] 5.85 1.85 2.3 -68.38 -60.68 24.32 T60[min] 7.77 3.19 4.35 -58.94 -44.02 36.36 T90[min] 11.42 5.32 7.58 -53.42 -33.63 42.48 T95[min] 12.67 5.93 8.55 -53.20 -32.52 44.18 T100[min] 16.26 7.49 11.26 -53.94 -30.75 50.33

TABLE 12

MDR 10 minutes at 170°C R2 R3 I2 Δ R3 relative to R2 (%) Δ I2 vs. R2 (%) Δ I2 relative to R3 (%) ML[daN/m) 3.3 6.97 5.95 111.21 80.30 -14.63 MH[daN/m) 26.96 27.98 41.3 3.78 53.19 47.61 TS1[min] 0.52 0.46 0.3 -11.54 -42.31 -34.78 TS2[min] 0.85 0.53 0.41 -37.65 -51.76 -22.64 T05[min] 0.59 0.47 0.39 -20.34 -33.90 -17.02 T30[min] 1.65 0.73 0.82 -55.76 -50.30 12.33 T60[min] 2.23 1.05 1.35 -52.91 -39.46 28.57 T90[min] 3.29 1.53 2.19 -53.50 -33.43 43.14 T95[min] 3.65 1.67 2.45 -54.25 -32.88 46.71 T100[min] 4.64 2.07 3.23 -55.39 -30.39 56.04

The results of Tables 11 and 12 show the greater reactivity of the compound of the present invention (I2) relative to the standard reference compound R2 and the reference compound R3. In fact, it should be that the minimum and especially the maximum torque values obtained for the I2 compound of the present invention are more than 50% higher than the corresponding values obtained for the R2 and R3 compounds, but despite this, T100 for I2 is lower than more than than 30% when compared to T100 for R2. The higher T100 for I2 compared to the T100 for R3 should be taken as an indicator of greater reactivity, given the different and higher MH value.

The higher MH data for the compound I2 of the invention relative to R2 and R3 indicates that the use of the compound of the present invention can be considered not only as a reasonable replacement for the commonly used zinc oxide with lower release of zinc to the environment, but also as a means of reducing the amount of zinc in the original compound without affecting the mechanical performance of the vulcanized compound.

TABLE 13

Static mechanical properties R2 R3 I2 Δ R3 relative to R2 (%) Δ I2 vs. R2 (%) Δ I2 relative to R3 (%) Ca0.1[MPa] 0.54 0.53 0.61 -1.85 12.96 15.09 Ca0.5[MPa] 1.33 1.01 1.36 -24.06 2.26 34.65 Ca1[MPa] 2.17 1.37 2.14 -36.87 -1.38 56.20 Ca3[MPa] 9.39 4.96 8.77 -47.18 -6.60 76.81 CR[MPa] 27.66 21.19 26.17 -23.39 -5.39 23.50

The results of Table 13 show for the compound of the invention (I2) higher tensile modulus values of 10% (Ca0.1) and 50% (Ca0.5) relative to both references (R2 and R3), resulting in more predictable resiliency, with more comfortable handling of the tire.

The results obtained for comparative compound R3 show that the APTES aminosilane added separately to the compound (i.e. not bonded to the silica in the zinc) significantly degrades the mechanical properties because it cannot bond to the compound, while the results obtained for comparative compound, surprisingly demonstrate that the use of the coupling agent of the present invention allows you to significantly restore the same values of Ca1, Ca3 and CR of the reference compound R2.

TABLE 14

Dynamic mechanical properties R2 R3 I2 Δ R3 relative to R2 (%) Δ I2 vs. R2 (%) Δ I2 relative to R3 (%) 10°C E'[MPa], 1Hz 5.642 4.855 5.956 -13.95 5.57 22.68 E'[MPa], 10Hz 6.142 5.579 6.716 -9.17 9.35 20.38 Tanδ, 1Hz 0.125 0.237 0.19 89.60 52.00 -19.83 Tanδ, 10Hz 0.155 0.249 0.22 60.65 41.94 -11.65 23°C E'[MPa], 1Hz 5.504 4.602 5.632 -16.39 2.33 22.38 E'[MPa], 10Hz 5.935 5.282 6.263 -11.00 5.53 18.57 Tanδ, 1Hz 0.108 0.224 0.163 107.41 50.93 -27.23 Tanδ, 10Hz 0.13 0.23 0.188 76.92 44.62 -18.26 100°C E'[MPa], 1Hz 5.223 4.095 5.277 -21.60 1.03 28.86 E'[MPa], 10Hz 5.452 4.492 5,564 -17.61 2.05 23.86 Tanδ, 1Hz 0.066 0.15 0.096 127.27 45.45 -36.00 Tanδ, 10Hz 0.076 0.166 0.106 118.42 39.47 -36.14

The results of Table 14 show the unexpected behavior of the compound I2 of the present invention relative to the comparative compound R3. The latter, in fact, shows high values of tanδ at all temperatures, and moreover, too high values at high temperatures, resulting in high hysteresis in dissipative heat loss and high rolling resistance at high speed, while vice versa the I2 compound is truly The invention shows a more limited and acceptable increase in tan δ at high temperatures, but a significant increase in this figure at low temperatures, which predicts better grip on dry roads and better grip on wet roads.

EXAMPLE 4

Obtaining functionalized silicon dioxide

The method described in example 1 is repeated using the compound N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDTMS) as a coupling agent (97% - Sigma-Aldrich). In the first step, 0.37 ml of ETDMS is used for every gram of SiO ₂ to be functionalized. The amount of ETDMS is chosen based on the number of hydroxyl groups on the silica surface, resulting in a molar ratio between ETDMS and hydroxyl groups on the silica surface (ETDMS/OH) of 1:2. In the second step, the amount of zinc precursor (Zn(NO ₃ ) ₂ ⋅H ₂ O) is varied to give a molar ratio between zinc and ETDMS (Zn/EDTMS) of 1:2, 1:1 and 2:1. Then three samples of SiO ₂ -EDTMS-Zn are obtained according to the following Table 15.

TABLE 15

Sample Zn/ETDM ratio SiO ₂ -ETDMS-Zn-1 1:2 SiO ₂ -ETDMS-Zn-2 1:1 SiO ₂ -ETDMS-Zn-3 2:1

Determination of the characteristics of the obtained materials

Samples are characterized as described in Example 1 by FTIR ATR spectroscopy to confirm effective functionalization of the material, by TGA and CHNS to quantify the silane actually deposited on the silica surface, and by ICP analysis to determine the amount of zinc, associated with silicon dioxide.

Figure 8 shows the FTIR ATR spectrum obtained for the material SiO ₂ -ETDMS.

When comparing the spectra of SiO ₂ -ETDMS and pure silicon dioxide (SiO ₂ ), a shift of the peak at 954 cm ^-1 is noted, which is attributed to the stretching of the bond of hydroxyl groups in Si-OH on the surface of silicon dioxide, towards higher wave numbers. This peak becomes the shoulder of the main peak at 1068 cm ^-1 , due to the formation of the Si-O-Si bond, after the reaction with partial replacement of the hydroxyl groups of silicon dioxide with other molecules, which confirms the reaction between the ETDMS molecules and the surface of silicon dioxide.

In addition, in the SiO ₂ -ETDMS sample, two peaks at 2948 and 2864 cm ^-1 can be seen, which are attributed to the symmetric and asymmetric stretching of the CH ₂ groups characteristic of the propyl and ethyl chains of the ETDMS molecules.

Finally, the authors note the appearance of an additional peak at 1459 cm ^-1 due to the secondary amino group of the ETDMS chain.

Figure 9 shows the TGA spectrum obtained for the material SiO ₂ -ETDMS and for the reference sample SiO ₂ . The overall weight loss for the SiO ₂ -ETDMS sample is 15.8%, compared to about 4% for the reference SiO ₂ sample.

The following Table 16 also shows the degree of surface coverage (expressed as a percentage by weight) and the surface density of the ETDMS molecules (expressed in molecules/nm ² ).

TABLE 16

Sample Coverage
surface (% by mass) n. molecules ETDMS /nm ² Reaction Yield (%) SiO2- _ETDMS 15.3 6.2 90

The data in Table 16 show that the number of ETDMS molecules on silica is approximately 6 molecules/nm ² , corresponding to a surface coverage of approximately 15% by weight, at high reaction yields (90%).

The following Table 17 compares the percentage nitrogen values calculated using the data obtained from the TGA analysis with the percentage nitrogen values obtained using the CHNS analysis data.

TABLE 17

Sample N% (TGA) N% (CHNS) _SiO2 0.00 0.00 SiO2- _ETDMS 4.25 3.74

Given the experimental error, the N% values are completely comparable, which provides additional confirmation of the formation of a bond between ETDMS and silica.

Table 18 below shows the results of the ICP analysis, in particular the amount of zinc actually bound on the three samples obtained using different amounts of zinc, calculated based on the molar ratio between zinc molecules and silane molecules in the original sample (Zn/ETDMS).

TABLE 18

Sample Zn/ETDMS (nominal value) Zn (% by mass) Zn (molecules/nm ² ) Zn/ETDMS (molecules/nm ² ) SiO ₂ -ETDMS-Zn-1 1:2 3.5±0.2 3.58±0.2 0.57 SiO ₂ -ETDMS-Zn-2 1:1 5.9±0.2 6.2±0.2 1.00 SiO ₂ -ETDMS-Zn-3 2:1 6.6±0.2 7.1±0.2 1.14

The results of the ICP analysis show that EDTMS promotes a different pattern of change than APTES and that the Zn/silane molar ratios vary according to the amount of zinc precursor used in the reaction. The first sample (1:2 molar ratio) has an effective Zn/silane molar ratio of approximately 0.5, suggesting that each zinc center is coordinated to two silane molecules and, accordingly, four nitrogen atoms. The formation of a structure that includes two EDTMS molecules for each zinc center is reasonably expected given the proximity of the silane molecules on the silica surface. In addition, the longer chain length of EDTMS (compared to APTES) may contribute to greater chain mobility and elasticity, and therefore coordinate zinc in a different way. In the other two samples prepared with nominal Zn/EDTMS molar ratios of 1:1 and 1:2, the measured Zn/EDTMS molar ratio is approximately 1 in both cases, suggesting that each zinc center is coordinating to the EDTMS molecule, probably as a result of chelating coordination.

EXAMPLE 5

Obtaining an elastomeric compound

Using the same method as described in Example 2 and the compositions described in the following Table 19, a reference compound (R4) was prepared containing silica (35 phr) and zinc oxide (corresponding to 1.49 phr Zn ²⁺ ) added separately, and the compound according to the present invention (I3), containing 42.7 phr SiO ₂ -EDTMS-Zn, obtained as described in example 4, corresponding to 1.49 phr Zn ²⁺ , 6.5 phr EDTMS, and 35 phr of silicon dioxide.

TABLE 19

Component R4 I3 Stage 1 IR 100 100 Silica 35.0 - SiO ₂ -APTES-3-Zn - 42.7 Silane 2.78 - Stearic acid 2 - 6PPD 2 2 ZnO 1.85 - Stage 2 CBS 1.6 1.6 Sulfur (67%) 3 3

Using the compounds of Table 19, specimens were prepared and rheometrically measured with a punched viscometer (MDR). The results are summarized in the following Table 20.

TABLE 20

R4 I3 Δ I3 relative to R4 (%) MH 17.7 22.8 +29 t50 2.61 1.02 -61 t100 5.00 2.85 -43

The results of Table 20 show greater reactivity and greater maximum torque (MH) for the compound of the invention (I1) compared to the reference compound.

Claims (32)

1. The compound represented by the following formula (II): CB-O-ROS-GC-Zn, (II) where CB is a white filler selected from the group consisting of silica and silicates in the form of fibers, flakes or granules, O is one or more oxygen bridges, ROS is an organosilane residue containing at least one linear or branched alkyl a chain having 1-6 carbon atoms bonded to a silicon atom, GC is one or more coordination groups chelated with zinc in ionic form, and Zn is zinc in ionic form coordinated by coordination groups, where the coordination groups of GC are linear , branched or cyclic alkyl chains having 1-6 carbon atoms and containing one or more heteroatoms inside or at the end of the alkyl chain. 2. A method for preparing a compound of formula (II) according to claim 1, wherein the method includes at least: providing a white filler (CB) selected from the group consisting of silica and silicates in the form of fibers, thin plates or granules, providing a binding agent having the following formula (I): GR-ROS-GC, (I) where GR is one or more reactive groups capable of forming oxygen bridges with a white filler surface, ROS is an organosilane residue containing at least one linear or branched alkyl chain having 1-6 carbon atoms bonded to a silicon atom, and GC represents one or more coordination groups, which are linear, branched or cyclic alkyl chains having 1-6 carbon atoms and containing one or more heteroatoms inside or at the end of the alkyl chain, providing a zinc compound (Zn ²⁺ ), reacting between the white filler (CB) and one or more reactive groups (GR) of the compound of formula (I) to form oxygen bridges (-O-) between the white filler (CB) and the organosilane residue (ROS), and carrying out a reaction between one or more coordination groups (GC) of a compound of formula (I) and a zinc compound to form a chelate, and isolating the resulting compound of formula (II) according to claim 1. 3. The compound according to claim 1, wherein the white filler is selected from the group consisting of bentonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, palygorskite, also referred to as attapulgite, montmorillonite, alloisite, possibly modified by processing acid and/or derivatized, and mixtures thereof. 4. The method according to claim 2, wherein the white filler is selected from the group consisting of bentonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, palygorskite, also referred to as attapulgite, montmorillonite, alloisite, possibly modified by processing acid and/or derivatized, and mixtures thereof. 5. The compound according to claim 1, where the GC coordination groups are functional groups represented by the formula -C _n H _2n -XC _m H _2m -Y, where n and m, the same or different from each other, mean an integer from 1 to 6 inclusive; and Y and X, the same or different from each other, represent a group selected from a mercapto group and an amino group. 6. The method according to claim 2, where the GC coordination groups are functional groups represented by the formula -C _n H _2n -XC _m H _2m -Y, where n and m, the same or different from each other, mean an integer from 1 to 6 inclusive; and Y and X, the same or different from each other, represent a group selected from a mercapto group and an amino group. 7. The method of claim 2 wherein the GR reactive groups are alkoxy groups having 1-4 carbon atoms. 8. The method according to claim 2, where the binding agent is represented by the general formula (Ia): (R) ₃ Si-C _n H _2n -XC _m H _2m -Y, (Ia) where the R groups, identical or different from each other, are selected from alkyl groups or alkoxy groups having 1-4 carbon atoms, provided that at least one of the R groups is an alkoxy group; n and m, identical or different from each other, mean an integer from 1 to 6 inclusive; Y and X, the same or different from each other, represent a group selected from a mercapto group and an amino group. 9. The method of claim 2, wherein the coupling agent is selected from the group consisting of (3-aminopropyl)triethoxysilane (APTES), N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (also known as N-[3-( trimethoxysilyl)propyl]ethylenediamine (EDTMS)), N-(2-aminoethyl)-3-aminopropyl-triethoxysilane, N-(2-aminoethyl)-3-aminopropyl-methyl-dimethoxysilane, 3-aminopropylmethyl-diethoxysilane, 3-ureidopropyl- trimethoxysilane, 3-ureidopropyltriethoxysilane, N-cyclohexyl(aminomethyl)methyldiethoxysilane, N-cyclohexyl(aminomethyl)triethoxysilane, N-cyclohexyl-3-aminopropyltrimethoxysilane, 3-(2-aminomethylamino)propyltriethoxysilane, N-(n- butyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-(2-(2-aminoethylamino)ethylamino ) propyl-trimethoxysilane, N-(n-butyl)-3-aminopropyl-triethoxysilane, Ν,Ν-diethylaminopropyl-trimethoxysilane, N, N-dimethylaminopropyl-trimethoxysilane, butylaminomethyl-triet oxysilane, N-cyclohexyl(aminomethyl)trimethoxysilane, 2-aminoethylaminomethyltriethoxysilane, diethylaminomethyltriethoxysilane, (3-mercaptopropyl)triethoxysilane and (3-mercaptopropyl)trimethoxysilane. 10. The method of claim 9 wherein the coupling agent is selected from the group consisting of (3-mercaptopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane (APTES), (3-aminopropyl)trimethoxysilane, N-(2-aminoethyl)-3 -aminopropyl-trimethoxysilane, (N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDTMS)) and N-(2-aminoethyl)-3-aminopropyltriethoxysilane. 11. The method of claim 2 wherein the zinc compound is selected from the group consisting of zinc oxide, zinc hydroxide and organic or inorganic zinc salts. 12. The method of claim 11 wherein the organic or inorganic zinc salts are selected from the group consisting of zinc nitrate, zinc sulfate, zinc chloride, zinc bromide and zinc acetate. 13. A method for producing a vulcanizable elastomeric tire compound, wherein the method includes at least: a step of mixing (1) at least one elastomeric polymer and at least one elastomeric compound additive, excluding a curing agent, to obtain a non-vulcanizable elastomeric compound; a step of mixing (2) a non-vulcanizable elastomeric compound and at least one curing agent to obtain a curable elastomeric compound; and the step of unloading the vulcanizable elastomeric compound, where the compound of formula (II) according to p. 1 is added at least one of the stages of mixing (1) and (2). 14. Vulcanizable elastomeric compound obtained by the method according to claim 13. 15. Tire element containing a vulcanizable compound according to claim 14 or a vulcanized compound obtained by vulcanizing a vulcanizable elastomeric compound according to claim 14. 16. Tire for vehicle wheels, including the element according to claim 15.

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