PROCESS FOR PREPARING COMPOUNDS FOR TYRES AND TYRES COMPRISING THEM

Abstract

The present invention relates to a compound represented by the formula (II): CB-O-ROS-GC-Zn (II) where CB represents the white filler, O represents one or more oxygen bridge bonds, ROS represents an organo-silane residue, GC represents one or more coordinating groups forming a chelate with zinc in ionic form represented by linear, branched or cyclic alkyl chains, comprising one or more heteroatoms inside or at the end of the alkyl chain, and Zn represents zinc in ionic form coordinated with the coordinating groups, a process for the preparation thereof, and the use thereof in the vulcanisation process of elastomeric compounds.

Claims

1. A compound represented by the following formula (II):
CB-O-ROS-GC-Zn  (II) wherein CB represents the white filler, O represents one or more oxygen bridge bonds, ROS represents an organo-silane residue, GC represents one or more coordinating groups forming a chelate with zinc in ionic form, and Zn represents zinc in ionic form coordinated with the coordinating groups, wherein said coordinating groups GC are linear, branched or cyclic alkyl chains, comprising one or more heteroatoms inside or at the end of the alkyl chain.

2. A process for the preparation of the compound of formula (II) as claimed in claim 1, wherein said method comprises at least: providing a white filler (CB) providing a coupling agent having the following formula (I):
GR-ROS-GC  (I) wherein GR represents one or more reactive groups capable of forming oxygen bridges with the surface of said white filler, ROS represents an organo-silane residue, and GC represents one or more coordinating groups, providing a zinc compound (Zn.sup.2+), reacting the white filler (CB) with one or more reactive groups (GR) of said compound of formula (I) so as to form oxygen bridges (—O—) between said white filler (CB) and said organo-silane residue (ROS), and reacting one or more coordinating groups (GC) of said compound of formula (I) with the zinc compound so as to form a chelate, and separating the resulting compound of formula (II) as claimed in claim 1.

3. The compound as claimed in claim 1 or the process as claimed in claim 2, wherein said white filler is selected from the group consisting of silica and silicates in the form of fibres, lamellae or granules.

4. The compound or process as claimed in claim 3, wherein said white filler is selected from the group consisting of bentonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, paligorskite also known as attapulgite, montmorillonite, alloisite and the like, possibly modified by acid treatment and/or derivatized, and mixtures thereof.

5. The compound or process as claimed in claim 1, wherein said coordinating groups GC are functional groups represented by the formula —C.sub.nH.sub.2n—XC.sub.mH.sub.2m—Y, where n and m, equal or different from each other, are an integer from 1 a 6 inclusive and Y and X, equal or different from each other, are a group selected from mercapto and amino.

6. The process as claimed in claim 2, wherein said GR reactive groups are alkoxy groups having 1 to 4 carbon atoms.

7. The process as claimed in claim 2, wherein said coupling agent is represented by the general formula (Ia):
(R).sub.3Si—C.sub.nH.sub.2n—X—C.sub.mH.sub.2m—Y  (Ia) wherein the R groups, equal to or different from each other, are selected from alkyl or alkoxy groups having 1 to 4 carbon atoms, provided that at least one of the R groups is an alkoxy group; n and m, equal or different from each other, are an integer from 1 to 6 inclusive; Y and X, equal or different from each other, are a group selected from mercapto and amino.

8. The process as claimed in claim 2, wherein said 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-trimethoxy silane, 3-ureidopropyl-triethoxysilane, N-cyclohexyl(aminomethyl) methyldiethoxy silane, N-cyclohexyl(aminomethyl) triethoxysilane, N-cyclohexyl-3-aminopropyl-trimethoxysilane, 3-(2-aminomethylamino)propyl-triethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxy-silane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminoisobutyl-methyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-(2-(2-aminoethylamino)ethylamino)propyl-trimethoxysilane, N-(n-butyl)-3-aminopropyl-triethoxysilane, N, N-diethylaminopropyl-trimethoxysilane, N, N-dimethylaminopropyl-trimethoxysilane, butylaminemethyl-triethoxysilane, N-cyclohexyl(aminomethyl) trimethoxy-silane, 2-aminoethylaminomethyl-triethoxysilane, diethylaminomethyl-triethoxysilane, (3-mercaptopropyl)triethoxysilane and (3-mercaptopropyl)trimethoxysilane.

9. The process as claimed in claim 8, wherein said coupling agent is selected from the group consisting of (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.

10. The process as claimed in claim 2, wherein said zinc compound is selected from the group consisting of zinc oxide, zinc hydroxide and organic or inorganic zinc salts.

11. The process as claimed in claim 10, wherein said organic or inorganic zinc salts are selected from the group consisting of zinc nitrate, zinc sulfate, zinc chloride, zinc bromide and zinc acetate.

12. A process for the preparation of a vulcanisable elastomeric compound for tyres, where said process comprises at least: a mixing step (1) of at least one elastomeric polymer and of at least one additive for elastomeric compounds, with the exception of a vulcanising agent, to give a non-vulcanisable elastomeric compound; a mixing step (2) of the non-vulcanisable elastomeric compound and of at least one vulcanising agent, to give a vulcanisable elastomeric compound, and a step of unloading of the vulcanisable elastomeric compound, wherein the compound of formula (II) as claimed in claim 1 is added in at least one of said mixing steps (1) and (2).

13. A vulcanisable elastomeric compound obtained as claimed in the process of claim 12.

14. A tyre component comprising the vulcanisable compound of claim 13 or the vulcanised compound obtained by vulcanisation thereof.

15. A tyre for vehicle wheels comprising a component as claimed in claim 14.

Description

DESCRIPTION OF THE DRAWINGS

[0188] FIG. 1 shows a radial half-section of a tyre for vehicle wheels according to the invention.

[0189] FIG. 2 shows the FTIR ATR spectrum of two silica samples functionalised with the coupling agent described in example 1.

[0190] FIG. 3 shows the TGA spectrum of four silica samples functionalised with the coupling agent described in example 1.

[0191] FIG. 4 shows the TGA spectrum of the reference sample SiO.sub.2 as described in example 1.

[0192] FIG. 5 shows the solid state NMR spectrum of the pure silica reference sample (SiO.sub.2) and of two silica samples functionalised with the coupling agent described in example 1.

[0193] FIG. 6 shows the NMR spectrum of the silica sample functionalised with the coupling agent and that of the same sample after forming the chelate with zinc, as described in example 1.

[0194] FIG. 7 shows the spectra obtained from XPS analysis of a silica sample functionalised with the zinc-chelated coupling agent, as described in example 1.

[0195] FIG. 8 shows the FTIR ATR spectrum of a silica sample functionalised with the coupling agent and of the pure silica reference sample (SiO.sub.2), as described in example 4.

[0196] FIG. 9 shows the TGA spectrum of a silica sample functionalised with the coupling agent and of the pure silica reference sample (SiO.sub.2), as described in example 4.

[0197] In particular, FIG. 1 shows a radial half-section of a tyre for vehicle wheels, comprising a vulcanised elastomeric compound prepared by vulcanisation of an elastomeric compound prepared according to the process of the invention.

[0198] In FIG. 1, “a” indicates an axial direction and “X” indicates a radial direction, in particular X-X indicates the outline of the equatorial plane. For simplicity, FIG. 1 shows only a portion of the tyre, the remaining portion not shown being identical and arranged symmetrically with respect to the equatorial plane “X-X”.

[0199] Tyre 100 for four-wheeled vehicles comprises at least one carcass structure, comprising at least one carcass layer 101 having respectively opposite end flaps engaged with respective annular anchoring structures 102, referred to as bead cores, possibly associated to a bead filler 104.

[0200] The carcass layer 101 is optionally made with an elastomeric compound.

[0201] The tyre area comprising the bead core 102 and the filler 104 forms a bead structure 103 intended for anchoring the tyre onto a corresponding mounting rim, not shown.

[0202] The carcass structure is usually of radial type, i.e. the reinforcing elements of the at least one carcass layer 101 lie on planes comprising the rotational axis of the tyre and substantially perpendicular to the equatorial plane of the tyre. Said reinforcement elements generally consist of textile cords, such as rayon, nylon, polyester (for example polyethylene naphthalate, PEN). Each bead structure is associated to the carcass structure by folding back of the opposite lateral edges of the at least one carcass layer 101 around the annular anchoring structure 102 so as to form the so-called carcass flaps 101a as shown in FIG. 1.

[0203] In one embodiment, the coupling between the carcass structure and the bead structure can be provided by a second carcass layer (not shown in FIG. 1) applied in an axially outer position with respect to the first carcass layer.

[0204] An anti-abrasive strip 105 optionally made with an elastomeric compound is arranged in an outer position of each bead structure 103.

[0205] The carcass structure is associated to a belt structure 106 comprising one or more belt layers 106a, 106b placed in radial superposition with respect to one another and with respect to the carcass layer, having typically textile and/or metallic reinforcement cords incorporated within a layer of vulcanised elastomeric compound.

[0206] Such reinforcement cords may have crossed orientation with respect to a direction of circumferential development of tyre 100. By “circumferential” direction it is meant a direction generally facing in the direction of rotation of the tyre.

[0207] At least one zero-degree reinforcement layer 106c, commonly known as a “0° belt”, may be applied in a radially outermost position to the belt layers 106a, 106b, which generally incorporates a plurality of elongated reinforcement elements, typically metallic or textile cords, oriented in a substantially circumferential direction, thus forming an angle of a few degrees (such as an angle of between about 0° and 6°) with respect to a direction parallel to the equatorial plane of the tyre, and coated with vulcanised elastomeric compound.

[0208] A tread band 109 of vulcanised elastomeric compound is applied in a position radially outer to the belt structure 106.

[0209] Moreover, respective sidewalls 108 of vulcanised elastomeric compound are applied in an axially outer position on the lateral surfaces of the carcass structure, each extending from one of the lateral edges of tread 109 at the respective bead structure 103.

[0210] In a radially outer position, the tread band 109 has a rolling surface 109a intended to come in contact with the ground. Circumferential grooves, which are connected by transverse notches (not shown in FIG. 1) so as to define a plurality of blocks of various shapes and sizes distributed over the rolling surface 109a, are generally made on this surface 109a, which for simplicity is represented smooth in FIG. 1.

[0211] An under-layer 111 of vulcanised elastomeric compound can be arranged between the belt structure 106 and the tread band 109.

[0212] A strip consisting of elastomeric compound 110, commonly known as “mini-sidewall”, of vulcanised elastomeric compound can optionally be provided in the connecting zone between sidewalls 108 and the tread band 109, this mini-sidewall generally being obtained by co-extrusion with the tread band 109 and allowing an improvement of the mechanical interaction between the tread band 109 and sidewalls 108. Preferably, the end portion of sidewall 108 directly covers the lateral edge of the tread band 109.

[0213] In the case of tubeless tyres, a rubber layer 112, generally known as “liner”, which provides the necessary impermeability to the inflation air of the tyre, can also be provided in a radially inner position with respect to the carcass layer 101.

[0214] The rigidity of the tyre sidewall 108 can be improved by providing the bead structure 103 with a reinforcing layer 120 generally known as “flipper” or additional strip-like insert.

[0215] Flipper 120 is a reinforcing layer which is wound around the respective bead core 102 and the bead filler 104 so as to at least partially surround them, said reinforcing layer being arranged between the at least one carcass layer 101 and the bead structure 103. Usually, the flipper is in contact with said at least one carcass layer 101 and said bead structure 103.

[0216] Flipper 120 typically comprises a plurality of textile cords incorporated within a layer of vulcanised elastomeric compound.

[0217] The bead structure 103 of the tyre may comprise a further protective layer which is generally known by the term of “chafer” 121 or protective strip and which has the function of increasing the rigidity and integrity of the bead structure 103.

[0218] Chafer 121 usually comprises a plurality of cords incorporated within a rubber layer of vulcanised elastomeric compound. Such cords are generally made of textile materials (such as aramide or rayon) or metal materials (such as steel cords).

[0219] A layer or sheet of elastomeric compound can be arranged between the belt structure and the carcass structure. The layer can have a uniform thickness.

[0220] Alternatively, the layer may have a variable thickness in the axial direction. For example, the layer may have a greater thickness close to its axially outer edges with respect to the central (crown) zone.

[0221] Advantageously, the layer or sheet can extend on a surface substantially corresponding to the extension surface of said belt structure.

[0222] In a preferred embodiment, a layer or sheet of elastomeric compound as described above can be placed between said belt structure and said tread band, said additional layer or sheet extending preferably on a surface substantially corresponding to the extension surface of said belt structure.

[0223] The elastomeric compound according to the present invention can be advantageously incorporated in one or more of the components of the tyre selected from the belt structure, carcass structure, tread band, under-layer, sidewall, mini-sidewall, sidewall insert, bead, flipper, chafer, sheet and anti-abrasive strip, preferably incorporated at least in the sidewalls and/or in the under-layer.

[0224] According to an embodiment not shown, the tyre may be a tyre for motorcycle wheels which is typically a tyre that has a straight section featuring a high tread camber.

[0225] According to an embodiment not shown, the tyre may be a tyre for bicycle wheels.

[0226] According to an embodiment not shown, the tyre may be a tyre for heavy transport vehicle wheels, such as trucks, buses, trailers, vans, and in general for vehicles in which the tyre is subjected to a high load. Preferably, such a tyre is adapted to be mounted on wheel rims having a diameter equal to or greater than 17.5 inches for directional or trailer wheels.

[0227] The description of some preparative examples according to the invention and comparative examples, given only for illustrative and non-limiting of the scope if the invention, is set out below.

EXPERIMENTAL PART

[0228] Analysis Methods

[0229] White Filler Functionalisation

[0230] The functionalisation of the white filler was verified with solid-state ATR-FTIR, TGA, CHNS, BET and NMR analysis.

[0231] The ATR-FTIR analysis was performed with a Perkin Elmer Spectrum 100 instrument (spectra with a resolution of 4 cm.sup.−1, region from 650 to 400 cm.sup.−1, 32 scans).

[0232] Thermoqravimetric analysis (TGA) was performed with a TGA/DCS1 STARe SYSTEM (Mettler Toledo) instrument with constant air flow (50 mL min.sup.−1). The method used involves applying a heating ramp of 10° C. min.sup.−1, starting from an initial temperature of 30° C., up to a final temperature of 1000° C. Two 15-minute isotherms were also added at 150° C. and 1000° C. Measurements were carried out in alumina crucibles of 75 μL by volume.

[0233] The CHNS analysis was performed with an Elementar VarioMICRO analyzer in CHNS configuration. The uncertainty of the measure is declared at 0.1%. The measurements were normalised to a sulphanilamide standard. The combustion column is at a temperature of 1150° C., while the reduction column is at 850° C. The BET analysis was performed with the Micromeritics Tristar II porosity and surface area analysis equipment.

[0234] The solid state NMR analysis was performed with a 400WB Bruker spectrometer operating at the proton frequency of 400.13 MHz. The Magic Angle Spinning (MAS) NMR spectra were acquired with single-pulse (SP) and cross-polarized (CP) experiments. The following experimental conditions were applied for frequency acquisitions .sup.29Si: 79.48 MHz, π/4 pulse 2 μs, decoupling length of 6.3 μs, recycling delay: 150 s, 3 k scans; for CP measurements: contact time 5 ms, πr/2 pulse 4 μs 2 k scans. For .sup.13C frequency measurements: 100.52 MHz, CP, π/2 pulse, 2 ms contact time, 6.3 μs decoupling length, 4 s recycle delay, 2 k scans. .sup.1H: single pulse seq. π/2 pulse 5 μs, recycle delay: 20 s, 32 scans. The samples were placed in 4 mm zirconia rotors, rotated at 7 kHz (10 kHz for proton) under air flow.

[0235] Determination of the Zinc Content

[0236] The zinc content can be measured by ICP-AES spectrometry (Inductively Coupled Plasma-Atomic Emission Spectroscopy) with ICP simultaneous plasma spectrometer (TJA IRIS II model; excitation source: radiofrequency generator with 27.12 MHz frequency and variable output power up to 1750 W).

[0237] XPS analysis was performed with a Perkin Elmer CD 5600-ci spectrometer instrument using a non-monochromatic dual-anode Al—Mg source. The samples were introduced into steel sample holders and introduced directly into a closed high-energy system in the analytical chamber of the instrument. The analysis area was 800 μm in diameter and the working pressure was less than 10.sup.−9 mbar.

[0238] UV-Vis spectroscopic analysis was performed with a UV Lambda 900 Perkin Elmer spectrometer on powder samples, in the wavelength range between 800 and 200 nm, with an accuracy of 0.08 nm.

[0239] MDR rheometric analysis (according to ISO 6502): a rheometer Alpha Technologies type MDR2000 was used. The tests were 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°, measuring the minimum torque value (ML), maximum torque (MH), the time required to increase the torque by one or two units (TS1 and TS2), and the time necessary to reach different percentages (5, 30, 50, 60, 90, 95 and 100%) of the maximum torque value (MH).

[0240] Properties of Vulcanised Materials

[0241] The elastomeric materials prepared in the previous examples were vulcanised to give specimens on which analytical characterisations and the assessment of dynamic mechanical properties were conducted. Unless otherwise indicated, vulcanisation was carried out in a mould, in hydraulic press at 170° C. and at a pressure of 200 bar for about 10 minutes.

[0242] Static modules: static mechanical properties were measured at 23° C. according to the ISO 37:2005 standard. In particular, the tensile modules at various elongation levels (10%, 50%, 100% and 300%, named in the order CA0.1, CA0.5, CA1 and CA3) were measured on samples of vulcanised elastomeric compositions.

[0243] Dynamic modules: dynamic mechanical properties were measured using an Instron dynamic device in compression and tension operation with the following method. A sample of vulcanised elastomeric cylindrical compositions (length=25 mm; diameter=18 mm), preload in compression up to 25% of longitudinal deformation with respect to the initial length and maintained at the predetermined temperature (10° C., 23° C. or 100° C.) during the test was subjected to a dynamic sinusoidal tension with amplitude ±3.5% with respect to the length of the preload, at a frequency of 1 Hz, 10 Hz and 100 Hz.

[0244] The dynamic mechanical properties are expressed in terms of dynamic elastic modulus (E′), viscous dynamic modulus (E″) and Tan delta (loss factor). The Tan delta value was calculated as the ratio between the viscous dynamic modulus (E″) and the dynamic elastic modulus (E′).

Example 1

[0245] Preparation of Functionalised Silica

[0246] Used Materials [0247] Rhodia Zeosil MP1165 precipitated silica (specific surface area BET 160 m.sup.2/g) produced by Rhodia [0248] Coupling agent (APTES): 3-aminopropyl)triethoxysilane H.sub.2N(CH.sub.2).sub.3Si (OC.sub.2H.sub.5).sub.3 (99%) produced by Sigma Aldrich; [0249] Zinc nitrate hexahydrate Zn(NO.sub.3).sub.2.6H.sub.2O (99%) produced by Alfa Aesar [0250] Toluene (99%) produced by Alfa Aesar; [0251] Anhydrous ethanol EtOH (99.9%) produced by Scharlau.

[0252] The preparation consists of a two-step process, in which first of all the silica is functionalised with the coupling agent and after recovery, the anhydrous powder is reacted with a zinc precursor (zinc nitrate hexahydrate) to bind the zinc through the formation of the chelate with coordinating groups GC.

[0253] First Step

[0254] In a 50 ml flask, 1 g of SiO.sub.2 powder was dispersed under stirring in 25 ml of toluene for ten minutes at 120° C. Then, an adequate amount of (3-aminopropyl)triethoxysilane was added to the dispersion and the reaction was maintained at 120° C. for 24 hours (reflux condition) under stirring. After cooling, the reaction product was recovered by centrifugation (9000 rpm, 10 minutes), washed twice with fresh toluene and dried in an oven at 80° C. overnight.

[0255] Different amounts of APTES were tested, as reported in the following Table 1, which were used for the preparation of samples with different zinc loads. The amount of silane was chosen based on the number of hydroxyl groups on the silica surface, adjusting the molar ratios between the hydroxyl groups and the silane.

TABLE-US-00001 TABLE 1 Sample APTES (mL) APTES/OH ratio SiO.sub.2-APTES-1 0.132   1:6.25 SiO.sub.2-APTES-2 0.274 1:3 SiO.sub.2-APTES-3 0.394 1:2 SiO.sub.2-APTES-4 0.788 1:1

[0256] Second Step

[0257] 1 g of the functionalised silica obtained in the first step (SiO.sub.2-APTES) was dispersed in 50 mL of ethanol under stirring for 20 minutes at 100° C., so as to obtain a homogeneous suspension. Subsequently, an adequate amount of zinc precursor (Zn(NO.sub.3).sub.2.H.sub.2O) was added and the reaction was carried out for 2 hours. After cooling, the powder was separated by centrifugation (9000 rpm, 10 minutes) and washed twice with fresh ethanol. The powder was dried at 80° C. overnight. For each previously prepared functionalised silica (SiO.sub.2-APTES-1, SiO.sub.2-APTES-2, SiO.sub.2-APTES-3, SiO.sub.2-APTES-4), a constant molar ratio Zn/APTES of 0.7 was used. This quantity was chosen considering that in these experimental conditions, the maximum quantity of zinc that can bind to SiO.sub.2-APTES corresponds to a molar ratio Zn/APTES equal to 0.5. A small excess of zinc with respect to the stoichiometric value was used to guarantee the reproducibility of the synthesis itself.

[0258] Preparation of Functionalised Sepiolite

[0259] In the case of sepiolite, an activation step was added to the process described above to improve the surface reactivity of sepiolite and increase its reactivity. Before the functionalisation of sepiolite with APTES (first step of the previous process), sepiolite was washed in an alkaline solution as follows.

[0260] 1 g of sepiolite was dispersed in 50 ml of 0.03 M NaOH solution and kept under stirring at room temperature for 24 hours. The sepiolite was recovered by centrifugation (9000 rpm, 30 minutes) and washed with fresh water until it reached a neutral pH (pH=7) in the washing solution. The powder was dried using the lyophilisation method. After this treatment, the same functionalisation steps with silane (APTES) and reaction with the zinc precursor were performed.

[0261] Characterisation of the Materials Obtained

[0262] FIG. 2 shows the FTIR ATR spectrum obtained with the SiO.sub.2-APTES-1 and SiO.sub.2-APTES-3 materials. In the SiO.sub.2-APTES samples two peaks at 2864 and 2932 cm.sup.−1 are always visible, attributed to the symmetrical and asymmetrical stretching of the CH.sub.2 groups, typical of the propyl chains of the APTES molecules. The intensity of these two peaks depends strictly on the amount of APTES used in the reaction, as shown in FIG. 2. This observation provided a first indication that the reaction proceeds proportionally with respect to the amount of APTES used in the reaction itself.

[0263] Moreover, from the comparison between the SiO.sub.2-APTES spectra and the pure silica (SiO.sub.2), not shown in FIG. 2, the shift of the peak at 958 cm.sup.−1 was observed, attributable to the stretching of the Si—OH bond of the hydroxyl groups of the silica surface, at higher wave numbers. The peak becomes a shoulder of the main peak at 1068 cm.sup.−1, due to the formation of the Si—O—Si bond, following the partial substitution reaction of the silica hydroxyl groups with other molecules, confirming the reaction between the APTES molecules and the surface of silica.

[0264] FIG. 3 shows the TGA spectrum obtained with the SiO.sub.2-APTES-1, SiO.sub.2-APTES-2, SiO.sub.2-APTES-3 and SiO.sub.2-APTES-4 materials, while FIG. 4 shows the TGA spectrum obtained with the reference sample SiO.sub.2.

[0265] The following Table 2 shows the total weight loss after treatment from 150° to 1000° C.

TABLE-US-00002 TABLE 2 % weight loss Sample 150-1000° C. SiO.sub.2 4,102 SiO.sub.2-APTES-1 7,087 SiO.sub.2-APTES-2 8,023 SiO.sub.2-APTES-3 10,366 SiO.sub.2-APTES-4 10,458

[0266] The TGA analysis allowed confirming the effective functionalisation of silica following the reaction with APTES. This was possible because the weight loss between 150° C. and 1000° C. is associated with the presence of organic material on the silica surface: comparing the TGA spectra of the SiO.sub.2-APTES samples with the reference sample SiO.sub.2, an increase in the weight loss associated with these samples is observed, confirming the presence of organic material due to the functionalisation reaction.

[0267] This weight loss is greater with the increase in the quantity of silane used, as expected, with the exception of the comparison between sample 3 and sample 4. In the latter, despite the use of a double amount of silane, a percentage weight loss was recorded that was completely similar to the sample 3. It is believed that this is due to the fact that starting from the sample 3, the silica has reached a condition of surface saturation, such that no silane molecule is able to further bind with the silica surface, totally covered with APTES molecules.

[0268] The following Table 3 also shows the degree of surface coating (expressed as a percentage by weight) and the surface density of APTES molecules (expressed in number/nm.sup.2).

TABLE-US-00003 TABLE 3 Coating degree n. APTES Reaction surface molecules/ yield Sample (% by weight) nm.sup.2 (%) SiO.sub.2-APTES-1 3.2 2.3 99 SiO.sub.2-APTES-2 6.2 4.4 95 SiO.sub.2-APTES-3 7.6 5.2 76 SiO.sub.2-APTES-4 7.8 5.3 41

[0269] The values reported in table 3 were obtained starting from the following formulas (1) and (2):

[00001]$\begin{array}{cc}{n}_R=\frac{2*\Delta w_{150-1000°C.}-n_{\mathrm{OH}}*w_{{\mathrm{sio}}_2\left(1000°C.\right)}*M{W}_{H_{2}O}}{2M{W}_R-M{W}_{H_{2}O}}& \left(1\right)\\ \frac{n.Math.\mathrm{molcules}}{\mathrm{surface}\mathrm{area}\left({\mathrm{nm}}^2\right)}=\frac{N_A*n_R}{\frac{n_{{\mathrm{sio}}_2}*{\mathrm{MW}}_{{\mathrm{sio}}_2}}{s_{BET}}*{10}^{18}}& \left(2\right)\end{array}$

[0270] where n.sub.R is the number of moles of APTES, Δw.sub.150-100° C. is the weight loss recorded in the range 150-1000° C., n.sub.OH is the number of surface hydroxyl groups of silica (determined by TGA analysis performed on pure silica), w.sub.SiO2(1000° C.) is the silica mass measured at 1000° C., MW.sub.H2O is the molecular weight of water, MW.sub.R is the molecular weight of the APTES residue, NA is the Avogadro number, MW.sub.SiO2 is the molecular weight of silica (60 g mol.sup.−1) and SBET is the surface area of silica (160 m.sup.2/g).

[0271] The data of Table 3 demonstrate that the number of APTES molecules on silica can be suitably modified between 2 and 6 molecules/nm.sup.2, corresponding to a degree of surface coating between 3 and 8% by weight, with high reaction yields (>80%). Above 8% by weight, the reaction yield decreases considerably, highlighting that this value corresponds to the weight value with which the silica surface can be considered saturated.

[0272] The following Table 4 compares the percentage values of nitrogen calculated with the data deriving from the TGA analysis with those obtained with the data deriving from the CHNS analysis.

TABLE-US-00004 TABLE 4 Sample N % (TGA) N % (CHNS) SiO.sub.2-APTES-1 0.75 0.90 SiO.sub.2-APTES-2 1.45 1.38 SiO.sub.2-APTES-3 1.78 1.51 SiO.sub.2-APTES-4 1.84 2.01

[0273] Considering the experimental error, the N % values are completely comparable, providing further confirmation of the formation of the bond between APTES and silica.

[0274] The following Table 5 shows the values of surface area BET of pure silica (SiO.sub.2) and of two SiO.sub.2-APTES-1 and SiO.sub.2-APTES-3 samples.

TABLE-US-00005 TABLE 5 Sample BET (m.sup.2/g) SiO.sub.2 160 SiO.sub.2_APTES_1 107 SiO.sub.2_APTES_3 107

[0275] For both functionalised samples, there is a decrease in the surface area value due to the presence of APTES molecules on the surface, which partially cover the pores and micropores of the silica particles, reducing the total surface area measured. FIG. 5 illustrates the solid-state NMR spectrum of pure silica (SiO.sub.2) and two SiO.sub.2-APTES-1 and SiO.sub.2-APTES-3 samples. The spectrum shows that the functionalised samples have the same spectrum as pure silica, with the addition of the T1 and T2 peaks due to the presence of APTES bound to the silica surface.

[0276] It has been observed that the quantity of T units increases with the percentage of functionalisation, while the Q3/Q4 ratio decreases significantly from pure silica to functionalised silica, suggesting a decrease in superficial Si—OH groups following functionalisation. It was also observed that the T2/T3 ratio decreases as the quantity of APTES increases, suggesting that the APTES molecules are probably bound to silica by two or three bonds per molecule. Finally, comparing the T/Q ratio, a semi-quantitative analysis was obtained, which showed that the APTES signals increase proportionally with the nominal concentration.

[0277] The following Table 6 shows the results of the ICP analysis, in particular the quantities of zinc actually bound on two SiO.sub.2-APTES-2-Zn and SiO.sub.2-APTES-3-Zn samples using different amounts of zinc, calculated on the basis of molar ratio between silane molecules in the starting sample and zinc molecules.

TABLE-US-00006 TABLE 6 n(Zn)/ % wt Zn % wt Zn Sample n(APTES) (nominal) (actual) SiO.sub.2-APTES-2-Zn ½ 2.2 2.2 ± 0.2 1 4.4 2 8.8 SiO.sub.2-APTES-3-Zn ½ 3.4 3.1 ± 0.2 1 6.8 2 11.3

[0278] The data in Table 6 clearly show that the amount of zinc present in the final sample does not depend on the amount of zinc precursor selected, but rather on the amount of silane previously bound to silica. Using significantly excess amounts of zinc nitrate, the final weight percentage remains unchanged. Furthermore, the Zn: APTES ratio is always 1:2, for each sample of SiO.sub.2-APTES. This result provided a first indication of the binding of zinc as an isolated centre to two APTES molecules via the amino group, with two other free positions around the zinc, probably occupied by anions present in the synthesis conditions, such as OH groups or NO.sub.3 groups.

[0279] Further experimental confirmation of the bond between zinc and amino groups came from the examination of NMR spectra. FIG. 6 shows the spectrum of the starting SiO.sub.2-APTES-3 sample and that of the final SiO.sub.2-APTES-3-Zn sample. The band 1 present at 1.9 ppm, attributable to NH.sub.2 groups, disappears following the interaction with zinc, in favour of a wider band 2 which appears at 7.3 ppm, precisely because of the interaction of the amino groups with zinc precursor. The information obtained from this analysis confirmed the amine-zinc interaction at the base of the formation of the zinc complexes on the silica surface.

[0280] FIG. 7 shows the spectra obtained from XPS analysis, highlighting the photoemission region of the N1S signal for a SiO.sub.2-APTES-Zn sample.

[0281] FIG. 7 shows that the recorded nitrogen signal is composed of two main components, one organic (relative to the amino group of the ligand) and one inorganic (deriving from the nitrate group). Through normalisation it was possible to derive the percentage of the two contributions and thus derive the quantitative ratios between the various elements.

[0282] Of particular interest are the NH/Zn and Zn/NO.sub.3 ratios, reported in the following table 7.

TABLE-US-00007 TABLE 7 Sample NH/Zn Zn/NO.sub.3 SiO.sub.2-APTES-3-Zn 1.7 1.5

[0283] The value of the NH/Zn ratio, which is approximately equal to 2, as expected within the experimental error, confirmed the coordination of each zinc atom with two APTES molecules by amino groups.

[0284] Furthermore, the value of the Zn/NO.sub.3 ratio confirmed that at least one of the other two free zinc positions is occupied by NO.sub.3 groups, deriving from the synthesis of zinc nitrate. It has therefore been confirmed that zinc is an isolated centre, coordinated to only two amino groups and actually has two free positions, in which labile ligands are present such as the NO.sub.3 group, easily replaceable in subsequent reactions with other molecules.

[0285] Finally, the UV-Visible spectroscopic analysis confirmed the absence of the typical zinc oxide absorption band, present around 370 nm, thus confirming the total absence of zinc oxide on the silica surface and in the system as a whole.

[0286] A sample of SiO.sub.2-APTES-3-Zn was subjected to the same analyses after model vulcanisation reaction, using a standard compound, performed in TME (2,3-dimethyl-2-butene) at 120° C., in the presence of CBS (N-cyclohexyl-2-benzothiazole sulphenamide) and sulphur, with an optimal vulcanisation time of 20 minutes.

[0287] The NMR spectrum of the sample after vulcanisation proved to be completely similar to the sample spectrum before the reaction, with the large band at 7.3 ppm still visible, due to the interaction between zinc and amino groups, as discussed in relation to FIG. 6.

[0288] The NH/Zn and Zn/NO.sub.3 ratios, derivable from the XPS analysis and reported in the following table 7bis, confirmed that the NH/Zn ratio remains almost constant following the model vulcanisation reaction in TME, indicating the absence of release of zinc from the vulcanised material, while they have shown an increase in the Zn/NO.sub.3 ratio, indicating the decrease of NO.sub.3 groups bonded to the zinc centres, following the reaction.

TABLE-US-00008 TABLE 7bis SiO.sub.2-APTES-3-Zn sample NH/Zn Zn/NO.sub.3 Pre-vulcanisation 1.7 1.5 Post-vulcanisation 1.5 2.3

[0289] In view of the results obtained, it has therefore been demonstrated that the zinc centres, although actively participating in the vulcanisation reaction as activators, remain stable and bonded to the silane molecules present on the silica surface. Furthermore, the participation of the zinc centre in the reaction was further demonstrated by the reduction of the nitrate groups coordinated to the zinc following the reaction, showing on the one hand the weakness of these bonds with respect to the bond with the amino group and on the other the possible interaction of zinc with other chemical agents involved in the reaction.

Example 2

[0290] Preparation of the Elastomeric Compound

[0291] The following Table 8 shows the formulations of the reference compound (R1) comprising silica (43 phr) and zinc oxide (equal to 1.49 phr of Zn.sup.2+) added separately and of the compound according to the present invention (I1) in which were introduced 49.4 phr of SiO.sub.2-APTES-3-Zn prepared as described in example 1, equal to 1.49 phr of Zn.sup.2+, 3.42 phr of APTES, 0.96 phr of nitrate, 0.54 phr of hydroxyl groups (—OH) and 43 phr of silica.

TABLE-US-00009 TABLE 8 Component R1 I1 Step 1 IR 100 100 Silica 43.0 — SiO.sub.2-APTES-3-Zn — 49.4 Silane 3.44 — Stearic acid 2 — 6PPD 2 2 ZnO 1.85 — Step 2 CBS 1.6 1.6 Sulphur (67%) 3 3 IR: high-cis synthetic polyisoprene (min. 96%), obtained by polymerisation in solution with Ziegler/Natta catalyst; Supplier NIZHNEKAMSKNEFTECHIM EXPORT; Silica: ZEOSIL 1115 MP (specific surface area BET 95-120 m.sup.2/g, white microbeads obtained by precipitation from sodium silicate solutions with sulphuric 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): 80% zinc oxide, 20% polymeric binder and dispersing agent, Supplier LANXESS ADD Silane: TESPD Bis-(3-triethoxy-silyl-propyl)disulphide, Supplier JINGZHOU JIANGHAN FINE CHEM CBS: N-cyclohexyl-2-benzothiazilsulphenamide, cyclohexylamine content <1%, DUSLO Supplier Sulphur: Crystex OT33 amorphous sulphur, insoluble in CS.sub.2 and in toluene. Treated with 33% hydrotreated heavy naphthenic distillate (petroleum), Supplier EASTMAN.

[0292] All the components, except for sulphur and the accelerant (CBS) were mixed together in an internal mixer (model Pomini PL 1.6) for about 5 minutes (1 st step). As soon as the temperature reached 145+5° C., the elastomeric blend was unloaded. Sulphur and the accelerant (CBS) were then added and mixing was performed in an open roll mixer (2nd step).

[0293] Using the compounds of table 8, specimens were made on which the MDR rheometric measurements were performed.

[0294] The results are summarised in the following Table 9.

TABLE-US-00010 TABLE 9 R1 I1 Δ I1 vs R1 (%) MH 22.2 28.8 +30 t50 2.05 0.52 −75 t100 4.40 2.50 −43

[0295] The results of Table 9 show the greater reactivity and the greater maximum torque (MH) of the compound of the invention (I1) compared to the reference compound.

Example 3

[0296] Preparation of the Elastomeric Compound

[0297] The following Table 8 shows the formulations of the reference compound (R32) comprising silica (43 phr) and zinc oxide (equal to 1.49 phr of Zn.sup.2+) added separately, of the reference compound R3 comprising silica (43 phr), zinc oxide (equal to 1.49 phr of Zn.sup.2+), and silane APTES (3.56 phr) added separately, and of the compound according to the present invention (I2) in which were introduced 49.4 phr of SiO.sub.2-APTES-3-Zn prepared as described in example 1, equal to 1.49 phr of Zn.sup.2P, 3.42 phr of APTES, 0.96 phr of nitrate, 0.54 phr of hydroxyl groups (—OH) and 43 phr of silica.

TABLE-US-00011 TABLE 10 Component R2 R3 I2 Step 1 IR 100 100 100 Carbon black 15.00 15.00 15.00 Silica 43.0 43.0 — SiO.sub.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 Step 2 DCBS 1.8 1.8 1.8 PVI 0.4 0.4 0.4 Sulphur (67%) 3.0 3.0 3.0 IR: high-cis synthetic polyisoprene (min. 96%), obtained by polymerisation in solution with Ziegler/Natta catalyst; Supplier NIZHNEKAMSKNEFTECHIM EXPORT; Carbon black: N375 Carbon Black, Supplier CABOT Silica: ZEOSIL 1115 MP (specific surface area BET 95-120 m.sup.2/g, white microbeads obtained by precipitation from sodium silicate solutions with sulphuric 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)-tetrasulphide, Supplier Evonik Stearic acid: Supplier TEMIX OLEO SRL ZnO (80): 80% zinc oxide, 20% polymeric binder and dispersing agent, 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-benzothiazilsulphenamide, cyclohexyl amine content <1%, Supplier LANXESS ADD PVI: N-cyclohexyl thiophthalimide, Supplier Solutia Sulphur: Crystex OT33 amorphous sulphur, insoluble in CS.sub.2 and in toluene. Treated with 33% hydrotreated heavy naphthenic distillate (petroleum), Supplier EASTMAN.

[0298] All the components, except for sulphur, the retardant (PVI) and the accelerant (CBS) were mixed together in an internal mixer (model Pomini PL 1.6) for about 5 minutes (first step). As soon as the temperature reached 145+5° C., the elastomeric blend was unloaded. Sulphur, the retardant (PVI) and the accelerant (CBS) were then added and mixing was performed in an open roll mixer (second step).

[0299] Using the compounds of table 10, specimens were made on which the MDR rheometric measurement (30 minutes at 151° C. and 10 minutes at 170° C.) and the measurement of static and dynamic mechanical properties after vulcanisation for 30 minutes at 151° C. were performed.

[0300] The results are summarised in the following Tables 11-13.

TABLE-US-00012 TABLE 11 MDR 30 minutes at 151° C. Δ R3 vs Δ I2 vs Δ I2 vs R2 R3 I2 R2 (%) R2 (%) R3 (%) MH[dN/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-US-00013 TABLE 12 MDR 10 minutes at 170° C. Δ R3 vs Δ I2 vs Δ I2 vs R2 R3 I2 R2 (%) R2 (%) R3 (%) ML[dN/m) 3.3 6.97 5.95 111.21 80.30 −14.63 MH[dN/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

[0301] The results of Tables 11 and 12 show the greater reactivity of the compound of the present invention (I2) with respect to the standard reference compound R2 and to the comparison compound R3. It should in fact be observed that the values of minimum and especially maximum torque obtained from the compound I2 of the present invention are more than 50% higher than those obtained with the compounds R2 and R3, but despite this, T100 of I2 is lower by more than 30% compared to the T100 of R2. The higher T100 value of 12 compared to the T100 of R3 must be considered indicative of greater reactivity, in consideration of the different and higher value of MH.

[0302] The higher MH data of the compound I2 of the invention with respect to R2 and R3 have shown that the use of the compound of the present invention can be considered not only as a valid substitute for conventional zinc oxide with a lower zinc release in the environment, but also as a means to reduce the amount of zinc in the raw compound without affecting the mechanical performance of the vulcanised compound.

TABLE-US-00014 TABLE 13 Static mechanical properties Δ R3 vs Δ I2 vs Δ I2 vs R2 R3 I2 R2 (%) R2 (%) 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

[0303] The results of Table 13 show for the compound of the invention (I2) higher values of the elongation modulus at 10% (Ca0.1) and at 50% (Ca0.5) with respect to both references (R2 and R3), resulting in greater predictive elasticity of better handling of the tyre.

[0304] The results obtained from the comparative compound R3 showed that the APTES amino silane added separately in the compound (i.e. not bound to silica in the zinc) considerably worsened the mechanical properties since it was not able to bind with the compound, while those obtained with the comparative compound surprisingly demonstrated that the use of the coupling agent of the present invention allowed substantially recovering the same values of Ca1, Ca3 and CR of the reference compound R2.

TABLE-US-00015 TABLE 14 Dynamic mechanical properties Δ R3 vs Δ I2 vs Δ I2 vs R2 R3 I2 R2 (%) R2 (%) R3 (%) 10° C. E′[MPa], 5.642 4.855 5.956 −13.95 5.57 22.68 1 Hz E′[MPa], 6.142 5.579 6.716 −9.17 9.35 20.38 10 Hz Tanδ, 0.125 0.237 0.19 89.60 52.00 −19.83 1 Hz Tanδ, 0.155 0.249 0.22 60.65 41.94 −11.65 10 Hz 23° C. E′[MPa], 5.504 4.602 5.632 −16.39 2.33 22.38 1 Hz E′[MPa], 5.935 5.282 6.263 −11.00 5.53 18.57 10 Hz Tanδ, 0.108 0.224 0.163 107.41 50.93 −27.23 1 Hz Tanδ, 0.13 0.23 0.188 76.92 44.62 −18.26 10 Hz 100° C.  E′[MPa], 5.223 4.095 5.277 −21.60 1.03 28.86 1 Hz E′[MPa], 5.452 4.492 5.564 −17.61 2.05 23.86 10 Hz Tanδ, 0.066 0.15 0.096 127.27 45.45 −36.00 1 Hz Tanδ, 0.076 0.166 0.106 118.42 39.47 −36.14 10 Hz

[0305] The results of Table 14 show a surprising behaviour of the compound I2 of the present invention with respect to the comparative compound R3. In fact, the latter showed high tan δ values at all temperatures, and above too high at high temperatures, resulting in high hysteresis with heat dissipation and high rolling resistance at high speed, while on the contrary the compound I2 of the present invention showed a more limited and acceptable increase in the tan δ at high temperatures, but a significant increase at low temperatures, predictive of better grip on dry roads and better grip on wet roads.

Example 4

[0306] Preparation of Functionalised Silica

[0307] The process described in example 1 was 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 were used for every gram of SiO.sub.2 to be functionalised. The amount of ETDMS was chosen based on the number of hydroxyl groups on the silica surface, to give a molar ratio between ETDMS and the hydroxyl groups of the silica surface (EDTMS/OH) equal to 1:2. In the second step, the amount of zinc precursor (Zn(NO.sub.3).sub.2.H.sub.2O) was varied to obtain a molar ratio between zinc and ETDMS (Zn/EDTMS) equal to 1:2, 1:1 and 2:1. Three SiO.sub.2-EDTMS-Zn samples were then obtained according to the following table 15.

TABLE-US-00016 TABLE 15 Sample Zn/ETDMS ratio SiO.sub.2-ETDMS-Zn-1 1:2 SiO.sub.2-ETDMS-Zn-2 1:1 SiO.sub.2-ETDMS-Zn-3 2:1

[0308] Characterisation of the Materials Obtained

[0309] The samples were characterised as described in example 1 by FTIR ATR spectroscopy to confirm the effective functionalisation of the material, TGA and CHNS to quantify the silane actually deposited on the silica surface, and ICP analysis to determine the amount of zinc bound to silica.

[0310] FIG. 8 shows the FTIR ATR spectrum obtained with the SiO.sub.2-ETDMS material. From the comparison between the SiO.sub.2-ETDMS spectra and the pure silica (SiO.sub.2), the shift of the peak at 954 cm.sup.−1 was observed, attributable to the stretching of the Si—OH bond of the hydroxyl groups of the silica surface, at higher wave numbers. The peak becomes a shoulder of the main peak at 1068 cm.sup.−1, due to the formation of the Si—O—Si bond, following the partial substitution reaction of the silica hydroxyl groups with other molecules, confirming the reaction between the ETDMS molecules and the surface of silica.

[0311] Furthermore, in the SiO.sub.2-ETDMS sample, two peaks are visible at 2948 and 2864 cm.sup.−1, attributed to the symmetrical and asymmetrical stretching of the CH.sub.2 groups, typical of the propyl and ethyl chains of the ETDMS molecules.

[0312] Finally, we observe the appearance of an additional peak at 1459 cm.sup.−1, due to the secondary amino group of the ETDMS chain.

[0313] FIG. 9 shows the TGA spectrum obtained with the SiO.sub.2-ETDMS material and with the reference sample SiO.sub.2. The total weight loss of the SiO.sub.2-ETDMS sample was 15.8%, compared to about 4% for the reference sample SiO.sub.2.

[0314] The following Table 16 also shows the degree of surface coating (expressed as a percentage by weight) and the surface density of ETDMS molecules (expressed in number/nm.sup.2)

TABLE-US-00017 TABLE 16 Surface coating degree n. ETDMS Reaction Sample (% by weight) molecules/nm.sup.2 yield (%) SiO.sub.2-ETDMS 15.3 6.2 90

[0315] The data of Table 16 show that the number of ETDMS molecules on silica was equal to about 6 molecules/nm.sup.2, corresponding to a surface coating degree of about 15% by weight, with high reaction yields (90%).

[0316] The following Table 17 compares the percentage values of nitrogen calculated with the data deriving from the TGA analysis with those obtained with the data deriving from the CHNS analysis.

TABLE-US-00018 TABLE 17 Sample N % (TGA) N % (CHNS) SiO.sub.2 0.00 0.00 S1O2-ETDMS 4.25 3.74

[0317] Considering the experimental error, the N % values are completely comparable, providing further confirmation of the formation of the bond between ETDMS and silica.

[0318] The following Table 18 shows the results of the ICP analysis, in particular the quantities of zinc actually bound on the three samples obtained using different quantities of zinc, calculated on the basis of the molar ratio between zinc molecules and silane molecules in the starting sample (Zn/ETDMS).

TABLE-US-00019 TABLE 18 Zn/ Zn Zn Zn/ETDMS ETDMS (% by (molecule/ (molecule/ Sample (nominal) weight) nm.sup.2) nm.sup.2) SiO.sub.2-ETDMS-Zn-1 1:2 3.5 ± 0.2 3.58 ± 0.2  0.57 SiO.sub.2-ETDMS-Zn-2 1:1 5.9 ± 0.2 6.2 ± 0.2 1.00 SiO.sub.2-ETDMS-Zn-3 2:1 6.6 ± 0.2 7.1 ± 0.2 1.14

[0319] The ICP results show that EDTMS promotes a different behaviour compared to APTES and that the molar ratios Zn/silane vary according to the amount of zinc precursor used in the reaction. The first sample (molar ratio 1:2) is characterised by an effective molar ratio Zn/silane of approximately 0.5, suggesting that each zinc centre is coordinated with two silane molecules and consequently with four nitrogen atoms. The formation of a structure that involves two molecules of EDTMS for each zinc centre is reasonable considering the proximity of the silane molecules on the silica surface. Furthermore, the longer chain length of the EDTMS (compared with APTES) could promote greater chain mobility and greater flexibility, to coordinate zinc in a different way. In the other two samples prepared with a nominal Zn/EDTMS molar ratio of 1:1 and 1:2, the measured molar ratio Zn/EDTMS was approximately 1 in both cases, suggesting the coordination of each zinc centre with a molecule of EDTMS, probably with a chelation coordination.

Example 5

[0320] Preparation of the Elastomeric Compound

[0321] Using the same process described in example 2 and the compositions described in the following Table 19, a reference compound (R4) comprising silica (35 phr) and zinc oxide (equal to 1.49 phr of Zn.sup.2+) added separately and a compound according to the present invention (I3), comprising 42.7 phr of SiO.sub.2-EDTMS-Zn prepared as described in example 4, equal to 1.49 phr of Zn.sup.2+, 6.5 phr of EDTMS and 35 phr of silica, were prepared.

TABLE-US-00020 TABLE 19 Component R4 I3 Step 1 IR 100 100 Silica 35.0 — SiO.sub.2-APTES-3-Zn — 42.7 Silane 2.78 — Stearic acid 2 — 6PPD 2 2 ZnO 1.85 — Step 2 CBS 1.6 1.6 Sulphur (67%) 3 3

[0322] Using the compounds of table 19, specimens were made on which the MDR rheometric measurements were performed. The results are summarised in the following Table 20.

TABLE-US-00021 TABLE 20 R4 I3 Δ I3 vs R4 (%) MH 17.7 22.8 +29 t50 2.61 1.02 −61 t100 5.00 2.85 −43

[0323] The results of Table 20 show the greater reactivity and the greater maximum torque (MH) of the compound of the invention (I1) compared to the reference compound.