VULCANISABLE ELASTOMERIC MATERIALS FOR COMPONENTS OF TYRES COMPRISING MODIFIED SILICATE FIBRES, AND TYRES THEREOF

Abstract

A vulcanisable elastomeric composition for tyre component is described. The vulcanisable elastomeric composition includes modified silicate fibres as fillers. Moreover, the tyre component contains elastomeric materials which are obtainable by vulcanisation of the vulcanisable elastomeric composition. A tyre for vehicles which includes one or more of the tyre components is also described. The vulcanised elastomeric materials are characterised by having good static and dynamic mechanical properties, and particularly low hysteresis. Advantageously, the tyre which contains one or more of the tyre components has a reduced rolling resistance.

Claims

1. Vulcanisable elastomeric composition for components of tyres comprising at least: a) 100 phr of at least one diene elastomeric polymer, b) from 1 to 80 phr of modified silicate fibres of nanometric size, with substantially preserved needle-shaped morphology, comprising from 3.8% to 12% by weight of magnesium with respect to the weight of the fibres themselves (measured via X-ray fluorescenceXRF); (c) from 0 to 120 phr of a standard reinforcement filler; (d) from 0.1 to 15 phr of a vulcanising agent, and (e) from 0 to 20 phr of a coupling agent.

2. Composition as claimed in claim 1 wherein said modified silicate fibres of nanometric size substantially preserve the crystalline structure.

3. Vulcanisable elastomeric composition for components of tyres as claimed in claim 1, comprising at least: (a) 100 phr of at least one diene elastomeric polymer; (b) from 1 to 80 phr of modified silicate fibres with needle-shaped morphology of nanometric size, said modified fibres being obtainable according to a process that comprises: providing silicate fibres with needle-shaped morphology of nanometric size comprising magnesium ions, suspending said fibres in a liquid medium, adding at least one acid compound to the suspension, allowing the reaction, up to extracting from 10% to 70% by weight of magnesium ions from the fibres with respect to the total weight of magnesium originally contained in the fibres, substantially preserving their crystalline structure and needle-shaped morphology and separating the fibres thus modified from the liquid medium; (c) from 0 to 120 phr of a standard reinforcement filler; (d) from 0.1 to 15 phr of a vulcanising agent, and (e) from 0.1 to 20 phr of a coupling agent.

4. Composition as claimed in claim 1 wherein said silicate fibres with needle-shaped morphology of nanometric size originally comprise from 12.5% to 15.5% of magnesium with respect to the weight of the fibres themselves.

5. The composition as claimed in claim 1 wherein said modified silicate fibres with needle-shaped morphology of nanometric size have an aspect ratio of at least 2:1, preferably of at least 3:1, more preferably of at least 5:1 or 8:1 or 10:1.

6. The composition as claimed in claim 1 wherein said silicate fibres with needle-shaped morphology of nanometric size comprising magnesium are sepiolite fibres.

7. The composition as claimed in claim 1 comprising said modified silicate fibres with needle-shaped morphology of nanometric size (b) in a quantity from 1 phr to 60 phr, preferably from 3 phr to 40 phr, more preferably from 5 phr to 30 phr.

8. The composition as claimed in claim 1 comprising a standard reinforcement filler (c), selected from among carbon black, precipitated amorphous silica, amorphous silica of natural origin, non-modified silicate fibres and mixtures thereof.

9. The composition as claimed in claim 8 comprising said standard reinforcement filler (c) in a quantity comprised between 1 phr and 120 phr, preferably between 20 phr and 90 phr.

10. The composition as claimed in claim 8 wherein the overall quantity of modified fibres (b) and standard filler (c) is comprised between 20 phr and 120 phr, more preferably between 30 phr and 90 phr.

11. The composition as claimed in claim 1 wherein said modified silicate fibres with needle-shaped morphology of nanometric size comprise from 9.5% to 12% by weight of magnesium with respect to the weight of the fibres themselves.

12-13. (canceled)

14. Tyre for vehicle wheels comprising at least one tyre component, wherein the at least one tyre component comprises a vulcanised elastomeric material obtainable via vulcanisation of the vulcanisable elastomeric composition as claimed in claim 1.

15. The tyre as claimed in claim 14 for high-performance vehicles (HP, SUV and UHP).

16. The tyre as claimed in claim 14 comprising at least one carcass structure comprising at least one carcass layer having opposite lateral edges associated with respective bead structures; one belt structure applied in radially external position with respect to the carcass structure, one tread band applied in radially outer position with respect to said belt structure, and possibly at least one under-layer and/or one anti-abrasive elongated element and/or one sidewall and/or one sidewall insert and/or one mini-sidewall and/or one under-liner and/or one rubber layer and/or one sheet, wherein the at least one tyre component is selected from the group consisting of said tread band and/or carcass structure and/or belt structure and/or under-layer and/or anti-abrasive elongated element and/or sidewall and/or sidewall insert and/or mini-sidewall and/or under-liner and/or rubber layer and/or bead structure and/or sheet.

17. Process for modifying silicate fibres with needle-shaped morphology of nanometric size to provide modified silicate fibres of nanometric size, with substantially preserved needle-shaped morphology comprising providing silicate fibres with needle-shaped morphology of nanometric size comprising magnesium, suspending said fibres in one or more C.sub.1-C.sub.6 mono- or poly-alcohols or mixtures thereof with water, adding, to the suspension, at least one acid compound in a quantity such to be in the reaction medium in a concentration not greater than 5N, allowing the reaction, up to extracting from 10% to 70% by weight of magnesium from the fibres with respect to the total weight of magnesium originally contained in the fibres, substantially preserving their crystalline structure and needle-shaped morphology and separating the fibres thus modified from the final medium.

18. The process as claimed in claim 17 wherein the acid compound is added in a quantity such to be in the reaction medium in a concentration not greater than 3.5N, than 3N, than 2N, than 1N.

19. The process as claimed in claim 17 wherein a silanising agent is added to the suspension of the fibres, preferably selected from among bis-(triethoxysilylpropyl)disulfide (TESPD), bis[3-(-(triethoxysilyl)propyl]tetrasulfide (TESPT), 3-thio-octanoyl-1-propyltriethoxysilane (NXT), Me.sub.2Si(OEt).sub.2, Me.sub.2PhSiCl, Ph.sub.2SiCl.sub.2, more preferably between TESPD and TESPT.

20. The process as claimed in claim 17 wherein said alcohol is isopropanol, preferably mixed with water.

21. The process as claimed in claim 17 wherein the reaction is prolonged up to extracting not more than 65%, 60%, 50%, 40% by weight of magnesium from the fibres with respect to the total weight of magnesium originally contained in the fibres.

22. The tyre as claimed in claim 14, wherein said tyre component is selected from the group consisting of the tread, under-layer, anti-abrasive elongated element, sidewall, sidewall insert, mini-sidewall, under-liner, rubber layers, bead filler and sheet, preferably from among the tread, under-layer and sidewall insert.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0180] FIG. 1 shows a radial half-section of a tyre for vehicle wheels.

[0181] FIG. 2 shows a FESEM (Field Emission Scanning Electron Microscopy, 100000 magnification) microscope image of modified sepiolite fibres with needle-shaped morphology F5 of Example 5.

[0182] FIG. 3 shows the FESEM (100000 magnification) microscope images of sepiolite fibres with needle-shaped morphology modified under controlled conditions according to the present process F1 (Example 1, FIG. 3A) and sepiolite fibres F2a modified by drastic acid treatment in which the needle-shaped morphology has been lost (comparative Example 2a, FIG. 3B).

[0183] FIGS. 4 (A and B) shows the microscope images (FESEM, 50000 magnification) of modified fibres F3 and F6 according to Examples 3 and 6, respectively (extracted magnesium: 35% and 20%).

[0184] FIG. 5 shows the XRD diffractograms of a sample of unmodified natural sepiolite F-SE (comparative) and of a sample of sepiolite F5 modified by mild acid treatment as per Example 5.

[0185] FIG. 6 shows the XRD diffractograms in the 2 theta range from 4 to 14, of samples of sepiolite fibres F1 modified as per Example 1, of comparative samples F2a, modified as per Example 2a, and of unmodified sepiolite fibres F-SE.

[0186] FIG. 7A shows the ATR-IR diagrams of a sample of modified sepiolite fibres F5 with needle-shaped morphology of Example 5 and a sample of original unmodified sepiolite fibres F-SE.

[0187] FIG. 7B shows a significant portion of the ATR-IR diagrams of samples of commercial silica (SIL), of unmodified sepiolite fibres (F-SE), of modified fibres of Example 1 (F1) and of the comparative Example 2a (F2a).

[0188] FIGS. 8 (A and B) shows the pattern of the dynamic elastic modulus and of the tan delta at increasing strain of samples of elastomeric materials comprising unmodified sepiolite fibres F-SE (V-MO) and sepiolite fibres F5 modified as per Example 5 (V-MP).

[0189] FIG. 9 is an STEM (Scanning Transmission Electron Microscopy) image of a thin section of a vulcanised elastomeric composition (V-MJ Example 13) comprising the sepiolite fibres F6 modified according to Example 6.

[0190] FIG. 10 is an STEM image of a thin section of a vulcanised elastomeric composition (V-MI Example 13) comprising the sepiolite fibres F5 modified according to Example 5.

[0191] FIG. 11 shows the XRD diffractograms of a sample of unmodified natural sepiolite F-SE (comparative) and of a sample of sepiolite F2b (prepared in Example 2b) modified by drastic acid treatment, in which the needle-shaped morphology has been preserved but the crystalline structure has been lost.

DESCRIPTION OF EXAMPLES OF THE INVENTION

[0192] The description of some examples of the invention is given hereinafter by way of non-limiting indication.

[0193] FIG. 1 shows a radial half-section of a tyre for vehicle wheels.

[0194] 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.

[0195] 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.

[0196] The carcass layer 101 is optionally made with an elastomeric composition.

[0197] 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. The carcass structure is usually of radial type, i.e. the reinforcement 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,

[0198] 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.

[0199] An anti-abrasive strip 105 optionally made with an elastomeric composition is arranged in an outer position of each bead structure 103.

[0200] 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 material. 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.

[0201] 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 material.

[0202] A tread band 109 of vulcanised elastomeric material is applied in a position radially outer to the belt structure 106.

[0203] Moreover, respective sidewalls 108 of vulcanised elastomeric material 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.

[0204] 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. An under-layer 111 of vulcanised elastomeric material can be arranged between the belt structure 106 and the tread band 109.

[0205] A strip consisting of elastomeric composition 110, commonly known as mini-sidewall, of vulcanised elastomeric material 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.

[0206] 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.

[0207] The rigidity of the tyre sidewall 108 can be improved by providing the bead structure 103 with a reinforcement layer 120 generally known as flipper or additional strip-like insert.

[0208] Flipper 120 is a reinforcement layer which is wound around the respective bead core 102 and the bead filler 104 so as to at least partially surround them, said reinforcement 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.

[0209] Flipper 120 typically comprises a plurality of textile cords incorporated within a layer of vulcanised elastomeric material.

[0210] 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.

[0211] Chafer 121 usually comprises a plurality of cords incorporated within a rubber layer of vulcanised elastomeric material. Such cords are generally made of textile materials (such as aramide or rayon) or metal materials (such as steel cords).

[0212] A layer or sheet of elastomeric material can be arranged between the belt structure and the carcass structure. The layer can have a uniform thickness. 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.

[0213] Advantageously, the layer or sheet can extend on a surface substantially corresponding to the extension surface of said belt structure.

[0214] In a preferred embodiment, a layer or sheet of elastomeric material 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.

[0215] The elastomeric composition according to the present invention can comprise at least:

(a) 100 phr of at least one diene elastomeric polymer;
(b) from 1 to 80 phr of modified silicate fibres of nanometric size, with substantially preserved needle-shaped morphology, comprising from 3.8% to 12% by weigh of magnesium with respect to the weight of the fibres themselves;
(c) from 0 to 120 phr of a standard reinforcement filler;
(d) from 0.1 to 15 phr of a vulcanising agent, and
(e) from 0 to 20 phr of a coupling agent.

[0216] The elastomeric composition according to the present invention can comprise at least: [0217] (a) 100 phr of at least one diene elastomeric polymer, [0218] (b) from 1 to 80 phr of modified silicate fibres with needle-shaped morphology of nanometric size, said modified fibres being obtainable according to a process that comprises: [0219] providing silicate fibres with needle-shaped morphology of nanometric size comprising magnesium ions, [0220] suspending said fibres in a liquid medium, [0221] adding at least one acid compound to the suspension, [0222] allowing the reaction, up to extracting from 10% to 70% by weight of magnesium ions from the fibres, substantially preserving their crystalline structure and needle-shaped morphology and [0223] separating the fibres thus modified from the liquid medium; [0224] (c) from 0 to 120 phr of a standard reinforcement filler; [0225] (d) from 0.1 to 15 phr of a vulcanising agent, and [0226] (e) from 0 to 20 phr of a coupling agent.

[0227] The elastomeric composition 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] The following examples are now provided to better illustrate the present invention.

Methods for the Analytical Characterisation of the Fibres

[0232] The original fibres, the fibres modified under drastic acid conditions (Examples 2a and 2b, comparative fibres) and the silanised and non-silanised fibres modified under controlled acid conditions (Examples 3-7), subsequently incorporated in the elastomeric materials according to the invention, were characterised with one or more of the following analytical techniques:

[0233] Determination of magnesium present in the fibres by X-ray fluorescence spectrometry (XRF spectroscopy): the Bruker AXS S4 Pioneer XRF spectrophotometer was used at room temperature. The samples were analysed by placing the powder in a sample holder having a window exposed to incident radiation with diameter of 34 mm, covered with a 4 micron polypropylene film. The measurement was conducted in helium at reduced pressure, using the standardless acquisition program Fast-He34.mm preset in the instrument, and processing data with the S4tools software using as the formula Si.sub.6H.sub.14OR.sub.23 as a calculation matrix. For greater accuracy, the determination of magnesium was carried out only on the component did not decompose when subjected in TGA to oxidative treatment up to 800 C., as better explained in Example 5.

[0234] Finally, the extraction percentage of magnesium was calculated based on the amount of magnesium present in the starting fibres, measured by the same method, as shown in Example 5.

Dosage of Mg in the Acid Reaction Medium by Complexometry

[0235] The magnesium extracted in the reaction medium can be measured by using, according to literature (Preparation of Silica by Acid Dissolution of sepiolite and Study of its reinforcing effect in Elastomers, Die Angewandte Makrom Chemie (1982), 103, 51-60), a complexometric method with EDTA.

[0236] In a typical procedure, 500 L of the filtration mother liquors are diluted with 100 mL of distilled water and treated with 4 mL of a buffer solution obtained by dissolving 5.4 g of NH.sub.4Cl in 60 mL of distilled water and 35 mL of aqueous NH.sub.3 at 29% by weight. Two drops of eriochrome black T in 1% methanol solution are then added to the buffered solution. The solution is heated to 40-50 C. and is titrated with disodium EDTA 0:01 M until the solution colour changes. The total extracted magnesium is calculated from the titre of magnesium in the buffered solution taking into account the amount of supernatant removed and the total fluid volume in the reaction mixture.

[0237] The percentage of extracted Mg is then calculated based on the initial weight of reacted magnesium-containing fibres, and the initial percentage of Mg in such fibres, calculated by the molecular formula of magnesium silicate.

[0238] Field emission scanning electron microscopy FESEM: observations on the powders of the samples in Example 5 (FIG. 2) were carried out with a Vega TS5136 XM Tescan microscope in high-vacuum configuration. The excitation of the electron beam was 30 kV with a current of 25 pA. Prior to the SEM analysis, the samples were attached to a metal target with adhesive tape and subjected to sputtering with gold to improve the conductivity of electrons through the material.

[0239] In the case of Examples 1 and 2a (FIG. 3) and of Examples 3 and 6 (FIG. 4), the samples were observed with a FESEM Ultra Plus Zeiss microscope, Gemini column, in InLens mode, excitation of the electron beam from 3.0 to 5.0 KV, working distance from 2.7 to 4.3 mm.

[0240] The samples were prepared as follows: 0.005 g of fibres were dispersed in 50 mL of solution consisting of a mixture of water and ethanol in a ratio of 8:2, admixed with 200 ppm of Nonidet P40 (surfactant purchased from Sigma-Aldrich) by treatment with ultrasound in immersion for 15 minutes. The fibres were separated by centrifugation at 1000 g/m for 20 minutes and dried in stove at 100 for 3 hours.

[0241] STEM characterisation of the vulcanised elastomeric materials: the observation was conducted on thin sections (50 nm) subjected to cold ultramicrotomy (120 C.) with a FESEM Ultra Plus Zeiss microscope, Gemini column, in InLens mode, excitation of the electron beam of 30 kV, working distance 2 mm.

[0242] X-ray diffraction (XRPD): The XRD diffraction patterns were recorded with a Bruker D8 Avance diffractometer (Cu K-alpha radiation) in the range of 2 up to 260 with (2)=0.02 and 4 s interval between each acquisition.

[0243] Thermogravimetric analysis (TGA): the determination of the weight loss profile was carried out with the apparatus Mettler Toledo TGA/DSC1 Star-e System and, in a temperature range of from 150 to 800 C. The measurements were carried out using a temperature program which involves a step with inert gas (ramp from 25 to 150 C. and a plateau at 150 C. in nitrogen flow) and an oxidation step (ramp from 150 to 800 C. in a flow of dry air).

[0244] Attenuated total reflectance infrared spectroscopy ATR-IR: the measurements were carried out with the instrument Perkin Elmer Spectrum 100 (1 cm.sup.1 resolution, range of 650-4000 cm.sup.1, 16 scans). This analytical technique allows easily distinguishing the original sepiolite fibres F-SE and those modified according to the present process, characterised by more intense signals in the range of 850-1040 cm.sup.1in two resolved signals or even in a single bandcompared to commercial silica, which shows very intense signals in the range of 1040-1300 cm.sup.1.

Preparation of the Fibres

Example 1

[0245] Preparation of Modified Sepiolite Fibres with Needle-Shaped Morphology F1 (Aqueous Environment, Partial Extraction of Magnesium)

[0246] Modified sepiolite fibres were prepared using the following materials:

sepiolite Pangel S9 (5 g)
3M aqueous HCl (50 mL)

[0247] Procedure

[0248] Sepiolite (5 g) is suspended in a 250 mL glass flask in 50 mL of the acid solution and is heated in an oil bath at 60 C. for 10 minutes under stirring.

[0249] The suspension is then filtered on Buchner. The solid is washed with abundant deionised water (about 1.5-2 L) until the wash water is free of chloride ions (AgNO3 test). The complexometric analysis shows the presence of 31% magnesium theoretically present in the starting silicate in the filtration mother liquors.

[0250] The recovered solid is finally dried in a stove at 70 C. for 120 hours. The XRF analysis on the modified fibres shows an extraction of magnesium equal to 33%, in agreement with the complexometric data.

[0251] As can be seen from the microscopic examination shown in FIG. 3A, the morphology of the fibres was substantially preserved. Moreover, the diffractogram in FIG. 6 and the IR spectrum in FIG. 7B confirm the substantial preservation of the crystalline structure of the sample.

[0252] In particular, in order to assess the preservation of the crystallinity, in the IR spectrum, the areas under the four curves were measured, in the ranges between 850 and 1040 cm.sup.1 (area of the typical signs of the crystalline structure) and between 1040 and 1300 cm.sup.1 (area of the typical signs of the amorphous structure) with the following results:

TABLE-US-00001 Material SIL F2 F1 F-SE Area 1 (850-1040 cm.sup.1) 2.7 4.7 7.6 11.6 Area 2 (1040-1300 cm.sup.1) 11.7 11.0 4.6 2.9 Area 1/Area 2 ratio 0.23 0.43 1.65 4

[0253] As can be seen from the ratios between the areas calculated above, the sepiolite fibres of Example 1 show a substantial preservation of the crystalline structure (ratio >0.8) while the modified sepiolite fibres of Example 2 have substantially lost the crystallinity (ratio <0.8).

Example 2a (Comparative)

[0254] Preparation of Modified Sepiolite Fibres F2a (Aqueous Environment, Total Extraction of Magnesium)

[0255] This example substantially reproduces the processes described in the literature to generate amorphous silica by means of exhaustive acid treatment of the sepiolite fibres.

[0256] In particular, the procedure of Example 1 was repeated but continuing the reaction for a total of 70 minutes under the same conditions.

[0257] At the end of the process, the magnesium extraction appeared high (95% according to the XRF method) and the morphology of the fibres was no longer needle-shaped, as visible in the FE-SEM image in FIG. 3B. Moreover, the crystalline structure was substantially lost, as shown by the diffractogram shown in FIG. 6 and by the IR spectrum in FIG. 7B. The amorphous silica thus obtained was subsequently incorporated in the elastomeric material and used as a term of comparison.

[0258] As can be seen from the XRD diffractogram in FIG. 6, the peak at 6-8diagnostic of the crystalline orderwas completely lost in the sample of Example 2a, while it appeared largely preserved in the sample of Example 1.

Example 2b (Comparative)

[0259] Preparation of Modified Sepiolite Fibres F2b (Aqueous Environment, Total Extraction of Magnesium)

[0260] This example substantially reproduces the processes described in the literature to generate amorphous silica by means of exhaustive acid treatment of the sepiolite fibres.

[0261] In particular, the procedure described in Preparation of Silica by Acid Dissolution of Sepiolite and Study of its Reinforcing Effect in Elastomers was repeated under the same conditions (60 C., HNO.sub.35N).

[0262] At the end of the process, the extraction of magnesium ions appeared high (97% according to the XRF method) but the morphology of the fibres remained substantially needle-shaped. Conversely, the crystalline structure was substantially lost, as shown by the diffractogram shown in FIG. 11. The amorphous needle-shaped silica thus obtained was subsequently incorporated in the elastomeric material and used as a term of comparison.

[0263] As can be seen from the XRD diffractogram in FIG. 11, the peak at 6-8diagnostic of the crystalline order (peak F-SE) is completely lost in the sample of Example 2b.

Example 3

[0264] Preparation of Modified Sepiolite Fibres F3 (Alcohol Environment, Partial Extraction of Magnesium)

[0265] Modified sepiolite fibres were prepared using the following materials:

sepiolite Pangel S9 (120 g)

Isopropanol (1.2 L)

[0266] Aqueous HCL, 37% by weight (480 mL)
Deionised water (3 L)
Aqueous NH.sub.3 29% by weight

[0267] Procedure

[0268] 120 g of sepiolite Pangel S9 were loaded into a 3 litre two-necked flask, equipped with mechanical stirrer and immersed in an oil bath at 80 C. 1.2 L of isopropyl alcohol preheated at 65 C. were added and the mixture was stirred for 15 minutes at 600 rpm. 480 mL aqueous HCl at 37% by weight were added. The mixture was kept under stirring for 120 minutes at 65 C. and then filtered on Buchner. The solid was suspended in 2 L of deionised water. An aqueous solution of NH.sub.3 at 29% by weight was then added up to reaching a pH 7.00.2. The solid was collected on Buchner and washed with 1 L of deionised water and then dried in a stove at 120 C. for 72 hours.

[0269] The XRF analysis of a product sample showed that 35% by weight of magnesium was extracted.

[0270] At the microscopic observation (FIG. 4A), the sample preserved the morphology of sepiolite fibres. The IR analysis showed predominant signals between 850 and 1040 cm.sup.1 in the characteristic region of unmodified sepiolite fibres and not between 1040 and 1300 cm.sup.1, area of the typical signals of amorphous silica, index of the substantial preservation of the crystalline structure.

Example 4

[0271] Preparation of Modified Sepiolite Fibres F4 (Alcohol Environment, Presence of Silanising Agents, Partial Extraction of Magnesium)

[0272] Modified sepiolite fibres were prepared using the following materials:

sepiolite Pangel S9 (120 g)
bis[3-(triethoxysilyl)propyl]tetrasulphide TESPT (64.7 g)

Isopropanol (1.2 L)

[0273] Aqueous HCL, 37% by weight (480 mL)
Deionised water (3 L)
Aqueous NH.sub.3 29% by weight

[0274] Procedure

[0275] 120 g of sepiolite Pangel S9 were loaded into a 3 litre two-necked flask, equipped with mechanical stirrer and immersed in an oil bath at 80 C. 1.2 L of isopropyl alcohol preheated at 65 C. were added and the mixture was stirred for 15 minutes at 600 rpm. 64.7 g TESPT and then 480 mL aqueous HCl at 37% by weight were added. The mixture was kept under stirring for 120 minutes at 65 C. and then filtered on Buchner. The solid was suspended in 2 L of deionised water. A solution of NH.sub.3 at 29% by weight was then added up to reaching a pH 7.00.2. The solid was collected on Buchner, washed with 1 L of deionised water and dried in a stove at 120 C. for 72 hours.

[0276] The XRF analysis of a product sample showed that 35% by weight of magnesium was extracted. The complexometric analysis showed the presence of 32% magnesium theoretically present in the starting silicate in the filtration mother liquors. The result is in good agreement with the XRF data.

[0277] At the microscopic observation, the sample preserved the morphology of sepiolite fibres. The IR analysis showed predominant signals between 850 and 1040 cm.sup.1 in the characteristic region of unmodified sepiolite fibres, the index of the substantial preservation of the crystalline structure, and not between 1040 and 1300 cm.sup.1, area of the typical signals of amorphous silica.

Example 5

[0278] Preparation of Modified Sepiolite Fibres F5 (Alcohol Environment, Presence of Sulphur Silanising Agents, Partial Extraction of Magnesium)

[0279] Modified sepiolite fibres were prepared using the following materials:

sepiolite Pangel S9 (sepiolite) supplied by Tolsa
TESPT bis[3-(triethoxysilyl)propyl]tetrasulphide, isopropanol and 37% aqueous hydrochloric acid supplied by Aldrich.
29% by weight aqueous NH.sub.3 was used for the final neutralisation of modified fibres, and deionised water for washing.

[0280] Procedure

[0281] 120 g of sepiolite in 1200 mL isopropanol were suspended in a reaction flask at 65 C. After 10 minutes of vigorous stirring (800 rpm, mechanical stirring), 13 g of TESPT were added, followed by 96 mL of 37% aqueous hydrochloric acid.

[0282] This was left under vigorous stirring (600 rpm) at 65 C. for 72 hours.

[0283] The reaction mixture was filtered on Buchner and the solid was suspended in 2 L of deionised water. A solution of NH3 at 29% by weight was then added up to reaching a pH 7.00.2. The solid was collected on Buchner, washed with 1 L of deionised water and dried in a stove at 120 C. for 48 hours.

[0284] The powder thus obtained (modified fibres) was characterised and compared with original sepiolite fibres using the following techniques and with the following results:

[0285] FE-SEM Microscope Evaluation (FIG. 2):

[0286] FIG. 2 shows the needle-shaped modified sepiolite fibres of nanometric size of Example 5. These fibres have an average diameter of 205 nm and a length of 460400 nm, with an aspect ratio of approximately 2310.

[0287] XRD Analysis (FIG. 5)

[0288] The XRD analysis on modified sepiolite according to Example 5 (F5) and on original unmodified sepiolite (F) shows that treatment under controlled acid conditions did not substantially change the crystalline structure of sepiolite. In fact, the typical diffractogram of original sepiolite (Pangel S9) is closely comparable with that of the modified sepiolite sample, in particular the peak at 2 theta 7.5 characteristic of sepiolite is recognisable.

[0289] Thermogravimetric Analysis TGA

[0290] The loss in weight during TGA (from 150 to 800 C.) was calculated to be equal to 6.5% by weight for the original unmodified sepiolite sample (F-SE) and 17.6% by weight for the sample in Example 5 silanised and treated under acid conditions (F5).

[0291] ATR-IR Spectroscopic Analysis (FIGS. 7A and 7B)

[0292] The samples of original unmodified sepiolite F-SE and of sepiolite F5 modified under controlled conditions of Example 5 were subjected to IR analysis to evaluate the controlled acid-induced treatment chemical changes.

[0293] As can be seen in FIG. 7A, the two diagrams are in general very similar: both show the signals due to stretching of the bonds of the OH groups linked to magnesium (3500-3700 cm.sup.1) and to silicon (3300-3500 cm.sup.1) and the double peak of the SiO bond stretching (SiOSi and SiOMg stretching) at about 1000 cm.sup.1 typical of magnesium silicates such as sepiolite and sepiolite fibres as modified according to the present process.

[0294] FIG. 7B instead shows a detail of the IR spectra of commercial silica (SIL), of the unmodified sepiolite (F-SE), of the sepiolite modified with partial extraction of magnesium of Example 1 (F1) and with full extraction of Example 2a (F2a).

[0295] As can be seen, the sample of Example 1, like that of the unmodified sepiolite, shows a strong absorption at between 850 and 1040 cm.sup.1 while the commercial silica and sample F2a, from which about 95% of Mg was extracted, generate more intense peaks at between 1040 and 1300 cm.sup.1.

[0296] Determination of Magnesium by Complexometry

[0297] The amount of magnesium extracted from the fibres was carried out by complexometric titration on the filtration mother liquors: 500 L of the filtration mother liquors were diluted with 100 mL of distilled water and treated with 4 mL of a buffer solution obtained by dissolving 5.4 g of NH.sub.4Cl in 60 mL of distilled water and 35 mL of a solution of aqueous NH.sub.3 at 29% by weight.

[0298] Two drops of eriochrome black T in 1% methanol solution were added to the buffered solution. After heating the solution to 40-50 C., it was titrated with disodium EDTA 0:01 M until the solution colour changes. The total extracted magnesium is calculated from the titre of magnesium in the buffered solution taking into account the amount of supernatant removed (500 L) and the total fluid volume in the reaction mixture (1296 L).

[0299] The percentage of extracted Mg was then calculated based on the initial amount of reacted magnesium-containing fibres (120 g), and the initial percentage of Mg in such fibres, calculated by the molecular formula of magnesium silicate Mg.sub.4Si.sub.6O.sub.15(OH).sub.2(H.sub.2O).sub.6, i.e. a 15% percentage of the starting weight of magnesium. The percentage of extracted Mg was equal to 25% of the initially present Mg.

[0300] Determination of Magnesium by XRF Spectroscopy

[0301] The amount of magnesium in the fibres before (sample F-SE, Sepiolite as is) and after controlled acid treatment (sample F5, sample treated as described above) was determined by XRF analysis.

[0302] The results of these analyses are presented in the following Table 1

TABLE-US-00002 TABLE 1 Mg % Mg % recalculated on Mg % measured residual TGA extracted sepiolite F-SE 13.1 14.0 modified sepiolite F5 8.6 10.4 26

[0303] For greater accuracy, the amount of magnesium was calculated on the samples after TGA, i.e. on the dry inorganic component of the same aloneequal to 93.5% for the sepiolite F-SE sample and to 82.4% for the modified sepiolite F5, respectivelywhich did not decompose by oxidative treatment at 800 C. As can be seen from the data in the table, the residual magnesium quantity in the sample subjected to controlled acid treatment according to the present process (F5) is lower (10.4%) and equal to about 74% of the initial quantity. Therefore, the acid treatment removed 26% of magnesium from the sepiolite fibres, preserving the original structure of the silicate, as demonstrated by the XRD spectrum in FIG. 5 and by the IR spectrum in FIG. 7A. The magnesium extraction data calculated according to this methodology on powders is in very good agreement with the complexometric data obtained on the filtration mother liquors.

Example 6

[0304] Preparation of Modified Sepiolite Fibres F6 (Aqueous Environment, Partial Extraction of Magnesium)

[0305] Modified sepiolite fibres were prepared using the following materials:

sepiolite Pangel S9 (120 g)
1M aqueous HCl (1.45 L)
Deionised water (2 L)
Aqueous NH.sub.3 29% by weight

[0306] Procedure

[0307] 120 g of sepiolite Pangel S9 were loaded into a 3 litre two-necked flask equipped with a mechanical stirrer. 1.45 L of HCl 1M were added and the mixture was stirred for 60 minutes at 600 rpm at 23 C. and then filtered on Buchner. The solid was suspended in 2 L of deionised water. A solution of NH.sub.3 at 29% by weight was then added up to reaching a pH 7.00.2. The solid was collected on Buchner and washed with 1 L of deionised water and then dried in a stove at 120 C. for 72 hours.

[0308] The XRF analysis of a product sample showed that 20% by weight of magnesium was extracted.

[0309] At the microscopic observation (FIG. 4B), the sample preserved the morphology of sepiolite fibres.

[0310] The IR analysis in the 850-1300 cm.sup.1 region showed signals between 850 and 1040 cm.sup.1 that were predominant over those between 1040 and 1300 cm.sup.1 indicating the substantial preservation of the crystalline structure.

Example 7

[0311] Preparation of Modified Sepiolite Fibres F7 (Alcohol Environment, Presence of Non-Sulphur Silanising Agents, Partial Extraction of Magnesium)

[0312] Modified sepiolite fibres were prepared using the following materials:

sepiolite Pangel S9 (sepiolite) supplied by Tolsa
Me.sub.2Si(EtO).sub.2 dimethyldiethoxysilane,
isopropanol,
37% aqueous hydrochloric acid
29% by weight NH.sub.3 was used for the final neutralisation of modified fibres, and deionised water for washing.

[0313] Procedure

[0314] 120 g of sepiolite in 1200 mL isopropanol were suspended in a reaction flask at 65 C. After 10 minutes of vigorous stirring (800 rpm, mechanical stirring), 35.6 g of Me.sub.2Si(EtO).sub.2 were added, followed by 480 mL of 37% aqueous hydrochloric acid. The mixture was kept under stirring for 120 minutes at 65 C. and then filtered on Buchner. The solid was suspended in 2 L of deionised water. A solution of NH.sub.3 at 29% by weight was then added up to reaching a pH 7.00.2. The solid was collected on Buchner, washed with 1 L of deionised water and dried in a stove at 120 C. for 72 hours.

[0315] The XRF analysis of a product sample showed that 28% by weight of magnesium was extracted.

[0316] At the microscopic observation, the sample preserved the morphology of sepiolite fibres. The IR analysis in the 850-1300 cm.sup.1 region showed signals between 850 and 1040 cm.sup.1 that were predominant over those between 1040 and 1300 cm.sup.1 indicating the substantial preservation of the crystalline structure.

[0317] The following summary Table 2 shows examples of preparation of the fibres, the quantity of magnesium extracted, the elastomeric materials in which the fibres were incorporated, with reference to the corresponding examples (green and vulcanised materials):

TABLE-US-00003 TABLE 2 % Preparation Preparation of extracted Elastomeric of the green the vulcanised Fillers/fibres Mg material material material Ref. silica SIL Standard 1 Ex. 8 MA Ex. 12 V-MA Ref. silica SIL Internal Ex. 9 ME Ex. 13 V-ME appl. Ref. silica SIL Tread Ex. 10 ML Ex. 14 V-ML Ref. sepiolite F- Standard 1 Ex. 8 MB Ex. 12 V-MB SE Ref. sepiolite F- Internal Ex. 9 MF Ex. 13 V-MF SE appl. Ref. sepiolite F- Tread Ex. 10 MM Ex. 14 V-MM SE Ref. sepiolite F- Standard 2 Ex. 11 MO Ex. 15 V-MO SE Inv. Ex. 1 F1 33% Standard 1 Ex. 8 MD Ex. 12 V-MD Ref. Ex. 2a F2a 95% Standard 1 Ex. 8 MC1 Ex. 12 V-MC1 Ref. Ex. 2b F2b 97% Standard 1 Ex. 9 MC2 Ex. 13 V-MC2 Inv. Ex. 3 F3 35% Internal Ex. 9 MG Ex. 13 V-MG appl. Inv. Ex. 4 F4 35% Internal Ex. 9 MH Ex. 13 V-MH appl. Inv. Ex. 4 F4 35% Tread Ex. 10 MN Ex. 14 V-MN Inv. Ex. 5 F5 26% Internal Ex. 9 MI Ex. 13 V-MI appl. Inv. Ex. 5 F5 26% Standard 2 Ex. 11 MP Ex. 15 V-MP Inv. Ex. 6 F6 20% Internal Ex. 9 MJ Ex. 13 V-MJ appl. Inv. Ex. 7 F7 28% Internal Ex. 9 MK Ex. 13 V-MK appl.

Preparation of the Elastomeric Materials (M)

[0318] The vulcanisable elastomeric materials of the following examples were prepared as described herein. The quantities of the various components are shown in phr.

[0319] All the components, except for sulphur and the vulcanisation accelerator (TBBS), were mixed in an internal mixer (Brabender) for about 5 minutes (1st step). As soon as the temperature reached 145 C.5 C., the elastomeric material was unloaded. Sulphur and the accelerator (TBBS) were added and mixing was carried out in an open roll mixer (2nd step).

Example 8

[0320] Preparation of Standard Vulcanisable Elastomeric Materials (1) Comprising Modified sepiolite fibres

[0321] The sepiolite fibres F1 modified as per Example 1 were incorporated together with conventional silica SIL in standard compositions (1) for vulcanisable elastomeric materials for tyre components. These materials (MD) were compared with comparative elastomeric materials, comprising standard fillers, in particular containing only conventional silica (SIL in MA) or conventional silica along with unmodified sepiolite fibres (F-SE in MB) or conventional silica along with sepiolite fibres treated under drastic acid conditions (F2a, F2b in MC1 and MC2, respectively) as shown in Example 2a and 2b, respectively. Particularly in materials (MB), (MC) and (MD), 10 phr of conventional silica were replaced with 10 phr of unmodified sepiolite or sepiolite modified by drastic treatment or sepiolite modified by bland treatment, respectively.

[0322] The elastomeric materials of this example comprise standard compositions (1) suitable for various applications, such as elastomeric under-layer materials (car and heavy vehicles), soft bead (heavy vehicles), sidewall insert (car), or sidewall and are similar to tread formulations (heavy vehicles). Therefore, the results shown by these elastomeric materials are representative of those obtainable with elastomeric materials for tyre components filled with silica or with silica and carbon black in general.

[0323] The following Table 3 shows the compositions in phr of the vulcanisable elastomeric materials (MA), (MB), (MC1) and (MD):

TABLE-US-00004 TABLE 3 MC1 MD MB Ref. Invention MA Ref. Silica + mod. Silica + mod. Example 8 Ref. Silica + sepiolite sepiolite Filler Silica sepiolite (Ex. 2a) (Ex. 1) % extracted Mg 95% 33% Zeosil 1115MK 45 35 35 35 sepiolite 0 10 0 0 modified sepiolite 0 0 10 0 Ex. 2 modified sepiolite 0 0 0 10 Ex. 1 NR 100 100 100 100 Stearic acid 2 2 2 2 TESPT silane 3.6 3.6 3.6 3.6 ZnO 3.6 3.6 3.6 3.6 6-PPD 2 2 2 2 TBBS 1.8 1.8 1.8 1.8 Sulphur 2.8 2.8 2.8 2.8
wherein NR: natural rubber; TESPT: Bis[3-(triethoxysilyl)propyl]tetrasulphide; Zeosil 1115MK: precipitated synthetic amorphous silica (Rhodia); sepiolite: Pangel S9; ZnO: zinc oxide; 6-PPD: N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine; TBSS: N-tert-butyl-2-benzothiazylsulphenamide.

Example 9

[0324] Preparation of Vulcanisable Elastomeric Materials for Internal Applications Comprising Modified Sepiolite Fibres

[0325] The sepiolite fibres F3, F4, F5, F6 and F7, modified as per Examples 3, 4, 5, 6 and 7, were incorporated together with conventional silica and carbon black in compositions for vulcanisable elastomeric materials for internal components of tyres, such as sidewall insert, bead or under-liner. These materials (MG), (MH), (MI), (MJ) and (MK) were compared with the same elastomeric materials but comprising standard fillers, particularly containing only carbon black and conventional silica (ME), carbon black and conventional silica together with unmodified sepiolite fibres (MF) or carbon black and conventional silica together with sepiolite fibres modified by total extraction of magnesium ions (MC2).

[0326] The mixing was conducted in three steps using an internal tangential rotor mixer (Pomini PL 1.6): in the first step, polymers, fillers, and silane were introduced and the mixing was continued for 4-5 minutes, up to reaching 135 C.5 C., when the composition was unloaded. After 12-24 hours, in the second step, conducted using the same mixer, ZnO, TMQ and 6-PPD were introduced and mixing was continued for about 3 minutes, up to reaching 125 C.5 C., when the composition was unloaded. After 12-24 hours, in the third step, conducted using the same mixer, TBBS and Sulphur were introduced and mixing was conducted for about 2 minutes, up to reaching 95 C.5 C., when the composition was unloaded.

[0327] The following Table 4 shows the compositions in phr of the vulcanisable elastomeric materials (ME), (MF), (MC2), (MG), (MH), (MI), (MJ) and (MK):

TABLE-US-00005 TABLE 4 Example 9 MC2 MG MH MI MJ MK Ref. Inv. Inv. Inv. Inv. inv. MF Silica + Silica + Silica + Silica + Silica + Silica + ME Ref. mod. sepiolite sepiolite sepiolite sepiolite sepiolite Ref. Silica + sepiolite mod. mod. mod. mod. mod. Filler Silica sepiolite (Ex. 2b) (Ex. 3) (Ex. 4) (Ex. 5) (Ex. 6) (Ex. 7) % ext. 97% 35% 35% 26% 20% 28% Mg CB N550 25 25 25 25 25 25 25 25 ZEOSIL 30 20 20 20 20 20 20 20 1115 MK sepiolite 7 Sepiolite 7 mod. ex. 2b sepiolite 8.29 mod. ex. 3 sepiolite 9.79 mod. ex. 4 sepiolite 8.55 mod. ex. 6 sepiolite 8.55 mod. ex. 5 sepiolite 8 mod. ex. 7 BR (Nd) 60 60 60 60 60 60 60 60 IR 40 40 40 40 40 40 40 40 Silane 5 5 5 5 5 5 5 5 Stearic 1 1 1 1 1 1 1 1 acid ZnO 4 4 4 4 4 4 4 4 TMQ 1 1 1 1 1 1 1 1 6-PPD 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 TBBS 80 4 4 4 4 4 4 4 4 Sulphur 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3
wherein BR(Nd): high-cis neodymium polybutadiene rubber (Europrene 40 Versalis); IR: synthetic polyisoprene (SKI3 produced by Nitzhnekamsk); silane: 50% TESPT: Bis[3-(triethoxysilyl)propyl]tetrasulphide on carbon black; CB: carbon black; Zeosil 1115MK: precipitated synthetic amorphous silica (Rhodia); sepiolite: Pangel S9 (Tolsa); ZnO: zinc oxide; TMQ: polymerised 2,2,4-trimethyl-1,2-dihydroquinoline; 6-PPD: N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine; TBSS: N-tert-butyl-2-benzothiazyl sulphenamide.

[0328] In the material (MF), 10 parts of silica were replaced with 7 parts of sepiolite.

[0329] In the material (MC2), 10 parts of silica were replaced with 7 parts of modified sepiolite as described in Example 2b.

[0330] In the case of materials (MG), (MH), (MI), (MJ) and (MK), the amount of modified sepiolite to be added, in replacement of 10 phr silica, was calculated taking into account the loss in weight of the samples in TGA, so as to add a quantity of modified fibres corresponding to 7 phr of dry inorganic component, with the aim to obtain mixtures having a comparable hardness.

Example 10

[0331] Preparation of Vulcanisable Elastomeric Materials for Tread Applications Comprising Modified Sepiolite Fibres

[0332] The sepiolite fibres F4 modified as per Example 4 (controlled acid treatment in the presence of silanising agents) were incorporated together with conventional silica in a composition for vulcanisable elastomeric materials for tread. This material (MN) was compared with elastomeric materials comprising standard fillers, in particular containing conventional silica alone (SIL in ML) or conventional silica together with unmodified sepiolite fibres (F-SE in MM).

[0333] The mixing was conducted in three steps using an internal tangential rotor mixer (Pomini PL 1.6): in the first step, polymers, fillers, silane, stearic acid and TDAE oil were introduced and the mixing was continued for 4-5 minutes, up to reaching 140 C.5 C., when the composition was unloaded. After 12-24 hours, in the second step, conducted using the same mixer, ZnO and 6-PPD were introduced and mixing was continued for about 3 minutes, up to reaching 125 C.5 C., when the composition was unloaded. After 12-24 hours, in the third step, conducted using the same mixer, TBBS, TBZTD and Sulphur were introduced and mixing was continued for about 2 minutes, up to reaching 95 C.5 C., when the composition was unloaded.

[0334] The following Table 5 shows the compositions in phr of the vulcanisable elastomeric materials (ML), (MM) and (MN):

TABLE-US-00006 TABLE 5 MM MN ML Reference Invention Example 10 Reference Silica + Silica + mod. Filler Silica sepiolite sepiolite (Ex. 4) % ext. Mg 35% ZEOSIL 1165 MK 85 75 75 sepiolite 7 sepiolite mod. ex. 4 (silane) 9.79 BR (Nd) 27 27 27 S-SBR 100 100 100 SI 69 6.8 6.8 6 Stearic acid 2 2 2 TDAE oil 13 13 13 ZnO 2.4 2.4 2.4 6-PPD 3.5 3.5 3.5 TBBS 2.5 2.5 2.5 TBZTD 0.5 0.5 0.5 Sulphur 1 1 1
wherein BR(Nd): high-cis neodymium polybutadiene rubber (Europrene 40 Versalis); S-SBR: styrene-butadiene rubber SLR 4630 from Styron Europe GmbH; SI 69: Liquid bis[3-(triethoxysilyl)propyl]tetrasulphide (Evonik); Zeosil 1165MK: precipitated synthetic amorphous silica (Rhodia); sepiolite: Pangel S9 (Tolsa); TDAE: distilled aromatic oil; ZnO: zinc oxide; 6-PPD: N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine; TBSS: N-tert-butyl-2-benzothiazyl sulphenamide; TBZTD: tetrabenzyl thiuram disulphide.

[0335] In the material (MM), 10 parts of silica were replaced with 7 parts of sepiolite.

[0336] In the case of material (MN), the amount of modified sepiolite to be added, in replacement of 10 phr silica, was calculated taking into account the loss in weight of the samples in TGA, a loss corresponding to the organic portion which in the ramp up to 800 C. was of 28.5%, so as to add a quantity of modified fibres corresponding to 7 phr of dry inorganic component, with the aim to obtain mixtures having a comparable hardness.

Example 11

[0337] Preparation of Standard Elastomeric Materials (2) Comprising Modified Sepiolite Fibres

[0338] The sepiolite fibres F5 modified as per Example 5 (controlled acid treatment in the presence of silanising agents) (36.4 phr) were incorporated as a single filler in a standard composition (2) for vulcanisable elastomeric materials. This material (MP) was compared with elastomeric materials comprising unmodified sepiolite fibres (MO).

[0339] The following Table 6 shows the compositions in phr of the vulcanisable elastomeric materials (MO) and (MP):

TABLE-US-00007 TABLE 6 MP MO Invention Example 11 Reference modified Filler sepiolite sepiolite (Ex. 5) % ext. Mg 26% sepiolite Pangel S9 35 sepiolite mod. ex. 5 36.4 S-SBR 100 100 TESPD 2.8 Stearic acid 0.85 0.85 ZnO 2.7 2.7 6-PPD 1 1 Sulphur 2 2 CBS 1.5 1.5
wherein S-SBR: styrene-butadiene rubber SLR 4630 from Styron Europe GmbH; TESPD: Bis(3-triethoxysilylpropyl)disulphide from Aldrich; 6-PPD: N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine Santoflex-6 PPD from Flexsys; stearic acid: Stearin TP8 from Undesa; Sulphur: S8 (soluble sulphur) from Zolfo Industria; ZnO: zinc oxide from Zincol Ossidi; CBS: N-cyclohexyl-2-benzothiazyl sulphenamide Vulkacit CZ/C from Lanxess.

[0340] FIG. 8A shows the pattern of module G for these materials (see Example 15 for a detailed review).

Preparation and Characterisation of the Vulcanised Elastomeric Materials

[0341] The elastomeric materials prepared in the previous examples were vulcanised to give specimens on which analytical characterisations and the assessment of static and dynamic mechanical properties were conducted.

[0342] 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.

[0343] In the present description, the vulcanised samples are named with the same initials of the starting green elastomeric material preceded by letter V (for example, the vulcanised material named V-MK derives from material MK).

[0344] The static mechanical properties were measured according to the ISO 37:2005 standard at different elongation (50%, 100%, 300%) on samples of the elastomeric materials vulcanised at 170 C. for 10 minutes. The tensile tests were carried out on Dumbell specimens.

[0345] The dynamic mechanical properties were evaluated using a Monsanto R.P.A. 2000 according to the following method: cylindrical test specimens with weights in the range of 4.5 to 5.5 g were obtained by punching the vulcanisable elastomeric composition of the samples and their vulcanisation in the instrument RPA (at 170 C. for 10 minutes). The vulcanised samples were subjected to dynamic measurement of the elastic shear modulus (G) at 70 C., 10 Hz frequency, 0.1% and 10% strain.

[0346] The Payne effect was evaluated by the difference between the shear modules (G) at 10% and 0.5%, unless otherwise indicated.

[0347] Moreover, the dynamic compression modules were measured using an Instron dynamic device in the compression mode according to the following methods. A test piece of cross-linked material having a cylindrical shape (length=25 mm; diameter=14 mm), preloaded in compression up to a longitudinal strain of 25% with respect to the initial length and maintained at the predetermined temperature (23 C. or 70 C.) for the whole duration of the test was subjected to a dynamic sinusoidal strain having an amplitude of 3.5% with respect to the length under pre-load, with a frequency of 100 Hz.

[0348] The dynamic mechanical properties are expressed in terms of dynamic elastic modulus (E) and Tan delta (loss factor).

[0349] The Tan delta value was calculated as the ratio between the viscous dynamic module (E) and the dynamic elastic modulus (E), both being determined by the above dynamic measurements.

[0350] The heat generation and flexing fatigue during compression were measured using a Goodrich flexometer according to ASTM D 623-07. The test consisted in subjecting a rubber sample of defined size and shape to compressive stresses by rapid oscillation under controlled conditions. The increase in temperature was also measured. In particular, the increase in temperature was measured up to an equilibrium temperature.

[0351] In this test method, a defined compressive load is applied on a test sample through a linkage system having high inertia, while imposing an additional high frequency cyclic compression of defined amplitude on the sample. The increase in temperature at the base of the test sample is measured with a thermocouple to provide an indication of the heat generated during the flexing of the sample.

[0352] The standard test sample, a cylinder with a diameter of 17.8 mm and a height of 25 mm, was moulded.

[0353] The test conditions were: excursion=6.35 mm; load (on beam)=216 N; time=30 minutes; temperature=23 C. The test ended after 30 minutes, when the final internal temperature of the sample was determined.

Example 12 (Standard Vulcanised Elastomeric Materials 1)

[0354] The elastomeric materials (MA), (MB), (MC1) and (MD) prepared in Example 8 and vulcanised at 170 C. for 10 minutes were subjected to measurement of the static and dynamic mechanical properties according to the previously described methods, except for the dynamic strain range of 0.4% to 35% in the shear test (G) carried out with the instrument RPA. The following table 7 shows the values measured for the four samples:

TABLE-US-00008 TABLE 7 V-MC1 V-MB Refer- V-MD V-MA Refer- ence Invention Refer- ence Silica + mod. Silica + mod. Example 12 ence Silica + sepiolite sepiolite Filler Silica sepiolite Ex. 2a Ex. 1 % ext. Mg 95% 33% Ca0.1 [MPa] 0.48 0.62 0.42 0.50 Ca0.5 [MPa] 1.45 2.47 1.23 1.67 Ca1 [MPa] 2.91 5.63 2.48 3.79 Ca3 [MPa] 16.76 18.50 12.69 16.68 CR [MPa] 21.57 23.39 22.83 21.94 AR [%] 361.05 371.34 462.04 376.85 G (0.4%) [Mpa] 1.51 1.48 1.21 1.31 G(0.4-35%)/ 0.30 0.31 0.27 0.27 G 0.4% Tan delta max 0.071 0.074 0.082 0.071

[0355] The analysis of the data in Table 7 shows that by replacing an aliquot of silica in a standard elastomeric material (1) (V-MA) with the same weight of unmodified sepiolite fibres F-IF, an elastomeric material (V-MB) is obtained with higher reinforcement but worsened hysteresis and Payne effect (see tan delta and G (0.4-35%)/G (0.4%).

[0356] Using sepiolite fibres modified by drastic acid treatment F2a (comparative V-MC1, prepared in Example 2a, with 95% magnesium extraction and loss of the needle-shaped morphology and of the crystalline structure), a worsening of both the static properties and, above all, of the hysteresis (higher tan delta) is observed. Conversely, by incorporating modified sepiolite fibres F1 according to the present controlled acid treatment (V-MD) in the elastomeric material, a lower hysteresis than that of the material comprising untreated sepiolite (V-MB) and comparable to that of the material comprising silica alone (V-MA) is observed, but with a significant improvement of the Payne effect and satisfactory static properties.

[0357] The result is a very advantageous elastomeric material, with comparable hysteresis but with reduced Payne effect compared to the standard elastomeric material 1 (V-MA).

[0358] Moreover, as can be seen from the data in Table 7, the sepiolite fibres treated in drastic acid conditions F2a (as per Example 2a) and incorporated into these reference elastomeric materials (V-MC1) involve a lower static reinforcement than that of commercial silica (V-MA), and a much higher hysteresis (tan delta of 0.082 compared to 0.071): it is particularly surprising that both the unmodified starting sepiolite (V-MB) and the exhaustive reaction product with acid (V-MC1) induce both a higher hysteresis in the materials, while the sepiolite modified by controlled acid treatment causes a hysteresis of the material (V-MD) lower than both reference materials.

Example 13 (Vulcanised Elastomeric Materials for Internal Applications)

[0359] The vulcanisable elastomeric materials (ME), (MF), (MC2), (MG), (MH), (MI), (MJ) and (MK) prepared in Example 9 and vulcanised at 170 C. for 10 minutes were subjected to measurement of the static and dynamic mechanical properties according to the methods described above. The following table 8 shows the values measured for the seven samples:

TABLE-US-00009 TABLE 8 Example 13 V-MC2 V-MG V-MH V-MI V-MJ V-MK Ref. Inv. Inv. Inv. Inv. Inv. V-MF Silica + Silica + Silica + Silica + Silica + Silica + V-ME Ref. mod. mod. mod. mod. mod. mod. Ref. Silica + sepiolite sepiolite sepiolite sepiolite sepiolite sepiolite Filler Silica Sep. Ex. 2b Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 % extracted Mg 97% 35% 35% 26% 20% 28% Ca0.5 [MPa] 2.34 2.48 2.00 2.51 2.47 2.28 2.60 2.60 Ca1 [MPa] 4.90 5.47 4.04 5.44 5.42 4.96 5.64 5.75 CR [MPa] 11.6 14.70 11.9 12.27 12.58 13.69 12.10 14.24 AR [%] 198.4 242.87 266.1 199.70 191.99 228.64 215.32 182.94 IRHD 23 C. 72.7 72.9 72.5 72.4 73.2 72.3 75.5 75.6 IRHD 100 C. 70.9 71.6 71.4 71.7 72.1 70.5 74.3 74.6 E [MPa] 23 C. 8.41 8.65 7.97 8.55 8.65 8.36 9.49 9.16 100 Hz E [MPa] 70 C. 100 Hz 8.44 8.60 8.02 8.65 8.66 8.46 9.56 9.15 Tan Delta 23 C. 100 Hz 0.094 0.101 0.097 0.075 0.074 0.093 0.082 0.084 Tan Delta 70 C. 100 Hz 0.066 0.070 0.066 0.052 0.050 0.065 0.056 0.058 G 70 C. (9%) Mpa 1.69 1.59 1.63 1.64 1.64 1.57 1.74 1.75 Tan Delta 70 C. 0.101 0.112 0.095 0.095 0.092 0.097 0.102 0.098 (9%) d_G(0.5-10) Mpa 1.0 1.1 0.8 0.9 0.9 0.9 1.0 0.9 Goodrich Final internal temp. 127.3 135.0 131.1 115.4 119.0 124.0 126.0 126.5 C. Permanent strain 2.3 2.9 2.3 1.4 1.9 1.9 2.0 2.0 Mod. sep.: modified sepiolite

[0360] The analysis of the data in Table 8 shows that by replacing an aliquot of silica in a conventional elastomeric material (V-ME) with 70% by weight of unmodified sepiolite F-SE, an elastomeric material (V-MF) is obtained, with higher static reinforcement and improved strength, but hysteresismeasured as tan delta at 70 C., both in compression and shearthe Payne effectmeasured as the difference of elastic shear modulus at 70 C. between 0.5% and 10% of dynamic strainand heat generationmeasured by the Goodrich testincrease, in addition to the permanent strain measured at the end of the Goodrich test.

[0361] By using sepiolite fibres modified by drastic acid treatment F2b (comparative V-MC2, prepared in Example 2b, with 97% magnesium extraction, loss of the crystalline structure and preservation of the needle-shaped morphology), a worsening of the static mechanical properties measured by parameters Ca0.5, Ca1 and CR and of the dynamic ones measured by parameter E is observed, both with respect to both reference elastomeric materials V-ME and V-MF and with respect to all samples of elastomeric materials according to the invention. Such a worsening is an indication of a deteriorated reinforcement capacity of these fibres modified by drastic acid treatment.

[0362] Moreover, the Goodrich test shows a final internal temperature higher than both that of the sample containing silica (V-ME) and of all samples according to the invention (Ex. 3 to 7), indicating that, disadvantageously, the material V-MC2 in use develops more heat.

[0363] Finally, the permanent strain of sample V-MC2 is higher compared to the samples according to the invention.

[0364] Conversely, by incorporating in the elastomeric material, in replacement of an aliquot of silica, the sepiolite fibres modified according to the present controlled acid treatment, with 35% of magnesium removal, in the absence (F3 in V-MG) or in the presence of sulphur silanising agents (F4 in V-MH), substantially the same static and dynamic reinforcement capacity of the unmodified sepiolite is preserved, the thermoplasticity measured as delta hardness is further enhanced but above all, the dissipative properties, measured as Tan Delta both in the compressive and in the shear test improve drastically.

[0365] Surprisingly, the tan delta at 70 C. is lower than 25% in the compression test in the case of samples according to the invention V-MG and V-MH, due to the improved hysteresis imparted by the modified sepiolite fibres F3 and F4. This result is even more significant if we consider that the composition was modified by less than 6% by weight. To further investigate the dissipative behaviour of the materials, flexometry measures were conducted according to Goodrich. This characterisation technique is particularly significant to evaluate compounds with different hysteresis properties. The test is conducted according to ASTM D 623-07 under conditions similar to the dynamic compression tests, but prolonging the test for 30 minutes, imposing a fixed preload and dynamic strain, with the further possibility of measuring the temperature of the samples at the end of the test. This gives an indication of the heat dissipated by the test material during the compression strain, which is directly related to the hysteretic behaviour and its modulus: the higher the modulus and hysteresis, the higher the final temperature.

[0366] Table 8 shows the final temperature values: it can be seen that the reference samples with sepiolite V-MF and V-MC2 are heated about 8 C. and 4 C., respectively, more than the reference sample V-ME, while sample V-MH according to the invention is heated 8 C. less than the reference V-ME and therefore 16 C. and 12 C., respectively, less than the corresponding V-MF and V-MC2 with the same dynamic module. In the case of V-MG, the temperature difference is even 20 C. compared to V-MF and 16 C. compared to V-MC2.

[0367] In the samples according to the invention, there is also a significant improvement of the permanent strain measured at the end of the Goodrich test, compared to all reference samples.

[0368] The sample (V-MJ) comprising fibres in which the removal of magnesium, with a rapid procedure in water, was 20% (F6), showed excellent static and dynamic reinforcement properties, even higher than those of the sample with unmodified sepiolite, keeping a reduced hysteresis both compared to the elastomeric material V-MF and compared to the elastomeric material with silica V-ME. Also the behaviour at the Goodrich tests confirms a better dynamic behaviour, leading to a lower final temperature than the references, despite the very high level of reinforcement. Considerations similar to those for sample V-MJ can be made for sample V-MK, comprising fibres in which the removal of magnesium, with a procedure in alcohol with a non-sulphur silanising agent, was 28%.

[0369] The sample containing fibres in which the removal of magnesium was 26% (F5 in V-MI), through a process in isopropanol-water, with little acid, in the presence of TESPT and long times, showed excellent strength, improved compared to the reference without sepiolite V-ME, keeping similar properties of static and dynamic reinforcement with reduced hysteresis and Payne effect, as shown also by the behaviour at the Goodrich test, which leads to a lower final temperature compared to the references, as well as to a lower permanent strain measured at the end of the Goodrich test.

[0370] Sample V-MJ and V-MI were observed at 100000 magnification microscope (STEM Scanning Transmission Electron Microscopy-characterizationon thin sections (50 nm) subjected to cold ultramicrotomy 120 C.). As can be seen in the images in FIGS. 9 and 10, the modified sepiolite fibres incorporated into the elastomeric matrix are clearly visible and it is clear that they have an aspect ratio well above three.

Example 14 (Elastomeric Materials for Tread Applications)

[0371] The vulcanisable elastomeric materials (ML), (MM) and (MN) prepared in Example 10 and vulcanised at 170 C. for 10 minutes were subjected to measurement of the static and dynamic mechanical properties according to the methods described above.

[0372] The following table 9 shows the values measured for the three samples:

TABLE-US-00010 TABLE 9 V-MM V-MN V-ML Reference Invention Example 14 Reference Silica + Silica + mod. Filler Silica sepiolite sepiolite Ex. 4 % ext. Mg 35% CA 0.5 [MPa] 1.49 1.50 1.46 CA 1 [MPa] 2.46 2.69 2.62 CA 3 [MPa] 9.88 9.88 10.64 CR [MPa] 14.68 15.24 15.32 AR % 436.1 463.9 441.2 IRHD 77.6 74.9 72.7 IRHD 100 C. 70.8 69.5 68.2 delta IRHD 6.8 5.4 4.5 E [MPa] 0 C. 100 Hz 15.11 14.39 13.95 E [MPa] 23 C. 100 Hz 10.57 9.88 9.72 E [MPa] 100 Hz 7.70 7.30 7.17 Tan Delta 0 C. 100 Hz 0.501 0.519 0.504 Tan Delta 100 Hz 0.296 0.298 0.281 Tan Delta 100 Hz 0.152 0.145 0.141 d_G(0.5-10) MPa 2.7 2.2 1.9

[0373] The analysis of the data in Table 9 shows that by incorporating sepiolite fibres modified according to the present controlled acid treatment (V-MN) in the elastomeric material, in even smaller amounts than the silica removed (10 phr silica were replaced with 9.79 phr of fibres modified as per Example 9, equal to 7 phr of inorganic residue at 800 C.), a reinforcement capacity is observed that is comparable to or even greater than that of unmodified silica and sepiolite and good strength properties. With the elastomeric material of the invention (V-MN), there is also a better thermoplasticity (delta IRHD), but above all, the dissipative properties, measured as Tan Delta at 70 C. improve drastically. Also the Payne effect is strongly improved.

Example 15 (Standard Elastomeric Materials 2)

[0374] The reference elastomeric materials (MO) comprising unmodified sepiolite fibres F-SE and according to the invention (MP) comprising sepiolite fibres F5 from which 26% magnesium was extracted, prepared in Example 11 and vulcanised at 170 C. for 10 minutes, were subjected to measurement of the dynamic mechanical properties using the methods described above.

[0375] The dynamic mechanical analysis RPA allowed evaluating the reinforcing effect imparted by the unmodified sepiolite fibres (sample V-MO) and modified according to the invention (sample V-MP) on the vulcanised materials as shown in FIG. 8. FIG. 8A shows how the change in module G upon varying the strain of the sample according to the invention V-MP is very low compared to that of the reference sample V-MO, indicating greater stability of the material with respect to the strain and therefore a reduced Payne effect.

[0376] FIG. 8B shows the hysteresis pattern for the two materials: as can be seen, the sample according to the invention has significantly lower and more constant tan delta values than those of the reference sample comprising unmodified sepiolite fibres. The data is particularly significant considering that no coupling agents was added in the mixing step to the sample according to the invention.

[0377] In conclusion, from the mechanical analysis conducted on the samples of elastomeric materials according to the invention and reference, it is clear that the presence of fibres modified according to the controlled acid treatment described herein clearly reduces the hysteresis of the elastomeric materials while maintaining a good reinforcement.

[0378] These mechanical properties make the elastomeric materials according to the invention particularly suitable for the production of tyres with a high reinforcement and simultaneously reduced rolling resistance.