Elastomeric materials for components of tyres and tyres comprising modified silicate fibres

Abstract

The present invention relates to new vulcanisable elastomeric compositions for components of tyres, comprising modified silicate fibres as fillers. The silicate fibres are modified according to the process with controlled pH of the invention. In addition, the invention regards components of tyres, comprising elastomeric materials obtainable by vulcanisation of said compositions, and tyres for vehicles comprising one or more of said components. The vulcanised elastomeric materials according to the invention are characterised by good static and dynamic mechanical properties, in particular by particularly low hysteresis. Advantageously the tyres of the invention comprising one or more of said components have a limited rolling resistance.

Claims

1. A process for modifying silicate fibres with needle-shaped morphology of nanometric size comprising: providing silicate fibres with needle-shaped morphology of nanometric size comprising magnesium, suspending the silicate fibres in a suitable liquid medium to generate a suspension, adding, to the suspension, at least one acid compound, and bringing the medium to a pH ranging from 2 to 4, maintaining the medium at the pH range from 2 to 4, by further adding the at least one acid compound, to extract from 10% to 70% by weight of magnesium from the silicate fibres to generate modified silicate fibres, wherein the modified silicate fibres are substantially preserved with a crystalline structure and needle-shaped morphology, and separating the modified silicate fibres from the liquid medium, wherein the modified silicate fibres with needle-shaped morphology of nanometric size comprise 9.5% to 12% of magnesium.

2. The process as claimed in claim 1, wherein the silicate fibres are sepiolite fibres.

3. The process as claimed in claim 1, wherein the liquid medium is chosen from water, alcohols, ethers, ketones, and mixtures thereof.

4. The process as claimed in claim 1, further comprising maintaining the medium at a pH range from 2.5 to 3.5.

5. The process as claimed in claim 1, wherein adding the at least one acid compound to the medium results in a concentration of the at least one acid compound not higher than 0.01N.

6. The process as claimed in claim 1, further comprising adding a silanising agent to the suspension.

7. The process as claimed in claim 6, wherein the silanising agent is chosen from bis-(triethoxysilylpropyl)disulphide (TESPD), bis[3-(triethoxysilyl)propyl]tetrasulphide (TESPT), 3-thio-octanoyl-1-propyltriethoxysilane (NXT), Me.sub.2Si(OEt).sub.2, Me.sub.2PhSiCl, and Ph.sub.2SiCl.sub.2.

8. The process as claimed in claim 1, wherein extracting continues to not more than 65%, by weight of magnesium from the silicate fibres.

9. The process as claimed in claim 4, further comprising maintaining the medium at a pH range from 2.8 to 3.2.

10. The process as claimed in claim 5, wherein adding the at least one acid compound to the medium results in a concentration of the at least one acid compound not higher than 0.005N.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a tyre for vehicle wheels in radial half-section.

(2) FIG. 2 reports an image at the FESEM microscope (Field Emission Scanning Electron Microscopy, 100000 power magnification) of modified sepiolite fibres with needle-shaped morphology F5 of the comparative example 5.

(3) FIG. 3 shows the images at the FESEM microscope (at 100000 power magnification) of sepiolite fibres with needle-shaped morphology modified under controlled conditions according to the known process F1 (Comparative example 1, FIG. 3A) and of sepiolite fibres F2a modified via drastic acid treatment in which the needle-shaped morphology has been lost (Comparative example 2a, FIG. 3B).

(4) FIG. 4 (A and B) reports the images at the microscope (FESEM at 50000 power magnification) of modified fibres F3 and F6 according to the comparative examples 3 and 6, respectively (magnesium extracted: −35% and −20%).

(5) FIG. 5 reports the images at the microscope (FESEM at 30000 power magnification) of modified fibres F8 and F9 according to the process of Examples 8 and 9 of the invention.

(6) FIG. 6 reports the diffractograms XRD of a sample of natural non-modified sepiolite F-SE (comparative) and of a sample of sepiolite F5 modified by means of mild acid treatment as in the comparative example 5.

(7) FIG. 7 reports the diffractograms XRD in the interval of 2theta from 4° to 14°, of samples of sepiolite fibres F1 modified as in the comparative example 1, of comparative samples F2a, modified as in the comparative example 2a, and of non-modified sepiolite fibres F-SE.

(8) FIG. 8 reports the diffractograms XRD of samples of sepiolite F8 and F9 modified by means of progressive acid treatment with controlled pH according to the examples of the invention 8 and 9.

(9) FIG. 9A shows the traces ATR-IR of a sample of modified sepiolite fibres F5 with needle-shaped morphology of the comparative example 5 and of a sample of original non-modified sepiolite fibres F-SE.

(10) FIG. 9B shows a significant portion of the traces ATR-IR of samples of commercial silica (SIL), of non-modified sepiolite fibres (F-SE), of modified fibres of the comparative example 1 (F1) and of the comparative example 2a (F2a).

(11) FIG. 10A shows the traces ATR-IR of samples of modified sepiolite fibres F8 and F9 with needle-shaped morphology of the examples 8 and 9 according to the invention.

(12) FIG. 10B shows a significant portions of the traces ATR-IR reported in FIG. 10A relative to the samples of modified fibres F8 and F9 according to the examples 8 and 9 of the invention.

(13) FIG. 11 reports the diffractograms XRD of a sample of natural non-modified sepiolite F-SE (comparative) and of a sample of comparative sepiolite F2b (prepared in example 2b) modified by means of drastic acid treatment, in which the needle-shaped morphology is maintained but the crystalline structure is lost.

(14) FIG. 12 (A and B) reports the progression of the dynamic elastic modulus and of the tan delta with increasing deformations of samples of elastomeric materials comprising non-modified sepiolite fibres F-SE (V-MO) and sepiolite fibres F5 modified as in the comparative example 5 (V-MP).

(15) FIG. 13 is the STEM image (Scanning Transmission Electron Microscopy) of a thin section of a vulcanised elastomeric composition (V-MJ Example 15) comprising the modified sepiolite fibres F6 according to the comparative example 6.

(16) FIG. 14 is the STEM image of a thin section of a vulcanised elastomeric composition (V-MI Example 15), comprising the modified sepiolite fibres F5 according to the comparative example 5.

(17) FIG. 15 reports the progression of the pH of the medium with the progression of the reaction during the gradual addition of the acid (ml of acid, indicated here as ml H÷) according to the process of the present invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(18) The description of several embodiments of the invention, provided only as a non-limiting example, is set forth hereinbelow.

(19) FIG. 1 illustrates a tyre for vehicle wheels in radial half-section.

(20) In FIG. 1, “a” indicates an axial direction and “X” indicates a radial direction, in particular X-X indicates the trace of the equatorial plane. For the sake of simplicity, FIG. 1 only shows a portion of the tyre, the remaining not represented portion being identical and symmetrically arranged with respect to the equatorial plane “X-X”.

(21) The tyre 100 for four-wheel vehicles comprises at least one carcass structure, comprising at least one carcass layer 101 having respectively opposite end flaps engaged with respective anchoring annular structures 102, termed bead cores, possibly associated with a bead filler 104.

(22) The carcass layer 101 is possibly made with an elastomeric composition.

(23) The zone of the tyre comprising the bead core 102 and the filler 104 forms a bead structure 103 intended for the anchoring of the tyre on a corresponding mounting rim, not illustrated.

(24) The carcass structure is usually of radial type, i.e. the reinforcement elements of the at least one carcass layer 101 are situated on planes comprising the rotation axis of the tyre and substantially perpendicular to the equatorial plane of the tyre. Said reinforcement elements are generally constituted by textile cords, for example rayon, nylon, polyester (e.g. polyethylene naphthalate (PEN)). Each bead structure is associated with the carcass structure by means of folding back the opposite lateral edges of the at least one carcass layer 101 around the anchoring annular structure 102 so as to form the so-called turning up of the carcass 101a as illustrated in FIG. 1.

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

(26) A bead protection layer 105 possibly made with elastomeric composition is arranged in an external position of each bead structure 103.

(27) The carcass structure is associated with a belt structure 106 comprising one or more belt layers 106a, 106b situated radially superimposed with respect to each other and with respect to the carcass layer, having reinforcement cords that are typically textile and/or metallic incorporated within a layer of vulcanised elastomeric material.

(28) Such reinforcement cords can have cross orientation with respect to a circumferential extension direction of the tyre 100. By “circumferential” direction it is intended a direction generically directed according to the rotation direction of the tyre.

(29) In radially more external position with respect to the belt layers 106a,106b, at least one zero degree reinforcement layer 106c can be applied, commonly known as “0° belt”, 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 (e.g. an angle between about 0° and 6°) with respect to a direction parallel to the equatorial plane of the tyre, and coated with vulcanised elastomeric material.

(30) In radially external position with respect to the belt structure 106, a tread band 109 made of vulcanised elastomeric material is applied.

(31) Respective sidewalls 108 made of vulcanised elastomeric material are also applied in axially external position on the lateral surfaces of the carcass structure, each extended from one of the lateral edges of the tread 109 up to the respective bead structure 103.

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

(33) An under-layer 111 of vulcanised elastomeric material can be arranged between the belt structure 106 and the tread band 109.

(34) A strip constituted by elastomeric composition 110, commonly known as “mini-sidewall”, made of vulcanised elastomeric material may possibly be present in the zone of connection between the sidewalls 108 and the tread band 109, this mini-sidewall generally being obtained by means of co-extrusion with the tread band 109 and allowing an improvement of the mechanical interaction between the tread band 109 and the sidewalls 108. Preferably, the end portion of the sidewall 108 directly covers the lateral edge of the tread band 109.

(35) In the case of tyres without air chamber, a rubber layer 112, generally known as “liner”, which provides the necessary impermeability to the tyre inflation air, can also be provided in a radially internal position with respect to the carcass layer 101.

(36) The rigidity of the tyre sidewall 108 can be improved by equipping the bead structure 103 with a reinforcement layer 120 generally known as “flipper” or additional strip-like insert.

(37) The flipper 120 is a reinforcement layer that is wound around the respective bead core 102 and around 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.

(38) The flipper 120 typically comprises a plurality of textile cords incorporated within a layer of vulcanised elastomeric material.

(39) The bead structure 103 of a tyre can comprise a further protection layer which is generally known with the term “chafer” 121 or protection strip and which has the function of increasing rigidity and integrity of the bead structure 103.

(40) The 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 (e.g. aramide or rayon) or of metallic materials (e.g. steel cords).

(41) 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 can have a variable thickness in axial direction. For example, the layer can have a greater thickness close to its axially external edges with respect to the central (crown) zone.

(42) Advantageously the layer or sheet can be extended on a surface substantially corresponding to the extension surface of said belt structure.

(43) In a preferred embodiment, a layer or sheet made of elastomeric material as described above can be placed between said belt structure and said tread band, said supplementary layer or sheet preferably being extended on a surface substantially corresponding to the extension surface of said belt structure. The elastomeric composition according to the present invention can be advantageously incorporated in one or more of the components of the tyre selected from among belt structure, carcass structure, tread band, under-layer, sidewall, mini-sidewall, sidewall insert, bead, flipper, chafer, sheet and bead protection layer.

(44) 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% of magnesium,
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, to the suspension, at least one acid compound bringing the pH of the medium to between 2 and 4, allowing the reaction, maintaining the pH of the medium to between 2 and 4, by further addition of acid, 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 separating the fibres thus modified from the liquid medium; (c) from 0 to 120 phr of a standard reinforcement filler; (e) from 0.1 to 15 phr of a vulcanisation agent, and (d) from 0 to 20 phr of a coupling agent.

(45) According to a non-illustrated embodiment, the tyre can be a tyre for motorcycle wheels, which is typically a tyre that has a straight section marked by a high transverse curvature.

(46) According to a non-illustrated embodiment, the tyre can be a tyre for heavy transport vehicle wheels, such as trucks, buses, trailers, vans and generally for vehicles in which the tyre is subjected to a high load.

(47) Preferably, one such tyre is adapted to be mounted on rims having diameter equal to or greater than 17.5 inches for directional or trailer wheels.

(48) In order to better illustrate the present invention, the following examples are now provided.

Methods for the Analytical Characterisation of the Fibres

(49) The original fibres, the fibres modified in drastic acidic conditions (Comparative examples 2a and 2b, comparative fibres) and the fibre, silanised and otherwise, modified in controlled acidic conditions (Comparative examples 3-7 and examples 8 and 9 of the invention), then incorporated in the elastomeric comparative materials and according to the invention, have been characterised with one or more of the following analytical techniques:

(50) Metering of the Magnesium Present in the Fibres by X-Ray Fluorescence Spectrophotometry (XRF Spectroscopy):

(51) the spectrophotometer Bruker AXS S4 Pioneer XRF was used, operating at ambient temperature. The samples were analysed by placing the powder in a sample holder having a window exposed to the incident radiation with 34 mm diameter, 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 the data with the software S4 tools using the formula Si.sub.6H.sub.14O.sub.23 as matrix for the calculation. For greater correctness, the determination of the magnesium was carried out on the only component that was not decomposed when subjected in the TGA to oxidative treatment up to 800° C., as better explained in the comparative example 5. Finally, the percentage of extraction of the magnesium was calculated based on the quantity of magnesium present in the starting fibres, measured with the same method, as illustrated in the comparative example 5.

(52) Metering of the Mg in the Acidic Reaction Medium by Complexometry

(53) The magnesium extracted in the reaction medium can be measured by using, as in the 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.

(54) In a typical procedure, 500 μl of 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% methanolic solution are added to the buffered solution. The solution is heated at 40-50° C. and titred with 0.01 M disodium EDTA up to colour change of the solution. From the titre of magnesium in the buffered solution, the total extracted magnesium is calculated, considering the quantity of supernatant drawn and the total volume of liquids in the reaction mixture.

(55) The percentage of extracted Mg is then calculated based on the initial weight of fibres containing magnesium that are made to react, and on the initial percentage of Mg in such fibres, calculated from the molecular formula of magnesium silicate.

(56) Field Emission Scanning Electron Microscopy FESEM:

(57) the observations on the powders of the samples of the comparative example 5 (FIG. 2) and of the examples according to the invention 8 and 9 (FIG. 5) were made with a microscope Vega TS5136 XM Tescan in high vacuum configuration. The excitation of the electron ray was 30 kV with a current of 25 pA. Before the SEM analysis, the samples were attached to a metallic target with adhesive strip and subjected to sputtering with gold in order to improve the conductivity of the electrons through the material.

(58) In the case of the comparative examples 1 and 2 (FIG. 3) and of the comparative examples 3 and 6 (FIG. 4), the samples were observed with a microscope FESEM Ultra Plus Zeiss, Gemini column, in InLens mode, excitation of the electron ray from 3.0 to 5.0 KV, work distance from 2.7 to 4.3 mm.

(59) The samples were thus prepared: 0.005 g of fibres were dispersed in 50 ml of solution constituted by a mixture of water and ethanol in 8:2 ratio, admixed with 200 ppm of Nonidet P40 (surfactant purchased from Sigma-Aldrich) for treatment with ultrasound in immersion for 15 minutes. The fibres were separated by centrifugation at 1000 g/m for 20 minutes and dried in an oven at 100° for 3 hours.

(60) Characterisation STEM of the Vulcanised Elastomeric Materials:

(61) the observation was conducted on ultramicrotome thin sections (50 nm) under cold conditions (−120° C.) with a microscope FESEM Ultra Plus Zeiss, Gemini column, in InLens mode, excitation of the electron ray of 30 KV, work distance 2 mm.

(62) X-Ray Diffraction (XRPD):

(63) The diffractograms XRD have been recorded with a diffractometer Bruker D8 Avance (Cu K-alpha radiation) in the interval 20 up to 260 with A (20)=0.02 and 4s of interval between each acquisition.

(64) Thermogravimetric Analysis (TGA):

(65) the determination of the profile of the weight loss was carried out with the device Mettler Toledo TGA/DSCl Star-e System, in a temperature interval from 150 to 800° C.

(66) The measurements were made by using a temperature program which provides for 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 dry air flow).

(67) Attenuated Total Reflectance Infrared Spectroscopy ATR-IR:

(68) the measurements were carried out with the instrument Perkin Elmer Spectrum 100 (1 cm.sup.−1 resolution, interval from 650-4000 cm.sup.−1, 16 scans).

(69) 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 interval 850-1040 cm.sup.−1—in two resolved signals or even in a single band—with respect to commercial silica, which instead shows very intense signals in the interval 1040-1300 cm.sup.−1.

Preparation of the Fibres

Comparative Example 1

(70) Preparation of Modified Sepiolite Fibres with Needle-Shaped Morphology F1 (Aqueous Environment, Partial Extraction of Magnesium) Modified sepiolite fibres were prepared by using the following materials: sepiolite Pangel S9 (5 g) 3M aqueous HCl (50 ml)
Procedure

(71) In a 250 ml glass flask, the sepiolite (5 g) is suspended in 50 ml of acid solution and it is heated in an oil bath at 60° C. for 10 minutes under stirring.

(72) Then, the suspension is filtered over Buchner. The solid is washed with abundant deionised water (about 1.5-2 l) until the washing water lacks chloride ions (test of AgNO3). The complexometric analysis showed the presence in the filtration mother liquors of 31% of magnesium theoretically present in the starting silicate.

(73) The recovered solid was finally dried in an oven at 70° C. for 120 hours. From the XRF analysis on the modified fibres, there was an extraction of magnesium equal to 33%, in good accordance with the complexometric data.

(74) As is inferred from the microscopic examination reported in FIG. 3A, the morphology of the fibres was substantially maintained. In addition, the diffractogram of FIG. 7 and the spectrum IR of FIG. 9B confirmed the substantial preservation of the crystalline structure of the sample.

(75) In particular, in order to evaluate the preservation of the crystillinity, in the spectrum IR, the areas under the four curves were measured, in the intervals between 850 and 1040 cm.sup.−1 (zone of the typical signals of the crystalline structure) and between 1040 and 1300 cm.sup.−1 (zone of the typical signals of the amorphous structure) with the following results:

(76) TABLE-US-00001 Material SIL F-SE F1 F2a F8 F9 Area 1 (850-1040 cm.sup.−1) 2.7 11.6 7.6 4.7 11.4 10.7 Area 2 (1040-1300 cm.sup.−1) 11.7 2.9 4.6 11.0 10.8 9.4 Ratio Area 1/Area 2 0.23 4 1.65 0.43 1.06 1.15

(77) As can be seen from the ratios between the above-calculated areas, the sepiolite fibres of the comparative example 1 showed a substantial preservation of the crystalline structure (ratio>0.8) while the modified sepiolite fibres of the following comparative example 2a substantially had lost the crystillinity (ratio<0.8). The same evaluation conducted on the fibres F8 and F9, prepared according to the process of the invention described hereinbelow in the examples 8 and 9, confirms the maintenance of the crystalline structure.

Comparative Example 2a

(78) Preparation of Modified Sepiolite Fibres F2a (Aqueous Environment, Total Extraction of Magnesium)

(79) This example substantially reproduces the processes described in the literature for generating amorphous silica by means of exhaustive acid treatment of the sepiolite fibres.

(80) In particular, the procedure of the comparative example 1 is repeated, however continuing the reaction for a total of 70 minutes in the same conditions.

(81) At the end of the process, the extraction of magnesium was high (95% according to the XRF method) and the morphology of the fibres no longer needle-shaped, as is visible in the image FE-SEM of FIG. 3B. In addition the crystalline structure was substantially lost, as shown by the diffractogram reported in FIG. 7 and by the IR spectrum in FIG. 9B. The amorphous silica thus obtained was subsequently incorporated in elastomeric materials and used as comparison term.

(82) As is inferred from the diffractogram XRD of FIG. 7, the peak at 6°—8°—diagnostic of the crystalline order—was completely lost in the sample of the comparative example 2a, while it appeared widely preserved in the sample of the comparative example 1.

Comparative Example 2b

(83) Preparation of Modified Sepiolite Fibres F2b (Aqueous Environment, Total Extraction of the Magnesium Ions)

(84) This example substantially reproduces the processes described in the literature for generating amorphous silica by means of exhaustive acid treatment of the sepiolite fibres.

(85) In particular, the procedure reported in the publication ‘Preparation of Silica by Acid Dissolution of Sepiolite and Study of its Reinforcing Effect in Elastomers’ was repeated in the same conditions (60° C., 5N HNO.sub.3).

(86) At the end of the process, the extraction of the magnesium ions was high (97% according to XRF method) but the morphology of the fibres is substantially needle-shaped. However the crystalline structure was substantially lost, as shown by the diffractogram reported in FIG. 11. The needle-shaped amorphous silica thus obtained was subsequently incorporated in elastomeric materials and used as comparison term.

(87) As is inferred from the diffractogram XRD of FIG. 11, the peak at 6°-8°, diagnostic of the crystalline order (peak F-SE), is completely lost in the sample of the example 2b.

Comparative Example 3

(88) Preparation of Modified Sepiolite Fibres F3 (Alcoholic Environment, Partial Extraction of Magnesium)

(89) Modified sepiolite fibres were prepared by using the following materials:

(90) TABLE-US-00002 sepiolite Pangel S9 (120 g) Isopropanol (1.2 l) aqueous HCl, 37% by weight (480 ml) Deionised water (3 l) aqueous NH.sub.3, 29% by weight
Procedure

(91) 120 g of sepiolite Pangel S9 was loaded in a two-neck 3-litre flask, equipped with mechanical stirrer and reflux and immersed in an oil bath at 80° C. 1.21 of isopropanol pre-heated at 65° C. were added and the mixture was stirred for 15 minutes at 600 rpm. 480 ml of aqueous HCl at 37% by weight were added. The mixture was held under stirring for 120 minutes at 65° C. and then filtered over Buchner. The solid was suspended in 2 l of deionised water. Then, an aqueous solution of NH.sub.3 at 29% by weight was added until pH 7.0±0.2 was reached. The solid was collected on Buchner and washed with 11 of deionised water and then it was dried in an oven 120° C. for 72 h.

(92) From the XRF analysis of a product sample, 35% by weight of magnesium resulted extracted.

(93) Upon microscopic observation (FIG. 4A), the sample maintained the morphology of the sepiolite fibres. The IR analysis showed predominant signals between 850 and 1040 cm.sup.−1 in the characteristic region of the non-modified sepiolite fibres and not between 1040 and 1300 cm.sup.−1, zone of the typical signals of amorphous silica, indication of the substantial maintenance of the crystalline structure.

Comparative Example 4

(94) Preparation of Modified Sepiolite Fibres F4 (Alcoholic Environment, Presence of Silanising Agents, Partial Extraction of Magnesium)

(95) Modified sepiolite fibres were prepared by using the following materials:

(96) TABLE-US-00003 sepiolite Pangel S9 (120 g) bis[3-(triethoxysilyl)propyl]tetrasulphide TESPT (64.7 g) Isopropanol (1.2 l) aqueous HCl, 37% by weight (480 ml) Deionised water (3 l) aqueous NH.sub.3, 29% by weight

(97) Procedure 120 g of sepiolite Pangel 39 were loaded in a two-neck 3-litre flask, equipped with a mechanical stirrer and reflex and immersed in an oil bath at 80° C. 1.2 l of isopropanol pre-heated at 65° C. were loaded and the mixture was stirred for 15 minutes at 600 rpm. 64.7 g of TESPT were added, and subsequently 480 ml of aqueous HCl at 37% by weight were added. The mixture was held under stirring for 120 minutes at 65° C. and then filtered over Buchner. The solid was suspended in 2 l of deionised water. Then a solution of NH.sub.3 at 29% by weight was added until pH 7.0±0.2 was reached. The solid was collected on Buchner, washed 1 l of deionised water and dried in oven at 120° C. for 72 h. From the XRF analysis of a product sample, 35% by weight of magnesium resulted extracted. The complexometric analysis indicated the presence, in the filtration mother liquors, of 32% of magnesium theoretically present in the starting silicate. The result is in good accordance with the XRF data.

(98) Upon microscopic observation, the sample maintained the morphology of the sepiolite fibres. The IR analysis showed predominant signals between 850 and 1040 cm.sup.−1 in the characteristic region of the non-modified sepiolite fibres, indication of the substantial maintenance of the crystalline structure, and not between 1040 and 1300 cm.sup.−1, zone of the typical signals of amorphous silica.

Comparative Example 5

(99) Preparation of Modified Sepiolite Fibres F5 (Alcoholic Environment, Presence of Sulfur Silanising Agents, Partial Extraction of Magnesium)

(100) Modified sepiolite fibres were prepared by 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. aqueous NH.sub.3 at 29% by weight was employed for the final neutralisation of the modified fibres, and deionised water was employed for the washing.
Procedure

(101) In a reaction flask, 120 g of sepiolite were suspended in 1200 ml of isopropanol 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.

(102) It was left under energetic stirring (600 rpm) at 65° C., for 72 hours.

(103) The reaction mixture was filtered over Buchner and the solid was suspended in 2l of deionised water. Then, a solution of NH3 at 29% by weight was added until pH 7.0±0.2 was reached. The solid was collected over Buchner, washed with 1 l of deionised water and dried in oven at 120° C. for 48 h.

(104) The powder thus obtained (modified fibres) was characterised and compared with original sepiolite fibres by means of the following techniques and with the following results:

(105) FE-SEM Microscope Evaluation (FIG. 2):

(106) FIG. 2 shows the modified sepiolite fibres, needle-shaped and of nanometric size, of the comparative example 5. These fibres have an average diameter of 20±5 nm and a length of 460±400 nm, with an aspect ratio of approximately 23±10.

(107) XRD Analysis (FIG. 6)

(108) The XRD analysis on modified sepiolite according to the comparative example 5 (F5) and on original non-modified sepiolite (F-SE) shows that the treatment in controlled acidic conditions has not substantially modified the crystalline structure of the sepiolite. Indeed, the typical diffractogram of the original sepiolite (Pangel S9) is strictly comparable with that of the comparative sample of modified sepiolite, in particular the peak at 2 theta 7.5° is recognisable, characteristic of the sepiolite. Analogous considerations hold true for the samples according to the invention F8 and F9 (FIG. 8).

(109) Thermogravimetric Analysis TGA

(110) The loss of weight during the TGA (from 150 to 800° C.) was calculated to be equal to 6.5% by weight for the sample of original non-modified sepiolite (F-SE) and to 17.6% by weight for the sample of the silanised comparative example 5 treated in controlled acidic conditions (F5).

(111) Spectroscopic Analysis ATR-IR (FIGS. 9A and 9B)

(112) The samples of original non-modified sepiolite F-SE and of sepiolite F5 modified in controlled conditions of the comparative example 5 were subjected to IR analysis in order to evaluate the chemical modifications induced by the controlled acid treatment.

(113) As can be seen in FIG. 9A, the two traces are generally very similar: appearing in both are the signals due to the stretching of the bonds of the groups OH bonded to the magnesium (3500-3700 cm.sup.−1) and to the silicon (3760-3730 cm.sup.−1) and the double peak of the stretching of the bond Si—O (stretching SiOSi and SiOMg) at about 1000 cm.sup.−1—typical of the magnesium silicates such as sepiolite and like the modified sepiolite fibres according to the present process.

(114) FIG. 9B instead shows a detail of the IR spectra of commercial silica (SIL), of the non-modified sepiolite (F-SE), of the modified sepiolite with partial extraction of the magnesium of the comparative example 1 (F1) and with total extraction of the comparative example 2a (F2a).

(115) As can be observed, the sample of the comparative example 1, like the non-modified sepiolite, shows a strong absorption between 850 and 1040 cm.sup.−1, while the commercial silica and the sample F2a, from which about 95% of Mg was extracted, give rise to more intense peaks between 1040 and 1300 cm.sup.−1. The same IR analysis (FIG. 10) conducted on samples according to the invention F8 and F9 showed, in the interval between 850 and 1040 cm−1, predominant signals with respect to those between 1040 and 1300 cm−1, indication of the substantial maintenance of the crystalline structure.

(116) Determination of the Magnesium by Complexometry

(117) The quantity of magnesium extracted from the fibres was carried out by means of complexometric titration on the filtration mother liquors: 500 μl of 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.4C.sub.1 in 60 ml of distilled water and 35 ml of aqueous solution of NH.sub.3 at 29% by weight.

(118) Two drops of eriochrome black T in 1% methanolic solution are added to the buffered solution. After having heated the solution at 40-50° C., titration with 0.01 M disodium EDTA up to colour change of the solution. From the titre of magnesium in the buffered solution, the extracted magnesium was calculated by considering the quantity of supernatant drawn (500 μl) and the total volume of liquids in the reaction mixture (1296 ml)

(119) The percentage of extracted Mg was then calculated based on the initial quantity of fibres containing magnesium that were made to react (120 g), and on the initial percentage of Mg in such fibres, calculated from the molecular formula of the magnesium silicate Mg.sub.4Si.sub.6O.sub.15(OH).sub.2(H.sub.2O).sub.6, i.e. of a percentage by initial weight of magnesium of 15%.

(120) The percentage of extracted Mg was equal to 25% of the initially present Mg.

(121) Determination of Magnesium by XRF Spectroscopy

(122) From XRF analysis, the quantity of magnesium in the fibres was determined, before (sample F-SE, Sepiolite as is) and after controlled acid treatment (comparative sample F5, sample treated as described above).

(123) The results of these analyses are shown in the following Table 1.

(124) TABLE-US-00004 TABLE 1 Mg % Mg % Recalculated on Mg % measured TGA residue extract sepiolite F—SE 13.1 14.0 — modified sepiolite F5 8.6 10.4 26

(125) For greater correctness, the quantity of magnesium was calculated on the samples after TGA, i.e. the only dry inorganic component thereof—respectively equal to 93.5% for the sepiolite sample F-SE and to 82.4% for the modified sepiolite F5—which was not decomposed by oxidative treatment at 800° C. As can be observed from the data in the table, the residual quantity of magnesium in the sample subjected to controlled acid treatment according to the comparative process (F5) is lower (10.4%) and equal to about 74% of the initial quantity. The acid treatment has therefore removed 26% of magnesium from the sepiolite fibres, preserving the original structure of the silicate, as demonstrated by the XRD spectrum of FIG. 6 and by the IR spectrum of FIG. 9A. The magnesium extraction data calculated according to this method on the powders is in optimal accordance with the complexometric data obtained on the filtration mother liquors.

Comparative Example 6

(126) Preparation of Modified Sepiolite Fibres F6 (Aqueous Environment, Partial Extraction of Magnesium)

(127) Modified sepiolite fibres were prepared by using the following materials:

(128) TABLE-US-00005 sepiolite Pangel S9 (120 g) 1M aqueous HCl (1.45 l) Deionised water (2 l) aqueous NH.sub.3, 29% by weight

(129) Procedure

(130) 120 g of sepiolite Pangel S9 were loaded in a two-neck 3-litre flask, equipped with a mechanical stirrer. 1.45 l of 1M HO were added and the mixture was stirred for 60 minutes at 600 rpm at 23° C. and then filtered over Buchner. The solid was suspended in 2 l of deionised water. A solution of NH.sub.3 at 29% by weight was then added until pH 7.0±0.2 is reached. The solid was collected over Buchner and washed with 1 l of deionised water and then it was dried in oven at 120° C. for 72 h.

(131) From the XRF analysis of a product sample, 20% by weight of magnesium resulted extracted.

(132) Upon microscopic observation (FIG. 4B) the sample maintained the needle-shaped morphology of the sepiolite fibres.

(133) The IR analysis in the region 850-1300 cm.sup.1 showed signals between 850 and 1040 cm.sup.1 that were predominant with respect to those between 1040 and 1300 cm.sup.−1, indication of the substantial maintenance of the crystalline structure.

Comparative Example 7

(134) Preparation of Modified Sepiolite Fibres F7 (Alcoholic Environment, Presence of Non-Sulfur Silanising Agents, Partial Extraction of Magnesium)

(135) Modified sepiolite fibres were prepared by using the following materials:

(136) TABLE-US-00006 sepiolite Pangel S9 (sepiolite) supplied by Tolsa Me.sub.2Si(EtO).sub.2 dimethyldiethoxysilane, isopropanol 37% aqueous hydrochloric acid solution of NH.sub.3 at 29% by weight for the final neutralisation of the modified fibres, and deionised water for the washing.

(137) Procedure

(138) In a reaction flask, 120 g of sepiolite were suspended in 1200 ml of isopropanol 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.

(139) The mixture was held under stirring for 120 minutes at 65° C. and then filtered over Buchner. The solid was suspended in 2l of deionised water. Then, a solution of NH.sub.3 at 29% by weight was added until pH 7.0±0.2 was reached. The solid was collected on Buchner, washed with 1 l of deionised water and dried in oven at 120° C. for 72 h.

(140) From the XRF analysis of a product sample, 28% by weight of magnesium resulted extracted.

(141) Upon microscopic observation, the sample maintained the morphology of the sepiolite fibres. The IR analysis in the region 850-1300 cm.sup.−1 showed signals between 850 and 1040 cm.sup.1 that were predominant with respect to those between 1040 and 1300 cm.sup.−1, indication of the substantial maintenance of the crystalline structure

Example 8 (Invention)

(142) Preparation of Sepiolite Fibres F8 with Needle-Shaped Morphology Modified by Acid Treatment with Controlled pH

(143) In a 3-litre reactor, 100 g of sepiolite Pangel S9 were suspended in 1500 ml of deionised water, at 70° C. under mechanical stirring (400 rpm). With an automatic meter driven by a pH-meter, 31 ml of aqueous 37% HCl were added over a period of 7 hours, at 70° C., maintaining the pH around 3.0±0.1. The suspension was then filtered, the solid filtered was then washed with deionised water up to pH 7 and dried in oven at 100° C. for 48 h.

(144) From the XRF analysis of a product sample, 33.3% by weight of magnesium resulted extracted. Upon microscopic observation (FIG. 5), the sample maintained the morphology of the sepiolite fibres. The IR analysis (FIG. 10), in the region 850-1300 cm.sup.−1 showed signals between 850 and 1040 cm.sup.−1 that were predominant with respect to those between 1040 and 1300 cm.sup.−1, indication of the substantial maintenance of the crystalline structure, data that is confirmed in the XRD analyses (FIG. 8) where the typical signals of the crystalline structure of the starting material are found.

(145) By comparing the results obtained with the example 8 according to the present process with those of the comparative examples 1, 2a and 2b, which are marked by the initial addition of all the acid and by a pH of the medium much lower than 2, it is observed that the present process given the same solvent and with comparable temperature—allows effectively removing the magnesium from the fibres in the desired quantity (−33%) without having to terminate the reaction in brief times (10 minutes) as shown in the Comparative example 1, which is not very practical industrially, and without risking an excessive depletion of magnesium even after 7 hours of reaction, which is instead verified only after 70 minutes (−95%) in the case of the comparative example 2a.

Example 9 (Invention)

(146) Preparation of Derivatised Sepiolite Fibres with Needle-Shaped Morphology F9 Modified by Acid Treatment with Controlled pH

(147) Microsample

(148) 6.81 g of derivatised sepiolite Pangel B5 (Tolsa, a sepiolite organically modified at the surface with a quaternary ammonium salt) was suspended in 135 ml of deionised water at 25° C. under magnetic stirring. 2.8 ml of 1M aqueous HCl was added over a period of 2 hours at 25° C., maintaining the pH at a value of 3.0±0.1. In FIG. 15, the acid volumes (ml HCl) added over time (t, seconds) are reported as well as the pH values measured in the reaction medium.

(149) Macroscale

(150) In a 3-litre reactor, 118 g of derivatised sepiolite Pangel B5 (Tolsa, a sepiolite organically modified at the surface with a quaternary ammonium salt) was suspended in 1500 ml of deionised water at 70° C. under mechanical stirring (400 rpm). 31 ml of aqueous 37% HCl were added over a period of 7 hours, at 70° C., maintaining the pH around 3.0±0.1.

(151) The suspension was then filtered, the filtered solid was washed with deionised water until pH 7 was reached and dried in oven at 100° C. for 48 h.

(152) From the XRF analysis of a product sample, 34.7% by weight of magnesium resulted extracted.

(153) Upon microscopic observation, the sample maintained the needle-shaped morphology of the sepiolite fibres (FIG. 5).

(154) The IR analysis (FIG. 10) between 850-1300 cm.sup.−1, showed signals in the interval between 850 and 1040 cm.sup.−1, that were predominant with respect to those between 1040 and 1300 cm.sup.−1, indication of the substantial maintenance of the crystalline structure. This data is confirmed in the XRD analyses, where the crystalline structure of the starting material is found (FIG. 8).

(155) Also in this example, where organically modified fibres are used as starting material, the same advantages reported for the process described in example 8 are confirmed. In particular, the process according to the invention has proven to be easily actuatable, even on industrial scale, with the use of normal steel apparatuses.

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

(157) TABLE-US-00007 TABLE 2 Preparation % Mg Elastomeric Preparation vulcanised Fillers/Fibres extracted material green material material Comp. silica SIL — Standard 1 Ex. 10 MA Ex. 14 V-MA Comp. silica SIL — Internal app. Ex. 11 ME1 Ex. 15 V-ME1 Comp. silica SIL — Internal app. Ex. 11 ME2 Ex. 15 V-ME2 Comp. silica SIL — Tread1 Ex. 12 ML1 Ex. 16 V-ML1 Comp. silica SIL — Tread2 Ex. 12 ML2 Ex. 16 V-ML2 Comp. sepiolite F-SE — Standard 1 Ex. 10 MB Ex. 14 V-MB Comp. sepiolite F-SE — Internal app. Ex. 11 MF1 Ex. 15 V-MF1 Comp. sepiolite F-SE — Internal app. Ex. 11 MF2 Ex. 15 V-MF2 Comp. sepiolite F-SE — Tread1 Ex. 12 MM Ex. 16 V-MM Comp. sepiolite F-SE — Standard 2 Ex. 13 MO Ex. 17 V-MO Comp. Ex. 1 F1 33% Standard 1 Ex. 10 MD Ex. 14 V-MD Comp. Ex. 2a F2a 95% Standard 1 Ex. 10 MC1 Ex. 14 V-MC1 Comp. Ex. 2b F2b 97% Standard 1 Ex. 11 MC2 Ex. 15 V-MC2 Comp. Ex. 3 F3 35% Internal app. Ex. 11 MG Ex. 15 V-MG Comp. Ex. 4 F4 35% Internal app. Ex. 11 MH Ex. 15 V-MH Comp. Ex. 4 F4 35% Tread1 Ex. 12 MN Ex. 16 V-MN Comp. Ex. 5 F5 26% Internal app. Ex. 11 MI Ex. 15 V-MI Comp. Ex. 5 F5 26% Standard 2 Ex. 13 MP Ex. 17 V-MP Comp. Ex. 6 F6 20% Internal app. Ex. 11 MJ Ex. 15 V-MJ Comp. Ex. 7 F7 28% Internal app. Ex. 11 MK Ex. 15 V-MK Inv. Ex. 8 F8 33% Internal app. Ex. 11 MQ Ex. 15 V-MQ Inv. Ex. 9 F9 35% Internal app. Ex. 11 MR Ex. 15 V-MR Inv. Ex. 8 F8 33% Tread2 Ex. 12 MS Ex. 16 V-MS Inv. Ex. 9 F9 35% Tread2 Ex. 12 MT Ex. 16 V-MT

Preparation of the Elastomeric Materials (M)

(158) The vulcanisable elastomeric materials of the following examples were prepared according to the modes described herein. The quantities of the various components are indicated in phr.

(159) All the components, except for the sulfur and the vulcanisation accelerator (TBBS), were mixed in an internal mixer (Brabender or Banbury) for about 5 minutes (1a step). As soon as the temperature has reached 145° C.±5° C., the elastomeric material was unloaded. The sulfur and the accelerator (TBBS) were added and the mixing was carried out in an open roller mixer (2a step).

Example 10

(160) Preparation of Standard (1) Vulcanisable Elastomeric Materials Comprising Modified Sepiolite Fibres

(161) The sepiolite fibres F1 modified as in the comparative 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 elastomeric comparative materials, comprising standard fillers, in particular only containing conventional silica (SIL in MA) or conventional silica together with non-modified sepiolite fibres (F-SE in MB) or conventional silica together with sepiolite fibres treated in more energetic acidic conditions (F2a in MC1) as in Comparative example 2a. In particular, in the materials (MB), (MC1) and (MD), 10 phr of conventional silica was substituted with 10 phr of non-modified sepiolite or sepiolite modified by drastic treatment or sepiolite modified by mild treatment, respectively.

(162) The elastomeric materials of this example comprise standard compositions (1) suitable for many different applications, such as elastomeric materials for under-layer (car and heavy vehicles), soft bead (heavy vehicles), sidewall insert (car), or sidewall and are similar to formulations for tread (heavy vehicles). Hence, the results showed 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.

(163) The following Table 3 reports the compositions in phr of the comparative vulcanisable elastomeric materials (MA), (MB), (MC1) and (MD):

(164) TABLE-US-00008 TABLE 3 Comparative example 10 MA MB MC1 MD Comp. Comp. Comp. Comp. Filler Silica Silica + Silica + Silica + sepiolite modified modified sepiolite sepiolite (Ex. 2a) (Ex. 1) % Mg extracted — — 95% 33% Zeosil 1115MK 45 35 35 35 sepiolite 0 10 0 0 modified sepiolite Ex. 2a 0 0 10 0 modified sepiolite Ex. 1 0 0 0 10 NR 100 100 100 100 Stearic acid 2 2 2 2 Silane TESPT 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 Sulfur 2.8 2.8 2.8 2.8
in which NR (natural rubber): 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-benzothiazylsulfenamide.

Example 11

(165) Preparation of Vulcanisable Elastomeric Materials for Internal Applications Comprising Modified Sepiolite Fibres

(166) The sepiolite fibres F2b, F3, F4, F5, F6 and F7, modified as in Comparative examples 2b, 3, 4, 5, 6 and 7, and the fibres F8, F9 as in examples of the invention 8 and 9, were incorporated together with carbon black and conventional silica in compositions for vulcanisable elastomeric materials for internal tyre components such as sidewall insert, bead or under-liner. These comparative materials (MC2), (MG), (MH), (MI), (MJ) and (MK), and (MQ) and (MR) of the invention, were compared with the same elastomeric materials comprising standard fillers (comparative), in particular containing only carbon black and conventional silica (ME1) or carbon black and conventional silica together with non-modified sepiolite fibres (MF1).

(167) The mixing was conducted in three steps by using an internal mixer with tangential rotors (Pomini PL 1.6): in the first step, the polymers, the fillers and the 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 the 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 sulfur were introduced and the mixing was conducted for about 2 minutes, up to reaching 95° C.±5° C., when the composition was unloaded.

(168) The following Table 4a reports the compositions in phr of the comparative vulcanisable elastomeric materials (ME1), (MF1), (MC2), (MG), (MH), (MI), (MJ) and (MK):

(169) TABLE-US-00009 TABLE 4a comparatives Example 11 ME1 MF1 MC2 MG MH MI MJ MK Comp. Comp. Comp. Comp. Comp. Comp. Comp. Comp. Filler Silica Silica + Silica + Silica + Silica + Silica + Silica + Silica + sepiolite mod. mod. mod. mod. mod. mod. sepiolite sepiolite sepiolite sepiolite sepiolite sepiolite (Ex. 2b) (Ex. 3) (Ex. 4) (Ex. 5) (Ex. 6) (Ex. 7) % Mg — — 97% 35% 35% 26% 20% 28% extracted CB N550 25 25 25 25 25 25 25 25 ZEOSIL 1115 30 20 20 20 20 20 20 20 MK sepiolite — 7 — — — — — — mod. sepiolite — — 7 — — — — — Ex. 2b mod. sepiolite — — — 8.29 — — — — Ex. 3 mod. sepiolite — — — — 9.79 — — — Ex. 4 mod. sepiolite — — — — — 8.55 — — Ex. 5 mod. sepiolite — — — — — — 8.55 — Ex. 6 mod. sepiolite — — — — — — — 8 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 acid 1 1 1 1 1 1 1 1 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 Sulfur 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3
in which BR(Nd): (high cis) neodymium polybutadiene rubber (Europrene 40 Versalis); IR: synthetic polyisoprene (SK13 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;

(170) TBSS: N-tert-butyl-2-benzothiazyl sulfenamide.

(171) In the comparative material (MF1), 7 parts sepiolite substituted 10 parts silica.

(172) In the comparative material (MC2), 7 parts modified sepiolite substituted 10 parts silica, as described in example 2b.

(173) In the case instead of the comparative materials (MG), (MH), (MI), (MJ) and (MK), the quantity of modified sepiolite to be added, always in substitution of 10 phr of silica, was calculated by considering the weight loss of the samples in the TGA, so as to add a quantity of modified fibres corresponding to 7 phr of dry inorganic component, with the objective of obtaining blends that had comparable hardness. The following Table 4b reports the compositions in phr of the vulcanisable elastomeric materials according to the invention (MQ) and (MR), with respect to the comparative materials (ME2) and (MF2):

(174) TABLE-US-00010 TABLE 4B Example 11 ME2 MF2 MQ MR Comp. Comp. Inv. Inv. Filler Silica Silica + Silica + Silica + Sepiolite mod. mod. sepiolite sepiolite (Ex. 8) (Ex. 9) % Mg extracted — — 33% 35% CB N550 25 25 25 25 ZEOSIL 1115 MK 30 20 20 20 Sepiolite — 7 — — mod. sepiolite Ex. 8 — — 7.5 — mod. sepiolite Ex. 9 — — — 8.5 BR (Nd) 60 60 60 60 IR 40 40 40 40 Silane TESPT 5 5 5 5 Stearic acid 1 1 1 1 ZnO 4 4 4 4 TMQ 1 1 1 1 6-PPD 1.5 1.5 1.5 1.5 TBBS 80 4 4 4 4 Sulfur 2.0 2.0 2.0 2.0

(175) The comparative compositions ME2 and MF2 differ from the compositions ME1 and MF1 reported in the preceding Table 4a due to the lower sulfur content.

(176) These compositions are technical blends of sidewall filler type. In the samples MF2, MQ and MR, 10 phr of silica was substituted with 7, 7.5 or 8.5 phr of sepiolite, of modified sepiolite as described in the examples 8 and 9 of the invention, respectively. The quantities used in the compositions (MQ) and (MR) of the modified materials according to the invention were calculated based on the TGA of the modified materials described in examples 8 and 9, as illustrated above for the compositions (MG), (MH), (MI), (MJ) and (MK).

Example 12

(177) Preparation of Vulcanisable Elastomeric Materials for Tread Applications Comprising Modified Sepiolite Fibres

(178) The sepiolite fibres F4 modified as in the comparative example 4 (controlled acid treatment in presence of silanising agents) and the fibres modified according to the process of the invention of examples 8 and 9 (F8 and F9) were incorporated together with conventional silica in compositions for vulcanisable elastomeric materials for tread (here named tread1). These materials (MN comparative, MS and MT according to the invention) were compared with elastomeric materials comprising standard fillers, in particular containing only conventional silica (SIL in ML1) or conventional silica together with non-modified sepiolite fibres (F-SE in MM).

(179) The mixing was conducted in three steps by using an internal mixer with tangential rotors (Pomini PL 1.6): in the first step, the polymers, the fillers, the silane, the stearic acid and the 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 the 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 sulfur were introduced and the mixing was conducted for about 2 minutes, up to reaching 95° C.±5° C., when the composition was unloaded.

(180) The following Table 5a reports the compositions in phr of the comparative vulcanisable elastomeric materials (ML1), (MM) and (MN):

(181) TABLE-US-00011 TABLE 5a comparatives Example 12 ML1 MM MN Comp. Comp. Comp. Filler Silica Silica + sepiolite Silica + modified sepiolite (Ex. 4) % Mg extracted — — 35% ZEOSIL 1165 MK 85 75 75 Sepiolite — 7 — mod. sepiolite Ex. 4 — — 9.79 (silane) BR (Nd) 27 27 27 S-SBR 100 100 100 SI 69 6.8 6.8 6 Stearic acid 2 2 2 TDAE olio 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 Sulfur 1 1 1
in which BR(Nd): (high cis) neodymium polybutadiene rubber (Europrene 40 Versalis); S-SBR styrene-butadiene rubber SLR 4630 (oil extended, contained in elastomer 73 phr) by 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-sulfenamide; TBZTD: tetrabenzyl thiuram disulphide.

(182) In the material (MM), 7 parts sepiolite substituted 10 parts silica.

(183) In the case instead of the material (MN), the quantity of modified sepiolite to be added, always in substitution of 10 phr of silica, was calculated by considering the weight loss of the samples in the TGA, loss corresponding to the organic portion, which in the ramp up to 800° C. was 28.5%, so as to add a quantity of modified fibres corresponding to 7 phr of dry inorganic component, with the objective of obtaining blends which had comparable hardness.

(184) The following Table 5b reports the compositions in phr of the vulcanisable elastomeric materials (named tread 2), comparative (ML2) and invention (MS) and (MT):

(185) TABLE-US-00012 TABLE 5b Example 12 ML2 MS MT Comp. Inv. Inv. Filler Silica Silica + modified Silica + modified sepiolite sepiolite (Ex. 8) (Ex. 9) % Mg extracted — 33% 35% ZEOSIL 1165 MK 85 55 55 mod. sepiolite Ex. 8 — 15 — mod. sepiolite Ex. 9 — — 17 BR (Nd) 27 27 27 S-SBR 100 100 100 SI 69 8 8 8 Stearic acid 2 2 2 Microcrystalline max 2 2 2 TDAE oil 5 5 5 N-Octylpyrrolidone 2.5 2.5 2.5 ZnO 3 3 3 TMQ 1.75 1.75 1.75 6-PPD 3 3 3 TBBS 80 2.5 2.5 2.5 Sulfur 1.4 1.4 1.4
in which microcrystalline wax: mixture of N-paraffins, Riowax BNO1 of SER S.P.A. (ozone protection); TMQ: 2,2,4-Trimethyl-1,2-Dihydrquinoline, Rubatan 184 General Quimica SA (Antioxidant); N-Octylpyrrolidone is Surfadone LP 100 of BASF; for the other ingredients reference is made to the key of table 5a.

(186) These compositions are technical blends of tread type. In the examples MS, and MT, 30 phr of silica were substituted with 15 or 17 phr of modified sepiolite as described in the examples 8 and 9 of the invention, respectively.

Example 13

(187) Preparation of standard (2) elastomeric materials comprising modified sepiolite fibres Sepiolite fibres F5 modified as in Comparative example 5 (controlled acid treatment in the presence of silanising agents) (36.4 phr) were incorporated as single filler in a standard composition (2) for vulcanisable elastomeric materials. This comparative material (MP) was compared with the comparative material comprising non-modified sepiolite fibres (MO).

(188) The following Table 6 reports the compositions in phr of the comparative vulcanisable elastomeric materials (MO) and (MP):

(189) TABLE-US-00013 TABLE 6 Example 13 MO Comp. MP Comp. Filler sepiolite modified sepiolite (Ex. 5) % Mg extracted — 26% sepiolite Pangel S9 35 — mod. sepiolite 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 Sulfur 2 2 CBS 1.5 1.5
in which S-SBR: styrene-butadiene rubber SLR 4630 by Styron Europe GmbH; TESPD: Bis (3-triethoxysilylpropyl) disulphide by Aldrich; 6-PPD: N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine Santoflex-6 PPD by Flexsys; stearic acid: Stearina TP8 by Undesa; Sulfur: S8 (soluble sulfur) by Zolfo industria; ZnO: zinc oxide by Zincol Ossidi; CBS: N-cyclohexyl-2-benzothiazolsulfenamide Vulkacit CZ/C by Lanxess.

(190) FIG. 12A reports the progression of the modulus G′ for these materials (see Example 17 for a detailed comment).

Preparation and Characterisation of the Vulcanised Elastomeric Materials

(191) The elastomeric materials prepared in the preceding examples were vulcanised to give rise to specimens on which analytical characterisations were carried out together with the evaluation of the static and dynamic mechanical properties.

(192) The vulcanisation, unless otherwise indicated, was conducted in a mould, in a hydraulic press at 170° C. and at the pressure of 200 bar for a time of about 10 minutes

(193) In the present description, the vulcanised samples were named with the same initials as the original elastomeric green material preceded by the letter V (for example, from the material MK, the specimen of vulcanised material named V-MK derives).

(194) The static mechanical properties were measured according to the standard ISO 37:2005 at different extensions (50%, 100%, 300.sup.0/0), on samples of the vulcanised elastomeric materials at 170° C. for 10 minutes. The traction tests were carried out on Dumbbell specimens.

(195) The dynamic mechanical properties were evaluated by using a rheometer Monsanto R.P.A. 2000 according to the following method: cylindrical test samples with weights in the range from 4.5 g to 5.5 g were obtained by means of 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 the measurement of the dynamic elastic shear modulus (G′) at 70° C., frequency 10 Hz, deformation from 0.1% to 10%.

(196) The Payne effect was evaluated through the difference between the shear moduli (G′) at 10% and at 0.5% except where otherwise indicated.

(197) In addition, the dynamic compression moduli were measured using a dynamic device Instron in the compression mode according to the following methods. A test piece of vulcanised material having a cylindrical shape (length=25 mm; diameter=14 mm), preloaded with compression up to a longitudinal deformation of 25% with respect to the initial length and maintained at the preset temperature (23° C. or 70° C.) for the entire duration of the test, was subjected to a dynamic sinusoidal stress having an amplitude of ±3.5% with respect to the length under preload, with a frequency of 100 Hz.

(198) The dynamic mechanical properties were expressed in terms of values of dynamic elastic modulus (E′) and Tan delta (loss factor).

(199) The value Tan delta was calculated as ratio between the viscous dynamic modulus (E″) and the elastic dynamic modulus (E′), both being determined with the abovementioned dynamic measurements.

(200) The generation of heat and the bending fatigue during the compression were measured by means of a Goodrich flexometer according to ASTM D 623-07. The test consisted of subjecting a rubber sample of defined size and shape to compression stresses by means of quick oscillation in controlled conditions. The increase of the temperature was measured. In particular, the increase of the temperature was measured up to an equilibrium temperature.

(201) In this method, a defined compression load is applied on a test sample through a lever system having high inertia, simultaneously imposing on the sample an additional high frequency cyclic compression with defined amplitude. The increase of the temperature at the base of the test sample is measured with a thermocouple in order to supply an indication relative to the heat generated during the bending of the sample.

(202) The standard test sample was moulded, a cylinder having a diameter of 17.8 mm and a height of 25 mm.

(203) The test conditions were: excursion=6.35 mm; load (on beam)=216 N; time=30 minutes; temperature=23° C. The test was terminated after 30 minutes, time at which the final internal temperature of the sample was determined.

Example 14 (Standard 1 Vulcanised Elastomeric Materials)

(204) The elastomeric comparative materials (MA), (MB), (MC1) and (MD) 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 previously described methods—except for the dynamic deformation interval from 0.4% to 35% in the shear test (G′), conducted with the instrument “RPA”, rather than 0.1%-10%. The following Table 7 reports the values measured for the four comparative samples:

(205) TABLE-US-00014 TABLE 7 example 14 V-MA V-MB V-MC1 V-MD Comp. Comp. Comp. Comp. Filler Silica Silica + sepiolite Silica + Silica + modified sepiolite Ex. 2a modified sepiolite Ex. 1 % Mg — — 80% 33% extracted 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%) 1.51 1.48 1.21 1.31 [MPa] ΔG′(0.4-35%)/ 0.30 0.31 0.27 0.27 G′ 0.4% max Tan delta 0.071 0.074 0.082 0.071

(206) From the analysis of the data reported in Table 7, it is inferred that by substituting an aliquot of silica in an elastomeric standard composition (1) (V-MA) with equivalent weight of non-modified sepiolite fibres F-SE, an elastomeric material (V-MB) is obtained with greater reinforcement but worsened hysteresis and Payne effect (see tan delta and ΔG′(0.4-35%)/G′ (0.4%).

(207) By employing modified sepiolite fibres for drastic acid treatment F2a (comparative V-MC1, prepared in the comparative example 2a, with extraction of the magnesium of 95% and loss of the crystalline structure and of the needle-shaped morphology), a worsening is observed both of the static properties and above all of the hysteresis (higher tan delta).

(208) By incorporating modified sepiolite fibres F1 in the elastomeric material according to comparative acid treatment processes, with addition of all the acid at the start and pH of the medium lower than 2 (V-MD), a hysteresis is observed that is lower than that of the material comprising non-treated sepiolite (V-MB) and comparable to that of the material comprising only silica (V-MA) but with significant improvement of the Payne effect and satisfactory static properties.

(209) A very advantageous elastomeric composition is thus obtained, with comparable hysteresis but with reduced Payne effect with respect to the elastomeric standard material 1 (V-MA).

(210) In addition, as can be seen from the data in Table 7, the sepiolite fibres treated in drastic acidic conditions F2a (as in the comparative example 2a) and incorporated in these elastomeric reference materials (V-MC1) involve a static reinforcement lower than that of the commercial silica (V-MA), and a much higher hysteresis (tan delta of 0.082 with respect to 0.071): it is particularly surprising that both the starting non-modified sepiolite (V-MB) and the product of the exhaustive reaction with acid (V-MC1) both induce higher hysteresis in the materials, while the sepiolite modified by comparative acid treatment F1 determines a hysteresis of the comparative material (V-MD) lower than both reference materials.

Example 15 (Vulcanised Elastomeric Materials for Internal Applications)

(211) The elastomeric comparative materials (ME1), (MF1), (MC2), (MG), (MH), (MI), (MJ) and (MK) prepared in example 11 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. The following Table 8a reports the values measured for the eight comparative samples:

(212) TABLE-US-00015 TABLE 8a example 15 V-ME1 V-MF1 V-MC2 V-MG V-MH V-MI V-MJ V-MK Comp. Comp. Comp. Comp. Comp. Comp. Comp. Comp. Filler Silica Silica + Silica + Silica + Silica + Silica + Silica + Silica + sepiolite mod. mod. mod. mod. mod. mod. sepiolite sepiolite sepiolite sepiolite sepiolite sepiolite Ex. 2b Ex. 3 Ex. 4 Ex. 5 Ex.6 Ex. 7 % Mg extracted — — 97% 35% 35% 26% 20% 28% Ca0.5 2.34 2.48 2.00 2.51 2.47 2.28 2.60 2.60 [MPa] 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. 8.44 8.60 8.02 8.65 8.66 8.46 9.56 9.15 100 Hz Tan Delta 23° C. 0.094 0.101 0.097 0.075 0.074 0.093 0.082 0.084 100 Hz Tan Delta 70° C. 0.066 0.070 0.066 0.052 0.050 0.065 0.056 0.058 100 Hz G′ 70° C. (9%) 1.69 1.59 1.63 1.64 1.64 1.57 1.74 1.75 MPa Tan Delta 70° C. 0.101 0.112 0.095 0.095 0.092 0.097 0.102 0.098 (9%) dG′(0.5-10) 1.0 1.1 0.8 0.9 0.9 0.9 1.0 0.9 MPa Goodrich Final internal 127.3 135.0 131.1 115.4 119.0 124.0 126.0 126.5 Temp. ° C. Permanent −2.3 −2.9 −2.3 −1.4 −1.9 −1.9 −2.0 −2.0 deformation

(213) From the analysis of the data reported in Table 8a, it is inferred that by substituting an aliquot of silica in a conventional elastomeric composition (V-ME1) with 70% by weight of non-modified sepiolite F-SE, an elastomeric material (V-MF1) is obtained with greater static reinforcement and greater tensile properties, but the following are increased: the hysteresis—measured as tan delta at 70° C. both under compression and shear—the Payne effect measured as difference of elastic shear modulus at 70° C. between 0.5% and 10% of dynamic deformation—and heat generation—measured by the Goodrich test, as well as the permanent deformation measured at the end of the Goodrich test.

(214) By employing sepiolite fibres modified by drastic acid treatment F2b (comparative V-MC2, prepared in example 2b, with extraction of the magnesium of 97%, loss of the crystalline structure and preservation of the needle-shaped morphology), the following is observed: a worsening of the static mechanical properties, measured by means of the parameters Ca0.5, Cal and CR, together with a worsening of the dynamic mechanical properties measured by means of the parameter E′, both with regard to the elastomeric reference materials V-ME1 and V-MF1 and with regard to all the samples of the elastomeric comparative materials reported in table 8a. Such worsening indicates a lower reinforcement capacity of these fibres modified with drastic acid treatment.

(215) From the Goodrich test, one also observes a final internal temperature higher than that of the sample comprising silica (V-ME1) and that of all the comparative samples comprising modified sepiolite (V-MG, V-MH, V-MI, V-MJ, V-MK), indicating that, disadvantageously, the material V-MC2 develops more heat during use.

(216) Finally, also the permanent deformation of the sample V-MC2 is higher with respect to the comparative samples.

(217) Instead, by incorporating in the elastomeric material, in substitution of an aliquot of silica, sepiolite fibres modified according to a comparative acid treatment, with removal of 35% of the magnesium, in the absence of (F3 in V-MG) or in the presence of sulfur silanising agents (F4 in V-MH), the same static and dynamic reinforcement capacity of the non-modified sepiolite is substantially maintained, and the thermoplasticity measured as hardness delta is further improved, though above all the dissipative properties are improved, measured as Tan Delta both in the compression test and in the shear test.

(218) In the case of the comparative samples V-MG and V-MH, the tan delta at 70° C. is lower in the compression test by over 25% due to the improved hysteresis conferred by the modified sepiolite fibres F3 and F4. This result is interesting if it is considered that the composition has been modified by less than 6% by weight.

(219) In order to further investigate the dissipative behaviour of the materials, flexometry measurements were conducted according to Goodrich. This characterisation technique is particularly important for evaluating compounds with different hysteretic properties. The test is conducted according to ASTM

(220) D 623-07 in conditions similar to the dynamic compression tests, but continuing the test for 30 minutes, setting a fixed preload and dynamic deformation, with the further possibility of measuring the temperature of the samples at the end of the test. In this manner, one obtains an indication of the heat dissipated by the material under examination, during the compression deformation step, which is directly correlated to its hysteretic behaviour and to its modulus: the higher the modulus and hysteresis, the higher the final temperature.

(221) Table 8a reports the values of the final temperatures: it can be observed that the comparative samples with sepiolite V-MF1 and V-MC2 are heated by about 8° C. and 4° C. more than the comparative sample V-ME1, while the comparative sample V-MH is heated 8° C. less than the comparative example V-ME1 and therefore respectively 16° C. and 12° C. less than the corresponding V-MF1 and V-MC2, given the same dynamic modulus. In the case of the comparative V-MG the temperature difference is 20° C. with respect to V-MF1 and 16° C. with respect to V-MC2.

(222) A significant improvement is also observed regarding the permanent deformation measured at the end of the Goodrich test.

(223) The comparative sample (V-MJ) comprising fibres in which the removal of the magnesium, with a quick procedure in water, was 20% (F6), showed excellent static and dynamic reinforcement properties, greater than those of the sample with non-modified sepiolite, maintaining a hysteresis that is reduced both with respect to the elastomeric comparative material V-MF1 and with respect to the elastomeric comparative material with silica V-ME1. Also the behaviour at the Goodrich test confirms an improved dynamic behaviour, leading to a final temperature that is lower than that of the references, notwithstanding the very high reinforcement level.

(224) Considerations analogous to those for the sample V-MJ can be made for the comparative sample V-MK, comprising fibres in which the removal of the magnesium, with a procedure in alcohol with a non-sulfur silanising agent, was 28%.

(225) The comparative sample comprising fibres in which the removal of the magnesium was 26% (F5 in V-MI), through a process in isopropanol-water, with 37% hydrochloric acid, in the presence of TESPT and over long times, showed excellent tensile properties, improved with respect to the comparative without sepiolite V-ME1, maintaining similar static and dynamic reinforcement properties, with a decreased hysteresis and Payne effect, as also shown by the behaviour at the Goodrich test, which leads to a final temperature that is lower with respect to the references, as well as a smaller permanent deformation measured at the end of the Goodrich test itself.

(226) The comparative samples V-MJ and V-MI were observed at the microscope at 100000 power magnification (STEM characterisation—Scanning Transmission Electron Microscopy—on ultramicrotome thin sections (50 nm) under cold conditions, −120° C.). As can be observed from the images of FIGS. 13 and 14, the modified sepiolite fibres incorporated in the elastomeric matrix are clearly visible, and it is evident that they have an aspect ratio considerably higher than three.

(227) The following Table 8b reports the values measured for the comparative vulcanised samples V-ME2, V-MF2 and those according to the invention V-MQ and V-MR:

(228) TABLE-US-00016 TABLE 8b example 15 V-ME2 V-MF2 V-MQ V-MR Comp. Comp. Inv. Inv. Filler Silica Silica + Silica + mod. Silica + sepiolite sepiolite mod. Ex. 8 sepiolite Ex. 9 % Mg extracted — — 33% 35% Ca1 [MPa] 4.00 4.47 5.03 4.92 CR [MPa] 9.72 12.32 9.66 10.45 AR [%] 213.7 261.60 184.6 195.6 IRHD 23° C. 74.7 74.9 75.1 74.9 IRHD 100° C. 73.2 73.9 74.1 73.7 Delta IRHD 1.5 1.0 1.0 1.2 E′ [MPa] 23° C. 100 Hz 8.68 8.90 9.22 9.53 E′ [MPa] 70° C. 100 Hz 8.69 8.68 9.23 9.63 Tan Delta 23° C. 100 Hz 0.108 0.12 0.107 0.095 Tan Delta 70° C. 100 Hz 0.079 0.08 0.077 0.067

(229) As can be observed from the data reported in Table 8b, the materials according to the invention V-MQ and V-MR have improved dynamo-mechanical characteristics with respect to the comparative materials in terms of balance between dynamic modulus E′ and hysteresis (Tan delta).

(230) In particular, the materials according to the invention show greater dynamic modulus E′, considered advantageous in the run-flat function, when the tyre travels deflated. This property makes the present materials particularly interesting in the use as filler of the sidewall of run-flat tyres.

(231) In addition, as is clear from the values of hardness difference measured with IRHD method between 23° C. and 100° C., the thermal stability of the samples according to the invention is improved. The samples V-MQ and V-MR according to the invention have an advantageous balance between hardness and hardness delta associated with an optimal modulus vs. hysteresis ratio. It can be observed that neither the comparative sample V-ME2 nor the comparative sample V-MF2 have the advantageous combination of all these properties (balance of hardness versus hardness delta together with high moduli versus low hystereses).

Example 16 (Elastomeric Materials for Tread Applications)

(232) The elastomeric comparative materials (ML1), (ML2), (MM), (MN) and according to the invention (MS) and (MT), prepared in example 12 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.

(233) The Table 9a reports the values measured for the three comparative samples:

(234) TABLE-US-00017 TABLE 9a (Tread 1) Example 16 V-ML1 V-MM V-MN Comp. Comp. Comp. Filler Silica Silica + sepiolite Silica + modified sepiolite Ex. 4 % Mg extracted — — 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 23° C. 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] 70° C. 100 Hz 7.70 7.30 7.17 Tan Delta 0° C. 100 Hz 0.501 0.519 0.504 Tan Delta 23° C. 100 Hz 0.296 0.298 0.281 Tan Delta 70° C. 100 Hz 0.152 0.145 0.141 dG′(0.5-10) MPa 2.7 2.2 1.9

(235) From the analysis of the data reported in Table 9a, it is inferred that by incorporating the sepiolite fibres modified according to a comparative acid treatment (V-MN) in the elastomeric material, in a quantity even lower than the removed silica (10 phr of silica were substituted with 9.79 phr of modified fibres as in example 12, equal to 7 phr of inorganic residue at 800° C.), one observes a reinforcement capacity comparable to or even greater than that of the silica and of the non-modified sepiolite, as well as good tensile properties. With the elastomeric comparative material (V-MN), one also observes an improved thermoplasticity (delta IRHD), but above all the dissipative properties are drastically improved, measured as Tan Delta at 70° C. The Payne effect also greatly improves.

(236) The following Table 9b reports the values measured for the comparative sample (V-ML2) and for that of the invention (V-MS) and (V-MT):

(237) TABLE-US-00018 TABLE 9b (Tread 2) Example 16 V-ML2 V-MS V-MT Comp. Inv. Inv. Filler Silica Silica + modified Silica + modified sepiolite Ex. 8 sepiolite Ex. 9 % Mg extracted — 33% 35% CA 0.5 [MPa] CA 1 [MPa] 2.92 4.15 3.82 CA 3 [MPa] CR [MPa] 13.09 12.09 13.11 AR % 366.2 287.2 333.4 IRHD 23° C. 74.0 73.3 70.7 IRHD 100° C. 69.1 68.5 67.1 Delta IRHD 5.1 4.8 3.6 E′ [MPa] 23° C. 100 Hz 8.68 9.13 8.77 E′ [MPa] 70° C. 100 Hz 6.51 7.08 6.88 E′ [MPa] 100° C. 100 Hz 6.22 6.89 6.81 Delta E′ (23-100° C.) 2.46 2.24 1.96 [MPa] Tan Delta 23° C. 100 Hz 0.275 0.240 0.218 Tan Delta 70° C. 100 Hz 0.128 0.113 0.098 Tan Delta 100° C. 0.071 0.063 0.051 100 Hz

(238) The materials according to the invention V-MS and V-MT have improved dynamo-mechanical characteristics with respect to the reference material V-ML2 in terms of balance between dynamic modulus and hysteresis.

(239) In particular, in the sample of the invention V-MS, it is observed that the modulus increases and the hysteresis decreases, while in the sample of the invention V-MT—which differs from the preceding due to the starting sepiolite fibres that are organically modified (Pangel B5)—one observes the maintenance of the value of the modulus associated however with a drastic reduction of the hysteresis.

(240) In addition, as is clear from the values of hardness difference measured with IRHD method between 23° C. and 100° C., the thermal stability of the samples according to the invention is improved.

(241) The tendency to exhibit a lower dependency of the mechanical properties on the temperature is also demonstrated by the smaller variation observed in the dynamic modules between 23° C. and 100° C., which passes from 2.46 MPa for the comparative composition V-ML2 to 2.24 MPa for the composition according to the invention V-MS in order to reach 1.96 in the case of the composition according to the invention V-MT.

(242) A lower dependence of the dynamic modulus on the temperature is an indication of stability of the performance in high difficulty conditions, such as driving at the adherence limit or emergency manoeuvres such as breaking, conditions in which the tread generally reaches very high temperatures.

Example 17 (Standard 2 Elastomeric Materials)

(243) The elastomeric comparative materials (MO) comprising non-modified sepiolite fibres F-SE and (MP) comprising sepiolite fibres F5 from which 26% of magnesium was extracted, prepared in example 13 and vulcanised at 170° C. for 10 minutes, were subjected to measurement of the dynamic mechanical properties according to the previously described methods.

(244) From the mechanical dynamic analysis RPA, the reinforcing effect imparted by the non-modified sepiolite fibres (sample V-MO) and the sepiolite fibres modified according to comparative processes (sample V-MP) on the vulcanised materials was evaluated, as reported in FIGS. 12A and 12B.

(245) In FIG. 12A, it is shown that the variation of the modulus G′ with the variation of the deformation of the comparative sample V-MP was quite limited with respect to that of the comparative sample V-MO, indicating a greater stability of the material with respect to the deformation and hence a limited Payne effect.

(246) FIG. 12B illustrates the progression of the hysteresis for the two comparative materials: as can be observed, the sample V-MP has tan delta values significantly lower and more constant than those of the sample V-MO comprising non-modified sepiolite fibres. The data is particularly significant considering that no coupling agent was added to the sample V-MP during mixing step.

(247) In conclusion, from the mechanical analyses conducted on the samples of the elastomeric materials according to the invention and comparatives, it is inferred that the presence of modified fibres according to the controlled acid treatment described herein clearly reduces the hysteresis of the elastomeric materials, simultaneously maintaining a good reinforcement.

(248) Such mechanical properties render the elastomeric materials according to the invention particularly suitable for producing tyres with high reinforcement and simultaneously limited rolling resistance.

(249) The process of the invention has proven particularly advantageous, especially when applied at the industrial level, since it allows the use of conventional apparatuses and plants made of steel, it can be carried out simply in water, with limited quantities of acid and hence without final neutralisation steps. In addition, the extraction of the magnesium in such conditions is gradual, hence the process does not require the strict control of the times, of the solvents and a continuous monitoring of the extraction level of the magnesium, so as to terminate the reaction in order to prevent the excessive removal of the magnesium, as occurred for the known processes.