Elastomeric compositions comprising silicate fibres with needle-shaped morphology of nanometric size and tyres for vehicles that comprise them

Abstract

The present invention regards a solid master elastomeric composition (masterbatch, MB) comprising silicate fibres with needle-shaped morphology of nanometric size, characterised by high fibre content and uniformity, a process advantageous for the preparation thereof and its use in manufacturing tyres for vehicles. Advantageously the present elastomeric composition allows minimising the drawbacks associated with the handling of the powdery fibres in the manufacturing of compounds for tyres, without altering the final performances thereof.

Claims

1. A process for preparing a solid master elastomeric composition, comprising silicate fibres of nanometric size with needle-shaped morphology and one or more diene elastomers, comprising: providing the fibres and an elastomeric latex comprising one or more diene elastomers and an aqueous phase, wherein a weight ratio of the fibres to the diene elastomer present in the latex is at least 0.5:1, combining the fibres and the latex to yield an aqueous suspension, bringing the pH of the aqueous suspension to, or maintaining the pH of the aqueous suspension within, a range from 7.5 to 12.0, bringing a volumetric ratio between the total volume of the aqueous suspension and the weight of the fibres to, or maintaining the volumetric ratio within, a range from 10:1 to 30:1 ml/g, to yield a final suspension (C), allowing the elastomeric composition to precipitate out of the final suspension (C).

2. The process as claimed in claim 1, wherein the fibres are in a solid wet form or are suspended in water to yield an aqueous suspension (A) comprising from 10 to 100 g/l, or from 30 to 60 g/l of fibres in relation to water.

3. The process as claimed in claim 1, wherein the fibres are in a solid wet form and are suspended in water to yield an aqueous suspension (A) comprising from 10 to 100 g/l, or from 30 to 60 g/l of fibres in relation to water.

4. The process as claimed in claim 2, wherein combining the fibres and the latex comprises adding the aqueous suspension (A) to the latex (direct addition) or adding the latex to the aqueous suspension (A) (inverse addition).

5. The process as claimed in claim 1, wherein the latex is a natural latex or has a pH ranging from 8 to 12.

6. The process as claimed in claim 1, wherein the latex is a natural latex and has a pH ranging from 8 to 12.

7. The process as claimed in claim 5, wherein the latex is a natural latex comprising 10% to 60% by weight of the diene elastomer.

8. The process as claimed in claim 1, wherein the weight ratio of the fibres to the diene elastomer in the latex is chosen from a range of 0.5:1 to 1.5:1, 0.7:1 to 1.3:1, 0.9:1 to 1.1:1, or about 1:1.

9. The process as claimed in claim 1, wherein combining the fibres and the latex comprises stirring and mixing the fibres with the latex for a time ranging from about 5 to 30 minutes at a temperature ranging from 10 to 50° C., or 20 to 30° C.

10. The process as claimed in claim 1, wherein the volumetric ratio of the final suspension (C) is from 15:1 to 25:1 ml/g, or 20:1 to 25:1 ml/g, or the pH of the final suspension (C) is from 7.5 to 11.

11. The process as claimed in claim 1, wherein the volumetric ratio of the final suspension (C) is chosen from a range of 15:1 to 25:1 ml/g, or 20:1 to 25:1 ml/g, and the pH of the final suspension (C) is from a range of 7.5 to 11.

12. The process as claimed in claim 1, wherein the fibres have an aspect ratio of at least 2:1, at least 3:1, or at least 5:1; or are sepiolite fibres, modified sepiolite fibres, or mixtures thereof; or are present in an amount chosen from at least 60 phr, 70 phr, 80 phr, or 90 phr, or from 50 to 200 phr, 60 to 150 phr, or 80 to 120 phr, per 100 parts by weight of the diene elastomer.

13. The process as claimed in claim 1, wherein the fibres have an aspect ratio of at least 2:1, at least 3:1, or at least 5:1; are sepiolite fibres, modified sepiolite fibres, or mixtures thereof; and are present in an amount chosen from at least 60 phr, 70 phr, 80 phr, or 90 phr, or from 50 to 200 phr, 60 to 150 phr, or 80 to 120 phr, per 100 parts by weight of the diene elastomer.

14. A solid master elastomeric composition prepared by a process comprising: providing silicate fibres of nanometric size with needle-shaped morphology and an elastomeric latex comprising one or more diene elastomers and an aqueous phase, wherein a weight ratio of the fibres to the diene elastomer present in the latex is at least 0.5:1, combining the fibres and the latex to yield an aqueous suspension, bringing the pH of the aqueous suspension to, or maintaining the pH of the aqueous suspension within, a range from 7.5 to 12.0, bringing a volumetric ratio between the total volume of the aqueous suspension and the weight of the fibres to, or maintaining the volumetric ratio within, a range from 10:1 to 30:1 ml/g, to yield a final suspension (C), allowing the elastomeric composition to precipitate out of the final suspension (C).

15. The solid master elastomeric composition as claimed in claim 14, consisting of 100 phr of one or more diene elastomers and at least 50 phr of the fibres.

16. The solid master elastomeric composition as claimed in claim 14, wherein the fibres have an aspect ratio of at least 2:1, at least 3:1, or at least 5:1; or are sepiolite fibres, modified sepiolite fibres, or mixtures thereof; or are present in the process or in the elastomeric composition in an amount chosen from at least 60 phr, 70 phr, 80 phr, or 90 phr, or from 50 to 200 phr, 60 to 150 phr, or 80 to 120 phr, per 100 parts by weight of the diene elastomer.

17. The solid master elastomeric composition as claimed in claim 14, wherein the fibres have an aspect ratio of at least 2:1, at least 3:1, or at least 5:1; are sepiolite fibres, modified sepiolite fibres, or mixtures thereof; and are present in the process or in the elastomeric composition in an amount chosen from at least 60 phr, 70 phr, 80 phr, or 90 phr, or from 50 to 200 phr, 60 to 150 phr, or 80 to 120 phr, per 100 parts by weight of the diene elastomer.

18. A vulcanisable elastomeric composition for tyre components, comprising: (a) 100 phr of one or more diene elastomers; (b) from 10 to 200 phr of a solid master elastomeric composition prepared by a process comprising: providing silicate fibres of nanometric size with needle-shaped morphology and an elastomeric latex comprising one or more diene elastomers and an aqueous phase, wherein a weight ratio of the fibres to the diene elastomer present in the latex is at least 0.5:1, combining the fibres and the latex to yield an aqueous suspension, bringing the pH of the aqueous suspension to, or maintaining the pH of the aqueous suspension within, a range from 7.5 to 12.0, bringing a volumetric ratio between the total volume of the aqueous suspension and the weight of the fibres to, or maintaining the volumetric ratio within, a range from 10:1 to 30:1 ml/g, to yield a final suspension (C), allowing the elastomeric composition to precipitate out of the final suspension (C); (c) from 0 to 120 phr of a standard reinforcing filler; (d) from 0.1 to 15 phr of a vulcanising agent; and (e) from 0.1 to 20 phr of a coupling agent.

19. A tyre component comprising a vulcanisable elastomeric composition comprising: (a) 100 phr of one or more diene elastomers; (b) from 10 to 200 phr of a solid master elastomeric composition prepared by a process comprising: providing silicate fibres of nanometric size with needle-shaped morphology and an elastomeric latex comprising one or more diene elastomers and an aqueous phase, wherein a weight ratio of the fibres to the diene elastomer present in the latex is at least 0.5:1, combining the fibres and the latex to yield an aqueous suspension, bringing the pH of the aqueous suspension to, or maintaining the pH of the aqueous suspension within, a range from 7.5 to 12.0, bringing a volumetric ratio between the total volume of the aqueous suspension and the weight of the fibres to, or maintaining the volumetric ratio within, a range from 10:1 to 30:1 ml/g, to yield a final suspension (C), allowing the elastomeric composition to precipitate out of the final suspension (C); (c) from 0 to 120 phr of a standard reinforcing filler; (d) from 0.1 to 15 phr of a vulcanising agent; and (e) from 0.1 to 20 phr of a coupling agent.

20. The tyre component as claimed in claim 19, wherein the vulcanisable elastomeric composition is at least partially vulcanised.

21. A tyre for vehicle wheels comprising at least one tyre component comprising a vulcanisable elastomeric composition comprising: (a) 100 phr of one or more diene elastomers; (b) from 10 to 200 phr of a solid master elastomeric composition prepared by a process comprising: providing silicate fibres of nanometric size with needle-shaped morphology and an elastomeric latex comprising one or more diene elastomers and an aqueous phase, wherein a weight ratio of the fibres to the diene elastomer present in the latex is at least 0.5:1, combining the fibres and the latex to yield an aqueous suspension, bringing the pH of the aqueous suspension to, or maintaining the pH of the aqueous suspension within, a range from 7.5 to 12.0, bringing a volumetric ratio between the total volume of the aqueous suspension and the weight of the fibres to, or maintaining the volumetric ratio within, a range from 10:1 to 30:1 ml/g, to yield a final suspension (C), allowing the elastomeric composition to precipitate out of the final suspension (C); (c) from 0 to 120 phr of a standard reinforcing filler; (d) from 0.1 to 15 phr of a vulcanising agent; and (e) from 0.1 to 20 phr of a coupling agent.

22. A tyre for vehicle wheels comprising at least one tyre component comprising a vulcanized elastomeric composition prepared by, at least partially, vulcanizing an elastomeric composition comprising: (a) 100 phr of one or more diene elastomers; (b) from 10 to 200 phr of a solid master elastomeric composition prepared by a process comprising: providing silicate fibres of nanometric size with needle-shaped morphology and an elastomeric latex comprising one or more diene elastomers and an aqueous phase, wherein a weight ratio of the fibres to the diene elastomer present in the latex is at least 0.5:1, combining the fibres and the latex to yield an aqueous suspension, bringing the pH of the aqueous suspension to, or maintaining the pH of the aqueous suspension within, a range from 7.5 to 12.0, bringing a volumetric ratio between the total volume of the aqueous suspension and the weight of the fibres to, or maintaining the volumetric ratio within, a range from 10:1 to 30:1 ml/g, to yield a final suspension (C), allowing the elastomeric composition to precipitate out of the final suspension (C); (c) from 0 to 120 phr of a standard reinforcing filler; (d) from 0.1 to 15 phr of a vulcanising agent; and (e) from 0.1 to 20 phr of a coupling agent.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is the representation of a tyre for cars comprising one or more components according to the invention.

(2) FIG. 2 is the thermogravimetric diagram (TGA) of commercial organically modified sepiolite fibres (Pangel B5) and of the MB according to the invention (MB5 Ex. 5) in which the percentage loss of weight is reported on the y-axis and the temperature in centigrades is reported on the x-axis, measured as described in the experimental part.

EMBODIMENTS OF THE INVENTION

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

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

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

(6) 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.

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

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

(9) The carcass structure is usually of radial type, i.e. the reinforcing 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 reinforcing 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 backward 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 turn-ups of the carcass 101a as illustrated in FIG. 1.

(10) In one embodiment, the coupling between the carcass structure and the 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.

(11) An anti-abrasive layer 105 possibly made with elastomeric composition is arranged in an external position of each bead structure 103.

(12) The carcass structure is associated with a belt structure 106 comprising one or more belt layers 106a, 106b situated in radial superimposition with respect to each other and with respect to the carcass layer, having typically textile and/or metallic reinforcement cords incorporated in a layer of vulcanised elastomeric material.

(13) Such reinforcing 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.

(14) In radially external position with respect to the belt layers 106a, 106b, at least one zero degree reinforcement layer 106c, commonly known as “0° belt”, can be applied which generally incorporates a plurality of elongated reinforcement elements, typically textile or metallic cords, oriented in a substantially circumferential direction, thus forming an angle of only 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 covered with vulcanised elastomeric material.

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

(16) 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.

(17) In radially external position, the tread band 109 has rolling surface 109a intended to come into 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 on the rolling surface 109a, are generally made in this surface 109a, which is represented smooth for the sake of simplicity in FIG. 1.

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

(19) A strip consisting of elastomeric composition 110, commonly known as “mini-sidewall”, made of vulcanised elastomeric material may 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.

(20) In the case of tyres without air chamber, 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 internal position with respect to the carcass layer 101.

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

(22) The flipper 120 is a reinforcing layer that is wound around the respective bead core 102 and the bead filler 104 so as to at least partially surround them, said reinforcing layer being arranged between the at least one carcass layer 101 and the bead structure 103. Usually, the flipper is in contact with said at least one carcass layer 101 and said bead structure 103.

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

(24) The tyre bead structure 103 can comprise a further protection layer that 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.

(25) The chafer 121 usually comprises a plurality of cords incorporated in a rubber-covered layer made of vulcanised elastomeric material. Such cords are generally made of textile materials (e.g. aramid or rayon) or of metallic materials (e.g. steel cords).

(26) A layer or sheet of elastomeric material can be arranged between the belt structure and the carcass structure (not shown in FIG. 1). The layer can have uniform thickness. Alternatively, the layer can have a variable thickness in axial direction.

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

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

(29) 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 supplementary layer or sheet preferably being extended over a surface substantially corresponding to the extension surface of said belt structure.

(30) The vulcanisable 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 anti-abrasive strip.

(31) The vulcanisable elastomeric composition according to the present invention can comprise at least

(32) (a) 100 phr of at least one diene elastomer

(33) (b) 10 to 200 phr of a solid master elastomeric composition in accordance with the invention,

(34) (c) 0 to 120 phr of a standard reinforcing filler,

(35) (d) 0.1 to 15 phr of a vulcanising agent, and

(36) (e) 0.1 to 20 phr of a coupling agent.

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

(38) 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. 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.

Analytical Methods

(39) Thermogravimetric Analysis (TGA)

(40) The determination of the profile of the weight loss was carried out with the apparatus Mettler Toledo TGA/DSC1 Star-e System, in a temperature range from 150 to 800° C. The measurements were carried out by using a temperature program which provides for an inert gas phase (ramp from 25 to 150° C. and a plateau at 150° C. in nitrogen flow) and an oxidation phase (ramp from 150 to 800° C. in dry air flow).

(41) Preparation of Comparative Elastomeric Solid Master Compositions (Comparative MB)

(42) The comparative compositions of Examples 1-2 were prepared, comprising carbon black instead of sepiolite or comprising organically modified sepiolite on the surface but using process conditions different from those of the process according to the invention.

EXAMPLE 1

Comparative

(43) Preparation of MB1 Comprising Carbon Black in Rubber Latex (Without and In the Presence of Acids)

(44) Experiments were conducted with different ratio between carbon black and rubber latex in simple apparatuses and according to the following general batch procedure. A suspension of carbon black N234 in water was prepared with a homogenisator (Silverson L5MHomogenisator, 5 minutes at 5000 rpm). The suspension thus prepared was mixed with 200 ml of 30% solid rubber latex (60 g), prepared by diluting 100 ml of Centex FA latex (60% solid content by weight equal to 120 g of solid, pH from 9 to 11, density 0.95 g/cm.sup.3) with 100 ml of water. After 20 minutes of stirring at 300 rpm, the coagulated material was collected, it was washed with 3×100 ml of water and dried in an oven at 80° C. for 12 hours, obtaining dry MB. A sample of MB was subjected to thermogravimetric analysis (TGA) according to the previously described procedure, and based on the thermograph, the actual content of carbon black therein was obtained.

(45) The quantities of the reagents used, the theoretical as well as the experimental values relative to the MB1 of the various experiments, are reported in the following Table 1:

(46) TABLE-US-00001 TABLE 1 .sup.4Tot. Theoretical Actual Yield .sup.6theoretical .sup.7actual .sup.3Tot. vol./ .sup.5CB/ weight weight % CB in CB in .sup.1CB .sup.2water vol. CB solid MB1 MB1 MB1 MB1 MB1 Ex. g g ml ml/g w/w g g % ww Phr phr 1a 12 120 320 27 0.2 72 32.4 45% 20 32.5 1b 18 180 380 21 0.3 78 49.2 63% 30 35 1c 24 240 440 18.3 0.4 84 63.1 75% 40 39 Key: Volume of latex: 200 ml; solid content of the latex: 60 g. .sup.1CB: carbon black; .sup.2quantity of water for suspending CB; .sup.3total volume of the final suspension obtained by mixing the suspension of CB with the latex; .sup.4ratio between the total volume of the suspension 3 and the weight of CB; .sup.5ratio between weight of CB and weight of solid contained in the latex; .sup.6theoretical CB content in the MB1; .sup.7actual CB content in the MB1 determined by TGA.

(47) From the results reported in Table 1, it can be observed that with quantity of carbon black equal to a theoretical content of 20 and 30 phr in the MB (Examples 1a and 1b), only partial coagulation of the latex was obtained, as underlined by the low yields in MB 45% and 63%, respectively. In addition, the coagulated material was enriched in carbon black, with an actual content of carbon black determined with the TGA analysis greater than the theoretical, 32.5 vs. 20 and 35 vs. 30 phr.

(48) The best results were obtained in the example 1c, in which the actual quantity of carbon black incorporated in the MB substantially corresponds to the theoretical, even if the yield in MB is quite far from being quantitative (75%).

(49) In conclusion, from the tests conducted, it appears that it is not possible to obtain concentrated MB with good yield, by simple mixing of suspensions of carbon black and rubber lattices, given the tendency of the carbon black—latex aqueous mixture to spontaneously and incompletely coagulate.

(50) Repeating the experiments using acids or other coagulant agents in batch procedures, it was not possible to obtain uniform MB with complete coagulation, comprising more than 40 phr of black.

EXAMPLE 2

Comparative

(51) Preparation of MB2 Comprising Modified Sepiolite Fibres in Rubber Latex (Without and In the Presence of Acids)

(52) Experiments were conducted at different ratio between organically modified sepiolite fibres (Pangel B5 by Tolsa) and rubber latex in simple apparatuses and according to the following general batch procedure.

(53) A suspension of Pangel B5 in water was prepared, under magnetic stirring for 30 minutes (suspension A) and this was added to 80 ml of 15% solid rubber latex, containing 12 g of solid, prepared by diluting 20 g of 60% solid rubber latex HA with 60 g of water (B). After 10 minutes of magnetic stirring, the coagulated material was collected, it was washed with 3×100 ml of water up to neutrality and it was dried in an oven at 50° C. for 20 hours, obtaining dry MB2.

(54) A sample of MB2 was subjected to thermogravimetric analysis (TGA) according to the previously described procedure, and based on the thermogram the actual content of PangelB5 in the same was determined.

(55) The quantities of the used reagents, the theoretical as well as the experimental values relative to the MB1 of the various experiments, are reported in the following Table 2:

(56) TABLE-US-00002 TABLE 2 .sup.4Tot. .sup.5fibres/ Theoretical Actual Yield .sup.6theoretical .sup.7actual .sup.3Tot. vol./ solid weight weight % fibres fibres .sup.lfibres .sup.2water vol. fibres w/w MB2 MB2 MB2 MB2 MB2 Ex. g g ml ml/g g/g g g ww % phr phr 2a 0.3 10 90 300 0.025 12.3 .sup.8no .sup.8no 2.5 .sup.8no 2b 0.6 20 100 167 0.05 12.6 2.4 19% 5 33 2c 1.2 40 120 100 0.1 13.2 4.2 32% 10 40 2d 2.4 80 160 67 0.2 14.4 6.4 44% 20 60 Key: Volume of latex: 80 ml containing 12 g of solid; .sup.1fibres: Pangel B5, organically modified sepiolite; .sup.2quantity of water for suspending PNB5; .sup.3total volume of the final suspension obtained by mixing the suspension of the fibres with the latex; .sup.4ratio between the total volume of the suspension 3 and the fibre weight; .sup.5ratio between fibre weight and weight of solid contained in the latex; .sup.6theoretical fibre content in the MB2; .sup.7actual fibre content in the MB2 determined by TGA; .sup.8no (Ex. 2a) indicates that there was no formation of coagulation.

(57) From the results reported in Table 2 and from the observation of the Applicant, it is indicated that, without acids, there is no coagulation formation with quantities of Pangel B5 corresponding to 2.5 phr. At 5 phr, the quick coagulation started of a part of the material but in none of the tests was it possible to make the entire solid of the latex coagulate, as shown by the yields % MB lower than 50% in relation to the theoretical and by the lactescent aspect of the supernatant.

(58) From the TGA analyses carried out on the coagulations, it was seen that they were enriched in Pangel B5 beyond the theoretical (see column 7, actual fibre content in MB determined by TGA), consistent with the fact that not all of the rubber of the latex was coagulated.

(59) Tests in the Presence of Acid

(60) Other experiments were carried out, by repeating the tests 2a-2d but adding sulphuric acid (2% by weight aqueous solution) to the mixture of rubber latex and Pangel B5 up to a pH between 4 and 5. With the addition of acid, a complete coagulation is obtained, but it was visibly evident that the coagulant was not uniform since the material part that coagulated initially was darker.

(61) In conclusion, by operating with low fibre/solid ratios in the latex, both in the absence and in the presence of acid, it was not possible to obtain elastomeric compositions of uniform composition and with quantitative yields.

EXAMPLE 3

Invention

(62) Preparation of MB3 Comprising Organically Modified Sepiolite Fibres (Pangel B5) Further Modified with Acid

(63) Preparation of Modified Fibres

(64) The organically modified sepiolite Pangel B5 was further modified with acid treatment according to the following procedure: 120 g of fibres (Pangel B5) were suspended in 1200 ml of isopropanol at 65° C. under stirring. 480 ml of 37% HCl in water were added to the suspension, it was stirred at 600 rpm for 2 h at 65° C., it was then filtered and washed exhaustively with deionised water up to pH 6.6-7.4 and finally it was dried in an oven at 120° C. for 48 h.

(65) Incorporation of the Modified Fibres in the MB3

(66) 10 g of this sepiolite Pangel B5 modified with acid treatment were suspended in 200 g deionised water, stirred for 10 min. at 500 rpm, sonicated for 10 minutes in a laboratory ultrasound bath and finally further stirred for 5 min. to yield a uniform suspension (A).

(67) The suspension A was added to 23.8 g of latex Von Bundit MA (containing 60% solid), equal to 14.3 g of solid (B), and the mixture (C) kept at 300 rpm, observing a nearly immediate coagulation.

(68) The mixture was kept under stirring at 300 rpm for 5 minutes.

(69) The coagulate was collected, washed with 3×100 ml of water and dried in an oven at 80° C. for 12 h, obtaining 21.3 g of master composition (MB3) (88% yield).

(70) The quantities of the used reagents, the theoretical as well as the experimental values relative to the MB3, are reported in the following Table 3:

(71) TABLE-US-00003 TABLE 3 .sup.4Tot. .sup.5fibres/ Theoretical Actual Yield .sup.6theoretical .sup.7actual .sup.3Tot. vol./ solid/ weight weight % fibres fibres .sup.1fibres .sup.2water vol. fibres w/w MB3 MB3 MB3 MB3 MB3 Ex. g g ml ml/g g/g g g % ww phr phr 3 10 200 224 22.4 0.7 24.3 21.3 88% 70 74 Key: Quantity of latex: 23.8 g; solid content of the latex: 14.3 g; .sup.1fibres: Pangel B5 modified with acids; .sup.2quantity of water for suspending the fibres; .sup.3total volume of the final suspension obtained by mixing the suspension of the fibres with the latex; .sup.4ratio between the total volume of the suspension 3 and the fibre weight; .sup.5ratio between fibre weight and weight of solid contained in the latex; .sup.6theoretical fibre content in the MB3; .sup.7actual fibre content in the MB3 determined by TGA.

(72) As can be observed from the table values, by using a high ratio between fibres and solid contained in the latex (around 0.70) it was possible to obtain the MB3 with good yields and with a fibre content in line with the theoretical.

EXAMPLE 4

Invention

(73) Preparation of MB4 Comprising Sepiolite Fibres (Pangel S9) Modified with Acid and Silanised

(74) Preparation of Modified Fibres

(75) 120 g of sepiolite fibres Pangel S9 were suspended in 1200 ml isopropanol at 65° C. under stirring. 480 ml 37% HCl in water and 64.7 g of Bis[3-(triethoxysilyl)propyl]tetrasulphide (TESPT) were added to the suspension, it was stirred at 600 rpm for 2 h at 65° C., it was then filtered and exhaustively washed with deionised water up to pH 6.6-7.4 and finally it was dried in an oven at 120° C. for 48 h.

(76) Incorporation of the Modified Fibres in the MB4

(77) 10 g of fibres as modified above were suspended in 200 ml of deionised water, stirred for 10 min. at 500 rpm, sonicated for 10 minutes (laboratory ultrasound bath), stirred for another 5 min. to yield a uniform suspension (A).

(78) The suspension A was added to 12.8 g of latex Von Bundit MA (B) containing 60% solid, equal to 7.7 g of solid, and maintained under stirring at 300 rpm for 3 minutes, observing a nearly immediate coagulation. The mixture was held under stirring at 300 rpm for another 5 minutes.

(79) The coagulate was collected, washed with 2×100 ml of water and dried in an oven at 80° C. for 12 h, obtaining 16.8 g of composition MB4 (95% yield, with an actual fibre content equal to 130.3 phr determined by TGA).

(80) The quantities of the used reagents, the theoretical as well as the experimental values relative to the MB4, are reported in the following Table 4:

(81) TABLE-US-00004 TABLE 4 .sup.4Tot. .sup.5fibres Theoretical Actual Yield .sup.6theoretical .sup.7actual .sup.3Tot. vol./ solid/ weight weight % fibres fibres .sup.1fibres .sup.2water vol. fibres w/w MB4 MB4 MB4 MB4 MB4 Ex. g g ml ml/g g/g g g % ww phr phr 4 10 200 213 21.3 1.3 17.7 16.8 95% 130 130.3 Key: Quantity of latex: 12.8 g; solid content of the latex: 7.7 g; .sup.1sepiolite Pangel S9 modified with acids and silanised; .sup.2quantity of water for suspending the fibres; .sup.3total volume of the final suspension obtained by mixing the suspension of the fibres with the latex; .sup.4ratio between the total volume of the suspension 3 and the fibre weight; .sup.5ratio between fibre weight and weight of solid contained in the latex; .sup.6theoretical fibre content in the MB4; .sup.7actual fibre content in the MB4 determined by TGA.

(82) As can be observed from the table values, by using a high ratio between fibres and solid contained in the latex (around 1.3) it was possible to obtain the MB4 with very good yields and with a fibre content in line with the theoretical.

EXAMPLE 5

Invention

(83) Preparation of MB5 Comprising Organically Modified Sepiolite Fibres (Pangel B5)

(84) 10 g of organically modified sepiolite fibres with quaternary ammonium salt talloyl benzyl dimethyl ammonium chloride (commercial Pangel B5, batch 1) were suspended in 200 ml deionised water, stirred for 10 min. at 500 rpm, sonicated for 10 minutes (laboratory ultrasound bath) and stirred for another 5 min. to yield a uniform suspension (A).

(85) The suspension A was added to 16.7 g of latex Von Bundit MA containing 60% solid, equal to 10 g of solid (B), and maintained at 300 rpm per 3 minutes, observing a nearly immediate coagulation. The mixture was kept under stirring at 300 rpm for another 5 minutes.

(86) The coagulate was collected, washed with 3×100 ml of water and dried in an oven at 80° C. for 12 h, obtaining 19.1 g of composition MB5 (96% yield) with a fibre content equal to 97.5 phr determined by TGA (see in FIG. 2 the TGA trace of the fibres of Pangel B5 and of the masterbatch MB5 that incorporates them).

(87) The quantities of the used reagents, the theoretical as well as the experimental values relative to the MB5, are reported in the following Table 5:

(88) TABLE-US-00005 TABLE 5 .sup.4Tot. .sup.5fibres/ Theoretical Actual Yield .sup.6theoretical .sup.7actual .sup.3Tot. vol./ solid weight weight % fibres fibres .sup.1fibres .sup.2water vol. fibres w/w MB5 MB5 MB5 MB5 MB5 Ex. g g ml ml/g g/g g g % ww phr phr 5 10 200 217 21.7 1 20.0 19.1 96% 100 97.5 Key: Quantity of latex: 16.7 g; solid content of the latex: 10 g; .sup.1fibres: commercial Pangel B5; .sup.2quantity of water for suspending the fibres; .sup.3total volume of the final suspension obtained by mixing the suspension of the fibres with the latex; .sup.4ratio between the total volume of the suspension 3 and the fibre weight; .sup.5ratio between fibre weight and weight of solid contained in the latex; .sup.6theoretical fibre content in the MB5; .sup.7actual fibre content in the MB5 determined by TGA

(89) As can be observed from the table values, by using a high ratio between fibres and solid contained in the latex (around 1:1) it was possible to obtain the MB5 with very high yields and with a fibre content in line with the theoretical.

EXAMPLE 6

Invention

(90) Preparation of MB6 Comprising Organically Modified Sepiolite Fibres (Pangel B5)

(91) 120 g of organically modified sepiolite fibres (commercial Pangel B5—batch 2) were suspended in 2000 ml of deionised water, stirred for 30 min. at 1000 rpm to yield a uniform suspension (A).

(92) 200 g of latex Centex FA (60% w/w solid content equal to 120 g of solid, pH from 9 to 11, density 0.95 g/cm.sup.3) were mixed with 600 ml of water and stirred for 10 min. at 800 rpm to yield a (15% solid) suspension (B).

(93) The suspension A was added to the suspension B stirred at 800 rpm in 3 minutes, observing nearly immediate coagulation. This suspension (C) was maintained under stirring at 500 rpm for another 5 minutes.

(94) The coagulate was collected, washed with 4×300 ml of water and dried in an oven at 45° C. for 16 h, obtaining 236 g of composition MB6 (98.3% yield) with a fibre content equal to 99.7 phr determined by TGA.

(95) The quantities of the used reagents, the theoretical as well as the experimental values relative to the MB6, are reported in the following Table 6:

(96) TABLE-US-00006 TABLE 6 .sup.4Tot. 5fibres/ Theoretical Actual Yield .sup.6theoretical .sup.7actual .sup.3Tot. vol./ solid weight weight % fibres fibres .sup.1fibres .sup.2water vol. fibres w/w MB6 MB6 MB6 MB6 MB6 Ex. g g ml ml/g g/g g g % ww phr phr 6 120 2000 2800 23.3 1 240 236 98.3% 100 99.7 Key: Quantity of latex: 200 g; solid content of the latex: 120 g; .sup.1fibres: commercial Pangel B5; .sup.2quantity of water for suspending the fibres; .sup.3total volume of the final suspension obtained by mixing the suspension of the fibres with the latex; .sup.4ratio between the total volume of the suspension 3 and the fibre weight; .sup.5ratio between fibre weight and weight of solid contained in the latex; 6theoretical fibre content in the MB6; .sup.7actual fibre content in the MB6 determined by TGA

(97) As can be observed from the table values, by using a high ratio between fibres and solid contained in the latex (around 1:1) it was possible to obtain the MB6 with very high yields and with a fibre content in line with the theoretical.

EXAMPLE 7

Invention

(98) Preparation of MB7 Comprising Organically Modified Sepiolite Fibres (Pangel B5) (Pilot Scale on 30 Kg of Fibres) (Inverse Addition)

(99) 30 kg of organically modified sepiolite fibres (commercial Pangel B5-batch 2) were suspended in 500 kg of deionised water in a reactor and stirred for 40 min. at 800 rpm to yield a uniform suspension (A).

(100) 50 kg of latex Von Bundit HA (60% w/v solid content, equal to 30 Kg of solid, pH from 9 to 11, density 0.95 g/cm.sup.3) were diluted with 150 kg of water and stirred for 10 min. at 400 rpm to yield a suspension (B).

(101) 160 kg of suspension (B) were added in 10 minutes to the suspension (A) (inverse addition) maintained under stirring at 350 rpm. The stirring was then brought to 200 rpm and the remaining 40 Kg of suspension (B) were added in another 5 minutes. The suspension thus obtained (C) was maintained under stirring at 200 rpm for further 5 minutes, during which other 40 kg of water were added.

(102) The coagulate was filtered, washed with about 1000 kg of water and dried in an oven at 95° C. for 16 h, obtaining 59 kg of composition MB7 (98% yield) with a fibre content equal to 101.3 phr determined by TGA.

(103) The quantities of the used reagents, the theoretical as well as the experimental values relative to the MB7, are reported in the following Table 7:

(104) TABLE-US-00007 TABLE 7 .sup.4Tot. .sup.5fibres/ Theoretical Actual Yield .sup.6theoretical .sup.7actual .sup.3Tot. vol./ solid weight weight % fibres fibres .sup.1fibres .sup.2water vol. fibres w/w MB7 MB7 MB7 MB7 MB7 Ex. kg kg l l/kg Kg/Kg Kg Kg % ww phr phr 7 30 500 740 24.7 1 60 59 98% 100 101.3 Key: Quantity of latex: 50 Kg; solid content of the latex: 30 Kg; .sup.1fibres: commercial Pangel B5; .sup.2quantity of water for suspending the fibres; .sup.3total volume of the final suspension obtained by mixing the suspension of the fibres with the latex; .sup.4ratio between the total volume of the suspension 3 and the fibre weight; .sup.5ratio between fibre weight and weight of solid contained in the latex; .sup.6theoretical fibre content in the MB7; .sup.7actual fibre content in the MB7 determined by TGA.

(105) As can be observed from the table values, by using a high ratio between fibres and solid contained in the latex (around 1) it was possible to obtain—on industrial scale—the MB7 with very high yields and with a fibre content in line with the theoretical. This MB, unlike that obtained via direct addition, appeared particularly fine.

Thermogravimetric Analysis

(106) In the following Tables 8 and 9, the results of the thermogravimetric analyses are reported, such analyses respectively conducted on the fibres and on the compositions that incorporate them:

(107) TABLE-US-00008 TABLE 8 TGA Fibres residual % i) Pangel B5 modified with acid 75.67 ii) Pangel S9 (sepiolite) modified with acid 72.46 and silanised with TESPT iii) commercial Pangel B5 - batch 1 77.99 iv) commercial Pangel B5 - batch 2 76.50

(108) TABLE-US-00009 TABLE 9 Composition TGA Ex. (MB) Fibres residual % 3 MB3 i) 32.2 4 MB4 ii) 41.0 5 MB5 iii) 38.5 6 MB6 iv) 38.2 7 MB7 iv) 38.5

(109) The following summary Table 10 reports the important data relative to all the MB prepared according to the invention:

(110) TABLE-US-00010 TABLE 10 60% actual solid actual yield theoretical fibres fibres rubber latex weight % fibres MB in in fibres .sup.2water NR .sup.3water MB MB MB (TGA) 100 g 100 g Ex. fibres [g] [g] [g] [g] [g] [%] phr phr MB MB 3 i) 10 200   23.8  0   21.3 88% 70 74 42.5 57.5 4 ii) 10 200   12.8  0   16.8 95% 130 130.3 56.6 43.4 5 iii) 10 200   16.7  0   19.1 96% 100 97.5 49.4 50.6 6 iv) 120  2000  200  600 236 98% 100 99.7 49.9 50.1 7 iv) .sup.  30.sup. 4 .sup.  500.sup. 4 .sup.  50.sup. 4 .sup.  150.sup. 4 .sup.   59.sup. 4 98% 100 101.3 50.3 49.7 .sup.2water for suspending the fibres; .sup.3water for diluting the latex; .sup.4 expressed in Kg

EXAMPLE 8

(111) Preparation of Elastomeric Compositions for Tyres Comprising MB7 (Invention) or the Same Fibres Directly Incorporated in the Elastomers in Dry Powder Form (Comparative)

(112) Specimens of vulcanised elastomeric materials were prepared in order to evaluate if the incorporation of the reinforcing fibres of the new MB of the invention involved a variation of the final properties of the materials themselves.

(113) For such purpose, two elastomeric compositions were prepared for anti-abrasive elongated elements (8A invention and 8B comparative) with the ingredients reported in the following Table 11:

(114) TABLE-US-00011 TABLE 11 Ex. 8A Ex. 8B Components (phr) (Inv.) (Comp.) NR 54 70 BR 30 30 MB7 Ex. 7 (PangelB5) 32 — Stearic acid 2 2 TESPT Silane 1 1 ZNO 3 3 6-PPD 2.4 2.4 CB 45 45 PANGEL B5 — 16 TBBS 1.4 1.4 PVI 0.3 0.3 Sulphur 2.76 2.76 in which NR: Natural rubber with controlled viscosity CV 60 provided by Von Bundit (Thailand). BR(Nd): neodymium high-cis polybutadiene (Europrene 40 Versalis) TESPT Silane: Bis[3-(triethoxysilyl)propyl]Tetrasulphide on carbon black; CB: carbon black; Zeosil 1115 MP: precipitated synthetic amorphous silica (Rhodia); Pangel B5: organo-modified sepiolite by Tolsa; ZnO: zinc oxide; 6-PPD: N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine; TBBS: N-tert-butyl-2-benzothiazyl sulfenamide. Sulphur: S8 (soluble sulphur) by Zolfo industria.

(115) MB7 is the composition prepared in Ex. 7; the 32 phr of MB7 comprise about 16 phr of fibres and 16 phr of rubber.

(116) The elastomeric materials were prepared according to this general procedure:

(117) The elastomers were loaded in an internal mixer (Brabender or Banbury)

(118) The Pangel B5 fibres or the MB7 were added into the mixer and mixed for about 5 minutes.

(119) Then the stearic acid, the 6PPD and the ZnO were added, continuing the mixing. As soon as the temperature reached 145° C.±5° C., the elastomeric material was unloaded.

(120) The material from the preceding step was then inserted in an internal mixer (Brabender or Banbury), the vulcanising system was added and the mixing was carried out at 90° C. for 3 minutes. The vulcanisable composition was then unloaded and cooled under air.

EXAMPLE 9

(121) Preparation of Elastomeric Compositions for Tyres Comprising MB7 (Invention) or the to Same Fibres Directly Incorporated in the Elastomers in Dry Powder Form (Comparative)

(122) Specimens of vulcanised elastomeric materials were prepared in order to evaluate if the incorporation of the reinforcing fibres in the new MB of the invention involved a variation of the final properties of the materials themselves.

(123) For such purpose, two elastomeric compositions for internal sidewall (9A invention and 9B comparative) were prepared with the ingredients reported in the following Table 12:

(124) TABLE-US-00012 TABLE 12 Components (phr) Ex. 9A (Inv) Ex. 9B (Comp.) NR 31.5 40 BR 60 60 MB7 17 — Pangel B5 modified with — 8.5 acid (i) CB N550 25 25 ZEOSIL 1115 MP 20 20 Stearic acid 1 1 TESPT Silane 5 5 ZnO 4 4 6-PPD 1.5 1.5 TBBS 80 4 4 TMQ 1 1 Sulphur 2.3 2.3 in which: NR: Natural rubber with controlled viscosity CV 60 provided by Von Bundit (Thailand), BR(Nd): neodymium high-cis polybutadiene (Europrene 40 Versalis); silane: 50% TESPT: Bis[3-(triethoxysilyl)propyl]Tetrasulphide on carbon black; CB: carbon black; Zeosil 1115 MP: precipitated synthetic amorphous silica (Rhodia); ZnO: zinc oxide; TMQ: polymerised 2,2,4-trimethyl-1,2-dihydroquinoline; 6-PPD: N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine; TBBS: N-tert-butyl-2-benzothiazyl sulfenamide; Sulphur: S8 (soluble sulphur) by Zolfo industria

(125) MB7 is the composition prepared in Ex. 7; the 17 phr of MB7 comprise about 8.5 phr of fibres and 8.5 phr of rubber)

Evaluation of the Properties of the Elastomeric Materials

(126) Properties of the Non-Vulcanised Materials

(127) The vulcanisable elastomeric materials (green) of Examples 8a, 8b, 9a and 9b were subjected to the following evaluations:

(128) Rheometric analysis MDR (according to the standard ISO 6502): a rheometer Alpha Technologies of type MDR2000 was used. The tests were carried out at 170° C. for 20 minutes, at an oscillation frequency of 1.66 Hz (100 oscillations minute) and an oscillation amplitude of ±0.5°, measuring the time necessary for attaining an increase of two rheometric units (TS2) and the time necessary for reaching respectively 60% (T60), and 90% (T90) of the final torque value (Mf). The value of maximum torque MH and the value of minimum torque ML were measured.

(129) Mooney ML (1+4) viscosity at 100° C.: was measured, according to the standard ISO 289-1:2005

(130) Properties of the Vulcanised Materials

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

(132) The vulcanisation, if not 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.

(133) The static mechanical properties were measured at 23° C. according to the standard ISO 37:2005.

(134) In particular the load at different elongation levels (50%,100% and 300%, termed CA0.5, CA1 and CA3) and the rupture load CR were measured on specimens of the abovementioned elastomeric materials.

(135) The tensile tests were carried out on specimens with rectilinear axis of Dumbbell type.

(136) The dynamic mechanical properties were measured by using a dynamic device, Instron, in compression-tensile mode according to the following methods.

(137) A vulcanised specimen of the elastomeric materials of Examples 8a and 8b having a cylindrical shape (length=25 mm; diameter=14 mm), subjected to pre-load compression up to 25% of the longitudinal deformation in relation to the initial length and maintained at the predetermined temperature (equal to −10° C., 0° C., +23° C. or +70° C.) for the entire duration of the test, was subjected to a dynamic sinusoidal tension having an amplitude of ±3.5% in relation to the length under pre-load, with a frequency of 100 Hz.

(138) The dynamic shear mechanical properties were evaluated for the specimens of Examples 8a and 8b by using a rheometer Monsanto R.P.A. 2000 according to the to following method: cylindrical test specimens with weights from 4.5 g to 5.5 g were obtained by means of punching from the vulcanisable elastomeric composition under examination.

(139) These specimens were vulcanised in the instrument “RPA” at 170° C. for 10 minutes or 15 minutes depending on the kinetics of vulcanisation, and they were subjected to the measurement of the dynamic shear elastic modulus (G′) at 70° C., frequency 10 Hz, deformation between 0.1% and 10%, and of Tan delta (hysteresis or dissipation factor), calculated as the ratio between the viscous modulus (G″) and the elastic modulus (G′) measured in the same conditions (70° C., 10 Hz).

(140) The Payne effect was evaluated in absolute terms through the difference between the moduli (G′) at 10% and at 0.5%, and in relative terms such as the percentage variation between 10% and 0.5% in relation to the modulus value G′ at 9%.

(141) The following Tables 13 and 14 report the results of the above-described analyses conducted on those specimens.

(142) TABLE-US-00013 TABLE 13 Ex. 8a (Inv.) Ex. 8b (Comp.) Properties of green materials (MDR) Viscosity ML 100° C. 70 68 ML [dN m] 2.27 2.04 MH [dN m] 24.20 24.59 Properties of vulcanised materials CA0.5 [MPa] 3.65 3.85 CA1 [MPa] 7.22 7.41 CA3 [MPa] 19.32 19.21 CR [MPa] 20.2 20.4 AR [%] 318.7 316.3 E′ 23° C. 10 Hz [MPa] 12.74 13.31 E′ 70° C. 10 Hz [MPa] 10.55 10.89 Tan Delta 23° C. 10Hz 0.174 0.167 Tan Delta 70° C. 10 Hz 0.127 0.119 RPA 10′/170° C. G′ 70° C. (9%) [MPa] 1.77 1.70 Tan Delta 70° C. (9%) 0.204 0.208 dG′ (0.5-10) [MPa] 3.2 3.0

(143) TABLE-US-00014 TABLE 14 Ex. 9a (Inv.) Ex. 9b (Comp.) Properties of green materials (MDR) Viscosity ML 100° C. 72 73 ML [dN m] 2.34 2.36 MH [dN m] 27.59 27.71 Properties of vulcanised materials CA1 [MPa] 2.68 2.46 CA3 [MPa] 6.05 5.47 CR [MPa] 10.31 8.56 AR [%] 165.3 153.5 RPA 10′/170° C. G′ 70° C. (9%) [MPa] 1.75 1.71 Tan Delta 70° C. (9%) 0.088 0.082 dG′ (0.5-10) [MPa] 1.0 0.9

(144) As can be reserved from the data reported in tables 13 and 14, the properties of the materials—whether green or vulcanised—are substantially comparable.

(145) Upon optical microscope observation of specimens of the compositions of Ex. 9A and 9B—compositions comprising both carbon black (N550) and white fillers (silica and modified fibres), the latter introduced as MB or in powder form, respectively—the fillers appeared dispersed in the elastomeric material in a comparable manner.

(146) Therefore, the master compositions (MB) of the invention can be used for incorporating the reinforcing fibres in the elastomeric compositions for tyres without altering the performances thereof but with undoubted advantages regarding the handling of the powders.

(147) Indeed, the preparation of the master compositions via incorporation of the fibres in the lattices according to the invention advantageously allows minimising their dispersion in the environment, unlike what occurs in the conventional approach of introduction of the powders during the standard mixing with solid rubbers in a Banbury mixer or in an extruder.

(148) In the process according to the invention, materials can in fact be used in the form of non-powdery wet cakes, coming from the preparation or derivatisation in aqueous environment of the fibres themselves, also eliminating the high energy step of drying. In addition, even using dried powders, in the present process it is possible to advantageously employ specific measures for reducing the powders, such as the water nebulisation, measures that are not applicable to the conventional procedures of powder mixing with solid rubber, carried out in mixers of Banbury type or in an extruder.