阅读说明：本技术 含复合增强填料的车轮用轮胎 (Tyre for vehicle wheels containing composite reinforcing filler ) 是由 L·喀斯特拉尼 L·祖亚 S·D·阿里 M·奥兰迪 T·汉尼尔 于 2018-09-12 设计创作，主要内容包括：本发明涉及用于车轮的轮胎(100),其包括至少一种结构元件,所述结构元件包括通过使可硫化弹性体组合物硫化而获得的硫化弹性体材料,所述可硫化弹性体组合物包括至少一种可硫化二烯烃弹性体聚合物和至少一种复合增强填料,含该复合增强填料的轮胎(100)的生产方法,含该复合增强填料的母炼胶及其生产方法,以及生产复合增强填料的方法。(The present invention relates to a tyre (100) for vehicle wheels comprising at least one structural element comprising a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising at least one vulcanizable diene elastomeric polymer and at least one composite reinforcing filler, a process for producing a tyre (100) comprising such a composite reinforcing filler, a masterbatch comprising such a composite reinforcing filler and a process for producing the same, and a process for producing a composite reinforcing filler.)

1. Tyre (100) for vehicle wheels comprising at least one structural element comprising a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising:

(a) at least one vulcanizable diene elastomeric polymer;

(b) at least one composite reinforcing filler comprising a core comprising nanocrystalline cellulose and an at least partial coating comprising silica.

2. The tire (100) of claim 1, wherein the composite reinforcing filler (b) has a core-shell structure comprising a core comprising nanocrystalline cellulose and a shell comprising silica.

3. Tyre (100) according to claim 1 or 2, wherein the composite reinforcing filler (b) has a diameter ranging from 10nm to 60nm and a length ranging from 100nm to 1000 nm.

4. Tyre (100) according to any one of claims 1 to 3, wherein the composite reinforcing filler (b) has a crystallinity ranging from 10% to 80%.

5. Tyre (100) according to any one of claims 1 to 4, wherein the density of the composite reinforcing filler (b) ranges from 1.5 to 1.9.

6. Tyre (100) according to any one of claims 1 to 5, wherein the composite reinforcing filler (b) has a BET total surface area ranging from 20 to 400m²/g。

7. Tyre (100) according to any one of claims 1 to 6, wherein the composite reinforcing filler (b) comprises from 20 to 80% by weight of silica, with respect to the total weight of the composite reinforcing filler (b).

8. Tyre (100) according to any one of claims 1 to 7, wherein the vulcanizable elastomeric composition comprises from 0.1 to 40phr of composite reinforcing filler (b) with respect to 100phr of vulcanizable diene elastomeric polymer (a).

9. Tyre (100) according to any one of claims 1 to 8, wherein the structural elements are selected from the group consisting of a crown (109), a carcass structure, a belt structure (106), an underlayer (111), a wear-resistant flipper (105), a sidewall (108), a sidewall insert, a mini-sidewall (110), a flipper (120), a chafer (121), an underlayer, a rubber layer, a bead filler (104) and a rubber sheet.

10. Process for producing a tyre (100) for vehicle wheels, wherein the process comprises:

-providing a vulcanizable elastomeric composition comprising:

(a) at least one vulcanizable diene elastomeric polymer;

(b) at least one composite reinforcing filler comprising a core comprising nanocrystalline cellulose and an at least partial coating comprising silica;

-providing a structural element of a tyre comprising a vulcanizable elastomeric composition;

-assembling the tyre structural elements into a green tyre;

-vulcanizing the green tyre.

11. The method of claim 10, wherein providing the vulcanizable elastomeric composition comprises:

-feeding at least the following components to at least one mixing device comprising at least one discontinuous mixer and/or at least one continuous mixer;

o a vulcanizable diene elastomeric polymer (a),

o a composite reinforcing filler (b);

-mixing and dispersing said components so as to obtain said vulcanizable elastomeric composition;

-discharging said vulcanizable elastomeric composition from said mixing device.

12. The method of claim 11, wherein the composite reinforcing filler (b) is fed to the at least one discontinuous mixer and/or the at least one continuous mixer in the form of a masterbatch comprising:

-at least one vulcanizable diene elastomeric polymer (a);

-a composite reinforcing filler (b).

13. A masterbatch, comprising:

(a) at least one vulcanizable diene elastomeric polymer;

(b) at least one composite reinforcing filler comprising a core comprising nanocrystalline cellulose and an at least partial coating comprising silica.

14. A masterbatch as claimed in claim 13 wherein the composite reinforcing filler (b) is as defined in any one of claims 2 to 7.

15. A masterbatch according to claim 13 or 14, comprising from 5 to 120phr of the composite reinforcing filler (b), with respect to 100phr of the vulcanizable diene elastomeric polymer (a).

16. A method of producing a masterbatch, the masterbatch comprising:

(a) at least one vulcanizable diene elastomeric polymer;

(b) at least one composite reinforcing filler comprising a core comprising nanocrystalline cellulose and an at least partial coating comprising silica;

wherein the method comprises the following steps:

I. providing an aqueous dispersion of a composite reinforcing filler (b);

adding the aqueous dispersion of step I to the latex containing the vulcanizable diene elastomeric polymer (a) by mixing;

coagulating the latex from step II so as to obtain a coagulated product containing the composite reinforcing filler (b);

purifying the coagulated product from step III.

17. The method of claim 16, wherein purifying the agglomerated product comprises at least one operation selected from the group consisting of filtration, washing, centrifugation, drying, and lyophilization.

18. A method of producing a composite reinforcing filler, wherein the method comprises:

(A) dispersing nanocrystalline cellulose in an aqueous dispersion medium in the presence of at least one surfactant selected from the group consisting of cationic surfactants and amphoteric surfactants at a temperature in the range of 70 to 90 ℃ so as to obtain an aqueous dispersion containing nanocrystalline cellulose;

(B) adding at least one precursor compound of silica to the aqueous dispersion from step (a);

(C) depositing an at least partial coating on the nanocrystalline cellulose by hydrolysis of a silica precursor compound, so as to obtain a composite reinforcing filler comprising a core comprising the nanocrystalline cellulose and the at least partial coating comprising silica;

(D) purifying the composite reinforcing filler from step (C).

19. The method of claim 18, wherein the surfactant is selected from the group consisting of benzalkonium chloride, cetrimide, cetyltrimethylammonium bromide, undecylamidopropyl trimethylammonium metasulfate, and cocoalkyltrimethylammonium metasulfate.

20. The method according to claim 18 or 19, wherein the surfactant is added in an amount ranging from 10 to 20 wt% with respect to the weight of the nanocrystalline cellulose.

21. The method of any one of claims 18-20, wherein the silica precursor compound is selected from the group consisting of:

I. an alkali metal silicate of the formula:

M₂O·n SiO₂(I)

where M ═ Na, K, L i, and where n ranges from 0.5 to 4, preferably n ═ 0.5 or 1 or 3 and M ═ Na or K,

a tetraalkyl derivative of silicic acid of the formula:

(RO)₄Si (II)

wherein the R groups, equal to or different from each other, represent C₁-C₆An alkyl group, a carboxyl group,

halosilanes of the formula:

SiX₄or (RO)₃SiX OR (RO)₂SiX₂Or (RO) SiX₃(III)

Wherein the R groups, equal to or different from each other, represent C₁-C₆Alkyl, and X, equal to or different from each other, are selected from the group consisting of chlorine, bromine, and iodine.

22. The method of claim 21, wherein the silica precursor compound is an alkali metal silicate (I).

23. The method of claim 22, wherein in step (B), the adding is performed while maintaining the aqueous dispersion in an alkaline medium and at a temperature in the range of 70 to 90 ℃.

24. The process of claim 22 or 23, wherein the amount of alkali metal silicate ranges from 50 to 150 wt.%, relative to the weight of nanocrystalline cellulose.

25. The process of any one of claims 22 to 24, wherein step (B) further comprises adding at least one acid selected from the group consisting of hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid, acetic acid, carbonic acid.

26. The method of any one of claims 22 to 25, wherein step (B) comprises:

(B1) adding at least one first portion of alkali metal silicate (I) to the aqueous dispersion from step (a), wherein the addition is carried out while maintaining the aqueous dispersion at a pH in the range of 8.5 to 9.5;

(B2) stirring the aqueous dispersion from step (B1) for a time ranging from 80 to 100 minutes;

(B3) adding at least one second portion of alkali metal silicate (I) to the aqueous dispersion from step (B2), wherein the addition is performed while maintaining the aqueous dispersion at a pH range of 7 to 8.

27. The process according to any one of claims 22 to 26, wherein step (C) of depositing an at least partial coating on the nanocrystalline cellulose comprises subjecting the aqueous dispersion from step (B) to an acidic medium so as to hydrolyze the alkali metal silicate (I) and obtain a composite reinforcing filler comprising a core comprising the nanocrystalline cellulose and an at least partial coating comprising silica.

28. The process of any one of claims 22-27, wherein step (C) comprises adding at least one acid selected from the group consisting of hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid, acetic acid, carbonic acid.

29. The method of any one of claims 18-28, wherein purifying the composite reinforcing filler comprises at least one operation selected from filtering, washing, centrifuging, drying, lyophilizing, or any combination thereof.

30. The process of any of claims 18 to 29, wherein the composite reinforcing filler from step (C) is as defined in any of claims 2 to 7.

Technical Field

The present invention relates to a new type of tyre for vehicle wheels comprising a reinforcing filler from renewable composite resources, characterized by good mechanical and rolling resistance properties, greater efficiency and lower weight.

In particular, the present invention relates to a tyre for vehicle wheels comprising at least one structural element comprising a vulcanised elastomeric material obtained by vulcanisation of a vulcanisable elastomeric composition comprising at least one vulcanisable diene elastomeric polymer and at least one composite reinforcing filler. The invention further relates to a method for producing a tyre containing a composite reinforcing filler, a master batch (masterbatch) containing a composite reinforcing filler and a method for producing the same, and a method for producing the composite reinforcing filler.

Prior Art

In the rubber industry, and more particularly in the tyre industry, it is known to add reinforcing fillers to elastomeric compositions in order to improve the mechanical properties and the wear resistance of the elastomeric materials obtained from them by vulcanization.

Carbon black is the most widely used filler, thanks to its high reinforcing power. However, carbon black imparts outstanding hysteresis to the manufactured article, i.e. it increases the amount of heat dissipated under dynamic conditions. In tires, this leads to an undesirable increase in rolling resistance and overall to greater fuel consumption and the production of more polluting emissions.

Most vehicle manufacturers are now increasingly demanding their suppliers to develop tires with low rolling resistance to reduce fuel consumption.

Improvements in this sense are achieved by using so-called "white" reinforcing fillers, such as gypsum, talc, kaolin, bentonite, titanium dioxide, and in particular silica, fillers which can partially or completely replace carbon black in elastomeric materials and impart them with less hysteresis while maintaining sufficient reinforcing action.

However, the use of silica as reinforcing filler for elastomeric compositions has various limitations.

One of the most significant drawbacks is the poor processability of the non-crosslinked silica-containing compositions, which is mainly caused by excessive viscosity.

Furthermore, when finely dispersed within the elastomeric polymer base, the silica particles have a strong tendency to aggregate and form aggregates. Therefore, in order to obtain a good dispersion of the silica in the elastomeric polymer base, a strong and long-term thermo-mechanical-processing of the composition is required.

In addition to this, the average density relative to a common elastomer (about 1 g/cm)³) The silica-based reinforcing fillers have a significantly higher density value (about 2 g/cm)³) And thus their use results in an increase in the density of the compositions in which they are used. The use of high density elastomeric compositions results in the manufacture of heavier tires and this can have a negative impact on their efficiency.

Recently, in order to replace partially or totally silica-based fillers, it has been proposed to use reinforcing fillers also surface-modified, derived from renewable resources based on cellulose fibers, in particular nanocrystalline cellulose fibers.

For example, S.H.xu et al, eXPRESS Polymer L etters, Vol.6, No. 1, No. 2012, 14-25, describe nanocrystalline cellulose modified with 3-aminopropyltriethoxysilane (KH 550. the modified crystalline cellulose was tested as a partial substitute for silica by coagulation in natural rubber composites.

Summary of The Invention

The applicant has observed that the solutions proposed in the prior art for using reinforcing fillers based on nanocrystalline cellulose fibers in elastomeric compositions have some technical and functional limitations.

In particular, the applicant has observed that the high hydrophilicity of the nanocrystalline cellulose fibers makes the dispersion thereof in the elastomeric matrix problematic even with coupling agents, such as sulfur-containing silane-based coupling agents (for example bis (3-ethoxysilyl-propyl tetrasulfide or TESPT). The strong and long-term thermomechanical processing of the composition itself, which may deteriorate the properties of the elastomer, is in any case necessary in order to obtain a homogeneous dispersion of the cellulose fibers in the elastomeric polymer base.

The applicant has further observed that fillers based on nanocrystalline cellulose fibers can exhibit a reinforcing effect overall lower than that of silica-based reinforcing fillers, even if the functionalization reaction is carried out or even if assisted by a coupling agent.

The applicant has therefore tackled the problem of identifying a new class of reinforcing fillers for elastomeric compositions which reduce and/or overcome the aforementioned drawbacks.

More particularly, the applicant has tackled the problem of identifying a reinforcing filler derived from raw materials of renewable origin, which is simple to manufacture and use and which, by reducing the weight of the tyre and by reducing the production costs, is capable of imparting to the tyre for vehicle wheels greater efficacy as well as good mechanical, rolling resistance properties.

In accordance with the present invention, the applicant has surprisingly found that these desired characteristics can be achieved by using a composite reinforcing filler comprising a core and an at least partial coating in a vulcanizable elastomeric composition for producing structural elements of tyres for vehicle wheels, and by manufacturing said composite reinforcing filler by means of a new process which makes it possible to produce an at least partial coating comprising silica around a core comprising crystalline cellulose, wherein said core comprises nanocrystalline cellulose and said at least partial coating comprises silica.

Accordingly, in a first aspect thereof, the present invention relates to a tyre for vehicle wheels comprising at least one structural element comprising a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising:

(a) at least one vulcanizable diene elastomeric polymer;

(b) at least one composite reinforcing filler comprising a core comprising nanocrystalline cellulose and an at least partial coating comprising silica.

The applicant has found that thanks to the use of a composite reinforcing filler structured in this way, it is thus possible to obtain a tyre which, with respect to the prior art, exhibits a series of good advantageous technical effects, including:

good mechanical and rolling resistance properties obtained by virtue of the reinforcing effect of the composite reinforcing filler. In particular, the applicant has found that the composite reinforcing filler according to the invention confers to the elastomeric material of the tyre in which it is used the unexpected properties of reinforcing said material in an overall better way with respect to conventional silica-based fillers. This allows the use of lower amounts of reinforcing filler to achieve properties similar to those obtainable with silica-based fillers;

lower weight with respect to a similar tire obtained with a silica-based reinforcing filler. In particular, the applicant has found that thanks to the lower density of the composite reinforcing filler according to the invention with respect to silica, this composite reinforcing filler allows to manufacture elastomeric materials of lower density and consequently lighter tyres, giving the latter greater efficacy;

the greater reinforcing effect of the composite reinforcing filler according to the invention, greater than that achieved by silica-based fillers, allows the use of a greater amount of reinforcing filler to achieve good mechanical and rolling resistance properties;

the manufacturing process of the tyre according to the invention is compatible with the tyre production processes of the prior art. The composite reinforcing filler according to the invention in fact demonstrates a relative ease of dispersion in the elastomeric composition with respect to the nanocrystalline cellulose fiber filler, making it possible to advantageously achieve its incorporation into the elastomeric material to be reinforced without requiring lengthy and intensive thermo-mechanical processing and/or employing complex additional processing steps;

the higher vulcanization kinetics of the compositions comprising the composite reinforcing filler of the invention, with respect to compositions comprising silica-based filler, lead to a greater productivity of the tyre production process. Higher vulcanization kinetics are in fact advantageous for obtaining high productivity in the process for manufacturing vulcanized elastomeric materials, thus reducing the production costs of the tyre;

the possibility of manufacturing tyres with good mechanical and rolling resistance properties comprising reinforcing fillers derived from renewable resources, which meet the requirements of using raw materials that do not sacrifice the next generation of natural resources.

Thanks to the technical effects outlined above, the tyre according to the invention is endowed with good mechanical and rolling resistance properties, lower weight and greater efficacy and lower production costs.

Within the framework of the present description and of the subsequent claims, the expression "nanocrystalline cellulose" is used to denote highly crystalline cellulose in the form of fibers having a size range, typically 5 to 30nm in diameter and 100 to 1000nm in length with acicular morphology. Nanocrystalline cellulose is typically obtained by means of an acid hydrolysis treatment of cellulose fibres, known to those skilled in the art, which treatment is intended to remove amorphous parts from the cellulose, leaving on the other hand crystalline parts that are substantially unchanged, and therefore present in greater quantities with respect to the starting cellulose at the end of the treatment.

Preferably, the nanocrystalline cellulose has a crystallinity of greater than 40%, more preferably greater than 50%, even more preferably greater than 60%, and still more preferably in the range of 70% to 95%.

For the purposes of the present invention, the crystallinity of the nanocrystalline cellulose and of the composite reinforcing filler (b) can advantageously be measured by means of X-ray diffraction using, for example, an XPert Pro Panalytical diffractometer set at 40kV and 40mA of Cu K α radiation and calculating the crystallinity by means of the following equation:

wherein:

cs is the degree of crystallinity (%),

I₀₀₂is the intensity of the planar (002) diffraction peak, and

I_amis the minimum intensity near the diffraction angle at 18.58 degrees.

In view of the above-described morphological characteristics of the nanocrystalline cellulose forming the core of the composite reinforcing filler of the invention, it is therefore essentially an anisotropic composite reinforcing filler.

Within the framework of the present description and of the subsequent claims, the expression "elastomeric polymer" or "elastomer" is used to denote a natural or synthetic polymer which, after vulcanization, can be repeatedly stretched at room temperature to at least twice its initial length and which recovers immediately after removal of the tensile load and under the action of an external force to its approximate initial length (as defined according to ASTM, the E8 committee, philadelphia 1976).

Within the framework of the present description and of the subsequent claims, the expression "diene polymer" is used to indicate a polymer or copolymer derived from the polymerization of one or more different monomers, at least one of which is a conjugated diene (conjugated diene).

In a second aspect thereof, the present invention relates to a process for producing tyres for vehicle wheels, wherein the process comprises:

-providing a vulcanizable elastomeric composition comprising:

(a) at least one vulcanizable diene elastomeric polymer;

(b) at least one composite reinforcing filler comprising a core comprising nanocrystalline cellulose and an at least partial coating comprising silica;

-providing a structural tyre component comprising a vulcanisable elastomeric composition;

-assembling the structural tyre elements in a green tyre;

-vulcanizing the green tyre.

Thanks to the dispersibility and handleability of the composite reinforcing filler, the process for producing the tyre according to the invention incorporating the filler can be easily carried out on a conventional production line, which, as mentioned above, contributes to reducing the production costs.

Within the framework of the present description and of the subsequent claims, the term "green" is used to indicate a material, a composition, a component or a tyre that has not yet been vulcanized.

In a third aspect of the present invention, the present invention relates to a masterbatch comprising:

(a) at least one vulcanizable diene elastomeric polymer;

(b) at least one composite reinforcing filler comprising a core comprising nanocrystalline cellulose and an at least partial coating comprising silica.

The composite reinforcing filler may be advantageously used in the manufacture of masterbatches, thanks to its dispersibility and handleability, which facilitate its storage, transport and metering during use, and further facilitate the dispersion of the filler within the elastomeric composition, thus contributing to an improvement in its reinforcing effect.

Within the framework of the present description and of the subsequent claims, the term "masterbatch" is used to indicate a polymer compound in which the additives (in the present case, the composite reinforcing filler) are dispersed and diluted in the polymer matrix, so as to be more easily metered in the subsequent processing steps.

In a fourth aspect of the invention, the invention relates to a method of producing a masterbatch, the masterbatch comprising:

(a) at least one vulcanizable diene elastomeric polymer;

(b) at least one composite reinforcing filler comprising a core comprising nanocrystalline cellulose and an at least partial coating comprising silica;

wherein the method comprises the following steps:

I. providing an aqueous dispersion of a composite reinforcing filler (b);

adding the aqueous dispersion of step i. to the latex containing the vulcanizable diene elastomeric polymer (a) by mixing;

coagulating the latex from step ii so as to obtain a coagulated product containing the composite reinforcing filler (b);

purifying the coagulated product from step III.

The dispersibility and processability of the composite reinforcing filler allow it to be easily and simply dispersed within the polymeric matrix to form a masterbatch which facilitates the storage, transport and metering of the composite reinforcing filler itself and further facilitates its dispersion within the elastomeric composition, thus facilitating its improvement in the reinforcing effect.

In a fifth aspect of the invention, the invention relates to a method of producing a composite reinforcing filler, wherein the method comprises:

(A) dispersing nanocrystalline cellulose in an aqueous dispersion medium in the presence of at least one surfactant selected from a cationic surfactant and an amphoteric surfactant at a temperature in the range of 70 to 90 ℃ to obtain an aqueous dispersion containing nanocrystalline cellulose;

(B) adding at least one precursor compound of silica to the aqueous dispersion from step (a);

(C) depositing an at least partial coating of silica on the nanocrystalline cellulose by hydrolysis of a precursor compound of silica so as to obtain a composite reinforcing filler comprising a core and an at least partial coating, the core comprising the nanocrystalline cellulose and the at least partial coating comprising silica;

(D) purifying the composite reinforcing filler from step (C).

In fact, the applicant has found that it is possible to provide aqueous dispersions containing nanocrystalline cellulose which are particularly stable and capable of promoting the deposition of a silica coating on nanocrystalline cellulose from a silica precursor compound, thanks to the addition of at least one cationic and/or amphoteric surfactant.

In this way, the nanocrystalline cellulose acts as a "template" for the silica and helps to obtain the anisotropic composite reinforcing filler of the present invention.

Within the framework of the present description and the subsequent claims, all numerical entities expressing quantities, parameters, percentages and so forth shall be considered in all cases as having the prefix term "about", unless otherwise indicated. Moreover, all ranges of numerical entities include all possible combinations of the maximum and minimum numerical values, and all possible intermediate ranges, except those specifically noted herein below.

Within the framework of the present description and of the subsequent claims, the term "phr" (synonym for parts of rubber 100) denotes the parts by weight of the specified components in the elastomeric compound, with the possible exclusion of plasticizing extender oil, per 100 parts by weight of elastomeric polymer.

All percentages are expressed as weight percentages unless otherwise indicated.

In one or more of the foregoing aspects of the invention, the invention has one or more of the preferred features set forth below, which can be combined as desired depending upon the requirements of the application.

The vulcanizable elastomeric composition of the present invention comprises 100phr of at least one vulcanizable diene elastomeric polymer (a).

Preferably, the vulcanizable diene elastomeric polymer (a) usable in the present invention may be chosen from those crosslinkable with sulfur which are particularly suitable for the manufacture of tyres commonly used in elastomeric materials, in other words from elastomeric polymers or copolymers having unsaturated chains with a glass transition temperature (Tg) generally lower than 20 ℃, preferably comprised in the range from 0 ℃ to-110 ℃. These polymers or copolymers may be of natural origin or may be obtained by polymerization in solution, in emulsion or in the gas phase of one or more conjugated dienes possibly mixed with at least one comonomer selected from monovinylarenes and/or polar comonomers in an amount of not more than 60% by weight.

The conjugated diolefins generally contain from 4 to 12, preferably from 4 to 8, carbon atoms and may be selected, for example, from: 1, 3-butadiene, isoprene, 2, 3-dimethyl-1, 3-butadiene, 1, 3-pentadiene, 1, 3-hexadiene, 3-butyl-1, 3-octadiene, 2-phenyl-1, 3-butadiene or mixtures thereof.

1, 3-butadiene and isoprene are particularly preferred.

Monovinylarenes possibly usable as comonomers usually contain from 8 to 20, preferably from 8 to 12, carbon atoms and can be selected, for example, from styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, various alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl derivatives of styrene, such as α -methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4- (4-phenylbutyl) styrene or mixtures thereof, styrene being particularly preferred.

Possibly usable polar comonomers may be selected, for example, from: vinylpyridines, vinylquinolines, esters of acrylic acid and alkyl acrylic acid, nitriles, or mixtures thereof, for example methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile or mixtures thereof.

Preferably, the vulcanizable diene elastomeric polymers (a) usable in the present invention may be chosen, for example, from: cis-1, 4-polyisoprene (natural or synthetic, preferably natural rubber), 3, 4-polyisoprene, polybutadiene (especially polybutadiene with a high 1, 4-cis content), possibly halogenated isoprene/isobutylene copolymers; 1, 3-butadiene/acrylonitrile copolymers, styrene/1, 3-butadiene copolymers, styrene/isoprene/1, 3-butadiene copolymers, styrene/1, 3-butadiene/acrylonitrile copolymers, or mixtures thereof.

According to a preferred embodiment, said vulcanizable elastomeric composition comprises at least 10 wt%, preferably from 20 wt% to 100 wt% of natural rubber, with respect to the total weight of said at least one diene elastomeric polymer (a).

The aforesaid vulcanizable elastomeric composition may optionally comprise at least one elastomeric polymer (a') of one or more monoolefins, which may be chosen from ethylene and α -olefins generally containing from 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene or mixtures thereof, with ethylenic comonomers or derivatives thereof, preferably copolymers of ethylene and α -olefins, optionally with dienes, isobutylene homopolymers or copolymers thereof with small amounts of dienes, which are optionally at least partially halogenated, optionally dienes generally containing from 4 to 20 carbon atoms and preferably chosen from 1, 3-butadiene, isoprene, 1, 4-hexadiene, 1, 4-cyclohexadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, vinyl norbornene or mixtures thereof, among these, particularly preferably copolymers of ethylene/propylene (EPR) or ethylene/propylene/EPDM, polyisobutylenes, butyl rubbers, especially halobutyl rubbers or bromobutyl rubbers, or chlorobutyl rubbers, or mixtures thereof.

It is also possible to use diene elastomeric polymers (a) or elastomeric polymers (a') functionalized by reaction with suitable blocking or coupling agents. In particular, diene elastomeric polymers obtained by anionic polymerization in the presence of organometallic initiators, in particular organolithium initiators, can be functionalized by reacting the residual organometallic groups derived from the initiator with suitable end-capping or coupling agents, such as imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes or aryloxysilanes.

The vulcanizable elastomeric composition comprises at least one composite reinforcing filler (b) comprising a core comprising and preferably consisting of nanocrystalline cellulose and at least a coating comprising and preferably consisting of silica.

Thus, the composite reinforcing filler (b) is obtained by coupling together different materials so as to exploit synergistically its properties and comprises an inner portion or core comprising nanocrystalline cellulose, and an outer portion or coating comprising silica. The coating may be present on a part of or advantageously on the entire outer surface of the core, in which case a shell is formed surrounding it. An example of a composite material having a similar structure in which the coating layer covers the entire core is referred to as a composite material having a core-shell structure.

Preferably, the composite reinforcing filler (b) has a core-shell structure comprising a core comprising nanocrystalline cellulose and a shell comprising silica.

Preferably, the composite reinforcing filler (b) has a diameter of 10nm to 60nm and a length in the range of 100nm to 1000 nm.

Preferably, the diameter and length of the composite reinforcing filler (b) are evaluated by means of microscopic observation, advantageously by means of electron scanning microscopy, preferably on at least 100 particles of composite reinforcing filler (b).

Preferably, the crystallinity of the composite reinforcing filler (b) ranges from 10% to 80%, more preferably from 25% to 80%, even more preferably from 35% to 75%, as a function of the weight ratio of nanocrystalline cellulose and silica.

As outlined above, in fact, despite the high degree of crystallinity that nanocrystalline cellulose typically has, the silica in the coating of the composite reinforcing filler is substantially amorphous.

The crystallinity of the composite reinforcing filler (b) can be advantageously measured by means of the X-ray diffraction method described above.

Preferably, the density of the composite reinforcing filler (b) ranges from 1.5 to 1.9.

For the purposes of the present invention, the density of the composite reinforcing filler (b) can advantageously be measured at 25 ℃ with the aid of a helium pycnometer, using, for example, an Accupyc 1330 type pycnometer (Micromeritics) set to a helium pressure of 1344hPa during the measurement, and after conditioning a sample of the composite reinforcing filler (b) at 100 ℃ for 24 hours.

In this way, the weight of both the elastomeric composition incorporating the reinforcing filler and the final tyre can be advantageously reduced with respect to the use of silica-based reinforcing fillers.

Preferably, the composite reinforcing filler (b) has a total BET surface area, measured according to standard ISO 5794/1, ranging from 20 to 400m²Per g, preferably from 50 to 250m²/g。

In a preferred embodiment, the composite reinforcing filler (b) comprises from 20% to 80%, more preferably from 30% to 70%, and even more preferably from 40% to 60% by weight of silica, relative to the total weight of the composite reinforcing filler (b).

The content of silica in the composite reinforcing filler (b) can be determined according to any method known to the person skilled in the art for this purpose, for example by means of gravimetric measurement, i.e. by determining the weight of silica in a given amount of reinforcing filler after the removal of other components. For example, the nanocrystalline cellulose may be removed by calcining the composite reinforcing filler (b), preferably by performing said calcination at a temperature of at least 600 ℃, according to any method known to the person skilled in the art for this purpose.

Preferably, the vulcanizable elastomeric composition comprises from 10 to 100phr of the composite reinforcing filler (b), more preferably from 15 to 50phr of the composite reinforcing filler (b), with respect to 100phr of the vulcanizable diene elastomeric polymer (a).

In a preferred embodiment and in order to meet specific application requirements, the vulcanizable elastomeric composition according to the invention comprises (c) a standard reinforcing filler.

Preferably, the standard reinforcing filler is selected from carbon black, precipitated amorphous silica, amorphous silica of natural origin, silicate fibres, or mixtures thereof.

Preferably, the standard reinforcing filler (c) is present in the vulcanizable elastomeric composition in an amount ranging generally from 1phr to 120phr, preferably from 20phr to 90 phr.

Preferably, the standard reinforcing filler (c) is a filler having a surface area of not less than 20m²Carbon black in a/g ratio (determined by STSA-statistical thickness surface area method according to ISO 18852: 2005).

Preferably, said carbon black standard reinforcing filler (c) is present in the vulcanizable elastomeric composition in an amount ranging from 1phr to 120phr, preferably from 20phr to 90 phr.

Preferably, the standard reinforcing filler is a silica selected from fumed silica, or preferably precipitated silica.

Preferably, the silica has a BET surface area (measured according to ISO Standard 5794/1) in the range of 50m²G to 500m²G, more preferably 70m²G to 200m²/g。

Preferably, in the vulcanizable elastomeric composition, the composite reinforcing filler (b) represents at least 75% by weight, more preferably at least 80% by weight, with respect to the total weight of the white reinforcing filler.

Within the framework of the present description and of the subsequent claims, the expression "white reinforcing filler" denotes a reinforcing filler in the vulcanizable elastomeric composition excluding carbon black-based fillers. Typical examples of white reinforcing fillers are gypsum, talc, kaolin, bentonite, titanium dioxide and silica, in the form of precipitated amorphous silica, amorphous silica of natural origin, silicate fibres, or mixtures thereof.

The vulcanizable elastomeric composition according to the present invention comprises at least one vulcanizing agent (d).

In the case of the use of accelerators, activators and/or retarders known to the person skilled in the art, the vulcanizing agent most advantageously used is sulfur or, alternatively, a sulfur-containing molecule (sulfur donor).

The sulphur or derivative thereof may advantageously be selected from, for example, (i) soluble sulphur (crystalline sulphur), (ii) insoluble sulphur (polymeric sulphur), (iii) oil-dispersed sulphur (e.g. 33% sulphur known by Eastman under the trade name Crystex OT 33), (iv) sulphur donors, such as caprolactam disulphide (C L D), bis [ (trialkoxysilyl) propyl ] polysulphide, phosphorodithioate esters, or mixtures thereof.

The vulcanizing agent (d) is present in the vulcanizable elastomeric composition of the invention in an amount of from 0.1 to 15phr, preferably from 1 to 10phr, even more preferably from 2 to 7 phr.

The vulcanizable elastomeric composition according to the invention further comprises at least one silane coupling agent (e) capable of interacting with the silica and/or the silicate possibly present as reinforcing filler and of bonding them to the diene elastomeric polymer during vulcanization.

Preferably, the silane coupling agent (e) used in the present invention is selected from those having at least one hydrolyzable silane substituent, such as a silane that can be identified by the following general formula (IV):

(R)₃Si-C_nH_2n-X (IV)

wherein the R groups, which may be the same or different, are selected from alkyl, alkoxy or aryloxy groups or halogen atoms, with the proviso that at leastOne R group is alkoxy or aryloxy or halogen; n is an integer from 1 to 6, inclusive; x is a group selected from: nitroso, mercapto, amino, epoxy, vinyl, imide, chlorine, - (S)_mC_nH_2n-Si-(R)₃and-S-COR, wherein m and n are integers from 1 to 6, inclusive, and the R group is as defined above.

Among the silane coupling agents (e), bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are particularly preferred. The coupling agents may be used as such or mixed with inert fillers (e.g. carbon black) to facilitate their incorporation into the vulcanizable elastomeric composition.

Preferably, said silane coupling agent (e) is present in the crosslinkable elastomeric composition in an amount ranging from 0.1phr to 15phr, preferably from about 0.5phr to 10 phr.

Preferably, the silane coupling agent (e) and the vulcanizing agent (d) are used in combination with an accelerator (f) and/or an activator (g) known to those skilled in the art.

Commonly used accelerators (f) may be selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulfenamides, thiurams, amines, xanthates (xanthates) or mixtures thereof.

Preferably, the vulcanization accelerator (f) is present in the vulcanizable elastomeric composition of the invention in an amount of from 0.1 to 8phr, preferably from 0.3 to 6 phr.

Particularly effective activators (g) are zinc compounds, and in particular ZnO, ZnCO₃Zinc salts of saturated or unsaturated fatty acids containing from 8 to 18 carbon atoms, such as zinc stearate, which are preferably formed in situ in the elastomeric composition from ZnO and fatty acids, or mixtures thereof.

Preferably, the vulcanization activator (g) is present in the vulcanizable elastomeric composition of the invention in an amount of from 0.2 to 15phr, preferably from 0.5 to 10 phr.

Finally, the vulcanizable elastomeric material according to the invention comprises other usual additives selected on the basis of the specific application for which the composition is intended. For example, the material may be added with: antioxidants, plasticizers, binders, antiozonants, modified resins, or mixtures thereof.

In particular, to further improve processability, the vulcanizable elastomeric composition may be added together with a plasticizer generally selected from mineral oils, vegetable oils, synthetic oils, liquid polymers or mixtures thereof, such as aromatic oils, naphthenic oils, phthalates, soybean oil or mixtures thereof. The amount of plasticizer used is generally in the range from 0 to 70phr, preferably from 5phr to 30 phr.

Advantageously vulcanising the vulcanisable elastomeric composition as set forth above, at least one structural element of the tyre for vehicle wheels according to the invention is obtained.

Preferably, the structural element is selected from the group consisting of a crown, a carcass structure, a belt structure, an underlayer, an abrasion-resistant chafer, a sidewall insert, a mini-sidewall, a flipper (flipper), a chafer (chafer), an undercushion (undercut), a rubber layer, a bead filler and a rubber sheet.

Preferably, in the tyre of the invention, at least the crown, and at least one component selected from the group consisting of underlayer, chafer, sidewall insert, mini-sidewall, flipper, chafer, undercushion, rubber layer, bead filler or rubber sheet, comprise said vulcanized elastomeric material obtained by vulcanizing the vulcanizable elastomeric composition containing the reinforcing filler of the invention.

One embodiment of the present invention relates to a tire for a vehicle, comprising at least:

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

-a belt structure applied in a radially external position with respect to the carcass structure;

-in a radially external position with respect to the crown applied to the belt structure, and possibly at least:

-an under-layer and/or an abrasion-resistant chafer and/or a sidewall insert and/or a mini-sidewall and/or an under-liner and/or a rubber layer and/or a flipper and/or a chafer and/or a bead filler and/or a rubber sheet,

wherein at least one of said carcass structure and/or crown and/or belt structure and/or under-layer and/or chafer and/or sidewall insert and/or mini-sidewall and/or under-liner and/or rubber layer and/or flipper and/or chafer and/or bead filler and/or rubber sheet comprises a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition containing the reinforcing filler of the present invention.

Preferably, the tyre according to the invention comprises, at least in the tread band, a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising the reinforcing filler of the invention.

Preferably, the tyre according to the invention comprises, at least in the underlayer, a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising the reinforcing filler of the invention.

Preferably, the tyre according to the invention comprises, at least in the sidewall insert, a vulcanized elastomeric material obtained by vulcanizing the vulcanizable elastomeric composition containing the reinforcing filler of the invention.

Preferably, the tyre according to the invention comprises, in the crown and in one or more components selected from the group consisting of underlayer, wear-resistant envelope, sidewall insert, mini-sidewall, undercushion, rubber layer, bead filler and rubber sheet, a vulcanized elastomeric material obtained by vulcanizing the vulcanizable elastomeric composition containing the reinforcing filler of the invention.

Preferably, the tyre according to the invention comprises, in the tread band and in the under-layer, a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising the reinforcing filler of the invention.

Preferably, the tyre according to the invention comprises, in the crown and in the sidewalls, a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising the reinforcing filler of the invention.

In one embodiment of the invention, the tire according to the invention is a tire for HP and UHP of high-performance and ultra-high-performance vehicles, the performance of which benefits in particular from the high reinforcing power associated with the light weight of the composite reinforcing filler (b) according to the invention.

The tyre according to the invention can be used on two-or four-wheeled vehicles, on heavy vehicles or on light transport vehicles.

The tyre according to the invention can be used for summer or winter use or for all seasons.

In a preferred embodiment of the process for producing tyres for vehicle wheels according to the present invention, the step of providing the vulcanizable elastomeric composition can be carried out according to any process known to those skilled in the art and capable of dispersing the composite reinforcing filler (b) in the vulcanizable diene elastomeric polymer (a).

Preferably, the step of providing a vulcanizable elastomeric composition comprises:

-feeding at least the following components to at least one mixing device comprising at least one discontinuous mixer and at least one continuous mixer:

omicron curable diene elastomeric polymer (a),

omicron composite reinforcing filler (b);

-mixing and dispersing said components so as to obtain said vulcanizable elastomeric composition;

-discharging said vulcanizable elastomeric composition from said mixing device.

Within the framework of the present description and of the subsequent claims, the term "discontinuous (or intermittent) mixer (or mixing device)" means a mixing device configured to periodically feed the various constituents of the material to be prepared in predetermined quantities and mix them for a predetermined time so as to obtain a batch of said material.

At the end of the mixing step, the entire batch of material obtained is discharged completely from the mixing device in a single operation. Examples of batch or discontinuous mixers are those with tangential rotorsOr with interpenetrating rotorsInternal mixers of the type.

Within the framework of the present description and of the subsequent claims, the term "continuous mixer (or mixing device)" denotes a mixing device which is typically constructed for continuously feeding the ingredients of the material to be prepared, mixing the ingredients in order to produce the material and discharging them in continuous flow (with the exception of possible stoppages of the mixing device due to maintenance, or changes in the material formulation), by means of a metering device for controlling the dosage.

In the jargon of mixers for elastomeric compounds, continuous mixing devices are sometimes termed: mixing extruder means, which is considered herein to be equivalent to a "continuous mixer".

The continuous mixer (in particular its working elements, such as screws or mixing means) is then equipped with a mixing section capable of imparting high shear stress to the material under mixing, interspersed with a mixing section, equipped with a transport section capable of imparting thrust to the material to be processed, directing it from one longitudinal end of the internal chamber to the other. The continuous mixer may further be provided with possible redistribution portions.

Examples of continuous mixing devices are twin-screw mixers or multi-screw mixers (e.g. ring mixers) of the interpenetrating and co-rotating or planetary type.

Furthermore, both discontinuous mixers and continuous mixers, in the case of cold feed of the ingredients, and in the case of materials containing elastomeric components, are capable of imparting to the material produced with them sufficient energy to mix and uniformly disperse the various components, in order to masticate the elastomeric compound, thereby raising its temperature so as to make it processable and plastic, in order to facilitate the incorporation and/or distribution of the ingredients within the elastomeric polymer matrix.

The vulcanizable elastomeric composition thus obtained can therefore be stored or directly conveyed to the subsequent step of producing the tyre according to the invention.

The composite reinforcing filler (b) can be fed into the at least one discontinuous mixer and/or the at least one continuous mixer according to any means known to the person skilled in the art and suitable for the purpose.

For example, the composite reinforcing filler (b) of the invention may be fed in the form of a powdered material or in the form of a masterbatch.

Preferably, the composite reinforcing filler (b) of the invention is fed to the at least one discontinuous mixer and/or to the at least one continuous mixer in the form of a masterbatch comprising:

-at least one vulcanizable diene elastomeric polymer (a) described above;

-a composite reinforcing filler (b).

Advantageously, the feeding of the masterbatch according to the invention facilitates and improves the dispersion of the composite reinforcing filler in the elastomeric composition, and thus the reinforcing effect by the filler itself.

Preferably, the vulcanizable diene elastomeric polymer (a) in the masterbatch according to the invention is any of the vulcanizable diene elastomeric polymers (a) described above.

Preferably, the composite reinforcing filler (b) in the masterbatch according to the invention is any of the composite reinforcing fillers (b) described above.

Preferably, the masterbatch according to the invention comprises, with respect to 100phr of vulcanizable diene elastomeric polymer (a), from 5 to 120phr, preferably from 5 to 80phr, of the composite reinforcing filler (b) according to the invention.

According to this preferred embodiment, the amount of composite reinforcing filler (b) will suitably vary with respect to the amount of vulcanizable diene elastomeric polymer (a) as a function of the particular type of masterbatch used.

Thus, for example, if the vulcanizable diene elastomeric polymer (a) in the masterbatch is used to constitute 100% of the polymer base of a particular structural element of a tire, the amount of composite reinforcing filler (b) used in the masterbatch may vary between 5phr and 100phr, with respect to 100phr of vulcanizable diene elastomeric polymer (a).

If, on the other hand, the vulcanizable diene elastomeric polymer (a) of the masterbatch is used in a mixture with other polymers, the quantity of composite reinforcing filler (b) in the masterbatch has a value greater than 100phr and varies between 5phr and 120phr, with respect to 100phr of the vulcanizable diene elastomeric polymer (a).

The masterbatch according to the invention, besides being advantageously usable in a process for producing tyres for vehicle wheels as described above, is also particularly advantageous in terms of storage and transport of the composite reinforcing filler (b) and can be stored or immediately carried on directly after its production into the subsequent tyre production step of the invention.

As outlined above, the method of producing a masterbatch comprises i.

Preferably, the aqueous dispersion obtained from step i. in the process for producing a masterbatch according to the invention comprises from 2 to 6% of the composite reinforcing filler (b).

The aqueous dispersion of the composite reinforcing filler (b) may be provided according to any method known to those skilled in the art and may comprise the use of different equipment, such as a bladed mechanical stirrer, a mechanical mixer, for example of the type used for mixing paints or mortars, a magnetic stirrer, or may comprise an ultrasonic treatment.

Preferably, in the process for producing a masterbatch, the aforementioned step iii of coagulating the latex obtained from the aforementioned step ii comprises the addition of an acid so as to bring the pH below 4.

Preferably, the acid is selected from acetic acid, sulfuric acid, carbonic acid, formic acid or mixtures thereof.

Other aspects of step iii. to coagulate the latex obtained from the aforementioned step ii. are known to the person skilled in the art and are therefore not further detailed herein.

Preferably, the aforementioned step iv of purifying the coagulated product comprises at least one operation selected from filtration, washing, centrifugation, drying, lyophilization.

Other aspects of the aforementioned step iv. of purifying the coagulated product are known to the person skilled in the art and are therefore not described in further detail herein.

Examples of nanocrystalline Cellulose that may be used according to the present invention are the products commercialized by Cellulose L ab (Canada), Melodea L td, Rohovot, Israel, American Process Inc., Atlanta, Georgia, USA, and the trade names of Cellulore Inc, Montreal, Quebec, CanadaAnd the trade name Celluforce

Preferably, the nanocrystalline cellulose has a diameter in the range of 5nm to 30nm and a length in the range of 100nm to 1000nm, more preferably in the range of 100nm to 500 nm.

Preferably, the diameter and length of the nanocrystalline cellulose is evaluated by means of microscopic observation, more preferably by means of electron scanning microscopy, preferably on at least 100 nanocrystalline cellulose particles.

Preferably, the nanocrystalline cellulose has a crystallinity of greater than 40%, more preferably greater than 50%, even more preferably greater than 60%, and still more preferably in the range of 70% to 95%, as measured according to the crystallinity determination method given above for the composite reinforcing filler.

Preferably, the density of the nanocrystalline cellulose ranges from 1.4 to 1.6g/cm as a function of the extraction method and the moisture content³。

More preferably, the density of the nanocrystalline cellulose is about 1.5g/cm³This was measured by the helium pycnometer method described above.

Preferably, the surfactant used in the process for manufacturing the composite reinforcing filler of the invention is selected from benzalkonium chloride, cetrimide, cetyltrimethylammonium bromide, for example undecylamidopropyl trimethyl ammonium partial sulfate commercialized by Elementis Specialty Products, Delden, the netherlands under the name Servamine Q8040, for example cocoalkyl trimethyl ammonium partial sulfate commercialized by Elementis Specialty Products, Delden, the netherlands under the name Servamine KAC 458.

More preferably, the surfactant is cetyltrimethylammonium bromide.

Preferably, the surfactant is added in an amount ranging from 10 to 20 wt% with respect to the weight of the nanocrystalline cellulose.

Preferably, the aqueous dispersion medium used in the method for producing the composite reinforcing filler of the present invention is used in a volume/weight ratio of 0.05 to 0.2l/g with respect to the nanocrystalline cellulose.

Within the framework of the process for producing the composite reinforcing filler of the invention, in the present description and in the subsequent claims, the term "precursor compound of silica" is used to indicate a compound or a mixture of compounds capable of generating silica by hydrolysis in situ, for example by heating and/or in the presence of an acid or a base.

Preferably, the precursor compounds of the aforementioned silicas are selected from:

I. an alkali metal silicate of the formula:

M₂O·n SiO₂(I)

where M ═ Na, K, L i, and where n ranges from 0.5 to 4, preferably n ═ 0.5 or 1 or 3 and M ═ Na or K, which in the presence of an acid yields silica,

a tetraalkyl derivative of silicic acid (or tetraalkoxysilane) of the formula:

(RO)₄Si (II)

wherein the R groups, equal to or different from each other, represent C₁-C₆An alkyl group which in the presence of water and preferably an acid or base forms silica,

halosilanes of the formula:

SiX₄or (RO)₃SiX OR (RO)₂SiX₂Or (RO) SiX₃(III)

Wherein the R groups, equal to or different from each other, represent C₁-C₆Alkyl, and X, equal to or different from each other, are selected from chlorine, bromine and iodine, preferably chlorine, which produces silica in the presence of water and possibly a base.

In general, hydrolysis of the precursor compounds of the silicate requires the presence of water in an equivalent amount at least equal to the equivalents of hydrolyzable groups present in the silica precursor compound. Given the amount of silica precursor compound used during step (B) of the process, the skilled person is therefore able to determine with certainty the amount of water required to hydrolyse the precursor compound.

Preferably, the precursor compound is dissolved or suspended in an aqueous liquid medium.

Preferably, in a first variant of the process, the precursor compound of silica is an alkali metal silicate (I).

According to said first variant, the addition of the precursor compound of silica is preferably carried out by keeping the aqueous dispersion in an alkaline medium at a temperature ranging from 70 to 90 ℃.

Preferably, the pH of the alkaline medium of step (B) ranges from 7 to 9.5.

According to said first variant, the alkali metal silicate (I) is preferably chosen from sodium silicate, lithium silicate, potassium silicate, more preferably sodium orthosilicate, sodium metasilicate and potassium orthosilicate.

Preferably, SiO is used₂/Na₂Sodium silicate with an O ratio of 2 to 4, more preferably 3 to 3.7.

More preferably, the alkali metal silicate (I) is in the form of an aqueous solution having a solid content ranging from 5% to 15% by weight.

According to the aforementioned first variant in which the precursor compound of silica is an alkali metal silicate (I), the amount of alkali metal silicate (I) added in step (B) is preferably in the range from 50 to 150% by weight, with respect to the weight of nanocrystalline cellulose.

According to the first variant described above, step (B) preferably comprises the addition of at least one acid chosen from hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid, acetic acid, carbonic acid.

Preferably, the amount of acid used is at least capable of neutralizing all of the basic functionality in the starting silicate.

Preferably, the acid is used in a weight ratio ranging from 1:1 to 1:20, relative to the weight of alkali metal silicate (I).

According to the aforementioned first variant, in which the precursor compound of silica is an alkali metal silicate (I), in step (B) of the process for producing the composite reinforcing filler of the invention, the aqueous dispersion is stirred at a temperature preferably ranging from 70 to 90 ℃ for a time ranging from 30 to 90 minutes, at the end of the addition of the alkali metal silicate.

In a preferred embodiment, step (B) of the process for producing a composite reinforcing filler according to the aforementioned first variant of the process of the invention comprises:

(B1) adding at least one first portion of alkali metal silicate (I) to the aqueous dispersion resulting from step (a), wherein the addition is carried out while maintaining the aqueous dispersion at a pH in the range of from 8.5 to 9.5;

(B2) stirring the aqueous dispersion resulting from step (B1) for a time ranging from 80 to 100 minutes;

(B3) adding at least one second portion of alkali metal silicate (I) to the aqueous dispersion resulting from step (B2), wherein the addition is carried out while keeping the aqueous dispersion at a pH in the range of 7 to 8.

According to said first variant of the process in which the precursor compound of silica is an alkali metal silicate (I), step (C) of depositing an at least partial silica coating on the nanocrystalline cellulose preferably comprises subjecting the aqueous dispersion resulting from step (B) to an acidic medium so as to hydrolyze the alkali metal silicate (I) and obtain a composite reinforcing filler comprising a core and an at least partial coating, said core comprising nanocrystalline cellulose and said at least partial coating comprising silica.

Preferably, according to said first variant, the pH of the acidic medium of step (C) ranges from 3.5 to 4.5.

According to the aforementioned first variant, in which the precursor compound of silica is an alkali metal silicate (I), step (C) of the process for producing the reinforcing filler preferably comprises the addition of at least one acid selected from hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid, acetic acid, carbonic acid.

Preferably, in a second variant of the process for producing the reinforcing filler according to the invention, the silica precursor compound is a tetraalkyl derivative (II) of silicic acid preferably chosen from tetramethyl orthosilicate, tetraethyl orthosilicate, tetra-n-propyl silicate, tetra-n-butyl silicate.

In this case, it is advantageous to hydrolyze the precursor in the presence of an acid or a base, preferably a base.

As regards the acid, in said second variant, the acid described above with reference to the first variant of the process can be used.

As regards the bases, these are preferably chosen from ammonia, ammonium hydroxide, hydroxylamine, primary, secondary or tertiary alkyl, aryl or arylalkyl amines, sodium hydroxide, potassium hydroxide.

More preferably the precursor is hydrolyzed advantageously in the presence of an amine or ammonium hydroxide.

According to the aforementioned second variant of the process for producing a reinforcing filler according to the invention, the amount of base is preferably in the range from 1 to 40% by weight, more preferably from 3 to 20% by weight, with respect to the weight of the silica precursor compound.

In a preferred embodiment of the method for producing a reinforcing filler according to the present invention, step (D) of purifying the composite reinforcing filler preferably comprises at least one operation selected from filtration, washing, centrifugation, drying, lyophilization or any combination thereof.

Preferably, step (D) of purifying the composite reinforcing filler comprises at least one washing operation, more preferably a washing operation carried out with an aqueous medium, so as to allow the removal of the surfactant used in step (a) of the process for producing the composite reinforcing filler (b) of the invention.

Preferably, the composite reinforcing filler obtained by step (C) of the process for producing a reinforcing filler according to the invention is any of the composite reinforcing fillers (b) described above.

Brief Description of Drawings

Additional features and advantages of the present invention will become apparent from the following description of some preferred embodiments thereof, given for purposes of illustration and not of limitation, with reference to the accompanying drawings.

In the drawings:

figure 1 illustrates a portion of a radial half of a tyre for vehicle wheels according to the present invention;

fig. 2 illustrates a photograph obtained using a Field Emission Scanning Electron Microscope (FESEM), which was obtained using a ZEISS U L TRA P L US instrument with a Gemini lens, in which the composite reinforcing filler (b) of example 1 can be observed.

Detailed description of the presently preferred embodiments

In fig. 1, a tire for vehicle wheels according to a preferred embodiment of the present invention is generally indicated by reference numeral 100.

Fig. 1 illustrates a portion of a radial half of a tire for a wheel.

In fig. 1, "a" denotes the axial direction and "X" denotes the radial direction, in particular X-X denotes the line of the equatorial plane. For the sake of simplicity, fig. 1 shows only a portion of the tyre, the remaining portions not represented being identical and symmetrically arranged with respect to the equatorial plane "X-X".

The tyre 100 for vehicles comprises at least one carcass structure comprising at least one carcass ply 101, each having opposite end flaps, called bead cores, fastened in respective annular anchoring structures 102, optionally associated with a bead filler 104.

The tyre region containing the bead core 102 and the bead filler 104 forms a bead structure 103 intended for anchoring the tyre to a corresponding mounting rim (not shown).

The carcass structure is generally of the radial type, i.e. the reinforcing elements of at least one carcass layer 101 lie in a plane containing the axis of rotation of the tyre and substantially perpendicular to the equatorial plane of the tyre. The reinforcing elements are usually composed of textile cords, such as rayon, nylon, polyesters, such as polyethylene naphthalate (PEN). To form the so-called flaps 101a of the carcass shown in fig. 1, each bead structure is associated with the carcass structure by bending the opposite side edges of at least one carcass ply 101 around the annular anchoring structures 102.

In one embodiment, the connection between the carcass structure and the bead structure may be provided by a second carcass layer (not shown in fig. 1) applied in an axially outer position with respect to the first carcass layer.

A chafer 105 is placed in an outward position of each bead structure 103.

The carcass structure is associated with a belt structure 106, said belt structure 106 comprising one or more belt layers 106a, 106b arranged radially one on top of the other and with respect to the carcass layer, typically with textile and/or metallic reinforcing cords incorporated in a layer of vulcanized elastomeric material.

Such reinforcing cords have a crossed orientation with respect to the circumferential direction of the tire 100. The term "circumferential" direction is used to refer to a direction generally facing the direction of tire rotation.

At a radially outermost position with respect to the belt layers 106a, 106b, at least one zero-degree reinforcing layer 106c, generally called "0 ° belt", can be employed, usually incorporating a plurality of elongated reinforcing elements, typically metal or textile cords, oriented in a substantially circumferential direction, so as to form an angle of several degrees (for example an angle of about 0 ° to 6 °) with respect to a direction parallel to the equatorial plane of the tyre, and coated with a vulcanized elastomeric material.

In a radially outer position with respect to the belt structure 106, a crown 109 made of vulcanized elastomeric material is used.

On the lateral surfaces of the carcass structure, in a radially external position, respective sidewalls 108 made of vulcanized elastomeric material are also employed, each extending from one of the lateral edges of the crown 109 to a respective bead structure 103.

In a radially outward position, the crown 109 has a rolling surface 109a intended to come into contact with the ground. Typically formed in this face 109a are circumferential flutes connected by transverse flutes (not shown in fig. 1) to define a plurality of blocks of various shapes and sizes distributed over the rolling surface 109a, which for simplicity is shown in fig. 1 as a smooth face.

A base layer 111 made of vulcanized elastomeric material may be interposed between the belt structure 106 and the crown 109.

Chafers 110 of vulcanized elastomeric material, often referred to as "mini-sidewalls", may optionally be present in the junction areas between the sidewalls 108 and the crown 109.

This mini-sidewall 110 is generally obtained by co-extrusion with the crown 109 and advantageously allows an improvement in the mechanical interaction between the crown 109 and the sidewall 108.

Preferably, the terminal portions of the sidewalls 108 (in the preferred embodiment shown in fig. 1, the mini-sidewalls 110) directly overlie the lateral edges of the crown 109.

In the case of tubeless tires, a rubber layer 112, commonly referred to as a "liner," may also be provided at a radially inward location relative to the carcass layer 101, which provides the necessary air-tightness for tire inflation.

A further rubber sheet (not shown) of vulcanized elastomeric material, also known by the name "undercushion", may also be placed between the rubber layer 112 and the carcass layer 101.

The stiffness of the tire sidewall 108 may be improved by providing the bead structure 103 with a reinforcing layer 120 (commonly referred to as "flipper") or an additional strip insert.

The flipper 120 is a reinforcement layer wrapped around the respective bead core 102 and bead filler 104 so as to at least partially surround them, said reinforcement layer being arranged between at least one carcass layer 101 and the bead structure 103.

Preferably, the flipper is in contact with the aforementioned at least one carcass layer 101 and with the bead structure 103.

Bead wrap 120 typically includes a plurality of textile cords incorporated within a layer of vulcanized elastomeric material.

The tire bead structure 103 may include an additional protective layer 121, commonly known under the term "chafer" or protective strip and functioning to increase the rigidity and integrity of the bead structure 103.

Preferably, the protective layer 121 or "chafer" comprises a plurality of cords incorporated within a layer of vulcanized elastomeric material. Such cords may be made of textile material (e.g. aramid or rayon) or metallic material (e.g. steel cords).

A layer of elastomeric material or a rubber sheet (not shown) may be arranged between the belt structure 106 and the carcass structure. The layer may have a uniform thickness.

Alternatively, the layer may have a varying thickness along the axial direction. For example, the layer has a greater thickness proximate its axially outer edge relative to the central (crown) region.

Advantageously, this layer or sheet of rubber may extend over a surface substantially corresponding to the development surface of the belt structure 106.

In a preferred embodiment, the layer of elastomeric material or sheet rubber described above, not shown, may be arranged-alternatively or in addition to the underlayer 111-between the belt structure 106 and the crown 109, said additional layer or sheet rubber preferably extending on a surface substantially corresponding to the development surface of the belt structure 106.

The vulcanized elastomeric material obtained by vulcanizing the vulcanizable elastomeric composition containing the composite reinforcing filler (b) of the present invention may advantageously be incorporated into one or more structural elements of the tyre 100 described above.

Preferably, the structural elements of the tyre 100 obtained by curing the vulcanizable elastomeric composition containing the composite reinforcing filler (b) of the present invention may be one or more of the following: a crown 109 of vulcanized elastomeric material, a carcass structure, a belt structure 106, an under-layer 111, a chafer 105, a sidewall 108, a sidewall insert, a mini-sidewall 110, a flipper 120, a chafer 121, an under-liner, a rubber layer, a bead filler 104 and a rubber sheet.

According to one embodiment, not shown, the tyre may be a tyre for motorcycle wheels, typically having a section characterised by a high transverse curvature.

According to one embodiment, not shown, the tyre may be a tyre for wheels of heavy transport vehicles, such as trucks, buses, trailers, vans, and vehicles in which the tyre is subjected to high loads.

Preferably, such a tire is adapted to be mounted on a rim having a diameter equal to or greater than 17.5 inches for a steering turbine or trailer wheel.

The invention will now be illustrated by some examples, which are intended to illustrate, but not to limit the purpose.

Example 1

Preparation of composite reinforcing filler

Substance(s)

Nanocrystalline Cellulose (12 wt% aqueous dispersion commercialized by Cellulose L ab Canada) having a diameter ranging from 5 to 20nm and a length ranging from 150 to 200nm, and a density of 1.5g/cm³Surface area of 1.45m²Per g, crystallinity 70-90%);

cetyltrimethylammonium bromide (CTAB) (Sigma-Aldrich);

silicon dioxide: ultrasil VN 3;

NaOH，98％(Sigma)；

sulfuric acid (15 wt% in water) (product from Sigma-Aldrich, 98% obtained by dilution).

Procedure (ii)

In a laboratory flask, 7g of silica and 2.8g of NaOH are mixed in 60ml of distilled water and kept at 80 ℃ for 1 hour with stirring at 300rpm, obtaining a clear solution of sodium silicate, which is then brought to a final volume of 90ml by adding further distilled water.

Thereafter, 42g of an aqueous dispersion of nanocrystalline cellulose (corresponding to 5g of nanocrystalline cellulose) and 0.8g of CTAB were added in 450ml of distilled water in a three-necked laboratory flask and kept at about 80 ℃ for 30 minutes with stirring, so as to form an aqueous dispersion of nanocrystalline cellulose.

The aqueous dispersion of nanocrystalline cellulose was added with a first portion of 60ml sodium silicate solution over about 90 minutes, always keeping the system at a temperature of about 80 ℃. During the addition of the sodium silicate solution, sulfuric acid was also added to maintain the pH at a value of about 9.3.

Once the first portion of sodium silicate was added, the reaction mixture was held at about 80 ℃ for about 15 minutes with stirring, and then sulfuric acid was added over 10 minutes until a pH of about 7.5 was achieved, always maintaining the temperature at about 80 ℃.

A second portion of 30ml of sodium silicate solution was then added to the resulting aqueous dispersion over about 45 minutes, maintaining the system at a temperature of about 80 c and a pH of about 7.4 by the addition of sulfuric acid.

Once the sodium silicate solution has been added, the pH is brought to a value of 4 within 20 minutes by adding further sulphuric acid and by keeping the reaction mixture always at about 80 ℃ in order to deposit a silica coating on the nanocrystalline cellulose, thus obtaining about 11g of composite reinforcing filler. The composite reinforcing filler thus obtained was then purified by means of centrifugation (1000-3000g for 10-20 minutes), followed by washing with distilled water and freeze-drying (24 hours), and subsequently characterized. Table 1 shows the characteristics of the composite reinforcing filler. Fig. 2 also shows an electron scanning micrograph of the composite reinforcing filler obtained.