Tyres for vehicle wheels

Abstract

The present invention relates to a tyre for vehicle wheels which comprises at least one structural element comprising a vulcanised elastomeric compound obtained by vulcanisation of a vulcanisable elastomeric composition comprising per 100 phr of diene elastomeric polymer: (i) a predispersion of a diene elastomeric polymer and nanometric lignin, in an amount to provide the elastomeric composition with 100 to 10 phr of diene elastomeric polymer and an amount of nanometric lignin equal to or greater than 5 phr, (ii) from 0 to 90 phr of at least one diene elastomeric polymer, (iii) from 0 to 110 phr of a reinforcing filler, (iv) from 0.1 to 12 phr of at least one vulcanising agent, where said nanometric lignin comprises lignin particles having an average hydrodynamic diameter D50 lower than 500 nm and greater than 50 nm.

Description

[0001] “Tyres for vehicle wheels’

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a tyre for vehicle wheels. More specifically, the present invention relates to a tyre comprising at least one structural element comprising a vulcanised elastomeric compound obtained by vulcanisation of a vulcanisable elastomeric composition comprising a predispersion of natural rubber and nanometric lignin.

[0004] PRIOR ART

[0005] A tyre for vehicle wheels typically comprises a carcass structure comprising at least one carcass layer having opposite lateral edges associated with respective bead structures, a belt structure applied in a radially external position to the carcass structure, and a tread band disposed in a position radially external to the belt structure.

[0006] The carcass structure is intended, in addition to supporting the weight of the vehicle, to resist the inflation pressure and all the lateral and longitudinal stresses to which the running tyre is subjected following contact with the road surface.

[0007] The belt structure is intended to transfer the aforementioned lateral and longitudinal stresses to the carcass structure and helps to confer the desired features of structural strength, grip, driving stability, controllability, directionality, road grip, comfort and to maintain these performances over time.

[0008] The bead structures are intended to withstand the circumferential, transverse and combined stresses that are transmitted between the wheel rim and the tyre during normal conditions of use, for example in acceleration, braking and when turning, optionally even at high speed.

[0009] The tread band is intended to ensure that the vehicle has correct road grip in all driving and weather conditions during the use of the tyre and for as long as possible.

[0010] In the manufacturing of the aforementioned tyre components, the use of elastomeric compositions typically comprising reinforcing fillers to obtain the mechanical properties of the resulting vulcanised elastomeric compounds is contemplated. The most commonly used reinforcement fillers are carbon black and silica, alone or in combination with each other, but both have some critical aspects which the tyre industry has always been committed to reducing.

[0011] Carbon black gives the cross-linked products marked hysteretic features, i.e. an increase in heat dissipated in dynamic conditions (heat accumulation) which, in a tyre, may cause an increase in the rolling resistance of the tyre itself and, in particular in the internal structural elements of a tyre, operating temperatures that are too high. The increase in rolling resistance leads to an increase in fuel consumption by vehicles, resulting in higher costs of locomotion and air pollution. Operating temperatures that are too high may lead to a decrease in the mechanical properties of the elastomeric materials included in the semi-finished products and a possible degradation of the performance and / or durability of the tyre.

[0012] Silica gives poor workability of non-cross-l inked compositions, mainly due to excessive viscosity. Therefore, to obtain a good dispersion of the silica in the elastomeric polymer base, an intense and prolonged thermo-mechanical kneading of the composition is necessary. Furthermore, silica particles have a strong tendency to coalescence and form agglomerates even when finely dispersed in the elastomeric polymer base.

[0013] The Applicant has long perceived the need to supply more eco-sustainable and eco-compatible tyres and components thereof, for example, through the reduction or replacement of raw materials from petroleum with raw materials produced from renewable sources with the aim of maintaining and possibly improve, the performance of the tyre.

[0014] Among the most abundant biopolymers from renewable sources for application in tyres, starch, cellulose, lignin, and hemicellulose may be mentioned as examples. In the past, various attempts have been made to use some of these materials as reinforcing agents, which also have a lower specific weight than traditional reinforcing fillers. Lignin, for example, has been used, as it is or modified in various ways, as a reinforcing filler in tyre compounds.

[0015] Lignin is an organic polymer complex having a three-dimensional polymeric structure consisting of phenylpropane units, and belonging to the class of so- called phenylpropanoid compounds.

[0016] Lignins have very different compositions and molecular weights, both as a function of the biomass chosen and the process with which they are obtained. The composition varies both in terms of functional groups, mainly of the phenolic type, hydroxyl and carboxylic types, and in terms of molecular weight.

[0017] Vehicle wheel tyres comprising lignin are described in patent applications US2010 / 0204368, W02009 / 145784, JP2008 / 308615, JP2010 / 242023, J P2010 / 248282, JP2014 / 129509, CN102718995, CN103756060,

[0018] WO201 4 / 097108, WO2017 / 109672, WO2022 / 144759, IT102021000029213, and IT102021000029831 , and in patents GB723751 , GB836393, US2610954, US2802815, US2906718, US3079360, US3163614, US3282871 ,

[0019] US3296158, US3312643, US3364158, US3817974, US3984362 and US3991022.

[0020] SUMMARY OF THE INVENTION

[0021] The Applicant has carried out an intense research activity in order to find the way to use lignin for the manufacturing of tyre compounds which has led to the filing of the international patent applications published with the number WO201 7 / 109672 and WO2022 / 144759.

[0022] WO201 7 / 109672 relates to a tyre for vehicle wheels comprising at least one structural element comprising a cross-linked elastomeric material obtained by vulcanising an elastomeric composition comprising a predispersion of natural rubber and lignin obtained by co-precipitation from natural rubber latex.

[0023] WO2022 / 144759 relates to a tyre for vehicle wheels comprising at least one structural element comprising a cross-linked elastomeric material obtained by vulcanisation of an elastomeric composition comprising a predispersion of natural rubber and lignin obtained by co-drying from natural rubber latex.

[0024] The Applicant has found that it is possible to make vulcanisable elastomeric compositions with improved elongation modulus, ultimate mechanical properties (i.e. , tensile strength and elongation at break), and hysteresis using the above predispersions in which a nanometric lignin is used.

[0025] For the purposes of the present invention, the term nanometric lignin means a non-functionalised lignin comprising lignin particles with an average hydrodynamic diameter D50 lower than 500 nm and greater than 50 nm.

[0026] Continuing the experimentation, the Applicant also found that the mechanical and hysteresis properties were further improved by realizing functionalised nanometric lignin.

[0027] For the purposes of the present invention, the term functionalised lignin means a lignin in which at least a part of the hydroxyl groups of the lignin, preferably the more superficial hydroxyl groups, have been functionalised with epihalohydrin, preferably epichlorohydrin.

[0028] Reduced hysteresis values, particularly in the case of external structural elements such as the tread band, reduce heat dissipation due to the rolling of the tyre during road use, and consequently lead to reduced rolling resistance and lower fuel consumption. The reduction of hysteresis values, in particular in the case of internal structural elements of a tyre, such as for example the carcass structure, the belt structure and the bead components, also prevents the onset of excessively high operating temperatures within the structural components, which may risk compromising the integrity of the tyre.

[0029] Higher elongation modulus values, particularly in external structural elements such as the tread, increase the tyre stiffness, improving steering precision and response, and reduce the tyre wear, increasing the lifespan thereof. Increasing elongation moduli, particularly in the case of internal structural elements of a tyre, such as the carcass structure, belt structure and bead components, provides greater stiffness and resistance to lateral forces, helping the tyre maintain its shape and improving high-speed stability.

[0030] The improvement of the ultimate mechanical properties, in particular in the external structural elements of a tyre, such as for example the tread band and the sidewalls, improves the resistance to mechanical stresses deriving from the rolling or sliding of the tyre during use, reducing tread wear and / or the risk of tearing of the sidewall and the blocks made on the tread surface, resulting in longer tyre life.

[0031] The present invention therefore relates to the use of non-functionalised nanometric lignin and / or nanometric lignin functionalised with epihalohydrin, preferably epichlorohydrin, in vulcanisable elastomeric compositions useful for the manufacturing of structural elements of tyres for vehicle wheels.

[0032] Therefore, in a first aspect thereof, the present invention relates to a tyre for vehicle wheels which comprises at least one structural element comprising a vulcanised elastomeric compound obtained by vulcanisation of a vulcanisable elastomeric composition comprising per 100 phr of diene elastomeric polymer:

[0033] (i) a predispersion of a diene elastomeric polymer and nanometric lignin, preferably functionalised with epihalohydrin, in an amount to provide the elastomeric composition with 100 to 10 phr of diene elastomeric polymer and an amount of nanometric lignin equal to or greater than 5 phr,

[0034] (ii) from 0 to 90 phr of at least one diene elastomeric polymer,

[0035] (iii) from 0 to 110 phr of a reinforcing filler,

[0036] (iv) from 0.1 to 12 phr of at least one vulcanising agent, where said nanometric lignin comprises lignin particles having an average hydrodynamic diameter D50 lower than 500 nm and greater than 50 nm.

[0037] In a second aspect thereof, the present invention relates to a vulcanisable elastomeric composition comprising per 100 phr of diene elastomeric polymer:

[0038] (i) a predispersion of a diene elastomeric polymer and nanometric lignin, preferably functionalised with epihalohydrin, in an amount to provide the elastomeric composition with 100 to 10 phr of diene elastomeric polymer and an amount of nanometric lignin equal to or greater than 5 phr,

[0039] (ii) from 0 to 90 phr of at least one diene elastomeric polymer,

[0040] (iii) from 0 to 110 phr of a reinforcing filler,

[0041] (iv) from 0.1 to 12 phr of at least one vulcanising agent, where said nanometric lignin comprises lignin particles having an average hydrodynamic diameter D50 lower than 500 nm and greater than 50 nm.

[0042] During the experimentation, the Applicant also found a more efficient method for the preparation of nanometric lignin functionalised through a mechano-chemical process which carries out the functionalisation in a milling apparatus, such as a ball mill, combined with a process for reducing the hydrodynamic diameter of the lignin particles.

[0043] Therefore, in a third aspect, the present invention relates to a process for preparing nanometric lignin functionalised with epihalohydrin by mechano- chemical means comprising:

[0044] (a) providing a solution of lignin in a first organic solvent

[0045] (b) separating the insoluble fraction of said lignin from the soluble fraction in said organic solvent,

[0046] (c) drying said soluble fraction of lignin,

[0047] (d) feeding and mixing in a grinding apparatus said soluble fraction of lignin obtained in step c) and a basic catalyst, optionally in aqueous solution, and an organic cation salt; (e) adding to the mixture of step (d) epihalohydrin and a basic compound, and mixing until the reaction is completed, obtaining said soluble fraction of lignin functionalised with said epihalohydrin;

[0048] (f) recovering said soluble fraction of lignin functionalised with said epihalohydrin,

[0049] (g) treating said insoluble fraction of lignin with a second organic solvent and an antisolvent to obtain nanometric lignin,

[0050] (h) mixing a solution of said soluble fraction of lignin functionalised with said epihalohydrin with a suspension of said nanometric lignin obtaining a suspension of nanometric lignin functionalised with said epihalohydrin; and

[0051] (i) recovering said suspension of nanometric lignin functionalised with said epihalohydrin.

[0052] DEFINITIONS

[0053] The term “elastomeric composition” means a composition comprising at least one diene elastomeric polymer and one or more additives, which by mixing and possible heating provides an elastomeric compound suitable for use in tyres and components thereof.

[0054] The components of the elastomeric composition are not generally introduced simultaneously into the mixer but typically added in sequence. In particular, the vulcanisation additives, such as the vulcanising agent and optionally the accelerant and retardant, are usually added in a downstream step with respect to the incorporation and processing of all the other components.

[0055] In the vulcanisable elastomeric compound, the individual components of the elastomeric composition may be altered or no longer individually traceable as modified, completely or in part, due to the interaction with the other components, of heat and / or mechanical processing. The term “elastomeric composition” herein is meant to include the set of all the components that are used in the preparation of the elastomeric compound, regardless of whether they are actually present simultaneously, are introduced sequentially or are then traceable in the elastomeric compound or in the final tyre.

[0056] The term “elastomeric polymer” indicates a natural or synthetic polymer which, after vulcanisation, may be stretched repeatedly at room temperature to at least twice its original length and after removal of the tensile load substantially immediately returns with force to approximately its original length (according to the definitions of the ASTM D1566-11 Standard terminology relating to Rubber).

[0057] The term “diene elastomeric polymer” indicates a polymer or copolymer derived from the polymerisation of one or more different monomers, among which at least one of them is a conjugated diene (conjugated diolefin).

[0058] The term “elastomeric compound” indicates the compound obtainable by mixing and optionally heating at least one elastomeric polymer with at least one of the additives commonly used in the preparation of tyre compounds.

[0059] The term “vulcanisable elastomeric compound” indicates the elastomeric compound ready for vulcanisation, obtainable by incorporation into an elastomeric compound of all the additives, including those of vulcanisation.

[0060] The term “vulcanised elastomeric compound” means the material obtainable or obtained by vulcanisation of a vulcanisable elastomeric compound.

[0061] The term “green” indicates a material, a compound, a composition, a component or a tyre not yet vulcanised.

[0062] The term “vulcanisation” refers to the cross-linking reaction of a material, a compound, a composition, a component or a tyre, containing a natural or synthetic rubber, induced by a cross-linking agent typically based on sulphur or peroxides.

[0063] The term “cross-linking agent” or “vulcanising agent” indicates a product capable of transforming natural or synthetic rubber into elastic and resistant material due to the formation of a three-dimensional network of inter- and intramolecular bonds. Typical vulcanising agents are sulphur-based compounds such as elemental sulphur, polymeric sulphur, sulphur-donor agents such as bis[(trialkoxysilyl)propyl]polysulphides, thiurams, dithiodimorpholines and caprolactam-disulphide and / or dicumyl peroxide (DCP) and 2,5-dimethyl-2,5- di(tert-butylperoxy)hexane (DBPH).

[0064] The term “vulcanisation accelerant” means a compound capable of decreasing the duration of the vulcanisation process and / or the operating temperature, such as sulphenamides, thiazoles, dithiophosphates, dithiocarbamates, guanidines, as well as sulphur donors such as thiurams. The term “vulcanisation activator” indicates a product capable of further facilitating the vulcanisation, making it happen in shorter times and possibly at lower temperatures. An example of activator is the stearic acid-zinc oxide system.

[0065] The term “vulcanisation retardant” indicates a product capable of delaying the onset of the vulcanisation reaction and / or suppressing undesired secondary reactions, for example N-(cyclohexylthio)phthalimide (CTP).

[0066] The term “vulcanisation bundle” is meant to indicate the vulcanising agent and one or more vulcanisation additives selected from among vulcanisation activators, accelerants and retardants.

[0067] The term “reinforcing filler” is meant to refer to a reinforcing material typically used in the sector to improve the mechanical properties of tyre rubbers, preferably selected from among carbon black, conventional silica, such as silica from sand or biomass (for example from rice husk ash) precipitated with strong acids, preferably amorphous, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibres and mixtures thereof.

[0068] The term “mixing step (1 )” indicates the step of the preparation process of the elastomeric compound in which one or more additives may be incorporated by mixing and optionally heating, except for the vulcanising agent which is fed in step (2). The mixing step (1 ) is also referred to as “non-productive step”. In the preparation of a compound there may be several “non-productive” mixing steps which may be indicated with 1a, 1 b, etc.

[0069] The term “mixing step (2)” indicates the next step of the preparation process of the elastomeric compound in which the vulcanising agent and, optionally, the other additives of the vulcanisation bundle are introduced into the elastomeric compound obtained from step (1 ), and mixed in the material, at controlled temperature, generally at a compound temperature lower than 120°C, so as to provide the vulcanisable elastomeric compound. The mixing step (2) is also referred to as “productive step”.

[0070] The term “structural element” of a tyre refers to any component comprising elastomeric material of the tyre. A structural element of a tyre may be the carcass structure, the belt structure, the tread, the sidewalls, the bead structure, the tread base, and so on. The terms “radial” and “axial” and the expressions “radially internal / external” and “axially internal / external” are used referring respectively to a direction substantially parallel to the equatorial plane of the tyre and to a direction substantially perpendicular to the equatorial plane of the tyre, i.e. respectively to a direction substantially perpendicular to the axis of rotation of the tyre and to a direction substantially parallel to the axis of rotation of the tyre.

[0071] The terms “circumferential” and “circumferentially” are used with reference to the direction of the annular extension of the tyre, i.e. to the rolling direction of the tyre, which corresponds to a direction lying on a plane coinciding with or substantially parallel to the equatorial plane of the tyre.

[0072] By “substantially axial direction” it is meant a direction inclined, with respect to the equatorial plane of the tyre, by an angle of between about 70° and about 90°.

[0073] By “substantially circumferential direction” it is meant a direction stretched, with respect to the equatorial plane of the tyre, at an angle of between about 0° and about 10°.

[0074] The term “phr” (acronym for parts per hundreds of rubber) indicates the parts by weight of a given elastomeric compound component per 100 parts by weight of the elastomeric polymer, considered net of any extension oils.

[0075] Unless otherwise indicated, all the percentages are expressed as percentages by weight.

[0076] Lignin

[0077] Natural lignin is a biopolymer synthesised in the plant world and second in amount produced only to cellulose. Biomass formed between cellulose and lignin represents approximately 70% of total biomass. Lignin is a heavy and complex organic polymer consisting mainly of phenolic compounds. In particular, lignin is composed of a cross-linked and three-dimensional polymer structure of phenylpropane units, above all phenylpropyl alcohols (coumaryl, coniferyl and sinapyl). Alcohols are synthesised by plants by reduction of the corresponding acids by the enzyme cinnamyl-CoA-NADPH oxidoreductase.

[0078] The components of the lignin are present in different quantities depending on the type of plant in which it forms. Coniferyl alcohol is the most abundant precursor of conifer lignin. The lignin of woody (broad-leaved) angiosperms derives mainly from sinapyl alcohol. In the composition of the lignin of herbaceous plants, mainly grasses, p-coumaryl, coniferyl and sinapyl alcohols are all present in comparable quantities.

[0079] The polymeric structure of lignin is very complex and develops in a three- dimensional way with the formation of cross-links that include ether bonds (C- O-C), carbon bonds (C-C), and ester bonds (CO-O-C) between the different phenylpropane units.

[0080] The main source of lignin comes from the paper manufacturing industry and the bio-fuel manufacturing industry. In both cases, lignin represents a byproduct which has to be separated from the main product, cellulose or bioethanol. The raw unpurified lignin obtained from the separation process is normally burnt to produce energy. The process used to separate the lignin from the other plant components (celluloses and hemicelluloses) produces different types of lignin.

[0081] In the industry, two main types of raw lignin are distinguished: sulphonated lignin, obtained with treatment processes which comprise treatment with sulphates or sulphites (sulphate or Kraft process, sulphite process, semichemical process), and sulphur-free lignin, obtained with treatment processes which comprise treatment with soda (soda pulping), with high pressure steam (steam explosion) or with organic solvents (solvent pulping). The presence of sulphur in raw sulphurous lignins produces sulphur dioxide during combustion and therefore it is preferable to use lignins that do not contain sulphur in the structure.

[0082] The alkaline metal salts of sulphonated lignins have a density of approximately 1.5 g / cm3, whereas sulphur-free lignins have a density of approximately 1.3 g / cm3. The density of raw lignins is therefore much lower than the density of carbon black.

[0083] As can easily be gathered from the chemical structure of the basic components of lignin, the latter is particularly rich in hydroxyl groups (-OH), predominantly of the phenolic or alcoholic type and, to a lesser degree, of the carboxylic type, which make the lignin particularly suitable for functionalisation.

[0084] Nanometric lignin

[0085] The nanometric lignin useful in the present invention comprises lignin particles having an average hydrodynamic diameter D50 lower than 500 nm, preferably lower than 400 nm, more preferably lower than 350 nm, and greater than 50 nm, preferably greater than 70 nm, more preferably greater than 100 nm.

[0086] According to an embodiment of the present invention, the nanometric lignin useful in the present invention comprises lignin particles having an average hydrodynamic diameter D50 equal to or greater than 55, 60, 65, 70, 75, 80, 85, 90, or 95 nm.

[0087] According to an embodiment of the present invention, the nanometric lignin useful in the present invention comprises lignin particles having an average hydrodynamic diameter D50 equal to or lower than 490, 480, 470, 460, 450, 440, 430, 420, 410, 400, 390, 380, 370, 360, or 350 nm.

[0088] Advantageously, the nanometric lignin useful in the present invention comprises lignin particles having an average hydrodynamic diameter D50 comprised between 100 nm and 350 nm, such as, for example, 100, 105, 110,

[0089] 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185,

[0090] 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260,

[0091] 265, 270, 275, 280, 285, 290, 295, 300, 305, 310, 315, 320, 325, 330, 335,

[0092] 340, 345, or 350 nm.

[0093] The preparation of the nanometric lignin useful in the present invention may be carried out according to preparation techniques known in the literature, in particular by precipitation from a lignin solution in an organic solvent, adding an antisolvent, for example, as described in the following scientific articles.

[0094] The first synthesis of lignin nanoparticles using the antisolvent technique was described in Qi Liu et al., Food Chemistry, Volume 135, Issue 1 ,2012, pages 63-67, where lignin nanoparticles were obtained by dissolving in acetone and using supercritical CO2 as the antisolvent.

[0095] The process was further refined and described in Yong Qian et al., Green Chemistry, 2014,16, pages 2156-2163, using acetylated alkaline lignin in tetrahydrofuran and using dialysis to add the antisolvent in a controlled manner.

[0096] A further extension of the process with alkaline lignin in acetone under flash precipitation regime was reported in S. R. Yearla et al., Journal of Experimental Nanoscience, Volume 11 , 2016 - Issue 4, pages 289-302.

[0097] The use of Kraft lignin dissolved in tetrahydrofuran or acetone with flash precipitation or dialysis has also been described in M. Lievonen et al., Green Chemistry, 2016, 18, 1416-1422, M. Sipponen et al., Green Chemistry, 2017, 19, 5831 -5840, and Zou Tao, Frontiers in Chemistry, May 2019, Vol. 7, Article 370.

[0098] Preferably, the organic solvent used to solubilise lignin is an organic solvent, such as acetone, dimethyl sulphoxide (DMSO), tetrahydrofuran (THF), ethanol, N,N-Dimethylformamide (DMF), and 1 ,4-dioxane.

[0099] The antisolvent used to precipitate lignin is a solvent that is miscible with the organic solvent, but is not capable of solubilising the lignin. Preferably, the antisolvent is selected from the group consisting of water and hexane.

[0100] Advantageously, the preferred solvent / antisolvent pair consists of acetone / water. The acetone / water pair shows several advantages, such as:

[0101] • Effectiveness: Acetone is a good solvent for many types of lignin, while water is an effective antisolvent which causes rapid precipitation.

[0102] • Affordability: Both acetone and water are relatively inexpensive and easily available.

[0103] • Low toxicity: Compared to other organic solvents, acetone has relatively low toxicity. The water, of course, is non-toxic.

[0104] • Ease of removal: Acetone has a low boiling point (56°C), making it easy to remove by evaporation.

[0105] • Sustainability: Water is environmentally friendly and acetone may be recovered and reused.

[0106] • Versatility: This pair works well with many types of lignin and may produce nanoparticles of various sizes by adjusting the process parameters.

[0107] • Safety: Although acetone is flammable, it is generally considered safer to handle than other, more dangerous organic solvents.

[0108] By appropriately varying the process conditions, such as the concentration of lignin in the solvent, the solvent / antisolvent volume ratio, the rate of addition of the lignin solution to the antisolvent, the temperature, the stirring speed, the pH and the presence of additives, it is possible to obtain lignin nanoparticles with dimensions ranging from a few tens to several hundreds of nanometres.

[0109] Generally, smaller particles are obtained by using a lower lignin concentration in the solvent, a lower solvent / antisolvent volume ratio, a lower addition rate, a lower temperature, a higher stirring rate, a lower pH, and / or the addition of surfactants or stabilisers which may influence the size and stability of the nanoparticles.

[0110] Functionalised lignin

[0111] For the purposes of the present invention, lignin may be functionalised by reaction with epihalohydrin, using known methods, such as the solution method described in Jablonskis A. et al., “Evaluation of Ligno Boost™ softwood kraft lignin epoxidation as an approach for its application in cured epoxy resins. Ind. Crops Prod. 112, 225-235 (2018), or preferably by mechano-chemical means using a basic catalyst, optionally in aqueous solution, and an organic cation salt.

[0112] In the reaction with epihalohydrin, the hydroxyl groups of nanometric lignin react with the halogen atom of epihalohydrin according to the following scheme where X is a halogen atom.

[0113] Advantageously, the halogen atom is selected from the group consisting of fluorine, chlorine and bromine, preferably chlorine.

[0114] Preferably, epihalohydrin is selected from the group consisting of epifluorhydrin, epichlorohydrin and epibromohydrin, preferably epichlorohydrin.

[0115] The reaction is preferably carried out in a mechanical mill which favours the mixing of the reagents and an effective reaction yield both through a partial depolymerisation of the lignin, making the hydroxyl groups of the lignin more accessible and promoting their interaction with the catalyst and epihalohydrin, and through the formation of more reactive species (radicals or ions) due to the mechanical breaking of bonds.

[0116] The mechanical mill may be selected from ball mills, planetary ball mills, hammer mills, blade mills, roller mills, high pressure compression mills, ring mills, vibrating rod or tube mills, centrifugal fluid mills. Preferably, the reaction is carried out in a ball mill.

[0117] The starting lignin may be any type of lignin. Preferably, the starting lignin is selected from the group comprising Softwood Kraft lignin, Hardwood Kraft lignin, Soda Grass lignin, Wheat Straw lignin, Rice Husk lignin, lignin obtained through biorefinery processes, Organosolv lignin. Sulphur-free lignins obtained with the process described in W02011 / 007369 and commercial sulphur-free lignins such as Protobind® lignins marketed by the company GreenValue SA, Switzerland and experimental lignins produced by means of the steam explosion process by Chemtex Italia Sri company, Italy may be used.

[0118] The reaction is carried out in the presence of a basic catalyst, particularly an alkali metal hydroxide or carbonate, such as sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate, optionally in aqueous solution, and an organic cation salt, which acts as a phase transfer agent, such as tetraalkylammonium, tetraarylammonium, and alkylarylammonium salts, quaternary phosphonium salts, and imidazolium salts, with halides or other non-coordinating anions such as triflate or hexafluorophosphate, and mixtures thereof. Examples of salts useful in the present invention are, for example, tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide.

[0119] Advantageously, the lignin is pre-treated in the mechanical mill with the basic catalyst and the phase transfer agent for a period of at least 10 minutes, preferably at least 15 minutes, more preferably for a period of between 20 and 60 minutes. When using a laboratory planetary ball mill, the rotation speed is preferably at least 100 rpm, more preferably at least 200 rpm, to promote uniform distribution of the catalyst and accessibility of the hydroxyl groups. In the case of industrial ball mills, the rotation speed may be reduced to at least 20 rpm, preferably at least 40 rpm.

[0120] Next, epihalohydrin and a basic compound are added, preferably a hydroxide or carbonate of an alkali metal, such as sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate, and the reaction is carried out for at least 1 hour, preferably at least 2 hours. When using a laboratory planetary ball mill, the rotation speed is preferably at least 100 rpm, more preferably at least 200 rpm. In the case of industrial ball mills, the rotation speed may be reduced to at least 20 rpm, preferably at least 40 rpm.

[0121] The reaction may be carried out at a temperature of between 20°C and 80°C, preferably between 20°C and 60°C. Advantageously, the reaction is carried out at room temperature, i.e. approximately 20°C-25°C.

[0122] The reaction product, lignin functionalised with epihalohydrin, is recovered with water, preferably distilled or deionised water, precipitated by acidification of the resulting solution with a strong acid, such as hydrochloric acid or sulphuric acid, and subsequently washed and filtered or centrifuged one or more times to isolate the purified product.

[0123] Preferably, the functionalised lignin used for the purposes of the present invention has a degree of functionalisation equal to or greater than 15%, preferably equal to or greater than 20%, and more preferably between 30% and 70%.

[0124] The expression “degree of functionalisation” used in the present description and in the following claims means the percentage ratio between the millimoles of hydroxyl groups functionalised with epihalohydrin (per gram of functionalised lignin) and the millimoles of hydroxyl groups present in one gram of the starting lignin. This percentage ratio is estimated by default as the percentage ratio between the following two terms: i) the difference between the millimoles of aliphatic hydroxyl groups present following epihalohydrin functionalisation (per gram of functionalised lignin) and the millimoles of aliphatic hydroxyl groups present in the starting lignin; ii) the millimoles of total hydroxyl groups present in one gram of the starting lignin. It is understood that the above millimoles of total, aliphatic, phenolic and carboxylic hydroxyl groups are measured by reaction of lignin with phosphorylating agents and NMR spectroscopy as detailed below.

[0125] Preferably, the functionalised lignin is obtained in nanometric form by applying a procedure similar to that used to obtain non-functionalised nanometric lignin. The preparation of functionalised nanometric lignin may proceed by first performing the functionalisation, and then reducing the particle size, or vice versa.

[0126] More preferably, as specifically described in Example 3 below, the functionalised nanometric lignin is obtained by the process of the present invention with which the lignin is first fractionated with an organic solvent, separating an insoluble fraction, which is made nanometric in size with the techniques described above, and a soluble fraction, which is functionalised with epichlorohydrin by mechano-chemical means and subsequently deposited on the surface of the nanometric particles of the insoluble fraction. In particular, the functionalised soluble fraction of lignin is dissolved in a suitable solvent mixture and added to an aqueous suspension of the nanometric solvent-insoluble lignin fraction, leading to the deposition of the dissolved functionalised lignin on the nanometric lignin particles.

[0127] In particular, the process for preparing nanometric lignin functionalised with epihalohydrin by mechano-chemical means of the present invention comprises:

[0128] (a) providing a solution of lignin in a first organic solvent

[0129] (b) separating the insoluble fraction of said lignin from the soluble fraction in said organic solvent,

[0130] (c) drying said soluble fraction of lignin,

[0131] (d) feeding and mixing in a grinding apparatus said soluble fraction of lignin obtained in step c) and a basic catalyst, optionally in aqueous solution, and an organic cation salt;

[0132] (e) adding to the mixture of step (d) epihalohydrin and a basic compound, and mixing until the reaction is completed, obtaining said soluble fraction of lignin functionalised with said epihalohydrin;

[0133] (f) recovering said soluble fraction of lignin functionalised with said epihalohydrin,

[0134] (g) treating said insoluble fraction of lignin with a second organic solvent and an antisolvent to obtain nanometric lignin,

[0135] (h) mixing a solution of said soluble fraction of lignin functionalised with said epihalohydrin with a suspension of said nanometric lignin obtaining a suspension of nanometric lignin functionalised with said epihalohydrin; and

[0136] (i) recovering said suspension of nanometric lignin functionalised with said epihalohydrin.

[0137] Preferably, the first organic solvent used in step (a) is a polar aprotic organic solvent, such as ethyl acetate, acetone, dimethyl sulphoxide (DMSO), and acetonitrile.

[0138] Advantageously, the basic catalyst used in step (d) is selected from the group consisting of alkali metal hydroxides or carbonates, and mixtures thereof, preferably sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate. Preferably, the organic cation salt used in step (d) is selected from the group consisting of tetraalkylammonium, tetraarylammonium, and alkylarylammonium salts, quaternary phosphonium salts, and imidazolium salts, with halides or other non-coordinating anions such as triflate or hexafluorophosphate, and mixtures thereof, such as tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, and mixtures thereof.

[0139] Preferably, the basic compound used in step (e) is selected from the group consisting of hydroxides or carbonates of an alkali metal, such as, for example, sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate.

[0140] Preferably, epihalohydrin is selected from the group consisting of epifluorhydrin, epichlorohydrin and epibromohydrin, preferably epichlorohydrin.

[0141] Preferably, the second organic solvent used in step (g) is an organic solvent, such as acetone, dimethyl sulphoxide (DMSO), tetrahydrofuran (THF), ethanol, N,N-Dimethylformamide (DMF), and 1 ,4-dioxane.

[0142] The antisolvent used in step (g) is a solvent that is miscible with the second organic solvent, but is not capable of solubilising the lignin. Preferably, the antisolvent is selected from the group consisting of water and hexane.

[0143] The preferred solvent / antisolvent pair is acetone / water, for which the considerations on advantages and process conditions discussed above apply.

[0144] Predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin

[0145] For the purposes of the following description, the term “functionalised and / or nanometric lignin” is used for brevity of exposition, it being understood that this term includes functionalised lignin, or nanometric lignin, or functionalised nanometric lignin. In other words, what is set forth in the following description is equally applicable to functionalised lignin, nanometric lignin, and functionalised nanometric lignin, prepared as described above.

[0146] Preferably, the diene elastomeric polymer of the predispersion used in the present invention is any diene elastomeric polymer as described below in the present description. More preferably, the diene elastomeric polymer is selected from natural (NR) or synthetic (IR) isoprene rubber, emulsion polymerisation styrenebutadiene rubber (ESBR), carboxylated emulsion polymerisation styrenebutadiene rubber (XSBR), nitrile rubber (NBR), carboxylated nitrile rubber (XNBR), chloroprene rubber (CR), butyl rubber (HR).

[0147] Advantageously, the diene elastomeric polymer is selected from natural (NR) or synthetic (IR) isoprene rubber.

[0148] Preferably, the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin comprises an amount of functionalised and / or nanometric lignin equal to or greater than 50 phr, preferably equal to or greater than 75 phr, even more preferably equal to or greater than 100 phr up to a maximum value of 160 phr.

[0149] According to a preferred embodiment, the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin is added to the elastomeric composition in an amount such as to provide the elastomeric composition itself from 100 to 20 phr of diene elastomeric polymer, advantageously from 100 to 25 phr of diene elastomeric polymer, the balance to 100 phr being provided by the separately added diene elastomeric polymer.

[0150] According to the invention at least 20 phr, preferably at least 25 phr, more preferably at least 30 phr, and even more preferably at least 35 phr of the diene elastomeric polymer of the elastomeric composition consists of natural or synthetic isoprene rubber, preferably natural.

[0151] According to a preferred embodiment, the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin is added to the elastomeric composition in such an amount as to provide the elastomeric composition itself with at least 10 phr of functionalised and / or nanometric lignin, preferably at least 15 phr of functionalised and / or nanometric lignin, more preferably at least 20 phr of functionalised and / or nanometric lignin.

[0152] According to a preferred embodiment, the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin is added to the elastomeric composition in such an amount as to provide the elastomeric composition itself with lower than 100 phr of functionalised and / or nanometric lignin, preferably lower than 80 phr of functionalised and / or nanometric lignin, more preferably lower than 70 phr of functionalised and / or nanometric lignin. Preferably, the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin is added to the elastomeric composition in such an amount as to provide the elastomeric composition with from 20 phr to 60 phr of functionalised and / or nanometric lignin, more preferably from 25 phr to 50 phr of functionalised and / or nanometric lignin.

[0153] Preferably, the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin is prepared according to the process described in WO2022 / 144759. In short, the process described in WO2022 / 144759 comprises: a) preparing a first suspension of functionalised and / or nanometric lignin in a dispersing liquid; b) preparing a second suspension comprising functionalised and / or nanometric lignin and diene elastomeric polymer latex by mixing the first functionalised and / or nanometric lignin suspension obtained from step a) with said latex; and c) removing the dispersing liquid from said second suspension comprising functionalised and / or nanometric lignin and diene elastomeric polymer latex until said predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin is obtained.

[0154] In an embodiment, step a) of preparing said first suspension of functionalised and / or nanometric lignin comprises adding to such suspension a dosed amount of at least one surfactant.

[0155] Preferably, the surfactant is an anionic surfactant, such as sodium lauryl sulphate (SLS), lauryl ethoxy sulphate (LES), alkyl-benzene-sulphonic acids (ABS) and salts thereof. More preferably, the surfactant is sodium dodecylbenzenesulphonate, a widely available low-cost anionic surfactant.

[0156] Preferably, step a) of preparing the first suspension of functionalised and / or nanometric lignin comprises adding to the first suspension of functionalised and / or nanometric lignin an amount of surfactant comprised between 0.1 and 10 parts by weight, preferably between 1 and 5 parts by weight, per 100 parts by weight of total suspension.

[0157] Preferably, the first suspension of functionalised and / or nanometric lignin has a solid residue comprised between 5% and 50% by weight, preferably between 7% and 30% by weight, with respect to the overall weight of the suspension.

[0158] Preferably, the first functionalised and / or nanometric lignin suspension obtained from step a) has a % by weight of particles having a size greater than 1 microns equal to or lower than 10% by weight, more preferably, equal to or lower than 2% by weight.

[0159] Preferably, the diene elastomeric polymer latex has a solid residue of between 10% and 80% by weight, more preferably between 30% and 70% by weight, with respect to the total weight of the latex.

[0160] Preferably, the diene elastomeric polymer latex is stabilised with a weak base, for example ammonia.

[0161] Preferably, step b) of preparing the second suspension comprising functionalised and / or nanometric lignin and diene elastomeric polymer latex is carried out by mixing from 80 to 2000 parts by weight, preferably from 100 to 1000 parts by weight, of the first functionalised and / or nanometric lignin suspension obtained from step a) per 100 parts by weight of diene elastomeric polymer latex.

[0162] In a particularly preferred embodiment, step b) of preparing the second suspension comprising functionalised and / or nanometric lignin and diene elastomeric polymer latex is carried out by mixing the first functionalised and / or nanometric lignin suspension obtained from step a) with said latex for a time such as to obtain a substantially homogeneous second suspension.

[0163] Preferably, the mixing time is between 5 minutes and 120 minutes.

[0164] In a preferred embodiment, the mixing contemplated in step b) is carried out by means of a batch mixer with mechanical stirrer.

[0165] Preferably, step c) of removing the dispersing liquid from the second suspension comprising functionalised and / or nanometric lignin and diene elastomeric polymer latex comprises d) drying the second suspension.

[0166] Preferably, step d) of drying the second suspension comprising functionalised and / or nanometric lignin and diene elastomeric polymer latex is carried out until a moisture content of the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin is brought to a value equal to or lower than 5% by weight, preferably equal or lower than 2% by weight.

[0167] Preferably, step d) of drying the second suspension comprising functionalised and / or nanometric lignin and diene elastomeric polymer latex is carried out in a static oven at a temperature of between 40 and 120°C, for example 60°C, for a time between 2 and 30 hours.

[0168] In an alternative embodiment, step c) of removing the dispersing liquid from the second suspension comprising functionalised and / or nanometric lignin and diene elastomeric polymer latex may comprise a step e) of removing part of the dispersing liquid, for example by filtration or centrifugation or decantation, before drying said second suspension.

[0169] In a preferred embodiment, the process of preparing the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin may comprise a step f) of compacting the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin obtained from step c).

[0170] Advantageously, this compacting step may be carried out by means of apparatuses normally used in the rubber field, such as, for example, an open roller mixer (open mill) or an internal mixer.

[0171] In this way, it is possible to obtain a semi-finished product in the form of a sheet which may be subsequently used in the operations for the manufacturing of the vulcanisable elastomeric composition which will be better described below.

[0172] Alternatively, the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin may be used in the form of bales as conventionally occurs in the case of compositions based on elastomeric polymer.

[0173] Diene elastomeric polymer

[0174] The diene elastomeric polymer that is used in the present invention may be selected from those commonly used in sulphur-cross-linkable elastomeric materials, which are particularly suitable for producing tyres, i.e. from elastomeric polymers or copolymers with an unsaturated chain characterised by a glass transition temperature (Tg) generally lower than 20°C, preferably in the range of from 0°C to -11 C C. These polymers or copolymers may be of natural origin or may be obtained by solution polymerisation, emulsion polymerisation or gas-phase polymerisation of one or more conjugated diolefins, optionally mixed with at least one comonomer selected from monovinylarenes and / or polar comonomers. The conjugated diolefins generally contain from 4 to 12, preferably from 4 to 8 carbon atoms and may be selected, for example, from the group comprising: 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.

[0175] Monovinylarenes, which may optionally be used as comonomers, generally contain from 8 to 20, preferably from 8 to 12 carbon atoms and may be selected, for example, from: styrene; 1 -vinylnaphthalene; 2-vinylnaphthalene; various alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl derivatives of styrene, such as, for example, a-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4- cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolyl- styrene, 4- (4-phenylbutyl)styrene, or mixtures thereof. Styrene is particularly preferred.

[0176] Polar comonomers that may optionally be used, can be selected, for example, from: vinylpyridine, vinylquinoline, acrylic acid and alkylacrylic acid esters, nitriles, or mixtures thereof, such as, for example, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile or mixtures thereof.

[0177] Preferably, the diene elastomeric polymer which can be used in the present invention can be selected, for example, from: cis-1 ,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (in particular polybutadiene with a high content of 1 ,4-cis), optionally halogenated isoprene / isobutene 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.

[0178] A diene elastomeric polymer functionalised by reaction with suitable terminating agents or coupling agents may also be used. In particular, the diene elastomeric polymers obtained by anionic polymerisation in the presence of an organometallic initiator (in particular, an organolithium initiator) may be functionalised by reacting the residual organometallic groups derived from the initiator with suitable terminating agents or coupling agents such as, for example, imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes or aryloxysilanes.

[0179] Reinforcing filler The reinforcing filler used in the tyre according to the present invention comprises carbon black and / or a white filler.

[0180] According to a preferred embodiment, the carbon black reinforcement filler which may be used in the present invention may be selected from those having a surface area of not lower than 20 m2 / g (as determined by STSA - Statistical Thickness Surface Area - according to ISO 18852:2005).

[0181] The white filler is preferably selected from conventional silica and silicates, in the form of fibres, flakes or granules, such as bentonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, paligorskite also known as attapulgite, montmorillonite, alloisite and the like, optionally modified by acid treatment and / or derivatised, and mixtures thereof, more preferably it is silica.

[0182] Silica may vary in shape, specific surface area and size.

[0183] Examples of silica are a pyrogenic silica, a precipitated amorphous silica, a wet silica (hydrated silicic acid), or mixtures thereof.

[0184] Examples of suitable commercial silicas are the precipitated silica Rhodia Zeosil MP1165 (BET specific surface area 160 m2 / g), Ultrasil VN3 GR (BET specific surface area 180 m2 / g) and Zeosil 1115 MP (BET specific surface area 95-120 m2 / g).

[0185] Preferably, the silica has a specific surface area (BET) of at least 120 m2 / g, more preferably of at least 140 m2 / g.

[0186] Preferably, the silica has a specific surface area (BET) lower than 220 m2 / g, more preferably lower than or equal to 180 m2 / g.

[0187] According to a preferred embodiment, the reinforcing filler is present in the elastomeric composition in an amount greater than about 15 phr, preferably greater than about 20 phr. Preferably, the reinforcement filler is present in the elastomeric composition in an amount lower than about 85 phr, preferably lower than about 65 phr.

[0188] Vulcanising agent

[0189] The elastomeric composition may be vulcanised according to known techniques, in particular with sulphur-based and / or peroxide-based vulcanising systems commonly used for diene elastomeric polymers.

[0190] To this end, in the elastomeric compound obtained from the elastomeric composition after one or more thermomechanical treatment steps, a sulphurbased or peroxide-based vulcanising agent is incorporated together with vulcanisation accelerants.

[0191] Specific examples of peroxides are organic peroxides, such as dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (DBPH), bis-(2 ,4- dichlorobenzoyl) (DCBP), di-tert-butyl peroxide.

[0192] In the final treatment step, the temperature is generally kept below 120°C and preferably below 100°C, so as to prevent any undesired pre-cross-linking phenomena.

[0193] Preferably, said vulcanising agent comprises sulphur-based vulcanising systems comprising sulphur or sulphur-containing molecules (sulphur donors) together with vulcanisation accelerants and / or activators known in the art.

[0194] Activators that are particularly effective are zinc compounds, and in particular ZnO, ZnCOs, zinc salts of saturated or unsaturated fatty acids containing from 8 to 18 carbon atoms, such as, for example, zinc stearate, which are preferably formed in situ in the elastomeric composition from ZnO and fatty acid, or mixtures thereof.

[0195] The accelerants which are commonly used may be selected from: dithiocarbamates, guanidine, thiourea, thiazoles, sulphenamides, thiurams, amines, xanthates or mixtures thereof.

[0196] According to a preferred embodiment, said cross-linkable elastomeric composition comprises an amount of vulcanising agent equal to or greater than about 1 phr, preferably equal to or greater than about 2 phr.

[0197] Preferably, the amount of vulcanising agent is lower than or equal to about

[0198] 7.5 phr, preferably lower than or equal to about 7.

[0199] Advantageously, the amount of sulphur is between about 2 phr and about

[0200] 6.5 phr.

[0201] Other additives

[0202] According to an embodiment, the elastomeric composition may comprise a silane coupling agent able to interact with the silica optionally present as reinforcing filler and / or the silicates and to bind it to the diene elastomeric polymer during the vulcanisation.

[0203] According to an embodiment, the silane coupling agent which may be used in the present invention may be selected from those having at least one hydrolysable silane group, which may be identified, for example, by the following general formula (II):

[0204] (R)3Si-CnH2n-X (II) where the R groups, which may be the same or different, are selected from: alkyl, alkoxy or aryloxy groups or from halogen atoms, provided that at least one of the R groups is an alkoxy or aryloxy group; n is an integer of between 1 and 6, inclusive; X is a group selected from: nitrous, mercapto, amino, epoxide, vinyl, imide, chlorine, -(S)mCnH2n-Si-(R)3 and -S-COR, where m and n are integers of between 1 and 6 inclusive and the R groups are as defined above.

[0205] Among the silane coupling agents, bis(3-triethoxysilylpropyl)tetrasulphide and bis(3-triethoxysilylpropyl)disulphide are particularly preferred. Said coupling agents may be used as such or as a suitable mixture with an inert filler (such as carbon black) so as to facilitate their incorporation into the elastomeric composition.

[0206] According to an embodiment, said silane coupling agent may be present in the elastomeric composition in an amount ranging between 0.01 phr and about 10 phr, preferably between about 0.5 phr and about 5 phr.

[0207] Said elastomeric composition may comprise other commonly used additives, selected on the basis of the specific application for which the composition is intended. For example, said materials may be admixed with: antioxidants, anti-ageing agents, plasticisers, adhesives, anti-ozone agents, modifying resins, or mixtures thereof.

[0208] In particular, in order to improve the processability, said vulcanisable elastomeric composition may be admixed with a plasticiser generally selected from mineral oils, vegetable oils, synthetic oils or mixtures thereof, such as, for example, aromatic oil, naphthenic oil, phthalates, soybean oil or mixtures thereof. The amount of plasticiser generally ranges from 0 phr and about 70 phr, preferably from about 5 phr to about 30 phr.

[0209] Preparation of the elastomeric composition

[0210] The elastomeric composition may be prepared by mixing the necessary amount of diene elastomeric polymer with the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin, the reinforcing filler, the vulcanising agent and any other additives optionally present according to the techniques known in the industry.

[0211] According to the invention at least 20 phr, preferably at least 25 phr, more preferably at least 30 phr, and even more preferably at least 35 phr of the diene elastomeric polymer of the elastomeric composition consists of natural or synthetic isoprene rubber, preferably natural.

[0212] The mixing may be carried out, for example, using at least one batch mixer and / or at least one continuous mixer.

[0213] The predispersion of a diene elastomeric polymer and functionalised and / or nanometric lignin may be fed to said at least one batch mixer and / or at least one continuous mixer according to any method known to those skilled in the art and suitable for the purpose.

[0214] For example, the predispersion may be fed in the form of material in bales or sheets obtained as described above in the process for preparing the predispersion.

[0215] In the context of the present description and the subsequent claims, the term “batch mixer (or mixing device)” indicates a mixing device configured to be periodically fed with the various ingredients of the material to be prepared in predefined amounts and for mixing them for a predetermined time in order to obtain a batch of said material.

[0216] At the end of the mixing step, the entire batch of material obtained is completely discharged from the mixing device in a single solution. Examples of batch mixers are internal mixers of the type with tangential rotors (Banbury®) or with interpenetrating rotors (Intermix®).

[0217] In the context of the present description and of the subsequent claims, the term “continuous mixer (or mixing device)” indicates a mixing device configured to continuously feed the ingredients of the material to be prepared, typically by means of controlled dosage dispensers, to mix the ingredients in order to produce the material and to discharge it in a continuous flow (except possible stoppages of the mixing device due to maintenance, or change of the recipe of the material).

[0218] In the jargon of the elastomeric mixers sector, the continuous mixing device is sometimes referred to as: “mixing extruder”, which is herein considered equivalent to a “continuous mixer”. The continuous mixer (in particular its active elements, such as screws or mixer satellites) is then provided with mixing portions able to impart a high shear stress to the material being mixed and, alternating with the mixing portions, transport portions able to impart a thrust to the material being processed to feed it from one longitudinal end to the other of the internal chamber. It may further be provided with possible redistribution portions.

[0219] Examples of continuous mixing devices are twin-screw or multi-screw mixers (e.g. ring mixers), co-penetrating and co-rotating, or planetary mixing devices.

[0220] Both the batch mixer and the continuous mixer are able to impart to the material to be produced with them sufficient energy to mix and homogeneously disperse the various components even in the case of cold feeding of the ingredients and, in the case of a material comprising an elastomeric component, to chew the elastomeric compound raising the temperature thereof so as to make it workable and plastic to facilitate the incorporation and / or distribution of the ingredients within the elastomeric polymeric matrix.

[0221] The elastomeric compound thus obtained may then be stored or sent directly to the subsequent manufacturing steps of the tyre according to the present invention.

[0222] The tyre

[0223] According to an embodiment, the tyre for vehicle wheels according to the invention comprises

[0224] - a carcass structure comprising at least a carcass ply having opposite lateral edges associated to respective bead structures;

[0225] - optionally, a belt structure applied in radially external position with respect to the carcass structure;

[0226] - a tread band applied in a radially external position to said carcass structure and to said belt structure, if present, and

[0227] - optionally, an underlayer and / or an anti-abrasive strip and / or a pair of sidewalls and / or a sidewall insert and / or a mini-sidewall and / or an underliner and / or a rubberising layer and / or flipper and / or chafer and / or a bead filler and / or a sheet.

[0228] According to an embodiment, the structural element according to the invention is selected from the group consisting of carcass structure, belt structure, tread band and pair of sidewalls.

[0229] The tyre according to the invention may be used on two, three or four- wheeled vehicles. The tyre according to the invention may be for summer or winter use or for all seasons.

[0230] The tyre according to the invention may be a tyre for passenger cars, including both automobile tyres, such as for example the high-performance tyres, and tyres for light transport vehicles, for example vans, campers, pickup, typically with total mass at full load equal to or lower than 3500 kg.

[0231] The tyre according to the invention may be a tyre for motorcycle wheels, such as for example motorcycles belonging to the scooter, road enduro, custom, hypersport, supersport, and sport touring categories. The term “tyre for motorcycle wheels” means a tyre having a high curvature ratio (typically greater than 0.200), capable of reaching high angles of inclination (roll angles) during cornering of the motorcycle.

[0232] The tyre according to the invention may be a tyre for bicycle wheels, such as for example racing bicycles, off-road bicycles, and city bicycles.

[0233] DRAWINGS

[0234] The description is given hereinafter with reference to the accompanying drawings, provided only for illustrative and, therefore, non-limiting purposes, in which:

[0235] - Figure 1 schematically shows a semi-sectional view of a tyre for vehicle wheels according to the present invention,

[0236] - Figure 2 illustrates the FT-IR / ATR plot of the soluble FS, soluble FSM- modified, and insoluble Fl fractions of lignin described in the preparation of the epichlorohydrin-functionalised nanometric lignin “LNP EPO” of Example 3,

[0237] - Figure 3 illustrates the FE-SEM images of the LNP L (a), LNP S (b), and LNP EPO (c) lignin particles of Examples 1 -3.

[0238] DETAILED DESCRIPTION OF THE INVENTION

[0239] The present invention will be illustrated in further detail by means of an illustrative embodiment with reference to the accompanying Figure 1 , where “a” indicates an axial direction and “r” indicates a radial direction. For simplicity, Figure 1 shows only a part of the tyre, the remaining part not shown being identical and disposed symmetrically with respect to the radial direction “r”.

[0240] The reference numeral 100 indicates in Figure 1 a tyre for vehicle wheels, which generally comprises a carcass structure 101 having respectively opposite end flaps engaged with respective annular anchoring structures 102, called bead cores, optionally associated with a bead filler 104. The tyre area comprising the bead core 102 and the filler 104 forms a bead structure 103 intended for anchoring the tyre onto a corresponding mounting rim, not shown. Each bead structure 103 is associated to the carcass structure by folding back of the opposite lateral edges of the at least one carcass layer 101 around the bead core 102 so as to form the so-called carcass flaps 101 a as shown in Figure 1.

[0241] The carcass structure 101 is optionally associated with a belt structure 106 comprising one or more belt layers 106a, 106b placed in radial superposition with respect to one another and with respect to the carcass structure 101 , having typically metal reinforcing cords. Such reinforcing cords may have crossed orientation with respect to a circumferential extension direction of the tyre 100. By “circumferential” direction we mean a direction generally facing according to the direction of rotation of the tyre, or in any case slightly inclined with respect to the direction of rotation of the tyre.

[0242] The belt structure 106 further comprises at least one radially external reinforcing layer 106c with respect to the belt layers 106a, 106b. The radially external reinforcing layer 106c comprises textile or metal cords, disposed according to a substantially zero angle with respect to the circumferential extension direction of the tyre and immersed in the elastomeric material. Preferably, the cords are disposed substantially parallel and side by side to form a plurality of turns. Such turns are substantially oriented according to the circumferential direction (typically with an angle of between 0° and 5°), such direction being usually called “zero degrees” with reference to the laying thereof with respect to the equatorial plane X-X of the tyre. By “equatorial plane” of the tyre it is meant a plane perpendicular to the axis of rotation of the tyre and which divides the tyre into two symmetrically equal parts.

[0243] A tread band 109 of a vulcanised elastomeric compound is applied in a radially internal position with respect to the carcass structure 101 and / or if present (as in the illustrated case) to the belt structure 106. In a radially external position, the tread band 109 has a rolling portion 109a intended to come into contact with the ground. Circumferential grooves, which are connected by transverse cuts (not shown in Figure 1 ) so as to define a plurality of blocks of various shapes and sizes distributed in the rolling portion 109a, are generally made in this portion 109a, which for simplicity is represented smooth in Figure 1 .

[0244] To optimise the performance of the tread, the tread band may be made in a two-layer structure.

[0245] Such two-layer structure comprises the rolling layer or portion 109a (called cap) and a substrate 111 (called base) forming the so-called cap-and-base structure.

[0246] Both the tread band 109 and the cap-and-base structure formed by the rolling layer 109a and the substrate 111 may advantageously be made with the elastomeric composition comprising the predispersion of dienic elastomeric polymer and functionalised and / or nanometric lignin described above, since a lower hysteresis means ( i) a lower dissipation of energy in the form of heat while driving, and (ii) a lower fuel consumption, and at the same time a greater resistance to tearing means a greater resistance to mechanical stresses deriving from the rolling or sliding of the tyre during use, resulting in longer tyre life.

[0247] Moreover, respective sidewalls 108 of vulcanised elastomeric compound are further applied in an axially external position to said carcass structure 101 , each extending from one of the lateral edges of the tread band 109 up to the respective bead structure 103.

[0248] A strip consisting of elastomeric compound 110, commonly known as “minisidewall”, of vulcanised elastomeric compound may optionally be provided in the connecting zone between sidewalls 108 and the tread band 109, this minisidewall generally being obtained by co-extrusion with the tread band 109 and allowing an improvement of the mechanical interaction between the tread band 109 and the sidewalls 108. Preferably, the end portion of sidewall 108 directly covers the lateral edge of the tread band 109.

[0249] In some specific embodiments, such as the one illustrated and described herein, the stiffness of the bead 103 may be improved by providing a reinforcing layer 120 generally known as a “flipper” in the tyre bead. The flipper 120 is wrapped around the respective bead core 102 and the bead filler 104 so as to at least partially surround them. The flipper 120 is disposed between the carcass layer 101 and the bead structure 103. Usually, the flipper 120 is in contact with the carcass layer 101 and said bead structure 103. The flipper 120 typically comprises a plurality of metal or textile cords incorporated in a vulcanised elastomeric compound.

[0250] In some specific embodiments, such as the one illustrated and described herein, the bead structure 103 may further comprise a further reinforcing layer 121 which is generally known by the term of “chafer” and which has the function to increase the rigidity and integrity of the bead structure 103.

[0251] The chafer 121 usually comprises a plurality of cords incorporated in a vulcanised elastomeric compound; such cords are generally made of textile material (for example aramid or rayon), or of metallic material (for example steel cords).

[0252] Optionally, an anti-abrasive strip 105 is disposed so as to wrap the bead structure 103 along the axially internal and external and radially internal areas of the bead structure 103, thus interposing itself between the latter and the wheel rim when the tyre 100 is mounted on the rim.

[0253] Moreover, a radially internal surface of tyre 100 is preferably internally lined by a layer of substantially airtight elastomeric material, or so-called liner 112.

[0254] According to an embodiment not shown, the tyre may be a tyre for motorcycle wheels. The profile of the straight section of the tyre for motorcycle (not shown) has a high transversal curvature since it must guarantee a sufficient footprint area in all the inclination conditions of the motorcycle. The transverse curvature is defined by the value of the ratio between the distance f of the ridge of the tread from the line passing through the laterally opposite ends of the tread itself, measured on the equatorial plane of the tyre, and the width C defined by the distance between the laterally opposite ends of the tread itself. A tyre with high transverse curvature indicates a tyre whose transverse curvature ratio (f / C) is at least 0.20.

[0255] According to an embodiment not shown, the tyre may be a tyre for bicycle wheels.

[0256] The reinforcing elements of the belt structure 106, and / or of the carcass structure 101 , and / or of the bead structure 103, such as the flipper 120 and / or the chafer 121 , may be advantageously made with the elastomeric composition comprising the predispersion of diene elastomeric polymer and functionalised and / or nanometric lignin described above, since a lower hysteresis means (i) a lower dissipation of energy in the form of heat during driving, preventing the onset of operating temperatures that are too high which may risk compromising the integrity of the tyre, and (ii) lower fuel consumption, and at the same time greater resistance to tearing means greater resistance to the mechanical stresses suffered by the tyre during use, in particular in the area of the bead in contact with the wheel rim.

[0257] The building of the tyre 100 as described above may be carried out by assembling respective semi-finished products onto a forming drum, not shown, by at least one assembly device.

[0258] At least a part of the components intended to form the carcass structure 101 of the tyre 100 is built and / or assembled on the forming drum. More particularly, the forming drum is intended to first receive the possible liner 112, and then the carcass ply 101 . Thereafter, devices non shown coaxially engage one of the annular anchoring structures 102 around each of the end flaps, position an external sleeve comprising the belt structure 106 and the tread band 109 in a coaxially centred position around the cylindrical carcass sleeve and shape the carcass sleeve according to a toroidal configuration through a radial expansion of the carcass ply 101 , so as to cause the application thereof against a radially internal surface of the external sleeve.

[0259] After building of the green tyre 100, a moulding and vulcanisation treatment is generally carried out in order to determine the structural stabilization of the tyre 100 through vulcanisation of the elastomeric compounds, as well as to impart a desired tread pattern on the tread band 109 and to impart any distinguishing graphic signs at the sidewalls 108.

[0260] The present invention will be further illustrated below by means of a number of preparatory examples, which are provided for indicative purposes only and without any limitation of the present invention.

[0261] EXAMPLE 1

[0262] Preparation of nanometric lignin 1 (LNP L)

[0263] A 10 g sample of UPM BioPiva™ 100 Softwood Kraft lignin oven-dried at approximately 70°C for approximately 18h (UPM Biochemicals - solids content 95%) was stirred for 3 h in a mixture of acetone and deionised water 3:1 by weight (acetone: 62.5 g, water: 20.8 g) to obtain a concentration of 0.120 g / g, understood as grams of lignin per gram of solvent. The lignin solution was then filtered using a sintered glass filter (size 1 ) to remove insoluble residues.

[0264] The filtrate was then poured into 833.3 g of deionised water and vigorously stirred using a piston pump with a flow rate of 50 ml / min, producing a nanometric lignin suspension “LNP L”.

[0265] The obtained nanometric lignin suspension “LNP L” was transferred into a flask and concentrated by rotary evaporator using gentle heating (50°C max) and stirring, up to a lignin concentration of 77 g / l.

[0266] EXAMPLE 2

[0267] Preparation of nanometric lignin 2 (LNP S)

[0268] A 10 g sample of UPM BioPiva™ 100 Softwood Kraft lignin oven-dried at approximately 70°C for approximately 18h (UPM Biochemicals - solids content 95%) was stirred for 3 h in a mixture of acetone and deionised water 3:1 by weight (acetone: 375.0 g, water: 125.0 g) to obtain a concentration of 0.020 g / g, understood as grams of lignin per gram of solvent. The lignin solution was then filtered using a sintered glass filter (size 1 ) to remove insoluble residues.

[0269] The filtrate was then poured into 1250.0 g of deionised water and vigorously stirred using a piston pump with a flow rate of 50 ml / min, producing a nanometric lignin suspension “LNP S”.

[0270] The resulting nanometric lignin suspension “LNP S” was transferred into a flask and concentrated by rotary evaporator using gentle heating (50°C max) and stirring, up to a lignin concentration of 77 g / L.

[0271] EXAMPLE 3

[0272] Preparation of nanometric lignin functionalised with epichlorohydrin (LNP EPO)

[0273] A 20 g sample of Softwood Kraft UPM BioPiva™ 100 lignin oven-dried at approximately 70°C for approximately 18 h (UPM Biochemicals - solids content 95%) was fractionated by stirring in 200 ml of ethyl acetate for 2 h.

[0274] The mixture was filtered using a sintered glass filter (size 1 ) separating the residual solid from the collected liquid. The residual solid was air-dried (insoluble fraction - Fl), while the collected liquid was dried by rotary evaporator (soluble fraction - FS).

[0275] 3.50 g of the soluble FS fraction were placed in a steel grinding jar containing 10 steel balls having a diameter of 1 cm, 0.093 g of sodium hydroxide (NaOH) and 0.202 g of tetrabutylammonium bromide (TBAB). The mixture was placed in a planetary ball mill (Retsch PM 100) and milled for 10 minutes at 400 rpm. Subsequently, the mixture was added with 4.90 ml of epichlorohydrin (ECH), and further ground for 2 hours at 400 rpm. Finally, the mixture was added with 1.40 g of sodium hydroxide (NaOH), and ground for 2.5 h at 400 rpm.

[0276] The resulting mixture was then dissolved in water, precipitated by adding HCI (0.1 M), centrifuged (4000 rpm, 5 minutes), and washed two or three more times. The resulting product (modified soluble fraction - FSM) was finally freeze-dried (average yield 49.5% weight). Then, 1.75 g of the modified FSM soluble fraction was dissolved under stirring in a mixture of acetone and deionised water 3:1 by weight at a concentration of 0.012 g / g (acetone: 86.3 g, water: 28.8 g) for 3 hours. The modified soluble fraction (FSM) solution was then filtered using a sintered glass filter (size 1 ) to remove insoluble residues.

[0277] Meanwhile, 8.25 g of insoluble fraction Fl was dissolved under stirring in a mixture of acetone and deionised water 3:1 by weight at a concentration of 0.020 g / g (acetone: 328.1 g, water: 109.4 g) for 3 hours. The insoluble fraction Fl solution was then filtered using a sintered glass filter (size 1 ) to remove insoluble residues. Then, the filtrate was poured into 1750.0 g of vigorously stirred deionised water using a piston pump with a flow rate of 50 ml / min to obtain a suspension of insoluble fraction (Fl), from which acetone was removed by forced evaporation.

[0278] The FSM-modified soluble fraction solution was added to the Fl-insoluble fraction suspension under vigorous stirring using a piston pump with a flow rate of 50 ml / min, obtaining the epichlorohydrin-functionalised nanometric lignin suspension “LNP EPO” which was concentrated by rotary evaporator using gentle heating (50°C max) and stirring, up to a lignin concentration of 77 g / L.

[0279] EXAMPLE 4

[0280] Characterisation of lignins in examples 1 -3

[0281] The morphology and particle size of the LNP L, LNP S, and LNP EPO lignins of Examples 1-3 were evaluated by field emission scanning electron microscopy (FE-SEM).

[0282] The FE-SEM images shown in Figure 3 were obtained using a Zeiss UltraPlus FE-SEM, Zeiss (Germany), operating at 5.0 kV and a working distance of 5-6 mm. Samples were prepared by evaporating a suspension of dilute particles (1 mg / ml) placed on the stub and sputtered with a gold layer lower than 5 nm thick.

[0283] The particle sizes of the lignins in Examples 1 -3 were evaluated by dynamic light scattering (DLS).

[0284] DLS measurements were performed on a Malvern Zetasizer, Malvern, UK, with a scattering angle of 90° at a temperature of 25°C. Data were calculated as the average of three measurements, each comprising 30-50 subsets. Before analysis, samples were diluted to a lignin concentration of 1 mg / ml.

[0285] The following Table 1 reports the values of the average hydrodynamic diameter D50 and the polydispersity (D) of the particles of the lignins LNP L, LNP S and LNP EPO of Examples 1 -3.

[0286] TABLE 1

[0287] Quantitative determination of the hydroxyl (OH) groups of the soluble FS, soluble modified FSM, and insoluble Fl fractions of lignin described in the preparation of the epichlorohydrin-functionalised nanometric lignin “LNP EPO” of Example 3 was achieved by nuclear magnetic resonance (31 P NMR) using a Bruker Avance NMR spectrometer operating at 500 MHz.

[0288] Samples were prepared according to the standard process described in Meng, X., Crestini, C., Ben, H., Hao, N., Pu, Y., Ragauskas, A.J., & Argyropoulos, D.S. (2019). Determination of hydroxyl groups in biorefinery resources via quantitative 31 P NMR spectroscopy, Nature Protocols, 14(9), 2627-2647.

[0289] The results are summarised in the following Table 2. TABLE 2

[0290] The results highlighted the differences between the insoluble fraction, richer in aliphatic hydroxyls, and the soluble fraction, richer in phenolic and carboxylic hydroxyls, while in the modified soluble fraction a considerable decrease in phenolic hydroxyls was found, caused by the reaction with epichlorohydrin, and a corresponding considerable increase in aliphatic hydroxyls due to the opening of the oxirane ring of epichlorohydrin caused by the phosphorylating agent.

[0291] The degree of functionalisation of the Modified Soluble Fraction was therefore estimated as approximately 59% (100*(4.68-1 ,00) / 6.19)

[0292] The ATR / FT-IR spectra of the soluble FS, soluble FSM-modified, and insoluble Fl fractions of lignin described in the preparation of the epichlorohydrin-functionalised nanometric lignin “LNP EPO” of Example 3 were recorded on a Nicolet iS10 spectrometer (Thermo Scientific) equipped with an iTR Smart device (32 total scan, range 3750-750 cm-1, resolution 1 cm-1) and reported in Figure 2.

[0293] From Figure 2, one can mainly notice the differences between the insoluble fraction (Fl) and the soluble fraction (FS) of lignin. Furthermore, in the spectrum of the modified soluble fraction (FSM), the presence of a new band at around 910 cm-1assigned to the oxirane ring of epichlorohydrin, and the decrease of the band at 1370 cm-1assigned to phenolic CO, can be noted.

[0294] EXAMPLE 5

[0295] Preparation of predispersions of a diene elastomeric polymer and lignin comprising 50% w / w lignin

[0296] The LNP L, LNP S and LNP EPO lignin suspensions prepared in Examples 1 -3 were used to prepare 50% lignin and natural rubber predispersions according to a co-drying process, similar to that described in WO2022 / 144759.

[0297] Specifically, 130 ml of lignin suspension was slowly poured into 16.6 g of NR latex (60 wt%, high ammonia content) under vigorous stirring and left to disperse for 30 min. The pre-dispersion was then dried in a fan oven for 36 hours at 60°C.

[0298] Using the lignin suspensions LNP L, LNP S and LNP EPO, the 50% lignin and natural rubber predispersions DISP-L. DISP-S and DISP-EPO were then prepared, respectively.

[0299] A comparison predispersion DISP-C was prepared by dispersing 10 g of UPM BioPiva™ 100 Softwood Kraft Lignin (UPM Biochemicals - solids content 65% - average hydrodynamic diameter D50 approx. 60pm) in water (77 g / l) and slowly pouring the resulting dispersion into 16.6 g of NR latex (60 wt%, high ammonia content) under vigorous stirring and allowing to disperse for 30 minutes. The DISP-C comparison predispersion was then dried in a convection oven for 36 hours at 60°C.

[0300] EXAMPLE 6

[0301] Use of DISP-L, DISP-S, DISP-EPO and DISP-C predispersions in the preparation of a natural rubber-based elastomeric compound as a 50% replacement for carbon black

[0302] The DISP-L. DISP-S and DISP-EPO predispersions were used to make the inventive vulcanisable elastomeric compounds M-L, M-S and M-EPO, respectively. The DISP-C predispersion was used to make the M-C vulcanisable elastomeric comparison compound.

[0303] The following Table 3A shows the phr compositions of the inventive vulcanisable elastomeric compounds M-L, M-S and M-EPO, of the comparison vulcanisable elastomeric compound M-C, and of the reference compound M- R comprising carbon black.

[0304] The predispersions DISP-L, DISP-S, DISP-EPO and DISP-C are added in quantities such as to provide 25 phr of natural rubber and 25 phr of lignin to the M-L, M-S, M-EPO and M-C compounds, the latter replacing 50% of the carbon black in the M-R compound.

[0305] TABLE 3A

[0306] NR: Indonesian Rubber Standard grade natural rubber, SIR20 from Aneka Bumi Pratama

[0307] CB: N326 grade carbon black from Cabot Corp; 6PPD: N-(1 ,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine, from Flexys;

[0308] Stearic acid: stearin from llndesa

[0309] ZnO: zinc oxide green seal, Zincol oxides

[0310] TBBS: N-tertbutylbenzothiazole-2-sulphenamide, Vulkacit NZ from Lanxess;

[0311] Sulphur: 66% Oleate Insoluble Sulphur, Crystex OT 33 from Eastman All the components, except for sulphur and the vulcanisation accelerant (TBBS), were mixed in an internal mixer (Brabender) for about 9 minutes (1ststep).

[0312] When the temperature of 135°C was reached, the material was mixed for another minute and then discharged. The unfinished compound was left to rest for a day then the sulphur and the accelerant (TBBS) were added and the mixing was carried out in the same mixer at about 60°C for 9 minutes (2ndstep).

[0313] Finally, the compound was vulcanised at 170°C for 10 minutes, in order to be able to measure its static mechanical properties, while the dynamic mechanical properties were measured on the vulcanisable compound.

[0314] The static mechanical properties of the compounds were evaluated according to the ISO 37-2011 standard at 23°C, on 3 Dumbell specimens. In this way the following parameters were measured:

[0315] - load at 10% elongation (Ca0.1 ),

[0316] - load at 50% elongation (Ca0.5),

[0317] - load at 100% elongation (Ca1 ),

[0318] - load at 300% elongation (Ca3),

[0319] - breaking load (CR), and

[0320] - % elongation at break (AR).

[0321] The dynamic mechanical properties of the compounds were evaluated using an Alpha Technologies R.P.A. 2000 oscillating chamber rheometer (Rubber Process Analyser) with chamber geometry as described in ASTM D6601 -19 Figure 1 , applying the following method.

[0322] An approximately cylindrical test sample with a volume in the range from 4.6 to 5 cm3was obtained by punching a sheet with a thickness of at least 5 mm of the green vulcanisable elastomeric composition to be characterised. Subsequently, the chambers of the R.P.A. 2000 were preliminarily preheated to 170°C.

[0323] The sample was loaded between the chambers of the rheometer and the chambers were closed. Between the sample of the green vulcanisable elastomeric composition and each chamber of the rheometer, two films were interposed to protect the chamber itself: in contact with the compound, a film of Nylon 6.6 cast about 25 microns thick and in contact with the chamber of the rheometer a polyester film about 23 microns thick. The sample was then vulcanised for a fixed time of 10 minutes at a temperature of 170°C while recording the vulcanisation curve, i.e. subjecting the sample to a sinusoidal deformation of 7% amplitude and 1 .67 Hz frequency for the entire duration of the vulcanisation.

[0324] The dynamic mechanical properties in compression of the compounds were evaluated using an Instron model 1341 dynamic device in the following modes.

[0325] A test piece of vulcanised material (170°C for 10 minutes) having a cylindrical shape (length = 25 mm; diameter = 18 mm), compressed preloaded up to a longitudinal deformation of 25% with respect to the initial length and maintained at the predetermined temperature of 70°C for the entire duration of the test.

[0326] After a waiting time of 2 minutes followed by a mechanical pre-conditioning of 125 cycles at 10Hz at 5% deformation amplitude with respect to the length under preload, the specimen was subjected to a dynamic sinusoidal stress having an amplitude of ± 3.5% of the length under pre-load, with a frequency of 10Hz.

[0327] In this way the following parameters were measured:

[0328] - dynamic elastic modulus E’,

[0329] - tan delta, i.e. the ratio between the viscous dynamic modulus E” and the dynamic elastic modulus E’.

[0330] The following Table 3B shows the results obtained from the characterisations carried out.

[0331] TABLE 3B

[0332] The M-L and M-S compounds of the invention proved superior in terms of dynamic reinforcement, elongation modulus (CA1 and CA3), and ultimate properties (CR and AR) compared to the M-C reference compound. The M- EPO compound of the invention demonstrated excellent performance in terms of ultimate properties and hysteresis even compared to the M-R reference compound. EXAMPLE 7

[0333] Use of DISP-L, DISP-S, DISP-EPO and DISP-C predispersions in the preparation of a natural rubber-based elastomeric compound as a 100% replacement for carbon black

[0334] The DISP-L. DISP-S and DISP-EPO predispersions were used to make the inventive vulcanisable elastomeric compounds M-L, M-S and M-EPO, respectively. The DISP-C predispersion was used to make the M-C vulcanisable elastomeric comparison compound. The following Table 4A shows the phr compositions of the inventive vulcanisable elastomeric compounds M-L, M-S and M-EPO, of the comparison vulcanisable elastomeric compound M-C, and of the reference compound M- R comprising carbon black. The predispersions DISP-L, DISP-S, DISP-EPO and DISP-C are added in quantities such as to provide 50 phr of natural rubber and 50 phr of lignin to the M-L, M-S, M-EPO and M-C compounds, the latter replacing 100% of the carbon black in the M-R compound.

[0335] TABLE 4A

[0336] NR: Indonesian Rubber Standard grade natural rubber, SIR20 from Aneka Bumi Pratama

[0337] CB: N326 grade carbon black from Cabot Corp;

[0338] 6PPD: N-(1 ,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine, from Flexys;

[0339] Stearic acid: stearin from llndesa

[0340] ZnO: zinc oxide green seal, Zincol oxides

[0341] TBBS: N-tertbutylbenzothiazole-2-sulphenamide, Vulkacit NZ from Lanxess;

[0342] Sulphur: 66% Oleate Insoluble Sulphur, Crystex OT 33 from Eastman

[0343] All the components, except for sulphur and the vulcanisation accelerant (TBBS), were mixed in an internal mixer (Brabender) for about 9 minutes (1ststep).

[0344] When the temperature of 135°C was reached, the material was mixed for another minute and then discharged. The unfinished compound was left to rest for a day then the sulphur and the accelerant (TBBS) were added and the mixing was carried out in the same mixer at about 60°C for 9 minutes (2ndstep).

[0345] Finally, the compound was vulcanised at 170°C for 10 minutes, in order to be able to measure its static mechanical properties, while the dynamic mechanical properties were measured on the vulcanisable compound.

[0346] The properties of the compounds were evaluated with the same procedures used for the elastomeric compounds of Example 6.

[0347] The following Table 4B shows the results obtained from the characterisations carried out.

[0348] TABLE 4B

[0349] The results in Table 4B demonstrated that the total replacement of carbon black from the M-R reference compound with lignin from the M-C comparison compound causes a suppression of static and dynamic reinforcement using lignin. The M-L compound offers limited advantages, especially in terms of dynamic mechanical properties and hysteresis, compared to the comparison compound M-C, while the M-S compound is more reinforcing, at the expense of a slight increase in hysteresis. The M-EPO compound demonstrated a surprising improvement in breaking properties compared to the M-C compound while keeping dynamic hysteresis under control, significantly improving compared to the M-R reference compound with CB.

Claims

CLAIMS1. A tyre for vehicle wheels which comprises at least one structural element comprising a vulcanised elastomeric compound obtained by vulcanisation of a vulcanisable elastomeric composition comprising per 100 phr of diene elastomeric polymer:(i) a predispersion of a diene elastomeric polymer and nanometric lignin, in an amount to provide the elastomeric composition with 100 to 10 phr of diene elastomeric polymer and an amount of nanometric lignin equal to or greater than 5 phr,(ii) from 0 to 90 phr of at least one diene elastomeric polymer,(iii) from 0 to 110 phr of a reinforcing filler,(iv) from 0.1 to 12 phr of at least one vulcanising agent, where said nanometric lignin comprises lignin particles having an average hydrodynamic diameter D50 lower than 500 nm and greater than 50 nm.

2. A vulcanisable elastomeric composition comprising per 100 phr of diene elastomeric polymer:(i) a predispersion of a diene elastomeric polymer and nanometric lignin, in an amount to provide the elastomeric composition with 100 to 10 phr of diene elastomeric polymer and an amount of nanometric lignin equal to or greater than 5 phr,(ii) from 0 to 90 phr of at least one diene elastomeric polymer,(iii) from 0 to 110 phr of a reinforcing filler,(iv) from 0.1 to 12 phr of at least one vulcanising agent, where said nanometric lignin comprises lignin particles having an average hydrodynamic diameter D50 lower than 500 nm and greater than 50 nm.

3. The tyre for vehicle wheels according to claim 1 or the elastomeric composition according to claim 2, characterised in that said pre-dispersion of diene elastomeric polymer and nanometric lignin is added to the elastomeric composition in such an amount as to provide the elastomeric composition with 100 to 20 phr of diene elastomeric polymer, preferably 100 to 25 phr of diene elastomeric polymer.

4. The tyre for vehicle wheels according to claim 1 or the elastomeric composition according to claim 2, characterised in that at least 20 phr, preferably at least 25 phr, more preferably at least 30 phr, and even more preferably at least 35 phr of the diene elastomeric polymer of the elastomeric composition is natural or synthetic isoprene rubber, preferably natural.

5. The tyre for vehicle wheels according to claim 1 or the elastomeric composition according to claim 2, characterised in that said predispersion of diene elastomeric polymer and nanometric lignin is added to the elastomeric composition in such an amount as to provide the elastomeric composition with from 10 phr to 100 phr of nanometric lignin, more preferably from 15 phr to 80 phr of nanometric lignin.

6. The tyre for vehicle wheels according to claim 1 or the elastomeric composition according to claim 2, characterised in that said predispersion of diene elastomeric polymer and nanometric lignin comprises an amount of nanometric lignin equal to or greater than 50 phr, preferably equal to or greater than 75 phr, even more preferably equal to or greater than 100 phr and up to 160 phr.

7. The tyre for vehicle wheels according to claim 1 or the elastomeric composition according to claim 2, characterised in that said nanometric lignin is functionalised with epihalohydrin.

8. The tyre for vehicle wheels or the elastomeric composition according to claim 7, characterised in that said epihalohydrin is selected from the group consisting of epifluorhydrin, epichlorohydrin and epibromohydrin, preferably epichlorohydrin.

9. A process for preparing nanometric lignin functionalised with epihalohydrin by mechano-chemical means comprising:(a) providing a solution of lignin in a first organic solvent(b) separating the insoluble fraction of said lignin from the soluble fraction in said organic solvent,(c) drying said soluble fraction of lignin,(d) feeding and mixing in a grinding apparatus said soluble fraction of lignin obtained in step c) and a basic catalyst, optionally in aqueous solution, and an organic cation salt;(e) adding to the mixture of step (d) epihalohydrin and a basic compound, and mixing until the reaction is completed, obtaining said soluble fraction of lignin functionalised with said epihalohydrin;(f) recovering said soluble fraction of lignin functionalised with said epihalohydrin,(g) treating said insoluble fraction of lignin with a second organic solvent and an antisolvent to obtain nanometric lignin,(h) mixing a solution of said soluble fraction of lignin functionalised with said epihalohydrin with a suspension of said nanometric lignin obtaining a suspension of nanometric lignin functionalised with said epihalohydrin; and(i) recovering said suspension of nanometric lignin functionalised with said epihalohydrin.

10. The process for preparing nanometric lignin functionalised with epihalohydrin according to claim 9, characterized in that said first organic solvent is selected from the group consisting of ethyl acetate, acetone, dimethyl sulphoxide (DMSO), and acetonitrile.

11. The process for preparing nanometric lignin functionalised with epihalohydrin according to claim 9, characterised in that said grinding apparatus is selected from ball mills, planetary ball mills, hammer mills, blade mills, roller mills, high-pressure compression mills, ring mills, vibrating rod or tube mills, and centrifugal fluid mills, and preferably is a ball mill.

12. The process for preparing nanometric lignin functionalised with epihalohydrin according to claim 9, characterised in that said basic catalyst is selected from the group consisting of alkali metal hydroxides or carbonates.

13. The process for preparing nanometric lignin functionalised with epihalohydrin according to claim 9, characterised in that said organic cation salt is selected from the group consisting of tetraalkylammonium, tetraarylammonium and alkylarylamonium salts, quaternary phosphonium salts, imidazolium salts, and mixtures thereof.

14. The process for preparing nanometric lignin functionalised with epihalohydrin according to claim 9, characterised in that said epihalohydrin is selected from the group consisting of epifluorhydrin, epichlorohydrin and epibromohydrin, preferably epichlorohydrin.

15. The process for preparing nanometric lignin functionalised with epihalohydrin according to claim 9, characterised in that said second organic solvent is selected from the group consisting of acetone, dimethyl sulphoxide (DMSO), tetrahydrofuran (THF), ethanol, N,N-Dimethylformamide (DMF) and 1 ,4-dioxane.

16. The process for preparing nanometric lignin functionalised with epihalohydrin according to claim 9, characterised in that said antisolvent is selected from the group consisting of water and hexane.

17. The process for preparing nanometric lignin functionalised with epihalohydrin according to claim 9, characterised in that said second organic solvent is acetone and said antisolvent is water.

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