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 an elastomeric composition comprising per 100 phr of diene elastomeric polymer: (i) a predispersion of (a) a first diene elastomeric polymer, (b) a copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and (c) lignin, said predispersion being in an amount to provide the elastomeric composition with at least 5 phr of said first diene elastomeric polymer and at least 5 phr of lignin, (ii) 0 to 95 phr of a second diene elastomeric polymer, (iii) at least 5 phr of a reinforcing filler, (iv) optionally, a reinforcing resin comprising at least 1 phr of a methylene acceptor compound associated with at least 1 phr of a methylene donor compound, and (v) 0.1 to 12 phr of at least one vulcanising agent.

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 for vehicle wheels comprising at least one structural element comprising a vulcanised elastomeric compound obtained by vulcanisation of an elastomeric composition comprising a predispersion of a diene elastomeric polymer, a copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and 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 designed, 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 designed 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 designed 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 designed 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 production of the aforementioned tyre components, the use of i elastomeric compositions comprising reinforcing fillers to improve the mechanical properties of the resulting vulcanised elastomeric compounds is known.

[0011] The most commonly used reinforcing fillers are carbon black and silica, alone or in combination with each other, but both have some negative aspects which the tyre industry has always been committed to reducing.

[0012] 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 tyre.

[0013] Silica gives poor workability of non-cross-linked 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.

[0014] 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.

[0015] Among the most abundant biopolymers from renewable sources for potential 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.

[0016] 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.

[0017] 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.

[0018] Vehicle wheel tyres comprising lignin are described in patent applications US2010 / 0204368, W02009 / 145784, JP2008 / 308615, JP2010 / 242023, JP2010 / 248282, JP2014 / 129509, CN102718995, CN103756060,

[0019] WO201 4 / 097108, WO2017 / 109672, WO2022 / 144759, IT102021000029213, and IT102021000029831 , and in patents GB723751 , GB836393, US2610954, US2802815, US2906718, US3079360, US3163614, US3282871 , 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 production of tyre compounds which has led to the filing of the international patent applications published with the number WO2017 / 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 vulcanisation of 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] Continuing the experimentation in this field, the Applicant has surprisingly found that the use of the predispersions described in the patent applications WO201 7 / 109672 and WO2022 / 144759A1 in partial replacement of the carbon black in the elastomeric compositions typically used for the rubberising of reinforcing elements for tyres to a substantial reduction of the hysteresis of the compositions themselves, with consequent reduction of energy dissipation during use of the tyre, and of fuel consumption.

[0025] The reduction of hysteresis values, in particular in the case of reinforcing elements used in the internal structural components 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.

[0026] This surprising result, never encountered in other applications of lignin, such as those described in WO2014 / 097108 and WO2017 / 109672, was obtained without penalising the mechanical properties of the vulcanised compound.

[0027] Continuing further experimentation in this field, the Applicant surprisingly found that the addition of a vinylpyridine copolymer with a conjugated diolefin and / or a monovinylarene to the predispersions described in WO2017 / 109672 and WO2022 / 144759A1 used as a partial replacement for carbon black in elastomeric compositions used for the production of tyres led to an improvement in the dispersion of the reinforcing filler and a substantial increase in the mechanical properties of the vulcanised compound. Furthermore, the Applicant found that such features could be achieved while also maintaining the reduction of hysteresis, in particular in the case of elastomeric compositions suitable for the rubberising of reinforcing elements used in the internal structural components of a tyre, such as for example the carcass structure, the belt structure and the bead components.

[0028] 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 an elastomeric composition comprising per 100 phr of diene elastomeric polymer:

[0029] (i) a predispersion of (a) a first diene elastomeric polymer, (b) a copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and (c) lignin, said predispersion being in an amount to provide the elastomeric composition with at least 5 phr of said first diene elastomeric polymer and at least 5 phr of lignin,

[0030] (ii) 0 to 95 phr of a second diene elastomeric polymer,

[0031] (iii) at least 5 phr of a reinforcing filler, (iv) optionally, a reinforcing resin comprising at least 1 phr of a methylene acceptor compound associated with at least 1 phr of a methylene donor compound, and

[0032] (v) 0.1 to 12 phr of at least one vulcanising agent.

[0033] In a second aspect, the present invention relates to a structural element for a tyre comprising a vulcanised elastomeric compound obtained by vulcanisation of an elastomeric composition comprising per 100 phr of diene elastomeric polymer:

[0034] (i) a predispersion of (a) a first diene elastomeric polymer, (b) a copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and (c) lignin, said predispersion being in an amount to provide the elastomeric composition with at least 5 phr of said first diene elastomeric polymer and at least 5 phr of lignin,

[0035] (ii) 0 to 95 phr of a second diene elastomeric polymer,

[0036] (iii) at least 5 phr of a reinforcing filler,

[0037] (iv) optionally, a reinforcing resin comprising at least 1 phr of a methylene acceptor compound associated with at least 1 phr of a methylene donor compound, and

[0038] (v) 0.1 to 12 phr of at least one vulcanising agent.

[0039] In a third aspect thereof, the present invention relates to an elastomeric composition comprising per 100 phr of diene elastomeric polymer:

[0040] (i) a predispersion of (a) a first diene elastomeric polymer, (b) a copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and (c) lignin, said predispersion being in an amount to provide the elastomeric composition with at least 5 phr of said first diene elastomeric polymer and at least 5 phr of lignin,

[0041] (ii) 0 to 95 phr of a second diene elastomeric polymer,

[0042] (iii) at least 5 phr of a reinforcing filler,

[0043] (iv) optionally, a reinforcing resin comprising at least 1 phr of a methylene acceptor compound associated with at least 1 phr of a methylene donor compound, and

[0044] (v) 0.1 to 12 phr of at least one vulcanising agent.

[0045] DEFINITIONS

[0046] 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.

[0047] 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 accelerator and retarder, are usually added in a downstream step with respect to the incorporation and processing of all the other components.

[0048] In the final 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.

[0049] The term “elastomeric polymer” means 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).

[0050] The term “diene elastomeric polymer” means 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).

[0051] The term “elastomeric compound” means 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.

[0052] The term “vulcanisable elastomeric compound” means the elastomeric compound ready for vulcanisation, obtainable by incorporation into an elastomeric compound of all the additives, including those of vulcanisation.

[0053] The term “vulcanised elastomeric compound” means the material obtainable by vulcanisation of a vulcanisable elastomeric compound. The term “green” means a material, a compound, a composition, a component or a tyre not yet vulcanised.

[0054] The term “vulcanisation” refers to the cross-linking reaction in a natural or synthetic rubber induced by a typically sulphur-based cross-linking agent.

[0055] The term “vulcanising agent” means a product capable of transforming natural or synthetic rubber into elastic and resistant material by virtue of the formation of a three-dimensional network of inter- and intra-molecular 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.

[0056] The term “vulcanisation accelerator” 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.

[0057] The term “vulcanisation activator” means 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.

[0058] The term “vulcanisation retarder” means a product capable of delaying the onset of the vulcanisation reaction and / or suppressing undesired secondary reactions, for example N-(cyclohexylthio)phthalimide (CTP).

[0059] The term “vulcanisation package” means the vulcanising agent and one or more vulcanisation additives selected from among vulcanisation activators, accelerators and retarders.

[0060] The term “reinforcing filler” means 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 precipitated with strong acids, preferably amorphous, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibres and mixtures thereof.

[0061] The term “mixing step (1)” means 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 “nonproductive step”. In the preparation of a compound there may be several “non-productive” mixing steps which may be indicated with 1a, 1 b, etc.

[0062] The term “mixing step (2)” means the next step of the preparation process of the elastomeric compound in which the vulcanising agent and, optionally, the other additives of the vulcanisation package 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”.

[0063] 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.

[0064] 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°.

[0065] 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°.

[0066] For the purposes of the present description and the following claims, 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.

[0067] Unless otherwise indicated, all the percentages are expressed as percentages by weight.

[0068] Predispersion of diene elastomeric polymer, copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and lignin

[0069] Preferably, the diene elastomeric polymer is any diene elastomeric polymer as described below in the present description. For the purposes of the following claims, the diene elastomeric polymer used in the predispersion is referred to as the first diene elastomeric polymer.

[0070] More preferably, the diene elastomeric polymer is selected from natural (NR) or synthetic (IR) isoprene rubber, emulsion polymerisation styrene- butadiene rubber (ESBR), chloroprene rubber (OR), butyl rubber (HR).

[0071] Advantageously, the diene elastomeric polymer is selected from natural (NR) or synthetic (IR) isoprene rubber.

[0072] Preferably, the copolymer of viny Ipyrid ine with a conjugated diolefin and / or a monovinylarene (hereinafter referred to for brevity as vinylpyridine copolymer) is a diene elastomeric copolymer obtained by copolymerisation of vinylpyridine with a conjugated diolefin selected from the group consisting of 1 ,3-butadiene, isoprene, 2,3-dimethyl-1 ,3-butadiene, 1 ,3-pentadiene, 1 ,3- hexadiene, 3-butyl-1 ,3-octadiene, and 2-phenyl-1 ,3-butadiene and / or a monovinylarene selected from the group consisting of styrene, a- methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4- dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4- phenylbutyl)styrene, 1 -vinylnaphthalene, and 2-vinylnaphthalene.

[0073] Preferably, the copolymer of vinylpyridine is selected from butadiene- vinylpyridine copolymer, isoprene-vinylpyridine copolymer, isoprene-styrene- vinylpyridine copolymer and styrene-butadiene-vinylpyridine copolymer, more preferably styrene-butadiene-vinylpyridine copolymer.

[0074] Preferably, the 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.

[0075] Preferably, the predispersion comprises an amount of vinylpyridine copolymer ranging from 0.5% to 45% by weight, preferably from 1 to 25% by weight, based on the total weight of diene elastomeric polymer and vinylpyridine copolymer.

[0076] Preferably, the predispersion comprises an amount of lignin equal to or greater than about 45 phr, preferably equal to or greater than about 50 phr, even more preferably equal to or greater than about 60 phr up to a maximum value of about 160 phr.

[0077] According to a preferred embodiment, the predispersion is added to the elastomeric composition in an amount such as to provide the elastomeric composition itself with at least 10 phr of diene elastomeric polymer, more preferably at least 15 phr of diene elastomeric polymer, and advantageously at least 20 phr of diene elastomeric polymer, the balance to 100 phr being provided by the separately added diene elastomeric polymer. According to a preferred embodiment, the predispersion is added to the elastomeric composition in such an amount as to provide the elastomeric composition itself with at least 10 phr of lignin, more preferably at least 15 phr of lignin, and advantageously at least 20 phr of lignin.

[0078] Preferably, the predispersion is prepared according to the process described in WO2017 / 109672 or WO2022 / 144759.

[0079] In particular, in an embodiment as described in WO2017 / 109672, the predispersion is obtained with a process comprising:

[0080] (a) adding lignin to a latex of diene elastomeric polymer and vinylpyridine copolymer,

[0081] (b) causing the co-precipitation (coagulation) of the predispersion of diene elastomeric polymer, vinylpyridine copolymer and lignin from the mixture resulting from step (a), and

[0082] (c) separating the predispersion of diene elastomeric polymer, vinylpyridine copolymer and lignin obtained from step (b) from a residual supernatant.

[0083] Preferably, the lignin is solubilised in an alkaline solution before addition to the diene elastomeric polymer and vinylpyridine copolymer latex.

[0084] In particular, the alkaline solution comprises an aqueous solution of a base, preferably selected from the group comprising hydroxides of alkali metals, such as, for example, sodium hydroxide (NaOH) or potassium hydroxide (KOH), and ammonia (NH3), in concentration between 0.01 M and 1 M, preferably between 0.1 M and 0.5M. The basic conditions of the solution ensure deprotonation of the lignin acid groups (phenols and carboxylic acids), and the negative charges make the lignin macromolecules soluble and stable in aqueous solution. The addition of the lignin to the basic solution is preferably carried out under stirring and at room temperature until complete solubilisation.

[0085] The addition of the lignin to the latex is preferably carried out slowly and under stirring, and at room temperature, in a variable time, preferably between 5 and 15 minutes, and the resulting mixture is left under stirring at room temperature for a variable time, preferably between 1 and 2 hours.

[0086] Co-precipitation (coagulation) from the resulting mixture occurs by adding an acid solution. In particular, the acid solution comprises an aqueous solution of an acid, preferably selected from the group comprising inorganic acids, such as for example hydrochloric or sulphuric acid, and organic acids, such as for example acetic acid, in a concentration comprised between 0.1M and 2M, preferably between 0.5M and 1.5M.

[0087] Advantageously, in another embodiment as described in WO2022 / 144759, the predispersion is achieved by a process comprising: a) preparing in a dispersing liquid a first suspension of lignin having a value of a median particle diameter D50 equal to or less than 10 microns, preferably equal to or less than 5 microns, more preferably, equal to or less than 2 microns; b) preparing a second suspension comprising lignin and diene elastomeric polymer and vinylpyridine copolymer latex by mixing the first lignin suspension obtained from step a) with said latex; and c) removing the dispersing liquid from said second suspension comprising lignin and diene elastomeric polymer and vinylpyridine copolymer latex until said predispersion of diene elastomeric polymer, vinylpyridine copolymer and lignin is obtained.

[0088] In a particularly preferred embodiment, step a) of preparing said first lignin suspension comprises: a1 ) preparing in the dispersing liquid a crude suspension of lignin having a value of a median particle diameter D50 equal to or greater than 10 microns, more preferably equal to or greater than 20 microns; a2) wet-grinding the lignin particles contained in said crude suspension until the median diameter D50 of the lignin particles is reduced to said value equal to or less than 10 microns.

[0089] In preferred embodiments, in the process of preparing the predispersion, step a) of preparing the first lignin suspension or step a1 ) of preparing the crude lignin suspension comprises adding to such suspension a metered amount of at least one surfactant.

[0090] 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. Preferably, step a) of preparing the first lignin suspension or step a1 ) of preparing the crude lignin suspension comprises adding to the first lignin suspension an amount of surfactant comprised between 0.1 and 60 parts by weight, preferably between 1 and 10 parts by weight, per 100 parts by weight of total suspension.

[0091] Preferably, the first lignin suspension or the aforementioned crude lignin suspension has a solid residue comprised between 20% and 80% by weight, preferably between 25% and 70% by weight, with respect to the overall weight of the suspension.

[0092] In a preferred embodiment, the crude suspension of lignin may be obtained by diluting lignin having a moisture content of between 1 and 60% with a suitable amount of liquid dispersant in order to obtain a suspension with a solid residue of between 20% and 80% by weight, more preferably of between 25% and 70% by weight with respect to the total weight of the crude suspension.

[0093] Preferably, step a2) of the aforementioned preferred predispersion preparation process involves wet-grinding the lignin particles contained in the crude lignin suspension until the median diameter D50 of the lignin particles is reduced to a value equal to or less than 5 microns, more preferably equal to or less than 2 microns.

[0094] Preferably, the first lignin suspension obtained from step a) has a % by weight of particles having a size greater than 10 microns equal to or less than 10% by weight, more preferably, equal to or less than 2% by weight.

[0095] In a preferred embodiment, step a2) of wet-grinding the lignin particles contained in the crude lignin suspension is carried out by means of a grinding apparatus selected from ball mills, hammer mills, blade mills, roller mills, high-pressure compression mills, ring mills, vibrating rod or tube mills, centrifugal fluid mills, preferably ball mills.

[0096] Preferably, the diene elastomeric polymer and vinylpyridine copolymer latex has a solid residue of between 10% and 80% by weight, more preferably between 30% and 60% by weight, with respect to the total weight of the latex.

[0097] Preferably, the diene elastomeric polymer and vinylpyridine copolymer latex is stabilised with a weak base, for example ammonia. Preferably, step b) of preparing the second suspension comprising lignin and diene elastomeric polymer and vinylpyridine copolymer latex is carried out by mixing from 30 to 200 parts by weight, preferably from 60 to 140 parts by weight, of the first lignin suspension obtained from step a) to 100 parts by weight of diene elastomeric polymer and vinylpyridine copolymer latex.

[0098] In a particularly preferred embodiment, step b) of preparing the second suspension comprising lignin and diene elastomeric polymer and vinylpyridine copolymer latex is carried out by mixing the first lignin suspension obtained from step a) with said latex for a time such as to obtain a substantially homogeneous second suspension.

[0099] Preferably, the mixing time is between 5 minutes and 120 minutes.

[0100] In a preferred embodiment, the mixing contemplated in step b) is carried out by means of a batch mixer with mechanical stirrer.

[0101] Preferably, step c) of removing the dispersing liquid from the second suspension comprising lignin and diene elastomeric polymer and vinylpyridine copolymer latex comprises d) drying the second suspension.

[0102] Preferably, step d) of drying the second suspension comprising lignin and diene elastomeric polymer and vinylpyridine copolymer latex is carried out until the moisture content of the predispersion is brought to a value equal to or less than 5% by weight, preferably equal to or less than 1 % by weight.

[0103] Preferably, step d) of drying the second suspension comprising lignin and diene elastomeric polymer and vinylpyridine copolymer 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.

[0104] In an alternative embodiment, step c) of removing the dispersing liquid from the second suspension comprising lignin and diene elastomeric polymer and vinylpyridine copolymer 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.

[0105] In a preferred embodiment, the process of preparing the predispersion may comprise a step f) of compacting the predispersion of diene elastomeric polymer, vinylpyridine copolymer and lignin obtained from step c).

[0106] 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.

[0107] 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 production of the vulcanisable elastomeric composition which will be better described below.

[0108] Alternatively, the predispersion may be used in the form of bales as conventionally occurs in the case of compositions based on elastomeric polymer.

[0109] Diene elastomeric polymer

[0110] The diene elastomeric polymer that is used in the present invention, referred to in the following claims as a second diene elastomeric polymer, 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.

[0111] 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.

[0112] 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.

[0113] Polar comonomers that may optionally be used, can be selected, for example, from among 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.

[0114] 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.

[0115] 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.

[0116] Reinforcing filler

[0117] The reinforcing filler used in the tyre according to the present invention comprises carbon black and / or a white filler.

[0118] According to a preferred embodiment, the carbon black reinforcing filler which may be used in the present invention may be selected from those having a surface area of not less than 20 m2 / g (as determined by STSA - Statistical Thickness Surface Area - according to ISO 18852:2005).

[0119] 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.

[0120] Silica may vary in shape, specific surface area and size. Examples of silica are a pyrogenic silica, a precipitated amorphous silica, a wet silica (hydrated silicic acid), or mixtures thereof.

[0121] 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).

[0122] Preferably, the silica has a specific surface area (BET) of at least 80 m2 / g, more preferably of at least 100 m2 / g.

[0123] Preferably, the silica has a specific surface area (BET) smaller than 220 m2 / g, more preferably smaller than or equal to 180 m2 / g.

[0124] 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 reinforcing filler is present in the elastomeric composition in an amount of less than about 45 phr, preferably less than about 40 phr.

[0125] Vulcanising agent

[0126] 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.

[0127] 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 accelerators.

[0128] 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) peroxide (DCBP), di-tert-butyl peroxide.

[0129] 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.

[0130] Preferably, said vulcanising agent comprises sulphur-based vulcanising systems comprising sulphur or sulphur-containing molecules (sulphur donors) together with vulcanisation accelerators and / or activators known in the art. 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.

[0131] The accelerators which are commonly used may be selected from: dithiocarbamates, guanidine, thiourea, thiazoles, sulphenamides, thiurams, amines, xanthates, or mixtures thereof.

[0132] 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.

[0133] Preferably, the amount of vulcanising agent is less than or equal to about

[0134] 7.5 phr, preferably less than or equal to about 7.

[0135] Advantageously, the amount of sulphur is between about 2 phr and about

[0136] 6.5 phr.

[0137] Other additives

[0138] 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.

[0139] 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):

[0140] (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.

[0141] 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.

[0142] According to an embodiment, said silane coupling agent may be present in the elastomeric composition in an amount ranging between 0.1 phr and about 10 phr, preferably between about 0.5 phr and about 5 phr.

[0143] 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, to such materials may be added: antioxidants, anti-ageing agents, plasticisers, adhesives, anti-ozone agents, modifying resins, or mixtures thereof.

[0144] 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 0 phr to about 30 phr.

[0145] Preparation of the elastomeric composition

[0146] The elastomeric composition may be prepared by mixing the necessary amount of the second diene elastomeric polymer with the predispersion of first diene elastomeric polymer, vinylpyridine copolymer and lignin, the reinforcing filler, the vulcanising agent and any other additives optionally present according to the techniques known in the industry.

[0147] According to a preferred embodiment, the predispersion is added to the elastomeric composition in an amount such as to provide the elastomeric composition itself with at least 10 phr of first diene elastomeric polymer, more preferably at least 15 phr of first diene elastomeric polymer, and advantageously at least 20 phr of first diene elastomeric polymer, the balance to 100 phr being provided by the second, separately added, diene elastomeric polymer.

[0148] According to a preferred embodiment, the predispersion is added to the elastomeric composition in such an amount as to provide the elastomeric composition itself with at least 10 phr of lignin, more preferably at least 15 phr of lignin, and advantageously at least 20 phr of lignin.

[0149] The mixing may be carried out, for example, using at least one batch mixer and / or at least one continuous mixer.

[0150] The predispersion 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.

[0151] 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.

[0152] 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.

[0153] 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®).

[0154] 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).

[0155] 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”.

[0156] 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. 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.

[0157] 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.

[0158] The elastomeric compound thus obtained may then be stored or sent directly to the subsequent production steps of the tyre according to the present invention.

[0159] The tyre

[0160] According to an embodiment, the tyre for vehicle wheels according to the invention comprises:

[0161] - a carcass structure comprising at least a carcass ply having opposite lateral edges associated to respective bead structures;

[0162] - optionally, a belt structure applied in radially external position with respect to the carcass structure;

[0163] - a tread band applied in a radially external position to said carcass structure and to said belt structure, if present, and

[0164] - 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.

[0165] According to one embodiment, the structural element according to the invention is selected from the group consisting of carcass structure, belt structure, bead structure, tread band, anti-abrasive strip and sidewalls.

[0166] 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. 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 less than 3500 kg.

[0167] The tyre according to the invention may be a tyre for motorcycles, 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.

[0168] DRAWINGS

[0169] The description is given hereinafter with reference to the accompanying drawings, provided only for illustrative and, therefore, non-limiting purposes, in which:

[0170] - Figure 1 schematically shows a semi-sectional view of a tyre for vehicle wheels according to the present invention.

[0171] DETAILED DESCRIPTION OF THE INVENTION

[0172] 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”.

[0173] 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 101a as shown in Figure 1 . 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.

[0174] 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.

[0175] 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.

[0176] 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 notches (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.

[0177] To optimise the performance of the tread, the tread band may be made in a two-layer structure.

[0178] 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.

[0179] Both the tread band 109 and the cap-and-base structure formed by the rolling layer 109a and the underlayer 111 may be advantageously made with the elastomeric composition comprising the predispersion of diene elastomeric polymer, vinylpyridine copolymer with a conjugated diolefin and / or a monovinylarene and lignin described above. The increase in mechanical properties means greater resistance to mechanical stress resulting from the rolling or sliding of the tyre during use, resulting in a longer tyre life.

[0180] 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.

[0181] A strip consisting of elastomeric compound 110, commonly known as “mini-sidewall”, of vulcanised elastomeric compound may optionally be provided in the connecting zone between sidewalls 108 and the tread band 109, this mini-sidewall generally being obtained by co-extrusion with the tread band 109 and allowing an improvement of the mechanical interaction between the tread band 109 and the sidewalls 108. Preferably, the end portion of sidewall 108 directly covers the lateral edge of the tread band 109.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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). 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.

[0186] The sidewalls 108, the mini-sidewalls 110, and / or the anti-abrasive strip 105 may be advantageously made with the elastomeric composition comprising the predispersion of diene elastomeric polymer, vinylpyridine copolymer with a conjugated diolefin and / or a monovinylarene and lignin described above. The increase in mechanical properties means greater resistance to mechanical stress resulting from the rolling or sliding of the tyre during use, resulting in a longer tyre life.

[0187] 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.

[0188] 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.

[0189] 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, vinylpyridine copolymer with a conjugated diolefin and / or a monovinylarene and lignin described above. The increase in mechanical properties means greater resistance to the mechanical stresses suffered by the tyre during use. Furthermore, the Applicant found - for these elastomeric compositions - a lower hysteresis, i.e. a lower dissipation of energy in the form of heat during driving, thus preventing the onset of excessively high operating temperatures which may risk compromising the integrity of the tyre.

[0190] The building of the tyre 100 as described above is carried out by assembling respective semi-finished products onto a forming drum, not shown, by at least one assembly device.

[0191] 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.

[0192] After building the green tyre 100, a moulding and vulcanisation treatment is generally carried out in order to determine the structural stabilisation 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.

[0193] 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.

[0194] EXAMPLE 1

[0195] Preparation of predispersions of a diene elastomeric polymer and lignin comprising 50% w / w lignin

[0196] Materials

[0197] Lignin: UPM BioPiva™ 200 Softwood Kraft process lignin (UPM Biochemicals) having a median particle diameter D50 egual to or greater than 20 microns;

[0198] Diene elastomeric polymer: natural rubber (NR) from HA latex obtained by centrifugation and stabilised with ammonia (60% by weight - marketed by Von Bundit Co. Ltd.);

[0199] RFL: agueous preparation containing 40% Vinylpyridine-styrene-butadiene latex (VP-SBR - Pliocord VP 106S by Synthomer), 3% resorcinol and 2% formaldehyde

[0200] VPL: Vinylpyridine-styrene-butadiene latex 40% (VP-SBR - Pliocord VP 106S by Synthomer)

[0201] Anionic surfactant: technical grade sodium dodecylbenzenesulphonate, Thermo Fischer Scientific.

[0202] Predispersion 1 - (Natural rubber + lignin)

[0203] The preparation procedure of the predispersion 1 was the following.

[0204] Step a1 ): 95 kg of wet lignin particles (solids content about 57%, starting D50 about 20 microns) were diluted in 95 kg of deionised water; subsequently, 2.85 kg of anionic surfactant were added and the mixture was stirred until homogeneous, thus obtaining 192.85 kg of a crude suspension of lignin SK having a solid lignin content of about 28% by weight.

[0205] Step a2): the lignin particles contained in the crude SK lignin suspension were wet-ground using a cylindrical mill model ZETA from NETZSCH (NETZSCH-Feinmahltechnik GmbH, Selb, Germany) using steel balls with a diameter of less than 4 mm, so as to reduce the median diameter D50 of the lignin particles to a value equal to or less than 1.5 microns. 192.85 kg of a first suspension S1 containing ground lignin (28% by weight) were thus obtained, in which the percentage of particles larger than 10 microns was less than about 2% by weight.

[0206] The median particle diameter D50 was measured with the Malvern Mastersizer 2000 laser analyser (Malvern Panalytical Ltd., Malvern, Great Britain).

[0207] Step b): the first suspension S1 containing ground lignin obtained from step a2) (192.85 kg) was mixed with 90 kg of natural rubber latex (solids content: 60% by weight) by mechanical stirrer, thus obtaining 282.85 kg of a second suspension S2 containing about 19% by weight of ground lignin and about 19% by weight of natural rubber.

[0208] Step c): the second suspension S2 containing ground lignin and natural rubber (282.85 kg) was then dried in a static oven at 60°C for about 4 hours, until it reached a moisture content lower than 1 % by weight.

[0209] The predispersion in flakes thus obtained was then subjected to a further compacting step by means of an open mixer with rollers spaced about 3 mm apart to obtain a predispersion or masterbatch in sheets of natural rubber at 50% and lignin at 50% by weight.

[0210] Predispersion 2 (Natural rubber + RFL (5% dry) + lignin)

[0211] For the preparation of predispersion 2, the same procedure as for Predispersion 1 was followed, using in step b) 81 kg of natural rubber latex (solid content: 60% by weight) and 13.5 kg of RFL (solid content: 40% by weight), thus obtaining 287.35 kg of a second suspension S2 containing about 19% by weight of ground lignin and about 19% by weight of natural rubber and VP-SBR.

[0212] Predispersion 3 (Natural rubber + VPL (5% dry) + lignin)

[0213] For the preparation of predispersion 3, the same procedure as for Predispersion 1 was followed, using in step b) 81 kg of natural rubber latex (solid content: 60% by weight) and 13.5 kg VPL (solid content: 40% by weight), thus obtaining 287.35 kg of a second suspension S2 containing about 19% by weight of ground lignin and about 19% by weight of natural rubber and VP-SBR.

[0214] Predispersion 4 (Natural rubber + VPL (2% dry) + lignin)

[0215] For the preparation of predispersion 4, the same procedure as for Predispersion 1 was followed, using in step b) 85.5 kg of natural rubber latex (solid content: 60% by weight) and 6.75 kg VPL (solid content: 40% by weight), thus obtaining 285.1 kg of a second suspension S2 containing about 19% by weight of ground lignin and about 19% by weight of natural rubber and VP-SBR.

[0216] Predispersion 5 (Natural rubber + VPL (10% dry) + lignin)

[0217] For the preparation of predispersion 5, the same procedure as for Predispersion 1 was followed, using in step b) 72 kg of natural rubber latex (solid content: 60% by weight) and 27 kg VPL (solid content: 40% by weight), thus obtaining 291.85 kg of a second suspension S2 containing about 19% by weight of ground lignin and about 19% by weight of natural rubber and VP-SBR.

[0218] Predispersion 6 (Natural rubber + VPL (20% dry) + lignin)

[0219] For the preparation of predispersion 6, the same procedure as for Predispersion 1 was followed, using in step b) 54 kg of natural rubber latex (solid content: 60% by weight) and 54 kg VPL (solid content: 40% by weight), thus obtaining 300.85 kg of a second suspension S2 containing about 19% by weight of ground lignin and about 19% by weight of natural rubber and VP-SBR.

[0220] EXAMPLE 2

[0221] Use of predispersions 1-3 of Example 1 in the preparation of elastomeric compounds

[0222] Predispersions 1 -3 prepared according to Example 1 were used to prepare vulcanisable elastomeric compounds.

[0223] The vulcanisable elastomeric compounds of the invention comprising predispersions 2-3 were compared with a lignin-free vulcanisable elastomeric compound (R1 ), considered as a conventional reference for structural elements of tyre, in particular reinforcing elements of the carcass structure, and a comparison vulcanisable elastomeric compound (C1 ) comprising predispersion 1 .

[0224] The following Table 1 shows the phr compositions of the vulcanisable elastomeric compounds R1 , C1 , INV1 and INV2. The predispersions are added in amounts to provide about 20 phr of rubber (NR or NR+RFL or NR+VP-SBR) and about 20 phr of lignin.

[0225] TABLE 1

[0226] NR: technical grade natural rubber SIR20

[0227] CB: Carbon Black, N326, Cabot Corporation;

[0228] Resin: Piccotac 1020, Eastman

[0229] ZnO: Zinc oxide, Zincol Ossidi;

[0230] Stearic acid: Stearin, llndesa;

[0231] 6PPD: N-(1 ,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine, Solutia Eastman;

[0232] HMMM 65%: Cyrez 963, Cytec;

[0233] Novolac: Alnovol PN 760, Allnex;

[0234] PVI: cyclohexylthiophthalimide, Santogard PVI;

[0235] CBS: N-cyclohexylbenzothiazole-2-sulphenamide, Rubenamid C, General Quimica;

[0236] Insoluble sulphur 66%: Sulphur, Redball Superfine, International Sulphur Inc.

[0237] All the components, with the exception of the sulphur, the vulcanisation accelerator (CBS) and the vulcanisation retarder (PVI), were mixed in an internal mixer (Brabender) for about 10 minutes (1ststep).

[0238] 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, the accelerator (CBS) and the retarder (PVI) were added and the mixing was carried out in the same mixer at about 60°C for 9 minutes (2ndstep). Finally, the compound was vulcanised at 170°C for 10 minutes, in order to measure the static and dynamic mechanical properties thereof in compression, while the dynamic mechanical properties in shear and the rheometric properties were measured on the vulcanisable compound.

[0239] The static mechanical properties of the compounds were evaluated according to the ISO 37-2011 standard at 23°C, on 5 Dumbell specimens. In this way the following parameters were measured: - load at 50% elongation (Ca0.5),

[0240] - load at 100% elongation (Ca1 ),

[0241] - load at 300% elongation (Ca3),

[0242] - breaking load (OR), and

[0243] - % elongation at break (AR).

[0244] The dynamic mechanical properties of dynamic shear modulus G' and Tan delta and the rheometric properties of the compounds were evaluated using an Alpha Technologies RPA oscillating chamber rheometer. (Rubber Process Analyser) with chamber geometry as described in ASTM D6601 -19 Figure 1 , applying the following method.

[0245] 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.

[0246] 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.

[0247] The temperature of the rheometer was then brought to 70°C. After a total time of 10 minutes since the chamber temperature was set at 70°C, a sequence of dynamic measurements is performed at a constant temperature of 70°C by sinusoidally stressing the sample in torsion at a fixed frequency of 10 Hz and amplitude progressively increasing from 0.4% to 10%, carrying out 10 stabilisation cycles and 10 measurement cycles for each condition.

[0248] Always keeping the temperature of the rheometer chambers at 70°C, a dynamic measurement is then carried out by sinusoidally stressing the sample in torsion at the fixed frequency of 10 Hz and amplitude of 9%, carrying out 10 stabilisation cycles and 20 measurement cycles.

[0249] In this way, the following parameters were measured as an average of what was recorded in the 20 measurement cycles:

[0250] - dynamic shear elastic modulus G’ at a strain amplitude of 9%,

[0251] - variation of the dynamic shear modulus d_G’ between an amplitude of the sample deformation of 0.4% and one of 10%;

[0252] - torsion tan delta, i.e. the ratio between the viscous elastic modulus G” and the dynamic elastic modulus G’, at a deformation amplitude of 9% (hereinafter Tan delta (9%)).

[0253] The dynamic mechanical properties in compression of the compounds were evaluated using an Instron model 1341 dynamic device in the following modes.

[0254] 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.

[0255] After a waiting time of 2 minutes followed by a mechanical preconditioning 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.

[0256] In this way the following parameters were measured:

[0257] - dynamic elastic modulus E’,

[0258] - tan delta, i.e. the ratio between the viscous dynamic modulus E” and the dynamic elastic modulus E’.

[0259] The dispersion efficiency was measured by automated image analysis. From a vulcanised sample of each elastomeric composition two sections, each of 1 micron thickness and 2 mm x 2 mm dimensions, were obtained by cold microtomy (-70°C). The sections were stretched on a slide and with a microscope in light transmitted at 100x, 10 images (of about 800 x 900 microns) were acquired in different points of the samples. The images are analysed to evaluate the dispersion of silica with the Image Pro Plus software by Media Cybernetic.

[0260] The percentage of undispersed silica (or other white filler present) was calculated as the sum of the clear areas having dimensions greater than 7 microns with respect to the silica (or more generally the sum of the white fillers) introduced. In compounds containing lignin, since the latter is lighter in colour than the compound, the non-dispersed lignin is counted as if it were silica.

[0261] The number of silica aggregates (or other white filler present) was calculated as a count of clear aggregates larger than 7 microns in size. The percentage of undispersed carbon black was calculated as the sum of the dark areas having dimensions greater than 7 microns with respect to the introduced carbon black.

[0262] The number of carbon black aggregates was calculated as the count of dark aggregates having dimensions greater than 7 microns. The following Table 2 shows the results obtained from the characterisations carried out.

[0263] TABLE 2

[0264] Compared to the reference compound (R1 ), the comparison compound (C1 ) and the invention compounds (INV1 and INV2) showed improved hysteresis, as visible from the “tan delta” values measured both in shear and compression. The compounds of the invention (INV1 and INV2) also showed a dynamic modulus higher than that of the comparison compound C1 and close to that of the reference compound, thus demonstrating a balance between dynamic stiffness and energy dissipation even more favourable than in the case of the comparison compound C1. The compounds of the invention (INV1 and INV2) also showed an improved dispersion of the filler compared to the comparison compound (C1 ), consequently showing a better mechanical reinforcement such as to reach and exceed the stiffness values at all deformation levels (Ca0.5, Ca1 , Ca3) of the reference compound (R1 ) and the comparison compound C1 , maintaining good ultimate properties.

[0265] EXAMPLE 3

[0266] Use of predispersions 1 and 3-6 of Example 1 in the preparation of elastomeric compounds

[0267] Predispersion 1 and predispersions 3-6 prepared according to Example 1 were used to prepare vulcanisable elastomeric compounds.

[0268] The vulcanisable elastomeric compounds of the invention comprising predispersions 3-6 were compared with a lignin-free vulcanisable elastomeric compound (R2), considered as a conventional reference for structural elements of tyre, in particular reinforcing for a sidewall compound and a comparison vulcanisable elastomeric compound (C2) comprising predispersion 1 .

[0269] The following Table 3 shows the phr compositions of the vulcanisable elastomeric compounds R2, C2, INV3-INV6. The predispersions are added in amounts to provide about 12 phr of rubber (NR or NR+VP-SBR) and about 12 phr of lignin.

[0270] TABLE 3

[0271] NR: technical grade natural rubber SIR20

[0272] BR HIGH CIS: SKDN from Nizhnikamsk Neftekim CB: Carbon Black, N550, Cabot Corporation;

[0273] ZnO: Zinc oxide, Zincol Ossidi;

[0274] Stearic acid: Stearin, Undesa;

[0275] 6PPD: N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine, Solutia Eastman;

[0276] TBBS: N-tertbutylbenzothiazole-2-sulphenamide, Vulkacit NZ, lanxess Insoluble sulphur 66%: Sulphur, Redball Superfine, International Sulphur Inc.

[0277] All the components, except for sulphur and the vulcanisation accelerator (TBBS), were mixed in an internal mixer (Brabender) for about 10 minutes (1ststep).

[0278] 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 accelerator (TBBS) were added and the mixing was carried out in the same mixer at about 60°C for 9 minutes (2ndstep). Finally, the compound was vulcanised at 170°C for 10 minutes, in order to be able to measure its static mechanical properties, while the shear and rheometric dynamic mechanical properties were measured on the vulcanisable compound.

[0279] The properties of the compounds were evaluated with the same procedures used for the elastomeric compounds of Example 2.

[0280] The following Table 4 shows the results obtained from the characterisations carried out. TABLE 4

[0281] Compared to the comparison compound (C2), the compounds of the invention (INV3-INV6) showed (i) static load values at high deformation, in particular at CA3, higher and closer to those of the reference compound R2 and ii) better ultimate properties, in particular the breaking load was in line with or even improved compared to the reference compound R2 for the compounds of the invention (INV3-INV6).

[0282] The compounds of the invention (INV3-INV6) showed shear moduli G' higher than that of the comparison compound C2, close to that of the reference compound R2, maintaining hysteresis substantially in line with that of R2 itself and therefore demonstrating a favourable balance between dynamic modulus and hysteresis compared to that of the comparison compound C2. Furthermore, the compounds of the invention (INV3-INV6) showed an improved dispersion of the white filler (reported as Silica) compared to the comparison compound (C2) with percentages of non-dispersed white filler particularly low in the case of predispersions 4 and 5, with the lowest content of viny Ipyridine co-polymer.

Claims

CLAIMS1. A tyre for vehicle wheels which comprises at least one structural element comprising a vulcanised elastomeric compound obtained by vulcanisation of an elastomeric composition comprising per 100 phr of diene elastomeric polymer:(i) a predispersion of (a) a first diene elastomeric polymer, (b) a copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and (c) lignin, said predispersion being in an amount to provide the elastomeric composition with at least 5 phr of said first diene elastomeric polymer and at least 5 phr of lignin,(ii) 0 to 95 phr of a second diene elastomeric polymer,(iii) at least 5 phr of a reinforcing filler,(iv) optionally, a reinforcing resin comprising at least 1 phr of a methylene acceptor compound associated with at least 1 phr of a methylene donor compound, and(v) 0.1 to 12 phr of at least one vulcanising agent.

2. A structural element comprising a vulcanised elastomeric compound obtained by vulcanisation of an elastomeric composition comprising per 100 phr of diene elastomeric polymer:(i) a predispersion of (a) a first diene elastomeric polymer, (b) a copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and (c) lignin, said predispersion being in an amount to provide the elastomeric composition with at least 5 phr of said first diene elastomeric polymer and at least 5 phr of lignin,(ii) 0 to 95 phr of a second diene elastomeric polymer,(iii) at least 5 phr of a reinforcing filler,(iv) optionally, a reinforcing resin comprising at least 1 phr of a methylene acceptor compound associated with at least 1 phr of a methylene donor compound, and(v) 0.1 to 12 phr of at least one vulcanising agent.

3. An elastomeric composition comprising per 100 phr of diene elastomeric polymer:(i) a predispersion of (a) a first diene elastomeric polymer, (b) a copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene, and (c) lignin, said predispersion being in an amount to provide the elastomeric composition with at least 5 phr of said first diene elastomeric polymer and at least 5 phr of lignin,(ii) 0 to 95 phr of a second diene elastomeric polymer,(iii) at least 5 phr of a reinforcing filler,(iv) optionally, a reinforcing resin comprising at least 1 phr of a methylene acceptor compound associated with at least 1 phr of a methylene donor compound, and(v) 0.1 to 12 phr of at least one vulcanising agent.

4. The tyre for vehicle wheels according to claim 1 or the structural element according to claim 2 or the elastomeric composition according to claim 3, characterized in that said first diene elastomeric polymer is selected from natural (NR) or synthetic (IR) isoprene rubber, emulsion polymerisation styrene-butadiene rubber (ESBR), chloroprene rubber (CR), and butyl rubber (HR), preferably natural (NR) or synthetic (IR) isoprene rubber.

5. The tyre for vehicle wheels according to claim 1 or the structural element according to claim 2 or the elastomeric composition according to claim 3, characterized in that said copolymer of vinylpyridine with a conjugated diolefin and / or a monovinylarene is a diene elastomeric copolymer obtained by the copolymerisation of vinylpyridine with a conjugated diolefin selected from the group consisting of 1 ,3-butadiene, isoprene, 2,3-dimethyl-1 ,3-butadiene, 1 ,3-pentadiene, 1 ,3-hexadiene, 3- butyl-1 ,3-octadiene and 2-phenyl-1 ,3-butadiene and / or a monovinylaryl selected from the group consisting of styrene, a-methylstyrene, 3- methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2- ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenylbutyl)styrene, 1 - vinylnaphthalene, and 2-vinylnaphthalene, preferably selected from the group comprising butadiene-vinylpyridine copolymer, isoprene-vinylpyridine copolymer, isoprene-styrene-vinylpyridine copolymer, and styrene-butadiene- vinylpyridine copolymer, more preferably styrene-butadiene-vinylpyridine copolymer.

6. The tyre for vehicle wheels according to claim 1 or the structural element according to claim 2 or the elastomeric composition according to claim 3, characterized in that said predispersion comprises an amount of said vinylpyridine copolymer with a conjugated diolefin and / or a monovinylarene between 0.5% and 45% by weight, preferably between 1 and 25% by weight, relative to the total weight of said first diene elastomeric polymer and said vinylpyridine copolymer with a conjugated diolefin and / or a monovinylarene.

7. The tyre for vehicle wheels according to claim 1 or the structural element according to claim 2 or the elastomeric composition according to claim 3, characterized in that said predispersion comprises an amount of said lignin equal to or greater than about 45 phr, preferably equal to or greater than about 50 phr, even more preferably equal to or greater than about 60 phr.

8. The tyre for vehicle wheels according to claim 1 or the structural element according to claim 2 or the elastomeric composition according to claim 3, characterized in that said predispersion is added to said elastomeric composition in an amount to provide said elastomeric composition with at least 10 phr of said first diene elastomeric polymer, more preferably at least 15 phr of said first diene elastomeric polymer, and advantageously at least 20 phr of said first diene elastomeric polymer, the complement to 100 phr being provided by said second diene elastomeric polymer.

9. The tyre for vehicle wheels according to claim 1 or the structural element according to claim 2 or the elastomeric composition according to claim 3, characterized in that said predispersion is added to said elastomeric composition in an amount to provide said elastomeric composition with at least 10 phr of said lignin, more preferably at least 15 phr of said lignin, and advantageously at least 20 phr of said lignin.

10. The tyre for vehicle wheels according to claim 1 or the structural element according to claim 2, characterized in that said structural element isselected from the group consisting of carcass structure, belt structure, bead structure, tread band, anti-abrasive strip and sidewall.

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