Cross-linkable elastomer compositions comprising modified cellulose

Abstract

The present invention relates to cross-linkable elastomer compositions comprising modified cellulose, a process for the preparation of the corresponding elastomer compound, tyre components comprising said elastomer compound and tyres comprising said tyre components. In particular, the present invention relates to the use of cellulose functionalized by lipase catalysed esterification with 1,2-dithiolane derivative acids, in particular lipoic acid and derivatives thereof, as reinforcing filler in cross-linkable elastomer compositions, in particular for tyre applications.

Description

[0001] TITLE

[0002] “Cross-linkable elastomer compositions comprising modified cellulose” FIELD OF THE INVENTION

[0003] The present invention relates to cross-linkable elastomer compositions comprising modified cellulose, a process for the preparation of the corresponding elastomer compound, tyre components comprising said elastomer compound and tyres comprising said tyre components.

[0004] Specifically, the present invention relates to the use of cellulose functionalized by lipase-catalysed esterification with 1 ,2-dithiolane derivative acids, in particular lipoic acid and derivatives thereof, as reinforcing filler in cross-linkable elastomer compositions, in particular for tyre applications.

[0005] STATE OF THE ART

[0006] The use of reinforcing fillers in elastomer compositions, in particular for tyre manufacturing, is widely known in the art. Indeed, despite their outstanding elasticity, elastomer compositions do not have the mechanical properties required for demanding applications, such as the one in tyre compounds.

[0007] Carbon black is one of the most widely used reinforcing filler: its addition to elastomer composites leads to the increase of both their static and dynamic-mechanical properties. However, carbon black is known to cause an increase of the hysteresis, hence of the dissipation of energy, of the elastomer compounds; in this sense, the reduction of carbon black is one of the primary objectives in tyre production. Moreover, carbon black is also cause for concern from an environmental standpoint, being a non-renewable raw material, derived mainly from processes of partial combustion of fossil fuels, and a potential pollutant if not disposed of correctly.

[0008] Replacement or reduction of carbon black with more environmentally sustainable and environmentally compatible reinforcing fillers is therefore an important goal in the elastomer composites field and in particular in tyre manufacturing.

[0009] Among the many substances used with this aim, cellulose is one of the most promising due to its natural abundance, good aspect ratio (the ratio between the length and diameter of a fibre) and flexibility. Moreover, cellulose is obtained from renewable sources, fully biodegradable once dispersed in the environment and nontoxic. The many advantages of cellulose are nonetheless countered by the hydrophilicity of the cellulose material, which shows a high affinity for water and are easily hydrated.

[0010] Nanocellulose is a particularly interesting material, having at least one dimension in the nanoscale, which can be obtained from any natural cellulose source via different physical and / or chemical treatments. This term covers several different cellulosic materials, i.e. cellulose nanofibers (CNF), cellulose nanocrystals (CNC), and microfibrillated cellulose (MFC).

[0011] Microfibrillated cellulose is cellulose which has been subjected to mechanical shearing, exposing the fibril bundles, and it contains a mixture of nano- and micron-scale particles rendering it more heterogeneous than CNF and CNC. It is of particular interest for its increased aspect ratio, which renders it particularly suitable as reinforcing agent.

[0012] Functionalization of cellulose with hydrophobic groups is known in the art, as well as its use in compositions, also elastomer compositions, for different applications.

[0013] W090 / 03411 discloses cellulose fibers modified by graft copolymerization with (meth)acrylate monomers and their use in rubber compounds for tyres. Similarly, JP7473798 discloses (meth)acrylate- modified cellulose nanocrystals and their use in rubber compounds for tyres. WO2013 / 086079 and WO2013 / 086080 also disclose elastomer composition comprising cellulose esters, and tyres comprising said compositions.

[0014] WO2024 / 076893 and WO2024 / 075899 both disclose functionalized alkene-grafted cellulose nanocrystals (CNC) filler for blending with styrene-butadiene or natural rubber.

[0015] Lipase catalysed esterification of cellulose is also known in the art, for example EP4310103 discloses lipase mediated esterification of cellulose with fatty acids.

[0016] The synthesis of a-lipoic acid esters of cellulose, and their binding onto gold surfaces, has been reported by Liebert T. and colleagues (Polymer Bulletin 2006, 57, 857-863). Of note, the authors highlight that the functionalization has to be carried out via in situ activation of the carboxylic moiety of lipoic acid with p-toluenesulphonyl chloride or N,N’- carbonyldiimidazole, due to the absence of reactive derivatives of the acid available resulting from the instability of the disulphide function in the five-membered ring.

[0017] Fumagalli M. et al. (Soft Matter 2018, 14(14), 2638-2648) describes the gas phase surface-esterification of different types of nanocellulose, i.e. CNC and MFC, with 3,3-dithiopropionic acid chloride, to yield disulfide groups capable of cross-linking with the dienic elastomer matrix during vulcanization. Of note, this functionalization leads to different reinforcement properties, depending on the type of cellulose used, showing a significant decrease of the relevant elastic modulus (E1) for SBR-based compounds comprising functionalized MFC with respect to the comparative SBR-based compounds comprising non-functionalized MFC.

[0018] SUMMARY OF THE INVENTION

[0019] The Applicants addressed the need for more environmentally friendly elastomer compositions and related elastomer compounds, in particular for tyre manufacturing, comprising reinforcing fillers from renewable biosources at the same time maintaining and possibly improving the mechanical properties of the compounds, hence of the tyres.

[0020] The Applicants have noted that a promising class of bio-sourced reinforcing fillers is that of cellulose fibers, which are however characterized by the drawbacks described above. The Applicants have therefore also addressed the need for an easy and environmentally friendly process for the functionalization of cellulose fibers, in order to increase their compatibility with the elastomer compounds, hence their ability to successfully improve their mechanical properties.

[0021] The Applicants have surprisingly found that cellulose can be efficiently functionalized with 1 ,2-d ithiolane derivative acids, in particular with lipoic acid, and derivatives thereof, via a facile enzymatic catalysed esterification using a lipase. To the best of the Applicants knowledge, this is the first time that lipase catalysed esterification of cellulose with said 1 ,2-dithiolane derivative acids, such as lipoic acid and derivatives thereof, is reported.

[0022] Moreover, the Applicants have surprisingly found that the use of the obtained modified cellulose as reinforcing filler in elastomer compositions together with other reinforcing fillers, e.g. carbon black, leads to improved mechanical properties of the relevant compounds, both in terms of reinforcement and of rolling resistance, when compared both to the compounds prepared by mixing the components of the elastomer compositions not comprising cellulose and to those comprising pristine cellulose, as well as to those comprising other kinds of modified cellulose known in the art, i.e. acrylate-functional ized cellulose. Even more surprisingly, these results have been obtained also for compositions with a reduced content of other fillers.

[0023] Thus, a first aspect of the present invention is a cross-linkable elastomer composition comprising: a) one or more elastomers, b) a modified cellulose having ester groups represented by formula I below: wherein

[0024] A is a linear C2-C9 alkyl or alkenyl group or a linear C2-C9 alkyl ether group, optionally substituted with one or more groups selected from hydroxyl, carboxyl, Ci-Ce alkyl, Ci-Ce alkoxy-alkyl, and C2-C6 alkoxy-alkenyl, and

[0025] R1and R2are independently selected from the group consisting of hydrogen, linear or branched C1-C6 alkyl, and hydroxyl, and R3is selected from hydrogen and C1-C3 alkyl; c) one or more additional reinforcing fillers; d) a cross-linking system; and e) optionally, one or more additives.

[0026] A second aspect of the present invention is a process for the preparation of an elastomer compound, comprising: i. providing one or more elastomers, the modified cellulose according to the present invention and as defined above, one or more additional reinforcing fillers, a cross-linking system, and optionally one or more additives; and ii. performing at least one mixing step.

[0027] In a third and fourth aspect, the present invention relates to a tyre component comprising the elastomer compound prepared by the process according to the present invention and to a tyre for vehicle wheels comprising at least one of said tyre components.

[0028] BRIEF DESCRIPTION OF THE FIGURES

[0029] The description is illustrated here with reference to the attached drawings, provided solely by way of example and not limiting the invention.

[0030] Figure 1 is an outline of the transverse half-section of a tyre comprising in one or more components the elastomer composition according to the present invention.

[0031] Figure 2 shows the IR spectrum of an exemplary modified cellulose according to the invention (solid line) compared to that of pristine cellulose (dotted line).

[0032] Figure 3 shows the desorption spectrum of an exemplary modified cellulose according to the invention.

[0033] Figure 4 is a graph showing the variation of G' (y axis) versus the deformation amplitude (x axis) for the elastomer compositions of examples 6-9.

[0034] Figure 5: graph showing the variation of tan delta (y axis) versus the deformation (x axis) for the elastomer compositions of examples 6-9.

[0035] DETAILED DESCRIPTION OF THE INVENTION

[0036] Definitions

[0037] The term “elastomer composition” refers to a formulation comprising at least one elastomer, preferably a diene elastomer polymer, and one or more reinforcing fillers, which, by mixing, provides an elastomer compound suitable for use in tyre components. The components of the elastomer composition generally are not introduced simultaneously into the mixer but typically added sequentially. In particular, the components of cross-linking system, such as the vulcanizing agent and optionally accelerators and retarders, are usually added at a stage downstream from the incorporation and processing of all other components. In the intermediate or final elastomer compound, the individual components of the elastomer composition do not always remain unaltered or individually traceable, as they may have been transformed, in whole or in part, by interaction with other components, heat and / or mechanical processing. The term “elastomer composition” herein is intended to include the totality of all components that are added in the preparation of the elastomer compound, irrespective of whether they are all actually present simultaneously, whether they are introduced sequentially, or whether they are subsequently traceable in the final elastomer compound or tyre.

[0038] The term “cross-linkable elastomer composition” refers to an elastomer composition comprising a cross-linking system.

[0039] The term "elastomer compound" means the mixture obtainable by mixing and preferably heating, at specific pressure and temperature conditions, at least one elastomer diene polymer with one or more reinforcing fillers, and optionally one or more additives commonly used in the preparation of compounds for tyres.

[0040] The term "elastomer" means a natural or synthetic polymer which, after vulcanization, can be repeatedly stretched at room temperature to at least twice its original length and after removal of the tensile load returns substantially immediately and forcefully to its approximate original length (as defined in ASTM D1566-11 Standard terminology relating to Rubber).

[0041] The term “vulcanization” refers to the cross-linking reaction in a natural or synthetic rubber induced for example by a sulphur-based vulcanizing agent.

[0042] The term “vulcanizing agent” refers to a cross-linking agent capable of transforming green rubber into an elastic and resistant material through the formation of a three-dimensional network of inter- and intra-molecular cross-links.

[0043] The term “vulcanization accelerator” refers to a chemical agent capable of decreasing the duration of the vulcanization process and / or operating temperature. Examples of vulcanization accelerators are TBBS, sulphenamides in general, thiazoles, dithiophosphates, dithiocarbamates, guanidines, as well as sulphur donors such as thiurams. The term “vulcanization activator” refers to a chemical agent that can further facilitate curing, causing it to take place at a shorter time and optionally lower temperature. An example of vulcanization activator is the stearic acid-zinc oxide system.

[0044] The term “vulcanization retarder” refers to a chemical agent capable of delaying the start of the vulcanization reaction and / or suppressing undesirable secondary reactions. An example of vulcanization retarder is N-(cyclohexylthio) phthalimide (CTP).

[0045] The term “cross-linking system” refers to a system of chemical agents comprising at least one vulcanizing agent and optionally at least one vulcanization accelerator, at least one vulcanization retarder and at least one vulcanization activator.

[0046] The term "reinforcing filler" refers to a reinforcing material typically used in the industry to improve the mechanical properties of tyre compounds.

[0047] For the purposes of the present description and the following claims, the term "phr" (parts per hundreds of rubber) indicates the parts by weight of a defined component of the elastomer composition per 100 parts by weight of the elastomer polymer.

[0048] Unless otherwise indicated, all the percentages are percentages by weight.

[0049] Detailed Description

[0050] A first aspect of the present invention is a cross-linkable elastomer composition comprising: a) one or more elastomers, b) a modified cellulose having ester groups represented by formula I below: wherein

[0051] A is a linear C2-C9 alkyl or alkenyl group or a linear C2-C9 alkyl ether group, optionally substituted with one or more groups selected from hydroxyl, carboxyl, Ci-Ce alkyl, Ci-Ce alkoxy-alkyl, and C2-C6 alkoxy-alkenyl, and

[0052] R1and R2are independently selected from the group consisting of hydrogen, linear or branched C1-C6 alkyl, and hydroxyl, and R3is selected from hydrogen and C1-C3 alkyl; c) one or more additional reinforcing fillers; d) a cross-linking system; and e) optionally, one or more additives.

[0053] Said group A is optionally substituted preferably with one or more groups selected from hydroxyl, C1-C3 alkyl, and C1-C3 alkoxy-alkyl.

[0054] Preferably, said group A is a linear C2-C8 alkyl group, more preferably a linear C2-C6 alkyl group, even more preferably a linear C4 alkyl group.

[0055] Preferably, said R1and R2are independently hydrogen or linear or branched C1-C3 alkyl, more preferably Ci alkyl, even more preferably said R1and R2are hydrogen.

[0056] Preferably, said R3is hydrogen or methyl, more preferably said R3is hydrogen.

[0057] In preferred embodiments, said ester groups of formula I are selected from esters of the following acids: lipoic acid, 5-(4-methyldithiolan-3- yl)pentanoic acid, 1 ,2-dithiolane-3-propanoic acid, 5-(3-methyl-1 ,2- dithiolan-3-yl)pentanoic acid, 3-(1 ,2-dithiolan-3yl-methoxy)propanoic acid, 4-(1 ,2-dithiolan-3-yl)butanoic acid, 1 ,2-dithiolane-3-nonanoic acid, 1 ,2-dithiolane-3-heptanoic acid, 1 ,2-dithiolane-3-pentanoic acid-5- methyl.

[0058] In a particularly preferred embodiment, said ester groups of formula I are represented by formula II below:

[0059] The cellulose useful for the cross-linkable elastomer compositions of the present invention can be any kind of cellulose, and particularly nanocellulose, such as cellulose nanocrystals, cellulose nanofibers and microfibri Hated cellulose. In a preferred embodiment, said modified cellulose is any kind of cellulose except for cellulose nanocrystals. In a particularly preferred embodiment, said modified cellulose is microfibri Hated cellulose.

[0060] Conventional cellulose is characterized by the repeating units shown below, containing three hydroxyl groups on each glucose unit. Each of these hydroxyl groups can be esterified, hence the substitution level can be expressed in terms of degree of substitution ("DS"), i.e. the average number of substituents per glucose unit, which is usually a value between zero and three. DS is a statistical value and does not imply that each of the glucose units has a specific number of substituents, as there can be at the same time unsubstituted units as well as mono- di- and three- substituted units.

[0061] In embodiments, the modified cellulose according to the present invention has a degree of substitution of from 0.02 to 1 .5, preferably from 0.05 to 1.0, more preferably from 0.07 to 0.5. The modified cellulose of the present invention can be obtained via conventional esterification methods known in the art. However, in a particularly preferred embodiment the modified cellulose is advantageously obtained via an environmentally friendly lipase-catalysed esterification process. According to a further aspect of the present invention, this process for obtaining the modified cellulose according to the invention comprises:

[0062] A. providing a mixture of a solvent, cellulose, at least one lipase, and a at least one carboxylic acid of formula III below: wherein

[0063] A is a linear C2-C9 alkyl or alkenyl group or a linear C2-C9 alkyl ether group, optionally substituted with one or more groups selected from the group consisting of: hydroxyl, carboxyl, C1-C6 alkyl, C1-C6 alkoxy-alkyl, C2-C6 alkoxy-alkenyl, and

[0064] R1and R2are independently selected from the group consisting of: hydrogen, linear or branched C1-C6 alkyl group, and hydroxyl, and R3is selected from hydrogen or C1-C3 alkyl; and

[0065] B. performing a lipase-catalysed esterification reaction between cellulose and the at least one carboxylic acid of formula III, at a temperature comprised between 30 and 60°C, to obtain the modified cellulose according to the present invention; and

[0066] C. optionally, isolating and purifying said modified cellulose.

[0067] Note that, said lipase is an immobilized lipase on a resin, preferably on a methacrylate copolymer resin functionalized with epoxy groups.

[0068] Preferably, said solvent is a sterically hindered alcohol, more preferably a tertiary alcohol, such as t-butanol, 2-methyl-2-butanol, 2 ethyl-2butanol, 3-methyl-3-pentanol, 3-ethyl-3-butanol, and 2-ethyl-3- pentanol.

[0069] Advantageously, said lipase can be selected from carboxyl ic-ester hydrolases, preferably triacylglycerol lipases, even more preferably said lipase is selected from Candida antarctica lipase-B and Pseudomonas cepacia lipase.

[0070] Said cellulose and said groups A and R1-R3of the carboxylic acid of formula (III) are as disclosed above. In particular, the cellulose can preferably be m icrofibrillated cellulose and the acid can preferably be lipoic acid.

[0071] Advantageously, the weight ratio between the cellulose and the carboxylic acid can be of 1 :3, preferably of 1 :2, even more preferably of 1 :1.6.

[0072] Advantageously, the weight ratio between the cellulose and the lipase can be of from 4.5:1 to 0.5:1 , preferably of from 4:1 to 1.5:1. In particular, when Candida antarctica lipase-B is used, the weight ratio between the cellulose and the lipase can be of 2: 1 , whilst when Pseudomonas cepacia lipase is used the weight ratio between the cellulose and the lipase can be of 3.6:1.

[0073] Preferably, step B is performed in presence of a water sequestering agent, preferably activated molecular sieves and / or anhydrous salts, such as for example calcium chloride, copper sulphate, or calcium oxide.

[0074] Preferably, step B can be carried out at a temperature of from 45°C to 55°C, more preferably at 50°C.

[0075] Preferably, step B is performed by stirring the mixture for a time comprised between 6 and 14 hours, more preferably between 8 and 12 hours, even more preferably equal to 10 hours.

[0076] According to a preferred embodiment, step C of isolating and purifying the modified cellulose comprises: C1. separating the modified cellulose from the enzyme by filtration using specific sieves, preferably metallic sieves, having a pore diameter comprised between 1 mm and 2 mm, preferably comprised between 1.3 mm and 1 .6 mm, even more preferably equal to 1 .5 mm; and

[0077] C2. washing the separated modified cellulose with anhydrous ethanol, to remove the excess free carboxylic acid of formula III in solution, and then evaporating the ethanol.

[0078] Preferably, the cross-linkable elastomer composition of the present invention contains an amount of said modified cellulose of at least 1 phr, preferably of at least 1 .5 phr, even more preferably of at least 2 phr.

[0079] In embodiments, said amount of modified cellulose is of from 1 phr to 30 phr, preferably of from 1 .5 phr to 20 phr, still more preferably of from 1.8 and 15, even more preferably of from 2 phr to 10 phr. In particularly preferred embodiments, said amount of modified cellulose is of from 2 phr to 6 phr, even more preferably equal to 4 phr.

[0080] Additional reinforcing fillers useful in the cross-linkable elastomer composition of the present invention are selected in the group consisting of: carbon black, silica, layer silicates, mixed oxides of aluminium and magnesium with lamellar structure, alumina, and silico aluminates. In a particularly preferred embodiment, the additional reinforcing filler is carbon black.

[0081] Note that, silica can be modified silica.

[0082] Silica can be modified, for example, by reaction with siloxanes (as described in W02018078480A1 ), with pyrroles (as described in W02016050887A1 ), or with suitable silanizing agents. Commercial examples of silanizing agents suitable for the purposes of the present invention include Si69, Dynasilan AMEO, and Dynasilan GLYEO by Evonik.

[0083] Modified silica can be sulfurized silanized silica. Sulfurized silanized silica is silica prepared by reaction of a silica or metal silicate with at least one sulfurized silanizing agent. A suitable commercial example of sulfurized silanized silica is Agilon 400 silica by PPG.

[0084] Commercial examples of suitable silica for the purposes of the present invention are Zeosil 1165 MP, Zeosil 1115 MP, Zeosil 185 GR, Solvay's Efficium, Wuxi's Newsil HD90 and Newsil HD200, Wilmar's K160 and K195, H160AT and H180 AT by IQE, Zeopol 8755 and 8745 by Huber, Perkasil TF100 by Grace, Hi-Sil EZ 120 G, EZ 160G, EZ 200G by PPG, Ultrasil 7000 GR and Ultrasil 9100 GR by Evonik, K 160 (silica from rice husk) by Wilmar.

[0085] Preferably, carbon black is selected from those having a surface area of not less than 20 m2 / g, preferably greater than 50 m2 / g (as determined by STSA - statistical thickness surface area according to ISO 18852:2005).

[0086] Examples of carbon blacks suitable for the purposes of the present invention are: N110, N115, N121 , N134, N220, N234, N326, N330, N375 or N550, N660, marketed by Birla Group (India) or Cabot Corporation, Vulcan® 1391 by Cabot Corporation or Birla Carbon™ 2115 by Birla Group.

[0087] Typically, said one or more additional reinforcing fillers are in an amount of from 10 phr to 130 phr, preferably of from 30 phr to 90 phr, even more preferably of from 45 phr to 60 phr.

[0088] Preferably, in the cross-linkable elastomer composition according to the present invention, the total amount of reinforcing fillers, understood to mean the sum of the amount of the modified cellulose according to the present invention and additional reinforcing fillers, is of from 20 phr to 150 phr, preferably of from 30 phr to 110 phr, still more preferably of from 45 to 90 phr, even more preferably of from 50 phr to 65 phr.

[0089] Preferably, the elastomers useful in the cross-linkable elastomer composition of the present invention are unsaturated elastomers selected from the group consisting of: cis-1 ,4-polyisoprene, either natural rubber or synthetic polymer, 3,4-polyisoprene, polybutadiene, in particular polybutadiene with a high content of cis-1 ,4 units, isoprene / isobutene copolymers, halogenated isoprene / isobutene copolymers such as for example halogenated butyl rubber, in particular chlorobutyl and bromobutyl rubber, 1 ,3-butadiene / acrylonitrile copolymers, styrene-butadiene copolymers, in particular styrene / 1 ,3- butadiene copolymers, styrene / isoprene / 1 ,3-butadiene copolymers, styrene / 1 ,3-butadiene / acrylonitrile copolymers, or mixtures thereof.

[0090] Polybutadiene with a high content of cis-1 ,4 means polybutadiene having a 1 ,4-cis monomer unit content of at least 95%.

[0091] The cross-linkable elastomer compositions can further contain an unsaturated, diene or non-diene monomers-based elastomer, functionalized by reaction with suitable functionalizing agents, such as terminating agents and / or coupling agents. In particular, the diene elastomer polymer can be obtained by anionic polymerization promoted by an organometallic initiator (in particular an alkyl-lithium) and terminated by reaction with suitable terminating agents or coupling agents such as, for example, epoxides, carbonyl compounds such as for example cyclohexanone and benzophenone, substituted or unsubstituted, imines, carbodiimides, alkyl-tin halides, alkoxysilanes or aryloxysilanes.

[0092] Elastomer diene polymers are preferably solid.

[0093] In a particularly preferred embodiment, said one or more elastomers are natural rubber (NR).

[0094] Suitable commercial natural rubbers (NR) for the purposes of the present invention include, for example, SIR20 solid natural rubber by Eatern GR Thailand - Chonburi, STR20 solid natural rubber by Von Bundit, SMR20-type natural rubber by LEE RUBBER CO. PTE LTD, KUALA KRAI, GEB type by Hevea-TEC.

[0095] Preferably, styrene-butadiene copolymers have a Tg between -70 and -10°C, more preferably between -65 and -25°C, and preferably includes 10 to 30% by weight styrene units and 25 to 67% by weight vinyl units.

[0096] Styrene-butadiene copolymers may contain, in addition to styrene units and butadiene units, a small amount, such as 5% by weight or less, of additional monomeric units such as isoprene, dimethylbutadiene, pentadiene, methylstyrene, ethylstyrene, divinylbenzene, and diisopropenylbenzene.

[0097] Preferably, styrene-butadiene copolymers are random polymers.

[0098] Styrene-butadiene copolymers can be prepared by solution polymerization (S-SBR).

[0099] Synthesis in solution generally provides polymers with a reduced molecular weight distribution, fewer chain branches, higher molecular weight and higher control of the butadiene insertion mode, compared to similar polymers obtainable in emulsion.

[0100] Styrene-butadiene copolymers can also be prepared by emulsion polymerization (E-SBR).

[0101] Preferably, styrene-butadiene copolymers are random and coupled polymers.

[0102] Preferably, styrene-butadiene copolymers are functionalized SBR copolymers with appropriate functionalizing groups.

[0103] Preferably, said functionalizing groups are chosen from the group consisting of: alkoxysilanes, mercaptosilanes, sulphur-containing groups, amine groups, amide groups, epoxides, hydroxides, and combinations thereof. The alkoxysilane groups suitable for the purposes of the present invention include monoalkoxy, dialkoxy, and trialkoxy silanes. Sulphur-containing groups suitable for the purposes of the present invention are chosen from the group consisting of: thiol, thioether, thioglycol, thioester, sulfide, or sulfanyl group. The amine functional groups suitable for the purposes of the present invention are chosen from the group consisting of primary, secondary, and tertiary amine groups. In a further preferred embodiment, styrene-butadiene copolymers are random, coupled, and functionalized copolymer.

[0104] Examples of commercial SBR copolymers suitable for the purposes of the present invention include SPRINTAN™ SLR 4630, SPRINTAN™ SLR 4602, and SPRINTAN™ SLR 3402 by Trinseo.

[0105] Examples of commercial polybutadiene (BR) suitable for the purposes of the present invention include Europrene Neocis® by Polimeri Europa, SKD NHEODIMIO NIZHN from PAO of Nizhnekamskneftekhim, HIGH CIS POLYBUTADIENE (NICKEL TYPE) from Trinseo, Europrene Neocis BR40 (S-0129) by Versalis.

[0106] The cross-linkable elastomer compositions according to the present invention can further contain at least one elastomer of one or more monoolefins. The mono-olefins can be selected from: ethylene and 1 -olefins with 3 to 12 carbon atoms, such as, for example, propylene, 1 -butene, 1 - pentene, 1 -hexene, 1 -octene, or mixtures of these mono-olefins. The elastomer of one or more mono-olefins can contain a diene, which generally has from 4 to 20 carbon atoms and is preferably selected from: 1 ,3-butadiene, isoprene, 1 ,4-hexadiene, 1 ,4-cyclohexadiene, 5- ethylidene-2-norbornene, 5-methylene-2-norbornene, vinylnorbornene or mixtures of these dienes. The diene can optionally be halogenated. Among these elastomers of one or more mono-olefins, the following are preferred: ethylene / propylene copolymers (EPR) or ethylene / propylene / diene copolymers (EPDM) and poly(isobutene).

[0107] Preferably, said cross-linking system comprises at least one vulcanizing agent. The vulcanizing agent is preferably selected from sulphur, in particular soluble or insoluble sulphur, sulfurized agents (sulphur donors), such as, for example, bis[(trialkoxysilyl)propyl]polysulphides, caprolactam-disulphide, and mixtures thereof. Preferably, the vulcanizing agent is sulphur.

[0108] Commercial examples of vulcanizing agent suitable for the purposes of the present invention include soluble sulphur by Zolfindustria (Italy) or insoluble sulphur (at 67%) by International Sulphur Inc..

[0109] In the present elastomer composition, the vulcanizing agent may be used together with adjuvants such as vulcanization activators, vulcanization accelerators and / or vulcanization retarders known to those skilled in the art.

[0110] Vulcanization activators which are particularly effective are compounds of zinc and in particular ZnO, ZnCOs and zinc salts of saturated or unsaturated fatty acids comprising from 8 to 18 carbon atoms, which are preferably formed in situ in the elastomer composition by reaction of ZnO and of the fatty acid or mixtures thereof. For example, zinc stearate is used, preferably zinc stearate formed in situ in the elastomer composition, from ZnO and fatty acid, or magnesium stearate, formed from MgO, or mixtures thereof.

[0111] An example of a commercially available vulcanization activator is Aktiplast ST by Reinchemie and ZnO by Zincol Ossidi.

[0112] Vulcanization accelerators that are commonly used may be, for example, selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulphenamides, sulphenimides, thiurams, amines, xanthates, or mixtures thereof. Preferably, the vulcanization accelerator is selected from mercaptobenzothiazole (MBT), 2,2'-dibenzothiazyl disulfide (MBTS), N-cyclohexyl-2-benzothiazol-sulfenamide (CBS), N-tert-Butyl-2- benzothiazolyl sulfonamide (TBBS) and mixtures thereof. Commercial examples of vulcanization accelerators suitable for use in this elastomer composition are N-cyclohexyl-2-benzothiazol sulfenamide by General Quimica, and N-tert-butyl-2-benzothiazolyl-sulfonamide, Vulkacit® NZ / EGC marketed by Lanxess.

[0113] Preferably, the at least one vulcanization retarder is selected from the group consisting of: urea, phthalic anhydride, N-nitrosodiphenylamine, N- cyclohexylthiophthalimide (CTP or PVI) and mixtures thereof. A commercial example of a vulcanization retarder suitable for the purposes of the present invention is N-cyclohexylthiophthalimide VULKALENT G by Lanxess.

[0114] According to a preferred embodiment, said cross-linkable elastomer composition contains a quantity of vulcanizing agent greater than or equal to about 1 phr, preferably greater than or equal to about 2 phr.

[0115] Preferably, the quantity of vulcanizing agent is less than or equal to about 12 phr, preferably less than or equal to about 7 phr.

[0116] Preferably, the quantity of sulphur lies between about 0.5 phr and about 7 phr, more preferably between 2 phr and 6.5 phr

[0117] The present cross-linkable elastomer composition may further comprise one or more additives, commonly used in the field, such as antioxidant and / or anti-ozone agents (anti-aging agents), plasticizers, adhesives, modifying resins, coupling agents, and the like.

[0118] Preferably, said at least one antioxidant agent is a quinolinic antioxidant, more preferably TMQ, and / or a phenolic antioxidant, more preferably 4,6-bis(octylthiomethyl)-o-cresol. Said at least one antioxidant may be added as such, or it may be supported on a reinforcing filler (such as, for example, carbon black or silica), so as to facilitate its incorporation into the elastomer compound.

[0119] The cross-linkable elastomer composition may comprise at least one anti-ozone agent. The anti-ozone agent is preferably selected from N- isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(-1 ,3-dimethyl-butyl)- n'-phenyl-p-phenylenediamine (6PPD), N,N'-bis-(1 ,4-dimethyl-pentyl)-p- phenylenediamine (77PD), N,N'-bis-(1 -ethyl-3-methyl-pentyl)-p- phenylenediamine (DOPD), N,N'-bis-(1 ,4-dimethyl-pentyl)-p- phenylenediamine, N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'- ditolyl-p-phenylenediamine (DTPD), N,N'-di-beta-naphthyl-p- phenylenediamine (DNPD), N,N'-bis(1 -methylheptyl)-p- phenylenediamine, N,N'-Di-sec-butyl-p-phenylenediamine (44PD), N- phenyl-N-cyclohexyl-p-phenylenediamine, N-phenyl-N '-1 -methylheptyl- p-phenylenediamine and the like, and mixtures thereof, preferably it is N- 1 ,3-dimethylbutyl-N-phenyl-p-phenylenediamine (6PPD).

[0120] In particular, for the purpose of improving workability, one or more plasticizers can be added to said cross-linkable elastomer composition.

[0121] Preferably, said plasticizers are at least one oil selected from the group consisting of: mineral oils, vegetable oils, synthetic oils, and mixtures thereof.

[0122] The at least one oil may be a petroleum-derived oil selected from paraffins (saturated hydrocarbons), naphthenes, polycyclic aromatics, and mixtures thereof.

[0123] Petroleum-derived oils are preferably selected from the group consisting of: aromatic, paraffinic and / or naphthenic oil, such as, for example, MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), and mixture thereof.

[0124] Examples of suitable petroleum-derived oils are NYTEX 4700 by Nynas, EXTENSOIL 1471 by Repsol, and VIVATEC 500 by H&R.

[0125] Suitable vegetable oils for the purposes of the present invention are preferably selected from the group consisting of: sunflower oil, soybean oil, flaxseed oil, rapeseed, castor oil, and cotton oil.

[0126] Examples of suitable commercial vegetable oils are RADIA 6132 by Oleon, Agripure AP 18 and Agripure AP 75 by Cargill, and soybean oil by Wilmar.

[0127] The amount of plasticizer is generally from 0 phr to about 40 phr, preferably from about 2 phr to about 20 phr.

[0128] Preferably, modifying resins comprise at least one resin selected from the group consisting of: hydrocarbon resin, phenolic resin, natural terpenic resin, natural rosin resin, and mixtures thereof. More preferably, the at least one resin is a hydrocarbon resin. The hydrocarbon resin may include at least one aliphatic resin, at least one aromatic resin, at least one resin comprising both aliphatic and aromatic monomers, or combinations thereof.

[0129] Hydrocarbon resin can be natural (e.g., of plant origin or derived from petroleum) or synthetic. In some cases, not limiting to the invention, this type of resin comprises essentially only hydrogen and carbon atoms.

[0130] Preferably, the hydrocarbon resin is selected from homo- or copolymers of cyclopentadiene (CPD), dicyclopentadiene (DCPD), homo- or co-polymers of terpenes, homo- or co-polymers of the C5 moiety, and mixtures thereof, preferably DCPD / vinylaromatics copolymers, DCPD / terpenes copolymers, DCPD / C5 fraction copolymers, terpenes / vinylaromatics copolymers, copolymers of the C5 / vinylaromatics fraction and combinations thereof.

[0131] Examples of aromatic vinyl monomers are styrene, alphamethylstyrene, ortho-, meta-, paramethylstyrene, vinyl-toluene, para-tert- butylstyrene, methoxy-styrene, chloro-styrene, vinyl-mesylene, divinyl- benzene, vinyl-naphthalene, aromatic vinyl monomers derived from the C8-C10 fraction, particularly C9.

[0132] Hydrocarbon resin is preferably selected from coumarone-indene, styrene-indene, styrene-alkylstyrene, and aliphatic resins.

[0133] Examples of suitable commercial hydrocarbon resins are NOVARES C by RUTGERS CHEMICAL GmbH resins (synthetic indene-coumarone resins), preferably NOVARES C10, C30 and C90.

[0134] Examples of commercially available styrene-indene hydrocarbon resins are UNILENE At 100 by Braskem and Novares TL 90 by Rain Carbon.

[0135] Examples of commercially available alkyl styrene hydrocarbon resins are: Sylvares SA 85 by Arzona Chemical, Kristalex F 85 by Synthomer, and Kristalex 5140 from Synthomer.

[0136] Commercially available aliphatic hydrocarbon resins suitable for the purposes of the present invention are, for example, Escorez® 1102 by ExxonMobil, Piccotac 1100 by Eastman, Quintone A 100 by Zeon Chemicals.

[0137] Phenolic resin can be selected from alkylphenol-formaldehyde resins, rosin-modified alkylphenol resins, alkylphenol-acetylene resins, modified alkylphenol resins, and terpene-phenol resins.

[0138] Examples of commercially available phenolic resins that can be used in the present invention are SP-1068 RESIN (octylphenol-formaldehyde resin) by SI GROUP Inc., DUREZ 32333 (phenol-formaldehyde resin) by Sumitomo Bakelite, KORESIN (p-t-butylphenol-acetylene resin) by BASF Company, SYLVARES TP 115 (terpen-phenol resin) by Arizona Chemicals.

[0139] The natural terpenic resin can be a polyterpenic resin selected from homo- or copolymers of alpha-pinene, beta-pinene, limonene, possibly blended with vinyl (styrene) and / or phenolic aromatic monomers.

[0140] Examples of commercially available natural terpene resins suitable for the purposes of the present invention are Piccolyte F90 and Piccolyte F105 from PINOVA, Dercolyte A 115, and Dercolyte M 115 from DRT.

[0141] The term rosinic commonly denotes mixtures of isomeric organic acids (rosinic acids), characterized by a common structure, including three fused C6 rings, double bonds in different numbers and positions, and a single carboxylic group, in which the main component is abietic acid (C20H30O2) and its dihydroabietic (C20H32O2) and dehydroabietic (C20H28O2) derivatives.

[0142] Preferably, the cross-linkable elastomer composition of the invention may comprise at least one coupling agent.

[0143] Preferably, the coupling agent is a silane coupling agent.

[0144] Preferably, the silane coupling agent is contained in the cross-linkable elastomer composition in an amount of at least 0.5 phr, more preferably at least 1 phr or 2 phr, even more preferably at least 2 phr or 3 phr. Preferably, said silane coupling agent is contained in the cross- linkable elastomer composition in an amount at most equal to 20.0 phr, more preferably at most equal to 15.0 phr, more preferably at most equal to 10.0 phr.

[0145] Preferably, said silane coupling agent is selected from those having at least one hydrolyzable silane group, which can be identified, for example, by the following general formula:

[0146] (R’)3Si-CnH2n-X in which equal or different R' groups 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; n is an integer between 1 and 6; 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 from 1 to 6 and the R' groups are as defined above.

[0147] Particularly preferred silane coupling agents are bis(3- triethoxysilylpropyl)tetrasulfide and bis(3-triethoxysilylpropyl)disulfide. These coupling agents can be added as such or in a mixture with an inert reinforcing filler (such as, for example, carbon black), so as to facilitate their incorporation into the elastomer compound.

[0148] Examples of silane coupling agents suitable for the purposes of the present invention are TESPT bis(3-triethoxyisylpropyl)tetrasulfide Si69 by Evonik, TESPD bis(3-triethoxyisylpropyl)disulfide Si266 by Evonik, and TESPD (50% by weight supported on carbon black) by Jingzhou Jianghan Fine Chemical Co., LTD.

[0149] A second aspect of the present invention is a process for the preparation of an elastomer compound, comprising: i. providing one or more elastomers, the modified cellulose according to the present invention and as defined above, one or more additional reinforcing fillers, a cross-linking system, and optionally one or more additives; and ii. performing at least one mixing step.

[0150] Of note, each of the components provided in step i. is as disclosed above for the cross-linkable elastomer composition according to the present invention.

[0151] The elastomer compound can be prepared by mixing the polymeric components with the modified cellulose according to the present invention, and together with the other reinforcing fillers and the other additives possibly present, according to techniques known in the art. The mixing can be performed, for example, using an open mixer of the “openmill” type and / or an internal mixer of the type with tangential rotors (Banbury®), and / or with intermeshing rotors (Intermix™), and / or in continuous mixers of the Ko-Kneader™ type, and / or of the twin screw or multiscrew type and / or of the planetary type.

[0152] The components of the elastomer composition are not generally introduced all simultaneously into the mixer but are typically added in sequence. In particular, the vulcanization additives, such as the vulcanizing agent and possibly the vulcanization activators, vulcanization accelerators, and / or the vulcanization retarders, are usually added in a downstream step relative to the incorporation and processing of all the other components.

[0153] In the elastomer compound, the individual components of the cross- linkable elastomer composition do not always remain unaltered or are individually traceable in that they may be transformed, completely or in part, by effect of the interaction with other components, heat and / or mechanical processing.

[0154] A third aspect of the present invention is a tyre component comprising the elastomer compound prepared by the process of preparation according to the present invention and disclosed above.

[0155] Advantageously, said tyre component is selected in the group consisting of tread band, sidewall, sidewall insert, layers of elastomer material radially internal relative to said tread band, for example, cushion and mini-sidewall, bead filler, and rubber coating of the textiles and the metals. In a particularly preferred embodiment, the tyre component is tread band, sidewall, sidewall insert, mini-sidewall, or bead filler.

[0156] Such tyre component can be advantageously prepared with the elastomer compound according to the present invention characterized by low hysteresis and a reduced Payne effect, thus obtaining a clear advantage on the road-holding and in general on the performance of the tyre, such as the resistance to the deformation due for example to an increase in the temperature. In particular, as disclosed above, the elastomer compound according to the present invention is able to impart the desired mechanical-dynamical properties to the tyre.

[0157] In a fourth and final aspect the present invention relates to a tyre comprising at least one tyre component as disclosed above. In particular, said tyre comprises at least one carcass structure having opposite lateral edges associated with respective annular reinforcing structures, a belt structure applied in a position radially external relative to said carcass structure, a tread band applied in a position radially external to said carcass structure, and a pair of sidewalls applied laterally on opposite sides relative to said carcass structure.

[0158] The tyre according to the invention can be used on vehicles with two, three or four wheels, or on heavy vehicles, or on light transport vehicles.

[0159] The tyre according to the invention can be for summer or winter use or for all seasons.

[0160] The tyre according to the present invention can be manufactured according to a process comprising:

[0161] - assembling components of a raw tyre on at least one building drum;

[0162] - shaping, moulding and vulcanizing the tyre; wherein at least one component of the raw tyre contains the elastomer compound obtained by the process of preparation according to the present invention.

[0163] The term “raw” is generally used to indicate a material, a compound, a component or a tyre not yet vulcanized.

[0164] The finishing of the tyres can be effected by assembly of respective semi-finished products on a moulding drum, not illustrated, by means of at least one assembly device.

[0165] At least a part of the components intended to form the carcass structure of the tyre can be constructed and / or assembled on the building drum. More particularly, the building drum is ready to receive firstly the liner, if any, then the carcass structure and the anti-abrasive strip. Then, devices not illustrated coaxially engage one of the annular anchoring structures around each of the terminal edges , place an external sleeve comprising the belt structure and the tread band in a position coaxially centred around the cylindrical carcass sleeve and shape the carcass sleeve according to a toroidal configuration by means of a radial dilatation of the carcass structure, such as to bring about its application against a radially internal surface of the external sleeve.

[0166] Following the manufacture of the raw tyre, a moulding and vulcanization treatment is performed in order to effect the structural stabilization of the tyre via crosslinking of the elastomer mixture, and also to impress a desired tread design on the tread band and to impress possible distinctive graphic signs on the sidewalls.

[0167] The vulcanization takes place according to the known techniques, in particular with vulcanization agents based on sulphur commonly used per for diene elastomer polymers. For this purpose, in the materials, after one or more steps of thermal-mechanical treatment, a vulcanizing agent based on sulphur is incorporated together with vulcanization accelerators. At the final treatment step, the temperature is generally maintained below 120°C and preferably below 100°C, so as to avoid any undesired pre-crosslinking phenomenon. Figure 1 illustrates in radial half-section a tyre for vehicle wheels according to the invention.

[0168] In Figure 1 , "a" indicates an axial direction and "X" indicates a radial direction, in particular X-X indicates the trace of the equatorial plane. For simplicity, Figure 1 shows only one portion of the tyre, the remaining portion not represented being identical and positioned symmetrically relative to the equatorial planeHX-X".

[0169] In the embodiment shown in Figure 1 , the tyre 100 for vehicle wheels is a 100 four-wheel vehicle tyre. The tyre 100 for four-wheeled vehicles comprises at least one carcass structure, comprising at least one carcass layer 101 presenting mutually opposite terminal edges bonded to respective annular anchoring structures 102, called bead cores, possibly combined with a bead filler 104.

[0170] The zone of the tyre comprising the bead core 102 and the filler 104 forms a bead structure 103 intended for the anchoring of the tyre on a corresponding mounting rim, not illustrated.

[0171] The carcass structure is usually of the radial type, namely the reinforcing elements of at least one carcass layer 101 lie essentially on planes comprising the axis of rotation of the tyre and essentially perpendicular to the equatorial plane of the tyre. Said reinforcing elements are generally represented by textile cords, for example rayon, nylon or polyester (for example polyethylene naphthalate PEN). Each bead structure is connected to the carcass structure by folding behind opposite lateral edges of the at least one carcass layer 101 around the annular anchoring structure 102, so as to form the so-called carcass turnups 101 a.

[0172] In one embodiment, the coupling between carcass structure and bead structure can be provided via a second carcass layer, not represented in Figure 1 , applied in an axially external position relative to the first carcass layer. An anti-abrasive strip 105 possibly implemented with an elastomer compound according to the invention is arranged in a position external to each bead structure 103.

[0173] To the carcass structure, a belt structure 106 comprising one or more belt layers 106a, 106b placed in radial superposition relative to one another and to the carcass layer, having typically textile or metal reinforcing cords incorporated within one layer of vulcanized elastomer material is associated.

[0174] Such reinforcing cords can have a crossed orientation relative to a circumferential development direction of the tyre 100. “Circumferential” direction is understood to mean a direction generally oriented in the direction of rotation of the tyre.

[0175] In a position radially more external to the belt layers 106a, 106b at least one reinforcing layer at zero degrees 106c can be applied, commonly known as "0° belt", which typically incorporates a plurality of elongated reinforcing elements, typically metal or textile cords, oriented in an essentially circumferential direction, thus forming an angle of a few degrees (for example an angle between about 0° and 6°) relative to a direction parallel to the equatorial plane of the tyre, and coated with vulcanized elastomer material.

[0176] In a position radially external to the belt structure 106, a tread band 109 in vulcanized elastomer material is applied.

[0177] Further, on the lateral surfaces of the carcass structure, each extending from one of the lateral edges of the tread 109 up to where it coincides with the respective bead structure 103, respective sidewalls 108 in vulcanized elastomer material are applied at an axially external position. For run-flat tyres, respective sidewall inserts (not shown in Figure 1 ) may be interposed in an inner position with respect to the sidewalls 108.

[0178] In a radially external position, the tread band 109 has a rolling surface 109a intended to make contact with the ground. Circumferential grooves, which are connected by transverse indentations (not shown in Figure 1 ) such as to define a plurality of small blocks of various forms and dimensions distributed on the rolling surface 109a, are generally implemented in this surface 109a, which for simplicity is shown smooth in Figure 1 .

[0179] An underlayer 111 in vulcanized elastomer material can be positioned between the belt structure 106 and the tread band 109.

[0180] A strip of the elastomer compound 110, commonly known as “minisidewall”, in vulcanized elastomer material can optionally be present in the connecting zone between the sidewalls 108 and the tread band 109, this mini-sidewall being generally obtained by co-extrusion with the tread band 109 and allowing an improvement in the mechanical interaction between the tread band 109 and the sidewalls 108. Preferably the end portion of the sidewall 108 directly covers the lateral edge of the tread band 109.

[0181] In the case of tubeless tyres, a layer of rubber 112, generally known as a "liner", which provides the necessary impermeability to the air inflating the tyre, can also be provided in a radially internal position relative to the carcass structure 101 .

[0182] The rigidity of the tyre 108 in the radial direction can be improved by endowing the bead structure 103 with a reinforcing layer 120 generally known as a "flipper" or strip additional insert.

[0183] The flipper 120 is a reinforcing layer which is wound around the respective bead core 102 and the bead filler 104 so as to at least partially surround them.

[0184] The flipper 120 typically comprises a plurality of textile cords, incorporated within a layer of vulcanized elastomer material.

[0185] The tyre bead structure 103 can contain a further protective layer which is generally known by the term "chafer" 121 or protective strip and which has the function of further increasing the rigidity and / or integrity of the bead structure 103.

[0186] The chafer 121 usually comprises a plurality of cords incorporated within a rubber coating layer of vulcanized elastomer material. Such cords are generally implemented in textile materials (for example aramid or rayon) or in metallic materials (for example steel cords).

[0187] A layer or sheet of elastomer material (cushion) can be positioned between the belt structure and the carcass structure (not shown in Figure 1 ). The layer can have a uniform thickness. Alternatively, the layer can have a thickness variable in the axial direction. For example, the layer can have a maximum thickness close to its axially external edges relative to the central (crown) zone.

[0188] Advantageously, the layer or sheet can extend over an area substantially corresponding to the development surface of said belt structure.

[0189] In a preferred embodiment, a layer or sheet of elastomer material as described above can be placed between the belt structure and the tread band, where said supplementary layer or sheet preferably extends over an area substantially corresponding to the development surface of the belt structure.

[0190] According to an embodiment not shown, the tyre may be a motorcycle wheel tyre, typically a tyre with a high tread curvature.

[0191] The construction of tyre 100, as described above, can be done by assembling the respective semi-finished products suitable for forming the tyre components, on a forming drum, not shown, by at least one assembly device.

[0192] At least some of the components intended to form the tyre's carcass structure may be constructed and / or assembled on the forming drum. Specifically, the forming drum is intended to receive first the liner layer, if any, and then the carcass structure. Thereafter, the devices not shown coaxially engage one of the annular anchor structures around each of the flaps, position an outer sleeve including the belt structure and the tread band in a coaxially centred position around the cylindrical carcass sleeve, and shape the carcass sleeve to a toroidal configuration through a radial expansion of the carcass structure so as to cause it to be applied against a radial inner surface of the outer sleeve.

[0193] After the raw tyre is constructed, a moulding and vulcanization treatment is carried out to determine the structural stabilization of the tyre by curing the elastomer compound contained therein, as well as to imprint the desired tread pattern on the tread band and any distinctive graphic markings on the sidewalls.

[0194] The elastomer compound according to the invention may be used in one or more of the tyre components described above, e.g. the tread band, the sidewalls, the sidewall inserts, one or more layers of elastomer compound radially internal relative to tread band, such as the cushion and the mini-sidewalls, as well in the elastomeric components of the bead structures (e.g. the bead filler and / or the anti-abrasive strip), and / or in the rubber coating of the textile and / or the metallic cords.

[0195] The present invention will be further illustrated hereinafter by means of a number of examples, which are provided for purely illustrative purposes and without any limitation of this invention.

[0196] EXPERIMENTAL SECTION

[0197] Materials

[0198] The cellulose used was Exilva, m icrofibrillated cellulose by Borregaard, or UNICELL PF 30, m icrofibrillated cellulose by Interfiber.

[0199] The lipase used was Candida antarctica lipase-B or Pseudomonas cepacia lipase, by Merck KGaA (Darmstadt, Germany).

[0200] All the other reagents and solvents used for the preparation of the modified cellulose are f-Butanol and ethanol (absolute anhydrous and having a purity of 95%) by Carlo Erba Reagents and used without further purification.

[0201] The elastomer used is poly(1 ,4-c / s-isoprene) (NR), solid natural rubber SIR20, from Eatern GR Thailand - Chonburi. Mooney viscosity (ML(1 +4) @ 100 °C): 73 MU.

[0202] The additional reinforcing filler used is Carbon black N326 from Cabot Corporation.

[0203] Other ingredients for the preparation of the elastomer compounds:

[0204] - Stearic acid from Undesa

[0205] - ZnO from Zincol Ossidi;

[0206] - CBS (N-cyclohexyl-2-benzothiazole sulfenamide) from General Quimica,

[0207] - 6PPD ((1 ,3-dimethylbutyl)- / \ / ’-phenyl-p-phenylenediamine) from Eastman;

[0208] - Insoluble sulphur (67%) from International Sulphur Inc.

[0209] Characterization

[0210] The modified cellulose obtained was characterized by IR spectra and Thermal Desorption - Gas Chromatography - Mass Spectrometry (TD - CG - MS).

[0211] The Degree of Substitution (“DS”) of modified cellulose was determined by a titration method based on the saponification of esters in heterogeneous systems, according to ASTM D817-96, 2010, as described in section “characterization" of Yin, Y. et al. Lipase-catalyzed laurate esterification of cellulose nanocrystals and their use as reinforcement in PLA composites. Cellulose 27, 6263-6273 (2020). In particular, ~0.2 g of modified MFC and 20 mL of 95% ethanol were added to a flask and stirred at 50 °C for 30 minutes. Then, 20 mL of 0.5 N NaOH solution was added, and the mixture was stirred for 48 hours at room temperature. The excess NaOH was titrated with 0.5 N HCI using phenolphthalein as the indicator. The unmodified MFC was used as a blank. The DS was calculated according to the following equations:

[0212] A = ((B - C) * D) / E

[0213] DS = (0.162 * A) / (1 - MW * A) with

[0214] A = consumed HCI volume per gram of sample

[0215] B = V of consumed HCI in blank cellulose

[0216] C = V of consumed HCI in sample

[0217] D = concentration of HCI (0.5 N)

[0218] E = sample weight

[0219] MW is the molecular weight of substituent.

[0220] The fillers were characterized with ATR-FTIR by a Thermo Fisher Nicolet iS20 FTIR spectrometer (1 cm-1resolution, 525 - 4000 cm-1region, 16 scans).

[0221] To analyze the volatile parts of the samples, it was employed Thermal Desorption - Gas Chromatography - Mass Spectrometry (TD - CG - MS) technique, by which the specimen was first heated at 160 °C for 15 minutes under N2 constant flow, to assure an inert atmosphere; then the fumes were analyzed through a gas chromatography and every chemical species was then identified with Mass spectrometer.

[0222] Then, the elastomer compounds were vulcanized and characterized by the following procedures and techniques.

[0223] The tensile tests were performed on test pieces of the dumbbell ISO 3 type with rectilinear axis. Dumbell samples were cut out of 100x100x1 mm rubber sheets obtained curing the green compound in a mould at 170°C for 15 minutes in a hydraulic press. The static mechanical properties were measured at 23°C in accordance with the standard ISO 37:2005. In particular, the load was measured at different levels of elongation, load at 100% elongation [MPa], load at 300% elongation [MPa], named respectively o100 and o300, and the stress at break and the elongation at break named respectively oB and sB. The dynamic mechanical properties were measured by applying a dynamic stress via shear stress, at constant frequency and at constant temperature, increasing the deformation amplitude. The test was performed with a Monsanto RPA 2000 rheometer. The samples of elastomer material composition were held in the rheometer at 50°C for 90 seconds, the stress was then applied at 70°C in the deformation amplitude range between 0.9% and 90%, with a frequency of 1 Hz, increasing the deformation amplitude in the range stated above. This treatment is performed to eliminate the “previous thermo-mechanical history”. The vulcanization was then performed at 150°C for 30 minutes, with a frequency of 1. 7 Hz and an angle of 6.95% (0.5 rad). The sinusoidal stress was then applied with the same conditions already stated, at 70°C. The sinusoidal stress is then again applied, always with the same experimental conditions. Curves are then obtained which state the value of the moduli as a function of the deformation amplitude. Such moduli are illustrated below. The G' modulus is the elastic modulus. The G” modulus is the viscous modulus. The ratio G" / G' is stated as Tan Delta. From the strain sweep test, the values of the following parameters are obtained: G'MIN which is the value of G’ at minimum tested deformation (3% strain), G'MAX which is the value of G' at maximum tested deformation (7.5% strain), AG' which is the difference between the value of G' at minimum deformation and the value of G' measured at the maximum deformation reached, G"MAX which is the maximum value of G" observed in the G" curve, and (tan delta)max which is the maximum value of tan delta observed in the curve.

[0224] The dynamic mechanical properties were further measured by application of an axial stress using an Instron dynamic device in compression modality in accordance with the following methods. A sample of the elastomer compounds vulcanized at 170°C for 15 minutes having a cylindrical shape (length = 25 mm; diameter = 14 mm), compression-preload up to 25% of the longitudinal deformation relative to the initial length and maintained at the predetermined temperature (equal to, +23°C +70°C and 100°C) for the entire time length of the test, was subjected to a sinusoidal dynamic deformation having an amplitude of ±3.5% relative to the length under preload, with a frequency of 100 Hz.

[0225] The dynamic mechanical properties are expressed in terms of elastic dynamic modulus (E1) and tan delta (dissipation factor) values. The value of Tan delta was calculated as the ratio between the viscous modulus (E") and the elastic modulus (E1). The static and dynamic mechanical properties measured are summarized in the following table 1 .

[0226] Table 1 EXAMPLES

[0227] Example 1 - Lipase catalysed esterification of cellulose. General procedure

[0228] 25 g of dry microfibrillated cellulose of the desired particle size was placed into a flask in tert-butanol as a solvent with (±)-a-Lipoic acid and Candida antarctica lipase-B or Pseudomonas cepacia lipase in a ratio cellulose: lipase equal to 2:1 for Candida antartica lipase-B and to 3.6:1 for Pseudomona cepacia lipase. The reactions were carried out in the presence of molecular sieves beads, 4-8 mesh type, 4 A porosity, inside a Brunswick Innova 40R shaker at 160 rpm and 50 °C. After 10 hours of reaction time, the solvent was removed via rotary evaporation, and the cellulose was separated from the enzyme using an appropriately sized sieve. The cellulose was then washed several times with anhydrous ethanol to remove unreacted acid. The ethanol was evaporated, and the modified cellulose was ready for analysis.

[0229] Example 2 - Preparation of modified cellulose

[0230] The procedure of Example 1 was used to obtain cellulose functionalized with different carboxylic acids. The acids tested were lipoic acid, 3,3'-dithiodipropionic acid, and acrylic acid. Table 2 below summarizes the reagents used and their weight ratio, as well as the Degree of Substitution (DS) obtained.

[0231] Table 2

[0232] ‘Comparison;Aaccording to the invention

[0233] Fig. 2 shows the IR spectrum of an exemplary modified cellulose according to the invention (solid line), which specifically refers to the modified cellulose obtained by the reagents and their weight ratio according to sample 2 of table 2 above, compared to that of pristine cellulose (dotted line). In the IR spectrum the peak at 1720 cm’1, attributable to the ester C=O bond and not present in the spectrum of pristine cellulose, indicates the successful functionalization. Similarly, the desorption spectrum (Fig. 3), referred to the modified cellulose obtained for said sample 2 above, shows peaks attributable to both the lipoic acid and to lipoic acid ethyl ester, which again is proof of the successful functionalization.

[0234] On the other hand, it was not possible to functionalize cellulose with 3,3’-dithio propionic acid: after the reaction only pristine cellulose was recovered, no signals attributable to the esterified cellulose were identified in the IR spectrum (not shown).

[0235] Example 3 - Preparation of elastomer compound based on natural rubber and the modified cellulose in combination with carbon black.

[0236] Elastomer compounds were prepared via melt blending, according to the formulations summarized in Table 3.

[0237] 100 phr of Natural Rubber (SIR-20), was fed into a Brabender® internal mixer and masticated at 130°C for 1 minute, then pristine or modified cellulose was mixed for 2 minutes, then. CB, ZnO, stearic acid and 6PPD were added into the mixer and mixed for 2 minutes at the same temperature. The so obtained compound was unloaded and then fed again into the internal mixer at 80°C and 50 rpm, mixing for 1 minute. Insoluble sulphur and CBS were then added, mixing for a further 2 minutes. The final rubber composite was discharged and cooled at room temperature and, before the characterization, mixed few times in 2 rolls open mill.

[0238] Table 3

[0239] *Comparison; According to the invention

[0240] As can be seen from the table above, the compositions comprised as reinforcing filler either carbon black N326 alone (comparative samples 5 and 10), a mixture of carbon black N326 and pristine cellulose (comparative samples 7, 11 -12, and 15), or a mixture of carbon black N326 and the modified cellulose obtained as explained in examples 1 -2 above (comparative sample 9 comprising cellulose functionalized with acrylic acid, and samples 8, 13-14 and 16 comprising the cellulose functionalized with lipoic acid according to the invention). Of note, different amounts of carbon black were tested (54 phr in samples 6-9, 49 phr in samples 10-16), as well as different amounts of cellulose (2 phr in samples 11 and 13, 4 phr in samples 7-9, 12, 14-16).

[0241] Characterization of the elastomer compositions by means of tensile tests The compounds obtained from the composition of example 3 were vulcanized at 170°C and at closing force of 40 tons for 15 minutes, according to the previously described operating modalities. Tensile properties were determined by quasi static measurements as disclosed above. In Tables 4-5, the data obtained from the tensile tests are shown. Table 4

[0242] Table 5

[0243] ‘comparison;Aaccording to the invention

[0244] Of note, all the samples according to the invention show better static properties when compared both to those not comprising any cellulose (comparative samples 6 and 10) and those comprising pristine cellulose (comparative samples 7, 11 -12, and 15) or cellulose functionalized with acrylic acid (comparative sample 9).

[0245] The values of o100 and o300 always show a significant increase in tensile modulus for the compounds comprising cellulose functionalized with lipoic acid, already at 2 phr, with predictable similar or slightly better load at break values when compared with the samples comprising pristine cellulose. Instead, comparison samples comprising cellulose functionalized with acrylic acid do not show any significant difference in tensile parameters (o100 and o300) compared with the samples comprising pristine cellulose.

[0246] Dynamic mechanical characterization of the elastomer compositions by means of shear stress

[0247] The dynamic mechanical characterization was performed by applying a sinusoidal stress by means of shear stress, in accordance with the previously described operative modalities. In Table 6, the data relating to G'MIN, G'MAX, AG', tan Delta are shown. The curves of the variation in G' and of tan delta relative to the deformation amplitude are shown respectively in Figure 4 and in Figure 5 (sample 6* solid line with squares, sample 7* dotted line with circles, sample 8Adotted line with triangles, sample 9* dotted line with rhombuses).

[0248] Table 6

[0249] The elastic modulus G' exhibited a well-known property of cellulose: its rigidity and ability to impart stiffness to the system. In table 6, pristine cellulose (sample 7) was able to impart rigidity to the system while modified cellulose with lipoic acid (sample 8) was able to impart an even higher rigidity, differently from modified cellulose with acrylic acid (sample 9), showing a modulus substantially aligned with the unmodified cellulose.

[0250] Tan delta (tanb) revealed that the interaction between the lipoic acid and the vulcanizing agents was effective, since although the increase in modulus tanb remained aligned to reference compound. An increase in tanb was instead observed in the case of comparative sample 9, indicating a worsening of RR of the tyre.

[0251] Dynamic mechanical characterization of the elastomer compositions by means of axial stress

[0252] In Table 7, the data obtained from the dynamic mechanical tests, performed by application of a sinusoidal axial stress, are shown. The experimental conditions for performing the tests have been stated above.

[0253] Table 7

[0254] *comparison;Aaccording to the invention

[0255] The data above show that samples comprising modified cellulose with lipoic acid (samples 13-14 and 16 according to the present invention) show an increase in dynamical reinforcement both at 23°C and 70°C, while at the same time not influencing hysteresis properties, i.e. showing similar or slightly lower Tan delta values with respect to comparative samples 10-12. This behavior is beneficial for the rolling resistance of tyres.

Claims

CLAIMS1 . Cross-linkable elastomer composition comprising: a) one or more elastomers, b) a modified cellulose having ester groups represented by formula I below:whereinA is a linear C2-C9 alkyl or alkenyl group or a linear C2-C9 alkyl ether group, optionally substituted with one or more groups selected from hydroxyl, carboxyl, Ci-Ce alkyl, Ci-Ce alkoxy-alkyl, and C2-C6 alkoxy-alkenyl, andR1and R2are independently selected from the group consisting of hydrogen, linear or branched C1-C6 alkyl, and hydroxyl, and R3is selected from hydrogen and C1-C3 alkyl; c) one or more additional reinforcing fillers; d) a cross-linking system; and e) optionally, one or more additives.

2. Cross-linkable elastomer composition according to claim 1 , wherein said group A is a linear C2-C6 alkyl group.

3. Cross-linkable elastomer composition according to any one of claims 1 -2, wherein said R1, R2and R3are hydrogen.

4. Cross-linkable elastomer composition according to any one of claims1 -3, wherein said ester groups of formula I are represented by5. Cross-linkable elastomer composition according to any one of claims 1 -4, wherein said cellulose is m icrofibrillated cellulose.

6. Cross-linkable elastomer composition according to any one of claims 1 -5, wherein said modified cellulose has a substitution degree of from 0.02 to 1.5.

7. Cross-linkable elastomer composition according to any one of claims 1 -6, wherein said one or more additional reinforcing filler is selected from the group consisting of carbon black, silica, layer silicates, mixed oxides of aluminium and magnesium with lamellar structure, alumina, and silico aluminates.

8. Cross-linkable elastomer composition according to claim 7, wherein said additional reinforcing filler is carbon black.

9. Cross-linkable elastomer composition according to any one of claims 1 -8, wherein said modified cellulose is present in an amount of from 1 phr to 30 phr.

10. Cross-linkable elastomer composition according to any one of claims 1 -9, wherein said one or more additional reinforcing fillers is present in an amount of from 10 phr to 130 phr.11 . Process for the preparation of an elastomer compound, comprising: i. providing the modified cellulose as defined in any one of claims 1-6, and said one or more elastomers, one or more additional reinforcing fillers, cross-linking system, and optionally one or more additives of the cross-linkable elastomer composition according to any one of claims 1 -10; and ii. performing at least one mixing step.

12. Tyre component comprising the elastomer compound prepared by the process according to claim 11 .

13. Tyre component according to claim 12, selected in the group consisting of: tread band, sidewall, sidewall insert, cushion, minisidewall, components of the bead structures, and rubber coating of the textile and the metallic cords.

14. Tyre for vehicle wheels comprising at least one tyre component according to any one of claims 12-13.

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