TYRE FOR VEHICLE WHEELS

Abstract

A tyre (100) for vehicle wheels is described comprising at least one structural element comprising a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising a predispersion of an elastomeric diene polymer and lignin obtained by a process comprising: a) providing in a dispersant liquid a first lignin suspension having a value of a median particle diameter D50 equal to or less than 10 microns; b) providing a second suspension comprising lignin and elastomeric diene polymer latex by mixing the first lignin suspension obtained from step a) with the latex; and c) removing the dispersant liquid from the second suspension comprising lignin and elastomeric diene polymer latex.

Claims

1-30. (canceled)

31. A tyre for vehicle wheels comprising at least one structural element comprising a vulcanized elastomeric material obtained by vulcanizing a vulcanizable elastomeric composition comprising a predispersion of an elastomeric diene polymer and lignin obtained by a process comprising: a) providing in a dispersant liquid a first lignin suspension having a value of a median particle diameter D50 equal to or less than 10 microns; b) providing a second suspension comprising lignin and elastomeric diene polymer latex by mixing the first lignin suspension obtained from step a) with the latex; and c) removing the dispersant liquid from the second suspension comprising lignin and elastomeric diene polymer latex until the predispersion of elastomeric diene polymer and lignin is obtained.

32. The tyre for vehicle wheels according to claim 31, wherein a) providing the first lignin suspension comprises: a1) providing in the dispersant liquid a coarse lignin suspension having a value of a median particle diameter D50 equal to or greater than 10 microns; and a2) wet-grinding the lignin particles contained in the coarse suspension until the median diameter D50 of the lignin particles is reduced to the value equal to or less than 10 microns, to obtain the first lignin suspension.

33. The tyre for vehicle wheels according to claim 31, wherein the predispersion of elastomeric diene polymer and lignin comprises an amount of lignin equal to or greater than about 45 phr.

34. The tyre for vehicle wheels according to claim 31, wherein the first lignin suspension has a solid residue ranging from 20% to 80% by weight, with respect to the total weight of the suspension.

35. The tyre for vehicle wheels according to claim 31, wherein the elastomeric diene polymer latex has a solid residue ranging from 10% to 80% by weight, with respect to the total weight of the latex.

36. The tyre for vehicle wheels according to claim 31, wherein the vulcanizable elastomeric composition comprises at least 10 phr of the predispersion of elastomeric diene polymer and lignin.

37. The tyre for vehicle wheels according to claim 31, wherein a polymeric component of the vulcanizable elastomeric composition is constituted only by the elastomeric diene polymer of the predispersion.

38. The tyre for vehicle wheels according to claim 31, wherein a concentration of lignin introduced in the vulcanizable elastomeric composition by the predispersion of elastomeric diene polymer and lignin ranges from 2.5 phr to 160 phr.

39. The tyre for vehicle wheels according to claim 31, wherein the lignin is chosen from Softwood Kraft lignin, Hardwood Kraft lignin, Soda Grass lignin, Wheat Straw lignin, Rice Husk lignin, lignin obtained by biorefinery processes, and Organosolv lignin.

40. The tyre for vehicle wheels according to claim 31, wherein the elastomeric diene polymer is chosen from natural rubber (NR), emulsion styrene butadiene rubber (ESBR), carboxylated styrene butadiene rubber (XSBR), nitrile rubber NBR, carboxylated nitrile rubber (XNBR), chloroprene rubber (CR), and butyl rubber (IIR).

41. The tyre for vehicle wheels according to claim 31, wherein the structural element is chosen from a tread band, a carcass structure, a belt structure, an underlayer, an antiabrasive strip, a sidewall, a sidewall insert, a mini-sidewall, a flipper, a chafer, an underliner, rubber layers, a bead filling, and rubber sheets.

42. A process for preparing a predispersion of an elastomeric diene polymer and lignin, the process comprising: a) providing in a dispersant liquid a first lignin suspension having a value of a median particle diameter D50 equal to or less than 10 microns; b) providing a second suspension comprising lignin and elastomeric diene polymer latex by mixing the first lignin suspension obtained from step a) with the latex; and c) removing the dispersant liquid from the second suspension comprising lignin and elastomeric diene polymer latex until the predispersion of elastomeric diene polymer and lignin is obtained.

43. The process according to claim 42, wherein a) providing the first lignin suspension comprises: a1) providing in the dispersant liquid a coarse lignin suspension having a value of a median particle diameter D50 equal to or greater than 10 microns; and a2) wet-grinding the lignin particles contained in the coarse suspension until the median diameter D50 of the lignin particles is reduced to the value equal to or less than 10 microns, to obtain the first lignin suspension.

44. The process according to claim 42, wherein a) providing in a dispersant liquid the first lignin suspension comprises adding to the first lignin suspension an amount of at least one surfactant ranging from 0.1 parts to 60 parts by weight, of total suspension.

45. The process according to claim 42, wherein the first lignin suspension has a solid residue ranging from 20% to 80% by weight, with respect to the total weight of the suspension.

46. The process according to claim 42, wherein 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.

47. The process according to claim 43, wherein a2) wet-grinding the coarse lignin suspension is carried out by means of a grinding apparatus chosen from ball mills, hammer mills, blade mills, roller mills, high-pressure compression mills, ring mills, vibrating tube or vibrating rod mills, and centrifugal fluid mills.

48. The process according to claim 42, wherein the elastomeric diene polymer latex has a solid residue ranging from 10% to 80% by weight, with respect to the total weight of the latex.

49. The process according to claim 42, wherein b) providing the second suspension comprising lignin and elastomeric diene polymer latex is carried out by mixing from 30 parts to 200 parts by weight, of the first lignin suspension obtained from step a) per 100 parts by weight of elastomeric diene polymer latex.

50. The process according to claim 42, wherein b) providing the second suspension comprising lignin and elastomeric diene polymer latex is carried out by mixing the first lignin suspension obtained from step a) with the latex for a time to obtain a substantially homogeneous second suspension.

51. The process according to claim 42, wherein c) removing the dispersant liquid from the second suspension comprising lignin and elastomeric diene polymer latex comprises d) drying the second suspension and, optionally, e) removing part of the dispersant liquid before drying the second suspension.

52. The process according to claim 51, wherein d) drying the second suspension comprising lignin and elastomeric diene polymer latex is carried out until a moisture content of the predispersion of elastomeric diene polymer and lignin is brought to a value equal to or less than 5% by weight.

53. The process according to claim 51, wherein d) drying the second suspension comprising lignin and elastomeric diene polymer latex is carried out in a static oven at a temperature ranging from 40 C. to 120 C. for a time ranging from 2 hours to 30 hours.

54. The process according to claim 42, further comprising f) compacting the predispersion of elastomeric diene polymer and lignin obtained from step c).

55. The process according to claim 42, wherein the lignin is chosen from Softwood Kraft lignin, Hardwood Kraft lignin, Soda Grass lignin, Wheat Straw lignin, Rice Husk lignin, lignin obtained through biorefinery processes, and Organosolv lignin.

56. The process according to claim 42, wherein the elastomeric diene polymer is chosen from natural rubber (NR), emulsion styrene butadiene rubber (ESBR), carboxylated styrene butadiene rubber (XSBR), nitrile rubber NBR, carboxylated nitrile rubber (XNBR), chloroprene rubber (CR), and butyl rubber (IIR).

57. A predispersion of elastomeric diene polymer and lignin obtained by a process according to claim 42.

58. The predispersion of elastomeric diene polymer and lignin according to claim 57, wherein the predispersion comprises an amount of lignin equal to or greater than about 45 phr.

59. A process for producing a vulcanizable elastomeric composition comprising: feeding to at least one mixing apparatus at least the following components of a vulcanizable elastomeric composition: at least one predispersion of an elastomeric diene polymer and lignin obtained by a process according to claim 42 and at least one vulcanizing agent, mixing and dispersing the components to obtain the vulcanizable elastomeric composition, and discharging the vulcanizable elastomeric composition from the mixing apparatus.

60. The process according to claim 59, wherein feeding to at least one mixing apparatus further comprises at least one elastomeric diene polymer.

61. The process according to claim 59, wherein feeding to at least one mixing apparatus further comprises at least one reinforcing filler.

62. A process for producing a tyre for vehicle wheels, wherein the process comprises: providing a vulcanizable elastomeric composition comprising a predispersion of an elastomeric diene polymer and lignin obtained by a process according to claim 42; providing a structural element of a tyre comprising the vulcanizable elastomeric composition; assembling the structural element of a tyre in a green tyre; and vulcanizing the green tyre.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0170] Additional features and advantages of the invention will become more readily apparent from the following description of some preferred embodiments thereof, made hereinafter for exemplifying and not limiting purposes, with reference to the attached drawings.

[0171] In the Drawings:

[0172] FIG. 1 illustrates a radial half-section of a tyre for vehicle wheels according to the invention;

[0173] FIGS. 2A and 2B illustrate respective microphotographs taken, on thin sections (50 nm) obtained in cold conditions (120 C.) by means of an ultramicrotome, with a FESEM Ultra Plus Zeiss microscope, Gemini column, in InLens mode, electron beam excitation of 30 KV, working distance 2 mm, in which lignin particles are visible in a comparative vulcanizable elastomeric material (Example 2, material E) and in a vulcanizable elastomeric material according to the invention (Example 2, material C).

DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

[0174] A tyre for vehicle wheels according to a preferred embodiment of the invention is generally indicated with reference numeral 100 in FIG. 1.

[0175] FIG. 1 illustrates a tyre for vehicle wheels in radial half-section.

[0176] In FIG. 1 a indicates an axial direction and X indicates a radial direction, in particular XX indicates the trace of the equatorial plane. For the sake of simplicity, FIG. 1 shows only a portion of the tyre, the remaining portion not represented being identical and arranged symmetrically with respect to the equatorial plane XX.

[0177] The vehicle tyre 100 comprises at least one carcass structure, comprising at least one carcass layer 101 having respectively opposite end flaps engaged with respective annular anchoring structures 102, called bead cores, possibly associated with a bead filling 104.

[0178] The area of the tyre comprising the bead core 102 and the filling 104 forms a bead structure 103 intended for anchoring the tyre on a corresponding mounting rim, not illustrated.

[0179] The carcass structure is usually of the radial type, i.e. the reinforcing elements of the at least one carcass layer 101 are located in planes comprising the rotating axis of the tyre and being substantially perpendicular to the equatorial plane of the tyre. Said reinforcing elements generally consist of textile cords, for example rayon, nylon, polyester (for example polyethylene naphthalate, PEN). Each bead structure is associated to the carcass structure by folding back the 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 flaps 101a as illustrated in FIG. 1.

[0180] In an embodiment, the coupling between carcass structure and bead structure may be provided by a second carcass layer (not represented in FIG. 1) applied at an axially outer position with respect to the first carcass layer.

[0181] An antiabrasive strip 105 is arranged at an outer position of each bead structure 103.

[0182] A belt structure 106 comprising one or more belt layers 106a, 106b placed in radial juxtaposition with respect to each other and with respect to the carcass layer, having typically textile and/or metallic reinforcing cords incorporated in a layer of vulcanized elastomeric material, is associated to the carcass structure.

[0183] Such reinforcing cords may have crossed orientation with respect to a direction of circumferential extraction of the tyre 100. The term circumferential direction is used to indicate a direction generically directed in the direction of rotation of the tyre.

[0184] At a radially outer position with respect to the belt layers 106a, 106b, at least one zero-degree reinforcing layer 106c, commonly known as a 0 belt, may be applied, which generally incorporates a plurality of elongated reinforcing elements, typically metal or textile cords, oriented in a substantially circumferential direction, thereby forming an angle of a few degrees (for example an angle between about 0 and 6) with respect to a direction parallel to the equatorial plane of the tyre, and coated with vulcanized elastomeric material.

[0185] A tread band 109 made of vulcanized elastomeric material is applied at a radially outer position with respect to the belt structure 106.

[0186] On the lateral surfaces of the carcass structure, each extending from one of the lateral edges of the tread band 109 up to the respective bead structure 103, respective sidewalls 108 made of vulcanized elastomeric material are also applied at an axially outer position.

[0187] At a radially outer position, the tread band 109 has a rolling surface 109a intended to come into contact with the ground. Circumferential grooves, which are connected by transverse notches (not shown in FIG. 1) so as to define a plurality of blocks of various shapes and sizes distributed on the rolling surface 109a, are generally made in this surface 109a, which in FIG. 1 is represented smooth for the sake of simplicity.

[0188] An underlayer 111 made of vulcanized elastomeric material may be arranged between the belt structure 106 and the tread band 109.

[0189] A strip 110 of vulcanized elastomeric material, commonly known as a mini-sidewall, may optionally be present in the connection area between the sidewalls 108 and the tread band 109.

[0190] This mini-sidewall 110 is generally obtained by co-extrusion with the tread band 109 and advantageously allows an improved mechanical interaction between the tread band 109 and the sidewalls 108.

[0191] Preferably, the end portion of the sidewall 108 (in the preferred embodiment illustrated in FIG. 1, of the mini-sidewall 110) directly covers the lateral edge of the tread band 109.

[0192] In the case of tubeless tires, a layer of rubber 112, generally known as a liner, which provides the necessary tightness to the inflation air of the tyre, may also be provided at a radially inner position with respect to the carcass layer 101.

[0193] A further sheet of vulcanized elastomeric material, not illustrated, also known as underliner, may also be arranged between the rubber layer 112 and the carcass layer 101.

[0194] The rigidity of the tyre sidewall 108 may be improved by providing the bead structure 103 with a reinforcing layer 120 generally known as a flipper or additional strip-shaped insert.

[0195] The flipper 120 is a reinforcing layer that is wound around the respective bead core 102 and bead filling 104 so as to at least partially surround them, said reinforcing layer being arranged between the at least one carcass layer 101 and the bead structure 103.

[0196] Preferably, the flipper is in contact with the aforementioned at least one carcass layer 101 and bead structure 103.

[0197] The flipper 120 typically comprises a plurality of textile cords incorporated in a layer of vulcanized elastomeric material.

[0198] The bead structure 103 of the tyre may comprise an additional protective layer 121, generally known as a chafer or protective strip, which has the function of increasing rigidity and integrity of the bead structure 103.

[0199] Preferably, the protective layer 121 or chafer comprises a plurality of cords incorporated in a layer of vulcanized elastomeric material. Such cords may be made of textile materials (for example aramid or rayon) or metallic materials (for example steel cords).

[0200] A layer or sheet of elastomeric material, not illustrated, may be arranged between the belt structure 106 and the carcass structure. The layer may have a uniform thickness.

[0201] Alternatively, the layer may have a variable thickness in the axial direction. For example, the layer may have a greater thickness close to its axially outer edges with respect to the central (crown) area.

[0202] Advantageously, the layer or sheet may extend over an area substantially corresponding to the surface of development of the belt structure 106.

[0203] In a preferred embodiment, a layer or sheet of elastomeric material as described above, not illustrated, may be arrangedas an alternative or in addition to the underlayer 111between the belt structure 106 and the tread band 109, said additional layer or sheet preferably extending over a surface substantially corresponding to the surface of development of the belt structure 106.

[0204] The vulcanized elastomeric material obtained by vulcanizing the vulcanizable elastomeric composition comprising the predispersion of elastomeric diene polymer and lignin according to the present invention may be advantageously incorporated in one or more of the structural elements of the tyre 100 described above.

[0205] Preferably, the structural element of the tyre 100 comprising a vulcanized elastomeric material obtained by vulcanizing the vulcanizable elastomeric composition comprising the predispersion of elastomeric diene polymer and lignin according to the present invention may be one or more of tread band 109, carcass structure, belt structure 106, underlayer 111, antiabrasive strip 105, sidewall 108, sidewall insert, mini-sidewall 110, flipper 120, chafer 121, underliner, rubber layers, bead filling 104, and sheets of vulcanized elastomeric material.

[0206] The tyre according to the invention may be a tyre for automobiles, i.e. including both tyres for motor cars, such as for example the high-performance tyres defined below, and tyres for light transportation vehicles, for example wagons, vans, camper vans, pick-up trucks, typically with a fully-laden mass equal to or less than 3500 kg. Tyres for heavy duty vehicles are thus excluded.

[0207] The term high performance tyres is used to indicate tyres typically intended to be used in wheels of high and ultra-high performance cars. Such tyres are commonly referred to as HP or UHP tyres and they allow to reach speeds in excess of 200 km/h, up to over 300 km/h. Examples of such tyres are those belonging to classes T, U, H, V, Z, W, Y, according to the E.T.R.T.O. (European Tyre and Rim Technical Organisation) standard and racing tyres, in particular for high-power four-wheeled vehicles. Typically, the tyres belonging to such classes have a section width equal to or greater than 185 mm, preferably comprised between 195 mm and 385 mm, more preferably comprised between 195 mm and 355 mm. Such tyres are preferably mounted on rims having fitting diameters equal to or greater than 330.2 mm (13 inches), preferably not exceeding 609.6 mm (24 inches), more preferably comprised between 406.4 mm (16 inches) and 584.2 mm (23 inches).

[0208] Such tyres can also be used on vehicles other than the aforementioned automobiles, for example on high-performance sport motorcycles, i.e. motorcycles capable of reaching speeds even over 270 km/h. Such motorcycles are those that belong to the category typically identified with the following classifications: hypersport, supersport, sport touring, and for lower speeds: scooter, street/enduro and custom.

[0209] The term tyre for motorcycle wheels is used to indicate a tyre having a high ratio of curvature (typically greater than 0,200), capable of reaching high camber angles (roll angles) when cornering a motorcycle.

[0210] The invention will now be described by means of some Examples to be understood as being intended for illustrating and not limiting purposes thereof.

EXAMPLE 1

Preparation of Predispersions of an Elastomeric Diene Polymer and Lignin Comprising 60 Phr, 75 Phr and 100 Phr of Lignin

[0211] Materials

[0212] Lignin: lignin from Softwood Kraft UPM BioPiva 200 process (UPM Biochemicals) having a median particle diameter D50 equal to or greater than 20 microns; [0213] elastomeric diene polymer: natural rubber from HA latex obtained by centrifuging and stabilized with ammonia (60% by weightcommercialized by Von Bundit Co. Ltd.); [0214] anionic surfactant: sodium dodecylbenzenesulfonate technical grade, Thermo Fischer Scientific.

[0215] Predispersion 1 (60 Phr of Lignin)

[0216] The process for preparing the predispersion was as follows.

[0217] Step a1): 50 kg of wet lignin particulate (solid content about 57%, starting D50 about 20 microns) were diluted in 50 kg of deionized water; subsequently, 1.5 kg of anionic surfactant was added and the mixture was stirred until homogeneous, thus obtaining 101.5 kg of a coarse lignin suspension SG having a solid lignin content of about 28% by weight.

[0218] Step a2): the lignin particles contained in the coarse lignin suspension SG were wet-ground in a cylindrical mill model ZETA by NETZSCH (NETZSCH-Feinmahltechnik GmbH, Selb, Germany) using steel balls with a diameter of less than 4 mm in order to reduce the median diameter D50 of the lignin particles to a value equal to or less than 1.5 microns. Thus, 101.5 kg of a first suspension S1 containing ground lignin (28% by weight) was obtained in which the percentage of particles larger than 10 microns was less than about 2% by weight.

[0219] The median particle diameter D50 was measured with Malvern Mastersizer 2000 laser analyzer (Malvern Panalytical Ltd., Malvern, Great Britain).

[0220] Step b): the first suspension S1 containing ground lignin obtained from step a2) (101.5 kg) was mixed with 83.3 kg of natural rubber latex (solid content: 60% by weight) by means of a mechanical stirrer, thus obtaining 184.8 kg of a second suspension S2 containing about 15% by weight of ground lignin and about 21% by weight of natural rubber.

[0221] Step c): the second suspension S2 containing ground lignin and natural rubber (184.8 kg) was then dried in a static oven at 60 C. for a time equal to about 4 hours until a moisture content of less than 1% by weight was reached.

[0222] The predispersion in flakes thus obtained was then subjected to a further compacting step by means of an open mixer with rollers spaced by about 3 mm to obtain a predispersion or masterbatch in sheets of natural rubber and lignin at 40% by weight (60 phr).

[0223] Predispersion 2 (75 Phr of Lignin)

[0224] For the preparation of this predispersion the same procedure as for Predispersion 1 was followed, using in step b) 68.8 kg of natural rubber latex so as to vary the amount of lignin incorporated in the final predispersion, in this case containing natural rubber and lignin at 45% by weight (75 phr).

[0225] Predispersion 3 (100 Phr of Lignin)

[0226] For the preparation of this predispersion the same procedure as for Predispersion 1 was followed, using in step b) 62.5 kg of natural rubber latex so as to vary the amount of lignin incorporated in the final predispersion, in this case containing natural rubber and lignin at 50% by weight (100 phr).

EXAMPLE 2

Preparation of Vulcanizable Elastomeric Materials (Invention, Reference and Comparative)

[0227] The predispersions 1-3 containing lignin according to Example 1 were used to prepare vulcanizable elastomeric materials for a tread band in amounts of 10 phr, 23.4 and 20 phr, materials (A), (B) and (C), respectively. These elastomeric materials were compared with: material (D): referenceconventional vulcanizable elastomeric material devoid of lignin, taken as a reference (model elastomeric composition for structural elements of tyres, in particular of tread bands); [0228] material (E): comparativeVulcanizable elastomeric material including lignin powder from the Softwood Kraft UPM BioPiva 200 process (UPM Biochemicals) having a median particle diameter D50 equal to or greater than 20 microns; and [0229] (material F): comparativevulcanizable elastomeric material including lignin powder having a median particle diameter D50 equal to about 1.5 microns obtained by drying the first suspension S1 obtained from step a2) according to the preparation procedure of predispersion 3 of example 1. Specifically, in this ground lignin powder, the percentage of particles larger than 10 microns was less than about 2% by weight.

[0230] In particular, the drying of the first suspension S1 containing ground lignin was carried out by means of a static oven at a temperature of 60 C. for a time of about 2 hours so as to reduce the moisture content to about 1%.

[0231] It should be noted that the comparative material F therefore comprises a same type of lignin with the same particle size, but in powder form, as the materials A-C obtained using predispersions 1-3 according to the invention of Example 1 (60, 75 and 100 phr of lignin). On the other hand, the amount of lignin is equal to that of material C according to the invention.

[0232] In order to have homogeneity of comparison, all these vulcanizable elastomeric materials are based on the model elastomeric composition for tyre structural elements, in particular tread bands (material D).

[0233] Therefore, the results shown by these materials are predictive of those obtainable on a tyre.

[0234] Table 1 below shows the compositions in phr of the vulcanizable elastomeric materials (A), (B), (C), (D), (E) and (F).

[0235] In Table 1, the values (in phr) of the amount of lignin actually contained in the elastomeric materials, irrespective of the physical dosage form, predispersion or powder, of the lignin have also been shown in brackets. The values indicated in brackets are not to be added to the total phr calculation but serve only as a reference.

TABLE-US-00001 TABLE 1 (A) (B) (C) (D) (E) (F) invention invention invention reference comparative comparative NR 27 19.6 23 33 33 33 S-SBR 67 67 67 67 67 67 TESPT 6.4 6.4 6.4 6.4 6.4 6.4 Silica 69 66 66 72 66 66 Predispersion 1 10 Predispersion 2 23.4 Predispersion 3 20 Lignin powder 10 Ground lignin 10 powder Actual lignin (4) (10) (10) (0) (10) (10) Wax 1.7 1.7 1.7 1.7 1.7 1.7 TDAE oil 8 8 8 8 8 8 Resin 5.5 5.5 5.5 15.5 5.5 5.5 Zn octanoate 4 4 4 4 4 4 TMQ 1.5 1.5 1.5 1.5 1.5 1.5 6PPD 3 3 3 3 3 3 TBBS 3 3 3 3 3 3 Soluble Sulfur 1 1 1 1 1 1

[0236] Materials [0237] NR: coagulated natural rubber, obtained by coagulation of HA natural rubber latex obtained by centrifuging and stabilized with ammonia (60% by weightcommercialized by Von Bundit Co. Ltd.); [0238] S-SBR: SPRINTAN SLR4602, Trinseo; [0239] TESPT: bis(3-triethoxysilylpropyl) tetrasulfide, Si69; [0240] Silica: Ultrasil 7000 Silica, Evonik; [0241] Predispersion 1: Natural rubber predispersion prepared according to Example 1 comprising 60 phr of lignin according to Example 1; [0242] Predispersion 2: Natural rubber predispersion prepared according to Example 1 comprising 75 phr of lignin according to Example 1; [0243] Predispersion 3: Natural rubber predispersion prepared according to Example 1 comprising 100 phr of lignin according to Example 1; [0244] Lignin powder: Softwood lignin UPM Biopiva 200, UPM Biochemicals; [0245] Powdered lignin: Softwood lignin UPM Biopiva 200 (UPM Biochemicals) wet-ground according to what is stated in Example 1 and dried to about 1% moisture content; [0246] Wax: Riowax BM 01, SER; [0247] Oil: Vivatec 500, Global Asia; [0248] Resin Krystalex F-85, Eastman; [0249] Zn octanoate: Struktol Aktivator 73, Struktol; [0250] TMQ: Polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, Kemai; [0251] 6PPD: N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine, Solutia Eastman; [0252] TBBS: N-tert-butyl-2-benzothiazylsulfenamide, Vulkacit NZ/EGC, Lanxess; [0253] Soluble Sulfur: S8 (soluble sulphur), Zolfo Industria.

[0254] Procedure

[0255] All components except sulfur and vulcanization accelerant (TBBS) were mixed in an internal mixer (Brabender) for about 10 minutes (1st step).

[0256] When the temperature of 135 C. was reached, the material was mixed for another minute and then it was discharged. The unfinished compound was left to stand for a day then the sulfur, the accelerant (TBBS) was added and mixing was carried out in the same mixer at about 60 C. for 9 minutes (2nd step).

[0257] In FIGS. 2A and 2B two microphotographs obtained by FESEM Microscopy of the vulcanizable elastomeric materials (C) according to the invention and (E) comparative visually showing the distribution of the lignin particles are shown for illustrative purposes.

[0258] As it may be inferred from the microphotograph 2A of the comparative vulcanizable elastomeric material (E) obtained by dosing lignin powder, the lignin is present in the material in the form of relatively large and spaced particles, with a few submicrometric fragments. This is indicative of the fact that mechanical stirring in the presence of rubber is by itself neither sufficient to significantly reduce the size of the starting lignin nor to distribute it uniformly in the polymer matrix.

[0259] Conversely and as can be deduced from the microphotograph 2B of the vulcanizable elastomeric material (C) according to the invention obtained by dosing the predispersion 3, the lignin is present in the material in the form of relatively small particles of micrometric or sub-micrometric size and distributed substantially uniformly in the polymeric matrix.

[0260] This substantially uniform distribution of micrometric or sub-micrometric lignin particles is predictive of comparable or improved mechanical properties of the vulcanized elastomeric materials according to the invention with respect to the reference lignin-free vulcanized elastomeric material as will become clearer hereinafter.

EXAMPLE 3

[0261] Characterization of the Vulcanizable Elastomeric Materials (A), (B), (C), (D), (E) and (F) after Vulcanization

[0262] The vulcanizable elastomeric materials (A), (B), (C), (D), (E) and (F) were vulcanized at 170 C. for 10 min in order to be able to measure their static mechanical properties.

Static Mechanical Properties

[0263] The static mechanical properties of the vulcanizable elastomeric materials (A), (B), (C), (D), (E) and (F) were evaluated according to the ISO 37-2011 standard at 23 C., on 5 Dumbell test pieces. In this way, the following parameters were measured: [0264] load at 100% elongation (Ca1), [0265] load at 300% elongation (Ca3), [0266] load at break (CR), and [0267] elongation % at break (AR).

[0268] Dynamic Mechanical Properties Under Torsion

[0269] The dynamic mechanical properties of dynamic shear modulus G and Tan delta of the vulcanizable elastomeric materials (A), (B), (C), (D), (E) and (F) were evaluated using an Alpha Technologies R.P.A. oscillating chamber rheometer. 2000 (Rubber Process Analyser) with chamber geometry as described in ASTM D6601-19 FIG. 1, applying the following method.

[0270] An approximately cylindrical test sample having a volume of between 4.6 and 5 cm.sup.3 is obtained by punching a sheet having a thickness of at least 5 mm of the green vulcanizable elastomeric composition to be characterized;

[0271] Subsequently, the chambers of the R.P.A. 2000 are preliminarily preheated to 170 C.

[0272] The sample is loaded between the chambers of the rheometer and the chambers are closed. Between the sample of the green vulcanizable elastomeric composition and each chamber of the rheometer two films are arranged to protect the chamber itself: in contact with the compound a film of Nylon 6.6 cast with a thickness of about 25 microns and in contact with the chamber of the rheometer a film of polyester with a thickness of about 23 microns. The sample is then vulcanized for a fixed time of 10 min at a temperature of 170 C. while at the same time recording the vulcanization curve, i.e. subjecting the sample for the entire time of vulcanization to a sinusoidal deformation of 7% amplitude and 1.67 Hz frequency.

[0273] The temperature of the rheometer chambers is then brought to 70 C. After a total time of 10 minutes from when the temperature of the chambers is set at 70 C., a sequence of dynamic measurements is carried out at a constant temperature of 70 C. by sinusoidally stressing the sample under torsion at a fixed frequency of 10 Hz and progressively increasing amplitude from 0.3% to 10% by carrying out 10 stabilization cycles and 10 measurement cycles for each condition.

[0274] Always keeping the temperature of the rheometer chambers at 70 C., a dynamic measurement is then carried out by sinusoidally stressing the sample under torsion at a fixed frequency of 10 Hz and an amplitude of 9%, carrying out 10 stabilization cycles and 20 measurement cycles.

[0275] In this way, the following parameters were measured as an average of what was recorded in the 20 measurement cycles: [0276] dynamic elastic shear modulus G, [0277] variation of the dynamic elastic shear modulus d_G between an amplitude of the deformation of the sample of 0.5% and one of 10%; [0278] tandelta under torsion, i.e. the ratio between the viscous elastic modulus G and the dynamic elastic modulus G, at an amplitude of the deformation of 9% (hereinafter Tandelta (9%)).

[0279] Vulcanization Properties

[0280] During the tests for the evaluation of the dynamic mechanical properties under torsion and again by means of the aforementioned rheometer, the following vulcanization parameters of the vulcanizable elastomeric materials (A), (B), (C), (D), (E) and (F) were also measured: [0281] minimum torque (ML), [0282] maximum torque (MH), [0283] vulcanization time necessary to reach 90% of maximum torque (T90), and [0284] vulcanization time necessary to reach a torque value 2 points higher than the minimum value (TS2).

[0285] Dynamic Mechanical Properties Under Traction-Compression

[0286] The dynamic mechanical properties under traction-compression of the vulcanizable elastomeric materials (A), (B), (C), (D), (E) and (F) were evaluated using an Instron model 1341 dynamic device in the traction-compression mode the following modes.

[0287] A test piece of vulcanized material (170 C. for 10 minutes) having a cylindrical shape (length=25 mm; diameter=18 mm), preloaded under compression up to a longitudinal deformation of 25% with respect to the initial length and kept at a predetermined temperature (for example 70 C.) for the entire duration of the test.

[0288] After a waiting time of 2 minutes followed by a mechanical pre-conditioning of 125 cycles at 100 Hz at 5% deformation amplitude with respect to the length under preload, the test piece was subjected to a dynamic sinusoidal stress having an amplitude of 3.5% with respect to the length under preload, with a frequency of 100 Hz.

[0289] In this way, the following parameters were measured: [0290] dynamic elastic modulus E, [0291] tandelta, i.e. the ratio between the viscous dynamic modulus E and the dynamic elastic modulus E.

[0292] Table 2 below shows the results obtained from the characterizations performed.

TABLE-US-00002 TABLE 2 (A) (B) (C) (D) (E) (F) invention invention invention reference comparative comparative Ca1 (MPa) 2.44 2.63 2.42 2.39 2.29 3.27 Ca3 (MPa) 11.64 12.15 11.90 11.07 8.98 13.01 CR (MPa) 20.79 20.81 19.94 21.07 18.43 20.07 AR (%) 470.28 453.64 446.29 462.12 512.79 427.39 ML (dNm) 4.58 4.78 4.25 5.01 3.40 3.71 MH (dNm) 18.91 17.61 16.95 22.08 18.86 25.45 T90 (min) 5.72 5.98 5.90 5.64 5.02 4.82 TS2 (min) 2.70 2.80 2.85 2.44 1.63 1.43 d_G (MPa) 0.80 0.58 0.57 1.06 1.15 1.21 G (MPa) 1.60 1.51 1.43 1.88 1.79 1.99 Tandelta (9%) 0.120 0.109 0.113 0.122 0.139 0.151 E 0 C. (MPa) 14.72 13.99 13.66 15.71 16.48 16.84 Tandelta 0 C. 0.657 0.666 0.658 0.653 0.656 0.616 E 23 C. (MPa) 8.80 8.27 8.12 9.50 9.96 11.16 Tandelta 23 C. 0.301 0.304 0.298 0.305 0.322 0.327 E 70 C. (MPa) 5.90 5.59 5.49 6.22 6.32 7.21 Tandelta 70 C. 0.118 0.117 0.121 0.120 0.134 0.140

[0293] From the analysis of the data shown in Table 2, it is clear that the vulcanizable elastomeric materials (A)-(C) according to the present invention respectively comprising 5 phr (material A) and 10 phr (materials B and C) of lignin added as a predispersion according to the invention, show: [0294] static mechanical properties after vulcanisation Ca1, Ca3 and CR, predictive of the rigidity of the tread band blocks of a tyre, comparable to or better than those of the reference material (D) and significantly better than those of the comparative material (E) incorporating commercial lignin powder; [0295] vulcanization properties ML, MH, T90 and TS2 comparable to those of the reference material (D); [0296] conversely, the comparative materials (E) and (F) display a very low TS2 value, indicative of possible problems of premature vulcanization; [0297] dynamic mechanical properties under torsion after vulcanization, G and especially d_G, predictive of maneuverability (the better the lower the value of d_G), typical of high performance tyres, for example HP and UHP tyres, better than those of the reference material (D) and significantly better than those of the comparative materials (E) incorporating commercial lignin powder and (F) incorporating ground lignin powder after drying; [0298] dynamic mechanical properties under traction-compression after vulcanization of dynamic elastic modulus E at 0 C., predictive of the wet and/or cold road holding of a tyre (the better the lower the value of E at this temperature), comparable to or better than those of the reference material (D) and significantly better than those of the comparative materials (E) incorporating commercial powdered lignin and (F) incorporating ground lignin powder after drying; [0299] dynamic mechanical properties under traction-compression after vulcanization of tandelta at 70 C., predictive of the rolling resistance of a tyre (the better the lower the tandelta value at this temperature), comparable to or better than those of the reference material (D) and significantly better than those of the comparative materials (E) incorporating commercial lignin powder and (F) incorporating ground lignin powder after drying.

[0300] In connection with the elastomeric material (F) incorporating powdered ground lignin obtained after drying in the same amount as the material (C) according to the invention, these tests have surprisingly shown that the same type of lignin subjected to the same type of grinding has markedly different reinforcing properties in the vulcanized elastomeric material depending on how it is dosed into the vulcanizable elastomeric composition.

[0301] As a matter of fact, if the lignin (for example obtained by wet-grinding) is incorporated in the vulcanizable elastomeric composition by means of a predispersion according to the invention (see measurements on compound C), there is a preservation or improvement of the dynamic mechanical properties under torsion or traction-compression with respect to the reference material (material D), whereas if lignin obtained by wet-grinding and with the same particle size is incorporated in the vulcanizable elastomeric composition in the form of powder, these same dynamic mechanical properties under torsion or traction-compression significantly deteriorate.

[0302] Without wishing to be bound by any interpretative theory, the Applicant believes that the step of mixing with an elastomeric diene polymer latex, for example and preferably natural rubber latex, leads to some interaction between the lignin particles in suspension with reduced particle size and the emulsion of the droplets of elastomeric diene polymer, which makes the predispersion subsequently obtained by physical means advantageously capable to homogeneously disperse the lignin in the polymeric matrix of the vulcanizable elastomeric composition thus obtaining optimal reinforcing properties in the vulcanized material.

EXAMPLE 4

Preparation of Vulcanizable Elastomeric Materials (Invention, Reference and Comparative)

[0303] The lignin-containing predispersion 3 according to Example 1 was used to prepare vulcanizable elastomeric materials for an antiabrasive strip in amounts of 12 and 36 phr, materials (G) and (H) respectively. These elastomeric materials were compared with: [0304] material (I): referenceconventional vulcanizable elastomeric material devoid of lignin, taken as a reference (model elastomeric composition for structural elements of tyres, in particular antiabrasive strip); [0305] materials (L) and (M): comparativevulcanizable elastomeric materials incorporating lignin powder with a median particle diameter D50 equal to about 20 microns, with two different lignin contents corresponding to the lignin content of materials (G) and (H).

[0306] All these vulcanizable elastomeric materials are based on a model elastomeric composition for structural tyre elements, in particular antiabrasive strip (material I).

[0307] Therefore, the results shown by these materials are predictive of those obtainable on a tyre.

[0308] Table 3 below shows the compositions in phr of the vulcanizable elastomeric materials (G), (H), (I), (L) and (M).

[0309] In Table 3, the values (in phr) of the amount of lignin actually contained in the elastomeric materials, irrespective of the physical dosage form, predispersion or powder, of the lignin have also been shown in brackets. The values indicated in brackets are not to be added to the total phr calculation but serve only as a reference.

TABLE-US-00003 TABLE 3 (G) (H) (I) (L) (M) invention invention reference comparative comparative NR 34 22 40 40 40 BR 60 60 60 60 60 Lignin powder 6 18 Predispersion 3 12 36 Actual lignin (6) (18) (0) (6) (18) Stearic acid 2 2 2 2 2 ZnO 3 3 3 3 3 Zn soap 5 5 5 5 5 CB 68 61 68 68 61 TMQ 0.7 0.7 0.7 0.7 0.7 6PPD 2 2 2 2 2 Bimodal wax 0.5 0.5 0.5 0.5 0.5 TBBS 1.4 2 1.4 1.4 2 PVI 0.2 0.2 0.2 0.2 0.2 Insoluble Sulfur 4.35 4.35 4.35 4.35 4.35

[0310] Materials [0311] NR: coagulated natural rubber, obtained by coagulation of HA natural rubber latex obtained by centrifuging and stabilized with ammonia (60% by weightcommercialized by Von Bundit Co. Ltd.); [0312] BR: butadiene rubber BUNA CB 25, Lanxess; Lignin powder: Softwood lignin UPM Biopiva 200, UPM Biochemicals; [0313] Predispersion 3: Natural rubber predispersion prepared according to Example 1 comprising 100 phr of lignin according to Example 1; [0314] Stearic acid: Stearin, Undesa; [0315] ZnO: Zinc Oxide, Zincol Ossidi; [0316] Zn soap: Struktol 40 MS, Struktol; [0317] CB: N550, Birla Carbon; [0318] TMQ: Polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, Kemai; [0319] 6PPD: N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine, Solutia Eastman; [0320] Bimodal wax: Riowax BM 01, SER; [0321] TBBS: N-tert-butyl-2-benzothiazylsulfenamide, Vulkacit@ NZ/EGC, Lanxess; [0322] PVI: cyclobexyl-thiophthalimide, Santogard PVI, Flexsys; [0323] Insoluble sulfur: Sulfur, Redbali Superfine, International Sulphur Inc.

[0324] Procedure

[0325] All components except sulfur and the vulcanization accelerant (TBBS) were mixed in an internal mixer (Brabender) for about 10 minutes (1st step).

[0326] When the temperature of 135 C. was reached, the material was mixed for another minute and then it was discharged. The unfinished compound was left to stand for a day then the sulfur, the accelerant (TBBS) was added and mixing was carried out in the same mixer at about 60 C. for 9 minutes (2nd step).

EXAMPLE 4

[0327] Characterization of Vulcanizable Elastomeric Materials (G), (H), (I), (L) and (M) after Vulcanization

[0328] The vulcanizable elastomeric materials G), (H), (I), (L) and (M) were vulcanized at 170 C. for 10 min in order to be able to measure their static mechanical and density properties.

[0329] The relevant mechanical properties for this type of component, static and dynamic in traction-compression, were evaluated in the same way as described in the previous Example 3.

[0330] The following Table 4 shows the results obtained from the characterizations carried out, with the exception of the vulcanization characterizations which indicated results that were substantially comparable to each other.

TABLE-US-00004 TABLE 4 (G) (H) (I) (L) (M) invention invention reference comparative comparative Ca 0.5 (MPa) 3.01 3.04 2.88 2.89 2.76 Ca1 (MPa) 5.98 5.81 5.82 5.59 5.17 CR (MPa) 14.02 12.26 13.68 12.34 10.87 AR (%) 252.1 246.8 238.3 226.5 232.2 E 70 C. (MPa) 12.14 12.56 11.14 11.58 12.07 Tandelta 70 C. 0.108 0.103 0.102 0.107 0.115 E 100 C. (MPa) 11.16 11.37 10.55 10.65 10.83 Tandelta 100 C. 0.080 0.081 0.076 0.079 0.090

[0331] From the analysis of the data shown in Table 4, it is clear that the vulcanizable elastomeric materials (G)-(H) according to the present invention respectively comprising 6 phr (material G) and 18 phr (material H) of lignin added as a predispersion according to the invention, show: [0332] static mechanical properties after vulcanization Ca0.5, Ca1 and CR, indicative of the rigidity and ultimate tensile strength of the antiabrasive strip, comparable to or better than those of the reference material (I) and those of the comparative materials (L) and (M) incorporating commercial lignin powder; [0333] dynamic mechanical properties under compression after vulcanization of dynamic elastic modulus E at 70 C. and at 100 C., indicative of the structural properties of the antiabrasive strip, significantly better than those of the reference material (I) and better than those of the comparative materials (L) and (M) incorporating commercial lignin powder; [0334] dynamic mechanical properties under compression after vulcanisation of tandelta at 70 C., and at 100 C., indicative of the rolling resistance of a tyre (the better the lower the value of tandelta at this temperature), comparable to or better than those of the reference material (I) and the comparative material (M) incorporating commercial lignin powder

[0335] The above examples are not intended to be exhaustive, but merely illustrative examples of the advantages of the invention as defined by the following claims.