Tire comprising a rubber composition

Abstract

A tire comprises a fluorescent rubber composition based on at least an elastomer matrix, a reinforcing filler comprising between 0 and 50 phr of carbon black and between 2.5 and 15 phr of a fluorescent pigment.

Claims

1. A tire comprising a fluorescent rubber composition based on at least: an elastomer matrix; a reinforcing filler comprising between 0 and 10 phr of carbon black; and between 2.5 and 7.0 phr of a fluorescent pigment, wherein the fluorescent pigment is a fluorescent colored acrylic pigment.

2. The tire according to claim 1, wherein the elastomer matrix comprises at least one diene elastomer selected from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers and mixtures thereof.

3. The tire according to claim 1, wherein the reinforcing filler predominantly comprises a reinforcing inorganic filler.

4. The tire according to claim 1, wherein the reinforcing filler comprises more than 40 phr of a reinforcing inorganic filler.

5. The tire according to claim 4, wherein the reinforcing inorganic filler predominantly comprises silica.

6. The tire according to claim 1, wherein a ratio of the content of fluorescent pigment to that of carbon black is between 0.5 and 10.

7. The tire according to claim 1, wherein the fluorescent pigment further comprises a fluorescent whitening agent.

8. The tire according to claim 1, wherein the fluorescent rubber composition further comprises a plasticizing agent selected from the group consisting of liquid plasticizers, hydrocarbon resins and mixtures thereof.

9. The tire according to claim 1, wherein the fluorescent rubber composition is an external rubber composition.

10. The tire according to claim 9, wherein a tread or a sidewall of the tire comprises the fluorescent external rubber composition.

11. The tire according to claim 10, wherein the tread comprises the fluorescent external rubber composition.

12. The tire according to claim 11, wherein the tread of the tire comprises a plurality of tread pattern elements delimited by cut-outs, the tread pattern elements respectively comprising at least one lateral face and a contact surface intended to come into contact with a ground during rolling, and the tread pattern elements respectively comprising a first rubber composition at least partially covered on the at least one lateral face with a layer of a second rubber composition which is different from the first rubber composition, and wherein the first rubber composition or the second rubber composition is the fluorescent external rubber composition.

13. The tire according to claim 12, wherein the second rubber composition is the fluorescent external rubber composition.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Other characteristics and advantages of the eighteenth or the nineteenth aspect arise from the description made hereafter in reference to the annexed drawings which schematically show (in particular not to a specific scale), as nonrestrictive examples, of the embodiments of the object of the invention.

(2) In these drawings:

(3) FIG. 1 depicts a partial plan view of blocks as tread pattern elements (1) of a tread of a tire according to the eighteenth or the nineteenth aspect;

(4) FIG. 2 shows the blocks of FIG. 1 in the cross section on the line of section mil.

DESCRIPTION OF EMBODIMENTS

(5) The annexed FIG. 1 represents a partial plan view of four rectangular blocks as a plurality of tread pattern elements (1) of a tread of a tire according to the eighteenth or the nineteenth. Each of the blocks is delimited by cut-outs (3, 4). The cut-outs are grooves (3) circumferentially extending and the other grooves (4) axially extending. Each of the blocks comprises four lateral faces (13, 14, 15, 16) and a contact surface (2) intended to come into contact with ground during the tire rolling. Each of the blocks has a length (L1) on a circumferential direction of the tire, and a width (L2) on an axial direction of the tire. Intersections of the lateral faces (13, 14, 15, 16) with the contact surface (2) form four edge corners (23, 24, 25, 26) which play important portions when driving particularly on a slippery road surface, notably through the presence of water, snow or ice.

(6) The FIG. 2 presents the two blocks in the cross section taken along the line of section II-II of FIG. 1. The cross section is perpendicular to the axial direction of the tire.

(7) In these figures, each of the blocks comprises a first rubber composition (FC: a mixture of base material), completely in this case, covered with a layer of a second rubber composition (SC: a mixture of covering material or a covering composition) on the four lateral faces (13, 14, 15, 16) bounding the grooves (3, 4) circumferentially (3) or axially extending (3, 4). The second rubber composition (SC) is different from the first rubber composition (FC). The first rubber composition (FC) or the second rubber composition is the fluorescent external rubber composition of the tire according to the fourteenth aspect. The layer of the second rubber composition (SC) has a thickness (E1) that is substantially constant (over an entire height (Hr) of covering, in this instance equal to a depth (H) of the grooves). Then, the depth (H) of the grooves is equal to a height of the blocks.

(8) According to a preferred embodiment of the eighteenth or the nineteenth aspect, the lateral faces (14, 16, 24, 26) have orientations which are perpendicular to the circumferential direction of the tire, preferably the layer of the second rubber composition (SC) covers on the lateral faces (14, 16, 24, 26) which have orientations which are perpendicular to the circumferential direction of the tire in order to allow an excellent grip performance(s) on several grounds (for example, wet, snowy and/or icy grounds).

(9) According to a preferred embodiment of the eighteenth or the nineteenth aspect, the second rubber composition extends, in a new condition of the tire, as far as the edge corners (23, 24, 25, 26) formed by a boundary between the contact surface (2) and the lateral faces (13, 14, 15, 16) of the tread pattern elements (1).

(10) According to a preferred embodiment of the eighteenth or the nineteenth aspect, the thickness (E1) is more than 0.1 mm (for example, between 0.1 and 5.0 mm), preferably more than 0.2 mm (for example, between 0.2 and 4.5 mm). More preferably, the thickness is between 0.2 and 4.0 mm, still more preferably between 0.3 and 1.0 mm in order to compromise and/or to improve grip performances on several grounds (for example, wet, snowy and/or icy grounds).

(11) A first step in a manufacture of the tread of the tire according to the eighteenth or the nineteenth aspect is to cover the first rubber composition (FC) with the layer of the second rubber composition (SC).

(12) For example, the first step can be done with a method described in the aforementioned application WO 2013/087878, namely by impregnating a two-dimensional fiber assembly such a fabric or non-woven, or a three-dimensional fiber assembly as a felt, previously placed in the appropriate dimensions, with the second rubber composition (SC). This impregnation can be done for example by hot calendering, by press molding or by injection under pressure.

(13) The presence of the fiber assembly impregnated with the second rubber composition (SC), allows to obtain an excellent cohesion of the layer of the second rubber composition (SC) before vulcanization of the tire and thus assist the layer of the second rubber composition (SC) to place on the first rubber composition (FC) during molding of the tire.

(14) Of course, means other than the fiber assembly could be used to improve the cohesion and the placement of the layer of the second rubber composition (SC) in the raw state, such as a rigid metal sheet, cellulose fiber (for instance, paper, cardboard) or another polymer.

(15) Of course, if such a fiber assembly, strip or other means, is used to help the laying of the second rubber composition (SC) to place on the first rubber composition (FC) during the manufacture of the tire according to the seventeenth aspect, the second rubber composition (SC) can comprise the fiber assembly, the strip or the other means unless the fiber assembly, the strip or the other means is extracted before the curing of the tire.

(16) Preferably, the fibers used are long fibers having a longest dimension of greater than 30 mm, more preferably of greater than 50 mm.

(17) Any type of fibers, preferably fibers selected from the group consisting of textile fiber, mineral fiber and the mixtures thereof, can be used to the layer of the second rubber composition (SC) with sufficient tensile rigidity to facilitate the placement of layer of the second rubber composition during molding of the tire.

(18) The textile fiber may be selected from the group consisting of natural origin fibers, synthetic fibers and the mixtures thereof. The natural origin fibers may be made at least one organic material selected from the group consisting of silk, cotton, bamboo, cellulose, wool and the mixtures thereof, preferably cotton, cellulose, wood and the mixtures thereof. The synthetic fibers may be made of at least one synthetic material selected from the group consisting of polyester, polyamide, carbon, aramid, polyethylene, polypropylene, polyacrylonitrile, polyimide, polysulfone, polyether sulfone, polyurethane, polyvinyl alcohol and the mixtures thereof.

(19) The mineral fiber may be selected from the group consisting of glass fibers, basalt fiber and the mixtures thereof.

(20) Then, one way of obtaining such a tread pattern is for example to cover the entirety of a green form of a tread comprising the first rubber composition (FC) with the layer of the second rubber composition (SC) of suitable thickness before molding the tread and the cut-outs. After molding, the second rubber composition (SC) on the contact surface (2) can be left in place or alternatively eliminated by a mechanical means (notably by grinding).

(21) Another way of industrially producing a tread of a tire according to the eighteenth or nineteenth aspect may consist in applying, to the unvulcanized green form of the tire provided with a tread made of the first rubber composition (FC), thin strips of the second rubber composition (SC), as described in patent EP 0510550 (it is possible for the thin strips to be applied to the tread in the circumferential and/or axial direction(s)). Another way may consist in producing the tread by coextruding two (or more) compounds when the tread is extruded. It is still possible to operate as described in FIGS. 5-6 and paragraph IV-B of WO2013/087878.

(22) After vulcanization of the tire of the eighteenth or nineteenth aspect, the specific layer of the second rubber composition (SC) described above has the advantage of providing a very suitable stiffness to the edges (23, 24, 25, 26) formed by the intersection of the contact surfaces (2) and the suitable rigidity lateral faces (13, 14, 15, 16), which is particularly favorable behavior of the tire on snowy ground, while giving the tire, thanks to the presence of the specific second rubber composition capable of compromising and/or improving grip performance(s) of the tire on several grounds (for example, wet, snowy and/or icy grounds).

(23) According to a preferred embodiment of the nineteenth aspect, the first rubber composition (FC) can be a conventional rubber composition which may be based on at least one diene elastomer (typically 50 to 100 phr of a diene elastomer selected from the group consisting of natural rubber, synthetic polyisoprenes, polybutadienes, butadiene copolymers, isoprene copolymers and the mixtures thereof, and 0 to 50 phr of another diene elastomer), between 50 and 200 phr of a reinforcing filler (for instance, silica and/or carbon black), more than 30 phr of a plasticizing agent (for instance, liquid plasticizer(s), hydrocarbon resin(s) or the mixtures thereof) and a crosslinking system (not counting other usual additives).

(24) The invention is further illustrated by the following non-limiting examples.

EXAMPLES

(25) In the test, thirteen rubber compositions identified as T-0 to T-5 (a reference and comparative examples) and C-1 to C-7 (examples according to the invention) are compared. They are based on a diene elastomer (a SBR) reinforced with silica only or a blend of at silica and carbon black with/without a fluorescent pigment. The formulations of the thirteen rubber compositions, with the content of the various products expressed in phr, and visual discrimination property after curing are given at Table 1.

(26) The reinforcing filler, its associated coupling agent, the fluorescent pigment, the elastomer matrix and the various other ingredient, with the exception of the vulcanization system, were successively introduced into an internal mixer having an initial vessel temperature of approximately 60° C.; the mixer was thus approximately 70% full (% by volume). Thermomechanical working (non-productive phase) was then carried out in one stage, which lasts in total approximately 3 to 4 minutes, until a maximum “dropping” temperature of 165° C. was reached. The mixture thus obtained was recovered and cooled and then sulphur and an accelerator of sulphenamide type were incorporated on an external mixer (homofinisher) at 20 to 30° C., everything being mixed (productive phase) for an appropriate time (for example, between 5 and 12 min).

(27) The compositions thus obtained were subsequently calendered, either in the form of sheets (thickness of 2 to 3 mm) or of fine sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of profiled elements which could be used directly, after cutting and/or assembling to the desired dimensions, for example as tire semi-finished products, in particular as tire treads.

(28) The visual discrimination property test for the rubber compositions in comparison with the reference rubber composition (T-0) were conducted by ten expert tire inspectors in a dark room under ultraviolet irradiation with a black light (distance between each rubber composition and the black right was about 10 cm) and in a bright room.

(29) The greater value of visual discrimination property for each rubber composition in Table 1 indicates the more inspectors visually discriminated between the rubber composition and the reference (T-0). It is decided that the rubber composition is acceptable when the value is more than 5 in the dark room, and less than 5 in the bright room.

(30) The results from Table 1 demonstrate that each of the rubber compositions (C-1 to C-7) according to the invention has excellent visual discrimination property in the dark room under ultraviolet irradiation with the black light in parallel with excellent sense of unity with blackness originated from carbon black in the bright room, in comparison with the comparative examples (T-1 to T-5).

(31) In conclusion, the rubber composition according to the invention has the visual discrimination property in a special condition, especially in a dark place under ultraviolet irradiation, with maintaining the sense of unity of the tire in an ordinary condition, especially in a bright place.

(32) TABLE-US-00001 TABLE 1 T-0 T-1 T-2 C-1 C-2 C-3 C-4 C-5 C-6 C-7 T-3 T-4 T-5 SBR (1) 100 100 100 100 100 100 100 100 100 100 100 100 100 Carbon black (2) 5.0 5.0 5.0 5.0 5.0 4.0 3.0 2.0 1.0 7.0 50 5.0 Silica (3) 120 120 120 120 120 120 120 120 120 120 120 120 120 Coupling agent (4) 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 Fluorescent pigment (5) 1.0 2.0 3.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 25 5.0 Hydrocarbon resin (6) 20 20 20 20 20 20 20 20 20 20 20 20 20 Liquid plasticizer (7) 45 45 45 45 45 45 45 45 45 45 45 45 45 Steric acid 1 1 1 1 1 1 1 1 1 1 1 1 1 Anti-ozone wax 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti-oxidant (8) 2 2 2 2 2 2 2 2 2 2 2 2 2 DPG (9) 3 3 3 3 3 3 3 3 3 3 3 3 3 ZnO 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Accelerator (10) 2 2 2 2 2 2 2 2 2 2 2 2 2 Sulphur 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 Visual discrimination property (11) Upon exposure to — 2 3 8 10 10 10 10 10 6 0 10 10 ultraviolet irradiation, in a dark room In a bright room — 0 0 0 0 0 0 0 0 0 0 7 10 (1) SBR1: solution SBR with 44% of styrene units, 41% of 1,2- unit of the butadiene parts, and 23% of cis-1,4 unit of butadiene parts (Tg.sub.DSC = −12° C.); (2) Carbon black: Carbon black (ASTM grade N234 from Cabot); (3) Silica: Silica (“Zeosil 1165MP” from Rhodia (CTAB, BET: about 160 m.sup.2/g)); (4) Coupling agent TESPT (“Si69” from Evonik); (5) Fluorescent colored acrylic pigment (SINLOIHI COLOR SX-105 Lemon Yellow, S SINLOIHI) (6) Cycloaliphatic hydrocarbon resins (ESCOREZ5600, Exxon mobil, Tg.sub.DSC = 52° C.); (7) TDAE oil (“Vivatec 500” from the Hansen & Rosenthal company); (8) N-(1,3-dimethylbutyl)-N-phenyl-para-phenylenediamine (“Santoflex 6-PPD” from Flexsys); (9) Diphenylguanidine (“Perkacit DPG” from Flexsys); (10) N-dicyclohexyl-2-benzothiazolesulphenamide (“Santocure CBS” from Flexsys). (11) Visual discrimination property test in comparison with T-0, conducted by ten expert tire inspectors in a dark room under ultraviolet irradiation or in bright room.