HIGH-RIGIDITY RUBBER COMPOSITION

Abstract

The rubber composition comprises at least one phenol/aldehyde resin based on:

at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted, and

at least one aldehyde of formula (A):

##STR00001##

in which:

X comprises N, S or O,

R represents —H or —CHO.

Claims

1.-18. (canceled)

19. A rubber composition comprising at least one phenol/aldehyde resin based on: at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted; and at least one aldehyde of formula (A) ##STR00022## in which X comprises N, S or O, and R represents —H or —CHO.

20. The rubber composition according to claim 19, wherein the at least one aromatic ring bears three hydroxyl functions in the meta position relative to one another.

21. The rubber composition according to claim 19, wherein the two positions ortho to each hydroxyl function are unsubstituted.

22. The rubber composition according to claim 19, wherein the remainder of the at least one aromatic ring is unsubstituted.

23. The rubber composition according to claim 19, wherein the at least one aromatic polyphenol comprises several aromatic rings, at least two of these each bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions of at least one aromatic ring being unsubstituted.

24. The rubber composition according to claim 23, wherein at least one of the aromatic rings of the at least one aromatic polyphenol bears three hydroxyl functions in the meta position relative to one another.

25. The rubber composition according to claim 23, wherein the two positions ortho to each hydroxyl function of at least one aromatic ring are unsubstituted.

26. The rubber composition according to claim 23, wherein the two positions ortho to each hydroxyl function of each aromatic ring are unsubstituted.

27. The rubber composition according to claim 19, wherein the at least one, or each, aromatic ring of the at least one aromatic polyphenol is a benzene ring.

28. The rubber composition according to claim 19, wherein the at least one aromatic polyphenol is selected from the group consisting of resorcinol, phloroglucinol, 2,2′,4,4′-tetrahydroxydiphenyl sulphide, 2,2′,4,4′-tetrahydroxybenzophenone, resins pre-condensed from at least one of these phenols, and mixtures thereof.

29. The rubber composition according to claim 19, wherein the at least one aldehyde is of general formula (A′) ##STR00023##

30. The rubber composition according to claim 19, wherein X represents NH, S or O.

31. The rubber composition according to claim 19, wherein the at least one aldehyde is selected from the group consisting of furfuraldehyde, 2,5-furandicarboxaldehyde, and mixtures thereof.

32. The rubber composition according to claim 19 further comprising a diene elastomer selected from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers, and mixtures thereof.

33. A method for manufacturing a rubber composition comprising the step of: mixing at least one elastomer, at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted, and at least one aldehyde of formula (A) ##STR00024## in which X comprises N, S or O, and R represents —H or —CHO.

34. The method according to claim 33 further comprising the steps of: incorporating, in the diene elastomer, during a first step, a reinforcing filler, to make a mixture and kneading the mixture thermomechanically until a maximum temperature of between 110° C. and 190° C. is reached; cooling the mixture to a temperature of less than 100° C.; then incorporating, during a second step, a crosslinking system, the at least one aromatic polyphenol and the at least one aldehyde of formula (A); and kneading the mixture up to a maximum temperature of less than 110° C.

35. A rubber composite reinforced with at least one reinforcing element embedded in a rubber composition, wherein the rubber composition is a rubber composition according to claim 19.

36. A tire comprising a rubber composition according to claim 19.

Description

[0143] By way of example, the single appended FIGURE represents very diagrammatically (without observing a specific scale) a radial section of a tyre in accordance with the invention for a vehicle of the heavy-duty type.

[0144] This tyre 1 comprises a crown 2 reinforced by a crown reinforcement or belt 6, two sidewalls 3 and two beads 4, each of these beads 4 being reinforced with a bead wire 5. The crown 2 is surmounted by a tread, not represented in this diagrammatic FIGURE. A carcass reinforcement 7 is wound around the two bead wires 5 in each bead 4, the turn-up 8 of this reinforcement 7 being, for example, positioned towards the outside of the tyre 1, which is here represented fitted onto its wheel rim 9. The carcass reinforcement 7 is, in a way known per se, composed of at least one ply reinforced by “radial” cords, for example made of metal, that is to say that these cords are positioned virtually parallel to one another and extend from one bead to the other so as to form an angle of between 80° and 90° with the median circumferential plane (plane perpendicular to the axis of rotation of the tyre which is located halfway between the two beads 4 and passes through the middle of the crown reinforcement 6).

[0145] This tyre 1 of the invention has, for example, the characteristic that at least a crown reinforcement 6 and/or its carcass reinforcement 7 comprises a rubber composition or a composite according to the invention. Of course, the invention relates to the objects described previously, namely the rubber composite and the tyre, both in the uncured state (before curing or vulcanization) and in the cured state (after curing).

[0146] Method According to the Invention

[0147] The manufacturing method described above and below makes it possible to manufacture the composition according to the invention.

[0148] The rubber composition may be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: [0149] a first phase of thermomechanical working or kneading (“non-productive” phase) at high temperature, up to a maximum temperature of between 110° C. and 190° C., preferably between 130° C. and 180° C., [0150] followed by a second phase of mechanical working (“productive” phase) down to a lower temperature, typically of less than 110° C., for example between 40° C. and 100° C., during which finishing phase the crosslinking system is incorporated.

[0151] In one embodiment, the method comprises the following steps: [0152] incorporating a reinforcing filler in a diene elastomer during a first (“non-productive”) step, everything being kneaded thermomechanically (for example, once or several times), until a maximum temperature of between 110° C. and 190° C. is reached; [0153] cooling the combined mixture to a temperature of less than 100° C.; [0154] then incorporating, during a second (“productive”) step, a crosslinking system, the aldehyde of formula (A) and the aromatic polyphenol; [0155] kneading everything up to a maximum temperature of less than 110° C.

[0156] By way of example, the non-productive phase is carried out in a single thermomechanical step during which firstly all the necessary base constituents (a diene elastomer, reinforcing filler) are introduced into an appropriate mixer, such as a standard internal mixer, then secondly, for example after kneading for one to two minutes, the other additives, optional additional agents for covering the filler or optional additional processing aids, with the exception of the crosslinking system. The total kneading time, in this non-productive phase, is preferably between 1 and 15 min.

[0157] After cooling the mixture thus obtained, the crosslinking system, the aldehyde of formula (A) and the aromatic polyphenol are then incorporated in an external mixer, such as an open mill, maintained at a low temperature (for example between 40° C. and 100° C.). The combined mixture is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.

[0158] The final composition thus obtained can subsequently be calendered, for example in the form of a sheet or of a slab, especially for laboratory characterization, or else extruded, for example in order to form a rubber profiled element used in the manufacture of a tyre.

[0159] Analogously to the composite according to the invention, the method for manufacturing the tyre comprises: [0160] the step of manufacturing the composition described above, and [0161] a step of crosslinking this composition, for example by vulcanization, preferably under pressure, to form the tyre according to the invention.

[0162] The invention and its advantages will be easily understood in the light of the exemplary embodiments which follow.

[0163] Exemplary Embodiments of the Invention and Comparative Tests

[0164] These tests demonstrate that: [0165] the stiffness of the rubber composition is vastly improved compared to a rubber composition using a conventional reinforcing resin based on a methylene acceptor with HMT or H3M as methylene donor, and [0166] the stiffness of the rubber composition is maintained at high temperatures, in particular for temperatures ranging up to 150° C.

[0167] In addition, the phenol/aldehyde resin of the composition according to the invention is devoid of formaldehyde and does not generate any formaldehyde during its formation.

[0168] For this purpose, several rubber compositions denoted hereinafter T0 to T14 and 15 were prepared as indicated above and are summarized in the appended table 1 below.

[0169] All the compositions T0 to T14 and 15 have the following portion in common in their formulations (expressed in phr, parts by weight per hundred parts of elastomer): 100 phr of natural rubber, 75 phr of carbon black N326, 1.5 phr of N-(1,3-dimethylbutyl)-N-phenyl-para-phenylenediamine, 1.5 phr of stearic acid, 5 phr of ZnO, 1 phr of N-(tert-butyl)-2-benzothiazolesulphamide and 2.5 phr insoluble sulphur 20H.

[0170] The composition T0 does not comprise any reinforcing resin added to this shared portion.

[0171] In addition to the shared portion, the composition T1 comprises a reinforcing resin based on hexamethylenetetramine (1.6 phr) and on a pre-condensed phenolic resin (4 phr). The composition T1 represents a conventional composition of the prior art, having greater stiffness than that of the composition T0.

[0172] In addition to the shared portion, each composition T2 to T7 comprises 14 phr of phenol and 14 phr of aldehyde, indicated in table 1.

[0173] In addition to the shared portion, each composition T8 to T14 comprises 14 phr of aromatic polyphenol and 14 phr of aromatic polyaldehyde, indicated in table 1.

[0174] In addition to the shared portion, the composition 15 comprises 14 phr of aromatic polyphenol and 14 phr of the aldehyde of formula (A), indicated in table 1.

[0175] The compositions T0 to T14 are not in accordance with the invention, unlike composition 15 which is in accordance with the invention.

[0176] The rubber composition 15 according to the invention comprises a phenol/aldehyde resin based on : [0177] at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted, and [0178] at least one aldehyde of formula (A).

[0179] Each aromatic polyphenol of the resin of each composition T8 to T14 and 15 according to the invention is selected from the group consisting of resorcinol, phloroglucinol, 2,2′,4,4′-tetrahydroxydiphenyl sulphide, 2,2′,4,4′-tetrahydroxybenzophenone, resins pre-condensed from these phenols and the mixtures of these compounds.

[0180] Each aromatic polyphenol of each composition T8 and T9 comprises a single aromatic ring, in this instance a benzene ring, bearing two, and only two, hydroxyl functions in the meta position relative to one another. In the case in point, this is resorcinol.

[0181] Each polyphenol of each composition T10 and T11 and 15 according to the invention comprises a single aromatic ring, in this case a benzene ring, bearing three, and only three, hydroxyl functions in the meta position relative to one another. In the case in point, this is phloroglucinol.

[0182] For the aromatic polyphenols of each composition T8 to T11 and 15 according to the invention, the remainder of the aromatic ring of the aromatic polyphenol is unsubstituted. In particular, the two positions ortho to each hydroxyl function are unsubstituted.

[0183] Each aromatic polyphenol of each composition T12 to T14 comprises several aromatic rings, in this case benzene rings, at least two of these each bearing at least two hydroxyl functions in the meta position relative to one another. The two positions ortho to at least one of the hydroxyl functions of each aromatic ring are unsubstituted.

[0184] The aromatic polyphenol of the composition T14 is a resin pre-condensed from resorcinol and formaldehyde.

[0185] As a variant in the composition according to the invention, use may be made, as a replacement for the phloroglucinol, of an aromatic polyphenol comprising a single aromatic ring, for example a benzene ring, bearing two, and only two, hydroxyl functions in the meta position relative to one another. For example, resorcinol as in the compositions T8 and T9.

[0186] In another variant in the composition according to the invention, use may be made, as a replacement for the phloroglucinol, of an aromatic polyphenol comprising several aromatic rings, for example benzene rings, at least two of these each bearing at least two hydroxyl functions in the meta position relative to one another, as in the compositions T12 and T13. The two positions ortho to at least one of the hydroxyl functions of each aromatic ring are unsubstituted.

[0187] In yet another variant in the composition according to the invention, use may be made, as a replacement for the phloroglucinol, of an aromatic polyphenol comprising a resin pre-condensed from resorcinol and formaldehyde, as in the composition T14.

[0188] Each aromatic polyaldehyde of each composition T8 to T14 is either 1,3-benzenedicarboxaldehyde or 1,4-benzenedicarboxaldehyde. As a variant, this could be a mixture of 1,3-benzenedicarboxaldehyde and 1,4-benzenedicarboxaldehyde.

[0189] The aldehyde of formula (A of the composition 15 according to the invention is selected from the group consisting of furfuraldehyde, 2,5-furandicarboxaldehyde and the mixtures of these compounds. In this case, the aldehyde of formula (A) is 2,5-furandicarboxaldehyde.

[0190] The compositions T1 to T14 and 15 were prepared in accordance with the method described above, then the compositions were characterized by means of several characterization tests described below.

[0191] Firstly, the stiffness at high temperature was characterized, by heating the mixture to 150° C. until the maximum rheometric torque was obtained.

[0192] Once vulcanized, the stiffness at 23° C. of the composition was characterized during a tensile test.

[0193] Characterization of the Stiffness at High Temperature—Maximum Rheometric Torque

[0194] The measurements are carried out at 150° C. with an oscillating disc rheometer, according to Standard DIN 53529-Part 3 (June 1983). The change in the rheometric torque as a function of the time describes the change in the stiffening of the composition following vulcanization and crosslinking of the phenol/aldehyde resin. From the change in the rheometric torque, the maximum rheometric torque Cmax is determined, and reported in table 1. The higher the maximum rheometric torque Cmax, the more the composition has a stiffness which can be maintained at high temperature.

[0195] Characterization of the Stiffness at 23° C.—Tensile Test

[0196] These tests make it possible to determine the elasticity stresses and the properties at break. Unless indicated otherwise, they are carried out in accordance with standard ASTM D 412, 1998 (test specimen C). The “nominal” secant moduli (or apparent stresses, in MPa) at 10% elongation (denoted “MA10”) are measured in second elongation (i.e., after an accommodation cycle). All these tensile measurements are carried out under normal temperature and relative humidity conditions, according to standard ASTM D 1349, 1999, and reported in table 1.

[0197] First of all, the results from table 1 show that the use of a reinforcing resin of the prior art (T1) makes it possible to obtain a stiffness at 23° C., and retention of this stiffness at higher temperatures, which are better than a composition devoid of reinforcing resin (T0). Nonetheless, despite better retention of the stiffness at high temperature than in compositions T2 to T7, the stiffness at 23° C. of the composition T1 is well below that of each composition T8 to T14 and 15 according to the invention.

[0198] Moreover, the results from table 1 show that the use of an aromatic monophenol (T2) does not make it possible to obtain sufficient stiffness at 23° C., nor retention of this stiffness at higher temperatures, unlike the aromatic polyphenols of the compositions T8 to T14 and 15 in accordance with the invention.

[0199] In addition, the results from table 1 show that the use of an aromatic aldehyde comprising a benzene ring bearing a single aldehyde function (T3 and T4) does not make it possible to obtain better stiffness at 23° C. compared to the composition T1, nor for this stiffness to be able to be maintained at higher temperatures, unlike the aldehyde of formula (A) of the composition 15. These results are relatively unexpected for those skilled in the art, given the fact that, a priori, the aldehyde of formula (A) of the composition 15 has lower reactivity than that of the aromatic monoaldehyde of the compositions T3 and T4.

[0200] The results from table 1 also show that while the use of 1,2-benzenedicarboxaldehyde (T5) makes it possible to obtain an improved stiffness at 23° C. compared to the composition T1, it does not make it possible to maintain this stiffness at high temperatures, unlike the aldehyde of formula (A) of the composition 15.

[0201] The use of an aromatic polyphenol, the two hydroxyl functions of which are in para positions (T6) relative to one another, does not make it possible to obtain an improved stiffness at 23° C. compared to the composition T1. Moreover, such a polyphenol does not enable the retention of this stiffness at higher temperatures.

[0202] Finally, the results from table 1 show that the use of an aromatic polyphenol, the two hydroxyl functions of which are in ortho positions (T7) relative to one another, does indeed make it possible to obtain an improved stiffness at 23° C. compared to the composition T1, without however enabling satisfactory retention of this stiffness at high temperatures, unlike the aromatic polyphenols in accordance with the invention (T8 to T14 and 15 in accordance with the invention).

[0203] The invention is not limited to the embodiments described above.

TABLE-US-00001 TABLE 1 Composition Methylene donor Phenol MA10 (MPa) Cmax (dN .Math. m) T0 / / 7.2 16 T1 Hexamethylenetetramine (1) SRF resin (2) 16.5 43 Composition Aldehyde Phenol MA10 (MPa) Cmax (dN .Math. m) T2 1,4-benzenedicarboxaldehyde (5) 3-tert-butylphenol (7) 4.7 7 T3 Benzaldehyde (6) Phloroglucinol (11) 14.7 14 T4 Benzaldehyde (6) Resorcinol (9) 12.1 7 T5 1,2-benzenedicarboxaldehyde (3) Resorcinol (9) 21.5 20 T6 1,4-benzenedicarboxaldehyde (5) Hydroquinone (10) 13.6 7 T7 1,4-benzenedicarboxaldehyde (5) 1,2-dihydroxybenzene (8) 36.2 25 Composition Aromatic polyaldehyde Aromatic polyphenol MA10 (MPa) Cmax (dN .Math. m) T8 1,3-benzenedicarboxaldehyde (4) Resorcinol (9) 28.7 30 T9 1,4-benzenedicarboxaldehyde (5) Resorcinol (9) 32 73 T10 1,3-benzenedicarboxaldehyde (4) Phloroglucinol (11) 39 35 T11 1,4-benzenedicarboxaldehyde (5) Phloroglucinol (11) 33 30 T12 1,4-benzenedicarboxaldehyde (5) 2,2′,4,4′-Tetrahydroxydiphenyl sulphide (12) 32 45 T13 1,4-benzenedicarboxaldehyde (5) 2,2′,4,4′-tetrahydroxybenzophenone (13) 36.1 50 T14 1,4-benzenedicarboxaldehyde (5) SRF resin (2) 35.1 50 Composition Aldehyde of formula (A) Aromatic polyphenol MA10 (MPa) Cmax (dN .Math. m) 15 2,5-Furandicarboxaldehyde (14) Phloroglucinol (11) 25.7 40 (1) Hexamethylenetetramine (from Sigma-Aldrich; purity of ≧99%); (2) Pre-condensed resin SRF 1524 (from Schenectady; diluted to 75%); (3) 1,2-Benzenedicarboxaldehyde (from ABCR; purity of 98%); (4) 1,3-Benzenedicarboxaldehyde (from ABCR; purity of 98%); (5) 1,4-Benzenedicarboxaldehyde (from ABCR; purity of 98%); (6) Benzaldehyde (from Sigma-Aldrich; purity of ≧99.5%); (7) 3-Tert-butylphenol (from Sigma-Aldrich; purity of 99%); (8) 1,2-Dihydroxybenzene (from Sigma-Aldrich; purity of 99%); (9) Resorcinol (from Sumitomo; purity of 99.5%); (10) Hydroquinone (from Sigma-Aldrich; purity of 99%); (11) Phloroglucinol (from Alfa Aesar; purity of 99%); (12) 2,2′,4,4′-Tetrahydroxydiphenyl sulphide (from Alfa Aesar; purity of 98%); (13) 2,2′,4,4′-Tetrahydroxybenzophenone (from Sigma-Aldrich; purity of 97%); (14) 2,5-Furandicarboxaldehyde (from Aldrich; purity of 97%).