HIGH-RIGIDITY RUBBER COMPOSITION

Abstract

A 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 aromatic polyaldehyde selected from 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde and mixtures of these compounds, the rubber composition having a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than or equal to 25 MPa.

Claims

1.-17. (canceled)

18. 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 aromatic polyaldehyde selected from 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde and mixtures thereof, wherein the rubber composition has a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than or equal to 25 MPa.

19. The rubber composition according to claim 18, wherein the at least one aromatic ring bears three hydroxyl functions in the meta position relative to one another.

20. The rubber composition according to claim 18, wherein the two positions ortho to each hydroxyl function are unsubstituted.

21. The rubber composition according to claim 18, wherein the remainder of the at least one aromatic ring is unsubstituted.

22. The rubber composition according to claim 18, 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.

23. The rubber composition according to claim 22, 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.

24. The rubber composition according to claim 22, wherein the two positions ortho to each hydroxyl function of at least one aromatic ring are unsubstituted.

25. The rubber composition according to claim 22, wherein the two positions ortho to each hydroxyl function of each aromatic ring are unsubstituted.

26. The rubber composition according to claim 18, wherein the at least one, or each, aromatic ring of the at least one aromatic polyphenol is a benzene ring.

27. The rubber composition according to claim 18, 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.

28. The rubber composition according to claim 18, wherein the at least one aromatic polyaldehyde is 1,4-benzenedicarboxaldehyde.

29. The rubber composition according to claim 18 further comprising a diene elastomer selected from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers, and mixtures thereof.

30. The rubber composition according to claim 18, wherein the rubber composition has a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than or equal to 30 MPa.

31. The rubber composition according to claim 30, wherein the rubber composition has a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than or equal to 35 MPa.

32. The rubber composition according to claim 31, wherein the rubber composition has a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than 39 MPa.

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 aromatic polyaldehyde selected from 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde and mixtures thereof, wherein the rubber composition has a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than or equal to 25 MPa.

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 aromatic polyaldehyde; 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 18.

36. A tire comprising a rubber composition according to claim 18.

Description

EXEMPLARY EMBODIMENTS OF THE INVENTION AND COMPARATIVE TESTS

[0140] These tests demonstrate that: [0141] 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 that [0142] the stiffness of the rubber composition is maintained at high temperatures, in particular for temperatures ranging up to 150 C. [0143] 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. [0144] Finally, the composition according to the invention does not require the use of an additional reinforcing resin for preventing the retention of the composition in compounding devices.

[0145] For this purpose, several rubber compositions, denoted hereinafter T0 to T7 and 8 and 16 were prepared as indicated above and are summarized in the appended table 1 below.

[0146] All the compositions T0 to T7 and 8 to 16 have the following shared portion 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.

[0147] The composition T0 does not comprise any reinforcing resin added to this shared portion.

[0148] 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.

[0149] In addition to the shared portion, the composition T1a comprising a reinforcing resin based on hexamethylenetetramine (3 phr) and on a pre-condensed phenolic resin (6 phr) and also an additional resin based on hexamethoxymethylmelamine (6 phr, H3M at 72%) and (4,4-dihydroxy-2,2-diphenylpropane) (Bisphenol A) (8 phr). The composition T1a represents a conventional composition of the prior art, having relatively high stiffness, greater than that of the composition T0.

[0150] 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.

[0151] In addition to the shared portion, each composition 8 to 14 comprises 14 phr of aromatic polyphenol and 14 phr of aromatic polyaldehyde, indicated in table 1.

[0152] In addition to the shared portion, each composition 15 and 16 comprises 28 phr of aromatic polyphenol and 28 phr of the aromatic polyaldehyde, indicated in table 1.

[0153] The compositions T0 to T7 are not in accordance with the invention, unlike compositions 8 to 16 which are in accordance with the invention.

[0154] Each rubber composition 8 to 16 according to the invention comprises a phenol/aldehyde resin based on: [0155] 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 [0156] at least one aromatic polyaldehyde selected from 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde and mixtures of these compounds, [0157] the rubber composition having a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998 of greater than or equal to 25 MPa, preferably greater than or equal to 30 MPa, more preferentially greater than or equal to 35 MPa and even more preferentially strictly greater than 39 MPa.

[0158] Each aromatic polyphenol of the resin of each composition 8 to 16 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.

[0159] Each aromatic polyphenol of each composition 8 and 9 according to the invention 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.

[0160] Each polyphenol of each composition 10, 11, 15 and 16 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.

[0161] For the aromatic polyphenols of each composition 8 to 11 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.

[0162] Each aromatic polyphenol of each composition 12 to 14 according to the invention 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.

[0163] The aromatic polyphenol of the composition 14 is a resin pre-condensed from resorcinol and formaldehyde.

[0164] Each aromatic polyaldehyde of each composition 8 to 16 according to the invention 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.

[0165] The compositions T1 to T17 and 8 to 16 were prepared in accordance with the method described above, then the compositions were characterized by means of several characterization tests described below.

[0166] Firstly, the stiffness at high temperature was characterized, by heating the mixture to 150 C. until the maximum rheometric torque was obtained.

[0167] Once vulcanized, the stiffness at 23 C. of the composition was characterized during a tensile test.

[0168] Throughout the manufacturing method, it was noted that none of the compositions according to the invention was retained in the compounding devices, despite a relatively high stiffness after crosslinking, in this case after vulcanization.

[0169] Characterization of the Stiffness at High TemperatureMaximum Rheometric Torque

[0170] The measurements are carried out at 150 C. with an oscillating disc rheometer, according to Standard DIN 53529Part 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.

[0171] Characterization of the Stiffness at 23 C.Tensile Test

[0172] 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.

[0173] 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 is 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 8 to 16 according to the invention.

[0174] 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 in accordance with the invention (8 to 16).

[0175] 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 aromatic polyaldehydes of the compositions 8 to 16. These results are relatively unexpected for those skilled in the art, given the fact that, a priori, the aromatic polyaldehyde of the compositions 9, 11 and 16, but above all the aromatic polyaldehyde of the compositions 8, 10 and 15, have lower reactivity than that of the aromatic monoaldehyde of the compositions T3 and T4.

[0176] 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 1,3-benzenedicarboxaldehyde (8) and 1,4-benzenedicarboxaldehyde (9).

[0177] 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.

[0178] 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 (8 to 14).

[0179] The composition 8 has a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than or equal to 25 MPa.

[0180] The compositions 9, 11 and 12 have a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than or equal to 30 MPa.

[0181] The compositions 10, 13 and 14 have a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of greater than or equal to 35 MPa.

[0182] The compositions 15 and 16 have a nominal secant modulus at 10% elongation, measured according to standard ASTM D 412, 1998, of strictly greater than 39 MPa.

[0183] The invention is not limited to the embodiments described above.

TABLE-US-00001 TABLE 1 MA10 Cmax Composition Methylene donor Phenol Additional resin (MPa) (dN .Math. m) T0 / / / 7.2 16 T1 Hexamethylenetetramine (1) SRF resin (2) / 16.5 43 T1a Hexamethylenetetramine (1) SRF resin (2) Yes 55 75 MA10 Cmax Composition Aldehyde Phenol Additional resin (MPa) (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 MA10 Cmax Composition Aromatic polyaldehyde Aromatic polyphenol Additional resin (MPa) (dN .Math. m) 8 1,3-benzenedicarboxaldehyde (4) Resorcinol (9) / 28.7 30 9 1,4-benzenedicarboxaldehyde (5) Resorcinol (9) / 32 73 10 1,3-benzenedicarboxaldehyde (4) Phloroglucinol (11) / 39 35 11 1,4-benzenedicarboxaldehyde (5) Phloroglucinol (11) / 33 30 12 1,4-benzenedicarboxaldehyde (5) 2,2,4,4-tetrahydroxydiphenyl sulphide (12) / 32 45 13 1,4-benzenedicarboxaldehyde (5) 2,2,4,4-tetrahydroxybenzophenone (13) / 36.1 50 14 1,4-benzenedicarboxaldehyde (5) SRF resin (2) / 35.1 50 15 1,3-benzenedicarboxaldehyde (4) Phloroglucinol (11) / 43 46 16 1,4-benzenedicarboxaldehyde (5) Phloroglucinol (11) / 40 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%).