Rubber compositions based on epoxy resins and aminobenzoate derivatives

Abstract

The present invention relates to rubber compositions providing a better compromise between processability and stiffness, said compositions being based on at least one diene elastomer, a reinforcing filler, a crosslinking system, from 1 to 30 phr of an epoxy resin and from 0.5 to 15 phr of a specific amino benzoate derivative.

Description

Technical Field

[0001] This invention relates to rubber compositions intended specifically for use in the manufacture of tires or tire semi-finished products. The subject matter of this invention also includes finished or semi-finished rubber articles comprising rubber compositions according to the invention, and tires comprising at least one composition according to the invention. Background Technology

[0002] The use of rubber compositions that exhibit high stiffness during low strain in certain parts of a tire is well-known, as described in application WO 02 / 10269. Low strain resistance is one of the properties that a tire must exhibit to cope with the stresses it experiences.

[0003] This reinforcement can be achieved by increasing the content of reinforcing filler or by adding certain reinforcing resins to the constituent rubber composition of the tire part.

[0004] Reinforcing resins commonly used to increase the stiffness of compositions are based on methylene acceptor / donor systems. The terms "methylene acceptor" and "methylene donor" are well-known to those skilled in the art and are widely used to refer to compounds capable of reacting together to form a three-dimensional reinforcing resin by condensation, which overlaps and permeates both a reinforcing filler / elastomer network and an elastomer / sulfur network (if the crosslinking agent is sulfur). The aforementioned methylene acceptors are coupled with a curing agent capable of crosslinking or hardening them; this curing agent is also commonly referred to as a "methylene donor." The three-dimensional resin network is then generated during the curing of the rubber matrix by crosslinking the resin through the formation of methylene bridges between the ortho- and para-positions of the carbon atoms in the phenolic core of the resin and the methylene donor.

[0005] Typically, the methylene acceptor is a phenolic resin. Linear phenolic resins have been described in rubber compositions intended specifically for use in tires or tire treads, with their application varying depending on the adhesive strength or reinforcement: for example, refer to patent EP 0649446. Furthermore, commonly used methylene donors are hexamethylenetetramine (abbreviated HMT), hexamethoxymethylmelamine (abbreviated HMMM or H3M), or hexaethoxymethylmelamine.

[0006] However, the combination of phenolic resins (methylene acceptors) with HMT or H3M (methylene donors) can generate formaldehyde during the vulcanization of rubber compositions. In fact, given the potential environmental impact of these compounds, it is desirable to reduce (or even eliminate) formaldehyde from rubber compositions in the long term.

[0007] To this end, alternative compositions to conventional compositions have been developed, which include a formaldehyde / phenol resin pair (methylene acceptor) and an HMT or H3M curing agent (methylene donor). As an example, application WO 2011 / 045342 describes compositions comprising an epoxy resin pair and an amine-containing curing agent. In addition to the advantage of not producing formaldehyde, these compositions exhibit greater stiffness after crosslinking than conventional compositions while maintaining acceptable rolling resistance. Application WO 2018 / 002538 describes compositions comprising an epoxy resin and an amine-containing curing agent, which are designed to improve the processability (particularly scorch time) / stiffness trade-off compared to known compositions.

[0008] However, it is also desirable to improve the properties of these compositions in their unprocessed state (especially their processability) in order to facilitate their production and thus reduce overall production costs, while maintaining a good level of stiffness in the compositions. Summary of the Invention

[0009] During the research, the applicant unexpectedly discovered that, compared to currently used compositions, the combination of specific aminobenzoate derivatives with epoxy resins can improve the processability of rubber compositions before curing (in the unprocessed state) (particularly the scorch time or viscosity of these compositions), while maintaining or even improving the stiffness properties in the cured state. Therefore, the compositions according to the invention have a processability / stiffness trade-off that is far superior to known compositions. Detailed Implementation

[0010] definition

[0011] For the purposes of this invention, the expression "parts by weight / parts per hundred parts by weight" (or phr) should be understood to mean parts by weight / parts per hundred parts by weight of elastomer or rubber.

[0012] In this application, unless otherwise expressly stated, all percentages (%) shown are weight percentages (%).

[0013] Furthermore, any numerical interval expressed as "between a and b" represents a range of values ​​extending from greater than a to less than b (i.e., excluding the limits a and b), while any numerical interval expressed as "from a to b" means a range of values ​​extending from a to b (i.e., including the strict limits a and b). In this application, when describing a numerical interval using the expression "from a to b," it is also preferable to describe the interval expressed as "between a and b."

[0014] The phrase “composition based” should be understood to mean that the composition comprises a mixture of various components used and / or in-situ reaction products, some of which are capable (and / or intended) to react with each other at least partially during the various stages of the composition’s preparation; therefore, the composition may be in a fully or partially crosslinked or non-crosslinked state.

[0015] When referring to a "major" compound, for the purposes of this invention, it is understood to mean that among compounds of the same type in the composition, this compound is dominant, that is, the compound that constitutes the largest amount by weight among compounds of the same type. Thus, for example, a major elastomer is the elastomer that constitutes the largest weight relative to the total weight of elastomers in the composition. Similarly, a "major" filler is the filler that constitutes the largest weight among the fillers in the composition. For example, in a system comprising only one elastomer, said elastomer is dominant to the purposes of this invention; in a system comprising two elastomers, the major elastomer constitutes more than half the weight of the elastomer. Conversely, a "minor" compound is a compound that does not constitute the largest weight fraction among compounds of the same type. Preferably, the term "major" is understood to mean present at a concentration greater than 50%, preferably greater than 60%, 70%, 80%, or 90%, and more preferably, the "major" compound constitutes 100%.

[0016] The carbon-containing compounds mentioned in the specification can be of fossil or biological origin. In the case of biological origin, they can be produced partially or entirely from biomass or obtained from renewable starting materials derived from biomass. This particularly relates to polymers, plasticizers, fillers, etc.

[0017] Detailed description of the invention

[0018] The present invention relates to at least one of the following embodiments:

[0019] 1. A rubber composition, said rubber composition being based at least on:

[0020] - Diene elastomers

[0021] -Reinforced filler,

[0022] - Crosslinking system,

[0023] -1 to 30 parts by weight per hundred parts by weight of elastomer (phr) epoxy resin, and

[0024] -0.5 phr to 15 phr aminobenzoate derivatives, said aminobenzoate derivatives corresponding to formula (I):

[0025]

[0026] in:

[0027] -n represents an integer from 1 to 5.

[0028] -Y represents the ester functional group.

[0029] -R1 and R2 can be the same or different, and are selected from hydrogen atoms and methyl, ethyl, propyl, butyl, isopropyl, isobutyl, tert-butyl, or benzyl groups.

[0030] -Ri groups can be the same or different and are selected from hydrogen atoms and straight-chain or branched C1-C6 alkyl groups.

[0031] 2. The rubber composition according to embodiment 1, wherein the aminobenzoate derivative corresponds to formula (II) or (III):

[0032]

[0033] 3. The rubber composition according to embodiment 1, wherein the aminobenzoate derivative corresponds to formula (IV):

[0034]

[0035] 4. The rubber composition according to any one of embodiments 1 to 3, wherein the aminobenzoate derivative corresponds to formula (V) or (VI):

[0036]

[0037] 5. The rubber composition according to any one of embodiments 1 to 4, wherein the straight-chain or branched C1-C6 alkyl groups of the Ri group are independently selected from methyl, ethyl, propyl, isopropyl, isobutyl and butyl groups, preferably selected from methyl and ethyl groups.

[0038] 6. The rubber composition according to any one of embodiments 1 to 4, wherein all Ri groups are hydrogen atoms.

[0039] 7. The rubber composition according to any one of embodiments 1 to 6, wherein n represents an integer from 2 to 4.

[0040] 8. The rubber composition according to any one of embodiments 1 to 7, wherein R1 and R2 may be the same or different, and are selected from hydrogen atoms and methyl or ethyl groups.

[0041] 9. The rubber composition according to any one of embodiments 1 to 8, wherein R1 and R2 are both hydrogen atoms.

[0042] 10. The rubber composition according to Embodiment 1, wherein the aminobenzoate derivative is selected from trimethylene bis(4-aminobenzoate), 3,3-dimethyl-1,5-pentanediol 1,5-bis(4-aminobenzoate), 2-ethyl-1,3-hexanediol 1,3-bis(4-aminobenzoate), 1,3-butanediol 1,3-bis(4-aminobenzoate), and 2-methyl-1,3-propanediol 1,3-bis(4-aminobenzoate). 2,2-Diethyl-1,3-propanediol 1,3-bis(4-aminobenzoate), 2,4-pentanediol 2,4-bis(4-aminobenzoate), 1,2-propanediol 1,2-bis(4-aminobenzoate), 1,4-butanediol 1,4-bis(4-aminobenzoate), 2,2-dimethyl-1,3-propanediol 1,3-bis(4-aminobenzoate), 1,2-ethylenediol 1,2-bis(4-aminobenzoate), and mixtures thereof.

[0043] 11. The rubber composition according to embodiment 10, wherein the aminobenzoate derivative is selected from trimethylene bis(4-aminobenzoate), 1,4-butanediol 1,4-bis(4-aminobenzoate), 1,2-ethylenediol 1,2-bis(4-aminobenzoate), and mixtures thereof.

[0044] 12. The rubber composition according to any one of embodiments 1 to 11, wherein the content of the aminobenzoate derivative is in the range of 1 phr to 10 phr, preferably 2 phr to 8 phr.

[0045] 13. The rubber composition according to any one of embodiments 1 to 12, wherein the elastomer is selected from natural rubber, synthetic polyisoprene, polybutadiene, butadiene copolymer, isoprene copolymer, and mixtures of these elastomers.

[0046] 14. The rubber composition according to any one of embodiments 1 to 13, wherein the epoxy resin is selected from aromatic epoxy resins, alicyclic epoxy resins and aliphatic epoxy resins.

[0047] 15. The rubber composition according to embodiment 14, wherein the epoxy resin is selected from epoxy cresol formaldehyde phenolic resin.

[0048] 16. The rubber composition according to any one of embodiments 1 to 13, wherein the epoxy resin is selected from 2,2-bis[4-(glycidoxy)phenyl]propane, poly[(o-tolyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-(hydroxybenzaldehyde glycidyl ether)], and mixtures of these compounds.

[0049] 17. The rubber composition according to any one of embodiments 1 to 16, wherein the epoxy resin content is between 10 phr and 25 phr, preferably between 15 phr and 20 phr.

[0050] 18. The rubber composition according to any one of the foregoing embodiments, wherein the reinforcing filler comprises carbon black, reinforcing inorganic filler, or a mixture of carbon black and reinforcing inorganic filler; preferably, the reinforcing filler mainly comprises carbon black.

[0051] 19. The rubber composition according to any one of the foregoing embodiments, wherein the content of reinforcing filler is in the range of 20 phr to 200 phr, preferably 30 phr to 150 phr.

[0052] 20. Finished or semi-finished rubber products, said finished or semi-finished rubber products comprising the rubber composition according to any one of the foregoing embodiments.

[0053] 21. A tire comprising a rubber composition according to any one of embodiments 1 to 19, or comprising a semi-finished rubber article according to embodiment 20.

[0054] 22. The tire according to embodiment 21, wherein the rubber composition according to any one of embodiments 1 to 19 is present in at least one inner layer.

[0055] 23. The tire according to embodiment 22, wherein the inner layer is selected from the carcass ply, crown ply, bead filler, crown underlayer, release layer, edge rubber, filler rubber, tread underlayer, and combinations of these inner layers.

[0056] Diene elastomers

[0057] The compositions according to the invention comprise at least one diene elastomer. Therefore, the composition may contain only one diene elastomer, or a mixture of multiple diene elastomers.

[0058] "Diene" elastomers (or indiscriminate rubbers) (whether natural or synthetic) should be understood in the known manner as meaning elastomers that are at least partially (i.e., homopolymers or copolymers) composed of diene monomer units (monomers with two conjugated or non-conjugated carbon-carbon double bonds).

[0059] These diene elastomers can be classified into two categories: "substantially unsaturated" or "substantially saturated." "Substantially unsaturated" is generally understood to mean diene elastomers that are at least partially derived from conjugated diene monomers and have a diene source (conjugated diene) unit content greater than 15% (mol%). Therefore, diene elastomers such as butyl rubber or EPDM-type copolymers of dienes and α-olefins do not fall within the aforementioned definition but can be specifically described as "substantially saturated" diene elastomers (low or very low diene source unit content, always less than 15%). The diene elastomers included in the compositions according to the invention are preferably substantially unsaturated.

[0060] "dien elastomers capable of being used in compositions according to the invention" are specifically understood to mean:

[0061] (a) Any homopolymer of conjugated or non-conjugated diene monomers having 4 to 18 carbon atoms;

[0062] (b) Any copolymer of a conjugated or non-conjugated diene having 4 to 18 carbon atoms with at least one other monomer.

[0063] Other monomers can be ethylene, olefins, or conjugated or non-conjugated dienes.

[0064] Suitable conjugated dienes are those having 4 to 12 carbon atoms, especially 1,3-dienes, such as 1,3-butadiene and isoprene.

[0065] Suitable olefins are vinyl aromatic compounds having 8 to 20 carbon atoms and aliphatic α-monoolefins having 3 to 12 carbon atoms.

[0066] Suitable examples of vinyl aromatic compounds include styrene, (o-, m-, or p-)methylstyrene, commercial mixtures of "vinyltoluene", or p-(tert-butyl)styrene.

[0067] Amorphous aliphatic α-monoolefins, particularly those with 3 to 18 carbon atoms, are suitable as aliphatic α-monoolefins.

[0068] Preferably, the diene elastomer is selected from polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. The butadiene copolymer is particularly selected from butadiene / styrene copolymer (SBR).

[0069] Preferably, the diene elastomer is an isoprene elastomer.

[0070] "Isoprene elastomer" is understood in a known manner to mean isoprene homopolymers or copolymers, in other words, diene elastomers selected from natural rubber (NR), synthetic polyisoprene (IR), various isoprene copolymers, and mixtures of these elastomers. Among isoprene copolymers, isobutylene / isoprene (butyl rubber-IIR) copolymers, isoprene / styrene (SIR) copolymers, isoprene / butadiene (BIR) copolymers, or isoprene / butadiene / styrene (SBIR) copolymers will be specifically mentioned. The isoprene elastomer is preferably natural rubber or synthetic cis-1,4-polyisoprene; among these synthetic polyisoprene, polyisoprene with a cis-1,4-bond content (mol%) greater than 90% is preferred, and even more preferably greater than 98%.

[0071] Preferably, the content of the diene elastomer (preferably isoprene elastomer (preferably natural rubber)) is 50 phr to 100 phr, more preferably 60 phr to 100 phr, even more preferably 70 phr to 100 phr, and still more preferably 80 phr to 100 phr, and most preferably 90 phr to 100 phr. In particular, the content of the diene elastomer (preferably isoprene elastomer (also preferably natural rubber)) is very preferably 100 phr.

[0072] Whether the rubber composition comprises only one diene elastomer or a mixture of multiple diene elastomers, the rubber composition according to the invention may also include small amounts of any type of synthetic elastomer other than the diene elastomer, or even polymers other than elastomers, such as thermoplastic polymers. Preferably, the rubber composition according to the invention does not contain any synthetic elastomer other than the diene elastomer or any polymer other than the elastomer, or contains less than 10 phr, preferably less than 5 phr, of any synthetic elastomer other than the diene elastomer or any polymer other than the elastomer.

[0073] Epoxy resin

[0074] The compositions according to the invention comprise epoxy resins between 1 phr and 30 phr.

[0075] The epoxy resins that can be used in this invention include all polyepoxide compounds. These may involve, for example, aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. For example, aromatic epoxy resins may be amine-aromatic epoxy resins. These resins are preferably linear epoxy phenolic resins, that is, epoxy resins obtained by acid catalysis compared to methyl phenolic resins obtained by alkaline catalysts. Preferably, these resins are epoxy-cresol-formaldehyde phenolic resins.

[0076] In particular, among aromatic epoxy compounds, preferred epoxy resins are selected from 2,2-bis[4-(glycidoxy)phenyl]propane, poly[(o-tolyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-(hydroxybenzaldehyde glycidyl ether)], and mixtures of these compounds.

[0077] Preferably, the epoxy resin is selected from poly[(o-tolyl glycidyl ether)-co-formaldehyde], poly[(o-phenyl glycidyl ether)-co-formaldehyde], amine aromatic epoxy resins, and mixtures of these compounds.

[0078] Examples of commercially available epoxy resins that may be used in the context of this invention include, for example, epoxy resin DEN 439 from Uniqema, epoxy resin tris(4-hydroxyphenyl)methane triglycidyl ether from Sigma-Aldrich, or epoxy cresol-formaldehyde phenolic resin Araldite ECN 1299 from Hunterman.

[0079] The amount of epoxy resin is between 1 phr and 30 phr. Considering the aminobenzoate derivatives used in the context of this invention, below the shown minimum resin content, the target technical effect is insufficient, while above the shown maximum content, there is a risk of excessively increasing stiffness and excessively impairing hysteresis and Mooney plasticity. For all these reasons, the epoxy resin content is between 10 phr and 25 phr. More preferably, the epoxy resin content in the compositions according to the invention is between 15 phr and 20 phr.

[0080] aminobenzoate derivatives

[0081] The rubber composition according to the invention further comprises 0.5 phr to 15 phr of an aminobenzoate derivative, said aminobenzoate derivative corresponding to formula (I):

[0082]

[0083] in:

[0084] -n represents an integer from 1 to 5.

[0085] -Y represents the ester functional group.

[0086] -R1 and R2 can be the same or different, and are selected from hydrogen atoms and methyl, ethyl, propyl, butyl, isopropyl, isobutyl, tert-butyl, or benzyl groups.

[0087] -Ri groups can be the same or different and are selected from hydrogen atoms and straight-chain or branched C1-C6 alkyl groups.

[0088] In the context of this invention, these aminobenzoate derivatives are capable of crosslinking resins under appropriate conditions (especially during the curing process).

[0089] Preferably, the aminobenzoate derivative corresponds to formula (II) or (III):

[0090]

[0091] The n, R1, R2 and Ri groups are defined as above.

[0092] Preferably, the aminobenzoate derivative corresponds to formula (II), wherein the n, R1, R2 and Ri groups are as defined above.

[0093] Preferably, the aminobenzoate derivative corresponds to one of formulas (I), (II) or (III), wherein for each aromatic ring of the aminobenzoate derivative, at least two Ri groups located in the ortho or para position relative to the primary amine functional group are hydrogen atoms.

[0094] Aminobenzoate derivatives can correspond to formula (IV):

[0095]

[0096] The n, R1, R2 and Ri groups are defined as above.

[0097] Preferably, the aminobenzoate derivative corresponds to formula (V) or (VI):

[0098]

[0099] The n, R1, R2 and Ri groups are defined as above.

[0100] Particularly advantageously, the aminobenzoate derivatives correspond to formula (V), wherein the n, R1, R2 and Ri groups are as defined above.

[0101] Regardless of whether the aminobenzoate derivative is one of formulas (I) to (VI), the Ri groups may be the same or different, and are preferably selected from hydrogen atoms and straight-chain or branched C1-C6 alkyl groups. The straight-chain or branched C1-C6 alkyl groups of the Ri groups are independently selected from the group consisting of or composed of the following groups: methyl, ethyl, propyl, isopropyl, isobutyl, and butyl groups, preferably selected from methyl and ethyl groups. More preferably, all Ri groups are hydrogen atoms.

[0102] Regardless of which of formulas (I) to (VI) the aminobenzoate derivative is, n preferably represents an integer from 2 to 4.

[0103] Regardless of whether the aminobenzoate derivative is any of formulas (I) to (VI), according to the invention, R1 and R2 may be the same or different, and are preferably selected from the group consisting of or composed of hydrogen atoms and methyl, ethyl, isobutyl or benzyl groups, more preferably selected from the group consisting of or composed of hydrogen atoms and methyl or ethyl groups. More preferably, both R1 and R2 are hydrogen atoms.

[0104] When the aminobenzoate derivative corresponds to formula (I), (II), (IV) or (V), the aminobenzoate derivative is advantageously selected from the group consisting of or composed of the following compounds: trimethylene bis(4-aminobenzoate), 3,3-dimethyl-1,5-pentanediol 1,5-bis(4-aminobenzoate), 2-ethyl-1,3-hexanediol 1,3-bis(4-aminobenzoate), 1,3-butanediol 1,3 - bis(4-aminobenzoate), 2-methyl-1,3-propanediol 1,3-bis(4-aminobenzoate), 2,2-diethyl-1,3-propanediol 1,3-bis(4-aminobenzoate), 2,4-pentanediol 2,4-bis(4-aminobenzoate), 1,2-propanediol 1,2-bis(4-aminobenzoate), 1,4-butanediol 1,4-bis(4-aminobenzoate), 2,2-dimethyl-1,3- Propylene glycol 1,3-bis(4-aminobenzoate), 1,2-ethylene glycol 1,2-bis(4-aminobenzoate), and mixtures thereof, preferably selected from trimethylene bis(4-aminobenzoate), 2-ethyl-1,3-hexanediol 1,3-bis(4-aminobenzoate), 1,3-butanediol 1,3-bis(4-aminobenzoate), 2-methyl-1,3-propanediol 1,3-bis(4-aminobenzoate), and 2,2-diethyl... 1,3-propanediol 1,3-bis(4-aminobenzoate), 2,4-pentanediol 2,4-bis(4-aminobenzoate), 1,2-propanediol 1,2-bis(4-aminobenzoate), 1,4-butanediol 1,4-bis(4-aminobenzoate), 2,2-dimethyl-1,3-propanediol 1,3-bis(4-aminobenzoate), 1,2-ethylenediol 1,2-bis(4-aminobenzoate), and mixtures thereof.

[0105] When the aminobenzoate derivative corresponds to formula (I), (II), (IV), or (V) and both R1 and R2 are hydrogen atoms, the aminobenzoate derivative is advantageously selected from the group consisting of or composed of the following compounds: trimethylenebis(4-aminobenzoate), 1,4-butanediol 1,4-bis(4-aminobenzoate), 1,2-ethylenediol 1,2-bis(4-aminobenzoate), and mixtures thereof. Particularly advantageously, the aminobenzoate derivative is trimethylenebis(4-aminobenzoate).

[0106] Furthermore, as examples of compounds corresponding to formulas (III) and (VI), succinic acid, 1,4-bis(4-aminophenyl) ester, glutaric acid, 1,5-bis(4-aminophenyl) ester, adipic acid and 1,6-bis(4-aminophenyl) ester may be mentioned.

[0107] Compounds corresponding to formulas (I) through (VI) are commercially available. For example, trimethylenebis(4-aminobenzoate) corresponding to formula (VII) is available from Air Products under the name Versalink 740M:

[0108]

[0109] This compound can also be obtained, for example, by the methods described in Rao et al., European Polymer Journal (2016), 77, 139-154; Saif Ullah Khan et al., Journal of Organometallic Chemistry (2013), 745-746, 312-328; or in US 2014 / 0142199 and WO 2001 / 093823.

[0110] According to the present invention, the content of the aminobenzoate derivative is in the range of 0.5 phr to 15 phr. Below the shown minimum value, insufficient target technical effect is found, while above the shown maximum value, stiffness is compromised. Preferably, the content of the aminobenzoate derivative is in the range of 1 phr to 10 phr, more preferably 2 phr to 8 phr, and more preferably 3 phr to 5 phr.

[0111] Reinforced packing

[0112] The tire composition according to the invention advantageously includes reinforcing filler.

[0113] The reinforcing filler may include any type of reinforcing filler known for its ability to reinforce rubber compositions used in the manufacture of tires, such as organic fillers (e.g., carbon black), reinforcing inorganic fillers (e.g., silica), or mixtures of carbon black and reinforcing inorganic fillers. More preferably, the reinforcing filler comprises primarily (or even only) carbon black, particularly when the composition is used for the inner layer. The reinforcing filler may also comprise primarily reinforcing inorganic fillers, particularly when the composition is used for the tread.

[0114] Such reinforcing fillers are typically composed of particles with an average (by weight) size of less than one micrometer, usually less than 500 nm, most typically between 20 nm and 200 nm, and particularly and more preferably between 20 nm and 150 nm.

[0115] All carbon blacks (particularly HAF, ISAF, or SAF type carbon blacks commonly used in tires (“tire-grade” carbon black)) are suitable as carbon blacks. Within “tire-grade” carbon blacks, more specific references will be made to reinforced carbon blacks of the 100, 200, and 300 series (ASTM grades) (e.g., N115, N134, N234, N326, N330, N339, N347, and N375 carbon blacks), or higher series carbon blacks depending on the target application (e.g., N660, N683, or N772). Carbon blacks can, for example, be incorporated into isoprene elastomers in masterbatch form (see, for example, applications WO 97 / 36724 and WO 99 / 16600). The BET specific surface area of ​​the carbon black is measured according to standard D6556-10 [multi-point (at least 5 points) method - gas: nitrogen - relative pressure P / P0 range: 0.1 to 0.3].

[0116] As examples of organic fillers other than carbon black, functionalized polyethylene organic fillers may be mentioned, such as those described in applications WO-A-2006 / 069792, WO-A-2006 / 069793, WO-A-2008 / 003434 and WO-A-2008 / 003435.

[0117] In this patent application, by definition, “reinforced inorganic filler” should be understood to mean any inorganic or mineral filler (regardless of its color and origin, natural or synthetic), which, relative to carbon black, is also referred to as “white filler,” “transparent filler,” or even “non-black filler,” capable of individually reinforcing rubber compositions intended for use in the manufacture of tires without the need for any method other than an intermediate coupling agent; in other words, capable of replacing conventional tire-grade carbon black in terms of reinforcement. Such fillers are known to be typically characterized by the presence of hydroxyl (-OH) groups on their surface.

[0118] Silica-based mineral fillers (especially silica (SiO2)) or alumina-based mineral fillers (especially alumina (Al2O3)) are particularly suitable as reinforcing inorganic fillers. The silica used can be any reinforcing silica known to those skilled in the art, especially those with a BET surface area and CTAB specific surface area both less than 450 m². 2 / g, preferably 30m 2 / g to 400m 2 / g of precipitated silica or pyrolytic silica. As highly dispersible precipitated silica (“HDS”), reference will be made to, for example, Ultrasil 7000 and Ultrasil 7005 silica from Degussa, Zeosil 1165MP, 1135MP and 1115MP silica from Rhodia, Hi-Sil EZ150G silica from PPG, Zeopol 8715, 8745 and 8755 silica from Huber, or silica with a high specific surface area as described in application WO 03 / 16837.

[0119] The BET specific surface area of ​​silica was determined by gas adsorption in a known manner using the Brunauer-Emmett-Teller method as described in "The Journal of the American Chemical Society" (Vol. 60, p. 309, February 1938), more specifically according to French Standard NF ISO 9277 (Multi-point (5-point) volumetric method - gas: nitrogen - exhaust: 160°C for 1 hour - relative pressure p / p0 range: 0.05 to 0.17) of December 1996. The CTAB specific surface area of ​​silica was determined according to French Standard NF T 45-007 (Method B) of November 1987.

[0120] Alumina-type mineral fillers (especially alumina (Al2O3) or aluminum hydroxide (oxide)) or reinforced titanium oxide (as described in, for example, US 6610261 and US 6747087) are also suitable as reinforced inorganic fillers.

[0121] It is not important what physical state the reinforcing inorganic filler is provided in, whether it is in the form of powder, microspheres, granules, beads, or any other suitable dense form. Of course, "reinforcing inorganic filler" is also understood to mean a mixture of different reinforcing inorganic fillers, especially a mixture of highly dispersible silica fillers and / or alumina fillers.

[0122] Those skilled in the art will understand that reinforcing fillers of another property (particularly organic properties, such as carbon black) can be used as fillers equivalent to the reinforcing inorganic fillers described in this section, provided that the reinforcing filler is covered with an inorganic layer (e.g., silica) or includes functional sites (particularly hydroxyl sites) on its surface that require the use of coupling agents to establish bonds between the filler and the elastomer.

[0123] To couple an inorganic filler to a diene elastomer, a coupling agent (or binder) that is at least bifunctional is used in a known manner to provide a connection between the inorganic filler (its particle surface) and the diene elastomer with satisfactory chemical and / or physical properties. Organosilanes or polyorganosiloxanes that are at least bifunctional are particularly used.

[0124] Examples of coupling agents can be found in the following documents by those skilled in the art: WO 02 / 083782, WO 02 / 30939, WO 02 / 31041, WO 2007 / 061550, WO 2006 / 125532, WO 2006 / 125533, WO 2006 / 125534, US 6849754, WO 99 / 09036, WO 2006 / 023815, WO 2007 / 098080, WO 2010 / 072685 and WO 2008 / 055986.

[0125] The coupling agent content is advantageously less than 12 phr, and it should be understood that it is generally desirable to use as little coupling agent as possible. Typically, when reinforcing inorganic fillers are present, the coupling agent content is 0.5% to 15% by weight relative to the amount of inorganic filler. The coupling agent content is preferably in the range of 0.5 phr to 12 phr, more preferably in the range of 4 phr to 8 phr. This content can be readily adjusted by those skilled in the art according to the content of the inorganic filler used in the composition.

[0126] Preferably, the composition according to the invention is free of reinforcing inorganic fillers. A composition free of the compound is understood to mean that the composition does not contain the compound intentionally introduced into the composition, and if the compound is present, it is present in trace amounts, for example, in relation to the method of manufacturing the composition. For example, a composition free of the compound comprises an amount less than or equal to 0.1 phr, preferably less than or equal to 0.05 phr.

[0127] According to the present invention, when reinforcing fillers are present, the reinforcing fillers preferably mainly include (or even only include) carbon black, and the content of reinforcing fillers can be in the range of 20 phr to 200 phr, preferably 30 phr to 150 phr, preferably 40 phr to 100 phr, preferably 50 phr to 80 phr.

[0128] Crosslinking system

[0129] The crosslinking system can be any type of system known to those skilled in the art of tire rubber compositions. The crosslinking system may be particularly based on sulfur and / or peroxides and / or bismaleimides.

[0130] Preferably, the crosslinking system is based on sulfur; it can then be referred to as a vulcanization system. Sulfur can be provided in any form (particularly molecular sulfur or sulfur donor). It is also preferred that at least one vulcanization accelerator is present, and optionally, and preferably, various known vulcanization activators or known vulcanization retarders can be used, such as zinc oxide, stearic acid or equivalent compounds (e.g., stearates and transition metal salts), guanidine derivatives (particularly diphenylguanidine).

[0131] The sulfur content is preferably between 0.5 phr and 12 phr, particularly between 1 phr and 10 phr. The vulcanization accelerator is preferably between 0.5 phr and 10 phr, more preferably between 0.5 phr and 5.0 phr.

[0132] As accelerators, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used, particularly thiazole-type accelerators and their derivatives, or sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate-type accelerators. Examples of such accelerators include, in particular, compounds such as 2-mercaptobenzothiazole disulfide (abbreviated MBTS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazole sulfenamide (DCBS), N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS), N-(tert-butyl)-2-benzothiazole sulfenimide (TBSI), tetrabenzylthiuram disulfide (TBZTD), zinc dibenzyl dithiuram (ZBEC), and mixtures of these compounds.

[0133] Various additives

[0134] The rubber composition according to the invention may also include all or part of common additives typically used in elastomer compositions, such as pigments, protective agents (e.g., anti-ozone waxes, chemical anti-ozone agents, or antioxidants), plasticizers, and anti-fatigue agents.

[0135] When the composition according to the invention is a tire inner layer composition, it advantageously does not contain antioxidants.

[0136] When the composition according to the invention is a tire inner layer composition, it may be free of plasticizer or contain less than 5 phr, preferably less than 1 phr, of plasticizer. Alternatively, and according to also preferred embodiments, the composition according to the invention further includes a plasticizer. Preferably, the plasticizer is a solid hydrocarbon resin (or plasticizing resin), a plasticizing oil (or plasticizing oil), or a mixture of both.

[0137] Furthermore, the compositions according to the invention may include cobalt salts, particularly when the compositions are used for inner layers. Therefore, preferably, the compositions according to the invention include cobalt salts, which are preferably selected from rosin salts, acetylacetone compounds, tallates, naphthenates, resin salts, and mixtures of these compounds. The content of the cobalt salt may, for example, be between 0.1 phr and 6 phr, for example between 0.3 phr and 4 phr, for example between 0.5 phr and 2.5 phr.

[0138] Finished or semi-finished rubber products and tires

[0139] Another subject of the present invention is finished or semi-finished rubber articles comprising compositions according to the present invention.

[0140] The subject matter of this invention also includes tires comprising compositions according to the invention.

[0141] It can define three zones within the tire:

[0142] • The radially outer region in contact with ambient air, which is essentially composed of the tire tread and the outer sidewall. The outer sidewall is an elastomeric layer located outside the tire carcass reinforcement relative to the tire's inner cavity and between the crown and the bead, thereby completely or partially covering the area of ​​the carcass reinforcement extending from the crown to the bead.

[0143] • The radially inner region in contact with the inflating gas, which is typically composed of a layer that is airtight to the inflating gas (sometimes referred to as the inner airtight layer or liner).

[0144] • The inner region of a tire, that is, the region between the outer region and the inner region. This region includes the layers or plies referred to herein as the tire inner layers. These layers or plies are, for example, the carcass plies, the tread base layer, the tire belt plies, or any other layers that do not come into contact with ambient air or the tire's inflation gas.

[0145] The compositions defined in this specification are particularly suitable for tire treads and tire inner layers.

[0146] According to the present invention, the inner layer may be selected from the carcass ply, the crown ply, the bead filler, the crown underlayer, the release layer, the edge rubber, the filler rubber, the tread underlayer, and combinations thereof. Preferably, the inner layer is selected from the carcass ply, the crown ply, the bead filler, the crown underlayer, the release layer, and combinations thereof.

[0147] The present invention relates in particular to tires intended for use with passenger vehicles, SUVs (“sport utility vehicles”), two-wheeled vehicles (especially motorcycles), aircraft, or industrial vehicles selected from trucks, heavy vehicles (i.e., subways, buses, heavy road transport vehicles (trucks, tractors, trailers) or off-road vehicles (e.g., heavy agricultural vehicles or engineering vehicles)).

[0148] The present invention relates to articles comprising rubber compositions according to the invention in both an unprocessed state (i.e., before curing) and a cured state (i.e., after crosslinking or vulcanization).

[0149] Preparation of rubber composition

[0150] The rubber composition according to the invention can be manufactured in a suitable mixer using two consecutive preparation stages known to those skilled in the art:

[0151] - The first stage of thermomechanical processing or kneading (“non-production” stage), which can be carried out in a single thermomechanical step, involves adding all necessary components (particularly the elastomer matrix, fillers, and optional other additives) to a suitable mixer (e.g., a standard closed mixer, such as a 'Banbury' type)). The filler can be added to the elastomer in one step or in batches via thermomechanical kneading. Where the filler has been fully or partially added to the elastomer in masterbatch form (e.g., as described in applications WO 97 / 36724 and WO 99 / 16600), in addition to the crosslinking system, the directly kneaded masterbatch, other elastomers or fillers not present in the composition in masterbatch form (if present), and optional other additives are added.

[0152] During the non-production phase at high temperatures, the maximum temperature is between 110°C and 190°C, preferably between 130°C and 180°C, and the duration is usually between 2 minutes and 10 minutes.

[0153] - After the mixture obtained in the first non-production stage is cooled to a lower temperature (typically less than 110°C, for example, between 40°C and 100°C), a second stage of machining (“production” stage) is carried out in an open mixer (e.g., a two-roll mill). The crosslinking system is then added, and the combined mixture is mixed for several minutes, for example, between 2 minutes and 15 minutes.

[0154] The preparation method of such compositions includes, for example, the following steps:

[0155] a) During the first step (referred to as the “non-production” step), the reinforcing filler is introduced into the diene elastomer, and all the material is thermomechanically kneaded (e.g., in one or more steps) until a maximum temperature between 110°C and 190°C is reached.

[0156] b) Cool the combined mixture to a temperature below 100°C;

[0157] c) The crosslinking system is then added during the second step (referred to as the "production" step);

[0158] d) Knead all the substances together until the maximum temperature is below 110°C.

[0159] The epoxy resin at a concentration between 1 phr and 30 phr and the aminobenzoate derivative of formula (I) at a concentration between 0.5 phr and 15 phr can be added independently of each other during either the non-production stage (a) or the production stage (c). Preferably, the epoxy resin is added during the non-production stage (a) and the aminobenzoate derivative is added during the production stage (c).

[0160] The resulting final composition can then be calendered, for example, in the form of sheets or plates (especially for laboratory characterization), or extruded in the form of rubber semi-finished (or molded) components for manufacturing tires.

[0161] The composition can be in an unprocessed state (before crosslinking or vulcanization) or a cured state (after crosslinking or vulcanization), and can be a semi-finished product that can be used in tires.

[0162] Example

[0163] Measurements and tests used

[0164] · Scorching time

[0165] According to French standard NF T 43-005, measurements are taken at 130°C or 115°C. The change in consistency index over time can determine the scorch time of the rubber composition, which is evaluated according to the above standard by parameter T5 (in the case of a large rotor) (expressed in minutes), and is defined as the time required for the consistency index (expressed in MU) to increase by 5 units above the minimum value of the index measurement.

[0166] It should be remembered that, in a manner known to those skilled in the art, the longer the scorching time, the greater the delay in cross-linking of the material before curing.

[0167] · Mooney Plasticity

[0168] An oscillating consistency meter as described in French Standard NF T 43-005 (1991) was used. Mooney plasticity was measured according to the following principle: the unprocessed composition (i.e., before curing) was molded in a cylindrical chamber heated to 100°C. After one minute of preheating, a rotor was rotated inside the specimen at 2 revolutions per minute, and the working torque used to maintain this motion was measured after 4 minutes of rotation. Mooney plasticity (ML 1+4) is expressed in Mooney units (MU, 1 MU = 0.83 N·m).

[0169] It should be remembered that, in a manner known to those skilled in the art, the lower the Mooney plasticity, the easier the material is to process. Of course, below a certain value (e.g., 20 MU), the material becomes too fluid to be used, especially for manufacturing inner layers.

[0170] · Dynamic properties

[0171] According to standard ASTM D 5992-96, the dynamic property G* (2%) was measured on a viscosity analyzer (Metravib VA4000). According to standard ASTM D 1349-99, vulcanized composition samples (4 mm thick, 400 mm cross-section) subjected to simple alternating sinusoidal shear stress at a frequency of 10 Hz were recorded under standard temperature conditions (23 °C) or at different temperatures depending on the specific circumstances. 2 The response of the cylindrical specimen was measured. Strain amplitude scans were performed from 0.1% to 50% (outward cycle) and then from 50% to 1% (backward cycle). The results were used as the complex dynamic shear modulus G*. For the backward cycle, the complex dynamic shear modulus G* (2%) at 2% strain at 40°C is shown.

[0172] It should be remembered that the value returned by G*(2%) at 40℃ represents the stiffness of the material: the larger the G*(2%) at 40℃, the greater the stiffness of the material.

[0173] · Preparation of the composition

[0174] The following tests were conducted as follows: Diene elastomers (excluding the vulcanization system), reinforcing fillers, epoxy resins between 1 phr and 30 phr, and various other components were continuously added to a closed mixer (final fill percentage: approximately 70% by volume) with an initial container temperature of approximately 60°C. Then, thermomechanical processing (non-production stage) was performed in a single step for approximately 3 to 4 minutes until the maximum "discharge" temperature of 165°C was reached.

[0175] The resulting mixture is recovered and cooled, and then the sulfur, sulfenamide accelerator and hardener are introduced into a mixer (homogenizer) at 30°C to mix all the substances (production stage) for an appropriate time (e.g., between 5 and 12 minutes).

[0176] The resulting composition is then calendered in the form of rubber sheets (2 mm to 3 mm thick) or rubber films (for measuring their physical or mechanical properties), or extruded in the form of molded elements.

[0177] · Testing of rubber compositions

[0178] Six rubber compositions were prepared as described above. Five of them do not conform to the present invention (hereinafter referred to as C.1 to C.5), and one conforms to the present invention (C.6). Table 1 below summarizes their formulations (in phr) and properties.

[0179] Except for control composition C.1, none of the compositions shown in Table 1 formaldehyde is formed during curing.

[0180] Compositions C.2 to C.6 comprise an epoxy resin and a polyamine-containing curing agent, replacing the phenol / formaldehyde resin / HMT curing agent pair present in the conventional control composition C.1.

[0181] Results based on scorch time and G* (2%) are expressed as 100 relative to control composition C.1. Mooney plasticity results are expressed as absolute values.

[0182] Table 1

[0183] NR(1) 100 100 100 100 100 100 Carbon black (2) 70 70 70 70 70 70 ZnO(3) 3 3 3 3 3 3 6PPD(4) 2.5 2.5 2.5 2.5 2.5 2.5 Stearic acid (5) 2 2 2 2 2 2 sulfur 3 3 3 3 3 3 CBS(6) 2 2 2 2 2 2 Phenol / formaldehyde resin (7) 12 - - - - - HMT(8) 4 - - - - - Epoxy resin (9) - 12 12 12 12 12 Control hardener (10) - 4 - - - - Control hardener (11) - - 4 - - - Control hardener (12) - - - 4 - - Control hardener (13) - - - - 4 - Hardener (14) 4 Scorching time 100 51 145 125 152 135 Mooney Plasticity (MU) 46 77 62 31 38 43 G*(2%) at 40℃ return 100 109 101 98 86 113

[0184] (1) Natural rubber;

[0185] (2) Carbon black N326 (named according to standard ASTM D-1765)

[0186] (3) Zinc oxide (industrial grade - Umicore)

[0187] (4) N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine (Santoflex 6-PPD from Flexsys)

[0188] (5) Stearin (Pristerene 4931 from Uniqema)

[0189] (6) N-Cyclohexylbenzothiazole sulfenamide (Santocure CBS from Flexsys)

[0190] (7) Phenol / formaldehyde linear phenolic resin (Peracit 4536K from Perstorp)

[0191] (8) Hexamethylenetetramine (from Degussa)

[0192] (9) Epoxy resin (DEN 439 from Uniqema)

[0193] (10) 1,3-bis(aminomethyl)cyclohexane (from Sigma-Aldrich)

[0194] (11) m-phenylenediamine from Sigma-Aldrich

[0195] (12) Lonzacure MDEA from Lonza

[0196] (13) Lonzacure MCDEA from Lonza

[0197] (14) Trimethylene bis(4-aminobenzoate) (from Air Products' Versalink 740M)

[0198] It is noted that, compared to the phenol / formaldehyde resin / HMT hardener pair of control composition C.1, the epoxy resin and the aminobenzoate derivative corresponding to formula (I) used in composition C.6 according to the present invention can achieve improved Mooney plasticity and extended scorch time.

[0199] Composition C.6 according to the invention has improved stiffness without compromising properties in the unprocessed state (Mooney plasticity and scorch time), demonstrating that the use of aminobenzoic acid ester derivatives corresponding to formula (I) in the compositions of the invention can yield rubber compositions with a processability / stiffness trade-off that is far greater than that of conventional compositions or compositions including other amine-containing curing agents (not according to the invention).

[0200] The test shows that the rubber composition can be used particularly for internal mixtures, such as carcass ply, crown ply, bead filler, crown underlayer, decoupled layer or tread underlayer, especially carcass ply, crown ply, bead filler, crown underlayer, decoupled layer or tread underlayer (areas requiring high stiffness and low strain).

Claims

1. A rubber composition, said rubber composition being based at least on: - Diene elastomers from 50 phr to 100 phr - Reinforcing filler, said reinforcing filler comprising 50 phr to 80 phr of carbon black, - A crosslinking system comprising sulfur between 1 phr and 10 phr and a vulcanization accelerator between 0.5 phr and 5.0 phr. - 10 to 25 phr epoxy resin, and - Aminobenzoate derivatives of 3 phr to 5 phr, said aminobenzoate derivatives corresponding to formula (VII): (VII)。 2. The rubber composition according to claim 1, wherein, The epoxy resin is selected from aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins.

3. The rubber composition according to claim 2, wherein, The epoxy resin is selected from epoxy cresol formaldehyde phenolic resin.

4. The rubber composition according to claim 1, wherein, The epoxy resin content is between 15 phr and 20 phr.

5. Finished or semi-finished rubber products, wherein the finished or semi-finished rubber products comprise the rubber composition according to any one of claims 1 to 4.

6. A tire comprising a rubber composition according to any one of claims 1 to 4, or comprising a finished or semi-finished rubber article according to claim 5.

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