Diene rubber composition containing polynitrone

Abstract

JPEG2025519759000021.jpg41135 The present invention relates to a rubber composition containing a diene elastomer, a reinforcing filler, and a compound of formula (I) or (II) (wherein n is an integer from 2 to 4, n' is an integer from 1 to 3, m is an integer of 2 or more, R 1 is a group of valence m connecting the furan aromatic ring of the compound of formula (II), and R 2 is a hydrocarbon group which can be separated by one or more heteroatoms).

Description

【Technical Field】 【0001】 The field of the present invention is a diene rubber composition reinforced with a filler, which can be used in particular for the manufacture of vehicle tires. 【Background Art】 【0002】 It is known to crosslink diene elastomers in rubber compositions in order to impart to the rubber compositions the elastic, rigid and reinforcing properties desired by the envisaged applications. The use of vulcanization in diene rubber compositions for tires has been a convention for many years. Also, in diene rubber compositions for tires, the use of crosslinking agents other than sulfur, such as polynitrones, has been proposed. For example, JP-A-2007-070439 teaches the addition of aromatic dinitrones, the compound diphenyl-p-phenylenedinitrone or the compound dimethyl-p-phenylenedinitrone to a diene rubber composition reinforced with carbon black for the purpose of improving the curing and fatigue properties of the rubber composition. JP-A-2015-098591 also describes the addition of an aromatic dinitrone, such as the compound N,N'-[benzene-1,4-diylidene]bis(N-phenylamine oxide), to a diene rubber composition reinforced with silica for the purpose of improving its properties at break. WO2015052131A1 proposes to replace in a rubber composition the vulcanization system conventionally used, which consists of sulfur, a primary or secondary accelerator, and a vulcanization activator, and which is relatively complex due to the number of its components, with a single compound dinitrone, such as the compound N,N'-[benzene-1,3-diylidene]bis(N-phenylamine oxide). 【Summary of the Invention】 【0003】 The applicant has discovered that the use of a specific group of aromatic polynitrones in a diene rubber composition reinforced with a filler makes it possible to further improve the mechanical properties, in particular the tensile properties, and the dynamic properties, the drawbacks in these properties. The polynitrones useful for the requirements of the present invention each contain at least two carbon atoms, each of which is a component of a separate nitrone dipole, whether separated or not, and each of which is included in a covalent bond with a carbon atom of a furan aromatic ring. Accordingly, a first subject of the present invention is a rubber composition comprising a diene elastomer, a reinforcing filler and a compound of formula (I) or (II): 【Chemical formula】 (wherein, n is an integer in the range of 2 to 4, n' is an integer in the range of 1 to 3, m is an integer of 2 or more, R 1 is a group of valence m connecting the furan aromatic rings of the compounds of formula (II), R 2 is a hydrocarbon group which can be separated by one or more heteroatoms) and a rubber composition containing the same. Another subject of the present invention is a tire containing the rubber composition according to the present invention. 【Mode for Carrying Out the Invention】 【0004】 Any interval of values indicated by the expression "between a and b" represents a range of values greater than "a" and less than "b" (i.e., the limiting values a and b are excluded), while any interval of values indicated by the expression "a to b" means a range of values extending from "a" to "b" (i.e., including the exact limits a and b). The abbreviation "phr" means parts by mass per 100 parts of elastomer (when several elastomers are present, of the total elastomers). The compounds mentioned in the description can be of fossil origin or can be bio-based. In the latter case, the compounds can be partially or fully derived from biomass or can be obtained from renewable starting materials that are partially or fully derived from biomass. Similarly, the compounds mentioned can also originate from the recycling of used materials, i.e., they can be partially or fully derived from the recycling process or, if not, can be obtained partially or fully from starting materials that themselves are derived from the recycling process. 【0005】 The term "diene elastomer" should be understood to mean an elastomer containing diene monomer units, in particular conjugated dienes, and in particular 1,3-diene monomer units. The term "diene monomer unit" is understood to mean any unit that is the result of the insertion of a diene into the polymer chain and that contains a carbon-carbon double bond. In the present invention, the term "tire" is understood to mean a pneumatic or non-pneumatic tire. A pneumatic tire generally consists of two beads intended to come into contact with a rim, a crown composed of at least one crown reinforcement and a tread, and two sidewalls, and the tire is reinforced by a carcass reinforcement fixed to the two beads. A non-pneumatic tire, on the other hand, generally includes, for example, a base designed to ride on a hard rim, a crown reinforcement ensuring connection to the tread, and a deformable structure such as spokes, ribs or cells, which is arranged between the base and the crown. Such a non-pneumatic tire does not necessarily include sidewalls. Non-pneumatic tires are described, for example, in documents WO03 / 018332 and FR2898077. According to any one embodiment of the present invention, the tire according to the present invention is preferably a pneumatic tire. 【0006】 The diene elastomers useful for the requirements of the present invention are (a) any homopolymer of a conjugated or non-conjugated diene monomer having from 4 to 24 carbon atoms, (b) Any copolymer of a conjugated or non-conjugated diene having 4 to 24 carbon atoms and at least one other monomer may be. The term "copolymer of a conjugated or non-conjugated diene having 4 to 24 carbon atoms and at least one other monomer" should be understood to mean a copolymer of a diene and one or more other monomers. As with other monomers, mention can be made of conjugated or non-conjugated dienes other than ethylene, olefins and the first diene. 【0007】 Suitable conjugated dienes are conjugated dienes having 4 to 24 carbon atoms, especially 1,3-dienes having 4 to 12 carbon atoms, such as in particular 1,3-butadiene and isoprene, or furthermore 1,3-dienes of the formula CH2=CR-CH=CH2 (wherein R represents a hydrocarbon chain having 3 to 20 carbon atoms), such as linear monoterpenes (C 10 H 16 ), such as myrcene, linear sesquiterpenes (C 15 H 24 ), such as farnesene, etc. More specifically, suitable conjugated dienes are 1,3-butadiene, isoprene, myrcene and farnesene. Suitable non-conjugated dienes are non-conjugated dienes having 6 to 12 carbon atoms, such as 1,4-hexadiene, ethylidene norbornene or dicyclopentadiene. Suitable olefins are vinyl aromatic compounds having 8 to 20 carbon atoms and aliphatic α-monoolefins having 3 to 12 carbon atoms. 【0008】 Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta- or para-methylstyrene, the commercial mixture "vinyltoluene" or para-(tert-butyl)styrene. Suitable aliphatic α-monoolefins are in particular acyclic aliphatic α-monoolefins having 3 to 18 carbon atoms. More specifically, the diene elastomer is (a’) Any homopolymer of a conjugated diene monomer, in particular any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms, (b’) Any copolymer obtained by copolymerization of one or more conjugated dienes with one or more vinyl aromatic compound monomers having 8 to 20 carbon atoms, (c’) Any copolymer obtained by copolymerization of ethylene with one or more conjugated dienes is. Preferably, the diene elastomer is selected from the group of elastomers consisting of 1,3-butadiene homopolymer, isoprene homopolymer, 1,3-butadiene copolymer, isoprene copolymer, and mixtures thereof. 【0009】 Another feature of the rubber composition according to the present invention is that it contains a reinforcing filler. The total content of the reinforcing filler in the rubber composition is preferably 20 phr or more and 200 phr or less, particularly preferably 25 phr or more and 160 phr or less. The total content of the reinforcing filler is adjusted by those skilled in the art as a function of the amount of the rubber composition used. The rubber composition can include any type of "reinforcing" filler known to be able to reinforce rubber compositions, particularly those used in tire preparation, reinforcing inorganic fillers such as carbon black, silica, or even a mixture of these two types of fillers. The reinforcing filler preferably includes carbon black, silica, or a mixture of carbon black and silica. Suitable as carbon black are all carbon blacks, especially those conventionally used in tires or tire treads. Among the latter, more specifically, reinforcing carbon blacks of the 100, 200, and 300 series, or carbon blacks of the 500, 600, or 700 series (ASTM D-1765-2017 grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772 carbon blacks, etc., are mentioned. These carbon blacks can be used in the isolated state as commercially available, or in any other form, for example, as an aid to some rubber additives used. As the carbon black, one kind of carbon black or a mixture of carbon blacks can be used. 【0010】 In this patent application, the term "reinforcing inorganic filler" is defined as any inorganic or mineral filler, regardless of its color and origin (natural or synthetic), and is even referred to as "white filler", "transparent filler", actually "non-black filler". In contrast to carbon black, it is capable of reinforcing the rubber composition intended for tire manufacturing alone, without means other than intermediate coupling agents. In other words, it should be understood that in its reinforcing role, it can replace conventional tire-grade carbon black. Such fillers are generally characterized as known by the presence of hydroxyl (-OH) groups on their surface. Siliceous type mineral fillers, preferably silica (SiO2), are particularly suitable as reinforcing inorganic fillers. The silica used is any reinforcing silica known to those skilled in the art, especially those with a BET specific surface area and a CTAB specific surface area both less than 450 m 2 / g, preferably 30 - 400 m 2 / g, especially 60 - 300 m 2It can be any precipitated silica or fumed silica that indicates the specific surface area per g. Any kind of precipitated silica, especially highly dispersed precipitated silica (HDS), can be used. These precipitated silicas are either highly dispersible or not highly dispersible and are well-known to those skilled in the art. For example, reference can be made to the silicas described in application WO03 / 016215-A1 and WO03 / 016387-A1. In this description, the BET specific surface area is determined by a known method of gas adsorption using the Brunauer-Emmett-Teller method described in The Journal of the American Chemical Society, Vol. 60, page 309, February 1938, and more specifically in accordance with the French standard NF ISO9277 of December 1996 (multi-point (5-point) volume method, gas: nitrogen, degassing: 1 hour at 160 °C, relative pressure p / p0 range: 0.05 - 0.17). The CTAB specific surface area is the external surface area and is determined in accordance with the French standard NF T45-007 (method B) of November 1987. 【0011】 To couple the silica to the diene elastomer, at least a bifunctional coupling agent (or binder) can be used in a known method, which is intended to provide a sufficient connection of the chemical and / or physical properties between the silica (the surface of its particles) and the elastomer. In particular, organosilanes or polyorganosiloxanes that are at least bifunctional are used. Preferentially, the organosilane is selected from the group consisting of polysulfide organosilanes (symmetric or asymmetric), for example abbreviated as TESPT and consisting of bis(3-triethoxysilylpropyl)tetrasulfide sold by Evonik under the name Si69. As another essential feature, the rubber composition is characterized by containing a polynitrone which is a compound of formula (I) or (II), preferably formula (I). 【Chemical formula】 (In the formula, n is an integer in the range of 2 to 4, n' is an integer in the range of 1 to 3, m is an integer of 2 or more, R 1 is a group of valence m that connects the furan aromatic ring of the compound of formula (II), R 2 is a hydrocarbon group that can be separated by one or more heteroatoms) 【0012】 Preferably, R 1 is a hydrocarbon group that can be separated by one or more heteroatoms, such as oxygen, sulfur, silicon or nitrogen. R 1 can be an aliphatic group containing 1 to 25 carbon atoms, or an aromatic group containing 6 to 25 carbon atoms. Preferably, R 1 is a saturated aliphatic group. R 1 When is a saturated aliphatic group, R 1 can be linear, cyclic or branched. According to the first alternative form, R 1 is an alkanediyl group of the formula -C y H 2y -(y is an integer in the range of 1 to 6, preferably 1 to 3). According to the second alternative form, R 1 is an alkanediyl group separated by one or more oxygen atoms of the formula -(C x H 2x -O) p -C x H 2x -(x is an integer in the range of 1 to 6, preferably 1 to 3, and p is an integer of 1 or more, preferably equal to 1 or 2). 【0013】 R 2 can be an aliphatic group containing 1 to 25 carbon atoms, or an aromatic group containing 6 to 25 carbon atoms. Preferably, R 2 is selected from an alkyl group, an aralkyl group, an alkylaryl group and an aryl group that are linear, branched or cyclic. In formula (I), n is preferably equal to 2. In formula (II), m is preferably equal to 2 and n' is equal to 1. According to the first alternative form, m is equal to 2 and R 1 is of the formula -C y H 2y-(where y is an integer in the range of 1 to 6, preferably 1 to 3) is an alkanediyl group. According to a second alternative form, m is equal to 2, and R 1 is of the formula -(C x H 2x -O) p -C x H 2x -(where x is an integer in the range of 1 to 6, preferably 1 to 3, and p is an integer of 1 or more, preferably equal to 1 or 2, more preferably equal to 1) is an alkanediyl group separated by one or more oxygen atoms. Particularly specifically suitable as the compound of formula (I) is a compound in which n is equal to 2 and R 2 is methyl or phenyl, more specifically, the compound of formula (III), N,N'-[2,5-furandiyl dimethylidine] bis(N-phenylamine oxide). 【Chemical formula】 Particularly specifically suitable as the compound of formula (II) is a compound in which m is equal to 2, n' is equal to 1, R 2 is methyl or phenyl, and R 1 is an alkanediyl group of the formula -C y H 2y -(where y is an integer in the range of 1 to 3), or a group of the formula -(C x H 2x -O) p -C x H 2x -(where x is an integer in the range of 1 to 3 and p is equal to 1), more specifically, the compound of formula (IV), N,N'-[oxybis(methylene-5,2-furandiyl methylidine)] bis(N-phenylamine oxide)]. 【0014】 【Chemical formula】 【0015】 According to any one embodiment of the present invention, the polynitrone is preferably of formula (III). Polynitrone can be synthesized according to a well-known synthesis method that synthesizes nitrone as a result of adding a reactant, which is hydroxylamine, to a substrate, which is an aldehyde. In the case of synthesizing polynitrone useful for the requirements of the present invention, the reactant is R 2 a hydroxylamine substituted by a 2 group, and the substrate is a compound containing at least two aldehyde functional groups covalently bonded to the carbon atoms of the furan aromatic ring. The polynitrone compound of formula (I) or (II) is useful for the requirements of the present invention as a crosslinking agent and constitutes a crosslinking system of the rubber composition. According to the present invention, the rubber composition contains a crosslinking agent that is a compound of formula (I) or a mixture of compounds of formula (I), a compound of formula (II) or a mixture of compounds of formula (II), or otherwise, a mixture of at least one compound of formula (I) and at least one compound of formula (II). The molar content of the compound of formula (I) or (II) in the rubber composition is adjusted by those skilled in the art according to the level of stiffness required for the rubber composition by the intended application, regardless of whether it is a single polynitrone compound or a mixture of polynitrones that is useful for the requirements of the present invention. The molar content is preferably 0.01 mol% to 10 mol%, more preferably 0.05 mol% to 2 mol% of the diene elastomer structural units. 【0016】 The rubber composition may additionally contain sulfur in the form of molecular sulfur or a sulfur donor, a vulcanization accelerator, and a vulcanization activator in its crosslinking system. Sulfur molecules (S8), sulfur donors, vulcanization accelerators, and vulcanization activators are compounds well known to those skilled in the field of diene rubber compositions and are as described in the literature "Compounding and Vulcanization" by R. Rajesh Babu et al., published in Advances in Elastomer I, Advanced Structured Materials, 11, published by Springer-Verlag Berlin Heidelberg, 2013, pages 83 - 135. They constitute a vulcanization system conventionally used, for example, in diene rubber compositions for tires. The use of the polynitrone of formula (I) or formula (II) in a diene rubber composition reinforced with a filler has the advantage that it is possible to reduce the proportion of the vulcanization system in the crosslinking system of the rubber composition according to the invention and even to dispense with the use of the vulcanization system in the rubber composition according to the invention. Since the vulcanization system generally contains at least three raw materials of sulfur or a sulfur donor, a vulcanization accelerator and a vulcanization activator, the use of polynitrone in the rubber composition can simplify the formulation of the rubber composition by simply replacing the vulcanization system with a single compound, polynitrone. According to any one embodiment of the present invention, the rubber composition according to the invention preferably has a sulfur content of less than 1 phr, regardless of whether it is sourced from the molecular source (S8) or a sulfur donor. Advantageously, according to any one embodiment of the present invention, the rubber composition contains no sulfur, regardless of whether it is sourced from the molecular source (S8) or a sulfur donor. 【0017】 The rubber composition according to the invention can also contain all or some of the usual additives conventionally used in elastomeric compositions intended to form finished rubber products, such as tires, for example plasticizers or extender oils, pigments, protective agents such as antiozonant waxes, chemical antiozonants or antioxidants, or antifatigue agents. The rubber composition according to the invention is produced using two successive preparation phases known to those skilled in the art with a suitable mixer: a first phase of thermomechanical work or kneading at a high temperature between a maximum temperature of 130 °C and 200 °C ("non-productive" phase), followed by a second phase of mechanical work at a lower temperature, typically below 110 °C, for example between 40 °C and 100 °C, during which the crosslinking system is incorporated in the finishing phase. 【0018】 The rubber composition can be calendered or extruded, especially for property evaluation in a laboratory, in the form of a sheet or plate, or in the form of a rubber semi-finished product (or profile element) that can be used in a tire. The composition can be in either the raw state (before crosslinking) or the cured state (after crosslinking), can form all or part of a semi-finished product, and is especially intended for use in pneumatic or non-pneumatic tires. Crosslinking is generally carried out at a temperature between 100 °C and 200 °C, preferably between 120 °C and 180 °C, for a sufficient time that can vary as a function of the curing temperature of the composition under consideration, for example, between 5 minutes and 90 minutes. Generally speaking, the present invention is preferably implemented according to any one of the following Embodiments 1 to 20. 【0019】 Embodiment 1: A rubber composition comprising a diene elastomer, a reinforcing filler, and a compound of formula (I) or (II). 【Chemical formula】 (In the formula, n is an integer in the range of 2 to 4, n’ is an integer in the range of 1 to 3, m is an integer of 2 or more, R 1 is a group of valence m that connects the furan aromatic ring of the compound of formula (II), R 2 is a hydrocarbon group that can be separated by one or more heteroatoms) Embodiment 2: The rubber composition according to Embodiment 1, wherein R 1 is a hydrocarbon group that can be separated by one or more heteroatoms. 【0020】 Embodiment 3: The rubber composition according to Embodiment 1 or 2, wherein R 1 is a saturated aliphatic group. Embodiment 4: R 1 is an alkanediyl group of the formula -C y H 2y -(where y is an integer in the range of 1 to 6), or a group of the formula -(C x H 2x -O)p -C x H 2x -(where x is an integer in the range of 1 to 6 and p is an integer of 1 or more), an alkane diyl group separated by one or more oxygen atoms, the rubber composition according to any one of Embodiments 1 to 3. Embodiment 5: The rubber composition according to Embodiment 4, wherein y is in the range of 1 to 3. Embodiment 6: The rubber composition according to Embodiment 4 or 5, wherein x is in the range of 1 to 3. Embodiment 7: The rubber composition according to any one of Embodiments 4 to 6, wherein p is equal to 1 or 2. Embodiment 8: R 2 is an alkyl group, an aralkyl group, an alkylaryl group, or an aryl group selected from a linear, branched, or cyclic group, the rubber composition according to any one of Embodiments 1 to 7. Embodiment 9: The rubber composition according to any one of Embodiments 1 to 8, wherein n is equal to 2 in formula (I). Embodiment 10: In formula (I), n is equal to 2, and R 2 is methyl or phenyl, the rubber composition according to any one of Embodiments 1 to 9. 【0021】 Embodiment 11: The rubber composition according to any one of Embodiments 1 to 10, wherein the compound of formula (I) is the compound N,N’-[2,5-furandiyl dimethylidine] bis(N-phenylamine oxide) of formula (III). 【Chemical formula】 【0022】 Embodiment 12: The rubber composition according to any one of Embodiments 1 to 11, wherein m is equal to 2 and n’ is equal to 1 in formula (II). Embodiment 13: m is equal to 2, n’ is equal to 1, and R in formula (II) 2 is methyl or phenyl, and R 1 is of the formula -C y H 2y -(where y is an integer in the range of 1 to 3), an alkane diyl group, or the formula -(C x H 2x-O) p -C x H 2x - (where x is an integer in the range of 1 to 3 and p is equal to 1), the rubber composition according to any one of Embodiments 1 to 12. Embodiment 14: The rubber composition according to any one of Embodiments 1 to 13, wherein the compound of formula (II) is N,N'-[oxybis(methylene-5,2-furandiylmethylene)]bis(N-phenylamine oxide) of formula (IV). 【Chemical formula】 【0023】 Embodiment 15: The rubber composition according to any one of Embodiments 1 to 14, wherein the molar content of the compound of formula (I) or (II) is 0.01 mol% to 10 mol% of the diene elastomer structural unit. Embodiment 16: The rubber composition according to any one of Embodiments 1 to 15, wherein the molar content of the compound of formula (I) or (II) is 0.05 mol% to 2 mol% of the diene elastomer structural unit. Embodiment 17: The rubber composition according to any one of Embodiments 1 to 16, wherein the reinforcing filler contains carbon black, silica, or a mixture of carbon black and silica. Embodiment 18: The rubber composition according to any one of Embodiments 1 to 17, wherein the diene elastomer is selected from the group of elastomers consisting of 1,3-butadiene homopolymer, isoprene homopolymer, 1,3-butadiene copolymer, isoprene copolymer, and mixtures thereof. Embodiment 19: The rubber composition according to any one of Embodiments 1 to 18, wherein the compound is of formula (I). 【0024】 Embodiment 20: A tire containing the rubber composition defined in any one of Embodiments 1 to 19. A better understanding of the present invention, as well as of other things, is obtained by reading the description of the following several practical examples of the present invention, which are given by way of illustration and without limitation. 【Examples】 【0025】 Dynamic properties: The dynamic property tanδ(max) is measured with a viscoanalyzer (Metravib VA4000) in accordance with ASTM D5992-96. A vulcanizate sample (cylindrical test piece having a thickness of 4 mm and a cross-sectional area of 400 mm 2 is subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz and 60 °C, and the response is recorded. The strain amplitude sweep is carried out from 0.1% to 100% (outward cycle), and then from 100% to 0.1% (return cycle). The results used are the loss coefficient tanδ and the shear elastic modulus G * shown at strains of 0.1% and 100%. For the return cycle, the maximum value of tanδ, indicated by tanδ max, is observed, and the difference in the shear elastic modulus indicated by ΔG * is shown. The results are expressed on a base 100. In the case of tanδ max, a result smaller than 100 indicates a decrease in the target value, i.e., a decrease in hysteresis, and conversely, a result larger than 100 indicates an increase in the target value. For ΔG * , a result smaller than 100 indicates a decrease in the target value, i.e., a decrease in non-linearity (Payne effect), and conversely, a result larger than 100 indicates an increase in the target value. 【0026】 Tensile test: Tensile testing makes it possible to determine the elastic stress and the characteristics at break. Unless otherwise indicated, the test is carried out at a tensile speed of 500 mm / min using H2 type test specimens in accordance with the French standard NF T 46-002 of September 1988. By processing the tensile record, it is also possible to plot the modulus curve as a function of elongation, where the modulus used here is the nominal (or apparent) secant modulus calculated by measuring at the first elongation and scaling to the starting cross-sectional area of the test specimen. The nominal secant modulus (or apparent stress, MPa) is measured at the first elongation which is 100% and 300% elongation at 23°C ± 2°C, and is denoted by MSA100 and MSA300 respectively. The breaking stress (MPa) and elongation at break (%) are also measured. The results are expressed at base 100. Values greater than 100 indicate improved results. Preparation of polynitrone: Polynitrone 1: According to the procedure described in JP 2007-070439, the compound N,N’-[benzene-1,4-diylbis(methylene)]bis(N-methylamine oxide) (CAS number 63418-55-3) is prepared. 【Chemical formula】 【0027】 Polynitrone 2: According to the procedure described in JP 2007-070439, the compound N,N’-[benzene-1,4-diylbis(methylene)]bis(N-phenylamine oxide) (CAS number 1586-93-2) is prepared. 【Chemical formula】 Polynitrone 3: According to the procedure described in WO2009136920, the compound N,N’-[benzene-1,3-diylbis(methylene)]bis(N-methylamine oxide) (CAS number 1161001-51-9) is prepared. 【Chemical formula】 【0028】 Polynitrone 4: According to the procedure described in Document WO2015052131, prepare the compound N,N’-[benzene-1,3-diylbis(methylene)]bis(N-phenylamine oxide) (CAS number 15351-52-7). 【Chem.】 Polynitrone 5: According to the procedure described in Document US Patent Application Publication No. 2009 / 0082580, prepare the compound N,N’-[2,5-thiophenediylbis(methylene)]bis(N-phenylamine oxide) (CAS number 1134370-29-8). 【Chem.】 Polynitrone 6: According to the procedure described in the paper Journal of Molecular Structure (2010), 977(1-3), 175-179, prepare the compound N,N’-[2,5-furandiylbis(methylene)]bis(N-phenylamine oxide) (CAS number 1251471-39-2). 【Chem.】 【0029】 Polynitrone 7: According to the following reaction scheme and the following procedure, prepare bisnitrone B (N,N′-[oxybis(methylene-5,2-furandiylmethylene)]bis(N-phenylamine oxide)). 【Chem.】 The compound 5,5’-(oxybis(methylene))bis(furan-2-carbaldehyde) is described in the literature and can be synthesized, for example, according to Angew. Chem. Int. Ed., 2016, 55, 8338-8342 and Chem. Asian J., 2017, 12, 2652-2655. In the second step, N-phenylhydroxylamine (3.02 g, 27.7 mmol) is added to a suspension of 5,5'-(oxybis(methylene))bis(furan-2-carbaldehyde) (2.95 g, 12.6 mmol) in absolute ethanol (50 ml). The reaction mixture is then stirred at 20 °C for 16 - 17 h, and then diluted with petroleum ether (40 ml). After vigorously stirring for 10 - 12 min at ambient temperature (AT), the resulting precipitate is filtered, washed successively with methyl tert-butyl ether (2 × 10 ml) and petroleum ether (2 × 10 ml), and then dried. A brown solid (3.928 g, 9.43 mmol) with a molar purity of 98% (NMR) is obtained in a yield of 75%. 1 H and 13 The signal assignments in the NMR of H and C are listed in the following table. 【0030】 【Chemical formula】 【Table 1】 【0031】 Preparation of the rubber composition: The preparation procedures for compositions C0 and C1 - C7 are as follows: Dien elastomer, reinforcing filler, and then various other raw materials except for the crosslinking system (polynitron compound) or vulcanization system (sulfur and sulfenamide accelerator) are introduced into an internal mixer filled to 70% and with an initial temperature in the container of approximately 90 °C. Then, a thermomechanical operation (non-production phase) is carried out in one step (the total kneading time is approximately equal to 5 min) until a maximum "drop" temperature of approximately 160 °C is reached. The mixture thus obtained is recovered, cooled, and then the crosslinking system (polynitron compound) or vulcanization system (sulfur and sulfenamide accelerator) is added to an external mixer (homofinisher) at 70 °C, and all are mixed for approximately 5 - 6 min (production phase). The thus-obtained compositions C0 and C1 to C7 are subsequently calendered into either a plate shape (2 to 3 mm thick) or a thin rubber sheet for measuring their physical or mechanical properties, or into the form of a profile element so as to be directly usable, for example, as a semi-finished product for a tire, after being cut and / or assembled to the desired dimensions. The test pieces are subsequently placed in a press at a temperature between 170 °C and 180 °C for 30 minutes for the compositions C1 to C6 based on polynitrone, or at a temperature between 150 °C and 160 °C for the composition C0 containing a vulcanization system. 【0032】 The formulations of the rubber compositions C0 and C1 to C7 are shown in Table 1, and the proportions of the raw materials of the rubber compositions are indicated in phr. The content of polynitrone introduced into the compositions C1 to C7 corresponds to a molar content of 0.42% relative to the SBR structural units. The rubber composition C0 is a rubber composition having a vulcanization system conventionally used in rubber compositions for tires as a crosslinking system. 【0033】 All of the rubber compositions C1 to C7 are rubber compositions in which the crosslinking agent is polynitrone. The rubber compositions C1 to C5 are not rubber compositions according to the present invention because they each contain polynitrones 1 to 5 which do not correspond to either of formula (I) and formula (II). The rubber compositions C6 and C7 are rubber compositions according to the present invention because they each contain the polynitrone of formula (I) and the polynitrone of formula (II). The results are shown in Table 2. Among the rubber compositions containing polynitrone, the compositions C6 and C7 are rubber compositions having the lowest tan δ max value and exhibiting the highest secant modulus at 100% and 300%. The use of the composition C6 and the composition C7 brings about an improvement in hysteresis and tensile properties with respect to other polynitrones, as shown through the tan δ max and secant modulus at 23 °C, 100% and 300% respectively. 【0034】 Furthermore, although polynitrone 6 has a furan ring in polynitrone 5 and a thiophene ring in polynitrone 6, which is different from polynitrone 5 only in the properties of the aromatic ring, and polynitrone 7 contains two furan rings instead of one, the use of polynitrone 6 and polynitrone 7 is observed to bring about both a reduction in hysteresis and a reduction in non-linearity in the rubber composition as compared to the use of polynitrone 5. Also, it is found that at both 23°C and 100°C, it is composition C6 that exhibits the fracture properties closest to those of composition C0. Even if the vulcanization system of composition C0 is replaced by the crosslinking system of composition 6, in the case of polynitrone 6, unlike other polynitrones, the tensile properties of the rubber composition are not substantially modified. Crosslinking using a polynitrone having the feature of containing at least two nitrone dipoles directly bonded to a furan aromatic ring has the advantage of most reducing the hysteresis of the rubber composition as compared to crosslinking using a nitrone that does not exhibit this feature. Furthermore, this result can be obtained without substantially modifying the hysteresis and tensile properties of the vulcanized rubber composition when using the polynitrone of formula (I). By replacing the vulcanization system conventionally used in diene rubber compositions with a single compound, namely polynitrone, which is useful for the requirements of the present invention, it becomes possible to significantly simplify the formulation of diene rubber compositions. 【0035】 [Table 2] 【0036】 [Table 3]

Claims

[Claim 1] A rubber composition comprising a diene elastomer, a reinforcing filler, and a compound of formula (I) or (II). 【Chemistry 1】 (In the formula, n is an integer in the range of 2 to 4. n' is an integer in the range of 1 to 3. m is an integer greater than or equal to 2, R 1 is a group with a bond value m that connects the furan aromatic ring of the compound of formula (II), R 2 (A hydrocarbon group that can be separated by one or more heteroatoms) [Claim 2] R 1 The rubber composition according to claim 1, wherein is a saturated aliphatic group. [Claim 3] R 1 is a formula -C y H 2y -(y is an integer in the range of 1 to 6) alkanediyl group, or formula -(C x H 2x -O) p -C x H 2x -(x is an integer in the range of 1 to 6, and p is an integer of 1 or more) alkanediyl group separated by one or more oxygen atoms, the rubber composition according to claim 1. [Claim 4] R 2 The rubber composition according to claim 1, wherein the alkyl group is selected from linear, branched, or cyclic alkyl groups, aralkyl groups, alkylaryl groups, and aryl groups. [Claim 5] The rubber composition according to claim 1, wherein n is equal to 2, m is equal to 2, and n' is equal to 1. [Claim 6] The rubber composition according to claim 1, wherein the molar content of the compound of formula (I) or (II) is 0.01 mol% to 10 mol% of the diene elastomer constituent units. [Claim 7] The rubber composition according to claim 1, wherein the reinforcing filler comprises carbon black, silica, or a mixture of carbon black and silica. [Claim 8] The rubber composition according to claim 1, wherein the diene elastomer is selected from the group consisting of 1,3-butadiene homopolymer, isoprene homopolymer, 1,3-butadiene copolymer, isoprene copolymer, and mixtures thereof. [Claim 9] The rubber composition according to claim 1, wherein the compound is of formula (I). [Claim 10] A tire containing a rubber composition as defined in any one of claims 1 to 9.

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