Urea masterbatch for the additivation of an elastomeric composition

Abstract

The invention relates to a urea masterbatch comprising at least one elastomer, an organic or inorganic filler, water and a urea compound of general formula (R1, R2)N-CO-[(NR5)-R6-(NR7)-CO]n-N(R3, R4) wherein each radical R1, R2, R3 and R4 is independently selected from the group consisting of a hydrogen atom, an alkyl radical having from 1 to 20 carbon atoms, a cycloalkyl radical having from 5 to 24 carbon atoms, an aryl radical having from 6 to 30 carbon atoms and an aralkyl radical having from 7 to 25 carbon atoms, it being possible for the radicals R2 and R3 together to form a ring, each radical R1, R2, R3 and R4 being optionally interrupted with one or more heteroatoms and / or substituted, the radical R6 being a divalent hydrocarbon radical, preferentially being a divalent methylphenyl radical, and n being an integer equal to 0 or 1, the weight ratio of water to organic or inorganic filler in said masterbatch being less than or equal to 2, said masterbatch not comprising a system for crosslinking the elastomer.

Description

[0001]UREA MASTERBATCH FOR ADDITIVATION OF AN ELASTOMERIC COMPOSITION Technical field of the invention The present invention relates to the field of components used for the manufacture of rubber compositions, and more particularly masterbatches comprising at least one urea compound. By urea masterbatch is meant a non-crosslinked rubber composition comprising a high urea content and intended to be used in the manufacture of rubber compositions. Prior art It is known to use in certain parts of tires,rubber compositions having high rigidity during low deformations of the tire as presented in application WO 02 / 10269. Resistance to low deformations is one of the properties that a tire must have to respond to the stresses to which it is subjected. This stiffening can be obtained by increasing the rate of reinforcing filler or by incorporating certain reinforcing resins in the rubber compositions constituting the parts of the tire. Among the numerous solutions developed, mention may be made of rubber compositions comprising a combination of an epoxy resin and a urea compound as presented,for example in document WO2021 / 181032. Urea derivatives can also be used as vulcanization activators for vulcanizable rubber compositions. Document US 5096978, for example, presents the use of substituted ureas for such use. However, urea, which is available in the form of granules, is a difficult compound to disperse homogeneously in elastomeric compositions. It is of course possible to increase the homogenization time or the mixing time, but this is often to the detriment of the rigidity of the final composition, in particular due to the breaking of the elastomeric chains. Continuing its research, the applicant discovered a urea masterbatch formulation allowing good incorporation into elastomeric compositions,thus making it possible to improve the performance of these compositions compared to compositions in which the urea is incorporated according to methods known to those skilled in the art, i.e. in the form of granules. Detailed description of the invention Thus, the invention relates to a urea masterbatch comprising at least one elastomer, an organic or inorganic filler, water and a urea compound of general formula (R1, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) in which each radical R1, R2, R3 and R4 is independently chosen from the group consisting of a hydrogen atom, an alkyl radical having from 1 to 20 carbon atoms, a cycloalkyl radical having from 5 to 24 carbon atoms, an aryl radical having from 6 to 30 carbon atoms and an aralkyl radical having from 7 to 25 carbon atoms, the radicals R2 and R3 together being able to form a cycle, each radical R1, R2, R3 and R4 being optionally interrupted by one or more heteroatoms and / or substituted,the radical R6 being a bivalent hydrocarbon radical, preferably being a bivalent methylphenyl radical, and n being an integer equal to 0 or 1, the mass ratio of water to organic or inorganic filler in said masterbatch being less than or equal to 2, said masterbatch not comprising a crosslinking system for the elastomer. Definitions The compounds comprising carbon mentioned in the description may be of fossil or biosourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This concerns in particular polymers, plasticizers, fillers, etc. Elastomer The urea masterbatch according to the invention comprises at least one elastomer. In a known manner, an elastomer is a polymer which, after crosslinking, has elastic properties. Preferably,the urea masterbatch according to the invention comprises at least one diene elastomer. It can therefore contain a single diene elastomer or a mixture of several diene elastomers. By "diene" elastomer (or indistinctly rubber), whether natural or synthetic, must be understood in a known manner an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not). These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". In general, "essentially unsaturated" means a diene elastomer derived at least in part from conjugated diene monomers,having a rate of units or patterns of diene origin (conjugated dienes) which is greater than 15% (mol %); thus diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins such as EPDM do not fall within the preceding definition and may in particular be described as "essentially saturated" diene elastomers (low or very low rate of patterns of diene origin, always less than 15%). The diene elastomers included in the composition according to the invention are preferably essentially unsaturated. The term "diene elastomer" which may be used in the compositions in accordance with the invention is understood in particular to mean: a) any homopolymer of a diene monomer, conjugated or not, having from 4 to 18 carbon atoms; (b) any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer. The other monomer may be ethylene, an olefin or a diene,conjugated or not. Suitable conjugated dienes are conjugated dienes having 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and isoprene. Suitable olefins are vinylaromatic compounds having 8 to 20 carbon atoms and aliphatic α-monoolefins having 3 to 12 carbon atoms. Suitable vinylaromatic compounds include, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene. Suitable aliphatic α-monoolefins include, in particular, acyclic aliphatic α-monoolefins having 3 to 18 carbon atoms. The urea masterbatch according to the invention preferably comprises at least one essentially unsaturated diene elastomer. Preferably, the urea masterbatch comprises for elastomers at least one elastomer chosen from the group consisting of polybutadienes (BR), natural rubber (NR),synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and blends of these elastomers. Butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR). By "isoprene elastomer" is meant, in a known manner, a homopolymer or a copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), the various isoprene copolymers and blends of these elastomers. Among the isoprene copolymers, mention will be made in particular of isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR) copolymers. This isoprene elastomer is preferably chosen from the group consisting of natural rubber, synthetic cis-1,4 polyisoprenes and their mixtures; among these synthetic polyisoprenes,preferably used are polyisoprenes having a rate (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%. Preferably and according to any of the arrangements herein, the diene elastomer is natural rubber. Very preferably, the urea masterbatch comprises for elastomers at least one elastomer chosen from the group consisting of natural rubber, synthetic polyisoprenes, butadiene-styrene copolymers and mixtures of these elastomers. Very preferably, the urea masterbatch comprises for elastomers a mixture of natural rubber or synthetic polyisoprene and a butadiene-styrene copolymer. It has been observed that the presence of SBR improves the solubilization of urea in the urea masterbatch during the manufacture of the latter. Preferably the level of diene elastomer in the urea masterbatch, preferably isoprene elastomer,preferably natural rubber, is 50 to 100 phr. Preferably, the SBR content in the urea masterbatch ranges from 0 to 50 phr. Filler The urea masterbatch according to the invention comprises an organic or inorganic filler. The presence of a filler in the urea masterbatch according to the invention makes it possible to minimize, or even prevent, the presence of water in the form of inclusion in the masterbatch, such inclusions being able to make it more difficult to incorporate the masterbatch into an elastomeric composition. Any type of filler that can be incorporated into an elastomeric composition may be suitable as an organic or inorganic filler, provided that this filler makes it possible to capture, at least in part, water. Preferably, the organic or inorganic filler is chosen from the group consisting of carbon black, silica, alumina, chalk, clay, bentonite, talc,kaolin and their mixtures. All carbon blacks are suitable as carbon blacks, in particular HAF, ISAF, SAF type blacks conventionally used in tires (so-called tire grade blacks). Among the latter, we will mention in particular the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as for example blacks N115, N134, N234, N326, N330, N339, N347, N375, or, depending on the intended applications, blacks of higher series (for example N660, N683, N772). These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a support for some of the rubber additives used. Carbon blacks could, for example, already be incorporated into an isoprene elastomer in the form of a masterbatch (see, for example, applications WO 97 / 36724 or WO 99 / 16600). Carbon blacks are characterized by different properties,in particular by the specific surface area, and by the oil absorption index of compressed samples (COAN for "Compressed Oil Absorption Number" in English). The COAN of carbon blacks is measured according to the ASTM D3493-16 standard. The BET specific surface area of ​​carbon blacks is measured according to the D6556-10 standard (multipoint method (at least 5 points) - gas: nitrogen - relative pressure range P / P0: 0.1 to 0.3). The physical state in which the inorganic filler is present is indifferent, whether in the form of powder, granules, beads or any other suitable densified form. The inorganic filler is preferably chosen from mineral fillers of the siliceous type, in particular silica (SiO2), or of the aluminous type, in particular alumina (Al2O3), chalk, clay, bentonite, talc, kaolin and mixtures thereof, preferably from silica, chalk, talc, kaolin and mixtures thereof, preferentially from silica, talc,kaolin and mixtures thereof. Very preferably, the inorganic filler is chosen from silica, kaolin and mixtures thereof. The silica used may be any silica known to those skilled in the art, in particular any precipitated or pyrogenic reinforcing silica having a BET surface area and a CTAB specific surface area both less than 450 m, 2 / g, preferably 30 to 400 m 2 / g. As highly dispersible precipitated silicas (called "HDS"), mention may be made, for example, of the silicas "Ultrasil 7000" and "Ultrasil 7005" from the company Degussa, the silicas "Zeosil 1165MP", "1135MP" and "1115MP" from the company Rhodia, the silica "Hi-Sil EZ150G" from the company PPG, the silicas "Zeopol 8715", "8745" and "8755" from the company Huber, the silicas with a high specific surface area as described in application WO 03 / 16837. The BET specific surface area of ​​silica is determined in a known manner by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" Vol.60, page 309, February 1938, more precisely according to the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points) - gas: nitrogen - degassing: 1 hour at 160°C - relative pressure range p / po: 0.05 to 0.17).The CTAB specific surface area of ​​silica is determined according to the French standard NF T 45-007 of November 1987 (method B). In the preferred case where the inorganic filler comprises silica, it preferably has a BET surface area of ​​between 45 and 400 m. 2 / g, more preferably between 60 and 300 m 2 / g. The composition according to the invention preferably does not comprise an inorganic filler-elastomer coupling agent or comprises less than 5% by mass relative to the mass of inorganic filler, preferably less than 2% by mass, more preferably less than 1% by mass relative to the mass of inorganic filler. By "coupling agent" (or "bonding agent") is meant, in a known manner, an agent capable of coupling the inorganic filler to the elastomer. Indeed, what is sought in the organic or inorganic filler is not a reinforcing effect of the urea masterbatch, but its hydrophilic effect. The use of fillers similar to those used in the elastomeric composition into which the urea masterbatch is intended to be incorporated is only a guarantee of increased compatibility when mixing these elements.The urea masterbatch according to the invention preferably comprises from 5 to 80 phr of organic or inorganic filler, preferably from 10 to 75 phr of organic or inorganic filler, these contents making it possible to capture the water present in the urea masterbatch in order to minimize, or even prevent, the presence of water inclusion. Water The urea masterbatch according to the invention comprises water, the mass ratio of water to organic or inorganic filler in said masterbatch being less than or equal to 2. The presence of water makes it possible to ensure greater homogeneity of the distribution of the urea in the urea masterbatch, in particular by facilitating the solubilization of the urea. Preferably, the mass ratio of water to organic or inorganic filler is less than or equal to 1.A water to organic or inorganic filler mass ratio of less than or equal to 2, preferably less than or equal to 1, surprisingly allows better performance to be achieved when the urea masterbatch is incorporated into an elastomeric composition. Preferably, the water content in the urea masterbatch according to the invention ranges from 3 to 50 phr, preferably from 5 to 30 phr. A lower content does not sufficiently improve the dispersion of the urea in the masterbatch, while too high a content increases the risk of water inclusions appearing.Urea The urea masterbatch according to the invention comprises a urea compound of general formula (R1, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) in which each radical R1, R2, R3, R4, R5 and R7 is independently chosen from the group consisting of: ^ a hydrogen atom, ^ an alkyl radical having from 1 to 20 carbon atoms, ^ a cycloalkyl radical having from 5 to 24 carbon atoms, ^ an aryl radical having from 6 to 30 carbon atoms and ^ an aralkyl radical having from 7 to 25 carbon atoms, the radicals R2 and R3 together being able to form a cycle, each radical R1, R2, R3 and R4 being optionally interrupted by one or more heteroatoms and / or substituted, the radical R6 being a bivalent hydrocarbon radical, preferably being a bivalent methylphenyl radical, and n being an integer equal to 0 or 1.By bivalent hydrocarbon radical is meant a bivalent radical consisting of carbon and hydrogen, preferably comprising from 1 to 20 carbon atoms, and more preferably comprising from 1 to 10 carbon atoms. In the case where n is equal to 0, the general formula (R1, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) becomes (R1, R2)N-CO-N(R3, R4). In the case where n is equal to 1, the general formula (R1, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) becomes (R1, R2)N-CO-(NR5)-R6-(NR7)-CO-N(R3, R4). In the general formula, it is understood that the divalent group CO represents a carbon atom linked by a double bond to an oxygen atom, that the group (R1, R2)N (respectively N(R3, R4)) represents a nitrogen atom linked to a group R1 and to a group R2 (respectively R3 and R4) by a covalent bond, that the group (NR5) (respectively (NR7)) represents a nitrogen atom linked to a group R5 (respectively R7).An example of a urea compound in which the radicals R2 and R3 together form a ring is 2-imidazolidinone, or ethyleneurea. Preferably, the radicals do not form a ring together. Preferably, the urea compound is a monourea (therefore n=0), and each radical R1, R2, R3 and R4 is independently selected from the group consisting of hydrogen and a hydrocarbon compound selected from: ^ an alkyl radical having from 1 to 20 carbon atoms, ^ a cycloalkyl radical having from 5 to 24 carbon atoms, ^ an aryl radical having from 6 to 30 carbon atoms and ^ an aralkyl radical having from 7 to 25 carbon atoms, each radical R1, R2, R3 and R4 being optionally substituted. Preferably, each radical R1 and R3 is a hydrogen atom. The urea is then a compound of formula R2-HN-CO-NH-R4. In a preferred arrangement, at least one radical R2 or R4 is an aryl radical having from 6 to 8 carbon atoms, preferably a phenyl radical.Preferably in this preferred arrangement, the urea compound may be an N-phenylurea or 1,3-diphenylurea. In a preferred arrangement, the urea compound is a diurea (therefore n=1) in which the radicals R1, R2, R3 and R4 are methyl radicals, R5 and R7 are the hydrogen atom and R6 is a bivalent methylphenyl radical. An example of such a diurea compound is the compound "Amicure UR2T" from the company Evonik, of formula 1,1'-(4 methyl-m-phenylene) bis(3,3-dimethyl urea). Preferably, the urea compound does not comprise an aromatic ring. Preferably, each radical R1, R2, R3 and R4 is a hydrogen atom. The urea compound is then a compound of formula H2N-CO-NH2 commonly referred to as "urea" or "carbamide".Thus, very preferably, the urea compound is chosen from the compounds urea, N,N'-dimethylurea, ethyleneurea, N-phenylurea, 1,3-diphenylurea, preferably chosen from the compounds urea, N,N'-dimethylurea, N-phenylurea, 1,3-diphenylurea and very preferably chosen from the compounds urea and N,N'-dimethylurea. Very preferably, the urea compound is urea of ​​formula H2N-CO-NH2. The urea content in the urea masterbatch is within a range from 20 to 150 phr, preferably from 30 to 140 phr, very preferably from 80 to 120 phr. Below the minimum indicated, too large a quantity of the other materials constituting the urea masterbatch would be introduced into the elastomeric composition. Beyond these contents, a homogeneous masterbatch allowing good dispersion of urea in the elastomeric composition for which this masterbatch is intended is more difficult to obtain.Crosslinking system The elastomeric compositions comprise a crosslinking system intended to give them, in particular, their elastic properties. The urea masterbatch according to the invention, which is intended to be incorporated into an elastomeric composition, does not comprise an elastomer crosslinking system, i.e. a system capable of crosslinking the elastomer present in the urea masterbatch. In particular, the urea masterbatch does not comprise a crosslinking system known to those skilled in the art, for example a crosslinking system based on sulfur, and / or peroxide and / or bismaleimides. Preferably, the urea masterbatch according to the invention does not comprise sulfur or comprises less than 0.5 phr, preferably less than 0.4 phr, more preferably less than 0.2 phr.Various additives The rubber compositions in accordance with the invention may also comprise all or part of the usual additives and processing agents, known to those skilled in the art and usually used in rubber compositions, in particular for pneumatic tires, such as for example plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents. In particular, the urea masterbatch according to the invention preferably comprises a plasticizer, preferentially chosen from C5-based resins, C9-based resins, process oils, stearic acid, rosin and mixtures of these compounds, preferably chosen from stearic acid, rosin and mixtures of these compounds.By "C5-based" (respectively "C9-based") is meant resins based on compounds comprising 5 carbon atoms (respectively 9). Preferably, the composition according to the invention does not comprise nitrile compounds or comprises less than 10 phr, preferably less than 5 phr, preferably less than 2 phr, very preferably less than 1 phr and even more preferably less than 0.5 phr.Preferably, the urea masterbatch consists of at least one elastomer, an organic or inorganic filler, water and a urea compound of general formula (R1, R2)N-CO-N(R3, R4) in which each radical R1, R2, R3 and R4 is independently chosen from the group consisting of a hydrogen atom, an alkyl radical having from 1 to 20 carbon atoms, a cycloalkyl radical having from 5 to 24 carbon atoms, an aryl radical having from 6 to 30 carbon atoms and an aralkyl radical having from 7 to 25 carbon atoms, the radicals R2 and R3 together being able to form a cycle, each radical R1, R2, R3 and R4 being optionally interrupted by one or more heteroatoms and / or substituted, the mass ratio of water to organic or inorganic filler in said masterbatch being less than or equal to 2, and optionally a plasticizer, all of these compounds being as described above.Rubber composition The invention also relates to a rubber composition based on an elastomer, preferably diene, a reinforcing filler, a crosslinking system, from 1 to 30 parts by weight per hundred parts by weight of elastomer, pce, of epoxy resin and from 1 to 15 pce of a urea compound introduced in the form of a urea masterbatch according to the invention. The epoxy resins that can be used in the present invention include all polyepoxide compounds. They may be, for example, aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. For example, the aromatic epoxy resin may be an amine-aromatic epoxy resin. These resins are preferably novolak epoxy resins, that is to say epoxy resins obtained by acid catalysis, as opposed to resol resins, obtained by basic catalysis.Particularly preferred among the aromatic epoxy compounds are epoxy resins selected from the group consisting of resins of the type 2,2 bis[4-(glycidyloxy)phenyl]propane, poly[(o-cresylglycidyl ether)-co-formaldehyde], poly[(o-phenylglycidyl ether)-co-formaldehyde], poly[(phenylglycidyl ether)-co(hydroxybenzaldehyde glycidyl ether)], tri(glycidoxyphenyl)methane, tetra(glycidoxyphenyl)ethane and mixtures of these resins. By "epoxy resin of the type" is meant resins based on units of the constituent, i.e. comprising this constituent, or oligomers of this constituent. The epoxy resin is a curing resin. By curing resin is meant a resin which, when incorporated into a rubber composition with a curing agent, makes it possible to increase the rigidity of the rubber composition after crosslinking.However, increasing the rigidity of a rubber composition generally goes hand in hand with an increase in hysteretic losses. More preferably, the epoxy resin is chosen from the group consisting of resins of the poly[(o-cresylglycidyl ether)-co-formaldehyde], poly[(o-phenylglycidyl ether)-co-formaldehyde], tri(glycidoxyphenyl)methane, tetra(glycidoxyphenyl)ethane type and mixtures of these resins. Very preferably, the epoxy resin used in the context of the invention is chosen from the epoxy resins of the following generic formula (I) and (II) and their derivatives, i.e. the oligomers of the compounds of generic formula (I) and (II): n being an integer expressing the degree of polymerization, n ranging from 1 to 15, preferably from 1 to 10, more preferably from 1 to 5 and very preferably from 1 to 3.Examples of commercially available epoxy resins that can be used in the context of the present invention include, for example, the epoxy resin "DEN 439" from the company Uniqema, the epoxy resin "Tris(4-hydroxyphenyl)methane triglycidyl ether" from the company Sigma-Aldrich, the araldite cresol novolac epoxy resin "ECN 1299" from the company Huntsman, the araldite phenol novolac epoxy resin "EPN 1138" from the company Huntsman, the resins "EPPN-502H", "EPPN-501H" and "EPPN-501HY" from the company Nippon Kayaku, or the resin "EPON 1031" from the company Hexion. Preferably, the rubber composition according to the invention does not comprise any hardening resins other than an epoxy resin, and in particular does not comprise resins of the formophenolic type. The composition according to the invention comprises between 1 and 30 pce of epoxy resin.Given the amine hardener used in the context of the present invention, below the minimum resin level indicated, the intended technical effect is insufficient, whereas above the maximum indicated, there is a risk of excessively high rigidity increase and excessive penalization of the hysteresis and extensibility properties of the material. For all these reasons, the epoxy resin level is preferably between 10 and 25 phr. More preferably, the epoxy resin level in the composition according to the invention is between 10 and 20 phr. The invention also relates to a method for manufacturing a rubber composition as described above, comprising a step of incorporating a urea compound within the meaning of the present invention into the rubber composition by means of a urea masterbatch according to the invention.Examples Measurement methods Tensile tests The tests were carried out in accordance with French standard NF T 46-002 of September 1988. All tensile measurements were carried out under normal temperature (23±2°C) and hygrometry (50±5% relative humidity) conditions, according to French standard NF T 40-101 (December 1979). The nominal secant modulus calculated by reducing to the initial section of the test piece (or apparent stress, in MPa) at 10% elongation noted MA10, was measured in second elongation (i.e. after accommodation), on samples baked for 60 minutes at 150°C. The results are expressed on a base of 100, the value 100 being assigned to composition C-1. A result greater than 100 indicates that the composition of the example considered has a higher rigidity than the control.The breaking stresses (in MPa) were also measured at 23°C ± 2°C, according to standard NF T 46-002, on raw samples or on samples cooked for 25 minutes at 150°C or 90 minutes at 160°C. The breaking energy is equal to the product of the breaking elongation and the breaking stress. The results are expressed on a base of 100, with the value 100 being assigned to composition C-1. A result greater than 100 indicates that the composition of the example considered has a higher breaking stress than the control. Impact losses The rolling resistance induced by the tested composition is estimated by measuring the energy losses by measuring, at a temperature of 60°C, the energy restored on the eighth rebound of a sample to which an initial energy has been imposed, as described in standard DIN 53-512 of April 2000. This measurement is noted P60 and calculated as follows: P60(%)=100x(E0-E1) / E0, where E0 represents the initial energy and E1 the restored energy.The lower this value, the less hysteretic losses the sample tested exhibits. The values ​​are expressed on a base of 100, the reference being the P60 of composition C-1. A value greater than 100 shows that the impact loss is lower, and therefore that the composition has better rolling resistance properties. The curing is expressed by the t90 value measured in minutes. The t90 value is determined according to the ISO6502 standard of 2018. Production of Urea masterbatches The masterbatches whose compositions are indicated in Table 1 are produced as follows: The diene elastomer, urea, organic or inorganic filler and water are successively introduced into an internal mixer (final filling rate: approximately 75% by volume), whose initial tank temperature is approximately 80 °C.A thermomechanical work (non-productive phase) is then carried out in one step, which lasts a total of approximately 4 to 5 minutes, with work of at least 1.5 minutes above 80°C, until a maximum "drop" temperature of 95°C is reached. The compositions in Table 1 are indicated in pce (part per cent of elastomer) [Table 1]. (1) Natural rubber (2) SBR: Styrene-butadiene rubber with 27% Styrene units, 24% vinyl units and 46% 1-4trans units, Tg: -48°C (3) Silica “165G” from Evonik, BET surface area of ​​approximately 180 m² / g (4) Carbon black N326 (denomination according to ASTM D-1765 standard) (5) Urea from Univar Solutions (6) Rosin from Diamantino Preparation of the compositions The following tests are carried out as follows: the diene elastomer, the reinforcing filler, the epoxy resin, and the various other ingredients, with the exception of the vulcanization system and the hardener. Thermomechanical work (non-productive phase) is then carried out in one step, which lasts a total of approximately 3 to 4 minutes, until a maximum “drop” temperature of 165°C is reached.The mixture thus obtained is recovered, cooled and then sulfur, a sulfenamide type accelerator and either urea in dispersed form (composition C-1) or one of the urea masterbatches manufactured in accordance with the protocol described above are incorporated on a mixer (homo-finisher) at 30°C, mixing everything (productive phase) for an appropriate time (for example between 5 and 12 min). When the urea is introduced in the form of a urea masterbatch, the quantity of masterbatch added is adjusted so as to obtain the quantity of urea compound in the composition. The compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin rubber sheets for the measurement of their physical or mechanical properties, or extruded in the form of a profile. The crosslinking of the composition is carried out at a temperature of 160°C, for 15 min under pressure.The reference composition is the rubber composition C-1 used as reference in document WO 2021 / 181032: [Table 2]. Contents in pce (1) Natural Rubber; (2) Carbon black N326 (designation according to ASTM D-1765 standard) (3) Zinc oxide (industrial grade – Umicore company) (4) N-1,3-dimethylbutyl-N-phenylparaphenylenediamine (Santoflex 6-PPD from Flexsys company) (5) Stearin (“Pristerene 4931” from Uniqema company) (6) N-cyclohexyl-benzothiazyl sulphenamide (Santocure CBS from Flexsys company) (7) Epoxy phenol novolac resin (“EPN 1138” from Huntsman company) The different compositions C-1 to C-13 are obtained by adding urea to the formulation presented in Table 2 either in dispersed form (composition C-1) or in the form of a urea masterbatch so as to obtain a urea content in each composition of 2 pce. For each composition, the mass percentage of urea masterbatch added is indicated in relation to the mass of the mixture without urea presented in table 2 so as to obtain 2 pce of urea in the manufactured composition.Table 3 presents the compositions C-1 to C-13 and the results obtained. [Table 3]. It is observed that the compositions in accordance with the invention have better rigidities and hysteretic performances than the non-compliant compositions, and in particular the reference composition C-1. The compositions in accordance with the invention also have better cures and excellent breaking stress properties.

Claims

CLAIMS

1. Urea masterbatch comprising at least one elastomer, an organic or inorganic filler, water and a urea compound of general formula (R1, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) in which each radical R1, R2, R3 and R4 is independently chosen from the group consisting of a hydrogen atom, an alkyl radical having from 1 to 20 carbon atoms, a cycloalkyl radical having from 5 to 24 carbon atoms, an aryl radical having from 6 to 30 carbon atoms and an aralkyl radical having from 7 to 25 carbon atoms, the radicals R2 and R3 together being able to form a cycle, each radical R1, R2, R3, R4, R5 and R7 being optionally interrupted by one or more heteroatoms and / or substituted, the radical R6 being a hydrocarbon radical bivalent, preferably being a bivalent methylphenyl radical, and n being an integer equal to 0 or 1, the mass ratio of water to organic or inorganic charge in said masterbatch being less than or equal to 2,said masterbatch not comprising an elastomer crosslinking system, the content of urea compound in the mixture being within a range from 20 to 150 phr.

2. Urea masterbatch according to claim 1 wherein the water / filler mass ratio is less than or equal to 1.

3. Urea masterbatch according to any one of the preceding claims also comprising a plasticizer, preferably chosen from C5-based resins, C9-based resins, process oils, stearic acid, rosin and mixtures of these compounds, preferably chosen from stearic acid, rosin and mixtures of these compounds.

4. Urea masterbatch according to any one of the preceding claims, wherein at least one radical R2 or R4 is an aryl radical having from 6 to 8 carbon atoms,preferably a phenyl radical.

5. Urea masterbatch according to any one of claims 1 to 3, wherein the urea compound does not comprise an aromatic nucleus.

6. Urea masterbatch according to any one of claims 1 to 3, wherein the urea compound is selected from urea compounds, N, N'-, dimethylurea, ethyleneurea, N-phenylurea, 1,3-diphenylurea, preferably chosen from the compounds urea, N,N'-dimethylurea, N-phenylurea, 1,3-diphenylurea and very preferably chosen from the compounds urea and N,N'-dimethylurea.

7. Urea masterbatch according to any one of the preceding claims in which the content of urea compound ranges from 30 to 140 phr, very preferably from 80 to 120 phr.

8. Urea masterbatch according to any one of the preceding claims in which the water content ranges from 3 to 50 phr, preferably from 5 to 30 phr.

9. Urea masterbatch according to any one of the preceding claims in which the content of organic or inorganic filler ranges from 5 to 80 phr, preferably from 10 to 75 phr.

10. A urea masterbatch according to any preceding claim wherein the organic or inorganic filler is selected from the group consisting of carbon black, silica, alumina, chalk, clay, bentonite, talc, kaolin and mixtures thereof.

11. A urea masterbatch according to any preceding claim wherein the elastomer is a diene elastomer, preferably an essentially unsaturated diene elastomer, more preferably selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers, and mixtures of these elastomers, and most preferably selected from the group consisting of natural rubber, synthetic polyisoprenes, butadiene-styrene copolymers and mixtures of these elastomers.

12. Rubber composition based on at least one elastomer, a reinforcing filler, a crosslinking system, from 1 to 30 parts by weight per hundred parts by weight of elastomer, pce, of epoxy resin and from 1 to 15 pce of a urea compound introduced in the form of a urea masterbatch according to any one of the preceding claims.

13. A method of manufacturing a rubber composition according to the preceding claim comprising a step of incorporating a urea compound into the rubber composition by means of a masterbatch according to any one of claims 1 to 11.

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