UREA MASTERMIX FOR ADDITIVING AN ELASTOMER 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]nN(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, the R2 and R3 radicals being able to form a ring together, each radical R1, R2, R3, and R4 being optionally interrupted by one or more heteroatoms and / or substituted, the R6 radical being a divalent hydrocarbon radical, preferably a divalent methylphenyl radical, and n being an integer equal to 0 or 1, the mass ratio of water to organic or inorganic charge in said master mixture being less than or equal to 2,said masterbatch not comprising an elastomer crosslinking system.

Description

Title of the invention: UREA MASTERMIX FOR THE ADDITIVATION OF AN ELASTOMER COMPOSITION Technical field of the invention

[0001] The present invention relates to the field of components used in the manufacture of rubber compositions, and more particularly to masterbatches comprising at least one urea compound. A urea masterbatch is understood to be a non-crosslinked rubber composition comprising a high urea content and intended for use in the manufacture of rubber compositions. Previous art

[0002] It is known to use in certain parts of pneumatic tires, rubber compositions exhibiting high rigidity under small deformations of the pneumatic tire as presented in application WO 02 / 10269. Resistance to small deformations is one of the properties that a pneumatic tire must exhibit to withstand the stresses to which it is subjected.

[0003] This stiffening can be achieved by increasing the rate of reinforcing charge or by incorporating certain reinforcing resins into the rubber compositions constituting the parts of the pneumatic tire.

[0004] Among the many solutions developed, we can mention rubber compositions comprising a combination of an epoxy resin and a urea compound such as presented, for example, in document WO2021 / 181032.

[0005] Urea derivatives can also be used as activators for the vulcanization of vulcanizable rubber compositions. US patent 5096978, for example, describes the use of substituted ureas for such a purpose.

[0006] However, urea, which is available in granular form, is a compound that is difficult to disperse homogeneously in elastomeric compositions. It is certainly possible to increase the homogenization time or the mixing time, but this is often at the expense of the rigidity of the final composition, particularly due to the breakage of the elastomeric chains.

[0007] Continuing its research, the applicant discovered a urea masterbatch formulation allowing good incorporation into elastomeric compositions, thus improving the performance of these compositions compared to compositions in which urea is incorporated according to methods known to the person skilled in the art, i.e. in the form of granules. Detailed description of the invention

[0008] Thus, the invention relates to a urea master mixture comprising at least one elastomer, an organic or inorganic filler, water, and a urea compound of general formula (RI, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4), wherein each radical RI, 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, the R2 and R3 radicals being able to form a ring together, each radical RI, R2, R3, and R4 being optionally interrupted by one or more heteroatoms and / or substituted, the R6 radical being a divalent hydrocarbon radical, preferably a radical divalent methylphenyl, and n being an integer equal to 0 or 1, the mass ratio of water to organic or inorganic charge in said master mixture being less than or equal to 2,said masterbatch not comprising an elastomer crosslinking system. Definitions,

[0009] The carbon-containing compounds mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. This includes, in particular, polymers, plasticizers, fillers, etc. Elastomer

[0010] The urea master mixture according to the invention comprises at least one elastomer. An elastomer is, as is known, a polymer which, after crosslinking, exhibits elastic properties.

[0011] Preferably, the urea master mixture according to the invention comprises at least one diene elastomer. It may therefore contain a single diene elastomer or a mixture of several diene elastomers.

[0012] By "dienic" elastomer (or indistinctly rubber), whether natural or synthetic, is to be understood in a known way as 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).

[0013] These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". Generally, "essentially unsaturated" means a diene elastomer derived at least in part from conjugated diene monomers, having a proportion of diene motifs or units (conjugated dienes) greater than 15% (mole percent); thus, diene elastomers such as butyl rubbers or EPDM-type diene-alpha-olefin copolymers do not fall under the preceding definition and may be in particular described as "essentially saturated" diene elastomers (low or very low content of diene-derived motifs, always less than 15%). The diene elastomers included in the composition according to the invention are preferably essentially unsaturated.

[0014] The term diene elastomer, which can be used in compositions according to the invention, is particularly understood 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.

[0015] The other monomer may be ethylene, an olefin or a diene, conjugated or not.

[0016] Suitable conjugated dienes are those having from 4 to 12 atoms of carbon, in particular 1,3-dienes, such as 1,3-butadiene and isoprene.

[0017] Suitable olefins are vinylaromatic compounds having 8 to 20 carbon atoms and aliphatic α-monoolefins having 3 to 12 carbon atoms.

[0018] Suitable examples of vinylaromatic compounds include styrene, ortho-, meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, para-tert-butylstyrene.

[0019] As aliphatic α-monoolefins, acyclic aliphatic α-monoolefins having from 3 to 18 carbon atoms are particularly suitable.

[0020] The urea mastermixture according to the invention preferably comprises at least one essentially unsaturated diene elastomer.

[0021] Preferably, the urea masterbatch comprises, as elastomers, at least one elastomer selected from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. Butadiene copolymers are particularly selected from the group consisting of butadiene-styrene copolymers (SBR).

[0022] The term "isoprene elastomer" is commonly understood to mean a homopolymer or copolymer of isoprene, in other words, a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), various isoprene copolymers, and mixtures of these elastomers. Among the isoprene copolymers, particular examples include isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR), and isoprene-butadiene-styrene (SBIR) copolymers. This isoprene elastomer is preferably selected from the group consisting of natural rubber, synthetic cis-1,4 polyisoprenes, and mixtures thereof; among these synthetic polyisoprenes, the following are used: Preference is given to polyisoprenes having a cis-1,4 bonding percentage (molar %) greater than 90%, and more preferably greater than 98%. Preferably, and according to any of the arrangements herein, the diene elastomer is natural rubber.

[0023] Preferably, the urea masterbatch comprises, as elastomers, at least one elastomer selected from the group consisting of natural rubber, synthetic polyisoprenes, butadiene-styrene copolymers, and mixtures of these elastomers. Most preferably, the urea masterbatch comprises, as 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 its manufacture.

[0024] Preferably, the proportion of diene elastomer in the urea masterbatch, preferably isoprene elastomer, preferably natural rubber, is 50 to 100 parts per cent. Preferably, the proportion of SBR in the urea masterbatch is 0 to 50 parts per cent. Charge

[0025] The urea mastermixture according to the invention comprises a filler, organic or inorganic. The presence of a filler in the urea mastermixture according to the invention makes it possible to minimize, or even prevent, the presence of water in the form of inclusions in the mastermixture, such inclusions being able to make the incorporation of the mastermixture into an elastomeric composition more difficult.

[0026] As an organic or inorganic filler, any type of filler that can be incorporated into an elastomeric composition may be suitable, provided that this filler allows the capture of water, at least in part.

[0027] Preferably, the organic or inorganic filler is chosen from the group consisting of carbon black, silica, alumina, chalk, clay, bentonite, talc, kaolin and mixtures thereof.

[0028] All carbon blacks are suitable as carbon blacks, particularly those of the HAF, ISAF, and SAF types conventionally used in tires (so-called tire-grade blacks). Among these, special mention should be made of reinforcing carbon blacks of the 100, 200, or 300 series (ASTM grades), such as NI 15, N134, N234, N326, N330, N339, N347, and N375, or, depending on the intended applications, blacks of higher series (e.g., N660, N683, N772). These carbon blacks can be used in isolation, as commercially available, or in any other form, for example, as a carrier for certain 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).

[0029] Carbon blacks are characterized by various properties, including their specific surface area and the oil absorption number of compressed samples (CO₂AN for "Compressed Oil Absorption Number"). The CO₂AN of carbon blacks is measured according to ASTM D3493-16.

[0030] The specific surface area BET of carbon blacks is measured according to standard D6556-10 (multipoint method (minimum 5 points) - gas: nitrogen - relative pressure range P / P0: 0.1 to 0.3).

[0031] The physical state in which the inorganic charge is presented is irrelevant, whether in the form of powder, granules, beads or any other suitable densified form.

[0032] The inorganic filler is preferably selected from siliceous mineral fillers, in particular silica (SiO2), or aluminous mineral fillers, in particular alumina (Al2O3), chalk, clay, bentonite, talc, kaolin and mixtures thereof. Most preferably, the inorganic filler is selected from silica, kaolin and mixtures thereof.

[0033] The silica used can be any silica known to those skilled in the art, in particular any precipitated or pyrogenated reinforcing silica having a BET surface area and a CTAB specific surface area both less than 450 m2 / g, preferably from 30 to 400 m2 / g. Examples of highly dispersible precipitated silicas (known as "HDS") include "Ultrasil 7000" and "Ultrasil 7005" silicas from Degussa, "Zeosil 1165MP", "1135MP" and "1115MP" silicas from Rhodia, "Hi-Sil EZ150G" silica from PPG, "Zeopol 8715", "8745" and "8755" silicas from Huber, and silicas with a high specific surface area as described in application WO 03 / 16837.

[0034] The specific surface area BET 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 specifically 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).

[0035] The CTAB specific surface area of ​​silica is determined according to the French standard NF T 45-007 of November 1987 (method B).

[0036] In the preferred case where the inorganic filler includes silica, the latter preferably has a BET surface area of ​​between 45 and 400 m2 / g, more preferably between 60 and 300 m2 / g.

[0037] 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, preferably less than 1% by mass relative to the mass of inorganic filler.

[0038] The term “coupling agent” (or “linking agent”) refers, in a known manner, to an agent capable of coupling the inorganic filler to the elastomer. Indeed, the desired effect of the organic or inorganic filler is not to enhance the urea masterbatch, but rather 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 merely ensures greater compatibility when these components are mixed.

[0039] The urea mastermixture according to the invention preferably comprises from 5 to 80 parts of organic or inorganic filler, preferably from 10 to 75 parts of organic or inorganic filler, these contents enabling the capture of water present in the urea mastermixture in order to minimize, or even prevent, the presence of water inclusion. Water

[0040] The urea mastermixture according to the invention comprises water, the mass ratio of water to organic or inorganic charge in said mastermixture being less than or equal to 2. The presence of water ensures greater homogeneity of the distribution of urea in the urea mastermixture, in particular by facilitating the solubilization of urea.

[0041] Preferably, the water mass ratio to organic or inorganic filler is less than or equal to 1. A water mass ratio to organic or inorganic filler less than or equal to 2, preferably less than or equal to 1, surprisingly allows better performance to be achieved when the urea mastermixture is incorporated into an elastomeric composition.

[0042] Preferably, the water content in the urea master mix according to the invention ranges from 3 to 50 parts per million (ppm), preferably from 5 to 30 ppm. A lower water content does not sufficiently improve the dispersion of the urea in the master mix, while an excessively high water content increases the risk of water inclusions forming. Urea

[0043] The urea masterbatch according to the invention comprises a urea compound of general formula (RI, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) in which each radical RI, R2, R3, R4, R5 and R7 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 5 to 24 carbon atony, • an aryl radical having 6 to 30 carbon atoms and • an aralkyl radical having 7 to 25 carbon atoms,

[0044] the radicals R2 and R3 being able to form together a ring, each radical RI, R2, R3 and R4 being optionally interrupted by one or more heteroatoms and / or substituted, the radical R6 being a divalent hydrocarbon radical, preferably being a divalent methylphenyl radical, and n being an integer equal to 0 or 1.

[0045] By divalent hydrocarbon radical, we mean a divalent radical consisting of carbon and hydrogen, preferably comprising from 1 to 20 carbon atoms, and preferably comprising from 1 to 10 carbon atoms.

[0046] In the case where n is equal to 0, the general formula (RI, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) becomes (RI, R2)N-CO-N(R3, R4). In the case where n is equal to 1, the general formula (RI, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) becomes (RI, R2)N-CO-(NR5)-R6-(NR7)-CO-N(R3,R4).

[0047] 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 (Ri, R2)N (respectively N(R3, RJ) represents a nitrogen atom linked to a group Ri 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).

[0048] An example of a urea compound in which the R2 and R3 radicals together form a ring is 2-imidazolidinone, or ethyleneurea.

[0049] Preferably, the radicals do not form a cycle together.

[0050] Preferably, the urea compound is a monourea (therefore n=0), and each radical RB R2, R3 and R4 is chosen independently from the group consisting of hydrogen and a hydrocarbon compound chosen 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 6 to 30 carbon atoms and • an aralkyl radical having 7 to 25 carbon atoms,

[0051] each radical RI, R2, R3 and R4 being possibly substituted.

[0052] Preferably, each radical Ri and R3 is a hydrogen atom. Urea is then a composed of the formula R2-HN-CO-NH-R4.

[0053] In a preferred arrangement, at least one radical R2 or Ri is an aryl radical having 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.

[0054] In a preferred arrangement, the urea compound is a diurea (hence n=l) in which the radicals RI, R2, R3, and R4 are methyl radicals, R5 and R7 are hydrogen atoms, and R6 is a divalent methylphenyl radical. An example of such a diurea compound is the compound "Amicure UR2T" from the Evonik company, with the formula 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethyl urea).

[0055] Preferably, the urea compound does not include an aromatic ring.

[0056] Preferably, each radical Rh R2, R3 and R4 is a hydrogen atom. The The compound urea is then a compound with the formula H2N-CO-NH2 commonly referred to as "urea" or "carbamide".

[0057] Thus, most preferably, the urea compound is selected from among the compounds urea, N,N'-dimethylurea, ethyleneurea, N-phenylurea, 1,3-diphenylurea, most preferably from among the compounds urea, N,N'-dimethylurea, N-phenylurea, 1,3-diphenylurea, and most preferably from among the compounds urea and N,N'-dimethylurea. Most preferably, the urea compound is urea with the formula H2N-CO-NH2.

[0058] The urea content in the urea masterbatch is in the range of 20 to 150 parts per million (ppm), preferably 30 to 140 ppm, and most preferably 80 to 120 ppm. Below the stated minimum, an excessive amount of the other materials constituting the urea masterbatch would be introduced into the elastomeric composition. Above these levels, obtaining a homogeneous masterbatch that allows for good dispersion of the urea in the elastomeric composition for which the masterbatch is intended is more difficult. Crosslinking system

[0059] Elastomeric compositions include a crosslinking system intended to impart, in particular, their elastic properties. The urea mastermixture according to the invention, which is intended to be incorporated into an elastomeric composition, does not include an elastomer crosslinking system, that is to say, a system capable of crosslinking the elastomer present in the urea mastermixture.

[0060] In particular, the urea mastermixture does not include any crosslinking system known to the person skilled in the art, for example, a sulfur-based crosslinking system, and / or a peroxide-based crosslinking system and / or a bismaleimide-based crosslinking system.

[0061] Preferably, the urea mastermixture according to the invention does not comprise sulfur or comprises less than 0.5 pc, preferably less than 0.4 pc, preferably less than 0.2 pc. Various additives

[0062] Rubber compositions according to the invention may also include all or part of the usual additives and processing agents known to the man of the art and usually used in rubber compositions, especially for pneumatic tires, such as plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents.

[0063] In particular, the urea mastermixture according to the invention preferably comprises a plasticizer, preferably selected from C5-based resins, C9-based resins, process oils, stearic acid, rosin and mixtures of these compounds, preferably selected from stearic acid, rosin and mixtures of these compounds.

[0064] By "C5-based" (respectively "C9-based"), we mean resins based on compounds comprising 5 carbon atoms (respectively 9).

[0065] Preferably, the composition according to the invention does not comprise nitrile compounds or comprises less than 10 pc, preferably less than 5 pc, preferably less than 2 pc, most preferably less than 1 pc and even more preferably less than 0.5 pc.

[0066] Preferably, the urea master mix consists of at least one elastomer, an organic or inorganic filler, water, and a urea compound of general formula (RI, R2)N-CO-N(R3, R4), wherein each radical RI, 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, the R2 and R3 radicals being able to form a ring together, each radical RI, R2, R3, and R4 being optionally interrupted by one or more heteroatoms and / or substituted, the water-to-organic-inorganic filler mass ratio in said master mix being less than or equal to 2, and optionally of a plasticizer, all of these compounds being as described previously. Rubber composition

[0067] The invention also relates to a rubber composition based on an elastomer, preferably diene, a reinforcing filler, a crosslinking system, 1 to 30 parts by weight per hundred parts by weight of elastomer, pc, of epoxy resin and 1 to 15 pc of a urea compound introduced in the form of a urea mastermixture according to the invention.

[0068] Epoxy resins usable in the present invention include all polyepoxide compounds. These may include, for example, aromatic epoxy resins, alicyclic epoxies, and aliphatic epoxies. For example, the epoxy resin Aromatic can be an amine-aromatic epoxy resin. These resins are preferentially novolac epoxy resins, that is, epoxy resins obtained by acid catalysis, as opposed to resol resins, obtained by basic catalysis.

[0069] In particular, among aromatic epoxide compounds, preferred are epoxide resins selected from the group consisting of 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.

[0070] By "epoxy resin type", we mean resins based on motifs of the constituent, that is to say comprising this constituent, or oligomers of this constituent.

[0071] Epoxy resin is a hardening resin. A hardening resin is defined as a resin which, when incorporated into a rubber composition with a hardening agent, increases the rigidity of the rubber composition after curing. However, an increase in the rigidity of a rubber composition generally goes hand in hand with an increase in hysteresis losses.

[0072] Preferably, the epoxy resin is chosen from the group consisting of poly[(o-cresylglycidyl ether)-co-formaldehyde], poly[(o-phenylglycidyl ether)-co-formaldehyde], tri(glycidoxyphenyl)methane, tetra(glycidoxyphenyl)ethane resins and mixtures of these resins.

[0073] Most preferably, the epoxy resin used in the context of the invention is chosen from among the following epoxy resins of generic formula (I) and (II) and their derivatives, i.e. the oligomers of the compounds of generic formula (I) and (II): a. oo (I) A ZV b. (II) / ..... X / X <1 K OO"

[0074] 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.

[0075] By way of example of commercially available epoxy resins that can be used in the context of the present invention, we may cite for example the epoxy resin "DEN 439" from Uniqema, the epoxy resin "Tris(4-hydroxyphenyl)methane triglycidyl ether" from Sigma-Aldrich, the cresol novolac araldite epoxy resin "ECN 1299" from Huntsman, the phenol novolac araldite epoxy resin "EPN 1138" from Huntsman, the resins "EPPN-502H", "EPPN-501H" and "EPPN-501HY" from Nippon Kayaku, or the resin "EPON 1031" from Hexion.

[0076] Preferably, the rubber composition according to the invention does not include any hardening resins other than an epoxy resin, and in particular does not include any formophenolic type resins.

[0077] The composition according to the invention comprises between 1 and 30 parts per 10 ...

[0078] 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

[0079] Tensile tests

[0080] 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 humidity (50+5% relative humidity) conditions, according to French standard NF T 40-101 (December 1979).

[0081]

[0082] The nominal secant modulus calculated by reducing to the initial section of the specimen (or apparent stress, in MPa) at 10% elongation, noted MAi0, was measured in the second elongation (i.e. after accommodation) on samples baked for 60 minutes at 150°C.

[0083] The results are expressed on a base of 100, with the value 100 being assigned to the composition CL. A result greater than 100 indicates that the composition of the example considered has a higher rigidity than the control.

[0084] The tensile strengths (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 tensile energy is equal to the product of the elongation at break and the tensile strength.

[0085] The results are expressed in base 100, the value 100 being assigned to the composition CL. A result greater than 100 indicates that the composition of the example considered has a higher breaking strength than the control.

[0086] Losses on impact

[0087] The rolling resistance induced by the tested composition is estimated by measuring the energy losses. This is done by measuring, at a temperature of 60°C, the energy released on the eighth bounce of a sample to which an initial energy has been applied, as described in DIN 53-512 of April 2000. This measurement is denoted P60 and calculated as follows: P60(%) = 100 x (E0 - El) / E0, where E0 represents the initial energy and El the released energy. The lower this value, the fewer hysteretic losses the tested sample exhibits.

[0088] The values ​​are expressed in base 100, the reference being the P60 of the CL composition. A value greater than 100 shows that the shock loss is lower, and therefore that the composition has better rolling resistance properties.

[0089] The cooking time is expressed by the t90 value measured in minutes. The t90 value is determined according to ISO 6502:2018.

[0090] Preparation of Urea Masterbatches

[0091] The masterbatches whose compositions are indicated in Table 1 are manufactured as follows:

[0092] The diene elastomer, urea, organic or inorganic filler, and water are successively introduced into an internal mixer (final filling rate: approximately 75% by volume), the initial tank temperature of which is approximately 80 °C. A thermomechanical process (non-productive phase) is then carried out in a single step, lasting approximately 4 to 5 minutes in total, with at least 1.5 minutes of work above 80 °C, until a maximum "drop" temperature of 95 °C is reached.

[0093] The compositions in Table 1 are indicated in pc (part percent of elastomer)

[0094] [Table 1] B1 B2 B3 84 BS B6 B7 BS 89 BIC Bll B12 NR fl) 5 fi 50 59 50 50 50 50 100 50 50 5Q 50 SBR (2) 59 50 50 50 50 50 50 50 50 50 ûO 50 Kaolin 0 0 Q n 0 0 u 0 o 75 0 0 Silica (3) 77 lu' 1(9 ■? 10 75 75 0 0 75 75 Mo ir (4) c> Q 0 0 û 0 0 7S 0 Q 0 Urea (5) 135 35 135 135 35 235 100 100 100 100 100 100 water 5 5. 5 25 25 25 25 25 25 25 25 25 rosin (6) 0 ri 0 9 9 0 a O 5 10 Water / charge 0 07 0.5 0.5 0.33 2.5 2.5 0.33 o.33 033 0.33 0.33 0.33

[0095] (1) Natural rubber

[0096] (2) SBR: Styrene-butadiene rubber with 27% styrene motifs, 24% motifs vinyl and 46% l-4trans patterns, Tg: -48°C

[0097] (3) Evonik “165G” silica, BET surface area of ​​approximately 180 m² / g

[0098] (4) N326 carbon black (designation according to ASTM D-1765)

[0099] (5) Univar Solutions urea

[0100] (6) Diamantino company rosin Preparation of compositions

[0101] 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 vulcanizing system and the hardener, are successively introduced into an internal mixer (final filling level: approximately 70% by volume), the initial tank temperature of which is approximately 50 °C. A thermomechanical process (non-productive phase) is then carried out in a single step, lasting approximately 3 to 4 minutes in total, until a maximum "drop" temperature of 165 °C is reached.

[0102] The mixture thus obtained is recovered, cooled, and then sulfur, a sulfenamide-type accelerator, and either urea in dispersed form (composition Cl) or one of the urea master mixtures prepared according to 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 Urea is introduced in the form of a urea mastermixture; the amount of mastermixture added is adjusted to obtain the amount of urea compound in the composition.

[0103] The compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties, or extruded in the form of a profile.

[0104] The crosslinking of the composition is carried out at a temperature of 160°C, for 15 min under pressure.

[0105] The reference composition is the Cl rubber composition used as a reference in document WO 2021 / 181032:

[0106] [Tables2] MR (1) Carbon moiety (2) 70 ZnO ■ 3 ; 2.5 Stear acid 2 Sulfur 3 CSS (S) 2 Epoxy resin [9] 22

[0107] Contents in pc

[0108] (1) Natural Rubber;

[0109] (2) Carbon black N326 (designation according to ASTM D-1765)

[0110] (3) Zinc oxide (industrial grade - Umicore company)

[0111] (4) Nl,3-dimethylbutyl-N-phenylparaphenylenediamine (Santoflex 6-PPD of the Flexsys company)

[0112] (5) Stearine (“Pristerene 4931” from Uniqema)

[0113] (6) N-cyclohexyl-benzothiazyl sulphenamide (Santocure CBS from Flexsys)

[0114] (7) Novolac phenol epoxy resin (“EPN 1138” from Huntsman)

[0115] The different compositions C1 to C13 are obtained by adding urea to the formulation shown in Table 2, either in dispersed form (composition C1) or as a urea master mix, so as to obtain a urea content of 2 parts per million in each composition. For each composition, the mass percentage of urea master mix added relative to the mass of the urea-free mixture shown in Table 2 is indicated so as to obtain 2 parts per million of urea in the final composition.

[0116] Table 3 shows the compositions Cl to C-13 and the results obtained.

[0117] [Table 3] Cl O2 C-3 C-4 CS C-6 C-7 CB C-9 cw C-ll C-I2 C-13 Urea block (%weight) Q.0% 1.5¾ 0 / 1% 1.5% 1.5¾ 5 1% 1.5% 2.0% 2.0% 2.0% 2.0% 2.0% 2.0% Urea origin grains ai. 82 B3 B4 35 85 B7 BS 810. 811 B12 MA1G 23*C fisse 100 100 :135 107 108 110 GG 91 109 114 110 109' 109 11.1 P60 Sa se 100 100 104 103 103 . 102 103 104 103 101 102 132 102 101 T 90 at 15°C 32 20 22 24 20- 25 27 21 20 24 21 21 Tensile strength Base 100 1G0 10 3 102 106 104 100 ibs: 107 110 105 108 135 107

[0118] It is observed that the compositions conforming to the invention exhibit better rigidities and hysteretic performance than the non-conforming compositions, and in particular the reference composition Cl.

[0119] Compositions according to the invention also exhibit better curing and excellent tensile strength properties.

Claims

Demands

1. Urea masterbatch comprising at least one elastomer, an organic or inorganic filler, water and a urea compound of general formula (RI, R2)N-CO-[(NR5)-R6-(NR7)-CO]nN(R3, R4) in which each radical RI, R2, R3, R4, R5 and R7 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, the R2 and R3 radicals being able to form a ring together, each radical RI, R2, R3, R4, R5 and R7 being optionally interrupted by one or more heteroatoms and / or substituted, the R6 radical being a divalent hydrocarbon radical, preferably being a divalent methylphenyl radical, and n being an integer equal to 0 or 1, the mass ratio of water to organic or inorganic charge in said master mixture being less than or equal to 2,said masterbatch not comprising an elastomer crosslinking system, the urea compound content in the mixture being in the range of 20 to 150 parts per annum,

2. Urea mastermixture according to claim 1 in which the water / load mass ratio is less than or equal to 1.

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

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

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

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

7. Urea mastermixture according to any one of the preceding claims wherein the urea compound content ranges from 30 to 140 pc, most preferably from 80 to 120 pc.

8. Urea mastermixture according to any one of the preceding claims wherein the water content ranges from 3 to 50 pc, preferably from 5 to 30 pc.

9. Urea mastermixture according to any one of the preceding claims wherein the organic or inorganic filler content ranges from 5 to 80 pc, preferably from 10 to 75 pc.

10. Urea mastermixture according to any one of the preceding claims 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. Urea mastermixture according to any one of the preceding claims wherein the elastomer is a diene elastomer, preferably an essentially unsaturated diene elastomer, 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, 1 to 30 parts by weight per hundred parts by weight of elastomer, pc, epoxy resin and 1 to 15 pc of a urea compound introduced as a urea mastermixture according to any one of the preceding claims.

13. A method for 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.