WO2015189365A1 - Method for preparing a natural rubber - Google Patents

Method for preparing a natural rubber Download PDF

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Publication number
WO2015189365A1
WO2015189365A1 PCT/EP2015/063124 EP2015063124W WO2015189365A1 WO 2015189365 A1 WO2015189365 A1 WO 2015189365A1 EP 2015063124 W EP2015063124 W EP 2015063124W WO 2015189365 A1 WO2015189365 A1 WO 2015189365A1
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WO
WIPO (PCT)
Prior art keywords
natural rubber
rubber
ammonia
natural
shaft
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Application number
PCT/EP2015/063124
Other languages
French (fr)
Inventor
Jérôme DUSSILLOLS
Jean-Luc MERCERON
Benoît DE GAUDEMARIS
Original Assignee
Compagnie Generale Des Etablissements Michelin
Michelin Recherche Et Technique S.A.
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Application filed by Compagnie Generale Des Etablissements Michelin, Michelin Recherche Et Technique S.A. filed Critical Compagnie Generale Des Etablissements Michelin
Publication of WO2015189365A1 publication Critical patent/WO2015189365A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C1/00—Treatment of rubber latex
    • C08C1/02—Chemical or physical treatment of rubber latex before or during concentration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
    • B60C1/0016—Compositions of the tread

Definitions

  • the invention relates to a process for the preparation of a treated natural rubber by means of the addition of an ammonia derivative and the homogenisation of the resulting assembly by a device providing high temperature mechanical work. .
  • the stabilization of the natural rubber can also be carried out in the latex phase by injection of the stabilizers into the latex.
  • the latex phase treatment has the disadvantage of losing stabilizer in the coagulation water which is released into the environment.
  • Document EP 0 950 485 describes a method of drying natural latex rubber comprising a step of adding a stabilizer. This document simply mentions a mixer or an extruder.
  • natural rubber can be treated by a process comprising a step of adding to the natural rubber predominantly in the form of a natural bottom cup rubber of one or more ammonia derived compounds, the one or more compounds being present in an amount ranging from 0.2 to 2.2 g per kilo gram of natural rubber, and a mechanical working step of the assembly at a temperature of at least 100 ° C, such a method allowing energy saving, productivity and investment cost compared to the usual plasticizing process .
  • the object of the invention is therefore a process for treating a natural rubber, comprising the following steps:
  • the natural rubber consisting of at least 80% by weight of natural bottom mastic and 0 to 20% by weight of natural latex rubber, relative to to the total weight of natural rubber, the one or more compounds derived from ammonia being chosen from the compounds of formula XNH 2 and their salts, or X is a group chosen from hydroxyl and hydroxyalkyl groups of C 1 -C 4 , the said compound or compounds being present in an amount ranging from 0.2 to 2.2 g per kilogram of natural rubber, then
  • natural rubber of the bottom of the cup is meant the part of natural rubber which, after bleeding from the tree and recoated in a cup, has coagulated in solid form in this cup, then underwent a cleaning work, homogenization and drying.
  • Natural latex rubber means the natural rubber which, after bleeding from the tree, has flowed into the cup, has been reco lted in liquid form and artificially coagulated, then has undergone cleaning, homogenisation and drying.
  • the cleaning, homogenization and drying work generally comprises one or more steps of reducing the size of the pieces of natural rubber, for example by means of a hammer mill, one or more washing steps in a water tray for removing impurities and contaminants, one or more crepe steps, one or more crumbling steps, and one or more drying steps. Then the natural rubber is compressed to be put in the form of bread or ball.
  • the natural rubber is a natural cup bottom rubber. This means that natural rubber does not contain natural latex rubber.
  • the natural rubber used in the process according to the invention is chosen from the natural rubbers derived from the rubber tree Brasiliensis.
  • the compound (s) derived from ammonia that are added to the natural rubber may be selected from hydroxylamine and hydroxylamine salts based on strong acid.
  • hydroxylamine salt based on strong acid mention may be made of hydroxylamine sulfate.
  • the compound (s) derived from ammonia are present in an amount ranging from 0.2 to 2.2 g per kilogram of natural rubber.
  • the compound derived from ammonia is hydroxylamine and is present in a content ranging from 0.2 to 0.8 g, preferably from 0.32 to 0.6 g, per kilogram of rubber. natural.
  • the compound derived from ammonia is hydroxylamine sulfate and is present in a content ranging from 0.5 to less than 2 g, preferably from 0.8 to 1.5 g, kilo gram of natural rubber.
  • the Mooney viscosity of the mixtures obtained with natural rubber treated with hydroxylamine at levels below 0.2 g / kg is too high compared to a plasticized natural rubber.
  • hydroxylamine levels greater than 0.8 g / kg the hysteresis of the natural rubber - containing mixture increases with respect to the hysteresis of a mixture containing the plasticized natural rubber.
  • the addition of the ammonia derivative compound (s) to the natural rubber may be by spraying the natural rubber with the desired amount of ammonia - derived compounds, or by soaking the natural rubber in a solution of ammonia - derived compounds.
  • the addition of the compound (s) derived from ammonia to the natural rubber is done by watering.
  • the process according to the invention comprises a step of mechanical working at a temperature of at least 100 ° C of the natural rubber to which has been added and the compound (s) derived from ammonia.
  • the mechanical work is carried out at a temperature of at least 110 ° C.
  • the mechanical work is preferably carried out by means of one or more shredding and homogenizing devices.
  • a shredding and homogenizing device is generally called "prebreaker”.
  • Such a device has an energy consumption of the order of 50 kW / ton of natural rubber, whereas a plasticizing process consumes around 140 kW / ton.
  • the mechanical work is performed by means of two shredding and homogenization devices arranged in series.
  • the use of two such devices is particularly advantageous to ensure that the natural rubber is maintained at a temperature of at least 100 ° C for a sufficient time which allows the ammonia derived compound to react.
  • the mechanical working stage advantageously has a duration varying from 25 seconds to 3 minutes.
  • the shredding and homogenizing device (s) usually each comprise a feed and shredding zone and a homogenization zone connected to each other, and a shaft passing through said zones, said shaft being provided with rotary knives.
  • the feed zone generally comprises an upper portion and a lower portion, said upper portion being adapted to feeding said lower portion, said lower portion comprising the first portion of said shaft.
  • the walls of the feed zone have first fixed knives.
  • Such first fixed knives prevent the assembly of natural rubber - compound derived from ammonia goes up in the upper part of the feeding zone once it has reached the lower part of the feeding zone.
  • the homogenization zone generally comprises the second part of said shaft and a sleeve inserting said second part of the shaft, said sleeve being provided with second fixed blades.
  • the shaft housed in the lower part of the feed zone and in the homogenization zone is preferably horizontal.
  • the speed of the shaft advantageously varies from 20 to 100 rpm, preferably from 20 to 60 rpm.
  • the chipping and homogenizing device or devices usually each have a die plate at the end of the homogenization zone, said die plate having orifices.
  • holes may be in the form of round holes or oblong holes or triangular holes.
  • these orifices have a variable opening.
  • the variation of the opening of the orifices makes it possible to increase or decrease the mechanical work provided to the natural rubber or to vary the flow rate in the device.
  • the temperature in the shredding and homogenizing zone can be adjusted by varying the mechanical work, using the following means, alone or in combination: number of fixed knives, number of rotary knives, length of shredding zone and homogenization, closure of the die plate, flow of natural rubber, heating of the body of the shredding device and homogenization.
  • the mechanical working step may be followed by a cutting step of the treated natural rubber.
  • the cutting step may be performed by means of a cutting device positioned at the output of the device conferring the mechanical work, in particular or of the shredding and homogenizing device or devices.
  • Another object of the invention is a treated natural rubber which can be obtained by the process obj and of the invention.
  • Another object of the invention is a reinforced rubber composition based on at least one reinforcing filler and an elastomeric matrix comprising at least one natural rubber treated according to the invention.
  • composition-based is meant a composition comprising the mixture and / or the reaction product of the various constituents used, some of these basic constituents being capable of or intended to react with one another, less in part, during the various phases of manufacture of the composition, in particular during its crosslinking or vulcanization.
  • the reinforced rubber composition according to the invention may be in the crosslinked state or in the uncrosslinked state, that is to say crosslinkable.
  • the elastomer matrix present in the composition according to the invention may also, in addition to the natural rubber treated according to the invention, comprise at least one other diene elastomer.
  • the mass fraction of the natural rubber treated according to the invention in the elastomer matrix is predominant and preferably greater than or equal to 10% by weight of the total mass of the matrix. more preferably still greater than or equal to 50% by weight of the total mass of the matrix, even more preferably greater than or equal to 70%.
  • the mass fraction of the natural rubber treated according to the invention in the elastomer matrix is preferably less than or equal to 85% by weight of the total mass of the matrix.
  • the majority mass fraction according to the invention is the highest mass fraction of the blend.
  • diene elastomer is any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms, or any copolymer obtained by copolymerization of one or more conjugated dienes with one another or with one or more compounds.
  • vinylaromatic compounds having 8 to 20 carbon atoms. In the case of copolymers, these contain from 20% to 99% by weight of diene units, and from 1 to 80% by weight of vinylaromatic units.
  • the diene elastomer constituting a part of the elastomer matrix of the composition according to the invention is preferably chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes (BR), synthetic polyisoprenes (IR) and natural rubber (NR). ) different from the natural rubber treated according to the invention, butadiene copolymers, isoprene copolymers and mixtures of these elastomers.
  • BR polybutadienes
  • IR synthetic polyisoprenes
  • NR natural rubber
  • Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-copolymers.
  • SBR butadiene-styrene copolymers
  • BIR isoprene-butadiene copolymers
  • SIR isoprene-styrene copolymers
  • SBIR butadiene-styrene
  • the elastomeric matrix consists solely of the natural rubber treated according to the invention.
  • the rubber composition of the invention comprises, in addition to at least one elastomeric matrix as described above, at least one reinforcing filler.
  • reinforcing filler known for its ability to reinforce a rubber composition that can be used for the manufacture of tire treads, for example carbon black, can be used, a reinforcing inorganic filler such as only silica with which is associated in a known manner a coupling agent, or a mixture of these two types of filler.
  • Suitable carbon blacks are all carbon blacks, used individually or in the form of mixtures, in particular blacks of the HAF, ISAF, SAF type conventionally used in tire treads (so-called pneumatic grade blacks).
  • the reinforcing carbon blacks of the series 100, 200 or 300 ASTM grades
  • the carbon blacks could for example be already incorporated into the isoprene elastomer in the form of a masterbatch (see for example WO 97/36724 or WO 99/16600).
  • reinforcing inorganic filler is meant by the present application, by definition, any inorganic or inorganic filler whatever its color and its origin (natural or synthetic), capable of reinforcing on its own, without any other means than an agent intermediate coupling, a rubber composition for the manufacture of tires; such a filler is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.
  • a filler is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.
  • Suitable reinforcing inorganic fillers are in particular mineral fillers of the siliceous type, in particular silica (SiO 2 ), or aluminous type, in particular alumina (Al 2 O 3 ).
  • the silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface both less than 450 m 2 / g, preferably from 30 to 400 m 2 / g, especially between 60 and 300 m2 / g.
  • Reinforcing fillers of another nature, especially carbon black are also suitable as reinforcing fillers. when these reinforcing fillers would be covered with a siliceous layer, or would comprise on their surface functional sites, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between the filler and the elastomer.
  • the physical state in which the reinforcing inorganic filler is present is indifferent whether in the form of powder, microbeads, granules, beads or any other suitable densified form.
  • the term "reinforcing inorganic filler” also refers to mixtures of different reinforcing fillers, in particular highly dispersible siliceous fillers as described above.
  • the level of total reinforcing filler is the level of total reinforcing filler
  • carbon black and / or other reinforcing filler such as silica is between 10 and 200 phr, more preferably between 30 and 150 phr, and even more preferably between 70 and 130 phr, the optimum being in a known manner different according to the particular applications targeted.
  • the reinforcing filler is predominantly other than carbon black, that is to say it comprises more than 50% by weight of the total weight of the filler, of one or more fillers other than carbon black, especially a reinforcing inorganic filler such as silica, or it consists exclusively of such a filler.
  • carbon black when carbon black is also present, it may be used at a level of less than 20 phr, more preferably less than 10 phr (for example between 0.5 and 20 phr, in particular from 1 to 10 phr).
  • a reinforcing filler comprising predominantly carbon black and optionally silica or other inorganic filler is used.
  • the rubber composition according to the invention further comprises, in a conventional manner, an agent capable of effectively provide this link.
  • the silica is present in the composition as a reinforcing filler, it is possible to use as coupling agents organosilanes, especially polysulfurized alkoxysilanes or mercaptosilanes, or at least bifunctional polyorganosiloxanes.
  • the level of coupling agent is advantageously less than 20 phr, it being understood that it is generally desirable to use as little as possible. Its rate is preferably between 0.5 and 12 phr.
  • the presence of the coupling agent depends on that of the reinforcing inorganic filler. Its rate is easily adjusted by the skilled person according to the rate of this charge; it is typically of the order of 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler other than carbon black.
  • the rubber composition according to the invention may also contain, in addition to the coupling agents, coupling activators, charge-recovery agents or, more generally, processing aid agents which can be used in known manner, thanks to an improvement of the dispersion of the filler in the rubber matrix and a lowering of the viscosity of the composition, to improve its ability to use in the green state, these agents being for example the hydrolysable silanes such as alkylalkoxysilanes, polyols, polyethers, primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes.
  • these agents being for example the hydrolysable silanes such as alkylalkoxysilanes, polyols, polyethers, primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes.
  • the rubber compositions in accordance with the invention may also contain reinforcing organic fillers which may replace all or part of the carbon blacks or other reinforcing inorganic fillers described above.
  • reinforcing organic fillers include fillers organic functionalized polyvinyl compounds as described in WO-A-2006/069792, WO-A-2006/069793, WO-A-2008/003434 and WO-A-2008/003435.
  • the rubber composition according to the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended for the manufacture of tires, for example pigments, non-reinforcing fillers, protective agents such as waxes anti-ozone, anti-chemical ozonants, anti-oxidants, anti-fatigue agents, plasticizing agents, reinforcing or plasticizing resins, acceptors (eg novo lacquer phenolic resin) or methylene donors (eg HMT or H3M) as described for example in the application WO 02/1 0269, a crosslinking system based on either sulfur, or sulfur and / or peroxide and / or bismaleimide donors, vulcanization accelerators, vulcanization activators.
  • additives usually used in elastomer compositions intended for the manufacture of tires for example pigments, non-reinforcing fillers, protective agents such as waxes anti-ozone, anti-chemical ozonants, anti-oxidants, anti-fatigue agents, plasticizing agents
  • composition is manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art: a first phase of work or thermomechanical mixing (so-called “non-productive” phase) at high temperature, up to a maximum of maximum temperature between 1 10 ° C and 190 ° C, preferably between 130 ° C and 1 80 ° C, followed by a second mechanical working phase (so-called “productive” phase) to a lower temperature, typically less than 1 10 ° C, for example between 40 ° C and 100 ° C, finishing phase during which is incorporated the crosslinking system.
  • a first phase of work or thermomechanical mixing at high temperature, up to a maximum of maximum temperature between 1 10 ° C and 190 ° C, preferably between 130 ° C and 1 80 ° C
  • a second mechanical working phase “productive” phase
  • finishing phase finishing phase during which is incorporated the crosslinking system.
  • the process for the preparation of a composition according to the invention generally comprises:
  • the invention also relates to a semi-finished tire rubber article, comprising a rubber composition according to the invention, crosslinkable or crosslinked, or consisting of such a composition.
  • the final composition thus obtained may then be calendered, for example in the form of a sheet, a plate or extruded, for example to form a rubber profile usable as a semi-finished rubber product for the tire.
  • the invention is therefore obj and a tire comprising a semi-finished article according to the invention, in particular a tread.
  • the natural rubber to which the compound (s) derived from ammonia has been added is introduced into a shredder and homogenizer 1.
  • the shredding and homogenizing device 1 comprises a feed and shredding zone 2 and a homogenization zone 3 interconnected, and a shaft 4 passing through said zones, said shaft being provided with rotary knives 5.
  • the feeding and shredding zone 2 comprises an upper part 2a and a lower part 2b.
  • the upper portion 2a is an elevated and open portion for the introduction of natural rubber and ammonia derived compounds.
  • This upper part 2a is generally of square shape whose length of the sides is equal to the diameter formed by the rotary knives 5 of the shaft 4.
  • the walls 6 of this part upper 2a are generally vertical, but can also be inclined to favor the feeding of large blocks of natural rubber. Preferably, the walls 6 are vertical to prevent the natural rubber from remaining on the inclined supply walls.
  • the lower part 2b comprises the first part of the shaft 4.
  • the lower part has a cylindrical bottom in which the shaft 4 is housed.
  • the walls 6 of the upper part 2a may be provided with first fixed knives (not shown) to prevent the natural rubber from rising in the upper part 2a of the feed zone 2.
  • the homogenization zone 3 is in the continuity of the feed and shredding zone 2 and is connected to it. This zone makes it possible to knead and homogenize the natural rubber.
  • This homogenizing zone 3 comprises a sheath 7 inserting the second part of the shaft 4.
  • the sheath 7 is provided with second fixed knives 8.
  • the second fixed knives 8 promote the homogenization and the mechanical work of the natural rubber. These second fixed knives 8 can be positioned on the lower and / or upper part of the sheath. These second fixed knives are removable.
  • the number of second fixed knives 8 may depend on the desired mechanical work. The more the number of second fixed knives is important, the more the mechanical work increases.
  • the rotary knives 5 of the shaft 4 pass on each side of the second fixed knives of the sheath 7.
  • the length of the homogenization zone 3 is variable. It is a function of the desired homogenization time and mechanical work. This length is fixed during the construction of the device.
  • the shredder and homogenizer 1 comprises at the end of the homogenization zone 3 a die plate 9.
  • the die plate 9 has orifices which may be in the form of round holes or oblong holes.
  • the variable opening of the orifices makes it possible to increase or decrease the mechanical work of the natural rubber.
  • the reduction in the opening of the holes in the die plate 9 also makes it possible to reduce the flow rate in the device 1.
  • the shaft 4 of the device 1 is preferably horizontal. It is supported on both sides of the device 1.
  • a cutting device (not shown) is positioned at the outlet of the die plate 9 to cut the natural rubber into pieces.
  • This cutting device can be fixed on the shaft 4 of the device 1 and rotate at the same speed as the shaft 4.
  • This cutting device is then installed on the shaft 4 leaving the device but may not rotate at the same speed as the shaft 4.
  • This cutting device is driven by an independent motor and can cut smaller pieces than when the cutting system is attached to the shaft of the device as it rotates faster.
  • the present invention is illustrated by the following example.
  • EXAMPLES The object of these examples is to compare the properties of rubber compositions according to the invention with the properties of comparative rubber compositions comprising a natural rubber different from the natural rubber treated according to the invention. Preparation of rubber compositions
  • the necessary basic constituents Natural rubber, reinforcing fillers, other additives
  • Thermomechanical work non-productive phase
  • Thermomechanical work is then carried out in one step, which lasts a total of about 3 to 5 min, until a maximum temperature of "fall” of 165 ° C is reached.
  • the mixture thus obtained is recovered and cooled.
  • the final composition thus obtained is then calendered in the form of a sheet or a plate for a characterization in the laboratory.
  • the rubber compositions are characterized after curing as indicated below.
  • Dynamic properties are measured on a viscoanalyzer (Metravib VA4000) according to ASTM D 5992-96.
  • the response of a sample of vulcanized composition (cylindrical specimen 4 mm in thickness and 400 mm 2 in section) is recorded, subjected to a sinusoidal solicitation in alternating simple shear, at a frequency of 10 Hz, at 60 ° C, at a strain amplitude sweep of 0, 1% to 50%> (forward cycle), then 50%> to 1%) (return cycle): for the forward cycle, the maximum value of the loss factor, denoted tan (ô) max.
  • compositions A1 and B1 are compositions according to the invention. Natural rubber is a natural bottom mug rubber. Composition C 1 is a comparative composition. Natural rubber is not a natural bottom mug rubber.
  • the natural rubber was treated with hydroxylamine sulfate, that is, hydroxylamine sulfate was added to the natural rubber in an amount of 0.8 g per kg. natural rubber.
  • the treatment of the natural rubber was carried out by means of two shredding and homogenization devices arranged in series, namely two "prebreakers" connected in series.
  • a residual extractable hydroxylamine content in the natural rubber was determined at the end of the natural rubber treatment process.
  • This assay is based on the method described in J. nat. Rubb. Res., 3 (1), 1-6, with the following extraction conditions: extraction with sulfuric acid at 190 ° C +/- 10 ° C, for 24 hours, the temperature being taken between the heating mantle and the flange during the extraction.
  • This assay carried out on samples taken at various points of the natural rubber treated according to the process, makes it possible to verify the good homogenization of the hydroxylamine in the rubber, by revealing a level of homogeneous residual hydroxylamine that is homogeneous in the whole of the natural rubber. treaty .
  • 224 ppm extractable residual hydroxylamine is assayed, the natural rubber having been treated with 0.8 g of hydroxylamine sulfate per kg of natural rubber.
  • compositions are given in Table 1. The amounts are expressed in parts per 100 parts by weight of elastomer (phr). Quantities of natural rubber are given not taking into account hydroxylamine sulphate. Table 1
  • compositions A 1 and B 1 according to the invention have an improved hysteresis compared to the control composition C 1 comprising 100% US S latex natural rubber ("unsmoke sheet"). This is very favorable for obtaining a tire with reduced rolling resistance when the composition according to the invention is used in a tread.
  • compositions A2 and B2 are compositions according to the invention. Natural rubber is a natural bottom mug rubber.
  • the composition C2 is a comparative composition. Natural rubber is not a natural bottom mug rubber.
  • the natural rubber was treated with hydroxylamine sulfate, i.e. hydroxylamine sulfate was added to the natural rubber in an amount of 1.5 g per kg of rubber. natural.
  • compositions are given in Table 3. The amounts are expressed in parts per 100 parts by weight of elastomer (phr). Quantities of natural rubber are given not taking into account hydroxylamine sulphate.
  • compositions A2 and B2 in accordance with the invention have an improved hysteresis compared to the control composition C 2 comprising 100% USS natural latex rubber ("unsmoke sheet"). This is very favorable for obtaining a tire with reduced rolling resistance when the composition according to the invention is used in a tread.

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Abstract

The invention relates to a method for treating a natural rubber, comprising the following steps: adding to the natural rubber one or more ammonia-derived compounds, said natural rubber being made up of at least 80 wt % of cup lump natural rubber and 0 to 20 wt % of natural latex rubber, relative to the total weight of natural rubber, said one or more ammonia-derived compounds being selected among the compounds with formula XNH2 and the salts thereof, wherein X is a group selected among the C1-C4 hydroxyl and hydroxyalkyl groups, and said one or more compounds being provided in an amount varying from 0.2 to 2.2 g per kilogram of natural rubber, and then subjecting the natural rubber to which the one or more ammonia-derived compounds have been added to machine work at a temperature of at least 100°C.

Description

Procédé de préparation d'un caoutchouc naturel  Process for preparing a natural rubber
L 'invention se rapporte à un procédé de préparation d 'un caoutchouc naturel traité au moyen de l ' addition d'un dérivé d' ammoniac et de l' homogénéisation de l' ensemble en résultant par un dispositif fournissant un travail mécanique à température élevée. The invention relates to a process for the preparation of a treated natural rubber by means of the addition of an ammonia derivative and the homogenisation of the resulting assembly by a device providing high temperature mechanical work. .
Il est connu que le caoutchouc naturel a tendance à durcir, et donc à perdre en plasticité, lors de son transport et de son stockage. Cette perte de plasticité se traduit par une augmentation de sa viscosité Mooney. Cette tendance à durcir est due au fait que les protéines du caoutchouc naturel réagissent notamment avec les fonctions carbonyles, et en particulier les fonctions aldéhydes, des chaînes polyisoprène pour former une macrostructure plus importante.  It is known that natural rubber has a tendency to harden, and therefore to lose plasticity during transport and storage. This loss of plasticity results in an increase in its Mooney viscosity. This tendency to harden is due to the fact that the proteins of the natural rubber react in particular with the carbonyl functions, and in particular the aldehyde functions, polyisoprene chains to form a larger macrostructure.
Il est connu de compenser ce durcissement du caoutchouc naturel, en abaissant la viscosité du caoutchouc naturel notamment par une plastification de ce caoutchouc naturel au moyen d'un travail mécanique dans un mélangeur interne.  It is known to compensate for this hardening of the natural rubber, by lowering the viscosity of the natural rubber in particular by plasticizing this natural rubber by means of mechanical work in an internal mixer.
Mais ce procédé de plastification présente un coût énergétique important, de l ' ordre de 140 kW/t, et nécessite des investissements importants.  But this plastification process has a significant energy cost, of the order of 140 kW / t, and requires significant investments.
Il est également connu de stabiliser le caoutchouc naturel sec avec des stabilisants, en particulier des composés hydroxylamines ou hydrazides, au moyen de machines de mélange fournissant un travail mécanique et à une température supérieure à 100° C .  It is also known to stabilize dry natural rubber with stabilizers, especially hydroxylamine or hydrazide compounds, by means of mixing machines providing mechanical work and at a temperature above 100 ° C.
La stabilisation du caoutchouc naturel peut également être effectuée en phase latex, par inj ection des stabilisants dans le latex. Le traitement en phase latex présente cependant l 'inconvénient de perdre du stabilisant dans les eaux de coagulation qui sont rejetées dans l ' environnement.  The stabilization of the natural rubber can also be carried out in the latex phase by injection of the stabilizers into the latex. However, the latex phase treatment has the disadvantage of losing stabilizer in the coagulation water which is released into the environment.
II est également connu de traiter des crêpes ou des granulés de caoutchouc naturel humides par arrosage ou trempage avec des stabilisants. Ces crêpes ou granulés sont ensuite passés dans des extrudeuses et/ou mis directement dans les séchoirs. Cependant, le traitement des crêpes ou des granulés de caoutchouc naturel humides par arrosage ou trempage avec des stabilisants présente l 'inconvénient de perdre de l ' eau et donc du produit lors du passage dans les crêpeuses ou dans les séchoirs . De plus, pour l ' arrosage, il est nécessaire de manipuler une grande quantité de stabilisant, par exemple de solutions d' hydroxylamines . I l est également possible de retrouver du stabilisant dans les effluents . It is also known to treat pancakes or wet natural rubber granules by watering or dipping with stabilizers. These pancakes or granules are then passed through extruders and / or put directly in the dryers. However, the treatment of crepes or wet natural rubber granules by watering or soaking with stabilizers has the disadvantage of losing water and therefore the product during passage in the crepe or in the dryers. In addition, for watering, it is necessary to handle a large amount of stabilizer, for example solutions of hydroxylamines. It is also possible to find stabilizer in the effluents.
Il est enfin connu de traiter le caoutchouc naturel sec avec des stabilisants. Le caoutchouc naturel et le stabilisant sont mélangés dans des machines fournissant un travail mécanique et de la température, pour disperser et faire réagir le stabilisant avec le caoutchouc naturel.  It is finally known to treat dry natural rubber with stabilizers. The natural rubber and the stabilizer are mixed in machinery providing mechanical work and temperature, to disperse and react the stabilizer with the natural rubber.
On peut citer le document EP 0 950 485 qui décrit un procédé de séchage du caoutchouc naturel de latex comprenant une étape d' ajout d'un stabilisant. Ce document mentionne simp lement un mélangeur ou une extrudeuse.  Document EP 0 950 485 describes a method of drying natural latex rubber comprising a step of adding a stabilizer. This document simply mentions a mixer or an extruder.
Il existe donc un besoin de disposer d'un procédé de traitement du caoutchouc naturel pendant la phase d'usinage qui présente un gain énergétique par rapport aux procédés de stabilisation usuels avec des hydroxylamines, et qui présente un gain énergétique, de productivité et de coût d' investissement par rapport au procédé de plastification habituel. De plus ce procédé ne doit pas rej eter de sulfate d' hydroxylamine dans les effluents liquides. De plus, les propriétés des compositions comprenant du caoutchouc naturel ainsi traité doivent être comparables à celles des compositions comprenant du caoutchouc naturel plastifié. En particulier, la résistance au roulement, la viscosité Mooney et la rigidité d'une composition contenant un tel caoutchouc naturel doit être comparable à celle obtenue pour une composition contenant un caoutchouc naturel plastifié.  There is therefore a need for a process for treating natural rubber during the machining phase, which has an energy gain compared to conventional stabilization processes with hydroxylamines, and which has an energy, productivity and cost saving. investment compared to the usual plasticization process. In addition, this process must not reject hydroxylamine sulphate in the liquid effluents. In addition, the properties of the compositions comprising natural rubber thus treated must be comparable to those of the compositions comprising plasticized natural rubber. In particular, the rolling resistance, the Mooney viscosity and the rigidity of a composition containing such a natural rubber must be comparable to that obtained for a composition containing a plasticized natural rubber.
Les demanderesses ont découvert de façon surprenante que le caoutchouc naturel pouvait être traité au moyen d'un procédé comprenant une étape d' addition au caoutchouc naturel majoritairement sous forme de caoutchouc naturel de fond de tasse d'un ou plusieurs composés dérivés d' ammoniac, le ou lesdits composés étant présents en une quantité variant de 0,2 à 2,2 g par kilo gramme de caoutchouc naturel, et une étape de travail mécanique de l ' ensemble à une température d' au moins 100 ° C , un tel procédé permettant un gain énergétique, de productivité et de coût d' investissement par rapport au procédé de plastification habituel. It has surprisingly been found by the Applicants that natural rubber can be treated by a process comprising a step of adding to the natural rubber predominantly in the form of a natural bottom cup rubber of one or more ammonia derived compounds, the one or more compounds being present in an amount ranging from 0.2 to 2.2 g per kilo gram of natural rubber, and a mechanical working step of the assembly at a temperature of at least 100 ° C, such a method allowing energy saving, productivity and investment cost compared to the usual plasticizing process .
L 'invention a donc pour obj et un procédé de traitement d 'un caoutchouc naturel, comprenant les étapes suivantes :  The object of the invention is therefore a process for treating a natural rubber, comprising the following steps:
- ajouter au caoutchouc naturel un ou plusieurs composés dérivés d' ammoniac, ledit caoutchouc naturel étant constitué d ' au moins 80% en poids de caoutchouc naturel de fond de tasse et de 0 à 20% en poids de caoutchouc naturel de latex, par rapport au poids total de caoutchouc naturel, le ou lesdits composés dérivés d' ammoniac étant choisis parmi les composés de formule XNH2 et leurs sels, ou X est un groupe choisi parmi les groupes hydroxyle et hydroxyalkyle en C 1 -C4 , le ou lesdits composés étant présents en une quantité variant de 0,2 à 2,2 g par kilogramme de caoutchouc naturel, puis adding to the natural rubber one or more compounds derived from ammonia, said natural rubber consisting of at least 80% by weight of natural bottom mastic and 0 to 20% by weight of natural latex rubber, relative to to the total weight of natural rubber, the one or more compounds derived from ammonia being chosen from the compounds of formula XNH 2 and their salts, or X is a group chosen from hydroxyl and hydroxyalkyl groups of C 1 -C 4 , the said compound or compounds being present in an amount ranging from 0.2 to 2.2 g per kilogram of natural rubber, then
soumettre le caoutchouc naturel auquel a été ajouté le ou les composés dérivés d' ammoniac à un travail mécanique à une température d' au moins 100 ° C .  subject the natural rubber to which the ammonia derivative compound (s) has been added to mechanical work at a temperature of not less than 100 ° C.
Par caoutchouc naturel de fond de tasse, on entend la partie de caoutchouc naturel qui, après saignée de l ' arbre et réco lte dans une tasse, a coagulé sous forme so lide dans cette tasse, puis a subi un travail de nettoyage, d' homogénéisation et de séchage.  By natural rubber of the bottom of the cup, is meant the part of natural rubber which, after bleeding from the tree and recoated in a cup, has coagulated in solid form in this cup, then underwent a cleaning work, homogenization and drying.
Par caoutchouc naturel de latex, on entend le caoutchouc naturel qui, après saignée de l ' arbre, s ' est écoulé dans la tasse, a été réco lté sous forme liquide et coagulé artificiellement, puis a subi un travail de nettoyage, d' homogénéisation et de séchage.  "Natural latex rubber" means the natural rubber which, after bleeding from the tree, has flowed into the cup, has been reco lted in liquid form and artificially coagulated, then has undergone cleaning, homogenisation and drying.
Le travail de nettoyage, d ' homogénéisation et de séchage comprend généralement une ou plusieurs étapes de réduction de la taille des morceaux de caoutchouc naturel, par exemple au moyen d'un broyeur à marteaux, une ou plusieurs étapes de lavage dans un bac à eau pour éliminer les impuretés et les contaminants, une ou plusieurs étapes de crêpage, une ou plusieurs étapes de mise en miettes et une ou plusieurs étapes de séchage. Puis le caoutchouc naturel est comprimé pour être mis sous forme de pain ou de balle. Selon un mode de réalisation préféré, le caoutchouc naturel est un caoutchouc naturel de fond de tasse. Cela signifie que le caoutchouc naturel ne contient pas de caoutchouc naturel de latex. The cleaning, homogenization and drying work generally comprises one or more steps of reducing the size of the pieces of natural rubber, for example by means of a hammer mill, one or more washing steps in a water tray for removing impurities and contaminants, one or more crepe steps, one or more crumbling steps, and one or more drying steps. Then the natural rubber is compressed to be put in the form of bread or ball. In a preferred embodiment, the natural rubber is a natural cup bottom rubber. This means that natural rubber does not contain natural latex rubber.
De préférence, le caoutchouc naturel utilisé dans le procédé selon l' invention est choisi parmi les caoutchoucs naturels issus de l ' hévéa Brasiliensis.  Preferably, the natural rubber used in the process according to the invention is chosen from the natural rubbers derived from the rubber tree Brasiliensis.
Le ou les composés dérivés d ' ammoniac qui sont ajoutés au caoutchouc naturel peuvent être choisis parmi l ' hydroxylamine et les sels d' hydroxylamine à base d' acide fort. A titre de sel d' hydroxylamine à base d' acide fort, on peut citer le sulfate d' hydroxylamine.  The compound (s) derived from ammonia that are added to the natural rubber may be selected from hydroxylamine and hydroxylamine salts based on strong acid. As the hydroxylamine salt based on strong acid, mention may be made of hydroxylamine sulfate.
Comme expliqué précédemment, le ou les composés dérivés d' ammoniac sont présents en une quantité variant de 0,2 à 2,2 g par kilo gramme de caoutchouc naturel.  As previously explained, the compound (s) derived from ammonia are present in an amount ranging from 0.2 to 2.2 g per kilogram of natural rubber.
Selon un mode de réalisation préféré, le composé dérivé d' ammoniac est l 'hydroxylamine et est présent à une teneur variant de 0,2 à 0, 8 g, de préférence de 0,32 à 0,6 g, par kilogramme de caoutchouc naturel.  According to a preferred embodiment, the compound derived from ammonia is hydroxylamine and is present in a content ranging from 0.2 to 0.8 g, preferably from 0.32 to 0.6 g, per kilogram of rubber. natural.
Selon un autre mode de réalisation préféré, le composé dérivé d' ammoniac est le sulfate d' hydroxylamine et est présent à une teneur variant de 0,5 à moins de 2 g, de préférence de 0, 8 à 1 ,5 g, par kilo gramme de caoutchouc naturel.  According to another preferred embodiment, the compound derived from ammonia is hydroxylamine sulfate and is present in a content ranging from 0.5 to less than 2 g, preferably from 0.8 to 1.5 g, kilo gram of natural rubber.
La viscosité Mooney des mélanges obtenus avec le caoutchouc naturel traité avec de l ' hydroxylamine à des taux inférieurs à 0,2 g/kg est trop élevée par rapport à un caoutchouc naturel plastifié. Avec des taux d' hydroxylamine supérieurs à 0, 8 g/kg, l ' hystérèse du mélange contenant le caoutchouc naturel augmente par rapport à l ' hystérèse d'un mélange contenant le caoutchouc naturel plastifié.  The Mooney viscosity of the mixtures obtained with natural rubber treated with hydroxylamine at levels below 0.2 g / kg is too high compared to a plasticized natural rubber. With hydroxylamine levels greater than 0.8 g / kg, the hysteresis of the natural rubber - containing mixture increases with respect to the hysteresis of a mixture containing the plasticized natural rubber.
L ' ajout du ou des composés dérivés d' ammoniac au caoutchouc naturel peut se faire par arrosage du caoutchouc naturel avec la quantité souhaitée de composés dérivés d' ammoniac, ou bien par trempage du caoutchouc naturel dans une solution de composés dérivés d' ammoniac. De préférence, l' ajout du ou des composés dérivés d' ammoniac au caoutchouc naturel se fait par arrosage . Après l ' étape d' addition au caoutchouc naturel d'un ou plusieurs composés dérivés d' ammoniac, le procédé selon l' invention comprend une étape de travail mécanique à une température d ' au moins 100 °C du caoutchouc naturel auquel a été ajouté et le ou les composés dérivés d' ammoniac. The addition of the ammonia derivative compound (s) to the natural rubber may be by spraying the natural rubber with the desired amount of ammonia - derived compounds, or by soaking the natural rubber in a solution of ammonia - derived compounds. Preferably, the addition of the compound (s) derived from ammonia to the natural rubber is done by watering. After the step of adding to the natural rubber one or more compounds derived from ammonia, the process according to the invention comprises a step of mechanical working at a temperature of at least 100 ° C of the natural rubber to which has been added and the compound (s) derived from ammonia.
De préférence, le travail mécanique est effectué à une température d' au moins 1 1 0°C .  Preferably, the mechanical work is carried out at a temperature of at least 110 ° C.
Le travail mécanique est de préférence effectué au moyen d 'un ou plusieurs dispositifs de déchiquetage et d' homogénéisation. Un tel dispositif est généralement appelé « prebreaker ».  The mechanical work is preferably carried out by means of one or more shredding and homogenizing devices. Such a device is generally called "prebreaker".
Un tel dispositif a une consommation énergétique de l ' ordre 50 kW/tonne de caoutchouc naturel, alors qu 'un procédé de plastification consomme de l 'ordre de 140 kW/tonne.  Such a device has an energy consumption of the order of 50 kW / ton of natural rubber, whereas a plasticizing process consumes around 140 kW / ton.
Selon un mode de réalisation particulièrement préféré, le travail mécanique est réalisé au moyen de deux dispositifs de déchiquetage et d ' homogénéisation disposés en série.  According to a particularly preferred embodiment, the mechanical work is performed by means of two shredding and homogenization devices arranged in series.
L 'utilisation de deux tels dispositifs est particulièrement avantageuse pour s ' assurer que le caoutchouc naturel soit maintenu à une température d' au moins 100° C pendant un temps suffisant qui permette au composé dérivé d ' ammoniac de réagir.  The use of two such devices is particularly advantageous to ensure that the natural rubber is maintained at a temperature of at least 100 ° C for a sufficient time which allows the ammonia derived compound to react.
En outre, l 'utilisation de deux tels dispositifs permet également d' atteindre une répartition homogène du ou des dérivés d ' ammoniac dans le caoutchouc naturel, cette répartition pouvant être contrôlée par dosage selon la méthode décrite dans le document J. nat. Rubb. Res., 3 (1), 1-6.  In addition, the use of two such devices also makes it possible to achieve a homogeneous distribution of the ammonia derivative (s) in the natural rubber, this distribution being able to be controlled by assaying according to the method described in the document J. nat. Rubb. Res., 3 (1), 1-6.
L ' étape de travail mécanique présente avantageusement une durée variant de 25 secondes à 3 minutes.  The mechanical working stage advantageously has a duration varying from 25 seconds to 3 minutes.
Le ou les dispositifs de déchiquetage et d'homogénéisation comprennent habituellement chacun une zone d' alimentation et de déchiquetage et une zone d ' homogénéisation reliées entre elles, et un arbre traversant lesdites zones, ledit arbre étant muni de couteaux rotatifs .  The shredding and homogenizing device (s) usually each comprise a feed and shredding zone and a homogenization zone connected to each other, and a shaft passing through said zones, said shaft being provided with rotary knives.
La zone d' alimentation comprend généralement une partie supérieure et une partie inférieure, ladite partie supérieure étant apte à alimenter ladite partie inférieure, ladite partie inférieure comprenant la première partie dudit arbre. The feed zone generally comprises an upper portion and a lower portion, said upper portion being adapted to feeding said lower portion, said lower portion comprising the first portion of said shaft.
Selon un mode de réalisation particulier, les parois de la zone d' alimentation présentent des premiers couteaux fixes. De tels premiers couteaux fixes permettent d ' éviter que l ' ensemble caoutchouc naturel - composé dérivé d' ammoniac ne remonte dans la partie supérieure de la zone d' alimentation une fois qu' il a atteint la partie inférieure de la zone d' alimentation.  According to a particular embodiment, the walls of the feed zone have first fixed knives. Such first fixed knives prevent the assembly of natural rubber - compound derived from ammonia goes up in the upper part of the feeding zone once it has reached the lower part of the feeding zone.
La zone d ' homogénéisation comprend généralement la seconde partie dudit arbre et un fourreau insérant ladite seconde partie de l ' arbre, ledit fourreau étant muni de seconds couteaux fixes.  The homogenization zone generally comprises the second part of said shaft and a sleeve inserting said second part of the shaft, said sleeve being provided with second fixed blades.
L ' arbre logé dans la partie inférieure de la zone d' alimentation et dans la zone d ' homogénéisation est de préférence horizontal.  The shaft housed in the lower part of the feed zone and in the homogenization zone is preferably horizontal.
La vitesse de l ' arbre varie avantageusement de 20 à 1 00 tours/min, de préférence de 20 à 60 tours/min.  The speed of the shaft advantageously varies from 20 to 100 rpm, preferably from 20 to 60 rpm.
Le ou les dispositifs de déchiquetage et d'homogénéisation présentent habituellement chacun une plaque filière en bout de la zone d'homogénéisation, ladite plaque filière présentant des orifices.  The chipping and homogenizing device or devices usually each have a die plate at the end of the homogenization zone, said die plate having orifices.
Ces orifices peuvent être sous forme de trous ronds ou de trous oblongs ou de trous triangulaires.  These holes may be in the form of round holes or oblong holes or triangular holes.
Avantageusement, ces orifices présentent une ouverture variable. La variation de l ' ouverture des orifices permet d' augmenter ou de diminuer le travail mécanique fourni au caoutchouc naturel ou de faire varier le débit dans le dispositif.  Advantageously, these orifices have a variable opening. The variation of the opening of the orifices makes it possible to increase or decrease the mechanical work provided to the natural rubber or to vary the flow rate in the device.
La température dans la zone de déchiquetage et d'homogénéisation peut être réglée en faisant varier le travail mécanique, en utilisant les moyens suivants, seuls ou en combinaison : nombre de couteaux fixes, nombre de couteaux rotatifs, longueur de la zone de déchiquetage et d'homogénéisation, fermeture de la plaque filière, débit de caoutchouc naturel, chauffage du corps du dispositif de déchiquetage et d' homogénéisation.  The temperature in the shredding and homogenizing zone can be adjusted by varying the mechanical work, using the following means, alone or in combination: number of fixed knives, number of rotary knives, length of shredding zone and homogenization, closure of the die plate, flow of natural rubber, heating of the body of the shredding device and homogenization.
L ' étape de travail mécanique peut être suivie d'une étape de coupe du caoutchouc naturel traité. L ' étape de coupe peut être effectuée au moyen d'un dispositif de coupe positionné en sortie du dispositif conférant le travail mécanique, en particulier ou du ou des dispositifs de déchiquetage et d'homogénéisation. The mechanical working step may be followed by a cutting step of the treated natural rubber. The cutting step may be performed by means of a cutting device positioned at the output of the device conferring the mechanical work, in particular or of the shredding and homogenizing device or devices.
Un autre obj et de l' invention est un caoutchouc naturel traité susceptible d' être obtenu par le procédé obj et de l ' invention.  Another object of the invention is a treated natural rubber which can be obtained by the process obj and of the invention.
Un autre obj et de l'invention est une composition de caoutchouc renforcée à base d'au moins une charge renforçante et d'une matrice élastomère comprenant au moins un caoutchouc naturel traité selon l 'invention.  Another object of the invention is a reinforced rubber composition based on at least one reinforcing filler and an elastomeric matrix comprising at least one natural rubber treated according to the invention.
Par l'expression composition "à base de" , il faut entendre une composition comportant le mélange et/ou le produit de réaction des différents constituants utilisés, certains de ces constituants de base étant susceptibles de, ou destinés à, réagir entre eux, au moins en partie, lors des différentes phases de fabrication de la composition, en particulier au cours de sa réticulation ou vulcanisation.  By the term "composition-based" is meant a composition comprising the mixture and / or the reaction product of the various constituents used, some of these basic constituents being capable of or intended to react with one another, less in part, during the various phases of manufacture of the composition, in particular during its crosslinking or vulcanization.
La composition de caoutchouc renforcée selon l'invention peut se présenter à l'état réticulé ou à l'état non réticulé, autrement dit réticulable.  The reinforced rubber composition according to the invention may be in the crosslinked state or in the uncrosslinked state, that is to say crosslinkable.
La matrice élastomère présente dans la composition selon l' invention peut également, outre le caoutchouc naturel traité selon l' invention, comprendre au moins un autre élastomère diénique.  The elastomer matrix present in the composition according to the invention may also, in addition to the natural rubber treated according to the invention, comprise at least one other diene elastomer.
Dans le cas d'un coupage avec au moins un autre élastomère diénique, la fraction massique du caoutchouc naturel traité selon l'invention dans la matrice élastomère est majoritaire et de préférence supérieure ou égale à 10% en masse de la masse totale de la matrice, encore plus préférentiellement supérieure ou égale 50% en masse de la masse totale de la matrice, encore plus préférentiellement supérieure ou égale 70% . La fraction massique du caoutchouc naturel traité selon l'invention dans la matrice élastomère est de préférence inférieure ou égale à 85 % en masse de la masse totale de la matrice. On appelle fraction massique majoritaire selon l'invention la fraction massique la plus élevée du coupage. Par élastomère diénique, doit être compris selon l'invention tout élastomère synthétique issu au moins en partie de monomères diènes. Plus particulièrement, par élastomère diénique, on entend tout homopo lymère obtenu par polymérisation d'un monomère diène conjugué ayant 4 à 12 atomes de carbone, ou tout copolymère obtenu par copolymérisation d'un ou plusieurs diènes conjugués entre eux ou avec un ou plusieurs composés vinylaromatiques ayant de 8 à 20 atomes de carbone. Dans le cas de copolymères, ceux-ci contiennent de 20 % à 99 % en masse d'unités diéniques, et de 1 à 80 % en masse d'unités vinylaromatiques. In the case of a blend with at least one other diene elastomer, the mass fraction of the natural rubber treated according to the invention in the elastomer matrix is predominant and preferably greater than or equal to 10% by weight of the total mass of the matrix. more preferably still greater than or equal to 50% by weight of the total mass of the matrix, even more preferably greater than or equal to 70%. The mass fraction of the natural rubber treated according to the invention in the elastomer matrix is preferably less than or equal to 85% by weight of the total mass of the matrix. The majority mass fraction according to the invention is the highest mass fraction of the blend. By diene elastomer, it should be understood according to the invention any synthetic elastomer derived at least in part from monomers dienes. More particularly, diene elastomer is any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms, or any copolymer obtained by copolymerization of one or more conjugated dienes with one another or with one or more compounds. vinylaromatic compounds having 8 to 20 carbon atoms. In the case of copolymers, these contain from 20% to 99% by weight of diene units, and from 1 to 80% by weight of vinylaromatic units.
L'élastomère diénique constituant une partie de la matrice élastomère de la composition selon l'invention est choisi préférentiellement dans le groupe des élastomères diéniques fortement insaturés constitué par les polybutadiènes (BR), les polyisoprènes (IR) de synthèse, le caoutchouc naturel (NR) différent du caoutchouc naturel traité selon l' invention, les copolymères de butadiène, les copolymères d'isoprène et les mélanges de ces élastomères. De tels copolymères sont plus préférentiellement choisis dans le groupe constitué par les copolymères de butadiène-styrène (SBR), les copolymères d' isoprène-butadiène (BIR), les copolymères d'isoprène- styrène (SIR) et les copolymères d' isoprène-butadiène-styrène (SBIR) . On peut également envisager un coupage avec tout élastomère synthétique autre que diénique, voire avec tout polymère autre qu'élastomère, par exemple un polymère thermoplastique.  The diene elastomer constituting a part of the elastomer matrix of the composition according to the invention is preferably chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes (BR), synthetic polyisoprenes (IR) and natural rubber (NR). ) different from the natural rubber treated according to the invention, butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-copolymers. butadiene-styrene (SBIR). It is also possible to cut with any synthetic elastomer other than diene, or with any other polymer other than elastomer, for example a thermoplastic polymer.
Plus préférentiellement, la matrice élastomère est uniquement constituée du caoutchouc naturel traité selon l ' invention.  More preferably, the elastomeric matrix consists solely of the natural rubber treated according to the invention.
La composition de caoutchouc de l'invention comprend, outre au moins une matrice élastomère telle que décrit ci-dessus, au moins une charge renforçante.  The rubber composition of the invention comprises, in addition to at least one elastomeric matrix as described above, at least one reinforcing filler.
On peut utiliser tout type de charge renforçante connue pour ses capacités à renforcer une composition de caoutchouc utilisable pour la fabrication de bandes de roulement de pneumatiques, par exemple du noir de carbone, une charge inorganique renforçante telle que de la silice à laquelle est associé de manière connue un agent de couplage, ou encore un mélange de ces deux types de charge. Any type of reinforcing filler known for its ability to reinforce a rubber composition that can be used for the manufacture of tire treads, for example carbon black, can be used, a reinforcing inorganic filler such as only silica with which is associated in a known manner a coupling agent, or a mixture of these two types of filler.
Comme noirs de carbone conviennent tous les noirs de carbone, utilisés individuellement ou sous forme de mélanges, notamment les noirs du type HAF, ISAF, SAF conventionnellement utilisés dans les bandes de roulement des pneumatiques (noirs dits de grade pneumatique) . Parmi ces derniers, on citera plus particulièrement les noirs de carbone renforçants des séries 100, 200 ou 300 (grades ASTM), comme par exemple les noirs N I 15 , N 134 , N234, N326, N330, N339, N347, N375. Les noirs de carbone pourraient être par exemp le déj à incorporés à l'élastomère isoprénique sous la forme d'un masterbatch (voir par exemple demandes WO 97/36724 ou WO 99/ 16600) .  Suitable carbon blacks are all carbon blacks, used individually or in the form of mixtures, in particular blacks of the HAF, ISAF, SAF type conventionally used in tire treads (so-called pneumatic grade blacks). Among these, there will be mentioned more particularly the reinforcing carbon blacks of the series 100, 200 or 300 (ASTM grades), such as for example the blacks N 15, N 134, N 234, N 326, N330, N339, N347, N375. The carbon blacks could for example be already incorporated into the isoprene elastomer in the form of a masterbatch (see for example WO 97/36724 or WO 99/16600).
Comme charge inorganique renforçante, doit être entendu dans la présente demande, par définition, toute charge inorganique ou minérale quelles que soient sa couleur et son origine (naturelle ou de synthèse), capable de renforcer à elle seule, sans autre moyen qu' un agent de couplage intermédiaire, une composition de caoutchouc destinée à la fabrication de pneumatiques; une telle charge se caractérise généralement, de manière connue, par la présence de groupes hydroxyle (-OH) à sa surface.  As reinforcing inorganic filler, is meant by the present application, by definition, any inorganic or inorganic filler whatever its color and its origin (natural or synthetic), capable of reinforcing on its own, without any other means than an agent intermediate coupling, a rubber composition for the manufacture of tires; such a filler is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.
Comme charges inorganiques renforçantes conviennent notamment des charges minérales du type siliceux, en particulier de la silice (Si02), ou du type alumineuse, en particulier de l'alumine (A1203) . La silice utilisée peut être toute silice renforçante connue de l'homme du métier, notamment toute silice précipitée ou pyrogénée présentant une surface BET ainsi qu'une surface spécifique CTAB toutes deux inférieures à 450 m2/g, de préférence de 30 à 400 m2/g, notamment entre 60 et 300 m2/g. On citera également les charges minérales du type alumineux, en particulier de l'alumine (A1203) ou des (oxyde)hydroxydes d'aluminium, ou encore des oxydes de titane renforçants, par exemp le décrits dans US 6 610 261 et US 6 747 087. Comme charges renforçantes conviennent également des charges renforçantes d'une autre nature, notamment du noir de carbone, dès lors que ces charges renforçantes seraient recouvertes d'une couche siliceuse, ou bien comporteraient à leur surface des sites fonctionnels, notamment hydroxyles, nécessitant l'utilisation d'un agent de couplage pour établir la liaison entre la charge et l'élastomère. A titre d'exemple, on peut citer par exemp le des noirs de carbone pour pneumatiques tels que décrits par exemp le dans les documents brevet WO 96/37547, WO 99/28380. Suitable reinforcing inorganic fillers are in particular mineral fillers of the siliceous type, in particular silica (SiO 2 ), or aluminous type, in particular alumina (Al 2 O 3 ). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface both less than 450 m 2 / g, preferably from 30 to 400 m 2 / g, especially between 60 and 300 m2 / g. Mention may also be made of mineral fillers of the aluminous type, in particular alumina (Al 2 O 3 ) or aluminum (oxide) hydroxides, or else reinforcing titanium oxides, for example described in US Pat. No. 6,610,261 and No. 6,747,087. Reinforcing fillers of another nature, especially carbon black, are also suitable as reinforcing fillers. when these reinforcing fillers would be covered with a siliceous layer, or would comprise on their surface functional sites, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between the filler and the elastomer. By way of example, mention may be made, for example, of carbon blacks for tires as described for example in documents WO 96/37547 and WO 99/28380.
L'état physique sous lequel se présente la charge inorganique renforçante est indifférent, que ce soit sous forme de poudre, de microperles, de granulés, de billes ou toute autre forme densifiée appropriée. Bien entendu, on entend également par charge inorganique renforçante des mélanges de différentes charges renforçantes, en particulier de charges siliceuses hautement dispersibles telles que décrites précédemment.  The physical state in which the reinforcing inorganic filler is present is indifferent whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing fillers, in particular highly dispersible siliceous fillers as described above.
De manière préférentielle, le taux de charge renforçante totale Preferably, the level of total reinforcing filler
(noir de carbone et/ou autre charge renforçante telle que silice) est compris entre 10 et 200 pce, plus préférentiellement entre 30 et 1 50 pce, et encore plus préférentiellement entre 70 et 130 pce, l'optimum étant de manière connue différent selon les applications particulières visées. (carbon black and / or other reinforcing filler such as silica) is between 10 and 200 phr, more preferably between 30 and 150 phr, and even more preferably between 70 and 130 phr, the optimum being in a known manner different according to the particular applications targeted.
Selon une variante de l'invention, la charge renforçante est majoritairement autre que du noir de carbone, c'est-à-dire qu'elle comprend plus de 50% en poids du poids total de la charge, d'une ou de plusieurs charges autres que du noir de carbone, notamment une charge inorganique renforçante telle que la silice, voire elle est exclusivement constituée d'une telle charge.  According to a variant of the invention, the reinforcing filler is predominantly other than carbon black, that is to say it comprises more than 50% by weight of the total weight of the filler, of one or more fillers other than carbon black, especially a reinforcing inorganic filler such as silica, or it consists exclusively of such a filler.
Selon cette variante, lorsque du noir de carbone est également présent, il peut être utilisé à un taux inférieur à 20 pce, plus préférentiellement inférieur à 10 pce (par exemple entre 0,5 et 20 pce, notamment de 1 à 10 pce) .  According to this variant, when carbon black is also present, it may be used at a level of less than 20 phr, more preferably less than 10 phr (for example between 0.5 and 20 phr, in particular from 1 to 10 phr).
Selon une autre variante de l'invention, on utilise une charge renforçante comportant majoritairement du noir de carbone, et optionnellement de la silice ou une autre charge inorganique. Lorsque la charge renforçante comprend une charge nécessitant l'utilisation d'un agent de couplage pour établir la liaison entre la charge et l'élastomère, la composition de caoutchouc selon l 'invention comprend en outre, de manière classique, un agent susceptible d'assurer efficacement cette liaison. Lorsque la silice est présente dans la composition à titre de charge renforçante, on peut utiliser comme agents de couplage des organosilanes, notamment des alkoxysilanes polysulfurés ou des mercaptosilanes, ou encore des polyorganosiloxanes au moins bifonctionnels. According to another variant of the invention, a reinforcing filler comprising predominantly carbon black and optionally silica or other inorganic filler is used. When the reinforcing filler comprises a filler requiring the use of a coupling agent to establish the bond between the filler and the elastomer, the rubber composition according to the invention further comprises, in a conventional manner, an agent capable of effectively provide this link. When the silica is present in the composition as a reinforcing filler, it is possible to use as coupling agents organosilanes, especially polysulfurized alkoxysilanes or mercaptosilanes, or at least bifunctional polyorganosiloxanes.
Dans la composition selon l' invention, le taux d' agent de couplage est avantageusement inférieur à 20 pce, étant entendu qu' il est en général souhaitable d' en utiliser le moins possible. Son taux est préférentiellement compris entre 0,5 et 12 pce. La présence de l'agent de couplage dépend de celle de la charge inorganique renforçante. Son taux est aisément ajusté par l'homme du métier selon le taux de cette charge; il est typiquement de l'ordre de 0,5 % à 15 % en poids par rapport à la quantité de charge inorganique renforçante autre que du noir de carbone.  In the composition according to the invention, the level of coupling agent is advantageously less than 20 phr, it being understood that it is generally desirable to use as little as possible. Its rate is preferably between 0.5 and 12 phr. The presence of the coupling agent depends on that of the reinforcing inorganic filler. Its rate is easily adjusted by the skilled person according to the rate of this charge; it is typically of the order of 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler other than carbon black.
La composition de caoutchouc selon l'invention peut également contenir, en complément des agents de couplage, des activateurs de couplage, des agents de recouvrement des charges ou plus généralement des agents d'aide à la mise en œuvre susceptibles de manière connue, grâce à une amélioration de la dispersion de la charge dans la matrice de caoutchouc et à un abaissement de la viscosité de la composition, d'améliorer sa faculté de mise en œuvre à l'état cru, ces agents étant par exemp le des silanes hydro lysables tels que des alkylalkoxysilanes, des polyo ls, des po lyéthers, des aminés primaires , secondaires ou tertiaires, des polyorganosiloxanes hydroxylés ou hydro lysables.  The rubber composition according to the invention may also contain, in addition to the coupling agents, coupling activators, charge-recovery agents or, more generally, processing aid agents which can be used in known manner, thanks to an improvement of the dispersion of the filler in the rubber matrix and a lowering of the viscosity of the composition, to improve its ability to use in the green state, these agents being for example the hydrolysable silanes such as alkylalkoxysilanes, polyols, polyethers, primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes.
Les compositions de caoutchouc conformes à l'invention peuvent également contenir, des charges organiques renforçantes qui peuvent remplacer tout ou partie des noirs de carbone ou des autres charges inorganiques renforçantes décrites plus haut. Comme exemples de charges organiques renforçantes, on peut citer les charges organiques de polyvinyle fonctionnalisé telles que décrites dans les demandes WO-A-2006/069792, WO-A-2006/069793 , WO-A- 2008/003434 et WO-A-2008/003435. The rubber compositions in accordance with the invention may also contain reinforcing organic fillers which may replace all or part of the carbon blacks or other reinforcing inorganic fillers described above. Examples of reinforcing organic fillers include fillers organic functionalized polyvinyl compounds as described in WO-A-2006/069792, WO-A-2006/069793, WO-A-2008/003434 and WO-A-2008/003435.
La composition de caoutchouc selon l'invention peut comporter également tout ou partie des additifs usuels habituellement utilisés dans les compositions d'élastomères destinées à la fabrication de pneumatiques, comme par exemple des pigments, des charges non renforçantes, des agents de protection tels que cires anti-ozone, anti- ozonants chimiques, anti-oxydants, des agents anti-fatigue, des agents plastifiants, des résines renforçantes ou plastifiantes, des accepteurs (par exemp le résine phéno lique novo laque) ou des donneurs de méthylène (par exemp le HMT ou H3M) tels que décrits par exemple dans la demande WO 02/ 1 0269, un système de réticulation à base soit de soufre, soit de donneurs de soufre et/ou de peroxyde et/ou de bismaléimides, des accélérateurs de vulcanisation, des activateurs de vulcanisation.  The rubber composition according to the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended for the manufacture of tires, for example pigments, non-reinforcing fillers, protective agents such as waxes anti-ozone, anti-chemical ozonants, anti-oxidants, anti-fatigue agents, plasticizing agents, reinforcing or plasticizing resins, acceptors (eg novo lacquer phenolic resin) or methylene donors (eg HMT or H3M) as described for example in the application WO 02/1 0269, a crosslinking system based on either sulfur, or sulfur and / or peroxide and / or bismaleimide donors, vulcanization accelerators, vulcanization activators.
La composition est fabriquée dans des mélangeurs appropriés , en utilisant deux phases de préparation successives bien connues de l'homme du métier : une première phase de travail ou malaxage thermomécanique (phase dite "non-productive") à haute température, jusqu'à une température maximale comprise entre 1 10° C et 190°C, de préférence entre 130°C et 1 80° C, suivie d'une seconde phase de travail mécanique (phase dite "productive") jusqu'à une plus basse température, typiquement inférieure à 1 10°C, par exemple entre 40° C et 100°C, phase de finition au cours de laquelle est incorporé le système de réticulation.  The composition is manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art: a first phase of work or thermomechanical mixing (so-called "non-productive" phase) at high temperature, up to a maximum of maximum temperature between 1 10 ° C and 190 ° C, preferably between 130 ° C and 1 80 ° C, followed by a second mechanical working phase (so-called "productive" phase) to a lower temperature, typically less than 1 10 ° C, for example between 40 ° C and 100 ° C, finishing phase during which is incorporated the crosslinking system.
Le procédé de préparation d 'une composition selon l' invention, comprend généralement :  The process for the preparation of a composition according to the invention generally comprises:
(i) la réalisation, à une température maximale comprise entre 130 °C et 200 °C , d'un premier temps de travail thermo-mécanique des constituants de la composition comprenant le caoutchouc naturel traité selon l' invention et une charge renforçante, à l ' exception d'un système de réticulation, puis (ii) la réalisation, à une température inférieure à ladite température maximale dudit premier temps, d'un second temps de travail mécanique au cours duquel est incorporé ledit système de réticulation. (I) the production, at a maximum temperature of between 130 ° C. and 200 ° C., of a first thermomechanical working time of the constituents of the composition comprising the natural rubber treated according to the invention and a reinforcing filler, with the exception of a crosslinking system, then (ii) the production, at a temperature below said maximum temperature of said first time, of a second mechanical working time during which said crosslinking system is incorporated.
L'invention a également pour obj et un article semi-fini en caoutchouc pour pneumatique, comprenant une composition de caoutchouc selon l' invention, réticulable ou réticulée, ou constitué d'une telle composition.  The invention also relates to a semi-finished tire rubber article, comprising a rubber composition according to the invention, crosslinkable or crosslinked, or consisting of such a composition.
La composition finale ainsi obtenue peut ensuite être calandrée, par exemp le sous la forme d'une feuille, d'une plaque ou encore extrudée, par exemple pour former un profilé de caoutchouc utilisable comme produit semi-fini en caoutchouc destiné au pneumatique.  The final composition thus obtained may then be calendered, for example in the form of a sheet, a plate or extruded, for example to form a rubber profile usable as a semi-finished rubber product for the tire.
L'invention a donc pour obj et un pneumatique comportant un article semi-fini selon l' invention, en particulier une bande de roulement.  The invention is therefore obj and a tire comprising a semi-finished article according to the invention, in particular a tread.
D ' autres buts, caractéristiques et avantages de la présente invention apparaîtront encore plus clairement à la lecture de la description suivante, donnée uniquement à titre d' exemple non limitatif, et faite en référence au dessin annexé sur lequel la figure unique représente un dispositif de déchiquetage et d ' homogénéisation.  Other objects, features and advantages of the present invention will emerge even more clearly on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawing in which the single FIGURE shredding and homogenization.
Le caoutchouc naturel auquel a été ajouté le ou les composés dérivés d' ammoniac sont introduits dans un dispositif de déchiquetage et d' homogénéisation 1 .  The natural rubber to which the compound (s) derived from ammonia has been added is introduced into a shredder and homogenizer 1.
Le dispositif de déchiquetage et d' homogénéisation 1 comprend une zone d' alimentation et de déchiquetage 2 et une zone de d'homogénéisation 3 reliées entre elles, et un arbre 4 traversant lesdites zones, ledit arbre étant muni de couteaux rotatifs 5.  The shredding and homogenizing device 1 comprises a feed and shredding zone 2 and a homogenization zone 3 interconnected, and a shaft 4 passing through said zones, said shaft being provided with rotary knives 5.
La zone d' alimentation et de déchiquetage 2 comprend une partie supérieure 2a et une partie inférieure 2b.  The feeding and shredding zone 2 comprises an upper part 2a and a lower part 2b.
La partie supérieure 2a est une partie surélevée et ouverte pour permettre l ' introduction du caoutchouc naturel et des composés dérivés d' ammoniac . Cette partie supérieure 2a est généralement de forme carrée dont la longueur des côtés est égale au diamètre formé par les couteaux rotatifs 5 de l ' arbre 4. Les parois 6 de cette partie supérieure 2a sont généralement verticales, mais peuvent également être inclinées pour favoriser l ' alimentation de gros blocs de caoutchouc naturel. De préférence, les parois 6 sont verticales pour éviter que le caoutchouc naturel ne reste co llé sur des parois d' alimentation qui seraient inclinées . The upper portion 2a is an elevated and open portion for the introduction of natural rubber and ammonia derived compounds. This upper part 2a is generally of square shape whose length of the sides is equal to the diameter formed by the rotary knives 5 of the shaft 4. The walls 6 of this part upper 2a are generally vertical, but can also be inclined to favor the feeding of large blocks of natural rubber. Preferably, the walls 6 are vertical to prevent the natural rubber from remaining on the inclined supply walls.
La partie inférieure 2b comprend la première partie de l ' arbre 4. La partie inférieure présente un fond cylindrique dans lequel l ' arbre 4 vient se loger.  The lower part 2b comprises the first part of the shaft 4. The lower part has a cylindrical bottom in which the shaft 4 is housed.
A cause de la gravité, les blo cs de caoutchouc naturel sont toujours en contact avec les couteaux rotatifs 5 de l ' arbre 4, et sont donc facilement attrapés pour être déchiquetés.  Due to gravity, the natural rubber blocks are always in contact with the rotary knives 5 of the shaft 4, and are therefore easily caught to be shredded.
Les parois 6 de la partie supérieure 2a peuvent être munies de premiers couteaux fixes (non représentés) pour éviter que le caoutchouc naturel ne remonte dans la partie supérieure 2a de la zone d' alimentation 2.  The walls 6 of the upper part 2a may be provided with first fixed knives (not shown) to prevent the natural rubber from rising in the upper part 2a of the feed zone 2.
La zone d ' homogénéisation 3 est dans la continuité de la zone d' alimentation et de déchiquetage 2 et est reliée à elle. Cette zone permet de malaxer et d'homogénéiser le caoutchouc naturel.  The homogenization zone 3 is in the continuity of the feed and shredding zone 2 and is connected to it. This zone makes it possible to knead and homogenize the natural rubber.
Cette zone d ' homogénéisation 3 comprend un fourreau 7 insérant la seconde partie de l ' arbre 4. Le fourreau 7 est muni de seconds couteaux fixes 8. Les seconds couteaux fixes 8 favorisent l' homo généisation et le travail mécanique du caoutchouc naturel. Ces seconds couteaux fixes 8 peuvent être positionnés sur la partie inférieure et/ou supérieure du fourreau. Ces seconds couteaux fixes sont amovibles. Le nombre de seconds couteaux fixes 8 peut dépendre du travail mécanique souhaité. Plus le nombre de seconds couteaux fixes est important, plus le travail mécanique augmente. Les couteaux rotatifs 5 de l ' arbre 4 passent de chaque côté des seconds couteaux fixes du fourreau 7.  This homogenizing zone 3 comprises a sheath 7 inserting the second part of the shaft 4. The sheath 7 is provided with second fixed knives 8. The second fixed knives 8 promote the homogenization and the mechanical work of the natural rubber. These second fixed knives 8 can be positioned on the lower and / or upper part of the sheath. These second fixed knives are removable. The number of second fixed knives 8 may depend on the desired mechanical work. The more the number of second fixed knives is important, the more the mechanical work increases. The rotary knives 5 of the shaft 4 pass on each side of the second fixed knives of the sheath 7.
La longueur de la zone d ' homogénéisation 3 est variable. Elle est fonction du temps d'homogénéisation et du travail mécanique souhaités . Cette longueur est fixée lors de la construction du dispositif. Le dispositif de déchiquetage et d' homogénéisation 1 comprend en bout de la zone d' homogénéisation 3 une plaque filière 9. La plaque filière 9 présente des orifices qui peuvent être sous la forme de trous ronds ou de trous oblongs. L ' ouverture variable des orifices permet d' augmenter ou de diminuer le travail mécanique du caoutchouc naturel. La réduction de l ' ouverture des trous de la plaque filière 9 permet également de diminuer le débit dans le dispositif 1 . The length of the homogenization zone 3 is variable. It is a function of the desired homogenization time and mechanical work. This length is fixed during the construction of the device. The shredder and homogenizer 1 comprises at the end of the homogenization zone 3 a die plate 9. The die plate 9 has orifices which may be in the form of round holes or oblong holes. The variable opening of the orifices makes it possible to increase or decrease the mechanical work of the natural rubber. The reduction in the opening of the holes in the die plate 9 also makes it possible to reduce the flow rate in the device 1.
L ' arbre 4 du dispositif 1 est préférentiellement horizontal. I l est soutenu de part et d' autre du dispositif 1 .  The shaft 4 of the device 1 is preferably horizontal. It is supported on both sides of the device 1.
Un dispositif de coupe (non représenté) est positionné en sortie de la plaque filière 9 pour couper le caoutchouc naturel en morceaux.  A cutting device (not shown) is positioned at the outlet of the die plate 9 to cut the natural rubber into pieces.
Ce dispositif de coupe peut être fixé sur l ' arbre 4 du dispositif 1 et tourner à la même vitesse que l ' arbre 4.  This cutting device can be fixed on the shaft 4 of the device 1 and rotate at the same speed as the shaft 4.
Il est possible d' avoir un dispositif de coupe indépendant de l ' arbre 4 du dispositif. Ce dispositif de coupe est alors installé sur l ' arbre 4 sortant du dispositif mais peut ne pas tourner à la même vitesse que l ' arbre 4. Ce dispositif de coupe est entraîné par un moteur indépendant et permet de couper des morceaux p lus petits que lorsque le système de coupe est fixé à l ' arbre du dispositif car il tourne plus vite.  It is possible to have a cutting device independent of the shaft 4 of the device. This cutting device is then installed on the shaft 4 leaving the device but may not rotate at the same speed as the shaft 4. This cutting device is driven by an independent motor and can cut smaller pieces than when the cutting system is attached to the shaft of the device as it rotates faster.
La présente invention est illustrée par l ' exemple qui suit. Exemples L 'obj et de ces exemples est de comparer les propriétés de compositions de caoutchouc selon l' invention avec les propriétés de compositions de caoutchouc comparatives comprenant un caoutchouc naturel différent du caoutchouc naturel traité selon l' invention. Préparation des compositions de caoutchouc  The present invention is illustrated by the following example. EXAMPLES The object of these examples is to compare the properties of rubber compositions according to the invention with the properties of comparative rubber compositions comprising a natural rubber different from the natural rubber treated according to the invention. Preparation of rubber compositions
On introduit successivement, dans un mélangeur interne usuel, tous les constituants de base nécessaires (caoutchouc naturel, charges renforçantes, autres additifs), à l'exception du système de réticulation. On conduit alors un travail thermomécanique (phase non-productive) en une étape, qui dure au total environ 3 à 5 min, jusqu'à atteindre une température maximale de « tombée » de 165 °C . On récupère le mélange ainsi obtenu et on le refroidit. The necessary basic constituents (natural rubber, reinforcing fillers, other additives), with the exception of the crosslinking system, are successively introduced into a usual internal mixer. Thermomechanical work (non-productive phase) is then carried out in one step, which lasts a total of about 3 to 5 min, until a maximum temperature of "fall" of 165 ° C is reached. The mixture thus obtained is recovered and cooled.
Après refroidissement du mélange ainsi obtenu, on incorpore alors dans un mélangeur externe (homo-finisseur) maintenu à basse température, le système de réticulation composé du soufre et du sulfénamide (CBS) . L'ensemble est alors mélangé (phase productive) pendant quelques minutes (une dizaine de minutes environ) .  After cooling the mixture thus obtained, is then incorporated in an external mixer (homo-finisher) maintained at low temperature, the crosslinking system composed of sulfur and sulfenamide (CBS). The whole is then mixed (productive phase) for a few minutes (about ten minutes).
La composition finale ainsi obtenue est ensuite calandrée sous la forme d'une feuille ou d'une plaque pour une caractérisation au laboratoire.  The final composition thus obtained is then calendered in the form of a sheet or a plate for a characterization in the laboratory.
Mesures et tests utilisés Measurements and tests used
Les compositions de caoutchouc sont caractérisées après cuisson comme indiqué ci-après . The rubber compositions are characterized after curing as indicated below.
Les propriétés dynamiques sont mesurées sur un viscoanalyseur (Metravib VA4000), selon la norme ASTM D 5992-96. On enregistre la réponse d'un échantillon de composition vulcanisée (éprouvette cylindrique de 4 mm d' épaisseur et de 400 mm2 de section), soumis à une so llicitation sinusoïdale en cisaillement simple alterné, à la fréquence de 10Hz, à la température de 60° C, à un balayage en amplitude de déformation de 0, 1 % à 50%> (cycle aller), puis de 50%> à 1 %) (cycle retour) : pour le cycle aller, on enregistre la valeur maximale du facteur de perte, notée tan(ô)max. Dynamic properties are measured on a viscoanalyzer (Metravib VA4000) according to ASTM D 5992-96. The response of a sample of vulcanized composition (cylindrical specimen 4 mm in thickness and 400 mm 2 in section) is recorded, subjected to a sinusoidal solicitation in alternating simple shear, at a frequency of 10 Hz, at 60 ° C, at a strain amplitude sweep of 0, 1% to 50%> (forward cycle), then 50%> to 1%) (return cycle): for the forward cycle, the maximum value of the loss factor, denoted tan (ô) max.
On rappelle que, de manière bien connue de l'homme du métier, la valeur de tan(ô)max (selon un balayage " en déformation" , à température donnée) est représentative de l'hystérèse et de la résistance au roulement (plus tan(ô)max est faible, plus basse est l'hystérèse et donc la résistance au roulement) . Exemple 1 It will be recalled that, in a manner well known to those skilled in the art, the value of tan (δ) max (according to a "deformation" sweep at a given temperature) is representative of hysteresis and rolling resistance (plus tan (δ) max is low, lower is the hysteresis and therefore the rolling resistance). Example 1
Les compositions Al et B l sont des compositions selon l' invention. Le caoutchouc naturel est un caoutchouc naturel de fond de tasse. La composition C l est une composition comparative. Le caoutchouc naturel n' est pas un caoutchouc naturel de fond de tasse. The compositions A1 and B1 are compositions according to the invention. Natural rubber is a natural bottom mug rubber. Composition C 1 is a comparative composition. Natural rubber is not a natural bottom mug rubber.
Pour chaque composition, le caoutchouc naturel a été traité avec du sulfate d' hydroxylamine, c ' est-à-dire que l'on a aj outé au caoutchouc naturel du sulfate d' hydroxylamine en une quantité de 0 , 8 g par kg de caoutchouc naturel.  For each composition, the natural rubber was treated with hydroxylamine sulfate, that is, hydroxylamine sulfate was added to the natural rubber in an amount of 0.8 g per kg. natural rubber.
Le traitement du caoutchouc naturel a été effectué au moyen de deux dispositifs de déchiquetage et d ' homogénéisation disposés en série, à savoir deux « prebreakers » montés en série.  The treatment of the natural rubber was carried out by means of two shredding and homogenization devices arranged in series, namely two "prebreakers" connected in series.
Un dosage du taux d' hydroxylamine résiduelle extractible dans le caoutchouc naturel a été effectué à l' issue du procédé de traitement du caoutchouc naturel. Ce dosage est basé sur la méthode décrite dans le document J. nat. Rubb. Res., 3 (1), 1-6, avec les conditions d' extraction suivantes : extraction à l ' acide sulfurique à 190°C +/- 10°C, pendant 24 heures, la température étant prise entre le manteau chauffant et la flasque lors de l ' extraction. Ce dosage, réalisé sur des prélèvements pris en différents points du caoutchouc naturel traité selon le procédé, permet de vérifier la bonne homogénéisation de l ' hydroxylamine dans le caoutchouc, en révélant un taux d' hydroxylamine résiduelle extractible homogène dans l ' ensemble du caoutchouc naturel traité . Dans cet exemple, il est dosé 224 ppm d' hydroxylamine résiduelle extractible, le caoutchouc naturel ayant été traité par 0, 8g de sulfate d' hydroxylamine par kg de caoutchouc naturel.  A residual extractable hydroxylamine content in the natural rubber was determined at the end of the natural rubber treatment process. This assay is based on the method described in J. nat. Rubb. Res., 3 (1), 1-6, with the following extraction conditions: extraction with sulfuric acid at 190 ° C +/- 10 ° C, for 24 hours, the temperature being taken between the heating mantle and the flange during the extraction. This assay, carried out on samples taken at various points of the natural rubber treated according to the process, makes it possible to verify the good homogenization of the hydroxylamine in the rubber, by revealing a level of homogeneous residual hydroxylamine that is homogeneous in the whole of the natural rubber. treaty . In this example, 224 ppm extractable residual hydroxylamine is assayed, the natural rubber having been treated with 0.8 g of hydroxylamine sulfate per kg of natural rubber.
Les formulations des compositions sont données dans le tableau 1 . Les quantités sont exprimées en parties pour 100 parties en poids d' élastomère (pce) . Les quantités de caoutchouc naturel sont données non compte-tenu du sulfate d' hydroxylamine. Tableau 1 The formulations of the compositions are given in Table 1. The amounts are expressed in parts per 100 parts by weight of elastomer (phr). Quantities of natural rubber are given not taking into account hydroxylamine sulphate. Table 1
Figure imgf000019_0002
Figure imgf000019_0002
( 1 ) caoutchouc naturel de fond de tasse (Hevea Brasiliensis)(1) Natural cup bottom rubber (Hevea Brasiliensis)
(2) caoutchouc naturel comprenant en poids 80%> de caoutchouc naturel de fonds de tasse et 20%> de caoutchouc naturel de latex (2) natural rubber comprising 80%> natural bottom cup rubber and 20%> natural latex rubber
(3) caoutchouc naturel de latex séché à l ' air libre (« unsmoke sheet »)  (3) natural rubber latex dried in the open air ("unsmoke sheet")
(4) N-cyclohexyl-2-benzothiazol-sulfénamide (« Santocure (4) N-cyclohexyl-2-benzothiazol sulfenamide ("Santocure
CBS » de la société Flexsys) CBS "from Flexsys)
Les résultats sont donnés dans le tableau 2 ci-dessous . The results are given in Table 2 below.
Tableau 2 Table 2
Figure imgf000019_0001
Les compositions A l et B l conformes à l' invention possèdent une hystérèse améliorée par rapport à la composition C l témoin comprenant 100% de caoutchouc naturel de latex US S (« unsmoke sheet). Cela est très favorable pour obtenir un pneumatique possédant une résistance au roulement réduite lorsque la composition selon l' invention est utilisée dans une bande de roulement.
Figure imgf000019_0001
The compositions A 1 and B 1 according to the invention have an improved hysteresis compared to the control composition C 1 comprising 100% US S latex natural rubber ("unsmoke sheet"). This is very favorable for obtaining a tire with reduced rolling resistance when the composition according to the invention is used in a tread.
Exemple 2 Example 2
Les compositions A2 et B2 sont des compositions selon l' invention. Le caoutchouc naturel est un caoutchouc naturel de fond de tasse. La composition C2 est une composition comparative. Le caoutchouc naturel n' est pas un caoutchouc naturel de fond de tasse. Compositions A2 and B2 are compositions according to the invention. Natural rubber is a natural bottom mug rubber. The composition C2 is a comparative composition. Natural rubber is not a natural bottom mug rubber.
Pour chaque composition, le caoutchouc naturel a été traité avec du sulfate d' hydroxylamine, c ' est-à-dire que l'on a ajouté au caoutchouc naturel du sulfate d' hydroxylamine en une quantité de 1 ,5 g par kg de caoutchouc naturel.  For each composition, the natural rubber was treated with hydroxylamine sulfate, i.e. hydroxylamine sulfate was added to the natural rubber in an amount of 1.5 g per kg of rubber. natural.
Les formulations des compositions sont données dans le tableau 3. Les quantités sont exprimées en parties pour 100 parties en poids d' élastomère (pce) . Les quantités de caoutchouc naturel sont données non compte-tenu du sulfate d 'hydroxylamine.  The formulations of the compositions are given in Table 3. The amounts are expressed in parts per 100 parts by weight of elastomer (phr). Quantities of natural rubber are given not taking into account hydroxylamine sulphate.
Tableau 3 Table 3
Figure imgf000020_0001
(1) caoutchouc naturel de fond de tasse (Hevea Brasiliensis)
Figure imgf000020_0001
(1) Natural cup bottom rubber (Hevea Brasiliensis)
(2) caoutchouc naturel comprenant en poids 80% de caoutchouc naturel de fonds de tasse et 20%> de caoutchouc naturel de latex(2) Natural rubber comprising 80% natural bottom cup rubber and 20% natural latex rubber>
(3) caoutchouc naturel de latex séché à l'air libre (« unsmoke sheet ») (3) natural rubber latex dried in the open air ("unsmoke sheet")
Les résultats sont donnés dans le tableau 4 ci-dessous. The results are given in Table 4 below.
Tableau 4 Table 4
Figure imgf000021_0001
Figure imgf000021_0001
Les compositions A2 et B2 conformes à l'invention possèdent une hystérèse améliorée par rapport à la composition C2 témoin comprenant 100% de caoutchouc naturel de latex USS (« unsmoke sheet »). Cela est très favorable pour obtenir un pneumatique possédant une résistance au roulement réduite lorsque la composition selon l'invention est utilisée dans une bande de roulement. The compositions A2 and B2 in accordance with the invention have an improved hysteresis compared to the control composition C 2 comprising 100% USS natural latex rubber ("unsmoke sheet"). This is very favorable for obtaining a tire with reduced rolling resistance when the composition according to the invention is used in a tread.

Claims

REVENDICATIONS
1 . Procédé de traitement d'un caoutchouc naturel, comprenant les étapes suivantes : 1. A method of treating a natural rubber, comprising the steps of:
ajouter au caoutchouc naturel un ou plusieurs composés dérivés d' ammoniac, ledit caoutchouc naturel étant constitué d ' au moins 80% en poids de caoutchouc naturel de fond de tasse et de 0 à 20% en poids de caoutchouc naturel de latex, par rapport au poids total de caoutchouc naturel, le ou lesdits composés dérivés d' ammoniac étant choisis parmi les composés de formule XNH2 et leurs sels, où X est un groupe choisi parmi les groupes hydroxyle et hydroxyalkyle en C 1 -C4 , et le ou lesdits composés étant présents en une quantité variant de 0,2 à 2,2 g par kilogramme de caoutchouc naturel, puis adding to the natural rubber one or more compounds derived from ammonia, said natural rubber consisting of at least 80% by weight of natural bottom mastic and 0 to 20% by weight of natural latex rubber, relative to total weight of natural rubber, the one or more compounds derived from ammonia being chosen from the compounds of formula XNH 2 and their salts, where X is a group chosen from hydroxyl and hydroxyalkyl groups of C 1 -C 4 , and said compound (s) being present in an amount ranging from 0.2 to 2.2 g per kilogram of natural rubber, then
soumettre le caoutchouc naturel auquel a été ajouté le ou les composés dérivés d' ammoniac à un travail mécanique à une température d' au moins 100 ° C .  subject the natural rubber to which the ammonia derivative compound (s) has been added to mechanical work at a temperature of not less than 100 ° C.
2. Procédé selon la revendication 1 , caractérisé en ce que le caoutchouc naturel est un caoutchouc naturel de fond de tasse.  2. Method according to claim 1, characterized in that the natural rubber is a natural rubber cup bottom.
3. Procédé selon la revendication 1 ou 2 caractérisé en ce que le caoutchouc naturel est choisi parmi les caoutchoucs naturels issus de l 'hévéa Brasiliensis.  3. Method according to claim 1 or 2 characterized in that the natural rubber is selected from natural rubber from the Hevea Brasiliensis.
4. Procédé selon l 'une quelconque des revendications précédentes caractérisé en ce que les composés dérivés d' ammoniac sont choisis parmi l ' hydroxylamine et les sels d' hydroxylamine à base d' acide fort, de préférence le sulfate d' hydroxylamine.  4. Method according to any one of the preceding claims, characterized in that the compounds derived from ammonia are chosen from hydroxylamine and hydroxylamine salts based on strong acid, preferably hydroxylamine sulfate.
5. Procédé selon l'une quelconque des revendications précédentes caractérisé en ce que le composé dérivé d' ammoniac est l ' hydroxylamine et est présent à une teneur variant de 0,2 à 0, 8 g, de préférence de 0,32 à 0,6 g, par kilogramme de caoutchouc naturel.  5. Process according to any one of the preceding claims, characterized in that the compound derived from ammonia is hydroxylamine and is present in a content ranging from 0.2 to 0.8 g, preferably from 0.32 to 0. , 6 g, per kilogram of natural rubber.
6. Procédé selon l 'une quelconque des revendications 1 à 4 caractérisé en ce que le composé dérivé d' ammoniac est le sulfate d' hydroxylamine et est présent à une teneur variant de 0,5 à moins de 2 g, de préférence de 0, 8 à 1 ,5 g, par kilogramme de caoutchouc naturel. 6. Method according to any one of claims 1 to 4 characterized in that the compound derived from ammonia is hydroxylamine sulfate and is present in a content ranging from 0.5 to less than 2 g, preferably from 0 to 8 to 1.5 g per kilogram of natural rubber.
7. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le travail mécanique est effectué à une température d' au moins 1 10° C . 7. Method according to any one of the preceding claims, characterized in that the mechanical work is carried out at a temperature of at least 1 10 ° C.
8. Procédé selon l'une quelconque des revendications précédentes caractérisé en ce que le travail mécanique est effectué au moyen d'un ou plusieurs dispositifs de déchiquetage et d'homogénéisation ( 1 ) .  8. Method according to any one of the preceding claims characterized in that the mechanical work is performed by means of one or more shredding and homogenization devices (1).
9. Procédé selon la revendication 8 , caractérisé en ce que le travail mécanique est réalisé au moyen de deux dispositifs de déchiquetage et d ' homogénéisation disposés en série.  9. Method according to claim 8, characterized in that the mechanical work is performed by means of two shredding and homogenization devices arranged in series.
10. Procédé selon la revendication 8 ou 9 caractérisé en ce que le ou les dispositifs de déchiquetage et d ' homogénéisation comprennent chacun une zone d' alimentation et de déchiquetage (2) et une zone d ' homogénéisation (3) reliées entre elles, et un arbre (4) traversant lesdites zones, ledit arbre étant muni de couteaux rotatifs (5) .  10. A method according to claim 8 or 9 characterized in that the shredding or homogenizing device or devices each comprise a feed zone and shredding (2) and a homogenization zone (3) connected together, and a shaft (4) passing through said zones, said shaft being provided with rotary knives (5).
1 1 . Procédé selon la revendication 10, caractérisé en ce que la zone d' alimentation et de déchiquetage (2) comprend une partie supérieure (2a) et une partie inférieure (2b), ladite partie supérieure (2a) étant apte à alimenter ladite partie inférieure (2b), ladite partie inférieure (2b) comprenant la première partie dudit arbre (4) .  1 1. Method according to Claim 10, characterized in that the feeding and shredding zone (2) comprises an upper part (2a) and a lower part (2b), the said upper part (2a) being able to supply the said lower part ( 2b), said lower part (2b) comprising the first part of said shaft (4).
12. Procédé selon la revendication 1 1 , caractérisé en ce que la zone d' homogénéisation (3) comprend la seconde partie dudit arbre (4) et un fourreau (7) insérant ladite seconde partie de l ' arbre (4), ledit fourreau (7) étant muni de seconds couteaux fixes (8) .  12. Method according to claim 1 1, characterized in that the homogenisation zone (3) comprises the second part of said shaft (4) and a sleeve (7) inserting said second part of the shaft (4), said sleeve (7) being provided with second fixed knives (8).
13. Procédé selon l'une quelconque des revendications 10 à 12, caractérisé en ce que l ' arbre (4) présente une vitesse de rotation variant de 20 à 100 tours/min, de préférence de 20 à 60 tours/min.  13. Method according to any one of claims 10 to 12, characterized in that the shaft (4) has a rotation speed ranging from 20 to 100 revolutions / min, preferably from 20 to 60 rev / min.
14. Procédé selon l'une quelconque des revendications 10 à 13 , caractérisé en ce que le ou les dispositifs de déchiquetage et d'homogénéisation présentent chacun une plaque filière (9) en bout de la zone d ' homogénéisation (3), ladite plaque filière (9) présentant des orifices. 14. Method according to any one of claims 10 to 13, characterized in that the shredding device and homogenization each have a die plate (9) at the end of the homogenization zone (3), said plate die (9) having orifices.
15. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que l ' étape de travail mécanique est suivie d'une étape de coupe du caoutchouc naturel traité. 15. Method according to any one of the preceding claims, characterized in that the mechanical working step is followed by a cutting step of the treated natural rubber.
16. Caoutchouc naturel traité susceptible d' être obtenu par le procédé tel que défini à l 'une quelconque des revendications précédentes .  16. Treated natural rubber obtainable by the process as defined in any one of the preceding claims.
17. Composition de caoutchouc à base d' au moins une charge renforçante et d'une matrice élastomère comprenant au moins un caoutchouc naturel traité tel que défini à la revendication 16.  17. A rubber composition based on at least one reinforcing filler and an elastomeric matrix comprising at least one treated natural rubber as defined in claim 16.
1 8. Article semi-fini en caoutchouc pour pneumatique, caractérisé en ce qu' il comprend une composition de caoutchouc réticulable ou réticulée selon la revendication 17.  8. Semi-finished rubber tire article, characterized in that it comprises a cross-linkable or cross-linked rubber composition according to claim 17.
19. Pneumatique caractérisé en ce qu' il comporte un article semi-fini tel que défini dans la revendication 1 8.  19. A tire characterized in that it comprises a semi-finished article as defined in claim 1 8.
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