Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/10—Metal compounds
• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0014—Use of organic additives
  • C08J9/0023—Use of organic additives containing oxygen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0066—Use of inorganic compounding ingredients
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0066—Use of inorganic compounding ingredients
  • C08J9/0071—Nanosized fillers, i.e. having at least one dimension below 100 nanometers
  • C08J9/008—Nanoparticles
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0095—Mixtures of at least two compounding ingredients belonging to different one-dot groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/06—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent
  • C08J9/08—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent developing carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/013—Fillers, pigments or reinforcing additives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L7/00—Compositions of natural rubber
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2201/00—Foams characterised by the foaming process
  • C08J2201/02—Foams characterised by the foaming process characterised by mechanical pre- or post-treatments
  • C08J2201/026—Crosslinking before of after foaming
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/02—CO2-releasing, e.g. NaHCO3 and citric acid
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2307/00—Characterised by the use of natural rubber
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2309/00—Characterised by the use of homopolymers or copolymers of conjugated diene hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2319/00—Characterised by the use of rubbers not provided for in groups C08J2307/00 - C08J2317/00
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2407/00—Characterised by the use of natural rubber
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2409/00—Characterised by the use of homopolymers or copolymers of conjugated diene hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2419/00—Characterised by the use of rubbers not provided for in groups C08J2407/00 - C08J2417/00

Definitions

• the invention relates to rubber compositions used as treads of tires for vehicles, in particular tires “winter” able to roll on floors covered with ice or ice without being provided with nails (also called “studless” tires).
• treads of winter tires specifically adapted for running under so-called "melting ice” conditions encountered in a temperature range typically between -5 ° C and 0 ° C. It is recalled that in such a field, the tire pressure at the passage of the vehicle causes a superficial melting of the ice which is covered with a thin film of water detrimental to the adhesion of these tires.
• Such powders solubilize more or less in contact with snow or melted ice, which allows on the one hand the creation on the surface of the tread of porosities likely to improve the attachment of the tread on the ground and on the other hand the creation of grooves acting as evacuation channels of the liquid film created between the tire and the ground.
• water-soluble powders include, for example, the use of cellulose powder, vinyl alcohol or starch, or powders of guar gum or xanthan gum (see for example patent applications). JP 3-159803, JP 2002-211203, EP 940,435, WO 2008/080750, WO 2008/080751).
• expansion agents such as, for example, nitro, sulfonyl or azo compounds
• expansion agents are capable of liberating, during a thermal activation, for example during the vulcanization of the tire, a large amount of gas, in particular nitrogen, and thus lead to the formation of bubbles within a sufficiently soft material such as a rubber composition comprising such expansion agents.
• Such winter tire foam rubber formulations have been described, for example, in JP 2003-183434, JP 2004-091747, JP 2006-299031, JP 2007-039499, JP 2007-314683, JP2008-001826, JP 2008-2. 150413, EP 826,522, US 5,147,477, US 6,336,487.
• the present invention relates to a tire in the uncured state whose tread comprises a heat-expandable rubber composition comprising at least one diene elastomer, more than 50 phr of a reinforcing filler, between 5 and 25 phr.
• the acidic salt being: either an acidic salt of polyacid inorganic, the anion of the acidic salt being selected from the group consisting of hydrogen sulphates, hydrogen sulphides, hydrogen sulphites, hydrogen phosphates and dihydrogen phosphates; an acidic salt of organic polyacid, the anion of the acidic salt being a monocarboxylate of diacid or triacid carboxylic acid, or a dicarboxylate of triacid carboxylic acid.
• the tires of the invention are particularly intended for equipping tourism-type motor vehicles, including 4x4 vehicles (four-wheel drive) and SUV vehicles ("Sport Utility Vehicles"), two-wheeled vehicles (especially motorcycles) as industrial vehicles chosen in particular from vans and "heavy goods vehicles” (eg metro, buses, road transport vehicles such as trucks, tractors).
• 4x4 vehicles four-wheel drive
• SUV vehicles Sport Utility Vehicles
• two-wheeled vehicles especially motorcycles
• industrial vehicles chosen in particular from vans
• "heavy goods vehicles” eg metro, buses, road transport vehicles such as trucks, tractors.
• any range of values designated by the expression “between a and b” represents the range of values greater than “a” and less than “b” (i.e., terminals a and b excluded). while any range of values designated by the term “from a to b” means the range of values from “a” to "b” (i.e. including the strict limits a and b).
• the tire of the invention therefore has the essential characteristic that its tread in the uncured state, at least for its portion (radially outermost home) intended to come into direct contact with the surface of the road, comprises a heat-expandable rubber composition comprising at least:
• the acid salt being: an acidic salt of an inorganic polyacid, the anion of the acidic salt being selected from the group consisting of hydrogen sulphates, hydrogen sulphides, hydrogen sulphites, hydrogen phosphates and dihydrogen phosphates;
• an acidic salt of organic polyacid the anion of the acidic salt being a monocarboxylate of diacid or triacid carboxylic acid, or a dicarboxylate of triacid carboxylic acid.
• elastomer or rubber, the two terms being synonymous
• dienes monomers carrying two double bonds carbon - carbon, conjugated or not
• the diene elastomers can be classified in known manner into two categories: those known as “essentially unsaturated” and those known as “essentially saturated”. Butyl rubbers, and for example copolymers of dienes and alpha-olefins of the EPDM type, fall into the category of essentially saturated diene elastomers, having a level of diene origin units which is low or very low, always less than 15% (mole%).
• essentially unsaturated diene elastomer is understood to mean a diene elastomer derived at least in part from conjugated diene monomers having a proportion of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%). .
• the term “highly unsaturated” diene elastomer is particularly understood to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.
• At least one diene elastomer of the highly unsaturated type in particular a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), polybutadienes (BR) and butadiene copolymers, copolymers of isoprene and mixtures of these elastomers.
• a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), polybutadienes (BR) and butadiene copolymers, copolymers of isoprene 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), isoprene-copolymers of butadiene-styrene (SBIR) and mixtures of such copolymers.
• SBR butadiene-styrene copolymers
• BIR isoprene-butadiene copolymers
• SIR isoprene-styrene copolymers
• SBIR isoprene-copolymers of butadiene-styrene
• the elastomers can be for example block, statistical, sequenced, microsequenced, and be prepared in dispersion or in solution; they may be coupled and / or starred or functionalized with a coupling agent and / or starring or functionalization.
• a coupling with carbon black there may be mentioned for example functional groups comprising a C-Sn bond or amino functional groups such as benzophenone for example; for coupling to a reinforcing inorganic filler such as silica, mention may be made, for example, of silanol or polysiloxane functional groups having a silanol end (as described, for example, in US Pat. No.
• alkoxysilane groups as described, for example, in US 5,977,238), carboxylic groups (as described, for example, in US 6,815,473 or US 2006/0089445) or polyether groups (as described for example in US 6,503,973).
• elastomers such as SBR, BR, NR or IR of the epoxidized type.
• Polybutadienes and in particular those having a 1,2-unit content of between 4% and 80%, or those having a cis-1,4 content of greater than 80%, polyisoprenes and copolymers of butadiene- styrene and in particular those having a styrene content of between 5% and 50% by weight and more particularly between 20% and 40%, a 1,2-butadiene content of the butadiene part of between 4% and 65%. %, a trans-1,4-linkage content of between 20% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90% by weight and a glass transition temperature.
• Tg "Tg" - measured according to ASTM D3418-82) from -40 ° C to -80 ° C, the isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg between -25 ° C and -50 ° C.
• butadiene-styrene-isoprene copolymers are especially suitable those having a styrene content of between 5% and 50% by weight and more particularly of between 10% and 40%, an isoprene content of between 15% and 60%.
• the diene elastomer is chosen from the group consisting of natural rubber, synthetic polyisoprenes and polybutadienes having a cis-1,4 bond ratio of greater than 90%, copolymers of butadiene-styrene and mixtures of these elastomers.
• the heat-expandable rubber composition comprises 50 to 100 phr of natural rubber or of synthetic polyisoprene, said synthetic rubber or synthetic polyisoprene can be used in particular in a blend (blend) with not more than 50 phr of a polybutadiene having a cis-1,4 bond ratio greater than 90%.
• the heat-expandable rubber composition comprises 50 to 100 phr of a polybutadiene having a cis-1,4 bond ratio of greater than 90%, said polybutadiene being able to be used in particular in blending with not more than 50 phr of natural rubber or synthetic polyisoprene.
• diene elastomers of the treads according to the invention could be associated, in a minor amount, synthetic elastomers other than diene, or even polymers other than elastomers, for example thermoplastic polymers.
• Any known charge for its ability to reinforce a rubber composition is usable, for example an organic charge such as carbon black, or an inorganic filler such as silica to which is associated in a known manner a coupling agent.
• Such a charge preferably consists of nanoparticles whose average size (in mass) is less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, in particular and more preferably between 20 and 150 nm.
• the content of total reinforcing filler is between 50 and 150 phr.
• a content equal to or greater than 50 phr is favorable for good mechanical strength; beyond 150 phr, there is a risk of excessive rigidity of the rubber layer.
• the total reinforcing filler content is more preferably within a range of 70 to 120 phr.
• Suitable carbon blacks are, for example, all the carbon blacks which are conventionally used in tires (so-called pneumatic grade blacks) such as blacks of the series 100, 200, 300 (ASTM grades), for example blacks NI 15, N134, N234, N326, N330, N339, N347, N375.
• the carbon blacks could for example already be incorporated into the diene elastomer, in particular isoprenic elastomer, in the form of a masterbatch (see, for example, applications WO 97/36724 or WO 99/16600).
• organic fillers other than carbon blacks mention may be made of functionalized polyvinyl organic fillers as described in applications WO-A-2006/069792 and WO-A-2006/069793, WO-A-2008/003434. and WO-A-2008/003435.
• Reinforcing inorganic filler means any inorganic or mineral filler, irrespective of its color and origin (natural or synthetic), also called “white” filler, “clear” filler or even “non-black filler””As opposed to carbon black, capable of reinforcing on its own, with no other means than an intermediate coupling agent, a rubber composition for the manufacture of tires, in other words able to replace, in its function of reinforcement, a conventional carbon black of pneumatic grade; such a filler is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.
• -OH hydroxyl groups
• Suitable reinforcing inorganic fillers are mineral fillers of the siliceous type, in particular silica (SiO 2 ).
• 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 m 2 / g.
• HDS highly dispersible precipitated silicas
• the majority filler used is a reinforcing inorganic filler, in particular silica, at a level within a range of 70 to 120 phr, reinforcing inorganic filler to which advantageously black of carbon at a minority rate at most equal to 15 phr, in particular in a range of 1 to 10 phr.
• an at least bifunctional coupling agent or bonding agent
• organosilanes or at least bifunctional polyorganosiloxanes are used.
• polysulfide silanes called “symmetrical” or “asymmetrical” silanes according to their particular structure, are used, as described for example in the applications WO03 / 002648 (or US 2005/016651) and WO03 / 002649 (or US 2005/016650).
• polysulphide silanes having the following general formula (I) are not suitable for the following definition:
• x is an integer of 2 to 8 (preferably 2 to 5);
• the symbols A which are identical or different, represent a divalent hydrocarbon group (preferably an alkylene Ci-Cig or an arylene group C 6 -C 2, more particularly alkylene Ci-Cio, in particular C 1 -C 4 , especially propylene);
• R2 R2 in which:
• the radicals R 1 which may be substituted or unsubstituted, which are identical to or different from one another, represent a Ci-C18 alkyl, C 5 -C 8 cycloalkyl or C 6 -C 18 aryl group (preferably C 1 -C 8 alkyl groups); C 6 , cyclohexyl or phenyl, especially C 1 -C 4 alkyl groups, more particularly methyl and / or ethyl).
• radicals R 2 substituted or unsubstituted, identical or different, represent an alkoxy group or Ci-Ci 8 cycloalkoxy, C 5 -C 8 (preferably a group selected from alkoxyls Cg and C cycloalkoxyls 5 -C 8 , more preferably still a group selected from C 1 -C 4 alkoxyls, in particular methoxyl and ethoxyl).
• polysulphurized silanes By way of examples of polysulphurized silanes, mention may be made more particularly of bis (C 1 -C 4 alkoxy) -alkyl (C 1 -C 4 ) silylalkyl (C 1 -C 4 ) polysulfides (especially disulfides, trisulphides or tetrasulfides). ), such as polysulfides of bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl).
• TESPT bis (3-triethoxysilylpropyl) tetrasulfide
• TESPD bis (3-triethoxysilylpropyl) tetrasulfide
• TESPD bis (3-triethoxysilylpropyl) tetrasulfide
• polysulphides in particular disulphides, trisulphides or tetrasulphides
• bis- (monoalkoxyl (Ci-C 4 ) -dialkyl (Ci-C 4 ) silylpropyl) more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide, such as described in the aforementioned patent application WO 02/083782 (or US Pat. No. 7,217,751).
• silanes carrying at least one thiol function (-SH) (called mercaptosilanes) and / or of at least one blocked thiol function, as described for example in patents or patent applications US 6,849,754, WO 99/09036, WO 2006/023815, WO 2007/098080.
• the rubber compositions When they are reinforced with an inorganic filler such as silica, the rubber compositions preferably comprise between 2 and 15 phr, more preferably between 3 and 12 phr of coupling agent.
• blowing agent in English
• a blowing agent is a thermally decomposable compound, intended to release during a thermal activation, for example during the vulcanization of the tire, a significant amount of gas and thus lead to the formation of bubbles.
• the release of gas in the rubber composition therefore comes from this thermal decomposition of the blowing agent.
• the blowing agent used in accordance with the present invention is sodium or potassium carbonate or hydrogencarbonate (also known as bicarbonate). In others In other words, it is selected from the group consisting of sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogencarbonate and mixtures of such carbonates (including, of course, their hydrated forms). Such an expansion agent has the advantage of only releasing carbon dioxide and water during its decomposition; it is therefore particularly favorable to the environment.
• Sodium hydrogencarbonate (NaHCO 3) is particularly used.
• the content of this blowing agent is between 5 and 25, preferably between 8 and 20 phr.
• Another essential feature of the invention is to add to the expansion agent described above, a specific acidic salt.
• the acid salt content is between 2 and 20 phr, preferably between 2 and 15 phr.
• this acidic salt has the function of chemically reacting with the blowing agent which, during its thermal decomposition, will release many more bubbles. gas (C0 2 and H 2 0) only if used alone.
• acidic salt is generally meant the product resulting from the partial reaction between a polyacid (or polyprotic acid), whether organic or inorganic, and a base; in such an acid, therefore, and by definition, at least one (i.e., one or more) acidic function is still present.
• the acid salt suitable for the invention is: or a salt inorganic polybasic acid
• the anion of the acid salt is selected from the group consisting of hydrogen sulfates (HS0 4 ⁇ ), hydrosulphides (HS ⁇ ) , hydrogensulfites (HS0 3 ⁇ ), hydrogen phosphates (HP0 4 2 ⁇ ) and dihydrogen (H 2 P0 4 ⁇ ), in particular consisting of hydrogen phosphates and dihydrogen phosphates;
• an acidic salt of organic polyacid the anion of the acidic salt being a monocarboxylate of diacid or triacid carboxylic acid (eg oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimellic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, tartaric acid, malic acid , ⁇ -ketoglutaric, tartaric, phthalic, isophthalic, terephthalic and citric), or a carboxylic triacid dicarboxylate (eg citric acid).
• a monocarboxylate of diacid or triacid carboxylic acid eg oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimellic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, tartaric acid, malic acid , ⁇
• the cation of the acidic salt is a metal cation, the metal of this cation being preferably an alkali metal, an alkaline earth metal or a transition metal. More preferentially, this cation is chosen from lithium, sodium, potassium, magnesium, calcium, barium, iron, manganese, copper and silver, in particular from lithium, sodium, potassium, magnesium and calcium, more particularly from lithium, sodium and potassium.
• acidic salts of polybasic inorganic acid mention may be made of sodium (NaHSO 4 ), potassium (KHSO 4 ), lithium (LiHSO 4 ) or calcium (Ca (HSO 4 ) 2 ) hydrogen sulphates, hydrogen sulphides and sodium (NaSH) or potassium (KSH), potassium hydrogen sulfide (KHSO 3 ), sodium (NaHSO 3 ), magnesium (Mg (HSO 3 ) 2 ) or calcium (Ca (HSO 3 ) 2 ), sodium hydrogen phosphates ( Na 2 HPO 4 ), potassium (K 2 HPO 4 ), calcium (CaHPO 4 ) or barium (BaHPO 4 ), sodium dihydrogen phosphates (NaH 2 PO 4 ), potassium (KH 2 PO 4 ), magnesium (Mg (H 2 P0 4 ) 2), calcium (Ca (H 2 PO 4 ) 2) or barium (Ba (H 2 PO 4 ) 2 ). More preferably still, the acidic
• acidic salt of organic polyacid mention may be made of monosodium salts (ie, with a single Na + cation), disodium (ie, with two Na + cations), and monopotassic salts (ie, with a single cation K + ), dipotassic (ie, with two K + cations), monoliths (ie, with a single Li + cation) or dilithians (ie, with two Li + cations) of a diacid or triacid carboxylic acid, in particular diacids or triacids carboxylic acid, especially citric acid.
• monosodium salts ie, with a single Na + cation
• disodium ie, with two Na + cations
• monopotassic salts ie, with a single cation K +
• dipotassic ie, with two K + cations
• monoliths ie, with a single Li + cation
• dilithians
• blowing agent and its associated activator (acid salt) must be greater than at 10 phr, preferably between 10 and 40 phr. This total amount is more preferably greater than 15 phr, in particular between 15 and 40 phr.
• the heat-expandable rubber composition may also comprise all or part of the usual additives normally used in rubber compositions for tire treads, such as, for example, protective agents such as antiozone waxes, chemical antiozonants, anti-oxidants plasticizers, a crosslinking system based on either sulfur, or sulfur and / or peroxide donors and / or bismaleimides, vulcanization accelerators, vulcanization activators.
• protective agents such as antiozone waxes, chemical antiozonants, anti-oxidants plasticizers, a crosslinking system based on either sulfur, or sulfur and / or peroxide donors and / or bismaleimides, vulcanization accelerators, vulcanization activators.
• the heat-expandable rubber composition also comprises a liquid plasticizing agent (at 20 ° C.) whose function is to soften the matrix by diluting the diene elastomer and the reinforcing filler; its Tg (glass transition temperature) is by definition less than -20 ° C, preferably less than -40 ° C.
• this liquid plasticizer is used at a relatively low level, such that the weight ratio reinforcing filler on liquid plasticizer is greater than 2.0, more preferably greater than 2.5, especially greater than 3.0.
• any extender oil whether aromatic or non-aromatic, any liquid plasticizer known for its plasticizing properties vis-à-vis diene elastomers, is usable.
• these plasticizers or these oils are liquids (that is to say, as a reminder, substances having the capacity to eventually take on the shape of their container) , in contrast to, in particular, hydrocarbon plasticizing resins which are inherently solid at room temperature.
• the liquid plasticizer is in particular a petroleum oil, preferably a non-aromatic oil.
• a liquid plasticizer is described as non-aromatic if it has a content of polycyclic aromatic compounds, determined with the extract in DMSO according to the IP 346 method, of less than 3% by weight, relative to the total weight of the plasticizer.
• liquid plasticizers selected from the group consisting of naphthenic oils (low or high viscosity, including hydrogenated or not), paraffinic oils, MES oils (Medium Extracted Solvates), oils DAE (Distillate Aromatic Extracts), Treated Distillate Aromatic Extracts (TDAE) oils, Residual Aromatic Extract oils (RAE), Treated Residual Aromatic Extract (TREE) oils, Residual Aromatic Extract oils (SRAE), mineral oils, vegetable oils, plasticisers ethers, ester plasticizers, phosphate plasticizers, sulphonate plasticizers and mixtures of these compounds.
• the liquid plasticizer is selected from the group consisting of MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these oils.
• phosphate plasticizers for example, mention may be made of those containing from 12 to 30 carbon atoms, for example trioctyl phosphate.
• ester plasticizers mention may be made in particular of compounds selected from the group consisting of trimellitates, pyromellitates, phthalates, 1,2-cyclohexane dicarboxylates, adipates, azelates, sebacates, glycerol and mixtures of these compounds.
• glycerol triesters preferably consisting predominantly (for more than 50%, more preferably more than 80% by weight) of an unsaturated fatty acid Ci 8 is i.e., selected from the group consisting of oleic acid, linoleic acid, linolenic acid and mixtures of these acids. More preferably, whether of synthetic or natural origin (for example vegetable oils of sunflower or rapeseed), the fatty acid used is more than 50% by weight, more preferably still more than 80% by weight. % by weight of oleic acid.
• Such high oleic acid triesters are well known and have been described, for example, in application WO 02/088238, as plasticizers in tire treads.
• reinforcing resins eg acceptors and donors of methylene
• the heat-expandable rubber composition may also contain coupling enhancers when a coupling agent is used, inorganic filler recovery agents when an inorganic filler is used, or more generally, filler agents.
• implementability likely in known manner, through an improvement in the dispersion of the load in the rubber matrix and a lowering of the viscosity of the compositions, to improve their processability in the green state; these agents are for example hydroxysilanes or hydrolysable silanes such as alkyl-alkoxysilanes, polyols, polyethers, amines, hydroxylated or hydrolysable polyorganosiloxanes.
• the rubber compositions are manufactured in appropriate mixers, for example using two successive preparation phases according to a general procedure known to those skilled in the art: a first thermomechanical working or mixing phase (sometimes referred to as a "no" phase). -productive ”) at high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C, during which is incorporated in particular the expansion activator (salt acid), followed by a second phase of mechanical work (sometimes called “productive" phase) at low temperature, typically below 120 ° C, for example between 60 ° C and 100 ° C, finishing phase during which the blowing agent and the crosslinking or vulcanization system are incorporated therein.
• a first thermomechanical working or mixing phase (sometimes referred to as a "no" phase).
• -productive ") at high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C, during which is incorporated in
• a process which can be used for the manufacture of such rubber compositions comprises, for example, and preferably the following steps: incorporating in a mixer, at the elastomer or in the mixture of elastomers, at least the feedstock and the acidic salt by thermomechanically mixing the whole , in one or several times, until reaching a maximum temperature of between 130 ° C and 200 ° C;
• blowing agent Na or K carbonate or hydrogencarbonate
• a suitable mixer such as a conventional internal mixer.
• the blowing agent and the crosslinking system After thermomechanical work, falling and cooling of the mixture thus obtained, it is then preferably incorporated in this order, the blowing agent, then the vulcanization retarder (if such a compound is used), finally the rest of the vulcanization system. (eg sulfur and accelerator) at low temperature, usually in an external mixer such as a roll mill; the whole is then mixed (productive phase) for a few minutes, for example between 5 and 15 min.
• the actual crosslinking system is preferably based on sulfur and a primary vulcanization accelerator, in particular a sulfenamide type accelerator.
• a primary vulcanization accelerator in particular a sulfenamide type accelerator.
• various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid, guanidine derivatives (especially diphenylguanidine), etc.
• the sulfur content is preferably between 0.5 and 5 phr, that of the primary accelerator is preferably between 0.5 and 8 phr.
• accelerator any compound capable of acting as accelerator for vulcanization of diene elastomers in the presence of sulfur, in particular thiazole-type accelerators and their derivatives, accelerators of the thiuram type, zinc dithiocarbamates.
• accelerators are for example selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS”), tetrabenzylthiuram disulfide (“TBZTD”), N-cyclohexyl-2-benzothiazyl sulfenamide (“CBS”), N, N dicyclohexyl-2-benzothiazylsulfenamide (“DCBS”), N-tert-butyl-2-benzothiazylsulfenamide (“TBBS”), N-tert-butyl-2-benzothiazylsulfenamide (“TBSI”), zinc dibenzyldithiocarbamate (“ ZBEC ”) and mixtures of these compounds.
• MBTS 2-mercaptobenzothiazyl disulfide
• TBZTD tetrabenzylthiuram disulfide
• CBS N-cyclohexyl-2-benzothiazyl sulfenamide
• the acidic salt having the possible effect of reducing the induction time (that is to say the time required for the beginning of the vulcanization reaction) during the baking of the composition, it is advantageous to use a vulcanization retarder. counteracting this phenomenon, thereby providing the rubber composition with the time necessary for complete expansion prior to vulcanization.
• the level of this vulcanization retarder is preferably between 0.5 and 10 phr, more preferably between 1 and 5 phr, in particular between 1 and 3 phr.
• Vulcanization retarders are well known to those skilled in the art. Mention may be made, for example, of N-cyclohexylthiophthalimide sold under the name "Vulkalent G” by the company Lanxess, N- (trichloromethylthio) benzenesulfonamide sold under the name "Vulkalent E / C" by Lanxess, or else marketed phthalic anhydride. under the name "Vulkalent B / C" by Lanxess.
• CTP N-cyclohexylthiophthalimide
• the final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for a characterization in the laboratory, or else calendered or extruded in the form of a heat-expandable tread.
• the density or density denoted Di of the heat-expandable rubber composition is preferably between 1, 100 and 1, 400 g / cm 3 , more preferably in a range from 1.50 to 1. 350 g / cm 3 .
• the vulcanization (or cooking) is conducted in a known manner at a temperature generally between 130 ° C and 200 ° C, for a sufficient time which may vary for example between 5 and 90 min depending in particular on the cooking temperature, the system of vulcanization adopted and the kinetics of vulcanization of the composition under consideration. It is during this vulcanization step that the blowing agent will release a significant amount of gas, lead to bubble formation in the foam rubber composition and eventually expand.
• the density denoted D 2 of the rubber composition once expanded is preferably between 0.700 and 1.000 g / cm 3 . more preferably within a range of 0.750 to 0.950 g / cm 3 .
• the rubber composition thus formulated based on high levels of a blowing agent and a specific activator combined, greatly improves the adhesion on melting ice tires treads, as evidenced by the examples following realization.
• the heat-expandable rubber composition described above is advantageously usable in winter tire treads for any type of vehicle, in particular in tires for passenger vehicles, as demonstrated in the following tests.
• compositions (denoted C-0 and C-1) were prepared whose formulation is given in Table 1 (rate of the various products expressed in phr).
• the composition C-0 is the control composition;
• the composition C-1 is that according to the invention, it further comprises the blowing agent (sodium hydrogen carbonate) and its associated specific acid salt.
• the reinforcing filler the diene elastomer (NR and BR), the acidic salt for the composition Cl, as well as the various other ingredients with the exception of the vulcanization system and the blowing agent; the mixer was thus filled to about 70% (% by volume).
• Thermomechanical work (non-productive phase) was then carried out in a step of about 2 to 4 minutes, until a maximum "falling" temperature of about 150 ° C. was reached.
• the mixture thus obtained was recovered, cooled to about 50 ° C., then the blowing agent (Na-hydrogencarbonate), the vulcanization retarder (CTP), then the sulfenamide accelerator and the sulfur were incorporated. on an external mixer (homoconductor) at 30 ° C, mixing the whole (productive phase) for a few minutes.
• Compositions C-0 and Cl thus prepared which can be used directly as tire treads for winter tires, were then vulcanized in press, and their properties measured before and after curing (see attached table 2): the rubber composition according to after firing, once in the state of foam rubber (ie, expanded), a density significantly reduced corresponding to a particularly high volume expansion rate of about 22%.
• compositions were then subjected to a laboratory test consisting in measuring their coefficient of friction on ice.
• the principle is based on a rubber composition slider sliding at a given speed (for example equal to 5 km / h) on an ice track (ice temperature set at -2 C) with an imposed load (for example equal to 3 kg / cm 2 ).
• a rubber composition slider sliding at a given speed for example equal to 5 km / h
• an ice track ice temperature set at -2 C
• an imposed load for example equal to 3 kg / cm 2 .

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