Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D30/00—Producing pneumatic or solid tyres or parts thereof
  • B29D30/0061—Accessories, details or auxiliary operations not otherwise provided for
• • 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
• • 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
  • B60C19/00—Tyre parts or constructions not otherwise provided for
  • B60C19/002—Noise damping elements provided in the tyre structure or attached thereto, e.g. in the tyre interior
• • 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
  • C08J9/10—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 nitrogen, the blowing agent being a compound containing a nitrogen-to-nitrogen bond
• • 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
  • C08J9/10—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 nitrogen, the blowing agent being a compound containing a nitrogen-to-nitrogen bond
  • C08J9/102—Azo-compounds
  • C08J9/103—Azodicarbonamide
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D30/00—Producing pneumatic or solid tyres or parts thereof
  • B29D30/0061—Accessories, details or auxiliary operations not otherwise provided for
  • B29D2030/0072—Attaching fasteners to tyres, e.g. patches, in order to connect devices to tyres
• • 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
  • C08J2321/00—Characterised by the use of unspecified rubbers
• • 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
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/22—Compounds containing nitrogen bound to another nitrogen atom
  • C08K5/23—Azo-compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/18—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms
  • C08L23/20—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms having four to nine carbon atoms
  • C08L23/22—Copolymers of isobutene; Butyl rubber; Homopolymers or copolymers of other iso-olefins
• • 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
  • C08L9/06—Copolymers with styrene
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
  • Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction 
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T152/00—Resilient tires and wheels
  • Y10T152/10—Tires, resilient
  • Y10T152/10036—Cushion and pneumatic combined
  • Y10T152/10054—Enclosed cushion
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T152/00—Resilient tires and wheels
  • Y10T152/10—Tires, resilient
  • Y10T152/10495—Pneumatic tire or inner tube

Definitions

• the invention relates to pneumatic tires for motor vehicles as well as rubber compositions usable for the manufacture of such tires.
• the noise emitted outside the vehicle are relevant the various interactions between the tire and the road surface, the tire and the air, which will cause an inconvenience to the residents of the vehicle when the latter rolls on a roadway.
• noise there are also in this case several sources of noise such as the so-called “indentation” noise due to the impact of roughness of the road in the contact area, the noise called “friction” essentially generated in the output of the 'contact area, the noise' says of sculpture 'due to the arrangement of the elements of sculpture and to the resonance in the various furrows.
• the frequency range concerned here typically corresponds to a range of about 300 to 3000 Hz.
• the so-called “road noise” refers rather to the perceived overall level in the vehicle and in a frequency range up to 2000 Hz.
• the cavity noise refers to the annoyance due to the resonance of the inflating cavity of the tire, this dominant noise in a specific frequency range of about 190 to 230 Hz.
• expansion agents such as, for example, nitro, sulphonyl or azo compounds
• nitro, sulphonyl or azo compounds 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 expanders.
• the Applicants have discovered in their research a rubber composition which makes it possible, by incorporating a specific hot melt compound, to substantially reduce the rate of expansion once the tire has been vulcanized, without otherwise affecting the properties of the noise absorption provided by the blowing agent.
• the control of the homogeneity of thickness of foam rubber in the cavity of the tire, in particular according to the radial position in question, is thus notably improved.
• the present invention relates to a tire in the unvulcanized state whose inner wall is provided with a heat-expandable rubber layer, said layer comprising an elastomeric composition comprising at least one elastomer, a reinforcing filler, between 10 and 80 phr of an expansion agent and between 10 and 50 phr of a hot melt compound whose melting temperature is between 70 ° C and 150 ° C.
• a tire in the unvulcanized state whose inner wall is provided with a heat-expandable rubber layer, said layer comprising an elastomeric composition comprising at least one elastomer, a reinforcing filler, between 10 and 80 phr of an expansion agent and between 10 and 50 phr of a hot melt compound whose melting temperature is between 70 ° C and 150 ° C.
• the invention also relates to a tire in the vulcanized state obtained after curing (vulcanization) of the green tire according to the invention as described above.
• the pneumatic tires of the invention are particularly intended to equip tourism-type motor vehicles, including 4x4 vehicles (four-wheel drive) and SUV vehicles ("Sport Utility Vehicles"), two-wheel vehicles (including motorcycles) as industrial vehicles chosen in particular from vans and "heavy goods vehicles” (ie, metro, buses, road transport equipment such as trucks, tractors).
• the invention relates to the above tires both in the green state (ie, before firing) and in the fired state (ie, after crosslinking or vulcanization).
• the invention as well as its advantages will be readily understood in the light of the description and the following exemplary embodiments, as well as FIGS. 1 to 4 relating to these examples, which schematize, in radial section, an example of a pneumatic tire conforming to FIG. invention, in the green (ie unvulcanized) state, whose inner wall is provided with a heat-expandable rubber layer extending under the apex, substantially from one shoulder to the other (Fig.
• FIG. 1 an example of a pneumatic tire according to the invention, in the fired (that is to say, vulcanized) state, the inner wall of which is provided with a foam rubber layer, therefore in the expanded state, obtained after firing the bandage of Figure 1 above (Fig. 2); another example of a bandage according to the invention, in the green state, whose inner wall is provided with a heat-expandable rubber layer which in this case substantially covers the entire inner wall of the tire (FIG 3);
• any range of values designated by the expression "between a and b" represents the range of values from more than a to 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 from a to b (i.e., including the strict limits a and b).
• the essential characteristic of the tire of the invention is that its inner wall is provided with a layer of thermally expandable rubber capable of reducing the cavity noise once expanded, said layer comprising an elastomer composition comprising at least:
• the elastomer (or indistinctly “rubber”) used is preferably of the diene type, although other elastomers are usable, for example elastomers of the polyurethane type or thermoplastic elastomers (TPE) such as thermoplastic styrene elastomers (TPS) .
• TPE thermoplastic elastomers
• TPS thermoplastic styrene elastomers
• iene elastomer in known manner an elastomer derived at least in part (i.e., a homopolymer or a copolymer) of monomers dienes (monomers bearing two carbon-carbon double bonds, 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”.
• essentially saturated diene elastomers having a rate of diene origin units which is low or very low, always less than 15% (% by 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%.
• iene elastomer that can be used is more particularly understood to mean:
• a diene elastomer selected from the group consisting of polybutadienes (BR) (especially those having a cis-1,4 bond ratio greater than 90%), synthetic polyisoprenes (IR), natural rubber (NR) 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), isoprene-copolymers butadiene-styrene (SBIR), copolymers of isobuten
• 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 agent for example, there may be mentioned for example functional groups comprising a C-Sn bond or amino functional groups such as benzophenone for example;
• 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.
• the diene elastomer used is a butyl rubber (optionally chlorinated or brominated), whether this copolymer is used alone or as a mixture with diene elastomers which are highly unsaturated as mentioned above, especially NR. or IR, BR or SBR.
• the elastomer composition of the heat-expandable rubber layer comprises, as diene elastomer, 50 to 100 phr of butyl rubber, the latter being combined or not with 0 to 50 another diene elastomer preferentially selected from the group consisting of natural rubber, synthetic polyisoprenes, polybutadienes having a cis-1,4 bond ratio greater than 90%, butadiene-styrene copolymers and mixtures of these elastomers.
• the diene elastomer used is chosen from the group consisting of natural rubber, synthetic polyisoprenes, polybutadienes, butadiene-styrene copolymers and mixtures of these elastomers. that the latter is used alone or in mixture with essentially saturated diene elastomers as mentioned above, in particular a butyl rubber.
• Polybutadienes having a content of -1.2 units of between 4% and 80%, or those having a cis-1,4 content of greater than 80%, in particular greater than 90%, are especially suitable.
• 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 ("Tg" - measured according to ASTM D3418-82) from -80 ° C to -40 ° C, the isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg between -50 ° C and -10 ° C.
• Tg glass transition
• butadiene-styrene-isoprene copolymers are especially suitable those having a styrene content of between 5% and 50% by weight and more particularly between 10% and 40%), an isoprene content of between 15% and 60%.
• the elastomeric composition of the heat-expandable rubber layer comprises 50 to 100 phr of natural rubber or synthetic polyisoprene, the latter being combined or not with 0 to 50 phr of another diene elastomer such as SBR, BR, or SBR / BR mixture.
• Another diene elastomer such as SBR, BR, or SBR / BR mixture.
• the use of natural rubber or synthetic polyisoprene can advantageously improve the strength, tear resistance of the foam rubber layer once expanded.
• To the 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 filler for its ability to reinforce a rubber composition is usable, for example an organic filler such as carbon black, or an inorganic filler such as silica to which is associated in a known manner a coupling agent.
• 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 10 and 100 phr.
• a content greater than 10 phr is favorable for good mechanical strength; beyond 100 phr, there is a risk of excessive rigidity, limited extensibility of the rubber layer.
• the total reinforcing filler content is more preferably between 10 and 50 phr.
• Suitable carbon blacks are all carbon blacks, especially blacks conventionally used in tires (so-called pneumatic grade blacks) such as blacks of the series 100, 200, 300, 500, 600 or 700 (ASTM grades), as for example Examples blacks NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772.
• 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
• an at least bifunctional coupling agent (or bonding agent) is used in a well-known manner to ensure a sufficient chemical and / or physical connection between the inorganic filler (surface of its particles) and the diene elastomer.
• 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 radical (preferably a C 1 -C 18 alkylene group or a C 6 -C 12 arylene group, more particularly a C 1 -C 10 , especially C 1 -C 4 , alkylene, in particular propylene);
• 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).
• the radicals R 2 substituted or unsubstituted, which are identical to or different from one another, represent a C 1 -C 8 alkoxyl or C 5 -C 8 cycloalkoxyl group (preferably a group chosen from C 1 -C 6 alkoxyls and C 5 cycloalkoxyls); -C 8 , more preferably still a group selected from C1-C4 alkoxyls, in particular methoxyl and ethoxyl).
• silane polysulfides are more particularly the bis (mono, trisulfide or tetrasulfide) of bis (alkoxyl (Ci-C 4) alkyl (Ci-C 4) silyl alkyl (Ci-C 4 )), such as polysulfides of bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl).
• TESPT bis (3-triethoxysilylpropyl) tetrasulfide
• TESPD bis (3-triethoxysilylpropyl) tetrasulfide
• TESPD bis-disulfide ( triethoxysilylpropyl)
• polysulfides in particular disulfides, trisulphides or tetrasulphides
• 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 elastomer compositions preferably comprise between 2 and 15 phr, more preferably between 3 and 12 phr of coupling agent.
• a blowing agent is a thermally decomposable compound, intended to release a large amount 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 gas formed is nitrogen but it also happens, depending on the nature of the blowing agent used, that this gas contains carbon dioxide.
• expansion agents of the endothermic or exothermic type. It is preferable to use chemical expansion agents, more preferably chemical expansion agents of the exothermic type.
• chemical expansion agents that may be used preferentially, mention may be made especially of those selected from the group consisting of azo, nitroso, hydrazine, carbazide, semicarbazide, tetrazole, carbonate and citrate compounds and mixtures of such compounds.
• blowing agents are more preferably selected from the group consisting of diazo compounds, dinitroso, sulfonyl semicarbazides, sulfonyl hydrazides and mixtures of such compounds.
• these there may be mentioned more particularly dinitroso-pentane-ethylene tetramine, dinitroso-pentane-styrene tetramine, azodicarbonamide, N, N'-dimethyl-N, N'-dinitroso-phthalamide, benzene sulfonyl- hydrazide, toluene sulphonyl hydrazide, p, p'-oxy-bis- (benzenesulfonyl) hydrazide, p-toluene sulphonyl semicarbazide or p, p'-oxy-bis- (benzenesulfonyl) semicarbazide; in these examples, the gas formed is composed of
• alkali metal or alkaline earth metal carbonates and bicarbonates such as sodium carbonate or bicarbonate, ammonium carbonate or bicarbonate, citrates such as sodium monocitrate, malonic acid, citric acid.
• the content of blowing agent in the elastomeric composition is between 20 and 70 phr, more preferably in a range of 25 to 65 phr.
• An essential feature of the invention is to add to the blowing agent described above a hot melt compound whose melting temperature is between 70 ° C and 150 ° C, preferably between 100 ° C and 150 ° C, more preferably between 110 ° C and 140 ° C.
• the melting temperature is a well-known basic physical constant (available for example in "Handbook of Chemistry and Physics") of thermo-fusible compounds, organic or inorganic; it can be controlled by any known method, for example by the Thiele method, the Kofler bench method or by DSC.
• the level of this thermally fusible compound is between 10 and 50 phr, preferably in a range of 15 to 45 phr. Its function is to turn into a liquid in the specific temperature range indicated above, before or at the moment when the blowing agent thermally decomposes and releases gas bubbles. Its addition to the high rates recommended above therefore makes it possible, unexpectedly, to limit the expansion rate of the foam rubber layer, to result in a more compact and homogeneous intercellular structure, ultimately more effective vis-à-vis screw noise for a given layer thickness.
• the rubber additives known to those skilled in the art may be used as being compatible, both in their form (for example in powder form) and by their chemical nature, with conventional rubber compositions for pneumatic tires.
• thermoplastic polymers such as polyethylene, polypropylene and polystyrene.
• Tg glass transition temperature
• - ISO 4625 is between 70 ° C and 150 ° C, preferably between 100 and 150 ° C.
• resin is hereby reserved, by definition known to those skilled in the art, to a compound that is solid at room temperature (23 ° C), as opposed to a liquid plasticizer such as an oil.
• hydrocarbon resins are polymers well known to those skilled in the art, essentially based on carbon and hydrogen, which can be used in particular as plasticizers or tackifying agents in polymeric matrices. They can be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, aliphatic / aromatic type that is to say based on aliphatic and / or aromatic monomers. They may be natural or synthetic, whether based on petroleum or not (if so, also known as petroleum resins).
• thermoplastic hydrocarbon resins may be chosen, for example, from the group consisting of cyclopentadiene homopolymer or copolymer resins, dicyclopentadiene homopolymer or copolymer resins, terpene homopolymer or copolymer resins, homopolymer resins or the like. terpene phenol copolymers, homopolymer or C5 cut copolymer resins, homopolymer or C9 cut copolymer resins, alpha-methyl-styrene homopolymer or copolymer resins and mixtures of these resins.
• the thermofusible compound chosen is urea or a hot-melt derivative of urea.
• Urea in particular has a melting temperature which is well adapted to the intended application.
• the total amount of blowing agent and hot-melt compound is between 30 and 115 phr, preferably in a range of 35 to 110 phr.
• the elastomeric composition of the heat-expandable layer may also comprise all or part of the usual additives normally used in tire rubber compositions, such as, for example, protective agents such as chemical antioxidants, anti-oxidants, plasticizers or plasticizers.
• extension oils whether these are of aromatic or non-aromatic nature, especially very low or non-aromatic oils, for example of the naphthenic or paraffinic type, with high or preferably low viscosity, MES or TDAE oils, vegetable oils, fillers other than those mentioned above, for example short fibers, lamellar fillers (eg phyllosilicates such as kaolin, talc, mica, graphite, clays or modified clays ("organo clays”)) capable of further improving the noise barrier effect, a crosslinking system based on either sulfur or sulfur and / or peroxide and / or bismal donors eimides, vulcanization accelerators, vulcanization activators.
• protective agents such as chemical antioxidants, anti-oxidants
• the elastomeric composition of the heat-expandable layer may also contain coupling enhancers when a coupling agent is used, inorganic filler recovery agents when an inorganic filler is used, or more generally assisting agents.
• these agents are for example hydroxysilanes or hydrolysable silanes such as alkyl-alkoxysilanes, polyols, polyethers, amines, hydroxylated or hydrolysable polyorganosiloxanes.
• the rubber compositions forming the foam rubber layer are manufactured in suitable mixers, for example using three 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 "non-productive" phase) at high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C, followed by a second (non-productive) phase at lower temperature (preferably less than 100 ° C) during which is incorporated the blowing agent, finally a third phase of mechanical work (sometimes called “productive” phase) at low temperature, typically less than 120 ° C, for example between 60 ° C and 100 ° C, finishing phase during which is incorporated the crosslinking system or vulcanization.
• a first thermomechanical working or mixing phase (sometimes referred to as "non-productive" phase) at high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C
• 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 filler and the hot-melt compound by thermomechanically kneading the whole on one or more occasions until a maximum temperature of between 130 ° C and 200 ° C is reached;
• thermomechanical work falling and cooling of the mixture thus obtained, a second (non-productive) phase of thermomechanical work is then conducted in the same internal mixer, during which phase the blowing agent is incorporated at a more moderate temperature. (eg 60 ° C), to reach a maximum temperature of fall below 100 ° C.
• the low temperature crosslinking system is then incorporated, 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 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 semi-finished product that can be used directly as an elastomeric layer.
• thermo-expandable In the green state (ie, uncured) and therefore unexpanded, the density or density denoted Di of the rubber layer is preferably between 1, 000 and 1, 300 g / cm 3 , more preferably in a range of from 1.025 to 1, 250 g / cm 3 ; its thickness is preferably between 0.5 and 5 mm, more preferably between 1 and 3 mm.
• 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 foam rubber layer is preferably in a range from 0.200 to 0.600 g / cm 3 , plus preferably from 0.250 to 0.450 g / cm 3 ; its thickness is preferably between 2 and 20 mm, more preferably between 4 and 12 mm.
• T E (expressed in%) is preferably between 100% and 400%, more preferably between 150% and 300%>, this expansion rate T E being calculated in a known manner from the Densities Di and D 2 above, as follows:
• T E [(D 1 / D 2 ) - 1] x 100.
• FIGS. 1 to 4 show in a very diagrammatic manner (in particular without respecting a specific scale) examples of radial cuts of tires for a radial carcass reinforcement motor vehicle according to the invention.
• these bandages being in the green state (ie, uncured) (Fig. 1 and 3) or in the cured state (ie, vulcanized) (Fig. 2 and 4).
• These pneumatic tires 1 comprise an upper zone 2 reinforced by a crown reinforcement or belt 6, two sidewalls 3 and two inextensible beads 4, each of these beads 4 being reinforced with a rod 5.
• the crown zone 2 delimited laterally by two shoulders ( 2a, 2b) is surmounted by a tread (not shown in this schematic figure, for simplification), the belt 6 being for example constituted by at least two superposed crossed plies reinforced by metal cables.
• a carcass reinforcement 7 is wound around the two rods 5 in each bead 4, the upturn 8 of this armature 7 being for example arranged to the outside of the tires which are here shown mounted on their rim 9.
• the carcass reinforcement 7 is in known manner constituted of at least one sheet reinforced by so-called "radial” cables, for example textile or metal, that is to say that these cables are arranged substantially parallel to each other and s' extend from one bead to the other so as to form an angle of between 80 ° and 90 ° with the median circumferential plane (plane perpendicular to the axis of rotation of the tire which is situated halfway between the two beads 4 and goes through the middle of the crown frame 6).
• radial cables for example textile or metal
• These pneumatic tires 1 also comprise, in a well known manner, an inner liner layer 10 (commonly called “inner liner” or “inner liner”) which defines the radially inner face of the tire, in contact with the inflation cavity 11
• This airtight layer 10 allows the swelling and pressurization of the bandage 1; its sealing properties enable it to guarantee a relatively low rate of pressure loss, making it possible to keep the swollen tire in a normal operating state for a sufficient duration, normally of several weeks or several months.
• These pneumatic tires according to the invention are characterized in that their inner wall 10 is at least partly covered, on the side of the cavity 11, with a rubber layer 12 (expandable when the tire is in the green state). expanded when baked) able to partially absorb the cavity noise when its structure is expanded (ie, after baking or vulcanization of the tire).
• said inner wall (10) has on its radially inner face a heat-expandable rubber layer (12) which extends substantially over the entire inner wall of the tire, extending from one flank to the other, substantially to the level of the rim hook when the tire 1 is in the mounted position, as illustrated for example in Figures 3 and 4.
• the layer 12 could however cover only, still on its radially inner face, only a part of the layer (10) airtight, for example only the crown area of the tire or s extend at least from the crown zone to the shoulders (as illustrated for example in FIGS. 1 and 2) or even up to the flank (equator) of said bandage.
• the layer 10 (for example of thickness equal to about 1.0 mm) is for example based on butyl rubber, it has a usual formulation for inner liner.
• the rubber layer 12 consists of an elastomer composition as previously described based on at least one elastomer (such as a butyl rubber, natural rubber used or not in combination with a synthetic elastomer such as SBR or BR), a filler such as carbon black or silica, an expanding agent such as azodicarbonamide and a hot melt compound such as urea.
• elastomer such as a butyl rubber, natural rubber used or not in combination with a synthetic elastomer such as SBR or BR
• a filler such as carbon black or silica
• an expanding agent such as azodicarbonamide
• a hot melt compound such as urea.
• this layer 12 is for example 1 to 3 mm in the green state (before vulcanization) and 4 to 12 mm in the cooked state (expanded).
• This layer 12, once expanded, placed between the sealing layer 10 and the cavity 11 of the tire, makes it possible to reduce Substantial, as the following examples demonstrate, the rolling noise perceived within the vehicle.
• thermo-expandable elastomeric composition can be applied in a conventional manner at the desired location.
• An advantageous manufacturing variant for those skilled in the tire industry, will for example consist, in a first step, in laying the thermoexpandable elastomer composition flat on a manufacturing drum in the form of a layer ( or “skim") of suitable thickness, before covering the latter with the airtight layer (“innerliner”) then the rest of the structure of the tire, according to manufacturing techniques well known to the man of the job.
• compositions (denoted C-1 and C-2) were prepared whose formulation is given in Table 1 (rate of the different products expressed in phr).
• the composition C-1 is the control composition, it comprises the blowing agent but is devoid of the hot-melt compound.
• composition C-2 is in accordance with the invention, it comprises both the blowing agent and the hot-melt compound.
• the reinforcing filler carbon black
• the elastomer were successively introduced into an internal mixer, the initial vessel temperature of which was approximately 60 ° C. diene (halogenated butyl rubber), the hot-melt compound (urea) for the composition C-2, and 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 was then carried out in a step of about 2 to 4 minutes, until a maximum "falling" temperature of 140 ° C. was reached.
• the mixture thus obtained was then cooled to a temperature of less than 100 ° C., the cooled mixture re-introduced into the same internal mixer (initial temperature 60 ° C.), and then the expansion agent (diazo compound) was incorporated into said mixture (mixer filled to about 70% by volume).
• a second thermomechanical work was then carried out in a step of about 2 to 4 minutes, until a maximum temperature of fall of less than 100 ° C. was reached.
• the two compositions thus obtained were then calendered in the form of a rubber band (12) of thickness equal to about 2 mm, which was then incorporated, as indicated previously, into a passenger car tire (dimensions 225/55 RI 7) as illustrated in FIG. 1.
• the thickness of the foam rubber layer (expanded) was about 8 mm (tire P1) and about 6 mm (tire P-2) respectively.
• Table 2 shows the densities of the rubber layer before and after baking of the tire, as well as the volume expansion rate and the average size of the bubbles formed after baking.
• the densities were measured in the usual manner by immersion in water, the volume expansion rate was calculated as indicated above, the average size (average number) of the bubbles was measured by SEM (magnification 200) on cross sections made on the foam rubber layers.
• SEM magnification 200
• the tire P1 (not in accordance with the invention) and the same control tire P-0, in a frequency range of 190 to 230 Hz ("cavity noise"), on the one hand, from 0 to 2 000 Hz ("road noise”) on the other hand.
• acoustic energy (dB (A)) which corresponds to the integration of the sound pressure as a function of the frequency over the frequency domain considered, a negative value indicating a reduction of the noise compared to the reference.
• the control bandage P-0 is identical to the bandages Pl and P-2 except that it does not contain a layer of foam rubber inside its cavity; it is used as a reference bandage in this test.
• This second test confirms the beneficial effect of the invention when another rubber formulation, here based on NR and SBR elastomers, is used to form the matrix of the foam rubber layer.
• a rubber composition (denoted C-3) was prepared as indicated previously for test 1. Its formulation is given in table 4 (rate of products in phr): this composition C-3 according to the invention comprises both an expansion agent and a hot-melt compound.
• composition C-3 was then calendered in the form of two rubber layers (12) of different thicknesses (1.5 mm and 2.0 mm in the green state) which were then incorporated, as indicated previously, two tires (respectively noted P-3 and P-4) for passenger vehicle (dimensions 225/55 RI 7), both in accordance with the invention, and as shown schematically in Figure 1.
• the combined use of the blowing agent and the hot-melt compound makes it possible to very greatly reduce the expansion ratio and therefore the thickness of the coating layer.
• final foamed foam rubber i.e., once vulcanized tire
• With a constant layer thickness it is possible to significantly increase the sound absorption capacity of this layer of foam rubber.

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• 2009
  • 2009-10-27 FR FR0957521A patent/FR2952645B1/fr not_active Expired - Fee Related
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