Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
• • 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
  • B60C5/00—Inflatable pneumatic tyres or inner tubes
  • B60C5/12—Inflatable pneumatic tyres or inner tubes without separate inflatable inserts, e.g. tubeless tyres with transverse section open to the rim
  • B60C5/14—Inflatable pneumatic tyres or inner tubes without separate inflatable inserts, e.g. tubeless tyres with transverse section open to the rim with impervious liner or coating on the inner wall of the tyre
  • B60C2005/145—Inflatable pneumatic tyres or inner tubes without separate inflatable inserts, e.g. tubeless tyres with transverse section open to the rim with impervious liner or coating on the inner wall of the tyre made of laminated layers
• • 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
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]

Definitions

• the present invention relates to "pneumatic" objects, i.e., by definition, objects that take their usable form when inflated with air or an equivalent inflation gas.
• the radially inner face has an airtight layer (or more generally any inflation gas) which allows the swelling and maintaining the pressure of the tire.
• airtight layer or more generally any inflation gas
• Its sealing properties enable it to guarantee a relatively low rate of pressure loss, making it possible to maintain the swollen bandage in normal operating condition for a sufficient duration, normally of several weeks or several months. It also serves to protect the carcass reinforcement from the diffusion of air from the interior space to the bandage.
• inner liner waterproof inner liner
• compositions based on rubber or butyl elastomer are well-known disadvantages of compositions based on rubber or butyl elastomer.
• they have significant hysteretic losses, moreover over a wide temperature spectrum, a disadvantage that penalizes the rolling resistance of tires.
• the present invention relates to a pneumatic object provided with an elastomeric layer impervious to inflation gases, characterized in that said elastomeric layer comprises at least:
• first styrenic thermoplastic elastomer at least 50 phr of a polystyrene and polyisobutylene block copolymer
• second styrenic thermoplastic elastomer at most 50 phr of an unsaturated thermoplastic styrene elastomer.
• the above styrenic elastomers have the major advantage, because of their thermoplastic nature, can be worked as such in the molten state (liquid), and therefore to offer a possibility of putting simplified implementation.
• the invention particularly relates to pneumatic objects of rubber such as pneumatic tires, or inner tubes, in particular tubes for pneumatic tires.
• the invention relates more particularly to pneumatic tires intended to equip tourism-type motor vehicles, SUVs ("Sport Utility Vehicles"), two wheels (in particular motorcycles), planes, such as industrial vehicles such as vans, heavy goods vehicles (that is, metros, buses, road transport vehicles such as trucks, tractors, trailers, off-the-road vehicles such as agricultural or civil engineering vehicles) and other transport or handling vehicles.
• SUVs Sport Utility Vehicles
• two wheels in particular motorcycles
• planes such as industrial vehicles such as vans, heavy goods vehicles (that is, metros, buses, road transport vehicles such as trucks, tractors, trailers, off-the-road vehicles such as agricultural or civil engineering vehicles) and other transport or handling vehicles.
• the invention also relates to the use as an inflation-tight layer, in a pneumatic object, of an elastomeric layer as defined above.
• 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 expression “phr” means parts by weight per hundred parts of elastomer (or “rubber”, the two terms being considered synonymous) total, that is to say of the total of the elastomers present in the elastomer composition. forming the gas-tight layer.
• the pneumatic object of the invention has the essential feature of being provided with a gas-tight layer formed of a thermoplastic elastomer composition, said layer or composition comprising at least:
• first styrenic thermoplastic elastomer at least 50 phr of a polystyrene and polyisobutylene block copolymer
• second styrenic thermoplastic elastomer at most 50 phr of a thermoplastic styrene elastomer of the unsaturated type
• additives such as an extension oil or a lamellar filler.
• the level of first elastomer is within a range from 50 phr to less than 100 phr and the level of second elastomer (different from the first elastomer and still present in the gas-tight layer) is included in a range of more than 0 phr to 50 phr maximum.
• thermoplastic styrene elastomers are thermoplastic elastomers in the form of block copolymers based on styrene.
• thermoplastic polymers and elastomers consist in a known manner of rigid polystyrene blocks connected by flexible elastomer blocks, for example polybutadiene, polyisoprene or poly (ethylene / butylene). They are often triblock elastomers with two rigid segments connected by a flexible segment. The rigid and flexible segments can be arranged linearly, star-shaped or connected. These TPS elastomers may also be diblock elastomers with a single rigid segment connected to a flexible segment.
• each of these segments or blocks contains at least more than 5, usually more than 10 base units (e.g., styrene units and isoprene units for a styrene / isoprene / styrene block copolymer).
• base units e.g., styrene units and isoprene units for a styrene / isoprene / styrene block copolymer.
• polystyrene and polyisobutylene block copolymer is intended to mean any styrenic thermoplastic copolymer comprising at least one polystyrene block (that is to say one or more polystyrene blocks) and at least one polyisobutylene block. (ie one or more polyisobutylene blocks), to which other saturated or unsaturated blocks (e.g. polyethylene and / or polypropylene) and / or other monomer units (e.g. unsaturated dienes).
• This polystyrene and polyisobutylene block copolymer also called “first TPS copolymer” in the present application, is in particular chosen from the group consisting of styrene / isobutylene diblock copolymers (abbreviated to "SIB”), triblock styrene / isobutylene copolymers / styrene (abbreviated as "SIBS”) and mixtures of these copolymers SBIB and SIBS, by definition totally saturated.
• SIB styrene / isobutylene diblock copolymers
• SIBS triblock styrene / isobutylene copolymers / styrene
• this first TPS copolymer in particular SIB or SIBS, provides the elastomeric layer with excellent sealing properties while significantly reducing the hysteresis compared to conventional butyl rubber layers.
• second styrenic thermoplastic elastomer also called “second TPS copolymer”
• unsaturated TPS elastomer a TPS elastomer which is provided with ethylenic unsaturations, that is to say, includes carbon-carbon double bonds (conjugated or otherwise).
• saturated TPS elastomer is meant a TPS elastomer which contains no ethylenic unsaturation (Le., No carbon-carbon double bond.
• the second TPS copolymer is a copolymer comprising styrene blocks and diene blocks, these diene blocks being in particular isoprene or butadiene blocks. More preferably, this second unsaturated TPS copolymer is chosen from the group consisting of styrene / butadiene (SB), styrene / isoprene (SI), styrene / butadiene / butylene (SBB), styrene / butadiene / isoprene (SBI) block copolymers.
• SB styrene / butadiene
• SI styrene / isoprene
• SI styrene / butadiene / butylene
• SBI styrene / butadiene / isoprene
• SBS styrene / butadiene / styrene
• SBBS styrene / butadiene / butylene / styrene
• SIS styrene / isoprene / styrene
• SI styrene / butadiene / isoprene / styrene
• this second unsaturated TPS copolymer in the gas-tight layer makes it possible to greatly improve the adhesion of this latter to another layer of unsaturated polymer, present for example in the pneumatic object of the invention.
• another such unsaturated polymer layer is a diene elastomer composition, in particular based on natural rubber, such as those which are commonly used for the carcass reinforcement of tires, generally and in a manner known in the art. direct contact of the inner sealing layer of such tires.
• the weight content of styrene in each (first and second) TPS copolymer is between 5% and 50%.
• the thermoplastic nature of the elastomers may decrease significantly while above the maximum recommended, the elasticity of the gas-tight layer may be affected.
• the styrene content is more preferably between 10 and 40%, in particular between 15 and 35%.
• styrene is meant in the present description any monomer containing styrene, unsubstituted as substituted; examples of substituted styrenes are methylstyrenes (for example ⁇ -methylstyrene, ⁇ -methylstyrene, ⁇ -methylstyrene, tert-butylstyrene) and chlorostyrenes (for example monochlorostyrene, dichlorostyrene).
• methylstyrenes for example ⁇ -methylstyrene, ⁇ -methylstyrene, ⁇ -methylstyrene, tert-butylstyrene
• chlorostyrenes for example monochlorostyrene, dichlorostyrene
• the Tg (glass transition temperature, measured according to ASTM D3418) of each (first and second) TPS copolymer is less than -20 ° C, especially less than -40 ° C.
• a value of Tg higher than these minima can reduce the performance of the waterproof layer during use at very low temperatures; for such use, the Tg of the TPS copolymers is more preferably still lower than -50 ° C.
• the number-average molecular weight (denoted Mn) of the first TPS copolymer is preferably between 30,000 and 500,000 g / mol, more preferentially between 40,000 and 400,000 g / mol.
• Mn number-average molecular weight
• the number average molecular weight of the second TPS copolymer it can be reduced compared to the first TPS elastomer, given the different function and a generally lower proportion of this second copolymer in the sealed composition; preferably, it is between 3000 and 500 000 g / mol, in particular between 4000 and 400 000 g / mol.
• the number-average molecular weight (Mn) of the TPS elastomers is determined in known manner by steric exclusion chromatography (SEC).
• SEC steric exclusion chromatography
• the sample is first solubilized in tetrahydrofuran at a concentration of about 1 g / l; then the solution is filtered on a 0.45 ⁇ m porosity filter before injection.
• the equipment used is a chromatographic chain "WATERS alliance”.
• the elution solvent is tetrahydrofuran, the flow rate 0.7 ml / min, the system temperature 35 ° C and the analysis time 90 min.
• a set of four WATERS columns in series, of trade names "STYRAGEL" ("HMW7", “HMW6E” and two "HT6E" is used.
• the injected volume of the solution of the polymer sample is 100 ⁇ l.
• the detector is a differential refractometer "WATERS 2410" and its associated software for the exploitation of chromatographic data is the “WATERS MILLENIUM” system.
• the calculated average molar masses relate to a calibration curve made with polystyrene standards.
• the level of first TPS copolymer is at least 70 phr, that is to say within a range from 70 phr to less than 100 phr.
• the level of second TPS copolymer is at most 30 phr, that is to say within a range of more than 0 phr to 30 phr maximum.
• the minimum amount of TPS (unsaturated) copolymer can be relatively small while producing the intended technical effect (improved adhesion to another layer of unsaturated polymer).
• the amount of second TPS copolymer recommended is at least 1 phr (in particular in a range from 1 to 30 phr), more particularly at least 2 phr (in particular in a range from 2 to 25 phr). ).
• the amount of first TPS copolymer can be in a range of 70 to 99 phr, in particular in a range of 75 to 98 phr.
• the gastight layer described above could comprise other elastomers than the two TPS copolymers described above.
• Such complementary elastomers, minority in weight compared to the first TPS copolymer could be, for example, diene elastomers such as natural rubber or synthetic polyisoprene, butyl rubber or even other saturated styrenic thermoplastic elastomers, within the limit of the compatibility of their microstructures.
• styrene / ethylene / butylene SEB
• SEP styrene / ethylene / propylene
• SEEP styrene block copolymers.
• SEBS ethylene / butylene / styrene
• SEPS styrene / ethylene / propylene / styrene
• SEEPS styrene / ethylene / ethylene / propylene / styrene
• the first and second TPS copolymers described above are the only thermoplastic elastomers, and more generally the only elastomers present in the gas-tight elastomeric layer.
• elastomers can be implemented in a conventional manner for TPE, by extrusion or molding, for example from a raw material available in the form of beads or granules.
• Unsaturated TPS elastomers which can be used as the second TPS copolymer such as, for example, SBS, SIS or SBBS
• SBS SIS
• SBBS Unsaturated TPS elastomers which can be used as the second TPS copolymer
• Kraton D eg, products Dl 161, Dl 118 , Dl 116, Dl 163 for examples of elastomers SIS and SBS
• Dynasol eg, products C405, C41 1, C412 for examples of SBS elastomers
• Tiftec eg, product P 1500 for an example of SBBS elastomer.
• Polystyrene and polyisobutylene block copolymers which can be used as the first TPS copolymer are also commercially available, sold for example by the company Kaneka under the name "SIBSTAR" (eg "Sibstar 103T", “Sibstar 102T “,” Sibstar 073T “or” Sibstar 072T “for SIBS,” Sibstar 042D “for SIBs).
• SIBSTAR eg "Sibstar 103T", “Sibstar 102T ",” Sibstar 073T “or” Sibstar 072T “for SIBS,” Sibstar 042D “for SIBs.
• the first and second TPS copolymers previously described are sufficient on their own for the gas-tight function to be performed with respect to the pneumatic objects in which they are used.
• the gas-tight layer may also comprise, as a plasticizer, an extension oil (or plasticizing oil) whose function is to facilitate the implementation, particularly the integration into the pneumatic object by a lowering of the module and an increase in the tackifying power of the gas-tight layer, at the cost, however, of a certain loss of tightness.
• an extension oil or plasticizing oil
• This optional extender oil is preferably used at a reduced rate, less than 100 phr - less than 100 parts by weight per hundred parts of total elastomer (ie, first and second TPS copolymers above, plus elastomer (s) additional (if applicable).
• extension oil preferably of a slightly polar nature, capable of extending and plasticizing elastomers, especially thermoplastics, may be used. At room temperature (23 ° C), these oils, more or less viscous, are liquids (that is to say, as a reminder, substances having the ability to eventually take the shape of their container), as opposed especially to resins that are inherently solid.
• the extender oil is chosen from the group consisting of polyolefinic oils (that is to say derived from the polymerization of olefins, monoolefins or diolefins), paraffinic oils, naphthenic oils (low or high viscosity), aromatic oils, mineral oils, and mixtures of these oils. More preferably, the extender oil is selected from the group consisting of polybutene oils, paraffinic oils and mixtures of these oils.
• Polybutene oils preferably polyisobutylene oils (abbreviated to "PIB"), which have demonstrated the best compromise of properties compared to the other oils tested, in particular paraffinic oils, are particularly used.
• polyisobutylene oils are sold in particular by the company UNIVAR under the name "Dynapak PoIy” (eg "Dynapak PoIy 190"), by BASF under the names “Glissopal” (eg "Glissopal 1000") or "Oppanol "(eg” Oppanol B 12 "), by INEOS Oligomer under the name” Indopol H 1200 ".
• Paraffinic oils are sold for example by Exxon under the name "Telura 618" or by Repsol under the name "Extensol 51".
• the number-average molecular mass (Mn) of the extender oil is preferably between 200 and 25,000 g / mol, more preferably between 300 and
• 4000 g / mol in particular between 400 and 3000 g / mol, has proved to be an excellent compromise for the intended applications, in particular for use in a tire.
• the number average molecular weight (Mn) of the extender oil is determined by SEC, the sample being solubilized beforehand in tetrahydrofuran at a concentration of about 1 g / l; then the solution is filtered on a 0.45 ⁇ m porosity filter before injection.
• the equipment is the chromatographic chain "WATERS alliance”.
• the elution solvent is tetrahydrofuran, the flow rate is 1 ml / min, the temperature of the system is 35 ° C. and the analysis time is 30 minutes.
• the injected volume of the solution of the polymer sample is 100 ⁇ l.
• the detector is a differential refractometer "WATERS 2410" and its associated software for the exploitation of chromatographic data is the “WATERS MILLENIUM” system.
• the calculated average molar masses relate to a calibration curve made with polystyrene standards.
• an extension oil it is preferred that its level be greater than 5 phr, in particular between 5 and 100 phr. Below the minimum indicated, the elastomeric layer or composition may have too high rigidity for certain applications while beyond the maximum recommended, there is a risk of insufficient cohesion of the composition and loss of tightness may be harmful depending on the application. For these reasons, particularly for use of the airtight layer in a tire, it is preferred that the extender oil content be greater than 10 phr, especially between 10 and 90 phr, more preferably still it is greater than 20 phr, in particular between 20 and 80 phr.
• lamellar filler at a volume ratio preferably greater than 5%, in particular between 5% and 50%, may advantageously make it possible to further reduce the coefficient of permeability (thus increasing the seal) of the elastomer composition. without increasing excessively its module, which keeps the ease of integration of the seal layer in the pneumatic object.
• lamellar fillers in English “platy fillers" are well known to those skilled in the art. They have been used in particular in pneumatic tires to reduce the permeability of conventional gastight layers based on butyl rubber. In these butyl-based layers, they are generally used at relatively low levels, usually not exceeding 10 to 15 phr (see, for example, US Patent Specification 2004/0194863, WO 2006/047509).
• L L / E
• L the length (or greater dimension)
• E the average thickness of these lamellar fillers, these averages being calculated in number. Form ratios of tens or even hundreds are common.
• Their average length is preferably greater than 1 .mu.m (that is to say that it is then said micrometric lamellar charges), typically between a few microns (for example 5 microns) and a few hundred microns (by 500 or 800 ⁇ m example).
• the lamellar fillers used in accordance with the invention are chosen from the group consisting of graphites, phyllosilicates and mixtures of such fillers.
• phyllosilicates there may be mentioned clays, talcs, micas, kaolins, these phyllosilicates may or may not be modified for example by a surface treatment; examples of such modified phyllosilicates include micas coated with titanium oxide, clays modified with surfactants ("organo clays").
• Lamellar fillers with a low surface energy are preferably used, such as those chosen from the group consisting of graphites, talcs, micas and mixtures of such fillers, the latter being able to be modified or no, more preferably still in the group consisting of graphites, talcs and mixtures of such fillers.
• the graphites can be mentioned including natural graphites, expanded graphites or synthetic graphites.
• micas examples include micas marketed by CMMP (Mica-MU®, Mica-Soft®, Briomica® for example), vermiculites (including Shawatec® vermiculite marketed by CMMP or vermiculite Microlite® marketed by WR Grace), modified or processed micas (for example, the Iriodin® range marketed by Merck).
• CMMP Milten-MU®
• Mica-Soft® Mica-Soft®
• Briomica® for example
• vermiculites including Shawatec® vermiculite marketed by CMMP or vermiculite Microlite® marketed by WR Grace
• modified or processed micas for example, the Iriodin® range marketed by Merck.
• graphites mention may be made of graphites marketed by Timcal (Timrex® range).
• talcs mention may be made of talcs marketed by Luzenac.
• the lamellar charges described above are preferably used at a high level, greater than 5%, more preferably at least 10% by volume of elastomer composition.
• a volume ratio typically corresponds, given the average density of the lamellar charges used (typically between 2.0 and 3.0) and that of the TPS copolymers used, to a weight ratio preferably greater than 20 phr, more preferably at least equal to 40 pce.
• an even higher layer loading rate at least equal to 15% or even 20% by volume, which typically corresponds to weight ratios of at least 50% by weight.
• Weight ratios higher than 100 phr are even advantageously possible.
• the level of lamellar filler is, however, preferably less than 50% by volume (typically less than 500 phr), the upper limit from which it may be exposed to problems of increase of the modulus, embrittlement of the composition, difficulties of dispersion. charge and implementation, not to mention a possible penalty for hysteresis.
• the introduction of the lamellar fillers into the elastomeric thermoplastic composition may be carried out according to various known methods, for example by mixing in solution, by mass mixing in an internal mixer, or by extrusion mixing.
• the airtight layer or composition described above may also include the various additives usually present in the airtight layers known to those skilled in the art.
• reinforcing fillers such as carbon black or silica
• non-reinforcing or inert fillers plasticizers other than the above-mentioned extension oils
• protective agents such as antioxidants or antiozonants, anti-UV agents
• coloring agents that can be advantageously used for coloring the composition
• the gas-tight composition could also comprise, still in a minority weight fraction relative to the first TPS copolymer, polymers other than elastomers, such as, for example, thermoplastic polymers compatible with TPS elastomers.
• the gas-tight layer or composition previously described is a solid (at 23 ° C.) and elastic compound, which is particularly characterized, thanks to its specific formulation, by a very high flexibility and very high deformability.
• this gas-tight layer or composition has a secant modulus in extension, at 10% elongation, which is less than 2 MPa, more preferably less than 1.5 MPa (in particular less than at 1 MPa).
• This quantity is measured at first elongation (ie without accommodation cycle) at a temperature of 23 ° C, with a pulling speed of 500 mm / min (ASTM D412), and reported in section initial test piece.
• the elastomeric layer described above can be used as an airtight layer (or any other inflation gas, for example nitrogen) in any type of pneumatic object.
• pneumatic objects include pneumatic boats, balls or balls used for play or sport.
• Such an airtight layer is preferentially disposed on the inner wall of the pneumatic object, but it can also be completely integrated into its internal structure.
• the thickness of the airtight layer is preferably greater than 0.05 mm, more preferably between 0.1 mm and 10 mm (especially between 0.1 and 1.0 mm). It will be readily understood that, depending on the specific fields of application, the dimensions and the pressures involved, the mode of implementation of the invention may vary, the airtight layer then having several preferential thickness ranges.
• the preferred thickness may be between 1 and 3 mm.
• the preferred thickness may be between 2 and 10 mm.
• the airtight composition described above has the advantage of having a significantly lower hysteresis, and thus of providing reduced rolling resistance to pneumatic tires, as demonstrated in the following embodiments.
• the gas-tight elastomeric layer previously described is advantageously usable in pneumatic tires of all types of vehicles, in particular passenger vehicles or industrial vehicles such as heavy goods vehicles.
• the single appended figure shows very schematically (without respecting a specific scale), a radial section of a tire according to the invention for a passenger vehicle.
• This tire 1 has a crown 2 reinforced by a crown reinforcement or belt 6, two sidewalls 3 and two beads 4, each of these beads 4 being reinforced with a rod 5.
• the crown 2 is surmounted by a tread represented in this schematic figure.
• 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 disposed towards the outside of the tire 1 which is shown here mounted on its 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 located halfway between the two beads 4 and goes through the middle of the crown frame 6).
• the inner wall of the tire 1 comprises an airtight layer 10, for example of thickness equal to about 1 mm, on the side of the internal cavity 11 of the tire 1.
• This inner layer covers the entire inner wall of the tire, extending from one side to the other, at least to the level of the rim hook when the tire is in the mounted position. It defines the radially inner face of said tire intended to protect the carcass reinforcement from the diffusion of air coming from the space 1 1 inside the bandage. It allows inflation and pressure maintenance of the tire; its sealing properties must enable it to guarantee a relatively low rate of pressure loss, to maintain the swollen bandage, in normal operating condition, for a sufficient duration, normally of several weeks or several months.
• thermoplastic elastomer composition comprising:
• the first TPS copolymer 82 phr of an SIBS elastomer ("Sibstar 102T" with a styrene content of about 15%, a Tg of about -65 ° C and an average molecular weight Mn of about 90,000 g / mol);
• the second TPS copolymer 18 phr of an SBBS elastomer ("Tuftec P 1500" with a styrene content of about 37%, a Tg of about -75 ° C. and a mass Mn of about 60,000 g / mol); as extension oil, approximately 55 phr of PIB oil ("Dynapak PoIy 190" - Mn of the order of 1000 g / mol);
• Layer 10 was prepared as follows.
• the mixture of the four constituents (SIBS, SBBS, PIB oil and lamellar filler) was conventionally produced using a twin-screw extruder (L / D equal to about 40) at a temperature typically greater than the melting temperature of the composition (about 190 ° C).
• the extruder used included a feed (hopper) for each TPS copolymer (SIBS and SBBS), another feed (hopper) for the lamellar feed and finally a pressurized liquid injection pump for the polyisobutylene extension oil; it was provided with a die for extruding the product to the desired dimensions.
• the tire provided with its airtight layer (10) as described above can be made before or after vulcanization (or cooking).
• the airtight layer is simply applied in a conventional manner to the desired location, for formation of the sealing layer 10.
• the vulcanization is then carried out conventionally.
• An advantageous manufacturing variant for those skilled in the tire industry, will for example consist in a first step of laying the airtight layer directly on a manufacturing drum in the form of a flat tire. a layer of suitable thickness, before covering the latter with the rest of the structure of the tire, according to manufacturing techniques well known to those skilled in the art.
• the sealing layer is applied inside the baked tire by any appropriate means, for example by gluing, extrusion, spraying or else by extrusion / blowing. a film of appropriate thickness.
• sealing properties were first analyzed on test specimens of butyl rubber compositions on the one hand, and SIBS and SBBS on the other hand (with and without PIB extension oil). for the second composition based on only two TPS copolymers).
• a rigid wall permeameter was used, placed in an oven (temperature of 60 ° C in this case), provided with a pressure sensor (calibrated in the range of 0 to 6 bars) and connected to a tube equipped with an inflation valve.
• the permeameter can receive standard specimens in the form of a disc (for example 65 mm diameter in this case) and with a uniform thickness of up to 3 mm (0.5 mm in the present case).
• the pressure sensor is connected to a National Instruments data acquisition card (four-channel analog 0-10V acquisition) which is connected to a computer performing a continuous acquisition with a frequency of 0.5 Hz (1 point every two seconds).
• the coefficient of permeability (K) is measured from the linear regression line (average over 1000 points) giving the slope ⁇ of the pressure loss, through the tested test piece, as a function of time, after stabilization of the system, that is to say obtaining a steady state during which the pressure decreases linearly with time.
• adhesion tests were conducted to test the ability of the gas-tight layer to adhere after firing to a diene elastomer layer, more specifically to a conventional rubber composition for tire carcass reinforcement, based on natural rubber (peptized) and N330 carbon black (65 parts per hundred parts of natural rubber), further comprising the usual additives (sulfur, accelerator, ZnO, stearic acid, antioxidant, cobalt naphthenate).
• a diene elastomer layer more specifically to a conventional rubber composition for tire carcass reinforcement, based on natural rubber (peptized) and N330 carbon black (65 parts per hundred parts of natural rubber), further comprising the usual additives (sulfur, accelerator, ZnO, stearic acid, antioxidant, cobalt naphthenate).
• SBBS second unsaturated TPS copolymer
• pneumatic tires according to the invention of the type for passenger vehicle (size 195/65 Rl 5), were manufactured; their inner wall was covered by an airtight layer (10) with a thickness of 1 mm (on the building drum, before making the rest of the tire), and the tires were then vulcanized.
• Said airtight layer (10) was formed of SIBS (82 phr), SBBS (18 phr), lamellar filler (40 phr of "Iriodin 153”), the whole extended with 55 phr of PIB oil, such as described above.
• pneumatic tires according to the invention were compared to control tires (Michelin "Energy 3" brand) comprising a conventional air-tight layer of the same thickness, based on butyl rubber.
• the rolling resistance of pneumatic tires was measured on a steering wheel according to ISO 87-67 (1992). It has been found that the pneumatic tires of the invention have a very significant and unexpectedly reduced rolling resistance for those skilled in the art, of nearly 4% compared with the control tires.
• the invention offers tire designers the opportunity to significantly reduce the hysteresis of the internal sealing layers, and therefore the fuel consumption of motor vehicles equipped with such tires, without penalty or in any other way. case without prohibitive penalty in the case of the use of an extension oil, sealing properties.

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