Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C73/00—Repairing of articles made from plastics or substances in a plastic state, e.g. of articles shaped or produced by using techniques covered by this subclass or subclass B29D
  • B29C73/16—Auto-repairing or self-sealing arrangements or agents
  • B29C73/163—Sealing compositions or agents, e.g. combined with propellant agents
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
  • C08L25/02—Homopolymers or copolymers of hydrocarbons
• • 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
  • B60C19/12—Puncture preventing arrangements
• • 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
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/20—Compounding polymers with additives, e.g. colouring
  • C08J3/201—Pre-melted polymers
• • 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
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/20—Compounding polymers with additives, e.g. colouring
  • C08J3/22—Compounding polymers with additives, e.g. colouring using masterbatch techniques
  • C08J3/226—Compounding polymers with additives, e.g. colouring using masterbatch techniques using a polymer as a carrier
• • 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
  • C08K3/011—Crosslinking or vulcanising agents, e.g. accelerators
• • 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
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
  • C08K5/0016—Plasticisers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L21/00—Compositions of unspecified rubbers
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2030/00—Pneumatic or solid tyres or parts thereof
• • 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
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
  • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
• • 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
  • C08K5/01—Hydrocarbons
• • 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
  • C08K5/29—Compounds containing one or more carbon-to-nitrogen double bonds
  • C08K5/31—Guanidine; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L45/00—Compositions of homopolymers or copolymers of compounds having no unsaturated aliphatic radicals in side chain, and having one or more carbon-to-carbon double bonds in a carbocyclic or in a heterocyclic ring system; 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
  • C08L91/00—Compositions of oils, fats or waxes; Compositions of derivatives thereof

Definitions

• the present invention relates to self-sealing compositions useful as anti-puncture layers in any type of "pneumatic" object, that is to say, by definition, any object which takes its usable form when it is inflated with air.
• Self-sealing compositions capable of achieving such an objective, by definition capable of ensuring automatically, that is to say without any external intervention, the sealing of a tire in case of perforation of the latter by a body such as a nail, are particularly difficult to develop.
• a self-sealing layer In order to be usable, a self-sealing layer must satisfy many conditions of a physical and chemical nature. In particular, it must be effective over a very wide range of operating temperatures throughout the life of the tires. It must be able to close the hole when the piercing object remains in place; at the expulsion of the latter, it must be able to fill the hole and make the tire tight.
• the level of liquid elastomer is reduced or if the latter is completely removed, another major manufacturing problem may arise: in the absence of reinforcing filler such as carbon black (otherwise undesirable , in a known manner, for this type of application), the composition is weakly cohesive. This lack of cohesion can be such that the stickiness of the composition, resulting from the high rate of tackifying resin used, is no longer compensated and prevails. It then follows a risk of parasitic bonding on the mixing tools, unacceptable under conditions of industrial implementation.
• reinforcing filler such as carbon black
• the present invention relates to a method of manufacturing a self-sealing elastomer composition, said method being characterized in that it comprises at least the following steps:
• a masterbatch comprising at least one diene elastomer and a hydrocarbon resin at a rate greater than 30 phr is manufactured by mixing these various components in a mixer at a temperature or a so-called "hot mixing" temperature. which is greater than the softening temperature of the hydrocarbon resin; then the masterbatch thus prepared is incorporated at least one crosslinking system, by mixing the whole, in the same mixer or in a different mixer, at a temperature or a temperature which is kept below 100 ° C., for the obtaining said self-sealing composition;
• this composition may have high levels of hydrocarbon resin without requiring the use of a liquid plasticizer at a particularly high rate.
• FIG. 1 an example of an extrusion-mixing device that can be used for carrying out a process according to the invention
• FIG. in radial section an example of a pneumatic tire using a self-sealing composition prepared according to the process according to the invention (FIG 2).
• 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 expression “from a to b” means the range of values from terminal "a" to terminal "b", that is to say including the strict limits "a” and "b".
• a masterbatch comprising at least one diene elastomer and a hydrocarbon resin at a rate greater than 30 phr is first produced by mixing these various components in a mixer at a temperature or a temperature known as hot mixing "or” first temperature "which is higher than the softening temperature of the hydrocarbon resin; b) then incorporating at least one cross-linking system into said masterbatch, by mixing the whole, in the same mixer or in a different mixer, at a temperature or a so-called "second temperature” which is kept below 100 ° C, for obtaining said self-sealing composition.
• Tg glass transition temperature
• the first and second temperatures above are of course those of the masterbatch and the self-sealing composition, respectively, measurable in situ and not the set temperatures of the mixers themselves.
• masterbatch (or “masterbatch”) is to be understood here, by definition, the mixture of at least one diene elastomer and more than 30 phr of the hydrocarbon resin, a precursor mixture of the final self-sealing composition, ready to work.
• the liquid plasticizer may be incorporated at any time, in whole or in part during any of the steps of the process of the invention, in particular during the manufacture of the masterbatch itself (in this case, before, during or after after incorporation of the hydrocarbon resin in the diene elastomer), "hot” (that is to say at a temperature above the softening temperature of the resin) as at a lower temperature, or for example after manufacture the masterbatch (in this case, before, during or after adding the crosslinking system).
• liquid plasticizer during step a) of manufacture of the masterbatch itself, more preferably in this case either at the same time as the hydrocarbon resin, or after introduction of the latter.
• a mixture of the hydrocarbon resin and the Liquid plasticizer may be prepared prior to incorporation into the diene elastomer.
• additives may be incorporated in this masterbatch, whether they are intended for the actual masterbatch (for example a stabilizing agent, a coloring or anti-UV agent, an antioxidant, etc.) or for the final self-sealing composition at which is the masterbatch.
• the masterbatch can be manufactured in any mixing tool, in particular in a paddle mixer, a roller mixer, an extruder, any mixer capable of mixing, kneading its various components sufficiently until a homogeneous and homogeneous mixture of said components is obtained. components.
• a mixer-screw extruder constant pitch or not, able in known manner to introduce significant shear of the mixture (diene elastomer and resin) being formed.
• the plasticizing hydrocarbon resin may be in the solid state or in the liquid state.
• the diene elastomer (solid) When the diene elastomer (solid) is brought into contact with the thermoplastic hydrocarbon resin, the latter may be in the solid state or, more preferably, already in the liquid state; it suffices for this to heat the resin at a temperature above its softening temperature.
• the hot mixing temperature is typically greater than 70 ° C., preferably greater than 80 ° C., for example between 100 ° C. and 150 ° C.
• the hydrocarbon resin is preferably injected in the liquid state, under pressure, into the mixer.
• the step a) hot mixing is conducted away from oxygen.
• Step b) of incorporating the crosslinking system is in turn conducted at a temperature or up to a maximum temperature (second temperature) which is maintained below 100 0 C, preferably below 80 0 C.
• the second temperature is kept below the softening temperature of the resin.
• the mixing temperature of step b) is preferably less than 50 ° C., more preferably between 20 ° C. and 40 ° C. (for example between 20 ° C. and 30 ° C. VS).
• an intermediate cooling step of the masterbatch to bring its temperature to a value less than 100 0 C, preferably less than 80 0 C, especially less than softening temperature of the resin, this before introduction of the crosslinking system in the previously prepared masterbatch.
• composition or self-sealing material capable of being prepared according to the process of the invention is therefore an elastomer composition
• a hydrocarbon resin as a solid plasticizer (at 23.degree. ° C.), a liquid plasticizer with a Tg lower than -20 ° C. at a level of less than 60 phr, and a crosslinking system; in addition to various optional additives, it may comprise or a small fraction of reinforcing filler.
• a hydrocarbon resin at 23.degree. ° C.
• a liquid plasticizer with a Tg lower than -20 ° C. at a level of less than 60 phr and a crosslinking system
• it may comprise or a small fraction of reinforcing filler. Its formulation is described in more detail below.
• the diene elastomers in known manner, can be classified in two categories, saturated or unsaturated.
• a diene elastomer of the unsaturated type is preferably used here, that is to say by definition a diene elastomer derived at least in part from conjugated diene monomers and having a proportion of units or units derived from conjugated dienes which is greater than 30%. (% in moles)
• the diene elastomer of the composition of the invention is by definition solid.
• its number-average molecular weight (Mn) is between 100,000 and 5,000,000, more particularly between 200,000 and 4,000,000 g / mol.
• the diene elastomer (preferably unsaturated) is selected from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), copolymers of butadienes (for example butadiene- styrene or SBR), isoprene copolymers and mixtures of such elastomers.
• the unsaturated diene elastomer of the composition of the invention is an isoprene elastomer, preferentially chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), butadiene-isoprene copolymers ( BIR), styrene-isoprene copolymers (SIR), styrene-butadiene-isoprene copolymers (SBIR) and mixtures of these elastomers.
• This isoprene elastomer is preferably natural rubber or a synthetic cis-1,4 polyisoprene.
• the unsaturated diene elastomer above in particular an isoprene elastomer such as natural rubber, may constitute the whole of the elastomer matrix or the majority weight (preferably more than 50%, more preferably more than 70%) of the latter when it comprises one or more other (s) elastomer (s), diene or non-dienic, for example of the thermoplastic type.
• the level of unsaturated diene elastomer (solid), in particular of isoprene elastomer such as natural rubber is greater than 50 phr, more preferably greater than 70 phr. . More preferably still, this level of unsaturated diene elastomer, in particular of isoprene elastomer such as natural rubber, is greater than 80 phr.
• the above unsaturated diene elastomer especially when it is an isoprene diene elastomer such as natural rubber, is the only elastomer present in the self-sealing composition of the invention. .
• this isoprene elastomer could be associated with other elastomers (solid) minority by weight, whether unsaturated diene elastomers (for example BR or SBR) or even saturated (for example butyl), or elastomers other than diene, for example thermoplastic styrene elastomers (so-called "TPS"), for example selected from the group consisting of styrene / butadiene / styrene block copolymers (SBS), styrene / isoprene styrene / styrene (SIS), styrene / butadiene / isoprene / styrene (SBIS), styrene / isobutylene / styrene (SIBS), styrene / ethylene / butylene / styrene (SBS), styren
• thermoplastic is reserved in the present application, by definition known to those skilled in the art, to a thermoplastic compound which 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 polymer matrices. They are inherently miscible (ie, compatible) with the levels used with the polymer compositions for which they are intended, so as to act as true diluents. They have been described, for example, in the book "Hydrocarbon Resins” by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), chapter 5 of which is devoted their applications, in particular pneumatic rubber (5.5 “Rubber Tires and Mechanical Goods”).
• Tg glass transition temperature
• these hydrocarbon resins can also be described as thermoplastic resins in that they soften by heating and can thus be molded. They can also be defined by a point or softening point, the temperature at which the product, for example in the form of powder, agglutinates; this datum tends to replace the melting point, which is rather poorly defined, of resins in general.
• the softening temperature of a hydrocarbon resin is generally greater by about 50 to 60 ° C. than the value of Tg.
• the softening temperature of the resin is preferably greater than 40 ° C. (in particular between 40 ° C. and 140 ° C.), more preferably greater than 50 ° C. (in particular between 50 ° C. C and 135 ° C).
• Said resin is used at a weight ratio preferably between 30 and 90 phr. Below 30 phr, the anti-puncture performance proved to be insufficient because of excessive rigidity of the composition. Beyond 90 phr, it can be exposed to insufficient mechanical strength of the material with further risk of performance degraded at high temperature (typically above 60 0 C). For all these reasons, the content of resin is preferably between 40 and 80 phr, more preferably still at least equal to 45 phr, in particular within a range of 45 to 75 phr.
• the hydrocarbon resin has at least one (any), more preferably all of the following characteristics:
• Tg greater than 25 ° C
• softening point greater than 50 ° C. (in particular between 50 ° C. and 135 ° C.); a number-average molecular weight (Mn) of between 400 and
• this hydrocarbon resin has at least one (any), more preferably all of the following characteristics:
• Tg of between 25 ° C. and 100 ° C. (in particular between 30 ° C. and 90 ° C.); a softening point greater than 60 ° C., in particular between 60 ° C. and
• Tg is measured according to ASTM D3418 (1999).
• the softening point is measured according to ISO 4625 ("Ring and Bail” method).
• the macrostructure (Mw, Mn and Ip) is determined by steric exclusion chromatography (SEC): solvent tetrahydrofuran; temperature 35 ° C; concentration 1 g / 1; flow rate 1 ml / min; filtered solution on 0.45 ⁇ m porosity filter before injection; Moore calibration with polystyrene standards; set of 3 "WATERS” columns in series (“STYRAGEL” HR4E, HR1 and HR0.5); differential refractometer detection (“WATERS 2410") and its associated operating software (“WATERS EMPOWER”).
• hydrocarbon resins By way of examples of such hydrocarbon resins, mention may be made of those selected from the group consisting of homopolymer or copolymer resins of cyclopentadiene (abbreviated as CPD) or dicyclopentadiene (abbreviated to DCPD), terpene homopolymer or copolymer resins. C5 homopolymer or copolymer resins, C9 homopolymer or copolymer resins, and mixtures of these resins.
• CPD cyclopentadiene
• DCPD dicyclopentadiene
• copolymer resins mention may be made more particularly of those selected from the group consisting of (D) CPD / vinylaromatic copolymer resins, (D) CPD / terpene copolymer resins, (D) copolymer resins CPD / C5 cut, terpene / vinylaromatic copolymer resins, terpene / phenol resins, C5 / vinylaromatic cut copolymer resins, and mixtures of these resins.
• (D) CPD / vinylaromatic copolymer resins (D) CPD / terpene copolymer resins, (D) copolymer resins CPD / C5 cut, terpene / vinylaromatic copolymer resins, terpene / phenol resins, C5 / vinylaromatic cut copolymer resins, and mixtures of these resins.
• pene here combines in a known manner the alpha-pinene, beta-pinene and limonene monomers; preferably, a limonene monomer is used which is present in a known manner in the form of three possible isomers: L-limonene (laevorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or the dipentene, racemic of the dextrorotatory and levorotatory enantiomers. .
• Suitable vinylaromatic monomers are, for example, styrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, any vinyl aromatic monomer from a C 9 fraction (or more generally from a C 8 to C 1 0).
• the resins selected from the group consisting of homopolymer resins (D) CPD, copolymer resins (D) CPD / styrene, polylimonene resins, limonene / styrene copolymer resins, resins of limonene / D copolymer (CPD), C5 / styrene cut copolymer resins, C5 / C9 cut copolymer resins, and mixtures of these resins.
• D homopolymer resins
• D copolymer resins
• D copolymer resins
• polylimonene resins limonene / styrene copolymer resins
• resins of limonene / D copolymer (CPD) resins of limonene / D copolymer
• C5 / styrene cut copolymer resins C5 / C9 cut copolymer resins
• the self-sealing composition further comprises, at a rate of less than 60 phr (in other words between 0 and 60 phr), a liquid plasticizer (at 23 ° C.) said to be "at low Tg” whose function is notably softening the matrix by diluting the diene elastomer and the hydrocarbon resin, in particular improving "cold" self-sealing performance (i.e., typically for a temperature below 0 ° C); its Tg is by definition less than -20 ° C., it is preferably less than -40 ° C.
• liquid elastomers with a low average molecular weight (Mn), typically between 300 and 90,000, more generally between 400 and 50,000, for example in the form of depolymerized natural rubber, liquid BR, SBR or IR, as described, for example, in the aforementioned US Pat. Nos. 4,913,209, 5,085,942 and 5,295,525. Can also be used mixtures of such liquid elastomers with oils as described below.
• Mn average molecular weight
• Extension oils are also suitable, in particular those chosen from the group consisting of polyolefinic oils (that is to say those resulting from the polymerization of olefins, monoolefins or diolefins), paraffinic oils and naphthenic oils (at low temperatures). or high viscosity, hydrogenated or not), aromatic oils or DAE (Distillate Aromatic
• Aromatic Extracts mineral oils, vegetable oils (and their oligomers, eg rapeseed, soybean, sunflower oils) and mixtures thereof.
• a polybutene-type oil is used, for example a polyisobutylene oil (abbreviated as "PIB"), which has demonstrated an excellent compromise of properties compared to the other oils tested, in particular to a conventional oil. of the paraffinic type.
• PIB oils are sold in particular by UNIVAR under the name "Dynapak PoIy"
• liquid plasticizers are ethers, esters, phosphates and sulphonates plasticizers, more particularly those chosen from esters and phosphates.
• phosphate plasticizers include those containing between 12 and 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, azela- lates, sebacates, and glycerol triesters. mixtures of these compounds.
• glycerol triesters are those which consist predominantly (for more than 50%, more preferably more than 80% by weight) of an unsaturated fatty acid Ci 8 is that is, a fatty acid 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, they have been described for example in the application WO 02/088238 (or US 2004/0127617), as plasticizers in treads for tires.
• the number-average molecular mass Mn of the liquid plasticizer is preferably between 400 and 25,000 g / mol, more preferably between 800 and 10,000 g / mol.
• Mn too low, there is a risk of migration of the plasticizer outside the composition, while too large masses can cause excessive stiffening of this composition.
• a mass M n between 1000 and 4000 g / mol has proved to be an excellent compromise for the intended applications, in particular for use in a tire.
• the average molecular weight Mn of the plasticizer can be determined in a known manner, in particular by SEC, the sample being previously solubilized in tetrahydrofuran with 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.
• the liquid plasticizer is preferably selected from the group consisting of liquid elastomers, polyolefinic oils, naphthenic oils, paraffmic oils, DAE oils, MES oils, TDAE oils, mineral oils, vegetable oils, ethers plasticizers, ester plasticizers, phosphate plasticizers, sulphonate plasticizers and mixtures of these compounds. More preferably, this liquid plasticizer is selected from the group consisting of liquid elastomers, polyolefin oils, vegetable oils and mixtures of these compounds.
• the level of liquid plasticizer is in a range of 5 to 40 phr, more preferably in a range of 10 to 30 phr.
• the elastomeric composition may have too rigidity for some applications while beyond the maximum recommended, there is a risk of insufficient cohesion of the composition and degraded auto-sealing properties.
• the self-sealing composition further comprises a system for crosslinking the diene elastomer, this crosslinking system being preferentially a sulfur-based crosslinking system, in other words a so-called "vulcanization" system.
• the sulfur-based vulcanization system preferably comprises, as a vulcanization activator, a guanidine derivative, ie a substituted guanidine.
• the substituted guanidines are well known to a person skilled in the art (see, for example, WO 00/05300): non-limiting examples are N, N'-diphenylguanidine (abbreviated as "DPG"), triphenylguanidine or else di-o-tolylguanidine. DPG is preferably used.
• the sulfur content is preferably between 0.1 and 1.5 phr, in particular between 0.2 and 1.2 phr (for example between 0.degree. , 2 and 1.0 phr) and the level of guanidine derivative is itself between 0 and 1.5 phr, in particular between 0 and 1.0 phr (especially in a range of 0.2 to 0.5 phr). ).
• the composition may therefore be devoid of such an accelerator, or at most comprise less than 1 phr, more preferably less than 0.5 phr.
• an accelerator there may be mentioned as an example any compound (primary or secondary accelerator) capable of acting as an accelerator for vulcanizing diene elastomers in the presence of sulfur, in particular thiazole accelerators and their derivatives, accelerators thiuram types, zinc dithiocarbamates.
• the above vulcanization system may be devoid of zinc or zinc oxide (known as vulcanization activators).
• sulfur donors are well known to those skilled in the art.
• the amount of such a sulfur donor will preferably be adjusted between 0.5 and 10 phr, more preferably between 1 and 5 phr, so as to reach the preferential equivalent sulfur levels indicated above (ie between 0.1 and 1.5 phr, in particular between 0.2 and 1.2 phr of sulfur).
• a vulcanization system as described above provides sufficient cohesion to the composition, without giving it true vulcanization: the measurable crosslinking, via a conventional swelling method known to those skilled in the art, is in fact close to detection limit.
• composition prepared according to the process of the invention has the essential characteristic of being unloaded or very weakly charged, that is to say of having from 0 to less than 30 phr of charge.
• charge here is meant any type of charge, whether it is reinforcing (typically with nanometric particles, of average size by weight preferably less than 500 nm, in particular between 20 and 200 nm) or that it is non-reinforcing or inert (typically with micro-metric particles, of average size in weight greater than 1 micron, for example between 2 and 200 microns).
• These fillers, reinforcing or not, are essentially there to give dimensional stability, that is to say a minimum mechanical strength to the final composition.
• the composition is preferably all the less so that the filler is known as a reinforcing agent with respect to an elastomer, in particular an isoprene elastomer such as natural rubber.
• the self-sealing composition preferably comprises 0 to less than 20 phr, more preferably 0 to less than 10 phr of charge.
• fillers known to be reinforcing by those skilled in the art, mention will in particular be made of nanoparticles of carbon black or of a reinforcing inorganic filler, or a blend of these two types of filler.
• carbon blacks for example, all carbon blacks are suitable, in particular blacks of the HAF, ISAF, SAF type conventionally used in tires (so-called pneumatic grade blacks). Among the latter, mention will be made more particularly of (ASTM) grade carbon blacks 300, 600 or 700 (for example N326, N33O, N347, N375, N683, N772).
• ASTM ASTM grade carbon blacks 300, 600 or 700
• reinforcing inorganic fillers are in particular mineral fillers like silica (SiO 2), especially precipitated or pyrogenic silica having a BET surface below 450 m 2 / g, preferably from 30 to 400 m 2 / g.
• fillers By way of examples of fillers known to be non-reinforcing or inert by those skilled in the art, mention will in particular be made of microparticles of natural (chalk) or synthetic calcium carbonates, of synthetic or natural silicates (such as kaolin, talc, mica). ), milled silicas, titanium oxides, aluminas or aluminosilicates. As examples of lamellar fillers, mention may also be made of graphite particles. Coloring or colored fillers may advantageously be used to color the composition according to the desired color.
• the physical state under which the charge is presented is indifferent, whether in the form of powder, microbeads, granules, beads or any other suitable densified form.
• charge is also understood to mean mixtures of different fillers, reinforcing and / or non-reinforcing.
• a filler is present in the composition of the invention, its content is preferably less than 5 phr (ie between 0 and 5 phr), in particular less than 2 phr. (between 0 and 2 phr).
• Such levels have proved particularly favorable to the manufacturing method of the invention, while offering excellent performance to the self-sealing composition of the invention.
• a rate of between 0.5 and 2 phr is more preferably used, in particular when it is carbon black.
• a filler such as carbon black
• it may be introduced during step a), that is to say at the same time as the unsaturated diene elastomer and the hydrocarbon resin, or during of step b) that is to say, at the same time as the crosslinking system. It has been found that a very small proportion of carbon black, preferably between 0.5 and 2 phr, further improves the mixing and the manufacture of the composition, as well as its final extrudability.
• the basic constituents described above are sufficient on their own for the self-sealing composition to fully fulfill its anti-puncture function vis-à-vis the pneumatic objects in which it is used.
• various other additives may be added, typically in small amounts (preferably at levels of less than 20 phr, more preferably less than 15 phr), such as, for example, protective agents such as anti-UV, anti-oxidants or anti-oxidants.
• protective agents such as anti-UV, anti-oxidants or anti-oxidants.
• ozonants various other stabilizers, coloring agents advantageously used for coloring the self-sealing composition.
• the self-sealing composition could also comprise, still in a minority weight fraction relative to the unsaturated diene elastomer, polymers other than elastomers, such as, for example, thermoplastic polymers compatible with the diene elastomer. unsaturated.
• the step a) of manufacturing the masterbatch is preferably carried out in a screw mixer-extruder as schematized in a simple manner in FIG.
• FIG. 1 shows a screw extruder-mixer (10) essentially comprising a screw (for example a single-screw) for extrusion (11), a first dosing pump (12) for the diene elastomer (solid) and at least one second metering pump (13) for the resin (solid or liquid) and the liquid plasticizer.
• the hydrocarbon resin and the liquid plasticizer can be introduced for example by means of a single metering pump, if they have already been mixed beforehand, or else introduced separately by means of a second pump and third pump (third pump not shown in this figure 1, for simplification), respectively.
• the dosing pumps (12, 13) make it possible to increase the pressure while maintaining the control of the dosage and the initial characteristics of the materials, the dissociation of the dosing functions (elastomer, resin and liquid plasticizer) and of mixing also offering better control of the process.
• the masterbatch thus extruded, ready to use, is then transferred and cooled, for example on a roll mixer for external introduction of the crosslinking system and the optional filler, the temperature within said external mixer being kept below 100 0 C, preferably below 80 0 C, and moreover preferably being lower than the softening temperature of the resin.
• the above cylinders are cooled, for example by circulation of water, at a temperature below 40 ° C., preferably below 30 ° C., so as to avoid any parasitic bonding of the composition onto the walls of the mixer. .
• composition or self-sealing material prepared according to the process of the invention is a solid and elastic compound, which is characterized in particular by virtue of its specific formulation, by a very high flexibility and high deformability. It can be used as a puncture-resistant layer in any type of "pneumatic" object, that is to say, by definition, any object that takes its usable form when it is inflated with air.
• pneumatic objects examples include pneumatic boats, balls or balls used for play or sport.
• Such an anti-puncture layer is preferably disposed on the inner wall of the pneumatic object, covering it completely or at least in part, but it can also be completely integrated into its internal structure.
• the self-sealing composition described here has the advantage of not presenting, in a very wide range of tire operating temperatures, virtually no penalty in terms of rolling resistance compared to a tire having no such layer. self-sealing; compared to the usual self-sealing compositions, it very significantly improves the closing speed of the hole, in particular during the delayed withdrawal of a perforating object.
• FIG. 2 shows very schematically (without respecting a specific scale) a radial section of a tire according to the invention.
• This tire 20 comprises an apex 21 reinforced by a crown reinforcement or belt 25, two sidewalls 22 and two beads 23, each of these beads 23 being reinforced with a bead wire 24.
• the crown 21 is topped with a non-corrugated tread. represented in this schematic figure.
• a carcass reinforcement 26 is wound around the two rods 24 in each bead 23, the upturn 27 of this armature 26 being for example disposed towards the outside of the tire 20 which is shown here mounted on its rim 28.
• the carcass reinforcement 26 is known per se consists 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 circumferential plane median (plane perpendicular to the axis of rotation of the tire which is located midway between the two beads 23 and passes through the middle of the crown reinforcement 25).
• radial cables for example textile or metal
• the tire 20 is characterized in that its inner wall comprises a multi-layer laminate (30) having two layers (30a, 30b), self-sealing thanks to its first layer (30a) and airtight thanks to its second layer (30b), for example based on butyl rubber.
• the two layers (30a, 30b) substantially cover 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.
• the laminate is here arranged such that the first self-sealing layer (30a) is radially outermost in the tire, with respect to the other layer (30b). In other words, the self-sealing layer (30a) covers the airtight layer (30b) on the side of the internal cavity 29 of the tire 20.
• the layer 30b (thickness 0.7 to 0.8 mm) is based on butyl rubber, has a conventional formulation for an "inner liner"("innerliner”) which usually defines, in a bandage conventional pneumatic tire, the radially inner face of said tire for protecting the carcass reinforcement from the diffusion of air from the interior of the tire.
• This airtight layer 30b therefore allows the tire 20 to be swollen and kept under pressure; 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.
• the layer 30a consists of a self-sealing composition prepared according to the process according to the invention, comprising the three essential constituents of natural rubber (100 phr), a hydrocarbon resin "Escorez 2101" from the company. Exxon Mobil (softening point equal to about 90 ° C.) at a weight ratio of about 50 phr, and about 15 phr of liquid polybutadiene ("Ricon 154" from Sartomer Cray Valley - Mn equal to about 5,200).
• the mixture of the three basic components (NR, resin and liquid plasticizer) was done at a temperature (between 100 and 130 0 C.) higher than the softening temperature of the resin.
• the extruder used had two different feeds (hoppers) (NR on the one hand, resin and plasticizer liquid on the other hand premixed at a temperature of 130 to 140 0 C approximately) and a liquid injection pump under pressure for the liquid resin / plasticizer mixture (injected at a temperature of 100 to about 0 ° C.); when the elastomer, the resin and the liquid plasticizer are thus intimately mixed, it has been found that the parasitic tackiness of the composition decreases very significantly.
• the above extruder was provided with a die for extruding the masterbatch to the desired dimensions to an external cylinder mixer for final incorporation of the other components, namely the sulfur vulcanization system (e.g.
• the layer 30a thus disposed between the layer 30b and the cavity 29 of the tire, provides the tire with an effective protection against pressure loss due to accidental perforations, allowing the automatic closure of these perforations.
• tires of the tourism type of size 205/55 Rl 6 (Michelin brand, "Energy 3" were tested.
• the inner wall of the tires (already comprising the airtight layer 30b) has been covered by the self-sealing layer (30a) previously described, with a thickness of 3 mm, and then the vulcanized tires.
• this tire withstood rolling at 150 km / h at a rated load of 400 kg, without loss of pressure for more than 1500 km, beyond which the roll was stopped.
• the tire thus perforated loses its pressure in less than a minute, becoming totally unfit for rolling.

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• 2008
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