阅读说明：本技术 自密封组合物 (Self-sealing composition ) 是由 C·肖伟尔 D·冈萨雷斯 S·帕加诺 于 2019-10-01 设计创作，主要内容包括：本发明涉及自密封组合物,所述自密封组合物至少基于：-热塑性苯乙烯弹性体；-聚烯烃,所述聚烯烃的数均摩尔质量Mn的范围为大于550000g/mol至5000000g/mol；以及-至少140phr的增量油。(The invention relates to a self-sealing composition based at least on: -a thermoplastic styrene elastomer; -a polyolefin having a number average molar mass Mn in the range of more than 550000 to 5000000 g/mol; and-at least 140phr of extender oil.)

1. A self-sealing composition based on at least:

-a thermoplastic styrene elastomer;

-a polyolefin having a number average molar mass Mn in the range of more than 550000 to 5000000 g/mol; and

-at least 140phr of extender oil.

2. The self-sealing composition according to claim 1, wherein the thermoplastic styrene elastomer is selected from saturated thermoplastic styrene elastomers and mixtures of these elastomers.

3. The self-sealing composition of claim 2, wherein the saturated thermoplastic styrene elastomer is selected from the group consisting of styrene/ethylene/butylene (SEB) copolymers, styrene/ethylene/propylene (SEP) copolymers, styrene/ethylene/butylene/Styrene (SEBs) copolymers, styrene/ethylene/propylene/Styrene (SEPs) copolymers, styrene/ethylene/propylene/Styrene (SEEPs) copolymers and mixtures of these copolymers.

4. The self-sealing composition as claimed in any one of claims 1 to 3, wherein the thermoplastic styrene elastomer has a number-average molar mass Mn less than or equal to 500000 g/mol.

5. Self-sealing composition according to any one of claims 1 to 4, wherein the content of thermoplastic styrene elastomer is greater than or equal to 10phr, preferably ranging from 10phr to 90 phr.

6. The self-sealing composition of any one of claims 1 to 5, wherein the polyolefin comprises units derived from an olefin monomer having from 4 to 8 carbon atoms.

7. The self-sealing composition of claim 6, wherein the olefin monomer having from 4 to 8 carbon atoms is selected from but-1-ene, but-2-ene, 2-methylpropene, pent-1-ene, pent-2-ene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene, hex-1-ene, 4-methyl-1-pentene, 3-methyl-1-pentene, hept-1-ene, oct-1-ene, and mixtures of these olefin monomers.

8. The self-sealing composition according to any one of claims 6 and 7, wherein the polyolefin comprises units derived from an olefin monomer having 4 carbon atoms selected from but-1-ene, but-2-ene, 2-methylpropene and mixtures of these olefin monomers.

9. Self-sealing composition according to any of the preceding claims, wherein the polyolefin has a number average molar mass Mn in the range of 600000 to 5000000g/mol, preferably in the range of 700000 to 4000000 g/mol.

10. Self-sealing composition according to any one of the preceding claims, wherein the content of polyolefin is greater than or equal to 10phr, preferably ranging from 10phr to 90 phr.

11. The self-sealing composition according to any one of the preceding claims, wherein the extender oil is selected from the group consisting of polyolefin oils, paraffin oils, naphthenic oils, aromatic oils, mineral oils and mixtures of these oils, preferably from the group consisting of polyolefin oils, paraffin oils and mixtures of these oils.

12. Self-sealing composition according to any one of the preceding claims, wherein the content of extender oil is in the range from 145phr to 500phr, preferably from 145phr to 400 phr.

13. Use of the self-sealing composition according to any one of the preceding claims as a puncture resistant layer, in particular for inflatable articles.

14. Laminate which is gas-tight and puncture-resistant to inflation gases, in particular for inflatable articles, and which comprises at least:

-a puncture resistant layer consisting of a self-sealing composition as defined in any one of claims 1 to 12; and

a layer which is gas-tight with respect to the inflation gas.

15. An inflatable article comprising at least one self-sealing composition as defined in any one of claims 1 to 12.

Technical Field

The present invention relates to a self-sealing composition and its use as a puncture-resistant layer for pneumatic articles, in particular pneumatic tires.

Background

Typically, a pneumatic article (e.g., a pneumatic tire) includes an air-tight inner layer that defines an interior volume thereof. This layer generally comprises a butyl rubber-based composition known to be impermeable to inflation gases (e.g., air).

During its use, the inflatable article may undergo perforation after being penetrated by a perforating object (such as, for example, a nail or screw). The perforations may cause inflation gas to escape. The pressure loss caused by the perforations renders the inflated article unusable. In the case of pneumatic tires, puncturing can lead to tire flattening, stumbling of the vehicle, and replacement of the associated wheel with a spare wheel.

To address this puncture problem, one of the many existing solutions consists in adding an additional layer of relatively flexible composition that is prone to buckling to the inner wall of the inflated article. Thus, during perforation, due to the flexibility and the ability of the composition of the additional layer to flex easily, the composition of the additional layer is able to penetrate into the perforation, re-close the perforation and prevent pressure loss caused by the perforation. Such compositions are known as self-sealing compositions.

In order to be usable, such self-sealing compositions must satisfy a number of conditions of physical and chemical nature. In particular, it must be effective over an extremely wide operating temperature range, and over the entire life of the inflatable article. It must be able to close the perforation or hole whether the perforation object that caused the perforation or hole remains in place or has been expelled.

Such compositions are described, for example, in document WO2008/080557A 1. The composition comprises a styrenic thermoplastic elastomer as the main elastomer and an extender oil in an amount of between 200phr and 700 phr.

In order to improve the self-sealing properties of these compositions, the applicant company has found that the addition of a specific quality of polyolefin to a self-sealing composition comprising a thermoplastic styrene elastomer and an extender oil makes it possible to obtain a novel composition with improved self-sealing properties, in comparison with the self-sealing compositions of the prior art, whatever the shape of the perforated object.

Disclosure of Invention

A first subject of the present invention therefore relates to a self-sealing composition based at least on:

-a thermoplastic styrene elastomer;

-a polyolefin having a number average molar mass Mn in the range of more than 550000 to 5000000 g/mol; and

-at least 140phr of extender oil.

The self-sealing composition according to the invention is particularly advantageous in that it has improved self-sealing properties, in particular when the perforating object is an elongated object with a threaded wall (e.g. a screw), while maintaining its self-sealing properties in the presence of an elongated perforating object with a smooth wall (e.g. a nail).

The self-sealing composition according to the invention is intended to be incorporated into a pneumatic article (for example a pneumatic tyre).

Another subject of the present invention is therefore the use of a self-sealing composition as defined above as a puncture-resistant layer, in particular for pneumatic articles (in particular pneumatic tires).

Another subject of the invention relates to a laminate which is gas-tight and resistant to puncture with respect to inflation gases, in particular for use in inflatable articles (for example pneumatic tires), comprising at least:

-a puncture resistant layer consisting of a self-sealing composition as defined above; and

a layer which is gas-tight with respect to the inflation gas.

Another subject of the invention relates to the use of a laminate as defined above as an inner wall of a pneumatic article (for example a pneumatic tire).

Another subject of the invention is a pneumatic article comprising at least one self-sealing composition as defined above or at least one laminate as defined above which is airtight to the inflation gas and resistant to puncture. Preferably, the pneumatic article is a pneumatic tire.

The self-sealing composition according to the invention is also advantageous, in particular, in that it can be applied directly to the inner wall of a cured pneumatic tire without the need to remove the film of release agent located on the surface of this inner wall.

This is because the inner wall of a pneumatic tire generally includes a layer having airtightness to the inflation gas with strong adhesion in a raw state. In order to prevent the green pneumatic tire from sticking to the curing bladder of the curing press and damaging the press, it is common practice to deposit a release agent in the form of a thin film on the surface of the inner wall. The release agent film acts as a non-tacky protective layer. Therefore, when it is necessary to adhesively bond an object to the inner wall of a cured (or vulcanized) pneumatic tire, it is necessary to remove the release agent film by scraping or using a solvent so as to adhesively bond the object.

Surprisingly, the self-sealing composition according to the invention can be deposited directly on the inner wall of the cured pneumatic tire without removing the film of release agent. This enables to simplify the process of depositing the self-sealing composition, saving time for the manufacturer and improving safety.

Drawings

1 description of the drawings

Figure 1 schematically shows (not to scale) a radial section of a pneumatic tire incorporating a laminate according to the invention.

Figures 2 to 5 show different aspects of the method for testing the resistance to pressure loss of a tyre, in the case of a tyre whose inner wall comprises a self-sealing composition.

Fig. 2 shows the case of a perforation with zero leakage rate.

Fig. 3(a) and 3(b) show the case of perforations with very low leakage rates.

Fig. 4 shows the case of perforations with a lower leakage rate.

Fig. 5(a) and 5(b) show the case of perforations with faster leak rates.

Detailed Description

2Method used

2.1 method for measuring number-average molar masses, weight-average molar masses and polydispersity index

The number average molar masses (Mn), weight average molar masses (Mw) and Polydispersity Index (PI) of the components (thermoplastic styrene elastomer, extender oil and polyolefin) that can be used in the composition of the layers of the laminate according to the invention are determined in a known manner by means of triple detection Size Exclusion Chromatography (SEC). The advantage of this technique is that the average molar mass is measured directly without calibration.

In a first step, the refractive index increase dn/dc of the sample (i.e. the component of the composition desired for the determination of Mn as well as Mw and PI, if appropriate) is determined. For this purpose, samples were dissolved in tetrahydrofuran in precisely known concentrations (0.5g/L, 0.7g/L, 0.8g/L, 1g/L and 1.5g/L) and each solution was then filtered through a filter having a porosity of 0.45. mu.m. Each solution was then injected directly into a Wyatt differential refractometer, sold under the trade name Optilab T-Rex, with a wavelength of 658nm and thermostatically controlled at 35 ℃, using a syringe pump. The refractive index was measured for each concentration by a refractometer. Astra software from Wyatt produces a line of detector signal as a function of sample concentration. The Astra software automatically determines the guiding coefficients of the lines corresponding to the refractive index increase (dn/dc) of the sample in tetrahydrofuran at 35 ℃ and a wavelength of 658 nm.

To determine the average molar mass, a sample solution of 1g/L which has been prepared and filtered beforehand is used and injected into the chromatography system. The device used was a Waters Alliance chromatogram. The elution solvent was tetrahydrofuran protected from oxidation with 250ppm BHT (2, 6-di (tert-butyl) -4-hydroxytoluene) at a flow rate of 1mL.min^-1The system temperature was 35 ℃ and the analysis time was 60 min. The columns used were a set of three Agilent columns sold under the trade name PL Gel Mixed B LS. The volume of the injected sample solution was 100. mu.L. The detection system consisted of a Wyatt differential viscometer with the trade name Viscostar II, a Wyatt differential refractometer with the trade name Optilab T-Rex with a wavelength of 658nm, and a Wyatt multi-angle static light scattering detector with the trade name Dawn Heleos 8+ with a wavelength of 658 nm.

The values of refractive index increment dn/dc of the sample solution of 1g/L obtained above were integrated to calculate Mn, Mw and PI. The software using chromatographic data was the Astra system from Wyatt.

2.2 method of measuring the thickness of a layer

The thickness of the layer is measured according to any conventional method known to those skilled in the art.

For example, a sample (2cm x 2cm) of the multilayer laminate was obtained, which was placed on a hemispherical magnetic viewing support of a Leica M205C stereomicroscope. The laminate was observed layer by layer to measure the thickness of each layer of the laminate.

2.3 method of measuring the glass transition temperature Tg of a Polymer

The glass transition temperature Tg (hereinafter Tg) is measured in a known manner by DSC (differential scanning calorimetry) according to the standard ASTM D3418 of 1999.

3Detailed description of the invention

The invention and its advantages will be readily understood from the description, the drawings and the exemplary embodiments.

In the present specification, all percentages (%) shown are percentages by weight unless explicitly stated otherwise.

Furthermore, any numerical interval denoted by the expression "between a and b" means a numerical range extending from more than "a" to less than "b" (i.e. excluding the limits a and b), while any numerical interval denoted by the expression "from a to b" means a numerical range extending from "a" up to "b" (i.e. including the strict limits a and b).

In the present patent application, "parts per hundred elastomer" or "phr" is understood to mean parts by weight of components per hundred parts by weight of elastomer, all elastomers being mixtures of thermoplastic or non-thermoplastic, diene or olefinic elastomers. Thus, in the present application, polyolefins having a molar mass of more than 550000g/mol, described in point 3.1.2 below, are considered in the total weight of the elastomer.

In the context of the present invention, the carbon-based products mentioned in the description may be of fossil or biological origin. In the case of biological origin, it may be partially or completely derived from biomass or obtained by renewable starting materials derived from biomass. In particular to polymers, plasticizers, fillers, and the like.

3.1 self-sealing composition

A first subject of the invention relates to a self-sealing composition based at least on:

-a thermoplastic styrene elastomer;

-a polyolefin having a number average molar mass Mn in the range of more than 550000 to 5000000 g/mol; and

-at least 140phr of extender oil.

The self-sealing composition of the invention described above is a solid (at 23 ℃) elastomeric compound, characterized in particular by a very high flexibility and deformability due to its specific formulation.

Within the meaning of the present invention, the term "composition based on" is understood to mean that the composition comprises a mixture and/or reaction product of the various components used, some of these essential components being able (or intended) to react at least partially with one another during the various manufacturing stages of the composition (in particular during the extrusion or mixing stages thereof).

3.1.1 thermoplastic styrene elastomer

As mentioned above, the composition according to the invention comprises at least one thermoplastic styrene elastomer.

In a known manner, thermoplastic styrene elastomers (abbreviated to TPS) belong to the category of thermoplastic elastomers (abbreviated to TPE). Its structure is intermediate between that of elastomers and thermoplastic polymers and consists of rigid thermoplastic styrene blocks connected by flexible elastomer blocks.

The thermoplastic styrene elastomers useful in the practice of the present invention are block copolymers whose thermoplastic and elastomeric block chemical characteristics can vary.

Structure of thermoplastic styrene elastomer

The number-average molar mass (expressed as Mn) of the thermoplastic styrene elastomer is preferably less than or equal to 500000 g/mol. More preferably, it is in the range of from 30000g/mol to 500000g/mol, preferably from 40000g/mol to 400000g/mol, still more preferably from 50000g/mol to 300000 g/mol. Below the minimum indicated, there is a risk that the cohesion between the elastomer chains of the thermoplastic styrene elastomer is affected, in particular due to its possible dilution (in the presence of extender oil); furthermore, there is a risk that an increase in the operating temperature affects the mechanical properties (in particular the fracture properties), with the result that the "hot" performance is reduced. In addition, too high Mn quality may be detrimental to processability. It has therefore been found that values in the preferred range of 50000g/mol to 300000g/mol are particularly suitable for the thermoplastic styrene elastomer a used in the self-sealing composition according to the invention.

The number-average molar mass (Mn), the weight-average molar mass (Mw) and the Polydispersity Index (PI) of the thermoplastic styrene elastomer are determined in a known manner by means of triple-detection Size Exclusion Chromatography (SEC) as described above.

The value of the polydispersity index PI (reminder: PI ═ Mw/Mn, where Mw is the weight average molar mass and Mn is the number average molar mass) of the thermoplastic styrene elastomer is preferably less than 3, more preferably less than 2, still more preferably less than 1.5.

In a known manner, TPS exhibits two peaks of glass transition temperature Tg, the lowest temperature being related to the elastomeric part of TPS and the highest temperature being related to the thermoplastic styrene part of TPS. Thus, the flexible block of TPS is defined by a Tg less than ambient temperature (25 ℃) while the rigid block has a Tg greater than or equal to 80 ℃.

In this patent application, when referring to the glass transition temperature of a thermoplastic styrene elastomer, reference is made to the Tg associated with the elastomer block. The thermoplastic styrene elastomer preferably has a Tg of less than 25 deg.C, more preferably less than or equal to 10 deg.C. Tg values greater than these minimum values may reduce the performance quality of the self-sealing composition when used at very low temperatures; for such use, the Tg of the thermoplastic styrene elastomer is still more preferably less than or equal to-10 ℃. Also preferably, the thermoplastic styrene elastomer has a Tg of greater than or equal to-100 ℃.

In order to have both elastomeric and thermoplastic properties, the thermoplastic styrene elastomer must have sufficiently incompatible blocks (i.e., different due to their respective weights/masses, their respective polarities, or their respective Tg values) to retain the properties of its elastomeric or thermoplastic block itself.

The TPS may be a copolymer with a small number of blocks (less than 5, usually 2 or 3), in which case these blocks preferably have a high weight/mass of more than 15000 g/mol. These TPS may for example be a diblock copolymer comprising a thermoplastic styrene block and an elastomeric block. These TPS's are also typically triblock elastomers having two rigid segments connected by a flexible segment. The hard and soft segments may be in a linear configuration, a star configuration, or a branched configuration. Typically, each of these segments or blocks typically comprises at least greater than 5, and often greater than 10, base units (e.g., styrene units and butadiene units for a styrene/butadiene/styrene block copolymer).

The TPS may also comprise a large number (greater than 30, typically 50 to 500) of small blocks, in which case these blocks preferably have a relatively low weight/mass, for example 500g/mol to 5000 g/mol. These TPS will be subsequently referred to as multi-block TPS and are elastomeric block/thermoplastic styrene block sequences.

According to a first alternative form, the thermoplastic styrene elastomer is provided in linear form. For example, thermoplastic styrene elastomers are diblock copolymers: thermoplastic block/elastomer block. The thermoplastic styrene elastomer may also be a triblock copolymer: thermoplastic block/elastomer block/thermoplastic block, i.e. a middle elastomer block and two terminal thermoplastic blocks at each of the two ends of the elastomer block. Likewise, the multi-block thermoplastic styrene elastomer may be a linear sequence of elastomer blocks/thermoplastic blocks.

According to another alternative form of the invention, the thermoplastic styrene elastomer used for the requirements of the invention is provided in the form of a star-shaped branch comprising at least three branches. For example, the thermoplastic styrene elastomer may consist of a star-branched elastomer block comprising at least three branches and a thermoplastic styrene block located at the end of each branch of the elastomer block. For example, the number of branches of the intermediate elastomer may vary from 3 to 12, preferably from 3 to 6.

According to another alternative form of the invention, the thermoplastic styrene elastomer is provided in branched form or in dendritic form. The thermoplastic styrene elastomer may be composed of a branched or dendriform elastomer block and a thermoplastic styrene block located at the branch end of the dendriform elastomer block.

Preferably, the thermoplastic styrene elastomer is selected from triblock thermoplastic styrene elastomers and mixtures of these elastomers.

Characterization of the elastomer blocks of the thermoplastic styrene elastomer

The elastomer block used in the thermoplastic styrene elastomer claimed in the present invention may be any elastomer known to those skilled in the art. The Tg is preferably less than 25 deg.C, preferably less than 10 deg.C, more preferably less than 0 deg.C, and very preferably less than-10 deg.C. Also preferably, the Tg of the elastomer block of the thermoplastic styrene elastomer is greater than-100 ℃.

For elastomer blocks comprising carbon-based chains, if the elastomer block of the thermoplastic styrene elastomer comprises ethylenic unsaturation (i.e. carbon-carbon double bonds), the term used will be unsaturated or diene elastomer (or unsaturated thermoplastic styrene elastomer) blocks. If the elastomer block of the thermoplastic styrene elastomer does not include ethylenic unsaturation, the term used will be a saturated elastomer (or saturated thermoplastic styrene elastomer) block.

In the case of unsaturated elastomer blocks, the elastomer block of the thermoplastic styrene elastomer preferably consists predominantly of diene elastomer portions. By "predominantly" it is understood to mean the highest content by weight of diene monomer with respect to the total weight of the elastomeric block, and preferably a content by weight of greater than 50%, more preferably greater than 75%, still more preferably greater than 85%. Alternatively, the unsaturation of the unsaturated elastomer block may be derived from monomers comprising double bonds and cyclic type unsaturation; this is the case, for example, with polynorbornene.

Preferably, the conjugation C₄-C₁₄The diene may be polymerized or copolymerized to form a diene elastomer block. Preference is given toThese conjugated dienes are selected from the group consisting of isoprene, butadiene, piperylene, 1-methylbutadiene, 2, 3-dimethyl-1, 3-butadiene, 2, 4-dimethyl-1, 3-butadiene, 1, 3-pentadiene, 2-methyl-1, 3-pentadiene, 3-methyl-1, 3-pentadiene, 4-methyl-1, 3-pentadiene, 2, 3-dimethyl-1, 3-pentadiene, 2, 5-dimethyl-1, 3-pentadiene, 2-methyl-1, 4-pentadiene, 1, 3-hexadiene, 2-methyl-1, 5-hexadiene, 3-methyl-1, 3-hexadiene, 4-methyl-1, 3-hexadiene, 5-methyl-1, 3-hexadiene, 2, 5-dimethyl-2, 4-hexadiene, 2-neopentyl-1, 3-butadiene, 1, 3-cyclopentadiene, methylcyclopentadiene, 2-methyl-1, 6-heptadiene, 1, 3-cyclohexadiene, 1-vinyl-1, 3-cyclohexadiene or mixtures thereof. More preferably, the conjugated diene is isoprene, butadiene or a mixture comprising isoprene and/or butadiene.

According to an alternative form, the diene monomer polymerized to form the elastomeric portion of the thermoplastic styrene elastomer a may be randomly copolymerized with at least one other monomer, so as to form an unsaturated elastomeric block. According to this alternative form, the molar fraction of polymerized monomers other than diene monomers, with respect to the total number of units of the elastomeric block, must be such that the block retains its elastomeric properties. Preferably, the molar fraction of the further comonomer may range from 0% to 50%, more preferably from 0% to 45%, still more preferably from 0% to 40%.

By way of example, this other monomer which is copolymerizable with the diene monomer may be chosen from ethylenic monomers (such as ethylene, propylene or butylene), monomers of the vinylaromatic type having from 8 to 20 carbon atoms, as defined below, or it may also relate to monomers such as vinyl acetate.

When the comonomer is a comonomer of the vinylaromatic type, it preferably represents a molar fraction of units ranging from 0% to 50%, preferably ranging from 0% to 45%, still more preferably ranging from 0% to 40%, with respect to the total number of units of the thermoplastic block. Particularly suitable as vinylaromatic compounds are the styrene monomers mentioned hereinafter, i.e.styrene, methylstyrene, p- (tert-butyl) styrene, chlorostyrene, bromostyrene, fluorostyrene or p-hydroxystyrene. Preferably, the comonomer of the vinylaromatic type is styrene.

Preferably, the thermoplastic styrene elastomer that can be used in the self-sealing composition of the invention is chosen from saturated thermoplastic styrene elastomers and mixtures of these elastomers.

Still more preferably, the thermoplastic styrene elastomer which can be used in the composition of the invention is chosen from saturated triblock thermoplastic styrene elastomers and mixtures of these elastomers.

The saturated elastomeric blocks consist of polymer sequences obtained by polymerization of at least one ethylenic monomer, i.e. a monomer comprising a carbon-carbon double bond. Among the blocks resulting from these ethylenic monomers, mention may be made of polyalkylene blocks, such as ethylene/propylene random copolymers or ethylene/butylene random copolymers. These saturated elastomer blocks can also be obtained by hydrogenation of unsaturated elastomer blocks. It may also be an aliphatic block derived from the polyether, polyester or polycarbonate family.

In the case of a saturated elastomer block, the elastomer block of the thermoplastic styrene elastomer preferably consists predominantly of ethylenic units. By "predominantly" it is understood to mean the highest weight content of ethylenic monomer relative to the total weight of the elastomeric block, and preferably a weight content greater than 50%, more preferably greater than 75%, more preferably greater than 85%, more preferably greater than 90%, still more preferably greater than 95%.

As an example, the other monomer copolymerizable with the ethylenic monomer may be chosen from diene monomers (as defined below), more particularly conjugated diene monomers having from 4 to 14 carbon atoms (for example butadiene) as defined below, monomers of the vinylaromatic type having from 8 to 20 carbon atoms as defined below, or else monomers such as vinyl acetate may be involved.

When the comonomer is of the vinylaromatic type, it is present in a weight content ranging from 0% to 50%, preferably from 0% to 45%, and still more preferably from 0% to 40%, with respect to the total weight of the elastomeric block. Particularly suitable as vinylaromatic compounds are the styrene monomers mentioned below, in particular styrene, methylstyrene, p- (tert-butyl) styrene, chlorostyrene, bromostyrene, fluorostyrene or p-hydroxystyrene. Preferably, the comonomer of the vinylaromatic type is styrene.

When the comonomer is a comonomer of diene type, the content by weight of this comonomer is in the range from 0% to 15%, preferably from 0% to 10%, still more preferably from 0% to 5%, relative to the total weight of the elastomeric block. Conjugation of C₄-C₁₄Dienes are particularly suitable as diene comonomers. In this case, it is a random copolymer. Preferably, these conjugated dienes are selected from the group consisting of isoprene, butadiene, 1-methylbutadiene, 2, 3-dimethyl-1, 3-butadiene, 2, 4-dimethyl-1, 3-butadiene, 1, 3-pentadiene, 2-methyl-1, 3-pentadiene, 3-methyl-1, 3-pentadiene, 4-methyl-1, 3-pentadiene, 2, 3-dimethyl-1, 3-pentadiene, 1, 3-hexadiene, 2-methyl-1, 3-hexadiene, 3-methyl-1, 3-hexadiene, 4-methyl-1, 3-hexadiene, 5-methyl-1, 3-hexadiene, 2-methyl-1, 3-pentadiene, 2-methyl-1, 3, 2, 3-dimethyl-1, 3-hexadiene, 2, 4-dimethyl-1, 3-hexadiene, 2, 5-dimethyl-1, 3-hexadiene, 2-neopentylbutadiene, 1, 3-cyclopentadiene, 1, 3-cyclohexadiene, 1-vinyl-1, 3-cyclohexadiene, or mixtures thereof. More preferably, the conjugated diene is isoprene or a mixture comprising isoprene.

Preferably, the total range of the number average molar mass (Mn) of the elastomer blocks of the thermoplastic styrene elastomer a is from 25000g/mol to 350000g/mol, preferably from 35000g/mol to 250000g/mol, in order to impart to the thermoplastic styrene elastomer good elastomeric properties as well as sufficient mechanical strength and compatible with the use as a self-sealing composition.

The elastomeric block may also be a block comprising various types of ethylenic monomers, diene monomers or styrene monomers as defined above.

The elastomeric block may also consist of a plurality of elastomeric blocks as defined above.

Characteristics of the thermoplastic styrene blocks of the thermoplastic styrene elastomer

The proportion of thermoplastic styrene blocks relative to the thermoplastic styrene elastomer defined for the self-sealing composition is determined in particular by the thermoplastic properties which the copolymer must have. The thermoplastic styrene blocks are preferably present in a proportion sufficient to maintain the thermoplastic character of the elastomer that can be used in the self-sealing composition of the invention. The minimum content of thermoplastic styrene blocks in the thermoplastic styrene elastomer may vary depending on the use conditions of the copolymer. Furthermore, the ability of the thermoplastic styrene elastomer to deform during the preparation of the self-sealing composition also contributes to determining the proportion of thermoplastic styrene blocks.

The thermoplastic styrene blocks are obtained from styrene monomers.

In the present specification, styrene monomer is understood to mean any monomer comprising unsubstituted or substituted styrene; among the substituted styrenes, mention may be made, for example, of methylstyrene (for example o-methylstyrene, m-methylstyrene or p-methylstyrene, α, 2-dimethylstyrene, α, 4-dimethylstyrene or stilbene), p- (tert-butyl) styrene, chlorostyrenes (for example o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2, 4-dichlorostyrene, 2, 6-dichlorostyrene or 2,4, 6-trichlorostyrene), bromostyrenes (for example o-bromostyrene, m-bromostyrene, p-bromostyrene, 2, 4-dibromostyrene, 2, 6-dibromostyrene or 2,4, 6-tribromostyrene), fluorostyrenes (for example o-fluorostyrene, p-bromostyrene, 2, 4-dibromostyrene, 2, 6-dibromostyrene or 2,4, 6-tribromostyrene), fluorostyrenes (for example o-fluorostyrene, M-fluorostyrene, p-fluorostyrene, 2, 4-difluorostyrene, 2, 6-difluorostyrene or 2,4, 6-trifluorostyrene) or p-hydroxystyrene.

Preferably, the thermoplastic styrene elastomer a has a styrene monomer (preferably unsubstituted styrene monomer) content by weight of between 5% and 50%. Below the minimum shown there is a risk of a significant reduction in the thermoplastic properties of the elastomer, whereas above the recommended maximum the elasticity of the self-sealing composition may be affected. For these reasons, the styrene monomer (preferably unsubstituted styrene monomer) content by weight in the thermoplastic styrene elastomer is more preferably between 10% and 40%.

Preferably, the total range of the number average molar mass (Mn) of the thermoplastic blocks of the thermoplastic styrene elastomer a is from 5000g/mol to 150000g/mol, in order to impart to the thermoplastic styrene elastomer good elastomeric properties and sufficient mechanical strength that is compatible with the use as a self-sealing composition.

The thermoplastic block may also consist of a plurality of thermoplastic blocks as defined above.

Examples of thermoplastic styrene elastomers

Thermoplastic styrene elastomers are well known to those skilled in the art and are commercially available.

Preferably, the thermoplastic styrene elastomer that can be used in the self-sealing composition according to the invention is a copolymer that is partially saturated with elastomer and comprises styrene blocks and alkylene blocks. The alkylene block is preferably ethylene, propylene or butylene.

For example, the saturated thermoplastic styrene elastomer is selected from the group consisting of styrene/ethylene/butylene (SEB) copolymers, styrene/ethylene/propylene (SEP) copolymers, styrene/ethylene/butylene/Styrene (SEBs) copolymers, styrene/ethylene/propylene/Styrene (SEPs) copolymers, styrene/ethylene/propylene/Styrene (SEEPs) copolymers and mixtures of these copolymers.

Still more preferably, the thermoplastic styrene elastomer that can be used in the self-sealing composition according to the invention is a copolymer that is partially saturated with elastomer and comprises three blocks (two styrene blocks and one alkylene block). The alkylene block is preferably ethylene, propylene or butylene.

Preferably, the saturated triblock thermoplastic styrene elastomer is selected from the group consisting of styrene/ethylene/butylene/styrene (SEBS) copolymers, styrene/ethylene/propylene/styrene (SEPS) copolymers and mixtures of these copolymers.

As examples of commercially available thermoplastic styrene elastomers, mention may be made of elastomers of the SEPS, SEEPS or SEBS type sold under the name Kraton G (for example the products G1650, G1651, G1654 and G1730) by Kraton, or under the name Septon (for example Septon 2007, Septon 4033 or Septon 8004) by Kuraray.

3.1.2 polyolefins

As mentioned above, the self-sealing composition according to the invention comprises at least one polyolefin having a number average molar mass Mn in the range of more than 550000 to 5000000 g/mol.

The number-average molar mass (Mn), the weight-average molar mass (Mw) and the Polydispersity Index (PI) of the polyolefins that can be used in the self-sealing composition according to the invention are determined in a known manner by triple detection Size Exclusion Chromatography (SEC) as described above.

Within the meaning of the present patent application, the term "polyolefin" is understood to mean an essentially saturated aliphatic polymer obtained by polymerization of at least one olefin monomer, i.e. a polymer having a content by weight of units of olefin origin greater than or equal to 85%. The olefin monomer includes one (and only one) carbon-carbon double bond.

Preferably, the polyolefin comprises units derived from olefin monomers having from 4 to 8 carbon atoms.

The content by weight of units derived from olefin monomers having from 4 to 8 carbon atoms is greater than or equal to 85% by weight, preferably greater than or equal to 90% by weight, and still more preferably greater than or equal to 95% by weight, relative to the total weight of the polyolefin.

As an example, the other monomer copolymerizable with the olefin monomer having from 4 to 8 carbon atoms may be selected from diene monomers (as described below), more particularly conjugated diene monomers having from 4 to 14 carbon atoms (e.g., butadiene) as defined below. The comonomer content by weight ranges from 0% to 15%, preferably from 0% to 10%, still more preferably from 0% to 5%, relative to the total weight of the polyolefin.

C₄-C₁₄Conjugated dienes are particularly suitable as diene comonomers. In this case, random copolymers are concerned. Preferably, these conjugated dienes are selected from the group consisting of isoprene, butadiene, 1-methylbutadiene, 2, 3-dimethyl-1, 3-butadiene, 2, 4-dimethyl-1, 3-butadiene, 1, 3-pentadiene, 2-methyl-1, 3-pentadiene, 3-methyl-1, 3-pentadiene, 4-methyl-1, 3-pentadiene, 2, 3-dimethyl-1, 3-pentadiene, 1, 3-hexadiene, 2-methyl-1, 3-hexadiene, 3-methyl-1, 3-hexadiene, 4-methyl-1, 3-hexadiene, 5-methylbutadieneThe group-1, 3-hexadiene, 2, 3-dimethyl-1, 3-hexadiene, 2, 4-dimethyl-1, 3-hexadiene, 2, 5-dimethyl-1, 3-hexadiene, 2-neopentylbutadiene, 1, 3-cyclopentadiene, 1, 3-cyclohexadiene, 1-vinyl-1, 3-cyclohexadiene or mixtures thereof. More preferably, the conjugated diene is isoprene or a mixture comprising isoprene.

Preferably, the polyolefin consists of units derived from one or more olefin monomers having from 4 to 8 carbon atoms.

Preferably, the olefin monomer having 4 to 8 carbon atoms is selected from but-1-ene, but-2-ene (cis and trans isomers of but-2-ene), 2-methylpropene, pent-1-ene, pent-2-ene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene, hex-1-ene, 4-methyl-1-pentene, 3-methyl-1-pentene, hept-1-ene, oct-1-ene and mixtures of these monomers.

Preferably, the polyolefin comprises units derived from an olefin monomer having 4 carbon atoms selected from but-1-ene, but-2-ene (cis and trans isomers of but-2-ene), 2-methylpropene, and mixtures of these monomers.

Preferably, the polyolefin consists of units derived from olefin monomers having 4 carbon atoms selected from but-1-ene, but-2-ene (cis and trans isomers of but-2-ene), 2-methylpropene and mixtures of these monomers.

Preferably, the polyolefin consists of units derived from 2-methylpropene monomers. In other words, the polyolefin is Polyisobutylene (PIB).

Preferably, the number-average molar mass Mn of the polyolefin is in the range from 600000g/mol to 5000000g/mol, preferably in the range from 700000g/mol to 4000000 g/mol. More preferably, the number average molar mass of the polyolefin is in the range of 800000g/mol to 3000000 g/mol.

Preferably, the polydispersity index PI of the polyolefin is in the range of 1.1 to 6, preferably 1.3 to 5.

For example, the polyolefins that can be used in the present invention can be obtained by any method known to those skilled in the art (e.g., suspension polymerization or gas phase polymerization with Ziegler-Natta or metallocene-type catalysts).

When the polyolefin is Polyisobutylene (PIB), it may also be prepared by reacting it with a Lewis acid type catalyst (e.g., AlCl aluminum chloride)₃Or boron trifluoride BF₃) In the presence of isobutylene.

These polyolefins are commercially available from suppliers (e.g., BASF) such as under the reference numbers Oppanol B50 or Oppanol N50.

The self-sealing composition according to the invention surprisingly shows very good self-sealing properties for perforations made in elongated objects having a threaded wall, due to the presence of at least one polyolefin as defined above, while also showing excellent self-sealing properties for perforations made in elongated objects having a smooth wall.

3.1.3 diene elastomers

The above-mentioned self-sealing composition according to the invention is capable of coping with the technical problems set forth alone; in particular, it can have excellent self-sealing properties, particularly when the inflatable article is perforated by an elongated perforated object having a threaded wall.

However, the self-sealing composition according to the invention may optionally comprise at least one diene elastomer.

"diene" elastomer (or rubber without distinction), whether natural rubber or synthetic rubber, is understood in a known manner to mean an elastomer which is at least partially (i.e. a homopolymer or a copolymer) composed of diene monomer units (monomers bearing two conjugated or non-conjugated carbon-carbon double bonds). These diene elastomers can be divided into two categories: "substantially unsaturated" or "substantially saturated". "essentially unsaturated" is generally understood to mean a diene elastomer resulting at least in part from conjugated diene monomers and having a content of units of diene origin (conjugated dienes) which is greater than 15% (mol%); thus, diene elastomers such as butyl rubbers or EPDM type copolymers of dienes and of alpha-olefins do not fall within the preceding definition, but can be described in particular as "essentially saturated" diene elastomers (low or very low content of units of diene origin, always less than 15%). In view of these definitions, the diene elastomer capable of being used in the composition according to the invention, whatever the above categories, is more particularly understood to mean:

(a) -any homopolymer obtained by polymerization of conjugated diene monomers having from 4 to 12 carbon atoms;

(b) any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms;

(c) any copolymer obtained by copolymerization of one or more conjugated or non-conjugated dienes with ethylene, an alpha-monoolefin or a mixture thereof, for example an elastomer obtained from ethylene and propylene with non-conjugated diene monomers having, for example, from 6 to 12 carbon atoms.

Preferably, the diene elastomer is chosen from the group consisting of polybutadienes (abbreviated to BR), synthetic polyisoprenes (abbreviated to IR), natural rubber (abbreviated to NR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers.

3.1.4 content of thermoplastic styrene elastomer, polyolefin and optionally other elastomer

In light of the following description and exemplary embodiments, the skilled person will know how to adjust the amount of thermoplastic styrene elastomer and the amount of polyolefin in the self-sealing composition according to the specific conditions of use of the composition in a pneumatic article, in particular according to the laminate for which the composition is intended to be used.

Preferably, the content of thermoplastic styrene elastomer a present in the self-sealing composition according to the invention is greater than or equal to 10phr, preferably ranging from 10phr to 90phr, more preferably from 20phr to 80phr and still more preferably from 25phr to 75 phr.

Preferably, the content of polyolefin in the self-sealing composition according to the invention is greater than or equal to 10phr, preferably ranging from 10phr to 90phr, more preferably from 20phr to 80phr and still more preferably from 25phr to 75 phr.

Preferably, the content of diene elastomer is in the range from 0 to 20phr, more preferably from 0 to 15phr and still more preferably from 0 to 10 phr.

Preferably, the self-sealing composition of the invention does not comprise a diene elastomer.

Preferably, the ratio of the content of thermoplastic styrene elastomer to the content of polyolefin in phr is strictly less than 1.

3.1.5 extender oils

A third essential component of the self-sealing composition according to the invention is an extender oil (or plasticizing oil) used in high contents of at least 140 phr.

In the present invention, any extender oil may be used, which preferably has less polar properties and is capable of extending or plasticizing the thermoplastic styrene elastomer.

At ambient temperature (23 ℃), these oils (more or less viscous) are liquids (what is to say here substances with the capacity to eventually assume the shape of their container), in particular in contrast to resins which are natural solids (in particular tackifying resins).

Preferably, the extender oil is chosen from polyolefin oils (i.e. oils resulting from the polymerization of mono-or di-olefins), 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 polyolefin oils, paraffin oils and mixtures of these oils.

Still more preferably, the extender oil is a polyolefin oil or a mixture of polyolefin oils. This oil has proved to have the best compromise of properties compared to the other oils tested, in particular compared to conventional paraffin-type oils.

Still more preferably, the extender oil is a polyolefin oil selected from the group consisting of polybutene oils and mixtures of these oils.

Still more preferably, the extender oil is selected from polyisobutylene oils and mixtures of these oils.

By way of example, polyisobutylene oils are sold by, inter alia, Univar under the name Dynapak Poly (e.g., Dynapak Poly190), BASF under the name Glissopal (e.g., Glissopal 1000), or Ineos under the names H100, H300, H1200, H1500, or H1900; paraffin oils are sold, for example, by ExxonMobil under the name Primol 352, Primol 382 or Primol 542 or under the name Flexon 815 or Flexon 715.

Preferably, the number average molar mass (Mn) of the extender oil is less than or equal to 5000g/mol, preferably in the range from 300 to 5000g/mol, still more preferably between 350 and 3000 g/mol. For a weight/mass Mn of less than 300g/mol, the oil may migrate to the outside of the self-sealing composition, while an excessively high weight/mass may result in the self-sealing composition being excessively hard.

The number-average molar mass (Mn), the weight-average molar mass (Mw) and the Polydispersity Index (PI) of the extender oil that can be used in the self-sealing composition according to the invention are determined in a known manner by triple detection Size Exclusion Chromatography (SEC) as described above.

Preferably, the content of extender oil is in the range of 145phr to 500phr, more preferably 145phr to 400phr, still more preferably 145phr to 350phr, preferably more than 150phr to 350phr, very preferably 160phr to 350 phr. Below the minimum shown there is a risk of the self-sealing composition presenting too high a hardness for certain applications, while above the recommended maximum there is a risk of facing insufficient cohesion of the self-sealing composition. For this reason, the content of extender oil is more preferably between 145phr and 500phr, in particular for the use of the self-sealing composition in pneumatic tires.

According to the following description and exemplary embodiments, the person skilled in the art will know how to adjust the amount of extender oil according to the specific working conditions of the self-sealing composition (in particular according to the aerated product intended to use the self-sealing composition).

3.1.6 other additives

The above-mentioned self-sealing composition according to the invention is capable of coping with the technical problems set forth alone; in particular, it can have excellent self-sealing properties, particularly when the inflatable article is perforated by an elongated perforated object having a threaded wall.

However, the self-sealing composition may additionally include various additives. In general, these additives are present in small amounts (preferably in an amount of less than 10phr, more preferably less than 5phr) and are, for example, reinforcing fillers (for example carbon black), non-reinforcing or inert fillers, protective agents (for example uv stabilizers, antioxidants or antiozonants), various other stabilizers or colorants which may preferably be used for the coloration of the self-sealing composition.

3.2 preparation of self-sealing compositions

The self-sealing composition according to the invention can be obtained by conventional methods, for example by adding the different components in a twin-screw extruder or blade mixer, particularly with Z-blades.

A first conventional method for obtaining the self-sealing composition according to the invention consists in adding in a first stage a thermoplastic styrene elastomer and an extender oil in a twin-screw extruder equipped with a sufficient number of conveying zones, shearing zones and retention zones, so as to melt the elastomer matrix and add the extender oil. The twin-screw extruder can be any type of twin-screw extruder equipped with a hopper (for feeding the thermoplastic styrene elastomer) and at least with a pressurized injection pump (for the extender oil), the L/D ratio between the screw length and the screw diameter of which is in the range from 20 to 40. At the point of addition of the thermoplastic styrene elastomer, the temperature was close to ambient temperature (23 ℃). The temperature is then brought further along the screw to a value substantially greater than the melting point of the selected thermoplastic styrene elastomer and in the range 220 ℃ to 290 ℃. The temperature at the point of addition of the extender oil is also in the range 220 ℃ to 290 ℃. The temperature at the exit point of the extruder is in the range of 110 ℃ to 170 ℃. The extruder is provided at its outlet with a die capable of shaping the product to the desired dimensions. The total outlet flow is in the range of 3kg/h to 10 kg/h. Rods with a diameter in the range of 10mm to 20mm were obtained with a cylindrical die. With a flat die, a strip (shaped element) having a thickness in the range of 1mm to 3mm and a width in the range of 20 to 250 was obtained.

In the second stage, the extruded product obtained in the previous stage and polyolefin are fed into a single-screw extruder or a twin-screw extruder using a hopper, the extruder having an L/D ratio between the screw length and the screw diameter in the range of 10 to 30. The temperature at the point of addition of the extruded product of the previous stage and the polyolefin at the screw inlet through a funnel is in the range of 100 ℃ to 180 ℃. At the screw outlet, the temperature decreases and is in the range of 100 ℃ to 150 ℃. The self-sealing composition according to the invention is obtained in the form of a stick, for example having a diameter in the range 10mm to 20mm, with a cylindrical die. The self-sealing composition according to the invention is obtained with a flat die in the form of a strip (shaped element) having a thickness for example in the range from 1mm to 3mm and a width in the range from 20mm to 250 mm.

When using a thermoplastic styrene elastomer (for example SEPS or SEBS) pre-extended with a high content of oil, it is possible to perform only the second extrusion stage, so as to obtain the self-sealing composition according to the invention. Pre-extended thermoplastic styrene elastomers are well known and commercially available. As an example, mention may be made of the product sold by Hexpol TPE under the name Dryflex (e.g., Dryflex 967100) or Mediprene (e.g., Mediprene 500000M), or the product sold by Multibase under the name Multiflex (e.g., Multiflex G00).

Another conventional method of obtaining the self-sealing composition according to the invention comprises using a Z-blade mixer with a working capacity of 1 liter (for example, the MK LII 1 mixer from Linden) and filling it with a thermoplastic styrene elastomer, an extender oil and a polyolefin. The container of the mixer is heated so that the mixture reaches a temperature in the range of 80 ℃ to 140 ℃ depending on the amount of ingredients used. The speed of the blade is chosen in the range of 10 to 100 revolutions per minute and the duration of compounding is chosen in the range of 30 to 24 hours. The skilled person knows how to adjust each of these parameters so as to obtain a homogeneous mixture that will subsequently be used as a self-sealing composition. In this case, a batch that does not exhibit a specific shape is obtained.

3.3 use of self-sealing compositions

Another subject of the invention relates to a self-sealing composition and to the use of the preferred embodiments thereof as defined above as a puncture-resistant layer, in particular for pneumatic articles (in particular pneumatic tires).

The inflated article may be any article that assumes its usable shape when inflated with one or more inflation gases (e.g., air). As examples of such pneumatic articles, mention may be made of inflatable boats, pneumatic tires or balls for games or sports.

Such a puncture resistant layer is preferably located on, completely or at least partially covering the inner wall of the inflatable article, but it is also possible to integrate the puncture resistant layer completely into the inner structure of the inflatable article. The term "inner wall" is understood to mean the wall of the inflated article that is in contact with the inflation gas. The wall is formed of a layer that is gas-tight to the inflation gas. Typically, the layer that is gas-tight to the inflation gas comprises at least one butyl rubber.

The thickness of the puncture-resistant layer is preferably greater than or equal to 0.3mm, more preferably in the range from 0.5mm to 10mm (in particular from 1mm to 7 mm). It will be readily appreciated that embodiments of the present invention may vary depending on the particular application, the dimensions and pressures involved, and thus the puncture resistant layer includes a number of preferred thickness ranges. Thus, for example, for a pneumatic tire of the passenger vehicle type, it may have a thickness of at least 0.4mm, preferably in the range of 0.8mm to 6 mm. According to another embodiment, for a pneumatic tire for a heavy or agricultural vehicle, the preferred thickness may be in the range of 1mm to 7 mm. According to another embodiment, the preferred thickness may be in the range of 2mm to 10mm for pneumatic tires for vehicles in the civil engineering field or for aircraft. Finally, according to another embodiment, for a pneumatic tire for a bicycle, the preferred thickness may be in the range of 0.4mm to 4 mm.

According to another particular embodiment of the invention, the self-sealing composition has an elongation at break of greater than 500%, more preferably greater than 800%, and a stress at break of greater than 0.2MPa, both measured in the first elongation (i.e. without conditioning cycles) relative to the initial section of the test specimen at a tensile rate of 500mm/min (standard ASTM D412 of 2016) at a temperature of 23 ℃.

3.4 laminate gas-tight and puncture-resistant to inflation gases and use thereof

Another subject of the invention relates to a laminate which is gas-tight and resistant to puncture with respect to inflation gases, in particular for use in inflatable articles (for example pneumatic tires), comprising at least:

a puncture resistant layer consisting of a self-sealing composition as defined above (including these preferred embodiments),

a layer which is gas-tight with respect to the inflation gas.

Preferably, the thickness of the puncture resistant layer of the laminate is greater than or equal to 0.3mm, more preferably in the range of 0.5mm to 10mm (in particular 1mm to 7 mm).

The layer of the laminate which is gas-tight to the inflation gas may comprise any type of material capable of acting as a thin film which is gas-tight to the inflation gas (e.g. air), whether or not it is for example a metallic material as thin as a polymeric material.

According to a preferred embodiment, the layer that is gas-tight to the inflation gas comprises a composition based on at least one butyl rubber. Preferably, the layer that is gas-tight to the inflation gas comprises a composition based on at least one butyl rubber. The term "butyl rubber" is understood in a known manner to mean copolymers of isobutylene and isoprene (abbreviated to IIR), and also halogenated forms (preferably chlorinated or brominated) of such copolymers. Preferably, the butyl rubber is a halogenated butyl rubber or a blend of halogenated butyl and non-halogenated butyl. The butyl rubber may be used alone or in combination with one or more other elastomers, particularly diene elastomers such as natural rubber or synthetic polyisoprene. The composition also comprises various additives known to the person skilled in the art and generally present in the layer having gas-tightness to the inflation gas, such as reinforcing fillers (for example carbon black), lamellar fillers improving gas-tightness (for example lamellar silicates, such as kaolin, talc, mica, clays or modified clays (organoclays)), protective agents (for example antioxidants or antiozonants), crosslinking systems (for example based on sulfur or peroxides), various processing aids or other stabilizers.

The composition based on at least one butyl rubber is manufactured in a suitable mixer using two successive preparation stages known to the person skilled in the art: a first stage of thermomechanical working or kneading at high temperature ("non-productive" stage), with a maximum temperature of between 110 ℃ and 190 ℃, preferably between 130 ℃ and 180 ℃, followed by a second stage of mechanical working ("productive" stage) reduced to a low temperature, generally lower than 110 ℃, for example between 40 ℃ and 100 ℃, during the finishing stage a crosslinking system is added. The final composition thus obtained is then calendered, for example in the form of a sheet or plate, or extruded in the form of a rubber profiled element that can be used as a layer that is gas-tight to the inflation gas. Subsequently, it may be vulcanized.

Preferably, the layer that is gas-tight to the inflation gas consists of a butyl rubber-based composition, and a film of a release agent is disposed on the surface thereof. The composition of the release agent film and its arrangement on the surface of the layer that is gas-tight to the inflation gas are explained below.

Preferably, the thickness of the layer which is gas-tight with respect to the inflation gas is greater than or equal to 0.05mm, more preferably in the range of 0.05mm to 6mm (for example, 0.1mm to 2 mm).

The inflation gas-tight and puncture-resistant layer of the present invention can be prepared according to methods known to those skilled in the art by separately preparing the two layers of the laminate and then combining the puncture-resistant layer with the inflation gas-tight layer before or after curing the inflation gas-tight layer. The combination of the puncture-resistant layer with the layer that is gas-tight with respect to the inflation gas can be carried out, for example, by a simple heat treatment (preferably under pressure), for example at 150 c for a few minutes at 16 bar. In one embodiment, the bonding of the puncture resistant layer to the layer that is gas-tight with respect to the inflation gas can be performed directly without the addition of an adhesive or the interposition of a third adhesive layer that integrates the two layers.

Another subject of the invention relates to a laminate which is gas-tight and puncture-resistant to inflation gases and the use of preferred embodiments thereof as an inner wall of a pneumatic article, in particular a pneumatic tire.

3.5 inflatable articles

Another subject of the present invention relates to an inflatable article comprising a self-sealing composition as defined above (including preferred embodiments thereof).

Preferably, the inflatable article comprises an inner wall on which said self-sealing composition is deposited. Preferably, the pneumatic article is a pneumatic tire (particularly for vehicles).

Another subject of the invention relates to an inflated article comprising a laminate (including preferred embodiments thereof) as defined above, which is gas-tight and puncture-resistant to the inflation gas. Preferably, the inflated article comprises a laminate that is gas-tight and puncture resistant to the inflation gas that constitutes the inner wall of the inflated article. Preferably, the pneumatic article is a pneumatic tire.

Figure 1 schematically shows (not to scale) a radial section of a pneumatic tire incorporating a laminate according to the invention.

This pneumatic tire 1 comprises a crown 2, two sidewalls 3 and two beads 4, said crown 2 being reinforced with a crown reinforcement or belt 6, each of these beads 4 being reinforced with a bead wire 5. The crown 2 is surmounted by a tread (not shown in this schematic view). A carcass reinforcement 7 is wound around the two bead wires 5 in each bead 4, the turn-up 8 of this reinforcement 7 being disposed, for example, towards the outside of the tyre 1, said tyre 1 being represented here as mounted on its rim 9. In a manner known per se, the carcass reinforcement 7 is formed by at least one ply reinforced by "radial" cords (for example made of fabric or metal), i.e. these cords are arranged almost parallel to each other and extend from one bead to the other, so as to form an angle of between 80 ° and 90 ° with the circumferential median plane (the plane perpendicular to the axis of rotation of the tire and located in the middle of the two beads 4 and passing through the centre of the crown reinforcement 6).

The pneumatic tire 1 is characterized in that its inner wall comprises a multilayer laminate according to the invention as defined above, said laminate comprising at least two layers 10a, 10b, the puncture-resistant layer 10a consisting of a self-sealing composition according to the invention and the layer 10b being gas-tight to the inflation gas.

According to a preferred embodiment of the invention, the two layers 10a, 10b cover substantially the entire inner wall of the pneumatic tire and extend from one sidewall to the other, at least up to the level of the rim flange when the pneumatic tire is in the mounted position. However, according to other possible embodiments, the puncture-resistant layer 10a may cover only a portion of the region (layer 10b) that is airtight to the inflation gas (for example only the crown region of the pneumatic tire), or may extend at least from the crown region up to the middle (equator) of the sidewalls of said tire.

According to another preferred embodiment, as schematically shown in fig. 1, the laminate is arranged in the following manner: the puncture-resistant layer 10a is located at the outermost side of the pneumatic tire in the radial direction with respect to the other layer 10 b. In other words, the puncture-resistant layer 10a covers the layer 10b that is airtight to the inflation gas on the side of the inner cavity 11 of the pneumatic tire 1. Another possible embodiment is that this layer 10a is radially innermost and is arranged between the inner liner 10b and the remaining structure of tyre 1.

The layer 10b, which is airtight to the inflation gas, is therefore capable of inflating the tyre 1 and maintaining it under pressure; its airtight nature makes it possible to ensure a relatively low pressure loss rate and to keep the tyre inflated for a sufficient time (typically weeks or months) under normal operating conditions.

The puncture-resistant layer 10a, consisting of the self-sealing composition according to the invention (including its preferred embodiments), is therefore arranged between the layer 10b of the tyre and the cavity 11. By making these perforations self-sealing, the puncture-resistant layer 10a can provide effective protection for the pneumatic tire against pressure loss caused by accidental perforations.

The self-sealing composition according to the invention, acting as a puncture-resistant layer, is subjected to various stresses if a perforating object (for example a nail or screw) passes through the structure of the pneumatic article, for example the wall (for example the sidewall 3) or the crown 6 of the pneumatic tire 1. In response to these stresses, the self-sealing composition according to the invention is capable of forming an airtight contact zone around the entire perforated object, thanks to the advantageous properties of deformability and elasticity. The flexibility of the self-sealing composition according to the invention enables the self-sealing composition to be squeezed into openings of minimum size, regardless of the shape of the object to be perforated. This interaction between the self-sealing composition according to the invention and the object of perforation confers airtightness to the area affected by the object of perforation.

In the event of accidental or deliberate removal of the perforated object, the perforation remains: depending on the size of the perforation, it may produce very significant or less significant leakage. The self-sealing composition according to the invention is sufficiently flexible and deformable when subjected to hydrostatic pressure to seal the puncture hole by deformation, preventing the escape of inflation gas. In the case of pneumatic tires in particular, it has been demonstrated that the flexibility of the self-sealing composition according to the invention is able to withstand without problems the strains of the surrounding walls, even in the phase in which the loaded pneumatic tire deforms while running.

Preferably, the pneumatic article is a pneumatic tire, particularly intended for fitting a vehicle. These vehicles may be motor vehicles of the passenger vehicle type, SUV ("sport utility vehicle") vehicles, two-wheeled vehicles (in particular motorcycles) or aircraft, as well as industrial vehicles selected from vans, heavy vehicles (i.e. subways, buses, heavy road transport vehicles (trucks, tractors, trailers) or off-road vehicles (e.g. agricultural vehicles or civil engineering equipment)) or other transport or handling vehicles.

Preferably, the inflatable article comprises an inner wall deposited with at least one self-sealing composition as defined above (including preferred embodiments thereof).

Preferably, the inner wall of the pneumatic article comprises on its surface a film of a release agent deposited with said self-sealing composition according to the invention. Mold release films are well known to those skilled in the art. The term "film" is understood to mean a thin layer of a material (or composition) deposited on the surface of a support.

Release agent films and their use are well known to manufacturers of pneumatic articles. Generally, the film is applied to the surface of the uncrosslinked layer that is gas-tight to the inflation gas according to any technique known to those skilled in the art. This is because the layer (or the inner wall of the pneumatic tire) having airtightness to the inflation gas has strong adhesiveness in a raw state. In order to prevent the green pneumatic tire from sticking to the curing bladder of the curing press and damaging the press, it is common practice to deposit a film of release agent on the inner wall. The film acts as a non-stick protective layer.

Preferably, the film of release agent comprises at least one silicone polymer, or a mixture of a silicone polymer and talc. Preferably, the film of release agent consists of a silicone polymer or a mixture of a silicone polymer and talc.

The film of release agent can be obtained, for example, by spraying an aqueous suspension of one or more silicone polymers and talc onto the surface of an uncrosslinked layer that is gas-tight to inflation gases.

Preferably, the thickness of the film of release agent is strictly less than 0.5 mm.

Preferably, the thickness of the mold release film is in the range of 0.02mm to 0.3 mm.

The thickness of the release agent film was measured according to the above method.

When the film of release agent is present on the surface of the layer which is gas-tight with respect to the inflation gas, the layers of the laminate according to the invention are superimposed in the following manner: a layer that is gas tight to the inflation gas (optionally crosslinked), a release agent film, and a self-sealing layer.

The inflated article may be manufactured by any technique known to those skilled in the art.

For example, when the pneumatic article is a pneumatic tire, the self-sealing composition as defined above (including its preferred alternatives) is applied before or after curing said pneumatic tire.

Before curing, it consists in disposing the self-sealing composition as defined above (including its preferred alternative forms) on the layer (or inner wall) that is gas-tight to the inflation gas, that is to say in applying the self-sealing composition according to the invention in the form of a layer having a thickness greater than or equal to 0.3mm to the inner rubber, and then in carrying out the curing of the pneumatic tire. It may be desirable to protect the puncture resistant layer with a non-stick layer or a protective film. The non-stick layer or protective film facilitates the manufacture of pneumatic tires by limiting direct contact between the puncture resistant layer and the tools used to assemble the tire preform or between the puncture resistant layer and the bladder of the curing press. These non-stick layers or protective films and their use are well known to those skilled in the art.

After curing, it comprises disposing a self-sealing composition as defined above (including its preferred alternatives) on a pre-cured (vulcanized) layer (or inner wall) that is gas-tight to the inflation gas. The self-sealing composition according to the invention forming the puncture-resistant layer is applied by any suitable method (for example by adhesive bonding, by spraying or extruding and blowing a layer having a thickness greater than or equal to 0.3 mm).

According to one embodiment, this arrangement of the self-sealing composition can be carried out on a cured layer that is gas-tight to the inflation gas, from which a film of release agent has been previously removed (in particular by scraping or dissolving with a solvent).

According to another embodiment, the provision of the self-sealing composition according to the invention (including its preferred forms) can also be carried out directly on a film of a release agent on the surface of the cured layer which is gas-tight to the inflating gas. This embodiment is advantageous because it is no longer necessary to remove the release agent film using a doctor blade or solvent. This saves time and improves safety for the manufacturer.

In addition to the above-mentioned subject matter, the present invention also relates to at least one of the subject matters specified in the following points:

1. a self-sealing composition based on at least:

-a thermoplastic styrene elastomer;

-a polyolefin having a number average molar mass Mn in the range of more than 550000 to 5000000 g/mol; and

-at least 140phr of extender oil.

2. The self-sealing composition according to point 1, wherein the thermoplastic styrene elastomer is selected from saturated thermoplastic styrene elastomers and mixtures of these elastomers.

3. The self-sealing composition according to point 2, wherein the saturated thermoplastic styrene elastomer is selected from the group consisting of styrene/ethylene/butylene (SEB) copolymers, styrene/ethylene/propylene (SEP) copolymers, styrene/ethylene/butylene/Styrene (SEBs) copolymers, styrene/ethylene/propylene/Styrene (SEPs) copolymers, styrene/ethylene/propylene/Styrene (SEEPs) copolymers and mixtures of these copolymers.

4. The self-sealing composition according to point 2, wherein the thermoplastic styrene elastomer is selected from the group consisting of saturated triblock thermoplastic styrene elastomers and mixtures of these elastomers.

5. The self-sealing composition according to point 4, wherein the saturated triblock thermoplastic styrene elastomer is selected from the group consisting of styrene/ethylene/butylene/styrene (SEBS) copolymers, styrene/ethylene/propylene/styrene (SEPS) copolymers and mixtures of these copolymers.

6. The self-sealing composition according to any one of the points 1 to 5, wherein the number average molar mass Mn of the thermoplastic styrene elastomer is less than or equal to 500000 g/mol.

7. The self-sealing composition according to any one of points 1 to 6, wherein the number average molar mass Mn of the thermoplastic styrene elastomer is in the range of 30000g/mol to 500000g/mol, preferably 40000g/mol to 400000g/mol, still more preferably 50000g/mol to 300000 g/mol.

8. The self-sealing composition according to any one of points 1 to 7, wherein the content of thermoplastic styrene elastomer is greater than or equal to 10phr, preferably ranging from 10phr to 90phr, more preferably ranging from 20phr to 80phr and still more preferably ranging from 25phr to 75 phr.

9. The self-sealing composition according to any one of points 1 to 8, wherein the polyolefin comprises units derived from an olefin monomer having 4 to 8 carbon atoms.

10. The self-sealing composition according to point 9, wherein the olefin monomer having 4 to 8 carbon atoms is selected from the group consisting of but-1-ene, but-2-ene, 2-methylpropene, pent-1-ene, pent-2-ene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene, hex-1-ene, 4-methyl-1-pentene, 3-methyl-1-pentene, hept-1-ene, oct-1-ene, and mixtures of these olefin monomers.

11. The self-sealing composition according to any of the points 9 and 10, wherein the polyolefin comprises units derived from an olefin monomer having 4 carbon atoms selected from but-1-ene, but-2-ene, 2-methylpropene and mixtures of these olefin monomers.

12. The self-sealing composition according to point 11, wherein the polyolefin consists of units derived from a 2-methylpropene monomer.

13. The self-sealing composition according to any of the points 1 to 12, wherein the polyolefin has a number average molar mass Mn in the range of 600000 to 5000000g/mol, preferably in the range of 700000 to 4000000g/mol, more preferably in the range of 800000 to 3000000 g/mol.

14. The self-sealing composition according to any one of the points 1 to 13, wherein the polydispersity index PI of the polyolefin ranges from 1.1 to 6, preferably from 1.3 to 5.

15. The self-sealing composition according to any one of points 1 to 14, wherein the content of polyolefin is greater than or equal to 10phr, preferably ranging from 10phr to 90phr, more preferably ranging from 20phr to 80phr and still more preferably ranging from 25phr to 75 phr.

16. The self-sealing composition according to any one of the points 1 to 15, wherein the extender oil is selected from the group consisting of polyolefin oils, paraffin oils, naphthenic oils, aromatic oils, mineral oils and mixtures of these oils.

17. The self-sealing composition according to point 16, wherein the extender oil is selected from the group consisting of polyolefin oils, paraffin oils and mixtures of these oils.

18. The self-sealing composition according to point 17, wherein the extender oil is a polyolefin oil selected from the group consisting of polybutene oils and mixtures of these oils.

19. The self-sealing composition according to point 18, wherein the extender oil is selected from the group consisting of polyisobutylene oils and mixtures of these oils.

20. The self-sealing composition according to any of the points 1 to 19, wherein the number average molar mass Mn of the extender oil is less than 5000g/mol, preferably in the range of 300 to 5000g/mol, preferably 350 to 3000 g/mol.

21. The self-sealing composition according to any one of points 1 to 20, wherein the content of extender oil is in the range of 145phr to 500phr, preferably 145phr to 400phr, more preferably 145phr to 350 phr.

22. Use of the self-sealing composition according to any one of points 1 to 21 as a puncture resistant layer, in particular for inflatable articles.

23. The use according to point 22, wherein the thickness of the puncture resistant layer is greater than or equal to 0.3mm, preferably in the range of 0.5mm to 10mm, more preferably 1mm to 7 mm.

24. Laminate which is gas-tight and puncture-resistant to inflation gases, in particular for inflatable articles, and which comprises at least:

-a puncture resistant layer consisting of a self-sealing composition defined by any of the points 1 to 21,

a layer which is gas-tight with respect to the inflation gas.

25. The laminate of point 24, wherein the puncture resistant layer has a thickness of greater than or equal to 0.3mm, preferably in the range of 0.5mm to 10mm, more preferably 1mm to 7 mm.

26. The laminate of points 24 or 25, wherein the layer that is gas tight for the inflation gas comprises butyl rubber.

27. The laminate according to any one of points 24 to 26, wherein the layer that is gas-tight to the inflation gas has a thickness greater than or equal to 0.05mm, preferably in the range of 0.05mm to 6mm, more preferably 0.1mm to 2 mm.

28. Use of the laminate according to any one of points 24 to 27 as an inner wall of a pneumatic article, in particular a pneumatic tire.

29. An inflatable article comprising at least one self-sealing composition as defined in any of points 1 to 21.

30. The inflatable article of manufacture of point 29, comprising an inner wall deposited with the self-sealing composition.

31. The pneumatic article of point 30, wherein the inner wall comprises a film of a release agent deposited with the self-sealing composition on a surface thereof.

32. An inflated article comprising at least one laminate that is air-tight to the inflation gas and puncture resistant as defined in any of points 24 to 27.

33. The pneumatic article according to any one of points 29 to 32, characterized in that the pneumatic article is a pneumatic tire.

4Examples

The following examples are intended to illustrate the invention, but not to limit it.

4.1 manufacture of self-sealing composition:

the self-sealing composition according to the invention is prepared in a conventional way by extruding the thermoplastic styrene elastomer a, the extender oil and the polyolefin in two stages.

In the first stage, a thermoplastic styrene elastomer a and extender oil are fed to a twin-screw extruder L/D ═ 40 via a feed hopper (for the elastomer) and a pressurized injection pump (for the extender oil). Twin screw extruders are provided with a flat die capable of extruding a product of a desired size. The temperature at the point of addition of the thermoplastic elastomer was ambient temperature (23 ℃). The temperature is then brought further along the screw to a value substantially greater than the melting point of the selected thermoplastic styrene elastomer (i.e. 275 c). At the point of addition of the oil, the temperature was also 275 ℃. At the exit point of the extruder, the temperature was 140 ℃. The total flow at the outlet was 4 kg/h.

During the second stage, the shaped element obtained by extrusion in the first stage and the polyolefin are fed through a hopper into a twin-screw extruder with an L/D of 20. The temperature at the point of introduction of the polyolefin and of the aforementioned forming elements comprising thermoplastic elastomer and extender oil through the hopper at the screw inlet was 125 ℃. At the screw outlet, the temperature was reduced to 125 ℃.

When a self-sealing composition is used as the puncture-resistant layer, the second stage extruder comprises an application nozzle known to the person skilled in the art instead of a die (see for example application WO2015/173120a1 paragraph [0048 ]).

A self-sealing composition of the prior art as described in document WO2008/080557a1 was prepared in the same way as the self-sealing composition according to the present invention, except that the second stage was not carried out. When these self-sealing compositions are used as puncture resistant layers, the first stage extruder comprises an application nozzle as defined above instead of a die.

4.2 preparation of pneumatic tires with a puncture-resistant layer

The self-sealing composition obtained above was subsequently used as a puncture-resistant layer of 225/55R18 Michelin Primacy 3 pneumatic tires.

The self-sealing composition is applied directly on the inner liner of a pneumatic tyre using the device and method described in application WO2015/173120a1 (which is also applicable to non-crosslinked self-sealing compositions).

More specifically, a self-sealing layer having a thickness of about 4mm was obtained by continuous cyclic deposition of a profiled element having a thickness of about 0.8mm and a width of about 10mm obtained at the outlet of the application nozzle. The self-sealing composition is applied directly on the air barrier without the release agent film.

4.3 testing of puncture resistance of pneumatic tires

The self-sealing properties of the self-sealing composition in pneumatic tires can be evaluated by tests of resistance to pressure loss caused by puncture. The test was performed according to the following method.

The pneumatic tires provided with the self-sealing composition to be tested obtained in section 4.2 were mounted on suitable wheels, respectively, and inflated to 2.5 bar. The pressure was adjusted to 2.5 bar.

The following perforated objects were used for testing:

12 screws of diameter 3.5mm and length 30mm and 12 screws of diameter 3.5mm and length 40 mm. 24 screws were placed on the same pneumatic tire. The screws were all brand new and rustless ("screw" test).

12 nails of diameter 3mm and length 30mm and 12 nails of diameter 3mm and length 40 mm. 24 nails were placed on the same pneumatic tire. The nails were all new and rustless ("nail" test).

One pneumatic tire was used for the "screw" test and the other pneumatic tire was used for the "nail" test.

Each perforated object is inserted perpendicularly with respect to the tread by means of hydraulic jacks until it is completely pierced, the head of the perforated object abutting the bottom of the longitudinal or transverse groove of the tread pattern. The perforated object is inserted on a pneumatic tire (not running) mounted, inflated and regulated to 2.5 bar, the temperature of the crown of the tire being equal to 50 ℃.

For each insertion, leakage was evaluated using the surfactants shown below. The mean of the scores obtained was taken to obtain the "insert" score.

The inflated pneumatic tire/wheel assembly is then attached to a hub having a drum with a deployed length of five to six meters.

The rolling conditions were as follows: the inflation pressure was adjusted to 2.5 bar, the applied load was about 70% of the rated load of the tire, the temperature of the roller chamber was adjusted to about 20 ℃, and the rolling was a straight rolling without applying torque, drift or camber. The speed was adjusted to 70km/h for 4 hours. A single scrolling stage is performed.

After this rolling phase is over, and when the mounted assembly is returned to ambient temperature (ambient temperature is about 23 ℃), the leakage is evaluated using the surfactants shown below. The average of the scores obtained was taken to obtain a "rolling" score.

Each perforated object, which was maintained in place, was then removed and immediately evaluated for leaks using the surfactants shown below. The average of the scores obtained was taken to obtain the "take out" score.

The test results were qualitative observations of the leakage of each puncture before rolling (or insertion), after rolling (rotation), and after withdrawal (or removal).

Leakage is assessed using a surfactant (e.g., an aerosol spray sold by Air Liquide under the trademark "1000 bullets"). The product was sprayed onto the perforations and the viewer recorded the presence, size and number of bubbles under high light using a magnifying glass.

The puncture leak rate was evaluated using the following scoring scheme:

-10: no visible air bubbles; no leakage;

-8: nano-scale leakage, very small bubbles (especially under a magnifying glass) with a diameter of less than 0.1mm can be seen;

-6: micron level leaks, small bubbles visible to the naked eye with diameters between 0.1mm and 1 mm;

-0: leakage, generation of bubbles with a diameter larger than 1mm, or absence of bubbles due to excessive pressure loss.

Fig. 2 to 5 show different situations observed while the perforated object is maintained in place (fig. 2, 3(a), 4 and 5(a)) and after removal or evacuation of the perforated object (fig. 3(b), 5 (b)). The piercing objects in the figures are nails.

In fig. 2, a nail 13 is visible passing through a perforation 14 located in a longitudinal groove 12 of the pneumatic tire. No air bubbles were seen and therefore no leaks were observed, and the perforations scored 10.

In fig. 3(a), nail 13 is visible through a perforation 15 located in a longitudinal groove 12 of the pneumatic tire. The use of surface-active products makes it possible to display a large number of very small bubbles 16 visible only with a magnifying glass and having a diameter of less than 0.1 mm. It is nanoscale leak with a score of 8.

In fig. 3(b) the perforation 17 caused by the nail which has been removed after the rolling has stopped can be seen. The perforations 17 are also located in the outer longitudinal grooves 12 of the pneumatic tire. The use of surface-active products also enables the display of a large number of very small bubbles 16 visible with a magnifying glass and having a diameter of less than 0.1 mm. The same score of 8 is given.

In fig. 4, nail 13 is visible through a perforation 19 located in the outer longitudinal groove 12 of the pneumatic tire. The use of a surface-active product enables the display of a few small bubbles 18 having a diameter substantially between 0.1mm and 1 mm. It is a micron-scale leak and scored 6.

In fig. 5(a), nail 13 is visible through a perforation 21 located in the outer longitudinal groove 12 of the pneumatic tire. The use of surface-active products enables the display of single large bubbles 20 with a diameter greater than 1 mm. Showing a leak with a score of 0.

In fig. 5(b), the perforation 22 caused by the nail which has been removed after stopping the rolling can be seen in the outer longitudinal groove 12 of the pneumatic tire. In the same way, only a single large bubble 20 with a diameter greater than 1mm is seen. Which is a leak with a score of 0.

4.4 testing

The purpose of this test is to demonstrate that the self-sealing composition according to the invention (composition C1) has improved self-sealing properties compared to compositions according to the teaching of WO2008/080557 (compositions T1 and T2) which do not comprise polyolefins having a high molecular weight.

The formulations of the compositions tested are shown in table I; the amounts are expressed in phr (parts by weight per 100 parts by weight of elastomer).

TABLE I

(a) Thermoplastic styrene elastomer (TPS): styrene/ethylene/butylene/styrene SEBS block copolymer sold by Kraton under reference number G1654; mn is 116000g/mol, PI is 1.1; mn and PI were measured according to the method described in the specification.

(b) Polyolefin: polyisobutylene sold by BASF under the reference number Oppanol 100. Mn is 1000000g/mol, PI is 3.1; mn and PI were measured according to the method described in the specification.

(c) Extender oil: polyisobutylene oil sold by Univar under the reference number Dynapak 190. Mn is 1000g/mol, PI is 1.4; mn and PI were measured according to the method described in the specification.

The composition C1 according to the invention differs from the compositions T1 and T2 in that it additionally comprises a polyolefin having a high molar mass.

Each self-sealing composition was obtained according to the method described in section 4.1 and then used as a puncture-resistant layer of a pneumatic tire according to the method described in section 4.2. The pneumatic tire was then tested for puncture resistance according to the method described in section 4.3.

The puncture resistance results of pneumatic tires comprising the self-sealing composition used as puncture resistant layer are shown in table II (nail test) and table III (screw test).

TABLE II

As can be seen from table 2, the self-sealing composition C1 according to the invention as well as the control compositions T1 and T2 all showed very good self-sealing properties when the perforation was made by a nail. This is because, in both the insertion stage and the rolling stage, no leakage was observed on the pneumatic tires P1, PT1, and PT 2. During the nail removal phase, nano-scale leakage was observed on pneumatic tires PT1 and PT 2. However, such leakage is not inconsistent with the use of these pneumatic tires.

TABLE III

As can be seen from table III, in the tests with screws 30mm in length, the occurrence of nano-scale and micro-scale leaks in pneumatic tires PT1 and PT2 was recorded in the insertion phase and the rolling phase. The perforation of these same pneumatic tires by screws of length 40mm during the insertion phase and the rolling phase would lead to leaks, rendering the pneumatic tire unusable after being perforated by the screws.

Compared to the tests with nails (table II), it was observed that the self-sealing properties of compositions T1 and T2 were significantly reduced when a screw was used instead of a nail as the object of perforation.

Surprisingly, the self-sealing composition according to the invention (composition C1) showed no reduction in the quality of performance compared to the composition T1 of the prior art. This is because, when a 30mm screw is used, no leakage is observed in the rolling stage, and when a 40mm screw is used, no leakage is observed except in the insertion stage (a small leakage is observed).

In summary, the self-sealing composition according to the invention has improved self-sealing properties compared to representative compositions of prior art WO2008/080557-a 1.