Snowshoe sole

Abstract

The invention relates to a snowshoe sole comprising a rubber composition based on at least a predominant isoprene elastomer, a reinforcing inorganic filler, a plasticiser, and a crosslinking system.

Description

[0001] The present invention relates to snowshoe soles.

[0002] Snowshoes have been around for many years. They were originally designed to allow people to move across snow-covered terrain. They are also very common in Nordic countries, which are frequently affected by heavy snowfall. However, these extreme conditions increasingly reflect the reality of snowshoe use today. In fact, these days, they are mainly used for "sport and leisure" by hikers. Since snowshoe enthusiasts come in a wide variety of levels, from beginners to expert hikers, the requirements of each level are very different. This heterogeneity forces manufacturers to constantly develop new products to best meet the diverse needs. Today, we therefore find several product ranges, each with specific advantages.But manufacturers continue to look for innovative solutions that can provide greater comfort and improved dynamic performance.

[0003] Generally speaking, snowshoes consist of a frame, a front tip, a rear portion, and a binding system. This basic configuration allows for easy movement on snow due to increased lift, preventing sinking into the snow.

[0004] Different types of snowshoe architecture have been developed to allow for an easy gait, with a rolling motion of the foot facilitating walking by making it more natural. Thus, in order to always improve the comfort of users when walking with snowshoes, the ergonomics of snowshoes have been improved according to various axes of development. One of these axes includes grip for use specifically on ice of snowshoes thanks to elastomer soles equipped with indentations and / or studs.

[0005] For example, WO9506502 describes a snowshoe formed from a semi-flexible platform comprising connecting means for connecting a user's shoe to the platform. The platform is molded from a semi-flexible plastic material that can flex with the shoe, such as thermoplastic polyurethane. The hardness of the platform is between 50 and 90 Shore D at about 18°C. This characteristic makes it a slightly flexible snowshoe but not sufficiently flexible to achieve real comfort when rolling the foot. Furthermore, the underside of the platform is formed with indentations and / or projections to increase traction when using the snowshoes. The circular recesses each contain an oval hollow oriented according to their location on the underside.The semi-flexible plastic material and the indentations allow for an increase in the grip of the rackets, which can still be improved.

[0006] Document FR2743501 describes a snowshoe for walking, particularly on snow, consisting of a substantially flat platform, equipped with reversible attachment members for the user's foot to said platform, made of cellular elastomer. This snowshoe is light, rigid but with a certain elasticity and with good grip. The underside has studs formed by molding, distributed according to the distribution of the load in use. These characteristics allow the user to have a more comfortable snowshoe than conventional snowshoes and also to have better grip thanks to the distribution of the studs. However, the grip provided by the elastomer studs and their distribution do not give the snowshoe optimal grip. In addition, the front part of the snowshoe forces the user to lift the foot more than usual, which can lead to premature fatigue.

[0007] Other examples are disclosed in documents: FR2548545, FR3022549 and US2014336311.

[0008] The applicant discovered that by adding to the basic structure of the snowshoe initially intended to come into contact with the ground, a sole which will be in contact with the ground, made using a specific rubber composition, the snowshoe surprisingly improved its grip properties.

[0009] The invention thus relates to a snowshoe sole comprising a rubber composition based on at least one predominantly isoprene elastomer, a reinforcing inorganic filler, a plasticizer and a crosslinking system.

[0010] Preferably, the plasticizer of the composition has a Tg less than or equal to 20°C.

[0011] More preferably, the plasticizer of the composition is chosen from plasticizing oils and their mixtures.

[0012] In particular, the plasticizing oils are chosen from the group consisting of naphthenic oils, paraffinic oils, MES (Medium Extracted Solvates) oils, TDAE (Treated Distillate Aromatic Extracts) oils, RAE (Residual Aromatic Extract) oils, TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these compounds.

[0013] Advantageously, the level of plasticizing agent in the composition is greater than or equal to 5 parts per hundred parts of elastomers, pce, preferably it ranges from 5 to 50 pce, more preferably from 10 to 40 pce and even more preferably from 25 to 40 pce.

[0014] According to a preferred embodiment of the invention, the isoprene elastomer content of the composition ranges from 60 to 100 pce, preferably from 70 to 100 pce, more preferably from 80 to 100 pce.

[0015] Preferably, the level of reinforcing inorganic filler in the composition ranges from 10 to 60 pce, preferably from 30 to 55 pce; the reinforcing inorganic filler preferably being silica.

[0016] The invention also relates to a snowshoe comprising a sole as described above.

[0017] The invention also relates to a snowshoe comprising a base structure made of non-rubber material forming a shoe area and a lift area and in which the lift area comprises a lateral overhang on each side of the shoe area, said lift area extends towards the rear of the shoe area to form a rear tip and forms a front portion of the snowshoe opposite the rear tip, the contact face of the base structure comprising a sole as described above. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention relates to a snowshoe sole comprising a rubber composition based on at least one predominantly isoprene elastomer, a reinforcing inorganic filler, a plasticizer and a crosslinking system.

[0019] The expression "composition based on" means a composition comprising the mixture and / or the reaction product in situ of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacturing the composition; the composition thus being able to be in a totally or partially crosslinked state or in a non-crosslinked state.

[0020] In this description, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass. On the other hand, any interval 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., limits a and b excluded) while any interval of values ​​designated by the expression "from a to b" means the range of values ​​from a up to b (i.e., including the strict limits a and b).

[0021] By the expression "part by weight per hundred parts by weight of elastomer" (or pce), it is meant, within the meaning of the present invention, the part, by mass per hundred parts by mass of elastomer.

[0022] When a "majority" compound is referred to, within the meaning of the present invention, this compound is the majority among the compounds of the same type in the composition, that is to say that it is the one which represents the greatest quantity by mass among the compounds of the same type. Thus, for example, a majority elastomer is the elastomer representing the greatest mass relative to the total mass of the elastomers in the composition. In the same way, a so-called majority filler is the one representing the greatest mass among the fillers in the composition. For example, in a system comprising a single elastomer, this is the majority within the meaning of the present invention; and in a system comprising two elastomers, the majority elastomer represents more than half of the mass of the elastomers.

[0023] The carbon-containing compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This includes, in particular, polymers, plasticizers, fillers, etc. Diene elastomer

[0024] By "diene" elastomer (or indistinctly rubber), whether natural or synthetic, must be understood in a known manner an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers carrying two carbon-carbon double bonds, conjugated or not).

[0025] These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". "Essentially unsaturated" generally means a diene elastomer derived at least in part from conjugated diene monomers, having a content of units or patterns of diene origin (conjugated dienes) which is greater than 15% (mol %); thus, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins such as EPDM do not fall within the previous definition and can be described in particular as "essentially saturated" diene elastomers (low or very low content of patterns of diene origin, always less than 15%).

[0026] The term diene elastomer capable of being used in the compositions in accordance with the invention is particularly understood to mean: (a) - any homopolymer of a diene monomer, conjugated or not, having from 4 to 18 carbon atoms; (b) - any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer.

[0027] The other monomer can be ethylene, an olefin or a diene, conjugated or not.

[0028] Suitable conjugated dienes are conjugated dienes having 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and isoprene.

[0029] Suitable olefins are vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic α-monoolefins with 3 to 12 carbon atoms.

[0030] Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene.

[0031] Suitable aliphatic α-monoolefins are, in particular, acyclic aliphatic α-monoolefins having from 3 to 18 carbon atoms.

[0032] Preferably, the diene elastomer is chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and blends of these elastomers. Butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR).

[0033] The term "isoprene elastomer" is understood to mean, in a known manner, a homopolymer or a copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), the various isoprene copolymers and mixtures of these elastomers. Among the isoprene copolymers, mention will be made in particular of isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR) copolymers. This isoprene elastomer is preferably natural rubber or a synthetic cis-1,4 polyisoprene; among these synthetic polyisoprenes, polyisoprenes having a rate (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%, are preferably used.

[0034] Although it applies to any type of diene elastomer, those skilled in the art of tires will understand that the present invention is preferably implemented with essentially unsaturated diene elastomers, in particular of type (a) or (b) above.

[0035] The diene elastomer can be modified, i.e. either coupled and / or star-shaped, or functionalized, or coupled and / or star-shaped and simultaneously functionalized.

[0036] Thus, the diene elastomer can be coupled and / or star-shaped, for example by means of a silicon or tin atom which links the elastomer chains together.

[0037] The diene elastomer may be simultaneously or alternatively functionalized and comprise at least one functional group. By functional group is meant a group comprising at least one heteroatom chosen from Si, N, S, O, P. Particularly suitable as functional groups are those comprising at least one function such as: silanol, an alkoxysilane, a primary, secondary or tertiary amine, cyclic or not, a thiol, an epoxide.

[0038] The rubber composition of the invention may contain a single diene elastomer or a mixture of several diene elastomers.

[0039] Preferably the rate of isoprene elastomer ranges from 60 to 100 pce, preferably from 70 to 100 pce, more preferably from 80 to 100 pce.

[0040] According to an alternative embodiment of the invention, the composition also comprises one or more elastomers chosen from the group consisting of polybutadienes (BR), butadiene copolymers and mixtures of these elastomers. Thus, advantageously, the composition comprises a content of 0 to 40 phr of these elastomers, preferably 0 to 30 phr, more preferably 0 to 20 phr. Fillers and coupling agents

[0041] By filler here is meant any type of filler, whether reinforcing, non-reinforcing or inert.

[0042] The rubber composition of the invention comprises at least one reinforcing filler. Any type of so-called reinforcing filler, known for its ability to reinforce a rubber composition suitable for use in particular in the manufacture of tires, may be used, for example an organic filler such as carbon black, an inorganic filler such as silica or a mixture of these two types of fillers.

[0043] Suitable carbon blacks are all carbon blacks, including those conventionally used in tires or their treads. Among the latter, we will particularly mention the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (ASTM D-1765-2017 grades), such as for example blacks N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772). These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a carrier for some of the rubber additives used. Carbon blacks could, for example, already be incorporated into the diene elastomer, in particular isoprene, in the form of a masterbatch (see, for example, applications WO97 / 36724-A2 or WO99 / 16600-A1).

[0044] By "reinforcing inorganic filler" is meant here any inorganic or mineral filler, whatever its color and origin (natural or synthetic), also called "white" filler, "clear" filler or even "non-black" filler as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires. As is known, certain reinforcing inorganic fillers can be characterized in particular by the presence of hydroxyl groups (-OH) on their surface.

[0045] Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, preferably silica (SiO2) or of the aluminous type, in particular alumina (Al2O3). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface area and a CTAB specific surface area both less than 450 m2 / g, preferably within a range from 30 to 400 m2 / g, in particular from 60 to 300 m2 / g.

[0046] Any type of precipitated silica may be used, in particular highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples include the silicas described in applications WO03 / 016215-A1 and WO03 / 016387-A1. Among the commercial HDS silicas, we can notably use the silicas “Ultrasil ®< 5000GR”, “Ultrasil ®< 7000GR” from the company Evonik, the silicas “Zeosil ®< 1085GR”, “Zeosil ®< 1115 MP”, “Zeosil ®< 1165MP”, “Zeosil ®< Premium 200MP”, “Zeosil ®< HRS 1200 MP” from the company Solvay.As non-HDS silica, the following commercial silicas can be used: silicas “Ultrasil ®< VN2GR”, “Ultrasil ®< VN3GR” from Evonik, silica, silicas “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

[0047] The physical state in which the reinforcing inorganic filler is presented is indifferent, whether in the form of powder, microbeads, granules, or even beads or any other suitable densified form. Of course, the term reinforcing inorganic filler also means mixtures of different reinforcing inorganic fillers, in particular silicas as described above.

[0048] Those skilled in the art will understand that, as a replacement for the reinforcing inorganic filler described above, a reinforcing filler of another nature could be used, provided that this reinforcing filler of another nature is covered with an inorganic layer such as silica, or else has functional sites on its surface, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between this reinforcing filler and the diene elastomer. By way of example, mention may be made of carbon blacks partially or completely covered with silica, or carbon blacks modified with silica, such as, without limitation, the “Ecoblack®” type fillers of the CRX2000 series or the “CRX4000” series from Cabot Corporation.

[0049] Advantageously, the total reinforcing filler rate is within a range from 10 to 100 pce, more preferably from 10 to 60 pce, more preferably from 20 to 60 pce; and even more preferably from 30 to 55 pce.

[0050] According to a preferred variant of the invention, the reinforcing filler is predominantly an inorganic reinforcing filler (preferably silica), that is to say that it comprises more than 50% (>50%) by weight of an inorganic reinforcing filler such as silica relative to the total weight of the reinforcing filler. Optionally according to this variant, the reinforcing filler also comprises carbon black. According to this option, the carbon black is used at a rate less than or equal to 20 phr, more preferably less than or equal to 10 phr and even more preferably the composition does not contain carbon black.

[0051] In this presentation, the BET specific surface area is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), and more precisely according to a method adapted from the NF ISO 5794-1 standard, appendix E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - vacuum degassing: one hour at 160°C - relative pressure range p / po: 0.05 to 0.2].

[0052] For inorganic fillers such as silica, for example, the CTAB specific surface area values ​​were determined according to standard NF ISO 5794-1, annex G of June 2010. The process is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler.

[0053] For carbon blacks, the STSA specific surface area is determined according to ASTM D6556-2016.

[0054] To couple the reinforcing inorganic filler to the diene elastomer, it is possible to use, in a well-known manner, an at least bifunctional coupling agent (or bonding agent) intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. By "bifunctional", we mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer.For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

[0055] Preferably, the organosilanes are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, marketed under the name “Si69” by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as “NXT-Silane” marketed by the company Momentive. More preferably, the organosilane is a polysulfurized organosilane.

[0056] Of course, mixtures of the coupling agents described above could also be used.

[0057] The content of coupling agent in the composition of the invention is advantageously less than or equal to 20 phr, it being understood that it is generally desirable to use as little as possible. Typically the level of coupling agent represents from 0.5% to 15% by weight relative to the quantity of reinforcing inorganic filler. Its level is preferably within a range from 0.5 to 12 phr, more preferably within a range from 3 to 10 phr. This level is easily adjusted by a person skilled in the art according to the level of reinforcing inorganic filler used in the composition.

[0058] The composition of the invention may further comprise an additional filler such as an inert filler, for example, a semi-reinforcing filler such as graphite or a mixture of these two types of fillers.

[0059] Preferably, the composition does not include any additional filler. The plasticizer

[0060] The composition according to the invention comprises at least one plasticizer.

[0061] In a manner known to those skilled in the art of rubber compositions, this plasticizer may preferably be chosen from hydrocarbon resins with a high glass transition temperature (Tg), plasticizing oils, and mixtures thereof. Preferably, the plasticizer is chosen from plasticizing oils, and mixtures thereof.

[0062] By definition, a high Tg hydrocarbon resin is by definition a solid at room temperature and pressure (20°C, 1 atm), while a plasticizing oil is liquid at room temperature and a low Tg hydrocarbon resin is viscous at room temperature.

[0063] Tg is measured according to ASTM D3418 (1999).

[0064] The total level of plasticizers in the composition is greater than or equal to 5 pce, preferably it ranges from 5 to 50 pce, preferably from 10 to 40 pce, and even more preferably from 25 to 40 pce. Below 5 pce, the intended technical effect may prove insufficient, whereas beyond the upper limit, the compromise of properties aimed for the rubber composition in question is no longer achieved.

[0065] According to one embodiment of the invention, the plasticizer mainly comprises plasticizing oils or their mixtures.

[0066] According to another preferred embodiment of the invention, the plasticizer consists of one or more plasticizing oils or their mixture. Thus the level of plasticizing oils is greater than or equal to 5 phr, preferably greater than 5 to 50 phr, preferably 10 to 40 phr, and even more preferably 25 to 40 phr.

[0067] The plasticizer may also contain an extender oil (or plasticizing oil) which is liquid at 20°C, known as “low Tg”, i.e. by definition it has a Tg of less than 20°C, preferably less than 40°C.

[0068] Any extender oil, whether aromatic or non-aromatic, known for its plasticizing properties towards elastomers, can be used. At room temperature (20°C), these oils, more or less viscous, are liquids (that is to say, as a reminder, substances having the capacity to eventually take the shape of their container), in contrast in particular to high Tg hydrocarbon resins which are by nature solid at room temperature.

[0069] Particularly suitable are plasticizing oils chosen from the group consisting of naphthenic oils (low or high viscosity, in particular hydrogenated or not), paraffinic oils, MES oils (Medium Extracted Solvates), TDAE oils (Treated Distillate Aromatic Extracts), RAE oils (Residual Aromatic Extract oils), TRAE oils (Treated Residual Aromatic Extract) and SRAE oils (Safety Residual Aromatic Extract oils), mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these compounds.

[0070] According to a particular embodiment of the invention, the liquid plasticizer is a petroleum oil, preferably non-aromatic. A liquid plasticizer is described as non-aromatic when it has a content of polycyclic aromatic compounds, determined with the extract in DMSO according to the IP 346 method, of less than 3% by weight, relative to the total weight of the plasticizer. For this purpose, a liquid plasticizer chosen from the group consisting of MES oils, TDAE oils, naphthenic oils (low or high viscosity, in particular hydrogenated or not), paraffinic oils and mixtures of these oils may be used. Also suitable as petroleum oil are RAE oils, TRAE oils and SRAE oils or mixtures of these oils, which contain low contents of polycyclic compounds.

[0071] Liquid polymers resulting from the polymerization of olefins or dienes, such as polybutenes, polydienes, in particular polybutadienes, polyisoprenes (also known as "LIR") or copolymers of butadiene and isoprene, or copolymers of butadiene or isoprene and styrene or mixtures of these liquid polymers, are also suitable as plasticizing oils. The number-average molar mass of such liquid polymers is preferably in a range from 500 g / mol to 50,000 g / mol, preferably from 1,000 g / mol to 10,000 g / mol. Examples include the "RICON" products from SARTOMER. Crosslinking system

[0072] The crosslinking system may be any type of system known to those skilled in the art in the field of rubber compositions. It may in particular be based on sulfur, and / or peroxide and / or bismaleimides.

[0073] Preferably, the crosslinking system is sulfur-based, in which case it is referred to as a vulcanization system. The sulfur can be provided in any form, in particular in the form of molecular sulfur, or a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators can be used, such as zinc oxide, stearic acid or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders.

[0074] Sulphur is used at a preferential rate of between 0.5 and 12 pce, in particular between 1 and 10 pce. The vulcanisation accelerator is used at a preferential rate of between 0.5 and 10 pce, more preferably between 0.5 and 5.0 pce.

[0075] Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds. Miscellaneous additives. Various additives:

[0076] The rubber compositions in accordance with the invention may also comprise all or part of the usual additives and processing agents, known to those skilled in the art and usually used in rubber compositions, such as for example pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, anti-oxidants. Manufacture of compositions of rubber :

[0077] The rubber compositions of the invention are manufactured in suitable mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first thermo-mechanical working or kneading phase (sometimes referred to as the "non-productive" phase) on a suitable mixer (for example a "Banbury" type mixer) at high temperature, up to a maximum temperature of between 110°C and 200°C, preferably between 135°C and 185°C, followed by a second mechanical working phase (sometimes referred to as the "productive" phase) at a lower temperature, typically below 120°C, for example between 40°C and 100°C, a finishing phase during which the crosslinking or vulcanization system is incorporated.

[0078] The final composition thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for characterization in the laboratory, or extruded in the form of a semi-finished (or profiled) rubber usable as a snowshoe sole.

[0079] The crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130°C and 200°C, under pressure.

[0080] A snowshoe sole according to the invention as described above may be glued or adhered to the basic structure of a snowshoe, which is intended to come into contact with the ground.

[0081] Advantageously, the shape of the sole can be adapted to the basic structure of the snowshoe and can form a plurality of separate elements.

[0082] In particular, such a sole can be adapted to a snowshoe such as described in patent applications FR 17 / 71369 or FR 17 / 71370, as illustrated in the single figure which is a schematic perspective representation of the snowshoe.

[0083] Such a snowshoe 1 comprises a base structure comprising a base structure made of non-rubber material forming a shoe zone 2 and a lift zone and in which the lift zone comprises a lateral overhang on each side of the shoe zone 2, said lift zone extends towards the rear of the shoe zone 2 to form a rear tip 3 and forms a front portion 4 of the snowshoe opposite the rear tip 3, the contact face of the base structure comprising a sole 5 according to the invention arranged on all or part of said contact face.

[0084] This sole 5 comprises a plurality of sculpture elements 51 made of rubber material arranged on all or part of said foot area.

[0085] This sole can be glued, as indicated previously, to the basic structure or made by molding or overmolding. EXAMPLES OF CARRYING OUT THE INVENTION

[0086] Numerous field tests carried out on various types of snow have shown a clear and significant advantage provided by the high grip of the sole according to the invention and in particular a sole whose composition includes 100 pce of natural rubber, 50 pce of silica, 5 pce of silane and 35 pce of plasticizing oil and a vulcanization system with ultra-accelerator.

[0087] This allows use without fear of slipping, whether uphill, downhill or on a transverse slope.

[0088] In addition, the combination of sculpture with a rubber material according to the invention, gives significantly better performance in grip on snow compared to many other snowshoes tested.

Claims

1. Sole (5) of a snowshoe (1), comprising a rubber composition based on at least a predominant isoprene elastomer, a reinforcing inorganic filler, a plasticizer and a crosslinking system.

2. Sole (5) according to Claim 1, wherein the plasticizer has a Tg of less than or equal to 20°C.

3. Sole (5) according to either of Claims 1 and 2, wherein the plasticizer is selected from plasticizing oils and mixtures thereof.

4. Sole (5) according to Claim 3, wherein the plasticizing oils are selected from the group consisting of naphthenic oils, paraffinic oils, MES (Medium Extracted Solvate) oils, TDAE (Treated Distillate Aromatic Extract) oils, RAE (Residual Aromatic Extract) oils, TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract) oils, mineral oils, plant oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and the mixtures of these compounds.

5. Sole (5) according to any one of the preceding claims, wherein the content of plasticizing agent is greater than or equal to 5 parts per hundred parts of elastomers, phr.

6. Sole (5) according to Claim 5, wherein the content of plasticizing agent ranges from 5 to 50 phr, preferably from 10 to 40 phr.

7. Sole (5) according to Claim 5 or 6, wherein the content of plasticizing agent ranges from 25 to 40 phr.

8. Sole (5) according to any one of the preceding claims, wherein the content of isoprene elastomer ranges from 60 to 100 phr, preferably from 70 to 100 phr, more preferentially from 80 to 100 phr.

9. Sole (5) according to any one of the preceding claims, wherein the content of reinforcing inorganic filler ranges from 10 to 60 phr, preferably from 30 to 55 phr.

10. Sole (5) according to any one of the preceding claims, wherein the reinforcing inorganic filler is silica.

11. Snowshoe (1) comprising a sole (5) according to any one of Claims 1 to 10.

12. Snowshoe (1) according to Claim 11, comprising a structure based on non-rubber material forming a shoe zone (2) and a flotation zone and wherein the flotation zone comprises a lateral overhang on each side of the shoe zone (2), said flotation zone is extended towards the rear of the shoe zone (2) in order to form a tail (3) and forms a frontal portion (4) of the snowshoe opposite the tail (3), the contact face of the base structure comprising the sole (5) arranged over all or part of said contact face.

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