Solid tire for running rollers comprising rubber composition

Abstract

The present invention relates to a solid tire for running rollers of a cable transport system, which solid tire exhibits an improved service life, is capable of supporting heavy loads, and is capable of reducing the energy consumption of the system. The invention relates to a solid tire comprising a rubber composition based on at least one elastomeric matrix comprising from 25 phr to 95 phr of polybutadiene and from 5 phr to 75 phr of polyisoprene comprising 1, 4-cis bonds in a weight content of at least 90% of the weight of polyisoprene, a reinforcing filler and a crosslinking system. The invention also relates to a cable transport system comprising at least one running roller comprising the solid tire.

Description

Technical Field

[0001] The present invention relates to a solid tire made of a rubber composition for a running roller of a cable transportation facility (such as a cableway or a cable car). Background Art

[0002] Transporting people or goods by cable (such as by means of a cableway, a cable car or a lift chair) is widely used in mountainous areas and has seen significant development in the urban transport sector, where this transport system has many advantages. In particular, it is not very invasive as it takes up little ground area and is relatively quiet compared to buses or trams.

[0003] Among the decisive criteria for choosing a cable transportation solution, the maximum transport capacity expressed in kg / h and / or number of persons / h is a particularly important criterion. The transport capacity is a combination of different parameters, such as:

[0004] - The size of the cabins, each of which can carry more or fewer people or goods. The total weight of the cabin and the people or goods it carries is added to the weight of the cable, and the size of the cable also depends on the weight of the cabin. Thus, the load to be carried increases overall with the size of the cabin.

[0005] - The density of the cabins, i.e., the distance between two consecutive cabins. The closer the cabins are, the greater the linear load and thus the greater the load to be carried.

[0006] - The speed at which the cable advances, which defines the loading and unloading rate of the cabins and determines, for example, the maximum capacity of a cableway line.

[0007] The total weight of an aerial transport line is usually supported by a series of pylons, each of which includes a greater or lesser number of rollers. Each roller is covered with an elastomeric layer in order to provide a certain degree of comfort for passengers or to keep goods intact and to protect the structure of the cable. This is because the cable is an essential element for the safety of such transport devices and it must not be damaged, worn or impaired by repeated contact with a plurality of rollers. This elastomeric part (called a tire) complies with regulations on modulus limits so as not to damage the cable.

[0008] One concern of installers of cable transportation lines is to minimize the number of rollers as much as possible. This is because, from an economic point of view, any additional roller gives rise to two main sources of cost:

[0009] - An increase in the number of pylons while the supporting capacity of the pylons (the load per pylon head and the number of rollers) remains the same. Apart from the cost, any additional pylon also leads to greater installation constraints;

[0010] - As the number of rollers increases, the system for distributing the load among all the rollers on the pylon head becomes increasingly complex and expensive.

[0011] Therefore, having rollers with a greater load-bearing capacity will enable the aerial transport system to be more efficient and thus more competitive. The element that limits this feature is the rubber tire, which provides contact with the cable and is thus compressed by the load to be carried. To increase the load-bearing capacity, it is advantageous to increase the stiffness of the rubber composition that makes up the tire.

[0012] Another major challenge regarding cable transport facilities is to minimize as much as possible the energy consumption required for their operation. To this end, it is advantageous to reduce the hysteresis of the rubber composition that makes up the tire.

[0013] In addition, the lifespan of the tire can reach several years, especially in the case of operation in mountainous areas. For urban cable transport lines, due to the almost continuous usage rate and the relatively wide daily swing hours, this lifespan may be shorter. This stress means an increase in the temperature of the rubber composition, which leads to a shortening of the tire's lifespan. In some of the most severe cases, the lifespan of the tire may be only about three months. This is disadvantageous to the operator of the transport line in two ways: the loss of operation and user service due to maintenance interruptions, and the costs associated with the maintenance and purchase operations of the tires.

[0014] Having a low-hysteresis composition will be able to limit the heating of the rubber tire and thus extend its lifespan.

[0015] In fact, it has been realized that finding a solution that can improve the trade-off between stiffness and hysteresis is particularly difficult.

[0016] Currently, the rubber compositions for the tires of cable transport facilities mainly consist of a mixture of polybutadiene and butadiene-styrene copolymer, as shown in JP2007284509 and JP2021088659, which propose using specific carbon blacks to improve the abrasion resistance of the rubber composition of the rollers while reducing its hysteresis.

[0017] However, there is still a need to further improve the hysteresis and stiffness of the rubber composition of the running rollers for cable transport facilities, so as to be able to increase their load-bearing capacity, extend their lifespan and reduce the energy consumption of the facilities. Summary of the Invention

[0018] In the course of continued research, the applicant company unexpectedly found that the combined use of polybutadiene and polyisoprene can further improve the above-mentioned performance quality trade-off.

[0019] Accordingly, the subject of the present invention is a solid tire for a running wheel of a cable transportation facility, said solid tire comprising a rubber composition based on at least one elastomeric matrix, reinforcing fillers and a crosslinking system, said elastomeric matrix comprising from 25 phr to 95 phr of polybutadiene and from 5 phr to 75 phr of polyisoprene, said polyisoprene comprising at least 90% by weight of cis-1,4 bonds relative to the weight of the polyisoprene.

[0020] The present invention also relates to a cable transportation facility comprising at least one running wheel, said running wheel comprising a tire according to the invention.

[0021] I - Definitions

[0022] The expression "the composition is based on" should be understood to mean that the composition comprises a mixture of the various components used and / or in-situ reaction products, some of these components being able and / or intended to react at least partially with one another during the course of the various manufacturing stages of the composition; thus, the composition can be in a fully or partially crosslinked state, or in an uncrosslinked state.

[0023] The term "elastomeric matrix" is understood to mean the combination of elastomers of the composition.

[0024] Within the meaning of the present invention, the expression "parts by weight per hundred parts by weight of elastomer" (or phr) should be understood to mean parts by weight per hundred parts of elastomer present in the rubber composition under consideration.

[0025] In the present application, all percentages (%) shown are weight percentages (%) unless otherwise expressly stated.

[0026] Furthermore, any numerical interval expressed by the expression "between a and b" represents a numerical range extending from greater than a to less than b (i.e. excluding the limits a and b), while any numerical interval expressed by the expression "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 application, when a numerical interval is expressed by the expression "a to b", the interval expressed by the expression "between a and b" is also preferably meant.

[0027] The compounds mentioned in the description can be compounds of fossil origin or bio-based compounds. In the case of bio-based compounds, they can be partially or completely derived from biomass, or partially or completely obtained from renewable starting materials derived from biomass. In the same way, the compounds mentioned can also be derived from the recycling of pre-used materials, i.e. they can be partially or completely derived from recycling processes, or partially or completely obtained from starting materials themselves derived from recycling processes. This particularly concerns polymers, plasticizers, fillers, etc.

[0028] Unless otherwise specified, all glass transition temperature "Tg" values described in this application are measured by DSC (Differential Scanning Calorimetry) in a known manner according to standard ASTM D3418 (1999). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] II - BRIEF DESCRIPTION OF THE DRAWINGS

[0030] All implementation details are given in the following description and supplemented by showing only by way of non-limiting examples, where: FIGURES 1 TO 4

[0031] Figure 1 Figure 1 is a schematic diagram of an example of a tire in a lateral view.

[0032] Figure 2 Figure 2 is Figure 1 the cross-section of the tire.

[0033] Figure 3 Figure 3 is a schematic diagram of an example of a roller including a tire mounted on a wheel in a lateral view.

[0034] Figure 4 Figure 4 is Figure 3 the cross-section of the roller. DETAILED DESCRIPTION OF THE INVENTION

[0035] III - DESCRIPTION OF THE INVENTION

[0036] III - 1 RUNNING ROLLER SOLID TYRE

[0037] In a known manner, a solid tire for a running roller of a cable transportation facility is attached around the metal hub of the roller and fixed in place by a mechanical fastening and clamping system.

[0038] The structure of the solid tire generally includes:

[0039] - A certain volume of rubber forming the body of the tire, which fills the space between the metal parts of the hub on which the tire is assembled and forms a groove profile for the interface connected to the cable, and

[0040] - A clamping belt layer generated at the inner diameter of the tire by winding several layers of non-metallic cord reinforcements.

[0041] Such a solid tire and its manufacturing method are described, for example, in the document JP2007284509.

[0042] ​​​​​​​​​Other structures have also been developed to extend the life of the solid tire and increase the load it can withstand. They can be, for example, such solid tires that include a body made of an elastomeric material and at least one annular insert, which is preferably integral (i.e., preferably made of a single piece, without reinforcing yarns or cords or fabrics) and is arranged radially inside the body. Such a tire and its manufacturing method are described in document WO 2020 / 208575A1.

[0043] The solid tire of the present invention is not limited to a specific structure and can therefore be used for any type of running roller for a cable transportation facility.

[0044] FIGURES 1 TO 4 Non-limiting examples of the tire and the roller are shown. In particular, Figure 1 and Figure 2 show examples of the tire alone. Tire 1 includes a solid body 2 made of rubber and a preferably integral annular insert 3 made of a material different from the body. Alternatively, it can include a solid body made of rubber that includes a fabric reinforcement in the radially innermost region (not shown), without an annular insert. As Figure 2 and Figure 4 shown, the tire includes a groove that forms a running area 7 for the cable. The presence of this area promotes straight and uniform running, despite the presence of lateral stresses (such as wind), which may tend to displace the cabins or seats of the cableway and thus move the cable to one edge of the running surface of the tire. Preferably, the depth of the groove of the tire is at least equal to 40% of the diameter of the load-bearing cable intended to contact the running surface of the tire.

[0045] Figure 3 and Figure 4 show non-limiting examples of a roller 4 with a tire 1 mounted on a wheel 5, whose outer surface forms a support surface 6 for the tire.

[0046] The annular insert 3 is arranged radially inside the body 2. In the Figure 1 and Figure 2 example, the insert has a substantially rectangular cross-section, as Figure 2 and Figure 4 shown. In this example, it occupies the entire radially inner region of the tire.

[0047] The composition of the body 2 is produced using the rubber composition of the solid tire 1 for the running roller 4 of the cable transportation facility of the present invention and is described in detail below. Those skilled in the art will readily understand that the composition of the solid tire 1 according to the present invention advantageously represents all or part of the composition of the body 2.

[0048] The solid tire 1 can be a solid tire for a cable transportation facility selected from a ropeway, a cable car, a chairlift, a ski lift, and a funitel. Preferably, the solid tire 1 can be a solid tire for a cable transportation facility selected from a ropeway and a cable car.

[0049] The present invention also relates to a cable transportation facility, which includes at least one running roller, and the running roller includes a tire according to the present invention. The cable transportation facility is preferably selected from a ropeway, a cable car, a chairlift, a ski lift, and a funitel, and preferably selected from a ropeway and a cable car.

[0050] The ropeway can be, in particular, a double-track reciprocating ropeway, a single-track reciprocating ropeway, a pulse ropeway, a detachable 2S or 3S ropeway. Preferably, the solid tire 1 is a solid ropeway tire, preferably a solid 2S or 3S ropeway tire.

[0051] III - 2 ELASTOMER MATRIX

[0052] According to the present invention, the elastomeric matrix of the rubber composition of the solid tire is based on at least one elastomeric matrix, and the elastomeric matrix contains 25 phr to 95 phr of polybutadiene and 5 phr to 75 phr of polyisoprene. The polyisoprene contains at least 90% by weight of cis-1,4 bonds based on the weight of the polyisoprene.

[0053] The term "polybutadiene" (abbreviated as "BR") will be understood to mean that it can refer to one or more polybutadienes. Polybutadiene is a well-known rubber, which is manufactured by polymerizing 1,3-butadiene monomers (usually homopolymerized) in a solution polymerization method while using appropriate catalysts known to those skilled in the art. Due to the presence of two double bonds in the butadiene monomer, the obtained polybutadiene can include three different forms: cis-1,4-polybutadiene, trans-1,4-polybutadiene, and 1,2-vinyl. The cis-1,4 elastomer and the trans-1,4 elastomer are formed by connecting the monomers head to tail, while the 1,2-vinyl elastomer is formed by connecting the monomers between the ends of the monomers. The selection of the catalyst and the process temperature are called variables, which are usually used to control the content of cis-1,4 bonds in the polybutadiene.

[0054] Advantageously, the content (mol%) of cis-1,4 linkages in the polybutadiene is greater than 55%, preferably greater than 90%, more preferably greater than 95%.

[0055] The content of polybutadiene in the rubber composition of the solid tire according to the present invention is preferably in the range of 45 phr to 90 phr, preferably 55 phr to 80 phr.

[0056] In the rubber composition of the solid tire according to the present invention, the content of polyisoprene having a cis-1,4 bond weight content of at least 90% of the weight of polyisoprene is preferably in the range of 15 phr to 55 phr, preferably 20 phr to 45 phr.

[0057] The polyisoprene having a cis-1,4 bond weight content of at least 90% of the weight of polyisoprene is preferably selected from natural rubber, synthetic polyisoprene, and mixtures thereof; preferably, natural rubber is considered.

[0058] In a particularly advantageous manner, the rubber composition of the solid tire according to the present invention contains 55 phr to 80 phr of polybutadiene and 20 phr to 45 phr of natural rubber.

[0059] Advantageously, the total content of polybutadiene and polyisoprene (preferably natural rubber) accounts for at least 75% by weight of the elastomeric matrix of the rubber composition, preferably at least 80% by weight, more preferably at least 90% by weight of the elastomeric matrix of the rubber composition of the solid tire according to the present invention. More preferably, the total content of polybutadiene and polyisoprene (preferably natural rubber) accounts for 100% by weight of the elastomeric matrix of the rubber composition of the solid tire according to the present invention.

[0060] When the rubber composition of the tire contains another elastomer in addition to polybutadiene or polyisoprene having a cis-1,4 bond weight content of at least 90% of the weight of polyisoprene, that is, when the total content of polybutadiene and polyisoprene is less than 100% by weight of the elastomeric matrix, the elastomer can be selected from butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. The butadiene copolymer is particularly selected from butadiene-styrene copolymers (SBR).

[0061] III - 3 REINFORCING FILLER

[0062] The rubber composition of the tire according to the present invention is based on at least one reinforcing filler. Such reinforcing fillers are generally composed of nanoparticles having an (average) size of less than one micron, usually less than 500 nm, most commonly between 20 nm and 200 nm, particularly and more preferably between 20 nm and 150 nm.

[0063] The reinforcing filler can include one of carbon black, silica, or a mixture thereof. Advantageously, the reinforcing filler of the composition according to the present invention includes more than 50% by weight, preferably more than 80% by weight of carbon black. More preferably, the reinforcing filler consists only of carbon black, that is, carbon black accounts for 100% by weight of the reinforcing filler.

[0064] Suitable as carbon black are all carbon blacks, in particular those conventionally used in tires or their treads. Among the carbon blacks, reinforcing carbon blacks of the 100, 200 and 300 series, or carbon blacks of the 500, 600 or 700 series (ASTM D-1765-2017 grades) will be mentioned more particularly, such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683 and N772 carbon blacks. These carbon blacks can be used in the separately commercially available state, or in any other form (for example as a carrier for some of the rubber additives used). The carbon black can for example already have been introduced into a diene elastomer (in particular an isoprene elastomer) in the form of a masterbatch (see for example applications WO97 / 36724-A2 and WO99 / 16600-A1).

[0065] Among the above-mentioned carbon blacks, carbon blacks with a BET specific surface area of from 33 m 2 / g to 69 m 2 / g, preferably from 33 m 2 / g to 60 m 2 / g, preferably from 40 m 2 / g to 49 m 2 / g are particularly preferred.

[0066] The BET specific surface area of the carbon black is measured according to standard ASTM D6556-10 [multi-point (at least 5 points) method - gas: nitrogen - relative pressure p / p0 range: 0.1 to 0.3].

[0067] Any type of precipitated silica (in particular highly dispersible precipitated silica (referred to as "HDS")) is suitable as silica. These precipitated silicas (which are or are not highly dispersible precipitated silicas) are well known to those skilled in the art. Silicas described in applications WO03 / 016215-A1 and WO03 / 016387-A1 may be mentioned for example. Among the commercial HDS silicas, 5000GR and 7000GR silicas from Evonik, or 1085GR, 1115MP, 1165MP, Premium 200MP and HRS1200MP silicas from Solvay can be used particularly. As non-HDS silicas, the following commercial silicas can be used: VN2GR and VN3GR silicas from Evonik, from Solvay 175GR silica, or silica such as Hi-Sil EZ120G(-D), Hi-Sil EZ160G(-D), Hi-Sil EZ200G(-D), Hi-Sil 243LD, Hi-Sil 210, and Hi-Sil HDP 320G from PPG.

[0068] To couple the silica to the diene elastomer, at least a bifunctional coupling agent (or binder) designed to provide satisfactory chemical and / or physical properties of connection between the inorganic filler (on the surface of its particles) and the diene elastomer can be used in a known manner. In particular, at least a bifunctional organosilane or polyorganosiloxane is used. The term "bifunctional" is understood to 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 can comprise a first functional group containing a silicon atom and a second functional group containing a sulfur atom, the first functional group being capable of interacting with the hydroxyl groups of the inorganic filler and the second functional group being capable of interacting with the diene elastomer.

[0069] Preferably, when used, the organosilane is selected from (symmetric or asymmetric) organosilane polysulfides (such as bis(3-triethoxysilylpropyl)tetrasulfide (abbreviated as TESPT) sold by Evonik under the name Si69, or bis(3-triethoxysilylpropyl)disulfide (abbreviated as TESPD) sold by Evonik under the name Si75), polyorganosiloxanes, mercapto silanes, capped mercapto silanes (e.g., S-(3-(triethoxysilyl)propyl)octanethioate sold by Momentive under the name NXT Silane). More preferably, the organosilane is an organosilane polysulfide.

[0070] When using a reagent for coupling silica to the elastomer, those skilled in the art can easily adjust the content of the coupling agent. Generally, the content of the coupling agent accounts for 0.5 wt% to 15 wt% relative to the amount of silica.

[0071] Those skilled in the art can easily adjust the content of the reinforcing filler according to the use of the rubber composition. Advantageously, the content of the reinforcing filler in the composition according to the invention is in the range of 45 phr to 85 phr, preferably 50 phr to 80 phr, more preferably 55 phr to 70 phr.

[0072] Preferably, the carbon black content in the composition according to the present invention is in the range of 45 phr to 85 phr, preferably 50 phr to 80 phr, more preferably 55 phr to 70 phr, and the composition does not contain fillers other than carbon black, or contains less than 10 phr, preferably less than 5 phr of fillers other than carbon black; more preferably, the composition does not contain fillers other than carbon black.

[0073] III - 4 CROSS - LINKING SYSTEM

[0074] The crosslinking system can be any type of system known to those skilled in the art of tire rubber compositions. The crosslinking system can be particularly based on sulfur and / or peroxides and / or bismaleimides.

[0075] Preferably, the crosslinking system is based on sulfur; then it is called a vulcanization system. Advantageously, the vulcanization system contains elemental sulfur and / or at least one sulfur donor. It is also preferably to have at least one vulcanization accelerator, and optionally, various known vulcanization activators or known vulcanization retarders can also be preferably used. Examples of such vulcanization activators are zinc oxide, stearic acid or equivalent compounds (such as stearates) and transition metal salts, guanidine derivatives (especially diphenylguanidine).

[0076] Sulfur is used in an amount preferably between 0.5 phr and 12 phr, especially between 1 phr and 10 phr. A vulcanization accelerator is used in an amount preferably between 0.5 phr and 10 phr, more preferably between 0.5 phr and 5.0 phr.

[0077] As the accelerator, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used, especially accelerators of the thiazole type and their derivatives, or accelerators of the type of sulfenamides, thiurams, dithiocarbamates, dithiophosphates, thioureas and xanthates. As examples of such accelerators, the following compounds can be particularly mentioned: 2-mercaptobenzothiazole disulfide (abbreviated as MBTS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazole sulfenamide (DCBS), N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS), N-(tert-butyl)-2-benzothiazole sulfenimide (TBSI), tetrabenzylthiuram disulfide (TBZTD), zinc dibenzyldithiocarbamate (ZBEC) and mixtures of these compounds.

[0078] III - 5 POSSIBLE ADDITIVES

[0079] The running roller rubber composition for a cable transportation facility according to the present invention may also optionally contain all or part of the common additives usually used in elastomeric compositions for running rollers containing rubber compositions, such as protective agents (such as anti-ozone agents, antioxidants), anti-fatigue agents, pigments, etc.

[0080] Advantageously, the rubber composition of the solid tire contains at least one antioxidant, and its content is preferably in the range of 3 phr to 10 phr, preferably 4 phr to 9 phr, preferably 5 phr to 8 phr.

[0081] At least one antioxidant is preferably selected from N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline, 2,2'-methylenebis(6-tert-butyl-4-methylphenol), N,N'-diphenyl-p-phenylenediamine, 2,6-di(tert-butyl)-4-methylphenol, N-isopropyl-N'-phenyl-1,4-phenylenediamine, 3,9-bis(3-cyclohexen-1-yl)-2,4,8,10-tetraoxaspiro[5.5]undecane, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, octyl 3-[3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl]propionate, methyl-2-mercaptobenzimidazole and mixtures thereof. More preferably, at least one antioxidant is selected from N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline and mixtures thereof.

[0082] Such antioxidants are commercially available, for example, sold by Flexsys under the name Santoflex 6-PPD, or sold by Lanxess under the name Pilnox TMQ.

[0083] Also advantageously, the rubber composition of the solid tire contains at least one anti-ozone agent well-known to those skilled in the art.

[0084] The anti-ozone agents that can be used in the context of the present invention can be particularly natural waxes, synthetic waxes or mixtures of natural waxes and synthetic waxes. For example, the anti-ozone agent can be a natural wax selected from mineral waxes (such as paraffin wax), vegetable waxes, animal waxes and mixtures thereof. The anti-ozone agent can also be a synthetic wax selected from Fischer-Tropsch waxes, polyethylene waxes and mixtures thereof.

[0085] Advantageously, the anti-ozone agent is selected from paraffin wax, Fischer-Tropsch wax and mixtures thereof. Preferably, the anti-ozone agent is paraffin wax or a mixture of paraffin waxes.

[0086] Advantageously, the anti-ozonant mainly comprises a linear or branched hydrocarbon chain having 18 to 70 carbon atoms, preferably 18 to 65 carbon atoms, more preferably 18 to 60 carbon atoms, preferably 18 to 55 carbon atoms, preferably 18 to 50 carbon atoms, preferably 22 to 38 carbon atoms. Preferably, the hydrocarbon chain of the anti-ozonant is substantially saturated. In the context of the present invention, the term "substantially saturated" is understood to mean that the content of diene units is less than 15%, preferably less than 10%, preferably less than 5%, for example 0%.

[0087] The ratio of branched (iso) / unbranched (n) hydrocarbon chains in the anti-ozonant can range from 0 / 100 to 80 / 20, preferably 5 / 95 to 65 / 35, more preferably 5 / 95 to 35 / 65, still more preferably 5 / 95 to 20 / 80.

[0088] Such anti-ozonants are commercially available, for example, Redezon wax from Repsol (such as series 500, PWM-80, 7335-G, and 7812), Varazon wax from Sasol (such as series 5998, 4959, and 6810), Ozoace 0355 wax from NipponSeiro, and OK2122 or OK5258H wax from Paramelt Co., Ltd.

[0089] Preferably, the content of at least one anti-ozonant in the rubber composition of the solid tire ranges from 1 phr to 3 phr.

[0090] III - 6 PREPARATION OF RUBBER COMPOSITION

[0091] The rubber composition for a solid roller tire according to the present invention can be manufactured in a suitable mixer using two consecutive preparation stages known to those skilled in the art:

[0092] - The first stage of thermomechanical processing or kneading (“non - production” stage), which can be carried out in a single thermomechanical stage. During this process, all the necessary components (especially the elastomeric matrix, reinforcing fillers, and optionally various other additives except for the cross - linking system) are introduced into a suitable mixer (such as a standard closed mixer (e.g., of the ‘Banbury’ type)). Optionally, fillers can be added to the elastomer either all at once or in batches during thermomechanical kneading. In the case where the fillers have been added in whole or in part to the elastomer in the form of a masterbatch (e.g., as described in applications WO 97 / 36724 and WO 99 / 16600), the added materials are the directly kneaded masterbatch, other elastomers or fillers (where appropriate) present in the composition not in the form of a masterbatch, and optionally various other additives except for the cross - linking system. The non - production stage can be carried out at a high temperature, with the maximum temperature between 110 °C and 200 °C, preferably between 130 °C and 185 °C, and the duration is usually between 2 minutes and 10 minutes.

[0093] - After cooling the mixture obtained during the first non - production stage to a lower temperature (usually less than 120 °C, e.g., between 40 °C and 100 °C), the second stage of mechanical processing (“production” stage) can be carried out in an open mixer (e.g., a two - roll mill). Then the cross - linking system is added, and all the materials are mixed for several minutes, e.g., between 5 minutes and 15 minutes.

[0094] These stages have been described in, for example, applications EP - A - 0501227, EP - A - 0735088, EP - A - 0810258, WO00 / 05300, and WO00 / 05301.

[0095] Subsequently, the final composition thus obtained is calendered (especially for laboratory characterization) in the form of sheets or plates, or extruded (or co - extruded with another rubber composition) in the form of a rubber semi - finished product (or molding element) such as a solid tire tread that can be used, for example, as a form roller for cable transportation facilities. Subsequently, these products can be used to manufacture tires according to techniques known to those skilled in the art.

[0096] The composition can be in an unprocessed state (before cross - linking or vulcanization) or in a cured state (after cross - linking or vulcanization).

[0097] Cross - linking 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.

[0098] IV - EXAMPLES

[0099] IV - 1 MEASUREMENTS AND TESTS USED

[0100] DYNAMIC PROPERTIES

[0101] According to the standard ASTM D5992-96, the dynamic properties G* and tan(δ) were measured on a viscosity analyzer (Metravib VA4000). max . The response of a sample of the vulcanized composition (4 mm in height and 400 mm in cross-section 2 ) subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz under a stress of 0.7 MPa was recorded. A temperature sweep was carried out at a constant heating rate of +1.5 °C / min, and the values of G* and tan(δ) at 60 °C were recorded max .

[0102] The results of G* at 60 °C are expressed as a base property of 100, and a value of 100 was assigned to the control. Results greater than 100 indicate that the composition of the example under consideration is harder, reflecting an improved ability to withstand heavy loads.

[0103] tan(δ) at 60 °C max The results are expressed as a base property of 100, and a value of 100 was assigned to the control. Results greater than 100 indicate that the composition of the example under consideration has lower hysteresis, reflecting lower rolling resistance of a tire incorporating such a composition.

[0104] IV - 2 PREPARATION OF COMPOSITIONS

[0105] In the following examples, the rubber compositions were prepared as described in point III.6 above. In particular, the "non-production" phase was carried out for 4.5 minutes in a 3.2-liter mixer at an average blade speed of 45 revolutions per minute until a maximum discharge temperature of 165 °C was reached. The "production" phase was carried out for 5 minutes on an open mill at 40 °C.

[0106] Crosslinking of the composition was carried out under pressure at a temperature of 150 °C.

[0107] IV - 3 RUBBER TESTS

[0108] The purpose of the examples shown below is to compare the performance trade-off between the rolling resistance and stiffness of the compositions according to the invention (C1 to C4) with two control compositions (T1 and T2).

[0109] Table 1 shows the compositions tested (in phr) and the results obtained.

[0110] The control composition T2 differs from the control composition T1 only in the use of natural polyisoprene instead of polybutadiene. The composition C2 differs from the control composition T1 only in the use of natural polyisoprene instead of a butadiene-styrene copolymer.

[0111] Compositions C1, C3, and C4 are capable of studying the effects of the respective changes in the amounts of polybutadiene and polyisoprene.

[0112] The results of the hysteresis and stiffness performance qualities at 60 °C are expressed as a percentage of 100 relative to the reference composition T1.

[0113] The compromise in performance quality between rolling resistance and stiffness is represented by the arithmetic mean of the results shown as a base of 100.

[0114] [Table 1]

[0115] COMPOSITIONS T1 T2 C1 C2 C3 C4 BR(1) 50 - 30 50 70 90 SBR(2) 50 50 NR(3) - 50 70 50 30 10 N550(4) 65 65 65 65 65 65 ANTIOZONANT(5) 1.5 1.5 1.5 1.5 1.5 1.5 ANTIOXIDANT 1(6) 5 5 5 5 5 5 ANTIOXIDANT 2(7) 2.5 2.5 2.5 2.5 2.5 2.5 STEARIC ACID(8) 3 3 3 3 3 3 ZnO(9) 4 4 4 4 4 4 CBS(10) 3.6 3.6 3.6 3.6 3.6 3.6 CTP(11) 0.4 0.4 0.4 0.4 0.4 0.4 SULFUR 1.8 1.8 1.8 1.8 1.8 1.8 PROPERTIES G* AT 60°C 100 88 101 105 112 114 Tan(δ) AT 60°C 100 79 106 106 127 143 STIFFNESS / HYSTERESIS COMPROMISE 100 83.5 103.5 105.5 119.5 128.5

[0116] (1) Neodymium polybutadiene, 98% cis-1,4-; Tg = -108 °C

[0117] (2) SBR, from Versalis 1500

[0118] (3) Natural rubber

[0119] (4) Carbon black N550 grade according to standard ASTM D-1765

[0120] (5) Anti-ozone wax, Varazon 4959 from Sasol Wax

[0121] (6) N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, Santoflex 6-PPD from Flexsys

[0122] (7) 2,2,4-trimethyl-1,2-dihydroquinoline, Pilnox TMQ from Lanxess

[0123] (8) Stearic acid, Pristerene 4931 from Uniqema

[0124] (9) Technical grade zinc oxide from Umicore

[0125] (10) N-cyclohexyl-2-benzothiazolesulfenamide, Santocure CBS from Flexsys

[0126] (11) N-cyclohexylthiophthalimide (CTP), sold by Lanxess under the name Vulkalent G

[0127] The results shown in Table 1 above indicate that the compositions according to the invention all improve the rolling resistance without affecting the stiffness and actually even improve the stiffness. Compositions C3 and C4, which contain more polybutadiene than polyisoprene, show particularly noteworthy results.

Claims

1. Solid tire (1) for a running roller (4) of a cable transport facility, said solid tire (1) comprising a rubber composition based on at least one elastomeric matrix, reinforcing filler and crosslinking system, said elastomeric matrix comprising 25 phr to 95 phr of polybutadiene and 5 phr to 75 phr of polyisoprene, said polyisoprene comprising at least 90% by weight of cis-1,4 bonds relative to the weight of the polyisoprene.

2. The solid tire (1) according to claim 1, wherein, The content of polybutadiene in the rubber composition is in the range of 45 phr to 90 phr, preferably 55 phr to 80 phr.

3. The solid tire (1) according to any one of the preceding claims, wherein, The content of polyisoprene in the rubber composition is in the range of 15 phr to 55 phr, preferably 20 phr to 45 phr.

4. The solid tire (1) according to any one of the preceding claims, wherein, The total content of polybutadiene and polyisoprene accounts for at least 75% by weight, preferably at least 80% by weight, more preferably at least 90% by weight of the elastomeric matrix of the rubber composition.

5. The solid tire (1) according to any one of the preceding claims, wherein, The total content of polybutadiene and polyisoprene accounts for 100% by weight of the elastomeric matrix of the rubber composition.

6. The solid tire (1) according to any one of the preceding claims, wherein, Polyisoprene is selected from natural rubber, synthetic polyisoprene and mixtures thereof; preferably, polyisoprene is natural rubber.

7. The solid tire (1) according to any one of claims 1 to 5, wherein, The rubber composition comprises 55 phr to 80 phr of polybutadiene and 20 phr to 45 phr of natural rubber.

8. The solid tire (1) according to any one of the preceding claims, wherein, The reinforcing filler comprises more than 50% by weight of carbon black.

9. The solid tire (1) according to any one of the preceding claims, wherein, The content of the reinforcing filler in the rubber composition is in the range of 45 phr to 85 phr, preferably 50 phr to 80 phr, more preferably 55 phr to 70 phr.

10. The solid tire (1) according to any one of the preceding claims, wherein, The rubber composition comprises at least one antioxidant, and the content of the antioxidant is preferably in the range of 3 phr to 10 phr, preferably 4 phr to 9 phr, more preferably 5 phr to 8 phr.

11. The solid tire (1) according to claim 10, wherein, The at least one antioxidant is selected from N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline, 2,2'-methylenebis(6-tert-butyl-4-methylphenol), N,N'-diphenyl-p-phenylenediamine, 2,6-di(tert-butyl)-4-methylphenol, N-isopropyl-N'-phenyl-1,4-phenylenediamine, 3,9-bis(3-cyclohexen-1-yl)-2,4,8,10-tetraoxaspiro[5.5]undecane, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, octyl 3-[3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl]propionate, methyl-2-mercaptobenzimidazole and mixtures thereof; preferably, the at least one antioxidant is selected from N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline and mixtures thereof.

12. The solid tire (1) according to any one of the preceding claims, wherein, The rubber composition comprises at least one anti-ozonant, and the content of the anti-ozonant is preferably in the range of 1 phr to 3 phr.

13. The solid tire (1) according to any one of the preceding claims, wherein, The crosslinking system is based on elemental sulfur and / or at least one sulfur donor.

14. The solid tire (1) according to any one of the preceding claims, wherein, The solid tire (1) is a solid tire for a cable transportation facility, and the cable transportation facility is selected from a cableway, a cable car, a chairlift, a ski lift and a funitel; preferably, it is selected from a cableway and a cable car.

15. A cable transport facility, said cable transport facility comprising at least one running roller (4), said running roller (4) comprising a solid tire (1) according to any one of claims 1 to 14.

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