RUBBER SHOE SOLE

Abstract

The invention relates to a shoe sole having high abrasion resistance. This sole comprises a rubber composition based on at least: an elastomer matrix comprising at least 70 pce of a polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene; 30 to 95 pce of silica; an agent for coupling the silica to the polyisoprene; 1 to 60 pce of at least one plasticizing agent chosen from liquid plasticizers at 20°C, hydrocarbon plasticizing resins whose Tg is greater than 20°C and their mixtures, said liquid plasticizers being chosen from the group consisting of vegetable oils, said hydrocarbon plasticizing resins being chosen from the group consisting of terpene homopolymer or copolymer resins, the silica content being higher than the plasticizing agent content; and a crosslinking system.

Description

Title of the invention: RUBBER SHOE SOLE

[0001] The invention relates to rubber soles for shoes. The invention particularly relates to shoes, especially sports shoes, which require good abrasion resistance qualities.

[0002] A shoe outer sole must comply in a known manner with a large number of technical requirements, often contradictory, including grip on various types of ground, in particular dry and wet, abrasion resistance, tear resistance, bending resistance, etc.

[0003] In order to obtain good abrasion resistance, the outer sole, i.e. the part of the sole which is intended to come into contact with the ground and which is also called the outsole, is generally made of synthetic elastomers such as polybutadienes or butadiene-styrene copolymers. Application KR 10-2012-0124616 A for example describes shoe sole compositions comprising a butadiene-styrene copolymer having a hydrophilic functional group which has good wear resistance.

[0004] Further improving the abrasion resistance of outsoles is a constant concern of manufacturers because it allows them to increase the lifespan of the shoes containing them. Abrasion resistance levels below 120 mm3 measured according to standard NF EN 12770: 1999 are particularly desirable for applications in sports shoes.

[0005] This improvement in abrasion resistance should preferably be achieved without penalizing tear resistance and wet grip.

[0006] Continuing its research, the Applicant unexpectedly discovered that the use of polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene, combined with silica and a particular plasticizing system at certain levels, makes it possible to improve the abrasion resistance of shoe soles comprising such a composition, without penalizing the tear resistance and the grip on wet ground, or even by improving them.

[0007] Thus, the subject of the invention is a shoe sole comprising a rubber composition based on at least: - an elastomer matrix comprising at least 70 pce of a polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene, - 30 to 95 pce of silica, - a silica-polyisoprene coupling agent, - 1 to 60 pce of at least one plasticizing agent chosen from liquid plasticizers at 20°C, hydrocarbon plasticizing resins with a Tg greater than 20°C and their mixtures, said liquid plasticizers being chosen from the group consisting of vegetable oils, said hydrocarbon plasticizing resins being chosen from the group consisting of terpene homopolymer or copolymer resins, the silica content being higher than the plasticizing agent content, and - a crosslinking system. I- DEFINITIONS

[0008] By the expression "based on" used to define the constituents of a composition, we mean the mixture of these constituents, or the product of the reaction of part or all of these constituents with each other, at least partially, during the different phases of manufacturing the composition.

[0009] By “elastomer matrix” is meant all of the elastomers in the composition.

[0010] Unless otherwise indicated, the rates of the units resulting from the insertion of a monomer in a copolymer are expressed as a molar percentage relative to the total monomer units of the copolymer.

[0011] 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 of elastomer present in the rubber composition considered.

[0012] Herein, unless expressly indicated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0013] 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., excluding limits a and b), while any interval of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict limits a and b). In the present document, when an interval of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also and preferably designated.

[0014] The 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. In the same way, the compounds mentioned may also come from the recycling of materials already used, that is to say they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This concerns in particular polymers, plasticizers, fillers, etc.

[0015] Unless otherwise indicated, all glass transition temperature "Tg" values ​​described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to ASTM D3418 (1999). II- DESCRIPTION OF THE INVENTION II-1 Elastomeric matrix

[0016] According to the invention, the rubber composition of the shoe sole comprises an elastomer matrix comprising at least 70 pce of a polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene.

[0017] The polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene is preferably chosen from the group consisting of natural rubber, synthetic polyisoprenes and their mixtures. Particularly advantageously, it is a natural rubber.

[0018] The level of polyisoprene comprising a mass level of 1,4-cis bonds of at least 90% of the mass of the polyisoprene, in the rubber composition of the shoe sole according to the invention, is preferably at least 80 phr, preferably at least 90 phr. For example, the level of polyisoprene comprising a mass level of 1,4-cis bonds of at least 90% of the mass of the polyisoprene may be 100 phr, that is to say that it represents the only elastomer in the elastomer matrix.

[0019] The elastomer matrix may comprise up to 30 pce of an elastomer other than polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene. This other elastomer may be chosen from the group consisting of polybutadienes (BR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. The butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR). Advantageously, if another elastomer is present, it is a polybutadiene or a butadiene-styrene copolymer or one of their mixtures.

[0020] When another elastomer is present, the level of polyisoprene comprising a mass level of 1,4-cis bonds of at least 90% of the mass of the polyisoprene may be within a range from 70 to 95 phr, preferably from 70 to 90 phr, preferably from 80 to 90 phr, and the level of the other elastomer (preferably BR, SBR or their mixture) is within a range from 5 to 30 phr, preferably from 10 to 30 phr, preferably from 10 to 20 phr. II-2 Reinforcing charge

[0021] According to the invention, the rubber composition of the shoe sole comprises from 30 to 95 pce of silica, as well as an agent for coupling the silica to the polyisoprene.

[0022] 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 CT AB 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.

[0023] In the present disclosure, the BET specific surface area of ​​silica 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 standard NF ISO 5794-1, 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 0.17].

[0024] The CT AB specific surface area values ​​of silica 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.

[0025] Any type of silica may be used, for example precipitated silicas, 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 that may be mentioned are 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 “Zeosil® 175GR” from Solvay, 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.

[0026] Preferably, the silica content in the rubber composition of the sole according to the invention is within a range from 45 to 90 pce, preferably from 50 to 80 pce, preferably from 55 to 70 pce.

[0027] To couple the silica 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.

[0028] 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). In the context of the present invention, the diene elastomer includes polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene.

[0029] As coupling agent, mention may in particular be made of at least bifunctional organosilanes or polyorganosiloxanes. By "bifunctional" is meant 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 a silica and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

[0030] 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 S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”. More preferably, the organosilane is a polysulfurized organosilane.

[0031] Of course, mixtures of the coupling agents described above could also be used.

[0032] 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 silica. Its level is preferably within a range from 0.5 to 20 phr, more preferably within a range from 1 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 of the invention.

[0033] Advantageously, the rubber composition of the shoe sole according to the invention does not comprise any reinforcing filler, preferably no filler, other than silica, or comprises less than 20 phr, preferably less than 10 phr, preferably less than 5 phr. As filler other than silica, mention may be made of carbon blacks, aluminous type fillers, in particular alumina (A12O3). II-3 Plasticizing system

[0034] According to the invention, the composition of the shoe sole comprises from 1 to 60 pce of at least one plasticizing agent chosen from liquid plasticizers at 20°C, hydrocarbon plasticizing resins whose Tg is greater than 20°C and their mixtures, said liquid plasticizers being chosen from the group consisting of vegetable oils, said hydrocarbon plasticizing resins being chosen from the group consisting of terpene homopolymer or copolymer resins.

[0035] Liquid plasticizers at 20°C are said to be “low Tg”, that is to say which by definition have a Tg lower than -20°C, preferably lower than -40°C.

[0036] The liquid plasticizer at 20°C is preferably a vegetable oil chosen from the group consisting of linseed, safflower, soybean, corn, cottonseed, rapeseed, castor, tung, pine, sunflower, palm, olive, coconut, peanut, grape seed oils and mixtures thereof. Particularly advantageously, the vegetable oil is chosen from the group consisting of sunflower oils, rapeseed oils and mixtures thereof.

[0037] Advantageously, the liquid plasticizer at 20°C comprises from 45% to 100% by weight, preferably from 50% to 100% by weight, more preferably from 60% to 100% by weight, of unsaturated fatty acid triester of glycerol. Particularly advantageously, the unsaturated fatty acid of the unsaturated fatty acid triester is an unsaturated fatty acid with C12-C22 (i.e. comprising from 12 to 22 carbon atoms).

[0038] By triester and fatty acid is also meant a mixture of triesters or a mixture of fatty acids, respectively. The fatty acid of the unsaturated fatty acid triester of glycerol is preferably a C18 unsaturated fatty acid, i.e. chosen from the group consisting of oleic acid, linoleic acid, linolenic acid and mixtures thereof.

[0039] Particularly advantageously, the unsaturated fatty acid triester of glycerol is glycerol trioleate. Such triesters with a high oleic acid content are well known; they have been described, for example, in application WO 02 / 088238, as plasticizing agents in tire treads.

[0040] As examples of liquid plasticizers at 20°C which can be used in the context of the present invention and are commercially available, mention may be made of sunflower oil “Lubrirob Tod 1880” from the company Novance or “Agripure-80” from the company Cargil, or even food-grade rapeseed oil marketed under the brand name “Lesieur”.

[0041] A hydrocarbon plasticizing resin with a Tg greater than 20°C is by definition a solid at room temperature and pressure (20°C, 1 atm), whereas a plasticizing oil is liquid at room temperature and a hydrocarbon plasticizing resin with a low Tg is viscous at room temperature.

[0042] Hydrocarbon resins, also called hydrocarbon plasticizing resins, are polymers well known to those skilled in the art, essentially based on carbon and hydrogen but which may contain other types of atoms, for example oxygen. They can be used in particular as plasticizing agents or tackifying agents in polymer matrices. They are by nature at least partially miscible (i.e., compatible) at the rates used with the polymer compositions for which they are intended, so as to act as true diluting agents. They have been described for example in the work entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9) of which chapter 5 is devoted to their applications, in particular in pneumatic rubber (5.5. "Rubber Tires and Mechanical Goods").As is known, these hydrocarbon resins can also be called thermoplastic resins in the sense that they soften upon heating and can thus be molded.

[0043] The softening point of hydrocarbon resins is measured according to ISO 4625 ("Ring and Bail" method). The Tg is measured according to ASTM D3418 (1999). The macrostructure (Mw, Mn and Ip) of the plasticizing hydrocarbon resin is determined by size exclusion chromatography (SEC): tetrahydrofuran solvent; temperature 35°C; concentration 1 g / l; flow rate 1 ml / min; solution filtered on a 0.45 pm porosity filter before injection; Moore calibration with polystyrene standards; set of 3 "WATERS" columns in series ("STYRAGEL" HR4E, HR1 and HR0.5); detection by differential refractometer ("WATERS 2410") and its associated operating software ("WATERS EMPOWER").

[0044] Hydrocarbon plasticizing resins can be aliphatic, or aromatic or of the aliphatic / aromatic type, i.e. based on aliphatic and / or aromatic monomers. They can be natural or synthetic, based on petroleum or not (if this is the case, also known as petroleum resins).

[0045] Suitable aromatic monomers include, for example, styrene, alpha-methylstyrene, indene, ortho-, meta-, para-methylstyrene, vinyl toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, any vinylaromatic monomer derived from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinylaromatic monomer is styrene or a vinylaromatic monomer derived from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinylaromatic monomer is the minority monomer, expressed as a molar fraction, in the copolymer under consideration.

[0046] According to the invention, the hydrocarbon plasticizing resins whose Tg is greater than 20°C are chosen from the group consisting of terpene homopolymer or copolymer resins.

[0047] The term "terpene" herein groups together in a known manner the alpha-pinene, beta-pinene and limonene monomers; the limonene monomer being present in a known manner in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or dipentene, racemic of the dextrorotatory and levorotatory enantiomers. Among the above hydrocarbon plasticizing resins, mention will be made in particular of the homo- or copolymer resins of alphapinene, betapinene, dipentene or polylimonene.

[0048] Preferably, the hydrocarbon plasticizing resin with a Tg greater than 20°C has at least one of the following characteristics: - a Tg greater than 30°C; - a number-average molecular mass (Mn) between 300 and 2000 g / mol, more preferably between 400 and 1500 g / mol; - a polymolecularity index (Ip) less than 3, more preferably less than 2 (reminder: Ip = Mw / Mn with Mw average molecular mass by weight).

[0049] More preferably, this high Tg hydrocarbon plasticizing resin has all of the above preferential characteristics.

[0050] As examples of plasticizing hydrocarbon resins, the Tg of which is greater than 20°C, which can be used in the context of the present invention and are commercially available, mention may be made of the polylimonene resins marketed by the company DRT under the name “Dercolyte L120” (Mn=625 g / mol; Mw=1010 g / mol; Ip=1.6; Tg=72°C) or by the company Kraton under the name “Sylvagum TR7125C” (Mn=630 g / mol; Mw=950 g / mol; Ip=1.5; Tg=70°C), or the alpha and beta-pinene resins marketed by the company DRT under the name “Dercolyte Ml 15” (Mn=900 g / mol; Mw=1400 g / mol; Ip=1.7; Tg=70°C) or by the company Kraton under the name “Sylvatraxx 1001” (density= 1060.00 kg / m3 at 20°C; SP=81°C).

[0051] The rate of T at least one plasticizing agent in the composition of the sole according to the invention may be included in a range from 5 to 45 pce, preferably from 6 to 40 pce, preferably from 7 to 30 pce. Preferably, the total level of plasticizer, whatever its nature, in the composition of the sole according to the invention is included in a range from 5 to 45 pce, preferably from 6 to 40 pce, preferably from 7 to 30 pce.

[0052] Advantageously, the rubber composition of the shoe sole according to the invention does not comprise any plasticizing agent other than liquid plasticizers at 20°C, hydrocarbon plasticizing resins whose Tg is greater than 20°C, or comprises less than 10 pce, preferably less than 5 pce. In a particularly advantageous manner, the rubber composition of the shoe sole according to the invention does not comprise any plasticizing agent other than liquid plasticizers at 20°C.

[0053] According to the invention, the at least one plasticizing agent may be a liquid plasticizer at 20°C which is a vegetable oil or a mixture of vegetable oils. In other words, the vegetable oils may be the only plasticizing agents in the rubber composition of the shoe sole according to the invention.

[0054] Alternatively, the at least one plasticizing agent may be a hydrocarbon plasticizing resin whose Tg is greater than 20°C which is a terpene homopolymer or copolymer resin or a mixture thereof. In other words, the terpene homopolymer or copolymer resins may be the only plasticizing agents in the rubber composition of the shoe sole according to the invention.

[0055] Alternatively also, the rubber composition of the shoe sole according to the invention may comprise a mixture of liquid plasticizer(s) at 20°C and hydrocarbon plasticizing resin(s) whose Tg is greater than 20°C.

[0056] Advantageously, the difference between the silica content and the content of the at least one plasticizing agent (i.e. the silica content less the content of the at least one plasticizing agent) is within a range from 35 to 65 phr, preferably from 40 to 60 phr, preferably from 42 to 58 phr. Advantageously, the difference between the silica content and the content of plasticizing agent, whatever its nature, is within a range from 35 to 65 phr, preferably from 40 to 60 phr, preferably from 42 to 58 phr. These preferential rates are particularly advantageous for improving the coefficient of static friction on wet ground and the tear resistance of rubber shoe soles, while preserving an excellent level of abrasion resistance. II-4 Crosslinking system

[0057] The crosslinking system may be any type of system known to those skilled in the art in the field of rubber compositions for shoe soles. It may in particular be based on sulfur, and / or peroxide and / or bismaleimide.

[0058] Preferably, the crosslinking system is sulfur-based. This is then referred to as a vulcanization system. Advantageously, the vulcanization system comprises molecular sulfur and / or at least one sulfur-donating agent. Examples of sulfur-donating agents include dipentamethylenethiuram tetrasulfide (DPTT), polymeric sulfur or caprolactam disulfide (CLD). At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators such as zinc oxide, stearic acid or equivalent compounds such as stearic acid salts and salts of transition metals, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders.

[0059] Sulphur is present in the composition of the shoe sole according to the invention at a preferential rate within a range from 0.5 to 12 pce, in particular from 1 to 10 pce.

[0060] Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, xanthate type and their mixtures. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (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.

[0061] Advantageously, the crosslinking system comprises molecular sulfur and / or at least one sulfur-donating agent, and comprises at least one vulcanization accelerator chosen from thiazole-type accelerators, sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, xanthate-type accelerators and mixtures thereof. More preferably, the crosslinking system comprises molecular sulfur and / or at least one sulfur-donating agent, and comprises at least one vulcanization accelerator selected from the group consisting of 2-mercaptobenzothiazyl disulfide (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), morpholine disulfide, N-morpholino-2-benzothiazyl sulfenamide (MBS), dibutylthiourea (DBTU), and mixtures of these compounds,and at least one vulcanization ultra-accelerator selected from the group consisting of tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetraisobutylthiuram disulfide (TiBTD), dipentamethylenethiuram tetrasulfide (DPTT), zinc dibutyldithiocarbamate (ZDBC), zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, tellurium diethyldithiocarbamate (TDEC), zinc dibenzyldithiocarbamate (ZBED), zinc diisononyldithiocarbamate, zinc pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate (ZBEC), zinc iso-propyl xanthate (ZIX), zinc butyl xanthate (ZBX), sodium ethyl xanthate (SEX), sodium iso-butyl xanthate (SIBX), iso-propyl xanthate, sodium (SIPX), sodium n-butyl xanthate (SNBX), sodium amyl xanthate (SAX), potassium ethyl xanthate (PEX), potassium amyl xanthate (PAX), zinc 2-ethylhexylphosphorodithioate (ZDT / S), and mixtures of these compounds.

[0062] Particularly advantageously, the crosslinking system comprises molecular sulfur and / or at least one sulfur donor agent, and comprises N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), and tetrabenzylthiuram disulfide (TBzTD).

[0063] The total level of vulcanization accelerator in the composition of the shoe sole according to the invention is preferably within a range from 0.5 to 12 phr, in particular from 1 to 10 phr. When several vulcanization accelerators are used, the level of each vulcanization accelerator is within a range from 0.2 to 8 phr, preferably from 0.3 to 5 phr. II-5 Possible additives

[0064] The rubber composition of the shoe sole may also comprise all or part of the additives usually used in rubber compositions for shoe soles, such as for example protective agents such as chemical anti-ozonants, anti-oxidants, anti-fatigue agents, pigments, etc.

[0065] 11-6 Preparation of rubber compositions and soles

[0066] The compositions used in the shoe soles according to the invention can be manufactured in suitable mixers, using two successive preparation phases: a first phase of thermomechanical working or mixing (so-called "non-productive" phase) at high temperature, up to a maximum temperature of between 110°C and 190°C, preferably between 130°C and 180°C, followed by a second phase of mechanical working (so-called "productive" phase) down to a lower temperature, typically below 110°C, for example between 40°C and 100°C, finishing phase during which the crosslinking system is incorporated.

[0067] An object described herein consists of a process for preparing the composition of the shoe sole according to the invention comprising the following steps: - incorporating into a mixer, the polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene and the optional other diene elastomer, during a first step (called "non-productive"), the silica, the coupling agent and the plasticizing agent, by thermomechanically kneading the whole (for example in one or more times), until reaching a maximum temperature of between 110°C and 190°C, preferably between 150°C and 180°C; - cool the assembly to a temperature below 100°C; - then incorporate, during a second stage (called "productive"), the crosslinking system; - mix everything until a maximum temperature of less than 110°C.

[0068] Another object described herein is a shoe sole comprising a rubber composition obtainable by this method.

[0069] For example, the non-productive phase can be carried out in a single thermomechanical step during which all the necessary basic constituents (natural rubber, reinforcing filler) are introduced into a suitable mixer such as a conventional internal mixer, firstly, and then, secondly, for example after one to two minutes of mixing, the other additives including plasticizers, any additional filler covering agents or processing agents, with the exception of the crosslinking system. The total mixing time in this non-productive phase is preferably between 1 and 15 min.

[0070] After cooling the mixture thus obtained, the crosslinking system is then incorporated into an external mixer such as a cylinder mixer, maintained at low temperature (for example between 40°C and 100°C). The whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.

[0071] Depending on the coloring requirement, the addition of pigments can be conventionally carried out in the last mixing phase, i.e. the step during which the crosslinking system is added.

[0072] The final composition thus obtained can then be molded, or even calendered, for example in the form of a sheet, from which the shapes of the sole will be cut, or of a plate in particular for characterization in the laboratory.

[0073] 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.

[0074] The invention relates to the shoe soles previously described both in the raw state (i.e., before cooking) and in the cooked state (i.e., after crosslinking).

[0075] A shoe is made up of different parts: an upper, a sockliner, an outsole, a possible midsole, etc. Before being assembled to form the shoe, each part is shaped independently. For example, the upper is placed on the last (called "last") and the materials will be worked to perfectly fit the chosen volumes.

[0076] Several types of mountings exist for securing the upper part of a shoe to the outer sole. In the case of sports shoes, the outer soles are often glued to the midsole by techniques well known to those skilled in the art.

[0077] Advantageously, the rubber composition of the sole according to the invention is present in the outer sole (or outsole). Preferably, it constitutes the outsole of the shoe. III- EXAMPLES III-1 Measurements and tests used

[0078] The rubber compositions used in the shoe soles according to the invention as well as the soles themselves, are characterized after curing, as indicated below. Shore A hardness

[0079] The Shore A hardness of the compositions after curing is assessed in accordance with ISO 868:2003. Abrasion test

[0080] The abrasion test is carried out according to standard NF EN 12770: 1999: Test methods applicable to outsoles - Abrasion resistance; this test consists of measuring the loss in volume, expressed in mm3, of a sample of elastomer composition rubbed on an abrasive surface. The sample is a cylinder 16mm in diameter, taken with a punch from a 6mm thick baked plate. Tear resistance

[0081] Tear resistance tests are carried out according to standard EN 12771: 2000. Measurement of the coefficient of friction

[0082] Friction coefficient (p) measurement tests on wet ground are carried out according to a method described in patent FR3063808. The measurements are carried out on samples of baked rubber plates with dimensions of 50x50x5mm. The measurement parameters are: - Rubber / ground sliding speed: 18mm / s - Normal force applied to the sample: 500 N - Sliding length: 80mm - Temperature: 23°C + / -2°C - Floor type: ceramic (tile) - Wet ground conditions: ground covered with a water depth of 2mm III-2 Preparation of compositions and soles

[0083] The following tests are carried out as follows: the natural rubber, the reinforcing filler, the plasticizers, and the various other ingredients, with the exception of the vulcanization system, are successively introduced into an internal mixer. Thermomechanical work (non-productive phase) is then carried out in one step, lasting a total of approximately 6 to 12 minutes, until a maximum "falling" temperature of between 120°C and 150°C is reached. The mixture thus obtained is recovered, cooled, and then sulfur, a sulfenamide-type accelerator, and a TBzTD-type ultra-accelerator are incorporated into a mixer (homo-finisher) whose temperature is between 30°C and 50°C, mixing everything (productive phase) for an appropriate time (for example between 8 and 16 min).

[0084] The compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber. These plates are then crosslinked in molds using a compression press at a temperature between 150°C and 170°C for a period of between 3 and 20 minutes depending on the thickness in a manner known to those skilled in the art. These crosslinked plates are used for measuring their physical or mechanical properties.

[0085] The compositions obtained after calendering can also be transformed directly into soles. As for the plates, crosslinking is carried out in molds using compression presses. III-3 Tests

[0086] The examples presented below are intended to compare the performance compromise between abrasion resistance, tear resistance and wet grip of compositions in accordance with the present invention (C1 to C7) with control compositions (T1 and T2).

[0087] Table 1 shows the compositions tested (in pce), as well as the results obtained.

[0088] The control composition T1 differs from the compositions in accordance with the invention in that it does not comprise a vegetable oil. The control composition T2 differs from the compositions in accordance with the invention in that it comprises more than 95 pce of silica.

[0089] The abrasion resistance performance results are presented in absolute value (in mm3) and in base 100 compared to the control composition TL. A value greater than 100 indicates better abrasion resistance.

[0090] The tear resistance and wet grip performance results are presented on a basis of 100 relative to the control composition TL. A value greater than 100 indicates better tear resistance and wet grip, respectively.

[0091] The compromise of the three performances that are abrasion resistance, tear resistance and wet grip can be obtained by calculating the arithmetic mean of results presented on a base of 100.

[0092] [Tables 1] Ingredients Tl Cl C2 C3 C4 C5 C6 C7 T2 NR(1) 100 100 100 100 100 100 100 100 100 Silica (2) 56 56 56 53 53 61 75 75 100 Coupling agent (3) 5.2 5.2 5.2 4.2 4.2 4.9 6 6 8 Liquid plasticizer 1 (4) 35 Liquid plasticizer 2 (5) 35 12 12 12.5 20 Liquid plasticizer 3 (6) 35 Resin 1 (7) 12 Resin 2 (8) 25 12.5 20 Silica - plasticizer 21 21 21 41 41 49 50 50 60 BPH (9) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 TMQ(10) 1 1 1 1 1 1 1 1 1 Wax (11) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 DPG(12) 1 1 1 Stearic acid (13) 2 2 2 2 2 2 2 2 2 ZnO (14) 1.5 1.5 1.5 1.5 1.5 1.5 1 1 1 TBzTD (15) 2 2 2 2 2 2 0.8 0.8 0.8 CBS (16) 1.6 1.6 1.6 0.5 0.5 0.5 1.6 1.6 1.6 Sulphur 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Performance Abrasion NF EN 127 70: 1999 (mm3) 128 106 111 105 116 90 110 113 191 Abrasion NF EN 127 70: 1999 (base 100) 100 121 115 122 110 142 116 113 67 Tear resistance (base 100) 100 102 139 157 173 204 196 242 192 Wet grip (base 100) 100 90 84 145 116 177 152 165 110

[0093] (1) Natural rubber (2) “Ultrasil VN3-G” silica from Evonik (3) Liquid TESPT “Si69” silane from Degussa as a silica - elastomer coupling agent (4) MES oil “PLAXOLENE MS 132” marketed by Total as a liquid plasticizer at 20°C (5) Glycerol trioleate (sunflower oil with 85% by weight oleic acid) “Lubrirob Tod 1880” from Novance as a liquid plasticizer at 20°C (6) Food - grade rapeseed oil marketed under the brand “Lesieur” as a liquid plasticizer at 20°C (7) Polyterpenic resin “Dercolyte Ml 15” from DRT as a plasticizing resin (8) Polylimonene resin “Dercolyte L120” from DRT as a plasticizing resin (9) 2,2'-methylene - bis(4 - methyl - 6 - tert - butylphenol) “BPH” from Sigma - Aldrich (10) 2,2,4-trimethyl-l,2-dihydroquinoline “Pilnox TMQ” from Nocil (11) anti-ozone wax “VARAZON 4959” from Sasol Wax (12) Diphenylguanidine “Denax DPG” from the company Lucebni Zavody Draslovka (13) Stearic acid “Pristerene 4931” from the company Uniqema (14) Industrial grade zinc oxide from the company Umicore (15) tetrabenzylthiuram disulfide “TBzTD” from Akrochem, as an ultra-vulcanization accelerator (16) N-cyclohexyl-2-benzothiazyl sulfenamide “Santocure CBS” from Flexsys as a vulcanization accelerator

[0094] Comparison of compositions C1 and C2 with the Control composition T1 shows that vegetable oils make it possible to improve abrasion resistance, and also tear resistance, with a low impact on wet grip. The results of compositions C3 to C5 show that the technical effect can be obtained at different levels of silica and plasticizer in accordance with the invention, the plasticizer being indifferently a vegetable oil, a terpene resin or one of their mixtures. Control T2 shows that the technical effect of abrasion resistance is not obtained for silica levels greater than 95 phr. Finally, the compositions in accordance with the invention and having a difference between the silica level and the level of T at least one plasticizing agent in a range from 35 to 65 phr, have an improved compromise of the three performances while improving abrasion resistance.

Claims

Claims

1. Shoe sole comprising a rubber composition based on at least: - an elastomer matrix comprising at least 70 pce of a polyisoprene comprising a mass content of 1,4-cis bonds of at least 90% of the mass of the polyisoprene, - 30 to 95 pce of silica, - an agent for coupling the silica to the polyisoprene, - 1 to 60 pce of at least one plasticizing agent chosen from plasticizers that are liquid at 20°C, said plasticizers that are liquid at 20°C being chosen from the group consisting of vegetable oils, the silica content being higher than the content of the at least one plasticizing agent, - a crosslinking system.

2. A shoe sole according to claim 1, wherein the polyisoprene is selected from the group consisting of natural rubber, synthetic polyisoprenes and mixtures thereof, preferably the polyisoprene is a natural rubber.

3. Shoe sole according to any one of the preceding claims, in which the level of polyisoprene in the rubber composition is at least 80 phr, preferably at least 90 phr, preferably 100 phr.

4. Shoe sole according to any one of the preceding claims, in which the silica content in the rubber composition is within a range of 45 to 90 phr, preferably 50 to 80 phr, preferably 55 to 70 phr.

5. Shoe sole according to any one of the preceding claims, in which the liquid plasticizer at 20°C is a vegetable oil selected from the group consisting of linseed, safflower, soybean, corn, cottonseed, rapeseed, castor, tung, pine, sunflower, palm, olive, coconut, peanut, grapeseed oils and mixtures thereof, preferably a vegetable oil selected from the group consisting of sunflower oils and mixtures thereof.

6. A shoe sole according to any preceding claim, wherein the liquid plasticizer at 20°C comprises from 45% to 100% by weight of unsaturated fatty acid triester of glycerol, the fatty acid of the unsaturated fatty acid triester of glycerol being preferentially chosen from the group consisting of oleic acid, linoleic acid, linolenic acid and their mixtures.

7. Shoe sole according to any one of the preceding claims, in which the level of the at least one plasticizing agent, in the rubber composition, is within a range from 5 to 45 phr, preferably from 6 to 40 phr, preferably from 7 to 30 phr.

8. Shoe sole according to any one of the preceding claims, in which the level of silica minus the level of the at least one plasticizing agent, in the rubber composition, is within a range from 35 to 65 phr, preferably from 40 to 60 phr, preferably from 42 to 58 phr.

9. Shoe sole according to any one of the preceding claims, wherein the crosslinking system comprises molecular sulfur and / or at least one sulfur donor agent, and comprises at least one vulcanization accelerator chosen from thiazole type accelerators, sulfenamide type accelerators, thiurams, dithiocarbamates, dithiophosphates, thioureas, xanthates and mixtures thereof.

10. A shoe sole according to any one of claims 1 to 8, wherein the crosslinking system comprises molecular sulfur and / or at least one sulfur-donating agent, and comprises at least one vulcanization accelerator selected from the group consisting of 2-mercaptobenzothiazyl disulfide (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), morpholine disulfide, N-morpholino-2-benzothiazyl sulfenamide (MBS), dibutylthiourea (DBTU), and mixtures thereof, and at least one ultra- ... tetrabenzylthiuram (TBzTD), tetramethyl thiuram monosulfide (TMTM), tetramethyl thiuram disulfide (TMTD), tetraethyl thiuram disulfide (TETD),tetraisobutyl thiuram disulfide (TiBTD), dipentamethylene thiuram tetrasulfide (DPTT), zinc dibutyl dithiocarbamate (ZDBC), zinc diethyl dithiocarbamate, zinc dimethyl dithiocarbamate, copper dimethyl dithiocarbamate, diethyl dithiocarbamate, tellurium (TDEC), zinc dibenzyl dithiocarbamate (ZBED), zinc diisononyl dithiocarbamate, zinc pentamethylene dithiocarbamate, zinc dibenzyldithiocarbamate (ZBEC), zinc isopropyl xanthate (ZIX), zinc butyl xanthate (ZBX), sodium ethyl xanthate (SEX), sodium isobutyl xanthate (SIBX), sodium isopropyl xanthate (SIPX), sodium n-butyl xanthate (SNBX), sodium amyl xanthate (SAX), potassium ethyl xanthate (PEX), potassium amyl xanthate (PAX), zinc 2-ethylhexylphosphorodithioate (ZDT / S), and mixtures of these compounds.

11. A shoe sole according to any one of claims 1 to 8, wherein the crosslinking system comprises molecular sulfur and / or at least one sulfur donor agent, and comprises N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), and tetrabenzylthiuram disulfide (TBzTD).

12. Shoe sole according to any one of the preceding claims, wherein the sulfur content in the rubber composition is in a range from 0.5 to 12 phr, preferably from 1 to 10 phr, and the total content of vulcanization accelerator is in a range from 0.5 to 12 phr, preferably from 1 to 10 phr.

13. A shoe sole according to any preceding claim, wherein the composition is present in, preferably constitutes, the outsole of the shoe.