EP1957576A2

EP1957576A2 - Crosslinked composition comprising a core/shell copolymer, method of obtaining same and uses thereof

Info

Publication number: EP1957576A2
Application number: EP06842083A
Authority: EP
Inventors: Laurent Gervat; Gilles Meunier; Christophe Navarro; Elisabeth Bay; Laure Mauboules
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2005-12-07
Filing date: 2006-12-01
Publication date: 2008-08-20
Also published as: WO2007066032A2; US20090306246A1; FR2894252A1; WO2007066032A3; FR2894252B1

Abstract

The invention relates to a crosslinked composition containing in parts by weight: 20 to 100 parts of at least one elastomer (I), 2 to 50 parts of at least one core/shell copolymer (II), and 0 to 100 parts of at least one thermoplastic polymer (III). The invention also relates to a method of producing one such crosslinked composition, which is characterised in that it consists in: mixing an elastomer and a core/shell copolymer optionally in the presence of a grafted polyolefin, a plasticiser, fillers and/or additives and a suitably-selected crosslinking system; and subsequently crosslinking said mixture at a suitable temperature. In a preferred embodiment of the invention, the mixture is crosslinked at a temperature of between 150 and 320 °C. The inventive method can be carried out in an internal mixer or, alternatively, in a twin screw extruder or a BUSS®-type co-kneader. Depending on the case, the resulting mass is calendered or extruded, cooled and subsequently granulated. The granules thus obtained are then ready to be transformed, by means of heating, into sheets, plates, profiles, tubes or other products. The invention further relates to the use of one such composition in the production of ducts, tubes, pipes, tubing, couplers or similar for conveying fluids, such as the fluid transfer conduits, pipes and other elements which are used in the automobile industry in braking, cooling, steering and air-conditioning systems. The inventive crosslinked composition can also be used in the production of belts, tyres, electric cable sheaths and shoe soles.

Description

CROSSLINKED COMPOSITION COMPRISING A CORE-BARKED COPOLYMER, METHOD FOR OBTAINING SAME, USES THEREOF

Field of the invention

The present invention relates to a crosslinked composition comprising a core-shell copolymer, its production process and its uses. It particularly describes a crosslinked composition comprising an elastomer and a core-shell copolymer, its production process based on crosslinking at high temperature and its uses.

The crosslinked composition of the invention finds its applications in the manufacture of certain articles such as tires, seals and insulation linings as well as conduits for transferring fluids such as those used in the automotive industry, for example in circuits. braking or cooling. Tire technology is described in applications WO 00 05300, WO 00 05301 and EP 501227, the content of which is incorporated into the present application. By way of example of a portion of tires that can benefit from these compositions, mention may be made, without limitation, of the crown (stuffing on a bead or apex), the sidewalls, the carcass and the gums loaded with steel wires, the shoulders but also the heel, the waterproof layers, the squeegees and the tread. Other applications may call upon the compositions of the invention, such as the manufacture of belts (such as transmission belts), sheaths of electric cables, soles of shoes, seals, elastic connections, tubes and pipes, membranes or anti-vibration devices, as well as applications in the mechanical industry, in the aeronautical industry, in transport, in the electrical industry, in the building, in medicine and in pharmacy, and in the industry nuclear. In these different applications, the elastomers can of course be combined with other materials such as metals, textiles and certain plastics.

According to a particular form, the crosslinked compositions of the invention can be transformed like thermoplastic materials. In fact, for certain flute applications and insulation linings or fluid transfer duct), it is desirable to have materials which, while presenting properties similar to those of elastomers and in particular, an ability to withstand significant deformations without rupture and an ability to return to their initial geometry after stresses of the elongation or compression type, even repeated, as well as good resistance to heat, to agents chemical and weathering, can be implemented by the techniques and equipment used by transformers of thermoplastic materials, and this, mainly, to allow the recycling of these articles as well as that of the waste produced during their manufacture, recycling that does not allow the use of elastomers.

The prior art and the technical problem

US-A-4,130,535 describes "thermoplastic elastomers" based on polyolefins which have a structure consisting of a non-crosslinked polypropylene matrix and crosslinked ethylene / propylene / diene terpolymer nodules (EPDM), so as to present at the temperature of use (which is lower than the melting temperature of polypropylene) a behavior similar to that of elastomers after vulcanization, while their heating above this melting temperature makes it possible to use them as thermoplastic materials . If these materials do indeed exhibit a certain number of properties equivalent to those of elastomers, they nevertheless show a significant residual elongation deformation (greater than 50%) at temperatures above 100 ^° C., which makes their use unsuitable for the manufacture of articles intended to be used in zones where prevailing temperatures of more than 100 ⁰ C as can be the joints and packing of insulation and / or sealing or even conduits, pipes, tubes and the like designed to transfer fluids into the engine compartment of an automobile.

To resolve this problem patent EP 0840763 A1 proposes a solution based on the use of a cross-linked elastomer with thermoplastic transformation obtained by crosslinking a mixture, designated below as "Végaprène ^®", comprising a base elastomer poly (octene / ethylene) obtained by metallocene catalysis and a polyolefin grafted with maleic anhydride. Although this solution is satisfactory, it nevertheless remains limited to certain applications. In fact, the properties of the mixtures are generally different from those predicted by a simple linear interpolation from those of the constituents taken separately (elastomers and plastics). Synergistic effects can sometimes be present but there are other cases where the properties are slightly lower. This can relate to the morphology of the different phases, to the distribution of the charges and plasticizers, to the nature of the interfaces or to the distribution of the vulcanization bridges in the different phases. To overcome these phenomena, use is generally made of compatibilizing agents or co-agents which are expensive and difficult to incorporate into mixtures.

In particular in the case of properties of resistance to repeated stresses, the fatigue behavior of the compounds is essential. This can be achieved using co-agents such as zinc methacrylate. However, due to the polarity of this compound, it is difficult to disperse in the mixtures. In addition, its high reactivity with the metal at high temperature leads to mixtures which adhere to the mixing tools. It is therefore little used. Another interesting property may be the resistance to high elongation. This characteristic is difficult to obtain with the mixtures described in EP 0840763 A1.

Finally, in certain cases, the improvement in the Remanent Compression Deformation, generally designated by DRC, obtained by applying the method described in EP 0840763 A1 may prove to be insufficient.

To solve the problems described above and many others, a solution has been found based on a crosslinked composition comprising at least one elastomer and at least one core-shell copolymer and optionally a thermoplastic polymer. This makes it possible to solve the problems mentioned above without adversely modifying the other mechanical characteristics of the mixtures (dynamic properties, dissipation, hardness, rebound, etc.). The mixture of polymers is easy to disperse according to the method described in the present invention. In addition, it has the advantage of not adhering to the equipment.

Another way to solve these problems has been described in patent application WO 2005-082996 which describes a crosslinked composition comprising: - at least one elastomer,

- at least one triblock block copolymer, and

- at least one thermoplastic polymer.

This solution being satisfactory, the skilled person has no reason to substitute the triblock block copolymer with a core-shell copolymer. The present invention is therefore an alternative to the solution of WO 2005-082996, making it possible to widen the range of products and applications related to this technology.

Brief description of the invention

The first object of the invention is therefore a crosslinked composition comprising in parts by weight the following different constituents:

> 20 to 100 parts of at least one elastomer (I),

> 2 to 50 parts of at least one core-shell copolymer (II), and

> 0 to 100 parts of at least one thermoplastic polymer (III),

the compounds (I), (II) and (III) being different in chemical nature and / or of different structure.

According to the invention, the elastomer (I) and the thermoplastic (III) are not in the form of core-shell.

The present invention also relates to a process for manufacturing a crosslinked composition as defined above, characterized in that it comprises:

- the mixture of an elastomer (I) and a core-shell copolymer (II) in the optional presence of a thermoplastic polymer (III), in particular a grafted polyolefin, a plasticizer, fillers and / or d additives and a suitably chosen crosslinking system,

- then the crosslinking of this mixture at an appropriate temperature.

According to a preferred embodiment of the process according to the invention, the temperature at which the crosslinking is carried out is between 150 and 320 ^° C.

This process can be implemented in an internal mixer or, as a variant, in a twin-screw extruder or a co-kneader of the BUSS® type. The resulting mass is, as the case may be, calendered or extruded, then cooled and subjected to granulation. The granules thus obtained are ready to be transformed (by heating these granules) into sheets, plates, profiles, tubes or other desired products.

The present invention also relates to the use of a crosslinked composition as defined above for the manufacture of joints and insulating and / or sealing gaskets as used for thermal, sound and / or waterproofing and humidity, especially in the building and the automotive industry (door fittings for example).

The present invention further relates to the use of such a composition in the manufacture of conduits, tubes, pipes, tubing, fittings or the like for the transfer of fluids. By way of examples, mention may be made of pipes, hoses and other elements intended for conveying fluids which are used by the automotive industry in braking, cooling, steering assistance or even air conditioning circuits. Thus, the subject of the invention is in particular the seals and linings for insulation and / or sealing comprising the crosslinked composition defined above. Likewise, the invention relates to conduits such as tubes, pipes, tubing fittings comprising the crosslinked composition defined above.

Mention may also be made of the use of the crosslinked composition of the invention in the manufacture of belts, tires, sheaths of electric cables and soles of shoes.

According to the invention, the composition may contain one or more elastomers (I) associated with one or more core-shell copolymers (II) and optionally one or more thermoplastic polymers.

The applicant has surprisingly found that the use of core-shell copolymer mixed with several elastomers (I) makes it possible to use elastomers normally chemically incompatible (for example mixture of natural rubber (NR) with 2-chloro 1, 3 butadiene commonly called chloroprene (CR), making them compatible. This advantage makes it possible to use the composition of the invention in a wide range of applications superior to those of the compositions of the prior art. conservation of the physico-chemical properties of each of the elastomers. Detailed description of the invention

With regard to the elastomer (I), it can be chosen from the group comprising natural rubbers (NR), synthetic rubbers (BR), elastomers with polymerization by metallocene catalysis, polyolefins elastomers modified or not, poly (ethylene / propylene) (EPR), poly (ethylene / propylene / diene) (EPDM), long chain polyacrylates such as polybutylacrylate or ethyl 2-hexylacrylate and fluorinated elastomers (FPM) such as copolymers based on tetrafluoroethylene and elastomeric silicones.

By synthetic rubber (BR) is meant conjugated polydienes such as polybutadiene, polyisoprene and their block or random copolymers, in particular styrene-diene copolymers with a majority of dienes content.

For the purposes of the present invention, the term “elastomer polymerized by a metallocene catalyst” means any elastomer constituted by a homopolymer, a copolymer or a terpolymer, the polymerization of which has been carried out using a metallocene catalyst such as poly (octene / ethylene) also called polyoctenes, which are available from DU PONT DOW Elastomers (DDE) under the trade name ENGAGE.

Regarding the core-shell copolymer (II), it is in the form of fine particles having an elastomer core and at least one thermoplastic shell, the particle size is generally less than μm and advantageously between 50 and 300 nm. By way of example of a core, mention may be made of isoprene or butadiene homopolymers, isoprene-butadiene copolymers, isoprene copolymers with at most 98% by weight of a vinyl monomer and butadiene copolymers with at most 98% by weight of a vinyl monomer. The vinyl monomer can be styrene, an alkylstyrene, acrylonitrile, an alkyl (meth) acrylate or butadiene or isoprene. The core of the core-shell copolymer can be crosslinked in whole or in part. It suffices to add at least difunctional monomers during the preparation of the core, these monomers can be chosen from poly (meth) acrylic esters of polyols such as butylene di (meth) acrylate and trimethylol propane trimethacrylate. Other multifunctional monomers are for example divinylbenzene, trivinylbenzene, vinyl acrylate and vinyl methacrylate, triallyl cyanurate. The heart can also be crosslinked by introducing therein, by grafting or as a comonomer during the polymerization, unsaturated functional monomers such as anhydrides of unsaturated carboxylic acids, unsaturated carboxylic acids and unsaturated epoxides. By way of example, mention may be made of maleic anhydride, (meth) acrylic acid and glycidyl methacrylate. It is also possible to crosslink using the intrinsic reactivity of the monomers, for example the dienics.

The bark or barks are homopolymers of styrene, of an alkylstyrene or of methyl methacrylate or of copolymers comprising at least 70% by weight of one of these preceding monomers and at least one comonomer chosen from the other preceding monomers , another alkyl (meth) acrylate, vinyl acetate and acrylonitrile. The bark can be functionalized by introducing, by grafting or as a comonomer during the polymerization, unsaturated functional monomers such as anhydrides of unsaturated carboxylic acids, unsaturated carboxylic acids and unsaturated epoxides. Mention may be made, for example, of maleic anhydride, (meth) acrylic acid, glycidyl methacrylate. Hydroxyethyl methacrylate and alkyl (meth) acrylamides. By way of example, mention may be made of core-shell copolymers having a polystyrene shell and core-shell copolymers having a PMMA shell. The bark may also contain imide functions, either by copolymerization with a maleimide, or by chemical modification of PMMA with a primary amine. Advantageously, the molar% of imide functions is 30 to 60% (relative to the whole of the bark). There are also core-bark copolymers with two barks, one made of polystyrene and the other outside of PMMA. Examples of copolymer and their preparation process are described in the following patents: US 4,180,494, US 3,808,180, US 4,096,202, US 4,260,693, US 3,287,443, US 3,657,391, US 4,299,928 , US 3,985,704, US 5,773,520.

Advantageously, the core represents in this invention, by weight, 5 to 90% of the core-shell copolymer and the shell 95 to 10%. By way of example of a copolymer, mention may be made of that consisting of (i) from 70 to 75 parts of a core comprising at least 93% of butadiene, 5% of styrene and 0.5 to 1% of divinylbenzene and (ii) ) 25 to 30 parts of two barks essentially of the same weight, one inside made of polystyrene and the other outside made of PMMA.

As another example, mention may be made of those having a core made of a copolymer of butyl acrylate and butadiene and a shell made of PMMA.

All these core-shell copolymers are sometimes called soft / hard because of the elastomer core.

It would not be departing from the scope of the invention to use core-shell copolymers such as hard / soft / hard, that is to say copolymers which in this order have a hard core, a soft shell and a hard shell. The hard parts can be made of the polymers of the bark of the previous soft / hard and the soft parts can be made of the polymers of the core of the previous soft / hard.

We can quote for example those described in EP 270865, and those constituted in this order:

- a core made of a copolymer of methyl methacrylate and ethyl acrylate,

- a bark made from a copolymer of butyl acrylate and styrene,

- a bark made of a copolymer of methyl methacrylate and ethyl acrylate.

There are still other types of core-shell copolymers such as hard (heart) / soft / semi-hard. Compared to the previous ones, the difference comes from the "semi-hard" outer bark which is made up of two barks: one intermediate and the other outer. The intermediate shell is a copolymer of methyl methacrylate, styrene and at least one monomer chosen from alkyl acrylates, butadiene and isoprene. The outer shell is a homopolymer or copolymer PMMA.

We can cite for example those constituted in this order:

- a core made of a copolymer of methyl methacrylate and ethyl acrylate,

- a bark made from a copolymer of butyl acrylate and styrene, - a shell made of a copolymer of methyl methacrylate, butyl acrylate and styrene,

- a bark made of a copolymer of methyl methacrylate and ethyl acrylate.

As regards the thermoplastic polymer (III), it is chosen for example from modified or unmodified polyolefins, polyamides, polyesters, thermoplastic polyurethanes, fluorinated polymers and chlorinated polymers such as polyvinyl chloride (PVC) ). The thermoplastic polymer (III) is advantageously a functionalized polyolefin. The thermoplastic polymer (III) is preferably a grafted polyolefin selected from the group comprising polyethylenes, polypropylenes and poly (ethylene / propylene) grafted with acrylic acid, maleic anhydride or glycidyl methacrylate. As regards the constituents of the composition of the invention, the proportions of the elastomer (I), of the core-shell copolymer (II), and of the thermoplastic polymer (III) are advantageously 60 to 90 parts of (I), 5 to 20 parts of (II) and 48 to 5 parts of (III).

According to one embodiment of the invention, the contents of elastomer (I), core-shell copolymer (II), and thermoplastic polymer (III) of the composition are between 30 and 80% for (I), 2 to 35% for (II) and 5 to 80% for (III).

According to a preferred embodiment of the invention, the contents of elastomer (I), core-shell copolymer (II), and thermoplastic polymer (III) of the composition are between 40 and 70% for (I), 2 to 20% for (II) and 10 to 70% for (III).

Other constituents of the composition:

Advantageously, the crosslinked composition in accordance with the invention may also comprise a polyacrylic elastomer such as a terpolymer of ethylene, acrylate and acrylic acid or a terpolymer of styrene, acrylonitrile and acrylate , which plays the role of anti-ultraviolet agent and film-forming agent and which makes it possible to improve the surface appearance of the composition when the latter is used by extrusion. When such a polyacrylic elastomer is used, it is preferably used at a rate of 2 to 20 parts by mass per 100 parts by mass of the elastomer / core-shell copolymer mixture.

Also advantageously, the composition of the invention may contain, in addition, a plasticizer whose presence makes it possible to increase its fluidity and, consequently, to facilitate its use, as well as to adjust the hardness of the products derived from this implementation as a function of a desired hardness value. Preferably, this plasticizer is a paraffinic plasticizer of the type sold by the company TOTAL under the trade name PLAXENE or by the company EXXON under the trade name FLEXON, and is used in an amount of 5 to 120 parts by mass per 100 parts by mass of the elastomer / core-shell copolymer (II) and optionally thermoplastic polymer (III) mixture. However, other plasticizers such as polyalkylbenzene may also be suitable.

The composition can also comprise fillers of the clear fillers type (silicas, carbonates, clays, chalk, kaolin, etc.) or carbon blacks. The use of the latter has been found to be particularly advantageous since they make it possible not only to modulate certain mechanical properties of the composition according to the invention such as the breaking strength or the tensile modules, but also to give it a excellent resistance to the action of ultraviolet. When such fillers are present in the composition, they are advantageously present at a level of 5 to 100 parts by weight per 100 parts by mass of the elastomer (I) / core-shell (II) copolymer and optional thermoplastic polymer (III) mixture.

When it is necessary to add fillers and in particular carbon black in the composition in order to give them good mechanical properties and / or UV resistance (properties necessary for certain applications), the applicant has surprisingly found , that the composition based on core-shell polymer facilitating the use of the charged composition, reduces its heating during the mixing of its different constituents and its viscosity, compared with charged compositions of the prior art. The composition may, in addition, contain a certain proportion of triblock block copolymers, at a rate, for example from 0.01 to 20% and in particular from 0.1 to 10% of the composition.

The crosslinked composition may also contain other adjuvants conventionally used in the polymer industry such as, for example, antistatic agents, lubricants, antioxidants, coupling agents, dyes, processing agents or still adhesion promoters according to the properties which it is desired to give it provided, of course, that these adjuvants are compatible with the other constituents of the composition of the invention.

The composition according to the invention is said to be “crosslinked” because its preparation involves crosslinking of the elastomer entering into its composition. Therefore, the composition according to the invention contains, before crosslinking, at least one crosslinking system comprising one or more crosslinking agents suitably chosen according to the nature of the polymers, in particular elastomers, forming part of its composition and one or more promoters of crosslinking whose function is to activate the kinetics of the crosslinking reaction and to increase the crosslinking density. The crosslinking agent is chosen according to its processing and crosslinking temperature of the elastomers constituting the composition.

According to a preferred arrangement of the invention, this crosslinking system comprises, as crosslinking agent (s), one or more organic peroxides chosen from the group comprising dicumyl peroxide, 1,3-bis- (t-butyl peroxide). -isopropyl) -benzene, 2,5-dimethyl-2,5-bis-t-butylhexane peroxide and 1,1-bis- (t-butyl) -3,3,5-trimethylcyclohexane, and as promoter ( s) of crosslinking, one or more compounds chosen from the group comprising zinc oxide, stearic acid, N, Nm-phenylene-dimaleimide, triallyl or triisoallyl cyanurates, methacrylates (such as tetrahydrofurfuryl methacrylates or 2-phenoxyethyl), di methacrylates (such as di methacrylates of ethylene glycol, tetraethylene glycol, 1,4-butanediol or zinc), tri methacrylates (such as trimethylolpropane trimethacrylate), diacrylates (such as zinc diacrylate) and triacrylates. According to another preferred arrangement of the invention, the crosslinking system is a sulfur-based system which comprises, in addition to zinc oxide and / or stearic acid as crosslinking promoter (s), one or more sulfur donor accelerators such as 4,4-dithiomorpholine, tetramethylthiuram disulfide, dipentamethylenethiuram tetrasulfide or zinc dibutyldithiocarbamate, and possibly an anti-reversion agent such as 1, 3-bis- (cistraconimido-methyl )benzene.

According to a particularly preferred arrangement of the invention, the crosslinking system comprises, as crosslinking agent, a phenolic resin chosen from reactive alkylated methyl-phenolformaldehyde and bromo-methyl-phenolformaldehyde resins, and as crosslinking promoter, a chlorinated polymer such as '' a chlorinated or chlorosulfonated polyethylene or a polychloroprene, optionally combined with zinc oxide and / or stearic acid. Indeed, this latter crosslinking system makes it possible to obtain elastomers which, apart from having extremely satisfactory mechanical properties and remanence at elongation and at compression, are characterized by a beautiful surface appearance.

In all cases, the crosslinking agent (s) are preferably present in the formulation up to 1 to 10 parts by mass per 100 parts by mass of the mixture of elastomer (I) / core-shell (II) and thermoplastic polymer copolymer (III) optional, while the crosslinking promoter (s) are preferably present at a level of 0.5 to 12 parts by mass per 100 parts by mass of the mixture.

When the vulcanization system is a sulfur-based system, the sulfur donor accelerator or accelerators are, for their part, preferably present in the formulation at a level of 1 to 7 parts by mass per 100 parts by mass of the elastomeric mixture ( I) / core-shell copolymer (II) and possible thermoplastic polymer (III).

According to the invention, the crosslinking of the composition can be carried out by means of two crosslinking systems. For example, a crosslinking system based on sulfur and a crosslinking system based on organic peroxides or a crosslinking based on a phenolic resin and a crosslinking system based on organic peroxides.

Depending on the nature and the proportions of (I) and (III), the compositions of the invention can be transformed by the techniques and materials used for the use of thermoplastic materials: thermoforming, injection molding, extrusion, forming ... In this particular case, the compositions of the invention are said to be "with thermoplastic transformation". By way of example of such compositions, mention may be made of those in which the elastomer I consists of a homopolymer, a copolymer or a terpolymer, the polymerization of which was carried out using a metallocene catalyst and the polymer III is present. Advantageously III is a functionalized polyolefin, preferably a grafted polyolefin. It can be chosen from grafted polyolefins as mentioned above. For example one can mixtures I and III known as "végaprène ^®" as described for example in FR 2667016, WO 97/44390, US Patent 4,130,535 and EP 0840763 B1.

The crosslinked thermoplastic transformation compositions in accordance with the invention, while having mechanical properties in terms of hardness, breaking strength and elongation at break equivalent to those of the previously mentioned thermoplastic elastomers of the prior art, have better remanence properties in compression and elongation than the latter. This advantage is observed not only in the short term but also in the long term where the compositions according to the invention show a less tendency to creep.

As regards the manufacturing process, it comprises the mixture of at least one elastomer (I), at least one core-shell copolymer (II) in the presence, optionally, of a thermoplastic polymer (III), of a plasticizer. , fillers and adjuvants and the crosslinking of this mixture by an appropriate crosslinking system at a suitably chosen temperature.

According to a particularly preferred embodiment, the manufacturing method according to the invention comprises:

a) the mixture of the elastomer, the core-shell copolymer (II) and the crosslinking system in the presence, optionally, of the polymer thermoplastic, polyacrylic elastomer, plasticizer, fillers and / or adjuvants;

b) heating this mixture to a temperature between 150 and

32O ⁰ C, and

c) keeping it at this temperature for a time between 1 and 15 minutes.

EXAMPLES:

Different formulations were prepared according to the following method: the ingredients necessary for the preparation of the crosslinked composition are introduced into an internal mixer and under appropriate shearing. While continuing the shearing, the internal temperature of the mixers is brought to a value of 170 ^° C. and, when this temperature is reached, the mixtures are kept there for approximately 5 minutes. The masses thus obtained are cooled at the outlet of the mixers and subjected to granulation.

We determine:

- Shore A hardness according to the method described in standard NF T 46-052,

- the breaking strength (R / R) and the elongation at break (PJR) according to the method described in standard ISO 37, of each of the compositions thus prepared, as well as:

- the remanent compression deformation (DRC) at the end of a compression of 25% applied for 22 hours at 100 ^° C., according to the method described in standard ISO 815, and

- the remanent deformation at elongation (DRA) at the end of an elongation of 20% applied for 70 hours according to the method described in standard ISO 2285.

The following tables summarize the compositions studied, expressed in parts by weight, as well as the results obtained.

In the following tables:

ML and MH designate the minimum and maximum couples and Max - Min the difference between these two couples, t'c (05), t '(50) and t' (95) designate the times to reach respectively 5, 50 and 95% maximum torque. MBS 1 designates a core-shell copolymer (in English terminology: core-shell) with a core essentially based on butadiene and styrene and a PMMA shell sold by Arkema®.

MBS 2 designates a core-shell copolymer (in English terminology: core-shell) composed by half by mass of a core essentially based on butadiene and styrene and a shell of PMMA.

MBS 3 designates a core-shell copolymer (in English terminology: core-shell) composed essentially of a core substructured into a central core of majority PMMA and a peripheral layer based on butadiene and a shell of PMMA.

The rubber mixing was carried out in two phases by direct method: The first phase uses an internal mixer in which the NR is preheated for one minute with a rotor temperature of 60 ^° C. and a rotor speed at 60 rpm. Then all the reagents are introduced except the vulcanization system and the speed of the rotors is increased to 80 rpm, ensuring that the mixing temperature does not exceed 140 ^° C. The mixture is dropped at the end 6 min. The pricking temperature of the mixture is around 16O ⁰ C. The second phase consists in working manually by means of a tool cutting the rubber on the open mixer. The temperature of the cylinders is 40 ^° C. and the coefficient of friction is 1.2. The vulcanization system is incorporated and at least 3 passes are made at the end. This work lasts about twenty minutes. The results are reported in the following table 1:

Table 1

It is noted that there is a significant improvement in the Delft tear, which is indicative of a better behavior in fatigue (under repeated mechanical stresses) and this without the other characteristics important for the application being modified (DRC, rebound). This is an improvement to the crosslinked formulations, whether or not they have a thermoplastic transformation mode. In Table 2 below, the mixtures are produced by the reverse method, that is to say by introducing for the first phase all the additives first and then the elastomers. The internal mixer is used at 30 ^° C. and with a plied speed of 120 rpm. The work takes approximately 7 minutes. The second phase is similar to the procedure used for the NR.

The mesh corresponds to premature vulcanization of a rubber mixture.

Table 2:

These results show that despite a decrease in the “Max-Min” torque difference, there is an improvement in elongation and Delft tearing which is important for the positioning and resistance of the part.

Table 3

These results (Table 3) show that despite a decrease in the “Max-Min” torque difference, there is an improvement in the Delft elongation and tear, which is important for the positioning and resistance of the part. . Table 4

It can be seen from reading this table 4 that the DRC at improved high temperature.

Table 5: Composition of the mixtures

Procedure for the preparation of mixtures:

All the ingredients are introduced at the start with the gum, except for the cooking agents (sulfur, etc.). The mixture is then kneaded until it reaches 170 ^° C. by self-heating. It is then cooled on a calender, and the cooking agents are then added to it.

: in brackets the values in Ib.inch Table 7: Mooney ML consistometric index (1 + 4) at 100 ⁰ C (ISO 289-1)

Table 8: Pre-vulcanization test at 135 ⁰ C (ISO 289-2)

: in brackets the values in Ib.inch

Table 9: Vulcanization time at 170 ^° C. of the test plates and test specimens

Table 10: Shore 1 hardness measurement (ISO 7619)

Table 11: Tensile properties (ISO 37)

Table 12: Tear resistance (ISO 34-2)

Tables 13: Dynamic viscoelastic characterization

at O ⁰ C

It can be seen from these examples that the introduction of MBS into formulas for tires gives the compositions an increase in their tear resistance, which (under repeated mechanical stresses in use) is indicative of a reduction in the rates of crack propagation. as well as better fatigue behavior without changing the other characteristics important for the application (hardness, tensile properties, dynamic viscoelastic properties). This is an improvement to existing crosslinked formulations.

Table 14

* in brackets the values in psi; : in brackets the values in Ib.inch

We see on this formulation (also used for the manufacture of tires) that again the incorporation of MBS significantly increases the resistance to tearing, while increasing in this example the modulus, which provides a new compromise of properties useful for limiting deformation while strengthening the composition.

Claims

1. Crosslinked composition comprising:

> 20 to 100 parts by weight of at least one elastomer (I)

> 2 to 50 parts by weight of at least one core-shell (II) copolymer

> 0 to 100 parts by weight of at least one thermoplastic polymer (III). the compounds (I), (II) and (III) being different in chemical nature and / or of different structure.

2. Composition according to claim 1 in which the elastomer (I) is a compound chosen from the group containing natural rubbers, synthetic rubbers, EPRs, EPDMs, polyolefins elastomers modified or not, elastomers with metallocene polymerization such as poly (octene / ethylene), long chain polyacrylates such as polybutylacrylate or ethyl 2-hexyl polyacrylate and fluorinated elastomers (FPM) such as copolymers based on tetrafluoroethylene and silicone elastomers.

3. Composition according to claim 2 in which the elastomer (I) is poly (octene / ethylene).

4. Composition according to any one of claims 1 to 3 characterized in that it can be transformed as a thermoplastic material.

5. Composition according to claim 1 or 2 in which the thermoplastic polymer (III) is chosen from grafted polyolefins such as polyethylenes, polypropylenes and poly (ethylene / propylene) grafted with acrylic acid, maleic anhydride or glycidyl methacrylate.

6. Composition according to any one of the preceding claims, characterized in that it contains, before crosslinking, at least one crosslinking system which comprises one or more crosslinking agents and one or more crosslinking promoters.

7. Composition according to claim 6 characterized in that the crosslinking system comprises as crosslinking agent one or more organic peroxides chosen from the group comprising dicumyl peroxide, the peroxid of 1,3-bis- (t-butylisopropyl) benzene , peroxide

2,5-dimethyl-2,5-bis-t-butyl-hexane and 1, 1 bis- (t-butyl) -3,3,5-trimethyl-cyclohexane, and as crosslinking promoters one or more several compounds chosen from the group comprising zinc oxide, stearic acid, N, Nm-phenylene dimaleimide, triallyl or triisoallyl cyanurates, dimethacrylates, trimethacrylates, diacrylates and triacrylates.

8. Composition according to claim 6 characterized in that the crosslinking system is based on sulfur and comprises, in addition to zinc oxide and / or stearic acid, as crosslinking promoters, one or more sulfur donor activators and possibly an anti-reversion agent.

9. Composition according to Claim 6, characterized in that the crosslinking system comprises as crosslinking agent a phenolic resin chosen from reactive alkylated methyl phenolformaldehyde and bromo-methylphenolformaldehyde resins and as crosslinking promoter a chlorinated polymer optionally combined with l zinc oxide and / or stearic acid.

10. Composition according to one of claims 6 to 9 characterized in that the crosslinking agent and the crosslinking promoter are present at a content of between 0.5 and 12 parts by mass per 100 parts of the mixture.

11. Crosslinked composition according to any one of the preceding claims further comprising a plasticizer and / or fillers of the clear or black carbon fillers type and / or adjuvants.

12. Method for preparing a crosslinked composition according to one of the preceding claims which comprises mixing at least one elastomer (I) and at least one core-shell copolymer (II) in the optional presence of a thermoplastic polymer (III), a plasticizer, fillers and adjuvants and the crosslinking of this mixture by an appropriate crosslinking system at a suitable temperature.

13. The method of claim 12 wherein the crosslinking is carried out at a temperature between 150 and 32O ⁰ C.

14. The method of claim 12 or 13 wherein the crosslinking is carried out for a time between 1 and 15 minutes.

15. Seals and insulating and / or sealing packings comprising a crosslinked composition according to any one of claims 1 to 11.

16. Ducts such as tubes, pipes, tubing, fittings comprising a crosslinked composition according to any one of claims 1 to 11.

17. Use of the compositions according to one of claims 1 to 11 in the manufacture of electrical cable sheaths.

18. Use of the compositions according to one of claims 1 to 11 in the manufacture of tires.

19. Use of the compositions according to one of claims 1 to 11 for the manufacture of belts.

20. Use of the compositions according to one of claims 1 to 11 for the manufacture of shoe soles.