WO2012059219A1

WO2012059219A1 - Use of precipitated silica, provided in the form of granules and having a specific pore distribution, and of 3-acryloxy-propyltriethoxysilane in an isoprene elastomer composition

Info

Publication number: WO2012059219A1
Application number: PCT/EP2011/005518
Authority: WO
Inventors: Laurent Guy
Original assignee: Rhodia Operations; Dow Corning Corporation
Priority date: 2010-11-03
Filing date: 2011-11-02
Publication date: 2012-05-10
Also published as: FR2966833A1; FR2966833B1

Abstract

The invention relates to the combined use, in an elastomer composition including an isoprene elastomer, of precipitated silica provided in the form of granules and having a specific pore distribution, as an inorganic reinforcing filler, and of 3-acryloxy-propyltriethoxysilane as an agent for binding the inorganic filler and the elastomer together. The invention also relates to the resulting elastomer compositions, and to articles manufactured from said compositions.

Description

USE OF PRECIPITED SILICE IN THE FORM OF PELLETS. HAVING A PARTICULAR POROUS DISTRIBUTION.

AND 3-ACRYLOXY-PROPYLTRIETHOXYSILANE IN AN ISOPRENE (S) ELASTOMER COMPOSITION

The invention relates to the joint use, in elastomer compositions (s) comprising an isoprene elastomer, such as natural rubber, of a particular reinforcing inorganic filler and a particular inorganic filler - elastomer coupling agent.

It also relates to the corresponding elastomer compositions and articles, in particular tires, comprising such compositions.

It is known that the elastomeric articles are generally subjected to various constraints, for example such as a temperature variation, a variation of high frequency stress in dynamic regime, a significant static stress and / or fatigue in significant bending in dynamic mode. Such articles are, for example, tires, shoe soles, floor coverings, conveyor belts, power transmission belts, hoses, seals, especially appliance seals, role of engine vibration extractors either with metal reinforcements or with a hydraulic fluid inside the elastomer, cable sheaths, cables, ropeway rollers.

It was then proposed to use in particular elastomer compositions (s) reinforced with specific inorganic fillers described as "reinforcing", preferably having a high dispersibility. These fillers, in particular white fillers such as precipitated silicas, are capable of competing with or even exceeding at least from the point of view reinforcing the conventionally used carbon black, and also offer these compositions a generally lower hysteresis, which is synonymous especially a decrease in internal heating of the elastomeric articles (s) during their use.

It is known to those skilled in the art that it is generally necessary to employ in the elastomer compositions containing such reinforcing fillers a coupling agent, also called a binding agent, whose function is, in particular, to providing the connection between the surface of the inorganic filler particles (for example a precipitated silica) and the elastomer (s), while facilitating the dispersion of this inorganic filler within the elastomeric matrix.

The term "inorganic filler-elastomer coupling agent" is understood to mean an agent capable of establishing a sufficient chemical and / or physical connection between the inorganic filler and the elastomer.

Such a coupling agent, at least bifunctional, has for example as simplified general formula "N-V-M", in which:

N represents a functional group ("N" function) capable of binding physically and / or chemically to the inorganic filler, such a bond being able to be established, for example, between a silicon atom of the coupling agent and the groups hydroxyl (OH) on the surface of the inorganic filler (for example surface silanols when it is silica);

M represents a functional group ("M" function) capable of binding physically and / or chemically to the elastomer, in particular via a suitable atom or group of atoms (for example an atom of sulfur);

- V represents a group (divalent / hydrocarbon) for connecting "N" and "M".

The coupling agents should not be confused with simple inorganic filler agents which, in a known manner, may have the "N" function active with respect to the inorganic filler but lack the "M" function. active with respect to the elastomer.

Coupling agents, in particular (silica-elastomer), have been described in numerous documents of the state of the art, the best known being (poly) sulphide silanes, in particular (poly) sulphidized alkoxysilanes. Among these (poly) sulphurized silanes, mention may be made especially of tetrasulphide of triethoxysilylpropyl (abbreviated TESPT), which is generally still considered today as a product providing, for vulcanisais comprising an inorganic filler as a reinforcing filler, such as silica, a very good or even the best compromise in term safety to the grid, ease of implementation and strengthening power.

The combined use of precipitated silica, in particular highly dispersible silica and a silane (or organosilic compound functionalized) polysulfide in a modified elastomer composition (s) allowed the development of the "green tire" for passenger vehicles (Light vehicles). This combination achieved a wear resistance performance comparable to that of carbon black-reinforced elastomer blends, while significantly improving rolling resistance (resulting in lower fuel consumption). fuel), and grip on wet ground.

It would therefore be interesting to also be able to use an inorganic filler such as silica in tires for trucks, tires which are obtained from compositions based on isoprene elastomer (s), mainly natural rubber.

However, the same polysulfide silica / silane combination applied to an isoprene elastomer, such as natural rubber, did not provide a sufficient level of reinforcement compared to what is obtained when carbon black is used as a filler. recessed reinforcement leading especially to poor wear resistance.

The object of the present invention is to propose in particular the combination for elastomer compositions comprising a diene elastomer, such as natural rubber, with a particular coupling agent with a particular reinforcing inorganic filler, this combination consisting of as an alternative to the use of known coupling agents with known reinforcing inorganic fillers, this combination further providing said elastomer compositions with a fairly satisfactory compromise of properties. Advantageously, it allows an improvement of the wear resistance. In addition, the elastomer compositions obtained preferably have good adhesion to both the filler and the filler. reinforcing inorganic agent and the substrates to which they are subsequently applied.

The invention relates in its first object to the use in an elastomer composition (s), comprising at least one isoprene elastomer:

a precipitated silica, as reinforcing inorganic filler, said precipitated silica being in the form of granules, having a porous distribution such that the pore volume constituted by the pores whose diameter is between 175 and 275 A represents less than 60% of the pore volume constituted by pores with diameters less than or equal to 400 Å, and having an aluminum content of less than 0.5% by weight, preferably less than 0.35% by weight, with

3-acryloxypropyltriethoxysilane (or γ-acryloxypropyltriethoxysilane), as an inorganic filler-elastomer coupling agent.

One of the essential characteristics of the precipitated silica used in the invention lies in the distribution, or distribution, of its pore volume, and in this case in the distribution of the pore volume which is generated by the pores of smaller diameters. This latter volume corresponds to the useful pore volume of the fillers employed in the reinforcement of the elastomers.

Thus, this precipitated silica has (and this can be illustrated by the analysis of porograms) a porous distribution such that the pore volume generated by the pores whose diameter is between 175 and 275 A (V2) represents less than 60% of the porous volume generated by pores with diameters less than or equal to 400 A (V1).

The porous volumes and pore diameters are measured by mercury porosimetry (Hg), using a MICROMERITICS Autopore 9520 porosimeter, and are calculated by the WASHBURN relation with a theta contact angle of 130 ° and a voltage. superficial gamma equal to 484 Dynes / cm (DIN 66133 standard).

In general, said precipitated silica has a porous distribution such as the pore volume constituted by the pores whose diameter is between 175 and 275 A (V2) represents more than 40%, in particular more than 45%, and less than 60%, of the pore volume constituted by pores with diameters less than or equal to 400 A (V1).

According to a variant of the invention, the precipitated silica used has a porous distribution such that the pore volume constituted by the pores whose diameter is between 175 and 275 A (V2) represents 40%, in particular 45% at 50% of the pore volume constituted by pores with diameters less than or equal to 400 A (V1).

According to another variant of the invention, the precipitated silica used has a porous distribution such that the pore volume constituted by the pores whose diameter is between 175 and 275 A (V 2) represents more than 50% (in particular more 52%) and less than 60% of the pore volume constituted by pores with diameters less than or equal to 400 A (V1). Another essential characteristic of the precipitated silica implemented in the invention consists in the fact that it is in the form of granules.

In general, these are of substantially parallelepipedal shape.

Their size is usually at least 1 mm, for example between 1 and 10 mm, in particular along the axis of their greatest length (it may be possible to use the NF X 11507 standard).

The physical state in which the precipitated silica to be used according to the invention is therefore not, among others, a powder.

Said precipitated silica employed in the invention has an aluminum content of less than 0.5% by weight, in particular less than 0.35% by weight, for example less than 0.2% by weight.

The aluminum content can be measured by any suitable method, for example by ICP-AES ("Inductively Coupled Plasma - Atomic Emission Spectroscopy") after dissolution in water in the presence of hydrofluoric acid.

Preferably, the precipitated silica used in the invention is highly dispersible, that is to say that in particular it exhibits an aptitude for deagglomeration and dispersion in a very large polymeric matrix, particularly observable by electron or optical microscopy, on thin sections. Preferably, the precipitated silica used according to the invention has a CTAB specific surface area of between 70 and 240 m ² / g.

This may be between 70 and 100 m ² / g, for example between 75 and 95 m ² / g.

However, very preferably, its CTAB surface area is between 100 and 200 m ² / g, in particular between 130 and 180 m ² / g.

Likewise, preferably, the precipitated silica used according to the invention has a BET specific surface area of between 70 and 240 m ² / g.

However, very preferably, its BET specific surface area is between 100 and 200 m ² / g, in particular between 150 and 185 m ² / g.

The precipitated silica implemented according to the invention can thus have a CTAB specific surface area of between 130 and 180 m ² / g and a BET specific surface area of between 150 and 185 m ² / g, especially when it has a porous distribution such as that the pore volume constituted by the pores whose diameter is between 175 and 275 A (V2) represents more than 50% (in particular more than 52%) and less than 60% of the pore volume constituted by the pores of smaller diameters or equal to 400 A (V1).

In particular, it may have a BET specific surface area of between 160 and 180 m ² / g. It may have a CTAB specific surface area of between 145 and 165 m ² / g.

The CTAB specific surface area is the external surface, which can be determined according to the NF T 45007 method (November 1987). The BET surface area can be measured according to the method of BRUNAUER - EMMETT - TELLER described in "The Journal of the American Chemical Society", vol. 60, page 309 (1938) and corresponding to standard NF T 45007 (November 1987). The dispersibility (and deagglomeration) ability of the precipitated silica implemented according to the invention can be assessed by means of the following test, by a granulometric measurement (by laser diffraction) carried out on a silica suspension previously deagglomerated by ultra-sonification (breaking objects from 0.1 to a few tens of microns). Ultrasonic deagglomeration is carried out using a VIBRACELL BIOBLOCK (750 W) sonicator equipped with a 19 mm diameter probe. The particle size measurement is carried out by laser diffraction on a SYMPATEC granulomer, using the Fraunhofer theory.

In a pillbox (height: 6 cm and diameter: 4 cm), 2 grams of silica are weighed and the mixture is made up to 50 grams by addition of deionized water: a 4% aqueous suspension of silica is thus obtained which is homogenized during 2 minutes by magnetic stirring. The deagglomeration is then carried out under ultrasound as follows: the probe being immersed over a length of 4 cm, it is put into action for 5 minutes and 30 seconds at 80% of its nominal power (amplitude). The granulometric measurement is then carried out by introducing into the vat of the granulometer a volume V (expressed in ml) of the homogenized suspension necessary to obtain an optical density of approximately 20.

The value of the median diameter ₅ o obtained according to this test is even lower than the silica has a high ability to deagglomerate.

A deagglomeration factor FD is given by the equation:

F _D = 10 x V / optical density of the suspension measured by the granulometer (this optical density is about 20).

This deagglomeration factor FD is indicative of the level of particles smaller than 0.1 μm which are not detected by the granulometer. This factor is all the higher as the silica has a high deagglomeration ability.

In general, the precipitated silica implemented according to the invention has a median diameter δ ₅₀ , after deagglomeration with ultrasound, less than 5 μm, in particular of at most 4.5 μm.

It usually has an ultrasonic deagglomeration factor F _D greater than 4.5 ml, in particular greater than 5.5 ml. The pH of the precipitated silica used according to the invention is generally between 6, 1 and 7.4.

The pH is measured according to the following method deriving from the ISO 787/9 standard (pH of a suspension at 5% in water):

Apparatus:

- calibrated pH meter (reading accuracy at 1 / 100th)

- combined glass electrode

- 200 mL beaker

- 100 mL test tube

- precision balance to 0.01 gram.

Operating mode:

5 grams of silica are weighed to the nearest 0.01 gram in the beaker of 200 ml. 95 mL of water measured from the graduated cylinder is then added to the silica powder. The suspension thus obtained is stirred vigorously (magnetic stirring) for 10 minutes. The pH measurement is then performed.

Precipitated silicas that can be used in the invention are commercially available.

Their preparation process usually comprises a final agglomeration step, which consists, for example, of direct compression, wet-path granulation (that is to say with use of a binder such as water, suspension of silica. ..), extrusion or, preferably, dry compaction.

The 3-acryloxypropyltriethoxysilane (or γ-acryloxypropyltriethoxysilane) used in the invention as an inorganic filler-elastomer coupling agent can be prepared by a process as described in US-A-3179612, starting from US Pat. allyl acrylate and triethoxysilane.

The precipitated silica used according to the present invention as reinforcing inorganic filler and 3-acryloxypropyltriethoxysilane used according to the present invention as reinforcing inorganic filler coupling agent - elastomer may be mixed together prior to use. A first variant is that the 3-acryloxypropyltriethoxysilane is not grafted onto said precipitated silica; a second variant consists in that the 3-acryloxypropyltriethoxysilane is grafted onto said precipitated silica which will thus be "precoupled" before mixing with the elastomer composition (s).

It is possible to use all or part of the 3-acryloxypropyltriethoxysilane used according to the invention as a coupling agent in supported form (the setting is carried out prior to its use) on a solid compatible with its chemical structure. this solid support may for example be carbon black or, preferably, precipitated silica used according to the present invention. The elastomer compositions in which 3-acryloxypropyltriethoxysilane is used according to the invention may contain at least one precipitated silica covering agent used as a reinforcing filler. This covering agent is capable, in a known manner, of improving the processability of the elastomer compositions in the green state.

Such a coating agent may consist, for example, of an alkylalkoxysilane (in particular an alkyltriethoxysilane), a polyol, a polyether (in particular a polyethylene glycol), a polyetheramine, a primary, secondary or tertiary amine (in particular a trialkanolamine), a α, ω-dihydroxylated polydimethylsiloxane or an α, ω-diamine polydimethylsiloxane.

This coating agent may optionally be mixed with said precipitated silica and 3-acryloxypropyltriethoxysilane prior to their use.

The elastomer compositions in which the 3-acryloxypropyltriethoxysilane and the precipitated silica described above are used according to the invention may optionally comprise at least one other inorganic filler-elastomer coupling agent, in particular a sulphurised silane. or polysulfide. Examples of such a coupling agent are:

bis-triethoxysilylpropyl disulphide (abbreviated TESPD) of formula:

(C2H ₅ O) 3Si- (CH 2) 3 -S 2 - (CH 2) 3 -Si (OC ₂ H 5) 3

bis-triethoxysilylpropyl tetrasulfide (abbreviated TESPT) of formula:

(C2H ₅ O) 3Si- (CH ₂ ) 3 -S 4 - (CH ₂ ) 3 -Si (OC ₂ H ₅ ) 3

bis-monohydroxydimethylsilylpropyl tetrasulfide of formula:

(HO) (CH ₃ ) 2Si- (CH 2) 3 -S 4 - (CH 2) 3 -Si (CH ₃ ) ₂ (OH)

bis-monoethoxydimethylsilylpropyl disulfide (abbreviated as MESPD) of formula:

(C2H5O) (CH3) 2Si- (CH2) 3-S2- (CH2) 3-Si (CH3) 2 (OC ₂ H5)

bis-monoethoxydimethylsilylpropyl tetrasulfide (abbreviated as MESPT) of formula:

(C 2 H ₅ O) (CH3) 2Si- (CH2) 3-S4- (CH2) 3-Si (CH3) 2 (OC ₂ H5)

bis-monoethoxydimethylsilylisopropyl tetrasulfide (abbreviated to MESiPrT) of formula:

(C2H5O) (CH3) 2 Si-CH2-CH- (CH3) -S4- (CH3) -CH-CH2-Si (CH3) 2 (OC2H ₅₎

However, preferably, said elastomer compositions (s) do not contain any other inorganic filler-elastomer coupling agent other than 3-acryloxypropyltriethoxysilane.

The use according to the invention may optionally be carried out in the presence of a free radical initiator (for example from 0.02 to 5%, in particular from 0.05 to 0.5%, by weight relative to the amount in question. weight of elastomer (s)), that is to say of a compound (especially organic compound) susceptible, in particular following energetic activation, to generate free radicals in situ, in its surrounding environment, in this case in the elastomer (s). The initiator of free radicals is here an initiator of the type with thermal initiation, that is to say that the energy supply, for the creation of free radicals, is in thermal form. Its decomposition temperature should generally be below 180 ° C, in particular below 160 ° C.

It is for example chosen from the group consisting of organic peroxides, organic hydroperoxides, azido compounds, bis (azo) compounds, peracids, peresters or a mixture of at least two of these compounds. compounds. It is in particular an organic peroxide, for example benzoyl peroxide, acetyl peroxide, lauryl peroxide, peroxide of 1, 1 bis (t-butyl) -3,3,5-trimethylcyclohexane, peroxide optionally being placed on a solid support, such as calcium carbonate.

However, preferably, the invention is implemented in the absence of any free radical initiator.

The elastomer composition (s) employed in the invention may advantageously not comprise other elastomers than the isoprene elastomer (s) it contains.

It may optionally (non-preferred variant) comprise at least one elastomer other than isoprene. In particular, it may optionally comprise at least one isoprene elastomer (for example natural rubber) and at least one diene elastomer other than isoprene, the amount of isoprene elastomer (s) relative to the total amount of elastomer (s) then being preferably greater than 50% (generally less than 99.5%, and for example between 70 and 99%) by weight.

The elastomer composition (s) used according to the invention generally comprises at least one isoprene elastomer (natural or synthetic) chosen from:

(1) synthetic polyisoprenes obtained by homopolymerization of isoprene or 2-methyl-1,3-butadiene;

(2) synthetic polyisoprenes obtained by copolymerization of isoprene with one or more ethylenically unsaturated monomers chosen from:

(2.1) conjugated diene monomers, other than isoprene, having from 4 to 22 carbon atoms, such as, for example, butadiene-1,3, 2,3-dimethyl-1,3-butadiene, 2-chloro butadiene-1,3 (or chloroprene), 1-phenyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene;

(2.2) vinyl aromatic monomers having from 8 to 20 carbon atoms, such as, for example, styrene, ortho-, meta- or para-methylstyrene, the commercial "vinyl-toluene" mixture, paratertiobutylstyrene, methoxystyrenes, chloro-styrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene;

(2.3) vinyl nitrile monomers having 3 to 12 carbon atoms, such as, for example, acrylonitrile, methacrylonitrile;

(2.4) acrylic ester monomers derived from acrylic acid or methacrylic acid with alkanols having from 1 to 12 carbon atoms, such as, for example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, methacrylate, isobutyl;

(2.5) a mixture of at least two of the aforementioned monomers (2.1) to (2.4); the copolymeric polyisoprenes containing between 20 and 99% by weight of isoprenic units and between 80 and 1% by weight of diene units, aromatic vinyls, vinyl nitriles and / or acrylic esters, and consisting, for example, in poly (isoprene-butadiene) ), poly (isoprene-styrene) and poly (isoprene-butadiene-styrene);

(3) natural rubber;

(4) copolymers obtained by copolymerization of isobutene and isoprene, as well as the halogenated versions, in particular chlorinated or brominated, of these copolymers;

(5) a mixture of at least two of the aforementioned elastomers (1) to (4);

(6) a mixture containing more than 50% (preferably less than 99.5%, and for example 70-99%) by weight of the aforementioned elastomer (1) or (3) and less than 50% (preferably more than 0.5%, and for example between 1 and 30% by weight of one or more diene elastomers other than isoprenic.

By diene elastomer other than isoprene, is meant in a manner known per se including: homopolymers obtained by polymerization of one of the conjugated diene monomers defined above in (2.1), such as polybutadiene and polychloroprene; copolymers obtained by copolymerization of at least two of the abovementioned conjugated dienes (2.1) with one another or by copolymerization of one or more of the abovementioned conjugated dienes (2.1) with one or more unsaturated monomers mentioned above (2.2), (2.3) and / or or (2.4), such as poly (butadiene-styrene) and poly (butadiene-acrylonitrile); ternary copolymers obtained by copolymerization of ethylene, of an α-olefin having from 3 to 6 carbon atoms with a non-conjugated diene monomer containing from 6 to 12 carbon atoms, for example elastomers obtained from ethylene propylene with a non-conjugated diene monomer of the aforementioned type, such as in particular hexadiene-1,4, ethylidene norbornene, dicyclopentadiene (elastomer EPDM).

Preferably, the elastomer composition (s) comprises at least one isoprene elastomer chosen from:

(1) homopolymeric synthetic polyisoprenes;

(2) the synthetic polyisoprenes copolymers consisting of poly (isoprene-butadiene), poly (isoprene-styrene) and poly (isoprene-butadiene-styrene);

(3) natural rubber;

(4) butyl rubber;

(5) a mixture of at least two of the aforementioned elastomers (1) to (4);

(6) a mixture containing more than 50% (preferably less than 99.5%, and for example 70-99%) by weight of the aforementioned elastomer (1) or (3) and less than 50% (preferably more than 0.5%, and for example from 1 to 30% by weight of non-isoprene diene elastomer consisting of polybutadiene, polychloroprene, polybutadiene-styrene, polybutadiene-acrylonitrile or a terpolymer (ethylene - propylene - nonconjugated monomeric diene).

More preferentially, the elastomer composition (s) comprises at least one isoprene elastomer chosen from: (1) homopolymeric synthetic polyisoprenes; (3) natural rubber; (5) a mixture of the aforementioned elastomers (1) and (3); (6) a mixture containing more than 50% (preferably less than 99.5%, and for example 70-99%) by weight of the aforementioned elastomer (1) or (3) and less than 50% (preferably more than 0.5%, for example from 1 to 30% by weight of diene elastomer other than isoprene, consisting of polybutadiene or polybutadiene-styrene.

According to a very preferred variant of the invention, the elastomer composition (s) comprises as isoprene elastomer at least natural rubber, or even only natural rubber. According to an even more preferred variant, the elastomer composition (s) comprises as elastomer (s) only natural rubber.

In general, the elastomer composition (s) used according to the invention also comprises all or part of the other constituents and auxiliary additives usually employed in the field of elastomeric compositions.

Thus, generally, it comprises at least one compound chosen from vulcanizing agents (for example sulfur or a sulfur-donor compound (such as a thiuram derivative)), vulcanization accelerators (for example a guanidine derivative or a thiazole derivative), vulcanization activators (for example, stearic acid, zinc stearate and zinc oxide, which may optionally be introduced in a fractional manner during the preparation of the composition), carbon, protective agents (especially antioxidants and / or antiozonants, such as, for example, N-phenyl-N '- (1,3-dimethylbutyl) -p-phenylenediamine), antireversions (such as for example hexamethylene-1,6-bis (thiosulfate), 1,3-bis (citraconimidomethyl) benzene), plasticizers.

The combined use according to the invention of the precipitated silica described in the previous discussion and 3-acryloxypropyltriethoxysilane can be done more particularly in shoe soles, floor coverings, gas barriers, flame retardant materials, ropeway rollers, appliance joints, liquid or gas line joints, braking system joints, hoses, ducts (including cable ducts), cables, supports motor, conveyor belts, transmission belts or, preferably, tires (especially tire treads), advantageously in tires for heavy goods vehicles, in particular for trucks.

The elastomer composition (s) obtained according to the use according to the invention contains an effective amount of 3-acryloxypropyltriethoxysilane. More particularly, the elastomer compositions resulting from the invention may comprise (parts by weight), per 100 parts of isoprene elastomer (s):

10 to 200 parts, in particular 20 to 150 parts, especially 30 to 110 parts, for example 30 to 75 parts, of precipitated silica as described above and used as reinforcing inorganic filler;

1 to 20 parts, in particular 2 to 20 parts, especially 2 to 12 parts, for example 2 to 10 parts, of 3-acryloxypropyltriethoxysilane used as reinforcing inorganic filler-elastomer coupling agent.

Preferably, the amount of 3-acryloxypropyltriethoxysilane used, especially chosen from the abovementioned ranges, is determined so that it generally represents 1 to 20%, in particular 2 to 15%, for example 4 to 12%, by weight relative to the amount used of the precipitated silica as described above.

In general, the total amounts of coupling agents + optional coating agent are identical to those mentioned above when using, in addition to the coupling agent (3-acryloxypropyltriethoxysilane) used according to the invention. another coupling agent (especially sulphide or polysulfide) and / or a covering agent.

The present invention has the second object the elastomer compositions (s) described above, and thus comprising:

at least one isoprene elastomer,

at least one reinforcing inorganic filler,

at least one inorganic filler - elastomer coupling agent,

characterized in that said reinforcing inorganic filler and said inorganic filler - elastomer coupling agent are as defined above according to the first subject of the invention, that is to say that said reinforcing inorganic filler is precipitated silica as described in the above disclosure and said inorganic filler-elastomer coupling agent is 3-acryloxypropyltriethoxysilane.

All that has been previously described in the context of the use according to the first subject of the invention applies to these elastomer compositions (s). In particular, these compositions may further comprise at least one covering agent for said precipitated silica used as a reinforcing filler. The elastomer compositions according to the invention may be prepared according to any conventional two-phase procedure. A first phase (called non-productive) is a thermomechanical work phase at high temperature. It is followed by a second phase of mechanical work (called productive) at temperatures generally below 110 ° C in which the vulcanization system is introduced.

The invention, taken in its second object, relates to elastomer compositions (s) both in the raw state (that is to say before cooking) and in the cooked state (that is to say, before cooking). say after crosslinking or vulcanization).

The elastomer compositions according to the invention can be used to manufacture finished or semi-finished articles comprising said compositions.

The present invention thus has for third object articles comprising at least one elastomer composition (s) as defined above, in particular a composition comprising (for example as sole elastomer) natural rubber, these articles consisting of soles footwear, floor coverings, gas barriers, fire-retardant materials, ropeway rollers, appliance joints, liquid or gas pipe joints, brake system seals, hoses (flexible ), sheaths (in particular cable sheaths), cables, motor supports, conveyor belts, transmission belts, or, preferably, tires (in particular tire treads), advantageously tires. for heavy goods vehicles, in particular for trucks.

The following example illustrates the invention without limiting its scope. EXAMPLE

This example illustrates the use and behavior of a precipitated silica S, having the following characteristics, and 3-acryloxypropyltriethoxysilane in an elastomeric composition.

The precipitated silica S has the following characteristics:

- CTAB specific surface area 156 m ² / g

- BET specific surface 174 m ² / g

- aluminum content by weight <0,5%

- V2 / V1 ratio 54%

It is subjected to the disagglomeration test as defined above in the description.

After deagglomeration with ultrasound, it has a median diameter (0 ₅ o) of 4.5 μιτι and an ultrasound deagglomeration factor (F _D ) of 6.5 ml.

2- In an internal mixer of the Haake type, elastomeric compositions are prepared whose constitution, expressed in part by weight per 100 parts of elastomers (phr), is shown in Table I below.

Table I: Formulations used for blends

(1) Natural rubber SMR 5 - CV60 (supplied by Safic-Alcan)

(2) Silica S

(3) TESPT (Z-6940 from Dow Corning Company)

(4) 3-acryloxypropyltriethoxysilane

(5) N-1,3-dimethylbutyl-N-phenyl-para-phenylenediamine (Santoflex

6-PPD from Flexsys)

(6) 2,2,4-trimethyl-1H-quinoline (Permanax TQ from Flexsys)

(7) N-cyclohexyl-2-benzothiazyl sulfenamide (Rhenogran CBS-80 from

RheinChemie company)

(8) Diphenylguanidine (Rhenogran DPG-80 from RheinChemie)

Process for the preparation of elastomeric compositions

The process for preparing the compositions is conducted in two successive preparation phases. A first phase consists in a thermomechanical work phase at high temperature. It is followed by a second phase of mechanical work at temperatures below 110 ° C; this phase allows the introduction of the vulcanization system. The first phase is carried out in a Haake type internal mixer (capacity of 300 mL). The fill factor is 0.75. The initial temperature and the speed of the rotors are fixed each time so as to reach mixing temperatures of the vicinity of 150-170 ° C.

The first phase is decomposed here in two passes.

It allows to incorporate, in a first pass, the elastomer (natural rubber), then the reinforcing inorganic filler consisting of silica (fractional introduction) with the coupling agent and stearic acid; the duration of this pass is between 4 and 10 minutes.

After cooling the mixture (temperature below 100 ° C.), a second pass makes it possible to incorporate the zinc oxide and the protective / antioxidant agents (6-PPD in particular); the duration of this pass is between 2 and 5 minutes.

After cooling the mixture (temperature below 100 ° C), the second phase allows the introduction of the vulcanization system (sulfur and accelerators, such as CBS). It is carried out on a roll mill, preheated to 50 ° C. The duration of this phase is between 2 and 6 minutes.

Each final mixture is then calendered in the form of plates 2-3 mm thick.

On these so-called raw mixtures obtained, an evaluation of their rheological properties makes it possible to optimize the duration and the vulcanization temperature.

Then, the mechanical and dynamic properties of the optimum vulcanized mixtures are measured. Rheological properties

- Viscosity of raw mixtures

The Mooney consistency is measured on the compositions in the uncured state at 100 ° C. by means of a MV 2000 rheometer according to the NF ISO 289 standard.

The value of the torque read after 4 minutes after preheating for 1 minute (Mooney Large (1 + 4) at 100 ° C) is shown in Table II. - Rheometry of the compositions

The measurements are performed on the compositions in the green state. The results relating to the rheology test, which is conducted at 150 ° C. using a Monsanto ODR rheometer according to the NF ISO 3417 standard, are shown in Table III.

According to this test, the composition to be tested is placed in the controlled test chamber at a temperature of 150 ° C. for 30 minutes, and the resistive torque opposed by the composition is measured at a low amplitude oscillation (3 °). a biconical rotor included in the test chamber, the composition completely filling the chamber in question.

From the curve of variation of the torque as a function of time, we determine:

the minimum torque (Cmin), which reflects the viscosity of the composition at the temperature considered;

- the maximum torque (Cmax);

- the delta-torque (ΔΟ = Cmax - Cmin);

the roasting time TS2 corresponding to the time required to have a rise of 2 points above the minimum torque at the temperature in question (150 ° C.) and reflecting the time during which it is possible to use the raw mixtures with this temperature without initiation of vulcanization (the mixture cures from TS2).

The results obtained are shown in Table II.

Table II

Compositions Witness Composition I

ML (1 + 4) - 100 ° C 90 91

Cmin (dN.m) 18.3 16.3

Cmax (dNm) 82.7 79.9

Delta torque (dN.m) 64.5 63.6

TS2 (min) 4.9 6.2 It is found that the composition resulting from the invention (composition I) has a satisfactory set of rheological properties, especially with respect to the control composition.

In particular, while having an acceptable viscosity, it has lower minimum and maximum torque values than those of the control composition, which reflects a greater ease of use of the mixture prepared.

And the composition resulting from the invention (composition I) has a satisfactory vulcanization kinetics (TS2), and without penalizing the viscosity of the raw mixture (illustrated in particular by the minimum torque).

Mechanical properties of vulcanisais

The measurements are carried out on the compositions vulcanized at the optimum (that is to say at a state of vulcanization corresponding to 98% of the complete vulcanization) for a temperature of 150 ° C.

The uniaxial tensile tests are carried out in accordance with the NF ISO 37 standard with type H2 specimens at a speed of 500 mm / min on an INSTRON 5564 device. The x% modules correspond to the stress measured at x% deformation. in tension and are expressed in MPa. It is possible to determine a reinforcement index (I.R.) which is equal to the ratio between the 300% deformation modulus and the 100% deformation modulus.

The measurement of loss of mass by abrasion is carried out according to the indications of standard NF ISO 4649, using a Zwick abraser where the cylindrical specimen is subjected to the action of an abrasive cloth of grains P60 and fixed on the surface of a drum rotating under a contact pressure of 10 N and a stroke of 40 m. The measured value is a volume of loss of substance (in mm ³ ) after wear by abrasion; the lower it is, the better the resistance to abrasion.

The measured properties are collated in Table III. Table III

It is found that the composition resulting from the invention (composition I) has a good compromise of mechanical properties compared to what is obtained with the control composition.

The composition I thus has relatively low 10% and 100% modules and a relatively high 300% modulus, hence a higher reinforcement index.

In addition, the composition I has a lower abrasion loss, that is to say a better resistance to abrasion, hence a gain in wear resistance, which is important in pneumatic application, in particular for heavy goods vehicles.

Dynamic properties of vulcanisais

Dynamic properties are measured on a viscoanalyzer (Metravib VA3000) according to ASTM D5992.

The values of loss factor (tan δ) and complex modulus in dynamic compression (E *) are recorded on vulcanized samples (cylindrical specimen of section 95 mm ² and height 14 mm). The sample is initially subjected to a predeformation of 10%, then to a sinusoidal deformation in alternating compression of +/- 2%. The measurements are carried out at 60 ° C. and at a frequency of 10 Hz.

The results, presented in Table IV, are thus the complex modulus in compression (E * - 60 ° C - 10 Hz) and the loss factor (tan δ - 60 ° C - 10 Hz). Table IV

The composition resulting from the invention (composition I) has good hysteretic properties at 60 ° C.

It can be seen from the results of Tables II to IV that the composition resulting from the invention (Composition I) has a good compromise of properties.

Claims

CLAIMS 1- Use in a composition of elastomer(s), comprising at least one isoprene elastomer: - of a precipitated silica, as a reinforcing inorganic filler, said precipitated silica being in the form of granules, having a porous distribution such that the pore volume constituted by pores whose diameter is between 175 and 275 A represents less than 60% of the pore volume constituted by pores with diameters less than or equal to 400 A, and having an aluminum content less than 0.5% in weight, preferably less than 0.35% by weight, with - 3-acryloxy-propyltriethoxysilane, as inorganic filler - elastomer coupling agent. 2- Use according to claim 1, characterized in that said precipitated silica has a porous distribution such that the porous volume constituted by the pores whose diameter is between 175 and 275 A represents more than 40%, in particular more than 45% , and less than 60%, of the pore volume constituted by pores with diameters less than or equal to 400 A. 3- Use according to one of claims 1 and 2, characterized in that said precipitated silica has a porous distribution such that the pore volume constituted by pores whose diameter is between 175 and 275 A represents 40%, in particular 45%, to 50% of the pore volume constituted by pores with diameters less than or equal to 400 A. 4- Use in a composition of elastomer(s), comprising at least one isoprene elastomer: - a precipitated silica, as reinforcing inorganic filler, said precipitated silica being in the form of granules and having a porous distribution such as the pore volume constituted by the pores whose diameter is between 175 and 275 A represents more than 50% and less than 60% of the pore volume constituted by pores with diameters less than or equal to 400 A, with - 3-acryloxy-propyltriethoxysilane, as coupling agent inorganic filler - elastomer. 5- Use according to one of claims 1 to 4, characterized in that said precipitated silica has: - a CTAB specific surface area of between 70 and 240 m2/g, in particular between 100 and 200 m2/g, for example between 130 and 180m2/g, and - a BET specific surface area of between 70 and 240 m2/g, in particular between 100 and 200 m2/g, for example between 150 and 185m2/g. 6- Use according to one of claims 1 to 5, characterized in that said precipitated silica has a median diameter (0so), after deagglomeration with ultrasound, less than 5 pm. 7- Use according to one of claims 1 to 6, characterized in that said precipitated silica has an ultrasonic deagglomeration factor (FD) greater than 4.5 ml. 8- Use according to one of claims 1 to 7, characterized in that the quantity used of 3-acryloxy-propyltriethoxysilane represents from 1 to 20%, in particular from 2 to 15%, relative to the quantity used of said silica rushed. 9 Use according to one of claims 1 to 8, characterized in that said precipitated silica and the 3-acryloxy-propyltriethoxysilane are mixed together beforehand. 10- Use according to one of claims 1 to 9, characterized in that said elastomer composition(s) further comprises at least one covering agent for said precipitated silica, optionally previously mixed with said precipitated silica and the 3- acryloxy-propyltriethoxysilane. 11- Use according to one of claims 1 to 9, characterized in that said elastomer(s) composition does not comprise another inorganic filler - elastomer coupling agent. 12- Use according to one of claims 1 to 11, in the absence of free radical initiator. 13- Use according to one of claims 1 to 12, characterized in that said composition of elastomer(s) does not comprise other elastomers than said isoprene elastomer(s). 14- Use according to one of claims 1 to 12, characterized in that said composition of elastomer(s) comprises at least one isoprene elastomer and at least one diene elastomer other than isoprene, the quantity of elastomer(s) isoprene(s) relative to the total quantity of elastomer(s) being preferably greater than 50% by weight. 15- Use according to one of claims 1 to 14, characterized in that said composition of elastomer(s) comprises at least one isoprene elastomer chosen from: (1) synthetic polyisoprenes obtained by homopolymerization of isoprene or methyl -2 butadiene-1,3; (2) synthetic polyisoprenes obtained by copolymerization of isoprene with one or more ethylenically unsaturated monomers chosen from: (2.1) conjugated diene monomers, other than isoprene, having 4 to 22 carbon atoms; (2.2) vinyl aromatic monomers having 8 to 20 carbon atoms; (2.3) vinyl nitrile monomers having 3 to 12 carbon atoms; (2.4) acrylic ester monomers derived from acrylic acid or methacrylic acid with alkanols having 1 to 12 carbon atoms; (2.5) a mixture of at least two of the aforementioned monomers (2.1) to (2.4); copolymer polyisoprenes containing between 20 and 99% by weight of isoprene units and between 80 and 1% by weight of diene units, aromatic vinyls, vinyl nitriles and/or acrylic esters; (3) natural rubber; (4) copolymers obtained by copolymerization of isobutene and isoprene, as well as halogenated versions of these copolymers; (5) a mixture of at least two of the aforementioned elastomers (1) to (4); (6) a mixture containing more than 50% by weight of the aforementioned elastomer (1) or (3) and less than 50% by weight of one or more diene elastomers other than isoprene. 16- Use according to claim 15, characterized in that said composition of elastomer(s) comprises at least one isoprene elastomer chosen from: (1) homopolymeric synthetic polyisoprenes; (2) synthetic polyisoprene copolymers consisting of poly(isoprene-butadiene), poly(isoprene-styrene) and poly(isoprene-butadiene-styrene); (3) natural rubber; (4) butyl rubber; (5) a mixture of at least two of the aforementioned elastomers (1) to (4); (6) a mixture containing more than 50% by weight of the aforementioned elastomer (1) or (3) and less than 50% by weight of diene elastomer other than isoprene consisting of polybutadiene, polychloroprene, poly(butadiene -styrene), poly(butadiene-acrylonitrile) or a terpolymer. 17- Use according to one of claims 1 to 16, characterized in that said composition of elastomer(s) comprises as isoprene elastomer at least natural rubber, preferably said composition of elastomer(s) comprising title of elastomer(s) only natural rubber. 18- Use according to one of claims 1 to 17, characterized in that said composition of elastomer(s) further comprises at least one compound chosen from vulcanization agents, vulcanization accelerators, vulcanization activators, carbon black, protective agents, plasticizing agents. 19- Use according to one of claims 1 to 18 in shoe soles, floor coverings, gas barriers, flame retardant materials, cable car rollers, household appliance joints, liquid pipe joints or gas, brake system seals, pipes, ducts, cables, engine mounts, conveyor belts, transmission belts or, preferably, tires. 20- Use according to one of claims 1 to 19 in a tire for heavy goods vehicles, in particular for trucks. 21- Composition of elastomer(s) comprising: - at least one isoprene elastomer, - at least one reinforcing inorganic filler, - at least one inorganic filler - elastomer coupling agent, characterized in that said inorganic filler - elastomer coupling agent is 3-acryloxy-propyltriethoxysilane, said reinforcing inorganic filler and said inorganic filler - elastomer coupling agent being as defined in one of claims 1 to 7. 22- Composition according to claim 21, characterized in that the quantity of 3-acryloxy-propyltriethoxysilane represents from 1 to 20%, in particular from 2 to 15%, relative to the quantity of said precipitated silica. 23- Composition according to one of claims 21 and 22, characterized in that said precipitated silica and the 3-acryloxy-propyltriethoxysilane are previously mixed together. 24- Composition according to one of claims 21 to 23, characterized in that said composition further comprises at least one covering agent for said precipitated silica, optionally previously mixed with said precipitated silica and 3-acryloxy-propyltriethoxysilane. 25- Composition according to one of claims 21 to 24, characterized in that said composition does not comprise another inorganic filler - elastomer coupling agent. 26- Composition according to one of claims 21 to 25, characterized in that said composition does not comprise a free radical initiator. 27- Composition according to one of claims 21 to 26, characterized in that said composition does not comprise any elastomers other than said isoprene elastomer(s). 28- Composition according to one of claims 21 to 26, characterized in that said composition comprises at least one isoprene elastomer and at least one diene elastomer other than isoprene, the quantity of isoprene elastomer(s) relative to to the total quantity of elastomer(s) being preferably greater than 50% by weight. 29- Composition according to one of claims 21 to 28, characterized in that said composition comprises at least one isoprene elastomer chosen from: (1) synthetic polyisoprenes obtained by homopolymerization of isoprene or 2-methyl-1-butadiene, 3; (2) synthetic polyisoprenes obtained by copolymerization of isoprene with one or more ethylenically unsaturated monomers chosen from: (2.1) conjugated diene monomers, other than isoprene, having 4 to 22 carbon atoms; (2.2) vinyl aromatic monomers having 8 to 20 carbon atoms; (2.3) vinyl nitrile monomers having 3 to 12 carbon atoms; (2.4) acrylic ester monomers derived from acrylic acid or methacrylic acid with alkanols having 1 to 12 carbon atoms; (2.5) a mixture of at least two of the aforementioned monomers (2.1) to (2.4); copolymer polyisoprenes containing between 20 and 99% by weight of isoprene units and between 80 and 1% by weight of diene units, aromatic vinyls, vinyl nitriles and/or acrylic esters; (3) natural rubber; (4) copolymers obtained by copolymerization of isobutene and isoprene, as well as halogenated versions of these copolymers; (5) a mixture of at least two of the aforementioned elastomers (1) to (4); (6) a mixture containing more than 50% by weight of the aforementioned elastomer (1) or (3) and less than 50% by weight of one or more diene elastomers other than isoprene. 30- Composition according to claim 29, characterized in that said composition comprises at least one isoprene elastomer chosen from:

(1) homopolymer synthetic polyisoprenes;

(2) synthetic polyisoprene copolymers consisting of poly(isoprene-butadiene), poly(isoprene-styrene) and poly(isoprene-butadiene-styrene);

(3) natural rubber;

(4) butyl rubber;

(5) a mixture of at least two of the aforementioned elastomers (1) to (4);

(6) a mixture containing more than 50% by weight of the aforementioned elastomer (1) or (3) and less than 50% by weight of diene elastomer other than isoprene consisting of polybutadiene, polychloroprene, poly(butadiene -styrene), poly(butadiene-acrylonitrile) or a terpolymer.

31- Composition according to one of claims 21 to 30, characterized in that said composition comprises, as isoprene elastomer, at least natural rubber, preferably said composition of elastomer(s) comprising, as elastomer(s), ) only natural rubber.

32- Composition according to one of claims 21 to 31, characterized in that said composition further comprises at least one compound chosen from vulcanization agents, vulcanization accelerators, vulcanization activators, carbon black, protective agents, anti-reversal agents, plasticizing agents. 33- Article comprising at least one composition according to one of claims 21 to 32, this article consisting of a shoe sole, a floor covering, a gas barrier, a flame retardant material, a cable car roller, a gasket household appliances, a liquid or gas pipe joint, a braking system joint, a pipe, a sheath, a cable, a motor support, a conveyor belt, a transmission belt or, preferably, a tire .

34- Tire according to claim 33 for heavy goods vehicles, in particular for trucks.