EP2956504A1

EP2956504A1 - Use of a polycarboxylic acid in the production of an elastomer composition

Info

Publication number: EP2956504A1
Application number: EP14705123.9A
Authority: EP
Inventors: Laurent Guy; Cédric BOIVIN; Soline DE CAYEUX; Philippe Jost
Original assignee: Rhodia Operations SAS
Current assignee: Rhodia Operations SAS
Priority date: 2013-02-14
Filing date: 2014-02-14
Publication date: 2015-12-23
Also published as: TW201444897A; MX2015010481A; FR3001971A1; WO2014125071A1; CA2900082A1; BR112015018969A2; US20150368428A1; TWI618739B; AR094793A1; KR20150119113A; FR3001971B1; CN105121537A; JP2016513154A

Abstract

The invention relates to the use of a polycarboxylic acid in the production of an elastomer composition comprising a precipitated silica as a reinforcing inorganic load and an elastomer, wherein said polycarboxylic acid and said precipitated silica are incorporated, independently from each other, into an elastomer. The invention also relates to elastomer compositions and to the method for the production thereof.

Description

USE OF A POLYCARBOXYLIC ACID DURING THE

PREPARATION OF ELASTOMERIC COMPOSITION (S)

The present invention relates to the use of polycarboxylic acid (s) in elastomer compositions (s) comprising at least one elastomer and a precipitated silica as reinforcing inorganic filler.

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

The object of the present invention is to propose in particular the use of a particular additive in elastomer compositions comprising a reinforcing filler, advantageously providing a reduction in the viscosity of these elastomer compositions. thus facilitating their implementation.

The present invention firstly proposes the use of polycarboxylic acid (s) during the preparation of elastomer composition (s) comprising at least one elastomer and a precipitated silica as reinforcing inorganic filler.

One of the objects of the invention is the use of at least one polycarboxylic acid in an elastomer composition (s) comprising at least one elastomer and a precipitated silica as reinforcing inorganic filler.

According to the invention, the precipitated silica and the polycarboxylic acid or acids are added independently of each other (optionally at the same time) to the elastomer (s).

In other words, according to the invention, a precipitated silica and one or more polycarboxylic acids not contained in / on said silica are added to the elastomer (s).

The invention amounts to using in the preparation of an elastomer composition (s), comprising at least one elastomer and a precipitated silica as reinforcing inorganic filler, at least one polycarboxylic acid, said precipitated silica and said polycarboxylic acid being incorporated , independently of one another, at least one elastomer. The invention also relates to a process for the preparation of an elastomer composition (s), in which a precipitated silica as a reinforcing inorganic filler and at least one polycarboxylic acid are incorporated, independently of one another, into at least one elastomer.

Advantageously, the invention relates to the use of at least one polycarboxylic acid in an elastomer composition (s) comprising at least one elastomer and a precipitated silica as reinforcing inorganic filler, for reducing the viscosity of said composition . According to the invention, the term "polycarboxylic acid" means polycarboxylic acids comprising at least two carboxylic acid functional groups. The term "carboxylic acid functional group" is taken here in its usual sense and refers to the -COOH functional group. The polycarboxylic acid employed according to the invention may have two, three, four or more carboxylic acid functional groups.

The polycarboxylic acid employed according to the invention may be a saturated or unsaturated polycarboxylic acid. In a preferred embodiment, the polycarboxylic acid employed is a saturated polycarboxylic acid.

According to the invention, the polycarboxylic acid is preferably chosen from dicarboxylic and tricarboxylic acids.

According to the invention, the polycarboxylic acid employed can be a linear or branched, saturated or unsaturated, preferably saturated, aliphatic polycarboxylic acid having from 2 to 20 carbon atoms or aromatic having from 7 to 20 carbon atoms. The carboxylic acid may optionally comprise hydroxyl groups and / or halogen atoms. The aliphatic polycarboxylic acid may optionally comprise heteroatoms on the main chain, for example N, S. Generally, the polycarboxylic acid used according to the invention is chosen from the group consisting of linear or branched, saturated or unsaturated aliphatic polycarboxylic acids. , preferably saturated, and aromatic polycarboxylic acids having from 2 to 16 carbon atoms.

Thus, advantageously, the polycarboxylic acid used according to the invention is chosen from the group consisting of linear or branched saturated aliphatic polycarboxylic acids having from 2 to 16 carbon atoms.

Among the aliphatic polycarboxylic acids, mention may be made of linear, saturated or unsaturated polycarboxylic acids, which are preferably saturated, having 2 to 14 carbon atoms, preferably 2 to 12 carbon atoms. The polycarboxylic acid employed may have 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms. Advantageously, the polycarboxylic acid employed may have 4, 5, 6, 7, 8, 9 or 10 carbon atoms, preferably 4, 5, 6, 7 or 8 carbon atoms. For example, the polycarboxylic acid employed may have 4, 5 or 6 carbon atoms.

In particular, non-limiting examples of linear aliphatic polycarboxylic acids used in the invention include the acids selected from the group consisting of oxalic acid, malonic acid, tricarballylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid.

Among the branched polycarboxylic acids that may be mentioned are methylsuccinic acid, ethylsuccinic acid, oxalosuccinic acid, methyladipic acid, methylglutamic acid and dimethylglutamic acid. By methylglutamic acid is meant both 2-methylglutaric acid and 3-methylglutaric acid and the mixture of these two isomers in all proportions. The term "2-methylglutaric acid" is used to indicate both the (S) and (R) forms of the compound and the racemic mixture.

Unsaturated polycarboxylic acids include maleic acid, fumaric acid, itaconic acid, muconic acid, aconitic acid, traumatic acid and glutaconic acid.

Among the polycarboxylic acids comprising hydroxyl groups, mention may be made of malic acid, citric acid, isocitric acid and tartaric acid.

Among the aromatic polycarboxylic acids, there may be mentioned phthalic acids, namely phthalic acid, orthophthalic acid, isophthalic acid, trimesic acid and trimellitic acid.

Preferably, the polycarboxylic acid employed according to the invention is selected from the group consisting of oxalic acid, malonic acid, tricarballylic acid, succinic acid, glutaric acid, adipic acid pheromic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutamic acid, dimethylglutamic acid, malic acid, citric acid, isocitric acid, tartaric acid.

Preferably, the dicarboxylic and tricarboxylic acids are chosen from adipic acid, succinic acid, ethylsuccinic acid, glutaric acid, methylglutamic acid, oxalic acid and citric acid. The polycarboxylic acid may also be selected from the group consisting of oxalic acid, malonic acid, carbarnalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutamic acid, dimethylglutamic acid, malic acid, citric acid, isocitric acid, tartaric acid. Preferably, the polycarboxylic acid may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutaric acid, dimethylglutamic acid, malic acid, citric acid, isocitric acid, tartaric acid. Very preferably, the polycarboxylic acids may be chosen from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid. , methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutaric acid, dimethylglutamic acid, malic acid, citric acid, tartaric acid.

In a first variant of the invention, a single polycarboxylic acid is used in the elastomer composition (s).

Preferably, the polycarboxylic acid used is succinic acid.

In a second variant, a mixture of polycarboxylic acids is used in the elastomer composition (s), said mixture comprising at least two polycarboxylic acids as defined above. The mixture may comprise two, three, four or more than four polycarboxylic acids.

Preferably, the polycarboxylic acids of the mixture are then chosen from adipic acid, succinic acid, ethylsuccinic acid, glutaric acid, methylglutaric acid, oxalic acid and citric acid.

According to the invention, the polycarboxylic acid mixture is preferably a mixture of dicarboxylic and / or tricarboxylic acids, especially a mixture of at least two, preferably at least three dicarboxylic and / or tricarboxylic acids, in particular a mixture of three dicarboxylic and / or tricarboxylic acids.

Preferably, the mixture of polycarboxylic acids is a mixture of dicarboxylic acids, especially a mixture of at least three dicarboxylic acids, in particular a mixture of three dicarboxylic acids. In Generally the mixture consists of three dicarboxylic acids, although impurities may be present in an amount not generally greater than 2.00% by weight of the total mixture. In a first preferred embodiment of this variant of the invention, the polycarboxylic acid mixture used in the invention comprises the following acids: adipic acid, glutaric acid and succinic acid. For example, the mixture of polycarboxylic acids comprises 15.00 to 35.00% by weight of adipic acid, 40.00 to 60.00% by weight of glutaric acid and 15.00 to 25.00% by weight. of succinic acid.

The mixture of polycarboxylic acids according to this first preferred embodiment of this variant of the invention may be derived from a process for the manufacture of adipic acid.

In a second preferred embodiment of this variant of the invention, the polycarboxylic acid mixture used in the invention comprises the following acids: methylglutaric acid, ethylsuccinic acid and adipic acid. For example, the mixture of polycarboxylic acids comprises 60.00 to 96.00% by weight of methylglutaric acid, 3.90 to 20.00% by weight of ethylsuccinic acid and 0.05 to 20.00% by weight. of adipic acid.

The mixture of polycarboxylic acids according to this second preferred embodiment of this variant of the invention may be derived from a process for the manufacture of adipic acid.

Advantageously, the mixture of polycarboxylic acids according to this second preferred embodiment can be obtained by acid hydrolysis, preferably by basic hydrolysis, of a mixture of methylglutaronithl, ethylsuccinonitrile and adiponitrile derived from the process for the manufacture of adiponitrile by hydrocyanation of butadiene, adiponitrile being an important intermediate for the synthesis of hexamethylenediamine.

A part or all of the polycarboxylic acid (s), in particular the dicarboxylic and / or tricarboxylic acids, used according to the invention may be in the form of anhydride, ester, alkali metal salt (carboxylate) (for example sodium or potassium), alkaline earth metal salt (carboxylate) (for example calcium) or ammonium salt (carboxylate).

Advantageously, some or all of the polycarboxylic acid (s) employed according to the invention may be in the form of a derivative chosen from anhydrides and salts (carboxylates). alkali metal (for example sodium or potassium), salts (carboxylates) of alkaline earth metal (for example calcium) or salts (carboxylates) of ammonium. For example, the mixture of polycarboxylic acids may be a mixture comprising:

methylglutamic acid (in particular from 60.00 to 96.00% by weight, for example from 90.00 to 95.50% by weight),

ethylsuccinic anhydride (in particular from 3.90 to 20.00% by weight, for example from 3.90 to 9.70% by weight),

adipic acid (in particular from 0.05 to 20.00% by weight, for example from 0.10 to 0.30% by weight).

The polycarboxylic acid mixture may also be a mixture comprising:

methylglutamic acid (in particular from 10.00 to 50.00% by weight, for example from 25.00 to 40.00% by weight),

methylglutamic anhydride (in particular from 40.00 to 80.00% by weight, for example from 55.00 to 70.00% by weight),

ethylsuccinic anhydride (in particular from 3.90 to 20.00% by weight, for example from 3.90 to 9.70%),

The mixtures used according to the invention may optionally contain impurities.

The polycarboxylic acid (s) can be used as an aqueous solution.

When used in solid form, the said polycarboxylic acid (s) may be in the form of a powder, or may be incorporated beforehand ( s) in a polymer matrix (masterbatch). 11 (s) can also be in supported form on a solid compatible with its structure: thus the polycarboxylic acid (s) in liquid form is (are) previously absorbed (s). ) on a powder.

According to the invention, the elastomer composition (s) in which is used (s) according to the invention or the polycarboxylic acids comprises a precipitated silica as reinforcing inorganic filler.

According to a preferred variant, the precipitated silica used according to the invention is a highly dispersible silica.

Highly dispersible silica is understood to mean, in particular, any silica having an ability to deagglomerate and to disperse in a matrix. very important polymer, 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 350 m ² / g.

This can be between 70 and 100 m ² / g, for example between 75 and

95 m ² / g.

However, preferably, the CTAB specific surface area of the precipitated silica according to the invention is between 100 and 350 m ² / g, in particular between 100 and 290 m ² / g, for example between 140 and 280 m ² / g . It may especially be between 140 and 200 m ² / g.

Likewise, preferably, the precipitated silica used according to the invention has a BET specific surface area of between 70 and 370 m ² / g.

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

However, preferably, the BET specific surface area of the precipitated silica used according to the invention is between 100 and 370 m ² / g, in particular between 100 and 310 m ² / g, for example between 140 and 300 m ² / boy Wut. It may especially be between 140 and 200 m ² / g.

The BET surface area is determined according to the method of BRUNAUER - EMMET - TELLER described in "The Journal of the American Chemical Society", Vol. 60, page 309, February 1938 and corresponding to standard NF ISO 5794-1 appendix D (June 2010). The CTAB specific surface is the external surface, which can be determined according to standard NF ISO 5794-1 appendix G (June 2010).

The dispersibility (and disagglomeration) ability of the silica used according to the invention can be assessed by means of the specific deagglomeration test below.

A granulometric measurement (by laser diffraction) is carried out on a silica suspension previously deagglomerated by ultra-sonification; the ability of the silica to deagglomerate (rupture of the objects from 0.1 to a few tens of microns) is thus measured. Ultrasonic deagglomeration is performed using a VIBRACELL BIOBLOCK (600 W) sonicator equipped with a 19 mm diameter probe. The particle size measurement is carried out by laser diffraction on a SYMPATEC HELIOS / BF granulometer (equipped with an R3 type optical lens (0.9 - 175 μιτι)), by implementing the Fraunhofer theory. 2 grams (+/- 0.1 gram) of silica are introduced into a beaker of 50 ml (height: 7.5 cm and diameter: 4.5 cm) and one completes to 50 grams by adding 48 grams ( +/- 0.1 gram) of permutated water. A 4% aqueous suspension of silica is thus obtained.

Then proceed with the deagglomeration under ultrasounds as follows: it presses the button "TIMER" of the sonifier and adjusts the time to 5 minutes and 30 seconds. The amplitude of the probe (corresponding to the nominal power) is adjusted to 80%, then the ultrasound probe is immersed for 5 centimeters in the silica suspension contained in the beaker. The ultrasonic probe is then ignited and the disagglomeration is carried out for 5 minutes and 30 seconds at 80% amplitude of the probe.

The particle size measurement is then carried out by introducing into the vat of the granulometer a volume V (expressed in ml) of the suspension, this volume V being such that one reaches on the granulometer 8% of optical density.

The median diameter 0 ₅ o, after deagglomeration with ultrasound, is such that

50% of the particles by volume have a size less than 0 ₅ o and 50% have a size greater than 0 ₅ o The value of the median diameter 0 ₅ o obtained is even lower than the silica has a ability to deagglomerate high.

The ratio (10 × V / optical density of the suspension detected by the granulometer) can also be determined, this optical density corresponding to the actual value detected by the granulometer during the introduction of the silica.

This ratio (disaggregation factor F _D ) is indicative of the rate of particles smaller than 0.1 μιτι which are not detected by the granulometer. This ratio is higher when the silica has a high deagglomeration ability.

In general, implementation precipitated silica according to the invention has a median diameter 0 ₅ o, after deagglomeration with ultrasound, of less than 5.0 μιτι, especially less than 4.5 μιτι, in particular at most 4 , 0 μιτι.

It usually has an ultrasonic deagglomeration factor F _D greater than 4.5 ml, especially greater than 5.5 ml, in particular greater than 9.0 ml.

The pH of the silica used according to the invention is generally between 6.0 and 7.5.

The pH is measured according to the following method derived from ISO 787/9

(pH of a 5% suspension in water):

Apparatus:

- calibrated pH meter (reading accuracy at ^1/100 ) - combined glass electrode

- 200 ml beaker

- 100 ml test tube

- precision balance 0.01 g.

Operating mode:

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

The physical state in which the precipitated silica to be used according to the invention may be any, that is to say that it may be in the form of substantially spherical beads (microbeads), powder or granules.

It can thus be in the form of substantially spherical balls of average size of at least 80 μm, preferably at least 150 μm, in particular between 150 and 300 μm, for example between 150 and 270 μm; this average size is determined according to standard NF X 1 1507 (December 1970) by dry sieving and determination of the diameter corresponding to a cumulative refusal of 50%.

It may also be in the form of a powder of average size of at least 3 μιτι, in particular of at least 10 μιτι, preferably of at least 15 μιτι. This is for example between 15 and 60 μιτι.

It may be in the form of granules (generally of substantially parallelepiped shape) of size of at least 1 mm, for example between 1 and 10 mm, especially along the axis of their largest dimension.

The precipitated silica implemented in the invention preferably has satisfactory dispersibility (dispersibility) in the elastomer compositions.

The precipitated silica implemented in the context of the invention as defined above can be obtained for example by a preparation process comprising a precipitation reaction of a silicate, in particular of an alkali metal silicate (silicate sodium, for example), with an acidifying agent (sulfuric acid for example). A suspension of precipitated silica is then obtained. Then, the precipitated silica obtained is separated, in particular by filtration, to obtain a filter cake, and dried, generally by atomization. The process for the preparation of precipitated silica may be arbitrary: in particular the addition of an acidifying agent to a silicate base stock or the simultaneous total or partial addition of acidifying agent and silicate to a base stock comprising water and silicate.

The precipitated silica used in the invention may be prepared for example by a process as described in patents EP0520862, EP0670813, EP0670814 and EP0901986.

The precipitated silica used in the invention may be a treated silica (for example "doped" with a cation such as aluminum).

It may be prepared for example by a process as described in patents EP0762992, EP0762993, EP0983966 and in applications EP1355856 and WO201 1/1 17400.

The precipitated silica employed in the invention may also be prepared for example by a process as described in EP0917519 and WO03 / 016215 and WO2009 / 1 12458.

As precipitated silica implemented according to the invention, it is possible to use a commercially available precipitated silica, in particular a commercially highly dispersible silica. Examples of commercial silicas that may be used include, among others, Zeosil 1 165MP, Zeosil 1 1 15MP, Zeosil Premium 200MP, Zeosil 1085GR, Zeosil 195HR, Zeosil HRS 1200MP, Ultrasil 5000GR, Ultrasil 7000GR, Ultrasil 9000GR, Hi-Sil EZ 160G-D, Hi-Sil EZ 150G, Hi-Sil HDP-320G, Hi-Sil 255CG-D, Zeopol 8755LS.

The elastomer composition (s) in which is used (s) according to the invention the polycarboxylic acid (s) comprises at least one elastomer (natural or synthetic).

According to the invention, the elastomer composition (s) used according to the invention comprises at least one elastomer 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) aromatic vinyl monomers having from 8 to 20 carbon atoms, such as, for example, styrene, ortho-, meta- or paramethylstyrene, "vinyl-toluene" commercial mixture, paratertiobutylstyrene, methoxystyrenes, chlorostyrenes, 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) polydienes obtained by homopolymerization of one of the abovementioned conjugated diene monomers (2.1), such as, for example, polybutadiene and polychloroprene;

(4) polydienes obtained by copolymerization of at least two of the abovementioned conjugated dienes (2.1) with one another or by copolymerization of one or more unsaturated monomers mentioned above (2.2), (2.3) and / or (2.4), for example poly (butadiene-styrene) and poly (butadiene-acrylonitrile);

(5) ternary copolymers obtained by copolymerization of ethylene, an α-olefin having from 3 to 6 carbon atoms with a non-conjugated diene monomer having 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, ethyldiene-norbornene, dicyclopentadiene (elastomer EPDM);

(6) natural rubber and epoxidized natural rubber;

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

(8) functionalized polymers associated with the abovementioned polymers (for example having polar groups during or at the end of the chain and capable of interacting with silica);

(9) a mixture of at least two of the aforementioned elastomers (1) to (8). Preferably, the elastomer composition (s) comprises at least one 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) homopolymeric synthetic polydienes consisting of polybutadiene and polychloroprene;

(4) polybutadiene styrene;

(5) ethylene-propylene-diene ternary copolymers (EPDM);

(6) natural rubber and epoxidized natural rubber;

(7) butyl rubber;

(9) a mixture of at least two of the aforementioned elastomers (1) to (8).

Even more preferably, the elastomer composition (s) comprises at least one elastomer chosen from:

(1) polyisoprene (IR), (2) poly (isoprene-butadiene) (BIR), poly (isoprene-styrene) (SIR), poly (isoprene-butadiene-styrene) (SBIR), (3) polybutadiene (BR), (4) poly (butadiene-styrene) (SBR, especially ESBR (emulsion) or SSBR (solution)), (5) ethylene-propylene-diene ternary copolymers (EPDM), (6) natural rubber (NR) and epoxidized natural rubber (ENR) and (8) their associated functionalized polymers (for example having polar groups during or at the end of the chain and capable of interacting with silica).

According to a very preferred variant of the invention, the elastomer composition (s) comprises, as elastomers, at least one mixture of polybutadiene-styrene and polybutadiene, in particular a mixture of polybutadiene-styrene. and polybutadiene.

According to a second very preferred variant of the invention, the elastomer composition (s) comprises, as elastomers, at least one mixture of polybutadiene-styrene and of natural rubber, in particular a mixture of polybutadiene- styrene) and natural rubber.

According to another very preferred variant of the invention, the elastomer composition (s) comprises as elastomer at least natural rubber, in particular 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 '- (dimethyl-1,3-butyl) -p-phenylenediamine), antireversions (such as for example hexamethylene-1,6-bis (thiosulfate), 1,3-bis (citraconimidomethyl) benzene), plasticizers.

It should be noted that the polycarboxylic acid (s) used according to the invention and as described in the foregoing disclosure may be mixed. prior to its use, at least one of the auxiliary additives usually employed in the field of elastomeric compositions. The elastomer compositions (s) used according to the invention can be vulcanized with sulfur (we then obtain vulcanizates) or crosslinked in particular with peroxides or other crosslinking systems (for example diamines or phenolic resins).

In general, the elastomer compositions (s) used according to the invention further comprise at least one coupling agent (silica / polymer) and / or at least one covering agent; they may also include, inter alia, an antioxidant.

Coupling agents that may be used as non-limiting examples include polysulphide silanes, called "symmetrical" or "asymmetrical" silanes; polysulfides (especially disulfides, trisulphides or tetrasulphides) of bis- (alkoxy (Ci-C) -alkyl (Ci-C) silyl-alkyl (CrC)), for example polysulfides of bis (3- (trimethoxysilyl) propyl) or polysulfides of bis (3- (triethoxysilyl) propyl), such as triethoxysilylpropyl tetrasulfide. Mention may also be made of monoethoxydimethylsilylpropyl tetrasulfide. Mention may also be made of silanes with thiol function, masked or otherwise.

The coupling agent may be grafted onto the elastomer beforehand. It can also be used in the free state (that is to say, not previously grafted) or grafted to the surface of the silica. The same is true of the possible collector.

The coupling agent may optionally be combined with a suitable "coupling activator", that is to say a compound which, when mixed with this coupling agent, increases the effectiveness of the coupling agent.

The proportion by weight of silica in the elastomer composition (s) can vary within a fairly wide range. It is usually 0.1 to 2 times by weight, in particular 0.2 to 1.5 times by weight, especially 0.2 to 0.8 times by weight (for example 0.3 to 0.7 times by weight). or 0.8 to 1, 2 times by weight (for example 0.9 to 1, 1 times by weight), the amount of the elastomer (s).

The silica used in the elastomer composition (s) used according to the invention may advantageously constitute all of the reinforcing inorganic filler, and even the whole of the reinforcing filler, of the elastomer composition (s).

However, to this silica used in the elastomer composition (s) according to the invention may be optionally associated with at least one other reinforcing filler, such as in particular a commercial highly dispersible silica such as, for example, Zeosil 1 165MP, Zeosil 1 15MP, a precipitated silica treated (for example "doped" with a cation such as aluminum); another reinforcing inorganic filler such as, for example, alumina, or even a reinforcing organic filler, especially carbon black (optionally covered with an inorganic layer, for example silica). The silica used in the elastomer composition (s) used according to the invention then preferably constitutes at least 50% or even at least 80% by weight of the totality of the reinforcing filler.

The use according to the invention of at least one polycarboxylic acid in an elastomer composition (s) as described in the previous discussion can be done more particularly in the context of the manufacture of shoe soles (preferably in presence of a coupling agent (silica / polymer), for example triethoxysilylpropyl tetrasulfide), floor coverings, gas barriers, flame retardant materials and also technical parts such as ropeway rollers, gaskets domestic appliances, liquid or gas line joints, brake system joints, hoses, ducts (including cable ducts), cables, motor mounts, battery separators, conveyor belts, transmission belts. Advantageously, the use according to the invention of at least one polycarboxylic acid in an elastomer composition (s) as described in the previous discussion can be done in the context of the manufacture of tires, in particular the treads of tires (in particular for light vehicles or for heavy goods vehicles (trucks, for example)).

The elastomer compositions (s) obtained according to the use according to the invention contain an effective amount of polycarboxylic acid (s).

More particularly, the elastomer compositions (s) resulting from the invention can comprise (parts by weight), per 100 parts of elastomer (s):

10 to 200 parts, in particular 20 to 150 parts, especially 30 to 120 parts, for example 35 to 110 parts, of precipitated silica as described above and used as reinforcing inorganic filler;

0.10 to 10.00 parts, preferably 0.15 to 5.00 parts, in particular 0.20 to 2.50 parts, especially 0.25 to 2.00, for example 0.25 to 1.00 parts of polycarboxylic acid (s).

As more specific examples, the elastomer compositions (s) resulting from the invention may comprise (parts by weight), per 100 parts of elastomer (s), 20 to 80 parts, especially 30 to 70 parts, or 80 to 120 parts, especially 90 to 110 parts, of precipitated silica as described above as reinforcing inorganic filler.

The elastomer compositions (s) resulting from the invention may further comprise (parts by weight), per 100 parts of elastomer (s), from 0.50 to 20.00 parts, in particular from 1.00 to 15, 00 parts, especially 1, 50 to 12.00 parts, for example 2.00 to 10.00 parts, of a coupling agent.

Advantageously, the use according to the present invention of polycarboxylic acid (s) in elastomer compositions may give the latter a reduction in the viscosity of said compositions facilitating their implementation while not not degrading their dynamic properties and their mechanical properties. It can thus make it possible to obtain a satisfactory compromise implementation / reinforcement / hysteretic properties.

The second subject of the present invention is the elastomer compositions described above, and therefore comprising at least one elastomer, a precipitated silica as reinforcing inorganic filler and at least one polycarboxylic acid, said polycarboxylic acid not being contained. in said precipitated silica. All that has been previously described in the context of the use of at least one carboxylic acid according to the first subject of the invention applies to these elastomer compositions (s) and to their process of preparation. 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 third subject of the present invention is a process for preparing the elastomer compositions according to the invention, said process comprising a step of mixing at least one elastomer, a precipitated silica and at least one polycarboxylic acid.

According to this method of preparation, the elastomer compositions according to the invention can 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 mechanical working phase (so-called productive) at temperatures generally below 110 ° C. in which the vulcanization system is introduced. 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 fourth object articles comprising at least one (in particular base) of said elastomer compositions (s) described above (in particular based on vulcanizates mentioned above), these articles consisting of shoe soles (preferably in the presence of a coupling agent (silica / polymer), for example triethoxysilylpropyl tetrasulfide), floor coverings, gas barriers, fire-retardant materials and also technical parts such as ropeway rollers, appliance seals, liquid or gas line seals, brake system seals, hoses, ducts (especially cable ducts), cables, motor mounts, separators battery, conveyor belts, transmission belts.

Advantageously, these articles comprising at least one (in particular base) of said elastomer compositions (s) described above consist of tires, in particular treads of tires (especially for light vehicles or for heavy goods vehicles ( trucks for example)). The following examples illustrate the invention without, however, limiting its scope.

EXAMPLES

EXAMPLE 1

In a Brabender type internal mixer (380 ml), the elastomeric compositions are prepared, the composition of which, expressed in part by weight per 100 parts of elastomers (phr), is shown in the table below:

Table I

(1) SBR solution (Buna VSL5228-2 from Lanxess) with 52 +/- 4% vinyl patterns; 28 +/- 2% of styrene units; Tg close to -20 ° C; 100 phr of extended SBR with 37.5 +/- 2.8% by weight of oil / BR (Buna CB 24 from Lanxess)

(2) Zeosil 1 165MP silica from Rhodia (Solvay)

(3) AGS acid mixture (adipic acid, glutaric acid, succinic acid from Rhodia - 26% by weight of adipic acid, 52% by weight of glutaric acid, 21% by weight of succinic acid, 1 % others)

(4) TESPT (LUVOMAXX TESPT from Lehvoss France sari)

(5) Vivatec 500 from H & R (6) N-1,3-dimethylbutyl-N-phenyl-para-phenylenediamine (Santoflex 6-PPD from Flexsys)

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

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

Process for the preparation of elastomeric compositions

The process for preparing the rubber 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 1 10 ° C. This phase allows the introduction of the vulcanization system.

The first phase is carried out by means of a mixing apparatus, internal mixer type Brabender brand (capacity of 380 ml). The filling factor is 0.6. The initial temperature and the speed of the rotors are fixed each time so as to reach mixing drop temperatures of about 140-160 ° C.

Decomposed here in two passes, the first phase allows to incorporate in a first pass, the elastomers and the reinforcing filler (fractional introduction) with the mixture of polycarboxylic acids, the coupling agent and stearic acid. For this pass, the duration 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 vulcanized mixtures at the optimum of firing (T98) are measured. Rheological properties

- Viscosity of raw mixtures The Mooney consistency is measured on the compositions in the raw state at

100 ° C using a MV 2000 rheometer as well as the determination of the Mooney stress relaxation rate 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. The test is carried out after preparation of the raw mixtures.

Table II

It is found that the composition of the present invention (Composition 1) allows a consequent reduction of the initial green viscosity, compared to the value of the reference composition (Control 1).

This type of behavior over time is very useful for those skilled in the art in the case of the implementation of rubber mixtures containing silica.

- 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 160 ° C. by means of an ODR MONSANTO rheometer according to the NF ISO 3417 standard, are shown in Table II.

According to this test, the composition to be tested is placed in the controlled test chamber at a temperature of 160 ° C. for 30 minutes, and the resistive torque, opposed by the composition, is measured at a low amplitude oscillation (3 °). ) of 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-pair (AC = Cmax - Cmin) which reflects the degree of crosslinking caused by the action of the crosslinking system and, if necessary, coupling agents;

the time T98 necessary to obtain a state of vulcanization corresponding to 98% of the complete vulcanization (this time is taken as the vulcanization optimum);

- and the roasting time TS2 corresponding to the time required to have a rise of 2 points above the minimum torque at the considered temperature (1 60 ° C) and which reflects the time during which it is possible to implement the raw mixtures at this temperature without initiation of vulcanization (the mixture cures from TS2).

The results obtained are shown in Table I. I.

The use of the composition of the present invention (Composition 1) makes it possible to reduce the minimum viscosity (sign of an improvement in the green viscosity) with respect to the reference (Control 1) without penalizing the vulcanization behavior.

- Mechanical properties of vulcanizates

The measurements are performed on the optimally vulcanized compositions (T98) for a temperature of 1 60 ° C.

The uni-axial tensile tests are carried out in accordance with the NF ISO 37 standard with specimens of type H2 at a speed of 500 mm / min on an INSTRON 5564. The modules x%, corresponding to the stress measured at x % tensile strain, and tensile strength are expressed in MPa; the elongation at break is expressed in%. It is possible to determine a reinforcement index (IR) which is equal to the ratio between the 300% deformation modulus and the 100% deformation modulus. The Shore A hardness measurement of the vulcanizates is carried out according to the indications of ASTM D 2240. The value given is measured for 15 seconds.

The measured properties are collated in Table IV.

Table IV

It is found that the composition resulting from the invention (Composition 1) has a compromise of mechanical properties close to that obtained with the control composition.

The use of the composition of the present invention (Composition 1) makes it possible to maintain a good level of reinforcement. Dynamic properties of vulcanizates

Dynamic properties are measured on a viscoanalyzer (Metravib VA3000) according to ASTM D 5992.

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 subjected initially to a pre-deformation of 10% then to a sinusoidal deformation in alternating compression of plus or minus 2%. The measurements are carried out at 60 ° C. and at a frequency of 10 Hz.

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

The values of the loss factor (tan δ) and elastic modulus amplitude in dynamic shear (ΔΘ ') are recorded on vulcanized samples (parallelepipedal specimen of section 8 mm ² and height 7 mm). The sample is subjected to sinusoidal deformation in double shear alternating at a temperature of 40 ° C and at a frequency of 10 Hz. The scanning processes in amplitude of deformations are carried out according to a round-trip cycle, ranging from 0.1% to 50% and then back from 50% to 0%. , 1%.

The results presented in Table V are derived from the return strain amplitude scan and relate to the maximum value of the loss factor (tan δ max return - 40 ° C - 10 Hz) as well as the amplitude of the elastic modulus (ΔΘ ' - 40 ° C - 10 Hz) between the values at 0.1% and 50% deformation (Payne effect).

Table V

The use of the composition of the present invention (Composition 1) makes it possible to obtain values that are close in terms of the maximum value of the loss and amplitude factor of the elastic modulus (or Payne effect) with respect to the reference (control). .

Examination of the different tables II to V shows that the composition according to the invention (Composition 1) makes it possible to obtain a satisfactory compromise implementation / reinforcement / hysteretic properties, in particular an improvement in the implementation (gain in viscosity), without deterioration of the mechanical and dynamic properties, compared to the reference (Control 1).

EXAMPLE 2 In a Haake-type internal mixer (380 ml), the elastomeric compositions are prepared, the composition, expressed in part by weight per 100 parts of elastomers (phr), is given in Table VI below: Table VI

(1) SBR solution (Bna VSL 5228-2 from Lanxess) with 52 +/- 4% vinyl patterns; 28 +/- 2% of styrene units; Tg close to -20 ° C; 100 phr of

Extended SBR with 37.5 +/- 2.8% by weight of CVR CV60 oil / natural rubber (supplied by Safic-Alcan)

(2) Zeosil 1 165MP silica from Rhodia (Solvay)

(3) Mixture of MGA acids (methylglutamic acid, ethylsuccinic acid and adipic acid from Rhodia - 94.8% by weight of methylglutaric acid, 4.9% by weight of ethylsuccinic anhydride, 0.2% by weight adipic acid, 0.1% other)

(4) TESPT (LUVOMAXX TESPT from Lehvoss France sari).

(5) N-1,3-dimethylbutyl-N-phenyl-para-phenylenediamine (Santoflex 6-PPD from FI exsys).

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

(7) N-cyclohexyl-2-benzothiazyl sulfenamide (Rhenogran CBS-80 from RheinChemie) Process for the preparation of elastomeric compositions

The process for preparing the rubber compositions is conducted in two successive preparation phases. A first phase consists in a thermomechanical work phase at high temperature. It is followed by second phase of mechanical work at temperatures below 1 10 ° C. This phase allows the introduction of the vulcanization system.

The first phase is carried out by means of a mixing apparatus, internal mixer type Haake brand (capacity of 380 ml). The filling factor is 0.6. The initial temperature and the speed of the rotors are fixed each time so as to reach mixing drop temperatures of about 140-160 ° C.

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

Then, the mechanical and dynamic properties of vulcanized mixtures at the optimum of firing (T98) 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 as well as the determination of the Mooney stress relaxation rate according to the NF ISO 289 standard.

The value of the torque read after 4 minutes after preheating for one minute (Mooney Large (1 + 4) - at 100 ° C) is shown in Table VII. The test is carried out after preparation of the raw mixtures. table VI I

It is found that the composition of the present invention (Composition 2) allows a consequent reduction of the initial green viscosity, compared to the reference (control 2).

- 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 160 ° C. by means of an ODR MONSANTO rheometer according to the NF ISO 3417 standard, are shown in Table VI.

According to this test, the composition to be tested is placed in the controlled test chamber at a temperature of 160 ° C. for 30 minutes, and the resistive torque opposite 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 maximum torque (Cmax);

- the delta-pair (AC = Cmax - Cmin) which reflects the degree of crosslinking caused by the action of the crosslinking system and, if necessary, coupling agents;

- and the toasting time TS2 corresponding to the time required to have a rise of 2 points above the minimum torque at the temperature considered (1 60 ° C) and which reflects the time during which it is possible to put The raw mixtures are used at this temperature without having initiation of the vulcanization (the mixture hardens from TS2).

The results obtained are shown in Table VIII.

Table VIII

The use of the composition of the present invention (Composition 2) makes it possible to reduce the minimum viscosity (sign of an improvement in the green viscosity) with respect to the reference (control 2) without penalizing the vulcanization behavior.

Mechanical properties of vulcanizates

The measurements are carried out on the optimally vulcanized compositions (T98) for a temperature of 160 ° C.

The uniaxial tensile tests are carried out in accordance with the NF ISO 37 standard with H2 specimens at a speed of 500 mm / min on an INSTRON 5564. The modules x%, corresponding to the stress measured at x% of deformation, and tensile strength are expressed in MPa; the elongation at break is expressed in%. 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 Shore A hardness measurement of the vulcanizates is carried out according to the indications of ASTM D 2240. The value given is measured at 15 seconds.

The measured properties are collated in Table IX. Your God IX

Compositions Witness 2 Composition 2

Module 10% (Mpa) 0.5 0.5

Module 100% (Mpa) 2.5 2,3

Module 300% (Mpa) 15.3 13.9

Breaking strength (Mpa) 20.4 20.0

Elongation at break (%) 374 386

I.R. 6.1 6.0

Shore hardness A-15s (pts) 56 55

It is found that the composition of the present invention (Composition 2) has a compromise of mechanical properties close to that obtained with the control composition.

The use of the composition of the present invention (Composition 2) makes it possible to maintain a reinforcement close to that of the reference (control 2).

Dynamic properties of vulcanizates

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 subjected initially to a predeformation of 10% then to a sinusoidal deformation in alternating compression of plus or minus 2%. The measurements are carried out at 60 ° C. and at a frequency of 10 Hz.

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

The values of the loss factor (tan δ) and elastic modulus amplitude in dynamic shear (ΔΘ ') are recorded on vulcanized samples (parallelepipedal specimen of section 8 mm ² and height 7 mm). The sample is subjected to an alternating double shear sinusoidal deformation at a temperature of 40 ° C. and at a frequency of 10 Hz. The amplitude-deformation sweep processes are carried out in a round-trip cycle, ranging from 0.degree. 1% to 50% then return 50% to 0.1%.

The results presented in Table X are derived from the amplitude sweep of the return strains and relate to the maximum value of the loss factor (tan δ max return - 40 ° C - 10 Hz) as well as the amplitude of the module. elastic (ΔΘ '- 40 ° C - 10 Hz) between the values at 0.1% and 50% deformation (Payne effect).

Paintings

The use of the composition of the present invention (Composition 2) makes it possible to obtain values that are close in terms of the maximum value of the loss factor and the amplitude of the elastic modulus or Payne effect relative to the reference (indicator 2).

Examination of the different tables VII to X shows that the composition in accordance with the invention (Composition 2) makes it possible to obtain a satisfactory compromise implementation / reinforcement / hysteretic properties, in particular an improvement in the implementation (gain in viscosity), without deterioration of mechanical and dynamic properties, compared to the control composition (control 2).

EXAMPLE 3

Table XI

(1) CV60 natural rubber CV60 (supplied by Safic-Alcan)

(2) Zeosil 1 165MP silica from Rhodia (Solvay)

(3) succinic acid (from Aldrich)

(4) TESPT (LUVOMAXX TESPT from Lehvoss France sari)

(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)

(8) Tetrabenzyl thiuram disulphide (Rhenogran TBzTD-70 from RhenChemie) Process for the preparation of elastomeric compositions

The first phase is carried out by means of a mixing apparatus, internal mixer type Brabender brand (capacity of 380 ml). The filling factor is 0.6. The initial temperature and the speed of the rotors are each time set so as to reach mixing fall temperatures of about 140-160 ° C.

Decomposed here in two passes, the first phase allows to incorporate in a first pass, the elastomers and the reinforcing filler (fractional introduction) with the polycarboxylic acid, the coupling agent and stearic acid. For this pass, the duration is between 4 and 10 minutes.

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

Rheological properties

- Viscosity of raw mixtures

The value of the torque read after 4 minutes after preheating for one minute (Mooney Large (1 +4) - at 100 ° C) is shown in Table XII. The test is carried out after preparation of the raw mixtures.

Table XII It is found that the composition of the present invention (Composition 3) allows a satisfactory reduction of the initial raw viscosity, relative to the value of the reference composition (control 3).

- 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 an ODR MONSANTO rheometer according to the NF ISO 3417 standard, are shown in Table XI.

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 opposite 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 maximum torque (Cmax);

- and the roasting time TS2 corresponding to the time required to have a rise of 2 points above the minimum torque at the temperature considered (1 50 ° C) and which reflects the time during which it is possible to implement the raw mixtures at this temperature without initiation of vulcanization (the mixture cures from TS2).

The results obtained are shown in Table XI I I. Table XIII

The use of the composition of the present invention (Composition 3) makes it possible to reduce the minimum viscosity (sign of an improvement in the green viscosity) with respect to the reference (control 3) without penalizing the vulcanization behavior.

- Mechanical properties of vulcanizates

The measurements are carried out on the optimally vulcanized compositions (T98) for a temperature of 150 ° C.

The uni-axial tensile tests are carried out in accordance with the NF ISO 37 standard with specimens of type H2 at a speed of 500 mm / min on an INSTRON 5564. The modules x%, corresponding to the stress measured at x % tensile strain, and tensile strength are expressed in MPa; the elongation at break is expressed in%. 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 measured properties are collated in Table XIV. Table XIV

It is found that the composition resulting from the invention (Composition 3) has a compromise of mechanical properties close to that obtained with the control composition.

The use of the composition of the present invention (Composition 3) makes it possible to maintain a good level of reinforcement with respect to the reference composition (control 3). Dynamic properties of vulcanizates

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

The values of the loss factor (tan δ) and elastic modulus amplitude in dynamic shear (ΔΘ ') are recorded on vulcanized samples (parallelepipedal specimen of section 8 mm ² and height 7 mm). The sample is subjected to an alternating double shear sinusoidal deformation at a temperature of 60 ° C. and at a frequency of 10 Hz. The amplitude-deformation sweep processes are carried out in a round-trip cycle, ranging from 0.degree. 1% to 50% then return 50% to 0.1%.

The results presented in Table XV are derived from the return strain amplitude scan and relate to the maximum value of the factor. of loss (tan δ max return - 60 ° C - 10 Hz) as well as the amplitude of the elastic modulus (ΔΘ '- 60 ° C - 10 Hz) between the values at 0.1% and 50% of deformation (Payne effect ).

Table XV

The use of the composition of the present invention (Composition 3) makes it possible to obtain values that are close in terms of the maximum value of the loss and amplitude factor of the elastic modulus (or Payne effect) with respect to the reference (indicator 3 ).

Examination of the different Tables XII to XV shows that the composition according to the invention (Composition 3) makes it possible to obtain a satisfactory compromise implementation / reinforcement / hysteretic properties, in particular an improvement in the implementation (gain in viscosity), without deterioration of the mechanical and dynamic properties, compared to the reference (control 3).

Claims

CLAIMS 1 - Use of at least one polycarboxylic acid during the preparation of an elastomer(s) composition comprising a precipitated silica as reinforcing inorganic filler and at least one elastomer, in which said polycarboxylic acid and said precipitated silica are incorporated , independently of each other, with at least one elastomer. 2- Use of at least one polycarboxylic acid in an elastomer(s) composition comprising at least one elastomer and a precipitated silica as reinforcing inorganic filler. 3- Use according to one of claims 1 and 2, to reduce the viscosity of said elastomer composition(s). 4- Composition of elastomer(s) comprising at least one elastomer, a precipitated silica as reinforcing filler and at least one polycarboxylic acid, said polycarboxylic acid not being contained in said precipitated silica. 5- Composition according to claim 4, characterized in that said polycarboxylic acid is chosen from dicarboxylic acids and tricarboxylic acids. 6- Composition according to one of claims 4 and 5, characterized in that said polycarboxylic acid is chosen from linear or branched, saturated or unsaturated, aliphatic polycarboxylic acids having from 2 to 20 carbon atoms or aromatic ones having from 7 to 20 carbon atoms. 7- Composition according to claim 5, characterized in that the dicarboxylic and tricarboxylic acids are chosen from adipic acid, succinic acid, ethylsuccinic acid, glutaric acid, methylglutac acid, oxalic acid, citric acid. 8- Composition according to one of claims 4 to 7, characterized in that said polycarboxylic acid is succinic acid. 9- Composition according to one of claims 4 to 7, characterized in that a mixture of polycarboxylic acids is used. 10- Composition according to claim 9, characterized in that the mixture of polycarboxylic acids is a mixture of dicarboxylic and/or tricarboxylic acids, in particular a mixture of at least three dicarboxylic and/or tricarboxylic acids, in particular a mixture of three dicarboxylic and/or tricarboxylic acids. 1 1 - Composition according to one of claims 9 and 10, characterized in that the mixture of polycarboxylic acids is a mixture of dicarboxylic acids, in particular a mixture of at least three dicarboxylic acids, in particular a mixture of three acids dicarboxylics. 12- Composition according to one of claims 9 to 1 1, characterized in that the mixture of polycarboxylic acids comprises the following acids: adipic acid, glutaric acid and succinic acid. 13- Composition according to claim 12, characterized in that the mixture of carboxylic acids comprises 15.00 to 35.00% by weight of adipic acid, 40.00 to 60.00% by weight of glutaric acid and 15, 00 to 25.00% by weight of succinic acid. 14- Composition according to one of claims 9 to 1 1, characterized in that the mixture of polycarboxylic acids comprises the following acids: methylglutaric acid, ethylsuccinic acid and adipic acid. 15- Composition according to claim 14, characterized in that the mixture of polycarboxylic acids comprises 60.00 to 96.00% by weight of methylglutaric acid, 3.90 to 20.00% by weight of ethylsuccinic acid and 0. 05 to 20.00% by weight of adipic acid. 16- Composition according to one of claims 9 to 15, characterized in that part or all of the polycarboxylic acids of the mixture used is in the form of anhydride, ester, salt (carboxylate) of alkali metal, alkaline earth metal salt (carboxylate) or ammonium salt (carboxylate). 17- Composition according to claim 16, characterized in that the mixture of polycarboxylic acids is a mixture comprising: - methylglutac acid, in particular in a proportion of 60.00 to 96.00% by weight, - ethylsuccinic anhydride, in particular in a proportion of 3.90 to 20.00% by weight, - adipic acid, in particular in a proportion of 0.05 to 20.00% by weight. 18- Composition according to claim 16, characterized in that the mixture of polycarboxylic acids is a mixture comprising: - methylglutac acid, in particular in a proportion of 10.00 to 50.00% by weight, - methylglutac anhydride, in particular in a proportion of 40.00 to 80.00% by weight, - ethylsuccinic anhydride, in particular in a proportion of 3.90 to 20.00% by weight, - acid adipic, in particular in a proportion of 0.05 to 20.00% by weight. 19- Composition according to one of claims 4 to 1 8, characterized in that said precipitated silica is a highly dispersible silica. 20- Composition according to one of claims 4 to 19, characterized in that said precipitated silica has a CTAB specific surface area of between 100 and 350 m2/g, in particular between 100 and 290 m2/g, in particular between 140 and 280 m2 /g, for example between 140 and 200 m2/g. 21 - Composition according to one of claims 4 to 20, characterized in that said precipitated silica has a BET specific surface area of between 100 and 370 m2/g, in particular between 100 and 310 m2/g, in particular between 140 and 300 m2 /g, for example between 140 and 200 m2/g. 22- Composition according to one of claims 4 to 21, characterized in that said composition of elastomer(s) comprises at least one elastomer chosen from:

(1) synthetic polyisoprenes obtained by homopolymerization of isoprene or 2-methylbutadiene-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 from 4 to 22 carbon atoms, such as for example 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro- 1,3-butadiene (or chloroprene), 1-phenyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene;

(2.2) aromatic vinyl monomers having 8 to 20 carbon atoms, such as for example styrene, ortho-, meta- or paramethylstyrene, the commercial mixture "vinyl-toluene", paratertiobutylstyrene, methoxystyrenes, chlorostyrenes , 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 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, d-methacrylate isobutyl;

(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, and consisting for example of poly(isoprene-butadiene ), poly(isoprene-styrene) and poly(isoprene-butadiene-styrene);

(3) polydienes obtained by homopolymerization of one of the aforementioned conjugated diene monomers (2.1), such as for example polybutadiene and polychloroprene;

(4) polydienes obtained by copolymerization of at least two of the aforementioned conjugated dienes (2.1) together or by copolymerization of one or more aforementioned unsaturated monomers (2.2), (2.3) and/or (2.4), such as for example poly(butadiene-styrene) and poly(butadiene-acrylonitrile);

(5) ternary copolymers obtained by copolymerization of ethylene, an a-olefin having 3 to 6 carbon atoms with an unconjugated diene monomer having 6 to 12 carbon atoms, such as for example elastomers obtained from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type such as in particular 1,4-hexadiene, ethyldiene-norbornene, dicyclopentadiene (EPDM elastomer); (6) natural rubber and epoxidized natural rubber;

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

(8) functionalized polymers associated with the aforementioned polymers;

(9) a mixture of at least two of the aforementioned elastomers (1) to (8).

23- Composition according to claim 22, characterized in that said composition of elastomer(s) comprises at least one elastomer chosen from: (1) homopolymer synthetic polyisoprenes;

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

(4) poly(butadiene-styrene);

(5) ternary ethylene-propylene-diene copolymers (EPDM);

(6) natural rubber and epoxidized natural rubber;

(7) butyl rubber;

(8) functionalized polymers associated with the aforementioned polymers;

(9) a mixture of at least two of the aforementioned elastomers (1) to (8).

24- Composition according to one of claims 22 and 23, characterized in that said elastomer composition(s) comprises at least one elastomer chosen from: polyisoprene, poly(isoprene-butadiene), poly(isoprene-styrene ), poly(isoprene-butadiene-styrene), polybutadiene, poly(butadiene-styrene), ternary ethylene-propylene-diene copolymers, natural rubber and epoxidized natural rubber and their associated functionalized polymers.

25- Composition according to one of claims 4 to 24, characterized in that said composition of elastomer(s) comprises as elastomer(s) at least one mixture of poly(butadiene-styrene) and polybutadiene, of preferably said composition of elastomer(s) comprising as elastomer(s) only a mixture of poly(butadiene-styrene) and polybutadiene. 26- Composition according to one of claims 4 to 24, characterized in that said composition of elastomer(s) comprises as elastomer(s) at least one mixture of poly(butadiene-styrene) and natural rubber, preferably said composition of elastomer(s) comprising as elastomer(s) only a mixture of poly(butadiene-styrene) and natural rubber.

27- Composition according to one of claims 4 to 24, characterized in that said elastomer(s) composition comprises as elastomer(s) at least natural rubber, preferably said elastomer(s) composition comprising as elastomer(s) only natural rubber.

28- Process for preparing an elastomer composition(s) according to one of claims 4 to 27, said process comprising a step of mixing at least one elastomer, a precipitated silica and at least one polycarboxylic acid.

29- Article comprising at least one composition according to one of claims 4 to 28, 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 battery separator, a conveyor belt, a transmission belt, or , preferably, a tire.

30- Pneumatic according to claim 29.