MXPA96003979A - Useful elastomeric composition as shoes for neumati - Google Patents

Abstract

The present invention is an: Elastomeric composition, vulcanizable with sulfur and / or sulfur-donors for the preparation of tire shoes, comprising: a) 100 parts of an elastomeric mixture comprising from 20 to 100% by an elastomer that is derives from the polymerization of a monovinylarene that is derived from the polymerization of a monovinylarene with a conjugated diene, the complement to 100 is selected from natural rubber, polybutadiene and other diolefin elastomers, b) from 10 to 150 parts of silica per 100 parts of ( a), c) from 0 to 150 parts of carbon black per 100 parts of a), characterized in that the elastomeric mixture (a) has a degree of epoxidation, defined by the number of moles of epoxidized double bonds with respect to the initial number of moles of diene double bonds, between 0.7 and 8.

Description

USEFUL ELASTOMERIC COMPOSITION AS TIRE PADS DESCRIPTION OF THE INVENTION The present invention relates to an elastomeric composition, partially epoxidized, useful for the preparation of tire shoes. The use of elastomers in the formulation of compounds for tires, requires the availability of vulcanized products, characterized by low hysteresis to reduce fuel consumption. To obtain good adhesion on wet surfaces and a good resistance to abrasion, it is also necessary that the above compounds be characterized by a suitable hysteresis dissipation at very high frequency voltages. To solve this problem, numerous studies have been carried out on the use of silica as a filler. These studies have given good results in the presence of polar elastomers, such as nitrile rubber or chloroprene, in the presence of which vulcanized products are obtained, characterized by their good tensile properties and wear resistance. On the contrary, the use of silica to reinforce slightly polar elastomers, such as copolymers of styrene-butadiene or polybutadiene, is hampered by the poor mechanical properties obtained from these elastomers. Attempts have been made to overcome these disadvantages by using, in the compounding phase, particular organosilanes containing sulfur, the so-called mercaptosilanes (EP-A-447,066). This solution is difficult because of the cost of these mercaptosilanes and has the disadvantage that special precautions are required for handling, in situ modification and vulcanization of the above compounds. It has now been found that an elastomer composition, which can be used for the production of tire shoes, can overcome the above disadvantages. In fact, the preparation of the elastomer composition of the present invention does not require particular mercaptosilanes. Accordingly, the present invention relates to an elastomer composition, vulcanizable with sulfur and / or sulfur donors, useful for the preparation of tire shoes, which comprises: a) 100 parts of an elastomeric mixture comprising at 100% by weight, preferably from 40 to 100% by weight, of an elastomer that is derived from the polymerization of a monovinylarene, with a conjugated diene, preferably a styrene-butadiene copolymer, the complement for 100, being selected of natural rubber, polybutadiene and other diolefin elastomers; b) from 10 to 150, preferably from 10 to 80, still preferably from 30 to 60 parts of silica per 100 parts of (a); c) from 0 to 150, preferably from 2 to 50, still preferably from 3 to 30 parts, of carbon black per 100 parts of (a); characterized in that the elastomeric mixture (a) has a degree of epoxidation, defined by the number of moles of epoxidized double bonds with respect to the initial number of moles of diene double bonds, between 0.7 and 8.0%, preferably between 1.5 and 6.0% The monovinylarene contains from 8 to 20 carbon atoms per molecule and can contain substituents, alkyl, cycloalkyl and aryl. Examples of these monovinylarene monomers are: styrene, α-methylstyrene, 3-methylstyrene, 4-n-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4- ( 4-phenyl-n-butyl) styrene, 1-vinylnaphthalene, 2-vinylnaphthalene. In the preferred embodiment, styrene is the preferred monovinylarene. The conjugated dienes useful for the preparation of the monovinylarene / conjugated diene elastomer contain from 4 to 12 carbon atoms per molecule, preferably from 4 to 8. Examples of these monomers are: 1,3-butadiene, chloroprene, isoprene, 2, 3-dimethyl-1,3-butadiene and the relative mixtures. Preferred are isoprene and 1,3-butadiene, 1,3-butadiene is more preferred. The weight ratio between vinylarene and conjugated diene is 10/90 to 40/60. The preferred conjugated monovinylarene-diene elastomer is the statistical styrene-butadiene copolymer (SBR). The monovinylarene-conjugated diene elastomer can be produced according to the well-known technique of active anionic polymerization, using organic alkali metal compounds and an inert solvent as initiators. Typical inert solvents are pentane, hexane, cyclohexane, benzene, etc.; mixtures of cyclohexane / hexane are preferred. The molecular weight of the above monovinylarene-diene statistical elastomer is between 100,000 and 1,000,000, preferably between 200,000 and 500,000. The viscosity of Mooney (ML1 + 4 at 100 ° C) is between 20 and 150, lower viscosities giving insufficient wear resistance and higher viscosities can cause processability problems.

As polymerization initiators of the conjugated diene or its copolymerization with monovinylarene, n-butyllithium, sec-butyllithium, t-butyllithium, 1,4-dithioxy-butane, the butyl- lithium and divinylbenzene, dilithioalkylene, phenyllithium, dilithium-stilbene, diisopropenylbenzene-dilithium, sodium-naphthalene, lithium-naphthalene, etc. In the case of copolymerization, a Lewis base can be used as a random agent and regulator of the diene microstructure in the copolymer. Typical examples of the above Lewis bases are ethers and tertiary amines, for example, dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol butyl ether, diethylene glycol dimethyl ether, triethylamine, pyridine, N-methylmorpholine, N, N, N '-N'-tetramethylethylenediamine, , 2-diperidinetane. The content of the monovinylarene bonded to the polymer is controlled by the amount of monomer present in the initial mixture, while the statistical distribution of the monovinylarene is obtained by the action of the aforementioned Lewis base, and is preferable for monovinylarene containing sequences. or more units, which is less than 10% of the total weight of monovinylarene. When 1,3-butadiene is used, the content of 1,2-butadiene units in the copolymer can be controlled by varying the polymerization temperature. In any case, the vinyl content in the copolymer, with reference to the butadiene part, must be within the range of 10 to 70%. The active polymer can be produced by feeding the monomers, the organic solvent, the initiator based on organometallic compounds of an alkali metal, and, if necessary, the Lewis base, to the reactor under an inert atmosphere. The addition can be carried out continuously or intermittently. The polymerization temperature is usually between -120 ° C. and + 150 ° C, preferably between -80 ° C and + 120 ° C, and the polymerization time is between 5 minutes and 24 hours, preferably between 10 minutes and 10 hours. The temperature can be maintained at a constant value within the indicated range or can be increased by means of a thermostatic fluid or the reaction can be carried out under adiabatic conditions and the polymerization process can be in a continuous or intermittent manner. The concentration of the monomers in the solvent is usually from 5 to 50% by weight, preferably from 10 to 35% by weight. In the formation of the active polymer, it is necessary to avoid the presence of deactivating compounds, for example, halogenated compounds, oxygen, water, carbon dioxide. At the end of the polymerization the reaction mixture is treated with polyfunctional coupling agents such as diphenyl or dialkyl carbonates, divinyl benzene, polyfunctional silicon derivatives (for example SiCl 4, trichloromethylsilane, trichlorophenylsilane), preferably with diphenyl or dialkyl carbonates. It is also possible to use extinguishing agents such as water, alcohols and generally substances that have labile hydrogens. The above SBR elastomer preferably has an interlaced styrene content of between 15 and 40% by weight, preferably between 20 and 30% by weight. According to the. present invention, the elastomeric mixture (a) must contain at least 20% by weight, preferably at least 40% by weight of the monovinylarene and conjugated diene elastomer, preferably, of styrene-butadiene statistical copolymer (SBR). As specified above, other elastomers may form part of the elastomeric mixture (a). Among these can be used polybutadiene, obtained by solution polymerization with catalysts of the Ziegler-Natta type, or with lithium catalysts, the polybutadiene has a vinyl content of between 0.5 and 80%.

In another embodiment of the present invention, the elastomeric mixture (a) consists of 20 to 50% by weight, preferably 30 to 40% by weight, of polybutadiene and 50 to 80%, preferably from 60 to 70% by weight of a styrene-butadiene statistical copolymer having an epoxide content of between 0.7 and 8.0%. As well as the polybutadienes, other elastomers, selected from natural rubber and homo- or diene copolymers, can form part of the elastomeric mixture (a). Among the latter, it is convenient to mention poly 1,4-cis isoprene, emulsion-polymerized styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, chloroprene, butadiene-acrylonitrile copolymer. With respect to the epoxide content in the elastomeric mixture (a), this should be between 0.7 and 8%, preferably between 1.5 and 6.0%. A smaller amount does not show significant advantages, while a higher percentage gives vulcanized products presenting poor tensile properties. In addition, an epoxide percentage higher than that specified, leads to an increase in the glass transition temperature of the polymer and therefore its use in tire compounds will be critical. The epoxy groups may be contained in any elastomer that forms part of the elastomeric mixture, but are preferably contained in the monovinylarene-conjugated diene elastomer, preferably in the statistical butadiene-styrene copolymer (SBR). Methods for epoxidizing these elastomers are well known to those skilled in the art.; for example, the epoxidized SBR preparation is described in US-A-4,341,672 and in Schulz, Rubber Chemistry & Technology, 5_5, 809 (1982). The amount of silica contained in the elastomeric composition is from 10 to 150 parts, preferably from 10 to 80 parts, more preferably from 30 to 60 parts, per 100 parts of elastomeric material (a). When the silica content is less than 10 parts, the reinforcing effect is insufficient and the wear resistance is poor; on the other hand, when it exceeds. at 150 parts by weight, processability and tensile properties are poor. In the preferred embodiment, the silica has a BET surface of between 100 and 250 m2 / g, a CTAB surface of between 100 and 250 m2 / g and an oil absorption (DBP) of between 150 and 250 ml / 100 g (see EP-A-157,703 for the determination of these measurements). In addition, from 0 to 150 parts of carbon black, preferably from 2 to 50, more preferably from 3 to 30, can be used as the reinforcing filler together with the silica.

The composition consisting of (a) + (b) + (c) can be vulcanized with the usual techniques that are well known to those skilled in the art, ie with sulfur and / or sulfur donors and acceleration systems ( for example, zinc oxide, stearic acid and accelerators). The vulcanized products thus obtained have a better wet grip and an improved hysteresis, as well as good tensile properties and good wear resistance. These properties make the above vulcanized products suitable for use as tire pads. The composition consisting of (a) + (b) + (c) can also be vulcanized in the presence, in addition to sulfur and / or sulfur donors, of silanes, hereinafter described. A further object of the present invention therefore relates to an elastomer composition for the production of tire shoes, which comprises, in addition to the components (a) to (c) specified above, from 0.2 to 15 phr, of 2-6 phr preference, of silane having the general formula (I) Y3-Si-CnH2nA, wherein Y is an alkoxide group having 1 to 4 carbon atoms or a chlorine atom, n is a whole number from 1 to 6; A is selected from -SmCnH2nSi-Y3, -X and SmZ, wherein X is selected from a group of nitroso, mercapto, amino, epoxy, vinyl, imide, chloro, Z is selected from 1 3 CH ^ CH3 I • C- • N. C- C = CH2 < II CH3 'II s o m is an integer from 1 to 6, and is as defined above. The addition of the component having the general formula (I) allows a better processability of the mixtures, even if the vulcanized product usually has properties similar to those of the vulcanized product without the chemicals having the general formula (I). Typical examples of the above silanes having the general formula (I) are: bis (2-triethoxysilylethyl) bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxypropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide ), 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2- ercaptoetiltrietoxisilano, 3-nitropropiltrimetoxisilano, 3-nitropropiltrietoxisilano, 3-chloropropyl, 3-cloropropiltrieto-xisilano, 2-chloroethyltriethoxysilane, N, N-3-trimethoxysilylpropyl dimetiltiocarbamoiltetrasulfuro of, 3-Trimethoxysilylpropyl benzothiazoltetrasulfide, 3-triethoxysilylpropyl methacrylate, and so on. Among the above compounds, bis (3-triethoxysilylpropyl) tetrasulfide, and 3-trimethoxysilylpropyl benzothiazolether sulphide are preferred. Among the components having the general formula (I) where three different Y are present, the following must be remembered: bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyl dimethoxymethylsilane, 3-nitropropyl dimethoxymethylsilane, 3-chloropropyldimethoxymethylsilane, N, -dimethyl thiocarbamoyltetrasulfide of dimethoxymethylsilylpropyl, and benzothiazolether sulphide of dimethoxymethylsilylpropyl. When desired, the above elastomeric composition of the present invention may also contain antioxidants, antiozonants, plasticizers, "processing aids", as well as fillers in the form of powders, such as calcium carbonate, silicates, fibrous fillers such as glass fiber, carbon fibers, etc. The mixtures are preferably prepared using internal mixers, for example of the Banbury type. It is also preferred to use two-step mixing cycles, the second of which for the addition of vulcanization systems, designed to obtain discharge temperatures between 130 and 170 ° C, preferably between 140 and 160 ° C. The vulcanization temperature is 130 to 180 ° C, preferably 140 to 170 ° C. The following examples provide a better illustration of the present invention. EXAMPLES The copolymerization reaction is carried out according to the active polymerization technique according to that described, for example, by M. Morton in "Anionic" Polymerization, Principies and Practice "(Academic Press, New York, 1983). As regards the epoxidation, the method of formation of permeation in situ is used, that is, by directly reacting hydrogen peroxide as an oxidant in the presence of a solution of an aliphatic acid, for example, formic acid, and acetic acid and the polymeric substrate. To maximize the performance of the epoxide and minimize the opening of the previously formed epoxy ring (hydroxylation reactions), it is preferred not to use drastic temperatures and conditions. The yield of the epoxide is obtained by analysis of R.M.N. made in the epoxidized polymer after coagulation and drying. The polymer thus isolated is dissolved in CDC13 and NMR-H and NMR-13C and the scrutiny is carried out in the above polymer solution, the ratio between the absorption of the protons with respect to the species -CH-CH- to 2.8 ppm (relative to internal norm Me4Si) and olefinic determine the epoxidation reaction yield (see Pinazzi et al., Bull. Soc. Chem. Franc, 1973, Vol. 59, page 1652. or RV Gemner and MA Golub, J. Pol. Soc, Polymer Chem. Ed. 1978, Vol.16, page 2985) The attribution of the percentage of epoxy groups bound to the polymer chain is confirmed by the presence in the 13 C-NMR spectrum of the signals at approximately 50 ppm (relative to the internal standard of Mß / iSi) characteristics of the species -CH-CH-. \ I or EXAMPLE 1 - Preparation and vulcanization of styrene-butadiene copolymers defined with the initials Al, A2 and A3.A mixture of 8000 grams of cyclohexane / anhydrous hexane in a ratio of 9/1 per weight, 64 grams of THF and subsequently 250 grams of styrene and 750 grams of butadiene, was fed to a stirred 20-liter reactor.

The temperature of the mass was brought to 40 ° C and 0.64 grams of lithium-n-butyl in cyclohexane were then fed. The start of the copolymerization was marked by the increase in temperature; when a maximum of about 80 ° C was reached, the solution was left under stirring for 5 minutes; then 0.6 grams of diphenyl carbonate was added in a hexane solution, and the mixture was allowed to stir for an additional 10 minutes until the coupling reaction of the active chains was complete. An aliquot (A2, 2,000 grams) of the polymer solution was transferred to another reactor, where it was subjected to the epoxidation reaction by the addition of formic acid and hydrogen peroxide with a molar ratio with respect to the double bonds of 15 / 15/100 The polymer solution, to which 21 grams of formic acid was added, was brought to a temperature of 70 ° C, and 58.6 grams of hydrogen peroxide (30% w / w) were added dropwise over a period of 5 hours. 30 minutes. Upon completion of the addition, the solution was maintained at about 70 ° C for a time of 1 to 5 hours. The epoxidation reaction was completely completed by removing both water and formic acid. ll.

Sodium acetate or sodium bicarbonate was then added in an amount sufficient to bring the pH to about 7. 2.9 grams of formic acid was added to a second aliquot (A3, 2,000 grams) of the polymer solution and the temperature was brought to approximately 70 ° C. 8.0 grams of hydrogen peroxide (at 30% by weight) were added and the same procedure as described above was adopted. 0.3 phr of BHT (2,6-diterbutylphenol) was added to the Al polyester solutions (this initial refers to the styrene-butadiene copolymer as such), A2 and A3, the mixture was coagulated with isopropyl alcohol and the coagulate was dried in an oven at 60 ° C for 4 hours. The characteristics of the polymers Al, A2 and A3 are shown in Table 1, where% Epox. it refers to the molar percentage of epoxidized double bonds with respect to the moles of the diene initial double bonds. GPC analyzes of the partially epoxidized polymers A2 and A3 give molecular weight distributions similar to those obtained from the non-epoxidized Al polymer. With respect to the low content of epoxy groups, sample A3 is not part of the present invention and is provided together with the relative mixture M1-A3, for comparison purposes. 37 TABLE 1 Copolymer Al A2 A3 Styrene% 25.1 25.0 25.0 Vinyl% 47.2 50.2 50.3 < Mw > 259,300 254,300 n.d. < Mn > 209,000 211,000 n.d. Tg -35 ° C -29 ° C -35 ° C% Epox. 0 5 0.58 ML1-4 100 ° C 58 67 54 Silica, carbon black, vulcanizing agents and other conventional additives were added to the control sample (Al) and the two copolymers A2 and A3 used a typical shoe formulation, provided below. 100 parts of styrene-butadiene copolymer (SSBR), 2-phrone-argon resin, VN3 53 phr silica, N330 carbon black, 4.25 phr, bis [3-triethoxysilylpropyl] tetrasulfide (Si69) 4.25 phr, ZnO 2.5 phr, stearic acid 1.0 phr, antioxidant 1.0 phr, microcrystalline wax 1.0 phr, aromatic oil 6.0 phr, CBS (N-cyclohexylbenzo-thiazolesulfenamide), 1 phr, DPG (diphenylguanidine) 1.5 phr, sulfur 1.8 phr. The compounds were produced using an internal laboratory mixer of the Banbury type and two-step mixing cycles: the first, to incorporate the charges and the Si69, was carried out in a Banbury mixer operating in order to obtain temperatures of discharge between 140 and 160 ° C; the second, for the addition of the vulcanization system, was carried out in an open mixer; The total mixing time is 9 minutes. The test samples for the determination of mechanical, dynamic and dynamic mechanical properties were vulcanized in a press at 151 ° C for 60 minutes. The properties of the vulcanized products are shown in Table 2. The tand measurements are particularly significant. In fact, it is generally known that the measurement of tand at a temperature of about 60-80 ° C and a resistance of between 2 and 5% is indicative of the rolling resistance of the vulcanized mixture, while a tand at about 0 ° C and low resistance (approximately 0.1%) can rather be correlated with wet grip. TABLE 2 Compound MI-Al M1-A2 M1-A3 100% Modules (MPa) 4.5 5.3 4.4 200% Modules (MPa) 8.9 11.3 9.3 Resistance to tension 16.3 17.5 18.3 Elongation at break (%) 332 282 349 Hardness (Shore A) 78 75 77 Loss of abrasion (mm3) 136 111 125 tanS 1Hz, 0.1% effort, 0 ° C 0.127 0.247 0.126 tana 1Hz, 5% effort, 60 ° C 0.138 0.097 0.142 tand 1Hz, 10% effort, 60 ° C 0.155 0.102 0.153 As can be seen from the data in Table 2, the epoxidized copolymer A2 (see compound M1-A2) produces a better interaction with the silica, compared to the corresponding non-epoxidized copolymer. The improvement in the interaction between rubber and filler is shown by the improvement in abrasion resistance and dynamic properties. In particular, the variation of tand with temperature and resistance is significant and indicates an improvement in wet grip and a resistance to winding (lower hysteresis). With respect to the degree of epoxidation useful to obtain an improvement in the dynamic properties, it can be observed how the properties of the compound M1-A3 are not significantly different from those of the compound without epoxy groups. EXAMPLE 2 - Preparation and Vulcanization of the Styrene-Butadiene Copolymers A4 and A5.

Using a system similar to that described in Example 1, the two styrene-butadiene copolymers were prepared, one non-epoxidized named A4 and the other epoxidized named A5 and derived from the former. The two copolymers A4 and A5 have the properties listed in Table 3. TABLE 3 Copolymer A4 A5 Styrene% 25.1 24.9 Vinyl% 63.5 64.9 < Mw > 246,800 239,400 < Mn > 191,000 180,000 Tg -21 ° C -20 ° C% Epox. 0 2.27 ML1-4 100 ° C 53 53 According to the procedure described in example 1, two other compounds were prepared with the two polymers, M1-A4 with the non-epoxidized copolymer A4 and M1-A5 with the partially epoxidized copolymer A5. The two compounds were vulcanized according to the procedure described above. The properties of the vulcanized products are shown in the Table.

TABLE 4 Compound M1-A4 M1-A5 100% Modules (Mpa) 4.2 4.4 200% Modules (MPa) 10.2 11.2 Resistance to tension (MPa) 17.0 17.5 Elongation at break (%) 294 282 Hardness (Shore A) 73 72 Loss due to abrasion (mm3) 153 146 tanS 1Hz, 0.1% effort, 0 ° C 0.432 0.648 tana 1Hz, 5% effort, 80 ° C 0.079 0.077 tan§ 110 Hz, 6% effort, 80 ° C 0.132 0.125 From the data in Table 4, it can be seen that the epoxidized copolymer A5 (compound M1-A5) has improved hysteretic properties (tand inferior to high frequency, high temperature and voltage conditions). In addition, the compound has an improved wet grip as shown by the value of tan d at 0 ° C. EXAMPLE 3 The Al and A2 copolymers described in Example 1 were formulated with silica and additives, but without ercaptosilane (compounds M2-A1 and M2-A2); the formulations are shown in Table 5, where, for comparison purposes, the above compound M1-A2 obtained from the epoxidized copolymer A2, but in the presence of mercaptosilane, is also indicated. In this table, bis [3-triethoxysilylpropyl] tetrasulfide is abbreviated as Si69. TABLE 5 Compound M1-A2 M2-A1 M2-A2 Component (phr) (phr) (phr) SSBR 100.0 100.0 100.0 Cumarona resin 2.0 2.0 2.0 Silica VN3 53.0 53.0 53.0 Black smoke N330 4.25 4.25 4.25 Si69 4.25 0.00 0.00 Zno 2.5 2.5 2.5 Stearic acid 1.0 1.0 1.0 Antioxidant 1.5 1.5 1.5 Wax 1.0 1.0 1 Aromatic oil 6.0 6.0 6.0 CBS 1.0 1.0 1.0 DPG 1.5 1.5 1.5 Sulfur 1.8 1.8 1.8 TOTAL PHR 179.8 175.55 175.55 The formulations indicated in Table 5 were then subjected to vulcanization under the conditions described in Example 1.

The properties of the vulcanized products are shown in Table 6. TABLE 6 Compound M1-A2 M2-A1 M2-A2 100% Modules (MPa) 5.3 2.4 4.3 200% Modules (MPa) 11.3 4.3 10.0 Resistance to tension (MPa) 17.5 18.4 15.0 Elongation at break (%) 282 634 310 Hardness (Shore A) 75 74 74 Loss due to abrasion ( mm3) 111 179 127 tanS 1Hz, 0.1% effort, 0 ° C 0 .247 0.109 0.250 tanS 1Hz, 5% effort, 60 ° C 0 .097 0.157 0.092 It is evident, from the data in Table 6, that, even without the addition of the formulation of a compatibilizing agent (i.e., the in situ silane modifier of the silica), the epoxidized copolymer A2 has an abrasion resistance. and improved hysteresis, the last one similar to that obtained with the compound vulcanized with silane.

EXAMPLE 4 - Preparation and Vulcanization of styrene-butadiene copolymers designated A6, A7 and A8. Using a procedure similar to that described in Example 1, three styrene-butadiene copolymers were prepared, the characteristics of which are shown in Table 7. TABLE 7 Copolymer A6 A7 A8 Styrene% 19.9 19.4 20.4 Vinyl% 67.3 71.1 74.3 < Mw > n.d. n.d. n.d. < Mn > n.d. n.d. n.d. Tg -24 ° C 19 ° C -15 ° C % Epox. 0 3.63 6.3 The above copolymers have been combined with and without mercaptosilanes according to the formulations indicated in Table 8. TABLE 8 Compound MI- (A6 -A7-A8) M2 (A6 -A7-A8) Component (phr) (phr) SSBR 100.0 100.0 Coumaron resin 2.0 2.0 Silica VN3 53.0 53.0 Black smoke N330 4.25 4.25 Si69 4.25 0.00 21.

Zno 2.5 2.5 Stearic acid 1.0 1.0 Antioxidant 1.5 1.5 Wax 1.0 1.0 Aromatic oil 6.0 6.0 CBS 1.0 1.0 DPG 1.5 1.5 Sulfur 1.8 1.8 TOTAL PHR 179.8 175.55 The formulations in Table 8 were vulcanized under the conditions described in Example 1. The properties of the vulcanized products are indicated in Table 9.

TABLE 9 Compound M1-A6 M2-A6 M1-A7 M2-A7 M1-A8 M2-A8 Vise, by Mooney 68 121 84 131 95 118 100% Modules 3.0 2.1 3.3 2.8 3.1 3.3 300% Modules 13.5 6.7 10.8 - - _ Resistance to tension 17.6 17.9 15.5 19.0 17.7 16.9 Alarg. to break 366 606 286 467 277 283 2b Hardness 69 70 70 71 72 72 Abrasion loss 138 191 134 160 128 127 From the data in Table 9 it can again be observed how epoxidation is capable by itself of improving the interaction of the polymer-silica, as shown by the improvement in abrasion resistance without mercaptosilane. However, the addition of mercaptosilane has the effect of improving processability, as shown by the Mooney viscosity of the compound. EXAMPLE 5 - Vulcanization of Mixtures with polybutadiene. Silica and conventional additives are added, except for mercaptosilane (abbreviated Si69), to the comparative copolymers Al and A4 and to the partially epoxidized copolymers A2 and A5 with polybutadiene, according to the formulations indicated in table 10. TABLE 10 Compound M3-A-1 M3 -A2 M3-A4 M3-A5 Component (phr) (phr) (phr) (phr) SSBR 65.0 65.0 65.0 65.0 Polibut. high cis 35.0 35.0 35.0 35.0 Cumarona resin 2.0 2.0 2.0 2.0 Silica VN3 53.0 53.0 53.0 53.0 Black smoke N330 4.25 4.25 4.25 4.25 Yes69 0.00 0.00 0.00 0.00 ZnO 2.5 2.5 2.5 2.5 Stearic acid 1.0 1.0 1.0 1.0 Antioxidant 1.5 1.5 1.5 1.5 Wax 1.0 1.0 1.0 1.0 Aromatic oil 6.0 6.0 6.0 6.0 CBS 1.0 1.0 1.0 1.0 DPG 1.5 1.5 1.5 1.5 Sulfur 1.8 1.8 1.8 1.8 TOTAL PHR 175.55 175.55 175.55 175.55 After vulcanization under the conditions indicated above, vulcanized products were obtained whose properties are shown in Table 11.

TABLE 11 Compound M3-A1 M3-A2 M3-A4 M3-A5 Vise, from Mooney 140 141 139 136 100% Modules (MPa) 2.0 3.6 2.0 2.9 300% Modules (MPa) 4.7 12.9 5.0 9.1 Resistance to tension (MPa) 17.8 14.2 17.7 18.3 Alarg. at break (%) 772 323 732 520 Hardness (Shore A) 75 77 74 77 Loss due to abrasion (mm3) 119 43 119 90 effort 0 ° C 0.099 0.147 0.120 0.137 effort 60 ° C 0.149 0.142 0.153 0.145 From the data in Table 11 it is evident that the two partially epoxidized polymers (A2 and A5), even without silane as a compatibilizing agent, produce compounds with a good interaction with silica, especially in mixtures which contain polybutadiene. Consequently, rolling resistance (lower hysteresis), abrasion resistance and wet grip are improved. Having described the invention as above, property is claimed as contained in the following:

Claims (16)

25 » CLAIMS

1. An elastomeric composition, vulcanizable with sulfur and / or sulfur donors useful for the preparation of tire shoes, comprising: a) 100 parts of an elastomeric mixture comprising from 20 to 100% by weight of an elastomer that is derived from the polymerization of a monovinylarene with a conjugated diene, the complement to 100 is selected from natural rubber, polybutadiene and other diolefin elastomers; b) from 10 to 150 parts of silica per 100 parts of (a); c) from 0 to 150 parts of carbon black per 100 parts of (a); characterized in that the elastomeric mixture (a) has a degree of epoxidation, defined by the number of moles of epoxidized double bonds with respect to the initial number of moles of diene double bonds, between 0.7 and 8.0%.

2. The elastomeric composition according to claim 1, characterized in that the weight ratio between vinylarene and the conjugated diene is from 10/90 to 40/60.

3. The elatomeric composition according to claim 1, characterized in that the elastomeric mixture (a) comprises from 40 to 100% by weight of a polymer that is derived from the polymerization of a monovinylarene with a conjugated diene.

4. The elastomeric composition according to claim 1, characterized in that the elastomer that is derived from the polymerization of a monovinylarene, with a conjugated dierium, is the statistical copolymer of styrene-butadiene (SBR).

5. The elastomeric composition according to claim 1, characterized in that the elastomeric mixture (a) has an epoxide content of between 1.5 and 6.0%.

6. The elastomeric composition according to claim 1, characterized in that the amount of silica is from 10 to 80 phr and the amount of carbon black is from 2 to 50 phr.

7. The elastomeric composition according to claim 6, characterized in that the amount of silica is from 30 to 60 phr and the amount of carbon black is from 3 to 30 phr.

8. The elastomeric composition according to claim 1, characterized in that the elastomeric mixture of (a) basically consists of the styrene-butadiene statistical copolymer having an epoxide content of between 0.7 and 8.0%.

9. The elastomeric composition according to claim 8, characterized in that the content of epoxides is from 1.5 to 6.0%.

10. The elastomeric composition according to claim 1, characterized in that the elastomeric mixture (a) consists of 20-50% by weight of polybutadiene and 50-80% by weight of the styrene-butadiene statistical copolymer having an epoxide content of between 0.7 and 8.0%.

11. The composition according to claim 10, characterized in that the elastomeric mixture (a) consists of 30-40% by weight of the polybutadiene and 60-70% by weight of the styrene-butadiene statistical copolymer.

12. The composition according to claim 10, characterized in that the styrene-butadiene statistical copolymer has an epoxide content between 1.5 and 6.0%.

13. An elastomeric composition vulcanizable with sulfur and / or sulfur donors useful for the production of tire shoes, is characterized in that it comprises: a) 100 parts of an elastomeric mixture comprising from 20 to 100% by weight preferably from 40 to 100% by weight of an elastomer that is derived from the polymerization of a monovinylarene with a conjugated diene, preferably a styrene-butadiene polymer, the complement at 100 is selected from natural rubber, polybutadiene and other diolefin elastomers; the elastomer (a) has an epoxidation degree of between 0.7 and 8%, preferably between 1.5 and 6.0%; b) from 10 to 150, preferably from 10 to 80, more preferably from 30 to 60 parts of silica per 100 parts of (a); c) from 0 to 150, preferably from 2 to 50, more preferably from 3 to 30 parts of carbon black per 100 parts of (a); d) from 0.2 to 15 phr of a coupling agent having the general formula (I) Y3-Si-Cn-H2nA, wherein Y is an alkoxide group having from 1 to 4 carbon atoms or a chlorine atom, n ee an integer from 1 to 6; A is selected from -SmCnH2nSi-Y3, -X and SmZ, wherein X is selected from a group of nitroso, mercapto, amino, epoxy, vinyl, imide, chlorine, Z is selected from m is an integer from 1 to 6, and is as defined above.

14. The composition according to claim 13, characterized in that the component (d) is in an amount of 2 to 6 phr.

15. The tire shoes obtained by the vulcanization of elastomeric compositions according to claims 1 to 14, with sulfur and / or sulfur donors in the presence of accelerators and vulcanization additives, at a temperature between 130 and 180 ° C. 3-1

16. The shoes according to claim 15, characterized in that the vulcanization is carried out at a temperature between 140 and 170 ° C.