Elastomeric composition and vulcanization accelerator used therein

Abstract

The present invention relates to a vulcanizable elastomeric composition comprising a secondary accelerator that may be used in combination with sulphenamide alone, completely avoiding the use of a guanidine. Moreover, said accelerator promotes dispersion of the silica in the compound and migrates with difficulty in the elastomeric composition itself. The invention also relates to the use of a vulcanization accelerator for said elastomeric composition, to the associated vulcanization process and to a tyre comprising same.

Claims

1. A vulcanizable elastomeric composition comprising: at least one diene elastomer, at least one reinforcing filler, at least one sulfur based vulcanization system, and at least one compound of formula (I) ##STR00025## wherein the compound of formula (I) is present in an amount ranging from 0.3 phr to 20 phr, and wherein X is chosen from: ##STR00026## wherein: R.sub.1, R.sub.2, R.sub.7, R.sub.8, R.sub.11, R.sub.16 and R.sub.19 are independently chosen from: hydrogen, C.sub.1-C.sub.22 linear or branched alkyl, C.sub.2-C.sub.22 linear or branched alkenyl or alkinyl, aryl, C.sub.1-C.sub.22 linear or branched alkyl-aryl, C.sub.2-C.sub.22 linear or branched alkenyl-aryl, C.sub.2-C.sub.22 linear or branched alkinyl-aryl, C.sub.2-C.sub.22 linear or branched acyl-alkyl, C.sub.3-C.sub.22 linear or branched acyl-alkenyl or acyl-alkinyl, acyl-aryl, acyl-alkyl-aryl with C.sub.2-C.sub.22 linear or branched acyl-alkyl, acyl-alkenyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkenyl, acyl-alkinyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkinyl, and heteroaryl; at least one of R.sub.3 and R.sub.4 and at least one of R.sub.5 and R.sub.6 is hydrogen; only one of R.sub.3 and R.sub.4 and only one of R.sub.5 and R.sub.6 are chosen from acyl, acyl-aryl, acyl-alkyl-aryl with C.sub.2-C.sub.22 linear or branched acyl-alkyl, acyl-alkenyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkenyl, and acyl-alkinyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkinyl; Z is chosen from: hydrogen, methyl, ethyl, and hydroxymethyl; R.sub.9 and R.sub.10 are independently chosen from: hydrogen, a C.sub.2-C.sub.22 linear or branched alkenyl group, a C.sub.2-C.sub.22 linear or branched alkylidene group, an aryl group, and an alkyl-aryl group with C.sub.1-C.sub.22 linear or branched alkyl, wherein: R.sub.9 and R.sub.10 are not simultaneously hydrogen; or R.sub.9 and R.sub.10 may form a ring, which may contain from 3 to 20 atoms and one or two heteroatoms selected from O or N, wherein: when the ring comprises one or two heteroatoms the total number of ring atoms is 5 or 6; when the ring contains two heteroatoms, the heteroatoms may be in position 1,2 or 1,3, when position 1 is the position nearest to the carbon atom of the imine group; or R.sub.9 and R.sub.10 may form polycycles formed by a number of carbon atoms which can range from 5 to 20, fused or spiro, with or without bridgehead atoms; R.sub.12 and R.sub.13 are independently chosen from: hydrogen, a C.sub.2-C.sub.22 linear or branched alkenyl group, a C.sub.2-C.sub.22 linear or branched alkylidene group, an aryl group, and an alkyl-aryl group with C.sub.1-C.sub.22 linear or branched alkyl, wherein: R.sub.12 and R.sub.13 are not simultaneously hydrogen; or R.sub.12 and R.sub.13 may form a ring, which may contain from 3 to 20 atoms and one or two heteroatoms selected from O or N, wherein: when the ring comprises one or two heteroatoms, the total number of ring atoms is 5 or 6; when the ring contains two heteroatoms, the heteroatoms may be in position 1,2 or 1,3, when position 1 is the position that is nearest to the carbon atom of the imine group; or R.sub.12 and R.sub.13 can form polycycles formed by a number of carbon atoms that can range from 5 to 20, fused or spiro, with or without bridgehead atoms; R.sub.14, R.sub.15, R.sub.17, and R.sub.18 are independently chosen from: hydrogen, C.sub.1-C.sub.22 linear or branched alkyl with no branch on C.sub.1, C.sub.2-C.sub.22 linear or branched alkenyl or alkinyl, alkyl-aryl with C.sub.1-C.sub.22 linear or branched alkyl with the aryl group not directly bound to the oxazolidine, alkenyl-aryl with C.sub.2-C.sub.22 linear or branched alkenyl with the aryl group not directly bound to the oxazolidine, alkinyl-aryl with C.sub.2-C.sub.22 linear or branched alkinyl with the aryl group not directly bound to the oxazolidine, C.sub.2-C.sub.22 linear or branched acyl-alkyl, and C.sub.3-C.sub.22 linear or branched acyl-alkenyl or acyl-alkinyl; or R.sub.14, R.sub.15, R.sub.17, and R.sub.18 may form cycles of 5 and 6 carbon atoms.

2. The composition according to claim 1, wherein R.sub.1 is hydrogen.

3. The composition according to claim 1, wherein X is: ##STR00027## R.sub.2 is chosen from: H, CH.sub.3, and CH.sub.2(CH.sub.2).sub.nCH.sub.3 with n from 0 to 16; R.sub.3 and R.sub.4 are hydrogen; and Z is chosen from: hydrogen, methyl, ethyl, and hydroxymethyl.

4. The composition according to claim 3, wherein n is from 0 to 9.

5. The composition according to claim 3, wherein R.sub.2 is hydrogen.

6. The composition according to claim 1, wherein X is: ##STR00028## R.sub.9 and R.sub.10 form fused polycyclic formed by a number of carbon atoms from 7 to 9; and R.sub.8 is chosen from: H, CH.sub.3, and CH.sub.2(CH.sub.2).sub.nCH.sub.3 with n from 0 to 16; or wherein R.sub.9 is H, R.sub.10 is —CH or —CH—C.sub.6H.sub.5 and R.sub.8 is chosen from: H, —CH.sub.3, and —CH.sub.2(CH.sub.2).sub.nCH.sub.3 with n from 0 to 16.

7. The composition according to claim 6, wherein n is from 0 to 9.

8. The composition according to claim 1, wherein X is: ##STR00029## R.sub.14 and R.sub.15 may be the same or different from each other and are chosen from: —CH.sub.3, —CH.sub.2CH.sub.3, —CH.sub.2CH.sub.2CH.sub.3, —CH(CH.sub.3).sub.2, and —CH.sub.2CH(CH.sub.3).sub.2; and R.sub.16 is chosen from: H, —CH.sub.3, and —CH.sub.2(CH.sub.2).sub.nCH.sub.3 with n from 0 to 16.

9. The composition according to claim 8, wherein n is from 0 to 9.

10. The composition according to claim 1, wherein the compound of formula (I) is present in the elastomeric composition in an amount ranging from 0.4 to 10 phr.

11. The composition according to claim 10, wherein the compound of formula (I) is present in the elastomeric composition in an amount ranging from 0.5 phr to 5 phr.

12. The composition according to claim 1, wherein the diene elastomer contains unsaturations in the main polymer chain and has a glass transition temperature (T.sub.g) lower than 20° C.

13. The composition according to claim 12, wherein the diene elastomer has a glass transition temperature (T.sub.g) ranging from 0 to −90° C.

14. The composition according to claim 1, wherein the diene elastomer is chosen from: poly (1,4-cis-isoprene), poly (3,4-isoprene), poly (butadiene), isoprene/isobutene halogenated copolymers, 1,3-butadiene/acrylonitrile copolymers, styrene/1,3-butadiene copolymers, styrene/isoprene/1,3-butadiene copolymers, styrene/1,3-butadiene/acrylonitrile copolymers, and mixtures thereof.

15. The composition according to claim 1, wherein the composition further comprises an elastomer of one or more mono-olefins, wherein the mono-olefins are chosen from ethylene and 1-olefins with from 3 to 12 carbon atoms.

16. The composition according to claim 15, wherein the elastomer of one or more mono-olefins contains a diene with from 4 to 20 carbon atoms.

17. The composition according to claim 16, wherein the diene is chosen from: 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, vinylnorbornene, and mixtures thereof.

18. The composition according to claim 16, wherein the diene is halogenated.

19. The composition according to claim 15, wherein the elastomer of one or more mono-olefins is chosen from: ethylene/propylene (EPR) copolymers or ethylene/propylene/diene (EPDM) copolymers, and poly (isobutene).

20. The composition according to claim 1, wherein the composition further comprises a primary accelerator chosen from triazoles, sulphenamides, and xanthogenates, and the primary accelerator is present in an amount ranging from 0.1 to 10 phr.

21. The composition according to claim 20, wherein the primary accelerator is present in an amount ranging from 0.5 to 5 phr.

22. The composition according to claim 1, wherein the reinforcing filler is chosen from: carbon black, silica, alumina, aluminosilicates, calcium carbonate, kaolin, and mixtures thereof; and is present in an amount ranging from 0.1 to 200 phr.

23. The composition according to claim 22, wherein the reinforcing filter is present in an amount ranging from 10 to 170 phr.

24. The composition according to claim 1, wherein the sulfur based vulcanization system comprises an amount of sulfur ranging from 0.5 to 10 phr.

25. The composition according to claim 24, wherein the sulfur based vulcanization system comprises an amount of sulfur ranging from 0.8 to 5 phr.

26. The composition according to claim 25, wherein the sulfur based vulcanization system comprises an amount of sulfur ranging from 1 phr to 3 phr.

27. A process for the vulcanization of elastomeric compositions comprising: mixing at least one diene elastomer, at least one sulfur based vulcanization system, at least one reinforcing filler, optionally at least one accelerator chosen from: thiazoles, sulphenamides and xanthogenates, in an amount ranging from 0.1 to 10 phr, and at least one accelerator of formula (I) ##STR00030## to form a blend, wherein the compound of formula (I) is present in an amount from 0.3 phr to 20 phr, and wherein X is chosen from: ##STR00031## wherein: R.sub.1, R.sub.2, R.sub.7, R.sub.8, R.sub.11, R.sub.16 and R.sub.19 are independently chosen from: hydrogen, C.sub.1-C.sub.22 linear or branched alkyl, C.sub.2-C.sub.22 linear or branched alkenyl or alkinyl, aryl, C.sub.1-C.sub.22 linear or branched alkyl-aryl, C.sub.2-C.sub.22 linear or branched alkenyl-aryl, C.sub.2-C.sub.22 linear or branched alkinyl-aryl, C.sub.2-C.sub.22 linear or branched acyl-alkyl, C.sub.3-C.sub.22 linear or branched acyl-alkenyl or acyl-alkinyl, acyl-aryl, acyl-alkyl-aryl with C.sub.2-C.sub.22 linear or branched acyl-alkyl, acyl-alkenyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkenyl, acyl-alkinyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkinyl, and heteroaryl; at least one of R.sub.3 and R.sub.4 and at least one of R.sub.5 and R.sub.6 is hydrogen; only one of R.sub.3 and R.sub.4 and only one of R.sub.5 and R.sub.6 are chosen from acyl, acyl-aryl, acyl-alkyl-aryl with C.sub.2-C.sub.22 linear or branched acyl-alkyl, acyl-alkenyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkenyl, and acyl-alkinyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkinyl; Z is chosen from: hydrogen, methyl, ethyl, and hydroxymethyl; R.sub.9 and R.sub.10 are independently chosen from: hydrogen, a C.sub.2-C.sub.22 linear or branched alkenyl group, a C.sub.2-C.sub.22 linear or branched alkylidene group, an aryl group, and an alkyl-aryl group with C.sub.1-C.sub.22 linear or branched alkyl, wherein: R.sub.9 and R.sub.10 are not simultaneously hydrogen; or R.sub.9 and R.sub.10 may form a ring, which may contain from 3 to 20 atoms and one or two heteroatoms selected from 0 or N, wherein: when the ring comprises one or two heteroatoms the total number of ring atoms is 5 or 6; when the ring contains two heteroatoms, the heteroatoms may be in position 1,2 or 1,3, when position 1 is the position nearest to the carbon atom of the imine group; or R.sub.9 and R.sub.10 may form polycycles formed by a number of carbon atoms which can range from 5 to 20, fused or spiro, with or without bridgehead atoms; R.sub.12 and R.sub.13 are independently chosen from: hydrogen, a C.sub.2-C.sub.22 linear or branched alkenyl group, a C.sub.2-C.sub.22 linear or branched alkylidene group, an aryl group, and an alkyl-aryl group with C.sub.1-C.sub.22 linear or branched alkyl, wherein: R.sub.12 and R.sub.13 are not simultaneously hydrogen; or R.sub.12 and R.sub.13 may form a ring, which may contain from 3 to 20 atoms and one or two heteroatoms selected from O or N, wherein: when the ring comprises one or two heteroatoms, the total number of ring atoms is 5 or 6; when the ring contains two heteroatoms, the heteroatoms may be in position 1,2 or 1,3, when position 1 is the position that is nearest to the carbon atom of the imine group; or R.sub.12 and R.sub.13 can form polycycles formed by a number of carbon atoms that can range from 5 to 20, fused or spiro, with or without bridgehead atoms; R.sub.14, R.sub.15, R.sub.17, and R.sub.18 are independently chosen from: hydrogen, C.sub.1-C.sub.22 linear or branched alkyl with no branch on C.sub.1, C.sub.2-C.sub.22 linear or branched alkenyl or alkinyl, alkyl-aryl with C.sub.1-C.sub.22 linear or branched alkyl with the aryl group not directly bound to the oxazolidine, alkenyl-aryl with C.sub.2-C.sub.22 linear or branched alkenyl with the aryl group not directly bound to the oxazolidine, alkinyl-aryl with C.sub.2-C.sub.22 linear or branched alkinyl with the aryl group not directly bound to the oxazolidine, C.sub.2-C.sub.22 linear or branched acyl-alkyl, and C.sub.3-C.sub.22 linear or branched acyl-alkenyl or acyl-alkinyl; or R.sub.14, R.sub.15, R.sub.17, and R.sub.18 may form cycles of 5 and 6 carbon atoms; and heating the blend to a pressure ranging from 5×10.sup.5 to 20×10.sup.5 Pa, and at a temperature ranging from 120 to 200° C., for a time ranging from 5 to 200 minutes.

28. The process according to claim 27, wherein the accelerator chosen from: thiazoles, sulphenamides, and xanthogenates, is present in an amount ranging from 0.5 to 5 phr.

29. The process according to claim 27, wherein the pressure ranges from 13×10.sup.5 to 18×10.sup.5 Pa.

30. The process according to claim 27, wherein the temperature ranges from 140 to 180° C.

31. The process according to claim 27, wherein the time ranges from 10 to 40 minutes.

32. A tyre comprising at least one semi-finished product comprising a vulcanizable elastomeric composition comprising: at least one diene elastomer, at least one reinforcing filler, at least one sulfur based vulcanization system, and at least one compound of formula (I) ##STR00032## wherein the compound of formula (I) is present in an amount ranging from 0.3 phr to 20 phr, and wherein X is chosen from: ##STR00033## wherein: R.sub.1, R.sub.2, R.sub.7, R.sub.8, R.sub.11, R.sub.16 and R.sub.19 are independently chosen from: hydrogen, C.sub.1-C.sub.22 linear or branched alkyl, C.sub.2-C.sub.22 linear or branched alkenyl or alkinyl, aryl, C.sub.1-C.sub.22 linear or branched alkyl-aryl, C.sub.2-C.sub.22 linear or branched alkenyl-aryl, C.sub.2-C.sub.22 linear or branched alkinyl-aryl, C.sub.2-C.sub.22 linear or branched acyl-alkyl, C.sub.3-C.sub.22 linear or branched acyl-alkenyl or acyl-alkinyl, acyl-aryl, acyl-alkyl-aryl with C.sub.2-C.sub.22 linear or branched acyl-alkyl, acyl-alkenyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkenyl, acyl-alkinyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkinyl, and heteroaryl; at least one of R.sub.3 and R.sub.4 and at least one of R.sub.5 and R.sub.6 is hydrogen; only one of R.sub.3 and R.sub.4 and only one of R.sub.5 and R.sub.6 are chosen from acyl, acyl-aryl, acyl-alkyl-aryl with C.sub.2-C.sub.22 linear or branched acyl-alkyl, acyl-alkenyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkenyl, and acyl-alkinyl-aryl with C.sub.3-C.sub.22 linear or branched acyl-alkinyl; Z is chosen from: hydrogen, methyl, ethyl, and hydroxymethyl; R.sub.9 and R.sub.10 are independently chosen from: hydrogen, a C.sub.2-C.sub.22 linear or branched alkenyl group, a C.sub.2-C.sub.22 linear or branched alkylidene group, an aryl group, and an alkyl-aryl group with C.sub.1-C.sub.22 linear or branched alkyl, wherein: R.sub.9 and R.sub.10 are not simultaneously hydrogen; or R.sub.9 and R.sub.10 may form a ring, which may contain from 3 to 20 atoms and one or two heteroatoms selected from O or N, wherein: when the ring comprises one or two heteroatoms the total number of ring atoms is 5 or 6; when the ring contains two heteroatoms, the heteroatoms may be in position 1,2 or 1,3, when position 1 is the position nearest to the carbon atom of the imine group; or R.sub.9 and R.sub.10 may form polycycles formed by a number of carbon atoms which can range from 5 to 20, fused or spiro, with or without bridgehead atoms; R.sub.12 and R.sub.13 are independently chosen from: hydrogen, a C.sub.2-C.sub.22 linear or branched alkenyl group, a C.sub.2-C.sub.22 linear or branched alkylidene group, an aryl group, and an alkyl-aryl group with C.sub.1-C.sub.22 linear or branched alkyl, wherein: R.sub.12 and R.sub.13 are not simultaneously hydrogen; or R.sub.12 and R.sub.13 may form a ring, which may contain from 3 to 20 atoms and one or two heteroatoms selected from O or N, wherein: when the ring comprises one or two heteroatoms, the total number of ring atoms is 5 or 6; when the ring contains two heteroatoms, the heteroatoms may be in position 1,2 or 1,3, when position 1 is the position that is nearest to the carbon atom of the imine group; or R.sub.12 and R.sub.13 can form polycycles formed by a number of carbon atoms that can range from 5 to 20, fused or spiro, with or without bridgehead atoms; R.sub.14, R.sub.15, R.sub.17, and R.sub.18 are independently chosen from: hydrogen, C.sub.1-C.sub.22 linear or branched alkyl with no branch on C.sub.1, C.sub.2-C.sub.22 linear or branched alkenyl or alkinyl, alkyl-aryl with C.sub.1-C.sub.22 linear or branched alkyl with the aryl group not directly bound to the oxazolidine, alkenyl-aryl with C.sub.2-C.sub.22 linear or branched alkenyl with the aryl group not directly bound to the oxazolidine, alkinyl-aryl with C.sub.2-C.sub.22 linear or branched alkinyl with the aryl group not directly bound to the oxazolidine, C.sub.2-C.sub.22 linear or branched acyl-alkyl, and C.sub.3-C.sub.22 linear or branched acyl-alkenyl or acyl-alkinyl; or R.sub.14, R.sub.15, R.sub.17, and R.sub.18 may form cycles of 5 and 6 carbon atoms.

33. The tyre according to claim 32, wherein at least one semi-finished product is a tread band.

34. The tyre according to claim 32, wherein the reinforcing filler comprises silica.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Features and advantages will become clearer from the description of embodiments that are preferred, but not exclusive, according to the present invention, illustrated as examples in the appended drawings, in which:

(2) FIG. 1 shows the vulcanization curve for the elastomeric compositions from Examples 8, 9, 10 in Table 1.

(3) FIG. 2 shows the vulcanization curve for the elastomeric compositions from examples 8, 9, 11, 12 in Table 1.

(4) FIG. 3 shows the vulcanization curve for the elastomeric compositions from examples 8, 9, 13, 14, 15 in Table 1.

(5) FIG. 4 shows the dynamic modulus G′ as a function of the amplitude of the strain for the elastomeric compositions from examples 8, 9, 10 in Table 1.

(6) FIG. 5 shows the dynamic modulus G′ as a function of the amplitude of the strain for the elastomeric compositions from examples 8, 9, 11, 12 in Table 1.

(7) FIG. 6 shows the dynamic modulus G′ as a function of the amplitude of the strain for the elastomeric compositions from Examples 8, 9, 13, 14, 15 in Table 1.

(8) FIG. 7 shows schematically a part of a tyre for vehicle wheels.

(9) The vulcanizable elastomeric composition according to the invention may be used advantageously in the production of tyres for vehicle wheels. For the purposes of the present invention, “tyre” means indifferently a finished tyre (i.e. a moulded and vulcanized tyre) or a green tyre (i.e. an assembly of semi-finished products in the green state, which at the end of the building step is ready for the step of moulding and vulcanization). In particular, the vulcanizable elastomeric composition according to the invention may be used for preparing one or more semi-finished products to be assembled into the green tyre, for example tyre tread, sidewalls, an optional cushion, chafer strips or elastomer fillers, carcass, belts etc. At the end of building, the green tyre comprising one or more semi-finished products predisposed using the elastomeric composition according to the invention is moulded and vulcanized to obtain a finished tyre.

(10) In an especially preferred embodiment, the vulcanizable elastomeric composition according to the invention may be used for making the tyre tread, and in particular when the elastomeric composition comprises silica-based reinforcing filler.

(11) Referring to FIG. 7, for simplicity only part of the tyre is shown, the remainder that is not shown being identical and arranged symmetrically with respect to the radial direction.

(12) Reference 1 in FIG. 7 indicates a tyre for vehicle wheels, which generally comprises a carcass structure 2 comprising at least one carcass ply 3 having respectively opposite terminal edges engaged in respective annular anchoring structures 4, optionally together with elastomeric fillers 4a, integrated in zones 5, usually identified with the name “beads”.

(13) The carcass structure 2 has an associated belt structure 6 comprising one or more belt layers 6a, 6b arranged in radial superposition with respect to one another and relative to the carcass ply 3, having reinforcing cords, typically metallic. These reinforcing cords may have a crossed orientation relative to a circumferential direction of development of the tyre 1. “Circumferential” direction means a direction generally in the direction of rotation of the tyre, or else slightly inclined relative to the direction of rotation of the tyre.

(14) A tyre tread 7 made of elastomer compound, like other semi-finished constituents of the tyre 1, is applied in a radially outer position to the belt structure 6.

(15) On the lateral surfaces of the carcass structure 2, each extending from one of the lateral edges of the tyre tread 7 until flush with the respective annular structure for anchoring the beads 5, moreover, respective sidewalls 8 made of elastomer compound are applied in an axially outer position.

(16) A radially inner surface of the tyre 1 is moreover preferably coated internally with a layer of elastomeric material that is substantially impermeable to air, the so-called liner 9.

(17) The belt structure 6 further comprises at least one radially outer reinforcing layer 6c relative to the belt layers 6a, 6b. The radially outer reinforcing layer 6c comprises textile or metal cords, arranged at a substantially zero angle relative to the direction of circumferential development of the tyre and embedded in the elastomeric material. Preferably, the cords are arranged substantially parallel and side by side so as to form a plurality of coils. These coils are substantially oriented in the circumferential direction (typically at an angle between 0° and 5°), this direction usually being called “zero degrees” with reference to its disposition relative to the equatorial plane X-X of the tyre. “Equatorial plane” of the tyre means a plane perpendicular to the rotation axis of the tyre, which divides the tyre into two symmetrically identical parts.

(18) The building of tyre 1 as described above is carried out by assembling respective semi-finished products on a building drum, not shown, by means of at least one assembly device.

(19) At least a part of the components intended to form the carcass structure 2 of tyre 1 is constructed and/or assembled on the building drum. More particularly, the building drum is suitable for receiving firstly the optional liner 9, and then the carcass ply 3. Next, devices that are not shown engage coaxially, around each of the terminal edges, one of the annular anchoring structures 4, position an outer sleeve comprising the belt structure 6 and the tyre tread 7 in a position coaxially centred around the cylindrical carcass sleeve and form the carcass sleeve according to a toroidal configuration by radially stretching the carcass ply 3, in order to ensure that it is applied against a radially inner surface of the outer sleeve.

(20) Following building of the green tyre 1, a treatment of moulding and vulcanization is carried out, intended to provide structural stabilization of the tyre 1 by means of crosslinking of the elastomer compounds, as well as impressing a desired tread pattern on the tyre tread 7 and impressing optional distinctive graphical symbols on the sidewalls 8.

(21) The tests carried out for the production, crosslinking and characterization of the elastomeric compositions will next be described.

(22) Tests for production of the compounds.

(23) Production of the Compounds in Table 1 and Table 6.

(24) Production was carried out in an internal mixer of the Brabender® type with a mixing chamber having a volume equal to 50 mL. The degree of filling of the mixing chamber was kept at 80%. The rubbers were fed into the mixer and masticated at 90° C. for 1 minute with the rotors rotating at 30 rpm. The filler was then added together with the silane, stearic acid and oil, and the composite material was mixed for 4 minutes, discharging it at the end of this period at a temperature of 135° C. After 16 hours this composite material was fed into the internal mixer, and mixed at 60° C. for 1 minute with the rotors rotating at 30 rpm. Then ZnO and 6PPD were added, mixing for a further 2 minutes and discharging the composite material at 120° C. The final step was carried out by loading sulphur, and accelerators containing sulphur and free from sulphur into the internal mixer. The composite was discharged at 90° C. after mixing lasting 2 minutes. The composite was finally homogenized by mixing in the roll mixer, maintained at 50° C., with one roll rotating at 38 rpm, and the other roll rotating at 30 rpm, with a 1-cm gap between the rolls.

(25) Production of the Compound in Table 9

(26) Mixing was carried out in three steps using an internal mixer with tangential rotors (Pomini PL 1.6): the polymers, fillers, silane, stearic acid, wax, oil, resin and TMQ were introduced in the first step; after mixing for 4-5 minutes, on reaching a temperature of 135° C.±5° C., the composition was discharged.

(27) After 12-24 hours, the second step was carried out, using the same mixer. ZnO, 6-PPD and the secondary accelerators according to the invention were introduced. Mixing was continued for about 3 minutes, until 125° C.±5° C. was reached, when the composition was discharged.

(28) After 12-24 hours, in the third step, carried out using the same mixer, TBBS, DPG, PVI and sulphur were introduced. Mixing took about 2 minutes, until 95° C.±5° C. was reached, when the composition was discharged.

(29) Production of the Compound in Table 14

(30) Mixing was carried out in three steps using an internal mixer with tangential rotors (Pomini PL 1.6): the polymers, fillers, silane, stearic acid and wax were introduced in the first step; after mixing for 4-5 minutes, on reaching a temperature of 150° C.±5° C., the composition was discharged.

(31) After 12-24 hours, in the second step, carried out using the same mixer, ZnO, TMQ, 6-PPD, DPG and the secondary accelerators according to the invention were introduced. Mixing was continued for about 3 minutes, until 125° C.±5° C. was reached, when the composition was discharged.

(32) After 12-24 hours, in the third step, carried out using the same mixer, CBS, PVI and sulphur were introduced. Mixing took about 2 minutes, until 95° C.±5° C. was reached, when the composition was discharged.

(33) Crosslinking Test

(34) As described above, in order to allow the phenomenon of entropic elasticity to occur, an elastomer must be crosslinked, i.e. bonds must be introduced between the polymer chains. In most applications, these bonds are of a covalent nature. To form these bonds, at least one ingredient that is reactive with the polymer chains is added to the elastomeric composition. One example of an ingredient is peroxide, which reacts both with saturated and with unsaturated polymer chains. In most of the elastomer compounds, sulphur is added, together with a primary accelerator and activators. The crosslinking ingredient is mixed with the elastomeric matrix, typically filled with a reinforcing filler, at low temperature. The crosslinking reaction is then carried out at high temperature, typically between 150° C. and 180° C. When crosslinking is carried out with sulphur and sulphur-based ingredients, it is called vulcanization. During the test, the moment of a force is measured, necessary to allow a disk to rotate in the rubber, at a specified temperature, for an interval of time. This moment is called the torque. The torque values are stated as values of Modulus. During the test, keeping the sample in the instrument, there is a gradual increase in the modulus. A curve of the modulus as a function of time is obtained. The following parameters are obtained from the curve. M.sub.L=minimum value of the modulus, which gives an indication of the viscosity of the compound, M.sub.H=maximum value of the modulus, which indicates the maximum value of modulus reached by the vulcanization curve, t.sub.s1=time taken for an increase in torque equal to 1 dNm, t.sub.90=time to reach a value of the modulus equal to 90% of the maximum value of the modulus.

(35) Crosslinking. Data given in Table 2 and Table 7.

(36) Crosslinking was performed with a Monsanto RPA 2000 rheometer, at 170° C. for 20 minutes, at a frequency of 1.667 Hz and an angle of 6.98% (0.5 rad).

(37) Crosslinking. Data given in Table 10 and Table 16

(38) This was carried out according to standard ISO 6502, using an Alpha Technologies type MDR2000 rheometer. The tests were performed at 170° C. for 20 minutes at a frequency of oscillation of 1.66 Hz (100 oscillations per minute) and an oscillation amplitude of ±0.5°, measuring the time taken to reach an increase of two rheometric units (TS2) and the time taken to reach respectively 30% (T30) and 90% (T90) of the final torque value (Mf). The value of maximum torque MH and the value of minimum torque ML were also measured.

(39) Scorch Time—Scorch Test

(40) The scorch test is carried out to verify the tendency of an elastomer compound to crosslink at a temperature not far from that to which the elastomeric composition is exposed during the production process.

(41) Scorch test presented in Table 3. The scorch test given in Table 3 was carried out with a Monsanto RPA 2000 rheometer. The samples of elastomeric composite material were put in the rheometer, conditioned at 130° C., and were subjected to a sinusoidal stress with a frequency of 0.5 Hz, keeping the amplitude of strain equal to 50%, for a duration of 60 minutes. The scorch test gives a curve that indicates the torque as a function of the test time. The torque and the time required for an increase in torque equal to 5 (t.sub.5) dNm are measured. The curve thus gives: the value of ML, i.e. the minimum value of Modulus and the so-called scorch time, which corresponds to the time t.sub.5. These values are shown in Table 3.

(42) Scorch test presented in Table 15. The scorch test given in Table 15 was carried out at 130° C. according to standard ISO 289-2:1994.

(43) Tensile Properties or Static Mechanical Properties

(44) The static mechanical properties were measured at 23° C. according to standard ISO 37:2005. The following were measured in particular: the load at different levels of elongation (50%, 100% and 300%, denoted hereinafter Ca.sub.05, Ca.sub.1, Ca.sub.3), the breaking load CR and the elongation at break AR on samples of the aforementioned elastomeric compositions, vulcanized at 170° C. for 10 minutes. The tensile tests were carried out on test specimens with a rectilinear axis of the Dumbbell type. The values obtained are given in Table 11 and Table 17.

(45) Hardness Tests

(46) The hardness in degrees IRHD was measured according to standard ISO 48:2007 at 23° C. and 70° C., on samples of the aforementioned elastomeric materials, vulcanized at 170° C. for 10 minutes. The values are given in Table 17.

(47) Dynamic Mechanical Properties

(48) By Shear Stress.

(49) “Strain sweep test” means application of a dynamic stress by a shear stress, at constant frequency and at constant temperature, increasing the amplitude of the strain.

(50) Strain Sweep Test. Data in Table 4 and Table 8

(51) The test was carried out with a Monsanto RPA 2000 rheometer.

(52) The samples of elastomeric composite material were held in the rheometer at 50° C. for 90 seconds, stress was then applied at 50° C. in the range of strain amplitude between 0.1% and 25%, with a frequency of 1 Hz, increasing the amplitude of the strain in the interval stated above. This treatment is carried out to cancel the “thermo-mechanical prior history”. Vulcanization was then carried out at 170° C. for 20 minutes, at a frequency of 1.667 Hz and an angle of 6.98% (0.5 rad). The vulcanized sample was left in the instrument for 10 minutes at 50° C. The sinusoidal stress was then applied in the same conditions already stated, at 50° C. The sinusoidal stress is then applied again, still with the same experimental conditions. Curves are then obtained that give the value of the moduli as a function of the amplitude of the strain. These moduli are illustrated hereunder. Modulus G′ is the elastic modulus, and modulus G″ is the loss modulus. The ratio G″IG′ is given as tan delta. The strain sweep test gives the values of the following parameters: G′.sub.γ=0.28%, which is the value of G′ at minimum strain, ΔG′, which is the difference between the value of G′ at minimum strain and the value of G′ measured at the maximum strain reached, G″.sub.max, which is the maximum value of G″ observed on the curve of G″, (Tan Delta).sub.max, which is the maximum value of tan delta observed on the curve.

(53) By Axial Stress. Data in Table 12 and Table 18

(54) The dynamic mechanical properties through application of an axial stress were measured using an Instron dynamic tester in compression-tension mode by the following methods. A sample of the crude elastomeric compositions, vulcanized at 170° C. for 10 minutes, having a cylindrical shape (length=25 mm; diameter=14 mm), compression-pre-load up to 25% of the longitudinal strain relative to the initial length and maintained at the specified temperature (equal to −10° C., 0° C., +23° C. or +70° C.) throughout the test, was submitted to dynamic sinusoidal tension having an amplitude of ±3.5% relative to the length under pre-load, at a frequency of 10 Hz.

(55) The dynamic mechanical properties are expressed in terms of values of dynamic elastic modulus (E′) and of tan delta (dissipation factor). The value of tan delta was calculated as the ratio of the loss modulus (E″) to the elastic modulus (E′).

(56) Extraction Test of the Secondary Accelerator from Silica.

(57) The aim of this test is to verify the stability of the interaction between the secondary accelerator and silica. In fact, it was written in the text that one of the intrinsic technical problems of diphenyl guanidine is migration in the elastomer compound. This migration brings it into contact with neighbouring elastomer compounds, causing unwanted reaction with sulphur and the accelerators contained in the neighbouring compounds. In the case when the secondary accelerator displays greater interaction with silica, its migration in the elastomer compound should be reduced.

(58) First Procedure:

(59) A 50-mL one-necked flask equipped with a magnetic stirrer is loaded successively with 0.500 g of silica (Zeosil 1165 MP Rhodia) and 0.500 g of accelerator. The mixture is stirred for 2 hours at 120° C. At the end of this time, the mixture is cooled to room temperature and 10 mL of hexane is added. The suspension is stirred for 12 hours at room temperature. 2 mL of hexane is taken with a piston pipette and put in a 3-mL analysis vial. The liquid is injected into a gas chromatograph coupled to a mass spectrometer Agilent 5973Network Mass Selective Detector with 6890 Series GC System.

(60) Second Procedure:

(61) With DPG as accelerator, the extraction test was also carried out according to a second method, described hereunder. DPG is dissolved in an ethyl acetate/hexane mixture=1:1, then silica is added to the solution (the accelerator and the silica are in the same ratio as used in the first procedure). The solvent is then removed by evaporation at reduced pressure. The solid mixture is stirred for 2 hours at 120° C. The test then continues as in Procedure 1.

(62) Materials

(63) The chemical compounds used for synthesis of the molecules according to the present invention are given below, with the supplier indicated in parentheses. Acetone (Aldrich), ethyl acetate (Aldrich), hexane (Aldrich), camphor (Aldrich), cinnamaldehyde (Aldrich), 2-amino-1,3-propanediol (serinol) (Bracco), isoserinol (Bracco), fluorenone (Aldrich), acetophenone (Aldrich), cyclohexanone (Aldrich), propanoyl chloride (Aldrich).

(64) Tris(hydroxymethyl)aminomethane (indicated hereunder as TRIS AMINO) (CAS 77-86-1) (ANGUS);

(65) 2-amino-2-methylpropane-1,3-diol (indicated hereunder as AMPD) (CAS 115-69-5) (ANGUS).

(66) The chemical compounds used for preparing the compounds, given in Table 1, Table 6, Table 9 and Table 14, are stated, with supplier, at the bottom of the Table.

EXAMPLES

Example 1

Synthesis of 4-hydroxymethyl-2,2-dimethyl-1,3-oxazolidine

(67) ##STR00018##

(2,2-dimethyloxazolidin-4-yl)methanol

(68) A 50-mL one-necked flask was charged with 1 g of serinol (10.98 mmol), 10 mL of acetone and 1 g of Na.sub.2SO.sub.4. The reaction mixture was stirred overnight at room temperature. After filtration, the mixture was concentrated in a rotary evaporator. 1.302 g of a colourless oil was recovered. Yield=90%.

(69) Characterization by H-NMR analysis gave the following results:

(70) .sup.1H-NMR (400 MHz, DMSO-d6): δ ppm 4.63 (br s, 1H, OH), 4.28 (br s, 1H, NH), 3.73-3.69 (t, 1H, CH—CH2-O), 3.48-3.45 (dd, 1H, CH2-OH), 3.39-3.35 (q, 1H, CH—CH2-O), 3.36-3.32 (dd, 1H, CH2-OH), 3.23-3.19 (m, 1H, CH2-CH—CH2), 1.27 (S, 3H, CH3), 1.16 (S, 3H, CH3).

(71) Characterization by gas chromatography gave the following results:

(72) GC-MS (solvent MeOH): 143 (M−2H+CH2), 128 (100), 116, 98, 83, 68, 55, 42.

(73) GC-MS (solvent acetone): 132 (M+1), 116 (100), 100, 83, 74, 72, 68, 58, 43.

(74) The .sup.1H-NMR and .sup.13C-NMR spectra were recorded using a Bruker 400 MHz instrument (100 MHz .sup.13C) at 298 K. The chemical shifts are given in ppm, referring to the peak of the solvent (DMSO-d6: δ.sub.H=2.50 ppm, CDCl.sub.3: δ.sub.H=7.26 ppm).

Example 2

Synthesis of (2,2-dimethyl-oxazolidin-5-yl)-methanol

(75) ##STR00019##

(2,2-Dimethyl-oxazolidin-5-yl)-methanol

(76) A 50-mL one-necked flask was charged with 1 g of isoserinol (10.98 mmol), 10 mL of acetone and 1 g of Na.sub.2SO.sub.4. The reaction mixture was stirred overnight at room temperature. After filtration, the mixture was concentrated in a rotary evaporator. 1.302 g of a colourless oil was recovered. Yield=90%.

Example 3

Synthesis of 2-(1-phenyl-ethylidenamino)propane-1,3-diol

(77) ##STR00020##

2-(1-phenyl-ethylidenamino)-propane-1,3-diol

(78) A 20-mL open ampoule is charged with 1 g of serinol (10.98 mmol) and 1.31 g (10.98 mmol) of acetophenone. The mixture is heated at 130° C., stirring vigorously. Water is gradually removed from the mixture and over the course of an hour the mixture becomes homogeneous. The product is isolated by crystallization in diethyl ether.

Example 4

Synthesis of 2-(1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidenamino)propane-1,3-diol

(79) ##STR00021##

2-(1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidenamino)propane-1, 3-diol

(80) A 20-mL open ampoule is charged with 0.910 g of serinol (9.98 mmol) and 2.0 g (13.14 mmol) of camphor. The mixture is heated at 170° C., vigorously stirring the two heterogeneous phases present. Water is gradually removed from the mixture and over the course of an hour the mixture becomes homogeneous. Periodically the camphor sublimed on the neck of the ampoule is melted and returned to the reaction mixture. After 4 hours the mixture is cooled, and is taken up 3 times in 5 mL of cold hexane, in which the excess camphor dissolves. The residue is taken up again in 5 mL of hexane, which is put under reflux, obtaining two phases: an oily phase of higher density and the hexane phase, which are separated by decanting. The oily residue is then taken up twice in hot hexane. White crystals precipitate in the cold from the hexane phases and are recrystallized from hexane (yield >70%).

(81) Characterization by H-NMR analysis gave the following results:

(82) .sup.1H-NMR (400 MHz, DMSO-d6): δ ppm 4.26 (br s, 2H) 3.53-3.45 (m, 2H), 3.39-3.32 (m, 2H), 3.26-3.20 (m, 2H), 2.39-2.36 (d, 1H), 1.93-1.83 (m, 2H), 1.79-1.74 (t, 1H), 1.60-1.54 (t, 1H), 1.31-1.25 (t, 1H), 1.18-1.12 (t, 1H), 0.87 (s, 3H), 0.84 (s, 3H), 0.73 (s, 3H), .sup.13C-NMR 180.5, 65.3, 62.96, 62.7, 53.0, 46.0, 43.2, 35.4, 31.9, 27.0, 19.3, 18.7, 11.5. ESI mass spectrum m/z (rel. int. %) (MeOH): 226 ([M+1] 74%), 248 ([M+Na+], 100%); Mass-mass spectrum spedi 226: m/z (rel. int. %): 226 (28), 208 (90), 196 (16), 190 (11), 183 (34), 178 (20), 170 (25), 164 (72), 152 (100), 143 (74), 135 (48), 122 (18), 107 (82), 102 (17), 96 (28), 93 (60), 81 (22), 74 (28).

(83) The .sup.1H-NMR and .sup.13C-NMR spectra were recorded using a Bruker 400 MHz (100 MHz .sup.13C) at 298 K. The chemical shifts are given in ppm, referring to the peak of the solvent (DMSO-d6: δ.sub.H=2.50 ppm, CDCl.sub.3: δ.sub.H=7.26 ppm).

Example 5

Synthesis of 2-(3-(phenylallylidene)amino)propane-1,3-diol

(84) ##STR00022##

2-(3-(phenylallylidene)amino)propane-1,3-diol

(85) A 100-mL one-necked flask equipped with a magnetic stirrer is charged with 6.61 g (50 mmol) of cinnamaldehyde and 4.55 g (50 mmol) of serinol. The mixture is stirred for 2 hours at 100° C. At the end of this time, the temperature is brought to 25° C. The pure product was obtained by filtering the yellow crystals with water and removing the traces of solvent at reduced pressure. 9.42 g of white crystals were obtained.

Example 6

Synthesis of 2-(fluoren-9-ylidenamino) propane-1,3-diol

(86) ##STR00023##

2-(Fluoren-9-ylidenamino) propane-1,3-diol

(87) A 50-mL one-necked flask equipped with a magnetic stirrer is charged with 0.910 g (9.98 mmol) of serinol and 1.8 g (9.98 mmol) of 9-fluorenone. The mixture is heated at 130° C.: after about 30 minutes a homogeneous mixture is obtained. It is left to react for 6 hours, and then is cooled. 20 mL of toluene is added to the mixture and it is refluxed, stirring for 5 minutes, and then the stirrer is stopped. A two-phase mixture is thus obtained, consisting of the toluene solution and a small amount of red oil of higher density. The toluene solution is separated hot by decanting: a yellow solid precipitates from it, and is filtered, washed with toluene, and recrystallized from toluene. Yield of crystallized product >80%.

(88) Characterization by H-NMR analysis gave the following results:

(89) .sup.1H-NMR (400 MHz, DMSO-d6): δ 8.13-8.11 (d, 1H, Ar—CH), 7.87-7.86 (d, 1H, Ar—CH), 7.79-7.77 (d, 1H, Ar—CH), 7.71-7.70 (d, 1H, Ar—CH), 7.53-7.44 (2t, 2H, Ar—CH), 7.38-7.30 (2t, 2H, Ar—CH), 4.70-4.64 (m, 3H, (1H of CH2-CH—CH2 and 2H—OH), 3.82-3.78 to 3.63-3.58 (two dd, 4H, (CH2-CH—CH2). .sup.13C-NMR 162.4, 143.3, 140.7, 138.5, 131.8, 131.4, 128.7, 128.2, 122.8, 121.0, 120.1, 66.0, 63.5. ESI mass spectrum, m/z (rel. int. %) (MeOH): 277 ([M+Na+], 97%), 254 ([M++H], 100%); mass-mass spectrum of 254: m/z (rel. int. %): 254 (35), 236 (58), 206 (13), 192 (100), 180 (77), 165 (47).

(90) The .sup.1H-NMR and .sup.13C-NMR spectra were recorded using a Bruker 400 MHz (100 MHz .sup.13C) at 298 K. The chemical shifts are given in ppm, referring to the peak of the solvent (DMSO-d6: δ.sub.H=2.50 ppm, CDCl.sub.3: δ.sub.H=7.26 ppm).

Example 7

Synthesis of N-(1,3-dihydroxypropyl)-propionamide

(91) ##STR00024##

N-(1,3-dihydroxypropyl)-propionamide

(92) A 100-mL one-necked flask equipped with a magnetic stirrer is charged with 0.500 g (5.5 mmol) of serinol and 0.100 g (1.1 mmol) of acryloyl chloride at 0° C. The mixture is stirred at this temperature for 30 min. At the end of this time, 10 mL of CH.sub.2Cl.sub.2 and then 10 mL of water are added. The organic phase is dried over Na.sub.2SO.sub.4, filtered and dried at reduced pressure. 0.270 g of product was obtained.

Examples 8, 9, 10, 11, 12, 13, 14, 15

Preparation of Elastomer Compounds

(93) The formulations of the elastomer compounds are given in Table 1.

(94) TABLE-US-00001 TABLE 1 Formulations for elastomeric compositions Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. 8 9 10 11 12 13 14 15 Ingredient Phr NR.sup.a 15.00 15.00 15.00 15.00 15.00 15.00 15.00 15.00 S-SBR.sup.b 96.25 96.25 96.25 96.25 96.25 96.25 96.25 96.25 BR.sup.c 15.00 15.00 15.00 15.00 15.00 15.00 15.00 15.00 Silane Si 69.sup.d 5.20 5.20 5.20 5.20 5.20 5.20 5.20 5.20 Silica.sup.e 65.00 65.00 65.00 65.00 65.00 65.00 65.00 65.00 MES oil.sup.f 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 Stearic acid.sup.g 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Zinc oxide.sup.h 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50 6PPD.sup.i 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 TBBS.sup.k 1.80 1.80 1.80 1.80 1.80 1.80 1.80 1.80 Sulphur.sup.l 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 DPG80.sup.m 0.00 2.40 0.00 0.00 0.00 0.00 0.00 0.00 Serinol.sup.n 0.00 0.00 0.83 0.00 0.00 0.00 0.00 0.00 camphor imine 0.00 0.00 0.00 2.04 0.00 0.00 0.00 0.00 (Ex. 4) cinnamaldehyde 0.00 0.00 0.00 0.00 1.87 0.00 0.00 0.00 imine (Ex. 5) serinol 0.00 0.00 0.00 0.00 0.00 1.19 0.00 0.00 oxazolidine (Ex. 1) isoserinol 0.00 0.00 0.00 0.00 0.00 0.00 1.19 0.00 oxazolidine (Ex. 2) serinol amide 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.34 (Ex. 7) .sup.anatural poly(1,4-cis-isoprene) (NR) commercial grade SMR GP (from Lee Rubber) .sup.bStyrene-butadiene rubber from solution; commercial grade Styron 4630 (from Styron), 25% as styrene content .sup.cPolybutadiene; commercial grade Europrene neocis (from Polimeri Europa) .sup.dbis[3-(triethoxysilyl)propyl]tetrasulphide from Evonik .sup.eZEOSIL 1165MP (supplier SOLVAY RHODIA OPERATIONS) .sup.fAliphatic oil, from Eni .sup.gStearin N, from SOGIS .sup.hfrom Zincol Ossidi .sup.iN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, from Crompton. .sup.kN-tert-butyl-2-benzothiazyl sulphenamide (TBBS), from Flexsys .sup.lfrom Solfotecnica .sup.mDiphenylguanidine (Rhenogran ® DPG80), from Rhein Chemie Additives .sup.n2-amino-1,3-propanediol, from Bracco

Example 8 (Comparative)

Preparation of Elastomer Compound (Comparative Example without Secondary Accelerator)

(95) 3.50 g of NR, 22.48 g of S-SBR and 3.50 g of BR were put in an internal mixer of the Brabender® type having a mixing chamber with a volume equal to 50 cc, and mastication was carried out at 145° C. for 1 minute. Then 15.18 g of Zeosil 1165 silica, 1.21 g of TESPT silane, 0.47 g of stearic acid, and 2.34 g of MES oil were added, mixing for a further 5 minutes and discharging the composite obtained at 150° C. The composite thus prepared was then put in the internal mixer at 50° C., adding 0.58 g of ZnO, 0.47 g of 6PPD, and mixing for 2 minutes. Then 0.28 g of sulphur and 0.42 g of N-tert-butyl-2-benzothiazyl sulphenamide (TBBS) were added, mixing for a further 2 minutes. The composite was discharged at 65° C.

Example 9 (Comparative)

(96) The compound was prepared as in example 9, except that 0.56 g of supported diphenyl guanidine (which corresponds to 0.45 g of pure DPG) was introduced in Step 0.0.

Example 10 (Invention)

Preparation of Elastomer Compound (with Serinol)

(97) The compound was prepared as in example 9, except that 0.195 g of serinol was supplied instead of 0.56 g of DPG. The molar amount of serinol is equal to the molar amount of pure DPG.

Example 11 (Invention)

Preparation of Elastomer Compound (with Camphor Imine)

(98) The compound was prepared as in example 9, except that 0.48 g of camphor imine was supplied instead of 0.56 g of DPG. The molar amount of camphor imine is equal to the molar amount of DPG.

Example 12 (Invention)

Preparation of Elastomer Compound (with Cinnamaldehyde Imine)

(99) The compound was prepared as in example 9, except that 0.44 g of cinnamaldehyde imine was supplied instead of 0.56 g of DPG. The molar amount of cinnamaldehyde imine is equal to the molar amount of pure DPG.

Example 13 (Invention)

Preparation of Elastomer Compound (with Oxazolidine from Serinol and Acetone)

(100) The compound was prepared as in example 9, except that 0.28 g of oxazolidine from serinol and acetone was supplied instead of 0.56 g of DPG. The molar amount of oxazolidine from serinol and acetone is equal to the molar amount of pure DPG.

Example 14 (Invention)

Preparation of Elastomer Compound (with Oxazolidine from Isoserinol and Acetone)

(101) The compound was prepared as in example 9, except that 0.28 g of oxazolidine from isoserinol and acetone was supplied instead of 0.56 g of DPG. The molar amount of oxazolidine from isoserinol and acetone is equal to the molar amount of pure DPG.

Example 15 (Invention)

Preparation of Elastomer Compound (with Amide from Serinol and Chloride of Propionic Acid)

(102) The compound was prepared as in example 9, except that 0.31 g of amide from serinol and chloride of propionic acid was supplied instead of 0.56 g of DPG. The molar amount of amide from serinol and chloride of propionic acid is equal to the molar amount of pure DPG.

(103) Vulcanization of the Compounds in Examples 8, 9, 10, 11, 12, 13, 14, 15

(104) The composites in examples 8-15 were vulcanized at 170° C. and at a pressure of 15×10.sup.5 Pa for 20 minutes, according to the operating procedure described above.

(105) Table 2 gives the data relating to the vulcanization reactions.

(106) FIG. 1 gives the vulcanization curves of the elastomeric compositions in Examples 8, 9 and 10.

(107) FIG. 2 gives the vulcanization curves of the elastomeric compositions in Example 8, Example 9, Example 11, and Example 12.

(108) FIG. 3 gives the vulcanization curves of the elastomeric compositions in Example 8, Example 9, Example 13, Example 14, and Example 15.

(109) TABLE-US-00002 TABLE 2 Values of M.sub.L, M.sub.H, t.sub.s1, t.sub.90 determined in the rheometric test for the elastomeric compositions in Table 1.sup.a Ex. prep. compound Ex. 8 Ex. Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 M.sub.L [dNm] 2.8 2.3 3.1 2.61 2.68 2.81 2.78 2.97 M.sub.H [dNm] 13.3 15.1 15.0 14.62 13.62 14.75 14.19 14.14 t.sub.s1 [min] 2.84 2.9 2.6 3.03 2.65 2.38 2.17 2.63 t.sub.90 [min] 11.52 7.14 9.53 10.51 9.2 9.17 8.32 10.42 .sup.aM.sub.L minimum value of torque, measured in dNewton x meter (dNm). M.sub.H maximum value of torque, measured in dNm. t.sub.s1: time required for an increase of 1 dNm in the torque value, relative to the minimum value M.sub.L. t.sub.90: time taken to reach 90% of the torque value, relative to the maximum value M.sub.H.

(110) The data in Table 2 show that the secondary accelerators according to the present invention produce an advantage relative to the compound that does not contain a secondary accelerator. In fact, the induction time to vulcanization (t.sub.s1) is less than or in line with the vulcanization time of the compound in the absence of secondary accelerator. In particular, the time taken to reach optimum vulcanization (t.sub.90) is less. The values of M.sub.L are in line or lower, indicating that the viscosity of the compound does not change substantially as a result of adding the secondary accelerators according to the present invention. The values of M.sub.H are higher for the compounds that contain both serinol, and the imines of serinol, and the oxazolidine and the amide of serinol. The data relating to the compounds that contain the secondary accelerators according to the present invention seem to be in line with those of the compound that contains DPG, apart from the values of t.sub.90. In fact, the value of t.sub.90 is lower in the case of the compound with DPG. It should, however, be noted that the accelerators according to the present invention offer the possibility of modulating the values of the vulcanization parameters by changing the substituents of the compound of formula (I).

(111) Determination of the Scorch Time of the Compounds in Examples 8, 9, 10, 11, 12, 13, 14, 15

(112) The scorch time of the composites in examples 8-15 was determined by rheometric measurements carried out at 130° C. according to the operating procedure described above.

(113) Table 3 shows the time taken for the elastomeric compositions prepared in examples 8-15 to reach an increase in the torque value equal to 5 dNm, i.e. the scorch time.

(114) TABLE-US-00003 TABLE 3 Values of M.sub.L and of scorch time t.sub.s5 scorch time (t.sub.s5) determined by the scorch test for the elastomeric compositions in Table 1.sup.a Ex. prep. compound Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 M.sub.L dNm 7.07 6.09 6.96 6.51 6.13 6.64 6.67 6.94 Scorch min 46.36 28.94 25.66 37.31 27.02 20.55 14.27 29.13 time .sup.aM.sub.L: minimum value of Modulus; Scorch time = t.sub.s5 = time taken for an increase in torque equal to 5 dNm.

(115) The values of scorch time given in Table 3 for the compounds that contain the secondary accelerator according to the present invention are all lower than for the compound without secondary accelerator. It should be noted, however, that the measured values are acceptable for conditions of normal use in industrial practice. However, the value of the scorch time for the compound that contains serinol camphor seems interesting; it is significantly higher than the values for the other compounds. Serinol camphor thus appears to be a secondary accelerator that gives vulcanizations in line with those obtained with DPG and at the same time absolutely does not present the technical problem of premature vulcanization during processing of the compound. The oxazolidine of isoserinol seems particularly reactive. This means it is possible to use a smaller amount of secondary accelerator, which would lead to an increase in scorch time, while using less accelerator. The values of scorch time for the compounds that contain the secondary accelerator according to the present invention are in line with the value measured for the compound that contains DPG.

(116) The scorch times and the vulcanization induction times (ts1) show a linear correlation.

(117) Dynamic-Mechanical Characterization of the Compounds in Examples 8, 9, 10, 11, 12, 13, 14, 15

(118) The composites in examples 8-15 were characterized by applying sinusoidal stressing by a shear stress, according to the operating procedure described above.

(119) Table 4 shows the data relating to the dynamic modulus G′ at minimum strain, with variation Δ of the modulus G′, (ΔG′), between 0.28% and 25% as amplitude of the strain, at the maximum value of the dissipative modulus G″, at the maximum value of tan delta.

(120) FIG. 4 shows the conservative dynamic modulus G′ as a function of the amplitude of the strain for the elastomeric compositions in Examples 8, 9 and 10.

(121) FIG. 5 shows the conservative dynamic modulus G′ as a function of the amplitude of the strain for the elastomeric compositions in Examples 8, 9, 10 and 12.

(122) FIG. 6 shows the conservative dynamic modulus G′ as a function of the amplitude of the strain for the elastomeric compositions in Examples 8, 9, 13, 14, 15.

(123) TABLE-US-00004 TABLE 4 Values of G′.sub.y=0.28%, ΔG′, G″.sub.max and (Tan Delta).sub.max determined by the strain sweep test for the elastomeric compositions in Table 1.sup.a Ex. prep. compound Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 G′.sub.y=0.28% MPa 1.43 1.621 1.64 1.6142 1.587 1.6322 1.5811 1.61 ΔG′ MPa 0.65 0.92 0.92 0.8886 0.8961 0.8733 0.829 0.8768 G″.sub.max MPa 0.169 0.18 0.19 0.1827 0.1911 0.2062 0.2035 0.2269 (Tan — 0.149 0.153 0.151 0.155 0.163 0.164 0.165 0.178 Delta).sub.max .sup.aG′.sub.y=0.28% = value of G′ at the minimum strain, equal to 0.28%. ΔG′ = difference between the value of G′ at minimum strain and the value of G′ measured at the maximum strain reached. G″.sub.max = maximum value of G″ observed on the curve of G″ (Tan Delta).sub.max = maximum value of tan delta observed on the curve.

(124) The values for the parameters given in Table 4, measured by the dynamic-mechanical tests, seem to be substantially in line for all the compounds. In particular, the value of ΔG′ is taken as an indicator of the phenomenon of formation and destruction of the network of the filler and therefore as an indicator of dissipation of energy. Thus, the secondary accelerators according to the present invention do not cause significant dissipation of energy.

Examples 16, 17, 18, 19

Tests of Extraction of the Secondary Accelerator from Silica

(125) The tests were performed according to the operating procedure described above.

(126) In example 16 (invention), serinol was used as secondary accelerator.

(127) In example 17 (invention), serinol camphor was used as secondary accelerator.

(128) In example 18 (invention), serinol cinnamaldehyde was used as secondary accelerator.

(129) In example 19 (comparative), diphenylguanidine was used as secondary accelerator.

(130) Table 5 shows the substances present in the hexane used for extraction. These substances were detected by GC-MS analysis.

(131) TABLE-US-00005 TABLE 5 Tests of extraction of diphenyl guanidine and of molecules according to the present invention from silica Example 16 17 18 19 Accelerator.sup.a serinol serinol serinol diphenyl camphor (from cinnamaldehyde guanidine example 4) (from example 5) Substance none camphor cinnamaldehyde diphenyl extracted.sup.b guanidine .sup.aContacted with silica. .sup.bDetected in the hexane used for extraction, by GC-MS analysis.

(132) The data given in Table 5 show how DPG is extracted from its adduct with silica by a solvent such as hexane. In contrast, the accelerators according to the present invention are not extracted from the adducts with silica. In fact, there is no trace of these accelerators in the hexane used for extraction.

(133) Examination of the data in Tables 2 to 5 shows that the class of secondary accelerators according to the present invention shows advantages relative to the compound without secondary accelerators. Moreover, this class of accelerators offers the possibility of selecting the ideal chemical compound for the desired properties of the compound itself.

Examples 20 (Comparative), 21 (Invention) and 22 (Invention)

(134) Table 6 gives other examples of elastomeric compositions according to the present invention.

(135) TABLE-US-00006 TABLE 6 Formulations for elastomeric compositions Ex. Ex. Ex. 20 21 22 Ingredient Phr S-SBR HP755.sup.a 90.00 90.00 90.00 BR.sup.b 35.00 35.00 35.00 Silica.sup.c 50.00 50.00 50.00 Silane TESPT/ 11.20 11.20 11.20 Carbon black.sup.d Silica Zeosil 1165.sup.e 20.00 20.00 20.00 MES oil.sup.f 8.00 8.00 8.00 Stearic acid.sup.g 2.00 2.00 2.00 Zinc oxide.sup.h 2.50 2.50 2.50 6PPD.sup.i 2.00 2.00 2.00 Sulphur.sup.k 1.20 1.20 1.20 TBBS.sup.l 2.00 2.00 2.00 DPG80.sup.m 2.40 0.00 0.00 Serinol.sup.n 0.00 0.83 0.00 Camphor imine 0.00 0.00 2.04 (Ex. 4) .sup.aStyrene-butadiene rubber from solution; commercial grade Styron 4630, from Styron. 25% as styrene content .sup.bPolybutadiene; commercial grade Europrene neocis, from Polimeri Europa .sup.c,eZEOSIL 1165MP, from SOLVAY RHODIA OPERATIONS .sup.dSilane TESPT: bis[3-(triethoxysilyl)propyl]tetrasulphide TESPT/Carbon black N330 = 1/1, from EVONIK .sup.fAliphatic oil, from Eni .sup.gStearin N, from SOGIS .sup.hfrom Zincol Ossidi .sup.iN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, from Crompton. .sup.kfrom Solfotecnica .sup.lN-tert-butyl-2-benzothiazyl sulphenamide, from Flexsys .sup.mDiphenylguanidine (Rhenogran ® DPG80), from Rhein Chemie Additives .sup.n2-amino-1,3-propanediol, from Bracco

(136) TABLE-US-00007 TABLE 7 Values of M.sub.L, M.sub.H, t.sub.s1, t.sub.90 determined by the rheometric test for the elastomeric compositions in Table 6.sup.a Ex. prep. compound 20 21 22 M.sub.L [dNm] 3.26 4.06 3.53 M.sub.H [dNm] 20.43 20.53 19.83 t.sub.s1 [min] 0.97 0.7 1.09 t.sub.90 [min] 3.06 3.71 4.69 .sup.aM.sub.L minimum torque value, measured in dNewton × meter (dNm). M.sub.H maximum torque value, measured in dNm. T.sub.s1: time taken for an increase of 1 dNm in the torque value, relative to the minimum value M.sub.L. T.sub.90: time taken to reach 90% of the torque value, relative to the maximum value M.sub.H.

(137) It can be seen from the data in Table 7 that the compounds containing DPG and serinol camphor have similar vulcanization induction times, whereas a shorter time is obtained with serinol as secondary accelerator. Serinol camphor also gives a lower vulcanization rate. It can therefore be seen that different vulcanization kinetics may be obtained with molecules according to the present invention, ascribable to the same general formula. By modulating the chemical nature of the molecules according to the present invention it is thus possible to modulate the vulcanization kinetics.

(138) TABLE-US-00008 TABLE 8 Values of G′.sub.γ = 0.28%, ΔG′ and (Tan Delta).sub.max determined by the strain sweep test for the elastomeric compositions in Table 6.sup.a Ex. prep. compound 20 21 22 G′.sub.γ = 0.28% MPa 2.80  2.64  2.46  ΔG′ MPa 1.73  1.55  1.45  (Tan Delta).sub.max — 0.200 0.190 0.195 .sup.aG′.sub.γ = 0.28% = value of G′ at the minimum strain, equal to 0.28%. ΔG′ = difference between the value of G′ at minimum strain and the value of G′ measured at the maximum strain reached. (Tan Delta).sub.max = maximum value of tan delta observed on the curve.

(139) It can be seen from the data in Table 8 that the greatest non-linearity of the modulus is obtained with the compound prepared with DPG. There is lower dissipation of energy with serinol camphor, and even lower with serinol.

Examples 23 (Comparative), 24 (Comparative), 25 (Invention) and 26 (Invention)

(140) Table 9 gives other examples of elastomeric compositions according to the present invention. The composition envisages silica as reinforcing filler.

(141) TABLE-US-00009 TABLE 9 Formulations for elastomeric compositions Ex. Ex. Ex. Ex. 23 24 25 26 Ingredient Phr NR.sup.a 15.00 15.00 15.00 15.00 BR.sup.b 15.00 15.00 15.00 15.00 HP755.sup.c 96.25 96.25 96.25 96.25 Silica.sup.d 85.00 85.00 85.00 85.00 Silane TESPT/ 13.00 13.00 13.00 13.00 Carbon black N330 = 1/1.sup.e Stearic acid.sup.f 2.00 2.00 2.00 2.00 TDAE oil.sup.g 8.00 8.00 8.00 8.00 TMQ.sup.h 1.25 1.25 1.25 1.25 Wax.sup.i 1.25 1.25 1.25 1.25 Adhesive resin.sup.k 4.50 4.50 4.50 4.50 Zinc oxide.sup.l 2.50 2.50 2.50 2.50 6PPD.sup.m 2.00 2.00 2.00 2.00 AMPD.sup.n 0.00 0.00 1.50 0.00 TRIS AMINO.sup.o 0.00 0.00 0.00 1.50 Sulphur.sup.p 1.40 1.40 1.40 1.40 TBBS.sup.q 2.00 2.00 2.00 2.00 DPG80.sup.r 0.00 2.50 0.00 0.00 PVI.sup.s 0.20 0.20 0.20 0.20 .sup.aSMR GP = Natural rubber (poly(1,4-cis)isoprene, supplier SENG HIN RUBBER) .sup.bBR40 Europrene neocis = High cis polybutadiene (97% min). Neodymium polymerized. (supplier VERSALIS) .sup.cHP755 = Solution Styrene-butadiene copolymer (styrene 39.5% and vinyl 38.5% on the dienic portion equivalent to 23.3% on the polymer), extended with 37.5 phr of TDAE oil (SUPPLIER JAPAN SYNTHETIC RUBBER) .sup.dSILICA ZEOSIL 1165MP (supplier SOLVAY RHODIA OPERATIONS) .sup.eTESPT (50%) = Silane TESPT/Carbon black N330 = 1/1 = ″Bis[3-(triethoxysilyl)propyl]tetrasulphide (supplier EVONIK) .sup.fSTEARIC acid = STEARIN N (supplier: SOGIS) .sup.gTDAE oil = Treated distillate aromatic extract (TDAE) VIVATEC 500 Supplier: H&R .sup.hTMQ = 2,2,4-trimethyl-1,2-dihydroquinoline polymerized (trade name = VULCANOX HS/LG; supplier = LANXESS) .sup.iWAX = Mixture of normal-paraffins, prevailing, and iso-paraffins (trade name: REDEZON 517 supplier REPSOL YPF) .sup.kADHESIVE RESIN = ALPHA-METHYL-STYRENE THERMOPLASTIC RESIN (trade name: IMPERA P1504 Supplier EASTMAN) .sup.lZINC OXIDE (supplier = ZINCOL OSSIDI) .sup.m6PPD = N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) (from Crompton) .sup.n2-amino-2-methylpropane-1,3-diol (AMPD) (from ANGUS). .sup.oTris(hydroxymethyl)aminomethane (TRIS AMINO) (from ANGUS), .sup.pSulphur (from ZOLFINDUSTRIA) .sup.qN-tert-butyl-2-benzothiazyl sulphenamide (TBBS) (from Flexsys) .sup.rDiphenylguanidine (Rhenogran ® DPG80) (from Rhein Chemie Additives) .sup.sN-cyclohexyl-thiophthalimide (PVI) (Vulkalent ®G, from Lanxess)

(142) Table 10 gives the data relating to the vulcanization reactions.

(143) TABLE-US-00010 TABLE 10 Values of M.sub.L, M.sub.H, t.sub.s1, t.sub.60, t.sub.90 determined by the rheometric test for the elastomeric compositions in TABLE 9.sup.a Ex. prep. compound 23 24 25 26 M.sub.L [dNm] 5.6 3.8 4.0 4.4 M.sub.H [dNm] 20.2 20.4 20.6 21.4 t.sub.s1 [min] 1.33 0.59 0.58 0.5 t.sub.60 [min] 4.83 3.00 3.2 3.19 t.sub.90 [min] 10.92 5.28 6.35 7.31 .sup.aM.sub.L minimum torque value, measured in dNewton × meter (dNm). M.sub.H maximum torque value, measured in dNm. T.sub.s1: time taken for a 1 dNm increase in the torque value, relative to the minimum value M.sub.L. t.sub.60: time taken to reach 60% of the torque value, relative to the maximum value M.sub.H. t.sub.90: time taken to reach 90% of the torque value, relative to the maximum value M.sub.H.

(144) It can be seen from the data given in Table 10 that both DPG and the molecules according to the present invention are very effective in reducing the value of M.sub.L, a parameter indicative of the viscosity of the crude product:

(145) The acceleration of the vulcanization kinetics is similar for DPG and for the molecules according to the present invention. The latter appear to reduce the reversion of the compound.

(146) Table 11 gives data obtained from the tensile tests

(147) TABLE-US-00011 TABLE 11 Values of the tensile properties for the elastomeric compositions in Table 9a Ex. prep. compound 23 24 25 26 Samples held at 23° C. for 5 min Ca0.5 [Mpa] 1.13 1.34 1.32 1.30 Ca1 [Mpa] 1.72 2.25 2.2 2.11 Ca3 [Mpa] 6.44 9.81 9.18 8.61 CR [Mpa] 17.06 18.38 18.18 15.68 AR [%] 668.4 534.8 551.5 511.4 .sup.aCa.sub.05, Ca.sub.1, Ca.sub.3: load at different levels of elongation, 50%, 100% and 300% respectively. CR: breaking load. AR: elongation at break

(148) The data in Table 11 show that AMPD reproduces the effect of DPG, whereas TRIS-AMINO leads to slightly lower reinforcement, but much greater than that of the reference without secondary accelerator.

(149) Table 12 gives the data obtained from the dynamic mechanical tests.

(150) TABLE-US-00012 TABLE 12 Values of the dynamic mechanical properties for the elastomeric compositions in TABLE 9.sup.a Ex. prep. compound 23 24 25 26 Measurements taken at 0° C. E′ [Mpa] 16.01 16.89 16.48 16.68 Tan delta 0.771 0.736 0.734 0.739 Measurements taken at 10° C. E′ [Mpa] 11.39 12.44 12.19 12.14 Tan delta 0.62 0.602 0.592 0.599 Measurements taken at 23° C. E′ [Mpa] 8.67 9.57 9.46 9.44 Tan delta 0.414 0.399 0.385 0.395 Measurements taken at 70° C. E′ [Mpa] 5.42 6.15 6.07 5.98 Tan delta 0.192 0.180 0.178 0.185 .sup.aE′: dynamic elastic modulus. Tan delta: ratio of the loss modulus (E″) to the elastic modulus (E′).

(151) The dynamic-mechanical data in Table 12 show substantial equivalence of the compounds obtained with the accelerators according to the invention relative to DPG.

(152) Table 13 gives the data obtained from the abrasion tests.

(153) TABLE-US-00013 TABLE 13 Values of volume loss (DIN abrasion test) for the elastomeric compositions in TABLE 9 Ex. prep. compound 23 24 25 26 Volume [mm.sup.3] 173 107 105 114 loss

(154) The DIN abrasion data in Table 13 show substantial equivalence of the compounds obtained with the accelerators according to the invention relative to DPG. Poorer DIN abrasion was obtained in the case of the compound without secondary accelerators.

Examples 27 (Comparative), 28 (Comparative), 29 (Invention), 30 (Invention) and 31 (Invention)

(155) Table 14 gives other examples of elastomeric compositions according to the present invention. The composition envisages carbon black as reinforcing filler.

(156) TABLE-US-00014 TABLE 14 Formulations for elastomeric compositions Ex. Ex. Ex. Ex. Ex. 27 28 29 30 31 Ingredient Phr NR.sup.a 60.00 60.00 60.00 60.00 60.00 BR.sup.b 40.00 40.00 40.00 40.00 40.00 Carbon black N115.sup.c 55.00 55.00 55.00 55.00 55.00 Silica VN3.sup.d 15.00 15.00 15.00 15.00 15.00 Silane TESPT/ 3.00 3.00 3.00 3.00 3.00 Carbon black N330 = 1/1.sup.e Stearic acid.sup.f 1.30 1.30 1.30 1.30 1.30 Zinc oxide.sup.g 3.00 3.00 3.00 3.00 3.00 Zinc stearate.sup.h 2.00 2.00 2.00 2.00 2.00 Wax.sup.i 2.00 2.00 2.00 2.00 2.00 TMQ.sup.k 1.00 1.00 1.00 1.00 1.00 6PPD.sup.l 3.00 3.00 3.00 3.00 3.00 Sulphur.sup.m 1.80 1.80 1.80 1.80 1.80 CBS.sup.n 1.10 1.10 1.10 1.10 1.10 DPG80.sup.o 0.00 1.25 0.00 0.00 0.00 AMPD.sup.p 0.00 0.00 0.75 1.00 0.00 TRIS AMINO.sup.q 0.00 0.00 0.00 0.00 1.00 PVI.sup.r 0.30 0.30 0.30 0.30 0.30 .sup.aSMR GP = Natural rubber (poly(1,4-cis)isoprene, supplier SENG HIN RUBBER) .sup.bBR40 Europrene neocis = High cis polybutadiene (97% min.). From catalysis with neodymium. (supplier VERSALIS) .sup.cfrom Cabot .sup.dULTRASIL ® VN 3 GR from Evonik .sup.efrom Evonik; Silane TESPT: bis[3-(triethoxysilyl)propyl]tetrasulphide .sup.fRadiacid 444 (Oleon) .sup.gfrom Zincol Ossidi .sup.hfrom Sogis .sup.iWAX = Mixture of normal-paraffins, prevailing, and iso-paraffins (trade name: REDEZON 517 supplier REPSOL YPF) .sup.kTMQ = 2,2,4-trimethyl-1,2-dihydroquinoline polymerized (trade name = VULCANOX HS/LG; supplier = LANXESS) .sup.l6PPD = N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) (from Crompton) .sup.mSulphur (from ZOLFINDUSTRIA) .sup.nN-cyclohexyl-2-benzothiazyl sulphenamide (CBS) (from Flexsys) .sup.oDiphenylguanidine (Rhenogran ® DPG80) (from Rhein Chemie Additives) .sup.p2-amino-2-methylpropane-1,3-diol (AMPD) (from ANGUS). .sup.qTris(hydroxymethyl)aminomethane (TRIS AMINO) (from ANGUS), .sup.rN-cyclohexyl-thiophthalimide (PVI) (Vulkalent ®G, from Lanxess)

(157) Table 15 gives the data relating to the vulcanization reactions. Vulcanization conditions, 140° C. and 120 minutes, were selected that are typical for formulations of this type, when they are applied for example in tyres for use in agriculture.

(158) TABLE-US-00015 TABLE 15 Values of M.sub.L and of scorch time t.sub.s5 determined by the scorch test for the elastomeric compositions prepared in Table 14.sup.a Ex. prep. compound 27 28 29 30 31 M.sub.L [dNm] 10.54 9.67 9.16 9.52 9.57 t.sub.s5 [min] 30.3 16.5 23.2 22.5 19.3 .sup.aML: minimum value of Modulus; Scorch time = t.sub.s5 = time required for an increase in torque equal to 5 dNm.

(159) M.sub.L is indicative of the viscosity of the crude product. It can be seen from the data in Table 15 that DPG is very effective in reducing it, and that the two molecules according to the present invention give similar results, even better than DPG in the case of TRIS-AMINO. The t5 at 130° C. is indicative of the window of processability of the compounds: it is desirable for it to be at least 15 minutes to avoid potential process problems: DPG leads to values that are acceptable but potentially critical, while the two molecules according to the present invention show improving results.

(160) TABLE-US-00016 TABLE 16 Values of M.sub.L, M.sub.H, t.sub.s1, t.sub.60, t.sub.90 determined by the rheometric test carried out at 140° C. for 120 minutes, for the elastomeric compositions in Table 14.sup.a Ex. prep. compound 27 28 29 30 31 M.sub.L [dNm] 5.2 4.8 4.7 4.8 5.0 M.sub.H [dNm] 23.7 27.2 26.6 27.8 28.7 t.sub.s1 [min] 10.8 5.8 8.3 7.5 7.5 t.sub.60 [min] 33.5 19.2 24.9 24.0 21.3 t.sub.90 [min] 55.9 35.8 44.2 40.9 36.5 .sup.aM.sub.L minimum torque value, measured in dNewton x meter (dNm). M.sub.H maximum torque value, measured in dNm. T.sub.s1: time taken for a 1 dNm increase in the torque value, relative to the minimum value M.sub.L. t.sub.60: time taken to reach 60% of the torque value, relative to the maximum value M.sub.H. t.sub.90: time taken to reach 90% of the torque value, relative to the maximum value M.sub.H.

(161) It can be seen from the data in Table 16 that both DPG and the molecules according to the present invention are effective in reducing the values of M.sub.L, indicative of the viscosity of the crude product. In particular, a larger reduction is obtained in the case of TRIS-AMINO.

(162) All the molecules added to the formulation with the role of secondary accelerator, both DPG and the molecules according to the present invention, cause a decrease in the vulcanization times, from the induction time to vulcanization t.sub.s1, to the reference times for the formation of the network t.sub.60 and t.sub.90.

(163) Table 17 gives the values obtained from the tensile tests.

(164) TABLE-US-00017 TABLE 17 Values of the tensile properties for the elastomeric compositions prepared in the examples in Table 14.sup.a Ex. prep. compound 27 28 29 30 31 Hardness @ IRHD 76.8 80.6 78.9 80.6 80.7 23° C. Hardness @ IRHD 69.9 73.2 72.6 73.8 74.1 70° C. Samples held at 23° C. for 5 min Ca.sub.0.5 [Mpa] 1.74 2.08 1.99 2.13 2.14 Ca.sub.1 [Mpa] 2.81 3.55 3.36 3.64 3.69 Ca.sub.3 [Mpa] 12.63 15.08 14.71 15.47 15.59 CR [Mpa] 20.65 21.08 21.16 21.74 19.07 AR [%] 501 445 447 449 395 .sup.aCa.sub.05, Ca.sub.1, Ca.sub.3: load at different levels of elongation, 50%, 100% and respectively. CR: breaking load. AR: elongation at break 300%

(165) It can be seen from the data in Table 17 that both DPG and the molecules according to the present invention cause an increase in hardness IRHD both at 23° C. and at 70° C. However, DPG also leads to an undesirable increase in the hardness difference between 23° C. and 70° C.

(166) TABLE-US-00018 TABLE 18 Values of the dynamic mechanical properties for the elastomeric compositions in Table 14.sup.a Ex. prep. compound 27 28 29 30 31 Measurements taken at 10° C. E′ [Mpa] 9.93  10.96  10.52 10.87 11.27 Tan delta 0.297  0.284 0.282 0.288 0.282 Measurements taken at 23° C. E′ [Mpa] 9.10  9.96  9.58 10.19 10.28 Tan delta 0.264 0.250 0.247 02512 0.248 Measurements taken at 70° E′ [Mpa] 7.03  7.83  7.54 7.77 8.07 Tan delta 0.206 0.193 0.188 0.193 0.187 .sup.aE′: dynamic elastic modulus. Tan delta: ratio of the loss modulus (E″) to the elastic modulus (E′).

(167) Table 19 gives the data obtained from the abrasion tests.

(168) TABLE-US-00019 TABLE 19 Values of volume loss (abrasion test) for the elastomeric compositions in Table 14 Ex. prep. compound 27 28 29 30 31 Volume [mm.sup.3] 35.4 34.6 34.8 34.7 35.1 loss

(169) Results that are substantially equivalent are thus obtained with DPG and with the molecules according to the present invention both with respect to the dynamic loads and with respect to abrasion.