Silane, rubber mixture containing the silane and vehicle tyre having the rubber mixture in at least one component

Abstract

The invention relates to a silane, to a rubber mixture comprising the silane and to a vehicle tire comprising the rubber mixture in at least one component. The inventive silane has the following formula I)
(R.sup.1).sub.oSiR.sup.2X-A-Y-[A-Y-].sub.m-A-S.sub.k-A-[-Y-A].sub.mY-A-XR.sup.2Si(R.sup.1).sub.o,
wherein, according to the invention, the silane has spacer groups between the respective silyl groups and the S.sub.k moiety which have at least two aromatic groups A and the linking units X and Y, wherein the groups X within a molecule may be identical or different from each other and are selected from the groups HNC(O), C(O)NH, C(O)O, OC(O), OC(O)NH, HNC(O)O, R.sup.3NC(O)NR.sup.3, R.sup.3NC(NR.sup.3)NR.sup.3, R.sup.3NC(S)NR.sup.3, wherein at least one R.sup.3 within each group X is a hydrogen atom; and wherein the groups Y within a molecule may be identical or different from each other and are selected from the groups HNC(O), C(O)NH, C(O)O, OC(O), OC(O)NH, HNC(O)O, R.sup.4NC(O)NR.sup.4, R.sup.4NC(NR.sup.4)NR.sup.4, R.sup.4NC(S)NR.sup.4, wherein at least one R.sup.4 within each group Y is a hydrogen atom. The inventive rubber mixture comprises at least one inventive silane.

Claims

1. A silane of formula I):
(R.sup.1).sub.oSiR.sup.2X-A-Y-[A-Y-].sub.m-A-S.sub.k-A-[-Y-A].sub.mY-A-XR.sup.2Si(R.sup.1).sub.o,I) wherein o may be 1, 2 or 3 and k is an integer greater than or equal to 2 and the radicals R.sup.1 within the silyl groups (R.sup.1).sub.oSi and on both sides of the molecule may be identical or different from each other and are selected from alkoxy groups having 1 to 10 carbon atoms, cycloalkoxy groups having 4 to 10 carbon atoms, phenoxy groups having 6 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, alkyl groups having 1 to 10 carbon atoms, alkenyl groups having 2 to 20 carbon atoms, alkynyl groups having 2 to 20 carbon atoms, aralkyl groups having 7 to 20 carbon atoms, halides or alkyl polyether groups O(R.sup.6O).sub.rR.sup.5 wherein R.sup.6 are identical or different and are branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C.sub.1-C.sub.30 hydrocarbon groups, preferably CH.sub.2CH.sub.2, r is an integer from 1 to 30, preferably 3 to 10, and R.sup.5 are unsubstituted or substituted, branched or unbranched, monovalent alkyl, alkenyl, aryl or aralkyl groups, preferably C.sub.13H.sub.27 alkyl group or two R.sup.1 form a cyclic dialkoxy group having 2 to 10 carbon atoms, in which case o is <3, or two or more silanes of formula I) can be bridged via radicals R.sup.1; and wherein the radicals R.sup.2 within a molecule may be identical or different and are linear or branched alkyl groups having 1 to 20 carbon atoms or cycloalkyl groups having 4 to 12 carbon atoms or aryl groups having 6 to 20 carbon atoms or alkenyl groups having 2 to 20 carbon atoms, alkynyl groups having 2 to 20 carbon atoms or aralkyl groups having 7 to 20 carbon atoms; and wherein the groups X within a molecule may be identical or different from each other and are selected from the groups: HNC(O), C(O)NH, C(O)O, OC(O), OC(O)NH, HNC(O)O, R.sup.3NC(O)NR.sup.3, R.sup.3NC(NR.sup.3)NR.sup.3, R.sup.3NC(S)NR.sup.3, wherein the radicals R.sup.3 within a group X and within a molecule may be identical or different and are selected from a hydrogen atom or as defined for R.sup.2 under the condition that at least one R.sup.3 within each group X is a hydrogen atom; and wherein the groups A within a molecule may be identical or different from each other and are aromatic groups; and, wherein the groups Y within a molecule may be identical or different from each other and are selected from the groups: HNC(O), C(O)NH, C(O)O, OC(O), OC(O)NH, HNC(O)O, R.sup.4NC(O)NR.sup.4, R.sup.4NC(NR.sup.4)NR.sup.4, R.sup.4NC(S)NR.sup.4, wherein the radicals R.sup.4 within a group Y and within a molecule may be identical or different and are selected from a hydrogen atom or as defined for R.sup.2 under the condition that at least one R.sup.4 within each group Y is a hydrogen atom; and wherein each m is independently an integer from 0 to 4, and wherein the silane may also be in the form of oligomers that are formed by hydrolysis and condensation of silanes of formula I).

2. The silane as claimed in claim 1, wherein each m=0.

3. The silane as claimed in claim 1, wherein the groups X are selected from the groups HNC(O), C(O)NH, OC(O)NH, HNC(O)O, R.sup.3NC(O)NR.sup.3, R.sup.3NC(NR.sup.3)NR.sup.3, and R.sup.3NC(S)NR.sup.3.

4. The silane as claimed in claim 1, wherein the groups Y are selected from the groups HNC(O), C(O)NH, OC(O)NH, HNC(O)O, R.sup.4NC(O)NR.sup.4, R.sup.4NC(NR.sup.4)NR.sup.4, and R.sup.4NC(S)NR.sup.4.

5. The silane as claimed in claim 1, wherein the aromatic groups A are selected from the group consisting of phenyl, naphthyl, pyridyl, pyridazyl, pyrimidyl, pyrazyl, triazyl, quinolyl, pyrrole, furan, thiophene, pyrazole, imidazole, thiazole and oxazole radicals.

6. The silane as claimed in claim 1, wherein the radicals R.sup.1 are alkyl groups having 1 to 6 carbon atoms or alkoxy groups having 1 to 6 carbon atoms or halides.

7. The silane as claimed in claim 1, wherein the radicals R.sup.2 are linear or branched alkyl groups having 2 to 8 carbon atoms or cycloalkyl groups having 4 to 8 carbon atoms.

8. The silane as claimed in claim 1, wherein the silane has the following formula II): ##STR00011##

9. The silane as claimed in claim 1, wherein the silane has the following formula III): ##STR00012##

10. The silane as claimed in claim 1, wherein k is an integer from 2 to 8.

11. A rubber mixture comprising at least the silane as claimed in claim 1.

12. A vehicle tire comprising the rubber mixture as claimed in claim 11 at least one component.

Description

(1) The silane of formula IV), as an example of the invention, was prepared in the following way:

(2) 1. Preparation of Bis(4-Carboxyphenyl) Disulfide According to the Synthesis Scheme of Formula VI)

(3) ##STR00005##

(4) A saturated ethanolic iodine solution (25 ml in total) was added dropwise at room temperature to a solution of 4-mercaptobenzoic acid (7.50 g, 48.6 mmol, 1.0 eq.) in ethanol (500 ml, EtOH). On addition, the iodine solution decolorized and the reaction mixture became cloudy. The addition of iodine was continued until the resulting suspension acquired a pale yellow color due to excess iodine.

(5) The reaction mixture was then filtered using a Buchner funnel and the residue was washed with cold demineralized water (450 ml) and cold ethanol (450 ml) to remove the excess iodine.

(6) After drying under high vacuum, the target compound was isolated in the form of a white powder (6.69 g, 21.8 mmol, 90%).

(7) .sup.1H NMR (500 MHz, DMSO-d.sub.6; Dimethyl sulfoxide) 13.08 (s, 2H), 7.97-7.88 (m, 4H), 7.67-7.59 (m, 4H).

(8) .sup.13C NMR (126 MHz, DMSO-d.sub.6) 167.22, 141.16, 130.83, 130.31, 126.54.

(9) 2. Preparation of 1-(4-Aminophenyl)-3-(3-(Triethoxysilyl)Propyl)Urea According to the Synthesis Scheme of Formula VII)

(10) ##STR00006##

(11) 3-(Isocyanatopropyl)triethoxysilane (11.44 ml, 11.44 g, 46.2 mmol, 1.0 eq.) was added dropwise at room temperature to a solution of para-phenylenediamine (10.00 g, 92.5 mmol, 2.0 eq.) in dichloromethane (300 ml of DCM). After stirring overnight, the solvent was removed on a rotary evaporator, affording a gray solid (21.57 g) as the crude product.

(12) Purification by column chromatography was performed in a plurality of small portions of approx. 3-4 g each (approx. 74% by weight yield in each case) on silica gel (DCM/EtOH 9:1).

(13) After drying under high vacuum, the target compound was isolated in the form of a light gray powder (extrapolated for the total product: 15.96 g, 44.9 mmol, 97% based on silane).

(14) .sup.1H NMR (500 MHz, DMSO-d.sub.6) 7.82 (s, 1H), 6.98 (d, J=8.7 Hz, 2H), 6.45 (d, J=8.7 Hz, 2H), 5.91 (t, J=5.8 Hz, 1H), 4.66 (s, 2H), 3.74 (q, J=7.0 Hz, 6H), 3.00 (q, J=6.8 Hz, 2H), 1.48-1.39 (m, 2H), 1.14 (t, J=7.0 Hz, 9H), 0.57-0.49 (m, 2H).

(15) .sup.13C NMR (126 MHz, DMSO-d.sub.6) 155.69, 143.33, 129.62, 120.22, 114.12, 57.70, 41.81, 23.49, 18.24, 7.25.

(16) 3. Preparation of Bis(4-Carboxylchloridophenyl) Disulfide (In Situ) According to the Synthesis Scheme of Formula VIII)

(17) ##STR00007##

(18) Dimethylformamide (0.1 ml of DMF, cat.) was added to a suspension of bis(4-carboxyphenyl) disulfide (1.96 g, 6.4 mmol, 1.0 eq.) in tetrahydrofuran (60 ml of THF). Oxalyl chloride (5.49 ml, 8.12 g, 64.0 mmol, 10.0 eq.) was added dropwise to the reaction mixture at 0 C. and the mixture was stirred at this temperature for 30 min. The resulting yellow solution was then stirred for a further 3 h at RT. The solvent and excess oxalyl chloride were then distilled off. A yellow solid was isolated that was used for the next synthesis step without further analysis or purification (on account of its reactivity).

(19) 4. Preparation of the Silane of Formula II) According to the Synthesis Scheme of Formula IX)

(20) ##STR00008##

(21) A solution of bis(4-carboxylchloridophenyl) disulfide (1.12 g, 3.26 mmol, 1.0 eq.) in THF (40 ml) was added dropwise at RT, over a period of 15 min, to a solution of 1-(4-aminophenyl)-3-(3-(triethoxysilyl)propyl)urea (2.55 g, 7.17 mmol, 2.2 eq.) and triethylamine (2.11 ml, 1.65 g, 16.3 mmol, 5.0 eq.) in THF (10 ml). The resulting pale yellow suspension was subsequently stirred overnight and then filtered. The filter cake was washed with cold THF (210 ml). After drying under high vacuum, the target compound was isolated in the form of a white powder (2.39 g, 2.44 mmol, 75%).

(22) .sup.1H NMR (500 MHz, DMSO-d.sub.6) 10.13 (s, 2H), 8.45 (s, 2H), 7.94 (d, J=8.5 Hz, 4H), 7.67 (d, J=8.6 Hz, 4H), 7.56 (d, J=9.0 Hz, 4H), 7.34 (d, J=9.0 Hz, 4H), 6.23 (t, J=5.8 Hz, 2H), 3.74 (q, J=7.0 Hz, 12H), 3.03 (q, J=6.6 Hz, 4H), 1.52-1.41 (m, 4H), 1.14 (t, J=7.0 Hz, 18H), 0.60-0.51 (m, 4H).

(23) .sup.13C NMR (126 MHz, DMSO-d.sub.6) 164.32, 155.34, 139.05, 136.78, 134.16, 132.49, 128.75, 126.38, 121.10, 117.79, 57.80, 56.12, 41.84, 23.45, 18.31, 7.32.

(24) .sup.29Si NMR (99 MHz, DMSO-d.sub.6) 44.52.

(25) The preparation of the silane V) as a further example of the invention, that is to say preparation of the silane possessing an ortho-linked disulfidic group, is effected in principle analogously to the preparation of silane IV). Therefore, only the differences are described hereafter.

(26) The synthesis proceeds from the commercially available bis(2-carboxyphenyl) disulfide, which is converted to bis(2-carboxylchloridophenyl) disulfide by means of oxalyl chloride according to scheme X):

(27) ##STR00009##

(28) DMF (0.15 ml, cat.) was added to a suspension of bis(2-carboxyphenyl) disulfide (2.94 g, 9.6 mmol, 1.0 eq.) in THF (60 ml). Oxalyl chloride (8.23 ml, 12.19 g, 96.0 mmol, 10.0 eq.) was added dropwise to the reaction mixture at 0 C. and the mixture was stirred at this temperature for 30 min. The resulting yellow solution was then stirred at RT for a further 3 h. The solvent and excess oxalyl chloride were then distilled off.

(29) A yellow solid was isolated that was used for the next synthesis step without further analysis or purification (on account of its reactivity).

(30) This was followed, according to synthesis scheme XI), by reaction with 1-(4-aminophenyl)-3-(3-(triethoxysilyl)propyl)urea, which is prepared as described above.

(31) ##STR00010##

(32) A solution of bis(2-carboxylchloridophenyl) disulfide (3.30 g, 9.6 mmol, 1.0 eq.) in THF (80 ml) was added dropwise at RT, over a period of 15 min, to a solution of 1-(4-aminophenyl)-3-(3-(triethoxysilyl)propyl)urea (7.51 g, 21.1 mmol, 2.2 eq.) and triethylamine (6.65 ml, 4.86 g, 48.0 mmol, 5.0 eq.) in THF (30 ml). The resulting pale yellow suspension was subsequently stirred overnight and then filtered. The filtrate was concentrated and the further solid that precipitated out was filtered off again. The filter cake was washed with cold THF (225 ml) and demineralized water (225 ml). After drying under high vacuum, the target compound was isolated in the form of a white powder (2.70 g, 2.75 mmol, 29%).

(33) .sup.1H NMR (500 MHz, DMSO-d.sub.6) 10.41 (s, 2H), 8.39 (s, 2H), 7.76 (d, J=7.6 Hz, 1H), 7.72 (d, J=8.1 Hz, 1H), 7.60 (d, J=9.0 Hz, 3H), 7.50 (ddd, J=8.5, 7.4, 1.5 Hz, 2H), 7.40-7.34 (m, 6H), 6.14 (t, J=5.7 Hz, 2H), 3.75 (q, J=7.0 Hz, 12H), 3.05 (q, J=6.6 Hz, 4H), 1.54-1.42 (m, 4H), 1.15 (t, J=7.0 Hz, 18H), 0.63-0.51 (m, 4H).

(34) .sup.13C NMR (126 MHz, DMSO-d.sub.6) 165.20, 155.21, 136.85, 136.49, 134.67, 132.32, 131.30, 128.37, 126.25, 126.09, 120.76, 117.77, 57.73, 41.77, 23.39, 18.25, 7.27.

(35) .sup.29Si NMR (99 MHz, DMSO-d.sub.6) 44.57.

(36) The prepared silane of formula IV) and/or V) is mixed into an inventive rubber mixture comprising at least one diene rubber and at least one silica as filler. To this end, the silane of formula IV) and/or V) is preferably adsorbed onto a silica beforehand and subsequently added in this form to the rubber mixture.

(37) Adsorption onto silica is carried out, for example, as follows:

(38) To a suspension of silica, for example granulated silica, in DMF is added, at room temperature, a solution of the silane of formula IV) and/or V) dissolved in DMF in the desired silica/silane ratio. For example, 31.2 g of silica (VN3, Evonik) and 4.62 g of the silane of formula IV) and/or V) are used. The resulting suspension is stirred overnight at 120 C. and the solvent is subsequently removed under reduced pressure. After drying for one day under high vacuum at 40 C., the modified silica thus obtained is comminuted by means of a mortar. It is then dried under high vacuum for a further day at 40 C.

(39) The inventive rubber mixture is by way of example applied in the form of a preformed tread of a vehicle tire (as described above) to a green tire and subsequently vulcanized with the latter.

(40) Exemplary inventive rubber mixtures comprising the silanes of formula IV) or V) are described hereafter and compared with rubber mixtures comprising a silane known from the prior art. The compositions and results are summarized in table 1. The comparative mixtures are identified with a C, the inventive mixtures with an I. The mixtures C1 and I1, and C2 and I2, and C3 and I3 and I4 in each case contain equal molar amounts of the silane from the prior art (C1, C2, C3) or of the inventive silane IV) (I1,I2,I3) or of the inventive silane V) (I4).

(41) The silanes are in each case adsorbed onto the silica (95 phr in each mixture) so that the respectively silane-modified silica was mixed in. The amounts indicated thus refer to the products of the modification reactions, with 95 phr of silica being used in each mixture.

(42) The remaining amount (difference: table value minus 95 phr) thus represents silane bound to the silica.

(43) The mixtures were otherwise produced by the process customary in the rubber industry under standard conditions in two stages in a laboratory mixer with a volume of 80 milliliters to 3 liters, in which, in the first mixing stage (base-mixing stage), all constituents apart from the vulcanization system (sulfur and vulcanization-influencing substances) were first mixed at 145 to 165 C., with target temperatures of 152 to 157 C., for 200 to 600 seconds. By adding the vulcanization system in the second stage (final mixing stage), the finished mixture was produced, with mixing at 90 to 120 C. for 180 to 300 seconds.

(44) All the mixtures were used to produce test specimens by vulcanization to t95 (measured on a moving disk rheometer to ASTM D 5289-12/ISO 6502) under pressure at 160 C., and these test specimens were used to determine material properties that are typical in the rubber industry by the test methods specified hereinafter.

(45) Shore A hardness (Sh A) at room temperature according to ISO 868 Rebound resilience at room temperature according to ISO 4662 Dynamic storage modulus E at 55 C. according to DIN 53 513 at 0.15% and 6% elongation Stress value at 50%, 100%, 200%, 300% and 400% elongation at room temperature according to ISO 37, test specimen type 3 dumbbell

(46) Substances Used: a) Silica: Ultrasil VN3, Evonik, in each case 95 phr, remaining amount in each case bound silane b) TESPD (3,3-bis(triethoxysilylpropyl) disulfide) c) Inventive silane of formula IV), prepared as described above d) Inventive silane of formula V), prepared as described above e) Aging stabilizers, antiozonant wax, zinc oxide, stearic acid f) DPG and CBS.

(47) As can be seen in table 1, the rubber mixtures I1 to I4 have a higher level of stiffness and have a higher hardness. The exemplary embodiments according to the invention, that is to say the mixtures comprising the silanes prepared according to the invention, thus in particular display improved handling indicators.

(48) The inventive examples I1 to I3 comprising the silane according to formula IV) additionally have, with the lower rebound resiliences (compared to C1 to C3), improved wet braking indicators.

(49) TABLE-US-00001 TABLE 1 Constituents Unit C1 C2 C3 I1 I2 I3 I4 NR phr 20 20 20 20 20 20 20 SSBR phr 80 80 80 80 80 80 80 TDAE phr 35 35 35 35 35 35 35 Silica.sup.a) + phr 98.4 99.4 100.5 TESPD.sup.b) Silica.sup.a) + phr 102.7 105.2 107.8 silane IV).sup.c) Silica.sup.a) + phr 107.8 silane V).sup.d) Other additives.sup.e) phr 9 9 9 9 9 9 9 Accelerator.sup.f) phr 3.6 3.6 3.6 3.6 3.6 3.6 3.6 Sulfur phr 2 2 2 2 2 2 2 Properties S50 MPa 1.1 1.2 1.2 1.4 1.5 1.9 1.8 S100 MPa 1.9 1.9 2.0 2.3 2.6 3.1 3.0 S200 MPa 3.9 4.0 4.2 4.7 5.8 6.3 6.1 S300 MPa 6.3 6.6 7.0 7.6 9.6 10.1 9.7 S400 MPa 9.0 9.2 9.9 10.8 13.4 13.8 13.3 E (6%) MPa 8.5 9.5 8.3 10.1 10.5 11.6 10.9 E (0.15%) MPa 17.0 18.7 16.0 21.5 21.6 24.9 29.8 Hardness RT Sh A 71.4 71.9 71.5 75 77.9 79 79.7 Rebound resilience % 17.4 18 15.8 RT 17.4 16.6 15.8 25.4