Silane-modified silicic acid, method for the production and use thereof

Abstract

The invention relates to silane-modified silicas having a BET surface area of 40 to 155 m.sup.2/g, a sulphur content between 0.05% and 25% by weight and a particle size d5 of 4 m, and d50 of 16 m. The silane-modified silicas are used in rubber mixtures.

Claims

1. A silane-modified silica, wherein the BET surface area is 40 to 155 m.sup.2/g; the sulphur content is between 0.05% and 25% by weight relative to the total weight of the silane-modified silica; and the particle size d.sub.5 is 4 m and d.sub.50 is 16 m.

2. The silane-modified silica according to claim 1, wherein the BET surface area is 50 to 135 m.sup.2/g.

3. The silane-modified silica according to claim 1 wherein the sulphur content is between 0.05% and 10% by weight relative to the total weight of the silane-modified silica.

4. The silane-modified silica according to claim 1 comprising SCN groups.

5. A process for preparing the silane-modified silica according to claim 1, the process comprising: reacting at least one silica having a BET surface area of 40 to 150 m.sup.2/g and a particle size d.sub.5 of 4 m and d.sub.50 of 16 m with at least one sulphur-containing silane.

6. The process for preparing the silane-modified silica according to claim 5, wherein the sulphur-containing silane is an organosilicon compound or a mixture of organosilicon compounds of the general formula (I)
Z-A-S.sub.x-A-Z(I) wherein, x is a number from 1 to 14; Z is SiX.sup.1X.sup.2X.sup.3; wherein, X.sup.1, X.sup.2, X.sup.3 are each independently a hydrogen (H), a halogen or hydroxyl (OH), an alkyl substituent, an alkyl acid substituent (C.sub.yH.sub.2y+1)C(O)O wherein y is 1 to 14, an alkenyl acid substituent or a substituted alkyl or alkenyl acid substituent, a linear or branched, cyclic hydrocarbon chain having 1-8 carbon atoms, a cycloalkyl radical having 5-12 carbon atoms, a benzyl radical or a halogen- or alkyl substituted phenyl radical, an alkoxy group having linear or branched hydrocarbon chains having (C.sub.1-24) atoms, an alkoxy group having linear or branched polyether chains having (C.sub.1-24) atoms, a cycloalkoxy group having (C.sub.5-12) atoms, or a halogen- or alkyl-substituted phenoxy group or a benzyloxy group; and A is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C.sub.1-C.sub.30-comprising hydrocarbon chain.

7. The process for preparing the silane-modified silica according to claim 5, wherein the sulphur-containing silane is an organosilicon compound or a mixture of organosilicon compounds of the general formula (II)
X.sup.1X.sup.2X.sup.3Si-A-SSiR.sup.1R.sup.2R.sup.3(II) wherein, X.sup.1, X.sup.2, X.sup.3 are each independently a hydrogen (H), a halogen or hydroxyl (OH), an alkyl substituent, an alkyl acid substituent (C.sub.yH.sub.2y+1)C(O)O wherein y is 1 to 14, an alkenyl acid substituent or a substituted alkyl or alkenyl acid substituent, a linear or branched, cyclic hydrocarbon chain having 1-8 carbon atoms, a cycloalkyl radical having 5-12 carbon atoms, a benzyl radical or a halogen- or alkyl-substituted phenyl radical, an alkoxy group having linear or branched hydrocarbon chains having (C.sub.1-24) atoms, an alkoxy group having linear or branched polyether chains having (C.sub.1-24) atoms, a cycloalkoxy group having (C.sub.5-12) atoms, or a halogen- or alkyl-substituted phenoxy group or a benzyloxy group; A is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C.sub.1-C.sub.30-comprising hydrocarbon chain; and R.sup.1, R.sup.2, R.sup.3 are each independently a (C.sub.1-C.sub.16) alkyl, a (C.sub.1-C.sub.16) alkoxy, a (C.sub.1-C.sub.16) haloalkyl, an aryl, a (C.sub.7-C.sub.16) aralkyl, H, a halogen or X.sup.1X.sup.2X.sup.3Si-A-S.

8. The process for preparing the silane-modified silica according to claim 5, wherein the sulphur-containing silane is an organosilicon compound or a mixture of organosilicon compounds of the general formula (III)
X.sup.1X.sup.2X.sup.3Si-A-Sub(III) wherein, X.sup.1, X.sup.2, X.sup.3 are each independently as a hydrogen (H), a halogen or hydroxyl (OH), an alkyl substituent, an alkyl acid substituent (C.sub.yH.sub.2y+1)C(O)O wherein y is 1 to 14, an alkenyl acid substituent or a substituted alkyl or alkenyl acid substituent, a linear or branched, cyclic hydrocarbon chain having 1-8 carbon atoms, a cycloalkyl radical having 5-12 carbon atoms, a benzyl radical or a halogen or alkyl-substituted phenyl radical, an alkoxy group having linear or branched hydrocarbon chains having (C.sub.1-24) atoms, an alkoxy group having linear or branched polyether chains having (C.sub.1-24) atoms, a cycloalkoxy group having (C.sub.5-12) atoms, or a halogen- or alkyl-substituted phenoxy group or a benzyloxy group; A is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C.sub.1-C.sub.30-comprising hydrocarbon chain; and Sub is SH or SCN.

9. The process for preparing the silane-modified silica according to claim 8, wherein the organosilicon compounds are of the formula (EtO).sub.3Si(CH.sub.2).sub.3SCN.

10. A rubber mixture comprising rubber, the silane-modified silica according to claim 1, and optionally at least one member selected from the group consisting of precipitated silica, carbon black, and rubber auxiliaries.

11. A process comprising producing pneumatic tyres for passenger and heavy goods vehicles, tyre treads for passenger and heavy goods vehicles, tyre constituents for passenger and heavy goods vehicles, cable sheaths, hoses, drive belts, conveyor belts, roller coverings, pedal cycle and motorcycle tyres and constituents thereof, shoe soles, gasket rings, profiles and damping elements comprising the rubber mixture according to claim 10.

12. The rubber mixture of claim 10, which has a reduced Mooney viscosity relative to a rubber mixture lacking the silane-modified silica.

13. The rubber mixture of claim 10, which has an improved dispersancy as measured by dispersion topography and a decreased vulcanization energy input relative to a rubber mixture lacking the silane-modified silica.

14. The rubber mixture of claim 10, which has an improved abrasion resistance relative to a rubber mixture lacking the silane-modified silica.

15. A paint, a lacquer, a printing ink, a coating, an adhesive, a lubricant, a cosmetic, a toothpaste, a building auxiliary, or a filler in vulcanizable rubber, silicones or plastics comprising the silane-modified silica according to claim 1.

16. A rubber mixture comprising rubber, the silane-modified silica according to claim 1, and at least one of precipitated silica, carbon black, and further rubber auxiliaries.

17. The silane-modified silica according to claim 1 obtained by reaction of at least one silica with at least one sulphur containing silane that is an organosilicon compound or a mixture of organosilicon compounds of the formula (EtO).sub.3Si(CH.sub.2).sub.3SCN.

Description

EXAMPLES

Sears Number

(1) The Sears numbers are determined based on G. W. Sears, Analyt. Chemistry 12 (1956) 1982, by the following method: Before the titration, the filler is ground in a mill, in the course of which it is homogenized and comminuted. 2.5 g of the sample thus obtained are admixed with 60 ml of methanol in a 250 ml titration vessel and, as soon as the solid has been fully wetted, a further 40 ml of water are added to the suspension. A stirrer (Ultra-Turrax) is used to disperse the suspension for 30 sec, which is then diluted with a further 100 ml of water. The suspension is equilibrated to 25 C. over at least 20 minutes. The titration is effected on a titroprocessor with pH electrode (e.g. DL 67, Mettler Toledo with DG 111 SC electrode), as follows: first stir for 120 sec; adjust suspension to pH 6 with 0.1 N potassium hydroxide or hydrochloric acid; meter in 20 ml of NaCl solution (250 g/l); titrate with 0.1 N KOH from pH 6 to pH 9; convert the result to 5 g of silica, i.e. to consumption of 0.1 N KOH in ml per 5 g of silica to reach pH 9 from pH 6.

(2) The present determination is a further development, increase in precision and improvement on the process described in G. W. Sears, Analyt. Chemistry 12 (1956) 1982.

(3) BET Surface Area

(4) The samples are dried at 105 C. for 15-20 h and the BET surface area is determined to DIN 66131 (volumetric method).

(5) Particle Size Distribution

(6) All the samples were screened through a 500 m screen. The particle size distribution of the samples is determined by laser diffraction analysis with ultrasound treatment for 3 minutes using a Cilas 1064 L (from Quantachrome) in accordance with the commonly known rules and operating instructions.

(7) The sample preparation for the analysis (purging etc.) by means of the Cilas 1064 L laser diffraction unit (S/N 152, from Quantachrome; measurement range 0.04-500 m and 400 ml wet dispersion unit with integrated ultrasound) is effected in the case of unmodified silicas with the aid of 0.05% m/m tetrasodium diphosphate in demineralized water as dispersion liquid, and in the case of silane-modified silicas with an ethanol/water mixture (volume ratio 1:1) as dispersion liquid.

(8) Before the start of the analysis, the laser diffraction system has to warm up for 2 hours. Thereafter, the Cilas 1064 L is purged two to four times.

(9) The material to be analysed is screened through a 500 m screen. From the <500 m fraction, about 0.5-1.0 g of sample is required for the analysis, depending on the nature of the material.

(10) The following parameters relevant for the particle analysis should be set:

(11) Ultrasound during dispersion: 180 seconds

(12) Number of measurements: 1

(13) Pump speed: 120 rpm (fixed on the instrument)

(14) Stirrer speed: 300 rpm (fixed on the instrument)

(15) Optical model: Fraunhofer (fixed on the instrument)

(16) After conducting the background measurement, the silica sample is added.

(17) After stirring the silica suspension for 60 seconds, followed by ultrasound treatment for 3 minutes, the analysis is effected while the suspension is being pumped in circulation. The target measurement concentration for the analysis is 120+/30. If the measurement concentration is below the target concentration level, the analysis should be stopped and the sample weight increased. If the measurement concentration is exceeded, there is the possibility of automatic dilution by the Cilas 1064 L.

(18) The software calculates the particle size distribution from the raw data curve with the aid of the Fraunhofer theory.

(19) Sulphur Content

(20) For the determination of the average sulphur content of the samples, samples are taken from the autoclave inserts at both ends of the insert and in the middle, and the sulphur content thereof is determined by known processes, by: Schniger digestion in an oxygen atmosphere (cf. F. Ehrenberger, S. Gorbauch, Methoden der organischen Elementar-und Spurenanalyse [Methods of organic elemental and trace analysis], Verlag Chemie GmbH, Weinheim/Bergstrasse, 1973) and downstream ion chromatography analysis (Metrohm 690 ion chromatograph; Hamilton PRP X-100 column; eluent: 2 mmol salicylate buffer, pH 7) to DIN ISO 10304-2.

(21) The average sulphur content of the overall sample is then obtained as the arithmetic mean of the 3 values thus determined for the individual samples.

(22) Water Content

(23) The water content of the samples is determined as follows:

(24) 10 g of the silanized silica are comminuted with a coffee grinder for 15 seconds and then the water content is determined by the known rules familiar to the person skilled in the art with a Karl Fischer titrator (from Metrohm, 720 KFS Titrino) and the Karl Fischer titration chemicals No. 1.09241, No. 1.09243 and No. 1.06664 available from Merck (disodium tartrate dihydrate).

(25) Carbon Content

(26) The carbon content of the samples is determined by known standard methods by means of a LECO CS-244 carbon/sulphur determinator.

(27) The silica used is Perkasil KS 300 from Grace.

Example 1: Preparation of Silica A

(28) A stainless steel reactor with propeller stirring system and jacket heating is initially charged with 1510 l of water and 46 kg of waterglass (density 1.348 kg/l, 27.0% SiO2, 8.05% Na.sub.2O). Subsequently, while stirring vigorously at 92 C. for 90 minutes, 6.655 kg/min of the abovementioned waterglass and about 0.832 kg/min of sulphuric acid (density 1.83 kg/l, 96% H.sub.2SO.sub.4) are metered in. This metered addition of sulphuric acid is regulated such that an alkali number of 7 prevails in the reaction medium. Subsequently, the addition of waterglass is stopped and further sulphuric acid is fed in until a pH of 8.5 (measured at room temperature) is attained. After a rest period of about 30 min, further sulphuric acid is metered in until a pH of 4.5 has been attained. The resulting suspension is filtered with a membrane filter press and washed with water and dried.

Example 2: Preparation of Silica B

(29) A stainless steel reactor with propeller stirring system and jacket heating is initially charged with 1550 l of water and 141.4 kg of waterglass (density 1.348 kg/l, 27.0% SiO2, 8.05% Na.sub.2O). Subsequently, while stirring vigorously at 92 C. for 100 minutes, 5.505 kg/min of the abovementioned waterglass and about 0.65 kg/min of sulphuric acid (density 1.83 kg/l, 96% H.sub.2SO.sub.4) are metered in. This metered addition of sulphuric acid is regulated such that an alkali number of prevails in the reaction medium. Subsequently, the addition of waterglass is stopped and further sulphuric acid is fed in until a pH of 9.0 (measured at room temperature) is attained. The addition of sulphuric acid is stopped and the suspension obtained is stirred at 90 C. for a further 60 minutes. Thereafter, the addition of sulphuric acid is restarted and a pH of 3.5 (measured at room temperature) is established. The resulting suspension is filtered with a membrane filter press and then dried.

(30) Table 1 shows the analytical data of the silicas and the particle sizes (Table 2).

(31) TABLE-US-00001 TABLE 1 Perkasil Unit KS 300 Silica A Silica B BET m.sup.2/g 125 127 120 CTAB m.sup.2/g 122 122 112 pH 7.2 7.2 6.5 Moisture % 5.5 5.5 6.4 content

(32) TABLE-US-00002 TABLE 2 Perkasil Unit KS 300 Silica A Silica B d5 m 3.9 5.85 6.14 d50 m 12.6 19.98 21.39 d95 m 35.1 40.89 42.45 dmedian m 15.2 21.11 22.34

(33) For the production of the silane-modified silicas, an FM40 Henschel mixer fluid mixer from the Zeppelin Reimelt company in Kassel is used. The Henschel mixer consists of a 40 liter mixing vessel with hinged lid, both provided with jackets for temperature control medium (oil). The mixing tools are driven from beneath by means of an electric motor with a drive belt. The mixing tool speed is variable up to 2500 rpm and is set by means of a handwheel.

(34) Si 69 is bis(triethoxysilylpropyl) tetrasulphide and Si 264 is 3-thiocyanatopropyltriethoxysilane from Evonik Industries AG.

Example 3: Preparation of the Inventive Silane-Modified Silica (Silica A+Si 264)

(35) The Henschel mixer is initially charged with the appropriate amount of filler and the mixer is switched on. The mixing tool speed is set to the appropriate value. The silane is sprayed into the mixer by means of an ultrasound nozzle. Subsequently, the mixer outlet valve is opened and the product is discharged from the mixer.

(36) The mixing conditions are listed in Table 3. The silica used is silica A (Example 1), and the silane Si 264.

Example 4: Preparation of the Inventive Silane-Modified Silica (Silica A+Si 69)

(37) The preparation is effected analogously to Example 3. The mixing conditions are listed in Table 3. The silica used is silica A (Example 1), and the silane Si 69.

Example 5: Preparation of the Inventive Silane-Modified Silica (Silica B+Si 264)

(38) The preparation is effected analogously to Example 3. The mixing conditions are listed in Table 3. The silica used is silica B (Example 2), and the silane Si 264.

Example 6: Preparation of the Inventive Silane-Modified Silica (Silica B+Si 69)

(39) The preparation is effected analogously to Example 3. The mixing conditions are listed in Table 3. The silica used is silica B (Example 2), and the silane Si 69.

Example 7: Preparation of Silane-Modified Silica (Perkasil KS 300P Silica+Si 264)

(40) The preparation is effected analogously to Example 3. The mixing conditions are listed in Table 3. The silica used is Perkasil KS 300P, and the silane Si 264.

Example 8: Preparation of Silane-Modified Silica (Perkasil KS 300P Silica+Si 69)

(41) The preparation is effected analogously to Example 3. The mixing conditions are listed in Table 3. The silica used is Perkasil KS 300P, and the silane Si 69.

(42) TABLE-US-00003 TABLE 3 Example Example Example Example Example Example 3 4 5 6 7 8 Flow temperature 20 20 20 20 20 20 ( C.) Amount of filler 3 3 3 3 3 3 (kg) Amount of silane 0.330 0.270 0.330 0.270 0.330 0.270 (kg) Mixing temperature (55) (55) (55) (55) (55) (55) ( C.) Stirrer speed (rpm) 1500 1500 1500 1500 1500 1500 Nozzle diameter (mm) (0.5) (0.5) (0.5) (0.5) (0.5) (0.5) Atomization pressure 40 40 40 40 40 40 (bar) Mixing time (min) 7 7 7 7 7 7

(43) Table 4 shows the particle sizes of the silane-modified silicas.

(44) TABLE-US-00004 TABLE 4 Example Example Example Example Example Example Unit 3 4 5 6 7 8 d5 m 4.47 4.21 4.13 4.31 3.84 3.87 d50 m 19.70 19.31 20.65 20.16 15.74 15.57 d95 m 43.33 43.55 46.20 47.12 46.17 46.46 Dmedian m 21.02 20.76 21.84 21.88 19.47 19.51 Sulphur % by 1.21 1.84 1.21 1.84 1.21 1.84 content weight

Example 9: Rubber Mixtures

(45) The formulation used for the rubber mixtures is specified in Table 5 below. The unit phr means parts by weight based on 100 parts of the raw rubber used. The general method for producing rubber mixtures and vulcanizates thereof is described in the following book: Rubber Technology Handbook, W. Hofmann, Hanser Verlag 1994.

(46) TABLE-US-00005 TABLE 5 Amount Amount Amount Amount Amount Amount Amount Amount [phr] [phr] [phr] [phr] [phr] [phr] [phr] [phr] Mixture 1 2 3 4 5 6 7 8 1st stage Buna.sup. EP G 150 150 150 150 150 150 150 150 5455 Perkasil KS 60 60 0 0 0 0 0 0 300 Inv. Example 3 0 0 61 0 0 0 0 0 Inv. Example 4 0 0 0 62 0 0 0 0 Inv. Example 5 0 0 0 0 61 0 0 0 Inv. Example 6 0 0 0 0 0 62 0 n Comparative 0 0 0 0 0 0 62 0 Example 7 Comparative 0 0 0 0 0 0 0 62 Example 8 Si 264 1 0 0 0 0 0 0 0 Si 69.sup. 0 2 0 0 0 0 0 0 Stearic acid 2 2 2 2 2 2 2 2 ZnO 4 4 4 4 4 4 4 4 Vivatec 500 30 30 30 30 30 30 30 30 Vulkanox 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 4020/LG 2nd stage Stage 1 batch Vulkacit 1 1 1 1 1 1 1 1 Mercapto C Robac TBED 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Rhenocure TP/S 2 2 2 2 2 2 2 2 Rhenogran DPG- 2.5 2.5 2.5 2.5 2..5 2.5 2.5 2.5 80 Sulphur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

(47) The polymer Buna EP G 5455 is an ethylene-propylene terpolymer having a moderate unsaturation level (ENB content=4.3) containing 50 phr paraffinic oil from Lanxess. The polymer has a Mooney viscosity (ML 1+4/125 C./ML(1+8)) of 46. The mineral oil used is Vivatec 500 from the H&R Group. Vulkanox 4020 is 6PPD from Lanxess. Vulkacit Mercapto C is a commercial product from Lanxess.

(48) Robac TBED is a commercial product from Robinson Brothers. Rhenocure TP/S and Rhenogran DPG-80 are commercial products from Rheinchemie.

(49) The rubber mixtures are produced in an internal mixer according to the mixing method in Table 6.

(50) TABLE-US-00006 TABLE 6 Stage 1 Settings Mixing unit Werner & Pfleiderer N type Speed 60 min.sup.1 Ram pressure 5.5 bar Capacity 1.60 l Fill level 0.70 Flow temp. 60 C. Mixing process 0 to 1 min Buna EP G 5455 silica or silanized silica, optionally silane, ZnO, stearic acid, Vulkanox 1 to 2 min clean and mix 2 to 3 min silica or silanized silica, Vivatec 3 to 4 min clean and mix 4 to 5 min silica or silanized silica, Vivatec 5 to 6 min clean and mix 6 to 7 min mix 7 min discharge Batch temp. 90-130 C. Storage 4 h at room temperature Stage 2 Settings Mixing unit As in stage 1 except: Flow temp. 40 C. Speed 50 min.sup.1 Fill level 0.68 Mixing process 0 to 2 min Stage 1 batch, accelerator, sulphur 2 min discharge Batch temp. 80-100 C. Storage 4 h at room temperature

(51) Table 7 summarizes the methods for rubber testing.

(52) TABLE-US-00007 TABLE 7 Physical testing Standard/conditions ML 1 + 4, 100 C., 3rd stage DIN 53523/3, ISO 667 Vulkameter test, 165 C. DIN 53529/3, ISO 6502 Dmax Dmin [dNm] t10% and t90% [min] Ring tensile test, 23 C. DIN 53504, ISO 37 Tensile strength [MPa] Stress values [MPa] Elongation at break [%] Shore A hardness, 23 C. [SH] DIN 53 505 Viscoelastic properties DIN 53 513, ISO 2856 0 and 60 C., 16 Hz, initial force 50N and amplitude force 25 N Dynamic modulus E* [MPa] Loss factor tan [ ] Ball rebound, 23 C., 60 C. [%] ASTM D 5308 DIN abrasion, force 10N [mm.sup.3] DIN 53 516

(53) The results of the rubber tests are compiled in Table 8.

(54) TABLE-US-00008 TABLE 8 Mixture 1 2 3 4 5 6 7 8 ML(1 + 4) 100 C. MU 76 77 64 63 63 64 67 71 1st stage ML(1 + 4) 100 C. MU 68 66 61 60 59 60 64 63 2nd stage Energy input, [kWh] 0.51 0.50 0.46 0.44 0.45 0.41 0.43 0.41 1st stage Specific energy/ [kWh/Kg] 0.45 0.44 0.41 0.38 0.39 0.35 0.38 0.36 1st stage MDR: 165 C.; 0.5 t20% min 0.6 1.0 0.6 0.7 0.7 0.7 0.5 0.5 t90% min 6.3 7.6 4.8 6.1 5.2 5.5 4.8 6.1 t80%-t20% min 3.5 4.2 2.6 3.3 2.7 2.9 2.6 3.3 100% modulus MPa 1.1 1.3 0.9 1.1 1.0 1.2 0.9 1.1 300% modulus MPa 3.8 4.6 4.5 5.9 4.8 6.3 4.5 5.9 300%/100% modulus 3.5 3.5 5.0 5.4 4.8 5.3 5.0 5.4 Elongation at % 491 469 584 413 505 355 584 413 break Shore A SH 46 48 45 48 46 49 45 48 hardness DIN abrasion, mm.sup.3 192 193 146 128 133 134 146 128 10N Ball rebound, % 72.9 72.9 67.8 68.6 67.5 69.7 67.8 68.6 RT Ball rebound, % 80.5 79.4 75.1 79.6 74.2 79.8 75.1 79.6 70 C. MTS, 16 Hz, 50N+/25N E*, 0 C. MPa 5.4 5.6 5.6 5.5 5.6 5.6 5.6 5.5 E*, 60 C. MPa 5.5 5.9 5.4 5.7 5.4 5.8 5.4 5.7 Dispersion 344 357 128 134 188 205 336 386 topography Sum of the peaks Peak area % 25.6 27.2 10.6 11.3 13.2 15.5 24.0 26.2 (topo)

(55) As is apparent from Table 8, mixtures 3-6 show a significant improvement in the energy required during the mixing operation. The Mooney viscosities of the mixtures with the inventive silanized silicas are much improved.

(56) The mixtures with the inventive silanized silicas show better (quicker) vulcanization characteristics combined with simultaneous retention of scorch resistance and improved abrasion resistance.

(57) The modulus, elongation at break and dynamic data of the mixtures with the inventive silanized silicas are at the same level as the comparative mixtures.