Title of Invention

"PROCESS FOR PREPARING PRECIPITATED SILICI C ACI D"

Abstract Process for preparing precipitated silicic acid having a Al 0 content of 0.2 to 5.0 wt.% and a wk coefficient of less 2 3 than 3.4 characterised in that alkali silicate solution is reacted with mineral acids and an aluminium salt solution such as herein described in aqueous media at temperatures of 60 to 95o C, at a pH of 7.0 to 10.0, the reaction is continued to a solids concentration of 40 to 110 g/1, the pH is adjusted to a value between 3 and 5, and the precipitated silicic acid obtained is worked up in a known manner.
Full Text The present invention relates to precipitated silicic acids, a process for their preparation, and their use in rubber mixtures.
It is known to incorporate precipitated silicic acids into rubber mixtures (see Wolff, Kautschuk, Gummi, Kunstst. 7 (1988) p.674). Precipitated silicic acids have to be readily dispersible when used in rubber mixtures. A poor dispersibility is often the reason why precipitated silicic acids are not used in tyre mixtures.
Document WO 95/09128 discloses precipitated silicic acids that can be used in tyres. Their use in tyre carcasses is however not mentioned.
On account of the more stringent requirements of the tyre industry, even the improved dispersion of this precipitated silicic acid is no longer sufficient for use in tyre treads.
WO 96/30304 describes a precipitated silicic acid that can be dispersed in tyre treads.
Using the known precipitated silicic acid described in WO 96/30304 it is possible to achieve a reduction in the rolling resistance of the tyre by 20 - 30% compared to tyres filled with carbon black. This corresponds to a saving in fuel of ca. 5%.
Different tyre constituents contribute in various proportions to the rolling resistance of an automobile tyre:

2

Tread: 50%
Belt: 20%
Carcase: 10%
Side wall: 10%
Tyre bead: 5%
Inner layer: 5%
In a lorry tyre the proportion of the individual tyre segments to the rolling resistance differs from the distribution in an automobile tyre:

Tread: 30%
Belt: 20%
Carcase: 24%
Side wall: 10%
Tyre bead: 16%
This distribution of the proportions contributing to the rolling resistance shows that in automobile tyres 50% and in lorry tyres even up to 70% of the rolling resistance is due to structural parts of the tyre carcase. Up to now carbon black has overwhelmingly been used as active filler in tyre carcasses.
The invention relates to the development of precipitated silicic acids for use in tyre carcasses, with the aim of achieving a further considerable reduction in the rolling resistance. The prerequisite for the use of precipitated silicic acids in tyre carcasses is their easy dispersibility.
Some sections of the automobile industry demand that the rolling resistance be reduced by approximately a further
10%. Up to now it has not been possible to achieve this.

3
Lorry tyre customers are in addition asking for an increase in the service life of lorry tyres. The use of precipitated silicic acids according to the invention is also meeting this request, combined with a reduction in the amount of heat generated.
The present invention provides a precipitated silicic acid that is characterised by an A12O3 content of 0.2 to 5.0 wt.% and a wk coefficient of less than 3.4.
The precipitated silicic acid according to the invention may have a BET surface of 80 to 180 m2/g.
The precipitated silicic acid according to the invention may have a CTAB surface of 80 to 139 m2/g.
The precipitated silicic acid according to the invention may be characterised by the following physico-chemical data:

BET surface 80 - 180 m2/g
CTAB surfacd
80 - 139 m2/g
BET/CTAB ratio Sears No. (com 1.0 - 1.6

sumption of
0.1 N NaOH) 5 - 2 5 ml
DBP No. 200 - 300 ml/100 g
A12O3 content wk coefficient
Degraded/particles Non-degradable particles 1.0 - 100 m
The physico-chemical data are determined using the following methods:

4
BET surface Areameter, Fa. Strohlein,
according to ISO 5794/Annex D
CTAB surface At pH 9, according to Jay, Janzen
and Kraus in "Rubber Chemistry and Technology" 44 (1971) 1287
Sears No. According to G. W. Sears, Analyt.
Chemistry 12 (1956) 1982
DBP No. ASTM D 2414-88
wk coefficient Cilas Granulometer 1064 L (for
description see below)
The precipitated silicic acid according to the invention may in a preferred embodiment exhibit the following physico-chemical data:
BET surface 90 - 150 m2/g
CTAB surface 80 - 130 m2/g
BET/CTAB ratio 1.0 - 1.6
Sears No. 5 - 25 ml
(consumption of
0.1 N NaOH)
DBP No. 200 - 300 ml/100 g
A12O3 content wk coefficient Degraded particles Non-degradable particles 1.0 - 30 m
The precipitated silicic acid according to the invention may in a particularly preferred embodiment exhibit the following physico-chemical data:

5
BET surface 90 - 150 m2/g
CTAB surface 80 - 130 m2/g
BET/CTAB ratio 1.0 - 1.6
Sears No. 5 - 25 ml
(consumption of
0.1 N NaOH)
DBP No. 200 - 300 ml/100 g
A12O3 content 0.2 - 0.66%
wk coefficient Degraded particles Non-degradable particles 1.0 - 30 m

The invention also provides a process for the preparation of the precipitated silicic acid with the following physico-chemical parameters:
BET surface 80 - 160 m2/g
CTAB surface 80 - 140 m2/g
BET/CTAB ratio 1.0 - 1.6
Sears No. 5 - 25 ml
(consumption of
0.1 N NaOH)
DBP No. 200 - 300 ml/100 g
A12O3 content 0.2 - 5%
wk coefficient Degraded particles
Non-degradable particles 1.0 - 100 m

which is characterised in that alkali silicate is reacted with mineral acids and aluminium sulfate solution at temperatures of 60 - 95°C at a pH of 7.0 - 11.0 while stirring continuously, the reaction is continued until a solids concentration of 40 g/1 - 110 g/1 is achieved, the pH is adjusted to a value between 3 and 5, and the precipitated silicic acid is filtered off, washed, then dried and optionally ground or granulated.

6
In a particular modification the addition of water glass, aluminium sulfate solution and sulfuric acid may be discontinued for 30 - 90 minutes and then continued.
In a preferred embodiment commercially available sodium water glass (modulus 3.2 - 3.5) may be reacted with sulfuric acid at a pH between 7.5 and 10.5, some of the sodium water glass being added beforehand to adjust the pH in the reaction vessel. The addition of water glass and sulfuric acid is maintained over a period of up to 120 minutes, wherein in a particular modification the addition may be discontinued for 30 - 90 minutes, following which the reaction mixture may be acidified to pH 3 - 5, filtered, washed and dried.
In order to achieve a particularly good dispersibility the simultaneous addition of sodium water glass and sulfuric acid preferably takes place over a period of between 40 and 90 minutes. The surface of the silicic acid can be adjusted via the precipitation duration.
Chamber filter presses or membrane filter presses or band filters or rotary filters or automatic membrane filter presses or two of the filters in combination may be used for the filtration.
A pneumatic drier, rack drier, flash drier, spin-flash drier or similar equipment may be used for the drying.
In a further embodiment of the invention liquefied filter cakes may be dried in a spray drier with an atomiser or two-substance nozzle or a single-substance nozzle and/or integrated flow bed.

7
A roller-type compactor or similar equipment may be used for the granulation.
In a particularly preferred modification the precipitated silicic acids may be dried by means of a flash drying.
The precipitated silicic acid according to the invention may be modified with organosilanes of the formulae I to
III:

in which
B denotes -SCN, -SH, -Cl, -NH2 (when q = 1)
or -Sx- (when q = 2),
R and R1 denote an alkyl group with 1 to 4 carbon
atoms, the phenyl radical, all radicals R and R in each case being the same or having a different meaning,
R denotes a C1 to C4-alkyl or C1 to C4-alkoxy
group,
n denotes 0, 1 or 2,

8
Alk denotes a divalent linear or branched
hydrocarbon radical with 1 to 18 carbon atoms,
m denotes 0 or 1,
Ar denotes an arylene radical with 6 to 12
carbon atoms, preferably with 6 carbon atoms,
p denotes 0 or 1, provided that p and n do
not simultaneously denote 0,
x denotes an integer from 2 to 8,
Alkyl denotes a monovalent linear or branched
saturated hydrocarbon radical with 1 to 20 carbon atoms, preferably 2 to 8 carbon atoms,
Alkenyl denotes a monovalent linear or branched
unsaturated hydrocarbon radical with 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms, and
q denotes 1 or 2.
The silanes listed in Table 1 may preferably be used:

Table 1
Silane

* limited availability

10
The modification with organosilanes may be carried out in mixtures of 0.5 to 50 parts, referred to 100 parts of precipitated silicic acid, in particular 2 to 15 parts, referred to 100 parts of precipitated silicic acid, wherein the reaction between the precipitated silicic acid and organosilane may be carried out during the preparation of the mixture (in situ) or outside (pre-modified) by spraying and then tempering the mixture, or by mixing the silane and the silicic acid suspension, followed by drying and tempering.
In a preferred embodiment of the invention
bis(triethoxysilylpropyl) tetrasulfane (trade name Si 69 of
Degussa AG) may be used as silane.
The precipitated silicic acid according to the invention may be incorporated as reinforcing filler into vulcanisable rubber mixtures in amounts of 2 to 200 parts, referred to 100 parts of rubber, as powder, microbeads or granules, with or without silane modification.
The addition of one or more of the aforementioned silanes to the rubber mixture may take place together with the silicic acids according to the invention, the reaction between the filler and silane occurring during the mixing process at elevated temperatures (in situ modification) or in an already pre-modified form (for example DE-PS 40 04 781) , in other words both reaction partners are reacted outside the actual preparation of the mixture.
A further possibility is to modify the precipitated silicic acids with organosilanes in mixtures of 0.5 to 50 parts, referred to 10 0 parts of precipitated silicic acid, in particular 2 to 15 parts, referred to 100 parts of precipitated silicic acid, wherein the reaction between the precipitated silicic acid and organosilane is carried out

11
during the preparation of the mixture (in situ) or outside the preparation, by spraying followed by tempering the mixture, or by mixing the silane and the silicic acid suspension followed by drying and tempering.
In addition to mixtures that contain as fillers exclusively the silicic acids according to the invention, with and without organosilanes according to formulae I to III, the rubber mixtures may in addition be filled with one or more fillers having a greater or lesser reinforcing effect. For example a blend of carbon blacks (for example furnace, gas, flame, acetylene carbon blacks) and the silicic acids according to the invention, with and without silane, as well as of natural fillers, for example clays, silica chalks, further known and commercially available silicic acids, and the silicic acids according to the invention, may be used.
The blend ratio is governed in this case, as in the metering of the organosilanes, according to the property spectrum to be achieved in the finished rubber mixture. The ratio of the precipitated silicic acids according to the invention to the other aforementioned fillers may be 5 - 95%.
In addition to the silicic acid according to the invention, the organosilanes and other fillers, the elastomers form a further important constituent of the rubber mixture. The silicic acids according to the invention may be used in all types of rubber crosslinkable with accelerators/sulfur, as well as rubbers crosslinkable with peroxides. Elastomers that may be mentioned in this connection are natural and synthetic elastomers, oil-extended or not, as individual polymers or blends with other rubbers, for example natural rubbers, butadiene rubbers, isoprene rubbers, butadiene-styrene rubbers, in particular SBR, produced by means of

12
solution polymerisation, as well as butadiene-acrylonitrile rubbers, butyl rubbers, and terpolymers of ethylene, propylene and unconjugated dienes. The following additional rubbers are also suitable for rubber mixtures with the aforementioned rubbers:
Carboxyl rubbers, epoxide rubbers, trans-polypentenamers, halogenated butyl rubbers, 2-chloro-butadiene rubbers, ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, and optionally also chemical derivatives of natural rubber as well as modified natural rubbers.
Further additives such as plasticisers, stabilisers, activators, pigments, anti-oxidants and processing aids may be used in the conventional amounts.
The precipitated silicic acids according to the invention, with and without silane, may be used in all rubber applications, particularly in tyres, above all in tyre carcasses, but also for example in conveyor belts, seals, V-belts, hoses, shoe soles, etc.
The precipitated silicic acid according to the invention may furthermore be used in battery separators, in silicone rubber, and as supporting silicic acid.
In order to achieve a good property spectrum in a polymer mixture, the dispersion of the precipitated silicic acid in the matrix, i.e. the polymer, is of decisive importance.
It has been found that the wk coefficient is a measure of the dispersibility of a precipitated silicic acid.
The wk coefficient is determined as follows:

13
The measurement is based on the principle of laser diffraction, a CILAS granulometer 1064 L being used for the measurement.
To carry out the determination 1.3 g of the precipitated silicic acid is added to 25 ml of water and treated for 4M minutes with ultrasound at 100 W (90% pulsed). The solution is then transferred to the measuring cell and treated for a further minute with ultrasound.
The detection is performed during the ultrasound treatment using two lasers diodes arranged at different angles to the sample. The laser beams are diffracted according to the principle of light diffraction. The resultant diffraction pattern is evaluated with a computer. The method enables the particle size distribution to be determined over a wide measurement range (ca. 4 0 nm - 500 m) .
An essential point in this connection is that the energy supplied by the ultrasound simulates the energy supplied by mechanical forces in industrial mixing equipment used in the tyre industry.
The results of the measurements of the particle size distribution of precipitated silicic acids according to the invention and of comparison silicic acids are shown in Figs. 1-6.
The curves show a first maximum in the particle size distribution in the range around 1.0 - 100 urn, and a further maximum in the range
14
that proportion of silicic acid particles that have been comminuted during the ultrasound treatment. These very-small particles can be dispersed extremely well in rubber mixtures.
The wk coefficient denotes the ratio of the peak height of the non-degradable particles (B), whose maximum is in the range 1.0 - 100 m (B1), to the peak height of the degraded particles (A), whose maximum is in the range The schematic diagram according to Fig. 7 illustrates these relationships.
The wk coefficient is thus a measure of the "degradability" (= dispersibility) of the precipitated silicic acid. It is found that a precipitated silicic acid is more easily dispersible the smaller the wk coefficient, i.e. the more particles that are degraded during incorporation into rubber.
The silicic acids according to the invention have wk coefficients The dispersibility of a precipitated silicic acid is expressed by the dispersion coefficient D. This is measured according to the following formula:

15
Sum of particle area/image area x 10 000 x Medalia factor
D[%] =
Filler volume x image area
Filler volume/100 + 0.78
Medalia factor =
2
The evaluation is carried out by light microscopy at 150 x magnification on polished sections of the vulcanisates. Particles of size larger than 28 urn were evaluated as non-dispersible particles. 40 images were evaluated.
Examples
The following substances are used in the examples:
SMR 2 0 Natural rubber
SMR 10 Natural rubber
Buna CB 10 Butadiene rubber
Krynol 1712 Styrene-butadiene rubber based on emulsion
polymerisation Buna SB 1500 Styrene-butadiene rubber based on emulsion
polymerisation X 50 S 50:50 blend of Si 69 (bis(3-triethoxy-
silylpropyl)tetrasulfane and N 330 ZnO RS Zinc oxide Stearic acid
Sunpar 150 Paraffin oil Naftolen ZD Aromatic oil Novares C 80 Resin
Koresin Phenol-formaldehyde resin (Pastilles) Antilux 654 Microcrystalline wax

16
Vulkanox 4020 N-(1,3-dimethylbutyl)-N'-phenyl-p-
phenylenediamine Vulkanox 4010 Antioxidant NA/LG
Vulkanox Antioxidant HS/LG
Protector Antiozonant wax
G 35 P
Cofill 11 GR Resorcinol-based bonding agent
HEXA K Hexamethylenetetramine
DPG Diphenyl guanidine
CBS N-cyclohexyl-2-benzthiazylsulfenamide
TBBS N-tert.butyl-2-benzthiazylsulfenamide
Sulfur
Crystex, Insoluble sulfur
insoluble
Comparison products:
Corax N 326 Carbon black from Degussa
Corax N 375 Carbon black from Degussa
Corax N 660 Carbon black from Degussa
Ultrasil VN2 Silicic acid from Degussa with a N2-surface
of ca. 125 m2/g; A12O3 content 0.16 wt. % Ultrasil Vn3 Silicic acid from Degussa with a N2-surface
of ca. 125 mz/g; A12O3 content 0.17 wt.% Hisil 233 Silicic acid from PPG with a N2-surface of
ca. 150 m2/g; A12O3 content 0.33 wt.%
Perkasil KS Silicic acid from Akzo with a N2-surface of
300 ca. 125 m2/g; A12O3 content 0.14 wt.%
Perkasil KS Silicic acid from Akzo with a N2-surface of
404 ca. 160 m2/g; A12O3 content 0.15 wt.%
Perkasil KS Silicic acid from Akzo with a N2-surface of
408 ca. 160 m2/g; A12O3 content 0.15 wt.%
Zeosil 1165 Silicic acid from Rhone-Poulenc with a N2-MP
surface of ca. 150 m2/g; A12O3 content
0.65 wt.%

17 Example 1
Preparation of a precipitated silicic acid in the N2-range from 120 to 140 m2 /g
46 m3 of water are heated in a vat to 88°C while stirring. While maintaining the temperature at 88°C there are added at pH 9.0, which is adjusted by addition of water glass, sufficient water glass (modulus 3.42, density 1.348) and 96% sulfuric acid under constant stirring, so that after 125 minutes a solids content of 88.5 g/1 is reached. In addition 265 1 of an aluminium sulfate solution {density 1.28) are metered in at the same time while stirring constantly. Sulfuric is then added until a pH of between 3 and 5 is reached. The solid is separated on a filter press, washed, and then dried and if necessary ground.
The precipitated silicic acid obtained has the following physico-chemical data:
4
BET surface 123 m2/g
CTAB surface 110 m2 g
BET/CTAB 1.12
DBP No. 203 ml/100 g
Sears No. 9.7
A12O3 content 0.59%
wk coefficient 0.5
Example 2
Preparation of a precipitated silicic acid in the N2-range
2
from 130 to 150 m /g
53.5 1 of water are heated to 80°C in a vat while stirring. While maintaining the temperature at 80°C, there are added at pH 9.0, which is adjusted by adding water glass,

18
sufficient water glass (modulus 3.42, density 1.348) and 50% sulfuric acid under constant stirring, so that after 61 minutes a solids content of 92.9 g/1 is reached. In addition 0.255 1 of an aluminium sulfate solution (density 1.28) is metered in while stirring constantly. Sulfuric acid is then added until a pH of between 3 and 5 is reached. The solid is separated on a filter press, washed, and then subjected to a brief or prolonged drying and if necessary ground.
The precipitated silicic acid obtained has the following physico-chemical data:
BET surface 129 m2/g
CTAB surface 124 m2g
BET/CTAB 1.04
DBP No. 243 ml/100 g
Sears No. 16.2
A12O3 content 0.59%
Example 3
Preparation of a precipitated silicic acid in the N2-range from 120 to 140 m2 /g
54.6 1 of water are heated to 80°C in a vat while stirring. While maintaining the temperature at 80°C there are added at pH 9.0, which is adjusted by adding water glass, sufficient water glass (modulus 3.42, density 1.348) and 50% sulfuric acid under constant stirring, so that after 6 7 minutes a solids content of 91.4 g/1 is reached. In addition 0.784 1 of an aluminium sulfate solution (density 1.28) is metered in while stirring constantly. Sulfuric acid is then added until a pH of between 3 and 5 is reached. The solid is separated on a filter press, washed,

19
and then subjected to a brief or prolonged drying and if necessary ground.
The precipitated silicic acid obtained has the following physico-chemical data:
BET surface 152 m2/g
CTAB surface 12 9 m2g
BET/CTAB 1.19
DBP No. 241 ml/100 g
Sears No. 16.4
A12O3 content 0.98%
Example 4
Preparation of a precipitated silicic acid in the N2-range
2
from 120 to 140 m g
50.4 1 of water are heated to 80°C in a vat while stirring. While maintaining the temperature at 80°C there are added at pH 9.0, which is adjusted by adding water glass, sufficient water glass (modulus 3.42, density 1.348) and 50% sulfuric acid under constant stirring, so that after 67 minutes a solids content of 97.6 g/1 is reached. In addition 1.47 1 of an aluminium sulfate solution (density 1.28) is metered in while stirring constantly. Sulfuric acid is then added until a pH of between 3 and 5 is reached. The solid is separated on a filter press, washed, and then subjected to a brief or prolonged drying and if necessary ground.
The precipitated silicic acid obtained has the following physico-chemical data:

20
BET surface 130 m2/g
CTAB surface 101 m2g
BET/CTAB 1.2 9
DBP No. 227 ml/100 g
Sears No. 18.4
A12O3 content 1.96%
Example 5
Preparation of a precipitated silicic acid in the N2-ra.nge
2
from 140 to 160 m /g
50.4 1 of water are heated to 80°C in a vat while stirring. While maintaining the temperature at 80°C there are added at pH 9.0, which is adjusted by adding water glass, sufficient water glass (modulus 3.42, density 1.348) and 50% sulfuric acid under constant stirring, so that after 67 minutes a solids content of 99.4 g/1 is reached. In addition 2.21 1 of an aluminium sulfate solution (density 1.28) is metered in while stirring constantly. Sulfuric acid is then added until a pH of between 3 and 5 is reached. The solid is separated on a filter press, washed, and then subjected to a brief or prolonged drying and if necessary ground.
The precipitated silicic acid obtained has the following physico-chemical data:
BET surface 154 m2/g
CTAB surface 100 m3g
BET/CTAB 1.54
DBP No. 222 ml/100 g
Sears No. 16.6
A12O3 content 4.28%

21
Example 6
Determination of the wk coefficient with the Cilas granulometer 1064 L on a silicic acid according to the invention having a BET surface of 110-130 m /g according to Example 1 and comparison with standard silicic acids in the same surface range. In addition the values B, A, B1 and A' according to Fig. 7 are specified.

Example 7
Determination of the wk coefficient with the Cilas granulometer 1064 L on a silicic acid according to the invention having a BET surface of 120-140 m2/g and comparison with standard silicic acid in the same surface range. In addition the values B, A, B' and A1 according to Fig. 7 are specified.

Example 8
Determination of the wk coefficient with the Cilas granulometer 10 64 L on a silicic acid according to the

22
invention having a BET surface of 140-160 m /g and comparison with standard silicic acids in the same surface range. In addition the values B, A, B' and A' according to Fig. 7 are specified.

Table 2
WK coefficients of the precipitated silicic acids according to the invention

Example 9
Measurement results of the precipitated silicic acids according to the invention of Example 6 and Example 7 compared to standard precipitated silicic acids (see Figs 1-6 in the Appendix).

23
Example 10
Precipitated silicic acid according to the invention of Example 4 (with a A12O3 content of 0.59 wt.%) compared to 3 standard silicic acid and the hitherto used blend of carbon black N 660 and carbon black N 375 in a NR/BR mixture for a tyre side wall:

The silicic acid according to the invention of Example 9 results in a higher vulcanisation rate, higher modulus values, lower heat build-up (corresponding to a longer tyre life) and a higher ball rebound 60 °C and a lower tan 5 60 °C (corresponding to a lower rolling resistance), compared to the standard silicic acid Zeosil 1165 MP with an Al203 content of 0.65 wt.% and a CTAB surface of 150 m2/g and a wk coefficient of 3.4, and to the carbon black N 375 hitherto used in a side wall mixture.

24
Example 11
Precipitated silicic acid according to the invention of Example 1 compared to the hitherto used carbon black N 32 6 in a NR/SBR mixture for a tyre carcase with a special bonding system:

The silicic acid according to the invention of Example 1 results in a higher separation strength (corresponding to a more reliable processing in the tyre assembly) compared to the carbon black N 326 hitherto used in a carcase mixture with a special bonding system.

980059,FH
25 Figs. 1 to 7
Fig. 1 Results of measurements on Ultrasil VN 2 by the laser diffraction method.
Fig. 2 Results of measurements on Perkasil KS 300 by the laser diffraction method.
Fig. 3 Results of measurements on silicic acid
according to the invention of Example 1 by the laser diffraction method.
Fig. 4 Results of measurements on Hisil 233 by the laser diffraction method.
Fig. 5 Results of measurements on silicic acid
according to the invention of Example 4 by
the laser diffraction method. Fig. 6 Results of measurements on silicic acid
according to the invention of Example 2 by
the laser diffraction method.
Fig. 7 Determination of the wk coefficient.

-26-WE CLAIMS
1. Process for preparing precipitated silicic acid having a
Al 0 content of 0.2 to 5.0 wt.X and a wk coefficient of less
2 3 than 3.4 characterised in that alkali silicate solution is
reacted with mineral acids and an aluminium salt solution such am
o herein described in aqueous media at temperatures of 60 to 95 C,
at a pH of 7.0 to 10.0, the reaction is continued to a solids concentration of 40 to 110 9/1, the pH is adjusted to a value between 3 and 5, and the precipitated silicic acid obtained is worked up in a known manner.
2. Process for preparing a precipitated silicic acid as claimed in claim 1 having the following parameters:
2
BET surface 80 - 180 m /9
2
CTAB surface 80 - 139 m /9
BET/CTAB ratio 1.0 - 1.6
Sears No. 5 - 25 ml
(consumption of 0.1 N NaOH)
DBP No. 200 - 300 ml/100 9
Al2 03 content wk coefficient Degraded particles Non-degradable particles 1.0 - 100 m

-27-
characterised in that alkali silicate solution is reacted with mineral acids and aluminium sulfate solution at temperatures of 60° - 95° C at a pH of 7.0 - 10.0 while stirring constantly, the addition of alkali silicate solution, mineral acid and aluminium sulfate solution is optionally discontinued for 30 to 90 minutes, the reaction is continued to a solids concentration of 40 - 110 g/1, the pH is adjusted to a value between 3 and 5, and the precipitated silicic acid is filtered off, washed and then dried, and is optionally ground or granulated.
3- Process as claimed in claim 1, wherein chamber filter presses or membrane filter presses or band filters or rotary filters or automatic membrance filter presses or two of the filters in combination are used for the filtration.
4. Process as claimed in claim 1 wherein a pneumatic dryer,
rack dryer, flash dryer, spin-flash dryer or similar devices are
used for the drying -
5. Process as claimed in claim 1 wherein 1iquefied filter
cakes are dried in a spray drier with an atomiser or two-
substance nozzle or single-substance nozzle and/or integrated
flow bed.
6- Process as claimed in claim i wherein a rolling compactor or similar devices are used for the granulation.

-28-
7. Process for preparing the silicic acids as claimed in claim 1, wherein their surfaces have been modified with organo-silanes of the formulae I to III

in which
B denotes -BCNt -SHt -Cl , -NH2 (when q =1)
or -Sx- ( when q = 2) , 1 R and R denote an alkyl group with i to 4 carbon atoms,
the phenyl radicalf all radicals R and
I R in each case being the same or
having a different meaning,
R denotes a C1 to C4 - alkyl or C1 to C4 -alkoxy
group,
n denotes 0, 1 or 2,
Alk denotes a divalent linear or branched hydrocarbon
radical with 1 to 18 carbon atoms,
m denotes 0 or 1,
Ar denotes an arylene radical with 6 to 12 carbon
atoms, preferably with 6 carbon atoms,

-29-
p denotes 0 or 1, provided that p and n do
not simultaneously denote 0,
x denotes an integer from 2 to 8,
Alkyl denotes a monovalent linear or branched
saturated hydrocarbon radical with 1 to 20 carbon atoms, preferably 2 to 8 carbon atoms,
Alkenyl denotes a monovalent linear or branched
unsaturated hydrocarbon radical with 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms, and
q denotes 1 or 2
the precipitated silicic acids are modifi ed with organosi1 fanes in mixtures of 0.5 to 50 parts, referred to 100 parts of precipitated silicic acid, in particular I to 15 parts, referred to 100 parts of precipitated silicic acid, the reaction between the precipitated silicic acid and organosiliane being carried out during the preparation of the mixture
- 30 -
preparation by spraying and then tempering the mixture, or by mixing the si lane and the silicic acid suspension, followed by drying and tempering.
Process for preparing precipitated silicic acid having a
Al 0 content of 0.2 to 5.0 wt.% and a wk coefficient of less
2 3 than 3.4 characterised in that alkali silicate solution is
reacted with mineral acids and an aluminium salt solution such as
herein described in aqueous media at temperatures of 60 to 95o C,
at a pH of 7.0 to 10.0, the reaction is continued to a solids concentration of 40 to 110 g/1, the pH is adjusted to a value between 3 and 5, and the precipitated silicic acid obtained is worked up in a known manner.

Documents:

00745-cal -1999 abstract.pdf

00745-cal -1999 claims.pdf

00745-cal -1999 correspondence.pdf

00745-cal -1999 description(complete).pdf

00745-cal -1999 drawings.pdf

00745-cal -1999 form-1.pdf

00745-cal -1999 form-18.pdf

00745-cal -1999 form-2.pdf

00745-cal -1999 form-5.pdf

00745-cal -1999 g.p.a.pdf

00745-cal -1999 letters patent.pdf

00745-cal -1999 others document.pdf

00745-cal -1999 priority document.pdf

00745-cal -1999 reply f.e.r.pdf


Patent Number 206431
Indian Patent Application Number 745/CAL/1999
PG Journal Number 17/2007
Publication Date 27-Apr-2007
Grant Date 27-Apr-2007
Date of Filing 01-Sep-1999
Name of Patentee DEGUSSA A.G
Applicant Address BENNIGSENPLATZ 1, D-40474 DUSSELDORF
Inventors:
# Inventor's Name Inventor's Address
1 BLUME ANKE ELDERBACHWEG 2,D-50374 ERFTSTADT
2 FREUND BURKHARD KOLNER RING 90,D-50374 ERFTSTADT
3 SCHWAIGER BERNHARD DROSSELWEG 26F,D-50374, ERFTSTADT
4 SIRAY MUSTAFA MICHAEL-LEVEILLY-STRASSE 14 D-53127 BONN,
5 UHRLANDT STEFAN LOORWEG 113, D-51143 KOLN;GERMANY
PCT International Classification Number C08K 3/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 19840153.1 1998-09-03 Germany