JP4898421B2 - Special precipitated silicic acid for use in rubber - Google Patents

Description

  The present invention relates to a precipitated silicic acid with extremely slight microporosity and high rubber activity, a process for its preparation and the use of the precipitated silicic acid as a filler for rubber mixtures.

  The use of precipitated silicic acid in elastomer mixtures, for example in tire tread mixtures, has long been known (EP 0501227). High requirements are imposed for the use of silicic acid as a reinforcing filler in rubber mixtures, for example, in particular for the production of air-filled tires and industrial rubber products. The silicic acid must be simple and well mixable in the rubber and dispersible, and must form a chemical bond with the rubber in conjunction with the coupling reagent, preferably the difunctional organosilicon compound, In this case, this chemical bond must lead to a high degree of reinforcement that is sought to achieve the rubber mixture. The basis for this strengthening characteristic can be particularly high static tension values and low wear values. For the strengthening properties of silicic acid, in particular, the particle size, the surface morphology, the surface activity and the binding ability of the coupling reagent are critically important.

In the use of rubber, a precipitated silicic acid having a primary particle size of 10 to 50 nm is usually used. The primary particle size can be measured, for example, by transmission electron spectroscopy (TEM) image evaluation (RH Lange, J. Bloedorn: "Das Elktronenmikroskop, TEM + REM" Thieme Verlag, Stuttgart, New York (1981)). . Surface area measured by adsorption of small nitrogen molecule N _2, below, is referred to as BET surface area, (S. Brunauer, PH Emmett , E. Teller, "Adsorption of Gases in Multimolecular Layers", J. Am. Chem. Soc 60, 309 (1938)) is typically in the range of 50 to 200 m ² / g, preferably 110 to 180 m ² / g. The normal surface area for rubber is the surface area measured by adsorption of even larger N-cetyl-N, N, N-trimethylammonium bromide molecules, hereinafter referred to as CTAB surface area (Janzen, Kraus, Rubber Chem. Technol. 44, 1287 (1971)). In order to perform the measurement accurately, detailed description will be made in accordance with the description of the specification. The difference between the BET surface area and the CTAB surface area can hereinafter be referred to as microporous and is expressed as a silicate surface area, in which case the silicate surface area is unacceptable for rubber and thus has a reinforcing action. I can't. Usually, the BET / CTAB ratio of commercial activated silicic acid exceeds 1.05, which indicates a correspondingly high degree of microporosity.

  Moreover, those skilled in the art will be able to physisorb and chemisorb low molecular weight compounds such as difunctional organosilicon compounds and vulcanization accelerators in the pores of microporous silicic acid, thereby relating to function. Thus, it is known that it can no longer influence rubber crosslinking as a rubber adhesion aid or vulcanization accelerator.

  Furthermore, those skilled in the art know coupling reagents, usually bifunctional organosilicon compounds, from S. Wolff, “Chemical Aspects of Rubber Reinforcement by Fillers”, Rubber Chem. Technol. 69, 325 (1996), The bifunctional organosilicon compound modifies the surface having the rubber action as uniformly and quantitatively as possible. Denaturation can be done by pre-coating of silicic acid in the substance or in the solvent / suspension (ex-situ) (U. Goerl, R. Panenka, "Silanisierte Kieselsaeuren-Eine neue Produktklasse fuer zeitgemaesse Mischungsentwicklung", Kautsch. Gummi Kunstst. 46, 538 (1993)) and during mixing (in-situ) (the ACS Meeting, April 4-6, 2000, Dallas, Texas / USA) Luginsland, "Processing of Silica / Silane-Filled Tread Compounds", paper No. 34), in which in-situ denaturation is preferential and in the manner normally used. is there. It is therefore necessary to deliberately increase the surface concentration with reactive silanol groups capable of binding organosilicon compounds to ensure rapid and quantitative silanization of the rubbery surface. is there. The internal aggregate structure of silicic acid is usually measured by DBP measurement (J. Behr, G. Schramm, "Ueber die Bestimmung der Oelzahl von Kautschuk fuellstoffen mit dem Brabender-Plastographen", Gummi Asbest Kunstst. 19, 912 (1966)). . A high DBP number is required to ensure an optimal dispersion of the filler in the rubber. Moisture above 4% is required to ensure rapid and complete silanization of silicic acid surfaces with organosilicon compounds (U. Goerl, A. Hunsche, A. Mueller, HG Koban, "Investigation into" the Silica / Silane Reaction System ", Rubber Chem. Technol. 70, 608 (1997)).

From the description in JP-A-14-179844, rubber mixtures with silicic acid are known in which the difference between the BET surface area and the CTAB surface area of silicic acid is less than 15 m ² / g. High Sears number V ₂ as a measure of the number of silanol groups required for high activity compared to difunctional organosilicon compounds and high required for very good dispersion in rubber The DBP number is not described. However, the two numbers are important for the high reinforcement criteria of the rubber mixture as well as for the good tire wear rate as well as the slight microporosity.

  In connection with the production of silicic acid, various methods are known to those skilled in the art. That is, precipitation at a constant pH value is described in EP 0937755. Silicic acid precipitated in the case of a constant cation excess is disclosed in DE 10124298. In DE 101 12 441 A1, EP 0 755 899 A2 and U.S. Pat. No. 4,0013,79, precipitation with a constant alkali number (AZ number) was described. .

  Silicic acid for use in rubber is generally produced by a process in which precipitation is carried out at a temperature of 60-95 ° C. and a constant pH value of 7-10. For example, see European Patent Application No. 0901986 specification A1.

  It is an object of the present invention to provide a new and easily dispersible precipitated silicic acid which can be incorporated into an elastomer mixture and improves the properties of this elastomer mixture. Furthermore, a corresponding process for the production of silicic acid should be provided.

Therefore, the subject of the present invention is
CTAB surface area 100-200 m ² / g, and advantageous ranges 100-160 m ² / g, 100-130 m ² / g and 110-125 m ² / g,
BET / CTAB ratio of 0.8 to 0.99,
DBP number 210-280 g / (100 g), advantageous range 250-280 g / (100 g),
Sears number V ₂
10-30 ml / (5 g), and preferred ranges 20-30 ml / (5 g) and 21-28 (ml / 5 g),
4-8% moisture,
The ratio of the Sears number _{V 2} pairs BET surface area
0.150 to 0.370 ml / (5 m ² )
It is an easily dispersible precipitated silicic acid characterized by having

Furthermore, the precipitated silicic acid according to the invention has the following physical and chemical parameters:
BET surface area of 80-210 m ² / g, in this case precipitated silicic acid is 80-110 m ² / g BET surface area in the first embodiment and 110-150 m ² / g, preferably 110-129 m ^{2 in the second} embodiment. / G,
The ratio of the Sears number _{V 2} and the BET surface area
0.150 ~0.370ml / ^(5m 2), and advantageous range 0. 170 to 0.320 ml / (5 m ² ), 0.180 to 0.300 ml / (5 m ² ), particularly preferably 0.190 to 0.280 ml / (5 m ² ) and 0.190 to 0.240 ml / (5 m ² ),
The primary particle size can advantageously have one or more of 10-50 nm.

In one preferred embodiment, the precipitated silicic acid according to the invention has a Sears number V ₂ of 22 to 25 ml / (5 g), further 25 to 28 ml / (5 g).

Precipitated silicas of the present invention, high the absolute number (Sears number V ₂₎ of silanol groups was significantly elevated compared to precipitated silica of the prior art, the enhanced ratio of the Sears number V ₂ and BET surface area Have. That is, the precipitated silicic acid according to the invention has a very high number of silanol groups, especially in relation to the total surface area.

  Along with the increased number of silanol groups, the precipitated silicic acid according to the invention exhibits a slight microporosity, ie a very low BET / CTAB ratio.

The combination of features described, in particular the high Sears number V ₂ / BET ratio, makes the precipitated silicic acid according to the invention outstandingly suitable as a reinforcing filler for elastomers. In this case, the precipitated silicic acid according to the invention exhibits an increased rubber activity, very good dispersion behavior and a much shorter vulcanization time.

Furthermore, the subject of the present invention is
CTAB surface area 100-200 m ² / g, and advantageous ranges 100-160 m ² / g, 100-130 m ² / g and 110-125 m ² / g,
BET / CTAB ratio 0.8-0,99 ,
DBP number 210-280 g / (100 g), advantageous range 250-280 g / (100 g),
Sears number V ₂
10-30 ml / (5 g), and preferred ranges 20-30 ml / (5 g) and 21-28 (ml / 5 g),
Moisture 4-8%
As well as the following physical and chemical parameters:
BET surface area of 80-210 m ² / g, in this case precipitated silicic acid is 80-110 m ² / g BET surface area in the first embodiment and 110-150 m ² / g, preferably 110-129 m ^{2 in the second} embodiment. / G,
The ratio of the Sears number _{V 2} and the BET surface area
0.150 ~0.370ml / ^(5m 2), and advantageous range 0. 170 to 0.320 ml / (5 m ² ), 0.180 to 0.300 ml / (5 m ² ), particularly preferably 0.190 to 0.280 ml / (5 m ² ) and 0.190 to 0.240 ml / (5 m ² ),
Alkaline metal silicates or alkaline earth metals which can be used for the preparation of precipitated silicic acid according to the invention having a primary particle size of preferably 10 to 50 nm and which initially have a pH value of 7 to 14 Charging an aqueous solution of silicate and / or an aqueous solution of an organic base and / or an inorganic base,
b) metering water glass and acidifying agent at 55-95 ° C. with stirring for 10-120 minutes, preferably 10-60 minutes simultaneously with stirring
g) The resulting suspension is further stirred at a high temperature of 80 to 98 ° C. for 1 to 120 minutes, preferably 10 to 60 minutes,
h) acidify the pH to about 2.5-5 with an acidifying agent;
i) A process characterized by filtration, washing, drying and optionally granulating.

  The charge may reach about 20, 30, 40, 50, 60, 70, 80 or 90% of the final volume of precipitation. The basic compound supplied to the charge is selected from the group of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkali metal bicarbonates and alkali metal silicates. Yes. Preferably, water glass and / or caustic soda liquid is used. The pH value of the charging solution is 7 to 14, preferably 10 to 11.

  The addition of water glass and acidifying agent in step b) can be carried out in such a way that the pH value of the reaction solution is kept constant or can be varied. However, it is also possible to carry out the precipitation with a certain alkali number. If the precipitation is carried out at a constant pH value, this pH value is preferably in the range from 7 to 11. Precipitation with a constant alkali number is preferably carried out with an alkali number of 15-40.

After step b), the method according to the invention comprises
c) Stop feeding for 30-90 minutes while maintaining temperature and d) Concurrent feeding of water glass and acidifying agent for 20-120 minutes, preferably 20-80 minutes, possibly with stirring at the same temperature. With up to two aiming points.

Subsequent to step b) or d), in the process according to the invention, the addition of water glass is stopped and, if the desired pH value is still not achieved, further acidifying agent is added in the next step e). Thus, the acidifying agent is metered in at the same or modified rate until a pH value of 5-11, preferably 7-10, is achieved.

In order to change the concentration of water glass used in the reaction, in some cases f) the pH value can be adjusted to 3-11 by addition of other acidifying agents and / or alkali metal hydroxides. By supplying one or more basic compounds from the group of alkaline earth metal hydroxides, alkali metal carbonates, alkali metal hydrogen carbonates and alkali metal silicates, preferably 9-10, in particular 7 It can be increased to a value of ~ 11. Preferably, water glass and / or caustic soda liquid is used.

  The supply of the acidifying agent in step e) or the supply of the basic compound in step f) can be carried out at 40-98 ° C. Preferably, the feeding is carried out at 55-95 ° C., particularly preferably at the temperature selected also for step b) or d).

  In some cases, another aiming point may be incorporated between steps d) and e).

  Furthermore, in some cases, additional addition of organic or inorganic salts may be performed during one or more of steps a) to h). This can be carried out in solution or as a solid, respectively, over the addition time of water glass and acidifying agent, respectively, or as a batch amount addition. It is also possible to dissolve the salt in one or two components and then add it together with the components at the same time.

As the inorganic salt, an alkali metal salt or an alkaline earth metal salt is preferably used. In particular, the following ions:
Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , H ⁺ , F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , SO ₃ ²⁻ , SO ₄ ^{2 −} , HSO ₄ ⁻ , PO ₃ ²⁻ , PO ₄ ³⁻ , NO ₃ ⁻ , NO ₂ −, CO ₃ ²⁻ , HCO ₃ ⁻ , OH ⁻ , TiO ₃ ²⁻ , ZrO ₃ ²⁻ , ZrO ₄ ⁴⁻ , AlO ₂ ⁻ , Al ₂ O ₄ ²⁻ , BO ₄ ³⁻
Any combination of the above may be used.

Formic acid, acetic acid and propionic acid salts are suitable as organic salts. Cations include the described alkali metal ions or alkaline earth metal ions. The concentration of the salt in the added solution is 0.01 to 5 mol / l. Preferably, Na ₂ SO ₄ is used as the inorganic salt.

  It is possible to supply the acidifying agent in steps b) and d) in the same or different manner, i.e. at the same or different concentrations and / or inflow rates.

  Similarly, water glass may be fed to the reaction in steps b) and d) either in the same way or in different ways.

  In a special embodiment, the components acidifying agent and water glass in steps b) and d) are fed such that the inflow rate of step d) is 125-140% of the inflow rate of step b), in this case The components are used in equimolar concentrations in the two steps, respectively. Preferably, the components are added at the same concentration and flow rate.

Also, other silicates such as potassium silicate or calcium silicate may be used together with water glass (sodium silicate solution). As the acidifying agent, another acidifying agent such as HCl, HNO ₃ , H ₃ PO ₄ or CO ₂ may be used together with sulfuric acid.

  Filtration and long-time or short-time drying of the silicic acid according to the invention is common for those skilled in the art and can be confirmed, for example, from the publications described.

  Preferably, the silicic acid by precipitation is dried in a flow dryer, spray dryer, shelf dryer, belt dryer, rotary tubular dryer, flash dryer, rotary flash dryer or nozzle tower. This drying variant involves operation with a nebulizer, a single or two mass flow nozzle or an integrated fluidized bed. After drying, optionally grinding and / or granulation may be carried out in a cylinder compactor (Walzenkompaktor). Preferably, the precipitated silicic acid according to the invention has a particle shape with an average diameter of more than 15 μm, in particular more than 80 μm, particularly preferably more than 200 μm after the drying step or pulverization or granulation (measured according to ISO 2591-1) December 1988). Particularly preferably, the precipitated silicic acid according to the invention is in the form of a powder having an average diameter of more than 15 μm, or in the form of essentially circular particles (microbeads) having an average diameter of more than 80 μm, or granules having an average diameter of more than 1 mm. It exists in the form of

Furthermore, the subject of the present invention is the production of elastomer mixtures, vulcanizable rubber mixtures and / or other vulcanizates,
CTAB surface area 100-200 m ² / g, and advantageous ranges 100-160 m ² / g, 100-130 m ² / g and 110-125 m ² / g,
BET / CTAB ratio of 0.8 to 0.99,
DBP number 210-280 g / (100 g), advantageous range 250-280 g / (100 g),
Sears number V ₂
10-30 ml / (5 g), and preferred ranges 20-30 ml / (5 g) and 21-28 (ml / 5 g),
Moisture 4-8%
As well as the following physical and chemical parameters:
BET surface area of 80-210 m ² / g, in this case precipitated silicic acid is 80-110 m ² / g BET surface area in the first embodiment and 110-150 m ² / g, preferably 110-129 m ^{2 in the second} embodiment. / G,
The ratio of the Sears number _{V 2} and the BET surface area
0.150 ~0.370ml / ^(5m 2), and advantageous range 0. 170 to 0.320 ml / (5 m ² ), 0.180 to 0.300 ml / (5 m ² ), particularly preferably 0.190 to 0.280 ml / (5 m ² ) and 0.190 to 0.240 ml / (5 m ² ),
Use of precipitated silicic acid according to the present invention having one or more primary particle sizes of 10 to 50 nm.

  Accordingly, another object of the present invention is to provide an elastomer mixture containing silicic acid according to the invention, a vulcanizable rubber mixture and / or other vulcanizates such as moldings such as pneumatic tires, tire treads, cable jackets. Tubes, drive belts, belt conveyors, roll coatings, tires, shoe soles, packing rings and cushioning members.

Furthermore, the silicic acid according to the invention is usually used in all fields of use where silicic acid is used, for example battery separators, as anti-sticking agents, as coloring agents and as matting agents in paints, as agricultural products and nutrients. It may be used as a carrier for coatings, printing inks, digested powders, plastics, non-impact printing, paper stock, personal care and special uses. The range of non-impact printing, for example, use for inkjet methods,
Use of the silica according to the invention in printing inks for thickening or to avoid spraying and storage,
Paper as a filler, coating pigments, tracing paper for thermal sublimation to avoid blurring of printing ink, improve contour visibility (Bildgrundruhe) and contrast, and improve dot sharpness and color brightness (LIchtpauspapier), the use of silicic acid according to the present invention for thermal transfer paper.

  The use of the personal care range is, for example, the use of the silicic acid according to the invention as a filler or thickener in the pharmaceutical or body care range.

In some cases, the silicic acid according to the invention has the formulas I to III:
[SiR ¹ _n (RO) _r (Alk) _m (Ar) _p ] _q [B] (I),
SiR ¹ _n (RO) _3-n (alkyl) (II), or SiR ¹ _n (RO) _3-n (alkenyl) (III)
[In the above formula,
B is —SCN, —SH, —Cl, —NH ₂ , —OC (O) CHCH ₂ , —OC (O) CCH ₃ ) CH ₂ (when q is 1) or —S _w — (q is In this case, B is chemically bonded to Alk,
R and R ¹ may optionally have the following groups: hydroxy group, amino group, alcoholate group, cyanide group, thiocyanide group, halogen group, sulfonic acid group, sulfonic acid ester group, thiol group, benzoic acid group, benzoic acid An aliphatic group having 2 to 30 C atoms, an olefinic group, an aromatic group or an optionally substituted acid group, carboxylic acid group, carboxylic acid ester group, acrylate group, methacrylate group or organosilane group Represents an aryl aromatic group, in which R and R ¹ may have the same or different meanings and may have the same or different substituents;
n is 0, 1 or 2;
Alk represents a divalent unbranched or branched hydrocarbon group having 1 to 6 carbon atoms;
m is 0 or 1,
Ar represents the following substituents: hydroxy group, amino group, alcoholate group, cyanide group, thiocyanide group, halogen group, sulfonic acid group, sulfonic acid ester group, thiol group, benzoic acid group, benzoic acid ester group, carvone Represents an aryl group having 6 to 12 C atoms, preferably 6 C atoms, which may be substituted with acid groups, carboxylic acid ester groups, organosilane groups;
p is 0 or 1, provided that p and n do not mean 0 at the same time,
q is 1 or 2,
w is a number from 2 to 8,
r is 1, 2 or 3, provided that r + n + m + p is 4,
Alkyl represents a monovalent unbranched or branched saturated hydrocarbon having 1 to 20 carbon atoms, preferably 2 to 8 carbon atoms,
Alkenyl represents a monovalent unbranched or branched unsaturated hydrocarbon having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms] or a silane or organosilane It may be modified with

The silicic acid according to the present invention has a composition formula:
SiR ² _4-n X _n (where n is 1, 2, 3, 4),
[SiR ² _x X _y O] _z (where x is 0 or more and 2 or less, y is 0 or more and 2 or less, z is 3 or more and 10 or less, provided that in this case , X + y is 2),
[SiR ² _x X _y N] _z (where x is 0 or more and 2 or less, y is 0 or more and 2 or less, z is 3 or more and 10 or less, provided that in this case , X + y is 2),
SiR ² _n X _m OSiR ² _o X _p (where n is 0 or more and 3 or less, m is 0 or more and 3 or less, o is 0 or more and 3 or less, and p is 0 or more and 3 or less, where n + m is 3 and o + p is 3),
SiR ² _n X _m NSiR ² _o X _p (where n is 0 or more and 3 or less, m is 0 or more and 3 or less, o is 0 or more and 3 or less, p is 0 or more and 3 or less, where n + m is 3 and o + p is 3),
SiR ² _n X _m [SiR ² _x X _y O] _z SiR ² _o X _p (where n is 0 or more and 3 or less, m is 0 or more and 3 or less, and x is 0 or more) 2 or less, y is 0 or more and 2 or less, o is 0 or more and 3 or less, p is 0 or more and 3 or less, z is 1 or more and 10,000 or less, However, in this case, n + m is 3, x + y is 2, and o + p is 3). This compound includes a linear silane compound, a cyclic silane compound and a branched silane compound, a linear silazane compound, a cyclic silazane compound and a branched silazane compound, a linear siloxane compound, and a cyclic siloxane compound. And branched siloxane compounds. R ² is a substituted alkyl group and / or aryl group having 1 to 20 carbon atoms and / or an unsubstituted alkyl group and / or aryl group, these groups being functional groups, for example It may be substituted with hydroxy groups, amino groups, polyether groups such as ethylene oxide and / or propylene oxide and halide groups such as fluoride. R ² may also contain groups such as alkoxy, alkenyl, alkynyl and aryl groups and sulfur-containing groups. X can be a silanol group, an amino group, a thiol group, a halogen group, an alkoxy group, an alkenyl group, and a hydrogen group.

Preferably, the composition formula is: SiR ² _n X _m [SiR ² _x X _y O] _z SiR ² _o X _p (where n is 0 or more and 3 or less, and m is 0 or more and 3 or less. , X is 0 or more and 2 or less, y is 0 or more and 2 or less, o is 0 or more and 3 or less, p is 0 or more and 3 or less, and z is 1 or more. , In which n + m is 3, x + y is 2, and o + p is 3), where R ² is It is preferably represented by methyl.

Particularly preferably, the composition formula: SiR ² _n X _m [SiR ² _x X _y O] _z SiR ² _o X _p (in this case, n is 0 or more and 3 or less, and m is 0 or more and 1 or less. X is 0 or more and 2 or less, y is 0 or more and 2 or less, o is 0 or more and 3 or less, p is 0 or more and 1 or less, and z is 1 In this case, n + m is 3, x + y is 2, and o + p is 3. In this case, R ² is preferably Represented by methyl.

  Precipitated silicic acid, optionally granulated, non-granulated, pulverized and / or unmilled, is 0.5 to 50 parts, in particular precipitated silicic acid, per 100 parts of precipitated silicic acid. Modified with one or more described organosilanes of 1 to 15 parts of the mixture per 100 parts, in which case the reaction of precipitated silicic acid with the organosilane is carried out during the preparation of the mixture (in-situ). Or else spraying of the mixture and subsequent heat treatment, mixing of organosilane and silicic acid suspension and subsequent drying and heat treatment (for example, DE 3437473). German Patent No. 19609619) or German Patent No. 19609619 or German Patent No. 40047. It can be carried out by the method described in the 81 specification.

  As the organosilicon compound, in principle, all difunctional silanes capable of realizing coupling to a silanol group-containing filler on one side and coupling to polymer on the other side are suitable. Yes. The usually used amount of the organosilicon compound is 1 to 10% by mass with respect to the total amount of precipitated silicic acid.

Examples of said organosilicon compounds are as follows:
Bis (3-triethoxysilylpropyl) tetrasulfane, bis (3-triethoxysilylpropyl) disulfane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane. Other organosilicon compounds are disclosed in WO 99/09036, European Patent No. 1108231, German Patent No. 10137809, German Patent No. 10163945, German Patent No. 10223658. It is described in.

  In one preferred embodiment of the invention, bis (triethoxysilylpropyl) tetrasulfane can be used as the silane.

  The silicic acid according to the invention is combined with the silane modifier as a powder, spherical product or granules in an amount of 5 to 200 parts per 100 parts of rubber as a reinforcing filler in an elastomer mixture, tire or vulcanizable rubber mixture. As well as silane modifiers. The rubber mixture and the elastomer mixture can be considered as equivalents within the scope of the present invention.

Silanol groups on the silicic acid surface function together with the coupling reagent as a possible chemical reaction component in the rubber mixture or in the natural rubber mixture. This coupling reagent is, for example, a bifunctional silane that allows the attachment of silicic acid onto the rubber matrix, such as bis (3-triethoxysilylpropyl) tetrasulfane. That is, the highest possible number of silanol groups achieves a high probability of coupling between silicic acid and the coupling reagent, thereby achieving a high probability of binding of silicic acid onto the rubber matrix, which is ultimately more It leads to higher reinforcement potential. Sears number V ₂ is one criterion to describe the number of silanol groups silicate, whereas, BET surface area of silica is a specific surface area of the silica, the specific surface area in this case, the compound processing behavior and another It has a great influence on the rubber industrial properties. However, the description of the absolute number of silanol groups is not sufficient to fully characterize precipitated silicic acid. This is because precipitated silicic acid having a high surface area generally has a higher absolute number of silanol groups than precipitated silicic acid having a low surface area. Therefore, the quotient from the Sears number V ₂ / BET is important. That is, the strengthening potential generated by the silanol group can be expressed in terms of the specific surface area units introduced.

  Along with a mixture containing silicic acid according to the invention with or without the described organosilane as filler, the elastomer mixture or rubber mixture is additionally filled with one or more somewhat reinforcing fillers. It may be.

The following materials can be used as other fillers:
Carbon black: The carbon black that can be used in this case is manufactured by the flame carbon black method, the furnace carbon black method or the gas carbon black method, and has a BET surface area of 20 to ²⁰⁰ m ² / g, for example, SAF carbon Black, ISAF carbon black, HSAF carbon black, HAF carbon black, FEF carbon black or GPF carbon black. In some cases, the carbon black may contain a heteroatom such as silicon.
For example, highly dispersible pyrogenic silicic acid produced by in-salt hydrolysis of silicon halides. In some cases, this silicic acid may be present as a mixed oxide of another metal oxide such as an Al oxide, Mg oxide, Ca oxide, Ba oxide, Zn oxide and titanium oxide.
Other commercial silicic acid.
Synthetic silicic acid having a BET surface area of 20 to 400 m ² / g and a primary particle size of 10 to 400 nm, such as aluminum silicate, alkaline earth metal silicates such as magnesium silicate or calcium silicate.
Synthetic or natural aluminum oxide and aluminum hydroxide.
Natural silicates such as kaolin, another naturally derived silicon dioxide compound.
Glass fibers and glass fiber products (mats, strands) or fine glass balls.
Starch and modified starch molds.
Natural fillers such as clay and silicate chalk.

  Also, in this case, the mixing ratio depends on the property profile to be achieved of the finished rubber mixture, as in the case of organosilane metering. A ratio of 5 to 95% between the silicic acid according to the invention and the other described fillers (and mixtures) mentioned above can be taken into account and is also realized within the said range.

  In a particularly preferred embodiment, silicic acid 10 consisting entirely or partly of the silicic acid according to the invention, optionally together with 0 to 100 parts by weight of carbon black and 1 to 10 parts by weight of organosilicon compound, relative to 100 parts by weight of rubber ~ 150 parts by weight may be used for the production of the mixture.

  Together with the silicic acid, organosilane and other fillers according to the invention, the elastomer forms another important component of the rubber mixture. In this case, it can be used as a single polymer or as a separate rubber, for example natural rubber, polybutadiene (BR), polyisoprene (IR), in particular 1-60% by weight, preferably 2 Styrene / butadiene copolymer (SBR) having a styrene content of 50% by weight, butyl rubber, isobutylene / isoprene copolymer (IIR), butadiene / acrylonitrile copolymer having an acrylonitrile content of 5 to 60% by weight, preferably 10 to 50% by weight (NBR), partially hydrogenated or fully hydrogenated NBR rubber (HNBR), ethylene / propylene / diene copolymer (EPDM) and mixtures with said rubber mixtures (compounds) diluted with oil Natural and synthetic elastomers that are either undiluted or undiluted. It will be the Rukoto.

  In addition, for rubber mixtures with the described rubbers, the following additional rubbers are applicable: carboxy rubber, epoxy rubber, transpolypentenamer, halogenated butyl rubber, 2-chloro-butadiene, Ethylene-vinyl acetate copolymers, rubbers from ethylene-propylene copolymers, optionally chemical derivatives of natural rubber as well as modified natural rubber.

  Preferred synthetic rubbers are described, for example, in W. Hofmann, “Kautschuktechnologie”, Genter Verlag, Stuttgart 1980.

  For the production of the tire according to the invention, an anionically polymerized LSBR rubber (solution SBR) and a mixture of this LSBR rubber and diene rubber, in particular having a glass transition temperature above -50 ° C., are important.

  The silicic acid according to the invention can be used in all rubber applications, with or without silane, such as molded bodies, pneumatic tires, tire treads, transport belts, belt conveyors, packing rings, drive belts, tubes, shoe soles, cables. It may be used for a jacket, a roll coating, a buffer member and the like.

  The incorporation of the silicic acid and the production of the mixture containing the silicic acid are preferably carried out at 80-200 ° C. on an internal mixer or rolling mill in the usual manner in the rubber industry. Silicic acid supply or use forms can occur as powders, spherical products or granules. Also in this case, the silicic acid according to the invention is not distinguished from known bright fillers.

  The rubber vulcanizate according to the present invention contains other rubber auxiliaries such as reaction accelerators, anti-aging agents, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, plasticizers, adhesives, foaming agents, dyes. Pigments, waxes, diluents, organic acids, retarders, metal oxides and activators such as triethanolamine, polyethylene glycol, hexanetriol can be included in the usual metering feed. Such compounds are known in the rubber industry.

  The rubber auxiliaries may be used in known amounts which depend, inter alia, on the intended use. The usual amount is, for example, 0.1 to 50% by mass relative to the rubber used. As the cross-linking agent, sulfur or a substance that donates sulfur is used. Furthermore, the rubber mixture according to the invention can contain a vulcanization accelerator. Examples of suitable main accelerators are mercaptobenzthiazole, sulfenamide, thiuram, dithiocarbamate in an amount of 0.5 to 3% by weight. Examples of co-promoters (Cobeschleuniger) are guanidine, thiourea and thiocarbonate in amounts of 0.5-5% by weight. Sulfur may normally be used in an amount of 0.1 to 10% by weight, preferably 1 to 3% by weight, based on the rubber used.

  The silicic acid according to the invention may be used in rubbers that are crosslinkable with accelerators and / or sulfur and with peroxides.

  Vulcanization of the rubber mixture according to the invention can be carried out at a temperature of 100 to 200 ° C., preferably 130 to 180 ° C. and in some cases a pressure of 10 to 200 bar. The mixing of the rubber with the filler, optionally with the rubber auxiliary and the organosilicon compound, may be carried out in known mixing equipment, for example in rolls, internal mixers and mixing extruders.

  The rubber mixtures according to the invention are used for the production of molded bodies, for example pneumatic tires, summer tires, winter tires and tires for all seasons, tire treads, passenger car (PKW) tires, transport vehicle tires, motorcycle tires, tires. Suitable for the production of substructure members, cable jackets, tubes, drive belts, belt conveyors, roll coverings, shoe soles, packing rings and cushioning members.

  The silicic acid according to the present invention has the advantage that the silicic acid is highly dispersible and the rubber vulcanizate has high rubber activity due to the slight microporosity of the rubber vulcanizate, thereby imparting high strength. Have.

  Furthermore, the silicic acid according to the invention exhibits advantages in vulcanization time compared to the same rubber mixtures as silicic acid according to the state of the art.

  The rubber mixtures according to the invention are particularly suitable for the production of passenger car tire treads and motorcycle tire treads, and for transport vehicles having reduced rolling resistance and good winter suitability during good wear resistance. Suitable for manufacturing tire treads.

  Furthermore, the rubber mixture according to the present invention is a compound with a typical tire tread carbon black without the addition of an organosilicon compound, and cut and chip of construction machinery tires, agricultural machinery tires and mining machinery tires ( (Cut & Chip) also suitable for improving the behavior (for definitions and other details, see "New insights into the tear mechanism" and references in Dr. W. Niedermeier's Tire Tech 2003 Hamburg) .

The reaction conditions and physical / chemical data of the precipitated silicic acid according to the invention are determined by the following method:
Measurement of moisture content of silicic acid In accordance with ISO 787-2, the volatile content of silicic acid (hereinafter referred to as moisture) is measured after drying for 2 hours at 105 ° C. . This drying loss generally consists mainly of humidity (Wasserfeuchtigkeit).

Implementation In a dry graduated flask with a polished lid (diameter 8 cm, height 3 cm), 10 g of powdered, spherical or granular silicic acid are accurately metered in 0.1 mg (metering rate E). When the lid is opened, the sample is dried at 105 ± 2 ° C. for 2 hours. Subsequently, the graduated flask is closed and dried with silica gel as a desiccant in a desiccator to room temperature. The assay amount A is measured by mass measurement.

  Moisture in% is measured by ((Eg-Ag) * 100%) / (Eg).

Measurement of the modified Sears number of silicic acid By titration of silicic acid with a potassium hydroxide solution in the range of pH 6 to pH 9, the modified Sears number (hereinafter referred to as the Sears number V ₂ ) It can be established as a standard for numbers.

The measurement method is based on the following chemical reaction, where “Si” —OH is an encoded silanol group of silicic acid:
"Si" -OH + NaCl → "Si" -ONa + HCl
HCl + KOH → KCl + H ₂ O.

Implementation 10.00 g of powdered, spherical or granular silicic acid having a moisture content of 5 ± 1% are pulverized for 60 seconds using an IKA-general mill M20 (550 W; 20000 rpm). In some cases, the moisture content of the starting material must be adjusted by drying at 105 ° C. in a drying box or by uniform wetting and the milling must be repeated. 2.50 g of the silicic acid thus treated are metered in a 250 ml titration vessel at room temperature and 60.0 ml of methanol are added with each treatment. After the sample is completely wetted, 40.0 ml of deionized water is added and 18,000 rpm is used with a Uitra Turrax T 25 stirrer (stirring axis KV-18G, diameter 18 mm). Disperse at rotation speed for 30 seconds. Using 100 ml of deionized water, the sample particles adhering to the container edge and the stirrer are washed away in the suspension and subjected to temperature treatment in a constant temperature water bath at 25 ° C.

pH measuring device (Knick, type: 766 Ph-Meter Calimatic with temperature sensor) and pH electrode (Schott's one-rod measuring unit (Einstabmesslkette), type N7680) using buffer solution (pH 7.00 and 9.00) While calibrating at room temperature. Using a pH meter, the starting pH value of the suspension is first measured at 25 ° C. and then depending on the result, potassium hydroxide solution (0.1 mol / l) or hydrochloric acid solution (0.1 mol) / L) to adjust the pH value to 6.00. The consumption of KOH solution or HCl solution in ml up to pH 6.00 corresponds to V ₁ ′.

Thereafter, 20.0 ml of sodium chloride solution (250.00 g of NaCl are filled with deionized water to 1 l for each treatment) is supplied. Next, titration is continued using 0.1 mol / l of KOH until the pH value reaches 9.00. The consumption of KOH solution in ml up to pH 9.00 corresponds to V ₂ '.

Subsequently, the volume V ₁ ′ or V ₂ ′ is first normalized to a theoretical metering amount of 1 g and expanded by 5, then V ₁ and Sears number V ₂ are generated in units of ml / (5 g).

Measurement of BET surface area Specific surface area (hereinafter referred to as BET surface area) is measured with powdered, spherical, or granular silicate nitrogen using an AREA instrument (Stroehlein, JUWE) as described in ISO 5794-1 / Annex D.

Measurement of CTAB surface area This method is related to ASTM 3765 or NFT45-007 (Chapter 5.12.1.3), and CTAB (N-hexadecyl-N, N, N--) on the “outer” surface of silicic acid. Based on the adsorption of trimethylammonium bromide), in this case this surface is also called "surface acting on the rubber". CTAB adsorption is performed under ultrasonic treatment while stirring in an aqueous solution. Excess unadsorbed CTAB was measured with a Titroprozessor by re-titration with NDSS (dioctyl sodium sulfosuccinate solution, “Aerosol OT” solution), where the end point is the solution Is determined by the maximum turbidity of and measured by Phototrode. The temperature during all operations carried out is 23-25 ° C. in order to prevent CTAB crystallization. Re-titration is based on the following reaction equation:
(C ₂₀ H ₃₇ O ₄ ) SO ₃ Na + BrN (CH ₃ ) ₃ (C ₁₆ H ₃₃ ) →
NDSS CTAB
(C ₂₀ H ₃₇ O ₄ ) SO ₃ N (CH ₃ ) ₃ (C ₁₆ H ₃₃ ) + NaBr
Equipment Titroprozessor METLLER Toledo DL 55 and Titroprozessor METTLER Toledo DL 70, each with pH electrode, industrial product Mettler, type DG 111 and Phototrode
Industrial product Mettler, type DP 550,
100 ml titration container made of polypropylene,
A titration flask with a lid, 150 ml,
Pressure filtration device, internal volume 100 ml,
Membrane filter made of cellulose nitrate, pore size 0.1 μm, 47 mmφ, for example Whatman (order number 7181-004).

Reagents CTAB (0.015 mol / l in deionized water) and NDSS (0.00423 mol / l in deionized water) were purchased for immediate use (Kraft, Duisburg: order number 6056.4700 CTAB Solution 0.015 mol / l; order number 6057.4700 NDSS solution 0.00423 mol / l), stored at 25 ° C. and used for 1 month.

Implementation Titration of blank test The consumption of NDSS solution to titrate 5 ml of CTAB solution can be tested once a day for all measurement sequences. For this purpose, the Phototrode is adjusted to 1000 ± 20 mV before starting the titration (corresponding to a transparency of 100%).

Pipet exactly 5.00 ml of CTAB solution into the titration vessel and add 50.0 ml of demineralized water. Titration with the NDSS solution is carried out with stirring until the turbidity of the solution is maximized with a Titroprozessor DL55 according to the measurement methods customary for the person skilled in the art. measuring the consumption _{V I} for NDSS solution in ml. All titrations can be performed as 3 measurements.

Adsorption 10.0 g of powdered, spherical or granular silicic acid with a moisture content of 5 ± 2% (in some cases the moisture content is adjusted by drying at 105 ° C. in a drying box or by uniform wetting) Mill for 30 seconds in a mill (Krups, model KM75, product number 2030-70). Transfer exactly 500.0 mg of the finely ground sample into a 150 ml titration vessel equipped with a magnetic stirring bar and feed exactly 100.0 ml of CTAB solution. The titration vessel is closed with a lid and stirred for 15 minutes with a magnetic stirrer. Hydrophobic silicic acid is stirred for up to 1 minute until completely wetted at 18000 rpm with a Uitra Turrax T25 stirrer (stirring axis KV-18G, diameter 18 mm). The titration vessel is screwed onto a Titroprozessor DL70 and the pH value of the suspension is adjusted to a value of 9 ± 0.05 with KOH (0.1 mol / l). The suspension in the titration vessel is exposed to ultrasound for 4 minutes at 25 ° C. in an ultrasonic bath (Bandelin, Sonorex RK 106 S, 35 kHz). Subsequently, immediate pressure filtration is carried out through the membrane filter with a nitrogen pressure of 1.2 bar. Discard 5 ml of the pre-filtrate.

Titration Pipet the remaining 5.00 ml of filtrate into a 100 ml titration vessel and fill to 50.00 ml with deionized water. The titration vessel is screwed onto a Titroprozessor DL55 and titration is carried out with stirring until turbidity is maximized with the NDSS solution. The consumption V _II for the NDSS solution in ml is measured. All turbidity can be performed as 3 measurements.

Calculation Measured value V _I = Consumption of NDSS solution in ml during titration of blank test sample V _II = Consumption of NDSS solution when using filtrate,
V _I / V _II = substance CTAB of blank test sample / substance CTAB still present in the filtrate sample.

From this it can be seen that for the amount of substance N adsorbed on CTAB in g:
N = ((V _I -V _II ) * 5.5 g * 5 ml) / (V _I * 1000 ml).

Since only 5 ml of the filtrate was titrated from 100 ml, using 0.5 g of defined moisture silicic acid, the demand for CTAB 1 g location is 578435 * 10 ⁻³ m ^2, which is evident from the following formula:
CTAB surface area (not corrected with ^water) m ^{2 /g=(N*20*578.435m} 2 ^/g)/(0.5g) and CTAB surface area (not corrected with ^water) m 2 / g = ( V _I -V _II ) * 636.2785 m ² / g) / V _I.

The CTAB surface area is related to silicic anhydride and therefore the following correction is performed.
CTAB surface area in m ² / g = (CTAB surface area (unmodified with water) m ² / g * 100%) / (100% -moisture%).

The DBP absorption rate (DBP number), which is one criterion for the absorption capacity of precipitated silicic acid, is measured as follows in connection with the standard DIN 53601:
Implementation 12.50 g of powdered or spherical silicic acid having a moisture content of 0-10% (in some cases the moisture content is adjusted by drying at 105 ° C. in a drying box) Brabender-Absorptometer) Feeding into the “E” kneading chamber (product number 279061) (without evaporation of the starting filter of the rotational moment feeder (Drehnomentaufnehmer)). In the case of granules, a 3.15 to 1 mm sieving fraction (Retsch special steel sieve) is used (the mildness of the granules with a plastic spatula through a sieve with a 3.15 mm opening). By compression). While mixing for several hours (kneader blade rotation speed 125 rpm), dibutyl phthalate was dropped into the mixture at a rate of 4 ml / min with "Dosimaten Brabender" T90 / 50 at room temperature. Add. Contamination occurs only with a small force demand and is tracked per digital display. At the end of the measurement, the mixture becomes pasty, which is indicated by a steep rise in force demand. When 600 digits (0.6 Nm rotational moment) are displayed, the kneader and DBP metering supply are switched off by electrical contact. The synchronous motor for supplying DBP is coupled with an automatic counter, so the consumption of DBP in ml can be read.

Evaluation The DBP absorption is described in g / (100 g) and is calculated from the DBP consumption measured for the following formula: The density of DBP is typically 1.047 g / ml at 20 ° C.

  DBP absorption rate g / (100 g) = ((DBP consumption ml) * (DBP density g / ml) * 100) / (12.5 g).

  DBP absorption is defined for dried silicic anhydride. If wet precipitated silicic acid is used, the value can be corrected by the following correction table. The correction value corresponding to the water content is added to the DBP value measured experimentally. For example, a water content of 5.8% means an additional amount of 33 g / (100 g) in relation to the DBP absorption rate.

Measurement of pH value The method according to DIN EN ISO 787-9 is used to measure the pH value of an aqueous suspension of silicic acid at 20 ° C. To that end, an aqueous suspension of the sample to be tested is produced. After the suspension is shaken briefly, the pH value of the suspension is measured with a previously calibrated pH meter.

Implementation Before carrying out the pH measurement, the pH measuring device (Schott's Einstabmesslkette, type N7680) can be calibrated daily at 20 ° C. using a buffer solution. The calibration function can be selected such that the two buffer solutions used contain the expected pH value of the sample (pH 4.00 and 7.00, pH 7.00 and pH 9.00 and in some cases pH 7. Buffer solution with 00 and 12.00). If granules are used, 20.0 g of silicic acid is first finely ground for 20 seconds in a mill (Krups, model KM 75, product number 2030-70).

  In powder form with a moisture content of 5 ± 1% (in some cases the moisture content is adjusted prior to optional milling by drying at 105 ° C. in a drying box or evenly wetting) or 5.00 g of spherical silicic acid is weighed and fed into a wide-mouth bottle whose net mass has been corrected with a weight accurately at 0.01 g on a precision balance. Supply 95.0 ml of deionized water to the sample. The suspension is subsequently shaken in a closed container for 5 minutes at room temperature with a shaking device (Gerhardt, Modell LS10, 55W, step 7). The pH value is measured immediately after this shaker. For this purpose, the electrode is first rinsed with deionized water and then with a part of the suspension and subsequently immersed in the suspension. After adding magnetfisch to the suspension, pH measurement is performed with the formation of a weak swirl of the suspension at a constant stirring speed. When the pH meter displays an unaltered value, the pH value is read from the display device.

  The same is carried out using hydrophobic silicic acid, but 5.00 g of an optionally pulverized sample having a moisture content of 5 ± 1% is accurately netted first at 0.01 g on a precision balance. Weigh in a wide-mouth bottle whose mass is corrected with a weight. For each treatment, 50.0 ml of methanol and 50.0 ml of deionized water are added and the suspension is subsequently shaken in a closed vessel for 5 minutes at room temperature with a shaker (Gerhardt, Modell LS10, 55W, step 7). The pH value is measured after exactly 5 minutes, but with stirring as well.

Determination of the solid content of the filter cake According to this method, the solid content of the filter cake is measured at 105 ° C. by removal of the volatile content.

Implementation 100.00 g of filter cake is weighed and fed into a dry ceramic petri dish (diameter 20 cm) with a net weight corrected by a weight (metering feed E). In some cases, the filter cake can be pulverized with a spatula to obtain a brittle nodule of up to 1 cm ³ . The sample is dried at 105 ± 2 ° C. in a drying box until the mass is constant. Subsequently, the sample is cooled to room temperature with silica gel as a desiccant in a desiccator. The assay amount A is measured by mass measurement.

  The solids content in% is measured by 100%-(((E g-A g) * 100%) / (E g)).

Conductivity measurement Conductivity of silicic acid (LF is carried out in an aqueous suspension.

Implementation When using granules, 20.0 g of silicic acid is first comminuted in a mill (Krups, model KM 75, product number 2030-70) for 20 seconds. In powder form with a moisture content of 5 ± 1% (in some cases the moisture content is adjusted prior to optional milling by drying at 105 ° C. in a drying box or evenly wetting) or 4.00 g of spherical silicic acid is suspended in 50.0 ml of deionized water and heated to 100 ° C. for 1 minute. The sample cooled to 20 ° C. is accurately increased to 100 ml and homogenized by shaking.

  The measurement cell of the conductivity measuring device LF 530 (WTW) is washed with a small amount of sample, and then this measurement cell LTA01 is immersed in the suspension. The value displayed on the display corresponds to the conductivity at 20 ° C. This is because the external temperature sensor TFK 530 performs automatic temperature compensation. The temperature coefficient as well as the cell constant k can be tested for all measurement sequences.

  As the calibration solution, 0.01 mol / l of potassium chloride solution is used (LF = 1278 μS / cm at 20 ° C.).

Determination of the solids content of the sedimentation suspension The solids content of the sedimentation suspension is determined by mass measurement after filtration of the sample.

Implementation 100.0 ml of homogenized sedimentation suspension (V _suspension ) are measured at room temperature with a measuring cylinder. The sample is filtered with suction through a circular filter (type 572, Schleicher & Schuell) in a ceramic suction funnel, but not filtered until dry to avoid filter cake cracking. Subsequently, the filter cake is washed with 100.0 ml of deionized water. The filter cake that has been washed and removed is completely filtered by suction, transferred to a ceramic petri dish whose net mass is corrected with a weight, and dried in a drying box at 105 ± 2 ° C. until the mass becomes constant. The mass (m _sample ) of the dried silicic acid is measured. The solids content is measured as follows:
Solid content g / l = (m _sample g) / (V _suspension 1)
Measurement of alkali number The measurement of alkali number (AZ) is based on the consumption of hydrochloric acid in ml by direct potentiometric titration of an alkaline solution or suspension up to a pH value of 8.30 (sample volume 50 ml, water 50 ml). And in the case of hydrochloric acid used at a concentration of 0.5 mol / l). Thereby, the free alkali content is detected in the solution or suspension.

Implementation A pH meter (Knick, pHmatic with a mold temperature sensor Calimatic) and a pH electrode () (Schott's Einstabmesslkette, type N7680) were added to two buffer solutions (pH = 7.00 and pH = 10.00) at room temperature. The one-rod measuring unit is immersed in a measuring solution or a measuring suspension, which is composed of 50.0 ml of a sample and 50.0 ml of deionized water and is temperature-controlled at 40 ° C. Subsequently, a hydrochloric acid solution having a concentration of 0.5 mol / l is added by a dropping method until a constant pH value of 8.30 is adjusted. Due to the initial gradual balance between the silicic acid and the free alkali metal content, a waiting time of 15 minutes is required until the acid consumption is finally read. For a selected substance amount and concentration, the read hydrochloric acid consumption in ml directly corresponds to the number of alkalis described dimensionlessly.

  The following examples illustrate the invention but are not limited to this range.

Example 1
Silicic acid 1
In a reactor made of stainless steel, equipped with a propeller stirring system and a double jacket heater, 1550 l water and 141.4 kg water glass (density 1.348 kg / l, SiO ₂ 27.0%, Na ₂ O 8 .05%). Subsequently, 5.505 kg / min of the above water glass and about 0.65 kg / min of sulfuric acid (density 1.83 kg / l, H ₂ SO ₄ 96%) are supplied at 92 ° C. for 80 minutes with vigorous stirring. The sulfuric acid metering is adjusted so that an AZ number of 20 is occupied in the reaction medium. Subsequently, the addition of water glass is stopped and sulfuric acid is further fed until a pH of 9.0 (measured at room temperature) is achieved. The addition of sulfuric acid is stopped and the resulting suspension is further stirred at 90 ° C. for 60 minutes. Subsequently, the added amount of sulfuric acid is again absorbed and the pH value (measured at room temperature) is adjusted to 3.5. The resulting suspension was filtered with a membrane filter press and washed with water. A filter cake having a solids content of 23% is liquefied with aqueous sulfuric acid and a shearing device. Subsequently, a silicic acid feed having a solids content of 19% and a pH value of 3.7 is spray-dried under a metering of ammonia.

The resulting powder Ia has a CTAB surface area of BET surface area and 123m ² / g of 114m ² / g. Micro Bead Produkt Ib which is selectively obtained the nozzle tower drying has a CTAB surface area of BET surface area and 123m ² / g of 126m ² / g.

Silicic acid II
In a reactor made of stainless steel, equipped with a propeller stirring system and a double jacket heater, 1550 l water and 141.4 kg water glass (density 1.348 kg / l, SiO ₂ 27.0%, Na ₂ O 8 .05%). Subsequently, 5.505 kg / min of the above water glass and about 0.65 kg / min of sulfuric acid (density 1.83 kg / l, H ₂ SO ₄ 96%) are supplied at 92 ° C. for 80 minutes with vigorous stirring. The sulfuric acid metering is adjusted so that an AZ number of 20 is occupied in the reaction medium. Subsequently, the addition of water glass is stopped and sulfuric acid is further fed until a pH of 7.0 (measured at room temperature) is achieved. The addition of sulfuric acid is stopped and the resulting suspension is further stirred at 90 ° C. for 60 minutes. Subsequently, the added amount of sulfuric acid is again absorbed and the pH value (measured at room temperature) is adjusted to 3.5. The resulting suspension was filtered with a membrane filter press and washed with water. A filter cake having a solids content of 22% is liquefied with an aqueous sulfuric acid solution and a shearing device. Subsequently, the silicic acid feed with a solids content of 19% and a pH value of 3.6 is dried in the nozzle tower under a metering of ammonia.

The resulting Micro Bead Produkt have CTAB surface area of BET surface area and 117m ² / g of 116m ² / g.

Silicic acid III
In a reactor made of stainless steel, equipped with a propeller stirring system and a double jacket heater, 1550 l water and 141.4 kg water glass (density 1.348 kg / l, SiO ₂ 27.0%, Na ₂ O 8 .05%). Subsequently, 5.505 kg / min of the above water glass and about 0.65 kg / min of sulfuric acid (density 1.83 kg / l, H ₂ SO ₄ 96%) are supplied at 92 ° C. for 100 minutes with vigorous stirring. The sulfuric acid metering is adjusted so that an AZ number of 20 is occupied in the reaction medium. Subsequently, the addition of water glass is stopped and sulfuric acid is further fed until a pH of 9.0 (measured at room temperature) is achieved. The addition of sulfuric acid is stopped and the resulting suspension is further stirred at 90 ° C. for 60 minutes. Subsequently, the added amount of sulfuric acid is again absorbed and the pH value (measured at room temperature) is adjusted to 3.5. The resulting suspension was filtered with a membrane filter press and washed with water. A filter cake having a solids content of 23% is liquefied with aqueous sulfuric acid and a shearing device. Subsequently, a silicic acid feed having a solids content of 19% and a pH value of 3.8 is spray-dried under a metering of ammonia.

The resulting powdery product has a CTAB surface area of BET surface area and 104m ² / g of 102m ² / g.

  The physical data of the silicic acid is listed in the following table:

Example 2
Precipitated silicic acid Ib and II according to the invention from Example 1 were tested in an S-SBR / BR rubber mixture. As a known state of the art, the easily dispersible silica silicate Ultrasil 7000 GR (Ref) from Degussa AG was selected. The formulations used for the rubber mixture are listed in Table 1 below. In this case, the unit phr is a mass content with respect to 100 parts of the used crude rubber.

  Polymer VSL 5025-1 is a Bayer solution polymerized SBR copolymer having a styrene content of 25 wt% and a butadiene content of 75 wt%. This copolymer contains 37.5 phr of oil and has a Mooney viscosity (ML1 + 4/100 ° C.) of 50 ± 4. The polymer Buna CB 24 is a Bayer cis-1,4-polybutadiene (neodymium type) having a cis-1,4-content of at least 97% and a Mooney viscosity of 44 ± 5.

  X50-S is a 50/50 mixture of Si 69 [bis (3-triethoxysilylpropyl) tetrasulfane] and carbon black, available from Degussa.

  As the aromatic oil, Naftolen ZD from Chemetall is used. Vulkanox 4020 is a Bayer 6PPD and Protektor G 3108 is an ozone protection wax from HB-Fuller. Vulkacit D / C (DPG) and Vulkacit CZ / EG (CBS) are Bayer's commercial products. Perkazit TBZTD is available from Akzo Chemie.

  The rubber mixture is produced in the internal mixer according to the mixing rules in Table 2. Table 3 lists the methods used for rubber testing. The mixture is vulcanized at 165 ° C. for 20 minutes. Table 4 shows the results of the rubber industry test.

  The dispersion coefficient was measured by surface topography including Medaliakorrektur (A. Wehmeier, “Filler Dispersion Analysis by Topography Measurements” Technical Report TR 820, Degussa AG, Advanced Fillers and Pigments Division). The dispersion coefficient thus measured is related to an optically measured dispersion coefficient as measured by, for example, Deutschen Institut fuer Katschuktechnologie eV, Hannover / Deutschland, with a specified standard exceeding 0.95 (DIK- Workshop, 27.-28. November 1997, published by Hannover / Germany, H. Geisler, "Bestimmung der Mischguete").

  As can be seen in the data in Table 4, the mixtures KS Ib and KS II with silicic acid according to the present invention are more responsive to the reference mixture REF due to the slight microporosity and thus the slightly accelerated adsorptivity on the surface. Also shows a rapid vulcanization time t90%. The preferred higher activity of the silicic acid is again reflected in the higher tension values of 100% and 300% and the increased strengthening factor. The dynamic property data of the mixture with silicic acid according to the invention is likewise improved. A low Ball-Reboud 0 ° C. that can improve the improved wet slip strength and a high Ball-Rebound 60 ° C. that represents the preferred slip resistance of the tire tread are found. The dynamic stiffness at 0 ° C. and 60 ° C. is at the same level compared to the reference mixture, while the hysteresis loss tan δ (60 ° C.) is advantageously low, indicating a low slip resistance. Moreover, the dispersibility of the silicic acid according to the invention is very high, above all better than the already easily dispersible silicic acid Ultrasil 7000 GR according to the state of the art, whereby the wear resistance advantage of the tire tread is achieved. .

Claims (17)

The following physical and chemical parameters:
CTAB surface area 100-200 m ² / g,
BET / CTAB ratio 0.8-0.99,
DBP number 210-280 g / (100 g),
Sears number _V 2 _10~30ml / (5g),
4-8% moisture,
It characterized by having a ratio 0.150~0.370ml / (5m ²⁾ Sears number _{V 2} pairs BET surface area precipitated silicas. The BET / CTAB ratio is 0.9 to 0.99, and / or the Sears number V ₂ is 20 to 30 ml / (5 g), and / or the CTAB surface area is 100 to 160 m ² / g, and / or The precipitated silicic acid according to claim 1, wherein the DBP number is 250 to 280 g / (100 g) and / or the ratio of the Sears number V ₂ to the BET surface area is 0.170 to 0.370 ml / (5 m ² ). . BET surface area of 80~110m ² / g, precipitated silica according to claim 1 or 2 wherein. BET surface area of 110~150m ² / g, precipitated silica according to claim 1 or 2 wherein. 5. The method for producing precipitated silicic acid according to claim 1, wherein a) an aqueous solution of alkali metal silicate or alkaline earth metal silicate having a pH value of 7 to 14 and / or organic in order. Charging an aqueous solution of a base and / or an inorganic base;
b) Metering water glass and acidifying agent at 55-95 ° C. for 10-120 minutes while stirring the charging solution,
g) The resulting suspension was further stirred at 80-98 ° C for 1-120 minutes,
h) acidify the pH value to 2.5-5 with an acidifying agent;
The method for producing a precipitated silicic acid according to any one of claims 1 to 4, wherein i) filtration and drying. Step b) 1 to 2 times following step c) stopping and d of the supply of 30 to 90 minutes while maintaining the temperature) water glass and between 20 to 120 minutes while stirring at the same temperature by the continued case after 6. A process according to claim 5, wherein the simultaneous supply of acidifying agent is additionally carried out.   Process according to claim 5 or 6, wherein after b) or d) the pH value is adjusted to 3-11 in step e) by addition of an acidifying agent.   8. The process according to claim 7, wherein after b) or d) the pH value is adjusted to 7-10 in step e) by addition of acid. 9. Process according to claim 7 or 8, wherein in step f) following step e) the pH value is raised to 8-14 by addition of a basic compound.   10. The process according to claim 9, wherein alkali metal silicate and / or alkaline earth metal silicate and / or alkali metal hydroxide and / or alkaline earth metal hydroxide are used as the base.   The method according to any one of claims 5 to 10, wherein an organic salt or an inorganic salt is added during one step of steps a) to h). A precipitated silicic acid according to any one of claims 1 to 4 or produced by the method according to any one of claims 5 to 11 , wherein the surface of the precipitated silicic acid is of formulas I to III:
[SiR ¹ _n (RO) _r (Alk) _m (Ar) _p ] _q [B] (I),
SiR ¹ _n (RO) _3-n (alkyl) (II), or SiR ¹ _n (RO) _3-n (alkenyl) (III)
[In the above formula,
B is —SCN, —SH, —Cl, —NH ₂ , —OC (O) CHCH ₂ , —OC (O) CCH ₃ ) CH ₂ (when q is 1) or —S _w — (q is In this case, B is chemically bonded to Alk,
R and R ¹ may optionally have the following groups: hydroxy group, amino group, alcoholate group, cyanide group, thiocyanide group, halogen group, sulfonic acid group, sulfonic acid ester group, thiol group, benzoic acid group, benzoic acid An aliphatic group having 2 to 30 C atoms, an olefinic group, an aromatic group or an optionally substituted acid group, carboxylic acid group, carboxylic acid ester group, acrylate group, methacrylate group or organosilane group Represents an aryl aromatic group, in which R and R ¹ may have the same or different meanings and may have the same or different substituents;
n is 0, 1 or 2;
Alk represents a divalent unbranched or branched hydrocarbon group having 1 to 6 carbon atoms;
m is 0 or 1,
Ar represents the following substituents: hydroxy group, amino group, alcoholate group, cyanide group, thiocyanide group, halogen group, sulfonic acid group, sulfonic acid ester group, thiol group, benzoic acid group, benzoic acid ester group, carvone acid group, a carboxylic acid ester group, an acrylate group, an aryl group having which may have 6 to 12 C atom substituted by methacrylate groups or organosilane group represents,
p is 0 or 1, provided that p and n do not mean 0 at the same time,
q is 1 or 2,
w is a number from 2 to 8,
r is 1, 2 or 3, provided that r + n + m + p is 4,
Alkyl represents a monovalent unbranched or branched saturated hydrocarbon having from 1 to 20 carbons atom,
Alkenyl is characterized by being modified with an organosilane represented by representing] a monovalent unbranched or branched unsaturated hydrocarbon having 2 to 20 carbons atom, Precipitated silicic acid described in any one of claims 1 to 4 or produced by the method of any one of claims 5 to 11. In the precipitated silicic acid described in any one of Claims 1 to 4 or manufactured by the method of any one of Claims 5 to 11, the surface of the precipitated silicic acid has a composition formula:
SiR ² _4-n X _n (where n is 1, 2, 3, 4),
[SiR ² _x X _y O] _z (where x is 0 or more and 2 or less, y is 0 or more and 2 or less, z is 3 or more and 10 or less, provided that in this case , X + y is 2),
[SiR ² _x X _y N] _z (where x is 0 or more and 2 or less, y is 0 or more and 2 or less, z is 3 or more and 10 or less, provided that in this case , X + y is 2),
SiR ² _n X _m OSiR ² _o X _p (where n is 0 or more and 3 or less, m is 0 or more and 3 or less, o is 0 or more and 3 or less, and p is 0 or more and 3 or less, where n + m is 3 and o + p is 3),
SiR ² _n X _m NSr ² _o X _p (where n is 0 or more and 3 or less, m is 0 or more and 3 or less, o is 0 or more and 3 or less, and p is 0 or more and 3 or less, where n + m is 3 and o + p is 3), and / or SiR ² _n X _m [SiR ² _x X _y O] _z SiR ² _o X _p (In this case, n is 0 or more and 3 or less, m is 0 or more and 3 or less, x is 0 or more and 2 or less, y is 0 or more and 2 or less, and o is , 0 or more and 3 or less, p is 0 or more and 3 or less, z is 1 or more and 10000 or less, provided that n + m is 3, x + y is 2, o + p is 3)
[In the above formula,
R ² represents a substituted alkyl group and / or aryl group having 1 to 20 carbon atoms and / or an unsubstituted alkyl group and / or aryl group and / or alkoxy group and / or alkenyl group and / or Represents an alkynyl group and / or a sulfur-containing group;
X represents a silanol group, an amino group, a thiol group, a halogen group, an alkoxy group, an alkenyl group and / or a hydrogen group]. Precipitated silicic acid as described in any one of the preceding claims or produced by the method according to any one of claims 5-11.   14. Elastomer mixture or battery separator or anti-blocking agent or coating or printing ink or fire extinguishing powder or plastic or paper stock containing the precipitated silicic acid according to any one of claims 1 to 4, or claim 12 or 13. Or personal care products. An ink or paint containing the precipitated silicic acid according to any one of claims 1 to 4, or claim 12 or 13, as a matting agent. Any one of claims 1 to 4, or a precipitated silica according to claim 12 or 13, wherein comprising as carrier agents, agricultural products or nutritional agents. The following physical and chemical parameters:
CTAB surface area 100-200 m ² / g,
BET / CTAB ratio 0.8-0.99,
DBP number 210-280 g / (100 g),
Sears number _V 2 _10~30ml / (5g),
4-8% moisture,
The precipitated silica of claim 1 having a ratio 0.150~0.370ml / (5m ²⁾ Sears number _{V 2} pairs BET surface area containing as a filler, vulcanizable rubber mixtures or vulcanizates.