MXPA96002031A

MXPA96002031A - Precipitated silicone acids, parasu procedure preparation and its use in mixes of cauchovulcanizab

Info

Publication number: MXPA96002031A
Application number: MXPA/A/1996/002031A
Authority: MX
Inventors: Esch Heinz; Gorl Udo; Siray Mustafa; Hunsche Andrea; Kuhlmann Robert
Original assignee: Degussa Aktiengesellschaft
Priority date: 1995-06-01
Filing date: 1996-05-29
Publication date: 1997-08-01

Abstract

The present invention relates to precipitated silicas characterized in that they have a CTAB surface (according to ASTM D 3765-92) of 200 to 400 m / g, a DBP value (according to ASTM D 2414) between 230 and 380 ml / 100. g, a density of silane groups (V2 use of NaOH) of 20 to 30 ml and the following average Hg porosimetry typical for the surface in question (DIN 66 133) that allows the size distribution of macropores for the size ranges of determined pores

Description

PRECIPITATED SILICON ACIDS. PROCEDURE FOR ITS PREPARATION AND ITS USE IN VULCANIZABLE RUBBER MIXTURES The precipitated silicas are used as reinforcement fillers in vulcanizable rubber mixtures. (S. Wolff, EH Tan: Performance of silicon with different surface areas in NR, Notes from the ACS meetings, New York City, NY, April 1986, S. Wolff, R. Panenka, EH Tan, Reduction d? the generation of heat in compounds for surfaces and sub-super fi ci of bearing of truck tires, notes taken from the International Conference on Rubber, Ja Shedpur (India), Nov. 1986). As an essential parameter for the characterization of a precipitated silica, the surface that is determined either by nitrogen adsorption (ISO 5794/1, Annex D) or by the adsorption of CTAB in accordance with ASTM D 3765-92 is useful. being this method of greater relevance for the rubber technique. Considering the technical data on the rubber obtained, the silicic acids according to ISO 5794/1 are divided into six classes of surfaces. However, for ST rims they use almost exclusively precipitated silicas with CTAB surfaces between 100 and 200 m2 / g.

(U.S. Patent No. 5,227,425) S. Wolff: The influence of fillers on rolling resistance, presented at 129a. Meeting of the Rubber Division of the American Chemical Society, New York, N.Y. , April 8-11, 1986). This is based on the fact that the silicic acids precipitated in the manufacture of tires must exhibit high values of solidity as well as in particular in the area of the contact surface a good resistance to friction. This can only be guaranteed by using precipitated silicas with the aforementioned surfaces. The precipitated silicas with CTAB surfaces > 200 m2 / g today are almost not used. However, these precipitated silicas should be characterized by a particularly good frictional resistance and therefore be of special interest in the manufacture of tires. The essential reason why they are not used is based on the fact that precipitated silicas with larger surfaces are distributed [disperse] extremely poorly in the rubber mixture. This poor dispersion capacity leads to these products do not give the expected values of them and thus do not have the advantages and partly the disadvantages of the precipitated silicas acids for tires used today.

The reason for the poor dispersion of precipitated silicas of large surface area is based on another important property of the precipitated silica, and this is its structure (measured by means of DBP absorption according to ASTM D 2414). However, especially important is its macropore size distribution (measured by means of Hg porosimetry according to DIN 66 133) and its variation with the surface. (U. Górl, R. Raush, H. Esch, R. Kuhlmann: Structure of silicic acid and its influence on the technical values of rubber, notes taken at the German Meeting on Rubber in Stuttgart, June 1994). In other words, the distribution of the size of macropores is usually reduced by growing the surface, when it is not achieved by means of suitable measures in the technique of precipitation during the preparation of the precipitated silicas, obtaining with the same surface additionally pores bigger. Especially the precipitated silicas with CTAB surfaces > 220 m2 / g require special measures in the precipitation techniques, so that despite the large surface area, they still have sufficiently large macropores and with this a good dispersion capacity. It is known to use precipitated silicas in rubber mixtures with the following physico-chemical parameters (DE-A 44 27 137): BET surface 35 to 350 m2 / g BET / CTAB surface area 0.8 to 1.1 PV pore volume 1.6 to 3.4 ml / g Density of the silane groups 6 to 20 ml (V2 = use of NaOH Average size of aggregation 250 to 1500 nm Surface CTAB 30 to 350 m2 / g Value DBP 150 to 300 ml / 100 g V2 / V by porosimetry from Hg 0.19 to 0.46, preferably 0.20 to 0.23 DBP / CTAB 1.2 to 2.4 Therefore, the objective of the invention is the preparation and characterization of precipitated silicas with C >surfaces; 200 m2 / g, which are characterized by an especially high macropore size distribution and with this by an especially good dispersion in the rubber mixtures. The object of the invention are precipitated silicas which are characterized in that they have a CTAB surface (according to ASTM D 3765-92) of 200 to 400 m2 / g, a DBP value (according to ASTM D 2414) between 230 and 380 ml / 100 g, a density of silane groups (V2 use of NaOH) of 20 to 30 ml and the following average Hg porosimetry typical for the surface in question (DIN 66 133) that allows the size distribution of macropores for the intervals of certain pore sizes (incremental scale): Another object of the invention is a process for the preparation of precipitated silicas according to claim 1, characterized in that in a container with water that has been heated to 30 to 90 ° C, preferably to 50 to 80 °. C, that with the addition of small amounts of sulfuric acid was adjusted to a pH value of 5 to 5.9, keeping the pH value at 5.0-5.9 constant, by means of the simultaneous flow of a solution of alkaline silicate and sulfuric acid, under constant tearing during the entire time of precipitation, the reaction is conducted to a solids concentration of 40 to 60 g / 1 by means of an interruption of the precipitation of 30 to 120 minutes, the suspension of precipitated silica is filtered, lava and the filter paste is subjected to drying for a short period, eventually it is milled or granulated. Another object of the invention are mixtures of vulcanizable rubber or the use of silicic acids according to the invention in vulcanizable rubber mixtures, which is characterized in that these mixtures contain from 5 to 100 parts, especially from 15 to 60 parts of acids silicic, in relation to 100 parts of rubber ,. The silicic acids according to the invention can be added to the mixture in powder form or in a powder-free form, for example as granules or microbeads, in the manner and manner customary in the rubber industry in a kneader or on the rollers of the rubber mixture. It is also possible to use fillers, beads or polymer powders, in which the silicic acids according to the invention are introduced during the preparation of the rubber mixture. Another object of the invention are the silicic acids according to the invention, characterized in that their surfaces are modified with organosilanes of the formulas I to III [RV (0) 3-n Si- (Alk) m- (Ar) p] q [B] (I) or (R0) 3.n Si- (Alkyl) (II) or Rln- (R0) 3.n Si- (Alkenyl) (III) in which they mean: B: -SCN, -SH , -Cl, -NH2 (when q = 1) or -Sx- (when q = 2), R and R1: an alkyl group with 1 to 4 carbon atoms, the phenyl radical, which can have all the radicals R and R1 meanings equal or different, n: 0, 1 or 2, Alk: a bivalent straight or branched hydrocarbon radical with 1 to 6 carbon atoms, m: 0 or 1, Ar: an aryl radical with 6 to 12 carbon atoms preferably 6 carbon atoms, p: 0 or 1 with the proviso that p and n do not mean 0 simultaneously. x: a number from 2 to 8, alkyl: a straight or branched chain saturated monovalent hydrocarbon radical with 1 to 20 carbon atoms, preferably 2 to 8 carbon atoms, alkenyl: a straight or branched chain unsaturated monovalent hydrocarbon radical with 2 to 20 carbon atoms , preferably 2 to 8 carbon atoms. Surface-modified precipitated silicas with organosilanes can be prepared by treating precipitated silicas with organosilanes in mixtures of 0.5 to 50 parts, based on 100 parts of precipitated silica. In a preferred embodiment of the invention, bis- (triethoxysilylpropyl) -tetrasulfane or a solid administration form can be used as an organosilane, for example in a mixture with industrial soot. The addition of one or more silanes results simultaneously with the silicic acids according to the invention, a rubber mixture, the reaction being carried out between the precipitated silicic acid and the silane during the mixing process at elevated temperatures. On the other hand, the addition of the silanes to the precipitated silicas / rubber mixture can be carried out in such a way that the silicas precipitated before the addition to the rubber mixture are treated with a plurality of silanes and the pre-modified silicic acid It is added to the rubber mixture. Such a measure can be carried out analogously to the method according to the patent application DE-A 40 04 781. Another object of the invention are mixtures of rubber and / or vulcanized, which contain the precipitated silicas that have been modified with organosilanes. The precipitated silicas according to the invention can be used with all types of rubber with accelerator / sulfur, but also with those crosslinkable with peroxide, such as those listed in DIN / ISO 1629. Here, for example, elastomers, elongated with natural or synthetic oils, as individual polymer or cut (mixed) with other rubbers, such as, for example, natural rubbers, butadiene rubbers, isoprene rubbers, butadiene-styrene rubbers, in particular SBR, prepared by means of the solution polymerization process , butadiene-acrylonitrile rubbers, butyl rubbers, ethylene, propylene terpolymers and non-conjugated dienes. The following additional rubbers are also suitable for rubbers with the rubbers mentioned: carboxyl rubber, epoxy rubbers, trans-polypentenmer, halogenated butyl rubber, 2-chloro-butadiene rubbers, ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, optionally also natural rubber chemical derivatives as well as modified natural rubbers. Other common constituents are also known as rubber soot, natural fillers, softeners, stabilizers, activators, pigments, anti-aging protectants and processing aids, in the usual amounts. The precipitated silicas according to the invention, with and without silane, can be used for all rubber applications, such as tires, conveyor belts, sealings, trapezoidal belts, hoses, shoe soles, etc. Examples The test procedures used in the examples are: F2H roughness factor ASTM D 2663-89 ML (1 + 4) DIN 53 523/524 Tensile strength DIN 53 504 Module 300% DIN 53 504 Extension elongation DIN 53 504 Shore-A hardness DIN 53 505 DIN friction DIN 53 516 MTS data DIN 53 513 Tear resistance across width DIN 53 507 The substances used in application examples are: Commercial name Description / Signature Buna VSL 1954 / S 25 Rubber styrene-butadiene, prepared according to the solution polymerization process (Bayer AG) Buna CB 11 S Butanene rubber (Bayer AG).

Protector G 35 Ozone protective wax (Fuller) X 50-S Bis (triethoxysilylpropyl) tetrasulphan / N 330 mixture 50:50 (Degussa AG). The density of silane groups is determined according to G.W. Sears, Analytucal Chemistry, 12, 1982-83 (1956). Determination of the size distribution of macropores by means of porosimetry of Hg. Procedure: DIN 66 133 Apparatus: Autopore II 9220 (Micromeritics GmbH) Preparation of the samples: - pre-drying of the sample 15 h / 100 ° C - cooling to room temperature in an Exsikkator - sample conduction (0.05-0.1 g) in a penetrometer Parameters of the apparatus: - pressure range 4 kPa-200 MPa (53 measurement points) - contact angle 140 ° - surface tension Hg 0.48 N / m Determination of the dispersion by means of measurement at rest of the surface of the vulcanized Procedure: ASTM D 2663-89 Apparatus: Surfanalyzer Form in which it proceeds: By means of a diamond tip that moves on the surface of a freshly cut vulcanizate, the surface roughness is determined and the asperity factor is calculated by means of electronic processing. This factor is based on the number of signals (F) and its intensity (H) as follows: Surface roughness factor = FH The interpretation of this factor shows that the dispersion of fillers in the polymer matrix is more effective the lower this factor is. Example 1: Preparation and characterization of precipitated silicas according to the invention in a CTAB surface range of 200-250 m2 / g. In a vat that is equipped with an Ekato paddle agitator and a MIG agitator from the Ekato Firm, 50 m3 of hot water and commercial sulfuric acid (96%) are introduced with agitation, until a pH of . 5. Maintaining a precipitation temperature of 78 ° C and a pH of 5.5, 7.6 m3 / h of sodium silicate solution are joined simultaneously (weight module 3.42, density 1. 348) and 0.7 m3 / h of sulfuric acid (96%) for 70 minutes. During the total precipitation period the paddle stirrer Ekato SR (diameter 320 mm, 6 sheets, 740 r / min) was kept running. After 12 minutes the addition to the educts of sodium silicate solution and sulfuric acid is interrupted for 80 minutes.

Also after that interruption period both agitators were kept running. The precipitated silica is separated on a filter press, washed and the filter cake is spray-dried or dried by rapid centrifugation and optionally dry-granulated between two rolls. The precipitated silica according to the invention has a CTAB surface of 206 m2 / g, a DBP value of 298 ml / 100 g as well as a silane group density (V2) of 20.5 ml. The distribution of macropore sizes is represented as follows: Example 2: In a tub that is equipped with an Ekato paddle stirrer and an MIG agitator from the Ekato firm, 50 m3 of hot water and commercial sulfuric acid (96%) are introduced with agitation, until a pH is reached. of 5.5. Maintaining a precipitation temperature of 78 ° C and a pH of 5.5, 7.6 m3 / h of sodium silicate solution (weight modulus 3.42, density 1348) and 0.7 m3 / h of sulfuric acid (96%) are added simultaneously during 56 minutes During the total precipitation period the paddle stirrer Ekato SR was kept running (diameter 320 mm, 6 sheets, 740 r / min). After 12 minutes the addition to the educts of sodium silicate solution and sulfuric acid is interrupted for 80 minutes. Also after that interruption period both agitators were kept running. The precipitated silica is separated on a filter press, washed and the filter cake is spray-dried or dried by rapid centrifugation and optionally dry-granulated between two rollers. The precipitated silicic acid according to the invention has a CTAB surface of 240 m2 / g, a DBP value of 314 ml / 100 g as well as a density of silane groups (V2) of 21.0 mi. The distribution of macropore sizes is represented as follows: Example 3: Preparation and characterization of a precipitated silicic acid according to the invention in the range of CTAB superificies of 250-300 m2 / g. In a vat that is equipped with an Ekato paddle agitator and a MIG agitator from the Ekato Firm, 57 m3 of hot water and commercial sulfuric acid (96%) are introduced with agitation, until a pH of 5.5 is reached. Maintaining a precipitation temperature of 55 ° C and a pH of 5.5, 8.2 m3 / h of sodium silicate solution (weight modulus 3.42, density 1348) and 0.75 m3 / h of sulfuric acid (96%) are mixed simultaneously during 56 minutes During the total precipitation period the paddle stirrer Ekato SR (diameter 320 mm, 6 sheets, 740 U / min) was kept running. After 13 minutes the addition to the educts of sodium silicate solution and sulfuric acid is interrupted for 90 minutes. Also after that interruption period both agitators were kept running. The precipitated silica is separated on a filter press, washed and the filter cake is spray-dried or dried by rapid centrifugation and optionally granulated dry between two rollers. The precipitated silica according to the invention has a CTAB surface of 283 m2 / g, a DBP number of 349 ml / 100 g as well as a silane group density (V2) of 24.0 ml. The distribution of macropore sizes is represented as follows: Example 4: Preparation and characterization of a precipitated silicic acid according to the invention in the range of CTAB superficies of 300-400 m2 / g. In a vat that is equipped with an Ekato paddle agitator and a MIG agitator from the Ekato Firm, 57 m3 of hot water and commercial sulfuric acid (96%) are introduced with agitation, until a pH of 5.5 is reached. Maintaining a precipitation temperature of 50 ° C and a pH of 5.5, 8.2 m3 / h of sodium silicate solution (weight modulus 3.42, density 1348) and 0.75 m3 / h of sulfuric acid (96%) are mixed simultaneously during 56 minutes During the total precipitation period the paddle stirrer Ekato SR (diameter 320 mm, 6 sheets, 740 r / min) was kept running. After 13 minutes the addition to the educts of sodium silicate solution and sulfuric acid is interrupted for 90 minutes. Also after that interruption period both agitators were kept running. The precipitated silica is separated on a filter press, washed and the filter cake is spray-dried or dried by rapid centrifugation and optionally dry-granulated between two rolls. The precipitated silica according to the invention has a CTAB surface of 360 m2 / g, a DBP number of 350 ml / 100 g and a silane group density (V2) of 29.0 ml. The distribution of macropore sizes is represented as follows: The characteristic physical-chemical data of the granulates d? precipitated silicon acid obtained d? according to examples 1 to 4 are the following: Example 5: Silicic acids precipitated in a mixture d? bearing surface of cargo trucks NR Mixing instructions: Mixer: GK 1.6 N Stage 1 Friction: 1: 1.1 Number of revolutions: 70 Degree of filling: 0.7 Stage 2 Friction: 1: 1.1 Number of revolutions: 70 Degree of filling: 0.68 Stage 3 Friction: 1: 1.1 Number of revolutions: 40 Degree of filling: 0.65 Vulcanization data: 150 ° C / t95% The use of the precipitated silicas according to the invention leads to an almost equal value of hardness and friction, at a value of tan d (60 ° C) clearly lower, which can reduce the resistance to rolling and with this the gasoline cost compared to a mixture of bearing surface of standard cargo trucks Example 6: Silicic acids precipitated in a mixture of bearing surface of cargo trucks NR / BR Mixing procedure: see example 5 Vulcanization data: 150 ° C / t95% The mixtures of the silicic acids according to the invention with almost identical values for the hardness and the modulus, show an excellent dispersion, a good resistance to friction and a very low d (60 ° C) value (^ rolling resistance) ) Example 7: Silicic acids precipitated in a mixture of vehicle bearing surface NR / S-SBR Mixing procedure: see example 5 Vulcanization data: 150 ° C / t95% For the use d? the precipitated silica d? According to the invention, with excellent dispersion and a comparable friction against the standard mixture, the value d (0 * C) can be improved (• slip resistance with humidity) as well as reducing rolling resistance [tan d (60SC) ] It is noted that in relation to this date, the best method known to the applicant to carry out the said invention, TS T1 which is clear from the present description of the invention Having described the invention as above, property is claimed as content in the following:

Claims

CLAIMS 1.- Precipitated silicas, characterized by having a CTAB surface (according to ASTM D 3765-92) of 200 to 400 m2 / g, a DBP value (according to ASTM D 2414) between 230 and 380 ml / 100 g, a density of silane groups (V2 use of NaOH) of 20 to 30 ml and the following typical Hg porosimetry for the surface in question (DIN 66 133) that allows the size distribution of macropores for the size ranges of determined pores (incremental scale):
2. - Process for the preparation of precipitated silicas according to claim 1, characterized in that in a water tank that has been heated to 30 to 90 ° C, preferably to 50 to 80 ° C, that with the addition of small quantities of sulfuric acid was adjusted to a pH value of 5 to 5.9, keeping the pH value at 5.0-5.9 constant, by means of the simultaneous flow of a solution of alkaline silicate and sulfuric acid, under constant tearing throughout the time of precipitation, the reaction is conducted to a solids concentration of 40 to 60 g / 1 by means of an interruption of the precipitation of 30 to 120 minutes, the suspension of precipitated silica is filtered, washed and the filtrate paste is subjected After drying for a short period, it is eventually milled or granulated.
3. Vulcanizable rubber mixtures, characterized in that these mixtures contain from 5 to 100 parts, especially 15 to 60 parts of precipitated silicas according to claim 1, in relation to 100 parts of rubber.
4. Silicic acids precipitated according to the re-division 1, characterized in that their surfaces are modified with organosilanes of the formulas I to III [R1n- (RO) 3-n Si- (Alk) m- (Ar) p] q [ B] (I) or (RO) 3.n Si- (Alkyl) (II) or (RO) 3.n Si- (Alkenyl) (III) in which they mean: B '-SCN, -SH, -Cl , -NH2 (when q = 1) or -S «- (when q = 2), R and R1: an alkyl group with d? 1 to 4 atoms d? carbon. The radical phenyl. being able to have all the radicals R and R1 mean equal or di? rent? s. n: O. 1 or 2. Alk: a bivalent straight or branched hydrocarbon radical with 1 to 6 atoms d? carbon m: 0 or 1, Ar: an aryl radical with d? 6 to 12 atoms d? carbon preferably 6 atoms d? carbon, p: 0 or 1 with the proviso that p and n do not mean simul- taneously 0, x. a number from 2 to 8. alkyl: a saturated straight-chain or branched-chain monovalent hydrocarbon radical with d? i to 20 atoms d? carbon, preferably from 2 to 8 carbon atoms. alkenyl: a straight or branched chain unsaturated monovalent hydrocarbon radical with 2 to 20 carbon atoms, preferably 2 to 8 atoms d? carbon.
5. - Rubber mixtures and / or vulcanizates, characterized in that they contain the silicic acids d? according to claim 1, which are optionally modified with organosilapo.