DE19916498A1 - Silane mixture, useful for the production of vulcanized rubber compositions, has a polysulfane content of less than 20 %. - Google Patents

Abstract

A silane mixture has a polysulfone content of less than 20%. A silane mixture (I) is of formula (1), whereby the polysulfane content (z=2-6) is no greater than 20%. An Independent claim is included for a process for the use of a sulfur and accelerator vulcanized rubber mixture (II) containing one or more natural or synthetic rubbers (III), a light oxidized (silicate) filler (IV), optionally carbon black (V) and other conventional components (VI) whereby, (III), (I), (IV), (V), a plasticizer, anti-oxidant and activators are mixed optionally in a Banbury(RTM; mixer) mixer at 160-200 deg C for 3-15 minutes, optionally in one step or a number of steps followed by the addition of a vulcanizing agent and mixing for a further 2-10 minutes. The product mixture (II) is removed as rubber sheet or bands. (RO)3Si(CH2)xS-S2-S(CH2)xSi(OR)3 (1) R = 1-8C allyl; x = 1-8; z = 0-6.

Description

The present invention relates to organosilane blends as well as vulcanizable rubber compounds.

The use of active silica fillers in high quality rubber compounds requires the use of bifunctional adhesion promoters, such as. As the organosilane bis (triethoxysilylpropyl) tetrasulfane (TESPT) [DE 21 41 159, DE 22 12 239] (S. Wolff, 29 ^th Meeting of the Rubber Division, American Chemical Society, April 8 to 11, 1986, New York / USA, N. Nakajima, WJ Shieh, ZG Wang, Intern. Polymer Processing VI, 290 (1991)).

Now it is known (S. Wolf, presented at the First Franco-German Rubber Symposium, Nov. 14-16, 1985, Obernai / France, S. Wolff, Third Annual Meeting and Conference on Tire Science and Technology, The Tire Society, March 28-29, 1984, Akron, Ohio / USA), that the value image that is related to Organosilanes can be achieved in rubber applications two independently occurring reactions. On the one hand, it happens before the mix is made moves in the 1st mixing stage, at high temperatures (130 to 200 ° C) to a reaction between the silanol groups Silicic acid and the trialkoxysilyl groups of the silane, ins especially at TESPT with the elimination of alcohol, this Hydrophobicization reaction with increasing mixing temperature is accelerated (A. Hunsche, U. Görl, H.G. Koban, T. Lehmann, Kautsch. Gummi Plastic 51, 525 (1998)).

On the other hand, the second, so-called rubber-reactive Group, in the case of TESPT consisting of an im statistical mean tetrasulfan group, during the Vulcanization of the rubber article to build a so-called filler / rubber bond lead, one Connection that ultimately is the rubber technical image of the finished article.

This reaction is desired during vulcanization, but due to the thermolability of the longer-chain polysulfane units (S ₄ -S ₈ ) it can take place at high temperatures during the preparation of the mixture (U. Görl, J. Munzenberg, paper presented at the ACS Meeting, May 6-9, 1997, Anaheim, California / USA, H.-D. Luginsland, presented on the 11 ^th international SRC meeting, May 25-26, 1999, Púchov / Slovakian). It therefore poses great problems if this pre-crosslinking of the unaccelerated mixture already occurs during the preparation of the mixture, ie while the reaction between filler and silane is normally also carried out, that is to say at the highest possible temperatures. The result of the partial build-up of filler / rubber bonds due to the undesired reaction is a tightening of the mixture skin, e.g. B. measurable in the increase in the mixture viscosity, which can lead to the inability to process this raw mixture. This undesired pre-crosslinking can be avoided by the advantageous use of disulfane silanes, ie organosulfane silane mixtures in which the proportion of S _{2 is} at least 50% and S ₄ -S ₈ does not exceed a proportion of 20% in the mixture. The advantageous use of such silane mixtures in rubber mixtures to increase the process reliability in the production of the unaccelerated mixture, ie generally the first mixing stage, is described in numerous patents, including DE 197 02 046 A1, EP 732 662 A1, WO 97/48264.

In contrast to the production of unaccelerated raw mixes require processing from accelerated rubber compounds to semi-finished products and molded articles, on the other hand, have a sufficiently long forcult time at given temperature (Mooney scorch t5 or t10%). During this time, vulcanization continues not yet noticeably a. H. there is still no formation continuous network that the flowability of the raw mix so low that processing does not is more possible. This scorch time determines the maximum possible extrudate temperature in the production of Semi-finished products, such as B. tire components, profiles and tubes, or the processing time in the production of Shaped bodies, e.g. B. in compression molding and Injection molding.

It has now been found that when organosilane polysulfide mixtures are used in accelerated rubber mixtures, the polysulfane silanes with S ₄ -S ₈ react very quickly with the rubber matrix and thus lead to short vulcanization times. In contrast, the formation of the filler / rubber bond with the use of disulfide silanes requires a previous incorporation of sulfur into the disulfane function ("Rubber Technology Handbook", W. Hofmann, Hanser Verlag 1994). This sulfur installation only takes place at high temperatures and the presence of a sulfur / accelerator system. This upstream reaction step leads to significantly longer vulcanization times and accordingly longer processing times and increased processing reliability. Surprisingly, it was also found that the use of disulfane silanes does not increase the vulcanization time (t90%), but rather shortens it, ie that the vulcanization rate is increased.

The invention therefore relates to mixtures of the general formula

(RO) ₃ Si (CH ₂ ) _x SS _z - S (CH ₂ ) _x Si (OR) ₃

R = alkyl, straight-chain or branched with 1-8 C atoms, in particular 1-3 C atoms,
x = 1-8,
z = 0-6, especially 2-6,

the proportion of longer-chain polysulfanes, ie the sum S ₄ -S ₈ and thus z = 2-6, does not exceed 20% in the mixture, and the proportion of disulfanes is at least 50%.

The use of the organosilane mixture according to the invention ensures a longer scorch time and thus improved processability of the rubber mixture. The proportion of longer chain polysulfanes in the mix can be easily determined using HPLC (U. Görl, J. Munzenberg, paper presented at the ACS Meeting, May 6-9, 1997, Anaheim, California / USA).

Find the organosilane blends according to the invention Use in vulcanizable rubber compounds and polymers used there, d. H. natural and synthetic elastomers, oil-stretched or not, as  Single polymer or blended with other rubbers such as natural rubbers, butadiene rubbers, Isoprene rubbers, butadiene-styrene rubbers, in particular SBR, made by the solution polymerization process.

All rubber compounds in which the organosilane mixtures according to the invention used are usually made with sulfur and Accelerators networked and contain in addition to the above. Polymers and the additives common in practice such as Activators, anti-aging agents, Processing aids, possibly soot and natural, bright fillers, high amounts of highly active Silica fillers in amounts of 10 to 200 parts, in particular 25 to 80 parts, based on the polymer.

These fillers are characterized in that they have BET surface areas of 1 to 700 m ² / g, in particular 100 to 250 m ² / g, and moreover a DBP number of 150 to 300 ml / 100 g. Powder is suitable as a dosage form, but also low-dust forms such as granules and microbeads. The amount of compounds according to the invention is between 0.5 and 30 parts, based on 100 parts of filler, amounts in the applications with high silica proportions, in which silicas with 100 to 250 m ² / g are generally used, between 4 and 10 parts of the compounds of the invention can be taken as a guide.

The compounds of the invention can be the Mix in situ or, for better administration, as Soot mixture are fed. Also a pre-modification of the silica filler, as for example in DE 196 09 619.7 is possible.

The mixing of the rubbers with the fillers, optionally rubber auxiliaries and the organosilanes can be used in conventional mixing units, such as rollers, internal mixers and mixing extruders ("Rubber Technology Handbook", W. Hofmann, Hanser Verlag 1994).  

The vulcanization of the rubber mixtures according to the invention can at temperatures of 80 to 200 ° C, preferably 130 to 180 ° C, optionally under pressure from 10 to 200 bar.

The compounds according to the invention can be used in almost all of them Rubber articles are applied. However, they stand out especially in mixtures filled with high silica, ins special tire tread compounds, in which in the Usually high amounts of silane to achieve the required Must be used from. use these mixtures can also be found in cable sheaths, Hoses, drive belts, conveyor belts, roller coverings, Shoe soles, sealing rings and damping elements.

Using examples 1 to 3, the advantageous ver longer scorch time in the invention Use of organosulfur silanes with a high di sulfane content shown. Comparative example 1 gives the status the technology when using the organopolysulfane silane TESPT again. For the silane blends in blends 2 and 3, the disulfane content is 75% and 85%, respectively.  

Examples Manufacture of rubber compounds and Vulcanizates General implementing regulation

The recipe used for the rubber compounds is in given in Table 1 below. The unity means phr parts by weight based on 100 parts of the used Raw rubber.  

Table 1

The polymer VSL 5025-1 is a in solution polymerized SBR copolymer from Bayer AG with a Styrene content of 25% by weight and a butadiene content of 75  % By weight. Of the butadiene, 73% are 1.2, 10% cis 1.4 and 17% trans 1.4 linked. The copolymer contains 37.5 phr oil and has a Mooney viscosity (ML 1 + 4/100 ° C) of 50 ± 4 on.

The polymer Buna CB 24 is a cis 1.4 Polybutadiene (neodymium type) from Bayer AG with cis 1,4-content of 97%, a trans 1,4-content of 2%, a 1,2-content of 1% and a Mooney viscosity of 44 ± 5.

The HD silica Ultrasil 7000 GR from Degussa AG has a BET surface area of 175 m ² .

Bis- (3- [triethoxysilyl] propyl) tetrasulfan (TESPT) is sold under the trade name Si69 by Degussa AG and has an average sulfane chain length of 4 and a disulfane content of 16% and polysulfane content (S ₄ -S ₈ ) of 53% . The disulfane silane bis- (3- [triethoxysilyl] propyl) disulfane (75) (TESPD-75) is a silane with a disulfane content of 75% and a polysulfane content S ₄ -S ₈ = 10.5%. The disulfane silane TESPD-85 is a silane with a disulfane content of 85% and a polysulfane content S ₄ -S ₈ = 4.5%. The disulfane silane mixtures were prepared by the process described in patent DE 195 41 404.

As an aromatic oil, Naftolen ZD became Chemetall used; Vulkanox 4020 is a PPD Bayer AG and Protektor G35P is an ozone protection wax from HB- Fuller GmbH. Vulkacit D (DPG) and Vulkacit CZ (CBS) are Trading products from Bayer AG.

The rubber mixture is divided into three stages in an internal mixer according to the following table manufactured:  

Table 2

The vulcanization time for the test specimens is 50 Minutes at 165 ° C.  

The rubber test is carried out in accordance with the table 3 specified test methods.

Table 3

Examples 1, 2 and 3 Rubber technical test

Implementation of Examples 1 (Comparative Example), 2 and 3 is in accordance with the General Implementation regulation, wherein in the mixture from Comparative Example 1 TESPT is used as the silane and the amount of added Sulfur is 1.5 phr. In comparison to the comparative example 1, in the mixture from Example 2, the silane TESPD-75 with 2 phr sulfur, and from example 3 the silane TESPD-85 and 2.1 phr of sulfur mixed in. The adjustment of the Amount of sulfur is necessary to make up the same total to ensure sulfur content in the mixture and so the to obtain the same crosslink density of the vulcanizate.

Table 4 shows the rubber data of the three examined mixtures compiled:  

Table 4

As can be seen from Table 4, the Mooney Scorch and t10% times for the mixtures from Examples 2 and 3 are significantly longer than those of the reference mixture 1. This increases the processing reliability of the mixtures according to the invention. Even an increase in temperature from 135 ° C to 145 ° C leads to lower t10% times for mixtures 2 and 3, i.e. even at a higher extruder or mold temperature, these mixtures remain free-flowing for longer (see Table 4 and Fig. 1 ). This can be used in extrusion to increase the extrusion temperature and allow the use of higher mold temperatures in the production of molded parts. This and the advantageously shortened vulcanization time (t90%) can contribute to increasing the output rate in the manufacturing process.

It can also be seen that the vulcanizate properties of the three investigated mixtures are comparable, d. H. through the No use of the silane mixtures according to the invention Losses in the rubber-technical image compared to the stand of technology.

Claims (5)

1. Silane mixtures according to the formula
(RO) ₃ Si (CH ₂ ) _x SS _z - S (CH ₂ ) _x Si (OR) ₃
in the mean
R = alkyl, straight-chain or branched with 1-8 C atoms, x: = 1-8,
z: = 0-6,
the proportion of polysulfanes in which z = 2-6 does not exceed 20% in the mixture. 2. Method of using sulfur and Accelerator (s) vulcanized rubber compounds, containing one or more natural or artificial Rubbers, light oxidic (silicate) fillers, and possibly soot and other usual Components, characterized in that the rubber component (s), the silane mixtures according to claim 1, the silicate filler and, if necessary existing soot and, if necessary, a plasticizer, Anti-aging agents and activators in a kneader, possibly a Banbury internal mixer, at one Temperature from 160 to 200 ° C for 3 to 15 minutes kneads, this mixing time range at the specified Mixed temperature range in one step or also is carried out in several stages, then a Adds vulcanization aids, then either in Banbury internal mixer or on a mixing roller, at suitable temperatures for a further 2 to 10 minutes and the finished rubber mixture as Rubber skin or in the form of strips.   3. The method according to claim 2, characterized in that as a bright oxidic Fillers, natural fillers (clays, pebbles) and / or precipitated silica or silicates in amounts of 10 to 200 parts, preferably 25 to 80 parts per 100 parts of polymer. 4. Process according to claims 2 and 3, characterized in that fillers with a BET surface area (ISO 5794 / 1D) of 1 to 700 m ² / g are used, the precipitated silicas and silicates also having a DBP number (ASTM D 2414) from 150 to 300 ml / 100 g. 5. The method according to claims 2 to 4, characterized in that one with the claim 1 described organosilane polysulfane mixture pretreated oxidic filler, the amount of organosilane polysulfane used per 100 Parts of filler amount to 0.5 to 30 parts.