DE19920788A1 - Carboxyl group-containing diene rubbers - Google Patents

Abstract

The invention relates to rubber mixtures containing diene rubber groups which contain 0.1 - 2 wt. % carboxyl groups and have a glass transition temperature of -120 to -50 DEG . The invention also relates to mixtures comprising filling materials, optionally other rubbers and rubber adjuvants and vulcanizates produced therefrom. The inventive rubber mixtures are suitable for use in the production of fully reinforcing, abrasion-resisting shaped bodies, especially in the production of tyre treads which exhibit a particularly high degree of anti-skid resistance in wet driving conditions, are resistant to abrasion and offer low rolling resistance. Said rubber mixtures are also suitable for use in the production of the side walls of tyres, where they display resistance to fatigue.

Description

The present invention relates to rubber mixtures containing diene rubbers with a carboxyl group content of 0.1 to 2 wt .-% and a glass temper rature from -110 to -50 ° and their mixtures with fillers, if appropriate other rubbers and rubber auxiliaries and vulcanis made therefrom sate. The rubber mixtures according to the invention are suitable for the production of highly reinforced, abrasion-resistant moldings, in particular for the production of Tire treads that have a particularly high wet skid resistance, abrasion resistance and have low rolling resistance as well as for tire sidewalls with special good fatigue resistance.

Double bond-containing anionically polymerized solution rubbers, such as Polybutadiene and solution styrene / butadiene rubbers have opposite Emulsion rubbers advantages in the production of low rolling resistance Tire treads. The advantages are u. a. in the controllability of the vinyl content and the associated glass temperature and the molecular branching. From this result ben practical advantages in relation to the wet Tire slip resistance and rolling resistance. So describes US-PS 5,227,425 Production of tire treads from a solution SBR rubber and pebble acid. There are numerous methods for improving the properties End group modification has been developed as described in EP-A 334 042, with dimethylaminopropyl acrylamide, or as described in EP-A 447.066 Silyl ethers. Due to the high molecular weight of the rubbers, the weight proportion the end group, however, is small and therefore the interaction between filler and affect the rubber molecule only little. It was u. a. a task of the present Invention diene rubbers with a significantly higher content of active full groups on filler interaction and particularly low glass temperature to manufacture.  

US-PS 2,662,874 describes the production of elastic materials made of metal ion-crosslinked polymeric carboxylates with a content of 0.001 to 0.3 Carboxyl equivalents per 100 g rubber. The elastic materials mentioned have a very wide carboxyl group content and are for tire users tion of the present invention due to its inherent sensitivity to hydrolysis the metal salts are unsuitable.

A process for the preparation of carboxyl group-containing (3.9 to 8.9% by weight Carboxyl groups) solution polybutadiene rubbers is u. a. in DE-OS 26 53 144. These rubbers have due to the high vinyl content and the high carboxyl group content too high glass temperatures (<-40 ° C) ver bundles with unfavorable damping properties are therefore no substitute for poly butadiene rubber.

The object of the present invention was therefore mixtures of carboxyl groups to provide solution rubber, from which tires with ver better wet skid resistance, lower rolling resistance and high mechanical Strength and improved abrasion behavior.

The present invention therefore relates to rubber mixtures tend one or more rubbers with in the range of 0.1 to 2 wt .-% on those carboxyl groups or their salts and a glass transition temperature in the range of -110 to -50 ° C and one or more fillers in the range of 10 to 500 Parts by weight based on 100 parts by weight of rubber.

Rubber mixtures according to the invention in which the carboxyl group-containing rubber containing bound carboxyl groups or their Salts from 0.1 to 1 wt .-% and has a glass transition temperature in the range of -110 to -50 ° C, preferably -100 to -60 ° C and has a content of 1,2-bonded Diolefins (vinyl content) in the range from 0 to 50% by weight, particularly preferably 1 to 15% by weight and a cis-1,4 content in the range from 30 to 100% by weight, particularly  preferably 90 to 100 wt .-%, and average molecular weights (number average) of 50,000 to 2,000,000, preferably 100,000 to 1,000,000 and Mooney viscosities ML 1 + 4 (100 ° C) from 10 to 200, preferably 30 to 150.

The glass temperature can be determined using known methods, e.g. B. means DSC (differential scanning calorimetry, heating rate 20 K / min.). The determination the carboxyl group content can also by known methods such. B. Free acid titration, spectroscopy, elemental analysis etc. are carried out.

The production of the rubbers according to the invention for the inventive Rubber mixtures are preferably made by polymerisation using a coordina tion catalysts or anionic solution polymerization. Under coordination co In this context, catalysts are Ziegler-Natta catalysts, Koordina tion catalysts and monometallic catalyst systems to understand. Before Coordinated catalysts are those based on Ni, Co, Ti or Nd. Kataly Catalysts for anionic solution polymerization are based on alkali or alkaline earths metal base, such as B. n-butyllithium. In addition, the well-known randomizer and control agents for the microstructure of the polymer can be used. Derar term solution polymerizations are known and z. B. in I. Fronta Elastomers and Rubber compounding materials; Elsevier 1989, pages 113-131 and in Houben- Weyl, Methods of Organic Chemistry, Thieme Verlag, Stuttgart, 1961, volume XIV / 1, pages 645 to 673 or in volume E 20 (1987), pages 114 to 134 and pages 134 to 153.

According to the invention, 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 1-vinyl-1,3-butadiene and / or 1,3-hexadiene. 1,3-Butadiene and isoprene are particularly preferably used.

The carboxyl groups can be introduced into the rubber by either adding carboxyl-providing compounds, for example CO ₂ , to metalated solution rubbers or by treating the finished rubber with compounds containing carboxyl groups, for example mercaptans containing carboxyl groups, in a subsequent reaction.

The carboxyl groups are preferably introduced into the rubber after the monomers used have been polymerized in solution by reacting the polymers obtained, if appropriate in the presence of radical initiators, with carboxyl mercaptans of the formula (I)

HS-R ¹ -COOX (I),

wherein
R ^{1 stands} for a linear, branched or cyclic C ₁ -C ₃₆ alkyl group which can optionally be substituted with up to 3 further carboxyl groups or can be interrupted by nitrogen, oxygen or sulfur atoms, and
X represents hydrogen or a metal or ammonium ion.

This method is a further subject of the invention.

C ₁ -C ₃₆ -alkyl is understood to mean all linear, cyclic or branched alkyl radicals with 1 to 36 C atoms known to the person skilled in the art, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t -Butyl, n-pentyl, i-pentyl, neo-pentyl, n-hexyl, cyclohexyl, i-hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl.

Preferred carboxyl mercaptans of the formula (I) are thioglycolic acid, 2-mercapto propionic acid (thiolactic acid), 3-mercaptopropionic acid, 4-mercaptobutyric acid, Mercaptoundecanoic acid, mercaptooctadecanoic acid, 2-mercaptosuccinic acid and their alkali and alkaline earth metal or ammonium salts. 3- are particularly preferred Mercaptopropionic acid, mercaptobutyric acid and 2-mercaptosuccinic acid as well  whose lithium, sodium, potassium, magnesium, calcium or ammonium salts puts. 3-Mercaptopropionic acid and its lithium are very particularly preferred, Sodium, potassium, magnesium, calcium or ammonium salts.

In general, the reaction of the carboxyl mercaptans with the solution is carried out rubbers in a solvent, for example hydrocarbons, such as pen tan, hexane, cyclohexane, benzene and / or toluene, by at temperatures from 40 to 150 ° C in the presence of radical starters, e.g. B. peroxides, such as dilauroyl peroxide, Azo initiators, such as azobisisobutyronitrile, benzpinacol silyl ethers or in the presence of photoinitiators and visible or UV light. Preferred radical initiators are Diacyl peroxides such as dilauroyl peroxide, didecanoyl peroxide, di (3,5,5-trimethyl-hexa noyl) peroxide and perketals, such as 1,1-di (tert-butylperoxy) -3,3,5-trimethyl-cyclo hexane, 1,1-di (tert-butylperoxy) cyclohexane and 1,1-di (tert-butylperoxy) butane.

The amount of carboxyl mercaptans to be used depends on the desired content of bound carboxyl groups or their salts in the in the rubber compounds to be used.

The carboxylic acid salts can also after the introduction of the carboxylic acid group in the rubber is made by neutralizing it.

All come as fillers for the rubber mixtures according to the invention known fillers used in the rubber industry, these comprising both active and inactive fillers.

To be mentioned are:

• - highly disperse silicas, manufactured e.g. B. by precipitation of solutions of silicates or flame hydrolysis of silicon halides with specific surfaces of 5-1000, preferably 20-400 m ² / g (BET surface area) and with primary particle sizes of 10-400 nm. The silicas can optionally also be mixed oxides other metal oxides, such as Al, Mg, Ca, Ba, Zn, Zr, Ti oxides;
• - Synthetic silicates, such as aluminum silicate, alkaline earth silicate, such as magnesium silicate or calcium silicate, with BET surfaces of 20-400 m ² / g and primary particle diameters of 10-400 nm;
• - natural silicates such as kaolin and other naturally occurring silica;
• - Glass fibers and glass fiber products (mats, strands) or micro glass balls;
• - metal oxides, such as zinc oxide, calcium oxide, magnesium oxide, aluminum oxide;
• Metal carbonates, such as magnesium carbonate, calcium carbonate, zinc carbonate;
• - Metal hydroxides, such as. B. aluminum hydroxide, magnesium hydroxide;
• - soot. The carbon blacks to be used here are produced using the soot, furnace or gas black process and have BET surface areas of 20-200 m ² / g, for. B. SAF, ISAF, HAF, FEF or GPF carbon blacks;
• Rubber gels, especially those based on polybutadiene, butadiene / styrene Copolymers, butadiene / acrylonitrile copolymers and polychloroprene.

Highly disperse silicas and / or are preferably used as fillers Russian.

The fillers mentioned can be used alone or in a mixture. In a particularly preferred embodiment contain the rubber mixtures as Fillers a mixture of light fillers, such as highly disperse silicas, and Carbon black, the mixing ratio of light fillers to carbon black at 0.05 to 20, preferably 0.1 to 10.  

The fillers are used in amounts ranging from 10 to 500 parts by weight based on 100 parts by weight of rubber. 20 to 200 are preferred Parts by weight used.

The rubber mixtures according to the invention can in addition to one, two, three or several different solutions containing carboxyl groups according to the invention still contain other rubbers, such as natural rubber as well as others Synthetic rubbers.

Preferred synthetic rubbers are described, for example, by W. Hofmann, Kautschuk Technologie, Gentner Verlag, Stuttgart 1980 and I. Franta, Elastomers and Rubber Coumpounding Materials, Elsevier, Amsterdam 1989. They include, among others
BR - polybutadiene
ABR - butadiene / acrylic acid C1-4 alkyl ester copolymers
CR - polychloroprene
IR - polyisoprene
SBR - styrene / butadiene copolymers with styrene contents of 1-60, preferably 20-50% by weight
IIR - isobutylene / isoprene copolymers
NBR - butadiene / acrylonitrile copolymers with acrylonitrile contents of 5-60, preferably 10-40% by weight
HNBR - partially hydrogenated or fully hydrogenated NBR rubber
EPDM - ethylene / propylene / diene copolymers
as well as mixtures of these rubbers. For the manufacture of motor vehicle tires, natural rubber, emulsion SBR and solution SBR rubbers with a glass transition temperature above -50 ° C., which may be combined with silyl ethers or other functional groups, for. B. can be modified according to EP-A 447.066, polybutadiene rubber with a high 1,4-cis content (<90%), which was produced with catalysts based on Ni, Co, Ti or Nd, and polybutadiene rubber with a vinyl content of up to 75% and their mixtures of interest.

Very particularly preferred rubber mixtures according to the invention also contain one or more rubbers containing carboxyl groups with a glass transition temperature between -110 ° to -50 ° C additional rubbers selected from the range Natural rubber, polysisoprene and styrene / butadiene copolymers with styrene contents between 10 and 50% by weight. The amount of these additional rubbers is usually in the range from 0.5 to 95, preferably 40 to 90% by weight, based on the total amount of rubber in the rubber mixture. The amount of additional added rubbers depend again on the respective use Purpose of the rubber mixtures according to the invention.

Of course, the rubber mixtures according to the invention can also do other Contain rubber auxiliaries, for example the crosslinking of the Rubber compounds produced vulcanizates serve, or the physical Properties of those produced from the rubber mixtures according to the invention Improve vulcanizates for their special purpose.

For example, sulfur or sulfur-supplying agents can be used as cross-linking agents Compounds are used, such as radical-providing crosslinking agents, such as organic peroxides. Sulfur is preferably used as crosslinking agent. About that In addition, as mentioned, the rubber mixtures according to the invention can be others Aids, such as the known reaction accelerators, anti-aging agents, heat stabilizers, light stabilizers, ozone protection agents, processing aids, soft makers, tackifiers, blowing agents, dyes, pigments, waxes, extenders, organic Acids, retarders, metal oxides and activators.

The rubber auxiliaries according to the invention are known in the usual Amounts used, the amount used after the later use purpose of the rubber compounds. For example, amounts of  Rubber auxiliaries in the range from 2 to 70 parts by weight, based on 100 parts by weight Parts of rubber.

For the rubber mixtures according to the invention which contain highly active silicas are filled, the use of additional filler activators is particularly important partial. Preferred filler activators are sulfur-containing silyl ethers, in particular Bis (trialkoxisilyl-alkyl) polysulfides, as described in DE 21 41 159 and DE 22 55 577 are described. In addition, oligomeric and / or polymeric are also suitable sulfur-containing silyl ethers as described in DE 44 35 311 and EP 670.347. Mercapatoalkyltrialkoxisilanes are also to be used, in particular Mercaptopropyltriethoxisilan and Thiocyanatoalkylsilylether (see DE 195 44 469). The filler activators are used in conventional amounts, i. H. in quantities of 0.1 to 15 parts by weight, based on 100 parts by weight of rubber.

The rubber mixtures according to the invention can, for. B. are produced by Mixing the carboxyl group-containing solution rubbers with the corresponding the fillers and optionally further rubbers and others Rubber auxiliaries in suitable mixing equipment, such as kneaders, rollers or Extruding.

The rubber mixtures according to the invention are preferably produced by one first carries out the polymerization of the monomers mentioned in solution, the Introduces carboxyl groups into the solution rubber and after termination of the Polymerization and the introduction of the carboxyl groups in the corresponding Solvent rubber present with the appropriate fillers and optionally further rubbers and further rubber auxiliaries, especially plasticizers, mixed in the appropriate amounts and then add the solvent with hot water and / or steam Temperatures of 50 to 200 ° C, optionally under vacuum, removed.  

Another object of the present invention is the use of the inventions rubber mixtures according to the invention for the production of moldings of all kinds, especially for the production of tires, particularly preferably tire treads and tire sidewalls.  

Examples example 1

A solution of 500 g of solution polybutadiene rubber Buna CB 65 (Bayer AG, Li type, cis 1,4-content approx. 40%) in 4 l cyclohexane is at 70 ° C with 12.5 g 3-mer captopropionic acid and 0.5 g dilauroyl peroxide. Then you stirred 5 Hours at 80-85 ° C after. At this point the 3-mercaptopropion had 36% acid converted. Then 2.5 g of the antioxidant Vulkanox 4020 (Bayer AG) and distilled off the solvent with steam (100-110 ° C). After drying at 70 ° C. in vacuo, 505 g of a colorless chew were obtained Tschuks with a sulfur content of 0.3% by weight (elemental analysis), carboxyl group Content 0.38% by weight, ML 1 + 4 (100 ° C) 92, cis 1,4-content 40%. Glass temperature: -90 ° C.

Example 2

A solution of 500 g of solution polybutadiene rubber Buna CB 65 (Bayer AG, Li type, cis 1,4-content approx. 40%) in 4 l cyclohexane at 70 ° C with 6.25 g 3-mer captopropionic acid and 0.5 g dilauroyl peroxide. Then you stirred 5 Hours at 80-85 ° C after. At this point the 3-mercaptopropion had acid converted to 46%. Then 2.5 g of the antioxidant Vulkanox 4020 (Bayer AG) and distilled off the solvent with steam (100-110 ° C). After drying at 70 ° C. in vacuo, 503 g of a colorless chew were obtained Tschuks with a sulfur content of 0.2% by weight (elemental analysis), carboxyl group Content 0.24% by weight, ML 1 + 4 (100 ° C) 84, cis 1,4-content 40%. Glass temperature: -90 ° C.  

Example 3 Production of a masterbatch from precipitated silica and carboxyl group pen-containing BR rubber

According to the procedure of Example 1, 500 g of BR rubber Buna CB 65 were reacted in 4 l of cyclohexane at 80 ° C. with 12.5 g of 3-mercaptopropionic acid and 0.5 g of dilauroyl peroxide. Response time: 5 hours. At this point, 36% of the 3-mercaptopropionic acid had reacted. Carboxyl group content of the polymer: 0.38% by weight. Then 2.5 g of stabilizer Vulkanox® 4020 (Bayer AG), 189.5 g of aromatic mineral oil Renopal® 450 (Fuchs Mineralölwerke) and 405 g of highly active precipitated silica Vulkasil® S (N ₂ surface) were added with stirring at 75 ° C approx. 180 m ² / g, Bayer AG) and stirred for approx. 30 minutes until uniform distribution at this temperature. The solvent was then removed by introducing steam (100-110 ° C). The reaction vessel was heated from the outside at 75-80 ° C. The moist solid was then removed and filtered through a sieve of finely divided silica and then dried at 65 ° C. in vacuo. 1090 g of a brown silica / rubber masterbatch (99% of theory) were obtained. The wastewater was free of silica.

Comparative Example 1

The procedure was as in Example 3, with a solution of 500 g of BR rubber Buna CB 65 and 2.5 g Vulkanox® 4020 in 4 l cyclohexane at 75 ° C with 400 g high active precipitated silica Vulkasil® S was mixed. Then removed the solvent by introducing steam (100-110 ° C), which Reaction vessel was heated from the outside at 75-80 ° C. Subsequently, the removed moist solid and filtered through a sieve of finely divided silica and then dried at 65 ° C in a vacuum. 597 g (66% of theory) of one were obtained  inhomogeneous silica / rubber masterbatches. The sewage contained large ones Quantities (approx. 75% of the quantity used) silica.

Claims (5)

1. rubber mixture containing one or more rubbers with im Range of 0.1 to 2 wt .-% of bound carboxyl groups or their Salt and a glass temperature in the range of -110 to -50 ° C and one or more fillers in the range of 10 to 500 parts by weight based on 100 parts by weight of rubber. 2. Rubber mixture according to claim 1, characterized in that the Rubber made from diolefins. 3. A process for the preparation of a rubber with in the range of 0.1 to 2 wt .-% of bound carboxyl groups, characterized in that the rubber after the polymerization in solution with carboxyl mercaptans of the general formula (I)
HS-R ¹ -COOX (I),
in which
R ^{1 represents} a linear, branched or cyclic C ₁ -C ₃₆ -alkyl group which can optionally be substituted with up to 3 further carboxyl groups or can be interrupted by nitrogen, oxygen or sulfur atoms, and
X represents hydrogen or a metal or ammonium ion,
if appropriate in the presence of free radical initiators. 4. Use of the rubber mixtures according to claim 1 for the production of moldings of all kinds.   5. Use of the rubber mixtures according to claim 1 for the production of tires.