EP1183305A1

EP1183305A1 - Hydroxyl group-containing diene rubber

Info

Publication number: EP1183305A1
Application number: EP00920733A
Authority: EP
Inventors: Thomas Scholl; Jürgen Trimbach
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1999-05-06
Filing date: 2000-04-20
Publication date: 2002-03-06
Also published as: JP2002544312A; DE19920894A1; CA2372507A1; MXPA01011278A; WO2000068311A1; AU4119800A; US6696523B1; KR20020010635A; BR0010333A

Abstract

The invention relates to rubber mixtures containing diene rubbers which contain 0.1 - 2 wt. % primary hydroxyl groups and have a glass transition temperature of -120 to -50 DEG C. The invention also relates to mixtures comprising filling materials, optionally other rubbers and rubber adjutants 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 tyres which exhibit a particularly high degree of anti-skid resistance in wet driving conditions.

Description

HYDROXYL GROUP-CONTAINING TUBE RUBBER

The present invention relates to rubber mixtures containing diene rubbers with a primary hydroxyl group content of 0.1 to 2% by weight and one

Glass temperature from -120 to -50 ° C and their mixtures with fillers, optionally other rubbers and rubber auxiliaries and vulcanizates produced therefrom. The rubber mixtures according to the invention are suitable for the production of highly reinforced, abrasion-resistant moldings, in particular for the production of tires which have a particularly high wet slip resistance.

Solution rubbers containing double bonds, such as solution polybutadiene and solution styrene / butadiene rubbers, have advantages over the corresponding emulsion rubbers in the production of low-rolling resistance tire treads. The advantages include in the controllability of the vinyl content and the associated glass temperature, the cis content and the molecular branching. In practical use, this results in particular advantages in relation to abrasion, wet skid resistance and rolling resistance of the tire. For example, US Pat. No. 5,227,425 describes the production of tire treads from a solution SBR rubber and silica. Numerous end group modification methods have been developed to further improve the properties, e.g. described in EP-A 334 042, with dimethylaminopropyl acrylamide or, as described in EP-A 447.066, with silyl ethers. Due to the high molecular weight of the rubbers, however, the weight fraction of the end group is low and can therefore have little influence on the interaction between the filler and the rubber molecule.

It was an object of the present invention to produce solution-diene rubbers, such as solution polybutadiene and polyisoprene, with a more favorable content of effective groups for the interaction of fillers.

A process for the preparation of hydroxyl-containing solution polybutadiene

Rubbers are also described in DE-OS 2,653,144. They own rubbers however, a significantly higher content of hydroxyl groups combined with significantly higher glass transition temperatures.

A process for the hydroxylation of rubbers is described in EP-A 464,478, but this involves the introduction of secondary hydroxyl groups which are far less effective than the primary hydroxyl groups of the present invention.

Emulsion and solution rubbers containing hydroxyl groups are also described in EP-806.452 A1, the hydroxyl contents described here for solution rubbers being due to the process in a significantly lower range (0.009 to 0.061%) and, in the case of the emulsion rubbers described, the glass transition temperatures being substantially higher due to the styrene content (> -40 ° C).

It has now been found that hydroxyl-containing solution diene rubbers with a content of 0.1 to 2% by weight of bound primary hydroxyl groups and a glass transition temperature of from -120 to -50 ° C. form rubber mixtures and rubber vulcanizates with surprisingly improved dynamic damping properties Have the temperature range relevant to wet slip resistance and in the temperature range relevant to rolling resistance and improved abrasion behavior. Further surprising advantages were obtained when the rubber mixture was not produced in the kneader as usual, but by mixing a solution of hydroxyl-containing rubber and oxidic or silicate filler in organic solvent and then removing the solvent with steam, since then the filler was completely with the rubber is precipitated and does not remain in the wastewater, as when using unmodified rubber.

The present invention therefore relates to rubber mixtures comprising one or more hydroxyl-containing rubbers composed of diolefins, characterized in that the or the hydroxyl-containing rubbers in the Contain range of 0.1 to 2 wt .-% bound primary hydroxyl groups and have a glass transition temperature between -120 to -50 ° C and fillers. Another object of the invention is the use of said rubber mixtures for the production of rubber vulcanizates, in particular tire treads filled with silica with particularly high abrasion resistance, particularly high wet skid resistance and low rolling resistance.

Suitable diolefins are in particular 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, l-phenyl-1,3-butadiene and 1,3-hexadiene. 1.3 butadiene and isoprene are particularly preferred.

The rubbers according to the invention for the rubber mixtures according to the invention are preferably produced by polymerization using coordination catalysts in the presence of a solvent or anionic solution polymerization. In this context, coordination catalysts are understood to mean Ziegler-Natta catalysts, coordination catalysts and monometallic catalyst systems. Preferred coordination catalysts are those based on Ni, Co, Ti or Nd. Catalysts for anionic solution polymerization are based on alkali or alkaline earth metals, e.g. n-butyllithium. In addition, the known randomizers and control agents for the microstructure of the

Polymers are used. Such solution polymerizations are known and, for example, in I. Franta 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 described. The primary hydroxyl groups are introduced in a subsequent reaction on the finished polymer. Methods for introducing the primary hydroxyl groups are, for example, the addition of primary hydroxyl-containing mercaptans, addition of formaldehyde, reaction with carbon monoxide and subsequent hydrogenation, hydroboration and subsequent oxidative hydrolysis of the borane compound. The hydroxyl groups are preferably introduced by the addition of hydroxyl mercaptans of the general formula (1) and / or hydroxyl group-containing mercaptocarboxylic esters of the general formula (2). The reaction is preferably carried out in solution, if appropriate in the presence of radical initiators.

HS - R -OH (1)

HS- (CHR ² ) _n - (CO ₂ -R ³ -OH) _r (2)

woπn

R ^{1 represents} a linear, branched or cyclic C 1 -C 6 -alkylene group which can optionally be substituted by up to 6 further hydroxyl groups or can be interrupted by nitrogen, oxygen or sulfur atoms,

R ^{2 is} hydrogen, or a C _j -Co alkyl group and

R ^{3 represents} a linear, branched or cyclic C2-C36 alkylene group which can optionally be substituted by up to 6 further hydroxyl groups or can be interrupted by nitrogen, oxygen or sulfur atoms,

OH represents a primary hydroxyl group,

n is an integer from 1 to 5,

m is an integer from 1 to 2.

C C g -alkylene is understood to mean all linear, cyclic or branched alkylene radicals with 1 to 36 C atoms known to the person skilled in the art, such as methylene,

Ethylene, n-propylene, i-propylene, n-butylene, i-butylene, t-butylene, n-pentylene, i-pentylene, neo-pentylene, n-hexylene, cyclohexylene, i-hexylene, heptylene, octylene, nonylene, decylene, undecylene and dodecylene.

Preferred hydroxyl mercaptans are mercaptoethanol, 1-mercapto-3-propanol, 1-mercapto-4-butanol, 3-mercapto-1, 2-propanediol (thioglycerol), α-mercapto-ω-hydroxy-oligoethylene oxides, e.g. α-mercapto-ω-hydroxy-octaethylene glycol or the corresponding ethylene oxide / propylene oxide mixed polyether. Mercapoethanol, thioglycerol and α-mercapto-ω-hydroxy-oligoethylene oxides are particularly preferred.

Preferred hydroxyl group-containing mercaptocarboxylic acid esters are esters of mercaptoacetic acid, mercaptopropionic acid and mercaptobutyric acid with ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, octaethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, methyl terepropylene glycol, methyl terepropylene glycol, and methyl tetra propylene glycol. The corresponding ones are particularly preferred

Esters of mercaptoacetic acid and 3-mercaptopropionic acid.

Suitable radical initiators for the attachment of the hydroxyl mercaptans to the hydroxyl-containing rubbers are e.g. Azo initiators, such as azobisisobutyronitrile, azobiscyclohexanenitrile and peroxides, such as dilauroyl peroxide, benzpinakolsilyl ether or photoinitiators in the presence of UV or visible light. Diacyl peroxides, in particular dilauroyl peroxide, didecanoyl peroxide, di- (3,3,5-trimethylhexanoyl) peroxide, disuccinoyl peroxide, dibenzoyl peroxide and perketals, such as II-di (tert-butylperoxy) -3,3,5-trimethyl- cyclohexane, ll-di (tert-butylperoxy) cyclohexane and 1.1-di (tert-butylperoxy) butane.

Preferred amounts of radical initiators are 0.5 to 20% by weight, based on hydroxyl mercaptan.

The average molecular weights of the hydroxyl-containing rubbers are between 50,000 and 2,000,000, preferably between 100,000 and 1,000,000. The Mooney viscosity ML 1 + 4 of the copolymers is between 10 to 200, preferably 30 to 150, measured at 100 ° C.

The content of polymerized 1,2-butadiene units (“vinyl content”) is between 0 and 60% by weight, preferably 1 to 50% by weight.

The glass transition temperature is between -120 to -50 ° C, preferably -120 to -70 ° C. The glass temperature can be determined using known methods e.g. can be determined by means of DSC (differential scanning calorimetry, heating rate 20 K / min.).

The cis-1.4 content of polymerized dienes is between 10 and 100%, preferably between 30 and 99%, particularly preferably between 90 and 99%.

The content of primary hydroxyl groups is between 0.1 to 2% by weight, preferably in the range from 0.1 to 1% by weight, particularly preferably in the range from 0.1 to 0.75% by weight, based on rubber .

The hydroxyl group content can be determined by known methods, e.g. by spectroscopy, tritrimetry, elemental analysis or by

Determination of the so-called hydroxyl number (OH number), that is to say by reaction with reagents which split off acids which can be titrated in contact with OH groups. See DIΝ 53.240.

The rubbers according to the invention with a glass transition temperature of -120 to -50 ° C. and 0.1 to 2% by weight of hydroxyl groups can be used alone, in a blend with aromatic or aliphatic oils or in a mixture with other rubbers. In addition to natural rubber, synthetic rubbers are also suitable as additional rubbers for the production of rubber vulcanizates. Preferred synthetic rubbers are for example from W. Hofmann, rubber technology, Gentner Verlag, Stuttgart 1980 and I. Franta, Elastomers and Rubber Compounding Materials, Elsevier, Amsterdam 1989. They include, among others

BR - polybutadiene ABR - butadiene / acrylic acid -CC-C4-alkyl ester copolymers

CR polychloroprene

IR - polyisoprene

SBR - styrene / butadiene copolymers with styrene contents of 1 to 60, preferably 20 to 50 wt .-% HR - isobutylene / isoprene copolymers

NBR - butadiene / acrylonitrile copolymers with acrylonitrile contents of 5 to 60, preferably 10 to 40% by weight

HNBR - partially hydrogenated or fully hydrogenated NBR rubber

EPDM - ethylene / propylene / diene copolymers

as well as mixtures of these rubbers. Natural rubber, emulsion SBR and solution SBR rubbers with a glass transition temperature above -50 ° C, polybutadiene rubber with a high 1.4-cis

Content (> 90%), which is made with catalysts based on Ni, Co, Ti or Nd, and polybutadiene rubber with a vinyl content of 0 to 75% and their

Mixtures of interest.

Very particularly preferred rubber mixtures according to the invention contain, in addition to the hydroxyl-containing rubber with a glass transition temperature between -120 ° to -50 ° C, additional rubbers selected from the series natural rubber,

Polysoprene 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 additionally added rubbers depends again on the particular intended use of the rubber mixtures according to the invention. The rubber mixtures according to the invention contain 5 to 300 parts by weight of an active or inactive filler, such as, for example

- highly disperse silicas, manufactured e.g. by precipitating solutions from

Silicates or flame hydrolysis of silicon halides with specific surface areas of 5 to 1000, preferably 20 to 400 m ² / g (BET surface area) and with primary particle sizes of 10 to 400 nm. The silicas can optionally also be mixed oxides with other metal oxides, such as Al, Mg, Ca, Ba, Zn, Zr, Ti oxides are present,

synthetic silicates, such as aluminum silicate, alkaline earth metal silicate, such as magnesium silicate or calcium silicate, with BET surface areas of 20 to 400 m ² / g and primary particle diameters of 10 to 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, e.g. Aluminum hydroxide, magnesium hydroxide,

Russian. The carbon blacks used here are produced using the flame black, furnace or gas black process and have BET surface areas of 20 to 200 m ² / g, such as 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 carbon blacks are particularly preferred.

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

The fillers are preferably added as solids or as a slurry in water or a solvent to the solution of the hydroxyl-containing rubbers polymerized in solution. The rubber solution can be prepared beforehand, but the solution originating from the polymerization is preferably used directly. The solvent is then removed thermally or preferably with the aid of steam. The conditions of this stripping process can easily be determined by preliminary tests.

The fillers for solid hydroxyl groups are also preferred

Rubber or a mixture of rubbers and added in a known manner, e.g. with a kneader, mixed in.

The rubber mixtures according to the invention optionally also contain crosslinking agents. Sulfur or peroxides can be used as crosslinkers

Sulfur is particularly preferred. The rubber mixtures according to the invention can contain further auxiliary rubber products, such as reaction accelerators, anti-aging agents, heat stabilizers, light stabilizers, anti-ozone agents, processing aids, plasticizers, tackifiers, blowing agents, dyes, pigments, waxes, extenders, organic acids, retarders, metal oxides and the like Activators such as triethanolamine, polyethylene glycol, hexanetriol etc. which are known to the rubber industry.

The use of additional filler activators is particularly advantageous in the preferred rubber mixtures with highly active precipitated silicas.

Preferred filler activators are sulfur-containing silyl ethers, in particular bis (trialkoxisilyl-alkyl) polysulfides, as described in DE 2,141,159 and DE-AS 2,255,577, oligomeric and / or polymeric sulfur-containing silyl ethers of DE-OS 4,435,311 and EP-A 670.347, mercapatoalkyltrialkoxisilane, in particular mercaptopropyltriethoxisilane and thiocyanatoalkylsilyl ether, such as, for example described in DE-OS 19,544,469.

The rubber auxiliaries are used in customary amounts, which depend, among other things, on the intended use. Common amounts are e.g. Amounts from 0.1 to 50 wt .-%, based on rubber.

The rubber mixtures according to the invention are outstandingly suitable for the production of moldings of all kinds.

Non-limiting examples of these shaped bodies are O-rings, profiles, seals,

Membranes, tires, tire treads, damping elements and tubes.

Tires and tire treads are particularly preferred.

example 1

A solution of 500 g of solution polybutadiene rubber Buna CB 65 (Bayer AG, Li type, cis-l, 4 content approx. 40%) in 4 1 cyclohexane is at 70 ° C with 12.5 g 1-mer - capto-2-ethanol and 1 g of dilauroyl peroxide were added. The mixture was then stirred at 80 ° C for 8 hours. At this point, 39% of the mercaptoethanol had reacted. Then 2.5 g of the antioxidant Vulkanox 4020 (Bayer AG) were added and the solvent was distilled off with steam (100-110 ° C.). After drying at 70 ° C. in vacuo, 508 g of a colorless rubber with an OH number of 7, an OH content of 0.21% by weight and a cis-1, 4 content of 40% were obtained. Glass temperature: -90 ° C

Example 2:

The procedure was as in Example 1, but only 6.25 g of l-mercapto-2-ethanol were used. After 8 hours at 80 ° C, 41% conversion was achieved. Then the solvent was distilled off with steam (100-110 ° C). After drying at 70 ° C under vacuum, 505 g of a colorless rubber with an OH content of 0.1%, cis-l, 4 content 40%, glass temperature: -90 ° C

Example 3:

A solution of 500 g of solution polybutadiene rubber Buna VI 47-0 (Bayer AG, Vinyl-BR, content of 1,2-bonded butadiene (“vinyl content”) approx. 47%) in 4 1 cyclohexane is at 12 ° C. with 70 , 5 g of 1-mercapto-2-ethanol and 1 g of dilauroyl peroxide were added, followed by stirring for 4 hours at 80 ° C. To this

At the time, 95% of the mercaptoethanol had reacted. Then 2.5 g of the antioxidant Vulkanox 4020 (Bayer AG) were added and the solvent was distilled off with steam (100-110 ° C.). After drying at 70 ° C. under vacuum, 512 g of a colorless rubber with an OH number of 17, an OH content of 0.5% by weight, a vinyl content of approximately 45% and a glass transition temperature of -54 ° C. were obtained.

Claims

claims

1. rubber mixtures containing one or more hydroxyl-containing rubbers composed of diolefins, characterized in that the or the hydroxyl-containing rubbers contain in the range of 0.1 to 2 wt .-% bound primary hydroxyl groups and have a glass transition temperature between -120 to -50 ° C. .

2. Rubber mixtures according to Anspmch 1, characterized in that 1,3-butadiene and / or isoprene are used as diolefins.

3. Rubber mixtures according to Anspmch 1, characterized in that the cis-1.4 content of the hydroxyl-containing rubber polymerized in solution is greater than 30%.

4. Rubber mixtures according to Anspmch 1, characterized in that in addition to the hydroxyl-containing rubber with a glass transition temperature between -120 ° to -50 ° C, additional rubbers selected from the series of natural rubber, polyisoprene and styrene / butadiene copolymers with styrene contents between 10 and 50% by weight. contained in the rubber mixture in an amount of 0.5 to 95% by weight, preferably 40 to 90% by weight, based on the total amount of rubber.

5. A process for the preparation of rubber mixtures according to spoke 1, characterized in that one or more fillers in amounts in the range from 0.5 to 500 parts by weight, based on 100 parts by weight of rubber, to the solution of the hydroxyl-containing rubbers and, if appropriate, further auxiliaries for working up and / or processing and / or stabilization are added and the solvent is then removed.

6. The method according to Anspmch 5, characterized in that the solvent is removed with the aid of steam.

7. Use of the rubber mixtures according to Anspmch 1 for the production of all kinds of moldings, in particular for the production of tires, particularly preferably of tire treads and tire sidewalls.