JP2002544311A - Carboxy group-containing diene rubber - Google Patents

Abstract

  (57) [Summary] The present invention relates to a rubber mixture containing a diene rubber group having a carboxyl group of 0.1 to 2% by mass and a glass transition point of -120 to -50C. The invention also relates to mixtures containing filler substances, optionally other rubbers and rubber additives, and vulcanized rubbers made therefrom. The rubber mixtures according to the invention are used in the production of high-strength, abrasion-resistant molded articles, in particular for tire treads which exhibit particularly high anti-skid resistance under wet operating conditions, are abrasion-resistant and exhibit low rolling resistance. Suitable for use in manufacturing. The rubber mixture is also suitable for use in the manufacture of tire sidewalls that exhibit fatigue resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD The present invention relates to a carboxyl group concentration of 0.1 to 2% by mass and -120 to -50 ° C.
And mixtures thereof with fillers, optionally with other rubbers and rubber auxiliary substances, and vulcanized rubbers produced therefrom. The rubber mixtures according to the invention have a particularly high fatigue resistance, in particular for the production of high-strength wear-resistant moldings, in particular for the production of tire treads having a high wet skid resistance and abrasion resistance and a low rolling resistance. Suitable for tire sidewalls.

BACKGROUND OF THE INVENTION [0002] Solution rubbers containing double bonds in anionic polymerization (eg, solution polybutadiene and solution styrene / butadiene rubber) are used to produce low rolling resistance tire treads relative to the corresponding emulsion rubbers. Have advantages. The advantages are, among others,
The ability to control the vinyl content, its associated glass transition point and molecular branching. The special advantages associated with wet skid resistance and rolling resistance of tires result in practical applications. Thus, US Pat. No. 5,227,425 describes the production of tire treads from solution SBR rubber and silica. To further improve the properties, a number of end group modification methods have been developed, e.g. EP-A 334 042 describes a method using dimethylaminopropylacrylamide and EP-A 447 066 describes a method using silyl ethers. Have been. However, due to the high molecular weight of the rubber, the mass proportion of the end groups is low and only a small extent affects the interaction between the filler and the rubber molecules. In particular, it is an object of the present invention to provide diene rubbers having a very high concentration of effective groups interacting with the filler and having a particularly low glass transition point.

[0003] US-A 2 662 874 describes the production of elastomers from metal ion-crosslinked polymer carboxylates having a concentration of 0.001 to 0.3 carboxyl equivalents per 100 g of rubber. This elastic material has a very wide range of carboxyl group contents, but is unsuitable for tire applications in the present invention because of its inherently hydrolytic sensitivity to metal salts.

[0004] A process for the production of solution polybutadiene rubbers containing carboxyl groups (3.9 to 8.9% by weight of carboxyl groups) is described, inter alia, in DE-OS 2653144. These rubbers are very high (>) due to the high concentration of vinyl and carboxyl groups.
It has a glass transition point, with unfavorable damping properties, and therefore does not replace 1,4-polybutadiene rubber in tire treads and tire sidewalls.

DISCLOSURE OF THE INVENTION [0005] Accordingly, an object of the present invention is to provide a solution-containing rubber mixture containing a carboxyl group, from which an improved wet skid resistance and a low wet skid resistance are obtained. Tires with rolling resistance, high mechanical strength and improved wear behavior can be produced.

[0006] Accordingly, the present invention provides a method for preparing a carboxyl group or a salt thereof having a concentration in the range of 0.1 to 2% by mass and one having a glass transition point in the range of -120 to -50 ° C. Or more rubber and a rubber mixture comprising one or more fillers in the range of 10 to 500 parts by weight per 100 parts by weight of rubber.

(Best Mode for Carrying Out the Invention) A preferred rubber mixture of the present invention has a carboxyl group-containing rubber having a content of 0.1.
Having a concentration of bound carboxyl groups or salts thereof of １1% by mass;
C., preferably having a glass transition point of -120 to -70 ° C., having a 1,2-bonded diolefin concentration (vinyl content) in the range of 0 to 50% by weight, especially 1 to 15% by weight, The cis-1,4 in the range of 30 to 100% by mass, particularly preferably 90 to 100% by mass.
-Having a content of between 50,000 and 2,000,000, preferably 100,
A rubber mixture having a (number average) molecular weight of 000 to 1,000,000 and a Mooney viscosity ML 1 + 4 (100 ° C.) of 10 to 200, preferably 30 to 150.

[0008] The glass transition point can be determined using known methods, for example, DSC (differential scanning calorimetry,
It can be measured by using a heating rate of 20 K / min). The carboxyl group concentration can also be measured using known methods (eg, free acid titration, spectroscopy, elemental analysis, etc.).

The rubbers of the invention for use in the rubber mixtures of the invention can preferably be produced by polymerization using a coordination catalyst or by anionic solution polymerization.
Coordination catalysts in this context are understood to be Ziegler-Natta catalysts, coordination catalysts and single metal catalyst systems. The coordination catalyst is preferably a catalyst based on Ni, Co, Ti or Nd. Catalysts for anionic solution polymerization are based on alkali or alkaline earth metals, for example n-butyllithium. In addition, known randomizers for the microstructure of the polymer can be used. These types of solution polymerizations are known and include, for example, I. Franta, Elastomers and Rubber C
ompounding Materials, Elsevier 1989, pp. 113-131, and Houben-Weyl
, Methoden der Organischen Chemie, Thieme Verlage, Stuttgart, 1961, No.
XIV / 1, pages 645-673 or E20 (1987), pages 114-134 and 134-153.

The diolefins used for the polymerization according to the invention are 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 1-vinyl-1,3-diene.
Butadiene and / or 1,3-hexadiene. 1,3-Butadiene and isoprene are particularly preferably used.

[0011] The carboxyl groups are treated by adding a carboxyl group-supplying compound (eg, CO ₂ ) to the curing solution rubber or treating the final rubber in a subsequent reaction with a carboxyl-containing compound (eg, a carboxyl-containing mercaptan). Either of these can be introduced into the rubber.

[0012] The carboxyl group is preferably obtained by polymerizing the resulting polymer after polymerization of the monomers used in the solution, optionally in the presence of a radical initiator, of the formula (I):

Embedded image [Wherein, R ¹ represents a linear, branched or cyclic C ₁ -C ₃₆ alkylene group;
X may represent hydrogen or a metal or ammonium ion, which may be substituted by up to a further carboxyl group or may be intervened by a nitrogen, oxygen or sulfur atom or a C ₆ -C ₁₂ arylene group. ] Into the rubber by reacting with a carboxyl mercaptan represented by This method is another subject of the present invention.

A C ₁ -C ₃₆ alkylene group is understood to be any straight-chain, cyclic or branched alkylene group having 1 to 36 carbon atoms known to the person skilled in the art, for example methylene, ethylene, n-propylene, i-propylene, n-butylene, i-butylene, t
-Butylene, n-pentylene, i-pentylene, neopentylene, n-hexylene,
Cyclohexylene, i-hexylene, heptylene, octylene, nonylene, decylene, undecylene and dodecylene.

Preferred carboxyl mercaptans of the formula (I) are thioglycolic acid, 2-mercaptopropionic acid (thiolactic acid), 3-mercaptopropionic acid,
Mercaptobutyric acid, mercaptoundecanoic acid, mercaptooctadecanoic acid, 2-mercaptosuccinic acid and their alkali and alkaline earth metal salts or ammonium salts. Particularly preferred are 3-mercaptopropionic acid, mercaptobutyric acid, 2-mercaptosuccinic acid, 2-mercaptobenzoic acid and 4-mercaptobenzoic acid and their lithium, sodium, potassium, magnesium, calcium or ammonium salts. 3-Mercaptopropionic acid and its lithium, sodium, potassium, magnesium, calcium or ammonium salts are particularly preferred.

In general, the reaction of a carboxyl mercaptan with a solution rubber is carried out in a solvent such as a hydrocarbon (eg, pentane, hexane, cyclohexane, benzene and / or toluene) at a temperature of 40-150 ° C., a radical initiator such as , Peroxides (eg, dilauroyl peroxide), azo-based initiators (eg, azobisisobutyronitrile), benzopinacolsilyl ether, or in the presence of a photoinitiator and visible or UV light. Preferred radical initiators are diacyl peroxides such as dilauroyl peroxide, didecanyl peroxide, di- (3,3,5-trimethylhexanoyl) -peroxide, and perketals such as 1,1-di- (tert- Butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di- (tert-butylperoxy) -cyclohexane and 1,1-
Di- (tert-butylperoxy) -butane.

The amount of carboxyl mercaptan used depends on the concentration of bound carboxyl groups or salts required in the solution rubber used in the rubber mixture. Carboxylates can also be prepared by introducing carboxylic acid groups into the rubber and then neutralizing them. Suitable fillers for the rubber mixtures of the present invention are any fillers known to be used in the rubber industry, including both active and inert fillers.

The following may be mentioned: Highly dispersed silica. Its preparation is, for example, by precipitation of a silicate solution or flame hydrolysis of a silicon halide. Its specific surface area is from 5 to 1,000 m ² / g, preferably from 20 to 400 m ² / g (BET surface area). Its primary particle size is 10-400n
m. Silica can optionally also be present as a mixed oxide with other metal oxides such as Al, Mg, Ca, Ba, Zn, Zr or Ti oxide. -Synthetic silicate. For example, aluminum silicate, alkaline earth metal silicate (eg, magnesium silicate or calcium silicate). Its BET surface area is 20 ~
400 m ² / g and its primary particle size is 10-400 nm. -Natural silicate. For example, kaolin and other naturally occurring silicas. -Glass fibers and glass fiber products (mats, ropes) or glass microbeads. -Metal oxides. For example, zinc oxide, calcium oxide, magnesium oxide, aluminum oxide. -Metal carbonate. For example, magnesium carbonate, calcium carbonate, zinc carbonate. -Metal hydroxide. For example, aluminum hydroxide and magnesium hydroxide. ·Carbon black. The carbon black used in the present invention is prepared by a flame black method, a furnace black method, or a gas black method.
It has a BET surface area of ２００200 m ² / g. For example, SAF, ISAF, HAF,
FEF or GPF carbon black. Rubber gels, especially those based on polybutadiene, butadiene / styrene copolymers, butadiene / acrylonitrile copolymers and polychloroprene. Preferably, highly dispersed silica and / or carbon black is used as a filler.

The above fillers can be used alone or as a mixture. In a particularly preferred embodiment, the rubber mixture contains a mixture of a light-colored filler (for example, highly dispersed silica) and carbon black as a filler, and the mixing ratio of the light-colored filler to carbon black is 0.05 to 20, preferably 0.1 to 0.1. It is 10. The filler is used in an amount ranging from 10 to 500 parts by mass per 100 parts by mass of rubber. 20 to 200 parts by mass are preferably used.

The rubber mixtures according to the invention contain, in addition to one, two, three or more different solution carboxyl-containing solution rubbers according to the invention, other rubbers, for example natural rubbers, as well as other synthetic rubbers. I can do it.

Preferred synthetic rubbers are, for example, W. Hoffmann, Kautschuktechnolgie, Gentner
Verlag, Stuttgart, 1980 and I. Franta, Elastomers and Rubber Compoun
ding Materials, Elsevier, Amsterdam, 1989. Said synthetic rubber comprises, inter alia: BR polybutadiene ABR butadiene / C ₁ -C ₄ alkyl acrylate copolymer CR polychloroprene IR polyisoprene SBR styrene content of 1 to 60% by weight, preferably 20 to 50% by weight % Styrene / butadiene rubber copolymer IIR isobutylene / isoprene copolymer NBR having an acrylonitrile content of 5 to 60% by mass, preferably 10 to 40% by mass.
Butadiene / acrylonitrile copolymer HNBR partially hydrogenated or fully hydrogenated NBR rubber EPDM ethylene / propylene / diene copolymer in weight%, and mixtures of these rubbers. Natural rubbers, emulsion SBR and solutions SBR, having a glass transition temperature above -50 ° C., optionally modified with silyl ethers or other functional groups, for example according to EP-A 447 066, and N
Polybutadiene rubbers having a high 1,4-cis content (> 90%) produced with catalysts based on i, Co, Ti or Nd, and polybutadiene rubbers having a vinyl content of up to 75% and these Are particularly important for the production of automotive tires.

Particularly preferred rubber mixtures for the present invention are natural rubbers, in addition to one or more carboxyl-containing rubbers having a glass transition point of -120 to -50 ° C.
Polyisoprene and styrene with a styrene content of between 10 and 50% by weight /
Contains an additional rubber selected from the group consisting of butadiene copolymers. The amount of these additional rubbers is usually 0.5 to 95% by mass based on the total amount of rubber in the rubber mixture,
Preferably it is in the range of 40 to 90% by mass. The amount of these additional rubbers will also depend on the particular purpose for which the rubber mixture of the present invention will be used.

Obviously, the mixtures according to the invention can also contain other rubber auxiliary substances. The rubber auxiliary substance, for example, to crosslink vulcanized rubber produced from a rubber mixture,
Alternatively, it is used to improve the physical properties of a vulcanized rubber produced from the rubber mixture of the present invention for a specific end use.

[0023] Sulfur or sulfur-supplying compounds, as well as radical-supply crosslinkers (eg, organic peroxides), can be used, for example, as crosslinkers. Sulfur is preferably used as a crosslinking agent. In addition, as mentioned above, the rubber mixture of the present invention may contain additional auxiliary substances, such as known reaction accelerators, antioxidants, heat stabilizers, light stabilizers, antiozonants, processing aids, plasticizers, tackifiers. Imparting agent, foaming agent, dye, pigment, wax,
Extenders, organic acids, retarders, metal oxides and activators can be included.

The rubber auxiliary substances according to the invention are generally used in the amounts disclosed, the amount used depending on the subsequent end use of the rubber mixture. For example, 2 parts per 100 parts by mass of rubber
Auxiliary substances for rubber in amounts of ７０70 parts by weight are usually used.

In the case of the rubber mixtures according to the invention filled with highly active silica, the use of additional filler activators is particularly advantageous. Preferred filler activators are sulfur-containing silyl ethers, such as those described in DE 2 141 159 and DE 2 255 577,
(Trialkoxysilylalkyl) polysulfide. In addition, DE 4 435 311
Also suitable are oligomers and / or polymers of sulfur-containing silyl ethers corresponding to those described in EP 670 347 and EP 670 347. Mercaptoalkyl trialkoxysilanes, in particular mercaptopropyltriethoxysilane and thiocyanatoalkylsilyl ethers (see DE 19 544 469) can also be used. The filler activator is used in conventional amounts, i.e. from 0.1 to 15 parts by weight per 100 parts by weight of rubber.

The rubber mixture according to the invention is, for example, mixed with a solution rubber containing carboxyl groups and a corresponding filler, if desired an additional rubber and an additional rubber auxiliary substance in a suitable mixing device (
For example, it can be manufactured by mixing in a compounding machine, a roller or an extruder.

The rubber mixture according to the invention is preferably first polymerized in solution with the monomers mentioned,
After the carboxyl groups have been introduced into the solution rubber and the polymerization and the introduction of the carboxyl groups have been completed, the solution rubber in the corresponding solvent and a suitable filler, optionally additional rubber and optionally additional rubber auxiliary substances (particularly plasticizers) ) Are mixed in appropriate amounts, and then
It is prepared by removing the solvent, preferably under reduced pressure, using hot water and / or steam at a temperature of 50-200 ° C.

The invention also provides the use of the rubber mixtures according to the invention for the production of molded articles of all kinds, in particular for the production of tires, especially tire treads and tire sidewalls.

Examples Example 1 6.25 g of 3-mercaptopropionic acid and 1 g of dilauroyl peroxide are mixed with 500 g of a solution of polybutadiene rubber in 500 g of 4 L of cyclohexane at 80 ° C.
CB 45 NF, Bayer AG, Li type, cis-1,4 content: about 40%). Then the mixture was stirred at 80 ° C. for 7 hours. Then 2.5 g of antioxidant (Vulkanox 4020, Bayer AG) and 101.3 g of aromatic mineral oil (Enerthene 18
49-1, BP) and the solvent was distilled off using steam (100-110 ° C.). After drying at 70 ° C. under reduced pressure, 593 g of a rubber oil-extended with 20 phr of mineral oil were obtained:
Sulfur content 0.3% by mass, carboxyl group content 0.5% by mass (based on rubber), viscosity ML 1 + 4 (100 ° C) 59, cis-1,4-content 40%, glass transition point − 88 ° C
.

Example 2 The following rubber mixture was produced in a 1.5 L kneader (mixing time 5 minutes, discharge temperature 150 ° C.). Thereafter, the sulfur and the accelerator were mixed on a mill (50 ° C.).

[0031]

[Table 1]

[0032]

[Table 2]

Next, the rubber mixture was vulcanized at 170 ° C. for 15 minutes. The following vulcanized rubber properties were obtained:

[Table 3] Experimental data (rebound and tan delta measurements) confirm that the dynamic braking at 70 ° C. is lower, which in practice leads to a considerable reduction in the rolling resistance of the tire.

Example 3 Preparation of Masterbatch from Precipitated Silica and Carboxyl-Containing BR Rubber Using the method of Example 1, 500 g of BR rubber in 4 L of cyclohexane
a CB 65 was added at 80 ° C. with 12.5 g of 3-mercaptopropionic acid and 0.5 g
Of dilauroyl peroxide. The reaction time was 5 hours. At this point, 36% of the 3-mercaptopropionic acid had reacted. The carboxyl group content of the polymer was 0.38% by mass. Then, with stirring at 75 ° C., 2.5
g stabilizer Vulkanox® 4020 (Bayer AG), 189.5 g aromatic mineral oil
Renopal® 450 (Fuchs Mineraloelwerke) and 405 g of highly active precipitated silica Vulkasil® S (N ₂ surface area approx. 180 m ² / g, Bayer AG) were added until these components were homogeneously dispersed. The mixture was stirred at this temperature for about 30 minutes. The solvent was then removed by passing steam (100-110 ° C.) through the mixture. In this procedure, the reaction vessel was heated from the outside to 75-80 ° C. Finally,
The wet solids are removed, the fine silica is filtered through a sieve and the product is
Dried at 5 ° C. 1090 g of brown silica / rubber masterbatch (99% in theory)
)was gotten. No silica remained in the wastewater.

Comparative Example 3.A: The same procedure as described in Example 3 was used, but with 50 L of cyclohexane.
A solution of 0 g of BR rubber Buna CB 65 and 2.5 g of Vulkanox® 4020 was mixed at 75 ° C. with 400 g of highly active precipitated silica Vulkasil® S. The solvent was then removed by passing steam (100-110 ° C.) through the mixture (the reaction vessel was heated from the outside to 75-80 ° C. during this procedure). Finally, the wet solids were removed, the fine silica was filtered through a sieve, and the product was dried at 65 ° C under reduced pressure. 597 g of an uneven silica / rubber masterbatch (66 in theory)
%)was gotten. A large amount (about 75% of the amount used) of silica remained in the wastewater.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR , HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA , ZWF term (reference) 4J002 AC012 AC062 AC082 AC101 AC111 DA036 DJ016 FD016 GN01

Claims (5)

[Claims] 1. One or more rubbers having a bound carboxyl group or a salt thereof in the range of 0.1 to 2% by weight and a glass transition point in the range of -120 to -50 ° C, and 100 parts by weight of the rubber. A rubber mixture comprising one or more fillers in the range from 10 to 500 parts by weight. 2. The rubber mixture according to claim 1, wherein the rubber comprises a diolefin. 3. A process for the production of rubbers having a bound carboxyl group in the range of 0.1 to 2% by weight, comprising, after polymerization in solution, optionally in the presence of a radical initiator, I): [Wherein, R ¹ represents a linear, branched or cyclic C ₁ -C ₃₆ alkylene group;
X may represent hydrogen or a metal or ammonium ion, which may be substituted by up to a further carboxyl group or may be intervened by a nitrogen, oxygen or sulfur atom or a C ₆ -C ₁₂ arylene group. ] It reacts with the carboxyl mercaptan represented by these. 4. Use of the rubber mixture according to claim 1 for producing all kinds of moldings. 5. Use of the rubber mixture according to claim 1 for producing tires.