CA2078414A1

CA2078414A1 - Sulfur-modified butadiene copolymers containing functional groups and mixtures thereof with other rubbers

Info

Publication number: CA2078414A1
Application number: CA 2078414
Authority: CA
Inventors: Werner Obrecht; Christiane Oppenheimer-Stix; Peter Wendling; Hans-Wilhelm Engels; Ulrich Eisele; Zsolt Szentivanyi
Original assignee: Individual
Current assignee: Bayer AG
Priority date: 1991-09-19
Filing date: 1992-09-16
Publication date: 1993-03-20
Also published as: EP0533015A1; JPH05202136A; DE4131186A1

Abstract

NEW SULFUR-MODIFIED BUTADIENE COPOLYMERS CONTAINING FUNC-TIONAL GROUPS AND MIXTURES THEREOF WITH OTHER RUBBERS
A b s t r a c t The new sulfur-modified butadienes copolymerized with ethylenically unsaturated monomers and containing function-al groups, which are produced in the presence of 0.05 to 2.5 parts by weight elemental sulfur or an equivalent quantity of sulfur donors, based on the monomers used, the sum of peptizing agents used being from 0.1 to 6.0 parts by weight, based on the monomers used, are used for the production of vulcanizates, even in admixture with other rubbers containing C=C double bonds.

Le A 28 515 - Foreign Countries

Description

207841~

NE~ 8ULFUR-MODIFIED BUTADIXNE COPOLYMERS CONTAINING FUNC-TIONAL GROUP8 AND MIXTURE8 ~HEREOF WITH OTHER RUBBERS

This invention relates to new sulfur-modified butadi-enes copolymerized with ethylenically unsaturated monomers and containing functional groups and to mixtures thereof with other rubbers containing C=C double bonds.
Sulfur-containing butadiene copolymers are described in East German patent 211 796. They are produced using balsam extract and/or tall resins disproportionated before-hand with sulfur. However, at least part of the elemental sulfur undergoes a chemical transformation during the disproportionation, 80 that the elemental sulfur cannot be used in the exact guantity required for the production of the butadiene copolymers. In addition, the polymerization is not accompanied or followed by selective peptization which leads to functional groups in the polymer and to the desired polymer viscosity.
Accordingly, the present invention relates to sulfur-modified butadienes copolymerized with ethylenically un-saturated monomers and containing functional groups, characterized in that they are produced in the presence of 0.05 to 2.5 parts by weight and preferably 0.1 to 1.5 parts by weight elemental sulfur or an equivalent quantity of sulfur donors, based on the monomers used ~butadiene ~
ethylenically unsaturated monomer~, the sum of peptizing agents used being from 0.1 to 6.0 parts by weight and preferably from 0.5 to 5.0 parts by weight, based on the monomers used.
Butadienes which may be copolymerized with the ethyl-enically unsaturated monomers are, for example, butadiene and/or isoprene, butadiene being preferred.
Ethylenically unsaturated monomers which may be copolymerized with the butadienes are, for example, acrylo-nitrile, methacrylonitrile, acrylic acid, methacrylic acid, Le A 28 515 - 1 Forei gn Countri es 2078~4 acrylates and methacrylates, styrene and ~-methyl styrene.
Acrylonitrile and styrene are preferred. Acrylonitrile is particularly preferred. The ethylenically unsaturated monomers may be used both individually and in admixture with one another.
The butadiene copolymers contain the ethylenically unsaturated monomers in quantities of 2 to 60% by weight and preferably 5 to 50% by weight.
The butadienes are incorporated in the copolymer in quantities of 40 to 98% by weight and preferably in quan-tities of 50 to 95% by weight (not including the sulfur units incorporated and the functional groups).
The sulfur-modified butadiene copolymers are produced in the presence of elemental sulfur or in the presence of sulfur donors, such as xanthogen polysulfides and thiuram polysulfides. Dipentamethylene thiuram tetra- and hexasul-fide are mentioned as representatives of these classes.
Elemental sulfur is preferably used. The sulfur may be used both in solution in the monomer and in the form of an agueous dispersion. It is preferably used in the form of an aqueous dispersion.
Both the sulfur and the sulfur donors may of course be used in admixture with one another.
The peptizing agents used are compounds known from the literature, such as dithiocarbamates, thiuram disulfides, xanthogenates, xanthogen disulfides, mercaptans, mercapto-benzthiazole and iodoform (cf. W. Obrecht in Houben-Weyl "Methoden der organischen Chemie", Vol. E20/2 (1987), pages 842 et seg., Georg Thieme Verlag, Stuttgart/New York). It is preferred to use water-soluble dithiocarbamates and/or xanthogenates containing the following anions:

Le A 28 515 2 207~14 (1) N_c_se R2/ ¦¦

or (2) R3_0_c_se Il s and/or also thiuram disulfides and/or xanthogen disulfides corresponding to the following formulae:

Rl Rl ( 3 ) N-C--S--S-C--N
2 0 R2 ¦¦ ¦¦ \R2 or 4 ) R3-o-c-s-s_c_O-R3 in which R1, R2 and R3 may be the same or different and represent C124 alkyl, C~ cycloalkyl or C5-~8 aryl, which may contain up to 3 heteroatoms, and in which Rl and R2 together may form a ring containing 3 to 5 carbon atoms which may 35 optionally be interrupted by heteroatoms, preferably one heteroatom.
In a particularly preferred embodiment, R1 and R2 independently of one another represent C14 alkyl and R3 represents C~ alkyl or 2,2-(2,4-dioxapentamethylene)-n-butyl corresponding to the following formula Le A 28 515 3 ~7~

\ /

/ \

Preferred heteroatoms are nitrogen and oxygen.
Preferred cations for the peptizing agents ~1) and (2) are alkali metal ions, more particularly sodium and potas-sium ions, and also ammonium ions.
The use of peptizing agents promotes cleavage of thesulfur segments in the polymer which lead ~o functional groups in the polymer (cf. K. Nitsumichi et ~l., Journal of the Society of Rubber Industry, 3apan, Vol. 63, pages 322-330 (1990); Y. Miyata et ~l., International Rubber Confer-ence Kyoto, 16A-12, pages 217-222 (1985) and A.L. Kleban-skii et al., Journal of Polymer Science, Vol. 30, pages 363-374 (1958), Prague Symposium).
The use of dithiocarbamates and thiuram disulfides and also xanthogenates and xanthogen disulfides leads to dithiocarbamate and xanthogenate functions.
The peptizing agents may also be used in combination with one another. They may be added before, during or after polymerization. It is particularly suitable to add dithiocarbamate and/or xanthogenate before the beginning of polymerization coupled with the addition of thiuram disul-fide and/or xanthogen disulfide in the shortstopping phase of the polymerization reaction or to the shortstopped latex before or after removal of the unreacted monomers. The additional introduction of mercaptans and/or xanthogen disulfides before the beginning of polymerization can be of advantage in this regard.
Sulfur-modified butadiene copolymer is produced in the same way as sulfur-modified polychloroprene as described, for example, in DE 19 11 439, 20 18 736, 27 55 074, 32 46 748, 35 07 825, 26 45 920, EP 21 212, 200 857, FR 1 457 004 and US-PS 2,264,713, 3,378,538 and 3,397,173 (af also W.
Le A 28 515 4 2~78~1~

Obrecht in Houben-Weyl ~Methoden der organischen Chemie", ~ol. E 20/2 (1987), pages 842 et seq., Georg Thieme Verlag, Stuttgart/New York).
The copolymers may be prepared either discontinuously or continuously both by solution polymerization and by emulsion polymerization. They are preferably prepared by emulsion polymerization at 0 to 70-C and preferably at 0 to 50-C.
The sulfur-modified butadiene copolymers according to the invention have Mooney viscosities (according to DIN 53 523) of generally 5 to 140 and preferably 10 to 120 MU (~lL
1+4/100 C).
Stabilizers, such as phenolic, aminic, phosphorus- and sulfur-containing compounds, may be added to the butadiene copolymers according to the invention to improve their stability in storage.
In addition to the polymerized butadiene units, the pre~erred sulfur-modified butadiene/acrylonitrile copoly-mers, hereina~ter referred to as S-NBR, contain 2 to 60% by weight and pre~erably 5 to 50% by weight, based on copoly-mer, o~ copolymerized acrylonitrile units. S-NBR is also understood to include:

- mixtures of crosslinked S-NBR (gel) with uncrosslinked2 5 S-NBR ( sol ); by gel is meant polymers insoluble in solvents, such as toluene or methyl ethyl ketone. The gel component may be up to 97% by weight, - mixtures of S-NBR with different nitrlle contents, the nitrile content of the individual mixture components being ~rom 2 to 60% by weight, - mixtures of S-NBR produced using different quantities of elemental sulfur or equivalent sulfur donor; the quantity of sulfur used in the preparation of the individual mixture components may be ~rom 0.05 to 2.5 parts by weight, based on the monomers used, Le A 28 515 5 2078~14 - mixtures of S-NBR with different nitrile contents and different quantities of sulfur or equivalent sulfur donors used in their production. The range of varia-tion for the individual components of the mixt~lre may be between nitrile contents of 2 to 60% by weight and quantities of sulfur of 0.05 to 2.5 parts by weight, based on the monomers used, - mixtures of S-NBR with crosslinked and/or uncrosslink-ed, sulfur-free NBR (i.e. free from elemental sulfur) and combinations of the variations mentioned above.

In general terms, the quantities in which the in-dividual components are used will be determined by the particular application envisaged. Thus, the properties of the crude rubbers, the mixtures and the vulcanizates can be influenced as known to the expert. For example, the swelling which extrudates undergo on extrusion can be influenced through the gel content. The nitrile contents influence such properties as, for example, the low-tempera-ture flexibility, swelling in fuels, tensile st~ngth andmodulus of the vulcanizates. ~
Crosslinked S-NBR's can be produced by polymerization to high conversions or, where the monomer inflow technique ic used, by polymerization at high internal conversions.
The S-NBR's may also be crosslinked by copolymerization of multifunctional compounds having a crosslinking effect.
Preferred crosslinking multifunctional comonomers are compounds containing at least 2 and preferably 2 or 3 copolymerizable C=C double bonds, such as for example diisopropenyl benzene, divinyl benzene, divinyl ether, divinyl sulfone, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene, N,N'-m-phenylene dimaleic imide, triallyl trimellitate and also the acry-lates and methacrylates of polyhydric, preferably dihydric to tetrahydric, C2~0 alcohols, for example ethylene glycol, Le A 28 515 6 2~78~4 propane-1,2-diol, propane-1,3-diol, butane-1,4-diol, hexane-1,6-diol, polyethylene glycol containing 2 to 20 and preferably 2 to 4 oxyethylene units, trimethylol ethane and propane, tetramethylol methane. Preferred crosslinking acrylates and methacrylates are ethylene diacrylate and dimethacrylate, propylene diacrylate and dimethacrylate, isobutylene diacrylate and dimethacrylate, butylene diacry-late and di~ethacrylate, hexanediol diacrylate and dimeth-acrylate, di-, tri- and tetraethylene glycol diacrylate and dimethacrylate, trimethylol ethane triacrylate and trimeth-acrylate, trimethylol propane triacrylate and trimethacry-late and/or tetramethylol methane tetraacrylate and tetra-methacrylate.
The sulfur-modified butadiene copolymers, particularly S-NBR, may be vulcanized at vulcanization rates suitable for practical requirements without any need for vulcaniza-tion accelerators. Uncrosslinked, i.e. soluble, S-NBR
~sol) in particular is distinguished by improved, i.e.
increased, mastication so that, as known to the expert, less energy i5 consumed during production of thq mixtures by virtue o~ this reduction in viscosity.
Accordingly, the present invention also compr~ses the vul¢anizates obtained from the sulfur-modified butadienes copolymerized with ethylenically unsaturated monomers and containing functional groups.
The sulfur-modified butadiene copolymers according to the invention containing functional groups may be vulcan-ized in the usual way in the presence of ~illers of any kind. Preferred fillers are carbon blacks. Preferred car-bon blacks have surfaces of 35 to 200 m'/g ~CTAB measure-ment). Particularly preferred carbon blacks are SAF, HAF, FEF, ISAF and SRF carbon blacks and mixtures thereof. Mix-tures of carbon blacks with silicas ~with and without filler activators) and silicas having particle sizes and surfaces comparable with those of the carbon blacks are Le A 2a 515 7 207~414 also suitable as fillers. The filler content may be varied within wide limits and, as known to the expert, should be adapted to the particular application.
The usual processing aids, plasticizers, antiagers, factices and resins may be added to the butadiene copoly-mers according to the invention in order to provide the crude mixtures or vulcanizates with desirable properties.
Suitable Grosslinking systems are any of the systems typically used in rubber technology, such as sulfur cross-linking, peroxide crosslinking, urethane crosslinking, metal oxide crosslinking, resin crosslinking, radiation crosslinking and combinations thereof. The particular crosslinking system used is determined by the composition of the butadiene copolymers according to the invention and ~5 the particular application.
Another valuable property of the sulfur-modified butadiene copolymers according to the invention is that, in mixtures with rubbers containing C=C double bonds, they lead to reduced hysteresis losses of the vulcanizates produced from them.
In rubber technology, a hysteresis loss is the amount o~ energy which is lrreversibly converted into heat in the event o~ dynamic stressing of the elastomer. Hysteresis lo~ses are measured as the tan ~ which is defined as the ratio of 1088 modulus to storage modulus, cf. also DIN 53 513, DIN 53 535. Reductions in the tan ~ in the applica-tionally important temperature/frequency or amplitude range lead, for example, to reduced heat build~up in the elas-tomer. Tire treads of rubber vulcanizate having a reduced hysteresis loss are distinguished by reduced rolling resistance and, hence, by lower fuel consumption of the vehicles to which they are ~itted.
Despite the large number of available rubbers, the attention of experts on tire manufacture has been directed above all to natural rubber (NR), cis-polybutadiene ~BR) and styrene/butadiene copolymers (SBR). These rubbers or Le A 28 515 8 2~78~1~

mixtures thereof are used worldwide for tire manufacture.
Numerous attempts to reduce the rolling resistance of tire treads have been described in the literature. Thus, mixtures of rubbers containing C=C double bonds and sulfur-modified polychloroprene gel have been proposed for this purpose (EP 405 216). However, the disadvantage of these mixtures is that an insoluble polymer (gel) has to be used.
Production of the gel requires high conversions, i.e.
relatively long polymerization times or the additional use of a crosslin~ed chemical. However, both lead to an increase in the production costs. Further disadvantages of using CR gel lie in the price of rubber and in the ecologlcal problems involved in the recycling of used tires on account of the chlorine-containing component.
Accordingly, the present invention also comprises mixtures of A) sulfur-modified butadienes copolymerized with ethylen-ically unsaturated monomers and containing functional groups and B) other rubbers containing C-C double bonds, the quantity of butadiene copolymer A) being from 1 to 90%
by weight and preferably from 3 to 70% by weight, based on component~ A) and B).
A higher percentage of sulfur-modified butadiene copolymer may of course also be used, depending on the application.
Preferred sulfur-modified copolymers A) are buta-diene/acrylonitrile copolymers of the type described in the foregoing.
Preferred rubbers B) contain C=C double bonds corre-sponding to iodine values of at least 2 and preferably in the range from 5 to 470. The iodine values are generally Le A 28 515 9 2078~1~

determined by addition of iodine chloride in acetic acid by the Wijs method (DIN 53 241, Part 1). The iodine value is the quantity of iodine in grams which is chemically bound by lOO g substance.
~he rubbers B) include inter ~li~ EPDM, butyl rubber, nitrile rubber, hydrogenated nitrile rubber, natural rubber, polyisoprene, polybutadiene and styrene/butadiene copolymers (SBR) and mixtures thereof.
The rubbers B) generally have Mooney viscosities (DIN
53 523) of 10 to 150 and preferably 25 to 80 (ML 1+4)/
100 C .
The abbreviation "EPDM" standæ for ethylene/propylene/
diene terpolymers. EPDNs include rubbers in which the ratio by weight of ethylene to propylene units is in the range from 40:60 to 65:35 and which may contain from 1 to 20 C=C double bonds per 1,000 carbon atoms. Examples of suitable diene monomers in EPDM are conjugated dienes, for example isoprene and 1,3-butadiene, and unconjugated dienes containing 5 to 25 carbon atoms, for example 1,4-penta-diene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene and 1,4-octadiene; cyclic dienes, for example cyclopentadiene, cyclohexadiene, cyclooctadiene and dicy-clopentadiene; alkylidene and alkenyl norbornenes, ~or example 5-ethylidene-2-norbornene, 5-butylidene-2-norbor-nene, 2-methylallyl-5-norbornene, 2-isopropenyl-5-norbor-nene and tricyclodienes.
The unconjugated dienes 1,5-hexadiene, ethylidene norbornene and dicyclopentadiene are preferred. The diene content in the EPDM is pre~erably ~rom 0.5 to 10% by weight, based on EPDM.
EPDM rubbers of the type in question are described, ~or example, in DE-OS 2 808 709.
In the context of the invention, the expression "butyl rubber" encompasses isobutene copolymers of 95 to 99.5% by weight and preferably 97.5 to 99.5% by weight isobutene and Le A 28 515 10 ~0784~4 0.5 to 5% by weight and preferably 0.5 to 2.5% by weight copolymerizable diene, such as for example butadiene, dimethyl butadiene, 1,3-pentadiene, more particularly iso-prene. On an industrial scale, butyl rubber is produced almost exclusively as an isobutene/isoprene copolymer by cationic solution polymerization at low temperatures, cf.
for example Kirk-Othmer, Encyclopedia of Chemical Technol-ogy, 2nd Edition, Vol. 7, page 688, Interscience Publ. New YorX/London/Sydney, 1965 and Winnacker-Kuchler, Chemische Technologie, 4th Edition, Vol. 6, pages 550-g55, Carl Hanser Verlag, Munchen/Wien 1962.
The expression "nitrile rubber" stands for butadiene/
acrylonitrile copolymers containing 5 to 60~ by weight and preferably 10 to 50~ by weight copolymerized acrylonitrile.
"Hydrogenated" in this context means that 90 to 98.5 and preferably 95 to 98% of the hydrogenatable C=C double bonds are hydrogenated while the C=N triple bonds of the nitrile groups are not hydrogenated. The hydrogenation of nitrile rubber is known (cf. US-PS 3,700,637, DE-OS 25 39 132, 30 46 008, 30 46 251, 32 27 650, 33 29 974, EP-A 111 412, FR-PS 2 540 503.
Preferred styrene/butadiene copolymers are those containing 18 to 60% by weight and preferably 20 to 50% by weight copolymerized styrene. Solution and emulsion polymers are particularly preferred.
~illers o~ any kind may of course be added to the rubber mixtures according to the invention. Preferred fillers are carbon blacks. Preferred carbon blacks have surfaces of 35 to 200 m2/g (CTAB measurement). Particular-ly preferred carbon blacks are SAF, HAF, FEF, ISAF and SRF
carbon blacks and mixtures thereof. Mixtures of carbon blacks with silicas (with and without filler activators) and silicas having particle sizes and surfaces comparable with those of the carbon blacks are also suitable as fillers. The filler content may vary within wide limits, Le A 28 515 11 ~078~4 but is often between 30 and 80 parts by weight filler per 100 parts by weight rubber (A+B).
The mixtures according to the invention may be pre-pared in various ways. On the one hand, it is of course possible to mix the solid individual components. Suitable mixing units are, for example, mixing rolls and internal mixers. However, they may also be prepared by mixing latices of the individual rubbers; the mixtures accord-ing to the invention thus prepared may be isolated in the usual way by concentration through evaporation, precipita-tion or freeze coagulation (cf. US-PS 2,187,146).
By incorporation of fillers in the latex mixtures, followed by working up, the mixtures according to the invention may be directly obtained as rubber/filler formulations. Ac-cordingly, the present invention also compri ses a process for the production of the described mixtures by combining the components.
The usual processing aids, plasticizers, antiagers, factices and resins, may be added to the mixtures according to the invention to provide the crude mixtures or vulcani-zates with desired properties.
Suitable crosslinking systems are any o~ the systems typically used in rubber technology, such as sul~ur cross-linking, peroxide crosslinking, urethane crosslinking,metal oxide crosslinking, resin crosslinking, radiation cro~slinking and combinations thereo~. Pre~erred cross-linking systems are dependent upon the rubbers B used in the mixtures according to the invention, sulfur crosslink-ing systems being particularly preferred.
The present invention also comprises the vulcanizatesproduced from the described mixtures.
The vulcanizates of the mixtures according to the invention show reduced hysteresis losses and are therefore eminently suitable for the production of tires.
Le A 28 515 12 2 ~ 7 l~xamples 1. Production of the sulfur-modified butadiene/acrylo-nitrile copolymers A and B according to the invention Polymerization was carried out in a 250 liter stirred reactor using the following basic formulation (quantities in parts by weight):
S-NBR A S-NBR B
Acrylonitrile 35 31.5 Butadiene 65 67.5 Divinyl benzene 0.8 Deionized water ~total quantity) 155 152 K salt of coconut oil fatty acid 3.5 2.6 Condensate of naphthalene sulfonic 0.5 0.4 acid and formaldehyde (Na salt) Tert. dodecyl mercaptan 0.07 0.15 Sul~ur 0.4 0.6 Triethanolamine 0.44 0.88 Dibutyl dithiocarbamate (Na salt) 2.0 2.0 Pota~slum peroxodi~ul~ate 0.92 1.84 (total quantity) Polymerization was shortstopped at a conversion of 70% and the latex stabilized as ~ollows:

Tetraethyl thiuram disulfide 1.5 1.5 Antiager (Vulkanox KB~, a product 1.25 1.25 o~ Bayer AG) Polymerization was carried out in-a nitrogen atmos-phere. The aqueous phase ~pH 12) consisting of deionized water, K salt of coconut oil fatty acid, triethanolamine and Na salt of naphthalene sul~onic acid/formaldehyde con-densate was introduced into the stirred reactor. Acrylo-nitrile (together with divinyl benzene in the case of S-NBR
B) and butadiene were then successively added. The sulfur Le A 28 515 13 2078~14 was added in the form of a 50% by weight aqueous dispersion while the dibutyl dithiocarbamate (Na salt)was added in the form of a 30~ aqueous solution. The temperature of the emulsion formed was adjusted to 25C and the polymerization was initiated with potassium peroxydisulfate in the form of a 3.5% aqueous solution, maintained at 25'C by addition of more potassium peroxodisulfate and continued to a conver-sion of 70%.
Polymerization was shortstopped by addition of tetra-ethyl thiuram disulfide in the form of a 25% aqueousemulsion of a toluene solution (25% by weight tetraethyl thiuram disulfide, 37~ by weight toluene, 6% by weight Na salt of the condensation product of naphthalene sulfonic acid and formaldehyde, 3.2% by weight dodecyl sulfate (Na ~alt), 28.8% by weight deionized water). The latex was freed from unreacted monomer by cyclone degassing in vacuo with steam and was stabilized with 2,6-di-tert.-butyl-o-cresol in the form of an aqueous dispersion.
The latex was precipitated with 20% NaC~ solution at 22'C, the polymer obtained was washed free from chloride at room temperature and was dried at 60-C in a recirculating air drying cablnet.
The S-NBR had a Mooney viscosity of 40 MU ~ML 1+4/
lOO-C). S-NBR B had a gel content of 88% and a swelling index of 10, as measured in toluene.

2. Production of NBR 1 NBR 1 was produced in the same way as S-NBR A, except that no elemental sulfur and no thiuram disulfide were used. The quantity of tert. dodecyl mercaptan was 0.3% by weight, based on monomers. Polymerization was shortstopped at a conversion of 70% by addition of 1.2% by weight Na dithionite, based on monomers. Degassing, stabilization and isolation of the polymer were carried out in the same way as for S-NBR A. The polymer of Comparison Example 1 Le A 28 515 14 2~78414 had a Mooney viscosity of 42 MU (ML 1+4/100C).

3. Production of the sulfur-modified CR gel in accordance with EP O 405 216 Polymerization was carried out in a 250 liter stirred reactor using the following basic formulation (quantities in parts by weight):

Chloroprene 95 Ethylene glycol dimethacrylate 5 Deionized water ~total quantity) 125 Na salt of disproportionated abietic acid 5.3 Na salt of naphthalene sulfonic acid/ 0.6 formaldehyde condensate KOH 0.5 K2S2t 0. 11 Na Salt of anthraquinone sulfonic acid 0.06 Sulfur 0-5 Na dibutyl dithiocarbamate (DBDTC) 1.0 Tetraethyl thiuram disulfide (TETD) 3.0 The aqueous phase consisting of deionized water, Na ~alt of dlsproportionated abietic acid, Na salt of methy-lene-bridged naphthalene ~ulfonic acid, Na salt of anthra-quinone ~ulfonic acid and KOH was introduced into thereactor, purged with nitrogen and heated to 30'C.
The nitrogen-purged monomers were then added. The crosslinking agent, ethylene glycol dimethacrylate, was dissolved in the monomer. After the intended reaction temperature of 30'C had been established, the sulfur was added in the form of a 50% by weight dispersion and the DBDTC in the form of a 30% by weight solution. Polymer-ization was then initiated by addition of a small quantity of a nitrogen-purged, dilute aqueous K2S208 solution and was maintained by addition of this aqueous nitrogen-purged Le A 28 515 15 2~7841~
persulfate solution.
The conversion was gravimetrically followed. At a conversion of g3%, the polymerization was shortstopped by addition of 0.03 part by weight, based on latex, of an aqueous 2.5% by weight solution of diethyl hydroxyl amine and tetraethyl thiuram disulfide (TETD) was added to the latex. TETD was used in the form of a 25~ by weight aqueous emulsion in a toluene solution.
The latex was degassed to approx. 500 ppm residual chloroprene (based on latex).
The sulfur-modified polychloroprene gel was precipita-ted from the latex by addition of 2% by weight aqueous CaCl2 solution (5 g CaCl2 per 100 g solids) and was dried at 60C
in a vacuum drying cabinet.

4. Performance tests S-NBR A according to the invention and NBR 1 were tested for mastication behavior. To this end, the polymers were masticated for 8 minutes at 40C on laboratory rolls with a small bead, after which the Mooney viscosity (ML
1+4/lOO-C) was measured. The following results were obtained:
O value 8 Minute (MU) value (Mn) Example 1 40 29 (polymer S-NBR A) Comparison Example 1 42 38 (polymer NBR 1) Vulcanization behavior was tested on the following basic mixture 1 (vulcanization temperature 150C):

Polymer 100 parts by weight Carbon black Corax N 550~ 50 ~ZnO aktiv2~ 3,0 Le A 28 515 16 2~78~14 ~Magelite DE3) 2.0 parts by weight 6Vulkanox HS 1.0 Vulkanox oCD5) 1.0 Vulkanox ZMB6) 2.0 Vulkanol OT7) 5.0 1) A product of Degussa AG, Hanau 2) Active zinc oxide, a product of Bayer AG, Leverkusen 3) Magnesium oxide, a product of Merck & Co. Inc., USA
~ 2,2,4-Trimethyl-~,2-dihydroquinoline, polymer (antiager), a product of Bayer AG, Leverkusen 5) Octylated diphenylamine (antiager), a product of Bayer AG, Leverkusen 6) Zn salt of 4- or 5-methylmercaptobenzimidazole (antiager), a product of Bayer AG, Leverkusen 7~ Ether thioether (plasticizer), a product of Bayer AG, Leverkusen.

The mixture was prepared in a 1.5 liter kneader at 100-C.

Bx~mple 2 In Example 2, the S-NBR A according to the invention was used in the basic mixture 1.
Comparison ~xample 2 In Comparison Example 2, NBR 1 was used in the basic mixture 1 and 1.5 parts by weight sulfur and 2.0 parts by weight Vulkacit CZ (benzothiazyl-2-cyclohexyl sulfenamide, vulcanization accelerator, a product of Bayer AG, Lever-kusen) were also added.
The ~ollowing Table shows that Example 2 according to the invention leads to vulcanization rates suitable forpractical purposes without vulcanization accelerators.

Le A 28 515 17 21~;~841~

Vulcanization at 150C
tlo t70 tg~
(mins.) (mins.) (mins.) Example 21.6 3.7 7.0 Comp. Example 22.6 4.1 7.6 Examples 3 and ~ and Comparison Ex~mple~ 3 and 4 Using test mixture 2 below, it is intended to show that the mixtures according to the invention of sulfur-modified butadiene copolymers with other rubbers containing C=C double bonds lead to vulcanizates having reduced hysteresis losses.

Test mixture 2 Buna SL 7501'*123.8 parts by weight ~dditional polymer** 10.0 parts by weight Carbon black Corax N 2202~ 70.0 parts by weight ZnO-RS3~ 3.0 parts by weight Ste~ric acid 1.0 part by weight ~Vulkanox 4010 NA4) 1.0 part by weight Sulfur 1.8 parts by weight Vulkacit NZ5) 1.2 parts by weight 5 1) Solution SBR containing 18% by weight copolymerized styrene, oil-extended (37.5% by weight oil), a product of Buna Werke Huls AG, Marl 2) A product of Degussa AG, Hanau 3) Zinc oxide, a product of ZinkweiB-Forschungsgesell~
schaft mbH
4) N-lsopropyl-N'-phenyl-p-phenylenediamine (antiager), a product of Bayer AG, Leverkusen 5) Tert. butyl benzthiazyl sulfenamide (vulcanization accelerator), a product of Bayer AG, Leverkusen Le A 28 515 18 2~7~41~

* Where Buna SL 750 is used on its own, 137.5 parts by weight are used (Comparison Example) ** S-NBR A(Example 3), S-NBRB (Example 4), sulfur-modi-fied CR gel according to EP 0 405 216 (Comparison Example 4) Preparation of mixture Additional polymer10.0 parts by weight Buna S~ 750123.8 parts by weight (used on its own)137.S parts by weight Carbon blacX N 22070,0 parts by weight Vulkanox 4010 NA~1.0 part by weight ZnO-RS3.0 parts by weight Stearic acid1.0 part by weight The polymers were blended in an internal mixer (jacket temperature 120'C, 80 r.p.m.) and compounded in accordance with the above formulation. 1.8 parts by weight sulfur and 1.2 parts by weight accelerator (Vulkacit~ NZ) were added on mixing rolls at 60-C.

Vulcanization 1 mm sheets were vulcanized at 150C. The vulcaniza-tion time was 20 minutes.
The procedures described above for preparation of the mixture and vulcanization apply both to the Examples according to the invention and to the Comparison Examples.

Performance properties The following data were determined on the vulcanizates of the Examples and Comparison Examples:

Le A 2~ 515 19 Properties Method of determination Tensile strength (MPa) DIN 53 504 Elongation at break (~) DIN 53 504 Modulus at 300% DIN 53 504 elongation (NPa) Tan delta at 70-C MER = Imass Mechanical Energy Ta~ delta at sO-C Resolver llO0 A

Le A 28 515 20 o ~ 2~7841~

~D
X

, o ~
' --~C tP
W
o o o o o O W ~r ~ ~ a~
~q O

0 ~ 1~ o a al ~1 0 ~i N

C
_~
-~J
~ a~
o O O ~ O
~a o O ~ O~ O O O O
., ~n ~ o O ~ CO
''I 1:: o O O ~ O
~P la o o ~ ~` O O O O
_l t`~
t~ U~
'15 o ~ ~ m ~ ~ ~ m ~.,, 0 ~ o Z Z
X

~r a O
a) r~
~ ~ W ~ C~
X ~ o W W C~

2~7841~

As the results in the above Table show (Examples 3, 4 and Comparison Example 3), the mixtures according to the invention give vulcanizates which have a distinctly lower hysteresis loss than pure tire rubber (Comparison Example 3).
~ he values of the mixtures according to the invention (Examples 3 and 4) are comparable within the limits of error with mixtures containing sulfur-modified polychloro-prene gel (Comparison Exa~ple 4). However, the use of sulfur-modified polychloroprene gel has the disadvantages described in the text (costs, ecological problems).

Le A 28 515 22

Claims

1. Sulfur-modified butadienes copolymerized with ethylen-ically unsaturated monomers and containing functional groups, characterized in that they are produced in the presence of 0.05 to 2.5 parts by weight elemental sulfur or an equivalent quantity of sulfur donors, based on the monomers used, the sum of peptizing agents used being from 0.1 to 6.0 parts by weight, based on the monomers used.

2. Sulfur-modified butadiene polymers as claimed in claim 1, characterized in that they are copolymerized with acrylonitrile.

3. Sulfur-modified butadiene copolymers as claimed in claims 1 and 2, characterized in that thiuram polysulfides and/or xanthogen polysulfides are used as the sulfur donors.

4. Sulfur-modified butadiene polymers as claimed in claims 1 to 3, characterized in that the peptizing agents used are water-soluble dithiocarbamates and/or xanthogenates based on the following anions:

(1) or (2) and/or thiuram disulfides and/or xanthogen disulfides corresponding to the following formulae:

Le A 28 515 23 (3) or (4) in which R1, R2 and R3 may be the same or different and represent C1-24 alkyl, C5-16 cycloalkyl or C5-18 aryl, which may contain up to 3 heteroatoms, and in which R1 and R2 together may form a ring containing 3 to 5 carbon atoms which may optionally be interrupted by heteroatoms.

5. Mixtures of A) sulfur-modified butadiene copolymers according to claim 1 and B) other rubbers containing C=C double bonds, the quantity of butadiene copolymer A) being from 1 to 90%
by weight, based on components A) + B).

6. Mixtures as claimed in claim 5, characterized in that the butadiene copolymer A) is a butadiene/acrylonitrile copolymer.

7. Mixtures as claimed in claims 5 and 6, characterized in that the rubber B) is selected from the group consisting of EPDM, butyl rubber, nitrile rubber, hydrogenated nitrile rubber, natural rubber, polyisoprene, polybutadiene and SBR.

8. The use of the sulfur-modified butadiene copolymers claimed in claim 1 for the production of vulcanizates.

9. The use of the mixtures claimed in claim 5 for the production of vulcanizates.

Le A 28 515 24