Note: Descriptions are shown in the official language in which they were submitted.
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
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(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
S 11
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~
O-CH2 CH2-
\ /
CH2 C
/ \
S O--CH2 C2H5
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
2078414
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~
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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
