Note: Descriptions are shown in the official language in which they were submitted.
~3443-261
It is known to use vulcanizablecompounds containing
nitrile rubber for producing materials or s-tructural elements for
sealing against non-polar organic media, mainly against aliphatic
hydrocarbons, for example fuels and mineral oils.
Copolymers of 1,3-butadiene and acrylonitrile are known
as nitrile rubber (nitrile butadiene rubber, NBR). Vulcanized pro-
ducts made from nitrile rubber are noted for high resistance
(resistance to swelling) to non-polar organic media, and are used
for elastic seals, tank-hoses, cable-casings and the like. In
many cases, however, they are not sufficiently impermeable to gases~
i.e. mainly components of the atmosphere.
Based upon the state of the art outlined above, it is
a purpose of the inven-tion to make available vulcanizable compounds
which are suitable for the production of materials and structural
elements, especially resilient seals, for sealing against non-
polar organic media, and which surpass existing vulcanizable com-
pounds as a result of an advantageous combination of properties.
This combination of properties includes satisfactory
processability during mixing and shaping operations; satisfactory
vulcanizing behaviourapproaching that of known, rapidly-reacting
all-purpose rubbers (NR, IR, BR and SBR) from the point of view of
cross-]inking speed and yield; satisfactory covulcanizing behaviour
when blended with all-purpose rubbers, NBR and also EPDM and IIR
(IIR meaning butyl-rubber and chlorina-ted and brominated butyl-
rubber which are known as chlorobutyl- and bromobutyl-rubber), and
satisfactory covulcanizing behaviour during the production of
multi-layer composite materials; the vulcanized products are to
be adequately gastight and, above all, adequately resistant to
, ~ , 7474/1~ - Zu - 1 - `~
O.Z. 3813/3874
31 2;~2~
swelling in non-polar organic media.
The present invention provides a vulcanizable compound
comprising: more than 30 to 100 parts by weight o:E a rubber
selected EroM the group of polyisoprenes, amorphous isoprene/sty-
rene copolymers and mixtures -thereof having a Mooney viscosity
(MLl+4, 100C DIN 53 523) of 30 to 1.20, a Defo elasticity (80~C,
DIN 53 51.4) of 12 to 45, a non-homogeneity (U = Mn - 1) of 0.8
to 5.5, and a glass transition temperature (Tg, torsional
vibration, damping maximum, DIN 53 520) between -35 and 0C; 0
to less than 70 parts by weight of another rubber of a mixture of
other rubbers per 100 parts by weight of rubber, an effec-tive
amount of a vulcanizing agent, wherein the polyisoprene is obtained
by homopolymerization of isop:rene or by polymerization o:E a monomer
mixture of 55 to less than 100% by weight of isoprene, 0 -to 20%
by weight of piperylene, 0 to 45% by weight of 1,3-butadiene, and
0 to less than 1% by weight of styrene in relation to the mGnomer
mixture, the said polyisoprene containing an average of between
60 and 85% by weight of structural units obtained by l.,2- and 3,4-
polymerization of the dienes; or the isoprene-styrene copolymer
is obtained by polymerizatlon of a monomer mixture of 35 to 99%
by weight of isoprene, 1 to 30% by weight of styrene, 0 to 25% by
weight of piperylene, and 0 tc- less than 50% by weight of 1,3-
butadiene in relation to the monomer mixture, and having an average
content of 55 to 90% by weight of structural units obtained by 1,2-
and 3,4-polymerization of the dienes and statistical copo.Lymeriza-
tion of styrene, the polymerization of the said polyisoprene or
isoprene/styrene copolymer being characterized by the following
conditions: polymerization in an inert organic solvent in the
- 2 -
~ 2~
presence of a catalyst system consisting of an amount effective
for polymeriza-tion of 0.008 to 0.1% by weigh-t of an organolithium
catalyst and 0.1 to 10% by weight of a cocatalyst selected from
the group of ethers, tert:iary amines and mixtures -thereof, the
weight ratio of cocatalyst:catalyst being between 2:1 and 1,000:1,
and in the presence of 0 to 0.1% by weight of divinyl-benzene,
related respectively to the monomer, and the polymerization of the
polyisoprene or the isoprene/styrene copolymer is carried out at
an increasing tempera-ture, starting at between 15 and 50C and
:Einishing at 70 -to 145C, the difference between the finishing and
starting temperatures being between 40 and 125C.
The vulcanizable compound can also contain the usual
additives.
Preferably the polyisoprene or isoprene/s-tyrene copoly-
mer possesses a Mooney viscosity of 40 to 100, a Defo elasticity
of 20 to 40, a non-homogeneity of 1 to 4, and a glass -transition
temperature between -30 and -5C.
~ preferred polyisoprene is obtained by polymerization
of a monomer mixture consisting of 65 to 90% by weight of isoprene,
0 to 10% by weight of piperylene, 0 to 35% by weight of 1,3-buta-
diene, and 0 to less than 1% by weight of styrene, in relation to
the monomer mixture, and has an average content of 65 to 80% by
weight of structural units obtained by 1,2- and 3,4-polymerization
of the dienes. A preferred isoprene/styrene copolymer is obtained
by polymerization of a monomer mixture consisting of 40 to 90% by
weight of isoprene, 10 to 25% by weight of styrene, 0 to 15% by
weight of piperylene, and 0 to 40% by weight of 1,3-butadiene, in
relation to the monomer mixture, with an average content of 60 to
- 3 -
J4a g~:~f~
85% by weight of structural units obtained by 1,2 and 3,4-polymer-
lzation of the dienes and by statistical copolymerization of
s-tyrene.
The polyisoprene or the isoprene/styrene copolymer may
exhibit a statistical distribution of the structural units corres-
ponding to the different monomers. Such copolymers are obtained
by polymerization of only one mixture of monomers the composition
of which is characterized by the amounts specified above. Under
preferxed conditions the difference between the finishing and
starting temperatures for the polymerization is between 70 and
120C and the polymerization is terminated at a temperature between
85 and 145C. Alternatively the polyisoprene or the isoprene/
styrene copolymer may exhibit block structures, although blocks
of homopolymerized styrene should not be present. The blocks are
characterized in that the chain segments, which join a block bound-
ary from both sides, differ from each other in the kind or in the
number of the basic monomers. All of the monomers of a block
polymer taken together have to correspond to the amounts ofthe
monomers specified above. Of course these amounts do not neces-
sarily apply -to a monomer mixture which is polymerized to yield
a block of the block copolymer. If a block structure is required,
the polymerization of the isoprene should take place in the lower
portion of the temperature range and -the polymeriza-tion of 1,3-
butadiene should take place in the upper portion of the tempera-ture
range. Preferably such block polymers are obtained by first poly~
merizing isoprene or a monomer mixture containing isoprene up to
a conversion of 50 to 90% of the isoprene and then continuing
polymerization while adding 1,3~butadiene or a monomer mixture
- 4
1~2~3~
containing 1,3-butadiene. Thus block polymers consis-ting of
th:ree blocks can be obtained.
The vulcanizable compounds according to the invention
are novel since the polyisoprenes and isoprene/styrene copolymers
contained therein (the rubbers according to the application) are
novel.
Polyisoprenes and isoprene/styrene copolymers prepared
by polymerization of monomers in amounts speciEied above are
known, (German published Patent Applications 17 70 928, 24 59 357
and 28 43 794), but production is described therein as being by
(almost) isothermal polymerization of isoprene or of monomer mix-
tures containing isoprene. (In the examples in German Application
23 43 794, the temperature range used in producing butadiene/
styrene copolymers is between 50 and 60C.) The macromolecules
thus obtained have (almost) uniform distribution of structural
units obtained by 1,2 and 3,4-polymerization of isoprene. This
results from the temperature-dependency o~ 1,2- and 3,4-polymeriza-
tion, relative to the 1,4-polymerization of 1,3-dienes, which has
been thoroughly investigated in the 1,3-butadiene example (German
Patent 21 58 575)~
Because of the temperatures used in the polymerization
of the polyisoprene or isoprene/styrene copolymer in accordance
with the invention, more particularly the preferred range of temper-
ature difference of 70 to 120C, the macromolecules obtained
possess non-uniform distribution of the structural units obtained
by 1,2- and 3,4-polymerization of isoprene and possibly also
piperylene and 1,3-butadiene.
This means that the frequency of these s-tructural units
5 -
~22~5
(and of the vinyl, isopropenyl and propenyl side groups corres-
ponding to them) decreases noticeably from one end to the other
along the main chain and, in the case of long-chain branches, also
along the side chains of the macromolecule (cf. German Patent
21 53 575).
Thus the rubbers according to the application, especial-
ly those polymerized with a difference of temperature in the pre-
ferred range of temperature difference differ structurally from
comparable rubbers known in the art.
In addition, they differ from comparable rubbers known
in the art in their technical properties. Vulcanized products
made from them have the advantage, over a wider range of tempera-
tures, of resisting swelling in non-polar organic media, of damp-
ing vibra-tions, and of impermeability to gases, and they also
behave better in the cold. This applies, in particular, to vulcan-
ized products made out of the vulcanizable compounds containing
rubbers polymerized with a difference of temperature in the pre-
ferred range of temperature difference and those which are having
block structures and which are obtained by polymerization of the
isoprene in the lower portion, and of the 1,3-butadiene in the
upper portion, of the total range be-tween the starting and
finishing temperatures.
The compounds according to the invention have the
additional advantage that the vulcanized products made from them
display a distinctly better vibra-tion-damping effect than all-
purpose rubbers. They are therefore suitable for the production
of structural elements used for damping vibration, especially in
applications where resistance to swelling in non-polar organic
J~ 6 -
~;.2~Z3~
media is also required, for example mountings for buildings,
machines and bridges, fenders, bumpers, buffer elements and
structural elements for acoustic absorption.
Another advantage of the compounds according to the
invention is that vulcanized products made from them build up rela-
tively little heat under dynamic loading. They are therefore suit-
able for the production of vulcanizable strip for the treads of
passenger-car tires, the treads being highly non-skid and providing
a high degree of comfort during travel and surprisingly low rolling
resistance.
The compounds according to the invention are also suit-
able for the production of materials and structural elements used
to provide sealing agains-t gases, for example the inner liners of
tubeless tires, also diaphragms and hoses.
In selecting the production parame-ters it should be
noted that the effects of different structural units in the macro-
molecules (proportion in percentage by weight) result in gradual
differences in the macroscopic properties of the rubbers according
to the application, i.e. (increase in Tg), the vulcanizable com-
pounds and the vulcanized products made from them (improvementsin gastightness and, above all, in resistance to swelling in non-
polar organic media).
The effect of the structural units corresponds to their
proportion in themacromoleculesand to their specific effec-t which
corresponds to the following sequence: structural units obtained
by statistical copolymerization of styrene, ~ structural units
obtained by 1,2- and 3,4-polymerization of isoprene or piperylene,
> structural units obtained by 1,2-polymerization of 1,3-butadiene,
- 7 -
~2%2~
> structural units obtained by 1,4-polymerization of isoprene or
piperylene, ~ s-tructural units obtained by 1,4-polymerization oE
1,3-butadiene.
The rubbers according to the application may be obtained
quite simply in analogy with the corresponding produc-tion methods
known in the art, including the known method of 1,2-polymerization
of 1,3-butadiene (German Patent 21 58 575).
The inert organic solvent is preferably a hydrocarbon
solvent.
The hydrocarbon solvent, the organolithiumcatalyst, and
the cocatalyst may be those mentioned in German Patent 21 58 575.
Preferred cocatalysts are bifunctional Lewis bases.
The amounts of catalyst and cocatalyst are preferably
0.01 to 0.08 and 0.3 to 2% by weight, in relation to the monomer,
the cocatalyst:catalyst weight ratio being between 5:1 and 200:1.
In order to reduce cold-flow in the rubbers according
to -the application, the rubbers may be produced in the presence
of divinyl-benzene as the branching agent, using preferably from
0.02 to 0.08% by weight, of divinyl-benzene in relation to the
monomer.
The rubbers according to the application may be
obtained by batch or continuous polymerization.
The rubbers according to the application may be used
in the vulcanizable compounds alone or blended with other rubbers,
especially known all-purpose rubbers, but also with special rubbers
such as NBR, or with weakly unsaturated rubbers, for example EPDM
or IIR. The amount of the rubbers according to the invention used
in the blend is preferably greater than 50% by weight and is govern-
23~
ed by the combination of properties required for the particular
application. The effect of the rubbers according to the invention
in the vulcanizable compoundsl and in the vulcanized products ob-
tained therefrom, corresponds to the proportion of the said rubbers
contained in the blend.
The term vulcanizing agents is intended to mean known
vulcanizing systems. A preferred vulcanizing system contains
sulphur combined with the usual accelerators.
The amount oE vulcanizing agent to be used depends upon
the other components of the mixture and may easily be determined
by investigative tests.
The additives used may be Eillers conventional in rubber
technology, for example carbon blacks of diEEerent activity, finely
divided mineral fillers such as silicic acids, chalks, silicates
and the like. The amounts used may vary very widely, depending
upon the particular application.
Process oils usual in rubber technology may be used as
additives, preference being given to aromatic, aliphatic and
naphthenic hydrocarbons and the amounts used being governed by the
particular application.
Other auxiliary agents, for example anti-agers and anti-
ozone waxes, may be used in effective amounts as additives.
For the purpose of producing the compounds according
to the invention from the mixture-components, and for processing
them into vulcanized products, the usual apparatus of the rubber-
industry for mixing, shaping and vulcanizing may be used, for
example closed mixers, rolling mills, extrudersl calenders, injec-
-tion-moulding units, vulcanizing presses, and continuously operat-
g _
~Z~23~5i
ing cross-lin]cing units.
The invention is illustrated by the following examples
wherein parts are by weight and percent (%) signiEies % by weight
(except in Table 3).
Production of the rubbers according to the applicatin.
400 parts of hexane, 100 parts of monomer, 0.03 parts
of divinyl-benzene and ethylene-glycol dimethyl-ether, in the
amounts indicated in Table 1, were placed in a stirred autoclave,
any air and moisture being carefully excluded. Polymerization was
initiated at 40C by the addition of n-butyl-lithium. Upon
completion of the polymerization process, 0.5 parts of 2,2-
methylene-bis-(4-methyl-6-tertiary butyl-phenol) was added. The
solvent was separated with steam and the polymer was dried.
Table 1
Production of rubbers 1 and 2 according to the invention.
Example 1 2
Monomer Isoprene Isoprene/Styrene (80 parts/
20 parts)
Ethyleneglycol-
dimethylether0.5 parts 0.6 parts
n-Butyllithium *)0.01 parts 0.05 parts
Final Temperature 100C 90C
Polymerization Time 24 min 16 min
*~ Effective amount of catalyst for polymerization.
1 0
~2~2~3~
Table 2
Characterization of rubbers 1 and 2 according to the invention.
Example 1 2
Gel Content *) 2.6~ 2.3%
1,2-Content of Dienes **) 6 % 5 %
3,4-Content of Iosprene **) 71 % 57 %
MLl+4 (100C, DIN 53 523) 100 90
Defo Elasticity (80C, DIN 53 514) 25 28
Tg (Torsional Vibration, Damping
Maximum, DIN 53 520) -12C -3C
*) Determined by the method described in German Pa-tent 21 58 575.
**) Determined by IR-Analysis.
Production of the vulcanizable compounds.
The vulcanizable compounds were produced in accordance
with the following formulation. A base-mixture of the following
was first produced in a laboratory kneader (type GK 2):
Rubber 100 parts
Carbon black N 330 50 parts
Aromatic oil 5 parts
VULKANOX* 4010 NA (N-phenyl-N'- 1 part
isopropyl-p-phenylene-diamine)
Zinc oxide 5 parts
Stearic acid 2 parts
After a storage period of 6 h, the vulcanizing system
was incorporated, the said system consisting of
Sulphur 2 parts
VULKACIT* CZ 0.75 parts
(N-cyclohexyl-mercaptobenzthiazole).
*Trade Mark
l~ - 11 -
~2~:3~L5
The rubbers used were rubbers 1 and 2 above and, for
purposes of comparison, the following state-of-the-art rubbers
SBR 1 500 (IISRP) (A), a eommereially available ehlorobutyl
rubber (B), and a eommercially available NBR (acrylonitrile/1,3-
butadiene mass ratio: 28/72) (C).
From -the eompounds 1, 2, A, B and C there were obtained,
under eross-linking conditions of 40 min/150C, vulcanized test
pieees 1, 2, A, B and C. They were eharacterized as follows:
- 12 -
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-- 13 --
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Vulcanized tes-t-pieces 1 and 2, obtained from the com-
pounds according to the application, exhibit an advantageous combin-
ation of properties.
They are superior to test-pieces A (based on SBR, i.e.
an all-purpose rubber) as regards resistance to swelling and
gast.ightness, which properties correspond to volume-swelling and
gas-permeability in Table 3. They equal tes-t-piece A in the matter
of layer welding, with one layer made of compound A (based upon
SBR), i.e. they exhibit similarly satisfactory covulcanization
behaviour during the production of multi-layer laminated materials.
They are superior to test-pieces B (based upon a chloro-
butyl rubber known -to produce vulcanized products highly imperme-
able to gases) in the matter of resistance to swelling and especial-
ly in the matter of layer welding. The values for gas permeability
are almost as low as the corresponding values for test-piece B.
They are superior to test-pieces C (based upon an NBR,
known to produce vulcanized products highly resistant to swelling
in non-polar organic media) in the matter of gastightness, which is
characterized by gas-permeability. The values for volume swelling
do not reach the low level of the corresponding values for test-
piece C, but they come comparably close.
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