Note: Descriptions are shown in the official language in which they were submitted.
4
1
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RUBBER COMPOSITION COMPRISING A SPECIFIC HYDROCARBON-BASED
RESIN
[0001] The invention relates to compositions, especially for tyres, and more
particularly
5 to compositions comprising a specific hydrocarbon-based resin to improve
the
compatibility of the resin with elastomers, in particular with elastomers
having a very
low glass transition temperature (Tg).
[0002] It is known from the prior art that elastomers having a low Tg enable
an
improvement in terms of abrasion performance (WO 2015/043902). However, these
10 low Tg elastomers have poor compatibility with the hydrocarbon-based
plasticizing
resins usually used in tyres, which does not make it possible to use them
easily and
optimally in compositions for tyres which may have the best compromise between
performance properties that are difficult to reconcile simultaneously, namely
wear
resistance and grip, which must be high, and rolling resistance, which must be
low in
15 order to minimize fuel consumption.
[0003] Thus, it is currently beneficial for tyre manufacturers to find
formulas which
make it possible to improve the balance between all these performance
properties,
especially by improving the compatibility of the elastomers with the
hydrocarbon-based
plasticizing resins.
20 [0004] Document W02013/176712 describes various
resins of
cyclopentadiene/dicyclopentadiene/methylcyclopentadiene type, having specific
weights and softening points. In this document, these resins are used at a
content of 12
phr in the examples to improve wet grip.
[0005] At present, the Applicants have shown that a particular composition
comprising
25 a specific elastomer and a specific hydrocarbon-based resin makes it
possible to obtain
compositions having high grip and low rolling resistance.
[0006] The invention therefore relates to a rubber composition based on at
least one
elastomer comprising from 50 to 100 phr of one or more copolymers of butadiene
and
of vinylaromatic monomer, having a context of kinglaromatic units of between 0
and 5%
30 by weight and a Tg within a range extending from -110 C to -70 C, a
reinforcing filler, a
crosslinking system and an optionally hydrogenated hydrocarbon-based resin,
predominantly composed of units selected from the group consisting of
cyclopentadiene, dicyclopentadiene, methylcyclopentadiene and mixtures
thereof, said
A
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hydrocarbon-based resin having an average molecular weight Mz of less than
2000
g/mol and a glass transition temperature Tg, expressed in C, such that:
Tg 80 ¨ 2*(%HA)
wherein %HA represents the content of aromatic protons of said resin, the
content of
said hydrocarbon-based resin is within a range extending from 15 to 150 phr.
[0007] The invention preferably relates to a composition as defined above,
wherein
said hydrocarbon-based resin has an Mz of less than 1500 g/mol. Preferably,
said
hydrocarbon-based resin has a glass transition temperature Tg, expressed in
C, such
that Tg 85 ¨ 2*(%HA). More preferably still, said hydrocarbon-based resin has
a
polydispersity index (PI) of less than 1.7, preferably less than 1.6.
Preferentially, the
resin has a content of aromatic protons of less than 50%, preferentially
within a range
extending from 0% to 20%, preferably from 0% to 15%. According to a
preferential
mode, the resin has a content of aromatic protons of less than 5%, preferably
within a
range extending from 0% to 4%, preferably from 0% to 2%, and more
preferentially of
0%. According to another preferential mode, the resin has a content of
aromatic
protons within a range extending from 3% to 15%, preferably from 5% to 10%.
Also
preferably, the resin has a content of ethylenic protons of less than 0.5%,
preferably
less than 0.1%. More preferentially, the resin does not comprise any ethylenic
units.
[0008] Preferentially, the invention relates to a composition as defined
above, wherein
the copolymer(s) of butadiene and of vinylaromatic monomer represent a total
content
of 75 to 100 phr, preferably of 90 to 100 phr, better still of 100 phr.
Preferentially, the
copolymer(s) of butadiene and of vinylaromatic monomer have a Tg within a
range
extending from -110 C to -80 C, preferably from -95 C to -80 C. Also
preferentially, the
copolymer(s) of butadiene and of vinylaromatic monomer have a Mooney viscosity
within a range extending from 50 to 80. Preferably, the copolymer(s) of
butadiene and
of vinylaromatic monomer have a content of vinylaromatic units of 1 to 4% by
weight
relative to the total weight of the copolymer, and also a content of
vinylaromatic units,
relative to the diene portion, ranging from 8 to 15% by weight, preferably
ranging from
10 to 15% by weight. Preferably, the vinylaromatic monomer of the copolymer(s)
of
butadiene and of vinylaromatic monomer is styrene. Also preferably, at least
70% by
weight of said copolymer of butadiene and of vinylaromatic monomer is
functionalized.
In this case, said copolymer of butadiene and of vinylaromatic monomer is
preferentially functionalized by an alkoxysilane group, optionally partially
or totally
hydrolysed to give silanol, the alkoxysilane group bearing or not bearing
another
lb
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function capable of interacting with a reinforcing filler, the alkoxysilane
group being
bonded to the diene elastomer via the silicon atom. Preferentially, said
copolymer of
butadiene and of vinylaromatic monomer is predominantly functionalized in the
middle
of the chain. According to a preferred embodiment of the invention, said
copolymer of
butadiene and of vinylaromatic monomer comprises more than 0 and up to 30%,
preferably between 0 and 20% by weight relative to the total weight of the
copolymer of
butadiene and of vinylaromatic monomer, of a star-branched copolymer of
butadiene
and of vinylaromatic monomer.
[0009] Preferentially, the invention relates to a composition as defined
above, wherein
the reinforcing filler is selected from the group consisting of silicas,
carbon blacks and
the mixtures thereof. Preferably, the content of reinforcing filler is within
a range
extending from 5 to 200 phr, preferably from 40 to 160 phr. According to a
preferred
embodiment, the predominant reinforcing filler is silica, preferably at a
content within a
range extending from 40 to 150 phr. Preferably, according to this preferred
embodiment, the composition also comprises a minority amount of carbon black,
preferably at a content within a range extending from 0.1 to 10 phr.
[0010] Preferably, the invention relates to a composition as defined above,
wherein the
content of said hydrocarbon-based resin is within a range extending from 25 to
120
phr, preferably from 40 to 115 phr.
[0011] The invention also relates to a tyre comprising a composition as
defined above,
preferably in all or part of the tread thereof.
[0012] Preferentially, the tyre according to the invention will be chosen from
the tyres
intended to equip a two-wheeled vehicle, a passenger vehicle, or else a "heavy-
duty"
vehicle (that is to say, underground train, bus, off-road vehicles, heavy road
transport
vehicles, such as lorries, tractors or trailers), or else aircraft,
construction equipment,
heavy agricultural vehicles or handling vehicles.
I- Constituents of the composition
[0013] The rubber compositions according to the invention are based on at
least one
elastomer comprising from 90 to 100phr of one or more copolymers of butadiene
and
of vinylaromatic monomer, having a content of vinylaromatic units of between 0
and 5%
by weight and a Tg within a range extending from -110 C to -80 C, a
reinforcing filler, a
crosslinking system and an optionally hydrogenated hydrocarbon-based resin,
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predominantly composed of units selected from the group consisting of
cyclopentadiene, dicyclopentadiene, methylcyclopentadiene and mixtures
thereof, said
hydrocarbon-based resin having an average molecular weight Mz of less than
2000
g/mol and a glass transition temperature Tg, expressed in C, such that:
Tg 80 ¨ 2*(%HA)
wherein %HA represents the content of aromatic protons of said resin, the
content of
said hydrocarbon-based resin is within a range extending from 15 to 150 phr
(parts by
weight per hundred parts by weight of elastomer).
[0014] The expression "composition based on" should be understood as meaning a
composition comprising the mixture and/or the product of the in situ reaction
of the
various base constituents used, some of these constituents being able to react
and/or
being intended to react with one another, at least partially, during the
various phases of
manufacture of the composition or during the subsequent curing, modifying the
composition as it is prepared at the start. Thus, the compositions as employed
for the
.. invention can be different in the non-crosslinked state and in the
crosslinked state.
[0015] In the present description, unless expressly indicated otherwise, all
the
percentages (%) shown are percentages by weight. Furthermore, any range of
values
denoted by the expression "between a and b" represents the range of values
extending
from more than a to less than b (that is to say, limits a and b excluded),
while any
range of values denoted by the expression "from a to b" means the range of
values
extending from a up to b (that is to say, including the strict limits a and
b),
[0016] When reference is made to a "predominant" compound, this is understood
to
mean, within the meaning of the present invention, that this compound is
predominant
among the compounds of the same type in the composition, that is to say that
it is the
one which represents the greatest amount by weight among the compounds of the
same type. Thus, for example, a predominant polymer is the polymer
representing the
greatest weight relative to the total weight of the polymers in the
composition. In the
same way, a "predominant" filler is that representing the greatest weight
among the
fillers of the composition. By way of example, in a system comprising just one
polymer,
the latter is predominant within the meaning of the present invention and, in
a system
comprising two polymers, the predominant polymer represents more than half of
the
weight of the polymers. On the contrary, a "minor" compound is a compound
which
does not represent the greatest fraction by weight among the compounds of the
same
type.
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[0017] For the purposes of the present invention, when reference is made to a
"predominant" unit (or monomer) within the same compound (or polymer), this is
intended to mean that this unit (or monomer) is predominant among the units
(or
monomers) forming the compound (or polymer), that is to say it is the one
which
represents the greatest fraction by weight among the units (or monomers)
forming the
compound (or polymer). Thus, for example, a resin predominantly composed of
cyclopentadiene units is a resin in which the cyclopentadiene units represent
the
greatest amount by weight among all the units composing said resin. Similarly,
a resin
predominantly composed of units selected from the group consisting of
cyclopentadiene, dicyclopentadiene, methylcyclopentadiene and the mixtures
thereof is
a resin in which the sum of the units selected from the group consisting of
cyclopentadiene, dicyclopentadiene, methylcyclopentadiene and the mixtures
thereof
represents the greatest number by weight among all the units composing said
resin. In
other words, a "predominant" monomer is a monomer which represents the
greatest
fraction by weight in the polymer. On the contrary, a "minor" monomer is a
monomer
which does not represent the greatest molar fraction in the polymer.
[0018] In the present application, when reference is made to a ratio of the
amounts of
a compound A and of a compound B, or a ratio between the content of a compound
A
and the content of a compound B, this is always a ratio in the mathematical
sense of
the amount of compound A over the amount of compound B.
1-1. Elastomer
[0019] The composition of the tyre tread according to the invention may
contain a
single diene elastomer or a mixture of several diene elastomers.
[0020] It is recalled here that elastomer (or "rubber", the two terms being
regarded as
synonymous) of the "diene" type should be understood, in a known way, as
meaning
an (one or more is understood) elastomer resulting at least in part (i.e., a
homopolymer
or a copolymer) from diene monomers (monomers bearing two conjugated or non-
conjugated carbon-carbon double bonds).
[0021] Diene elastomers can be classified into two categories: "essentially
unsaturated" or "essentially saturated". "Essentially unsaturated" is
understood to
mean generally a diene elastomer resulting at least in part from conjugated
diene
monomers having a content of units of diene origin (conjugated dienes) which
is
greater than 15% (mol%); thus, diene elastomers such as butyl rubbers or
copolymers
=
CA 03017422 2018-09-11
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of dienes and of a-olefins of EPDM type do not fall under the preceding
definition and
may especially be described as "essentially saturated" diene elastomers (low
or very
low content, always less than 15%, of units of diene origin). In the category
of
"essentially unsaturated" diene elastomers, "highly unsaturated" diene
elastomer is
5 understood in particular to mean a diene elastomer having a content of
units of diene
origin (conjugated dienes) which is greater than 50%.
[0022] Given these definitions, and as is well known by those skilled in the
art, diene
elastomer is understood more particularly to mean:
(a) any homopolymer obtained by polymerization of a conjugated diene
monomer
10 having from 4 to 12 carbon atoms;
(b) any copolymer obtained by copolymerization of one or more conjugated
dienes
with one another or with one or more vinylaromatic compounds having from 8 to
20
carbon atoms;
(c) a ternary copolymer obtained by copolymerization of ethylene and of an
a-olefin
15 having from 3 to 6 carbon atoms with a non-conjugated diene monomer
having from 6
to 12 carbon atoms, such as, for example, the elastomers obtained from
ethylene and
propylene with a non-conjugated diene monomer of the abovementioned type, such
as,
especially, 1,4-hexadiene, ethylidene norbornene or dicyclopentadiene;
(d) a copolymer of isobutene and of isoprene (butyl rubber) and also the
20 halogenated versions, in particular chlorinated or brominated versions,
of this type of
copolymer.
[0023] For the purposes of the invention, the tread composition comprises an
elastomer comprising from 90 to 100 phr of one or more copolymers of butadiene
and
of vinylaromatic monomer, having a content of vinylaromatic units of between 0
and 5%
25 by weight and a Tg within a range extending from -110 C to -70 C. Thus,
the
copolymers of butadiene and of vinylaromatic monomer may contain from 95 to
less
than 100% by weight of diene units and from more than 0 to 5% by weight of
vinylaromatic units.
[0024] The following, for example, are suitable as vinylaromatic compounds:
styrene,
30 ortho-, meta- or para-methylstyrene, the "vinyltoluene" commercial
mixture, para-(tert-
butyl)styrene, methoxystyrenes, chlorostyrenes, vinylmesitylene,
divinylbenzene or
vinylnaphthalene. Preferably, the vinylaromatic monomer of the copolymer of
butadiene
and of vinylaromatic monomer is styrene.
CA 03017422 2018-09-11
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[0025] The elastomers can have any microstructure, which depends on the
polymerization conditions used, especially on the presence or absence of a
modifying
and/or randomizing agent and on the amounts of modifying and/or randomizing
agent
employed. The elastomers can, for example, be block, random, sequential or.
microsequential elastomers and can be prepared in dispersion or in solution.
In the
case of a copolymer based on a diene and on a vinylaromatic, especially
containing
butadiene and styrene, preferentially the two monomers are randomly
distributed.
[0026] Said copolymer of butadiene and of vinylaromatic monomer may be coupled
and/or star branched or functionalized by a group introduced via a coupling
and/or star-
branching or functionalization agent known to those skilled in the art. This
group may
be located at the end of the linear main elastomer chain. It will then be
stated that the
diene elastomer is chain-end functionalized. This is generally an elastomer
obtained by
reaction of a living elastomer with a functionalization agent, that is to say
any at least
monofunctional molecule, the function being any type of chemical group known
by
those skilled in the art to react with a living chain end.
[0027] This group may be located in the linear main elastomer chain. It will
then be
stated that the diene elastomer is coupled or functionalized in the middle of
the chain,
as opposed to the "chain end" position and although the group is not located
precisely
in the middle of the elastomer chain. This is generally an elastomer obtained
by
reaction of two chains of the living elastomer with a coupling agent, that is
to say any at
least difunctional molecule, the function being any type of chemical group
known by
those skilled in the art to react with a living chain end.
[0028] This group may be central, to which n elastomer chains (n>2) are
bonded,
forming a star-branched structure. It will then be stated that the diene
elastomer is star-
branched. This is generally an elastomer obtained by reaction of n chains of
the living
elastomer with a star-branching agent, that is to say any polyfunctional
molecule, the
function being any type of chemical group known by those skilled in the art to
react with
a living chain end.
[0029] Those skilled in the art will understand that a functionalization
reaction with an
agent comprising more than one function which is reactive with regard to the
living
elastomer results in a mixture of entities functionalized at the chain end and
in the
middle of the chain, constituting the linear chains of the functionalized
elastomer, and
also, if appropriate, star-branched entities. Depending on the operating
conditions,
CA 03017422 2018-09-11
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mainly the molar ratio of the functionalization agent to the living chains,
certain entities
are predominant in the mixture.
[0030] Preferentially, for the purposes of the invention, said copolymer of
butadiene
and of vinylaromatic monomer has a Tg within a range extending from -110 C to -
80 C,
preferably from -95 C to -80 C.
[0031] Also preferably, said copolymer of butadiene and of vinylaromatic
monomer
has a Mooney viscosity within a range extending from 50 to 80. In the present
description, Mooney viscosity is intended to mean the ML(1+4)100 C Mooney
viscosity
of a compound, especially of the copolymer of butadiene and of vinylaromatic
monomer of use to the invention, measured according to standard ASTM D1646.
[0032] According to a preferred embodiment, said copolymer of butadiene and of
vinylaromatic monomer has a content of vinylaromatic units of 1 to 4% by
weight
relative to the total weight of the copolymer, and also a content of vinyl
units, relative to
the diene portion, ranging from 8 to 15% by weight, preferably ranging from 10
to 15%
by weight.
[0033] Preferably, at least 70% by weight of said copolymer of butadiene and
of
vinylaromatic monomer is functionalized, preferentially by an alkoxysilane
group,
optionally partially or totally hydrolysed to give silanol, the alkoxysilane
group bearing
or not bearing another function capable of interacting with a reinforcing
filler, the
alkoxysilane group being bonded to the diene elastomer via the silicon atom.
Preferentially, said copolymer of butadiene and of vinylaromatic monomer is
predominantly functionalized in the middle of the chain. The microstructure of
these
elastomers may be determined by the presence or absence of a polar agent and
the
amounts of polar agent employed during the anionic polymerization step.
Preferentially,
when the diene elastomer is based on a diene and styrene, a polar agent is
used
during the polymerization step in amounts such that it promotes the random
distribution
of the styrene along the polymer chains while retaining the content of 1,2-
bonds at
preferably between 8% and 15%, preferably from 10% to 15%.
[0034] The term "alkoxysilane group interacting favourably with the
reinforcing filler" or
"function capable of interacting with a reinforcing filler" is understood to
mean any other
alkoxysilane group or function, preferentially amine, capable of forming,
within a rubber
composition reinforced by means of a filler, a physical or chemical bond with
said filler.
This interaction can be established, for example, via covalent, hydrogen,
ionic and/or
electrostatic bonds between said function and functions present on fillers.
e
N
CA 03017422 2018-09-11
-9-.
[0035] The alkoxy radical of the alkoxysilane group may be of formula R10-,
where R'
represents a substituted or unsubstituted C1-Clo, or even C1-08, alkyl group,
preferably
a Cl-C4 alkyl group, more preferentially methyl and ethyl.
[0036] The other function as mentioned above may for example be an amine, a
thiol,
5 a polyoxyethylene or polyether group. Very preferentially, the other
function capable of
interacting with a reinforcing filler is a primary, secondary or tertiary
amine. This variant
of the invention is particularly advantageous due to the improvement in
hysteresis
properties.
[0037] In the present description, primary or secondary amine is intended to
mean a
10 primary or secondary amine protected or not protected by a protecting
group known to
those skilled in the art.
[0038] Mention may be made, as secondary or tertiary amine function, of amines
substituted by C1-C10, preferably C1-C4, alkyl radicals, more preferentially a
methyl or
ethyl radical, or else cyclic amines forming a heterocycle containing a
nitrogen atom
15 and at least one carbon atom, preferably from 2 to 6 carbon atoms. For
example, the
methylamino-, dimethylamino-, ethylamino-,
diethylamino-, propylamino-,
dipropylamino-, butylamino-, dibutylamino-, pentylamino-, dipentylamino-,
hexylamino-,
dihexylamino- or hexamethyleneamino- groups, preferably the diethylamino- and
dimethylamino- groups, are suitable.
20 [0039] Preferably, the function capable of interacting with a
reinforcing filler is a
tertiary amine function, preferably diethylamine or dimethylamine.
[0040] According to a variant of the invention, the function, preferentially
primary,
secondary or tertiary amine, capable of interacting with a reinforcing filler
is directly
bonded to the silicon atom itself directly bonded to the diene elastomer.
25 [0041] According to another variant of the invention, the function,
preferentially
primary, secondary or tertiary amine, capable of interacting with a
reinforcing filler and
the silicon atom bonded to the diene elastomer are connected to one another
via a
spacer group which may be an atom or a group of atoms. The spacer group may be
a
saturated or unsaturated, cyclic or non-cyclic, linear or branched, divalent
C1-C18
30 aliphatic hydrocarbon-based radical or a divalent C6-Cie aromatic
hydrocarbon-based
radical and may contain one or more aromatic radicals and/or one or more
heteroatoms. The hydrocarbon-based radical may optionally be substituted.
1
x
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[0042] Preferably, said copolymer of butadiene and of vinylaromatic monomer
comprises more than 0 and up to 30% by weight (more preferentially between 0
and
20%), relative to the total weight of the copolymer of butadiene and of
vinylaromatic
monomer, of a star-branched copolymer of butadiene and of vinylaromatic
monomer.
[0043] Preferably, said copolymer of butadiene and of vinylaromatic monomer is
present at a total content of 75 to 100 phr, preferably of 90 to 100 phr,
better still of 100
phr.
[0044] When the composition comprises them, the supplemental elastomers of the
copolymers of butadiene and of vinylaromatic monomer may be any elastomers
known
to those skilled in the art and especially an elastomer selected from the
group
consisting of polybutadienes, natural or synthetic polyisoprenes, isoprene
copolymers,
butadiene copolymers other than those already required for the invention, and
mixtures
thereof. Preferably, these supplemental elastomers are selected from the group
consisting of polybutadienes, natural or synthetic polyisoprenes, copolymers
of
isoprene and of vinylaromatic monomer, copolymers of butadiene and of
vinylaromatic
monomer having a Tg of greater than -70 C, and mixtures thereof.
1-2 Reinforcing filler
[0045] The composition according to the invention comprises a reinforcing
filler. Use
may be made of any type of reinforcing filler known for its abilities to
reinforce a rubber
composition which can be used for the manufacture of tyres, for example an
organic
filler, such as carbon black, a reinforcing inorganic filler, such as silica
or alumina, or
also a blend of these two types of filler.
[0046] All carbon blacks, especially "tyre-grade" blacks, are suitable as
carbon blacks.
Mention will more particularly be made, among the latter, of the reinforcing
carbon
blacks of the 100, 200 or 300 series (ASTM grades), such as, for example, the
N115,
N134, N234, N326, N330, N339, N347 or N375 blacks, or else, depending on the
applications targeted, the blacks of higher series (for example N660, N683 or
N772).
The carbon blacks might, for example, be already incorporated in an isoprene
elastomer in the form of a masterbatch (see, for example, Applications WO
97/36724
or WO 99/16600).
t
t
CA 03017422 2018-09-11
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[0047] Mention may be made, as examples of organic fillers other than carbon
blacks,
of functionalized polyvinyl organic fillers, such as described in applications
WO-A-
2006/069792, WO-A-2006/069793, WO-A-2008/003434 and WO-A-2008/003435.
[0048] The composition can comprise one type of silica or a blend of several
silicas.
5 The silica used can be any reinforcing silica known to those skilled in
the art, especially
any precipitated or fumed silica exhibiting a BET surface area and a CTAB
specific
surface area both of less than 450 m2/g, preferably from 30 to 400 m2/g.
Mention will be
made, as highly dispersible precipitated silicas ("HDSs"), for example, of the
Ultrasil
7000 and Ultrasil 7005 silicas from Degussa, the Zeosil 1165MP, 1135MP and
1115MP
10 silicas from Rhodia, the Hi-Sil EZ150G silica from PPG, the Zeopol 8715,
8745 and
8755 silicas from Huber, treated precipitated silicas, such as, for example,
the silicas
"doped" with aluminium described in Application EP-A-0735088, or the silicas
with a
high specific surface as described in Application WO 03/16837.
[0049] The silica preferably has a BET specific surface of between 45 and 400
m2/g,
15 more preferentially of between 60 and 300 m2/g.
[0050] These compositions can optionally also comprise, in addition to the
coupling
agents, coupling activators, agents for covering the inorganic fillers or more
generally
processing aids capable, in a known way, by virtue of an improvement in the
dispersion
of the filler in the rubber matrix and of a lowering of the viscosity of the
compositions, of
20 improving their ability to be processed in the raw state, these agents
being, for
example, hydrolysable silanes, such as alkylalkoxysilanes, polyols, fatty
acids,
polyethers, primary, secondary or tertiary amines, or hydroxylated or
hydrolysable
polyorganosiloxanes.
[0051] Use is made especially of silane polysulfides, referred to as
"symmetrical" or
25 "asymmetrical" depending on their specific structure, such as described,
for example, in
applications WO 03/002648 (or US 2005/016651) and WO 03/002649 (or US
2005/016650).
[0052] Suitable in particular, without the definition below being limiting,
are silane
polysulfides referred to as "symmetrical", corresponding to the following
general
30 formula (Ill):
(Ill) Z - A - Sx - A - Z, in which:
- x is an integer from 2 to 8 (preferably from 2 to 5);
=
= CA 03017422 2018-09-11
- 12 -
- A is a divalent hydrocarbon radical (preferably C1-C18 alkylene groups or C6-
C12
arylene groups, more particularly Cl-Clo alkylenes, in particular C1-C4
alkylenes,
especially propylene);
- Z corresponds to one of the formulae below:
R1 R1 R2
1 1 i
¨S
. i¨R1 = ¨ , Si¨R2 _i¨R2 ,
,
RI2 RI2 Ri2
in which:
- the R1 radicals, which are substituted or unsubstituted and identical to or
different
from one another, represent a C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl
group
(preferably CI-Cs alkyl, cyclohexyl or phenyl groups, in particular Ci-C4
alkyl groups,
more particularly methyl and/or ethyl),
- the R2 radicals, which are substituted or unsubstituted and identical to or
different
from one another, represent a C1-C18 alkoxy or C5-C18 cycloalkoxy group
(preferably a
group chosen from C1-C8 alkoxys and C5-C8 cycloalkoxys, more preferentially
still a
group chosen from C1-C4 alkoxys, in particular methoxy and ethoxy).
[0053] In the case of a mixture of alkoxysilane polysulfides corresponding to
the above
formula (III), especially normal commercially available mixtures, the mean
value of the
"x" indices is a fractional number preferably of between 2 and 5, more
preferentially of
approximately 4. However, the invention can also advantageously be carried
out, for
example, with alkoxysilane disulfides (x = 2).
[0054] Mention will more particularly be made, as examples of silane
polysulfides, of
bis((Ci-C4)alkoxy(Ci-C4)alkylsily1(C1-C4)alkyl) polysulfides (especially
disulfides,
trisulfides or tetrasulfides), such as, for example, bis(3-
trimethoxysilylpropyl) or bis(3-
triethoxysilylpropyl) polysulfides. Use is made in particular, among these
compounds,
of bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, of formula
[(C2H50)3Si(CH2)3S2]2, or bis(3-triethoxysilylpropyl) disulfide, abbreviated
to TESPD, of
formula [(C2H50)3Si(CH2)3S]2. Mention will also be made, as preferential
examples, of
bis(mono(Ci-C4)alkoxyldi(Ci-C4)alkylsilylpropyl) polysulfides (in particular
disulfides,
trisulfides or tetrasulfides), more particularly
bis(monoethoxydimethylsilylpropyl)
tetrasulfide, such as described in Patent Application WO 02/083782 (or US
2004/132880).
CA 03017422 2018-09-11
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[0055] Mention will also be made, as coupling agent other than alkoxysilane
polysulfide, of bifunctional POSs (polyorganosiloxanes) or else of
hydroxysilane
polysulfides (R2 = OH in the above formula III), such as described in Patent
Applications WO 02/30939 (or US 6 774 255) and WO 02/31041 (or US
2004/051210),
or else of silanes or POSs bearing azodicarbonyl functional groups, such as
described,
for example, in Patent Applications WO 2006/125532, WO 2006/125533 and WO
2006/125534.
[0056] In the rubber compositions in accordance with the invention, the
content of
coupling agent is preferentially between 1 and 15 phr, more preferentially
between 3
and 14 phr.
[0057] Those skilled in the art will understand that, as filler equivalent to
silica
described in the present section, use might be made of a reinforcing filler of
another
nature, especially organic, provided that this reinforcing filler is covered
with a layer of
silica or else comprises functional sites, especially hydroxyl sites, at its
surface which
require the use of a coupling agent in order to form the bond between the
filler and the
elastomer.
[0058] The physical state in which the reinforcing filler is provided is not
important,
whether it is in the form of a powder, of micropearls, of granules, of beads
or any other
appropriate densified form.
[0059] For the purposes of the invention, the content of total reinforcing
filler (carbon
black and/or reinforcing inorganic filler, such as silica) is from 5 to 200
phr, more
preferentially from 40 to 160 phr. Below 5 phr of filler the composition might
not be
sufficiently reinforced, whereas above 200 phr of filler the composition might
have
poorer performance with regard to rolling resistance.
[0060] Use is preferably made of silica as predominant filler, preferably at a
content
ranging from 40 to 150 phr, more preferentially from 90 to 150 phr; and
optionally
carbon black. The carbon black, when it is present, is used in a minor amount,
preferably at a content within a range extending from 0.1 to 10 phr, more
preferentially
from 0.5 to 10 phr, especially from Ito 5 phr,
1-3 Crosslinkinq system
[0061] In the composition of the invention, any type of crosslinking system
known to
those skilled in the art for rubber compositions may be used.
,
c
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[0062] The crosslinking system is preferably a vulcanization system, that is
to say
based on sulfur (or on a sulfur-donating agent) and a primary vulcanization
accelerator.
Various known secondary vulcanization accelerators or vulcanization
activators, such
as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives
(in
5 particular diphenylguanidine), may be added to this base vulcanization
system, being
incorporated during the first non-productive phase and/or during the
productive phase,
as described subsequently.
[0063] The sulfur is used at a preferential content of between 0.5 and 10 phr,
more
preferentially of between 0.5 and 5 phr, in particular between 0.5 and 3 phr.
10 [0064] The vulcanization system of the composition according to the
invention may
also comprise one or more additional accelerators, for example compounds of
the
family of the thiurams, zinc dithiocarbamate derivatives, sulfenamides,
guanidines or
thiophosphates. Use may in particular be made of any compound capable of
acting as
accelerator of the vulcanization of diene elastomers in the presence of
sulfur,
15 especially accelerators of thiazoles type and also their derivatives,
accelerators of the
thiurams type, and zinc dithiocarbamates. These accelerators are more
preferentially
selected from the group consisting of 2-mercaptobenzothiazole disulfide
(abbreviated
to "MBTS"), N-cyclohexy1-2-benzothiazolesulfenamide (abbreviated to "CBS"),
N,N-
dicyclohexy1-2-benzothiazolesulfenamide (abbreviated to "DCBS"), N-(tert-
buty1)-2-
20 benzothiazolesulfenamide (abbreviated to "TBBS"), N-(tert-buty1)-2-
benzothiazolesulfenimide (abbreviated to "TBSI"), zinc dibenzyldithiocarbamate
(abbreviated to "ZBEC") and the mixtures of these compounds. Use is preferably
made
of a primary accelerator of the sulfenamide type.
25 1-4 Specific hydrocarbon-based resin
[0065] The composition according to the invention comprises a specific
hydrocarbon-
based resin.
[0066] This optionally hydrogenated hydrocarbon-based resin is predominantly
composed of units selected from the group consisting of cyclopentadiene,
30 dicyclopentadiene, methylcyclopentadiene and mixtures thereof.
[0067] Preferably, the hydrocarbon-based resin of use for the purposes of the
invention has a content of aromatic protons of less than 50%, preferably
within a range
extending from 0% to 20%, preferably from 0% to 15%.
=
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[0068] According to a preferential embodiment, the hydrocarbon-based resin of
use for
the purposes of the invention has a content of aromatic protons of less than
5%,
preferably within a range extending from 0% to 4%, preferably from 0% to 2%,
preferably of 0%.
[0069] According to another, also preferential, embodiment, the hydrocarbon-
based
resin of use for the purposes of the invention has a content of aromatic
protons within a
range extending from 3% to 15%, preferably from 5% to 10%.
[0070] Also preferably, the hydrocarbon-based resin of use for the purposes of
the
invention has a content of ethylenic protons of less than 0.5%, preferably of
less than
0.1%. More preferentially, the resin does not comprise any ethylenic units.
[0071] The hydrocarbon-based resin of use for the purposes of the invention
has an
average molecular weight Mz of less than 2000 g/mol, preferably less than 1500
g/mol.
[0072] The hydrocarbon-based resin of use for the purposes of the invention
also has
a glass transition temperature Tg, expressed in C, such that Tg 80 ¨ 2*(%HA)
¨
wherein %HA represents the content of aromatic protons of said resin ¨
preferably
such that Tg 85¨ 2*(c/oHA). The Tg is measured according to ASTM D3418 (1999).
[0073] Preferably, the hydrocarbon-based resin of use for the purposes of the
invention has a polydispersity index (PI) of less than 1.7, preferably of less
than 1.6.
[0074] Numerous hydrocarbon-based resins are available commercially. These
resins
may have characteristics, especially of chemical composition, of Mz, of Tg, of
content
of aromatic protons or else of PI, which differ depending on the suppliers.
[0075] The macrostructure (Mw, Mn, PI and Mz) of the hydrocarbon-based resin
is
determined by size exclusion chromatography (SEC) on the basis of standards
ISO
16014 (Determination of average molecular mass and molecular mass distribution
of
polymers using size exclusion chromatography), ASTM D5296 (Molecular Weight
Averages and molecular weight distribution of polystyrene by High performance
size
exclusion chromatography), and DIN 55672 (size exclusion chromatography).
[0076] For these measurements, the resin sample is dissolved in non-
antioxidized
tetrahydrofuran up to a concentration of 1.5 g/I. The solution is filtered
with a Teflon
filter with a porosity of 0.45 pm, using for example a disposable syringe
fitted with a
filter. A volume of 100 pl is injected through a set of size exclusion
chromatography
columns. The mobile phase is eluted at a flow rate of 1 ml/min. The columns
are
thermostatically controlled at 35 C in an oven. Detection is carried out by a
CA 03017422 2018-09-11
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refractometer thermostatically controlled at 35 C. The stationary phase of the
columns
is based on a polystyrene divinylbenzene gel with controlled porosity. The
polymer
chains are separated according to the space that they occupy when they are
dissolved
in the solvent: the larger the volume they occupy, the less the pores of the
columns are
accessible to them and the shorter their elution time.
[0077] A Moore calibration curve connecting the logarithm of the molar mass
(logM)
with the elution time (te) is produced beforehand with polystyrene standards
and
modelled using a third degree polynomial: Log (molar mass of polystyrene) = a
+ b te +
c te2 + d te3.
[0078] For the calibration curve, polystyrene standards with narrow molecular
distributions are used (polydispersity index, PI, of less than or equal to
1.1). The range
of molar masses of these standards extends from 160 to approximately 70 000
g/mol.
These standards may be grouped together in "families" of 4 or 5 standards
having a
logM increment of approximately 0.55 between each family.
[0079] Use may be made of certified (ISO 13885 and DIN 55672) standards kits
such
as, for example, the kits of vials from PSS (polymer standard service,
reference PSS-
pskitr11-3), and also an additional standard PS with Wp = 162 g/mol
(Interchim,
reference 178952). These kits are in the form of 3 vials each containing a
family of
polystyrene standards in suitable amounts:
- Black vial: Wp = 1220, 4850, 15 500 and 67 500 g/mol.
- Blue vial: Wp = 376, 3470, 10 400, 46 000 g/mol.
- Yellow vial: Wp = 266, 1920, 7200, 28 000 g/mol.
- PS162: Wp = 162 g/mol.
[0080] The number-average molar mass (Mn), weight-average molar mass (Mw), the
Mz and the polydispersity of the resin analysed are calculated from this
calibration
curve. This is why reference is made to molar masses relative to a polystyrene
calibration.
[0081] For the calculation of the average masses and the PI, the limits of
integration of
the product elution are defined on the chromatogram corresponding to the
injection of
the sample. The refractometric signal defined between the two limits of
integration is
"cut" every second. For each of these "elementary cuts", the elution time ti
and the area
of the signal from the detector Ai are read off.
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[0082] It is recalled here that: PI = Mw/Mn with Mw being the weight-average
molecular weight and Mn being the number-average molecular weight. It is also
recalled that the weights Mw, Mn and Mz are average weights calculated
according to
the following formulae:
EAi *MO.
MZ
=
EAi*Mi
E A r
Mn =a A g
E
Edit * Mt
Mw
E At
in which Ai is the amplitude of the signal from the refractometric detector
corresponding
to the weight Mi and to the elution time ti.
[0083] The equipment used for the SEC measurement is a liquid chromatography
system, for example the Waters Alliance 2690 system comprising a pump, a
degasser
and an injector; a differential refractometer (for example the Waters 2410
refractometer), software for acquiring and processing the data, for example
the Waters
Empower software, a column oven, for example the Waters "Columns Heater
Module"
and 4 columns mounted in series in the following order:
Range of Referenc
Internal
Plum molar Length Particle es (for
Brand diameter Trade name
her masses (mm) size (pm) inform all
(mm)
(g/mol) on only)
Colu
Polymer 200- 400 PL1110-
mns 1 300 7.5 5 MIXED-D
Laboratories 000 6504
and 2
Colu
Polymer 200- 30 PL1110-
mns 3 300 7.5 3 MIXED-E
Laboratories 000 6300
and 4
[0084] The content of aromatic protons (%HA) and the content of ethylenic
protons
(%HE) are measured by 1H NMR. This is determined relative to all the signals
detected. Thus, the results obtained are expressed as % of area of peak.
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[0085] The samples are dissolved in deuterated chloroform (CDCI3) at an amount
of
approximately 10 mg of resin in approximately 1 ml of solvent. The spectra are
acquired on a Bruker Avance 500 MHz spectrometer fitted with a Bruker "broad
band"
BBO z-grad 5 mm probe. The 1H NMR experiment uses a 30 single pulse sequence
and a repetition time of 5 seconds between each acquisition. 64 accumulations
are
carried out at ambient temperature. The chemical shifts are calibrated with
respect to
the protonated impurity of the deuterated chloroform; 6ppm 1H at 7.20 ppm. The
1H
NMR signals of the aromatic protons are located between 8.5 ppm and 6.2 ppm.
The
ethylenic protons give rise to signals between 6.2 ppm and 4.5 ppm. Finally,
the signals
corresponding to aliphatic protons are located between 4.5 ppm and 0 ppm. The
areas
of each category of protons are related to the sum of these areas to thereby
give a
distribution in terms of % of area for each category of protons.
[0086] The commercially available resins below were analysed using the methods
described above in order to determine their characteristics; Table 1
summarizes the
results obtained.
Table 1
Trade Resin Chemical Mz Tg %HA %HE
80¨ 2
Resin resin PI
*(%HA)
reference manufacturer nature (g/mol) (,,C) (%) (%) ("C)
Resin
E5600 Exxon Mobil Hydrogenated 1337 52 10 0
1.63 60
1 DCPD ¨ C9
Resin
PR-383 Exxon Mobil Hydrogenated 1416 55 10 0
1.65 60
2 DCPD ¨ C9
Resin Arizona Terpene
TP7042 1201 93 10 2 1.25 60
3 Chemical phenolic
Resin ARKON
Arakawa Alicyclic2284 75 3 0 1.67 74
4 P125 hydrogenated
Resin
E5415 Exxon Mobil Hydrogenated
1268 66 0 0 1.65 80
5 DCPD
Resin
E5320 Exxon Mobil Hydrogenated 1263 74 0 0
1.63 80
6 DCPD
Resin Hydrogenated
E5340 Exxon Mobil 1187 86 0 0 1.53 80
7 DCPD
Resin Hydrogenated
PR-100 Exxon Mobil 1139 88 0 0 1.49 80
8 DCPD
Resin
E5615 Exxon Mobil Hydrogenated 1332 68 10 0
1A8 60
9 DCPD ¨ C9
Resin Hydrogenated
E5637 Exxon Mobil 1459 80 5 0 1.51 70
10 DCPD ¨ C9
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[0087] By analysis of the commercial resins, Table 1 shows that only the
resins 7 to 10
meet the criteria of the resin of use for the purposes of the invention.
[0088] The resin of use for the purposes of the invention, predominantly
composed of
units selected from the group consisting of cyclopentadiene,
dicyclopentadiene,
methylcyclopentadiene and the mixtures thereof, may comprise, in addition to
these
units and in a minor amount, aliphatic or aromatic units or else units of
aliphatic/aromatic type, that is to say based on aliphatic and/or aromatic
monomers.
[0089] Suitable as aromatic monomers are, for example: styrene, a-
methylstyrene,
ortho-, meta- or para-methylstyrene, vinyltoluene, para-(tert-butyl)styrene,
methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene,
vinylnaphthalene,
indene, or any vinylaromatic monomer resulting from a C9 fraction (or more
generally
from a Ce to Clo fraction). Preferably, the vinylaromatic monomer is styrene
or a
vinylaromatic monomer resulting from a C9 fraction (or more generally from a
CB to C10
fraction).
[0090] According to a particularly preferential embodiment, the resin of use
for the
purposes of the invention is selected from the group consisting of resins of
homopolymers of cyclopentadiene, dicyclopentadiene or methylcyclopentadiene
and
the mixtures thereof, or resins of copolymers consisting of monomers selected
from the
group consisting of cyclopentadiene, dicyclopentadiene, methylcyclopentadiene
and
the mixtures thereof, and the mixtures of these copolymeric resins. Likewise,
the resin
of use for the purposes of the invention may be a mixture of the
abovementioned
monomeric or copolymeric resins.
[0091] According to another embodiment which is also very preferential, the
resin of
use for the purposes of the invention is selected from the group consisting of
resins
predominantly composed of units selected from the group consisting of
cyclopentadiene, dicyclopentadiene, methylcyclopentadiene and a minor amount
of
aromatic units or else units of aliphatic/aromatic type, and the mixtures
thereof.
[0092] The content of resin in the composition according to the invention is
within a
range extending from 15 phr to 150 phr, preferentially from 25 to 120 phr,
more
preferentially from 40 to 115 phr, even more preferentially from 50 to 110
phr, better
still from 65 to 110 phr. Indeed, below 15 phr of the resin of use for the
purposes of the
invention, the effect of the resin would be insufficient and the composition
could have
problems of grip, whereas above 150 phr, the composition could present
manufacturing
difficulties in terms of readily incorporating all the resin into the
composition.
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1-5 Other possible additives
[0093] The rubber compositions in accordance with the invention optionally
also
comprise all or a portion of the normal additives customarily used in
elastomer
compositions intended especially for the manufacture of treads, such as, for
example,
pigments, protective agents, such as antiozone waxes, chemical antiozonants or
antioxidants, plasticizing agents other than those described above, anti-
fatigue agents,
reinforcing resins, or methylene acceptors (for example novolac phenolic
resin) or
donors (for example HMT or H3M).
[0094] The composition according to the invention may also comprise a
plasticizing
system. This plasticizing system may be composed of a hydrocarbon-based resin
with
a Tg of greater than 20 C, in addition to the specific hydrocarbon-based resin
described above, and/or a plasticizing oil.
[0095] Of course, the compositions in accordance with the invention can be
used alone
or in a blend (i.e., in a mixture) with any other rubber composition which can
be used in
the manufacture of tyres.
[0096] It is obvious that the invention relates to the rubber compositions
described
above both in the "uncured" or non-crosslinked state (i.e., before curing) and
in the
"cured" or crosslinked, or else vulcanized, state (i.e., after crosslinking or
vulcanization).
II- Preparation of the rubber compositions
[0097] The compositions are manufactured in appropriate mixers, using two
successive phases of preparation which are well known to those skilled in the
art: a first
phase of thermomechanical working or kneading (sometimes referred to as "non-
productive" phase) at high temperature, up to a maximum temperature of between
110 C and 200 C, preferably between 130 C and 180 C, followed by a second
phase
of mechanical working (sometimes referred to as "productive" phase) at lower
temperature, typically below 110 C, for example between 60 C and 100 C, during
which finishing phase the crosslinking or vulcanization system is
incorporated; such
phases have been described, for example, in applications EP-A-0 501 227, EP-A-
0 735
088, EP-A-0 810 258, W000/05300 or W000/05301.
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[0098] The first (non-productive) phase is preferentially carried out in
several
thermomechanical stages. During a first step, the elastomers, the reinforcing
fillers and
the hydrocarbon-based resin (and optionally the coupling agents and/or other
ingredients, with the exception of the crosslinking system) are introduced
into an
appropriate mixer, such as a customary internal mixer, at a temperature
between 20 C
and 100 C and preferably between 25 C and 100 C. After a few minutes,
preferentially
from 0.5 to 2 min, and a rise in the temperature to 90 C or to 100 C, the
other
ingredients (that is to say, those which remain, if not all were put in at the
start) are
added all at once or in portions, with the exception of the crosslinking
system, during a
mixing ranging from 20 seconds to a few minutes. The total duration of the
kneading, in
this non-productive phase, is preferably between 2 and 10 minutes at a
temperature of
less than or equal to 180 C and preferentially of less than or equal to 170 C.
[0099] After cooling the mixture thus obtained, the crosslinking system is
then
incorporated at low temperature (typically less than 100 C), generally in an
external
mixer, such as an open mill; the combined mixture is then mixed (productive
phase) for
a few minutes, for example between 5 and 15 min.
[0100] The final composition thus obtained is subsequently calendered, for
example in
the form of a sheet or slab, in particular for laboratory characterization, or
else
extruded, in order to form, for example, a rubber profiled element used in the
manufacture of semi-finished products for tyres. These products may then be
used for
the manufacture of tyres, according to techniques known to those skilled in
the art, with
the advantage of the invention, namely good tack of the layers on one another
before
curing of the tyre.
[0101] The crosslinking (or curing) is carried out in a known way at a
temperature
generally of between 130 C and 200 C, under pressure, for a sufficient time
which can
vary, for example, between 5 and 90 min, as a function in particular of the
curing
temperature, of the crosslinking system adopted, of the kinetics of
crosslinking of the
composition under consideration or else of the size of the tyre.
[0102] The examples which follow illustrate the invention without, however,
limiting it.
Ill- Exemplary embodiments of the invention
III-1 Preparation of the examples
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[0103] In the examples which follow, the rubber compositions were produced as
described above.
III-2 Characterization of the examples
.. [0104] In the examples, the rubber compositions are characterized, before
and/or after
curing, as indicated below.
Dynamic properties (after curing):
[0105] The dynamic properties G* and tan(6)max are measured on a viscosity
analyser (Metravib V A4000) according to Standard ASTM 0 5992-96. The response
of
a sample of vulcanized composition (cylindrical test specimen with a thickness
of 4 mm
and a diameter of 10 mm), subjected to a simple alternating sinusoidal shear
stress, at
a frequency of 10 Hz, during a temperature sweep from -80 C to +100 C with a
temperature gradient of +1.5 C/min, under a maximum stress of 0.7 MPa, is
recorded.
The value of the tangent of the loss angle (tan(6)) is then noted at 0 C and
60 C.
[0106] The lower the value for the tan(6) at 60 C, the lower will be the
hysteresis of the
composition and thus the lower will be the rolling resistance. The results are
expressed
in terms of performance base 100, that is to say that the value 100 is
arbitrarily
assigned to the best control, in order to subsequently compare the tan(6) at
60 C (that
is to say the hysteresis - and hence the rolling resistance) of the various
solutions
tested. The value in base 100 is calculated according to the operation: (value
of tan(6)
at 60 C of the control / value of tan(6) at 60 C of the sample)* 100. In this
way, a lower
value represents a reduction in the hysteresis performance (that is to say an
increase
in the hysteresis), while a higher value represents a better hysteresis
performance (that
.. is to say a lower hysteresis).
[0107] For the value of tan(6) 0 C, the higher the value, the more the
composition will
enable good wet grip. The results are expressed in terms of performance base
100,
that is to say that the value 100 is arbitrarily assigned to the best control,
in order to
calculate and subsequently compare the tan(6) at 0 C of the various solutions
tested.
The value in base 100 is calculated according to the operation: (value of
tan(6) at 0 C
of the sample/ value of tan(6) at 60 C of the control) * 100. In this way, a
lower value
represents a reduction in the grip performance (that is to say a lower tan(6)
value at
,
. CA 03017422 2018-09-11
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0 C), while a higher value represents a better grip performance (that is to
say a higher
tan(6) value at 0 C).
III-3 Examples
5 Example 1 - Preparation of an SBR that is aminoalkoxvsilane-functional in
the middle
of the chain with a Tq of -88 C
[0108] Methylcyclohexane, butadiene, styrene and tetrahydrofurfuryl ethyl
ether are
continuously introduced into a stirred continuously fed 32 I reactor, assumed
to be
10 perfectly stirred according to those skilled in the art, according to
the following
proportions: butadiene flow rate by weight = 4.013 kg.h-1, styrene flow rate
by weight =
0.122 kg.h-1, concentration by weight of monomer = 9.75 wt.%, 15 ppm of
tetrahydrofurfuryl ethyl ether. n-Butyllithium (n-BuLi) is introduced in a
sufficient
amount in order to neutralize the protic impurities introduced by the
different
15 constituents present in the inlet of the first reactor; 850 pmol of n-
BuLi per 100 g of
monomer are introduced.
[0109] The different flow rates are calculated in order for the mean residence
time in
the reactor to be 35 min. The temperature is maintained at 95 C. A sample of
polymer
20 solution is withdrawn at the outlet of the polymerization reactor. The
polymer thus
obtained is subjected to an antioxidizing treatment with addition of 0.4 phr
of 2,2'-
methylenebis(4-methy1-6-(tert-butyl)phenol) and 0.2 phr of N-(1,3-
dimethylbutyI)-N'-
phenyl-p-phenylenediamine. The polymer thus treated is subsequently separated
from
its solution by a steam stripping operation and then dried on an open mill at
100 C.
25 The "initial" intrinsic viscosity measured is 1.98 dl.g-1. The number-
average molar mass
Mn, determined by the SEC technique, is 90 000 g.m01-1 and the polydispersity
index
PI is 1.90. At the outlet of the polymerization reactor, 440 pmol per 100 g of
monomer
of (3-N,N-dimethylaminopropyl)trimethoxysilane (coupling and star-branching
agent
CA) in solution in methylcyclohexane are added to the solution of living
polymer (CA/Li
30 = 0.52).
[0110] The polymer thus obtained is subjected to an antioxidizing treatment
with
addition of 0.4 phr of 2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and
0.2 phr of N-
(1,3-dimethylbuty1)-N'-phenyl-p-phenylenediamine. The polymer thus treated is
CA 03017422 2018-09-11
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subsequently separated from its solution by a steam stripping operation and
then dried
on an open mill at 100 C.
[0111] The "final" intrinsic viscosity measured is 2.52 dl.g-1. The jump in
viscosity,
defined as the ratio of said "final" viscosity to said "initial" viscosity, is
in this instance
1.27. The Mooney viscosity of this polymer A is 70. The number-average molar
mass
Mn, determined by the SEC technique, is 168 600 g.mo1-1 and the polydispersity
index
PI is 1.68. The microstructure of this polymer is determined by the NIR
method. The
content of 1,2- units is 12.7% relative to the butadiene units. The content by
weight of
styrene is 2.1%. The glass transition temperature of this polymer is -88 C.
The cold
flow CF(1+6)100 C of the polymer is 0.52. The distribution of the entities
after
functionalization is given with the modelling method described above: 86% of
functional chains, 77% of which are functional in the middle of the chain, and
14% of
star-branched non-functional chains.
Example 2 ¨ Compositions
[0112] The compositions are manufactured with introduction of all of the
constituents
onto an internal mixer, with the exception of the vulcanization system. The
vulcanization agents (sulfur and accelerator) are introduced onto an external
mixer at
low temperature (the constituent rolls of the mixer being at around 30 C).
[0113] The object of the examples presented in Table 2 is to compare the
different
rubber properties of control compositions (TO to T7) to the properties of
compositions in
accordance with the invention (Cl to C4). The properties measured, before and
after
curing, are presented in Table 3.
Table 2
T1 T2 T3 T4 T5 T6 Cl C2 C3 C4
SBR (1) 100 100 100 100 100 100 100 100 100 100
Carbon black (2) 4 4 4 4 4 4 4 _ 4 4 4
Silica (3) 130 130 130 130 130 130 130 130 130 130
Resin 1 (4)
Resin 2 (4)
Resin 3 (4)
Resin 4 (4)
Resin 5 (4)
Resin 6 (4) _
Resin 7 (4)
CA 03017422 2018-09-11
- 25
Resin 8 (4)
Resin 9 (4) _
Resin 10 (4)
Antioxidant (5) 6 6 6 6 6 6 6 6 6 6
Coupling agent (6) 13 13 13 13 13 13 13 13 13 13
DPG (7) 2.5 2.5 2.5
2.5 2.5 2.5 2.5 2.5 2.5 2.5
Stearic acid (8) 3 3 3 3 3 3 3 3 3 3
ZnO (9) 0.9 0.9 0.9
0.9 0.9 0.9 0.9 0.9 0.9 0.9
Accelerator (10) 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3
2.3 2.3
Soluble sulfur 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7
0.7 0.7
(1) SBR of Tg = -88 C of example 1
(2) Carbon black, ASTM N234 grade
(3) Silica, Zeosil 1165 MP from Solvay, HDS type
(4) Resins 1 to 10: cf Table 1 described above
(5) N-(1,3-DimethylbutyI)-N'-phenyl-p-phenylenediamine (Santoflex 6-PPD) from
Flexsys and 2,2,4-trimethy1-1,2-dihydroquinoline (TMO)
(6) Coupling agent: Si69 from Evonik Degussa
(7) Diphenylguanidine, Perkacit DPG from Flexsys
(8) Stearin, Pristerene 4931 from Uniqema
(9) Zinc oxide, industrial grade - Umicore
(10) N-Cyclohexy1-2-benzothiazolesulfenamide (Santocure CBS from Flexsys)
Table 3
Ti T2 T3 T4 T5 T6 Cl C2 C3 C4
Grip performance 100 94 41 62 90 88 88 88 94 89
(base 100)
Hysteresis
performance at 100 100 60 102 104 106 115 114 118 126
60 C (base 100)
Mean of the
performance
properties (base 100 97 51 82 97 97 101 101 106 107
100)
[0114] Relative to the control compositions, it is noted that the composition
Ti, which
is not in accordance with the invention and which does not comprise
plasticizing resin,
has a rolling resistance (measured by the tan(a) value at 60 C) which is low
and which
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requires improvement. The rolling resistance of this composition therefore
serves as
base 100 for comparing the performance of the other compositions. It is noted
that all
the compositions, with the exception of T3, comprising a resin make it
possible to
improve this performance. On the other hand, only the compositions Cl to C4
enable
more than 10% improvement in rolling resistance. Other means for improving
rolling
resistance are known to those skilled in the art, but only at the expense of
grip. By
virtue of the present invention, it is noted that only the compositions Cl to
C4 have
good hysteresis performance (measured by the tan(0) value at 60 C), and grip
which
is reduced to a limited extent, such that the mean of the two performances is
improved.
***
[0115] In some aspects, embodiments of the present disclosure as described
herein
include the following items:
Item 1. Rubber composition based on at least
- one elastomer comprising from 50 to 100phr of one or more copolymers of
butadiene
and of vinylaromatic monomer, having a content of vinylaromatic units of more
than 0
to less than 5% by weight and a Tg within a range extending from -110 C to -70
C,
- a reinforcing filler,
- a crosslinking system and,
- an optionally hydrogenated hydrocarbon-based resin, predominantly composed
of
units selected from the group consisting of cyclopentadiene,
dicyclopentadiene,
methylcyclopentadiene and mixtures thereof, said hydrocarbon-based resin
having
an average molecular weight Mz of less than 2000 g/mol and a glass transition
temperature Tg, expressed in C, such that:
Tg 80 ¨ 2*(%HA)
wherein %HA represents the content of aromatic protons of said resin, the
content of
said hydrocarbon-based resin is within a range extending from 15 to 150 phr,
and
wherein said copolymer of butadiene and of vinylaromatic monomer is
functionalized
by an alkoxysilane group bearing or not bearing another function capable of
interacting with the reinforcing filler, the alkoxysilane group being bonded
to the
copolymer of butadiene and of vinylaromatic monomer via the silicon atom.
Item 2.The rubber composition according to item 1, wherein said hydrocarbon-
based
resin has an Mz of less than 1500 g/mol.
Date Recue/Date Received 2023-07-25
- 27 -
Item 3.The rubber composition according to item 1 or 2, wherein said
hydrocarbon-
based resin has a glass transition temperature Tg, expressed in C, such that:
Tg 85 ¨ 2*(%HA).
Item 4.The rubber composition according to any one of items 1 to 3, wherein
said
hydrocarbon-based resin has a polydispersity index (PI) of less than 1.7.
Item 5. The rubber composition according to any one of items 1 to 4, wherein
the resin
has a content of aromatic protons of less than 50%.
Item 6. The rubber composition according to any one of items 1 to 4, wherein
the resin
has a content of aromatic protons within a range extending from 0% to 20%.
Item 7. The rubber composition according to any one of items 1 to 4, wherein
the resin
has a content of aromatic protons of less than 5%.
Item 8.The rubber composition according to item 7, wherein the resin has a
content
of aromatic protons of 0%.
Item 9. The rubber composition according to any one of items 1 to 4, wherein
the resin
has a content of aromatic protons within a range extending from 3% to 15%.
Item 10. The rubber composition according to any one of items 1 to 9,
wherein
the resin has a content of ethylenic protons of less than 0.5%.
Item 11. The rubber composition according to item 10, wherein the resin
does
not comprise any ethylenic units.
Item 12. The rubber composition according to any one of items 1 to 11,
wherein the copolymer(s) of butadiene and of vinylaromatic monomer represent a
total content of 75 to 100 phr.
Item 13. The rubber composition according to any one of items 1 to 12,
wherein the copolymer(s) of butadiene and of vinylaromatic monomer have a Tg
within a range extending from -110 C to -80 C.
Date Recue/Date Received 2023-07-25
- 28 -
Item 14. The rubber composition according to any one of items 1 to 13,
wherein the copolymer(s) of butadiene and of vinylaromatic monomer have a
Mooney viscosity within a range extending from 50 to 80.
Item 15. The rubber composition according to any one of items 1 to 14,
wherein the copolymer(s) of butadiene and of vinylaromatic monomer have a
content of vinylaromatic units of 1 to 4% by weight relative to the total
weight of the
copolymer, and also a content of vinylaromatic units, relative to the diene
portion,
ranging from 8 to 15% by weight.
Item 16. The rubber composition according to any one of items 1 to 15,
wherein the vinylaromatic monomer of the copolymer(s) of butadiene and of
vinylaromatic monomer is styrene.
Item 17. The rubber composition according to any one of items 1 to 16,
wherein at least 70% by weight of said copolymer of butadiene and of
vinylaromatic
monomer is functionalized by the alkoxysilane group.
Item 18. The rubber composition according to any one of items 1 to 17,
wherein the alkoxysilane group present on the copolymer of butadiene and of
vinylaromatic monomer is partially or totally hydrolysed to give silanol.
Item 19. The rubber composition according to any one of items 1 to 18,
wherein said copolymer of butadiene and of vinylaromatic monomer is
predominantly functionalized in the middle of the chain.
Item 20. The rubber composition according to any one of items 1 to 19,
wherein said copolymer of butadiene and of vinylaromatic monomer comprises
more
than 0 and up to 30% by weight, relative to the total weight of the copolymer
of
butadiene and of vinylaromatic monomer, of a star-branched copolymer of
butadiene and of vinylaromatic monomer.
Item 21. The rubber composition according to item 20, wherein said
copolymer of butadiene and of vinylaromatic monomer comprises more than 0 to
less than 20% by weight of the star-branched copolymer of butadiene and of
vinylaromatic monomer.
Date Recue/Date Received 2023-07-25
- 29 -
Item 22. The rubber composition according to any one of items 1 to 21,
wherein
the reinforcing filler is selected from the group consisting of silicas,
carbon blacks and
mixtures thereof.
Item 23. The rubber composition according to any one of items 1 to 22,
wherein
the content of reinforcing filler is within a range extending from 5 to 200
phr.
Item 24. The rubber composition according to any one of items 1 to 23,
wherein
the predominant reinforcing filler is silica.
Item 25. The rubber composition according to item 24, also comprising
carbon
black within a range extending from 0.1 to 10 phr.
Item 26. The rubber composition according to any one of items 1 to 25,
wherein
the content of said hydrocarbon-based resin is within a range extending from
25 to
120 phr.
Item 27. Tyre comprising a composition according to any one of items 1
to 26.
Item 28. The tyre according to item 27, comprising the composition in
all or part
of the tread thereof.
Date Recue/Date Received 2023-07-25
