U.S. patent application number 15/877181 was filed with the patent office on 2018-07-12 for continuous synthesis method for a modified diene elastomer, facility for implementing same.
This patent application is currently assigned to COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN. The applicant listed for this patent is COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN, MICHELIN RECHERCHE ET TECHNIQUE S.A.. Invention is credited to Charlotte DIRE, Margarita DORATO, Mathieu MANCEAU, Jean-Marc MARECHAL, Nuno PACHECO.
Application Number | 20180194867 15/877181 |
Document ID | / |
Family ID | 49876775 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180194867 |
Kind Code |
A1 |
DIRE; Charlotte ; et
al. |
July 12, 2018 |
CONTINUOUS SYNTHESIS METHOD FOR A MODIFIED DIENE ELASTOMER,
FACILITY FOR IMPLEMENTING SAME
Abstract
A system for the continuous synthesis of a modified diene
elastomer is provided. The system comprises a device for modifying
a living diene elastomer resulting from an anionic polymerization
step, modelled on one of the following models: 1. a tubular reactor
with axial dispersion, 2. a tubular reactor with axial dispersion,
in series with at least one continuous stirred reactor, presumed to
be perfectly stirred, 3. at least one tubular reactor with axial
dispersion, in series with a continuous stirred reactor, presumed
to be perfectly stirred, 4. several tubular reactors with axial
dispersion, in series with several continuous stirred reactors,
presumed to be perfectly stirred, 5. at least two continuous
stirred reactors, presumed to be perfectly stirred, in series.
Inventors: |
DIRE; Charlotte;
(Clermont-Ferand, FR) ; MARECHAL; Jean-Marc;
(Clermont-Ferrand, FR) ; DORATO; Margarita;
(Clermont-Ferrand, FR) ; MANCEAU; Mathieu;
(Clermont-Ferrand, FR) ; PACHECO; Nuno;
(Clermont-Ferrand, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN
MICHELIN RECHERCHE ET TECHNIQUE S.A. |
Clermont-Ferrand
Granges-Paccot |
|
FR
CH |
|
|
Assignee: |
COMPAGNIE GENERALE DES
ETABLISSEMENTS MICHELIN
Clermont-Ferrand
FR
MICHELIN RECHERCHE ET TECHNIQUE S.A.
Granges-Paccot
CH
|
Family ID: |
49876775 |
Appl. No.: |
15/877181 |
Filed: |
January 22, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14910213 |
Feb 4, 2016 |
9908949 |
|
|
PCT/EP2014/064977 |
Jul 11, 2014 |
|
|
|
15877181 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08F 236/10 20130101;
B01J 19/1862 20130101; B01J 19/2415 20130101; C08L 15/00 20130101;
C08C 19/25 20130101; B01J 19/245 20130101; B01J 2219/24 20130101;
C08C 19/44 20130101; B01J 2219/00033 20130101; B01J 19/18
20130101 |
International
Class: |
C08C 19/25 20060101
C08C019/25; C08F 236/10 20060101 C08F236/10; C08C 19/44 20060101
C08C019/44; C08L 15/00 20060101 C08L015/00; B01J 19/24 20060101
B01J019/24; B01J 19/18 20060101 B01J019/18 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2013 |
FR |
1357888 |
Claims
1. A system for the continuous synthesis of a modified diene
elastomer, comprising a device for modifying a living diene
elastomer resulting from an anionic polymerization step, modelled
on one of the following models: 1. a tubular reactor with axial
dispersion, 2. a tubular reactor with axial dispersion, in series
with at least one continuous stirred reactor, presumed to be
perfectly stirred, 3. at least one tubular reactor with axial
dispersion, in series with a continuous stirred reactor, presumed
to be perfectly stirred, 4. several tubular reactors with axial
dispersion, in series with several continuous stirred reactors,
presumed to be perfectly stirred, 5. at least two continuous
stirred reactors, presumed to be perfectly stirred, in series.
2. A system according to claim 1, wherein the device is modelled on
a tubular reactor with axial dispersion.
3. A system according to claim 1, wherein the device is modelled on
a tubular reactor with axial dispersion, in series with at least
one continuous stirred reactor.
4. A system according to claim 3, wherein the at least one
continuous stirred reactor is perfectly stirred.
5. A system according to claim 1, wherein the device is modelled on
at least one tubular reactor with axial dispersion, in series with
a continuous stirred reactor.
6. A system according to claim 5, wherein continuous stirred
reactor is perfectly stirred.
7. A system according to claim 1, wherein the device is modelled on
several tubular reactors with axial dispersion, in series with
several continuous stirred reactors.
8. A system according to claim 7, wherein the several continuous
stirred reactors are perfectly stirred.
9. A system according to claim 1, wherein the device is modelled on
at least two continuous stirred reactors, in series.
10. A system according to claim 9, wherein the at least two
continuous stirred reactors are perfectly stirred.
11. A unit for the continuous preparation of a modified diene
elastomer, wherein the unit incorporates the system according to
claim 1 and in that the modifying device is in contact downstream
with a device for recovering the diene elastomer.
12. A system for the continuous synthesis of a modified diene
elastomer, comprising a device for modifying a living diene
elastomer resulting from an anionic polymerization step, modelled
on one of the following models: 1. a tubular reactor with axial
dispersion, 2. a tubular reactor with axial dispersion, in series
with at least one continuous stirred reactor, 3. at least one
tubular reactor with axial dispersion, in series with a continuous
stirred reactor, 4. several tubular reactors with axial dispersion,
in series with several continuous stirred reactors, 5. at least two
continuous stirred reactors, in series, and wherein the system is
used for the implementation of a method for the continuous
synthesis of a modified diene elastomer, comprising the steps: of
anionic polymerization of at least one conjugated diene monomer in
the presence of a polymerization initiator, of modifying the diene
elastomer in a functionalizing device, by bringing the living diene
elastomer bearing an active site obtained in the previous step into
contact, in a single step, with a non-polymerizable functionalizing
agent comprising (a) where appropriate, a function capable of
interacting with a reinforcing filler and (b) a trialkoxysilane
group, the optionally hydrolysable alkoxy radical having 1 to 10
carbon atoms, the modification comprising three reactions in series
TABLE-US-00008 Reaction Mechanism R1 PLi + A .sup.k.sup.1fi PA R2
PLi + PA .sup.k.sup.2fi P.sub.2A R3 PLi + P.sub.2A .sup.k.sup.3fi
P.sub.3A
where A represents the functionalizing agent, PLi represents a
living elastomer chain, PA represents the chain-end functionalized
elastomer, P.sub.2A represents the coupled elastomer, P.sub.3A
represents the three-arm star-shaped elastomer, and k.sub.i
represents the rate constant of the reaction R.sub.i, that are
carried out according to the following rate law: TABLE-US-00009
Reactions Rate of reaction R1 V.sub.1 = k.sub.1[PLi][A] R2 V.sub.2
= k.sub.2[PLi][PA] R3 V.sub.3 = k.sub.3[PLi][P.sub.2A]
where k.sub.1, k.sub.2 and k.sub.3 are the rate constants
respectively of the reactions R1, R2 and R3 (expressed in
(m.sup.3/mol)s.sup.-1), [PLi] is the concentration of living chains
(expressed in mol/m.sup.3), [A] is the concentration of modifying
agent A (expressed in mol/m.sup.3), [PA] is the concentration of
chain-end functionalized helastomer (expressed in mol/m.sup.3),
[P.sub.2A] is the concentration of coupled elastomer (expressed in
mol/m.sup.3), [P.sub.3A] is the concentration of the three-arm
star-shaped elastomer (expressed in mol/m.sup.3), with a ratio of
the rate constants, defined as: K = k 1 k 2 = k 2 k 3 ,
##EQU00009## of greater than 1, and the residence time distribution
in a functionalizing device (i) or (ii) is expressed respectively
according to equations 1 or 3 below: (i) in a functionalizing
device having at least one tubular continuous reactor or having at
least one cascade of at least two stirred reactors, E 1 ( t ) = 1 2
( P .pi..theta. 1 t ) 1 2 e - P ( .theta. 1 - t ) 2 4 .theta. 1 t
Eq 1 ##EQU00010## in which: P is the dimensionless parameter of
resistance to dispersion, .theta..sub.1 is the residence time
defined as the reactor volume/total volume flow rate ratio, t is
the variable time of the residence time distribution, (ii) in a
functionalizing device that is a combination of the device (i) and
of a device having at least one continuous stirred reactor, having
a residence time distribution characterized by the following
equation: E 2 ( t ) = e ( - t .theta. 2 ) .theta. 2 Eq 2
##EQU00011## in which: .theta..sub.2 is the residence time defined
as the reactor volume/total volume flow rate ratio, t is the
variable time of the residence time distribution, the device (ii)
having a residence time distribution characterized by the equation
3 below, which is the result of the convolution of equations 1 and
2: E 12 ( t ) = .intg. 0 t E 1 ( t - T ) E 2 ( T ) dT E 12 ( t ) =
.intg. 0 t 1 2 ( P .pi..theta. 1 ( t - T ) ) 1 2 e - P ( .theta. 1
- ( t - T ) ) 2 4 .theta. 1 ( t - T ) e ( - T .theta. 2 ) .theta. 2
dT Eq 3 ##EQU00012## in which: .theta..sub.1 and .theta..sub.2 are
the residence times as defined above, P is the dimensionless
parameter of resistance to dispersion, t is the variable time of
the residence time distribution, T is the integration variable.
13. A system according to claim 12, wherein .theta..sub.1 is at
least 0.1 minute and at most 10 minutes.
14. A system according to claim 13, wherein .theta..sub.1 is at
most 5 minutes.
15. A system according to claim 12, wherein .theta..sub.2 is
between 0 and 60 minutes.
16. A system according to claim 15, wherein .theta..sub.2 is
between 5 and 50 minutes.
Description
[0001] This divisional application claims the benefit of U.S.
patent application Ser. No. 14/910,213, which is a 371 national
phase entry of PCT/EP2014/064977, filed 11 Jul. 2014, which claims
benefit of French Patent Application No. 1357888, filed 8 Aug.
2013, the entire content of which is incorporated herein by
reference for all purposes.
BACKGROUND
1. Field
[0002] The present invention relates to a continuous method for
synthesizing a diene elastomer that is modified by an alkoxysilane
group.
2. Description of Related Art
[0003] Now that savings in fuel and the need to protect the
environment have become a priority, it is desirable to produce
polymers having good mechanical properties and a hysteresis that is
as low as possible in order to be able to process them in the form
of rubber compositions that can be used for the manufacture of
various semi-finished products that are incorporated in the
composition of tires. In order to achieve the objective of the drop
in hysteresis, many solutions have already been tested. In
particular, mention may be made of the modification of the
structure of the diene polymers and copolymers at the end of the
polymerization using functionalizing agents for the purpose of
obtaining a good interaction between the polymer thus modified and
the filler, whether this is carbon black or a reinforcing inorganic
filler. It has in particular been proposed to use diene polymers
functionalized by alkoxysilane derivatives. By way of illustration
of this prior art relative to reinforcing inorganic fillers,
mention may for example be made of US patent U.S. Pat. No.
5,066,721 and patent application EP A 0 299 074.
[0004] It has also been proposed to combine functionalization by
amine functions with functionalization by alkoxysilane functions.
By way of illustration of this prior art, mention may for example
be made of patent EP 0 992 537 which describes an extended
elastomer that is modified at the chain end by an alkoxysilane
function and that bears, at the other end or along its chain, one
or more amine functions. Furthermore, elastomers have also been
proposed that are functionalized at the chain end by alkoxysilane
functions bearing an amine group. Mention may be made, for example,
of patent application US 2005/0203251 which describes an elastomer
functionalized at the chain end by an alkoxysilane bearing an amine
group.
[0005] The applicant companies have described, in document WO
2009/133068 A1, a functionalized diene elastomer essentially
consisting of the species coupled by an elastomer having within the
chain a group bearing an alkoxysilane function and an amine
function, the silicon atom of this group bonding the two parts of
the diene elastomer chain. This functionalized elastomer gives the
composition containing it improved mechanical and dynamic
properties, especially an improved hysteresis while maintaining a
satisfactory processability in the uncured state, with a view in
particular to use as a tire tread.
[0006] For those who develop materials intended for the manufacture
of tires, improving the compromise of mechanical and dynamic
properties of the rubber compositions, with a view to improving the
performance of the tire containing them, is a constant
preoccupation. This concern for improving the compromise of
properties must, in so far as possible, come under an approach that
aims to minimize the impact on the aspects further upstream which
are, for example, the synthesis of the components of rubber
compositions and their specific characteristics.
[0007] In U.S. Pat. No. 7,807,747 B2, it has been proposed to
improve in particular the processability of a functionalized
elastomer by using a single functionalizing agent, an alkoxysilane
compound bearing an amine function, by targeting a specific
distribution of the species within the elastomer. The strategy
consists in adding the amine-containing alkoxysilane compound,
preferably amine-containing trialkoxysilane compound, in two steps
during the functionalizing step: i) first addition in an amount
such that the n(amine-containing trialkoxysilane)/n(butyl lithium)
molar ratio is between 0.05 and 0.35, ii) then second addition in
an amount such that the final n(amine-containing
trialkoxysilane)/n(butyl lithium) molar ratio is greater than or
equal to 0.5. This process makes it possible to obtain a functional
diene elastomer mixture comprising 40 to 80% by weight of chain-end
functionalized elastomer, 5 to 45% by weight of elastomer
functionalized in the middle of the chain and 3 to 30% by weight of
star-shaped elastomer. The functionalized elastomer is synthesized
according to a batch process.
[0008] The modification of the elastomers is an important means for
improving the properties of the rubber compositions containing them
with a view to improving the performance of the tire containing
them. Yet it is observed that in the past the processes for
modifying a diene elastomer requiring a control of the distribution
of the species within the modified elastomer are essentially
carried out in batch mode. Only the batch process makes it possible
to refine the content of each species. Yet such a process is not
always productive and sufficiently competitive and economic for
industrial production.
SUMMARY
[0009] The technical problem that the invention proposes to solve
is to be able to have a method of synthesis that is competitive,
economic and flexible, suitable for industrial production, which
makes it possible to control the distribution of the species within
a modified diene elastomer.
[0010] The present invention proposes a continuous method, the
functionalizing step of which is characterized by a particular
residence time distribution and a specific kinetic model, which
solves this technical problem in the sense that it makes it
possible to control the proportions of the various species of a
modified elastomer. By thus controlling the distribution of the
species within the modified elastomer, it is possible to improve
the properties of rubber compositions containing it. Since the
method of the invention is a continuous method, it is particularly
suitable for an economically advantageous industrial production
with increased competitiveness.
[0011] One subject of the invention is therefore a method for the
continuous synthesis of a modified diene elastomer comprising a
step referred to as a "polymerization step" during which the living
diene elastomer is synthesized and a step referred to as a
"functionalizing step" or "modifying step" during which the living
diene elastomer reacts with a specific functionalizing agent
comprising a trialkoxysilane group and where appropriate another
function capable of interacting with a reinforcing filler, the
latter step being characterized in particular by a determining
kinetic model and a particular flow represented by a specific
residence time distribution.
[0012] Another subject of the invention is the diene elastomer
modified by a trialkoxysilane functionalizing agent optionally
bearing a function capable of interacting with a reinforcing
filler, synthesized by such a method.
[0013] Another subject of the invention is a system intended for
the implementation of this continuous synthesis method and that is
suitable for an industrial-scale application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a diagram of a system that may be incorporated
into a unit for the continuous preparation of a modified diene
elastomer in accordance with one embodiment of the invention
according to which the modifying device comprises one tubular-type
reactor and one continuous stirred reactor.
[0015] FIG. 2 is a diagram of a system that may be incorporated
into a unit for the continuous preparation of a modified diene
elastomer in accordance with one embodiment of the invention
according to which the modifying device comprises two tubular-type
reactors and one continuous stirred reactor.
[0016] FIG. 3 is a graph illustrating a distribution of P, PA,
P.sub.2A and P.sub.3A species as a function of functionalizing
agent/living polymer chains (PLi) molar ratio according to Example
1.
[0017] FIG. 4 is a graph comparing simulated yields to measured
yields as a function of reaction time in a batch, perfectly stirred
reactor according to Example 2.
[0018] FIG. 5 is a graph illustrating inherent viscosity changes
(VC) according to Example 3.
[0019] FIG. 6 is a graph illustrating calculated VC determined from
a distribution of species calculated by a kinetic model
incorporated into a tubular and continuous perfectly stirred
reactor models according to Example 3.
DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0020] In the present description, unless expressly indicated
otherwise, all the percentages (%) indicated are % by weight.
Moreover, 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 (i.e. with limits a and b excluded), whereas any range
of values denoted by the expression "from a to b" signifies the
range of values extending from a through to b (i.e. including the
strict limits a and b).
[0021] In the present description, a modified diene elastomer
according to an embodiment of the invention is understood to mean a
diene elastomer that comprises a group comprising a silicon atom,
directly bonded to the elastomer chain, and, where appropriate, a
function capable of interacting with a reinforcing filler. It is
the elastomer obtained by the implementation of the continuous
synthesis method that is the subject of an embodiment of the
invention comprising the modification of the elastomer by means of
a trialkoxysilane functionalizing agent bearing, where appropriate,
a function capable of interacting with a reinforcing filler.
[0022] When the group lies at the chain end, it will then be said
that the diene elastomer is chain-end functionalized.
[0023] When the group lies in the linear main elastomer chain, it
will then be said that the diene elastomer is coupled or else
functionalized in the middle of the chain, as opposed to the "chain
end" position, even though the group does not lie precisely in the
middle of the elastomer chain. The silicon atom of this group bonds
the two fragments of the diene elastomer chain.
[0024] When the group is central, to which three elastomer chains
or branches are bonded forming a star-shaped structure of the
elastomer, it will then be said that the diene elastomer is
star-shaped. The silicon atom of this group bonds the three
branches of the modified diene elastomer together.
[0025] In the present description, a "group" or "function capable
of interacting with a reinforcing filler" is understood to mean any
group or function capable of forming, within a rubber composition
reinforced by means of a filler, a physical or chemical bond with
said filler. This interaction may be established, for example, by
means of covalent, hydrogen, ionic and/or electrostatic bonds
between said function and functions present on fillers.
[0026] A first subject of the invention is a method for the
continuous synthesis of a modified diene elastomer, characterized
in that it comprises the steps: [0027] of anionic polymerization of
at least one conjugated diene monomer in the presence of a
polymerization initiator, [0028] of modification of the diene
elastomer in a functionalizing device, by bringing the living diene
elastomer bearing an active site obtained in the previous step into
contact, in a single step, with a non-polymerizable functionalizing
agent comprising (a) where appropriate, a function capable of
interacting with a reinforcing filler and (b) a trialkoxysilane
group, the optionally hydrolysable alkoxy radical having 1 to 10
carbon atoms, the modification comprising three reactions in
series
TABLE-US-00001 [0028] Reaction Mechanism R1 PLi + A .sup.k.sup.1fi
PA R2 PLi + PA .sup.k.sup.2fi P.sub.2A R3 PLi + P.sub.2A
.sup.k.sup.3fi P.sub.3A
[0029] where
A represents the functionalizing agent, PLi represents a living
elastomer chain, PA represents the chain-end functionalized
elastomer, P.sub.2A represents the coupled elastomer, P.sub.3A
represents the three-arm star-shaped elastomer, and k.sub.i
represents the rate constant of the reaction R.sub.i,
[0030] that are carried out according to the following rate
law:
TABLE-US-00002 Reactions Rate of reaction R1 V.sub.1 =
k.sub.1[PLi][A] R2 V.sub.2 = k.sub.2[PLi][PA] R3 V.sub.3 =
k.sub.3[PLi][P.sub.2A]
[0031] where
k.sub.1, k.sub.2 and k.sub.3 are the rate constants respectively of
the reactions R1, R2 and R3 (expressed in (m.sup.3/mol)s.sup.-1),
[PLi] is the concentration of living chains (expressed in
mol/m.sup.3), [A] is the concentration of modifying agent A
(expressed in mol/m.sup.3), [PA] is the concentration of chain-end
functionalized elastomer (expressed in mol/m.sup.3), [P.sub.2A] is
the concentration of coupled elastomer (expressed in mol/m.sup.3),
[P.sub.3A] is the concentration of the three-arm star-shaped
elastomer (expressed in mol/m.sup.3),
[0032] the ratio K of the rate constants defined as:
K = k 1 k 2 = k 2 k 3 ##EQU00001##
being greater than 1, and the residence time distribution in the
functionalizing device being expressed according to equations 1 or
3 below: [0033] (i) in a functionalizing device having at least one
tubular continuous reactor or having at least one cascade of at
least two stirred reactors,
[0033] E 1 ( t ) = 1 2 ( P .pi..theta. 1 t ) 1 2 e - P ( .theta. 1
- t ) 2 4 .theta. 1 t Eq 1 ##EQU00002## [0034] in which: [0035] P
is the dimensionless parameter of resistance to dispersion, [0036]
.theta..sub.1 is the residence time defined as the reactor
volume/total volume flow rate ratio, preferably equal to at least
0.1 minute and at most to 10 minutes, more preferably at most to 5
minutes, [0037] t is the variable time of the residence time
distribution, [0038] (ii) in a functionalizing device that is a
combination of the device (i) and of a device having at least one
continuous stirred reactor, having a residence time distribution
characterized by the following equation:
[0038] E 2 ( t ) = e ( - t .theta. 2 ) .theta. 2 Eq 2 ##EQU00003##
[0039] in which: [0040] .theta..sub.2 is the residence time defined
as the reactor volume/total volume flow rate ratio, preferably
between 0 and 60 minutes, more preferably between 5 and 50 minutes,
[0041] t is the variable time of the residence time distribution,
[0042] the device (ii) having a residence time distribution
characterized by the equation 3 below, which is the result of the
convolution of equations 1 and 2:
[0042] E 12 ( t ) = .intg. 0 t E 1 ( t - T ) E 2 ( T ) dT E 12 ( t
) = .intg. 0 t 1 2 ( P .pi..theta. 1 ( t - T ) ) 1 2 e - P (
.theta. 1 - ( t - T ) ) 2 4 .theta. 1 ( t - T ) e ( - T .theta. 2 )
.theta. 2 dT Eq 3 ##EQU00004## [0043] in which: [0044]
.theta..sub.1 and .theta..sub.2 are the residence times as defined
above, [0045] P is the dimensionless parameter of resistance to
dispersion, [0046] t is the variable time of the residence time
distribution, [0047] T is the integration variable.
[0048] In these equations, P is the dimensionless parameter of
resistance to dispersion as defined in the bibliography
"Villermeaux, J; Genie de la reaction chimique [Chemical reaction
engineering]; 1993". It is preferably greater than 6.9, more
preferably greater than or equal to 9.6, or even greater than or
equal to 12. P is not limited by a maximum value within the context
of an embodiment of the invention. It may tend towards infinity. If
it tends towards infinity, the device in which the
functionalization takes place then acts as an ideal plug-flow
reactor.
[0049] The method that is the subject of an embodiment of the
invention comprises a first step of anionic polymerization of at
least one conjugated diene monomer in the presence of a
polymerization initiator.
[0050] The anionic polymerization may be carried out continuously
in a manner known per se. The polymerization generally takes place
at temperatures between 0.degree. C. and 110.degree. C. and
preferably from 60.degree. C. to 100.degree. C., or even from
70.degree. C. to 90.degree. C. The temperature may be kept constant
throughout this step or may be variable, depending on the targeted
characteristics of the elastomer synthesized. The polymerization
process may be carried out in solution, in a more or less
concentrated or dilute medium. The polymerization solvent is
preferably an inert hydrocarbon solvent which may be, for example,
an aliphatic or alicyclic hydrocarbon such as pentane, hexane,
heptane, isooctane, cyclohexane or methylcyclohexane or an aromatic
hydrocarbon such as benzene, toluene or xylene.
[0051] Suitable conjugated diene monomers are in particular
1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C1-C5
alkyl)-1,3-butadienes such as, for example,
2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene,
2-methyl-3-ethyl-1,3-butadiene or
2-methyl-3-isopropyl-1,3-butadiene, an aryl-1,3-butadiene,
1,3-pentadiene or 2,4-hexadiene.
[0052] According to certain variants of the method of the
invention, the conjugated diene monomer may be homopolymerized.
[0053] According to other variants of the method of the invention,
the conjugated diene monomer may be copolymerized with one or more
conjugated diene monomers and/or with one or more vinylaromatic
compounds having from 8 to 20 carbon atoms. Suitable vinylaromatic
compounds are in particular styrene, ortho-, meta- or
para-methylstyrene, the "vinyltoluene" commercial mixture,
para-(tert-butyl)styrene, methoxystyrenes, vinylmesitylene,
divinylbenzene, vinylnaphthalene, etc.
[0054] These variants can be combined with the preferred or
alternative variants and aspects described below.
[0055] As polymerization initiator, use may be made of any known
monofunctional anionic initiator. However, an initiator containing
an alkali metal such as lithium is preferably used. Suitable
organolithium initiators are in particular those comprising a
carbon-lithium bond and a nitrogen-lithium bond. Representative
compounds are aliphatic organolithium compounds such as
ethyllithium, n-butyllithium (n-BuLi), isobutyllithium, and the
lithium amides obtained from a cyclic secondary amine, such as
pyrrolidine and hexamethyleneimine.
[0056] The diene elastomer may have any microstructure which
depends on the polymerization conditions used. The elastomer may be
a block, random, sequential, microsequential, etc. elastomer. The
microstructure of this elastomer may be determined by the presence
or absence of a modifying and/or randomizing agent and on the
amounts of modifying and/or randomizing agent used.
[0057] The anionic polymerization of at least one conjugated diene
monomer in the presence of a polymerization initiator generates
elastomer chains having a reactive site at the chain end which can
be represented by a schematic formula: PLi, P representing the
elastomer chain, and Li a lithium atom. Reference is then commonly
made to a living elastomer or living chain. These living chains or
living elastomers then react with the functionalizing agent.
[0058] One of the essential elements of an embodiment of the
invention lies in the choice of this functionalizing agent in order
to correspond to the kinetic model of the functionalization defined
above with a ratio of the rate constants, denoted by K, of greater
than 1. This ratio K is preferably greater than or equal to 10, or
even greater than or equal to 100. Below this value of 1, the
distribution of the various species leads to a modified elastomer,
the use of which in a reinforced rubber composition results in
processing and hysteresis properties that are not always optimized
for satisfactory use as a tire tread. There is no upper limit of K.
A person skilled in the art will understand that the higher K is,
the more the reaction is controlled by the molar ratio of the
functionalizing agent to polymerization initiator. When this value
tends towards infinity, the method is quantitative and
stoichiometric.
[0059] The functionalizing agent in accordance with an embodiment
of the invention may bear, on the silicon atom, hydrolysable alkoxy
groups or else non-hydrolysable alkoxy groups, and optionally a
function capable of interacting with a reinforcing filler, the two
functions being bonded to one another directly or by means of a
spacer group. The function capable of interacting with a
reinforcing filler and the spacer group are as defined below.
[0060] According to variants of the invention, the functionalizing
agent may be represented by the following formula 1:
##STR00001##
[0061] in which,
R, a spacer group, is a C.sub.1-C.sub.18 cyclic or non-cyclic,
saturated or unsaturated, aliphatic or C.sub.6-C.sub.18 aromatic
divalent hydrocarbon radical, preferably a C.sub.1-C.sub.10
aliphatic, linear or branched, divalent hydrocarbon radical, more
preferably a C.sub.1-C.sub.6 aliphatic, linear, divalent
hydrocarbon radical, more preferably still the C.sub.3 linear
hydrocarbon radical, X is a hydrogen atom or a function capable of
interacting with a reinforcing filler, the R' radicals, which are
substituted or unsubstituted, identical or different, represent a
C.sub.1-C.sub.10, or even C.sub.1-C.sub.8, alkyl group, preferably
a C.sub.1-C.sub.4 alkyl group, more preferably methyl and
ethyl.
[0062] The foregoing various preferred or non-preferred aspects can
be combined with one another.
[0063] According to variants of the invention, the functionalizing
agent comprises no other function than that comprising the silicon
atom of trialkoxysilane type.
[0064] According to other variants of the invention, the
functionalizing agent comprises a function capable of interacting
with a reinforcing filler. This wording does not however exclude
the possibility of the function comprising the silicon atom also
interacting with a reinforcing filler.
[0065] A function capable of interacting with a reinforcing filler
is understood preferably to mean functions comprising at least one
heteroatom selected from N, S, O, P. By way of example, mention may
be made, among these functions, of cyclic or non-cyclic, primary,
secondary or tertiary amines, isocyanates, imines, cyano compounds,
thiols, carboxylates, epoxides and primary, secondary or tertiary
phosphines.
[0066] Thus, according to variants of the invention, the function
capable of interacting with a reinforcing filler is a protected or
unprotected primary amine, a protected or unprotected secondary
amine or a tertiary amine. The nitrogen atom may then be
substituted by two identical or different groups, possibly being a
trialkylsilyl radical, the alkyl group having 1 to 4 carbon atoms,
or a C.sub.1-C.sub.10 alkyl, preferably C.sub.1-C.sub.4 alkyl
radical, more preferably a methyl or ethyl radical, or else the two
substituents of the nitrogen form with the latter a heterocycle
containing a nitrogen atom and at least one carbon atom, preferably
2 to 6 carbon atoms.
[0067] Mention may for example be made, as a functionalizing agent
where the function capable of interacting with a reinforcing filler
is an amine, of (N,N-dialkylaminopropyl)trialkoxysilanes,
(N-alkylaminopropyl)trialkoxysilanes where the secondary amine
function is protected by a trialkylsilyl group and
aminopropyltrialkoxysilanes where the primary amine function is
protected by two trialkylsilyl groups. The alkyl substituents
present on the nitrogen atom are linear or branched and
advantageously have from 1 to 10, preferably 1 to 4, more
preferably 1 or 2 carbon atoms. For example, the following are
suitable as alkyl substituents: methylamino-, dimethylamino-,
ethylamino-, diethylamino, propylamino-, dipropylamino-,
butylamino-, dibutylamino-, pentylamino-, dipentylamino,
hexylamino, dihexylamino and hexamethyleneamino groups, preferably
diethylamino and dimethylamino groups. The alkoxy substituents are
linear or branched and generally have from 1 to 10, or even 1 to 8,
preferably 1 to 4, more preferably 1 or 2 carbon atoms.
[0068] Preferably, the functionalizing agent may be selected from
3-(N,N-dimethylaminopropyl)trimethoxysilane,
3-(N,N-dimethylaminopropyl)triethoxysilane,
3-(N,N-diethylaminopropyl)trimethoxysilane,
3-(N,N-diethylaminopropyl)triethoxysilane,
3-(N,N-dipropylaminopropyl)trimethoxysilane,
3-(N,N-dipropylaminopropyl)triethoxysilane,
3-(N,N-dibutylaminopropyl)trimethoxysilane,
3-(N,N-dibutylaminopropyl)triethoxysilane,
3-(N,N-dipentylaminopropyl)trimethoxysilane,
3-(N,N-dipentylaminopropyl)triethoxysilane,
3-(N,N-dihexylaminopropyl)trimethoxysilane,
3-(N,N-dihexylaminopropyl)triethoxysilane,
3-(hexamethyleneamino-propyl)trimethoxysilane,
3-(hexamethyleneaminopropyl)triethoxysilane,
3-(morpholinopropyl)trimethoxysilane,
3-(morpholinopropyl)triethoxysilane,
3-(piperidinopropyl)trimethoxysilane and
3-(piperidinopropyl)triethoxysilane. More preferably, the
functionalizing agent is
3-(N,N-dimethylaminopropyl)trimethoxysilane.
[0069] Preferably, the functionalizing agent may be selected from
3-(N,N-methyl-trimethylsilylaminopropyl)trimethoxysilane,
3-(N,N-methyltrimethylsilylaminopropyl)-triethoxysilane,
3-(N,N-ethyltrimethylsilylaminopropyl)trimethoxysilane,
3-(N,N-ethyltrimethylsilylaminopropyl)triethoxysilane,
3-(N,N-propyltrimethylsilylamino-propyl)trimethoxysilane and
3-(N,N-propyltrimethylsilylaminopropyl)triethoxysilane. More
preferably, the functionalizing agent is
3-(N,N-methyl-trimethylsilylaminopropyl)trimethoxysilane.
[0070] Preferably, the functionalizing agent may be selected from
3-(N,N-bis(trimethylsilyl)aminopropyl)trimethoxysilane and
3-(N,N-bis(trimethylsilyl)amino-propyl)triethoxysilane. More
preferably, the functionalizing agent is
3-(N,N-bis(trimethylsilyl)aminopropyl)trimethoxysilane.
[0071] According to variants of the invention, the function capable
of interacting with a reinforcing filler is an isocyanate function.
Preferably, the functionalizing agent may be selected from
3-(isocyanatopropyl)trimethoxysilane and
3-(isocyanatopropyl)triethoxysilane.
[0072] According to variants of the invention, the function capable
of interacting with a reinforcing filler is an imine function.
Preferably the functionalizing agent may be selected from
N-(1,3-dimethylbutylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine,
N-(1,3-methylethylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(1,3-methylethylidene)-3-(triethoxysilyl)-1-propanamine,
N-ethylidene-3-(trimethoxysilyl)-1-propanamine,
N-ethylidene-3-(triethoxysilyl)-1-propanamine,
N-(1-methylpropylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine,
N-(4-N,N-dimethylaminobenzylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(4-N,N-dimethylaminobenzylidene)-3-(triethoxysilyl)-1-propanamine,
N-(cyclohexylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(cyclohexylidene)-3-(triethoxysilyl)-1-propanamine,
N-(3-trimethoxysilylpropyl)-4,5-dihydroimidazole,
N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole,
N-(3-trimethoxysilylpropyl)-4,5-imidazole and
N-(3-triethoxysilylpropyl)-4,5-imidazole.
[0073] According to variants of the invention, the function capable
of interacting with a reinforcing filler is a cyano function.
Preferably the functionalizing agent may be selected from
3-(cyanopropyl)trimethoxysilane and
3-(cyanopropyl)triethoxysilane.
[0074] According to variants of the invention, the function capable
of interacting with a reinforcing filler is a protected or
unprotected thiol function. By way of example, mention may be made
of (S-trialkylsilylmercaptopropyl)trialkoxysilanes. Preferably the
functionalizing agent may be selected from
(S-trimethylsilyl-mercaptopropyl)trimethoxysilane,
(S-trimethylsilylmercaptopropyl)triethoxysilane,
(S-(tert-butyl)dimethylsilylmercaptopropyl)trimethoxysilane and
(S-(tert-butyl)dimethyl-silylmercaptopropyl)triethoxysilane.
[0075] According to variants of the invention, the function capable
of interacting with a reinforcing filler is a carboxylate function.
Mention may be made, as carboxylate function, of acrylates or
methacrylates. Such a function is preferably a methacrylate.
Preferably, the functionalizing agent may be selected from
3-(methacryloyloxypropyl)trimethoxysilane and
3-(methacryloyloxypropyl)triethoxysilane.
[0076] According to variants of the invention, the function capable
of interacting with a reinforcing filler is an epoxide function.
Preferably the functionalizing agent may be selected from
2-(glycidyloxyethyl)trimethoxysilane,
2-(glycidyloxyethyl)triethoxysilane,
3-(glycidyloxypropyl)trimethoxysilane,
3-(glycidyloxypropyl)triethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.
[0077] According to variants of the invention, the function capable
of interacting with a reinforcing filler is a protected or
unprotected primary phosphine, protected or unprotected secondary
phosphine or tertiary phosphine function. Preferably, the
functionalizing agent may be selected from
3-(P,P-bis(trimethylsilyl)phosphino-propyl)trimethoxysilane,
3-(P,P-bis(trimethylsilyl)phosphinopropyl)triethoxysilane,
3-(methyltrimethylsilylphosphinopropyl)trimethoxysilane,
3-(methyltrimethylsilylphosphino-propyl)triethoxysilane,
3-(ethyltrimethylsilylphosphinopropyl)trimethoxysilane,
3-(ethyltrimethylsilylphosphinopropyl)triethoxysilane,
3-(dimethylphosphino-propyl)trimethoxysilane,
3-(dimethylphosphinopropyl)triethoxysilane,
3-(diethylphosphinopropyl)trimethoxysilane,
3-(diethylphosphinopropyl)triethoxysilane,
3-(ethylmethylphosphinopropyl)trimethoxysilane,
3-(ethylmethylphosphinopropyl)-triethoxysilane,
3-(diphenylphosphinopropyl)trimethoxysilane and
3-(diphenylphosphinopropyl)triethoxysilane.
[0078] These functionalizing agents satisfy one of the essential
criteria according to which the ratio of the rate constants K is
greater than 1, preferably greater than or equal to 10, or even
greater than or equal to 100.
[0079] According to advantageous variants of the invention, at
least one of the following three features, and preferably all three
features, is (are) respected: [0080] the function capable of
interacting with a reinforcing filler is a tertiary amine, more
particularly diethylamine or dimethylamine, [0081] the spacer group
is a C.sub.1-C.sub.6 aliphatic, linear, divalent hydrocarbon
radical, more preferably still the C.sub.3 linear hydrocarbon
radical, [0082] in the trialkoxysilane group, the alkyl radicals
are identical and have 1 to 4, preferably 1 or 2 carbon atoms.
[0083] The molar ratio of the coupling agent to the metal of the
polymerization initiator depends essentially on the type of
modified diene elastomer that is desired. Thus, with a ratio
ranging from 0.40 to 0.75, preferably from 0.45 to 0.65 and more
preferably still from 0.45 to 0.55, the formation of coupled
species within the modified elastomer is favoured. Similarly, with
a ratio ranging from 0.15 to 0.40, preferably from 0.20 to 0.35,
more preferably still from 0.30 to 0.35, star-shaped species (3
arms) are predominantly formed within the modified elastomer. With
a ratio greater than or equal to 0.75, preferably greater than 1,
chain-end functionalized species are predominantly formed.
[0084] Another essential element of the modification step according
to an embodiment of the invention lies in the continuous contacting
of the living diene elastomer and of the functionalizing agent in a
functionalizing device, composed of at least one reactor, having a
residence time distribution characterized by one of the equations 1
and 3 above.
[0085] The combination of the functionalizing kinetic model defined
above with the model of the functionalizing reaction device that
satisfies equation 1 or equation 3, makes it possible to obtain,
according to a continuous method suitable for economically
advantageous industrial production, a modified diene elastomer with
a control of the distribution of the species within the
elastomer.
[0086] It is especially possible, by the implementation of the
method of an embodiment of the invention, to carry out the
synthesis of a novel modified diene elastomer in a competitive,
economical and flexible manner which is suitable for industrial
production, which novel modified diene elastomer gives a
composition containing it an optimal compromise of hysteresis
property and processing in the uncured state, without adversely
affecting the properties of the elastomer, especially its cold flow
resistance. For example, it is possible to directly obtain this
modified diene elastomer by modifying the living diene elastomer
with a molar ratio of functionalizing agent to polymerization
initiator within the range of from 0.48 to 0.52. This elastomer
comprises:
[0087] a) at least 55% by weight, relative to the total weight of
the modified diene elastomer, of a species coupled by a functional
group bearing a function of formula --SiOR, in which R is a
hydrogen atom or an alkyl radical having 1 to 10 carbon atoms, and
optionally a function capable of interacting with a reinforcing
filler, the group being bonded to the two arms of the diene
elastomer by means of the silicon atom,
[0088] b) from 5% by weight to 30% by weight, relative to the total
weight of the modified diene elastomer, of a star-shaped species
having three elastomer arms connected to one and the same silicon
atom belonging to a functional group optionally bearing a function
capable of interacting with a reinforcing filler,
[0089] c) a content less than or equal to 15% by weight, relative
to the total weight of the modified diene elastomer, of a species
chain-end functionalized by a functional group bearing a
--Si(OR).sub.2 function, in which R is a hydrogen atom or an alkyl
radical having 1 to 10 carbon atoms, and optionally a function
capable of interacting with a reinforcing filler, the group being
bonded to the diene elastomer by means of the silicon atom,
[0090] and d) a content less than or equal to 15% by weight,
relative to the total weight of the modified diene elastomer, of
non-functional diene elastomer.
[0091] This modified diene elastomer is also the subject of an
embodiment of the present invention. It gives the rubber
compositions containing it a remarkable and unexpected improvement
of the processing in the uncured state/hysteresis compromise, while
maintaining a satisfactory cold flow resistance without the
addition of an additional coupling or star-branching agent.
[0092] Regarding the star-shaped species b), the modified diene
elastomer preferably comprises at least 10% by weight, relative to
the total weight of the modified diene elastomer, of said
star-shaped species b). Also preferably, the modified diene
elastomer comprises at most 25%, more preferably at most 20% by
weight, relative to the total weight of the modified diene
elastomer, of said star-shaped species b).
[0093] Regarding the non-functional species d), the modified diene
elastomer preferably comprises a content of strictly greater than
0% by weight and less than 10% by weight, relative to the total
weight of the modified diene elastomer, of said non-functional
species d).
[0094] Regarding the coupled species a), the modified diene
elastomer preferably comprises a content of greater than or equal
to 65%, or even greater than or equal to 70%, by weight, relative
to the total weight of the modified diene elastomer, of said
coupled species a).
[0095] Regarding the chain-end functionalized species c), the
modified diene elastomer preferably comprises a content of less
than or equal to 10% by weight, relative to the total weight of the
modified diene elastomer, of said chain-end functionalized species
c).
[0096] The preferred aspects regarding the species a), b), c) and
d) can be combined with one another.
[0097] A diene elastomer is understood according to an embodiment
of the invention to mean any homopolymer obtained by polymerization
of a conjugated diene monomer having from 4 to 12 carbon atoms, or
any block, random, sequential or microsequential 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. In the case of copolymers, these contain from
20% to 99% by weight of diene units, and from 1% to 80% by weight
of vinylaromatic units.
[0098] Preferably, the diene elastomer is selected from
polybutadienes, butadiene-styrene copolymers,
butadiene-styrene-isoprene copolymers, styrene-isoprene copolymers,
butadiene-isoprene copolymers and synthetic polyisoprene.
Advantageously, the diene elastomer is a butadiene-styrene
copolymer.
[0099] The method for synthesizing the modified diene elastomer
according to an embodiment of the invention may be followed, in a
manner known per se, by the steps of recovering the modified
elastomer.
[0100] According to the variants of the invention according to
which the functionalizing agent bears a protected primary or
secondary amine function, the method of synthesis may be followed
by a step of deprotecting the primary or secondary amine. This step
is carried out after the modification reaction. By way of example,
it is possible to react the chains functionalized by the protected
amine group with an acid, a base, a fluorinated derivative such as
tetrabutylammonium fluoride, a silver salt such as silver nitrate,
etc. in order to de-protect this amine function. These various
methods are described in the book "Protective Groups in Organic
Synthesis, T. W. Green, P. G. M. Wuts, Third Edition, 1999". This
deprotecting step may have the effect of hydrolysing all or some of
the hydrolysable alkoxysilane functions of the modified diene
elastomer in order to convert them into silanol functions.
[0101] According to the variants of the invention according to
which the functionalizing agent bears a protected thiol function,
the method of synthesis may be followed by a step of deprotecting
the thiol. This step is carried out after the modification
reaction. By way of example, it is possible to react the chains
functionalized by the protected thiol group with water, an alcohol
or an acid (hydrochloric acid, sulphuric acid, carboxylic acid).
This deprotecting step may have the effect of hydrolysing all or
some of the hydrolysable alkoxysilane functions of the modified
diene elastomer in order to convert them into silanol
functions.
[0102] According to the variants of the invention according to
which the functionalizing agent bears a protected primary or
secondary phosphine function, the method of synthesis may be
followed by a step of deprotecting the phosphine. This step is
carried out after the modification reaction. By way of example, it
is possible to react the chains functionalized by the protected
phosphine group with water, an alcohol or an acid (hydrochloric
acid, sulphuric acid, carboxylic acid). This deprotecting step may
have the effect of hydrolysing all or some of the hydrolysable
alkoxysilane functions of the modified diene elastomer in order to
convert them into silanol functions.
[0103] According to variants of the invention, the method of
synthesis may comprise a step of hydrolysis of the hydrolysable
alkoxysilane functions, by addition of an acidic, basic or neutral
compound as described in document EP 2 266 819 A1. The hydrolysable
functions are then converted into silanol functions.
[0104] The method for synthesizing the modified diene elastomer
according to an embodiment of the invention may be followed, in a
manner known per se, by the steps of recovering the modified
elastomer.
[0105] According to variants of this method, the steps comprise a
stripping step with a view to recovering the elastomer from the
prior steps in dry form. This stripping step may have the effect of
hydrolysing all or some of the hydrolysable alkoxysilane functions
of the modified diene elastomer in order to convert them into
silanol functions. Advantageously, at least 50 to 70 mol % of the
functions may thus be hydrolysed.
[0106] Another subject of the invention is any system intended for
the implementation of the method for the continuous synthesis of a
diene elastomer that is suitable for industrial-scale
application.
[0107] The system according to an embodiment of the invention
comprises a polymerization device fed continuously by a stream of
monomers and a stream of anionic polymerization initiator. The
system according to an embodiment of the invention also comprises a
modifying device fed continuously by a stream of living elastomer
from the polymerization reactor and by a stream of functionalizing
agent.
[0108] The polymerization device may consist, in a manner known per
se, of at least one polymerization reactor. It may be modelled on
at least one continuous stirred reactor, presumed to be perfectly
stirred.
[0109] The device for the functionalization of the living diene
elastomer must enable a flow that satisfies one of equations 1 and
3 defined above. Thus, this device may be modelled on one of the
following models:
a tubular reactor with axial dispersion, or alternatively a tubular
reactor with axial dispersion, in series with at least one
continuous stirred reactor, presumed to be perfectly stirred, or
alternatively, at least one tubular reactor with axial dispersion,
in series with a continuous stirred reactor, presumed to be
perfectly stirred, or alternatively, several tubular reactors with
axial dispersion, in series with several continuous stirred
reactors, presumed to be perfectly stirred, or alternatively, at
least two continuous stirred reactors, presumed to be perfectly
stirred, in series.
[0110] The residence time in each tubular reactor with axial
dispersion is preferably between 0 and 10 minutes, more preferably
between 0.1 and 5 minutes.
[0111] The residence time in each continuous perfectly stirred
reactor, presumed to be perfectly stirred, is preferably between 5
and 60 minutes, more preferably between 10 and 50 minutes,
[0112] By way of illustration and non-limitingly, two systems for
the continuous synthesis of a diene elastomer in accordance with
two embodiments of the method of synthesis of an embodiment of the
invention are more particularly described with reference to FIGS. 1
and 2, each forming a schematic representation of a system.
[0113] FIG. 1 is a diagram of a system that may be incorporated
into a unit for the continuous preparation of a modified diene
elastomer in accordance with one embodiment of the invention
according to which the modifying device comprises one tubular-type
reactor and one continuous stirred reactor.
[0114] FIG. 2 is a diagram of a system that may be incorporated
into a unit for the continuous preparation of a modified diene
elastomer in accordance with one embodiment of the invention
according to which the modifying device comprises two tubular-type
reactors and one continuous stirred reactor.
[0115] The system illustrated in FIG. 1 comprises a polymerization
reactor 1 at least connected to: [0116] several continuous supply
sources including at least a source 2 for supplying polymerization
initiator, a source 3 for supplying at least one monomer, where
appropriate mixed with an inert hydrocarbon-based solvent, and
[0117] an outlet suitable for discharging from said reactor 1,
continuously, the living diene elastomer as an outgoing stream 4
leaving via a discharge device.
[0118] The system illustrated in FIG. 1 also comprises a device 5
for functionalizing the living diene elastomer downstream of the
polymerization reactor 1.
[0119] The functionalizing device is composed of two reactors in
series, namely a reactor 6 of tubular type with Kenics static mixer
and a continuous stirred reactor 7, presumed to be perfectly
stirred.
[0120] The functionalizing device 5 is at least provided with:
[0121] an inlet connected to a source for supplying elastomer
discharged from the polymerization reactor 1, [0122] an inlet
connected to a source 8 for supplying functionalizing agent, and
[0123] an outlet suitable for discharging from the functionalizing
device, continuously, the modified elastomer as an outgoing stream
8.
[0124] The outgoing stream of modified elastomer 9 is conveyed,
downstream of the production line, to a device for recovering the
modified diene elastomer, not illustrated in the figure. This
device may comprise conventional elements such as for example a
granulator, a device intended for eliminating the solvent, the
residual monomer(s), the residual reactant(s) (functionalizing
agent, etc.), etc.
[0125] The system illustrated in FIG. 2 comprises the same elements
as those represented in FIG. 1, up to the polymerization reactor
1.
[0126] The difference lies in the functionalizing device 10, which
is composed, in the system illustrated in FIG. 2, of two
tubular-type reactors 11 and 12 and one continuous stirred reactor
13.
[0127] The aforementioned features of the present invention, and
others, will be better understood on reading the following
description of several exemplary embodiments of the invention,
given by way of illustration and non-limitingly.
[0128] I--Measurements and Tests Used
[0129] (a) Determination of the Distribution of Molar Masses of the
Elastomers by the Size Exclusion Chromatography (Conventional SEC)
Technique
[0130] The SEC (Size Exclusion Chromatography) technique makes it
possible to separate the macromolecules in solution, according to
their size, through columns filled with a porous gel. The
macromolecules are separated according to their hydrodynamic
volume, the bulkiest being eluted first.
[0131] Without being an absolute method, SEC makes it possible to
determine the distribution of the molar masses of a polymer. From
commercial standard products, the various number-average molar
masses (M.sub.n) and weight-average molar masses (M.sub.w) can be
determined and the polydispersity index (I.sub.p=M.sub.w/M.sub.n)
calculated via a "Moore" calibration.
[0132] There is no particular treatment of the polymer sample
before analysis. This sample is simply dissolved in the elution
solvent at a concentration of around 1 gL.sup.-1. Then the solution
is filtered through a filter with a porosity of 0.45 .mu.m before
injection.
[0133] The equipment used is a "Waters Alliance" chromatographic
chain. The elution solvent is either tetrahydrofuran or
tetrahydrofuran+1 vol % of diisopropylamine+1 vol % of
triethylamine, the flow rate is 1 mLmin.sup.-1, the temperature of
the system is 35.degree. C. and the analysis time is 30 min. A set
of two Waters columns having the trade name "Styragel HT6E" is
used. The injected volume of the solution of the polymer sample is
100 .mu.L. The detector is a "Waters 2410" differential
refractometer and the software for processing the chromatographic
data is the "Waters Empower" system.
[0134] The average molar masses calculated are relative to a
calibration curve produced for SBRs having the following
microstructure: 25 wt % of styrene type units, 23 wt % of 1,2-type
units and 50 wt % of trans-1,4-type units.
[0135] (b) Determination of the Distribution of the Chain-End,
Middle-Chain and 3-Arm Star-Shaped Functionalized Chains by the
High-Resolution Size Exclusion Chromatography (High-Resolution SEC)
Technique
[0136] The high-resolution SEC technique is used to determine the
weight percentages of the various populations of chains present in
a polymer sample.
[0137] There is no particular treatment of the polymer sample
before analysis. This sample is simply dissolved in the elution
solvent at a concentration of around 1 gL.sup.-1. Then the solution
is filtered through a filter with a porosity of 0.45 .mu.m before
injection.
[0138] The equipment used is a "Waters Alliance 2695"
chromatographic chain. The elution solvent is tetrahydrofuran, the
flow rate is 0.2 mLmin.sup.-1 and the temperature of the system is
35.degree. C. A set of three identical columns in series is used
(Shodex, length 300 mm, diameter 8 mm). The number of theoretical
plates of the set of columns is greater than 22 000. The injected
volume of the solution of the polymer sample is 50 .mu.L. The
detector is a "Waters 2414" differential refractometer and the
software for processing the chromatographic data is the "Waters
Empower" system.
[0139] The molar masses calculated are relative to a calibration
curve produced for SBRs having the following microstructure: 25 wt
% of styrene type units, 23 wt % of 1,2-type units and 50 wt % of
trans-1,4-type units.
[0140] (c) Characterization of the Microstructure of the Elastomers
by the Near Infrared (NIR) Spectroscopy Technique
[0141] Near infrared (NIR) spectroscopy is used to quantitatively
determine the weight content of styrene in the elastomer and also
the microstructure thereof (relative distribution of the 1,2-,
trans-1,4- and cis-1,4-butadiene units). The principle of the
method is based on the Beer-Lambert law applied to a multicomponent
system. Since the method is indirect, it requires a multivariate
calibration [Vilmin, F.; Dussap, C.; Coste, N. Applied Spectroscopy
2006, 60, 619-29] carried out using standard elastomers having a
composition determined by .sup.13C NMR. The styrene content and the
microstructure are then calculated from the NIR spectrum of an
elastomer film of around 730 .mu.m in thickness. The spectrum is
acquired in transmission mode between 4000 and 6200 cm.sup.-1 with
a resolution of 2 cm.sup.-1, using a Bruker Tensor 37 Fourier
transform near infrared spectrometer equipped with a Peltier-cooled
InGaAs detector.
[0142] (d) Determination of the Mooney ML.sub.(1+4)100.degree. C.
Viscosities for the Elastomers and the Rubber Compositions
According to the ASTM D-1646 Standard
[0143] Use is made of an oscillating consistometer as described in
the ASTM D-1646 standard. The Mooney plasticity measurement is
carried out according to the following principle: the elastomer (or
the composition in the uncured state (i.e. before curing)) is
moulded in a cylindrical chamber heated to 100.degree. C. After
preheating for one minute, the rotor rotates within the test
specimen at 2 rpm and the working torque for maintaining this
movement is measured after rotating for four minutes. The Mooney
plasticity (ML.sub.(1+4)) is expressed in "Mooney units" (MU, with
1 MU=0.83 Nm).
[0144] (e) Determination of the Glass Transition Temperatures (Tg)
of the Elastomers Using a Differential Calorimeter ("Differential
Scanning Calorimeter").
[0145] (f) Determination of the Inherent Viscosity of the
Elastomers at 25.degree. C. Starting from a 0.1 gdL.sup.-1 Solution
of Elastomer in Toluene, According to the Following Principle:
[0146] The inherent viscosity is determined by the measurement of
the flow time t of the polymer solution and of the flow time
t.sub.0 of toluene, in a capillary tube.
[0147] The flow time of toluene and the flow time of the 0.1
gdL.sup.-1 polymer solution are measured in a Ubbelhode tube
(diameter of the capillary: 0.46 mm, capacity of 18 to 22 mL),
placed in a bath thermostatically controlled at 25.+-.0.1.degree.
C.
[0148] The inherent viscosity is obtained by the following
relationship:
h inh = 1 C ln [ ( t ) ( t 0 ) ] ##EQU00005##
[0149] with:
[0150] C: concentration of the toluene solution of polymer in
gdL.sup.-1,
[0151] t: flow time of the toluene solution of polymer in
seconds,
[0152] t.sub.0: flow time of the toluene in seconds,
[0153] h.sub.inh: inherent viscosity expressed in dLg.sup.-1.
[0154] The measurement of the "initial" inherent viscosity, which
is the viscosity of the polymer before functionalization, and of
the "final" inherent viscosity, which is the viscosity of the
polymer after functionalization, makes it possible to calculate the
change in viscosity which is the ratio of said "final" inherent
viscosity to said "initial" inherent viscosity.
[0155] (g) Determination of the Cold Flow of the Elastomers
(CF.sub.(1+6)100.degree. C.) According to the Following Measurement
Method:
[0156] This is a question of measuring the mass of rubber extruded
through a calibrated die over a given time (6 hours) and under set
conditions (T=100.degree. C.). The die has a diameter of 6.35 mm, a
thickness of 0.5 mm and is located at the bottom and at the centre
of a 52 mm diameter hollowed-out cylindrical dish.
[0157] Placed in this device are 40.+-.4 g of rubber preshaped into
a pellet (2 cm thick and 52 mm diameter). A calibrated piston of 1
kg (-5 g) is positioned on the rubber pellet. This assembly is then
placed in an oven at 100.+-.0.5.degree. C.
[0158] Since the conditions are not stabilized during the first
hour in the oven, the product extruded at t=1 hour is cut off and
then discarded.
[0159] The measurement is then continued for 6 hours.+-.5 min,
during which time the product is left in the oven. At the end of
the 6 hours, the sample of product extruded is cut off and then
weighed. The result of the measurement is the mass of rubber
weighed. The lower this result, the better the elastomer withstands
cold flow.
[0160] (h) Determination of the Dynamic Properties Tan d Max
[0161] The dynamic properties, in particular tan d max, are
measured on a viscosity analyser (Metravib VA4000), according to
the ASTM D 5992-96 standard. The response of a sample of vulcanized
composition (cylindrical test specimen with a thickness of 2 mm and
a cross section of 79 mm.sup.2), subjected to a simple alternating
sinusoidal shear stress, at a frequency of 10 Hz, under standard
temperature conditions (23.degree. C.) according to the ASTM D
1349-99 standard is recorded. A peak-to-peak strain amplitude scan
ranging from 0.1% to 50% (forward cycle) then from 50% to 0.1%
(return cycle) is carried out. The result made use of is the loss
factor tan .delta.. For the return cycle, the maximum value of tan
.delta. observed (tan .delta. max) is indicated. This value is
representative of the hysteresis of the material and, in the
present case, of the rolling resistance: the lower the tan .delta.
max value, the lower the rolling resistance.
[0162] (i) Determination of the Distribution of the Species of a
Modified Elastomer.
[0163] 1--Example of Determining the Ratio of the Rate Constants
(K) of the Kinetic Model for Functionalization in a Batch Stirred
Reactor
[0164] Experimental Determination of the Weight Percentage of the
Chain-End, Middle-Chain and (3-Arm) Star-Shaped Functionalized
Chains and of the Change in Viscosity as a Function of the
3-(N,N-dimethylaminopropyl)trimethoxysilane/n-BuLi Molar Ratio
[0165] Introduced into eleven 250 mL glass bottles (Steinie
bottles) are 91.6 mL (70.5 g) of methylcyclohexane, 14.8 mL (9.65
g) of butadiene and 0.49 mL of a 0.078 molL.sup.-1 solution of
tetrahydrofurfuryl ether in methylcyclohexane. After neutralizing
the impurities in the solution to be polymerized by addition of
n-butyllithium (n-BuLi), 1.90 mL of 0.097 molL.sup.-1 n-BuLi in
methylcyclohexane are added. The polymerization is carried out at
60.degree. C.
[0166] After 15 minutes, the degree of monomer conversion reaches
95%. This degree is determined by weighing an extract dried at
140.degree. C., under the reduced pressure of 200 mmHg. A control
bottle (bottle no. 1) is stopped with an excess of methanol with
respect to the lithium. The "initial" inherent viscosity is 0.66
dLg.sup.-1. 0.88 mL of a 0.1 molL.sup.-1 solution of
3-(N,N-dimethylaminopropyl)trimethoxysilane in methylcyclohexane is
added to the living polymer solutions (0.48 molar eq. vs Li)
contained in bottles 2 to 9, 0.73 mL of this same solution is added
to bottle 10 (0.40 molar eq. vs Li) and 1.83 mL of this same
solution are added to bottle 11 (1.0 molar eq. vs Li). After
reacting for 15 minutes at 60.degree. C., the solutions are
antioxidized by addition of 0.4 part per hundred parts of elastomer
(phr) of 4,4'-methylenebis(2,6-tert-butylphenol) and 0.2 part per
hundred parts of elastomer (phr) of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. The polymers
thus treated are separated from the solution by drying at
60.degree. C. under reduced pressure and a stream of nitrogen for
12 hours.
[0167] The "final" inherent viscosities, the changes in viscosity
defined as the ratios of the "final" inherent viscosities to the
"initial" inherent viscosity, and also the weight percentages of
deactivated chains (P), chain-end functionalized chains (PA),
middle-chain functionalized chains (P.sub.2A) and star-shaped
functionalized chains (P.sub.3A) are presented in Table 1
below.
TABLE-US-00003 TABLE 1 Change in the distribution of the P +
PA/P.sub.2A/P.sub.3A species and of the change in viscosity as
function of the 3-(N,N- dimethylaminopropyl)trimethoxysilane/n-BuLi
molar ratio. 3-(N,N- P + PA/ dimethylaminopropyl)trimethoxysilane/
Viscosity P.sub.2A/P.sub.3A Bottle Li molar ratio change (wt. %) 2
0.48 12/77/10 3 0.48 13/77/9 4 0.48 13/78/9 5 0.48 13/82/5 6 0.48
13/83/5 7 0.48 13/83/4 8 0.48 14/83/4 9 0.48 1.54 11/84/4 10 0.40
1.61 15/53/25 11 1.00 1.09 72/20/7
[0168] The living diene elastomer is functionalized according to
the following reaction mechanism:
PLi+A.sup.k.sup.1fiPA R1
PLi+PA.sup.k.sup.2fiP.sub.2A R2
PLi+P.sub.2A.sup.k.sup.3fiP.sub.3A R3
[0169] of which the model of the kinetics of the reactions is
presumed to be:
V.sub.1=k.sub.1[PLi][A] R1
V.sub.2=k.sub.2[PLi][PA] R2
V.sub.3=k.sub.3|PLi]|P.sub.2A] R3
[0170] where:
[0171] k.sub.1, k.sub.2 and k.sub.3 are the rate constants of the
reactions R1, R2 and R3 (m.sup.3/mol/s),
[0172] [PLi] is the concentration of living chains
(mol/m.sup.3),
[0173] [A] is the concentration of the aminotrialkoxysilane
functionalizing agent A (mol/m.sup.3). The functionalizing agent A
is characterized by a ratio of rate constants K
K = k 1 k 2 = k 2 k 3 ##EQU00006##
[0174] [PA] is the concentration of chain-end functionalized
polymer (mol/m.sup.3),
[0175] [P.sub.2A] is the concentration of middle-chain
functionalized polymer (mol/m.sup.3),
[0176] [P.sub.3A] is the concentration of star-shaped polymer
(mol/m.sup.3). [0177] The functionalizing kinetic model
incorporated, according to a person skilled in the art, into a
batch perfectly stirred reactor model (bibliography: Villermeaux,
J; Genie de la reaction chimique [Chemical reaction engineering];
1993) makes it possible to determine the distribution of the PLi,
PA, P.sub.2A and P.sub.3A species. Furthermore, the chains may be
deactivated (P) during the polymerizing and/or functionalizing
step. Thus, the final product is a mixture of deactivated elastomer
(P), chain-end functionalized elastomer (PA), middle-chain
functionalized elastomer (P.sub.2A) and star-shaped elastomer
(P.sub.3A). [0178] For the experimental points of Table 1 above,
the value of K=10.sup.2.+-.1 has been estimated according to the
description of the batch perfectly stirred reactor model, which
represents the reactor used for these experiments. [0179] FIG. 3
represents the distribution of the P, PA, P.sub.2A and P.sub.3A
species as a function of the functionalizing agent/living polymer
chains (PLi) molar ratio: simulated (lines) and measured
(points).
[0180] 2--Example of Determining the Functionalization Kinetics in
a Batch Stirred Reactor
[0181] Experimental Determination of the Weight Percentage of the
Chain-End, Middle-Chain and (3-Arm) Star-Shaped Functionalized
Chains as a Function of the Coupling Time with
3-(N,N-dimethylaminopropyl)trimethoxysilane (.about.0.5 mol. Eq. vs
Li)
[0182] Introduced into twenty-two 250 mL glass bottles (Steinie
bottles) are 91.6 mL (70.5 g) of methylcyclohexane, 14.8 mL (9.65
g) of butadiene and 0.49 mL of a 0.078 molL.sup.-1 solution of
tetrahydrofurfuryl ether in methylcyclohexane. After neutralizing
the impurities in the solution to be polymerized by addition of
n-butyllithium (n-BuLi), 1.90 mL of 0.097 molL.sup.-1 n-BuLi in
methylcyclohexane are added. The polymerization is carried out at
60.degree. C.
[0183] After 15 minutes, the degree of monomer conversion reaches
95%. This degree is determined by weighing an extract dried at
140.degree. C., under the reduced pressure of 200 mmHg, 0.88 mL of
a 0.1 molL.sup.-1 solution of
3-(N,N-dimethylaminopropyl)trimethoxysilane in methylcyclohexane is
added to the living polymer solutions (0.48 molar eq. vs Li)
contained in the remaining twenty-one bottles. After reacting for
10 seconds (bottles 12, 13 and 14), 15 seconds (bottles 15, 16 and
17), 20 seconds (bottles 18, 19 and 20), 30 seconds (bottles 21 and
22), 2 minutes (bottle 23) and 15 minutes (bottles 24, 25, 26, 27,
28, 29, 30, 31 and 32) at 60.degree. C., the solutions are
antioxidized by addition of 0.4 part per hundred parts of elastomer
(phr) of 4,4'-methylenebis(2,6-tert-butylphenol) and 0.2 part per
hundred parts of elastomer (phr) of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. The polymers
thus treated are separated from the solution by drying at
60.degree. C. under reduced pressure and a stream of nitrogen for
12 hours.
[0184] The weight percentages of deactivated chains (P), chain-end
functionalized chains (PA), middle-chain functionalized chains
(P.sub.2A) and star-shaped functionalized chains (P.sub.3A) are
presented in Table 2 below.
TABLE-US-00004 TABLE 2 Change in the distribution of the P +
PA/P.sub.2A/P.sub.3A species as a function of the reaction time
with 3-(N,N-dimethylaminopropyl)trimethoxysilane. Reaction time
with 3-(N,N- dimethylaminopropyl)- P + PA P.sub.2A P.sub.3A Bottle
trimethoxysilane (wt. %) (wt. %) (wt. %) 12 10 s 23 76 1 13 10 s 23
76 1 14 10 s 22 77 1 15 15 s 19 79 1 16 15 s 20 79 1 17 15 s 19 79
1 18 20 s 18 81 1 19 20 s 17 81 1 20 20 s 18 81 1 21 30 s 16 82 2
22 30 s 14 83 2 23 2 min 11 86 2 24 15 min 12 77 10 25 15 min 13 77
9 26 15 min 13 78 9 27 15 min 13 82 5 28 15 min 13 83 4 29 15 min
13 83 4 30 15 min 14 83 4 31 15 min 11 84 4 32 15 min 9 88 3
[0185] By using the same kinetic model from the preceding example
and the value of K=10.sup.2.+-.1, the value of k.sub.1[PLi], in the
kinetic model, is estimated at 10.sup.4.+-.0.2. FIG. 4 compares the
simulated yields to the measured yields as a function of the
reaction time in a batch, perfectly stirred reactor.
[0186] 3--Example of Determining the Ratio of Functionalization
Rate Constants (K) in Continuous Configuration
[0187] In a continuous polymerization pilot plant, at the outlet of
the continuous polymerization stirred reactor, presumed to be
perfectly stirred, a variable amount of functionalizing agent is
injected in order to characterize the continuous functionalizing
section. The functionalizing section is composed of a 4 L, 36
element Kenics static mixer and of a continuous stirred reactor
with a volume of 32.5 L that is presumed to be perfectly stirred.
The minimum residence time in the stirred reactors is 20
minutes.
[0188] Introduced continuously into a 32.5 L continuous stirred
reactor, presumed to be perfectly stirred according to a person
skilled in the art, are methylcyclohexane, butadiene, styrene and
tetrahydrofurfuryl ethyl ether, in the following proportions: mass
flow rate of butadiene=2.85 kgh.sup.-1, mass flow rate of
styrene=1.25 kgh.sup.-1, mass concentration of monomer=11 wt. %, 60
ppm tetrahydrofurfuryl ethyl ether. n-Butyllithium (n-BuLi) is
introduced in an amount sufficient to neutralize the protic
impurities introduced by the various constituents present in the
line inlet. At the reactor inlet, 850 .mu.mol of n-BuLi per 100 g
of monomers are introduced.
[0189] The various flow rates are calculated so that the mean
residence time in the reactor is 40 min. The temperature is
maintained at 90.degree. C.
[0190] The degree of conversion, measured on a sample taken at the
reactor outlet, is 92.6%. On leaving the polymerization reactor,
3-(N,N-dimethylaminopropyl)trimethoxysilane in solution in
methylcyclohexane is added to the living polymer solution in
various amounts (various
3-(N,N-dimethylaminopropyl)trimethoxysilane/PLi molar ratios) in
order to characterize the functionalizing process. This solution is
mixed in a Kenics KMR static mixer consisting of 36 mixing
elements, then passes through a vacuum tube, the total residence
time in the tube being 3 minutes (static mixer+vacuum tube), and a
32.5 L continuous stirred reactor, presumed to be perfectly stirred
according to person skilled in the art, having a residence time of
40 minutes. The polymers are then subjected to an antioxidizing
treatment with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-tert-butylphenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine.
[0191] The polymers thus treated are separated from their solution
by a steam stripping operation, then dried on an open mill at
100.degree. C.
[0192] The inherent viscosity changes (VC) measured are presented
in FIG. 5.
[0193] The functionalizing kinetic model described above is
incorporated, according to a person skilled in the art, into a
tubular reactor model (representative of the Kenics static mixer)
followed by continuous perfectly stirred reactor (representative of
the stirred functionalizing reactor) (bibliography: Villermeaux, J;
Genie de la reaction chimique [Chemical reaction engineering];
1993) and makes it possible to determine the distribution of the
PLi, P, PA, P.sub.2A and P.sub.3A species.
[0194] To make the connection between the distribution of the PLi,
P, PA, P.sub.2A and P.sub.3A species calculated by the
functionalizing kinetic model and the experimental ratio of
inherent viscosities before and after functionalizing (VC), the VC
is calculated theoretically by the equation below:
VC = ( i = 1 n w PiA M _ w , P i A a g i ' M _ w , P a )
##EQU00007##
[0195] where,
[0196] wP.sub.iA is the weight fraction of the P.sub.iA, PLi, P
species;
[0197] Mw is the weight-average molecular weight;
[0198] a is the parameter from the MHS (Mark Houwink Sakurada)
equation and is equal to 0.75
[0199] g.sub.i' is a correction for the star-shaped polymers, for
example:
g i ' = ( 3 i - 2 i 2 ) b ##EQU00008##
[0200] where,
[0201] b is equal to 0.58 (bibliography: Structure and Rheology of
Molten Polymers)
[0202] assuming that the residence time is long enough to be
considered to be infinite, the ratio of the rate constants K is
estimated by minimizing the differences in the experimental and
calculated VC. The value of K is 10.sup.1.+-.1 as represented in
FIG. 5.
[0203] The calculated VC is determined from the distribution of
species calculated by the kinetic model incorporated into the
tubular and continuous perfectly stirred reactor models (FIG.
6).
[0204] II--Tests
[0205] II-1. Elastomer Preparation
Preparation of Polymer 1: Polymer Functionalized by
3-(N,N-dimethylamino-propyl)trimethoxysilane in the Middle of the
Chain According to an Embodiment of the Invention
[0206] Introduced continuously into a 32.5 L continuous stirred
reactor, presumed to be perfectly stirred according to a person
skilled in the art, are methylcyclohexane, butadiene, styrene and
tetrahydrofurfuryl ethyl ether, in the following proportions: mass
flow rate of butadiene=2.85 kgh.sup.-1, mass flow rate of
styrene=1.25 kgh.sup.-1, mass concentration of monomer=11 wt. %, 60
ppm tetrahydrofurfuryl ethyl ether. n-Butyllithium (n-BuLi) is
introduced at the line inlet in an amount sufficient to neutralize
the protic impurities introduced by the various constituents
present in the line inlet. At the reactor inlet, 850 .mu.mol of
n-BuLi per 100 g of monomers are introduced.
[0207] The various flow rates are calculated so that the mean
residence time in the reactor is 40 min. The temperature is
maintained at 90.degree. C.
[0208] The degree of conversion, measured on a sample taken at the
reactor outlet, is 92.6% and the inherent viscosity is 1.68
dLg.sup.-1.
[0209] On leaving the reactor, 386 micromol, per 100 g of monomers,
of 3-(N,N-dimethylaminopropyl)trimethoxysilane in solution in
methylcyclohexane are added to the living polymer solution. This
solution is mixed in a Kenics KMR static mixer consisting of 36
mixing elements, then passes through a vacuum tube, the total
residence time in the tube being 3 minutes (static mixer+vacuum
tube), and in a 32.5 L continuous stirred reactor, presumed to be
perfectly stirred according to a person skilled in the art, having
a residence time of 40 minutes. The polymer is then subjected to an
antioxidizing treatment with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-tert-butylphenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine.
[0210] The polymer thus treated is separated from its solution by a
steam stripping operation, then dried on an open mill at
100.degree. C., in order to obtain the polymer 1 functionalized by
3-(N,N-dimethylaminopropyl)trimethoxysilane in the middle of the
chain according to an embodiment of the invention.
[0211] The inherent viscosity of this polymer 1 is 2.15 dLg.sup.-1,
the change in viscosity is 1.28 and the ML.sub.(1+4)100.degree. C.
viscosity is 72.0. The number-average molar mass Mn of the polymer,
determined by the conventional SEC technique, is 145 000
gmol.sup.-1 and the polydispersity index Ip is 1.72. The
CF.sub.(1+6)100.degree. C. cold flow of this elastomer is 0.452.
The microstructure of this polymer is determined by the NIR method:
the weight content of 1,2-units is 24.1%, this content relating to
the butadiene units. The weight content of styrene is 26.5%.
Preparation of Polymer 2: Polymer Functionalized by
3-(N,N-dimethylamino-propyl)trimethoxysilane in the Middle of the
Chain According to an Embodiment of the Invention
[0212] Introduced continuously into a 32.5 L continuous stirred
reactor, presumed to be perfectly stirred according to a person
skilled in the art, are methylcyclohexane, butadiene, styrene and
tetrahydrofurfuryl ethyl ether, in the following proportions: mass
flow rate of butadiene=2.85 kgh.sup.-1, mass flow rate of
styrene=1.25 kgh.sup.-1, mass concentration of monomer=11 wt. %, 60
ppm tetrahydrofurfuryl ethyl ether. n-Butyllithium (n-BuLi) is
introduced at the line inlet in an amount sufficient to neutralize
the protic impurities introduced by the various constituents
present in the line inlet. At the reactor inlet, 845 .mu.mol of
n-BuLi per 100 g of monomers are introduced.
[0213] The various flow rates are calculated so that the mean
residence time in the reactor is 40 min. The temperature is
maintained at 90.degree. C.
[0214] The degree of conversion, measured on a sample taken at the
reactor outlet, is 92.7% and the inherent viscosity is 1.66
dLg.sup.-1.
[0215] On leaving the reactor, 396 micromol, per 100 g of monomers,
of 3-(N,N-dimethylaminopropyl)trimethoxysilane in solution in
methylcyclohexane are added to the living polymer solution. This
solution is mixed in a Kenics KMR static mixer consisting of 36
mixing elements, then passes through a vacuum tube, the total
residence time in the tube being 3 minutes (static mixer+vacuum
tube). The polymer is then subjected to an antioxidizing treatment
with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-tert-butylphenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine.
[0216] The polymer thus treated is separated from its solution by a
steam stripping operation, then dried on an open mill at
100.degree. C., in order to obtain the polymer 2 functionalized by
3-(N,N-dimethylaminopropyl)trimethoxysilane in the middle of the
chain according to an embodiment of the invention.
[0217] The inherent viscosity of this polymer 2 is 2.12 dLg.sup.-1,
the change in viscosity is 1.28 and the ML.sub.(1+4)100.degree. C.
viscosity is 70.4. The number-average molar mass Mn of the polymer,
determined by the conventional SEC technique, is 142 000
gmol.sup.-1, the molar mass and the polydispersity index Ip is
1.73. The CF.sub.(1+6)100.degree. C. cold flow of this elastomer is
0.614.
[0218] The microstructure of this polymer is determined by the NIR
method: the weight content of 1,2-units is 23.6%, this content
relating to the butadiene units. The weight content of styrene is
26.6%.
Preparation of Polymer 3: Polymer Functionalized by
3-(N,N-dimethylamino-propyl)trimethoxysilane in the Middle of the
Chain
[0219] Introduced continuously into a 32.5 L continuous stirred
reactor, presumed to be perfectly stirred according to a person
skilled in the art, are methylcyclohexane, butadiene, styrene and
tetrahydrofurfuryl ethyl ether, in the following proportions: mass
flow rate of butadiene=2.85 kgh.sup.-1, mass flow rate of
styrene=1.25 kgh.sup.-1, mass concentration of monomer=11 wt. %, 60
ppm tetrahydrofurfuryl ethyl ether. n-Butyllithium (n-BuLi) is
introduced at the line inlet in an amount sufficient to neutralize
the protic impurities introduced by the various constituents
present in the line inlet. At the reactor inlet, 840 .mu.mol of
n-BuLi per 100 g of monomers are introduced.
[0220] The various flow rates are calculated so that the mean
residence time in the reactor is 40 min. The temperature is
maintained at 90.degree. C.
[0221] The degree of conversion, measured on a sample taken at the
reactor outlet, is 93.5% and the inherent viscosity is 1.66
dLg.sup.-1.
[0222] This living polymer solution is introduced continuously into
a second 32.5 L continuous stirred reactor, presumed to be
perfectly stirred according to a person skilled in the art, having
a residence time of 40 minutes, into which 393 micromol, per 100 g
of monomers, of 3-(N,N-dimethylaminopropyl)trimethoxysilane in
solution in methylcyclohexane are introduced continuously.
[0223] The polymer is then subjected to an antioxidizing treatment
with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-tert-butylphenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.
[0224] The polymer thus treated is separated from its solution by a
steam stripping operation, then dried on an open mill at
100.degree. C., in order to obtain the polymer 3 functionalized by
3-(N,N-dimethylaminopropyl)trimethoxysilane in the middle of the
chain.
[0225] The inherent viscosity of this polymer 3 is 2.14 dLg.sup.-1,
the change in viscosity is 1.29 and the ML.sub.(1+4)100.degree. C.
viscosity is 76.4. The number-average molar mass Mn of the polymer,
determined by the conventional SEC technique, is 144 000
gmol.sup.-1, and the polydispersity index Ip is 1.80. The
CF.sub.(1+6)100.degree. C. cold flow of this elastomer is 0.216.
The microstructure of this polymer is determined by the NIR method:
the weight content of 1,2-units is 24.4%, this content relating to
the butadiene units. The weight content of styrene is 27.0%.
[0226] The characteristics of the various elastomers are listed in
Table 3:
TABLE-US-00005 TABLE 3 Comparative Examples example 1 2 3
ML.sub.(1+4) 100.degree. C. 72.0 70.4 76.4 CF.sub.(1+6) 100.degree.
C. 0.452 0.614 0.216 Viscosity change (dL g.sup.-1) 1.28 1.28 1.29
Non-functional chains (%)* 8.0 8.0 8.0 Unfunctionalized living
chains (%)* 0.0 5.4 0.0 Chain-end functionalized chains (%)* 5.4
9.0 8.9 Middle-chain functionalized 70.5 66.8 51.3 chains (%)*
Star-shaped chains (%)* 16.1 10.8 31.8 *Theoretical estimate of the
chain distributions (working on the assumption of the reaction
mechanism (above), the kinetic model (above) and K = 10)
[0227] II-2. Preparation of the Compositions
[0228] The procedure for the tests below is as follows: the
previously synthesized modified diene elastomers are introduced
into an 85 cm.sup.3 Polylab internal mixer, which is filled to 70%
and the initial vessel temperature of which is around 110.degree.
C. Next, the reinforcing fillers, the coupling agent and then,
after 1 to 2 minutes of kneading, the various other ingredients,
with the exception of the vulcanization system, are introduced into
the mixer. Thermomechanical working (non-productive phase) is then
carried out in one step (total kneading time equal to around 5
min), until a maximum "dropping" temperature of 160.degree. C. is
reached. The resulting mixture is recovered and cooled and then the
vulcanization system (sulphur) is added on an external mixer
(homo-finisher) at 25.degree. C., with everything being mixed
(productive phase for around 5 to 6 min.
[0229] The resulting compositions are subsequently calendered in
the form of slabs (thickness of 2 to 3 mm) or thin sheets of rubber
for the measurement of their physical or mechanical properties.
[0230] The rubber compositions are given in Table 4. The amounts
are expressed in parts per 100 parts by weight of elastomer
(phr).
TABLE-US-00006 TABLE 4 Comparative Examples example Composition 1 2
3 Polymer 1 100 Polymer 2 100 Polymer 3 100 Silica (1) 80 80 80
N234 1 1 1 MES oil (2) 15 15 15 Resin (3) 15 15 15 Coupling agent
(4) 6.4 6.4 6.4 ZnO 2.5 2.5 2.5 Stearic acid 2 2 2 Antioxidant (5)
1.9 1.9 1.9 Anti-ozone wax "C32ST" (6) 1.5 1.5 1.5
Diphenylguanidine 1.5 1.5 1.5 Sulphur 1.2 1.2 1.2 Sulphenamide (7)
2 2 2 (1) "Zeosil 1165MP" silica from Rhodia. (2) Catenex .RTM. SBR
from Shell. (3) Dercolyte L120 resin from DRT. (4) "Si69" from
Degussa. (5) N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.
(6) Anti-ozone from Repsol. (7)
N-cyclohexyl-2-benzothiazylsulphenamide.
[0231] The results of dynamic property measurements are expressed
in Table 5 below:
TABLE-US-00007 [0231] TABLE 5 Comparative Examples example
Compositions 1 2 3 tan d max 23.degree. C. 0.197 0.203 0.217
[0232] It is observed that elastomers 1 and 2 have cold flow values
that are considered to be low enough to limit the flow problems,
while minimizing, in the reinforced rubber composition, the tan
.delta. value, expressing a reduced hysteresis. Conversely,
elastomer 3 has an even lower cold flow value, but to the detriment
of the hysteresis of the reinforced rubber composition containing
it. The cold flow of the elastomers/hysteresis of the rubber
composition containing them compromise is optimized and entirely
satisfactory for elastomers 1 and 2 according to an embodiment of
the invention.
* * * * *