Note: Descriptions are shown in the official language in which they were submitted.
~ C A S E 24 1 4
"RADIAL AND BRANCHED BLOCK COPOLYMERS, COMPOSlTIONS WHICH
CONTAIN THEM, THEIR PREPARATION AND THEIR USE IN
BITUMINOUS COMPOSITIONS"
The present invention relates to radial and branched
block copolymers, to the polymeric compositions which
contain them, to the process for preparing them, and to
the;r use in bituminous compositions.
In the art, polymerizing by anionic way suitable
monomers in the presence of metal-alkyl or metal-aryl
catalysts is known, with "living" polymers being
obtained, which are then suitable to undergo further
transformations, as described, e.g., by M.Shwarc,
"Carbanions, Living Polymers and El. Transfer Processes",
Interscience Publishers, J. Wiley ~ Sons, New York, 1968.
; By the technique of the "living" polymers, it is
; possible to prepare linear or radial block copolymers.
Among the linear block copolymers, e.g., polymers of A-B-
A type can be obtained, wherein "A" is a polystyrene
block endowed with non-elastomeric thermoplastic
properties, and "B" is an elastomeric polybutadiene
block.
The radial block copolymers can be obtained by means
of the reaction of the living polymer with a suitable
coupling agent.
In case, e.g., silicon tetrachloride is used,
polymers are obtained, which can be represented by the
formula
Si(B-A)4
wherein B and A can have the above specified meaning.
In the art, the use is also known of such both
linear and radial block copolymers~ in bituminous
2. ~
compositions, for the purpose of improving the general
characteristics of bitumens, in particular their
properties of eLasticity, adhesion and anti-creeping
behaviour.
S For example, in BE-738,281 patent, bituminous
compositions are disclosed, which contain approximately
15% by weight of a linear block copolymer A-B-A, wherein
"A" is a thermoplastic block (in general a polystyrene
block~, and "B" is an elastomeric block, generalLy a
polybutadiene block.
The use of radial block copolymers of polystyrene-
polybutadiene type in bituminous compositions is
disclosed, e.g., in BE-853,210 patent.
Finally, U.S. Patent 4,464,427 discloses bituminous
compositions containing both a linear block copolymer and
a radial block copolymer, belonging to the above
mentioned types.
It was observed that the block copolymers of radial
type give the bituminous compositions into which they are
incorporated, characteristics of adhesion, elasticity,
anticreeping, which are generally better than obtainable
with the use of linear block copolymers.
The larger the number of polymeric segments in the
radial copolymer, the more meaningful such improvement.
Therefore, it would be desirable to have available
block copolymers of radial type with a large number of
polymeric segments linked to the polyfunctional coupling
agent.
But, as a practical matter of fact, such a
realization is limited by the difficulties and/or high
costs to be faced when radial block copolymers are
3.
prepared, which contain more than four segments connected
to said coupling agent.
The present Applicant found now that it is possible
to exceed the present state of the art, and prepare block
copolymers of radial type, containing four polymeric
segments linked to the tetrafunctional coupling agent,
characterized in that said polymeric segments show a
controlled branching degree.
The radial and branched block copolymers of the
present invention are capable of giving the bituminous
compositions into which they are incorporated,
nechanical-technological characteristics which are
unexpectedly improved as compared to the corresponding
radial block copolymers not containing such branchings.
Another purpose of the present invention is
constituted by polymeric compositions which contain said
radial and branched block copolymers.
A further purpose of the present invention is
constituted by the process for the preparation of said
radial and branched block copolymers and of the polymeric
compositions which contain said radial and branched
copolymers.
Still a further purpose of the present inYention is
constituted by the bituminous compositions containing
said radial and branched block copolymersS or said
polymeric compositions.
Other purposes of the invention will become evident
from the following disclosure.
ln particular, according to the present invention,
the radial and branched block copolymers show a
structure:
4 . ~ 7 ~ -~
~A - B) - B tB - A)
q i I m
: A - B - Z - B - A
tA - B) B - (B - A)
P I n
A
wherein: Z is a radical deriv;ng from a
~ tetrafunctional coupling agent;
: A is a polystyrene block;
B is a polybutadiene block
m, o, e, 9 are either 1 or zero, with the
condition that their sum is comprised
within the range of from 1 to 4.
The polystyrene block "A" shows in general a
molecular weight comprised within the range of from
10,000 to 40,000, and preferably comprised within the
range of from 15,000 to 25,000.
The polybutadiene block l'B" shows in general a
molecular weight comprised within the range of from
20,000 to 70,000, and preferably comprised within the
range of from 40,000 to 50,000.
The sum of _, n, p, g is preferably comprised within
the range of from 1 to 3~
The polymeric compositions according to the present
invention contain at least 50% by weight~ and preferably
at least 60~ by weight, of the above disclosed radial and
branched block copolymers, the balance being constituted
by two-block copolymers B-A~ and by "A" homopolymer,
wherein "A" and "B" have the above explained meanings.
The process for preparing such polymeric
compositions comprises the following steps, carried out
sequentially:
~ ~ ~L r~ r~
a) polymerization of styrene monomer, by means of the
technique of the living polymers, and by operat;ng at
a temperature of from approximately 35 C to
approximately 65 C, using catalysts constituted by
metal-alkyl or metal-aryl compounds, to yield a
polystyrene block, hav;ng a molecular weight of from
10,000 to 40,000, containing a metal atom linked to
the end of the polymeric chain: A-M ~wherein "M" is
the metal of the metal-alkyl or metal-aryl catalyst
and "A" is the polystyrene block).
b) polymerization of 1,3-butadiene monomer by the
technique of the living polymers, in the presence of
the polystyrene block wherein the metal atom is linked
to the end of the polymeric chain coming from previous
(a) step, by operating at a temperature of from
approximately 60 C to 100 C, yield a two-block
copolymer, wherein the metal atom is linked to the end
of the polystyrene chain: A-~-M, wherein "A" is the
polystyrene block, "s" is the polybutadiene block
having a molecular weight of from 20,000 to 70,000,
and "M" has the above disclosed meaning.
c) heating of the reaction mixture obtained in the (b)
step, at a temperature comprised within the range of
more than 100 C up to approximately 140 C, generally
comprised within the range of from 110 C to 125 C, for
- a long enough time to cause a grafting of the two-
block copolymer B-A, and to obtain grafted and metal-
containing structures which can be represented by the
formula:
A - B
A - B - M
6.
~ herein A, B, M have the above disclosed meaning.
d) coupl;ng of the metal-containing structures coming
from the (c) step, by means of a tetrafunctional
coupling agent;
e) recovery of the polymeric species from the m;xture
deriving from the coupling reaction of the (d) step,
and, optionally,
f) separation of the radial and branched block copolymers
of the polymeric species recovered in the (e) step.
According to a preferred form of practical
embodiment of the present invention, the styrene
polymerization (the (a) step) and the subsequent
copolymerization with butadiene (the (b) step) are
carried out adiabatically, so that at the end of the (b)
step a temperature is obtained, which is higher than
100 C, up to a maximum of 140 C. The fact that the
temperature, at the end of the copolymerization with
butadiene, is higher than 100 C, is essential in order to
obtain radial and branched block copolymers according to
the present invention.
In fact, if the end temperature of the
copolymerization with butadiene is lower than 100 C, and
a heating to increase such temperature to the previously
mentioned values is not carried out, the reaction of
grafting of the B-A copolymer on the polybutadiene B
blocks does not take place, and the end products, after
the coupling, are not-branched radiaL copolymers.
In practice, the styrene polymerization (the (a)
step) is carried out under anhydrous conditions, as it is
required for the obtainment of living polymers, in
solution in inert hydrocarbon solvents, such as, e.g~,
r~
~3~3~
7.
cyclohexane and n-hexane, at an ;n;tiaL temperature of
about 50 C, us;ng as the catalyst an alkyl-metal or an
aryl-metal compound, ;n part;cular, n-butyl-l;thium or
sec-butyl-l;th;um, ;n a styrene/catalyst molar ratio
compr;sed w;th;n the range of from 1,000 to 5,000, and,
preferably, compr;sed w;th;n the range of from 1,500 to
2,500.
The react;on ;s left proceed for approx;mately 60
m;nutes, unt;l the complete, or substant;ally complete,
convers;on of styrene ;s achieved, and polymeric blocks
of a molecular we;ght compr;sed w;th;n the range of from
10,000 to 4û,000, and, preferably, compr;sed w;thin the
range of from 15,000 to 25,000, are obta;ned.
To the solut;on conta;n;ng the polystyrene blocks
conta;n;ng the metal atom at an end of the;r polymeric
cha;n, such solut;on be;ng at a temperature of
approx;mately 60-65 C, 1,3-butad;ene is added, and,
w;th;n a time of approx;mately 40 minutes, linear
polymers B-A are obtained,- in which the "B" block has a
molecular weight comprised with;n the range of from
20,000 to 70,000, and, preferably, compr;sed w;th;n the
range of from 40,000 to 50,000.
~he solut;on der;v;ng from the copolymer;zat;on with
butad;ene ;s left stay at a temperature h;gher than
100 C, and preferably compr;sed with;n the range of from
- 110 C to 125 C for a time of from 10 to 20 minutes.
After this time per;od, to the mixture a
tetrafunct;onal coupl;ng agent is added, ~h;ch can be
selected from the esters of al;phat;c and aromatic
b;carboxyl;c ac;ds; the chloroder;vat;ves of al;phat;c or
aromat;c hydrocarbons; the chloroder;vat;ves of al;phatic
8. ~ 7 ~ ~
or aromatic silanes; the substituted unsaturated arenes,
such as, e.g., divinylbenzene; tetrachloroderivatives of
tin, silicon, germanium, and, preferably, SiCl4, in a
molar ratio of SiCl4/styrene equivalent to the
stoichiometric, or approximately stoichiometric, ratio.
The coupling reaction is carried out at a
temperature comprised within the range of from 100 C to
140 C, and, preferably, çomprised within the range of
from 110 C to 125 C, for a time of from 5 to 15 minutes,
1û and the yield generally reaches a value of approximately
90% .
To the polymeric species contained in the solution
an amount of from 1 to 1.5% by weight of an antioxidant
is added, and sa;d polymeric species are recovered from
the reaction mixture by solvent str;pping, and drying in
a vacuum oven at 60 C.
The so-obtained polymeric composition can be added
as such to the bituminous compositions, or, as an
alternative, the radial and branched copolymers can be
separated from the other polymeric species.
The polymeric composition deriving from the (e) step
comprises at least 50% by weight, and, preferably, at
least 60% by weight, of the radial and branched
copolymers, the balance to 100% being constituted by the
styrene-butadiene linear copolymer, and by polybutadiene.
The radial and branched block copolymers of the
instant invention are capable of supplying a considerable
improvement in the mechanical and technological
propert;es of the bituminous compositions into which they
are incorporated, relatively to the corresponding not-
branched, radial polymers.
9.
It is furthermore possible to obtain b;tuminous
compos;tions which are endowed with the same
characteristics as of the prior art, by using said
copolymers in amounts which are smaller than known from
the prior art~
Such radial and branched block copolymers of the
present invention can be used in amounts comprised
within the range of from 2 to 30 parts by weight per each
100 parts of bitumen, and, preferably, comprised within
the range of from 8 to 13 parts by weight per each 100
parts of bitumen.
The following Examples are to be considered as being
illustrative and not limitative of the purview of the
invention.
E_3m~
To a reactor of 1 litre of capacity, from which
moisture is removed by means of warm nitrogen, equipped
with stirrer, thermometer and cooling chamber, 400 ml of
anhydrous cyclohexane and 15 y (0.144 mol~ of styrene
distilled over calcium hydride are charged. Cyclohexane
contains 0.035 9 of THF.
The mixture is stirred at 50 C and is kept stirred.
0.047 9 (0.73 mmol) of sec-butyl-lithium is added 35
the polymerization initiator, and the reaction is allo~ed
to proceed for 60 minutes, with the temperature being
maintained at 50 C, until styrene conversion is complete.
At the end of this time period~ 35 9 tO.648 mmol) of
1,3-butadiene is added, and the polymerization is allo~ed
to proceed for 40 minutes.
The end temperature of the polymerization is of
5 C~ The block copolymer, a living copolymer, which is
10. ~3~
formed, is left for one minute at 100 C, and to the
reactor 0.028 9 (0.165 mmol) of SiCl4 is subsequently
added.
The react;on is allowed to procesd for 15 minutes at
97 C, and, at the end of this time period, the obtained
polymeric mass is discharged from the reactor into a
glass flask containing 45 9 of BHT and Poly~ard.
The polymeric solution is then stripped ;n steam
stream, and is dried in a vacuum oven at 60 C for 2
hours.
The polymeric composition was characterized by gel
permeation chromatography, and the results are shown in
Table I.
Tabl__I
Mw tAB) :70.10
Mw (AB) 260.10
Mw/Mn (AB) : 1.03
Mw/Mn (A9) : 1.02
The polymeric composition was used for the
preparation of a bituminous composition, by blending 13
parts of the polymer;c composition with 100 parts of
bitumen (SOLEA 180/200).
The characteristics of the b;tuminous composition
are reported in Table II, in accordance with ASTM D5-65
and ASTM D36-66T Standards.
Ta_le_Il
Viscosity (at 180 C) = 2,100 cps
R;ng Ball = 125 - 130 C
Penetration = 40 - 45 dmm
Exa_ele 2
The same amounts of reactants of Example 1 are used,
* trade name.
v
but the reactions are carried out under adiabatic
conditions: the initial temperature of styrene
polymerization ;s of 60 C, and, within a time of 20
m;nutes, the reaction temperature rises up to reach 65 C,
when monomer conversion ;s complete.
At the end of the copolymer;zat;on with 1,3-
butacliene, the temperature, due to the effect of the
exothermic heat released by the reaction, reaches the
value of 120 C.
The polymeric solution, at the end of the reaction
~ith butad;ene, is left for 15 minutes at 120 C, then the
process is continued by adding silicon tetrachloride, as
disclosed in Example 1.
The characteristics of the polymeric composition are
reported in Table III.
The end polymeric composition is used for preparing
a bituminous composition, by mixing 10 parts of the
polymeric composi~ion with 100 parts of bitumen (SOLEA
180/200).
The characteristics of the so obta;ned bituminous
composition are reported in Table IV, in accordance with
ASTM D5-65 and ASTM D36-66T Standards.
T3bl__III
Mw ~AB) : 100.10
M~ (AB) : 330.10
MwtMn ~A9) : 1.4
Mw/Mn (A9) : 1.4
Ta~ IV
Viscos;ty (at 180 C) = 1,700 cps
Ring Ball = 127 C
Penetration = 56 dmm
