Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~9~35~r~3
1 .
CASE 2967
'POLYMERIC COMPOSITIONS AND METHOD FOR PREPARING THEM'
The present invention relates to polymeric
compositions comprising:
a linear copolymer constituted by four alternating blocks
which can be represented by the formula (I) or tlI):
Bl-T-A1-B2-A2 (I)
or
Bl-A~-B2-T-A2 (II)
wherein A1, A2 , Bl, 82 and T respectively are 2
vinylaromatic blocks, 2 dienic bLocks and a portion of
random copolymer formed by dienic and vinylaromatic
monomer units;
and
a copolymer constituted by two blocks, which can be
represented by the formulae ~III) or (IV)
B3-T-A3 tIII)
or
B3~A3 (IV)
wherein:
A3 is a polyvinylaromatic block different from, or equal
to, Al block or A2 block; B3 is a polydienic block
different from, or equal to, Bl block or Bz block, and T
represents the hereinabove seen randorn copolymer~
Also the processes for obtaining both oF the above
said components of said blend simultaneously and during
the same process of synthesis fall within the scope of
the present invention.
The polymeric compositions are endowed w;th very good
characteristics of impact strenyth and processability,
combined with a hiyh transparence, which make them
suitable for all of the uses provided for the
20()5285
transparent, impact resistant materials.
During the past years~ the block copolymers obtained
from the block-copolymerization of conjugated dienic
monomers with vinylaromatic monomers, such as, e.g., the
block copolymers of polybutadiene and polystyrene, and
the block copolymers of polyisoprene with polystyrene,
have shown a particular development. Such copolymers can
be used as such, i.e., in the same form as they are
produced by the living anionic copo1ymerization, as well as
after their partial or total hydrogenation.
This is the case of the linear block copolymers
const;tuted by alternating blocks of polydienes and
polyvinylarenes, with a particular structure and
distribution of the ;ndiv;dual blocks, and having a
structural formula of (I) or (II) type, which show an
extremely favourable balance of physical and mechanical
characteristics. Such block copolymers, as well as their
derivatives, are disclosed by the present Applicant in
the Canadian Patent Application N.551.131 and in a co-
pending patent application.
The blending of block copolymers both with oneanother, and with impact-resistant and non-impact-
resistant polystyrene in order to achieve resins endowed
with improved properties, is known from the prior art as
well.
Compositions and/or block copolymers characterized
by the use of polymeric structures suitable for all of
those uses for which transparent impact-resistant
polystyrene has been used in the past, or is still being
used at present, are reported, e.g., in BP patent No.
1,130,770; BP patent No. 1,335,077; and U.S. patent No.
201~5X~35
3.
4,086,298.
However, the copolymers claimed in these references do
not show an optimum balance of rheoLogic properties,
impact strength and transparency.
Such a balance of properties is further modified by
the possible use of polystyrene which, if, on the one
hand, enhances the optical characteristics, on the other
hand decreases the impact strength of the so-obta;ned
compositions.
The drawbacks which affect the prior art are
overcome by the polymeric compositions according to the
instant invention, constituted by blends of the two block
copolymers respectively complying with the general
formulae tI) or (II) and (III) or (IV), as hereinabove
seen.
In accordance therew;th, and according to a first
aspect thereof, the present invention relates to new
polymeric compositions comprising:
(a) from 40 to 90% by weight of a block copolymer of
general formula (I) or (II);
(b) from 10 to 60~ by weight of a block copolymer of
general formula (III) or (IV), wherein the symbols
Al, Az, A3, Bl, Bz, B3 and T have the hereinabove
seen meaning.
The polymeric compositions according to the present
invention are characterized in that the weight average
molecular weight of the four-block copolymer of formula
(I) or (II) is comprised within the range of from 50,000
to 300,000, whilst the weight aver3ge molecular weight of
the two-block copolymer is comprised within the range of
from 20,000 to 150,000.
zoos~as
In the same compositions, the percentage by weight
of the random block T is comprised within the range of
from 5 to 50%, preferably of from 10 to 25%, as referred
to the total of the two copolymers which constitute the
blend.
In the same compositions, the total amount of
vinylaromatic monomeric units is comprised w;thin the
range of from 60 to 90~ by weight, with the balance to
100% being constituted by the dienic monomeric units.
In the above definitions, the blocks Al, Az, A3 and
Bl, Bz and B3 are practically pure blocks; i.e., they are
nearly totally constituted by vinylarenic and dienic
units.
In the preferred form of practical embodiment, the
blocks Bl, Bz and B3 are polystyrenic blocks and T is a
random styrene-butadiene copolymer.
Still in the preferred form of practicaL embodiment,
the total content of dienic units in the polymeric
composition is comprised within the range of from 20 to
30U/o by weight, and the weight average molecular weight of
the 4-block copolymer is comprised within the range of
from 100,00û to 200,000; and the weight average molecular
weight of the 2-block copolymer is comprised within the
range of from 40,000 to 100,000. To said compositions,
another polystyrenic resin, such as, e.g., polystyrene or
impact-resistant polystyrene, can be added in such an
amount as not to endanger the combination of properties
of the binary composition.
Polymeric compositions according to the present
invention constitute a progress from the viewpoint of the
properties, as compared to the block copolymer of formula
Z005X8S
5.
(I) or (II), when considered on an individual basis.
The linear block copolymer constituted by 4
alternating blocks complying with the general formula tI)
or (II) according to the present invention can be
obtained by polymerization, by operating in an organic
solvent to ~hich suitable amounts are optionally added of
an aliphatic or cycloal;phatic polar compound selected
from among ethers or amines, at temperatures comprised
within the range of from 300C to 1500C, and under
pressures equal to, or higher than, atmospheric pressure,
in the presence of said alkyl-metaL or aryl-metaL
initiators, as customarily used in the synthesis of
polymers according to the living anionic polymerization
method.
Such a synthesis route is disclosed in the
Canadian Patent Applicatiorl N . 551.131 relating to the
disclosure of such copolymers and to the method for
synthetizing them. The two-block copolymers complying
with the above formulae (III) or (IV) can be synthetized,
on the contrary, according to methods as known from the
prior art, as well as by means of the same process of
synthesis as disclosed in the above said patent
application, with the reaction being limited to the first
step. More particularly, for the synthesis of the
copolymers of formula '.(III), metered amounts of butadiene
and styrene are fed to~a reactor as a mixture with one
another, and the polymerization is carried out in a
solution in a hydrocarbon, with a suitable initiator for
the living anionic polymerization, until monomer
conversion is complete or substantially complete; in this
way, a living two-block copolymer
~005X~35
6.
B3-T-A3
is formed, which is constituted by non-pure blocks, i.e.,
by blocks linked to each other by a copolymer;c portion
of chain, constituted by randomly linked monomeric units
of butadiene and styrene.
The polymer formed is recovered after the
preliminary quenching of the living active centres, by
feeding a compound having an acidic character.
The recovery of the polymeric material is carried
out according to the customary methods, such as, e.g., by
steam evaporating the solvent and drying the polymer.
The copoLymer of formula tIV) is obtained by anionic
polymerization, with the sequential addition of the
monomers according to the prior art.
The constituents of the polymeric compositions
according to the instant invention can be blended and
compounded according to the modalit;es and routes as
weLl-known from the prior art. So, e.g., the ingredients
can be blended in the molten state and extruded or mixed
in Banbury type mixers, or they can be blended as
solutions. The present Applicant has also developed --
and they constitute a further purpose of the present
invention -- novel and original processes which make it
possible the 2 components to be produced s;multaneously
and by means of one single synthesis process.
According to one of such processes, the synthesis is
carried out according to the following steps:
(1) a first step during which a mixture is copolymerized
in the presence of initiators, until the conversion
of the monomers is nearly complete, which mixture is
composed by a vinylaromatic monomer and a coniugated
~005285
7.
dienic monomer in an apolar solvent selected from
among the solvents in which poLystyrene having a
weight average molecular weight comprised within the
range of from 30,000 to 120,000 is soluble at
S concentrations of from 5 to 20% by weight. The
initiators are alkyl-lithium compounds in order to
originate a living polymeric system. The solvent
system can contain polar compounds (such as ethers,
amines, and so forth), at a maximum concentration of
0.1% by weight relatively to the solvent.
The percentage by weight of the monomers fed in
mixture to the first reaction step accord;ng to the
process of the present invention, is compr;sed within
the range of from 30 to 60% by weight, relatively to
all of the monomers fed to the reaction. During the
above d;sclosed react;on, a l;v;ng copolymer of
Bl-T-A
type is formed.
t2) A second step, ;n which a percentage of the living
active centres generated during the first reaction
step are quenched by means of the addition to the
reaction system of compounds characterized in that
they contain acidic hydrogen atoms (H20, alcohols,
and so forth ) in their chemical structure.
The amount of active centre quenchers added to the
second step of such a process is comprised within the
range of from lO to 50~ by mol, relative~y to the
moles of initiator fed to the first step.
(3) A third step, in which a conjugated diene is fed to
the living system coming from the second step and
undergoes a complete conversion.
ZOOSX85
t4) A fourth step in which a vinylaromatic monomer is fed
and is nearly totally converted
~5) A fifth step in wh;ch the living active centres are
totally quenched by feeding a compound with an acidic
S reactivity.
In such a way, the blend of the two copolymers
B1-T-Al-B2-A2 ~ B1-T-A
is obtained.
This process is carried out under the above
indicated general conditions of temperature and pressure,
i.e., at temperature values comprised within the range of
from 300c to 1500C and under atmospheric, or
superatmospher;c pressure.
One of the variants constituting alternative routes
for the above said process compr;ses, at the end of the
first step of polymerization of the mixture of monomers,
a second step in which a second aliquot of initiator is
fed.
Such a route leads to the formation of an additional
number of active centres, on which pure block copolymers,
previously described by means of the formula
B3-T-A3
are formed.
In that case, the various sequential steps are:
(1) Synthesis of a pure dienic block;
(2) Synthesis of a pure vinylaromatic block in sequence
to the dienic block;
(3) Feed of a further aliquot of initiator;
(4) Feed of a mixture constituted by a dienic monomer and
a vinylaromatic monomer. The amount of monomers fed
in mixture with each other is comprised within the
Z005X85
9.
range of from 30 to 60% relatively to all of the
monomers fed to the reaction.
(5) Quench;ng of the l;v;ng act;ve centres by means of a
compounds which contains acidic hydrogen atoms.
By means of processes analogous to those as
hereinabove disclosed, two polymer blends can be
respectively obtained:
Bl-Al-B2-T-A2 + B1-A
or
Bl-T-A1-B2-Az ~ Bz-A2.
The initiators preferred for the intended purpose
are those belong;ng to the group consisting of both
linear and branched alkyl-lithium compounds, and, among
them, n-butyl-lithium and sec.-butyl-lithium.
These initiators are customar;ly used in the various
steps of the process in amounts comprised within the
range of from 0.025 to 0.2 parts by weight per each 100
parts of monomer submitted to polymer;zation.
The solvents su;table for the ;ntended purpose are
the apolar solvents and, among them, those ;n which the
polyvinylaromatic blocks with a weight average molecular
weight comprised with;n the range of from 50,000 to
200,000 are soluble; among the most suitable of them
cyclohexane and benzene can be c;ted.
Said solvents can contain polar compounds (such as
ethers, am;nes, and so forth), whose presence also
causes, bes;des an ;ncrease in the speed of reaction of
polymerization which takes in the various steps, an
increase in the weight of the random copolymeric portion
T; among them, tetrahydrofuran is preferred.
The following experimental examples are illustrative
Z0~)5~85
1 0 .
and non limitative of the purview of the present
invention.
Exam el _1
600 9 of anhydrous cyclohexane, 55 9 of (99.9~ pure)
styrene and 13 9 of (99.~5% pure) butadiene are fed to a
stirred reactor of 1000 cm3; the temperature of the mass
is increased up to 500C, and 0.055 9 of sec.-butyl-
lithium (in solution in n~hexane) is fed.
25 minutes later, the react;on mass reaches the
temperature of 75OC and the conversion of the monomers is
practically complete. Then, to the system 0.009 9 of pure
methanol and, in sequence, 7 9 of butadiene are added.
After 10 minutes, the reaction mass reaches the
temperature of 85OC and the conversion of butadiene is
practically complete.
Finally, 25 9 of styrene is added, and 15 minutes
later the conversion is practically complete, with the
temperature of the mass having reached the value of 900C.
The quenching of the l;ving active centres is
carried out by adding 0.5 cc of H20 to the polymeric
solution.
1.0 9 of triphenyl-nonyl-phosphite and 0.2 9 of
Cpentaerythrityl-tetraalkyl-(3,5-di-tert.-butyl-4-
hydroxyphenyl-propionate)~ are added to the polymeric
solution.
The recovery of the polymeric blend is carried out
by means of the steam distillation of the reaction
solvent and subsequent drying in a vacuum oven at 60OC
for 2L hours.
The physical characteristics of the two components
of the polymeric blend are reported in Table No. 1. The
~g~5;~
1 1 .
mechanical and optical propert;es of specimens
compression-moulded at 180C are summarized in Table No.
2.
I - -b 1- - N o
Mw x 10-3 Mw x 10-3 Total Block MFI (4)
Example (BlTA B2A2) (BlTAl) styrene styrene (gl10
No. ~ (1) % (2) % (3) _ minutes)
1 140 80 80 684.5
Ana1Y_1_
GPC (1)
I.R. analysis (2)
Demolition with OSO4 (3)
2000C, 5 kg (4)
Table_No _2
- Transparency % 92
- Tensile strength kg/cmZ 23û
- Elongation at break 'X 35
- Modulus kg/cm~ ~000
- IZOD with notch at 23OC kg x cm/cm 2.5
E__mpl_ 2
850 9 of anhydrous cyclohexane, 37.5 9 of styrene
and 12~5 9 of butadiene are fed to a stirred reactor of
2000 cm3; l:he temperature of the system is increased up
to 55OC, and 0.040 9 of n-butyL-lith;um (in solution in
n-hexane) is fed.
minutes later, the reaction mass reaches -the
temperature of 68OC and the conversion of ~he monomers is
practically complete.
Then, to the reaction solution 0.032 ~ of n-butyl-
lithium and, in sequence, 37.5 9 of butadiene are added;after 20 minutes, the reaction mass reaches the
zaos~s~
temperature of 780C and the conversion is practically
complete.
112.5 9 of styrene is then added to the polymeric
solution and, 60 minutes later, the conversion of the
monomer is complete.
The reaction is then quenched by adding 2 g of
methanol to the solution containing the polymeric blend.
The add;tion of the antioxidant, and the recovery and
drying of the polymer are carried out ;n the same way as
in Example 1.
The physical characteristics of the two components
of the polymeric blend are reported in Table No. 3.
The mechanical and optical properties of specimens
compress;on-moulded at 180C are summarized in Table No.
154~
T_ble_NQ _3
Total Block MFI
Example Mw x 10-3 Mw x 10-3 styrene styrene ~g/10
NQ ____ tBlTA1B2Az) (B2~)____ ___%__- ___.%___ m1_ut__)
2û 2 170 85 75 653.5
T3ble_NQ _~
- Transparency % 86
- Tensile strength kg/cm2 165
- Elongation at break ~ 100
- Modulus kg/cm2 7,000
- IZOD with notch at 230C kg x cm/cm 3.2
E_3m~ol__3
1.2 kg of cyclohexane, 0.3 9 of tetr3hydrofuran, 100
g of styrene and 45 9 of butadiene are fed to a
reactor of 1.5 litres of capacity; the temperature of the
mass is increased up to 500C, and 0.12 g of n-butyl-
13.
lithium (in solution in n-hexane) is fed.
30 minutes later, the re3ct;0n mass reaches the
temperature of 80C and the conversion of the monomers is
practicalLy comple-te.
Then, 0.012 9 of H20 and, in sequence, 15 9 of
butadiene are added to the system.
10 minutes later, the reaction mass reaches the
temperature of 90OC and the conversion of butadiene is
complete.
1û Finally, 40 9 of styrene is added and after 15
minutes of reaction the conversion is complete.
Before recovering the solid polymer, the Living
active centres are quenched by adding 2 9 of isopropyl
alcohol to $he system.
After the addition of antioxidant as in Example 1,
the recovery of the solid polymer is carried out
by steam distillation of the solvent, and subsequent drying of
the solid residue at 65C for 24 hours.
The physical-chemical characteristics are reported in
Table 5.
Table Nc~ 5
Block MFI
Example styrene styrene Mw x 10-3 Mw x 10-3 lg/10
No ____ ___~___ ___%___ (~TAlB2A2) (BlTA2)____ minutes)
3 70 50 130 80 8.5
___mole 4
5 kg of the blend disclosed in Ex3mple 3 is mixed
with 5 kg of commercial crystal polystyrer,e cMwrGpc)
250 x 103]. Said mass is fed to a twin-screw extruder
equipped hlith a heated jacket. This operatior is repeated
~ r~ 3
1 ~, .
twice in order to enable the optimal mixing to be
obtained; the material is then transformed into granules
of 0.5 cm of lensth.
The properties of the so prepared compound are
determined on specimens compression-moulded at 180C and
are reported in Table No. 6.
Table No 6
- MfI 9/10 minutes 8.2
- Transparency % 90
- Tensile strength kg/cm2 185
- Elongation at break % 100
- Modulus kg/cm212,000
- IZOD with notch kg x cm/cm 3.5
Exam,ol_ 5
60û 9 of anhydrous cyclohexane and 30 9 of t99.84%
pure) butadiene are fed to a reactor of 1 litre of
capacity; the mass is heated up to 600C, and 0.09 9 of
sec.-butyl-lithium is added.
20 minules later, the polymerization of butadiene is
complete and the reaction temperature is of about 600C.
70 9 of (99.9~ pure) styrene is therl added to the
system~ and the reaction is complete within a time of 20
minutes; during said time period, the reaction mass
reaches the temperature of 820C.
To the reaction mass 0.058 9 of initiator (n-butyl-
lithium) and, in sequence, a reaction mixture composed by
70 9 of styrene and 30 9 of butadiene are added~
The reaction takes place within a ZS-minutes time
and the end reaction temperature is of 1020C.
Z00~5
At the end of the process, 3 9 of methyl alcohol is
added to the system in order to quench the active
centres.
To the polymeric solution 0.8 9 of TNPP (triphenyl-
nonyl-phosph;te) and 0,15 9 of pentaerythrityl-
tetraalkyl-t3,5-di-tert.-butyl-4-hydroxyphenyl)-
propionate are added to the polymeric solution.
The polymer is recovered by means of the steam
distillation of the solvent, and the recovered polymer is
subsequently dried in a vacuum-oven at 60OC for 36 hours.
The physical-chem;cal characteristics and the
mechanical characteristics of the polymeric blend are
reported in Tables No. 7 and 8.
T3bl__No _7
Total Block MFI
Example styrene styrene Mw x 10-3 Mw x 10-3 (9/10
No ____ ___~/~___ ___Z___ tE;lAl~TA2) (B1TA2)____ mi_ut_s)
56 125 75 10
_3ble_No _8
- Transparency % 85
- Elongation at break % 125
- Tensile strength kg/cm2 1.10
- Modulus kg/cm2 6,800
- IZOD with notch at 230C kg x cm/cm 5.0
