Note: Descriptions are shown in the official language in which they were submitted.
~CI SOll~S
1 This invention relates to a thermoplastic
resin composition. More particularly, it relates to
a thermoplastic resin composition which is transparent,
excellent in mechanical properties, particularly in
elongation and practical strengths, and resistant
to flexural stress clouding~ and has excellent hing-
ing characteristics~ said resin composition consisting
essentially of a block copolymer resin of styrer.e and
butadiene and a liquid butadiene polymer or copolymer
or a modified product thereof, such as, for example,
a low-molecular-weight homopolymer of butadiene or
a low-molecular-weight copolymer of butadiene with
styrene~ or a modified product of these liquid butadiene
polymers with maleic anhydride or by epoxidation.
Although excellent in transparency, elonga-
tion~ and impact strength, resistant to flexural
- stress clouding, and having excellent hinging charac- ir
teristics, conventional styrene-~utadiene block co-
polymers have presented a problem of inferior strengths
of practical significance.
The present inventors have now found that
i~ order to markedly improve the impact strength of
a styrene-butadiene block copolymer resin without
deteriorating other characteristic properties thereof~ ¦
it is very effective to incorporate therein a liquid
butadiene homopolymer or copolymer~ or a modified
product of these liquid pol~ners (hereina~ter referred
to simply as liquid polybutadiene resin).
An objcct of this invention is to provide
a composition conS:istirlg ess~ntially Or a styrene
_l_ ~ ' :
.
:~50~8S
1 butadiene block copolymer resin and a liquid poly-
butadiene resin; said composition being excellent in
transparency and elongation, resistant to flexural
stress clouding~ and having good hinging characteristics
and excellent practical strengths.
Although the reason for the retention in
the present composition of the transparency in~erent
to the styrene-butadiene copolymer is yet to be
elucidated, it seems that the transparency is the
result of so uniform a dispersion of the liquid
polybutadiene resin in the styrene-butadiene block
copolymer resin that the former can no longer be
recognizable as a dispersed phase upon observation
~ of the microstructure by means of an electron micro-
scope.
- ~ The invention is explained below in detail.
The styrene-butadiene block copolymer
resin for use in this invention is that obtained
by polymerizing in an inert solvent 65 to 90% by
. .
weight of styrene and 10 to 35% by weight of butadiene
in the presence of a polymeriz~tion initiator of
the organolithium type. Depending on the mode of
addition of styrene and butadiene~ varlous blocks
can be formed. A preferable block copolymer is
repr~sented by the general formula,
Al - Bl - C - B2 - A2 t
(wherein Al and A2 are non-elastomcric blo-ks com-
prising a polymerized styrene chain; Bl and B2 are
elastom~ric blocks comprising a random copolymer
2 --
~L~50~1~S
1 chain in which styrene and butadiene are uniformly
distributed; C is an elastomeric block comprising a
butadiene homopolymer chain or a styrene-butadiene
eopolymer chain; the proportion of the sum of Al and
A2 in the block copolymer is 40 to 80% by weight;
the proportion of the sum o.f Bl and.B2 in the block
copolymer is 10 to 60% by weight; the proportion of
C in the block copolymer is 0 to 25% by weight and
is always smaller than the proportion of the sum of
Bl and B2; the weight ratio of Al to A2 is in the range
from 2/8 to 8/2; the weight ratio of Bl to B2 is in
the range from 0/10 to 10/0; the weight ratio of
styrene to butadiene in Bl and B2 is in the range
from 10/90 to 75/25; and the weight ratio of styrene
to butadiene in C is in the range from 0/100 to
: 1~/90) and has a total styrene content of 65 to 90%
by weight, a total butadlene content of 10 to 35% by
weight, and an intrinsic viscosity of 0~.35 to 1.8
.dl/g as measured in toluene at 30C.
Of the liquid butadiene polymers, that is,
low-moleeular~weight homopolymers of butadiene~ a
polymer containing a major amount of 1,4-cis eonfigura-
tion is obtained in the presence of a.Ziegler catalyst
such as a catalyst system comprising an organo-
aluminum compound and a niekel eompound; a polymer
containing a major amount o~ trans configuration
is obtained by polymerization of 1~3-butadiene in
the presence of a transi-tion metal catalyst system
o~ the Ziegler type or a radiçal polymerization
initiator; and a polymer cont~ini.ng a major proportion
~50~85
1 of 1,2-vinyl configuration is obtained by polymeriza
tion of l,3-butadiene with a polymerization catalyst
system comprising an elementary alkali metal or an
organoalkali-metal compound. The average molecular .
.weight of these liquid polymers is 300 to 10,000,
preferably 1~000 to 7~000.
The low-molecular-weight copolymer of
-. butadiene and styrene is obtained by polymerizing
40% by weight or less of styrene and 60% by weight
or more of butadiene with a catalyst system of the
Ziegler type and has an average molecular weight of
300 to 5,000.
,
. The low-molecular-weight homopolymer of
butadiene modified with maleic anhydride is obtained
15 preferably by modifying a low-molecular-weight ~ ~.
butadiene polymer having an average molecular weight
: . - of 250 to 5,000 with 20~ by weight or less of maleic
anhydride.
~he low-molecular-weight butadiene homo-
polymer modified by epoxidation is obtained by epoxidiæ-
ing a low-molecular-weight butadiene polymer having
an average molecular weight of 250 to 5J000 with an
organic peracid such as performic acid or peracetic
acid and has an oxi~ane-oxygen content of preferably
0.5 to 20% by weigh-t.
Although the liquid polybutadiene resin
.- content of the present composition is generally
1 to 30~ by weight, the most effective content for
improving the practical strengths without deteriora-
tion in transparency of thè styrene-butadiene block
~ 85
1 copolymer resin depends upon the structure Or the
liquid polybutadiene resin. The liquid tlow-molecular-
weight) butadiene homopQlymer among the liquid poly-
butadiene resins gives good transparency and markedly
improved impact strength when its content of the
present composition is 3 to 27% by weight, the specimen
becoming unbreakable in the Izod impact test particularly
when the content is 10% by weightO If the content is
below 3% by weight~ the improvement in impact strength
is insufficient, while if it exceeds 27% by weight,
the transparency decreases to some extent and also
the impact strength rather decreases. Such tendencies
are generally recognizable when a liquid (low-molecular-
weight) butadiene homopolymer contains a major amount
of 1~4-cis configuration~ trans configuration,
or 1,2-vinyl configuration.
The liquid (low-molecular weight) copolymer
of butadiene and styrene gives a composition excellent
in both transparency and impact strength when its
content of the composition is 3 to 27~ by weight. If
the content is below 3% by weight, the impact streng-th
is unsatisfactory, while if it exceeds 27% by weight,
the transparency becomes decreased.
The liquid (low-mo~ecular-weight) butadiene
2~ polymer modified with maleic anhydride gives a com-
position having good transparency and excellent impact
- strength when its content is 2 to 12% by weight.
If the content is below 2% by weight, the impact
strength is unsatisfactoIy~ w~lile if it excecds 12%
by weight, the transparency is considcrably decreased.
~LID51[)~L85
1 The liquid (low-molecular-weight) butadiene polymer
modified by epoxidation gives a composition having
comparatively good transparency and excellent impact
strength when its content of the composition is 2 to
10% by weight. If the contént is below 2% by weight,
the impact strength is unsatisfactoryg while if it
exceeds 10% by weight, the transparency becomes
markedly inferior.
Blending of the styrene-butadiene block
copolymer and the liquid polybutadiene resin may be
effected by use of customary mixing equipements such
as a mixing roll mill9 Banbury mixer~ and extruder.
Since the present thermoplastic resin composition
thus obtained is excellent in transparency and
elongation, resistant to flexural stress clouding,
and has good hinging characteristics and improved
practical strengths, it is really suitable for use
as a material for sheeting and film.
The present composition can be incorporated
with a plasticizer such as widely used phthalate
esters and dibasic aliphatic acid esters.
The invention is further illustrated below
in detail with reference to Referential Example and
Examples.
Referential Example
Preparation of the styrene-butadiene block
copolyme`r for use in this invention was carried out
in the following manner.
Preparation of styrene-butadiene block
~os~g85
1 copolymer A:
Into a 25-liter autoclave provided with
a stirrer and a jacket, which had been flushed with
nitrogen to replace the air, were charged 15-liters
of dried cyclohexane as solvent, 1.25 kg of styrene,
9.0g o~ tetrahydrofuran, and a n-hexane solution
containing 75 millimoles of n-butyllithium as initiator.
The polymerization was started and after 1.5 hours
o~ polymerization at 60C a second-stage monomer
.
mixture of 1.25 kg of styrene and 1.25 kg of butadiene
was added. The polymerization was continued for
further 3.0 hours at 60C. ~hen~ 1.25 kg of styrene
was added as a third-stage monomer and thé polymeriza-
tion was continued for ~urther 1.5 hours. The poly-
merization was terminated by addition of 50 ml of
ethanol. The resulting viscous polymerizate solution
was mixed with a large quantity of methanol with
. .
vigorous stirring to precipitate a polymer which was
collected by filtration and dried in vacuo. The
polymer, which was obtained in a yield of substantially
100%~ showed on analysis an intrinsic viscosity of
0.74 dl/g as measured in toluene at 30C~ a butadiene
content of 25% by weight, and a melt i.ndex (JIS K 6760)
of 0.5 g/10 min. as measured at l90C and under a load
of 2.16 kg.
Preparation of styrene-butadiene block
copolymer B:
The above procedure was repeated, except
that 1~50 kg of styrene was used as the first-stage
monomer; a second-stage monomer mi~ture of 375 g of
- 7 -
,
- ~ ~05~185
styrene and 375 g of butadiene was added at a constant
rate over a period of 1 hour; 500 g of butadiene was
sdded as the third-stage monomer and polymerization
was continued for 1 hour; a fourth-stage monomer
mixture o~ 375 g of styrene and 375 g of butadiene
was added at a constant rate over a period of 1 hour;
and polymerization was continued after addition of
1.50 kg of styrene as a fifth-stage monomer. There
was obtained a polymer having an intrinsic viscosity
of 0,76 dl/g9 a butadiene content of 25% by weight,
and a melt index of 0O30 g/10 min.
Example 1 ~ '
Compositions were obtained by mixing on
a 8-inch roll mill at a roll-surface temperature
,15 of 150C for 10 to 15 minutes prescribed amounts of
the styrene'-butadiene block copolymer A obtained in
' Referential Example and a liquid high-cis poly-
butadiene having an average molecular weight of
3~000; a liquid 1~2-polybutadiene having an average
molecular weight of 1~000; a liquid styrene-
butadiene copolymer having an average molecular
weight of 1,000 and a styrene content of 20%; a liquid
high-cis polybutadiene having an aver~ge molecular
weight of 520 modified with 5% by weight of maleic
anhydride; or a liquid high-cis polybutadiene having
an average molecular weight of 520 modiI'ied by epoxi-
- dation to contain 9c5% by weight O.r oxirane-oxygen.
The compositlons thus obtaine,d were molded by compres-
sion to yie]d pr~scribed test sp~cimens for physical
~CI 56)18~
testsO
The results obtained were summarized in
Table lo
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`- ! iq~5018~
1 .~ Physical properties shown in Table 1 had
been measured in the following way:
Izod impact strength: According to JIS
K 6871 (notched).
Energy of rupture in high-speed tensile
test: Energy required to rupture
JIS No. 3 dumbbell test specimen at
a testing speed of 500 mm/minD
. Luminous transmittance: According to
- ASTM D 1003 - 52.
Example 2 . ~
. . The procedure of Example 1. was followed,
: . except that the styrene-butadiene block copolymer B
obtained in Referential Example was used. The
resuits obtained were as summarized in Table 2.
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- 13 -
1135
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