Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~14~93 8CL-2978
The present invention relates to improving
both the aged impact strength and the low temperature
impact strength of high molecular weight, aromatic
polycarbonate resins.
It is well known that polycarbonate resins have
high impact strength below a critical thickness of between
about l/2 and 1/4 inches. ~bove this average thickness the
impact strength of polycarbonate resins is low.
Additionally, the impact strength of polycarbonate resins
decreases rapidly as temperatures decrease below about
-5 C and also after aging the polymers at elevated
temperatures above about 100C. These characteristics
consequently limit the fields of applications of these
resins. Thus, unmodified polycarbonate materials are not
practical for use at low or high temperatures when good
impact strength is required. Therefore, it is desirable
to improve both the impact strength of polycarbonate resins
at low and high temperatures and their aged impact strength
to thereby expand the fields of application of such resins.
It has now been discovered that ternary
compositions, which comprise a high molecular weight,
thermoplastic, aromatic poly-carbonate, an acrylate
copolymer and a butadiene-styrene copolymer, exhibit not
only improved aged impact strength, but certain
formulations thereof also exhibit improved impact strength
at both low and high temperatures when compared to
unmodified polycarbonate resins. These novel compositions
also exhibit good weld-line strength.
High molecular weight, thermoplastic, aromatic
polycarbonates in the sense of the present invention are
to be understood as homopolycarbonates and copolycarbonates
and mixtures thereof which have average molecular weights
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of about 8,000 to more than 200,000, preferably of about
20,000 to 80,000 and an I.V. of 0.40 to 1.0 dl/g as
measured in methylene chloride at 25C. These
polycarbonates are derived from dihydric phenols such as,
for example, 2,2-bis(4-hydroxyphenyl)propane, bis
(4-hydroxyphenyl) methane, 2, 2-bis (4-hydroxy-3-
methylphenyl)propane, 4,4-bis(4-hydroxyphenyl)heptane,
2,2-(3,5,3',5'-tetrachloro-4,4'-dihydroxyphenyl)propane,
2,2-(3,5,3',5'-tetramromo-4,4'-dihydroxydiphenyl) propane,
and (3,3'-dichloro-4,4'-dihydroxydiphenyl)methane. Other
dihydric phenols which are also suitable for use in the
preparation of the above polycarbonates are disclosed in
U.S. Patent No. 2,999,835 - issued September 12, 1961 -
Goldberg; U.S.Patent No. 3,028,365 - issued April 3, 1962 -
Schnell et al; U.S. Patent No. 3,334,154 - issued
August 1, 1967 - Kim; and U.S. Patent No. 4,131,575 -
issued December 26, 1978 - Adelmann.
These aromatic polycarbonates can be manufactured
by known processes, such as, for example, by reacting a
dihydric phenol with a carbonate precursor such as phosgene
in accordance with methods set forth in the above-cited
literature and U.S. Patent No. 4,018,750 - issued April
19, 1977 - Onizawa and U.S. Patent No. 4,123,436 -
issued October 31, 1978 - Holub et al or by
transesterification processes such as are disclosed in
U.S. Patent No. 3,153,008 - issued October 13, 1964 -
Fox, as well as other processes known to those skilled in
the art.
The aromatic polycarbonates utilized in the present
inyention also include the polymeric derivates of a
dihydric phenol, a dicarboxylic acid, and carbonic acid,
such as are disclosed in U.S. Patent No. 3,169~131 -
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issued February 9, 1965 - Kagan et al.
It is also possible to employ two or more
different dihydric phenols or a copolymer of a dihydric
phenol with a glycol or with hydroxy or acid terminated
polyester, or with a dibasic acid in the event a carbonate
copolymer or interpolymer rather than a homopolymer is
desired for use in the preparation of the aromatic
polycarbonate utilized in the practice of this invention.
Also employed in the practice of this invention can be
blends of any of the above materials to provide the aromatic
polycarbonate.
Branched polycarbonates, such as are described in
U.S. patent No. 4,001,184 - issued January 4, 1977 -
Scott, can also be utilized in the practice of this
inyention, as can blends of a linear polycarbonate and a
branched polycarbonate.
The "acrylate" copolymer utilized in the present
invention is a copolymer of a Cl-C5 methacrylate and a
Cl-C5 acrylate, wherein the term "Cl-C5" represents both
saturated and unsaturated, straight or branched chained
aliphatic hydrocarbon radicals having from 1 to 5 carbon
atoms.
Preferred acrylates for use in the copolymer are
methyl acrylate, ethyl acrylate, isobutyl acrylate, 1,
4-butanediol diacrylate, n-butyl acrylate, and 1, 3-butylene
diacrylate. Preferred methacrylates for use in this
copolymer include methyl methacrylate, isobutyl,
methacrylate, 1,3-butylene dimethacrylate, butyl
methacrylate and ethyl methacrylate.
The acrylate portion of the copolymer, based on
the total weight of the copolymer, can range from about
50 to about 85 weight percent. The methacrylate portion of
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the copolymer can range from about 15 to about 50 weight
percent.
The preferred acrylate copolymer for use in this
invention is a copolymer of n-butyl acrylate and methyl
methacrylate in which the weight ratio of the n-butyl
acrylate fraction to the methyl methacrylate fraction in
the copolymer is about 3 to 2.
Suitable acrylate copolymers, as defined above,
can be prepared by methods well known to those skilled
in the a`~t or can be obtained commercially. For example,
Rohm and Haas' Acryloid ~ KM 330 copolymer, which is a
copolymer of n-butyl acrylate and methyl methacrylate, is
suitable for use in the present invention.
In the butadiene-styrene copolymer utilized herein,
the butadiene portion of the copolymer, based on the total
weight of the copolymer, can range from about 15 to about
40 ~eight percent. The styrene portion of the copolymer can
range from about 60 to about 85 weight percent.
In the preferred butadiene-styrene copolymer for
use herein, the weight ratio of the styrene fraction to
the butadiene fraction ranges from about 2 to 1 to about
3 to 1.
Suitable butadiene-styrene copolymers, as defined
above, can be prepared by methods well known to those
skilled in the art or can be obtained commercially. For
example, Phillipe Petroleum K-Resin ~ KR03 BDS polymer is
suitable for use in the present invention.
The amount of the butadiene-styrene copolymer
present in the ternary composition of the present invention
can range from about 0.5 to about 4 parts, by weight, per
hundred parts of the aromatic polycarbonate. Preferably,
the butadiene-styrene copolymer is present in amounts of
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~5~93 8CL-2978
from about 1 to about 3 parts, by weight, per hundred
parts of the aromatic polycarbonate. The amount of the
acrylate copolymer present in the ternary composition
can vary from about 2 to about 6 parts, by weight, per
hundred parts of the aromatic polycarbonate. Preferably,
the acrylate copolymer is present in amounts of from about
3 to 5 parts, by weight, per hundred parts of the aromatic
polycarbonate.
It is also regarded to be among the features of
this invention to include in the ternary polycarbonate
composition conventional additives for purposes such as
reinforcing, coloring or stabilizing the composition in
conventional amounts.
The compositions of the invention are prepared by
mechanically blending the high molecular weight aromatic
polycarbonate with the butadiene-styrene copolymer and the
acrylate copolymer by conventional methods.
The following examples are set forth to
illustrate the invention and are not to be construed to
limit the scope of the invention. In the examples and
comparative study, all parts and percentages are on a
weight basis unless otherwise specified. EXAMPLE 1
Ninety-four and one-half (94.5) parts of an
aromatic poly-carbonate, derived from 2,2-bis(4-hydroxyphenyl)
propane and having an intrinsic viscosity (I.V.) in the
range of from about 0.46 to about 0.49 dl/g as determined
in methylene chloride solution at 25C, was mixed with
four (4~ parts of a copolymer of n-butyl acrylate and methyl
methacrylate (hereinafter acrylate copolymer), said
copolymer having a weight ratio of n-butyl-acr~rlate to
methyl methacrylate of about 3 to 2, and one and one-half
(1.5) parts of a butadiene-styrene copolymer (hereinafter
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referred to as BDS), said copolymer having a weight ratio
of styrene to butadiene of from about 2 to 1 to about 3 to
1. The ingredients were then blended together by
mechanically mixing them in a ].aboratory tumbler and the
resulting mixture was fed to an extruder which was operated
at about 265 C. The resulting extrudate was comminuted
into pellets. The pellets were injection molded at about
290C to 310C into test specimens of about 5" by 1/2"
by 1/4" and 5" by 1/2" by 1/8", the latter dimension being
the specimen thickness. Izod impact strengths of these
specimens are measured according to the notched Izod test,
ASTM D256, and are set forth in Table I. The ductile-
brittle transition temperature (D/B), which is the highest
temperature at which a sample begins to exhibit a brittle
mode of failure rather than a ductile mode of failure, was
obtained according to the procedures of ASTM D256 and is
also listed in Table I. The sample labeled CONTROL was
obtained from a polycarbonate resin having an I.V. from
about 0.46 to about 0.49 dl/g and was prepared without
either the acrylate copolymer of BDS. EXAMPLE 2
The procedure of Example 1 was repeated exactly,
except that the weight parts of polycarbonate, acrylate
copolymer and BDS in the test specimen were, respectively,
96, 3 and 1. The results of the notched Izod impact
tests and the B/D are listed in Table 1. EXAMPLE 3
The procedure of Example 1 was repeated exactly,
except that the weight parts of polycarbonate, acrylate
copolymer and BDS in the test specimen were, respectively,
95, 4 and 1. The results of the notched Izod impact
tests are listed in Table I.
~5~)93
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5~3
8CL-2978
EXAMPLE 4
The procedure of Example l was followed exactly,
and the resulting composition, which contained 94.5 weight
parts polycarbonate, 4 weight parts acrylate copolymer,
and 1.5 weight part BDS, was tested, using the notched Izod
test, for subzero temperature impact performance of 1/8"
thick samples which were each maintained at -18C and
-29C for 45 minutes.
The results of these tests, as expressed in ft.
lb./in., are set forth in Table II. The results of these
tests illustrate the excellent low temperature impact
strength of the invention's ternary composition.
COMPARATIVE EXAMPLE 1
The procedure of Example 1 was followed except that
BDS was not added to the mixture. The resulting composition,
which contained 96 weight parts polycarbonate and 4 weight
parts acrylate copolymer, was tested for subzero
temperature impact performance of a 1/8" thick sample at
-18C and -29C. The results of these tests are set forth
in Table II.
TABLE II
Composition of: ImPact Strength, `ft. lb./in.
l/8" Thick at
-18~C -29~C
Example 4 12.4 4.9
Comparative Example 1 4.0 2.6
The invention's ternary compositions also
exhibited good weld-line strength as shown in double gate
Izod impact tests which were conducted to procedures as
specified in ASTM D256.
