Composition of an aromatic carbonate polymer, a styrene-butadiene styrene radial black copolymer and an acrylate copolymer

A composition comprising an aromatic polycarbonate, a styrene-butadiene-styrene radial block copolymer and an acrylate copolymer useful in molded articles.

BACKGROUND OF THE INVENTION 
High molecular weight aromatic carbonate polymers (aromatic carbonate 
polymer) are well known for their toughness as evidenced by their impact 
strength and other high performance characteristics. However, because of 
their relative difficulty in processing as illustratively exemplified by 
the temperature necessary to mold articles, certain thin wall intricate 
articles useful in engineering applications are very difficult if not 
impossible to economically mold. Therefore, it would be advantageous to 
have an aromatic carbonate polymer containing composition which is readily 
processable but substantially maintains aromatic carbonate polymer 
toughness characteristics in thin section test systems. Concurrent 
upgrading of the toughness characteristics in thick section test systems 
is also desirable. Additionally, improved thermal aging stability is also 
a desirable characteristic. 
DESCRIPTION OF THE INVENTION 
A new composition has been discovered which has these aforesaid toughness 
characteristics of an aromatic carbonate polymer but is readily 
processable and has improved thick section toughness compared with the 
aromatic carbonate polymer. Additionally, the composition has improved 
thermal aging stability. In accordance with the invention there is a 
composition which comprises 
(a) a major amount of an aromatic carbonate polymer, 
(b) a styrene-butadiene-styrene (SBS) radial block copolymer, and 
(c) an acrylate copolymer which is a copolymer of a C.sub.1-5 acrylate and 
a C.sub.1-5 methacrylate. 
Aromatic carbonate polymers in the sense of the present invention are to be 
understood as homopolycarbonates and copolycarbonates and mixtures thereof 
which have average molecular weights 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 25.degree. C. These carbonate polymers 
are derived from dihydric phenols such as, for example, 
2,2-bis(4-hydroxyphenyl)propane (bisphenol-A), 
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'-tetrabromo-4,4'-dihydroxydiphenyl)propane, and 
(3,3'-dichloro-4,4'-dihydroxyphenyl)methane. Other dihydric phenols which 
are also suitable for use in the preparation of the above carbonate 
polymers are disclosed in U.S. Pat. Nos. 2,999,835; 3,028,365; 3,334,154 
and 4,131,575, all of which are incorporated by reference. Bisphenol-A is 
preferred. 
These aromatic carbonate polymers 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. Pat. Nos. 4,018,750 and 4,123,436, herein 
incorporated by reference, or by transesterification processes such as are 
disclosed in U.S. Pat. No. 3,153,008, herein incorporated by reference, as 
well as other processes known to those skilled in the art. 
The aromatic carbonate polymers utilized in the present invention also 
include the polymeric derivatives of a dihydric phenol, a dicarboxylic 
acid, and carbonic acid, or carbonic acid derivatives, for example, 
phosgene, such as are disclosed in U.S. Pat. No. 3,169,131. 
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 carbonate polymer 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 carbonate 
polymer. 
Branched carbonate polymers, such as are described in U.S. Pat. No. 
4,001,184, can also be utilized in the practice of this invention, as can 
blends of a linear carbonate polymer and a branched carbonate polymer. 
The preferred aromatic carbonate polymer is a homopolymer derived from 
bisphenol-A as the dihydric phenol. 
In the styrene-butadiene-styrene radial block copolymer utilized herein, 
the weight ratio of the components is in the range of about 15-50 styrene: 
85-50 butadiene, preferably about 60-70 butadiene: 40-30 styrene. 
Suitable SBS block radial copolymers, as defined above, can be prepared by 
known block copolymerization methods or can be obtained commercially from 
Phillips as Solprene 414. 
The "acrylate" copolymer utilized in the present invention is a copolymer 
of a C.sub.1 -C.sub.5 methacrylate and a C.sub.1 -C.sub.5 acrylate, 
wherein the term "C.sub.1 -C.sub.5 " represents both saturated and 
unsaturated, straight or branched chain aliphatic hydrocarbon radicals 
having from 1 to 5 carbon atoms. 
Although various acrylate copolymers can be employed, the preferred 
copolymer is a multiphase composite interpolymer which comprise a C.sub.1 
-C.sub.5 acrylate and C.sub.1-5 methacrylate as disclosed in U.S. Pat. No. 
4,260,693 and U.S. Pat. No. 4,096,202 both of which are incorporated by 
reference. These interpolymers comprise about 25-95 weight percent of a 
first elastomeric phase and about 75 to 5 weight percent of a final rigid 
thermoplastic phase. One or more intermediate phases are optional, for 
example a midle stage polymerized from about 75 to 100 percent by weight 
styrene. The first stage is polymerized from about 75 to 99.8 weight 
percent C.sub.1 to C.sub.5 alkyl acrylate resulting in an acrylic rubber 
core and crosslinked with 0.1 to 5 weight percent crosslinking monomer and 
further containing 0.1 to 5 percent by weight graftlinking monomer. The 
preferred alkyl acrylate is butyl acrylate. 
The crosslinking monomer is a polyethylenically unsaturated monomer having 
a plurality of addition polymerizable reactive groups all of which 
polymerize at substantially the same rate of reaction. Suitable 
crosslinking monomers include poly acrylic and poly methacrylic esters of 
polyols such as butylene diacrylate and dimethacrylate, trimethylol 
propane trimethacrylate, and the like; di- and trivinyl benzene, vinyl 
acrylate and methacrylate, and the like. The preferred crosslinking 
monomer is butylene diacrylate. 
The graftlinking monomer is a polyethylenically unsaturated monomer having 
a plurality of addition polymerizable reactive groups, at least one of 
which polymerizing at substantially different rate of polymerization from 
at least one other of said reactive groups. The function of the 
graftlinking monomer is to provide a residual level of unsaturation in the 
elastomeric phase, particularly in the latter stages of polymerization 
and, consequently, at or near the surface of the elastomer particles. 
Among the effective graftlinking monomers are allyl group-containing 
monomers of allyl esters of ethylenically unsaturated acids such as allyl 
acrylate, allyl methacrylate, diallyl maleate, diallyl fumarate, diallyl 
itaconate, allyl acid maleate, allyl acid fumarate, and allyl acid 
itaconate. Somewhat less preferred are the diallyl esters of 
polycarboxylic acids which do not contain polymerizable unsaturation. The 
preferred graftlinking monomers are allyl methacrylate and diallyl 
maleate. 
A preferred interpolymer has only two stages, the first stage comprising 
about 60 to 95 percent by weight of the interpolymer and being polymerized 
from a monomer system comprising 95 to 99.8 percent by weight butyl 
acrylate, 0.1 to 2.5 percent by weight butylene diacrylate as crosslinking 
agent, 0.1 to 2.5 percent by weight allyl methacrylate or diallyl maleate 
as a graftlinking agent, with a final stage polymerized from about 60 to 
100 percent by weight methyl methacrylate. 
A preferred multiphase composite interpolymer of the copolymer is 
commercially available from Rohm and Haas as Acryloid KM-330. This 
interpolymer has a weight ratio of about 4 parts n-butyl acrylate to about 
1 part methyl methacrylate, the remainder of the weight provided by the 
crosslinking and graftlinking agents. 
The amount of SBS radial block copolymer present in the composition of the 
present invention can range from about three to about twenty-five percent, 
by weight of the total composition. Preferably, the SBS radial block 
copolymer is present in amounts of from about four to about twelve weight 
percent of the total composition. The amount of the acrylate copolymer 
present in the composition can vary from about 2 to about 20 weight 
percent of the total composition. Preferably, the acrylate copolymer is 
present in amounts of from about 2 to about 15, more preferably about 3 to 
10 weight percent of the total composition. The remainder of the 
composition is aromatic carbonate polymer. The term "total composition" is 
the sum of all the polymeric constituents of the composition. 
It is also regarded to be among the features of this invention to include 
in the composition of the invention conventional additives for purposes 
such as reinforcing, coloring, stabilizing or flame retarding the 
composition in conventional amounts. 
The compositions of the invention are prepared by mechanically blending the 
high molecular weight aromatic polycarbonate with the 
styrene-butadiene-styrene radial block copolymer and the acrylate 
copolymer by conventional methods. Double or twin screw extrusion is 
preferred, particularly where additives are added to the composition.

EXAMPLES 
The following examples are set forth to illustrate the invention and are 
not to be construed to limit the scope of the invention. All percentages 
are on a weight basis of the total composition unless otherwise specified. 
EXAMPLE 1 
Ninety-two (92) parts of an aromatic polycarbonate, 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 25.degree. C., was mixed with three (3) 
parts of Acryloid KM-330, previously identified, and hereinafter referred 
to as acrylate copolymer; five (5) parts of a styrene-butadiene-styrene 
(SBS) radial block copolymer, said copolymer containing 60 weight percent 
butadiene and 40 weight percent styrene. The ingredients were then blended 
together by mechanically mixing them in a laboratory tumbler and the 
resulting mixture was fed to an extruder which was operated at about 
255.degree. C. The resulting extrudate was comminuted into pellets. The 
pellets were injection molded at about 250.degree. C. to 270.degree. C. 
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 numerical superscript refers to 
the percent ductility at the foot lb. value. When H is used as a 
superscript, it refers to a hinged failure. The sample labeled CONTROL was 
a bisphenol-A polycarbonate having an I.V. from about 0.46 to about 0.49 
dl/g. No other polymers were present in the control. 
EXAMPLES 2-3 
Further samples of the composition of the invention were prepared as in 
Example 1 each containing the same kind and quantity of acrylate copolymer 
as in Example 1, (3%). However, the amount of SBS was increased in each 
sample to 10% and 20% respectively. Each increase in SBS concentration 
brought about a concomitant decrease in aromatic polycarbonate 
concentration. The samples were tested as in Example 1. Below are the 
results for the impact test. 
TABLE 1 
______________________________________ 
NOTCHED IZOD, ft-lb/in. 
EXAMPLE SBS WT. % 1/8inch 1/4inch 
______________________________________ 
Control -- 14.8.sup.100 
1.6.sup.0 
1 5 14.0.sup.100 
6.6.sup.60 
2 10 11.9.sup.100 
4.1.sup.H 
3 20 7.9.sup.100 
2.4.sup.H 
______________________________________ 
The results demonstrate that the impact strength of the new composition is 
substantially retained in comparison to the control with respect to the 
1/8" samples. The impact strengths are substantially improved in the 1/4" 
samples. A hinged failure is significantly better than a brittle failure 
in that some of the sample remains in a continuous mass. Processability of 
the novel composition is significantly improved over the control. 
As used in the specification, improved thermal aging stability relates to 
retention of ductility in the Notched Izod test system.