A thermoplastic molding composition containing a blend of polycarbonate, vinyl copolymer, such as SAN, and a graft polymer, such as ABS is disclosed. The invention resides in the finding that the incorporation of a compatibilizing agent which comprises a polymeric resin having a number average molecular weight of at least about 21,000 and which is miscible with the grafted phase of the graft polymer and which contains secondary amine reactive groups in its structure yields stable compositions having improved mechanical properties especially at low temperatures.

BACKGROUND OF THE INVENTION 
This invention relates to thermoplastic molding composition and 
particularly to compositions containing a compatibilized blend of an 
aromatic polycarbonate resin and a graft copolymer. The composition is 
useful in making molded articles having improved energy absorption at low 
temperatures. 
Thermoplastic molding compositions containing polycarbonates (PC) and ABS 
polymers have been known for some time. Such compositions which find use 
in a variety of applications are available commercially, for instance, 
from Bayer Corporation under the Bayblend trademark. Also, the art is 
noted to include a large number of relevant patents, including U.S. Pat. 
No. 5,420,181 which disclosed stabilized PC/ABS system, and U.S. Pat. Nos. 
5,672,645 and 5,674,924 which disclosed flame resistant PC/ABS molding 
compositions. However, the energy absorption at low temperatures 
characterizing these compositions is recognized to be inadequate for some 
applications. While it is possible to increase the energy absorbing 
characteristics of the composition by adding rubber, this often results in 
decreased modulus. It has now been found that the incorporation of a 
particular compatibilizer in the polycarbonate/ABS blend improves its 
energy absorption characteristics without the addition of more rubber. 
U.S. Pat. No. 4,713,415 which disclosed a compatibilizing agent for a 
polymeric system containing nylon and ABS is relevant in the present 
context. 
The present invention concerns a thermoplastic molding composition 
comprising: 
A) 20 to 90 parts by weight (pbw) of an aromatic polycarbonate resin, 
B) 4.5 to 70 pbw of a vinyl copolymer, 
C) 5 to 70 pbw of a graft polymer, and 
D) 0.5 to 5 pbw of a compatibilizer. 
Articles molded from the inventive composition are characterized in their 
improved capacity to absorb energy at low temperature. 
DETAILED DESCRIPTION OF THE INVENTION 
The thermoplastic molding composition of the present invention comprises: 
A) 20 to 90 pbw, preferably 30 to 80 pbw and, more preferably, 40 to 70 pbw 
of an aromatic polycarbonate, 
B) 4.5 to 70 pbw, preferably 5 to 60 pbw and, more preferably, 10 to 50 pbw 
of a vinyl copolymer of 
B.1) 50 to 99 percent relative to the weight of the copolymer of at least 
one member selected from the group consisting of styrene, alpha-methyl 
styrene, nucleus-substituted styrene, C.sub.1-8 -alkyl methacrylate and 
C.sub.1-8 -alkyl acrylate and 
B.2) 1 to 50 percent relative to the weight of the copolymer of at least 
one member selected from the group consisting of acrylonitrile, 
methacylonitrile, C.sub.1-8 -alkyl methacrylate, C.sub.1-8 -alkyl 
acrylate, maleic anhydride, C.sub.1-4 -alkyl-N-substituted maleic imide 
and C.sub.1-4 -phenyl-N-substituted maleic imide, 
C) 5 to 70 pbw, preferably 10 to 60 pbw and, more preferably, 20 to 50 pbw 
of a graft polymer containing 
C.1) 5 to 95 percent, preferably 30 to 80 percent, relative to the weight 
of the graft polymer of a grafted phase, and 
C.2) 5 to 95 percent, preferably 30 to 80 percent, relative to the weight 
of the graft polymer of a graft base, 
wherein said grafted phase contains a polymerized mixture of 
C.1.1) 50 to 99 percent, relative to the weight of said mixture, of at 
least one member selected from the group consisting of styrene, 
alpha-methyl styrene, nucleus-substituted styrene, C.sub.1-8 -alkyl 
methacrylate and C.sub.1-8 -alkyl acrylate and 
C.1.2) 1 to 50 percent, relative to the weight of said mixture, of at least 
one polar monomer selected from the group consisting of acrylonitrile, 
methacrylonitrile, C-.sub.1-8 -alkyl methacrylate, C.sub.1-4 -alkyl 
acrylate, maleic anhydride, C.sub.1-4 -alkyl-N-substituted maleic imide 
and C.sub.1-4 -phenyl-N-substituted maleic imide, and 
wherein said graft base includes 
C.2) a crosslinked elastomer in particulate form having an average particle 
diameter (d.sub.50 value) of 0.05 to 5, preferably 0.1 to 0.6, micron and 
a glass transition temperature lower than 10.degree. C., preferably lower 
than -10.degree. C., the sum of the pbw of A, B and C being 100 pbw, and 
D) 0.5 to 5 parts by weight per one hundred parts of the total A, B and C, 
herein phr, of a compatibilizing agent which contains 0.05 to 4 mole 
percent, relative to the moles of monomers making up the compatibilizer, 
of secondary amine functional groups. 
Aromatic polycarbonates within the scope of the present invention are 
homopolycarbonates and copolycarbonates and mixtures thereof. 
The polycarbonates generally have a weight average molecular weight of 
10,000 to 200,000, preferably 20,000 to 80,000 and their melt flow rate, 
per ASTM D-1238 at 300.degree. C., is about 1 to about 65 g/10 min., 
preferably about 2 to 15 g/10 min. They may be prepared, for example, by 
the known diphasic interface process from a carbonic acid derivative such 
as phosgene and dihydroxy compounds by polycondensation (see German 
Offenlegungsschriften 2,063,050; 2,063,052; 1,570,703; 2,211,956; 
2,211,957 and 2,248,817; French Patent 1,561,518; and the monograph H. 
Schnell, "Chemistry and Physics of Polycarbonates", lnterscience 
Publishers, New York, N.Y., 1964, all incorporated herein by reference). 
In the present context, dihydroxy compounds suitable for the preparation of 
the polycarbonates of the invention conform to the structural formulae (1) 
or (2). 
##STR1## 
wherein 
A denotes an alkylene group with 1 to 8 carbon atoms, an alkylidene group 
with 2 to 8 carbon atoms, a cycloalkylene group with 5 to 15 carbon atoms, 
a cycloalkylidene group with 5 to 15 carbon atoms, a carbonyl group, an 
oxygen atom, a sulfur atom, --SO-- or --SO.sub.2 -- or a radical 
conforming to 
##STR2## 
e and g both denote the number 0 to 1; Z denotes F, Cl, Br or C.sub.1 
-C.sub.4 -alkyl and if several Z radicals are substituents in one aryl 
radical, they may be identical or different from one another; d denotes an 
integer of from 0 to 4; and f denotes an integer of from 0 to 3. 
Among the dihydroxy compounds useful in the practice of the invention are 
hydroquinone, resorcinol, bis-(hydroxyphienyl)-alkanes, 
bis-(hydroxyphenyl)-ethers, bis-(hydroxyphenyl)-ketones, 
bis-(hydroxyphenyl)-sulfoxides, bis-(hydroxyphenyl)-sulfides, 
bis-(hydroxyphenyl)-sulfones, and 
.alpha.,.alpha.-bis-(hydroxyphenyl)-diisopropylbenzenes, as well as their 
nuclear-alkylated compounds. These and further suitable aromatic dihydroxy 
compounds are described, for example, in U.S. Pat. Nos. 3,028,356; 
2,999,835; 3,148,172; 2,991,273; 3,271,367; and 2,999,846, all 
incorporated herein by reference. 
Further examples of suitable bisphenols are 
2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A), 
2,4-bis-(4-hydroxyphenyl)-2-methylbutane, 
1,1-bis-(4-hydroxyphenyl)-cyclohexane, 
.alpha.,.alpha.'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene, 
2,2-bis-(3-methyl-4-hydroxyphenyl)-propane, 
2,2-bis-(3-chloro-4-hydroxyphenyl)-propane, 
bis-(3,5-dimethyl-4-hydroxyphenyl)-methane, 
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane, 
bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfide, 
bis-(3,5-dimethyl-4-hydroxy-phenyl)-sulfoxide, 
bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfone, dihydroxybenzophenone, 
2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-cyclohexane, 
.alpha.,.alpha.'-bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene 
and 4,4'-sulfonyl diphenol. 
Examples of particularly preferred aromatic bisphenols are 
2,2,-bis-(4-hydroxyphenyl)-propane, 
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane and 
1,1-bis-(4-hydroxyphenyl)-cyclohexane. 
The most preferred bisphenol is 2,2-bis-(4-hydroxyphenyl)-propane 
(bisphenol A). 
The polycarbonates of the invention may entail in their structure units 
derived from one or more of the suitable bisphenols. 
Among the resins suitable in the practice of the invention are included 
phenolphthalein-based polycarbonates, copolycarbonates and 
terpolycarbonates such as are described in U.S. Pat. Nos. 3,036,036 and 
4,210,741, both incorporated by reference herein. 
The polycarbonates of the invention may also be branched by condensing 
therein small quantities, e.g., 0.05 to 2.0 mol % (relative to the 
bisphenols) of polyhydroxyl compounds. 
Polycarbonates of this type have been described, for example, in German 
Offenlegungsschriften 1,570,533; 2,116,974 and 2,113,374; British Patents 
885,442 and 1,079,821 and U.S. Pat. No. 3,544,514. The following are some 
examples of polyhydroxyl compounds which may be used for this purpose: 
phloroglucinol; 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane; 
1,3,5-tri-(4-hydroxyphenyl)-benzene; 1,1,1-tri-(4-hydroxyphenyl)-ethane; 
tri-(4-hydroxyphenyl)-phenylmethane; 
2,2-bis-4,4-(4,4'-dihydroxydiphenyl)!-cyclohexyl-propane; 
2,4-bis-(4-hydroxy-1-isopropylidine)-phenol; 
2,6-bis-(2'-dihydroxy-5'-methylbenzyl)4-methylphenol; 2,4-dihydroxybenzoic 
acid; 2-(4-hydroxylphenyl)-2-(2,4-dihydroxyphenyl)-propane and 
1,4-bis-(4,4'-dihydroxy-triphenylmethyl)-benzene. Some of the other 
polyfunctional compounds are 2,4-dihydroxybenzoic acid, trimesic acid, 
cyanuric chloride and 3,3-bis-(4-hydroxyphenyl)-2-oxo-2,3-dihydroindole. 
In addition to the polycondensation process mentioned above, other 
processes for the preparation of the polycarbonates of the invention are 
polycondensation in a homogeneous phase and transesterification. The 
suitable processes are disclosed in the incorporated herein by reference, 
U.S. Pat. Nos. 3,028,365; 2,999,846; 3,153,008; and 2,991,273. 
The preferred process for the preparation of polycarbonates is the 
interfacial polycondensation process. 
Other methods of synthesis in forming the polycarbonates of the invention 
such as are disclosed in U.S. Pat. No. 3,912,688, incorporated herein by 
reference, may be used. 
Suitable polycarbonate resins are available in commerce, for instance, 
Makrolon FCR, Makrolon 2600, Makrolon 2800 and Makrolon 3100, all of which 
are bisphenol based homopolycarbonate resins differing in terms of their 
respective molecular weights and characterized in that their melt flow 
indices (MFR) per ASTM D-1238 are about 16.5 to 24, 13 to 16, 7.5 to 13.0 
and 3.5 to 6.5 g/10 min., respectively. These are products of Bayer 
Corporation of Pittsburgh, Pa. 
A polycarbonate resin suitable in the practice of the invention is known 
and its structure and methods of preparation have been disclosed, for 
example in U.S. Pat. Nos. 3,030,331; 3,169,121; 3,395,1119; 3,729,447; 
4,255,556; 4,260,731; 4,369,303 and 4,714,746, all of which are 
incorporated by reference herein. 
The rubber-free, thermoplastic vinyl copolymer, Component B, of the present 
invention, contains 
B.1) 50 to 99 percent relative to the weight of the copolymer of at least 
one member selected from the group consisting of styrene, alpha-methyl 
styrene, nucleus-substituted styrene, C.sub.1-8 -alkyl methacrylate and 
C.sub.1-8 -alkyl acrylate and 
B.2) 1 to 50 percent relative to the weight of the copolymer of at least 
one member selected from the group consisting of acrylonitrile, 
methacrylonitrile, C.sub.1-8 -alkyl methacrylate, C.sub.1-8 -alkyl 
acrylate, maleic anhydride, C.sub.1-4 -alkyl-N-substituted maleic imide 
and C.sub.1-4 -phenyl-N-substituted maleic imide. 
The molecular weight (weight average, as determined by gel permeation 
chromatography) of the copolymer of Component B is in the range of 15,000 
to 200,000. 
Particularly preferred ratios by weight of the components making up the 
copolymer B are 60 to 95 percent of B.1 and 40 to 5 percent of B.2. 
Particularly preferred copolymers B include those of styrene with 
acrylonitrile, optionally with methyl methacrylate; copolymers of 
alpha-methyl styrene with acrylonitrile, optionally with methyl 
methacrylate and copolymers of styrene and alpha-methyl styrene with 
acrylonitrile, optionally with methyl methacrylate. 
The styrene/acrylonitrile copolymers of Component B are known and the 
methods for their preparation by radical polymerization, more particularly 
by emulsion, suspension, solution and bulk polymerization, are also well 
documented in the literature. 
Component C according to the invention, a graft polymer having 
rubber-elastic properties, is well known in the art and is commercially 
available. A general description of such graft polymers is included in 
"Methoden der Organischen Chemie" (Houben Weyl), Vol. 14/1, Georg Thieme 
Verlag, Stuttgart 1961, pages 393-406 and in C. B. Bucknall, "Toughened 
Plastics", Appl. Science Publishers, London 1977, incorporated herein by 
reference. The graft polymer, incorporated as 5 to 70 pbw, preferably 10 
to 60 pbw and, more preferably, 20 to 50 pbw relative to the total A, B 
and C, contains 
C.1) 5 to 95 percent, preferably 30 to 80 percent, relative to the weight 
of the graft polymer of a grafted phase, and 
C.2) 5 to 95 percent, preferably 30 to 80 percent, relative to the weight 
of the graft polymer of a graft base, 
wherein said grafted phase contains a polymerized mixture of 
C.1.1) 50 to 99 percent, relative to the weight of said mixture, of at 
least one member selected from the group consisting of styrene, 
alpha-methyl styrene, nucleus-substituted styrene, C.sub.1-8 -alkyl 
methacrylate and C.sub.1-8 -alkyl acrylate and 
C.1.2) 1 to 50 percent, relative to the weight of said mixture, of at least 
one member selected from the group consisting of acrylonitrile, 
methacrylonitrile, C.sub.1-8 -alkyl methacrylate, C.sub.1-8 -alkyl 
acrylate, maleic anhydride, C.sub.1-4 -alkyl-N-substituted maleic imide 
and C.sub.1-4 -phenyl-N-substituted maleic imide, and 
wherein said graft base includes 
C.2) at least one crosslinked elastomer selected from the group consisting 
of diene and alkylacrylate in particulate form having an average particle 
diameter (d.sub.50 value) of 0.05 to 5, preferably 0.1 to 0.6, micron and 
a glass transition temperature lower than 10.degree. C., preferably lower 
than -10.degree. C. 
Suitable graft polymers have been disclosed in U.S. Pat. Nos. 3,564,077; 
3,644,574 and 3,919,353 which are incorporated herein by reference. 
Particularly preferred graft polymers C are obtainable by grafting of at 
least one (meth) acrylate and/or acrylonitrile and/or styrene as the 
grafted phase onto a graft base containing butadiene polymer having a gel 
content of at least 70% by weight (as measured in toluene), the degree of 
grafting (that is, the ratio between the weight of graft monomers grafted 
on to the graft base and the weight of the graft base) being between 0.15 
and 0.75. In addition to butadiene units, the graft base may contain up to 
50% by weight, based on the weight of the butadiene units, of other 
ethylenically unsaturated monomers, such as styrene, acrylonitrile, esters 
of acrylic or methacrylic acid containing 1 to 4 carbon atoms in the 
alcohol component (such as methyl acrylate, ethyl acrylate, methyl 
methacrylate, ethyl methacrylate), vinyl esters and/or vinyl ethers. The 
preferred graft base contains polybutadiene or is a copolymer of 
polybutadiene/acrylonitrile or a copolymer of polybutadiene/styrene. 
Since the graft monomers do not have to be completely grafted onto the 
graft base in the grafting reaction, graft polymers C in the context of 
the invention are also understood to include products which are obtained 
by polymerization of the graft monomers in the presence of the graft base. 
The average particle size (d.sub.50) is the diameter above which 50% by 
weight of the particles and below which 50% by weight of the particles 
lie. It may be determined by ultracentrifuge measurement (W. Scholtan, H. 
Lange, Kolloid Z. und Z. Polymere 250 (1972), 782-796). 
Other particularly preferred polymers useful as the graft base include 
acrylate rubber having a glass transition temperature below -20.degree. 
C., as the graft base. These include alkyl acrylates, optionally with up 
to 40% by weight of other polymerizable, ethylenically unsaturated 
monomers. Most preferred polymerizable acrylic acid esters include 
C.sub.1-8 -alkyl esters, for example methyl, ethyl, butyl, n-octyl and 
2-ethylhexyl ester and haloalkyl esters, and mixtures of these monomers. 
Preferred "other" polymerizable, ethylenically unsaturated monomers which 
may optionally be used in addition to the acrylates for the production of 
the graft base include, for example, acrylonitrile, styrene, alpha-methyl 
styrene, acrylamides, vinyl C.sub.1-6 -alkyl ethers, methyl methacrylate 
and butadiene. 
Other suitable graft bases are silicone rubbers containing graft-active 
sites of the type described in DE-OS 3 704 657, DE-OS 3 704 655, DE-OS 3 
631 540 and DE-OS 3 631 539. 
For attaining crosslinking, monomers containing more than one polymerizable 
double bond are copolymerized according to known procedures. Examples of 
crosslinking monomers are esters of unsaturated monocarboxylic acids 
containing 3 to 8 carbon atoms and unsaturated monohydric alcohols 
containing 3 to 12 carbon atoms or saturated polyols containing 2 to 4 OH 
groups and 2 to 20 carbon atoms, for example ethylene glycol 
dimethylacrylate, allyl methacrylate; polyunsaturated heterocyclic 
compounds, such as for example trivinyl and triallyl cyanurate; 
polyfunctional vinyl compounds, such as di- and trivinyl benzenes; and 
also triallyl phosphate and diallyl phthalate. Preferred crosslinking 
monomers are allyl methacrylate, ethylene glycol dimethacrylate, diallyl 
phthalate and heterocyclic compounds containing at least three 
ethylenically unsaturated groups. Particularly preferred crosslinking 
monomers are the cyclic monomers triallyl cyanurate, triallyl 
isocyanurate, trivinyl cyanurate, triacryloyl hexahydro-s-triazine, 
triallyl benzenes. 
The crosslinking monomers are incorporated preferably at a level of 0.02 to 
5 percent, preferably 0.05 to 2 percent, based on the weight of the graft 
base. In the case of cyclic crosslinking monomers containing at least 
three ethylenically unsaturated groups, it is of advantage to limit the 
quantity to below 1% by weight of the graft base. 
The gel content of the graft base may be determined in dimethyl formamide 
at 25.degree. C. (M. Hoffmann, H. Kromer, R. Kuhn, Polymeranalytik I und 
II, Georg Thieme-Verlag, Stuttgart 1977). 
The graft polymers may be produced by known methods, such as bulk, 
suspension, emulsion or bulk suspension polymerization. 
Preferred polymers are crosslinked and have gel contents of more than 20% 
by weight, preferably more than 40% by weight and, more preferably, more 
than 60% by weight. 
The compatibilizing agent, Component D, is a polymeric resin having a 
number average molecular weight (measured by gel permeation 
chromatography) of at least about 21,000 and preferably at least about 
30,000 and a weight average molecular weight of at least about 40,000 and 
preferably at least about 60,000, miscible with the grafted phase of the 
grafted rubber (Component C) and containing about 0.05 to 4.0 mole percent 
of secondary amine reactive groups. The secondary amine reactive groups of 
the compatibilizing agent react under the time and temperature conditions 
prevailing in the course of its melt blending with the Components A, B, 
and C, with the carbonate groups of Component A. Determining the 
miscibility of component D in the grafted phase is preferably carried out 
by measurements of the relevant glass transition temperatures. 
An example of the compatibilizer, Component D, is an amine-functional 
copolymer of (a) and (b) where (a) is a vinylaromatic monomer selected 
from the group consisting of styrene, alpha-methyl styrene, 
nucleus-substituted styrene, C.sub.1-8 -alkyl methacrylate and C.sub.1-8 
-alkyl acrylate and where (b) at least one member selected from the group 
consisting of acrylonitrile, methacrylonitrile, C.sub.1-4 -alkyl 
methacrylate, C.sub.1-4 -alkyl acrylate in a weight ratio of (a) to (b) in 
the range of 85:15 to 15:85. 
The vinylaromatic polymer may be functionalized by polymerizing the 
vinylaromatic monomer with monomers (a) and/or (b) with minor amount of 
monomer containing a carboxylic acid such as acrylic or methacrylic acid 
or C.sub.1-2 -monoalkyl esters of diacids such as monomethyl maleate and 
mono-dodecyl fumarate, a dicarboxylic acid such as fumaric acid, maleic 
acid, itaconic acid, aconitic acid or citraconic acid, an anhydride, such 
as maleic, itaconic, aconitic or citraconic anhydride, or other monomers 
containing similar functional groups. Critically, the functional group is 
then converted to a secondary amine. The preparation of a compound 
suitable as a compatibilizer has been disclosed in co-pending U.S. patent 
application Ser. No. 08/992,729 filed Dec. 17, 1997. The preparation of a 
suitable compatibilizer is disclosed in the experimental section below. 
The preferred Component D is a terpolymer containing styrene, 
alpha-methylstyrene or p-methylstyrene, acrylonitrile and from about 0.05 
to about 4.0 mole percent amine functionality. A more preferred Component 
D is a styrene-acrylonitrile-maleic anhydride terpolymer containing from 
about 0.3 to about 9.5 mole percent maleic anhydride and the most 
preferred contains about I mole percent maleic anhydride. The styrene 
monomer:acrylonitrile weight ratio in Component D is in the range of 85:15 
to 15:85 and is preferably in the range of 80:20 to 50:50. Preferably, the 
same styrene monomer is selected for the graft of component C and the 
compatibilizer, Component D. With such a terpolymer, miscibility with the 
grafted phase of the graft polymer, Component C, is obtained when the 
graft polymer and the compatibilizer both contain styrene and 
acrylonitrile and the weight percentage of the styrene monomer in the 
graft copolymer differs from the weight percentage of styrene monomer in 
Component D by no more than +/-5 percent. 
The preferred amount of Component D in the polyblend is in the range of 0.5 
to 5 percent relative to the total weight of A, B and C. A more preferred 
amount of Component D in the polyblend is 2 to 3 weight percent. 
In addition to the above components, the composition of the invention may 
advantageously contain conventional additives such as plasticizers, 
antioxidants, stabilizers, flame-retardants, fibers, mineral fibers, 
mineral fillers, dyes, pigments and the like in conventional, functional 
amounts. 
The inventive composition was found useful for the preparation of 
thermoplastically molded articles, including injection molded and extruded 
articles. 
The components of the polyblend can be melt blended by any of the known 
customary and convenient processes. Usually, however, the components are 
blended in a high intensity blender such as a Banbury Mixer or twin-screw 
extruder.

The invention is described below with reference to the specific examples 
which are for the purposes of illustration only and are not intended to 
imply any limitation on the scope of the invention. 
COMPONENTS USED 
The polycarbonate used was a linear aromatic polycarbonate resin based on 
Bisphenol A having a melt index of 4.5 grams per 10 minutes at 300.degree. 
C. with 1.2 kg load. 
ABS refers to an emulsion graft containing polymerized styrene and 
acrylonitrile in a weight ratio of 70:30 in the presence of 
polybutadiene/acrylonitrile (93/7 by weight) rubber. It contained 40 
percent by weight rubber. The weight average molecular weight of the 
un-grafted SAN copolymer fraction (determined by gel permeation 
chromatography--GPC) is about 150,000. ASTM Method D-3536-76 is used in 
GPC, modified in that four columns in series using micro Styragel..TM.. (A 
trademark of Waters Assoc.) packing are used with a nominal exclusion 
limit of 5,000 nm, 10,000 nm, 100,000 nm and 1,000,000 nm. The detector is 
an ultraviolet light detector set at wavelength 254 nm. The test samples 
are prepared at a concentration of 0.25 weight percent of polymer in 
tetrahydrofuran. The sample injection size is 0.2 ml and a flow rate of 2 
ml/min. at ambient temperature is used. The grafted rubber has a weight 
average particle size (d.sub.50) of about 0.2 micron, measured by Photon 
Correlation Spectroscopy using a Brookhaven Instrument Company BI-90 
Particle Sizer. 
The ABS polymer is recovered from the emulsion by conventional coagulation, 
filtration and washing. 
SAN refers to a copolymer of styrene and acrylonitrile made by continuous 
bulk polymerization. The copolymer contains 67.2 weight % styrene and 32.5 
weight % acrylonitrile. The number and weight average molecular weights, 
as measured by GPC, are 51,000 and 107,000, respectively. 
Compatibilizer refers to a terpolymer and is prepared as follows: 
A mixture of 49.8 parts styrene, 29.1 parts acrylonitrile, 0.8 parts maleic 
anhydride, 20 parts methylethyl ketone, 0.105 parts t-butyl-2-ethyl-hexyl 
peroxycarbonate (peroxide initiator) and 0.25 parts isooctyl thioglycolate 
(chain transfer agent) were fed to a continuously stirring reactor 
operating at 145.degree. C. at a rate necessary to give a 45 minute 
residence time. The level of solids in the reactor of about 45% is 
achieved at steady state and the polymer solution is continuously 
devolatilized to yield a precursor polymer having 
styrene:acrylonitrile:maleic anhydride in a weight ratio of 66.5:32.5:1.0. 
The weight average molecular weight is about 119,000, measured by GPC and 
intrinsic viscosity (MEK, 25.degree. C.) of 0.45 dl/g. The precursor 
polymer was then fed to a 34 mm Leistritz co-rotating twin screw extruder 
fitted with an injection port, a vacuum vent devolatilization zone, and a 
die face peiletizer. The extruder was operated at 150 RPM and 260.degree. 
C. with a vacuum of 5 to 50 mm Hg. The precursor was fed at a rate of 9.1 
kg/hr. The difunctional amine, 1-(2-aminoethyl)-piperazine, was pumped to 
the injection port at rates from about 1.25 to 2.0 moles per mole of 
anhydride or 2.5 to 4.0 ml/min. 
In each of the examples and the control example, 1.0% of a lubricant, 0.2% 
of an antioxidant and 0.2% of citric acid (the percents based on the total 
weight of the composition) were addled. None of these are believed to have 
criticality in the present context. 
The components were physically blended by an extrusion process. This 
involves a pre-blending step of physically mixing the ABS, SAN, 
polycarbonate, terpolymer and antioxidant and feeding the mixture into a 
34 mm Leistritz twin-screw extruder (L:D=24:1 screw) at about 250 
revolutions per minute at 260.degree.C. The extruder is connected to a die 
also maintained at 260.degree. C. The extruded material is passed through 
a water bath and pelletized. The rate of extrusion is 20 kgs per hour. 
The pelletized blended material is then injection molded into specimens for 
testing according to the procedures as set forth above with the testing 
results concurrently listed for each example in Table 1. The injection 
molding is conducted using an Engel 225 molding machine, possessing a 
general purpose screw with a check ring and a straight through nozzle. The 
minimum injection pressure required to fill the mold is measured as a 
means of assessing the melt viscosity of the composition. 
Multi-axial impact strength was measured on a Fractovis manufactured by 
CEAST according to ASTM 3763. The energy to maximum (E(max)) is the energy 
needed to achieve the yielding of the sample. The energy to failure 
(E(fail)) represents the energy necessary to cause a failure of a sample. 
The samples are conditioned at room temperature and at -30.degree. C. to 
determine the effect of temperature on the performance of the polymer. 
Examples 1 to 6 and Control 1, shown in Table 1, illustrate the effect of 
varying the amount of compatibilizer in the polymer blend. At room 
temperature, no effect of the compatibilizer on energy absorption is 
noted. However, at -30.degree. C., improved energy absorption is observed, 
with the maximum improvement noted at about 3% of compatibilizer. 
TABLE 1 
______________________________________ 
Control 
1 2 3 4 5 6 
______________________________________ 
ABS 25 25 25 25 25 25 25 
SAN 25 24.5 24 23 22 21 20 
Polycarbonate 
50 50 50 50 50 50 50 
Compatibilizer 
0 0.5 1 2 3 4 5 
Stock Temp, .degree. C. 
265 265 265 265 265 265 265 
Mold Temp, .degree. C. 
77 77 77 77 77 77 77 
Molding pressure, 
624 600 609 624 638 653 667 
PSI 
Emax, 23.degree. C. 
38.5 39.3 37.8 38.8 37.6 35.8 34.1 
Efail, 23.degree. C. 
43.9 44.4 43.3 43.5 43.9 43.1 41.2 
Emax, -30.degree. C. 
36.7 41.8 40.7 41.9 43.9 39.5 40.1 
Efail, -30.degree. C. 
41.6 43.8 43.8 43.6 46.1 42.2 42.7 
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Although the invention has been described in detail in the foregoing for 
the purpose of illustration, it is to be understood that such detail is 
solely for that purpose and that variations can be made therein by those 
skilled in the art without departing from the spirit and scope of the 
invention except as it may be limited by the claims.