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Background of the Invention
Polycarbonate polymers are known as being excellent
molding materials since products made therefrom exhibit such
properties as high impact strength, toughness, high transparency, wide temperature limits (high impact resistance
o o
5 below -60 C and a UL. thermal endurance rating of 115 C with
impact), good dimensional stability, good creep resistance,
and the like. However, aromatic polycarbonate resins are
relatively costly to produce and attempts have been made to
reduce this cost by combining the polycarbonate with other
10 monomers or polymers. But not all monomers and polymers
are compatible with polycarbonates and those that are generally modify the excellent molding properties of the polycarbonate
to an extent that the resultant composition has limited used and
15 For example, U. S. Patent 3, 162, 695 discloses blends of
polycarbonate and methyl methacrylate butadiene-styrene (MBS)
which have improved properties such as tensile, elongation,
impact, hardness and the like.
U. S. Patent 3, 431, 224 discloses blends of polycarbonate
20 with one or more members of the class consisting of polyethylene, polypropylene, polyisobutylene, a copolymer of
ethylene and an alkyl acrylate, a copolymer of ethylene and
propylene, a cellulose ester, a polyamide, a polyvinyl acetate,

OMPI an alkyl cellulose ether, and a polyurethane elastomer. These blends are considered to be more resistant to environmental stress crazing and cracking.
U. S. Patent 3, 862, 998 discloses a polycarbonate- styrene/ maleic acid anhydride copolymer blend having improved hot water stability.
U. S. Patent 3, 873, 641 discloses blends of polycarbonate with a mixture of a butadiene polymer and a copolymer of styrene, OQ -methyl styrene, methyl methacrylate and
mixtures thereof, and a copolymer of acrylonitrile, metha-crylonitrile, methyl methacrylate and mixtures thereof. These blends are considered to have improved thermal stability and moduli of elasticity.
U. S. Patent 3, 891, 719 discloses an improved thermo-plastic molding composition consisting of a blend of polycarbonate and a graft copolymer of styrene and acrylonitrile and an acrylic acid ester homo- and/or co-polymer.
U. S. Patent 3, 954, 905 discloses an improved thermoplastic molding composition consisting of a blend of a poly-carbonate and (1) a graft copolyxper of styrene, methyl methacrylate or mixtures thereof and acrylonitrile or acrylic acid esters onto a butadiene homo- or co-polymer; and (2) a copolymer of styrene and/or
or a copolymer of acrylonitrile and/or acrylic acid ester.
U. S. Patent 3, 966, 842 discloses a blend of polycarbonate with a rubber reinforced styrene /maleic anhydride composition having copolymerized therein styrene, maleic anhydride and rubber.
Polycarbonate-polystyrene blends are disclosed and dis-cussed in a paper entitled Structure and Properties of Hetero-phase and Blended Polymers given at the PI Research Meeting No. 4 on April 8, 1975 at the University of- Bristol.

" BU
A ' W1 A blend of tetramethyl bisphenol -A (2, 2-bis (4-hydroxy-phenyl) propane) with polystyrol grafted on natural rubber base to obtain a composition having high impact and long term creep strength is dis closed in a paper entitled Structure and Proper-ties of Multi-Phas e Synthetics - II/Natural Rubber- Modified
Polycarbonates by G. Humme, H. Roehr and V. Serini which
appeared in DieAngewandte Makromalekulare Chemie, 158 / 59
(1977), 85- 94 (No. 860).
While thes e prior art attempts at blending polycarbonate
with other polymers and/or copolymers have resulted in obtaining compositions having limited improved properties , they have been at the expense of greatly modifying the excellent properties of the polycarbonate. Furthermore, the limited improvement in properties of the blends has curtailed their range of application.
Suirci-tary of the invention
It has now been found that polycarbonates can be blended
with one or more polymers to obtain a composition or alloy
having sufficiently good properties to enable the composition or alloy to be used over a wide range of applications .
The compositions or alloys of this invention consist of
binary blends of polycarbonate and polystyrene and ternary
blends of polycarbonate polystyrene and methyl methacrylate
butadiene- styrene (MBS) . While the properties of the polycarbonate are modified, thos e of the polystyrene are improved.
Thus, the binary and ternary blends of the invention result in compositions or alloys that are not only more economical to
produce, but which also exhibit good flow, proces sing, tensile and heat distortion properties enabling them to be used over a wide range of applications .
The term "alloy" as used herein is intended to mean and
should be understood as meaning a composite material made by blending polymers or copolymers with other polymers or elastomers .
A $ W1PO In the practice of this invention, any of the aromatic polycarbonates can be employed that are prepared by reacting a diphenol with a carbonate precursor. Typical of some of the diphenols that can be employed are bisphenol-A (2, 2-bis(4-5 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'-dihydroxydiphenyl) propane, 2, 2-(3, 5, 3', 5'-tetrabromo-4, 4'-dihydroxydiphenyl) propane, (3, 3'-dichloro-4, 4'-dihydroxyphenyl)methane. Other 0 halogenated and nonhalogenated diphenols of the bisphenoltype can also be used such as are disclosed in U. S. Patents 2, 999, 835, 3, 028, 365 and 3, 334, 154.
It is possible to employ two or more different diphenols or a copolymer with a glycol or with hydroxy or acid terminated 5 polyester or with a dibasic acid in the event a carbonate copolymer or interpolymer rather than a homopoly er is desired for use in preparing the aromatic polycarbonate. Blends of any of these materials can also be used to obtain the aromatic polycarbonates.
0 These diphenols can then be employed to obtain the high molecular weight aromatic polycarbonates of the invention which can be linear or branched homopolymers or copolymers as well as mixtures thereof or polymeric blends and which generally have an intrinsic viscosity (IV) of about 0. 40-1. 0 dl/g as measure 5 in methylene chloride at 25 C.
The carbonate precursor used can be either a carbonyl halide, a carbonate ester or a halof ormate. The carbonyl halides can be carbonyl bromide, carbonyl chloride and mixtures thereof. The carbonate esters can be diphenyl carbonate, di-θ(halophenyl) carbonates such as di- (chlorophenyl) carbonate, di- (bromophenyl) carbonate, di-(trichlorophenyl) carbonate, di-(tri- bromophenyl) carbonate, etc. , di- (alkylphenyl) carbonate such as

OM di(tolyl) carbonate, etc., di(naphthyl) carbonate, di- (chloronaphthayl) carbonate, phenyl tolyl
carbonate, chlorophenyl chloronaphthyl carbonate, etc., or mixtures thereof. The haloformates that can be used include bis-haloformates of dihydric phenols (bischloro-formates of hydroquinone , etc.) or glycols (bishaloformates of ethylene glycol, neopentyl glycol, polyethylene glycol, etc.) While other carbonate precursors will occur to those skilled in the art, carbonyl chloride, also known as phosgene, is preferred.
Also included are the polymeric derivatives of dihydric phenol, a dicarboxylic acid and carbonic acid such as disclosed in U.S. Patent 3,169,121 which is incorporated herein by reference, and which are particularly preferred. This class of
compounds is generally referred to as copolyester-carbonates .
Molecular weight regulators, acid acceptors and catalysts can also be used in obtaining the aromatic polycarbonates of this invention. The useful molecular weight regulators include monohydric phenols such as phenol, chroman-I, paratertiary-butylphenol, parabromophenol, primary and secondary amines, etc. Preferably, phenol is employed as' the molecular weight regulator.
A suitable acid acceptor can be either an organic or an inorganic acid acceptor. A suitable organic acid acceptor is a tertiary amine such as pyridine, trieth lamine, dimethylaniline.

tributylamine, etc. The inorganic acid acceptor can be either a hydroxide, a carbonate, a bicarbonate, or a phosphate of an alkali or alkaline earth metal. The catalysts which can be employed are those that typically aid the polymerization of the
diphenol with phosgene. Suitable catalysts include tertiary amines such as trieth lamine, tripropyl-a ine, N,N-dimethylaniline, quaternary ammonium compounds such as, for example, tetraethylammonium bromide, cetyl triethyl ammonium bromide, tetra-n-heptylammonium iodide, tetra-n-propyl ammonium bromide, tetramethylammonium chloride, tetramethyl ammonium hydroxide, tetra-n-butyl ammonium iodide, benzyltrimethyl ammonium chloride and quaternary phosphoniu compounds such as, for example,
n-butyltriphenyl phosphonium bromide and methyltri-phenyl phosphonium bromide.
Also included herein are branched polycarbonates wherein a pol functional aromatic compound is
reacted with the diphenol and carbonate precursor to provide a thermoplastic randomly branched polycarbonate. These polyfunctional aromatic compounds contain at least three functional groups which are carboxyl, carboxylic anhydride, haloformyl, or mixtures thereof. Illustrative of polyfunctional aromatic compounds which can be employed include trimellitic anhydride, trimellitic acid, trimellityl trichloride, 4-chloroformyl phthalic anhydride, pyromellitic acid, pyromellitic dianhydride,
mellitic acid, mellitic anhydride, trimesic acid, benzophenonetetracarboxylic acid, benzophenone-tetracarboxylic anhydride, and the like. The
preferred polyfunctional aromatic compounds are trimellitic anhydride and trimellitic acid or their acid halide derivatives.
Blends of linear and branched aromatic polycarbonates are also included within the scope of this invention.
Other well known materials can also be employed • for their intended function and include such
materials as antistatic agents, mold release agents, thermal stabilizers, ultraviolet light stabilizers, reinforcing fillers such as glass and other inert fillers, forming agents and the like.
The polystyrene resins that can be employed in the practice of this invention are those such as are disclosed in U.S. Patent 4,073,765 and which are commercially available such as from the Foster Grant Company under their product identification 834.'
Illustrative of these styrene resins are those having at least 25 percent by weight polymer units derived from the compound having the formula:

wherein R is hydrogen, lower alkyl or halogen; Z is a member selected from the group consisting of vinyl, hydrogen, chlorine and lower alkyl; and p is a whole number equal to from 0 to 5. The term "styrene resin" as used throughout this disclosure and in the claims and as defined by the above
formula includes, by way of example, homopolymers, such as polystyrene and polychlorostyrene, the modified polystyrenes, such as rubber-modified polystyrenes and the styrene containing copolymers such as the styrene-acrylonitrile copolymers (SAN) , styrene-butadiene copolymers, styrene-maleic
anhydride, styrene-acrylonitrile-butadiene
copolymers (ABS) , poly -methylstyrene, copolymers of ethylvinyl benzene and divinylbenzene, and the like.
Preferably, the styrene resin is a rubber-modified, high impact styrene resin, such as poly-styrene which has been modified with natural and sunthetic rubber, such as polybutadiene, polyisoprene rubbery, copolymers of dienes with other co-monomers, such as styrene, acrylonitrile, acrylic esters and the like, including block copolymers of the A-B-A and A-B type wherein A is a vinyl aromatic, such as styrene, and B is a diene such as butadiene, as well as EPDM rubber and the like. Most preferably, the polystyrene is one modified with a butadiene rubber. The methyl methacrylate- butadiene-styrenes
(MBS) that can be employed in the invention are the same as those disclosed in U.S. Patent 3,162,695 referred to earlier and in U.S. Patent 3,792,122 and which are commercially available from Rohm and Haas Company under their product identification

Preferred Embodiment of the Invention
The following examples are set forth to more fully and clearly illustrate the present invention and are intended to be, and should be construed as being, exemplary and not limitative of the invention. Unless otherwise stated, all parts and percentages are by weight.
One hundred (100) parts of an aromatic polycarbonate, prepared by reacting a copolymer of tetra-bromo-bisphenol-A (2 , 2-bis (4-hydroxyphenyl) propane) and bisphenol-A with phosgene in the presence of an acid acceptor and a molecular weight regulator and having an intrinsic viscosity of 0.57 was mixed with polystyrene and MBS at the weight ratios shown in the Table by tumbling the ingredients together in a laboratory tumbler. The resulting mixture was then fed through an extruder which was operated at about

280°F and the extrudate was comminuted into pellets.

The pellets were then injection molded at about 490°F into test bars of about 6.35 cm x 0.32 cm (2-1/2 in. by 1/8 in.) and into test bars of about 6.35 cm x 1.27 cm (2-1/2 in. by 1/2 in.) by about 0.32 cm (1/8 in.) thick. The test bars (5 for each test listed in the Table) were subject to the test procedures set forth below.
Tensile yield, tensile strength and percent elongation results were determined using the ASTM-D-638 procedure and, impact results were determined in accordance with ASTM-D-256.

The heat- distortion temperature, i.e., heat distortion temperature under load (HDTUL) , for the test specimens was determined in accordance with ASTM-D-648. The results are expressed in degrees at a given pressure which, in each instance, was
18.6 kg/cm2 C264 psi.).
In the Table, "PC" identifies the polycarbonate "PS" identifies the polystyrene and "MBS" identifies the methyl methacrylate butadiene-styrene components of the alloy.

Tensile Yield Tensile Strength Impact
Alloy (wt.%) (psi x 10~3) (psi x 10~3) Elongation (ft./lbs./in.) HDTUL
PC PS MBS kg/cm2x 10"3 kg/cm2x 10~3 (%) kg-cm/cm (°F)C°

1) 100 - 2) - 100 (4.5)0.32 (4.3) .30 53.0 (2.80)15.2 (178)81
3) 100
4) 40 40 20 (5.8)0,41 (5,3) .37 69.7 (4.75)25,8 (209)98 i

5) 40 50 10 (5,9)0.41 (2.3) ,16 32,0 (1.87)10.2 (206)97 -γ

6) 40 60 (5.8)0.41 (5,1) .36 42.6 (2.30)12.5 (204)96
7) 50 50 (5,3)0.37 (5.1) .36 93.9 (7.84)42.6 (234)112

8) 50 25 25 (6.2)0.43 (6,0) ,42 105.0 (9.67)52.6 (232)111

9) 50 50 (6.8)0.48 (6.1) .43 59.3 (2.77)15.1 (216)102

10) 75 - 25 (7.2)0.51 (7.4) .52 89.5 (10,94)59.5 (278)137

11) 75 12.! 12, (7.8)0.55 (7.4) .52 85.4 (12.43)67.6 (274)134

12) 75 25 (8.7)0.62 (6.6) .46 80.6 (4.88)26.5 (274)134

The results in the foregoing Table reveal that good properties are obtained with a binary allo of polycarbonate and polystyrene but that better properties are obtained with the ternary alloy comprising polycarbonate, polystyrene and MBS.