CA1211587A - Polycarbonate resin mixtures - Google Patents

Abstract

POLYCARBONATE RESIN MIXTURES
ABSTRACT OF THE DISCLOSURE
Novel compositions with high resistance to environmental stress cracking and crazing comprise (a) an aromatic carbonate polymer; and (b) a modifier combination therefor comprising (i) a coupled resinous block copolymer of a polymerized vinyl aromatic compound and a polymerized diene; and (ii) an olefin-acrylate or methacrylate copolymer, alone, or in further combination with (iii) a polyolefin.

Description

POLYCARBONATE RESIN MIXTIJRES
BACKGROUND OF TIE INVENT
This invention relates to thermoplastic resin compositions and more particularly is concerned with polycarbonate resin mixtures having improved impact strength, especially in thick sections, and extra-ordinary resistance to environmental stress crazing and cracking.
Aromatic carbonate polymers are well known, commercially available materials having a variety of applications in the plastics art Such carbonate polymers may be prepared by reacting a dihydric phenol, such as

2,2-bis(4-hydroxyphenyl)-propane, with a carbonate precursor, such as phosgene, in the presence of an acid binding agent. Generally speaking, aromatic polycarbonate resins offer a high resistance to the attack of mineral acids, may be easily molded, and are physiologically harm-less as well as stain resistant. In addition, such polyp mews have a high tensile and impact strength (except in thick molded sections), and a dimensional stability surpassing that of other thermoplastic materials. However, in certain applications, the use of aroma-tic polycarbonate resins is limited because they exhibit severe environ-mental stress crazing and cracking. "Environmental stress crazing and cracking" refers to the type of failure which is hastened by the presence of organic solvents such as, for example, gasoline, particularly high octane, no lead gasoline, acetone, Hutton and carbon tetrachloride when when such solvents ore in contact with stressed parts fabricated from aromatic polycarbonate resins. The most significant effect is a loss in vital impact strength and also an increase in brittle type failure. Contact with such solvents may occur, for example, when parts are used under the hood of automobiles, or near the gasoline filler ports thereof, or when solvents are used to clean or decrease stressed parts made from polycarbonate resins At present, no entirely satisfactory means is available for reducing environmental stress crazing and cracking of polycarbonate resins although a variety of methods have been proposed.
In US. Patent 3,431~224, issued March 4, 1969 to Goldblum, assigned to the same assignee as this application, for example, it is proposed to add modifiers to polyp carbonate, in certain proportions, the modifiers comprising at least one member of the class consisting of polyp ethylene, polypropylene, polyisobutylene, a copolymer of ethylene and an ethyl acrylate, a copolymer of ethylene and propylene, a cellulose ester, a polyurethane elastomers While the results with such modifiers are generally excellent, in thin sections, e.g., 1/8 inch, it has been found, as will be shown later herein, that there is a tendency for failure to occur with these modifiers in thicker molded parts, e.g., of 1/4 inch thickness, and such failure is of the undesirable brittle type, especially after exposure to high test gasoline. Another modifier proposed to be added to polycarbonate is reported in Research Disclosure No. 20810, Dow Chemical Company, August, 1981. Data are provided showing that polycarbonate modified with a linear low density polyolefin, namely, ethylene/octene-l copolymer, provide good impact strength at increased part thickness. There is no suggestion therein that such a modifier will significantly enhance resistance to environmental stress crazing and cracking, and, as will be shown hereinafter, soaking a composition

- 3 CLUE 6141 modified with a linear low density copolymer of ethylene and octene-l, even ion -thin sections, causes the impact strength to deteriorate substantially and results in brittle failure. Still other modifiers have been proposed for impact strength improvement t but none of them provides optimum environmental stress crazing and cracking resistance -- applicant's earlier filed commonly assigned Canadian Application Serial No 399,992, filed March 31, 1982; US. Patent No. 4,444,94~, issued April 24, 1984;
and US. Patent No. 4,430,476~ issued February 7, 1984 being expressly mentioned in this connection. The aforementioned Canadian Application Serial No. 399,992 and US. Patent No. 4,444,948 describe polycarbonates modified with a combination of a butadienestyrene block copolymer of the coupled resinous type, an acrylate core-shell inter polymer and, optionally, an olefin/acrylate copolymer. Such compositions process well and are toughened, but there is no disclosure of significant solvent resistance and, as will be shown later herein by themselves, the coupled resinous block copolymers do not provide significant resistance to environment stress crazing and cracking, at relatively low and moderate blending levels, even in thin sections. The aforementioned US. Patent No. 4,430,476 describes polycarbonate resins modified with a combination of the coupled resinous block copolymers and a linear low density polyolefin resin.
There is no mention that such modifier combinations will provide enhanced resistance to environmental stress crazing and cracking.
SUGARY OF THE IN TON
Unexpectedly, in view of the foregoing, it has now been discovered that polycarbonate resins may be rendered more resistant to environment stress crazing and cracking by incorporating therewith, in certain proportions, a modifier combination comprising a coupled resinous dine-vinyl aromatic block copolymer and an olefin copolymer with

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an acrylate or methacry]ate comonomer. In a preferred feature, the modifier combination will comprise the said coupled resinous block copolymer, the olefin copolymer with an acrylate or methacrylate comonomer and, in addition, a polyolefin, preferably a linear low density polyolefin.
I-t has now been found that when either of -the above-mentioned modifier combinations is added to the polycarbonate resin, within a certain range, the resultant mixture possesses a resistance to environmental stress crazing and cracking greater than that possessed by the polycarbonate resin itself.
DESCRIPTION OF THE INVENTION
In accordance with the invention it has been found that the foregoing desirable properties are obtained with resin mixtures comprising pa) an aromatic polycarbonate resin; and (b) a modifier combination therefore comprising (i) a coupled resinous block copolymer having blocks comprising polymerized vinyl aromatic units connected to blocks comprising polymerized dine units, and (ii) a copolymer of an olefin and at least one of a Cluck alkyd acrylate, a Cï-C5 alkyd methacrylate~ acrylic acid methacryli.c acid, or a mixture of any of the foregoing said modifier being present in said mixture in an amount at least sufficient to impart to said mixture a resistance to environmental stress crazing and cracking greater than that possessed by said polycarbonate resin.
In accordance with another aspect of the invention there are provided resin admixtures comprising (a) an aromatic polycarbonate resin; and (b) a modifier combination therefore comprising (i) a coupled resinous block copolymer having blocks comprising vinyl aromatic units

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connected to blocks comprising polyp merited dine units;
(ii) a copolymer of an oleEin and at least one of a Cluck alkyd acrylate, a Cluck alkyd methacrylale, acrylic acid or methacrylic acid; and (iii) a polyolefin resin, preferably a linear low density polyolefin resin, said modifier being present in an amount sufficient to impart to said mixture a resistance to environmental stress crazing and cracking greater than that possessed by said polycarbonate resin The amounts of modifier combination to be employed vary broadly but, in general best results will be obtained when the modifier is added to the polycarbonate resin in amounts ranging from about 4 parts to about 50 parts by weight per 100 parts by weight of the polycarbonate resin and the modifier. When less than about 1 parts are used, the improvement in the craze resistance of the polycarbonate is generally not readily detectable and, where the amount exceeds about 50 parts the mixture begins to lose the beneficial properties of the polycarbonate.
Preferably, the modifier is added in amounts ranging from about 10 to 30 parts per hundred of combined (a) and (b).
Such addition may be accomplished in any manner so long as a thorough distribution of the modifier in the polycarbon-ate resin is obtained. For example the mixing of materials may be accomplished by a -variety of methods normally employed for incorporation of plasticizers or fillers into thermoplastic polymers including but not limited to mixing rolls, dough mixers, Danbury mixers, extrudes, and other mixing equipment. The resulting mixtures may be handled in any conventional manner employed for the fabrication or manipulation of thermoplastic resins. The materials may be formed or molded using compression, injection calendering, extrusion and blow molding tech-piques, alone, or in any combination. Also multiprocessing

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methods, such as extrusion-blow molding or coextrusion-co-injection; can be used, ego for mulli-layer containers It should be understood that -the posy carbonate resin mixtures prepared in accordance with the invention may also contain, in addition to the above-mentioned polymers other additives to lubricate, reinforce, prevent oxidation, or lend color to the material. Other additives such as mold release agents and stabilizers, are well known in -the art, and may be incorporated without departing -from the scope of the invention.
In addition to exhibiting an increased resistance to environmental stress crazing and cracking, the improved polycarbonate resin mixtures of the invention exhibit a relatively high impact strength without a substantial loss of tensile properties, and to a large extent retain the high softening temperatures of unmodified polycarbona-te resin materials.
The fact that the addition of the combination of components specified above to a polycarbonate resin system provides a resinous mixture having an improved resistance to environmental stress crazing and cracking is totally unexpected and not fully understood.
The aromatic carbonate polymers (a) used to provide polycarbonate mixtures of the present invention may be prepared by reacting a dihydric phenol with a carbonate precursor, such as phosgene, a haloform ate or a carbonate ester. Generally speaking, such carbonate polymers may be typified as possessing recurring structural units of the formula:
r 1 O A O C t wherein A is a diva lent aromatic radical of the dihydric phenol employed in the polymer producing reaction.

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Preferably, the carbonate polymers used to provide the resinous mixtures of -the invention have an intrinsic viscosity (as measured in ethylene chloride at 25C.) ranging from about Q.30 to about l.00 dug The dihydric phenols which may be employed to provide such aromatic carbonate polymers are mononuclear or polynuclear aromatic compounds, containing as functional groups two hydroxy radicals, each of which is attached directly to a carbon atom of an aromatic nucleus. Typical dihydric phenols I are .2l2-bis (4-hydroxyphenyl)propanei hydroquinone;
resorcinol, 2,2-bis-(4-hydroxyphenyl)pentane;
2,4i-(dihydroxydiphenyl)methane;
bis-(2-hydroxyphenyl)methane;
bis-(4~hydroxyphenyl)methane;
bis-(4-hydroxy-5-nitrophenyl)methane;
l,l-bis(4-hydroxyphenyl)e-thane;
3,3-bis(4-hydroxyphenyl)pentane;
2,2-dihydroxydiphenyl/
2,6-dihydroxynaphthalene;
bis-(4-hydroxydiphenyl)sulfone;
bis-(3,5-diethyl-4-hydroxyphenyl)sulfone;
2,2-bis-(3,5-di.methyl-4-hydroxyphenyl)propane;
2,4' dihydroxydiphenyl cellophane;
5'-chloro-2,4l-dihydroxydiphenyl cellophane;
bis-(4-hydroxyphenyl)diphenyl cellophane;
4,4'-dihydroxydiphenyl ether;
4,4' dihydroxy-3,3'-dichlorodiphenyl ether;
4,4'-dihydroxy-2,5-dihydroxydiphenyl ether;
and the like.
A variety of additional dihydric phenols which may be employed to provide such carbonate polymers are disclosed in commonly assigned US. Patent 2,999,835, issued September 12, 1961 to Goldberg. I-t is, of course,

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possible to employ two or more different dihydric phenols or a dihydric phenol in combination with a glycol, a hydra terminated polyester, or a dibasic acid in the event that a carbonate copolymer rather than a homopolymer is desired for use in the preparation of the polycarbonate mixtures of the invention. Branched polycarbonates are also useful. To avoid unnecessarily detailed description, reference is made to the disclosures of US. Patents 3,028,365, issued April 3, 1962 to Chenille et at;
10 3,334,154, issued August 1, 1967 to Kim; issued January 4, 1977 to Scott; 4,131,575, issued December 26, 1~78 to Adelmann. In any event, the preferred aromatic carbonate polymer is a homopolymer derived from Boyce-(4-hydro~yphenyl)propane (bisphenol A).
Generally speaking, the modifier combination components I (it) and (byway) which are admixed with polycarbonate resins to provide the resins mixtures of the invention are themselves well known commercially available thermoplastic resin materials.
The coupled block copolymer resin component by will comprise block polymerized units of vinyl aromatic compounds, e.g., styrenes alpha-methylstyrene, vinyl Tulane, para-methylstyrene and the like connected to blocks of polymerized dine units, e.g., units of butadiene, isoprene, 1,3-pentadiene, and the like. The preferred block copolymers will comprise units of polyp merited styrenes and polymerized butadiene. The butadiene portion, based on the total weight of the copolymer, can range from about 15 to about 40 weight percent The styrenes portion can range from about 60 to about 35 weight percent. In especially preferred butadiene styrenes copolymers, the weight ratio of the styrenes fraction to the butadiene fraction ranges from about 2 to 1 to about 3 to 1. The residual dunk unsaturation can be removed by selective hydrogenation, but is not preferred. The block copolymers may be made by any of several procedures well known to -those skilled in the art.

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suitable commercial material is Phillips Petroleum K Resin CRY BUS polymer. This has a styrene-bu-tadiene weight ratio of about 3:1 and a density of the order of about 1.01 g./cm3. See US. Patents, issued February 1, 1972 to Kitchen et at and 4,091,053, issued May 23, 1978 to Kitchen.
Copolymer component byway) is made from an olefin, e.g., ethylene, propylene, or the like, Capella--merited with one or more of a comonomer comprising a Cluck alkyd acrylate, e.g., methyl acrylate, ethyl acrylate, Huxley acrylate and the like, a Cluck alkyd methacrylate, e.g., methyl methacrylate, ethyl methacrylate, Huxley methacrylate, and the like; acrylic acid; or methacrylic acid. Especially preferred are the well known copolymers of ethylene with an alkyd ester of acrylic acid. These are disclosed in US. Patent 2,953,551, issued September 20, 1960 to White. Generally, the acrylate or methacrylate portion of the copolymer can range from about 10 to about 30 weight percent. The olefin portion of the copolymer can range from about 70 to about 90 weight percent. The preferred copolymer for use as component (it) is an ethylene-ethyl acrylate copolymer in which the weight ratio of the ethylene fraction to the ethyl acrylate fraction is about 4.5 to 1. Suitable olefin-acrylate copolymers, as defined above, can be prepared by methods well known to those skilled in the art or can be obtained commercially. For example, Union Carbide's Booklet DPD-6169 ethylene-ethyl acrylate copolymer is suitable for use in the present invention.
Component byway which may be an olefin homopolymer or copolymer, is selected from among the materials well known in the art as comprising this class.
Preferred for use in this invention are polymers which have been derived from olefins containing from 2 to 10 carbon atoms. Special mention is made of polyethylene, polypropylene, polyisobutylene and ethylene-propylenle of

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copolymers and EPDM copolymers in their various forms, since these are the most readily available commercially.
Methods for the preparation of these polymers, both commercial and non-commercial, are abundantly described in the literature and known to those skilled in the art. The polyethylene can be prepared by various procedures, using anionic, cat ionic or free-radical initiating catalysts, with conditions varied to produce a range of molecular weights and densities and different degrees of branching or non-branching for the polymer.
In one procedure, which involves free radical initiation, ethylene gas is polymerized in the presence of a peroxide initiating catalyst at a pressure between 15~000 and 40,000 psi and a temperature between 100 and 200C., to produce a relatively low density polymer, 0.90 to 0-9~ g/cm .
The polyethylene can also be prepared by low pressure processes effective to attain a polymer of higher molecular weight and a higher density. In one such procedure, known as the Phillips process, ethylene is contacted in an insert solvent with a slurry of a catalyst, such as chromium oxide supported on silica alumina at pressures of 400 to 500 Sue and temperatures of 130 to 170C., followed by extraction of the polymer with hot solvent and purification, to produce a polyethylene product having a density between 0.96 to 0.97 g/cm3~
Still other procedures are possible, such as emulsion polymerization in aqueous media in the presence of a proxy compound, as well as suspension polymerize-lion at low temperatures using a silver salt-peroxide redo system.
Any of the foregoing processes are utilizable to obtain polymers of ethylene suitable for use in the present compositions.
Also employable as component (lit) is polypropylene, a common commercial form of which is of CLUE

crystalline isotactic polypropylene. Such polymers can be prepared anionic ally initiated reactions using Ziegler type catalysts,, e.g., -titanium halide such as Tokyo in combination with an organome-tallic co-catalyst such as trialkyl aluminum halide. Polymerization generally proceeds rapidly at temperatures between 25 and 100C.
to yield a polymer in the form of a slurry of insoluble granular powder.
Copolymers of ethylene and propylene can be prepared using procedures similar to those for polyethylene and other polyolefins; for instance, by the polymerization reaction of a mixture of ethylene and propylene in -the presence of a Ziegler -type catalyst (e.g., transition metal compound and organometallic compound), or by free radical initiation under high pressures.
Polymers based on still higher olefins are not as readily available and, therefore, not as preferred.
Examples of such higher polyolefins are polymers based n 3 methyl-l-butene (H2C=CHCH(CH3)2)~
(~2C=CHCH2CH3); 4-methyl-1-pentene (H2C=CHCH2CH2-(C~3)2) and isobutylene. They can be prepared by known procedures including those described in The Encyclopedia of Polymer Science and Technology, John Wiley & Sons, Inc., Volume 9, pages 440-460 (1965).
The preferred linear low density polyolefin component (lit) may be prepared by state-of-the-art polymerization processes such as those described in US. Patent 4,076,698, issued February 28, 1978 to Anderson et at and Eur. Pat. Apply 4,645. The polymer may have a density between 0.89 and 0.96 gag and a controlled concentration of simple side chain branching as opposed -to random branching which distinguishes it from polymers such as high pressure low density polyethylene and high density polyethylene. The preferred range of density is 0.915 to 0.945 gag The linear low density polymers preferably are made from ethylene and an alpha o]efin of C3 to C8 carbon content, e.g., buttonhole and I

octene-l, or mixtures of such alpha-olefins. The comonomer is used in a minor amount, e.g., 10 mow or less of the total amount of monomers. A preferred range is about 1-3 mow 6. The preferred copolymer is a copolymer made from ethylene and buttonhole such as Escorene LPX-15 of Exxon, Houston, Texas.
Within the broad composition ranges specified above, the following have been found to provide desirable properties for the ternary mixtures: polyp carbonate component (a) comprises from about 50 to Abbott parts by weight; A-B diabolic copolymer component by comprises from about 2 to about 25 parts by weight; and olefinacrylate or methacrylate component (it) comprises from about 2 to about 25 parts by weight, per 100 parts by weight of components (a), by and (it) combined.
Desirable ranges for the qua ternary mixtures are as follows:
polycarbonate component (a) comprises from about 60 to about 89 parts by weight; component by comprises from about 5 to about 20 parts by weight; olefin-acrylate or methacrylate component (it) comprises from about 5 to about 20 parts by weight; and polyolefin component (lit) comprises from about 1 to about 10 parts by weight, per 100 parts by weight of components (a), I
(it) and (lit) combined.
The resistance to environmental stress crazing and cracking of the polycarbonate resin mixtures prepared in accordance with the invention was determined by subject-in stressed specimens to gasoline soaking and then measuring their impact strengths with special attention to the mode of failure, ductile failure being preferable.
The specimens are STYMIE D-256 impact test bars of two sizes: I x 1/2" x 1/8" and I x 1/2" x 1/4". Values of the desired stress were applied to each test bar by mounting on an Acutely stress jig (1 percent strain). The mounted bars were soaked 24 hours at room temperature in AMOCO unleaded premium grade gasoline. They were then removed from the jig, evaporated and dried for 24 hours. Issued impact strengths were then determined according to ASTM D 256 procedures on notched specimens.
In all cases, the properties are compared with those of identical unslaked, molded mixtures. Those which retain a substantial amount of impact resistance after soaking obviously are the best a-t resisting environmental stress cracking.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In order that those skilled in -the art may better understand how the present invention may be practiced, the following examples are given by way of illustration and not by way of limitation. ~11 parts and percentages are by weight unless otherwise noted. The various polycarbonate resin mixtures were molded into the test specimens in a 3 oz. Van Down injection molding machine. The temperatures used were 270C. on the cylinder and nozzle with a range of from 265C. to 285C.
EXAMPLES 1 and 2 An aromatic polycarbonate derived from Boyce-(4-hydroxyphenyl)propane and having an intrinsic viscosity (ivy.) in the range of from about 0.46 to about 0.49 dug as determined in ethylene chloride solution at 25C.
was mixed with a butadiene-styrene coupled resinous block copolymer (Phillips Petroleum CRY, hereinafter referred to as BUS), said copolymer having a weight ratio of styrenes to butadiene of about 3:1; and an olefin acrylate copolymer having a weight ratio of ethylene: ethyl acrylate of about 4.5:1 (Union Carbide DUD 6169). The ingredients were then blended together by mechanically mixing them in a laboratory tumbler and the resulting mixture was fed to an extrude which was operated at about 255C. The resulting extradites were commented into pellets. The pellets were injection molded a-t about 265C. -to about 285C. in-to test specimens of about I by I" by I" and byway I" by 1/8", -the latter dimension being specimen thickness. Some of the specimens were mount on an ASTM stress jig (1% strain) and soaked in Amoco premium unleaded gasoline for 24 hours. They were removed from the jig, the gasoline allowed to evaporate a-t room temperature for I hours, and then -they were tested Where indicated, Issued impact strengths of these specimens were measured according to the notched Issued test, ASTM D 256, and are set forth in Table 1. The weld line strength of the samples was measured with the specimens prepared in a double gate mold in thy same way as the notched Issued samples.
When polymer melt was injected through the gates, a weld line was then formed in the center of the sample. Measure-mints were made according to ASSET D 256. The superscript refers to the percent ductility at the foot lb. value. The samples labeled control was the bisphenol A polycarbonate, unmodified, or modified as indicated. The formulations used, and the results obtained are set forth in Table 1:
TABLE 1. POLYCARBONATE MODIFIED WITH COUPLED RESINOUS

COPOLYMER AND OLEFIN-ACRYLATE COPOLYMER

.
EXAMPLE A* B* C* D* E* 1 2 Composite n (pow) polycarbonate 100 96 94 95.7 94.3 80 85 BUS Block Copolymer - - - 4.3 5.7 15 10 Ethylene-Ethyl Acrylate Copolymer - 4 6 - - 5 5 PROPERTIES:
Notched Impact Strength 1~8" ft. lbs.-in.14.8** 15.9 14.8 15.2 14.3 12.8 13.5 1/4" ft. lbs.-in. 1.6 11.9 1106 8.9 11.2 11.0 10.8 Weld line strength, ft-lb ~40 3.8 3.8 8 86 8 980 5 OH 9 OH
SOAKED IN GASOLINE
Notched Impact Strength 1/8" ft. lbs.-in.broke 0.9 1.3 0.5 1.0 12.8 5.8 1/4" ft. lbs.-in. - 0.6 1.0 - - 10.8 1.4 *Control **unless otherwise specified, all were ductile at failure.

The results demonstrate -that tire impact strengths the new compositions of Examples 1 and 2 were substantially retained or better than polycarbonate alone in both regular and gasoline soaked testing. In comparison with controls showing polycarbonate plus by or (it), the impact resistance after normal testing procedures is generally retained. however, after soaring in gasoline, the controls with by or (it) experienced severe loss of impact resistance and a change to a brittle failure mode. The examples of the invention substantially retain their impact resistance at -the 1/8" thickness. Some loss is observed for 1/4" thickness in Example 2 but it is s-till somewhat better than the controls. Weld line strength remains relatively high in the invention examples whereas gasoline resistance is substantially lowered in the controls. Example 1 is clearly preferred over Example 2.

The general procedures of Examples 1 and 2 are repeated, also including in the mixture a q linear low density polyolefin which is a cMopolymer of ethylene and buttonhole ~Escorene LPX-15). The formulations used and the results obtained are set forth in Table 2:
/

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TABLE 2. POLYCAR~ONATE MODIFIED WITH CO~TPLEI) RESINOUS
BLOCK COPOLYMER, OLEFIN-~CRYLAI'E COPOLYMER AND
LINEAR LOW DENSITY POLYOLEFIN
__ EXAMPLE A* F* GO 3 4 5 6 Composition (pow) _ _ polycarbonate 100 90 83 96 82 82 8282 BUS Block Copolymer - - 10 - 10 10 6 10 Ethylene - Ethyl Acrylate Copolymer - 7 - - 6 4 6 2 Linear low density polyethylene - 3 8 4 2 4 6 6 PROPERTIES
Notched Impact Strength 1/8" ft. lobs. - inn** 15.313.2 13.6 14.0 14.1 13.6 12.0 1/4" ft. lobs. - in. 1.6 1.108.1 11.4 9.1 8.8 9.1 9.7 Weld line strength, f-t.-lb. 408.9 4.9 10.9 5 8 4 926 OH 4 OH

SOCKED IN GASOLINE
Notched Impact Strength 1/8" ft. lobs. - inObroke 10.6 12.6 1.0 14.0 14.1 12.1 12.9 1/4" ft. lobs. - in. - 1.1 logo _ 7.8 1.3 1.8 2.8 __ _ *Control **Unless otherwise specified, all won ductile at failure The results demonstrate that the impact strengths of the new compositions of Examples 3-6 were substantially retained in comparison with the controls in the 1/8 inch samples and that the impact strengths in the 1/4 inch samples were substantially retained or better than the controls. Furthermore even after soaking in gasoline, the samples of the invention show retention of strength and desirable ductile mode failure in the 1/8" -thickness. Two of the four controls showed significant decreases. In the 1/4"
thickness test samples, the controls -that maintained impact strength in the l/8" -test thickness test system lost their impact resistance and the failure mode changed from ductile to brittle.

a The invention samples generally retained -their ductility upon wreak and in one case, Example 3, retained virtually all of its impact resistance. The weld line strength remains relatively high in the invention examples.

The general procedures of Examples 1 and 2 are repeated, also including polyolefin resins of various types. The formulations used and the results obtained are set forth in Table 3:

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The results demonstrate that, even after soaking in gasoline, the Examples show a retention of strength and desirable ductile mode failure of all of the 1/8" samples and most of the 1/4" samples.
The weld line strength data is consistent with the use of polyolefins in the compositions.
The compositions of this invention also maintain their beneficial properties to a remarkable extent after re-extrusion, showing high resistance to shearing at elevated temperatures. The mixture of Example 3, polycarbonate, 82 parts; BUS coupled resinous block copolymer, 10 parts; ethylene ethyl acrylate copolymer, 6 parts; and ethylene-butene-l LLDPE, 2 parts, was extruded and re-extruded 3,6 and 9 times, and the extradites were molded N aged in gasoline, and impact-tested by the foregoing procedures with the results set forth in Table 4:
TABLE 4. RECYCLABILITY OF POLYCARBONATE

MU Re-extruded Unwished Iota Impact Strength Virgin 3X 6X 9X
1/8", ft. lbs.-in., unaged 15.3 14.714.8 1/8", Et. lbs.-in., aged in gasoline 15.3 14.7 14.8 1/4", ft. lbs.-in., unaged 9.2 9.2 9.2 All parts failed in the desirable ductile mode.

Glass filled compositions are prepared, molded and tested according to the general procedure of Example 1. The formulations used and the results obtained are set forth in Table 5.
-I

TABLE. JUICY FILLED COMPOSITIONS COMPRISING POLYP
CARBONATE, COUPLED RESINOUS BLOCK COPOLYME,R, ETHYLENE-ETHYLAC~YLATE COPOLYMER Arid POLYOLEFIN
__ . __ _ _ __ E AM LYE It 16 5 Compost Al (pow) Aromatic polycarbonate 77.9 73.8 BUS Block Copolymer I 9.0 Ethylene-ethylacrylate copolymer 5.7 I
Linear low density polyethylene 1.9 1.8 10 Glass fibers, 1/8" chopped 5.0 10.0 PROPERTIES
Notched Idea impact strength Unaged, 1/8", ft. lbs./i,n. 7.2 4.7 Unaged, I ft. lbs./in. 4.2 3.4 15 Soaked, 1/8" r ft. lbs./in. 4.4 5.3 Soaked, 1/4", ft. lbs./in. 2.9 2.9 a bisphenol A polycarbonate, LEAN 140 b CRY, Phillips c DUD 610~ Union Carbide d LPX-15, Exxon e OF, Owen Corning Fiberglass, ~15 BY
Reinforced compositions with excellent gasoline resistance were obtained.
Obviously, many variations will suggest themselves to those skilled in this art in light of the detailed description herein. For example, instead of a bisphenol-A
polycarbonate, one containing units derived from twitter-methylbisphenol A or from dixylenol cellophane can be used.
Instead of a butadiene-styrene copolymer an isoprene-styrenes copolymer can be used. Instead of an ethylene-ethyl acrylate copolymer, there can be used copolymers of ethylene and methyl methacrylate, ethylene and acrylic acid and ethylene and methacrylic acid. Instead of a linear low density polyethylene comprising units of ethylene and buttonhole, there can be substituted one come prosing units of ethylene and octene-l. The COlTlpOSi lions can be provided in flame retardant modifications All such obvious variations are within the full intended scope of the appended claims.

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A resin mixture comprising:
(a) an aromatic polycarbonate resin, and (b) a modifier combination therefor comprising (i) a coupled resinous block-copolymer having blocks comprising polymerized vinyl aromatic units connected to blocks comprising polymerized diene units, said diene retaining its residual unsaturation; and (ii) a copolymer of an olefin and at least one of a C1-C6 alkyl acrylate, a C1-C6 alkyl methacrylate, acrylic acid, methacrylic acid, or a mixture of any of the foregoing, said modifier being present in said mixture in an amount of at least sufficient to impart to said mixture a resistance to environmental stress crazing and cracking greater than that possessed by said polycarbonate resin and wherein component (a) comprises from about 50 to about 96 parts by weight; component (b)(i) comprises from about 2 to about 25 parts by weight; and component (b)(ii) comprises from about 2 to about 25 parts by weight, per 100 parts by weight of components (a), (b)(i) and (b)(ii) combined.

2. A resin mixture as defined in claim 1, wherein the aromatic carbonate polymer comprises recurring structural units of the formula:
wherein A is a divalent aromatic radical of a dihydric phenol.

3. A resin mixture as defined in claim 2 wherein in said formula, A is derived from a 4,4'-dihydroxy-di-(mononuclear aryl) alkane.

4. A resin mixture as defined in claim 1 wherein said aromatic polycarbonate (a) comprises poly(2,2-dyhydroxydiphenylpropane) carbonate.

5. A resin mixture as defined in claim 1 wherein said copolymer resin (b)(i) comprises polymerized styrene units and polymerized diene units.

6. A resin mixture as defined in claim 1 wherein said copolymer component (b)(ii) comprises a copolymer of ethylene and ethyl acrylate.
7. A resin mixture comprising:
(a) an aromatic polycarbonate resin, and (b) a modifier combination therefor comprising (i) a coupled resinous block copolymer having blocks comprising polymerized vinyl aromatic units connected to blocks comprising polymerized diene units, said diene retaining its residual unsaturation;
(ii) a copolymer of an olefin and at least one of a C1-C6 alkyl acrylate, a C1-C6 alkyl methacrylate, acrylic acid or methacrylic acid; and (iii) a polyolefin resin, said modifier being present in an amount sufficient to impact to said mixture a resistance to environmental stress crazing and cracking greater than that possessed by said polycarbonate resin, and wherein component (a) comprises from about 60 to about 89 parts by weight;
component (b)(i) comprises from about 5 to about 20 parts by weight; component (b)(ii) comprises from about 5 to about 20 parts by weight; and component (b)(iii) comprises from about 1 to about 10 parts by weight, per 100 parts by weight of components (a), (b)(i), (b)(ii) and (b)(iii) combined.
8. A resin mixture as defined in claim 7 wherein the aromatic carbonate polymer comprises recurring structural units of the formula:

wherein A is a divalent aromatic radical of a dihydric phenol.
9. A resin mixture as defined in claim 8 wherein in said formula, A is derived from a 4,4'-dihydroxy-di(mononuclear)alkane.
10. A resin mixture as defined in claim 7 wherein said aromatic polycarbonate (a) comprises poly(2,2-dihydroxydiphenylpropane) carbonate.
11. A resin mixture as defined in claim 7 wherein said copolymer resin (b)(i) comprises polymerized styrene units and polymerized butadiene units.
12. A resin mixture as defined in claim 7 wherein said copolymer component (b)(ii) comprises a copolymer of ethylene and ethyl acrylate.
13. A resin mixture as defined in claim 7 wherein said polyolefin resin (b)(iii) is selected from a polyethylene resin, a polypropylene resin or an ethylene-propylene copolymer resin.
14. A resin mixture as defined in claim 7 wherein said polyolefin resin (b)(iii) is a linear low density polyolefin resin.
15. A resin mixture as defined in claim 13 wherein said linear low density polyolefin resin is a linear low density polyethylene resin.
16. A resin mixture as defined in claim 15 wherein said linear low density polyethylene resin is a copolymer of ethylene and butene-1.
17. A resin mixture as defined in claim 1 including a reinforcing amount of a reinforcing agent.
18. A resin mixture as defined in claim 7 including a reinforcing amount of a reinforcing agent.
19. A resin mixture as defined in claim 17 wherein said reinforcing agent is chopped glass filaments.
20. resin mixture as defined in claim 18 wherein said reinforcing agent is chopped glass filaments.
21. An article molded from the composition of claim 1.

22. An article molded from the composition of

claim 7.