GRAPHITE FILLED POLYESTER-CARBONATE COMPOSITIONS

Abstract: Novel thermoplastic molding compositions comprising a polyester-carbonate polymer and graphite fibers. The compositions possess improved rigidity and heat distortion temperature properties with the addition of 0.5% to about 45% by weight of graphite fibers. In an example, a polyester-carbonate was prepared from bisphenol A, terephthalaloyl dichloride, isophthaloyl dichloride and phosgene. Graphite fibers were added to the above polymer in the amount of 10%by weight.

Description: Description Graphite filled Polyester-Carbonate Compositions. This invention relates to reinforced thermoplastic molding compositions. More particularly, it relates to thermoplastic molding compositions containing a polyester-carbonate resin and graphite fibers. BACKGROUND OF THE • INVENTION Polyester-carbonate resins and the methods for their preparation are well known in the art as disclosed in U.S. Patents 3,303,331; 3,169,121 and 3,207, 814. Other prior art discloses of polyester-carbonates and methods of their preparation include U.S. Patent 4,189,549 which discloses polyester-carbonate compositions which are obtained from a melt polymerization process employing para hydroxy benzoic acid; U.S. Patent 4,156,069 which discloses a process for preparing an alternating ester-carbonate block copolymer from dihydric phenols, dicarboxylic acid dihalides, phosgene and a molecular weight regulator all in the presence of pyridine; and U.S.Patent 4,194,038 which discloses a process for preparing poly(ester-carbonates) SUBSTITUTE SHEET OMPI fro dihydric phenols, especially bisphenol A, aromatic or cycloaliphatic dicarboxylic acids, especially terephthalic acid, and phosgene as a carbonate precursor wherein a reaction of the acid and phosgene is carried out in a first stage forming dicarboxylic acid chloride and then phosgene and bisphenol A are added in separate streams, simultaneously during most of the second or condensation stage. Application Serial No. 33,389 filed April 26, 1979 and assigned to the same assignee as the instant application discloses copolyester-carbonate compositions employing diacid chloride copolymers in the preparation of the polyester portion of the polyester-carbonate. The use of these polyester-carbonates is desirable as such resins are in general easy to process and result in economic savings in both manufacturing and materials cost. However, the use of these resins is somewhat limited as they do not generally exhibit all of the highly desirable physical properties of high molecular weight aromatic polycarbonates. DESCRIPTION OF THE INVENTION It has now been found that polyester-carbonate resin compositions can be obtained whose physical properties permit them to be used in a broader range of applications than was previously possible. This is accomplished by adding graphite fibers to the polyester-carbonate resin composition. The preparation of polyester-carbonates which may be employed in the compositions of the present invention is described in U.S. Patents 3,030,331; 3,169,121; 4,194,038 and 4,156,069, as well as in co-pending application SHEετ Serial No. 33,389 filed April 26, 1979 and assigned to the same Assignee as the instant application, all of which are incorporated herein by reference. The polyester-carbonates can generally be termed copolyesters containing carbonate groups, carboxylate groups, and aromatic carbocyclic gorups in the polymer chain, in which at least some of the carboxylate groups and at least some of the carbonate groups are bonded directly to ring carbon atoms of the aromatic carbocyclic groups. These polyester-carbonates are, in general, prepared by reacting a difunctional carboxylic acid or a reactive derivative of the acid such as the acid dihalide, a dihydric phenol and a carbonate precursor. The dihydric phenols useful in formulating the polyester-carbonates useful in the practice of the present invention in general are represented by the general formula in which A represents an aromatic group such as phenylene, biphenylene, naphthylene, etc. E may be an alkylene or alkylidene group such as methylene, ethylene, propylene, propylidene, isopropylidene, butylene, butylidene, isobutylidene, amylene, isoa ylene, amylidene, isoamylidene, etc. Where E is an alkylene or alkylidene group, it may also consist of two or more alkylene or alkylidene groups, connected by a non-alkylene or non-alkylidene group such as an aromatic linkage, a tertiary amino linkage, an ether linkage, a carbonyl linkage, a silicon-containing linkage, or by a sulfur-containing linkage such as sulfide, sulfoxide, SUBSTITUTE SHEET OMPI sulfone, etc. In addition, E may be a cycloaliphatic group (e.g. cyclopentyl, cyclohexyl); a sulfur-containing linkage such as sulfide, sulfoxide or sulfone; an ether linkage; a carbonyl group; a tertiary nitrogen group; or a silicon-containing linkage such as silane or siloxy. Other groups which E may represent will occur to those skilled in the art. R represents hydrogen or a monovalent hydrocarbon group such as alkyl (methyl, ethyl, propyl, etc.), ary (phenyl, naphthyl, etc.), aralkyl (benzyl, ethylphenyl, etc.) or cycloaliphatic (cyclopentyl, cyclohexyl, etc.) Y may be an inorganic atom such as a halogen (fluorine, bromine, chlorine, iodine), an inorganic group such as the nitro group, an organic group such as R above, or an oxy group such as OR, it being only necessary that Y be inert to and unaffected by the reactants and the reaction conditions. The letter m represents any integer from and including zero through the number of positions on A available for substitution; p represents an integer from and including zero through the number of positions on E available for substitution; t represents an integer equal to at least one; s is either zero or one; and u represents an integer including zero. In the dihydric phenol compound represented by Formula I above, when more than one Y substituent is present, they may be the same or different. The same holds true for the R substituent. Where s is zero in Formula I and u is not zero, the aromatic rings are directly joined with no intervening alkylene or other bridge. The positions of the hydroxyl groups and Y on the aromatic nuclear residues A can be varied in the ortho, meta, or para positions and the groupings can be in a asymmetrical or symmetrical SUBSTITUTE SHEET OMPI relationship, where two or more ring carbon atoms of the aromatic hydrocarbon residue are substituted with Y and hydroxyl group. Some nonlimiting examples of dihydric phenol compounds falling within the scope of Formula I which can be used in the preparation of the polyester-carbonates useful in the practice of the present invention include: 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A); 2,4'-dihydroxydiphenylmethane; bis-(2-hydroxyphenyl)-methane; bis-(4-hydroxyphenyl)-methane; bis-(4-hydroxy-5-nitrophenyl)-methane; bis-(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)-methane; l,l-bis-(4-hydroxyphenyl)-ethane; l,l-bis-(4-hydroxy-2-chlorophenyl)-e hane; 2,2-bis-(3-phenyl-4-hydroxyphenyl)-propane; bis-(4-hydroxyphenyl)-cyelohexylmethane; and 2,2-bis-(4-hydroxyphenyl)-l-phenylpropane. These dihydric phenols may be used alone or as mixtures of two or more different dihydric phenols. In general any difunctional carboxylic acid, or its reactive derivative such as the acid dihalide, conventionally used in the preparation of polyesters may be used for the preparation of the polyester-carbonates useful in formulating the compositions of the present invention. In general the carboxylic acids which may be used are aliphatic carboxylic acids, aliphatic-aromatic carboxylic acids, or aromatic carboxylic acids. The aromatic dicarboxylic acids or their reactive derivatives such as the aromatic acid dihalides are preferred as they produce the aromatic poplyester-carbonates which are most useful 'in the practice of the instant invention. These carboxylic acids may be represented by the SUBSTITUTE SHEET general formula wherein R represents an alkylene, alkylidene or cycloaliphatic group in the same manner as set out above for E in Formula I; an alkylene, alkylidene or cycloaliphatic group containing ethylenic unsaturation; an aromatic radical such as phenylene, naph hylene, biphenylene, substituted phenylene, etc.; two or more aromatic groups connected through non-aromatic linkages such as those defined by E in Formula I; or an aralkyl 2 radical such as tolylene, xylene, etc. R is either a carboxyl or a hydroxyl group. The letter q represents one 2 where R is a hydroxyl group and either zero or one where 2 R is a carboxyl group. Thus the difunctional acid will either be a monohydroxy (monocarboxylic) acid or a dicarboxylic acid. For purposes of the present invention the dicarboxylic acids or their reactive derivatives such as the acid dihalides are preferred. As mentioned previously the aromatic dicarboxylic acids are preferred. Thus in these preferred acids R„ is a carboxyl group and R. is an aromatic radical such as phenylene, naphthylene, biphenylene, substituted phenylene, etc.; two or more aromatic groups connected through non-aromatic linkages; or an aralkyl radical. Some non-limiting examples of suitable preferred aromatic and aliphatic-aromatic dicarboxylic acids which may be used in preparing the polyester-carbonates useful in the practice of the present invention include phthalic, isophthalic, terephtalic, homophthalic, o-, m-, and p-phenylenediacetic acid; the polynuclear aromatic acids such as diphenic acid, SUBSTITUTE SHEET and 1,4-naphthalic acid. These acids may be used either alone or as mixtures of two or more different acids. The carbonate precursor may be either a carbonyl halide, a carbonate ester or a haloformate. The carbonyl halides which can be employed herein are carbonyl bromide, carbonyl chloride and mixtures thereof. Typical of the carbonate esters which may be employed herein are diphenyl carbonate, di-(halophenyl) carbonates such as di-(chlorophenyl) carbonate, di-(bromophenyl) carbonate, di-(trichlorophenyl) carbonate, di-(tribo ophenyl) carbonate, etc., di-(alkylphenyl) carbonate, such di-(tolyl) carbonate, etc., di-(naphthyl) carbonate, di-(chloronaphthyl) carbonate, phenyl tolyl carbonate, chlorophenyl chloronaphthyl carbonate, etc., or mixtures thereof. The haloformates suitable for use herein include bishaloformates of dihydric phenols (bischloroformates 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. The polyester-carbonates which are preferred in the practice of the present invention are the aromatic polyester-carbonates derived from dihydric phenols, aromatic dicarboxylic acids or their reactive derivatives such as the aromatic acid dihalides, e.g., di-chlorides, and phosgene. A quite useful class of aromatic polyester-carbonates are those derived from bisphenol A, aromatic dicarboxylic acids or their rective derivatives such as terephthalic or isophthalic acid or terephthaloyl or isophthaloyl dichloride, and phosgene. Some particularly useful aromatic polyester-carbonates are those SUBSTITUTE SHEET OMPI -8- derived from bisphenol A, a mixture of isophthalic and terephthalic acids or isophtthaloyl dichloride and terephthaloyl dichloride in a weight ratio of from 5:95 to 95:5, and phosgene. The polyester-carbonate compositions of the instant invention are formulated by admixing graphite fibers with the polyester-carbonate resin. These graphite fibers may generally have a diameter of between about 0.1 and 0.001 millimeters, and preferable have a diameter between about 0.05 and about 0.005 millimeters. Such graphite fibers are commercially available and are marketed, for example, by Celanese under the tradename Celion and by Union Carbide under the tradename Thornel. The amount of the graphite fibers employed in the practice of this invention may generally vary from between 0.5 to about 45 weight percent based on the weight of the polyester-carbonate resin composition. Preferably the composition contains from about 5 to about 30 weight percent of the graphite fibers, and more preferably from about 10 to about 20 weight percent of the graphite fibers. Generally if less than about 0.5 weight percent of the graphite fibers are employed in the composition there is usually no appreciable improvement in the physical properties of the polyester-carbonate composition. If, on the other hand, the composition contains more than about 45 weight percent of the graphite fibers the physical properties, such as impact strength and processability, of the resin composition begin to be adversely affected thereby reducing the usefulness of the resin composition in providing molded articles of good quality. The addition or incorporation of these graphite fibers in the aforedescribed amounts in a polyester-carbonate composition results in a composition having improved heat OMPI distortion, flame retardance, rigidity and electrical conductivity. The graphite fibers are added to the polyester-carbonate resins and are mixed or blended therewith by generally mechanical means such as stirring, shaking, blending in a mechanical blender, etc., to form the compositions of the present invention. The compositions of the present invention may optionally contain other commonly known and used additives such as antistatic agents, antioxidants, mold release agents, colorants, glass fibers, impact modifiers stabilizers, fillers, and the like. DESCRIPTION-OF THE ■ PREFERRED EMBODIMENT The following examples are set forth to further illustrate the present invention and are not to be construed as limiting the invention thereto. Unless otherwise specified, where parts or percents are mentioned, they are parts or percents by weight. EXAMPLE- This example illustrates the preparation of an aromatic polyester-carbonate derived from bisphenol A, a mixture of terephthaloyl dichloride and isophthaloyl dichloride, and phosgene. The resin of this example is prepared by following the single pH profile process disclosed in copending application Serial No. 957,426 filed November 2, 1978 of common assignee and which is incorporated herein by reference. To a ten gallon reactor vessel there are added 8 liters of methylene chloride, 6 liters of water, 1906 grams (8.36 moles) of bisphenol A, 20 milliliters of triethylamine, 4 grams of sodium gluconate, and 125 grams of chroman (I) (93% purity) chain terminator. At a pH of between about 9-10.5, 1089.6 grams (5.37 moles) of a mixture of 15% by weight of isophthaloyl dichloride and 85% by weight SUBSTITUTE SHEET OMPI terephthaloyl dichloride in 2 liters of methylene chloride are added over a 10 minute interval while controlling the pH at about 9-10.5 with 35% aqueous caustic. After the addition of the diacid chloride mixture, phosgene is added at a rate of 36 grams per minute for 12 minutes while controlling the pH at about 10-11 with 35% aqueous caustic. The polymer mixture is diluted with 5 liters of methylene chloride and the brine phase is separated. The resulting polymer phase is washed with 0.1N_ HC1 (twice) and water (three times) and is then recovered by high pressure steam precipitation to yield a white powder having an IV of 0.5 dl/g in methylene chloride. To this powder are added minor amounts (less than about one part per hundred parts of resin) of a phosphite stabilizer and an epoxy stabilizer. This resin product is then fed to an extruder operating at a temperature of about 600 F to extrude the resin into strands and the extruded strands are chopped into pellets. The pellets are then injection molded at about 650 F into test samples measuring about 2.5" x 1/2" x 1/8". EXAMPLE ■ 2 This example illustrates a polyester-carbonate composition falling outside the scope of the instant invention. A polyester-carbonate resin is prepared substantially in accordance with the procedure of Example 1. To the powdered polyester-carbonate resin is added glass fiber in an amount of 10% by weight of the resin composition. The glass and resin powder are mixed by tumbling the ingredients together in a laboratory tumbler. The mixture is then fed to an extruder operating at a temperature of about 600 F to extrude the resin composition into strand; and the extruded strands are chopped into pellets. The pellets are then injection molded at about 650 F into test samples measuring about 2.5" x 1/2" x 1/S". SUBSTITU EXAMPLE-3 This example also illustrates a polyester-carbonate composition falling outside the scope of! the instant invention. A polyester-carbonate resin is prepared substantially in accordance with the procedure of Example 1. To the powdered polyester-carbonate resin is added glass fiber in an amount of 20% by weight of the resin composition. The glass and the resin powder are mixed by tumbling the ingredients together in a laboratory tumbler. The mixture is then fed to an extruder operating at a temperature of about 600 F to extrude the resin composition into strands and the extruded strands are chopped into pellets. The pellets are then injection molded at about 650 F into test samples measuring 2.5" x 1/2" x 1/8". EXAMPLE This example illustrates a polyester-carbonate composition falling within the scope of the present invention. A polyester-carbonate resin is prepared substantially in accordance with the procedure of Example 1. To the powdered polyester-carbonate resin are added graphite fibers 'in an amount of 10% by weight of the resin composition. The graphite fibers and the resin powder are mixed by tumbling the ingredients together in a laboratory tumbler. The mixture is then fed to an extruder operating at a temperature of about 600 F to extrude the composition into strands and the extruded strands are chopped into pellets. The pellets are then injection mmoollddeedd aatt aalbout 650 F into test samples measuring 2.5" x 1/2" x 1/8". SUBSTITUTE SHEET , OMPI EXAMPLE-5 This example illustrates a polyester-carbonate composition of the present invention. A polyester-carbonate resin is prepared in substantial accordance with the procedure of Example 1. To the powdered resin are added graphite fibers in an amount of 20% by weight of the resin composition. The fibers and the resin are mixed by tumbling the ingredients together. The mixture is then fed to an extruder operating at a temperature of about 600 F to extrude the composition into strands and the extruded strands are chopped into pellets. The pellets are then injection molded at about 650 F into test samples measuring about 2.5'.' x 1/2" x 1/8". Various physical properties of the test samples obtained in Examples 1-5 were determined according to the following test procedures: Heat Distortion Temperature Under Load (DTUL) of the molded samples was determined according to ASTM D-648; Notched Izod (NI) and Uhnotched Izod(UNI) impact on the 1/8" thick molded samples were determined according to ASTM D-256; Flexural Yield (FY) and Flexural Modulus (FM) were determined according to ASTM D-790; Flame Retardancy (FR) of the molded samples was determined by subjecting the sample (5 samples for each Example) to the test procedures set forth in Underwriters' Laboratories, Inc. Bulletin UL-94, Burning Test for Classifying Materials. In accordance with this test procedure, materials so investigated are rated either V-0, V-I or V-II based on the results of 5 specimens. The criteria for each V (for vertical) rating per UL-94 is briefly as follows: SUBSTITUTE SHEET "& JR£ ^ _ OMPI "V-0": Average flaming and/or glowing after removal of the igniting flame shall not exceed 5 seconds and none of the specimens shall drip flaming particles which ignite absorbent cotton. "V-I": Average flaming and/or glowing after removal of the igniting flame shall not exceed 25 seconds and the glowing does not travel vertically for more than 1/8" of the specimen after flaming ceases and glowing is incapable of igniting absorbent cotton. "V-II": Average flaming and/or glowing after removal of the igniting flame shall not exceed 25 seconds and the specimens drip flaming particles which ignite absorbent cotton. In addition, a test bar which continues to burn for more than 25 seconds after removal of the igniting flame is classified, not by UL-94 but by the standard of the present invention, as "burns". Further, UL-94 requires that all test bars in each test group must meet the V-type rating to achieve that particular classification. Otherwise, the 5 bars receive the rating of the worst single bar. The results of these tests are set forth in Table I. SUBSTITUTE SHEET -14- TABLE I Example Example Example Example Example - - 1 - 2 -- 3 - -4 - -5 (FY) 13,800 16,300 23,600 22,600 28,900 s i. p.s.i. p.s.i. p.s.i. p.s.i. (FM) 319,000 474,000 718,000 797,000 1,420,000 p.s.i. p.s.i. p.s.i. p.s.i. p.s.i. (DTUL) 165°C. 176°C. 179°C. 180°C. 181°C. (NI) 7.3 2.7 2.4 1.5 1.4 ft.lb./ ft.lb./ ft.lb./ ft.lb./ ft.lb./ 10 in.width in. w. in. w. in. w. in. w. (UNI) 40 29.1 16.0 9.6 10.2 ft.lb./ ft.lb./ ft.b./ ft.lb./ ft.lb./ (FR) Burns Burns V-II V-I V-II The test samples were 1/16 inch thick. 15 As can be seen from the data in Table I the graphite fiber filled polyester-carbonate compositions, i.e., Examples 4 and 5, have a higher flexural yield (FY) and flexural modulus (FM) than the unfilled polyester-carbonate resin, i.e., Example 1, and the polyester-carbonate 20 compositions which contain comparable amounts of glass fibers, i.e., Examples 2 and 3. Furthermore, there is a SUBSTITUTE SHEET dramatic increase in the heat distortion temperature of the graphite filled compositions as compared to the unfilled polyester-carbonate resin and a significant increase-as compared to the glass fiber filled polyester-carbonate compositions. Furthermore, the graphite fiber containing polyester-carbonate compositions of Examples 4 and 5 exhibit superior flame retardancy than the unfilled polyester-carbonate resin of Example 1 and the glass fiber filled polyester-carbonate compositions of Examples 2 and 3. It will thus be seen that the objects set forth above among those made apparent from the preceding description are efficiently attained and since certain changes may be made in the processes and compositions described above without departing from the scope of this invention, it is intended that all matters contained in the above description shall be interpreted as illustrative and not in a limiting sense. SUBSTITUTE SHEET OMPI

Claims: -16- Claims 1. A thermoplastic molding composition having improved rigidity and heat distortion temperature comprising an admixture of an aromatic polyester-carbonate resin and graphite fibers. 2. The composition of claim 1 wherein said composition contains from about 0.5 to about 45 percent by weight of graphite fibers. 3. The composition of claim 2 wherein said composition contains from about 5 to about 30 percent by weight of the graphite fibers. 4. The composition of claim 3 wherein said composition contains from about 10 to about 20 percent by weight of the graphite fibers. 5. The composition of claim 1 wherein said aromatic polyester carbonate resin is derived from bisphenol A, an aromatic dicarboxylic acid or a reactive derivative thereof, and a carbonate precursor. 6. The composition of claim 5 wherein said reactive derivative of an aromatic dicarboxylic acid is terephthaloyl dichloride. 7. The composition of claim 5 wherein said reactive derivative of an aromatic dicarboxylic acid is isophthaloyl dichloride. SUBSTITUTE SHEET 8. The composition of claim 5 wherein the reactive derivative of an aromatic dicarboxylic acid is a mixture of isophthaloyl dichloride and terephthaloyl dichloride. 9. The composition of claim 6 wherein said carbonate precursor is phosgene. 10. The composition of claim 7 wherein said carbonate precursor is phosgene. 11. The composition of claim 8 wherein said carbonate precursor is phosgene. 12. The composition of claim 2 wherein said aromatic polyester-carbonate is derived from bisphenol A, at least one dicarboxylic acid selected from the group consisting of terephthalic acid and isophthalic acid or at least one acid chloride selected from the group consisting of terephthaloyl dichloride and isophthaloyl dichloride, and phosgene. sv.εετ OMPI

Inventors: MILLER KENNETH FREDERICK
Applicants: GEN ELECTRIC, GENERAL ELECTRIC CO
Application year: 1981
Main classification: C08K7
IPC codes: C08K7, C08L67