Abstract:
An aromatic copolyestercarbonate having from about 35 to 95 mole percent ester content which comprises isophthalate or isophthalate and terephthalate units, said copolyestercarbonate endcapped with a compound of the formula ##STR1## wherein R 1  -R 8  are independently selected from the group consisting of hydrogen and alkyl radicals of 1-9 carbon atoms and wherein R 5  -R 8  are further independently selected from the group consisting of bromo and chloro.

Description:
BACKGROUND OF THE INVENTION 
     Aromatic copolyestercarbonates have been known for many years. Their chief property improvement over polycarbonate is a higher distortion temperature under load, allowing it to be used in applications wherein higher temperature properties are required than standard polycarbonates. However, together with the higher temperature properties is the increased difficulty in molding. The melt viscosity is high, therefore requiring a higher temperature and/or more pressure to mold in comparison to the standard polycarbonates. 
     Various monofunctional groups have been employed to terminate polymers of the polycarbonate family. The standard endcapping monomers are pheno and paratertiary butylphenol. However, other endapping agents have been disclosed from time to time. In U.S. Pat. No. 3,697,481, Bialous, et al assigned to General Electric Company, a chromanyl radical has been employed to end-cap polycarbonates. The description of polycarbonates is broad enough to include copolyestercarbonates such as disclosed in U.S. Pat. Nos. 3,030,331 and 3,169,121, see the 3,697,481 U.S. Pat. No. at column 3, lines 59-69. In U.S. Pat. No. 4,238,596 issued to Quinn and assigned to General Electric Company, a new method for preparing copolyestercarbonates is disclosed. Following this new method, Examples 3 and 6 utilize chroman-I as a chain stopper. In Example 3, an aromatic copolyestercarbonate of 18 mole percent ester content in prepared utilizing 100 percent isophthalate units. In Example 6 an aromatic copolyestercarbonate is prepared having 11 percent ester content utilizing 100 percent terephthalate units. The data in the Tables in the U.S. Pat. No. 4,238,596 patent compares all of the examples. Reducing the ester content and going to chroman as the endcapping agent, see Examples 1-3, increases the Notched Izod. However, in Examples 4 and 6, which are 100 percent terephthalate content, the Notched Izod does not shift from Example 4 to Example 6. The only difference in the Examples is the chroman endcap compared with the phenol endcap. With respect to melt viscosity the melt index is somewhat higher in Example 3 than Examples 1 and 2 in the &#39;596 patent wherein the ester content goes down but chroman replaces the phenol. In Examples 4 and 6 the melt index is lower in Example 6 than Example 4. In none of the Chroman endcapped examples is there a significant shift in distortion temperature under load to a higher value. 
     New aromatic copolyestercarbonates are being disclosed and patented. An example of such a copolyestercarbonate is found in U.S. Pat. No. 4,506,065 issued to Miller, et al and assigned to General Electric Company, wherein the specific content of the ester units and ester mole percent is emphasized. The standard methods for preparation is disclosed by reference to specific patents. These patents are U.S. Pat. Nos. 4,238,596, previously mentioned, and the U.S. Pat. No. 4,238,597 counterpart which were both incorporated into U.S. Pat. No. 4,506,065 by reference, see column 2, lines 58-61. 
     New chainstopped aromatic copolyestercarbonates have been discovered. These copolyestercarbonates end-capped with a member of the chromanyl family, preferably chromanyl-I, exhibit interesting processing and physical properties. These polymers can exhibit increased distortion temperature under load and improved impact resistance under normal conditions as well as under heat and aging conditions. Additionally, the lower viscosity chromanyl endcapped polymers show positive advantages in color retention and smaller loss in viscosity upon processing than the higher viscosity chromanyl endcapped polymers without sacrificing certain physical properties. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention there is a composition comprising a chromanyl endcapped aromatic copolyestercarbonate, said copolyestercarbonate having from about 35 to about 95 mole percent ester content, said ester content comprising isophthalate and/or terephthalate units. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Typical dihydric phenols which can be employed to prepare copolyestercarbonates of the invention are: 
     2,2-bis(4-hydroxyphenyl)propane (also known as bisphenol-A); 
     2,4&#39;-dihydroxydiphenyl)methane; 
     bis(2-hydroxyphenyl)methane; 
     bis(4-hydroxyphenyl)methane; 
     bis(4-hydroxyphenyl-5-propylphenyl)methane; 
     bis(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)methane; 
     1,1-bis(4-hydroxyphenyl)ethane; 
     1,1-bis(4-hydroxy-2-ethylphenyl)ethane; 
     2,2-bis(3-phenyl-4-hydroxyphenyl)propane; 
     bis(4-hydroxyphenyl)cyclohexylmethane; and 
     2,2-bis(4-hydroxyphenyl)-1-phenylpropane. 
     Bisphenols other than those having a carbon atom between the two phenols can also be used. Examples of such bisphenols include bis(hydroxyphenyl)sulfides, bis(hydroxyphenyl)ethers, and bis(hydroxyphenyl)sulfoxides, and the like. 
     The preferred family of dihydric phenols is illustrated below: ##STR2## wherein R&#39; 1  and R&#39; 2  are the same or different and are hydrogen or alkyl of one to eight carbon atoms, inclusive. 
     The aromatic copolyestercarbonates suitable for use in the present invention are derived from carbonate precursors and dihydric phenols which are also useful in the preparation of a comparable aromatic polycarbonate. However, more than one appropriate dihydric phenol may be used to prepare copolyestercarbonates of the invention. The aromatic dicarboxylic acid employed in the preparation of the copolyester carbonate is preferably isophthalic acid or mixtures of isophthalic and terephthalic acid. Any ester forming derivative of a carboxylic acid which is reactive with the hydroxyl of a dihyric phenol may be employed. The acid halides are generally employed because of their ease of reactivity and availability. The acid chlorides are preferred. 
     The standard methods for preparing copolyestercarbonate as indicated in all of the above noted documents and the state of the art preparations available in the journals can be employed to make the endcapped aromatic copolyestercarbonates of this invention. Generally, from about 2 to about 8 mole percent of the endcapping agent can be employed, preferably from about 3 to about 6 mole percent, most preferably 4 to 5 mole percent. The mole percent of the endcapping agent is based on the number of moles of dihydric phenol present. 
     The chroman family is illustrated in the figure below: ##STR3## wherein R 1  -R 8  can be independently selected from the group consisting of hydrogen and alkyl radicals of 1-9 carbon atoms and wherein R 5  -R 8  can be further independently selected from the group consisting of bromine and chlorine. The polymer is prepared by reacting a substituted chroman with a dihydric phenol and a carbonate precursor. 
     The substituted chroman as employed herein is chroman-I (2,2-4-trimethyl-4-(4-hydroxyphenyl)chroman) and the further substituted derivatives of Chroman-I wherein the substitution is as described above. 
     The substituted chromans that can be employed in the practice of this invention in addition to chroman-I are: 
     2,2,4,6-tetramethyl-4-(3,5-dimethyl-4-hydroxyphenyl)chroman, 
     2,3,4-trimethyl-2-ethyl-4-(4-hydroxyphenyl)chroman, 
     2,2,4-trimethyl-4-(3-nonyl-4-hydroxyphenyl)-7-nonylchroman, 
     2,2,4-trimethyl-4-(3,5-diethyl-4-hydroxyphenyl)-6-ethylchroman, 
     2,2,4,6,8-pentamethyl-4-(3,5-dimethyl-4-hydroxyphenyl)chroman, 
     2,2,4-triethyl-3-methyl-4-(4-hydroxyphenyl)chroman, 
     2,2,4-trimethyl-4-(3-bromo-4-hydroxyphenyl)chroman, 
     2-methyl-2,4 diethyl-4-(4-hydroxyphenyl)chroman; 
     2,3,4-trimethyl-3-ethyl-2-isobutyl-4-(4-hydroxy phenyl)Chroman-I; 
     2,4-diisobutyl-2-methyl-4-(4-hydroxyphenyl) Chroman-I; 
     2,2,4-trimethyl-4-(3-bromo-4-hydroxyphenyl)-6-bromo chroman, 
     2,2,4-trimethyl-4-(3,5-dibromo-4-hydroxyphenyl)-6-bromochroman and 
     2,2,4-trimethyl-4-(3,5-dibromo-4-hydroxyphenyl)-6, 8-dibromochroman. 
     In the practice of this invention, the preferred substituted chroman is chroman-I. 
     The preferred aromatic copolyestercarbonates have above about 40, preferably 50 mole percent ester content. Of these preferred aromatic copolyestercarbonates it is preferred to have at least about 50 mole percent of the ester content be isophthalate, and more preferred to have greater than 80 percent of the ester content isophthalate. The remainder of the ester content is generally made up primarily of terephthalate. 
     Below are examples of the invention which are utilized to demonstrate the specific advantages and properties of the invention. These examples are intended to be illustrative and not narrow the broad inventive concept. 
    
    
     EXAMPLE 1 
     Bisphenol-A copolyestercarbonates having 40 mole percent ester content which was 100 percent terephthalate or 100 percent isophthalate were prepared using 3.2 mole percent of various chainstoppers and tested for a number of properties. Below are the results: 
     
                       TABLE I______________________________________EFFECT OF 3.2 MOLE % CHAIN STOPPER ONPERFORMANCE FOR POLYTEREPHTHALATECARBONATES        CHAIN STOPPERPROPERTY       PHENOL    PTBP.sup.1                            CHROMAN-1______________________________________Tensile Yield (PSI)          9693      9433    9266Tensile Break (PSI)          12,810    12,930  13,590Tensile Elongation (%)          68.1      68.3    78.4Flexural Yield (PSI)          13,810    13,220  13,860Flexural Modulus (PSI)          304,500   298,500 326,000DTUL (°C.)          156.6     161.4   157.4.125 in. Notched Izod          8.0       6.9     8.0(ft.lbs./in.).250 in. Notched Izod          7.8       7.2     8.6(ft.lbs./in.).125 in. Double Gate Izod          37.3*     36.6*   38.6**(ft.lbs./in.)S-Tensile Impact          184       209     197(ft.lbs./in.sup.2)Yellowness Index          8.2       8.3     7.0Melt Viscosity (KI,6 min.)          72,800    116,860 66,770cs..sup.2Melt Viscosity (KI part)          60,130    88,240  50,770cs..sup.2Melt Stability (%)          83        76      76______________________________________ .sup.1 Para tertiarybutyl phenol *100% Brittle Failure **100% Ductile Failure .sup.2 Centiseconds 
    
     Two significant property improvements observed with Chroman-I endcapped polymers were that the unnotched double gate was significantly enhanced by changing from completely brittle to completely ductile and that tensile elongation was increased. 
     
                       TABLE II______________________________________EFFECT OF 3.2 MOLE % CHAIN STOPPER ONPERFORMANCE FOR POLYISOPHTHALATECARBONATES        CHAIN STOPPERPROPERTY       PHENOL    PTBP.sup.1                            CHROMAN-1______________________________________Tensile Yield (PSI)          9956      9753    9565Tensile Break (PSI)          10,620    12,280  11,670Tensile Elongation (%)          80.3      107.1   99.7Flexural Yield (PSI)          14,890    14,630  14,460Flexural Modulus (PSI)          326,900   317,600 313,200DTUL (°C.)          149.6     152.4   153.1.125 in. Notched Izod          10.3      13.5    13.1(ft.lbs./in.).250 in. Notched Izod          2.4       2.1     2.4(ft.lbs/in.).125 in. Double Gate Izod          39.9*     34.6*   37.9**(ft.lbs./in.)S-Tensile Impact          345       305     320(ft.lbs./in..sup.2)Yellowness Index          4.5       4.3     5.0Melt Viscosity (KI,6 min.)          17,130    17,310  17,330cs..sup.2Melt Viscosity (KI part)          15,990    15,270  15,270cs..sup.2Melt Stability (%)          93        88      88______________________________________ .sup.1 Para tertiarybutyl phenol *100% Brittle Failure **100% Ductile Failure .sup.2 Centiseconds 
    
     The Chroman-I endcapped copolyestercarbonates show an increase in the impact resistance with respect to a shift to a completely ductile break from a completely brittle break in the double gate impact test. In comparison to the data in the Table of U.S. Pat. No. 4,238,596, there is no increase in Notched Izod impact resistance or tensile elongation observed when comparing phenol to Chroman-I in U.S. Pat. No. 4,238,596. The DTUL is increased 3.5° C. by going from phenol to a chroman endcap in Table II. 
     
                       TABLE III______________________________________RETENTION OF IMPACT AFTER VARIOUS HOURS OFEXPOSURE TO HEAT (90° C.) FOR THE 100% POLYISO-PHTHALATE COPOLYESTERCARBONATECHAIN  125 NOTCHED IZOD ATTERSTOP-  HOURS OF EXPOSURE ft.lb./in.PER    0      1      2    4    8    16   24  48   96______________________________________Phenol 10.3   3.6    3.3PTBP   13.5   14.9   13.4 3.8  3.4Chroman  13.1   13.1   14.0 13.2 13.0 13.3 4.0 13.7 14.0______________________________________ 
    
     In this testing of impact resistance retention after aging the 1/8 inch Notched Izod bar at elevated temperature, the 100 percent polyisophthalate Chroman-I endcapped polycarbonate clearly outperformed the PTBP and phenol endcapped polymer. 
     When the 100 percent terephthalate Chroman-I end-capped copolyestercarbonates were tested, there was no significant difference over the phenol or PTBP end-capped copolyestercarbonates. 
     Isophthalate containing copolyestercarbonates are clearly more affected by endcapping agents and are easier to process as the chroman endcapped material than the equivalent terephthalate containing copolyestercarbonate as judged by reduced K.I. 
     In the following Tables, copolyestercarbonates were tested and prepared from bisphenol-A, terephthaloyl chloride, isophthaloyl chloride and phosgene while utilizing different levels, based on bisphenol-A of the chainstoppers phenol, paratertiarybutylphenol (PTBP) and Chroman-I. The copolyestercarbonate prepared has 78 weight percent ester content of which 93% is isophthalate and 7% is terephthalate. 
     KI is a measure of melt viscosity of the resin and is calculated according to the procedure of U.S. Pat. No. 4,506,065, column 3, line 60 to column 4, line 13, incorporated by reference. 
     
                       TABLE IV______________________________________  PHENOL    PTBP        CHROMAN-I% CHAIN  KI      DTUL    KI    DTUL  KI    DTULSTOPPER  CSEC    °F.                    CSEC  °F.                                CSEC  °F.______________________________________3.5      40,270  322     34,460                          327   47,240                                      3274.2      26,570  319     28,830                          317   27,920                                      3274.4      17,510  312     19,370                          323   23,430                                      3214.6      17,970  317     17,220                          319   19,240                                      325______________________________________ 
    
     In general, the data of Table IV shows that with Chroman-I as the melt viscosity becomes substantially lowered, the distortion temperature under load is significantly maintained in comparison to either the phenol or PTBP endcapped copolyestercarbonates. Therefore, a more easily processable but still highly temperature resistant polymer is present when a chroman is used as the endcapping agent in higher ester, high isophthalate containing polymers. 
     In Table V below, the KIs of extruded pellets as well as a molded part are reported. The 1/8 inch Notched Izod, DTUL° F and Yellowness Index of molded parts are also reported. Below are the results: 
     
                       TABLE V______________________________________MOLE %   KI CS        1/8 NICHROMAN  PELLET   PART    FT.LBS./IN.                              DTUL °F.                                      YI______________________________________3.5      44,500   39,200  10.4     326     7.44.2      27,200   23,900  10.5     326     4.94.4      23,100   20,400  10.3     324     3.74.6      19,200   18,000  10.3     326     3.5______________________________________ 
    
     The drop in melt viscosity from pellet to part decreased significantly as the chain stopper level was increased to 4.6% from 3.5%, i.e. from 88% retention to 94% retention. The impact resistance and the DTUL stayed essentially the same while the Y.I. actually improved. 
     The above noted parts were then tested for impact resistance, 1/8 inch Notched Izod, after aging at 90° C. for a specific number of hours. 
     
                       TABLE VI______________________________________    X = HOURS AT 90° C. WHILE RETAININGMOLE %   INITIAL IMPACTCHROMAN  PTBP            CHROMAN______________________________________3.5      8 &lt; X &lt; 24      X &gt; 1444.2      X &lt; 1           48 &lt; X &lt; 724.4      X &lt; 1           8 &lt; X &lt; 244.6      X &lt; 1           8 &lt; X &lt; 24______________________________________ 
    
     From this data it is very clear that the Chroman endcapped copolyestercarbonate retains its impact strength for a substantially longer period of time when aged at an elevated temperature. 
     In summation, the collected data shows that the use of a chromanyl endcapping agent in comparison to the standard phenol or PTBP endcapping agent for aromatic copolyestercarbonates brings about significant unexpected changes in the properties of the aromatic copolyestercarbonates.