EP0523087A1

EP0523087A1 - High impact polyethylene terephthalate-polycarbonate blend compositions

Info

Publication number: EP0523087A1
Application number: EP19910906621
Authority: EP
Inventors: Murali Krishna Akkapeddi; Charles Driscoll Mason
Original assignee: AlliedSignal Inc
Current assignee: Honeywell International Inc
Priority date: 1990-04-04
Filing date: 1991-02-26
Publication date: 1993-01-20
Also published as: JPH05501128A; WO1991015545A1; BR9106113A; CA2075910A1

Abstract

Compositions polymères comprenant du poly(éthylène téréphthalate), du polycarbonate et un constituant de therpolymère présentant des propriétés de résistance à l'impact améliorées, notamment après un vieillissement thermique.Polymeric compositions comprising poly (ethylene terephthalate), polycarbonate and a therpolymer component having improved impact resistance properties, especially after thermal aging.

Description

"HIGH IMPACT POLYETHYLENE TEREPHTHALATE-POLYCARBONATE

BLEND COMPOSITIONS"

BACKGROUND

1. Technical Field of the Invention:

The present invention relates to particular polyester molding compositions which are characterized by exceptional toughness subsequent to annealing. More particularly, the present invention is directed towards a composition which comprises a polyester and

polycarbonate or a polyarylate which further includes a reactive impact modifier.

2. Description of the Prior Art;

Engineered plastics enjoy widespread popularity for the production of articles through the use of molding or casting processes. The materials typically comprise one or more polymeric materials which exhibit specific properties, i.e., toughness, rigidity,

chemical resistance, long-term hygrothermal dimensional stability, dielectric strength, and the like.

Frequently, materials which exhibit particular features such as those listed are utilized as constitutents in the formation of so called "blended polymers" which comprise two or more constituent materials, such as a two or more polymers, or a polymer with a non-polymeric material, which constitutents will ideally form a material which exhibits the beneficial features of the constituents, with few if any detrimental qualities. Unfortunately, as is well known to the art, the

formation of blended polymeric materials are rarely attained which offer the desirable characteristics of the constituents, without simultaneously suffering fro m some detrimental quality.

One polymer which is widely used in the

formulation of engineered plastics is a polymer of an aromatic carbonate. Such carbonate polymers, also generically termed in the art as "PC's", may readily be prepared by reacting a dihydric phenol, such as

2,2-bis-(4-hydroxyphenyl) propane with a carbonate precursor, such as a phosgene, in the presence of an acid binding agent. Generally, aromatic polycarbonate plastics may be easily -molded, have a high tensile and impact strength, and exhibit an excellent degree of dimensional stability in most articles formed

therefrom. However, in particular applications, aromatic polycarbonates are unsuitable as they are also known to exhibit severe environmental stress crazing and cracking, i.e., a type of failure which is enhanced by the presence of organic solvents such as basic solvents such as many hydrocarbons, alcohols, ketones, etc which are the constituents of may common automobile fluids, gasoline, paints, and the like. Most

significantly, the loss of impact strength and an increase in brittle type failures in standard testing procedures has been observed. Certain formulations of polycarbonates have been devised which increase the resistance of polycarbonates to environmental stress cracking including the addition of a minor amount of a polyalkylene terephthalate such as poly(ethylene terephthalate) and ρoly(butylene terephthalate).

However, articles formed from a blend of a

polycarbonate and a minor amount of a polyalkylene terephthalate have been observed to have a lower impact resistance to that of the polycarbonate itself. This has led to the suggestion of using additional

constituents in a polycarbonate and polyalkylene terephthalate blend in order to improve the impact resistance of such materials.

Polyalkylene terephthalates including

poly(ethylene terephthalate), also known to the art by its acronym "PET", and ρoly(butylene terephthalate), similarly referred to as "PBT" are aromatic polyesters which enjoy frequent use either as the sole materials or as constituents in plastic products where rigidity, impact resistance, and abrasion resistance, are

required. This is known to the art to be due to the relatively high degree of crystallinity which

polyalkylene terephthalates, particularly PBT, exhibit subsequent to cooling fromthe melt, and thus encourages their use in many molding operations, particularly injection molding processes. However, these materials, most particularly PET, are known to exhibit poor impact resistance properties subsequent to annealing or heat aging. In contrast to PBT, injection molding of PET results in a slow rate of crystallization and

non-uniform or low crystallinity in molded articles. Subsequent annealing or heat exposure of PET molded articles causes further crystallization resulting in larger, non-uniform crystalline structures. However, as is well known to the art, polymers which exhibit large, non-uniform crystalline structures also exhibit low impact resistance, a quality which is frequently undesirable in molded articles. Thus, unfilled PET is not normally preferred as injection molding resins due to its lower impact resistance as compared to PBT, after crystallization.

Further suggested improvements in the processing and the physical properties of plastic materials comprising a blend or mixture of a polycarbonate and an ρoly(alkylene terephthalate) have included the addition of further constituents to these two polymers, or the use of specific molding processes for the production of articles formed from polycarbonate and poly(alkylene terephthalate) blends. Some examples include U.S.

Patent 4,522,979 to Chung et.al. for "Molding

Compositions Having An Enhanced Resistance to Gasoline" which discloses PE and PC blended with rubbery impact modified and a blocked polyisocyanate prepolymer, U.S. Patent 4,764,556 to Lausberg et.al. for "Thermoplastic Molding Materials of Polyester and Polycarbonate" disclosing a thermoplastic molding material comprising polyalkylene terephthalates, polycarbonates and a rubber toughener and rubbery ethylene copolymers; U.S. Patent 4,897,448 for "Polyester/Polycarbonate Blends" to Romance for PE/PC blends which include core shell rubbers as impact modifiers; U.S. Patent 4,737,545 to Liu et.al. for "Ternary Polycarbonate Blends"

disclosing compositions having a major amount of an aromatic carbonate polymer, and a minor amount of an aromatic carbonate polymer impact modifying composition comprising a "teleblock" copolymer of a vinyl aromatic compound and an olefinic elastomer, and an olefin alkylacrylate. Further are U.S. Patent 4,629,760 to Liu et.al. for "Composition of Polycarbonate,

Polyester , Acrylate Elastomeric Copolymer and a Phenoxy Resin" discusses a polymer composition which comprises a PC, polyalkylene terephthalate and an elastomeric acrylate copolymer, and of particular note is U.S.

Patent 4,753,980 to Deyrup for "Toughened Thermoplastic Polyester Compositions" where Deyrup describes

compositions which include a polyester resin, which may be a poly(alkylene terephthalate) polymer, such as PET or ρoly(butylene terephthalate), which is commonly known as "PBT" either as a homopolymer or a copolymer, or mixtures of PET and PBT, and an ethylene terpolymer such as ethylene/methacrylate/glycidyl methacrylate.

Further, European Application 0 180 648 to Toray Industries, Inc. for a "Polyester Composition and

Moldings Thereof" discloses a polymer composition comprising an aromatic polyester, an aromatic

polycarbonate having a number average molecular weight of 10,000 to 80,000 and a copolymer consisting

essentially of an alpha-olefin and the glycidyl ester of an alpha, beta-ehylenically unsaturated carboxylic acid.

While some of these techniques have provided compositions yielding articles having

satisfactory properties, their diversity and number indicate that the need for novel

compositions which exhibit further improvements in properties, and processability

exists.

SUMMARY OF THE INVENTION

In accordance with the instant invention there is provided an impact modified polyester-polycarbonate composition comprising:

a polyester,

a polycarbonate represented by recurring structural units of che formula:

where A is a divalent aromatic radical derived from a dihydric aromatic compound, and a reactive terpolymer constituent (hereinafter interchangeably referred to as "graft terpolymer") which comprises a compound having the formula:

[Formula 1] E/A/X where "E" is representative of an alpha-olefin, or in the alternative, an alkadiene, "A" is representative of a material having the formula.

[Formula 3]

where "Y" is -H or an alkyl substituent, "Z" is -COOR, -CN, -OCOR, or -Ar, wherein "R" may be a methyl, ethyl, butyl or other alkyl group, and "Ar" may be a phenyl or substitued phenyl, and "X" represents a comonomer exhibiting the structure

[Formula 4]

which contains a reactive functionality "P" which is selected from epoxide, isocyanate, 1,3-oxazoline, or acyllactam functionalities, where the terpolymer forms graft linked bonds with other polymeric materials in a composition, particularly with polycarbonates and the poly(ethylene terephthalates).

Molded articles comprising the inventive composition are also provided.

It has also been unexpectedly discovered that a polymer composition having improved properties may be produced wherein the inventive polymer composition comprises a polycarbonate and a poly(ethylene

terephthalate) and an active graft terpolymer according to the aforementioned formula "E/A/X" which graft terpolymer exhibits the reactive ability of forming graft-type bonds with polycarbonates and with the terminal groups of poly(ethylene terephthalate) exhibits improved properties, especially retention of high impact resistance properties subsequent to heat aging.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, the polycarbonates which may be used are the carbonate polymers of dihydric phenols. Such polycarbonates may be prepared by reacting a dihydric phenol with a carbonate

precursor such as a phosgene, a halo formate, or a carbonate ester. In general, the resulting polycarbonate may be represented by recurring

structural units of the formula:

[Formula 2]

where A is a divalent aromatic radical derived from a dihydric aromatic compound, preferably bisphenol A. These dihydroxy aromatic compounds are defined as 4,4'- dihydroxydi(mononuclear aryl)A compounds where the mononuclear aryl may be phenyl, tolyl, xylyl,

ethylphenyl, isopropylphenyl, etc., and the connecting A groups may be -CH₂-, -C-H₄-, -C₃H₆,

-C₄H₈-, -SO₂-, -S-, -O-, -C₃F₆, etc.

Typical dihydric phenols are

2,2-bis(4-hydroxyphenyl)propane

2,2-bis(4-hydroxyphenyl)hexafluoropropane;

2,2-bis(4-hydroxyphenyl)pentane;

2,4'-(dihydroxydiphenyl)methane;

bis-(4-hydroxyphenyl)methane;

bis-(2-hydroxyphenyl)methane;

hydroquinone;

Resorcinol;

bis-(4-hydroxy-5-nitrophenyl)methane;

1,1-bis(4-hydroxyphenyl)ethane;

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-dimethyl-4-hydroxyphenyl)propane;

2,4'-dihydroxydiphenyl sulfone;

5'-chloro-2,4'-dihydroxydiphenyl sulfone;

bis-(4-hydroxyphenyl)diphenyl sulfone;

4,4'-dihydroxydiphenyl ether;

4,4'-dihydroxy-3,3'-dichlorodiphenyl ether; 4,4'-dihydroxy-2,5'-dihydroxydiphenyl ether; and the like.

Other suitable dihydric phenols are disclosed in U.S. Patents 4,126,602, 2,999,835, 3,028,365,

3,334,154, and 4,131,575. It is also possible to employ two or more different dihydric phenols for the preparation of the polycarbonate.

These aromatic polycarbonates can be manufacture by known processes, such as noted above, by reacting a dihydric phenol with a carbonate precursor, such as a phosgene with the methods set forth, and disclosed in U.S. Patent 4,018,750, or by transesterification processes disclosed in U.S. Patent 3,153,008, as well as other processes well known to the art.

Further, as noted above, two or more different dihydric phenols may be utilized, as well as a

copolymer of a dihydric phenol with a glycol or with a hydroxy or acid-terminated polyester or with a dibasic acid in the event a carbonate copolymer rather than a homopolymer is desire for use in the preparation of the polycarbonate. Branched polycarbonates are also useful, such as those described in U.S. Patent

4,001,184. Further, blends of a linear polycarbonate and a branched polycarbonate may also be used.

Moreover, blends of any of the above materials may be employed in the practice of this invention to provide the aromatic polycarbonate. In any event, the

preferred aromatic polycarbonates are those selected from the group consisting of:

poly(2,2-bis(4-hydroxypehyl)alkane) carbonates. The most preferred of these polycarbonates is a

polycarbonate derived from

2,2-bis(4-hydroxyphenyl)propane.

Polycarbonates utilizable with the invention should have a number-average molecular weight of 10,000 to 80,000. Preferably, the range of the number-average molecular weight is in the range of 15,000 to 40,000. While the specific number-average molecular weight of the polycarbonate is recognized not to be detrimental to the operation of the novel graft terpolymer which provides improved properties in polymer compositions within which it is utilized, it has been observed that when the number-average molecular weight of the

polycarbonate is less than about 10,000 or more than about 80,000, the resultant product polymer composition has been observed to be inferior in molding and

processability, or deficient in mechanical properties, particularly tensile strength subsequent to heat aging.

The polycarbonates should preferably exhibit an intrinsic or inherent viscosity of about 0.2 to 1.2 dl/g, (deciliters/gram) more preferably of about 0.3 to 0.9 dl/g in dichloromethane by standard Ubbehlohde viscometry at room temperature. Although not

essential, the polycarbonates should preferably contain hydroxyl end groups.

Suitable polyesters include polymers which exhibit an inherent viscosity of 0.3 dl/g or greater and which generally are the linear saturated

condensation products of glycols and dicarboxylic acids, or reactive derivates thereof. Preferably, they will comprise condensation products of aromatic

dicarboxylic acids having 8 to 14 carbon atoms and at least one glycol selected from the group consisting of cyclohexane dimethanol, neopentyl glycol, and aliphatic glycols of the formula HO(CH₂)_nOH where the letter "n" may be any integer of 2 to 10. Up to 50 mole percent of the aromatic dicarboxylic acids can be replaced by at least one different aromatic

dicarboxylic acid having from 8 to 14 carbon atoms, and/or up to 20 mole percent can be replaced by an aliphatic dicarboxylic acid having from 2 to 12 carbon atoms.

In accordance with the present invention , suitable oolyesters include : poly(ethylene terephthalate);

poly(1,4-butylene) terephthalate;

1,4-cyclohexylene dimethylene

terephthalate/isophthalate copolymer and other linear homopolymer esters derived from aromatic dicarboxylic acids, including but not limited to isophthalic, bibenzoic, naphthalene-dicarboxylic including

1,5-naphthalenedicarboxylic acid;

2,6-naphthalenedicarboxylic acid;

2,7-naphthalenedicarboxylic acid;

4,4'-diphenylenedicarboxylic acid;

bis(p-carboxyphenyl)methane;

1,4-tetramethylene bis(ρ-oxybenzoic) acid;

ethylene bis(p-oxybenzoic) acid;

ethylene bis-p-benzoic acid;

1,3-trimethylene bis(p-oxybenzoid) acid; and

1,4-tetramethylene bis(p-oxybenzoic) acid;

and glycols selected from but not limited to

2,2-dimethyl-1,3-propane diol;

neopentyl glycol;

cyclohexane dimethanol and

aliphatic glycols of the general formula HO(CH₂)_nOH where "n" may be an integer from to 10, and thereby, for example and not by limitation, may be one of the following:

ethylene glycol;

1,3-trimethylene glycol;

1,4-tetramethylene glycol;

1,6-hexaraehtylene glycol;

1,8-octamethylene glycol;

1,10-decamethylene glycol;

1,3-proρylene glycol; and

1,4-butylene glycol. Up to 20 mole percent, as indicated above, or one or more aliphatic acid may be included. For example, suitable aliphatic acids include adipic, sebacic, azzelaic dodeandioic and

1,4-cyclohexanedicarboxylic. Prefereably, the polyester is one or more of the poly(alkylene terephthalates), either as a homopolymer or as a copolymer of two or more poly(alkylene

terephthalates). The acronym "PAT" will be

interchangeably used as a designator for poly(alkylene terephthalates) as a labelling convention herein.

The preferred compositions include PET

homopolymers, or PET copolymers containing minor amounts of comonomers, as distinct from PBT

homopolymers as as is well known to the art, these two materials exhibit different morphologies due to the differences in their crystallization behavior. This difference, viz. the lower crystallization rate and the tendency to form large, non-uniform crystalline

structures in the case of PET as compared to PBT, in finished articles is known to the art to account for the different impact strengths of these materials subsequent to an annealing operation, or subsequent to any extended exposure to heat. PET's relatively rigid non-uniform crystalline morphology is known to cause more brittleness, and is thus less desirable as a material for use in forming articles, particularly in the absence of fillers and reinforcing agents.

The polyester should preferably have an

intrinsic viscosity of about 0.2 dl/g to about 1.2 dl/g; more preferably the viscosity should be in the range of between about 0.4 to about 0.95 dl/g. These viscosity values are determined with the use of a standard Ubbehlohde viscometer in a

phenol-tetrachloroethane (60/40 v/v) solution in a concentration of 0.5% at room temperature. The

polyesters should preferably have active chain end groups viz., carboxylic acid and/or hydroxyl end groups in a concentration of at least 0.01 meq/g. The end groups are determined by standard titrametric methods for carboxyl or hydroxyl determination. The compositions in accordance with the present invention, based on the total weight percentage of the composition, includes relative weight ratios of the polycarbonate in the range of about 30 to about 60 percent; the polyester in the range of about 30 to about 60 percent; and the graft terpolymer more fully discussed below in a range of weight ratios of between about 2 and about 30 percent. More preferably the polyester should comprise about 40 percent of the composition, with the polycarbonate and the graft terpolymer comprising the remaining amount of the composition, as it has been observed that favorable impact properties subsequent to heat aging have has not been realized where the polyester is present in less than such a proportion.

According to the invention, the compositions will further include a terpolymer constituent, or as interchangeably referenced above, a "graft terpolymer" comprising a compound having the formula:

[Formula 1] E/A/X where "E" is representative of an alpha-olefin, or in the alternative, an alkadiene, "A" is representative of a material having the formula,

[Formula 3]

where "Y" is -H or an alkyl substituent, "Z" is -COOR, -CN, -OCOR, or -Ar, of which "R" may be a methyl, ethyl, butyl or other alkyl group, and "Ar" may be a phenyl or substitued phenyl, and "X" represents a comonomer exhibiting the structure

[Formula 4]

which contains a reactive function "P" which is selected from epoxide, isocyanate, 1,3-oxazoline, or acyllactam functionalities. Typically, "X" has a moiety derived from acrylic and methacrylic acid or allyl alcohol, e.g., glycidyl acrylates, glycidyl methacrylates, or glycidyl allyl ether. The terpolymer forms graft type bonds with other polymeric materials in a composition, particularly with polycarbonates and the poly(ethylene terephthalates).

In accordance with the invention, the

constituents of X are epoxide, isocyanate, acyllactam or oxazoline. Accordingly, X having epoxide

functionalities may be derived from glycidyl acrylate, glycidyl methcrylate, glycidyl allyl ether, and other glycidyl containing compounds. Where X is to have an isocyanate functionality, X may be derived from

2-isocyanotoethylmethacrylate, p-isopropenyl

alpha, alpha-dimethyl benzyl isocyanate, m-isopropenyl alpha, alpha-dimethyl benzyl isocyanate, and the like. Where oxazoline functionalities are desired, X may be derived from 2-isopropenyl-1,3-oxazoline, 2-(p-vinyl phenyl)-1,3-oxazoline, and the like. Where acyllactam functionality is desired, X may be derived from

methacryloyl caprolactam, methacryloyllaurolactam, compounds of the general formula:

[Formulaa 5] where "x" may have a value of 3 to 10, and "y" may be -H or -CH₃.

The grafted terpolymer may be synthesized by copolymerization of E, A or X in bulk or solution phase, catalyzed by free radical initiators or other types of initiators. The relative weight ratios of the constituents comprising the graft terpolymer may be present in proportions which, relative to the total weight of the terpolymer of between about 98.9 and 45 weight percent E, between about 1 and 40 weight percent A, and between about 0.1 and about 15 weight percent X. It is to be noted that the relative proportions of the constituents relative to the total weight are subject to a great deal of variation and are dependent upon the weight of the individual constituents.

Further, their relative proportions may be adjusted to suit the reactivity of a particular composition.

All of these functional groups of the terpolymer disclosed in this invention are found to exhibit grafting with the PET and the PC due to their high reactivity; E/A/X compositions where X exhibits an epoxide or oxazoline functionality were found to be highly advantageous.

An advantageous feature of the terpolymer is that the "X" functionalities also act as "water

scavengers" within the polymer, and during the

production of the polymer may act to remove free water molecules from the polymer melt. Such a feature eliminates the necessity of drying the poly(ethylene terephthalate) before it is melted during processing, which is a feature especially advantageous when

recycled PET is used as a feedstock. This is

beneficial in forming polymer compositions which have lower water contents, and hence, require less or no drying.

It should be evident to those skilled in the art that minor amounts of organic modifiers, generally to comprise no more than about 10% of a composition, may be added to the composition according to the

invention. Examples of such typical modifiers include heat stabilizers, flame retardants, pigments and coloring agents, nucleators, lubricants and flow modifiers, especially ethylene copolymers which are frequently used additives for improving the melt flowcharacteristics of many polymer materials. Also, the use of in-organic materials as in-organic

modifiers, such as fillers, and reinforcing agents

(including glass fibers, talc carbon fibers, and the like) may be included in any suitable amount, which is preferably in a range typically used in the art, between about 40 and 50%.

The compositions in the Examples were generally prepared by one of two methods. In the first method, where there is no preblending of the components, the melt blend is prepared by first dry blending the constituents in their appropriate weight percentages by tumble blending or in a rotary drum, then feeding in the blended constituents into the hopper of a single screw extruder which was heated so to form a melt of the constituents and then extruding it through a die to form strands. The extrudate was rapidly passed through a water bath in order to quench and cool the strands. The strands were then passed through a pelletizing machine and the pellets were collected and dried.

In the second method where an additional preblending step is included in the formation process, the polycarbonate utilized and the terpolymer are first preblended before combining them with the PET of any desired composition. This second method is the

preferred one as the preblending allows for a more homogeneous phase distribution of the terpolymer and the polycarbonate, which being preblended, improves the distribution of the terpolymer within the polycarbonate and PET, increasing the amount of grafting in the final composition and thereby enhancing the improved

properties of the final composition. According to this second method, the polycarbonate and the termpolymer are first preblended via a melt extrusion before blending with the PET by another melt extrusion

operation, thus essentially constituting a 2-step single screw extrusion process. Alternatively, the melt blend may be prepared by use of a 2-stage, single pass extrusion process. In such a process, a dry blend of the polycarbonate and the terpolymer in their appropriate weight percentages is introduced into a first hopper of a single screw extruder. The

appropriate amount of PET is introduce into a second hopper of the extruder at location downstream

approximately midway between the first hopper and the die at the exit of the extruder. Similarly, the extrudate was rapidly passed through a water bath in order to quench and cool the strands which were then pelletized, and collected, and when necessary, dried.

The pellets were utilized to mold test specimens which were 1/8 inch test bars which are a standardized sample size well known to the art by use of an

injection molding machine. Both tensile bars and Izod impact bars were prepared utilizing this process.

Subsequently, a quantity of the test bars were annealed in an annealing oven at a temperature of about 150 deg.C where they were retained for periods of either 16 hours or 72 hours in accordance with testing parameters well known to the art.

Testing of the test bars was accomplished in accordance with the standardized testing

procedures prevalent in the art; the tensile strength was tested in accordance with

ASTM D-3029 standards using a falling weight impact tester, and the impact strength

was determined under the testing conditions of D-256 using a notched Izod pendulum

impact apparatus for measurement. EXAMPTES OF THE INVENTlON

The following examples show particular embodiments of the present invention, and illustrate the extraordinary toughness properties of specific compositions of PET and polycarbonates by the inclusion of a reactive terpolymer disclosed herein. It is to be understood that the following examples of the invention are for illustration only and the scope of the

invention is bounded only by the accompanying claims.

Unless otherwise indicated, the use of

percentages within any Example are to be understood as the weight percentages of the individual constitutents relative to the total weight of the constituents.

Example 1.

Example 1 is a melt blend composition consisting essentially of 40% PET, 40% of a polycarbonate and 20% of an ethylene/ethyl acrylate/glycidyl methacrylate terpolymer. The PET used was a bottle grade resin with 0.67 I.v. ( as determined in phenol/TCE) and typically containing between about 0.035-0.04 meg/g of carboxyl chain ends. The polycarbonate used was commercially available from the under the trade name "Lexan", a name used for a family of polycarbonate materials. The particular polycarbonate used was "Lexan 101". The ethylene/ethyl acrylate/glycidyl terpolymer was

described as having a relative weight ratio of 75% ethylene, 17% ethyl acrylate and 8% glycidyl

functionality.

The melt blend was prepared by first dry

blending all of the constituents together and

subsequently, the dry blended constituents were then fed into the hopper of a Killion 1 inch single screw extruder with a L/D ratio of 30/1 using a feed screw equipped with a Maddox mixing head. The extruder barrel temperatures for each zone were kept at the following approximate temperatures of: Zone 1, 205 deg.C; Zone 2, 250 deg.C; Zone 3, 270 deg.C; Zone 4, 250 deg.C. The temperature of the flange was kept at approximately 250 deg.C and the temperature of the dies was kept at approximately 210 deg.C. The extruder screw rotational speed was maintained at about 60 rpm. The extrudate was rapidly passed through a water bath in order to quench and cool the strands. The cooled strands were then passed through a pelletizing machine and the pellets formed were collected and dried.

Thereafter, the pellets were molded into test specimens by injection molding using an injection molding machine. The barrel temperature of the machine during the injection process was maintained within a temperature range of about 280 - 287 deg.C and the mold was kept at a temperature of about 50 deg.C. During the molding operation, the cycle time was approximately 10 seconds during the injection step, and approximately 20 second during cooling. The pressure of the

operation was approximately 300 psi, with a pressure hold of 500 psi. Standardized tensile bars and Izod impact bars were prepared. A quantity of the test bars were annealed, or heat aged in a circulating hot air oven at about 150 deg.C for periods of either 16 hours or 72 hours.

Testing of the samples included impact testing, tensile elongation, tensile modulus and yield stress according to known testing procedures. The physical properties measured indicate extraordinary toughness of the material subsequent to annealing. Results of the tests are summarized under the heading "Ex.1" on Tables 1 and 2 below.

Comparative Examples A, B, C, D, E

The comparative examples A, B, C, D and E are compositions comprising PET, PC and various impact modifiers. Each of these examples was prepared in the same manner as the composition of Example 1, and consisted essentially of 40% PET, 40% of a

polycarbonate and 20% of one of the various impact modifiers. Comparative Example A used an methyl

methacrylate-butadiene-styrene, (which is frequently catergorized in the art as an "interpolymer") or "MBS" core shell rubber as its impact modifier. This rubber enjoys significant usage in the art as an impact modifier as this material exhibits good elasticity and provides good impact absorption.

The impact modifier used in the composition of Comparative Example B was an

acrylonitrile-butadiene-styrene, or "ABS" rubber which similarly to MBS exhibits good elasticity and good impact absorption. The formulation B was commercially obtained from Mobay Chemical Co. under the trade designation "Makroblend UT1018".

The impact modifier used in comparative example

C is an all-acrylate core shell rubber, which is marketed under the trademark "Paraloid KM 330" by Rohm & Haas, and consists of a cross linked

polybutylacrylate core and polymethylmethacrylate shell.

In the formulation of Comparative Example D, an ethyl/ethyl acetate copolymer was used as the impact modifier.

Comparative Example E utilizes an ethyl/glycidyl methacrylate copolymer as the impact modifier. The particular copolymer is commercially marketed under the tradename "Bondfast 2C" and is available from the

Sumitomo Chemical Co. The relative weight ratios of the ethyl to the glycidyl methacrylate in the copolymer is 94/6.

The compositions of examples A, B, C, D and E were all produced, molded and subsequently tested in the manner utilized in the production of example 1, so to more clearly illustrate the distinct advantage of compositions made in accordance with the invention.

Likewise, the testing of the samples included impact testing, tensile elongation, tensile modulus and yield stress according to the same testing procedures

utilized in testing the composition of Example 1. The physical properties measured for these Comparative Examples indicate the marked reduction in the toughness of the material subsequent to annealing, or heat aging at 150 deg.C. Results of the tests are also summarized under the appropriate headings and listed on Tables 1 and 2 below.

The resultant physical test data particularly illustrates that the compositions of the present invention, namely, the compositions which include a reactive graft-terpolymer show the unexpected

advantages of improved toughness subsequent to

annealing and superior impact strength retention. This is attributed to the functionality of the terpolymer in its ability to form a graft copolymer through reaction with the terminal end groups, carboxyl and hydroxyl, of PET and PC. Further, the excellent elasticity of the terpolymer imparts good impact energy absorption qualities to the molded composition, and which is further believed to act as a compatibilizing agent for the PET and PC used.

Examples 2-6

Examples 2,3,4,5 and 6 are further embodiments of the invention which utilized the constituents as used to formulate Example 1, but varies the relative proportions of the PET, PC and the reactive terpolymer used in Example 1. The range of variation for the respective components based on the total weight of the composition was: 30% to 80% PET, 0% to 50% PC, and a constant 20% of the terpolymer. The specific

proportions

are outlined in Table 3.

The compositions of Examples 2-6 were produced in the same manner as that used for the production of Example 1.

The physical characteristics of the materials produced from the compositions outlined in Table 3 are summarized in Table 4.

As may be determined from Tables 3 and 4, the composition of Example 5 exhibited

particularly good retention of impact properties and elongation strength.

Examples 7-12

Examples 7-12 exemplify the second, alternative method of preparing the compositions. According to this second method, an additional step, "preblending" of the polycarbonate and the reactive terpolymer. This preblending may be accomplished by methods known to the art, including a two-step process, or a two-stage, single pass extrusion process. This latter process was used for the formation of the compositions of Examples 7-12.

Table 5 indicates the various ratios of constituents utilized in the compositions of Examples 7-12 which were produced using a preblending step. The percentages shown are percent by weight of the

compos i tion of each Example .

The corresponding physical properties observed during the testing of these materials is summarized on Table 6.

As may be discerned from the results shown on Table 6, the compositions showed good retention of impact strength throughout, especially for Examples 7-10. It may further be observed that the second method of forming compositions, where there is preblending may be advantageous to the first method without preblending of the constitutents by a

comparison of the physical test data of Tables 2 and 3 with Tables 5 and 6 which contrasts similar

compositions produced by processes including no preblending with processes including preblending.

Particularly, the following paired compositions having the same ratio of constituents, and their resultant physical properties may be compared: Example 5 and Example 7, Example 4 and 10. Particularly, the impact test values (notched Izod) indicate improved

toughness. Such results are believed to be

attributable to improved grafting of the reactive graft terpolymer and the polycarbonate prior to the

introduction of the ρoly(ethylene terephthalate.)

Example 13. Comparative Example E

The composition of Example 13 was a composition consisting essentially of 40% PET, 40% PC and 20% ethylene/ethyl acrylate/glycidyl methacrylate

terpolymer was produced. Comparative Example E was a composition of PET, PC and an

acrylonitrile-butadiene-styrene terpolymer, which is marked under the tradename "Makroblend" was tested with the composition of Example 13. Both compositions were subjected to drop weight impact testing at low

temperatures (-40 deg.C) prior to, and subsequent to heat aging, and the results of these tests is listed on Table 7.

The composition of Example 13 was noted to be completely ductile before heat-aging, and the

composition of Comparative Example E was noted to be completely brittle after heat aging, and showed poor strength retention.

Example 14. 15, 16

Three exemplary compositions comprising the terpolymer of the present invention by melt blending the constituents in accordance with the method

described for Example 1, with the following particular compositions outlined on Table 8.

The following physical properties outlined on Table 8A were observed.

The resultant testing data reveals that the compositions containing an amount of an ethylene copolymer, such as E/EA noted above, but not to be limited solely to E/EA, may be included in compositions, generally in amounts of up to about 10% so to replace up to about half of the reactive

terpolymer may be used without detracting from the beneficial qualities of the present invention.

While these exemplary embodiments have described various aspects of the invention, it is to be

understood that the scope of the invention is to be limited only by the following claims.

Claims

WE CLAIM:

1. An impact modified polyester-polycarbonate composition which includes

at least one polyester,

at least one polycarbonate represented by

recurring structural units of the formula:

where "A" is a divalent aromatic radical derived from a dihydric aromatic compound,

c h a r a c t e r i z e d by:

further including a terpolymer constituent having the formula:

E/A/X

where "E" is representative of an alpha-olefin, or in the alternative, an alkadiene, "A" is representative of a material having the formula,

where "Y" is -h or an alkyl substituent, "Z" is -COOR, -CN, -OCOR, or -Ar, "R" is a methyl, ethyl, butyl or other alkyl group, andd "Ar" is a phenyl or substituted phenyl, and

"X" represents a comonomer exhibiting the

structure,

which contains a reactive functionality, "P" which is selected from among epoxide, isocyanate, 1,3-oxazoline or acyllactam functionalities.

2. The impact modified polyester-polycarbonate composition of claim 1 wherein the at least one

polyester is selected from the group which includes: linear condensation products of saturated glycols;

linear condensation products of a saturated

dicarboxylic acid;

poly(alkylene terephthalte)s;

poly(ethylene terephthalate);

poly(butylene terephthalate);

condensation products of an aromatic dicarboxylic acid having 8 - 14 carbon atoms and at least one glycol selected from among cyclohexane dimethanol, neopentyl glycol, aliphatic glycols of the formula HO(CH₂)_nOH where the letter "n" represents an integer of 2 - 10.

3. The impact modified polyester-polycarbonate composition of claim 1 wherein the at least one polycarbonate is selected from the group which

includes:

4,4'-dihydroxydi(mononuclear aryl)A compounds where the mononuclear aryl may be phenyl, tolyl, xylyl,

ethylphenyl, isopropylphenyl, and where the connecting "A" groups may be -CH₂-, -C₂H₄-, -C₃H₆-, -C₄H₈-, -SO₂-, -O- , -S-, or "C₃F₆;

polycarbonates derived from a dihydric phenol and a dibasic acid;

poly(2,2-bis(4-hydroxyphenyl)alkane) carbonates;

poly(2,2-bis(4-hydroxyphenyl)proρane). 4. The impact modified polyester-polycarbonate composition of claim 1 wherein the at least one

terpolymer constituent is selected from the group which includes:

terpolymer constituents which have an isocyanate functionality derived from a material selected from the group consisting of; 2-isocyanoethylmethacrylate, pisopropenyl-alpha,alpha-dimethyl benzyl isocyanate, nisopropenyl-alpha, alpha-dimethylbenzyl isocyanate;

terpolymer constituents which have an acyllactam

functionality derived from a material selected from the group consisting of; methacroyl caprolactam,

methacryloyllaurolactam, compounds of the general formula

where "x" may have a value of 3 to 10.

5. The composition according to claim 1 wherein the relative weight ratios of the constituents comprising the graft terpolymer are of the following relative weight percentages: 45-98% of "E", 1-40% of "A", 1-15% of "X".

6. The composition according to any preceeding claim further

c h a r a c t e r i z e d by:

further including an ethylene copolymer.

7. The composition according to any preceeding claim further

c h a r a c t e r i z e d by:

including at least one modifier selected from among the group which includes; organic modifiers, inorganic modifiers.

8. The composition according to any preceeding claim further

c h a r a c t e r i z e d by: the relative weight ratios of the constituents of the impact modified polyester-polycarbonate composition consists of at least 40% polyester, 40% polycarbonate, and 10% of the terpolymer constituent having the formula:

E/A/X.

9. A molded article

c h a r a c t e r i z e d by:

comprising the impact modified polyester-polycarbonate composition according to any preceeding claim.