WO1991005823A1 - Improving the toughness and processibility of high heat polycarbonate compositions - Google Patents

Abstract

Compositions of polycarbonate having good resistance to thermal deformation, good impact resistance and reduced notch sensitivity are formed from a high heat polycarbonate, an elastomeric toughening agent such as a thermoplastic or core-shell rubber, and a flow modifier such as an olefin/carbon monoxide copolymer, a styrenic thermoplastic resin, a polyester or a polyamide. The presence of the flow modifier in the composition reduces the viscosity of the high heat polycarbonate and thus the temperature at which it can be processed or compounded. Compounding at such lower temperature allows formation of the composition at a temperature which is low enough that the toughening agent will not be degraded. The flow modifier should be added to the composition no later than the addition of the toughening agent so that there is an opportunity for the flow modifier to perform this function.

Description

IMPROVING THE TOUGHNESS AND PROCESSIBILITY OF HIGH HEAT POLYCARBONATE COMPOSITIONS

This invention relates to carbonate polymers, particularly those which have good resistance to thermal deformation, and to compositions formed therefrom.

Polycarbonate is a useful engineering

thermoplastic because it possesses, in general, a combination of several different favorable properties. Certain polycarbonates, known as "high heat"

polycarbonates, additionally have better resistance to thermal deformation than others. However, it is often found that a high heat polycarbonate is not ductile, and is undesirably subject to failure by brittle fracture. Brittle fracture, in this context, is usually indicated when a point of applied stress exhibits smooth fracture surfaces, does not exhibit shear lips, and is not hinged. As a consequence of its brittleness, a high heat polycarbonate typically exhibits a lack of

toughness, manifested particularly as notch sensitivity, at a sufficiently high level to outweigh the benefits which would otherwise be obtainable from its superior resistance to thermal deformation. Previous efforts to modify polycarbonate by blending it with materials such as a polyester and a graft copolymer, as disclosed for example by U.S. Pats. No. 3,864,428 and 4,654,400, fail to address the special problems posed when a material possessing both the brittleness and heat resistance of a high heat

polycarbonate is incorporated into a blend. It would accordingly be desirable if, by employing appropriate methods and materials, the notch sensitivity of high heat polycarbonate could be reduced, and its toughness could be transformed into a characteristic as valuable as, and existing simultaneously with, its resistance to thermal deformation. This invention involves an admixture of a high heat polycarbonate, a toughening agent, and a flow modifier which is effective to enable thorough

dispersion of the toughening agent within the

polycarbonate without degradation of the toughening agent. In this invention, the flow modifier is also effective to improve various physical properties and the melt processibility of the polycarbonate and the admixture. This invention also involves a composition of matter comprising

(a) a high heat polycarbonate having a glass transition temperature exceeding 155°C,

(b) an elastomeric toughening agent containing greater than 40% rubber by weight, and

(c) one or more flow modifiers selected from the group consisting of an olefin/carbon monoxide copolymer, a styrenic thermoplastic resin, a polyester, and a polyamide. In another aspect, this invention involves a method of preparing a composition comprising (i) a high heat polycarbonate having a glass transition temperature exceeding 155°C and (ii) an elastomeric toughening agent containing greater than 40% rubber by weight, comprising the steps of

(a) lowering the viscosity of said high heat

polycarbonate, and

(b) admixing said toughening agent with said high heat polycarbonate;

wherein the step of lowering viscosity is performed no later than the step of admixing said toughening agent. This invention also involves a method of preparing a composition comprising a high heat polycarbonate having a glass transition temperature exceeding 155°C,

comprising the steps of

(a) admixing with said high heat polycarbonate an elastomeric toughening agent containing greater than 40% rubber by weight,

(b) admixing with said high heat polycarbonate a

flow modifier selected from from the group consisting of an olefin/carbon monoxide copolymer, a styrenic thermoplastic resin, a polyester and a polyamide;

wherein the step of admixing the elastomeric toughening agent is performed no later than the step of admixing the flow modifier.

It has been found that a melt mixed composition of a high heat polycarbonate, a toughening agent and a flow modifier possesses a superior balance of toughness, impact resistance and resistance to thermal deformation not previously attained in high heat polycarbonate compositions. The high heat polycarbonate compositions of this invention are useful, for example, in the

production of films, fibers, extruded sheets, multilayer laminates and molded or shaped articles of virtually all varieties, especially appliance and instrument housings and components for use in the automotive and electronics industries, such as motor vehicle wheel covers, body panels, doors and fenders.

Figure 1 is a log/log plot of viscosity in relation to shear rate for (a) ABS-modified BA/TBBA copolycarbonate, (b) unmodified BA/TBBA copolycarbonate at 275°C, and (c) unmodified BA/TBBA copolycarbonate at 300°C.

Figure 2 is a log/log plot of viscosity in relation to shear rate for (a) SAN-modified BA/TBBA copolycarbonate, (b) unmodified BA/TBBA copolycarbonate at 275°C, and (c) unmodified BA/TBBA copolycarbonate at 300°C.

Figure 3 is a log/log plot of viscosity in relation to shear rate for (a) PET-modified BA/TBBA copolycarbonate, (b) unmodified BA/TBBA copolycarbonate at 275°C, and (c) unmodified BA/TBBA copolycarbonate at 300°C.

Figure 4 is a log/log plot of viscosity in relation to shear rate for (a) ECO-modified BA/TBBA copolycarbonate, (b) unmodified BA/TBBA copolycarbonate at 275°C, and (c) unmodified BA/TBBA copolycarbonate at 300°C. In this invention, compositions are formed by blending (a) at least one high heat polycarbonate with (b) at least one elastomeric toughening agent containing greater than 40 percent rubber by weight, and with (c) at least one flow modifier which protects the toughening agent from degradation by improving the melt

processibility of the high heat polycarbonate in the composition.

A polycarbonate with good thermal stability - a high heat polycarbonate - is defined as that which has a glass transition temperature (T_g) in excess of 155°C, advantageously in excess of 170°C, preferably in excess of 185°C, and most preferably in excess of 195°C. It typically contains on the backbone of the repeating unit numerous bulky substituents, such as halogen, higher or branched alkyl, aryl, alkoxy or aryloxy substituents. T_g is the temperature or temperature range at which an amorphous polymeric material shows an abrupt change in its physical properties, including, for example, mechanical strength. T_g can be determined by

differential scanning calorimetry using, for example, a DuPont Instruments model 910 calorimeter.

Representative examples of high heat

polycarbonates are those formed from

•2,2-bis(3,5-dihalo-4-hydroxyphenyl)propane ("Tetrahalo

Bisphenol-A") where the halogen can be fluorine, chlorine, bromine or iodine, for example 2,2-bis(3,5-dibromo-4- hydroxyphenyl)propane ("Tetrabromo Bisphenol-A" or "TBBA");

•2,2-bis(3,5-dialkyl-4-hydroxyphenyl)propane

("Tetraalkyl Bisphenol-A") where the alkyl can be methyl or ethyl, for example 2,2-bis(3,5- dimethyl-4-hydroxyphenyl)propane ("Tetramethyl Bisphenol-A");

•1,1-bis(4-hydroxyphenyl)-1-phenyl ethane ("Bisphenol-

AP" or "Bis-AP");

•Bishydroxy fluorene [Bishydroxy(α-diphenylenemethane)];

or from

•copolymers formed from any of the foregoing with 2,2- bis(4-hydroxyphenyl)propane ("Bisphenol-A" or

"Bis-A").

A polycarbonate formed from Bisphenol-A alone does not meet the definition of a high heat polycarbonate of this invention.

An undesirable feature of a high heat

polycarbonate is that, not being ductile, it is

typically subject to failure by brittle fracture, and correspondingly suffers from a significant degree of notch sensitivity. We toughen a high heat

polycarbonate, and reduce its brittleness and notch sensitivity, by admixing with it an elastomeric

toughening agent containing greater than 40 percent rubber by weight. However, for a toughening agent to reduce brittleness to the desired extent, it must be thoroughly dispersed in the polycarbonate, i.e.

intermixed to an extent sufficient to give the desired increase in toughness and reduction in notch sensitivity to both the high heat polycarbonate and compositions formed therefrom. Obtaining such thorough dispersion of a toughening agent in a high heat polycarbonate requires heating a mixture of such materials to a temperature at which the polycarbonate, or the mixture, has a

sufficiently low viscosity that it is melt processible, i.e. that it can be worked sufficiently in a mixing apparatus to the extent necessary to obtain the desired dispersion.

In the case of a high heat polycarbonate, which has a T_g in excess of at least 155°C, reaching such a processing temperature frequently results in the

application of so much heat that the toughening agent is thereby degraded. Thermal degradation of the toughening agent is characterized, for example, by chain scission, cross-linking, formation of a backbone radical site with consequent unzipping [a particular problem with

poly(methyl methacrylate)], or any other thermally- induced chemical reaction which alters the physical properties of the toughening agent. The degradation of a toughening agent is observable when, because of the application during compounding of more heat than it can tolerate, the toughening agent does not thereafter provide to a composition the desired increase in

toughness. A temperature at which a toughening agent is not degraded is one which is lower than a temperature which would cause degradation such as described above.

When degradation occurs, the toughening agent itself suffers embrittlement and promotes in the high heat polycarbonate little or none of the desired ductile behavior. A flow modifier, when admixed with a

composition of a high heat polycarbonate and a

toughening agent, improves the melt processibility of the polycarbonate, and consequently the composition, to enable thorough dispersion of the toughening agent therein without degradation of the toughening agent. The flow modifier protects a toughening agent from degradation during mixing by allowing thorough

dispersion of it in the polycarbonate of the composition at a temperature below that at which the toughening agent suffers degradation. This results because a high heat polycarbonate with which a flow modifier is admixed is thereby flow modified, i.e. it displays a

significantly lower viscosity at a selected temperature than it displays at the same temperature when not admixed with the flow modifier. Because the viscosity of a high heat polycarbonate at a selected temperature is lower when admixed with a flow modifier than when not, use of a flow modifier enables obtaining a

viscosity low enough to allow thorough dispersion of a toughening agent in a high heat polycarbonate at a temperature below that at which the toughening agent is degraded by the heat of compounding.

For example, in Figure 1 a log/log plot of viscosity in relation to shear rate is given for a carbonate copolymer formed by copolymerizing Bisphenol-A ("BA") and Tetrabromo Bisphenol-A ("TBBA"). They are copolymerized in a 4:1 BA:TBBA molar ratio under conditions (as fully described below) which yield a

BA/TBBA co-polycarbonate ("BA/TBBA"). BA/TBBA, a high heat material, has a T_g of approximately 177°C. The viscosity of BA/TBBA at 275°C is seen to be uniformly higher over the range of shear rates plotted than that of BA/TBBA at 300°C, or than that of a mixture at 275°C of 90 parts (by weight of the mixture) BA/TBBA and 10 parts "ABS" (acrylonitrile/butadiene/styrene copolymer), an example of one of the various flow modifiers used in this invention. The viscosity results in relation to other flow modifiers are shown in Figs. 2-4. A plot comparing viscosity curves in the same manner for

BA/TBBA at 275°C, BA/TBBA at 300°C and BA/TBBA modified with 10 wt% "SAN" (styrene/acrylonitrile copolymer) is shown in Figure 2, viscosity curves showing the same comparison for BA/TBBA modified with 10 wt% "PET"

[poly(ethylene terephthalate)] appear in Figure 3, and viscosity curves showing the same comparison for BA/TBBA modified with 10 wt% "ECO" (ethylene/carbon monoxide copolymer) appear in Figure 4.

When other factors such as pressure, mechanical force and molecular weight and structure remain

constant, the effect of the admixture of flow modifier with the high heat polycarbonate (BA/TBBA) is to lower its viscosity at a selected temperature (275°C) as compared with BA/TBBA not admixed with the flow

modifier. Moreover, it can be seen in each figure that the lower viscosity imparted to BA/TBBA admixed with flow modifier at 275°C is nearly the same as the

viscosity of BA/TBBA not admixed with flow modifier at 300°C. This demonstrates the improvement in

processibility obtainable at a lower temperature by admixing flow modifier with a high heat polycarbonate because BA/TBBA admixed with flow modifier has nearly as low a viscosity as BA/TBBA alone has when heated to a temperature 25°C higher. The flow modifier imparts to a high heat polycarbonate a lower viscosity at a selected temperature than the high heat polycarbonate alone has at the same temperature. The viscosities shown in Figs. 1-4 were determined with an Instron Capillary Rheometer.

In addition to lowering the viscosity of a high heat polycarbonate, or a mixture containing same, a flow modifier may also promote the phase break up of a toughening agent, particularly a thermoplastic

elastomer, during the mixing process.

The effectiveness of a flow modifier in admixture with a high heat polycarbonate and a

toughening agent, as described above, allows the use of

lowering the viscosity of a high heat polycarbonate (i) in a method of forming a high heat polycarbonate

composition by admixing a toughening agent and a flow modifier with a high heat polycarbonate where mixing of the flow modifier occurs either prior to or during the mixing of the toughening agent, or (ii) in a method forming a composition where the viscosity of a high heat polycarbonate is lowered either prior to or during admixture therewith of a toughening. If a toughening agent is admixed with a high heat polycarbonate before a flow modifier is added, or before the viscosity of the high heat polycarbonate is lowered, the toughening agent will not be protected from degradation during

compounding.

The materials involved in this invention, being

(a) at least one high heat polycarbonate, (b) at least one elastomeric toughening agent containing greater than 40 percent rubber by weight, and (c) at least one flow modifier such as (i) at least one olefin/carbon monoxide copolymer, (ii) at least one styrenic thermoplastic resin, (iii) at least one polyester, or (iv) at least one polyamide, or a combination of two or more of the foregoing, are more particularly described below.

Suitable ranges of content of the compositions of this invention formed from said materials, by weight of the total composition, are as follows: polycarbonate from about 40 parts to about 95 parts, toughening agent from about 0.1 parts to about 20 parts, and flow modifier from about 0.1 parts to about 50 parts. Preferred ranges of content of the compositions of this invention formed from said materials, by weight of the total composition, are as follows: polycarbonate from about 50 parts to about 90 parts, toughening agent from about 5 parts to about 20 parts, and flow modifier from about 5 parts to about 40 parts.

The compositions of this invention, and those formed by the methods of this invention, are

characterized in that

(a) the glass transition temperature, or the highest glass transition temperature, thereof (i) is at least 95 percent, and preferably at least 98%, of the glass transition temperature of the high heat polycarbonate contained therein, or (ii) exceeds 148°C, advantageously exceeds 162°C, preferably exceeds 176°C, and most preferably exceeds 185°C;

(b) the heat deflection temperature under load thereof, determined according to ASTM 648-82 at 264 psi

(1.82 MPa), (i) is at least 95 percent, and preferably at least 98%, of the heat deflection temperature under load of the high heat polycarbonate contained therein, or (ii) exceeds 280°F (137.8°C), advantageously exceeds 290°F (143.3°C), and preferably exceeds 295°F (146.1°C); and/or

(c) the Izod impact value thereof, determined according to ASTM 256-84 (Method A), (i) is at least two times, and is preferavly at least three times, as great as the Izod impact value of the high heat polycarbonate contained therein, or (ii) exceeds 6.0 ft-lb/in (320.3 J/m) and exhibits a ductile mode of failure, advantageously exceeds

9.0 ft-lb/in (480.4 J/m), and preferably exceeds 11.5 ft-lb/in (613.9 J/m).

Preparation of the compositions of this invention can be accomplished by any suitable means known in the art. Typically the substances to be admixed with polycarbonate in the composition being made are dry blended in particulate form with sufficient agitation to obtain thorough distribution thereof within the polycarbonate. Thereafter, the dry-blended

formulation can, if desired, be melt mixed in an

extruder, although other forms of compounding may be useful. Alternatively, a master batch formulation can be prepared containing polycarbonate and the substances to be admixed or blended with it wherein polycarbonate is present in only a minor proportion, e.g. 20 parts.

The master batch is then available for shipment in commerce or storage, and can be diluted with additional polycarbonate at the time of use. The compositions of this invention can be formed or molded using

compression, injection, calendering, vacuum forming, extrusion and/or blow molding techniques, alone or in combination. The compositions can also be formed into films, fibers, multi-layer laminates or extruded sheets on any machine suitable for such purpose.

(a) Polycarbonate. The polycarbonate involved in this invention can be prepared from those aromatic dihydroxy compounds which yield a high heat

polycarbonate, being that which has a glass transition temperature (T_g) in excess of 155°C, advantageously in excess of 170°C, preferably in excess of 185°C, and most preferably in excess of 195°C. The aromatic dihydroxy compounds which yield a high heat polycarbonate are typically derivatives of a diol such Bisphenol-A, and frequently are those which yield a polycarbonate product containing on the backbone of the repeating unit numerous bulky substituents, such as halogen, higher or branched alkyl, aryl, alkoxy or aryloxy substituents or the like, and mixtures thereof. A dihydroxy compound capable of producing a high heat polycarbonate can be reacted with a carbonate precursor, such as a carbonic acid derivative. A carbonic acid derivative such as the carbonyl halide phosgene is useful for such purpose. However, even with the application of heat, the direct contact of an aromatic dihydroxy compound and a carbonic acid

derivative does not produce a reaction with a rate sufficient to form polycarbonate. The reaction should therefore be facilitated by the presence in the reaction mixture of pyridine or another tertiary amine. The salt-like adduct of the carbonic acid derivative which is formed with the amine reacts more favorably with the dihydroxy compound than the carbonic acid derivative itself. The reaction should be carried out in the absence of water to avoid hydrolysis of the carbonic acid derivative, and a non-reactive organic solvent is used which will keep the polycarbonate product in a viscous solution as it forms. The non-reactive solvent is frequently methylene chloride or another halogenated hydrocarbon, or benzene or toluene. When the formation of polycarbonate is complete, the reaction mixture is washed with an aqueous solution of a mineral acid to convert any remaining amine to its corresponding salt, and the organic phase is washed further with water to remove acidic electrolytes. The solvent can be removed from the organic phase by distillation. Alternatively, the polycarbonate may be precipitated from the organic phase by a non-solvent such as petroleum ether,

methanol, isopropanol or an aliphatic hydrocarbon.

Even at temperatures as low as from 0°C to 40°C, a carbonic acid derivative reacts at a better rate with deprotonated aromatic dihydroxy compounds than it does in a non-aqueous system. A solution is formed of (i) an aromatic dihydroxy compound and a strong base in aqueous phase, and (ii) an inert, immiscible organic solvent which will dissolve both the carbonic acid derivative and the polycarbonate product. Solvents such as xylene or methylene chloride or other chlorinated hydrocarbons are suitable for such purpose. Caustic such as the the alkali or alkaline earth carbonates, oxides or

hydroxides function best as the base, the total amount of which may be added at the beginning of, or

incrementally during, the reaction. A pH of about 10 to 13 is typically maintained throughout the reaction. The base forms the dianion of the aromatic dihydroxy

compound in the aqueous phase, and the aqueous phase forms a continuous phase with the organic solvent dispersed, upon agitation, as droplets therein.

Carbonic acid derivative is bubbled into this mixture, is dissolved in the organic solvent, and reacts with the aromatic dihydroxy compound at the interface of the droplets with the aqueous phase. Catalysts accelerate the rate of the reaction sufficiently to allow the formation of high polycarbonates at the same low

temperature at which the reaction began. Suitable catalysts for such purpose are tertiary amines such as triethylamine or N,N-dimethyl-cyclohexylamine, or quaternary ammonium bases such as tetramethyl ammonium hydroxide or triethyl benzyl ammonium hydroxide, or quaternary phosphonium, quaternary arsenium or tertiary sulfonium compounds. A bisaryl ester can be used in place of a carbonic acid derivative.

Polycarbonate can additionally be made by transesterification, which is accomplished by reacting a dihydroxy compound with a bis carbonic acid ester. A strongly alkaline catalyst such as the alkali metals and the alkaline earth metals and their oxides, hydrides or amides, or the basic metal oxides such as zinc oxide, lead oxide and antimony oxide is used as an accelerator, and the reaction is run at temperatures of between 150°C and 300°C, using vacuum to remove the residue of the bis carbonic acid ester. At temperatures between 150°C and 200°C, low molecular weight polycarbonate terminated with bis carbonic acid ester groups is formed, which can then interreact at temperatures above 250°C to form higher weight polycarbonate by splitting off the

original bis carbonic acid ester. This process is carried out at reduced pressure.

Suitable dihydroxy compounds for the

preparation of polycarbonate are those wherein the sole reactive groups are two hydroxyl groups, such as variously bridged, substituted or unsubstituted aromatic diols (or mixtures thereof) represented by the general formula

where (a) X is a substituted or unsubstituted

divalent hydrocarbon radical containing 1-15 carbon atoms, or is a mixture of more than one of such

radicals, or is -S-, -S-S-, -SO-, SO₂-, -O-, -CO-, or a single bond; (b) Y is independently hydrogen; ahalogen such as fluorine, chlorine, bromine or

iodine; or is a monovalent organic radical such as an alkyl group of 1-4 carbons, an aryl group of 6-8 carbons {e.g. phenyl, tolyl, xylyl or the like), an alkoxy group of 1-4 carbons, or an aryloxy group of 6-8 carbons; and (c) m is 0 or 1, and n is 1-4 inclusive. When Y is a halogen, the high heat polycarbonate will contain at least 20 percent halogen by weight.

The carbonate polymers employed in the present invention are also high heat polycarbonates based on dihydroxy benzenes such as pyrocatechol, resorcinol and hydroquinone (and their halo- and alkyl-substituted derivatives), and on dihydroxy naphthalenes and anthracenes.

Although the polycarbonates mentioned above, such as those derived from Bisphenol-A or from Bisphenol-AP, can each be employed in this invention as a homopolymer ( i.e. the product obtained when only one dihydroxy compound is used to prepare the polycarbonate), the carbonate polymers used herein can also be derived from two or more

different dihydroxy compounds, or mixtures thereof, in the event a carbonate copolymer or interpolymer rather than a homopolymer is desired. For example, a typical copolymer is that which is made from

Bisphenol-A and Tetrabromo Bisphenol-A wherein either co-monomer can be present in a 1-99 or 99-1 molar ratio.

Copolymers can also be formed when a bisphenol is reacted with a carbonic acid derivative and a polydiorganosiloxane containing α,ω- bishydroxyaryloxy terminal groups to yield a siloxane/carbonate block copolymer (as are discussed in greater detail in Paul, USP 4,569,970), or when a bisphenol is reacted with a bis(ar-haloformylaryl) carbonate to yield an alternating

copolyestercarbonate, the bis(ar-haloformylaryl) carbonate being formed by reacting a hydroxycarboxylic acid with a carbonic acid

derivative under carbonate forming conditions. The copolyestercarbonates are discussed in greater

detail in Swart, USP 4,105,533-

Also useful in this invention are physical blends of two or more of the carbonate homo- and/or copolymers described above. The term

"polycarbonate" as used herein, and in the claims appended hereto, should therefore be understood to include carbonate hpmopolymers, carbonate copolymers (as described above), and/or blends of various

carbonate homopolymers and/or various carbonate

copolymers, so long as the resulting homopolymer, copolymer or miscible polycarbonate blend has a T_g exceeding at least 155°C, or in the case of an

immiscible blend, the component(s) thereof

constituting more than 50 weight parts of the blend has a T_g exceeding at least 155°C.

The methods generally described above for preparing carbonate polymers suitable for use in the practice of this invention are well known; for

example, several methods are discussed in detail in Moyer, USP 2,970,131; Schnell, USP 3,028,365;

Campbell, USP 4,384,108; Glass USP 4,529,791; and

Grigo, USP 4,677,162.

(b) Toughening Agent. The toughening agent used in this invention is a rubbery or elastomeric substance, typically with a Υg less than 0°C, which is suitable or effective for the purpose of imparting enough flexibility and freedom of chain rotation to a high heat polycarbonate to improve its toughness; reduce its notch sensitivity; and enable it, in response to the deformation of an applied stress, to recover with stored modulus rather than fracture. The rubber content of the toughening agent used in this invention is greater than 40 percent by weight, and a mixture of two or more elastomeric substances can be used as the toughening agent.

Illustrative examples of elastomeric toughening agents useful in this invention are thermoplastic elastomers and emulsion-type, core-shell graft copolymer elastomers.

The thermoplastic elastomers useful in this invention are those which typically have a T_g less than 0°C. They are characterized, for example, in that they can be melted and recooled, or dissolved and reformed upon removal of the solvent, without undergoing any change in properties. The thermoplastic elastomers suitable herein are also characterized by the randomness of the shape and size they take on when mixed by

shearing forces with the other components making up the compositions of this invention, especially when heat is applied during such mixing. Because the thermoplastic elastomer is typically a long chain molecule, segments of thermoplastic elastomer in the polymer composition matrix are generally elongated, linear ribbons or bands. The molecules tend to fuse and flow together in a continuous structure. However, chain coiling can yield globule-shaped segments of thermoplastic elastomer in the matrix. The random shape and size assumed in the polymer compositon matrix by a thermoplastic elastomer is to be distinguished from the shape and size assumed by a core-shell graft copolymer.

A core-shell graft copolymer is uniformly present in the polymer matrix in a bead shape both before and after mixing by application of shearing forces, whether heat is used or not, and is typiclly present in a rather narrow size range, for example 0.05- 0.8 microns. The retention of this core-shell, or spherical, shape by the graft polymer, even after heating and mixing, results from the fact that the outer layers, which surround the core, are formed by grafting appropriate monomers onto the core. A core-shell graft copolymer typically cannot be melted and recooled without a change in properties because the graft polymer will tend to decompose or crosslink, and the bead-shaped segments of graft polymer will tend to agglomerate upon melting, making dispersion of them by mixing very difficult.

The thermoplastic elastomers useful as a toughening agent in this invention are based generally on a long-chain, typically olefininc backbone. They may be somewhat less susceptible to thermal degradation than other elastomeric toughening agents. Representative examples of a few of these thermoplastic elastomers are described below to illustrate the variation in the known substances which would suffice for such purpose.

b(i) Butyl rubber is the product of

copolymerizing isobutylene and isoprene where the isoprene typically makes up no more than 2.5 mole percent of the copolymer. Although a solution process can be used to manufacture butyl rubber, most of it is made by a precipitation (slurry) method wherein the monomers are copolymerized in methyl chloride diluent using a catalyst such as aluminum chloride. Butyl rubbers, as described above, are discussed in greater detail in Green, USP 2,401,754 and Nelson, USP

2,462,123.

b(ii) Chlorosulfonated polyethylene rubbers are prepared by bubbling a mixture of chlorine and sulfur dioxide into a solution containing polyethylene, and the rubber product typically contains 20-40 parts chlorine as secondary alkyl chlorides and 1-2 parts sulfur as secondary sulfonyl chlorides.

Chlorosulfonated polyethylene rubbers, as described above, are discussed in greater detail in Beekly, USP 2,640,048 and Kalil, USP 2,923,979.

b(iii) Although the presence of the pendant methyl group gives EPM (ethylene/propylene) copolymer rubber a structure similar to that of natural rubber, EPM rubber has no double bonds in the backbone. The ratio of ethylene to propylene in EPM rubber is from about 50/50 to about 75/25. However, this lack of unsaturation in the backbone precludes vulcanization, and a diene, such as hexadiene-1,5-norbornadiene- ethylidene-norbornene, is therefore frequently added to the copolymer to furnish a pendant group containing an addition polymerizable C=C bond. When a diene is copolymerized with ethylene and propylene, the product is known as EPDM rubber. EPM/EPDM rubbers, which can be made by the solution process, are described above and are discussed in greater detail in Paige, USP 3,341,503.

b(iv) Fluorinated rubbers, such as the fluorocarbon elastomer poly(tetrafluoroethylene-co- propylene), are made in a high pressure, free radical aqueous emulsion, using organic or inorganic peroxy compounds as initiators. A fluorinated carboxylic acid soap is usually used as the emulsifying agent.

Fluorinated elastomers and methods for making same, as described above, are discussed in greater detail in Rexford, USP 3,051,677, Honn, USP 3,053,818 and

Pailthorp, USP 2,968,649.

b(v) Formation of neoprene rubber is by polymerization of 2-chloro-1,3-butadiene and can result from addition involving both of the double bonds, or through just one of the two leaving the other as a pendant group. Neoprene rubber is typically made by free radical batch emulsion polymerization, but can also be made in a continuous process. Neoprene rubber, as described above, is discussed in greater detail in

Collins, USP 1,967,865 and Aho, USP 2,831,842.

b(vi) Nitrile rubber, which is polymerized from 1 ,3-butadiene and acrylonitrile, typically has about 15-50 parts acrylonitrile content. It is usually preferred to make nitrile rubbers by emulsion, as an aqueous system is more easily operated than one, for example, requiring a solvent. Nitrile rubber and methods for making same, as described above, are

discussed in greater detail in Konrad, USP 1,973,000.

b(vii) As with rubbers involving derivatives of butadiene, formation of polybutadiene can be by either 1,4 or 1,2 (vinyl) addition of the butadiene molecule. Polybutadiene rubber is typically

manufactured by solution polymerization, using organic lithium compounds or coordination catalysts containing metals in reduced valence states. Polybutadiene rubber, as described above, is discussed in greater detail in Brockway, USP 2,977,349 and Ueda, USP 3,170,907.

b(viii) Polyisoprene, with its pendant methyl group on what would otherwise be a butadiene unit, also polymerizes in cis-1,4, trans- 1 ,4 or 1,2 (vinyl) form.

Cis-1,4 polyisoprene is the synthetic equivalent of natural rubber. Ziegler catalysts can be used in the polymerization of polyisoprene. Polyisoprene and methods for making same, as described above, are

discussed in greater detail in Kahn, USP 3,165,503.

b(ix) Polyether rubbers include

epichlorohydrin elastomers, which can be prepared either by a coordination polymerization mechanism using an aluminum alkyl-water catalyst in a hydrocarbon solvent, or in solution using benzene, toluene or methylene chloride as the solvent. Propylene oxide elastomers can also be prepared in solution, by copolymerization with allyl glycidyl ether, using a coordination catalyst such as diethyl zinc water. Polyether rubbers, as described above, are discussed in greater detail in Vandenberg, USP 3,634,303 and 3,639,267. Polyether block amides are generally represented by the structure

H0-[-C(O)-PA-C(O)-O-PE-O-]_n-H, where PA is a polyamide segment, PE is a polyether segment, and n is an integer from 2 to 50.

b(x) Urethane elastomers are described in

Schollenberger, USP 3,015,650 and Saunders, USP

3,214,411; and copolyester-ether elastomers are

described in Witsiepe, USP 3,651,014.

b(xi) Block copolymers can be either linear or branched, and can be either a di-block ("A-B") copolymer or tri-block ("A-B-A") copolymer with or without tapered sections, i.e. portions of the polymer where the monomers alternate or are in random order close to the point of transition between the A and B blocks. The A portion is made by polymerizing one or more mono-alkenyl or vinyl aromatic hydrocarbon monomers, and has an average molecular weight of about 4,000 to about 115,000, and a weight preferably of about 8,000 to about 60,000. The B portion of the block copolymer results from polymerizing a diene and has a molecular weight of about 20,000 to about 450,000, and a weight preferably of about 50,000 to about 300,000. In the A-B di-block copolymer, each block, A or B, can vary from 10-90% of the total weight of the copolymer. In the A-B-A tri-block copolymer, the A end groups typically constitute about 2 wt% to about 55 wt% of the whole block copolymer, and preferably are between 5 wt% and 30 wt% of the whole block copolymer.

The A block of the block copolymer has properties characteristic of thermoplastic substances in that it has the stability necessary for processing at elevated temperatures and yet possesses good strength below the temperature at which it softens. The A block is polymerized predominantly from vinyl aromatic hydrocarbons, and substituted derivatives thereof wherein the aromatic moiety can be either mono- or polycyclic. Monomers from which the thermoplastic end blocks can be formed are, for example, styrene and substituted derivatives thereof such as α-methyl styrene, vinyl xylene, vinyl naphthalene, and the like, and mixtures of two or more thereof. Other vinyl monomers such as methyl acrylate, methyl methacrylate, acrylonitrile or vinyl pyridine may be used in the formation of the A block together with the aromatic monomers. The polymerization can be initiated by lithium metal, or alkyl- or aryl lithium compounds such as butyl lithium or isoamyl lithium. Polymerization is normally conducted at temperatures ranging from about - 20°C to about 100°C.

The B block of the copolymer can be formed, for example, simply by injecting suitable monomer into the reaction vessel and displacing the lithium radical from the just-polymerized A block, which then acts as an initiator because it is still charged. The B block is formed predominantly from substituted or unsubstituted C₂-C₁₀ dienes, particularly conjugated dienes such as butadiene or isoprene. Other diene, vinyl or olefinic monomers such as chloroprene, 1 ,4-pentadiene,

isobutylene, ethylene or vinyl chloride may be used in the formation of the B block provided that they are present at a level low enough to not alter the

fundamental olefinic character of the B block. The mid block will be characterized by elastomeric properties which allow it to to absorb and dissipate an applied stress and then regain its shape.

In the A-B-A tri-block copolymer, the second end block A can be formed in a manner similar to the first, by injecting appropriate alkenyl aromatic monomer (as described above) into the reaction vessel.

Alternatively, a bivalent lithium initiator can be used, which, when brought together with the diene monomer under the same conditions described above, will form an elastomeric mid block B which carries a charge at each end. Then, upon addition of alkenyl aromatic monomer to the reaction mixture, a thermoplastic end block A will form on both ends of the mid block B, yielding a

thermoplastic elastomeric A-B-A copolymer.

To reduce oxidative and thermal instability, the block copolymers used herein can also desirably be hydrogenated to reduce the degree of unsaturation on the polymer chain and on the pendant aromatic rings.

Typical hydrogenation catalysts utilized are Raney nickel, molybdenum sulfide, finely divided palladium and platinum oxide. The hydrogenation reaction is typically run at 75-450°F and at 100-1,000 psig for 10-25 hours.

The most preferred thermoplastic elastomers are vinyl aromatic/conjugated diene block copolymers formed from styrene and butadiene or styrene and isoprene.

When the styrene/butadiene copolymers are hydrogenated, they are frequently represented as

styrene/ethylene/butylene (or

styrene/ethylene/butylene/styrene in the tri-block form) copolymers. When the styrene/isoprene copolymers are hydrogenated, they are frequently represented as styrene/ethylene/propylene (or

styrene/ethylene/propylene/styrene in the tri-block form) copolymers. The block copolymers described above are discussed in greater detail in Haefele, USP

3,333,024 and Wald, USP 3,595,942.

b(xii) The core-shell graft copolymer elastomers used in this invention can be based on either a diene rubber, an acrylate rubber or on mixtures thereof.

A diene rubber contains a substrate latex, or core, which is made by polymerizing a diene, preferably a conjugated diene, or by copolymerizing a diene with a mono-olefin or polar vinyl compound, such as styrene, acrylonitrile, or an alkyl ester of an unsaturated carboxylic acid such as methyl methacrylate. The substrate latex is typically made up of about 40-85% diene, preferably a conjugated diene, and about 15-60% of the mono-olefin or polar vinyl compound. The

elastomeric core phase should have a glass transition temperature ("T_g") of less than about 0°C, and

preferably less than about -20°C. A mixture of monomers is then graft polymerized to the substrate latex. A variety of monomers may be used for this grafting purpose, of which the following are exemplary: vinyl compounds such as vinyl toluene or vinyl chloride;

vinyl aromatics such as styrene, alpha-methyl styrene or halogenated styrene; acrylonitrile, methacrylonitrile or alpha-halogenated acrylonitrile; a C₁-C₈ alkyl acrylate such as ethyl acrylate or hexyl acrylate; a C₁-C₈ alkyl methacrylate such as methyl methacrylate or hexyl methacrylate; acrylic or methacrylic acid; or a mixture of two or more thereof.

The grafting monomers may be added to the reaction mixture simultaneously or in sequence, and, when added in sequence, layers, shells or wart-like appendages can be built up around the substrate latex, or core. The monomers can be added in various ratios to each other although, when just two are used, they are frequently utilized in equal amounts. A typical weight ratio for methyl methacrylate/butadiene/styrene

copolymer ("MBS" rubber) is about 60-80 parts by weight substrate latex, about 10-20 parts by weight of each of the first and second monomer shells. A preferred formulation for an MBS rubber is one having a core built up from about 71 parts of butadiene, about 3 parts of styrene, about 4 parts of methyl methacrylate and about 1 part of divinyl benzene; a second phase of about 11 parts of styrene; and a shell phase of about 11 parts of methyl methacrylate and about 0.1 part of 1,3-butylene glycol dimethacrylate, where the parts are by weight of the total composition. A diene-based, core-shell graft copolymer elastomer and methods for making same, as described above, are discussed in greater detail in Saito, USP 3,287,443, Curfman, USP 3,657,391, and

Fromuth, USP 4,180,494.

An acrylate rubber has a first phase forming an elastomeric core and a second phase forming a rigid thermoplastic phase about said elastomeric core. The elastomeric core is formed by emulsion or suspension polymerization of monomers which consist of at least about 50 weight percent alkyl and/or aralkyl acrylates having up to fifteen carbon atoms, and, although longer chains may be used, the alkyls are preferably C₂-C₆, most preferably butyl acrylate. The elastomeric core phase should have a T_g of less than about 25°C, and preferably less than about 0°C.

The rigid thermoplastic phase of the acrylate rubber is formed on the surface of the elastomeric core using suspension or emulsion polymerization techniques. The monomers necessary to create this phase together with necessary initiators are added directly to the reaction mixture in which the elastomeric core is formed, and polymerization proceeds until the supply of monomers is substantially exhausted. Monomers such as an alkyl ester of an unsaturated carboxylic acid, for example a C₁-C₈ alkyl acrylate like methyl acrylate, hydroxy ethyl acrylate or hexyl acrylate, or a C₁-C₈ alkyl methacrylate such as methyl methacrylate or hexyl methacrylate, or mixtures of any of the foregoing, are some of the monomers which can be used for this purpose. Either thermal or redox initiator systems can be used. Because of the presence of the graft linking agents on the surface of the elastomeric core, a portion of the chains which make up the rigid thermoplastic phase are chemically bonded to the elastomeric core. It is preferred that there be at least about 20% bonding of the rigid thermoplastic phase to the elastomeric core.

A preferred acrylate rubber is made up of more than about 40% to about 95% by weight of an elastomeric core and about 60% to about 5% of a rigid thermoplastic phase. The elastomeric core can be polymerized from about 75% to about 99.8% by weight C₁-C₆ acrylate, preferably n-butyl acrylate. The rigid thermoplastic phase can be polymerized from at least 50% by weight of C₁-C₈ alkyl methacrylate, preferably methyl

methacrylate. Acrylate rubbers and methods for making same, as described above, are discussed in greater detail in Owens, USP 3,808,180 and Witman, USP

4,299,928.

(c) Flow Modifier. The flow modifier used in this invention is a substance which is suitable or effective for lowering the viscosity of a high heat polycarbonate enough to allow the mixing needed to obtain thorough dispersion of a toughening agent in a high heat polycarbonate at a temperature below that at which the toughening agent is degraded. The flow modifier is miscible with the high heat polycarbonate only to the extent that trie glass transition temperature of the high heat polycarbonate composition, or the highest glass transition temperature of the composition, falls within the ranges set forth above for the

compositions of this invention. Certain representative classes of flow modifiers are set forth below. A mixture of two or more suitable flow modifiers can also be used in this invention.

c (i) Olefin Copolymer. An olefin copolymer which contains a carbonyl functionality in its backbone is advantageously utilized in this invention, and the preferred such olefin copolymer is ethylene/carbon monoxide ("ECO"). ECO is formed from ethylene and carbon monoxide in a pressure vessel using a peroxy catalyst or a metallic {e.g. palladium) compound as the catalyst. A hydrocarbon liquid which is non-reactive under the polymerization conditions is used as a diluent and reaction medium, and any such medium which acts as a solvent for the catalyst system and in which the

catalyst is stable is typically suitable for use as the reaction medium. Air and water are preferably excluded from the reaction chamber. The polymerization can be performed at temperatures in the range from as low as 10°C up to 200°C, but is preferably run in the range of 50°C to 140°C. Pressures as high as 3,000 atmospheres (303 MPa) may be employed in the reaction, but the usual pressure of operation is in the range of 20 atmospheres (2.02 MPa) to about 1,500 atmospheres (151.5 MPa). Both yield and molecular weight increase with increasing pressure. Alternatively, an olefin/carbon monoxide copolymer can be made without solvent under high

pressure conditions, using a free radical initiator in a stirred autoclave.

A variety of olefin monomers in place of ethylene, and numerous vinyl monomers in addition to ethylene, can be used to form the olefin copolymer backbone along with carbon monoxide. Any ethylenically unsaturated compound containing the >C=C< alkene bond which will undergo polymerization across the double bond can form part of the olefin/carbon monoxide

("olefin/CO") copolymer backbone, although olefin monomers such as propylene, isobutylene and 1-butene, and vinyl monomers such as butadiene, allyl esters, vinyl acetate, vinyl chloride, vinyl aromatics such as styrene, alkyl acrylates such as ethyl acrylate,

acrylonitrile, tetrafluoroethylene and other vinyl monomers and other substituted and un-substituted higher C₁-C₈ alpha alkenes or alpha mono-olefins, and

mixtures of the foregoing, are preferred. The portion of the olefin/CO copolymer used in this invention derived from carbon monoxide is from about 0.1 parts to about 50 parts, and preferably, from about 0.5 parts to about 30 parts, by weight. A copolymer of carbon monoxide and an alpha-mono-olefin, and methods for preparation thereof, as described above, are discussed in greater detail in Lancaster, USP 4,600,614, Brubaker, USP 2,495,286, Loeb, USP 3,083,184, Fenton, USP

3,530,109 and Nozaki, USP 3,694,412.

What is set forth above concerning methods of making ECO applies equally to other forms of said olefin/CO copolymer which result from variation in the backbone monomer mix. The backbone of the olefin/CO copolymer used in this invention can be made (in

conjunction with carbon monoxide) from any of the various monomers, and can be made by any of the various methods, which are included above in the discussion relating specifically to the manufacture of ECO.

However, the most preferred olefin/CO copolymer is ECO. c(ii) Styrenic Thermoplastic Resin. The styrenic thermoplastic resin used in this invention, such as styrene/acrylonitrile copolymer ("SAN"), can be made by the emulsion, suspension or bulk methods. When a styrenic thermoplastic resin is made in emulsion, a reaction mixture of water, monomer, an emulsifying agent and a suitable polymerization catalyst are charged to the reaction vessel, for example a stirred autoclave. The reaction can be run in the range of 100°F to 200°F, usually between 175°F and 200°F. A variety of

emulsifying agents can be used. Frequently, soaps such as those based on the salt of a fatty acid or an alkyl aromatic sulfonic acid; a rosin acid soap; or non-ionic emulsifying agents are used. Catalysts may be

persulfates or of the peroxide type, the azo type or the redox type. The slurry containing the product particles is dewatered in a centrifuge, and the resin is dried. A styrenic thermoplastic resin made by the emulsion process, as described above, is discussed in greater detail in Childers, USP 2,820,773, Calvert, USP

3,238,275, Murray, USP 3,547,857 and Kohlpoth, USP

3,772,257.

Alternatively, a styrenic thermoplastic resin such as SAN can be prepared by the suspension process. An aqueous mixture of monomers, initiator and suspending agent is reacted in a pressure vessel at a temperature between 100°C and 200°C, and between 6.9 and 690 kPa, after which the residual monomers are removed by steam stripping. The product in slurry form can be dewatered in a centrifuge or by filtration and is then dried.

Suspending agents which can be used are materials such as polyvinyl pyrrolidone, carboxymethyl cellulose, lecithin or calcium phosphate. A styrenic thermoplastic resin made by the suspension process, as described above, is discussed in greater detail in Aliberti, USP 3,444,270, Carrock, USP 3,515,692 and Ackerman, USP 4,151,128.

A styrenic thermoplastic resin such as SAN can also be prepared by the bulk or mass process wherein polymerization occurs because of the direct contact between the monomers in the presence of heat, but without need for any sort of suspending or emulsifying agent. However, because of the viscosity developed by the polymer product, a solvent such as benzene, toluene or xylene is frequently added to the reaction mixture to facilitate machine processing. The process can be run in either a continuous tube or a stirred vessel. Reflux condensation can be used to control temperature and pressure in the reaction zone or vessel. If a solvent is used, it is removed during devolatilization by subjecting the product to high temperature, usually in excess of 200°C, and reduced pressure. A styrenic thermoplastic resin made by the bulk or mass process, as described above, is discussed in greater detail in

Hanson, USP 2,989,517, Latinen, USP 3,813,369, Simon, USP 4,252,911 and Weber, USP 4,526,926.

What is set forth above concerning methods of making a styrenic thermoplastic resin used in this invention in the form of SAN applies equally to the other forms of said styrenic thermoplastic resin, such as acrylonitrile/butadiene/styrene copolymer ("ABS"), which result from variation in the monomer mix.

Representative monomers, in addition to styrene, which can be utilized in making the styrenic thermoplastic resin used in this invention are olefinically

unsaturated substances; vinyl compounds (especially when they bear a polar, electronegative group or

functionality) such as vinyl toluene, alphamethyl styrene, halogenated styrene, methacrylonitrile or alpha-halogenated acrylonitrile; a C₁-C₈ alkyl

acrylate such as ethyl acrylate, hexyl acrylate or hydroxy ethyl acrylate; a C₁-C₈ alkyl methacrylate such as hexyl methacrylate; an acrylic or methacrylic acid; the vinylidene monomers, especially when they bear a polar, electronegative group or functionality such as a halogen group, or an organic group having a double or triple bond such as phenyl, carboxy, cyano or the like: vinyl chloride, vinyl acetate, vinylidene chloride or vinyl esters or vinyl ethers; styrene and substituted derivatives thereof; maleimides; mononitriles having alpha-beta-olefinic unsaturation and lower alkyl or halogen substituents; esters of olefinically unsaturated carboxylic acids; vinyl esters; vinyl ethers; alpha- olefins; vinyl toluenes; vinyl xylenes; the maleates; the fumarates; and the like; or mixtures of two or more of any of the foregoing. In general, vinyl and

vinylidene monomers from groups such as the vinyl and vinylidene -esters, -ethers, -organic acids, -epoxies, - aromatics, -alcohols, -halides, -nitriles and -amides, or mixtures thereof, can be used in making the styrenic thermoplastic resin used in this invention. c(iii) Polyester. The polyester used in this invention may be made by a variety of methods. Although the self-esterification of hydroxycarboxylic acids is known, direct esterification, which involves the

reaction of a diol with a dicarboxylic acid with the resulting elimination of water, is a more frequently used method for commercial production, giving an

-[-AABB-]- polyester. Although the presence of a

catalyst such as p-toluene sulfonic acid, a titanium alkoxide or a dialkyltin oxide is helpful, the primary driving force behind the direct esterification reaction is heat. Temperatures applied exceed the melting points of the reactants and typically approach the boiling point of the diol being used, and usually range from about 150°C to about 280°C. The ester of the diacid initially formed from the diol, having -OH end groups, undergoes alcoholysis and polymerization to form

polymeric esters and the diol is split out as a

byproduct and removed from the reaction zone. The reaction is typically carried out in the presence of an inert gas.

Alternatively, but in like manner, ester- forming derivatives of a dicarboxylic acid can be heated with a diol to obtain polyesters in an ester interchange reaction. Suitable acid derivatives for such purpose are esters, halides, salts or anhydrides of the acid. When a bis ester of the diacid is used for purposes of the interchange reaction, the alcohol from which the ester is formed (the alcohol to be displaced) should be lower boiling than the diol to be used for formation of polyester (the displacing alcohol). The reaction can then be conveniently run at a temperature at or below the boiling point of the displacing alcohol but well above that of the displaced alcohol, and is usually run in a temperature range similar to that for direct esterification. The ester interchange reaction is typically run in the presence of a diluent, for example, an inert organic solvent such as chloroform or

tetrachloroethane, and in the presence of a base, for example a tertiary organic base such as pyridine.

Typical catalysts used when ester interchange involves alcoholysis are weak bases such as carbonates or

alkoxides of sodium, lithium, zinc, calcium, magnesium or aluminum, whereas catalysts such as antimony oxide, titanium butoxide or sodium acetate are often used when acidolysis occurs in the interchange reaction. Diol derivatives such as an acetate can be used effectively when it is desired to conduct acidolysis.

Polyesters can also be produced by a ring- opening reaction of cyclic esters or lactones, for which organic tertiary bases and alkali and alkaline earth metals, hydrides and alkoxides can be used as

initiators. Advantages offered by this type of reaction are that it can be run at lower temperatures, frequently under 100°C, and there is no need to remove a

condensation product from the reaction.

Suitable reactants for making the polyester used in this invention, other than hydroxycarboxylic acids, are diols and dicarboxylic acids either or both of which can be aliphatic or aromatic. A polyester which is a poly(alkylene alkanedicarboxylate), a

poly(alkylene phenylenedicarboxylate), a poly(phenylene alkanedicarboxylate), or a poly(phenylene

phenylenedicarboxylate) is therefore appropriate for use herein. Alkyl portions of the polymer chain can be substituted with, for example, halogens, alkoxy groups or alkyl side chains and can contain divalent

heteroatomic groups (such as -O-, -S- or -SO₂-) in the paraffinic segment of the chain. The chain can also contain unsaturation and non-aromatic rings. Aromatic rings can contain substituents such as halogens, alkoxy or alkyl groups, and can be joined to the polymer backbone in any ring position and directly to the alcohol or acid functionality or to intervening atoms.

Typical alkylene diols used in ester formation are the C₂ - C₁₀ glycols, such as ethylene-,

propylene-, and butylene glycol. Alkanedicarboxylic acids frequently used are oxalic acid, adipic acid and sebacic acid. Diols which contain rings can be, for example, a 1,4-cyclohexylenyl glycol or a

1,4-cyclohexane-dimethylene glycol. resorcinol,

hydroquinone, 4.4'-thiodiphenol, bis-(4- hydroxyphenyl)sulfone, a dihydroxynaphthalene, a

xylylene diol, or can be one of the many bisphenols such as 2,2-bis-(4-hydroxyphenyl)propane. Aromatic diacids include, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid,

diphenyletherdicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid,

diphenoxyethanedicarboxylic acid .

In addition to polyesters formed from one diol and one diacid only, the term "polyester" as used herein includes random, patterned or block copolyesters, for example those formed from two or more different diols and/or two or more different diacids, and/or from other divalent heteroatomic groups. Mixtures of such

copolyesters, mixtures of polyesters derived from one diol and diacid only, and mixtures of members from both of such groups, are also all suitable for use in this invention, and are all included in the term "polyester". For example, use of cyclohexanedimethylol together with ethylene glycol in esterification with terephthalic acid forms a clear, amorphous copolyester ("PETG") of

particular interest. Also contemplated are liquid crystalline polyesters derived from mixtures of 4- hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid; or mixtures of terephthalic acid, 4-hydroxybenzoic acid and ethylene glycol; or mixtures of terephthalic acid, 4- hydroxybenzoic acid and 4,4'-dihydroxybiphenyl.

Aromatic polyesters such as the poly(alkylene phenylenedicarboxylates) polyethylene terephthalate and polybutylene terephthalate, or mixtures thereof, are particularly useful in this invention.

Methods and materials useful for the production of polyesters, as described above, are discussed in greater detail in Whinfield, USP 2,465,319, Pengilly, USP 3,047,539 and Russell, USP 3,756,986. c(iv) Polyamide. The polyamides used in this invention, wherein the polymer chain contains primarily if not entirely recurring amide groups, include those of the class which are frequently referred to as nylons. These polyamides can be produced by the condensation of bifunctional monomers, typically those containing acid and amine functionalities, where the monomers have either the same or different functional groups. For example, if hexamethylenediamine is reacted with adipic acid, an -[-AABB-]- type polyamide is obtained wherein the diamine and diacid units alternate. Or, when a monomer such as an amino acid or a cyclic lactam is self-polymerized, an -[-AB-]- type polyamide results from a regular head-to-tail polymerization, similar to an addition mechanism. For example, when nylon-6 is made, heat is applied to raise the temperature of the

caprolactam to 240-280°C, and catalysts such as water and phosphoric acid are added to the system. Hydrolysis ensues, the ring opens and polymerization takes place while unreacted monomer is removed from the system and recycled. Polycondensation and growth of the polymer chain results from the removal of water from the system.

The polyamides of this invention also include those wherein two or more different diamines, and/or different diacids and/or different amino acids are polymerized together to form a random or block copolyamide. The carbon chain between the functional groups may be linear or branched aliphatic, alicyclic or aromatic hydrocarbons. The chains may also contain hetero atoms such as oxygen, sulfur or nitrogen. Also suitable for use herein are block or random copolymers, such as those resulting, for example, from melt mixing two or more different polyamides, from reaction of a diamine or diacid monomer that contains an amide linkage with another diamine or diacid, or from reaction of a diisocyanate with a dicarboxylic acid.

Polyamides are most often prepared by direct amidation in which the amine group of a diamine or an amino acid bonds to the carboxyl of a diacid with the accompanying elimination of water. Derivatives of the acid function, such as an ester, acyl halide or amide, may be used as an alternative source of the carboxyl functionality, in which case the by-product is an alcohol, a hydrogen halide or ammonia, respectively. For example, when an acid chloride is used, the diacid chloride in a water-immiscible solvent can be added to an aqueous solution of the diamine, an inorganic base and a surface active agent, and interfacial

polymerization occurs in the organic layer. When polymerization occurs in solution, an organic base such as pyridine is used as the acid acceptor. Formation of polyamides can also occur by ring-opening polymerization of a caprolactam, such as when nylon-6 is made from ε- caprolactam. Such a reaction can be run at high temperature, in which case water or an amino acid is used as the initiator, or if it is run at low

temperature, the ring opening is effected by a strong base, such as NaOH, usually with the addition of an acylating cocatalyst such as acetic anhydride.

The polyamides used in this invention, as described above, and methods for preparing same, are discussed in greater detail in U.S. Pats. No. 2,071,253,

2,130,523 and 2,130,948.

Oxidative stabilizers can advantageously be utilized in this invention, examples of which are hindered phenols, hydroquinones, phosphites, including substituted members of those groups and/or mixtures of more than one thereof. A preferred phenolic anti- oxidant is Irganox™ 1076 anti-oxidant, available from Ciba-Geigy Corp. Ultra-violet stabilizers such as various substituted resorcinols, salicylates,

benzotriazoles, benzophines and hindered phenols can also be usefully included in the compositions of this invention, as can be lubricants, colorants, fillers such as talc, pigments, ignition resistant additives, mold release agents, and reinforcement agents such as

fiberglass. Numerous additives in addition to the foregoing are known in the art, and the decision as to which of any of them should be used is not critical to this invention. However, the total of such additives, if used, will generally not exceed 25 parts by weight of the total composition.

To illustrate the practice of this invention, examples of several preferred embodiments are set forth below. It is not intended, however, that these examples (Examples 1-5) should in any manner restrict the scope of this invention. Some of the particularly desirable features of this invention may be seen by contrasting the characteristics of Examples 1-5 with those of various controlled formulations (Controls A-L) which do not possess the features of, and are not therefore embodiments of, this invention.

Controls A-D and Examples 1 and 2. Control A is a carbonate homopolymer made from Bisphenol-A ("Bis-A PC") having a melt flow range of 8-12, as measured by ASTM Designation D 1238-85, Condition 0.

Control B is a carbonate copolymer ("BA/TBBA coPC") made, in molar ratio, from 4 parts of Bisphenol-A and 1 part of Tetrabromo Bisphenol-A. Control B has a T_g of about 177°C and a melt flow range of 8-12, as measured by ASTM Designation D 1238-85, Condition 0.

Controls C and D and Examples 1 and 2 contain varying amounts of the copolymer used in Control B, BA/TBBA coPC, in admixture with varying amounts of other substances as follows:

•an ethylene/carbon monoxide copolymer ("ECO"), having a melt flow range of 8-12, as measured by ASTM

D Designation 1238-85, Condition E, of which the portion derived from carbon monoxide is about 10% of the copolymer by weight; and/or •an MBS rubber.

The following tests were performed on Controls A-D and Examples 1 and 2:

Deflection temperature under load ("DTUL") was measured in accordance with ASTM Designation D 648-82 at 264 psi (1.82 MPa).

The Gardner dart drop impact test was performed at room temperature by dropping a 16 pound (7.26 km) weight which carries a ½" (12.7 mm) dart onto a circular test sample which is 2J" (63.5 mm) in diameter and 1/8"

(3.175 mm) thick. The weighted dart falls freely on a slotted track and impacts the sample, which is secured in position in the path of descent on an aluminum cast base with a 0.640 inch (16.26 mm) hole to accept the dart after it impacts the sample. The instrument is a

Pacific Scientific model no. IG-1120. The sample fails if it shows a crack or perforation on the side on which impact did not occur. The results are either pass (no break or perforation by the dart at the point of impact) or fail (material exhibits crack or perforation) when the dart has developed a particular amount of energy by falling from the necessary height on the track, as indicated thereon, to develop such energy. The reading recorded in Table I is the greatest amount of energy a sample could accept without failing, except with respect to Controls A and B, which passed at 640 in-1b (72.3 J), the greatest amount of energy the machine is capable of developing.

Impact resistance was measured by the Izod test according to ASTM Designation D 256-84 (Method A) at 23°C. The notch is 10 mils (0.01 inch or 0.254 mm) in radius. The result of this test is referred to in the appended claims as Izod impact value.

Percent elongation at break was measured in accordance with ASTM Designation D 638-84. It is measured with respect to a sample which has been placed under 0.7% strain while submerged in a bath of 60 wt% isooctane and 40 wt% toluene for 5 minutes and then allowed to dry without strain for at least one hour before being tested, and with respect to a second sample which has had no solvent contact prior to testing. The processing temperature of each sample was determined by observing the lowest barrel temperature, when processing a sample in the same extruder [a 55-ton (49.5 Mg) Negri Bossi] under constant conditions [such as injection pressure (50 bar, 5 MPa), and screw speed], at which the sample will completely fill a mold which is maintained at 175°F (79.4°C) so as to produce a properly formed part.

The content of Controls A-D and Examples 1 and 2, in parts by weight, and the results of the above mentioned tests, are shown below in Table I. "NM" indicates no measurement.

The results of the tests on Controls A-D and Examples 1 and 2 reported above show that, in a high heat polycarbonate composition, the presence of a flow modifier allows the effective use therein of an

elastomeric toughening agent because the temperature at which such composition can be processed is low enough to avoid degradation of the toughening agent. For

instance, since it is a high heat polycarbonate, the BA/TBBA coPC of Control B has a higher DTUL than the Bis-A homopolymer of Control A, and has a

correspondingly higher processing temperature as well. However, the BA/TBBA coPC of Control B has a noticeably lower Izod impact value than the Bis-A PC of Control A. This lower Izod value in the high heat polycarbonate

(Control B) is illustrative of the notch sensitivity and the lack of toughness and impact strength which is displayed in general by high heat polycarbonates, and is a condition which it is desired that a toughening agent improve in a high heat polycarbonate while a balance of desirably high values is maintained as to other

properties.

When an elastomeric toughening agent is compounded with the BA/TBBA coPC in the absence of a flow modifier, as in Control C, not only are the DTUL, dart drop and percent elongation readings undesirably lowered, the processing temperature is increased as well. The desired effect of the toughening agent is not obtained because the processing temperature is so high that the elastomer is degraded. When an elastomeric toughening agent is compounded with the BA/TBBA coPC before the addition of a flow modifier to the mixture, as in Control D, an even lower Izod impact value is obtained because degradation of the rubber occurred before the benefits of the flow modifier were provided to the mixture.

However, when a flow modifier such as ECO is admixed with a high heat polycarbonate before addition of an elastomeric toughening agent, as in Excample 1, or simultaneously with the toughening agent, as in Example

2, the high heat character of the BA/TBBA coPC is substantially retained (as shown by the DTUL reading) while the notch sensitivity (as shown by the increase in the Izod impact value) is significantly reduced. The importance of adding a flow modifier to a high heat polycarbonate composition before or during addition of an elastomeric toughening agent is clearly demonstrated. When this order of addition is observed, as in Examples 1 and 2, the desired balance of resistance to both thermal deformation and notch sensitivity is obtained. The flow modifier is allowed to lower the viscosity and consequently the processing temperature of the high heat polycarbonate so that the elastomeric toughening agent is not degraded by the temperature at which compounding must occur. In Controls C and D, when this order of addition was not observed, the desirably high levels of both DTUL and Izod impact value were not obtained.

Controls E and F and Example 3. Control E is a carbonate homopolymer made from Bisphenol-A ("Bis-A PC") having a melt flow range of 8-12, as measured by ASTM

Designation D 1238-85 , Condi tion 0.

Control F is a carbonate homopolymer made from

Bisphenol-AP ("Bis-AP PC") having a T_g of about 190°C, and a melt flow range of 1-3, as measured by ASTM

Designation D 1238-85, Condition 0.

Example 3 contains the Bis-AP PC used in

Control F in admixture with other substances as follows: •an ethylene/carbon monoxide copolymer ("ECO"), having a melt flow range of 8-12, as measured by ASTM Designation D 1238-85, Condition E, of which the portion derived from carbon monoxide is about 10% of the copolymer by weight; and

•an MBS rubber.

The following tests were performed on Controls E and F and Example 3 :

The DTUL and Izod impact values and the processing temperature were determined according to the conditions therefor described above.

Flexural Modulus was measured in accordance with ASTM Designation D 790-84a.

Percent critical strain in solvent was measured by flexing injection molded bars to various strains from 0.1 to 2.0% and then immersing them in a bath of 60 wt% isooctane and 40 wt% toluene for 10 minutes. The stress is relieved immediately after the sample is taken out of the bath, and the sample is examined visually for surface cracks. The greatest amount of strain the sample is able to tolerate without showing surface cracks is reported.

The content of Controls E and F and Example 3, in parts by weight, and the results of the above mentioned tests on Controls E and F and Example 3, are shown below in Table II.

Example 3 shows a definite improvement in Izod impact value over Control F, a high heat polycarbonate, while at the same time Example 3 displays a desirable level of resistance to thermal deformation as shown by its DTUL reading.

Controls G-L and Examples 4 and 5. Control G is a carbonate homopolymer made from Bisphenol-A ("Bis-A PC") which has a melt flow range of 8-12, as measured by ASTM Designation D 1238-85, Condition 0.

Controls H and J contain the Bis-A PC used in Control G admixed with 10% by weight of one or both of the following:

•poly(ethylene terephthalate) ("PET") having an

intrinsic viscosity of 0.59, as measured

according to ASTM Designation D

4603-86, and

•hydrogenated styrene/butadiene block copolymer

("Kraton-G™ 1651") available from Shell Oil

Company.

Control K is a carbonate copolymer ("BA/TBBA coPC") made, in molar ratio, from 4 parts of Bisphenol-A and 1 part of Tetrabromo Bisphenol-A. The BA/TBBA coPC, as a high heat material, has a T_g of about 177°C and a melt flow range of 8-12, as measured by ASTM Designation D 1238-85, Condition 0.

Control L contains 90% by weight of the BA/TBBA coPC used in Control K, and 10% by weight of Kraton-G™ 1651.

Examples 4 and 5 contain 80% by weight of the BA/TBBA coPC used in Control K, and 10% by weight of Kraton-G™ 1651 and either PET (Example 4) or an ethylene/carbon monoxide copolymer ("ECO"), having a melt flow range of 8-12, as measured by ASTM Designation

D 1238-85, Condition E, of which the portion derived from carbon monoxide is about 10% of the copolymer by weight (Example 5).

Results of the 10 mil notched Izod impact test performed on Controls G-L and Examples 4 and 5,

according to the conditions therefor described above, as well as the content of G-L and Examples 4 and 5, in parts by weight of the total composition, are set forth below in Table III.

Controls G-J show that the Izod impact value of a non-high heat polycarbonate (Control G) is actually lowered by the addition thereto of either an elastomeric toughening agent alone (Control H), or both a flow modifier and a toughening agent together (Control J). This progression in Izod values as to Controls G-J is a characteristic of a non-high heat polycarbonate which is totally absent from a high heat polycarbonate which has been so modified. This Izod data for a non-high heat polycarbonate gives no indication whatever that the use of a flow modifier and toughening agent might be

desirable for increasing the Izod impact value of a high heat polycarbonate, such as a Bis-A/TBBA co- polycarbonate. However, Controls K and L and Examples 4 and 5 show that, in fact, this does occur. Significant increases in the Izod impact value are seen for Examples 4 and 5 as compared to a high heat polycarbonate alone (Control K), or Control K admixed with a toughening agent alone (Control L).

Further, a high heat polycarbonate which has been admixed with a flow modifier and a toughening agent desirably possesses a decreased ductile/brittle

transition tempearture. For example, Control K (100% high heat polycarbonate) is brittle at 23°C whereas Examples 4 and 5 are both clearly ductile at that tempearture. The ductile/brittle transition temperature for Examples 4 and 5, a high heat polycarbonate admixed with a flow modifier and a toughening agent in each case, must therefore be lower than that for 100% high heat polycarbonate, Control K.

This demonstrates that non-high heat

polycarbonate does possess entirely different properties as compared with high heat polycarbonate insofar as the effect thereon obtained by admixture with a flow

modifier and toughening agent. Izod values decrease in the case of non-high heat polycarbonate while they increase dramatically in the case of high heat

polycarbonate.

Formulations are prepared wherein a polysulfone (T_g: about 190°C), and a polyarylate ( T_g: about 192°C, made from 1 part terephthalic acid, 1 part isophthalic acid and 2 parts Bis-A), are each mixed with a

toughening agent and a flow modifier. Contrary to the experience with high heat polycarbonate, it is found that the combination of a toughening agent and a flow modifier with these other high heat materials either does not impart an improvement in notch sensitivity, or that, if notch sensitivity is improved, impact

resistance is reduced to unacceptably low levels. The experience with other high heat materials does not therefore suggest the desirable improvements in notch sensitivity and impact resistance possessed by a high heat polycarbonate which has been admixed with a flow modifier and toughening agent. It is within the skill in the art to practice this invention in numerous modifications and variations in light of the above teachings It is, therefore, to be understood that changes may be made in the various described embodiments of this invention without

departing from the spirit and scope of this invention as defined by the appended claims.

Claims

1. A method of preparing a composition comprising (i) a high heat polycarbonate having a glass transition temperature exceeding 155°C and (ii) an elastomeric toughening agent containing greater than 40% rubber by weight, comprising the steps of

(a) lowering the viscosity of said high heat

polycarbonate, and

(b) admixing said toughening agent with said high heat polycarbonate;

wherein the step of lowering viscosity is performed no later than the step of admixing said toughening agent.

2. The method of Claim 1 wherein the step of lowering viscosity is performed before the step of admixing said toughening agent is performed.

3. The method of Claim 1 wherein the step of lowering viscosity is performed while the step of admixing said toughening agent is performed.

4. The method of Claim 1 wherein the viscosity of said high heat polycarbonate is lowered to a level at which said elastomeric toughening agent is thoroughly dispersable within said high heat polycarbonate at a temperature below that at which said toughening agent is degraded.

5. A method of preparing a composition comprising a high heat polycarbonate having a glass transition temperature exceeding 155°C, comprising the steps of

(a) admixing with said high heat polycarbonate an elastomeric toughening agent containing greater than 40% rubber by weight,

(b) admixing with said high heat polycarbonate one or more flow modifiers selected from from the group consisting of an olefin/carbon monoxide copolymer, a styrenic thermoplastic resin, a polyester and a polyamide;

wherein the step of admixing the elastomeric toughening agent is performed no later than the step of admixing the flow modifier(s).

6. The method of Claim 5 wherein the step of admixing the flow modifier(s) is performed prior to the step of admixing the elastomeric toughening agent.

7. The method of Claim 5 wherein the step of admixing the flow modifier(s) is performed while the step of admixing the elastomeric toughening agent is performed.

8. The method of Claim 1 or 5 wherein the composition formed thereby has a heat deflection temperature under load, determined according to ASTM 648-82 at 264 psi (1.82 MPa), exceeding 280°F (137.8°C) .

9. The method of Claim 8 wherein the

composition formed thereby has an Izod impact value, determined according to ASTM 256-84 (Method A),

exceeding 6.0 ft-lb/in (320.3 J/m).

10. The method of Claim 9 wherein the glass transition temperature, or the highest glass transition temperature, of the composition formed thereby exceeds 148°C.

11. A method of molding a composition

comprising preparing a composition by the method of Claim 1 or 5, and molding said composition.

12. A composition of matter comprising

(a) a high heat polycarbonate having a glass transition temperature exceeding 155°C,

(b) an elastomeric toughening agent containing greater than 40% rubber by weight, and

(c) one or more flow modifiers selected from the group consisting of an olefin/carbon monoxide copolymer, a styrenic thermoplastic resin, a polyester, and a polyamide.

13. The composition of Claim 12 having a heat deflection temperature under load, determined according to ASTM 648-82 at 264 psi (1.82 MPa), exceeding 280°F (137.8°C).

14. The composition of Claim 12 having an Izod impact value, determined according to ASTM 256-84

(Method A), exceeding 6.0 ft-lb/in (320.3 J/m).

15. The composition of Claim 12 having a heat deflection temperature under load, determined according to ASTM 648-82 at 264 psi (1.82 MPa), exceeding 280°F (137.8°C), and an Izod impact value, determined

according to ASTM 256-84 (Method A), exceeding 6.0 ft- lb/in (320.3 J/m).

16. The composition of Claim 15 wherein the glass transition temperature, or the highest glass transition temperature, exceeds 148°C.

17. The composition of Claim 12 wherein said high heat polycarbonate is present in said composition in an amount from about 40 parts to about 95 parts, said toughening agent is present in said composition in an amount from about 0.1 parts to about 20 parts, and said flow modifier is present in said composition in an amount from about 0.1 parts to about 50 parts, each by weight of the total composition.

18. An object molded from the composition of Claim 12.

19. The molded object of Claim 18 in the form of a motor vehicle part.