EP0462185A4

EP0462185A4 - Molding compositions comprising carbonate polymer, rubber modified vinyl aromatic-nitrile graft copolymer and methyl(meth)acrylate-butadiene-styrene graft copolymer and blow molding and thermoforming processes using such compositions

Info

Publication number: EP0462185A4
Application number: EP19900904582
Authority: EP
Inventors: Michael K. Laughner
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1989-03-08
Filing date: 1990-03-07
Publication date: 1992-08-19
Also published as: JPH04505628A; WO1990010674A1; AU5187490A; BR9007201A; CA2047667A1; KR920701360A; EP0462185A1

Abstract

Carbonate polymers (PC) such as randomly branched carbonate polymers, linear carbonate polymers and blends thereof are blended with rubber-modified vinyl aromatic-nitrile graft copolymers where the rubber is other than a conjugated diene and an MBS-type rubber is added as impact modifier. The MBS impact modifiers are located at the interface of the PC phase and the vinyl aromatic-nitrile copolymer phase or in the PC phase so that higher melt elasticity and better blow molding is achieved.

Description

MOLDING COMPOSITIONS COMPRISING CARBONATE POLYMER, RUBBER MODIFIED VINYL AROMATIC-NITRILE GRAFT COPOLYMER .

AND METHYL(METH)ACRYLATE-BUTADIENE-STYRENE GRAFT COPOLYMER AND BLOW MOLDING AND THERMOFORMING PROCESSES

USING SUCH COMPOSITIONS

This invention relates to thermoplastic resin compositions and more particularly relates to improved blends of carbonate polymers, core/shell graft copolymers and rubber modified vinyl aromatic- acrylonitrile graft copolymers where the rubber is other than a conjugated diene polymer and a method of using the compositions.

More specific examples of this invention include molding compositions comprising a blend of (1) one or more carbonate polymer with (2) one or more graft copolymer of vinyl aromatic-nitrile copolymer onto one or more rubbery polymer of ethylene-propylene- nonconjugated diene monomer (EPDM) , which includes an EPDM-vinyl aromatic hydrocarbon copolymer rubber; or onto one or more rubbery polymer of al yl acrylate(s), which include an alkyl acrylate-vinyl aromatic hydrocarbon copolymer rubber; or onto both of these types of rubbers and (3) one or more core/shell graft copolymer having as a core a rubbery polymer of alkyl acrylate or butadiene, including copolymers thereof such as butadiene-vinyl aromatic hydrocarbon or butadiene- vinyl aromatic hydrocarbon-alkyl acrylate copolymers, with optionally a second inner shell phase of a polymer of vinyl aromatic hydrocarbon monomer and an outer shell of an alkyl (meth)acrylate polymer.

The graft copolymers of component (2) above are commonly referred to as AES resins where an EPDM-type polymer rubber is used or as ASA resins where an alkyl acrylate-type polymer rubber is used. The core/shell

10 graft copolymers of component (3) above are often referred to as MBS rubbers or resins when they are a butadiene rubber core grafted with a polymer of methyl methacrylate and styrene or as butyl acrylate core/shell _1C- rubbers when a butyl acrylate rubber core is grafted with an alkyl acrylate polymer.

Although polycarbonate blend compositions have been found to be thermoplastically moldable under a

20 broad range of injection molding conditions, only select polycarbonate blends are suitable for blow molding. This is due to the unique requirements of blow molding operations.

_?j- In the conventional blow molding operation, as taught in U.S. Patent Nos. 4,652,602 and 4,47-4,999, a tube or parison of the heat softened thermoplastic blend may be extruded vertically downward into a mold. The extrudate is then pressed unto the mold surfaces with a

30 pressurized gas flow (usually air or inert gas), shaping the heat softened resin.

As appreciated by those skilled in the art, the successful molding of a given thermoplastic resin is dependent upon a number of factors, including the characteristics and physical properties of the heat softened resin. The length and diameter of the tube and the quantity of material forming the tube are limiting factors in determining the size and wall thickness of the object that can be molded by this process. The fluidity of the melt obtained from polycarbonate blends, or the lack of melt strength as well as the paucity of extrudate swelling, serve to limit blow molding applications to relatively small, thin walled parts. These factors alone are of considerable importance in the successful blow molding of any resin, particularly in regard to the molding of large articles.

It is known from Japanese Patent Publication No. JP 58/59258 (1983) that resin compositions with good weld strength can be obtained from blends of linear polycarbonate resins, acrylonitrile-butadiene-styrene resins (ABS), and rubbery graft copolymer resins (MBS). This patent is attempting to modify only the ABS phase to improve the weldline by utilizing MBS resins containing 30 to 50 percent rubber and styrene in the outer shell. It is believed that having styrene in the outer shell helps to drive the MBS resins into the ABS phase where the added rubber helps to improve the poor weldline properties of the ABS.

It is further known from U.S. Patent No. 4,677,162 that a moldable blend of either linear or branched polycarbonate resins (PC), acrylonitrile- butadiene-styrene resins (ABS), and rubbery graft copolymers (MBS) is useful to form articles with good impact resistance and low gloss. However, both of these references utilize only ABS resins (based on butadiene polymer rubbers) and do not suggest using AES or ASA rubbers to prepare a more environmentally stable resin nor the increase in resin blend melt strength obtained by the use of these graft copolymers in carbonate polymer blends to control MBS rubber placement.

The present invention is directed to a moldable thermoplastic blend composition comprising:

A) 20 to 94 percent by weight and preferably 35 to 85 percent by weight carbonate polymer selected from:

(i) randomly branched carbonate polymers,

(ii) linear carbonate polymers, and

(iii) blends of randomly branched carbonate polymers with linear carbonate polymers,

B) 5 to 75 percent by weight, preferably at least 10, more preferably at least 15 to preferably 70 and more preferably 60 percent by weight of one or more graft copolymer of vinyl aromatic-nitrile copolymer and one or more rubbery polymer other than a conjugated diene polymer, and

C) 0.5 to 20 percent by weight, preferably at least 1 and more preferably at least 2 to preferably 15 percent by weight of core/shell graft copolymer having as a core a rubbery polymer of butadiene and/or alkyl acrylate(s) with an outer shell of an alkyl (meth)acrylate polymer wherein said percents by weight are based on components A), B) and C).

A further aspect of the present invention is a process of preparing molded articles using the above composition. The articles produced and/or molded by using the compositions of the invention are useful as automotive components, bottles, tool housings and the like.

Figures 1 and 2 are transmission electron micrograph (TEM) photographs of Experimental Compositions 1 and 4 showing that the blends of polycarbonate (PC) and the rubber modified vinyl aromatic-nitrile graft copolymer surprisingly have the MBS rubber (small black spheres) located at the interface of the dark gray polycarbonate phase with the lighter gray, vinyl aromatic-nitrile copolymer phase and in polycarbonate phase. In addition, the photographs show the location of the rubbery impact modifier in the vinyl aromatic-nitrile copolymer (SAN) resin phase, as would be expected.

This location of the rubber particles in both phases and the interface of the two phases results in better combinations of physical properties, such as higher melt elasticity, elastic modulus and higher zero shear viscosity. These properties are especially desirable and/or useful in the thermoforming or blow molding of large parts since high R* values (a measure of melt elasticity based on a calculation using these values) are needed, especially for the blow molding of parisons weighing 0.9 kilogram (2 pounds) or more. The ability to control the placement of rubber, such that rubber now resides in each phase and the interfaces of a multi-phase polymer blend, is desirable to increase the melt elasticity of compositions used for large part blow molding or thermoforming applications.

The carbonate polymers employed in the present invention are advantageously the known aromatic carbonate polymers such as the trityl diol carbonates described in U.S. Patent Nos. 3,036,036; 3,036,037; 3,036,038 and 3,036,039; polycarbonates of bis(ar- hydroxyphenyl) -alkylidenes (often called bisphenol-A type diols) including their aromatically and aliphatically substituted derivatives such as disclosed in U.S. Patent Nos. 2,999,835; 3,028,365 and 3,334,154; and carbonate polymers derived from other aromatic diols such as described in U.S. Patent No. 3,169,121.

It is understood, of course, that the polycarbonate may be derived from (1) two or more different dihydric phenols or (2) a dihydric phenol and a glycol or a hydroxy- or acid-terminated polyester or a dibasic acid in the event a carbonate copolymer or interpolymer rather than a homopolymer is desired. Also suitable for the practice of this invention are blends of any one of the above carbonate polymers. Also included in the term "carbonate polymer" are the ester/carbonate copolymers of the types described in U.S. Patent Nos. 3,169,121; 4,156,069; 4,260,731; 4,330,662; 4,360,656; 4,374,973; 4,388,455; 4,355,150; and 4,105,633. Of the aforementioned carbonate polymers, the polycarbonates of bisphenol-A are preferred. Methods for preparing carbonate polymers for use in the practice of this invention are well known. For example, several suitable methods are disclosed in the aforementioned patents. The known randomly branched chain polycarbonates are also well suited for use according to the present invention either as the sole carbonate polymer or blended with an amount of linear polycarbonate. The branched chain polycarbonates used in this invention are prepared by reacting a dihydric phenol with phosgene in the presence of a trihydric and/or tetrahydric phenol, as shown in U.S. Patent No. 3,544,514.

Blow moldable resins and their desired properties are known to those skilled in the art and are taught in U.S. Patent Nos. 4,652,602 and 4,474,999. U.S. Patent No. 4,652,602 is particularly pertinent since it gives a definition of R* which is a measure of blow moldability that is used in the below Experiments to illustrate the performance of the compositions according to the present invention.

The rubber modified vinyl aromatic-nitrile graft copolymer(s) used in the compositions of the present invention are generally characterized as having a dispersed elastomeric phase and a rigid thermoplastic matrix phase and are typically prepared by means of an emulsion, mass or suspension polymerization process. As mentioned above, the rubber is selected from the known rubbery polymers other than the conjugated diene-type rubbers. The preferred rubber materials for preparing the rubber modified vinyl aromatic-nitrile graft copolymers for use according to the present invention have a Tg less than 0°C, more preferably less than -20°C. Examples of these types types of rubbers are well known and include the rubbery polymers of ethylene-propylene- nonconjugated diene monomer or alkyl acrylate(s). Examples of suitable graft copolymers include acrylonitrile/EPDM(rubber)/styrene graft copolymers (AES resins) and acrylonitrile/styrene/acrylate(rubber) graft copolymers (ASA resins). The rubber modified vinyl aromatic-nitrile graft copolymer component for use according to the present invention can also advantageously be a blend or combination of AES and ASA resins.

AES resins may be characterized as an ethylene- propylene-nonconjugated diene (EPDM) polymer rubber

10 grafted with and dispersed in a matrix thermoplastic resin which matrix resin is a vinyl aromatic-nitrile copolymer. EPDM-type rubber materials suitable for the preparation of AES-type resins are well known and m m. commercially available. EPDM-type rubber is typically employed in an AES resin in amounts of from 5 to 40 percent by weight, preferably from 10 to 30 percent by weight with the balance typically being a vinyl aromatic-nitrile copolymer containing from 10 to 40,

20 preferably from 15 to 30 percent by weight nitrile monomer residue. Such AES resins are commercially available from The Dow Chemical Company, for example as R0VEL™ 300 brand resin and are further described in U.S. Patent Nos. 4,202,948 and 3,642,950.

25

ASA resins may be characterized as an alkyl (meth)acrylate polymer rubber grafted with and dispersed in a matrix thermoplastic resin which matrix resin is a vinyl aromatic-nitrile copolymer. By the term alkyl

30 (meth)acrylate polymer rubber is meant rubbery polymers of alkyl acrylate where alkyl is a C-_j to C _Q hydrocarbyl radical or alkyl methacrylates where alkyl is a Cg to C 2 hydrocarbyl radical, including copolymers with other monomers, such as for example, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, and the like. Acrylate rubber materials suitable for use in the preparation of ASA-type resins are well known and are typically prepared by an emulsion process where additional amounts of a rigid alkyl (meth)acrylate or vinyl aromatic-nitrile polymer can also advantageously be grafted thereto while still in the emulsion. A grafted rubber concentrate obtained in such a process usually contains in excess of 40 weight percent of acrylate rubber and is then typically combined with

10 further amounts of a separately prepared vinyl aromatic-, nitrile copolymer to produce a final ASA-type resin having the desired acrylate rubber content.

Acrylate-type rubber is typically employed in _.,- an ASA resin in amounts of from 5 to 40 percent by weight, preferably from 10 to 30 percent by weight with the balance typically being a vinyl aromatic-nitrile copolymer containing from 10 to 40, preferably from 15 to 30 percent by weight nitrile monomer residue. 20 Acrylonitrile-styrene-acrylate rubber graft copolymers suitable for use in the blend compositions according to the present invention are commercially available and well known from U.S. Patent No. 3,944,631.

25 Suitable rubber modified vinyl aromatic-nitrile graft copolymer resins can be prepared by grafting a styrene-acrylonitrile (SAN) copolymer onto the desired rubber substrate in the form of a latex. The rubber elastomeric component is grafted with SAN copolymer and

30 dispersed as a discrete phase in a thermoplastic component formed by the ungraf ed SAN. These products are recovered from the water phase and can advantageously be mixed with further amounts of ungrafted SAN copolymer for use in the blend compositions according to the present invention.

It is also well known to prepare such resins by one of the known mass, solution, mass-solution, or mass- suspension processes where the styrene and acrylonitrile monomers are copolymerized in the presence of a previously prepared rubber substrate while the rubber is swollen with or dissolved in the monomers or other organic solvent in which the monomers, rubber and SAN.

10 copolymer are at least partially soluble. In this type of process, the forming styrene-acrylonitrile (SAN) copolymer advantageously forms both grafted polymer onto the rubber and all or part of the balance of the matrix -i_t-; polymer for the graft copolymer component.

The rubber content of the rubber-modified vinyl aromatic-nitrile thermoplastic graft copolymer resin used in this invention is not more than 40 percent by 0 weight. Preferably the rubber content of this component is at least 5 percent by weight, more preferably at least 10 percent by weight and preferably not more than 30 percent by weight, more preferably not more than 25 percent by weight. This aspect of the graft copolymer 25 together with the flexibility of varying the molecular weight of the respective components, the degree of grafting, and rubber particle size and morphology are important, as are the precise vinyl aromatic and nitrile monomer contents, in obtaining desirable properties and

30 can be adjusted accordingly as known to those skilled in the art.

In general, the rubber-modified vinyl aromatic- nitrile thermoplastic graft copolymer resin used in this invention should contain 10 to 40 percent by weight nitrile monomer based on total weight rubber-modified vinyl aromatic-nitrile thermoplastic graft copolymer resin, more preferably 15 to 35 weight percent. It has also been found that within these ranges further improved properties are obtained if the nitrile content of this component is maintained at levels greater than 18 percent by weight. This achieves sufficient polarity and an appropriate solubility parameter in the vinyl aromatic-nitrile copolymer phase to facilitate the location of the core/shell graft copolymer into the carbonate polymer phase and its interface with the ABS- type polymer.

The thermoplastic vinyl aromatic-nitrile copolymer can be manufactured from nothing other than nitrile and vinyl aromatic monomers, or other monomers can be substituted (partially) or mixed in with them. Although alteration of the monomer mix yields a variation in the properties of the composite, usually it does not, nor is it intended to, cause a variation in the fundamental substrate-graft-matrix structure which is characteristic of rubber-modified thermoplastic vinyl aromatic-nitrile copolymers. However, the monomer mix (especially the nitrile monomer) does influence the solubility parameter of the thermoplastic SAN phase and can be used to direct or place the core/shell graft copolymer component in the carbonate polymer when the three are blended.

The preferred core/shell grafted copolymers have a Tg less than 0°C and a rubber content greater than 40 percent. They are generally obtained by polymerizing certain monomers in the presence of an alkyl (meth)acrylate or diene polymer rubber core. By the term diene polymer rubber as suitable for use as the core rubber is meant homopolymers of conjugated dienes having 4 to 8 carbon atoms such as butadiene, isoprene, piperylene, chloroprene, and copolymers of such dienes with less than 50 weight percent, preferably less than 20 weight percent, more preferably less than 10 weight percent other monomers, such as for example, acrylonitrile, methacrylonitrile, butyl acrylate, methyl methacrylate, styrene, α-methylstyrene, and the like. As mentioned above, by the term alkyl (meth)acrylate polymer rubber as suitable for use as the core rubber is. meant homopolymers of alkyl acrylate where alkyl is a C-_| to C-_|o hydrocarbyl radical or alkyl methacrylates where alkyl is a Cg to C22 hydrocarbyl radical and copolymers thereof with less than 50 weight percent, preferably less than 20 weight percent, more preferably less than 10 weight percent other monomers, such as for example, acrylonitrile, methacrylonitrile, styrene, α- methylstyrene, and the like. The rubber core may be at least partially crosslinked, and is preferably a latex polymer. Preferred alkyl (meth)acrylate polymer rubbers include the rubber polymers based on butyl acrylate.

Then, certain monomers are grafted onto the rubber core to form one or more grafted shell and/or small amounts of ungrafted matrix polymer. A variety of monomers may be used for this grafting purpose, such as: vinyl aromatic compounds such as vinyl toluene, alpha- methyl styrene, halogenated styrene, naphthalene; nitriles such as acrylonitrile, methacrylonitrile or alpha-halogeπated acrylonitrile; C-_j to Cg alkyl acrylates such as methacrylate, ethylacrylate or hexyl acrylate; C-- to Cg alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, glycidyl methacrylate or hexyl methacrylate; unsaturated carboxylic acids such as an acrylic or methacrylic acid, including derivatives of such acids such as anhydrides; or a mixture of two or more of the foregoing. The extent of grafting is sensitive to the substrate latex particle size and particle size may be influenced by controlled coagulation techniques among other methods. When the graft level is allowed to reach an excessively high level, the rubbery effect of the relative substrate latex content is reduced.

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.

Examples of suitable grafted copolymers of the core/shell type are a methylmethacrylate/buta- diene/styrene grafted copolymer (MBS rubber), and a ■ butyl acrylate core-rigid methyl methacrylate thermoplastic shell copolymer.

An MBS-type rubber contains a substrate latex or core which is made by polymerizing a conjugated diene, or by copolymerizing a conjugated diene with a mono- olefin or polar vinyl compound, such as styrene, acrylonitrile or methyl methacrylate. The substrate latex is typically made up of 50 to 100 percent conjugated diene and up to 50 percent of one or more additional mono-olefin or polar vinyl compound. One or more of the above-listed suitable grafting monomers is graft polymerized to the substrate latex. A typical weight ratio for an MBS rubber is 60 to 80 parts by weight substrate latex, 10 to 20 parts by weight first grafting monomer and 10 to 20 parts by weight second grafting monomer. A preferred formulation of 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 inner shell phase of about 11 parts of styrene; and an outer 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. A product having substantially such content is available commercially from Rohm and Haas Company as Paralpid™ EXL 3607 core-shell MBS polymer. The MBS rubber and methods for making same, as described above, are discussed in greater detail in U.S. Patent Nos. 3,243,481, 3,287,443, 3,509,237, 3,657,391, 3,660,535, 4,180,494, 4,221,833, 4,239,863 and 4,617,345.

As known to those skilled in this area of technology, these compositions may also contain other ingredients such as UV and antioxidant stabilizers, fillers such as talc, reinforcement agents and such as mica or glass fibers, ignition resistant additives, pigments, dyes, antistatic agents, mold release additives, and the like. These compositions may be useful for injection molding, blow molding or thermoforming applications. The following experiments and controls are presented to further illustrate the invention.

AES-type Graft Copolymer Experiments - Control 1

One thousand three hundred parts by weight of a linear polycarbonate (Calibre™ 300-10, Dow Chemical Company) was mixed with 700 parts by weight acrylonitrile-EPDM-styrene (AES) copolymer, 2 parts by weight epoxidized soybean oil (Plas Chek™ 775 from the Ferro Company), and 4 parts by weight Irganox™ 1076 antioxidant (from Ciba Geigy) .

The mixture was uniformly blended together in a laboratory tumbler. The blend was introduced into a 30 millimeter (mm) Werner-Pfleiderer melt extruder with heating set points of 270°C. The extrudate was pelletized and dried. The pellets were fed to a 70 ton Arburg injection molding machine to mold test bars of . 12.6 centimeter (cm) x 2.25 cm with a thickness of 3.175 mm. The moldings were subjected to tests to determine their blow moldability (R* value) and 0.025 millimeter (10 mil) notched Izod.

The blowmoldability was determined by a method generally as described in U.S. Patent No. 4,652,602.

This evaluation is based on the fact that blowmoldable resins need to have two properties, reasonably low viscosity in the extrusion annulus as the parison is extruded (moderate shear conditions) and sufficient melt strength and higher viscosity to allow a suspended part to be formed (low shear conditions). On this basis a value for blowmoldability, R*, is defined as the ratio of viscosities at shear rates of 0.1 and 100 reciprocal seconds at a processing temperature that has experimentally been determined to be sufficient to form a reasonable parison or calculated to be the temperature at which the material viscosity is 20,000 poise at a shear rate of 100 reciprocal seconds. According to this method the R* values for this and the other Experimental compositions prepared below are determined.

The composition of this and several further experimental blends is given in Table 1 below. Each of - -

the Experimental Compositions was made by following the procedure for the above control with the indicated amounts of the core/shell graft copolymer being combined with the balance of the composition in the tumbler mixer. As used in the Tables below: "Lin. PC" is a linear polycarbonate having a melt flow rate (MFR) of 10 grams per 10 minutes commercially available from The Dow Chemical Company as Calibre™ 300-10; "Bran. PC" is a randomly branched polycarbonate with a 3 MFR 0 commercially available from The Dow Chemical Company in the Calibre™ 600 series; "Para 3607" is Paraloid™ 3607 methylmethacrylate-styrene-butadiene (MBS) core/shell graft copolymer from Rohm and Haas having as a core a rubbery polymer of butadiene with an inner shell of a 5 styrene polymer and an outer shell of a methylmethacrylate polymer, containing greater than 70 percent rubber by weight and having a Tg of about -70°C; "Para 3330" is Paraloid™ 3330 core/shell graft copolymer from Rohm and Haas having as a core a rubbery 0 polymer of butyl acrylate with an outer shell of methylmethacrylate graft copolymer, containing greater than 70 percent rubber by weight and having a Tg of . about -30°C; "AES" is an acrylonitrile-EPDM-styrene r- copolymer commercially available from The Dow Chemical Company as Rovel™ F-300 containing about 23 percent by weight of an EPDM rubber and 20 percent by weight acrylonitrile.

0 The test results are given in Table 2 below. As can be seen from the desirable physical property combinations, compositions according to the present invention may be useful for injection molding, blow molding or thermoforming applications. In the following Table 2, "Izod J_" refers to notched Izod impact resistance values measured according to ASTM D-256 in joules/meter perpendicular to the direction of polymer flow at the given temperatures and "Izod II"refers to values measured parallel to the direction of polymer flow. "R*" refers, as mentioned above, to a viscosity ratio which gives a measure of blowmoldability, higher values indicating better blowmoldability.

Table 1

PC/AES

Lin. Bran. AES Para Para

PC PC 3607 3330

(wt pts/ (wt pts/ (wt pts/ (wt pts/ (wt pts/- wt % ) wt % ) wt % ) t % ) wt % )

Control Experiment 1300/65 0 700/35 0 0

Experiment 120/6 1 1240/62 0 640/32 0

Experiment 2 620/31 620/31 640/32 120/6 0

Experiment 3 620/31 620/31 640/32 120/6

Table 2 RESIN BLEND PROPERTIES USING AES RESINS

± Izod il Izod 5

R* ______ -29°C 23°C -29^CC

Control Experiment

1 3.7 416 85 562 133

Experiment 1 4.6 406 134 571 235 0

Experiment 2 5.6 417 139 561 240

Experiment 3 4.7 422 112 577 171 Control Experiment 1 is an example of a PC/AES composition not in accordance with the present invention. Experiment 1 illustrates that higher R* vales and better low temperature izod impact values are obtained over Control 1 when MBS is added and preferentially located in the polycarbonate phase and/or interface with the vinyl aromatic-nitrile copolymer matrix of the AES resin, as can be seen in Figure 1. Experiment 2 shows an even larger increase in R* values can be obtained by utilizing a branched polycarbonate in. the blend while Experiment 3 shows other core/shell graft copolymer rubbers, like a butyl acrylate rubber based graft copolymer, may also be used to obtain high R* values and high impact properties.

Thus, it is desirable to locate the core/shell graft copolymer rubber preferentially in each phase or in the interface of a multi-phase polymer composition. Such compositions then exhibit good combinations of physical properties including increased melt elasticity at low shear rates which is desirable for improved blow molding or thermoforming applications.

ASA-type Graft Copolymer Experiments - Control 2

One thousand three hundred parts by weight of a linear polycarbonate (Calibre™ 300-10, Dow Chemical Company) was mixed with 700 parts by weight acrylonitrile-styrene-acrylate rubber copolymer (ASA), 2 parts by weight epoxidized soybean oil (Plas Chek™ 775 from the Ferro Company), and 4 parts by weight Irganox™ 1076 antioxidant (from Ciba Geigy). Blends and molded articles were prepared and tested according to the procedures of Control 1 and the AES Experiments above. The composition of each blend is given in Table 3 below and the test results are given in Table 4 below.

The abbreviations used in the following Tables are the same as used in Tables 1 and 2 above with the addition that "ASA" refers to an acrylonitrile-styrene- acrylate graft copolymer rubber containing 15 percent by weight acrylate rubber and at least 20 percent by weight acrylonitrile.

Table 3 - PC/ASA Blends

Lin. Bran. ASA Para Para PC PC 3607 3330

(wt pts/ (wt pts/ (wt pts/ (wt pts/ (wt pts/ wt % ) wt % ) wt % ) wt % ) t % )

Control

Experiment

2 1300/65 700/35 0 0

Experiment 4 1240/62 640/32 120/6 0

Control

Experiment

3 650/32.5 650/32.5 700/35 0 0

Experiment

4 620/31 620/31 640/32 120/6 0

Experiment 5 620/31 620/31 640/32 0 120/6

Experiment

6 460/23 460/23 1000/50 80/4 0

0

Control Experiment 2 is an example of a PC/ASA composition not in accordance with the present invention. Experiment 4 illustrates that higher R* Table 4

X Izod II Izod

___ 23°C -29°C _____ -29°C

Control

Experiment 2 3.6 443 58 560 101

Experiment 4 4.7 433 96 539 176

Control

Experiment 3 4.6 192 37 512 69

Experiment 5 5.7 411 96 550 208

Experiment 6 5.0 438 69 619 144

Experiment 7 5.6 80 NA 187 NA

values_^ and better low temperature izod impact values are obtained over Control Experiment 2 when MBS rubber is added and preferentially located in the polycarbonate phase and/or the interface with the other phase, as can be seen Figure 2. Experiment 4 uses only linear PC which has fairly low melt elasticity, thus locating a rubber in the PC phase or interface can increase the melt elasticity required for improved blow molding or thermoforming resins.

Another way to increase the melt elasticity of a PC resin is to use a branched polycarbonate. As expected, Control Experiment 3 shows a large increase in R* values with the addition of a branched resin, however in doing so impact properties in the perpendicular direction drop substantially. Experiments 5, 6 and 7 show once again large improvements in R* and impact values with the addition of a core/shell graft copolymer rubber to a blend of a linear and/or branched polycarbonate with an ASA-type resin.

Claims

Claims: 1. A moldable composition comprising:

A) 20 to 94 percent by weight of a carbonate polymer selected from:

(i) randomly branched carbonate polymers,

(ii) linear carbonate polymers, and

B) 5 to 75 percent by weight of one or more graft copolymer of vinyl aromatic-nitrile copolymer and one or more rubbery polymer other than a conjugated diene polymer, and

C) 0.5 to 20 percent by weight of core/shell graft copolymer(s) having as a core a rubbery polymer of butadiene or alkyl (meth)acrylate(s) with an outer shell of a alkyl (meth)acrylate polymer,

wherein said percents by weight are based on components A), B) and C) . 2. A moldable composition according to Claim 1 wherein the rubbery polymer of graft copolymer(s) B) is one or more of the rubbery polymers of ethylene- propylene-nonconjugated diene monomer or alkyl (meth)acrylate(s) .

3. A moldable composition according to Claim 2 wherein graft copolymer B) comprises one or more rubbery polymer of ethylene-propylene-nonconjugated diene monomer. 0

4. A moldable composition according to Claim 2 wherein graft copolymer B) comprises one or more rubbery polymer of alkyl (meth)acrylate(s)

5 5. A moldable composition according to Claim 2 comprising:

A) 35 to 85 percent by weight carbonate polymer, 0

B) 10 to 60 percent by weight of graft copolymer B), and

C) 2 to 15 percent by weight of core-shell y_t- graft copolymer C).

6. A moldable composition according to Claim 1 wherein the carbonate polymer comprises a randomly branched carbonate polymer. 0 7. A moldable composition according to Claim 6 wherein the carbonate polymer consists of a randomly branched carbonate polymer.

8. A moldable composition according to Claim 6 wherein the carbonate polymer is a blend of 20 to 80 weight percent randomly branched carbonate polymer with 80 to 20 weight percent linear carbonate polymer.

9. A process for the preparation of a shaped article comprising the steps of:

5

A) providing a composition according to one of the Claims 1 through 8 above having high melt viscosity and melt strength and

10 B) thermoforming or blowmolding said composition to form an article.

10. The process according to Claim 9 wherein said carbonate polymer comprises a randomly branched

.._ carbonate polymer and the molding process is a thermoforming process.

11. The process according to Claim 9 wherein said carbonate polymer comprises a randomly branched

P₀ carbonate polymer and the molding process is a blowmolding process.

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