WO2005075549A1

WO2005075549A1 - Polycarbonate composition with enhanced flex-fold properties

Info

Publication number: WO2005075549A1
Application number: PCT/US2005/002806
Authority: WO
Inventors: Shiping Ma; Thomas Ebeling; Shrish Rane
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2004-02-03
Filing date: 2005-02-02
Publication date: 2005-08-18
Anticipated expiration: 2006-08-03
Also published as: TW200606200A

Abstract

Polycarbonate compositions containing a specific combination of additives which achieve desirable flexural modulus and flex-fold characteristics are used in polycarbonate articles. These compositions contain a polycarbonate/siloxane component that includes a polycarbonate siloxane copolymer and optionally additional polycarbonate resin; and a mineral filler selected from wollastonite, clay, a combination of clay and talc and mixtures thereof. The composition contains at least 50% by weight of polycarbonate, and the polycarbonate siloxane copolymer and the mineral filler are present in amounts effective to achieve a flex modulus of 29,000 kg/cm2 or greater, for example 30,000 kg/cm2 or greater, good flex-fold strength and good impact strength. If desired, the composition may also include a flame retardant to enable the composition to obtain a UL94 rating of VO at test thicknesses of 1.2 mm.

Description

POLYCARBONATE COMPOSITION WITH ENHANCED FLEX-FOLD PROPERTIES

Background of the Invention

This application relates to a polycarbonate composition with enhanced properties, particularly as they relate to flex-fold strength.

Polycarbonate has shown excellent adaptability for a wide variety of applications. Numerous additives are known in the art for a variety of purposes, for example to provide flame retardance, to enhance impact strength, and to enhance resistance to degradation resulting from exposure to light and/or chemicals. While each of these additives has a beneficial affect, in many cases this benefit is achieved only at the expense of some other property. Thus, for any given application, careful selection of additives is necessary to achieve the properties needed for that application.

In the case of injection molded articles, so-called "weld lines" can form as a matter of course during the molding process as a result of a meeting of separate flows from different entrances in the molding cavity, or due to flow around obstructions within the mold. These weld lines are points of weakness at which an article may break if the characteristic properties desirable for optimum performance are not present. These properties include flexural modulus and flex-fold strength to prevent breakage along weld lines, and may also include fire resistance and impact strength. Materials which increase fire resistance, however, frequently degrade both impact strength and flex- fold strength. Thus, obtaining specific compositions with the desired properties can present a challenge.

Summary of the Invention

The present invention provides polycarbonate compositions containing a specific combination of additives which achieve desirable flexural modulus and flex-fold characteristics when used in polycarbonate articles. These compositions comprise: (a) a polycarbonate/siloxane component, said polycarbonate/siloxane component being a polycarbonate siloxane copolymer, or a mixture of a polycarbonate siloxane copolymer and polycarbonate resin; and

(b) a mineral filler selected from wollastonite, clay, a combination of clay and talc and mixtures thereof.

The composition comprises at least 50% by weight polycarbonate when the polycarbonate of the polycarbonate siloxane copolymer and any polycarbonate resin (linear or branched) are considered together. The polycarbonate siloxane copolymer and the mineral filler are present in amounts effective to achieve a flex modulus of 29,000 kg/cm or greater, for example 30,000 kg/cm or greater, good flex-fold strength and good impact strength. If desired, the composition may also include a flame retardant to enable the composition to obtain a UL94 rating of V0 at test thicknesses of 1.2 mm. The invention further provides articles made from this composition, and a method for making such articles.

Detailed Description of the Invention

The present invention provides polycarbonate compositions containing a specific combination of additives which achieve desirable characteristics in terms of flexural modulus and weld line flex strength. In addition, acceptable fire retardance and impact strength may be achieved.

Numerical values in the specification and claims of this application, particularly as they relate to polymer compositions, reflect average values for a composition that may contain individual polymers of different characteristics. Furthermore, the numerical values should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of the measurement technique used in the present application to determine the value.

The present invention refers to fire retardance using at rating system of UL94 test. These results are presented in terms of a rating, for example V0, achieved at a given thickness of test material. Several different material thicknesses can be used in the test, and it will be appreciated that where a VO rating is achieved at one thickness this rating would also be attained if thicker test pieces were used. Thus, when the specification and claims refer to compositions that obtain a UL94 VO rating at 1.2 mm this refers to the minimum level of fire retardance and does not indicate or imply that better fire retardance, for example VO at 0.8 mm as in many of the examples, may not be obtainable within the scope of the claims.

The composition of the invention comprises a polycarbonate/siloxane component and a mineral filler selected from wollastonite, clay, a combination of clay and talc, or mixtures thereof. The composition may further comprise additional resin components, as well as additional additives. The polycarbonate in the polycarbonate/siloxane component makes up at least 50% by weight of the composition of the invention, for example at least 60% or at least 65% by weight of the composition. In preferred embodiments of the invention, the composition of the invention comprises 0.5 to 6% by weight of the total composition of siloxane copolymer, for example 1-4%, and 1- 20% by weight of the total composition of the mineral filler, for example 5-15%.

As reflected in Table 1, the combination achieves a desirable balance of properties, and specifically flexural modulus of 29,000 kg/cm or greater, for example 34,000- 36,000 kg/cm², a weld line flex strength of 55 MPa or higher, and a notched IZOD impact of 25 kgf-cm/cm or greater. In contrast, the comparative examples, in which one of the components is omitted, suffer from reduced performance in one or more of these properties. Thus, the composition as claimed represents an improved combination of ingredients to produce the specific desired results.

The polycarbonate/siloxane component in the compositions of the invention may be a polycarbonate siloxane copolymer, or a mixture of a polycarbonate siloxane copolymer and polycarbonate resin In some embodiments in order to obtain levels of polycarbonate of at least 50% by weight and the appropriate level of siloxane. It will be appreciated that where the proportional amount of siloxane in the polycarbonate siloxane copolymer is low, one can achieve both the desired levels of polycarbonate and siloxane with very little or even no added polycarbonate resin. On the other hand, where the proportional amount of siloxane is high, it will be appropriate to include polycarbonate resin in the composition.

When present, the polycarbonate/siloxane component of the present invention comprises a polycarbonate resin. There are numerous polycarbonate resin formulations known, and the polycarbonate resin in the composition may be selected to achieve addition properties desired for a given application. Thus, the polycarbonate resin may be a high heat polycarbonate, or a polycarbonate selected to have good flow properties consistent with use in molding applications or extrusion.

The polycarbonate may be one made by either an interfacial process or a melt transesterification process. In the most common embodiment of the interfacial process, bisphenol A (BPA) and phosgene are reacted to form polycarbonate. When a melt transesterification process is used, polycarbonate is made by reacting a diaryl carbonate and a dihydric phenol. The techniques for performing melt transesterification reactions are well known, and are, for example, described in Organic Polymer Chemistry by K. J. Saunders, 1973, Chapman and Hall Ltd., as well as in a number of U.S. patents, including U.S. Pat. Nos. 3,442,854; 5,026,817; 5,097,002; 5,142,018; 5,151,491 ; and 5,340,905. As is known in the art, there are numerous diaryl carbonates and dihydric phenols which may be employed. The specific diaryl carbonate and the specific dihydric phenol selected will depend on the nature of the desired polycarbonate. Common diaryl carbonates which may be employed include but are not limited to diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate; m-cresyl carbonate; dinaphthyl carbonate; bis(diphenyl) carbonate; diethyl carbonate; dimethyl carbonate; dibutyl carbonate; and dicyclohexyl carbonate. Common dihydric phenols include but are not limited to bis(hydroxyaryl) alkanes such as bis(4-hydroxyphenyl)methane; l,l-bis(4-hydroxyphenyl)ethane; 2,2- bis(4-hydroxyphenyl)propane (also known as bisphenol A); 2,2-bis(4- hydroxyphenyl)butane; 2,2-bis(4-hydroxyphenyl)octane; bis(4- hydroxyphenyl)phenylmethane; 2,2-bis(4-hydroxy- 1 -methylphenyl)propane; 1 ,1- bis(4-hydroxy-t-butylphenyl) propane; and 2,2-bis(4-hydroxy-3- bromophenyl)propane; bis(hydroxyaryl)cycloalkanes such as 1,1 -(4- hydroxyphenyl)cyclopentane and 1 , 1 -bis(4-hydroxyphenyl)cyclohexane; dihydroxyaryl ethers such as 4,4'-dihydroxydiphenyl ether and 4,4'dihydroxy-3,3'- dimethylphenyl ether; dihydroxydiaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; dihydroxydiaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfoxide and 4,4'-dihydroxy-3, 3 '-dimethyl diphenyl sulfoxide; and dihydroxydiaryl sulfones such as 4,4'-dihydroxydiphenyl sulfone and 4,4'- dihydroxy-3,3'-dimethyldiphenyl sulfone. In one common for of polycarbonate, the aromatic dihydroxy compound is bisphenol A (BPA) and the diaryl carbonate is diphenyl carbonate.

The polycarbonate resins used in the invention comprise repeating structural units of the formula (I):

O R'-O — ^u — O (I)

in which at least about 60 percent of the total number of R¹ groups are aromatic organic radicals and the balance thereof are aliphatic, alicyclic, or aromatic radicals. Preferably, R¹ is an aromatic organic radical and, more preferably, a radical of the formula (II): A¹— Y¹— A² — (H)

wherein each of A¹ and A² is a monocyclic divalent aryl radical and Y¹ is a bridging radical having one or two atoms which separate A¹ from A². In an exemplary 1 embodiment, one atom separates A from A . Illustrative non-limiting examples of radicals of this type are -O-, -S-, -S(O)-, -S(O)₂-, -C(O)-, methylene, cyclohexyl- methylene, 2-[2.2.1]-bicycloheptylidene, ethylidene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene, and adamantylidene. The bridging radical Y¹ can be a hydrocarbon group or a saturated hydrocarbon group such as methylene, cyclohexylidene or isopropylidene. Preferred polycarbonates are based on bisphenol A, in which each of A¹ and A² is p- phenylene and Y¹ is isopropylidene. Preferably, the average molecular weight of the polycarbonate is in the ranges from about 5,000 to about 100,000, more preferably in the range from about 10,000 to about 65,000, and most preferably in the range from about 15,000 to about 35,000. When present, the polycarbonate resin is employed in amounts of about 1 to about 99 weight percent, based on the total weight of the composition. Preferably the polycarbonate resin is present in an amount of about 1 to about 95, more preferably about 5 to about 90 and most preferably about 5 to about 85, based on the total weight of the composition.

In addition to linear homo-polycarbonates, the polycarbonate resin in the polycarbonate/siloxane component may include hetero-polycarbonate species including two or more different dihydric phenols or a copolymer of a dihydric phenol with a glycol or with a hydroxy- or acid-terminated polyester or with a dibasic acid or hydroxy acid. Polyarylates and polyester-carbonate resins or their blends can also be employed. Branched polycarbonates are also useful, as well as blends of linear polycarbonate and a branched polycarbonate. The branched polycarbonates may be prepared by adding a branching agent during polymerization. These branching agents are well known and may comprise polyfunctional organic compounds containing at least three functional groups which may be hydroxyl, carboxyl, carboxylic anhydride, haloformyl and mixtures thereof. Specific examples include trimellitic acid, trimellitic anhydride, trimellitic trichloride, tris-p-hydroxy phenyl ethane, isatin-bis-phenol, tris- phenol TC (l,3,5-tris((p-hydroxyphenyl)- isopropyl)benzene), tris-phenol PA (4(4(1,1 -bis(p-hydroxyphenyl)-ethyl) alpha,alpha-dimethyl benzyl)phenol), 4- chloroformyl phthalic anhydride, trimesic acid and benzophenone tetracarboxylic acid. The branching agents may be added at a level of about 0.05-2.0 weight percent. Branching agents and procedures for making branched polycarbonates are described in U.S. Patent. Nos. 3,635,895 and 4,001 ,184 which are incorporated by reference. All types of polycarbonate end groups are contemplated as being useful in the polycarbonate composition. The polycarbonate resin in the polycarbonate/siloxane component may also be a blend of several polycarbonate polymers of differing characteristics selected to achieve desired final product conditions. For example, the polycarbonate may be a blend of homo- or hertero-polycarbonates of different molecular weights to achieve a target molecular weight. (See US Patent No. 6,441,068, which is incorporated herein by reference).

The composition may further contain an additional thermoplastic resin that is not a polycarbonate in an amount up to 45 % by weight of the total composition. Non- limiting examples of thermoplastic resins that may be included in the composition include (a) polymers including as structural components aromatic vinyl monomers, (b) polymers including as structural components aromatic vinyl monomers and a vinyl cyanide monomers; (c) polymers including as structural component an aromatic vinyl monomers, a vinyl cyanide monomers and a rubber like polymer; (d) aromatic polyesters, (e) polyphenylene ethers, (f) polyether imides and (g) polyphenylene sulfides. Specific examples of such additional thermoplastic resins are styrene acrylonitrile copolymers and polymethyl(methacrylate). Rubber-like polymers may be any of several different types rubbery modifiers, including without limitations graft or core shell rubbers or combinations of two or more of these modifiers. Suitable are the groups of modifiers known as acrylic rubbers, ASA rubbers, diene rubbers, organosiloxane rubbers, EPDM rubbers, styrene-butadiene-styrene (SBS) or styrene- ethylene-butadiene-styrene (SEBS) rubbers, ABS rubbers (made by either the emulsion or bulk process, or a mixture thereof), MBS rubbers, silicone-containing core/shell impact modifiers such as Metabine S2001 from Mitsubishi Rayon, and glycidyl ester impact modifiers.

The composition may also include an anti-drip agent such as a fluoropolymer. The fluoropolymer may be a fibril forming or non-fibril forming fluoropolymer. Preferably the fluoropolymer is a fibril forming polymer. In some embodiments polytetrafluoroethylene is the preferred fluoropolymer. In some embodiments it is preferred to employ an encapsulated fluoropolymer i.e. a fluoropolymer encapsulated in a polymer as the anti-drip agent. An encapsulated fluoropolymer can be made by polymerizing the polymer in the presence of the fluoropolymer. Alternatively, the fluoropolymer can be pre-blended in some manner with a second polymer, such as for, example, an aromatic polycarbonate resin or a styrene-acrylonitrile resin as in, for example, U.S. Patent Nos. 5,521 ,230 and 4,579,906 to form an agglomerated material for use as an anti-drip agent. Either method can be used to produce an encapsulated fluoropolymer.

The fluoropolymer in the encapsulated fluoropolymer comprises a fluoropolymer with a melting point of greater than or equal to about 320°C, such as polytetrafluoroethylene. A preferred encapsulated fluoropolymer is a styrene- acrylonitrile copolymer encapsulated polytetrafluoroethylene (i.e., TSAN). TSAN can be made by copolymerizing styrene and acrylonitrile in the presence of an aqueous dispersion of polytetrafluoroethylene (PTFE). TSAN can, for example, comprise about 50 wt% PTFE and about 50 wt% styrene-acrylonitrile copolymer, based on the total weight of the encapsulated fluoropolymer. The styrene- acrylonitrile copolymer can, for example, be about 75 wt% styrene and about 25 wt% acrylonitrile based on the total weight of the copolymer. TSAN offers significant advantages over polytetrafluoroethylene, namely TSAN is more readily dispersed in the composition.

When present, the anti-drip agent is present in an amount effective to reduce the potential for dripping, for example in an amount of from 0.1 to 1.4 % by weight, more commonly 0.5 to 1% by weight.

The composition of the invention may also contain an effective flame-retarding amount of a flame retardant. The flame retardant may comprise a phosphate based flame retardant or a sulfonate salt flame retardant. When the composition comprises flammable components such as alkylaromatic copolymers it is preferable for the flame retardant to comprise an organic phosphate flame retardant. An organic phosphate flame retardant is suitably an aromatic phosphate compound of the formula (Ilia): R ^'O-I'— OK' OR '

(Ilia)

where R⁷ is the same or different and is alkyl, cycloalkyl, aryl, alkyl substituted aryl, halogen substituted aryl, aryl substituted alkyl, halogen, or a combination of any of the foregoing, provided at least one R is aryl.

Suitable phosphate flame retardants include phosphoric ester of the formula. (Illb):

0 o n'-o-p 1-ϋ - Ip -*;- -O-R* I I OR* OR*

(Illb)

In the formula 1Kb, R¹, R², R³, and R⁴ are each independently a hydrocarbon group with 1 to 30 carbon atoms, and preferably 1 to 5, and preferably a substituted or unsubstituted aromatic hydrocarbon group. If it is substituted, examples of substituents include alkyl groups, alkoxy groups, alkylthio groups, halogens, aryl groups, and aryloxy groups.

Examples of R¹, R², R³, and R⁴ here include a phenyl group, cresyl group, xylenyl group (such as a 2,6-xylenyl group), trimethylphenyl group, ethylphenyl group, cumyl group, and butylphenyl group. If a hydrocarbon group is thus contained, the resulting resin composition will have particularly outstanding flame retardancy.

X is a C| to C ₀ divalent organic group that may contain an oxygen atom and/or a nitrogen atom. This X is, for instance, -O-Y'-O- (where Y¹ is a substituted or unsubstituted aromatic hydrocarbon group, and preferably a 1 ,4-phenylene group, 1,3- phenylene group, etc.) or -O-Y²-R⁵-Y³-O- (where Y² and Y³ are divalent substituted or unsubstituted aromatic hydrocarbon groups, specific examples of which include substituted or unsubstituted phenylene groups; and R⁵ is a Ci to C₈ divalent hydrocarbon group or an oxy hydrocarbon group (-R⁶-O-; where R⁶ is a Ci to C₈ divalent hydrocarbon group), and more specifically is a Ci to C₉ divalent, aliphatic hydrocarbon group, such as a 2,2'-propylene group). X may be an organic group in which a nitrogen atom is bonded directly to a phosphorus atom, an example of which is a 1 ,4-piperadinyl group (following formula).

m is an integer from 0 to 5.

Favorable phosphoric esters include bisphenol A tetraphenyl diphosphate (BPADP), triphenyl phosphate, tricresyl phosphate, cresyldiphenyl phosphate, bisphenol A tetracresyl diphosphate, resorcinol tetrakis(2,6-dimethylphenyl) phosphate, and tetraxylylpiperidine phosphoramide. Of these, bisphenol A tetraphenyl diphosphate (BPADP) and bisphenol A tetracresyl diphosphate are preferable as the phosphoric ester.

Other fire retardant that can be used are those such as bisphenol A bis (diphenyl phosphate) which is described in US Patent No. 6,566,428 which is incorporated herein by reference. The flame retardant materials may also be a sulfonate salt such as Rimar salt (potassium perfluorobutane sulfonate) and potassium diphenylsulfone sulfonate. See also the perfluoroalkane sulfonates described in US Patent No. 3,775,367, which is incorporated herein by reference.

The composition of the of the invention may also include other optional components of the type commonly employed in polycarbonate compositions. Such components include without limitations antioxidants, UV stabilizers, mold release agents, reinforcing agents such as glass fibers, and antistats.

Polycarbonate-siloxane copolymers useful in the composition of the invention are known, for example from US Patents Nos. 4,746,701, 4,994,532, 5,455,310 and 6,252,013, which are incorporated herein by reference, and are sold commercially under the name LEXAN ST by General Electric Company. Mitsubishi Engineering Plastics has described a polycarbonate type resin composition that comprises (A) 100 parts weight (pts. wt.) polycarbonate type resin which consists of (a) 1-99 wt.% of polycarbonate resin, and (b) 99-1 wt. % polycarbonate-organopolysiloxane copolymer; (B) 0.1-5 pts. wt. of phosphate type compound; and (C) 0.2-2 pts. wt. of fibril-forming polytetrafluoroethylene in JP 10007897. The polycarbonate- polysiloxane copolymer from this disclosure may also be used in the present invention.

In general, the polycarbonate-siloxane copolymers useful in the invention are formed from polycarbonate blocks and poly(diorganosiloxane) blocks. These block copolymers can be made by introducing phosgene under interfacial reaction conditions into a mixture of a dihydric phenol, such as BPA, and a hydroxyaryl- terminated polydiorganosiloxane. The polymerization of the reactants can be facilitated by use of a tertiary amine catalyst. The polycarbonate blocks comprise repeating structural units of the formula (I) in which at least about 60 percent of the total number of Rl groups are aromatic organic radicals and the balance thereof are aliphatic, alicyclic, or aromatic radicals. Preferably, Rl is an aromatic organic radical and, more preferably, a radical of the formula (II) wherein each of Al and A2 is a monocyclic divalent aryl radical and Yl is a bridging radical having one or two atoms which separate Al from A2. In an exemplary embodiment, one atom separates Al from A2. Illustrative non-limiting examples of radicals of this type are -O-, -S-, - S(O)-, -S(O)2-, -C(O)-, methylene, cyclohexyl-methylene, 2-[2.2.1]- bicycloheptylidene, ethylidene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene, and adamantylidene. The bridging radical Yl can be a hydrocarbon group or a saturated hydrocarbon group such as methylene, cyclohexylidene or isopropylidene.

The poly(diorganosiloxane) blocks comprise repeating structural units of the formula (IV)

(IV)

wherein each occurrence of R2 may be the same or different and is selected from C(l- 13) monovalent organic radicals, and n is an integer greater than or equal to 1, preferably greater than or equal to about 10, more preferably greater than or equal to about 25 and most preferably greater than or equal to about 40. It is desirable to have n be an integer less then or equal to about 1000, preferably less than or equal to about 100, more preferably less than or equal to about 75 and most preferably less than or equal to about 60. As is readily understood by one of ordinary skill in the art, n represents an average value.

Some of the hydroxyaryl-terminated polydiorganosiloxanes that may be used include phenol-siloxanes of the formula (V)

where each R may be the same or different and is selected from the group of radicals consisting of hydrogen, halogen, C(i_-8) alkoxy, C(i- ) alkyl and C(₆-ι₃) aryl, R¹ is a _2-8) divalent aliphatic radical, R is selected from the same or different C(i.ι₃₎ monovalent organic radicals, and n is an integer greater than or equal to 1, preferably greater than or equal to about 10, more preferably greater than or equal to about 25 and most preferably greater than or equal to about 40. It is also preferred to have n be an integer less then or equal to 1000, preferably less than or equal to 100, more preferably less than or equal to about 75 and most preferably less than or equal to about 60. In one embodiment n is less than or equal to 50. Particularly preferred hydroxyaryl-terminated polydiorganosiloxanes are those where R is methyl and R is hydrogen or methoxy and located in the ortho position to the phenolic substituent and where R¹ is propyl and located ortho or para to the phenolic substituent.

Some of the radicals included within R in the above formula (V) are hydrogen, halogen radicals, such as bromo, and chloro; alkyl radicals such as methyl, ethyl, and propyl; alkoxy radicals such as methoxy, ethoxy, and propoxy; aryl radicals such as phenyl, chlorophenyl, and tolyl. Radicals included within R¹ are, for example, dimethylene, trimethylene and tetramethylene. Radicals included within R² are, for example, C_{( M )} alkyl radicals, haloalkyl radicals such as trifluoropropyl and cyanoalkyl radicals; aryl radicals such as phenyl, chlorophenyl and tolyl. R is preferably methyl, or a mixture of methyl and trifluoropropyl, or a mixture of methyl and phenyl.

The siloxane-polycarbonate block copolymers have a weight-average molecular weight (Mw, measured, for example, by Gel Permeation Chromatography, ultra- centrifugation, or light scattering) of greater than or equal to about 10,000, preferably greater than or equal to about 20,000. Also preferred is a weight average molecular weight of less than or equal to about 200,000, preferably less than or equal to about 100,000. It is generally desirable to have the polyorganosiloxane units contribute about 0.5 to about 80 wt% of the total weight of the siloxane-polycarbonate copolymer. The chain length of the siloxane blocks corresponds to about 10 to about 100 chemically bound organosiloxane units. They can be prepared such as described in for example US-A-5, 530,083, incorporated herein by reference in its entirety.

In the examples below, the polycarbonate-siloxane copolymer is LEXAN ST (General Electric) which is a polycarbonate/polydimethylsiloxane (PC/PDMS) copolymer having 20% weight percent siloxane content based on the total weight of the copolymer and a block length of 50 units of the poly(diorganosiloxane) (n in formulas IV and V)

The compositions of the invention also include a mineral filler. This mineral filler is selected from the group consisting of wollastonite, clay, a combination of clay and talc and mixtures thereof. Clay is an silica-alumina material with the general formula SiO A12O₃. Any type of clay in market place can be used. Desirable diameter are between 1-50 micron. 1-15 micron is most desirable. Talc has the chemical composition SiOMgO. Any type of commercialize talc can be used. Desirable diameter : l-50micron, 1-15 micron are most desirable. Wollastonite has the chemical composition CaOSiO₂, in a fiber shape with length of 2 to 1000 :m, for exp, 3-500:m, or 5-200. Diameters between 1-50 micron are desirable, for example diameters of 1 to 15 micron. It is also desirable that the wollastonite have an aspect ratio, L/D of 1-1000 or greater.

The compositions of the invention are suitably used for making injection molded articles that are prone to the formation of weld lines. Thus, the invention also provides a method for forming a molded article comprising the steps of: preparing a composition comprising:

(a) a polycarbonate/siloxane component, said polycarbonate/siloxane component being a polycarbonate siloxane copolymer, or a mixture of a polycarbonate siloxane copolymer and polycarbonate resin; and

(b) a mineral filler selected from the group consisting of wollastonite, clay, a combination of clay and talc and mixtures thereof, wherein the polycarbonate in the polycarbonate/siloxane components makes up at least 50% by weight of the composition ; and wherein the polycarbonate siloxane copolymer and the mineral filler are present in amounts effective to achieve a flex modulus of 29,000 kg/cm or greater; and forming the composition into a molded article by injection molding.

The invention will now be described with reference to the following, non-limiting example. EXAMPLE

Composition were prepared as outlined in Table 1 from

PC 1 LEXAN 145 (General Electric Co.) ~ linear polycarbonate with a melt index of 12.3 g/10 min at 300^C/ 1.2 kg loading.

PC 2 LEXAN 6739 branched polycarbonate

PC-PDMS LEXAN ST (General Electric) which is a polycarbonate/polydimethylsiloxane (PC/PDMS) copolymer having 20% weight percent siloxane content based on the total weight of the copolymer and a block length of 50 units of the poly(diorganosiloxane) (n in formulas IV and V)

Clay Composition : SiO2AL2O3. Any type of clay in market place can be used. Desirable diameter are between 1-50 micron. 1-15 micron is most desirable.

Huber Clay HG90 used as an example.

Talc Composition : SiOMgO. Any type of commercial talc can be used. Desirable diameter : l-50micron, 1-15 micron are most desirable.

Hayashi chemical HST05 used as an example.

Wollastonite Composition : CaOSiO2, in a fiber shape with length of 2 to 1000 :m( Micron), for exp, 3-500:m, or 5-200. Diameter between 1- 50 micron are desirable. 1 to 15 micron for example. Desirable L/D= 1 -1000 or greater.

Nyco Nyglos 4 used as an example.

ABS ABS (internal designation C29449; General Electric) with rubber content of 16%. PTFE Polytetrafluoroethylene. Daikin chemical Polyfuron D-2C. PTFE water dispersion.

BPADP bis-phenol A tetraphenyl diphosphate (CR741 S from Diahachi

Chemicals)

The compositions polycarbonate pellets of bisphenol-A polycarbonate made by a and branched polycarbonate, where applicable, were compounded with the remaining ingredients on a Werner & Pfleiderer co-rotating twin screw extruder (25 millimeter screw) and subsequently molded according to ISO294 on a ENGEL injection molding machine, using Axxicon ISO Manufactured (AIM) Mould system for producing the UL bars specimens. Where wollastonite was included in the composition, it was added in a separate downstream addition.

Tests were performed on the compositions according to the following protocols:

Flexural modulus ASTM D790

Notched ASTM D256 tests performed at room temperature

Izod

UL94 burn determined in accordance with UL94 standard test protocols using time and rating bars of the indicated thicknesses.

Weld line flex The weld line flex strength measured in a folding speed of 3mm/min strength with a span of 20mm. The specimen with a thickness of 1.2mm and molded by injection from two direction. Thus, the specimen has weld line in the center place where the materials cross together.

Heat Deflection ASTM D648 (loading level of 18.6 kg/cm²)

Temperature (HDT)

The results are summarized in Table 1.

Table 1

Table 1 - continued

Claims

What is claimed is:

1. A composition comprising:

(b) a mineral filler selected from the group consisting of wollastonite, clay, a combination of clay and talc and mixtures thereof,

wherein the composition comprises at least 50% by weight of polycarbonate, taking into account the polycarbonate portion of the polycarbonate siloxane copolymer and any polycarbonate resin, and wherein the polycarbonate siloxane copolymer and the mineral filler are present in amounts effective to achieve a flex modulus of 29,000 kg/cm² or greater, and a weld line flex strength of 55 MPa or greater.

2. The composition of claim 1, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

3. The composition of claim 2, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 1 to 4% by weight of the total composition.

4. The composition of claim 1, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

5. The composition of claim 4, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

6. The composition of claim 1 , wherein the siloxane in the polycarbonate siloxane copolymer is polydimethylsiloxane.

7. The composition of claim 6, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

8. The composition of claim 7, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 1 to 4% by weight of the total composition.

9. The composition of claim 6, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

10. The composition of claim 9, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

11. The composition of claim 1 , wherein the mineral filler is wollastonite.

12. The composition of claim 11, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

13. The composition of claim 12, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 1 to 4% by weight of the total composition.

14. The composition of claim 11, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

15. The composition of claim 14, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

16. The composition of claim 1 1, wherein the siloxane in the polycarbonate siloxane copolymer is polydimethylsiloxane.

17. The composition of claim 16, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

18. The composition of claim 17, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 1 to 4% by weight of the total composition.

19. The composition of claim 16, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

20. The composition of claim 19, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

21. The composition of claim 19, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 1 to 4% by weight of the total composition.

22. The composition of claim 1 , wherein the composition further comprises an additional thermoplastic that is not a polycarbonate.

23. The composition of claim 22, wherein the additional thermoplastic is selected from among polymers including as structural components aromatic vinyl monomers, polymers including as structural components aromatic vinyl monomers and a vinyl cyanide monomers, polymers including as structural component an aromatic vinyl monomers, a vinyl cyanide monomers and a rubber like polymer; aromatic polyesters, polyphenylene ethers, polyether imides, and polyphenylene sulfides.

24. The composition of claim 23, wherein the additional thermoplastic as an ABS rubber.

25. The composition of claim 24, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

26. The composition of claim 25, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 1 to 4% by weight of the total composition.

27. The composition of claim 24, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

28. The composition of claim 27, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

29. The composition of claim 24, wherein the siloxane in the polycarbonate siloxane copolymer is polydimethylsiloxane.

30. The composition of claim 1 , further comprising a phosphate flame retardant.

31. The composition of claim 30, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

32. The composition of claim 31, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 1 to 4% by weight of the total composition.

33. The composition of claim 30, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

34. The composition of claim 33, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

35. The composition of claim 30, wherein the siloxane in the polycarbonate siloxane copolymer is polydimethylsiloxane.

36. The composition of claim 35, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

37. The composition of claim 36, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 1 to 4% by weight of the total composition.

38. The composition of claim 35, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

39. The composition of claim 38, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

40. The composition of claim 30, wherein the composition achieves a V0 flame retardance rating as a thickness of 0.8 mm.

41. The composition of claim 1, wherein the composition achieves a V0 flame retardance rating as a thickness of 0.8 mm.

42. The composition of claim 1, wherein the composition comprises at least 60% by weight of polycarbonate, taking into account the polycarbonate portion of the polycarbonate siloxane copolymer and any polycarbonate resin.

43. The composition of claim 1, wherein the composition comprises at least 65% by weight of polycarbonate, taking into account the polycarbonate portion of the polycarbonate siloxane copolymer and any polycarbonate resin.

44. The composition of claim 1 , wherein the polycarbonate/siloxane component contains both a polycarbonate siloxane copolymer and a polycarbonate resin.

45. A method for forming a molded article comprising the steps of:

preparing a composition comprising: (a) a polycarbonate/siloxane component, said polycarbonate/siloxane component being a polycarbonate siloxane copolymer, or a mixture of a polycarbonate siloxane copolymer and polycarbonate resin; and

wherein the composition comprises at least 50% by weight of polycarbonate, taking into account the polycarbonate portion of the polycarbonate siloxane copolymer and any polycarbonate resin, and wherein the polycarbonate siloxane copolymer and the mineral filler are present in amounts effective to achieve a flex modulus of 29,000 kg/cm² or greater, and a weld line flex strength of 55 MPa or greater; and

forming the composition into a molded article by injection molding.

46. The method of claim 45, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

47. The method of claim 45, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

48. The method of claim 47, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

49. The method of claim 47, wherein the siloxane in the polycarbonate siloxane copolymer is polydimethylsiloxane.

50. The method of claim 45, wherein the mineral filler is wollastonite.

51. The method of claim 50, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

52. The method of claim 50, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

53. The method of claim 52, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

54. The method of claim 50, wherein the siloxane in the polycarbonate siloxane copolymer is polydimethylsiloxane.

55. The method of claim 45, wherein the composition further comprises an additional thermoplastic that is not a polycarbonate.

56. The method of claim 55, wherein the additional thermoplastic is selected from among polymers including as structural components aromatic vinyl monomers, polymers including as structural components aromatic vinyl monomers and a vinyl cyanide monomers, polymers including as structural component an aromatic vinyl monomers, a vinyl cyanide monomers and a rubber like polymer; aromatic polyesters, polyphenylene ethers, polyether imides, and polyphenylene sulfides.

57. The method of claim 56, wherein the additional thermoplastic as an ABS rubber.

58. The method of claim 57, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

59. The method of claim 57, wherein the mineral filler is present in an amount of from 1 to 20% by weight of the total composition.

60. The method of claim 59, wherein the siloxane in the polycarbonate/siloxane components is present in an amount of from 0.5 to 6% by weight of the total composition.

61. The method of claim 57, wherein the siloxane in the polycarbonate siloxane copolymer is polydimethylsiloxane.

62. The method of claim 45, wherein the composition further comprises a phosphate based flame retardant.

63. An article formed by the method of claim 45.