CA1197937A - Polycarbonate-silicate compositions - Google Patents

Abstract

Mo-2225-CIP

POLYCARBONATE SILICATE COMPOSITIONS
ABSTRACT OF THE DISCLOSURE
Polycarbonate compositions comprising an aro-matic polycarbonate resin, wherein dispersed are sili-cate particulates, are particularly suitable for the preparation of films having a low coefficient of static friction, high light transmission and virtual freedom from haze.

Mo-2225-CIP

Description

Mo-2225-CIP

POLYCARBONATE-SILICATE COMPOSITIONS
Field of the Invention The present invention is directed to polycarbonate compositions and~ more particularly, ~o aromatic poly- ``
carbonate-silicate blends.
Brief Description of the Invention A polycarbonate composition comprising an aromatic thermoplastic polycarbonate resin and .025 to 5 phr of a silicate particulate having an average particle size of about .05 to about 20 microns and selected from the group consisting of hydrous alumino silicates, anhydrous alumino silicates, sillimanite minerals and wollastonite was found to be especially suitable for the preparation of films of low coefficient of static friction, high light transmission and virtual freedom from haze.
Description of the Pr~or Art Polycarbonates derived from reaction involving organic dihydroxy compounds and carbonic acid derivatives have found extensive commercial application because of their excellent mechanical and physical properties. These thermoplastic polymers are particu:Larly suited for the manufacture of molded articles for which impact strength, rigidity, toughness, thermal and d:Lmensional stability as well as excellent electrical properties are required.
Furthermore, polycarbonates are eminently suited for casting or extrusion into films which are characteristically of high clarity, color and oxidative sta~ility as well as flame resistance.
One deficiency of polycarbonate-based films has been the high coefficient of static friction, a factor effecting their handling and somewhat restricting their usefulness. It has been the experience of Mo-2225-CIP

3~

- 2 -those skilled in the art that the surfaces of films tend to stick when they are made to slide over similar surfaces, a tendency sometimes referred to as "block-iness", due largely to their high coefficient of static friction.
In this connection, see "Slip and Antiblock Agents - A Guide to Their Use", by H. W. Mock et al, Plastics Technology, August 1974, page 41; "Slip and Antiblocking Agents - Attaining that Delicate ~alance", by A. M. Birks, Plastics Technology, July 1977, page 131; and "Does the slip of your web help or hurt its performance?", by R. L. Mueller, Package Engineering, April 1973, page 61.
Attempts to lower that friction by chemical modifiers are not entirely satisfactory in that such modifications adversely affec~ other, desirable prop-erties of the films. U.S. 3,424,703 teaches lowering the coefficient of friction of polycarbonate films by adding small amounts of either silica or talc. One notable disadvantage entailed in the use of silica relates to the limit of about 1 phr that may be incorp-orated in polycarbonates be~ore processin~ difficulties are encountered. It is thus an obJect of the present invention to provide a polycarbonate-silicate composi-tion of improved processability suitable for the ~re-~-aration of films of low static coeflicient of fric-tion. It is a further object to provide a polycarbonate-silicate concentrate composition compris-ing up to about 5 phr silicate.
DETAILE~ DESCRIPTION_OF T~E INVENTION
The polycarbonate resins useful in the prac-tice of the invention are homopolycarbonates, copoly-~lo-2225-CIP

~7~37 carbonates and terpolycarbonates or mixtures thereof.
The polycarbonates generally have molecular weights of 10,000-200,000 (weight average molecular weight) pre-ferably 20,000-80,000, and are additionally character-ized by their melt flow of 1-24 gm/10 min. at 300C per ASTM D-1238. These polycarbonates may be prepared, for example, by the known diphasic interface process from phosgene and bisphenols by polycondensation (see German OS 2,063,050; 2,063,052; 1,570,703; 2,211,956; 2,211,957 and 2,248,817 and French Patent 1,561,518, and the mono-graph, "H. Schnell, Chemistry and Physics of Polycar-bonates", Interscience Publishers, New York, 1964).
The aromatic polycarbonates may be based on the ollowing bisphenols: hydro~uinone, resorcinol, dihydroxy diphenyls, bis-(hydroxyphenyl)-alkanes, bis~(hydroxyphenyl)-cycloalkanes, bis-(hydroxyphenyl)-sulphides, bis-(hydroxyphenyl)-ethers, bis-(hydroxy-phenyl)-ketones, bis-(hydroxyphenyl)-sulphoxides, bis-(hydroxyphenyl)-sulphones and ~ bis-(hydroxy-phenyl)-diisopropyl benzenes, as well as the correspond~
ing compounds substituted in the nucleus. These and other suitable aromatic dihydroxy compounds have been described in U.S. Patents 3,028,3S5; 2,999,835;

3,148,172; 3,271,368; 2,991,273; 3,271,367; 3,780,078;
2S 3,014,891 and 2,999,84Z and in German OS 1,570,703;
2,063,050 and 2,063,052 and in French Patent 1,561,518.
Preferred aromatic polycarbonates are those in ~hich 5-100 mol ~ of the structural units corres-pond to formula (1):

Mo-2225-CIP

~. . ,~, ~9~

t ~ ~ R X - C ~ O-C ~ (l) wherein Rl, R2, R3 and R4 Cl C10 Y ~
Cl, Br, phenyl and ~, X = a single bond, -O-, -CO-, S, SO, -S02, -Cl-C10 alkylene, Cl-C10 alkylidene, C5-C15 cycloalkylene, C5-C15 cycloalkylidene, C7 C20 cycloalkyl alkylene, C6-C20 cycloalkyl alkylidene or lS CH3 ~ CH3 and/or formula (2) o ~ ~ ~ O-C ~ (2) wherein 7, = C5-C20 alkylene, C5-C20 al y C5-C15 cycloalkylene, C5-C15 cycloalkylidene, C7~C20 cycloalkyl alkylene or C6-C20 cycloalkyl alkylidene.
Aromatic polycarbonates containing 5-30 mol %
of structural units of formula (1) and/or (2) as well as those containing 50-100 mol % of these structural units are ~articularly preferred.
PreÇerred structural units of formula (1) are those of formula ~3):
Mo-2225-CIP

119793~

--r --~ x ~--o-c I - (3) wherein X is as defined above.
The structural units of Eormula (3) may be based on the following bisphenols, for example:
bis:(3,5-dimethyl-4-hydroxyphenyl); bis-t3,5-dimethyl-

4-hydroxyphenyl)-ether; bis-(3,5-dimethyl-4-hydroxy-phenyl)-carbonyl; bis-(3,5-dimethyl-4-hydroxy~henyl)-sulphone; bis-(3,5-dimethyl-4-hydroxyphenyl)-methane;
1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-ethane; l,l-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane; 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-butane; 2,4-bis-(3,5-di-methyl-4-hydroxyphenyl)-2-methyl butane; 2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-butane; 3,3-bis-(3,5-di-methyl-4-hydroxyphenyl)-pentane; 3,3-bis-(3,5-dimethyl-4-hydroxyphenyl)-hexane; 4,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-heptane; 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)~octane; 2,2-bis-(3,5-dimethyl-4-hydroxy-phenyl)-nonane; 2,2-bis-(3,5-dimethyl-4-hydroxy-phenyl)-decane; l,l-bis-(3,5-dimethyl-4-hydroxy-phenyl)-cyclohexane; 1,4-bis-(3,5-dimethyl-4-hydroxy-phenyl)-cyclohexane; ~ bis-~3,5-dimethyl-4-hydroxy-phenyl)-p-diisopropyl benzene; and ~,~'-bis-(3,5-dimethyl-4-hydroxy2henyl~-m-diisopropyl benzen~.
Those structural units of formulae (1) and (2) which are based on the followin~ bisphenols are particularly preferred: bis-(3,5-dimethyl-4-hydroxy-phenyl)-methane; 2,2-bis-(3,5-dimethyl-4-hydroxy-phenyl)-propane; 2,4-bis-(3,5-dimethyl-4-hydroxy-Mo-2225-CIP

~9~7937 phenyl)-2-methyl butane; 1,1-bis-(3,5-dimethyl-4-hydroxyphenyl~-cyclohexane; ~, a I -bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropyl benzene; 2,2-bis-(3,5-di-chloro-4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane; 1,1-bis-(4-hydroxyphenyl)-cyclohexar-e; ~a, a ' -bis-(4-hydroxyphenyl)-m-diisopropyl benzene; a, a I -bis-(4-hydroxyphenyl)-p-diisopropyl benzene; 2,4-bis-(4-hydroxyphenyl)-2-methyl butane;
2,2-bis-(3-methyl-4-hydroxyphenyl)-propane; and 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane.
In addition to containing structural units of formulae (1) and (2), the preferred polycarbona-tes preferably contain structural units of formula (4):

~ o ~ c ~ \ O-c ~ (4) Polycarbonates based solely on the above-mentioned o,o,ol,o'-tetramethyl-substituted bisphenols are particularly important; in particular, the ho~nopoly-car~onate based on 2,2-bis-(3,5-dimethyl-4 hydroxyphenyl)-propane.
Also suitable ~or the preparation of the poly-carbonates of the invention are dihydroxybenzenes ofthe structural formula:
HO~ X --~ OH

(R )m (R )m Mo-2225-CIP

793~
--7~
wherein Rt and Rs independ~ntly denote C1-C10 alkyls, m is an integer of from 0 to 2, X is S, C, O, or S
.. .. ..
O O S
and n is either 0 or 1.
Among the resins suitable in the practice of the invention are included phenolphthalic-based poly-carbonate, copolycarbonates and terpolycarbonates such as are described in U.S. Patents 3,036,036 and 4,2I0,741.
In order to obtain special properties, mixtures of various di-~monohydroxyaryl)-alkanes can also be used; thus mixed polycarbonate resins are obtained. By far the most useful polycarbonate resins are those'based on 4,4'-dihydroxydiaryl methanes and more particularly bisphenol A [2,2-(4,4'-dihydroxydiphenyl)-propane].
Thus, when flame re~ardant characteristics are'to be imparted to the basic polycarbonate resin, a mixture' of bisphenol A and tetrabromobisphenol A ~2,2-(3,5,3',5'-tetrabromo-4,4'-dihydroxydiphenyl)-propane~ is utilized when reacting with phosgene or a like carbonic acid derivative. Other halogenated phenolic diols are any suitable his-hydroxyaryl such as the halogenated con-taining bisphenols such as 2 J 2'-(3,5,3',5'-tetra-chloro-4,4'-dihydroxydiphenyl)-propane; 2,2-(3,5,3',5'-tetra-bromo-4,4'-dihydroxydiphenyl)-propane; 2,2-(3,5-dichloro-4~4'-dihydroxydiphenyl)-propane; 2,2-(3,31-dichloro-

5,5'-dimethyl-4,4'-dihydroxydiphenyl)-propane; 2,2-(3,3'-dibromo-4,4'-dihydroxydiphenyl)-propane and the like.
Thbs'e halogenated diols are incorporated into the polycarbonates at levels sufficient to impart flame retardant characteristics. For example, a halogen con-3~ tent of about 3 to 10% hy weight is normally sufficient.

Mo-2225-CIP

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The polycarbonates of the invention may also be branched by incorporating small quantities o~ poly-hydroxyl compounds in them by condensation, e.g., 0.05-2.0 mol % (based on the quantity o~ bisphenols used).
Polycarbonates o~ this type have been described, for example, in German OS 1,570,533,' 2,116,974 and 2,113,347, British Patents 885,442 and 1,079,821 and U.S~ Patents 3,'544,514 and 4,185,009. The following are some examples of polyhydroxyl compounds which'may be used for this purpose: phIoroglucinol; 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl~-heptane-2; 4,6-dimethyl-2,4,6~tri-(4-hydroxyphenyl)~heptane; 1,3,5-tri-(4-hydroxyphenyl)-benzene; l,l,l-tri-(4-hydroxyphenyl) ethane; tri-(4-hydroxyphenyl)-phenyl-methane; 2,2-bis-[4, 4 (4,4'-dihydroxydiphenyl)-cyclohexyl]-propane;
2,4-bis-~4-hydroxyphenyl-4-isopropyl)-phenol; 2,6-bis-(2'-dihydroxy-5'-methylbenzyl)-4-methylphenol; 2,4-dihydroxy-benzoic acid; 2-(4-hydroxyphenyl)-2-(2,4-dihydroxy-phenyl)-propane; l,4-bis-t4',4"-dihydrox~-triphenylmethyl)-benzene and 3,3-bis-(4-hydroxyphenyl)-oxindole.
In addition to the polycondensation process mentioned above and which essentials are described below, other processes for the preparation o~ the poly-carbonates o~the invention are polycondensation in ahomogeneous phase and transesteri~ication. The suit-able processes are disclosed in ~.S. Patents 3,02Z,365i 2,999,~46; 3,248,414; 3,153,008; 3,215,668, 3,'187,065;
2,064,974; 2,070,137; 2,991,273 and 2,000,835.

~o-2225-CIP
RC-10~/106-CIP

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The preferred process is the interfacial poly-condensation process.
According to the interfacial polycondensa~ion process, copolycarbonate resins are obtained by reacting the aromatic dihydroxy compounds with an alkali metal hydroxide or alkaline earth metal oxide or hydroxide to form the salt of the hydroxy compounds.
The salt mixture is yresent in an aqueous solution or suspension and is reacted with phosgene, carbonyl bro-mide or bis-chloroformic esters of the aromatic dihy-droxy compounds. An organic solvent is provided in the reaction admixture wllich is a solvent for the polylner but not or the aromatic dihydroxy salts. Thus, chlorinated aliphatic hydrocarbons or chlorinated aro-matic hydrocarbons are used as the organic solventwhich dissolves the condensation product. In order to limit the molecular weight one may use monofunctional reactants such as monophenols, for example the propyl-, isoprop~l- and butyl-phenols, especially p-tert-butyl-~o phenol and phenol itself. In order to accelerate the reaction, catalysts such as tertiary amines, quaternary ammonium, phosphonium or arsonium salts and the like may be used. The reaction temperature should be about ~20 to ~150C, pre~erably 0 to about 100C.
2S According to the polycondensation process in a homogeneous phase, the dissolved reaction components are ~olycondensed in an inert solvent in the presence of an equivalent amount of a tertiary amine base required for absorption of t~e generated ~Cl, such as, e.g. 9 I~ dimethyl-aniline, I~,W-dimethyl-cyclohexyl-amine or, preferably, pyridine and the like. In still another process, a diaryl carbonate can be transesteri-Mo-2225-ClP
PC-10~/106-CIP

~9~937 fied with the aromatic dihydroxy compounds to form the polycarbonate resin.
It is to be understood that it is possible to combine in the processes described above in a chem-ically meaningful way both the aromatic dihydroxy com-pounds and the monohydroxy compounds in the form of the alkali metal salts and/or bis-haloformic acid esters and the amount of phosgene or carbonyl bromide then still required in order to obtain high molecular pro-ducts. Other methods of synthesis in forming the poly-carbonates of the invention such as disclosed in U.S.
Patent 3,912,688, incorporated herein by reference, may be used.
In the context of the present invention sili-cates are aluminosilicates either hydrous (clays) oranhydrous (Feldspars) as well as the sillimanite group of minerals (conforming to A12SiO5) and Wollastonite (conforming to CaSiO3).
Silicates useful in the practice of the inven-tion may be surface treated, such as by the applicationof coupling agents thereon to render improved compati-bility with the polycarbonate matrix.
Clays are aluminum silicate minerals charac-terized by their crystal structure and chemical makeup and are widely known and used in a variety of appli-cations.
In the practice of the in~ention, clays, preferably calcined clays, may be used provided théir moisture content does not exceed 2.0%, preferably 0.5%.
Among the clays suitable in the context of the present invention are bentonite, such as is available from Whittaker, Clark & Daniels, Inc. of South Plain-Mo-2225-CIP

field, New Jersey, under the tradename 660 Bentonite, and calcined kaolin, such as is available from Engel 'nard Minerals & Chemicals Corporation of Edison, ,~ew Jersey, under the tradename Satintone, as well as from other commercial sources some of which are referred to in the working examples of this disclosure. Typically, calcined kaolin suitable in the practice of the inven-tion is characterized by the properties listed below:
Average particle size, microns 0.8 lO Residue 325 mesh, max. % 0.01 Oil absorption (ASTM DZ 81-31) 85-95 Oil absorption (Gardner Coleman) 100-120 Color (G.E. brightness~ 90-92 Refractive index 1.62 15 Specific gravity 2.63 pH 4.5-5.5 Bulking value: lbs./gal. 21.9 Bulk density, lbs./~t.3: loose 10-15 fi.rm 15-20 20 Free moisture, max. % 0.5 Other silicates suitable in the context of the present i.nvention are synthetlc sodium aluminum sili-cates such as are available in commerce from Degussa Corporation of Teterboro, New Jersey under the trade-name Sipernat~ 44. Conforming approximately to the formula Na20-A1203-2SiO2-4H20, Sipernat~ 44 is characterized by the properties listed below.

l~lo-2225-CIP

~793~7 _o~erty Test Method Medium size of aggregates DI~ 51 033 3-4 ~m (Andreasen) Sieve residue DIN 53 580 <0.1 %
(Mocker, 45 ~m) Tamped density DIN 53 194 approx. 450 g/l Drying loss DIN 55 921 **
(2 hrs. at 105C~
Ignition loss *** DIN 55 ~21 approx. 20 %
(1 hr. at 800C) pH-value DII~l 53 200 approx. 11.8 (in 5% aqueous dispersion) 20 Sio2 * ap~)rox. 42 %
A1203 * approx. 36 %
Na2O approx. 22 %

Fe203 * approx. 0.02%

* referre~ to the substance ignited for 1 hr. at ** measured values are not consistent *** total ignition loss, re-ferred to the original substance Generally, the silicates suitable in the prac-tice of the invention may range in their average par-ticle size from about 0.05 to about 20 microns, pre-ferably from 0.075 to about 15 microns and most prefer-ably from 0.075 to about 5 microns.
The polycarbonate com~ositions of the inven-tion may incorporate from 0.025 to 5 phr silicates and be thus particularly suitable as concentrates to be Mo-2225-CIP

~7~3~

diluted by admixing with polycarbonate resin to a prede-~ermined loading.
Further, the polycarbonate compositions of the invention may incorporate 0.025 phr to about 1.0 phr, preferably 0.025 to about 0.1 phr, of silicates and be thus particularly suitable for the preparation of films which are characterized by their low static coef~icient of friction.
Although the results tabulated below, wherein summarized are test results indicative of the inventive concept, are believed clear, the following notes are offered by way of further elucidation:
The results reported in the tableswere ob-tained upon testing of the solution cast films and as is ~ell known in the art, these results are indicative of trends to be expected upon ~he evaluation of ex-truded films. It should further be noted that the values o the coefficient of friction thus obtained are significantly higher than the values obtainable upon testing the corresponding extruded films. Accordingly, ~s and ~k are respectively the static and kinetic coefficients of friction as measured per ASTM D-1894-78. The symbols O-0, 0-I and I-I are significant in identifying the surface of the sample tested. The films whose properties are reported below were all cast from solution onto glass and the "air side" of the fil is designa~ed as 0 while the glass side is designated I. The "torture test" is conduc-ted on a 3 oz. injec-tion molding machine at a temperature of 725F and mold-ing cycles of one minute and is designe~ to test thethermal stabili~y of a resinous composition. A skilled operator may determine, by evaluating the par~s molded Mo-2225-CIP

under the processing parameters above, whether the composition suffers thermal degradation, for instance, upon the incorporation of additives thereto. A subjective evaluation indicative of the sufficiency of thermal stability is reported in the table below.
Measurements of melt flow were carried out as an added criteria indicating structural or chemical changes that may occur upon the incorporation of the silicate additive. An abnormal change in flow, which may indicate depolymerization or cross-linking may point ~o processing difficulties which can be expected upon the extruding of the compound into films. Surprisingly, the silicates used in the present invention appears to bring about a degree of improved thermal stability to the silicate-polycarbonate system.
The compositions of polycarbonate silicates of the invention are prepared by blending a polycarbonate resin with a predetermined amount of sui.table sillcate to provide a homogeneous dispersion thereof in the resin. Such blending may be carried out in any of suitable blenders or mixers commonly used in the art. The preparation of films by the solu~ion casting method~ extrusion and by blow molding techniques are described in the monograph, "Chemistry and Physics of Polycarbonates", H. Schnell, Interscience Publishers, 1~64, and in "Polycarbonates", by Christopher and Fox, Rheinhold Publishing Corporation, 1962. The compositions of the instant invention are suitable for the preparation oF thin films (less than 10 mils) o excellent clarity and low static coefficient of friction.

Mo-2225-CIP

3793~

The polycarbonate resin used in the course of the experiments is HMS 3119, a branched poIycarbonate resin of 1.29-1.30 relative viscosity (measured on 0.5%
solution in methylene chloride) and having a melt flow rate of 1.5-2.5 g/10 min., per ASTM-D 1238 and is a product of Mobay Chemical Corporation. The coefficient of static friction (0-O) of llMS 3119 is about 10Ø
The haze and light transmission values of HMS 3119 are 0.4% and 91.9% respectively. The thickness of the films which properties are tabulated below was l mil.

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Notes to table:
(1) The clay additives were blended in a poly-carbonate resin HMS 3119, Mobay Chemical Corporation. (2) Calcined kaolin, from Engelhard Minerals &
Chemicals Corporation, Edison, New Jersey (3) Silane treated Satintone (4) Hydrous kaolin from Burgess Pigment Company, Sandersville, Geor~ia (5) Ground calcined kaolin from ~nittaker, Clark &
Daniels, Inc., South Plainfield, New Jersey

(6) Per ASTM D-1238

(7) See explanatory note in the specification;
F - fair; & - good; E - excellent

(8) Per ASTM D-1894-78

(9) Per ASTM D-1003-61 (]0) ~entonite frorn Whittaker, Clark & Daniels, Inc., South Plainfield, New Jersey.

Fil~s according to the invention comprising aluminum silicate (synthetic) Table 2 and Wollastonite Table 3 were prepared and tested as presented below.

Mo-2225-CIP
PC-10~/106-CIP

~L~97937 PROPERTIES OY CAST FILMS MADE OF
POLYCA~30~ATE~SILICATE COMPOSITIONS

Polycarbonate resin(pbw) loo~l) lOOt ) 100( ) 100( ) 10Silicate(3) (pbw) 1.0 1.0 - _ Compositions melt flow( ), gm/10 min. 3.1 3.4 2.0 15Pellet r.v. 1.291 1.302 1.29 Film properties Haze, 96 4.4 5.1 0.4 0.2 20Light transmission, ~ 91.6 91.6 91~9 91.8 Coefficient of Friction 25~ ~s 0.716 5.94 10.0 10.36 ~K 0.761 ~528 0-I lls 1.52 0. 564 8. 53 ~ 0.888 0.508 0.812 30 k I-I ~s 10.15 0.787 6.35 ~k - 1.19 0.508 .*
35 (1) Merlon HMS 3119 (2) Merlon ~50 (3) Sip~rnat~44 (4) P~r ASTM D-1238 ~ ~ ~0~ w~

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Claims (18)

The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:

1. A polycarbonate film comprising (i) an aromatic thermoplastic polycar-bonate resin, and (ii) between 0.025 to 5 phr of a silicate having an average particle size of about 0.05 to about 20 microns, said silicate selected from the group con-sisting of hydrous alumino silicates, anhydrous alumino silicates, silli-manite minerals and wollastonite.

2. The composition of Claim 1, wherein said silicate is calcined clay.

3. The composition of Claim 1 or 2, wherein said (ii) is between 0.025 and 1 phr.

4. The composition of Claim 1 or 2, wherein said particle size is about 0.075 to about 5 microns.

5. The composition of Claim 1, wherein said silicate is treated with a coupling agent.

6. The composition of Claim 1 or 5, wherein said (i) is a bisphenol-A based polycarbonate.

7. In the solution cast process for the preparation of films, the improvement comprising using a polycarbonate composition comprising (i) an aromatic thermoplastic polycar-bonate resin, and (ii) between 0.025 to 5 phr of a silicate having an average particle size of about 0.05 to about 20 microns, said silicate selected from the group consisting of hydrous alumino sili-cates, anhydrous alumino silicates, sillimanite minerals and wolla-stonite.
Mo-2225-CIP

8. The process of Claim 7, wherein said sili-cate is calcined clay.

9. The process of Claim 7, wherein said sili-cate is treated with a coupling agent.

10. In the extrusion process for the prepara-tion of films, the improvement comprising using a poly-carbonate composition comprising (i) an aromatic thermoplastic polycar-bonate resin, and (ii) between 0.025 to 5 phr of a silicate having an average particle size of about 0.05 to about 20 microns, said silicate selected from the group con-sisting of hydrous alumino silicates, anhydrous alumino silicates, silli-manite minerals and wollastonite.

11. The process of Claim 10, wherein said silicate is calcined clay.

12. The process of Claim 10, wherein said silicate is treated with a coupling agent.

13. In the blow molding process for the prep-aration of films, the improvement comprising using a polycarbonate composition comprising (i) an aromatic thermoplastic polycar-bonate resin, and (ii) between 0.025 to 5 phr of a silicate having an average particle size of about 0.05 to about 20 microns, said silicate selected from the group con-sisting of hydrous alumino silicates, anhydrous alumino silicates, silli-manite minerals and wollastonite.

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14. The process of Claim 13, wherein said sili-cate is calcined clay.

15. The process of Claim 13, wherein said sili-cate is treated with a coupling agent.

16. Thin, aromatic polycarbonate films of the composition of Claim 1.

17. The films of Claim 16 having thicknesses of about 10 mils or less.

18. Thin, aromatic polycarbonate films of the composition of Claim 2.

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