Flame retardant non-dripping polycarbonate compositions exhibiting improved thick section impact

Flame retardant, non-dripping polycarbonate compositions exhibiting good thick section impact comprised of, in admixture: PA0 (i) a minor amount of a fluorinated polyolefin; and PA0 (ii) a carbonate copolymer based on the reaction products of PA1 (a) a carbonate precursor, PA1 (b) at least one halogen-free and sulfur free dihydric phenol, and PA1 (c) at least one halogen-free thiodiphenol.

BACKGROUND OF THE INVENTION 
Polycarbonates are well known thermoplastic materials which, due to their 
many advantageous physical and mechanical properties, find use as 
thermoplastic engineering materials in many commercial and industrial 
applications. The polycarbonates exhibit, for example, excellent 
properties of toughness, flexibility, impact resistance, and high heat 
distortion temperatures. The polycarbonates and their preparation are 
disclosed, for example, in U.S. Pat. Nos. 2,964,974; 2,999,835; 3,028,365; 
3,334,154; 3,275,601; and 3,915,926. 
However, these polycarbonates generally suffer from two disadvantages. The 
first disadvantage is the low critical thickness values of polycarbonates, 
i.e., the thickness at which a discontinuity in Izod impact values occurs. 
These low critical thickness values tend to limit wall thickness of molded 
polycarbonate to a thickness below the critical thickness. Polycarbonates 
exhibit notched Izod impact values which are dependent on the thickness of 
the polycarbonates. Thus, for example, while typical notched Izod impact 
values for a one-eighth inch thick polycarbonate test specimen are 
generally in the range of about 16 foot pounds per inch, typical notched 
Izod impact values for a one-fourth inch thick polycarbonate test specimen 
are generally in the range of about 2.5 foot pounds per inch. The high 
Izod values of the one-eighth inch thick polycarbonate test specimen are 
due to the fact that these specimens are thinner than the critical 
thickness of the polymer and, therefore, upon impact a hinged or ductile 
break occurs. The low Izod impact values of the one-fourth inch thick 
polycarbonate test specimens are due to the fact that these specimens 
exceed the critical thickness of the polymer and, therefore, upon impact a 
clean or brittle break occurs. 
The second disadvantage of polycarbonates is that they, like most other 
plastics, are relatively flammable. Thus polycarbonates are generally 
unsuitable for applications where high temperatures and exposure to flames 
may be encountered. In order to render the polycarbonates suitable for 
high temperature or open flame environments they must be modified to be 
made flame retardant. One of these modifications involves the inclusion a 
halogenated moiety, such as halogenated diphenol, in the backbone of the 
carbonate polymer. These halogen containing carbonate copolymers are 
generally flame retardant. However, the presence of these halogen 
containing moieties adversely affects the critical thickness values of the 
polycarbonates. Thus, for example, the critical thickness of a carbonate 
copolymer containing 5 to 6 percent by weight bromine in the form of a 
halogenated diphenol is about 130-140 mils. 
U.S. Pat. No. 4,043,980 discloses polycarbonate compositions obtained as 
the reaction products of an aromatic diol, a halogenated phenol, and a 
carbonic acid coreacted with an aromatic thiodiphenol, which compositions 
exhibit flame retardancy stated to be the result of the synergism between 
the sulfur and the halogen present in the compositions. However, this 
patent teaches the necessity of the presence of a halogen containing 
moiety in the polycarbonate compositions and states that the resultant 
flame retardancy is the result of synergism between the sulfur present in 
the thiodiphenol and the halogen present in the halogenated phenol. 
International Application No. WO 82/00468, published Feb. 18, 1982 
discloses that polycarbonate compositions can be rendered flame retardant 
by either admixing with the carbonate polymer a polymer based on a 
thiodiphenol, or incorporating into the polycarbonate backbone a 
thiodiphenol residue. While these compositions are quite effective and 
useful in most applications, they suffer from the disadvantage that 
relatively large amounts of thiodiphenol, typically from about 23-98 mole 
percent, must be employed to render said compositions flame retardant. 
Since thiodiphenol is relatively expensive, as compared with dihydric 
phenols such as bisphenol-A, its use in relatively large amounts places 
these flame retardant polycarbonate compositions at an economic 
disadvantage. Also in some applications, particularly those where the 
polycarbonate resin is required to exhibit properties of substantially 
sulfur-free bisphenols, such as bisphenol-A, or where the presence of 
large amounts of sulfur would be disadvantageous, such large amounts of 
thiodiphenol are undesirable. 
It would thus be very advantageous if flame retardant polycarbonate 
compositions could be provided which are halogen free and which, 
consequently, exhibit the properties of halogen-free polycarbonates such 
as good thick section impact strengths. It would also be very advantageous 
if flame retardant polycarbonate compositions could be provided which not 
only exhibit the properties and characteristics of halogen-free 
polycarbonates, but also exhibit the properties and characteristics of 
substantially sulfur-free polycarbonates such as good processability and 
economic competitiveness. 
It is, therefore, an object of the instant invention to provide 
polycarbonates which are flame retardant, are halogen-free, and contain 
relatively minor amounts of sulfur in the form of thiodiphenol residues. 
SUMMARY OF THE INVENTION 
Polycarbonate compositions are provided which exhibit good thick section 
impact strengths and are simultaneously flame retardant and 
drip-resistant. These compositions are comprised of, in physical 
admixture, (i) a carbonate resin based on the polymerized reaction 
products of (a) a carbonate precursor, (b) at least one halogen-free and 
sulfur-free diphenol, and (c) at least one thiodiphenol; and (ii) a minor 
amount of a fluorinated polyolefin. 
DESCRIPTION OF THE INVENTION 
It has surprisingly been discovered that polycarbonate compositions 
containing a halogen-free polycarbonate resin can be provided which are 
flame retardant, non-dripping, and exhibit good thick section impact. 
These polycarbonate compositions are comprised of, in admixture, (i) a 
halogen-free carbonate resin based on the reaction products of (a) a 
carbonate precursor, (b) at least one halogen-free and sulfur-free 
dihydric phenol, and (c) at least one thiodiphenol; and (ii) a minor 
amount of a fluorinated polyolefin. 
The fluorinated polyolefins used in this invention as drip retarding agents 
are commercially available or may be readily prepared by known processes. 
They are solids obtained by polymerization of tetrafluoroethylene, for 
example, in aqueous media with free radical catalysts, e.g., sodium, 
potassium or ammonium peroxydisulfides at 100 to 1,000 psi at 
0.degree.-200.degree. C., and preferably at 20.degree.-100.degree. C. The 
preparation of some of these fluorinated polyolefins is disclosed in U.S. 
Pat. No. 2,393,967, which is hereby incorporated herein by reference. 
While not essential, it is preferred to use these fluorinated polyolefin 
resins in the form of relatively large particles, e.g., of average 
particle size of from about 0.3 to about 0.7 mm, mostly about 0.5 mm. 
These are generally better than the usual polytetrafluoroethylene powders 
which have particles of from about 0.05 to about 0.5 millimicrons in 
diameter. It is especially preferred to use the relatively large particle 
size material because it tends to disperse readily in polymers and bond 
them together into fibrous material. Such preferred 
polytetrafluoroethylenes are designated by ASTM as Type 3, and are 
available commercially from the E. I. du Pont de Nemours & Company under 
the tradename TEFLON type 6. 
The instant compositions contain an amount of fluorinated polyolefin which 
when admixed with the sulfur containing polycarbonate is effective to 
enhance the flame retardancy of said compositions and to render said 
compositions non-dripping. Generally, this is a relatively minor amount 
and is generally in the range of from about 0.01 to about 1 weight 
percent, based on the amount of the polycarbonate resin present, and 
preferably from about 0.01 to about 0.5 weight percent. 
The halogen-free and sulfur-free dihydric phenols employed in the practice 
of the instant invention to produce the halogen-free carbonate resin may 
be represented by the general formula 
##STR1## 
wherein: 
A is selected from divalent hydrocarbon radicals containing from 1 to about 
16 carbon atoms; --O--; and 
##STR2## 
R is independently selected from monovalent hydrocarbon radicals containing 
from 1 to about 15 carbom atoms; 
n is independently selected from whole numbers having a value of from zero 
to four inclusive; and 
y has a value of either zero or one. 
The divalent hydrocarbon radicals represented by A include alkylene 
radicals, alkylidene radicals, cycloalkylene radicals, and cycloalkylidene 
radicals. Some illustartive non-limiting examples of alkylene and 
alkylidene groups represented by A include methylene, ethylene, propylene, 
propylidene, isopropylidene, butylene, isobutylene, butylidene, amylene, 
isoamylene, amylidene, isoamylidene, and the like. 
When A represents a cycloalkylene or cycloalkylidene radical it is 
preferred that these cycloalkylene and cycloalkylidene radicals contain 
from 4 to 7 carbon atoms in the cyclic structure. These preferred 
cycloalkylene and cycloalkylidene groups may be represented by the general 
formula 
##STR3## 
wherein: 
Cy is selected from cycloalkylene and cycloalkylidene radicals containing 
from 4 to about 7 carbon atoms in the cyclic structure; 
R.sup.1 is independently selected from lower alkyl radicals, preferably 
lower alkyl radicals containing from 1 to about 5 carbon atoms; and 
b is a whole number having a value from 0 up to the number of replaceable 
hydrogen atoms present on Cy, preferably having a value of from 0 to 6 
inclusive. 
Some non-limiting illustrative cycloalkylene and cycloalkylidene radicals 
represented by Formula II include, cyclopentylene, cyclopentylidene, 
cyclohexylene, cyclohexylidene, methylcyclohexylene. 
methylcyclohexylidene, and the like. 
The monovalent hydrocarbon radicals represented by R include alkyl 
radicals, aryl radicals, aralkyl radicals, and alkaryl radicals. 
Preferred alkyl radicals are those containing from 1 to about 10 carbon 
atoms. Illustrative of these preferred alkyl radicals are methyl, ethyl, 
propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, neopentyl, and the 
like. 
Preferred aryl radicals represented by R include those containing from 6 to 
12 carbon atoms, i.e., phenyl and naphthyl. 
Preferred alkaryl and aralkyl radicals represented by R are those 
containing from 7 to about 15 carbon atoms. 
Preferably R is selected from alkyl radicals containing from 1 to about 10 
carbon atoms. 
In the dihydric phenol compound represented by Formula I above when more 
than one R substituent is present they may be the same or different. Where 
y is zero in Formula I the aromatic rings are directly joined with no 
intervening alkylene or other bridge. The positions of the hydroxyl groups 
and R on the aromatic nuclear residues can be varied in the ortho, meta, 
or para positions and the groupings can be in a vicinal, asymmetrical or 
symmetrical relationship where two or more ring carbon atoms of the 
aromatic hydrocarbon residue are substituted with R and hydroxyl group. 
Some non-limiting illustrative examples of the dihydric phenols of Formula 
I include: 
2,2-bis(4-hydroxyphenyl)propane (bisphenol-A); 
2,4'-dihydroxydiphenylmethane; 
bis(2-hydroxyphenyl)methane; 
bis(4-hydroxyphenyl)methane; 
1,1-bis(4-hydroxyphenyl)ethane; 
1,3-bis(3-methyl-4-hydroxyphenyl)propane; 
2,2-bis(3-isopropyl-4-hydroxyphenyl)propane; 
bis(4-hydroxyphenyl)cyclohexylmethane; 
1,1-bis(4-hydroxyphenyl)cyclohexane; 
bis(3-ethyl-4-hydroxyphenyl)ether; 
bis(4-hydroxyphenyl)ether; 
3,3'-dimethyl-4,4'-dihydroxydiphenyl; 
p,p'-dihydroxydiphenyl; and the like. 
It is, of course, possible to employ mixtures of two or more different 
dihydric phenols of Formula I in the practice of the present invention. 
Therefore, whenever the term dihydric phenol is used herein it is to be 
understood that this term encompasses mixtures of dihydric phenols as well 
as individual dihydric phenols. 
The thiodiphenols useful in the practice of this invention are those 
represented by the general formula 
##STR4## 
wherein: 
R.sup.2 is independently selected from alkyl, alkaryl, aralkyl, and aryl 
radicals; and 
m is independently selected from whole numbers having a value of from 0 to 
4 inclusive. 
Preferred alkyl radicals represented by R.sup.2 are those containing from 1 
to about 10 carbon atoms. Some illustrative non-limiting examples of these 
preferred alkyl radicals include methyl, ethyl, propyl, isopropyl, butyl, 
tertiarybutyl, pentyl, neopentyl, hexyl, and the like. 
Preferred aryl radicals represented by R.sup.2 are those containing 6 or 12 
carbon atoms, i.e., phenyl and naphthyl. 
The preferred aralkyl and alkaryl radicals are those containing from 7 to 
about 15 carbon atoms, e.g., benzyl, ethylphenyl, propylphemyl, etc. 
Preferred thiodiphenols of Formula III are those wherein R.sup.2 is 
independently selected from alkyl radicals. 
In the thiodiphenol compounds represented by Formula III when more than one 
R.sup.2 substituent is present they may be the same or different. The 
positions of R.sup.2 and the hydroxyl groups on the aromatic nuclear 
residues can be varied in the ortho, meta, or para positions and the 
groupings can be in a vicinal, asymmetrical or symmetrical relationship, 
where two or more ring carbon atoms of the aromatic hydrocarbon residue 
are substituted with R.sup.2 and hydroxyl groups. 
Some illustrative non-limiting examples of the thiodiphenols of Formula III 
include: 
4,4'-thiodiphenol; 
2-methyl-4,4'-thiodiphenol; 
2,2'-dimethyl-4,4'-thiodiphenol; 
2,2'-di-tertiary-butyl-4,4'-thiodiphenol; and the like. 
Such thiodiphenols can be prepared by known methods such as those disclosed 
in U.S. Pat. No. 3,931,335, which is hereby incorporated herein by 
reference. 
It is of course possible to employ mixtures of two or more different 
thiodiphenols of Formula III in the practice of the instant invention. 
Therefore, wherever the term thiodiphenol is used herein it is to be 
understood that this term includes mixtures of two or more different 
thiodiphenols as well as individual thiodiphenols of Formula III. 
The preferred halogen-free thiodiphenols of Formula III are the 
4,4'-thiodiphenols. 
The carbonate precursor may be a carbonyl halide, a bishaloformate or a 
diarylcarbonate. The carbonyl halides include carbonyl bromide, carbonyl 
chloride, and mixtures thereof. The bishaloformates include the 
bishaloformates of dihydric phenols such as bischloroformates of 
2,2-bis(4-hydroxyphenyl)propane, 
2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, hydroquinone, and the like; 
or the bishaloformates of glycols such as the bischloroformates of 
ethylene glycol, neopentyl glycol, polyethylene glycol, and the like. 
Typical of the diarylcarbonates which may be employed are diphenyl 
carbonate, and the di(alkylphenyl carbonates such as di(tolyl)carbonate. 
Some other non-limiting illustrative examples of suitable diarylcarbonates 
include di(naphthyl)carbonate, phenyl tolyl carbonate, and the like. 
The preferred carbonate precursors are the carbonyl halides, whith carbonyl 
chloride, also known as phogene, being the preferred carbonyl halide. 
Also included with the scope of the instant invention are the high 
molecular weight thermoplastic randomly branched polycarbonates. These 
randomly branched polycarbonates are prepared by coreacting a minor amount 
of a polyfunctional organic compound with the dihydric phenol compounds of 
Formula I and the thiodiphenols of Formula III. The polyfunctional organic 
compounds useful in making the branched polycarbonates are disclosed in 
U.S. Pat. Nos. 3,635,895 and 4,001,184, both of which are incorporated 
herein by reference. These polyfunctional compounds are generally aromatic 
and contain at least three functional groups which may be carboxyl, 
hydroxyl, carboxylic anhydride, haloformyl, or mixtures thereof. Some 
illustrative non-limiting examples of these polyfunctional compounds 
include trimellitic anhydride, trimellitic acid, trimellityl trichloride, 
4-chloroformyl phthalic anhydride, pyromellitic acid, pyromellitic 
dianhydride, mellitic acid, mellitic anhydride, trimesic acid, 
benzophenonetetracarboxylic acid, benzophenonetetracarboxylic acid 
anhydride, and the like. 
One method which may be utilized in preparing the polycarbonates of the 
instant invention involves the heterogeneous interfacial polymerization 
system utilizing an aqueous caustic solution, an organic water immiscible 
solvent, at least one dihydric phenol of Formula I, at least one 
thidiphenol of Formula III, a catalyst, a carbonate precursor, and a 
molecular weight regulator. A preferred heterogeneous interfacial 
polymerization system is one which utilizes phosgene as a carbonate 
precursor. 
Another useful method for preparing the carbonate polymers of the instant 
invention involves the use of an organic solvent system wherein the 
organic solvent system may also function as an acid acceptor, at least one 
dihydric phenol of Formula I, at least one thiodiphenol of Formula III, a 
molecular weight regulator, and a carbonate precursor. A preferred method 
is one wherein phosgene is employed as the carbonate precursor. 
Generally, in both of the aforediscussed methods phosgene is passed into 
the reaction mixture containing at least one dihydric phenol of Formula I 
and at least one thiodiphenol of Formula III. The temperature at which the 
phosgenation reaction proceeds may vary from below 0.degree. C. to above 
100.degree. C. The reaction proceeds satisfactorily at temperatures from 
room temperature (25.degree. C.) to about 50.degree. C. Since the reaction 
is exothermic, therate of phosgene addition may be used to control the 
reaction temperature. 
A suitable acid acceptor may be either organic or inorganic in nature. A 
suitable organic acid acceptor is a tertiary amine and includes such 
materials as pyridine, triethylamine, dimethylaniline, tributylamine, etc. 
The inorganic acid acceptor may be a hydroxide, such as an alkali or 
alkaline earth metal hydroxide, a carbonate, a bicarbonate, a phosphate, 
and the like. An inorganic acid acceptor is preferred when an aqueous 
system is utilized. 
The catalysts which may be employed can be any of the well known catalysts 
which aid the polymerization reaction of the dihydric phenol with the 
phosgene. Suitable catalysts include, but are not limited to, tertiary 
amines, secondary amines, quaternary ammonium compounds, quaternary 
phosphnoium compounds, amidines, and the like. 
The molecular weight regulators employed may be any of the known compounds 
which regulate the molecular weight of the carbonate polymers by a chain 
stopping or terminating mechanism. These compounds include, but are not 
limited to, phenol, tertiarybutyl phenol, and the like. 
The high molecular weight aromatic carbonate polymers of the instant 
invention generally have a weight average molecular weight in the range of 
from about 5,000 to about 200,000, preferably from about 10,000 to about 
100,000, and more preferably from about 25,000 to about 50,000. 
The polycarbonates of the instant invention may optionally have admixed 
therewith certain commonly known and used additives such as, for example, 
antioxidants; antistatic agents; fillers; ultraviolet radiation absorbers 
such as the benzophenones, benzotriazoles, benzylidene malonates, and the 
like; hydrolytic stabilizers such as the epoxides disclosed in U.S. Pat. 
Nos. 3,489,716, 4,138,379 and 3,839,247, all of which are hereby 
incorporated herein by reference; mold release agents; color stabilizers 
such as the organophosphites disclosed in U.S. Pat. Nos. 3,305,520 and 
4,118,370, both of which are hereby incorporated herein by reference; and 
the like. 
The carbonate copolymers of the instant invention will generally contain 
the following repeating structural units: 
##STR5## 
wherein R, R.sup.2, A, n, y and m are as defined above. The structural 
units of Formula V will be present in relatively minor amounts. The amount 
of structural units of Formula V present will be an amount which when said 
polycarbonate resin is admixed with the fluorinated polyolefin is 
effective to render said compositions flame retardant. This amount is 
generally in the range of from about 1 to about 15 mole percent, based on 
the amount of structural units of Formula IV and Formula V present, and 
preferably from about 1 to about 10 mole percent, based on the total 
amount of structural units of Formulae IV and V present. 
Rather than containing a carbonate resin of the type described hereinafore, 
i.e. a copolycarbonate comprised of the reaction products of (i) a 
halogen-free and sulfur-free dihydric phenol of Formula I, (ii) a 
halogen-free thiodiphenol of Formula III, and (iii) a carbonate precursor, 
hereinafter referred to as Polymer A, the instant compositions may contain 
blends of Polymer A and a polycarbonate derived from (i) a halogen-free 
and sulfur-free dihydric phenol of Formula I, and (ii) a carbonate 
precursor, hereinafter referred to as Polymer B. The instant compositions 
may thus contain blends of (a) at least one halogen-free and 
sulfur-containing copolycarbonate derived form (i) a dihydric phenol of 
Formula I, (ii) a thiodiphenol of Formula III, and (iii) a carbonate 
precursor, i.e. Polymer A,; and (b) at least one halogen-free and 
sulfur-free polycarbonate derived from (i) a dihydric phenol of Formula I, 
and (ii) a carbonate precursor, i.e. Polymer B. 
When the compositions contain blends of Polymers A and B, the amount of the 
structural units of Formula V present in Polymer A may be increased above 
the 15 mole percent limit specified above, providing, that the amount of 
structural units of Formula V present in the final blends, i.e. the blends 
of Polymers A and B, is in the range of from about 1 to about 15 mole %, 
and preferably in the range of from about 1 to about 10 mole %, based on 
the total amount of structural units IV and V present in Polymers A and B. 
Thus, for example, Polymer A may contain 30 mole percent of structural 
units of Formula V. This Polymer A is then blended with Polymer B which 
contains only structural units of Formula IV. The final blend contains 
amounts of Polymer A and Polymer B such that the mole % of structural 
units of Formula V present in the blend, based on the total amount of 
structural units of Formulae IV and V present in Polymer A and structural 
units of Formula IV present in polymer B, is in the range of from about 1 
to about 15, and preferably from about 1 to about 10 mole percent. 
Generally, if the compositions contain less than about 1 mole % of 
structural units of Formula V there will be no appreciable improvement in 
flame retardancy of the compositions. If, on the other hand, the 
compositions contain more than about 15 mole percent of the structural 
units of Formula V, the compositions will begin to be economically 
adversely affected, and the concentration of sulfur in these compositions 
will begin to render these compositions unsuitable for applications where 
the presence of sulfur is undesirable, or where polycarbonates exhibiting 
the characteristics of sulfur-free and halogen-free polycarbonates, such 
as those based on bisphenol-A, are required. 
It is, of course, possible to utilize polycarbonate blends comprised of 
Polymer B, and a polycarbonate containing up to about 95 mole % repeating 
structural units of Formula V, as long as the amount of structural units V 
in the total composition is in the range of 1 to 15 mole %. Thus, for 
example, it would be possible to utilize a blend comprised of 85% resin B 
and 15% of a resin containing up to about 95 mole % repeating structural 
units of Formula V. 
Generally the blends comprised of Polymer A and Polymer B contain from 
about 20 to about 80 weight percent of at least one Polymer A, and from 
about 80 to about 20 weight percent of at least one Polymer B. These 
blends may be conveniently prepared by simply physically admixing the two 
polymers together, either as powders or as pellets. 
The instant compositions may also optionally contain certain commonly known 
and used additives such as, for example, antioxidants; antistatic agents; 
inert fillers such as talc, clay, mica, and glass; mold release agents; 
ultraviolet radiation absorbers such as the benzophenones, benzotriazoles, 
and benzylidene malonates; hydrolytic stabilizers such as the epoxides 
disclosed in U.S. Pat. Nos. 3,489,716, 4,138,379 and 3,839,247, all of 
which are incorporated herein by reference; and color stabilizers such as 
the organophosphites disclosed in U.S. Pat. Nos. 3,305,520 and 4,118,370, 
both of which are incorporated herein by reference.

PREFERRED EMBODIMENT OF THE INVENTION 
The following examples are presented to more fully and clearly illustrate 
the invention. Although the examples set forth the best mode presently 
known to practice the invention they are intended to be and should be 
considered as illustrative rather than limiting the invention. In the 
examples, all parts and percentages are by weight unless otherwise 
specified. 
The following examples illustrate polycarbonate compositions falling 
outside the scope of the instant invention and are presented for 
comparative purposes only. 
EXAMPLE 1 
This example illustrates a prior art copolycarbonate which is derived from 
bisphenol-A and thiodiphenol. This polycarbonate composition contains no 
fluorinated polyolefin. 
Into a mixture of 2283 grams of bisphenol-A (10 moles), 218 grams (1 mole) 
of 4,4'-thiodiphenol, 5700 grams of water, 9275 grams of methylene 
chloride, 32 grams of phenol and 10 grams of triethylamine are introduced, 
at ambient temperature, 1180 grams of phosgene over a period of 97 minutes 
while maintaining the pH of the two phase system at about 11, i.e. pH 
10-12.5, by stimultaneously adding a 25% aqueous sodium hydroxide 
solution. At the end of the phosgene addition period the pH of the aqueous 
phase is 11.7 and the bisphenol-A content of this phase is less than 1 
part per million as determined by ultraviolet analysis. 
The methylene chloride phase is separated from the aqueous phase, washed 
with an excess of dilute (0.01N) aqueous HCL and then washed three times 
with deionized water. The polymer is precipitated by steam and dried at 
95.degree. C. The resultant polycarbonate is fed to an extruder, which 
extruder is operated at about 500.degree. C. and the extrudate is 
comminuted into pellets. 
The pellets are then injection molded at about 600.degree. C. into test 
bars of about 5 in. by 1/2 in. by 1/8 in. thick. These test bars are 
subjected to the test procedure set forth in underwriters' Laboratories, 
Inc. Bulletin UL-94, Burning Test for Classified Materials. In accordance 
with this test procedure, materials that pass are rated V-0, V-I or V-II 
based on the results of 5 specimens. The criteria for each V (for 
vertical) rating per UL-94 is briefly as follows: 
"V-0": Average flaming and/or glowing after removal of the igniting flame 
shall not exceed 5 seconds and none of the specimens shall drip flaming 
particles which ignite absorbent cotton. 
"V-I": Average flaming and/or glowing after removal of igniting flame shall 
not exceed 25 seconds and the glowing does not travel vertically for more 
than 1/8" of the specimen after flaming ceases and glowing is incapable of 
igniting absorbent cotton. 
"V-II": Average flaming and/or glowing after removal of the igniting flame 
shall not exceed 25 seconds and the specimens drip flaming particles which 
ignite absorbent cotton. 
In addition, a test bar which continues to burn for more than 25 seconds 
after removal of the igniting flame is classified, not by UL-94, but by 
standars of the invention, as "burns". Further, UL-94 requires that all 
test bars in each test group must meet the V-type rating to achieve the 
particular classification. Otherwise, the 5 test bars receive the rating 
of the worst single bar. For example, if one bar is classified as V-II and 
the other four are classified as V-0, then the rating for all 5 bars is 
V-II. 
EXAMPLE 2 
This example also illustrates a prior art copolycarbonate which is derived 
from bisphenol-A and thiodiphenol. This polycarbonate composition contains 
no fluorinated polyolefin. 
The procedure of Example 1 is repeated with a mixture of 1712.5 grams (7.5 
moles) of bisphenol-A and 545.7 grams of 4,4'-thiodiphenol (2.5 moles). 
Test bars are prepared substantially in accordance with the procedure of 
Example 1, and these test bars are subjected to test procedure UL-94. 
EXAMPLE 3 
This example illustrates a prior art polycarbonate resin which does not 
contain either the thiodiphenol moieties or the fluorinated polyolefin. 
Into a mixture of 2283 grams of pure bisphenol-A, 5700 grams of water, 9275 
grams methylene chloride, 32 grams phenol and 10 grams triethylamine are 
introduced, at ambient temperature, 1180 grams of phosgene over a period 
of 97 minutes while maintaining the pH of the two phase system at about 
11, i.e. 10-12.5, by simultaneously adding a 25.degree. aqueous sodium 
hydroxide solution. At the end of the addition period, the pH of the 
aqueous phase is 11.7 and the BPA content of this phase is less than 1 
part per million as determined by ultraviolet analysis. 
The methylene chloride phase is separated from the aqueous phase, washed 
with an excess of dilute (0.01N) aqueous HCl and then washed three times 
with deionized water. The polymer is precipitated by steam and dried at 
95.degree. C. The resultant pure bisphenol-A polycarbonate is fed to an 
extruder, which extruder is operated at about 550.degree. F. and the 
extrudate is comminuted into pellets. 
The pellets are then molded into test bars in accordance with the procedure 
set forth in Example 1, and the test bars are subjected to test procedure 
UL-94. 
EXAMPLE 4 
This example illustrates a polycarbonate composition falling outside the 
scope of the instant invention in that the composition contains 
fluorinated polyolefin but the polycarbonate does not contain any 
thiodiphenol residues. 
To 1470 grams of the powdered polycarbonate resin prepared substantially in 
accordance with the procedure of Example 3 are added 30 grams of TEFLON 6. 
This mixture is then thoroughly stirred. The resultant mixture contains 2 
weight percent TEFLON. This mixture is then molded into test bars 
substantially in accordance with the procedure of Example 1 and the test 
bars are subjected to test procedure UL-94. 
The following example illustrates compositions falling within the scope of 
the instant invention. 
EXAMPLE 5 
Into a mixture of 1826.4 grams of bisphenol-A, 436.6 grams of 
4,4'-thiodiphenol, 6 liters of water, 7 liters of methylene chloride, 31.1 
grams of phenol, and 20.2 grams of triethylamine is introduced phosgene at 
the rate of 30 grams/minute for a period of 30 minutes, while maintaining 
the pH of the two phase system at about 11 by the simultaneous 
introduction of a 25% aqueous NaOH solution. At the end of the phosgene 
addition the bisphenol-A content of the aqueous phase is less than 1 part 
per million as determined by ultraviolet analysis. 
The methylene chloride phase is separated from the aqueous phase, washed 
with an excess of dilute (0.01N) aqueous HCl and then washed three times 
with deionized water. The polymer is precipitated by steam and dried at 
95.degree. C. The resultant copolycarbonate has an intrinsic viscosity 
(IV) in methylene chloride at 25.degree. C. of 0.533 dl/g. 
650 grams of this copolycarbonate, in powder form, are thoroughly mixed 
with 850 grams of the polycarbonate powder prepared substantially in 
accordance with the procedure of Example 3. The resultant polycarbonate 
blend contains about 8.67 mole percent of the thiodiphenol residue. To 
this polycarbonate blend are added 1.5 grams of TEFLON 6 to give a 
composition containing 0.1 weight percent TEFLON. The resultant 
composition is then formed into test bars substantially in accordance with 
the procedure of Example 1 and the test bars are subjected to the test 
procedure UL-94. 
Additionally the resins of Examples 3, 4 and 5 are molded into test squares 
of about 2 in..times.2 in..times.1/4 in. thick. Impact measurements by the 
notched Izod test were determined according to ASTM D-1238. The results of 
these tests, as well as the UL-94 tests, are set forth in Table I. 
TABLE I 
______________________________________ 
MOLE % WEIGHT NOTCHED 
EXAMPLE THIODI- % IZOD 
NO. PHENOL TEFLON (ft. lb.) 
UL-94 
______________________________________ 
1 9 0 -- V-II 
2 25 0 -- V-0 
3 0 0 2.11 BURNS 
4 0 2 1.86 BURNS 
5 8.6 0.1 2.13 V-0 
______________________________________ 
As illustrated by the data in Table I the instant compositions are flame 
retardant, non-dripping, and exhibit good thick section impact. The flame 
retardant and non-dripping characteristics of the instant compositions are 
obtained using much lower concentrations of thiodiphenol than required in 
the prior art compositions to achieve comparable results. Thus, at similar 
concentrations of thiodiphenol but absent the fluorinated polyolefin the 
prior art compositions of Example 1 are V-II. In order to have a V-0 
rating a polycarbonate composition which does not contain any fluorinated 
polyolefin must contain relatively large amounts of thiodiphenol, i.e. the 
25 mole % of Example 2. The presence of relatively large amounts of 
fluorinated polyolefin in the non-thiodiphenol containing polycarbonate 
compositions of Example 2 does nothing to improve the flame retardancy of 
said compositions. 
However, as illustrated by the data for Example 5, the use of relatively 
small amounts of fluorinated polyolefins renders polycarbonate 
compositions containing minor concentrations of thiodiphenol flame 
retardant and non-dripping. Thus, the instant invention provides 
compositions which are flame retardant, non-dripping, and exhibit good 
thick section impact. All of this is achieved using substantially smaller 
amounts of thiodiphenol than would be required to obtain the same results 
absent the fluorinated polyolefin. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are efficiently attained, and 
since certain changes may be made in carrying out the above processes and 
in the composition set forth is intended that all matters contained in the 
above description shall be interpreted as illustrative and not in a 
limiting sense.