Bis(cyclic carbonates), precursors thereof, and polycarbonate compositions containing them

Novel bis(cyclic carbonates) are useful as cross-linking agents for polycarbonate compositions (including cyclic polycarbonate oligomers), and, in combination with flame retardant agents, as anti-drip agents for polycarbonate resins. This bis(cyclic carbonates) may be prepared by the reaction of phosgene with novel tetraphenols, which in turn may be prepared by the condensation of aliphatic dialdehydes with phenols.

This invention relates to new polycyclic compositions, methods for their 
preparation and uses thereof. In particular, it relates to bis(cyclic 
carbonates) and their phenolic precursors, and the use of said bis(cyclic 
carbonates) as crosslinking and anti-drip agents for polycarbonate resins. 
Polycarbonates are well known polymers which have good property profiles, 
particularly with respect to impact resistance, electrical properties, 
optical clarity, dimensional rigidity and the like. These polymers are 
generally linear, but can be made with branched sites to enhance their 
properties in specific ways. Low levels of branching are generally 
incorporated into the resin by copolymerizing into the polymer backbone a 
polyfunctional reagent to yield a thermoplastic polycarbonate resin with 
enhanced rheological properties and melt strength which make it 
particularly suitable for such types of polymer processing procedures as 
the blow molding of large, hollow containers and the extrusion of complex 
profile forms. Special manufacturing runs must be set aside to prepare 
these branched polycarbonate resins. 
Sufficiently higher levels of branching sites in the resin will cause resin 
chains actually to join to each other to form partially or fully 
crosslinked resin networks which will no longer be thermoplastic in nature 
and which are expected to exhibit enhancements over corresponding linear 
resins in physical properties and/or in their resistance to abusive 
conditions, such as exposure to organic solvents. A wide variety of means 
have been employed to produce crosslinking in polycarbonate resins. These 
generally involve the incorporation of a suitably reactive chemical group 
into the resin chain at its time of manufacture, as an additive to the 
resin after manufacture, or both. These reactive groups and the reactions 
they undergo are generally dissimilar from those characteristic of 
polycarbonate resins themselves and are therefore prone to have 
detrimental side effects on the physical and/or chemical properties of the 
polymer. The conventional test used to judge the success of these means 
for crosslinking is to observe the formation of gels due to the 
crosslinked material when a resin sample is mixed with a solvent, such as 
methylene chloride, in which normal linear polycarbonate resin is highly 
soluble. 
It is well known in the art that polycarbonates may be rendered flame 
retardant by the use of conventional flame retarding additives. While 
these conventional flame retardant polycarbonates are quite useful in many 
areas, there are some applications wherein an even greater degree of flame 
retardancy is required. This is particularly the case when dealing with 
rather thin polycarbonate articles, e.g., less than about 125 mils thick. 
These thin polycarbonate articles are very prone to the dripping of 
flaming particles, thereby making it very difficult for them to meet 
certain flame retardant standards such as, for example, those of 
Underwriters Laboratories UL-94. This problem of dripping flaming 
particles, or drip, has been addressed by the use, in addition to the 
conventional flame retardant agents, of various types of drip retardants 
or drip inhibitors. However, many of these drip retardants are, to a 
certain degree, incompatible with polycarbonates and when used in 
quantities sufficient to render the polycarbonates drip retardant 
adversely affect their properties, such as optical clarity and surface 
appearance. There thus exists a need for drip retardants which are 
compatible with polycarbonates. 
A principal object of the present invention, therefore, is to provide 
useful new compositions of matter, precursors therefor, and a method for 
their preparation. 
A further object is to provide compositions which react with polycarbonates 
under suitable conditions to produce crosslinked resins. 
A still further object is to provide compatible compositions which may be 
incorporated in polycarbonates, optionally in combination with flame 
retardant additives, to inhibit drip. 
A still further object is to provide new polycarbonate compositions with 
advantageous properties. 
Other objects will in part be obvious and will in part appear hereinafter. 
In one of its aspects, the present invention includes additives for 
polycarbonate resins which have structures and reactivities very similar 
to those of the polycarbonate itself. Thus, they offer the dual advantages 
of allowing branch sites to be incorporated into polycarbonates during or 
subsequent to the manufacture thereof and of providing this branching or 
crosslinking by a method which produces residual structural groups in the 
final composition which are expected to be physically and chemically 
compatible with the resin. 
The compositions contemplated as this aspect of the invention are 
polycyclic compounds having formula I in the drawings, wherein: 
E is an alkylene radical containing from 2 to about 12 carbon atoms; 
each of Q.sup.1, Q.sup.2, Q.sup.3 and Q.sup.4 is OH, or either or both of 
Q.sup.1 and Q.sup.2 together and Q.sup.3 and Q.sup.4 together form a 
carbonate group (i.e., a group of formula II); 
each X is independently hydrogen or lower alkyl; and 
each Z is independently lower alkyl. 
As will be apparent from formula I and the foregoing description, the 
polycyclic compounds of this invention are bis(cyclic carbonates) and 
tetraphenols which may be considered their precursors. In formula I, the E 
value is an alkylene radical containing from 2 to about 12 carbon atoms. 
Included in the alkylene radicals are alkylidene radicals; i.e., divalent 
aliphatic hydrocarbon radicals in which both free valence bonds are 
attached to the same carbon atom. Illustrative E values are ethylene, 
propylene, trimethylene, butylene, isobutylene, 2,3-dimethylbutylene, 
hexylene, dodecylene, isopropylidene and 3,3-decylidene. Normal alkylene 
radicals having 2-6 carbon atoms are preferred. 
The various Q values may be hydroxy groups or may be combined to form 
carbonate groups. Thus, the invention includes tetraphenols in which 
Q.sup.1, Q.sup.2, Q.sup.3 and Q.sup.4 are each hydroxy. It also includes 
bis(cyclic carbonates) in which Q.sup.1 and Q.sup.2 together and Q.sup.3 
and Q.sup.4 together, from carbonate groups. Also contemplated are 
mono(cyclic carbonates) in which either of the Q.sup.1 -Q.sup.2 and 
Q.sup.3 -Q.sup.4 combinations, but not both, form a carbonate group. While 
such mono(cyclic carbonates) are not a preferred part of the invention, 
they may be encountered as intermediate or transition stages in the 
conversion of the tetraphenols into the bis(cyclic carbonates). 
Each X value may independently be hydrogen or any lower alkyl radical 
(i.e., alkyl radical containing up to 7 carbon atoms) and each Z value may 
independently be any lower alkyl radical. The alkyl radicals may be normal 
or branched; examples are methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 
2-butyl, isobutyl, t-butyl, 1-pentyl, neopentyl, hexyl, 2,3-dimethylbutyl 
and 1-heptyl. Preferred are the n-alkyl radicals and especially those 
containing 1-3 carbon atoms. The methyl radical is most preferred. 
It is within the scope of the invention for all alkyl radicals to be 
different. Most often, however, all Z values are the same and all X values 
are the same. 
The tetraphenols of this invention may be prepared by the condensation of a 
dialdehyde of formula III with at least one phenol of formula IV. This 
method of preparation is another aspect of the invention. Illustrative 
dialdehydes are succinaldehyde, dimethylmalonaldehyde, glutaraldehyde, 
suberaldehyde and sebacaldehyde; illustrative phenols are p-cresol, 
2,4-dimethylphenol and 2-ethyl-4-n-butylphenol. If a mixture of phenols is 
used, the distribution of the X and Z substituents on the tetraphenol will 
vary according to the molecular structures of the phenol reactants and 
their relative reactivities with the dialdehyde. Most often, however, a 
single phenol reactant is used and all four of the phenolic moieties in 
the tetraphenol have the same substituents. 
As will be apparent from formula I, the stoichiometry of the reaction 
requires at least four moles of phenol reactant for each mole of 
dialdehyde. Most often, an excess of phenol is used, typically a 50-100% 
excess. The reaction is ordinarily carried out in the presence of a 
mineral acid such as hydrochloric or sulfuric acid, using a catalytic 
amount of a mercaptan such as mercaptoacetic acid. Normal reaction 
temperatures are in the range of about 30.degree.-100.degree. C., with 
40.degree.-60.degree. C. being preferred. 
The preparation of the tetraphenols of this invention is illustrated by the 
following examples.

EXAMPLE 1 
A 2000-ml. four-neck flask was fitted with a mechanical stirrer, a gas 
inlet tube, a dropping funnel and drying tube which had a nitrogen purge 
line passing past its outlet. The flask was placed in a 
50.degree.-55.degree. C. water bath. To the flask was added 1000 grams 
(9.25 moles) of melted p-cresol. The flask was purged with nitrogen, then 
anhydrous hydrogen chloride was introduced until the p-cresol was 
saturated with it and 2 ml. of mercaptoacetic acid was added. With good 
agitation and continuous slow addition of hydrogen chloride, 256 grams 
(1.28 mole) of a 50% aqueous solution of glutaraldehyde was added dropwise 
over 3 hours. During the addition of the aldehyde, a precipitate began to 
form and by the end of the addition of the reaction mixture had become a 
thick paste. The water bath was then removed and the reaction mixture 
allowed to stand 3 days at room temperature. Volatiles were removed with a 
water aspirator vacuum and a water layer which had formed on the surface 
of the mixture was removed by decanting. Toluene was then added to the 
flask and the mixture stirred until it formed a uniform slurry. The 
mixture was transferred to a larger flask where it was mixed with 
additional toluene to a final total volume of 4000 ml. The precipitate was 
collected by vacuum filtration and washed with an additional 1400 ml. of 
toluene. The resulting hard paste was washed twice with 1500 ml. of water, 
with a Waring blender being used initially to produce a uniform aqueous 
slurry. The final pH of the water filtrate was 4 to 5. The sample was 
dried in a vacuum desiccator (about 1 torr) to yield 405 grams (65%) of 
the desired 1,1,5,5-tetra-(5-methyl-2-hydroxyphenyl)-pentane as a white 
powder (m.p. 220.degree.-228.degree. C.). 
EXAMPLE 2 
A 500-gram sample of 25% aqueous glutaraldehyde was extracted five times 
with 250-ml. portions of methylene chloride and the combined extracts 
dried over MgSO.sub.4, filtered and the solvent partially removed on a 
rotary evaporator to yield 200 ml. of a methylene chloride solution of 
glutaraldehyde. By NMR analysis, the solution was found to contain 
approximately 48 grams (0.48 mole) of glutaraldehyde. 
A 1000-ml. four-neck flask was fitted with a mechanical stirrer, a gas 
inlet tube, a dropping funnel and a drying tube which had a nitrogen purge 
line passing past its outlet. The flask was placed in a 60.degree. C. 
water bath. To the flask was added 489 grams (4.0 moles) of 
2,4-dimethylphenol. The flask was purged with nitrogen and anhydrous HCl 
was added until saturation, followed by 1 ml. of mercaptoacetic acid. With 
good agitation and continuous slow addition of HCl, the glutaraldehyde 
solution was added dropwise over three hours. A precipitate began to form 
after about 130 ml. of the solution had been added. The reaction mixture 
was allowed to stand at room temperature for 16 hours, then it was 
slurried in 1200 ml. of toluene, vacuum filtered and the precipitate 
re-slurried in 500 ml. of toluene, filtered and allowed to air dry. The 
resultant powder was washed four times with 500 ml. of distilled water, 
then two times with 250 ml. of toluene. The sample was dried in a vacuum 
desiccator (about 1 torr) to yield 242 grams (91%) of the desired 
1,1,5,5-tetra-(3,5-dimethyl-2-hydroxyphenyl)-pentane as a white powder 
(m.p. 236.degree.-242.degree. C.). 
The bis(cyclic carbonates) of this invention may be prepared by reacting 
the above-identified tetraphenols with phosgene, said reaction being 
another aspect of the invention. It is typically carried out at 
temperatures within the range of about 30.degree.-100.degree. C., 
preferably about 40.degree.-85.degree. C. 
In one embodiment of the invention, the reaction is conducted in solution 
in a substantially inert organic diluent such as methylene chloride, 
chloroform, benzene, toluene or xylene. A basic reagent, typically a 
tertiary amine such as pyridine or triethylamine, is usually incorporated 
in the reaction mixture as a hydrogen chloride scavenger. The phosgene is 
typically employed in about 10-25% excess of the 2:1 stoichiometric molar 
ratio, and the tertiary amine in an approximately stoichiometric amount 
with respect to liberated hydrogen chloride. 
Another embodiment employs an interfacial system analogous to those used 
for preparation of polycarbonates from bisphenols and phosgene. In such 
systems, there are present an aqueous phase and an organic phase 
substantially immiscible therewith. The aqueous phase is maintained 
strongly basic by the preence of an alkaline reagent such as sodium 
hydroxide. A catalyst, usually a tertiary amine such as triethylamine, is 
also generally present. The temperature and proportion of phosgene 
employed are typically within the ranges employed in the solution method 
and/or known in the art. Interfacial systems of this type are well known 
in the art and no detailed description thereof is deemed necessary. U.S. 
Pat. Nos. 4,384,108 and 4,471,105, for example, contain general 
disclosures of such systems and are incorporated by reference herein 
principally for said disclosures. 
The preparation of the bis(cyclic carbonates) of this invention is 
illustrated by the following examples. 
EXAMPLE 3 
A 2000-ml. four-neck flask was fitted with a mechanical stirrer, a gas 
inlet tube, a dry ice condenser which had its outlet connected through a 
drying tube to a caustic scrubber and an inlet tube about an inch long 
connected through polypropylene tubing to a liquid metering pump ("Lab 
Pump, Jr.", RHSY, Fluid Metering, Inc.) to which was connected an 
additional funnel. A solution of 74.5 grams (0.15 mole) of the tetraphenol 
of Example 1 and 55 ml. (0.68 mole) of pyridine diluted to a total volume 
of 300 ml. with methylene chloride was placed in the addition funnel. 1.25 
liters of methylene chloride was placed in the flask. With the flask in a 
10.degree. C. water bath, 34 grams (0.34 mole) of phosgene was added at 1 
gram/min. The bath was then warmed to 38.degree.-40.degree. C. and, with 
vigorous stirring, the tetraphenol solution was added dropwise over a 
period of 8 hours. The flask was then allowed to cool to room temperature 
and the reaction mixture allowed to stand 16 hours, during which time 
large crystals of pyridinium hydrochloride formed. The solution was 
decanted from the crystals, washed three times with 400 ml. of distilled 
water, dried over MgSO.sub.4 and filtered. The solvent was removed on a 
rotary evaporator to yield a white paste which was placed under a 0.5-torr 
vacuum for 16 hours to yield a hard, brittle solid. The solid was broken 
up and stirred with 60 ml. of toluene to yield a uniform slurry which upon 
vacuum filtration yielded a white powder. The powder was washed a second 
time with 60 ml. of toluene, then twice with 60 ml. of methanol, and dried 
under vacuum to yield 36 grams (44%) of the desired bis(cyclic carbonate) 
as a fine white powder (m.p. 269.degree.-276.degree. C.). 
EXAMPLE 4 
The apparatus was set up as in Example 3. A solution of 74.5 grams (0.15 
mole) of the tetraphenol of Example 1 and 55 ml. (0.68 mole) of pyridine 
diluted to a total volume of 200 ml. with methylene chloride was placed in 
the addition funnel. 1.25 liter of toluene was placed in the flask. With 
the flask in a 10.degree. C. water bath, 5 grams of phosgene was added at 
1 gram/min. The water bath temperature was then raised to 85.degree. C. 
and over a period of 60 minutes with vigorous stirring the solution was 
added dropwise with simultaneous addition of phosgene at 0.5 gram/min. (35 
grams, 0.35 mole total phosgene). A white precipitate formed during the 
addition. After allowing the reaction mixture to cool to room temperature 
and to stand 16 hours, the precipitate, which was a mixture of product and 
pyridinium hydrochloride, was collected by vacuum filtration and dried to 
a white powder under vacuum. (Removal of solvent from the filtrate on a 
rotary evaporator yields a viscous oil and no additional precipitate.) The 
powder was washed twice with 500 ml. of water, then once with 150 ml. of 
methanol, and dried under vacuum to yield 29 grams (35%) of the desired 
bis(cyclic carbonate) as a fine, white powder (m.p. 
260.degree.-277.degree. C.). 
EXAMPLE 5 
A 2000-ml. four-neck flask is fitted with a mechanical stirrer, a pH probe, 
a gas inlet tube and a Claisen adaptor to which is attached a dry ice 
condenser and an aqueous caustic inlet tube. To the flask is added 900 ml. 
of methylene chloride, 560 ml. of distilled water, 3.4 ml. of 
triethylamine, and a 11-gram (0.02 mole) portion of the tetraphenol of 
Example 2. Phosgene is introduced into the flask at 1 gram/min. for 50 
minutes, with simultaneous addition at 5-minute intervals of additional 
11-gram portions of the tetraphenol to a total of 50 grams (0.5 mole) of 
phosgene and 110 grams (0.2 mole) of tetraphenol. The pH is maintained at 
9-11 with addition of 25% aqueous NaOH. The methylene chloride layer is 
separated, washed once with 350 ml. of 3% aqueous HCl and three times with 
350 ml. of distilled water, dried over MgSO.sub.4, filtered and the 
solvent removed on a rotary evaporator to yield a solid residue. The solid 
is washed twice with 200-ml. portions of acetone, then recrystallized from 
toluene to yield the desired bis(cyclic carbonate) as a white powder (m.p. 
231.5.degree.-235.5.degree. C.). 
As previously mentioned, the bis(cyclic carbonates) of this invention are 
useful as crosslinking and anti-drip agents for polycarbonates. 
Accordingly, another aspect of the invention is a composition comprising a 
major proportion of at least one polycarbonate compound having a plurality 
of structural units of formula V, wherein A.sup.1 is a divalent aromatic 
radical, and a minor proportion of at least one bis(cyclic carbonate) as 
described hereinabove. 
In one embodiment of the invention, the polycarbonate compound is one of 
the aromatic polycarbonate resins known in the art. They are generally 
derived from dihydroxyaromatic compounds of which the following are 
examples: 
2,2-bis-(4-hydroxyphenyl)propane (bisphenol A) 
hydroquinone 
resorcinol 
2,2-bis-(4-hydroxyphenyl)pentane 
2,4'-dihydroxydiphenylmethane 
bis-(2-hydroxyphenyl)methane 
bis-(4-hydroxyphenyl)methane 
bis-(4-hydroxy-5-nitrophenyl)methane 
1,1-bis(4-hydroxyphenyl)ethane 
3,3-bis(4-hydroxyphenyl)pentane 
2,2-dihydroxybiphenyl 
2,6-dihydroxynaphthalene 
bis-(4-hydroxydiphenyl) sulfone 
bis-(3,5-diethyl-4-hydroxyphenyl) sulfone 
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane 
2,4'-dihydroxydiphenyl sulfone 
5 '-chloro-2,4'-dihydroxydiphenyl sulfone 
bis-(4-hydroxybiphenylyl) sulfone 
4,4'-dihydroxydiphenyl ether 
4,4'-dihydroxy-3,3'-dichlorodiphenyl ether 
4,4'-dihydroxy-2,5-dihydroxydiphenyl ether. 
Other dihydroxyaromatic compounds which are suitable for use in the 
preparation of aromatic polycarbonate resins are disclosed in U.S. Pat. 
Nos. 2,999,835, 3,038,365, 3,334,156 and 4,131,575. 
The A.sup.1 values preferably have formula VI, wherein each of A.sup.2 and 
A.sup.3 is a single-ring divalent aromatic radical and Y is a bridging 
radical in which one or two atoms separate A.sup.2 from A.sup.3. The free 
valence bonds in formula VI are usually in the meta or para positions of 
A.sup.2 and A.sup.3 in relation to Y. Such A.sup.1 values may be 
considered as being derived from bisphenols of the formula HO-A.sup.2 
-Y-A.sup.3 -OH. 
In formula VI, the A.sup.2 and A.sup.3 values may be unsubstituted 
phenylene or substituted derivatives thereof, illustrative substituents 
(one or more) being alkyl, alkenyl (e.g., crosslinkable-graftable moieties 
such as vinyl and allyl), halo (especially chloro and/or bromo), nitro, 
alkoxy and the like. Unsubstituted phenylene radicals are preferred. Both 
A.sup.2 and A.sup.3 are preferably p-phenylene, although both may be o- or 
m-phenylene or one o- or m-phenylene and the other p-phenylene. 
The bridging radical, Y, is one in which one or two atoms, preferably one, 
separate A.sup.2 from A.sup.3. It is most often a hydrocarbon radical and 
particularly a saturated radical such as methylene, cyclohexylmethylene, 
2-[2.2.1]-bicycloheptylmethylene, ethylene, isopropylidene, 
neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene 
or adamantylidene, especially a gem-alkylene radical. Also included, 
however, are unsaturated radicals and radicals which are entirely or 
partially composed of atoms other than carbon and hydrogen. Examples of 
such radicals are 2,2-dichloroethylidene, carbonyl, thio and sulfone. For 
reasons of availability and particular suitability for the purposes of 
this invention, the preferred radical of formula II is the 
2,2-bis(4-phenylene)propane radical, which is derived from bisphenol A and 
in which Y is 2,2-propylene and A.sup.2 and A.sup.3 are each p-phenylene. 
These aromatic polycarbonate resins can be manufactured by known processes, 
such as by reacting a dihydric phenol with a carbonate precursor such as 
phosgene, in accordance with methods set forth in the aforementioned 
patents and U.S. Pat. Nos. 4,018,750 and 4,123,426, or by 
transesterification process such as are disclosed in U.S. Pat. No. 
3,153,008, as well as other processes known to those skilled in the art. 
It is possible to employ two or more different dihydric phenols, a 
copolymer of a dihydric phenol with a glycol, a hydroxy- or 
acid-terminated polyester or a dibasic acid in the event a carbonate 
copolymer or interpolymer or polyester-polycarbonate rather than a 
carbonate homopolymer is desired for use in the preparation of the 
resinous compositions of this invention. Branched polycarbonates, such as 
those described in U.S. Pat. No. 4,001,184, are also useful. The 
disclosures of all of the aforementioned patents are incorporated by 
reference herein. Blends of any of the above materials may also be 
employed. 
Crosslinking according to the present invention may be carried out by 
reacting the bis(cyclic carbonate) with the aromatic polycarbonate in the 
melt form in the presence of catalytic quantities of a transesterification 
catalyst. One of the benefits of using a cyclic carbonate is that there 
should be significantly less fragmentation of the polycarbonate chain. The 
cyclic carbonate opens up, thus allowing addition at either side of the 
carbonate group. This allows for formation of structures of the type 
represented by formula VII, wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 
represent polycarbonate moieties of various chain lengths which may be 
derived from polycarbonates of the formulas R.sup.1 OCOOR.sup.2 and 
R.sup.3 OCOOR.sup.4. 
The amount of bis(cyclic carbonate) used will depend on the extent of 
crosslinking desired. In general, about 0.001-10 mole percent is used, 
based on polycarbonate structural units. 
The reaction temperature should be sufficiently high to create a melt of 
the reactants, generally in the range of about 200.degree.-350.degree. C. 
When a polycarbonate resin is employed, such temperatures are typically 
achieved in an extruder or a molding machine such as an injection or 
compression molder normally employed for extruding or molding such resins. 
The final physical form of the crosslinked polycarbonate is at least 
partially dependent upon the quantity of bis(cyclic carbonate) present. If 
desired, gel-like forms such as highly crosslinked thermoset materials can 
be avoided by utilizing relatively small quantities of the bis(cyclic 
carbonate). The gels occur when greater quantities of the bis(cyclic 
carbonate) are present. Also of significance are the reaction temperature 
and time. 
Also useful as polycarbonate compounds in the compositions of this 
invention are the cyclic polycarbonate oligomers. These are cyclic 
compounds containing a plurality of structural units of formula V. They 
include dimers, trimers and tetramers of the type disclosed in the 
following U.S. patents: 
______________________________________ 
3,155,683 
3,386,954 
3,274,214 
3,422,119. 
______________________________________ 
They also include cyclic polycarbonate oligomer mixtures of the type 
disclosed in copending, commonly owned application Ser. No. 704,122, filed 
Feb. 22, 1985, the disclosure of which is incorporated by reference 
herein. 
The cyclic oligomer mixtures consist essentially of oligomers having 
degrees of polymerization from 2 to about 30 and preferably to about 20, 
with a major proportion being up to about 12 and a still larger proportion 
up to about 15. Since they are mixtures, these compositions have 
relatively low melting points as compared to single compounds such as the 
corresponding cyclic trimer. The cyclic oligomer mixtures are generally 
liquid at temperatures above 300.degree. C. and most often at temperatures 
above 225.degree. C. 
The mixtures useful in this invention contain very low proportions of 
linear oligomers. In general, no more than about 10% by weight, and most 
often no more than about 5%, of such linear oligomers are present. The 
mixtures also contain low percentages (frequently less than 30% and 
preferably no higher than about 20%) of polymers (linear or cyclic) having 
a degree of polymerization greater than about 30. Such polymers are 
frequently identified hereinafter as "high polymer". These properties, 
coupled with the relatively low melting points and viscosities of the 
cyclic oligomer mixtures, contribute to their utility in the invention. 
These mixtures may be prepared by a condensation reaction involving 
bishaloformates having the formula A.sup.1 (OCOQ.sup.5).sub.2, wherein 
A.sup.1 is as defined hereinabove and Q.sup.5 is chlorine or bromine. The 
condensation reaction typically takes place interfacially when a solution 
of said bishaloformate in a substantially non-polar organic liquid is 
contacted with a tertiary amine from a specific class and an aqueous 
alkali metal hydroxide solution. 
In one method for preparing the cyclic oligomer mixture, at least one such 
bishaloformate is contacted with at least one oleophilic aliphatic or 
heterocyclic tertiary amine and an aqueous alkali metal hydroxide solution 
having a concentration of about 0.1-10 M, said contact being effected 
under conditions resulting in high dilution of bishaloformate, or the 
equivalent thereof, in a substantially non-polar organic liquid which 
forms a two-phase system with water; and subsequently, the resulting 
cyclic oligomer mixture is separated from at least a portion of the high 
polymer and insoluble material present. 
While the Q.sup.5 values may be chlorine or bromine, the bischloroformates, 
in which Q.sup.5 is chlorine, are most readily available and their use is 
therefore preferred. (Frequent reference to bischloroformates will be made 
hereinafter, but it should be understood that other bishaloformates may be 
substituted therefor as appropriate.) 
The tertiary amines useful in the preparation of the cyclic polycarbonate 
oligomers generally comprise those which are oleophilic (i.e., which are 
soluble in and highly active in organic media, especially those used in 
the oligomer preparation method of this invention), and more particularly 
those which are useful for the formation of polycarbonates. Reference is 
made, for example, to the tertiary amines disclosed in the aforementioned 
U.S. Pat. Nos. 4,217,438 and in 4,368,315, the disclosure of which is also 
incorporated by reference herein. They include aliphatic amines such as 
triethylamine, tri-n-propylamine, diethyl-n-propylamine and 
tri-n-butylamine and highly nucleophilic heterocyclic amines such as 
4-dimethylaminopyridine (which, for the purposes of this invention, 
contains only one active amine group). The preferred amines are those 
which dissolve preferentially in the organic phase of the reaction system; 
that is, for which the organic-aqueous partition coefficient is greater 
than 1. This is true because intimate contact between the amine and the 
bischloroformate is essential for the formation of the cyclic oligomer 
mixture. For the most part, such amines contain at least about 6 and 
preferably about 6-14 carbon atoms. 
The most useful amines are trialkylamines containing no branching on the 
carbon atoms in the 1- and 2-positions. Especially preferred are 
tri-n-alkylamines in which the alkyl groups contain up to about 4 carbon 
atoms. Triethylamine is most preferred by reason of its particular 
availability, low cost, and effectiveness in the preparation of products 
containing low percentages of linear oligomers and high polymers. 
The aqueous alkali metal hydroxide solution is most often lithium, sodium 
or potassium hydroxide, with sodium hydroxide being preferred because of 
its availability and relatively low cost. The concentration of said 
solution is about 0.2-10 M and preferably no higher than about 3 M. 
The fourth essential component in the cyclic oligomer preparation method is 
a substantially non-polar organic liquid which forms a two-phase system 
with water. The identity of the liquid is not critical, provided it 
possesses the stated properties. Illustrative liquids are aromatic 
hydrocarbons such as toluene and xylene; substituted aromatic hydrocarbons 
such as chlorobenzene, o-dichlorobenzene and nitrobenzene; chlorinated 
aliphatic hydrocarbons such as chloroform and methylene chloride; and 
mixtures of the foregoing with ethers such as tetrahydrofuran. 
To prepare the cyclic oligomer mixture according to the above-described 
method, the reagents and components are maintained in contact under 
conditions wherein the bischloroformate is present in high dilution, or 
equivalent conditions. Actual high dilution conditions, requiring a large 
proportion of organic liquid, may be employed but are usually not 
preferred for cost and convenience reasons. Instead, simulated high 
dilution conditions known to those skilled in the art may be employed. For 
example, in one embodiment of the method the bischloroformate or a mixture 
thereof with the amine is added gradually to a mixture of the other 
materials. It is within the scope of this embodiment to incorporate the 
amine in the mixture to which the bischloroformate is added, or to add it 
gradually, either in admixture with the amine or separately. Continuous or 
incremental addition of the amine is frequently preferred, whereupon the 
cyclic oligomer mixture is obtained in relatively pure form and in high 
yield. 
Although addition of the bischloroformate neat (i.e., without solvents) is 
within the scope of this embodiment, it is frequently inconvenient because 
many bischloroformates are solids. Therefore, it is preferably added as a 
solution in a portion of the organic liquid. The proportion of organic 
liquid used for this purpose is not critical; about 25-75% by weight, and 
especially about 40-60%, is preferred. 
The reaction temperature is generally in the range of about 
0.degree.-50.degree. C. It is most often about 0.degree.-40.degree. C. and 
preferably 20.degree.-40.degree. C. 
For maximization of the yield and purity of cyclic oligomers as opposed to 
high polymer and insoluble and/or interactable by-products, it is 
preferred to use not more than about 0.7 mole of bischloroformate per 
liter of organic liquid present in the reaction system, including any 
liquid used to dissolve said bischloroformate. Preferably, about 0.003-0.6 
mole of bischloroformate is used. It should be noted that this is not a 
molar concentration in the organic liquid when the bischloroformate is 
added gradually, since it is consumed as it is added to the reaction 
system. 
The molar proportions of the reagents constitute another important feature 
for yield and purity maximization. The preferred molar ratio of amine to 
bischloroformate is about 0.1-1.0:1 and most often about 0.2-0.6:1. The 
preferred molar ratio of alkali metal hydroxide to bischloroformate is 
about 1.5-3:1 and most often about 2-3:1. 
Step II of the cyclic oligomer preparation method is the separation of the 
oligomer mixture from at least a portion of the high polymer and insoluble 
material present. When other reagents are added to the alkali metal 
hydroxide and the preferred conditions and material proportions are 
otherwise employed, the cyclic oligomer mixture (obtained as a solution in 
the organic liquid) typically contains less than 30% by weight and 
frequently less than about 20% of high polymer and insoluble material. 
When all of the preferred conditions are employed, the product may contain 
10% or even less of such material. Depending on the intended use of the 
cyclic oligomer mixture, the separation step may then be unnecessary. 
Therefore, a highly preferred method for preparing the cyclic oligomer 
mixture comprises the single step of conducting the reaction using as the 
amine at least one aliphatic or heterocyclic tertiary amine which, under 
the reaction conditions, dissolves preferentially in the organic phase of 
the reaction system, and gradually adding bischloroformate, amine and 
alkali metal hydroxide simultaneously to a substantially non-polar organic 
liquid or a mixture of said liquid with water, said liquid or mixture 
being maintained at a temperature in the range of about 
0.degree.-50.degree. C.; the amount of bischloroformate used being up to 
about 0.7 mole for each liter of said organic liquid present in the 
reaction system, and the molar proportions of amine and alkali metal 
hydroxide to bischloroformate being 0.2-1.0:1 and 2-3:1, respectively; and 
recovering the cyclic oligomers thus formed. 
As in the embodiment previously described, another portion of said liquid 
may serve as a solvent for the bischloroformate. Addition of each reagent 
is preferably continuous, but may be incremental for any or all of said 
reagents. 
When a separation step is necessary, the unwanted impurities may be removed 
in the necessary amounts by conventional operations such as combining the 
solution with a non-solvent for said impurities. Illustrative non-solvents 
include ketones such as acetone and methyl isobutyl ketone and esters such 
as methyl acetate and ethyl acetate. Acetone is a particularly preferred 
non-solvent. Recovery of the cyclic oligomers normally means merely 
separating the same from diluent (by known methods such as vacuum 
evaporation) and, optionally, from high polymer and other impurities. 
The preparation of cyclic oligomer mixtures useful in this invention is 
illustrated by the following examples. All parts and percentages in the 
examples herein are by weight unless otherwise indicated. Temperatures are 
in degrees Celsius. Molecular weights, whenever referred to herein, are 
weight average unless otherwise indicated and were determined by gel 
permeation chromatography relative to polystyrene. 
EXAMPLES 6-23 
Bisphenol A bischloroformate was reacted with aqueous sodium hydroxide and 
triethylamine in an organic liquid (chloroform in Example 12, methylene 
chloride in all other examples) according to the following procedure: The 
bischloroformate was dissolved in half the amount of organic liquid 
employed and was added gradually, with slow stirring, to the balance of 
the reaction mixture. In Examples 6-15 and 17, the triethylamine was all 
originally present in the reaction vessel; in Examples 19-21, it was added 
gradually at the same time as the bischloroformates; and in Examples 16, 
18, 22 and 23, it was added incrementally at the beginning of 
bischloroformate addition and at intervals of 20% during said addition. 
The amount of sodium hydroxide used was 2.4 moles per mole of 
bischloroformate. After all the bischloroformate had been added, the 
mixture was stirred for about 2 minutes and the reaction was quenched by 
the addition of a slight excess of 1M aqueous hydrochloric acid. The 
solution in the organic liquid was washed twice with dilute aqueous 
hydrochloric acid, dried by filtration through phase separation paper and 
evaporated under vacuum. The residue was dissolved in tetrahydrofuran and 
high polymers were precipitated by addition of acetone. 
The reaction conditions for Examples 6-23 are listed in Table I together 
with the approximately percentage (by weight) of cyclic polycarbonate 
oligomer present in the product before high polymer precipitation. The 
weight average molecular weights of the cyclic oligomer mixtures were 
approximately 1300, corresponding to an average degree of polymerization 
of about 5.1. 
TABLE I 
__________________________________________________________________________ 
Bischloroformate 
Bischloroformate 
Molar ratio, Addition 
amt., mmole/l. 
amt., total 
NaOH amine: Temper- 
time, 
% oligomer 
Example 
org. liquid 
mmol. molarity 
bischloroformate 
ature 
min. in product 
__________________________________________________________________________ 
6 100 2 0.313 
0.5 20 30 97 
7 100 2 0.625 
0.5 20 30 95 
8 100 2 2.5 0.5 35 55 93 
9 100 2 2.5 0.5 0 30 77 
10 100 2 2.5 0.5 20 30 87 
11 100 2 2.5 0.5 35 30 78 
12 100 2 2.5 0.5 50 30 88 
13 100 2 2.5 0.25 20 30 74 
14 100 1 2.5 0.2 20 15 75 
15 200 4 2.5 0.5 20 30 88 
16 500 10 2.5 0.25 25 105 83 
17 500 10 2.5 0.25 25 105 78 
18 500 10 2.5 0.25 25 105 83 
19 500 10 2.5 0.25 25 105 87 
20 500 10 2.5 0.29 30 90 78 
21 500 10 2.5 0.25 30 20 75 
22 500 10 2.5 0.25 40-45 
105 79 
23 500 10 2.5 0.4 25 105 79 
__________________________________________________________________________ 
EXAMPLE 24 
Bisphenol A bischloroformate (2.0 mmol.) was reacted with aqueous sodium 
hydroxide and 4-dimethylaminopyridine in methylene chloride. The procedure 
employed was that of Example 6, except that 66.67 mmol. of bisphenol A per 
liter of methylene chloride was employed, the aqueous sodium hydroxide 
concentration was 5.0 M and the reaction temperature was about 25.degree. 
C. The product comprised 85% cyclic oligomer. 
The transesterification catalysts used in the reaction of the polycarbonate 
resin or oligomer with the bis(cyclic carbonate) may be any basic 
catalysts usually employed in such reactions. These include oxides, 
hydrides, hydroxides or amides of the alkali or alkaline earth metals as 
well as basic metal oxides such as zinc oxides, salts of weak acids such 
as lithium stearate and organotitanium, organoaluminum and organotin 
compounds such as tetraoctyl titanate, as well as the tetraphenylborate 
salts disclosed in copending, commonly owned application Ser. No. 723,672, 
filed Apr. 16, 1985 now U.S. Pat. No. 4,605,731 the disclosure of which is 
incorporated by reference herein. Because of potential steric hindrance, 
it is preferred to use catalysts with less bulky groups, e.g. lithium 
stearate as opposed to tetraoctyl titanate. 
The preparation of the polycarbonate compositions of this invention is 
illustrated by the following examples. Molar proportions are based on 
polycarbonate structural units. 
EXAMPLE 25 
2.5 grams (0.01 mole) of bisphenol A polycarbonate powder (intrinsic 
viscosity of 0.49-0.52 in methylene chloride at 25.degree. C.) was 
combined with 10.sup.-5 mole of tetraoctyl titanate (TOT) or lithium 
stearate (LiST) catalyst (0.1 mole percent) and 2 or 5 mole percent of 
bis(cyclic carbonate) at 300.degree. C. under N.sup.2 for a period of 
twenty minutes with thorough stirring of the melt. The quantity of gel was 
determined by swelling the resin thus produced with methylene chloride, 
filtering and washing with additional methylene chloride. The results are 
shown in Table II. 
TABLE II 
______________________________________ 
Bis(cyclic carbonate) Percent gel 
Example Quantity, mole % TOT LiST 
______________________________________ 
3 2 23 25 
3 5 57 47 
5 2 5 25 
5 5 4 52 
______________________________________ 
In addition to these samples, five separate controls were run at the same 
time and temperature: bisphenol A polycarbonate alone and in combination 
with tetraoctyl titanate, lithium stearate, the Example 3 bis(cyclic 
carbonate) and the Example 5 bis(cyclic carbonate). No gels were formed 
with any of the control formulations. 
EXAMPLE 26 
A solid mixture of 25 parts of a cyclic bisphenol A polycarbonate oligomer 
mixture similar to that of Example 6, 3 parts of the bis(cyclic carbonate) 
of Example 3 and 0.1 mole percent of the bisisopropoxyaluminum salt of 
ethyl acetoacetate was heated for 4 hours at 250.degree. C., under 
nitrogen. The crosslinked polymer thus obtained was weighed and the 
unreacted polycarbonate was removed therefrom by extraction with methylene 
chloride for 48 hours in a Soxhlet extractor. The crosslinked residue was 
dried under vacuum at 75.degree. C. for 12 hours and weighed. It was found 
to comprise 46.5% of the total polycarbonate obtained. 
EXAMPLE 27 
The procedure of Example 26 was repeated, except that the polymerization 
catalyst was tetramethylammonium tetraphenylborate. The crosslinked 
product comprised 99.7% of the total polymer. 
The bis(cyclic carbonates) of this invention are also useful as anti-drip 
agents for polycarbonate resins, especially when used in combination with 
known flame retardant agents. Accordingly, another aspect of the invention 
is a polycarbonate resin composition which, in addition to the bis(cyclic 
carbonate), also contains an effective amount of at least one such flame 
retardant agent. The flame retardant agents are conventional that 
positively upgrade the flame retardancy of polycarbonates. 
Some particularly useful flame retardants are the alkali and alkaline earth 
metal salts of organic sulfonic acids. These types of flame retardants are 
disclosed, for example, in the following U.S. patents, all of which are 
hereby incorporated by reference: 
______________________________________ 
3,775,367 3,926,908 
3,951,810 
3,836,490 3,931,100 
3,953,396 
3,909,490 3,933,734 
3,953,399 
3,917,559 3,940,366 
3,978,024. 
3,919,167 3,948,851 
______________________________________ 
They include sodium 2,4,5-trichlorobenzenesulfonate, sodium 
benzenesulfonate, disodium naphthalene-2,6-disulfonate, sodium 
p-iodobenzenesulfonate, sodium 4,4'-dibromobiphenyl-3-sulfonate, sodium 
2,3,4,5,6-pentachloro-.beta.-styrenesulfonate, sodium 
4,4'-(dichlorodiphenyl sulfide)-3-sulfonate, disodium (tetrachlorodiphenyl 
ether) disulfonate, disodium 4,4'-dichlorobenzophenone-3,3'-disulfonate, 
sodium 2,5-dichlorothiophene-3-sulfonate, sodium 
diphenylsulfone-3-sulfonate, sodium dimethyl 
2,4,6-trichloro-5-sulfoisophthalate, potassium 
2,4,5-trichlorobenzenesulfonate, calcium 
2,4,5-trichlorobenzenesulfonanilide-4'-sulfonate, sodium 
4'-(1,4,-5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-en-endo-2-yl)-benzenesulfo 
nate and sodium perfluoroalkylsulfonate wherein alkyl is butyl or octyl. 
Conventional flame retardants other than the aforementioned sulfonates may 
also be employed. These conventional flame retardant additives generally 
contain a halogen, preferably chlorine and/or bromine. That is to say, 
they are a halogen source. They may be inorganic or organic. Typical of 
the inorganic halogen sources are NaCl, KBr, etc. The organic halogen 
sources are preferably aromatic although certain aliphatic compounds are 
also useful. They include disodium hexafluoroglutarate, disodium 
chloranilate, the halodiphenyl ethers such as tetrabromodiphenyl ether, 
polycarbonates derived from tetrabromobisphenol A and carbonate copolymers 
derived from tetrabromobisphenol A and bisphenol A. 
These flame retardant additives are present in the instant compositions in 
a flame retardant amount. By flame retardant amount is meant an amount 
effective to render said compositions flame retardant. Generally this 
amount is about 0.01-10 weight percent of flame retardant or of halogen in 
a halogenated flame retardant, based on the total weight of the 
composition. About 0.1-5 weight percent is preferred. The bis(cyclic 
carbonates) are present in an anti-drip amount which is usually about 
0.1-5.0% by weight. 
The compositions of this invention may also contain other commonly known 
and used additives. These include ultraviolet radiation absorbers such as 
the benzophenones, benzotriazoles, cyanoacrylates, 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; and color stabilizers such as the 
organophosphites disclosed in U.S. Pat. Nos. 3,305,520 and 4,118,370. The 
disclosures of all of the foregoing are incorporated by reference herein. 
The preparation of the flame-retardant resin compositions of the present 
invention is illustrated by the following examples. 
EXAMPLES 28-29 
The blends listed in Table III were prepared by extrusion at 265.degree. C. 
followed by comminution of the extrudate into pellets. 
TABLE III 
__________________________________________________________________________ 
Parts by weight 
Example 
Example 
Control 
Control 
Control 
Control 
Ingredient 28 29 1 2 3 4 
__________________________________________________________________________ 
Bisphenol A polycarbonate similar 
100 976.8 
100 100 100 976.8 
to that of Example 25 
Copolycarbonate of 1,1-bis(4-hydroxyphenyl)- 
-- 232.2 
-- -- -- 232.2 
propane and 1,1-bis(3,5-dibromo-4- 
hydroxyphenyl)propane, containing 4.2% Br 
Sodium 2,4,5-trichlorobenzenesulfonate 
0.6 -- -- 0.6 0.6 -- 
Lithium hydroxide 0.00055 
-- -- -- 0.00055 
-- 
Bis(cyclic carbonate) of Example 3 
1.1 -- -- -- -- -- 
Bis(cyclic carbonate) of Example 5 
-- 1.72 
-- -- -- -- 
__________________________________________________________________________ 
The blends were injection molded at about 315.degree. C. into test bars 
which were subjected to the test procedure described in Underwriters 
Laboratories Bulletin 94. In accordance with this test procedure, the 
materials were rated V-O, V-I or V-II based on the burning properties of 
five specimens. The criteria for each rating was as follows. 
V-O: Average flaming and/or glowing after removal of the igniting flame 
shall not exceed 5 seconds, and none of the specimens shall drip particles 
which ignite absorbent cotton. 
V-I: Average flaming and/or glowing after removal of the igniting flame 
shall not exceed 25 seconds and none of the specimens shall drip particles 
which ignite absorbent cotton. 
V-II: Average flame and/or glowing after removal of the igniting flame 
shall not exceed 25 seconds and the specimens drip flaming particles which 
ignite absorbent cotton. 
UL-94 requires that all test parts must meet the V type rating to achieve 
the particular rating. Otherwise, the 5 bars receive the rating of the 
worst single bar. For example, if one bar is classified as UL-94 V-II and 
the other four (4) are classified as UL-94 V-O, then the rating for all 5 
bars is UL-94 V-II. In addition, a test bar which continued to burn for 
more than 25 seconds after removal of the igniting flame was classified, 
not by UL-94 but by the standards of the instant invention, as "burning". 
The results are shown in Table IV. 
TABLE IV 
______________________________________ 
Example Flammability rating 
______________________________________ 
28 V-O 
29 V-O 
Control 1 Burns 
Control 2 V-II 
Control 3 V-II 
Control 4 V-II 
______________________________________ 
As illustrated by these data, the examples containing a flame retardant 
additive but no bis(cyclic carbonate) inhibit a certain degree of flame 
retardance but nevertheless also exhibit dripping. On the other hand, when 
the bis(cyclic carbonate) of this invention is used in conjunction with 
the flame retardant additives, they exhibit drip retardant 
characteristics. 
EXAMPLE 30 
To 100 parts by weight of the polycarbonate of Examples 28-29 was added 0.6 
parts of sodium 2,4,5-trichlorobenzenesulfonate. The mixture was extruded, 
molded into test bars and tested in the same manner as Examples 28-29. 
Each of the five test bars had at least one flaming drip and had an 
average flame-out time of 3.9 seconds and a range of flame-out times of 
1.2 to 11.6 seconds. 
EXAMPLE 31 
To the composition of Example 30 prior to extrusion was added 1.1% of the 
bis(cyclic carbonate) of Example 3. Only three of the five test bars had 
at least one flaming drip. The average flame-out time was 1.9 seconds with 
a range of flame-out times from 0.1 to 4.3 seconds.