Method for making cyclic carbonates and polymers therefrom

A method is provided for making cyclic carbonates of 2,2-bis(4-hydroxyphenyl)-1,1-dichloroethylene, such as the cyclic trimer, by effecting the polymerization of the aforementioned bis(4-hydroxyphenyl)dichloroethylene to a linear polycarbonate, and then agitating a solution of the resulting polycarbonate in the presence of a tertiary organic amine. The cyclic carbonates made by the aforementioned process are useful as flame retardants in polycarbonates.

The present invention relates to a method for making cyclic carbonates from 
2,2-bis(4-hydroxyphenyl)-1,1-dichloroethylene by initially forming a 
linear polycarbonate and thereafter converting the resulting polymer in 
the presence of a tertiary organic amine to the cyclic state. 
The cyclic carbonates made in accordance with the method of the present 
invention have the formula, 
##STR1## 
where n is an integer equal to 3 or 4. The cyclic carbonates of formula 
(1) can be employed as flame retardants when incorporated into 
thermoplastic organic polymers, such as Lexan polycarbonate, Valox 
polyester, which are thermoplastics manufactured by the General Electric 
Company, high impact polystyrene, etc. The cyclic carbonates of formula 
(1) can be made by phosgenating a mixture of a bisphenol of the formula, 
##STR2## 
water, organic solvent, sodium hydroxide and a tertiary organic amine. 
Phosgenation of a bisphenol of formula (2) is shown by Z. Wielgosz and S. 
Porejko, "Synthesis and Properties of Polycarbonates from 
Chlorobisphenols", Polimery-Tworzywa Wielkoczasteczkowe, 1971, pages 
495-500. I have found that in instances where a bisphenol of formula (2) 
was phosgenated in an aqueous basic medium containing an organic solvent 
and a tertiary organic amine to produce cyclic carbonates of formula (1), 
a relatively low yield of cyclic carbonate, such as 18%, is obtained. 
Cyclic carbonates of bisphenol-A, also can be made directly from 
bisphenol-A by phosgenation procedures, such as shown in U.S. Pat. Nos. 
3,155,683 and 3,211,025. 
The present invention is based on the discovery that cyclic carbonates of 
formula (1) can be made in yields as high as 95% or greater by initially 
phosgenating bisphenols of formula (2) in the presence of an aqueous 
alkali hydroxide and a tertiary amine catalyst to produce linear 
polycarbonate, effecting the removal of the aqueous phase from the 
resulting reaction mixture and thereafter agitating the organic phase in 
the presence of tertiary organic amine catalyst. 
In the practice of the invention, there is provided a method for making 
cyclic carbonates of formula (1) which comprises 
(A) phosgenating a mixture of a bisphenol of formula (2), an organic 
solvent, water and a tertiary organic amine catalyst to produce a 
polycarbonate, 
(B) effecting the removal of the aqueous layer from the mixture of (A), 
(c) agitating the organic phase remaining from (B) in the presence of an 
effective amount of a tertiary organic amine, and 
(D) removing cyclic carbonate of formula (1) from the mixture of (C). 
Included by the tertiary organic amines which can be employed in the method 
of the practice of the present invention are, for example, triethylamine, 
N-methyl piperidine, lutedine, diisopropylethylamine, pyridine, 
tributylamine, etc. Included by the organic solvents which can be used in 
the practice of the present invention are, for example, methylene 
chloride, chloroform, tetrahydrofuran, chlorobenzene, dioxane, 
dichlorobenzene, trichloroethylene, etc. Some of the alkali metal 
hydroxides which can be used in the practice of the method of the present 
invention are, for example, sodium hydroxide, potassium hydroxide, calcium 
hydroxide, etc. 
In the practice of the invention, the cyclic carbonates of formula (1) can 
be made by initially polymerizing the bisphenol of formula (2) to 
polycarbonate and thereafter agitating an organic solvent solution of the 
polycarbonate in the presence of a tertiary organic amine catalyst. During 
phosgenation, the mixture is agitated and agitation can be continued after 
the phosgenation has been completed. The mixture is allowed to settle and 
the organic phase is recovered. The organic phase is then agitated at a 
temperature in the range of 0.degree. C. to 200.degree. C. while 
maintaining an effective amount, such as 0.1 to 10%, of tertiary organic 
amine in the mixture. After the mixture has been agitated sufficiently, 
cyclic trimer can be separated from the mixture by filtration, where the 
amount of trimer formed is dependent on time and temperature to effect the 
separation of the cyclic. In instances where cyclic tetramer recovery is 
desired, the reaction mixture can be filtered, poured into a C.sub.(5-15) 
hydrocarbon solvent, such as hexane, followed by filtering the hydrocarbon 
phase and stripping the hydrocarbon solvent containing the cyclic tetramer 
therefrom. A molecular sieve can be used to facilitate drying. 
Phosgenation of the mixture of the bisphenol of formula (1) can be 
performed at a temperature in the range of from 25.degree. C. to 
75.degree. C. There can be employed from 20 to 50% by weight of alkali 
hydroxide, or 0.5 to 5% of tertiary organic amine, based on the weight of 
the mixture. 
The cyclic carbonates made in accordance with the practice of the present 
invention can be employed as intermediates for making polycarbonate 
substantially free of impurities normally associated with such 
polycarbonate made by direct phosgenation from the bisphenol of formula 
(2). In addition, the cyclic carbonates can be employed as flame 
retardants when used with bisphenol-A polycarbonates at from 5 to 30% by 
weight of cyclic carbonates, based on the total weight of the cylic 
carbonate-polycarbonate blend.

In order that those skilled in the art will be better able to practice the 
invention, the following examples are given by way of illustration and not 
by way of limitation. All parts are by weight. 
EXAMPLE 1 
A mixture of 1,1-bis(4-hydroxyphenyl)-2,2-dichloroethylene, 0.05 parts 
triethylamine, 12 parts of methylene chloride and 1 part of sodium 
hydroxide pellets was phosgenated over a period of 20 minutes while the 
mixture was stirred at a temperature of 25.degree.-35.degree. C. The 
phosgene addition was terminated and the mixture was stirred for an 
additional 5 minutes. The mixture was then acidified, washed twice with 
water, then poured into 50 parts of methanol to produce 1.1 part of 
polycarbonate which represented a yield of 92%. 
A mixture of 0.5 part of the above polycarbonate, 13 parts of methylene 
chloride and 0.1 part of triethylamine was stirred for 66 hours under 
nitrogen and under ambient conditions. A white precipitate formed and the 
mixture was filtered under vacuo. A precipitate was washed with methylene 
chloride and ether and dried under reduced pressure at 100.degree. C. to 
provide 0.48 part of product, representing a yield of 97%. Based on its IR 
spectrum and further confirmed by NMR, GPC and MS the product was the 
cyclic trimer of formula (1). 
EXAMPLE 2 
In accordance with the procedure of Example 1, several tertiary organic 
amines were employed at different concentrations and methylene chloride 
solutions of the polycarbonate of Example 1. The following results were 
obtained, where "Polycarbonate" indicates the parts of polycarbonate 
employed in the mixture, "& Solids" indicates the total content of the 
solids in the mixture, "Organic Amine" indicates the percent by weight of 
the tertiary organic amine employed in the mixture, "Time" indicates the 
time in hours the mixture was stirred under ambient conditions and "Yield" 
indicates the percent by weight of cyclic trimer recovered from the 
mixture. 
______________________________________ 
Poly- Organic 
carbonate 
% Solids Amine Time Yield 
______________________________________ 
4 17 2,2,6,6,N- 40 38% 
pentamethyl- 
piperidine (20) 
0.5 5 (C.sub.2 H.sub.5).sub.3 N (20) 
66 98% 
50 5 (C.sub.2 H.sub.5).sub.3 N (20) 
16 99% 
120 8 (C.sub.2 H.sub.5).sub.3 N (20) 
16 96% 
2 5 (C.sub.2 H.sub.5).sub.3 N (20) 
16 91% 
______________________________________ 
The above results show that solids concentration has a significant effect 
on yield of cyclic trimer. 
EXAMPLE 3 
Polycarbonate of the bisphenol of formula (2) was prepared in accordance 
with the procedure of Example 1. The polycarbonate was dissovled in 100 
parts by weight of dichlorobenzene, and 0.5 parts 
2,2,6,6,N,-pentamethylpiperdine added. The mixture was then refluxed to a 
temperature of up to 180.degree. C., resulting in the production of 
dichlorobenzene solution of various polycarbonates. The mixture was 
allowed to cool to ambient temperatures. It was then poured into hexane, 
and thereafter filtered. The filtrate was evaporated to dryness to provide 
a 60% yield of a cyclic. Based on its IR, NMR and MS spectra, the cyclic 
was the tetramer of formula (1), as shown by the formula, 
##STR3## 
EXAMPLE 4 
A mixture consisting of 10 parts of the cyclic trimer of formula (1), 0.174 
part of p-cumylphenylcarbonate, 0.78 part of 
2,2,6,6,N-pentamethylpiperdine and 130 parts of o-dichlorobenzene was 
heated to reflux with stirring under nitrogen for 1 hour. Complete 
solution of the mixture occurred and it was heated for an additional 3 
hours with stirring and thereafter allowed to cool to room temperature. 
The mixture was then extracted three times with about 500 parts of a 1% 
aqueous HCl solution, followed by three times with distilled water. The 
solution was filtered, then precipitated by pouring it into excess 
methanol. There was obtained a stringy product which was dried at 
100.degree. C. for 2 hours, then dissolved in methlene chloride, then 
filtered and reprecipitated. After being dried for 24 hours at 60.degree. 
C., there was obtained 9.3 parts or a 93% yield of a white stringy 
product. Based on method of preparation, the product was a polycarbonate 
and it had an intrinsic viscosity of 0.43, M.sub.n = 18,270, M.sub.w = 
73,100, M.sub.w /M.sub.n = 4. The above procedure was repeated, except 
that 0.01 part of cyclic tetramer was employed in ortho-dichlorobenzene 
and the mixture heated to 100.degree. C. After 2 hours, the gel permiation 
chromatograph (GPC) showed the presence of a high molecular weight polymer 
having M.sub.n of about 25,000 and the disappearance of the cyclic 
tetramer. The high molecular weight polymer consisted essentially of 
chemically combined units of the formula, 
##STR4## 
EXAMPLE 5 
A mixture of 2.0 part of polycarbonate of Example 1, 40 parts of methylene 
chloride and 0.5 part of triethylamine was allowed to stir for 18 hours 
under ambient conditions. A copious white precipitate formed and the 
mixture was filtered under reduced pressure. The precipitate was washed 
with methylene chloride, followed by ether and dried in vacuo at 
70.degree. C. There was obtained 1.82 parts or 91% yield of the cyclic 
trimer included by formula (1). The identity of the trimer was confirmed 
by its IR, NRM, GPC and MS spectra. 
In addition to example 4, polycarbonates consisting essentially of 
chemically combined units of the formula, 
##STR5## 
can be made by agitating a mixture of cyclic carbonate of formula (1) and 
an organic solvent in the presence of an effective amount of a tertiary 
organic amine and from about 1 to 10 mol percent based on total moles of 
carbonate units in the mixture of a C.sub.(6-20) aryl carbonate, at a 
temperature in the range of from 0.degree. C. to 300.degree. C. 
As shown in copending applications RD-9080 of Keith N. Sannes, and my 
copending application RD-9987, both applications being filed concurrently 
herewith and assigned to the same assignee as the present invention, 
cyclic trimers and higher cyclics are described respectively as well as 
methods for making such materials. 
Although the above examples are directed to only a few of the very many 
variables which can be employed in the practice of the method of the 
present invention, it should be understood that a mcuh broader variety of 
organic solvents and tertiary organic amines can be utilized to produce 
cyclopolycarbonates, as shown by formula (1).