CA1238914A - Cyclic polycarbonate of thiol analog oligomers - Google Patents

Abstract

CYCLIC POLYCARBONATE OR
THIOL ANALOG OLIGOMERS

ABSTRACT OF TIE DISCLOSURE

Cyclic polycarbonate (or thiol analog) oligomer mixtures are prepared by the reaction of bishaloformates or their thio analogs or mixtures thereof with dihydroxy or dimercapto compounds, with alkali metal hydroxides and various amines. The oligomer mixtures may be converted to polycarbonates or their thio analogs by a method which is particularly adaptable to integration with polycarbonate processing operations.

Description

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CYCLIC POLYCARBONATE OF
_ THIOL ANALOG OLIGO~lERS

This invention relates to compositions of matter useful in the preparation of high molecular weight resins such as polycarbonates, and to methods for their preparation and use.
Polycarbonates are typically produced by the reaction of bisphenols with phosgene. This reaction is normally conducted interfacially; that is, in a mixed aqueous-organic system which results in recovery of the polycarbonate in the organic phase. Before the polycarbonate can be extruded, molded or otherwise worked, it must be freed of organic solvent and traces of water and by-products. It is then normally obtained as a solid which must be subjected to relatively cumbersome, high-temperature processing techniques.
Another method of preparing polycarbonates is by transesterification with a bisphenol of a carbonate ester such as diphenyl carbonate or a bis-polyfluoroalkyl carbonate. This method is similar to the phosgene method in the necessity for separation from the product of by-products, many of which are relatively volatile, before processing is possible.
The preparation of low molecular weight cyclic aromatic carbonate polymers and their conversion to , 3~

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linear polycarbonates are known. Reference is made, for example, to the following U.S. Patents:- 3,155,683 Lo S. Moody issued November 3, 1964; 3,386,954 H. Sehnell et al issued June 4, 1968, 3,274,214 R. J. Prochaska issued September 20, 1968; 3,422,119 R. J. Prochaska issued January 14, 1969.
The cyclic polymers disclosed therein, however, are single compounds having melting points which are generally too high to permit their convenient use as polycarbonate precursors. For example, the cyclic bisphenol A carbonate trimer disclosed in Example 2 of the aforementioned U.S. Patent 3,274,214 melts at 335-340C, with polymerization.
According to U.S. Patent 4,299,948 K. Weirauch et al issued November 10, 1981, cyclic polycarbonates of high molecular weight (15,000 or akove) may be prepared rom a bisphenol bischloroformate in the presenee of triethylamin~ as eatalyst. However, this eyclie produet is a final polymer which cannot conveniently be used as an intermediate for the production of linear poly-carbonates because of its high viscosity A principal objeet of the present invention, therefore, is to provide eonvenient intermediates for the preparation of polycarbonate resins and their thiol analogs.
Another object is to provide intermediates which are easily prepared and have properties which enable them to be used in integrated resin preparation-processing methods.
further objeet is to provide a method for preparation of such intermediates.
A further objeet is to provide novel polyearbonates and thiol analogs thereof, as well as methods for their preparation.

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A still further object is to prepare articles comprising very high molecular weight polycarbonates.
A still rurther object is to provide a method for preparing resins, said method being capable of integration with processing operations thereon.
Other objects will in part be obvious and will in part appear hereinafter.
In one of its embodiments, the present invention is directed to compositions consisting essentially of mixtures of cyclic oligomers having degrees of polymer-ization from 2 to about 30, the structural units in said oligomers having the formula (I) _yl -R-Y -C-wherein each R .is independently a divalent ali.phatic, alicyclic or aromatic radical and each yl is independently oxygen or sulfur.
Before proceeding with a detailed discussion of the invention, it may be useful to explain some terms used herein. The term "thiol analog", when used with reference to dihydroxy compounds, oligomers and poly-carbonates, includes monothio and dithio compounds in which the carbon-sulfur bonds are single bonds only. The terms "resin" and " resinous composition" include poly-carbonates and their thiol analogs.
As will be apparsnt from the above, the cyclic oligomer mixtures of this invention may contain organic carbonate, thi~lc~rl~xlat~ and/o~ dithiolcarbonate units.
The various R values therein may be different but are usually the same, and may be aliphatic, alicyclic, aromatic or mixed; those which are aliphatic or ~;~3~9~ RD-15514 alicyclic generally contain up to about 8 carbon atoms.
Suitable R values include ethylene, propylene, tri-methylene, tetramethylene, hexamethylene, dodecamethylene, poly-l, 4-(2-butenylene), poly-1,-10-(2-ethyldecylene), 1,3-cyclopentylene, 1,3-cyclohexylene, 1,4-cyclohexylene, m-phenylene, p-phenylene, 4,4'-diphenylene,

2,2-bis(4-hydroxyphenylene)propane, benzene-l, 4-dimethylene (which is a vinylog of the ethylene radical and has similar properties) and similar radicals such as those which correspond to the dihydroxy compo~mds disclosed by name or formula (generic or specific) in U.S. Patent 4,217,438 srunelle et al issued August 12, 1980. The values are usually aromatic and preferably have the formula (II) ~Al~Y2-A2-wherein each of l and A2 is a single-ring divalent aromatic radical and y2 is a bridging radical in which one or two atoms separate Al from A2. The free valence bonds in for[nula II are usually in the meta or para positions of Al and A2 in relation to y2~
In formula II, the A and A values may be unsubstituted phenylene or substituted derivatives thereof, illustrative substituents (one or more) heing 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 and A 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, y2/ is one in which one or 35 two atoms, preferably one, separate A from A . It is ~8~

most often a hydrocarbon radical and particularly a saturated radical such as methylene, cyclohexylmethylene, 2-[2.2.1]- bicycloheptylmethylene, ethylene, 2,2-propylene, 1,1-(2,2-dimethylpropylene), l,l-cyclohexylene, 1,1-cyclopentadecylene, l,l-cyclododecylene or 2,2-adamantylene, 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 Aand in which y2 is isopropylidene and Al and A are each p phenylene.
As noted, each yl value is independently oxygen or sulfur. Yost often, all yl values are oxygen and the corresponding compositions are cyclic polycarbonate oligomer mixtures.
The cyclic oligomer mixtures consist essentially of oligomers having degrees of polymer-ization 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 300C and preferably at temperatures above 225C.
It has been discovered that the cyclic oligomer mixtures of 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 abou-t 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 mlxtures, contribute to their uti.lity as resin precursors, especially for high molecular weight resins, as described hereinafter.
The cyclic oligomer mixtures of this invention may be prepared by a condensation reaction involving at least one compound selected from the group consisting of bishaloformates and thiol analogs thereof, said compounds having the formula (III) R(.Y COXl2 , wherein R and yl are as defined hereinabove and X is chlorine or bromine. The condensation reaction typically takes place interfacially when a solution of said compound in a substantially non-polar organic diluent is contacted with a tertiary amine from a specific class and an aqueous alkali metal hydroxide solution.
Accordi.ngly, another embodiment of the present invention is a method for preparing a composition comprising cyclic polycarbonate or thiol analog oligomers which comprises the steps of:
I. contacting (A)(l) at least one compound having formula III, or a mixture thereof with (2) at least one difunctional compound having the formula (IVY R(Y H)2 wherein each Y3 is independently sulfur when the cor-responding R is aliphatic or alicyclic and oxygen or I: , ~38~

sulfur when the corresponding R is aromatic, with (B) at least one oleophilic aliphatic or hetero-cyclic tertiary amine and (C) an aqueous alkali metal hydroxide solution having a concentration of about 0.1-10 M;
said contact being effected under conditions of high dilution of reagent A in a substantially non-polar organic diluent which forms a two-phase system with water, and subsequently II. separating the resulting cyclic oligomer mixture from at least a portion of the high polymer and insoluble material present.
While the X values in formula III may be chlorine or bromine, the compounds in which X is chlorine are most readily available and their use is therefore preferred.
Suitable difunctional compounds of formula IV include diols and thiol analogs thereof having divalent radicals of formula II which are different from the correspondiny di~alent radicals in reagent A-l, as well as other dihydroxyaromatic compounds and thiol analogs thereof.
When such difunctional compounds are present, they generally comprise up to about 50%, most often up to about 20% and preferably up to about 10%t of reagent A.
Most preferably, however, reagent A consists essentially of at least one and most desirably only one bishalo-formate. Any oligomers containing divalent aliphatic radicals tor their vinylogs) flanked by two oxygen atoms are prepared by using a mixture of bishaloformates; that is, a mixture of compounds identifiable as reagent A-l.
The tertiary amines useful as reagent B ("tertiary"
in this context denoting the absence of N-H bonds) 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 ~3~

useful for the formation of polycarbonates. Reference is made, for example, to the ter-tiary amines disclosed in the aforementioned U.S. Patent 4,217,438 and in U.S.
Patent 4,368,315 - Sikdar issued January 11, 1983. They include aliphatic amines such as triethylamine, tri-n-propylamine, dlethyl-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 reagent 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 earbon atoms.
The amines most useful as reayent B are trialkyl-amines containiny no branehing on the carbon atoms in the l- and 2- positions. Preferred are tri-n-alkylamines in which the alkyl yroups eontain up to about 4 carbon atoms.
Triethylamine is most preferred by reason of its particular availability, low eost, and effectiveness in the preparation of produets eontaining low pereentages of linear oligomers and high polymers Reagent C is an aqueous alkali metal hydroxide solution. It is most often lithium, sodium or potassium hydroxide, with sodium hydroxide being preferred beeause of its availability and relatively low cost. The coneentration of said solution is about 0.2-10 M and preferably no higher than about 3 M.
The fourth essential component in the eyelic oligomer preparation method of this invention is a substantially non-polar organic diluent which forms a two-phase system with water. The identity of the diluent ~2~

_ g is not critical, provided it possesses the stated properties. Illustrative diluents are aromatic hydro-carbon such as toluene and xylene; subs-tituted 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, in step I
of the above-described method the reagents and components are reacted under conditions of high dilution of reagent A. In a preferred embodiment, reagent A or reagents A
and B are added gradually to a mixture of the other materials. It is within the scope of this embodiment to incorporate reagent B in the mixture to which reagent A
is added, or to add it gradually, either in admixture with reagent A or separately. Gradual or incremental additicn of reagent B is frequently preferred, whereupon the cyclic oligomer mixture is obtained in relatively pure form and in high yield.
Although addition of reagent A alone is within the scope of this embodiment, it is frequently inconvenient because many bischlorofor~ates are solids. Therefore, it is preferably added as a solution in a portion of the organic diluent, especially when it consists entirely of reagent A-l. The proportion of diluent 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 0-50C. It is most often about 0-40C and preferably 20-40 C.
For maximization of the yield and purity of cyclic oligomers as opposed to high polymer and insoluble and/or intractable by-products, it is preferred to use not more than about 0.7 mole of reagent A per liter or organic diluent present in the reaction system, including any diluen-t used to dissolve reagent A. Preferably, about 0.003-0.6 mole of reagent A is used when it consists entirely of reagent A-l, and no more than about 0.5 mole when it is a mixture of reagents A-l and A-2. It should be noted that this is not a molar concentration of reagent A in the organic diluent when that reagent 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 reagent B to reagent A is about 0.1-1.0:1 and most often about 0.2-0.6:1. The preferred ratio of reagent C to reagent A is about 2-3:1 and most often about 2.0-2~5:1.
Step II of the cyclic oli~omer preparation method is the separation oE the oligomer mixture from at least a portion oE the high polymer and insoluble material present. When the preferred conditions and material proportions are employed, the cyclic oligomer mixture (obtained as a solution in the organic diluent) typically contains less than 30% by weight of high polymer and insoluble material, frequently less than about 20~ and preferably less than about 15~ thereof. 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 reagent B at least one aliphatic or - heterocyclic tertiary amine which, under the reaction conditions, dissolves preferentially in the organic phase ox the reaction system, and conducting said reaction by gradually adding reagent A or reagents A and B to a mixture of the other materials, said mixture being maintained at a temperature in the range of about 0-50C;
the amount of reagent A used being up to about 0.7 mole _ 11 _ RD-15514 for each liter of said organic diluent present in the reaction system, and -the molar proportions of reagents A, B and C being approximately as follows:
B:~ 0~2-1.0:1 C:A - 2-3:1;

and recovering the cyclic oligomers thus formed.
When step II is necessary, the unwanted impurities ma 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 preEerred non-solvent.
Recovery of the cyclic oligomers normally means merely separating the same rom diluent (by known methods such as vacuum evaporation) and, optionally, from high polymer and other impurities. As previously suggested, the degree oE sophistication of reCovery will depend on such variables as the intended end use of the product.
The distributions of the molecular species in polycarbonate oligomer products obtained by the method of this invention have been proved by reversed phase high pressure liquid uid chromatography. The product was first dissolved in a mixture of tetrahydrofuran and water, whereupon high molecular weight polymer separated by precipitation and the proportion thereof in the product was determined. The material remaining in solution was chromatographed using a relatively non-polar packing, whereupon more polar constituents including linear oligomers were eluted first, followed by cyclic oligomers of progressively increasing degrees of polymerization.
For each molecular species, two values were determined and used for identification: the retention time (in ~8~

minutes) and the "254/280 value". The latter is defined as the ratio of the areas under the ultraviolet absorption peaks at 254 and 280 nm. soth of these wavelengths are characteristic of compounds of this type, and the 254/280 values for individual oligomers are uniquely identifiable.
The standards used for assignment of retention time and 254/280 value were separately prepared linear and cyclic polycarbonate oligomers of bisphenol A having degrees of polymerization of 2-5 and 3-6, respectively.
The linear dimer was prepared by protecting one blsphenol A hydroxy group with a triethylsilyl moiety by reaction with triethylsilyl chloride, reacting two moles of the protected molecule with one mole of phosgene, and removing the protective moiety under acidic conditions.
The linear trimer was prepared by a similar reaction in which bisphenol A bischloroformate was substituted for the phosgene. Reaction of one mole of the dimer and trimer with two moles oE the monochloroformate of the protected bisphenol Al followed by removal of the protective moiety, yielded the linear oligomers with degrees oE polymerization of 4 and 5, respectively. Each of these linear oligomers was then reacted with bisphenol A bischloroformate at high dilution to produce the cyclic oligomer having the next higher degree of polymerization.
By comparison with said separately prepared compounds, the cyclic bisphenol A polycarbonate oligomer mixtures of the present invention have been shown to contain a substantial proportion of material having degrees of polymerization from 2 to about 12, with about 50-70% thereof being in the range from 2 to 5. It is generally preferred to use said mixtures as prepared/ or optionally with separation of high polymer and/or insolubles. It is frequently possible, however, to isolate individual oligomers in substantially pure Norm .

by fractional precipitation techniques. For example, cyclic bisphenol A carbonate tetramer may be isolated by the successive steps of l precipitating high polymer by precipitation with acetone, (2) removing oligomers of high degree of polymerization by dissolution in a 20~ (by volume) solution of acetone in hexane, (3) extracting the residue with a 60~ (by volume) solution of acetone in hexane, and (4) refrigerating the extracts to precipitate the tetramer~
Upon extraction and refrigeration a second time according to steps 3 and 4, there is obtained cyclic bisphenol A carbonate dimer, a compound not previously known. The presence of similar dimers in cyclic oligomer mixtures from other bisphenols was shown by chromato-graphic comparison with known linear oligomers end-capped with diphenyl carbonate. Substantial amounts of cyclic carbonate dimers also appear in mixtures prepared from chloroformates o other bisphenols having meta and/or para configurations. Accordingly, the present invention also includes compositions comprising cyclic dimers having the formula o yl A3_y2_A4-yl~C
(VI) C-Yl-A4_y2_A3 yl Il wherein each of A3 and A4 is a single-ring divalent aromatic radical in which the linkages to oxygen and y2 are in the meta or para and especially in the para position, and yl and Ye are as previously defined.
The preparation of cyclic oligomer mixtures of this invention is illustrated by the following examples.

All parts and percentages in the examples herein are by weight unless otherwise indicated.
Examples 1-1_ Bisphenol A bischloroformate was reacted with aqueous sodium hydroxide and triethylamine in methylene chloride according to the following procedure: The chloroformate was dissolved in half the amount of methylene chloride employed and was added gradually, with slow stirring, to the balance of the reaction mixture.
In Examples 1-10 and 12, the triethylamine was present with the methylene chloride and sodium hydroxide; in Examples 14-16, it was added gradually at the same time as the bischloroformates and in Examples 11, 13, 17 and 18, it was added incrementally at the beginning of bischloroformate addition and at intervals of 20% during sald addition. The amount of sodium hydroxide used was 2~4 moles per mole oE bischloroformate. After all the bischloro:Eormate had been added, the mixture was stirred :Eor about 2 minutes and the reaction was quenched by the addition of a slight excess oE 1 M aqueous hydrochloric acid. The methylene chloride solution was washed twice with dilute aqueous hydrochloric acid, dried by filtration through phase separation paper and evaporated under vacuum. The residue was dissolved in tetrahydro-furan and high polymers were precipitated by addition ofacetone. The remaining solution was analyzed by high pressure liquid-liquid chromatography as previously described.
The reaction conditions for Examples 1-18 are listed in Table I together with the approx.imate percentage (by weight) of cyclic polycarbonate oligomer present in the product. The weight average molecular weights of the cyclic oligomer mixtures were approximately 1300 as determined by gel permeation chromatography, corresponding to an average degree of polymerization of about 5.1.

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TABLE I

Bis-chlor~-formate Molar amt. ratio, 5(moles amine: Addi-per NaOHbis-Temper- tion % olig-liter molar- chloro- ature, time, omer in Example CH2Cl~ y ~ormate C min. product 1 0 1 0.3150.5 20 30 97 2 0 1 0 6250.5 20 30 95

3 0.1 ~.50 5 35 55 93

4 0.1 2.50.5 0 30 77 0 1 2.50.5 20 30 87 6 0.1 2.50.5 35 30 78 7 0 1 2.50.5 50 30 88 8 0.1 ~.50.25 20 30 74 9 0.1 2.50.2 20 lS 75 0.2 2.50 5 20 30 ~0 11 0.5 2.50.25 25 105 83 lS 12 0.5 2.50.25 25 105 78 13 0.5 2.50.25 25 105 83 14 0.5 2.5~ 25 25 105 87 0.5 2.50.29 30 90 78 16 0.5 2.50.25 30 20 75 17 0.5 2.50 25 40-45 105 79 18 0.5 2.50.4 25 105 79 ~xamPl e 19 n . . _ _ ~isphenol A bischloroformate was reac-ted with aqueous sodium hydroxide and 4-dimethylaminopyridine in methylene chloride. The procedure employed was that of Example 1, except that 0.0667 mole 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 C. The product comprised 85%
cyclic oligomer.
Example 20 A solution of 1.4 mmol. of bisphenol A bischloro-formate and 0.6 mmol. of 1,4-benzenedimethanol bischloroformate in 10 ml. of a tetrahydrofuran-methylene chloride solution comprising 10% by volume tetrahydrofuran was added over 30 minutes at 30C, with ~3~g~L

stirring, to a mixture of 10 ml. of methylene chloride, 2 ml. of 2.5 M aqueous sodium hydroxide and 1 mmol. of triethylamine. After addition was complete, the mixture was washed three times with dilute aqueous hydrochloric acid and the organic layer was separated, dried by filtration through phase separation paper and evaporated under vacuum. The product was the desired mixed cyclic polycarbonate oligomer of bisphenol A and benzene-1!4-dimethanol.
Examples`21-31 Following the procedure of Example 20, products containing at least about 80% mixed cyclic polycarbonate oligomers were prepared from mixtures of 90 mole percent bisphenol A bischloroformate and 10 mole percent of the dihydroxy compounds or dithiols listed in Tab]e II. In each case, a total ox 2 mmol. of reagen-t A was used.
TABLE II
.. . . . . .. .. .
Example Dihydroxy compound or dithiol ___ __ _ 27 1,1-Bis(4-hydroxyphenyl)cyclohexane 22 1,1-Bis(4-hydroxyphenyl)cyclododecane 23 2,2-Bis(4-hydroxy-3,5-dimethylphenyl)propane 24 2,2-Bis(4-hydroxy-3,5-dibromophenyl)propane Bis(4-hydroxyphenyl) sulfone 26 4,4'-Thio]diphenol 27 Bis(4-hydroxy-3,5-dimethylphenyl) sulfone 28 2,2-Bis(4-hydroxyphenyl)~ dichloroethylene 29 ~Iydroquinone 4,4'-Biphenyldithiol 31 1,12-Dodecanedithiol The cyclic oligomer mixtures of this invention are useful as intermediates for conversion to polycarbonates or their thiol analogs Accordingly, the present invention includes a method for the preparation of a resinous composition which comprises contacting at least one of the previously defined cyclic oligomer mixtures with a polycarbonate formation catalyst at a temperature up to about 350 C, and the resins so prepared. The ~23~

oligomer mixtures may frequently be employed in this method without separation of high polymer therefrom, but if desired, high polymer may be removed as previously described.
Previously known methods for forming (e.g., molding) polycarbonates are often cumbersome because of their high viscosities On the other hand, it has not been possible to integra-te preparation methods, involving the use of phosgene or various monomeric esters, with forming operations because of the volatility of the reagents involved. By contrast, the cyclic oligomer mixtures of this invention are liquid and have low viscosities. Moreover, they are substantially non-volatile at resin formation temperatures. Thus, it is possible to integrate resin formation therefrom with such forming operations. For example, the cyclic oligomer mixture may be simultaneously polymerized and injection molded by application of heat to the mold.
The polycarbonate formation catalysts which can be used in the resin formation method of this inventlon include various bases, Lewis acids and titanium chelates.
It is known that basic catalysts may be used for poly-carbonate preparation; reference is made to the afore-mentioned U.S. Patents 3,155,683; 3,274,214; 4,217,438;
and 4,368,315. Among the preferred bases for use in the present invention are lithium stearate, lithium 2,2,2-trifluoroethoxide, n-butyllithium and tetramethyl-ammonium hydroxide.
Also useful as polycarbonate formation catalysts 3Q are various Lewis acids, examples of which are dioctyltin oxide, triethanolamine titanium isopropoxide and tetra(2-ethylhexyl) titanate. Titanium chelates which are useful include bisisopropoxytitanium bisacetylacetonate. Presently preferred catalysts are lithium stearate and bisisopropoxytitanium 8~

bisacetylacetonate.
The resin Eormation reaction is typically effected by merely contacting the cyclic oligomer mixture with the catalyst at temperatures up to 350C, preferably about 200-300C, until polymerization has proceeded to the extent desired. Although the use of a solvent is within the scope of the invention, it is generally not preferred In general, the amount of catalyst used is about 0.001-0.2 mole percent based on oligomer mixture.
It is also contemplated to employ known chain transfer or endcapping agents, of which diphenyl carbonate is an example, to control molecular weight, typically in amounts up to about 2.5 mole percent based on oligomer mixture.
Resinous compositions ox various structures may be prepared by the use oE various cyclic oligomer mixtures.
For example, the use of polycarbonate oligomer mixtures prepared from a single material such as bisphenol A
cloroformate aEfords homopolycarbonates. Random copoly-carbonates may be obtained by using oligomer mixtures prepared from a mix-ture oE reayent A-l and reagent A-2.
The preparation of block copolycarbonates may be effected, for example, by reacting a bisphenol A cyclic oligomer mixture with a cyclic oligomer mixture derived from another bisphenol such as 2,2-bis(4-hydroxyphenyl)-1, l-dichloroethylene; the size of the blocks can be varied by controlling the time of addition and, if desired, by prepolymerizing one or both mixtures before combining - them. Another possibility is the formation of a cyclic oligomer mixture containing about 50 mole percent of (for example) bisphenol A units and about 50% of sterically hindered units which will not condense with themselves, illustrated by 2,2-bis(4--hydroxy-3,

5-dimethylphenyl)propane. The resul-ting cyclic mixtures contain alternating bisphenol A and sterically hindered ~3~

units, and may be converted to alternating copoly-carbonates.
The above-described method for resin preparation may be used to produce polymers of very high molecular weights, particularly when no endcapping agents are used. While high molecular weight polycarbonates of this type are known, they have been of little or no use in molding operations because ox their intractability under normal molding conditions This property is irrelevant, however, when the cyclic oligomer mixtures of the present invention are used as polycarbonate precursors since said mixtures can be simultaneously polymerized and molded to produce ar-ticles which are very tough and resistant to severe temperature and solvent conditions. Accordingly, another embodiment of the invention is molded articles of manufacture comprising a polycarbonate having a weight average molecular weight (ow) of at least 250,000 and more specifically at least 300/000 (all molecular weights herein being determined by gel permeation chromatography), said polycarbonate consisting essentially of structural units o formula I.
The preparation of polycarbona-tes from the cyclic oligomer mixtures of this invention is illustrated by the following examples.
Examples 32-37 Five parts of a crude cyclic bisphenol A poly-carbonate oligomer, having a weight average molecular weight of about 1340, prepared by a method similar to that of Examples 1-18 (excluding dissolution in tetrahydrofuran for chromatography purposes) but still containing the high polymer constituents, was heated under nitrogen at 300 C and a solution of catalyst in - methylene chloride was added after about 3 minutes. In Examples 35-37, diphenyl carbonate was added to the oligomer mixture as an endcapping agent. Polymerization was allowed to continue for 10 minutes, after which the polycarbona-te was removed, dissolved in methylene chloride, filtered and precipi-tated by the addition of methanol. The weight average molecular weight, intrinsic viscosity and glass transition temperature (Tg) were also determined. The relevant parameters and results are given in Table III. Intrinsic viscosities (IV) were determined in chloroform at 25 C.

T _LE III
Catalyst Diphenyl carbonate _ IV Tg, ExamPle Identity Mole % mole % Mw dig C
32Lithium 0.1 - 300,000*
stearate 33Bisiso- 0.01 - 265 000 propoxy-titanium bisacetyl-acetonate 34 " 0.002 - 269 000 " 0.002 1.0 117,000 0.646 157 36 " 0.002 1.5 141,000 0.903 152 37 " 0.002 2.0 65 300 *Minimum value; 300 000 is highest figure determinable on apparatus used.

Claims (26)

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

1. A composition consisting essentially of a mixture of cyclic oligomers having varying degrees of polymerization from 2 to about 30, the structural units in said oligomers having the formula , wherein each R is independently an aliphatic, alicyclic or aromatic radical at least about 60% of the total number of R values is aromatic, and each Y1 is independently oxygen or sulfur.

2. A composition according to claim 1 which consists essentially of cyclic oligomers having degrees of polymerization of from 2 to about 20 and wherein each Y1 is oxygen.

3. A composition according to claim 2 which contains no more than about 10% by weight of linear oligomers.

4. A composition according to claim 3 wherein each R has theformula , wherein each of A1 and A2 is a single-ring divalent aromatic radical and Y2 is a radical wherein A1 and A2 are separated by one or two atoms.

5. A composition according to claim 4 wherein each of A1 and A2 is p-phenylene and Y2 is isopropylene.

6. A composition according to claim 5 wherein a major proportion of the oligomers have degrees of polymerization of from 2 to about 12.

7. A composition comprising cyclic dimers having the formula wherein each of A3 and A4 is a single-ring divalent aromatic radical in which the linkages to oxygen and Y2 are in the meta or para positions, Y1 is independently oxygen or sulfur, and Y2 is a radical wherein A3 and A4 are separated by one or two atoms.

8. A composition according to claim 7 wherein each A3 and A4 is p-phenylene, each Y1 is oxygen and Y2 is isopropylene.

9. A method for preparing a composition comprising cyclic polycarbonate or thiol analog oligomers which comprises the steps of:
I. contacting (A)(1) at least one compound selected from the group consisting of bishaloformates and thiol analogs thereof, said compounds having the formula R(Y1COX)2 , wherein X is chlorine or bromine, or a mixture thereof with (2) at least one difunctional compound having the formula R(Y3H)2 , wherein each Y3 is independently sulfur when the corresponding R is an aliphatic or an alicyclic radical and oxygen or sulfur when the corresponding R is an aromatic radical, with (B) at least one oleophilic aliphatic or heterocyclic tertiary amine and (C) an aqueous alkali metal hydroxide solution having a concentration of about 0.1-10M;
said contact being effected under conditions of high dilution of reagent A in a substantially non-polar organic diluent which forms a two-phase system with water, and subsequently II. separating the resulting cyclic oligomer mixture from at least a portion of the high polymer and insoluble material present.

10. A method according to claim 9 wherein reagent A consists essentially of a bischloroformate in which Y1 is oxygen, X is chlorine and R has the formula -A1-Y2-A2- , wherein each A1 and A2 is a single-ring divalent aromatic radical and Y2 is a radical wherein A1 and A2 are separated by one or two atoms.

11. A method according to claim 10 wherein each of A1 and A2 is p-phenylene and Y2 is isopropylene.

12. A method according to claim 11 wherein reagent B is triethylamine, reagent C is sodium hydroxide and the diluent is methylene chloride.

13. A method for preparing a composition comprising cyclic polycarbonate or thiol analog oligomers which comprises contacting (A)(1) at least one compound selected from the group consisting of bishaloformates and thiol analogs thereof, said compounds having the formula R(Y1COX)2 , wherein X is chlorine or bromine, or a mixture thereof with (2) at least one difunctional compound having the formula R1(Y3H)2 , wherein Y3 is sulfur when R is an aliphatic or an alicyclic adical and oxygen or sulfur when R is an aromatic radical, with (B) at least one aliphatic or heterocyclic tertiary amine which, under the reaction conditions, dissolves preferentially in the organic phase of the reaction system; and (C) an aqueous alkali metal hydroxide solution having a concentration of about 0.1-10 M;
said contact being effected by gradually adding reagent A or reagents A and B to a mixture of the other reagents with a substantially non-polar organic diluent which forms a two-phase system with water, said mixture being maintained at a temperature in the range of about 0-50°C;
the amount of reagent A used being up to about 0.7 mole fox each liter of said organic diluent present in the reaction system, and the molar proportions of reagents A, B and C being approximately as follows:
B:A - 0.2-1.0:1 C:A - 2-3:1;
and recovering the cyclic oligomers thus formed.

14. A method according to claim 13 wherein reagent A consists essentially of a bischloroformate in which y1 is oxygen, X is chlorine and R has the formula wherein each of A1 and A2 is a single-ring divalent aromatic radical and y2 is a radical wherein A1 and A2 are separated by one or two atoms.

15. A method according to claim 14 wherein each of A1 and A2 is p-phenylene and y2 is isopropylene.

16. A method according to claim 15 wherein reagent B is triethylamine, reagent C is sodium hydroxide and the diluent is methylene chloride.

17. A method for the preparation of a resinous composition which comprises contacting a composition according to claim 1 with a polycarbonate formation catalyst at a temperature up to about 350°C.

18. A method according to claim 17 wherein the polycarbonate formation catalyst is a base, a Lewis acid or a titanium chelate.

19. A method according to claim 18 wherein the polycarbonate formation catalyst is lithium stearate or bisisopropoxytitanium bisacetylacetonate.

20. A method according to claim 19 wherein R has the formula wherein each of A1 and A2 is a single-ring divalent aromatic radical and Y2 is a radical wherein A1 and A2 are separated by one or two atoms.

21. A method according to claim 20 wherein each of A1 and A2 is p-phenylene and Y2 is isopropylene.

22. A resinous composition prepared by the method of claim 17.

23. A resinous composition prepared by the method of claim 21.

24. A molded article of manufacture comprising a polycarbonate having a weight average molecular weight of at least about 250,000, said polycarbonate consisting essentially of structural units of the formula wherein each R is independently a divalent aliphatic, alicyclic or aromatic radical.

25. An article according to claim 24 wherein each R has the formula wherein each of A1 and A2 is a single-ring divalent aromatic radical and Y2 is a radical wherein A1 and A2 are separated by one or two atoms.

26. An article according to claim 25 wherein each of A1 and A2 is p-phenylene and Y2 is 2,2-propylene.