Method for the preparation of cross-linked polycarbonates, and compositions made therefrom

An improved method for the preparation of cross-linked polycarbonates is disclosed, comprising the reaction at elevated temperature of a composition containing cyclic carbonate oligomers with at least one polyglycidyl acrylate copolymer formed by the reaction of at least one olefin with a glycidyl acrylate monomer. This invention also includes network polycarbonates wherein the carbonate chains are linked to each other via polyglycidyl acrylate copolymer groups. Further included within the scope of this invention are prepreg compositions which comprise a filler and a mixture of cyclic carbonate oligomers with a polyglycidyl acrylate copolymer.

BACKGROUND OF THE INVENTION 
This invention relates to polymer compositions and their preparation, and 
more particularly to the preparation of cross-linked polycarbonates. 
Polycarbonates are a class of well-known, commercially available 
thermoplastic materials possessing physical and chemical properties which 
are useful in a wide variety of applications. Some of the notable 
attributes of polycarbonates include high impact strength and thermal 
stability, along with good transparency. However, the use of 
polycarbonates in some applications, e.g., automotive, is limited somewhat 
because of their relatively poor resistance to various organic solvents 
and other chemicals. Furthermore, glass transition and heat distortion 
temperatures for some of the conventional polycarbonates are not high 
enough to permit reasonable molding cycle times. 
One method for correcting these deficiencies involves cross-linking the 
polycarbonate chains to form thermoset compositions. For example, U. S. 
Pat. No. 3,098,056 describes the reaction of epoxy resins with linear 
polycarbonates and hardeners, while U.S. Pat. No. 3,261,808 describes the 
preparation and cure of polycarbonates containing epoxy end groups. While 
polycarbonates cross-linked in this manner have better properties than 
those of polycarbonate alone, these methods may not be suitable for use in 
some of the more advanced molding techniques. For example, the high melt 
viscosities of linear polycarbonates make these methods unsuitable for use 
under reactive processing conditions such as reaction injection molding 
(RIM). 
A recent development in the area of polycarbonates involves cyclic 
polycarbonate compositions. The preparation and use of cyclic 
polycarbonates have been previously disclosed in numerous applications 
filed for inventors on behalf of the assignee of the present invention. 
For example, these materials are described in U.S. Pat. No. 4,644,053. As 
described in this and in other references, the cyclic oligomer mixtures 
have low viscosities and can be simultaneously polymerized and molded upon 
the application of heat. 
Thermoset compositions prepared by reacting cyclic polycarbonate oligomers 
with polyepoxy compounds are described in application Ser. No. 019,153 of 
T. Evans et al., filed Feb. 25, 1987, now U.S. Pat. No. 4,746,725, and 
assigned to the assignee of the present invention. Although various 
polyepoxides are described in that application, the material of choice is 
either a triglycidyl isocyanurate or a bis-epoxy-terminated bisphenol 
A-epichlorohydrin condensate. 
While the materials described by T. Evans et al. are suitable for a wide 
variety of applications, there is continuing interest in developing 
cross-linked polycarbonates which are thermally stable at high processing 
temperatures, e.g., above about 280.degree. C. 
It is therefore a primary objective of the present invention to provide an 
improved method for the preparation of highly cross-linked polycarbonates. 
It is another objective of this invention to provide a method for preparing 
cross-linked polycarbonates which are stable at high processing 
temperatures. 
It is a further objective of the present invention to provide a 
cross-linked polycarbonate preparation method which is amenable to 
reactive processing conditions such as reaction injection molding. 
It is still another objective to provide thermoset polycarbonate 
compositions characterized by high density cross-linking. 
SUMMARY OF THE INVENTION 
One aspect of the present invention is an improved method for the 
preparation of cross-linked polycarbonates, comprising the reaction at 
elevated temperature of a composition containing cyclic carbonate 
oligomers, a polycarbonate formation catalyst, and at least one 
polyglycidyl acrylate copolymer which is the reaction product of A and B, 
wherein A is at least one glycidyl acrylate monomer, and B is at least one 
monoethylenically unsaturated monomer free of an epoxy group having a 
reactivity such that B forms a copolymer with A. This invention also 
includes polycarbonate compositions which are highly cross-linked through 
glycidyl acrylate functionalities.

DETAILED DESCRIPTION OF THE INVENTION 
As mentioned above, the polyglycidyl acrylate copolymer is the reaction 
product of A and B. Each A unit is a glycidyl acrylate monomer of the 
formula 
##STR1## 
wherein R.sup.1 is selected from the group consisting of hydrogen, alkyl 
groups containing about 1-10 carbon atoms, and aromatic groups containing 
about 6-20 carbon atoms. Exemplary alkyl groups suitable for R.sup.1 are 
methyl, ethyl, propyl, and isobutyl, while exemplary aromatic groups 
suitable for R.sup.1 include phenyl, tolyl, naphthyl, xylyl, and the like. 
Methyl (i.e., glycidyl methacrylate) is the most preferred. "Acrylate" as 
used herein refers to any of the acrylic acid-based groups included in 
formula I, unless otherwise indicated. 
Each B unit in this copolymer is an olefin having a reactivity such that B 
forms a copolymer with A. In terms of overall process efficiency, olefins 
or combinations of olefins which provide the highest percentage of 
copolymer with the glycidyl acrylate monomer are preferred. 
Reactivities for the glycidyl acrylates of formula I and for many olefins 
used to form the B units have been established. For example, when A is 
derived from glycidyl methacrylate (GMA), olefins for B which have 
reactivities suitable for copolymer formation include styrene, 
acrylonitrile, methyl methacrylate, ethyl methacrylate, butyl acrylate, 
and ethyl acrylate. 
For A units other than glycidyl methacrylate and for B units other than the 
olefins mentioned herein, relative reactivities can be established through 
simple experimentation by those of ordinary skill in the art, if such 
values are not readily found in the literature. For example, the monomers 
in question might be mixed together under reactive conditions, followed by 
an analysis of the product (monomer, homopolymer, and copolymer content) 
by well-known analytical techniques, such as solvent extraction of each 
component, gel permeation chromatography (e.g., separation based on 
contrasting molecular weights), infrared spectroscopy, nuclear magnetic 
spectroscopy (NMR), and the like. 
Exemplary copolymer compositions useful for this invention are those formed 
by the reaction of glycidyl methacrylate with styrene; and glycidyl 
methacrylate with methylmethacrylate. 
Exemplary terpolymer compositions for this invention are those formed by 
the reaction of glycidyl methacrylate with styrene and acrylonitrile; 
glycidyl methacrylate with methyl methacrylate and acrylonitrile; and 
glycidyl methacrylate with styrene and methyl methacrylate. 
A useful description of the preparation of polymers and copolymers from 
glycidyl methacrylate is provided by M. Yoshino et al. in the Journal of 
Paint Technology, Volume 44, Number 564, January 1972, pages 116-123. 
Furthermore, many copolymers suitable for the present invention are 
commercially available from several sources, including Nippon Oil and Fats 
Company, Ltd., under the name "Blemmer G" resins. Some of these copolymers 
are described, for example, in Blemmer G--Versatile Polymer Modifier, 
Revised Edition, Nippon Oil and Fats Company, Ltd., Oil and Fat Products 
and Chemicals Division. 
In preferred embodiments, less than about 50% of the total molecular units 
in the polyglycidyl acrylate copolymer are A units, since the presence of 
a greater amount of glycidyl groups can sometimes adversely affect 
copolymer stability. In particularly preferred embodiments, 20-40% of the 
total molecular units in the polyglycidyl acrylate copolymer are A units. 
The relative amounts of various olefin B units in the copolymer depends on 
the particular properties desired for the final product. An exemplary 
copolymer composition contains about 25 to 40 mole percent glycidyl 
methacrylate and about 40 to about 75 mole percent styrene. Another 
exemplary composition contains about 30 to 40 mole percent glycidyl 
methacrylate, about 40 to 65 mole percent styrene, and about 5 to 20 mole 
percent acrylonitrile. Those of ordinary skill in the art will be able to 
select particular monomers and monomer ratios to satisfy desired end use 
requirements without undue experimentation. 
The polyglycidyl acrylate copolymers of the present invention are random 
copolymers, i.e., the comonomers are substantially random in their 
distribution throughout the polymer chain. Such copolymers may still 
contain small blocks of homopolymers in the polymer structure in amounts 
which do not adversely or substantially affect the unique properties of 
the copolymers. These properties include high reactivity and excellent 
thermal stability in comparison to some of the other conventional epoxy 
materials such as triglycidyl isocyanurate or the diglycidyl ethers of 
bisphenols (e.g., of bisphenol A). The high reactivity generally results 
in faster and more complete cross-linking of the polycarbonate (as 
described below), while the thermal stability characteristic results in 
greater part integrity during and after high temperature molding 
operations. 
As mentioned above, the polyglycidyl acrylate copolymer is reacted with a 
composition comprising mixtures of cyclic carbonate oligomers according to 
this invention. Such oligomers are generally characterized by varying 
degrees of polymerization and comprise structural units of the formula 
##STR2## 
wherein each R.sup.2 is independently a divalent aliphatic, alicyclic or 
aromatic group, and each Y.sup.1 is independently oxygen or sulfur. These 
oligomers are generally well-known in the art and described, for example, 
in the following U.S. Patents, all of which are incorporated herein by 
reference: 
______________________________________ 
4,740,583 4,644,053 
4,701,519 4,605,731. 
______________________________________ 
The cyclic carbonate oligomer mixtures (sometimes referred to herein as 
"cyclics" or "cyclics mixture") of this invention may contain organic 
carbonate, thiolcarbonate, and/or dithiolcarbonate units. The various 
R.sup.2 groups may be different, but are usually the same, and may be 
aliphatic, alicyclic, aromatic or mixed. Those which are aliphatic or 
alicyclic generally contain up to about 8 carbon atoms. Illustrative 
R.sup.2 groups are ethylene, propylene, trimethylene, tetramethylene, 
hexamethylene, dodecamethylene, 1,4-(2-butenylene), 
1,10-(2-ethyldecylene), 1,3-cyclopentylene, 1,3-cyclohexylene, 
1,4-cyclohexylene, m-phenylene, p-phenylene, 4,4'-biphenylene, 
2,2-bis(4-phenylene)propane, benzene-1,4-dimethylene, and similar groups 
such as those which correspond to the dihydroxy compounds disclosed by 
name or formula (generic or specific) in U.S. Pat. No. 4,217,438, the 
disclosure of which is incorporated by reference herein. Also included are 
groups containing non-hydrocarbon moieties. These may be substituents such 
as chloro, nitro, alkoxy and the like, and also linking radicals such as 
thio, sulfoxy, sulfone, ester, amide, either and carbonyl. Most often, 
however, all R.sup.2 groups are hydrocarbon groups. 
Preferably at least about 60%, and more preferably at least about 80%, of 
the total number of R.sup.2 groups in the cyclic oligomer mixtures, and 
most desirably all of said R.sup.2 groups, are aromatic. The aromatic 
R.sup.2 groups preferably have the formula 
EQU --A.sup.1 --Y.sup.2 --A.sup.2 -- III 
wherein each of A.sup.1 and A.sup.2 is a single-ring divalent aromatic 
group and Y.sup.2 is a bridging group in which one or two atoms separate 
A.sup.1 from A.sup.2. The free valence bonds in formula III are usually in 
the meta or para positions of A.sup.1 and A.sup.2 in relation to Y.sup.2. 
Such R.sup.2 groups may be considered as being derived from bisphenols of 
the formula 
EQU HO--A.sup.1 --Y.sup.2 --A.sup.2 --OH. IV 
In formulas III and IV, the A.sup.1 and A.sup.2 groups may be unsubstituted 
phenylene or substituted derivatives thereof. Exemplary substituents are 
alkyl, alkenyl, halo (especially chloro and/or bromo), nitro, alkoxy, and 
the like. In preferred embodiments, both A.sup.1 and A.sup.2 are 
preferably p-phenylene. 
The bridging group, Y.sup.2, is one in which one or two atoms, preferably 
one, separate A.sup.1 from A.sup.2. It is most often a hydrocarbon group 
and, particularly, a saturated group such as methylene, 
cyclohexylmethylene, 2-[2.2.1]-bicycloheptylmethylene, ethylene, 
isopropylidene, neopentylidene, and the like. Unsaturated groups and 
groups containing atoms other than carbon and hydrogen might be used also, 
such as 2,2-dichloroethylidene, carbonyl, thio, and sulfone. 
Other exemplary R.sup.2 groups are those derived from dihydroxy compounds 
such as ethylene glycol, propylene glycol, resorcinol, hydroquinone, 
2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)ether, 
bis(4-hydroxyphenyl)sulfone, and 
6,6'-dihydroxy-3,3,3',3'-tetramethylspiro(bis)indane ("spirobiindane 
bisphenol"). 
Based on various considerations such as availability and particular 
suitability for this invention, the preferred group of formula III is the 
2,2-bis(4-phenylene)-propane radical, which is derived from bisphenol A. 
Furthermore, while the Y.sup.1 groups in formula II may be oxygen or 
sulfur, they are preferably all oxygen. 
The cyclic oligomer mixtures usually comprise oligomers having degrees of 
polymerization of from 2 to about 30, and preferably to about 20. The 
mixtures sometimes contain very low proportions of linear oligomers, 
generally no more than about 10% by weight, and most often less than about 
5% by weight. The mixtures may also contain low percentages (usually less 
than 30% by weight and preferably no greater than about 10% by weight) of 
linear or cyclic polymers having a degree of polymerization greater than 
about 30. 
The particular method of preparing the cyclics mixture is not critical to 
the present invention; various methods are well-known in the art. One 
example is preparation via a condensation reaction involving at least one 
compound selected from the group consisting of bishaloformates and thiol 
analogs thereof having the formula 
EQU R.sup.2 (Y.sup.1 --COX).sub.2, V 
wherein R.sup.2 and Y.sup.1 are as defined above, and X is chlorine or 
bromine. The condensation reaction usually takes place interfacially when 
a solution of the compound in a substantially nonpolar organic liquid is 
contacted with a tertiary amine such as triethylamine and an aqueous 
alkali metal hydroxide solution. 
The relative amount of cyclic carbonate oligomers to polyglycidyl acrylate 
copolymer depends in part on the amount of cross-linking desired in the 
polycarbonate. In preferred embodiments, at least 8 mole percent of 
glycidyl groups should be used, based on the number of carbonate units in 
the cyclic carbonate oligomer composition, it being understood that each 
glycidyl group contains one epoxide group. A preferred upper limit for 
glycidyl group content is about 25 mole percent, since in some instances, 
a higher epoxy content could result in very brittle polycarbonates. An 
especially preferred epoxy level is about 12 mole percent to about 15 mole 
percent of glycidyl groups, based on the number of carbonate units in the 
cyclic carbonate oligomer composition. 
As mentioned above, a polycarbonate formation catalyst is used to ring-open 
the cyclic carbonate oligomers. When used, these catalysts also appear to 
initiate ring-opening of the epoxide groups in the polyglycidyl acrylate. 
The ring-opened epoxides then react with the polycarbonate to form a 
cross-linked, thermoset material. 
Polycarbonate formation catalysts are known in the art, and are usually 
various bases and Lewis acids, with bases being preferred for this 
invention. Some of the polycarbonate formation catalysts useful for this 
invention are those employed to prepare polycarbonates by the interfacial 
method and by other techniques, as described in U.S. Pat. Nos. 3,155,683, 
3,274,214, 4,217,438, and 4,368,315, each of which is incorporated herein 
by reference. Examples of such catalysts are lithium phenoxide, lithium 
2,2,2-trifluoroethoxide, n-butyl lithium, and tetramethylammonium 
hydroxide. Also useful are various basic salts such as sodium benzoate and 
lithium stearate. 
A class of bases which is particularly useful under many conditions is 
described in U.S. Pat. No. 4,605,731. It comprises numerous 
tetraarylborate salts, including lithium tetraphenylborate, sodium 
tetraphenylborate, sodium bis(2,2'-biphenylene)borate, potassium 
tetraphenylborate, tetramethylammonium tetraphenylborate, 
tetra-n-butylammonium tetraphenylborate, tetramethylphosphonium 
tetraphenylborate, tetra-n-butylphosphonium tetraphenylborate, and 
tetraphenylphosphonium tetraphenylborate. The preferred catalysts within 
this class are the tetra-n-alkylammonium and tetra-n-alkylphosphonium 
tetraphenylborates. Tetra-n-butylammonium tetraphenylborate is 
particularly preferred because of its high activity, relatively low cost 
and ease of preparation from tetra-n-butylammonium hydroxide and an alkali 
metal tetraphenylborate. 
Another class of particularly useful basic catalysts is disclosed in U.S. 
Pat. No. 4,701,519 of T. Evans et al., the disclosure of which is also 
incorporated by reference herein. It comprises polymers containing alkali 
metal phenoxide moieties, especially lithium phenoxide moieties. The 
moieties are usually present as end groups on the polymer chain, although 
they can also be present in the polymer chain, or as substituents on the 
chain. The preferred polymers for these catalysts are polycarbonates, 
especially linear polycarbonates having a number average molecular weight 
in the range of about 8,000-20,000, as determined by gel permeation 
chromatography relative to polystyrene. Such catalysts may be produced by 
reacting a suitable polymer with an alkali metal base, typically at a 
temperature in the range of about 200.degree.-300.degree. C. 
Lewis acids which may be used as polycarbonate formation catalysts are 
usually selected from non-halide compounds and include dioctyltin oxide, 
triethanolaminetitanium isopropoxide, tetra(2-ethylhexyl) titanate and 
polyvalent metal (especially titanium, nickel, zinc, tin, and aluminum) 
chelates such as bisisopropoxytitanium bisacetylacetonate (commercially 
available under the trade name "Tyzor AA") and the bisisopropoxyaluminum 
salt of ethyl acetoacetate. 
For most purposes, the preferred polycarbonate formation catalyst for this 
invention is a lithium phenoxide-terminated polycarbonate or 
tetra-n-butylammonium tetraphenylborate. 
An effective amount of polycarbonate formation catalyst employed is usually 
about 0.001-0.5 mole percent, and preferably about 0.05-0.25 mole percent, 
based on the total number of carbonate units present in the oligomer 
composition. 
In some embodiments, the cyclics mixture, polyglycidyl acrylate copolymer, 
and polycarbonate formation catalyst can first be mixed together to form a 
nonpolymerized product, i.e., prior to linearization, polymerization, and 
cross-linking of the polycarbonate. The components are dissolved in an 
organic solvent such as methylene chloride, followed by evaporation of the 
solvent and drying of the residue for about 3 hours to about 15 hours at a 
temperature of from about 80.degree. C. to about 110.degree. C. 
Alternatively, the components may be dissolved in solvent and then sprayed 
into hot water (usually about 90.degree.-100.degree. C.), followed by 
filtration and drying of the precipitate. 
Formation of the cross-linked polycarbonate is then effected by heating the 
cyclics/polyglycidyl acrylate copolymer/polycarbonate formation catalyst 
mixture at an elevated temperature. Suitable temperatures are usually in 
the range of about 200.degree. C. to 300.degree. C. and, preferably, from 
about 230.degree. C. to about 275.degree. C. 
It should be apparent from the foregoing that another aspect of this 
invention is a polycarbonate polymer cross-linked through linking groups 
derived from at least one polyglycidyl acrylate copolymer which comprises 
glycidyl acrylate-derived units A and olefin units B, wherein A and B are 
as defined above. The exact cross-linking mechanism is not fully 
understood, although it appears that the epoxy functionality appears to be 
the main cross-linking agent, with the ester group of the polyglycidyl 
acrylate copolymer contributing to a small extent in cross-linking. 
Some of the cross-linked polycarbonates of this invention are often 
additionally characterized by a very high cross-linking density, and can 
thus be referred to as "network" polycarbonates, which have all of the 
desirable attributes of thermosetting polymers, such as high strength and 
solvent resistance, as well as excellent molded part integrity at high 
temperatures. 
As described below, the degree of cross-linking and cross-linking density 
of compositions of this invention can be measured by two tests which are 
generally known in the art and further described below: the gel test and 
the swell test. A gel content of greater than about 80% after prolonged 
extraction of the polymerized product in methylene chloride indicates that 
the polycarbonate is substantially cross-linked. In preferred embodiments, 
the gel content is greater than 90%, and in especially preferred 
embodiments, is at least 95%. 
Furthermore, a network polycarbonate according to this invention is one 
having a swell test value of less than about 6 times its original weight 
after immersion in chloroform, as described below. 
Compositions formed by the method of this invention may be used in the 
preparation of a variety of molded, extruded, and cast articles. They may 
also be used in laminates, and as lacquers, binding agents, and adhesives. 
The compositions are especially useful in reactive processing operations 
such as RIM. In such operations, two liquid streams are fed into a mold 
where they react to form a resinous article, as described in the 
above-mentioned T. Evans et al. application, Ser. No. 019,153, 
incorporated herein by reference. Since polycarbonate formation catalysts 
which are unreactive with the polyglycidyl acrylate copolymer material can 
be selected, a molded thermoset article can easily be prepared. For 
example, a heated mold can be supplied with two liquid streams, one 
comprising the polyglycidyl acrylate copolymer material, and the other 
comprising the cyclic polycarbonate oligomer composition and, optionally, 
a polycarbonate formation catalyst as described above. Alternatively, the 
catalyst can be sprayed onto the mold walls or, in the case of a composite 
or prepreg (as mentioned below), may be applied to the filler material. 
Reaction then takes place in the mold to form the desired article. 
The nonpolymerized compositions of this invention, i.e., the cyclic 
carbonate oligomer composition in admixture with the polyglycidyl acrylate 
copolymer and the polycarbonate formation catalyst, may be combined with 
inert filler materials to produce prepreg compositions which can then be 
polymerized and cross-linked to form thermosetting network polycarbonate 
compositions having excellent impact resistance, moisture resistance, 
ductility, solvent resistance, and part integrity (i.e., a part's 
capability of retaining its exact dimensions after being exposed to high 
temperature and then being cooled). 
Details regarding various aspects of prepreg formation and use are 
well-known in the art and do not require an exhaustive discussion here. 
Exemplary techniques are described by Brunelle et al, in U.S. Pat. No. 
4,740,583. 
Suitable fillers for the prepreg compositions include talc, quartz, wood 
flour, finely divided carbon, silica, or mixtures thereof. Continuous 
fiber fillers, including carbon, glass, or highly oriented polyamide or 
boron fibers, are particularly useful. Polymerization conditions for the 
prepregs are generally the same as described above. Upon polymerization, 
reinforced, cross-linked polycarbonate articles are obtained which have a 
wide range of excellent physical and chemical properties. Furthermore, the 
presence of the inert filler material advantageously does not affect the 
degree of cross-linking and network formation. 
The following specific examples describe novel embodiments of the present 
invention and procedures used therein. They are intended for illustrative 
purposes only, and should not be construed as a limitation upon the 
broadest aspects of the invention. All parts, percentages, and ratios are 
by weight, unless otherwise indicated. 
EXAMPLES 
Gel Test 
Polymerized samples or portions of samples were placed in a woven stainless 
steel screen (200 mesh) and extracted with methylene chloride in a Soxhlet 
apparatus for 15 hours. Drying and weighing of the samples indicated the 
amount of insoluble (i.e., gel) material. 
Swell Test 
The density of cross-linking was measured by a swell test, in which the 
product extracted from the gel test was dried, weighed, and then dipped in 
chloroform for 15 minutes, after which the product was weighed again to 
determine how much chloroform had been absorbed. Less absorbance of 
chloroform indicates a higher density polycarbonate network, while a 
greater absorbance of chloroform indicates a lower density polycarbonate 
network. 
Example 1 
This example describes one method of preparation of a cross-linked 
polycarbonate composition according to the present invention. A bisphenol 
A-derived cyclic carbonate mixture (4.5 grams, 0.018 mole), 50 grams of 
Blemmer.RTM. G CP50S, which is a polyglycidyl methacrylate/styrene 
copolymer (50% by weight styrene), and tetrabutylammonium 
tetraphenylborate (0.025 gram, 0.044 millimole) were dissolved in 
methylene chloride. The solvent was evaporated and the residue was then 
dried in a vacuum oven for 15 hours at 80.degree. C. 
Polymerization of the sample was then carried out on a 0.5 gram scale in 
test tubes under a nitrogen atmosphere at about 250.degree. C. to 
300.degree. C. for 15 minutes. 
An "in mold" polymerization was performed, using a one inch closed circular 
mold at 275.degree. C.-280.degree. C. (pressure of about 4000-6000 pounds) 
over the course of 15 minutes. 
Example 2 
A bisphenol A-based cyclic polycarbonate oligomer mixture was mixed with 
various polyglycidyl methacrylate copolymers according to the 
carbonate/glycidyl methacrylate ratios listed in Table 1. The glycidyl 
methacrylate copolymers of Samples 1-8 fall within the scope of the 
present invention, and were Blemmer G products of a Nippon Oil and Fats 
Company, Ltd. The glycidyl methacrylate homopolymer of Sample 9 was 
obtained from Polyscience Company. Sample 10 utilized triglycidyl 
isocyanurate (TGIC) as the cross-linking agent, rather than a polyglycidyl 
acrylate agent of this invention. 
The cyclic polycarbonate oligomer mixture contained about 25-30% by weight 
linear polycarbonate. 
The cyclics were mixed with the indicated copolymer or homopolymer, 
followed by polymerization for 15 minutes at 300.degree. C., using a 0.1% 
by weight lithium-terminated polycarbonate formation catalyst. In addition 
to the gel and swell tests, each sample was visually examined to observe 
the development of any color or foaming that might indicate thermal 
instability. The results are provided in Table 1 below. 
Table 1 
Cross-Linking Evaluation for Blends of Polycarbonate Oligomers and Various 
Glycidyl Methacrylate Copolymers 
TABLE 1 
______________________________________ 
Cross-Linking Evaluation for Blends of Polycarbonate 
Oligomers and Various Glycidyl Methacrylate Copolymers 
Mole % 
Sam- Wt of glycidyl 
% Gel in 
ple % Wt %.sup.(a) 
methacrylate 
insoluble 
Swell 
No. GMA Comonomer(s) 
(or TGIC).sup.(b) 
fraction 
value.sup.(c) 
______________________________________ 
1 10 90(S + A) 15 81 8 
2 15 85S 15 96 7 
3 20 80S 15 96 6 
4 20 80(S + A) 15 96 6 
5 20 80(M + A) 15 96 6 
6 30 70S 15 95 6 
7 50 50S 15 98 4 
8 50 50M 15 97 4 
9 100 -- 15 95 .sup.(d) 
10 -- -- 10 88 8 
______________________________________ 
.sup.(a) S = styrene 
A = acrylonitrile 
M = methylmethacrylate 
.sup.(b) Based on the total number of moles of bisphenol A carbonate 
units. 
##STR3## 
.sup.(d) No value obtained. 
The data of Example 2 demonstrate that use of the cross-linking agents of 
this invention generally results in a high level of cross-linking. 
Although the polyglycidyl methacrylate homopolymer of Sample 9 exhibited 
good cross-linking, it was subject to degradation, as described in Example 
4 below, and is thus not part of this invention. 
The TGIC-based system of Sample 10 (also outside the scope of this 
invention) did not cross-link as completely as most of the polyglycidyl 
methacrylate-based systems, and was also found to be more susceptible to 
degradation at molding temperatures greater than about 280.degree. C. 
Example 3 
Various products according to this invention were prepared by mixing a 
cyclic polycarbonate oligomer mixture as used in Example 1 with a 
polyglycidyl methacrylate copolymer containing 50% by weight glycidyl 
methacrylate and 50% by weight styrene. The reaction mixture also 
contained 0.25 mole percent tetrabutylammonium tetraphenylborate as a 
polycarbonate formation catalyst. As shown in Table 2, the relative 
percentage of polyglycidyl methacrylate was varied for each sample. The 
results are provided below: 
Table 2 
Physical Properties of Various Cross-linked Polycarbonates of this 
Invention 
TABLE 2 
______________________________________ 
Physical Properties of Various Cross-linked 
Polycarbonates of this Invention 
Sample No. 
11 12 13 
______________________________________ 
% PGMA/Styrene Copolymer.sup.(a) 
7 14 20 
% Polycarbonate 93 86 80 
% Gel 77 96 95 
T.sub.g (.degree.C.) 
149 158 158 
HDT (.degree.C.) (264 psi).sup.(b) 
131 145 146 
Tensile Modulus (psi).sup.(c) 
342,000 366,000 374,000 
% Strain.sup.(c) 6 5-6 4 
______________________________________ 
.sup.(a) Copolymer itself contained 50% by wt GMA, 50% by wt styrene. 
.sup.(b) As measured by ASTM D648. 
.sup.(c) As measured by ASTM D638. 
Each of the samples exhibited acceptable tensile and strain properties. 
However, the data show that a glycidyl content greater than 7% is 
generally preferable for inducing cross-linking of the polycarbonates. 
Furthermore, as the level of polycarbonate is decreased, there is also a 
decrease in some ductility. 
The high tensile modulus properties indicated good part integrity. This is 
confirmed by aging of the molded sample at 250.degree. C. for 1 hour, 
followed by examination of the sample for any changes in its dimensions or 
shape. 
Example 4 
This example demonstrates some of the disadvantages of using a glycidyl 
methacrylate homopolymer for the present invention. 
Polyglycidyl methacrylate was obtained from the Polyscience Company as a 
solution (10% by weight) in methyl ethyl ketone. A mixture of bisphenol 
A-derived cyclic polycarbonates (10.0 grams, 39.4 millimoles) was mixed 
with the solution of polyglycidyl methacrylate (5.63 grams, 0.394 
millimole) and tetramethylammonium tetraphenylborate (22.1 milligrams, 
0.04 millimole) in methylene chloride (50 mL). The solvents were 
evaporated, and the residue was dried in a vacuum oven at 110.degree. C. 
for 15 hours. 
Attempts were made to compression-mold a disk (about one inch (2.54 cm) in 
diameter, containing about 2 grams of the mixture) at a temperature of 
250.degree. C. and a pressure of 4000 pounds. These attempts failed, 
resulting in excessive foaming and complete degradation of the material. 
It appears that failure was in part due to the low thermal stability of 
the glycidyl methacrylate homopolymer. 
Example 5 
This example describes the preparation of a cross-linked polycarbonate 
composite article. 
An eight ply laminate containing about 70% by weight glass and 25% by 
weight resin (a mixture of the cyclic polycarbonate material and the 
polyglycidyl methacrylate-styrene copolymer used in Example 1) was 
compression-molded. 
The mold was placed in the tool piece, and the temperature was raised to 
225.degree. C. while the pressure was maintained at 50 psi. After reaching 
225.degree. C., the pressure was increased to 200 psi. These conditions 
were held for 15 minutes to achieve thorough impregnation of the resin 
into the glass fibers. While maintaining the pressure at 200 psi, the tool 
temperature was then raised to 280.degree. C. and held there for 10 
minutes. After cooling under pressure (200 psi), the part was demolded. A 
gel test as described above yielded 100% insoluble material, demonstrating 
that the cross-linking tendency of these compositions is not adversely 
affected by the presence of filler materials. 
Modifications and variations of the present invention might be desirable in 
light of the above teachings. It is, therefore, to be understood that 
changes may be made in the particular embodiments of the invention 
described herein which are within the full intended scope of the invention 
as defined by the appended claims.