A homogeneous mixture of a polyanhydride and an epoxy compound is prepared by the copolymerization of an olefinically unsaturated monomer capable of polymerization by free-radical means with an olefinically unsaturated monoanhydride and an olefinically saturated polyanhydride in the presence of a saturated epoxy compound and an anhydride accelerator without substantial anhydride-epoxide cross-linking. As an example, reinforcing glass fibers are impregnated with a solution of styrene, maleic anhydride, styrene-maleic anhydride copolymer, phenyl glycidyl ether and 1-methylimidazole and the resin is thickened in situ by copolymerization of the styrene, maleic anhydride and styrene-maleic anhydride copolymer to form a moldable, homogeneous mixture of styrene-maleic anhydride copolymer, phenyl glycidyl ether, 1-methylimidazole and reinforcing glass fibers.

In our U.S. patent application Ser. No. 590,460, filed June 26, 1975, we 
described the preparation of homogeneous, heat curable, resin mixtures by 
copolymerizing an olefinically unsaturated monomer capable of 
polymerization by free-radical means with an olefinically unsaturated 
monoanhydride in the presence of an epoxide composition and an anhydride 
accelerator without the occurrence of substantial anhydride-epoxide 
reaction. In this prior application the epoxide composition consisted of 
at least 50 percent, determined as epoxy equivalents, of a polyepoxide 
with the remainder being a monoepoxide. In the present invention we have 
discovered that the homogeneous, heat curable, resin mixtures can also be 
prepared in the same manner as described in Ser. No. 590,460, but 
utilizing an epoxide composition in which the majority or all of the epoxy 
equivalents are provided by a monoepoxy compound, with a polyepoxide 
providing less than 50 percent of the epoxy equivalents. 
This homogeneous resin mixture is a substantially noncross-linked 
thermosettable composition which can be heat cured to a hard, infusible 
resin through the reaction of the anhydride groups and the epoxy groups. 
In an application of this invention a solution of an unsaturated 
monoanhydride such as maleic anhydride, an olefinically unsaturated 
monomer which is capable of polymerization by free-radical means such as 
styrene, a polyanhydride such as preformed styrene-maleic anhydride 
copolymer, an anhydride accelerator such as 1-methylimidazole and a 
saturated monoepoxide such as phenyl glycidyl ether is intermixed with 
reinforcing fibers such as chopped glass fibers and an inert filler. This 
soft, sticky mass cannot be handled or molded. By our invention it is 
thickened in a first stage polymerization reaction to a non-tacky, 
handleable intermediate composition which is suitable for fabrication in a 
second stage polymerization reaction to a desired product of superior 
properties. 
In this first stage reaction to prepare the thickened intermediate 
compound, the olefinic double bonds of the olefinically unsaturated 
components are interreacted in situ by free radical initiation, preferably 
by a chemical free radical initiator in the reaction mixture, into 
polyanhydride molecules which are homogeneously intermixed with the other 
resin components. This first stage reaction is carried out at conditions 
at avoid substantial reaction of the anhydride and epoxy groups. In the 
second stage reaction the anhydride and epoxy groups in the intermediate 
compound are interreacted under the influence of heat and the anhydride 
accelerator to form a rigid, thermoset resin product having excellent 
physical, chamical and electrical properties. 
The olefinically unsaturaged monomer such as styrene also functions in the 
initial resin mixture as a solvent for the other resin components. Since 
this olefinically unsaturated monomer is reacted in the first stage 
copolymerization reaction, the intermediate composition can be prepared 
with no component of substantial volatility, which, if present, would 
interfere with proper second-stage curing or with storage stability of the 
intermediate composition. The thickened intermediate compound can range 
from a relatively hard, rigid material to a flexible material by 
adjustment of the resin formulation and appropriate control of the first 
stage reaction without substantial anhydride-epoxy reaction. The initial 
mixture of resin and reinforcing fiber can be spread out in a 
comparatively thin sheet for the thickening reaction. This not only makes 
possible better temperature control in the first stage reaction but also 
provides an intermediate product which is in a convenient form for further 
fabrication. Thus, the intermediate composition in sheet form can be used 
directly, after cutting into suitably sized pieces as desired, in 
compression molding. Also, a hardened intermediate composition in sheet 
form, hardened by appropriate choice of the resin formulation and not by 
substantial anhydride-epoxide reaction, can be reduced to granules or 
chips for use in injection molding or transfer molding fabrication. A 
nonreinforced intermediate resin product can be prepared by our procedure 
and pulverized for use in thermosetting powder coating or powder molding 
applications. In a further application of the resin formulation, glass 
fibers in the form of roving, tapes, and the like for use in filament 
winding can be coated with the liquid resin which is then solidified by 
the first-stage reaction for subsequent winding into the form of the 
desired product prior to anhydride-epoxy cure. The non-reinforced, 
unfilled formulations cure to a clear, transparent resin product, which 
evidences homogeneity comprising a single polymeric species. In contrast a 
cloudy, opaque product evidences heterogeneity. 
The intermediate resin comprising a homogeneous mixture of polyanhydride 
molecules and molecules of the epoxy compound together with the anhydride 
accelerator is a thermosettable material which melts or softens and flows 
at an elevated temperature prior to curing through the anhydride-epoxy 
reaction. Since the anhydride-epoxy reaction is a cross-linking, 
thermosetting reaction, substantial anhydride-epoxy reaction in the 
first-stage cure results in a gelled intermediate. This gelation, which is 
the result of cross-linking, interferes with the proper resin flow that is 
required to produce the desired fabricated product in the second-stage 
cure. Therefore, the first stage cure must be carried out without 
substantial anhydride-epoxy reaction, that is, less anhydride-epoxy 
reaction in the first-stage reaction than that amount which would 
interfere with the resin flow which is required in the second stage 
fabrication. Some anhydride-epoxy reaction can be tolerated in the 
first-stage reaction without significantly interfering with second-stage 
fabrication but the maximum permissible amount will vary depending on the 
second-stage curing conditions and the nature of the final product. 
First-stage anhydride-epoxy reaction can be minimized or substantially 
eliminated by appropriate selection of the formulation including the free 
radical initiation and the anhydride accelerator, exclusion of undesirable 
impurities, adjustment of first-stage copolymerization conditions, and the 
like. 
It is well known that the copolymerization reaction of styrene and maleic 
anhydride is a highly exothermic reaction. Since this copolymerization 
reaction is highly exothermic and since the anhydride-epoxy reaction is 
driven by heat, it is surprising that the first-stage exothermic 
copolymerization reaction can be carried out in accordance with our 
procedures without concurrently causing a substantial amount of the 
heat-sensitive, thermosetting reaction which would prevent resin flow in 
the second-stage cure or would interfere with successful second-stage 
molding. And it is particularly surprising that this reaction to the 
intermediate product can be carried out in the presence of the anhydride 
accelerator without a substantial amount of the flow-preventing, 
anhydride-epoxy reaction. 
It is also well known that styrene and maleic anhydride preferentially 
polymerize into a styrene-maleic anhydride copolymer having substantially 
equal molar proportions of each component. However, we have surprisingly 
discovered that styrene and maleic anhydride can be reacted in our novel 
process to form a styrene-maleic anhydride copolymer having a styrene to 
maleic anhydride ratio substantially greater than one to one under 
conditions that the prior art indicates produce a one to one molar ratio. 
Since styrene is an excellent and inexpensive solvent, it may be desirable 
to incorporate an excess of this reactive monomer into the resin to obtain 
the desired resin fluidity and adjust the cross-link density in the cured 
resin, provided that the excess styrene does not significantly detract 
from the excellent properties of the finally cured product. As stated, it 
would be expected from existing knowledge that the maleic anhydride would 
react with styrene in equal molar proportions. It would also be expected 
that excess styrene would form property-degrading polystyrene molecules 
interspersed therein. It has been discovered that under the conditions at 
which the copolymerization is carried out, excess styrene attaches to 
styrene-maleic anhydride copolymer by graft polymerization in the form of 
relatively short graft branches that do not cause a significant 
degradation of the properties of the fully cured resin. Due to this graft 
polymerization, an initial resin solution containing a substantial molar 
excess of styrene can be utilized without the formation of sufficient 
polystyrene to degrade or cloud the resin product. 
In preparing a styrene-maleic anhydride copolymer in situ in admixture with 
a saturated epoxy compound by the copolymerization of styrene and maleic 
anhydride, we have found that the presence of preformed styrene-maleic 
anhydride copolymer is preferred in the starting resin solution in 
addition to the styrene and maleic anhydride monomers due to the 
beneficial effect in the overall properties of the fully cured product. 
This preformed polyanhydride provides a nucleus for styrene and maleic 
anhydride addition, including styrene grafting, in a more controlled 
reaction. The presence of preformed polyanhydride also exercises a 
beneficial control of the free radical reaction and reduces the amount of 
the styrene-maleic anhydride copolymer to be produced by the highly 
exothermic reaction of styrene with maleic anhydride in order to obtain 
the requisite anhydride-epoxy cross-link density, thereby reducing the 
overall amount of heat generated by this reaction. This reduction in the 
generation of heat in the thickening reaction is enhanced by the fact that 
the graft reaction of styrene to the styrene-maleic anhydride copolymer 
generates much less heat than the reaction of styrene with maleic 
anhydride. The presence in the resin formulation of the preformed 
polyanhydride, the reinforcing fiber, the filler and other components that 
are used in the formulation also moderates the temperature rise in the 
reacting mixture by absorbing some of the heat generated in the reaction. 
Styrene-maleic anhydride copolymers are solids. The room temperature 
(25.degree. C.) solubility in styrene of an equimolar copolymer of styrene 
and maleic anhydride is very low. Copolymers of styrene and maleic 
anhydride having styrene to maleic anhydride ratios that are greater than 
one to one can be prepared by special techniques. The room temperature 
solubility in styrene of a copolymer having a styrene to maleic anhydride 
ratio of two to one is also very low. When the styrene-maleic anhydride 
copolymer possesses large styrene to maleic anhydride ratios, the 
copolymer possesses a significant solubility in styrene. However, a large 
ratio of styrene to maleic anhydride in the copolymer lowers the quality 
of the resulting thermoset product for many uses by lowering its 
cross-link density. Similarly, a large proportion of solvent styrene in 
the initial reaction mixture can lower the quality of the thermoset 
product by producing a heterogeneous, polystyrene-containing product, by 
lowering its cross-link density and the like. 
Maleic anhydride is also a solid. At room temperature styrene-maleic 
anhydride solutions can be prepared having a maximum solids content of 
about 22 weight percent. Larger amounts of maleic anhydride can be 
dissolved in the styrene at an elevated temperature, but the excess maleic 
anhydride will precipitate out to a 22 percent content when the solution 
is cooled to room temperature. However, we have discovered that if the 
solution of styrene and maleic anhydride is moderately heated to dissolve 
more than 22 percent maleic anhydride and if the solid styrene-maleic 
anhydride copolymer is dissolved into the warmed solution, the maleic 
anhydride in excess of the original 22 percent will stay in solution when 
the solution is cooled to room temperature. 
We have also discovered that a styrene-maleic anhydride solution at a 
slightly elevated temperature which contains an excess of maleic anhydride 
over that which is soluble at room temperature will dissolve a surprising 
excess of a low styrene content styrene-maleic anhydride copolymer over 
the amount which is soluble in styrene alone at that temperature or in a 
styrene-maleic anhydride solution containing a lesser amount of maleic 
anhydride at that same temperature. The overall result is a surprising 
reciprocal solubility effect, that is, the solid maleic anhydride enhances 
the solubility of the solid styrene-maleic anhydride copolymer and the 
solid styrene-maleic anhydride copolymer concurrently enhances the 
solubility of the solid maleic anhydride. 
We have made a further advantageous discovery. That is, the presence of the 
copolymer solubilizing maleic anhydride monomer provides the surprising 
effect of producing a resin solution having a substantially lower room 
temperature viscosity than possessed by a styrene solution of a 
styrene-maleic anhydride copolymer having the same weight proportion of 
these two components but no maleic anhydride. Thus, a solution prepared at 
an elevated temperature from equal amounts by weight of styrene and a two 
to one styrene-maleic anhydride copolymer will be a putty-like, semi-solid 
at room temperature. However, this equal parts by weight solution of 
styrene and this copolymer can be prepared at a lower temperature with 
maleic anhydride as a solubility enhancer to form a solution having a room 
temperature viscosity of less than 1,000 cps. This surprising effect 
results in a plurality of desirable advantages, that is, a room 
temperature resin solution having a very high solids content, a relatively 
low overall styrene content, a high fluidity, and the like. These 
discoveries regarding solution properties have enabled us to optimize 
proportions with regard to cost, polymerization characteristics and 
product properties. 
Since the first stage copolymerization reaction is a free radical reaction, 
suitable free radical initiation is used to obtain the desired 
copolymerization. The copolymerization reaction is preferably carried out 
at a moderately elevated temperature. At a low temperature the free 
radical reaction is inconveniently slow and at a high temperature the 
anhydride-epoxy cross-linking reaction becomes excessive. Since the 
first-stage reaction is exothermic, the internal resin temperature will 
rise during the reaction above the temperature of the resin at which the 
reaction is initiated. This first stage reaction can successfully be 
carried out at a maximum internal temperature of the resin as determined 
by an embedded thermocouple of about 150.degree. C., preferably about 
125.degree. C. and most preferably about 100.degree. C. At the higher 
internal temperatures short reaction times are insured by using 
particularly active free radical initiators, preferably accompanied by 
rapid heat up and cool down of the resin mixture in order to minimize the 
cross-linking reaction. Although the thickening reaction can be initiated 
at a resin temperature below room temperature, this procedure is less 
desirable than the initiation of the reaction at about room temperature or 
more preferably at a moderately elevated temperature. 
Suitable free radical initiation includes the use of chemical free radical 
initiators, ionizing radiation, ultraviolet radiation, and the like. 
Suitable chemical free radical initiators include the organic peroxides 
such as methyl ethyl ketone peroxide with vanadium neodecanoate or cobalt 
naphthenate as a promotor, dicyclohexyl peroxydicarbonate, t-butyl 
peroxyneodecanoate, t-butyl peroxypivalate, and the like; azo compounds 
such as 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis 
(2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyronitrile), 
2-t-butylazo-2-cyano-4-methoxy-4-methylpentane, and the like. It is of 
critical significance that the selection of the anhydride accelerator be 
carefully correlated with the free radical initiation to insure that the 
desired copolymerization reaction occurs without substantial 
cross-linking. For example, if a chemical free radical initiator is used, 
the anhydride accelerator must be substantially inactive during the 
copolymerization reaction at the temperature and for the time that the 
free radical reaction is carried out. Thus, when a chemical free radical 
initiator is used, it should have a relatively short half-life at a 
moderate temperature and be used in suitable amount to cause an a active 
copolymerization reaction at a moderate temperature. In contrast with the 
activity of the free radial initiation, the anhydride accelerator will 
possess a low activity for the anhydride-epoxy reaction. That is, low 
activity as applied to the anhydride accelerator is a relative term which 
is applied as a contrast with the substantially greater activity of the 
free radical initiation at the same conditions. Furthermore, the selection 
of the chemical free radical initiator must be correlated with the 
anhydride accelerator to avoid any interference of the effect of the free 
radical initiator by the anhydride accelerator. The peroxide initiators 
appear to be more susceptible to a deactivating effect by some anhydride 
accelerators. 
The compositions comprise an olefinically unsaturated monomeric compound 
containing one olefinic double bond capable of polymerization by free 
radical means as its only functional group. As used herein and in the 
claims, functional group is used to mean any group which is reactive at 
the conditions and in the environment involved in the first-stage 
copolymerization. Olefinically unsaturated monomeric compounds which 
polymerize by a free radical mechanism are well known in the art and are 
generally terminally unsaturated compounds which contain a substituent 
directly connected to the double bond that activates the double bond for 
polymerization by effecting a net electron withdrawal from the olefinic 
double bond. Examples of useful olefinically unsaturated monomers which 
are capable of polymerization by free radical means include vinyl 
substituted mononuclear aromatic compounds such as styrene, ring 
substituted chloro-, bromo- or lower alkyl styrene, such as 
p-chlorostyrene, 3-bromostyrene, vinyl toluene, and the like, but not the 
.alpha. or .beta.-substituted styrene such as .alpha.-methylstyrene and 
.beta.-bromostyrene. Also useful are lower alkyl acrylates and 
methacrylates, such as methyl methacrylate, methyl acrylate, ethyl 
acrylate, and the like; vinyl acetate, acrylonitrile; vinyl chloride; 
vinyl bromide; vinylidene chloride; diallyl phthalate; and the like. Also 
useful as -alkenes, olefinically unsaturated monomeric compounds are 
alkenes, preferably 1-alienes, and halogen-substituted, preferably 
chloro-substituted, alkenes having from 6 to 18 carbon atoms. Examples of 
suitable alkenes include 1-hexene, 2-methylpentene-1,5-chlorohexane-1, 
cyclohexene, 5-decene, 1-octadecene, and the like. As used herein, the 
expression lower alkyl refers to alkyl having one to four carbon atoms, 
inclusive. 
The unsaturated monoanhydride which can be used in making the intermediate 
composition by copolymerization includes maleic anhydride, chloromaleic 
anhydride, methylmaleic anhydride, ethylmaleic anhydride, dichloromaleic 
anhydride, dimethylmaleic anhydride, n-butylmaleic anhydride, phenylmaleic 
anhydride, diphenylmaleic anhydride chloromethylmaleic anhydride, 
bromophenylmaleic anhydride, itaconic anhydride, and the like. 
The preformed polyanhydride which can be used in making the molding 
composition is the copolymer of an olefinically unsaturated monomer which 
is capable of free radical polymerization as described and the described 
unsaturated monoanhydride. For example, useful polyanhydrides include the 
copolymer of styrene and maleic anhydride having a ratio of styrene to 
maleic anhydride from about 1:1 to about 10:1, preferably from about 1:1 
to about 3:1, and most preferably about 2:1, and having an average between 
two and about 500, preferably between two and about 200 repeating units, 
and the like. Also the preformed polyanhydride can be the equimolar 
copolymer of the unsaturated monoanhyride as described and one or more two 
to 20 carbon, preferably two to 10 carbon, 1-alkenes or 
halogen-substituted 1-alkenes having an average of two to about 500, 
preferably two to about 200 repeating units. Suitable 1-alkenes include 
ethylene, vinyl chloride, 1-propene, 1-butene, 1-pentene, 1-hexene, 
1-heptene, 1-octene, 1-nonene, 1-decene, 5-chlorohexene-1, 1-undecene, 
1-dodecene, 1-tridecene, 1-tetradecene, 1-octadecene, 4-methyl-1-heptene, 
and the like. 
A saturated monoanhydride can replace a part of the preformed 
polyanhydride, preferably no greater than 50 percent measured in anhydride 
equivalents. Since the saturated monoanhydride may reduce the cross-link 
density of the fully cured product with a concomittant effect on its 
properties, it is less preferred than the polyanhydride for this reason. 
The preformed polyanhydride and the saturated monoanhydride comprise the 
saturated anhydride component. Suitable saturated monoanhydrides include 
phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic 
anhydride, methyltetrahydrophthalic anhydride, dodecenylsuccinic 
anhydride, chlorendic anhydride, a mixture of methyl bicyclo 
(2.2.1)-heptane-2,3-dicarboxylic anhydride isomers (Nadic methyl 
anhydride), mixtures thereof, and the like. 
The saturated monoepoxide which is used in forming the molding compound 
herein is a liquid or solid at room temperature (20-25.degree. C.) having 
between three and about 20 carbon atoms, preferably between three and 
about 12 carbon atoms, per molecule. The lower molecular weight liquid 
monoepoxides that are useful herein will also contribute a solvent effect 
to the resin mixture in addition to that provided by the olefinically 
unsaturated monomer. When the intermediate composition that is made in 
accorcance with the invention herein is to be stored for a significant 
period of time prior to the final curing, it is preferred that only an 
epoxide composition of relatively low volatility be used in the resin 
formulation. 
The saturated monoepoxide can suitably be an aliphatic, cycloaliphatic, 
aromatic or mixed aliphatic-aromatic monoepoxide consisting of hydrogen 
atoms, carbon atoms and the one oxygen atom. The saturated monoepoxide can 
also be an aliphatic, cycloaliphatic, aromatic or mixed aliphatic-aromatic 
epoxy-containing ether or epoxy-containing ester consisting of hydrogen 
atoms, carbon atoms and the epoxy and ether or ester oxygen atoms. These 
saturated monoepoxides can further contain one or more halogen atoms, 
preferably chlorine atoms. Mixtures of two or more of these saturated 
monoepoxy are available both as 1,2-epoxy compounds in which the epoxy 
group is located in a terminal position in the molecule and as compounds 
in which the epoxy group is in an internal position in the molecule. 
Saturated monoepoxides which are useful in preparing the moldable resin 
compositions include 1,2-epoxy hexane; 1,2-epoxy decane; 
1,2-epoxy-7-propyl decane; 1,2-epoxy dodecane; 1,2-epoxy octadecane; 
1,2-epoxy eicosane; 7,8-epoxy hexadecane; 3,4-epoxy hexane; 2,3-epoxy- 
2,3-dimethylbutane, and the like. Also useful in preparing these moldable 
resin compositions are 2,3-epoxy-2-phenylhexane; cyclohexane oxide; 
epoxycyclohexane; styrene oxide; epoxy isopropylbenzene, and the like. The 
group of epoxy-containing ethers which are useful includes 
1,2-epoxy-2phenoxypropane; 1,2-epoxy-2-butoxypropane; methyl glycidyl 
ether; butyl glycidyl ether; octyl glycidyl ether; 2-propyloctyl glycidyl 
ether; phenyl glycidyl ether; isopropyl glycidyl ether; octadecyl glycidyl 
ether; amyl glycidyl ether; tolyl glycidyl ether; naphthyl glycidyl ether; 
and the like. 
The group of epoxy containing esters which are useful includes glycidyl 
benzoate; glycidyl p. methyl benzoate; glycidyl acetate; diacetate of 
monoglycidyl ether of glycerol; dipropionate of the monoglycidyl ether of 
glycerol; glycidyl propionate; glycidyl methyl maleate; glycidyl stearate; 
methyl 1,2-epoxypropionate; butyl 1,2-epoxypropionate; glycidyl caprolate, 
and the like. Useful halogen-substituted saturated monoepoxides of the 
above groups include epichlorohydrin; epibromohydrin; 
2,3-epoxy-2,4-dimethyl-4-chlorobutane; 1,2-epoxy-3-chlorobutane; 
1,2-epoxy-5-chlorodecane; chlorophenyl glycidyl ether; pentachlorophenyl 
glycidyl ether; hexachlorocyclohexyl glycidyl ether, and the like. 
The saturated monepoxide can be substituted, in part, by an epoxy resin in 
such amount that less than 50 percent of the epoxy equivalents in the 
total resin composition will be in the epoxy resin. That is, the ratio of 
epoxy equivalents in the saturated monoepoxy compound to the epoxy 
equivalents in the epoxy resin will be greater than 1:1. 
The epoxy resin, also designated by the term polyepoxide, can be a single 
compound containing at least two epoxy groups in which case it is a 
diepoxide. It can also contain a variety of molecular species having a 
varying number of epoxy groups per molecule such that the average number 
of epoxy groups per molecule, that is the epoxy equivalent value, is 
specified. The epoxy equivalent of these polyepoxides comprising a mixture 
of molecular species is greater than one and is preferably about two or 
more, but will generally not be a whole integer. The epoxy equivalent 
value is obtained by dividing the average molecular weight of the 
polyepoxide by its epoxide equivalent weight (grams of the polyepoxide 
containing one gram equivalent of epoxide). The polyepoxide can be 
aliphatic, cycloaliphatic, aromatic, heterocyclic mixtures of these, 
saturated or unsaturated, and the like. It can be liquid or solid but must 
be soluble in the resin solution, or if not soluble capable of forming a 
homogeneous dispersion in the resin solution. 
This broad class of epoxy resins which is useful is exemplified by 
reference to several of the better known types. The glycidyl group of 
epoxy resins is an important and useful type of epoxy resin. This group 
includes the glycidyl ethers, the glycidyl esters, the glycidyl amines, 
and the like. The glycidyl ethers include the glycidyl ethers of 
mononuclear polyhydric phenols, polynuclear polyhydric phenols and the 
aliphatic polyols. They may be single compounds or more commonly are a 
mixture of compounds, some of which are polymeric in nature. Illustrative 
of glycidyl ethers are the di- or polyglycidyl ethers of ethylene glycol; 
trimethylene glycol; glycerol; diglycerol; erythritol; mannitol; sorbitol; 
polyallyl alcohol; butanediol; hydrogenated bisphenol A; and the like. 
The glycidyl ethers of polyhydric phenols include the glycidyl ethers of 
resorcinol; hydroquinone; catechol; pyrogallol; and the like as well as 
the glycidyl ethers of polynuclear phenols such as bisphenol A; 
bis(4-hydroxyphenyl)methane; and the like, and glycidyl ethers of the 
novolac resins such as bisphenol F and the like. The epoxy resins also 
include epoxidized olefins generally based on naturally occurring oils 
such as epoxidized soybean oil, epoxidized cotton seed oil, epoxidized 
castor oil, epoxidized linseed oil, epoxidized menhaden oil, epoxidized 
lard oil and the like, but also including epoxidized butadiene, epoxidized 
polybutadiene, and the like. 
Additional useful epoxy resins are diglycidyl isophthalate; triglycidyl 
p-aminophenyl; diglycidyl phenyl ether; triglycidyl ether of 
trihydroxybiphenyl; diglycidyl ether of bisphenol PA; 
triglycidoxy-1,1,3-triphenylpropane; and the like. Further examples of 
epoxy resins are vinylcyclohexenedioxide; limonene dioxide; 
2,2-bis(3,4-epoxycyclohexyl)propane; diglycidyl ether; bis 
(2,3-epoxycyclopentyl)ether; dicyclopentadiene dioxide; 
3,4-epoxycyclohexylmethyl-(3,4-epoxy) cyclohexane carboxylate; and the 
like. Further information on these epoxy resins and additional examples of 
useful epoxy resins are discussed and/or referred to in HANDBOOK OF EPOXY 
RESINS by H. Lee and K. Neville, McGraw-Hill Book Co., 1967. 
The presence of active hydrogen atoms such as found in water and in 
hydroxyl and carboxyl induce the anhydride-epoxy reaction and are 
particularly active in the presence of the anhydride accelerators. This is 
described in the above book by Lee and Neville, For this reason, it is 
essential particularly for significant shelf life of the intermediate 
composition that the presence of active hydrogen be minimized or 
substantially eliminated as a component or impurity in the initial resin 
mixture, particularly in the form of water, carboxyl or hydroxyl, or in 
the anhydride accelerator. This is accomplished by assuring that the 
initial anhydride reactants are substantially carboxyl-free and that all 
reactants are protected against contamination from atmospheric moisture. 
Predrying of one or more of the reactants may be desirable. Some 
polyepoxides such as the diglycidyl ether of bisphenol A contain reactive 
hydroxyl in each repeating unit. Hydroxyl is substantially eliminated in 
this instance by selecting a diglycidyl ether of bisphenol A which has a 
relatively low epoxy equivalent weight. As used herein, the expression 
"substantially free of active hydrogens" is used to mean that the reaction 
mixture contains insufficient active hydrogens to cause, in the presence 
of the anhydride accelerator, substantial anhydride-epoxy reaction in the 
first stage reaction. 
In preparing the initial resin mixture the olefinically unsaturated monomer 
which is capable of polymerization by free radical means is used both as a 
reactant and as a solvent for the other resin components. It is used in an 
amount of about five to about 80 weight percent of the total resin 
components, preferably about 10 to about 60 weight percent of the resin 
mixture and most preferably about 15 to about 50 weight percent of the 
resin mixture. The molar ratio of the olefinically unsaturated monomer to 
the unsaturated monoanhydride that is conveniently used is from about 
0.5:1 to about 8:1, preferably about 1:1 to about 4.5:1 and most 
preferably about 1:1 to about 3:1. For optimum properties in the fully 
cured product using styrene and maleic anhydride, a ratio of about 1:1 to 
about 3:1 is preferred, while a much higher ratio can be effectively used 
when methyl methacrylate and maleic anhydride are the copolymerization 
reactants, In contrast certain of the olefinically unsaturated monomers, 
such as the alkenes, will react with the unsaturated monoanhydrides in 
about a 1:1 molar ratio; therefore, these components are preferably used 
in this ratio. Thus it is noted that the preferred relative proportion of 
reactants depends upon the specific reactants used as well as the desired 
product properties. 
The unsaturated monoanhydride is preferably used with a saturated 
polyanhydride as described. The anhydride equivalent ratio of the 
unsaturated monoanhydride to the sum of the unsaturated monoanhydride and 
the saturated anhydride component can suitably be as low as about 0.2:1, 
preferably as low as about 0.4:1 and most preferably as low as about 
0.5:1; and as high as about 1:1, preferably as high as about 0.9:1 and 
most preferably as high as about 0.8:1. The anhydride to epoxide 
equivalent ratio; that is the A/E ratio, is conventionally used to express 
the relative proprtions of the anhydride groups and the epoxy groups 
present in a resin mixture, particularly when mixtures of molecules of 
different sizes in the anhydride and epoxide components are involved. We 
have found that the A/E ratio can suitably be from about 0.1:1 to about 
2.5:1, preferably from about 0.3:1 to about 1.5:1 and most preferably from 
about 0.5:1 to about 1.3:1. 
The resin composition is preferably formed in sheets using a fiber glass 
reinforcement. Fiber glass in various forms is well known and commercially 
available for resin-fiber glass compositions. The fiber glass can be in 
the form of a woven glass fabric or randomly distributed glass fibers. 
When chopped glass fivbers are used, they can suitably range from about 3 
mm. to about 50 mm. in length and preferably from about 5 mm. to about 25 
mm. in length. Other fibrous material can be used as the reinforcement or 
core material in the form of randomly distributed particles, fibers, 
fluff, paper, woven fabric, and the like. This can be made from natural 
materials such as cellulose, including sisal, hemp, cotton and linen, 
asbestos, etc., or a synthetic such as nylon, polyester, polyolefin, and 
the like. 
The resin compositions can contain constituents in addition to the monomers 
and core material such as pigments or dyes for coloring the finished 
product, plasticizers, fillers, and the like. The fillers provide the 
desirable function of reducing the cost of the final product without 
significantly reducing the physical properties and can improve certain 
properties such as fire resistance, arc resistance and the like. Suitable 
filler material includes powdered calcium carbonate, clay, sands, powdered 
metals such as aluminum and iron, metal oxides such as iron oxide, 
alumina, etc., powdered silica, wood flour, walnut shell flour and the 
like. The filler is preferably inert in the composition, that is, it 
should not react with any of the reactants or catalyze a reaction 
involving the reactants. Also a material such as fused silica can be added 
to the resin formulation to increase its viscosity can be added to the 
resin formulation to increase its viscosity prior to the thickening 
reaction. Other additives which can be used are a suitable mold release 
agent or a material such as poly(methylmethacrylate, finely ground 
polyethylene, finely ground polystyrene and the like to impart a low 
profile, that is, a smooth surface, to the molded product. 
It may be desirable to incorporate in the initial mixture a non-reactive 
plasticizer or a reactive plasticizing monomer which possesses the ability 
to enhance the flow characteristics during molding. Such plasticizing 
components include epoxidized vegetable oils such as epoxidized soy bean 
oil, di-2-ethylhexyl phthalate, dioctyl phthalate, dihexyl phthalate, 
di-isooctyl phthalate, polyethylene glycols such as those having a 
molecular weight between 600 and 1,000, Nadic methyl anhydride, and the 
like. 
As pointed out, polymerization of the double bond is highly exothermic. In 
view of this, care must be exercised in order that the material does not 
heat high enough in the first stage polymerization to cause a significant 
anhydride-epoxy, cross-linking reaction to a gel such that the 
intermediate resin will not properly melt or flow or cannot be easily 
molded. However, it may be desirable that the intermediate product contain 
some anhydride-epoxy bonding below the gelation stage to increase the melt 
viscosity of the resin when excessive fluidity during molding becomes a 
problem. When the fiber glass-resin mixture has been laid down in 
relatively thin sheets, the exothermic heat of reaction is more readily 
dissipated than when thick sheets are used. Furthermore, the rate of the 
first stage reaction and therefore the heat buildup can be partially 
controlled by control of the free radical initiation itself. Since 
chemical free radical initiators generate free radicals at different 
rates, polymerization can be controlled by an appropriate selection of the 
chemical initiator, the amount used, and the time and temperature of the 
polymerization reaction. If ionizing radiation is used, a reduction in the 
intensity of the radiation source will reduce the rate of heat buildup in 
the material. 
In the first-stage polymerization reaction the olefinically unsaturated 
monomer is completely reacted to form an intermediate product which is 
substantially free of volatile components. This intermediate composition 
is dry and handleable, that is, it can be handled, cut and the like 
without sticking to the hands, shears, and the like, and is readily 
moldable. When styrene is used without filler or reinforcing fiber, a 
clear intermediate product is obtained which is indicative of a 
homogeneous material and the absence of polystyrene. Since polystyrene and 
styrene-maleic anhydride copolymers are mutually insoluble, their 
concurrent presence in the intermediate product would be indicated by 
opacity. This homogeneous intermediate product results in a homogeneous 
fully cured resin product. In contrast a non-homogeneous intermediate 
product would result in a non-homogeneous resin product with inferior 
properties. The complete insolubility of the fully cured resin product in 
methyl ethyl ketone also indicates the absence of polystyrene in the final 
product. 
In preparing the reaction solution the unsaturated monoanhydride can be 
added to the ethylenically unsaturated monomer and stirred at a mildly 
elevated temperature, if necessary, until solution is obtained, next the 
olefinically saturated polyanhydride can be added with stirring until 
solution is obtained, then finally the epoxide can be added. 
Alternatively, all four components can be added together with stirring 
until solution is obtained or the epoxide can be added to the 
ethylenically unsaturated monomer and then the unsaturated monoanhydride 
and the saturated polyanhydride can be added. The anhydride accelerator 
and free radical initiator are generally added last, but prior to the 
first-stage reaction. Other procedures are also possible. In some 
instances one or more of the components may not be completely soluble in 
the solution. In this instance such component can be finely granulated, 
with the resin components then formed into a homogeneous, liquid 
dispersion or mixture, rather than a true solution. As a result of the 
fineness of the particles and the thoroughness of the dispersion, the 
mixture will function in the process similar to a true solution of the 
reacting components. The pigments, catalysts, filler and other optional 
components are then introduced and then the mixture can be thickened by 
copolymerization to form the intermediate compound, such as sheet molding 
compound. 
The term sheet molding compound is a designation of the Society of the 
Plastics Industry for resin-fiber reinforced, thermosetting composition in 
sheet form which is designed for compression molding. This molding 
compound can be formed as a sheet in a continuous process by depositing 
dry, chopped glass fiber moving between resin-coated plastic film such as 
polyethylene film. The resulting sandwich is then roller kneaded and 
compacted to uniformly interdisperse the resin and the glass fibers and to 
accomplish uniform thickness. This sticky, plastic contained mixture is 
then thickened by copolymerization of the ethylenically unsaturated 
components to form the sheet molding compound. The sheet molding compound 
can then be cut to the desired mold shape and molded under heat and 
pressure to form the fully cured product. 
The sheet molding compound can also be formed by a spray-up method in which 
the catalyzed resin in liquid form and chopped fiber glass roving are 
sprayed or blown simultaneously onto a surface such as a polyethylene film 
and covering this with a second polyethylene film. Wetting of the glass 
fibers by the resin solution is obtained in flight. Kneading or compaction 
of the sprayed up material can be utilized, if necessary, to complete the 
wetting of the fibers and insure uniform distribution of the resin in the 
fiber. Whichever method is used for preparing the sheet molding compound, 
it is necessary that the reinforcing fibers be sufficiently long to give 
the final product adequate strength but not so long that they will 
interfere with the flow of the resin-fiber mixture in the mold during 
curing. Under the influence of the heat and pressure, the resin component 
will soften. If it does not soften enough due to too much anhydride-epoxy 
cross-linking, it will not flow properly in the mold. Or if the 
anhydride-epoxy reaction is too rapid at the molding temperature, the 
resin will gel in the mold before it has flowed sufficiently to fill out 
the mold. If the resin softens too much, it will flow away from the 
reinforcing fiber during molding. 
As described, a suitable anhydride-accelerator must be used in order to 
obtain a satisfactory second stage cure, particularly when mold curing is 
utilized. In order to prepare the intermediate compound without 
substantial anhydride-epoxy reaction, the anhydride accelerator must be 
substantially inactive at the conditions required for the free-radical 
reaction including the time and temperature of the reaction. Furthermore, 
adequate control of active hydrogen must be effected to insure that 
substantial anhydride-epoxy reaction does not occur. Therefore, an 
anhydride accelerator is preferably used which is substantially free of 
active hydrogen. If the temperature of the free radical reaction is 
increased, a less active anhydride accelerator is used. The relative 
inactivity of the anhydrade accelerator in contrast with the activity of 
the free radical initiation is further emphasized when significant storage 
stability of the intermediate composition is desired. The anhydride 
accelerator functions by opening up the anhydride group for reaction with 
the epoxy group. This accelerator can suitably be a nitrogen containing 
anhydride accelerator, preferably a non-volatile liquid, which is 
incorporated into the initial reaction mixture in the amount of about 0.01 
to about 10 weight percent, preferably about 0.1 to about 5 percent based 
on the resin components. Since the presence of an anhydride accelerator 
for the second stage anhydride-epoxide that may take place in the 
first-stage copolymerization procedure or during storage of the 
intermediae composition, its selection, particularly with respect to its 
activity and the amount used, must be carefully correlated with the other 
components and the conditions in the first-stage copolymerization to avoid 
a substantial amount of such anhydride-epoxy reaction in the first stage, 
as described above. 
The preferred accelerators are tertiary nitrogen compounds particularly 
those in which one or more tertiary nitrogen atoms are in a ring structure 
including pyridine and its mono- and di-lower alkyl-substituted 
derivatives, N-lower alkyl-substituted imidazole, N-lower 
alkyl-substituted morpholine, N-lower alkyl-substituted piperidine, 
N,N-di-lower alkyl-substituted piperazine, and the like. Also included are 
the compounds containing tertiary nitrogen atoms in which the ring is 
attached to the nitrogen atom with one bond including N,N-di-lower 
alkylcyclohexylamine, benzyl di-lower alkylamine, benzyl tri-lower 
alkylammonium chloride and the like. We have further discovered that 
nitrogen containing anhydride accelerators can be used successfully in 
which there is labile hydrogen attached to the nitrogen, especially when 
used in minor amounts or with particular care, to avoid substantial 
anhydride-epoxy reaction in the copolymerization reaction, although the 
intermediate product containing these accelerators tends to be less 
storage stable. As used herein, lower alkyl includes methyl, ethyl, 
propyl, and butyl. The group of suitable anhydride accelerators includes 
morpholine; N-ethylmorpholine; N-aminopropylmorpholine; 
N,N-dimethylcyclohexylamine; dimethylamine; 3-picoline; melamine; 
diallylmelamine and the like; imidazoles such as imidazole; 
1-methylimidazole; 2-methylimidazole; 2-ethylimidazole; 
1,2-dimethylimidazole; and the like; benzyltrimethylammonium chloride, 
dicyandiamide, piperazine; piperidine; and the like. A solid accelerator, 
such as dicyandiamide, can be finely powdered and thoroughly incorporated 
throughout the resin mixture. 
The intermediate compound can be cured at an elevated temperature of about 
65.degree. C. to about 220.degree. C., preferably about 140.degree. C. to 
about 190.degree. C. for a sufficient time to effect cure, namely, about 
30 seconds to about 24 hours. The molding pressure, when utilized, 
generally will be taken between 3 amd about 200 kg./cm.sup.2 and 
preferably about 25 to about 100 kg./cm.sup.2. The cure conditions are 
related in part to the resin composition including the particular 
accelerator that is used. For suitable molding the total combined content 
of the reinforcing fiber and filler should be no greater than about 80 
percent of the total composition. When fiber glass reinforcement is used, 
it will comprise about 10 percent to about 80 percent, preferably about 20 
percent to about 65 percent of the total composition. The filler will 
ordinarily be used in the range of about 5 percent to about 80 percent, 
preferably about 10 percent to about 40 percent of the total composition.

In the following description of specific embodiments of the invention, the 
polyanhydride was Arco Chemical Company SMA 2000 resin, a styrene-maleic 
anhydride copolymer having a styrene to maleic anhydride mol ratio of 
about 2:1 and a molecular weight of about 1,700. The fumed silica was 
Cab-O-Sil M-5, a fire-dry fumed silica with a nominal particle size of 
0.012 microns manufactured by Cabot Corporation. The flexural strength was 
determined by ASTM D-790, the tensile strength by ASTM D-638 and the 
spiral flow was determined by ASTM D-3123-72. 
EXAMPLE 1 
Into a one liter blend was mixed 216.6 g. of styrene, 290.0 g. of phenyl 
glycidyl ether, 102.0 g. of maleic anhydride, and 212.4 g. of a 
styrene-maleic anhydride copolymer having a styrene to maleic anhydride 
mol ratio of about 2:1. The ingredients were blended at high speed until 
solution was evident. This solution of resin components was cooled and the 
viscosity was measured at 25.degree. C. in a Brookfield viscometer and 
found to he 72 cps. This viscosity was increased with one percent of a 
fumed silica to an average reading of 707 cps. at 25.degree. C. To 500 g. 
of this base resin were added 5 g. of 
2,2'-azobis(2,4-dimethylvaleronitrile) and 1.25 cc. of 1-methylimidazole. 
A resin-fiber glass mixture was made by kneading 240 g. of the catalyzed 
base resin with 160 g. of 8 mm. copped Owens Corning Fiberglass 832 in a 
10-inch by 20-inch polyethylene bag. This resin-fiber glass mixture was 
formed into a mat by rolling it out in the plastic bag to a mat of about 
160 square inches. This A-stage resin fiber glass mat was B-staged in a 
200.degree. F. oven for 10 minutes. The B-staged product was flexible and 
handleable and was found to have a spiral flow in excess of 48 inches. The 
B-staged product was molded between heated plates at 325.degree. F. for 10 
minutes to a thickness of about one-eighth inch. This molded product was 
determined to have a flexural strengh of 10,207 psi. and a tensile 
strength of 2,580 psi. 
EXAMPLE 2 
The procedures and conditions of Example 1 were repeated in the preparation 
of a molding compound and a product molded therefrom using a different 
epoxy compound. The resin solution was prepared by blending 181.2 g. of 
styrene, 85.4 g. of maleic anhydride, 177.7 g. of the 2/1 copolymer of 
styrene and maleic anhydride and 355.7 g. of Cordura E Ester (Shell 
Chemical Company's glycidyl ester of a mixture of nine and eleven carbon 
carboxylic acids). Its 25.degree. C. Brookfield viscosity of 64 cps. was 
adjusted to 431 cps. by the addition of one percent fumed silica. The free 
radical initiator, anhydride accelerator and fiber glass were incorporated 
in the same proportions. A 400 g. quantity of this material was B-staged 
as before to a pliable, handleable product having a spiral flow in excess 
of 48 inches. It was then molded to a product having a flexual strength of 
8,930 psi. and a tensile strength of 2,760 psi. 
EXAMPLE 3 
The procedures and conditions of Example 1 were again repeated using 
another epoxy compound. The resin solution was prepared with 250.5 g. of 
styrene, 118 g. of maleic anhydride, 245.7 g. of the 2:1 styrene-maleic 
anhydride copolymer and 185.7 g. of epichlorohydrin. The 25.degree. C. 
Brookfield viscosity of this resin solution was increased from 48 cps. to 
572 cps. using one percent fumed silica. After mixing in the same free 
radical initiator, anhydride accelerator and fiber glass in the same 
proportions, a 400 g. sample was thickened to a pliable molding compound. 
This material was determined to have a spiral flow by the spiral flow test 
of 10 inches. The material was molded as before to a product having a 
flexural strength of 8,660 psi. and a tensile strength of 5,270 psi. 
EXAMPLE 4 
In this experiment styrene oxide was used in preparing a molding compound 
and a molded product using the same procedures and conditions as set out 
in Example 1 except as noted below. The resin solution was prepared from 
234.3 g. of styrene, 110.4 g. of maleic anhydride, 229.8 g. of the 2:1 
styrene-maleic anhydride copolymer and 225.5 g. of the styrene oxide. The 
25.degree. C. Brookfield viscosity of 62 cps. was increased to 232 cps. 
with one percent of the fumed silica. The same free radical initiator, 
anhydride accelerator and fiber glass were mixed in the same proportions 
as before. The 400 g. sample of this material was B-staged to a hard 
molding compound having a spiral flow of eight inches. This material 
required a preheat cycle of two minutes at 225.degree. F. before it was 
molded as described in Example 1. The molded product had a flexural 
strength of 10,600 psi. and a tensile strength of 1,640 psi. 
EXAMPLE 5 
In this experiment n-butyl glycidyl ether was used as the epoxy compound in 
preparing a molding compound and a molded product by the procedures and 
conditions of Example 1. 251.3 g. of styrene, 107.6 g. of maleic 
anhydride, 224.1 g. of the same styrene-maleic anhydride polyanhydride and 
239.8 g. of the n-butyl glycidyl ether were blended together to a solution 
having a Brookfield viscosity of 30 cps. at 25.degree. C. After adding 1.5 
g. of fumed silica to increase the viscosity to 200 cps., the same free 
radical initiator and anhydride accelerator were added in the same 
proportions and then the fiber glass was added, also in the same 
proportion. This material (400 g.) was thickened to a pliable molding 
compound which was determined to have a spiral flow greater than 48 
inches. It was molded to a product having a flexural strength of 11,450 
psi. and a tensile strength of 3,980 psi. 
In like manner a thickened, moldable intermediate is produced when 
appropriate amounts, as described herein, of styrene, methylmaleic 
anhydride, a 1,2-epoxy octadecane, a 1:1 styrene-maleic anhydride 
copolymer and pyridine are heated to about 45.degree. C. in the presence 
of t-butyl peroxypivalate. Also a thickened, moldable intermediate is 
produced when appropriate amounts of styrene, chloromaleic anhydride, 
2,3-epoxy-2-phenylhexane, a 3:1 styrene-maleic anhydride copolymer and 
N-metnylpiperazine are heated to about 45.degree. C. in the presence of 
2-t-butylazo-2-cyano-4-methoxy-4-methypentane. 
Many analyses of the thickened intermediate and the fully cured product 
involving styrene and maleic anhydride as the vinyl reactants and a 
polyepoxide have revealed no evidence of polystyrene notwithstanding the 
fact that a substantial molar excess of styrene to maleic anhydride was 
used in the initial resin mixture. Evidence strongly suggests that the 
excess styrene reacts with the styrene-maleic anhydride copolymer present 
in the mixture by graft polymerization forming relatively short 
styrene-based chains. There is also some evidence which indicates that 
during the first-stage reaction free styrene and free maleic anhydride 
disappear from the system in an approximate 1:1 molar ratio until the free 
maleic anhydride was fully reacted and following this any unreacted 
styrene reacted further until it was fully reacted. 
Cured resins can be prepared by the procedure described herewith with 
excellent properties for a wide variety of uses. The reinforced molded 
products possess exceptional mechanical properties including exceptionally 
high tensile and flexural strength and excellent retention of these 
properties at elevated temperatures. The electrical characteristics are 
excellent including the retention of the electrical properties upon 
exposure to moisture and heat. The reinforced thickened compositions can 
be readily compression molded into complex, detailed shaped with 
exceptionally uniform glass fiber distribution throughout at comparatively 
short cure times. 
It is to be understood that the above disclosure is by way of specific 
example and that numerous modifications and variations are available to 
those of ordinary skill in the art without departing from the true spirit 
and scope of the invention.