Method of making prepreg

A formable prepreg, and a method of making a formable prepreg by a pultrusion process. The method includes (a) impregnating reinforcing fiber with a thermosetting resin matrix, and (b) passing the resin impregnated reinforcing fiber through a die within which the resin impregnated reinforcing fiber is subjected to conditions sufficient to thicken the thermosetting resin matrix, to provide a formable prepreg. The present invention also provides a method of making a molded article using the prepreg of the present invention.

FIELD OF THE INVENTION 
The present invention relates to reinforced resin technology, and 
particularly to a method of making prepreg. 
BACKGROUND OF THE INVENTION 
Prepreg is a composite consisting of fiber reinforcements preimpregnated 
with resin, which is typically molded with pressure or vacuum to provide a 
variety of molded articles. Prepregs have applications in aerospace, 
transportation, appliances, sanitary ware, and the like. 
Various techniques for making prepreg are well known. For example, U.S. 
Pat. No. 4,495,017 to Abe et al. proposes a process for continuous 
production of prepreg sheets. The process involves contacting fiber 
bundles with a solvent and continuously taking up the individual fiber 
bundle units under tension over curved surfaces of spreader bodies, 
thereby spreading out and drying the fiber bundles. According to this 
method, the fiber bundles are spread with a solvent prior to being 
impregnated with a resin. U.S. Pat. No. 3,959,209 to Lake proposes a 
curable solid polyester resin prepared by mixing a polyester and 
crosslinking agent with one or more of a filler, fibrous reinforcements or 
amorphous polyester. U.S. Pat. No. 4,892,764 to Drain et al. also proposes 
fiber/resin matrices and a method for making them. Drain et al. proposes a 
method of making a filament wound article including rotating a mandrel, 
impregnating a winding filament with a resin composition comprising an 
actinic radiation-cured first resin component and a curable second resin 
component, filament winding the mandrel, exposing the wound filament to 
actinic radiation contemporaneously with filament winding, terminating the 
rotation of the mandrel, and curing the second resin component. 
Although several means of producing formable prepreg have been proposed, 
there remains a need in the art for a method of preparing continuous 
prepreg which is faster than conventional methods and can be automated. 
Conventional forms of prepreg include sheet molding compound (SMC), which 
typically requires extensive manual labor in preparation and final 
molding. Additionally, SMC produces waste in the form of carrier film, and 
trim waste produced by cutting the SMC into desired shapes. Accordingly, 
there is also a need in the art for a method of making prepreg which 
reduces the amount of waste produced by conventional techniques. 
In addition, there is a need in the art for a method of preparing prepreg 
which achieves a more efficient use of fiber reinforcements. Conventional 
SMC technology is limited with respect to the ability to optimize the 
placement of reinforcing fiber in the SMC. Accordingly there is a need in 
the art for a method of making prepreg which improves on efficient use of 
fiber reinforcements. In addition, the method of the present invention 
allows more reinforcements to be added to the prepreg composition than 
conventional methods. 
There is also a need in the art for a method of preparing prepreg which 
permits the optimization of conditions of the method of preparing prepreg 
to provide a more efficient and designed product. Conventional methods of 
preparing prepreg permit only limited control over the conditions under 
which the prepreg is prepared, thus restricting the ability of the artisan 
to optimize the product by controlling a variety of reaction conditions. 
The method of the present invention, permits more thorough impregnation of 
the reinforcing fibers by providing the ability to apply pressure and 
dearation during the impregnation process. In addition, environmental 
conditions, such as temperature and atmosphere, can be controlled in the 
method of the present invention. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a formable 
prepreg. It is a further object of the present invention to provide a 
method of making a formable prepreg. It is yet a further object of the 
present invention to provide an automated method of making a formable 
prepreg which reduces waste. 
These and other objects, features and advantages are provided by the 
formable prepreg of the present invention. The term "prepreg" as used 
herein refers to a ready to mold composite in either rod, rope, or sheet 
form, which consists of reinforcing fiber impregnated with a thermosetting 
resin. The phrase "formable prepreg" as used herein refers to an 
incompletely cured prepreg which may be thermally reshaped subsequent to 
formation. Inasmuch as the prepreg of the present invention is only 
partially cured, the prepreg retains chemical reactive sites which provide 
improved bonding between the prepreg material and other resinous 
materials, such as for example, in the preparation of prepreg bars or rods 
clad with sheet molding compound. 
The formable prepreg of the present invention comprises reinforcing fiber 
impregnated with a curable thermosetting resin matrix wherein the prepreg 
is formed by a pultrusion process. The term "thermosetting resin" as used 
herein refers to resins which irreversibly solidify or "set" when fully 
cured such that the fully cured resin cannot be post-formed. 
The method of making the prepreg of the present invention comprises (a) 
impregnating reinforcing fiber with a thermosetting resin matrix, and (b) 
passing the resin impregnated reinforcing fiber through a die within which 
the resin impregnated reinforcing fiber is subjected to conditions 
sufficient to thicken the thermosetting resin matrix, to provide a 
formable prepreg. 
The term "thicken" as used herein refers to an increase in the viscosity of 
the resin such that the resin is transformed from a liquid to a 
non-dripping paste form. The resulting paste form of the resin is 
typically referred to as "B-stage". The term "partially cure" as used 
herein refers to incompletely polymerizing the resin matrix by initiating 
polymerization and subsequently arresting the polymerization before the 
curable thermosetting resin is fully cured. 
The curable thermosetting resin matrix typically comprises unsaturated 
polyester, phenolic, and/or vinyl ester resins. The reinforcing fiber 
typically comprises fiberglass roving. Additionally, the thermosetting 
resin matrix may also include various chemical and physical thickening 
agents. 
As another aspect, the present invention also provides a method of making a 
molded article from the formable prepreg of the present invention. The 
method comprises (a) impregnating reinforcing fiber with a curable 
thermosetting resin matrix, (b) passing the resin impregnated reinforcing 
fiber through a die within which the resin impregnated reinforcing fiber 
is subjected to conditions sufficient to thicken the curable thermosetting 
resin matrix to provide a formable prepreg, and (c) molding the formable 
prepreg under conditions sufficient to cure the thickened thermosetting 
resin matrix, to form a molded article having a predetermined shape. 
These and other objects and aspects of the present invention are explained 
in detail in the specification set forth below. 
DETAILED DESCRIPTION OF THE INVENTION 
The formable prepreg of the present invention is formed by a pultrusion 
process. In one embodiment, the method comprises (a) impregnating 
reinforcing fiber with a thermosetting resin matrix, and (b) passing the 
resin impregnated reinforcing fiber through a die within which the resin 
impregnated reinforcing fiber is subjected to conditions sufficient to 
thicken the thermosetting resin matrix. In operation, the method is 
carried out using conventional pultrusion apparatus. 
Pultrusion is an automated process for manufacturing composite materials 
into linear, continuous, profiles having constant cross-sections. 
Typically, the pultrusion process begins with reinforcing fibers which are 
strung from creels at the beginning of the system to pullers at the end. 
The fibers typically pass through a resin bath where they are impregnated 
with resin. The resin impregnated fibers are continuously pulled through a 
die which typically has both cooling and heating zones, and which fashions 
the final shape of the profile. The heating zone of the die initiates and 
accelerates the polymerization of the resin and the profile exits as a 
hot, fully cured profile having a constant cross-section, and is cooled 
with the aid of ambient or forced air or cooling fluids. The pullers 
continuously pull the profile toward a flying cutoff saw which cuts the 
pultruded composite into the desired lengths. 
The resin used in conventional pultrusion processes is typically a 
thermosetting resin which is ultimately shaped and fully cured by the die. 
In conventional pultrusion processes, the shaped profile cannot be 
reshaped after leaving the die. Hence, conventional pultruded composite 
articles typically exhibit the linear shape and always exhibit a constant 
cross-section which is fashioned by pulling the impregnated fibers through 
the die. Pultruded composites can be in the form of hollow or solid rod or 
bar stock. These pultruded composites have a variety of applications 
including fishing rods and electrical insulator rods. Structural profiles 
can also be produced by a pultrusion process. Typically, structural 
profiles include a combination of axial fibers and multidirectional fiber 
mats. 
As mentioned above, the fibers may be impregnated by passing through a 
resin bath. This is conventionally known as a "wet-bath" pultrusion 
system. A second pultrusion system, effects fiber impregnation by 
injecting resin into the fibers from a pressurized resin holding tank. 
The temperature of the die is dependent upon the thermosetting resin 
employed, and the rate of pultrusion, and can be determined by one skilled 
in the art. The rate of pultrusion through the system can range from 1 
inch/minute upwards to 10 to 50 ft/min. A typical pultrusion process 
operates in the range of from 2 to 4 ft/min. 
As summarized above, the Inventors have developed a pultrusion process 
which produces a formable prepreg, as opposed to a fully cured linear 
article. The formable prepreg of the present invention comprises 
reinforcing fiber impregnated with a thermosetting resin formed by a 
pultrusion process, wherein the resin impregnated reinforcing fiber is 
pultruded through a die within which the resin impregnated reinforcing 
fiber is subjected to conditions sufficient to thicken the thermosetting 
resin matrix. In one embodiment, the method of making the formable prepreg 
of the present invention comprises (a) impregnating reinforcing fiber with 
a thermosetting resin matrix, and (b) passing the resin impregnated 
reinforcing fiber through a die within which the resin impregnated 
reinforcing fiber is subjected to conditions sufficient to thicken the 
thermosetting resin matrix. 
The reinforcing fiber of the present invention can be any reinforcing fiber 
conventionally known in the art. Preferably, the reinforcing fiber is 
adaptable to a conventional pultrusion machine. Suitable reinforcing 
fibers comprise fiberglass, polyester, graphite, aramid or natural fibers. 
The fibers may be continuous or staple fibers and may be in the form of 
roving or mat. Preferably, the reinforcing fiber comprises fiberglass 
roving. 
The thermosetting resin matrix useful in the present invention comprises a 
thermosetting resin. Useful thermosetting resins include unsaturated 
polyesters, phenolics, vinyl esters, and the like and mixtures and blends 
thereof. Additionally, the thermosetting resins useful in the present 
invention may be mixed with other thermosetting or thermoplastic resins. 
Exemplary thermosetting resins include epoxies. Exemplary thermoplastic 
resins include polyvinylacetate, styrene butadiene copolymers, 
polymethylmethacrylate, polystyrene, cellulose acetatebutyrate, saturated 
polyesters, urethane-extended saturated polyesters, 
methacrylate-butadiene-styrene copolymers and the like. 
Unsaturated polyester, phenolic and vinyl ester resins are the preferred 
thermosetting resins of the present invention. Suitable unsaturated 
polyester resins include practically any esterification product of a 
polybasic organic acid and a polyhydric alcohol, wherein either the acid 
or the alcohol, or both, provide the reactive ethylenic unsaturation. 
Typical unsaturated polyesters are those thermosetting resins made from 
the esterification of a polyhydric alcohol with an ethylenically 
unsaturated polycarboxylic acid. Examples of useful ethylenically 
unsaturated polycarboxylic acids include maleic acid, fumaric acid, 
iraconic acid, dihydromuconic acid and halo and alkyl derivatives of such 
acids and anhydrides, and mixtures thereof. Exemplary polyhydric alcohols 
include saturated polyhydric alcohols such as ethylene glycol, 
1,3-propanediol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 
2-ethylbutane-l,4-diol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 
1,8-octanediol, 1,4-cyclohexanediol, 1,4-dimethylolcyclohexane, 2,2- 
diethylpropane-1,3 -diol, 2,2-diethylbutane-l,3-diol, 3methylpentane-1,4 
-diol, 2,2-dimethylpropane-l,3-diol, 4,5-nonanediol, di ethylene glycol, 
triethylene glycol, dipropylene glycol, glycerol, pentaerythritol, 
erythritol, sorbitol, mannitol, 1,1,1-trimethylolpropane, 
trimethylolethane, hydrogenated bisphenol-A and the reaction products of 
bisphenol-A with ethylene or propylene oxide. 
Unsaturated polyester resins can also be derived from the esterification of 
saturated polycarboxylic acid or anhydride with an unsaturated polyhydric 
alcohol. Exemplary saturated polycarboxylic acids include oxalic acid, 
malonic acid, succinic acid, methylsuccinic acid, 2,2-dimethylsuccinic 
acid, 2,3-dimethylsuccinic acid, hydroxylsuccinic acid, glutaric acid, 
2-methylglutaric acid, 3-methylglutaric acid, 2,2-dimethylglutaric acid, 
3,3-dimethylglutaric acid, 3,3-diethylglutaric acid, adipic acid, pimelic 
acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic 
acid, terephthalic acid, tetrachlorophthalic acid, tetrabromophthalic 
acid, tetrahydrophthalic acid, 1,2-hexahydrophthalic acid, 
1,3-hexahydrophthalic acid, 1,4-hexahydrophthalic acid, 
1,1-cyclobutanedicarboxylic acid and trans-1,4-cyclohexanedicarboxylic 
acid. 
Unsaturated polyhydric alcohols which are suitable for reacting with the 
saturated polycarboxylic acids include ethylenic unsaturation-containing 
analogs of the above saturated alcohols (e.g.,2-butene-l,4-diol). 
Suitable phenolic resins include practically any reaction product of a 
aromatic alcohol with an aidehyde. Exemplary aromatic alcohols include 
phenol, orthocresol, metacresol, paracresol, Bisphenol A, p-phenylphenol, 
p-tert-butylphenol, p-tert-amylphenol, p-tert-octylphenol and 
p-nonylphenol. Exemplary aldehydes include formadehyde, acetaldehyde, 
propionaldehyde, phenylacetaldehyde, and benzaldehyde. Particularly 
preferred, are the phenolic resins prepared by the reaction of phenol with 
formaldehyde. 
Suitable vinyl ester resins include practically any reaction product of an 
unsaturated polycarboxylic acid or anhydride with an epoxy resin. 
Exemplary acids and anhydrides include (meth) acrylic acid or anhydride, 
.alpha.-phenylacrylic acid, .alpha.-chloroacrylic acid, crotonic acid, 
mono-methyl and mono-ethyl esters of maleic acid or fumaric acid, vinyl 
acetic acid, cinnamic acid, and the like. Epoxy resins which are useful in 
the preparation of the polyvinyl ester are well known and commercially 
available. Exemplary epoxies include virtually any reaction product of a 
polyfunctional halohydrin, such as epichlorohydrin, with a phenol or 
polyhydric phenol. Suitable phenols or polyhydric phenols include for 
example, resorcinol, tetraphenol ethane, and various bisphenols such as 
Bisphenol-A, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxy biphenyl, 
4,4'-dihydroxydiphenylmethane, 2,2'-dihydroxydiphenyloxide, and the like. 
Typically, the thermosetting resin matrix of the present invention also 
includes a vinyl monomer, in which the thermosetting resin is solubilized. 
Suitable vinyl monomers include styrene, vinyltoluene, methyl 
methacrylate, p-methylstyrene, divinyl benzene, diallyl phthalate and the 
like. Styrene is the preferred vinyl monomer for solubilizing unsaturated 
polyester or vinyl ester resins. 
The thermosetting resin matrix typically also includes a thickening agent. 
Suitable thickening agents are commonly known to those skilled in the art 
and include, for example, crystalline unsaturated polyesters, 
polyurethanes, alkali earth metal oxides and hydroxides, and polyureas. 
Preferably, the thickening agent cooperates with the conditions within the 
die to thicken the thermosetting resin matrix to form the prepreg. The 
conditions within the die which are required to thicken the thermosetting 
resin matrix are dependent upon the thickening agent employed. Typically, 
the die comprises an entry zone, a center zone and an exit zone. At least 
one of the zones, and often more than one zone, is capable of being 
heated. Additionally, at least one of the zones and often more than one 
zone, is capable of being cooled. Typically cooling is accomplished using 
ambient or forced air, or cooling water. The conditions of the die which 
are required to thicken the thermosetting resin matrix are discussed in 
detail below, with reference to the particular thickening agent employed. 
Suitable resins employing a crystalline polyester thickening agent are 
described in U.S. Pat. No. 3,959,209 to Lake, the disclosure of which is 
incorporated herein by reference in its entirety. Typically, in the 
embodiment of the invention wherein the thermosetting resin matrix is 
thickened with a crystalline polyester, the thermosetting resin matrix 
comprises a thermosetting resin solubilized in a vinyl monomer. The 
crystalline polyesters useful in the present invention are preferably 
ethylenically unsaturated, and react with the vinyl monomer, although 
saturated crystalline polyesters may also be employed. 
Methods of preparing crystalline polyester are well known in the art and 
include polyesterifying a symmetrical, aliphatic diol with fumaric acid, 
alkyl esters of fumaric acid, or symmetrical saturated diacids such as 
terephthalic acid, isophthalic acid, and sebacic acid. Maleic anhydride or 
maleic acid or lower alkyl esters of maleic acid may also be used in the 
presence of an appropriate catalyst. Likewise, mixtures of fumaric acid or 
esters with maleic anhydride or maleic acid or its esters may also be 
used. Exemplary crystalline polyesters which may be employed in the 
present invention include polyfumarates of 1,6-hexanediol, neopentyl 
glycol, bis-(hydroxyethyl)resorcinol, ethylene glycol, 1,4-butanediol, 
1,4-cyclohexanediol, 1,4-cyclohexanedimethanol or 
bis(hydroxyethyl)hydroquinone. 
The amount of crystalline polyester added to the thermosetting resin matrix 
will vary depending upon the particular thermosetting resin employed. 
Typically, about 2 to about 80 percent by weight of crystalline polyester 
is required to thicken about 20 to about 98 percent by weight of a 
thermosetting resin. 
The conditions in the die which are sufficient to thicken the thermosetting 
resin matrix including a crystalline polyester thickening agent typically 
comprise subjecting the thermosetting resin matrix to sufficient heat to 
thicken the thermosetting resin matrix. Typically, sufficient heat is 
provided by operating the die under conditions which include heating at 
least one zone of the die. In one preferred embodiment, the conditions 
within the die include maintaining the entry zone at a temperature of from 
about 25 to about 85.degree. C., heating the center zone to a temperature 
of from about 35 to about 120.degree. C., and maintaining the exit zone at 
a temperature of from about 0 to about 90.degree. C. 
The thermosetting resin matrix of the present invention may also be 
thickened with polyurethanes. Exemplary thermosetting resin matrices 
thickened with a polyurethane are described in U.S. Pat. No. 3,886,229 to 
Hutchinson, the disclosure of which is incorporated herein by reference in 
its entirety. Typically, in the embodiment of the invention wherein the 
thermosetting resin is thickened with a polyurethane, the thermosetting 
resin matrix comprises a thermosetting resin solubilized in a vinyl 
monomer. 
The polyurethanes useful in the present invention typically comprise the 
reaction product of a polyol and an isocyanate compound. The polyol may be 
saturated or unsaturated. Exemplary saturated polyols include ethylene 
glycol, propylene glycol, butane-1,4-diol, pentane-1,5-diol, 
hexane-1,6-diol, di(ethylene glycol), and di(propylene glycol). Polymers 
of glycols may also be employed. Exemplary polymers include poly(ethylene 
glycol), poly(propylene glycol), and poly(butylene glycol) and polyols of 
functionality greater than two, for example, glycerol, pentaerythritol, 
and trialkylol alkanes, e.g., trimethylol propane, triethylol propane, 
tributylol propane and oxyalkylated derivatives of said trialkylol 
alkanes, e.g., oxyethylated trimethylol propane and oxypropylated 
trimethylol propane. 
In the embodiment wherein the thermosetting resin is thickened with a 
polyurethane including an unsaturated polyol, the unsaturated polyol 
crosslinks the urethane groups with the ethylenically unsaturated 
polyester and vinyl monomer of the thermosetting resin matrix. Exemplary 
unsaturated polyols include polyesters, and vinyl esters. In one 
particularly preferred embodiment, the unsaturated polyol is a diester of 
propoxylated bisphenol-A. 
The isocyanate compound is typically a polyisocyanate. The polyisocyanate 
may be aliphatic, cycloaliphatic or aromatic or may contain in the same 
polyisocyanate molecule aliphatic and aromatic isocyanate groups, 
aliphatic and cycloaliphatic isocyanate groups, aliphatic cycloaliphatic 
and aromatic isocyanate groups or mixtures of any two or more 
polyisocyanates. 
Exemplary polyisocyanates include 4,4'-diphenylmethane diisocyanate, 
2,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone 
diisocyanates (e.g., 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl 
isocyanate), tetramethylene diisocyanate, pentamethylene diisocyanate, 
hexamethylene diisocyanate and octamethylene diisocyanate, and 
cycloaliphatic diisocyanates (e.g., 4,4'-dicyclohexylmethane 
diisocyanate). 
The polyurethane may be reacted with the thermosetting resin of the 
thermosetting resin matrix according to any method known to those skilled 
in the art. The amount of polyurethane added to the thermosetting resin 
matrix will vary depending upon the particular thermosetting resin 
employed. Typically, the polyurethane comprises about 1 to about 60 
percent by weight of the thermosetting resin matrix. 
The conditions in the die which are sufficient to thicken the thermosetting 
resin matrix including a polyurethane thickening agent typically comprise 
subjecting the thermosetting resin matrix to sufficient heat to thicken 
the thermosetting resin matrix. Typically, sufficient heat is provided by 
operating the die under conditions which include heating at least one zone 
of the die. In one preferred embodiment, the conditions within the die 
include maintaining the entry zone at a temperature of from about 
10.degree. to about 35.degree. C., heating the center zone to a 
temperature of from about 30.degree. to about 200.degree. C., and 
maintaining the exit zone at a temperature of from about 0.degree. to 
about 200.degree. C. 
The thermosetting resin matrix may also be thickened using alkali earth 
metal oxides or hydroxides. Typical thickeners of this type include 
calcium and magnesium oxides or hydroxides. The addition of these 
components to the thermosetting resin matrix transforms the liquid 
thermosetting resin matrix to a solid form. The amount of oxide or 
hydroxide employed will vary depending upon the particular thermosetting 
resin employed. Typically, the alkali metal oxide or hydroxide comprises 
about 1 to about 15 percent by weight of the thermosetting resin matrix. 
The conditions in the die which are sufficient to thicken the thermosetting 
resin matrix including an alkali metal oxide or hydroxide typically 
comprise subjecting the thermosetting resin matrix to sufficient heat to 
thicken the thermosetting resin matrix. Typically, sufficient heat is 
provided by operating the die under conditions which include heating at 
least one zone of the die. In one preferred embodiment, the conditions 
within the die include maintaining the entry zone at a temperature of from 
about 10.degree. to about 35.degree. C., heating the center zone to a 
temperature of from about 30.degree. to about 130.degree. C., and 
maintaining the exit zone to a temperature of from about 0.degree. to 
about 80.degree. C. 
The thermosetting resin matrix may also be thickened using a polyurea 
thickening agent. Suitable formulation of resins thickened with polyurea 
are described in U.S. Pat. No. 4,296,020 to Magrans, Jr., the disclosure 
of which is incorporated herein by reference in its entirety. Typically, 
in the embodiment of the invention wherein the thermosetting resin matrix 
is thickened with polyurea, the thermosetting resin matrix comprises a 
thermosetting resin solubilized in a vinyl monomer. 
The polyureas useful in the present invention comprise the product of 
polyamines with polyisocyanates. The polyisocyanates useful in the present 
invention include those described above with reference to urethane 
thickeners. 
Aliphatic, cycloaliphatic and aromatic polyamines free of ethylenic 
saturation are preferred polyurea precursors in that they form individual 
polyurea chains which are relatively cross-linked with the polymer chain 
formed by the copolymerization of the ethylenically unsaturated resin and 
monomers in solution therewith. 
Aryl diamines and mixtures thereof such as metaphenylene diamine, 
paraphenylene diamine, naphthalene diamine, benzidene, 
bis)4-aminophenyl)methane, 4,4'-diaminodiphenyl sulfone and halogenated 
derivatives such as those containing halogen on the benzenoid ring such as 
3,3'-dichlorobenzidine, bis,4-amino-2-chlorophenyl (sulfone), 
4-bromo-l,3-phenylene diamine, to name a few, are operable. 
Low molecular weight aliphatic and cycloaliphatic diamines are also 
suitably employed, such as: ethylene diamine, propylene diamine, 
hexamethylene diamine, trimethyl hexamethylene diamine, isophorone 
diamine, 1-amino-3-amino-3,5,5-trimethyl cyclohexane, hydrogenated 
di-(aminophenyl)methane, hydrogenated methylene dianiline, diamino 
methane, and hydrogenated toluene diamine. The most useful of these are 
those that are liquids up to 75.degree. C. For those which are solids 
under these conditions, vinyl monomer solutions can be employed to form 
the homogeneous mix rapidly. In addition, other suitable amines include 
polyoxyalklene polyamines and cyanoalkylated polyoxyalklene polyamines 
having a molecular weight of about 190 to about 2,000 with a preferred 
range of about 190 to about 1,000. 
These amines are described and prepared according to procedures outlined in 
a U.S. Pat. No. 4,296,020 to Magrans, Jr., the teachings of which are 
hereby incorporated by reference. 
The conditions in the die which are sufficient to thicken the thermosetting 
resin matrix including a polyurea thickening agent typically comprise 
subjecting the thermosetting resin matrix to sufficient heat to thicken 
the thermosetting resin matrix. Typically, sufficient heat is provided by 
operating the die under conditions which include heating at least one zone 
of the die. In one preferred embodiment, the conditions within the die 
include maintaining the entry zone at a temperature of from about 
10.degree. to about 35.degree. C., heating the center zone to a 
temperature of from about 30.degree. to about 200.degree. C., and 
maintaining the exit zone at a temperature of from about 0.degree. to 
about 200.degree. C. 
The thermosetting resin matrix also may include an initiator system which 
cooperates with the conditions of the die to thicken the thermosetting 
resin matrix by partially curing the thermosetting resin matrix. The 
initiator system may be present in addition to any of the foregoing 
thickening agents, or as an alternative thereto. 
The initiator system may comprise any number of polymerization initiators. 
Where multiple polymerization initiators are employed, the initiator 
system typically comprises polymerization initiators which can be 
activated by different conditions. For simplicity, where multiple 
polymerization initiators are employed, we refer to the polymerization 
initiator requiring the least activation energy as the "first 
polymerization initiator", and the initiator requiring the most activation 
energy as the "second polymerization initiator". Any practical number of 
polymerization initiators having activation energies between the first and 
second polymerization initiators may also be incorporated into the 
thermosetting resin matrix. It should not be implied from our use of the 
terms "first" and "second" polymerization initiator that we restrict our 
invention to the use of no more than two polymerization initiators. 
Polymerization initiators which are useful in the practice of the present 
invention typically include free-radical initiators. Typical free-radical 
initiators include peroxy initators. The reactivity of such initiators is 
evaluated in terms of the 10 hour half-life temperature, that is, the 
temperature at which the half-life of a peroxide is 10 hours. Suitable 
first polymerization initiators include polymerization initiators having a 
low 10 hour half-life, i.e., a more reactive peroxide initiator, as 
compared to initiators having a higher 10 hour half-life. Suitable second 
polymerization initiators include polymerization initiators having a 
higher 10 hour half-life than the 10 hour half-life of the polymerization 
initiator selected as the first polymerization initiator. Exemplary 
free-radical initiators useful in the present invention include diacyl 
peroxides, (e.g., lauroyl peroxide and benzoyl peroxide), 
dialkylperoxydicarbonates, (e.g., di(4-tert-butylcyclohexyl) peroxy 
dicarbonate), tert-alkyl peroxyesters, (e.g., t-butyl perbenzoate), 
di-(tert-alkyl)peroxyketals, (e.g., 1,1-di-(tamylperoxy) cyclohexane), 
di-tert-alkyl peroxides, (e.g., dicumyl peroxide), azo initiators, (e.g., 
2,2'-azobis(isobutyronitrile), ketone peroxides, (e.g., methylethylketone 
peroxide and hydroperoxides). 
In the embodiment wherein the initiator system comprises only one 
polymerization initiator, the thermosetting resin matrix preferably 
includes a vinyl monomer. The vinyl monomer and the polymerization 
initiator may be independently activated under different conditions, thus 
permitting the partial polymerization of the thermosetting resin matrix. 
The amount of polymerization initiator(s) used is dependent upon the number 
of initiators employed, the conditions at which the selected initiators 
will initiate polymerization, and the time desired for partial curing. 
Typically the amount of time desired for partial curing is a short period, 
i.e., less than 3 hours, and often less than 1 hour. In the embodiment 
wherein the thermosetting resin matrix includes only one polymerization 
initiator, the amount of the initiator is typically about 0.1 to about 10 
percent by weight of the thermosetting resin matrix. In the embodiment 
wherein the thermosetting resin matrix includes two polymerization 
initiators, the amount used is about 0.01 to about 4 percent by weight of 
the first polymerization initiator and about 0 to about 5 percent by 
weight of the second polymerization initiator based on the weight of the 
thermosetting resin matrix. 
The initiator system and amounts of each polymerization initiator 
incorporated into the thermosetting resin matrix should be such that as 
the resin impregnated reinforcing fiber is pultruded through the die, the 
conditions therein are sufficient to activate at least one, but preferably 
not all polymerization initiators, resulting in the partial polymerization 
of the thermosetting resin matrix. Typically, in the embodiment wherein 
the initiator system comprises only one polymerization initiator, the 
resin impregnated reinforcing fiber is pultruded through a die within 
which the the reinforcing fiber is subjected to sufficient heat to 
activate the polymerization initiator without attaining the 
self-polymerization temperature of the matrix. 
In the embodiment wherein multiple polymerization initiators are employed, 
typically the resin impregnated reinforcing fiber is pultruded through a 
die within which the reinforcing fiber is subjected to sufficient heat to 
activate at least one, and preferably the first, polymerization initiator 
to partially cure the thermosetting resin matrix. 
The conditions in the die which are sufficient to activate at least one 
polymerization initiator to partially cure the thermosetting resin will 
depend on the particular polymerization initiator(s) and the thermosetting 
resin selected, and will be readily determinable be one skilled in the 
art. Typically, the conditions within the die which are required for the 
activation of at least one polymerization initiator comprise subjecting 
the thermosetting resin matrix to sufficient heat to activate the most 
reactive, e.g., the first polymerization initiator to partially cure the 
thermosetting resin matrix. As the prepreg exits the exit zone and is 
cooled, the polymerization initiated by the activation of the first 
polymerization initiator is arrested, providing the partially cured 
prepreg rather than a fully cured article. 
Yet another method of thickening the thermosetting resin matrix comprises 
subjecting the thermosetting resin matrix to sufficient radiation to 
thicken the matrix. Exemplary forms of radiation include ultraviolet, 
infrared, radiofrequency waves, microwaves, and electron beams. According 
to this method, the resin impregnated reinforcing fiber is pultruded 
through a die within which the resin impregnated reinforcing fiber is 
subjected to radiation. The wavelength of radiation which is sufficient to 
thicken the thermosetting resin matrix is dependent upon the form of 
radiation and the particular thermosetting resin employed, and is readily 
determinable by one skilled in the art. For example, a thermosetting resin 
matrix comprising an unsaturated polyester resin or vinyl ester resin 
solubilized in styrene may be thickened using ultraviolet light having a 
wavelength ranging from about 200 to about 600 nm. 
The conditions within the die which are sufficient to thicken the 
thermosetting resin matrix typically comprise subjecting the resin 
impregnated reinforcing fiber to radiation of a sufficient wavelength to 
thicken the thermosetting resin matrix. Preferably, the radiation source 
is located at the center zone of the die so that as the resin impregnated 
reinforcing fiber is passed through the center zone, it is irradiated. In 
one embodiment, typically the entry zone of the die is maintained at a 
temperature of from about 10.degree. to about 200.degree. C., the center 
zone is equipped with a source of radiation operating at a predetermined 
wavelength, and the exit zone is maintained at a temperature of from about 
10.degree. to about 200.degree. C. Alternatively, the radiation source may 
be located at either the entry or exit zone of the die. 
The method of making the prepreg of the present invention comprises (a) 
impregnating reinforcing fiber with a thermosetting resin matrix, and (b) 
passing the resin impregnated reinforcing fiber through a die within which 
the resin impregnated reinforcing fiber is subjected to conditions 
sufficient to thicken the thermosetting resin matrix, to provide a 
formable prepreg. 
The impregnation of the reinforcing fiber may be accomplished by any 
suitable means. As described above, conventional pultrusion apparatus 
typically include a resin bath or resin injection apparatus. In one 
preferred embodiment, the reinforcing fiber is impregnated by passing the 
reinforcing fiber through a bath containing the thermosetting resin 
matrix. Typically, the thermosetting resin matrix is liquid in form and is 
readily absorbed into the reinforcing fibers as they are passed through 
the resin bath. In another preferred embodiment, the reinforcing fiber is 
impregnated by injecting the thermosetting resin matrix onto the 
reinforcing fiber. Conventional injection pultrusion machines may be 
employed in the practice of this embodiment. 
The thermosetting resin matrix may be thickened using only one of the 
foregoing methods or by using two or more methods in combination. Any 
combination of the foregoing thickening methods may be used to prepare the 
formable prepreg of the present invention. In embodiments wherein multiple 
methods of thickening the thermosetting resin matrix are employed, the 
conditions within the die which are sufficient to thicken the 
thermosetting resin matrix will depend on the particular combination of 
methods employed. The necessary conditions within the die which will 
effect thickening will be readily determinable by one skilled in the art. 
The rate at which the resin impregnated reinforcing fiber is passed through 
the die is dependent upon several factors including the thermosetting 
resin employed, the method of thickening the thermosetting resin matrix, 
and the conditions within the die, and will be readily determined by one 
skilled in the art. Typically the resin impregnated reinforcing fiber is 
passed through the die at a rate of about 1 in/min to about 100 ft/min. 
Although the thermosetting resin matrix is effectively thickened by the 
conditions within the die to form the prepreg of the present invention, in 
some applications it may be advantageous to initiate some thickening 
before the resin impregnated reinforcing fiber enters the die. Thickening 
of the thermosetting resin matrix may be initiated by pretreating the 
resin impregnated reinforcing fiber according to any suitable method known 
to those skilled in the art. Suitable methods of pretreating to initiate 
thickening include subjecting the resin impregnated reinforcing fiber to 
heat, ultraviolet light, microwaves or radiofrequency waves prior to 
passing the resin impregnated reinforcing fiber through the die. 
Pretreating with radiofrequency waves is the preferred method of 
initiating thickening prior to passing the resin impregnated reinforcing 
fiber through the die. Although pretreating the resin impregnated 
reinforcing fiber initiates the thickening process, additional thickening 
of the thermosetting resin matrix still occurs within the die, by the 
conditions therein. 
The present invention also provides a method of making a molded article 
having a predetermined shape. The method comprises (a) impregnating 
reinforcing fiber with a thermosetting resin matrix, (b) passing the resin 
impregnated reinforcing fiber through a die within which the resin 
impregnated reinforcing fiber is subjected to conditions sufficient to 
thicken the thermosetting resin to provide a formable prepreg, and (c) 
molding the formable prepreg under conditions sufficient to fully cure the 
thickened thermosetting resin matrix, and to form a molded article having 
a predetermined shape. 
The method of making the molded article having a predetermined shape 
utilizes the prepreg of the present invention prepared according to the 
foregoing description of the method. Additionally, the method of making 
the molded article further comprises the step of molding the formable 
prepreg under conditions sufficient to fully cure the thickened 
thermosetting resin. The predetermined shape of the molded article may be 
enhanced by the addition of selective reinforcements at predetermined 
locations. Suitable selective reinforcements may be selected from the 
reinforcing fibers previously mentioned. 
Typically, the step of molding the formable prepreg under conditions 
sufficient to cure the prepreg comprises molding the prepreg under heat 
and pressure to form a molded article. Preferably, the step of molding the 
formable prepreg under conditions sufficient to cure the prepreg comprises 
compression molding the prepreg to form a molded article. Suitable 
compression molding techniques and parameters for molding the formable 
prepreg of the present invention will be readily apparent to one skilled 
in the art. Compression molding transforms the partially cured prepreg to 
a fully cured article which cannot then be further formed with heating.

The following examples are provided to illustrate the present invention, 
and should not be construed as limiting thereof. In these examples, 
.degree. F. means degrees Fahrenheit, .degree. C. means degrees 
Centigrade, in. means inches, ft means feet, ft.sup.2 means square feet, 
oz means ounces, and min means minutes. 
EXAMPLE 1 
Preparation of Prepreg 
A conventional wet-bath pultrusion apparatus having a 0.5 inch die opening 
was equipped with roving strung between guides, through the resin bath, 
through the die, and secured to the pulling mechanism. The resin bath was 
charged with 100 parts DION.TM. 31022-00, 0.1 parts 
di-(4-tert-butylcyclohexyl) peroxy dicarbonate, 0.1 parts styrene monomer, 
1.0 part t-butylperbenzoate, 3.5 parts zinc stearate internal mold release 
agent and 50 parts calcium carbonate filler. The entry zone of the die was 
chilled using cooling water, while the center zone was heated to 
280.degree. F., and the exit zone was heated to 300.degree. F. The roving 
was pultruded at several different rates to produce prepreg with varying 
properties. Roving pultruded at 9 in/min. produced a firm rod which could 
be cut with scissors. Roving pultruded at either 12 in/min. or 18 in/min. 
produced a semi-dry, loose, non-tacky bundle of roving, which was easy to 
bend. 
EXAMPLE 2 
Post-Forming by Compression Molding 
The loose prepreg of Example 1, was manually bent 360 degrees. The charge 
was then placed into the mold cavity of a compression molding device. The 
upper mold was heated to 145.degree. C. while the lower mold was heated to 
148.degree. C. Thereafter, the mold was closed and 1020 psi of pressure 
was applied for 3 min. The fully cured part was rigid and could not be 
deformed without damage. 
EXAMPLE 3 
Post-Forming by Compression Molding 
Four-12 in sections of the firm rod prepreg of Example 1 was positioned in 
a flat mold cavity in a conventional compression molding device. The upper 
mold was heated to 145.degree. C. while the lower mold was heated to 
148.degree. C. Thereafter, the mold was closed and 100 tons of pressure 
was applied for 3 min. The fully cured part assumed the shape of the mold 
cavity. 
EXAMPLE 4 
Preparation of Prepreg 
A conventional wet-bath pultrusion apparatus having an 8 in..times.0.15 in. 
profile die opening was strung with an 8 in top layer of 1.5 oz/ft.sup.2 
continuous strand mat, 75 glass rovings spread over 8 in, and an 8 in 
bottom layer of 1.5 oz/ft.sup.2 continuous strand mat. The reinforcing 
layers were strung through guides, the resin bath, and the die, and then 
secured to the pulling mechanism. The resin bath was charged with 100 
parts ATLAC.TM. 580-05, 0.35 parts di-(4-tert-butylcyclohexyl) peroxy 
dicarbonate, 0.35 parts peroxy 2-ethylhexanoate, 0.35 parts 
t-butylperbenzoate, 0.35 parts PS-125.TM. liquid internal mold release 
agent and 30 parts calcium carbonate filler. The entry zone of the die was 
chilled using cooling water, while the center zone was heated to 
250.degree. F., and the exit zone was heated to 275.degree. F. The 
reinforcing layers were pultruded at 18 in/min. to produce a flexible, 
non-tacky 8 in. sheet of prepreg which could easily be cut with scissors. 
EXAMPLE 5 
Post-Forming by Compression Molding 
The prepreg of Example 4 was post-formed in a compression molding 
apparatus. A 12 in. piece was placed in a 14 in..times.14 in. flat mold 
cavity of a conventional compression molding device. The upper mold was 
heated to 145.degree. C., while the lower mold was heated to 148.degree. 
C. Thereafter, the mold was closed and 100 tons of pressure was applied 
for 3 min. The fully cured part was smooth and glossy, indicating that the 
prepreg spread under pressure carrying the glass fibers together with the 
resin matrix. 
The foregoing is illustrative of the present invention and is not to be 
construed as limiting thereof. The invention is defined by the following 
claims, with equivalents of the claims to be included therein.