Prepreg of reinforcing fibers, epoxy resins, crosslinked rubber particles and curing agent

Disclosed are epoxy resin compositions for fiber-reinforced composite materials, comprising an epoxy resin containing 70 parts by weight or more, per 100 parts by weight of the epoxy resin, of a bi-functional epoxy resin, fine particles comprising a rubber phase and substantially insoluble in epoxy resins and a curing agent. Also disclosed are prepregs and fiber-reinforced composite materials comprising the composition.

FIELD OF THE INVENTION 
The present invention relates to epoxy resin compositions capable of giving 
composite materials with excellent impact resistance and also to prepregs 
and fiber-reinforced composite materials to be obtained from the 
compositions. 
BACKGROUND OF THE INVENTION 
As having especially excellent mechanical characteristics, fiber-reinforced 
composite materials comprising, as the intermediate bases, prepregs that 
comprise reinforcing fibers and matrix resins are widely used not only in 
sports goods but also in the aerospace industry and other various general 
industries. 
Various methods are employed to produce fiber-reinforced composite 
materials. Above all, a method of using a prepreg which is a sheet-like 
intermediate base to be prepared by impregnating reinforcing fibers with a 
matrix resin is popularly used. The method gives shaped articles by 
laminating a plurality of such prepregs followed by heating the resulting 
laminate. 
Recently, more lightweight sports goods with higher durability are desired. 
In particular, for ball game goods that shall undergo great instantaneous 
shock, such as golf club shafts, baseball bats, tennis and badminton 
rackets and hockey sticks, it is an important theme to improve the impact 
resistance of the materials for those goods in order to make them 
lightweight and have improved durability. 
At present, (cured) epoxy resins with excellent mechanical and chemical 
characteristics including high heat resistance, high hardness, high 
dimension stability and high chemical resistance are essentially used as 
the matrix resins for fiber-reinforced composite materials (The term 
"epoxy resin" is generally used to mean both a prepolymer and a cured 
product to be obtained by mixing a prepolymer with a curing agent and 
other additives followed by curing the resulting composition. Unless 
otherwise specifically indicated, the term "epoxy resin" as referred to 
herein means a prepolymer.) However, since (cured) epoxy resins are 
defective in that they are brittle or, that is, their toughness is poor, 
there often occurs a problem in that fiber-reinforced composite materials 
comprising them have poor impact resistance. 
Various attempts have heretofore been made to toughen (cured) epoxy resins 
to thereby improve the impact resistance of fiber-reinforced composite 
materials comprising the resins. To toughen (cured) epoxy resins, in 
general, methods of improving epoxy resins themselves and also curing 
agents and methods of adding modifiers to epoxy resins have been proposed. 
One example of the methods of toughening (cured) epoxy resins by improving 
epoxy resins themselves and curing agents is to add thereto epoxy resins 
with flexible skeletons or flexibility-imparting curing agents. According 
to this, however, the degree of elastic modulus and the heat resistance of 
the resulting (cured) epoxy resins are lowered. Contrary to this, another 
example is to introduce rigid skeletons into epoxy resins and curing 
agents to lower the crosslinking degree of the cured resins while 
controlling the toughness, the elastic modulus and the heat resistance of 
the cured resins. For instance, in ACS Polym. Preprints, Vol. 29, No. 1 
(1988), it is reported that the (cured) epoxy resins as obtained from 
fluorene type epoxy resins and curing agents can have improved toughness 
while preventing the lowering of their glass transition temperature. 
However, the proposed improvement requires extremely expensive epoxy 
resins and curing agents and shall be applied to only limited use. 
One example of the methods of adding modifiers to epoxy resins is to add 
rubber components or thermoplastic resins to epoxy resin compositions to 
obtain cured resins with high toughness. (The term "rubber" as used herein 
includes all elastomers except thermoplastic elastomers.) 
For example, Japanese Patent Publication Nos. 61-29613 and 62-34251 have 
proposed the addition of rubber components, in which carboxyl-terminated 
butadiene-acrylonitrile copolymer rubbers (CTBN) or nitrile rubbers are 
added to epoxy resins to modify the resins. Some of the proposed 
techniques have already been put to practical use. In the proposed 
methods, however, the rubber components added are once dissolved in epoxy 
resins and thereafter subjected to phase-separation during curing the 
resins. Therefore, the method are problematic in that it could not always 
produce the intended modifying results due to the possible change in the 
morphology of the cured products that depends on the types of the epoxy 
resins used and the curing conditions employed and that the rubber 
component added partly dissolves in the cured epoxy resin phase thereby 
often lowering the elastic modulus and the glass transition temperature of 
the (cured) epoxy resins. 
To solve the problem in the morphology change that occurs in the toughening 
of (cured) epoxy resins by means of the addition of rubber components 
thereto, one method of dispersing rubber particles in epoxy resins is 
known. For example, Japanese Laid-Open Patent Nos. 58-83014 and 59-138254 
have disclosed methods of polymerizing monomers such as acrylates and 
functional group-containing monomers capable of reacting with epoxy 
resins, such as acrylic acid, in epoxy resins to obtain epoxy resin 
compositions containing rubber particles formed and dispersed in the epoxy 
resins, which are to increase the shear strength of the adhesives. In 
these methods, however, the dissolution of a part of the rubber component 
in the cured epoxy resin phase is still inevitable and, in fact, these 
methods could not ensure sufficient heat resistance for the cured resin 
products. 
In the method of adding thermoplastic resins, if thermoplastic resins 
having a high glass transition temperature are added, it may be possible 
to obtain cured products which are tough and which maintain their 
intrinsic heat resistance. However, in order to attain the intended object 
to obtain highly-toughened products, large amounts of such thermoplastic 
resins must be added, resulting in the increase in the viscosity of the 
reaction system and in the difficulty in the handling of the system. Thus, 
the method has such problems. 
SUMMARY OF THE INVENTION 
In order to attain the above-mentioned objects, the present invention 
provides an epoxy resin composition having the constitution mentioned 
below. 
Precisely, the present invention provides an epoxy resin composition for 
fiber-reinforced composite materials, comprising the following 
constitutive elements [A], [B] and [C]. 
[A] An epoxy resin containing 70 parts by weight or more, per 100 parts by 
weight of the epoxy resin, of a bi-functional epoxy resin; 
[B] fine particles which comprise a rubber phase and which are 
substantially insoluble in epoxy resins; and 
[C] a curing agent. 
The present invention also provides a prepreg to be prepared by 
impregnating reinforcing fibers with the above-mentioned epoxy resin 
composition. The present invention further provides a fiber-reinforced 
composite material comprising a cured product of the above-mentioned epoxy 
resin composition and reinforcing fibers. 
DETAILED DESCRIPTION OF THE INVENTION 
The constitutive element [A] is a single epoxy resin or a mixture of plural 
epoxy resins. The epoxy resin to be used herein is a compound having one 
or more epoxy groups in one molecule. It preferably includes epoxy resins 
to be derived from precursors of phenols, amines and compounds with 
carbon-carbon double bond(s) in view of the mechanical properties of the 
(cured) epoxy resins and of the reactivity thereof with curing agents. 
Epoxy resins to be derived from precursors of phenols are obtained by 
reacting phenols and epichlorohydrin. The precursors include, for example, 
bisphenols such as bisphenol A and bisphenol F; resorcinol, 
dihydroxynaphthalene, trihydroxynaphthalene, dihydroxybiphenyl, 
bishydroxyphenylfluorene, trishydroxyphenylmethane, 
tetrakishydroxyphenylethane, novolaks, condensates of dicyclopentadiene 
and phenols, etc. 
Epoxy resins to be derived from precursors of amines are obtained by 
reacting amines and epichlorohydrin. The precursors include, for example, 
tetraglycidyldiaminodiphenylmethane, aminophenol, aminocresol, 
xylenediamine, etc. 
Epoxy resins to be derived from precursors of compounds with carbon-carbon 
double bond(s) are obtained by oxidizing the carbon-carbon double bond(s) 
in the precursors into epoxy group(s). The precursors include, for 
example, vinylcyclohexene, bis(3-vinylcyclohexylmethyl) adipate, 
3-vinylcylohexylmethyl 3-vinylcyclohexane-carboxylate, etc. that are 
obtained from butadiene, crotonaldehyde, etc. 
The fine particles comprising a rubber phase and insoluble in epoxy resins, 
which constitute the constitutive element [B] for use in the present 
invention, are to improve the toughness of the cured product of the epoxy 
resin composition containing them, and their effect depends on the 
compositional ratio of the components constituting the epoxy resin 
composition. Concretely, the toughness-improving effect is higher for the 
cured product with a lower crosslinking density. However, if the 
crosslinking density of the cured product is too low, such is unfavorable 
as lowering the elastic modulus and the heat resistance of the product. 
Accordingly, the constitutive element [A] desirably has a composition 
capable of being cured into a cured product with a suitable crosslinking 
density. To adjust the crosslinking density of the cured product, in 
general, a plurality of different epoxy resins each having a different 
functional group number (this means the number of epoxy groups herein) per 
one molecule may be mixed at controlled ratios. 
In order to make the cured product have a suitable crosslinking density, 
preferably employed are bi-functional epoxy resins (having two epoxy 
groups in one molecule) as the major moiety of the constitutive element 
[A]. In order to make the cured product have well-balanced physical 
properties, the epoxy resin for the constitutive element [A] comprises 
from 70 to 100 parts by weight, more preferably from 80 to 100 parts by 
weight, of a bi-functional epoxy resin per 100 parts by weight of the 
epoxy resin. 
The constitutive element [A] may contain, as optional components other than 
the bi-functional epoxy resin, tri-functional or more multifunctional 
epoxy resins (having 3 or more epoxy groups in one molecule), and also 
reactive diluents (compounds having 1 or 2 epoxy groups in one molecule). 
If, however, tri-functional or more multifunctional epoxy resins having a 
too large functional group number are employed in the invention, the 
viscosity of the epoxy resin composition of the invention comes to be too 
high. If the composition having such a high viscosity is applied to 
reinforcing fibers to obtain a fiber-reinforced composite material, the 
impregnation of the fibers with the composition is difficult. Therefore, 
from tri-functional to hexa-functional epoxy resins are preferably 
employed in the invention. 
Such tri-functional or more multifunctional epoxy resins are effective in 
improving the elastic modulus and the heat resistance of the cured product 
of the epoxy resin composition of the invention. If, however, too much 
amounts of such multifunctional epoxy resins are added, the cured product 
may have a too large crosslinking density and therefore could not have 
high toughness. It is desirable that the proportion of the tri-functional 
or more multifunctional epoxy resin is 30 parts by weight or less per 100 
parts by weight of the epoxy resin for [A]. 
To mix the bi-functional epoxy resin and the tri-functional or more 
multifunctional epoxy resin to prepare the epoxy resin for [A], it is 
desirable that 100 parts by weight of the epoxy resin for [A] contains 70 
parts by weight or more of the bi-functional epoxy resin and from 1 to 30 
parts by weight of the tri-functional or more multifunctional epoxy resin, 
more preferably 80 parts by weight or more of the former and from 1 to 20 
parts by weight of the latter. 
Reactive diluents (compounds having 1 or 2 epoxy groups in one molecule) 
are generally compounds with a low viscosity and are effective for 
lowering the viscosity of the epoxy resin composition of the invention and 
also for lowering the crosslinking density of the cured product of the 
composition. However, if the composition contains a too large amount of 
such a reactive diluent, the elastic modulus and the heat resistance of 
the cured product will be often lowered. Therefore, it is preferable that 
the epoxy resin for [A] contains 30 parts by weight or less, per 100 parts 
by weight of the epoxy resin, of the reactive diluent but the epoxy resin 
may not contain the reactive diluent. 
Another criterion for optimizing the crosslinking density of the cured 
epoxy resin product of the present invention is based on the epoxy 
equivalent of the constitutive element [A], which is obtained by dividing 
the mass (g) of the element [A] by the molar number of the epoxy groups in 
[A]. The epoxy equivalent of [A] can be obtained by means of titration or 
through calculation of the individual epoxy equivalents of the epoxy 
resins that constitute [A]. 
The priority application, Japanese Patent Application No. 7-110888 has 
disclosed an epoxy resin composition comprising 80 parts by weight or 
more, relative to 100 parts by weight of the total epoxy resin therein, of 
a bi-functional epoxy resin. The total epoxy equivalent of the epoxy resin 
in the composition disclosed therein is from 168 to 925, which is obtained 
through calculation of the individual epoxy equivalents of commercial 
epoxy resins constituting the composition. 
If the total epoxy equivalent of the constitutive element [A] is large, the 
cured product may have a small crosslinking density. Therefore, the epoxy 
equivalent of [A] may be 250 or more. However, if the epoxy equivalent of 
[A] is too large, the cured product shall often have lowered elastic 
modulus and heat resistance or the epoxy resin composition shall often 
have an increased viscosity. Therefore, the epoxy equivalent of [A] is 
preferably from 250 to 400. 
The bi-functional epoxy resin to be in the constitutive element [A] 
includes, for example, bisphenol A-type epoxy resins (epoxy resins to be 
derived from a precursor, bisphenol A), bisphenol F-type epoxy resins 
(epoxy resins to be derived from a precursor, bisphenol F), bisphenol 
S-type epoxy resins (epoxy resins to be derived from a precursor, 
bisphenol S), resorcinol-type epoxy resins (epoxy resins to be derived 
from a precursor, resorcinol), naphthalene-type epoxy resins (epoxy resins 
to be derived from a precursor, dihydroxynaphthalene), biphenyl-type epoxy 
resins (epoxy resins to be derived from a precursor, dihydroxybiphenyl), 
dicyclopentadiene-type epoxy resins (epoxy resins comprising condensates 
of dicyclopentadiene and phenols), fluorene-type epoxy resins (epoxy 
resins to be derived from a precursor, bishydroxyphenylfluorene), etc. Of 
these, preferred are bisphenol A-type epoxy resins and bisphenol F-type 
epoxy resins, as being effective in well controlling the viscosity and the 
epoxy equivalent of the epoxy resin composition. 
Commercially-available bisphenol A-type epoxy resins are usable in the 
present invention, which include, for example, "Epikote 825" (having a 
mean molecular weight of 350 and an epoxy equivalent of from 172 to 178), 
"Epikote 828" (having a mean molecular weight of 378 and an epoxy 
equivalent of from 184 to 194), "Epikote 834" (having a mean molecular 
weight of 500 and an epoxy equivalent of from 230 to 270), "Epikote 1001" 
(having a mean molecular weight of 950 and an epoxy equivalent of from 450 
to 500), "Epikote 1004" (having a mean molecular weight of 1850 and an 
epoxy equivalent of from 875 to 975), "Epikote 1009" (having a mean 
molecular weight of 5700 and an epoxy equivalent of from 2400 to 3300) 
(all produced by Yuka-Shell Epoxy Co.); "Epotohto YD-128" (having a mean 
molecular weight of 378 and an epoxy equivalent of from 184 to 194) 
(produced by Thoto kasei Co.); "Epiclon 840" (having a mean molecular 
weight of 370 and an epoxy equivalent of from 180 to 190), "Epiclon 850" 
(having a mean molecular weight of 378 and an epoxy equivalent of from 184 
to 194), "Epiclon 830" (having a mean molecular weight of 350 and an epoxy 
equivalent of from 165 to 185), "Epiclon 1050" (having a mean molecular 
weight of 950 and an epoxy equivalent of from 450 to 500) (all produced by 
Dainippon Ink and Chemicals, Inc.); "Sumi-epoxy ELA-128" (having a mean 
molecular weight of 378 and an epoxy equivalent of from 184 to 194) 
(produced by Sumitomo Chemical Co.); DER 331 (having a mean molecular 
weight of 374 and an epoxy equivalent of from 182 to 192) (produced by Dow 
Chemical Co.), etc. These have the following chemical structures. 
##STR1## 
wherein n represents a positive number and preferably n is 0 to 13. 
Commercially-available bisphenol F-type epoxy resins are usable in the 
present invention, which include, for example, "Epikote 806" (having a 
mean molecular weight of 330 and an epoxy equivalent of from 160 to 170), 
"Epikote 807" (having a mean molecular weight of 335 and an epoxy 
equivalent of from 160 to 175) (both produced by Yuka-Shell Epoxy Co.); 
"Epiclon 830" (having a mean molecular weight of 345 and an epoxy 
equivalent of from 165 to 180) (produced by Dainippon Ink and Chemicals, 
Inc.), etc. These have the following chemical structures. 
##STR2## 
wherein n represents a positive number and preferably n is 0 to 2. 
The bi-functional epoxy resin to be in the constitutive element [A] is 
preferably comprised of a liquid, bi-functional epoxy resin with a low 
molecular weight (n is 0-0.5) and a low epoxy equivalent and a solid, 
bi-functional epoxy resin with a high molecular weight (n is 1-13) and a 
high epoxy equivalent, by which the viscosity and the epoxy equivalent of 
the epoxy resin composition may be suitably controlled. 
The liquid, bi-functional epoxy resin preferably has a mean molecular 
weight of from 200 to 600 and an epoxy equivalent of from 100 to 300, more 
preferably a mean molecular weight of from 300 to 400 and an epoxy 
equivalent of from 150 to 200. The solid, bi-functional epoxy resin 
preferably has a mean molecular weight of from 730 to 10000 and an epoxy 
equivalent of from 350 to 5000, more preferably a mean molecular weight of 
from 800 to 4000 and an epoxy equivalent of from 400 to 2000. 
The tri-functional or more multifunctional epoxy resin, which may be 
optionally added to the constitutive element [A], includes 
phenol-novolak-type epoxy resins, cresol-novolak-type epoxy resins, 
glycidylamine-type epoxy resins such as 
tetraglycidyldiaminodiphenylmethane and triglycidylaminophenol, glycidyl 
ether-type epoxy resins such as tetrakis(glycidyloxyphenyl)ethane and 
tris(glycidyloxy)methane, etc. Of these, preferred are phenol-novolak-type 
epoxy resins (epoxy resins to be derived from precursors, phenol-novolaks) 
in view of the viscosity of the resin compositions comprising them and of 
the elastic modulus and the heat resistance of the cured products of the 
compositions. Commercially-available phenol-novolak-type epoxy resins are 
usable in the present invention, which include, for example, "Epikote 152" 
(having a mean molecular weight of 351 and an epoxy equivalent of from 172 
to 179), "Epikote 154" (having a mean molecular weight of 625 and an epoxy 
equivalent of from 176 to 181) (both produced by Yuka-Shell Epoxy Co.); 
DER 438 (having a mean molecular weight of 625 and an epoxy equivalent of 
from 176 to 181) (produced by Dow Chemical Co.); "Araldite EPN1138" 
(having a mean molecular weight of 625 and an epoxy equivalent of from 176 
to 181), "Araldite EPN1139" (having a mean molecular weight of 351 and an 
epoxy equivalent of from 172 to 179) (both produced by Ciba Co.), etc. 
These have the following chemical structures. 
##STR3## 
wherein n represents a positive number and preferably n is 0.2 to 4. 
Specific examples of the reactive diluent for use in the present invention 
include butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl 
ether, cresyl glycidyl ether, p-sec-butyl glycidyl ether, p-tert-butyl 
glycidyl ether, etc. 
The epoxy resin composition of the present invention that comprises, as the 
constitutive element [B], fine particles comprising a rubber phase and 
insoluble in epoxy resins can give a cured product having heat resistance 
which is comparable to that of the cured product of an epoxy resin 
composition not containing such fine particles, since the fine particles 
in the composition are insoluble in epoxy resins. In addition, the epoxy 
resin composition of the present invention is additionally characterized 
in that the physical properties including toughness of the cured product 
of the composition are stable since the morphology of the cured product 
does not vary irrespective of the types of the epoxy resin matrices used 
and the curing conditions employed. The fine particles for use in the 
present invention which comprise a rubber phase and which are insoluble in 
epoxy resins are referred to. Rubber polymers as obtained by polymerizing 
monomers in epoxy resins contain rubber components as dissolved in the 
dispersing media, epoxy resins. If added to epoxy resin compositions, 
these have negative influences on the heat resistance and other physical 
properties of the cured products of the compositions. Therefore, such 
rubber polymers as polymerized in epoxy resins are unsuitable to the 
present invention. If, on the other hand, fine particles added to epoxy 
resin compositions contain volatile dispersing media, such volatile 
dispersing media must be removed in any step for the production of 
fiber-reinforced composite materials using the resin compositions. If the 
removal is unsatisfactorily conducted, the remaining volatile dispersing 
media produce voids in the fiber-reinforced composite materials. For these 
reasons, in conducting the present invention, it is desirable that the 
fine particles constituting the element [B] are directly added to epoxy 
resins, without being dispersed in any volatile dispersing media such as 
water and organic solvents, and are uniformly dispersed in the epoxy 
resins, for example, by stirring under heat. Specifically, it is desirable 
that the constitutive element [B] of fine particles which comprise a 
rubber phase and which are insoluble in epoxy resins is directly added to 
the constitutive element [A] of epoxy resins and uniformly dispersed in 
the latter at from 50.degree. C. to 200.degree. C. by using a kneader such 
as a stirring motor, a kneader or a three-roll mill. 
In order to uniformly disperse the fine particles comprising a rubber phase 
and substantially insoluble in epoxy resin, that constitute the 
constitutive element [B], in the epoxy resins constituting the 
constitutive element [A], preferably employed is a method of previously 
dispersing the fine particles in a liquid epoxy resin to prepare a master 
resin followed by adding the other components thereto to prepare the resin 
composition of the present invention. 
The fine particles comprising a rubber phase and insoluble in epoxy resins 
include, for example, fine, crosslinked rubber particles comprising only a 
rubber phase and fine core/shell polymer particles comprising a rubber 
phase and a non-rubber resin phase. 
The fine, crosslinked rubber particles can be obtained, for example, by 
copolymerizing single or plural unsaturated compounds with crosslinking 
monomers. 
The unsaturated compound includes, for example, aliphatic olefins such as 
ethylene, propylene; aromatic vinyl compounds such as styrene, 
methylstyrene; conjugated diene compounds such as butadiene, 
dimethylbutadiene, isoprene, chloroprene; unsaturated carboxylates such as 
methyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, 
propyl methacrylate, butyl methacrylate; vinyl cyanides such as 
acrylonitrile, etc. 
The unsaturated compound may have functional group(s) reactive with epoxy 
resins or curing agents, such as carboxyl, epoxy, hydroxyl, amino and 
amido groups. Examples of the compound include acrylic acid, glycidyl 
methacrylate, vinylphenol, acrylamide, etc. 
Examples of the crosslinking monomer are compounds having a plurality of 
polymerizing double bonds in the molecule, such as divinylbenzene, diallyl 
phthalate, ethylene glycol dimethacrylate, etc. 
The fine particles can be produced by various conventional polymerization 
modes of, for example, emulsion polymerization, suspension polymerization, 
etc. One typical emulsion polymerization is to polymerize the unsaturated 
compound(s) and crosslinking monomers in the presence of a radical 
polymerization initiator, a molecular weight-controlling agent such as 
mercaptan or halogenated hydrocarbons, and an emulsifier. At the 
pre-determined degree of conversion for polymerization, a polymerization 
stopper is added to the polymerization system, by which the polymerization 
is stopped. Next, the non-reacted monomers are removed from the 
polymerization system, for example, through distillation with steam to 
finally obtain a copolymer latex. The removal of water from the latex thus 
obtained by the emulsion polymerization produces crosslinked rubber 
particles. 
Commercially-available, crosslinked rubber particles can also be used in 
the present invention, which include, for example, XER-91 comprising a 
crosslinked product of a carboxyl-modified butadiene-acrylonitrile 
copolymer (produced by Japan Synthetic Rubber Co.), CX-MN series 
comprising fine acrylic rubber particles (produced by Nippon Shokubai 
Co.), YR-500 series (produced by Thoto kasei Co.), etc. 
Fine core/shell polymer particles usable in the present invention are fine, 
spherical polymer particles where the core and the surface layer are made 
of different polymers. As such particles, known are fine, 
two-phase-structured core/shell polymer particles with a single core phase 
and a single shell phase, and fine, multi-phase-structured core/shell 
polymer particles composed of, for example, a single soft core and plural 
shell phases of a hard shell, a soft shell and a hard shell that cover the 
core in that order. The term "soft" as referred to herein indicates a 
rubber phase, while "hard" indicates a non-rubber resin phase. The term 
"rubber" as referred to herein is meant to indicate a polymer having a 
glass transition temperature lower than room temperature (25.degree. C.). 
Of the above-mentioned fine particles, those with soft core/hard shell 
structures are preferably employed in the present invention as being well 
dispersed in epoxy resins. 
The core component to be in the fine, core/shell polymer particles with 
soft core/hard shell structures may include the same polymers as those 
referred to hereinabove for the crosslinked rubber particles. 
Of these, conjugated diene rubbers, alkyl acrylate rubbers having a carbon 
number of an alkyl group of 2 to 8 or mixtures of these rubbers are 
preferably used as a main component. Such conjugated dienes or alkyl 
acrylates can be copolymerized with monomers which are copolymerizable. 
The monomers include, for example, aromatic compounds such as styrene, 
vinyl toluene, aromatic vinylidene, vinyl cyanides such as acrylonitrile 
and methacrylonitrile, and alkyl methacrylate such as methyl methacrylate. 
The shell component to be in the particles may be a polymer having a glass 
transition temperature not lower than room temperature (25.degree. C.), 
which includes, for example, Polystyrenes, homopolymers of acrylonitrile, 
methyl acrylate or methyl methacrylate, copolymers such as methyl 
methacrylate/alkyl acrylates and methacrylic acid/acrylic acid, and also 
terpolymers such as styrene/acrylonitrile/glycidyl methacrylate. Also 
usable are copolymers with unsaturated compounds having functional 
group(s) reactive with epoxy resins or curing agents (e.g., carboxyl, 
epoxy, hydroxyl, amino and amido groups), such as acrylic acid, 
methacrylic acid, itaconic acid, glycidyl methacrylate, hydroxyethyl 
methacrylate, dimethylaminomethyl methacrylate, methacrylamide, etc. 
Rather preferably, the shell component comprises a polymer with no 
reactive functional group, such as polymethyl methacrylate, since the 
dispersibility of the fine particles in epoxy resins is good. 
Of these, the core/shell polymer particles are preferably such that the 
core is a polybutadiene or polybutyl acrylate and the shell is an acrylate 
or methacrylate polymer. In this regard, it is particularly preferred that 
the core or the shell comprises the respective compound in an amount of 
65% or more by weight. Among these core/shell polymer particles, it is 
even more preferred that the core comprises butadiene in an amount of 65 
to 85% by weight and styrene in an amount of 15 to 35% by weight, and the 
shell comprises methylmethacrylate in an amount of 70 to 97% by weight and 
alkylmethacrylate having a carbon number of an alkyl group of 2 to 8 in an 
amount of 3 to 30% by weight as giving a high impact strength. 
Preferably, the fine core/shell polymer particles are such that the content 
of the core component is from 10 to 90% by weight and that of the shell 
component is from 10 to 90% by weight. If the content of the core 
component is less than 10% by weight, a sufficient effect for the 
improvement in toughness of the cured product could not often be obtained, 
but if it is more than 90% by weight, the complete covering of the core 
with the shell would often be difficult with the result that the 
dispersibility of the fine particles would be insufficient. 
The fine core/shell polymer particles can be produced by known methods, for 
example, by the methods disclosed in U.S. Pat. No. 4,419,496, European 
Patent 45,357, Japanese Laid-Open Patent No. 55-94917, etc. 
Commercially-available products of fine core/shell polymer particles can 
be used in the present invention. Such commercially-available products 
include, for example, "Kureha Paraloid EXL-2655" comprising 
butadiene-alkyl methacrylate-styrene copolymers (produced by Kureha 
Chemical Industry Co.); "Staphyloid AC-3355, TR-2122" comprising 
acrylate-methacrylate copolymers (produced by Takeda Chemicals Industry 
Co.); "Paraloid EXL-2611, EXL-3387" comprising butyl acrylate-methyl 
methacrylate copolymers (produced by Rohm & Haas Co.), etc. 
A plurality of different types of the fine particles which comprise a 
rubber phase and which are insoluble in epoxy resins, such as those 
mentioned hereinabove, can be combined for use in the present invention. 
The fine particles preferably have a mean particle size of 10 .mu.m or 
less, more preferably 5 .mu.m or less. If their sizes are too large, it 
would be difficult for them to pass through the voids between reinforcing 
fibers when the fibers are impregnated with the matrix resin and, as a 
result, it would be often difficult to make them uniformly distributed 
throughout the fibers. 
The proportion of the constitutive element [B] comprising the fine 
particles, which comprise a rubber phase and which are insoluble in epoxy 
resins, to the constitutive element [A] is from 1 to 20 parts by weight of 
the particles to 100 parts by weight of the epoxy resin. If it is less 
than 1 part by weight, the effect for the improvement in impact resistance 
of the cured product may be insufficient, but if it is more than 20 parts 
by weight, the viscosity of the resin composition may be too high and, as 
a result, it would be often difficult to make the particles infiltrated 
into reinforcing fibers. 
The curing agent to be used as the constitutive element [C] includes, for 
example, aromatic amines such as diaminodiphenylmethane, 
diaminodiphenylsulfone; aliphatic amines such as triethylenetetramine, 
isophoronediamine; imidazole derivatives; dicyandiamide; 
tetramethylguanidine; carboxylic acid anhydrides such as 
methylhexahydrophthalic anhydride; carboxylic acid hydrazides such as 
adipic acid hydrazide; carboxylic acid amides; polyphenol compounds; 
polymercaptans; Lewis acid complexes such as boron trifluoride-ethylamine 
complex, etc. 
Additives with curing activity that are obtained by reacting the curing 
agents with epoxy resins can also be employed in the present invention. 
Microcapsules of the curing agents are preferably employed, since they 
prolong the shelf life of the prepregs comprising them. 
The curing agents can be combined with curing accelerators in order to 
increase their curing activity. Preferred examples include a combination 
of dicyandiamide and a curing accelerator selected from urea derivatives 
and imidazole derivatives, and a combination of a carboxylic anhydride or 
polyphenol compound and a curing accelerator selected from tertiary amines 
and imidazole derivatives. 
Urea derivatives usable as the curing accelerator may be compounds that are 
obtained by reacting secondary amines with isocyanates, for example, those 
having the following chemical structures. 
##STR4## 
wherein R.sup.1 and R.sup.2 each represent a group selected from H, Cl, 
CH.sub.3, OCH.sub.3 and NO.sub.2 ; and n=1 or 2. 
Concretely, 3-phenyl-1,1-dimethylurea and 
3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) are preferably used. 
The epoxy resin composition for fiber-reinforced composite materials of the 
present invention, which comprises the constitutive elements [A], [B] and 
[C], may additionally contain a thermoplastic resin as the optional 
component. The addition of such a thermoplastic resin may control the 
viscosity of the resin composition, may facilitate the handlability of the 
prepreg comprising the composition and may improve the adhesiveness 
between the matrix resin and reinforcing fibers. 
The thermoplastic resin to be used preferably has hydrogen-bonding 
functional groups in view of its compatibility with epoxy resins and its 
adhesiveness to reinforcing fibers. 
The hydrogen-bonding functional groups include, for example, alcoholic 
hydroxyl groups, amido groups, imido groups and sulfonyl groups. 
Thermoplastic resins with alcoholic hydroxyl groups include, for example, 
polyvinylacetal resins such as polyvinyl formal and polyvinyl butyral, and 
phenoxy resins; those with amido groups include, for example, polyamides; 
those with imido groups include, for example, polyimides; those with 
sulfonyl groups include, for example, polysulfones. The polyamides, 
polyimides and polysulfones may have ether bonds and functional groups 
such as carbonyl groups in their main chains. The polyamides may have a 
substituent at the nitrogen atom of the amide group. 
Examples of commercially-available thermoplastic resins which are soluble 
in epoxy resins and which have hydrogen-bonding functional groups include 
polyvinyl acetal resins of "Denka Butyral" and "Denka Formal" (both 
produced by Denki Kataku kogyo K.K.), "Vinylec" (produced by Chisso Co.); 
phenoxy resins of "UCAR PKHP" (produced by Union Carbide Co.); polyamide 
resins of "Macromelt" (produced by Henchel-Hakusui Co.), "Amilan CM4000" 
(produced by Toray Industries, Inc.); polyimide resins of "Ultem" 
(produced by General Electric Co.), "Matrimide 5218" (produced by Ciba 
Co.); polysulfone resins of "Victrex" (produced by Mitsui Toatsu Chemical 
Co.), "UDEL" (produced by Union Carbide Co.). These have the following 
chemical structures in which n, l and m each represent a positive number 
and preferably, as follows: 
##STR5## 
where n is 219-240, m is 60-72, and l is 0-9; 
##STR6## 
where n is 365, m is 22-30, and l is 42-59; 
##STR7## 
where n is 37-40, m is 32-35, and l is 23-26; 
##STR8## 
where n is about 20; 
##STR9## 
where n is 50-80; 
##STR10## 
where n is 35-57; 
##STR11## 
where n is 5-60 wherein D represents a hydrocarbon group having 32 carbon 
atoms in the dimer acid molecule. 
The polyvinyl acetal resins are preferably polyvinyl formal resins having 
vinyl formal moieties at 60% by weight or more in view of their mechanical 
properties. Two or more of the above-mentioned resins may be combined for 
use in the present invention. 
Of the above-mentioned thermoplastic resins, those having a degree of 
bending elastic modulus of 10 MPa or more at room temperature, concretely 
at 25.degree. C. are preferred, since they hardly lower the elastic 
modulus of the cured product of the epoxy resin composition. 
Preferably, the thermoplastic resins are thermodynamically soluble in epoxy 
resins at from 50.degree. C. to 200.degree. C. at least when they are 
added to the composition of the present invention. Even though soluble 
therein but if their solubility is too low, they are ineffective in 
improving the physical properties of the resulting composites. Therefore, 
it is desirable that their solubility in epoxy resins is above a 
pre-determined level. As the index for selecting and using thermoplastic 
resins with high solubility, employable is a solubility parameter Sp that 
can be calculated on the basis of their molecular structures. In order to 
attain the sufficient solubility of thermoplastic resins in epoxy resins, 
it is preferable that the difference in Sp between the total thermoplastic 
resins used and the total epoxy resins used is between 0 and 2, more 
preferably between 0 and 1.5, in terms of the absolute value. 
In order to reduce the absolute difference in Sp between them, the epoxy 
resins to be used are optimally selected while the proportion of the 
thermoplastic resins to the epoxy resins is optimized and the structures 
of the thermoplastic resins to be used are optimally selected. Where a 
plurality of epoxy resins are combined with a plurality of thermoplastic 
resins, the mean Sp value of the epoxy resins that shall be calculated by 
totaling the data to be obtained by multiplying the Sp value of each epoxy 
resin used by the weight fraction thereof is compared with the Sp value of 
each thermoplastic resin used. 
The solubility parameter reflects the polarity of the molecular structure. 
Since epoxy resins have large polarity, it is preferable that the 
thermoplastic resins to be added thereto have suitable polar moieties in 
their molecular structures. 
Where the composition of the present invention contains thermoplastic 
resins such as those mentioned hereinabove, the proportion of the 
thermoplastic resins is desirably from 1 to 20 parts by weight relative to 
100 parts by weight of the epoxy resins in the composition, as giving a 
suitable viscoelasticity parameter to the epoxy resin composition while 
producing composite materials with good physical properties. 
The epoxy resin composition of the present invention may further contain, 
in addition to the above-mentioned epoxy resins, fine particles, curing 
agents and thermoplastic resins, additives such as polymer compounds other 
than the above-mentioned ones, antioxidants, organic or inorganic 
particles with no rubber phase. 
As polymer compounds, those soluble in epoxy resins can be added to the 
composition for various purposes. Concretely mentioned are 
amino-functional silicone resins which are to roughen the cured products, 
such as those described in European Patent 475611 (corresponding to 
Japanese Laid-Open Patent No. 6-93103). For controlling the rheology of 
the matrix resins, polyester-type or polyamide-type thermoplastic 
elastomers can be used. 
As antioxidants, preferably used are phenolic antioxidants such as 
2,6-di-tert-butyl-p-cresol (BHT), butylated hydroxyanisole, tocopherol; 
and sulfur antioxidants such as dilauryl 3,3'-thiodipropionate, distearyl 
3,3'-thiodipropionate, etc. 
As organic particles other than the epoxy resin-insoluble, fine particles 
with a rubber phase which are indispensable in the present invention, 
employable are fine particles of thermoplastic resins, thermosetting 
resins (including cured resins), etc. The particles of thermoplastic 
resins include those of polyamide resins; the particles of thermosetting 
resins include those of cured epoxy resins and phenolic resins. These 
organic particles are added essentially for the purpose of additionally 
improving the toughness of the cured products and of controlling the 
rheology of the compositions. 
As inorganic particles, employable are particles of silica, alumina, 
smectite, synthetic mica, etc. These inorganic particles are added 
essentially for the purpose of controlling the rheology of the 
compositions or, that is, increasing the viscosity of the compositions or 
making the compositions thixotropic. 
By impregnating reinforcing fibers with the epoxy resin composition of the 
present invention, a prepreg is formed which is used as the intermediate 
base for fiber-reinforced composite materials. 
Where prepregs comprising epoxy resins are handled, their tackiness and 
drapability have great influences on their handlability and therefore 
shall be optimized. The tackiness and drapability of prepregs with epoxy 
resins have relation to the viscoelasticity of the matrix resins therein. 
The dynamic viscoelasticity of epoxy resins varies, depending on the 
temperature and the frequency at which it is measured. As the value that 
typically indicates the viscoelastic behavior of epoxy resins at about 
room temperature, referred to is a complex coefficient of viscosity .eta.* 
of epoxy resins to be measured at a temperature of 50.degree. C. and at a 
frequency of 0.5 Hz. Epoxy resins having a complex coefficient of 
viscosity .eta.* of from 200 to 2,000 Pa.multidot.s may produce prepregs 
with especially excellent characteristics including tackiness and 
drapability as mentioned above and are therefore preferable. 
High-viscosity epoxy resins having a complex coefficient of viscosity 
.eta.* above the scope often produce prepregs with insufficient 
drapability, and the impregnation of reinforcing fibers with such 
high-viscosity epoxy resins is often difficult. Unidirectional prepregs 
with low-viscosity epoxy resins having a complex coefficient of viscosity 
.eta.* below the scope are problematic in that their shape retention is 
often poor. 
As the reinforcing fibers, employable are glass fibers, carbon fibers, 
aramide fibers, boron fibers, alumina fibers, silicon carbide fibers, etc. 
Two or more types of these fibers can be combined. 
The morphology and the location of the reinforcing fibers for use in the 
present invention are not specifically defined. For example, employable 
are long fibers as paralleled in one direction, single tows, woven 
fabrics, mats, knitted fabrics, braids, etc. 
In order to obtain more lightweight shaped articles with higher durability, 
carbon fibers are especially preferably employed. In order to produce more 
lightweight sports goods such as golf club shafts and fishing rods, it is 
desirable to use carbon fibers with high elastic modulus in prepregs. 
Using even a small amount of such carbon fibers, the products may exhibit 
sufficient toughness. The carbon fibers preferably have a modulus of 
elastic modulus of 200 GPa or more, more preferably from 210 to 800 GPa. 
To produce prepregs of the present invention, employable are a wet method 
of dissolving the matrix resin in a solvent such as methyl ethyl ketone or 
methanol to thereby lower the viscosity of the resin followed by 
impregnating reinforcing fibers with the resulting solution, and a 
hot-melting (dry) method of heating the matrix resin to thereby lower its 
viscosity followed by impregnating reinforcing fibers with the resin. 
According to the wet method, reinforcing fibers are dipped in a solution of 
the epoxy resin composition and then drawn up, and the solvent is 
vaporized in an oven or the like to obtain a prepreg. 
According to the hot-melting method, the epoxy resin composition as 
previously heated to lower its viscosity is directly applied to 
reinforcing fibers to obtain a resin-impregnated prepreg; or 
alternatively, the epoxy resin composition is once coated on a release 
paper or the like to form a resin-coated film, and the film is applied 
onto one or both surfaces of a sheet of reinforcing fibers and then 
pressed under heat to obtain a resin-impregnated prepreg. The hot-melting 
method is preferred since no solvent remains in the prepreg. 
To produce a composite article from the prepreg, for example, a plurality 
of the prepregs are laminated and subjected to pressure under heat to 
thereby cure the resins therein. 
To apply heat and pressure to the laminate of prepregs, for example, 
employable are a pressing method, an autoclaving method, a packing method, 
a tape-wrapping method and an inner pressure method. For the production of 
sports goods, a tape-wrapping method and an inner pressure method are 
especially preferably employed. 
According to the tape-wrapping method, prepregs are wound around a mandrel 
or the like to be shaped into a cylindrical article. The method is 
suitable for producing rod-like articles such as golf club shafts and 
fishing rods. Concretely, prepregs are wound around a mandrel and then 
wrapped with a wrapping tape made of a thermoplastic resin film, by which 
the prepregs are fixed and through which pressure is applied to the 
prepregs, and the thus-wound mandrel is heated in an oven to thereby cure 
the resins in the prepregs. After this, the mandrel is pulled out to 
obtain a cylindrical article. 
According to the inner pressure method, prepregs are wound around an inner 
pressure support such as a thermoplastic resin tube or the like to give a 
preform, this is set in a mold, and a high-pressure vapor is introduced 
into the inner pressure support to apply pressure to the preform, while 
heating the mold, to obtain a shaped article. This method is suitably 
employed for shaping articles with complicated forms, such as golf club 
shafts, bats, tennis and badminton rackets, etc. 
Without previously forming prepregs, the epoxy resin composition of the 
present invention may be directly applied to reinforcing fibers and then 
cured under heat. For this, for example, employable are a hand-lay-up 
method, a filament-winding method, a pultrusion-molding method, a 
resin-injection-molding method, a resin-transfer-molding method, etc. 
According to these methods, fiber-reinforced composite materials are also 
obtained. In these, two liquids, one comprising the essential components 
of the constitutive elements [A] and [B] and the other comprising a curing 
agent of the constitutive element [C], may be mixed just before use. 
The fiber-reinforced composite material of the present invention, which may 
be shaped by various shaping methods such as those mentioned hereinabove, 
has excellent impact resistance and therefore can be used in various ball 
game goods, such as golf club shafts, baseball bats, tennis or badminton 
rackets, hockey sticks, etc., and also in aircraft parts. 
Since the fiber-reinforced composite material to be obtained by combining 
the epoxy resin composition of the present invention and reinforcing 
fibers has higher impact resistance than any conventional fiber-reinforced 
composite material in the prior art, even a smaller amount of the former 
can exhibit impact resistance comparable to that of a larger amount of the 
latter. Therefore, using the former of the present invention, it is 
possible to design lightweight articles. 
Next, the present invention is described in detail by means of the 
following examples, in which the solubility parameter, the epoxy 
equivalent, the dynamic viscoelasticity, the Charpy impact strength and 
the glass transition temperature were measured or evaluated under the 
conditions mentioned below. 
A. Solubility Parameter: 
The solubility parameter Sp was obtained according to the method described 
in Polym. Eng. Sci., 14 (2), 147-154 (1974). 
B. Epoxy Equivalent: 
The epoxy equivalent indicates the mass weight of the resin composition 
containing one g-equivalent of epoxy group. This was obtained through 
titration of the epoxy resin composition in accordance with JIS K 7236 for 
"Test Method for Determining Epoxy Equivalent of Epoxy Resin" or from the 
epoxy equivalent of each epoxy resin used to prepare the composition. 
C. Dynamic Viscoelasticity: 
To determine the dynamic viscoelasticity, used was Dynamic Analyzer RDA II 
Model produced by Rheometrix Co. Briefly, parallel discs each having a 
radius of 25 mm were used, and the complex coefficient of viscosity .eta.* 
was obtained at a temperature of 50.degree. C. and at a frequency of 0.5 
Hz. 
D. Charpy Impact Test for Fiber-reinforced Composite Material: 
The Charpy impact test was conducted according to JIS K 7077. Briefly, a 
test piece having a width of 10 mm and a length of 80 mm was cut out of 
the fiber-reinforced composite material to be tested, a flat-wise impact 
of 300 kg.multidot.cm was imparted to one surface of the test piece in the 
direction vertical to its surface. No notch was formed in the test piece. 
E. Glass Transition Temperature of Fiber-Reinforced Composite Material: 
Using Mettler DSC-T 3000 System (produced by Mettler Co.), the glass 
transition temperature of each sample was measured at a heating rate of 
40.degree. C./min.

EXAMPLE 1 
(1) Preparation of Matrix Resin Composition: 
Of the following raw materials, fine rubber particles were first dispersed 
in liquid bisphenol A-type epoxy resin "Epikote 828" to prepare a master 
resin, which was then kneaded along with the other components in a kneader 
to prepare a matrix resin composition. The chemical structures of the raw 
materials used are shown below. 
__________________________________________________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" produced by Yuka-Shell Epoxy 
Co.; having a mean molecular 35 parts by 
weight of 378 and 
an epoxy equivalent 
of from 184 to 
194) weight 
Bisphenol A-type 
epoxy resin 
("Epikote 1001" 
produced by 
Yuka-Shell Epoxy 
Co.; having a mean 
55 parts by 
molecular weight 
of 950 and an 
epoxy equivalent 
of from 450 to 
500) weight 
Phenol-novolak-typ 
e epoxy resin 
("Epikote 154" 
produced by 
Yuka-Shell Epoxy 
Co.; having a mean 
10 parts by 
molecular weight 
of 625 and an 
epoxy equivalent 
of from 176 to 
181) weight 
Fine rubber 
particles ("Kureha 
Paraloid EXL-2655" 
produced by 
Kureha Chemical 
Industry Co.; 10 
parts by 
core/shell polymer particle is composed of a core comprising butadiene-s 
tyrene weight 
copolymer and a 
shell comprising 
alkyl methacrylate 
polymer) 
Dicyandiamide ("Epicure DICY7" produced by Yuka-Shell Epoxy Co.; 
having a molecular 
weight of 84.1) 4 
parts by weight 
DCMU ("DCMU-99" 
produced by 
Hodogaya Chemical 
Industry Co.; 
having a molecular 
weight of 233.1) 4 
parts by weight 
Polyvinyl formal 
resin ("Vinylec K" 
produced by 
Chisso Co.) 3 
parts by weight 
"Epikote 828" (n 
= 0.14) and 
"Epikote 1001" (n 
= 2.0): 
#STR12## 
- "Epikote 154" (n = 1.5): 
#STR13## 
- "Epicure DICY7": 
#STR14## 
- "DCMU-99" : 
#STR15## 
- "Vinylec K" (n = 365, m = 22-30, l = 42-59): 
##STR16## 
__________________________________________________________________________ 
(2) Formation of Prepreg: 
The resin composition prepared above was coated onto a release paper, using 
a reverse roll coater, to form a resin film. Next, carbon fibers "Torayca 
T700S" (produced by Toray Co.) with a modulus of tensile elastic modulus 
of 230 GPa that had been sheet-wise oriented in one direction were 
sandwiched between two sheets of the resin film, pressed under heat to 
thereby make the fibers impregnated with the resins. Thus was formed a 
unidirectional prepreg having a weight of carbon fibers of 150 g/m.sup.2 
and a weight fraction of the matrix resin of 33%. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
21 pieces as cut out of the prepreg were laminated and autoclaved at 
135.degree. C. for 2 hours under 0.29 MPa (3 kgf/cm.sup.2) to obtain a 
sheet of fiber-reinforced composite material. 
The sheet was subjected to a Charpy impact test, which showed a high impact 
value of 138 kJ/m.sup.2. The glass transition temperature of the sheet was 
measured according to the DSC method to be 130.degree. C. The results are 
shown in Table 1 below. 
Since the epoxy resin composition contained fine core/shell polymer 
particles comprising a rubber phase and insoluble in epoxy resins, the 
fiber-reinforced composite material comprising the composition had 
excellent impact resistance and heat resistance. 
EXAMPLE 2 
(1) Preparation of Matrix Resin Composition: 
Of the following raw materials, fine rubber particles were first dispersed 
in liquid bisphenol A-type epoxy resin "Epikote 828" to prepare a master 
resin, which was then kneaded along with the other components in a kneader 
to prepare a matrix resin composition. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" 
35 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 378 and an epoxy equivalent of 
from 184 to 194) 
Bisphenol A-type epoxy resin ("Epikote 1001" 40 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 950 and an epoxy equivalent 
of 
from 450 to 500) 
Phenol-novolak-type epoxy resin ("Epikote 154" 25 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 625 and an epoxy equivalent 
of 
from 176 to 181) 
Fine rubber particles ("Staphyloid AC-3355" 10 parts by weight 
produced by Takeda Chemicals Industry Co.; core/ 
shell polymer particles comprising acrylate- 
methacrylate copolymers) 
Dicyandiamide ("Epicure DICY7" produced by 4 parts by weight 
Yuka-Shell Epoxy Co.; having a molecular weight 
of 84.1) 
DCMU ("DCMU-99" produced by Hodogaya 4 parts by weight 
Chemical Industry Co.; having a molecular weight 
of 233.1) 
Polyvinyl formal resin ("Vinylec K" produced 5 parts by weight 
by Chisso Co.) 
______________________________________ 
(2) Formation of Prepreg: 
Using the resin composition prepared above, et prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 130 kJ/m.sup.2 and the glass transition 
temperature thereof was 138.degree. C. (see Table 1). 
Since the resin composition of Example 2 contained a larger amount of the 
multifunctional epoxy resin, phenol-novolak-type epoxy resin than that of 
Example 1, the glass transition temperature of the fiber-reinforced 
composite sheet of Example 2 was somewhat hither than that of the sheet of 
Example 1 but the Charpy impact strength of the former was somewhat lower 
than that of the latter. 
EXAMPLE 3 
(1) Preparation of Matrix Resin Composition: 
Of the following raw materials, fine rubber particles were first dispersed 
in liquid bisphenol A-type epoxy resin "Epikote 828" to prepare a master 
resin, which was then kneaded along with the other components in a kneader 
to prepare a matrix resin composition. The chemical structure of the raw 
material, "Victrex PES5003P" used is shown below. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" produced by 
40 parts by 
Yuka-Shell Epoxy Co.; having a mean molecular weight of weight 
378 and an epoxy equivalent of from 184 to 194) 
Bisphenol A-type epoxy resin ("Epikote 1001" produced 60 parts by 
by Yuka-Shell Epoxy Co.; having a mean 
molecular weight weight 
of 950 and an epoxy equivalent of from 450 to 500) 
Fine rubber particles ("Kureha Paraloid EXL-2655" 10 parts by 
produced by Kureha Chemical Industry Co.; core/shell weight 
polymer particle is composed of a core comprising 
butadiene-styrene copolymer and a shell comprising alkyl 
methacrylate polymer) 
Dicyandiamide ("Epicure DICY7" produced by Yuka-Shell 4 parts by 
Epoxy Co.; having a molecular weight of 84.1) 
weight 
DCMU ("DCMU-99" produced by Hodogaya Chemical 4 parts by 
Industry Co.; having a molecular weight of 233.1) weight 
Polyether sulfone ("Victrex PES5003P" produced by 6 parts by 
Mitsui Toatsu Chemical Co.) weight 
"Victrex PES5003P" (n = 50-80) 
##STR17## 
______________________________________ 
(2) Formation of Prepreg: 
Using the resin composition prepared above, a prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 147 kJ/m.sup.2 and the glass transition 
temperature thereof was 125.degree. C. (see Table 1). 
Since the resin composition of Example 3 did not contain the 
multifunctional epoxy resin, phenol-novolak-type epoxy resin, unlike the 
resin compositions of Examples 1 and 2, the Charpy impact strength of the 
sheet of Example 3 was higher than that of the sheets of Examples 1 and 2 
but the glass transition temperature of the former was somewhat lower than 
that of the latter. 
EXAMPLE 4 
(1) Preparation of Matrix Resin Composition: 
Of the following raw materials, fine rubber particles were first dispersed 
in liquid bisphenol A-type epoxy resin "Epikote 828" to prepare a master 
resin, which was then kneaded along with the other components in a kneader 
to prepare a matrix resin composition. The chemical structure of the raw 
material, "Epiclon HP-4032H" used is shown below. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" produced by 
40 parts by 
Yuka-Shell Epoxy Co.; having a mean molecular weight of weight 
378 and an epoxy equivalent of from 184 to 194) 
Naphthalene-type epoxy resin ("Epiclon HP-4032H: 60 parts by 
produced by Dainippon Ink and Chemicals, Inc.; having a weight 
molecular weight of 300 and an epoxy equivalent of 150) 
Fine rubber particles ("Paraloid EXL-2611" produced by 15 parts by 
Rohm & Haas Co.; core/shell polymer particles) 
weight 
Dicyandiamide ("Epicure DICY7" produced by Yuka-Shell 4 parts by 
Epoxy Co.; having a molecular weight of 84.1) 
weight 
DCMU ("DCMU-99" produced by Hodogaya Chemical 4 parts by 
Industry Co.; having a molecular weight of 233.1) weight 
"Epiclon HP-4032H" 
##STR18## 
______________________________________ 
(2) Formation of Prepreg: 
Using the resin composition prepared above, a prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 151 kJ/m.sup.2 and the glass transition 
temperature thereof was 150.degree. C. (see Table 1). 
Since the resin composition of Example 4 contained a naphthalene-type epoxy 
resin with a rigid skeleton in place of the bisphenol A-type epoxy resin 
used in Example 3, the glass transition temperature of the 
fiber-reinforced composite sheet comprising the composition was much 
higher. 
EXAMPLE 5 
(1) Preparation of Matrix Resin Composition: 
Of the following raw materials, fine rubber particles were first dispersed 
in liquid bisphenol A-type epoxy resin "Epikote 828" to prepare a master 
resin, which was then kneaded along with the other components in a kneader 
to prepare a matrix resin composition. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" 
40 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 378 and an epoxy equivalent of 
from 184 to 194) 
Bisphenol A-type epoxy resin ("Epikote 1001" 60 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 950 and an epoxy equivalent 
of 
from 450 to 500) 
Fine rubber particles ("XER 91" produced by 7 parts by weight 
Nippon Synthetic Rubber Co.; crosslinked product 
of carboxyl-modified butadiene-acrylonitrile 
copolymer) 
Dicyandiamide ("Epicure DICY7" produced by 4 parts by weight 
Yuka-Shell Epoxy Co.; having a molecular weight 
of 84.1) 
DCMU ("DCMU-99" produced by Hodogaya 4 parts by weight 
Chemical Industry Co.; having a molecular weight 
of 233.1) 
______________________________________ 
(2) Formation of Prepreg: 
Using the resin composition prepared above, a prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 142 kJ/m.sup.2 and the glass transition 
temperature thereof was 128.degree. C. (see Table 1). 
The resin composition of Example 5 contained crosslinked rubber particles 
in place of the core/shell polymer particles used in Examples 1 to 4, and 
the fiber-reinforced composite sheet comprising the composition had good 
impact resistance and heat resistance. 
EXAMPLE 6 
(1) Preparation of Matrix Resin Composition: 
Of the following raw materials, fine rubber particles were first dispersed 
in liquid bisphenol A-type epoxy resin "Epikote 828" to prepare a master 
resin, which was then kneaded along with the other components in a kneader 
to prepare a matrix resin composition. The chemical structure of the raw 
material, "Sumi-epoxy ELM-120" used is shown below. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" produced by 
30 parts by 
Yuka-Shell Epoxy Co.; having a mean molecular weight of weight 
378 and an epoxy equivalent of from 184 to 194) 
Bisphenol A-type epoxy resin ("Epikote 1001" produced 60 parts by 
by Yuka-Shell Epoxy Co.; having a mean 
molecular weight weight 
of 950 and an epoxy equivalent of from 450 to 500) 
Glycidylamine-type epoxy resin ("Sumi-epoxy ELM-120" 10 parts by 
produced by Sumitomo Chemical Industry Co.; 
having a weight 
mean molecular weight of 360 and an epoxy equivalent of 
from 110 to 130) 
Fine rubber particles ("Kureha Paraloid EXL-2655" 10 parts by 
produced by Kureha Chemical Industry Co.; core/shell weight 
polymer particle is composed of a core comprising 
butadiene-styrene copolymer and a shell comprising 
alkyl methacrylate polymer) 
Dicyandiamide ("Epicure DICY7" produced by Yuka-Shell 4 parts by 
Epoxy Co.; having a molecular weight of 84.1) 
weight 
DCMU ("DCMU-99" produced by Hodogaya Chemical 4 parts by 
Industry Co.; having a molecular weight of 233.1) weight 
Polyvinyl formal resin ("Vinylec K" produced by Chisso 8 parts by 
Co.) weight 
"Sumi-epoxy ELM-120" : 
##STR19## 
______________________________________ 
(2) Formation of Prepreg: 
Using the resin composition prepared above, a prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 159 kJ/m.sup.2 and the glass transition 
temperature thereof was 134.degree. C. (see Table 1). 
The resin composition of Example 6 contained a multifunctional, 
glycidylamine-type epoxy resin, and the fiber-reinforced composite sheet 
comprising the composition had good impact resistance and heat resistance. 
EXAMPLE 7 
(1) Preparation of Matrix Resin Composition: 
Of the following raw materials, fine rubber particles were first dispersed 
in liquid bisphenol A-type epoxy resin "Epikote 828" to prepare a master 
resin, which was then kneaded along with the other components in a kneader 
to prepare a matrix resin composition. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" 
45 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 378 and an epoxy equivalent of 
from 184 to 194) 
Bisphenol A-type epoxy resin ("Epikote 1004" 40 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 1850 and an epoxy equivalent 
of from 875 to 975) 
Phenol-novolak-type epoxy resin ("Epikote 154" 35 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 625 and an epoxy equivalent 
of 
from 176 to 181) 
Fine rubber particles ("Kureha Paraloid EXL-2655" 4 parts by weight 
produced by Kureha Chemical Industry Co.; core/ 
shell polymer particle is composed of a core 
comprising butadiene-styrene copolymer and a 
shell 
comprising alkyl methacrylate polymer 
Dicyandiamide ("Epicure DICY7" produced by 4 parts by weight 
Yuka-Shell Epoxy Co.; having a molecular weight 
of 84.1) 
DCMU ("DCMU-99" produced by Hodogaya 4 parts by weight 
Chemical Industry Co.; having a molecular weight 
of 233.1) 
______________________________________ 
(2) Formation of Prepreg: 
Using the resin composition prepared above, a prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 169 kJ/m.sup.2 and the glass transition 
temperature thereof was 93.degree. C. (see Table 1). 
The resin composition of Example 7 had a large total epoxy resin equivalent 
and gave a toughened, fiber-reinforced composite material having a large 
Charpy impact strength. However, since the viscosity of the composition 
was high, the impregnation of the reinforcing fibers with the composition 
was not good. The composite material obtained had a glass transition 
temperature lower than that of the others. 
COMATIVE EXAMPLE 1 
(1) Preparation of Matrix Resin Composition: 
Of the following raw materials, fine rubber particles were first dispersed 
in liquid bisphenol A-type epoxy resin "Epikote 828" to prepare a master 
resin, which was then kneaded along with the other components in a kneader 
to prepare a matrix resin composition. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" 
30 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 378 and an epoxy equivalent of 
from 184 to 194) 
Bisphenol A-type epoxy resin ("Epikote 1001" 35 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 950 and an epoxy equivalent 
of 
from 450 to 500) 
Phenol-novolak-type epoxy resin ("Epikote 154 35 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 625 and an epoxy equivalent 
of 
from 176 to 181) 
Fine rubber particles ("Kureha Paraloid EXL-2655" 10 parts by weight 
produced by Kureha Chemical Industry Co.; core/ 
shell polymer particle is composed of a core 
comprising butadiene-styrene copolymer and a 
shell 
comprising alkyl methacrylate polymer 
Dicyandiamide ("Epicure DICY7" produced by 4 parts by weight 
Yuka-Shell Epoxy Co.; having a molecular weight 
of 84.1) 
DCMU ("DCMU-99" produced by Hodogaya 4 parts by weight 
Chemical Industry Co.; having a molecular weight 
of 233.1) 
______________________________________ 
(2) Formation of Prepreg: 
Using the resin composition prepared above, a prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 119 kJ/m.sup.2 and the glass transition 
temperature thereof was 140.degree. C. (see Table 1). 
Since the resin composition of Comparative Example 1 contained more than 30 
parts by weight of the multifunctional, phenol-novolak-type epoxy resin, 
it did not express the advantage of the core/shell polymer particles 
contained therein and the Charpy impact value of the sheet comprising the 
composition was low. 
COMATIVE EXAMPLE 2 
(1) Preparation of Matrix Resin Composition: 
The following raw materials were kneaded in a kneader to prepare a matrix 
resin composition. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" 
30 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 378 and an epoxy equivalent of 
from 184 to 194) 
Bisphenol A-type epoxy resin ("Epikote 1001" 35 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 950 and an epoxy equivalent 
of 
from 450 to 500) 
Phenol-novolak-type epoxy resin ("Epikote 154 35 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 625 and an epoxy equivalent 
of 
from 176 to 181) 
Dicyandiamide ("Epicure DICY7" produced by 4 parts by weight 
Yuka-Shell Epoxy Co.; having a molecular weight 
of 84.1) 
DCMU ("DCMU-99" produced by Hodogaya 4 parts by weight 
Chemical Industry Co.; having a molecular weight 
of 233.1) 
Polyvinyl formal resin ("Vinylec K" produced 4 parts by weight 
by Chisso Co.) 
______________________________________ 
(2) Formation of Prepreg: 
Using the resin composition prepared above, a prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 103 kJ/m.sup.2 and the glass transition 
temperature thereof was 141.degree. C. (see Table 1). 
Since the resin composition of Comparative Example 2 did not contain fine 
particles which comprise a rubber phase and which are insoluble in epoxy 
resins, the composite sheet comprising the composition did not have good 
impact resistance. 
COMATIVE EXAMPLE 3 
(1) Preparation of Matrix Resin Composition: 
The following raw materials were kneaded in a kneader to prepare a matrix 
resin composition. 
______________________________________ 
Bisphenol A-type epoxy resin ("Epikote 828" 
40 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 378 and an epoxy equivalent of 
from 184 to 194) 
Bisphenol A-type epoxy resin ("Epikote 1001" 60 parts by weight 
produced by Yuka-Shell Epoxy Co.; having a mean 
molecular weight of 950 and an epoxy equivalent 
of 
from 450 to 500) 
CTBN-epoxy reactant 10 parts by weight 
Dicyandiamide ("Epicure DICY7" produced by 4 parts by weight 
Yuka-Shell Epoxy Co.; having a molecular weight 
of 84.1) 
DCMU ("DCMU-99" produced by Hodogaya 4 parts by weight 
Chemical Industry Co.; having a molecular weight 
of 233.1) 
______________________________________ 
The CTBN-epoxy reactant used was a reaction product of "Hycar CTBN 
1300.times.13" (produced by Ube Industries, Ltd.; having an AN content of 
27%) and "Epikote 828" and had a number-average molecular weight of 9600. 
(2) Formation of Prepreg: 
Using the resin composition prepared above, a prepreg was formed in the 
same manner as in Example 1. 
(3) Formation and Evaluation of Fiber-Reinforced Composite Material: 
Using the prepreg prepared above, a sheet of fiber-reinforced composite 
material was formed in the same manner as in Example 1. The Charpy impact 
strength of the sheet was 149 kJ/m.sup.2 and the glass transition 
temperature thereof was 108.degree. C. (see Table 1). 
Since the resin composition of Comparative Example 3 contained rubber 
soluble in epoxy resins, the glass transition temperature of the sheet 
comprising the composition was low and the sheet had poor heat resistance 
though the impact resistance of the sheet was good. 
TABLE 1 
______________________________________ 
Exam- Exam- Exam- Exam- Exam- 
ple 1 ple 2 ple 3 ple 4 ple 5 
______________________________________ 
Resin Composition 
[A] Epoxy Resin 
(wt. pts.) 
[A-1] Bi-functional 
Epoxy Resin 
"Epikote 828" (epoxy 35 35 40 40 40 
equivalent: 184-184, Sp: 
10.6 cal.sup. 1/2 /cm.sup. 2/3 ) 
"Epikote 1001" (epoxy 55 40 60 -- 60 
equivalent: 450-500, Sp: 
11.5 cal.sup.1/2 /cm.sup.2/3) 
"Epikote 1004" (epoxy -- -- -- -- -- 
equivalent: 875-975) 
"Epiclon HP-4032H" -- -- -- 60 -- 
(epoxy equivalent: 250) 
[A-2] Multifunctional 
Epoxy Resin 
"Epikote 154" (epoxy 10 25 -- -- -- 
equivalent: 176-181, Sp: 
10.8 cal.sup. 1/2 /cm.sup. 2/3) 
"Sumi-epoxy ELM-120" -- -- -- -- -- 
(epoxy equivalent: 118) 
[B] Fine Rubber 
Particles(*1) 
"Kureha Paraloid 10 -- 10 -- -- 
EXL-2655" 
"Paraloid EXL-2611" -- -- -- 15 -- 
"Staphyloid AC-3355" -- 10 -- -- -- 
"XER-91" -- -- -- -- 7 
CTBN-Epoxy -- -- -- -- -- 
Reactant(*1) 
[C] Curing Agent, 
Curing Accelerator(*1) 
DICY (dicyandiamide) 4 4 4 4 4 
DCMU 4 4 4 4 4 
Thermoplastic Resin(*1) 
"Vinylec K" (elastic 3 5 -- -- -- 
modulus: 2.0 GPa, Sp: 
11.5 cal.sup. 1/2 /cm.sup. 2/3) 
"Victrex 5003P" (elastic -- -- 6 -- -- 
modulus: 2.6 GPa, Sp: 
11.2 cal.sup. 1/2 /cm.sup. 2/3) 
Mean Epoxy Equivalent 345 301 361 226 361 
of Resin composition 
Dynamic Visco- 780 690 170 250 350 
elasticity of Resin 
.eta.* (Pa's) at 50.degree. C. 
Physical Properties of 
Composite Material 
Charpy Impact Value 139 130 147 151 142 
(KJ/m.sup.2) 
Glass Transition 130 138 125 150 128 
Temperature (.degree. C.) 
______________________________________ 
Com- Com- Com- 
parative parative parative 
Exam- Exam- Exam- Exam- Exam- 
ple 6 ple 7 ple 1 ple 2 ple 3 
______________________________________ 
Resin Composition 
[A] Epoxy Resin 
(wt. pts.) 
[A-1] Bi-functional 
Epoxy Resin 
"Epikote 828" (epoxy 30 45 30 30 40 
equivalent: 184-184, Sp: 
10.6 cal.sup. 1/2 /cm.sup. 2/3) 
"Epikote 1001" (epoxy 60 -- 35 35 60 
equivalent: 450-500, Sp: 
11.5 cal.sup. 1/2 /cm.sup. 2/3) 
"Epikote 1004" (epoxy -- 40 -- -- -- 
equivalent: 875-975) 
10.8 cal.sup. 1/2 /cm.sup. 2/3) 
"Epiclon HP-4032H" -- -- -- -- -- 
(epoxy equivalent: 250) 
[A-2] Multifunctional 
Epoxy Resin 
"Epikote 154" (epoxy -- 35 35 35 -- 
equivalent: 176-181, Sp: 
"Sumi-epoxy ELM-120" 10 -- -- -- -- 
(epoxy equivalent: 118) 
[B] Fine Rubber 
Particles(*1) 
"Kureha Paraloid 10 4 10 -- -- 
EXL-2655" 
"Paraloid EXL-2611" -- -- -- -- -- 
"Staphyloid AC-3355" -- -- -- -- -- 
"XER-91" -- -- -- -- -- 
CTBN-Epoxy -- -- -- -- 10 
Reactant(*1) 
[C] Curing Agent, 
Curing Accelerator(*1) 
DICY (dicyandiamide) 4 4 4 4 4 
DCMU 4 4 4 4 4 
Thermoplastic Resin(*1) 
"Vinylec K" (elastic 8 -- -- 4 -- 
modulus: 2.0 GPa, Sp: 
11.5 cal.sup. 1/2 /cm.sup. 2/3) 
"Victrex 5003P" (elastic -- -- -- -- -- 
modulus: 2.6 GPa, Sp: 
11.2 cal.sup. 1/2 /cm.sup. 2/3) 
Mean Epoxy Equivalent 354 519 286 286 361 
of Resin composition 
Dynamic Visco- 230 3100 210 680 270 
elasticity of Resin 
.eta.* (Pa's) at 50.degree. C. 
Physical Properties of 
Composite Material 
Charpy Impact Value 159 169 119 103 149 
(KJ/m.sup.2) 
Glass Transition 134 93 140 141 108 
Temperature (.degree. C.) 
______________________________________ 
(*1)Parts by weight relative to 100 part by weight of epoxy resins. 
As has been described in detail hereinabove, the epoxy resin composition of 
the present invention is suitably used as the matrix resin for prepregs. 
Typically, reinforcing fibers such as carbon fibers or glass fibers may be 
impregnated with the composition to give prepregs, which may be laminated 
and processed into fiber-reinforced composite materials or are wound 
around mandrels and processed into shafts, rods, etc. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.