U.S. patent application number 12/934614 was filed with the patent office on 2011-04-28 for epoxy resin composition, fiber-reinforced composite material, and method for producing the same.
This patent application is currently assigned to Toray Industries, Inc. Invention is credited to Toshiya Kamae, Shinji Kochi, Masayuki Miyoshi, Kenichi Yoshioka.
Application Number | 20110097568 12/934614 |
Document ID | / |
Family ID | 41113660 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110097568 |
Kind Code |
A1 |
Kamae; Toshiya ; et
al. |
April 28, 2011 |
EPOXY RESIN COMPOSITION, FIBER-REINFORCED COMPOSITE MATERIAL, AND
METHOD FOR PRODUCING THE SAME
Abstract
Disclosed herein are an epoxy resin composition for
fiber-reinforced composite materials which has low viscosity, high
Tg, high elastic modulus, and excellent fracture toughness and a
fiber-reinforced composite material using such an epoxy resin
composition which has excellent thermal properties, compressive
strength, impact resistance, fatigue resistance, and open-hole
tensile strength and which is suitable for producing structural
parts of aircraft and the like. The epoxy resin composition
comprises at least a given bifunctional epoxy resin as a component
(A), a liquid aromatic diamine curing agent as a component (B), and
core-shell polymer particles as a component (C), wherein the
core-shell polymer particles as the component (C) contain epoxy
groups in their shell and have a volume-average particle size of 50
to 300 nm.
Inventors: |
Kamae; Toshiya; (Ehime,
JP) ; Kochi; Shinji; (Ehime, JP) ; Miyoshi;
Masayuki; (Ehime, JP) ; Yoshioka; Kenichi;
(Ehime, JP) |
Assignee: |
Toray Industries, Inc
|
Family ID: |
41113660 |
Appl. No.: |
12/934614 |
Filed: |
March 23, 2009 |
PCT Filed: |
March 23, 2009 |
PCT NO: |
PCT/JP2009/055573 |
371 Date: |
January 10, 2011 |
Current U.S.
Class: |
428/222 ;
264/279; 523/428; 525/524 |
Current CPC
Class: |
C08G 59/38 20130101;
B29C 70/443 20130101; Y10T 428/249922 20150401; B29C 70/06
20130101; B29C 71/02 20130101; C08J 2363/00 20130101; C08G 59/5033
20130101; B29K 2063/00 20130101; C08J 5/04 20130101; C08J 2463/02
20130101; C08J 2477/06 20130101; B29K 2307/04 20130101; C08K 7/02
20130101; C08G 59/3209 20130101; C08J 3/20 20130101; C08J 5/047
20130101; C08L 63/00 20130101 |
Class at
Publication: |
428/222 ;
525/524; 523/428; 264/279 |
International
Class: |
D03D 13/00 20060101
D03D013/00; C08L 63/00 20060101 C08L063/00; B29C 39/00 20060101
B29C039/00; B29C 45/14 20060101 B29C045/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 2008 |
JP |
2008-077721 |
Oct 3, 2008 |
JP |
2008-258102 |
Claims
1. An epoxy resin composition comprising at least the following
components (A), (B), and (C): (A) at least one bifunctional epoxy
resin represented by any one of the following formulas (I), (II),
and (III): ##STR00003## wherein R.sub.1 to R.sub.17 are each
independently a substituent selected from among hydrogen, halogens,
and C1 to C4 alkyl groups; (B) a liquid aromatic diamine curing
agent; and (C) core-shell polymer particles, wherein the core-shell
polymer particles as the component (C) contain epoxy groups in
their shell and have a volume-average particle size of 50 to 300
nm.
2. The epoxy resin composition according to claim 1, which contains
the component (A) in an amount of 15 to 60 parts by mass with
respect to 100 parts by mass of a total epoxy resin.
3. The epoxy resin composition according to claim 1, further
comprising a tri- or higher-functional aromatic epoxy resin as a
component (D) in an amount of 30 to 70 parts by mass with respect
to 100 parts by mass of the total epoxy resin.
4. The epoxy resin composition according to claim 1, wherein the
component (B) is at least one represented by any one of the
following formulas (IV) to (VI): ##STR00004## wherein R.sub.18 to
R.sub.29 are each independently a substituent selected from among
hydrogen, halogens, and C1 to C4 alkyl groups.
5. The epoxy resin composition according to claim 4, which contains
40 to 90 parts by mass of any one of liquid aromatic diamine curing
agents represented by the formulas (IV) to (VI) or a mixture of two
or more of them and 10 to 40 parts by mass of
diaminodiphenylsulfone with respect to 100 parts by mass of a total
amine curing agent.
6. The epoxy resin composition according to claim 5, wherein the
diaminodiphenylsulfone is a mixture of 3,3'-diaminodiphenylsulfone
and 4,4'-diaminodiphenylsulfone.
7. The epoxy resin composition according to claim 1, wherein a core
of the component (C) is composed of a polymer obtained by
polymerization of a monomer containing butadiene.
8. The epoxy resin composition according to claim 1, which contains
the component (C) in an amount of 1 to 12 parts by mass with
respect to 100 parts by mass of the total epoxy resin.
9. The epoxy resin composition according to claim 1, wherein a
cured product obtained by curing the epoxy resin composition at
180.degree. C. for 2 hours has a glass transition temperature
different from that of the core of the component (C) by 210.degree.
C. or more and a fracture toughness (GO at -54.degree. C. of 120
J/m.sup.2 or higher.
10. A fiber-reinforced composite material comprising at least a
cured product of the epoxy resin composition according to claim 1
and a fiber substrate composed of reinforcing fibers.
11. A fiber-reinforcing composite material comprising at least a
cured product of the epoxy resin composition according to claim 1
and a fiber substrate composed of carbon fibers.
12. The fiber-reinforced composite material according to claim 11,
wherein the fiber substrate composed of carbon fibers is a
non-crimp fabric comprising warps each of which is composed of one
or more strands of the carbon fibers, auxiliary warps each of which
is a glass fiber bundle or a chemical fiber bundle and which are
arranged in parallel with the warps, and wefts each of which is
composed of one or more glass fibers or chemical fibers and which
are arranged perpendicularly to the warps and the auxiliary warps
and interlaced with the auxiliary warps to integrally hold the
carbon fiber strands.
13. A method for producing a fiber-reinforced composite material
comprising: placing a fiber substrate composed of reinforcing
fibers in an inside of a mold; impregnating the fiber substrate
with the epoxy resin composition according to claim 1; and
thermally curing the epoxy resin composition.
14. A method for producing a fiber-reinforced composite material
comprising: placing a fiber substrate composed of carbon fibers in
an inside of a mold; impregnating the fiber substrate with the
epoxy resin composition according to claim 1; and thermally curing
the epoxy resin composition.
15. A method for producing a fiber-reinforced composite material
comprising: placing, in an inside of a mold, a non-crimp fabric
comprising warps each of which is composed of one or more strands
of carbon fibers, auxiliary warps each of which is a glass fiber
bundle or a chemical fiber bundle and which are arranged in
parallel with the warps, and wefts each of which is composed of one
or more glass fibers or chemical fibers and which are arranged
perpendicularly to the warps and the auxiliary warps and interlaced
with the auxiliary warps to integrally hold the carbon fiber
strands; impregnating the non-crimp fabric with the epoxy resin
composition according to claim 1; and thermally curing the epoxy
resin composition.
16. A method for producing a fiber-reinforced composite material
comprising: placing, in an inside of a mold, a non-crimp fabric
comprising warps each of which is composed of one or more strands
of carbon fibers, auxiliary warps each of which is a glass fiber
bundle or a chemical fiber bundle and which are arranged in
parallel with the warps, and wefts each of which is composed of one
or more glass fibers or chemical fibers and which are arranged
perpendicularly to the warps and the auxiliary warps and interlaced
with the auxiliary warps to integrally hold the carbon fiber
strands; impregnating the non-crimp fabric with the epoxy resin
composition according to claim 1 by evacuating the inside of the
mold; and thermally curing the epoxy resin composition.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an epoxy resin composition
for use as a matrix resin of fiber-reinforced composite materials
suitable for producing structural parts of aircraft, spacecraft,
vehicles, ships, and the like. More specifically, the present
invention relates to an epoxy resin composition having low
viscosity, high glass transition temperature (hereinafter, glass
transition temperature is sometimes abbreviated as "Tg"), high
elastic modulus, and excellent fracture toughness. Further, the
present invention relates to a fiber-reinforced composite material
produced using such an epoxy resin composition and a method for
producing such a fiber-reinforced composite material.
BACKGROUND ART
[0002] Fiber-reinforced composite materials composed of reinforcing
fibers such as glass fibers, carbon fibers, and aramid fibers and
cured products of thermosetting resins such as unsaturated
polyester resins, vinyl ester resins, epoxy resins, phenol resins,
cyanate ester resins, and bismaleimide resins are lightweight and
have excellent mechanical properties such as strength and elastic
modulus, and are therefore used in various fields such as aircraft
structural parts, spacecraft structural parts, vehicle structural
parts, ship structural parts, civil engineering and construction
materials, and sporting goods. Particularly, fiber-reinforced
composite materials using continuous fibers are used for
applications requiring high performance. In this case, carbon
fibers excellent in specific strength and specific elastic modulus
are often used as reinforcing fibers and epoxy resins excellent in
adhesion to carbon fibers are often used as matrix resins.
[0003] However, epoxy resin cured products obtained by curing epoxy
resin compositions are generally brittle, and therefore an
improvement in the toughness of epoxy resin cured products is an
important issue in improving the impact resistance and fatigue
resistance of fiber-reinforced composite materials. In addition, it
is also necessary to suppress crack propagation from holes to
improve the open-hole tensile strength of fiber-reinforced
composite materials. Also from such a viewpoint, an improvement in
the toughness of epoxy resin cured products is an important
issue.
[0004] It is known that the toughness of a cured product of an
epoxy resin composition can be improved by adding rubber or a
thermoplastic polymer to the epoxy resin composition. As a method
for adding rubber, a method using rubber such as
carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN) rubber
or nitrile rubber has been proposed (see, for example, Patent
Documents 1 and 2).
[0005] According to this method, rubber is once dissolved in an
epoxy resin composition, but thereafter phase separation occurs
during curing process. This causes a problem that a desired
toughness-improving effect cannot be obtained due to a change in
the morphology of a cured product depending on the kind of epoxy
resin composition used or curing conditions. In addition, a rubber
component is partially dissolved in an epoxy resin phase of an
epoxy resin cured product, which causes a problem that the
viscosity of the epoxy resin composition is increased and the Tg
and elastic modulus of the epoxy resin cured product are
lowered.
[0006] In order to solve such problems, various methods using
polymer particles substantially insoluble in epoxy resins have been
proposed. For example, a method using core-shell polymer particles
formed by partially or fully coating the surface of particles as a
core mainly made of a polymer with a polymer different from the
polymer constituting the core by, for example, graft polymerization
has been proposed (see, for example, Patent Documents 3 to 6). It
is known that such a method makes it possible to suppress an
increase in the viscosity of an epoxy resin composition and a
lowering of the Tg of an epoxy resin cured product.
[0007] However, in order to obtain a sufficient toughness-improving
effect, it is necessary to add a large amount of core-shell polymer
particles. Therefore, there is a remaining problem that addition of
a large amount of core-shell polymer particles lowers the elastic
modulus of an epoxy resin cured product, thereby lowering the
compressive strength of a fiber-reinforced composite material in
its fiber direction. [0008] Patent Document 1: JP-B-61-29613 [0009]
Patent Document 2: JP-B-62-34251 [0010] Patent Document 3:
JP-A-5-65391 [0011] Patent Document 4: JP-A-7-224144 [0012] Patent
Document 5: JP-A-2003-277579 [0013] Patent Document 6:
JP-A-2006-257391
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0014] In view of the foregoing background of the related art, it
is an object of the present invention to provide an epoxy resin
composition having low viscosity, high Tg, high elastic modulus,
and excellent fracture toughness and a fiber-reinforced composite
material using such an epoxy resin composition which has excellent
heat resistance, compressive strength, impact resistance, fatigue
resistance, and open-hole tensile strength and which is optimum for
producing structural parts of aircraft and the like.
[0015] In order to achieve the above object, the present invention
provides the following means. More specifically, the present
invention provides an epoxy resin composition comprising at least
the following components (A), (B), and (C):
[0016] (A) at least one bifunctional epoxy resin represented by any
one of the following formulas (I), (II), and (III):
##STR00001##
[0017] wherein R.sub.1 to R.sub.17 are each independently a
substituent selected from among hydrogen, halogens, and C1 to C4
alkyl groups;
[0018] (B) a liquid aromatic diamine curing agent; and
[0019] (C) core-shell polymer particles, wherein the core-shell
polymer particles as the component (C) contain epoxy groups in
their shell and have a volume-average particle size of 50 to 300
nm.
[0020] The epoxy resin composition according to the present
invention preferably contains the component (A) in an amount of 15
to 60 parts by mass with respect to 100 parts by mass of a total
epoxy resin. Further, the epoxy resin composition according to the
present invention preferably further comprises a tri- or
higher-functional aromatic epoxy resin as a component (D) in an
amount of 30 to 70 parts by mass with respect to 100 parts by mass
of the total epoxy resin.
[0021] The present invention also provides a fiber-reinforced
composite material preferably comprising at least a cured product
of the epoxy resin composition according to the present invention
and carbon fibers. The fiber-reinforced composite material
according to the present invention preferably uses, as a
reinforcing fiber substrate made of carbon fibers, a non-crimp
fabric comprising warps each composed of one or more strands of the
carbon fibers, auxiliary warps each of which is a glass fiber
bundle or a chemical fiber bundle and which are arranged in
parallel with the warps, and wefts each of which is composed of one
or more glass fibers or chemical fibers and which are arranged
perpendicularly to the warps and the auxiliary warps and interlaced
with the auxiliary warps to integrally hold the carbon fiber
strands.
[0022] The present invention also provides a method for producing a
fiber-reinforced composite material preferably comprising: placing,
in an inside of a mold, a non-crimp fabric comprising warps each
composed of strands of carbon fibers, auxiliary warps each of which
is a glass fiber bundle or a chemical fiber bundle and which are
arranged in parallel with the warps, and wefts each of which is
composed of one or more glass fibers or chemical fibers and which
are arranged perpendicularly to the warps and the auxiliary warps
and interlaced with the auxiliary warps to integrally hold the
carbon fiber strands; injecting the epoxy resin composition
according to the present invention into the mold and impregnating
the non-crimp fabric with the epoxy resin composition; and
thermally curing the epoxy resin composition. In this case, the
epoxy resin composition is preferably injected into the mold by
evacuating the inside of the mold.
EFFECTS OF THE INVENTION
[0023] According to the present invention, it is possible to
provide an epoxy resin composition which has low viscosity allowing
good impregnation of reinforcing fibers therewith, high Tg
important to allow a fiber-reinforced composite material to have
heat resistance, high elastic modulus important to allow a
fiber-reinforced composite material to have excellent compressive
strength, and excellent fracture toughness necessary to allow a
fiber-reinforced composite material to have excellent impact
resistance, fatigue resistance, and open-hole tensile strength.
Therefore, a fiber-reinforced composite material comprising at
least a cured product of the epoxy resin composition according to
the present invention and carbon fibers is excellent in heat
resistance, compressive strength, impact resistance, fatigue
resistance, and open-hole tensile strength. Such a fiber-reinforced
composite material is suitable for producing structural parts of
aircraft, spacecraft, vehicles, ships, and the like.
BRIEF DESCRIPTION OF THE DRAWING
[0024] FIG. 1 is a schematic perspective view of a non-crimp fabric
used in one embodiment of a fiber-reinforced composite material
according to the present invention.
DESCRIPTION OF THE REFERENCE NUMERALS
[0025] 1 Warp [0026] 2 Auxiliary warp [0027] 3 Weft
BEST MODE FOR CARRYING OUT THE INVENTION
[0028] The present inventors have extensively studied an epoxy
resin composition having low viscosity, high Tg, high elastic
modulus, and excellent fracture toughness, and as a result have
found that an epoxy resin composition obtained by using, in
combination, a bifunctional epoxy resin having a certain structure,
a liquid aromatic diamine curing agent, and specific core-shell
polymer particles containing epoxy groups in their shell and having
a volume-average particle size of 50 to 300 nm satisfies all these
characteristics. Although it is conventionally known that
elasticity and fracture toughness are mutually contradictory
characteristics, the present inventors have surprisingly found that
both elastic modulus and fracture toughness can be improved by
using, in combination, the above-mentioned bifunctional epoxy
resin, liquid aromatic curing agent, and core-shell polymer
particles used in the present invention.
[0029] In the present invention, the term "epoxy resin" refers to a
compound having an epoxy group in its molecule, the term "epoxy
resin composition" refers to an uncured composition containing an
epoxy resin, a component for curing the epoxy resin (generally
referred to as a "curing agent", "curing catalyst", or "curing
accelerator"), and, if necessary, a modifier (e.g., plasticizer,
dye, organic pigment, inorganic filler, polymer compound,
antioxidant, ultraviolet absorber, coupling agent, surfactant), and
the term "epoxy resin cured product" or "cured product" refers to a
cured product obtained by curing the epoxy resin composition.
Further, the term "amine curing agent" refers to a compound having
an amine nitrogen atom and two or more active hydrogens in its
molecule. It is to be noted that the term "active hydrogen" used
herein refers to a hydrogen atom bonded to an amine nitrogen
atom.
[0030] An epoxy resin represented by the above formula (I) used as
a component (A) of an epoxy resin composition according to the
present invention is obtained by reaction between aniline or its
substituted derivative and epichlorohydrin. Here, R.sub.1 to
R.sub.5 are each independently a substituent selected from among
hydrogen, halogens, and C1 to C4 alkyl groups. From the view point
of obtaining a cured product having high Tg, R.sub.1 to R.sub.5 are
preferably each independently a substituent selected from among
hydrogen and C1 to C4 alkyl groups. Further, from the viewpoint of
imparting flame retardancy, at least one of R.sub.1 to R.sub.5 is
preferably a halogen. Specific examples of the epoxy resin
represented by the formula (I) include N,N-diglycidylaniline,
N,N-diglycidyl-o-toluidine, N,N-diglycidyl-m-toluidine,
N,N-diglycidyl-p-toluidine, N,N-diglycidyl-2,3-xylidine,
N,N-diglycidyl-2,4-xylidine, N,N-diglycidyl-2,5-xylidine,
N,N-diglycidyl-2,6-xylidine, N,N-diglycidyl-3,4-xylidine,
N,N-diglycidyl-3,5-xylidine, 2-bromo-N,N-diglycidylaniline,
3-bromo-N,N-diglycidylaniline, and
4-bromo-N,N-diglycidylaniline.
[0031] An epoxy resin represented by the above formula (II) used as
the component (A) is obtained by reaction between phthalic acid or
its substituted derivative and epichlorohydrin. Here, R.sub.6 to
R.sub.9 are each independently a substituent selected from among
hydrogen, halogens, and C1 to C4 alkyl groups. From the viewpoint
of obtaining a cured product having high Tg, R.sub.6 to R.sub.9 are
preferably each independently a substituent selected from among
hydrogen and C1 to C4 alkyl groups. Further, from the viewpoint of
imparting flame retardancy, at least one of R.sub.6 to R.sub.9 is
preferably a halogen. Specific examples of the epoxy resin
represented by the formula (II) include phthalic acid diglycidyl
ester, 3-methylphthalic acid diglycidyl ester, 4-methylphtahlic
acid diglycidyl ester, 3,4-dimethylphthalic acid diglycidyl ester,
3,5-dimethylphthalic acid diglycidyl ester, 3,6-dimethylphthalic
acid diglycidyl ester, 4,5-dimethylphthalic acid diglycidyl ester,
3-bromophthalic acid diglycidyl ester, and 4-bromophthalic acid
diglycidyl ester.
[0032] An epoxy resin represented by the above formula (III) used
as the component (A) is obtained by reaction between
hexahydrophthalic acid or its substituted derivative and
epichlorohydrin. Here, R.sub.10 to R.sub.17 are each independently
a substituent selected from among hydrogen, halogens, and C1 to C4
alkyl groups. From the viewpoint of obtaining a cured product
having high Tg, R.sub.10 to R.sub.17 are preferably each
independently a substituent selected from among hydrogen and C1 to
C4 alkyl groups. Further, from the viewpoint of imparting flame
retardancy, at least one of R.sub.10 to R.sub.17 is preferably a
halogen. Specific examples of the epoxy resin represented by the
formula (III) include hexahydrophthalic acid diglycidyl ester,
3-methylhexahydrophthalic acid diglycidyl ester,
4-methylhexahydrophthalic acid diglycidyl ester,
3,4-dimethylhexahydrophthalic acid diglycidyl ester,
3,5-dimethylhexahydrophthalic acid diglycidyl ester,
3,6-dimethylhexahydrophthalic acid diglycidyl ester,
4,5-dimethylhexahydrophthalic acid diglycidyl ester,
3-bromohexahydrophthalic acid diglycidyl ester, and
4-bromohexahydrophthalic acid diglycidyl ester.
[0033] The amount of the epoxy resin contained as the component (A)
in the epoxy resin composition according to the present invention
is preferably 15 to 60 parts by mass, more preferably 15 to 50
parts by mass, even more preferably 15 to 40 parts by mass, with
respect to 100 parts by mass of a total epoxy resin. By setting the
amount of the epoxy resin contained as the component (A) in the
epoxy resin composition according to the present invention to a
value within the above range, particularly excellent Tg, elastic
modulus, and fracture toughness can be achieved. More specifically,
by setting the amount of the epoxy resin contained as the component
(A) in the epoxy resin composition according to the present
invention to 15 parts by mass or more, a cured product having
higher elastic modulus and higher fracture toughness can be
obtained, and by setting the amount of the epoxy resin contained as
the component (A) in the epoxy resin composition according to the
present invention to 60 parts by mass or less, a cured product
having higher Tg can be obtained.
[0034] It is to be noted that, in the present invention, the term
"total epoxy resin" refers to a mixture of the component (A), a
component (D), and one or more other epoxy resins. It is to be
noted that when a component (C) is prepared as a masterbatch
obtained by previously mixing core-shell polymer particles and an
epoxy resin, the epoxy resin is included in the "total epoxy
resin". However, the component (C) is not regarded as an epoxy
resin, although the core-shell polymer particles used as the
component (C) contain an epoxy resin in their shell.
[0035] Further, the epoxy resin composition according to the
present invention preferably contains a tri- or higher-functional
aromatic epoxy resin as a component (D) to obtain a cured product
having high Tg. The amount of the tri- or higher-functional
aromatic epoxy resin contained as the component (D) in the epoxy
resin composition according to the present invention is preferably
30 to 70 parts by mass, more preferably 40 to 70 parts by mass,
even more preferably 50 to 70 parts by mass, with respect to 100
parts by mass of the total epoxy resin. More specifically, by
setting the amount of the tri- or higher-functional aromatic epoxy
resin contained as the component (D) in the epoxy resin composition
according to the present invention to 30 parts by mass or more, a
cured product having higher Tg and higher elastic modulus can be
obtained, and by setting the amount of the tri- or higher-aromatic
epoxy resin contained as the component (D) in the epoxy resin
composition according to the present invention to 70 parts by mass
or less, a cured product having higher fracture toughness can be
obtained. It is to be noted that the term "tri- or
higher-functional aromatic epoxy resin" used herein refers to a
compound having three or more epoxy groups and an aromatic ring in
its molecule.
[0036] From the viewpoint of obtaining a cured product having
excellent balance among Tg, elastic modulus, and toughness, the
tri- or higher-functional aromatic epoxy resin used as the
component (D) is preferably a glycidyl amine-type epoxy resin such
as N,N,O-triglycidyl-m-aminophenol,
N,N,O-triglycidyl-p-aminophenol,
N,N,O-triglycidyl-4-amino-3-methylphenol,
N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane,
N,N,N',N'-tetraglycidyl-4,4'-diamino-3,3'-diethyldiphenylmethane,
or N,N,N',N'-tetraglycidyl-m-xylylenediamine.
[0037] The epoxy resin composition according to the present
invention may further contain an epoxy resin other than the
components (A) and (D). Such an epoxy resin to be used in the
present invention preferably has two or more epoxy groups in one
molecule from the viewpoint of obtaining a cured product having
high Tg and high elastic modulus. Examples of such an epoxy resin
include bi- or higher-functional glycidyl ether-type epoxy resins.
Examples thereof include glycidyl ether-type epoxy resins obtained
by reaction between epichlorohydrin and bisphenol A, bisphenol F,
bisphenol AD, bisphenol S, tetrabromobisphenol A, phenol novolac,
cresol novolac, hydroquinone, resorcinol,
4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl,
1,6-dihydroxynaphthalene, 9,9-bis(4-hydroxyphenyl)fluorene,
tris(p-hydroxyphenyl)methane, or tetrakis(p-hydroxyphenyl)ethane.
Other examples of the epoxy resin other than the components (A) and
(D) include epoxy resins having a dicyclopentadiene skeleton, epoxy
resins having a biphenylaralkyl skeleton, and triglycidyl
isocyanurate. Further, the epoxy resin composition according to the
present invention may further contain an aliphatic epoxy resin
and/or an alicyclic epoxy resin as long as Tg is not significantly
lowered.
[0038] When the structures and amounts of the components (A) and
(D) and one or more other epoxy resins contained in the epoxy resin
composition according to the present invention are unknown, they
can be determined by dissolving the epoxy resin composition in a
solvent if necessary, separating the epoxy resin composition into
its components by HPLC (High Performance Liquid Chromatography),
and analyzing each of the separated components by NMR (Nuclear
Magnetic Resonance). The amount of each of the components contained
in the epoxy resin composition (i.e., the ratio of each component
to the sum of all the components of the epoxy resin composition)
can be determined from the area of each peak detected by HPLC and
the structure of each of the components can be determined from its
NMR spectrum. Further, a cured product of the epoxy resin
composition according to the present invention can be analyzed by
thermo GC/MS (Gas Chromatography/Mass Spectrum).
[0039] A component (B) of the epoxy resin composition according to
the present invention is a liquid aromatic diamine curing agent. It
is to be noted that the term "liquid" used herein means that the
aromatic diamine curing agent is liquid at 25.degree. C. and 0.1
MPa, and the term. "aromatic diamine curing agent" refers to a
compound having two amine nitrogen atoms directly bonded to an
aromatic ring and two or more active hydrogens in its molecule. The
term "active hydrogen" used herein refers to a hydrogen atom bonded
to an amine nitrogen atom. In order to achieve good impregnation of
reinforcing fibers with the epoxy resin composition according to
the present invention, a diamine curing agent used as the component
(B) needs to be liquid. Further, in order to obtain a cured product
having high Tg, a diamine curing agent used as the component (B)
needs to be aromatic.
[0040] Examples of the liquid aromatic diamine curing agent used as
the component (B) include 4,4'-methylenebis(2-ethylaniline),
4,4'-methylenebis(2-isopropylaniline),
4,4'-methylenebis(N-methylaniline),
4,4'-methylenebis(N-ethylaniline),
4,4'-methylenebis(N-sec-butylaniline),
N,N'-dimethyl-p-phenyelendiamine, N,N'-diethyl-p-phenylenediamine,
N,N'-di-sec-butyl-p-phenylenediamine,
2,4-diethyl-1,3-phenylenediamine, 4,6-diethyl-1,3-phenylenediamine,
2,4-diethyl-6-methyl-1,3-phenylenediamine, and
4,6-diethyl-2-methyl-1,3-phenylenediamine. These liquid aromatic
diamine curing agents may be used singly or in combination of two
or more of them. Alternatively, the liquid aromatic diamine curing
agent may be used together with one or more other amine curing
agents. From the viewpoint of achieving low viscosity and good
impregnation of reinforcing fibers with the epoxy resin composition
according to the present invention, any one of liquid aromatic
diamine curing agents represented by the following formulas (IV) to
(VI) or a mixture of two or more of them is preferably used. As
such a liquid aromatic diamine curing agent, "jER cure.TM." W
manufactured by Japan Epoxy Resins Co., Ltd. can be used. From the
viewpoint of obtaining a cured product having high Tg, R.sub.18 to
R.sub.29 are preferably each independently a substituent selected
from among hydrogen and C1 to C4 alkyl groups. Further, from the
viewpoint of imparting flame retardancy, at least one of R.sub.28
to R.sub.22, at last one of R.sub.22 to R.sub.25, and at least one
of R.sub.26 to R.sub.29 are preferably a halogen.
##STR00002##
[0041] wherein R.sub.28 to R.sub.29 are each independently a
substituent selected from among hydrogen, halogens, and C1 to C4
alkyl groups.
[0042] The epoxy resin composition according to the present
invention may further contain an amine curing agent other than the
component (B). Examples of such an amine curing agent other than
the component (B) include solid aromatic diamine compounds such as
4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylsulfone, and
4,4'-diaminodiphenylsulfone. From the viewpoint of obtaining a
cured product having high Tg and high toughness, such a solid
aromatic diamine compound is preferably used by dissolving it in
any one of liquid aromatic diamine curing agents represented by the
above formulas (IV) to (VI) or a mixture of two or more of them.
Particularly, from the viewpoint of obtaining a cured product
having particularly excellent Tg and toughness,
diaminodiphenylsulfone is preferably used by dissolving it in any
one of liquid aromatic diamine curing agents represented by the
above formulas (IV) to (VI) or a mixture of two or more of
them.
[0043] In general, diaminodiphenylsulfone tends to be easily
crystallized, and therefore even when dissolved in a liquid
aromatic diamine curing agent at high temperature,
diaminodiphenylsulfone is likely to be deposited as crystals in the
course of cooling. However, when two isomers of
diaminodiphenylsulfone, that is, 3,3'-diaminodiphenylsulfone and
4,4'-diaminodiphenylsulfone are mixed with any one of liquid
aromatic diamine curing agents represented by the above formulas
(IV) to (VI) or a mixture of two or more of them, deposition of
crystals is much less likely to occur than when one of the isomers
of diaminodiphenylsulfone is mixed with any one of liquid aromatic
diamine curing agents represented by the above formulas (IV) to
(VI) or a mixture of two or more of them. The amount of
diaminodiphenylsulfone contained in the epoxy resin composition
according to the present invention is preferably 10 to 40 parts by
mass, more preferably 20 to 35 parts by mass, with respect to 100
parts by mass of a total amine curing agent. More specifically, by
setting the amount of diaminodiphenylsulfone contained in the epoxy
resin composition according to the present invention to 10 parts by
mass or more, a cured product having higher Tg and higher toughness
can be obtained, and by setting the amount of
diaminodiphenylsulfone contained in the epoxy resin composition
according to the present invention to 40 parts by mass or less,
deposition of crystals can be more effectively suppressed. When
3,3'-diaminodiphenylsulfone and 4,4'-diaminodiphenylsulfone are
used in combination to suppress deposition of crystals, the mass
ratio between them is preferably 10:90 to 90:10. When the mass
ratio between 3,3'-diaminodiphenylsulfone and
4,4'-diaminodiphenylsulfone is closer to 50:50, the effect of
suppressing the deposition of crystals becomes higher.
[0044] If necessary, the epoxy resin composition according to the
present invention may further contain, as another component, a
curing accelerator, a plasticizer, a dye, a pigment, an inorganic
filler, an antioxidant, an ultraviolet absorber, a coupling agent,
and/or a surfactant.
[0045] The epoxy resin composition according to the present
invention is made curable by mixing an epoxy resin and an amine
curing agent in a predetermined ratio. The mixing ratio between the
epoxy resin and the amine curing agent is determined depending on
the kind of epoxy resin used and the kind of amine curing agent
used. More specifically, the epoxy resin and the amine curing agent
are mixed in such a manner that the ratio between the number of
epoxy groups contained in the epoxy resin in the epoxy resin
composition and the number of active hydrogens contained in the
amine curing agent in the epoxy resin composition is preferably 0.7
to 1.3, more preferably 0.8 to 1.2. By setting such a ratio to 0.7
to 1.3, a cured product having higher Tg and higher elastic modulus
can be obtained.
[0046] It is generally known that a cross-linking reaction proceeds
slowly in the case of using a liquid aromatic diamine curing agent
to be used as the component (B) of the epoxy resin composition
according to the present invention. Therefore, the component (B) of
the epoxy resin composition according to the present invention may
contain a curing accelerator for accelerating a cross-linking
reaction. Such a curing accelerator contained in the component (B)
is preferably small in size so that the concentration of the curing
accelerator can be made uniform in reinforcing fiber bundles
impregnated with the epoxy resin composition according to the
present invention when a fiber-reinforced composite material
according to the present invention is produced using the epoxy
resin composition according to the present invention. More
specifically, the volume-average particle size of the curing
accelerator is preferably 0.5 .mu.m or less, more preferably 0.1
.mu.m or less. Even more preferably, the curing accelerator is
completely dissolved in the liquid aromatic curing agent used as
the component (B) so that the liquid aromatic diamine curing agent
contains no solid matter. By satisfying the foregoing requirement,
a fiber-reinforced composite material having stable mechanical
properties can be obtained. It is to be noted that the term
"completely dissolved" used herein means that a liquid product
having no solid matter and no concentration distribution is formed
and deposition of crystals does not occur even when the liquid
product is allowed to stand at 25.degree. C. for 1 month or
longer.
[0047] Examples of the curing accelerator contained in the
component (B) of the epoxy resin composition according to the
present invention include tertiary amines, Lewis acid complexes,
onium salts, imidazole, and phenol compounds. Particularly, t-butyl
catechol as a phenol compound is preferably used, because its
reaction-accelerating effect is enhanced at temperatures of
100.degree. C. or higher but is low at temperatures of 50 to
80.degree. C. Therefore, the epoxy resin composition according to
the present invention can have a long pot life before curing but
can be quickly cured at a curing temperature during curing process
when a fiber-reinforced composite material using the epoxy resin
composition according to the present invention is molded.
[0048] The amount of the curing accelerator contained in the
component (B) of the epoxy resin composition according to the
present invention is preferably 0.5 to 3 parts by mass, more
preferably 1 to 2.5 parts by mass, with respect to 100 parts by
mass of the total epoxy resin. If the amount of the curing
accelerator, especially t-butyl catechol, contained in the
component (B) is not within the above range, a balance between
viscosity increase during resin injection and a reaction rate at an
elevated temperature is affected.
[0049] The component (C) of the epoxy resin composition according
to the present invention is core-shell polymer particles. The term
"core-shell polymer particles" used herein refers to particles
obtained by partially or fully coating the surface of particles as
a core mainly made of a polymer with a polymer different from the
polymer constituting the core by, for example, graft
polymerization.
[0050] The core of the core-shell polymer particles used as the
component (C) is made of a silicone resin or a polymer obtained by
polymerization of one or more of monomers selected from among
conjugated diene-based monomers, acrylic acid ester-based monomers,
and methacrylic acid ester-based monomers.
[0051] Examples of the conjugated diene-based monomers include
butadiene, isoprene, and chloroprene. The core is preferably made
of a cross-linked polymer obtained from one or more of the
conjugated diene-based monomers. From the viewpoint of obtaining a
polymer having excellent properties and of easily performing
polymerization, butadiene is preferably used as the conjugated
diene-based monomer, that is, the core is preferably made of a
polymer obtained by polymerization of a monomer containing
butadiene.
[0052] The core-shell polymer particles used as the component (C)
need to contain epoxy groups in their shell. During the curing
process of the epoxy resin composition, hydroxyl groups are
generated and therefore the polarity of the epoxy resin is changed.
As a result, agglomeration of the core-shell polymer particles
occurs due to a difference in polarity between the core-shell
polymer particles and the epoxy resin, which may cause a problem
that a sufficient toughness-improving effect cannot be obtained.
However, by introducing epoxy groups into the shell of the
core-shell polymer particles, a highly-dispersed state of the
core-shell polymer particles can be achieved because hydroxyl
groups are generated by reaction with the amine curing agent during
curing process and the core-shell polymer particles are finally
incorporated into a cured product. As a result, a sufficient
toughness-improving effect of the core-shell polymer particles can
be obtained even when the amount of the core-shell polymer
particles contained in the epoxy resin composition according to the
present invention is small. This makes it possible to improve the
toughness of the epoxy resin composition according to the present
invention while maintaining high Tg and high elastic modulus. Epoxy
groups can be introduced into the shell of the core-shell polymer
particles by, for example, performing, on the surface of the core,
graft polymerization of a monomer containing a glycidyl
group-containing acrylic acid ester-based monomer and/or a glycidyl
group-containing methacrylic acid ester-based monomer. In order to
improve the dispersibility of the core-shell polymer particles and
to obtain a sufficient toughness-improving effect, the shell of the
core-shell polymer particles may further contain hydroxyl groups
and/or carboxyl groups.
[0053] The core-shell polymer particles used as the component (C)
need to have a volume-average particle size of 50 to 300 nm,
preferably 50 to 200 nm, more preferably 50 to 150 nm. It is to be
noted that the volume-average particle size can be measured using a
nanotrac particle size analyzer (manufactured by NIKKISO Co., Ltd.,
dynamic light scattering method). Alternatively, the volume-average
particle size may be measured by observing a thin section of a
cured product cut by a microtome with a TEM to obtain a TEM image
and processing the TME image using image processing software. In
this case, it is necessary to measure the particle size of at least
100 particles to determine an average particle size. When the
volume-average particle size of the core-shell polymer particles is
50 nm or larger, the toughness-improving effect of the core-shell
polymer particles is high because the specific surface area of the
core-shell polymer particles is moderately small, which is
energetically favorable and therefore agglomeration is less likely
to occur. When the volume-average particle size of the core-shell
polymer particles is 300 nm or smaller, the toughness-improving
effect of the core-shell polymer particles is high because the
distance between the core-shell polymer particles is moderately
small. The mechanism of improvement in the toughness of a cured
product by core-shell polymer particles is based on that cavitation
of the core-shell polymer particles occurs in the vicinity of a
crack tip of the cured product, which induces plastic deformation
of a surrounding resin, leading to energy absorption. Therefore, it
can be considered that when the distance between core-shell polymer
particles is moderately small, plastic deformation of a resin is
likely to occur.
[0054] A method for producing the core-shell polymer particles used
as the component (C) is not particularly limited, and core-shell
polymer particles produced by a well-known method can be used as
the component (C). In usual, core-shell polymer particles are
available as powder obtained by taking out a mass of core-shell
polymer particles and pulverizing it, and therefore such a
core-shell polymer powder is often dispersed in an epoxy resin
again. In this case, however, there is a problem that it is
difficult to stably disperse core-shell polymer particles in the
form of primary particles. Therefore, core-shell polymer particles
are preferably prepared as a masterbatch, in which core-shell
polymer particles are finally dispersed as primary particles in an
epoxy resin, without once taking out a mass of core-shell polymer
particles in the course of production. Such core-shell polymer
particles can be produced by, for example, a method disclosed in
JP-A-2004-315572. According to this method, a suspension in which
core-shell polymer particles are dispersed is first obtained by a
method for polymerizing a core-shell polymer in an aqueous medium
typified by emulsion polymerization, dispersion polymerization, or
suspension polymerization. Then, the suspension is mixed with an
organic solvent having partial solubility in water, such as an
ether-based solvent (e.g., acetone or methyl ethyl ketone), and the
thus obtained mixture is brought into contact with an aqueous
electrolyte such as sodium chloride or potassium chloride to
separate it into an organic solvent phase and an aqueous phase. The
aqueous phase is removed to obtain an organic solvent in which the
obtained core-shell polymer particles are dispersed. Then, an epoxy
resin is mixed with the organic solvent, and then the organic
solvent is removed by evaporation to obtain a masterbatch in which
the core-shell polymer particles are dispersed as primary particles
in the epoxy resin. As an epoxy masterbatch having core-shell
polymer particles dispersed therein prepared by such a method,
"Kane Ace.TM." commercially available from Kaneka Corporation can
be used.
[0055] The amount of the core-shell polymer particles contained as
the component (C) in the epoxy resin composition according to the
present invention is preferably 1 to 12 parts by mass, more
preferably 1 to 7 parts by mass, even more preferably 3 to 7 parts
by mass, with respect to 100 parts by mass of the total epoxy
resin. More specifically, by setting the amount of the core-shell
polymer particles contained as the component (C) in the epoxy resin
composition according to the present invention to 1 part by mass or
more, a cured product having higher fracture toughness can be
obtained, and by setting the amount of the core-shell polymer
particles contained as the component (C) in the epoxy resin
composition according to the present invention to 12 parts by mass
or less, a cured product having higher Tg and higher elastic
modulus can be obtained.
[0056] The epoxy resin composition according to the present
invention and the fiber-reinforced composite material according to
the present invention using the epoxy resin composition according
to the present invention are suitable for producing structural
parts, especially aircraft structural parts. Fiber-reinforced
composite materials used for aircraft are often required to have
high heat resistance. Epoxy resin cured products are amorphous and
have glass transition temperature. The stiffness of epoxy resin
cured products is significantly lowered in an atmosphere having a
temperature equal to or higher than their glass transition
temperature, which leads to deterioration of mechanical properties
of fiber-reinforced composite materials. For this reason, the glass
transition temperature of an epoxy resin cured product is used as
an indicator of heat resistance of a fiber-reinforced composite
material. There is a correlation between the glass transition
temperature of an epoxy resin cured product and a peak temperature
in the thermal history of its curing process. In the case of
fiber-reinforced composite materials for aircraft, the peak
temperature in curing process is often about 180.degree. C.
Therefore, the glass transition temperature of a cured product
obtained by finally thermally curing the epoxy resin composition
according to the present invention at 180.degree. C. for 2 hours is
preferably 180.degree. C. or higher, more preferably 190.degree. C.
or higher. However, since it is said that the pyrolytic temperature
of an epoxy resin is about 240.degree. C. irrespective of whether
it is in an uncured state or a cured state, the upper limit of the
glass transition temperature is substantially equal to or less than
the pyrolytic temperature.
[0057] On the other hand, fiber-reinforced composite materials used
for aircraft flying at particularly high altitudes are exposed to
an atmosphere having a very low temperature of -50.degree. C. or
lower, and therefore it is particularly important for such
fiber-reinforced composite materials to have high fracture
toughness at extremely low temperatures. For this reason, the core
of the core-shell polymer particles used in the epoxy resin
composition according to the present invention needs to have a
glass transition temperature lower than that of a cured product
obtained by curing the epoxy resin composition according to the
present invention by 210.degree. C. or more, preferably 220.degree.
C. or more. More specifically, the core has a glass transition
temperature of -30.degree. C. or lower, preferably -40.degree. C.
or lower, and is preferably made of a polymer obtained by
polymerization of a monomer containing butadiene. In a case where
it is difficult to measure the glass transition temperature of the
core after it is coated with a shell, the glass transition
temperature of the core may be previously measured by forming only
a core polymer and then determining the glass transition
temperature of the core polymer with a thermal analysis instrument
such as a DSC.
[0058] In usual, epoxy resin compositions are divided into two
types, one-component type and two-component type. A one-component
type epoxy resin composition is produced by previously mixing an
epoxy resin and a curing agent component capable of curing the
epoxy resin. On the other hand, in the case of a two-component type
epoxy resin composition, an epoxy resin and a curing agent are
separately stored and mixed together just before use.
[0059] In the case of a one-component type epoxy resin composition,
curing reaction proceeds even during storage, and therefore a solid
curing agent having low reactivity is often selected as a curing
agent component. However, as described above, since curing reaction
proceeds at room temperature slowly but steadily, such a
one-component type epoxy resin composition needs to be refrigerated
during storage, which increases its storage cost. Further, as
described above, since a solid curing agent is used, a high
pressure needs to be applied to the one-component type epoxy resin
composition by a press roll to impregnate the reinforcing fibers
with it, which increases the production cost of a fiber-reinforced
composite material.
[0060] On the other hand, in the case of a two-component type epoxy
resin composition, a base component composed of an epoxy resin and
a curing agent are separately stored, and therefore its storage
conditions are not particularly limited and long-term storage is
achieved. Further, since both the base component and the curing
agent can be made liquid, a liquid mixture having low viscosity can
be obtained by mixing the base component and the curing agent.
Therefore, reinforcing fibers can be impregnated with the
two-component type epoxy resin composition and then molded by a
simple method such as RTM (Resin Transfer Molding).
[0061] The epoxy resin composition according to the present
invention may be either of a one-component type or a two-component
type, but is preferably of a two-component type in view of the
above advantages.
[0062] In a case where the epoxy resin composition according to the
present invention is of a two-component type, a base component is
preferably composed of an epoxy resin obtained by mixing the
component (A) used in the present invention and, if necessary, the
component (D) and core-shell polymer particles used as the
component (C) in the present invention, and a curing agent is
preferably one obtained by mixing and dissolving together the
component (B) used in the present invention and, if necessary, an
aromatic diamine other than the component (B) and a curing
accelerator.
[0063] In a case where the epoxy resin composition according to the
present invention is of a two-component type, the viscosity of its
main component at 70.degree. C. is 500 mPas or less, preferably 300
mPas or less. It is to be noted that the viscosity is measured
according to "Method of measurement of viscosity using cone-plate
rotary viscometer" specified in JIS Z 8803 (1991) with the use of
an E-type viscometer equipped with a standard cone rotor (1.degree.
34'.times.R24) (TVE-30H manufactured by Toki Sangyo Co., Ltd.) at a
rotation speed of 50 rpm. If the viscosity of the base component at
70.degree. C. is higher than 500 mPas, there is a case where
removal of the base component from a container, weighing, mixing
with the curing agent, and deaeration are not efficiently
performed. The viscosity of the base component at 70.degree. C. can
be made 500 mPas or less by preventing an epoxy resin having a
molecular weight of 500 or more from being contained in the base
component in an amount of preferably 30 parts by mass or more with
respect to 100 parts by mass of the base component and by
preventing a particulate additive such as a core-shell polymer from
being contained in the base component in an amount of preferably 12
parts by mass or more. The lower limit of the viscosity of the base
component at 70.degree. C. is not particularly limited, but is
preferably as low as possible because good impregnation of
reinforcing fibers with the epoxy resin composition according to
the present invention is achieved and therefore a high-quality
fiber-reinforced composite material can be obtained.
[0064] Further, in a case where the epoxy resin composition
according to the present invention is of a two-component type, the
viscosity of its curing agent at 70.degree. C. is 500 mPas or less,
preferably 300 mPas or less. It is to be noted that the viscosity
of the curing agent can be measured in the same manner as described
above with reference to a case where the viscosity of the base
component is measured. If the viscosity of the curing agent at
70.degree. C. is higher than 500 mPas, there is a case where
removal of the curing agent from a container, weighing, mixing with
the base component, and deaeration are not efficiently performed.
The lower limit of the viscosity of the curing agent at 70.degree.
C. is not particularly limited, and is preferably as low as
possible because good impregnation of reinforcing fibers with the
epoxy resin composition according to the present invention is
achieved and therefore a high-quality fiber-reinforced composite
material can be obtained. As described above, the viscosity of the
curing agent at 70.degree. C. can be made 500 mPas or less by
preventing a solid aromatic diamine curing agent such as
diaminodiphenylsulfone from being contained in the curing agent in
an amount of 40 parts by mass or more with respect to 100 parts by
mass of the total amine curing agent and by preventing a
particulate additive such as a core-shell polymer from being
contained in the curing agent in an amount of 15 parts by mass or
more.
[0065] Further, the initial viscosity of the epoxy resin
composition according to the present invention at 70.degree. C. is
preferably 500 mPas or less, more preferably 400 mPas or less, even
more preferably 300 mPas or less. It is to be noted that the
initial viscosity of the epoxy resin composition according to the
present invention can be measured in the same manner as described
above with reference to a case where the viscosity of the base
component or the curing agent is measured. The initial viscosity of
the epoxy resin composition according to the present invention is
measured after the epoxy resin composition is maintained at
70.degree. C. for 5 minutes after its preparation. By setting the
initial viscosity of the epoxy resin composition according to the
present invention at 70.degree. C. to 500 mPas or less, excellent
impregnation of reinforcing fibers with the epoxy resin composition
according to the present invention is achieved and therefore a
higher-quality fiber-reinforced composite material can be
obtained.
[0066] A cured product of the epoxy resin composition according to
the present invention can be obtained by thermally curing the epoxy
resin composition according to the present invention at any
temperature in a range of preferably 50 to 200.degree. C. for any
length of time in a range of preferably 0.5 to 10 hours, depending
on the activity of the component (B), an amine curing agent other
than the component (B), and a curing accelerator used. The thermal
curing of the epoxy resin composition according to the present
invention may be performed either by one-stage heating or
multi-stage heating under different heating conditions. When the
curing temperature of the epoxy resin composition according to the
present invention is higher, an obtained fiber-reinforced composite
material can have higher heat resistance. However, when the heating
temperature of the epoxy resin composition heated in the inside a
mold during molding is higher, the cost of facilities and heat
source is increased and the length of time during which the mold is
occupied by the epoxy resin composition is also increased, which is
economically disadvantageous. Therefore, a cured product of the
epoxy resin composition according to the present invention is
preferably obtained by performing initial curing at any temperature
in the range of 50 to 140.degree. C., demolding a molded product,
and finally curing the molded product at a relatively-high
temperature with the use of a heating apparatus such as an
oven.
[0067] A desired resin cured product suitable for aircraft
structural parts can be obtained by, for example, performing final
curing at a temperature of 180.degree. C. for 1 to 10 hours.
[0068] The mode I fracture toughness (G.sub.IC) of a cured product
of the epoxy resin composition according to the present invention
at 25.degree. C. is preferably 150 J/m.sup.2, more preferably 200
J/m.sup.2, even more preferably 250 J/m.sup.2. The measurement of
G.sub.IC is performed at 25.degree. C. in accordance with ASTM
D5045-99 using a cured product obtained by curing the epoxy resin
composition at 180.degree. C. for 2 hours. When the G.sub.IC is 150
J/m.sup.2 or more, a fiber-reinforced composite material having
excellent impact resistance, fatigue resistance, and open-hole
tensile strength can be obtained.
[0069] Further, the mode I fracture toughness (G.sub.IC) of a cured
product of the epoxy resin composition according to the present
invention at -54.degree. C. is preferably 120 J/m.sup.2, more
preferably 170 J/m.sup.2, even more preferably 220 J/m.sup.2. It is
to be noted that the measurement of G.sub.IC is performed at
-54.degree. C. in accordance with ASTM D5045-99 using a cured
product obtained by curing the epoxy resin composition at
180.degree. C. for 2 hours. When the G.sub.IC is 150 J/m.sup.2 or
more, a fiber-reinforced composite material having excellent impact
resistance, fatigue resistance, and open-hole tensile strength at
low temperatures can be obtained.
[0070] The flexural modulus of a cured product of the epoxy resin
composition according to the present invention at 25.degree. C. is
preferably in the range of 2.5 to 4.5 GPa, more preferably in the
range of 3.0 to 4.5 GPa, even more preferably in the range of 3.5
to 4.5 GPa. It is to be noted that the measurement of the flexural
modulus is performed at 25.degree. C. in accordance with JIS
K7171-1994 using a cured product obtained by curing the epoxy resin
composition at 180.degree. C. for 2 hours. When the flexural
modulus is 2.5 GPa or more, a fiber-reinforced composite material
having high compressive strength can be obtained. When the flexural
modulus is 4.5 GPa or less, a fiber-reinforced composite material
having excellent impact resistance, fatigue resistance, and
open-hole tensile strength can be obtained.
[0071] Examples of reinforcing fibers to be used in the present
invention include glass fibers, carbon fibers, and aramid fibers.
Among them, carbon fibers are preferably used from the viewpoint of
obtaining a lightweight fiber-reinforced composite material having
excellent mechanical properties such as strength and elastic
modulus.
[0072] Examples of such carbon fibers to be used in the present
invention include PAN-based carbon fibers, pitch-based carbon
fibers, and rayon-based carbon fibers. Among them, PAN-based carbon
fibers are preferably used due to its high tensile strength.
[0073] From the viewpoint of obtaining a lightweight
fiber-reinforced composite material having excellent elastic
modulus, the tensile elastic modulus of carbon fibers to be used in
the present invention is preferably 200 GPa or more, more
preferably 250 GPa or more, even more preferably 280 GPa or more.
By using carbon fibers having a tensile elastic modulus of 200 GPa
or more, a fiber-reinforced composite material having higher
weight-reducing effect and higher elastic modulus can be
obtained.
[0074] Further, as carbon fibers to be used in the present
invention, flat yarn such as one disclosed in Japanese Patent No.
2955145 is preferably used. Such flat yarn has a fineness of 3000
to 20000 deniers, a yarn width of 4 to 16 mm, and a ratio of yarn
width to yarn thickness of 30 or more. By using such flat yarn, a
reinforcing fiber substrate whose crimps of carbon fiber strands
are small can be obtained and therefore a fiber-reinforced
composite material having excellent mechanical properties such as
compressive strength can be obtained.
[0075] The reinforcing fibers to be used in the present invention
may be used in the form of a reinforcing fiber substrate composed
of one or more kinds of the above-mentioned reinforcing fibers and,
if necessary, one or more kinds of other chemical fibers. Such a
reinforcing fiber substrate preferably contains at least carbon
fibers. Examples of the reinforcing fiber substrate to be used in
the present invention include those obtained by arranging
reinforcing fibers in substantially one direction, fabrics, knits,
braids, and mats. Among them, a so-called unidirectional fabric
obtained by fixing reinforcing fibers arranged in substantially one
direction by glass fibers or chemical fibers is preferably used
from the viewpoint of obtaining a fiber-reinforced composite
material having a high fiber volume content.
[0076] Examples of such a unidirectional fabric to be used in the
present invention include a plain-woven fabric obtained by
interlacing warps each composed of one or more carbon fiber strands
with wefts each of which is composed of one or more glass fibers or
chemical fibers and which are perpendicular to the warps and a
non-crimp fabric shown in FIG. 1 comprising warps (shown by
reference numeral 1 in FIG. 1) each composed of one or more carbon
fiber strands, auxiliary warps (shown by reference numeral 2 in
FIG. 1) each of which is composed of a glass fiber bundle or a
chemical fiber bundle and which are arranged in parallel with the
warps, and wefts (shown by reference numeral 3 in FIG. 1) each of
which is composed of one or more glass fibers or chemical fibers
and which are arranged perpendicularly to the warps and auxiliary
warps and interlaced with the auxiliary warps to integrally hold
the carbon fiber strands. Among them, a non-crimp fabric is
preferably used from the viewpoint of achieving excellent
straightness of carbon fibers and obtaining a fiber-reinforced
composite material having excellent compressive strength.
Particularly, a fiber-reinforced composite material composed of a
cured product of the epoxy resin composition according to the
present invention and a non-crimp fabric has particularly excellent
compressive strength due to a synergistic effect between the
non-crimp fabric having excellent straightness of carbon fibers and
the cured product having high elastic modulus, and further has
particularly excellent impact resistance, fatigue resistance, and
open-hole tensile strength.
[0077] The fineness of each auxiliary warp of a unidirectional
fabric to be used in the present invention is preferably 20% or
less, more preferably 10% or less, even more preferably 5% or less
of that of each warp composed of one or more carbon fiber strands.
By setting the fineness of each auxiliary warp of a unidirectional
fabric to be used in the present invention to a value within the
above range, the auxiliary warps are more easily deformed than the
carbon fiber strands and therefore a unidirectional fabric whose
crimps of the carbon fiber strands are small can be obtained, which
makes it possible to obtain a fiber-reinforced composite material
having more excellent mechanical properties such as compressive
strength.
[0078] The fineness of each weft of a unidirectional fabric to be
used in the present invention is preferably 20% or less, more
preferably 10% or less, even more preferably 5% or less of that of
each warp composed of one or more carbon fiber strands. By setting
the fineness of each weft of a unidirectional fabric to be used in
the present invention to a value within the above range, a
unidirectional fabric whose crimps of the carbon fiber strands
formed at intersecting points between the warps and the wefts are
small can be obtained, which makes it possible to obtain a
fiber-reinforced composite material having more excellent
mechanical properties such as compressive strength.
[0079] If necessary, a binder may be attached to the reinforcing
fiber substrate to be used in the present invention for the purpose
of preventing misalignment of reinforcing fibers, temporarily
bonding reinforcing fiber substrates together, and obtaining a
fiber-reinforced composite material having improved impact
resistance. The composition of the binder is not particularly
limited, and any existing binder can be used. However, a binder
mainly composed of a thermoplastic resin is preferably used because
the aforementioned purposes can be achieved and, in addition, its
physical properties are not significantly changed during
storage.
[0080] In a case where the fiber-reinforced composite material
according to the present invention is used for aircraft structural
parts, it is required to have excellent heat resistance, and
therefore the thermoplastic resin to be used as a binder is
preferably an engineering plastic having a high glass transition
temperature. Particularly preferred examples of such an engineering
plastic include polysulfone, polyethersulfone, polyimide, and
polyetherimide.
[0081] A binder composition composed of a thermoplastic resin
preferably contains an appropriate plasticizer component to adjust
its glass transition temperature to a value within an appropriate
range, more specifically within a range of 50 to 70.degree. C. As
such a plasticizer component, a compound that can be reacted with
the epoxy resin composition according to the present invention is
preferably used. The plasticizer component is particularly
preferably an epoxy resin. The epoxy resin to be used as a
plasticizer component is not particularly limited, and examples
thereof include: glycidyl ether-type epoxy resins obtained by
reaction between epichlorohydrin and bisphenol A, bisphenol F,
bisphenol AD, bisphenol S, tetrabromobisphenol A, phenol novolac,
cresol novolac, hydroquinone, resorcinol,
4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl,
1,6-dihydroxynaphthalene, 9,9-bis(4-hydroxyphenyl)fluorene,
tris(p-hydroxyphenyl)methane, or tetrakis(p-hydroxyphenyl)ethane;
epoxy resins having a dicyclopentadiene skeleton; epoxy resins
having a biphenylaralkyl skeleton; triglycidyl isocyanurate; and
glycidyl amine-type epoxy resins such as
N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-p-aminophenol,
N,N,O-triglycidyl-4-amino-3-methylphenol,
N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane,
N,N,N',N'-tetraglycidyl-4,4'-diamino-3,3'-diethyldiphenylmethane,
and N,N,N',N'-tetraglycidyl-m-xylylenediamine. Examples of the
plasticizer component other than epoxy resins include polyphenols,
polyamines, polycarboxylic acids, polycarboxylic acid anhydrides,
polyacrylates, and sulfoneamindes.
[0082] The reinforcing fiber volume content of the fiber-reinforced
composite material according to the present invention is preferably
45 to 70%, more preferably 50 to 65%, even more preferably 55 to
60%. When the reinforcing fiber volume content of the
fiber-reinforced composite material according to the present
invention is 45% or higher, the fiber-reinforced composite material
has excellent weight-reducing effect and higher elastic modulus.
When the reinforcing fiber volume content of the fiber-reinforced
composite material according to the present invention is 70% or
less, lowering of strength of the fiber-reinforced composite
material due to rubbing between reinforcing fibers can be prevented
and the fiber-reinforced composite material has excellent
mechanical properties such as tensile strength.
[0083] As a method for molding the fiber-reinforced composite
material according to the present invention, a method for obtaining
a fiber-reinforced composite material by impregnating reinforcing
fibers with a liquid epoxy resin composition and then curing the
epoxy resin composition is preferably employed from the viewpoint
of efficiently obtaining a fiber-reinforced composite material.
Examples of such a method include a hand lay-up method, a filament
winding method, and a pultrusion method, and a RTM (Resin Transfer
Molding) method. Among these methods, a RTM method is preferably
employed from the viewpoint of efficiently obtaining a
fiber-reinforced composite material having a complicated shape. The
term "RTM method" used herein refers to a method for obtaining a
fiber-reinforced composite material by impregnating a reinforcing
fiber substrate placed in the inside of a mold with a liquid epoxy
resin composition and then curing the epoxy resin composition.
[0084] In the RIM method to be employed in the present invention, a
mold to be used may be either a closed mold made of a stiff
material or an open mold made of a stiff material and used together
with a flexible film (bag). In the latter case, a reinforcing fiber
substrate can be placed between the open mold made of a stiff
material and the flexible film. Examples of the stiff material
include various existing materials such as metals (e.g., steel,
aluminum), fiber-reinforced plastics (FRP), wood, and plaster.
Examples of a material of the flexible film include polyamides,
polyimides, polyesters, fluorine resins, and silicone resins.
[0085] In the RIM method using a closed mold made of a stiff
material, the mold is usually closed under pressure and an epoxy
resin composition for fiber-reinforced composite material is
injected into the inside of the mold under pressure. In this case,
a suction port to be connected to a vacuum pump may be provided
separately from an injection port to inject the epoxy resin
composition into the inside of the mold by suction. When suction is
performed, the epoxy resin composition may be injected into the
inside of the mold only at atmospheric pressure without using any
special pressurizing means. This method is preferably employed
because a large-sized member can be produced by providing a
plurality of suction ports.
[0086] In the RTM method using an open mold made of a stiff
material together with a flexible film, suction is usually
performed to inject an epoxy resin into the inside of the mold only
at atmospheric pressure without using any special pressurizing
means. In order to achieve good impregnation of a reinforcing fiber
substrate with the epoxy resin by injecting the epoxy resin only at
atmospheric pressure, the use of a resin distribution medium is
effective. Further, before a reinforcing fiber substrate or a
preform composed of reinforcing fibers is placed in the inside of a
mold, a gel coat is preferably applied to the surface of a stiff
material constituting the mold.
[0087] It is to be noted that when a closed mold made of a stiff
material is used as a mold, the term "inside of a/the mold" refers
to the inside of a cavity formed by the closed mold, and when an
open mold made of a stiff material and a flexible film are used,
the term "inside of a/the mold" refers to the inside of a space
enclosed by the open mold and the flexible film.
[0088] In the RTM method to be employed in the present invention, a
reinforcing fiber substrate is impregnated with an epoxy resin
composition, and then the epoxy resin composition is thermally
cured. The temperature of a mold during thermal curing is usually
higher than that during injection of an epoxy resin composition.
The temperature of a mold during thermal curing is preferably 80 to
200.degree. C. The length of time for thermal curing is preferably
1 to 20 hours. After the completion of thermal curing, an obtained
fiber-reinforced composite material is taken out of the mold. Then,
the fiber-reinforced composite material may be post-cured by
heating at a higher temperature. Post-curing is preferably
performed at 150 to 200.degree. C. for 1 to 4 hours.
[0089] In the present invention, a method derived from the RTM
method such as a VaRTM (Vacuum-assisted Resin Transfer Molding)
method, SCRIMP (Seeman's Composite Resin Infusion Molding Process),
or a method disclosed in JP-T-2005-527410 for more properly
controlling a resin infusion process, particularly a VaRTM process
by evacuating a resin feed tank to a pressure below atmospheric
pressure, employing cyclic compaction, and controlling a net
compaction pressure can be appropriately employed.
[0090] When a fiber-reinforced composite material is produced by
such an RTM method as described above, as a reinforcing fiber
substrate, the above-described unidirectional fabric is preferably
used, and the above-described non-crimp fabric is more preferably
used. In a non-crimp fabric, gaps between warps (shown by reference
numeral 1 in FIG. 1) each composed of one or more carbon fiber
strands and auxiliary warps (shown by reference numeral 2 in FIG.
1) each of which is a glass fiber bundle or a chemical fiber bundle
and which are arranged in parallel with the warps function as resin
flow channels. Therefore, by using such a non-crimp fabric as a
reinforcing fiber substrate, a fiber-reinforced composite material
can be efficiently obtained. Further, the epoxy resin composition
according to the present invention has low viscosity, which makes
it possible to more efficiently obtain a fiber-reinforced composite
material. The thus obtained fiber-reinforced composite material has
particularly excellent compressive strength, impact resistance,
fatigue resistance, and open-hole tensile strength.
[0091] Further, when a fiber-reinforced composite material is
produced by such a RTM method as described above, impregnation of a
reinforcing fiber substrate, which is preferably the
above-described unidirectional fabric, more preferably the
above-described non-crimp fabric, with the epoxy resin composition
according to the present invention is preferably performed by
evacuating the inside of a mold with the use of, for example, a
vacuum pump. In the case of using a non-crimp fabric, as described
above, since gaps between warps (shown by reference numeral 1 in
FIG. 1) each composed of one or more carbon fiber strands and
auxiliary warps (shown by reference numeral 2 in FIG. 1) each of
which is a glass fiber bundle or a chemical fiber bundle and which
are arranged in parallel with the warps function as resin flow
channels, a large-sized fiber-reinforced composite material can be
efficiently obtained by evacuating the inside of a mold. Further,
the epoxy resin composition according to the present invention has
low viscosity, which makes it possible to more efficiently obtain a
large-sized fiber-reinforced composite material. The thus obtained
fiber-reinforced composite material has particularly excellent
compressive strength, impact resistance, fatigue resistance, and
open-hole tensile strength.
[0092] The fiber-reinforced composite material according to the
present invention has excellent thermal properties, compressive
strength, impact resistance, and open-hole tensile strength, and
therefore can be preferably used for various structural parts such
as aircraft structural parts including main bodies, main wings,
tails, rotor blades, fairings, cowls, doors, seats, interior
materials, spacecraft structural parts including motor cases and
main wings, satellite structural parts including bodies and
antennas, vehicle structural parts including exterior panels,
chassis, aerodynamic parts, and seats, railway car structural parts
including bodies and seats, and ship structural parts including
hulls and seats.
EXAMPLES
[0093] Hereinbelow, the present invention will be more specifically
described with reference to the following examples. Resin raw
materials, a method for preparing an epoxy resin composition, a
method for producing a cured product, and measurement methods of
various properties used in the examples are as follows.
[0094] <Resin Raw Materials>
[0095] An epoxy resin composition was prepared using the following
commercially-available products.
[0096] (1) Epoxy Resins
[0097] (a) Bifunctional Epoxy Resins (Component A)
[0098] GAN (N,N-diglycidyl aniline manufactured by Nippon Kayaku
Co., Ltd., epoxy equivalent: 125 g/mol)
[0099] GOT (N,N-diglycidyl-o-toluidine manufactured by Nippon
Kayaku Co., Ltd., epoxy equivalent: 135 g/mol)
[0100] "DENACOL.TM." EX721 (phthalic acid diglycidyl ester
manufactured by Nagase Chemtex Corporation, epoxy equivalent: 154
g/mol)
[0101] AK601 (hexahydrophthalic acid diglycidyl ester manufactured
by Nippon Kayaku Co., Ltd., epoxy equivalent: 154 g/mol)
[0102] (b) Tri- or Higher-Functional Aromatic Epoxy Resins
(Component D)
[0103] "Araldite.TM." MY721
(N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane manufactured
by Huntsman Advanced Materials, epoxy equivalent: 113 g/mol)
[0104] "jER.TM." 630 (N,N,O-triglycidyl-p-aminophenol manufactured
by Japan Epoxy Resins Co., Ltd., epoxy equivalent: 98 g/mol)
[0105] "Araldite.TM." MY0600 (N,N,O-triglycidyl-m-aminophenol,
manufactured by Huntsman Advanced Materials, epoxy equivalent: 106
g/mol)
[0106] (c) Other Epoxy Resins "jER.TM." 825 (diglycidyl ether of
bisphenol A manufactured by Japan Epoxy Resins Co., Ltd., epoxy
equivalent: 175 g/mol)
[0107] (2) Liquid Aromatic Diamine Curing Agents
[0108] (a) Liquid Aromatic Diamine Curing Agents (Component B)
[0109] "jER Cure.TM." W (mixture of
2,4-diethyl-6-methyl-1,3-phenylenediamine and
4,6-diethyl-2-methyl-1,3-phenylenediamine manufactured by Japan
Epoxy Resins Co., Ltd., active hydrogen equivalent: 45 g/mol)
[0110] UOP No. 225 (product number)
(4,4'-methylenebis(N-sec-butylaniline) manufactured by Nikki
Universal Co., Ltd., active hydrogen equivalent: 155 g/mol)
[0111] (b) Other Amine Curing Agents
[0112] 3,3'-DAS (3,3'-diaminodiphenylsulfone, manufactured by
Konishi Chemical Inc Co., Ltd., active hydrogen equivalent: 62
g/mol) (solid aromatic diamine curing agent)
[0113] "Seikacure.TM." S (4,4'-diaminodiphenylmethane, manufactured
by Seika Corporation, active hydrogen equivalent: 62 g/mol) (solid
aromatic diamine curing agent)
[0114] aniline (manufactured by Tokyo Chemical Industry Co., Ltd.,
active hydrogen equivalent: 46 g/mol) (liquid aromatic monoamine
curing agent)
[0115] m-xylylene diamine (manufactured by Tokyo Chemical Industry
Co., Ltd., active hydrogen equivalent: 34 g/mol) (liquid diamine
curing agent which is not aromatic)
[0116] (3) Core-Shell Polymer Particles
[0117] (a) Core-Shell Polymer Particles (Component (C))
[0118] "kane Ace.TM." MX125 (manufactured by Kaneka Corporation as
a masterbatch of 75% by mass of diglycidyl ether of bisphenol A and
25% by mass of core-shell polymer particles (volume-average
particle size: 100 nm, core: butadiene/styrene copolymer (Tg:
-45.degree. C.), shell: methyl methacrylate/glycidyl
methacrylate/styrene copolymer))
[0119] "kane Ace.TM." MX125 Large Particle Type (manufactured by
Kaneka Corporation as a masterbatch of 75% by mass of diglycidyl
ether of bisphenol A and 25% by mass of core-shell polymer
particles (volume-average particle size: 250 nm, core:
butadiene/styrene copolymer (Tg: -45.degree. C.), shell: methyl
methacrylate/glycidyl methacrylate/styrene copolymer))
[0120] "Kane Ace.TM." MX416 (manufactured by kaneka Corporation as
a masterbatch of 75% by mass of "Araldite.TM." MY721 and 25% by
mass of core-shell polymer particles (volume-average particle size:
100 nm, core: cross-linked polybutadiene (Tg: -70.degree. C.),
shell: methyl methacrylate/glycidyl methacrylate/styrene
copolymer))
[0121] Core-shell polymer particles A (prepared as a masterbatch of
75% by mass of "Araldite.TM." MY721 and 25% by mass of core-shell
polymer particles (volume-average particle size: 100 nm, core:
butadiene/styrene copolymer (Tg: -25.degree. C.), shell: methyl
methacrylate/glycidyl methacrylate/styrene copolymer)) [0122]
Core-shell polymer particles A were synthesized by a method
disclosed in JP-A-2005-248109. The ratio between butadiene and
styrene was 50:50 (% by mass). After a butadiene/styrene rubber
latex was produced, 5% by mass of methyl methacrylate, 5% by mass
of glycidyl methacrylate, and 5% by mass of styrene were added to
100% by mass of the butadiene/styrene rubber latex to perform graft
polymerization.
[0123] (b) Other Core-Shell Polymer Particles
[0124] "Paraloid.TM." EXL-2655 (core-shell polymer particles
(volume-average particle size: 100 nm, core: butadiene/styrene
copolymer, shell: PMMA/styrene copolymer) manufactured by Kureha
Corporation) (core-shell polymer particles containing no epoxy
groups in their shell)
[0125] "Staphyloid.TM." AC-3355 (core-shell polymer particles
(volume-average particle size: 500 nm, core: cross-linked polybutyl
acrylate, shell: cross-linked polystyrene) manufactured by Ganz
Chemical Co., Ltd.) (core-shell polymer particles containing no
epoxy groups in their shell and having a volume-average particle
size outside the range of 50 to 300 nm)
[0126] <Preparation of Epoxy Resin Compositions>
[0127] Epoxy resin Compositions shown in Table 1 were prepared in
the following manner. A predetermined amount of epoxy resin heated
to 70.degree. C. was weighed in a 300-mL stainless beaker, and was
stirred using a spatula until homogenized. When core-shell polymer
particles were used, the core-shell polymer particles were added to
the homogenized epoxy resin and stirred using a homogenizer to
obtain a base component of an epoxy resin composition. Then, an
amine curing agent heated to 70.degree. C. was added to the base
component and stirred using a spatula to obtain an epoxy resin
composition. It is to be noted that when diaminodiphenylsulfone was
used, an amine curing agent was prepared separately from the base
component by adding diaminodiphenylsulfone to a liquid aromatic
diamine curing agent heated to 150.degree. C. and stirring the
mixture using a spatula until the mixture was homogenized.
[0128] <Measurement of Initial Viscosity of Epoxy Resin
Composition at 70.degree. C.>
[0129] The initial viscosity of the epoxy resin composition
obtained by the above method at 70.degree. C. was measured
according to "viscosity measurement method using cone-plate
rotational viscometer" specified in JIS 28803 (1991) using an
E-type viscometer equipped with a standard cone rotor (1.degree.
34'.times.R24) (TVE-30H manufactured by Toki Sangyo Co., Ltd.) at a
rotation speed of 50 rpm. It is to be noted that the initial
viscosity was measured after the epoxy resin composition was
maintained at 70.degree. C. for 5 minutes after its
preparation.
[0130] <Measurement of Volume-Average Particle Size of
Core-Shell Polymer Particles>
[0131] One hundred grams of the base component of the epoxy resin
composition obtained by the above method was mixed with 20 g of
methyl ethyl ketone to obtain a mixture. The volume-average
particles size of the core-shell polymer particles was measured
according to JIS 28826 (2005) using the obtained mixture and a
nanotrac particle size analyzer UPA-EX150 (manufactured by NIKKISO
Co., Ltd.).
[0132] <Method for Producing Epoxy Resin Cured Product>
[0133] The epoxy resin composition obtained by the above method was
injected into the inside of a mold having a plate-shaped cavity
with a thickness of 2 mm and into the inside of a mold having a
plate-shaped cavity with a thickness of 6 mm, and was then
thermally cured in an oven under the following conditions to obtain
cured resin plates.
[0134] (1) The temperature in the oven was increased from
30.degree. C. to 180.degree. C. at a rate of 1.5.degree.
C./min.
[0135] (2) The temperature in the oven was kept at 180.degree. C.
for 2 hours.
[0136] (3) The temperature in the oven was decreased from
180.degree. C. to 30.degree. C. at a rate of 2.5.degree.
C./min.
[0137] <Measurement of Glass Transition Temperature (Tg) of
Epoxy Resin Cured Product>
[0138] Specimens each having a width of 12.7 mm and a length of 55
mm were cut out from the cured resin plate with a thickness of 2 mm
obtained by the above method, and their Tg was measured by DMA in
accordance with SACMA SRM18R-94 using a rheometer ARES manufactured
by Rheometrics Co., Ltd. At this time, a temperature rise rate was
5.degree. C./min and a measuring frequency was 1 Hz. In an obtained
temperature-storage elastic modulus G' curve, the temperature value
at the intersection between a tangent drawn to a curve in the glass
state and a tangent drawn to a curve in the transition state was
defined as Tg.
[0139] <Measurement of Flexural Modulus of Epoxy Resin Cured
Product>
[0140] Specimens each having a width of 10 mm and a length of 60 mm
were cut out from the cured resin plate with a thickness of 2 mm
obtained by the above method, and their flexural modulus was
measured by performing a three-point bending test in accordance
with JIS K7171-1994 under the conditions of a testing speed of 2.5
mm/min and a support span length of 32 mm. At this time, a
measurement temperature was 25.degree. C.
[0141] <Measurement of Mode I Fracture Toughness (G.sub.IC) of
Epoxy Resin Cured Product>
[0142] The cured resin plate with a thickness of 6 mm obtained by
the above method was machined into specimens specified in ASTM
D5045-99, and their mode I fracture toughness was measured in
accordance with ASTM D5045-99. At this time, measurement
temperatures were 25.degree. C. and -54.degree. C.
[0143] <Preparation of Reinforcing Fiber Substrate 1 Composed of
Carbon Fibers>
[0144] A reinforcing fiber substrate 1 composed of carbon fibers
used in Example 34 and Comparative Examples 10 and 11 was prepared
in the following manner. A unidirectional sheet-like reinforcing
fiber bundle group was formed by arranging carbon fiber bundles
"Torayca.TM." T800S-24K-10E (PAN-based non-twisted yarn
manufactured by Toray Industries Inc., 24000 filaments) as warps at
a density of 1.8 ends/cm. Then, glass fiber bundles ECE225 1/0 1Z
(manufactured by Nitto Boseki Co., Ltd., 200 filaments) were
arranged as wefts at a density of 3 ends/cm in a direction
perpendicular to the unidirectional sheet-like reinforcing fiber
bundle group and interlaced with the warps with the use of a
weaving machine to prepare a plain-woven fabric in which carbon
fibers were arranged in substantially one direction. The thus
obtained plain-woven fabric was used as a reinforcing fiber
substrate. The weight of carbon fibers per unit area of the
reinforcing fiber substrate was 190 g/m.sup.2. Then, 60 parts by
mass of "Sumika Excel.TM." 5003P (manufactured by Sumitomo Chemical
Co., Ltd.), 23.5 parts by mass of "jER.TM." 806 (glycidyl ether of
bisphenol F manufactured by Japan Epoxy Resins Co., Ltd.), 12.5
parts by mass of an epoxy resin having a biphenylaralkyl skeleton
(NC-3000 manufactured by Nippon Kayaku Co., Ltd.), and 4 parts by
mass of triglycidyl isocyanurate (TEPIC-P manufactured by Nissan
Chemical Industries, Ltd.) were melt-kneaded at 210.degree. C. by a
twin screw extruder to obtain a resin composition. Then, the resin
composition was frozen, pulverized, and classified to obtain binder
particles having a volume-average particle size of 100 .mu.m and a
glass transition temperature of 73.degree. C. The binder particles
were naturally dropped through a vibration net so as to be
uniformly dispersed on one of the surfaces of the reinforcing fiber
substrate while dispensed using an embossing roller and a doctor
blade so that the weight of the binder particles per unit area was
25 g/m.sup.2. Then, the reinforcing fiber substrate was allowed to
pass through a far-infrared heater at 200.degree. C. at 0.3 m/min
to fusion-bond the binder particles to the entire one surface of
the reinforcing fiber substrate. In this way, a reinforcing fiber
substrate 1 having binder particles was obtained.
[0145] <Preparation of Reinforcing Fiber Substrate 2 Composed of
Carbon Fibers>
[0146] A reinforcing fiber substrate 2 composed of carbon fibers
used in Examples 35 and 36 was prepared in the following manner.
Carbon fiber bundles "Torayca.TM." T800S-24K-10E (PAN-based
non-twisted yarn manufactured by Toray Industries Inc., 24000
filaments) were arranged as warps at a density of 1.8 ends/cm, and
glass fiber bundles ECE225 1/0 1Z (manufactured by Nitto Boseki
Co., Ltd., 200 filaments) were arranged as auxiliary warps in
parallel with the warps at a density of 1.8 ends/cm in such a
manner that the warps and the auxiliary warps were alternately
arranged to form a unidirectional sheet-like reinforcing fiber
bundle group. Then, polyamide fiber bundles (polyamide 66, 7
filaments) were arranged as wefts in a direction perpendicular to
the unidirectional sheet-like reinforcing fiber bundle group at a
density of 3 ends/cm and interlaced with the auxiliary warps using
a weaving machine in such a manner that the auxiliary warps and the
wefts were intersected with each other to form a unidirectional
non-crimp fabric as shown in FIG. 1. In such a unidirectional
non-crimp fabric having no crimps, carbon fiber bundles were
arranged in substantially one direction. The weight of carbon
fibers per unit area of the reinforcing fiber substrate was 190
g/m.sup.2. Further, binder particles were fusion-bonded to the
entire one surface of the reinforcing fiber substrate in the same
manner as in the case of the above-described reinforcing fiber
substrate 1 to obtain a reinforcing fiber substrate 2 having binder
particles.
[0147] <Preparation of Reinforcing Fiber Substrate 3 Composed of
Carbon Fibers>
[0148] A reinforcing fiber substrate 3 composed of carbon fibers
used in Example 37 was prepared in the following manner. A
unidirectional non-crimp fabric as shown in FIG. 1 was prepared in
the same manner as in the case of the reinforcing fiber substrate 2
except that glass fiber bundles ECE225 1/0 1Z (manufactured by
Nitto Boseki Co., Ltd. 200 filaments) were used as wefts. The
weight of carbon fibers per unit area of the thus obtained
reinforcing fiber substrate was 190 g/m.sup.2. Further, binder
particles were fusion-bonded to the entire one surface of the
reinforcing fiber substrate in the same manner as in the case of
the above-described reinforcing fiber substrate 1 or 2 to obtain a
reinforcing fiber substrate 3 having binder particles.
[0149] <Preparation of Fiber-Reinforced Composite Material for
Measurement of Glass Transition Temperature (Tg) and 0.degree.
Compression Test>
[0150] A fiber-reinforced composite material for measurement of Tg
and 0.degree. compression test used in Examples 34, 35, and 37 and
Comparative Examples 10 and 11 were prepared by RTM in the
following manner. Six 395 mm.times.395 mm pieces were cut out from
the above-described reinforcing fiber substrate having binder
particles, and were then stacked on top of one another in a mold
having a plate-shaped cavity of 400 mm.times.400 mm.times.1.14 mm
in such a manner that their carbon fibers were unidirectionally
oriented to form a preform. At this time, the orientation direction
of the carbon fibers was defined as 0.degree. direction. Then, the
mold was clamped. Then, the mold was heated to 70.degree. C., and
an epoxy resin composition shown in Table 6 previously heated to
70.degree. C. separately from the mold was injected into the inside
of the mold at an injection pressure of 0.2 MPa with a resin
injector to impregnate the reinforcing fiber substrate with the
epoxy resin composition. After the completion of impregnation, the
temperature of the mold was increased to 130.degree. at a rate of
1.5.degree. C./min, maintained at 130.degree. C. for 2 hours, and
decreased to 30.degree. C., and then an obtained cured product was
demolded. The cured product was post-cured in an oven under the
following conditions to obtain a fiber-reinforced composite
material.
[0151] (1) The temperature in the oven was increased from
30.degree. C. to 180.degree. C. at a rate of 1.5.degree.
C./min.
[0152] (2) The temperature in the oven was maintained at
180.degree. C. for 2 hours.
[0153] (3) The temperature in the oven was decreased from
180.degree. C. to 30.degree. C. at a rate of 2.5.degree.
C./min.
[0154] A reinforcing fiber composite material for measurement of Tg
and 0.degree. compression test used in Example 36 was prepared in
the same manner as described above except that an epoxy resin
composition was injected into the inside of the mold at an
injection pressure of 0.2 MPa with the use of a resin injector
while the inside of the mold was evacuated using a vacuum pump
connected to the mold.
[0155] <Preparation of Specimen for Measurement of Tg of
Fiber-Reinforce Composite Material>
[0156] Rectangular specimens each having a length of 55 mm and a
width of 12.7 mm were cut out from the fiber-reinforced composite
material obtained by the above method. In this case, a 90.degree.
direction was defined as the length direction of the specimen.
[0157] <Measurement of Tg of Fiber-Reinforced Composite
Material>
[0158] The measurement of Tg was performed by DMA in accordance
with SACMA SRM18R-94 using the specimen for Tg measurement obtained
by the above method and a rheometer ARES manufactured by
Rheometrics Co., Ltd. A temperature rise rate was 5.degree. C./min
and a measuring frequency was 1 Hz. In an obtained
temperature-storage elastic modulus G' curve, the temperature value
at the intersection between a tangent drawn to a curve in the glass
state and a tangent drawn to a curve in the transition state was
defined as Tg.
[0159] <Preparation of Specimen for 0.degree. Compression Test
of Fiber-Reinforced Composite Material>
[0160] Tabs were bonded to the fiber-reinforced composite material
obtained by the above method in accordance with SACMA-SRM 1R-94,
and rectangular specimens each having a length of 80.0 mm and a
width of 15.0 mm were cut out from the fiber-reinforced composite
material. In this case, the 0.degree. direction was defined as the
length direction of the specimen.
[0161] <0.degree. Compression Test of Fiber-Reinforced Composite
Material>
[0162] A compression test was performed in accordance with SACMA
SRM 1R-94 using the specimen for 0.degree. compression test
obtained by the above method at 23.degree. C. and a testing rate of
1.0 mm/min. The number of samples was 5, and their average measured
value was determined.
[0163] <Preparation of Fiber-Reinforced Composite Material for
Open-Hole Tensile Test>
[0164] A fiber-reinforced composite material for open-hole tensile
test used in the Examples 34, 35, and 37 and Comparative Examples
10 and 11 was prepared by RTM in the following manner. Eight pieces
of 395 mm.times.395 mm were cut out from the above-described
reinforcing fiber substrate having binder particles, and were then
stacked on top of one another in a mold having a plate-shaped
cavity of 400 mm.times.400 mm.times.1.52 mm to obtain a laminate
having a stacking sequence of
+45.degree./0.degree./-45.degree./90.degree./90.degree./-45.degree./0.deg-
ree./+45.degree.. In this case, the orientation direction of carbon
fibers was defined as 0.degree. direction. In this way, a preform
was formed. Then, a mold was clamped. Then, the mold was heated to
70.degree. C., and an epoxy resin composition shown in Table 6
previously heated to 70.degree. C. separately from the mold was
injected into the inside of the mold at an injection pressure of
0.2 MPa with the use of a resin injector to impregnate the
reinforcing fiber substrate with the epoxy resin composition. After
the completion of impregnation, the temperature of the mold was
increased to 130.degree. at a rate of 1.5.degree. C./min,
maintained at 130.degree. C. for 2 hours, and decreased to
30.degree. C., and then an obtained cured product was demolded. The
cured product was post-cured in an oven under the following
conditions to obtain a fiber-reinforced composite material.
[0165] (1) The temperature in the oven was increased from
30.degree. C. to 180.degree. C. at a rate of 1.5.degree.
C./min.
[0166] (2) The temperature in the oven was maintained at
180.degree. C. for 2 hours.
[0167] (3) The temperature in the oven was decreased from
180.degree. C. to 30.degree. C. at a rate of 2.5.degree.
C./min.
[0168] A fiber-reinforced composite material for open-hole tensile
test used in Example 36 was prepared in the same manner as
described above except that an epoxy resin composition was injected
into the inside of the mold at an injection pressure of 0.2 MPa
with the use of a resin injector while the inside of the mold was
evacuated using a vacuum pump connected to the mold.
[0169] <Preparation of Specimen for Open-Hole Tensile Test of
Fiber-Reinforced Composite Material>
[0170] Rectangular specimens each having a length of 300 mm and a
width of 36.0 mm were cut out from the fiber-reinforced composite
material obtained by the above method, and then a hole having a
diameter of 6.0 mm was formed in the specimen using a drill and a
reamer in accordance with ASTM D5766-95. In this case, the
0.degree. direction was defined as the length direction of the
specimen.
[0171] <Open-Hole Tensile Test of Fiber-Reinforced Composite
Material>
[0172] An open-hole tensile test was performed in accordance with
ASTM D5766-95 using the specimen for open-hole tensile test
obtained by the above method at 23.degree. C. and a testing rate of
1.27 mm/min. The number of samples was 5, and their average
measured value was determined.
Examples 1 to 9
[0173] Epoxy resin compositions were prepared using the resin raw
materials shown in Table 1, and the initial viscosity of each of
the epoxy resin compositions at 70.degree. C. was measured. As a
result, all the epoxy resin compositions had sufficiently low
viscosity. Then, the epoxy resin compositions were cured to obtain
cured products, and the Tg, flexural modulus, and mode I fracture
toughness of each of the cured products were measured. As a result,
all the cured products had high Tg, high elastic modulus, and high
toughness. From the result, it was found that all the cured
products of Examples 1 to 9 were excellent. Among them, the cured
products of Examples 2, 3, 5, 6, and 8 had very high Tg, very high
elastic modulus, and very high toughness. From the result, it was
found that the cured products of Examples 2, 3, 5, 6, and 8 were
particularly excellent.
TABLE-US-00001 TABLE 1 Unit of resin raw material content: part(s)
by mass Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 1
ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 ple 9 Compo- GAN
(manufactured by Nippon Kayaku 30 30 30 30 30 30 10 50 70 nent Co.,
Ltd.) (A) N,N-diglycidyl aniline GOT (manufactured by Nippon Kayaku
-- -- -- -- -- -- -- -- -- Co., Ltd.) N,N-diglycidyl-o-toluidine
"DENACOL .TM." EX721 (manufactured by -- -- -- -- -- -- -- -- --
Nagase Chemtex Corporation) Phthalic acid diglycidyl ester AK601
(manufactured by Nippon Kayaku -- -- -- -- -- -- -- -- -- Co.,
Ltd.) Hexahydrophthalic acid diglycidyl ester Other "jER" 825
(manufactured by Japan 64 55 40 25 55 40 75 35 15 Epoxy Epoxy
Resins Co., Ltd.) Resins Diglycidyl ether of bisphenol A Compo-
"JER Cure" W (manufactured by Japan 28.7 28.6 28.4 28.2 28.6 28.4
26.5 30.7 32.7 nent Epoxy Resins Co., Ltd.) (B) Mixture of
2,4-diethyl-6-methyl-1,3-phenylene diamine and
4,6-diethyl-2-methyl-1,3-phenylene diamine Compo- "kane Ace" MX125
(manufactured by 8 20 40 60 -- -- 20 20 20 nent Kaneka Corporation)
[2] [5] [10] [15] [5] [5] [5] (C) Modified with epoxy groups,
Volume-average particle size: 100 nm Value within [ ]: Core-shell
polymer particle content "kane Ace" MX125 Large Particle Type -- --
-- -- 20 40 -- -- -- (manufactured by Kaneka Corporation) [5] [10]
Modified with epoxy groups, Volume-average particle size: 250 nm
Value within [ ]: Core-shell polymer particle content Resin Initial
viscosity at 70.degree. C. [mPa s] 42 48 61 76 46 57 60 41 36 Prop-
Tg [.degree. C.] 170 170 169 167 170 168 183 154 139 erties
Flexural modulus [.degree. C.] 3.4 3.3 3.1 2.9 3.3 3.1 2.4 3.7 4.0
Mode I fracture toughness 166 242 265 267 203 224 219 263 281
(25.degree. C.) [J/m.sup.2] Mode I fracture toughness 192 265 286
283 216 235 240 287 295 (-54.degree. C.) [J/m.sup.2]
Examples 10 and 11
[0174] Epoxy resin compositions were prepared using the resin raw
materials shown in Table 2, and the initial viscosity of each of
the epoxy resin compositions at 70.degree. C. was measured. As a
result, both the epoxy resin compositions had sufficiently low
viscosity. Then, the epoxy resin compositions were cured to obtain
cured products, and the Tg, flexural modulus, and mode I fracture
toughness of each of the cured products were measured. As a result,
both the cured products had high Tg, high elastic modulus, and high
toughness. From the result, it was found that the cured products of
Examples 10 and 11 were excellent. However, the epoxy resin
compositions of Examples 1 and 2 had lower viscosity as compared to
the epoxy resin compositions of Examples 10 and 11, and the cured
products of Examples 1 and 2 had higher Tg as compared to the cured
products of Examples 10 and 11. From the result, it was found that
the cured products of Examples 1 and 2 were more excellent as
compared to the cured products of Examples 10 and 11.
Examples 12 to 20
[0175] Epoxy resin compositions were prepared using the resin raw
materials shown in Tables 2 and 3, and the initial viscosity of
each of the epoxy resin compositions at 70.degree. C. was measured.
As a result, all the epoxy resin compositions had sufficiently low
viscosity. Then, the epoxy resin compositions were cured to obtain
cured products, and the Tg, flexural modulus, and mode I fracture
toughness of each of the cured products were measured. As a result,
all the cured products had high Tg, high elastic modulus, and high
toughness. From the result, it was found that all the cured
products of Examples 12 to 20 were excellent. Among them, the cured
products of Examples 13, 14, 16, 17, 19, and 20 had very high Tg,
very high elastic modulus, and very high toughness. From the
result, it was found that the cured products of Examples 13, 14,
16, 17, 19, and 20 were particularly excellent.
Examples 21 to 24
[0176] Epoxy resin compositions were prepared using the resin raw
materials shown in Table 3, and the initial viscosity of each of
the epoxy resin compositions at 70.degree. C. was measured. As a
result, all the epoxy resin compositions had sufficiently low
viscosity. Then, the epoxy resin compositions were cured to obtain
cured products, and the Tg, flexural modulus, and mode I fracture
toughness of each of the cured products were measured. As a result,
all the cured products had high Tg, high elastic modulus, and high
toughness. From the result, it was found that all the cured
products of Examples 21 to 24 were excellent. Among them, the cured
products of Examples 22 and 23 had very high Tg, very high elastic
modulus, and very high toughness. From the result, it was found
that the cured products of Examples 22 and 23 were particularly
excellent.
TABLE-US-00002 TABLE 2 Unit of resin raw material content: part(s)
by mass Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 10 ple
11 ple 12 ple 13 ple 14 ple 15 ple 16 ple 17 Compo- GAN
(manufactured by Nippon Kayaku Co., Ltd.) 30 30 -- -- -- -- -- --
nent N,N-diglycidyl aniline (A) GOT (manufactured by Nippon Kayaku
Co., Ltd.) -- -- 10 30 50 -- -- -- N,N-diglycidyl-o-toluidine
"DENACOL .TM." EX721 (manufactured by Nagase -- -- -- -- -- 10 30
50 Chemtex Corporation) Phthalic acid diglycidyl ester AK601
(manufactured by Nippon Kayaku Co., -- -- -- -- -- -- -- -- Ltd.)
Hexahydrophthalic acid diglycidyl ester Other "jER" 825
(manufactured by Japan Epoxy Resins 64 55 75 55 35 75 55 35 Epoxy
Co., Ltd.) Resins Diglycidyl ether of bisphenol A Compo- "jER Cure"
W (manufactured by Japan Epoxy -- -- 26.3 27.8 29.3 25.9 26.6 27.3
nent Resins Co., Ltd.) (B) Mixture of
2,4-diethyl-6-methyl-1,3-phenylenediamine and
4,6-diethyl-2-methyl-1,3-phenylenediamine UOP No.225 (manufactured
by Nikki Universal 98.9 98.9 -- -- -- -- -- -- Co., Ltd.)
4,4'-methylenebis (N-sec-butylaniline) Compo- "kane Ace" MX125
(manufactured by Kaneka 8 20 20 20 20 20 20 20 nent Corporation)
[2] [5] [5] [5] [5] [5] [5] [5] (C) Modified with epoxy groups,
Volume-average particle size: 100 nm Value within [ ]: Core-shell
polymer particle content Resin Initial viscosity at 70.degree. C.
[mPa s] 51 58 58 45 35 78 62 59 Prop- Tg [.degree. C.] 166 165 183
166 151 186 178 166 erties Flexural modulus [.degree. C.] 3.3 3.2
2.4 3.2 3.5 2.3 3.1 3.5 Mode I fracture toughness (25.degree. C.)
[J/m.sup.2] 169 252 223 241 258 230 252 277 Mode I fracture
toughness (-54.degree. C.) [J/m.sup.2] 193 269 240 263 271 252 269
291
TABLE-US-00003 TABLE 3 Unit of resin raw material content: part(s)
by mass Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 18 ple 19 ple
20 ple 21 ple 22 ple 23 ple 24 Compo- GAN (manufactured by Nippon
Kayaku Co., Ltd.) -- -- -- 30 30 30 20 nent N,N-diglycidyl aniline
(A) GOT (manufactured by Nippon Kayaku Co., Ltd.) -- -- -- -- -- --
-- N,N-diglycidyl-o-toluidine "DENACOL .TM." EX721 (manufactured by
Nagase Chemtex -- -- -- -- -- -- -- Corporation) Phthalic acid
diglycidyl ester AK601 (manufactured by Nippon Kayaku Co., Ltd.) 10
30 50 -- -- -- -- Hexahydrophthalic acid diglycidyl ester Compo-
"Araldite" MY721 (manufactured by Huntsman Advanced -- -- -- 5 25
45 65 nent Materials) (D)
N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane Other "jER" 825
(manufactured by Japan Epoxy Resins Co., 75 55 35 50 30 10 10 Epoxy
Ltd.) Resins Diglycidyl ether of bisphenol A Compo- "jER Cure" W
(manufactured by Japan Epoxy Resins Co., 25.9 26.6 27.3 31.7 34.6
37.4 39.2 nent Ltd.) (B) Mixture of
2,4-diethyl-6-methyl-1,3-phenylenediamine and
4,6-diethyl-2-methyl-1,3-phenylenediamine Compo- "kane Ace" MX125
(manufactured by Kaneka Corporation) 20 20 20 -- -- -- -- nent
Modified with epoxy groups, Volume-average particle [5] [5] [5] (C)
size: 100 nm Value within [ ]: Core-shell polymer particle content
"kane Ace" MX416 (manufactured by Kaneka Corporation) -- -- -- 20
20 20 20 Modified with epoxy groups, Volume-average particle [5]
[5] [5] [5] size: 100 nm Value within [ ]: Core-shell polymer
particle content Resin Initial viscosity at 70.degree. C. [mPa s]
64 58 53 68 89 110 143 Prop- Tg [.degree. C.] 184 175 162 173 178
182 192 erties Flexural modulus [.degree. C.] 2.3 3.0 3.4 3.2 3.6
3.8 3.4 Mode I fracture toughness (25.degree. C.) [J/m.sup.2] 225
248 276 231 222 214 185 Mode I fracture toughness (-54.degree. C.)
[J/m.sup.2] 252 273 290 256 249 243 216
Examples 25 to 30
[0177] Epoxy resin compositions were prepared using the resin raw
materials shown in Table 4, and the initial viscosity of each of
the epoxy resin compositions at 70.degree. C. was measured. As a
result, all the epoxy resin compositions had sufficiently low
viscosity. Then, the epoxy resin compositions were cured to obtain
cured products, and the Tg, flexural modulus, and mode I fracture
toughness of each of the cured products were measured. As a result,
all the cured products had high Tg, high elastic modulus, and high
toughness. From the result, it was found that the cured products of
Examples 25 to 30 were particularly excellent in Tg and elastic
modulus as compared to the cured product of Example 2. Among them,
the epoxy resin compositions of Examples 26, 27, 29, and 30 had low
viscosity and the cured products of Examples 26, 27, 29, and 30 had
very high Tg, very high elastic modulus, and very high toughness.
From the result, it was found that the cured products of Examples
26, 27, 29, and 30 were particularly excellent.
Examples 31 and 32
[0178] Epoxy resin compositions were prepared using the resin raw
materials shown in Table 4, and the initial viscosity of each of
the epoxy resin compositions at 70.degree. C. was measured. As a
result, both the epoxy resin compositions had relatively-low
viscosity. Then, the epoxy resin compositions were cured to obtain
cured products, and the Tg, flexural modulus, and mode I fracture
toughness of each of the cured products were measured. As a result,
both the cured products had high Tg, high elastic modulus, and high
toughness. From the result, it was found that the cured products of
Examples 31 and 32 were particularly excellent in Tg, elastic
modulus, and fracture toughness as compared to the cured product of
Example 26.
Example 33
[0179] An epoxy resin composition was prepared using the resin raw
materials shown in Table 4, and the initial viscosity of the epoxy
resin composition at 70.degree. C. was measured. As a result, the
epoxy resin composition had sufficiently low viscosity. Then, the
epoxy resin composition was cured to obtain a cured product, and
the Tg, flexural modulus, and mode I fracture toughness of the
cured product were measured. As a result, the cured product had
high Tg, high elastic modulus, and high toughness at 25.degree. C.,
but its toughness at -56.degree. C. was slightly lower than that of
Example 26.
TABLE-US-00004 TABLE 4 Unit of resin raw material content: part(s)
by mass Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple
25 ple 26 ple 27 ple 28 ple 29 ple 30 ple 31 ple 32 ple 33 Compo-
GAN (manufactured by Nippon Kayaku 30 30 30 30 30 30 30 30 30 nent
Co., Ltd.) (A) N,N-diglycidyl aniline Compo- "jER" 630
(manufactured by Japan 5 25 45 -- -- -- 25 25 25 nent Epoxy Resins
Co., Ltd.) (D) N,N,O-triglycidyl-p-aminophenol "Araldite" MY0600
(manufactured by -- -- -- 5 25 45 -- -- -- Huntsman Advanced
Materials) N,N,O-triglycidyl-m-aminophenol, Other "jER" 825
(manufactured by Japan 50 30 10 50 30 10 30 30 30 Epoxy Epoxy
Resins Co., Ltd.) Resins Diglycidyl ether of bisphenol A Compo-
"JER Cure" W (manufactured by Japan 32.0 36.1 40.1 31.9 35.2 38.6
28.2 21.4 36.1 nent Epoxy Resins Co., Ltd.) (B) Mixture of
2,4-diethyl-6-methyl-1,3-phenylene diamine and
4,6-diethyl-2-methyl-1,3-phenylene diamine Other 3,3'-DAS
(manufactured by Konishi -- -- -- -- -- -- 6.0 10.7 -- amine
Chemical Inc Co., Ltd.) curing 3,3'-diaminodiphenylsulfone agent
"Seikacure" S (manufactured by Seika -- -- -- -- -- -- 6.0 10.7 --
Corporation) 4,4'-diaminodiphenylsulfone Compo- "kane Ace" MX416
(manufactured by 20 20 20 20 20 20 20 20 -- nent Kaneka
Corporation) [5] [5] [5] [5] [5] [5] [5] [5] (C) Modified with
epoxy groups, Volume-average particle size: 100 nm Value within [
]: Core-shell polymer particle content Core-shell polymer A -- --
-- -- -- -- -- -- 20 Modified with epoxy groups, [5] Volume-average
particle size: 100 nm Value within [ ]: Core-shell polymer particle
content Resin Initial viscosity at 70.degree. C. [mPa s] 45 39 32
59 69 74 77 180 40 Prop- Tg [.degree. C.] 172 177 179 170 174 176
180 183 175 erties Flexural modulus [.degree. C.] 3.2 3.5 3.6 3.2
3.6 3.8 3.6 3.7 3.5 Mode I fracture toughness 221 209 202 219 205
196 217 220 204 (25.degree. C.) [J/m.sup.2] Mode I fracture
toughness 246 241 220 245 232 219 243 245 189 (-54.degree. C.)
[J/m.sup.2]
Comparative Example 1
[0180] An epoxy resin composition was prepared using the resin raw
materials shown in Table 5, and the initial viscosity of the epoxy
resin composition at 70.degree. C. was measured. As a result, the
epoxy resin composition had sufficiently low viscosity. Then, the
epoxy resin composition was cured to obtain a cured product, and
the Tg, flexural modulus, and mode I fracture toughness of the
cured product were measured. As a result, the cured product had
significantly low toughness. From the result, it was found that the
cured product of Comparative Example 1 was poor in toughness.
Comparative Examples 2 to 5
[0181] Epoxy resin compositions were prepared using the resin raw
materials shown in Table 5, and the initial viscosity of each of
the epoxy resin compositions at 70.degree. C. was measured. As a
result, all the epoxy resin compositions had sufficiently low
viscosity. Then, the epoxy resin compositions were cured to obtain
cured products, and the Tg, flexural modulus, and mode I fracture
toughness of each of the cured products were measured. As a result,
these cured products had low toughness. From the result, it was
found that the cured products of Comparative Examples 2 to 5 were
poor in toughness. Thin sections of the cured products were cut by
a microtome and were observed using a transmission microscope. As a
result, many aggregates of core-shell polymer particles were
observed in the thin sections.
Comparative Example 6
[0182] An epoxy resin composition was prepared using the resin raw
materials shown in Table 5, and the initial viscosity of the epoxy
resin composition at 70.degree. C. was measured. As a result, the
epoxy resin composition had sufficiently low viscosity. Then, the
epoxy resin composition was cured to obtain a cured product, and
the Tg, flexural modulus, and mode I fracture toughness of the
cured product were measured. As a result, the cured product had
significantly low elastic modulus. From the result, it was found
that the cured product of Comparative Example 6 was poor inelastic
modulus.
Comparative Example 7
[0183] An epoxy resin composition was prepared using the resin raw
materials shown in Table 5. However, the viscosity of the epoxy
resin composition could not be measured because its curing agent
remained as crystals. If this epoxy resin composition is used in
RTM, there is a fear that the crystals of the curing agent cannot
pass through the gaps between carbon fibers and therefore part of
the epoxy resin composition is poorly cured.
Comparative Example 8
[0184] An epoxy resin composition was prepared using the resin raw
materials shown in Table 5, and the initial viscosity of the epoxy
resin composition at 70.degree. C. was measured. As a result, the
epoxy resin composition had sufficiently low viscosity. Then, the
epoxy resin composition was cured to obtain a cured product, and
the Tg, flexural modulus, and mode I fracture toughness of the
cured product were measured. As a result, the cured product had low
Tg. From the result, it was found that the cured product of
Comparative Example 8 was poor in Tg.
Comparative Example 9
[0185] An epoxy resin composition was prepared using the resin raw
materials shown in Table 5, and the initial viscosity of the epoxy
resin composition at 70.degree. C. was measured. As a result, the
epoxy resin composition had sufficiently low viscosity. Then, the
epoxy resin composition was cured to obtain a cured product, and
the Tg, flexural modulus, and mode I fracture toughness of the
cured product were measured. As a result, the cured product had low
Tg. From the result, it was found that the cured product of
Comparative Example 9 was poor in Tg.
TABLE-US-00005 TABLE 5 Unit of resin raw material content: part(s)
by mass Compar- Compar- Compar- Compar- Compar- ative ative ative
ative ative example 1 example 2 example 3 example 4 example 5
Compo- GAN (manufactured by Nippon Kayaku Co., 30 30 30 30 30 nent
Ltd.) (A) N,N-diglycidyl aniline Other "jER" 825 (manufactured by
Japan Epoxy 70 70 70 70 70 Epoxy Resins Co., Ltd.) Resins
Diglycidyl ether of bisphenol A Compo- "jER Cure" W (manufactured
by Japan Epoxy 28.8 28.8 28.8 28.8 28.8 nent Resins Co., Ltd.) (B)
Mixture of 2,4-diethyl-6-methyl-1,3-phenylenediamine and
4,6-diethyl-2-methyl-1,3-phenylenediamine Other "Seikacure" S
(manufactured by Seika -- -- -- -- -- amine Corporation) curing
4,4'-diaminodiphenylsulfone agent aniline (manufactured by Tokyo
Chemical -- -- -- -- -- Industry Co., Ltd.) m-xylylene diamine
(manufactured by Tokyo -- -- -- -- -- Chemical Industry Co., Ltd.)
Compo- "kane Ace" MX125 (manufactured by Kaneka -- -- -- -- -- nent
Corporation) (C) Modified with epoxy groups, Volume-average
particle size: 100 nm Value within [ ]: Core-shell polymer particle
content Other "Paraloid" EXL-2655 (manufactured by -- 5 10 -- --
Core- Kureha Corporation) [5] [10] shell Unmodified with epoxy
groups, polymer Volume-average particle size: 100 nm particle Value
within [ ]: Core-shell polymer content particle content
"Staphyloid" AC-3355 (manufactured by -- -- -- 5 10 Takeda
Pharmaceutical Co., Ltd.) [5] [10] Unmodified with epoxy groups,
Volume-average particle size: 500 nm Value within [ ]: Core-shell
polymer particle content Resin Initial viscosity at 70.degree. C.
[mPa s] 40 49 58 46 57 Prop- Tg [.degree. C.] 171 170 169 170 168
erties Flexural modulus [.degree. C.] 3.5 3.2 3.0 3.3 3.0 Mode I
fracture toughness (25.degree. C.) [J/m.sup.2] 46 136 142 115 144
Mode I fracture toughness (-54.degree. C.) [J/m.sup.2] 69 97 104 93
105 Compar- Compar- Compar- Compar- ative ative ative ative example
6 example 7 example 8 example 9 Compo- GAN (manufactured by Nippon
Kayaku Co., -- 30 30 30 nent Ltd.) (A) N,N-diglycidyl aniline Other
"jER" 825 (manufactured by Japan Epoxy 85 55 55 55 Epoxy Resins
Co., Ltd.) Resins Diglycidyl ether of bisphenol A Compo- "JER Cure"
W (manufactured by Japan Epoxy 25.5 -- -- -- nent Resins Co., Ltd.)
(B) Mixture of 2,4-diethyl-6-methyl-1,3-phenylenediamine and
4,6-diethyl-2-methyl-1,3-phenylenediamine Other "Seikacure" S
(manufactured by Seika -- 39.4 -- -- amine Corporation) curing
4,4'-diaminodiphenylsulfone agent aniline (manufactured by Tokyo
Chemical -- -- 29.6 -- Industry Co., Ltd.) m-xylylene diamine
(manufactured by Tokyo -- -- -- 21.6 Chemical Industry Co., Ltd.)
Compo- "kane Ace" MX125 (manufactured by Kaneka 20 20 20 20 nent
Corporation) [5] [5] [5] [5] (C) Modified with epoxy groups,
Volume-average particle size: 100 nm Value within [ ]: Core-shell
polymer particle content Other "Paraloid" EXL-2655 (manufactured by
-- -- -- -- Core- Kureha Corporation) shell Unmodified with epoxy
groups, polymer Volume-average particle size: 100 nm particle Value
within [ ]: Core-shell polymer content particle content
"Staphyloid" AC-3355 (manufactured by -- -- -- -- Takeda
Pharmaceutical Co., Ltd.) Unmodified with epoxy groups,
Volume-average particle size: 500 nm Value within [ ]: Core-shell
polymer particle content Resin Initial viscosity at 70.degree. C.
[mPa s] 68 not 27 43 Prop- measured erties Tg [.degree. C.] 194 167
40 151 Flexural modulus [.degree. C.] 2.2 3.4 3.8 3.2 Mode I
fracture toughness (25.degree. C.) [J/m.sup.2] 207 220 143 148 Mode
I fracture toughness (-54.degree. C.) [J/m.sup.2] 228 249 167
174
Example 34
[0186] A fiber-reinforced composite material was produced by RTM
using the epoxy resin composition of Example 22 and the reinforcing
fiber substrate 1 having binder particles. As a result, a
high-quality molded product whose carbon fiber volume content was
56% was obtained. The Tg, 0.degree. compressive strength, and
open-hole tensile strength of the fiber-reinforced composite
material were measured and found to be excellent.
Example 35
[0187] A fiber-reinforced composite material was produced by RTM
using the epoxy resin composition of Example 22 and the reinforcing
fiber substrate 2 having binder particles. As a result, a
high-quality molded product whose carbon fiber volume content was
56% was obtained. The Tg, 0.degree. compressive strength, and
open-hole tensile strength of the fiber-reinforced composite
material were measured and found to be excellent. Particularly, the
0.degree. compressive strength of the fiber-reinforced composite
material was very high. From the result, it was found that the
fiber-reinforced composite material of Example 35 was particularly
excellent in 0.degree. compressive strength.
Example 36
[0188] A fiber-reinforced composite material was produced by RTM
using the epoxy resin composition of Example 22 and the reinforcing
fiber substrate 2 having binder particles while the inside of a
mold was evacuated by a vacuum pump connected to the mold. As a
result, a high-quality molded product whose carbon fiber volume
content was 56% was obtained. In Example 35, the length of time
required to inject the epoxy resin composition into the mold and
impregnate the reinforcing fiber substrate with the epoxy resin
composition was 11 minutes, but in Example 36, it was reduced to 7
minutes. The Tg, 0.degree. compressive strength, and open-hole
tensile strength of the fiber-reinforced composite material were
measured and found to be excellent. Particularly, the 0.degree.
compressive strength of the fiber-reinforced composite material was
very high. From the result, it was found that the fiber-reinforced
composite material of Example 36 was particularly excellent in
0.degree. compressive strength.
Example 37
[0189] A fiber-reinforced composite material was produced by RTM
using the epoxy resin composition of Example 22 and the reinforcing
fiber substrate 3 having binder particles. As a result, a
high-quality molded product whose carbon fiber volume content was
56% was obtained. The Tg, 0.degree. compressive strength, and
open-hole tensile strength of the fiber-reinforced composite
material were measured and found to be excellent. Particularly, the
0.degree. compressive strength of the fiber-reinforced composite
material was very high. From the result, it was found that the
fiber-reinforced composite material of Example 37 was particularly
excellent in 0.degree. compressive strength.
Comparative Example 10
[0190] A fiber-reinforced composite material was produced by RTM
using the epoxy resin composition of Comparative Example 1 and the
reinforcing fiber substrate 1 having binder particles. As a result,
a high-quality molded product whose carbon fiber volume content was
56% was obtained. The Tg, 0.degree. compressive strength, and
open-hole tensile strength of the fiber-reinforced composite
material were measured, and as a result, the open-hole tensile
strength was significantly low. From the result, it was found that
the fiber-reinforced composite material of Comparative Example 10
was excellent in Tg and 0.degree. compressive strength but poor in
open-hole tensile strength.
Comparative Example 11
[0191] A fiber-reinforced composite material was produced by RTM
using the epoxy resin composition of Comparative Example 6 and the
reinforcing fiber substrate 1 having binder particles. As a result,
a high-quality molded product whose carbon fiber volume content was
56% was obtained. The Tg, 0.degree. compressive strength, and
open-hole tensile strength of the fiber-reinforced composite
material were measured, and as a result, the 0.degree. compressive
strength was significantly low. From the result, it was found that
the fiber-reinforced composite material of Comparative Example 11
was excellent in Tg and open-hole tensile strength but poor in
0.degree. compressive strength.
TABLE-US-00006 TABLE 6 Unit of resin raw material content: part(s)
by mass Compar- Compar- ative ative Exam- Exam- Exam- Exam- example
example ple 34 ple 35 ple 36 ple 37 10 11 Epoxy Compo- GAN
(manufactured by Nippon Kayaku Co., Ltd.) 30 30 30 30 30 85 resin
nent N,N-diglycidyl aniline composi- (A) tions Compo- "Araldite"
MY721 (manufactured by Huntsman 25 25 25 25 -- -- nent Advanced
Materials) (C) N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl-
methane Other "jER" 825 (manufactured by Japan Epoxy Resins 30 30
30 30 70 -- Epoxy Co., Ltd.) Resins Diglycidyl ether of bisphenol A
Compo- "jER Cure" W (manufactured by Japan Epoxy Resins 34.6 34.6
34.6 34.6 28.8 25.5 nent Co., Ltd.) (B) Mixture of
2,4-diethyl-6-methyl-1,3-phenylenediamine and
4,6-diethyl-2-methyl-1,3-phenylenediamine Compo- "kane Ace" MX125
(manufactured by Kaneka -- -- -- -- -- 20 nent Corporation) [5] (C)
Modified with epoxy groups, Volume-average particle size: 100 nm
Value within [ ]: Core-shell polymer particle content "kane Ace"
MX416 (manufactured by Kaneka 20 20 20 20 -- -- Corporation) [5]
[5] [5] [5] Modified with epoxy groups, Volume-average particle
size: 100 nm Value within [ ]: Core-shell polymer particle content
Reinforcing fiber Sub- Sub- Sub- Sub- Sub- Sub- substrate strate 1
strate 2 strate 2 strate 3 strate 1 strate 1 Molding method Not Not
Evacuat- Not Not Not evacu- evacu- ed evacu- evacu- evacu- ated
ated ated ated ated Properties of Carbon fiber volume content [%]
56 56 56 56 56 56 fiber-reinforced Tg [.degree. C.] 180 181 181 182
172 194 composite 0.degree. compressive strength [MPa] 1330 1460
1490 1450 1260 890 material Open-hole tensile strength [MPa] 535
542 545 544 508 530
* * * * *