U.S. patent application number 16/970765 was filed with the patent office on 2021-04-01 for curable composition and fiber reinforced composite material.
This patent application is currently assigned to DIC Corporation. The applicant listed for this patent is DIC Corporation. Invention is credited to Makoto Kimura, Atsuko Kobayashi, Shigeki Matsui.
Application Number | 20210095066 16/970765 |
Document ID | / |
Family ID | 1000005301919 |
Filed Date | 2021-04-01 |
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United States Patent
Application |
20210095066 |
Kind Code |
A1 |
Kobayashi; Atsuko ; et
al. |
April 1, 2021 |
CURABLE COMPOSITION AND FIBER REINFORCED COMPOSITE MATERIAL
Abstract
The present invention provides a curable composition comprising
a urethane-modified epoxy resin (A) as an essential component of a
main material, and an acid anhydride (B) as an essential component
of a curing agent, wherein the urethane-modified epoxy resin (A) is
a reaction product of a polyisocyanate compound (a1), a polyester
polyol (a2), and a hydroxyl group-containing epoxy resin (a3) as
essential reaction raw materials. The curable composition of the
invention is advantageous in that a cured product having excellent
fracture toughness and excellent tensile strength can be formed
from the composition.
Inventors: |
Kobayashi; Atsuko;
(Ichihara-shi, JP) ; Matsui; Shigeki;
(Ichihara-shi, JP) ; Kimura; Makoto;
(Ichihara-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DIC Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
DIC Corporation
Tokyo
JP
|
Family ID: |
1000005301919 |
Appl. No.: |
16/970765 |
Filed: |
February 12, 2019 |
PCT Filed: |
February 12, 2019 |
PCT NO: |
PCT/JP2019/004795 |
371 Date: |
August 18, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 2203/30 20130101;
C08J 2363/02 20130101; C08L 2312/00 20130101; C08G 18/12 20130101;
C08J 5/042 20130101; C08G 18/4238 20130101; C08L 63/00 20130101;
C08G 59/245 20130101; C08G 18/58 20130101; C08G 59/28 20130101;
C08G 18/755 20130101; C08G 59/4223 20130101 |
International
Class: |
C08G 18/58 20060101
C08G018/58; C08L 63/00 20060101 C08L063/00; C08G 59/28 20060101
C08G059/28; C08G 59/24 20060101 C08G059/24; C08G 59/42 20060101
C08G059/42; C08J 5/04 20060101 C08J005/04; C08G 18/12 20060101
C08G018/12; C08G 18/75 20060101 C08G018/75; C08G 18/42 20060101
C08G018/42 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2018 |
JP |
2018-027835 |
Claims
1. A curable composition comprising a urethane-modified epoxy resin
(A) as an essential component of a main material, and an acid
anhydride (B) as an essential component of a curing agent, wherein
the urethane-modified epoxy resin (A) is a reaction product of a
polyisocyanate compound (a1), a polyester polyol (a2), and a
hydroxyl group-containing epoxy resin (a3) as essential reaction
raw materials.
2. The curable composition according to claim 1, wherein the
polyester polyol (a2) is a polyester diol having a number average
molecular weight (Mn) of 500 to 4,000.
3. The curable composition according to claim 1, wherein a linear
aliphatic diol compound having 2 to 8 carbon atoms constitutes 80%
by mass or more of a polyol raw material for the polyester polyol
(a2).
4. The curable composition according to claim 1, wherein the
polyisocyanate compound (a1) has an isocyanate group content of 35%
by mass or more.
5. The curable composition according to claim 1, wherein the
proportion of the mass of the urethane-modified epoxy resin (A) to
the total mass of the epoxy resin component contained in the main
material is in the range of 30 to 100% by mass.
6. The curable composition according to claim 1, wherein the main
material contains an aliphatic epoxy resin, in addition to the
urethane-modified epoxy resin (A).
7. The curable composition according to claim 6, wherein the mass
ratio of the urethane-modified epoxy resin (A) and the aliphatic
epoxy resin [urethane-modified epoxy resin (A)/aliphatic epoxy
resin] is in the range of 30/70 to 100/0.
8. A cured product of the curable composition according to claim
1.
9. A fiber-reinforced composite material comprising the curable
composition according to claim 1 and a reinforcing fiber as
essential components.
10. A fiber-reinforced resin molded article comprising the cured
product according to claim 8 and a reinforcing fiber as essential
components.
11. A method for producing a fiber-reinforced resin molded article,
the method comprising heat-curing the fiber-reinforced composite
material according to claim 9.
12. A cured product of the curable composition according to claim
2.
13. A cured product of the curable composition according to claim
3.
14. A cured product of the curable composition according to claim
4.
15. A cured product of the curable composition according to claim
5.
16. A cured product of the curable composition according to claim
6.
17. A fiber-reinforced composite material comprising the curable
composition according to claim 2 and a reinforcing fiber as
essential components.
18. A fiber-reinforced composite material comprising the curable
composition according to claim 3 and a reinforcing fiber as
essential components.
19. A fiber-reinforced composite material comprising the curable
composition according to claim 4 and a reinforcing fiber as
essential components.
20. A fiber-reinforced composite material comprising the curable
composition according to claim 5 and a reinforcing fiber as
essential components.
Description
TECHNICAL FIELD
[0001] The present invention relates to a curable composition
advantageous in that a cured product obtained therefrom has
excellent fracture toughness and excellent tensile strength and a
cured product thereof, a fiber-reinforced composite material, a
fiber-reinforced resin molded article, and a method for producing a
fiber-reinforced resin molded article.
BACKGROUND ART
[0002] A fiber-reinforced resin molded article which is reinforced
with a reinforcing fiber has drawn attention due to advantageous
features of being lightweight and having excellent mechanical
strength, and the use of the fiber-reinforced resin molded article
is expanding in the application of various structures including
housings and various members for automobiles, aircrafts, vessels,
and the like. The fiber-reinforced resin molded article can be
produced by molding a fiber-reinforced composite material by a
molding method, such as a filament winding method, a press molding
method, a hand lay-up method, a pultrusion method, or an RTM
method.
[0003] The fiber-reinforced composite material is obtained by
impregnating a reinforcing fiber with a resin. The resin used in
the fiber-reinforced composite material is required to have
excellent stability at ordinary room temperature and to provide a
cured product having excellent durability and strength, and
therefore a thermosetting resin is generally used. Further, as
mentioned above, the resin is used in the fiber-reinforced
composite material in such a way that a reinforcing fiber is
impregnated with the resin, and hence the resin having a viscosity
as low as possible is advantageous to the impregnation step.
[0004] Further, the properties required for the resin vary
depending on the use of the fiber-reinforced resin molded article.
For example, when used in structural parts for an engine and the
like or electric wire core materials, the fiber-reinforced resin
molded article must be durable in a severe use environment for a
long term, and therefore demands a resin such that a cured product
thereof has excellent heat resistance and excellent mechanical
strength. Meanwhile, when used in a housing and members for a
vessel, the fiber-reinforced resin molded article must be durable
in the long-term use in water, and therefore demands a resin such
that a cured product thereof has excellent low water-absorption
properties as well as excellent mechanical strength.
[0005] As a resin composition for a fiber-reinforced composite
material, for example, an epoxy resin composition containing a main
material containing a bisphenol epoxy resin and a curing agent
containing an acid anhydride has been widely known (see, for
example, PTL 1). Such an epoxy resin composition has features that
it has high impregnation properties for a reinforcing fiber, and
that a cured product obtained from the composition has excellent
heat resistance and the like; however, the epoxy resin composition
cannot achieve satisfactory mechanical strength evaluated by a
fracture toughness test and a tensile strength test.
CITATION LIST
Patent Literature
[0006] PTL 1: JP-A-2010-163573
SUMMARY OF INVENTION
Technical Problem
[0007] Accordingly, an object to be achieved by the present
invention is to provide a curable composition advantageous in that
a cured product obtained therefrom has excellent fracture toughness
and excellent tensile strength and a cured product thereof, a
fiber-reinforced composite material, a fiber-reinforced resin
molded article, and a method for producing a fiber-reinforced resin
molded article.
Solution to Problem
[0008] The present inventors have conducted extensive and intensive
studies with a view toward solving the above-mentioned problems. As
a result, it has been found that the problems can be solved by
using, as an epoxy resin component, a urethane-modified epoxy resin
obtained from a polyisocyanate compound, a polyester polyol, and a
hydroxyl group-containing epoxy resin (a3) as essential reaction
raw materials, and using an acid anhydride as a curing agent, and
the present invention has been completed.
[0009] Specifically, the present invention provides a curable
composition containing a urethane-modified epoxy resin (A) as an
essential component of a main material, and an acid anhydride (B)
as an essential component of a curing agent, wherein the
urethane-modified epoxy resin (A) is a reaction product of a
polyisocyanate compound (a1), a polyester polyol (a2), and a
hydroxyl group-containing epoxy resin (a3) as essential reaction
raw materials.
[0010] The present invention further provides a cured product of
the above-mentioned curable composition, a fiber-reinforced
composite material using the curable composition, a
fiber-reinforced resin molded article, and a method for producing a
fiber-reinforced resin molded article.
Advantageous Effects of Invention
[0011] In the present invention, there can be provided a curable
composition advantageous in that a cured product obtained therefrom
has excellent fracture toughness and excellent tensile strength and
a cured product thereof, a fiber-reinforced composite material, a
fiber-reinforced resin molded article, and a method for producing a
fiber-reinforced resin molded article.
DESCRIPTION OF EMBODIMENTS
[0012] The curable composition of the present invention is a
curable composition which contains a urethane-modified epoxy resin
(A) as an essential component of a main material, and an acid
anhydride (B) as an essential component of a curing agent, wherein
the urethane-modified epoxy resin (A) is a reaction product of a
polyisocyanate compound (a1), a polyester polyol (a2), and a
hydroxyl group-containing epoxy resin (a3) as essential reaction
raw materials.
[0013] With respect to the polyisocyanate compound (a1) which is
the reaction raw material of the urethane-modified epoxy resin (A),
examples of the compounds include aliphatic diisocyanate compounds,
such as butane diisocyanate, hexamethylene diisocyanate,
2,2,4-trimethylhexamethylene diisocyanate, and
2,4,4-trimethylhexamethylene diisocyanate; alicyclic diisocyanate
compounds, such as norbornane diisocyanate, isophorone
diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated
diphenylmethane diisocyanate; aromatic diisocyanate compounds, such
as tolylene diisocyanate, xylylene diisocyanate,
tetramethylxylylene diisocyanate, diphenylmethane diisocyanate, and
1,5-naphthalene diisocyanate; a polymethylene polyphenyl
polyisocyanate having a repeating structure represented by the
structural formula (1) below; and an isocyanurate modification
product, a biuret modification product, and an allophanate
modification product of the above compounds. These maybe used
individually or in combination.
##STR00001##
[0014] In the formula, each R.sup.1 is independently a hydrogen
atom or a hydrocarbon group having 1 to 6 carbon atoms, each
R.sup.2 is independently an alkyl group having 1 to 4 carbon atoms
or a bonding site for linking the structure portion represented by
the structural formula (1) through a methylene group indicated by
symbol *, m is 0 or an integer of 1 to 3, and 1 is an integer of 1
or more.
[0015] With respect to the polyisocyanate compound (a1), in view of
obtaining a curable composition advantageous not only in that a
cured product obtained therefrom has high fracture toughness and
high tensile strength, but also in that the composition exhibits
excellent impregnation properties for a reinforcing fiber,
preferred are diisocyanate compounds, and more preferred are
diisocyanate compounds having a cyclic structure in the molecular
structure thereof, that is, alicyclic diisocyanates or aromatic
diisocyanates are more preferred. Further, those having an
isocyanate group content of 35% by mass or more are especially
preferred. When two or more types of the polyisocyanate compounds
(a1) are used in combination, it is preferred that a diisocyanate
compound constitutes 80% by mass or more of the polyisocyanate
compounds (a1), and it is more preferred that an alicyclic
diisocyanate or an aromatic diisocyanate constitutes 80% by mass or
more of the polyisocyanate compounds (a1).
[0016] With respect to the polyester polyol (a2), for example,
there can be mentioned a polyester polyol obtained from a polybasic
acid raw material and a polyol raw material as reaction raw
materials, and a lactone compound may be contained as part of the
reaction raw materials. Specific examples of the polybasic acid raw
materials include aliphatic dicarboxylic acid compounds, such as
oxalic acid, malonic acid, succinic acid, maleic acid, fumaric
acid, glutaric acid, adipic acid, pimelic acid, suberic acid,
azelaic acid, and sebacic acid, and derivatives thereof, such as
acid anhydrides, acid halides, and alkyl esters of these compounds;
[0017] alicyclic dicarboxylic acid compounds, such as
tetrahydrophthalic acid, hexahydrophthalic acid, and
methyltetrahydrophthalic acid, and derivatives thereof, such as
acid anhydrides, acid halides, and alkyl esters of these compounds;
[0018] aromatic dicarboxylic acid compounds, such as phthalic acid,
isophthalic acid, and terephthalic acid, and derivatives thereof,
such as acid anhydrides, acid halides, and alkyl esters of these
compounds; [0019] tri- or more polyfunctional aliphatic
polycarboxylic acid compounds, such as 1,2,5-hexanetricarboxylic
acid, and derivatives thereof, such as acid anhydrides, acid
halides, and alkyl esters of these compounds; [0020] tri- or more
polyfunctional alicyclic polycarboxylic acid compounds, such as
1,2,4-cyclohexanetricarboxylic acid, and derivatives thereof, such
as acid anhydrides, acid halides, and alkyl esters of these
compounds; and [0021] tri- or more polyfunctional aromatic
polycarboxylic acid compounds, such as trimellitic acid,
trimellitic anhydride, 1,2,5-benzenetricarboxylic acid, and
2,5,7-naphthalenetricarboxylic acid, and derivatives thereof, such
as acid anhydrides, acid halides, and alkyl esters of these
compounds. These may be used individually or in combination.
[0022] Of these, in view of obtaining a curable composition
advantageous not only in that a cured product obtained therefrom
has high fracture toughness and high tensile strength, but also in
that the composition exhibits excellent impregnation properties
fora reinforcing fiber, preferred are bifunctional compounds, more
preferred are the above-mentioned aliphatic dicarboxylic acid
compounds and derivatives thereof, such as acid anhydrides, acid
halides, and alkyl esters of the above compounds, and further
especially preferred are the aliphatic dicarboxylic acid compounds
having 4 to 10 carbon atoms and derivatives thereof, such as acid
anhydrides, acid halides, and alkyl esters of the above compounds.
When two or more types of the polybasic acid raw materials are used
in combination, it is preferred that a bifunctional compound
constitutes 80% by mass or more of the polybasic acid raw
materials, it is more preferred that the above-mentioned aliphatic
dicarboxylic acid compound or a derivative thereof, such as an acid
anhydride, an acid halide, or an alkyl ester of the compound,
constitutes 80% by mass or more of the polybasic acid raw
materials, and further it is especially preferred that the
aliphatic dicarboxylic acid compound having 4 to 10 carbon atoms or
a derivative thereof, such as an acid anhydride, an acid halide, or
an alkyl ester of the compound, constitutes 80% by mass or more of
the polybasic acid raw materials.
[0023] Specific examples of the polyol raw materials include linear
aliphatic diol compounds, such as ethylene glycol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol,
1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and
1,12-dodecanediol; [0024] aliphatic diol compounds having a
branched chain, such as propylene glycol, 2-methyl-1,3-propanediol,
neopentyl glycol, 2-ethyl-1,3-propanediol, 2-methyl-1,4-butanediol,
2-ethyl-2-methyl-1,3-propanediol, 2-ethylbutane-14-butanediol,
2,3-dimethyl-1,4-butanediol, 3-methyl-1,5-pentanediol,
2,4-dimethyl-1,5-pentanediol, 3,3-dimethylpentane-1,5-diol,
2,2-diethyl-1,3-propanediol, 3-propylpentane-1,5-diol,
2,2-diethyl-1,4-butanediol, 2,4-diethyl-1,5-pentanediol,
2,2-dipropyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, and
2,5-diethyl-1,6-hexanediol; [0025] alicyclic structure-containing
diol compounds, such as cyclohexanediol and cyclohexanedimethanol;
[0026] aromatic ring-containing diol compounds, such as biphenol
and bisphenol; [0027] tri- or more polyfunctional aliphatic polyol
compounds, such as trimethylolethane, trimethylolpropane, glycerol,
hexanetriol, and pentaerythritol; [0028] tri- or more
polyfunctional aromatic polyol compounds, such as
trihydroxybenzene; [0029] polyether-modified polyol compounds
obtained by ring-opening polymerization of the above-mentioned diol
or tri- or more polyfunctional polyol compound and a cyclic ether
compound, such as ethylene oxide, propylene oxide, tetrahydrofuran,
ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether,
phenyl glycidyl ether, or allyl glycidyl ether; and [0030]
polycarbonate polyol. These may be used individually or in
combination.
[0031] Of these, in view of obtaining a curable composition
advantageous not only in that a cured product obtained therefrom
has high fracture toughness and high tensile strength, but also in
that the composition exhibits excellent impregnation properties
fora reinforcing fiber, preferred are bifunctional compounds, more
preferred are the above-mentioned aliphatic diol compounds, and
further especially preferred are the linear aliphatic diol
compounds having 2 to 8 carbon atoms. When two or more types of the
polyol raw materials are used in combination, it is preferred that
a bifunctional compound constitutes 80% by mass or more of the
polyol raw materials, it is more preferred that the above-mentioned
aliphatic diol compound constitutes 80% by mass or more of the
polyol raw materials, and further it is especially preferred that
the linear aliphatic diol compound having 2 to 8 carbon atoms
constitutes 80% by mass or more of the polyol raw materials.
[0032] In view of obtaining a curable composition advantageous not
only in that a cured product obtained therefrom has high fracture
toughness and high tensile strength, but also in that the
composition exhibits excellent impregnation properties for a
reinforcing fiber, it is preferred that the polyester polyol (a2)
is a polyester diol. Further, the polyester polyol (a2) preferably
has a number average molecular weight (Mn) in the range of 500 to
4,000, more preferably in the range of 1,000 to 3,000. In the
present invention, the number average molecular weight (Mn) of the
polyester polyol (a2) is a value published by the manufacturer or a
value measured by gel permeation chromatography (GPC) under the
conditions shown below. [0033] Measuring apparatus: HLC-8220GPC,
manufactured by Tosoh Corp. Columns: Guard column "HXL-L",
manufactured by Tosoh Corp.
[0034] +"TSK-GEL G2000HXL", manufactured by Tosoh Corp.
[0035] +"TSK-GEL G2000HXL", manufactured by Tosoh Corp.
[0036] +"TSK-GEL G3000HXL", manufactured by Tosoh Corp.
[0037] +"TSK-GEL G4000HXL", manufactured by Tosoh Corp. [0038]
Detector: RI (differential refractometer) [0039] Conditions for
measurement:
[0040] Column temperature: 40.degree. C.
[0041] Solvent: THF
[0042] Flow rate: 1.0 ml/min [0043] Standard: Using a calibration
curve prepared from polystyrene standard samples. [0044] Sample: A
0.1% by mass THF solution, in terms of the amount of the resin
solids, which has been subjected to filtration using a microfilter
(sample amount per injection: 200 .mu.l)
[0045] With respect to the hydroxyl group-containing epoxy resin
(a3), there is no particular limitation as long as the resin has a
hydroxyl group and a glycidyl group in the molecular structure
thereof. Further, a single type of the hydroxyl group-containing
epoxy resin (a3) may be individually used, or two or more types of
the hydroxyl group-containing epoxy resins (a3) may be used in
combination. Especially, in view of obtaining a curable composition
advantageous not only in that a cured product obtained therefrom
has high fracture toughness and high tensile strength, but also in
that the composition exhibits excellent impregnation properties for
a reinforcing fiber, preferred is a hydroxyl group-containing
bifunctional epoxy resin obtained by glycidyl etherification of a
diol compound.
[0046] The theoretical structure of the hydroxyl group-containing
bifunctional epoxy resin can be represented by, for example, the
following structural formula (2):
##STR00002##
wherein X is a structure portion derived from a diol compound, n is
0 or an integer of 1 or more, and an average of n's is a value of
more than 0.
[0047] Examples of the diol compounds include aliphatic diol
compounds, such as ethylene glycol, propylene glycol,
1,3-propanediol, 2-methylpropanediol,
1,2,2-trimethyl-1,3-propanediol,
2,2-dimethyl-3-isopropyl-1,3-propanediol, 1,4-butanediol,
1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol,
3-methyl-1,5-pentanediol, neopentyl glycol, 1,6-hexanediol,
1,4-bis(hydroxymethyl)cyclohexane, and
2,2,4-trimethyl-1,3-pentanediol; and aromatic diol compounds, such
as biphenol, tetramethylbiphenol, bisphenol A, bisphenol AP,
bisphenol B, bisphenol BP, bisphenol C, bisphenol E, bisphenol F,
and bisphenol S.
[0048] Of these, in view of obtaining a curable composition
advantageous in that a cured product obtained therefrom has high
fracture toughness and high tensile strength as well as excellent
heat resistance and the like, a hydroxyl group-containing aromatic
bifunctional epoxy resin obtained using the above-mentioned
aromatic diol compound is preferably used. When two or more types
of the hydroxyl group-containing epoxy resins (a3) are used in
combination, the proportion of the mass of the hydroxyl
group-containing aromatic bifunctional epoxy resin to the total
mass of the hydroxyl group-containing epoxy resins (a3) is
preferably 35% by mass or more, more preferably in the range of 40
to 90% by mass.
[0049] The hydroxyl group-containing epoxy resin (a3) preferably
has an epoxy equivalent in the range of 100 to 400 g/equivalent,
more preferably in the range of 100 to 250 g/equivalent. Further,
the hydroxyl group-containing epoxy resin (a3) more preferably has
a hydroxyl equivalent in the range of 600 to 3,500
g/equivalent.
[0050] In the present invention, the hydroxyl equivalent of the
hydroxyl group-containing epoxy resin (a3) is a value measured by
the method described below.
[0051] 1. About 100 g of the hydroxyl group-containing epoxy resin
(a3) and 25 mL of anhydrous dimethylformaldehyde were placed in a
flask, and the resin was dissolved.
[0052] 2. About 30 mg of dibutyltin laurate and 20 mL of an
anhydrous toluene solution of phenyl isocyanate (1 mol/L) were
added to the resultant solution, and the flask was dipped in a
water bath at 50.degree. C. and the resultant mixture was stirred
for 60 minutes.
[0053] 3. 20 mL of an anhydrous toluene solution of dibutylamine (2
mol/L) was added and the resultant mixture was stirred at room
temperature for 30 minutes.
[0054] 4. 30 mL of methyl cellosolve and 0.5 mL of a Bromocresol
Green indicator were added, and the resultant mixture was subjected
to titration using a methyl cellosolve solution of perchloric acid
(1 mol/L). A blank measurement was also conducted.
[0055] 5. A hydroxyl equivalent of the hydroxyl group-containing
epoxy resin (a3) was calculated from the following formula.
(Hydroxyl equivalent(g/equivalent))=1,000.times.(Amount[g] of the
sample of hydroxyl group-containing epoxy
resin(a3))/[(Concentration[1 mol/L] of the methyl cellosolve
solution of perchloric acid).times.{(Titer[mL] of the solution of
hydroxyl group-containing epoxy resin(a3))-(Titer[mL] of
blank)}]
[0056] The urethane-modified epoxy resin (A) uses the
above-mentioned polyisocyanate compound (a1), polyester polyol
(a2), and hydroxyl group-containing epoxy resin (a3) as essential
reaction raw materials, but an additional reaction raw material
other than these raw materials may be further used. Examples of
additional reaction raw materials include polyol compounds other
than the above-mentioned polyester polyol (a2), such as an
aliphatic polyol, an aromatic polyol, a polyether polyol, a
polyolefin polyol, and a polycarbonate polyol. When an additional
reaction raw material is used, in view of satisfactorily exhibiting
effects of the present invention such that a cured product of the
curable composition has excellent fracture toughness and excellent
tensile strength, the proportion of the total mass of the
polyisocyanate compound (a1), the polyester polyol (a2), and the
hydroxyl group-containing epoxy resin (a3) to the total mass of the
reaction raw materials for the urethane-modified epoxy resin (A) is
preferably 70% by mass or more, more preferably 90% by mass or
more.
[0057] With respect to the method for producing the
urethane-modified epoxy resin (A), there is no particular
limitation as long as the above-mentioned polyisocyanate compound
(a1), polyester polyol (a2), and hydroxyl group-containing epoxy
resin (a3) are used as essential reaction raw materials, and the
urethane-modified epoxy resin (A) can be produced by any method. As
examples of the method for producing the urethane-modified epoxy
resin (A), there can be mentioned the following methods.
[0058] Method 1: a method in which all the reaction raw materials
are charged at the same time and reacted with each other.
[0059] Method 2: a method in which the polyisocyanate compound
(a1), the polyester polyol (a2), and an additional polyol compound
optionally used are reacted with each other to obtain an isocyanate
group-containing intermediate, and then the hydroxyl
group-containing epoxy resin (a3) is reacted with the
intermediate.
[0060] Method 3: a method in which the polyisocyanate compound (a1)
and the hydroxyl group-containing epoxy resin (a3) are reacted with
each other to obtain an isocyanate group-containing intermediate,
and then the polyester polyol (a2) and an additional polyol
compound optionally used are reacted with the intermediate.
[0061] Method 4: a method in which the polyisocyanate compound
(a1), part of or all of the polyester polyol (a2), part of or all
of the hydroxyl group-containing epoxy resin (a3), and part of or
all of an additional polyol compound optionally used are reacted
with each other to obtain an isocyanate group-containing
intermediate, and then the rest of the polyester polyol (a2), the
hydroxyl group-containing epoxy resin (a3), and the additional
polyol compound is reacted with the intermediate.
[0062] In any of the methods 1 to 4 above, in view of obtaining the
curable composition having excellent storage stability and the
like, the molar ratio of the isocyanate group and the hydroxyl
group in the reaction raw materials [(NCO)/(OH)] is preferably in
the range of 1/0.95 to 1/5.0.
[0063] Further, in view of exhibiting more remarkable effects such
that a cured product of the curable composition has excellent
fracture toughness and excellent tensile strength, the proportion
of the mass of the polyester polyol (a2) to the total mass of the
reaction raw materials is preferably in the range of 5 to 50% by
mass, more preferably in the range of 15 to 35% by mass.
[0064] In view of obtaining a curable composition advantageous not
only in that a cured product obtained therefrom has high fracture
toughness and high tensile strength, but also in that the
composition exhibits excellent curing properties and excellent
impregnation properties fora reinforcing fiber, the
urethane-modified epoxy resin (A) preferably has an epoxy
equivalent in the range of 150 to 300 g/equivalent.
[0065] The main material in the curable composition of the
invention may contain an additional component, in addition to the
urethane-modified epoxy resin (A). As examples of additional
components, there can be mentioned additional epoxy resins other
than the urethane-modified epoxy resin (A).
[0066] Examples of the additional epoxy resins include
diglycidyloxybenzene, diglycidyloxynaphthalene, an aliphatic epoxy
resin, a biphenol epoxy resin, a bisphenol epoxy resin, a novolak
epoxy resin, a triphenolmethane epoxy resin, a tetraphenolethane
epoxy resin, a phenol- or naphthol aralkyl epoxy resin, a
phenylene- or naphthylene ether epoxy resin, a
dicyclopentadiene-phenol addition reaction product epoxy resin, a
phenolic hydroxyl group-containing compound-alkoxy group-containing
aromatic compound copolycondensation epoxy resin, a glycidylamine
epoxy resin, and naphthalene skeleton-containing epoxy resins other
than these resins.
[0067] With respect to the aliphatic epoxy resin, for example,
there can be mentioned glycidyl etherification products of various
aliphatic polyol compounds. A single type of the aliphatic epoxy
resin may be individually used, or two or more types of the
aliphatic epoxy resins may be used in combination. Examples of the
aliphatic polyol compounds include aliphatic diol compounds, such
as ethylene glycol, propylene glycol, 1,3-propanediol,
2-methylpropanediol, 1,2,2-trimethyl-1,3-propanediol,
2,2-dimethyl-3-isopropyl-1,3-propanediol, 1,4-butanediol,
1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol,
3-methyl-1,5-pentanediol, neopentyl glycol, 1,6-hexanediol,
1,4-bis(hydroxymethyl)cyclohexane, and
2,2,4-trimethyl-1,3-pentanediol; and tri- or more polyfunctional
aliphatic polyol compounds, such as trimethylolethane,
trimethylolpropane, glycerol, hexanetriol, pentaerythritol,
ditrimethylolpropane, and dipentaerythritol.
[0068] With respect to the biphenol epoxy resin, for example, there
can be mentioned epoxy resins obtained by polyglycidyl
etherification of a biphenol compound, such as biphenol or
tetramethylbiphenol, using an epihalohydrin. Of these, preferred
are those having an epoxy equivalent in the range of 150 to 200
g/eq.
[0069] With respect to the bisphenol epoxy resin, for example,
there can be mentioned epoxy resins obtained by polyglycidyl
etherification of a bisphenol compound, such as bisphenol A,
bisphenol F, or bisphenol S, using an epihalohydrin. Of these,
preferred are those having an epoxy equivalent in the range of 158
to 200 g/eq.
[0070] With respect to the novolak epoxy resin, for example, there
can be mentioned epoxy resins obtained by polyglycidyl
etherification, using an epihalohydrin, of a novolak resin formed
from one phenol compound or two or more phenol compounds, such as
phenol, cresol, naphthol, bisphenol, or biphenol.
[0071] With respect to the triphenolmethane epoxy resin, for
example, there can be mentioned epoxy resins having a structure
portion represented by the following structural formula (3) as
repeating structure units.
##STR00003##
[0072] In the formula, each of R.sup.3 and R.sup.4 is independently
a hydrogen atom or a bonding site for linking the structure portion
represented by the structural formula (3) through a methine group
indicated by symbol *, and n is an integer of 1 or more.
[0073] With respect to the phenol- or naphthol aralkyl epoxy resin,
for example, there can be mentioned epoxy resins having a molecular
structure in which a glycidyloxybenzene or glycidyloxynaphthalene
structure is bonded through a structure portion represented by any
one of the following structural formulae (4-1) to (4-3).
##STR00004##
[0074] In the formula, X is an alkylene group having 2 to 6 carbon
atoms, an ether linkage, a carbonyl group, a carbonyloxy group, a
sulfide group, or a sulfonic group.
[0075] With respect to the naphthalene skeleton-containing epoxy
resin, for example, there can be mentioned epoxy compounds
represented by any one of the following structural formulae (5-1)
to (5-3).
##STR00005##
[0076] Among the above-mentioned additional epoxy resins, in view
of obtaining a curable composition advantageous not only in that a
cured product obtained therefrom has high fracture toughness and
high tensile strength, but also in that the composition exhibits
excellent impregnation properties for a reinforcing fiber,
preferred is an aliphatic epoxy resin, a bisphenol epoxy resin, a
triphenolmethane epoxy resin, a glycidylamine epoxy resin, or a
naphthalene skeleton-containing epoxy resin, more preferred is an
aliphatic epoxy resin or a bisphenol epoxy resin, and especially
preferred is an aliphatic epoxy resin.
[0077] The amount of each epoxy resin contained in the main
material is not particularly limited, and can be appropriately
controlled according to the desired performance, the use and the
like. It is more preferred that the proportion of the mass of the
urethane-modified epoxy resin (A) to the total mass of the epoxy
resin component is in the range of 30 to 100% by mass. When an
aliphatic epoxy resin is used as the additional epoxy resin, the
mass ratio of the epoxy resins [urethane-modified epoxy resin
(A)/aliphatic epoxy resin] is preferably in the range of 30/70 to
100/0.
[0078] The curing agent in the curable composition of the invention
contains an acid anhydride (B) as an essential component. A single
type of the acid anhydride (B) may be individually used, or two or
more types of the acid anhydrides (B) may be used in combination.
Specific examples of acid anhydrides (B) include tetrahydrophthalic
anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic
anhydride, methylhexahydrophthalic anhydride,
methyl-endo-ethylenetetrahydrophthalic anhydride, a
trialkyltetrahydrophthalic anhydride, methyl nadic anhydride,
phthalic anhydride, trimellitic anhydride, pyromellitic anhydride,
and maleic anhydride.
[0079] In the present invention, an additional curing agent or
curing accelerator (B') may be used in combination with the acid
anhydride (B). With respect to the additional curing agent or
curing accelerator (B'), one which is generally used as a curing
accelerator for an epoxy resin and an acid anhydride can be used in
the present invention, and specific examples of such curing agents
or curing accelerators include an imidazole derivative, a tertiary
amine, an amine complex salt, an amide compound, a phenolic
hydroxyl group-containing compound or phenolic resin, a phosphorus
compound, a urea derivative, an organic acid metal salt, and a
Lewis acid.
[0080] In the curable composition of the invention, with respect to
the ratio of the amounts of the main material and curing agent
incorporated is not particularly limited, and can be appropriately
controlled according to the desired performance of the cured
product and the use. As an example of the amounts of the main
material and curing agent incorporated, it is preferred that,
relative to 1 mol of the epoxy group of the epoxy resin component
in the main material, the total of the acid anhydride group of the
acid anhydride (B) in the curing agent is in the range of 0.5 to
1.05 mol.
[0081] Further, when the additional curing agent or curing
accelerator (B') is used, the amount of the additional curing agent
or curing accelerator incorporated is not particularly limited, and
can be appropriately controlled according to the desired
performance of the cured product and the use. Especially, it is
preferred that the additional curing agent or curing accelerator
(B') is incorporated into the curable composition in an amount of
0.1 to 30% by mass. The additional curing agent or curing
accelerator (B') may be blended with the curing agent, together
with the acid anhydride (B), or may be added when blending the main
material and the curing agent.
[0082] The curable composition of the invention may contain an
additional resin component or various types of additives in one of
or both of the main material and the curing agent. Examples of the
additional resin components include an acid-modified polybutadiene,
a polyether sulfone resin, a polycarbonate resin, and a
polyphenylene ether resin.
[0083] With respect to the acid-modified polybutadiene, there can
be mentioned an acid-modified polybutadiene obtained by modifying
polybutadiene with an unsaturated carboxylic acid. Further, as a
commercially available acid-modified polybutadiene, for example,
there can be used maleic anhydride-modified liquid polybutadiene,
manufactured by Evonik Degussa GmbH (such as polyvest MA75 and
Polyvest EP MA120), maleic anhydride-modified polyisoprene,
manufactured by Kuraray Co., Ltd. (LIR-403, LIR-410), and the
like.
[0084] With respect to the polycarbonate resin, for example, there
can be mentioned a polycondensation product of a dihydric or
bifunctional phenol and a carbonyl halide, and a product obtained
by subjecting a dihydric or bifunctional phenol and a carbonic
diester to polymerization by a transesterification method. Further,
the polycarbonate resin may have a molecular structure of the
polymer chain thereof, which is a linear structure, or may have a
branched structure in the molecular structure.
[0085] The polyphenylene ether resin may be a modified
polyphenylene ether resin which has introduced into the resin
structure thereof a reactive functional group, such as a carboxyl
group, an epoxy group, an amino group, a mercapto group, a silyl
group, a hydroxyl group, or a dicarboxyl anhydride group, by a
method, such as a graft reaction or copolymerization.
[0086] Examples of the above-mentioned various types of additives
include a flame retardant or flame retardant auxiliary, a filler,
the other additives, and an organic solvent. Examples of the flame
retardants or flame retardant auxiliaries include a phosphorus
flame retardant, a nitrogen flame retardant, a silicone flame
retardant, a metal hydroxide, a metal oxide, a metal carbonate
compound, a metallic powder, a boron compound, low melting-point
glass, ferrocene, an acetylacetonato metal complex, an organometal
carbonyl compound, an organocobalt salt compound, an organosulfonic
acid metal salt, and a compound having a metal atom and an aromatic
compound or a heterocyclic compound which are ionically bonded or
coordinately bonded to each other. These may be used individually
or in combination.
[0087] Examples of the fillers include titanium oxide, glass beads,
a glass flake, a glass fiber, calcium carbonate, barium carbonate,
calcium sulfate, barium sulfate, potassium titanate, aluminum
borate, magnesium borate, fused silica, crystalline silica,
alumina, silicon nitride, aluminum hydroxide, fibrous reinforcing
materials, such as a kenaf fiber, a carbon fiber, an alumina fiber,
and a quartz fiber, and non-fibrous reinforcing materials. These
may be used individually or in combination. Further, these fillers
may be coated with an organic material, an inorganic material, or
the like.
[0088] Further, when a glass fiber is used as a filler, the glass
fiber can be selected from roving of a continuous fiber type, a
chopped strand of a short fiber type, a milled fiber, and the like.
It is preferred to use the glass fiber which has been
surface-treated for the resin used in the composition. By
incorporating a filler into the composition, a non-combustible
layer (or carbide layer) formed upon combustion can be further
improved in strength. The non-combustible layer (or carbide layer)
formed upon combustion is unlikely to be broken, enabling the
resultant material to exhibit stable heat insulation ability, so
that a larger flame retardancy effect can be obtained. Further, it
is possible to impart high rigidity to the material.
[0089] Examples of the other additives include a plasticizer, an
antioxidant, an ultraviolet light absorber, stabilizers, such as a
light stabilizer, an antistatic agent, a conductivity imparting
agent, a stress relaxation agent, a release agent, a
crystallization promoter, a hydrolysis suppressing agent, a
lubricant, an impact imparting agent, a sliding property improving
agent, a compatibilizing agent, a nucleating agent, a
reinforcement, a reinforcing material, a flow modifier, a dye, a
sensitizer, a coloring pigment, a rubber polymer, a thickener, an
anti-settling agent, an anti-sagging agent, an anti-foaming agent,
a coupling agent, a rust preventive agent, an anti-fungus or
mildewproofing agent, a stainproofing agent, and a conductive
polymer.
[0090] The above-mentioned organic solvent is advantageously used
when, for example, a fiber-reinforced resin molded article is
produced using the curable composition of the invention by a
filament winding method. With respect to the type and amount of the
organic solvent added, there is no particular limitation, and they
are appropriately selected according to the dissolving power of the
solvent for the compounds contained in the curable composition of
the invention, the operation properties in the molding step, and
the like. Examples of the organic solvents include methyl ethyl
ketone acetone, dimethylformamide, methyl isobutyl ketone,
methoxypropanol, cyclohexanone, methyl cellosolve, ethyl diglycol
acetate, and propylene glycol monomethyl ether acetate.
[0091] The curable composition of the invention can be used in
various applications, such as a coating composition, electric and
electronic materials, a bonding agent, and a molded article. The
curable composition of the invention can be advantageously used not
only in such an application that the curable composition itself is
cured, but also in a fiber-reinforced composite material, a
fiber-reinforced resin molded article and the like.
[0092] The method for obtaining a cured product from the curable
composition of the invention may be conducted in accordance with a
general curing method for an epoxy resin composition, and, for
example, heating temperature conditions may be appropriately
selected according to the type of the curing agent used in
combination with the curable composition, and the use of the cured
product, and the like. For example, there can be mentioned a method
in which the curable composition is heated at a temperature in the
range of room temperature to about 250.degree. C. With respect to
the molding method and the like, a general method for a curable
composition can be used, and conditions characteristic of the
curable composition of the invention are not particularly
needed.
[0093] The fiber-reinforced composite material of the present
invention is a material having a reinforcing fiber impregnated with
the curable composition which is in a state before being cured. The
reinforcing fiber used in the fiber-reinforced composite material
may be any of a twisted yarn, an untwisted yarn, a non-twisted
yarn, and the like, but is preferably an untwisted yarn or a
non-twisted yarn because such a fiber has excellent formability in
the fiber-reinforced composite material. Further, with respect to
the form of the reinforcing fiber, a reinforcing fiber obtained by
unidirectionally arranging the fiber, or woven fabric of a
reinforcing fiber can be used. The woven fabric can be arbitrarily
selected from plain weave, satin weave, and the like according to
the part in which the resultant composite material is used or the
use of the composite material. Specifically, as examples of
reinforcing fibers having excellent mechanical strength and
durability, there can be mentioned a carbon fiber, a glass fiber,
an aramid fiber, a boron fiber, an alumina fiber, and a silicon
carbide fiber, and two or more types of these fibers can be used in
combination. Of these, especially, in view of obtaining a molded
article having excellent strength, a carbon fiber is preferred,
and, with respect to the carbon fiber, those of various types, such
as a polyacrylonitrile, pitch, or rayon type, can be used.
[0094] With respect to the method for obtaining a fiber-reinforced
composite material from the curable composition of the invention,
there is no particular limitation, but, for example, there can be
mentioned a method in which the components constituting the curable
composition are uniformly mixed with each other to prepare a
varnish, and then a unidirectional reinforcing fiber obtained by
unidirectionally arranging a reinforcing fiber is immersed in the
obtained varnish (in a state before being cured in a pultrusion
method or a filament winding method), and a method in which woven
fabric of a reinforcing fiber is set in a female mold so that the
woven fabric is stacked on one another, and then the mold is
closely sealed with a male mold and a resin is injected so as to
subject the fabric to pressure impregnation with the resin (in a
state before being cured in an RTM method).
[0095] With respect to the carbon fiber, there is no particular
limitation, but, from the viewpoint of the mechanical strength and
rigidity, preferred is a carbon fiber having a tensile strength in
the range of 3,000 to 7,000 MPa, a tensile elongation in the range
of 1.5 to 2.3%, and a tensile modulus of 200 MPa or more. Further,
more preferred is a carbon fiber having a tensile strength in the
range of 4,500 to 6,500 MPa, a tensile elongation in the range of
1.7 to 2.3%, and a tensile modulus of 230 MPa or more. Examples of
commercially available carbon fiber products include "TORAYCA
(registered trademark)" T800S-24000, "TORAYCA (registered
trademark)" T700SC-12000, "TORAYCA (registered trademark)"
T700SC-24000, and "TORAYCA (registered trademark)" T300-3000.
[0096] Further, with respect to the carbon fiber bundle, it is
preferred that the number of filaments per fiber bundle is in the
range of 3,000 to 5,0000. When the number of filaments is less than
3,000, the fiber is likely to be bent, causing the strength to be
poor. Conversely, when the number of filaments is 50,000 or more,
impregnation of the composite material containing such a fiber with
the resin is likely to be a failure, and therefore it is more
preferred that the number of filaments is 5,000 to 40,000.
[0097] Further, in the fiber-reinforced composite material of the
invention, the volume content of the reinforcing fiber in the whole
volume of the fiber-reinforced composite material is preferably 40
to 85%, and, from the viewpoint of the strength, the volume content
is further preferably in the range of 50 to 70%. When the volume
content of the reinforcing fiber is less than 40%, it is likely
that the amount of the curable composition contained in the
composite material is so large that the resultant cured product has
only unsatisfactory flame retardancy, or it is impossible to
satisfy the properties required for the fiber-reinforced composite
material having excellent specific modulus and specific strength.
Further, when the volume content of the reinforcing fiber is more
than 85%, it is likely that the adhesion between the reinforcing
fiber and the resin composition becomes poor.
[0098] The fiber-reinforced resin molded article of the invention
is a molded article having a reinforcing fiber and a cured product
of the curable composition, and is obtained by heat-curing a
fiber-reinforced composite material. With respect to the
fiber-reinforced resin molded article of the invention,
specifically, the volume content of the reinforcing fiber in the
fiber-reinforced molded article is preferably in the range of 40 to
85%, and, from the viewpoint of the strength, the volume content is
especially preferably in the range of 50 to 70%. Examples of such
fiber-reinforced resin molded articles include parts for an
automobile, such as a front sub-frame, a rear sub-frame, a front
pillar, a center pillar, a side member, a cross member, a side
sill, a roof rail, and a propeller shaft, a core member for wires
and cables, pipe materials for submarine oil fields, roll and pipe
materials for printers, robot fork materials, and primary
structural materials and secondary structural materials for
aircrafts.
[0099] With respect to the method for obtaining a fiber-reinforced
molded article from the curable composition of the invention, there
is no particular limitation, but a pultrusion method, a filament
winding method, an RTM method, or the like is preferably used. The
pultrusion method is a method in which a fiber-reinforced composite
material is introduced into a mold and cured by heating, and then
drawn out of the mold using a pultrusion apparatus to form a
fiber-reinforced resin molded article, the filament winding method
is a method in which a fiber-reinforced composite material
(containing a unidirectional fiber) is wound round an aluminum
liner, a plastic liner, or the like while rotating the liner, and
then cured by heating to form a fiber-reinforced resin molded
article, and the RTM method is a method in which, using two types
of molds, i.e., a female mold and a male mold, a fiber-reinforced
composite material within the molds is cured by heating to form a
fiber-reinforced resin molded article. When forming a
fiber-reinforced resin molded article of a large product size or of
a complicated shape, an RTM method is preferably used.
[0100] With respect to the molding conditions for a
fiber-reinforced resin molded article, molding is conducted by
heat-curing the fiber-reinforced composite material preferably at a
temperature in the range of 50 to 250.degree. C., more preferably
at a temperature in the range of 70 to 220.degree. C. When the
molding temperature is too low, it is likely that satisfactory
fast-curing properties cannot be obtained, and conversely, when the
molding temperature is too high, it is likely that thermal strain
causes the molded article to suffer warpage. With respect to the
other molding conditions, there can be mentioned a method in which
the fiber-reinforced composite material is cured in two stages, for
example, the fiber-reinforced composite material is precured at 50
to 100.degree. C. to obtain a tack-free cured product, and then the
cured product is subjected to further treatment under conditions at
a temperature of 120 to 200.degree. C.
[0101] As further examples of the method for obtaining a
fiber-reinforced molded article from the curable composition of the
invention, there can be mentioned a hand lay-up method and a
spray-up method in which fiber aggregate is placed on the bottom of
a mold and the above-mentioned varnish and fiber aggregate are laid
on one another so that multiple layers are formed, a vacuum bag
method in which, using any one of a male mold and a female mold, a
substrate formed from a reinforcing fiber is stacked on one another
while impregnating the substrate with a varnish, and molded, and
covered with a flexible mold capable of applying a pressure to the
molded material, and the resultant airtight-sealed material is
subjected to vacuum forming, and an SMC pressing method in which a
varnish containing a reinforcing fiber, which has been
preliminarily in a sheet form, is subjected to compression molding
using a mold.
EXAMPLES
[0102] Hereinbelow, the present invention will be described in more
detail with reference to the following Examples and Comparative
Example, and, in the following Examples and Comparative Example,
"part (s) " and "%" are given by mass unless otherwise
specified.
Production Example 1: Production of a Urethane-Modified Epoxy Resin
(A-1)
[0103] 29 parts by mass of isophorone diisocyanate was charged into
a four-neck flask equipped with a nitrogen gas introducing pipe, a
cooling pipe, a thermometer, and a stirrer, and heated to
80.degree. C. Subsequently, 161 parts by mass of a polyester diol
(obtained from ethylene glycol and adipic acid as reaction raw
materials; hydroxyl value: 55 mg KOH/g; number average molecular
weight (Mn): 2,000) was added to the isophorone diisocyanate in the
flask. Then, 0.1 parts by mass of a urethane-forming reaction
catalyst ("NEOSTANN U-28", manufactured by Nitto Kasei Co., Ltd.)
was added, and the resultant mixture was subjected to reaction for
2 hours to obtain an intermediate (1) having an isocyanate group
content of 2.1% by mass.
[0104] Then, 342 parts by mass of a bisphenol A epoxy resin
("EPICLON 850-S", manufactured by DIC Corporation; epoxy
equivalent: 188 g/equivalent; hydroxyl equivalent: 2,900
g/equivalent) was added to the intermediate, and the resultant
mixture was subjected to reaction under conditions at a temperature
of 80.degree. C. before ensuring that the isocyanate group
disappeared, obtaining a urethane-modified epoxy resin (A-1). The
urethane-modified epoxy resin (A-1) had an epoxy equivalent of 293
g/equivalent.
Production Example 2: Production of a Urethane-Modified Epoxy Resin
(A-2)
[0105] 23 parts by mass of tolylene diisocyanate was charged into a
four-neck flask equipped with a nitrogen gas introducing pipe, a
cooling pipe, a thermometer, and a stirrer, and heated to
80.degree. C. Subsequently, 156 parts by mass of a polyester diol
(obtained from ethylene glycol and adipic acid as reaction raw
materials; hydroxyl value: 55 mg KOH/g; number average molecular
weight (Mn): 2,000) was added to the tolylene diisocyanate in the
flask. Then, 0.1 parts by mass of a urethane-forming reaction
catalyst ("NEOSTANN U-28", manufactured by Nitto Kasei Co., Ltd.)
was added, and the resultant mixture was subjected to reaction for
2 hours to obtain an intermediate (2) having an isocyanate group
content of 1.8% by mass.
[0106] Then, 341 parts by mass of a bisphenol A epoxy resin
("EPICLON 850-S", manufactured by DIC Corporation; epoxy
equivalent: 188 g/equivalent; hydroxyl equivalent: 2,900
g/equivalent) was added to the intermediate, and the resultant
mixture was subjected to reaction under conditions at a temperature
of 80.degree. C. before ensuring that the isocyanate group
disappeared, obtaining a urethane-modified epoxy resin (A-2). The
urethane-modified epoxy resin (A-2) had an epoxy equivalent of 287
g/equivalent.
Production Example 3: Production of a Urethane-Modified Epoxy Resin
(A-3)
[0107] 24 parts by mass of tolylene diisocyanate was charged into a
four-neck flask equipped with a nitrogen gas introducing pipe, a
cooling pipe, a thermometer, and a stirrer, and heated to
80.degree. C. Subsequently, 88.8 parts by mass of a 1,4-butanediol
epoxy resin ("Denacol EX-214", manufactured by Nagase Chemtex
Corporation; epoxy equivalent: 137 g/equivalent; hydroxyl
equivalent: 1,460 g/equivalent) and 165 parts by mass of a
polyester diol (obtained from ethylene glycol and adipic acid as
reaction raw materials; hydroxyl value: 55 mg KOH/g; number average
molecular weight (Mn): 2,000) were added to the tolylene
diisocyanate in the flask. Then, 0.1 parts by mass of a
urethane-forming reaction catalyst ("NEOSTANN U-28", manufactured
by Nitto Kasei Co., Ltd.) was added, and the resultant mixture was
subjected to reaction for 2 hours to obtain an intermediate (3)
having an isocyanate group content of 0.8% by mass.
[0108] Then, 543 parts by mass of a bisphenol A epoxy resin
("EPICLON 850-S", manufactured by DIC Corporation; epoxy
equivalent: 188 g/equivalent; hydroxyl equivalent: 2,900
g/equivalent) was added to the intermediate, and the resultant
mixture was subjected to reaction under conditions at a temperature
of 80.degree. C. before ensuring that the isocyanate group
disappeared, obtaining a urethane-modified epoxy resin (A-3). The
urethane-modified epoxy resin (A-3) had an epoxy equivalent of 202
g/equivalent.
Production Example 4: Production of a Urethane-Modified Epoxy Resin
(A-4)
[0109] 23 parts by mass of tolylene diisocyanate was charged into a
four-neck flask equipped with a nitrogen gas introducing pipe, a
cooling pipe, a thermometer, and a stirrer, and heated to
80.degree. C. Subsequently, 159 parts by mass of a polyester diol
(obtained from hexamethylene glycol and adipic acid as reaction raw
materials; hydroxyl value: 55 mg KOH/g; number average molecular
weight (Mn): 2,000) was added to the tolylene diisocyanate in the
flask. Then, 0.1 parts by mass of a urethane-forming reaction
catalyst ("NEOSTANN U-28", manufactured by Nitto Kasei Co., Ltd.)
was added, and the resultant mixture was subjected to reaction for
2 hours to obtain an intermediate (4) having an isocyanate group
content of 1.8% by mass.
[0110] Then, 317 parts by mass of a bisphenol A epoxy resin
("EPICLON 850-S", manufactured by DIC Corporation; epoxy
equivalent: 188 g/equivalent; hydroxyl equivalent: 2,900
g/equivalent) was added to the intermediate, and the resultant
mixture was subjected to reaction under conditions at a temperature
of 80.degree. C. before ensuring that the isocyanate group
disappeared, obtaining a urethane-modified epoxy resin (A-4). The
urethane-modified epoxy resin (A-4) had an epoxy equivalent of 285
g/equivalent.
Production Example 5: Production of a Urethane-Modified Epoxy Resin
(A-5)
[0111] 29 parts by mass of isophorone diisocyanate was charged into
a four-neck flask equipped with a nitrogen gas introducing pipe, a
cooling pipe, a thermometer, and a stirrer, and heated to
80.degree. C. Subsequently, 161 parts by mass of a polyester diol
(obtained from ethylene glycol and adipic acid as reaction raw
materials; hydroxyl value: 55 mg KOH/g; number average molecular
weight (Mn): 2,000) was added to the isophorone diisocyanate in the
flask. Then, 0.1 parts by mass of a urethane-forming reaction
catalyst ("NEOSTANN U-28", manufactured by Nitto Kasei Co., Ltd.)
was added, and the resultant mixture was subjected to reaction for
2 hours to obtain an intermediate (1) having an isocyanate group
content of 2.0% by mass.
[0112] Then, 342 parts by mass of a bisphenol A epoxy resin
("EPICLON 850-S", manufactured by DIC Corporation; epoxy
equivalent: 188 g/equivalent; hydroxyl equivalent: 2,900
g/equivalent), 188 parts by mass of a 1,4-butanediol epoxy resin
("Denacol EX-214", manufactured by Nagase Chemtex Corporation;
epoxy equivalent: 137 g/equivalent; hydroxyl equivalent: 1,460
g/equivalent), and 280 parts by mass of a trimethylolpropane epoxy
resin ("Denacol EX-321", manufactured by Nagase Chemtex
Corporation; epoxy equivalent: 140 g/equivalent; hydroxyl
equivalent: 695 g/equivalent) were added to the intermediate, and
the resultant mixture was subjected to reaction under conditions at
a temperature of 80.degree. C. before ensuring that the isocyanate
group disappeared, obtaining a urethane-modified epoxy resin (A-5).
The urethane-modified epoxy resin (A-5) had an epoxy equivalent of
190 g/equivalent.
Examples 1 to 5 and Comparative Example 1
[0113] The components were mixed according to the formulation shown
in Table 1 below, and uniformly stirred to obtain a curable
composition. With respect to the obtained curable composition,
evaluation tests were conducted according to the procedures
described below. The results are shown in Table 1.
[0114] Details of the components used in the Examples and
Comparative Example are as follows.
[0115] Aliphatic polyol epoxy resin (C-1): "Denacol EX-214",
manufactured by Nagase Chemtex Corporation; 1,4-butanediol epoxy
resin; epoxy equivalent: 137 g/equivalent
[0116] Aliphatic polyol epoxy resin (C-2): "Denacol EX-321",
manufactured by Nagase Chemtex Corporation; trimethylolpropane
epoxy resin; epoxy group equivalent: 140 g/equivalent
[0117] Bisphenol A epoxy resin: "EPICLON 850-S", manufactured by
DIC Corporation; epoxy equivalent: 188 g/equivalent
[0118] Acid anhydride (B-1): Methyltetrahydrophthalic anhydride
("EPICLON B-570-H", manufactured by DIC Corporation)
[0119] Curing accelerator: N,N-Dimethylbenzylamine
Test for Tensile Strength
[0120] Using a filament winding apparatus, a carbon fiber
("T700SC-12,000", manufactured by Toray Industries Inc.) was
impregnated with a curable composition while winding the fiber, and
the resultant carbon fiber was cured by heating at 120.degree. C.
for 2 hours and then at 140.degree. C. for 2 hours to obtain a
fiber-reinforced resin molded article having a fiber volume content
(Vf) of 60% and a thickness of 2 mm. The obtained plate of the
molded article was cut and subjected to tensile test in accordance
with JIS K7161.
Measurement of a Fracture Toughness
[0121] A curable composition was cast into a frame having a size of
200 mm.times.100 mm.times.6 mm, and cured by heating at 120.degree.
C. for 2 hours and then at 140.degree. C. for 2 hours to obtain a
cured product. With respect to the obtained cured product, a
K.sub.IC value was measured in accordance with ASTM D 5045.
TABLE-US-00001 TABLE 1 Example Example Example Example Example
Comparative Curable composition 1 2 3 4 5 Example 1
Urethane-modified epoxy resin Part(s) 28 (A-1) by Urethane-modified
epoxy resin mass 27 (A-2) Urethane-modified epoxy resin 27 (A-3)
Urethane-modified epoxy resin 26 (A-4) Urethane-modified epoxy
resin 53 (A-5) Aliphatic polyol epoxy resin 10 10 (C-1) Aliphatic
polyol epoxy resin 15 15 22 28 (C-2) Bisphenol A epoxy resin 53
Acid anhydride (B-1) 47 48 51 46 47 47 Curing accelerator 1 1 1 1 1
1 Tensile strength [MPa] 2,500 2,300 2,300 2,300 2,400 1,970
Fracture toughness (K.sub.IC) [MPa m.sup.1/2] 1.49 1.4 1.5 1.48
1.52 0.55
* * * * *