U.S. patent application number 10/569277 was filed with the patent office on 2007-01-11 for latent hardener.
Invention is credited to Kazunobu Kamiya, Makoto Yoshinari.
Application Number | 20070010636 10/569277 |
Document ID | / |
Family ID | 34426681 |
Filed Date | 2007-01-11 |
United States Patent
Application |
20070010636 |
Kind Code |
A1 |
Kamiya; Kazunobu ; et
al. |
January 11, 2007 |
Latent hardener
Abstract
A latent curing agent that can cure a thermosetting epoxy resin
in a relatively short period of time and at a relatively low
temperature has a structure in which an aluminum chelating agent is
held by a porous resin carrier obtained through interfacial
polymerization of a polyfunctional isocyanate compound. The
aluminum chelating agent is preferably a complex compound
comprising .beta.-ketoenolate anion ligands coordinated to
aluminum. The latent curing agent can be produced by dissolving the
aluminum chelating agent and the polyfunctional isocyanate compound
in a volatile organic solvent, adding the resulting solution to an
aqueous phase containing a dispersing agent, and stirring the
resulting mixture to cause interfacial polymerization of the
isocyanate compound while the mixture is being heated.
Inventors: |
Kamiya; Kazunobu; (TOCHIGI,
JP) ; Yoshinari; Makoto; (Tochigi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Family ID: |
34426681 |
Appl. No.: |
10/569277 |
Filed: |
August 30, 2004 |
PCT Filed: |
August 30, 2004 |
PCT NO: |
PCT/JP04/12895 |
371 Date: |
February 23, 2006 |
Current U.S.
Class: |
525/523 ;
524/437 |
Current CPC
Class: |
H05K 3/323 20130101;
C08G 59/188 20130101; C08G 18/0852 20130101; C08G 18/79 20130101;
C08G 59/70 20130101; C08G 18/58 20130101 |
Class at
Publication: |
525/523 ;
524/437 |
International
Class: |
C08L 63/00 20060101
C08L063/00; C08K 3/10 20060101 C08K003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 8, 2003 |
JP |
2003-315984 |
Aug 5, 2004 |
JP |
2004-228771 |
Aug 26, 2004 |
JP |
2004-246231 |
Claims
1. A latent curing agent comprising an aluminum chelating agent and
a porous resin carrier for the aluminum chelating agent, the porous
resin carrier being obtained through interfacial polymerization of
a polyfunctional isocyanate compound.
2. The latent curing agent according to claim 1, wherein the
aluminum chelating agent is a complex compound in which a
.beta.-ketoenolate anion ligand is coordinated to aluminum.
3. The latent curing agent according to claim 1, wherein the
aluminum chelating agent is aluminum monoacetylacetonate
bis(ethylacetoacetate).
4. A method for producing the latent curing agent according to
claim 1, comprising: dissolving an aluminum chelating agent and a
polyfunctional isocyanate compound in a volatile organic solvent;
adding the resulting solution to an aqueous phase containing a
dispersing agent; and stirring the resulting mixture while the
mixture is heated to cause interfacial polymerization of the
isocyanate compound.
5. The method according to claim 4, wherein the volatile organic
solvent is an acetic aced lower alkyl ester.
6. The method according to claim 4, wherein the aluminum chelating
agent and the polyfunctional isocyanate compound are dissolved in
the volatile organic solvent and the viscosity of the resulting
solution is adjusted to in the range of 1 to 2.5 mPa.S.
7. The method according to claim 6, wherein the aluminum chelating
agent is used in an amount of one-half or less by weight of the
polyfunctional isocyanate compound.
8. The method according to claim 4, wherein the aluminum chelating
agent is used in an amount of an equal amount or more by weight of
the polyfunctional isocyanate compound.
9. A thermosetting resin composition containing the latent curing
agent according to claim 1, a silane coupling agent, and a
thermosetting resin.
10. The thermosetting resin composition according to claim 9,
wherein the thermosetting resin is a thermosetting epoxy resin.
11. The method according to claim 5, wherein the aluminum chelating
agent and the polyfunctional isocyanate compound are dissolved in
the volatile organic solvent and the viscosity of the resulting
solution is adjusted to in the range of 1 to 2.5 mPa.S.
12. The method according to claim 5, wherein the aluminum chelating
agent is used in an amount of an equal amount or more by weight of
the polyfunctional isocyanate compound.
13. A thermosetting resin composition containing the latent curing
agent according to claim 2, a silane coupling agent, and a
thermosetting resin.
14. A thermosetting resin composition containing the latent curing
agent according to claim 3, a silane coupling agent, and a
thermosetting resin.
Description
TECHNICAL FIELD
[0001] The present invention relates to a latent curing agent that
can initiate curing of thermosetting epoxy resin compositions at
relatively low temperature. The present invention also relates to a
method for producing such a latent curing agent, as well as to a
thermosetting epoxy resin composition that contains the latent
curing agent and is thus highly stable during storage.
BACKGROUND ART
[0002] Thermosetting epoxy resin compositions are widely used as
adhesives and molding materials. Among different curing agents used
to cure thermosetting epoxy resin compositions are imidazole latent
curing agents. These imidazole latent curing agents do not cure
under normal storage conditions and are thus widely used to make
thermosetting epoxy resin compositions into one-pack type curable
compositions that are easy to handle and are stable during storage.
One example of such imidazole latent curing agents includes an
agent provided in the form of microcapsules in which particles of
an imidazole compound are coated with a cured epoxy resin. The
imidazole compound is capable of curing epoxy resins.
[0003] However, since the coating of this microcapsule-type
imidazole latent curing agent is mechanically and thermally stable,
this latent curing agent must be heated to 180.degree. C. or above
under pressurized conditions to initiate the curing reaction. This
makes the imidazole latent curing agent inapplicable to recently
developed epoxy resin compositions that are designed to cure at low
temperatures.
[0004] For this reason, new latent curing agents have been proposed
that can cure epoxy resin compositions quickly at low temperature.
One is a microcapsule-type aluminum chelating agent-based latent
curing agent (Japanese Patent Application Laid-Open No.
2002-212537). This latent curing agent comprises particles of an
aluminum chelating agent (mother particles) and fine particles of
polyvinyl alcohol (child particles) hybridized to the surface of
the mother particles. The aluminum chelating agent acts with a
silane coupling agent to cause an epoxy resin to polymerize
cationically. Another is also a microcapsule-type aluminum
chelating agent-based latent curing agent (Japanese Patent
application Laid-Open No. 2002-363255). This agent comprises
particles of an aluminum chelating agent (mother particles) and
fine particles of a fluorine resin (child particles) hybridized to
the surface of the mother particles.
[0005] The detail of the curing process of the aluminum
chelator-based latent curing agent is described in Japanese Patent
Application Laid-Open No. 2002-212537, paragraphs 0007 through
0010.
DISCLOSURE OF THE INVENTION
[0006] However, the hybridization technique for forming
microcapsules of aluminum chelator-based latent curing agents
involves allowing child particles to collide to mother particles to
form the microcapsule wall. As a result, the microcapsules obtained
tend to have non-uniform and rough surfaces, and the resulting
curing agents cannot achieve stable curing characteristics, making
it difficult to control the conditions for curing.
[0007] In view of the aforementioned problems of the conventional
art, it is an objective of the present invention to provide an
aluminum chelator-based latent curing agent that can cure
thermosetting epoxy resins in a relatively short period of time and
at a relatively low temperature. It is another objective of the
present invention to provide a method for producing such an
aluminum chelator-based latent curing agent in which curing
conditions for the curing agent can be controlled in a relatively
easy fashion. It is still another objective of the present
invention to provide a thermosetting resin composition containing
such a latent curing agent.
MEANS TO SOLVE THE PROBLEMS
[0008] The present inventors have found that the above-described
objectives can be achieved by a polymer obtained through
interfacial polymerization of a polyfunctional isocyanate compound,
which is carried out in the presence of an aluminum chelating
agent. The present invention has been achieved based on this
discovery.
[0009] Accordingly, the present invention provides a latent curing
agent comprising an aluminum chelating agent and a porous resin
carrier for the aluminum chelating agent, the porous resin carrier
being obtained through interfacial polymerization of a
polyfunctional isocyanate compound.
[0010] The present invention also provides a method for producing
the above-described latent curing agent, comprising dissolving an
aluminum chelating agent and a polyfunctional isocyanate compound
in a volatile organic solvent, adding the resulting solution to an
aqueous phase containing a dispersing agent, and stirring the
resulting mixture while the mixture is heated to cause interfacial
polymerization of the isocyanate compound.
[0011] The present invention further provides a thermosetting resin
composition comprising the latent curing agent, a silane coupling
agent and a thermosetting resin.
ADVANTAGE OF THE INVENTION
[0012] The latent curing agent of the present invention, which
consists of an aluminum chelating agent and a porous resin carrier
for the aluminum chelating agent, the carrier being obtained
through interfacial polymerization of a polyfunctional isocyanate
compound, can cure thermosetting epoxy resins at a relatively low
temperature and in a relatively short period of time. In addition,
curing conditions for the latent curing agent can be controlled in
a relatively easy fashion by the method of the present invention
for producing the latent curing agent, since the method involves
dissolving an aluminum chelating agent and a polyfunctional
isocyanate compound in a volatile organic solvent, adding the
resulting solution to an aqueous phase containing a dispersing
agent, and stirring the mixture while the mixture is heated to
cause interfacial polymerization of the isocyanate compound.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A is an electron micrograph of a single particle of a
latent curing agent.
[0014] FIG. 1B is an enlarged electron-micrograph showing the
central region of the particle of the latent curing agent of FIG.
1A.
[0015] FIG. 2 is a DSC (differential scanning calorimetry) diagram
of a thermosetting epoxy resin prepared in Example 8.
[0016] FIG. 3 is a DSC diagram of a thermosetting epoxy resin
prepared in Example 9.
[0017] FIG. 4 is a DSC diagram of a thermosetting epoxy resin
prepared in Example 10.
[0018] FIG. 5A is a chart showing a particle size distribution of a
latent curing agent prepared in Experiment Example 11b of Example
11.
[0019] FIG. 5B is a chart showing a particle size distribution of a
latent curing agent prepared in Experiment Example 11c of Example
11.
[0020] FIG. 5C is a chart showing a particle size distribution of a
latent curing agent prepared in Experiment Example 11d of Example
11.
[0021] FIG. 5D is a chart showing a particle size distribution of a
latent curing agent prepared in Experiment Example 11e of Example
11.
[0022] FIG. 6A is an electron micrograph of the latent curing agent
of Experiment Example 11b of Example 11.
[0023] FIG. 6B is an electron micrograph of the latent curing agent
of Experiment Example 11e of Example 11.
[0024] FIG. 7A is an electron micrograph of a latent curing agent
of Experiment Example 12a of Example 12.
[0025] FIG. 7B is an electron micrograph of a latent curing agent
of Experiment Example 12b of Example 12.
[0026] FIG. 7C is an electron micrograph of a latent curing agent
of Experiment Example 12c of Example 12.
[0027] FIG. 7D is an electron micrograph of a latent curing agent
of Experiment Example 12d of Example 12.
[0028] FIG. 7E is an electron micrograph of a latent curing agent
of Experiment Example 12e of Example 12.
[0029] FIG. 7F is an electron micrograph of a latent curing agent
of Experiment Example 12f of Example 12.
[0030] FIG. 8A is an electron micrograph of particles of a
conventional latent curing agent using partially saponified
PVA.
[0031] FIG. 8B is an electron micrograph of particles of a
conventional latent curing agent using fully saponified PVA.
REFERENCE NUMERALS
[0032] 1. Latent curing agent
[0033] 2. Porous resin matrix
[0034] 3. Pore
BEST MODE FOR CARRYING OUT THE INVENTION
[0035] The latent curing agent of the present invention consists of
an aluminum chelating agent and a porous resin carrier for the
aluminum chelating agent, obtained through interfacial
polymerization of a polyfunctional isocyanate compound. The
aluminum chelating agent imparts to the latent curing agent an
ability to cure thermosetting resin compositions quickly and at low
temperatures. Furthermore, the aluminum chelating agent is carried
by the porous resin carrier obtained through interfacial
polymerization. Therefore, when a thermosetting resin composition
is mixed with the latent curing agent (in other words, when a
one-pack type composition is composed of the thermosetting resin
composition and the latent curing agent), the thermosetting resin
composition is improved in respect of stability during storage.
[0036] Rather than the simple microcapsule structure in which the
shell of porous resin is formed around the aluminum chelator core,
the latent curing agent 1 of the present invention has a structure
in which the aluminum chelating agent is retained in numerous pores
3 formed in a porous resin matrix 2 as shown in an electron
micrograph of the latent curing agent 1 (FIG. 1A) and an enlarged
electron-micrograph of the central region of the latent curing
agent (FIG. 1B).
[0037] The latent curing agent 1 of the present invention is
produced by interfacial polymerization and thus is formed into
spheres, which are preferably sized from 0.5 to 100 .mu.m in terms
of the curability and dispersibility. The pores 3 are preferably
sized from 5 to 150 nm in terms of the curability and latency.
[0038] If the degree of crosslinking of the porous resin is too
small, the latency of the latent curing agent 1 tends to decrease,
whereas if the degree of crosslinking of the porous resin is too
large, the heat response of the latent curing agent tends to
decrease. Thus, a porous resin with a controlled degree of
crosslinking is preferably used depending on the intended use of
the curing agent. The degree of crosslinking of the porous resin
can be determined by microcompression test.
[0039] It is preferred that the latent curing agent 1 of the
present invention is substantially organic solvent-free.
Specifically, it preferably contains 1 ppm or less organic solvent
for use in interfacial polymerization to ensure stability of
curing.
[0040] The amount of the aluminum chelating agent relative to the
porous resin in the latent curing agent 1 of the present invention
is preferably 10 to 200 parts by mass and, more preferably, 10 to
150 parts by mass relative to 100 parts by mass of the porous
resin. Too little of the aluminum chelating agent results in a
decreased heat response of the latent curing agent, whereas too
much of the aluminum chelating agent results in a decreased latency
of the latent curing agent.
[0041] One example of the aluminum chelating agents for use in the
latent curing agent of the present invention includes a group of
complex compounds in which three .beta.-ketoenolate anions are
coordinated to aluminum as shown in the following formula (1):
##STR1## wherein R.sup.1, R.sup.2, and R.sup.3 are each
independently an alkyl or alkoxyl group. Examples of the alkyl
group include methyl and ethyl. Examples of the alkoxyl group
include methoxy, ethoxy, and oleyloxy.
[0042] Specific examples of the aluminum chelating agents
represented by the formula (1) include aluminum
tris(acetylacetonate), aluminum tris(ethylacetoacetate), aluminum
monoacetylacetonate bis(ethylacetoacetate), aluminum
monoacetylacetonate bisoleylacetoacetate, ethylacetoacetate
aluminum diisopropylate, and alkylacetoacetate aluminum
diisopropylate.
[0043] The polyfunctional isocyanate compound for use in the
present invention preferably contains two or more, in particular
three isocyanate groups in one molecule. Preferred examples of such
trifunctional isocyanate compounds are trimethylolpropane (TMP)
adducts obtained by reacting 1 mol of TMP with 3 mol of a
diisocyanate compound, as represented by the following formula (2);
isocyanurates obtained by self-condensation of 3 mol of a
diisocyanate compound, as represented by the following formula (3);
and biurets obtained by condensation of diisocyanate urea obtained
from 2 mols of 3 mols of a diisocyanate compound with the remaining
1 mol of a diisocyanate compound, as represented by the following
formula (4): ##STR2##
[0044] In the formulas (2) through (4), the substituent R is the
moiety of the diisocyanate molecule other than the isocyanate
group. Specific examples of the diisocyanate compound include
toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, m-xylylene
diisocyanate, hexamethylene diisocyanate, hexahydro-m-xylylene
diisocyanate, isophorone diisocyanate, and
methylenediphenyl-4,4'-diisocyanate.
[0045] During the interfacial polymerization of the polyfunctional
isocyanate compounds for forming the porous resin, a part of the
isocyanate group is hydrolyzed to an amino group, which reacts with
an isocyanate group by forming a urea bond, thus forming a porous
polyurea. When the latent curing agent composed of such a porous
resin and the aluminum chelating agent retained in the pores of the
resin is heated for curing, the retained aluminum chelating agent
comes into contact with the silane coupling agent and the
thermosetting resin that coexists with the latent curing agent,
though the underlying mechanism is unknown. As a result, the curing
reaction proceeds.
[0046] Although the aluminum chelating agent is considered to be
present on the outer surface of the particles of the latent curing
agent due to its structure, the chelating agent on the surface of
the latent curing agent is immediately inactivated by the water
present in the reaction system during the interfacial
polymerization. Thus, only the aluminum chelating agent retained
within the porous resin remains active. This active chelating agent
within the porous resin is thought to be responsible for the
latency of the resulting curing agent.
[0047] The latent curing agent of the present invention can be
produced in the following manner: An aluminum chelating agent and a
polyfunctional isocyanate compound are dissolved in a volatile
organic solvent, and the resulting solution is added to an aqueous
phase containing a dispersing agent. The mixture is then stirred
while heated to cause interfacial polymerization of the isocyanate
compound.
[0048] In this method, the aluminum chelating agent and the
polyfunctional isocyanate compound are first dissolved in a
volatile organic solvent to form a solution to serve as the organic
phase in the interfacial polymerization. The volatile organic
solvents are used for the following reason: Other organic solvents
with high boiling points of 300.degree. C. or above that are
normally used in interfacial polymerization processes do not
evaporate during the interfacial polymerization. As a result, the
chance of isocyanate coming into contact with water does not
increase significantly, so that the polymerization does not proceed
to a sufficient degree at the interface. This makes it difficult to
obtain polymer products with high shape-retaining characteristic by
interfacial polymerization, and even if it is obtained, the
high-boiling-point solvent remaining in the polymer product
undesirably affects the physical properties of the cured product of
the thermosetting resin composition when the latent curing agent is
used to cure the thermosetting resin composition. For this reason,
volatile organic solvents are used as organic solvents in the
preparation of the organic phase.
[0049] Preferably, the volatile organic solvents can effectively
dissolve both the aluminum chelating agent and the polyfunctional
isocyanate compound (i.e., the solubility of each solute in the
organic solvent is preferably 0.1 g/ml (organic solvent) or
higher), is substantially incompatible with water (i.e., the
solubility of water in the organic solvent is 0.5 g/ml (organic
solvent) or lower), and has a boiling point of 100.degree. C. or
below under the atmospheric pressure. Examples of such volatile
organic solvents are alcohols, acetic acid esters, and ketones. Of
these solvents, ethyl acetate is particularly preferred because of
its high polarity, low boiling point, and poor solubility in
water.
[0050] The volatile organic solvent is preferably used in an amount
of 100 to 500 parts by mass relative to 100 parts by mass of the
sum of the aluminum chelating agent and the polyfunctional
isocyanate compound. Too little of the volatile organic solvent
results in a decreased latency, whereas too much of solvent causes
a decrease in the heat response.
[0051] The viscosity of the solution to serve as the organic phase
can be reduced, for example, by using a relatively large amount of
the volatile organic solvent within the above-specified range.
Lowering the viscosity can improve the efficiency of stirring the
solution. This enables the formation of fine, uniform particles of
the organic phase in the reaction system. As a result, the size of
the particles of the resultant latent curing agent can be
controlled to submicron to several microns to follow a monodisperse
size distribution. The viscosity of the organic phase solution is
preferably adjusted to 1 to 2.5 mPa.S.
[0052] When PVA is used to emulsify the polyfunctional isocyanate
compound, the hydroxide groups of PVA react with the polyfunctional
isocyanate compound, causing deposition of a by-product material
around the particles of the latent curing agent (FIG. 8A, with
partially saponified PVA) or deformation of the particles (FIG. 8B,
with fully saponified PVA). The measures to prevent these phenomena
include facilitating of the reaction between the polyfunctional
isocyanate compound and water and suppressing of the reaction
between the polyfunctional isocyanate compound and PVA.
[0053] To facilitate the reaction between the polyfunctional
isocyanate compound and water, the aluminum chelating agent is used
in an amount of preferably one-half or less, and more preferably
one-third or less of the weight of the polyfunctional isocyanate
compound. In this manner, the chance of the polyfunctional
isocyanate compound coming into contact with water increases, so
that the polyfunctional isocyanate compound tends to react with
water before PVA comes into contact with the surfaces of the
particles of the organic phase.
[0054] In addition, to suppress the reaction between the
polyfunctional isocyanate compound and PVA, the amount of the
aluminum chelating agent in the organic phase is increased.
Specifically, the aluminum chelating agent is used in an amount of
preferably 1.0 or more times, and more preferably 1.0 to 2.0 times
(by weight) the polyfunctional isocyanate compound. In this manner,
the concentration of isocyanate at the surface of the particles of
the organic phase is decreased. Furthermore, the chance of the
polyfunctional isocyanate compound reacting with PVA can be
decreased since the reaction (interfacial polymerization) rate of
the polyfunctional isocyanate compound with the amine generated by
hydrolysis is higher than that with the hydroxyl groups.
[0055] While the aluminum chelating agent and the polyfunctional
isocyanate compound may be dissolved in the volatile organic
solvent under atmospheric pressure and at room temperature, the
resulting reaction mixture may be heated, if necessary.
[0056] In this method, the organic phase solution obtained by
dissolving the aluminum chelating agent and the polyfunctional
isocyanate compound in the volatile organic solvent is then added
to an aqueous phase containing a dispersing agent and the resulting
mixture is stirred while heated to cause interfacial polymerization
of the isocyanate compound. The dispersing agent may be polyvinyl
alcohol, carboxymethylcellulose, gelatin, or other dispersing
agents commonly used in the interfacial polymerization processes.
The dispersing agent is typically used in an amount of 0.1 to 10.0
mass % of the aqueous phase.
[0057] The amount of the organic phase solution relative to the
aqueous phase is preferably 5 to 50 parts by mass relative to 100
parts by mass of the aqueous phase. Too little of the organic phase
solution results in polydisperse size distribution, whereas too
much of the organic phase solution causes formation of aggregates
of fine particles.
[0058] Emulsification for the interfacial polymerization is
preferably carried out under such a stirring condition that the
size of the organic phase becomes 0.5 to 100 .mu.m (e.g., under
stirring speed 8000 rpm or more using a homogenizer). The reaction
mixture is typically stirred under atmospheric pressure at a
temperature of 30 to 80.degree. C. for 2 to 12 hours while being
heated.
[0059] Upon completion of the interfacial polymerization, the
resulting fine particles of the polymer are separated by filtration
and are allowed to dry to give the latent curing agent of the
present invention.
[0060] The above-described production method of the present
invention makes it possible to control the curing characteristics
of the latent curing agent by changing the types and the amounts of
the polyfunctional isocyanate compound and the aluminum chelating
agent, and the conditions for interfacial polymerization. For
example, lowering temperature for the polymerization can decrease
the curing temperature. Conversely, increasing temperature for
polymerization can increase the curing temperature.
[0061] The latent curing agent of the present invention can be used
in the same applications as the conventional imidazole latent
curing agents. The latent curing agent of the present invention is
preferably used together with a silane coupling agent and a
thermosetting resin to provide thermosetting resin compositions
that cure quickly at low temperatures.
[0062] The amount of the latent curing agent in the thermosetting
resin composition is typically 1 to 70 parts by mass, and more
preferably 1 to 50 parts by mass relative to 100 parts by mass of
the thermosetting resin. Too little of the latent curing agent
cannot provide sufficient curing characteristics, whereas too much
of the agent results in a decrease in the resin properties (e.g.,
flexibility) of the cured product of the composition.
[0063] The silane coupling agent, as described in paragraphs 0007
through 0010 of Japanese Patent Application Laid-Open No.
2002-212537, cooperates with the aluminum chelating agent to
initiate cationic polymerization of thermosetting resins (e.g.,
thermosetting epoxy resins). The silane coupling agent has 1 to 3
lower alkoxyl groups in its molecule and may have vinyl, styryl,
acryloyloxy, methacryloyloxy, epoxy, amino, mercapto, and other
functional groups that can react with the functional groups of the
thermosetting resins.
[0064] Since the latent curing agent of the present invention is a
cationic curing agent, the coupling agents with amino or mercapto
groups can be used only if the amino or mercapto groups
substantially do not capture the generated cation species.
[0065] Examples of such silane coupling agents include
vinyltris(.beta.-methoxyethoxy)silane, vinyltriethoxysilane,
vinyltrimethoxysilane, .gamma.-styryltrimethoxysilane,
.gamma.-methacryloxypropyltrimethoxysilane,
.gamma.-acryloxypropyltrimethoxysilane,
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
.gamma.-glycydoxypropyltrimethoxysilane,
.gamma.-glycydoxypropylmethyldiethoxysilane,
N-.beta.-(aminoethyl)-.gamma.-aminopropyltrimethoxysilane,
N-.beta.-(aminoethyl)-.gamma.-aminopropylmethyldimethoxysilane,
.gamma.-aminopropyltriethoxysilane,
N-phenyl-.gamma.-aminopropyltrimethoxysilane,
.gamma.-mercaptopropyltrimethoxysilane, and
.gamma.-chloropropyltrimethoxysilane.
[0066] The amount of the silane coupling agent in the thermosetting
resin composition is typically 50 to 1500 parts by mass, and more
preferably 300 to 1200 parts by mass relative to 100 parts by mass
of the latent curing agent. Too little of the silane coupling agent
results in a decreased curability, whereas too much of the agent
causes a decrease in the resin properties (e.g., stability during
storage) of the cured product of the composition.
[0067] Examples of the thermosetting resin include a thermosetting
epoxy resin, thermosetting urea resin, thermosetting melamine
resin, or thermosetting phenol resin. Of these thermosetting
resins, thermosetting epoxy resins are particularly preferred in
view of their strong adhesion after curing.
[0068] Such thermosetting epoxy resins may be either liquid or
solid and typically have an epoxy equivalent of about 100 to about
4000. These thermosetting epoxy resins preferably include two or
more epoxy groups in their molecules. Preferred examples include
bisphenol A epoxy compounds, phenol novolac epoxy compounds, cresol
novolac epoxy compounds, ester epoxy compounds, and alicyclic epoxy
compounds. These compounds may be monomers or oligomers.
[0069] When necessary, fillers such as silica and mica, pigments
and antistats may be added to the thermosetting resin composition
of the present invention. Preferably, the thermosetting resin
composition of the present invention contains 1 to 10 mass % of
conductive particles, metal particles or resin cores of the order
of several micrometers covered with metal plating layer, which may
further be covered with insulation film. This allows the use of the
thermosetting resin composition of the present invention as an
anisotropic conductive adhesive paste or anisotropic conductive
film.
[0070] The thermosetting resin composition of the present invention
can be produced by uniformly mixing the latent curing agent, the
silane coupling agent, the thermosetting resin and other optional
additives according to conventional techniques.
[0071] The thermosetting resin composition so obtained contains the
curing agent in its latent state and is thus highly stable during
storage despite its one-pack type composition.
[0072] Furthermore, the latent curing agent cooperates with the
silane coupling agent to cause the thermosetting resin to undergo
cationic polymerization quickly and at low temperatures.
EXAMPLES
[0073] The present invention will now be described in detail with
reference to examples.
Example 1
[0074] 800 parts by weight of distilled water, 0.05 parts by weight
of a surfactant (Newrex, available from NOF Co., Ltd.), and 4 parts
by weight of polyvinyl alcohol (PVA-205, available from KURARAY
Co., Ltd.) to serve as a dispersing agent were placed in a
three-liter thermometer-equipped vessel intended for interfacial
polymerization, and the mixture was thoroughly mixed. Meanwhile, 11
parts by weight of a 24% isopropanol solution of aluminum
monoacetylacetonate bis(ethylacetoacetate) (Alumichelate D,
available from KAWAKEN FINE CHEMICALS Co., Ltd.) and 11 parts by
weight of a methylenediphenyl-4,4'-diisocyanate (3
mol)/trimethylolpropane (1 mol) adduct (D-109, available from
MITSUI TAKEDA CHEMICALS Inc.) were dissolved in 30 parts by weight
of ethyl acetate to form an organic phase solution. This solution
was added to the above-prepared mixture and the resulting mixture
was emulsified by a homogenizer (at 11000 rpm for 10 min). Then,
the interfacial polymerization was allowed to proceed overnight at
60.degree. C.
[0075] Upon completion of the reaction, the reaction mixture was
allowed to cool down to room temperature. The particles resulting
from the interfacial polymerization were then collected by
filtration and were allowed to dry to give 20 parts by weight of a
spherical latent curing agent sized approximately 10 .mu.m.
Example 2
[0076] The same procedure was followed as in Example 1, except that
toluene diisocyanate (3 mol)/methylenediphenyl-4,4'-diisocyanate (3
mol)/trimethylolpropane (1 mol) adduct (D-103M-2, MITSUI TAKEDA
CHEMICALS Inc.) was used in place of
methylenediphenyl-4,4'-diisocyanate (3 mol)/trimethylolpropane (1
mol) adduct, to obtain 20 parts by weight of a spherical latent
curing agent sized approximately 10 .mu.m.
Example 3
[0077] The same procedure was followed as in Example 1, except that
toluene diisocyanate (3 mol)/trimethylolpropane (1 mol) adduct
(D-103, available from MITSUI TAKEDA CHEMICALS Inc.) was used in
place of methylenediphenyl-4,4'-diisocyanate (3
mol)/trimethylolpropane (1 mol) adduct, to obtain 20 parts by
weight of a spherical latent curing agent sized approximately 10
.mu.m.
Example 4
[0078] The same procedure was followed as in Example 1, except that
m-xylylene diisocyanate (3 mol)/trimethylolpropane (1 mol) adduct
(D-110N, available from MITSUI TAKEDA CHEMICALS Inc.) was used in
place of methylenediphenyl-4,4'-diisocyanate (3
mol)/trimethylolpropane (1 mol) adduct, to obtain 20 parts by
weight of a spherical latent curing agent sized approximately 10
.mu.m.
Example 5
[0079] The same procedure was followed as in Example 1, except that
hexahydro-m-xylylene diisocyanate (3 mol)/trimethylolpropane (1
mol) adduct (D-120N, available form MITSUI TAKEDA CHEMICALS Inc.)
was used in place of methylenediphenyl-4,4'-diisocyanate (3
mol)/trimethylolpropane (1 mol) adduct, to obtain 20 parts by
weight of a spherical latent curing agent sized approximately 10
.mu.m.
Example 6
[0080] The same procedure was followed as in Example 1, except that
isophorone diisocyanate (3 mol)/trimethylolpropane (1 mol) adduct
(D-140N, available from MITSUI TAKEDA CHEMICALS Inc.) was used in
place of methylenediphenyl-4,4'-diisocyanate (3
mol)/trimethylolpropane (1 mol) adduct, to obtain 20 parts by
weight of a spherical latent curing agent sized approximately 10
.mu.m.
Example 7
[0081] The same procedure was followed as in Example 1, except that
isocyanurate form of isophorone diisocyanate (Z-4470, available
from SUMITOMO BAYER URETHANE Co., Ltd.) was used in place of
methylenediphenyl-4,4'-diisocyanate (3 mol)/trimethylolpropane (1
mol) adduct, to obtain 20 parts by weight of a spherical latent
curing agent sized approximately 10 .mu.m.
Example 8
[0082] 2 parts by weight of each of the latent curing agents
obtained in Examples 1 through 7, 90 parts by weight of an
alicyclic epoxy resin (CEL-2021P, available from DAICEL CHEMICAL
INDUSTRIES Co., Ltd.), and 8 parts by weight of a silane coupling
agent (A-187, available from NIPPON UNICAR Co., Ltd.) were
thoroughly mixed to form thermosetting epoxy resin compositions.
Each composition was analyzed using a differential scanning
calorimeter (DSC6200, available from SEIKO INSTRUMENT Co., Ltd.).
The results are shown in Table 1 and FIG. 2. With regard to the
curing characteristics of the latent curing agents, the heat
generation initiation temperature corresponds to a temperature at
which the composition starts to cure, the heat generation peak
corresponds to a temperature at which the curing of the composition
is at its peak, the heat generation termination temperature
corresponds to a temperature at which the curing of the composition
completes, and the peak area corresponds to the amount of heat
generated. TABLE-US-00001 TABLE 1 Heat generation Heat Heat
initiation Glass gener- generation Latent tempera- transition ation
termination curing ture temperature peak temperature Peak area
agent (.degree. C.) (.degree. C.) (.degree. C.) (.degree. C.)
(mJ/mg) Example 1 75 No 106 203 -478.425 measurement Example 2 103
No 131 214 -368.224 measurement Example 3 136 206 160 206 -251.807
Example 4 124 122 148 232 -100.666 Example 5 101 147 131 239
-220.929 Example 6 131 203 158 228 -204.317 Example 7 118 No 149
218 -211.21 measurement
[0083] As shown in Table 1 and FIG. 2, the results for the latent
curing agents of Examples 1 through 6 indicate that the curing
characteristics of the latent curing agent can be controlled by
changing the type of the polyfunctional isocyanate compound. The
latent curing agent of Example 1 started to cure the thermosetting
composition at a temperature equal to or lower than 100.degree.
C.
[0084] The results also indicate that the heat generation
initiation temperature, the heat generation peak temperature and
the heat generation termination temperature tend to shift to higher
temperatures (i.e., the curing temperature is increased) as the
glass transition point of the polyurea structure becomes higher
(Examples 3 through 6).
Example 9
[0085] Latent curing agents were prepared in the same manner as in
Example 1, except that the amount of the 24% isopropanol solution
of aluminum monoacetylacetonate bis(ethylacetoacetate)
(Alumichelate D, available from KAWAKEN FINE CHEMICALS Co., Ltd.)
to serve as the aluminum chelating agent was changed as shown in
Table 2 (Experiment Examples 9a through 9e). The results of Table 2
indicate that the polymer particles tend to aggregate as the amount
of the aluminum chelating agent is increased and particles of the
interfacial polymer can no longer be obtained as the aluminum
chelating agent is further increased. It is also shown that the
heat generation peak decreases as the aluminum chelating agent is
increased (FIG. 3). TABLE-US-00002 TABLE 2 Aluminum Particles of
Heat Experiment chelating agent interfacial generation Example
(Parts by weight) polymer peak (.degree. C.) 9a 2.78 Obtained 134
9b 5.55 Obtained 111 9c 11.10 Obtained 103 9d 16.65 Aggregate 97
formation 9e 22.20 No particle -- formation
Example 10
[0086] 2 parts by weight of the latent curing agent obtained in
Example 1, 90 parts by weight of an alicyclic epoxy resin
(CEL-2021P, available from DAICEL CHEMICAL INDUSTRIES Co., Ltd.),
and 8 parts by weight of each of the silane coupling agents shown
in Table 3 were thoroughly mixed to obtain thermosetting epoxy
resin compositions (Experiment Examples 10a through 10h).
[0087] Each of the composition obtained was analyzed using a
differential scanning calorimeter (DSC6200, available from SEIKO
INSTRUMENT Co., Ltd.). The results are shown in FIG. 4. The results
of FIG. 4 indicate that the curing characteristics of the latent
curing agent can be controlled by changing the type of the silane
coupling agent. TABLE-US-00003 TABLE 3 Experiment Example Silane
coupling agent 10a .gamma.-glycydoxypropyltrimethoxysilane (A-187,
available from NIPPON UNICAR) 10b
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (KBM303,
available from Shin-Etsu Chemical) 10c
.sigma.-styryltrimethoxysilane (KBM1403, available from Shin-Etsu
Chemical) 10d .gamma.-methacryloxypropyltrimethoxysilane (KBM503,
available from Shin-Etsu Chemical) 10e
.gamma.-acryloxypropyltrimethoxysilane (KBM5103, available from
Shin-Etsu Chemical) 10f .gamma.-aminopropyltriethoxysilane (KBM903,
available from Shin-Etsu Chemical) 10g
.gamma.-chloropropyltrimethoxysilane (KBM703, available from
Shin-Etsu Chemical) 10h .gamma.-mercaptopropyltrimethoxysilane
(KBM803, available from Shin-Etsu Chemical)
Example 11
[0088] To examine the effect of the viscosity of the organic phase
solution on the particle size distribution of the latent curing
particles, latent curing agents of Experiment Examples 11a through
11e were prepared. The curing agents were prepared in the same
manner as in Example 1, except that the amount of ethyl acetate in
the organic phase solution prepared in Example 1 (in which aluminum
monoacetylacetonate bis(ethylacetoacetate) and
methylenediphenyl-4,4'-diisocyanate (3 mol)/trimethylolpropane (1
mol) adduct were dissolved in ethyl acetate) was increased to
change the viscosity of the solution as shown in Table 4.
Experiment Example 11b corresponded to Example 1.
[0089] The organic phase solutions were analyzed for the viscosity
by a rheometer PK 100 (available from HAAKE). The results are shown
in Table 4. TABLE-US-00004 TABLE 4 Experiment Viscosity of organic
Examples phase (mPa S) Note 11a 224.9 No solvent 11b 5.521
Equivalent to Example 1 11c 2.535 -- 11d 2.074 -- 11e 1.321 --
[0090] The particle size distribution of the latent curing agents
of Experiment Examples 11b through 11e were measured by a sheath
flow particle size distribution analyzer (SD-2000, available from
Sysmex). FIGS. 5A through 5D show the size distribution charts (by
volume) for the latent curing agents. As shown by the charts, the
particle size distribution was a normal distribution when the
viscosity of the organic phase was 2.5 mPa.S. Moreover,
monodisperse emulsion particles having a size in the order of
microns (center diameter=3 .mu.m) were obtained when the viscosity
of the organic phase was 2.0 mPa.S. Monodisperse emulsion particles
having a size in the order of microns (center diameter=2 .mu.m)
were also obtained when the viscosity of the organic phase was 1.3
mPa.S. These results suggest that monodisperse emulsion particles
can be effectively obtained by adjusting the viscosity of the
organic phase in the range of 1 to 2.5 mPa.S. FIGS. 6A and 6B are
electron micrographs of the particles of the latent curing agents
of Experiment Examples 11b and 11e, respectively. These photographs
also demonstrate that the size distribution of the particles of the
latent curing agent of Experiment Example 11e show a better
monodispersion pattern than the latent curing agent of Experiment
Example 11a.
Example 12
[0091] To obtain particles of a latent curing agent with good
monodisperse property and good surface condition, the
polyfunctional isocyanate compound and the aluminum chelating agent
were mixed in different proportions. The amount of ethyl acetate
used was the same as in Example 11e to make monodisperse particles.
Specifically, latent curing agents of Experiment Examples 12a
through 12f were prepared in the same manner as in Example 1,
except that the amounts of the aluminum chelating agent and the
polyfunctional isocyanate compound in the organic phase solution
(in which aluminum monoacetylacetonate bis(ethylacetoacetate)
(aluminum chelating agent) and methylenediphenyl-4,4'-diisocyanate
(3 mol)/trimethylolpropane (1 mol) adduct (polyfunctional
isocyanate compound) were dissolved the same amount of ethyl
acetate as in Example 11e) were changed as shown in Table 5 below.
TABLE-US-00005 TABLE 5 Aluminum chelating Polyfunctional Experiment
agent (Parts by isocyanate compound Examples weight) (Parts by
weight) 12a 5.0 11.0 12b 6.0 11.0 12c 10.0 11.0 12d 11.0 11.0 12e
14.0 11.0 12f 17.0 11.0
[0092] Electron micrographs of the resulting latent curing agents
of Experiment Examples 12a through 12f are shown in FIGS. 7A
through 7F, respectively. The size of the particles of the
resulting latent curing agents could be controlled to at most 5
.mu.m in diameter since fine oil particles were formed before the
polymerization took place. The results also indicate that the
deposition of undesired materials around the particles can be
avoided by adjusting the amount of the aluminum chelating agent to
one-half or less (by weight) of the polyfunctional isocyanate
compound. The deposition of unwanted materials can also be avoided
by adding an equal amount or more (by weight) of the aluminum
chelating agent than the polyfunctional isocyanate compound. Thus,
when it is desired to make particles of the latent curing agent
that have good monodisperse property and good surface condition,
the amount of the aluminum chelating agent is preferably adjusted
to one-half or less, or the same amount or more (by weight), of the
polyfunctional isocyanate compound.
INDUSTRIAL APPLICABILITY
[0093] The aluminum chelator-based latent curing agent of the
present invention can cure thermosetting epoxy resins in a
relatively short period of time and at a relatively low temperature
and is thus suitable for use as a curing agent for anisotropic
conductive adhesives that are used to form anisotropic connection
quickly and at low temperatures.
* * * * *