Note: Descriptions are shown in the official language in which they were submitted.
CA 02481168 2004-09-10
SPECIFICATION
Title of the Invention:
Cationic Coating Composition and Coating Film-Forming
Method
Background of the Invention:
Field of the Invention:
The present invention relates to a cationic coating
composition, curable by both irradiation and heating, a
coating film-forming method and a coated product.
Description of Background Art:
In the field of the automobile coating, various kinds
of developments and approaches have been proposed from the
standpoints of an optimization of a production cost and a
measure to cope with the environment.
In the production cost optimization, for the purpose of
providing a cheap product to a user, approaches to
improvements in production cost, for example, reviews of
automobile body production steps such as reduction in steps,
energy saving, reduction in space, tact up, an integrated
coating of a plastic part and steel plate and the like,
reduction in a starting material cost and the like, have been
proposed.
As measures to cope with the environment, studies in
the production environment, for example, provision of a water
based or powder intercoat coating composition and topcoat
coating composition, and deletion of the intercoat coating
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composition for the purpose of reducing an exhaust gas, gum
and soot from a drying oven, and reducing a volatile organic
compound have been made, and in the case of the product
environment, provision of an electrodeposition coating film
free of a harmful metal such as lead, tin and the like has
been promoted.
A coating composition containing an acrylic resin
having a functional group reactive with light, and a heat-
curable curing agent is disclosed in Japanese Patent
Application Laid-Open No. 11169/89 (Patent Reference 1).
However, the above coating composition can not be subjected
to an electrodeposition coating and may result unsatisfactory
corrosion resistance due to the use of the acrylic resin.
Japanese Patent Application Laid-Open No. 97/241533,
published'September 16, 1997 discloses a photocurable putty used
in an automobile repair, containing bisphenol A type epoxy
di(meth)acrylate and capable of forming a cured coating film by a
photopolymerization reaction (Patent Reference 2). However,
a satisfactory curing can not be achieved by photo-curing
only, resulting in unsatisfactory properties in finish
properties and corrosion resistance.
International Patent Application Laid-Open No. 99/125660
(W099/12660), published March 18, 1999, Japan, PCT/JP98/04099
discloses a coating method which comprises coating
a cationic electrodeposition coating composition, followed by
coating an intercoat coating composition by a wet - on - wet
coating method for the purpose of reduction in steps and
energy savings (Patent Reference 3).
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However, the wet=on - wet coating of the intercoat
coating composition onto the cationic electrodeposition
coating film develops mixing between the electrodeposition
coating film and the intercoat coating film, resulting in
reducing finish properties and corrosion resistance.
Japanese Patent Application Laid-Open No. 2002-265822
(Patent Reference 4) discloses a novel cationic
electrodeposition coating composition containing, as a
coating film-formi.ng resin, a resin composition having
sulfonium group and propargyl group, and a coating film-
forming method which comprises subjecting the cationic
electrodeposition coating composition to electrodeposition
coating, followed by photopolymerizing to form a cured
coating film for the purpose of making possible a low
temperature curing and short time curing. However, Patent
Reference 4 may result a volatilization of sulfur (S) in the
sulfonium group into the air on heat curing, and an eluation
thereof from the coating film on recycling a coating
substrate, resulting in providing heavy loads onto
environment.
In view of the above background, provision of a
cationic coating composition, and a multi-layer coating film-
forming method using an intercoat coating composition and/or
a topcoat coating composition in addition to the cationic
coating composition, which make possible the optimization of
a production cost, for example, reduction in steps and energy
savings by omission of heating and drying oven and heating
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step, and providing reduced loads onto environment and
showing good properties in finish properties and corrosion
resistance, has been demanded.
Summary of the Invention:
It is an object of the present invention to provide a
cationic coating composition, and a method of forming a mono-
layer electrodeposition coating film or a multi-layer coating
film by use of the cationic coating composition, which are
capable of achieving reduction in steps, energy saving,
reduction in space, and reduction in loads onto environment,
for example, reduction in an exhaust gas, gum soot from a
drying oven.
The present inventors made intensive studies for the
purpose of solving the problems in the art to find out a
cationic coating composition containing an unsaturated group-
modified blocked polyisocyanate crosslin:king agent (A), a
cationic epoxy resin (B) and a photopolymerization initiator
(C), an unsaturated group-modified cationic epoxy resin (A),
a blocked polyisocyanate crosslinking agent (B) and a
photopolymerization initiator (C), a mono-layer coating film-
forming method which comprises subjecting a cationic coating
film to irradiation and heating to obtain a cured mono-layer
coating film, and a multi-layer coating film-forming method,
which comprises subjecting a cationic coating film to
irradiation only, followed by coating an intercoat coating
composition and/or a topcoat coating composition, and
simultaneously heating and curing the resulting multi-layer
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coating film, resulting in accomplishing the present
invention.
That is, the present invention provides
1. A cationic coating composition containing (A) an
unsaturated group-modified blocked polyisocyanate
crosslinking agent obtained by reacting a hydroxyl group-
containing unsaturated compound (a), a blocking agent (b) and
a polyisocyanate compound (c), (B) a cationic epoxy resin,
and (C) a photopolymerization initiator,
2. A cationic coating composition as defined in paragraph
1, wherein an unsaturated group concentration of the
unsaturated group-modified blocked polyisocyanate
crosslinking agent (A) is in the range of 0.25 to 4.5
moles/kg on the basis of the solid content of the
crosslinking agent (A),
3. A cationic coating composition as defined in paragraph
1 or 2, wherein the cationic coating composition further
contains a polymerizable unsaturated group-containing
compound (D),
4. A mono-layer coating film-forming method, which
comprises subjecting a cationic electrodeposition coating
composition as the cationic coating composition as defined in
any one of paragraphs 1 to 3 to electrodeposition coating to
form an electrodeposition coating film, followed by
subjecting the electrodeposition coating film to both
irradiation and heating to form a cured niono-layer coating
film,
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5. A multi-layer coating film-forming method which
comprises the following successive steps (1) to (4):
a step (1) of coating the cationic coating composition as
defined in any one of paragraphs 1 to 3 onto a coating
substrate to form a cationic coating film,
a step (2) of subjecting the cationic coating film formed in
the step (1) to irradiation,
a step (3) of coating an intercoat coating composition and/or
a topcoat coating composition to form an intercoat coating
film and/or a topcoat coating film, and
a step (4) of simultaneously heating and curing the cationic
coating film, and the intercoat coating film and/or the
topcoating film,
6. A multi-layer coating film-forming method as defined in
paragraph 5, wherein the cationic coating film formed by the
step (1) in paragraph 5 is preheated at a temperature of 60
to 120 C,
7. A multi-layer coating film-forming method as defined in
paragraph 5, wherein the cationic coating composition is a
cationic electrodeposition coating composition, and
8. A coated product obtained by any one of the methods as
defined in paragraphs 4 to 7.
Detailed Description of the Invention:
The present invention provides a coating film-forming
method, which uses a cationic coating composition curable by
irradiation and heating, and which makes possible reduction
in steps, energy saving, reduction in space, reduction in
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production cost and reduction in loads onto environment, for
example, reduction in exhaust gas, gum and soot from a drying
oven, and provides a coated product showing good properties
in finish properties and water resistance.
The present invention also provides a multi-layer
coating film-forming method which comprises subjecting a
cationic coatirig film to irradiation only, followed by
coating an intercoat coating composition and/or a topcoat
coating composition to form an intercoat coating film and/or
a topcoat coating film, and simultaneously heating and curing
the resulting multi-layer coating film.
Cationic Coating Composition
The cationic coating composition of the present
invention contains an unsaturated group-modified blocked
polyisocyanate crosslinking agent (A), a cationic epoxy resin
(B) and a photopolymerization initiator (C), and preferably a
polymerizable unsaturated group-containing compound (D).
Unsaturated group-modified blocked polyisocyanate
crosslinking agent (A):
The unsaturated group-modified blocked polyisocyanate
crosslinking agent (A) is an addition reaction product of a
hydroxyl group-containing unsaturated compound (a), a
blocking agent (b) and a polyisocyanate compound (c). The
use of the hydroxyl group-containing unsaturated compound (a)
makes possible to introduce an unsaturated group into the
crosslinking agent by reaction of the hydroxyl group with the
polyisocyanate compound. Examples of the hydroxyl group-
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containing unsaturated compound may include 2-hydroxyethyl
(meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-
hydroxybutyl (meth)acrylate, an addition product of 2-
hydroxyethyl (meth)acrylate with caprolactone, for example,
Placcel FA-2, FM-3, etc. (trade names, marketed by Daicel
Chemical Industries, Ltd.) and the like. These may be used
alone or in combination.
The blocking agent is such that addition of the
blocking agent to an isocyanate group in the polyisocyanate
compound.blocks the isocyanate group, and a resulting blocked
polyisocyanate compound is stable at nor:mal temperatures, but
heating at a heat-curing temperature usually in the range of
about 100 C to 200 C may dissociate the blocking agent to
regenerate a free isocyanate group.
The blocking agent to satisfy the above requirements
may include, for example, a lactam based compound such as 6-
caprolactam, y-butylolactam and the like; an oxime compound
such as methylethylketoxime, cyclohexanoneoxime and the like;
phenol based compound such as phenol, p-t-butylphenol, cresol
and the like; aliphatic alcohols such as n-butanol, 2-
ethylhexanol and the like; aromatic alkyl alcohols such as
phenyl carbitol, methylphenyl carbitol and the like; and
ether alcohol compounds such as ethylene glycol monobutyl
ether, ethylene glycol monoethyl ether and the like.
The polyisocyanate compound (c) may include, for
example, aromatic, aliphatic or alicyclic polyisocyanate
compound such as tolylene diisocyanate, xylene diisocyanate,
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phenylene diisocyanate, diphenylmethane-2,4 -diisocyanate,
diphenylmethane-4,4'-diisocyanate (or MDI), crude MDI,
bis(isocyanatomethyl)cyclohexane, tetramethylene diisocyanate,
hexamethylene diisocyanate, methylene diisocyanate,
isophorone diisocyanate and the like; a cyclic polymerization
product of these polyisocyanate compounds, isocyanate biuret
type adducts, a terminal isocyanate-containing compound
obtained by reacting an excess amount of these polyisocyanate
compounds with a low molecular active hydrogen-containing
compound such as ethylene glycol, propylene glycol,
trimethylolpropane, hexane triol, castor oil and the like,
and the like. These may be used alone or in combination.
The unsaturated group concentration of the unsaturated
group-modified blocked polyisocyanate crosslinking agent (A)
is in the range of 0.25 to 4.5 moles/kg on the basis of the
solid content of the crosslinking agent (A).
When outside the above range, an unbalance between
coating film curing due to irradiation and coating film
curing due to heating may cause a non-un:iform crosslinking,
resulting in reducing finish properties and anti-corrosive
properties.
Cationic epoxy resin (B):
The epoxy resin used in the cation_ic epoxy resin (B)
may preferably include, from the standpoint of corrosion
resistance of the coating film, an epoxy resin prepared by
reaction of a polyphenol compound with an epihalohydrin such
as epichlorohydrin.
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The polyphenol compound used for obtaining the epoxy
resin may include ones known in the art, for example, bis(4-
hydroxyphenyl)-2,2-propane (bisphenol A), 4,4-
dihydroxybenzophenone, bi.s(4-hydroxyphenyl)methane (bisphenol
F), bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-
1,1-isobutane, bis(4-hydroxy-tert-butyl-phenyl)-2,2-propane,
bis(2-hydroxynaphthyl)methane, tetra(4-h_ydroxyphenyl)-
1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone (bisphenol S),
phenol novolak, cresol novolak, and the like.
The epoxy resin obtained by the reaction of the
polyphenol compound with epichlorohydrin may particularly
include ones derived from bisphenol A and represented by the
following formula:
/O\ CH3 CH3 i_ 0
HpC-HC-HZC-O C O-CHZ CH-CHZ O C O-CHZ CH-CH2
\ , CH
3 3 -~
where n is 0 to 8.
The epoxy resin has an epoxy equivalent in the range of
180 to 2,500, preferably 200 to 2,000, more preferably 400 to
1,500, and a number average molecular weight in the range of
at least 200, particularly 400 to 4,000, more particularly
800 to 2,500.
Examples of commercially available trade names of the
epoxy resin may include Epikote 828 EL, Epikote 1002, Epikote
1004 and Epikote 1007 (trade names marketed by Japan Epoxy
Resin Co., Ltd.).
The cationic group-containing compound in the cationic
epoxy resin (B) is a compound containing a cationic group
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such as amino group, arnmonium salt group, sulfonium salt
group, phosphonium salt group and the like. Of these, amino-
group is preferable from the standpoint of water
dispersibility. The amino group may be introduced into the
epoxy resin by addition of the amino group-containing
compound to the epoxy resin.
The amino group-containing compound is a cationic
properties-imparting component which introduces amino group
into the epoxy resin base and cationizes the epoxy resin, and
may include one having at least one active hydrogen to react
with epoxy group.
The amino group-containing compound used for the above
purpose may include, for example, mono- or di-alkylamine such
as monomethylamine, dimethylamine, monoethylamine,
diethylamine, monoisopropylamine, diisopropylamine,
monobutylamine, dibutylamine and the like; alkanolamine such
as monoethanolamine, diethanolamine, mono(2-
hydroxypropyl)amine, di(2-hydroxypropyl)amine, tri(2-
hydroxypropyl)amine, monomethylaminoethanol,
monoethylaminoethanol and the like; alkylene polyamine such
as ethylenediamine, propylenediamine, butyleriediamine,
hexamethylenediamine, tetraethylenepentamine,
pentaethylenehexamine, diethylaminopropylamine,
diethylenetriamine, triethylenetetramine and the like, and a
ketiminized product of these polyamines; an alkyleneimine
such as ethyleneimine, propyleneimine and the like; a cyclic
amine such as piperazine, morpholine, pyrazine and the like,
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and the like.
A mixing ratio of the cationic group-containing
compound as a reaction component relative to the epoxy resin
is not specifically limited and may arbitrarily be varied
depending on uses of the coating composition, but is
preferably such that the epoxy resin is in the range of 60 to
95% by weight, preferably 65 to 90% by weight, and the
cationic group-containing compound is in. the range of 5 to
40% by weight, preferably 10 to 35% by weight based on a
total solid content of the epoxy resin and the cationic
group-containing compound.
The above addition reaction may be carried out in a
suitable solvent under the conditions of about 80 C to about
170 C, preferably about 90 C to about 150 C and 1 to 6 hours,
preferably about 1 to 5 hours. The above solvent may include,
for example, hydrocarbons such as toluene, xylene,
cyclohexane, n-hexane and the like; esters such as methyl
acetate, ethyl acetate, butyl acetate and the like; ketones
such as acetone, methyl ethyl ketone, methyl isobutyl ketone,
methyl amyl ketone and the like; amides such as dimethyl
formamide, dimethyl acetamide and the like; alcohols such as
methanol, ethanol, n-propanol, iso-propanol and the like, and
mixtures thereof.
The cationic epoxy resin (B) may also be plasticized
and modified. An epoxy resin-plasticizing modifier may
include ones having a good compatibility with the epoxy resin
and hydrophobic properties_
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An amount of the modifier used for plasticization must
be in a minimum amount necessary for plasticization, and is
in the range of 3 to 40 parts by weight, preferably 5 to 30
parts by weight per 100 parts by weight of the epoxy resin.
The modifier may preferably include, for example, ones having
reactivity with epoxy group such as xylene formaldehyde resin,
polycaprolactone polyol and the like.
The cationic epoxy resin (B) may also be unsaturated
group-modified.
An unsaturated group may be introduced into the epoxy
resin by addition of an unsaturated grou.p-containing compound
to the epoxy resin.
The unsaturated group-containing compound may include,
for example, a carboxyl group-containing unsaturated monomer
such as acrylic acid, methacrylic acid, crotonic acid,
itaconic acid, maleic acid, fumaric acid and the like; a
hydroxyl group-containing unsaturated monomer such as 2-
hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,
4-hydroxybutyl (meth)acrylate, adducts of 2-hydroxyethyl
(meth)acrylate with caprolactone, for example, Placcel FA-2,
Placcel FM-3 (trade names, marketed by Daicel Chemical
Industries, Ltd., respectively) and the like, and an adduct
thereof with a diisocyanate compound such as tolylene
diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene
diisocyanate, hexamethylene diisocyanate, isophorone
diisocyanate, 4,4'-methylenebiscyclohexyl isocyanate and the
like. Of these, the mono-adduct with the diisocyanate
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compound is preferable from the standpoint of a degree of
freedom on synthesis.
An unsaturated group concentration of the cationic
epoxy resin (B) is preferably in the range of 0 to 1.0 mol/kg
based on a solid content of the cationic epoxy resin (B). A
concentration outside the above range may reduce storage
stability.
A mixing ratio of the unsaturated group-modified
blocked polyisocyanate crosslinking agent (A) and the
cationic epoxy resin (B) is such that the crosslinking agent
(A) is 10 to 50% by weight, preferably 15 to 40% by weight,
and the cationic epoxy resin (B) is 50 to 90% by weight,
preferably 60 to 85% by weight based on a total solid content
of the unsaturated group-modified blocked polyisocyanate
crosslinking agent (A) and the cationic epoxy resin (B)
respectively_
Photopolymerization Initiator (C):
The photopolymerization initiator (C) in the cationic
coating composition may include, for example, benzoin,
benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl
ether, diethoxyacetophenone, 2-hydroxy-2-methyl-l-
phenylpropane-l-on, 2-benzyl-2-dimethylamino--l- (4-
morpholinophenyl)-butanone, 2,4,6-trimethylbenzoylphenyl-
phosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine
oxide, benzophenone, methyl, o-benzoyl benzoate,
hydroxybenzophenone, 2-isopropyl-thioxanthone, 2,4-
dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-
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dichlorothioxanthone, 2,4,6-tris(trichloromethyl)-S-triazine,
2-methyl-4,6-bis(trichloro)-s-triazine, 2-(4-methoxyphenyl)-
4,6-bis(trichloromethyl)-s-triazine and the like.
Specifically, trade names of the photopolymerization
initiator may include, for example, Cyracure UVI-6970,
Cyracure UVI-6974, Cyracure UVI-6990, Cyracure UVI-6950
(marketed by USA Union Carbide Corp., trade names
respectively), Irgacure 184, Irgacure 819, Irgacure 261
(marketed by Ciba Specialty Chemicals K.K., trade names
respectively), SP-150, SP-170 (marketed by Asahi Denka Co.,
Ltd., trade names respectively), CG-24-61 (marketed by Ciba
Specialty Chemicals K.K., trade name), CI-2734, CI-2758, CI-
2855 (marketed by Nippon Soda Co., Ltd., trade names
respectively), PI-2074 (marketed by Rhone-Poulenc S.A., trade
name, pentafluorophenylborate toluylcumyl iodonium salt),
FFC509 (marketed by 3M Co., Ltd., trade name), BBI102
(marketed by Midori Kagaku Co., Ltd., trade riame) and the
like.
These photopolymerization initiators may be used alone
or in combination. A mixing amount of the
photopolymerization initiator (C) is preferably in the range
of 0.1 to 15% by weight, preferably 0.2 to 10% by weight
based on a total solid content of the unsaturated group-
modified blocked polyisocyanate crosslinking agent (A) and
the cationic epoxy resin (B) from the standpoint of
photocurability.
The photopolymerization initiator (C) may be used in
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combination with a photosensitizer for the purpose of
promoting the photopolymerization reaction. The
photosensitizer used in combination may include, for example,
a tertiary amines such as triethylamine, triethanolamine,
methyldiethanolamine, methyl 4-dimethylaminobenzoate, ethyl
4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-
dimethylamino)ethyl benzoate, Michler's ketone, 4,4'-
diethylaminobenzophenone and the like; alkylphosphines such
as triphenylphosphine and the like, thioethers such as thiodiglycol and the
like, and the like.
The photosensitizers may be used alone or in
combination. A mixing amount of the photosensitizer is in
the range of 0 to 5% by weight based on a total solid content
of the unsaturated group-modified blocked polyisocyanate
crosslinking agent (A) and the cationic epoxy resin (B).
Polymerizable Unsaturated Group-Containing Compound (D):
The cationic coating composition may further contain a
polymerizable unsaturated group-containing compound (D). The
polymerizable unsaturated group-containi.ng compound (D) is a
compound having at least one radically polymerizable
unsaturated group in one molecule, preferably at least two
from the standpoint of curing properties.
The compound (D) specifically may include, for example,
as a mono-functional polymerizable monomer, styrene, methyl
(meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate,
cyclohexyl (meth)acrylate, cyclohexenyl (meth)acrylate, 2-
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hydroxyl (meth)acrylate, hydroxypropyl (meth)acrylate,
tetrahydro-furfuryl (meth)acrylate, E-caprolactone-modified
tetrahydrofurfuryl (meth)acrylate, phenoxyethyl
(meth)acrylate, phenoxy-polyethylene glycol (meth)acrylate,
dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl
(meth)acrylate, isobornyl (meth)acrylate, benzyl
(meth)acrylate, s-caprolactone-modified hydroxyethyl
(meth)acrylate, polyethylene glycolmono (meth)acrylate,
polypropylene glycolmono (meth)acrylate, 2-hydroxy-3-
phenoxypropyl (meth)acrylate, 2-hydroxy-3-butoxypropyl
(meth)acrylate, monohydroxyethyl phthalate (meth)acrylate,
Aronix M110 (trade name, marketed by Toagosei Chemical
Industry Co., Ltd.), N-methylol (meth)acrylamide, N-methylol
(meth)acrylamide butyl ether, acryloylmorpholine,
dimethylaminoethyl (meth)acrylate, N-vinyl-2-pyrrolidone and
the like; as bifunctional polymerizable monomer, for example,
ethylene glycol di(meth)acrylate, diethylene glycol
di(meth)acrylate, polyethylene glycol di(meth)acrylate,
propylene glycol di(meth)acrylate, dipropylene glycol
di(meth)acrylate, polypropylene glycol di(meth)acrylate,
neopentyl glycol di(meth)acrylate, 1,4-butanediol
di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol
A ethylene oxide-modified di(meth)acrylate, bisphenol A
propylene oxide-modified di(meth)acrylate, 2-hydroxy-l-
acryloxy-3-methacryloxypropane, tricyclodecanedimethanol
di(meth)acrylate, di(meth)acryloyloxy-ethyl acid phosphate,
Kayarad HX-220, 620, R-604, MANDA (trade name, marketed by
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Nippon Kayaku Co., Ltd., respectively), Photomer (trade name,
marketed by Cognis Japan Ltd., epoxy oligomer), and the like;
and as tri- or higher functional polymerizable monomer, for
example, trimethylolpropane tri(meth)acr_ylate,
trimethylolpropane ethylene oxide-modified tri(meth)acrylate,
trimethylolpropane propylene oxide-modified tri(meth)acrylate,
glycerin tri(meth)acrylate, glycerin ethylene oxide-modified
tri(meth)acrylate, glycerin propylene oxide-modified
tri(meth)acrylate, pentaerythritol tri(meth)acrylate,
pentaerythritol tetra(meth)acrylate, isocyanuric acid
ethylene oxide-modified triacrylate, dipentaerythritol,
hexa(meth)acrylate, and the like. These compounds may be
used alone or in combination.
A mixing amount of the polymerizable unsaturated group-
containing compound (D) is such that the polymerizable
unsaturated group-containing compound (D) is in the range of
0 to 45% by weight based on a total solid content of the
unsaturated group-modified blocked polyisocyanate
crosslinking agent (A) and the cationic epoxy resin (B).
The cationic coating composition may preferably include
a cationic electrodeposition coating composition obtained by
a method, which comprises mixing the unsaturated group-
modified blocked polyisocyanate crosslinking agent (A), the
cationic epoxy resin (B), the photopolymerization initiator
(C), preferably the polymerizable unsaturated group-
containing compound (D) and additives with sufficient
agitation, followed by neutralizing with a water-soluble acid
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in a water based medium to make water-soluble or water-
dispersible.
Preferable examples of the acid used for neutralization
may include an organic carboxylic acid such as acetic acid,
formic acid and the like, preferably mixtures thereof. Use
of the organic carboxylic acid for neutralization may improve
finish properties and throwing power properties resulting
from the coating composition, and coating composition
stability.
The cationic coating composition of the present
invention may contain a bismuth compound as an anticorrosive
agent. The bismuth compound may not be particularly limited,
but may include an inorganic bismuth compound such as bismuth
oxide, bismuth hydroxide, basic carbonate bismuth, bismuth
nitrate, bismuth silicate and the like. Of these, bismuth
hydroxide is preferable.
The bismuth compound may also include an organic acid
bismuth salt prepared by reacting at least two organic acid,
at least one of which is aliphatic hydroxycarboxylic acid,
with the above bismuth compound.
An organic acid used in preparation of the organic acid
bismuth salt may include, for example, glycol acid, glycerin
acid, lactic acid, dimethylolpropionic acid, dimethylol
butyric acid, dimethylol valeric acid, tartaric acid, malic
acid, hydroxymalonic acid, dihydroxysuccinic acid,
trihydroxysuccinic acid, methyl malonic acid, benzoic acid,
citric acid and the like.
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These inorganic bismuth compounds and organic acid
bismuth salts may be used alone or in combination.
A mixing amount of these bismuth compounds in the
cationic coating composition of the present invention may not
be particularly limited and may widely be varied depending on
performances required for the coating composition, but is
such that a bismuth content is in the range of 0 to 10 parts
by weight, preferably 0.05 to 5 parts by weight per 100 parts
by weight of the resin solid content in the coating
composition.
The cationic coating composition of the present
invention may optionally contain a tin compound as a curing
catalyst. The tin compound may include, for example, an
organic tin compound such as dibutyltin oxide, dioctyltin
oxide and the like; aliphatic or aromatic carboxylic acid
salt of dialkyltin, for example, dibutyltin dilaurate,
dioctyltin dilaurate, dibutyltin diacetate, dioctyltin
dibenzoate, dibutyltin dibenzoate and the like. Of these
dialkyltin aromatic carboxylic acid salt is preferable.
A mixing amount of the above tin compounds in the
cationic coating composition of the present invention may not
particularly be limited and may widely be varied depending on
performances required for the coating composition, but is
such that a tin content is in the range of 0.01 to 8.0 parts
by weight, preferably 0.05 to 5.0 parts by weight per 100
parts by weight of a resin solid content in the coating
composition.
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CA 02481168 2004-09-10
The cationic coating composition may optionally and
preferably contain a modifying resin such as a xylene resin,
acrylic resin and the like, and may optionally contain a
coating composition additive such as a color pigment,
extender pigment, anti-corrosive pigment, organic solvent,
pigment dispersant, surface controlling agent and the like.
A coating method to form a coating film may include a
cationic electrodeposition coating method, spray coating
method, electrostatic coating method and the like.
The cationic electrodeposition coating may be carried
out under conditions of a solid content concentration of
about 5 to 40% by weight by diluting with deionized water, a
pH in the range of 5.5 to 9.0, an electrodeposition coating
bath temperature of 15 to 35 C and a loading voltage of 100
to 400 V.
A cationic electrodeposition coating film thickness may
not particularly be limited, but generally is in the range of
to 40 m, particularly 15 to 35 m as a cured coating film.
Curing and drying of the coating film may be carried out by
the following methods, that is, (1) a method of subjecting a
coating film to irradiation followed by heating, (2) a method
of subjecting a coating film to heating followed by
irradiation, (3) a method of subjecting a coating film to
irradiation and heating simultaneously, and (4) a method of
subjecting a coating film to irradiation only, followed by
heating the resulting coating film, and an intercoat coating
film and/or a topcoat coating film simultaneously.
- 21 -
CA 02481168 2004-09-10
Curing by irradiation of the coating film may be
carried out by irradiation of an ultraviolet light having a
wave length of 200 to 450 nm. On irradiation of the
ultraviolet light, an irradiation source having a highly
sensitive wave length may be selected depending on a kind of
the photopolymerization initiator. An irradiation source of
the ultraviolet light may include, for example, high pressure
mercury lamp, ultrahigh pressure mercury lamp, xenone lamp,
carbon arc, metal halide lamp, sunlight and the like.
Conditions of ultraviolet light irradiation onto the coating
film are such that an irradiation dose is in the range of 100
to 5,000 mj/cm2, preferably 500 to 3,000 mj/cm2. An
irradiation time of about several minutes makes it possible
to cure the coating film.
Heat= curing conditions are such that a surface
temperature of the coating film is in the range of about 120
to about 200 C, preferably about 130 to about 180 C, and a
heat curing time is about 5 to 60 minutes, preferably about
to 30 minutes.
Heat curing may also be carried out by a multi-layer
coating film-forming method which comprises heat curing a
cationic coating film or the cationic electrodeposition
coating film, and an intercoat coating film and/or a topcoat
coating film simultaneously.
Multi-Layer Coating Film-Forming Method
A multi-layer coating film-forming method, which
comprises heat curing a cationic coating film, and an
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CA 02481168 2004-09-10
intercoat coating film and/or a topcoat coating film
simultaneously, is explained hereinafter.
That is, the multi-layer coating film-forming method
comprises the following successive steps (1) to (4):
a step (1) of coating the cationic coating composition as
defined in any one of paragraphs 1 to 5 onto a coating
substrate to form a cationic coating film,
a step (2) of subjecting the cationic coating film formed in
the step (1) to irradiation,
a step (3) of coating an intercoat coating composition and/or
a topcoat coating composition to form an intercoat coating
film and/or a topcoat coating film, and
a step (4) of simultaneously heating and curing the cationic
coating film, and the intercoat coating film and/or the
topcoating film_
The above steps (1) to (4) are explained more in detail
hereinafter.
The step (1) is a step of coating a cationic coating
composition to form a cationic coating film. In the case
.where the cationic coating composition is a cationic
electrodeposition coating composition, a cationic
electrodeposition coating may be applied onto a coating
substrate, for example, an automobile body, parts, electrical
products, architectural material and the like, made of iron,
aluminum, tin, zinc, alloys thereof and the like. These
electrically conductive coating substrates are preferably
subjected to a surface treatment with a zinc phosphate prior
- 23 -
CA 02481168 2004-09-10
to coating the cationic electrodeposition coating composition
from the standpoint of improving corrosion resistance.
The cationic electrodeposition coating film formed by
the electrodeposition coating is washed with water,
preferably followed by subjecting to preheating at a
temperature of 60 to 120 C, setting at room temperature, air
blowing and the like from the standpoints of improvements in
finish properties and corrosion resistance.
The step (2) is a step of subjecting the cationic
coating film to irradiation for crosslinking. The cationic
coating film is crosslinked and cured by irradiation of an
ultraviolet light having a wave length of 200 to 450 nm. On
irradiation of the ultraviolet light, an irradiation source
having a highly sensitive wave length may be selected
depending on a kind of the photopolymerization initiator. An
irradiation source of the ultraviolet light may include, for
example, high pressure mercury lamp, ultrahigh pressure
mercury lamp, xenone lamp, carbon arc, metal halide lamp,
sunlight and the like. Conditions of ultraviolet light
irradiation onto the coating film are such that an
irradiation dose is in the range of 100 to 5,000 mj/cm2,
preferably 500 to 3,000 mj/cm2. An irradiation time of about
several minutes makes it possible to cure the coating film.
The step (3) is a step of coating an intercoat coating
composition and/or a topcoat coating composition to form an
intercoat coating film and/or a topcoat coating film. The
intercoat coating composition and the topcoat-coating
- 24 -
CA 02481168 2004-09-10
composition may include a water based, powder or organic
solvent based ones comprising a base resin and a crosslinking
agent respectively. However, from the standpoint of measures
to environment, a water based coating composition comprising
a water dispersion on emulsion of an acrylic resin or
polyester resin containing carboxyl group and hydroxyl group
respectively is preferable. Nevertheless a water based
intercoat coating composition and a water based topcoat
coating composition are usually an anionic coating
composition, curing of the cationic coating film by
irradiation can prevent mixing or agglomeration between the
cationic coating film, and the intercoat coating film and/or
the topcoat coating film, resulting in making it possible to
form an intercoat coating film and/or a topcoat coating film
showing improved finish properties.
The base resin in the above water based coating
composition may include any ones containing hydroxyl group
and carboxyl group as known in the art, for example,
polyester resin, acrylic resin, fluorocarbon resin, silicon-
containing resin and the like. The base resin has a hydroxyl
value of 30 to 200 mg KOH/g, particularly 50 to 150 mg KOH/g,
an acid value of 10 to 100 mg KOH/g, particularly 15 to 75 mg
KOH/g, a number average molecular weight of 1,000 to 100,000,
particularly 5,000 to 50,000.
A crosslinking agent used in combination with the base
resin may include, for example, melamine resin, urea resin,
benzoguanamine resin, methyloled product thereof, etherified
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CA 02481168 2004-09-10
amino resin obtained by etherifying a part of all of the
methyloled product with mono-alcohol having 1 to 8 carbon
atoms, and blocked polyisocyanate.
The water based coating composition may optionally
contain a color pigment, extender pigment, ultraviolet light
absorber and the like. A mixing amount of the pigment is 0
to 150 parts by weight per 100 parts by weight of a total
weight of the base resin and the crosslinking agent.
The intercoat coating composition and/or the topcoat
coating composition are prepared by mixing and dispersing the
base resin and the crosslinking agent with water respectively.
A mixing ratio to water may not particularly be limited, but
mixing is preferably be carried out so that a solid content
on coating can be in the range of 15 to 60% by weight. The
topcoat coating composition may optionally contain a color
pigment, metallic pigment, extender pigment, ultraviolet
light absorber and the like.
The intercoat coating composition and/or the topcoat
coating composition may be coated by at least one layer
respectively by a coating method such as an air spray coating,
airless spray coating, rotary spray coating or electrostatic
coating and the like so as to a film thickness of about 10 to
50 m.
The step (4) is a step of simultaneously heating and
curing the cationic coating film, and the intercoat coating
film and/or the topcoat coating film at a heating temperature
of about 100 to 200 C, preferably about 120 to 180"C for 1 to
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CA 02481168 2004-09-10
120 minutes, preferably 10 to 30 minutes.
A heating method may include a direct or indirect hot
air drying method by use of an electric furnace, gas furnace
and the like, a heating method by use of infrared rays and
far infrared rays, a dielectric heating method by use of high
frequency, and the like. As measures to refuse and dust, the
multi-layer coating film comprising the cationic coating film,
and the intercoat coating film and/or the topcoat coating
film can be heated and cured by subjecting to the heating
method by use of infrared rays and far infrared rays,
followed by subjecting to the hot air drying method.
The present invention can provide the following
particular effects.
In the case where the cationic electrodeposition
coating composition is used as the cationic coating
composition of the present invention, the combined use of
both irradiation and heating in the crosslinking reaction of
the electrodeposition coating film makes possible reduction
in steps, energy savings and reduction in space, resulting in
making it possible to reduce exhaust gas, gum and soot from
the drying oven and to reduce loads onto environment, and
resulting in reducing a heating loss, i.e. a weight loss
after heat curing and drying of the electrodeposition coating
film.
According to the conventional multi-layer coating film-
forming method, which comprises coating a cationic
electrodeposition coating composition as a cationic coating
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CA 02481168 2004-09-10
composition to form an uncured electrodeposition coating film,
followed by coating onto the uncured electrodeposition
coating film an intercoat coating composition and/or topcoat
coating composition to form an intercoat coating film and/or
topcoat coating film, and heat curing simultaneously, the
resulting multi-layer coating film may show poor properties
in finish properties and water resistance.
Contrary thereto, the multi-layer coating f:ilm-forming
method of the present invention prevents mixing between the
cationic coating film, and the intercoat coating film and/or
the topcoat coating film, and makes possible improvements in
finish properties and water resistance.
Example
The present invention.will be explained more in detail
by the following Examples and Comparative Examples, in which
"part" and "o" mean "part by weight" and "o by weight"
respectively. The present invention should not be limited
thereto.
Preparation Example 1
Preparation of Crosslinking Agent No. 1 (for Example):
A reactor was charged with 222 g of isophorone
diisocyanate and 97 g of methyl isobutyl ketone, followed by
heating up to 50 C, slowly adding 116 g of hydroxyethyl
acrylate, 96 g of methyl ethyl ketoxime and 0.5 g of
hydroquinone, heating up to 100 C, sampling with time while
keeping at that temperature, and confirming that absorption
of an unreacted isocyanate disappeared by an infrared
- 28 -
CA 02481168 2004-09-10
absorption spectral measurement to obtain an unsaturated
group-modified crosslinking agent No. 1 having an unsaturated
group concentration of 2.4 mol/kg and a solid coritent of 80%.
Preparation Example 2
Preparation of Crosslinking Agent No. 2 (for Example):
A reactor was charged with 168 g of hexamethylene
diisocyanate and 87 g of methyl isobutyl ketone, followed by
heating up to 50 C, slowly adding 130 g of hydroxyethyl
methacrylate, 96 g of methyl ethyl ketoxime and 0.5 g of
hydroquinone, heating up to 100 C, sampling with time, while
keeping at that temperature, and confirming that absorption
of an unreacted isocyanate disappeared by an infrared
absorption spectral measurement to obtain an unsaturated
group-modified crosslinking agent No. 2 having an unsaturated
group concentration of 2.6 mol/kg and a solid content of 80%.
Preparation Example 3
Preparation of Crosslinking Agent No. 3 (for Comparative
Example):
A reactor was charged with 222 g of isophorone
diisocyanate and 99 g of methyl isobutyl ketone, followed by
heating up to 50 C, slowly adding 174 g of methyl ethyl
ketoxime, heating up to 70 C, sampling with time, while
keeping at that temperature, and confirming that absorption
of an unreacted isocyanate disappeared by an infrared
absorption spectral measurement to obtain a crosslinking
agent No. 3 having a solid content of 80%.
Preparation Example 4
- 29 -
CA 02481168 2004-09-10
Preparation of cationic epoxy resin No. 1:
A mixture of lOlOg of Epikote 828EL (trade name,
marketed by Japan Epoxy Resin Co., Ltd., epoxy resin), 390g
of bisphenol A and 0.2g of dimethylbenzylamine was reacted at
130 C so as to be an epoxy equivalent of 800, followed by
adding 160g of diethanolamine and 65g of a ketiminized
product of diethylenetriamine, reacting at 120 C for 4 hours,
and adding 355g of butylcellosolve to obtain a cationic epoxy
resin No. 1 having an amine value of 67 mg KOH/g, and a solid
content of 80%.
Preparation Example 5
(Preparation of cationic epoxy resin No. 2)
A 21-separable flask equipped with a thermonleter,
reflux condenser and stirrer was charged with 240q of 50%
formalin, 55g of phenol, lOlg of 98% technical sulfuric acid
and 212g of m-xylene, followed by reacting at 84 to 88 C for
4 hours, leaving at rest to separate a resin phase from a
sulfuric acid water phase, washing the resin phase with water
three times, and stripping unreacted m-xylene under the
condition of 20-30 mmHg/120-130 C to obtain 240g of a phenol-
modified xylene formaldehyde resin having a viscosity of 1050
centipoise (25 C) .
Next, another flask was charged with 1000g of Epikote
828EL (trade name, marketed by Japan Epoxy Resin Co., Ltd.,
epoxy resin, epoxy equivalent 190, molecular weight 350),
400g of bisphenol A and 0.2g of dimethylbenzylamine, followed
by reacting at 130 C so as to be an epoxy equivalent of 750,
- 30 -
CA 02481168 2004-09-10
adding 300g of xylene formaldehyde resin, 140g of
diethanolamine and 65g of a ketiminized product of
ethylenetriamine, reacting at 120 C for 4 hours, and adding
420g of butylcellosolve to obtain a cationic epoxy resin No.
2 having an amine value of 52 mg KOH/g, and a resin solid
content of 80%.
Preparation Example 6
(Preparation of unsaturated group-modified cationic epoxy
resin No. 3)
A 21-separable flask equipped with a thermometer,
reflux condenser and stirrer was charged with 240g of 50%
formalin, 55g of phenol, 102g of 98% technical sulfuric acid
and 212g of m-xylene, followed by reacting at 84 to 88 C for
4 hours, leaving at rest to separate a resin phase from a
sulfuric acid water phase, washing the resin phase with water
three times, and stripping unreacted m-xylene under the
condition of 20-30 mmHg/120-130 C to obtain 240g of a phenol-
modified xylene formaldehyde resin having a viscosity of 1050
centipoise (25 C)
Next, another flask was charged with 1000g of Epikote
828EL (trade name, marketed by Japan Epoxy Resin Co., Ltd.,
epoxy resin, epoxy equivalent 190, molecular weight 350),
400g of bisphenol A and 0.2g of dimethylbenzylamine, followed
by reacting at 130 C so as to be an epoxy equivalent of 750,
adding 300g of the phenol-modified xylene formaldehyde resin,
36g of acrylic acid, 0.1g of hydroquinone, 95g of
diethanolamine and 65g of a ketiminized product of
- 31 -
CA 02481168 2004-09-10
ethylenetriamine, reacting at 120 C for 4 hours, and adding
394g of butylcellosolve to obtain an unsaturated group-
modified cationic epoxy resin No. 3 having an amine value of
41 mg KOH/g, an unsaturated group concentration of 0.29
mol/kg and a resin solid content of 80%.
Preparation Example 7
(Preparation of Emulsion No. 1)
A mixture of 37.5g (30g as resin solid content) of
crosslinking agent No. 1, 87.5g (70g as resin solid content)
of cationic epoxy resin No. 1, 3g of Irgacure 184 (Note 2),
5g of Irgacure 819 (Note 3) and 15g of 10% acetic acid was
uniformly stirred, followed by dropping 170g of deionized
water over about 15 minutes while strongly stirring to obtain
an emulsion No. 1 having a solid content of 34%.
Preparation Examples 8-13
(Preparation of Emulsions No. 2 to No. 7)
Preparation Example 7 was duplicated except that
formulations shown in Table 1 were used respectively to
obtain emulsions No. 2 to No. 7. In Table 1, the solid
content is parenthesized.
- 32 -
CA 02481168 2004-09-10
~
o cm
-.-i -4
+' ~ m ~r o
N ~ - ~ -
o C. (D `O tf) 61 O
~4 rl= C~ M t'~- t~ '"'1 =-{ N c-t
0
z M v ~ v
N m
~+
o,w
~
O N
-ri ri
-P
rtJ U) n ~ 0~ c O
4,-A r ~ o o~ un rn o
r I N -i
a ~ 0 z `Y'
v ~
u
ww
r:
o +
-.4 r-i
4-1 L.C) OD M
~6 N ~ Oo m
c--i lfl ~ N M t.!') ~ r- ri O
~'-~ '~
-i W 1-1
p -I M rl
~a a z ~ o~
a,
, x
a
~
O o
-ri
~w 'll Ln n ,-- o m o0
rtt N
cn u~ ~ c- -i
s-i .--~ ~ ~ C) CD
p r-i M -1
s~. z m V ~ v
N ru
u
w w
~
0
=~rn
~ M un Lf) ~-. , .-.
O 0o O~
1-1 1-4 ~ ~ ~ c+~ ~ ,~-{ ['- r-i O
S]. z `'~ V ~ v M
v ro
~,x
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0
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t!) Ln
N O 00 N
~4 -i ~ M ~ ~ [- r-1 O
O M
m
Q,~
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a
~
0
-~ r
4,' ~ n Ln
~ ~ . . o OD co
l-3 r-i M r- O m u) LO c-i C. 15 M ~ M --1
a, m
~,
aw
r-t N M
c-I N (~1 = - =
O 0 0
= = = z z z
0 0 0 ~
z z z
+-) u] U) v2 l~ N N
f-: aW r, olo S:. d (D o1o Q) ao (D o!o 0 1-) 4-)
N O v O N O S-I C) S4 O 1-I O z O O
~~ M co r~Go Go 00 00 z z ~ ~+
. . ~ (U ~ >1 >1 .71 -~ a)
41 -u .u x -u x -P x +J kO O 4-3
0~ r4 ON " p G 0 ~ o a ,-i ~r rn ~6 ra r-
mC: v tL w Q, N o, a) o OD ,-i :3: 0
=ri -u =.-i .u =,i .LJ 4) 30 Q) P 4) 11 M r-I OD U -rl
x r- x C x f--: r~ F: ~ -ri -CS v,
-+ 5-: C: 0 ~ o ~ O U o U o u o~+ (D o) -P v.-+
0 -r-i U =r-{ U =li U =.-i U -r-I U -.-i U O1 7-4 S-r U) N ~J
ay -.A .-, 1-i r--~ ~ ~ ~ r ::s a o - ~ ~
~ U) ul CS ul T3 a2 27 O T3 O T5 O TS 0 D U ~ ~ U)
'-i Ul =r-i u1 -r-I (a -.i -ri -r-I -.i -.-i -.1 -=i 4-) (d fu 0
:5 0 r{ 0 r-i 0 .-1 .U H 1J =-1 J--) r-1 0 iT CT do -rl dao
f~ r~: S-I O ~4 0 14 0 (J 0 M 0 cO O .Ql s-t S-t O 61 v+
[- w 0 al 0 ul U cn U cn U M U rf) 04 t- f ,-i C1 rM
CA 02481168 2004-09-10
(Note 1) Photomer 3016 (trade name, marketed by Cognis
Japan Ltd., epoxyoligomer).
(Note 2) Irgacure 184 (trade name, marketed by Ciba-Geigy
Japan Ltd., photopolymerization initiator).
(Note 3) Irgacure 819 (trade name, marketed by Ciba-Geigy
Japan Ltd., photopolymerization initiator).
Preparation Example 14
(Preparation of Pigment-Dispersed Paste)
To a mixture of 5.83 parts (solid content 3.5 parts) of
60% solid content quaternary ammonium salt type epoxy resin,
parts of titanium white and 2.0 parts of bismuth hydroxide
was added 6.3 parts of deionized water, followed by
sufficiently stirring to obtain a pigment-dispersed paste
having a solid content of 55%.
Preparation Example 15
To 318 parts (solid content 108 parts) of Emulsion No.
1 were added 19.1 parts (solid content 10.6 parts) of the
pigment-dispersed paste, and 255.4 parts of deionized water
to obtain a cationic electrodeposition coating composition No.
1 having a solid content of 20%.
Preparation Examples 16-23
Example 15 was duplicated except that respective
formulations shown ir. Table 2 were used to obtain cationic
electrodeposition coating compositions No. 2 to No. 9 having
a solid content of 20% respectively. In Table 2, the solid
content is parenthesized.
-34-
CA 02481168 2004-09-10
~
0
rn
+' v~ o D o 0
M C3~ =.-I p~ O O O O
N ~ S~ ~ O N f-i N tn i-=I
-4 o 0
U U CJ
N 6l O = " 61 N O
p N '--1 M u) r=1
d O
~ 61 N O
Ol C)
N O M Ln -i
Z N f) I
~
0
l0 ri
4'3 o:) Oo N ^ Gq
,-I O = ?m ''-i
,-=I O N v~ O
L1'' N Os4 -~ U)O M r-1 N Ln ,-I
z N RS
-1 o 0
U U
O _
n Cl Ln t)
i-> co 00 = =
fCi cr~ . 1-4 C. tf7 N OD
~''~ p M ri 61 0 Ln al r-I
m z N Ln e--I
04
v
u
w
Ln LO
aO m . = M
~ r-i (D = N a0
O M --f c u) rn rA
z N LC) r-i
cn
OO CD = = =
1-i C) tn N co
O M r-i Ul a) -4
Z N un --I
N e-1 t.f)
k,O Cp pJ _ . . .
rl O ~ N OD
' o M ~ ~ Ln rn ,i
z v N uo -I
-{ - r-I Ln ~ry
M dp pJ . . . .
--~ `l O 1 O t.f) N Oo
O M r-I r-i -i N (M rH
Z v N u7 ri
~ t7 "t1 LS ZS 'C3 'Z7 'U
-I -0 4 0 0 0 0 0 0 0
'CS d
O-L) U) v1 U) U) U) U) tq Ul ~) -
-r{ .r{ y LC) ~4
11 U3 1-1 N cM c' LC) t0 [- S-1 4)
-ri O N -U -W
O~ Od.- Oao Ooto O~ Ocw Oolo O~ N N 3 t3 9::
CV iD,O ZIr Zrr Z~r Zv~ Z~r Z~r Z~r =ri .i-~ ~-i O
N U m M M M M M (r) T$ F: '0 -rl =ri
U T7 z 0 41 41 d-~
-H O tT O-I-) O-l--i O-t-) O=t-) 0 4-) 0 v 0 4-) J-) U N rtf ,-f
ci 31-1 ~ -=i c: -==1 r~ -e=I r- -,1 1-: -=-I r~ =r-I r- =r-1 r- c: =.-1 O vi
..~ O 4-1 =.-I 77 (1) v! N U) (1) cA (1) W N (n 4) tn Q3 U) Q) F_: C3 O r~ =-I
U 4.1 -1 4-) -I 1-3 -I 13 1-=4 .U -I 1J r-I 41 -I +-3 ~ J-) -H 0 C1,
4-) Q7 N G ~::: '~ G ~ ~ r ~~ z G b~ ul .-i =ri ao ~
ro~ O o ~ o E o 0 ~ o tr: o -.-i (IJ o a) o 0
U N U w o w U w U w U O wo w U P+ Cl, U] A N U
CA 02481168 2004-09-10
Water Based Intercoat Coating Composition:
WP-300T (trade name, marketed by Kansai Paint Co., Ltd.,
water based intercoat coating composition) was used.
Preparation Example 24
(Preparation of Water Based Topcoat Coating Composition)
To a mixture of 70 parts of acrylic resin (hydroxyl
value 60 mg KOH/g, acid value 35 mg KOH/g, number average
molecular weight 6,000), 30 parts of butyl etherified
melamine and dimethylethanolamine as a neutralizing agent was
added 60 parts of JR-806 (trade name, marketed by Tayca
Corporation, titanium oxide), followed by mixing to obtain a
water based topcoat coating composition.
Coating Substrate:
A cold-rolled steel plate (70 x 150 x 0.8 mm)
chemically treated with Palbond #3020 (trade name, marketed
by Nippon Parkerizing Co., Ltd., zinc phosphate treating
agent) was used as a coating substrate.
Example and Comparative Example
Example 1
The cationic electrodeposition coating composition No.
1 was coated so as to a film thickness of 20 m, followed by
washing with water, preheating at 100 C for 5 minutes,
subjecting to irradiation of ultraviolet light from a 120
W/cm metal halide lamp at an irradiation dose of 2000 mj/cm2
for 10 seconds for photocuring, and heating at 140 C for 10
minutes to obtain a cured mono-layer coating film.
Examples 2-6
- 36 -
CA 02481168 2004-09-10
Cationic electrodeposition coating compositions No. 2
to No. 6 were used in place of cationic electrodeposition
coating composition No. 1 in Example 1, and were subjected to
the conditions shown in Table 3 to obtain respective cured
mono-layer films.
Example 7
The cationic electrodeposition coating composition No.
1 was coated so as to be a film thickness of 20 m, followed
by washing with water, preheating at 100 C for 5 minutes,
subjecting to irradiation of ultraviolet light from a 120
W/cm metal halide lamp at an irradiation dose of 2000 mj/cm2
for 10 seconds for photocuring, coating a water based
intercoat coating composition, WP-300T (trade name as above
mentioned) so as to be a film thickness of 35 m, coating the
topcoat coating composition obtained in Preparation Example
24 so as to be a film thickness of 35 m, and heating three
coating films simultaneously to obtain a cured multi-layer
coating film. Steps of Examples 1-7 are.shown in Table 3.
-37-
CA 02481168 2004-09-10
~
v ~ ~
> ~ - r-+
=r-I 61 7r 44 J-t rt `~ o !~-. O p y NN o -,~-t
=ri O O
~
S4 -i ri .C'. ~ pp .r~, O O O LO ~ ~ .
~p ~ y -4 (V O O
4
fi N
O x :1 0
>, W Ei U
~
N ri
S-~d a) ~ p ~ O o N
~-i ~
fd ~ ~ -~ z
o x ~ o
U W U U
N ~
> N -~
+H~ 4-4 u
.
.+ ~, ' u p ~
tIJ N r6 ~ p '.-1 ~ O y-
0 O
rI r1
r (d
~ W 0 O
~i
LI - ri
r-1 t0 N W U .
N
fC 6f f6 ~ N p =.i O
S-1 .-i ~-i L: 6
N
-+ o
0 -. '-1 N C)
-0 r1
0 x 0 0
u W ~ U
r4
r-i
u .H
. ~ r~V ~ M p ri N O N O F4
a" t ~~ -7r O ~ ~ N 0
W 0~ O
~ Y
x-I =ri
l9 (D W N V ~ U
O o ~
U) fil 0) O N
O v~ . .
Z' ~ N C.
-~. O J-t N
~ r, ru
W r:i U
ri
r-1
H ri
G) Vt t v ~ a U o ~
N rtY LT p ~ri ~ O y O -~
,- ~ o
~ o 4-) z ~ ~ N ~
~ r~ ru
W r=; U
N >~ oI U)
N ~0 OJ U rr4i E~ -P N ~ -1r44
q =rl r:: ~ .u ri, t6 C. +)
S-1 l) -ri
0 -.-t (1 .t-) .iJ iH rn U U
U t -.i 4-) rU m -11
-rl O 1.> bl =ri ts ZP 0 tS U) 1-) i~ tT
r. S-t rl r- UI ~ I iS U!~ r~ (if d-t r.
0+) N-.-t 0 -r-i 0 t~ -.i S=+ -.i X 0 =rl
~. -rl U 0 JJ [2~ t 13 l) -+i . 1~ N l) U U~i 4-)
=-+ +1 a) p, (s ~ v~r o u ra +.) (a r-i sz r+ ru
=,A m,1 v o 0 54 v X: ~l a~ r 0 o-,t a~
c~ '++ u a~ u v U a, =.4 0 4.) .v w .~
~
(U ~ ri N rvl V~
a
ro (D a~ m a~
~ 0 .N .u 4-3 .u
~ ~ n ul zR U)
CA 02481168 2004-09-10
Comparative Example 1
The cationic electrodeposition coating composition No.
1 was coated so as to be a film thickness of 20 m, followed
by washing with water, and heating at 140 C for 10 minutes
without subjecting to irradiation to form a cured mono-layer
coating film.
Comparative Examples 2-5
Respective cured mono-layer coating films were obtained
according to the steps shown in Table 4.
Comparative Example 6
The cationic electrodeposition coating composition No.
1 was coated so as to be a film thickness of 20 m, followed
by washing with water, preheating at 100"C for 5 minutes,
coating the water based intercoat coating composition, WP-
300T (trade name as above mentioned) so as to be a film
thickness of 35 m, coating the topcoat coating composition
obtained in Preparation Example 24 so as to be a film
thickness of 35 m, and heating three coating films
simultaneously to obtain a cured multi-layer coating film.
Comparative Example 7
A cured three-layer coating film of Comparative Example
7 was obtained accordirig to the steps shown in Table 4.
Steps of Comparative Examples 1-7 are shown in Table 4
respectively.
- 39 -
CA 02481168 2004-09-10
a) N '-~i
> a -.A
r >, w r o F3 U ~
rt ar ~A tn o ,i
~ 0 0 0 0 0
+j r~j r ~j
o
+
~. rtS -i Rf N
r
o x ~ o
c~w ~ v
~
-> (D ~, w
,
~p ~
co a~ b~ Q. o -~ ~ ~ ~ ~ ~ o 9
sa -4 t G 0 0 ~ 0 0 0 0 0
M M o
-14 ~~ z un
o x o
U W ~ U
~
Q) .-i
4J~ w 0) U~ N N N N U ~ ~4 ~O ~O ~O 0 0
rKI ~4 -,A z o
a~ ra v N
0 k r ~ - i H O
U W U U
~
> ~4 -H
(D w 03 U ~
s-~a .-a)i -rei ty~ ' ~O OO ~O OO 0
~ R, i -~ z o
~ ~
~ w ~
-,->i M 41 W
t U ~
O ~ ~y
0 a,~ o~ z 0 0 0 0
~ o 0
~. RS C.' (is N
O x O O
U W ~ U
~
(D ~i
> N -rA
-.-i N N 4-I r a ~
s-i r-I .-I $7, 0 0 0 0 ~ rt 0 rt
~
O DC O O
U W 4 U
1~
a) I-A
> la -,-+
-rl 1-+ N W
~ rt 0 rt 0 0 0 0 ~ o
~
U w 0 v
U ~ U( TS ~ Ol ~ u! Q)
U
rI \ \ o -,..~~= 'ri Ol U V.
s-j +1 -,1 41 .~-i O ~x o a,
0 -,i -.-i rtS -P +J W rn U U
U i -rl JP rtf in
-.-i O l) tS -H CS b~ O tS 9) -P C 0~
Gõ" s4 -rl z Ul r- I iS ~., Uz '~" ci$ -P
0 wJ m-a 0 -+ Or- -.i sa -.-I .sc 0
-~
~ -rd U O V CL t V 4V ri Y QJ -P U tJ F! 41
~ a-) a) Q. r6 .Q, (l rt o 3-1 rQ ,u rt-rl (1, r-1 r0
w r0 .-1 N O o 6-t N ,~ ~ 0) ~ 0t; O-.-i a)
v a) ~ v U a, ~ p, v A -~A U4-3 N w ~
N 0,
J-> !], 0.
H 0 ~ ~ .i~ ~
U U) U) U) rn
CA 02481168 2004-09-10
U
-4
a
F-:
~
N N ~
co = I
~ CY) li) N
~
Ln
~f)
N
E- . . I.
RS ~C
E-1 w
~ v ~
f
04 Ln
O ~
~ w
~
S- I
([S
[~ ~` = = ~r
UI w
~
rt
fLS ~p N ~-i
I
tt7 N
4-4
0 U) 4)
U d Ln
a) LO
~4
O w
44
~4 N U ~
O I:, ~4 (0 >~
O 0) LO -.i f6 l0 rtS -IJ I- r[f a0
-r-i T, ul 1) 1-i U 1-}
J..) 0) -.-1 U) O VI N :3 N 0) s-1 Ul Q.t
=r-I U dJ .P tll 4-3 S4 =H -P U r-I 4-1 N=ri .JJ
-4 af --~ O (Z v) O sa u! 0 OJ u-i O 4-~ cn 0
~ UJ s I do Z 61 O Z O NZ LL N Z rU NZ
iS W -- -- f_l r-I U S-I - rD s-a - :3: ~4 ~
='-I II) O 1 tT - - tS
-~-~ 1a -ri ~ I f.,
O r-I 0 O) U Or- +3 r:: +1 Ul -P ~-:
r~ >v Q1 Q. 0 N.-f ri >+ tu .-i
O r6 r=-i UI =.i O=r-i ::I m O-,i
~ ~ i U1 TS 1J 0 ~i-a ~ r-i U 44
CA 02481168 2004-09-10
N
-~1 r
4J
m (D s4 f f ~ x
f(S la4
o x
U w
~ y
-~ ~
N 4-)
M a) o
>a f f ~ x
o x
~ a)
-,i Ln
41
'
--i
ro a ~
rt
~y o x
~4 u w
~ ~ ~ ~ ` = ~
~4 -i ~ N = -
N C2 ~ N
N
r-I 0 w
Q
x 1 M
CD Go
~ f=I -1 ~ C\j = ~'
.~
~ o x
~4 a)
r~ >
~ rl N
~
O r0 N N
u 34 ri k-0 C> I E
4-4 U
0 0 x
V) ~
a) y
U _,-q
+)
~ m (D O, ~n m
s4 .-i LO
Ln ~
O
4-+ 0 x
~4 ~ w
N
p, v
a~ U v
o ~ - õ ~ ^ ~ ,
0 ~r 01 ~n -.-I (U ko r6 i~ r ~ o~
=ri =ri $:I vI JP ~-I U 4-)
t}...f =1-~ N -.1 4) 0 al N ::I a) 0) ~4 rn 4)
U dJ .i.-a rA .t3 1-7 -ri -- -tU U r-i 11 tI) -rf -U RJ -- O (t aI 0 s.i (0 0
4) w 0 A-s ul 0
O) 14 oW ,.'T. N OZ O N '.. Q~ N'Z rtS v'z,
CT W- [=-I ~ U S i CO s-i y -
=ri lD
4-)
(o G) 0 1 bt tT
O r I s-i =ri t~ t r.
U ~ 0 o ~ i c~i o~ -u ~ .v v~
E, r~ >,(D a,0 (a-i .-I >.(u r-i
om 1-i a) =-1 0 -4 :3 ro o-.i
~ rt av =0 +.> 0 44 ~-4 0 44
CA 02481168 2004-09-10
(Note 4) Gel fraction was measured according to the
following steps (1) to (3).
Step (1): a step of measuring a weight 01 of a test panel.
Step (2): a step of carrying out electrodeposition coating
by 20 m, followed by measuring a weight Z of a cured
coating film.
Step (3): a step of dippina respective test panels into
acetone at 20 C for 24 hours, followed by drying at room
temperature, and measuring a resulting weight Q. A gel
fraction was determined according to the following formula
(1) from respective weights measured in steps (1) to (3).
The higher, the better curing properties is.
Gel fraction = { (~3 - 1(~) / c02 - 1Q) } x 100 .. . (1)
(Note 5) Heating Loss:
Heating loss was determined by the method comprising
steps (1) to (3):
step (1) of measuring a weight ~l of a test panel; step (2)
of measuring a weight 0 of a coating film and the test
panel; and step (3) of curing a coating film by mono-layer
film-forming methods of Examples 5-7 and Comparative Examples
4-6, followed by measuring a weight 30 of a cured coating
film and test panel. That is, the heating loss was
determined according to the following formula (2):
Heating loss (%) = { ( 2~-Q) / ((2)- Q) } x 100 . . . (2)
Corrosion Resistance:
Cross cuts were formed by use of a knife on the surface
of a mono-layer electrodeposition reacting film-coated test
- 43
CA 02481168 2004-09-10
panel so as to reach the coating substrate, followed by
subjecting to a 840 hours salt water spray test, and
evaluating development of rust from the cross cut, and width
of blisters as follows.
good: maximum width of rust and blisters less than 3 mm from
cut (one side)
fair: maximum width of rust and blisters 3 mm or more less
than 4 mm from cut (one side)
poor: maximum width of rust and blisters 4 mm or more from
cut (one side)
(Note 7) Specular Reflectance (o): A multi-layer coating
film-coated test panel was subjected to a 60 specular gloss
measurement in accordance with JIS K-5400.
(Note 8) Water resistance: A multi-layer coating film-
coated test panel was introduced into a blister box at 50 C,
followed by taking out the test panel 240 hours after, drying
at room temperature for 2 hours, forming 100 cut squares at
an interval of 2 mm, applying a vinyl tape thereonto,
strongly peeling off the tape, and examining a number of
remaining squares for evaluating as follows.
O: number of remaining squares: 100
A: number of remaining squares: 90-99
x: number of remaining squares: le.ss than 90
- 44 -
