U.S. patent application number 09/784342 was filed with the patent office on 2001-11-15 for cationic electrodeposition coating composition.
This patent application is currently assigned to Nippon Paint Co., Ltd.. Invention is credited to Kawakami, Ichiro, Kawanami, Toshitaka, Kokubun, Takayuki, Okumura, Yoshiaki, Sakamoto, Hiroyuki, Yoshizawa, Kenichi.
Application Number | 20010041757 09/784342 |
Document ID | / |
Family ID | 18562347 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010041757 |
Kind Code |
A1 |
Sakamoto, Hiroyuki ; et
al. |
November 15, 2001 |
Cationic electrodeposition coating composition
Abstract
It is an object of the present invention to provide a cationic
electrodeposition coating composition which is free of toxic
rust-preventive pigments such as lead compounds and capable of
giving coating films having high resistance to corrosion and
rusting, even when applied to a substrate surface which is only
insufficiently subjected, to a chemical conversion treatment. The
present invention provides a cationic electrodeposition coating
composition which comprises a rust inhibitor comprising at least
one compound selected from the group consisting of compounds
containing any of elemental metals belonging to the period 4, 5 or
6 of group 3 of the periodic table and a sulfonium- and propargyl
group-containing resin composition. For, example, the content of
said rust inhibitor is 0.03 to 10 weight parts in terms of the
elemental metal in the rust inhibitor based on 100 weight parts of
the solid resins in the resin composition.
Inventors: |
Sakamoto, Hiroyuki;
(Kobe-shi, JP) ; Kokubun, Takayuki; (Suita-shi,
JP) ; Yoshizawa, Kenichi; (Takahama-shi, JP) ;
Kawanami, Toshitaka; (Kawabe-gun, JP) ; Okumura,
Yoshiaki; (Joyo-shi, JP) ; Kawakami, Ichiro;
(Takatsuki-shi, JP) |
Correspondence
Address: |
Connolly Bove Lodge & Hutz LLP
Suite 800
1990 M Street, N.W.
Washington
DC
20036-3425
US
|
Assignee: |
Nippon Paint Co., Ltd.
Osaka
JP
|
Family ID: |
18562347 |
Appl. No.: |
09/784342 |
Filed: |
February 16, 2001 |
Current U.S.
Class: |
523/514 |
Current CPC
Class: |
C09D 5/082 20130101;
C09D 5/4492 20130101 |
Class at
Publication: |
523/514 |
International
Class: |
C08K 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2000 |
JP |
2000-038647 |
Claims
1. A cationic electrodeposition coating composition which comprises
a rust inhibitor comprising at least one compound selected from the
group consisting of compounds containing any of elemental metals
belonging to the period 4, 5 or 6 of group 3 of the periodic table
and a sulfonium- and propargyl group-containing resin
composition.
2. The cationic electrodeposition coating composition according to
claim 1, wherein the content of said rust inhibitor is 0.03 to 10
weight parts in terms of said elemental metal in the rust inhibitor
based on 100 weight parts of the solid resins in said resin
composition.
3. The cationic electrodeposition coating composition according to
claim 1 or 2, wherein said resin composition has a sulfonium group
content of 5 to 400 millimoles and a propargyl group content of 10
to 495 millimoles per 100 grams of the solid resins in said resin
composition, and the sum total of the sulfonium and propargyl group
contents is not more than 500 millimoles per 100 grams of the solid
resins in said resin composition.
4. The cationic electrodeposition coating composition according to
any of claims 1 to 3, wherein said resin composition has a
sulfonium group content of 5 to 250 millimoles and a propargyl
group content of 20 to 395 millimoles per 100 grams of the solid
resins in said resin composition, and the sum total of the
sulfonium and propargyl group contents is not more than 400
millimoles per 100 grams of said solid resins in said resin
composition.
5. The cationic electrodeposition coating composition according to
any of claims 1 to 4, wherein said resin composition comprises an
epoxy resin as a skeleton thereof.
6. The cationic electrodeposition coating composition according to
claim 5, wherein said epoxy resin is a novolak cresol type epoxy
resin or novolak phenol type epoxy resin and has a number average
molecular weight of 700 to 5,000.
Description
FILED OF THE INVENTION
[0001] The present invention relates to a cationic
electrodeposition coating composition and more particularly to a
lead-free cationic electrodeposition coating composition which can
be applied to a substrate which has not been subjected to a
chemical conversion treatment or any local area of a substrate that
has not been sufficiently so pretreated to impart a high resistance
to corrosion and rusting.
PRIOR ART
[0002] Electrodeposition coating compositions are excellent in rust
preventing effect, corrosion resistance and throwing power and can
form uniform coatings and, therefore, are widely used on metallic
shaped articles, especially as primers for automotive bodies and
parts. From the standpoint of corrosion resistance and rust
prevention, in particular, cationic electrodeposition coating
compositions have now been in use almost universally.
[0003] In cationic electrodeposition coating compositions, rust
inhibitor pigments, such as lead compounds, for example basic lead
silicate, have been used to attain high corrosion and rusting
resistance. In recent years, however, the use of lead compounds has
been restricted because of their toxicity which causes an
environmental pollution problem, among others.
[0004] As rust inhibitor pigments other than lead compounds, such
pigments as phosphate, molybdate and borate pigments, among others,
have heretofore been evaluated. These, however, have a drawback;
they are inferior in rust preventing effect when compared with lead
compounds. As for other proposals, Japanese Kokai Publication
Hei-02-279773 discloses the use of iron oxide, Japanese Kokai
Publication Hei-04-325572 discloses the use of copper, nickel,
zinc, cobalt, chromium, aluminum, manganese, zirconium, tin or
iron, Japanese Kokai Publication Hei-05-140487 discloses the use of
bismuth hydroxide/tin, cerium hydroxide/tin or nickel
hydroxide/tin, Japanese Kokai Publication Hei-05-239386 discloses
the use of lantanum compounds, Japanese Kokai Publication
Hei-05-247385 discloses the use of bismuth compounds/tin and,
further, Japanese Kokai Publication Hei-06-220371 discloses the use
of tungsten compounds. In all these cases, however, the
anticorrosive and rust-preventing effects have been found
inadequate.
[0005] Moreover in order to achieve high corrosion resistance and
rust inhibition by the application of a cationic electrodeposition
coating, the metal substrate must be subjected to a chemical
conversion treatment, using zinc phosphate, for instance, in
advance. However, when the metal substrate has a "bag"-like
recessed structure, an effective chemical conversion film may not
be formed in the recessed area so that no sufficient corrosion
resistance or rust inhibition is obtained at times.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a
cationic electrodeposition coating composition which is free of
toxic rust-preventive pigments such as lead compounds and capable
of giving coating films having high resistance to corrosion and
rusting, even when applied to a substrate surface which has not
been subjected, or only insufficiently subjected, to a chemical
conversion treatment.
[0007] The present invention provides a cationic electrodeposition
coating composition
[0008] which comprises a rust inhibitor comprising at least one
compound selected from the group consisting of compounds containing
any of elemental metals belonging to the period 4, 5 or 6 of group
3 of the periodic table and a sulfonium- and propargyl
group-containing resin composition.
[0009] It is preferred that the content of said rust inhibitor is
0.03 to 10 weight parts in terms of the elemental metal in the rust
inhibitor based on 100 weight parts of the solid resins in the
resin composition.
[0010] It is also preferred that the resin composition has a
sulfonium group content of 5 to 400 millimoles and a propargyl
group content of 10 to 495 millimoles per 100 grams of the solid
resins in the resin composition, and the sum total of the sulfonium
and propargyl group contents is not more than 500 millimoles per
100 grams of the solid resins in the resin composition, and still
more preferred that the resin composition has a sulfonium group
content of 5 to 250 millimoles and a propargyl group content of 20
to 395 millimoles per 100 grams of the solid resins in the resin
composition, and the sum total of the sulfonium and propargyl group
contents is not more than 400 millimoles per 100 grams of the solid
resins in the resin composition.
[0011] The resin composition comprises an epoxy resin as a skeleton
thereof
[0012] and said epoxy resin is preferably a novolak cresol type
epoxy resin or novolak phenol type epoxy resin and has a number
average molecular weight of 700 to 5,000.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The cationic electrodeposition coating composition of the
present invention contains a rust inhibitor comprising at least one
compound selected from the group consisting of compounds containing
any of elemental metals belonging to the period 4, 5 or 6 of group
3 of the periodic table and a sulfonium- and propargyl
group-containing resin composition.
[0014] The rust inhibitor in the cationic electrodeposition coating
composition is at least one compound selected from the group
consisting of compounds containing any of the elemental metals
belonging to the period 4, 5 or 6 of group 3 of the periodic table.
As specific examples of such elemental metals, there can be
mentioned scandium, yttrium and lanthanoid elements. Promethium,
however, is a radioactive element and can hardly be obtained from
commercial sources. Therefore, this element is unsuited for all
practical purposes.
[0015] As examples of the compounds containing such elements, there
can be mentioned organic or inorganic compounds containing, as one
constituent, an yttrium compound, a cerium compound, a praseodymium
compound, a neodymium compound, samarium compound, europium
compound, gadolinium compound, terbium compound, dysprosium
compound, holmium compound, erbium compound, thulium compound,
ytterbium compound or lutetium compound. More specifically, there
can be mentioned salts with organic acids, such as yttrium formate,
cerium acetate, neodymium acetate, europium acetate, terbium
acetate, holmium acetate, erbium acetate, ytterbium acetate,
samarium lactate, neodymium lactate, cerium lactate, samarium
oxalate, etc. and salts with inorganic acids or inorganic
compounds, such as yttrium nitrate, yttrium tungstate, praseodymium
molybdate, yttrium amido sulfate, neodymium amidosulfate, samarium
amidosulfate, neodymium oxide, samarium hydroxide and so on.
[0016] The rust inhibitor mentioned above may be water-soluble or
more or less water-insoluble but one having a solubility of not
less than 1 g/dm.sup.3 in water is preferred because a high degree
of corrosion resistance can be attained at a low concentration. As
such rust inhibitors, among the compounds mentioned above, there
can be mentioned cerium acetate, neodymium acetate, yttrium
amidosulfate, neodymium amidosulfate and samarium amidosulfate.
[0017] The content of the above rust inhibitor in the cationic
electrodeposition coating composition of the present invention is
preferably 0.03 to 10 weight parts, more preferably 0.05 to 8
weight parts, in terms of the elemental metal in the rust inhibitor
based on 100 weight parts of the solid resins in the resin
composition. When the content of said rust inhibitor is less than
0.03 weight parts in terms of the elemental metal in the rust
inhibitor, the coatings obtained will be insufficient in corrosion
resistance and rust preventing effect. When it is in excess of 10
weight parts, the physical properties of the coating films obtained
will possibly be reduced.
[0018] The resin composition in the cationic electrodeposition
coating composition of the present invention contains a sulfonium
group and a propargyl group. The term "resin composition" as used
herein means a composition comprised exclusively of a resin having
both sulfonium and propargyl groups permolecule or a composition
containing both a sulfonium group-containing resin and a propargyl
group-containing resin. In the latter case, the resin composition
as a whole has the two kinds of curing functional groups. Thus, the
resin composition may be a sulfonium- and propargyl
group-containing resin or a mixture of a sulfonium group-containing
resin and a propargyl group-containing resin, or a mixture of all
of these. The resin composition in the cationic electrodeposition
coating composition of the present invention has sulfonium and
propargyl groups in the above sense.
[0019] The sulfonium group mentioned above is a hydratable
functional group in the resin composition. When a voltage or
current not lower than a certain level is applied in the process of
electrodeposition coating, the sulfonium group is irreversibly
converted to a passive state as the result of its electrolytic
reduction on the electrode, hence loss of its ionicity. This is
supposedly the reason why the cationic electrodeposition coating
composition of the present invention can show high throwing
power.
[0020] It is also presumable that, in this process of
electrodeposition coating, an electrode reaction is induced to form
a hydroxide ion and the sulfonium ion hold this hydroxide ion to
form an electrolytically generated base in the electrodeposited
coat.
[0021] The sulfonium group content in the above resin composition
in the cationic electrodeposition coating composition of the
present invention is 5 to 400 millimoles per 100 grams of the solid
resins in said resin composition on condition that the requirement
relative to the total content of sulfonium and propargyl groups,
which is to be mentioned later herein, is satisfied. When it is
less than 5 millimoles per 100 grams, no sufficient throwing power
or curability cannot be attained and the hydratability and bath
stability will be poor. If it is in excess of 400 millimoles per
100 grams, the coating deposition on the substrate surface becomes
poor. Said sulfonium group content can be selected within a more
preferred range, which depends on the resin skeleton employed. In
the case of novolak phenol type epoxy resins and novolak cresol
type epoxy resins, for instance, it is preferably within the range
of 5 to 250, most preferably 10 to 150 millimoles, per 100 grams of
the solid resins in the resin composition.
[0022] The propargyl group in the resin composition of the cationic
electrodeposition coating composition of the present invention is
improved in reactivity upon conversion to an allene bond by an
electrolytically generated base in the electrodeposited coating,
and thus can constitute a curing system of the cationic
electrodeposition coating composition of the present invention.
Furthermore, for unknown reasons, the throwing power of the
cationic electrodeposition coating composition can be further
improved when the propargyl group coexists with the sulfonium
group.
[0023] The propargyl group content in the resin composition
contained of the cationic electrodeposition coating composition of
the present invention is 10 to 495 millimoles per 100 grams of the
solid resins in said resin composition on condition that the
requirement relative to the total content of sulfonium and
propargyl groups, which is to be mentioned later herein, is
satisfied. If it is less than 10 millimoles per 100 grams,
sufficient throwing power or curability cannot be obtained. If it
is in excess of 495 millimoles per 100 grams, the hydration
stability of the cationic electrodeposition coating composition in
which said resin composition is used may adversely be affected.
Said propargyl group content can be selected within a more
preferred range, which depends on the resin skeleton employed. In
the case of novolak phenol type epoxy resins and novolak cresol
type epoxy resins, for instance, it is preferably within the range
of 20 to 395 millimoles per 100 grams of the solid resins in the
resin composition.
[0024] The resin, which constitute the skeleton of the resin
composition in the cationic electrodeposition coating composition
of the present invention, is not particularly restricted but is
preferably an epoxy resin. Suited for use as the epoxy resin are
those having at least two epoxy groups per molecule, more
specifically epibisepoxy resins, derivatives thereof as obtained by
chain extension with a diol, a dicarboxylic acid, a diamine or the
like; epoxidized polybutadiene; novolak phenol type polyepoxy
resins; novolak cresol type polyepoxy resins; polyglycidyl
acrylate; aliphatic polyol or polyether polyol polyglycidyl ethers;
polybasic carboxylic acid polyglycidyl esters; and like polyepoxy
resins. Among them, novolak phenol type polyepoxy resins, novolak
cresol type polyepoxy resins and polyglycidyl acrylate are
preferred because they can easily be polyfunctionalized for
curability improvement. Said epoxy resin may partly comprise a
monoepoxy resin.
[0025] The resin composition in the cationic electrodeposition
coating composition of the present invention comprises a resin the
skeleton of which is the above epoxy resin. It has a number average
molecular weight of 500 to 20,000. When the number average
molecular weight is below 500, the coating efficiency of the
cationic electrodeposition coating is poor. If it is above 20,000,
no good coat can be formed on the surface of a substrate to be
coated. Said number average molecular weight can be selected within
a more preferred range, which depends on the resin skeleton. In the
case of novolak phenol type epoxy resins and novolak cresol type
epoxy resins, for instance, it is preferably within the range of
700 to 5,000.
[0026] The total content of the sulfonium and propargyl groups in
the above resin composition is not more than 500 millimoles per 100
grams of the solid resins in the resin composition. If it is in
excess of 500 millimoles per 100 grams, no resin may be obtained in
practice or the desired performance characteristics may not be
obtained in certain instances. Said total content of sulfonium and
propargyl groups in the resin composition mentioned above can be
selected within a more preferred range, which depends on the resin
skeleton employed. In the case of novolak phenol type epoxy resins
and novolak cresol type epoxy resins, for instance, it is
preferably within the range of not more than 400 millimoles.
[0027] The propargyl groups in the resin composition in the
cationic electrodeposition coating composition of the present
invention may partly be in an acetylide form. The acetylide is a
salt-like metal compound with acetylene. The content of those
propargyl groups occurring in the form of acetylide in the above
resin composition is preferably 0.1 to 40 millimoles per 100 grams
of the solid resins in the resin composition. When it is less than
0.1 millimole, the effect of the acetylide form cannot be fully
produced, while it is difficult to attain an acetylide content
exceeding 40 millimoles. Said content can be selected within a more
preferred range which depends on the metal employed.
[0028] In the case that some of propagyl groups are converted to an
acetylide-form, the metal in the acetylide-form propargyl group is
not particularly restricted but may be any metal showing catalytic
activity. As examples, there may be mentioned transition metals
such as copper, silver and barium and some of the elemental metals
belonging to the period 4, 5 or 6 of group 3 of the periodic table.
Among them, copper, silver and cerium are preferred because of
their environmental friendliness and copper and cerium are more
preferred in view of its readily availability. Where copper or
cerium is used for converting the propargyl group to an acetylide
form, the content of the propargyl group in acetylide form is more
preferably 0.1 to 20 millimoles per 100 grams of the solid resins
in the resin composition.
[0029] By converting some of the propargyl groups in the resin
composition in the cationic electrodeposition coating composition
of the present invention to an acetylide form, it is possible to
introduce a curing catalyst into the resin. By doing so, it becomes
generally unnecessary to directly add, to the coatings, an organic
transition metal complex, hardly soluble or dispersible in organic
solvents or water. Since even a transition metal can easily be
introduced, in an acetylide form, into the resin, the transition
metal can be freely used in the coating composition even when the
corresponding transition metal compound is a hardly soluble one.
Furthermore, the occurrence of an organic acid anion in the
electrodeposition bath, as is found when a transition metal organic
acid salt is used, can be avoided and, in addition, the problem
that the metal ion is removed upon ultrafiltration is no more
caused. The bath control and cationic electrodeposition coating
composition designing become easy.
[0030] The resin composition in the cationic electrodeposition
coating composition of the present invention may contain a
carbon-carbon double bond, if desirable. The carbon-carbon double
bond is highly reactive and, therefore, can further improve the
curability.
[0031] The content of said carbon-carbon double bond is preferably
10 to 485 millimoles per 100 grams of the solid resins in the resin
composition on condition that the requirement relative to the
propargyl group and carbon-carbon double bond content, which is to
be mentioned later herein, is satisfied. If it is less than 10
millimoles per 100 grams, said bond cannot contribute toward
attaining sufficient curability. When it is in excess of 485
millimoles per 100 grams, the stability of the hydrated form when
said resin composition is used in a cationic electrodeposition
coating composition may possibly be adversely affected. Said
carbon-carbon double bond content can be selected within a more
preferred range depending on the resin skeleton employed. In the
case of novolak phenol type epoxy reins and novolak cresol type
epoxy resins, for instance, said content is preferably 20 to 375
millimoles per 100 grams of the solid resins in the resin
composition.
[0032] In cases where the resin composition contains the above
carbon-carbon double bond, the total content of the above propargyl
group and carbon-carbon double bond is preferably within the range
of 80 to 450 millimoles per 100 grams of the solid resins in the
resin composition. When it is less than 80 millimoles, the
curability may possibly be insufficient. If it exceeds 450
millimoles, the sulfonium group content must be reduced and, as a
result, the throwing power may possibly become insufficient. The
total content of the propargyl group and carbon-carbon double bond
can be selected within a more preferred range depending on the
resin skeleton employed. In the case of novolak phenol type epoxy
resins and novolak cresol type epoxy resins, for instance, said
total content is preferably 100 to 395 millimoles.
[0033] Furthermore, in cases where the resin composition contains
the above carbon-carbon double bond, the total content of the above
sulfonium group, propargyl group and carbon-carbon double bond is
preferably not more than 500 millimoles per 100 grams of the solid
resins in the resin composition. If it exceeds 500 millimoles, no
resin may be obtained in practice or the desired performance
characteristics may not be obtained in certain instances. Said
total content of sulfonium group, propargyl group and carbon-carbon
double bond can be selected within a more preferred range depending
on the resin skeleton employed. In the case of novolak phenol type
epoxy resins and novolak cresol type epoxy resins, for instance,
said total content is preferably not more than 400 millimoles.
[0034] The resin composition to be contained in the cationic
electrodeposition coating composition of the present invention can
judiciously be produced, for example, by the step (i) of reacting
an epoxy resin having at least two epoxy groups per molecule with a
compound having a propargyl group and a functional group capable of
reacting with the epoxy group, to give a propargyl group-containing
epoxy resin composition and the step (ii) of reacting the remaining
epoxy group(s) in the propargyl group-containing epoxy resin
composition obtained in step (i) with a sulfide/acid mixture to
thereby introduce a sulfonium group or groups into said resin
composition.
[0035] Said compound having a propargyl group and a functional
group capable of reacting with the epoxy group (hereinafter such
compound is referred to as "compound (A)") may have a propardyl
group and a hydroxy or carboxyl group or like functional group
capable of reacting with the epoxy group, and specifically includes
propargyl alcohol, propargylic acid and the like. Among them,
propargyl alcohol is preferred because of its ready availability
and ease of reaction.
[0036] In cases where the resin composition to be contained in the
cationic electrodeposition coating composition of the present
invention has a carbon-carbon double bond as necessary, a compound
having a carbon-carbon double bond and a functional group capable
of reacting with the epoxy group (hereinafter such compound is
referred to as "compound (B)") is used in combination with the
above-mentioned compound (A) in the above step (i). Said compound
(B) may have, for example, a carbon-carbon double bond and a
hydroxy or carboxyl group or like functional group capable of
reacting with the epoxy group. Specifically, when the functional
group capable of reacting with the epoxy group is a hydroxy group,
there may be mentioned 2-hydroxyethyl acrylate, 2-hydroxyethyl
methacrylate, hydroxypropyl acrylate, hydroxypropyl methacryalte,
hdyroxybutyl acrylate, hydroxybutyl methacryalte, allyl alcohol,
methallyl alcohol and the like. When the functional group capable
of reacting with the epoxy group is a carboxyl group, mention may
be made of acrylic acid, methacrylic acid, ethacrylic acid,
crotonic acid, maleic acid, phthalic acid, itaconic acid; half
esters such as maleic acid ethyl ester, fumaric acid ethyl ester,
itaconic acid ethyl ester, succinic acid mono(meth)acryloyloxyethyl
ester and phthalic acid mono (meth) acryloyloxyethyl ester;
synthetic unsaturated fatty acids such as oleic acid, linolic acid
and ricinolic acid; and natural unsaturated fatty acids such as
linseed oil and soybean oil, among others.
[0037] In the above step (i), said epoxy resin having at least two
epoxy groups per molecule is reacted with said compound (A) to give
a propargyl group-containing epoxy resin composition, or said epoxy
resin is reacted with said compound (A) together with said compound
(B), as necessary, to give a propargyl- and carbon-carbon double
bond-containing epoxy resin composition. In the latter case, said
compound (A) and compound (B) may be admixed beforehand and
submitted to reaction in step (i) or said compound (A) and compound
(B) may be separatedly submitted to reaction in said step. That
functional group capable of reacting with the epoxy group which the
compound (A) has may be the same as or different from that
functional group capable of reacting with the epoxy group which the
compound (B) has.
[0038] In the above step (i), the proportions of compound (A) and
compound (B), both to be submitted to reaction, may be selected so
that the desired functional group contents, for instance the
propargyl group and carbon-carbon double bond contents specifically
mentioned hereinabove, may be obtained.
[0039] The reaction in the above step (i) is generally carried out
at room temperature or 80 to 140.degree. C. for several hours. If
necessary, a known component or components required for the
reaction to proceed, for example a catalyst and/or a solvent, may
be used. The completion of the reaction can be checked by measuring
the epoxy equivalent, and the functional group(s) introduced can be
confirmed by subjecting the resin composition obtained to
nonvolatile matter measurement and/or instrumental analysis.
Generally, the thus-obtained reaction product is a mixture of epoxy
resins having one or a plurality of propargyl groups or a mixture
of epoxy resins having a propargyl group or groups and one or a
plurality of carbon-carbon double bonds. In this sense, the above
step (i) gives a propargyl group-containing, or propargyl- and
carbon-carbon double bond-containing resin composition.
[0040] In the above step (ii), the remaining epoxy groups in the
propargyl group-containing epoxy resin composition obtained in the
above step (i) is reacted with a sulfide/acid mixture for the
introduction of a sulfonium group. The sulfonium group introduction
is carried out, for instance, by the method comprising reacting the
sulfide/acid mixture with the epoxy group for sulfide introduction
and conversion to sulfonium or by the method comprising effecting
sulfide introduction and further converting the sulfide introduced
to a sulfonium using an acid or an alkyl halide, such as methyl
fluoride, methyl chloride and methyl bromide, followed by anion
exchange when necessary. From the viewpoint of ready availability
of raw materials, the method which uses a sulfide/acid mixture is
preferred.
[0041] The sulfide mentioned above is not particularly restricted
but includes, among others, aliphatic sulfides, aliphatic-aromatic
mixed sulfides, aralkyl sulfides and cyclic sulfides. More
specifically, there may be mentioned diethyl sulfide, dipropyl
sulfide, dibutyl sulfide, dihexyl sulfide, diphenyl sulfide,
ethylphenyl sulfide, tetramethylene sulfide, pentamethylene
sulfide, thiodiethanol, thiodipropanol, thiodibutanol,
1-(2-hydroxyethylthio)-2-propanol, 1-(2-hydroxyethylthio)--
2-butanol, 1-(2-hydroxyethylthio)-3-butoxy-1-propanol and the
like.
[0042] The acid mentioned above is not particularly restricted but
includes, among others, formic acid, acetic acid, lactic acid,
propionic acid, boric acid, butyric acid, dimethylolpropionic acid,
hydrochloric acid, sulfuric acid, phosphoric acid, N-acetylglycine,
N-acetyl-.beta.-alanine and the like.
[0043] Generally, the mixing ratio between said sulfide and said
acid in the sulfide/acid mixture (sulfide/acid) is preferably about
100/60 to 100/100 by mole.
[0044] The reaction in the above step (ii) can be carried out, for
example, by mixing the propargyl group-containing epoxy resin
composition obtained in the step (i) and a mixture of predetermined
amounts of said sulfide and said acid sufficient to give the
sulfonium group content mentioned above, for instance, with water
in an amount 5 to 10 moles per mole of the sulfide used and then
stirring generally at 50 to 90.degree. C. for several hours. The
end point of the reaction can be estimated by the fact that the
residual acid value becomes 5 or less. The sulfonium group
introduction into the resin composition obtained can be confirmed
by potentiometric titration. In cases where sulfide introduction is
followed by conversion to sulfonium, the process can be carried out
in the same manner as mentioned above. By effecting sulfonium
introduction after propargyl group introduction, as mentioned
above, the sulfonium group can be prevented from being decomposed
upon heating.
[0045] In cases where the propargyl groups possessed by the resin
composition to be contained in the cationic electrodeposition
coating composition of the invention are partly converted to an
acetylide form, the step of acetylidization may comprise reacting
the propargyl group-containing epoxy resin composition obtained in
the above step (i) with a metal compound to thereby convert some of
the propargyl groups in said epoxy resin composition to the
corresponding acetylide form. Said metal compound is preferably a
transition metal compound capable of acetylide formation and
includes, among others, complexes and salts of transition metals
such as copper, silver and barium. More specifically, there may be
mentioned copper acetylacetonate, copper acetate, silver
acetylacetonate, silver acetate, silver nitrate, barium
acetylacetonate, barium acetate and the like. Among them, copper
and silver compounds are preferred from the viewpoint of
environment-friendliness, and copper compounds are more preferred
from the viewpoint of ready availability. Thus, for instance,
copper acetylacetonate is suited for use in view of ease of bath
control.
[0046] As for the reaction conditions, the conversion of some of
the propargyl groups to an acetylide form is generally carried out
at 40 to 70.degree. C. for several hours. The progress of the
reaction can be checked, for example, by coloration of the resin
composition obtained or by nuclear magnetic resonance spectrometry,
namely through disappearance of the methyne proton signal. The time
point of the acetylide formation reaction at which conversion of a
desired proportion of the propargyl groups to an acetylide form is
attained is confirmed in that manner and, at that time point, the
reaction is terminated. The reaction product obtained is generally
a mixture of epoxy resins in which one or a plurality of propargyl
groups are in an acetylide form. The thus-obtained epoxy resin
composition having some of the propargyl groups in an acetylide
form can be subjected to the above step (ii) for sulfonium
introduction thereinto.
[0047] The step of converting some of the propargyl groups in the
epoxy resin composition to an acetylide form and the above step
(ii) can be carried out simultaneously since common reaction
conditions can be selected for both steps. When both steps are
carried out simultaneously, the production process can
advantageously be simplified.
[0048] In this manner, a propargyl- and sulfonium group-containing
and optionally carbon-carbon double bond-containing resin
composition optionally having some of the propargyl groups in an
acetylide form can be produced while preventing the sulfonium
group(s) from being decomposed. Although acetylides, when in a dry
state, have explosiveness, the acetylidization reaction in the
practice of the present invention can be carried out in an aqueous
medium to give the desired substance as an aqueous composition, so
that no safety problems arise.
[0049] The cationic electrodeposition coating composition of the
present invention contains the above resin composition. In the
cationic electrodeposition coating composition of the, present
invention, the use of a curing agent is not always necessary, since
said resin composition itself has curability. For further improving
the curability, however, a curing agent may be used. As such a
curing agent, there may be mentioned, among others, compounds
obtained by reacting a compound having a plurality of propargyl
groups and/or carbon-carbon double bonds, such as polyepoxides
derived from novolak phenol or the like, or pentaerythritol
tetraglycidiyl ether, with a propargyl group-containing compound,
such as propargyl alcohol, and/or a carbon-carbon double
bond-containing compound, such as acrylic acid in the manner of
addition reaction.
[0050] In the cationic electrodeposition coating composition of the
present invention, it is not always necessary to use a curing
catalyst. In cases where it is necessary to further improve the
curability depending on the curing reaction conditions, however, a
transition metal compound or some other curing catalyst in general
use may be added, when necessary, in an appropriate amount. Such
compounds are not particularly restricted but include, among
others, complexes or compounds resulting from binding of a ligand,
such as cyclopentadiene and acetylacetone, or a carboxylic acid,
such as acetic acid, to a transition metal, such as nickel, cobalt,
manganese, palladium and rhodium. Said curing catalyst is used
preferably in an amount of 0.1 to 20 millimoles per 100 grams of
the solid resins in the cationic electrodeposition coating
composition.
[0051] An amine may be incorporated in the cationic
electrodeposition coating composition of the present invention. The
incorporation of an amine results in an increased rate of
conversion of the sulfonium group to a sulfide form as a result of
electrolytic reduction in the electrodeposition process. Said amine
is not particularly restricted but includes, among others, amine
compounds, for example primary to tertiary, monofunctional or
polyfunctional aliphatic amines, alicyclic amines and aromatic
amines. Among them, water-soluble or water-dispersible ones are
preferred and thus, for instance, mention may be made of
alkylamines containing 2 to 8 carbon atoms, such as
monomethylamine, dimethylamine, trimethylamine, triethylamine,
propylamine, diisopropylamine and tributylamine; monoethanolamine,
diethanolamine, methylethanolamine, dimethylethanolamine,
cyclohexylamine, morpholine, N-methylmorpholine, pyridine,
pyrazine, piperidine, imidazoline, imidazole and the like. These
may be used singly or two or more of them may be used combinedly.
Among them, hydroxyamines, such as monoethanolamine, diethanolamine
and dimethylethanolamine, are preferred owing to their affording
stable aqueous dispersions.
[0052] Said amine can be directly incorporated into the cationic
electrodeposition coating composition of the present invention.
While, in the prior art cationic electrodeposition coating
compositions of the neutralized amine type, the addition of a free
amine results in deprivation of the neutralizing acid in the resin,
leading to a marked decrease in stability of the electrodeposition
solution, such bath stability impairment is never encountered in
the practice of the present invention.
[0053] Said amine is added preferably in an amount of 0.3 to 25 meq
(milliequivalents) per 100 grams of the solid resins in the
cationic electrodeposition coating composition. When it is less
than 0.3 meq/100 grams, the effect on the throwing power cannot be
sufficient. At addition amounts above 25 meq/100 grams, any
additional effect corresponding to the addition amount cannot be
obtained and this is uneconomical. An addition amount of 1 to 15
meq/100 grams is more preferred.
[0054] It is also possible to incorporate an aliphatic hydrocarbon
group-containing resin composition in the cationic
electrodeposition coating composition of the present invention. By
incorporating said aliphatic hydrocarbon group-containing resin
composition, the coating films obtained are improved in shock
resistance. As said aliphatic hydrocarbon group-containing resin
composition, there may be mentioned those which contain 5 to 400
millimoles of a sulfonium group, 80 to 135 millimoles of an
aliphatic hydrocarbon group containing 8 to 24 carbon atoms (and an
optional unsaturated double bond in the chain thereof), and 10 to
315 millimoles of an unsaturated double bond-terminated organic
group containing 3 to 7 carbon atoms and/or a propargyl group, per
100 grams of the solid resins in the resin composition and which
has a total content of said sulfonium group, an aliphatic
hydrocarbon group containing 8 to 24 carbon atoms (and an optional
unsaturated double bond in the chain thereof) and unsaturated
double bond-terminated organic group containing 3 to 7 carbon atoms
and/or propargyl group of not more than 500 millimoles per 100
grams of the solid resins in the resin composition.
[0055] When such aliphatic hydrocarbon group-containing resin
composition is incorporated in the above cationic electrodeposition
coating composition, it is preferred that the sulfonium group
content is 5 to 400 millimoles, the content of the aliphatic
hydrocarbon group containing 8 to 24 carbon atoms (and an optional
unsaturated double bond in the chain thereof) is 10 to 300
millimoles and the total content of the propargyl group and the
unsaturated double bond-terminated organic group containing 3 to 7
carbon atoms is 10 to 485 millimoles, per 100 grams of the solid
resins in the cationic electrodeposition coating composition, the
total content of the sulfonium group, an aliphatic hydrocarbon
group containing 8 to 24 carbon atoms (and an optional unsaturated
double bond in the chain thereof), propargyl group and unsaturated
double bond-terminated organic group containing 3 to 7 carbon atoms
is not more than 500 millimoles per 100 grams of the solid resins
in the cationic electrodeposition coating composition and the
content of said aliphatic hydrocarbon group containing 8 to 24
carbon atoms (and an optional unsaturated double bond in the chain
thereof) is 3 to 30% by weight relative to the solid resins in the
cationic electrodeposition coating composition.
[0056] If, when an aliphatic hydrocarbon group-containing resin
composition is incorporated in the above cationic electrodeposition
coating composition, the sulfonium group content is less then 5
millimoles per 100 grams, sufficient throwing power and/or
curability cannot be attained and the hydratability and bath
stability tends to become worse. If said content exceeds 400
millimoles per 100 grams, the coating deposition on the substrate
surface becomes poor. If the content of the aliphatic hydrocarbon
groups containing 8 to 24 carbon atoms (and an optional unsaturated
double bond in the chain thereof) is less than 80 millimoles per
100 grams, the shock resistance cannot be improved to a
satisfactory extent. If it exceeds 350 millimoles per 100 grams,
the resin composition becomes difficult to handle. If the total
content of the propargyl group and unsaturated double
bond-terminated organic group containing 3 to 7 carbon atoms is
less than 10 millimoles per 100 grams, sufficient curability cannot
be obtained even when another resin and/or a curing agent is used
in combination. If it is above 315 millimoles per 100 grams, the
shock resistance is improved only to an unsatisfactory extent. The
total content of the sulfonium group, an aliphatic hydrocarbon
group containing 8 to 24 carbon atoms (and an optional unsaturated
double bond in the chain thereof), propargyl group and unsaturated
double bond-terminated organic group containing 3 to 7 carbon atoms
is not more than 500 millimoles per 100 grams of the solid resins
in the resin composition. If it exceeds 500 millimoles, no resin
may be obtained in practice or the desired performance
characteristics may not be obtained in some instances.
[0057] The cationic electrodeposition coating composition of the
present invention comprises said resin composition and said rust
inhibitor. The method of mixing said resin composition with said
rust inhibitor is not particularly restricted but may for example
comprise dispersing said rust inhibitor in a pigment-dispersing
resin to prepare a dispersion paste in the first place and mixing
this paste with said resin composition. The above
pigment-dispersing resin is employed for a dual purpose, namely
dispersing said rust inhibitor uniformly in said resin composition
and maintaining the resulting mixture stably dispersed in the
resultant cationic electrodeposition coating composition. The
pigment-dispersing resin is not particularly restricted but any of
those pigment-dispersing resins in routine use for the purpose can
be employed. Pigment-dispersing resins containing both a sulfonium
group and an unsaturated bond per molecule can also be utilized.
Such a pigment-dispersing resin containing both a sulfonium group
and an unsaturated bond per molecule can be obtained by reacting a
sulfide compound with a hydrophobic epoxy resin obtainable by the
reaction of a bisphenol type epoxy resin with a half-blocked
isocyanate or reacting a sulfide compound with said resin in the
presence of a monobasic acid and a hydroxyl group-containing
dibasic acid, among other methods.
[0058] The cationic electrodeposition coating composition of the
present invention may contain a further component or components
commonly used in cationic electrodeposition coating compositions in
general, if necessary. Said further components are not particularly
restricted but include, among others, such coating additives as
color pigments, pigment-dispersing resins, surfactants,
antioxidants and ultraviolet absorbers.
[0059] Said color pigments are not particularly restricted but
include, among others, those used in cationic electrodeposition
coating compositions in general, such as titanium dioxide, carbon
black, iron oxide red and like color pigments; kaolin, clay, talc
and like extenders. In cases where such a color pigment is used in
the cationic electrodeposition coating composition of the present
invention, the total amount of said color pigment and said rust
inhibitor is preferably not more than 50% by weight relative to the
solid resins in the cationic electrodeposition coating composition.
As the method of mixing said color pigment with said resin
composition, the same techniques as mentioned for incorporation of
said rust inhibitor can be mentioned.
[0060] The cationic electrodeposition coating composition of the
present invention can be prepared, for example by admixing the
above resin composition with the ingredients mentioned above as
necessary, followed by effecting dissolution or dispersion in
water. When said composition is to be used for cationic
electrodeposition coating, adjustment is preferably made so that a
bath liquid with a nonvolatile matter content of 10 to 30% may be
obtained. It is also preferred that the propargyl group,
carbon-carbon double bond and sulfonium group contents are adjusted
without departing from the respective ranges specified above in
relation to the resin composition.
[0061] The cationic electrodeposition coating composition according
to present invention is preferably adjusted so that the curing
temperature therefor may be within the range of 130.degree. C. to
220.degree. C. If the curing temperature is lower than 130.degree.
C., the smoothness of the multi-layer coating films obtained by
subjecting a coating film obtained by using the cationic
electrodeposition coating composition of the present invention to a
further coating procedure may possibly be deteriorated. If the
curing temperature is above 220.degree. C., such multi-layer
coating films may have poor film properties due to decreased
curability or the multi-layer coating films resulting from further
application of a top coating to said multi-layer coating films may
have the problem of color difference.
[0062] The substrate to be coated, to be subjected to
electrodeposition coating using the cationic electrodeposition
coating composition of the present invention is not particularly
restricted but may be any one having electroconductivity, for
example, a panel, for example, iron, steel or aluminum, a
surface-treated version thereof, or a molding thereof.
[0063] Said electrodeposition coating is carried out by immersing
the substrate, which is to serve as a cathode, in a bath comprising
the cationic electrodeposition coating composition and applying a
voltage generally of 50 to 450 V between said cathode and an anode.
If the voltage applied is lower than 50 V, the electrodeposition
will be insufficient. If it exceeds 450 V, the power consumption
will become uneconomically excessive. When the composition of the
present invention is used and a voltage within the above range is
applied, a uniform coating film can be formed all over the
substrate without an abrupt increase in coating thickness in the
process of electrodeposition. When the above voltage is applied, it
is generally preferred that the cationic electrodeposition coating
composition bath temperature is 10 to 45.degree. C. The period for
voltage application may be selected generally within the range of 2
to 4 minutes although it may vary depending on the
electrodeposition conditions.
[0064] In the above electrodeposition coating process, a voltage
can be further applied to the coating deposited upon application of
a voltage between the substrate, which is the cathode, and the
anode, to thereby increase the electric resistance per unit volume
of said coating.
[0065] After completion of the electrodeposition process, the
thus-obtained electrodeposited coating is cured, either as such or
after washing with water, by baking at 120 to 260.degree. C.,
preferably 160 to 220.degree. C., for 10 to 30 minutes to complete
the electrodeposition coating process. It is also possible to adopt
the two-coat one-bake technique which comprises forming an uncured
intermediate coating film on the electrodeposited coating obtained
in the above manner by applying an intermediate coating, which is
to be mentioned later herein, without curing said electrodeposited
coating, in the so-called wet-on-wet manner, and heating both the
uncured coating films simultaneously to give a multi-layer coating
film.
[0066] It is preferred that the cured electrodeposited coating film
formed by using the cationic electrodeposition coating composition
of the present invention have a thickness of 10 to 25 .mu.m. If it
is less than 10 .mu.m, the rust resistance will be insufficient. If
it exceeds 25 .mu.m, the extra amount of the coating may mean a
waste of material.
[0067] The substrate having a cured coating film formed from the
cationic electrodeposition coating composition of the present
invention can further be provided with an intermediate coat and/or
a top coat required for the intended use.
[0068] Thus, when the substrate is an automotive shell plate, for
instance, an intermediate coating of the heat-curing type is
generally used which comprises a binder and a curing agent and
meets those performance characteristics requirements imposed on the
intermediate coating for automobiles with respect to adhesiveness,
smoothness, sharp reflectiveness, overbaking resistance and
weathering resistance, among others. As said binder, there may be
mentioned, among others, acrylic resins, polyester resins, alkyd
resins and epoxy resins. Said curing agent may be selected from
among a variety of species, such as amino resins, blocked
isocyanate compounds, aliphatic polybasic carboxylic acids and
anhydrides thereof, epoxy resins and so forth, according to the
curing functional group(s) in said binder. The above intermediate
coating may take various forms such as the solvent-based,
water-based or water-dispersion type, or the powder form.
[0069] On the other hand, the top coating to be used is preferably
generally used as a top coating for automobiles and capable of
giving a top coat excellent in such properties as finished
appearance (sharp reflectiveness, smoothness, gloss, etc.),
weathering resistance (gloss retention, color retention, chalking
resistance, etc.), chemical resistance, water resistance, moisture
resistance and curability. As such, there may be mentioned solid
color coatings used as one-coat solids as well as base coatings and
clear coatings capable of being applied by the two-coat one-bake
coating technique. These top coatings preferably are of the
heat-curing type and contain a binder and a curing agent. Those
binders and curing agents specifically mentioned hereinabove in
relation to the intermediate coatings may be used also as said
binder and curing agent in the top coatings. The above-mentioned
solid color coatings contain one or more of inorganic or organic
color pigments well known in the art, such as carbon black,
phthalocyanine blue and titanium dioxide. Said base coatings may
contain a well-known luster color pigment, such as flaky aluminum
or flaky mica, in addition to the above-mentioned inorganic or
organic color pigments. The clear coatings mentioned above, on the
other hand, essentially contain no pigment. They may, however,
contain such color pigments and/or luster color pigments in amounts
not impairing the transparency thereof. These top coatings may be
of the water-based, solvent-based or powder type. From the
environmental protection viewpoint, however, they are preferably of
the water-based or powder type. The water-based form can be
obtained, for example by neutralizing the carboxyl groups of the
binder with an amine to provide solubility in water, while the
powder form can be obtained by adjusting the glass transition
temperature to a level higher than room temperature.
[0070] The above intermediate coatings and top coatings may contain
one or more of extenders, curing accelerators, leveling agents,
ultraviolet absorbers, light stabilizers, and other additives. When
the rust inhibitor to be contained in the cationic
electrodeposition coating composition of the present invention is
incorporated also in the intermediate coating in an amount of 2 to
30% by weight on the solid basis, the corrosion resistance and rust
preventing property can further be improved.
[0071] Said intermediate coatings and said top coatings can be
applied by a method well known in the art as selected depending on
the form of the coating. Thus, for instance, spray coating,
brushing, dipping or electrostatic coating can be employed. In the
coating step in an automotive body production line, in particular,
the electrostatic coating method is preferably employed. As regards
the coating thicknesses of said intermediate coatings and said top
coatings as well as the heating conditions to be employed after
application, appropriate values and conditions can be selected
according to the respective coating composition species.
[0072] Multi-layer coating films can be obtained by providing a
coating obtained from the cationic electrodeposition coating
composition of the present invention with an intermediate coat
layer and a top coat layer.
[0073] Since the cationic electrodeposition coating composition of
the present invention contains a rust inhibitor comprising at least
one compound selected from the group consisting of compounds
containing any of elemental metals belonging to the period 4, 5 or
6 of group 3 of the periodic table and a sulfonium- and propargyl
group-containing resin composition and is excellent in resistance
to corrosion and rusting, the coating film obtained therefrom is
free from a toxic rust inhibitor such as lead compound and can
minimize the environmental pollution.
[0074] As the reasons why high resistance to corrosion and rusting
can be obtained without using any lead compound, there may be
mentioned not only the addition of the rust inhibitor mentioned
above but also the fact that the resin composition in the cationic
electrodeposition coating composition of the present invention is
by itself excellent in resistance to corrosion and rusting. The
high resistance to corrosion and rusting of this resin composition
is presumably ascribable to the excellent throwing power of said
composition which allows a uniform film formation all over the
substrate surface and/or to the sulfonium and propargyl groups in
said resin composition which contribute to improved corrosion
resistance and rust preventing property in some way or other.
[0075] Therefore, even when the substrate is thoroughly not
subjected to a chemical conversion, the use of the cationic
electrodeposition coating composition enables formation of a highly
corrosion-resistant, rust-preventing coating film on the substrate
surface.
[0076] In the cationic electrodeposition coating compositions of
the present invention, a curing system based on addition
polymerization, which is different from the conventional blocked
isocyanate-based curing system, is employed, hence the curability
is not so much influenced by the presence of a lead compound.
Therefore, even when the system is deprived of the lead compound,
it is not necessary to increase the amount of the metal
catalyst.
EXAMPLES
[0077] The following examples illustrate the present invention in
further detail. They are, however, by no means limitative of the
scope of the present invention.
Production Example
[0078] Production of a Sulfonium- and Propargyl Group-containing
Epoxy Resin Composition
[0079] A separable flask equipped with a stirrer, thermometer,
nitrogen inlet tube and reflux condenser was charged with 100.0
weight parts of Epo Tohto YDCN-701 (cresol novolak type epoxy
resin; product of Tohto Kasei) with an epoxy equivalent of 200.4,
23.6 weight parts of propargyl alcohol and 0.3 weight part of
dimethylbenzylamine, the temperature was raised to 105.degree. C.,
and the reaction was allowed to proceed for 3 hours, to give a
propargyl group-containing resin composition with an epoxy
equivalent of 1580. To this was added 2.5 weight parts of copper
acetylacetonate, and the reaction was allowed to proceed at
90.degree. C. for 1.5 hours. Partial disappearance of the terminal
hydrogen of the propargyl group as a result of addition was
confirmed by proton (1H) NMR (the content of the acetylide-form
propargyl corresponding to 14 millimoles per 100 grams of the solid
resins). Thereto were added 10.6 weight parts of
1-(2-hydroxyethylthio)-2,3-propanediol, 4.7 weight parts of glacial
acetic acid and 7.0 weight parts of deionized water, and the
reaction was allowed to proceed while maintaining the temperature
at 75.degree. C. for 6 hours. Then, after confirming that the
residual acid value was not more than 5, 43.8 weight parts of
deionized water was added, to give a solution of the desired resin
composition in solution form. This had a solid content of 70.0% by
weight, a sulfonium value of 28.0 millimoles per 100 grams of the
varnish. The number average molecular weight (GCP expressed in
terms of polystyrene equivalent) was 2443.
Example 1
[0080] Cationic Electrodeposition Coating Composition 1
[0081] To 143 weight parts of the epoxy resin composition obtained
in Production Example (solids concentration: 70 wt. %) were added
525.8 weight parts of deionized water and 1.2 weight parts of
cerium acetate, and, after 1 hour of stirring using a high-speed
rotary mixer, deionized water was further added to thereby adjust
the solid concentration of the aqueous solution to 15% by weight.
Thus was obtained a cationic electrodeposition coating composition
1 containing 0.5 weight part of cerium acetate in terms of the
elemental metal based on 100 weight parts of the solid resins in
the composition.
Example 2
[0082] Cationic Electrodeposition Coating Composition 2
[0083] Cationic electrodeposition coating composition 2 was
prepared in the same manner as in Example 1 except that neodymium
acetate in lieu of cerium acetate was used in a proportion of 0.5
weight part in terms of elemental neodymium per 100 weight parts of
the solid resins in the composition.
Examples 3 to 9
[0084] Cationic Electrodeposition Coating Compositions 3 to 9
[0085] Except that europium acetate, holmium acetate, ytterbium
acetate, yttrium acetate, yttrium amidosulfate, neodymium
amidosulfate or samarium sulfate was used in lieu of cerium acetate
and that each of these metal-containing organic or inorganic
compounds was formulated in an amount of 0.5 weight part, in terms
of elemental metal, based on 100 weight parts of the coating
solids, the procedure of Example 1 was repeated to prepare cationic
electrodeposition coating compositions 3 to 9, respectively.
Comparative Example 1
[0086] Cationic Electrodeposition Coating Composition 10
[0087] Except that the rust inhibitor was omitted from the
formulation of Example 1, the procedure of Example 1 was repeated
to give a rust inhibitor-free cationic electrodeposition coating
composition 10.
Comparative Example 2
[0088] Cationic Electrodeposition Coating Composition 11
[0089] Except that lead acetate was used in lieu of cerium acetate
and this lead acetate was formulated in an amount of 0.5 weight
part, in terms of elemental metal, based on 100 weight parts of the
coating solids, the procedure of Example 1 was repeated to give a
cationic electrodeposition coating composition 11.
[0090] <Evaluation Test>
[0091] The cationic electrodeposition coating compositions 1 to 11
obtained in Examples 1 to 9 and Comparative Examples 1 and 2 were
each transferred to a stainless steel tank and used as an
electrodeposition bath. A cold-rolled steel panel not provided with
a chemical conversion film (degreased with Surf Cleaner, Nippon
Paint) and a steel panel provided with a chemical conversion film
(degreased with Surf Cleaner and treated with Nippon Paint's zinc
phosphate-based treating agent Surfdyne SD-5000) were each immersed
in said bath as the substrate-cathode, and electrodeposition
coating was carried out to a dry film thickness of 15 .mu.m. The
coated panel was then taken out of the electrodeposition bath,
washed with water and heated in a drying oven maintained at
180.degree. C. for 30 minutes to give a cationically
electrodeposited coating film.
[0092] Smoothness of Film
[0093] The appearance of the coated surface of each product steel
panel was macroscopically evaluated. The evaluation criteria used
are as follows. The results are shown in Table 1.
[0094] .smallcircle.: Good
[0095] .DELTA.: Slightly poor
[0096] X: Poor
[0097] Rust Preventing Property
[0098] On the coated side of each test steel panel, a cross-cut
reaching the base metal was made with a cutter knife and a salt
spray test (5 wt. % NaCl/H.sub.2O, 35.degree. C.) was performed for
240 hours for the steel panel not provided with a chemical film or
480 hours for the steel panel provided with a chemical film. The
blistering of the coated surface as a whole was macroscopically
evaluated. In addition, the coat around the cut was peeled off with
an adhesive tape and the maximum peel distance from the cut was
measured and evaluated. The evaluation criteria used are shown
below. The results are shown in Table 1.
[0099] Blister
[0100] .smallcircle.: Minimal
[0101] .DELTA.: Slight
[0102] X: Severe
[0103] Peel
[0104] .smallcircle.: <2 mm
[0105] .DELTA.: .gtoreq.2 mm, <4 mm
[0106] X: .gtoreq.4 mm
[0107] Corrosion Resistance
[0108] On the coated side of each test steel panel, a cross-cut
reaching the base metal was made with a cutter knife and a salt
immersion test (5 wt. % NaCl/H.sub.2O, 55.degree. C.) was performed
for 120 hours for the steel panel not provided with a chemical film
or 240 hours for the steel panel provided with a chemical film. The
blistering of the coated surface as a whole was macroscopically
evaluated. In addition, the coat around the cut was peeled off with
an adhesive tape and the maximum peel distance from the cut was
measured and evaluated. The evaluation criteria used are shown
below. The results are shown in Table 1.
[0109] Blister
[0110] .smallcircle.: Minimal
[0111] .DELTA.: Slight
[0112] X: Severe
[0113] Peel
[0114] .smallcircle.: <2 mm
[0115] .DELTA.: .gtoreq.2 mm, <4 mm
[0116] X: >4 mm
[0117] Environmental Compatibility
[0118] It was investigated whether the test panels contains harmful
metals.
[0119] .smallcircle.: No harmful metal
[0120] X: Some harmful metal
1 TABLE 1 Compar. Example Ex. 1 2 3 4 5 6 7 8 9 1 2 Untreated
Smoothness of film .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. X steel panel Corrosion
Blister .largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .DELTA. .largecircle. resistance Peeling
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .DELTA. .largecircle. Rust- Blister .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. X
.largecircle. preventing Peeling .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .DELTA. .largecircle.
property Steel panel Smoothness of film .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. X subjected
to Corrosion Blister .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. chemical
resistance Peeling .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. conversion
Rust- Blister .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. preventing
Peeling .largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. property Environmental
.largecircle. .largecircle. .largecircle. .largecircle.
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.largecircle. .largecircle. X compatibility
[0121] It can be seen that the cationic coating film obtained from
a cationic electrodeposition coating composition comprising at
least one rust inhibitor compound selected from the group of
compounds containing any of metal elements belonging to the period
4, 5 or 6 of group 3 of the periodic table and a sulfonium- and
propargyl group-containing resin composition is not only excellent
in corrosion resistance and rust preventing property but also has a
good appearance.
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