The present invention relates to a pre-coated metal sheet used for automobiles,
household appliances, building materials, civil engineering, machinery, furniture,
containers, and the like, and to pre-coated metal sheets which are excellent in
contamination resistance, end surface coating film peeling property after processing,
and corrosion resistance.
(Related Art]
[0002]
Pre-coated metal sheets coated with colored coating films are used in place of
conventional post -coated products coated after processing for home appliances,
building materials, automobiles, and the like. This pre-coated metal sheet is a metal
sheet subjected to a pre-treatment for metal and coated with a coating material, and
pre-coated metal sheet is generally cut and press formed for use after being coated with
a coating material.
[0003]
Since the pre-coated metal sheet is used by being formed and processed after
coating, a flexible coating film having a high elongation rate is general!y coated
thereon; however, on the other hand, such a resin has disadvantages in that
contaminants often penetrate into or physically attach to the coating film and the
contamination resistance is deteriorated. In particular, in a case of outdoor use, there
is a problem in that contamination such as exhaust gasses included in the air is attached
to the surface and wetted by rain, thereby generating a rain stripe pattern.
- 1 -
[0004]
In general, the generation of a rain stripe pattern is called raindrop staining.
The cause of the raindrop staining is said to be the relationship between the water
contact angle of the coating film and the raindrop staining and it is suggested that the
raindrop staining resistance is better as the hydrophilicity of the coating film is higher.
However, if contamination attaches to a coating film deteriorated (weather resistance
deterioration) under the influence of light, wind, rain, or the like under outdoor
conditions, the contamination is physically embedded in the coating film. For this
reason, even if the coating film has hydrophilicity, removing such contamination is
difficult, and even with a coating film with high hydrophilicity, the raindrop staining
resistance deteriorates due to weather resistance deterioration. For this reason, in
order to improve the long-term raindrop staining resistance of the pre-coated metal
sheet, it is essential to provide a contamination-resistant coating film on a metal sheet,
for which not only is hydrophilicity imparted to the coating film, but the long-term
atmospheric corrosion resistance thereof is also excellent and there is little penetration
or physical attachment of contaminants into the coating film.
[0005]
However, on the other hand, since such a contamination-resistant coating film
is full hard, there are problems such as the workability of the coating film itself being
low and the coating film adhesion of the processed portion being low. For this reason,
on such a pre-coated metal sheet, the coating film tends to peel off in the vicinity of the
cut end surface portion at the time of the cutting process. Since the peeled coating
film attaches to the surface of the product, when pressing is performed, there are
problems in that scratches caused by coating film parts peeled off from the end surface
portion appear in the coating film and the aesthetic appearance of the product is
- 2 -
impaired. In this manner, in a case where such a contamination resistant coating film
is used, there is a problem that the end surface coating film peeling property is
deteriorated.
[0006]
Several reports on pre-coated metal sheets with excellent contamination
resistance have been produced. For example, Patent Document I discloses, as a precoated
steel sheet excellent in contamination resistance, a pre-coated steel sheet where
a coating film, in which 20 to 50 parts by weight of a methyl etherified hexamethylol
melamine resin are blended with respect to 100 parts by weight of a polyester resin
having a number average molecular weight of 10,000 to 35,000 and a hydroxyl value
of 50 to 5, is formed on a surface treatment film on steel sheet surface. However,
since the disclosed coating film contains melamine, there are problems in that the
coating film is decomposed by heat or acid and becomes soft, and the long-term
contamination resistance is deteriorated due to physical contamination being embedded
therein.
[0007]
In addition, Patent Document 2 discloses, as a top coating composition
excellent in workability and contamination resistance, a top coating composition for
pre-coating containing a polyester resin having a number average molecular weight of
2,000 to 6,000 and an acrylic resin having a number average molecular weight of 1,500
to 8,000. It is recognized that the bending workability of the coating composition of
Patent Document 2 is improved by including a polyester resin; however, since a hard
acrylic resin is mixed therein, the end surface coating film peeling property is not yet
resolved.
[0008]
- 3 -
In addition, Patent Document 3 discloses a coated metal sheet excellent in end
surface coating film peeling property which combines a soft primer having a glass
transition point temperature (Tg) of30°Corlower beneath a hard topcoat. However,
methods of absorbing the stress during processing in the soft primer insufficiently
alleviate the stress generated in the top coating film in a case where the top coating
film is an acrylic resin or a polyester-modified acrylic resin and the end surface coating
film peeling property still remains a problem in the case of such a coating film
configuration.
[0009]
As described above, in the techniques disclosed so far, there is no disclosure
of a technique for obtaining a pre-coated metal sheet excellent in contamination
resistance, end surface coating film peeling property, and corrosion resistance.
[Prior Art Document]
[Patent Document]
[0010]
[Patent Document 1] Japanese Unexamined Patent Application, First
Publication No. Hl0-314664
[Patent Document 2] Japanese Unexamined Patent Application, First
Publication No. 2008-201842
[Patent Document 3] Japanese Unexamined Patent Application, First
Publication No. 2006-175826
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
[0011]
The present invention has been made in view of the problems described above
- 4 -
and the present invention has an object of providing a pre-coated metal sheet excellent
in long-term contamination resistance, end surface coating film peeling property, and
corrosion resistance.
[Means for Solving the Problem]
[0012]
As a result of an intensive investigation by the present inventors, it was found
that it is possible to secure long-term contamination resistance by applying a full hard
acrylic resin or a polyester-modified acrylic resin to a resin of a top coating film. In
addition, it was found that adhesion of the coating film to the steel sheet is improved
by using an epoxy-modified polyester resin as the resin of the primer coating film layer.
Furthermore, it was found that, by setting the fracture critical elongation rate of the
coating film layer, which is a combination of a primer coating film layer and a top
coating film layer, to 1 0% or more and 25% or less and setting the glass transition
point temperature ofthe primer coating film layer to be higher than 50°C and 1 oooc or
less, when the coating film is stretched by a die at the time of pressing, fine cracks are
generated in the primer coating film layer and the top coating film layer, and the stress
is alleviated. In addition, as a result, it was found that adhesion between the hard top
coating film and the steel sheet is maintained and the coating fihn itself is not peeled
off, and the end surface coating fihn peeling property is improved. Furthermore, by
using any one of magnesium phosphate, calcium phosphate, aluminum phosphate, and
zinc phosphate in the primer coating film layer as a rust -preventive pigment, even if
cracking occurs, the generation of zinc oxide (white rust) from the cracks is suppressed
and the long-term corrosion resistance is improved. It is presumed that this is
because a compound with zinc is formed due to the elution of a rust -preventive
pigment component including a phosphorus component and the elution of zinc is
- 5 -
suppressed.
[0013]
The present invention has been completed based on these findings and the gist
of the present invention is as follows.
(I) A pre-coated metal sheet including a metal sheet, an underlying coating film layer
which does not contain chromate and which is provided on the metal sheet, a primer
coating film layer which does not contain chromate and which is provided on the
underlying coating film layer, and a top coating film layer which is provided on the
primer coating film layer, in which a fracture critical elongation rate of a coating film
which combines the primer coating film layer and the top coating film layer is 10% or
more and 25% or less, a glass transition point temperature of the primer coating film
layer is more than 50°C to 1 00°C or less, the top coating film layer includes a resin
component and the resin component includes an acrylic resin or a polyester-modified
acrylic resin, and, when the pre-coated metal sheet is subjected to 2T close contact
bending, there are a total of 5 or more and 30 or less cracks having a width of 0.1 mm
or less in the top coating film layer in a range centered on a vertex section of the bend
and having a length of 1 mm in a direction orthogonal to the bending direction.
(2) The pre-coated metal sheet according to (1 ), in which the fracture critical
elongation rate ofthe primer coating film layer is 40% or more and 50% or less, the
fracture critical elongation rate of the top coating film layer is 5% or more and l 0% or
less, the primer coating film layer includes a rust-preventive pigment and a resin
component and the rust-preventive pigment includes at least one of magnesinm
phosphate, calcium phosphate, aluminum phosphate, and zinc phosphate, and the resin
component in the primer coating film layer may include an epoxy-modified polyester
resin.
- 6 -
(3) The pre-coated metal sheet according to (1) or (2), in which the primer coating film
layer includes a rust-preventive pigment and a concentration of the rust-preventive
pigment may be 10 parts by mass or more and 160 parts by mass or less with respect to
100 parts by mass of resin solid content.
( 4) The pre-coated metal sheet according to any one of (1) to (3), in which the top
coating film layer may not contain a melamine resin.
( 5) The pre-coated metal sheet according to any one of (I) to ( 4 ), in which a dynamic
friction coefficient of a surface of the top coating film layer may be 0.06 or more and
0.25 or less.
( 6) The pre-coated metal sheet according to any one of the above (I) to ( 5), in which a
water contact angle on a surface of the top coating film layer after standing for 72
hours in a humid environment of 50°C and 95% RH may be 60° or less.
(7) The pre-coated metal sheet according to any one of (I) to ( 6), in which the top
coating film layer may contain an organosilicate.
(8) The pre-coated metal sheet according to (7), in which amount of the organosilicate
in the top coating film layer may be 0.1 parts by mass or more and 20 parts by mass or
less with respect to 100 parts by mass of resin solid content of the top coating film
layer.
(9) The pre-coated metal sheet according to any one of (1) to (8), in which the
underlying coating film layer may contain at least one of fine particulate silica, a silane
coupling agent, and tannic acid.
(I 0) The pre-coated metal sheet according to any one of (1) to (9), in which a film
thickness of the primer coating film layer may be 3 to 10 J..lll1 and a film thickness of
the top coating film layer is 5 to 25 J..Lm.
[Effects of the Invention]
- 7 -
[0014]
According to the present invention, it is possible to provide a pre-coated metal
sheet excellent in contamination resistance, end surface coating film peeling property
after processing, and corrosion resistance.
[Brief Description of the Drawings]
[0015]
Fig. 1 is a diagram which schematically shows the state of cracks when a precoated
metal sheet according to an embodiment of the present invention is cut away
orthogonally with respect to the bending direction centered on the vertex section of the
bend after 2T close contact bending and the cross-section of the cutaway surface is
observed.
Fig. 2 is a diagram which schematically shows a state in which a pre-coated
metal sheet according to an embodiment of the present invention is subjected to 2T
close contact bending and which expands the vicinity of the vertex section of the bend
and schematically shows the state of cracks occurring in this portion.
[Embodiments of the Invention]
[0016]
A detailed description will be given below of suitable embodiments of the
present invention with reference to the drawings.
The pre-coated metal sheet according to the embodiment of the present
invention has a metal sheet, an underlying coating film layer which does not contain
chromate and which is provided on the metal sheet, a primer coating film layer which
does not contain chromate and which is provided on the underlying coating film layer,
and a top coating film layer which is provided on the primer coating film layer.
The underlying coating film layer and the primer coating film layer do not
- 8 -
contain chromate. In a case where the underlying coating film layer and the primer
coating film layer do not contain chromate or phosphate, the underlying coating film
layer and the primer coating film layer are excellent in terms of not using substances ..
which adversely affect the environment or the human body.
[0017]
The fracture critical elongation rate of the coating film layer which combines
the primer coating film layer and the top coating film layer is 10% or more and 25% or
less. When the fracture critical elongation rate is less than 10%, cracks in the coating
film may be large, corrosion resistance may be poor in the processed portion, and
coating film peeling may occur. In addition, when the fracture critical elongation rate
is more than 25%, the contamination resistance is deteriorated.
The glass transition point temperature of the primer coating film layer is more
than 50°C and l00°C or less. In addition, the glass transition point temperature is
preferably more than 60°C and 80°C or less.
[00 18]
It is possible to determine the glass transition point temperature in accordance
with differential scanning calorimetry (DSC method) of the plastic transition
temperature measurement method (TIS K 7121 1987) using a peeled or scraped coating
film.
[0019]
The fracture critical elongation rate of the primer coating film layer is
preferably 40% or more and 50% or less. Due to this, the stress of the top coating
film is alleviated, appropriate cracks are generated, and an effect of further suppressing
coating film peeling is obtained.
The fracture critical elongation rate of the top coating film layer is preferably
- 9 -
5% or more and 10% or less. Due to this, the top coating film is hardened and the
contamination resistance ofthe pre-coated metal sheet is excellent.
[0020]
It is possible to measure the fracture critical elongation rate of each coating
film by performing a tensile test using a small table top testing machine on a coating
film isolated for each layer by slicing flakes with a microtome or the like in parallel to
the surface.
[0021]
It is not possible to determine the fracture critical elongation rate of a
combination of the primer coating film layer and the top coating film layer only by the
fracture critical elongation rates of the primer coating film layer and the top coating
film layer alone, and the adhesion at the interface of the primer coating film layer and
the top coating film layer has an effect thereon. It is possible to adjust the fracture
critical elongation rate of the combined primer coating film layer and top coating film
layer according to, for example, the concentration of the rust-preventive pigment.
When the concentration of the rust -preventive pigment is 10 parts by mass or more
with respect to 100 parts by mass of the resin solid content, the adhesion between the
primer coating film layer and the top coating film layer is improved, furthermore, by
setting the fracture critical elongation rate of the primer coating film layer to 40% or
more and 50% or less and the fracture critical elongation rate of the top coating film
layer to 5% or more and 10% or less, and the like, the fracture critical elongation rate
of the coating film of the combined primer coating film layer and top coating film
layer is 10% or more and 25% or less.
[0022]
In this manner, that the fracture critical elongation rate of the coating film of
- 10 -
the combined primer coating film layer and top coating film layer is I 0% or more and
25% or less, is a structural feature of the coating film of the present invention and this
feature is obtained by appropriately selecting the fracture critical elongation rates of
the primer coating film layer and the top coating film layer alone, the concentration of
the rust -preventive pigment, and the like.
[0023]
[Table 1]
Range of Combination Combination Concentration of
fracture critical oflower limit of upper limit rust -preventive
elongation rate pigment (parts by
mass with respect to
I 00 parts by mass of
resin solid content
Top coating 5% or more and
5% 10%
0 parts by mass
film layer 10% or less
Primer coating 40% or more I 0 parts by mass or
film layer and 50% or less 40% 50% more and 160 parts
by mass or less
Top coating 10%ormore
film layer and and 25% or less
10% 25%
primer coating
film layer
[0024]
Table 1 summarizes the fracture critical elongation rates and the
concentrations of the rust -preventive pigment in the top coating film layer, the primer
coating film layer, and the coating film layer which combines the primer coating film
layer and the top coating film layer in the present embodiment. In principle, the use
of a (soft) coating film having a high elongation rate in the top coating film layer as an
upper layer having a large strain and a (hard) coating film having a low elongation rate
in the primer coating film layer as a lower layer having a small strain is generally
considered. However, the present application uses the reverse of this idea and has a
feature of using a (hard) coating film having a low elongation rate in the top coating
- ll -
film layer and using a (soft) coating film having a high elongation rate in the primer
coating film layer.
That is, when the elongation rate of the top coating film layer a!l~theprimer
coating film layer is set within the above range, even when a coating film having a low
elongation rate is used as the top coating film layer of the upper layer, it is possible to
set the overall elongation rate of the combined top coating film layer and the primer
coating film layer to be high. At this time, it was found that the contribution of the
elongation rate of the top coating film layer to the overall elongation rate is smaller
than usual. Due to this, it was found that the overall elongation rate was secured, and
at the same time, the width of the cracks generated in the processed portion of the top
coating film layer was limited to 0.1 nun or less when 2T close contact bending was
performed after coating the film.
[0025]
As shown in Fig. 1, the primer coating film layer 3 and the top coating film
layer 2 are provided on the metal sheet and the underlying coating film layer; however,
cracks may occur only in the top coating film layer 2 and or may occur in both the top
coating film layer 2 and the primer coating film layer 3.
[0026]
It is possible to measure the width 1 of the cracks occurring in the processed
portion of the top coating film layer 2 by cutting the width of the pre-coated metal
sheet 4 after processing as shown in Fig. 2 in parallel to the bending direction (the
longitudinal direction of the pre-coated metal sheet 4 after the 2T bending test) so as to
divide it into 10 equal parts, and observing the I 0 cutaway surfaces. The width 1 of
the crack is obtained by measuring the outermost layer of the top coating film layer 2
(refer to Fig. 1). Here, the width 1 of the cracks generated in the processed portion of
- 12 -
the top coating film layer 2 may be measured by observing the coating film surface of
the pre-coated metal sheet 4.
[0027]
The maximum width of the cracks was determined by measuring the crack
widths I of the top coating film layer included in a range A centered on the vertex
section of the bend and having a length of 1 mm in a direction orthogonal to the
bending direction in the ten cutaway surfaces, and taking the absolute maximum value
among all the measured values.
[0028]
The number of cracks was calculated by totaling the number of cracks in the
top coating film layer included in the range A having a length of 1 mm in the direction
orthogonal with respect to the bending direction centering on the vertex section of the
bend in each of the ten cutaway surfaces, and taking the absolute maximum value
among the total values.
[0029]
The relationship between each elongation rate and the overall elongation rate
was analyzed by multiple correlation using the combinations of the top coating fihn
layer and the primer coating film layer in the examples ofthe present invention in the
Examples described below.
[0030]
As a result, in the range ofthe examples of the present invention, the
following Equation (I) was obtained, and the contribution of the elongation rate ofY
(top coating film layer) to the overall elongation was very small.
Z = -1.7 + 0.46 X+ 0.03 Y (1)
X is the elongation rate of the primer coating film layer
- 13 -
i
Y is the elongation rate of the top coating film layer
Z is the overall elongation rate
[0031]
On the other hand, in the range of the comparative examples, the following
Equation (2) was obtained, and the contribution of the elongation rate of the top
coating film layer to the overall elongation rate was large.
Z = -3.5 + 0.61 X+ 0.32 Y (2)
[0032]
As described above, factors behind the differences in the contribution of the
elongation rate of the top coating film layer to the overall elongation rate between the
present invention examples and the comparative examples are considered to be the
influence of adhesion between the top coating film layer and the primer coating film
layer, the influence of adhesion between the primer coating film layer and the
underlying coating film layer, and the like according to the type of the resin and
differences in the structure.
[0033]
At the time when the pre-coated metal sheet according to the embodiment of
the present invention is subjected to 2T close contact bending, when a total of 5 to 30
cracks having a width ofO.l mm or less are generated in the top coating film layer, the
stress is suitably alleviated, thus, the adhesion after processing the primer coating film
and steel sheet is excellent. When the width of the cracks is larger than 0.1 mm, the
adhesion between the primer coating film and the steel sheet is deteriorated and the
adhesion after processing is deteriorated. In addition, if the width of the crack is
larger than 0.1 mm, it is not possible to obtain the effect of eluting the rust-preventive
pigment, thus, the corrosion resistance at the processed portion is deteriorated. When
- 14 -
the number of cracks is less than 5, the stress is not alleviated and thus the adhesion
after processing is deteriorated. When the number of cracks is more than 30, the
adhesion bet\veen the primer coating film and the steel sheet is deteriorated and the
adhesion after processing is deteriorated.
In this manner, by adjusting the glass transition point temperature of the
primer coating film layer and the fracture critical elongation rate of the coating film
layer which combines the primer coating film layer and the top coating film layer, the
pre-coated metal sheet has adhesion and moderate elongation, and fine cracks are
generated and stress is alleviated when the coating film is stretched by a die during
shearing processing or pressing, thus the end surface coating film peeling property is
excellent.
As the fracture critical elongation rate of the primer coating film layer
increases, the fracture critical elongation rate of the coating film layer which combines
the primer coating fihn layer and the top coating film layer also increases due to the
influence thereof, and, as a result, has a higher value than the fracture critical
elongation rate of the top coating film layer alone.
[0034]
The top coating film layer includes a resin component, and the resin
component includes an acrylic resin or a polyester-modified acrylic resin. Due to this,
the pre-coated metal sheet is excellent in contamination resistance, particularly
atmospheric corrosion resistance, and thus excellent in long-term contamination
resistance.
[0035]
The acrylic resin is a copolymer obtained by heating and reacting an acrylic
monomer or methacrylic monomer having a hydroxyl group with an acrylic acid ester,
- 15 -
a methacrylic acid ester, or the like by a well-known method. As the acrylic
monomer or methacrylic monomer having a hydroxyl group described above, it is
possible to use, for example, 2-hydroxyethyl methacrylate, 2-hydroxyt;:th.Ylacrylate,
hydroxypropyl methacrylate, hydroxypropyl acrylate, and the like, and these may be
used alone or a combination thereof may be used. In addition, as the acrylic acid
ester or methacrylic acid ester described above, it is possible to use, for example,
methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl
acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl
methacrylate, 2-ethylhexyl methacrylate, and the like, and these may be used alone or a
combination thereof may be used.
[0036]
As the polyester-modified acrylic resin, it is possible to use resins obtained by
complex.ing and copolymerizing a polyester and an acrylate or cross-linking a
polyester and an acrylate with other cross-linking agents, or the like. When the
polyester-modified acrylic resin is a resin obtained by polymerizing a lactone-modified
acrylic-based polyol and a carboxyl group-containing vinyl-based monomer in
particular, the resin is excellent in contamination resistance, which is more preferable_
The lactone-modified acrylic-based polyol is obtained by adding a lactone compound
to an acrylic resin obtained by carrying out typical radical copolymerization on a
mixture of a hydroxyl group-containing vinyl-based monomer, a carboxyl groupcontaining
vinyl-based monomer and other vinyl-based monomers in a typical organic
solvent using a typical radical polymerization initiator, and carrying out a ring opening
addition reaction in the absence of a catalyst. Examples of carboxyl group-containing
vinyl-based monomers include acrylic acid, methacrylic acid, maleic acid, fumaric acid,
citraconic acid, itaconic acid, adducts of hydroxyl group-containing vinyl-based
- 16 -
monomers and phthalic anhydride or hexahydrophthalic anhydride, and the like.
[0037]
The primer coating film layer preferably includes a rust-preventive pigment
and a resin component. Including the rust -preventive pigment in the primer coating
film layer makes it possible to adjust the fracture critical elongation rate of the
combination of the top coating film layer and the primer coating film layer.
Furthermore, even when cracks occur, since the generation of oxides of zinc (white
rust) from the cracks is suppressed and the rust-preventive pigment is eluted instead,
the corrosion resistance is good. In order to impart long-term corrosion resistance, it
is preferable that the rust-preventive pigment includes at least one of magnesium
phosphate, calcium phosphate, aluminum phosphate, and zinc phosphate. In addition,
it is preferable that the resin component in the primer coating fihn layer includes (I) an
epoxy resin and a polyester resin, or (2) an epoxy-modified polyester resin. The
adhesion between the coating film and the steel sheet is determined by the adhesion
between the primer coating film layer and the underlying coating fihn layer; however,
it is preferable that the resin component in the primer coating fihn layer includes an
epoxy-modified polyester resin in order to improve the adhesion.
[0038]
Suitable examples ofthe epoxy-modified polyester resin include reactiun
products of a carboxyl group of a polyester resin and an epoxy group-containing resin,
or reaction products obtained by reactions such as addition, condensation, or grafting
of a polyester resin and an epoxy resin, such as products obtained by bonding a
hydroxyl group in a polyester resin and a hydroxyl group in an epoxy resin via a
polyisocyanate compound, and the like.
[0039]
- 17 -
Examples of the polyester resin include various polyester resins obtained from
polyvalent alcohols and polybasic acids by known esterification methods. Here,
examples of polyvalent alcohols include ethylene glycol, diethylene gl)'col,propylene
glycol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,
hydrogenated bisphenol, ethylene oxide adducts or propylene oxide adducts of
bisphenol A, glycerin, trimethylol ethane, trimethylol propane, pentaerythritol and the
like, and examples of polybasic acids include phthalic anhydride, isophthalic acid,
terephthalic acid, tetral1ydrophthalic anhydride, hexal1ydrophthalic anhydride, azelaic
acid, sebacic acid, maleic anhydride, fumaric acid, trimellitic anhydride, pyromellitic
anhydride, and the like, and furthermore, as necessary, it is also possible to use
monobasic acids such as benzoic acid and p-tertiary butyl benzoic acid in combination
therewith.
[0040]
Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F
type epoxy resin, novolac type epoxy resin, and the like.
[0041]
Examples of polyisocyanate compounds include toluene diisocyanate, xylene
diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, hexamethylene
diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate,
norbomene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated
xylene diisocyanate and/or adducts, biurets, isocyanurates or the like thereof, and
adducts, biurets, or isocyanurates of a non-yellowing type polyisocyanate compound
such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and
isophorone diisocyanate are particularly preferable. One polyisocyanate compound
may be used, or two or more types may be used in combination.
- 18 -
[0042]
For aluminum phosphate used for rust-preventive pigments, it is possible to
use commonly known aluminum phosphates such as reagents .. For alumi,·_c:n_u::_mcc, ....... .
dihydrogen tripolyphosphate, it is possible to use commonly known aluminum
tripolyphosphates. It is possible to use commercial products, for example, "KWHITE"
(registered trademark), which is aluminum dihydrogen tripolyphosphate
manufactured by Tayca Corporation, and the like.
[0043]
As calcium phosphate, it is possible to use commonly known phosphates,
such as reagents. In particular, calcium-treated aluminum dihydrogen
tripolyphosphate is preferable and, for example, it is possible to use "K-WHITE/Ca
650" (calcium treated) manufactured by Tayca Corporation or the like.
[0044]
It is possible to use generally known magnesium phosphates as the
magnesium phosphate. In particular, magnesium-treated aluminum dihydrogen
tripolyphosphate is preferable and, for example, it is possible to use "K-WHITE/KGl05",
which is magnesium-treated aluminum dihydrogen tripolyphosphate
manufactured by Tayca Corporation, or the like.
[0045]
As zinc phosphate, it is possible to use generally known zinc phosphates such
as reagents. ln particular, zinc-treated aluminum dihydrogen tripolyphosphate is
preferable and, for example, it is possible to use "K-WHITE/#1 05" manufactured by
Tayca Corporation, or the like.
[0046]
The glass transition point temperature of the primer coating film layer is more
- 19 -
than 50°C and 100°C or less. When the glass transition point temperature is 50°C or
less, fine cracks do not occur when the coating film is stretched by a die at the time of
pressing and the end surface coating film peeling property is deteriorated, which is not
preferable. When the glass transition point temperature is more than 1 00°C, since the
generated cracks are excessively large and the fragmented coating film is peeled off,
the end surface coating film peeling property is deteriorated, which is not preferable.
[0047]
It is possible to control the glass transition point temperature of the primer
coating film layer according to the glass transition point temperature of the epoxymodified
polyester resin which is the main resin. In particular, it is possible to control
the glass transition point temperature of the primer coating film layer by changing the
glass transition point temperature of the polyester resin portion.
[0048]
It is preferable that the top coating film layer does not contain a melamine
resm. In a case where the top coating film layer contains no melamine resin, in
particular, since there is little deterioration due to acid rain, the atmospheric corrosion
resistance is more excellent. In addition, since physical contamination is prevented
from being attached, the contamination resistance is more excellent.
[0049]
The dynamic friction coefficient of the surface of the pre-coated metal sheet
according to the embodiment of the present invention is determined by the dynamic
friction coefficient of the surface of the top coating film layer and is preferably 0.06 or
more and 0.25 or less, and more preferably 0.06 or more and 0.13 or less. When the
dynamic friction coefficient is 0.06 or more, in a case where the pre-coated metal sheet
is used as a coil, the coil does not collapse, which is preferable. In addition, when the
- 20 -
dynamic friction coefficient is 0.25 or less, the coating film is not damaged at the time
of pressing and the pressability is not deteriorated, which is preferable.
[0050]
It is possible to adjust the dynamic friction coefficient by using a generally
used wax and adjusting the added amount of the wax to the top coating film layer.
[0051]
The water contact angle of the surface of the top coating film layer after
standing the pre-coated metal sheet according to the embodiment of the present
invention in a humid environment of 50°C and 95% RH for 72 hours is preferably 60°
or less. In a case where the water contact angle under such conditions is 60° or less,
the rain more easily washes off the contamination. The smaller the magnitude of the
water contact angle under such conditions, the better, but the lower limit value thereof
is not particularly limited. It is possible to measure the water contact angle using a
known measuring instrument. As a method of setting the water contact angle under
such conditions to 60° or less, a method of adding an organosilicate to the top coating
film may be considered, but other methods may also be used. The top coating film
layer preferably contains an organosilicate.
[0052]
The organosilicate is a compound containing a hydrolyzable silicon group and
is a compound represented by Genera! Formula (I) or a partially decomposed
condensate thereof.
- 21 -
[0053]
........... ./.O J R,..\.. ....... .
R,O r Si- o-J- R, \ t /n 2
• . . ( l )
(In Formula (1 ), R1 toR; each represent organic groups which may be the same or
different from each other. In addition, n represents an integer of 1 or more.)
[0054]
The amount of the organosilicate included in the top coating film layer is
preferably OJ parts by mass or more and 20 parts by mass or less with respect to 100
parts by mass of the resin solid content of the top coating film layer, and more
preferably 5 parts by mass or more and 15 parts by mass or less. When the amount of
the organosilicate is OJ parts by mass or more, the contamination resistance is
improved, which is preferable. In addition, when the amount of the organosilicate
exceeds 20 parts by mass (more than 20 parts by mass), defects in the appearance are
easily generated.
[0055]
The concentration of the rust -preventive pigment in the primer coating film
layer is preferably I 0 parts by mass or more and 160 parts by mass or less with respect
to 100 parts by mass of the resin solid content, and more preferably 50 parts by mass or
more and 160 parts by mass or less. \Vhen the concentration of the rust-preventive
pigment is I 0 parts by mass or more, the corrosion resistance is improved, which is
preferable, and when the concentration of the rust-preventive pigment is more than 160
parts by mass, the end surface coating film peeling property is deteriorated because the
- 22 -
resin content is small.
[0056]
As the rust-preventive pigment of the primer coatingfil!111ayercoated on the
pre-coated metal sheet, it is possible to use known rust-preventive pigments in
combination and, for example, it is possible to use calcium ion-exchanged silica,
magnesium silicate compounds, non-hexavalent chromium-based rust preventive
agents, for example, molybdates, vanadate/phosphoric acid combined pigments
(commonly called VP pigments), and the like. These may be commerciaHy available
products. Calcium ion-exchanged silica refers to a generally known type of silica in
which calcium is ion-exchanged with a silanol group on the surface of a silica, and it is
also possible to use commercially available calcium ion-exchanged silica. Examples
of commercially available calcium ion-exchanged silica include "Shieldex" (registered
trademark) manufactured by W. R. Grace & Co.-Conn. and the like.
[0057]
By containing at least one of fine particulate silica, silane coupling agent and
tannic acid in the underlying coating film layer, the adhesion to the epoxy-modified
polyester resin of the primer coating film layer is excellent, which is more preferable.
[0058]
The adhered amount of the underlying coating film layer is not particularly
limited, but it is preferable that the total solid content mass is in the range of 10 to
1000 mg/m2
. When the adhered amount of the underlying coating film layer is less
than 10 mg/m2
, there are concerns that the corrosion resistance may be deteriorated and
the end surface coating film peeling property may be lowered, which is not preferable.
In addition, when the adhered amount of the underlying coating film layer is more than
1000 mg/m2
, there are concerns that the end surface coating film peeling property may
- 23 -
be deteriorated, which is not preferable.
[0059]
The added amount oftannic acid is more preferably 2 to 80 g/1. When the
added an1ount of tannic acid is less than 2 g/1, rust preventive effect and coating film
adhesion are not sufficiently obtained, while when the added amount of tannic acid
exceeds 80 g/1, the rust prevention effect and coating film adhesion are decreased or
the added amount is not dissolved in an aqueous solution.
[0060]
Examples of usable silane coupling agents include y-(2-aminoethyl)
aminopropyltrimethoxysilane, y-(2-aminoethyl) aminopropylmethyldimethoxysilane,
y-(2-aminoethyl) aminopropyl triethoxysilane, y-(2-aminoethyl)
aminopropylmethyldiethoxysilane, y-(2-aminoethyl)
aminopropylmethyldimethoxysilane, y-methacryloxypropyltrirnethoxysilane, yrnethacryloxypropyl
methyldimethoxysilane, y-methacryloxypropyl triethoxysilane, ymethacryloxypropylmethyldiethoxysilane,
N-~-(N-vinylbenzylaminoethyl)-yaminopropyltrimethoxysilane,
N-~-(N-vinylbenzyl aminoethyl) -y-amino propyl
methyl dimethoxysilane, N-~-(N-vinylbenzylaminoethyl)-yaminopropyltriethoxysilane,
N-~-(N-vinylbenzylaminoethyl)-yaminopropylmethyldiethoxysilane,
y-glycidoxypropyltrimethoxysilane, yglycidoxypropylmethyldimethoxysilane,
y-glycidoxypropyltriethoxysilane, yglycidoxypropylmethyldiethoxysilane,
y-mercaptopropyltrimethoJ..-ysilane, yrnercaptopropylmethyldimethoxysilane,
y-mercaptopropyltriethoxysilane, ymercaptopropylmethyldiethoxysilane,
methyltrimethoxysilane,
dirnethyldimethoxysilane, rnethyltriethoxysilane, dimethyldiethoxysilane,
vinyltriacetoxysilane, y-chloropropyltrimethoxysilane, y-
- 24 -
chloropropylmethyldimethoxysilane, y-chloropropyltriethoxysilane, ychloropropylmethyldiethoxysilane,
hexamethyldisilazane, yanilinopropyltrimethoxxsilane,
y-anilinopropylmethyldimethoxysilane,.y~
anilinopropyltriethoxysilane, y-anilinopropylmethyldiethoxysilane,
vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane,
vinylmethyldiethoxysilane, octadecyldimethyl [3-(trimethoxysilyl) propyl] ammonium
chloride, octadecyldimethyl [3-(methyldimethoxysilyl) propyl] ammonium chloride,
octadecyldimethyl [3-(triethoxylsilyl)propyl] ammonium chloride, octadecyldimethyl
[3-(methyldiethoxysilyl) propyl] ammonium chloride, ychloropropylmethyldimethoxysilane,
y-mercaptopropylmethyldimethoxysilane,
methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and the like.
[0061]
From the viewpoint of coating film adhesion and corrosion resistance, it is
preferable that the amount of the silane coupling agent is 2 to 80 g/1.
[0062]
In the present embodiment, fine particulate silica refers to silica which is able
to stably maintain a water-dispersed state in a case of being dispersed in water due to
having a fme grain diameter. As the fine particulate silica, it is possible to use
commercially available silica gel such as "Snowtex N", "Snowtex C", "Snowtex UP",
"Snowtex PS" (all manufactured by Nissan Chemical Industries, Ltd.), "Adelite AT-
20Q" (manufactured by Asahi Denka Kogyo, Ltd.) or powdered silica such as Aerosil #
300 (manufactured by Nippon Aerosil Co., Ltd.), or the like. The fine particulate
silica may be appropriately selected according to the required performance.
[0063]
In addition, as a drying and baking method in the coating, it is possible to use
- 25 -
generally known drying and baking methods such as a hot air oven, a direct fire oven, a
far infrared oven, an induction heating oven, and the like.
[0064]
The film thickness of the primer coating film layer and the top coating film
layer according to the present embodiment is preferably 1 to 30 J..Lm, respectively.
When the film thickness is less than 1 J..Lm, there is a concern that functions (for
example, coloring properties) as a coating film may not be obtained, while when the
film thickness is more than 30 J..Lm, there is a concern that coating defects referred to as
cratering may occur during coating and baking.
[0065]
As the metal sheet used for the pre-coated metal sheet according to the
embodiment of the present invention, it is possible to use a generally known metal
material. Such a metal material may be an alloy material. Examples of such a metal
material include a steel sheet, a stainless steel sheet, an aluminum plate, an aluminum
alloy plate, a titanium plate, a copper plate, and the like. Various kinds of plating may
be applied to the surfaces of these materials.
[0066]
Examples of the type of plating include zinc plating, aluminum plating,
copperplating, nickel plating, and the like, and alloy platings of these platings may be
used. In the case of a steel sheet, it is possible to apply commonly known steel sheets
and plated steel sheets such as hot-dip galvanized steel sheets, electrolytic zinc-coated
steel sheets, zinc-nickel alloy plated steel sheets, molten alloyed galvanized steel
sheets, aluminum-plated steel sheets, aluminum-zinc alloyed plated steel sheets, and
stainless steel sheets. In particular, in the case of a zinc-plated steel sheet, the
corrosion resistance is further improved, which is more preferable. Here, the zinc-
- 26 -
plated steel sheet refers to galvanized steel sheets plated with zinc such as a hot -dip
galvanized steel sheet or an electrolytic zinc-coated steel sheet, alloy plated steel sheets
of zinc and another metal such as a zinc-nickel alloy plated steel sheet, a molten
alloyed galvanized steel sheet, and an aluminum-zinc alloyed-plated steel .sheet.
Among these zinc-plated steel sheets, galvanized steel sheets such as hot-dip
galvanized steel sheets and electrolytic zinc-coated steel sheets have a large sacrificial
protection effect and are more excellent in corrosion resistance, which is more
preferable. In addition, when the plating adhered amount of these zinc-plated steel
sheets is 40 to 90 g/m2 per side, both workability and corrosion resistance are satisfied,
which is preferable. When the plating adhered amount per side is less than 40 g/m2
,
there is a concern that the corrosion resistance may be deteriorated, while when the
plating adhered amount per side more than 90 g/m2
, there is a concern that plating
cracking may occur during processing and the workability may be deteriorated.
[0067]
The coating method of each coating film is not particularly limited, and it is
possible to adopt generally known coating methods such as roll coating, ringer roll
coating, air spraying, airless spraying, dipping methods, and the like. Furthermore,
when coating is carried out with a continuous coating line called a general coil coating
line or sheet coating line, \¥hich is equipped with these coating apparatuses, mass
production with high coating operation efficiency is possible, which is preferable.
[Examples]
[0068]
The details of the examples are described below.
1. Metal Original Plate
As an original plate, the following were used: a hot-dip galvanized steel sheet
- 27 -
"NS Silver Zinc (registered trademark)" manufactured by Nippon Steel & Sumitomo
Metal Corporation (hereinafter referred to as GI), an electrolytic zinc-coated steel sheet
"NS JINCOAT (registeredtradefi1ark)" manufactured by Nippon Steel & Sumitomo
Metal Corporation (hereinafter referred to as EG), a zinc-nickel alloy plated steel sheet
"NS Zinclite (registered trademark)" manufactured by Nippon Steel & Sumitomo
Metal Corporation (hereinafter referred to as ZL), an aluminum plate "JIS 3004"
(hereinafter referred to as Al), a stainless steel sheet "SUS 430" (hereinafter referred to
as SUS), a zinc-aluminum alloy-plated steel sheet "Galvanium (registered trademark)"
manufactured by Nippon Steel & Sumikin Coated Sheet Corporation (hereinafter
referred to as GL), a zinc-aluminum-magnesium-silicon alloy plated steel sheet
"SuperDima (registered trademark)" manufactured by Nippon Steel & Sumitomo
Metal Corporation (hereinafter referred to as SD), a zinc-aluminum-magnesium alloy
plated steel sheet "ZAM (registered trademark)" manufactured by Nisshin Steel Co.,
Ltd. (hereinafter referred to as ZAM). The sheet thickness of the original plate was
0.6mm.
[0069]
The plating adhered amount ofZL used in this experiment was 20 glm2 per
side, and the amount of nickel in the plating layer was 12% by mass. In addition, GI,
SD, GL, and ZAM were used with plating adhered amounts of 60 g/m2 on one surface
and EG was used with a plating adhered amount of 20 glm2 on one surface.
[0070]
2. Coating
In this example, pre-coated metal sheet was manufactured in which, on a
metal sheet (original plate), there is a three-layer coating film of an underlying coating
film layer not containing chromate on one surface (front surface), a primer coating film
- 28 -
layer on the underlying coating film layer, and a top coating film layer on the primer
coating film layer, and on the other surface (rear surface), there is the same underlying
coating film layer as the front sur:face, t~e san1e primer coating fihnlayer O!lthe
underlying coating film layer, and a rear surface coating film on the primer coating
film layer.
[0071]
(Underlying coating film layer Coating)
Underlying Coating 1: EC2000 manufactured by NIPPONPAINT Co., Ltd.
Underlying Coating 2: An aqueous solution which includes 5 giL of a silane
coupling agent (y-glycidoxypropyltrimethoxysilane), 1.0 giL of a water-dispersed
colloidal silica ("Snowtech-N" manufactured by Nissan Chemical Industries, Ltd.), and
25 giL of an aqueous polyester resin (MD-llOO manufactured by Toyobo Co., Ltd.)
[0072]
(Primer coating film layer Coating)
With the resins described in Table 2 as the main resin, the resins were
dissolved in an organic solvent (a solvent in which cyclohexanone and Solvesso 150
are mixed at 1: l by mass ratio is used) such that the resin solid content concentration
was 30% by mass. In a case where the two types of main resins are mixed, 50% by
mass of each main resin is mixed therein. The glass transition point temperature of
the resin described in Table 2 was measured by differential scarming calorimetry.
[0073]
Next, a melamine resin "Cyme! (registered trademark) 303" manufactured by
Cytec Industries Incorporated was added to the main resin as a cross-linking agent.
The added amount of the melamine resin was such that the mass ratio ofthe resin solid
content was main resin solid content: melamine resin solid content= 80: 20.
- 29 -
Furthermore, 0.5% by mass of an acidic catalyst "Catalyst (registered trademark) 600"
manufactured by Cytec Industries Incorporated was added to the mixed solution of the
polyester resin and the melamine resin, and these were stirred to obtain a clear coating.
Next, primer coatings were obtained (refer to Table 3 below) by adding and stirring
necessary amounts of dihydrogen aluminum tripolyphosphate "K-WHITE G-1 05"
(hereinafter referred to as P-Al) manufactured by Tayca Corporation as a rustpreventive
pigment, calcium ion-exchanged silica "Shieldex C303" (hereinafter
referred to as Ca-Si), manufactured by W. R. Grace & Co.-Conn., a zinc phosphatebased
rust-preventive pigment "EXPERT (registered trademark)-NP 500" (hereinafter
referred to as P-Zn), magnesium dihydrogenphosphate (hereinafter referred to as PMg)
as a reagent, and calcium phosphate as a reagent (hereinafter referred to as P-Ca)
in this coating. The glass transition point temperature of the resin described in Table
3 was measured by differential scarming calorimetry.
[0074]
[Table 2]
Resin Type Tg(OC)
Bl Epoxy-modified polyester resin 40
B2 Epoxy-modified polyester resin 50
B3 Epoxy-modified polyester resin 55
B4 Epoxy-modified polyester resin 70
BS Epoxy-modified polyester resin 100
B6 Epoxy-modified polyester resin 110
B7 Epoxy resin 65
B8 Polyester resin 55
Bl4 Polyester resin 79
Epoxy modified polyester resin: Copolymer ofbisphenol A type epOlcJ' resin
and polyester (each grade of Byron manufactured by Toyobo Co., Ltd.)
- 30 -
Epoxy resin: Bisphenol A type epoxy resin
Polyester resin (glass transition point temperature 55°C): Byron (registered
trademark) 660
- 31 -
!-
[0075]
[Table3]
Rust-preventi~·e pigment added amoWlt
(parts by mass with respect to 100 -parts by mass of resin solid content)
Ele>ngation rate
Primer ~oaring type Resin P-Al P-Z. P-Mg Ca-Si P-Ca
Rust-preventive (%)
Tg(OC)
added added added added added
pigment added amount
amount amount amoWJt amount amount
Primer coating I Bl 0 0 50 0 0 50 60 40
Primer coating 2 B2 0 0 50 0 0 50 55 50
Primer ooating3 B3 0 0 50 0 0 50 50 55
Primer coating 4 B4 0 0 50 0 0 so 45 70
Primer coating 5 B5 0 0 50 0 0 50 40 100
Primer coating 6 B6 0 0 50 0 0 50 30 110
Primer ooating 7 B7 0 0 50 0 0 50 20 65
Primer coating 8 B8 0 0 50 0 0 50 60 55
Primer coating 9 B7+B8 0 0 50 0 0 so 45 60
Primer coating 10 B3 50 0 0 0 0 50 45 55
Primer coating II B3 0 50 0 0 0 50 45 55
Primer coating I2 3 0 0 50 0 0 70 45 55
Primer coating I3 B3 0 0 0 20 0 20 5 55
Primer coating 14 B3 0 0 30 20 0 50 45 55
Primer coating 15 B3 0 0 5 0 0 5 45 55
Primer coating 16 B3 0 0 10 0 0 10 45 55
Primer coating 17 B3 0 0 100 0 0 100 42 55
Primer coating 18 B3 0 0 160 0 0 160 42 55
Primer coming 19 B3 0 0 170 0 0 170 40 55
Primer coating 20 B3 0 0 0 0 50 50 45 55
Primer coating 21 B14 0 0 10 0 0 10 5 79
- 32 -
[0076]
In order to measure the fracture critical elongation rate of the primer coating
film layer, a tensile test was carried out. In the tensile test, 100 mg/m2 of the
underlying coating 2 was attached to the GI original plate, thereafter, the primer
coating was coated thereon with a thickness of 5 ~m and the plate was pulled at a
speed of200 mm/min. The fracture critical elongation rate of the original plate is
60%, and less than 60% corresponds to the elongation rate ofthe film.
[0077]
(Top Coating film layer Coating)

The resins described in the following Table 4 were used as the main resin.
Here, the glass transition point temperatures of the resins described in Table 4 were
measured by differential scanning calorimetry.
[0078]
[Table 4]
Resin type Tg(OC)
B9 Acrylic resin 55
BlO
Polyester-modified acrylic
55 resm
Bll Polyester resin 55
Bl2
Polyester-modified acrylic
resm 21
Bl3 Polyester resin 79
Acrylic resin (glass transition point temperature 55°C): Udouble (registered trademark)
S-2818
Polyester resin (glass transition point temperature 55°C): Byron (registered trademark)
660
- 33 -
Polyester resin (glass transition point temperature 79°C): Byron (registered trademark)
885
Polyester-modified acrylic resin (glass transition point temperature 21 oc and 55°C):
copolymer described above
[0079]

As the amino resin cross-linking agent, "Cyme! (registered trademark) 303"
(described as "Me") which is a methylated melamine resin manufactured by MitsuiCytec
Ltd., Desmodur BL-3175 (described as BI) which is an isocyanate manufactured
by Sumika Bayer Urethane Co., Ltd., and Epoxy resin EX-252 (described as EP)
manufactured by N agase ChemteX Corporation were added such that the ratio of the
main resin: cross-linking agent was 80:20 parts by mass. "Catalyst 602"
manufactured by Mitsui-Cytec Co., Ltd., was used as a catalyst. The added amount
of the catalyst was 0.5 parts by mass based on 100 parts by mass of the main resin
solid content.
[0080]

Methyl silicate 51 (manufactured by Col coat Co., Ltd.) was added as the
organosilicate.
[0081]

A wax manufactured by Nippon Seiro Co., Ltd., having a melting point of
61 oc was used. The dynamic friction coefficient was changed depending on the
added amount of the wax.
[0082]
- 34 -

Commercially available titanium oxide, iron oxide, and carbon black were
used for coloring. The total pigment concentration was 20 parts by mass with respect
to 100 parts by mass of the solid content.
[0083]
Table 5 shows the top coating composition obtained by mixing the above to
form a coating. In the following Table 5, the added amounts of the silicates are in
parts by mass with respect to 100 parts by mass of the resin solid content. These were
dissolved in an organic solvent (a mixture in which cyclohexanone: Solvesso !50 = 1:
1 by mass ratio) such that the resin solid content concentration was 30% by mass.
[0084]
[Table 5]
Top coating Cross-linking
S iii cate added
Elongation
Water
Resin amount (parts contact
type agent
by mass)
rate(%)
angle (0
)
Top coating 1 B9 Bl 0 5 82
Top coating 2 B!O BI 0 10 82
Top coating 3 Bll Me 0 20 82
Top coating 4 B10 Me 0 10 82
Top coating 5 BlO BI 0.05 10 65
Top coating 6 B10 BI 0.1 10 60
Top coating 7 BlO BI 1 10 55
Top coating 8 B!O BI 10 10 50
Top coating 9 BlO BI 20 10 45
Top coating 10 BlO BI 25 5 45
Top coating 11 Bl2 BI 1 38 55
Top coating 12 Bl3 BI 1 5 55
Top coating 13 BlO EP 1 10 55
[0085]
A tensile test was carried out to measure the fracture critical elongation rate of
- 35 -
the top coating film layer. In the tensile test, 100 mg/m2 of the underlying coating 2
was attached to the GI original plate, thereafter the top coating was coated at a
thickness of 5 J.Lm, and the plate was pulled at a speed of 200 mm/min. The fracture
critical elongation rate of the original plate is 60%, and less than 60% corresponds to
the elongation rate of the film.
[0086]
3. Preparation of Pre-Coated Metal sheet
Various metal sheets were degreased by dipping in an aqueous solution at 2%
by mass concentration ofFC-4336 (manufactured by Nihon Parkerizing Co., Ltd.) at a
temperature of 60°C for 10 seconds, cleaned with water, and then dried. Next, the
underlying coating was coated on both sides of the metal sheet with a roll coater and
dried in a hot air oven. Drying conditions in a hot -air oven were set such that the
target temperature of the metal sheet was 60°C. Regarding the adhered amount of the
chromate-free treatment, the coating was carried out so as to attach 80 g/m2 as the total
solid content.
[0087]
Next, the primer coating films prepared as described above were coated on
both sides of the metal sheet on which the underlying coating was coated with a roll
coater so as to have a dry film thickness of 5 f.Uil, respectively, and dried and hardened
in an induction heating furnace in which hot air was blown under conditions such that
the target temperature of the metal sheet was 21 ooc. After drying and baking, water
was sprayed on the coated metal sheet to carry out water-cooling.
[0088]
Furthermore, a top coating was coated on one side of the primer coating film
layer and gray "FL 100 HQ", which is a rear surface coating manufactured by Nippon
- 36 -
Fine Coatings Co., Ltd., was coated on the other side with a roll coater such that the
top coating had a dry film thickness of 15 fLID, the rear coating had a dry film thickness
of 5 fLID, and simultaneously dried and baked in an induction heating furnace in which
hot air was blown under conditions that the temperature of the metal sheet reached
230°C, and water cooling was carried out to obtain a pre-coated steel sheet which is a
sample material.
[0089]
The configuration of the surface of the prepared sample is described in Table
6 below.
- 37 -
[Table 6]
Elongation rate
Elongation Elongation
Level Original plate Underlying coating Primer coating
(primer)(%)
Top coating rate (top) rate (overall)
(%) (%)
I GI Underlying coating 2 Primer coating 3 50 Top coating 8 10 25
2 GI Underlying coating 2 Primer coating 4 45 Top coating 8 10 20
~ 3~ GI-- Underly.ing--coating--2-- -- -Primer-coatino---5--- -40 --- --- - -- -Top-coating-S 10 ~]~5 ....
4 GI Underlying coating 2 Primer coating 9 45 Ton coating 8 10 20
5 GI Underlying coating 2 Primer coating 10 45 Top coating 8 10 20
6 Gl Underlying coating 2 Primer coating 11 45 Top coating 8 10 20
7 GI Underlying coating 2 Primer coating 12 45 Top coating 8 10 20
8 GI Underlying coating 2 Primer coating 14 45 Top coating 8 10 20
9 GI Underlying coating 2 Primer coating 15 45 Top coating 8 10 20
10 GI Underlying coating 2 Primer coating 16 45 Top coating 8 10 20
II GI Underlying coating 2 Primer coating 17 42 Top coating 8 10 15
12 GI Underlying coating 2 Primer coating 18 42 Ton coating 8 10 15
13 GI Underlying coating 2 Primer coating 19 40 Top coating 8 10 10
14 GI Underlying coating 2 Primer coating 4 45 Top coating 1 5 20
15 GI Underlying coating 2 Primer coating 4 45 Top coating 2 10 20
16 GI Underlying coating 2 Primer coating 4 45 Top coating 4 10 20
17 GI Underlying coating 2 Primer coating 4 45 Too coating 5 10 20
18 GI Underlying coating 2 Primer coating 4 45 Too c_oating 6 10 20
19 GI Underlying coating 2 Primer coating 4 45 Top coating 7 10 20
20 GI Underlying coating 2 Primer coating 4 45 Top coating 8 10 20
21 GI Underlying coating 2 Primer coating 4 45 Too coating 9 10 20
22 GI Underlying coating 2 Primer coating 4 45 Too coating 10 5 15
23 Gl Underlying coating 1 Primer coating 4 45 Top coating 8 10 20
24 EG Underlying coating 2 Primer coating 4 45 Top coatimr 8 10 20
25 ZL Underl 'ing coating 2 Primer coating 4 45 Top coating 8 10 20
26 SD Underlying coating 2 Primer coating 4 45 Too coating 8 10 20
27 GL Underlying coating 2 Primer coating 4 45 Top coating 8 10 20
28 ZAM Underlying coating 2 Primer coating 4 45 Ton coating 8 10 20
29 GI Underlying coating 2 Primer coating 4 45 Ton coating 8 10 20
30 GI Underlying coating 2 Primer coating 4 45 Ton coating 8 10 20
31 GI Underlying coating 2 Primer coating 4 45 Top coatinp; 8 10 20
32 GI Underlying coating 2 Primer coating 4 45 Top coating 8 10 20
33 GI Underlying coating 2 Primer coating 4 45 Ton coating 8 10 20
34 GI Underlying coating 2 Primer coating 20 45 Ton coating 8 10 20
35 GI Underlying coating 2 Primer coating 5 40 Top coating 10 5 10
36 GI Underlying coating 2 Primer coating 4 45 Top coatine: 13 10 20
37 GI Underlving coating 2 Primer coating 7 20 Top coating 8 10 10
38 GI Underlying coating 2 Primer coating 8 60 Top coating 8 10 35
39 GI Underlying coating 2 Primer coating 13 45 Top coating 8 10 20
40 GI Underlying coating 2 Primer coating 3 50 1 Ton coating 3 20 40
41 GI Underlving coating 2 Primer coating 1 60 Ton coating 8 10 35
42 GI Underlying coating 2 Primer coating 2 55 Ton coating 8 10 35
43 GI Underlying coating 2 Primer coating 6 30 Top coating 8 10 5
44 Gl Underlying coating 2 Primer coating 8 60 Top coating 3 20 50
45 GI Underlying coating 2 Primer coating 3 50 Top coating 11 38 35
46 GI Underlving coating 2 Primer coating 4 45 Top coating 11 38 35
47 GI Underlying coating 2 Primer coating 5 40 Top coating 11 38 30
48 GI Underlying coating 2 Primer coating 8 60 Top coating 12 5 30
49 GI Underlying coating 2 Primer coating 21 5 Top coating 12 5 5
- 38 -
[0090]
A detailed description will be given of the evaluation method of the precoated
metal sheet.
1. Water Contact Angle
The prepared pre-coated metal sheet was allowed to stand in a humid
environment of50°C and 95% RH for 72 hours, and 2.0 ~I water droplets were
dropped on the surface of the top coating film layer using "DM-501" manufactured by
Kyowa Interface Science Co., Ltd., and the water contact angle was measured by the
9/2 method after 1 second. Five measurements were taken and the average value
thereof was taken as the evaluation object.
[0091]
2. Contamination Resistance Test
The prepared samples were subjected to an exposure test for 3 months at an
outdoor exposure test site located near the coast of Futtsu City in Chiba Prefecture.
With respect to the sample after the test, the presence or absence of contamination was
visually evaluated and a case where no contamination was observed at all was
evaluated as A, a case where contamination was slightly observed was evaluated as B,
and a case where contamination was clearly observed was evaluated as C. In a case
where the evaluation was C, it was judged that the contamination resistance was
deteriorated.
[0092]
3. Raindrop Staining Resistance Test
The prepared samples were subjected to an exposure test for 12 months at an
outdoor exposure test site located near the coast of Futtsu City in Chiba Prefecture.
With respect to the san1ple after the test, the presence or absence of contamination
- 39 -
including raiudrop marks was visually evaluated and a case where there were no
raindrop marks or contamination at all was evaluated as A, a case where the raindrop
marks were observed in part, but there were no stains on the whole and the
contamination property was good was evaluated as B, a case where raindrop marks
were observed in part and the whole was contaminated was evaluated as C, and a case
where raindrop marks were clearly observed and the whole was contaminated was
evaluated as D. In a case where the evaluation was D, it was judged that the raiudrop
staining resistance was deteriorated.
[0093]
4. End Surface Coating Film Peeling Property After Processing
The prepared pre-coated metal sheet was cut, the lower burr portion was
further lowered in the burr direction using a die, the tape was firmly attached to the
coatiug film of the end surface portion, and, after peeling off the tape, peeling of the
coating film was examined by visual observation. A case without peeling was
evaluated as A, a case where a slight crack or peeliug was observed in the coating film
was evaluated as B, and a case where there were clearly large cracks or peeling in the
coatiug film was evaluated as C. In a case where the evaluation was C, it was judged
that the end surface coatiug film peeling property after processiug was deteriorated.
[0094]
5. Processiug Crack Evaluation
2T bending was carried out on a test piece cut into a width of 5 em in an
atmosphere at 20°C by a test method according to JIS. G 3312. Specifically, two of
the same coated plate as the test piece were sandwiched inward, and 180° close contact
bending was performed with the surface coated with the top coating film faciug out
(refer to Fig. 2). After attaching an adhesive tape (trade name: cellophane tape) to the
- 40 -
entire bent portion, the adhesive tape was peeled off. The parts not peeled off were
cut in parallel to the bending direction so that the width of the test piece was equally
divided by I 0, and 10 cutaway surfaces were observed. The crack width I was
measured by measuring the outermost layer of the top coating film layer 2 shown in
Fig. l. On the ten cutaway surfaces, the crack width 1 of the top coating film layer
included in the range A 1 mm long in the direction orthogonal to the bending direction
centering on the vertex section of the bend was measured, and the absolute maximum
value of all the measured values was taken as the maximum width (mm) of the cracks.
In addition, on each of the I 0 cutaway surfaces, the number of cracks of the top
coating film layer included in the range A I mm long in the direction orthogonal to the
bending direction centering on the vertex section of the bend is totalled (in the case of
Fig. 2, the number of cracks included in the range A is seven) and the absolute
maximum value among the total values was taken as the number of cracks. The
bending direction is the longitudinal direction of the pre-coated metal sheet 4 after the
2T bending test. Table 7 below shows the number of cracks and the maximum width
(mm) for each test piece.
[0095]
6. Corrosion Resistance Test
A sample subjected to 2T bending in an environment of20°C was subjected to
a salt water spray test according to the method described in ITS K 5400.9.1. Salt
water was sprayed on the processed portion. The test time was 240 hours for samples
using EG and ZL for the original plate and 500 hours for the samples used for the other
original plates. The white rust area ratio of the processed portion was measured and a
case of 5% or less was evaluated as A, a case of20% or less was evaluated as B, a case
of 50% or less was evaluated as C, and a case of more than 50% was evaluated as D.
- 41 -
In a case where the evaluation was D, it was judged that the corrosion resistance was
deteriorated.
[0096]
7. Dynamic Friction Coefficient
Measurement was carried out under the conditions of a load of 100 g, a ball
indenter cjJ of 1 0 mm, and a moving speed of 150 mm/min using a surface property
measuring machine HEIDON-14 type (manufactured by Shinto Scientific Co., Ltd.).
[0097]
The evaluation results of the tests described above are summarized in Table 7.
- 42 -
[Table 7]
~ater ~nd Maxim
~longation Anti- No. of ~~mic
m
]Level
on tact Stalning urface
rack
Corrosion
friction Other 'otes
f'ng1e ate(%) esistance aindrop jpeeling racks esistance
0) ~roperty
width oefficient
(mm)
l 0 j - ... 7 .U.Oi A .0.13 ood ___ RESENJ:Th._l"\~NTiillLEXAMl'LE
0 0 10 0.08 0.13 Good RESE}.'T INVE~TION EXAMJ'LE
0 15 A "' 0 0.1 0.13 Good RESENT INVE:s!TION EX.'\MPLE
0 0 "' "' 10 0.08 "' 0.13 Good RESENT INVEYI10N EXAMPLE
5 0 0 "' "' 10 0.08 "' 0.13 Good RESENT INVE:s!TION EXAMPLE
6 0 0 10 0.08 0.13 Good RESEl\'T INVE:s!TION EXAMPLE
7 0 0 "' 10 0.08 0.13 Good RESEl\'T INVE::l"TION EXAMPLE
8 0 0 lA lA 10 0.08 lA 0.13 Good RESENT INVE:!JTION EXAMPLE
0 0 lA lA 10 0.08 IB 0.13 Good RESEl\'T INVE:'>JTION EXAMPLE
10 0 0 10 0.08 0.13 Good RESENT II\TVENTION EXAMPLE
11 0 15 "' 0 0.1 0.13 Good RESEl\'T Il\TVCYTION EXAMPLE
12 0 15 lA lA 0 0.1 "' 0.13 Good RESET'>;'T INVD!TION EXAMPLE
13 0 10 "' "' 8 0 0.1 "' 0.13 Good RESENT INVENTION EXAMPLE
14 82 0 10 0.08 0.13 Good RESF.l\'T Il\TVENTION EXAMPLE
15 82 ~0 "' IB 10 0.08 0.13 Good RESEl\TINVENTIONEXAMPLE
16 82 0 "' c 10 0.08 "' 0.13 !Good RESEl\'T INVENTION EXAMPLE
17 5 0 "' IB 10 0.08 "' 0.13 pood RESEl\'T INVENTION EXAMPLE
18 ~0 0 10 0.08 "' 0.13 !Good RESEI\'T INVENTION EXAMPLE
19 5 0 "' 10 0.08 0.13 Good RESENT n.TVENTION EXAMPLE
0 0 0 "' lA 10 0.08 "' ~.13 (iood RESENT INVENTION EXAMPLE
1 5 0 f"- A 10 0.08 0.13 Pood RESENT INVENTIOK EXAMPLE
2 5 15 A r. A 0 0.1 A r13 r,.~pearance
efects RESENT INVENTION EXAMPLE
23 0 0 10 0.08 .13 !Good RESENT Th'VENTION EXAMPLE
4 0 0 "'- 10 0.08 .13 ~ood RESENT INVENTION EXAM:PLE
5 0 0 "' A 10 0.08 .13 !Good RESENT INVENTION EXAMPLE
6 0 0 lA A 10 0.08 .13 !Good RESENT INVENTION EXA.\U'LE
7 0 0 10 0.08 .13 !Good RESENT IKVENTION EXAMPLE
8 0 0 10 0.08 .13 jGood RESENT IKVENTION EXAMPLE
9 0 20 A A A 10 0.08 A .05 r;oil
RESENT IKVENTION EXAMPLE ollapse
0 0 0 10 0.08 0.06 Good RESENTIKYCNTION EXAM:PLE
1 10 0 A 10 0.08 0.2 (iood RESENTIKVENTION EXAMPLE
2 10 0 A 10 0.08 0.25 !Good RESDIT IKVENTION EXAMPLE
oratch
3 ·o 0 A A A 10 0.08 A 0.3 ~~eration RESENTIKVENTION EXAMPLE
" bressing
4 0 0 A 10 ~.08 0.13 Pood RESENTII\'VEJ\'TION EXAMPLE
5 5 10 A A 10 ~.08 013 KJood RESENTIKVEJ\110~ EXAMPLE
6 5 0 10 .08 0.13 ood RESENTIKVENTION EXAMPLE
7 50 10 eeling eeling D 0.13 ood OMPARATIVE EXAMPLE
8 50 ~5 A A 0 A 0.13 Good OMPARATIVE EXAMPLE
9 50 0 A A lA 10 .08 D 0.13 Good OMPARATIVE EXAMPLE
0 82 0 D 5 .05 A 0.13 -ood OMPARATIVE EXAMPLE
1 0 5 .05 0.13 ood Ol\4PARATIVE EXAMPLE
2 0 5 c .05 A 0.13 Good OWARATIVE EXAMPLE
3 0 A A c 5 0.2 D 0.13 Good OWARATIVE EXA!vfPLE
4 82 0 c D c 0 0 A 0.13 Good OMPARATIVE EXMfPLE
5 5 5 D c 0 0.13 ood OMPARATIVE EXAMPLE
6 5 5 D c 0 lA 0.13 Good OMPARATI\'E EXMfPLE
7 5 0 D c 0 "' 0.13 Good OMPARATIVE EXAMPLE
8 5 0 c D c 0 "' 0.13 Good 'OMPARATIVE EXMfPLE
9 5 5 D c eeling eeling 0.13 ood 0!11PARATIVE EXMfPLE
- 43 -
[0098]
A tensile test was carried out in order to measure the fracture critical
elongation rate ofthe coating film which combined the primer coating film layer and
the top coating film layer. In the tensile test, the underlying coating 2 was attached to
the GI original plate at 100 mg/m2
, then the primer paint was coated at 5 /-till, the top
paint was coated at 5 /-LID, and the film was pulled at a speed of200 mm/min. The
fracture critical elongation rate of the original plate is 60%, and less than 60%
corresponds to the elongation rate of the film.
A tensile test was performed on the pre-coated metal sheet according to the
embodiment of the present invention until the fracture critical elongation rate reached
10%, but no cracks were formed therein.
(0099]
As is clear from the above Table 7, it is understood that the pre-coated metal
sheet ofthe present invention example is excellent in contamination resistance, end
surface coating film peeling property after processing, and corrosion resistance.
In addition, as is apparent from the above Table 7, it is understood that the
pre-coated metal sheet of the example of the present invention has a total of 5 to 30
cracks having a width of 0.1 mm or less occur in the top coating film layer in a range A
centered on the vertex section of the bend and having a length of 1 mm in a direction
orthogonal to the bending direction when 2T close contact bending is carried out.
[0100]
As is apparent from the above Table 7, in a case where the fracture critical
elongation rate of the coating film layer which combines the primer coating film layer
and the top coating film layer was set to less than 10% (level43), the cracks of the
coating film are larger than the present invention example, and the end surface coating
- 44 -
film peeling property after processing is clearly deteriorated. In addition, in a case
where the fracture critical elongation rate of the coating film layer which combines the
primer coating film layer and the top coating film layer was set to more than 25%
(level 38, 40 to 42, and 44 to 48), it was found that the contamination resistance or the
end surface coating film peeling property after processing was deteriorated in
comparison with the present invention example.
In addition, in the case where the fracture critical elongation rate of the top
coating film layer is more than 10% and the fracture critical elongation rate of the
primer coating film layer is 40% or more and 50% or less (level 40 and 45 to 4 7), it
was found that the contamination resistance was clearly deteriorated in comparison
with the present invention example.
Furthermore, in a case where the fracture critical elongation rate of the top
coating film layer is 5% or more and 10% or less and the fracture critical elongation
rate of the primer coating film layer is less than 40% (levels 3 7, 43 and 49), it was
found that the cracks of the coating fihn were large and the end surface coating film
peeling property after processing was clearly deteriorated in comparison with the
present invention example.
[0101]
As is apparent from the above Table 7, in a case where the resin components
of both of the primer coating film layer and the top coating film layer were polyester
resin and the fracture critical elongation rate of the coating film layer which combines
the primer coating film layer and the top coating film layer was less than 10% (level
49), it is understood that the contamination resistance and the end surface coating film
peeling property after processing are deteriorated in comparison with the present
invention example. ln addition, in a case where the resin components of both of the
- 45 -
primer coating film layer and the top coating film layer were polyester resin and the
fracture critical elongation rate of the primer coating film layer was more than 50%
(level48), it was found that the contamination resistance and the end surface coating
film peeling property after processing were clearly deteriorated in comparison with the
present invention example.
In addition, in the same marmer as a case where the fracture critical elongation
rate of the top coating film layer was more than l 0% (levels 45 to 4 7), it was found
that the contamination resistance and the end surface coating film peeling property
after processing were clearly deteriorated in comparison with the present invention
example.
[0102]
Although the embodiments of the present invention were described in detail
with reference to the drawings, the present invention is not limited to such examples.
Those having ordinary knowledge in the technical field to which the present invention
belongs will be able to clearly see various modifications or improvements within the
scope of the technical idea described in the claims and these are naturally understood
as belonging to the technical scope of the present invention.
[Industrial Applicability]
[0103]
According to the embodiment of the present invention, it is possible to
provide a pre-coated metal sheet that is excellent in long-term contamination resistance,
end surface coating film peeling property, and corrosion resistance.
[Brief Description of the Reference Symbols]
[0104]
1: CRACK WIDTH
- 46 -
2: TOP COATING FILM LAYER
3: PRIMER COATING FILM LAYER
4: PRE-COATED METAL SHEET
A: A RANGE OF I MM LONG IN A DIRECTION ORTHOGONAL TO
THE BENDING DIRECTION CENTERING ON THE VERTEX SECTION OF THE
BEND
- 47 -
[Document Type]

What is claimed is:
l. A pre-coated metal sheet comprising:
a metal sheet;
an underlying coating film layer which does not contain chromate and which
is provided on the metal sheet;
a primer coating film layer which does not contain chromate and which is
provided on the underlying coating film layer; and
a top coating film layer which is provided on the primer coating film layer,
wherein a fracture critical elongation rate of a coating film layer which
combines the primer coating film layer and the top coating film layer is 10% or more
and 25% or less,
a glass transition point temperature of the primer coating film layer is more
than 50°C to 100°C or less,
the top coating film layer includes a resin component and the resin component
includes an acrylic resin or a polyester-modified acrylic resin, and,
when the pre-coated metal sheet is subjected to 2T close contact bending,
there are a total of 5 or more and 30 or less cracks having a width of 0.1 mm or less in
the top coating film layer in a range centered on a vertex section of the bend and
having a length of 1 mm in a direction orthogonal to the bending direction.
2. The pre-coated metal sheet according to claim 1,
wherein the fracture critical elongation rate of the primer coating film layer is
40% or more and 50% or less,
the fracture critical elongation rate of the top coating film layer is 5% or more
- 48 -
and 10% or less,
the primer coating film layer includes a rust-preventive pigment and a resin
component and the rust-preventive pigment includes at least one of magnesium
phosphate, calcium phosphate, aluminum phosphate, and zinc phosphate, and
the resin component in the primer coating film layer includes an epoxymodified
polyester resin.
3. The pre-coated metal sheet according to claim 1 or 2,
wherein the primer coating film layer includes a rust-preventive pigment and
a concentration of the rust -preventive pigment is 10 parts by mass or more and 160
parts by mass or less with respect to 100 parts by mass of resin solid content.
4. The pre-coated metal sheet according to any one of claims 1 to 3,
wherein the top coating fihn layer does not contain a melamine resin.
5. The pre-coated metal sheet according to any one of claims 1 to 4,
wherein a dynamic friction coefficient of a surface of the top coating film
layer is 0.06 or more and 0.25 or less.
6. The pre-coated metal sheet according to any one of claims 1 to 5,
wherein a water contact angle on a surface of the top coating film layer after
standing for 72 hours in a humid envirornnent of 50°C and 95% RH is 60° or Jess.
7. The pre-coated metal sheet according to any one of claims 1 to 6,
wherein the top coating film layer contains an organosilicate.
- 49 -
8. The pre-coated metal sheet according to claim 7,
wherein amount of the organosilicate in the top coating film layer is 0.1 parts
mass or more and 20 parts by mass or less with respect to 100 parts by mass of resin
solid content of the top coating film layer.
9. The pre-coated metal sheet according to any one of claims 1 to 8,
wherein the underlying coating film layer contains at least one offme
particulate silica, a silane coupling agent, and tannic acid.
10. The pre-coated metal sheet according to any one of claims 1 to 9,
wherein a film thickness of the primer coating film layer is 3 to 1 0 f.U11 and a
film thickness of the top coating film layer is 5 to 25 f.UTI.