DESCRIPTION
PRIMARY RUST-PREVENTIVE COATING COMPOSITION AND USES THEREOF
5 Technical Field
[00011
The present invention relates to a primary rust-preventive
coating composition (shop primer) suitable for use in steel-plate
pretreatmentconductedinprocessingsteelplatesofships,marine
10 structures, plants, bridges, overlandtanks andthe like; anduses
thereof. In more detail, the present invention relates to a
primary rust-preventive coating composition including a
siloxane-based binder and a flaky zinc-based powder and being
capable of forming a rust-preventive coating film having an
15 averagedry filmthickness ofnotmorethan10pm; andusesthereof.
Background Art
[00021
Conventionally, large steel structures such as ships,
20 marine structures, plants, bridges andoverlandtanks whilebeing
built, in order to be prevented from rusting, have their steel
plate surfaces coated with primary rust-preventive coating
materials. Known primary rust-preventive coating materials
include organic primary rust-preventive coating materials such
as wash primers, non-zinc epoxy primers and epoxy zinc-rich
primers as well as inorganic zinc primary rust-preventive coating
materials including siloxane-basedbinders and zinc powders. Of
theseprimaryrust-preventive coatingmaterials, mostwidelyused
5 are inorganic zinc primary rust-preventive coating materials,
which are excellent in weldability.
[0003]
Primary rust-preventive coating films formed from
conventional inorganic zinc primary rust-preventive coating
10 materials have an average dry film thickness of about 15 pm. The
formation of a coating film with its thickness smaller than the
above could increase the speed of process-treatment in welding
andcutting step subsequent to coating step, which is advantageous
in terms of productivity.
15 [00041
There are three methods for applying conventional primary
rust-preventive coating materials so as to provide thin films
(e.g., a thickness of not more than 10 pm).
[0005]
20 A first method is to reduce the discharge flow amount of
a primary rust-preventive coating material at the time of its
application. However, this method requires the discharge flow
rate of a currently-available coating machine to be below the
discharge flow rate limit allowing for stable coating procedure,
resulting in the failure of uniform coating.
[0006]
A second method is the development of a coating machine
itself. Yet, relying on a conventional primary rust-preventive
5 coating material and a conventional apparatus that are currently
available in order to provide thin films is difficult. Even if
such a machine is developed, the need to replace a conventional
apparatus with a new one would require huge expense.
[0007]
A third method is to dilute a primary rust-preventive
coatingmaterial with a considerable amount of an organic solvent
to reduce the solidcontent concentrationofthecoatingmaterial.
This method is a practical one that achieves the formation of a
thin film under current circumstances; however, this method will
15 consequently increase the volatile organic compounds (VOC)
emissionamountpercoatedarea, adverselyaffectingenvironment.
Even if a thin film is obtained, the film has reduced amount of
binder amount per unit area of a steel plate surface to be coated,
so that coating effect is lost and the performance of the rust
20 prevention of steel plates is lowered.
[0008]
Thus, the application of conventional primary
rust-preventive coating materials so as to form thin films was
substantially impossible.
[00091
On the other hand, Patent Literature 1, for the purpose of
providing a primary rust-preventive coating composition giving
superior weldability at the time of gas sealed welding, studies
5 reducing the amount of zinc powder to be used, and further
describesthat forthe reduction ofthe amount ofthe zinc powder,
using zinc flake is effective. However, Patent Literature 1 is
entirely silent on reducingthethickness of coating films formed
from said composition, said coating films having an average dry
10 film thickness of 15 to 25 pm. Thus, the use amount per coated
area of the coating material cannot be reduced, so that VOC
emission amount cannot be reduced. There is obviouslynomention
provided therein about long-term rust prevention properties of
coating films with reduced thickness.
15 [OOlO]
Patent Literature 2 discloses a rust-preventive coating
composition containing an organic silicon compound, an organic
titanate compound, a metal powder, e.g., a flaky zinc powder, and
an organic solvent, the composition being capable of forming a
20 coating film that has an average dry film thickness of about 10
pm and exhibits high anticorrosiveness. However, in order to
obtain such a coating film, a step is required to heat, at 200
to 400°C, the rust-preventive coating composition applied on a
metal surface. For this reason, said composition is not suited
insteel-platepretreatmentcarriedoutinprocessingsteelplates
of ships, marine structures, plants, bridges, overland tanks and
the like.
[OOll]
Patent Literature 3 discloses a rust-preventive coating
material containing a spherical zinc powder, a flaky zinc powder,
a spherical or flaky aluminum powder and a curable silicone
compound. However, if this coating material is used to give a
film with an average dry film thickness of approximately 15 pm
10 and the application of said coating material is followed by
treatments such as welding treatment, problems in terms of
insufficient anticorrosiveness and welding defect occur. Thus,
this coating material is not suited for use in steel-plate
pretreatment carried out in processing steel plates of ships,
15 marine structures, plants, bridges, overland tanks and the like.
Citation List
Patent Literature
[00121
20 [Patent Literature 11 JP-A-1985-133072
[Patent Literature 21 W0-A-2009/093319
[Patent Literature 31 JP-A-2012-036279
Summary of the Invention
Technical Problem
[00131
It is an object of the present invention to solve the
problems associated with the above conventional techniques and
5 to provide a primary rust-preventive coating composition which
bybeingdriedandcured at roomtemperature is capable of forming
a coating film having an average dry film thickness of not more
than 10 pm even with the use of conventional coating machines,
and having excellent rust prevention properties and
10 overcoatability as well as excellent weldability/cut-ability at
the time of welding and cutting steel plates, and uses thereof.
Technical Solution
[0014 I
The present inventors, seeking the solution to the above
problems, studied a coating composition containing a
siloxane-basedbinderanda zincdust including a flaky zinc-based
powder, and focused on how the formation of a coating film having
an average dry film thickness not more than 10 pm is affected by
20 a pigment volume concentration (PVC) and a weight average
molecular weight (Mw) of the siloxane-based binder, as well as
amass ratioof zincdusttosiloxane-basedbinder (Zn/SiOz), which
are described later.
[00151
As a result of the study, it has been found that in Patent
Literature 1, PVC of a coating composition exceeds 60%, and this
makes it difficult to form a coating film that has an average dry
film thickness of not more than 10 pm and exhibits superior
5 properties. It has also been found that in Patent Literature 2,
the use of a low-molecular-weight substance as an organosilicon
compound makes it difficult for curing to be conducted at room
temperature.
[0016]
In Patent Literature 3, a coating composition has PVC lower
than 35% or has a significantly high mass ratio of zinc dust to
siloxane-based binder (Zn/Si02). Thus, it has been found that
applying the composition having PVC in an amount lower than 35%
so as to give a film with an average dry film thickness of
15 approximately 15 pm is expected to cause the film to have
insufficient anticorrosiveness, and that applying the
composition having a significantly high mass ratio of zinc dust
to siloxane-basedbinder (Zn/SiOz) leadstodefectiveweldability
and the use of such a composition as a primary rust-preventive
20 coating material is difficult.
[0017]
Basedontheabove findings, thepresentinventorsconducted
further extensive studies regarding PVC and Mw of the
siloxane-based binder as well as the mass ratio of zinc dust to
siloxane-based binder. Then, it has been found that when these
are within specific ranges, the problems can be solved. The
present invention has been completed based on these findings.
[0018]
That is, a primary rust-preventive coating composition
according to an embodiment of the present invention is provided
which includes a siloxane-basedbinder (A) havingarieightaverage
molecularweight (Mw) asmeasuredbygelpermeationchromatography
(GPC) in terms of standard polystyrene being 1000 to 6000 and a
10 zinc dust (B) including a flaky zinc-based powder ( b - ) the
primary rust-preventive coating composition having a pigment
volume concentration (PVC) of 35 to 60%, and having a mass ratio
( (B) / (A) ) of the zinc dust (B) to the siloxane-based binder (A)
in terms of SiO2 being 1.0 to 5.0.
15 [0019]
It is preferable that based on 100% by mass of the total
content of the zinc dust (B) , the content of the flaky zinc-based
powder (b-1) is not less than 15% by mass. It is preferable that
the mass ratio b - A of the flaky zinc-based powder (b-1)
20 to the siloxane-based binder (A) in terms of Si02 is 1.0 to 5.0.
[0020]
As the zinc dust (B), it is also preferable that a spherical
zinc-based powder (b-2) is further contained together with the
flaky zinc-basedpowder (b-1). Basedon 100% bymass ofthe total
content ofthe zincdust ( B ) , it is alsopreferablethatthecontent
of the flaky zinc-based powder (b-1) is 15 to 90% by mass and the
content of the spherical zinc-based powder (b-2) is 10 to 85% by
mass.
5 [0021]
It is preferable that the composition further contains a
conductive pigment (C) such as zinc oxide.
[0022]
It is preferable that the flaky zinc-based powder (b-1)
10 contains at least one selectedfroma flaky zincpowder anda flaky
zinc alloy powder. It is preferable that the flaky zinc-based
powder (b-1) has a median diameter (D50) of not more than 30 pm
and an average thickness of not more than 1 pm. It is preferable
that the siloxane-based binder (A) is a condensate of at least
15 one compound selected from alkylsilicates and
methyltrialkoxysilanes.
[0023]
An embodiment of the present invention is a primary
rust-preventive coating film which is formed from the primary
20 rust-preventive coating composition and has an average dry film
thickness of not more than 10 pm.
LO0241
An embodiment of the present invention is a substrate with
a primary rust-preventive coating filmwhich includes a substrate
and a coating film, the coating film being provided on a surface
of the substrate and formed from the primary rust-preventive
coating composition.
[0025]
An embodiment of the present invention is a substrate rust
prevention method or a process for producing a substrate with a
primary rust-preventive coating film, which includes a step of
applying the primary rust-preventive coating composition on a
substrate surface and a step of curing the coating composition
10 applied to form a primary rust-preventive coating film.
Advantageous Effects of the Invention
[0026]
The present invention canprovide a primdry rust-preventive
16 coating composition which by being dried and cured at room
temperature is capable of forminga coating filmhavinganaverage
dry film thickness of not more than 10 pm even with the use of
conventional coating machines, and having excellent rust
prevention properties and overcoatability as well as excellent
20 weldability/cut-ability at the time of welding and cutting steel
plates; and can provide uses thereof.
Brief Description of Drawings
[0027]
[Fig. 11 Fig. 1 shows a sandblasted plate used in evaluations in
Examples.
[Fig. 21 Fig. 2 shows conditions of welding of the sandblasted
plate.
Embodiments of the Invention
[0028]
Hereinafter, aprimary rust-preventive coating composition
of the present invention (hereinafter, also referred to as the
10 "coating composition") , a primary rust-preventive coat iny film,
a substrate with the primary rust-preventive coating filmand its
production process, and a substrate rust prevention method,
includingpreferredembodimentsthereof, aredescribedingreater
detail.
15 [0029]
[Primary rust-preventive coating composition]
The primary rust-preventive coating composition of the
present invention contains a siloxane-basedbinder (A) and a zinc
dust (B) including a flaky zinc-bases powder - 1 . The
20 composition may further contain one type or two or more types
selected from other coating film-forming main elements such as
binders excluding the binder (A), other pigment components
excluding the zinc dust (B), additives, organic solvents and the
like.
[0030]
<>
A coating film-forming main element is a main element
necessary to form a coating film. For example, high-molecular
5 substances such as polymerized oil, natural resins, synthetic
resins, cellulose derivatives andthe like fall within the coating
film-forming main element. The siloxane-based binder (A) and
other binders, described below, fall within the coating
film-forming main element.
10 [0031]

The coating composition of the present invention contains
the siloxane-based binder (A) as an essential component.
[0032]
The siloxane-basedbinder (A) has aweightaveragemolecular
weight (Mw) of 1000 to 6000, preferably 1200 to 5000, more
preferably 1300 to 4000. The Mw is a value in terms of standard
polystyrene that is measured by gel permeation chromatography
(GPC), and its detail is as described in Examples.
20 [0033]
When Mw is in the above range, at the time of drying, the
coatingmaterialcanbecuredatroomtemperature (e.g., 5to 40°C)
in a short period of time, and the coating film has improved rust
prevention properties andadhesion strength and is prevented from
causingblowhole (internal bubble) at the time of weld-treatment.
On the other hand, if Mw is below the lower limit described above,
the curing reaction of the siloxane-based binder (A) is so slow
that a coating film in its drying needs to be cured by heating
5 at high temperature (e.g., 200 to 400°C) when needing to be cured
in a short periodof time. If Mwexceeds the upper limit, in which
case the siloxane-based binder (A) coats the surface of the zinc
dust ( B ) , the coating film has inferior rust prevention
properties.
10 [0034]
Examples of the siloxane-based binder (A) include
condensates of at least one compound selected fromalkylsilicates
and methyltrialkoxysilanes; specifically, partial hydrolyzate
condensates of the above-mentioned compounds.
15 [0035]
Examples of the alkylsilicates include compounds such as
tetramethylorthosilicate, tetraethylorthosilicate,
tetra-n-propylorthosilicate, tetra-i-propylorthosilicate,
tetra-n-butylorthosilicate, tetra-sec-butylorthosilicate; and
20 compounds such as methylpolysilicate and ethylpolysilicate.
[0036]
Examples of the methyltrialkoxysilane are compounds
including methyltrimethoxysilane and methyltriethoxysilane.
[0037]
Of these, condensates of alkylsilicates are preferable;
condensates of tetraethylorthosilicate are more preferable; and
particularly preferable is a partial hydrolyzate condensate of
Ethyl Silicate 40 (product name; COLCOAT CO., LTD. ) , which is an
5 initial condensate of tetraethylorthosilicate.
[0038]
The siloxane-basedbinder (A) can be producedby a hitherto
known method. For example, e.g., hydrochloric acid is added to
amixture solution of an organic solvent andat least one selected
10 from alkylsilicates and methyltrialkoxysilanes, followed by
stirring, to prepare a partialhydrolyzate condensate. Thereby,
the siloxane-based binder (A) can be prepared.
[0039]
The siloxane-based binders (A) may be used singly, or two
15 or more kinds thereof may be used in combination.
[0040]
In the coating composition of the present invention, the
content of the siloxane-based binder (A) is usually 8 to 40% by
mass, preferably 12 to 35% by mass, more preferably 15 to 25% by
20 mass of the amount of the whole composition. When the content
is in the above range, a coating film even when having an average
dry film thickness of not more than 10 pm allows a steel plate
surface to have an increased amount of binder per its unit area,
and the flaky zinc-based powder (b-1) has its planar surface
oriented substantially in parallel to the surface ofthe coating
film. For this reason, continuousness of the coating film is
maintained, sothatthebaresurfaceofasteelplateisnotexposed.
In this way, it is possible to prevent steel plates from rusting.
5 [0041]
When the coating composition of the present invention is
atwocomponent-typecompositiondescribedlater, it ispreferable
that the content of the siloxane-based binder (A) in a coating
material obtained by mixing a main agent component with a pigment
10 paste component is controlled to be in the above range.
[0042]

Thecoatingcompositionofthepresentinventionmaycontain
other binders in addition to the siloxane-based binder (A) in a
15 range that is not detrimental to the objects and effects of the
present invention. Examples of the other binders include
polyvinylbutyral resin. Examples of commercially-available
products of the polyvinylbutyral resin include S-LEC B BM-2
(product name; Sekisui Chemical Co., Ltd.).
20 [0043]
<<2. Pigment Component>>
The pigment component is, for example, the zinc dust (B)
such as the flaky zinc-based powder (b-1) and the spherical
zinc-based powder (b-2), the conductive pigment (C) excluding (B)
described above, rust-preventive pigments excluding (B) and (C)
describedabove, inorganicpowdersexcluding (B) and (C) described
above, molybdenum and molybdenum compounds. The coating
compositionofthepresent inventioncontain sthe flakyzinc-based
5 powder (b-1) as an essential component, and may further contain
such other pigment components as described above.
[0044]

The coating composition of the present invention contains
10 the zinc dust (B) .
[0045]
In the present invention, "zinc dust" refers to a powder
of a metal zinc or a powder of an alloy mainly composed of zinc
(e.g., an alloy formed by zinc and at least one selected from
15 aluminum, magnesium and tin) .
[0046]
In the coating composition of the present invention, it is
preferable that the mass ratio ( (B) / (A) ) of the zinc dust (B) to
the siloxane-based binder (A) in terms of Si02 is controlled to
20 be 1.0 to 5.0, more preferably 1.2 to 4.5, still more preferably
1.5 to 3.5. The mass ratio ( (B) / (A) ) being in the above range
is preferable in terms of anticorrosiveness and weldability. If
the mass ratio ( (B) / (A) ) exceeds the above range, the occurrence
of welding defects tends to be more frequent. If the mass ratio
( (B) / (A) ) is below the above range, the anticorrosiveness tends
to be insufficient.
[0047]
When the coating composition of the present invention is
5 atwocomponent-typecompositiondescribedlater,itispreferable
that the mass ratio ((B)/(A)) in a coating material obtained by
mixing a main agent component with a pigment paste component is
controlled to be in the above range.
[0048]
The coating composition ofthe present invention contains,
as the zinc dust (B), the flaky zinc-based powder (b-1). Based
on 100% by mass of the total content of zinc dust (B), the content
of the flaky zinc-based powder (b-1) is preferably not less than
15% by mass.
15 [0049]
In a preferred embodiment ofthe coating composition ofthe
present invention, based on 100% by mass of the total content of
the zinc dust (B), it is preferable that the content of the flaky
zinc-based powder (b-1) exceeds 85% by mass, more preferably the
20 content exceeds 90% by mass, still more preferably the content
exceeds 95% by mass. Using the (b-1) in the above range is
preferable in terms of being able to form a coating film superior
in rust prevention properties, overcoatability and
weldability/cut-ability.
[00501
A preferred embodiment of the coating composition of the
present invention contains, together with the flaky zinc-based
powder (b-l), the spherical zinc-basedpowder (b-2). For example,
5 based on 100% by mass of the total content of the zinc dust (B),
it is preferable that the content of the flaky zinc-based powder
(b-1) is 15 to 90% by mass and the content of the spherical
zinc-based powder (b-2) is 10 to 85% by mass; and it is more
preferable that the content of the flaky zinc-based powder (b-1)
10 is 15 to 70% by mass and the content of the spherical zinc-based
powder (b-2) is 30 to 85% by mass. Using (b-1) and (b-2) described
above in the above range is preferable in terms of reducing the
use amount of expensive flaky zinc-basedpowder, and as described
later, being able to form a coating film superior in rust
15 prevention properties, overcoatability and
weldability/cut-abilitywithout impairingthe actionofthe flaky
zinc-based powder.
[00511
In the latter preferred embodiment, it is preferable that
20 the coating composition ofthe present invention further contains
the conductive pigment (C). Using (C) described above together
with (b-1) and (b-2) described above can lead to the formation
of a coating film superior particularly in rust prevention
properties, overcoatability and weldability/cut-ability.
[0052]
If a coating film is heated at a high temperature exceeding
800°C at the time of e.g., welding and cutting, since the flaky
zinc-based powder has a large specific surface area, metal zinc
5 c a n b e o x i d i z e d a n d a n t i c o r r o s i v e n e s s a f t e r h e a t i n g c a n b e r e d u c e d .
On the other hand, when the spherical zinc-based powder is used
together with the flaky zinc-based powder, even if the coating
film is heated at such a high temperature as described above, by
metal zinc remaining within the spherical zinc-based powder,
10 anticorrosiveness after heating can be ensured.
[0053]
The flaky zinc-basedpowder, whichhas ametalglossycolor,
has its planar surface oriented toward a coating film surface at
the time of forming a coating film. Thus, even if the coating
16 composition contains another coloring pigment, its coating film
surface tends to have a hue of metal glossy color. Thus, using
the flaky zinc-basedpowdercanrestricthuedesigning. Theabove
tendency is alleviated and free hue designing can be attained by
using the spherical zinc-based powder together with the flaky
20 zinc-based powder in combination, since doing so relatively
reduces the content of the flaky zinc-based powder.
[0054]
Flaky Zinc-based Powder (b-1)
The coating composition of the present invention contains
the flaky zinc-based powder (b-1) as an essential component.
[0055]
The flaky zinc-based powder (b-1) functions as a
rust-preventive pigmentthatprevents a steel plate fromrusting.
5 Examples of the flaky zinc-based powder (b-1) include at least
one selectedfroma flakyzincpowderanda flaky zincalloypowder.
Examples of the zinc alloy include an alloy formed by zinc and
at least one selectedfromaluminum, magnesiumandtin, preferably
zinc-aluminum alloy and zinc-tin alloy.
10 [0056]
It is preferable that the flaky zinc-based powder (b-1) has
a median diameter (D50) of not more than 30 pm and an average
thickness of not more than 1 pm; and it is more preferable that
the flaky zinc-based powder (b-1) has a median diameter (D50) of
15 5 to 20 pm and an average thickness of 0.2 to 0.9 pm. The aspect
ratio, represented by the ratio of a median diameter (D50) to an
average thickness, (median diameter/average thickness), is
preferably 10 to 150, more preferably 20 to 100.
[0057]
20 The median diameter can be measured by using a laser
scattering diffraction-type particle size distribution
measurement apparatus, for example "SALD 2200" (product name;
manufacturedbyShimadzuCorporation). Theaveragethickness can
be determined as follows: by using a scanning electronic
microscope (SEM) , for example, "XL-30" (product name;
manufactured by Phillips) to observe the flaky zinc-based powder
( - 1 ) the thicknesses of several tens to several hundreds of the
powder particles are measured and an average value thereof is
5 determined.
[0058]
The flaky zinc-based powder (b-1) with such a shape has a
larger specific surface area as compared with the spherical
zinc-based powder (b-2), enabling close contact among particles
10 in the coating film, so that a coating film even if having a small
amount of the zinc dust (B) (e. g., not more than 36 g/m2) can be
formed which is excellent in rust prevention properties after
long-term exposure. The median diameter (D50) that is not more
than the above-mentioned upper limit can lead to the prevention
15 ofthe cloggingofthe coatingmaterialina coating machine. The
specific surface area can be measured by using a flowing-type
specific surface area automaticmeasuringinstrument, for example
"FlowSorbII 2300" (product name; manufactured by Shimadzu
Corporation) .
20 [0059]
Examples of commercially-available products of the flaky
zinc powder include STANDART Zinc flake GTT, STANDART Zinc flake
GandSTANDART ZincflakeAT (productnames;manufacturedbyECKART
GmbH). Examples of commercially-available products ofthe flaky
zinc alloy powder include STAPA 4 ZNAL7 (alloy of zinc and
aluminum; product name; manufactured by ECKART GmbH) and STAPA
4 ZNSN30 (alloy of zinc and tin; product name; manufactured by
ECKART GmbH) .
5 [0060]
The flaky zinc-based powders (b-1) may be used singly, or
two or more kinds thereof may be used in combination.
[0061]
In a preferred embodiment, it is preferable that in the
10 coating composition of the present invention, the mass ratio
((-1) (A)) of the flaky zinc-based powder (b-1) to the
siloxane-based binder (A) in terms of SiO2 is controlled to be
1.0 to 5.0, more preferably 1.2 to 4.5, still more preferably 1.5
to 3.5. The mass ratio b - A in the above range is
15 preferable in terms of allowing the distance among particles in
a coating film obtained by drying and curing to be close.
[0062]
When the coating composition of the present invention is
atwo component-type composition describedlater, in a preferred
20 embodiment, it is preferable that the mass ratio ( (b-1) /(A) ) in
a coating material obtained by mixing a main agent component with
a pigment paste component is controlled to be in the above range.
[0063]
Spherical Zinc-based Powder (b-2)
A preferred embodiment of t h e coating composition of the
present invention contains a s p h e r i c a l zinc-based powder (b-2) .
[0064]
The s p h e r i c a l zinc-based powder (b-2) functions as a
6 rust-preventive pigmentthatprevents a s t e e l p l a t e f r o m r u s t i n g .
Examplesofthe spherical zinc-basedpowder (b-2) include a t l e a s t
one s e l e c t e d from a s p h e r i c a l zinc powder and a s p h e r i c a l zinc
alloy powder. Examples of the zinc alloy include an a l l o y formed
by zinc and a t l e a s t one selected from aluminum, magnesium and
10 t i n , preferably zinc-aluminum a l l o y and zinc-tin a l l o y .
[0065]
Theterm"spherica1"usedinthe spherical zinc-basedpowder
(b-2) r e f e r s t o the s p h e r i c a l shape of the powder, with no
p a r t i c u l a r range defined. However, usually, the aspect r a t i o is
15 preferably 1 t o 3. The s p h e r i c a l zinc-based powder (b-2) is
inexpensive compared with t h e f l a k y zinc-based powder - 1 , and
using the s p h e r i c a l zinc-based powder (b-2) can lead t o the
reduction of cost for the coating composition. The aspect r a t i o
canbemeasuredbythe samemethodas i n t h e flakyzinc-basedpowder
20 (b-1) .
[0066]
It is preferable t h a t the spherical zinc-basedpowder (b-2)
has amediandiameter (D50) of 2 t o 1 5 pm; a n d i t i s more p r e f e r a b l e
t h a t t h e median diameter (D50) is 2 t o 7 pm. The median diameter
can be measured by using a laser scattering diffraction-type
particle size distribution measuring instrument, for example
"SALD2200" (product name; manufacturedby Shimadzucorporation).
[0067]
Examples of commercially-available products of the
spherical zinc powder include F-2000 (product name; manufactured
by The Honjo Chemical Corporation).
[0068]
The spherical zinc-based powders (b-2) may be used singly,
10 or two or more kinds thereof may be used in combination.
[0069]

Thecoatingcompositionofthepresentinventionmaycontain
a conductive pigment (C). Using (C) described above in
15 combinationispreferableintermsofachievingeffectiveelectric
anticorrosive effect of zinc and improving rust prevention
properties. Where the flaky zinc-based powder (b-1) is used
togetherwiththespherical zinc-basedpowder (b-2), inparticular
when the content of the flaky zinc-based powder (b-1) is 15 to
20 70% by mass and the content of the spherical zinc-based powder
(b-2) is 30 to 85% by mass based on 100% by mass of the zinc dust
(B), using (C) described above in combination is preferable in
particularintermsofenhancingtheelectricanticorrosiveeffect
of the spherical zinc-based powder.
[00701
The above is f u r t h e r described i n d e t a i l as follows. In
order to ensure r u s t prevention p r o p e r t i e s of primary
rust-preventive coating materials, e f f i c i e n t l y supplying
5 electronsgeneratedwhenzincparticles a r e i o n i z e d t o a s u b s t r a t e
such as a s t e e l p l a t e is important i n terms of accomplishing
s a c r i f i c i a l a n t i c o r r o s i v e e f f e c t . I n general, by allowing zinc
p a r t i c l e s i n a dry coating film t o contact with one another, t h e i r
electroconductive e f f e c t can be a t t a i n e d . When the p a r t i c l e s
10 contact withone another, the shape o f t h e flaky zinc-basedpowder
i s p a r t i c u l a r l y s u i t a b l e . However, it can happen t h a t contacting
ofparticleswithoneanotheris l o s t a n d t h e i r e f f e c t is not e a s i l y
exhibited when the proportion of the flaky zinc-based powder is
reduced and the proportion o f t h e s p h e r i c a l zinc-based powder is
15 increased. A t t h i s time, by allowing a conductive pigment t o be
contained i n the coating film i n order f o r the conducting pigment
t o serve as a connection among zinc p a r t i c l e s , t h e i r
electroconductive e f f e c t can be supplemented. By doing so,
e f f e c t i v e s a c r i f i c i a l a n t i c o r r o s i v e e f f e c t can be obtained, and
20 superior r u s t prevention properties can be exhibited.
[0071]
Examples of the conductive pigment (C) include zinc oxide,
metal powders other than zinc dust and carbon powders. Of these,
preferred is zinc oxide, which is inexpensive and has high
conductivity.
[0072]
Examples of commercially-available products of zinc oxide
include zinc oxide of JIS 1 grade (manufactured by Sakai Chemical
5 Industry Co., Ltd.) and zinc oxide of JIS 3 grade (manufactured
byHakusuiTechCo., Ltd.,manufacturedbySakaiChemicalIndustry
Co., Ltd.).
[0073]
Examples of the metal powders include Fe-Si powder, Fe-Mn
10 powder, Fe-Cr powder, magnetic iron porider and iron phosphide.
Examples of commercially-available products of the metal powder
include ferrosilicon (product name; manufacturedby KINSEI MATEC
CO., LTD.), ferromanganese (product name; manufactured by KINSEI
MATEC CO., LTD.), ferrochrome (product name; manufactured by
15 KINSEI MATECCO., LTD.), iron sand powder (manufacturedby KINSEI
MATEC CO., LTD. ) and Ferrophos 2132 (manufactured by Occidental
Chemical Corporation).
100741
An example of the carbon powders is carbon black used as
20 a coloring pigment. Examples ofcommercially-available products
of the carbon powder include Mitsubishi carbon black MA-100
(product name; manufacturedby Mitsubishi Chemical Corporation).
[0075]
The conductive pigments (C) may be used singly, or two or
more kinds thereof may be used in combination.
[0076]
When the conductive pigment (C) is used, the content of the
conductive pigment (C), based on 100 parts by mass of the zinc
5 dust (B), is preferably 5 to 100 parts by mass, more preferably
10 to 50 parts by mass, still more preferably 15 to 35 parts by
mass. The content of (C) described above in the above range is
preferable in terms of enhancing electric anticorrosive effect
and improving rust prevention properties of the coating film.
10 100771
In particular, when based on 100% by mass of the zinc dust
(B), the flaky zinc-based powder (b-1) is used in an amount of
15 to 70% by mass and the spherical zinc-based powder (b-2) is
used in an amount of 30 to 85% by mass, it is preferable that the
15 content of the conductive pigment (C) in the coating composition
is 15 to 35 parts by mass based on 100 parts by mass of the zinc
dust (B) .
[0078]
It is preferable that the content ofthe conductive pigment
20 (C) is more than 0% by mass and not more than 35% by mass and more
preferablyloto 20%bymasswithrespecttononvolatilecomponents
in the coating composition. The content of (C) described above
in the above range is preferable in terms of maintaining
anticorrosivenesswhilereducingthecontentofthe zincdust (B).
[0079]

Thecoatingcompositionofthepresentinventionmaycontain
rust-preventive pigments other than the zinc dust (B) and the
5 conductive pigment (C), in order to supplementarily ensure rust
prevention properties of the coating film. Examples of such
rust-preventivepigmentsinclude zincphosphate-basedcompounds,
calcium phosphate-based compounds, aluminum phosphate-based
compounds, magnesium phosphate-based compounds, zinc
10 phosphite-based compounds, calcium phosphite-based compounds,
aluminum phosphite-based compounds, strontium phosphite-based
compounds, aluminum tripolyphosphate-based compounds, zinc
cyanamide-based compounds, boric acid salt compounds, nitro
compounds and composite oxides.
15 [0080]
Examples of commercially-available products of the
rust-preventivepigmentsinclude zincphosphate-based (aluminum)
compound: LF BOWSEI CP-Z (product name; manufactured by KIKUCHI
COLOR & CHEMICALS CORPORATION), zinc phosphite-based (calcium)
20 compound: Protex YM-70 (product name; manufactured by Taihei
Chemical Industrialco., Ltd.), zinc phosphite-based (strontium)
compound: Protex YM-92NS (product name; manufactured by Taihei
Chemical Industrial Co., Ltd.), aluminumtripolyphosphate-based
compound: K White #84 (product name; manufactured by TAYCA
Corporation) and zinc cyanamide-based compound: LF BOWSEI ZK-32
(manufactured by KIKUCHI COLOR & CHEMICALS CORPORATION) .
[00811
The rust-preventive pigments may be used singly, or two or
5 more kinds thereof may be used in combination.
[0082]

The coatingcompositionofthepresentinventionmaycontain
at least one inorganicpowder selected from zinc compoundpowders
10 (excluding zinc oxide, zinc phosphate-based compounds, zinc
phosphite-based compounds and zinc cyanamide-based compounds),
mineral powders, alkali glass powders, and pyrolysis
gas-generating inorganic compound powders.
[0083]
The zinc compound powders are considered to serve as
controlling the activity of oxidation reaction such as the degree
of ionization of the zinc dust (B) (production of zn2+). The
inclusion ofthe zinc compound powders in the coating composition
of the present invention can provide the composition with
20 appropriate rust prevention properties. Examples of the zinc
compound powders include powder of any of zinc chloride, zinc
sulfide, zinc sulfate and the like. Examples of
commercially-available products of the zinc compound powders
include "Sachtolich HD (zinc sulfide; product name; manufactured
by Sachleben Chemie GmbH)" and "Zinc Chloride" (manufactured by
Nagai Chemical Industrial Co., Ltd.)".
[0084]
Examples of the mineral powders include titanium mineral
5 powder, silica powder, soda feldspar, potassium feldspar,
zirconium silicate, wollastonite and diatomaceous earth.
Examples of commercially-available products of the mineral
powders include Rutile Flour S (manufactured by KINSEI MATEC CO.,
LTD. ) , Ilmenite Powder (manufactured by KINSEI MATEC CO., LTD. ) ,
10 A-PAX (manufactured by KINSEI MATEC CO., LTD.), Ceramic Powder
OF-T (manufactured by KINSEI MATEC CO., LTD.) , Aplite
(manufactured by KINSEI MATEC CO., LTD.), Silica MC-0
(manufacturedbyMaruoCalciumCo., Ltd.), BariteBA (manufactured
by Sakai Chemical Industry Co., Ltd.), Radiolite (manufactured
15 by ShowaChemical IndustryCo., Ltd.) andcelite 545 (manufactured
by Johns Manville) .
[0085]
The alkali glass powders function such that alkali metal
ions contained in the glass powders activate zinc and stabilize
20 arc at the time of welding steel plates. Exemplary alkali glass
powders are those preparedby crushing generallyusedplate glass
or bottle glass to a size of about 5 pm to prepare glass powder
and then acid-washing said glass powder so as to have pH of not
more than 8. Examples of commercially-available products ofthe
alkaliglasspowdersinclude "APS-325" (manufacturedbyPureMick,
co., Ltd.) .
[0086]
Thepyrolysisgas-generatinginorganiccompoundpowders are
5 inorganic compound powders that undergo thermal decomposition
(e.g., thermal decomposition at 500 to 1500°C) to generate a gas
(e . g . , COz, F2) . The inorganic compound powders are incorporated
into a coating composition from which a coating film is formed,
and when a steel plate having said coating film is welded in a
10 melting pool, a bubble, generated from organic substances
contained in binders and the like, is removed from the melting
pool together with a gas derived from said inorganic compound
powders. Examples of the inorganic compound powders include
calcium fluoride, calcium carbonate, magnesium carbonate and
15 strontium carbonate. Examples of commercially-available
products of the inorganic compound powders include Fluorite
400-mesh (manufactured by KINSEI MATEC CO., LTD.), NS#400
(manufactured by NITTO FUNKA KOGYO K.K.), Magnesium Carbonate
(manufactured by Tomita Pharmaceutical Co., Ltd.) and Strontium
20 Carbonate A (manufactured by The Honjo Chemical Corporation).
[0087]

Thecoatingcompositionofthepresentinventioncancontain
either or both of molybdenum (metal molybdenum) and a molybdenum
compound. These function as an antioxidant of zinc (as so-called
a white-rust i n h i b i t o r ) .
100881
Where a s u b s t r a t e coated with the coating composition of
5 the present invention is exposedoutdoors, it canhappen t h a t zinc
or a zinc alloy present i n t h e coating f i l m r e a c t s with water,
oxygen or carbon dioxide gas whereby powdery white r u s t (mixture
of zinc oxide, zinc hydroxide, zinc carbonate or t h e l i k e ) is
formed on the surface of t h e coating film. When t h e surface of
10 the coating film having white r u s t is coated with an overcoating
film formed from an overcoating material, adhesion between these
c o a t i n g f i l m s canbe lowered. Tocopewithsuchaproblem, removal
work t o remove white r u s t formed on the rust-preventive coating
film by appropriate means is needed p r i o r t o the a p p l i c a t i o n of
15 the overcoating m a t e r i a l , b u t such removal work can be never
permitteddepending upon the demand fromcustomers and a s p e c i f i c
purpose.
[0089]
For l e s s frequent occurrence ofwhite r u s t , it is preferable
20 t h a t the coating composition of the present invention contains,
as an antioxidant of zinc (so-calledwhiterustinhibitor), e i t h e r
or both of molybdenum (metal molybdenum) and a molybdenum
compound.
[0090]
Examples of the molybdenum compound include molybdenum
oxides such as molybdenum trioxide, molybdenum sulfide,
molybdenum halides, molybdic acid, ammonium molybdate,
phosphomolybdic acid, silicomolybdic acid, alkali metal salts of
5 molybdic acid, alkalimetal salts ofphosphomolybdicacid, alkali
metal salts of silicomolybdic acid, alkali earth metal salts of
molybdic acid, alkali earth metal salts of phosphomolybdic acid,
alkali earth metal salts of silicomolybdic acid, manganese salt
of molybdic acid, manganese salt of phosphomolybdic acid,
10 manganese salt of silicomolybdicacid, basic nitrogen-containing
compound salts of molybdic acid, basic nitrogen-containing
compound salts of phosphomolybdic acid, and basic
nitrogen-containing compound salts of silicomolybdic acid.
[0091]
The molybdenum compounds may be used singly, or two or more
kinds thereof may be used in combination.
[00921
When either or both ofmolybdenumandamolybdenumcompound
areused, thetotalcontentofmolybdenumandamolybdenumcompound
20 is preferably 0.05 to 5.0 parts by mass, more preferably 0.3 to
3.0 parts bymass, stillmore preferably 0.5to 2.0 parts bymass,
based on 100 parts by mass of the zinc dust (B) . When the content
is the above range, sufficient zinc-antioxidization effect is
achieved, the rust-preventive ability of the zinc dust (B) is
prevented from decreasing, and the rust prevention properties of
the coating film can be maintained.
[0093]
<3. Additive>
The coatingcompositionofthepresentinventionmaycontain
additives. The additives are materials used in order to improve
ormaintainthe performance of coatingmaterials andcoating films.
Examples of the additives include anti-settling agents, drying
agents, fluidity control agents, antifoaming agents, dispersing
10 agents, color-separationpreventiveagents, anti-skinningagents,
plasticizers and ultraviolet absorbers.
[0094]
The additives may be used singly, or two or more kinds
thereof may be used in combination.
15 [0095]

Examples of the anti-settling agent include organic
bentonite type, oxidizedpolyethylene type, humed silica type and
amide type. Examples of commercially-available products of the
20 anti-settling agents include TIXOGEL MPZ (product name;
manufactured by Rockwood Clay Additives GmbH), Disparlon 4200-20
(product name; manufactured by Kusumoto Chemicals, Ltd.),
Disparlon A630-20X (product name; manufactured by Kusumoto
Chemicals, Ltd.) and AEROSIL 200 (product name; manufactured by
Nippon Aerosil Co., Ltd.).
[0096]
The anti-settling agents may be used singly, or trio or more
kinds thereof may be used in combination.
5 [0097]
When the coating composition of the present invention is
a two component-type composition described later, the content of
the anti-settling agent is usually 0.5to 5.0% by mass, preferably
1.5 to 4.0% by mass in a pigment paste component. The content
10 of the anti-settling agent in the above range is preferable in
terms of causingless precipitation of the pigment component and
also in terms of workability at the time of mixing the pigment
paste component with a main agent component.
[0098]
15 <4. Organic Solvent>
The coating compositionofthe present inventionpreferably
contains an organic solvent in terms of improving the
dispersibilityofthe zincdust (B) includingthe flaky zinc-based
powder (b-1) and obtaining a coating film with excellent
20 conformabilityandsuperioradhesionwithrespectto steel plates
at the time of coating procedure.
[0099]
Examples of the organic solvent include organic solvents
commonly used in the field of coating materials, such as alcohol
solvents, ester solvents, ketone solvents, aromatic solvents and
glycol solvents.
[ OlOO]
Examples ofthe alcoholsolventsincludemethanol, ethanol,
5 propanol and butanol. Examples of the ester solvents include
ethyl acetate andbutylacetate. Examples ofthe ketone solvents
include methyl isobutyl ketone and cyclohexanone. Examples of
the aromatic solvents include benzene, xylene and toluene.
Examples of the glycol solvents include propylene glycol
10 monomethyl ether and propylene glycol monomethyl ether acetate.
[OlOl]
Theorganic solventsmaybeusedsingly, ortwoormore kinds
thereof may be used in combination.
[0102]
In the coating composition of the present invention, the
content of the organic solvent is usually 30 to 90% by mass,
preferably 40 to 85% by mass, more preferably 45 to 80% by mass.
The coating composition of the present invention is preferably
such an organic solvent-type composition as described above.
20 [0103]
When the coating composition of the present invention is
atwocomponent-typecompositiondescribedlater,itispreferable
that the content of the organic solvent in a coating material
obtained by mixing a main agent component with a pigment paste
component is controlled to be in the above range.
[0104]

The coating composition of the present invention satisfies
5 the requirement that the pigment volume concentration (PVC) is
35 to 60%. PVC is preferably 37 to 55%, more preferably 40 to
52%. In the present invention, the pigment volume concentration
(PVC) refers to a ratio (in terms of volume) of the pigment
component and solid particles in additives relative to the
10 nonvolatile components in the coating composition of the present
invention, the ratio representing a concentration indicated in
terms of percentage.
[0105]
PVC = (Whole Volume of Pigment Component + Whole Volume of
15 Solid Particles in Additives) / (Whole Volume of Nonvolatile
Components of Coating Composition) xlOO [%]
[0106]
The term "nonvolatile componentsN refers to heating
residues in the coating composition ofthe present invention that
20 remainatthetimeofheatingundertheconditionsdescribedbelow,
and is usually composed of the coating film-forming main element
including the siloxane-based binder (A), the pigment component
and solid particles in additives. The heating residues of the
coating composition can be measured in accordance with JIS K5601
1-2 (heating temperature: 125'C, heating time: 60 minutes).
[0107]
Examples of the 'pigment componentN are the zinc dust (B)
such as the flaky zinc-based powder (b-1) and the spherical
5 zinc-based powder (b-2), the conductive pigment (C) excluding (B)
described above, rust-preventive pigments excluding (B) and (C)
describedabove, inorganicpowders excluding (B) and (C) described
above, molybdenum and molybdenum compounds. Examples of the
"additives" are anti-settling agents, drying agents, fluidity
10 control agents, defoaming agents, dispersing agents,
color-separation preventive agents, anti-skinning agents,
plasticizers and ultraviolet absorbers.
[01081
For the calculation of PVC, from the mass of each component
15 and its density, the volume of each component is calculated. For
the siloxane-basedbinder (A), fromthemass ofthe siloxane-based
binder (A) in terms of Si02 and its density, its volume is
calculated.
[0109]
20 The coating composition of the present invention, as
described above, may contain, as the pigment component, at least
one selected from rust-preventive pigments, inorganic powders,
molybdenum and molybdenum compounds. The contents of these
components are not particularly limited as long as PVC is in the
above range.
[ O l l O ]
Bydefiningthe PVCofthe coating compositionofthepresent
invention as being i n the above range, coating films with an
5 average dry f i l m thickness of not more than 10 pm can be formed
byusingconventionalcoatingmachines under conventionalcoating
conditions. By defining the PVC as being i n the above range, the
distance among p a r t i c l e s of the pigment component in the coating
films is appropriately maintained, so t h a t the flaky zinc-based
10 powder (b-1) has its planar surface o r i e n t e d s u b s t a n t i a l l y in
p a r a l l e l t o the surface of the coating film with the thickness
d i r e c t i o n o f t h e flaky zinc-basedpowder (b-1) being the v e r t i c a l
d i r e c t i o n o f t h e s u b s t r a t e surface. The flaky zinc-based powder
(b-1) usually has an extremely small thickness of not more than
15 1 pm i n average, so t h a t a t h i n coating film can be provided.
[ O l l l ]
By the above configuration, the following can be achieved:
(1) the coating material amount per coated area is reduced, and
VOC emission amount per coated area is usually not more than 95
20 g/m2: t h i s hardly has adverse influence on environment, and
moreover the zinc dust (B) content per coated area is u s u a l l y n o t
more than 36 g/m2, which provides advantages i n terms of
conservation of resources; ( 2 ) the coating film a f t e r i t s
long-termexposure r e t a i n s excellent rustpreventionproperties,
which are comparable to those of inorganic zinc primary
rust-preventive coating materials that are currently prevalent;
(3) the coating film has superior adhesion in overcoating,
enabling various overcoating materials to be applied on the
5 primary rust-preventive coating film of the present invention;
and (4) the coating film is thin enough to increase the treatment
speed in welding/cutting steel plates.
[01121
If PVC exceeds 60%, the distance among particles of the
10 pigment component in the coating film cannot be appropriately
maintained, so that the flaky zinc-based powder (b-1) fails to
have its planar surface oriented substantially in parallel tothe
surface of the coating film. This makes the pigment components
overlap one another, or causes the flaky zinc-based powder (b-1)
15 to have its planar surface oriented in the vertical direction of
the coating film surface. This makes it difficult to form a
coating filmhaving anaverage dry filmthickness of not more than
10 pm in production using conventional coating machines under
conventional coating conditions, resulting in the failure to
20 provide thin films. If PVC is below 35%, the rust prevention
properties of the coating film are poor.
[0113]

The primary rust-preventive coating composition of the
present invention is usually used as a two component-type
composition. That is, the coating composition is usually
composed of a main agent component (vehicle) and a pigment paste
component. It is preferable that before use, the main agent
5 component and the pigment paste component are separately stored,
and immediately before use, these are sufficiently stirred and
mixed with each other to prepare the primary rust-preventive
coating material.
[0114]
The main agent component usually contains the
siloxane-based binder (A) and an organic solvent. The main agent
component maybe preparedbymixingthe siloxane-based binder (A)
withan organic solvent. Alternatively, themain agent component
may be prepared by adding e.g., hydrochloric acid to a mixture
15 solution of an organic solvent and at least one selected from
alkylsilicates andmethyltrialkoxysilanes, followedbystirring,
to prepare a partial hydrolyzate condensate. The main agent
component may contain such coating film-forming main elements as
other binders excluding the siloxane-based binder (A).
20 [0115]
The pigment paste componentusuallycontains the zincdust
(B) including the flaky zinc-based powder (b-1) and an organic
solvent. The pigment paste component is prepared, for example,
by mixing the zinc dust (B) including the flaky zinc-based powder
(b-1) withanorganicsolvent, andwithanothercomponent asneeded
in accordance with a common method. Said another component is,
for example, at least one selected from pigment components such
as the conductive pigment (C), rust-preventive pigments,
5 inorganic powders, molybdenum and molybdenum compounds and
additives such as anti-settling agents.
[0116]
The blending ratio between the main agent component and the
pigment paste component canbe appropriatelydetermined such that
10 after mixing, the content of the siloxane-based binder (A), the
zinc dust (B) including the flaky zinc-based powder (b-1) and an
organic solvent as well as PVC are within the above-described
ranges.
[0117]
15 [Primary Rust-Preventive Coating Film and Substrate with Primary
Rust-preventive Coating Film]
A primary rust-preventive coating film of the present
invention is formed from the above-described primary
rust-preventive coating composition; and a substrate with a
20 rust-preventive coating film of the present invention includes
a substrate, e.g., a steel plate, and the primary rust-preventive
coating film composed of the above-described primary
rust-preventive coating composition that is formedon the surface
of the substrate.
[0118]
The primary rust-preventive coating film usually has an
average dry film thickness of not more than 10 pm, preferably 5
to 9 pm, and has an average dry film thickness which may be more
5 than 10 pm depending on applications. Hereinafter, a primary
rust-preventive coating filmhaving an average dry filmthickness
of not more than 10 pm is also referred to as the "thin film-type
primary rust-preventive coating film". The average dry film
thickness is measured by using an electromagnetic film thickness
10 measuring instrument.
[0119]
In the primary rust-preventive coating film, the zinc dust
(B) content per coated area can be set usually at not more than
36 g/m2, preferably 10 to 30 g/mZ. The zinc dust (B) content per
15 coated area can be calculated from the content of the zinc dust
(B) per unit volume of the coating film which is calculated from
the content of zincdust (B) incorporatedinthe coatingmaterial,
and by using an average dry film thickness determined by such a
measurement as described above.
20 [01201
[Substrate Rust Prevention Method and Method for Producing
Substrate with Primary Rust-Preventive Coating Film]
A substrate rust prevention method and a method for
producingasubstratewithaprimaryrust-preventivecoatingfilm,
according t o the present invention, include a step of applying
the above-described primary rust-preventive coating composition
on a surface of a s u b s t r a t e such as a s t e e l p l a t e (coating s t e p )
and a step of curing the coating composition applied t o form a
5 primary rust-preventive coating f i l m (curing s t e p ) .
[0121]
In the coating s t e p , t h e coating composition o f t h e present
invention ( i n the case of a two component-type composition, a
coatingmaterialobtainedbymixingthe main agent component with
10 thepigmentpaste component) is applied, by a h i t h e r t o knownmethod
such as an a i r spray and an a i r l e s s spray, on a surface of a
s u b s t r a t e such as s t e e l p l a t e s , t o form an uncured coating film.
Acoatingmachine g e n e r a l l y u s e d i n t h e a p p l i c a t i o n o f t h e coating
material in e . g . , ship yards and iron works is primarily a l i n e
16 coatingmachine. In the l i n e coatingmachine, the f i l m t h i c k n e s s
is controlledby coating conditions i n c l u d i n g l i n e speed, coating
p r e s s u r e o f a n a i r s p r a y a n d a i r l e s s sprayandso onprovidedwithin
the coating machine, and the s i z e of spray chips (aperture
diameter).
20 [0122]
In the curing step, the curing temperature (drying
temperature) is usually 5 t o 40°C, preferably 10 t o 30°C; and
d r y i n g t i m e i s u s u a l l y 3 t o 1 5 m i n u t e s , preferably 5 t o l O m i n u t e s .
The present invention, u s i n g t h e siloxane-basedbinder (A) having
Mw in the above range, enables the coating material to be cured
at about room temperature as described above in a shorter period
of time. Thus, the coating composition of the present invention
is suited for steel-plate pretreatment carried out in processing
5 steel plates of ships, marine structures, plants, bridges,
overland tanks and the like.
[01231
Meanwhile, the attempt to form a thin film-type primary
rust-preventive coating film from a conventional primary
10 rust-preventive coating composition would require the discharge
flow rate of a currently-available coating machine to be below
adischarge flowratelimitallowingforstablecoatingprocedure,
and therefore uniformcoating couldnot be conducted. Thus, this
leads tothe need for a coatingmaterial tobe dilutedwitha large
15 amount of an organic solvent thereby lowering the solid-content
concentration of a coating material, consequentlyincreasing VOC
emission amount. Thus, as long as conventional primary
rust-preventive coating compositions areused: (i) forming athin
film-type primary rust-preventive coating film without reducing
20 VOC emission amount is difficult; (ii) a coating film even if
obtained without considering VOC emission amount has reduced
amount of binder per unit area of a steel plate surface, with the
continuousness of the coating film lost and bare surface of some
parts of the steel plate exposed, which causes a steel plate to
rust in a short time period; and (iii) a coating film even if
obtained without considering VOC emission amount has reduced
amount of zinc content, thus having significantly lowered rust
prevention properties after long-term exposure. From the
5 foregoing reasons, the application of conventional primary
rust-preventive coating compositions is conducted under coating
conditions that allow the average dry film thickness to be, for
example, 15 to 30 pm.
[0124]
By contrast, as described above, the primary
rust-preventive coating composition ofthe present invention has
PVCdefinedinthe specific range, inwhich casethedistance among
particles of the pigment component in the coating film is
appropriately maintained. At this time, the flaky zinc-based
15 powder (b-1) has its planar surface oriented substantially in
parallel tothecoating filmsurface, withthe thickness direction
ofthe flaky zinc-basedpowder (b-1) being the vertical direction
of the substrate surface. The average thickness of the flaky
zinc-based powder (b-1) is so thin, usually not more than 1 pm,
20 that a thin coating film can be obtained. Thus, without reducing
the discharge flow amount of the coating material from a coating
machine, a thin film-type primary rust-preventive coating film
can be stably formed without the problems (i)-(iii) described
above.
[0125]
In the present invention, when the substrate with the thin
film-type primary rust-preventive coating film has been
weld-treated, the probability is considerably low that weld bead
5 has defects such as pits (through hole), bloriholes (internal
bubble), gas groove and wormholes. That is, the substrate with
the thin film-type primary rust-preventive coating film of the
present invention has attained improved rust prevention
properties and weldability at the same time. Meanwhile, the
10 primary rust-preventive coating film of the present invention,
even if having an average dry film thickness of 10 pm or more as
in conventional primary rust-preventive coating films, can
exhibit excellent rust prevention properties.
15 Examples
[01261
Hereinafter, the present invention will be described more
specificallywithreferencetoExamples, butthepresent invention
is in no way limited by these Examples. In the following section
20 including Examples, "part (s) " means "part (s) by mass" unless
otherwise noted.
[0127]
[Preparation Example 11 Preparation of Alkylsilicate Condensate
31.5 g of Ethyl Silicate 40 (manufactured by COLCOAT CO.,
LTD.) , 10.4 g of industrial ethanol, 5 g of deionized water, and
0.1gof 35mass% hydrochloricacidwereintroducedto acontainer,
and stirred at 50°C for a period of time indicated in Table 1,
and thereto 53 g of isopropyl alcohol was added. A solution
5 containing any of alkylsilicate condensates 1 to 6 was thus
prepared.
[0128]
By gel permeation chromatography (GPC) , the weight average
molecular weights (Mw) of the condensates 1 to 6 were measured.
10 GPC measurement conditions are as follows. A small amount of the
condensate samplewas collectedanddilutedwithtetrahydrofuran.
Further, the solution was filtered by using a membrane filter,
to obtain a sample for GPC measurement.
Apparatus: 2695 separation module, manufactured by Nihon Waters
15 K.K. (Alliance GPC Multisystem)
Column: TSKgel Super H4000 and TSKgel Super H2000, each of which
is manufactured by Tosoh Corporation
Eluent: tetrahydrofuran (THF)
Flow rate: 0.6 ml/min
20 Detector: Shodex RI-104
Column thermostatic chamber temperature: 40°C
Standard substance: polystyrene
[0129]
[Table 11
1 how and 4 hours and 7 hours and
Stirring Time / 1 I l5 lninuteS 1 30minutes I 40niinutes I 30minutes 1
Table 1
[0130]
[Preparation Example 2-11 Preparation of Pigment Paste Component
5 -1
Condensate
1
Weight Average
Molecular Weight
(MI) of
Alkylsilicate
Condensate
0.9 p a r t of TIXOGEL MPZ (product name; manufactured by
Rockwood Clay Additives GmbH) as an a n t i - s e t t l i n g agent; and 4 . 6
p a r t s of xylene, 2.3 p a r t s of butyl a c e t a t e and 2.3 p a r t s of
isobutyl alcohol as organic solvents were introduced i n t o a
10 polyethylene container, t o which glass beads were added, andwere
shaken with a paint shaker f o r 3 hours. Subsequently, 18.2 p a r t s
of STANDART Zinc flake GTT (product name; manufactured by ECKART
GmbH) as a flaky zinc powder was added, andthemixture was f u r t h e r
shaken for 5 minutes t o disperse the pigment component.
15 Thereafter, byusingan 80-meshnet, t h e g l a s s b e a d s were removed.
A pigment paste component 1 was thus prepared.
[0131]
[Preparation Example 2-21 Preparation o f Pigment Paste Component
-2
20 2.0 p a r t s of TIXOGEL MPZ (product name; manufactured by
Condensate
4
Condensate
2
1500
Condensate
5
Condensate
3
Condensate
6
6200 800 1100 2500 5800
Rockwood Clay Additives GmbH) as an a n t i - s e t t l i n g agent; and 58.0
p a r t s of xylene, 10.0 p a r t s of butyl a c e t a t e and 10.0 p a r t s of
isobutyl alcohol as organic solvents were introduced i n t o a
polyethylene container, t o which glass beads were added, and were
5 s h a k e n w i t h a p a i n t s h a k e r f o r 3 hours. Subsequently, 110.0parts
of F-2000 (product name; manufactured by The Honjo Chemical
Corporation) as a s p h e r i c a l zinc powder was added. The mixture
was f u r t h e r s h a k e n f o r 5 m i n u t e s t o d i s p e r s e t h e p i g m e n t c o m p o n e n t .
Thereafter, byusingan 80-mesh net, t h e g l a s s beads were removed.
10 A pigment paste component 2 was thus prepared.
[OX321
[Preparation Example 2-31 Preparation of Pigment Paste Component
-3
Preparation Example 2-2 was repeated except t h a t i n
15 PreparationExample2-2, 1 7 0 . 0 p a r t s o f x y l e n e , 1 0 . O p a r t s o f b u t y l
a c e t a t e and 10.0 p a r t s of isobutyl alcohol were used as organic
solvents. A pigment paste component 3 was thus prepared.
[0133]
[Preparation Example 2-41 Preparation o f Pigment Paste Component
20 -4
Preparation Example 2-1 was repeated except t h a t i n
Preparation Example 2-1, STANDART Zinc flake G (product name;
manufactured by ECKART GmbH) was used as a flaky zinc powder. A
pigment paste component 4 was thus prepared.
[01341
[Preparation Example 2-51 Preparation of Pigment Paste Component
-5
Preparation Example 2-1 was repeated except that in
5 Preparation Example 2-1, STANDART Zinc flake AT (product name;
manufactured by ECKART GmbH) was used as a flaky zinc powder. A
pigment paste component 5 was thus prepared.
[01351
[Preparation Example 2-61 Preparation of Pigment Paste Component
10 -6
1.3 parts of TIXOGEL MPZ (product name; manufactured by
Rockwood Clay Additives GmbH) as an anti-settling agent; and 6.3
parts of xylene, 3.1 parts of butyl acetate and 4.1 parts of
isobutyl alcohol as organic solvents were introduced into a
15 polyethylene container, to which glass beads were added, and were
shaken with a paint shaker for 3 hours. Subsequently, 20.0 parts
of STANDART Zinc flake GTT (product name; manufactured by ECKART
GmbH) as a flaky zinc powder was added. The mixture was further
shaken for 5 minutes to disperse the pigment component.
20 Thereafter, byusingan 80-mesh net, the glass beadswere removed.
A pigment paste component 6 was thus prepared.
[Preparation Example 2-71 Preparation of Pigment Paste Component
Preparation Example 2-6 was repeated except t h a t i n
Preparation Example 2-6, STANDART Zinc flake GTT (product name;
manufactured by ECKART GmbH) as a flaky zinc powder was replaced
with F-2000 (product name; manufactured by The Honjo Chemical
5 Corporation) as a s p h e r i c a l zinc powder. A pigment paste
component 7 was thus prepared.
[0137]
[Preparation Examples 2-8 and 2-91 Preparation of Pigment Paste
Components 8 and 9
The Preparation Examples 2-6 and 2-7 were repeated except
t h a t i n Preparation Examples 2-6 and 2-7, 4.0 p a r t s of zinc oxide
of JIS 3 grade (zincoxide;manufacturedbyHakusuiTechCo., Ltd.)
was used togetherwith the zinc powder. Pigment paste components
8 and 9 were thus prepared.
15 [0138]
[PreparationExample 2-10] Preparationof Pigment Pastecomponent
-10
1.5 p a r t s of TIXOGEL MPZ (product name; manufactured by
Rockwood Clay Additives GmbH) as an a n t i - s e t t l i n g agent; and 7.5
20 p a r t s of xylene, 3.8 p a r t s of butyl acetate and 5.0 p a r t s of
isobutyl alcohol as organic s o l v e n t s were introduced i n t o a
polyethylene container, t o which glass beads were added, andwere
shaken with a paint shaker f o r 3 hours. Subsequently, 4.8 p a r t s
of STANDART Zinc flake GTT (product name; manufactured by ECKART
GmbH) as a flaky zinc powder, 19.2 parts of F-2000 (product name;
manufactured by The Honjo Chemical Corporation) as a spherical
zincporider, and4.8 parts of zincoxideof JIS 3 grade (zincoxide;
manufactured by Hakusui Tech Co., Ltd.) as a conductive pigment
5 were added. The mixture was further shaken for 5 minutes to
disperse the pigment component. Thereafter, by using an 80-mesh
net, the glass beads were removed. A pigment paste component 10
was thus prepared.
[0139]
10 [Preparation Example 2-11] Preparationof Pigment Pastecomponent
-11
Preparation Example 2-10 was repeated except that in
Preparation Example 2-10, the blending amount of the conductive
pigment was changed to 8 parts. A pigment paste component 11 was
15 thus prepared.
[0140]
[Examples 1A to 11A and Comparative Examples 1A to 16A]
Any of the solutions of the alkylsilicate condensates 1 to
6 as amainagentcomponentwas mixedwithany ofthe pigment paste
20 components 1 to 5 as a pigment paste component. The proportions
of ingredients in any of the pigment paste components 1 to 5 and
the proportion of any of the solutions of the condensates 1 to
6 are indicated in any of Table 1A to Table 3A (in terms of mass).
A primary rust-preventive coating material was thus prepared.
[01411
[Examples 1B to 2B and Comparative Examples 1B to 2B]
The solution of the alkylsilicate condensate 1 as a main
agent component wasmixedwithany ofthepigment paste components
5 6 to 9 as a pigment paste component. The proportions of
ingredients in any of the pigment paste components 6 to 9 and the
proportion of the solution of the condensate 1 are indicated in
Table 1B (in terms of mass). A primary rust-preventive coating
material was thus prepared.
10 [0142]
[Examples 1C to 6C and Comparative Examples 1C to 4C]
The solution of the alkylsilicate condensate 1 as a main
agent component was mixed with the pigment paste component 10 or
11 as a pigment paste component. The proportions of ingredients
15 of the pigment paste component 10 or 11 and the proportion of the
solution of the condensate 1 are indicated in Table 1C (in terms
of mass). A primary rust-preventive coating material was thus
prepared.
[0143]
20 [Examples 7C to 14Cl
The solution of the alkylsilicate condensate 1 as a main
agent component was mixed with a pigment paste containing a flaky
zinc powder, a spherical zinc powder, a conductive pigment, an
anti-settling agent andorganic solvents. The proportions ofthe
ingredients are indicated in Table 2C (in terms of mass). A
primary rust-preventive coating material was thus prepared. The
preparation of the pigment paste component was conducted in the
same manner as in Preparation Example 2-10.
5 [01441
[Examples 15C to 19C and Comparative Examples 5C to llC]
The solution of the alkylsilicate condensate 1 as a main
agent component was mixed with a pigment paste component
containing a flaky zinc powder, a spherical zinc powder, an
10 anti-settling agent and organic solvent. The proportions of the
ingredients are indicated in Table 3C (in terms of mass). A
primary rust-preventive coatingmaterial was thus prepared. The
preparation of the pigment paste component was conducted in the
same manner as in Preparation Example 2-10.
15 [0145]
[Examples ID to 4D and Comparative Examples ID to 2Dl
50 g of the solution of the alkylsilicate condensate 1 (Mw
of the condensate 1 = 1500) was collected and was blended, with
stirring, with 3.1 g of S-LEC B BM-2 (manufactured by Sekisui
20 Chemical Co., Ltd.) , to prepare a solution. In the same manner,
41.0 g of the solution containing the condensate 1 was blended
with 3.8 g of the above "S-LEC", to prepare a solution; and 38.0
g of the solution containing the condensate 1 was blended with
4.0 g of the above "S-LEC", to prepare a solution.
[01461
Subsequently, a main agent component indicated in Table ID
was mixed with a pigment paste component that had been prepared
at a blending ratio indicated in Table ID. The mixing ratio of
5 the respective components is indicated in Table ID (in terms of
mass). A primary rust-preventive coating material was thus
prepared.
[0147]
Details of the respective components are as follows.
Solutions of alkylsilicate condensates 1 to 6: solutions
obtainedinPreparationExample1 (in100 gofeachofthe solutions
obtained in Preparation Example 1, the content of any of the
alkylsilicate condensates 1 to 6 in terms of Si02 = mass of Ethyl
Silicate 40 (31.5 g) x mass concentration of Ethyl Silicate 40
15 in terms of SiOz (about 40% by mass) = 12.6 g; specific gravity
of SiO2 = 2.2 g/cm3)
Polyvinyl butyral resin: S-LEC B BM-2 (manufactured by
Sekisui Chemical Co., Ltd. )
Flaky zinc powder: STANDART Zinc flake GTT (manufactured
20 byECKARTGmbH; specificgravity=7.1g/cm3; mediandiameter (D50)
= 17 pm, average thickness = 0.7 pm, aspect ratio (median
diameter/average thickness) = 24; specific surface area = 1.67
m2/g) (D50 is anaveragevalueofmediandiametersofthree samples
measured by using a laser scattering diffraction-type particle
s i z e d i s t r i b u t i o n analyzer "SALD 2200" manufactured by Shimadzu
Corporation. The samplesrierepretreatedbyaddinga small amount
of a n e u t r a l detergent i n t o zinc powder and u l t r a s o n i c a l l y
dispersing the powder f o r 5 minutes. Further, the p r e t r e a t e d
5 samples were introduced t o c i r c u l a t i n g water of the analyzer,
which was ion exchange water t o which a small amount of a neutral
detergent hadbeen added, and thereby theirmedian diameters were
measured. The dispersing time i n t h i s measurement was 1 minute.)
[0148]
10 The average thickness was determined i n such a manner as
follows. A sample was attached on a cellophane tape, and the
surfacewas observedbyusinga scanningelectronmicroscope (SEM)
"XL-30" (product name; manufactured by Philips) . Thirty samples
riith t h e i r thickness d i r e c t i o n being v e r t i c a l t o the observation
15 d i r e c t i o n were randomly s e l e c t e d . The thicknesses of t h e i r
p a r t i c l e s were measured, and an average value thereof was
calculated. The s p e c i f i c s u r f a c e a r e a was measured by using
"FlowSorb I1 2300" (product name; manufactured by Shimadzu
Corporation) .
20 [0149]
STANDART Zinc flakeG (manufacturedbyECKARTGmbH; s p e c i f i c
g r a v i t y = 7 . 1 g/cm3; median diameter (D50) = 8.5 pm, average
thickness = 0.4 pm, aspect r a t i o (median diameter/average
thickness) = 21)
STANDART Zinc flake AT (manufactured by ECKART GmbH;
specific gravity = 7.1 g/cm3; median diameter (D50) = 20 pm, average
thickness = 0.4 pm, aspect ratio (median diameter/average
thickness) = 50)
Spherical zinc powder: F-2000 (manufactured by The Honjo
Chemical Corporation; specific gravity = 7.1 g/cm3; median
diameter (D50) = 5 pm; specific surface area = 0.54 m2/g)
Zinc oxide: zinc oxide of JIS 3 grade (manufactured by
Hakusui Tech Co. , Ltd. )
Anti-settling agent: TIXOGEL MPZ (manufactured by Rockwood
Clay Additives GmbH; specific gravity = 1.7 g/cm3)
[Calculation of Pigment Volume Concentration (PVC)]
An example of the calculation of PVC (Example 1A) is as
follows.
15 [0150]
PVC = (Whole Volume of Pigment Component + Whole Volume of
Solid Particles in Additives))/ (Whole Volume of Nonvolatile
Components of Coating Composition) xlOO [%]
= (18.2 (g)/7.l (g/cm3) + 0.9 (g)/1.7 (g/cm3)) / (12.6
20 (g) /2.2 (g/cm3) + 18.2 (g) /7.l (g/cm3) + 0.9 (g) /l. 7 (g/cm3) ) xlOO
[%I
= 35 [ % I
[0151]
[Evaluation Method and Evaluation Criteria]
In such a manner that a coating film formed from a
conventional primary rust-preventive coating material (coating
material of Comparative Example 13A) would have an average dry
filmthickness of15 pm, line conditions of aline coatingmachine
6 (name of apparatus: conveyer coatingmachine for SP, manufactured
by Takeuchi Kosakusho, Co., Ltd. ) were adjusted (line speed: 10
m/min, coating pressure: 0.2 Mpa) . Under these line conditions,
the primary rust-preventive coating material obtained in any of
Examples andcomparative Examples was usedtoprepare atest plate
10 under conditions described in (1) to (3) below, and subjected to
evaluations (1) to (3) described below.
[0152]
(1) Rust-Prevention Properties of Primary Rust-Preventive
Coating Film (Rusting and White Rust)
A sandblasted surface of a sandblasted plate (JIS G3101,
55400, dimension: 150 mm x 70 mm x 2.3 mm) was coated with the
primaryrust-preventivecoatingmaterialbyusingthelinecoating
machine. Subsequently, in accordance with JIS K5600 1-6, the
coated plate was dried in a thermostatic chamber at a temperature
20 23OC at a relative humidity of 50% for 1 week, to prepare a test
plate composed of the primary rust-preventive coating film and
the sandblasted plate. Tables provided below indicate the
average dry filmthickness ofthe primary rust-preventive coating
film. The average dry film thickness was measured by using an
electromagnetic film thickness measuring instrument "LE-370"
(product name; manufactured by Kett Electric Laborary).
[0153]
As a test plate for the evaluation of rust prevention
5 p r o p e r t i e s a f t e r h e a t i n g a t 8 0 0 ° C , atestplateobtainedbyheating
a test plate prepared in the same manner as described above at
800°C for 3 minutes in a muffle furnace "FM48" (product name;
manufactured by Yamato Scientific Co., Ltd.) was used.
[0154]
This test plate was set on an outdoor exposure stand (in
the site of Otake Research Center of Chugoku Marine Paints, Ltd.)
and allowed to stand for 2 months or for 3 months. Here, the test
plate was fixed in such a manner that the coated surface of the
test plate faced south and that the test plate was inclined at
15 45 degrees to the horizontal plane.
[0155]
After the test plate was allowed to stand for 2 months or
for 3 months, a percentage ( % ) of an area of the surface of the
test plate having rusting and a percentage (%) of an area of the
20 surface of the test plate having white rust, each relative to an
area of the whole surface of the test plate, were measured to
evaluate the state of rusting and the occurrence state of white
rust. The evaluation criteria are as follows.
[0156]
[Evaluation Criteria for State of Rusting (ASTM D610)l
10: Rusting is not observed, or rusting area percentage is not
more than 0.01%.
9: Rusting is observed extremely slightly, or rusting area
6 percentage is more than 0.01% and not more than 0.03%.
8: Rusting is observed slightly, or rusting area percentage is
more than 0.03% and not more than 0.1%.
7: Rusting area percentage is more than 0.1% and not more than
0.3%.
10 6: Spot rusting is observed conspicuously, or rusting area
percentage is more than 0.3% and not more than 1%.
5: Rusting area percentage is more than 1% and not more than 3%.
4: Rusting area percentage is more than 3% and not more than 10%.
3: Rusting area percentage is more than 10% and not moEe than
15 1/6 (16%).
2: Rusting area percentage is more than 1/6 (16%) and not more
than 1/3 (33%).
1: Rusting area percentage is more than 1/3 (33%) and not more
than 1/2 (50%).
20 0: Rusting area percentage is almost more than 1/2 (50%) and up
to 100%.
[Evaluation Criteria for Occurrence State of White Rust]
10: White rust is not observed, or white rust area percentage is
not more than 0.01%.
9: White rust is observed extremely slightly, or white rust area
percentage is more than 0.01% and not more than 0.03%.
8: White rust is observedslightly, orwhite rust area percentage
is more than 0.03% and not more than 0.1%.
5 7 : White rust area percentage is more than 0.1% and not more than
0.3%.
6: White rust spots are observed conspicuously, or white rust
area percentage is more than 0.3% and not more than 1%.
5: White rust area percentage is more than 1% and not more than
10 3%.
4: White rust area percentage is more than 3% and not more than
10%.
3: White rust area percentage is more than 10% and not more than
1/6 (16%).
15 2: White rust area percentage is more than 1/6 (16%) and not more
than 1/3 (33%).
1: White rust area percentage is more than 1/3 (33%) and not more
than 1/2 (50%).
0: White rust area percentage is almost more than 1/2 (50%) and
20 up to 100%.
(2) Adhesion Property of Overcoating Film
A sandblasted surface of a sandblasted plate (JIS G3101,
SS400, dimension: 150 mm x 70 mm x 2.3 mm) was coated with the
primary rust-preventive coating material with the line coating
machine. Subsequently, in accordance with JIS K5600 1-6, the
coated plate was allowed to stand in a thermostatic chamber at
a temperature of 23°C at a relative humidity of 50% for 1 week,
to form a primary rust-preventive coating film with an average
5 dry film thickness indicated in tables set forth below. On this
primary rust-preventive coating film, a high-solidepoxy coating
material (product name: NOVA2000, manufacturedby ChugokuMarine
Paints, Ltd.) was applied with an air spray gun, and the coated
plate was allowed to stand for 1 week, to form a cured coating
10 film with a film thickness of 320 pm (overcoating film).
[01571
To a surface of the overcoating film, a bottom surface of
a cylindrical mild-steel jig having a diameter of 16 mm (area:
2 cm2) and a length of 20 mm was bonded with an epoxy adhesive,
15 and they were allowed to stand for 24 hours. Thereafter, a head
ofthe jig was pulledinthe vertical direction ofthe overcoating
film surface by using a pull gauge (manufactured by Motofuji Co.,
Ltd. ) to peel the jig from the overcoating film surface, whereby
an adhesive strength (force required for cohesive failure and/or
20 interfacial peeling) was measured.
[0158]
(3) Weldability Test
Surfaces of two sandblastedplates (JIS G3101, SS400, lower
plate dimension: 600 mm x 100 mm x 12 mm, upper plate dimension:
600mm x 50mmx 12mm) were coatedriiththeprimaryrust-preventive
coatingmaterialbyusingtheline coatingmachine. Subsequently,
i n accordance with JIS K5600 1-6, the coated p l a t e was allowed
t o stand i n a thermostatic chamber a t a temperature 23°C a t a
5 r e l a t i v e humidity of 50% f o r 1 week, whereby an upper p l a t e and
a lower p l a t e as shown i n Fig. l ( a ) having an average dry f i l m
thickness indicated i n Tables described belori were prepared. In
Figs. 1 (a) t o (c) , shaded p a r t s in the sandblasted p l a t e represent
p a r t s t h a t were coated.
Subsequently, by means of carbonic acid gas automatic a r c
welding, the upper p l a t e and the lower p l a t e were welded a t the
both layers ( f i r s t layer side, l a s t layer s i d e ) simultaneously
while maintaining a given torch angle and a given torch s h i f t ,
15 as shown i n Fig. 2 (a) t o ( c ) . Welding conditions a t t h i s time
are indicated i n Table 2.
[Table 21
Table 2
Welding Method
Welding Speed (mmlmin)
Electric Current (A)
Voltage (V)
Welding Wire
Torch Angle
Torch Shift (mm)
Wire Extension Length (mm)
Route Gap
Twin-Single Method
600
320
32
MX 2-200, cp 1.2 mm
45O, fonvard tilt 5O
100
25
0
[01611
Subsequently, weldability was evaluated in the following
manner.
[0162]
F i r s t , t h e number of p i t s formed in the region of a length
of 500 mm of the welded portion, except the region of each length
of 50 mm of the welding s t a r t portion and the welding end portion
including the tack weld portion before rielding, and a length (mm)
of a gas groove were checked. Further, under welding conditions
10 described in Table 2, a l a s e r notch (V-shaped cut) was made on
t h e w e l d l i n e o n t h e f i r s t layer side, andthe l a s t layer side welded
portion was f r a c t u r e d by using a press along the weldline. Then,
the t o t a l area of blowholes occurring on the f r a c t u r e d surface
(width of blowholes x length of blowholes x number of blowholes)
15 was divided by an evaluation a r e a t o determine a blowhole
occurrence percentage ( % ) .
101631
[Table lA]

Composition
of Coating
matcrial
Volume of Nonvolatile C
I I / Composition (%by mass) 1 1 1 1 1 1 "" I ," , ,
@)/(A) (mass ratio) 1 1.4 1 1.8 1 2.2 I 2.7 1 3.3 1 4.0
@-l)l(A) (mass ratio) 1.4 1.8 2.2 2.7 3.3 4.0
@-2)l(A) <<.S .p herical Zinc-based Powdcr/Si02> 0.0 0.0 0.0 0.0 0.0 0.0

[0166]
[Evaluation of Examples and Comparative Examples]
FromTable 1AtoTable 3A, the followinghasbeenmade clear.
[0167]
The average dry film thickness was not more than 10 pm when
PVC was not more than 60%, but was more than 10 pm when PVC was
not less than 65% (Comparative Examples 7A to 13A). That is, it
has been foundthat defining PVCasbeingnotmorethan 60% results
in the provision of coating films having a thickness of not more
10 than 10 pm even under conventional coating conditions.
[0168]
The rust-preventive properties were superior when PVC was
not less than 35%, but were poor when PVC was not more than 30%
(Comparative Examples 1A to 6A). The test plate obtained by
15 applyinga conventional primary rust-preventive coating material
so as toprovideanaverage dry filmthickness of 8 pm (Comparative
Example 14A) had inferior and poor rust-preventive properties.
In the embodiments of the primary rust-preventive coating
materials containing the alkylsilicate condensate 2 or 3
20 (Comparative Examples 15A and 16A), rust-preventive properties
were poor.
[01691
Regarding overcoatability, the adhesion strength was
sufficient, being not less than 2.4 MPa-s, when PVC was not more
than 60%, but the adhesion strength was insufficient, being not
more than 1.0 MPa-s, when PVC was not less than 65% (Comparative
Examples 7A to 12A).
[0170]
Regarding weldability, the blowhole occurrence percentage
was superior, being not more than lo%, when PVC was not more than
60%, but the blowhole occurrence percentage was poor, being more
than lo%, when PVC was not less than 65% (Comparative Examples
7A to 14A). In the embodiment of the primary rust-preventive
10 coating material containing the alkylsilicate condensate 3
(Comparative Example 16A), theblowholeoccurrence percentagewas
poor, being more than 10%.
[0171]
[Table lB]

[0172]
[Evaluation of Examples and Comparative Examples]
From Table lB, the following can be illustrated.
[0173]
Whentheconductivepigmenttogetherwiththe spherical zinc
powder were used, the rust-preventive properties were evaluated
to be 3, which was not a particular improvement as compared with
whennoconductivepigmentwas used (evaluation: 3). On the other
hand, when the flaky zinc powder was used together with the
10 conductive pigment, the rust-preventive properties were
evaluated to be 10, namely improvement as compared with when no
conductive pigment was used (evaluation: 9).
[0174]
[Table lC]
7 5
Table 1C
Table 1 C (continued)
Pigment Paste Conductive Pigment ( zinc oxide of JIS 3 grade I 7.2 I 12.0 I 8.0 1 8.8
Component Anti-Settling Agent I TEOGEL MPZ 2.3 2.3 2.5 2.8
.. . .. - .. I .- ? I .-"
Composition
of Coating
material
Properties of
Coating
Ex6C Ex.4C ExSC I CO~PEx.. 4C
~omponent
Material I
Organic Solvent
Coating
Film
Properties
100
Pigment Paste Component No.
Flaky Zinc Powder I STANDART Zinc flake GTT
Spherical Zinc Powder I F-2000
1 M- ainAgent 1 Solution ofAlkvlsilicate Condensate 1 W ~ 1 5 0 0 ) 100
Xylene
Butyl Acetate
Isobutyl Alcohol
10
7.2
28.8
Total (in terms of mass)
1 Volume of Nonvolatile Components (cm3)
Volume of Pipent Componcnt (cm') I 6.4 I 7.2 7.1 1 7.8
100
11.3
5.6
7.4
Volume of Solid Particles ofAdditive (cm3)
Amount of Zinc Powder ($3) in Nonvolatile Components in
Coating Composition (%by mass)
@)/(A) (mass ratio)
@-I)/(A)
100
11
7.2
28.8
169.8
13.4
1.3 1.3 1.5 1.6
I '..< I e.> I ,.." 1 -.u (mass ratio)
1 White Rust (hcating at 80O0C for 3 mio) I 8 I 9 I 8 7
Weldability ( (Welding speed = 600 d m i n ) 1 Blowhole Occnrrence Percentage (%) 1 9.5 9.9 9.9 16.0
11.3 1
5.6
7.4
62
2.9
0.6
7 7
(J3) (%by mass)
Amount of Spherical Zinc-based Powder @-2) in Zinc
Powder (B) (Oh by mass)
Amount of Zinc Powder @)per Coated Area (dm2)
10
8.0
32.0
174.6
14.3
-Pig ment Volume Concentration (PVC) (%) I
20.0
10
8.8
35.2
I L . ~
6.3
8.3
57
57
2.9
0.6
7 a
Amount of Flakey Zinc-based Powder @-I) in Zinc Powder / 20.0 20.0
26.9
15.6
6.9
9.1
177.5
14.3
60 60 62
20.0
185.3
15.1
63
3.2
0.6
7 <
80.0
25.2
65
3.5
0.7
7 2
80.0
28.1
80.0
34.9
[0175]
[Table 2C]
Table 2C

[0176]
[Table 3C]
Table 3C
Table 3C (continued)
[0177]
[Table 4C]
[0178]
[Evaluation of Examples and Comparative Examples]
It has been found from Table 1C that in the combined use
of the flaky zinc powder and the spherical zinc powder, the
5 rust-preventive properties were superior when PVC was not less
than 35%, but were poor when PVC was less than 35%; regarding
weldability, the blowhole occurrence percentage was superior,
being not more than 10% when PVC was not more than 60%, but the
blowhole occurrence percentage was poor, beingmore than 10% when
10 PVC was more than 60%.
[0179]
It has been found fromTable 2C and Table 3Cthatevenwhere
the ratio of the flaky zinc powder to the spherical zinc powder
was varied, as long as PVC was 35 to 60%, evaluation results of
15 coating film properties and weldability were superior.
[0180]
From the comparison between Example 18C and Example 2C in
Table 4C and the comparison between Example 19C and Example 3C
in Table 4C, it has been found that in the combined use of the
20 flaky zinc powder and the spherical zinc powder, further using
the conductive pigment resulted in further improvement of
rust-preventive properties and weldability.
[0181]
[Table ID]
SF-2658
8 3
Table ID
[Evaluation of Examples and Comparative Examples]
From Table ID, the following points have been made clear.
[0183]
When the mass ratio of the zinc dust (B) to the
siloxane-based binder (A) in terms of SiOz ( ( B ) / ( A ) ) was in the
range of 1.0 to 5.0, the evaluation results of coating film
properties andweldabilitywere superior. Ontheotherhand, when
the mass ratio was less than 1.0, the rust-preventive properties
10 were poor. When the mass ratio was more than 5.0, the blor- hole
occurrence percentage was poor, being more than 10%.
Reference Signs List
[0184]
15 10 ... sandblasted plate (lower plate)
20 ... sandblasted plate (upper plate)
CLAIMS
1. A primary rust-preventive coating composition
comprising a siloxane-based binder (A) having a weight average
molecularweight (Mw) asmeasuredbygelpermeationchromatography
(GPC) in terms of standard polystyrene being 1000 to 6000 and a
zinc dust (B) comprising a flaky zinc-based powder (b-l), the
primary rust-preventive coating composition having a pigment
volume concentration [PVC) of 35 to 60%, and having a mass ratio
((B)/(A)) of the zinc dust (B) to the siloxane-based binder (A)
in terms of SiOz being 1.0 to 5.0.
2. The primary rust-preventive coating composition
according to claim 1, wherein based on 100% by mass of the total
content of the zinc dust (B), the content of the flaky zinc-based
powder (b-1) is not less than 15% by mass.
3. The primary rust-preventive coating composition
according to claim 1 or 2, wherein the mass ratio ( - 1 ) / A ) of
the flaky zinc-based powder (b-1) to the siloxane-based binder
(A) in terms of Si02 is 1.0 to 5.0.
4. The primary rust-preventive coating composition
according to claim 1 or 2, which further contains, as the zinc
dust (B) , a spherical zinc-based powder (b-2) together with the
flaky zinc-based powder (b-1) .
5. The primary rust-preventive coating composition
according to claim 4, wherein based on 100% by mass of the total
content of the zinc dust (B) , the content of the flaky zinc-based
powder (b-1) is 15 to 90% by mass and the content of the spherical
zinc-based powder (b-2) is 10 to 85% by mass.
6. The primary rust-preventive coating composition
according to any one of claims 1 to 5, which further comprises
a conductive pigment (C) .
7. The primary rust-preventive coating composition
according to claim 6, wherein the conductive pigment (C) is zinc
oxide.
8. The primary rust-preventive coating composition
according toany oneof claims 1to 7, wherein the flaky zinc-based
powder (b-1) comprises at least one selected from a flaky zinc
powder and a flaky zinc alloy powder.
9. The primary rust-preventive coating composition
according to anyone of claims 1to 8, wherein the flaky zinc-based
powder (b-1) has a median diameter (D50) of not more than 30 pm
and an average thickness of not more than 1 pm.
10. The primary rust-preventive coating composition
according to any one of claims 1 to 9, wherein the siloxane-based
binder (A) is a condensate of at least one compound selected from
alkylsilicates and methyltrialkoxysilanes.
11. A primary rust-preventive coating film which is
formed from the primary rust-preventive coating composition
according to any one of claims 1 to 10 and has an average dry film
thickness of not more than 10 um.
12. A substrate with a primary rust-preventive coating
film which comprises a substrate and a coating film, the coating
film being provided on a surface of the substrate and formed from
the primary rust-preventive coating composition according to any
. . one of claims 1 to 10.
13. A substrate rust prevention method comprising a step
of applying the primary rust-preventive coating composition
according to any one of claims 1 to 10 on a substrate surface and
a step of curingthe coating composition appliedto forma primary
rust-preventive coating film.
14. A process for producing a substrate with a primary
rust-preventive coating film comprising a step of applying the
primary rust-preventive coating composition according to any one
of claims 1 to 10 on a substrate surface and a step of curing the
coating composition applied to form a primary rust-preventive
coating film.
Dated this 02.01.2015
MNJNA MEHTA-DUTT]
OF EMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]
ABSTRACT
Provided is a primary rust-preventive coating composition
which by being dried and cured at room temperature is capable of
forming a coating film having an average dry film thickness of
not more than 10 pm even with the use of conventional coating
machines and which has excellent rust prevention properties and
overcoatability as well as excellent weldability/cut-ability at
the time of welding and cutting steel plates. The primary
rust-preventive coating composition includes a siloxane-based
binder (A) having a weight average molecular weight (Mw) as
measured by gel permeation chromatography (GPC) in terms of
standard polystyrene being 1000 to 6000 and a zinc dust (B)
including a flaky zinc-based powder - 1 the primary
rust-preventive coating composition having a pigment volume
concentration (PVC) of 35to 60%, andhavingamass ratio ((B)/(A))
of the zinc dust (B) to the siloxane-based binder (A) in terms
of SiOz being 1.0 to 5.0.