U.S. patent application number 14/915226 was filed with the patent office on 2016-07-21 for friction modifier for top coating agent for trivalent chromium chemical conversion coating film or chromium-free chemical conversion coating film, and top coating agent including same.
The applicant listed for this patent is DIPSOL CHEMICALS CO., LTD.. Invention is credited to Toshiki Inomata, Manabu Inoue, Yasuhiro Kato.
Application Number | 20160208115 14/915226 |
Document ID | / |
Family ID | 52586399 |
Filed Date | 2016-07-21 |
United States Patent
Application |
20160208115 |
Kind Code |
A1 |
Kato; Yasuhiro ; et
al. |
July 21, 2016 |
FRICTION MODIFIER FOR TOP COATING AGENT FOR TRIVALENT CHROMIUM
CHEMICAL CONVERSION COATING FILM OR CHROMIUM-FREE CHEMICAL
CONVERSION COATING FILM, AND TOP COATING AGENT INCLUDING SAME
Abstract
Provided is a friction modifier for a top coating agent for a
hexavalent chromium-free trivalent chromium chemical conversion
coating film or chromium-free chemical conversion coating film,
said friction modifier including a polyoxyalkylene fatty acid
ester.
Inventors: |
Kato; Yasuhiro;
(Funabashi-shi, Chiba, JP) ; Inomata; Toshiki;
(Koshigaya-shi, Saitama, JP) ; Inoue; Manabu;
(Katsushika-ku, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DIPSOL CHEMICALS CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
52586399 |
Appl. No.: |
14/915226 |
Filed: |
August 19, 2014 |
PCT Filed: |
August 19, 2014 |
PCT NO: |
PCT/JP2014/071642 |
371 Date: |
February 27, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 22/83 20130101;
C23C 2222/10 20130101; C09D 171/02 20130101; C09D 7/63 20180101;
C09D 183/06 20130101; C09D 183/12 20130101; C09D 7/61 20180101;
C09D 5/08 20130101; C09D 7/65 20180101; C08G 77/46 20130101 |
International
Class: |
C09D 7/12 20060101
C09D007/12; C09D 183/06 20060101 C09D183/06; C23C 22/83 20060101
C23C022/83; C09D 5/08 20060101 C09D005/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 28, 2013 |
JP |
2013-176901 |
Claims
1. A friction modifier for a top coating agent for a trivalent
chromium chemical conversion film or a chromium-free chemical
conversion film, the friction modifier comprising a polyoxyalkylene
fatty acid ester.
2. A top coating agent for a hexavalent chromium-free trivalent
chromium chemical conversion film or a chromium-free chemical
conversion film, the top coating agent comprising: a
polyoxyalkylene fatty acid ester; a modified organopolysiloxane; a
water-soluble glycol ether; and water.
3. The top coating agent according to claim 2, wherein the content
of the polyoxyalkylene fatty acid ester is 1 to 100 g/L, the
content of the modified organopolysiloxane is 50 to 450 g/L, and
the content of the water-soluble glycol ether is 50 to 400 g/L.
4. The top coating agent according to claim 2, further comprising a
colloidal metal oxide.
5. The top coating agent according to claim 4, wherein the
colloidal metal oxide is at least one selected from the group
consisting of silicon oxide, titanium oxide, aluminum oxide,
zirconium oxide, zinc oxide, and dichromium trioxide
(Cr.sub.2O.sub.3).
6. The top coating agent according to claim 2, further comprising a
black pigment.
7. The top coating agent according to claim 6, wherein the black
pigment is at least one selected from carbon black and black
dyes.
8. The top coating agent according to claim 2, further comprising
an ultraviolet absorber.
Description
TECHNICAL FIELD
[0001] The present invention relates to a top coating agent used on
a trivalent chromium or chromium-free chemical conversion film for
aluminum, magnesium, zinc, and zinc alloys to improve the corrosion
resistance and scratch resistance.
BACKGROUND ART
[0002] Conventionally, a chromate treatment using hexavalent
chromium has been used to improve the corrosion resistance of
aluminum, magnesium, zinc, and zinc alloys. However, because of the
harmfulness to the human body, the use of hexavalent chromium has
been regulated. For this reason, a chemical conversion treatment
using trivalent chromium has been used as an alternative to the
chromate treatment. Moreover, to improve the corrosion resistance
and the scratch resistance, atop coat may be applied on a chemical
conversion film or on a finished surface prepared by subjecting a
chemical conversion film to a finishing treatment as described in,
for example, Japanese Patent Application Publication No.
2005-23372, WO2012/137680, etc. In the top coating treatment, a
polyolefin wax-based friction modifier is generally mixed and
dispersed in a top coating agent to adjust the friction
coefficient. However, an acidic water solvent-based top coating
agent, which is generally used for a trivalent chromium chemical
conversion film or a chromium-free chemical conversion film, has
such a problem that the dispersed polyolefin wax separates, and
hence a stable friction coefficient cannot be obtained.
SUMMARY OF INVENTION
[0003] Accordingly, an object of the present invention is to
provide a friction modifier for a top coating agent for a trivalent
chromium chemical conversion treatment coating film or a
chromium-free chemical conversion treatment coating film, the
friction modifier making it possible to obtain a stable friction
coefficient, and to provide a top coating agent comprising the
friction modifier.
[0004] It has been newly found that a polyoxyalkylene fatty acid
ester is effective as a friction modifier for a top coating agent
in imparting a stable friction coefficient to a topcoat film on a
hexavalent chromium-free trivalent chromium chemical conversion
film or a chromium-free chemical conversion film formed on a
surface of a substrate of a metal such as aluminum, magnesium,
zinc, or a zinc alloy. It is also found that the above-described
object can be achieved by a treatment using a top coating agent in
which a modified organopolysiloxane and a water-soluble glycol
ether are contained in a water solvent and to which a
polyoxyalkylene fatty acid ester is added as an friction modifier.
The present invention has been made based on these findings.
[0005] Specifically, the present invention provides a friction
modifier for a top coating agent for a trivalent chromium chemical
conversion film or a chromium-free chemical conversion film, the
friction modifier comprising a polyoxyalkylene fatty acid
ester.
[0006] The present invention also provides a top coating agent for
a trivalent chromium chemical conversion film or a chromium-free
chemical conversion film, the top coating agent comprising: a
polyoxyalkylene fatty acid ester; a modified organopolysiloxane; a
water-soluble glycol ether; and water.
[0007] The present invention makes it possible to impart a stable
friction coefficient, a high corrosion resistance, and the like to
a surface of a substrate of a metal such as aluminum, magnesium,
zinc, or a zinc alloy on which a trivalent chromium chemical
conversion film or a chromium-free chemical conversion film is
formed.
DESCRIPTION OF EMBODIMENTS
[0008] A friction modifier for a top coating agent for a trivalent
chromium chemical conversion film or a chromium-free chemical
conversion film of the present invention comprises a
polyoxyalkylene fatty acid ester.
[0009] The polyoxyalkylene fatty acid ester is preferably a
saturated or unsaturated fatty acid ester of a poly(lower
oxyalkylene) such as polyethylene glycol, polypropylene glycol, or
polyisobutylene. Specific examples of the polyoxyalkylene fatty
acid ester include polyethylene glycol mono- or di-stearate,
polypropylene glycol mono- or di-stearate, polypropylene glycol
isostearate, polyethylene glycol mono- or di-oleate, polyethylene
glycol mono- or di-laurate, and the like. The HLB of the
polyoxyalkylene fatty acid ester is preferably in a range from 8 to
20, and more preferably in a range from 15 to 18. These
polyoxyalkylene fatty acid esters are readily available as
commercial products. One of the above-described polyoxyethylene
fatty acid esters can be used alone, or two or more thereof can be
used in combination. The friction modifier may further comprise a
known friction modifier other than the polyoxyalkylene fatty acid
ester in combination, unless an effect of the friction modifier of
the present invention is impaired.
[0010] The composition of a top coating agent to which the friction
modifier of the present invention used for a top coating agent for
a trivalent chromium chemical conversion film or a chromium-free
chemical conversion film and comprising the polyoxyalkylene fatty
acid ester is added is not particularly limited. However, the top
coating agent is preferably a water-soluble solvent top coating
agent comprising a water-soluble resin, a water-soluble organic
solvent, water, and the like, and further preferably a water
solvent-based top coating agent comprising a water-soluble resin
and water.
[0011] In addition, atop coating agent for a trivalent chromium
chemical conversion film or a chromium-free chemical conversion
film of the present invention comprises: a polyoxyalkylene fatty
acid ester; a modified organopolysiloxane; a water-soluble glycol
ether; and water.
[0012] The polyoxyalkylene fatty acid ester is as described above.
The concentration of the polyoxyalkylene fatty acid ester in the
top coating agent is preferably in a range from 1 to 100 g/L, and
more preferably in a range from 20 to 60 g/L.
[0013] In the modified organopolysiloxane, a hydrophilic segment is
bonded to a silicon atom at a terminal or in a side chain of an
organopolysiloxane segment. The hydrophilic segment may be a
polyalkylene glycol, a polyalkylene glycol monoalkyl ether, an
N-acylalkyleneimine, acrylic acid, vinyl alcohol, or the like. The
hydrophilic segment is preferably a polyalkylene glycol, and
particularly preferably propylene glycol. Accordingly, preferred
modified organopolysiloxanes are polyoxyalkylene-modified
organopolysiloxanes. Polyoxypropylene-modified organopolysiloxanes
(polypropylene glycol-modified organopolysiloxanes) are
particularly preferable. These polysiloxanes are readily available
as commercially available polypropylene glycol-modified silicones.
One of the modified organopolysiloxanes can be used alone, or two
or more thereof can be used in combination. The concentration of
the modified organopolysiloxane in the top coating agent is
preferably in a range from 50 to 450 g/L, and more preferably in a
range from 150 to 350 g/L.
[0014] The above-described water-soluble glycol ether is preferably
an alkylene glycol alkyl ether, and is, for example, a monoalkylene
glycol monomonoalkyl ether or a monoalkylene glycol dialkyl ether.
More preferred are ethylene glycol monoalkyl ethers (cellosolves).
Specific examples include ethylene glycol monomethyl ether (methyl
cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve),
ethylene glycol monobutyl ether (butyl cellosolve), propylene
glycol monomethyl ethers (2-methoxy-1-propanol,
1-methoxy-2-propanol, and the like), butylene glycol monomethyl
ethers (2-methoxy-1-butanol, 3-methoxy-1-butanol,
1-methoxy-2-butanol, and the like), diethylene glycol monomethyl
ether, triethylene glycol monomethyl ether, ethylene glycol
dimethyl ether (dimethyl cello solve), ethylene glycol diethyl
ether (diethyl cellosolve), and the like. Of these glycol monoalkyl
ethers, particularly preferred are ethylene glycol monobutyl ether
and butylene glycol monomethyl ethers. One of the above-described
water-soluble glycol ethers can be used alone, or two or more
thereof can be used in combination. The concentration of the
water-soluble glycol ether in the top coating agent is preferably
in a range from 50 to 400 g/L, and more preferably in a range from
100 to 200 g/L.
[0015] The top coating agent of the present invention may further
comprise a colloidal metal oxide. The colloidal metal oxide is
preferably silicon oxide, titanium oxide, aluminum oxide, zirconium
oxide, zinc oxide, dichromium trioxide (Cr.sub.2O.sub.3), or the
like. One of the above-described colloidal metal oxides can be used
alone, or two or more thereof can be used in combination. The
concentration of the colloidal metal oxide in the top coating agent
is preferably 150 g/L or less, more preferably in a range from 10
to 100 g/L, and further preferably in a range from 20 to 50
g/L.
[0016] The top coating agent of the present invention may further
comprise any coloring agent for a coating material, for example, a
pigment or dye for coloring. The concentration of the pigment or
dye for coloring in the top coating agent is generally in a range
from 5 to 100 g/L, and more preferably in a range from 7 to 30 g/L.
Examples of blackening agents for blackening include carbon black
pigments, carbon-based black pigments used for coating materials,
solvent-soluble black dyes, such as metal complex salt dyes
including chromium complex salt azo dyes, used for coating
materials and being soluble in a solvent such as an organic solvent
or water, and the like. As the blackening agent, a combination of a
carbon black pigment and a black dye is preferable, because a
better black is obtained. In this case, the ratio of the carbon
black pigment and the black dye is preferably such that the ratio
of carbon black pigment/black dye is in a range from 90/10 to
10/90.
[0017] The top coating agent of the present invention may further
comprise an ultraviolet absorber. The ultraviolet absorber may be
benzophenone, benzotriazole, hydroxyphenylbenzotriazole,
hydroxybenzophenone, hydroxyphenyl Striazine, an oxanilide
derivative, or the like. One of the above-described ultraviolet
absorbers can be used alone, or two or more thereof can be used in
combination. The concentration of the ultraviolet absorber in the
top coating agent is preferably 150 g/L or less, and more
preferably in a range from 5 to 100 g/L.
[0018] The top coating agent of the present invention may further
comprise additives for coating materials, a so-called
stain-proofing agent for preventing stain and an anti-mold agent
for preventing the development of mold used for metal surface
treatment agents and the like, a surfactant and a water-soluble
resin for improving the uniformity and gloss of the finished
appearance, an anti-tarnish agent, and the like. The balance of the
top coating agent of the present invention other than the
above-described components is water. In addition, as in the case of
ordinary coating materials, the top coating agent can be used after
being diluted to a moderate concentration with, for example, water
and a water-soluble organic solvent, for example, water and butyl
cellosolve, for the purposes of adjustment of the coating
workability, the storability, the thickness of the coated film, and
the like. For example, the concentration of the top coating agent
in the diluted top coating agent solution is 30 to 100% by weight,
and preferably 50 to 80% by weight.
[0019] A topcoat film to be formed on a trivalent chromium chemical
conversion film or a chromium-free chemical conversion film can be
obtained by immersing a workpiece in the above-described top
coating agent, or by applying the above-described top coating agent
to a workpiece with a spray, then sufficiently draining the top
coating agent by centrifugation, and sufficiently drying the film.
The centrifugal drainage is preferably performed at 200 to 1000
rpm. In addition, the draining time is preferably 2 to 5 minutes.
The drying temperature is preferably 100 to 220.degree. C. In
addition, the drying time is preferably 10 to 60 minutes. If the
drying temperature is below the range, the corrosion resistance
decreases. If the drying temperature is too high, the corrosion
resistance decreases. If the drying time is shorter than 10
minutes, the corrosion resistance decreases. In addition, too long
a drying time is not economical. In addition, as a method for
drying the topcoat film, a two-stage drying method is preferable
which includes preliminary drying and subsequent main drying. The
preliminary drying is preferably conducted at a drying temperature
of 30.degree. C. to 80.degree. C. for a drying time of 3 to 30
minutes. The main drying is preferably conducted at a drying
temperature of 100.degree. C. to 220.degree. C. for a drying time
of 10 to 60 minutes. The preliminary drying at 80.degree. C. or
below is preferable, because it is possible to prevent failures of
the film such as breakage and an attachment failure of the film due
to the shrinkage of the film during drying at high temperature.
[0020] In addition, the thickness of the above-described topcoat
film is generally 0.8 to 5 .mu.m, and preferably 1 to 3 .mu.m. When
the thickness is within this range, a topcoat film having a high
corrosion resistance can be obtained with excellent appearance, and
it is also possible to prevent the formation of a pool of the
liquid, the generation of a stain, and the decrease in dimensional
precision.
[0021] Metal substrates used in the present invention include
substrates of metals and alloys such as various metals including
iron, nickel, copper, and aluminum, alloys thereof, and aluminum
subjected to a zincate conversion treatment in various shapes such
as a plate, a cuboid, a solid cylinder, a hollow cylinder, or a
sphere.
[0022] The above-described metal substrate may be plated with zinc
or a zinc alloy in a usual manner. To deposit zinc plating on the
substrate, it is possible to use any one of acidic or neutral baths
such as a sulfuric acid bath, a fluoborate bath, a potassium
chloride bath, a sodium chloride bath, and an ammonium chloride
eclectic bath, and alkaline baths such as a cyanide bath, a zincate
bath, and a pyrophosphate bath. Especially, a zincate bath is
preferable. In addition, the zinc alloy plating may be conducted by
using any alkaline bath such as an ammonium chloride bath or an
organic chelate bath. In addition, the zinc alloy plating may be
zinc-iron alloy plating, zinc-nickel alloy plating, zinc-cobalt
alloy plating, tin-zinc alloy plating, or the like. The thickness
of the zinc or zinc alloy plating may be any, and is preferably 1
.mu.m or more, and more preferably 5 to 25 .mu.m.
[0023] A method for using the top coating agent of the present
invention is not particularly limited, as long as the top coating
agent of the present invention is used for a top coating on a
trivalent chromium chemical conversion film or a chromium-free
chemical conversion film formed on the above-described substrate
metal or on various films optionally formed on the trivalent
chromium chemical conversion film or the chromium-free chemical
conversion film. A method for using the top coating agent of the
present invention is, for example, as follows. Specifically, the
above-described substrate metal as it is or the substrate metal on
which zinc or zinc alloy plating has been deposited is optionally
subjected to a pretreatment such as washing with water or washing
with water and a subsequent activation treatment with nitric acid.
Then, a chemical conversion treatment is conducted by, for example,
a method based on an immersion treatment or the like by using a
treatment solution for forming a trivalent chromium chemical
conversion film or a chromium-free chemical conversion film. After
that, the chemical conversion film is optionally subjected to a
finishing treatment described in, for example, Japanese Patent
Application Publication No. 2005-23372 or WO2012/137680. After
that, the top coating agent of the present invention is used as an
agent for top coating.
[0024] Specifically, for example, when a trivalent chromium
chemical conversion film is formed on a metal substrate having a
zinc or zinc-based alloy plating layer, the metal substrate is
generally immersed in a trivalent chromium chemical conversion
treatment solution, for example, for 5 to 600 seconds with the
liquid temperature being 10 to 80.degree. C. Thus, a trivalent
chromium chemical conversion film having a thickness of about 0.1
to 0.3 .mu.m is formed on the zinc or zinc-based alloy plating
layer. Note that when the metal substrate is plated with zinc, the
workpiece is generally immersed in a diluted nitric acid solution
before the trivalent chromium chemical conversion treatment to
increase the gloss of the trivalent chromium chemical conversion
film. This pretreatment may be employed, but does not necessarily
have to be employed in the present invention. Moreover, when a
finishing treatment is performed on the thus formed trivalent
chromium chemical conversion film, a layer of a finishing agent is
formed on the trivalent chromium chemical conversion film as
follows. Specifically, after or without washing the metal substrate
having the trivalent chromium chemical conversion film, the
trivalent chromium chemical conversion film is brought into contact
with the finishing agent in the form of an aqueous solution
(preferably, immersed in an aqueous finishing agent solution) to
attach the finishing agent. Then, without washing with water, the
metal substrate is dehydrated and dried to form the layer of the
finishing agent. In the finishing treatment, the contact
temperature (preferably, the immersion temperature) is generally 10
to 80.degree. C., the contact time (preferably, immersion time) is
3 to 30 seconds, the drying temperature is 50.degree. C. to
200.degree. C., and the drying time is 5 minutes to 60 minutes. In
addition, the thickness of the finished layer may be any, and is
preferably about 0.05 to 0.3 .mu.m.
[0025] In the present invention, a treatment solution used for
forming the trivalent chromium chemical conversion film or the
chromium-free chemical conversion film is not particularly limited,
and any one of various known chemical conversion treatment
solutions for zinc, a zinc alloy, aluminum, an aluminum alloy, or
the like can be used. For example, as the trivalent chromium
chemical conversion treatment liquid, it is possible to use any one
of various trivalent chromate treatment liquids described in U.S.
Pat. No. 5,415,702, Japanese Patent Application Publication Nos.
2003-166074, 2003-166075, 2002-053975, 2005-171296, and
2004-285373, etc. In addition, black trivalent chromate treatment
solutions described in Japanese Patent Application Publication Nos.
2003-26856 and 2007-100206, WO2007/094496, WO2007/100135, etc. are
particularly preferable.
[0026] Meanwhile, examples of the chromium-free chemical conversion
treatment solution include chromium-free chemical conversion
treatment solutions described in Japanese Patent Application
Publication Nos. 2010-031332 and 2009-138132 etc.
[0027] Of these chemical conversion treatment solutions, for
example, a trivalent chromium black chemical conversion treatment
liquid for zinc or zinc alloy plating is described in further
detail. As a supply source of trivalent chromium ions, any chromium
compound containing trivalent chromium ions can be used. It is
preferable to use a trivalent chromium salt such as chromium
chloride, chromium sulfate, chromium nitrate, chromium phosphate,
or chromium acetate. One of the above-described supply sources of
trivalent chromium can be used alone, or two or more thereof can be
used in combination. The concentration of trivalent chromium in the
treatment liquid is not limited in terms of performance, but is
preferably made as low as possible from the viewpoint of the
wastewater treatment. Accordingly, considering the corrosion
resistance performance and the like, the concentration of trivalent
chromium ions in the treatment liquid is preferably in a range from
0.5 to 20 g/L, and more preferably in a range from 1 to 10 g/L. A
concentration of trivalent chromium ions within this range is
advantageous in terms of the wastewater treatment and is also
economically advantageous. Note that the above-described trivalent
chromium black chemical conversion treatment liquid is a trivalent
chromium black chemical conversion treatment liquid for forming a
coating generally called a hexavalent chromium-free trivalent
chromium black chemical conversion film.
[0028] The above-described trivalent chromium black chemical
conversion treatment liquid does not necessarily have to contain a
chelating agent. However, it is preferable to contain a chelating
agent, because a more uniform chemical conversion film can be
obtained. The chelating agent may be an organic carboxylic acid
having a chelate-forming ability, a salt thereof, or the like. In
addition, among organic carboxylic acids, preferred are
dicarboxylic acids such as oxalic acid, malonic acid, succinic
acid, citric acid, and adipic acid, oxycarboxylic acids such as
citric acid, tartaric acid, and malic acid, and polycarboxylic
acids such as tricarballylic acid. These organic carboxylic acids
may be in the form of salts (for example, salts with sodium,
potassium, ammonium, or the like). One of the above-described
chelating agents can be used alone, or two or more thereof can be
used in combination. The concentration of the chelating agent in
the treatment liquid is preferably in a range from 1 to 40 g/L, and
more preferably in a range from 5 to 35 g/L. In addition, when a
chelating agent is contained, the mole ratio of the chelating agent
to the trivalent chromium ions [(concentration of chelating agent
(mol/L)/concentration of trivalent chromium ions (mol/L)] is
preferably 0.2 to 4, and more preferably 1 to 2. In addition, a
method for mixing the chelating agent with the trivalent chromium
compound is not particularly limited. For example, the formation of
the complex may be promoted in advance by mixing under heating at a
temperature of 60.degree. C. or above, and then the mixture may be
used.
[0029] The above-described trivalent chromium black chemical
conversion treatment liquid may further contain additional metal
ions other than trivalent chromium ions. As the metal ions, metal
ions selected from the group consisting of Co, V, Ti, W, Zr, Mn,
Mo, Ta, Ce, Sr, Fe, and Al ions may be contained. The supply source
of the metal ions maybe a chloride, nitrate, sulfate, acetate,
oxoacid salt, or the like of the metal ions. One of the
above-described metal ion species can be used alone, or two or more
thereof can be used in combination. The concentration of the metal
ions in the treatment liquid is preferably in a range from 0.1 to
50 g/L, and more preferably in a range from 0.5 to 20 g/L.
[0030] In addition to the above-described components, it is
possible to add one or more selected from phosphorous acid,
phosphinic acid, alkali salts thereof, and phosphate esters and
phosphite esters such as phosphoric acid alkyl esters and
phosphorous acid alkyl esters. In this case, the concentration in
the treatment liquid is preferably 0.1 to 50 g/L, and more
preferably 0.5 to 20 g/L.
[0031] The treatment liquid may further comprise a sulfur compound.
The sulfur compound may be an inorganic sulfur compound or an
organic sulfur compound. Of these sulfur compounds, the sulfur
compound is preferably an organic sulfur compound. Especially,
thiourea, thioacetic acid, thioglycolic acid, thiomalic acid,
thiomaleic acid, dithioglycolic acid, sodium salts thereof, and
ammonium salts thereof are preferable. The concentration of the
sulfur compound in the treatment liquid is preferably 0.1 to 10
g/L.
[0032] The zinc ion concentration in the above-described trivalent
chromium black chemical conversion treatment liquid increases with
the progress of the chemical conversion treatment. The zinc ion
concentration in the treatment bath during the use is 20 g/L or
less. It is preferable that the zinc ion concentration be in a
range from 0.1 g/L to 20 g/L, and that the zinc ion concentration
at the initial stage (at the initial make-up of the bath) be in a
range from 0.1 g/L to 10 g/L. Too high a zinc ion concentration in
the treatment bath is not preferable, because the corrosion
resistance and the degree of blackness decrease. In addition, a
zinc ion measurement method employed for managing the zinc ion
concentration during the chemical conversion treatment is not
particularly limited, and the zinc ion concentration can be managed
precisely based on a known method such as a titration analysis, ion
plasma spectrometry, or atomic absorption spectrometry. The
trivalent chromium ion concentration can also be managed using the
same method.
[0033] The above-described trivalent chromium black chemical
conversion treatment liquid may further comprise one or more
inorganic acid ion species selected from the group of ions of
phosphorus oxoacids other than phosphorous acid, phosphinic acid,
alkali salts thereof, phosphoric acid alkyl esters, and phosphorous
acid alkyl esters, chlorine ions, nitrate ions, sulfate ions, and
the like. The supply source of the inorganic acid may be phosphoric
acid, phosphinic acid, hydrochloric acid, nitric acid, sulfuric
acid, a salt thereof, or the like. One of the above-described
inorganic acids can be used alone, or two or more thereof can be
used in combination. The total concentration of the inorganic acid
ions in the treatment liquid is preferably in a range from 1 to 80
g/L, and more preferably in a range from 2 to 20 g/L.
[0034] The pH of the above-described trivalent chromium black
chemical conversion treatment liquid is preferably 0.5 to 5, and
more preferably 1 to 4. The pH may be adjusted by using the
above-described inorganic acid or an alkaline agent such as an
alkali hydroxide or ammonia water. The balance of the
above-described trivalent chromium black chemical conversion
treatment liquid other than the above-described components is
water.
[0035] For example, when a topcoat film formed from the top coating
agent of the present invention is a black topcoat film containing a
blackening agent, the trivalent chromium black chemical conversion
film used as a lower layer is preferably formed by using a
hexavalent chromium-free trivalent chromium black chemical
conversion treatment liquid having a Zn ion concentration of 20 g/L
or less. In addition, the amount of chromium ions attached in the
trivalent chromium black chemical conversion film is preferably 0.2
to 3.0 mg/dm.sup.2. When the amount of chromium ions attached is
within the range, an excellent black appearance and a high
corrosion resistance can be obtained.
[0036] Next, the present invention will be described based on
Examples and Comparative Examples; however, the present invention
is not limited to Examples.
EXAMPLES
[0037] Films were measured according to the following methods.
(Method for Evaluating Stability of Top Coating Agent)
[0038] Atop coating agent (500 mL) is placed in a 500 mL plastic
bottle, and allowed to stand at room temperature for one week.
After that, the separation of the liquid is visually observed.
(Method for Measuring Thickness of Topcoat Film)
[0039] A bolt is cut at the center between two surfaces of the head
portion, and the film thickness is measured with an electron
microscope.
(Method for Evaluating Finished Appearance)
[0040] The color of the exterior is visually observed.
(Method for Corrosion Resistance Test)
[0041] A salt spray test was conducted according to JIS Z 2371 to
evaluate the time to the formation of white rust.
(Total Friction Coefficient)
[0042] The total friction coefficient is measured by the fastening
test method according to JIS B 1084.
Example 1
[0043] M6 bolts (iron) plated with zinc by a zincate process (using
NZ-110 bath manufactured by DIPSOL CHEMICALS Co., Ltd.) to a
thickness of 8 .mu.m were used. On the bolts, trivalent chromium
chemical conversion films were formed by using a trivalent chromium
chemical conversion treatment liquid (ZT-444DSMT type manufactured
by DIPSOL CHEMICALS Co., Ltd., ZT-444DSM1: 75 mL/L and ZT-444DST: 1
mL/L, chemical conversion treatment conditions; 35.degree.
C..times.20 seconds). Subsequently, the bolts were subjected to a
centrifugal dehydrator (700 rpm, 3 minutes). After that, topcoat
films were formed by using a top coating agent shown in Table 1
below to which a friction modifier was added, and the bolts were
subjected to a centrifugal dehydrator (700 rpm, 3minutes), and
dried (200.degree. C., 10 minutes).
[0044] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
Example 2
[0045] On zinc-plated bolts of the same type as in Example 1,
trivalent chromium black chemical conversion films were formed by
using a trivalent chromium black chemical conversion treatment
liquid (ZTB-447S123C3 type manufactured by DIPSOL CHEMICALS Co.,
Ltd., ZTB-44751: 50 mL/L, ZTB-44752: 20 mL/L, and ZTB-44753: 7
mL/L, chemical conversion treatment conditions: 30.degree.
C..times.40 seconds). Subsequently, the bolts were subjected to a
centrifugal dehydrator (700 rpm, 3 minutes). After that, black
topcoat films were formed by using a black top coating agent shown
in Table 1 below to which a friction modifier was added, and
subjected to a centrifugal dehydrator (700 rpm, 3 minutes),
preliminary drying (40.degree. C., 5 minutes), and then main drying
(200.degree. C., 10 minutes).
[0046] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
Example 3
[0047] On zinc-plated bolts of the same type as in Example 1,
trivalent chromium black chemical conversion films were formed by
using a trivalent chromium black chemical conversion treatment
liquid (ZTB-447S123C3 type manufactured by DIPSOL CHEMICALS Co.,
Ltd., ZTB-44751: 50 mL/L, ZTB-44752: 20 mL/L, and ZTB-44753: 7
mL/L, chemical conversion treatment conditions: 30.degree.
C..times.40 seconds). Further, a finishing treatment was conducted
(ZTB-118 type manufactured by DIPSOL CHEMICALS Co., Ltd., ZTB-118:
150 mL/L, 45.degree. C., 10 seconds). Subsequently, the bolts were
subjected to a centrifugal dehydrator (700 rpm, 3 minutes). After
that, black topcoat films were formed by using a black top coating
agent shown in Table 1 below to which a friction modifier was
added. Then, the bolts were subjected to a centrifugal dehydrator
(700 rpm, 3 minutes), and dried (200.degree. C., 10 minutes).
[0048] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
Comparative Example 1
[0049] On zinc-plated bolts of the same type as in Example 1,
trivalent chromium chemical conversion films were formed by using a
trivalent chromium chemical conversion treatment liquid (ZT-444DSMT
type manufactured by DIPSOL CHEMICALS Co., Ltd., ZT-444DSM1: 75
mL/L and ZT-444DST: 1 mL/L, chemical conversion treatment
conditions: 35.degree. C..times.20 seconds). Subsequently, the
bolts were subjected to a centrifugal dehydrator (700 rpm, 3
minutes). After that, topcoat films were formed by using a top
coating agent shown in Table 1 below. Then, the bolts were
subjected to a centrifugal dehydrator (700 rpm, 3 minutes), and
dried (200.degree. C., 10 minutes).
[0050] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
Comparative Example 2
[0051] On zinc-plated bolts of the same type as in Example 1,
trivalent chromium black chemical conversion films were formed by
using a trivalent chromium black chemical conversion treatment
liquid (ZTB-447S123C3 type manufactured by DIPSOL CHEMICALS Co.,
Ltd., ZTB-44751: 50 mL/L, ZTB-44752: 20 mL/L, and ZTB-44753: 7
mL/L, chemical conversion treatment conditions: 30.degree.
C..times.40 seconds). Subsequently, the bolts were subjected to a
centrifugal dehydrator (700 rpm, 3 minutes). After that, black
topcoat films were formed by using a black top coating agent shown
in Table 1 below. Then, the bolts were subjected to a centrifugal
dehydrator (700 rpm, 3 minutes), and dried (200.degree. C., 10
minutes).
[0052] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
Comparative Example 3
[0053] On zinc-plated bolts of the same type as in Example 1,
trivalent chromium chemical conversion films were formed by using a
trivalent chromium chemical conversion treatment liquid (ZT-444DSMT
type manufactured by DIPSOL CHEMICALS Co., Ltd.,
[0054] ZT-444DSM1: 75 mL/L and ZT-444DST: 1 mL/L, chemical
conversion treatment conditions: 35.degree. C..times.20 seconds)
Subsequently, the bolts were subjected to a centrifugal dehydrator
(700 rpm, 3 minutes), and dried (200.degree. C., 10 minutes).
[0055] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
Comparative Example 4
[0056] On zinc-plated bolts of the same type as in Example 1,
trivalent chromium black chemical conversion films were formed by
using a trivalent chromium black chemical conversion treatment
liquid (ZTB-447S123C3 type manufactured by DIPSOL CHEMICALS Co.,
Ltd., ZTB-44751: 50 mL/L, ZTB-44752: 20 mL/L, and ZTB-44753: 7
mL/L, chemical conversion treatment conditions: 30.degree.
C..times.40 seconds). Further, a finishing treatment was conducted
(ZTB-118 type manufactured by DIPSOL CHEMICALS Co., Ltd., ZTB-118:
150 mL/L, treatment conditions: 45.degree. C..times.10 seconds).
Subsequently, the bolts were subjected to a centrifugal dehydrator
(700 rpm, 3 minutes), and dried (80.degree. C. 10 minutes).
[0057] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
Comparative Example 5
[0058] On zinc-plated bolts of the same type as in Example 1,
trivalent chromium chemical conversion films were formed by using a
trivalent chromium chemical conversion treatment liquid (ZT-444DSMT
type manufactured by DIPSOL CHEMICALS Co., Ltd., ZT-444DSM1: 75
mL/L and ZT-444DST: 1 mL/L, chemical conversion treatment
conditions: 35.degree. C..times.20 seconds). Subsequently, the
bolts were subjected to a centrifugal dehydrator (700 rpm, 3
minutes). After that, topcoat films were formed by using a top
coating agent shown in Table 1 below to which a conventional
polyolefin wax friction modifier was added. Then, the bolts were
subjected to a centrifugal dehydrator (700 rpm, 3minutes), and
dried (200.degree. C., 10 minutes).
[0059] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
Comparative Example 6
[0060] On zinc-plated bolts of the same type as in Example 1,
trivalent chromium black chemical conversion films were formed by
using a trivalent chromium black chemical conversion treatment
liquid (ZTB-4475123 C3 type manufactured by DIPSOL CHEMICALS Co.,
Ltd., ZTB-44751: 50 mL/L, ZTB-44752: 20 mL/L, and ZTB-44753: 7
mL/L, chemical conversion treatment conditions: 30.degree.
C..times.40 seconds). Subsequently, the bolts were subjected to a
centrifugal dehydrator (700 rpm, 3 minutes). After that, black
topcoat films were formed by using a black top coating agent shown
in Table 1 below to which a conventional polyolefin wax friction
modifier was added. Then, the bolts were subjected to a centrifugal
dehydrator (700 rpm, 3 minutes), and dried (200.degree. C., 10
minutes).
[0061] The obtained bolts were measured for the topcoat film
thickness, the finished appearance, the corrosion resistance, the
scratch resistance, and the total friction coefficient.
TABLE-US-00001 TABLE 1 Composition of Top Coating Agents Comp.
Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 5 Ex. 6
Polyoxyethylene sorbitan monolauric acid 50 50 50 -- -- -- -- ester
(HLB value: 17) (g/L) Polyethylene wax -- -- -- -- -- 50 50
Polypropylene glycol-modified silicone 250 250 250 250 250 250 250
(g/L) Butyl cellosolve (g/L) 150 150 150 150 150 150 150 Carbon
black (g/L) -- 10 10 -- 10 -- 10 Colloidal silica (g/L) 30 30 30 30
30 -- -- Benzophenone (g/L) 50 50 50 50 50 -- -- The balance was
water.
TABLE-US-00002 TABLE 2 Ex. 1 Ex. 2 Ex. 3 Stability of top coating
agent Not separated Not Not separated separated Thickness of
topcoat film (.mu.m) 2 2 2 Finished appearance Silver-white Black
Black Corrosion resistance 600 480 600 Time for which white rust
was not formed (h) Total friction coefficient 0.23 0.23 0.23
TABLE-US-00003 TABLE 3 Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1
Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Stability of top coating agent Not
Not -- -- Separated Separated separated separated Thickness of
topcoat film 2 2 0 0 2 2 (.mu.m) Finished appearance Silver-white
Black Light Black Silver-white Black blue Corrosion resistance 600
480 72 72 480 380 Time for which white rust was not formed (h)
Total friction coefficient 0.45 0.45 0.45 0.45 0.23 0.23
* * * * *