U.S. patent application number 13/714746 was filed with the patent office on 2013-06-20 for method of removing oxide film on surface of copper or copper-base alloy and copper or copper-base alloy recovered using the method.
This patent application is currently assigned to MITSUBISHI MATERIALS CORPORATION. The applicant listed for this patent is Mitsubishi Materials Corporation. Invention is credited to Naoki Kato, Kenji Kubota, Jyunichi Kumagai, Hiroaki Nakayama, Kenzi Okada, Yoshie Tarutani.
Application Number | 20130156631 13/714746 |
Document ID | / |
Family ID | 47351497 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130156631 |
Kind Code |
A1 |
Kumagai; Jyunichi ; et
al. |
June 20, 2013 |
METHOD OF REMOVING OXIDE FILM ON SURFACE OF COPPER OR COPPER-BASE
ALLOY AND COPPER OR COPPER-BASE ALLOY RECOVERED USING THE
METHOD
Abstract
A pickling solution, including: 50 g/L to 400 g/L of sulfuric
acid; 1 g/L to 100 g/L of at least one oxidant selected from a
group consisting of nitric acid, hydrogen peroxide, peroxodisulfate
ions, and iron (III) ions; 0.01 g/L to 10 g/L of at least one
additive selected from a group consisting of aromatic sulfonic
acid, aromatic sulfonate, alkylamine, aromatic carboxylic acid, and
aromatic carboxylate; 0.005 g/L to 10 g/L of at least one
surfactant selected from a group consisting of alkylbenzene
sulfonic acid and alkylbenzene sulfonate; and 10 g/L to 300 g/L of
copper sulfate, is used to remove oxide film, and then reused by
being electrolyzed and adding the oxidant, the additive and the
surfactant in amounts equivalent to consumed amounts.
Inventors: |
Kumagai; Jyunichi;
(Aizuwakamatsu-shi, JP) ; Tarutani; Yoshie;
(Aizuwakamatsu-shi, JP) ; Nakayama; Hiroaki;
(Sakai-shi, JP) ; Okada; Kenzi; (Sakai-shi,
JP) ; Kato; Naoki; (Naka-shi, JP) ; Kubota;
Kenji; (Naka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Materials Corporation; |
Tokyo |
|
JP |
|
|
Assignee: |
MITSUBISHI MATERIALS
CORPORATION
Tokyo
JP
|
Family ID: |
47351497 |
Appl. No.: |
13/714746 |
Filed: |
December 14, 2012 |
Current U.S.
Class: |
420/469 ;
205/722 |
Current CPC
Class: |
Y02P 10/212 20151101;
C25F 1/04 20130101; C25C 1/12 20130101; C23G 1/103 20130101; C23G
1/36 20130101; Y02P 10/20 20151101 |
Class at
Publication: |
420/469 ;
205/722 |
International
Class: |
C25F 1/04 20060101
C25F001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2011 |
JP |
2011-274719 |
Feb 24, 2012 |
JP |
2012-039190 |
Apr 24, 2012 |
JP |
2012-099274 |
Claims
1. A method of removing oxide film formed on a surface of a copper
or copper-base alloy, the method comprising steps of: dipping a
copper or copper-base alloy having oxide film formed on a surface
thereof, to remove the oxide film, in a pickling bath which
contains a pickling solution including: 50 g/L to 400 g/L of
sulfuric acid; 1 g/L to 100 g/L of at least one oxidant selected
from a group consisting of nitric acid, hydrogen peroxide,
peroxodisulfate ions, and iron (III) ions; 0.01 g/L to 10 g/L of at
least one additive selected from a group consisting of aromatic
sulfonic acid, aromatic sulfonate, alkylamine, aromatic carboxylic
acid, and aromatic carboxylate; 0.005 g/L to 10 g/L of at least one
surfactant selected from a group consisting of alkylbenzene
sulfonic acid and alkylbenzene sulfonate; and 10 g/L to 300 g/L of
copper sulfate; electrolyzing the pickling solution containing the
removed oxide film in an electrolytic bath so as to recover a
copper or copper-base alloy from the oxide film; adding the
oxidant, the additive, and the surfactant to the electrolyzed
pickling solution in amounts equivalent to those consumed when the
oxide film is removed and when the electrolysis is performed; and
returning the electrolyzed pickling solution, to which the oxidant,
the additive, and the surfactant are added, to the pickling bath to
be reused as a new pickling solution.
2. The method of removing oxide film on a surface of a copper or
copper-base alloy according to claim 1, wherein a surface tension
of the pickling solution is less than or equal to
50.times.10.sup.-3 N/m.
3. The method of removing oxide film on a surface of a copper or
copper-base alloy according to claim 1, further comprising steps
of: in the electrolyzing step, adjusting a concentration of copper
ions in the pickling solution containing the removed oxide film is
20 g/L to 60 g/L; controlling a current density in a range of 1
A/dm.sup.2 to 25 A/dm.sup.2; and rotating a cathode having a
cylindrical body at a peripheral speed in a range of 0.08 m/s to
0.48 m/s.
4. The method of removing oxide film on a surface of a copper or
copper-base alloy according to claim 2, further comprising steps
of: in the electrolyzing step, adjusting a concentration of copper
ions in the pickling solution containing the removed oxide film is
20 g/L to 60 g/L; controlling a current density in a range of 1
A/dm.sup.2 to 25 A/dm.sup.2; and rotating a cathode having a
cylindrical body at a peripheral speed in a range of 0.08 m/s to
0.48 m/s.
5. The method of removing oxide film on a surface of a copper or
copper-base alloy according to claim 3, wherein in the
electrolyzing, the flow rate of the pickling solution supplied to
the electrolytic bath and the current density in the electrolytic
bath are adjusted such that the concentration of copper ions in the
pickling solution containing the removed oxide film is 20 g/L to 60
g/L.
6. The method of removing oxide film on a surface of a copper or
copper-base alloy according to claim 4, wherein in the
electrolyzing, a flow rate of the pickling solution supplied to the
electrolytic bath is adjusted such that a concentration of copper
ions in the pickling solution containing the removed oxide film is
20 g/L to 60 g/L.
7. A copper or copper-base alloy which is recovered using the
method of removing oxide film on a surface of a copper or
copper-base alloy according to claim 1 and is capable of being used
as a recycled material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of removing oxide
film on a surface of a copper or copper-base alloy and more
specifically relates to a method of removing oxide film on a
surface of a copper or copper-base alloy in which a copper or
copper-base alloy, to having oxide film formed on a surface
thereof, is dipped in a pickling bath to remove the oxide film; and
a pickling solution containing the oxide film is electrolyzed in an
electrolytic bath so as to recover a high-purity copper or
copper-base alloy having superior handleability and to return the
electrolyzed pickling solution to the pickling bath for reuse.
[0003] Priority is claimed on Japanese Patent Application No.
2011-274719 filed on Dec. 15, 2011, Japanese Patent Application No.
2012-039190 filed on Feb. 24, 2012, and Japanese Patent Application
No. 2012-099274 filed on Apr. 24, 2012, the contents of which are
incorporated herein by reference.
[0004] 2. Description of Related Art
[0005] For example, a copper or copper-base alloy, which is
subjected to heat treatment such as hot rolling or hot extrusion,
is normally pickled or etched in order to remove oxide film or fine
defects formed on a surface thereof. As a pickling solution or an
etchant, sulfuric acid, a sulfuric acid-based acid obtained by
mixing hydrogen peroxide with sulfuric acid, hydrochloric acid, and
nitric acid are used. In some cases, additives such as hydrofluoric
acid and another surfactant may also be used as a pickling solution
or an etchant. Recently, from the viewpoints of resource recovery
and effluent treatment problems, it has been widely attempted to
recover copper oxide or metallic copper, which is dissolved in a
pickling solution or an etchant after the treatment, with an
electrolytic method and to reuse a used pickling solution or
etchant.
[0006] Japanese Examined Patent Application, Second Publication No.
S61-60148 discloses a method of recycling and recovering nitric
acid and metallic copper powder through electrolysis from a waste
solution containing copper and nitric acid, which is generated in
the finishing process of pickling copper. In this method, in a
device in which at least an anode of two electrodes is a ferrite
electrode; and an anode region, an intermediate region, and a
cathode region are formed between the anode and a cathode with a
combination of an anionic membrane and a cationic membrane or with
a combination of plural amphoteric membranes, the waste solution
containing copper and nitric acid, which is generated in the
process of pickling a product formed from a copper or copper-base
alloy, is electrolyzed while maintaining the pH value of the
cathode region in a range of 0.5 to 2.0, thereby recovering nitric
acid in the anode region and copper powder in the cathode
region.
[0007] Japanese Unexamined Patent Application, First Publication
No. 2003-342763 discloses a method of efficiently removing tin,
efficiently recovering copper in a treatment solution, and reusing
sulfuric acid after treatment without generating fine solid
materials, such as tin oxide and hydroxide, which cause problems
when a waste solution after pickling the copper-base alloy is
reused. This method is a method of recycling the waste solution
after pickling the copper-base alloy in which the waste solution is
heated at 40.degree. C. or higher to selectively separate tin by
precipitation as a pretreatment for recycling.
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0008] In a method of removing oxide film formed on a surface of a
copper or copper-base alloy of the related art, after oxide film is
removed in a pickling bath, it is difficult to electrolyze a
pickling solution containing the oxide film in an electrolytic bath
and efficiently recover a high-purity copper or copper-base alloy
capable of being reused as a recycled material having superior
handleability, and furthermore it is also difficult to return the
electrolyzed pickling solution to the pickling bath for reuse.
Means for Solving the Problem
[0009] According to the present invention, there is provided a
method of removing oxide film on a surface of a copper or
copper-base alloy, in which the above-described problems can be
solved; and after the copper or copper-base alloy having oxide film
formed on a surface thereof is dipped in a pickling bath to remove
the oxide film, a pickling solution containing the oxide film is
electrolyzed in an electrolytic bath so as to efficiently recover a
high-purity copper or copper-base alloy, capable of being reused as
a recycled material having superior handleability, and furthermore
to return the electrolyzed pickling solution to the pickling bath
for reuse.
[0010] As a result of thorough investigation in consideration of
such circumstances, the present inventors found that oxide film can
be efficiently removed by using a pickling solution including 50
g/L to 400 g/L of sulfuric acid, 1 g/L to 100 g/L of at least one
oxidant selected from a group consisting of nitric acid, hydrogen
peroxide, peroxodisulfate ions, and iron (III) ions, 0.01 g/L to 10
g/L of at least one additive selected from a group consisting of
aromatic sulfonic acid, aromatic sulfonate, alkylamine, aromatic
carboxylic acid, and aromatic carboxylate, 0.005 g/L to 10 g/L of
at least one surfactant selected from a group consisting of
alkylbenzene sulfonic acid and alkylbenzene sulfonate, and 10 g/L
to 300 g/L of copper sulfate; and a high-purity copper or
copper-base alloy, capable of being reused as a recycled material
having superior handleability, can be recovered by electrolyzing a
pickling solution containing the removed oxide film in an
electrolytic bath.
[0011] Furthermore, the present inventors found that a pickling
solution can be efficiently reused by adding the oxidant, the
additive, and the surfactant to the electrolyzed pickling solution
in amounts equivalent to those consumed when the oxide film is
removed and when the electrolysis is performed.
[0012] That is, according to the present invention, there is
provided a method of removing oxide film formed on a surface of a
copper or copper-base alloy, the method including steps of: dipping
the copper or copper-base alloy having oxide film formed on a
surface thereof, to remove the oxide film, in a pickling bath which
contains a pickling solution including 50 g/L to 400 g/L of
sulfuric acid, 1 g/L to 100 g/L of at least one oxidant selected
from a group consisting of nitric acid, hydrogen peroxide,
peroxodisulfate ions, and iron (III) ions, 0.01 g/L to 10 g/L of at
least one additive selected from a group consisting of aromatic
sulfonic acid, aromatic sulfonate, alkylamine, aromatic carboxylic
acid, and aromatic carboxylate, 0.005 g/L to 10 g/L of at least one
surfactant selected from a group consisting of alkylbenzene
sulfonic acid and alkylbenzene sulfonate, and 10 g/L to 300 g/L of
copper sulfate; electrolyzing the pickling solution containing the
removed oxide film in an electrolytic bath so as to recover the
copper or copper-base alloy from the oxide film; adding the
oxidant, the additive, and the surfactant to the electrolyzed
pickling solution in amounts equivalent to those consumed when the
oxide film is removed and when the electrolysis is performed; and
returning the electrolyzed pickling solution, to which the oxidant,
the additive, and the surfactant are added, to the pickling bath to
be reused as a new pickling solution.
[0013] When the amount of the sulfuric acid is less than 50 g/L, an
effect of removing oxide film deteriorates, and when the amount of
the sulfuric acid is greater than 400 g/L, the effect is saturated
and the cost is wasted.
[0014] When the amount of at least one oxidant selected from a
group consisting of nitric acid, hydrogen peroxide, peroxodisulfate
ions, and iron (III) ions is less than 1 g/L, an effect of removing
oxide film deteriorates, and when the amount of the oxidant is
greater than 100 g/L, the amount of gas generated during removal
increases, which is disadvantageous. The generated gas is mainly
NO.sub.X and oxygen gas generated by the oxidant used.
[0015] Even when a treatment oil, which is attached onto a surface
of the copper or copper-base alloy and is introduced in the
previous step, contaminates a pickling solution, at least one
additive selected from a group consisting of aromatic sulfonic
acid, aromatic sulfonate, alkylamine, aromatic carboxylic acid, and
aromatic carboxylate deposits a high-purity copper or copper-base
alloy, capable of being used as a recycled material having superior
handleability, on a cathode during the electrolysis and prevents
the reductive degradation of hydrogen peroxide on the cathode. In
addition, the additive works as a stabilizer for the oxidant in the
pickling solution and thus also serves to suppress the consumption
of the oxidant. When the addition amount thereof is less than 0.01
g/L or greater than 10 g/L, the effect cannot be obtained.
[0016] At least one surfactant selected from a group consisting of
alkylbenzene sulfonic acid and alkylbenzene sulfonate is chemically
stable in the pickling solution, lowers the surface tension of the
pickling solution for a long period of time to prevent dispersion
of mist, and increases the osmotic strength of the pickling
solution to enhance pickling capability. In particular, the
additive can prevent a large amount of sulfuric acid mist from
being dispersed by oxygen gas which is generated from a cathode
during the electrolysis. When the addition amount thereof is less
than 0.005 g/L or greater than 10 g/L, the above-described effect
cannot be obtained.
[0017] Advantageous effects of the present invention can be
obtained with a combination of at least one additive selected from
a group consisting of aromatic sulfonic acid, aromatic sulfonate,
alkylamine, aromatic carboxylic acid, and aromatic carboxylate and
at least one surfactant selected from a group consisting of
alkylbenzene sulfonic acid and alkylbenzene sulfonate.
[0018] When the amount of the copper sulfate is less than 10 g/L,
the efficiency of the electrolysis in the next step decreases. When
the amount of the copper sulfate is greater than 300 g/L, the
amount approaches saturated solubility and thus unnecessary copper
sulfate is deposited in the pickling solution.
[0019] By adding the oxidant, the additive, and the surfactant to
the electrolyzed to pickling solution in amounts equivalent to
those consumed when the oxide film is removed and when the
electrolysis is performed and returning the electrolyzed pickling
solution, to which the oxidant, the additive, and the surfactant
are added, to the pickling bath, the pickling solution can be
efficiently reused as a new pickling solution. As a result, oxide
film on a surface of the copper or copper-base alloy can be removed
not only in a batch treatment but in a continuous treatment. The
amounts of the oxidant, the additive, and the surfactant added
(consumed) vary depending on the kind of the copper or copper-base
alloy, but are about 0.5% to 10% of the initial amounts.
[0020] In the method of removing oxide film on a surface of a
copper or copper-base alloy according to the present invention, it
is preferable that a surface tension of the pickling solution be
less than or equal to 50.times.10.sup.-3 N/m.
[0021] The surface tension of the pickling solution is adjusted to
be less than or equal to 50.times.10.sup.-3N/m (50 dyn/cm) mainly
by at least one surfactant selected from a group consisting of
alkylbenzene sulfonic acid and alkylbenzene sulfonate. As a result,
a large amount of sulfuric acid mist can be efficiently prevented
from being dispersed by oxygen gas which is generated from a
cathode during the electrolysis and a high-purity copper or
copper-base alloy, capable of being used as a recycled material
having superior handleability, can be further efficiently
recovered.
[0022] In the method of removing oxide film on a surface of a
copper or copper-base alloy according to the present invention, it
is preferable that the method further have steps of: in the
electrolyzing step, adjusting a concentration of copper ions in the
pickling solution containing the removed oxide film is 20 g/L to 60
g/L; controlling a current density in a range of 1 A/dm.sup.2 to 25
A/dm.sup.2; and rotating a cathode having a cylindrical body at a
peripheral speed in a range of 0.08 m/s to 0.48 m/s.
[0023] The efficiency of the electrolysis can be increased to a
large degree and the size of the electrolytic bath can be reduced
by setting the concentration of copper ions in the pickling
solution containing the removed oxide film to be 20 g/L to 60 g/L,
the current density to be 1 A/dm.sup.2 to 25 A/dm.sup.2, the
cathode to be a rotating cylindrical body, and the peripheral speed
of the rotating cylindrical body to be 0.08 m/s to 0.48 m/s.
[0024] If the concentration of copper ions, the current density,
and the peripheral speed of the rotating cathode do not fall within
the above-described range, the efficiency of the electrolysis does
not increase to a large degree.
[0025] In addition, in the method of removing oxide film on a
surface of a copper or copper-base alloy according to the present
invention, it is preferable that in the electrolyzing, the flow
rate of a pickling solution supplied to the electrolytic bath and
the current density in the electrolytic bath be adjusted such that
the concentration of copper ions in the pickling solution
containing the removed oxide film is 20 g/L to 60 g/L.
[0026] When the removal method according to the present invention
is performed in a continuous treatment, there are many cases where
the amounts of the copper or copper-base alloy having oxide film
formed on a surface thereof, which is to be dipped in the pickling
bath, or the characteristics of the oxide film are uneven and
different. As a result, the concentration of copper ions in the
pickling solution containing the removed oxide film does not fall
within the range of 20 g/L to 60 g/L and the electrolysis is not
stably performed in the electrolytic bath, which may adversely
affect the stable recovery of the copper or copper-base alloy.
[0027] Therefore, when the concentration of copper ions in the
pickling solution is greater than 60 g/L, the recovery of the
copper or copper-base alloy temporarily increases and the
concentration of copper ions in the pickling solution is adjusted
to be less than or equal to 60 g/L by increasing the amount of a
pickling solution, which is supplied to the electrolytic bath, to
increase the flow rate of the pickling solution to the electrolytic
bath and increasing a current, which is applied to the electrolytic
bath, to increase the current density in the electrolytic bath.
When the concentration of copper ions in the pickling solution is
less than 20 g/L, the recovery of the copper or copper-base alloy
temporarily deteriorates and the concentration of copper ions in
the pickling solution is adjusted to be greater than or equal to 20
g/L by reducing the amount of a pickling solution, which is
supplied to the electrolytic bath, to reduce the flow rate of the
pickling solution to the electrolytic bath and reducing a current,
which is applied to the electrolytic bath, to reduce the current
density in the electrolytic bath. Through this operation, stable
electrolysis can be continuously performed in the electrolytic
bath. In this case, when only the current density is changed, the
precipitation state of the copper or copper-base alloy recovered
easily changes. Therefore, the flow rate is also changed at the
same time to control the thickness of a diffusion layer in the
pickling solution, thereby promoting stable electrolysis without
changing the precipitation state of the copper or copper-base alloy
recovered in the electrolytic bath.
[0028] In addition, in order to continuously measure the variable
concentration of copper ions in the pickling solution using a
detector and make measured values fall within a prescribed value
range, it is more preferable that the amount of the pickling
solution supplied to the electrolytic bath, be adjusted with a
supply pump and that the current applied between electrodes of an
electrolyzer be adjusted to adjust the current density in the
electrolytic bath, thereby automatically promoting stable
electrolysis in the electrolytic bath. In this case, in order to
continue more stable electrolysis, it is preferable that the
optimum concentration of copper ions in the pickling solution be
set to be 30 g/L to 40 g/L.
[0029] A copper or copper-base alloy according to the present
invention is recovered using the above-described method of removing
oxide film on a surface of a copper or copper-base alloy and is
capable of being used as a recycled material.
[0030] The pickling solution contains the desired and optimum
amounts of electrolytic solution components which are necessary
when a metallic copper or metallic copper-base alloy is recovered
through electrolysis. Therefore, the pickling solution containing
the removed oxide film can be electrolyzed without using special
means. As a result, the copper or copper-base alloy, capable of
being used as a recycled material, can be efficiently
recovered.
[0031] Furthermore, according to the present invention, unlike the
related art, the copper or copper-base alloy, which is recovered on
a cathode through electrolysis, has not a powder form but a
plate-like or columnar form having high purity and appropriate
hardness. Therefore, handleability is superior, rinsing is easy,
and impurities can be prevented from being mixed. Accordingly, an
ingot obtained by melting and casting the recovered copper or
copper-base alloy as the recycled material has a lower impurity
content and barely causes problems, such as cracking, during hot
rolling or hot extrusion thereafter.
Effects of the Invention
[0032] In the method of removing oxide film on a surface of a
copper or copper-base alloy according to the present invention,
after the copper or copper-base alloy having oxide film formed on a
surface thereof is dipped in a pickling bath to remove the oxide
film, a pickling solution containing the oxide film is electrolyzed
in an electrolytic bath. Therefore, a high-purity copper or
copper-base alloy, capable of being used as a recycled material
having superior handleability, can be efficiently recovered and the
electrolyzed pickling solution can be returned to the pickling bath
for reuse.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a diagram schematically illustrating a device
according to an embodiment of the present invention.
[0034] FIG. 2 is a diagram schematically illustrating a device
according to another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] FIG. 1 is a diagram schematically illustrating a device
according to an embodiment of the present invention. In an oxide
film removal device 1 according to the present invention, a
pickling bath 3 is filled with a pickling solution 2 for oxide film
on a surface of a copper or copper-base alloy, a copper or
copper-base alloy 4 is dipped in the pickling bath 3, and the oxide
film on the surface is removed in the pickling solution 2. The
thickness of the oxide film is 0.05 .mu.m to 10 .mu.m although it
varies depending on heat treatment and the like in the previous
step, an appropriate temperature of the pickling solution 2 for the
oxide film is 30.degree. C. to 60.degree. C., and the dipping time
is preferably 30 minutes to 120 minutes. The copper or copper-base
alloy 4 from which the oxide film is removed is transported from
the pickling bath 3 for the next step.
[0036] The pickling solution 2 includes: 50 g/L to 400 g/L of
sulfuric acid; 1 g/L to 100 g/L of at least one oxidant selected
from a group consisting of nitric acid, hydrogen peroxide,
peroxodisulfate ions, and iron (III) ions; 0.01 g/L to 10 g/L of at
least one additive selected from a group consisting of aromatic
sulfonic acid, aromatic sulfonate, alkylamine, aromatic carboxylic
acid, and aromatic carboxylate; 0.005 g/L to 10 g/L of at least one
surfactant selected from a group consisting of alkylbenzene
sulfonic acid and alkylbenzene sulfonate, and 10 g/L to 300 g/L of
copper sulfate.
[0037] When the amount of the sulfuric acid is less than 50 g/L, an
effect of removing the oxide film is deteriorated, and when the
amount of the sulfuric acid is greater than 400 g/L, the effect is
saturated and the cost is wasted.
[0038] When the amount of at least one oxidant selected from a
group consisting of to nitric acid, hydrogen peroxide,
peroxodisulfate ions, and iron (III) ions is less than 1 g/L, the
effect of removing oxide film is deteriorated, and when the amount
of the oxidant is greater than 100 g/L, the amount of gas generated
during removal increases, which is disadvantageous. The generated
gas is mainly NO.sub.x and oxygen gas generated by the oxidant
used.
[0039] Even when a treatment oil, which is attached onto a surface
of the copper or copper-base alloy 4 and is introduced in the
previous step, contaminates the pickling solution 2, at least one
additive selected from a group consisting of aromatic sulfonic
acid, aromatic sulfonate, alkylamine, aromatic carboxylic acid, and
aromatic carboxylate deposits a high-purity copper or copper-base
alloy 8, capable of being used as a recycled material having
superior handleability, on a cathode 7 during the electrolysis and
prevents the reductive degradation of hydrogen peroxide on the
cathode 7. In addition, the additive works as a stabilizer for the
oxidant in the pickling solution 2 and thus also serves to suppress
the consumption of the oxidant.
[0040] When the addition amount thereof is less than 0.01 g/L or
greater than 10 g/L, the effect cannot be obtained.
[0041] Examples of the aromatic sulfonic acid as the additive
include benzene sulfonic acid, toluene sulfonic acid, xylene
sulfonic acid, ethyl benzene sulfonic acid, cumene sulfonic acid,
phenol sulfonic acid, cresol sulfonic acid, sulfosalicylic acid,
and sulfanilic acid. Examples of the alkylamine include
methylamine, ethylamine, propylamine, butylamine, and pentylamine.
Examples of the aromatic carboxylic acid include benzoic acid,
salicylic acid, p-hydroxybenzoic acid, aminobenzoic acid,
sulfobenzoic acid, and phthalic acid.
[0042] At least one surfactant selected from a group consisting of
alkylbenzene sulfonic acid and alkylbenzene sulfonate is chemically
stable in the pickling solution 2, lowers the surface tension of
the pickling solution 2 for a long period of time to prevent
dispersion of mist, and increases the osmotic strength of the
pickling solution 2 to enhance pickling capability. In particular,
oxygen gas is generated from the cathode 7 during the electrolysis
and a large amount of sulfuric acid mist is dispersed. However, the
surface tension of the pickling solution can be reduced and the
dispersion of the sulfuric acid mist can be prevented by adding the
additive.
[0043] When the addition amount thereof is less than 0.005 g/L or
greater than 10 g/L, the above-described effect cannot be
obtained.
[0044] Examples of the surfactant include octylbenzene sulfonic
acid, nonylbenzene sulfonic acid, decylbenzene sulfonic acid,
undecylbenzene sulfonic acid, dodecylbenzene sulfonic acid,
tridecylbenzene sulfonic acid, tetradecylbenzene sulfonic acid, and
mixtures thereof.
[0045] Advantageous effects of the present invention can be
obtained with a combination of at least one additive selected from
a group consisting of aromatic sulfonic acid, aromatic sulfonate,
alkylamine, aromatic carboxylic acid, and aromatic carboxylate and
at least one surfactant selected from a group consisting of
alkylbenzene sulfonic acid and alkylbenzene sulfonate.
[0046] When the amount of the copper sulfate is less than 10 g/L,
the efficiency of the electrolysis in the next step decreases. When
the amount of the copper sulfate is greater than 300 g/L, the
amount approaches saturated solubility and thus unnecessary copper
sulfate is deposited in the pickling solution.
[0047] In addition, it is preferable that surface tension of the
pickling solution 2 be less than or equal to 50 dyn/cm
(50.times.10.sup.-3 N/m). The surface tension of the pickling
solution 2 is adjusted to be less than or equal to 50 dyn/cm
(50.times.10.sup.-3 N/m) mainly by at least one surfactant selected
from a group consisting of alkylbenzene sulfonic acid and
alkylbenzene sulfonate. As a result, a large amount of sulfuric
acid mist can be efficiently prevented from being dispersed by
oxygen gas which is generated from the cathode 7 during the
electrolysis and the high-purity copper or copper-base alloy 8,
capable of being used as the recycled material having superior
handleability, can be further efficiently recovered.
[0048] Next, a pickling solution X containing the oxide film which
is removed in the oxide film removal device 1 is transported to an
electrolyzer 5 by a pump P1. An anode 6 and the cathode 7 are set
in the electrolyzer 5 and a current is applied therebetween. As a
result, the pickling solution X containing the removed oxide film
is electrolyzed and the copper or copper-base alloy 8, capable of
being used as a recycled material, is efficiently recovered on the
cathode 7.
[0049] As the cathode 7, tough pitch copper is generally used, but
it is preferable that the optimum material for the recovered copper
or copper-base alloy be used. In addition, the form of the cathode
is generally a thin plate shape, but is preferably a rotating
cylindrical body. In the pickling solution X, for electrolysis, a
concentration of copper ions is set to be 20 g/L to 60 g/L, current
density is set to be 1 A/dm.sup.2 to 25 A/dm.sup.2, and peripheral
speed of the rotating cylindrical cathode is set to be 0.08 m/s to
0.48 m/s. As a result, the efficiency of the electrolysis increases
to a large degree and the size of the electrolytic bath can be
reduced. If the concentration of copper ions, the current density,
and the peripheral speed of the rotating cathode do not fall within
the above-described range, the efficiency of the electrolysis does
not increase to a large degree.
[0050] It is preferable that an iridium oxide coated titanium plate
be used as the anode 6. The current density is set to be 3
A/dm.sup.2 to 10 A/dm.sup.2 and the electrolysis is performed for
about 6 hours to 10 hours although different conditions may be set
depending on the state of the oxide film. As a result, the copper
or copper-base alloy 8, derived from the oxide film, is deposited
on the cathode 7 in a plate shape having superior
handleability.
[0051] The pickling solution 2 contains the desired and optimum
amounts of electrolytic solution components which are necessary
when a metallic copper or metallic copper-base alloy is recovered
through electrolysis. Therefore, the pickling solution X containing
the removed oxide film can be electrolyzed without using special
means. As a result, the copper or copper-base alloy 8, capable of
being used as the recycled material, can be efficiently
recovered.
[0052] Unlike the related art, the copper or copper-base alloy 8,
which is recovered on a cathode through electrolysis according to
the present invention, has not a powder form but a plate-like or
columnar form having high purity and appropriate hardness.
Therefore, handleability is superior, rinsing is easy, and
impurities can be prevented from being mixed. Accordingly, an ingot
obtained by melting and casting the recovered copper or copper-base
alloy 8 as the recycled material has advantageous effects in that
it has a lower impurity content and barely causes problems, such as
cracking, during hot rolling or hot extrusion thereafter.
[0053] Next, the amounts of the oxidant, the additive, and the
surfactant consumed when the oxide film is removed during the
electrolysis are determined by an analyzer, and the equivalent
amounts of the oxidant, the additive, and the surfactant Z are
added to an electrolyzed pickling solution Y in the electrolyzer 5.
Then, the electrolyzed pickling solution Y is transported to the
oxide film removal device 1 by the pump P2 and reused as a pickling
solution. The amounts of the oxidant, the additive, and the
surfactant Z vary depending on the amount of the attached oxide
film or the kind of the copper or copper-base alloy, but are about
0.5 to 10% of the amounts before being consumed.
[0054] The above-described processes are performed in a batch
treatment but may be performed in a continuous treatment. The
optimum dipping time is selected according to the kind of the
copper or copper-base alloy and the state of the oxide film
thereof, the pickling solution 2 is circulated, and as a result,
the oxide film on the surface thereof can be continuously
removed.
[0055] In this case, there are many cases where the amount of the
copper or copper-base alloy 4 having the oxide film formed on the
surface thereof, which is to be dipped in the pickling bath 3, or
the characteristics of the oxide film are uneven and different. As
a result, there is a case in which the concentration of copper ions
in the pickling solution 2 containing the removed oxide film does
not fall within the range of 20 g/L to 60 g/L and the electrolysis
is not stably performed in the electrolytic bath 5, which may
adversely affect the stable recovery of the copper or copper-base
alloy 8.
[0056] Therefore, when the concentration of copper ions in the
pickling solution 2 is greater than 60 g/L, the recovery of the
copper or copper-base alloy 8 is temporarily increased and the
concentration of copper ions in the pickling solution X is adjusted
to be less than or equal to 60 g/L by increasing the amount of the
pickling solution X, which is supplied to the electrolytic bath 5,
to increase the flow rate of the pickling solution X to the
electrolytic bath and increasing a current, which is applied to the
electrolytic bath 5, to increase the current density in the
electrolytic bath 5. When the concentration of copper ions in the
pickling solution X is less than 20 g/L, the recovery of the copper
or copper-base alloy 8 is temporarily deteriorated and the
concentration of copper ions in the pickling solution X is adjusted
to be greater than or equal to 20 g/L by reducing the amount of the
pickling solution X, which is supplied to the electrolytic bath 5,
to reduce the flow rate of the pickling solution X to the
electrolytic bath 5 and reducing a current, which is applied to the
electrolytic bath 5, to reduce the current density in the
electrolytic bath 5. Through this operation, stable electrolysis
can be continuously performed in the electrolytic bath 5. In this
case, when only the current density is changed, the precipitation
state of the recovered copper or copper-base alloy 8 easily
changes. Therefore, the flow rate is also changed at the same time
to control the thickness of a diffusion layer in the pickling
solution X, thereby promoting stable electrolysis without changing
the precipitation state of the recovered copper or copper-base
alloy 8 in the electrolytic bath 5.
[0057] In addition, as illustrated in FIG. 2, in order to
continuously measure the variable concentration of copper ions in
the pickling solution 2 using a detector 10 and make measured
values fall within a prescribed value range, it is more preferable
that the amount of the is pickling solution X supplied to the
electrolytic bath 5, be adjusted (the flow rate of the pickling
solution X in the electrolytic bath 5 be adjusted) with the pump P1
and that the current applied between the electrodes 6 and 7 through
a rectifier 9, which are connected to a power supply (not
illustrated) of the electrolyzes, be adjusted to adjust the current
density in the electrolytic bath 5, thereby automatically promoting
stable electrolysis in the electrolytic bath 5. In this case, in
order to continue more stable electrolysis, it is preferable that
the optimum prescribed value of the concentration of copper ions in
the pickling solution X be set to be 30 g/L to 40 g/L.
EXAMPLES
[0058] A plate of tough pitch copper (manufactured by Mitsubishi
Materials Corporation; Cu: 99.92%, O: 300 ppm, P: 0 ppm) having a
length of 500 mm, a width of 100 mm, and a thickness of 30 mm was
subjected to hot rolling (600.degree. C., roll reduction: 50%),
followed by rapid cooling. As a result, a tough pitch copper plate
having a thickness of 15 mm was prepared. On a surface of this
tough pitch copper plate, oxide film having a thickness of about
0.7 .mu.m was formed.
[0059] This tough pitch copper plate was dipped in a pickling bath
containing 1 m.sup.3 of pickling solution having a composition and
a surface tension shown in Table 1 at 40.degree. C. for 30 minutes
to be pickled and remove the oxide film. Then, a surface of the
tough pitch copper plate after the oxide film was removed was
visually inspected.
[0060] In Table 1, A represents nitric acid, B represents hydrogen
peroxide, C represents peroxodisulfate ion, D represents iron (III)
ion, E represents benzene sulfonic acid, F represents sodium
benzene sulfonic acid, G represents polyoxyethyleneamine, H
represents dodecylbenzene sulfonic acid, I represents sodium
dodecylbenzene sulfonic acid, J represents benzoic acid, and K
represents sodium benzoic acid. In Table 1, when two or more kinds
of is compounds are added, the compounds are denoted adjacently and
the concentrations thereof are denoted in the mentioned order.
[0061] The results are shown in Table 1. The results in which the
oxide film on a surface of the tough pitch copper plate was
completely removed and traces of gas adhesion were not observed are
indicated as "good". The result in which the oxide film was not
completely removed and traces of gas adhesion were observed are
indicated as "bad".
[0062] For reference, when a normal mixed acid (sulfuric
acid+nitric acid) was used as a pickling solution, the oxide film
was not removed until dipping was continued at 40.degree. C. for 70
minutes and the traces of gas adhesion were observed to a large
degree.
TABLE-US-00001 TABLE 1 Pickling Composition of Pickling Solution
Solution Surface of Sulfuric Oxidant Additive Surfactant Copper
Surface Copper Acid Kind Kind Kind Sulfate Tension After Oxide
(g/L) (g/L) (g/L) (g/L) (g/L) (.times.10.sup.-3 N/m) Film Removal
Example 1 50 B(45) G(0.09) H(0.005) 300 50 good 2 350 A(100) F,
G(2, 5) I(5) 104 45 good 3 75 B(60) E(0.01) I(0.01) 250 50 good 4
89 C(30) F(3.5) H, I(0.3, 0.5) 73 60 good 5 255 D(55) G(0.05)
H(0.09) 220 10 good 6 370 A, C(30, 30) E, F(5, 5) H, I(0.7, 5.5) 65
35 good 7 55 B, D(20, 50) E(8.5) I(10) 10 32 good 8 400 B(1) G,
F(0.1, 0.5) H(4) 55 14 good 9 370 B, D(20, 50) J(4) H, I(0.3, 0.5)
55 15 good 10 75 A(100) K(5) H(0.09) 180 55 good Comparative 450
A(0.5) E(11) H(0.003) 310 60 bad Example 1 2 40 B(110) G(0.008)
H(12) 100 50 bad 3 350 C(110) F(0.008) H, I(5, 6) 310 75 bad 4 45
D(0.8) E(12) H(0.004) 6 65 bad 5 420 A, C(0.2, 0.2) G(11) I(0.004)
8 65 bad
[0063] Next, the total amount of the pickling solution containing
the removed oxide film which had the composition shown in Table 1
was poured into an electrolytic bath. By using a tough pitch copper
plate as a cathode and using an iridium oxide coated titanium plate
as an anode, electrolysis was performed for 8 hours under
conditions of a temperature of 40.degree. C., a current density of
5 A/dm.sup.2, a distance between the electrodes of 50 mm, and a
flow rate of 0.5 m/min. As a result, copper, derived from the oxide
film, was deposited on the cathode in a plate shape. This
plate-like copper was collected from the electrolytic bath to
measure the average surface roughness Ra, the purity of copper, and
the hardness of the surface. Furthermore, this plate-like copper
was pickled with sulfuric acid aqueous solution, followed by
melting and casting to obtain an ingot. This ingot was heated at
600.degree. C. to be molded into a bar through extrusion, and the
content of sulfur (content of S) and whether there were cracks or
not were visually inspected.
(1) The surface roughness Ra of the surface of the copper plate was
measured using an SPM (manufactured by SIT NanoTechnology Inc.).
(2) The hardness of the surface of the copper plate was measured
using a MVK-G1 (manufactured by Akashi K.K.) according to Vickers
hardness test (JIS Z 2244, N=3). (3) The purity of the copper plate
was measured by measuring impurities included in copper and
subtracting the content of the impurities from 100%. (4) Impurities
other than C were measured using Glow Discharge Mass Spectrometry
(GD-MS) and C was measured by measuring the infrared absorption of
CO.sub.2 gas, which was generated after combustion of a degreased
copper sample in a high-frequency induction furnace in an oxygen
atmosphere, to be converted to an amount of C. (5) The content of S
was measured by measuring the content of S in the ingot with
infrared absorption spectrometry.
[0064] The results are shown in Table 2. It can be seen from these
results that, in the plate-like coppers of Examples, a high purity,
an appropriate hardness, and superior handleability were exhibited;
there was little effect caused by S, included in the pickling
solution, in the next pickling process; bars obtained by melting,
casting, and extruding the plate-like coppers had a lower content
of S; and there were no cracks.
TABLE-US-00002 TABLE 2 Characteristics of Treatment for Recovered
Copper Plate Extruded Bar Surface Purity of Surface Content
Hardness Copper Ra of S (HV) (Mass %) (mm) (ppm) Cracks Example 1
87.6 99.92 0.16 10 None 2 85.2 99.92 1.21 5 None 3 85.3 99.91 0.55
7 None 4 80.6 99.92 2.55 23 None 5 89.3 99.90 1.45 8 None 6 84.2
99.91 1.65 15 None 7 85.7 99.92 0.87 12 None 8 85.3 99.91 1.87 11
None 9 87.2 99.92 2.32 12 None 10 85.9 99.91 1.45 18 None Compar-
66.2 99.80 3.67 145 Observed ative Example 1 2 Non- 99.92 5.5 85
Observed measurable 3 65.2 99.91 Non- 42 Observed measurable 4 Non-
99.92 Non- 64 Observed measurable measurable 5 69.3 99.81 6.55 115
Observed
[0065] Next, the total amount of the pickling solution containing
the removed oxide film which had the composition of Example 4 was
poured into an electrolytic bath. By using a rotating cylindrical
tough pitch copper bar as a cathode and using an iridium oxide
coated titanium plate as an anode, electrolysis was performed under
conditions of a distance between the electrodes of 50 mm, a flow
rate of 0.5 m/min, and a temperature of 40.degree. C.; and a
concentration of copper ions, a current density and a peripheral
speed of the rotating cathode shown in Table 3. A time was measured
which was taken to deposit the same amount of copper on the cathode
as that of a case where a tough pitch copper plate was used in the
pickling solution having the above-described composition of Example
4 (where electrolysis was performed for 8 hours under conditions of
a temperature of 40.degree. C., a current density of 5 A/dm.sup.2,
a distance between the electrodes of 50 mm, and a flow rate of 0.5
m/min).
[0066] Furthermore, this cylindrical copper was collected from the
electrolytic bath to measure the average surface roughness Ra, the
purity of copper, and the hardness of the surface. Then, the
cylindrical copper was pickled with sulfuric acid aqueous solution,
was heated at 600.degree. C. and was molded into a bar through
extrusion. In the bar, the content of sulfur (content of S) and
whether there were cracks or not were visually inspected.
(1) The surface roughness Ra of the surface of the copper bar was
measured using a SPM (manufactured by SII NanoTechnology Inc.). (2)
The hardness of the surface of the copper bar was measured using a
MVK-G1 (manufactured by Akashi K.K.) according to Vickers hardness
test (JIS Z 2244, N=3). (3) The purity of the copper bar was
measured by measuring impurities included in copper and subtracting
the content of the impurities from 100%. (4) Impurities other than
C were measured using Glow Discharge Mass Spectrometry (GD-MS) and
C was measured by measuring the infrared absorption of CO.sub.2
gas, which was generated after combustion of a degreased copper
sample in a high-frequency induction furnace in an oxygen
atmosphere, to be converted to an amount of C. (5) The content of S
was measured with infrared absorption spectrometry.
[0067] The results are shown in Table 3. It can be seen from these
results that 8 hours was required for electrolysis in the case of
Example 4 where the tough pitch copper plate was used, whereas in
Examples 41 to 45, 2.8 hours to 4.2 hours was required to obtain
the tough pitch copper bars which have almost the same results as
those of the bars obtained in the case of using the tough pitch
copper plate.
TABLE-US-00003 TABLE 3 Characteristics of Recovered Treatment for
Electrolysis Conditions Copper Bar Extruded Bar Concentration
Current Peripheral Required Surface Purity of Surface Content of
Copper ions Density Speed of Time Hardness Copper Roughness of S
(g/L) (A/dm.sup.2) Cathode (m/s) (hr) (HV) (Mass %) Ra (mm) (ppm)
Cracks Example 41 20 5 0.12 4.2 80.6 99.90 2.55 8 None 42 40 1 0.35
3.5 85.3 99.92 0.88 15 None 43 60 20 0.08 3.8 87.6 99.91 1.12 21
None 44 30 25 0.22 2.8 84.1 99.92 0.16 17 None 45 50 15 0.48 3.2
83.5 99.91 1.88 23 None Comparative 70 30 0.06 7.8 80.6 99.92 0.35
14 None Example 41 42 15 0.8 0.55 7.9 84.1 99.90 2.33 22 None
[0068] Next, the electrolyzed pickling solution was analyzed to add
an oxidant, an additive, and a surfactant (total amount: 0.002 g)
to the pickling solution in amounts equivalent to the consumed
amounts. The total amount of the pickling solution was poured again
into the pickling bath to be used as a pickling solution in the
next process. Oxide films of other tough pitch copper were removed
in the same manner as those of Examples 1 to 8 and 41 to 45. These
processes were further repeated twice. The respective results of
the fourth test of removing the oxide film are shown in Table 4.
Accordingly, it could be seen that the results of the fourth test
were the same as those of the first test.
TABLE-US-00004 TABLE 4 Surface of Characteristics of Recovered
Copper Copper Plate or Copper Bar Treatment for After Surface
Purity Surface Extruded Bar Oxide Hard- of Rough- Content Film ness
Copper ness of S Removal (HV) (Mass %) Ra (mm) (ppm) Cracks Exam-
good 85.3 99.92 0.18 6 None ple 1 2 good 85.2 99.92 1.21 11 None 3
good 85.8 99.91 0.36 7 None 4 good 80.6 99.92 2.55 23 None 5 good
89.3 99.90 1.45 11 None 6 good 89.4 99.91 1.57 14 None 7 good 85.7
99.92 0.75 12 None 8 good 85.2 99.92 1.45 14 None 41 good 89.3
99.92 2.43 8 None 42 good 89.4 99.91 1.45 14 None 43 good 80.5
99.92 0.38 19 None 44 good 81.4 99.91 1.25 14 None 45 good 83.7
99.90 2.05 23 None
[0069] In addition, the pickling solution of Example 1 was
circulated and oxide films of plural tough pitch copper plates were
continuously and sequentially removed for 150 hours. The thickness
of these tough pitch copper plates was 5 mm, and oxide films having
is thicknesses of about 0.4 .mu.m to 0.9 .mu.m were formed on
surfaces thereof. During the continuous removal of the oxide films,
temporarily, the maximum concentration of copper ions was 80 g/L
and the minimum concentration thereof was 15 g/L in the pickling
solution of the pickling bath. However, stable electrolysis was
continued in the electrolytic bath and the characteristics of the
recovered copper plates or copper bars are the same as those of
Example 1, by setting the prescribed value of concentration of
copper ions to 35 g/L and automatically adjusting the flow rate of
the pump and the current, applied to the rectifier, based on values
of concentration of copper ions determined by the detector.
[0070] It can be seen from these results that, when a copper or
copper-base alloy, which is obtained and recovered with the method
of removing oxide film on a surface of a copper or copper-base
alloy according to the present invention, is used, a high-purity
copper or copper-base alloy, capable of being used as a recycled
material having superior handleability, can be efficiently
recovered; and that the pickling solution according to the present
invention can be appropriately reused in a pickling bath by adding
the oxidant, the additive, and the surfactant thereto in amounts
equivalent to the consumed amounts.
[0071] The present invention is not limited to the above-described
embodiments, and various modifications can be made within a range
not departing from the concepts of the present invention.
[0072] According to the present invention, after a copper or
copper-base alloy having oxide film formed on a surface thereof is
dipped in a pickling bath to remove the oxide film, a pickling
solution containing the oxide film is electrolyzed in an
electrolytic bath so as to recover a high-purity copper or
copper-base alloy having superior handleability and to return the
electrolyzed pickling solution to the pickling bath for reuse.
* * * * *