U.S. patent application number 13/823366 was filed with the patent office on 2013-08-15 for steel sheet for containers and manufacturing method for same.
This patent application is currently assigned to JFE STEEL CORPORATION. The applicant listed for this patent is Yuka Miyamoto, Norihiko Nakamura, Takeshi Suzuki, Yoichi Tobiyama. Invention is credited to Yuka Miyamoto, Norihiko Nakamura, Takeshi Suzuki, Yoichi Tobiyama.
Application Number | 20130209830 13/823366 |
Document ID | / |
Family ID | 45831655 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130209830 |
Kind Code |
A1 |
Suzuki; Takeshi ; et
al. |
August 15, 2013 |
STEEL SHEET FOR CONTAINERS AND MANUFACTURING METHOD FOR SAME
Abstract
A manufacturing method for steel sheets for containers produces
steel sheets with excellent film adhesion qualities. This steel
sheet for containers has, on a steel sheet, a chemical conversion
coating with a metal Zr content of 1-100 mg/m.sup.2, a P content of
0.1-50 mg/m.sup.2, and an F content of no more than 0.1 mg/m.sup.2,
upon which is formed a phenolic resin layer with a C content of
0.1-50 mg/m.sup.2. Moreover, the manufacturing method for steel
sheets for containers is a method for obtaining the steel sheet for
containers wherein the chemical conversion coating is formed on the
steel sheet by subjecting the steel sheet to immersion in or
electrolytic treatment with a treatment solution containing Zr
ions, phosphoric acid ions, and F ions; and subsequently, the steel
sheet upon which the chemical conversion coating has been formed is
immersed in, or undergoes topical application of, an aqueous
solution containing phenolic resin, then dried.
Inventors: |
Suzuki; Takeshi; (Chiba,
JP) ; Nakamura; Norihiko; (Chiba, JP) ;
Miyamoto; Yuka; (Kanagawa, JP) ; Tobiyama;
Yoichi; (Okayama, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Suzuki; Takeshi
Nakamura; Norihiko
Miyamoto; Yuka
Tobiyama; Yoichi |
Chiba
Chiba
Kanagawa
Okayama |
|
JP
JP
JP
JP |
|
|
Assignee: |
JFE STEEL CORPORATION
Tokyo
JP
|
Family ID: |
45831655 |
Appl. No.: |
13/823366 |
Filed: |
September 14, 2011 |
PCT Filed: |
September 14, 2011 |
PCT NO: |
PCT/JP2011/070980 |
371 Date: |
April 26, 2013 |
Current U.S.
Class: |
428/626 ;
148/257; 148/261; 205/196 |
Current CPC
Class: |
C23C 22/05 20130101;
C23C 22/62 20130101; C23C 22/77 20130101; C21D 8/0205 20130101;
C21D 8/0236 20130101; C23C 22/73 20130101; C23C 28/34 20130101;
B32B 15/18 20130101; C23C 22/07 20130101; C23C 22/82 20130101; C23C
28/00 20130101; B32B 1/08 20130101; C23C 22/78 20130101; B32B
2255/205 20130101; C25D 11/34 20130101; C23C 28/3455 20130101; C23C
22/34 20130101; Y10T 428/12569 20150115; C23C 22/36 20130101; B32B
2255/28 20130101; B32B 2250/40 20130101; C25D 5/48 20130101; B32B
2250/03 20130101; C23C 22/83 20130101; C23C 28/321 20130101; C21D
8/0278 20130101; C23C 22/00 20130101; B32B 2255/26 20130101; C25D
5/505 20130101; C23C 22/361 20130101; C21D 8/0263 20130101; C23C
10/28 20130101; C21D 9/46 20130101; C25D 5/36 20130101; B32B 15/09
20130101; C21D 8/0226 20130101; B32B 2439/66 20130101; C23C 28/325
20130101; B32B 2255/06 20130101; C25D 5/12 20130101; C23C 28/322
20130101 |
Class at
Publication: |
428/626 ;
148/261; 148/257; 205/196 |
International
Class: |
C23C 22/82 20060101
C23C022/82; C23C 28/00 20060101 C23C028/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 15, 2010 |
JP |
2010-207347 |
Claims
1. A steel sheet for containers, having a chemical conversion
coating formed on the steel sheet and containing 1 to 100
mg/m.sup.2 of zirconium metal, 0.1 to 50 mg/m.sup.2 of phosphorus
and up to 0.1 mg/m.sup.2 of fluorine; and having a phenolic resin
layer formed on the chemical conversion coating and containing 0.1
to 50 mg/m.sup.2 of carbon.
2. The steel sheet for containers according to claim 1, wherein the
steel sheet for containers is obtained by forming the chemical
conversion coating on the steel sheet by subjecting the steel sheet
to immersion in a treatment solution containing zirconium ions,
phosphate ions and fluorine ions or to electrolytic treatment using
the treatment solution; then immersing the steel sheet having the
chemical conversion coating formed thereon in an aqueous solution
containing a phenolic resin or applying the aqueous solution onto
the chemical conversion coating; and then drying the steel
sheet.
3. The steel sheet for containers according to claim 1, wherein the
steel sheet has a surface-treatment layer formed on at least one
side of the steel sheet and containing 10 to 1,000 mg/m.sup.2 of
nickel in terms of nickel metal amount or 100 to 15,000 mg/m.sup.2
of tin in terms of tin metal amount.
4. The steel sheet for containers according to claim 1, wherein a
surface of the steel sheet is plated with nickel or an iron-nickel
alloy to form a nickel undercoat layer, a tin-plating coating is
then provided on the nickel undercoat layer, and part of the
tin-plating coating is alloyed with part or all of the nickel
undercoat layer by tin melting treatment to form a tin-plating
layer containing tin islands, wherein the nickel undercoat layer
contains 5 to 150 mg/m.sup.2 of nickel in terms of nickel metal
amount, and wherein the tin-plating layer contains 300 to 3,000
mg/m.sup.2 of tin in terms of tin metal amount.
5. A method of manufacturing a steel sheet for containers for
obtaining the steel sheet for containers according to claim 1,
comprising: forming the chemical conversion coating on the steel
sheet by subjecting the steel sheet to immersion in a treatment
solution containing zirconium ions, phosphate ions and fluorine
ions or to electrolytic treatment using the treatment solution;
then immersing the steel sheet having the chemical conversion
coating formed thereon in an aqueous solution containing a phenolic
resin or applying the aqueous solution onto the chemical conversion
coating; and then drying the steel sheet.
6. The method of manufacturing a steel sheet for containers
according to claim 5, wherein a temperature for the drying is
70.degree. C. or more.
7. The method of manufacturing a steel sheet for containers
according to claim 5, wherein the drying is followed by washing
with water at a temperature of 80.degree. C. or more and
redrying.
8. The steel sheet for containers according to claim 2, wherein the
steel sheet has a surface-treatment layer formed on at least one
side of the steel sheet and containing 10 to 1,000 mg/m.sup.2 of
nickel in terms of nickel metal amount or 100 to 15,000 mg/m.sup.2
of tin in terms of tin metal amount.
9. The steel sheet for containers according to claim 2, wherein a
surface of the steel sheet is plated with nickel or an iron-nickel
alloy to form a nickel undercoat layer, a tin-plating coating is
then provided on the nickel undercoat layer, and part of the
tin-plating coating is alloyed with part or all of the nickel
undercoat layer by tin melting treatment to form a tin-plating
layer containing tin islands, wherein the nickel undercoat layer
contains 5 to 150 mg/m.sup.2 of nickel in terms of nickel metal
amount, and wherein the tin-plating layer contains 300 to 3,000
mg/m.sup.2 of tin in terms of tin metal amount.
10. A method of manufacturing a steel sheet for containers for
obtaining the steel sheet for containers according to claim 2,
comprising: forming the chemical conversion coating on the steel
sheet by subjecting the steel sheet to immersion in a treatment
solution containing zirconium ions, phosphate ions and fluorine
ions or to electrolytic treatment using the treatment solution;
then immersing the steel sheet having the chemical conversion
coating formed thereon in an aqueous solution containing a phenolic
resin or applying the aqueous solution onto the chemical conversion
coating; and then drying the steel sheet.
11. A method of manufacturing a steel sheet for containers for
obtaining the steel sheet for containers according to claim 3,
comprising: forming the chemical conversion coating on the steel
sheet by subjecting the steel sheet to immersion in a treatment
solution containing zirconium ions, phosphate ions and fluorine
ions or to electrolytic treatment using the treatment solution;
then immersing the steel sheet having the chemical conversion
coating formed thereon in an aqueous solution containing a phenolic
resin or applying the aqueous solution onto the chemical conversion
coating; and then drying the steel sheet.
12. A method of manufacturing a steel sheet for containers for
obtaining the steel sheet for containers according to claim 4,
comprising: forming the chemical conversion coating on the steel
sheet by subjecting the steel sheet to immersion in a treatment
solution containing zirconium ions, phosphate ions and fluorine
ions or to electrolytic treatment using the treatment solution;
then immersing the steel sheet having the chemical conversion
coating formed thereon in an aqueous solution containing a phenolic
resin or applying the aqueous solution onto the chemical conversion
coating; and then drying the steel sheet.
13. A method of manufacturing a steel sheet for containers for
obtaining the steel sheet for containers according to claim 8,
comprising: forming the chemical conversion coating on the steel
sheet by subjecting the steel sheet to immersion in a treatment
solution containing zirconium ions, phosphate ions and fluorine
ions or to electrolytic treatment using the treatment solution;
then immersing the steel sheet having the chemical conversion
coating formed thereon in an aqueous solution containing a phenolic
resin or applying the aqueous solution onto the chemical conversion
coating; and then drying the steel sheet.
14. A method of manufacturing a steel sheet for containers for
obtaining the steel sheet for containers according to claim 9,
comprising: forming the chemical conversion coating on the steel
sheet by subjecting the steel sheet to immersion in a treatment
solution containing zirconium ions, phosphate ions and fluorine
ions or to electrolytic treatment using the treatment solution;
then immersing the steel sheet having the chemical conversion
coating formed thereon in an aqueous solution containing a phenolic
resin or applying the aqueous solution onto the chemical conversion
coating; and then drying the steel sheet.
Description
TECHNICAL FIELD
[0001] The present invention relates to a steel sheet for
containers and a method of manufacturing the same.
BACKGROUND ART
[0002] In any type of can, steel sheets for use in cans (steel
sheets for containers) have conventionally been coated but in
recent years a film lamination technique has drawn attention as a
technique to replace coating and has spread rapidly from the
viewpoint of global environmental protection.
[0003] A chromate coating has conventionally been formed on a steel
sheet for use in the undercoat of a laminated film but recently
there have started to be calls for restrictions to be imposed on
the use of hazardous substances such as lead and cadmium and for
attention to be paid to the working environment of manufacturing
plants and there have been requests to stop the use of a chromate
coating.
[0004] In the beverage container market, cans face competition from
containers such as PET bottles, bottles and drink boxes in terms of
cost and quality, and steel sheets for laminated containers are
also required to have more excellent formability in can manufacture
(in particular, in terms of film adhesion, formed film adhesion,
corrosion resistance).
[0005] For example, Patent Literature 1 discloses, as a steel sheet
meeting such requirements, a steel sheet for containers having a
zirconium compound coating formed on the steel sheet by subjecting
the steel sheet to immersion or electrolytic treatment in a
solution containing zirconium ions, fluorine ions, ammonium ions
and nitrate ions, the coating weight of the zirconium compound
coating being 1 to 100 mg/m.sup.2 in terms of zirconium metal
content and up to 0.1 mg/m.sup.2 in terms of fluorine content
([Claim 1]).
CITATION LIST
Patent Literature
[0006] Patent Literature 1: JP 2010-13728 A
SUMMARY OF INVENTION
Technical Problems
[0007] As described above, competition in terms of quality has been
increasing recently in the beverage container market and steel
sheets for laminated containers are also required to have more
excellent film adhesion. In particular, the film in the neck
portion of a can formed after necking is generally prone to coming
off and therefore a steel sheet for containers in which
delamination does not occur in the neck portion even under severe
conditions has been desired.
[0008] The inventors of the invention have conducted studies on
film adhesion in the neck portion (hereinafter also referred to as
"high film adhesion") using the steel sheet for containers as
disclosed in Patent Literature 1 and found that the film adhesion
does not reach the level now required and an improvement is
necessary.
[0009] Accordingly, the present invention aims to provide a steel
sheet for containers which is excellent in terms of high film
adhesion and aims to provide a method of manufacturing the
same.
Solution to Problems
[0010] The inventors of the invention carried out intensive studies
to solve the above-described problems and as a result found that a
steel sheet for containers obtained by forming a specified chemical
conversion coating on a steel sheet and forming a specified
phenolic resin layer on the chemical conversion coating is
excellent in terms of high film adhesion and the invention has been
thus completed.
[0011] Specifically, the invention provides the following (1) to
(7).
[0012] (1) A steel sheet for containers, having a chemical
conversion coating formed on the steel sheet and containing 1 to
100 mg/m.sup.2 of zirconium metal, 0.1 to 50 mg/m.sup.2 of
phosphorus and up to 0.1 mg/m.sup.2 of fluorine; and a phenolic
resin layer formed on the chemical conversion coating and
containing 0.1 to 50 mg/m.sup.2 of carbon.
[0013] (2) The steel sheet for containers according to (1) above,
wherein the steel sheet for containers is obtained by forming the
chemical conversion coating on the steel sheet by subjecting the
steel sheet to immersion in a treatment solution containing
zirconium ions, phosphate ions and fluorine ions or to electrolytic
treatment using the treatment solution; then immersing the steel
sheet having the chemical conversion coating formed thereon in an
aqueous solution containing a phenolic resin or applying the
aqueous solution onto the chemical conversion coating; and then
drying the steel sheet.
[0014] (3) The steel sheet for containers according to (1) or (2)
above, wherein the steel sheet has a surface-treatment layer formed
on at least one side of the steel sheet and containing 10 to 1,000
mg/m.sup.2 of nickel in terms of nickel metal amount or 100 to
15,000 mg/m.sup.2 of tin in terms of tin metal amount.
[0015] (4) The steel sheet for containers according to (1) or (2)
above, wherein a surface of the steel sheet is plated with nickel
or an iron-nickel alloy to form a nickel undercoat layer, a
tin-plating coating is then provided on the nickel undercoat layer,
and part of the tin-plating coating is alloyed with part or all of
the nickel undercoat layer by tin melting treatment to form a
tin-plating layer containing tin islands, wherein the nickel
undercoat layer contains 5 to 150 mg/m.sup.2 of nickel in terms of
nickel metal amount, and wherein the tin-plating layer contains 300
to 3,000 mg/m.sup.2 of tin in terms of tin metal amount.
[0016] (5) A method of manufacturing a steel sheet for containers
for obtaining the steel sheet for containers according to any one
of (1) to (4) above, comprising: forming the chemical conversion
coating on the steel sheet by subjecting the steel sheet to
immersion in a treatment solution containing zirconium ions,
phosphate ions and fluorine ions or to electrolytic treatment using
the treatment solution; then immersing the steel sheet having the
chemical conversion coating formed thereon in an aqueous solution
containing a phenolic resin or applying the aqueous solution onto
the chemical conversion coating; and then drying the steel
sheet.
[0017] (6) The method of manufacturing the steel sheet for
containers according to (5) above, wherein a temperature for the
drying is 70.degree. C. or more.
[0018] (7) The method of manufacturing the steel sheet for
containers according to (5) or (6) above, wherein the drying is
followed by washing with water at a temperature of 80.degree. C. or
more and redrying.
Advantageous Effects of Invention
[0019] The invention can provide a steel sheet for containers which
is excellent in terms of high film adhesion and a method of
manufacturing the same.
DESCRIPTION OF EMBODIMENTS
[Steel Sheet for Containers]
[0020] The steel sheet for containers according to the invention is
a steel sheet including a chemical conversion coating formed on the
steel sheet and containing 1 to 100 mg/m.sup.2 of zirconium metal,
0.1 to 50 mg/m.sup.2 of phosphorus and up to 0.1 mg/m.sup.2 of
fluorine, and a phenolic resin layer formed on the chemical
conversion coating and containing 0.1 to 50 mg/m.sup.2 of
carbon.
[0021] The structure of the steel sheet for containers according to
the invention is described below in detail.
[0022] [Steel Sheet]
[0023] A steel sheet that may be used in the invention is not
particularly limited and base steel sheets for use as container
materials can be generally used. There are also no particular
limitations on the method of manufacturing the base steel sheets
and the type of material, and use may be made of base steel sheets
obtained through manufacturing steps including an ordinary billet
forming step, hot rolling, pickling, cold rolling, annealing and
temper rolling.
[0024] The steel sheet for use in the invention may have a
surface-treatment layer formed on at least one side thereof and
containing nickel (Ni) and/or tin (Sn).
[0025] Such a surface-treatment layer is, for example, a
nickel-plating layer, a tin-plating layer or a tin-nickel-alloy
plating layer.
[0026] Nickel affects, for example, coating adhesion, film
adhesion, corrosion resistance and weldability. The nickel metal
content in the surface-treatment layer is preferably from 10 to
1,000 mg/m.sup.2 for the reason that these properties are more
excellent when the nickel metal content is within this range and
from an economic point of view.
[0027] Tin affects, for example, formability, weldability and
corrosion resistance. With regard to this, the tin metal content in
the surface-treatment layer is preferably from 100 to 15,000
mg/m.sup.2 for the reason that these properties are more excellent
when the tin metal content is within this range and from an
economic point of view, preferably from 200 to 15,000 mg/m.sup.2
because of more excellent weldability, and more preferably from
1,000 to 15,000 mg/mr because of more excellent formability.
[0028] The method for forming the surface-treatment layer (plating
layer) is not particularly limited. For example, known methods
including electroplating, immersion plating, vacuum deposition and
sputtering can be used and heating treatment may also be combined
to form a diffusion layer.
[0029] The nickel-plating layer may be a layer formed by nickel
metal plating or an iron-nickel-alloy plating layer formed by iron
(Fe)-nickel (Ni) alloy plating.
[0030] The tin-plating layer is formed by tin metal plating (tin
plating) but the tin plating as used in the invention includes
cases where irreversible impurities are incorporated in the tin
metal and cases where trace elements are added to the tin
metal.
[0031] In the practice of the invention, a tin-plating layer
containing tin islands may be formed. In this case, the surface of
the steel sheet is plated with nickel or an iron-nickel alloy to
form a nickel undercoat layer, on which is then provided a
tin-plating coating, and part of the tin-plating coating is alloyed
with part or all of the nickel undercoat layer by tin melting
treatment to form the tin-plating layer containing tin islands.
[0032] Tin is melted by the tin melting treatment (reflow
treatment) and alloyed with the steel sheet or the nickel undercoat
layer to form a tin-iron-alloy layer or a tin-iron-nickel-alloy
layer, whereby the alloy layer has improved corrosion resistance
and tin alloy islands are formed. The tin alloy islands can be
formed by properly controlling the tin melting treatment.
[0033] Since nickel is a metal which is highly resistant to
corrosion, the iron- and tin-containing alloy layer formed by the
tin melting treatment can have improved corrosion resistance.
[0034] The nickel undercoat layer preferably contains 5 to 150
mg/m.sup.2 of nickel metal from the viewpoint of realizing the
corrosion resistance and from an economic point of view.
[0035] In cases where heating treatment is performed to form a
diffusion layer as the nickel undercoat layer, nitriding treatment
may he performed before or after the heating treatment or
simultaneously therewith.
[0036] The excellent corrosion resistance of tin is significantly
improved at a tin metal content of 300 mg/m.sup.2 or more and the
degree of improvement of the corrosion resistance is also increased
with increasing tin content. Therefore, the tin metal content in
the tin-island-containing tin-plating layer is preferably 300
mg/m.sup.2 or more. In addition, the corrosion-resistance-improving
effect becomes saturated at a tin metal content exceeding 3,000
mg/m.sup.2 and hence the tin content is preferably up to 3,000
mg/m.sup.2 from an economic point of view.
[0037] Tin, which has low electric resistance, is flexible and is
spread by application of voltage between electrodes during welding
to ensure a stable electric conduction area, and hence exhibits
particularly excellent weldability. The excellent weldability is
exhibited at a tin metal content of 100 mg/m.sup.2 or more. The
weldability-improving effect does not become saturated at a tin
metal content within a range in which the excellent corrosion
resistance as described above is exhibited. Therefore, the tin
metal content is preferably at least 300 mg/m.sup.2 but not more
than 3,000 mg/ m.sup.2 in order to ensure that the steel sheet has
excellent corrosion resistance and weldability.
[0038] The nickel metal content or the tin metal content in the
surface-treatment layer may be measured by, for example, a
fluorescent X-ray method. In this case, a nickel deposition amount
sample in which the nickel metal content is known is used to
specify the calibration curve for the nickel metal content in
advance and the calibration curve is used to relatively specify the
nickel metal content. The same applies to the tin metal content,
and a tin deposition amount sample in which the tin metal content
is known is used to specify the calibration curve for the tin metal
content in advance and the calibration curve is used to relatively
specify the tin metal content.
[Chemical Conversion Coating]
[0039] The steel sheet for containers according to the invention
includes a chemical conversion coating formed on the
above-described steel sheet and containing 1 to 100 mg/m.sup.2 of
zirconium metal, 0.1 to 50 mg/m.sup.2 of phosphorus and up to 0.1
mg/m.sup.2 of fluorine.
[0040] Exemplary methods for forming the chemical conversion
coating include a method involving immersion treatment in which a
steel sheet is immersed in a treatment solution (acidic solution)
containing zirconium ions, phosphate ions and fluorine ions
dissolved therein; and a method involving cathodic electrolytic
treatment in a treatment solution containing zirconium ions,
phosphate ions and fluorine ions. A method involving cathodic
electrolytic treatment is preferable because a uniform coating can
be obtained.
[0041] In addition, particularly in the cathodic electrolytic
treatment, the treatment solution preferably contains both nitrate
ions and ammonium ions. This makes it possible to perform the
treatment in a short period of time from about a few seconds to
about several tens of seconds and to form a chemical conversion
coating having an excellent effect in improving the corrosion
resistance and adhesion.
[0042] In cases where the cathodic electrolytic treatment is
performed, the cell temperature in the cathodic electrolytic
treatment is preferably from 10 to 40.degree. C. from such
viewpoints as efficiency in coating formation, cost and uniformity
in the structure of the formed coating (cathodic electrolytic
treatment at low temperatures). The electrolytic current density in
the cathodic electrolytic treatment is preferably from 0.05 to 50
A/dm.sup.2 from the viewpoint of suppression of a decrease in
coating weight, stable coating formation, treatment time and
suppression of a decrease in coating characteristics. In addition,
the current flow time in the cathodic electrolytic treatment is
preferably from 0.01 to 5 seconds from the viewpoint of suppression
of decrease in coating weight, stable coating formation, treatment
time and suppression of a decrease in coating characteristics.
[0043] The chemical conversion coating contains a zirconium
compound. The zirconium compound serves to secure the corrosion
resistance and adhesion. Examples of the zirconium compound are
considered to include a zirconium hydrous oxide and a
zirconium-phosphorus oxide and these zirconium compounds have
excellent corrosion resistance and adhesion. "Zirconium hydrous
oxide" refers to a compound formed by mixing zirconium oxide and
zirconium hydroxide together.
[0044] The chemical conversion coating containing at least 1
mg/m.sup.2 of zirconium metal ensures that the corrosion resistance
and adhesion are at levels causing no practical problem. At a
zirconium metal content in excess of 100 mg/m.sup.2, the adhesion
of the chemical conversion coating itself is deteriorated and the
electric resistance is increased, which deteriorates the
weldability. Therefore, the zirconium metal content in the chemical
conversion coating is from 1 to 100 mg/m.sup.2, preferably from 1
to 20 mg/m.sup.2 and more preferably from 1 to 10 mg/m.sup.2.
[0045] More excellent corrosion resistance and adhesion are
achieved with increasing content of the zirconium-phosphorus oxide
but this effect can be clearly recognized when the phosphorus
content is at least 0.1 mg/m.sup.2. At a phosphorus content in
excess of 50 mg/m.sup.2, the adhesion is deteriorated and the
electric resistance is increased, which deteriorates the
weldability. Therefore, the phosphorus content in the chemical
conversion coating is from 0.1 to 50 mg/m.sup.2, preferably from
0.1 to 20 mg/m.sup.2 and more preferably from 0.1 to 10
mg/m.sup.2.
[0046] Fluorine is included in the treatment solution and is hence
incorporated in the coating together with the zirconium compound.
Fluorine in the coating does riot affect the adhesion of a coating
material or a film at a general level but may deteriorate the
adhesion upon performance of retort treatment or other
high-temperature sterilization treatments and may deteriorate
resistance to rusting or corrosion under the coated film. This is
presumably because fluorine in the coating leaches out into water
vapor or an etching solution and decomposes the bonds with an
organic coating or corrodes the underlying steel sheet.
[0047] The fluorine content in the chemical conversion coating is
up to 0.1 mg/m.sup.2 because these properties obviously begin to
deteriorate at a fluorine content in excess of 0.1 mg/m.sup.2.
[0048] In order to adjust the fluorine content in the chemical
conversion coating to 0.1 mg/m.sup.2 or less, formation of the
chemical conversion coating should be followed by cleaning through
immersion in hot water or spraying. In this process, the fluorine
content can be reduced by increasing the treatment temperature or
the treatment time.
[0049] For example, the fluorine content in the chemical conversion
coating can be adjusted to 0.1 mg/m.sup.2 or less by immersion in
hot water at 40.degree. C. or more for at least 0.5 seconds or
spraying.
[0050] The zirconium metal content, phosphorus content and fluorine
content in the chemical conversion coating can be measured by, for
example, a quantitative analysis method such as fluorescent X-ray
analysis.
[0051] The ammonium ion concentration and the nitrate ion
concentration in the treatment solution may be appropriately
adjusted in accordance with the production equipment and the
production rate (capacity) in ranges of about 100 to about 10,000
ppm and about 1,000 to about 20,000 ppm, respectively.
[Phenolic Resin Layer]
[0052] The steel sheet for containers according to the invention
includes a phenolic resin layer formed on the chemical conversion
coating and containing a phenolic resin.
[0053] The phenolic resin contains as a constituent, for example, a
water-soluble phenolic resin modified with N,N-diethanolamine.
[0054] Since the phenolic resin itself is an organic substance, the
steel sheet for containers of the invention, which includes the
phenolic resin layer, has exceptionally good adhesion to the
laminated film.
[0055] On the one hand, carbon content in the phenolic resin layer
of less than 0.1 mg/m.sup.2 does not ensure adhesion at a practical
level. On the other hand, at a carbon content in excess of 50
mg/m.sup.2, the electric resistance may be increased, which would
deteriorate the weldability and cohesion failure in the phenolic
resin layer may reduce the adhesion.
[0056] In contrast, a carbon content of 0.1 to 50 mg/m.sup.2
ensures adhesion at a level causing no practical problem and also
suppresses the increase of electric resistance. Therefore, the
carbon content in the phenolic resin layer is from 0.1 to 50
mg/m.sup.2, preferably from 0.1 to 10 mg/m.sup.2 and more
preferably from 0.1 to 8 mg/m.sup.2.
[0057] The carbon content in the phenolic resin layer can be
measured by subtracting the amount of carbon present in the steel
sheet using a TOC (total organic carbon meter).
[0058] The method of forming the phenolic resin layer is not
particularly limited and examples thereof include a method which
includes immersing a steel sheet having a chemical conversion
coating formed thereon in a phenolic resin-containing aqueous
solution and drying; and a method which includes applying a
phenolic resin-containing aqueous solution to a chemical conversion
coating formed on a steel sheet and drying.
[0059] In the case of immersion, the immersion time is not
particularly limited and is preferably at least 1 second.
[0060] In any of the methods, the drying temperature is preferably
70.degree. C. or more.
[Cleaning]
[0061] In the practice of the invention, for the reason that the
steel sheet for containers is more excellent in terms of high film
adhesion, the steel sheet for containers as obtained after the
formation of the phenolic resin layer may be washed with water and
preferably water at a temperature of 80.degree. C. or more and then
dried.
[0062] It is deemed that such cleaning properly roughens the
surface of the phenolic resin layer to enhance the high film
adhesion.
[0063] Such cleaning is also effective in reducing the fluorine
content by removing fluorine present in the chemical conversion
coating.
[0064] The cleaning method is not particularly limited and examples
thereof include a method in which the resulting steel sheet for
containers is immersed in water; and a method in which water is
sprayed or otherwise applied to the resulting steel sheet for
containers.
[0065] In the case of immersion, the immersion time is preferably
at least 1 second.
[0066] The drying temperature is preferably 70.degree. C. or
more.
EXAMPLES
[0067] The invention is described below more specifically by way of
examples. However, the invention should not be construed as being
limited to these examples.
[Surface-Treatment Layer]
[0068] The following treatment processes (1-0) to (1-7) were used
to form a surface-treatment layer on each steel sheet with a sheet
thickness of 0.17 to 0.23 mm.
[0069] (1-0) A base sheet subjected to annealing and pressure
adjustment after cold rolling was degreased and pickled to prepare
a steel sheet.
[0070] (1-1) A base sheet subjected to annealing and pressure
adjustment after cold rolling was degreased, pickled and plated
with a tin-nickel alloy in a sulfuric acid-hydrochloric acid bath
to prepare a nickel/tin-plated steel sheet.
[0071] (1-2) A base sheet subjected to annealing and pressure
adjustment after cold rolling was degreased, pickled and plated
with nickel using a Watts bath to prepare a nickel-plated steel
sheet.
[0072] (1-3) Cold rolling was followed by nickel plating using a
Watts bath and a nickel diffusion layer was formed during annealing
to prepare a nickel-plated steel sheet.
[0073] (1-4) A base sheet subjected to annealing and pressure
adjustment after cold rolling was degreased, pickled and plated
with tin using a Ferrostan bath to prepare a tin-plated steel
sheet.
[0074] (1-5) A base sheet subjected to annealing and pressure
adjustment after cold rolling was degreased, pickled, plated with
tin using a Ferrostan bath and subjected to tin melting treatment
(reflow treatment) to prepare a tin-plated steel sheet having a tin
alloy layer.
[0075] (1-6) A base sheet after cold rolling was degreased,
pickled, plated with nickel using a Watts bath, underwent formation
of a nickel diffusion layer during annealing, was degreased,
pickled, plated with tin using a Ferrostan bath, and then subjected
to tin melting treatment to prepare a nickel/tin-plated steel sheet
having a tin alloy layer.
[0076] (1-7) A base sheet subjected to annealing and pressure
adjustment after cold rolling was degreased, pickled, plated with
an iron-nickel alloy using a sulfuric acid-hydrochloric acid bath
and subsequently plated with tin using a Ferrostan bath and then
subjected to tin melting treatment (reflow treatment) to prepare a
nickel/tin-plated steel sheet having a tin alloy layer.
[0077] When the treatments of (1-6) and (1-7) were performed, the
surface was observed with an optical microscope and evaluated in
terms of the state of the tin islands. Then, islands were confirmed
to be formed over the entire surface.
[Chemical Conversion Coating]
[0078] After the surface-treatment layer was formed by the
above-described treatments, a chemical conversion coating was
formed by the following treatment processes (2-1) to (2-3).
[0079] (2-1) The above-described steel sheets were immersed in a
treatment solution containing K.sub.2ZrF.sub.6 (4.3 g/L) and
phosphoric acid (1.2 g/L) dissolved therein and adjusted to a pH of
2.65 by addition of ammonium nitrate, and subjected to cathodic
electrolysis at a cell temperature of 30.degree. C. under the
conditions shown in Table 1 to form a chemical conversion
coating.
[0080] (2-2) The above-described steel sheets were immersed in a
treatment solution containing K.sub.2ZrF.sub.6 (4.3 g/L),
phosphoric acid (1.2 g/L) and a phenolic resin (0.7 g/L) dissolved
therein and adjusted to a pH of 2.65 by addition of ammonium
nitrate, and subjected to cathodic electrolysis at a cell
temperature of 30.degree. C. under the conditions shown in Table 1
to form a chemical conversion coating.
[0081] (2-3) The above-described steel sheets were immersed in a
treatment solution containing K.sub.2ZrF.sub.6 (4.3 g/L) and sodium
phosphate (1.4 g/L) dissolved therein and adjusted to a pH of 2.65
by addition of phosphoric acid, and subjected to cathodic
electrolysis at a cell temperature of 30.degree. C. under the
conditions shown in Table 1 to form a chemical conversion
coating.
[0082] [Water Washing]
[0083] After the chemical conversion coating was formed by the
above-described treatments, water washing was performed by the
following treatment process (3-1) to control the amount of fluorine
in the chemical conversion coating.
[0084] (3-1) The chemical conversion coating was immersed in hot
water at 40.degree. C. for 1 second.
[Phenolic Resin Layer]
[0085] After the chemical conversion coating was formed by the
above-described treatments and washed with water by the
above-described treatment, the following treatments (4-1) to (4-5)
were performed to form a phenolic resin layer.
[0086] (4-1) An aqueous solution containing 0.1 g/L of phenolic
resin dissolved therein was applied by a roll coater and dried at
75.degree. C. to form a phenolic resin layer.
[0087] (4-2) The above-described steel sheets were immersed for 1
second in an aqueous solution containing 0.5 g/L of phenolic resin
dissolved therein, pressed with a roll and dried at 75.degree. C.
to form a phenolic resin layer.
[0088] (4-3) An aqueous solution containing 3.0 g/L of phenolic
resin dissolved therein was applied by a roll coater and dried at
75.degree. C. to form a phenolic resin layer.
[0089] (4-4) The above-described steel sheets were immersed for 1
second in an aqueous solution containing 0.01 g/L of phenolic resin
dissolved therein, pressed with a roll and dried at 75.degree. C.
to form a phenolic resin layer.
[0090] (4-5) An aqueous solution containing 10.0 g/L of phenolic
resin dissolved therein was applied by a roll coater and dried at
75.degree. C. to form a phenolic resin layer.
[0091] In each case, the above-described water-soluble phenolic
resin modified with N,N-diethanolamine (weight-average molecular
weight: 5,000) was used as the phenolic resin.
[Cleaning]
[0092] After the phenolic resin layer was formed by the
above-described treatments, cleaning was performed by the following
treatment process (5-1).
[0093] (5-1) The above-described steel sheets were immersed in
water at 85.degree. C. for 1 second and dried at 75.degree. C.
[0094] In each of Examples and Comparative Examples, the nickel
metal content and the tin metal content in the surface-treatment
layer were measured by a fluorescent X-ray method and specified
using calibration curves. The amounts of zirconium metal,
phosphorus and fluorine contained in the chemical conversion
coating were measured by a quantitative analysis method such as
fluorescent X-ray analysis. The amount of carbon contained in the
chemical conversion coating and the phenolic resin layer was
measured by subtracting the amount of carbon present in the steel
sheet using a TOC (total organic carbon meter).
[Performance Evaluation]
[0095] The samples obtained by the above-described treatments were
evaluated for the high film adhesion.
[0096] First, both surfaces of the sample in each of Examples and
Comparative Examples were laminated with a PET film with a
thickness of 20 .mu.m at 200.degree. C. and the sample was
subjected to drawing and ironing to prepare a can. The thus
prepared can was necked to form a neck portion. The can was
subjected to retort treatment at 120.degree. C. for 30 minutes to
evaluate the state of film delamination at the neck portion.
[0097] More specifically, a sample having no delamination was rated
"excellent", a sample having slight delamination that does riot
cause a practical problem was rated "good", a sample having partial
delamination that does cause a practical problem was rated "fair"
and a sample in which delamination occurred over large areas
thereof was rated "poor." The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Chemical conversion coating Elec-
Surface-treatment layer trol- Phenol resin layer Evalu- Ni Sn
Current ysis Zr P F C Water C ation Treat- content content Treat-
density time content content content content wash- Treat- content
Clean- High film ment (mg/m.sup.2) (mg/m.sup.2) ment (A/dm.sup.2)
(sec) (mg/m.sup.2) (mg/m.sup.2) (mg/m.sup.2) (mg/m.sup.2) ing ment
(mg/m.sup.2) ing adhesion EX 1 1-0 -- -- 2-1 55 2 80 16 0.01 or
less -- 3-1 4-1 0.6 -- Good 2 1-0 -- -- 2-1 55 2 76 15 0.01 or less
-- 3-1 4-1 0.6 5-1 Excellent to good 3 1-1 80 450 2-1 17 1 22 8
0.01 or less -- 3-1 4-2 7 -- Excellent 4 1-2 460 -- 2-1 18 1 23 8
0.01 or less -- 3-1 4-3 31 -- Good 5 1-3 930 -- 2-1 24 2 41 11 0.01
or less -- 3-1 4-3 17 -- Excellent 6 1-4 -- 2600 2-3 3 1 8 4 0.01
or less -- 3-1 4-3 14 -- Good 7 1-5 -- 13500 2-3 2 1 6 3 0.01 or
less -- 3-1 4-3 19 -- Good 8 1-6 70 800 2-1 12 1 19 8 0.01 or less
-- 3-1 4-3 21 -- Excellent 9 1-7 40 1200 2-1 3 1 9 4 0.01 or less
-- 3-1 4-3 25 -- Excellent CE 1 1-0 -- -- 2-1 55 2 78 16 0.01 or
less -- 3-1 -- -- -- Poor 2 1-1 80 450 2-1 17 1 23 8 0.01 or less
-- 3-1 -- -- -- Poor 3 1-2 460 -- 2-1 18 1 24 8 0.01 or less -- 3-1
-- -- -- Fair 4 1-3 930 -- 2-1 24 2 41 11 0.01 or less -- 3-1 -- --
-- Fair 5 1-4 -- 2600 2-3 3 1 8 4 0.01 or less -- 3-1 -- -- -- Poor
6 1-5 -- 13500 2-3 2 1 6 3 0.01 or less -- 3-1 -- -- -- Poor 7 1-6
70 800 2-1 12 1 20 8 0.01 or less -- 3-1 -- -- -- Poor 8 1-7 40
1200 2-1 3 1 9 4 0.01 or less -- 3-1 -- -- -- Poor 9 1-2 450 -- 2-2
5 1 15 7 0.01 or less 32 3-1 -- -- -- Fair 10 1-1 80 450 2-1 17 1
22 8 0.01 or less -- 3-1 4-4 0.02 -- Poor 11 1-1 80 450 2-1 17 1 22
8 0.01 or less -- 3-1 4-5 68 -- Fair
[0098] The results shown in Table 1 revealed that Comparative
Examples 1 to 11 are all inferior in terms of high film
adhesion.
[0099] In particular, it was revealed that sufficiently high film
adhesion is also not obtained in Comparative Example 9 in which the
chemical conversion coating contains the phenolic resin.
[0100] In addition, it was revealed that sufficiently high film
adhesion is also not obtained in Comparative Examples 10 and 11 in
which the phenolic resin layer is formed but the carbon content is
outside the scope of the invention.
[0101] In contrast, it was revealed that Examples 1 to 9 are all
superior in terms of high film adhesion. It was revealed that
Example 2 in which cleaning was performed after the phenolic resin
layer was formed is superior in terms of high film adhesion to
Example 1 in which cleaning was not performed.
* * * * *