U.S. patent application number 11/439469 was filed with the patent office on 2006-09-21 for resin film laminated metal sheet for can and method for fabricating the same.
This patent application is currently assigned to NKK CORPORATION. Invention is credited to Hiroki Iwasa, Hiroshi Kubo, Shinsuke Watanabe, Yoichiro Yamanaka, Yoshinori Yomura.
Application Number | 20060210817 11/439469 |
Document ID | / |
Family ID | 27335690 |
Filed Date | 2006-09-21 |
United States Patent
Application |
20060210817 |
Kind Code |
A1 |
Yamanaka; Yoichiro ; et
al. |
September 21, 2006 |
Resin film laminated metal sheet for can and method for fabricating
the same
Abstract
The present invention relates to a resin film laminated metal
sheet for can, in which both faces of the metal sheet have resin
film laminated layers, and a surface free energy .gamma. s of a
face of the resin film is 10 dyn/cm or more to less than 30 dyn/cm,
the face becoming an inside of can after can-making and being
contacted with stuffed food contents. As the resin film, applicable
is a polypropylene film or a propylene ethylene based random
copolymer film of polypropylene being a main component. Further, a
resin film of polyester being a main component and containing a wax
component of 0.1 to 2.0% is used in a resin film to be an inside of
can after can-making. The resin film laminated metal sheet for can
according to the invention has excellent formability and adhesion
while can-making and superior taking-out property of stuffed food
contents.
Inventors: |
Yamanaka; Yoichiro;
(Fukuyama, JP) ; Iwasa; Hiroki; (Fukuyama, JP)
; Kubo; Hiroshi; (Fukuyama, JP) ; Watanabe;
Shinsuke; (Fukuyama, JP) ; Yomura; Yoshinori;
(Kawasaki, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
220 Fifth Avenue
16TH Floor
NEW YORK
NY
10001-7708
US
|
Assignee: |
NKK CORPORATION
Tokyo
JP
|
Family ID: |
27335690 |
Appl. No.: |
11/439469 |
Filed: |
May 23, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10719797 |
Nov 20, 2003 |
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11439469 |
May 23, 2006 |
|
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09665323 |
Sep 19, 2000 |
6723441 |
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10719797 |
Nov 20, 2003 |
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Current U.S.
Class: |
428/458 |
Current CPC
Class: |
B32B 15/18 20130101;
Y10T 428/31692 20150401; B32B 2274/00 20130101; Y10T 428/31678
20150401; B32B 2309/04 20130101; B32B 15/20 20130101; B32B 2307/746
20130101; B32B 2311/30 20130101; Y10T 428/31855 20150401; B32B
2250/03 20130101; B32B 2311/00 20130101; B32B 2367/00 20130101;
B32B 2309/02 20130101; B32B 2439/70 20130101; B32B 27/36 20130101;
Y10T 428/31786 20150401; B32B 2250/40 20130101; B32B 2307/518
20130101; B32B 2323/10 20130101; Y10T 428/31681 20150401; B32B
15/08 20130101; B32B 15/09 20130101; B32B 37/04 20130101; B32B
2439/66 20130101 |
Class at
Publication: |
428/458 |
International
Class: |
B32B 15/09 20060101
B32B015/09 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 1999 |
JP |
11-268989 |
Mar 16, 2000 |
JP |
2000-074316 |
Aug 7, 2000 |
JP |
2000-238166 |
Claims
1. A film laminated metal sheet for a container, comprising: a
metal sheet; a resin film A laminated on a surface A of the metal
sheet, the surface A being an outer surface side of the container
after formation of the container; a resin film B laminated on a
surface B of the metal sheet, the surface B being an inner surface
side of the container after formation of the container; the resin
film A being a thermoplastic resin film containing polyester as a
main component; and the resin film B being a thermoplastic resin
film containing polyester as a main component and containing a wax
component in an amount of 0.10% to 2.0% by mass with respect to the
resin of the resin film B.
2. The film, laminated metal sheet according to claim 1, wherein
the wax component of the resin film B is carnauba wax or ester
stearate.
3. The film laminated metal sheet according to claim 1, wherein the
resin film A and/or the resin film B is a biaxially oriented
polyester film having a relaxation time T1.rho.of a benzene ring
carbon at a 1,4 coordinate in a structure analysis according to a
high solid resolution NMR is 150 msec or longer.
4. The film laminated metal sheet according to claim 1, wherein 90
mol % or more of polyester units constituting the resin film A
and/or resin film B are ethylene terephthalate units.
5. The film laminated metal sheet according to claim 1, wherein the
resin film A and/or the resin film B are constituted of at least
two layers, and the difference between intrinsic viscosities of a
laminate layer contacting the metal sheet and a layer other than
the laminate layer is in a range of 0.01 to 0.5.
6. The film laminated metal sheet according to claim 1, wherein the
resin film B is constituted of at least two layers, and the resin
film B is formed such that only an uppermost layer to be in contact
with the content substance contains 0.10 to 2.0% in a ratio by mass
of the wax component with respect to the resin.
Description
[0001] This is a Divisional application of Ser. No. 10/719,797
filed Nov. 20, 2003 (now pending) which is a Divisional application
of Ser. No. 09/665,323 filed Sep. 19, 2000 (now U.S. Pat. No.
6,723,441).
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a resin film laminated
metal sheet to be mainly used to drums and caps of food stuffed
cans, in particular resin film laminated metal sheet for can, which
has excellent formability and adhesion while can-making and
superior taking-out property of stuffed food contents, and to a
method for fabricating the same.
[0004] 2. Description of Related Art
[0005] Conventionally, coatings have been carried out on metal
sheets such as tin free steel (TFS) or aluminum as blank materials
for can to be used to food stuffed cans. The coating technique was
involved with many problems of being complicated in a baking
procedure, taking much treating time, or exhausting much solvent.
Therefore, instead of coating, a lot of methods have been proposed
for laminating a thermoplastic resin film to heated metal
sheets.
[0006] The object of these methods is to improve formability and
adhesion of resin film laminated metal sheets, mainly {circle
around (1)} by applying a resin film having a polar group such as a
polyester resin (for example Japanese Patent Laid Open No.
63-236640) or {circle around (2)} by carrying out a treatment such
as corona discharge on a surface of resin film so as to increase a
surface free energy .gamma. s of resin film (for example, Japanese
Patent Laid Open No. 5-200961). In particular, Japanese Patent Laid
Open No. 5-200961 discloses that the .gamma. s of resin film should
be specified in a range of 38 to 54 dyn/cm for securing adhesion
after forming polyethylene film laminated metal sheets.
[0007] On the other hand, there is a problem that if such a resin
film laminated metal sheet is applied to food stuffed cans, when
removing fully stuffed food contents from the can, it is difficult
to take out them because they are firmly stuck to an inside of the
can. This problem weakens consumers' purchasing desires, and a
resolution of the problem is seriously important, however up to now
no investigation has been ever performed.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
resin film laminated metal sheet for can, which is excellent in
formability and adhesion while can-making and in taking-out
property of stuffed food contents, and a method for fabricating the
same.
[0009] This object can be accomplished by such a resin film
laminated metal sheet for can, in which both faces of the metal
sheet have resin film laminated layers, and a surface free energy
.gamma. s of a face of the resin film is 10 dyn/cm or more to less
than 30 dyn/cm, the face becoming an inside of can after can-making
and being contacted with stuffed food contents.
[0010] As the resin film, available is, for example, a
polypropylene film or a propylene ethylene based random copolymer
film of polypropylene being a main component.
[0011] It is more effective to use a resin film of polyester being
a main component and contain a wax component of 0.1 to 2.0% in the
resin film which will be an inside of can after can-making.
[0012] The resin film laminated metal sheet for can having such a
resin film may be fabricated by a method comprising a step of
laminating a resin film composed of a polypropylene film or a
propylene ethylene based random copolymer film of polypropylene
being a main component on the surface of the metal sheet which will
become an inside of can after can-making, wherein the temperature
of the metal sheet is above the melting point of the resin film
after passing laminating rolls; otherwise by another method
comprising a step of laminating a resin film of polyester being a
main component on the surface of the metal sheet, wherein the
temperature of the face of the resin film to be adhered to the
metal sheet is above the melting point of the resin film between 1
and 20 msec.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1A and 1B are cross sectional views of the resin film
laminated metal sheet of the invention;
[0014] FIG. 2 is a view showing one example of resin film
laminating apparatus for metal sheet; and
[0015] FIG. 3 is a view showing another example of resin film
laminating apparatus for metal sheet.
DETAILED DESCRIPTION OF THE INVENTION
[0016] We earnestly studied the relation between the resin film and
the taking-out property of stuffed food contents in a resin film
laminated metal sheet for can, and consequently found that the
taking-out property has a close relation with a surface free energy
.gamma. s of the resin film, and if the .gamma. s is more than 30
dyn/cm, the sticking between the resin film and the stuffed
contents is excessive so that the taking-out property of stuffed
food contents is poor. Accordingly, if the resin film of .gamma. s
being less than 30 dyn/cm, more preferably less than 22 dyn/cm is,
as seen in FIG. 1A, laminated on a face of the metal sheet which
will be an inside of can after can-making, the .gamma. s of the
face S1 contacting stuffed food contents can be less than 30
dyn/cm, whereby it is possible to provide a resin film laminated
metal sheet for can excellent in taking-out property of stuffed
food contents.
[0017] As mentioned above, since an ordinary resin film to be used
to a resin film laminated metal sheet receives a surface activation
treatment such as corona discharge, its .gamma. s is more than 30
dyn/cm. For setting .gamma. s to be less than 30 dyn/cm, it is
necessary to select an appropriate resin film, and to omit the
surface activation treatment such as corona discharge. This
omission does not cause any problem in the fabrication of the resin
film, but is advantageous in production cost.
[0018] As far as the .gamma. s is less than 10 dyn/cm, the
taking-out property is almost saturated, and since the fabrication
of the resin film having such a .gamma. s is difficult, it should
be 10 dyn/cm or more.
[0019] Even if using the resin film of .gamma. s of not less than
10 dyn/cm to less than 30 dyn/cm, the formability and the adhesion
are not spoiled while can-making.
[0020] Ordinarily, to the outside face S3 of can shown in FIG. 1B,
since trade names or trade marks are printed, a wettability to ink
should be improved, and therefore, the .gamma. s of the face of the
resin film contacting an atmospheric air should be preferably
determined to be 25 dyn/cm or higher.
[0021] It is preferable that the .gamma. s of the faces S2 and S4
of the resin film shown in FIGS. 1A and 1B to be adhered to the
metal sheet is smaller than the .gamma. s of the metal sheet so as
to further improve the adhesion.
[0022] As the resin film of .gamma. s being 10 to less than 30
dyn/cm, available is a polypropylene film or a propylene ethylene
based random copolymer film of polypropylene being a main
component. Since these resin films have a molecular structure
containing no polar group, the .gamma. s is low, and having good
elongation and strength, they are advantageous for formability
while can-making.
[0023] Further, if using, to the face S2 contacting the metal sheet
shown in FIG. 1A, for example, a resin film having an adherent
layer comprising a polar group composed of a polypropylene film
modified with maleic acid anhydride or a propylene ethylene based
random copolymer film modified with maleic acid anhydride, the
adhesion is improved while can-making and such a resin film can be
applied to beverage cans requiring more excellent adhesion.
[0024] When the polypropylene film or the propylene ethylene based
random copolymer film as mentioned above is laminated on the metal
sheet, a thermal adhesion method is ordinarily employed. At this
time, if a degree of crystallization of the resin film is more than
70%, the formability of the resin film is deteriorated and often
causes breakage of film, and therefore preferably the degree of
crystallization should be less than 70%, more preferably less than
60%.
[0025] As the resin film where the .gamma. s of the face to be an
outside of can after can-making is 25 dyn/cm or higher, the resin
film of polyester being a main component may be used. The resin
film of polyester being a main component is defined by such a resin
film containing polyester 50 mass % or more and further containing
polyolefin and the like. For example, PET (polyethylene
terephthalate) film having excellent formability is suited.
[0026] These resin films may be produced by melting a polymer resin
under heating and shearing force through an extrusion machine,
forming a wide and thin film through a T type die, instantly
cooling by a chilled roll and coiling it, otherwise by an ordinary
method of subjecting the resin film to biaxial orienting of
longitudinal and lateral directions after passing through a T type
die. Then, with respect to the resin film to be an inside of can
after can-making, the treatment such as corona discharge for
activating one surface is omitted.
[0027] If using the resin film of polyester being a main component
to the face contacting stuffed food contents, and containing a wax
component of 0.1 to 2.0% in the resin film to be an inside of can
after can-making, it is possible not only to lower .gamma. s of the
resin film, but also to improve lubricity of the film surface, so
that the taking-out property of stuffed food contents is improved
by leaps and bounds, provided that if the wax component is
contained less than 0.1%, an effect thereby is small, and if
exceeding 2.0%, the effect is saturated and the film fabrication is
difficult.
[0028] The effect of the wax component cannot be provided by
coating the wax component on the surface of the resin film. This is
because the wax component pre-coated on the surface of the resin
film is absorbed into the stuffed contents while retort-treatment
which is conducted for sterilizing the contents after stuffing. If
the wax component is contained in the resin film, as is the case of
the present invention, the wax component is gradually thickened on
the surface during the retort treatment, and therefore it is not
all absorbed into the stuffed contents but the effect thereof can
be usefully brought out.
[0029] As the wax component, both of an organic and an inorganic
lubricants are available, and the organic lubricant such as fatty
acid ester is desirable, and among them, more preferable is a
carnauba wax [a main component is
CH.sub.3(CH.sub.2).sub.24COO(CH.sub.2).sub.29CH.sub.3 and the other
various components composed of aliphtic material and alcohol are
contained] which is one of vegetable waxes and a natural wax, or
stearic acid ester. These wax components are easily added to the
resin film of polyester being a main component due to their
molecular structure. The polyester film containing the wax
component is produced by mixing the wax component of a
predetermined amount with polyester and passing through an ordinary
film forming method.
[0030] When aiming at an application of the present resin film to a
can such as DTR can which receives a severe forming, it is
preferable that the resin film of polyester being a main component
is a biaxial oriented polyester film where a relaxation time
T1.rho. of benzene ring carbon of 1,4 coordination measured by a
solid high resolution NMR is 150 msec or more. Because the biaxial
oriented film is more excellent than a non-oriented film in
characteristics such as tensile strength, tearing strength, impact
strength, steam permeability, gas permeability and others. Herein,
the relaxation time T1.rho. shows molecular maneuverability, and if
the relaxation time T1.rho. is increased, the restraint force of
non crystal parts in the resin film is increased. Thereby,
crystallization of non crystal parts can be controlled while
can-making. That is, the maneuverability of the non crystal parts
is reduced and the re-orientating for crystallization is
controlled. If the relaxation time T1.rho. is set to be 150 msec or
more, the above mentioned excellent effects can be exhibited, and
even if a severe forming is performed after lamination, the
excellent formability and the impact resistance can be
provided.
[0031] As a way for exceeding the relaxation time T1.rho. above 150
msec, a high temperature preheating method and a high temperature
orienting method are combined in the longitudinal orienting
procedure when the resin film is produced. Otherwise, this is
enabled by rationalizing, for example, an intrinsic viscosity of
resin, a catalyst, an amount of diethylene glycol, orienting
conditions, heat treating conditions and the like. The preheating
temperature of the longitudinal orienting when producing the resin
film is preferably 90.degree. C. or higher, more preferably
100.degree. C. or higher, and still more preferably 110.degree. C.
or higher. The orientating temperature is preferably 105.degree. C.
or higher, more preferably 110.degree. C. or higher, and still more
preferably 115.degree. C. or higher.
[0032] Polyester as the main component of the resin film is polymer
composed of dicarboxylic acid and glycol. As the dicarboxylic acid,
applicable is terephthalic acid, isophthalic acid, naphthalene
dicarboxylic acid, or diphenyldicarboxylic acid, and among them,
terephthalic acid or isophthalic acid is preferable. As a glycol,
there are enumerated ethylene glycol, propanediol and butanediol,
and among them, ethylene glycol is preferable. More than two kinds
of dicarboxylic acid or glycol may be used together. Further,
polyester may be, if required, mixed with anti-oxidant, heat
stabilizer, ultraviolet asborbent, plasticizer, pigment, antistatic
agent, or crystal nucleus.
[0033] Polyester has excellent mechanical characteristics such as
tensile strength, elastic modulus and impact strength, and has
polarity, and therefore the formability and the adhesion of the
resin film of polyester being a main component are improved up to
the level durable to can-making and improve the impact resistance
after can-making.
[0034] In the above mentioned resin film laminated metal sheet for
can according to the invention, no limitation is especially defined
to thickness of the resin film which will be an inside or outside
of can after can-making. Ordinary thickness of around 10 to 50
.mu.m is sufficient.
[0035] Further, as the metal sheet, applicable are aluminum sheets
or soft steel sheets. In particular, optimum is a surface treated
steel sheet (TFS) formed with double layered films comprising a
lower layer of metallic chrome and an upper layer of chrome
hydroxide. Also in this case, no limitation is especially made to
amounts of the metallic chrome layer and the chrome hydroxide layer
of TFS, but in view of the adhesion and the corrosion resistance
after can-making, it is desirable that the metallic chrome layer
is, in terms of chrome, 70 to 200 mg/m.sup.2 and the chrome
hydroxide is 10 to 30 mg/m.sup.2.
[0036] With respect to the fabrication method thereof, when
laminating the resin film composed of polypropylene film or
propylene ethylene based random copolymer film of polypropylene
being a main component on the surface of the metal sheet which will
be an inside of can after can-making, the temperature of the metal
sheet after passing laminating rolls (adhesion pressing rolls)
should be above the melting point of the resin film. Thereby, when
laminating, the resin film is substantially completely melted to
increase fluidity, so that a wettability is improved to increase a
contacting area with the metal surface, and the adhesion is
improved. Since the crystal structure in the film is destroyed in
company with melting of the film, crystal component obstructing the
formability can be changed into non-crystal component, securing the
formability of the resin film necessary for can-making.
[0037] Then, it is desirable that a time until cooling after
passing the laminating rolls is 1 to 5 seconds. Being less than 1
second, since a wetting time is short, an enough contacting area
cannot be secured, while exceeding 5 seconds, recrystallization of
the film advances after passing the laminating rolls. In addition
to these conditions, if the temperature of the metal sheet is set
to be (the melting point of the resin film-30).degree. C., the
wetting on the metal surface is made more secure, and the
recrystallization is validly controlled, enabling the degree of
crystallization to be less than 70%. This effect is made more
effective by setting to be (the melting point of the resin
film-10).degree. C., enabling the degree of crystallization to be
less than 60%. An upper limit of the temperature is not especially
defined, but it is desirable to be set at least less than (the
melting point of the resin film+90).degree. C.
[0038] Also in case the resin film has a resin layer having a polar
group in the face adhering the metal sheet, the lamination should
be carried out under the same conditions as mentioned above.
[0039] On the other hand, when laminating the resin film of
polyester being a main component on the metal surface, it is
necessary that the temperature of the face of the resin film
adhering the metal sheet is above the melting point of the resin
film between 1 and 20 msec. Being less than 1 msec, it is not
sufficient for the resin film to adhere the metal sheet, while
exceeding 20 msec, the controlling performance of the molecular
maneuverability in the vicinity of the face adhering the metal
sheet is lost.
[0040] For getting the above effects, in addition to the lamination
at a high speed, a cooling is also effective during adhering. No
limitation is especially defined to pressing when laminating, but a
surface pressure is preferably 1 to 30 kg/cm.sup.2. If the surface
pressure is too low, the sufficient adhesion is difficult to
realize because a time is short though being above the melting
point, while if the surface pressure is large, a force loading to
the laminating rolls is large, necessitating strength in facility
and inviting a large scale in facility.
[0041] A method of laminating the resin film on the metal surface
is not limited to the above mentioned thermal adhesion method.
EXAMPLE 1
[0042] A steel sheet of 0.18 mm thickness and 977 mm width having
passed through cold rolling, annealing and temper rolling was
degreased and pickled, followed by chrome plating. The chrome
plating was performed in a bath of CrO.sub.3, F.sup.- and
SO.sub.4.sup.2-, subjected to an intermediate rinse and thereafter
to an electrolysis in a chemical conversion treatment solution
containing CrO.sub.3 and F.sup.-. At that time, electrolyzing
conditions (such as current density, amount of electricity) were
changed to control amount of metallic chrome, amount of chrome
hydroxide and .gamma. s.
[0043] The .gamma. s of the chrome plated steel sheet was evaluated
by measuring a contact angle after a surface free energy-known
liquid (pure water, glycerol, formamide, ethyleneglycol,
dimethylglycol) was dropped on the steel surface at a humidity of
55 to 65% and at a temperature of 20.degree. C.
[0044] The resin film laminating apparatus for metal sheet shown in
FIG. 2 was used in which the above mentioned chrome plated steel
sheets 1 were heated in the heating apparatus 2, and then laminated
by the laminating rolls 3 with each kind of film 4a shown in Table
1 on the face to be an inside of can after can-making and with PET
film 4b of .gamma. s being all 32 dyn/cm on the face to be an
outside of can after can-making respectively through the thermal
adhesion method.
[0045] Thus produced resin film laminated metal sheets were
subjected to the measurement of .gamma. s by the above mentioned
method, and to the evaluation of taking-out property of stuffed
food contents 1), formability 2) and adhesion after forming 3) by
the following methods.
1) Taking-Out Property of Stuffed Food Contents
[0046] The resin film laminated metal sheets having 100 mm blank
diameter were formed into cups at a drawing ratio (diameter before
forming/diameter after forming) of 1.88 using a drawing machine.
The contents of uniformly mixed eggs, meats oatmeals were stuffed
in the cups, covered and followed by retort treatments (130.degree.
C..times.90 minutes). Thereafter, the cups were turned over,
manually shaked two or three times, and after the contents were
taken out, degrees of the contents remained within the cups were
observed, and the taking-out properties of stuffed food contents
were evaluated as follows. [0047] .largecircle.: The taking-out is
easy, and no stuck food remains in the inside of the cup. [0048]
.times.: The taking-out is hard by shaking by hands, and the stuck
food can not be taken out without using a spoon or the like. 2)
Formability
[0049] The resin film laminated metal sheet was coated with wax,
punched into discs of 179 mm diameter, and formed into cups at a
drawing ratio of 1.65. The cups were redrawn at a drawing ratio of
1.40. The observation of resin film of the above deep drawn cups
was conducted, and the formability was evaluated as follows. [0050]
{circle around (.smallcircle.)}: No injury exists in the film after
forming, and no whiting is recognized therein. [0051]
.largecircle.: The forming is possible, but the whiting is
recognized. [0052] .times.: The cup is broken at the barrel, and
the forming is impossible. 3) Adhesion After Forming
[0053] From the barrel of the cup formed in the above 2), samples
(15 mm width and 120 mm length) were cut out for peeling tests. The
resin film was partially delaminated from the edge of the face of
the cut-out sample, corresponding to the inside of the cup, and the
delaminated film was peeled out by a tensile tester in an opposite
direction (angle 180.degree.) to the chrome plated steel sheet at a
tensile rate of 30 mm/min. Then the adhesion force was measured and
the adhesion after forming was evaluated as follows. [0054] {circle
around (.smallcircle.)}: 0.15 kg/15 mm or more [0055]
.largecircle.: 0.10 kg/15 mm or more to less than 0.15 kg/15 mm
[0056] .times.: Less than 0.10 kg/15 mm
[0057] As shown in Table 1. The inventive examples are all
excellent, while the comparative examples are inferior in the
taking-out property of stuffed food contents. TABLE-US-00001 TABLE
1 Film laminated steel sheet Chrome plated steel sheet Face
corresponding to an Cr coating inside after can-making Evaluation
of performance weight Surface Surface Taking-out Metallic Cr free
Film free property chrome oxide energy thickness energy .sup.3) of
stuffed No. (mg/m.sup.2) (mg/m.sup.2) (dyn/cm) Film types .sup.1)
(.mu.) (dyn/cm) contents Formability Adhesion E1 120 15 35 PP 30 18
.largecircle. .circleincircle. .circleincircle. E2 '' '' 35 PP - PE
Mixture '' 19 .largecircle. .circleincircle. .circleincircle. E3 ''
'' 35 PP + Adhered 20 18 .largecircle. .circleincircle.
.circleincircle. layer .sup.2) E4 '' '' 30 PP 15 18 .largecircle.
.circleincircle. .circleincircle. E5 '' '' 35 PE 30 19
.largecircle. .circleincircle. .circleincircle. E6 '' '' 30 PTFE ''
12 .largecircle. .largecircle. .largecircle. E7 120 10 20 PP '' 18
.largecircle. .largecircle. .largecircle. C1 120 15 35 PP + Corona
'' 35 X .circleincircle. .circleincircle. discharge treatment (both
sides) C2 '' '' 35 PET '' 32 X .circleincircle. .circleincircle.
Note .sup.1) PP: Polypropylene film PE: Polyethylene film PP - PE
Mixture: Propylene ethylene based random copolymer film PTFE:
Polytetorafluoroethylene film (poly-4-ethylene fluoride film) PET:
Polyethylene terephthalate film Note .sup.2) Adhered layer: Maleic
acid anhydride graft modified polypropylene resin. Film thickness
5.mu. Note .sup.3) Surface free energy is equivalent in both
surfaces excepting the Inventive example 3, Side of adhered layer
of the Inventive example 3 is 32 dyn/cm E: Example C: Comparative
example
EXAMPLE 2
[0058] The resin film laminating apparatus for metal sheet shown in
FIG. 3 was used in which the same chrome plated steel sheets 1 as
those of Example 1 were heated in the heating apparatus 2,
laminated by the laminating rolls 3 with various kinds of film 4a
shown in Table 2 on the face to be an inside of can after
can-making and with PET film 4b on the face to be an outside of can
after can-making respectively, sprayed with the cooled water 8
controlled to be at constant temperature by the heat exchanger 13
from the spraying apparatus 14 in the cooling apparatus 5 so as to
cool the films, and then pulled upward via the sink roll 7 from the
cooling water tank 6. At that time, the sheet temperature at the
inlet of the laminating rolls 3, the temperature of the laminating
rolls 3 and the position of the spray apparatus 14 were controlled
so as to variously change the sheet temperature immediately after
passing the laminating rolls 3, the time until starting of cooling
after passing the laminating rolls 3, and the sheet temperature at
starting of cooling as shown in Table 2.
[0059] With respect to the thus produced resin film laminated metal
sheets, the taking-out property of stuffed food contents, the
formability and the adhesion after forming were evaluated in the
same ways as Example 1.
[0060] The melting point of the resin film was calculated from the
endothermic peaks obtained by means of a differential scanning
calorimeter (DSC-2 made by Perkin-Elmar Inc.) under the conditions
where samples were heated to 300.degree. C. at a nitrogen flowing
amount of 20 ml/min and at a heating rate of 10.degree. C./min.
[0061] The degree of crystallization of the resin film was measured
as follows.
4) Degree of Crystallization of the Resin Film After Lamination
[0062] The density of the resin film adopted by melting the metal
part of the resin film laminated metal sheet was obtained by a
density gradient method, and the degree of crystallization of the
resin film was calculated by the following equation.
X=[{(1/dam)-(1/d}/{(1/dam)-(1/dc)}].times.100
[0063] Herein, [0064] X: Degree (%) of crystallization of the film
[0065] dam: Density (0.860 g/cc) of completely amorphous
polypropylene resin [0066] dc: Density (0.938 g/cc) of completely
crystallized polypropylene resin [0067] d: Density (g/cc) of the
resin film after lamination
[0068] The density gradient method was carried out by the density
gradient pipe of JIS K 7112 as follows. [0069] i) The density
gradient pipe is made using a high density and a low density
solutions. [0070] ii) The relation between the depth of water of
the density gradient pipe and the density is measured using a float
having a known specific gravity. [0071] iii) A sample is laid in
the density gradient pipe, and after 2 hr a position where the
sample stands still (the depth of water) is read out. [0072] iv)
The density of the sample is calculated from the relation between
the depth of water of the density gradient pipe and the
density.
[0073] As shown in Table 2, the inventive examples show that the
degrees of crystallization of the resin film are all less than 70%,
and each of the properties is excellent. In particular, when the
temperature of the metal sheet was above (the melting point of the
resin film-10).degree. C. at starting of cooling, the degree of
crystallization of the film is less than 60.degree. C., and more
excellent formability and adhesion may be obtained.
[0074] On the other hand, the degrees of crystallization of the
films of the comparative examples 1, 3, 4 are 70% or more, and the
formability and the adhesion are inferior. In the comparative
example 2 where PET was used to the face to be an inside of can
after can-making, the taking-out property is poor. TABLE-US-00002
TABLE 2 Laminating conditions Degree Laminated film Sheet T. Time
until of Chrome plated Face corresponding immediately start of
crystal- steel sheet to an inside after after cooling Sheet
lization Evaluation of Cr coating can-making passing after the T.
at of film performance weight Film Melting the passing starting
after Taking-out Metallic Cr thick- point of laminating laminating
of lamina- property chrome oxide Film types ness film rolls rolls
cooling tion of stuffed Form- Adhe- No. (mg/m.sup.2) (mg/m.sup.2)
1), 2) (.mu.m) (.degree. C.) (.degree. C.) (sec) (.degree. C.) (%)
contents ability sion E1 120 15 PP + 20 165 180 2 170 52
.largecircle. .circleincircle. .circleincircle. Adhered layer E2
120 15 PP + 20 165 175 1 170 54 .largecircle. .circleincircle.
.circleincircle. Adhered layer E3 120 15 PP + 20 165 182 3 177 52
.largecircle. .circleincircle. .circleincircle. Adhered layer E4
120 15 PP + 20 165 165 4 145 65 .largecircle. .largecircle.
.circleincircle. Adhered layer E5 120 15 PP + 20 165 182 5 162 58
.largecircle. .circleincircle. .circleincircle. Adhered layer E6
120 15 PP + 30 145 160 3 145 58 .largecircle. .circleincircle.
.circleincircle. Adhered layer E7 120 15 PP + 30 145 145 3 130 63
.largecircle. .largecircle. .circleincircle. Adhered layer E8 120
15 PP - 30 165 180 3 165 52 .largecircle. .circleincircle.
.circleincircle. PE Mixture E9 120 15 PP 20 165 180 3 165 52
.largecircle. .circleincircle. .circleincircle. E10 120 15 PP + 20
165 180 1 177 50 .largecircle. .circleincircle. .largecircle.
Adhered layer E11 120 15 PP + 20 165 180 6 150 63 .largecircle.
.largecircle. .largecircle. Adhered layer E12 120 15 PP + 20 165
165 7 130 68 .largecircle. .largecircle. .largecircle. Adhered
layer C1 120 15 PE 30 120 120 2 110 40 .largecircle. X X C2 120 15
PET 20 220 180 2 170 20 X .circleincircle. .circleincircle. C3 120
15 PP + 20 165 155 2 145 78 .largecircle. X X Adhered layer C4 120
15 PP + 20 165 150 1 145 74 .largecircle. X X Adhered layer Note 1)
PP: Polypropylene film PP + PE Mixture: Propylene ethylene based
random copolymer film PE: Polyethylene film PET: Polyethylene
terephthalate film Note 2) Adhered layer: Maleic acid anhydride
graft modified polypropylene resin. Film thickness 5 .mu.m E:
Example C: Comparative example T.: Temperature
EXAMPLE 3
[0075] The resin film laminating apparatus for metal sheet shown in
FIG. 2 was used in which the chrome plated steel sheets of the
chrome amount being 120 mg/m.sup.2 and the chrome hydroxide amount
being 15 mg/m.sup.2 fabricated in the same method in Example 1 were
heated in the metal sheet heating apparatus 2, and the laminating
rolls 3 laminated the film 4a on the face of the steel sheets to be
an inside of can after can-making and laminated the resin film 4b
on the face of them to be an outside of can after can-making. At
that time, as the resin film 4a on the inside of can after
can-making, the resin film 4b on the outside of can after
can-making which was added with wax was used. Table 3 shows the
laminated resin films and the laminating temperature conditions.
The laminating rolls 3 were internal cooling rolls, and the cooling
water was forcibly circulated during laminating so as to carry out
the cooling while adhering the film.
[0076] With respect to the thus produced resin film laminated metal
sheets, the formability and the adhesion after forming were
evaluated in the same ways as Example 1. The taking-out properties
of stuffed food contents were evaluated in the following 3 steps
more in detail than Example 1. [0077] {circle around
(.smallcircle.)}: The taking-out is easy, and no stuck food remains
in the inside of the cup. [0078] .largecircle.: The taking-out is
hard only by shaking by hands, but stuck food can be taken out by a
spoon or the like, and little food stuck to the inside of the cup
are left. [0079] .times.: The taking-out is hard only by shaking by
hands, and stuck food can be taken out by a spoon or the like. Much
food is left in the inside of the cup after taking out.
[0080] Further, the relaxation time T1.rho., the melting point of
polyester and the impact resistance were measured as follows.
5) Relaxation Time T1.rho. of Polyester
[0081] For measuring solid NMR, used were a spectrometer JNM-GX270
made by Japan Electron Optics Laboratory Co., Ltd., a solid
amplifier made by the same, MAS controller NM-GSH27MU, and a probe
NM-GSH27T made by the same. The measurement of T1.rho. (vertical
relaxation in the rotational coordinate) of .sup.13C nucleus was
practiced. The measuring conditions were temperature of
24.5.degree. C., humidity of 50% RH, static magnetic field of 6.34
T (Tesla), and resonant frequencies of .sup.1H, .sup.13C being
270.2 MHz and 67.9 MHz respectively. MAS (rotation of magic angle)
method was employed for canceling influences of anisotropy of
chemical shift. The rotation number was 3.5 to 3.7 kHz. The
conditions of pulse series were 90.degree. for .sup.1H, pulse width
of 4 .mu.sec, the strength of rocking magnetic field of 62.5 kHz.
The contacting time of CP (cross polarization) for shifting the
polarization of .sup.1H to .sup.13C was 1.5 msec. As the holding
times .tau., 0.001, 0.5, 0.7, 1.3, 7, 10, 20, 30, 40, 50 msec were
used. Free induction decrement (FID) of .sup.13C magnetization
vector after the holding time .tau. was measured (a high output
coupling was done for removing influences of dipole mutual action
by .sup.1H during measuring FID. For improving S/N, integrations
were made 512 times.). The pulse repeating time was between 5 and
15 sec.
[0082] T1.rho. values can be ordinarily described by the following
equation and can be obtained from the slope when the peak strength
measured for each of the holding times is plotted in a scale of
semi-logarithm. I(t)=.SIGMA.(Ai)exp(-t/T1.rho.i) [0083] Ai:
Percentage of components with respect to T1.rho.i
[0084] Herein, analyses were made by the 2 components (T1.rho.1:
Non-crystal component, T1.rho.2: Crystal component), and the
following equation was used so as to obtain the value by a least
square method. I(t)=fa1exp(-t/T1.rho.1)+fa2exp(-t/T1.rho.2) [0085]
fa1: Percentage of components with respect to T1.rho.1 [0086] fa2:
Percentage of components with respect to T1.rho.2 fa1+fa2=1 [0087]
herein, T1.rho.2 is used for T1.rho.1. 6) Melting Point of
Polyester
[0088] After crystallizing polyester, the melting point was
measured at a heating rate of 10.degree. C./min by the same
differential scanning calorimeter as described above.
7) Impact Resistance
[0089] With respect to the cups formed in the above 2) for the
evaluation of the formability, those were filled with water, 10
cups per each of tests were dropped on a vinyl chloride floor from
a height of 1.25 m, then the voltage of 6 V was supplied to the
electrodes and the cups for reading the current after 3 seconds,
and the impact resistances were evaluated as follows. [0090]
{circle around (.smallcircle.)}: Less than 0.01 mA [0091]
.largecircle.: 0.01 mA or more to less than 0.1 mA [0092] .times.:
0.1 mA or more
[0093] As shown in Table 3, the inventive examples are all
excellent in the taking-out property of stuffed food contents, the
formability, the adhesion, and the impact resistance. In
particular, in the inventive examples where the relaxation time
T1.rho.is 150 msec or more, or the time when the temperature of the
resin film contacting the metal sheet goes above the melting point
of the resin film, is 1 to 20 msec, the formability, the adhesion
and the impact resistance are more excellent. On the other hand,
the comparative examples 1 to 3 are poor in the taking-out property
of food stuffed contents, and the comparative examples 4 and 5 are
inferior in the formability. TABLE-US-00003 TABLE 3 Sheet T. at
starting Time at Wax.sup.6) Film of above Taking-out Clas- Addition
Melting thick- lamina- melting property Form- Impact sifi- amount
point ness T1.rho. tion point of stuffed abil- Adhe- resis- cation
Film Types (wt %) (.degree. C.) (.mu.m) (msec) (.degree. C.) (msec)
contents ity sion tance E1 PET.sup.1) Carnauba 0.50 255 15 220 282
15 .circleincircle. .circleincircle. .circleincircle.
.circleincircle. E2 PET Carnauba 0.75 255 15 220 282 15
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
E3 PET Carnauba 0.10 255 15 220 282 15 .largecircle.
.circleincircle. .circleincircle. .circleincircle. E4 PET Carnauba
1.50 255 15 220 282 15 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. E5 PET Stearylstearey.sup.2) 0.50
255 15 220 282 15 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. E6 PET Stearylstearey 0.75 255 15
220 282 15 .circleincircle. .circleincircle. .circleincircle.
.circleincircle. E7 PET Silicone 1.50 255 15 220 282 15
.largecircle. .circleincircle. .circleincircle. .circleincircle. E8
PET Carnauba 0.50 255 15 400 282 15 .circleincircle.
.circleincircle. .circleincircle. .circleincircle. E9 PET Carnauba
0.50 255 15 160 282 15 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. E10 PET Carnauba 0.50 255 15 120
282 15 .circleincircle. .largecircle. .largecircle. .largecircle.
E11 PET Carnauba 0.50 255 15 220 260 3 .circleincircle.
.circleincircle. .circleincircle. .circleincircle. E12 PET Carnauba
0.50 255 15 220 255 0.5 .circleincircle. .largecircle.
.largecircle. .largecircle. E13 PET Carnauba 0.50 255 15 220 293 25
.circleincircle. .largecircle. .largecircle. .largecircle. E14
PET/I.sup.3) Carnauba 0.50 226 15 210 282 20 .circleincircle.
.circleincircle. .circleincircle. .circleincircle. E15 PET Carnauba
0.50 255 25 220 282 15 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. E16 PET Carnauba 0.50 255 12 220
282 15 .circleincircle. .circleincircle. .circleincircle.
.circleincircle. C1 PET -- -- 255 15 220 282 15 X .circleincircle.
.circleincircle. .circleincircle. C2 PET Carnauba 0.05 255 15 220
282 15 X .circleincircle. .circleincircle. .circleincircle. C3 PET
Stearylstearey 0.05 255 15 220 282 15 X .circleincircle.
.circleincircle. .circleincircle. C4 PP.sup.4) -- -- 160 20 -- 190
17 .circleincircle. X -- -- C5 PE.sup.5) -- -- 110 50 -- 140 19
.circleincircle. X -- -- .sup.1)PET: Polyethylene terephthalate
(Biaxial orientated film) .sup.2)Stearylstearey: Stearic acid ester
(C18-C18) .sup.3)PET/I: Isophthalic acid copolymer polyethylene
terephthalate (Ratio of copolymerization of isophthalaic acid: 12
mol %, Biaxial oriented film) .sup.4)PP: Polypropylene (Biaxial
oriented film) .sup.5)PE: Polyethylene .sup.6)Wax is added to only
a resin film to be an inside of can E: Example C: Comparative
example T.: Temperature
* * * * *