U.S. patent application number 12/021379 was filed with the patent office on 2008-06-12 for coating composition having improved release properties and the process for making the same.
Invention is credited to Daniel Bode, Deborah L. Howard, Timothy I. Memmer.
Application Number | 20080139716 12/021379 |
Document ID | / |
Family ID | 32681468 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080139716 |
Kind Code |
A1 |
Bode; Daniel ; et
al. |
June 12, 2008 |
COATING COMPOSITION HAVING IMPROVED RELEASE PROPERTIES AND THE
PROCESS FOR MAKING THE SAME
Abstract
A protective coating composition and a method for coating a
metal substrate are provided. The composition and method are
particularly suitable for coating can ends. The coating composition
includes a film-forming polymer that includes an epoxy-based resin,
a lubricant system, and a solvent or water component or mixture of
solvent and water. The lubricant system includes a first surface
modifier that reduces the coefficient of friction and a second
surface modifier that reduces the abrasion of the cured
coating.
Inventors: |
Bode; Daniel; (Cleveland,
OH) ; Memmer; Timothy I.; (Strongsville, OH) ;
Howard; Deborah L.; (Kingsbury Nr. Tamworth, GB) |
Correspondence
Address: |
BENESCH, FRIEDLANDER, COPLAN & ARONOFF LLP;ATTN: IP DEPARTMENT DOCKET
CLERK
2300 BP TOWER, 200 PUBLIC SQUARE
CLEVELAND
OH
44114
US
|
Family ID: |
32681468 |
Appl. No.: |
12/021379 |
Filed: |
January 29, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10338520 |
Jan 8, 2003 |
7341762 |
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12021379 |
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Current U.S.
Class: |
524/277 ;
524/442; 524/502; 524/515; 524/612 |
Current CPC
Class: |
C09D 163/00 20130101;
C09D 163/00 20130101; C09D 163/00 20130101; C08L 91/06 20130101;
C08L 23/00 20130101; C09D 163/00 20130101; C08L 23/06 20130101;
C08L 91/08 20130101; C09D 5/00 20130101; C08L 2666/04 20130101;
C08L 91/06 20130101; C08L 2666/02 20130101; C09D 7/65 20180101 |
Class at
Publication: |
524/277 ;
524/612; 524/442; 524/502; 524/515 |
International
Class: |
C09D 163/00 20060101
C09D163/00; C09D 123/10 20060101 C09D123/10; C09D 123/04 20060101
C09D123/04; C09D 123/02 20060101 C09D123/02 |
Claims
1. A coating composition which comprises: from about 10% to about
50% solids based on the weight of the coating composition, the
solids comprising: an epoxy-based resin; from about 0.1% to about
20% by weight lubricant compound which comprises: a first surface
modifier; a second surface modifier that is different from the
first surface modifier; and wherein the coefficient of friction
(COF) of the coating composition when dried is less than about
0.15.
2. The coating composition of claim 1, wherein the coating
composition comprises: from about 50% to about 99.5% by weight
epoxy-based resin; from about 0.25% to about 16% by weight of the
first surface modifier; and from about 0.25% to about 16% by weight
of the second surface modifier.
3. A coating composition which comprises: an epoxy-based resin; a
lubricant system that comprises: at least about 0.1% by weight
based on the weight of the total solids, a first surface modifier
selected from the group consisting of carnauba wax, petroleum
waxes, paraffin wax, microcrystalline waxes, semicrystalline waxes,
silicones, beeswax, candelilla, japan wax, ouricury wax,
Douglas-fir bark wax, rice-bran wax, jojoba, castor wax, and
bayberry wax; hydrogenated castor oil; high molecular weight acids
and alcohols; mineral waxes, monton wax, peat wax, ozokerite,
ceresin; and mixtures of the above; and at least about 1% by weight
based on the weight of the total solids, a second surface modifier
selected from the group consisting of polyolefins and polyolefin
copolymers, polypropylene, modified polypropylenes, polyethylene
and modified polyethylenes; polytetrafluoroethylene;
Fischer-Tropsch waxes, and mixtures of the above.
4. The coating composition of claim 3 wherein the coating
composition comprises from about 50% to about 99.8% epoxy-based
resin.
5. The coating composition of claim 3 wherein the coating
composition comprises from about 0.25% to about 16% of the first
surface modifier and from about 0.25% to about 16% of the second
surface modifier.
6. The coating composition of claim 5 wherein the lubricant system
is present in a dispersion having an average particle size
distribution that ranges from about 0.5 to about 5 microns.
7. The coating composition of claim 5 wherein the first surface
modifier comprises at least one of carnauba wax and silicone.
8. The coating composition of claim 7 wherein the second surface
modifier comprises polyethylene.
9. The coating composition of claim 3 wherein the first surface
modifier comprises carnauba wax and the second surface modifier
comprises polyethylene.
10. The coating composition of claim 3, further comprising, by
weight, from about 0.1% to about 40% cross-linker.
11. The coating composition of claim 3, wherein the lubricant
system further comprises at least one of a surfactant and a
dispersing polymer.
12. The coating composition of claim 3, wherein the coefficient of
friction of the coating when dried is less than about 0.1.
13. The coating composition of claim 3, wherein the epoxy-based
resin is in an epoxy-acrylic resin.
14. The coating composition of claim 9, wherein the epoxy-based
resin is in an epoxy-acrylic resin.
15. A method for coating a metal substrate, which comprises:
applying a coating composition to the metal substrate; heating the
metal substrate and coating composition until the coating is cured
to produce a cured coating film having a film weight that ranges
from about 1 mg/in.sup.2 to about 8 mg/in.sup.2; wherein the cured
coating film comprises, by weight, based on the total solids in the
coating composition, from about 50% to about 99.5% epoxy-based
resin; from at least about 0.1% of a first surface modifier; from
at least about 0.1% of a second surface modifier; and wherein the
cured coating film has a coefficient of friction that is less than
about 0.15.
Description
FIELD
[0001] This invention relates to a coating composition,
particularly useful as can coatings for beverage and food
containers and the process for making the coating compositions
Invention also relates to a process for making can ends using the
coating composition.
BACKGROUND
[0002] Coating compositions for metal containers require physical
properties that withstand the processing conditions in
manufacturing the metal containers Lids for metal containers, for
example, are typically manufactured by first coating flat sheets of
a metal substrate, heating the coated substrate and then stamping
or shaping the coated substrate into a container having a desired
shape.
[0003] Coating compositions generally contain a film-forming
synthetic resin component which is applied to metal sheet substrate
in the form of dispersion and is then heat-cured to a dried film.
The coatings applied to food and beverage can ends, for example,
are applied in film weights of approximately 1 milligram per square
inch to approximately 9 milligrams per square inch on high speed
coil coating lines. High speed coating lines require a coating
material that will dry and cure within a few seconds as it is
heated very rapidly to peak metal temperatures that can range from
approximately 200.degree. C. to approximately 300.degree. C.
(392.degree. F. to about 550.degree. F.).
[0004] Polyvinylchloride (PVC)-based coatings have been used to
coat the interior and exterior of metal containers for foods and
beverages because these coatings exhibit an acceptable combination
of adhesion to a metal substrate, flexibility, chemical resistance,
and corrosion inhibition. These PVC containing coatings, however,
are being replaced by solvent and water-borne epoxy systems in
order to eliminate excessive levels of bisphenol A diglycidyl
ether, a stabilizer used in PVC coatings, and to eliminate the
potential of dioxin production if the PVC coating is improperly
burned Concerned industrial applicators are acting to eliminate
these polyvinylchloride-based coating compositions to eliminate the
environmental and health concerns associated with them.
[0005] Due to these concerns and the environmental concerns
associated with organic solvents, there is an increasing demand for
aqueous coating compositions. Water-borne epoxy systems have been
used to coat the outside of easy open ends of beverage cans, for
example, but their use has caused problems in productivity and
quality on certain tooling designs.
[0006] More specifically, repeated stamping of a coil that is
coated with alternative coating compositions, i.e. those which do
not contain PVC, can result in build up of the coating on the
forming tool as well as a scuffed coating on the can ends. When
coated metal coil is fed into a forming press, the coating is
contacted by the tool under pressure as the tool forms the shape of
the can end, and then the tool is separated from the surface of the
coated metal. The repeated contact of the tool with the coating
during shaping produces a gradual build-up of the coating on the
tool. Also, the coating along the perimeter of the can end is
scuffed as the formed can ends are separated from the tool. This
scuffing problem not only results in can ends having thickened
edges, but also results in the need for high maintenance efforts
surrounding the forming press and, in some cases, results in
complete shutdown of a production line.
SUMMARY
[0007] The present invention provides for a coating composition
which demonstrates improved release properties during fabrication
of the coated substrate. The coating composition herein eliminates
the toxicological issues associated with the use of PVC coatings
and can also minimize the environmental problems associated with
the use of organic solvents. The coating composition of the present
invention also provides excellent adhesion, flexibility and
chemical resistance necessary for a high quality metal
container.
[0008] In one embodiment of the invention, the coating composition
includes a film-forming resin component, a lubricant system and a
solvent. The film-forming resin component includes an epoxy
resin-based polymer. The lubricant system includes at least two or
more surface modifiers. The lubricant system includes a first
surface modifier that reduces the coefficient of friction of the
coating composition relative to a coating system containing an
epoxy-based resin and that does not contain the first surface
modifier. The lubricant system also contains a second surface
modifier that is different from the first surface modifier and that
increases the abrasion resistance of the coating composition
relative to a coating composition containing an epoxy-based resin
and that does not contain the second surface modifier. The solvent
can include an organic material, water, or a mixture of an organic
material and water.
[0009] In one embodiment of the invention, the coating composition
includes an epoxy-acrylic resin, a lubricant system and a solvent
that includes both water and organic material. In another
embodiment of the invention, the coating composition includes an
epoxy-polyester resin, a lubricant system and a solvent that is an
organic material. In these embodiments, the coating composition
contains from about 0.2% by weight to about 20% by weight lubricant
solids, preferably from about 0.5% to about 7%, based on the total
weight of solids in the coating composition, and at least about
0.25% by weight of the first surface modifier and at least 0.25% by
weight of the second surface modifier.
[0010] The present invention also provides a method of coating a
metal substrate to provide a cured film on at least one surface of
the substrate. The method includes applying the coating composition
onto the surface of the metal substrate to form a coating layer.
The coated metal substrate is then heated so that the coating layer
cures to form a cured film adhered to the substrate surface. The
coating metal substrate is typically cured by heating for about 5
to about 25 seconds in an oven to achieve a peak metal temperature
of about 200.degree. C. to about 250.degree. C. The cured film
typically has a film weight of at least about 1 mg/in.sup.2 and,
preferably, from about 1 mg/in.sup.2 to about 9 mg/in.sup.2.
[0011] The present invention also provides a composite material
which includes a metal substrate having at least one surface
covered with a cured film, which is the result of coating the
substrate surface with the above-described coating composition and
heating the coated metal substrate for a period of from about 5 to
about 25 seconds to achieve a peak metal temperature of 200.degree.
C. to 250.degree. C. The cured film preferably has a film weight of
at least about 1 Mg/in.sup.2, and preferably from about 1
mg/in.sup.2 to about 8 mg/in.sup.2.
DETAILED DESCRIPTION
[0012] The coating composition of the present invention includes a
film-forming epoxy-based resin component, a lubricant system and a
solvent. It has been found that when a film-forming component that
is an epoxy-based resin is combined with a lubricant system having
a first surface modifier that reduces the coefficient of friction
and a second surface modifier that increases the resistance to
abrasion, the coating has excellent release properties after
curing. Whereas epoxy-based coating systems have caused problems
during formation and release of coated metal substrate in some
applications, the present coating composition has been found to
improve the quality of the formed substrate and to increase
productivity.
Coating Composition
[0013] The coating composition of the present invention contains
total solids present in a weight that ranges from about 10% to
about 50%, preferably from about 25% to about 45%, and more
preferably from about 25% to about 40%, and the remainder is
solvent. The solvent can include water, an organic solvent, or a
co-solvent of two or more solvents, such as, for example, water and
organic solvent. A coating composition having from about 25% to
about 35% by weight solids allows application of a dried film
weight of about 1-3 milligrams per square inch, and a coating
composition having from about 30% to about 40% by weight solids
allows application of a dried film weight of about 6-8 milligrams
per square inch.
[0014] The amount of solvent in the coating composition varies,
however, there is at least about 50% by weight solvent, based on
the liquid coating composition. If water is present, the amount of
water in the coating composition ranges from about 20% to about
50%, and is preferably from about 30% to about 45%, and the amount
of solvent ranges from about 20% to about 45%, and preferably, from
about 25% to about 40% solvent.
[0015] The coating composition includes a film-forming component
that is an epoxy-based resin. The coating composition includes, by
weight, based on the weight of total solids, from about 5% to about
99.8%, preferably from about 25% to about 99.8%, more preferably
from about 50% to about 99.5%, and even more preferably, from about
53% to about 99.5% epoxy-based resin.
[0016] The fully cured and dried coating composition also includes,
by weight, at least about 0.1%, preferably from about 0.2% to about
20%, more preferably from about 0.3% to about 10%, and even more
preferably from about 1% to about 5% lubricant system. The
lubricant system includes at least a first surface modifier and a
second surface modifier. The first surface modifier is present in
the coating composition in an amount, by weight, of at least about
0.1%, preferably from about 0.25% to about 16%, more preferably
from about 0.3% to about 12%, and even more preferably from about
0.5% to about 8%. The second surface modifier is present in the
coating composition in an amount that is, by weight, of at least
about 0.1%, preferably from about 0.25% to about 16%, more
preferably from about 0.3% to about 12%, and even more preferably
from about 0.5% to about 8%.
[0017] Optionally, a cross-linker is included for curing the
epoxy-based resin. The type and amount of cross linker can depend
upon the type and amount of epoxy-based resin that is present in
the coating composition. The coating composition comprises, by
weight, based upon the total solids in the coating composition,
preferably from about 0% to about 50%, more preferably from about
0.1% to about 40%, and even more preferably from about 2% to about
10%, and most preferably from about 2% to about 8%
cross-linker.
[0018] The coating composition of the present invention which
includes a film-forming component of an epoxy-based resin and a
lubricant system having a first surface modifier that reduces the
coefficient of friction and a second surface modifier that
increases the resistance to abrasion, when cured and dried, yields
improved release properties. It has been further found that
improved release properties are achieved when the dried and cured
coating of the present invention has a coefficient of friction
(COF) that is less than 0.15, preferably less than about 0.1, more
preferably less than about 0.07, and even more preferably less than
about 0.05, and abrasion that is very slight or substantially zero
as measured by the Olsen Abrasion tests. The results of these tests
are listed in Table II and correspond to Examples 5-8 below.
[0019] The cured coating composition of the present invention
demonstrates excellent adhesion to the metal substrate, excellent
chemical resistance and scratch resistance, and excellent
flexibility. The coating composition also effectively inhibits the
corrosion of metal substrate, such as, but not limited to,
aluminum, iron, steel and copper. Details regarding the above
constituents of the coating composition of the present invention
are discussed in more detail below.
Epoxy-Based Resin
[0020] The coating composition of the present invention includes a
film-forming component that is an epoxy-based resin. Suitable
epoxy-based resins and methods of making them are well known by
those skilled in the art. Epoxy-based resins can be made in the
form of dispersions in organic solvents and co-solvents, including
water.
[0021] In one embodiment of the invention the epoxy-based resin is
an epoxy-acrylic resin. The epoxy-acrylic resins and method for
making them are varied and well known by those skilled in the art.
Suitable epoxy-acrylic resins in aqueous dispersions are described
in U.S. Pat. No. 6,306,914 B1 to Bode et al. and is hereby
incorporated by reference herein. Additional suitable epoxy-acrylic
resins include, but are not limited to, those described in U.S.
Pat. No. 6,008,273 to Leibelt et al. and U.S. Pat. No. 5,830,952 to
Pedersen et al.
[0022] Other suitable epoxy-based resins include, but are not
limited to, epoxy-acrylic resins, epoxy-polyester resins and
epoxy-phosphate resins. Suitable epoxy resin-based polymers for use
in the present composition are disclosed, for example, in U.S. Pat.
No. 5,567,781 to Martino et al. which discloses a polyester
modified solvent based end coating; U.S. Pat. No. 5,635,049 to
Mysliwczyk et al. which discloses water based electrocoats for ends
based on epoxy phosphate; U.S. Pat. No. 5,527,840 to Chutko et al,
which discloses epoxy-acrylic resin grafted by amine catalyzed
esterification and cured with t-butyl phenolic resin; U.S. Pat. No.
5,296,525 to Spencer which discloses grafting the aqueous polymer
by pre-reacting methacrylic acid to some of the epoxy groups before
emulsification; U.S. Pat. No. 4,480,058 to Ting et al, which
discloses amine catalyzed epoxy-acrylic esterification; U.S. Pat.
No. 4,476,262 to Chu et al which discloses aqueous polymerization
in presence of epoxy-acrylic; U.S. Pat. No. 4,446,258 to Chu et al.
which discloses additional stage polymerization in presence of
epoxy-acrylic in solution; U.S. Pat. No. 4,302,373 to Steinmetz
which discloses esterification with tertiary amine catalyst of
epoxy-acrylic by blocking some of the epoxy groups; U.S. Pat. No.
4,247,439 to Matthews et al. which discloses quaternary amine salt
plus ester graft; and EP Patent No. 0 006 334 B1 to Brown et al.
which discloses amine catalyzed esterification. This above list of
epoxy-based resins and dispersions thereof is not exhaustive
Lubricant System
[0023] It has been found that the lubricant system of the present
invention, which includes a first surface modifier and a second
surface modifier provide improved release properties, as measured
by the coefficient of friction and abrasion resistance, when
present in a coating composition containing epoxy-based resin.
[0024] As mentioned above, whereas conventional coating
compositions which include epoxy-based resins without a lubricant
system will have a COF of 0.25 or greater, it has been found that
coating composition of the present invention, containing an
epoxy-based resin and the lubricant system described herein results
in a coating with improved release properties. The dried and cured
coating of the present invention has a coefficient of friction
(COF) that is less than about 0.15, preferably, less than about
0.1, more preferably, less than about 0.07, and even more
preferably, less than about 0.05. Also the abrasion of the cured
coating is very slight or substantially zero as measured by the
Olsen Abrasion test.
[0025] The first surface modifier which reduces the COF can
include, but is not limited to the following materials: carnauba
wax; petroleum waxes including paraffin wax, microcrystalline
waxes, semicrystalline waxes; silicones; insect and animal waxes
including, beeswax, candelilla, japan wax, ouricury wax,
Douglas-fir bark wax, rice-bran wax, jojoba, castor wax, and
bayberry wax; hydrogenated castor oil; high molecular weight acids
and alcohols; mineral waxes including monton wax, pcat wax,
ozokerite, ceresin; and mixtures of the above.
[0026] The second surface modifier which increases the abrasion
resistance of the coating composition can include, but is not
limited to the following materials: polyolefins and polyolefin
copolymers including, polypropylene, modified polypropylenes,
polyethylene and modified polyethylenes; polytetrafluoroethylene;
Fischer-Tropsch waxes, and mixtures of the above. The first surface
modifier is different than the second surface modifier, and
preferably, the second surface modifying has a higher molecular
weight than the first surface modifier.
[0027] Surprisingly, the presence of the second surface modifier
appears to enhance the effectiveness of the first surface modifier.
Although not wishing to be bound by any particular theory, the
second surface modifier which is not very soluble in the
epoxy-based resin tends to rise to the surface of the coating away
from the substrate upon exposure to heat when the coating
composition is dried and cured. In addition, the first surface
modifier which may have a higher degree of solubility in the
epoxy-based resin may be soluble in the second surface modifier,
and therefore, also tends to rise to the surface of the coating
upon exposure to heat. Therefore, it is believed that the
combination of the first surface modifier and the second surface
modifier are effective in producing a coating surface that has a
lower coefficient of friction, improved abrasion resistance and
better release properties, upon curing, as compared to a coating
composition that does not include both the first surface modifier
and the second surface modifier.
[0028] The first surface modifier and the second surface modifier,
preferably in the form of solid particles, are dispersed in organic
solvent or water or a mixture of both. The first surface modifier
and the second surface modifier can be mixed into the epoxy-base
resin dispersion, preferably, such that the particles are
homogeneously dispersed in the liquid coating.
[0029] The lubricant system of the present invention optionally
includes from about 0.5% to about 30% by weight, based on the total
solids in the coating composition, surfactant or dispersing polymer
or mixtures thereof. Surfactants and dispersing polymers are well
known in the art and include, but are not limited to, anionic and
nonionic surfactants. Various dispersing polymers may include the
epoxy-based resins and cross-linker used in the present
invention.
[0030] In another embodiment of the present invention, the coating
composition includes an epoxy-based resin and a lubricant system
that includes a first surface modifier that is carnauba wax and a
second surface modifier that includes polyethylene.
[0031] In another embodiment of the present invention, the coating
composition includes an epoxy-acrylic resin and a lubricant system
that includes a first surface modifier that is carnauba wax and a
second surface modifier that includes polyethylene. The
polyethylene typically has a molecular weight that is less than
about 20,000.
Cross-Linker
[0032] Cross linkers that can optionally be used in the coating
composition of the present invention to achieve the required
physical properties of the cured coating on the substrate. A
suitable cross-linker can include, but is not limited to,
melamine-formaldehyde, ureas formaldehyde, phenol-formaldehyde,
benzoguanamine-formaldehyde resins, and the like, optionally
partially or fully etherified with alcohols are well known in the
art. They may be used individually or blended together. Others may
be possible as well, and this list is not meant to be exhaustive.
The cross linkers may also be used to disperse the lubricant
components.
[0033] In one embodiment the coating composition includes an
epoxy-acrylic resin and uses a phenol-formaldehyde resin made from
Bisphenol A and an alkyl phenol in conjunction with a
melamine-formaldehyde resin.
Solvent
[0034] Solvents such as xylene, benzene, ethyl benzene, toluene,
and the alkoxy alkanols are satisfactory. Alcohols such as
methanol, ethanol, propanol, butanol, and the like, are suitable,
with alkyl ethers of ethylene or propylene glycol being preferred
for solvent systems that contain water. The ethylene glycol
monobutyl ether, ethylene glycol ethyl ether, diethylene glycol
monobutyl ether, and the like are preferred. For subsequent
dispersion into water, the solvents selected should be
water-soluble materials, such as butanol, propanol, ethylene glycol
monoethyl ether, and the like, although small amounts of mineral
spirits, hexane, and similar aliphatics may be used.
[0035] The method of coating a metal substrate according to another
aspect of the present invention includes: applying the liquid
coating composition of the present invention to a metal substrate
and drying the coating. The coating can be applied to the substrate
by a roller which wipes the coating onto the surface of the metal.
A second roll can also apply a coating to the opposite side of the
substrate. For a beverage can lid, for example, the inside surface
which contacts the beverage, is applied such that the it is coated
with about 8 milligrams per square inch of metal of dried coating,
and the outside surface receives about 2 mg per square inch of
dried coating . . . . The coated metal strip enters an oven within
a second or two, and travels through the oven with a residence time
that varies with the speed of the line, typically from about 8 to
about 25 seconds. It metal reaches a peak metal temperature of
about 230.degree. C. to about 250.degree. C. and the volatile
components of the coating are evaporated. The coating chemically
cures, and is aided by reaction of the cross-linker, if present, to
become solid.
[0036] The present invention may be further described by reference
to the following examples.
WORKING EXAMPLES
Sample Preparation
[0037] The coating compositions of Examples 1-4 were prepared by
mixing the aqueous epoxy-acrylic emulsion with the
phenol-formaldehyde crosslinking resins and a predispersion of
waxes, The weight of each component based on the total weight of
the coating composition is listed in Table I. Additional water or
co-solvent may be added to reduce viscosity and nonvolatile
content. Colorants or predispersed pigments can be mixed into the
system if decorative properties are desired.
TABLE-US-00001 TABLE I Wt. % Ex. 1 Ex. 2 Ex. 3 Ex. 4 Epoxy-acrylic
287.9 287.9 287.9 287.9 Phenol-formaldehyde 7.1 7.1 7.1 7.1
Carnauba wax 12.0 -- 8.0 -- Polyethylene wax -- 3.0 3.0 --
Carnauba/polyethylene blend -- -- -- 13.6 (1) Aqueous modified
epoxy acrylic per U.S. Pat. No. 6,306,934 at 33% NV (2)
Phenol-formaldehyde crosslinker supplied by DSM Resins, HRJ 12632
(3) Carnauba wax emulsion supplied by Michelman Chemicals,
Michemlube 160 (4) Polyethylene wax supplied by Micro Powders,
Mpp-620F (5) Carnauba/Polyethylene blend dispersion supplied by
Lubrizol, Lanco Glidd TPG-102
[0038] In examples 5-8, laboratory test panels having an aluminum
substrate were prepared by using wire round rods to make draw-downs
of uniform coating weights of 1.0-8.0 milligrams per square inch
(msi). These panels were baked to peak metal temperatures of
224-250.degree. C. with oven dwell times of 10-20 seconds. The
results of the coefficient of friction and a qualitative abrasion
resistance test is listed below in Table II.
TABLE-US-00002 TABLE II Test Method Ex. 5 Ex. 6 Ex. 7 Ex. 8 Altek
Lubricity (COF) .07-.09 .1-.12 .05-.07 .05-.07 Olsen Abrasion
(Pick-Off) Severe None None None Olsen Abrasion (2000 lbs.) Heavy
Slight Very slight Very slight
[0039] In Examples 9-15 below, several coatings were tested in the
making of easy open ends of aluminum cans. The coating compositions
of Example 4 above was used in Examples 9 and 10 and conventional
or proprietary coating compositions were used in Comparative
Examples 11-15. The coatings were applied aluminum coil by a roller
which wipes the coating onto one surface (the outside surface of
the coil can lid) at a dried coating thickness that ranged from
about 2-3 milligrams per square inch. The weight of coating in
Example 9 was about 2 milligrams per square inch and the weight of
the dried coating in Example 10 was about 3 milligrams per square
inch. All samples except one of the comparative examples had the
same coating applied to both sides of the coil, with the outside of
the coil having a dried thickness of about 7-8 milligrams per
square inch.
[0040] The coated metal cold rolled out as a strip was immediately
(within 1-2 seconds) run through an oven in a residence time of
about 11 seconds. The temperature of the oven ranged from about
225.degree. C. to about 240.degree. C.
[0041] The coated coil containing each coating composition was cut
into strips and the strips were fabricated on the Redicon End Level
II pilot press. The coated and stamped shells for the easy open
cans were inspected at 10,000 stroke intervals and were inspected
until the scuffing was determined to be unacceptable. The shells
were given a scuffing index rating that ranged from 1-4 with 4
being the worst, based on visual inspection. The ratings given to
shells with the various coating compositions according to the
number of press strokes is listed in Table III.
TABLE-US-00003 TABLE III Press Compar. Compar. Compar. Compar.
Compar. Strokes Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 500
1 1 1 2 1 3.5 1 2500 1 1 1 2 2.5 4 1 5000 1 1 1 2 3 1 10000 1 1 1.5
2 3 2 20000 1 1 1.5 2 4 2.5 30000 1 1 1.5 2 2.5 40000 1 1 1.5 2.5 3
50000 1 1 2 2.5 3 60000 1 1 2 2.5 3 70000 1 1 2 2.5 3.5 80000 1 1
2.5 3 4 90000 1 1 3 3 4 100000 1 1 3 3 4 110000 1 1 4 120000 1 1
4
[0042] The results show that the coating of the present invention
used in Examples 9 and 10 showed no visual scuffing as far as the
trial was run to 275,000 press strokes.
[0043] The invention has been described with reference to various
specific and preferred embodiments and techniques. It should be
understood, however, that many variations and modifications may be
made while remaining within the spirit and scope of the
invention.
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