U.S. patent application number 15/281495 was filed with the patent office on 2017-05-25 for polyurethane coating composition.
This patent application is currently assigned to Valspar Sourcing, Inc.. The applicant listed for this patent is Valspar Sourcing, Inc.. Invention is credited to Larry Brandenburger, Carl Cavallin, Danny G. Hartinger, T. Howard Kilillea.
Application Number | 20170145254 15/281495 |
Document ID | / |
Family ID | 43759034 |
Filed Date | 2017-05-25 |
United States Patent
Application |
20170145254 |
Kind Code |
A1 |
Cavallin; Carl ; et
al. |
May 25, 2017 |
Polyurethane Coating Composition
Abstract
A polymer useful in coating compositions is described. The
polymer is preferably an unsaturated polyurethane polymer, which
preferably has an iodine value of at least 10. The polymer may be
combined with one or more liquid carriers to form a liquid coating
composition useful in coating a variety of substrates, including
planar metal substrates.
Inventors: |
Cavallin; Carl; (Needville,
TX) ; Kilillea; T. Howard; (North Oaks, MN) ;
Brandenburger; Larry; (Lino Lakes, MN) ; Hartinger;
Danny G.; (Centre Hall, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Valspar Sourcing, Inc. |
Minneapolis |
MN |
US |
|
|
Assignee: |
Valspar Sourcing, Inc.
Minneapolis
MN
|
Family ID: |
43759034 |
Appl. No.: |
15/281495 |
Filed: |
September 30, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14464217 |
Aug 20, 2014 |
9487672 |
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15281495 |
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13496758 |
Mar 16, 2012 |
8840966 |
|
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PCT/US2010/049356 |
Sep 17, 2010 |
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14464217 |
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PCT/US2010/042254 |
Jul 16, 2010 |
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13496758 |
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61300647 |
Feb 2, 2010 |
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61243888 |
Sep 18, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 18/12 20130101;
C08G 18/755 20130101; C08G 18/4202 20130101; C08G 18/12 20130101;
C09D 167/06 20130101; B32B 15/08 20130101; B05D 2350/65 20130101;
C08G 18/348 20130101; C09D 175/14 20130101; C08F 283/008 20130101;
C08G 64/04 20130101; C08L 75/04 20130101; C07C 39/16 20130101; Y10T
428/264 20150115; B05D 2252/02 20130101; Y10T 428/1352 20150115;
C07C 37/20 20130101; C08G 18/698 20130101; C08L 75/04 20130101;
C08G 18/4891 20130101; Y10T 428/1355 20150115; C08G 18/0823
20130101; C08L 67/06 20130101; B05D 3/02 20130101; B05D 2202/25
20130101; C08G 63/676 20130101; B05D 7/14 20130101; C09D 151/08
20130101; C08F 220/32 20130101; C08F 283/008 20130101; C08L 2666/02
20130101; C07C 37/68 20130101; B32B 1/08 20130101; C08G 18/4211
20130101; C08K 5/06 20130101; Y10T 428/31551 20150401; C08F 283/008
20130101; C08L 2666/04 20130101; C08G 18/3271 20130101; C09D 151/08
20130101; C08F 220/18 20130101; B05D 2503/00 20130101; Y10T
428/31605 20150401; Y10T 428/31692 20150401; B05D 3/0254
20130101 |
International
Class: |
C09D 175/14 20060101
C09D175/14; B05D 3/02 20060101 B05D003/02; B05D 7/14 20060101
B05D007/14 |
Claims
1-20. (canceled)
21. A coated article, comprising: a planar metal substrate with a
coating disposed thereon, the coating derived from a coating
composition comprising: at least 5 wt % of an unsaturated
polyurethane polymer that includes one or more aliphatic
carbon-carbon double bonds with heat of hydrogenation of at least
about -28.25 kcal/mol; and a liquid carrier.
22. The article of claim 1, wherein the one or more aliphatic
carbon-carbon double bonds have heat of hydrogenation of at least
about -33.13 kcal/mol.
23. The article of claim 1, wherein the unsaturated polyurethane
polymer is self-crosslinkable.
24. The article of claim 1, wherein the unsaturated polyurethane
polymer includes one or more segments formed from an unsaturated
polybutadiene.
25. The article of claim 1, wherein the unsaturated polyurethane
polymer includes one or more ether linkages.
26. The article of claim 1, wherein the coating composition
comprises an aqueous dispersion of the polyurethane polymer.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. application Ser.
No. 14/464,217 filed Aug. 20, 2014 (now U.S. Pat. No. ______) and
entitled "POLYURETHANE COATING COMPOSITION," which is a
continuation of U.S. application Ser. No. 13/496,758 filed on Mar.
16, 2012, now U.S. Pat. No. 8,840,966, and entitled "POLYURETHANE
COATING COMPOSITION," which is the National Stage filing under 35
U.S.C. 371 of International Application No. PCT/US2010/049356 filed
on Sep. 17, 2010 and entitled "POLYURETHANE COATING COMPOSITION,"
which claims the benefit of U.S. Provisional Patent Application No.
61/300,647 filed on Feb. 2, 2010 and entitled "POLYURETHANE COATING
COMPOSITION," and is a continuation-in-part of International
Application No PCT/US2010/042254 filed on Jul. 16, 2010, and
entitled "COATING COMPOSITION AND ARTICLES COATED THEREWITH."
International Application No. PCT/US2010/042254 claims the benefit
of U.S. Provisional Application No. 61/243,888 filed Sep. 18, 2009
and entitled "COATING COMPOSITION AND ARTICLES COATED THEREWITH,"
the disclosure of each is incorporated herein by reference in its
entirety.
TECHNICAL FIELD
[0002] This invention relates to a polymer coating composition. In
particular, the present invention relates to a polymer coating
composition useful in coating metal substrates.
BACKGROUND
[0003] Polymer coating compositions are routinely applied to
substrates, especially metal substrates. Such coatings are used for
a variety of reasons, including, for example, to protect the
substrate from degradation, to beautify the substrate (e.g., to
provide color, brightness, etc.), and/or to reflect light.
[0004] Many such polymer coating compositions are applied on planar
substrate (e.g., using a coil coating process) that is subsequently
formed into a finished article. The designer of such coatings is
faced with a multitude of challenges in developing suitable
coatings. For example, coating compositions are desired that
perform well when applied to a variety of different types of
metals, which may have differing surface characteristics and
differing levels of cleanliness. In general, it is desired that the
coatings adhere well to a variety of different substrates; exhibit
suitable flexibility, hardness, and abrasion resistance (e.g., to
endure fabrication steps that may be required to form a finished
article); and exhibit suitable aesthetic qualities. Achieving a
suitable balance of coating properties at a suitably low cost can
be difficult because, oftentimes, improvements made to one coating
property are associated with degradation of another coating
property. For example, improved coating hardness is often achieved
to the detriment of coating flexibility.
[0005] Accordingly, there is a continuing need for coating
compositions that exhibit one or more enhanced coating
properties.
SUMMARY
[0006] The present invention provides a polymer useful in coating
applications.
[0007] In one embodiment, the polymer is an unsaturated polymer,
more preferably an unsaturated polyurethane polymer, and even more
preferably an unsaturated polyurethane polymer having an iodine
value of at least 10. The unsaturated polymer preferably includes
one or more aliphatic carbon-carbon double bonds, and more
preferably includes one or more "reactive" aliphatic carbon-carbon
double bonds such as, for example, a vinylic double bond, a
conjugated double bond, a double bond present in a strained ring
group, a double bond present in an unsaturated bicyclic group, or a
combination thereof.
[0008] In another embodiment, the polymer is an unsaturated
polymer, more preferably an unsaturated polyurethane polymer, and
even more preferably an unsaturated polyurethane polymer having an
iodine value of at least 10, which includes one or more unsaturated
segments formed from a (poly)alkene compound, more preferably a
functionalized polybutadiene-containing compound. The unsaturated
polymer preferably includes at least 5% by weight of the
(poly)alkene compound, and more preferably at least 5% by weight of
functionalized polybutadiene-containing compound.
[0009] The present invention also provides a coating composition
that includes an unsaturated polymer described herein. The coating
composition preferably includes one or more optional liquid
carriers. Suitable liquid carriers may include one or more organic
solvents, water, or a combination thereof.
[0010] The present invention also provides a coated article. In one
embodiment, the coated article has a metal substrate where at least
a portion of the metal substrate is coated with a coating
composition described herein.
[0011] The present invention further provides a method for forming
a coated article. The method typically includes applying a coating
to at least a portion of a planar metal substrate. The coating
composition preferably includes a film-forming amount of an
unsaturated polymer of the present invention (preferably an
unsaturated polyurethane polymer) and one or more optional liquid
carriers. The coated metal substrate is preferably heated to form a
cured coating, which is preferably a crosslinked coating. The
coated metal substrate is preferably heated to a peak metal
temperature of at least about 350.degree. F. (177.degree. C.).
[0012] The above summary of the present invention is not intended
to describe each disclosed embodiment or every implementation of
the present invention. The description that follows more
particularly exemplifies illustrative embodiments. In several
places throughout the application, guidance is provided through
lists of examples, which can be used in various combinations. In
each instance, the recited list serves only as a representative
group and should not be interpreted as an exclusive list.
[0013] The details of one or more embodiments of the present
invention are set forth in the description below. Other features,
objects, and advantages of the present invention will be apparent
from the description and from the claims.
Selected Definitions
[0014] Unless otherwise specified, the following terms as used
herein have the meanings provided below.
[0015] A group that may be the same or different is referred to as
being "independently" something. Substitution is anticipated on the
organic groups of the compounds of the present invention. As a
means of simplifying the discussion and recitation of certain
terminology used throughout this application, the terms "group" and
"moiety" are used to differentiate between chemical species that
allow for substitution or that may be substituted and those that do
not allow or may not be so substituted. Thus, when the term "group"
is used to describe a chemical substituent, the described chemical
material includes the unsubstituted group and that group with 0, N,
Si, or S atoms, for example, in the chain (as in an alkoxy group)
as well as carbonyl groups or other conventional substitution.
Where the term "moiety" is used to describe a chemical compound or
substituent, only an unsubstituted chemical material is intended to
be included. For example, the phrase "alkyl group" is intended to
include not only pure open chain saturated hydrocarbon alkyl
substituents, such as methyl, ethyl, propyl, t-butyl, and the like,
but also alkyl substituents bearing further substituents known in
the art, such as hydroxy, alkoxy, alkylsulfonyl, halogen atoms,
cyano, nitro, amino, carboxyl, etc. Thus, "alkyl group" includes
ether groups, haloalkyls, nitroalkyls, carboxyalkyls,
hydroxyalkyls, sulfoalkyls, etc. On the other hand, the phrase
"alkyl moiety" is limited to the inclusion of only pure open chain
saturated hydrocarbon alkyl substituents, such as methyl, ethyl,
propyl, t-butyl, and the like. As used herein, the term "group" is
intended to be a recitation of both the particular moiety, as well
as a recitation of the broader class of substituted and
unsubstituted structures that includes the moiety.
[0016] The term "substantially free" of a particular mobile
compound means that the compositions of the present invention
contain less than 1,000 parts per million (ppm) of the recited
mobile compound. The term "essentially free" of a particular mobile
compound means that the compositions of the present invention
contain less than 100 ppm of the recited mobile compound. The term
"essentially completely free" of a particular mobile compound means
that the compositions of the present invention contain less than 5
ppm of the recited mobile compound. The term "completely free" of a
particular mobile compound means that the compositions of the
present invention contain less than 20 parts per billion (ppb) of
the recited mobile compound. If the aforementioned phrases are used
without the term "mobile" (e.g., "substantially free of XYZ
compound") then the compositions of the present invention contain
less than the aforementioned amount of the compound whether the
compound is mobile in the coating or bound to a constituent of the
coating.
[0017] The term "crosslinker" refers to a molecule capable of
forming a covalent linkage between polymers or between two
different regions of the same polymer.
[0018] The terms "self-crosslinking" or "self-crosslinkable," when
used in the context of a self-crosslinking polymer, refers to the
capacity of a polymer to enter into a crosslinking reaction with
itself and/or another molecule of the polymer, in the absence of an
external crosslinker, to form a covalent linkage therebetween.
Typically, this crosslinking reaction occurs through reaction of
complementary reactive functional groups present on the
self-crosslinking polymer itself or two or more separate molecules
of the self-crosslinking polymer.
[0019] The term "water-dispersible" in the context of a
water-dispersible polymer means that the polymer can be mixed into
water (or an aqueous carrier) to form a stable mixture. For
example, a mixture that readily separates into immiscible layers is
not a stable mixture. The term "water-dispersible" is intended to
include the term "water-soluble." In other words, by definition, a
water-soluble polymer is also considered to be a water-dispersible
polymer.
[0020] The term "dispersion" in the context of a dispersible
polymer refers to the mixture of a dispersible polymer and a
carrier. The term "dispersion" is intended to include the term
"solution."
[0021] The term "on," when used in the context of a coating applied
on a substrate, includes both coatings applied directly or
indirectly to the substrate. Thus, for example, a coating applied
to a primer layer overlying a substrate constitutes a coating
applied on the substrate.
[0022] The term "polymer" includes both homopolymers and copolymers
(i.e., polymers of two or more different monomers). Similarly, the
term "polyurethane polymer" is intended to include both
homopolymers and copolymers (e.g., polyester-urethane
polymers).
[0023] The term "aliphatic" when used in the context of a
carbon-carbon double bond includes both linear (or open chain)
aliphatic carbon-carbon double bonds and cycloaliphatic
carbon-carbon double bonds, but excludes aromatic carbon-carbon
double bonds of aromatic rings.
[0024] The term "unsaturation" when used in the context of a
compound refers to a compound that includes at least one
non-aromatic (i.e., aliphatic) carbon-carbon double bond.
[0025] The term "vinyl polymer" refers to a polymer prepared by
addition polymerizing an ethylenically unsaturated component (e.g.,
a mixture of ethylenically unsaturated monomers and/or
oligomers).
[0026] The term "(meth)acrylate" includes both acrylates and
methacrylates.
[0027] The term "polycyclic" when used in the context of a group
refers to an organic group that includes at least two cyclic groups
in which one or more atoms (and more typically two or more atoms)
are present in the rings of both of the at least two cyclic groups.
Thus, for example, a group that consists of two cyclohexane groups
connected by a single methlylene group is not a polycyclic
group.
[0028] The term "comprises" and variations thereof do not have a
limiting meaning where these terms appear in the description and
claims.
[0029] The terms "preferred" and "preferably" refer to embodiments
of the present invention that may afford certain benefits, under
certain circumstances. However, other embodiments may also be
preferred, under the same or other circumstances. Furthermore, the
recitation of one or more preferred embodiments does not imply that
other embodiments are not useful, and is not intended to exclude
other embodiments from the scope of the present invention.
[0030] As used herein, "a," "an," "the," "at least one," and "one
or more" are used interchangeably. Thus, for example, a coating
composition that comprises "an" additive can be interpreted to mean
that the coating composition includes "one or more" additives.
[0031] Also herein, the recitations of numerical ranges by
endpoints include all numbers subsumed within that range (e.g., 1
to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Furthermore,
disclosure of a range includes disclosure of all subranges included
within the broader range (e.g., 1 to 5 discloses 1 to 4, 1.5 to
4.5, 1 to 2, etc.).
DETAILED DESCRIPTION
[0032] In one aspect, the present invention provides a coating
composition useful in a variety of applications. The coating
composition is useful for forming an adherent coating on various
metal substrates and is particularly suited for use in metal coil
coating applications. In preferred embodiments, the coating
composition includes an unsaturated polyurethane binder polymer
that is preferably present in a film-forming amount. The
unsaturated polyurethane polymer preferably includes at least one
aliphatic carbon-carbon double bond, and more preferably includes a
plurality of aliphatic carbon-carbon double bonds. While not
intending to be bound by any theory, the inclusion of an
efficacious amount of aliphatic carbon-carbon double bonds in the
polyurethane polymer of the present invention has been observed to
yield a desirable balance of coating properties such as good
coating hardness, good chemical resistance, and good coating
flexibility, which is believed to be attributable, at least in
part, to the formation of crosslinks through the aliphatic
carbon-carbon double bonds upon coating cure.
[0033] In certain preferred embodiments, at least some of the
aliphatic carbon-carbon double bonds are "reactive" carbon-carbon
double bonds that are preferably sufficiently reactive under
typical coating cure conditions (more preferably coil coating cure
conditions) to participate in a reaction with one or more other
functionalities present in the coating composition to form a
covalent linkage. Non-limiting examples of reactive aliphatic
carbon-carbon double bonds include vinylic double bonds (e.g.,
--C(R.sub.1).dbd.C(R.sub.2R.sub.3)), conjugated aliphatic double
bonds (e.g.,
--C(R.sub.4).dbd.C(R.sub.5)--C(R.sub.6).dbd.C(R.sub.7)--),
aliphatic double bonds present in strained ring groups, aliphatic
double bonds present in certain unsaturated polycyclic groups
(e.g., polycyclic groups including an unsaturated bridged bicyclic
group), and combinations thereof. (In the above representative
structural formulas, R.sub.1 preferably denotes a hydrogen atom, a
halogen atom, or a methyl group; R.sub.2 and R.sub.3 preferably
each independently denote a hydrogen or halogen atom; and R.sub.4
to preferably each independently denote a hydrogen atom, a halogen
atom, or an organic group such as, for example, a methyl group, a
substituted or unsubstituted alkyl group, a substituted or
unsubstituted cycloalkyl group, a substituted or unsubstituted aryl
group, or a substituted or unsubstituted alkenyl or alkynyl
group.)
[0034] Heat of hydrogenation may be a useful indicator of the
reactivity of an aliphatic carbon-carbon double bond. In some
embodiments, the unsaturated binder polymer includes one or more
aliphatic carbon-carbon double bonds having a heat of hydrogenation
greater than that of cyclohexene. Such aliphatic carbon-carbon
double bonds may be present in either an open chain portion of the
polymer or in a cyclic group of the polymer. In certain
embodiments, the unsaturated binder polymer includes one or more
aliphatic carbon-carbon double bonds having a heat of hydrogenation
that is at least about as high as that of bicyclo[2.2.2]octene
(e.g., -28.25 kcal/mole), and more preferably, at least about as
high as that of bicyclo[2.2.1]heptene (e.g., -33.13 kcal/mole). As
used herein, when a heat of hydrogenation is stated to be, for
example, "at least X," "greater than X," or the like, it should be
understood that reference is made to the absolute value of the heat
of hydrogenation because heats of hydrogenation are typically
reported as negative values, with a larger negative value
indicating a higher heat of hydrogenation (e.g., -40 kcal/mole is a
higher heat of hydrogenation than -10 kcal/mole).
[0035] The unsaturated polyurethane polymer of the present
invention may include any suitable number of aliphatic
carbon-carbon double bonds. Iodine value is a useful measure of the
number of aliphatic carbon-carbon double bonds present in a
material. The unsaturated polyurethane polymer of the present
invention may have any suitable iodine value to achieve a desired
result. In preferred embodiments, the unsaturated polyurethane
polymer has an iodine value of at least about 10, more preferably
at least about 20, even more preferably at least about 35, and
optimally at least about 50. The upper range of suitable iodine
values is not particularly limited, but in most embodiments the
iodine value typically will not exceed about 100 or about 120. The
aforementioned iodine values are expressed in terms of the
centigrams of iodine per gram of the material. Iodine values may be
determined, for example, using ASTM D 5768-02 (Reapproved 2006)
entitled "Standard Test Method for Determination of Iodine Values
of Tall Oil Fatty Acids." In certain embodiments, the total
polyurethane content of the coating composition exhibits an average
iodine value pursuant to the aforementioned values.
[0036] In some embodiments, at least a substantial portion (e.g.,
greater than 5%, greater than 10%, greater than 25%, greater than
50%, etc.) of the aforementioned iodine values for the unsaturated
polyurethane polymer is attributable to the presence of one or more
of: vinylic carbon-carbon double bonds, conjugated aliphatic
carbon-carbon double bonds, aliphatic carbon-carbon double bonds
present in strained ring groups, aliphatic carbon-carbon double
bonds present in unsaturated bicyclic groups, and combinations
thereof. In certain embodiments, of the total measured iodine value
for the unsaturated polyurethane polymer, at least about 10,
preferably at least about 20, more preferably at least about 35,
and optimally at least about 50 centigrams of iodine per gram of
unsaturated polyurethane polymer is attributable to the presence of
aliphatic carbon-carbon double bonds and more preferably to the
presence of reactive aliphatic carbon-carbon double bonds.
[0037] In certain preferred embodiments, the unsaturated
polyurethane polymer includes alkene and/or polyalkene groups
(referred to collectively herein as "(poly)alkene" groups), more
preferably one or more alkene and/or polyalkene moieties, having at
least one aliphatic carbon-carbon double bond. In some embodiments,
the (poly)alkene groups include at least some vinylic carbon-carbon
double bonds and/or conjugated carbon-carbon double bonds. The
(poly)alkene groups may be monovalent or polyvalent (e.g., divalent
or trivalent), are preferably monovalent or divalent, and are even
more preferably divalent.
[0038] The (poly)alkene groups may be substituted or unsubstituted
and may be present as backbone and/or pendant groups. Non-limiting
examples of suitable (poly)alkene groups include groups formed from
functionalized butadiene or polybutadiene, unsaturated fatty acids
(e.g., mono- or poly-unsaturated fatty acids such as arichidonic,
eleostearic, erucic, licanic, linoleic, linolenic, oleic,
palmitoleic, ricinoleic acid, and derivatives or mixtures thereof),
polyisoprene, poly-EPDM (ethylene propylene diene monomer),
modified poly-EPDM (e.g., modified with dicyclopentadiene, vinyl
norbornene, etc.), or a combination thereof. Groups formed from
fully hydrogenated polyalkene compounds, such as, for example,
backbone segments formed from fully hydrogenated polybutadiene
compounds, are not (poly)alkene groups.
[0039] As discussed above, in some embodiments, a functionalized
(poly)alkene compound may be used as a reactant for forming the
polyurethane of the present invention. The functionalized
(poly)alkene compound may be monofunctional or polyfunctional
(e.g., difunctional, trifunctional, etc.), preferably
monofunctional or difunctional, more preferably difunctional.
Suitable functional groups may include any of the functional groups
described herein, including, for example, reactive hydrogen
groups.
[0040] Unsaturated polybutadiene-containing groups, and unsaturated
polybutadiene backbone segments in particular, are preferred
(poly)alkene groups. Hydroxyl-terminated polybutadiene is a
presently preferred compound for incorporating (poly)alkene groups
into the polyurethane polymer of the present invention.
Functionalized polybutadiene-containing compounds such as
hydroxylated polybutadiene are commercially available. Non-limiting
examples of commercial functionalized polybutadiene materials
include the POLY BD R45HTLO, POLY BD R20LM, KRASOL LBH 2000, KRASOL
LBH 2040, KRASOL LBH 3000, KRASOL LBH 5000, KRASOL LBH 10000,
KRASOL LBH-P 2000, KRASOL LBH-P 3000, and KRASOL LBH-P 5000
products (all available from Cray Valley). Preferred functionalized
polybutadiene-containing compounds have a number average molecular
weight ("Mn") of from about 500 to about 10,000, more preferably
from about 1,000 to about 5,000, and even more preferably from
about 2,000 to about 3,000.
[0041] When present in the unsaturated polyurethane, the
(poly)alkene groups are preferably present in an amount of at least
about 1 weight percent ("wt-%"), more preferably at least about 5
wt-%, and even more preferably at least about 15 wt-%, based on the
total weight of the unsaturated polyurethane polymer. The
(poly)alkene groups are preferably included in an amount of less
than about 80 wt-%, more preferably less than about 50 wt-%, and
even more preferably less than about 20 wt-%, based on the total
weight of the unsaturated polyurethane polymer. The above weight
percentages are based on the amount of
(poly)alkene-group-containing compounds used to form the
polyurethane polymer.
[0042] As previously discussed, in some embodiments, the
unsaturated binder polymer of the present invention includes one or
more polycylic groups, and more preferably one or more strained
polycyclic groups such as, for example, an unsaturated bridged
bicyclic group. In some embodiments, the unsaturated polyurethane
polymer includes one or more unsaturated bicyclic structures
represented by the IUPAC (International Union of Pure and Applied
Chemistry) nomenclature of Expression (I) below:
bicyclo[x.y.z]alkene
[0043] In Expression (I), [0044] x is an integer having a value of
2 or more, [0045] y is an integer having a value of 1 or more,
[0046] z is an integer having a value of 0 or more, and [0047] the
term alkene refers to the IUPAC nomenclature designation (e.g.,
hexene, heptene, heptadiene, octene, etc.) for a given bicyclic
molecule and denotes that the bicyclic group includes one or more
double bonds (e.g. .gtoreq.1, .gtoreq.2, .gtoreq.3 double
bonds).
[0048] Preferably z in Expression (I) is 1 or more. In other words,
preferred bicyclic groups include a bridge with a least one atom
(typically one or more carbon atoms) interposed between a pair of
bridgehead atoms, where the at least one atom is shared by at least
two rings. By way of example, bicyclo[4.4.0]decane does not include
such a bridge.
[0049] Preferably, x has a value of 2 or 3 (more preferably 2) and
each of y and z independently have a value of 1 or 2.
[0050] Non-limiting examples of some suitable unsaturated bicyclic
groups represented by Expression (I) include monovalent or
polyvalent (e.g., divalent) variants of bicyclo[2.1.1]hexene,
bicyclo[2.2.1]heptene (i.e., norbornene), bicyclo[2.2.2]octene,
bicyclo[2.2.1]heptadiene, and bicyclo[2.2.2]octadiene.
Bicyclo[2.2.1]heptene is a presently preferred unsaturated bicyclic
group. Suitable unsaturated bridged bicyclic groups may also
include Diels-Alder adducts of maleic anhydride and rosin (see,
e.g., U.S. Pat. No. 5,212,213 for further discussion of such
adducts).
[0051] It is contemplated that the unsaturated bicyclic groups
represented by Expression (I) may contain one or more heteroatoms
(e.g., nitrogen, oxygen, sulfur, etc.) and may be substituted to
contain one or more additional substituents. For example, one or
more cyclic groups (including, e.g., pendant cyclic groups and ring
groups fused to a ring of the bicyclic group) or acyclic groups may
be attached to the bicyclic group represented by Expression (I).
Thus, for example, in some embodiments the bicyclic group of
Expression (I) may be present in a tricyclic or higher polycyclic
group.
[0052] Non-limiting examples of suitable unsaturated strained ring
groups (other than those that may be present in an unsaturated
bridged bicyclic group) may include substituted or unsubstituted,
monovalent or polyvalent (e.g., divalent) variants of the
following: cyclopropene (e.g., 1,2-dimethylcyclopropene),
ethylidenecyclopropane, cyclobutene, methylenecyclobutane,
trans-cyclooctene, trans-cyclononene, cyclobutadiene,
cyclopentadiene, 1,3-cyclohexadiene, 1,3-cycloheptadiene,
1,3-cyclooctadiene, 1,3-cyclononadiene, and 1,3-cyclodecadiene, and
derivatives and combinations thereof. By way of example, a
cyclohexene group is not typically considered to be a strained ring
group. In the context of monocyclic ring systems, rings including 3
to 5 atoms, and especially 3 or 4 atoms, tend to exhibit the
greatest amount of total ring strain. Examples of such strained
monocylic ring systems are included in the above list.
[0053] The unsaturated polyurethane polymer preferably includes a
sufficient number of urethane linkages to provide the desired
coating properties for the desired end use. Such coating properties
may include flexibility, abrasion resistance, and/or fabrication
(e.g., to accommodate stamping processes used to form articles from
coated planar metal substrate). Preferred unsaturated polyurethane
polymers preferably include on average at least about 2 urethane
linkages, more preferably at least about 10 urethane linkages, and
even more preferably at least about 20 urethane linkages per
molecule of the polymer. While the number of urethane linkages
present in the unsaturated polyurethane polymer is not particularly
restricted on the high end and may vary depending upon molecular
weight, in certain embodiments, the polyurethane polymer includes
on average less than about 1,000 urethane linkages, less than about
200 urethane linkages, or less than about 50 urethane linkages per
molecule of the polymer.
[0054] Isocyanate content may be another useful measure of the
number of urethane linkages in a polymer. In presently preferred
embodiments, the unsaturated polyurethane polymer is formed from
reactants including, based on total nonvolatiles, at least about
0.1 wt-%, more preferably at least about 1 wt-%, and even more
preferably at least about 5 wt-% of an isocyanate compound. The
upper amount of suitable isocyanate compound concentration is not
particularly limited and will depend upon the molecular weight of
the one or more isocyanate compounds utilized as reactants.
Typically, however, the unsaturated polyurethane polymer is formed
from reactants including, based on total nonvolatiles, less than
about 35 wt-%, more preferably less than about 30 wt-%, and even
more preferably less than about 25 wt-% of an isocyanate compound.
Preferably, the isocyanate compound is incorporated into a backbone
of the unsaturated polyurethane polymer via a urethane linkage, and
more preferably a pair of urethane linkages.
[0055] The unsaturated polyurethane polymer may include a backbone
of any suitable structural configuration. The backbone may have
different structural configurations depending on a variety of
factors such as the materials used to form the backbone, cost, and
the desired end use for the polymer. The backbone may optionally
include one or more other backbone step-growth linkages (e.g.,
condensation linkages) such as, for example, amide, ester,
carbonate ester, ether, imide, imine, urea linkages, or a
combination thereof. Moreover, the backbone of the unsaturated
polyurethane polymer may optionally include one or more oligomer or
polymer segments selected from, for example, acrylic, epoxy,
polyamide, polyester, poly(carbonate ester), polyether, polyimide,
polyimine, polyurea, copolymer segments thereof, or a combination
thereof.
[0056] In some embodiments, the polyurethane polymer is a linear
polymer or a substantially linear, polymer. In other embodiments,
the polyurethane polymer may include branching.
[0057] The polyurethane polymer of the present invention may have
any suitable end groups and/or optional side groups.
[0058] The unsaturated polyurethane polymer of the present
invention may be of any suitable molecular weight. In embodiments
where the unsaturated polyurethane polymer is water-dispersible,
the Mn of the polymer after optional chain extension, if any, is
typically no greater than 500,000, more typically no greater than
100,000, and even more typically no greater than 40,000. In such
embodiments, the Mn of the unsaturated polyurethane polymer after
optional chain extension, if any, is preferably at least 5,000,
more preferably at least 10,000, and even more preferably at least
30,000. The molecular weight of the polyurethane polymer in
solvent-based coating embodiments may be similar to, or different
from, that described above.
[0059] The coating composition of the present invention preferably
includes at least about 5% by weight (wt-%), more preferably at
least about 20 wt-%, even more preferably at least about 30 wt-%,
and even more preferably at least about 45 wt-% of the unsaturated
polyurethane polymer, based on the total weight of nonvolatile
material in the coating composition. In some embodiments, the
coating composition includes from about 50 to about 100 wt-% of
unsaturated polyurethane polymer, based on the total weight of
nonvolatile material in the coating composition. The upper amount
of unsaturated polyurethane polymer included in the coating
composition of the present invention is not especially limited. In
some embodiments, the coating composition includes less than 100
wt-%, more preferably less than 95 wt-%, and even more preferably
less than 85 wt-% of unsaturated polyurethane polymer, based on the
total weight of nonvolatile material in the coating composition. In
some embodiments, the coating composition includes less than about
50 wt-% of unsaturated polyurethane polymer, based on the total
weight of nonvolatile material in the coating composition
[0060] The unsaturated polyurethane polymer of the present
invention may be formed using any suitable reactants and any
suitable process. Polyurethane polymers are typically formed by
reacting ingredients that include one or more polyols, one or more
isocyanate-functional compounds, and optionally one or more
additional reactants (e.g., organic materials having one or more
active hydrogen groups). If desired, the polyurethane polymer may
be formed through an optional polyurethane prepolymer intermediate.
If such a prepolymer is used, the prepolymer may be optionally
chain extended using one or more chain extender agents.
Chain-extending techniques and materials (e.g., amine-functional
chain extenders) such as those described in International
Application No. PCT/US10/42254 can be used.
[0061] Any suitable polyol or mixture of polyols may be used to
form the unsaturated polyurethane polymer of the present invention.
The one or more polyols may be a monomer, an oligomer, a polymer,
or a mixture thereof. In addition, the one or more polyols can be a
diol, a triol, a polyol having 4 or more hydroxyl groups, or a
mixture thereof. Diols are presently preferred. Non-limiting
examples of suitable oligomer and/or polymer polyols include
polyether polyols, polyester polyols, polyether-ester polyols,
polyimide polyols, polyurea polyols, polyamide polyols,
polycarbonate polyols, saturated or unsaturated polyolefin polyols,
polyurethane polyols, and combinations thereof. Suitable polyol
monomers may include, for example, glycols and/or glycerol.
[0062] A variety of isocyanate-functional compounds may be used to
form the polyurethane polymer. In some embodiments, the isocyanates
are incorporated into the polyurethane polymer predominantly or
exclusively through urethane linkages. In other embodiments, at
least some of the isocyanate compound may be incorporated into the
backbone of the polyurethane polymer via one or more non-urethane
step-growth linkages (e.g., urea) formed through a reaction
involving an isocyanate group (--NCO) of the isocyanate
compound.
[0063] The isocyanate compound may be any suitable compound,
including an isocyanate compound having 1 isocyanate group; a
polyisocyanate compound having 2, 3, or 4 or more isocyanate
groups; or a mixture thereof. Suitable diisocyanates may include
isophorone diisocyanate (i.e.,
5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane);
5-isocyanato-1-(2-isocyanatoeth-1-yl)-1,3,3-trimethylcyclohexane;
5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane;
5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane;
1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane;
1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane;
1-isocyanato-2-(4-isocy-anatobut-1-yl)cyclohexane;
1,2-diisocyanatocyclobutane; 1,3-diisocyanatocyclobutane;
1,2-diisocyanatocyclopentane; 1,3-diisocyanatocyclopentane;
1,2-diisocyanatocyclohexane; 1,3-diisocyanatocyclohexane;
1,4-diisocyanatocyclohexane; dicyclohexylmethane 2,4'-diisocyanate;
trimethylene diisocyanate; tetramethylene diisocyanate;
pentamethylene diisocyanate; hexamethylene diisocyanate;
ethylethylene diisocyanate; trimethylhexane diisocyanate;
heptamethylene diisocyanate;
2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentyl-cyclohexane; 1,2-,
1,4-, and 1,3-bis(isocyanatomethyl)cyclohexane; 1,2-, 1,4-, and
1,3-bis(2-isocyanatoeth-1-yl)cyclohexane;
1,3-bis(3-isocyanatoprop-1-yl)cyclohexane; 1,2-, 1,4- or
1,3-bis(4-isocyanatobuty-1-yl)cyclohexane; liquid
bis(4-isocyanatocyclohexyl)-methane; and derivatives or mixtures
thereof.
[0064] In some embodiments, the isocyanate compounds are preferably
non-aromatic. Non-aromatic isocyanates are particularly desirable
for coating compositions intended for use on an interior surface
(e.g., a food-contact surface) of a food or beverage can.
Therefore, in certain embodiments, the polyurethane polymer of the
present (and preferably the coating composition) does not contain
any structural units derived from an aromatic isocyanate compound.
Isophorone diisocyanate (IPDI) and hexamethylene diisocyanate
(HMDI) are preferred non-aromatic isocyanates.
[0065] The reactants used to produce the unsaturated polyurethane
polymer (e.g., one or more polyol and one or more isocyanate
compounds) of the present invention may include any suitable ratio
of isocyanate to hydroxyl groups. In some embodiments, the ratio of
isocyanate to hydroxyl groups (NCO:OH) is preferably from 1.05:1 to
2:1, more preferably from 1.1:1 to 1.8:1, and even more preferably
from 1.2:1 to 1.6:1.
[0066] In some embodiments, at least some, or alternatively all, of
the one or more isocyanate compounds may be a partially blocked
polyisocyanate. Certain embodiments may benefit from the inclusion
of one or more blocked isocyanate groups (e.g., deblockable
isocyanate groups) in the polyurethane polymer as a means for
forming covalent linkages with other components of the coating
composition, including, for example, the polyurethane polymer
itself. Preferred partially blocked polyisocyanates contain, on
average, at least about 1.5, more preferably at least about 1.8,
and even more preferably at least about 2 free (or unblocked)
isocyanate groups per molecule of partially blocked polyisocyanate
and on average, at least about 0.5, more preferably at least about
0.7, and even more preferably at least about 1 blocked isocyanate
groups (preferably deblockable isocyanate groups) per molecule of
partially blocked polyisocyanate. For further discussion of
suitable materials and methodologies relating to the use of
partially blocked isocyanate compounds in forming polyurethane
polymers see International Application Nos. PCT/US2009/065848 and
PCT/US10/42254.
[0067] Aliphatic carbon-carbon double bonds may be incorporated in
the unsaturated polyurethane polymer of the present invention using
any suitable process. For example, one or more reactants including
one or more aliphatic carbon-carbon double bonds can be included in
the reactants used to form the polyurethane polymer. Alternatively,
the polyurethane polymer may be post modified to include some, or
all, of the aliphatic carbon-carbon double bonds. In some
embodiments, the aliphatic carbon-carbon double bonds are
incorporated into the polyurethane polymer via a step-growth
reaction involving unsaturated monomers, oligomers, and/or polymers
having one or more active hydrogen groups (e.g., such as those
described herein). An unsaturated polyol is an example of one such
reactant. In some embodiments, an addition reaction may be used to
incorporate aliphatic carbon-carbon double bonds into the
polyurethane polymer. For example, an unsaturated compound such as
a polybutadiene compound may be incorporated into the polyurethane
polymer itself, or another reactant used to form the polyurethane
polymer (e.g. an unsaturated reactant having one or more active
hydrogen groups), via an addition reaction such as a free-radical
polymerization.
[0068] As previously discussed, in some embodiments, the
unsaturated polyurethane polymer of the present invention includes
one or more (poly)alkene groups. By way of example, the following
reaction pathways may be used to incorporate the (poly)alkene
groups into the polyurethane polymer: step-growth reactions (e.g.,
using a functionalized (poly)alkene-containing compound having one
or more active hydrogen groups), free radical initiated reactions,
Diels-Alder reactions, etc. Non-limiting examples of suitable
groups for linking the (poly)alkene segment to one or more other
portions of the polyurethane polymer include any of the linkage
groups disclosed herein, including, for example, step-growth or
addition (e.g., hydrocarbyl) linkages.
[0069] In some embodiments, the (poly)alkene group may be
incorporated into the polymer via reaction of (i) one or more
active hydrogen groups present in a compound containing the
(poly)alkene group with (ii) a complementary active hydrogen group
present on the polymer or a reactant used to form the polymer.
Non-limiting examples of suitable active hydrogen groups include
groups having a hydrogen attached to an oxygen (O), sulfur (S),
and/or nitrogen (N) atom as in the groups --OH, --COOH, --SH,
.dbd.NH, and NH.sub.2. It is further contemplated that such
reactions and/or linkage groups may also be used to incorporate any
of the other aliphatic carbon-carbon double bond containing groups
disclosed herein (e.g., unsaturated polycyclic groups, unsaturated
strained ring groups, vinylic groups, etc.).
[0070] Below are some specific examples of methods for introducing
(poly)alkene groups into the polyurethane polymer. It is also
contemplated that similar such methods may be used to incorporate
one or more other aliphatic carbon-carbon double bond containing
groups disclosed herein. [0071] 1. A hydroxyl-functional
(poly)alkene compound may be incorporated into the polyurethane
polymer via reaction of the one or more hydroxyl groups with
isocyanate and/or carboxylic acid groups present on the
polyurethane polymer or a reactant used to form the polyurethane
polymer. [0072] 2. A maleinized (poly)alkene (e.g., a (poly)alkene
compound modified with maleic anhydride such as maleinized
polybutadiene) may be incorporated into the polyurethane polymer
via reaction of the acid groups/anhydride group with hydroxyl
groups present on the polyurethane polymer or a reactant used to
form the polyurethane polymer. [0073] 3. A maleinized (poly)alkene
compound (e.g., maleinized polybutadiene) may be incorporated into
the polyurethane polymer through hydrolysis of an anhydride group
and subsequent epoxy esterification with a group present on the
polyurethane polymer or a reactant used to form the polyurethane
polymer. [0074] 4. A maleinized (poly)alkene compound (e.g.,
maleinized polybutadiene) may be incorporated into the polyurethane
polymer via amide formation through reaction of the acid
groups/anhydride group with a primary amine group on the
polyurethane polymer or a reactant used to form the polyurethane
polymer. [0075] 5. An epoxy-functional (poly)alkene compound may be
incorporated into the polymer through reaction of an epoxy group
with a carboxylic acid group present on the polymer or a reactant
used to form the polymer, or through quaternary ammonium salt
formation. [0076] 6. A (poly)alkene compound having acrylic or
methacrylic functionality may be incorporated into the polyurethane
polymer or a reactant used to form the polyurethane polymer via
free radical polymerization. [0077] 7. A carboxylic acid-functional
(poly)alkene compound may be incorporated into the polyurethane
polymer or a reactant used to form the polyurethane polymer via
esterification with hydroxyls or epoxy esterification with oxirane
groups.
[0078] As discussed previously herein, the unsaturated polyurethane
polymer of the present invention may include unsaturated bicyclic
groups. Such bicyclic groups may be introduced in the polyurethane
polymer of the present invention using any suitable process. For
example, a reactant having (i) one or more unsaturated bicyclic
groups and (ii) one or more active hydrogen groups may be used in
forming the polyurethane. Non-limiting examples of such reactants
include nadic acid or anhydride, tetrahydrophthalic acid or
anhydride, methyl-nadic acid or anhydride, and mixtures thereof.
Alternatively, a Diels-Alder reaction may be used to modify an
unsaturated polyurethane polymer (or an unsaturated reactant to be
further reacted to form the polyurethane polymer) to include an
unsaturated bicyclic group, more preferably an unsaturated, bridged
bicyclic group (e.g., a norbornene group). Materials and methods
for producing a bicyclic Diels-Alder reaction product are discussed
in WO 2008/124682. Non-limiting examples of useful Diels-Alder
reactants may include anthracene, cyclohexadiene, cyclopentadiene
(including, e.g., 1-alkyl cyclopentadienes or 2-alkyl
cyclopentadienes), dicyclopentadiene, furan, thiophene, alpha
terpine rosin, and combinations thereof.
[0079] In some embodiments, the unsaturated polyurethane polymer of
the present invention includes one or more optional ether linkages.
It was a surprising and unexpected result that certain cured
coating compositions of the present invention that included a
suitable amount of unsaturated polyurethane polymer having a
suitable number of ether linkages exhibited significantly enhanced
coating properties (e.g., coating hardness as determined by pencil
hardness testing) as compared to cured coating compositions of the
present invention that included an unsaturated polyurethane polymer
lacking such ether linkages. While not intending to be bound by any
theory, it is believed that the presence of such ether linkages can
contribute to the formation of crosslinks upon coating cure. Such
crosslinks are believed to be formed between aliphatic
carbon-carbon double bonds of the polyurethane polymer (as
intra-polymer crosslinks within the same polymer strand or
crosslinks between separate polymer strands).
[0080] In some embodiments, the unsaturated polyurethane polymer
preferably includes an efficacious amount of ether linkages. A
useful measure of the amount of ether linkages present in a polymer
is the total mass of ether oxygen relative to the total mass of the
polymer. As used herein the term "ether oxygen" refers to the
oxygen atom present in an ether linkage. Thus, for example, the
total mass of ether oxygen present in a polymer does not include
the mass of any non-ether oxygen atoms that may be present, for
example, in a polyether segment. In some embodiments, the
unsaturated polyurethane polymer of the present invention includes
at least about 1 wt-% of ether oxygen, more preferably at least 1.5
wt-% of ether oxygen, and even more preferably at least 3.0 wt-% of
ether oxygen. The upper range of ether linkages present in the
unsaturated polyurethane polymer is not particularly limited, but
the polymer will typically include less that about 6 wt-% or less
than about 4.5 wt-% of ether oxygen.
[0081] Any suitable compound may be used to incorporate the
optional ether linkages into the unsaturated polyurethane polymer.
Functionalized ether or polyether compounds can be used such as,
for example, an ether-containing ethylene glycol (e.g., diethylene
glycol, triethylene glycol, tetraethylene glycol, etc.); an
ether-containing propylene glycol (e.g., dipropylene glycol,
tripropylene glycol, tetrapropylene glycol, etc.); an
ether-containing butylene glycol (e.g., dibutylene glycol,
tributylene glycol, tetrabutylene glycol, etc.); a polyethylene
glycol; a polypropylene glycol; polybutylene glycol; or a copolymer
or mixture thereof. In some embodiments, a functionalized ether- or
polyether-containing compound is attached to one or more other
portions of the polyurethane polymer via one or more step-growth
linkages (e.g., ester linkages). In certain embodiments, a
structural unit derived from an ether- or polyether-containing
compound is located in a backbone of the unsaturated polyurethane
polymer and is attached on at least one end, and in some instances
both ends, to another portion of the polyurethane backbone via a
step-growth linkage (e.g., an ester linkage).
[0082] It is contemplated that the benefits of ether linkages may
also be realized, at least in part, by incorporating an efficacious
amount of ether linkages into one or more other components of the
coating composition. For example, the coating composition may
include a second polymer that includes a suitable amount of ether
linkages such as, for example, an amount pursuant to that described
above for the unsaturated polyurethane polymer. The ether linkages
may also be present in a non-polymer ingredient such as, for
example, a volatile organic compound such as tripropylene glycol or
the like.
[0083] In preferred embodiments, the coating composition of the
present invention preferably includes one or more optional liquid
carriers. Preferably, the liquid carrier(s) are selected to provide
a dispersion or solution of the unsaturated polyurethane polymer of
the present invention for further formulation. The liquid carrier
can be an organic solvent or mixture of organic solvents, water, or
a combination thereof. Depending upon the particular embodiment,
the coating composition can be a water-based coating composition or
a solvent-based coating composition. Non-limiting examples of
suitable organic solvents for use in the water-based and/or
solvent-based coating compositions of the present invention include
aliphatic hydrocarbons (e.g., mineral spirits, kerosene, VM&P
NAPHTHA solvent, and the like); aromatic hydrocarbons (e.g.,
benzene, toluene, xylene, the SOLVENT NAPHTHA 100, 150, 200
products and the like); alcohols (e.g., ethanol, n-propanol,
isopropanol, n-butanol, iso-butanol and the like); ketones (e.g.,
acetone, 2-butanone, cyclohexanone, methyl aryl ketones, ethyl aryl
ketones, methyl isoamyl ketones, and the like); esters (e.g., ethyl
acetate, butyl acetate and the like); glycols (e.g., butyl glycol);
glycol ethers (e.g., ethylene glycol monomethyl ether, ethylene
glycol monoethyl ether, ethylene glycol monobutyl ether, propylene
glycol monomethyl ether, and the like); glycol ether esters (e.g.,
butyl glycol acetate, methoxypropyl acetate and the like); and
mixtures thereof.
[0084] The coating composition of the present invention typically
has a total solids content of from about 10 to about 75 wt-%. In
some embodiments, such as, for example, certain water-based
embodiments, the coating composition preferably has a total solids
of at least about 20 wt-% and more preferably at least about 30
wt-%. The coating composition preferably has a total solids of less
than about 50 wt-%, and more preferably less than about 40
wt-%.
[0085] In some embodiments, the coating composition is a
solvent-based coating composition that preferably includes no more
than a de minimus amount (e.g., 0 to 2 wt-%) of water. In other
embodiments, the coating composition can include a substantial
amount of water.
[0086] In some embodiments, the coating composition is prepared
using one or more hydroxyl-functional organic solvents.
Non-limiting examples of suitable hydroxyl-functional organic
solvents include any of the alcohols described above, methanol,
2-butanol, t-butanol, n-pentanol and isomers of pentanol, n-hexanol
and isomers of hexanol, diacetone alcohol, benzyl alcohol, ethylene
glycol, propylene glycol, 1,3-propane diol, 1,3-butane diol,
1,4-butane diol, ethylene glycol monomethyl ether, ethylene glycol
monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol
mono n-butyl ether, ethylene glycol mono-n-hexyl ether, propylene
glycol monomethyl ether, propylene glycol monoethyl ether,
propylene glycol monopropyl ether, propylene glycol mono-n-butyl
ether, propylene glycol mono-t-butyl ether, propylene glycol mono
phenyl ether, diethyleneglycol mono-methyl ether, diethylene glycol
mono-ethyl ether, diethylene glycol mono-propyl ether, diethylene
glycol mono butyl ether, dipropylene glycol monomethyl ether,
dipropylene glycol monomethyl ether, dipropylene monoethyl ether,
dipropylene glycol monopropyl ether, dipropylene glycol monobutyl
ether, tripropylene glycol monomethyl ether, tripropylene glycol
monoethyl ether, tripropylene glycol monobutyl ether,
2,2,4-trimethyl-1,3-pentandiol monoisobutyl ester, and combinations
thereof. If used, the one or more hydroxyl-functional organic
solvents are typically present in the coating composition in an
amount of from about 1% to about 50%, more preferably from about 5%
to about 40%, and even more preferably about 10% to about 30%.
[0087] In some embodiments, the coating composition preferably
includes at least about 10 wt-%, more preferably at least about 20
wt-%, and even more preferably at least about 30 wt-% of water,
based on the total weight of the coating composition. In some such
embodiments, the coating composition preferably includes less than
about 60 wt-%, more preferably less than about 50 wt-%, and even
more preferably less than about 40 wt-% of water, based on the
total weight of the coating composition. In some water-containing
embodiments, the coating composition preferably includes one or
more organic solvents in an amount from about 10 to about 70 wt-%,
more preferably from about 20 to about 60 wt-%, and even more
preferably from about 25 to about 45 wt-%, based on the total
weight of the coating composition. The inclusion of a suitable
amount of organic solvent in certain water-based coating
compositions of the present invention may be advantageous, for
example, for certain coil coating applications to modify flow and
leveling of the coating composition, control blistering, and
maximize the line speed of the coil coater. Moreover, vapors
generated from evaporation of the organic solvent during coating
cure may be used to fuel the curing ovens. The ratio of water to
organic solvent in the coating composition can vary widely
depending on the particular coating end use and application
methodology.
[0088] In some embodiments, the weight ratio of water to organic
solvent in the final coating composition ranges from about 0.1:1 to
10:1 (water:organic solvent), more preferably from about 0.2:1 to
5:1, and even more preferably from about 0.7:1 to 1.3:1.
[0089] When an aqueous dispersion is desired, the unsaturated
polyurethane polymer of the present invention may be rendered
water-dispersible using any suitable means, including the use of
non-ionic water-dispersing groups, salt groups, surfactants, or a
combination thereof. As used herein, the term "water-dispersing
groups" also encompasses water-solubilizing groups. In certain
preferred embodiments, the unsaturated polyurethane polymer
contains a suitable amount of water-dispersing groups, preferably
salt and/or salt-forming groups, such that the polymer is capable
of forming a stable aqueous dispersion with an aqueous carrier.
[0090] In water-based coating embodiments, the unsaturated
polyurethane polymer is typically dispersed using salt groups. A
salt (which can be a full salt or partial salt) is typically formed
by neutralizing or partially neutralizing salt-forming groups
(e.g., acidic or basic groups) of the polyurethane polymer with a
suitable neutralizing agent. Alternatively, the polyurethane
polymer may be formed from ingredients including preformed salt
groups. The degree of neutralization required to form the desired
polymer salt may vary considerably depending upon the amount of
salt-forming groups included in the polymer, and the degree of
solubility or dispersibility of the salt which is desired.
Ordinarily in making the polymer water-dispersible, the
salt-forming groups (e.g., acid or base groups) of the polymer are
at least 25% neutralized, preferably at least 30% neutralized, and
more preferably at least 35% neutralized, with a neutralizing agent
in water. Non-limiting examples of suitable salt groups include
anionic salt groups, cationic salt groups, or combinations
thereof.
[0091] Non-limiting examples of anionic salt groups include
neutralized acid or anhydride groups, sulphate groups
(--OSO.sub.3.sup.-), phosphate groups (--OPO.sub.3.sup.-),
sulfonate groups (--SO.sub.2O.sup.-), phosphinate groups
(--POO.sup.-), phosphonate groups (--PO.sub.3.sup.-), and
combinations thereof. Non-limiting examples of suitable cationic
salt groups include:
##STR00001##
(referred to, respectively, as quaternary ammonium groups,
quaternary phosphonium groups, and tertiary sulfate groups) and
combinations thereof. Non-limiting examples of non-ionic
water-dispersing groups include hydrophilic groups such as ethylene
oxide groups. Compounds for introducing the aforementioned groups
into polymers are known in the art.
[0092] Non-limiting examples of neutralizing agents for forming
anionic salt groups include inorganic and organic bases such as an
amine, sodium hydroxide, potassium hydroxide, lithium hydroxide,
ammonia, and mixtures thereof. In certain embodiments, tertiary
amines are preferred neutralizing agents. Non-limiting examples of
neutralizing agents for forming cationic salt groups include
organic and inorganic acids such as formic acid, acetic acid,
hydrochloric acid, lactic acid, sulfuric acid, and combinations
thereof.
[0093] When acid or anhydride groups are used to impart water
dispersibility, the acid- or anhydride-functional polyurethane
polymer preferably has an acid number of at least 5, and more
preferably at least 40 milligrams (mg) KOH per gram resin. The
acid-functional polyurethane polymer preferably has an acid number
of no greater than 400, and more preferably no greater than 100 mg
KOH per gram resin.
[0094] Alternatively, a surfactant may be used in place of
water-dispersing groups to aid in dispersing the polyurethane in an
aqueous carrier. Non-limiting examples of suitable surfactants
include alkyl sulfates (e.g., sodium lauryl sulfate), ether
sulfates, phosphate esters, sulphonates, and their various alkali,
ammonium, amine salts and aliphatic alcohol ethoxylates, alkyl
phenol ethoxylates, and mixtures thereof.
[0095] The coating composition of the present invention may
optionally include one or more vinyl polymers. For example, vinyl
polymers such as those described in U.S. Application No. 61/243,888
can be included. The unsaturated polyurethane polymer of the
present invention and the vinyl polymer can be present as separate
polymers (i.e., polymers that are not covalently attached to one
another), covalently attached polymers, or a mixture thereof.
Optional covalent linkages may be formed between the polyurethane
and the vinyl polymer at any suitable time, including prior to
coating cure (e.g., during formation of the vinyl polymer), during
and/or after coating cure, or a combination thereof. In some
embodiments, the unsaturated polyurethane polymer and the vinyl
polymer are not covalently attached while present in one or both
of: a liquid coating composition or a cured coating resulting
therefrom.
[0096] The optional vinyl polymer may be an acrylic polymer or a
non-acrylic vinyl polymer. Typically, the vinyl polymer is formed
via vinyl addition polymerization of an ethylenically unsaturated
component. In some embodiments, the ethylenically unsaturated
component is a mixture of monomers and/or oligomers that are
capable of free radical initiated polymerization in aqueous medium.
It is further contemplated that a cationic or anionic
polymerization process may be used to form the vinyl polymer.
[0097] Suitable ethylenically unsaturated monomers and/or oligomers
for inclusion in the ethylenically unsaturated component include,
for example, alkyl (meth)acrylates; vinyl monomers; alkyl esters of
maleic acid, fumaric acid, sorbic acid, or cinnamic acid; oligomers
thereof; and mixtures thereof.
[0098] In certain embodiments, the vinyl polymer is an
acrylic-containing vinyl polymer. Suitable alkyl (meth)acrylates
include, for example, those having the structure:
CH.sub.2.dbd.C(R.sup.8)--CO--OR.sup.9 wherein R.sup.8 is hydrogen
or methyl, and R.sup.9 is an alkyl group preferably containing one
to sixteen carbon atoms. The R.sup.9 group can be substituted with
one or more, and typically one to three, moieties such as hydroxy,
halo, phenyl, and alkoxy, for example. Suitable alkyl
(meth)acrylates therefore encompass hydroxy alkyl (meth)acrylates.
The alkyl (meth)acrylate typically is an ester of acrylic or
methacrylic acid. Preferably, R.sup.8 is hydrogen or methyl and
R.sup.9 is an alkyl group having two to twenty-two carbon atoms.
More typically, R.sup.8 is hydrogen or methyl and R.sup.9 is an
alkyl group having two to four carbon atoms.
[0099] Suitable alkyl (meth)acrylates include, but are not limited
to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl
(meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate,
isobutyl (meth)acrylate, pentyl (meth)acrylate, isoamyl
(meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
cyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl
(meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate,
isobornyl (meth)acrylate, octyl (meth)acrylate, nonyl
(meth)acrylate, hydroxyethyl acrylate (HEA), hydroxyethyl
methacrylate (HEMA), hydroxypropyl (meth)acrylate (HPMA), glycidyl
(meth)acrylate (GMA), and mixtures thereof.
[0100] Difunctional (meth)acrylate monomers may be used in the
monomer mixture as well. Examples include ethylene glycol
di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, allyl
(meth)acrylate, and the like.
[0101] Suitable vinyl monomers include, but are not limited to,
styrene, methyl styrene, alpha-methylstyrene, halostyrene,
isoprene, diallylphthalate, divinylbenzene, conjugated butadiene,
vinyl toluene, vinyl naphthalene, and mixtures thereof.
[0102] Other suitable polymerizable vinyl monomers for use in the
ethylenically unsaturated component include acrylonitrile,
acrylamide, methacrylamide, methacrylonitrile, vinyl acetate, vinyl
propionate, vinyl butyrate, vinyl stearate, N-isobutoxymethyl
acrylamide, N-butoxymethyl acrylamide, acrylic acid, methacrylic
acid, and mixtures thereof.
[0103] In some embodiments, at least 40 wt-% of the ethylenically
unsaturated component used to form the vinyl polymer, more
preferably at least 50 wt-%, will be selected from alkyl acrylates
and methacrylates.
[0104] In some embodiments, the ethylenically unsaturated component
includes one or more groups capable of forming a covalent linkage
with one or more of the following: another group of the
ethylenically unsaturated component, a group of the unsaturated
polyurethane polymer, a group of another ingredient of the liquid
composition (e.g., a crosslinking agent) and/or the finished
coating composition. Some examples of such groups and covalent
attachment methodologies are provided in International Application
No. PCT/US10/42254.
[0105] The one or more optional vinyl polymers can be included in
the coating composition in any suitable amount. In some
embodiments, the coating composition includes at least 5 wt-%, more
preferably at least 10 wt-%, even more preferably at least 25 wt-%,
and even more preferably at least 50 wt-% of vinyl polymer, based
on the total solids weight of vinyl polymer and unsaturated
polyurethane polymer present in the coating composition. The
coating composition preferably includes no greater than 95 wt-%,
more preferably no greater than 90 wt-%, and even more preferably
no greater than 85 wt-% of vinyl polymer, based on the total solids
weight of vinyl polymer and unsaturated polyurethane polymer
present in the coating composition.
[0106] In some embodiments, the vinyl polymer is formed in the
presence of the unsaturated polyurethane polymer. In one such
embodiment, the vinyl polymer is formed by polymerizing (e.g.,
emulsion polymerizing) an ethylenically unsaturated component in
the presence of an aqueous dispersion including a water-dispersible
unsaturated polyurethane polymer of the present invention. With
regard to the conditions of the polymerization, the ethylenically
unsaturated component is preferably polymerized in aqueous medium
with a water-soluble free radical initiator in the presence of the
water-dispersible polyurethane. For a further discussion of
suitable polymerization techniques see U.S. application Ser. No.
12/505,236 filed on Jul. 17, 2009.
[0107] Certain preferred coating compositions of the present
invention (e.g., compositions intended for food-contact
applications) are substantially free of mobile bisphenol A (BPA)
and aromatic glycidyl ether compounds (e.g., BADGE, BFDGE, and
epoxy novalacs), more preferably essentially free of these
compounds, even more preferably essentially completely free of
these compounds, and most preferably completely free of these
compounds. Certain preferred coating compositions (and, hence, the
unsaturated polyurethane polymer) are also preferably substantially
free of bound BPA and aromatic glycidyl ether compounds, more
preferably essentially free of these compounds, most preferably
essentially completely free of these compounds, and optimally
completely free of these compounds.
[0108] Certain preferred unsaturated polyurethane polymers of the
present invention are at least substantially "epoxy-free," more
preferably "epoxy-free." The term "epoxy-free," when used herein in
the context of a polymer, refers to a polymer that does not include
any "epoxy backbone segments" (i.e., segments formed from reaction
of an epoxy group and a group reactive with an epoxy group). Thus,
for example, a polymer made from ingredients including an epoxy
resin would not be considered epoxy-free. Similarly, a polymer
having backbone segments that are the reaction product of a
bisphenol (e.g., bisphenol A, bisphenol F, bisphenol S,
4,4'dihydroxy bisphenol, etc.) and a halohydrin (e.g.,
epichlorohydrin) would not be considered epoxy-free. However, a
vinyl polymer formed from vinyl monomers and/or oligomers that
include an epoxy moiety (e.g., glycidyl methacrylate) would be
considered epoxy-free because the vinyl polymer would be free of
epoxy backbone segments. In some embodiments, the coating
composition of the present invention is also preferably at least
substantially epoxy-free, more preferably epoxy-free.
[0109] In certain preferred embodiments, the unsaturated
polyurethane polymer is "PVC-free," and preferably the coating
composition is also "PVC-free." That is, each composition
preferably contains less than 2 wt-% of vinyl chloride materials,
more preferably less than 0.5 wt-% of vinyl chloride materials, and
even more preferably less than 1 part per million (ppm) of vinyl
chloride materials.
[0110] Coating compositions of the present invention may include an
efficacious amount of one or more so called "metal driers." While
not intending to be bound by any theory, it is believed that the
presence of an efficacious amount of one or more metal driers may
enhance crosslinking upon coating cure (e.g., by enhancing and/or
inducing the formation of crosslinks between aliphatic
carbon-carbon double bonds of the polyurethane polymer).
Non-limiting examples of suitable metal driers may include aluminum
(Al), antimony (Sb), barium (Ba), bismuth (Bi), calcium (Ca),
cerium (Ce), chromium (Cr), cobalt (Co), copper (Cu), iridium (Ir),
iron (Fe), lead (Pb), lanthanum (La), lithium (Li), manganese (Mn),
Neodymium (Nd), nickel (Ni), rhodium (Rh), ruthenium (Ru),
palladium (Pd), potassium (K), osmium (Os), platinum (Pt), sodium
(Na), strontium (Sr), tin (Sn), titanium (Ti), vanadium (V),
Yttrium (Y), zinc (Zn), zirconium (Zr), any other suitable rare
earth metal or transition metal, as well as oxides, salts (e.g.,
acid salts such as octoates, naphthenates, stearates,
neodecanoates, etc.) or complexes of any of these, and mixtures
thereof. The amount used will depend, at least partially, upon the
particular drier(s) chosen for a particular end use. In general,
however, the amount of metal drier present in the coating
composition, if any, may suitably be greater than about 10 ppm by
weight, preferably greater than about 25 ppm by weight, and more
preferably greater than about 100 ppm by weight, based on the total
weight of metal in the metal drier relative to the total weight of
the coating composition. The amount of metal drier may suitably be
less than about 10,000 ppm by weight, preferably less than about
1,000 ppm by weight, and more preferably less than about 600 ppm by
weight, based on the total weight of metal in the metal drier
relative to the total weight of the coating composition.
[0111] Coating compositions of the present invention may be
formulated using one or more optional curing agents (i.e.,
crosslinking resins, sometimes referred to as "crosslinkers"). The
choice of particular crosslinker typically depends on the
particular product being formulated. Non-limiting examples of
crosslinkers include aminoplasts, phenoplasts, blocked isocyanates,
and combinations thereof.
[0112] The amount of crosslinker included, if any, may depend on a
variety of factors, including, for example, the type of curing
agent, the time and temperature of the bake, the molecular weight
of the polymer, and the desired coating properties. If used, the
crosslinker is typically present in an amount of up to 50 wt-%,
preferably up to 30 wt-%, and more preferably up to 15 wt-%. If
used, the crosslinker is typically present in an amount of at least
0.1 wt-%, more preferably at least 1 wt-%, and even more preferably
at least 1.5 wt-%. These weight percentages are based upon the
total weight of the resin solids in the coating composition.
[0113] Phenoplast resins include the condensation products of
aldehydes with phenols. Formaldehyde and acetaldehyde are preferred
aldehydes. Various phenols can be employed such as phenol, cresol,
p-phenylphenol, p-tert-butylphenol, p-tert-amylphenol, and
cyclopentylphenol.
[0114] Aminoplast resins include, for example, the condensation
products of aldehydes such as formaldehyde, acetaldehyde,
crotonaldehyde, and benzaldehyde with amino- or
amido-group-containing substances such as urea, melamine, and
benzoguanamine. Examples of suitable aminoplast resins include,
without limitation, benzoguanamine-formaldehyde resins,
melamine-formaldehyde resins, esterified melamine-formaldehyde, and
urea-formaldehyde resins.
[0115] Condensation products of other amines and amides can also be
employed such as, for example, aldehyde condensates of triazines,
diazines, triazoles, guanadines, guanamines and alkyl- and
aryl-substituted melamines. Some examples of such compounds are
N,N'-dimethyl urea, benzourea, dicyandiimide, formaguanamine,
acetoguanamine, glycoluril, ammelin
2-chloro-4,6-diamino-1,3,5-triazine,
6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole,
triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine,
3,4,6-tris(ethylamino)-1,3,5-triazine, and the like. While the
aldehyde employed is typically formaldehyde, other similar
condensation products can be made from other aldehydes, such as
acetaldehyde, crotonaldehyde, acrolein, benzaldehyde, furfural,
glyoxal and the like, and mixtures thereof.
[0116] Non-limiting examples of suitable isocyanate crosslinkers
include blocked or non-blocked aliphatic, cycloaliphatic or
aromatic di-, tri-, or poly-valent isocyanates, such as
hexamethylene diisocyanate (HMDI), cyclohexyl-1,4-diisocyanate and
the like, and mixtures thereof. Further non-limiting examples of
generally suitable blocked isocyanates include isomers of
isophorone diisocyanate, dicyclohexylmethane diisocyanate, toluene
diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate,
tetramethyl xylene diisocyanate, xylylene diisocyanate, and
mixtures thereof. In some embodiments, blocked isocyanates are used
that have an Mn of at least about 300, more preferably at least
about 650, and even more preferably at least about 1,000.
[0117] For coating compositions of the present invention that
employ a self-crosslinking embodiment of the unsaturated
polyurethane polymer, it may not be necessary or desirable to
include a separate curing agent such as a crosslinker.
[0118] The coating composition of the present invention may also
include other optional polymers that do not adversely affect the
coating composition or a cured coating resulting therefrom. Such
optional polymers are typically included in a coating composition
as a filler material, although they can be included as a
crosslinking material, or to provide desirable properties. One or
more optional polymers can be included in a sufficient amount to
serve an intended purpose, but not in such an amount to adversely
affect a coating composition or a cured coating composition
resulting therefrom.
[0119] The coating composition of the present invention may also
include other optional ingredients that do not adversely affect the
coating composition or a cured coating composition resulting
therefrom. Such optional ingredients include, for example,
catalysts, dyes, pigments, toners, extenders, fillers, lubricants,
anticorrosion agents, flow control agents, thixotropic agents,
dispersing agents, antioxidants, adhesion promoters, light
stabilizers, surfactants, and mixtures thereof. Each optional
ingredient is preferably included in a sufficient amount to serve
its intended purpose, but not in such an amount to adversely affect
a coating composition or a cured coating composition resulting
therefrom.
[0120] One preferred optional ingredient is a catalyst to increase
the rate of cure. Examples of catalyst, include, but are not
limited to, strong acids (e.g., dodecylbenzene sulphonic acid
(DDBSA, available as CYCAT 600 from Cytec)), methane sulfonic acid
(MSA), p-toluene sulfonic acid (pTSA), dinonylnaphthalene
disulfonic acid (DNNDSA), and triflic acid), quaternary ammonium
compounds, phosphorous compounds, tin and zinc compounds, and
combinations thereof. Specific examples include, but are not
limited to, a tetraalkyl ammonium halide, a tetraalkyl or tetraaryl
phosphonium iodide or acetate, tin octoate, zinc octoate,
triphenylphosphine, and similar catalysts known to persons skilled
in the art. If used, a catalyst is preferably present in an amount
of at least 0.01 wt-%, and more preferably at least 0.1 wt-%, based
on the total weight of nonvolatile material in the coating
composition. If used, a catalyst is preferably present in an amount
of no greater than 3 wt-%, and more preferably no greater than 1
wt-%, based on the total weight of nonvolatile material in the
coating composition.
[0121] Another useful optional ingredient is a lubricant (e.g., a
wax), which facilitates manufacture of fabricated metal articles by
imparting lubricity to sheets of coated metal substrate.
Non-limiting examples of suitable lubricants include, for example,
natural waxes such as Carnauba wax or lanolin wax,
polytetrafluoroethane (PTFE) and polyethylene type lubricants. If
used, a lubricant is preferably present in the coating composition
in an amount of at least 0.1 wt-%, and preferably no greater than 2
wt-%, and more preferably no greater than 1 wt-%, based on the
total weight of nonvolatile material in the coating
composition.
[0122] Another useful optional ingredient is a pigment, such as
titanium dioxide. If used, a pigment is preferably present in the
coating composition in an amount of no greater than 70 wt-%, more
preferably no greater than 50 wt-%, and even more preferably from
0.01 to 40 wt-%, based on the total weight of nonvolatile material
in the coating composition.
[0123] Surfactants can be optionally added to the coating
composition to aid in flow and wetting of the substrate. Examples
of surfactants, include, but are not limited to, nonylphenol
polyethers and similar surfactants known to persons skilled in the
art. If used, a surfactant is preferably present in an amount of at
least 0.01 wt-%, and more preferably at least 0.1 wt-%, based on
the total weight of resin solids in the coating composition. If
used, a surfactant is preferably present in an amount no greater
than 10 wt-%, and more preferably no greater than 5 wt-%, based on
the total weight of resin solids in the coating composition.
[0124] Preferred cured coatings of the present invention adhere
well to metal (e.g., steel, tin-free steel (TFS), tin plate,
electrolytic tin plate (ETP), aluminum, etc.) and provide high
levels of resistance to corrosion or degradation that may be caused
by prolonged exposure to corrosive environments (e.g., harsh
weather conditions, intimate contact with food or beverage
products, etc.).
[0125] The coating composition of the present invention has utility
in a multitude of applications. The coating composition of the
present invention may be applied, for example, as a mono-coat
coating system direct to metal (or direct to pretreated metal), as
a primer coat, as an intermediate coat, as a topcoat, or any
combination thereof. The coating composition may be applied to
planar metal stock such as is used, for example, for lighting
fixtures; architectural metal skins (e.g., gutter stock, window
blinds, siding and window frames); interior or exterior steel
building products; HVAC applications; agricultural metal products;
industrial coating applications (e.g., appliance coatings);
packaging coating applications (e.g., food or beverage cans, drug
cans, etc.) and the like. The coating composition is particularly
suited for a coil coating operation where the composition is
applied on planar metal coil substrate and then baked as the coated
substrate travels toward an uptake coil winder.
[0126] The coating composition can be applied to a substrate using
any suitable procedure including, for example, spray coating, roll
coating, coil coating, curtain coating, immersion coating, meniscus
coating, kiss coating, blade coating, knife coating, dip coating,
slot coating, slide coating, vacuum coating, and the like, as well
as other types of premetered coating. Other commercial coating
applications and curing methods are also envisioned, including, for
example, electrocoating, extrusion coating, laminating, powder
coating, and the like.
[0127] The coating composition can be applied on a substrate prior
to, or after, forming the substrate into an article. In some
embodiments, at least a portion of a planar metal substrate (e.g.,
metal coil) is coated with a layer of the coating composition of
the present invention, which is then cured before the planar
substrate is formed (e.g., stamped) into an article.
[0128] After applying the coating composition onto a substrate, the
composition can be cured using a variety of processes, including,
for example, oven baking by either conventional or convectional
methods, or any other method that provides an elevated temperature
suitable for curing the coating. The curing process may be
performed in either discrete or combined steps. For example,
substrates can be dried at ambient temperature to leave the coating
compositions in a largely un-crosslinked state. The coated
substrates can then be heated to fully cure the compositions. In
certain instances, coating compositions of the present invention
can be dried and cured in one step.
[0129] The cure conditions will vary depending upon the method of
application and the intended end use. The curing process may be
performed at any suitable temperature, including, for example, oven
temperatures in the range of from about 100.degree. C. to about
300.degree. C., and more typically from about 177.degree. C. to
about 250.degree. C. If metal coil is the substrate to be coated,
curing of the applied coating composition may be conducted, for
example, by heating the coated metal substrate over a suitable time
period to a peak metal temperature ("PMT") of preferably greater
than about 350.degree. F. (177.degree. C.). More preferably, the
coated metal coil is heated for a suitable time period (e.g., about
5 to 900 seconds) to a PMT of at least about 425.degree. F.
(218.degree. C.).
[0130] In some embodiments, such as for example certain water-based
coating applications, it may be possible to cure the coating
composition of the present invention at a lower temperature, such
as, for example, a PMT of greater than about 160.degree. F., or
from about 160.degree. F. to 250.degree. F. (i.e., from 71.degree.
C. to 121.degree. C.). In such embodiments, it may be advantageous
to include or more metal driers.
[0131] As previously discussed the coating composition of the
present invention can be present as a layer of a mono-layer coating
system or one or more layers of a multi-layer coating system. The
coating thickness of a particular layer and the overall coating
system will vary depending upon the coating material used, the
coating application method, and the end use for the coated article.
Mono-layer or multi-layer coil coating systems including one or
more layers formed from a coating composition of the present
invention may have any suitable overall coating thickness, but will
typically have an overall average dry coating thickness of from
about 5 to about 60 microns and more typically from about 10 to
about 45 microns.
[0132] Preferred coatings of the present invention display one or
more of the properties described in the Test Methods or Examples
sections.
[0133] Some non-limiting embodiments of the present invention are
provided below to further exemplify the present invention.
Embodiment 1
[0134] A method, comprising: [0135] providing a coating composition
comprising: [0136] (i) an unsaturated polyurethane polymer having
an iodine value of at least 10, and [0137] (ii) a liquid carrier;
[0138] applying the coating composition to at least a portion of a
planar metal substrate; and [0139] heating the coated metal
substrate to a peak metal temperature of at least 350.degree. F.
(177.degree. C.) to form a crosslinked coating.
Embodiment 2
[0140] A composition, comprising:
[0141] a crosslinkable coating composition, comprising: [0142] at
least 30% by weight, based on total solids of the coating
composition, of an unsaturated polyurethane polymer having an
iodine value of at least 10; [0143] a liquid carrier, wherein the
liquid carrier preferably includes an amount of organic solvent
that constitutes at least 15% by weight of the coating
composition.
Embodiment 3
[0144] An article, comprising:
[0145] a metal substrate,
[0146] the coating composition of Embodiment 2 applied to at least
a portion of the metal substrate.
Embodiment 4
[0147] The method, composition, or article of any of Embodiments
1-3, wherein the unsaturated polyurethane polymer is a
self-crosslinkable polymer.
Embodiment 5
[0148] The method, composition, or article of any of Embodiments
1-4, wherein the unsaturated polyurethane polymer includes one or
more aliphatic carbon-carbon double bonds.
Embodiment 6
[0149] The method, composition, or article of any of Embodiments
1-5, wherein the unsaturated polyurethane polymer includes one or
more reactive aliphatic carbon-carbon double bonds.
Embodiment 7
[0150] The method, composition, or article of Embodiment 6, wherein
the one or more reactive aliphatic carbon-carbon double bonds
comprise a vinylic double bond, a conjugated double bond, a double
bond present in a strained ring group, a double bond present in an
unsaturated bicyclic group, or a combination thereof.
Embodiment 8
[0151] The method, composition, or article of any of Embodiments
1-7, wherein the unsaturated polyurethane polymer includes one or
more unsaturated segments formed from an unsaturated polybutadiene
compound, another (poly)alkene-containing compound, or a
combination thereof.
Embodiment 9
[0152] The method, composition, or article of Embodiment 8, wherein
the unsaturated polyurethane polymer is formed from reactants
including, based on nonvolatile content, at least 1%, more
preferably at least 5%, and even more preferably at least 15% by
weight of a functionalized polybutadiene compound.
Embodiment 10
[0153] The method, composition, or article of any of Embodiments
1-9, wherein the unsaturated polyurethane polymer includes one or
more ether linkages.
Embodiment 11
[0154] The method, composition, or article of any of Embodiments
1-10, wherein the unsaturated polyurethane polymer includes at
least 1% by weight of ether oxygen.
Embodiment 12
[0155] The method, composition, or article of any of Embodiments
1-11, wherein the coating composition includes at least 30% by
weight of the unsaturated polyurethane polymer, based on the total
solids of the coating composition.
Embodiment 13
[0156] The method, composition, or article of any of Embodiments
1-12, wherein the coating composition further comprises one or more
metal driers.
Embodiment 14
[0157] The method, composition, or article of Embodiment 13,
wherein the coating composition comprises at least 100 ppm of the
one or more metal driers.
Embodiment 15
[0158] The method, composition, or article of any of Embodiments
1-14, wherein the coating composition comprises an aqueous
dispersion of the polyurethane polymer.
Embodiment 16
[0159] The method, composition, or article of any of Embodiments
1-14, wherein the coating composition comprises a solvent-based
coating composition that may optionally include water.
Embodiment 17
[0160] The method, composition, or article of any of Embodiments
1-16, wherein the coating composition includes a liquid carrier
that includes an amount of one or more organic solvents that
constitutes at least 15% by weight of the coating composition.
Embodiment 18
[0161] The method, composition, or article of any of Embodiments
1-17, wherein the coating composition includes a liquid carrier
that includes an amount of water that constitutes at least 10% by
weight of the coating composition.
Embodiment 19
[0162] The method, composition, or article of any of Embodiments
1-14, wherein the coating composition comprises:
[0163] from 15 to 75% by weight of solids;
[0164] from 15 to 70% by weight of one or more organic solvents;
and
[0165] from 10 to 70% by weight of water.
Embodiment 20
[0166] The method, composition, or article of any of Embodiment
1-14, wherein the coating composition comprises:
[0167] from 25 to 50% by weight of solids;
[0168] from 25 to 50% by weight of one or more organic solvents;
and
[0169] from 25 to 50% by weight of water.
Embodiment 21
[0170] The method, composition, or article of any of Embodiments
1-20, wherein the coating composition further comprises a vinyl
polymer.
Embodiment 22
[0171] The method, composition, or article of Embodiment 21,
wherein the coating composition includes at least 5 wt-%, at least
10 wt-%, at least 25 wt-%, or at least 60 wt-% of vinyl polymer,
based on the total solids weight of vinyl polymer and unsaturated
polyurethane polymer included in the coating composition.
Embodiment 23
[0172] The method of any one of Embodiments 1-22, wherein the
coated metal substrate is heated for 5 to 900 seconds to a PMT of
at least 425.degree. F. (218.degree. C.) to form a crosslinked
coating composition.
Embodiment 24
[0173] The method of any of Embodiments 1-23, further comprising
forming the coated planar metal substrate, having the crosslinked
coating disposed thereon, into an article.
Embodiment 25
[0174] The method, composition, or article of any of Embodiments
1-24, wherein the liquid carrier includes one or more
hydroxyl-functional organic solvents in an amount that comprises at
least 5% by weight of the coating composition.
Embodiment 26
[0175] The method, composition, or article of any of Embodiments
1-25, wherein the coating composition, when applied to a planar
chrome metal coil substrate at an average dry film weight of 9.3
grams per square meter and cured for 10 seconds in a heated oven to
achieve a PMT of 253.degree. C. to yield a cured coating, initially
passes less than 10 milliamps (mA), more preferably less than 5 mA,
most preferably less than 2 mA, and optimally less than 1 mA when
subjected to the Fabrication Test described below.
Test Methods
[0176] Unless indicated otherwise, the following test methods were
utilized in the Examples that follow.
A. Solvent Resistance
[0177] The extent of "cure" or crosslinking of a coating is
measured as a resistance to solvents, such as methyl ethyl ketone
(MEK, available from Exxon, Newark, N.J.). This test is performed
as described in ASTM D 5402-93. The number of double-rubs (i.e.,
one back- and forth motion) is reported. This test is often
referred to as "MEK Resistance."
B. Adhesion
[0178] Adhesion testing is performed to assess whether the coating
adheres to the coated substrate. The adhesion test was performed
according to ASTM D 3359--Test Method B, using SCOTCH 610 tape
(available from 3M Company of Saint Paul, Minn.). Adhesion is
generally rated on a scale of 0-10 where a rating of "10" indicates
no adhesion failure, a rating of "9" indicates 90% of the coating
remains adhered, a rating of "8" indicates 80% of the coating
remains adhered, and so on.
C. Blush Resistance
[0179] Blush resistance measures the ability of a coating to resist
attack by various solutions. Typically, blush is measured by the
amount of water absorbed into a coated film. When the film absorbs
water, it generally becomes cloudy or looks white. Blush is
generally measured visually using a scale of 0-10 where a rating of
"10" indicates no blush and a rating of "0" indicates complete
whitening of the film. Blush ratings of at least 7 are typically
desired for commercially viable coatings and optimally 9 or
above.
D. Acidified Coffee Testing
[0180] An acidified coffee solution was prepared by dissolving 4
grams of citric acid per liter of brewed coffee. Coated substrate
samples (2 inch by 4 inch coated metal strip reverse impacted,
after coating, in the center of the strip) were placed in a vessel
and partially immersed in the acidified coffee solution. While
partially immersed, the coated substrate samples were placed in an
autoclave and subjected to heat of 121.degree. C. and pressure of 1
atm above atmospheric pressure for a time period of 60 minutes.
After the time was complete, the samples were immersed in cool tap
water, rinsed with tap water, and then stored in water (deionized
or tap) until tested for adhesion, blush resistance, or stain
resistance. Adhesion and blush resistance was performed using the
methods described herein. Stain resistance was assessed visually on
a scale of 0 to 10, with a "0" indicating that the coating was
stained as dark as the coffee grinds, a "5" indicating moderate
staining of the coating (e.g., as indicated by the test piece being
quite gold in color), and a "10" indicating no detectable staining
of the coating.
E. Dowfax Detergent Test
[0181] The "Dowfax" test is designed to measure the resistance of a
coating to a boiling detergent solution. The solution is prepared
by mixing 5 ml of DOWFAX 2A1 (product of Dow Chemical) into 3000 ml
of deionized water. Typically, coated substrate strips are immersed
into the boiling Dowfax solution for 15 minutes. The strips are
then rinsed and cooled in deionized water, dried, and then tested
and rated for blush and adhesion as described previously.
F. Pencil Hardness
[0182] This test measures the hardness of a cured coating. Pencil
hardness was assessed using ASTM D3363, with the test run against
metal grain. The data is reported in the form of the last
successful pencil prior to film rupture. Thus, for example, if a
coating does not rupture when tested with a 2H pencil, but ruptures
when tested with a 3H pencil, the coating is reported to have a
pencil hardness of 2H.
G. Fabrication Test
[0183] This test measures the ability of a coated substrate to
retain its integrity as it undergoes the formation process
necessary to produce a fabricated article such as a beverage can
end. It is a measure of the presence or absence of cracks or
fractures in the formed end. The end is typically placed on a cup
filled with an electrolyte solution. The cup is inverted to expose
the surface of the end to the electrolyte solution. The amount of
electrical current that passes through the end is then measured. If
the coating remains intact (no cracks or fractures) after
fabrication, minimal current will pass through the end.
[0184] For the present evaluation, fully converted 202 standard
opening beverage ends were exposed for a period of 4 seconds to a
room-temperature electrolyte solution comprised of 1% NaCl by
weight in deionized water. The coating to be evaluated was present
on the interior surface of the beverage end at a dry film thickness
of 6 to 7.5 milligrams per square inch ("msi") (or 9.3 to 11.6
grams per square meter), with 7 msi being the target thickness.
Metal exposure was measured using a WACO Enamel Rater II (available
from the Wilkens-Anderson Company, Chicago, Ill.) with an output
voltage of 6.3 volts. The measured electrical current, in
milliamps, is reported. End continuities are typically tested
initially and then after the ends are subjected to pasteurization,
dowfax, or retort.
[0185] Preferred coatings of the present invention initially pass
less than 10 milliamps (mA) when tested as described above, more
preferably less than 5 mA, most preferably less than 2 mA, and
optimally less than 1 mA. After pasteurization, dowfax, or retort,
preferred coatings give continuities of less than 20 mA, more
preferably less than 10 mA, even more preferably less than 5 mA,
and even more preferably less than 2 mA.
H. Iodine Value
[0186] Iodine values were determined using ASTM D 5758-02
(Reapproved 2006) entitled "Standard Method for Determination of
Iodine Values of Tall Oil Fatty Acids," and are expressed in terms
of centigrams of iodine per gram of resin. Methylene chloride (HPLC
grade or better) was used as the diluent solvent in place of
iso-octane or cyclohexane.
EXAMPLES
[0187] The present invention is illustrated by the following
examples. It is to be understood that the particular examples,
materials, amounts, and procedures are to be interpreted broadly in
accordance with the scope and spirit of the present inventions as
set forth herein. Unless otherwise indicated, all parts and
percentages are by weight. Unless otherwise specified, all
chemicals used are commercially available from, for example,
Sigma-Aldrich, St. Louis, Mo.
Example 1--Polyurethane Polymer
TABLE-US-00001 [0188] TABLE 1 Amount INGREDIENT (grams) 1.
Tripropylene glycol/isophthalic acid polyester 80.30 g 2. Poly BD
R45HTLO.sup.A 40.15 g 3. Propylene glycol/dimer fatty acid
polyester 40.15 g 4. Dimethylolpropionic acid 12.63 g 5. Isophorone
diisocyanate 51.33 g 6. Dipropylene glycol dimethyl ether 85.70 g
7. Methyl methacrylate 147.14 g 8. 2,6-di-tertbutyl-4-methyl phenol
0.07 g 9. Triethylamine 4.76 g 10. Deionized water 462.45 g 11.
Propylene glycol monomethyl ether 88.40 g 12. Deionized water 32.74
g 13. Aminoethylethanol amine 6.48 g 14. Methyl methacrylate 67.31
g 15. n-butyl acrylate 89.18 g 16. Glycidyl methacrylate 43.37 g
17. Propylene glycol monomethyl ether 50.41 g 18. Tert-butyl hydro
peroxide (70% aq) 0.99 g 19. Deionized water 63.01 g 20.
Isoascorbic acid 0.99 g 21. Sodium feredetate (7% aq) 0.04 g 22.
Triethylamine 0.50 g 23. Deionized water 49.11 g .sup.AThe Poly BD
R45HTLO product is commercially available from Sartomer Company,
Inc., Exton, PA.
[0189] Items 1 through 8 of Table 1 were charged to a two-liter
round bottom flask equipped with a stirrer, an air sparge, a
thermocouple, and a heating mantle. These items were mixed until
uniform, and then the contents of the flask were heated gradually
to 88.degree. C. over about 1 hour. After the reactor reached
88.degree. C., it was held at this temperature for 3 hours and the
isocyanate content was titrated to ensure that the isocyanate
hydroxyl reaction was complete. The batch was then cooled to
54.degree. C. over about 1 hour and item 9 was added to the reactor
and the contents were allowed to mix for about 3 minutes. In a
separate three-liter stainless steel pot equipped with a
thermocouple, a nitrogen blanket, and agitation, items 10 and 11
were added. These materials were chilled to 10 to 12.degree. C.
prior to addition to the pot. The contents of the two-liter flask
(urethane prepolymer) were then dispersed into the water and
solvent in the three-liter pot over 3 to 5 minutes. (It is normal
to lose approximately 5% of the prepolymer due to the material
clinging to the walls of the two-liter flask. The amounts of the
other materials in the formulation are prorated appropriately to
keep the ratios of materials the same as listed above.)
[0190] After all of the prepolymer was in the dispersion pot, items
12 and 13 were added as a premix. The batch was then allowed to
exotherm and was stirred for approximately 35 to 45 minutes to
allow the amine/isocyanate chain extension reaction to proceed.
Example 2--Polyurethane/Acrylic Dispersion
[0191] After the 35 to 45 minute hold of Example 1, items 14, 15,
and 16 were added as a premix and item 17 was added as a rinse for
the premix container. After about 10 minutes of mixing time, item
18 was added to the dispersion pot and a premix of items 19 to 22
was added to the batch at an even rate over about 20 to 30 minutes.
During this addition, the batch was allowed to exotherm. After the
exotherm peaked and the temperature began to fall, item 23 was
added slowly to adjust the solids of the material to approximately
41%. The measured iodine value of the finished dispersion was about
16 (accordingly, the polyurethane had a calculated iodine value of
about 95) and the viscosity was 120 cps.
Example 3--Coating Composition
[0192] A coating composition was formed using the ingredients of
Table 2 below.
TABLE-US-00002 TABLE 2 AMOUNT INGREDIENT (in grams) 1.
Polyurethane/Acrylic Dispersion of Example 1 73.87 g 2. Phenolic
crosslinker 1.60 g 3. 2-butanol 1.75 g 4. Michelman 160PF.sup.B
1.60 g 5. Ethylene glycol 12.93 g .sup.BThe Michelman 160PF product
is a lubricant wax commercially available from Michelman, Inc. of
Cincinnati, Ohio.
[0193] Item 1 was charged to a stainless mixing vessel and
agitated. Each of items 2-5 were added separately with good
agitation. The resultant finish had a solids content of
approximately 35% and a #4 Ford cup viscosity of 16 seconds.
Example 4--Coated Article
[0194] The coating composition of Example 3 was applied as a coil
coating to chrome-pretreated aluminum metal coil. Steps were taken
to improve flow and leveling prior to a 10-second dwell in an oven
to achieve a 253.degree. C. peak metal temperature (PMT) and cure
the coating.
[0195] The cured coating samples were tested for a variety of
coating properties. The data for some of the coating property tests
are included in Table 3 below.
TABLE-US-00003 TABLE 3 Coating Composition Example 3 Film Weight
(mg/in2) 6 to 7 mg/in2 Pencil Hardness F MEK Resistance >100 MEK
Double Rubs Coffee Process Stain 4 Blush 10 Adhesion 7 Fabrication
Initial (prior to Dowfax)* 0.2 mA After Dowfax* 0.4 mA *202
Beverage Can Ends coated on interior surface.
[0196] The complete disclosure of all patents, patent applications,
and publications, and electronically available material cited
herein are incorporated by reference. The foregoing detailed
description and examples have been given for clarity of
understanding only. No unnecessary limitations are to be understood
therefrom. The present invention is not limited to the exact
details shown and described, for variations obvious to one skilled
in the art will be included within the present invention defined by
the claims.
* * * * *