U.S. patent application number 14/518223 was filed with the patent office on 2016-04-21 for polyethers derived from benzene dimethanol.
This patent application is currently assigned to PPG Industries Ohio. Inc.. The applicant listed for this patent is PPG Industries Ohio. Inc.. Invention is credited to Kareem Kaleem, Youssef Moussa.
Application Number | 20160107818 14/518223 |
Document ID | / |
Family ID | 54478225 |
Filed Date | 2016-04-21 |
United States Patent
Application |
20160107818 |
Kind Code |
A1 |
Kaleem; Kareem ; et
al. |
April 21, 2016 |
POLYETHERS DERIVED FROM BENZENE DIMETHANOL
Abstract
Containers comprising a food-contacting surface and a coating
thereon are disclosed. The coating comprises polyethers derived
from benzene dimethanol.
Inventors: |
Kaleem; Kareem; (Loveland,
OH) ; Moussa; Youssef; (Loveland, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PPG Industries Ohio. Inc. |
Cleveland |
OH |
US |
|
|
Assignee: |
PPG Industries Ohio. Inc.
Cleveland
OH
|
Family ID: |
54478225 |
Appl. No.: |
14/518223 |
Filed: |
October 20, 2014 |
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
B65D 81/34 20130101;
C08G 59/24 20130101; C08G 65/34 20130101; C09D 167/025 20130101;
C09D 171/00 20130101; C08G 59/066 20130101; C09D 163/00
20130101 |
International
Class: |
B65D 81/34 20060101
B65D081/34 |
Claims
1. A container comprising a food-contacting surface wherein at
least a portion of the food-contacting surface is coated with a
composition comprising a polyether composition derived from benzene
dimethanol containing at least one of the following segments:
##STR00019## where R.sub.1 is phenylene; R.sub.2 is a saturated
aliphatic radical, R.sub.3 is a (cyclo)aliphatic radical, an
arylene radical or an alkarylene radical, m is 0 to 12, n is 1 to
12 and p is less than 5, or ##STR00020## where R.sub.1 is
phenylene, R.sub.2 is a saturated aliphatic radical, R.sub.3 is a
(cyclo)aliphatic radical, an arylene radical or an alkarylene
radical, t is less than 5, u is 0 to 12 and v is 1 to 12.
2. The container of claim 1 in which (A) is terminated with epoxy
groups or phenolic hydroxyl groups.
3. The container of claim 1 in which (C) is terminated with epoxy
groups or phenolic hydroxyl groups.
4. The container of claim 1 where Ar is phenylene.
5. The container of claim 1 where R.sub.2 is a linear alkylene
radical containing from 4 to 12 carbon atoms.
6. The container of claim 1 where p is 1 to 2.
7. The container of claim 1 where R.sub.3 is ##STR00021##
8. The container of claim 1 where R.sub.3 is phenylene.
9. The container of claim 8 where the phenylene radical is derived
from resorcinol, hydroquinone and/or catechol.
10. The container of claim 1 in which the polyether composition is
aqueous based and in which the polyether (A) and/or (C) is grafted
to a (meth)acrylic polymer.
Description
[0001] The present invention relates to polyethers derived from
benzene dimethanol and to food-contacting containers coated with
compositions containing the polyethers.
BACKGROUND OF THE INVENTION
[0002] A wide variety of coatings have been used to coat the
surfaces of food and beverage containers. For example, metal cans
are sometimes coated using coil coating or sheet coating
operations, that is, a coil or sheet of steel or aluminum, is
coated with a suitable composition and cured. The coated substrate
is then formed into the can body or can end. Alternatively, the
coating composition may be applied, for example, by spraying and
dipping, to the formed can and then cured. Coatings for food and
beverage containers should preferably be capable of high speed
application to the substrate and provide the necessary properties
when cured to perform in a demanding end use environment. For
example, the coating should be safe for food contact and have
excellent adhesion to the substrate.
[0003] Many of the coating compositions for food and beverage
containers are based on polyether resins that are based on
polyglycidyl ethers of bisphenol A. Bisphenol A in container
coatings either as bisphenol A itself (BPA) or derivatives thereof,
such as diglycidyl ethers of bisphenol A (BADGE), epoxy novolak
resins and polyols prepared with bisphenol A and bisphenol F are
problematic. Although the balance of scientific evidence available
to date indicates that small trace amounts of BPA or BADGE that
might be released from existing coatings does not pose health risks
to humans, these compounds are nevertheless perceived by some as
being harmful to human health. Consequently, there is a strong
desire to eliminate these compounds from coatings for food and
beverage containers. Accordingly, what are desired are container
coating compositions for food and beverage containers that do not
contain extractable quantities of BPA, BADGE or other derivatives
of BPA and yet have commercially acceptable properties.
SUMMARY OF THE INVENTION
[0004] The present invention provides a container comprising a
food-contacting surface wherein at least a portion of the
food-contacting surface is coated with a polyether composition
derived from benzene dimethanol containing at least one of the
following segments:
##STR00001##
where R.sub.1 is phenylene; R.sub.2 is a saturated aliphatic
radical, R.sub.3 is a (cyclo)aliphatic radical, an arylene radical
or an alkarylene radical, m is 0 to 12, n is 1 to 12 and p is less
than 5, or
##STR00002##
where R.sub.1 is phenylene, R.sub.2 is a saturated aliphatic
radical, R.sub.3 is a (cyclo)aliphatic radical, an arylene radical
or an alkarylene radical, t is less than 5, u is 0 to 12 and v is 1
to 12.
[0005] The invention also provides for a container comprising a
food-contacting surface wherein at least a portion of the
food-contacting surface is coated with a composition comprising the
polyethers of (A) and/or (C) grafted to a (meth)acrylic
polymer.
DETAILED DESCRIPTION
[0006] As used herein, unless otherwise expressly specified, all
numbers such as those expressing values, ranges, amounts or
percentages may be read as if prefaced by the word "about", even if
the term does not expressly appear. Moreover, it should be noted
that plural terms and/or phrases encompass their singular
equivalents and vice versa. For example, "a" polymer, "a"
crosslinker, and any other component refers to one or more of these
components.
[0007] When referring to any numerical range of values, such ranges
are understood to include each and every number and/or fraction
between the stated range minimum and maximum.
[0008] As employed herein, the term "polyol" or variations thereof
refers broadly to a material having an average of two or more
hydroxyl groups per molecule. The term "polycarboxylic acid" refers
to the acids and functional derivatives thereof, including
anhydride derivatives where they exist, and lower alkyl esters
having 1-4 carbon atoms.
[0009] As used herein, the term "polymer" refers broadly to
prepolymers, oligomers and both homopolymers and copolymers. The
term "resin" is used interchangeably with "polymer".
[0010] The terms "acrylic" and "acrylate" are used interchangeably
(unless to do so would alter the intended meaning) and include
acrylic acids, anhydrides, and derivatives thereof, such as their
C.sub.1-C.sub.5 alkyl esters, lower alkyl-substituted acrylic
acids, e.g., C.sub.1-C.sub.2 substituted acrylic acids, such as
methacrylic acid, ethacrylic acid, etc., and their C.sub.1-C.sub.5
alkyl esters, unless clearly indicated otherwise. The terms
"(meth)acrylic" or "(meth)acrylate" are intended to cover both the
acrylic/acrylate and methacrylic/methacrylate forms of the
indicated material, e.g., a (meth)acrylate monomer. The term
"acrylic polymer" refers to polymers prepared from one or more
acrylic monomers.
[0011] (Cyclo)aliphatic refers to both cyclic aliphatic compounds
and to straight chain aliphatic compounds.
[0012] Carboxylic acid refers to both acid and equivalent
functionality such lower alkyl esters [C(1)-C(4)] thereof.
[0013] As used herein, "a" and "the at least one" and "one or more"
are used interchangeably. Thus, for example, a coating composition
that comprises "a" polymer can be interpreted to mean the coating
composition includes "one or more" polymers.
[0014] As used herein, the molecular weights are determined by gel
permeation chromatography using a polystyrene standard. Unless
otherwise indicated, molecular weights are on a number average
basis (Mn).
[0015] By "food" in "food-contacting surface" is meant to include
solid foodstuffs as well as beverages.
[0016] The polyethers of the invention are derived from benzene
dimethanol:
HO--CH.sub.2--R.sub.1--CH.sub.2--OH
where R.sub.1 is phenylene.
[0017] The benzene dimethanol can be modified by a subsequent
reaction with a hydroxy aromatic carboxylic acid such as 4-hydroxy
benzoic acid to form a phenolic-terminated adduct.
##STR00003##
where Ar is arylene.
[0018] The phenolic adduct (2) can further be reacted with a
diglycidyl ether such as:
##STR00004##
where R.sub.3 is a divalent (cyclo)aliphatic radical; an arylene
radical or an alkarylene radical, and m is 0 to 12, to form a
polyether having the following structure:
##STR00005##
where m is 0 to 12 and n is 1 to 12.
[0019] The diglycidyl ethers can be diglycidyl ethers of
(cyclo)aliphatic diols, arylene diols or alkarylene diols including
mixed diols. Examples of such diols include 1,4-butanediol,
cyclohexane dimethanol, resorcinol, hydroquinone and catechol. An
example of an alkaryl diol is alkyl-substituted catechol such as
t-butyl catechol.
[0020] To enhance the flexibility of the polyether, the polyethers
can be modified with a dicarboxylic acid such as a saturated
aliphatic dicarboxylic acid containing from 4 to 12 carbon atoms,
such as a linear alkylene dicarboxylic acid, for example, adipic
acid and/or sebacic acid. An adduct or an oligomeric polyester can
be prepared from the dicarboxylic acid and the benzene dimethanol
to form a hydroxy-terminated adduct or oligomer that could be
further reacted with the hydroxy aromatic carboxylic acid or the
lower alkyl ester thereof to give a material having the following
segments:
##STR00006##
where Ar is arylene; R.sub.1 is phenylene; R.sub.2 is a divalent
saturated aliphatic group and n is less than 5.
[0021] In the above structure (5), n is 0 when no polyester is
prepared; with a polyester, n is typically 1 to 2.
[0022] The modified diphenolic compound (5) could then be reacted
with a diglycidyl ether (3 above) to form a polyether having the
following segments:
##STR00007##
where R.sub.1 is phenylene; R.sub.2 is a saturated aliphatic
radical, R.sub.3 is a (cyclo)aliphatic radical, an arylene radical
or an alkarylene radical, m is 0 to 12, n is 1 to 12 and p is less
than 5. In the above structure, p is 0 when no polyester is
prepared; with a polyester, p is typically 1 to 2.
[0023] The polyether (A) may be terminated with epoxy groups or
phenolic hydroxyl groups such as polyethers of the following
structures:
##STR00008##
where X is
##STR00009##
and where Y is
##STR00010##
The identity of X and Y will depend on the equivalent ratio of (2)
to (3). Typically the equivalent ratio of (2) to (3) is from
0.8-121.
[0024] Modification of the benzene dimethanol or the polyester
thereof with the hydroxy aromatic carboxylic acid or ester thereof
to prepare the polyether depicted by (5) above is done by
traditional esterification techniques such as heating the benzene
dimethanol with the hydroxy aromatic carboxylic acid or ester
thereof typically in the presence of a tin catalyst while
distilling off the water or alcohol depending on whether the
hydroxy aromatic carboxylic acid or its lower alkyl ester is used.
The hydroxy aromatic carboxylic acid is typically used in an
equivalent excess, i.e., the acid equivalents of the hydroxy
aromatic carboxylic acid to the hydroxy equivalents of the
polyester is greater than 1, to provide phenolic hydroxyl groups
for further reaction with the diglycidyl ether.
[0025] The reaction conditions for reaction of the diphenolic
compound (5) with the diglycidyl ether (3) are conditions typically
used for diphenolic advancement of diglycidyl ether. The reaction
is conducted in organic solvent such as a ketone and in the
presence of catalyst such as an onium compound at elevated
temperatures such as 100 to 160.degree. C. and for a time
sufficient to achieve the desired epoxy equivalent weight,
typically 30 minutes to 3 hours.
[0026] For the more flexible polyethers, a polyester adduct or
oligomer is prepared from reacting benzene dimethanol with a
dicarboxylic acid anhydride to prepare the adduct or oligomeric
product having segments of the following structure:
##STR00011##
where R.sub.1 is phenylene and R.sub.2 is a saturated aliphatic
radical such as a saturated alkylene radical containing from 4 to
12 carbon atoms; n is less than 5 such as 1 to 2. The reaction
conditions for preparing the adduct or oligomeric polyester are
those typically used in polyester synthesis. The polyesters are
prepared by condensation polymerization conditions as generally
described by Zeno Wicks, Jr. et al. in Organic Coatings Science and
Technology, Vol. 1, pages 122-132 (John Wiley & Sons; New York,
1992).
[0027] Besides the polyethers described above, polyethers can be
prepared by reacting benzene dimethanol with epichlorohydrin to
form a diglycidyl ether having the following structure:
##STR00012##
where r is from 0 to 12.
[0028] The diglycidyl ether (6) can be advanced with a
(cyclo)aliphatic diol or a dihydric phenol.
HO--R.sub.3--OH (7)
where R.sub.3 is a (cyclo)aliphatic radical, an arylene radical or
an alkarylene radical, to ring open the epoxide group to form a
polyether with the following structure:
##STR00013##
where r is 0 to 12 and s is 1 to 12.
[0029] When modified with a dicarboxylic anhydride to form the
polyester adduct or oligomer with the benzene dimethanol as
generally described above and further reaction with epichlorohydrin
would produce a diglycidyl ether having the following
structure:
##STR00014##
where R.sub.2 is a saturated aliphatic radical, t is less than 5,
such as 1 to 2, and u is 0 to 12.
[0030] The diglycidyl ether (9) can be advanced or chain extended
with a (cyclo)aliphatic diol or a dihydric phenol (7) that ring
opens the epoxide groups to give a polyether having the following
structure:
##STR00015##
where R.sub.1 is phenylene, R.sub.2 is a saturated aliphatic
radical, R.sub.3 is a (cyclo)aliphatic radical, an arylene radical
or an alkarylene radical, t is less than 5, u is 0 to 12 and v is 1
to 12. In the above structure, t is 0 when no polyester is
prepared. With a polyester, t is typically 1 to 2.
[0031] Examples of suitable chain-extenders are 1,4-butanediol,
cyclohexane dimethanol, resorcinol, hydroquinone, catechol and
t-butyl catechol.
[0032] The polyether (C) may be terminated with epoxy groups or OH
groups such as polyethers of the following structures:
##STR00016##
where X' is H or
##STR00017##
and Y' is O--R.sub.3--OH, or
##STR00018##
[0034] Reaction conditions for reacting the benzene dimethanol or
the polyester adduct or oligomer thereof with epichlorohydrin can
be those generally described in U.S. Pat. No. 3,041,300. For
example, in one-liter flask equipped with stirrer, reflux condenser
and thermometer, one mole (138 gms) of benzene dimethanol (BDM), 3
moles of epichlorohydrin (277.5 gms) and 50% aqueous sodium
hydroxide (160 gms, 2 moles) can be heated to specific temperature
(e.g. 90-95.degree. C.). After holding at reaction temperature, the
reaction mixture can be heated to remove water to complete the
reaction using Dean Stark apparatus. The resultant mixture would be
washed with water to remove sodium chloride. The water insoluble
layer will be extracted with methylene chloride and dried over
anhydrous sodium sulfate. The diglycidyl ether can be recovered
after removal of methylene chloride by vacuum distillation.
[0035] Advancement or chain extension reactions mentioned above can
be conducted under conditions typically used for advancement of
diglycidyl ethers. The reaction is conducted in organic solvent
such as a ketone and in the presence of a catalyst such as an onium
compound at elevated temperatures such as 100 to 160.degree. C. and
for a time to achieve the desired epoxy equivalent weight,
typically 30 minutes to 3 hours.
[0036] The polyethers of the invention, that those have the
segments (A) and (C) are applied to the substrate as a component in
a coating composition that includes a liquid carrier. The liquid
carrier may be water, organic solvent or mixtures thereof.
Accordingly, the liquid coating compositions of the present
invention may be aqueous based (containing water and optionally
some water-miscible organic solvent) or be organic solvent based,
that is, substantially no water (i.e., less than 2% by weight water
based on total weight of the coating composition). Examples of
suitable organic solvents are glycol ethers, alcohols, aromatic or
aliphatic hydrocarbons, ketones, esters and mixtures thereof. The
liquid carriers are selected to provide a dispersion or solution of
the polyether for further coating formulation.
[0037] The polyethers can be dissolved in an organic solvent and
formulated with a crosslinking agent such as an aminoplast or
phenolplast curing agent (as described below) and normal additives
known in coatings for food-contacting surfaces of containers.
Typically, organic solvent-based coating compositions based on the
polyethers have resin solids contents of 20 to 50% by weight based
on total weight of the coating composition. The polyethers may also
be formulated in aqueous-based coating compositions, for example,
the polyether can be prepared with terminal 1,2-epoxy functionality
that can be reacted with phosphoric acid and at least partially
neutralized with a base to form phosphate salt groups making the
polyether dispersible in an aqueous carrier.
[0038] Because of the activated methylene group in benzene
dimethanol, the polyether can be grafted via proton abstraction to
a water-dispersible (meth)acrylic polymer such as by grafting with
a (meth)acrylic acid functional monomer that contains double bonds,
which is polymerizable by a free radical mechanism. Examples of
such monomers are (meth)acrylic acid and ethylenically unsaturated
monomers not containing acid groups such as (meth)acrylic acid
esters, styrene and the like. The resulting graft copolymer can
then be at least partially neutralized with a base such as a
tertiary amine. The resin solids content of the aqueous-based
coating compositions is typically from 20 to 50% by weight resin
solids based on total weight of the coating composition.
[0039] The acrylic portion of the polyether-(meth)acrylic graft
copolymer comprises polymerized ethylenically unsaturated monomers
which include carboxyl functional monomers such as (meth)acrylic
acid and unsaturated dicarboxylic acids such as maleic or fumaric,
to provide carboxyl functionality for dispersing the
polyether-(meth)acrylic copolymer mixture into water. The balance
of the monomers preferably are non-functional under the
contemplated conditions of polymerization, although small amounts
of other reactive monomers may be used such as hydroxy monomers
illustrated by 2-hydroxy ethyl(meth)acrylate, amide monomers
illustrated by (meth)acrylamide, or N-methylol monomers illustrated
by N-methylol(meth)acrylamide. The remaining monomers are
non-functional but copolymerizable ethylenic monomers illustrated
by (meth)acrylate esters, such as ethyl(meth)acrylate,
methyl(meth)acrylate or isobutyl(meth)acrylate, vinyl aromatic
compounds, styrene, or vinyl toluene, vinyl acetate, vinyl
chloride, vinylidene chloride and other ethylenically unsaturated
monomers such as butadiene and (meth)acrylonitrile. The
(meth)acrylic polymer component comprises by weight between about
5% and 40% based on the weight of the (meth)acrylic grafted
polyether.
[0040] The polyether-acrylic graft copolymer may be prepared by
non-aqueous polymerization of the ethylenic monomers with the
polyether resin. The polyether resin can be healed in a reactor
wherein the polymerizable monomer can be added slowly over a period
of at least two or three hours along with a solvent and a free
radical initiator. Although the reaction may be conducted in the
absence of a solvent, some solvent is desirable for the
polymerization of monomers in the presence of polyether resin.
Solvents such as xylene, benzene, ethyl benzene, toluene, and the
alkoxy alkanols are satisfactory. Alcohols such as methanol,
ethanol, propanol, butanol, and the like, are suitable, with
ethylene glycol monobutyl ether and butanol being preferred.
Ethylene glycol monobutyl ether, ethylene glycol monohexyl ether,
diethylene glycol monobutyl ether, and the like are most suitable.
For subsequent dispersion into water, the solvents selected are
usually water-soluble materials, such as butanol, propenol,
ethylene glycol monoethyl ether, and the like, although small
amounts of mineral spirits, hexane, and similar aliphatic may be
used.
[0041] As mentioned above, the coating compositions of the present
invention contain a crosslinking agent. Examples of crosslinking
agents are phenolplast and aminoplast.
[0042] Suitable 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-et-butylphenol,
p-tert-amylphenol, and cyclopentylphenol.
[0043] Suitable aminoplast resins are 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 crosslinking resins include, without limitation,
benzoguanamine-formaldehyde resins, melamine-formaldehyde resins,
etherified melamine-formaldehyde, and urea-formaldehyde resins.
[0044] The level of curing agent (e.g., crosslinker) used will
typically depend on the type of curing agent, the time and
temperature of the bake, the molecular weight of the binder
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, a crosslinker is preferably 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.
[0045] 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 composition resulting
therefrom. Such optional polymers are typically included in a
coating composition as a filler material, although they can also be
included, for example, as a binder polymer, a crosslinking
material, or to provide desirable properties. One or more optional
polymers (e.g., filler 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.
[0046] Such additional polymeric materials can be nonreactive, and
hence, simply function as fillers. Such optional nonreactive filler
polymers include, for example, polyesters and (meth)acrylic
polymers. Alternatively, such additional polymeric materials or
monomers can be reactive with other components of the composition.
If desired, reactive polymers can be incorporated into the
compositions of the present invention, to provide additional
functionality for various purposes, including crosslinking or
dispersing the polymer of the present invention into water.
Examples of such reactive polymers include, for example,
functionalized polyesters and functionalized (meth)acrylic
polymers.
[0047] Another optional ingredient is a catalyst to increase the
rate of cure. Examples of catalysts include, but are not limited
to, strong acids, e.g., phosphoric acid, dodecylbenzene sulphonic
acid (DDBSA), available as CYCAT 600 from Cytec, methane sulfonic
acid (MSA), p-toluene sulfonic acid (pTSA), dinonylnaphthalene
disulfonic acid (DNNDSA). If used, a catalyst is preferably present
in an amount of at least 0.01 wt-%, such as at least 0.1 wt-%,
based on the weight of nonvolatile material in the coating
composition. If used, a catalyst is preferably present in an amount
of no greater than 3 wt-%, such as no greater than 1 wt-%, based on
the weight of nonvolatile material in the coating composition.
[0048] Another useful optional ingredient is a lubricant (e.g., a
wax), which facilities manufacture of fabricated metal articles
(e.g., closures and food or beverage can ends) 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-%, such as no greater than 2 wt-%, and typically no
greater than 1 wt-%, based on the total weight of nonvolatile
material in the coating composition.
[0049] Another useful optional ingredient is a pigment, such as
titanium dioxide. If used, a pigment is present in the coating
composition in amount of no greater than 70 wt-%, such as no
greater than 50 wt-%, and typically no greater than 40 wt-%, based
on the total weight of solids in the coating composition.
[0050] Surfactants can be optionally added to the coating
composition, e.g., to aid in flow and wetting of the substrate.
Examples of surfactants include, but are not limited to,
nonylphenol polyethers and salts 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-%, such as at least 0.1
wt-%, based on the weight of resin solids. If used, a surfactant is
usually present in an amount no greater than 10 wt-%, and typically
no greater than 5 wt-%, based on the weight of resin solids.
[0051] The coating compositions used in the practice of this
invention are substantially free, may be essentially free and/or
may be completely free of bisphenol A and derivatives or residues
thereof, including bisphenol A and bisphenol A diglycidyl ether
("BADGE"). A reaction product and/or coating that is substantially
bisphenol A free is sometimes referred to as "BPA non intent"
because BPA, including derivatives or residues thereof, are not
intentionally added but may be present in trace amounts such as
because of impurities or unavoidable contamination from the
environment. The reaction product and/or coatings of me present
invention can also be substantially free, essentially free and/or
completely free of biphenol F and derivatives or residues thereof,
including bisphenol F and bisphenol F diglycidyl ether ("BPFDG").
The term "substantially free" as used in this context means the
reaction product and/or coating compositions contain less than 1000
parts per million (ppm), "essentially free" means less than 100 ppm
and "completely free" means than 20 parts per billion (ppb) of any
of the above compounds or derivatives or residues thereof.
[0052] The coating composition 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 composition can be used
as a primer coat, an intermediate coat, a top coat, or a
combination thereof. The coating thickness of a particular layer
and the overall coating system will vary depending upon the coating
material used, the substrate, the coating application method, and
the end use for the coated article. Mono-layer or multi-layer
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 1 to about 60 microns and more,
typically from about 2 to about 15 microns. Typically, the average
total coating thickness for rigid metal food or beverage can
applications will be about 3 to about 10 microns. Coating systems
for closure applications may have an average total coating
thickness up to about 15 microns. In certain embodiments in which
the coating composition is used as an interior coating on a drum
(e.g., a drum for use with food or beverage products), the total
coating thickness may be approximately 25 microns.
[0053] The coating composition of the present invention may be
applied to a substrate either prior to, or after, the substrate is
formed into an article (such as, for example, a food or beverage
container or a portion thereof). In one embodiment, a method is
provided that includes: applying a coating composition described
herein to a metal substrate (e.g., applying the composition to the
metal substrate in the form of a planar coil or sheet), curing the
composition, and forming (e.g., via stamping) the substrate into a
packaging container or a portion thereof (e.g., a food or beverage
can or a portion thereof). For example, riveted beverage can ends
having a cured coating of the present invention on a surface
thereof can be formed in such a process. In another embodiment, the
coating composition is applied to a preformed metal food or
beverage can, or a portion thereof. For example, in some
embodiments, the coating composition is spray applied to an
interior surface of a preformed food or beverage can (e.g., as
typically occurs with "two-piece" food or beverage cans). 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 nay 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.
[0054] 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 (PM) 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, more typically about 5 to 30 seconds) to a PMT of at
least about 425.degree. F. (218.degree. C.).
[0055] The coating composition of the present invention are
particularly useful for coating metal substrates. The coating
compositions may be used to coat packaging articles such as a food
or beverage container, or a portion thereof. In preferred
embodiments, the container is a food or beverage can and the
surface of the container is the surface of a metal substrate. The
polymer can be applied to a metal substrate either before or after
the substrate is formed into a can (e.g., two-piece cans,
three-piece cans) or portions thereof, whether it be a can end or
can body. Polymers of the present invention are suitable for use in
food-contact situation and may be used on the inside of such cans.
They are particularly useful on the interior of two-piece or
tee-piece can ends or bodies.
[0056] The metal substrate used in forming rigid food or beverage
cans, or portions thereof, typically has a thickness in the range
of about 0.005 inches to about 0.025 inches. Electro tinplated
steel, cold-rolled steel, and aluminum are commonly used as metal
substrates for food or beverage cans, or portions thereof. In
embodiments in which a metal foil substrate is employed in forming,
e.g., a packaging article, the thickness of the metal foil
substrate may be even thinner than that described above.
[0057] The coating compositions of the present invention may be
suitable, for example, for spray coating, coil coating, wash
coating, sheet coating, and side seam coating (e.g., food can side
seam coating). A further discussion of such application methods is
provided below. It is contemplated that coating compositions of the
present invention may be suitably used in each of these application
methods discussed further below, including the end uses associated
therewith.
[0058] Spray coating includes the introduction of the coating
composition into the inside of a preformed packaging container.
Typical preformed packaging containers suitable for spray coating
include food cans, beer and beverage containers, and the like. The
spray process preferably unless a spray nozzle capable of uniformly
coating the inside of the preformed packaging container. The
sprayed preformed container is then subjected to heat to remove any
residual carriers (e.g., water or solvents) and harden the
coating.
[0059] A coil coating is described as the coating of a continuous
coil composed of a metal (e.g., steel or aluminum). Once coated,
the coating coil is subjected to a short thermal curing cycle, for
hardening (e.g., drying and curing) of the coating. Coil coatings
provide coated metal (e.g., steel and/or aluminum) substrates that
can be fabricated into formed articles, such as two-piece drawn
food cans, three-piece food cans, food can ends, drawn and ironed
cans, beverage can ends, and the like.
[0060] A wash coating is commercially described as the coating of
the exterior of two-piece drawn and ironed ("D&I") cans with a
thin layer of protectant coating. The exterior of these D&I
cans are "wash-coated" by passing pre-formed two-piece D&I cans
under a curtain of a coating composition. The cans are inverted,
that is, the open end of the can is in the "down" position when
passing through the curtain. This curtain of coating composition
tales on a "waterfall-like" appearance. Once these cans pass under
this curtain of coating composition, the liquid coating material
effectively coats the exterior of each can. Excess coating is
removed through the use of an "air knife". Once the desired amount
of coating is applied to the exterior of each can, each can is
passed through a thermal, ultraviolet, and/or electromagnetic
curing oven to harden (e.g., dry and cure) the coating. The
residence time of the coated can within the confines of the curing
oven is typically from 1 minute to 5 minutes. The curing
temperature within this oven will typically range from 150.degree.
C. to 220.degree. C.
[0061] A sheet coating is described as the coating of separate
pieces of a variety of materials (e.g., steel or aluminum) that
have been pre-cut into square or rectangular "sheets". Typical
dimensions of these sheets are approximately one square meter. Once
coated, the coating is hardened (e.g., dried and cured) and the
coated sheets are collected and prepared for subsequent
fabrication. Sheet coatings provide coated metal (e.g., steel or
aluminum) substrates that can be successfully fabricated into
formed articles, such as two-piece drawn food cans, three-piece
food cans, food can ends, drawn and ironed cans, beverage can ends
(including, e.g., riveted beverage can ends having a rivet for
attaching a pull tab thereto), and the like.
[0062] A side seam coating is described as the application of a
powder coating or the spray application of a liquid coating over
the welded area of formed tree-piece food cans. When three-piece
food cans are being prepared, a rectangular piece of coated
substrate is formed into a cylinder. The formation of the cylinder
is rendered permanent due to the welding of each side of the
rectangle via thermal welding. Once welded, each can typically
requires a layer of coating, which protects the exposed "weld" from
subsequent corrosion or other effects to the contained foodstuff.
The coatings that function in this role are termed "side seam
stripes". Typical side seam stripes are spray applied and cured
quickly via residual heat from the welding operation in addition to
a small thermal cure in an oven.
EXAMPLES
[0063] The following examples are offered to aid in understanding
of the present invention and are not to be construed as limiting
the scope thereof. Unless otherwise indicated, all parts and
percentages are by weight.
Example 1
Diphenolic Adduct of Benzene Dimethanol and Methyl 4-Hydroxy
Benzoate
[0064] In a 4-neck flask equipped with stirrer, thermometer, packed
column with head temperature, water condenser and nitrogen inlet,
charge 106.4 parts of Methyl 4-hydroxy benzoate (MHBA,
Sigma-Aldrich) and 96.6 grams of 1,4-Benzene dimethanol (BDM, Ark
Pharm, Inc.). 0.6 grams of Butyl Titanate catalyst (Sigma-Aldrich)
was added to effect transesterification. The mixture was heated
slowly to 180.degree. C. (356.degree. F.). As the distillate
started to collect, increase batch temperature accordingly to
maximum reactor temperature of 220.degree. C. (428.degree. F.) not
allowing column temperature to exceed 65.degree. C. Maintain steady
rate of distillation to remove methanol continuously. Process until
material no more methanol is collected. 70-75% of theoretical
methanol was collected. The batch was cooled to 200.degree. C. and
poured into glass container. The brittle material was washed with
methanol and dried to remove residual methanol.
Example 2
Diphenolic Adduct of BDM and 4-Hydroxy Benzoic Acid
[0065] In a 4-neck flask equipped with stirrer, thermometer,
Dean-Stark apparatus with xylene, water condenser and nitrogen
inlet, charge 211 parts of 4-Hydroxy benzoic acid (HBA,
Sigma-Aldrich), 105.5 grams of 1,4-Benzene dimethanol (BDM, Ark
Pharm, Inc.) and 34 parts of Xylene. 0.2 grams of Fascat 2003
catalyst was added to effect esterification. The mixture was heated
slowly to 160.degree. C. As the distillate started to collect,
increase batch temperature accordingly to maximum reactor
temperature of 215.degree. C. Maintain steady rate of reflux to
remove water continuously. Process until material no more water is
collected. 80% of theoretical water was collected. The batch was
cooled to 200.degree. C. and poured into glass container. The
brittle material was washed with methanol and dried.
Example 3
Polyether from Advancing Cyclohexane Diglycidyl Ether with
Diphenolic Adduct of Benzene Dimethano and Methyl 4-Hydroxy Benzoic
Acid
[0066] In a 4-neck flask equipped with stirrer, thermometer, water
condenser and nitrogen inlet, charge 60 parts of above diphenolic
adduct (BDM/MHBA), 62.54 grams of CHDMDGE (EEW.about.159, Erisys
22S), 21 parts of MIBK and 0.6 grams of Ethyl triphenyl phosphonium
iodide catalyst (Sigma-Adrich). The mixture was heated slowly to
115.degree. C. (239.degree. F.) and the mixture turned clear.
Continue to heat to 155.degree. C. and mixture started to reflux
heavily. Hold the batch for one hour and mixture became viscous.
After one hour hold, heat was turned off and 120 parts of Butyl
Cellosolve solvent was added to obtain 45.6% solids resin solution.
The Epoxy Equivalent Weight of final polyether resin was determined
to be .about.816 based on solids. The resin was drawn down on metal
tin plate and baked at 400.degree. F. (204.degree. C.) for 10
minutes and was tack free.
[0067] Whereas particular embodiments of this invention have been
described above for purposes of illustration, it will be evident to
those skilled in the art that numerous variations of the details of
the present invention may be made without departing from the
invention as defined in the appended claims.
[0068] Although various embodiments of the invention have been
described in terms of "comprising", embodiments consisting
essentially of or consisting of are also within the scope of the
present invention.
* * * * *