Note: Descriptions are shown in the official language in which they were submitted.
99~P~4
Background of the Invention
As a result of the increased emphasis by Federal and State
governments in combating air pollution, the coatings industry is expending
considerable effort in eliminating or at least substantially minimizing
the emission of solvent vapors to the atmosphere from coating compositions.
9~4
As a part of this effort, the coatings industry has launched a major
effort to develop aqueous or water-based coating compositions in which
organic solvents have been completely eliminated or in which the
organic solvents constitute only a very minor proportion of the total
liquid medium.
In view of the excellent properties of solvent-based epoxy
coating compositions for various coating applications, those in the
coatings art have been extremely interested in developing aqueous coating
compositions derived from epoxy resins. Prior attempts to develop such
compositions involved reacting hydroxy carboxylic acids and epoxy
compounds. However, in reacting such compounds, two types of reaction
may result due to the chemical nature of the materials used. The hydroxyl
groups of the hydroxy acid may react with the epoxide groups to form
ether linkages, or the carboxyl group or groups of the acid may react with
the epoxide to form ester groups. Both reactions may occur in an uncontrolled
reaction to yield products having mixed ether or ester linkages to a non-
predetermined degree. Such reaction with the epoxides and acids previously
employed have not been tolerable since the ultimate products have not
generally been suitable for any practical purpose.
Early efforts to solve these problems involved attempts to
optimize the etherification portion of the reaction while minimizing the
esterification portion of the reaction. (See, e.g., U.S. Patents Nos.
3,404,018 and 3?410,773). In addition, attempts were made to utilize products
containing both ester and ether linkages. (See, e.g., U.S. Patents Nos.
3,707,526 and 3,792,112). However, these efforts were not particularly
successful since compositions produced from these techniques exhibited
significant disadvantages including poor cured film saponification resistance,
low hydrolysis resistance, and lack of adequate package stability.
~s~9~P4~L
It has recently been proposed, as disclosed in U.S. Patent No.
3,960,795, to prepare aqueous-based epoxy resins by a process which involves
reacting an epoxy-containing organic material with a compound containing
at least one phenolic hydroxyl group and a group hydrolyzable to a
carboxyl group following which the resultant composition is hydrolyzed to
generate carboxyl groups and then solubilized in known manner by neutral-
izing at least a portion of the carboxyl groups with a basic compound
such as an alkali metal hydroxide or amine. In addition, it has also
been proposed, as described in U.S. Patent No. 4,029,621, issued
June 14, 1977, commonly assigned to Applicant's assignee herein,
to produce aqueous-based epoxy resins by a process which involves
reacting an epoxy-containing organic material with a compound containing
a mercaptan group and at least one group hydrolyzable to a carboxyl group,
following which the resultant composition is hydrolyzed to generate carboxyl
groups and then solubilized by neutralizing a portion of the carboxyl
groups with a basic compound.
While the processes and products disclosed in the aforementioned
patent and application are advantageous in many respects, they also exhibit
significant disadvantages. Thus, for example, the processes described in
the aforementioned patent and copending applications ordinarily require
saponification, neutralization and filtration steps prior to neutralization
with the base and solubilization in water. As will be evident, such pro-
c-esses, in view of the number of processing steps and procedures, can be
time consuming and costly.
Beer, carbonated and non-carbonated soft drinks, and fruit
juices (hereinafter referred to generically as beverages) are often packed ~ -
in containers made from aluminum, tin-free steel, blackplate or tinplate,
which is cold rolled steel to which a thin layer of tin is applied. Many
of these beverages exert corrosive action upon the metal and in order to
adequately protect the container and to prevent contamination of the
packaged material, a sanitary liner must be applied to the internal sur-
B -3-
~L~99~44
face of the container. However, the use of such liners also presents
several problems, one of the most troublesome being the residual turbidity
and taste which tends to result from some liner materials.
Because of their relatively taste-free characteristics and other
excellent properties, epoxy resins have been extensively employed in
sanitary liners in contact with beverages. While such epoxy resins
have been extremely useful in the past, they possess a serious disadvan-
tage which materially diminishes their desirability as sanitary liners
at this time. Thus, these epoxy resins are generally applied from volatile
organic solvent solutions at relatively low solids contents and these
solvent rich solutions either add to hydrocarbon air pollution or require
expensive control equipment.
In recent times the increased emphasis on safety and environ-
mental pollution control has resulted in a need for water-based compositions
for such liners. By "water-based" it is meant compositions in solvents
consisting predominantly of water, thus greatly reducing the handling and
emissions of organic solvent vapors. However, the types of solvent-based
epoxy resin liners known and used heretofore have not been readily obtain-
able as satisfactory water-based systems and, indeed, it has been found
that water-based materials as a class often provide liners which impart
undesirable turbidity and taste characteristics to beverages, even when the
other necessary properties of such liners can be obtained.
The combination of properties which is necessary to successful
utili7ation of any composition for container liners is as follows:
A. PROPERTIES OF THE CURED LINER:
1. Metal Adhesion - Excellent adhesion to metals, including the
aluminum, tin-free steel, blackplate and tin plate employed in beverage
containers.
~94~
2. Taste Characteristics - Taste characteristics at least as
good as the best "tasteless" epoxy polymers applied from solvent solutions
utilized in the container industry at the present time.
3. Turbidity Resistance - Beverages after packing, pasteurization
and storage must not develop undesirable turbidity and loss of appearance
due to contact with the liner.
4. Fabricating Properties - Fabricating properties represent a
combination of flexibility, extensibility and adhesion so as to permit
forming operations to be carried out on the coated metal without cracking
or otherwise impairing the continuity of the film.
5. Pasteurization Resistance - Beer is generally pasteurized at
a temperature of 150F. for 15 to 40 minutes; occasionally during the
pasteurization temperatures as high as 160F. to 180F. may be reached.
6. Low Bake Properties - The curing or baking temperature in
metal beverage containers should not be excessively high because the exterior
of some containers may be coated with lithographic coatings and inks which
may discolor and lose their appearance at high temperatures. In addition,
some containers employ adhesives as bonding agents and such adhesives may
be adversely affected by high baking temperatures.
2
7. Extractability - The liner should not contain undesirable
materials which can be extracted from the liner during processing and storage.
8. Intercoat Adhesion - In order to permit use of primer or base
coat, if desired, or added coats to repair defects, the liner composition
should have good adhesion to itself and other conventionally utilized
materials.
B. PROPERTIES OF THE UNCURED CO~POSITION:
1. Application Properties - Application by equipment and methods
~L~99~
conventionally employed in the coatings industry. Thus, the composition
should be capable of being applied by methods such as dipping, roll coating,
spraying and the like. In addition, the composition should be capable of
being applied by electrodeposition if desired.
2. Storage Stability - The coating composition must be in a
physical form which permits handllng and storage over varying conditions.
Water-based compositions in emulsion form, for example, usually are not
storage-stable unless additives are employed which generally are undesirable
in liners for containers used for comestible products.
Summary of the Invention
In accordance with this invention, water-reducible epoxy resins
are prepared by a method which obviates substantially all of the above
disadvantages. Thus, water-reducible epoxy resins are prepared by reacting
a polyepoxide having a 1,2-epoxy equivalency greater than 1.0 with an
aromatic amino acid containing at least one amine group and one carboxyl group
which are both attached to the aromatic ring, wherein the amine groups of the
acid are preferentially reactive with the epoxy groups of the polyepoxide
the reaction product having unreacted carboxyl groups which are neutralized
with a base to form anionic salt groups. The resultant product can then be
solubilized (i.e., rendered water-reducible) by neutralizing at least a portion
of the acid functionality therein with an amine or other base. Especially
valuable amino acids are the aromatic amino acids such as snthranilic acid,
p-aminobenzoic acid, m-aminobenzoic acid, and 3-amino-p-toluic acid.
Whçn used in electrodeposition, the compositions herein deposit
on the anode. The resultant appropriately crosslinked films, as well as
those applied by conventional coating techniques, are characterized by
increased cured film saponification resistance, improved hydrolytic
B - 6 -
1~99~
stability, improved salt spray resistance and good hardness. Additionally,
these compositions have excellent package stability. Since the reaction
products contain hydroxyl functionality, a wide variety of conventional
crosslinking agents can be employed in formulations with these new resins.
Further, highly useful products can be obtained when the reaction
products of the present invention are blended with reactive or non~reactive
resins such as water-soluble acrylics, acrylic interpolymer dispersions,
acrylic polymer emulsions, aminoplast resins, phenolic resins, polyester
resins, blocked or semi-blocked polyisocyanates and the like.
Highly-useful water-based products can be obtained from the
reaction products and the above-mentioned resin products which are suitable
for use as water-based coating compositions for a variety of protective and
decorative coating applications. In a particular embodiment, a water-based
coating composition which is suitable for use as an internal sanitary
liner for metal beverage containers is formulated by blending the reaction
product with an aminoplast resin.
3escription of the Invention
.
In formulating a coating composition for use as an internal
sanitary liner for metal containers in which beverages are to be stored,
it is extremely important that cured films produced from such coating
compositions do not contain certain materials, even in residual amounts,
which can be extracted by the beverage from the cured film. Thus, it has
been found that certain additives commonly employed in formulating prior
aqueous-based coating compositions may remain in residual amounts in cured
films produced from such compositions and that even residual amounts of
such additives can adversely affect the characteristics of beverages in
contact with such films. For example, residual amounts of such materials
i~9V~9~
as surfactants and dispersion stabilizers commonly employed in formulatlng
aqueous compositions have been found to exert adverse effects on the
turbidity and/or taste characteristics of beverages such as beer. Accordingly,
in formulatlng the water-based coating compositions employed ln this inven-
tlon, such materials are avoided.
As mentioned above, the water-based coating compositions utilized
in the present invention contain at least two essential components: (1) an
at least partially neutralized reaction product of a polyepoxide and an
amlno acid containing at least one amine group and at least one carboxyl
group, wherein the amine groups of the amino acid are preferentially reactive
with the epoxy groups of the polyepoxide, and (2) a curing or crossllnking
agent.
The polyepoxide having a 1,2-epoxy equivalency greater than 1.0,
that is, in which the average number of 1,2-epoxy groups per molecule is
greater than 1, can be any of the well-known epoxides,
such as, for example, those described in ~.S. Patents Nos. 2,467,171;
2,615,007; 2,716,123; 3jO30,336; 3,053,855 and 3,075,999. A particularly
preferred class of polyepoxides are the polyglycidyl ethers of polyphenols,
such as bisphenol-A or bisphenol-F produced, for example, by etherification
of a polyphenol with epichlorohydrin or dichlorohydrin in the presence of
an alkali. The phenolic compound may be bis(4-hydroxyphenol)-2, 2-propane
4,4'-dihydroxybenzophenone, bis(4-hydroxyphenyl)l,l-ethane, bis(4-hydroxy-
phenyl)l,l-isobutane; bis(4-hydroxytertiary-butyl-phenyl)2,2-propane, bis
(2-hydroxynaphthyl)methane, 1,5-dihydroxynaphthalene, or the like. Another
qoite useful class of polyepoxides are produced similarly from Novolak resins
B
~996~
or similar polyphenol resins.
Also suitable in some instances are the similar polyglycidyl
ethers of polyhydric alcohols which may be derived from such polyhydric
alcohols as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-
propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol,
glycerol, bis(4-hydroxycyclohexyl)-2,2-propane, and the like.
There can also be used polyglycidyl esters of polycarboxylic
acids which are produced by the reaction of eplchlorohydrin or a similar
epoxy compound with an aliphatic or aromatic polycarboxylic acid, such
as oxalic acid, succinic acid, glutaric acid, terephthalic acid, 2,6-
naphthalene dicarboxylic acid, dimerized linolenic acid and the like.
~xamples are diglycidyl adipate and diglycidyl phthalate.
In addition, polyepoxides derived from the epoxidation of an
olefinically unsaturated alicyclic compound may also be employed. Included
are diepoxides comprising in part one or more monoepoxides. ~hese poly-
epoxides are non-phenolic and are obtained by epoxidation of alicyclic
olefins, for example, by oxygen and selected metal catalysts, by perbenzoic
acid, by acetaldehyde monoperacetate, or by peracetic acid. Among such
polyepoxides are the epoxyalicyclic ethers and esters, which are well-known
in the art.
Another class of polyepoxides which may be employed are those
containing oxyalkylene groups in the epoxy molecule. Polyepoxides containing
oxyalkylene groups can be produced by reacting some of the epoxy groups of
a polyepoxide, such as the polyepoxides mentioned above, with a monohydric
alcohol containing oxyalkylene groups.
Other epoxy-containing compounds and resins which may be employed
include nitrogeneous diepoxides such as disclosed in U.S.Patent No.
~9~
3,365,471; epoxy resins from l,l-methylene bis(5-substituted hydantoin),
U. S. Patent No. 3,391,097; bis-imide containing diepoxides, U.S. Patent
No. 3,450,711; heterocyclic N,N'-diglycidyl compounds, U.S. Patent No.
3,503,979; amino epoxyphosphonates, and the like.
Amino acids which may be employed in forming the reaction product
component of the compositions herein are amino acids which contain at
least one amine group and one carboxyl group in which the amine group of
the amino acid is preferentially reactive with the epoxy groups of the
polyglycidyl ether.
;0 It was surprising and unexpected to find in this invention that
certain amino acids contain amine groups which are preferentially or selec-
tively reactive with epoxy groups and that such amino acids can be directly
reacted with epoxy resins to form reaction products containing free car-
boxyl groups available for solubilization purposes without first blocking
the carboxyl groups of the amino acid as by reaction with an alcohol (i.e.,
ester formation) or strong base (e.g., NaOH). This was particularly unex-
pected since previous attempts to prepare such water-reducible products
utilizing simple (i.e., short chain) aliphatic amino acids indicated that
the epoxy groups of the epoxy resin reacted principally with the carboxyl
20 groups of the amino acid, thereby resulting in a product containing little
if any free carboxyl functionality available for solubilization purposes.
The preferred amino acids for use in preparing the reaction product
component of the compositions are aromatic amino acids in which the amine
group and carboxyl group are both attached to the aromatic ring. ~specially
preferred amino acids of this type are the aminobenzoic acids, including
anthranilic acid, p-aminobenzoic acid and m-aminobenzoic acid, and other
aromatic amino acids such as 3-amino-p-toluic acid.
--10--
l~r;9:9~"D~,
Anthranilic acid is a particularly preferred amino acid for use
in forming the reaction product component of the sanitary liner composition
because its methyl ester, i.e., methyl anthranilate, is a component of
naturally-occurring foods such as grape juice and, in addition, the free
form of the acid is often present in North American wines. Other amino
acids useful in many instances include 3-aminosalicylic acid, 3-amino-4-
methoxybenzoic acid, 6-amino-m-toluic acid, 3-amino-4-chlorobenzoic acid,
2-amino-5-nitrobenzoic acid, 2-nltro-5-aminobenzoic acid. In some cases
it may be necessary to use a specific solvent chosen to dissolve certain
difficult-to-dissolve amino acids, one example being 5-aminoisophthalic acid
which otherwise does not react.
In reacting the polyepoxide with the amino acid, in general,
the equivalent ratio of epoxy groups contained in the polyepoxide to amino
groups contained in the amino acid should be between about 1.0 and 0.20 and
1.0 to 1.25, and preferably 1.0 to 0.5 and 1.0 to 1Ø It is generally
preferred that the carboxyl content of the reaction product be at least
equivalent, when in an unneutralized state, to an acid value of at least
about 15 at 100 percent solids.
In reacting the polyepoxide and the amino acid, a catalyst may
be used, if desired. Suitable catalysts include acid catalysts such as
p-toluene-sulfonic acid, butylphosphoric acid, methane sulfonic acid, and
the like. In general, where catalysts are employed, they should be used
in amounts from about 0.01 to about 3.0 percent by weight based on total
weight of the epoxy-containing material and aromatic amino acid. Usually,
it is desirable to react the components at moderately elevated temperatures,
and for this purpose, temperatures of from about 200F. to about 350~F.
are generally acceptable. Of course, it is to be recognized that the reaction
9~
temperature can be varied between the lowest temperature at which the
reaction reasonably proceeds and the temperatures indicated above.
It is not absolutely necessary to employ a solvent in the
preparation of the reaction product, for example, when the reactants are
mutually soluble and of suitable viscosity but one is usually used in
order to provide for more efficient processing. The organic solvent used
should be a non-epoxy reactive solvent and, since the finished product is
intended to be water-reducible, it is preferred to employ water-miscible
or at least partially water-miscible organic solvents. Preferred solvents
of this type include the monoalkyl ethers of ethylene glycol, propylene
glycol and dipropylene glycol such as, for example, ethylene glycol
monoethyl ether, ethylene glycol monobutyl ether, propylene glycol
monomethyl ether, dipropylene glycol monomethyl ether and the like.
Mixtures of these ether type alcohols and lower alkanols such as ethanol,
propanol and isopropyl alcohol may also be employed. Additionally, in
some instances, minor proportions of hydrocarbon solvents such as toluene
and xylene may be utilized in combination with the preferred solvents.
The reaction products can then be solubilized (i.e., rendered
water-reducible) by neutralizing at least a portion of the carboxyl groups
thereof with an amine or other base. As will be apparent, the term "solu-
bilized" as employed herein refers to the neutralization or partial
neutralization of the acid groups of the reaction product to form the salt
or partial salt of the product to thereby render it water-reducible or
water-thinnable.
Volatile bases are preferred, particularly when the composition
is to be applied by spraying, rolling, dipping or the like (by "volatile
bases" is meant bases which evaporate at temperatures at or below that at
which the material is cured). Non-volatile bases, such as alkali metal
-12-
1~99~
hydroxides, may be used when application by electrodeposition or other
methods which remove the solubilizing agent are to be used. Amines are
the preferred volatile neutralizing agents, although others, such as quater-
nary ammonium hydroxides, can be used.
In general, the amines which may be employed herein for neutrali-
zation purposes include any of the amines used for solubilizing resin
systems known heretofore including ammonia; alkylamines such as ethylamine,
propylamine, dimethylamine, dibutylamine, triethylamine, cyclohexylamine
.
and the like; allylamine; alkanolamines such as monoethanolamine, dimethyl-
ethanolamine, diethylethanolamine, 2-amino-2-methyl-1-propanol, 2-dimethyl-
amino-2-methyl-1-propanol and the like; aralkylamines such as benzylamine
and the like; cyclic amines such as morpholine, piperidine and the like;
and diamines such as ethyl diamine and the like. The preferred amines for
use herein are dimethylethanolamine and diethylethanolamine. Mixtures of
such solubilizing agents may also be used. If desired, moderately elevated
temperatures may be employed in solubilizing the product. Essentially any
amount of solubilizing agent may be utilized as long as the desired degree
of water-solubility or water-dispersibility is obtained. In general, the
amount of solubilizing agent will be dependent upon the acid value of the
reaction product. It is usually preferred to react one equivalent of
solubilizing agent per equivalent acid group, although higher and lower
amounts may be used. In general, it is preferred to utilize the minimum
amount of solubilizing agent to obtain the solubilized product.
As indicated heretofore, this invention is principally concerned
with aqueous compositions which are formulated from the above described
reaction products. However, in certain cases, solvent-based coating
compositions containing these reaction products may be valuable for certain
1~99~4
applications and such compositions are considered to be within the scope
of this invention. When it is deslred to prepare solvent-based compositions
utilizing these reaction products, this can readily be accomplished by
dissolving or dispersing the reaction products in conventional organic
solvents which are well-known to those in the coatings art. Thus, organic
solvents such as the hydrocarbons, alkanols, esters, ethers, and ketones
may be employed for that purpose. As noted above, it is often desirable to
prepare coating compositions from the reaction products herein in which the
liquid medium is a mixture of water and organic solvents. This can be con-
viently accomplished, as indicated above, by utilizing a water-miscible or
partially water-miscible organic solvent to first prepare the reaction
product in organic solvent solution and then after solubilization with the
amine, water can be added to the solution or the reaction product solution
can be dissolved or dispersed in water.
For use as sanitary liners for metal containers, a curing
or crosslinking agent is included in the compositions. The preferred
crosslinking agents include aminoplast resins, phenolic resins and blocked
or semi-blocked polyisocyanates.
The aminoplast resins used may be alkylated methylol melamine
resins, alkylated methylol urea, and similar compounds. Products obtained
from the reaction of alcohols and formaldehyde with melamine, urea or
benzoguanamine are most common and are preferred herein. However,
condensation products of other amines and amides can also be employed, for
example, aldehyde condensates of triazines, diazines, triazoles, guanidines,
guanamines and alkyl- and aryl-substituted derivatives of such compounds,
including alkyl- and aryl-substituted ureas and alkyl- and aryl-substituted
melamines. Some examples of such compounds are N,N'-dimethyl urea, benzyl
-14-
1~990~4
urea, formoguanamine, acetoguanamine, ammeline, 2-chloro-4,6-diamino-
1,3,5-triazine, 6 methyl-2,4-diamino-1,3,5-triazine, 3,5-diamino triazole,
triaminopyrimidine, 2-mercapto-4,6-diaminopyridine, and the like.
While the aldehyde employed is most often formaldehyde, other
similar condensation products can be made from other aldehydes or mixtures
thereof, such as acetaldehyde, crotonaldehyde, acrolein, benzaldehyde,
furfural, glyoxal and the like.
The aminoplast resins contain methylol or similar alkylol
,
groups, and in most instances at least a portion of these alkylol groups
are etherified by a reaction with an alcohol to provide organic solvent-
soluble resins. Any monohydric alcohol can be employed for this purpose,
including such alcohols as methanol, ethanol, propanol, butanol, pentanol,
hexanol, heptanol and monoethers of glycols. The preferred aminoplast
resins are substantially etherified with methanol or butanol.
The phenolic resins which may be used as curing agents herein
are formed by the condensation of an aldehyde and a phenol. The most used
aldehyde is formaldehyde, although other aldehydes, such as acetaldehyde,
can also be employed. Aldehyde-releasing agents such as paraformaldehyde
and hexamethylenetetramine, can be utilized as the aldehyde agent if desired.
Various phenols can be used; for instance, the phenol employed can be phenol
per _, a cresol, or a substituted phenol in which a hydrocarbon radical
having either a straight chain, a branched chain or a cyclic structure is
substituted for a hydrogen in the aromatic ring. Mixtures of phenols are
also often employed. Some specific examples of phenols utilized to produce
these resins include p-phenylphenol, p-tert-butylphenol~ p-tert-amylphenol,
cyclopentylphenol and unsaturated hydrocarbon-substituted phenols, such as
monobutenyl phenols containing a butenyl group in the ortho, meta, or para
1~399~4
position, and where the double bond occurs in various positions in the hydro-
carbon chain. A common phenolic resin is phenol formaldehyde resin.
Any blocked or semi-blocked organic polyisocyanate may be used as
the curing agent herein. The organic polyisocyanates are blocked with a
volatile alcohol, -caprolactam, ketoximes, or the like, and will unblock
at elevated temperatures. These curing agents are well-known in the art.
The amounts of curing or crosslinking agents employed in com-
bination with the reaction products herein can vary somewhat depending
on desired properties. However, it is preferred to use from about 3
to about 30 percent by weight of the crosslinking agents, based upon the
combined total solids weight of the crosslinking agent and reaction
product.
As noted above, various other reactive or non-reactive resins
other than the aforementioned curing or crosslinking agents may be included
in the water-based coating composition. Thus, hydrocarbon resins, such
as polybutadiene, maleic anhydride adducts of polybutadiene, styrene-
butadiene latices, etc.; water-soluble acrylic resins such as those in
U. S. Patent No. 3,403,088; acrylic polymer emulsions; aqueous dispersions
of amide-containing acrylic interpolymers; and the like may be included.
The compositions may also include polyesters, polyamides, and the like.wnlen using such modifying materials, such materials generally comprise from
95 to 5 percent by weight, and preferably from 50 to 5 percent by weight,
based on total weight of resin solids.
It should be noted that in certain instances reactive resins such
as the amide-containing acrylic interpolymers mentioned above may be used
as a crosslinking agent, either alone or in combination with the preferred
crosslinking agents discussed above.
~99~4
Suitable acrylic polymer emulsions which may be employed
in the compositions are copolymerized latex products which are prepared
by conventional emulsion polymerization in aqueous medium of various
vinyl and equivalently-reactive unsaturated monomers in the presence of
conventional emulsion polymerization catalysts and surface-active
water-soluble anionic or non-ionic dispersing agents.
Various vinyl and equivalently-reactive unsaturated monomers
.
may be utilized such as, for example, alkyl acrylates having from 4 to
15 carbon atoms, alkyl methacrylates having from 5 to 15 carbon atoms,
unsaturated carboxylic acids, particularly acrylic acid and methacrylic
acid, and other monomers containing a CH2=C~ group in the terminal position,
such as, for example, the vinyl aromatic hydrocarbons, unsaturated organoni-
triles and the like.
The acrylic polymer emulsions are prepared by conventional
emulsion polymerization of these vinyl or equivalently reactive monomers
in the presence of conventional emulsion polymerization catalysts and
surface-active water-soluble anionic or non-anionic dispersing agents.
Various conventional emulsion polymerization catalysts may be employed,
including among others the conventional peroxides such as benzoyl
peroxide, cumene peroxide, tertiary-butyl perbenzoate, etc., and the persul-
fates such as ammonium, sodium and potassium persulfates. Various anionic
~99~ 4
and non-ionic dispersing agents may be employed, including among others
the alkyl phenoxy polyethoxyethanols, sulfur-containing agents such as
those obtained by condensing ethylene oxide with mercaptans and alkyl
thiophenols, and the like. In addition, conventional co-initiators and
buffers may be utilized in preparing the high molecular weight acrylic
polymer emulsions.
Aqueous acrylic interpolymer dispersions which may preferably
be blended with the reaction products herein are aqueous dispersions of
amide-containing acrylic interpolymers such as those described in U. S.
Patent No. 3,991,216. As described in the aforementioned patent, the
interpolymers of these aqueous dispersions are formed from substituted
carboxylic acid amides, ethylenically unsaturated carboxylic acids and
certain ethylenically unsaturated hardening and flexibilizing monomers.
Aqueous dispersions of these interpolymers are prepared by neutralizing
or partially neutralizing the acid groups of the interpolymer with an
amine or other base.
-18-
1~99~44
As set forth in the patent, the preferred materials employed in
forming these interpolymers are N-alkoxyalkyl-substituted amides such as
N-(butoxymethyl)acrylamide, N-(butoxymethyl)methacrylamide and the like;
ethylenically unsaturated carboxylic acids such as acrylic and methacrylic
acid; unsaturated hardening monomers such as styrene, vinyl toluene or
alkyl methacrylates having 1 to 4 carbon atoms and unsaturated flexibilizing
monomers such as alkyl acrylates having up to 13 carbon atoms and alkyl
methacrylates having from 5 to 16 carbon atoms.
The finished water-based coating composition can be prepared in
various ways. Thus, for example, the partially neutralized reaction product,
usually in organic solvent solution, can be blended witll the crosslinking
agent and the resultant mixture can then be reduced or thinned with water
or, if desired, a mixture of water and water-miscible organic solvents.
Alternatively, the unneutralized reaction product can be blended with the
crosslinking agent and solubilizing agent and the resultant mixture can then
be reduced with water or a mixture of water and water-miscible organic
solvents. Still further, the partially neutralized reaction product can be
dissolved in or dispersed in water following which the crosslinking agent can
be blended with the mixture.
The liquid medium of the water-based coating compositions used in
the invention is an aqueous medium, which ordinarily contains at least about
60 percent by weight of water. The liquid medium preferably contains at
least about 70 percent by weight of water and may contain up to about 95
percent by weight of water, the balance being water-miscible or partially
water-miscible organic solvents of the type described above.
The water-based coating compositions employed in the invention can
be applied by methods conventionally employed in the coatings industry, such
as brushing, dipping, roll coating, spraying, electrodeposition, and the like
and they are particularly adapted to be applied by the methods used to coat
containers.
--19--
~ 1~9~90~
Eor a detailed descrlption of these a~ueolls acrylic interpolymer
dispersions and their method of preparation, reference can be made to the
aforementioned U.S. Patent 3,991,216.
In addition to the components above, the compositions may, if
desired, contain other optional ingredients, including any of the pigments
ordinarily used in coating compositions of this general class. In addition,
various fillers, antioxidants, flow control agents, surfactants, and other
such formulating additives may be employed.
The compositions herein can be aPplied by essentially any
coating method, including brushing, spraying, dipping, roll coating,
flow coating and electrodeposition. When used in electrodeposition, the
compositions deposit on the anode. The compositions may be applied over
virtually any substrate, including wood, metals, glassj cloth, plastics,
foams, and the like, as well as over various primers, to provide protective
and decorative coatings. They can be used, for example, to coat metal
containers.
The invention will be further described in connection with the
several examples which follow. These examples are given as illustrative of
the invention and are not to be construed as limiting it to their details.
All parts and percentages in the examples and throughout tl-e specification
nre by weight unless otherwise indicated.
EX~MPLE 1
To a reactor equipped with a heating means, stirrer, thermometer,
reflux condenser and means for providing an inert gas blanket were charged
*
1482.0 grams of Epon 829 (a liquid polyglycidyl ether of Bi.sphenol A having
an epoxide equivalent of about 198, containing an epoxy condensation catalyst,
available from Shell Chemical Company) and 616.0 grams of Bisphenol A. The
reaction mixture was heated to 280E. and the heat removed to allow for an
* Trade Mark
B -20-
1~99~
exotherm. Tl~e maximum temperature reaclled during exotllcrm was 390F.
During this period, cooling was ap~)lied and the mixture was held above
350F. for 1 hour. The epoxy equivalent of the polyepoxide produced was
1,015. After the hold period, 600 0 grams of ethylene glycol monoethyl
ether (hereinafter ethyl Cellosolve~ were added to the reactor. During
this addition, the temperature decreased to 250F. Ileating was then
resumed and 5.0 grams of Cyzac 4040 (a 40 percent solution of p-toluene-
sulfonic acid in isopropyl alcohol available from American Cyanamid Company)
and 302.0 grams of p-aminobenzoic acid were added to the reactor. The
reaction mixture was then held for 3 hours at a temperature of about 290F.
Following this hold period, 692~0 grams of propylene glycol isobutyl ether
were added.
The resultant reaction product had a non-volatile solids content
of 64.9 percent, a Gardner-Holdt viscosity of ~10 and an acid value of 33.4
(51.4 at 100 percent solids).
To a 65.5 gram sample of the above reaction product were added
3.5 grams of dimethylethanolamine and 90.2 grams of deionized water with
stirring. The resultant composition had a non-volatile solids content of
about 26.7 percent and a pH of 8.3.
EXAMPLE 2
To a reactor equipped as in Example 1 were charged 1493.U
grams of Epon 829 and 706.0 grams of Bisphenol A. The reaction mixture
was heated to 280F. and the heat removed to allow for an exotherm (maximum
temperature 400F.). During this period, cooling was applied and the
mixture was held above 350F. for 1 hour. The polyepoxide produced had an
epoxy equivalent of 1,554. After this hold period, ~00.0 grams of ethyl
Cellosolve were added to the reactor~ During this addition, the temperature
decreased to 260F. Heating was resumed and then 5.0 grams of Cyzac 4040
and 201.0 grams of p-aminobenzoic acid were added. The reaction mixture was
* Trade Mark
B -21-
1~99q~44
then held for 3 hours at 280F. - 290F. After tl-is hold period,
692.0 grams of propylene glycol isobutyl ether were added.
- The resultant reaction product had a non-volatile solids content
of 64.3 percent and an acid value of 22~0 (34.2 at 100 percent solids).
To a 65.5 gram sample of the above reaction product were added
2,3 grams of dimethyletilanolamine and 91.4 grams of deionized water with
stirring. The resultant composition had a non-volatile solids content
of 25.3 and a pll of 8.5.
E~LE 3
To a reactor equipped as in Example 1 were charged 1,497.0 grams
of Epon 829 and 753.0 grams of Bisphenol A. The mixture was heated to 280F.
following which the heat was removed to allow for an exotherm which reached
a maximum temperature of 407F. The reaction mixture was held above 350F.
for 1 hour and then cooled to 300F. The polyepoxide produced had an epoxy
equivalent of 1,869. At this point, 600.0 grams of ethylene glycol monobutyl --
ether (hereinafter butyl Cellosolve) were added to the reactor and the
temperature decreased to 260F. Heating was again resumed and when the
temperature reached about 280F., 5.0 grams of Cyzac 4040 and 150.0 grams of
p-aminobenzoic acid were added to the reactor. The reaction mixture was then
held for 3 hours at temperature. After the hold period (temperature 280F.),
692.0 grams of propylene glycol isobutyl ether were added.
The resultant reaction product had a non-volatile solids content
of 64.3 percent and an acid value of 16.2 (25.2 at 100 percent solids).
To a 65.5 gram sample of the above reaction product were added
1.7 grams of diinethylethanolamine and 92~0 grams of deionized water with
stirring. The resultant composition had a non-volatile solids content of
26.4 percent and a pH of 9Ø
-22-
1~99~44
~XAMPLE 4
To a reactor equipped as in Exaniple 1 were charged 750.0
grams of Epon 829 and 375.0 grams of Bisphenol A. The mixture was heated
to 300F. following which the heat was removed and the mixture allowed to
exotherm reaching a maximum temperature of 420F. The reaction mixture was
held above 350F. for 1 hour and then cooled to 300F~ At this point, 75.0
grams of anthranilic acid were added and the reaction mixture then held for
2 hours at 310-320F. The reaction mixture was then cooled and 600.0 grams
of butyl Cellosolve was added to the reactor. The resultant reaction product
had a non-volatile solids content of 66.2 percent and an acid value of 19.7
(29.8 at lO0 percent solids).
To a 100.0 gram sample of the above reaction product (temperature
at 160F.) was added 2.1 grams of dimethylethanolamine with stirring, following
which 114.0 grams of deionized water was added. The resultant composition had
a non-volatile solids contene of about 33.0 percent and a pH of 9.1.
EXAMPLE 5
To a reactor equipped as in Example 1 were charged 1656.0 grams
of Epon 829 and 481.0 grams of Bisphenol A. The mixture was heated to
280F~ and the heat then removed to allow for exotherm (maximum 360F.).
The reaction mixture was then held for 1 hour above 350F. The product was --
a polyepoxide having an epoxide equivalent of 522. Af ter the hold period,
600.0 grams of butyl Cellosolve were added to the reaction mixture. After
this addition was complete, 10.0 grams of Cyzac 4040 and 263,0 grams of p-
aminobenzoic acid were added to the reactiOn mixture with the temperature
at 300F. The reaction mixture was thén held for 3 hours at about 300F.
Following this period, 428.0 grams of butyl Cellosolve were added to the
reactor.
1~9~
The resultant reaction product had a non-volatile solids content
of about 70.0 percent and an acid value of 24.8 (35.5 at 100 percent solids).
To a 55.5 gram sample of the above reaction product were added
11.2 grams of butyl Cellosolve, 2.2 grams of dimethylethanolamine and 91.1
grams of deionized water. The resultant composition had a non-volatile
solids content of 28.9 percent, a Gardner-Holdt viscosity af ~9 and a p}l
of 8.25.
EXAMPLE 6
To a reactor equipped as in Example 1 were charged 1510.0 grams
of Epon 829 and 627.0 grams of Bisphenol A~ The reaction mixture was
heated to 280F. and the heat was then removed to al]ow for exotherm
(maximum temperature 440F.). The reaction mixture was then held at above
350F. for 1 hour~ The polyepoxide produced had an epoxy equivalent of 858.
Following the hold period, the reaction mixture was cooled to about 380F.
and 600~0 grams of butyl Cellosolve were added. Then, 10.0 grams of Cyzac
4040 and 263.0 grams of p-aminobenzoic acid were added to the reaction
mixture (temperature about 260F.). The reaction mixture was then heated to
300F. and held for 3 hours at thi.s temperature~ Following this hold period,
428.0 grams of butyl Cellosolve were added to the reactor.
The resultant reaction product had a non-volatile solids content
of about 70.0 percent and an acid value of 30~2 (43.1 at 100 percent solids).
To a 57.1 gram sample of the above reaction product were added
9.6 grams of butyl Cellosolve, 2.7 grams of dimethylethanolamine and 90.6 grams
of deionized water~ The resultant composition had a non-volatile solids
content of 27.8 percent, a Gardner-Holdt viscosity of W and a pH of 8.35.
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1~99~
EX~MPLE 7
To a reactor equipped as in Example 1 were charged 1,656.0 grams
of Epon 829 and 481.0 grams of Bisphenol A. The reaction mixture was heated
to 280F. and the heat then removed to allow for exotherm (maximum temperature
380F.). The reaction mixture was then held for 1 hour above 350F. The
polyepoxide produced had an epoxy equivalent of 500. After this hold period,
600.0 grams of butyl Cellosolve were added to the reaction m-ixture and the
temperature decreased to about 270F~ After the temperature of the reaction
mixture again reached 300F., 10.0 grams of Cyzac 4040 and 263.0 grams of
p-aminobenzoic acid were added. The reaction mixture was then held for 1
hour at this temperature. Following this addition, the contents of the
reactor were cooled to about 280F. and then 428.0 grams of butyl Cellosolve
were added.
The resultant reaction product had a non-volatile solids content
of about 70.0 percent and an acid value of 28.9 (41~3 at 100 percent solids).
To a 55.5 gram sample of the above reaction product were added
11.2 grams of butyl Cellosolve, 2.7 grams of dimethy]ethanolamine, and 91.0
grams of deionized water. The resultant composition had a non-volatile solids
content of 27.3 percent, a Gardner-Holdt viscosity of ~6 and a pH of 8.75.
2 EXAMPLES 8-11
o
To a reactor equipped as in Example 1 were charged 3,750.0 grams
of Epon 829 and 1,875.0 grams of Bisphenol A. The reaction mixture was heated
to 300F. and the heat was then remoYed to allow for exotherm, (maximum
temperature attained was 404F.). The reaction mixture was then held for 1
llour above 350F. The polyepoxide had'an epoxy equivalent of 1,616. ~fter
this hold period, 1,500.0 grams of butyl Cellosolve were added to the reaction
mixture at wilich time the temperature decreased to about 290F. Af ter the
temperature again reached 300F., 25.0 grams of Cyzac 4040 and 375.0 grams of
-25-
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p-aminobenzoic acid were added~ Following this addition, the reaction
mixture was held at about 300F. for 3 hours. Following this period, 1,730.0
grams of butyl Cellosolve were added to the reactor.
The resultant reaction product had a non-volatile solids content
of 64.3 percent, a Gardner-~loldt viscosity of X10 and an acid value of --
15.7 (24.4 at 100 percent solids).
The above reaction product was neutralized with various basic
compounds by admixing the following ingredients:
Parts by Weight (Grams)
Ingredients Ex~ No. 8 9 10 11
Reaction product above 61 561.5 61.5 61.5
butyl Cellosolve 5.2 5.2 5.2 5.2
dimethylethanolamine 1.5 - - -
triethylamine - 1.8 - -
NH40H (28 percent solution in H20) - - 2.5
2-amino-2-methyl-1 propanol - - - l.S
deionized water 91.891.S 90.8 91.8
The resultant compositions had the following properties:
.
8 9 10 11
Non-volatile solids content (%)27~3 27.7 26.7 27.2
Gardner-Holdt viscosity K-L ~-E W X4
pH 8~6 9.0 8.7 8.5
Appearance Clear Trans- Clear Clear
solution lucent solution solution
solution
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~ ~LES 12-14_
To a reactor equipped as in Example l were charged 750.0 grams
of Epon 829 and 375.0 grams of Bisphenol ~. The reaction mixture was heated
to 300F. and the heat was then removed to allow for an exDtherm (maximum
temperature reached was 400F.). The mixture was then held above 350F.
for 1 hour. Tlle polyepoxide produced had an epoxy equivalent of 1,800.
Following this hold period, 300.0 grams of butyl Cellosolve were added to
the reaction mixture with cooling until the temperature reached 300F.
(about 1 hour). Then, 5.0 grams of Cyzac 4040 and 75.0 grams of p-amino-
benzoic acid were added to the reactor. The reaction mixture was then held
at 300F. for about 4 hours. After this hold period, 300.0 grams of butyl
Cellosolve were added.
The resultant reaction product had a non-volatile solids content
of 67~2 percent and an acid value of 15~3 (22~8 at 100 percent solids).
This reaction product was neutralized by admixing the following --
ingredients:
Parts by Weight (Grams)
Ingredients Ex. No`12 13 14
Reaction product above 100.0 100.0 100.0
buty~ Cellosolve 11.8 11.8
dimethylethanolamine 2.4 3.0 3.0
deionized water 109.4 154.4 157.0
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1~9~
The resultant compositlons had the following properties:
12 ]3 14
Non-volatile solids content (%) 29.8 26.3 26.2
pl~ 8.1 8.7 8~9
Comments Composition C]ear solu~ Clear solution
settled* after tion stable stable after
aging overnight after aging aging overnight
- overnight
(*due to slightly low level of neutralization)
EXA~LE 15
To a reactor equipped as in Example I were charged 750.0 grams
of Epon 829 and 375.0 grams of Bisphenol A. The reaction mixture was heated
to 300F. and the heat was then removed to allow for an exotherm (maximum
temperature 400F.). The mixture was then held above 350F. for 1 hour.
The resultant polyepoxide had an epoxy equivalent of 1,800. Following this
hold period, 300.0 grams of butyl Cellosolve were added to the reaction
mixture with cooling until the temperature reached 300F. (about 1 hour).
Then, 5.0 grams of Cyzac 4040 and 75~0 grams of p-aminobenzoic acid were
added to the reactor. The reaction mixture was then held at 300F. about
4 hours. After this period, 300~0 grams of butyl Cellosolve were added.
The resultant reaction product had a non-volatile solids content
of 67.2 percent and an acid value of 15.3 (22.8 at 100 percent solids).
A sample of the above reaction product was solubilized in the
following manner:
To a reactor equipped with heating means, stirrer, thermometer,
and dropping funnel was charged 1,000.0 grams of the reaction product. The
reaction product was heated to 145F. and then 118.0 grams of butyl Cellosolve
were added to the reactor with stirring. After about 20 minutes of stirring,
29.0 grams of dimethylethanolamine were added. ~fter about 30 minutes of
stirring, 125.3 grams of deionized water were added dropwise over a 1 hour
- -28-
_."
D
1~99~14~ '
period. The contents of the reactor were then he~ù ~or 2 bours at 140-150F.
Following this period, lS0.0 grams of deionized watcr were added to the
reactor.
The resultant composition had the following properties:
Non-volatile solids content 26.2 percent
Gardner-Holdt viscosity Y
Acid Value 6.5 (22.8 at 100 percent
solids)
pH 8.6
Composition of Liquid Medium (% by weight)
Deionized water 74.7
butyl Cellosolve 23.8
dimethylethanolamine 1.5
The following examples illustrate various utilizations of the
reaction products herein.
,
EXA~PLE 16
A coating composition was prepared by blending the following:
Parts by l~eight
Product of Example 1 159.20
* *
Cymel 303 7.50
*A higllly methylated melamine resin llaving a non-voIatile
percentage of 98 minimum, a Gardner-Holdt viscosity at
25C. of X-~2, a Cardner color of 2 maximum, and a methylol
content of about l.S percent, available from American Cyanamid
Company.
The composition was then drawn down on ~onderite 1000 pretreated
steel panels (3 mil wet film thickness) and baked at 325F. for 20 minutes).
The resultant film exhibited excellent properties having a pencil hardness
of 411; a direct impact strength in excess of 160 inch-pounds; a reverse impact
strength of 140 inch-pounds and passed 100 acetone ùouble rubs.
* Trade Mark
r -29-
B
1~`99C~
EX~MPLr 17
A coating composition was prepared by blendiIlg the following:
Parts by Weight
Product of Example 2 159.20
Cymel 303 7.50
The composition was drawn down and baked as in Example 16.
The resultant film had a pencil hardness of 3H, a direct and reverse impact
strength in excess of 160 inch-pounds, and passed 50 acetone double rubs.
EXAMPLE 18
A coating composition was prepared by blending the following:
Parts by Weight
Product of Example 3 l.59.20
Cymel 303 7 50
The composition was drawn down and baked as in Example 16.
The resultant film had a pencil hardness of 3H, a direct and reverse impact
strength in excess of 160 inch-pounds and passed 25 acetone double rubs.
.
E ~IPLE 19
A pigment paste was prepared by grinding the following ingredients
to a number 7.5 Hegman in a steel ball rolling mill:
Parts by Weight
Resin vehicle* 78.0
~arytes 79.1
Red iron oxide 15.8
Bentone 34 talc 2.1
Blanc iixe 1.1
** Trade Mark
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v 1~399~
Parts by l~eight
Fumed litharge l.l
Carbon black 0.8
Witco 912 surfactant 2.0
Deionized water 20.0
*A 30 percent solids epoxy-fatty acid ester prepared by
reacting a mixture consisting of 64.3 percent Epon 82~,
a condensation produc~ of epiclllorohydrin and Bispllello] ~
having an epoxide equivalent of about 185-192, con-mercially
available from Shell Chemical Co.; 20.1 percent of Pamolyn*
200, a fatty acid composition containing 17 percent by
weight oleic acid, 70 percent by weight linoleic acid and
11 percent by weight conjugated linoleic acid, which is
commercially available from Hercules, Inc.; and 15.6
percent maleic anhydride.
The pigment paste contains 62.5 percent total solids of which
80 percent is pigment and 20 percent is resinous vehicle.
A coating composition for use as a metal primer was prepared
by b]ending the following ingredients:
Parts by Weight
Product of Example 15 120.8
Acrylic polymer latex(l) 97.2
* (2)
Beetle 80 7.8
Pigment paste (above) 39.0
Deionized water 15.2
(1) ~n acrylic polymer emulsion having a total solids content
of 38.9 percent by weight and a viscosity of 30 ccnti-
poises, prepared by emulsion polymerization of a monomer
mixture consisting of 51.0 percent ethyl acrylate, 40.0
percent styrene, 5.0 percent hydroxypropyl acrylate ancl
4.0 percent acrylic acid in accordance with the procedure
describecl in the specification above.
(2) A butylated urea formaldehyde resin having a solids
content of about 96 percent, a Gardner-Holdt viscosity
of X-Z3 and a methylol content of less than one percent,
commercially available from ~nerican Cyanamicl Company.
* Trade Mark
B -31-
~, 1~99~J4~
Tlle primer coating composition was then spray applicd to botll
untreated steel and Bonderite 40 pretreated steel panels. When baked at
325F. for 30 minutes a film of 1.5 mil thickness was produced. The coated
panels were then topcoated with a commercial acrylic enamel coating and
evaluated for impact resistance and salt spray resistance utilizing standard
impact resistance and salt spray resistance tests. Tlle primer coating on the
untreated steel Danel exhibited good impact resistance> passing up to 80
inch-pounds whi~e the primer coating on the treated panel had excellent
impact resistance, passing over 80 inch-pounds. The primer coating on the
untreated steel panels exhibited good salt spray resistance, showing a scribe
creepage of 3/]6" after 11 days exposure to a 5 percent aqueous salt spray
at 100F. while tlle treated panel showed excellent salt spray resistance,
exhibiting virtually no scribe creepage under the same exposure conditions.
EXAMPLE 20
A prinler coating composition was prepared by blending the following
ingredients:
Parts by ~eight
Reaction product of Example 15 120.8
Acrylic polymer latex* 97.2
Beetle 80 7.8
Pigment paste of Example 19 39.0
*An acrylic polymer emulsion having a total solids content of
38.9 percent by weight and a viscosity of 45 centipoises
prepared by emulsion polymerization of a monomer mixture
consisting of 51.0 percent butyl acrylate, 40.0 percellt
styrene, 5.0 percent hydroxypropyl acrylate and 4.0 percent
acrylic acid, in accordance with the procedure described
in the specification above.
Tlle primer coating composition was spray applied to untreated and
treated steel panels, baked, topcoated and evaluated for impact rèsistance
as in Example 19.
* Trade Mark
32-
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1~99?44
The primer coating on both the untreated and treated steel panels
exhibited excellent impact resistance, passing ln excess of 80 inch-pounds
and excellent salt spray resistance, showing a scribe creepage of less than
1/8" after 11 days exposure to the salt spray.
EX~lPLE 21
A water-based coating composition for use as an internal sanitary
liner for a metal beverage container was prepared by blending the following
ingredients:
.
Ingredients Parts by Weight (Grams)
Reaction product used in Examples 8~
(unneutralized) 1600.00
Cymel 370* 61.50
Triethylamine 54.50
Deionized water 2300.00
Butyl Cellosolve 145.00
*A partially methylated melamine resin having a non-volatile percentage
of 88 + 2, a Gardner-Holdt viscosity at 25C. of ~2 - ~4, a Gardner color
of 1 maximum, and a methylol content of 12 percent, available from American
Cyanamid Company.
20` The resultant water-based coating composition had a non-volatile
solids content of 26.0 percent by weight and a No. 4 Ford Cup viscosity of
20.8 seconds. The liquid medium of the composition consisting of 76.1
percent by weight of water and 23.9 percent by weight of organic solvents.
The composition was sprayed into two-piece aluminum cans utilizing
a conventional airless gun. The coated cans were cured using a two cycle
bake; the first cycle involving baking for 2.5 minutes at 270F. and the
second cycle involving baking for 2.5 minutes at 400F.
A visual examination of the cans indicated good coating coverage and
appearance. The film integrity of each can was evaluated using a standard
beverage container coating test referred to in the coating field as an enamel
99~4
rater quick test. Tllis is a test in which a l percent sodium chloride salt
solution is placed inside the coated can and a circuit is produced by placing
an electrode in the salt solution and a connection on the outside surface
of the can. A flow of electrica1 current will result if there are any bare
spots on the coated interior of the can. The current, if present, is
measured with an ampmeter in milliamps.
In this test, cans were obtained having film weights of 220
milligrams and 240 milligrams respectively and these produced readings of l9
and 8.5 mi]liamps respectively. Tllese readings indicate good fi]m integrity.
Other tests run on the coated cans were buffer resistance and beer
pasteurization resistance~ In the buffer resistance test, a coated sample is
placed in a borax buffer solution having a pll of 9.20 and a concentration of
3~8 gra~s of Na2B4O7.l0H20 per liter of water for 30 minutes at 160~F.
and the coating is then checked for blushing, blistering and adhesion
failure. The beer pasteurization resistance test is performed and evalua~ed
in the same manner except that the coated sample is placed in beer. In these
tests, the cured coatings produced ~rom the abo~e composition exhibited
excellent buffer and beer pasteurization resistance.
A sample of the above water-based coating composition was drawn
down on treated aluminum in a 3 mil thickness and cured as mentioned above.
The cured coating was then tested utilizing several standard tests employed
in evaluating container coatings. Test results were as follows:
-Pencil hardness 1l
Dye stain* 4
Cross hatch adhesion Excellent
Wedge bend flexibility 90 mm failure
Buffer resistance 1xcellent
Beer pasteurization resistance Excellent
* Measures the state of cure on a rating scale of O to l0 wherein 0 is excellent
and l0 is poor. Values of 5 or less are considered to indicate a good state
of cure.
B -34-
9~
EXAMPLES 22 & 23
Into a reactor equipped with a heating means, stirrer, reflux
condenser and means for providing an inert gas blanket were charged 1493
grams of Epon 829 and 706 grams of Bisphenol A. The reaction mixture was
heated to 300F. and tlle heat then removed to allow for an exotl-erm
(maximum temperature 399F.). The reaction mixture was then hcld for one
llour above 350F. The polyepoxide produced had an epoxy equivalent of 1582.
Following this hold perlod, 600 grams of butyl Cellosolve were added to the
reaction mixture at which time the temperature decreased to 250F. Then 201
grams of anthranilic acid were added. Following this addition, the reaction
mixture was held at about 300F. for about 3 hours. After this hold period,
692 grams of butyl Cellosolve were added to the reaction.
The resultant reaction product had a non-volatile solids content
of 64.6 percent and an acid value of 18.6 (28.8 at 100 percent solids).
Water-based coating compositions for use as sanitary liners for
metal beverage containers were prepared by blending the following ingredients:
Ingredients Parts by Weight (grams)
Example 22Example 23
Reaction product above 1400.0 1400.0
Cymel 370 114.2
Cymel 1156* - 114.2
Dimethylethanolamine 38.0 38.0
Deioni7ed water 1500.0 1500.0
*A butylated melamine resin having a non-volatile percentage
of 100 percent, a Gardner-~loldt viscosity of Zl-Z4, a
Gardner color of 1 maximum, available from American Cyanamid
Company.
Tlie resultant water-based coating composition of Exanple 22 had a
non-volatile solids content of 32.9 percent by weight while that of Example 23
- _ -35-
B
~ 3P~L
In~d a non-volatile solids content of 33.3 percent by weight. The liquid
medium of the composition of both examples consisted of 75.0 percent by
weight of water and 25.0 percent by weight of organic solvents.
The above compositions were drawn down in 3 mil thickness on
treated alumlnum substrates (l.e., container stoclc) and the coated substrates
were then cured by baking for 2.5 minutes at 400F. The cured coatings were
then evaluated utilizing the same tests as in Example 21. Test results were
as follows:
Example No. 22 Example No. 23
Pencil Hardness 3H 2H
Dye Stain 4-5 4~5
Cross Hatch AdhesionExcellent Excellent
l~edge Bend Flexibility 35 mm/110 mm failure 35 mm/110 mm failure
Buffer Resistance Excellent Excellent
Beer Pasteurization Resistance Excellent Excellent
As an additional test, samples of the compositions of the above
examples were sprayed into-two piece aluminum cans, cured and then evaluated
for buffer resistance and beer pasteurization resistance using the procedures
of Example 21. The cured coatings on the aluminum cans exhibited excellent
buffer resistance and beer pasteurization resistance.
According to the provisions of the Patent Statutes, there are
described above the invention and what are now considered to be its best
embodiments. However, within the scope of the appended claims, it is to be
understood that the invention can be practiced otherwise than as specifically
described.
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