Note: Descriptions are shown in the official language in which they were submitted.
8'~L -
STORAGE STABLE WATEfi-DILUTABLE ACID_ADDUCTED EPOXY
~ASED COATING FOR METAL FOOD CONTACT SURFACES
This invention relates to epoxy based resins
water-solubilizable with ammonia or an amine and with
water based coating compositions containing them.
It has been proposed to form water dilutable
emulsions or dispersions containing epoxy resins for use
as water based coatings. Such coatings have
disadvantages and it is highly desirable to provide
water-soluble epoxy based coatings. Prior epoxy based
coatirgs have poor shelf life due to the presence of
oxirane groups and/or unreacted anhydride.
In U.S. Patent No. 4,105,614 of K.G. Davis et al, granted August
8, 1978 there is disclosed a resin in which the epoxy groups of
"~
there is aisclosed a resin in which the epoxy groups of
a diglycidyl ether are capped with a bisphenol and the
resultant material is reacted with an anhydride to
provide water-solubilizable carboxyl groups. The resins
of this invention utilizing a monocarboxylic acid, such
1as stearic acid, have advantages over the resins of U.S.
Patent No. 4,105,614.
1. Coatings made therefrom do not absorb
n-heptyl p-hydroxybenzoate, a preservative
used to stabilize unpasteurized beer.
2. Coatings made therefrom have less effect
on the flavor of beer on short term storage.
. ' ~
--2--
3. The coating formulations have higher
solids content at application viscosity, which
permits use of a single coating to attain
coating weights necessary in standard
applications. Application viscosity is
generally 154-100 sec., preferably 25-70 sec.,
#2 Zahn cup.
4. The final coating formulation has better
shelf life, as measured by viscosity change.
Insafar as is now known a resin system of this
type and coatings containing thern have not been
proposed.
This invention provides a water solubilzable
resin that comprises an adduct of a monocarboxylic acid
and a digly^idyl ether of a bisphenol or of a
monocarboxylic acid, a bisphenol and a diglycidyl ether
of a bisphenol, using an equivalent ratio of total
monocarboxylic acid and bisphenol, if used, to
diglycidyl ether between about 1:1 and about 1.2:1,
further adducted with an anhydride in an amount
sufficient to provide an acid number between about 35
and about 150.
It also provides a coating composition
coMprising such resin and~an aminoplast, in a weight
ratio between about 95:5 and about~70:30 solubilized
with a volatile tertiary amineJ amrnonia or ammonium
hydroxide to a pH of about 7.0 to about 9.1 in at least
one solvent of the group alcohols, alkoxyethanols,
ketones and alkyl ethers of diethylene glycol, each
present in between about ane weight percent and abaut 20
--3--
weight percent of the weight of the final composition
and diluted with water to a solids content between about
10 weight percent and about 25 weight percent.
It also provides substrates coated with such
coating composition and metal packaging containers,
interior coated with such coating composition and baked,
containing a food or beverage.
The water dilutable resins of this invention
are prepared by adducting sufficient monocarboxylic acid
or Monocarboxylic acid and bisphenol to a diglycidyl
ether of a bisphenol to react with all epoxy groups.
The diglycidyl ether is usually heated to about 80-90C
in a suitable solvent which is not only a solvent for
the reaction but can be a component of a binary
azeotrope with water. Then the monocarboxylic acid or
monocarboxylic acid and bisphenol are added and the
adduction is usually continued at about 150C for 2-3
hours until the epoxy value is 0.008 or less. This
adduction reaction can be carried out in any order,
i.e., monocarboxylic acid first followed by bisphenol,
if used; or bisphenol, if used, first followed by
monocarboxy-lic acid. It is preferred to react
monocarboxylic acid, bisphenol and diglycidyl ether of a
bisphenol, simultaneously.
Suitable solvents are ketones, ethers and
esters. Non-lirniting examples of suitable solvents are
methyl ethyl ketone, methyl isobutyl ketone, diisobutyl
ether and n-propyl acetate, n-butyl acetate, isobutyl
acetate, n-propyl propionate and ethyl butyrate.
~etones are especially preferred.
-4--
The reaction mixture should be refluxed to
remove all water that may be present. Anhydrous
conditions are necessary before the anhydride is added.
After all water that may be present has been removed, an
anhydride is added in an amount sufficient to provide an
acid number between about 35 and about 150, preferably
40-90. Generally the reaction is carried out at about
100-120C for about 2-4 hours. The reaction of the
anhydride is complete when the alcoholic acid number and
the,aqueous acid number are substantially the same,
usually within two units of each other. In order to
ensure good shelf life, the anhydride number must be
below about 6 and preferably zero. The anhydride number
is the difference between the alcoholic acid number and
the aqueous acid number.
An alkoxy ethanol boiling at about 130C or
higher and other solvents, such as alcohols, are added
to reduce solids content to between about 60 and about
75 weight percent.
The epoxy resin utilizable herein is a
diglycidyl ether of a bisphenol, a class of compounds
which are constituted by a pair of phenolic groups
interlinked through an aliphatic bridge. While any of
the bisphenols may be used, the compound 2,2-bis(p-
hydroxyphenyl)propane, coMmonly known as bisphenol A, is
more widely available in commerce and is preferred. The
diglycidyl ethers of bisphenol A are readily available
commercially. The epoxy resin, i.-e., the diglycidyl
ether of a bisphenol, will have an epoxy equivalent
weight between about 180 and about 2500.
The aliphatic rnonocarboxylic acids utilizable
herein have between 8 and 18 carbon atoms and a
molecular weight between about 140 and about 290.
--5--
Mixtures of monocarboxylic acids are contemplated.
Non-limiting examples of the aliphatic monocarboxylic
acids and mixtures thereof are octanoic acid, nonanoic
acid, decanoic acid, undecanoic acid, lauric acid,
tridecanoic acid, myristic acid, pentadecanoic acid,
palmitic acid, heptadecanoic acid, stearic acid, oleic
acid, linoleic acid, linolenic acid, ricinoleic acid,
linseed fatty acids, safflower fatty acids, soya fatty
acids, tall oil fatty acids, cottonseed fatty acids,
castor oil fatty acids, dehydrated castor oil fatty
acids and tung oil fatty acids.
The bisphenol that is adducted with the epoxy
resin can be any bisphenol as disclosed hereinabove.
Preferably a bisphenol A is used. The equivalent ratio
of total monocarboxylic acid and bisphenol, if used, to
diglycidyl ether of a bisphenol will be between about
1:1 and about 1.2:1. The equivalent ratio of
monocarboxylic acid to diglycidyl ether of a bisphenol
will be between about 0.1:1 and about 1:1. The
equivalent ratio of bisphenol to diglycidyl ether of a
bisphenol will be between about 0.0:1 and about 0.9:1.
The basic purpose of using a bisphenol is to upgrade the
molecular weight (MW) of the diglycidyl ether of a
bisphenol to ensure sufficient molecular weight of the
final acidic resin. If the diglycidyl ether of a
bisphenol has sufficiently high molecular weight, a
bisphenol is not used. In general, the molecular weight
of the final resin, as measured by Gel Permeation
Chromatography, will be between about 5,000 and about
25,000. Preferably the Mh~ should be between about 8,0Q0
and about 20,000. Most preferably, the MW should be
between about 11,000 and about 13,000.
--6--
The preferred anhydride used in the resins of
this invention is trimellitic anhydride. Other cyclic
anhydrides which can be used include succinic anhydride,
methyl succinic anhydride, tricarballylic anhydride,
phthalic anhydride, hexahydrophthalic anhydride and
maleic anhydride.
The amount of anhydride used should be
sufficient to obtain an acid number of 35 to 150,
preferably between about 40 and about 90, in order to
ensure water solubility when the resin is neutralized.
In order to obtain good shelf life of the
coating composition, there should be no unreacted
anhydride groups. The amount of anhydride to be used
can be readily calculated from the hydroxyl number of
the monocarboxylic acid and bisphenol adducted epoxy.
In forming a coating composition containing
the acidic resin, the resin is neutralized with a
tertiary amine, ammonia or ammonium hydroxide to a pH of
about 7.0 to about 9.1. Typical amines utilizable
include triethylamine, tripropyl amine, dimethylethanol
amine, diethylethanol amine, dimethylethyl amine and
methyldiethyl amine.
The material used to thermoset the coating is
a conventional aminoplast cross-linking agent. Such
agents are well known in the art. There can be used any
of the thermosetting alkylated arninoplast resins, such
as the ureaaldehyde resins, the melaminealdehyde resins,
the dicyandiamide-aldehyde resins and other aminoplast-
aldehyde resins such as those triazine resins produced
by the reaction of an aldehyde with formoguanamine,
ammeline, 2-chloro-4,6-diamino-1,3,5-triazine,
2-phenyl-p-oxy-4,6-diamino-1,3,5-triazine, 6-methyl-
38
2,4-diamino-173,5-triazine; 2,4,6-trihydrazine-
1,3,5-triazine and 2,4,6-triethyl-triamino-1,3,5-
triazine. The mono-, di- or triaralkyl or mono-, di- or
triaryl melamines, for instance 2,4,6-triphenyltriamino-
1,3,5-triazine are preferred. As aldehydes used to
react with the amino compound to form the resinous
matérial, one may use such aldehydes as formaldehyde,
acetaldehyde, crotonic aldehyde, acrolein or compounds
which engender aldehydes, such as hexamethylene-
tetramine, paraldehyde, paraformaldehyde and the like.
The preferred aminoplast is hexamethoxymethylmelamine.
The weight ratio of acidic resin to aminoplast will be
between about 95:5 and about 70:30.
The solvent system used in the coating
composition will include alcohols, alkoxy ethanols,
ketones and alkyl ethers of diethylene glycol. Suitable
alcohols are those having between about 2 and about 8
carbon atoms and having a boiling point up to about
180C. Non-limiting examples of utilizable alcohols
include special denatured ethanols (Formula 1),
propanol, butanol, isobutanol, t-butanol, pentanol,
hexanol, 2-methylpentanol, 3-methylpentanol, heptanol,
isoheptanol, octanol, isooctanol and 2-ethylhexanol.
The alkoxy ethanols utilizable are those
having between 1 and 6 carbon atoms in the alkoxy group.
I~on-limiting examples include methoxy ethanol, ethoxy
ethanol, butoxy ethanol and hexoxy ethanol. Also
utilizable are propoxy propanol and butoxy propanol.
The ketones utilizable are aliphatic ketones
containing between 3 and 8 carbon atoms. Non-limiting
examples of utilizable ketones are acetone, diethyl
ketone, methylethyl ketone, methylpropyl ketone,
--8--
methylisobutyl ketone, methylamyl ketone, methylhexyl
ketone, ethylpropyl ketone, ethylbutyl ketone, ethylamyl
ketone and methoxy acetone.
The utilizable alkyl ethers of diethylene
glycol will contain between 1 and 4 carbon atoms in the
alkyl group. Non-limiting examples include the
monomethyl ether of diethylene glycol, the monoethyl
ether of diethylene glycol and the monobutyl ether of
diethylene glycol.
In general, alkylethanols, ketones and alkyl
ethers of diethylene glycol are primarly solvents for
resin and aminoplast. Lower alcohols, such as ethanol,
t-butanol, also assist in wetting the surface being
coated. Higher alcohols, such as isooctanol, also serve
- as defoamants. In controlling viscosity of the final
coating composition, higher boiling solvents, such as
hexoxyethanol, tend to increase viscosity and lower
boiling solvents, such as butoxyethanol and methyl ethyl
ketone, tend to decrease viscosity.
- Although mixtures of organic solvents are
highly pref`erred, satisfactory coating compositions can
be prepared using a single methoxy ethanol, ketone or
alkyl ether of diethylene glycol.
In the finished coating composition, the
solids content (resin and aminoplast) will be between
about 10 and about 25 weight percent, preferably about
20-23 weight percent. The volatile system (including
arnine, ammonia or ammonium hydroxide) will be between
about 90 weight percent and about 75 weight percent of
the finished coating composition, preferably about 77-80
weight percent. About 65 to 90 weight percent of the
volatile system will be water and the balance (35 to 10
- 9 -
weight percent) will be organic volatile solvents,
including amine, ammonia or ammoniuM hydroxide.
Preferably, the ratio of water to organic volatiles will
be about 70:30 to ~0:20 in the volatile system. Each
component of the solvent system will be present in
between about 1 weight percent and about 20 weight
percent of the weight of the final composition. A
typical and preferred solvent system is defined in the
working examples.
In the following illustrative examples all
parts are parts by weight, unless otherwise indicated.
Example 1
Into a reaction kettle there was charged 55.4
parts of an 80 weight percent solids solution in methyl
ethyl ketone (MEK) of a diglycidyl ether of bisphenol A
having an epoxy equivalent weight of 450-550 and an
epoxy value of 0.22, based on solids. The solution was
heated to ~8C (190F) and there were added 10.02 parts
bisphenol A, 5.84 parts of a mixture of 70 weight
percent stearic acid and 30 weight percnt palmitic acid,
and 0.17 part tri-n-butylamine (catalyst). The reaction
mixture was heated to 149C (300F), removing MEK
distillate as necessary. At 149C, the reaction mixture
was held at total reflux for 2 hours and sampled for
solids and epoxy value. Reflux was maintained until
epoxy value was 0.008 maximum. Then, the reaction was
cooled to 115C (240F), adjusting solids to 92 + 0.5
weight percent with MEK distillate. At 115C, there
were added 5.95 parts trimellitic anhydride and the
reaction was heated 118C (245F) for 2 hours. Then,
the reaction mixture was sampled for anhydride number
which was to be 6.0 maximum. After 2 1/2 hours at `l18C
the reaction was sampled for anhydride number and 15.06
--10--
parts n-butanol and 7.52 parts butoxy ethanol were added
and held until the mixture was uniform. Final values
for acid number, anhydride number, weight percent solids
and molecular weight are set forth in Table 1.
Examples 2 through 9
A series of runs were carried out in a manner
similar to Example l, with the following exceptions:
Example Z is a laboratory repeat cf Example 1; Example 3
is a pilot plant run of Example 1; Example 4 uses excess
stearic acid; Example 5 uses less stearic acid; in
Example 6 the stearic acid was reacted first, followed
by bisphenol A; in Example 7, more stearic acid was used
and less bisphenol A; Example 8 was the same as Example
2, except that the final solvent was butyl ether of
diethylene glycol instead of the 2:1 weight ratio
Mixture of butanol and butoxy ethanol used in the other
examples; an in Example 9, a greater amount of
trimellitic anhydride was used. Pertinent data and
final values for these examples are set forth in Table 1
along with Example 1.
O O ~I N CO
O ~ N--. ~ N
~1 0 0 00 ~ 3 ~
~1
O O N N ~
cu ~~ o o ~--
~i 0 0 00 ~ ^
~1
0 3
c~
. .
r~l O O OCJ~ N N ~
~D¦ O 0~ N tnt--~1 0 ~D ~1
.. -- --U~
~1 0 0 0
O
O t~
o o t~
~ O O O O ~I C~J ` N C)
~ 0 .. . _ .
H .. .... _ _.
~ ~ ~~ ~ E
E ~ r1 0 0 0 ~r ~ ~ cd
K
~0~0~ ^ ~0
t--Ln N ¢
0
0 0 r1 ~
~11 o c~o~r .c
1--i 0 o o O o.es
O O G 1
O ::1 ~ O-rl
G C:l ~ 5~ 5
r3 ~ o o ~ o
C O S: C~ ~ U~ ~ ~ V bO
~ ~ ~ 0 ~ ~3' a~
tlS o ~. ~ ~ ,~
u~ ~ ~ 3 c: C ~~`~
ii-
- 12 -
Examples 10 and 11
Using the general procedure of Example 1,
resins of this invention can be prepared using
relatively low molecular weight diglycidyl ethers of
bisphenol h. Example 10 is like Example 1 except for
the use of a different epoxy resin. In Example 11, the
diglycidyl ether of bisphenol A is upgraded in molecular
weight with bisphenol A and then reacted with stearic
acid.
The formulations, in parts, for these examples
are set forth in Table II.
TABLE II
Example_10 Example_11
Epoxy resin X (1) 34.42 ---
Epoxy resin Y (2) --- 33.88
EK 5-54 5'35
Bisphenol A 18.50 13.84
Stearic acid (3) 10.78 15.98
Tri-n-butylamine 0.31 0.19
TriDIellitic anhydride 6.30 6.30
Butoxy ethanol 8.05 12.23
n-Butanol 16.10 ---
t-Butanol -~- 12.23
(1) Diglycidyl ether of bisphenol A. Epoxy equivalent
is 185 - 192. Epoxy value is 0. 52.
(2) Diglycidyl ether of bisphenol A. Epoxy equivalent
is 193 - 203.
(3) k,ixture 70 wt ~ stearic acid/30 wt p palmitic acid.
-13~
Example 12
This example demonstrates the preparation of a
resin in which the epoxy is of sufficiently high
molecular weight that no bisphenol A, but only stearic
acid, was used. In a reaction kettle were charged 47.72
parts of diglycidyl ether of bisphenol A having an epoxy
equivalent weight of 850 and 5.35 parts of methyl ethyl
ketone (MEK). The mixture was heated to about 88C to
dissolve the resin (about 55 minutes). Then, 15.98
parts stearic acid and 0.19 part tri-n-butylamine were
added and the reaction mixture was heated to 150C,
collecting about 146 g MEK distillate, and held at 150C
for 2 hours. After 1 1/2 hours, a sample of the
reaction mixture showed an epoxy value of 0.004. The
MEK distillate was added back to the reaction mixture
and 6.30 parts trimellitic anhydride were added. The
reaction mixture was heated to reflux at about 116C,
removing 11-12 g MEK distillate and held at reflux form
2 1/2 hours. The mixture was sampled and then reduced
with 12.23 parts butoxy ethanol and 12.23 parts
t-butanol. The final values of the resin solution were:
Wt. % solids 68.8
Acid No. 65.8
Anhydride No. 3.6
Mol. Wt. 7,000
The following Examples 13 through 15
illustrate the preparation of coating compositions using
the resins of this invention.
Example 1 3
A mixture of 28.93 parts of the product
described in Example 1, 2.25 parts hexamethoxymethyl-
-14-
melamine, 3.37 parts n-butanol, 0.30 part hexoxy ethanol
and 0.37 part butyl ether of diethylene glycol was
stirred until uniform, while not permitting the
temperature to exceed 54C. Then, there were added 1.29
parts denatured alcohol (Synaso~), which contains
denaturants in the proportions of 100 gallons of special
denatured alcohol Formula 1, 1 gallon of methyl isobutyl
ketone, 1 gallon ethyl acetate and 1 gallon aviation
gasoline. This was stirred until uniform. There was
added a premixed mixture of 1.30 parts aqueous ammonia
(26 Baume) and 2.19 parts deionized water. This was
stirred until uniform and then diluted with 60.00 parts
deionized water.
The final coating composition has a solids
content of 22.63 weight percent, containing 90.06 weight
percent resin of Example 1 and 9.94 weight perce~nt hexa-
mett.oxymethylmelamine. The pH was 8.5 - 9Ø
Examples 14 and 15
In an alternative mixing procedure, n-butanol,
butoxy ethanol and hexamethoxymethylmelamine were
charged and agitation was begun. The product described
in Example 1 was added and stirred until uniform, not
~ermitting the temperature to exceed 49C. A premixed
mixture of aqueous ammonia (26 Baume) and deionized
water was added and stirred until uniform. Finally, the
composition was diluted with deionized water to produce
the final coating composition. The amounts of
components, in parts, in each Example 14 and 15 and
pertinent data on the final coating compositions are set
forth in Table III.
*Tr~d~Erk
. ~
JB~
--15--
TABLE III
Ex. 14 Ex. 15
n-Butanol 0. 86 2.99
Butoxy ethanol 3.26 4. 36
Hexamethoxymethylmelamine2.35 2.33
Example 1 product 30.03 29.73
Aqueous ammonia 1.25 1.36
Deionized water 2.00 1.98
Deionized water 60.25 57.25
Solids, wt ~ 23.5 23.27
pH 8.5-9.0 8.5-9.0
Resin/aminoplast, wt % 90/10 90/10
The coating composition of this invention is
primarily useful for coating aluminum, tin plated steel,
pretreated metals, steel and metals coated with the same
or different resin composition (i.e., a second coat).
The coating composition can be used however for coating
other substrates such as wood1 paper and leather. The
most preferred and useful use of the coating composition
is for interior coating of metal containers that will
come in contact with food or beverages. Coating can be
done by any coating procedure well known to those
skilled in the art including direct rollcoating, reverse
rollcoating, electrodeposition, spraying, flow coating
and the like. The preferred method however in coating
the interior of metal containers is by spraying. After
coating the substrate, the coating is baked for about 5
seconds to about 5 minutes at between about 250F and
about 600F. A typical bake is for about 2 minutes at
about 400F.
-16-
The coating compositions of Examples 13, 14
and 15 were tested for adhesion, pasteurized adhesion
and blush. The adhesion test is carried out by cross-
hatching a coated area with individual score lines
approximately 1/16 inch apart. The"Scotch"tape is
firmly applied to the cross-hatched area and removed
with a quick snap. The amount of coating remaining on
the panel is viewed visually and rated on a 0-10 scale
(10 = perfect adhesion). Pasteurization is carried out
by immersing the coated panels in water at 145F for 30
minutes. Then the panels are wiped dry with absorbent
to~els and the adhesion test is carried out as above
described. The amount of blush is rated on the
pasteurized panel using a scale of 0 to 10 in which 0 is
very severe blush and 10 is no blush.
Example 16
Treated aluminum test panels were coated with
the coating compositions of Examples 13, 14 and 15 with
a bar coater to a film weight of 2.5 to 3.0 milligrams
per square inch. These test panels showed an adhesion
rating of 10 in the adhesion test. In the
pasteurization test, the panels gave a rating of 10
adhesion and 10 on blush.
The effect of a coating on the flavor of a
packaged product is determined in a Flavor Difference
Evaluation. Bottles of commercial beer are chilled to
about 40-45F and uncapped. Sheets of aluminum foil
(1 nlil) are bar coated on both sides with the coating
being evaluated and baked. Then, a sheet of foil is
rolled lightly and inserted into each bottle of beer and
the bottle is recapped with a new cap.
*~r~rk of 3-M Company for a brand of pressure-sensitive adhesive tape
-17-
For cornparison, additional bottles of the same
beer are provided with rolls of aluminum foil that have
been coated on both sides with an accepted commercial
coating for interior coating (solvent-based epoxy
coating) and baked. The test coating and the control
coating were baked for 30 seconds at 400F metal
temperature.
After storage for 3 days at 100F, the bottles
of beer are again chilled and taste rated by 9
experienced tasters comparing the test coatings vs. the
control. The arithmetic average of the ratings is
calculated (x). Then, all rating values outside x + 2
are excluded and another average is calculated as the
quality rating (QR). The following rating scale was
used on a basis of 1-9.
1 = no flavor difference
1.0 - 1.5 = excellent flavor
1.5 - 2.0 = very good flavor
2.0 - 2.5 = good flavor
2.5 - 3.0 = acceptable flavor
>3.0 = not acceptable
In unpasteurized beer, n-heptyl p-hydroxy
benzoate is used in an amount of 12 ppm to inhibit
microbial growth. It is highly desirable that a coating
used to coat the interior of metal beer containers does
not absorb an appreciable amount of the n-heptyl
p-hydroxybenzoate (sold under the registered tradernark
"Staypro").
This property is tested using a simulated
beer, an aqueous solution of 8 volume percent ethanol
and 12 ppm "Staypro." Metal beer containers are
interior coated hith the coating composition under test
-18-
and baked in the usual baking cycle, e.g., 2 minutes at
400F. Then, the containers are filled with simulated
beer and stored at room temperature for one week. At
the end of the week the simulated beer is analyzed to
determine the amount of heptyl p-hydroxybenzoate
remaining. This is done by measuring light transmission
on a spectrophotometer at a wavelength of 255
millimicrons, in comparison with the original.
Examples 17, 18 and 19
; Using resins as described in Examples 1 and 9
herein and in Example 1 of U.S.
Patent No. 4,105,614, coating formulations were prepared
by the procedure of Example 14. Each formulation
contained 1Q weight percent (on solids basis)
hexamethoxymethylrnelamine and the volatile system had a
volume percent ratio of water/.organic solids of 80/20.
The formulations were used in testing for beer flavor
rating and for resistance to absorption of n-heptyl
p-hydroxybenzoate. Pertinent data and test results are
2d set forth in Table IV.
TABLE IV
. .
Resin Description Beer Flavor Staypro
Ex. Ex. Source QR ppm rem-aining
17 1 Herein 1.2 11.9
18 9 Herein 1.1 11.8
19 1 U.S. Patent 1.3 10.5
4,105,614
Storage stability (shelf life) of a coating
composition is measured by the cl~ange in viscosity. A
significant increase in viscosity is not desirable. A
3D coating composition as described in Example 17 and, for
-
--19--
comparison, a coating composition as described in
Example 19 were placed in lined coating containers and
stored at 80F. Periodically the compositions were
tested for viscosity at 80F using #2 Zahn cup. The
results are set forth in Table V.
TABLE V
Viscosity, seconds
Time, weeks Exarnple 17 Example 19
Initial 25 - 40 40 - 50
8 20 - 30 7 - 80
14 20 - 30 ---
16 --- 90
