Note: Descriptions are shown in the official language in which they were submitted.
~3~
F-2079(2080) -1-
AQUEOUS COATING COMPOSITIONS AND
METHOOS FOR PREPARING SAME
This invention relates to aqueous coating compositions and
methods for preparing same.
A variety of aqueous coating compositions comprising epoxy
resins and acrylic polymers are known in the art and several are
commercially available. In order to obtain desirable
characteristics for many critical end use applications, such as
coatings for sanitary cans, it is considered necessary to include a
high proportion of epoxy resin in the composition. Epoxy contents
of 60 to 80 percent are commonly used. Typical epoxy acrylate
compositions are disclosed in U.S. Patent Nos. 4,247,439, 4,212,781,
4,308,185 and 4,~02,373.
U.S. Patent No. 4,285,847 discloses epoxy acrylic
compositions in which the epoxy acrylic is made by free-radical
grafting of ionizable side chains onto an epoxy backbone; dispersing
this product ln water and thereafter polymerizing, in situ, addition
polymerizable monomers which may or may not also contain ionizable
groups. Ry this means the solids conten~ of the composition is
increased and the proportion of total epoxy resin in the composition
is reduced by replacement with the cheaper addition polymer thereby
reducing the cost of the composition.
In accordance with the present invention cost reduction as
well as several other advantages over U.S. Patent 4,285,847 are
obtained. By using an epoxy acrylate prepared by an esterification
reaction between an epoxy resin and an acrylic polymer instead of
the graft epoxy-acrylic of U.S. Patent 4,285,847, benefits are
obtained in the latitude of solids and viscosity which can be
conveniently obtained, and in the ability to reduce the amount of
~'
~Y ~- .
'
, ' " ~ .
:,
~L~3~Y~
F-2079(2080) -2-
am~ne neutralizing agent necessary to obtain stable water
dispersions having useful viscosity.
The present invention resides in one aspect in an aqueous
coating composition comprising
A. an ionic polymer component containing sufficient
carboxyl groups to render it self dispersible in water in
neutralized form which is the reaction product of an epoxy resin
containing 1,2~ep~y groups, and a preforn~d addition poly~r~ containing
carboxyl groups, said ionic polymer containing hydroxy ester groups
from the reaction of 1,2-epoxy groups on said epoxy resin with
carboxyl groups on said preformed addition polymer, and ~eing
substantially free o~ unreacted 1,2-epoxy groups;
B. an addition polymer different from said preformed
addition polymer defined in (A); and
C. ammonia or an organic amine neutralizing agent in
an amount sufficient to render the composition stably dispersible in
water.
In a further aspect, the invention resides in a method for
preparing a coating composition comprising the steps o~
~ A. preparing an ionic polymer component containing
sufficient carboxyl groups to render it self dispersible in water in
neutralized form by reacting an epoxy rcsin containing 1,2-epoxy
groups, and a preformed addition polymer containing carboxyl groups,
said ionic polymer containing hydroxy ester groups ~rom the reaction
of 1,2-epoxy groups on said epoxy resin with carboxyl groups on said
preformed addition polymer9 and being substantially free of
unreacted 1,2-epoxy groups;
.. , -
.~ . , - .
.
,, . . . . . , , - .
.
.. . . .
F-2079(2080) -3-
B~ dispersing said ionic polymer component in water
with the addition of ammonia or an organic amine neutralizing agent
in an amount suf~icient to render the composition stably dispersible
in water; and
C. incorporating an addition polymer difFerent from
said addition polymer defined in (A) into the aqueous dispersion of
said ionic polymer component.
Conveniently, said incorporating step is effected by mixing
the different addition polymer with the pre~ormed addition polymer
prior to reaction with the epoxy resin or by mixing the different
addition polymer with the ionic polymer component before, during or
after dispersal thereof in ~ater. Alternatively, the diffe~ent
addition polymer can be prepared in situ in the presence of the
ionic polymer dispersion in which case the ionic polymer acts as a
polymeric sur~actant.
The ionic polymer component A o~ said coating composition
:is prepared by reackion of a preformed addition polymer containing
carboxyl groups with an epoxy resin containing 1,2 epoxy groups,
conveniently using the methods disclosed in U.S~ Patent 4,247,439 or
U.S. Patent 4,302,373. It may, however, be necessary to modify
conditions to promote esterification instead of quaternization, for
example by using tertiary amine in an amount which is less than
su~icient to react with all of the epoxy groups on the epoxy
resin.
Briefly, the reaction between the epoxy resin and the
preformed addition polymer containing carboxyl groups is conducted
in the presence of a tertiary amine, with the conditions being
chosen so that an esteri~ication reaction occurs between the epoxy
:,'
.
"' "'' ' ~ .
~2~
F-2079(2080) -4-
groups of the epoxy resin and the carboxyl groups o~ the addition
polymer. By way of contrast, the reaction conditions in the
a~orementioned patents are selected in order to promote a reaction
between the tertiary amine and epoxy groups giving quaternary
ammonium groups in accordance with a well known reaction. It is
believed that the reaction which is intended to promote
esterification also results in the formation of significant amounts
of quaternary ammonium groups by reaction between the epoxy groups
and the tertiary amine. Indeed, more of the epoxy groups may be
converted to quaternary ammonium groups than are converted to
hydroxy ester linkages. Also, the reaction described in said
patents intended to produce quaternary ammonium groups can, under
appropriate condi-tions, result in significant ester formation. The
products prepared in accordance with the present process there~ore
can contain significant, even predominant amounts of quaternary
groups, providing that hydroxy ester groups obtained by the reaction
of epoxy groups with carboxyl groups are also present. A-t a minimum
at least 5 percent of the epoxy groups on the epoxy resin should be
converted to hydroxy ester groups. Whatever the relative
proportions o~ quaternary and hydroxy ester groups, the polymer
component A is ionic in character and is substantially free of
unreacted 1,2-epoxy groups.
The ionic polymer may contain carboxyl polymer grafted to
carbon atoms on the epoxy resin backbone but it is preferred that
the polymer is prepared under conditions where grafting is avoided.
In general, the epoxy resin constitutes at least about 40
percent of the ionic polymer and the carboxyl containing polymer
comprises the balance. Preferably the epoxy content is at least 60
percent and most preferably about 75 percent.
A w de variety of epoxy resins may be used herein but the
preferred epoxy resins are aromatic polyethers, particularly those
derived ~rom the oondensation o~ a bisphenol such as Bisphenol A,
'. , . : ~ -' . -
' '
~ 2~
F-2079(2080) -S-
and epichlorohydrin. These epoxy resins possess hydroxy groups inaddition to epoxy groups. The higher the molecular weight of the
epoxy resin the more hydroxy groups are present. These hydroxy
groups can participate in the final curing reaction. The preferred
epoxy resins are aromatic polyethers having a number average
molecular weight (Mn) of at least 1,500. However, the n~m~er
average molecular weight of these resins can vary from 350 to 6000.
As recognized in the art, epoxy resins prepared by the
condensation o~ bisphenols and epichlorohydrin contain a mixture of
diepoxides, monoepoxides and aromatic polyethers which are ~ree of
epoxy groups. The average functionality of such mixtures may range
widely from 0.2 epoxy groups per molecule to nearly 2 epoxy groups
per molecule. Suitable mixtures of epoxy resins can be obtained by
reacting a lower molecular weight epoxy resin having a ~unctionality
of between 1 and 2, for example, with a defunctionalizing agent
which is capable of reacting with the epoxy groups. The
de~unctionalizing agent can contain carboxyl groups, hydroxy groups
or amide groups. Specific suitaDle materials include acids such as
benzoic acid and fatty acids such as octanoic acid; hydroxy
compounds such as phenols, in particular bisphenols and lower
alkanols; and amides such as acrylamide. Defunctionalization with
bisphenols is of` particular interest since the epoxy resin is
thereby upgraded to higher molecular weight at the same time as some
of the epoxy groups are defunctionalized.
The carboxyl polymer is prepared by the addition
polymerization o~ ethylenically unsaturated monomers comprising at
least about 20 percent of an ethylenically unsaturated carboxylic
acid based on the total weight of the monomers. Polymers and
copolymers of this type are well known although the copolymers with
particularly high proportions of carboxylic acid as preferred herein
are somewhat unusual. Preferably the carboxyl containing polymer is
~' ~
',: .-
-. , - ' .. ' ,' :
7~
F-2079(2080) -6-
a copolymer with ethylenically unsaturated monomers which are
non-reactive under the contemplated conditions of polymerization and
reaction with epoxy resin. However, small amounts of reactive
. .
monomers, e.g., hydroxy monomers such as 2-hydroxy
ethylmethacrylate9 amide monomers such as acrylamide, and N-methylol
monomers such as N-methylol acryLamide, can be used. Suitable
non-reactive monomers are, ~or example, acrylate and mzthacrylate
esters such as ethyl acrylate, methyl acrylate, butyl acrylate,
styrene or vinyl toluene, vinyl acetate, vinyl chloride, vLnylidene
chloride, and acrylonitrile. The function of these monomers is to
enhance solvent solubility and to provide good film formation.
Otherwise the nature and proportions are not critical.
The presence of a large proportion of carboxyl functional
monomer is important. The preferred minimum proportion of carboxyl
monomer is 30 percent of the weight of the monomers used to prepare
the carboxyl containing polymer. Methacrylic acid provides the best
hydrolytic stability and is very much preferred, but other acids
such as fumaric acid, acryLic acid, crotonic acid and itaconic acid
are useful. Up to about 80 pqrcent of the monomers can be carboxyl
functional, the maximum being determined by retention of solvent
solubility of the copolymer.
The preferred polymers containing carboxyl groups generally
having a number average molecular weight (Mn) in the range of ~000
to 20,000, preferably 3,000 to 6,400. Molecular weight can be
controlled by monomer content during polymerization9 catalyst
concentration and polymeri ation temperature in known manner.
Mercaptan chain termination is preferably avoided especially where
the product is intended for use in coating of sanitary cans because
of the offensive odor o~ mercaptans.
Generally, the addition polymer containing carboxyl groups
is preformed and is reacted with the epoxy resin as a solvent
, . . .. .
..
.
:, :
7~ r
F-2079(2080) ~7-
soLution in the presence of sufficient amine, preferably a tertiary
amine,to promote the reaction. However, the addition copolymer can
also be prepared by reacting a carboxyl containing monomer such as
methacr~lic acid with the epoxy group in the presence of tertiary
amine and subsequently polymerizing additional monomers, in situ.
The reaction between the oxirane groups of the epoxy resin and the
carboxyl groups o~ the addition polymer is carried out in the
presence of an esterification catalyst.
The preferred esterification catalysts are tertiary amines,
particularly dimethylaminoethanol,but other esterification
catalysts,particularly tertiary amines such as dimethylbenzylamine,
trimethylamine, and tributylamine,can be used. The amount of
catalyst used can vary widely. For example, where a tertiary amine
is used as little as 0.1-û.3 percent by weight of the catalyst based
on the total amount of epoxy resin and carboxyl containing polymer
can be used nr the amount can be much larger up to about 10 percent
and more of the reactants.
Another way of defining the amount of amine used is the
relation to the total carboxyl content of the acid polymer. The
amount of amine present during the reaction o~ the epoxy resin and
carboxyl polymer should be sufficient to neutralize from about 5 to
50 percent of the carboxyl groups in the acid polymer. Preferably,
the amine is suf~icient to neutralize between 10 and 35 percent of
the carboxyl groups. Still another way of defining the amount of
tertiary amine present during reaction of the epoxy resin and
carboxyl polymer is by the equivalent ratio of amine to 1,2-epoxy
groups. Preferably, this ratio is less than one thereby ensuring
that some of the epoxy groups will be consumed in hydroxy ester
formation by reaction with carboxyl groups.
The amount of amine has a significant effect on the nature
of the product of the reaction. In general9 the smaller the amount
7~;~
F-2079(2080) -8-
of amine present during reaction the higher the viscosity of the
product. This difference in viscosity is apparent in both the
solvent solution and when the product is emulsified in water. The
e~fect of the a~ount of amine used is observed even where the total
amount of amine present in the dispersed product is identical.
Thus, for example, the same product is not obtained when amine is
present at the 40 percent neutralization level during reaction as
when amine sufficient to neutralize 5 percent of the car~oxyl groups
is present during reaction and supplemented with 35 percent of the
neutralization amount prior ta dispersion in water.
The amount of amine present during reaction also has a
pronounced effect on the particle size of the final dispersion. The
relationship of amirle content to particle size is illustrated in the
following examples.
The second polymer different from the addition polymer used
to prepare the ionic epoxy resin-acid polymer product can be
prepared from a wide variety of unsaturated monomers. Particularly
preferred are monomers which are free oF functional groups reactive
with epoxy resin or which would render the polymer self-dispersible
in water. For example there may be mentioned the esters of acrylic
and methacrylic acid such as methyl acrylate, butyl acrylate, methyl
methacrylate and butyl methacrylate; aromatic monomers such as
styrene and methylstyrene; vinyl and vinylidene halides such as
vinyl chloride and vinylidene chloride; isoprene; butadiene; and
acrylonitrile. In certain applications it may be advantageous to
include in the copolymer self-crosslinking monomers such as
N-methylol acrylamide or N-isobutoxy acrylamide. Presently
preferred monomers include styrene, methylstyrene and butyl acrylate
and acrylonitrile.
The second polymer can be introduced at any convenient
stage of the reaction. Preferably, the second polymer is prepared9
.
.: ' '
, - ' ~
7~
F-2079(2080) -9~
in situ, in the presence of an aqueous dispersion of the ionic
epoxy-acidic polymer reaction product. The reaction is conducted in
known manner and advantageously is initlated by a redox system.
Inorganic or organic peroxides such as hydrogen peroxide or t-butyl
hydroperoxide; or persulfates such as ammonium persulfate and alkali
metal persulfates can be coupled with a suitable reducing agent such
as hydrazine, ammonium or alkali metal sulfites, bisul~ites,
metabisul~ites or hydrosul~ites. The procedures disclosed in U.S.
Patent 4,285,847 are suitable for conducting the polymerization.
The second polymer can also be introduced as a pre~ormed
polymer into either the aqueous dispersion of the ionic epoxy-acid
polymer product or can be mixed with the ionic epoxy resin-acid
polymer product before it is dispersed in water. Similarly, the
second polymer can be mixed with a solvent solution of the acidic
polymer prior to its reaction with the epoxy resin either by making
the addition polymers separately or by preparing one in the presence
of the other. The proportion of the second polymer in the
composition can vary widely. The maximum is limited by the amount
which can be stably dispersed in water by the ionic polymer
component and the retention of desired film properties. Usually the
weight ratio of the second addition polymer (B) to the ionic polymer
(A) ls from 0.05:1 to 10:1 but more preferably is 0.2;1 to 5:1.
The resins used in preparing the compositions o~ this
invention are used by dissolution in a volatile organic solvent. A
wide variety o~ solvents are suitable. Organic solvents~of limited
water miscibility, such as xylene, toluene, butanol and
2-butoxyethanol are useful, and they may be used alone or together
with water miscible sblvents, such as 2-ethoxyethanol or methyl
ethyl ketone.
The final composition includes su~ficient ammonia or amine
to render the mixture self-dispersible in water. Preferably, a
.
: : '
~l~3~
F-2079(2080) -10-
tertiary amine such as dimethylethanolamine is used. In general,
the total amount of an amine or an ammonia present in the Final
product will be sufficient to neutralize at least 25 to 90 percent
of the carboxyl groups present in the polymers used to prepare their
composition. Finally, compositions, as used, preferably include a
curing agent such as an aminoplast or a phenoplast resin in an
amount of 1 to 25 percent, preferably from 3 to 10 percent, based on
the solids of the composition.
In some cases it may be found that the process described
above yields an aqueous coating composition containing an
undesirable residue of the monomer used to produce the second
polymer. For example, the use of styrene and butyl acrylate in the
preparation of the second polymer may result in a product having an
objectionable odor due to residual butyl acrylate which polymerizes
more slowly than styrene. In such a case, the undesired monomer
residue can be reduced by conducting an additional polymerization
step in the presence of the second polymer containing residual
monomer, with another monomer which is capable of copolymerizing
with the undesired mollomer and which results in a less undesirable
monomer residue or a residue which is more easily removable. For
example, where the monomer residue is butyl acrylate an additional
polymerization step using further styrene as the comonomer can be
effected on the second polymer at any convenient stage during
preparation of the coating composition.
This invention is illustrated by the following non-limiting
examples.
',' ~ ~ '
,
~ 23~
~-207~(2080)
EXAMPLE 1
A polymer surfactant dispersion is prepared by reacting an
acid containing acrylic prepolymer with an epoxy resin, neutralizing
wlth base and dispersing in water.
The acrylic prepolymer is prepared as follows:
Parts by Weight
Butanol 2755.2
Methacrylic Acid 1197.7
Styrene 597.8
EthyL Acrylate 197.5
Benzoyl Peroxide 142.8
(70~, Water Wet)
2-Butoxyethanol 1995.8
6886.8
The butanol is charged to a 12-liter reactor equipped with
a stirrer, reflux condenser, thermometer, addition funnel and
nitrogen inlet. A premix is made of the monomers and benzoyl
peroxide and 20 percent is added to the reactor. The nitrogen flow
is started and the reactor is heated to 93~C and held at this
temperature for 15 minutes. The remaining premix is added uni~ormly
over 5 hours while maintaining 93C. After the premix is added, the
temperature is held for two hours to complete the polymerization.
The 2-butoxyethanol is then added to dilute the prepolymer. The
resulting solution has a solids content of 30.3 percent, an acid
number of 385 and a viscosity of 2600 centipoise.
An epoxy acrylate adduct is formed by esterifying an epoxy
resin with the above acrylic prepolymer under amine catalysis as
follows:
. '' ~ , .
- . . .
~31~7~2
F-2079(2080) -12-
Parts by Weight
DER 3311 698.1
- 3isphenol A 374.9
2-Butoxyethanol 116.8
Tri-n-butylamine 2.2
Acrylic Prepolymer 1299.0
Dimethylaminoethanol
(first portion) 28.6
Dimethylaminoethanol
(second portion) 40.4
"Cymel 11562'* 107.7
Deionized Water 2331.5
4999.2
lDER-331 (Dow Chemical Co.) - A 182-190 epoxy equivalent ~eight
diglycidyl ether of bisphenol A ~D~R-331 is a tradem~r~.
2Cymel 1156"(American Cyanamid Co.) - A butylated melamine curing agent.
The first four items above are charged to a 5-liter reactor
with stirrer, reflux condenser, thermometer and nitrogen inlet.
Nitrogen flow is started and the reactants are heated to 130C.
After exotherm, 150C is maintained until the oxirane content of the
reaction mixture falls to 0.37 meq/g. The acrylic prepolymer is
then added. The mixture is stirred until uniform and the
temperature is adjusted to 94C. The first portion of
dimethylaminoethanol (esteri~ication catalyst) is then added and
this temperature is held for 3 hours. The reaction mixture turns
from opaque to translucent and the acid number drops by the amount
indicating complete reaction of the epoxy. The epoxy acrylate resin
solution has a solids content of 57.3, an acid number o~ 85.0 and a
specific viscosity of 0.33. There is no residual oxirane content.
To form a dispersion, the epoxy acrylate adduct is furthe~
neutralized with the second portion of ~imethylaminoethanol and the
curing agent is added. Water is added with efficient stirring to
produce a stable9 small particle size dispersion with a solids
content of 31.5 percent.
* Trademark
.. ..
. - . .
.', . .... ~ . : ''.,,.'. . ' ., ' : " ''
: ~ , - .
,
~.~3~7~
f-207Y(2080)
EXAMPLE 2 ~
The above polymeric surfactant dispersion (2,000 parts) is
transferred to a 5 liter reactor together with 500 parts of
deionized water and 30 parts of dimethylaminoethanol. A nitrogen
blanket is applied and the reactor is heated to 80C. A mixture of
303 parts of styrene and 17 parts of benzoyl peroxide (70Y0, water
wet) is added with stirring over ~ hrs. at 80C. Then, t-Butyl
hydroperoxide (0.5 part) is added. After a 5-minute wait, O.S parts
of sodium bisulfite in 15 parts water is added over 15 minutes. The
emulsion is held at 80C for 1/2 hour. Water (800 parts) is added
and the emwlsion is cooled. The product has a solids content of
24.1 percent acid number of 62, speoific viscosity of 0.76 and
dispersion viscosity o~ 125 cp.
The above emulsion was drawn down on aluminum and tinplate
substrates and baked for 2 minutes at 400~F. Properties of gloss,
adhesion, wedgebend flexibility and pasteurization resistance were
all rated excellent at beer and soft drink weights.
EXAMPLE 3
The polymeric surfactant of Example 1 (2000 parts) is
charged to a 5 liter reactor together with 500 parts of deionized
water and 5 parts of sodium bisulfite. The mixture is heated to
65C under a nitrogen blanket. A premix of 225 parts of styrene9 75
parts of acrylonitrile and 5 parts of t-butyl hydroperoxide (70%) is
added over 1 hour at 65 and the mixture then held for an additional
1/2 hour. An additional 0.5 parts of t-butyl hydroperoxide (70~) is
added. After 5 minutes a mixture of 0.5 parts sodium bisulfite in
15 parts water is added. Temperature (65C) is held for an
additional 1/2 hour, then a mixture of 800 parts water and 15 parts
,
- '' ', . ~: ~
,
~lZ3
F-2079(2080) -14-
diméthylaminoethanol are added. The resulting coating emulsion has
a solids content of 24.8 percent, an acid number of 59.5 and
viscosity of 85 centipoise.
Test results on aluminum and tinplate panels, as in Example
2, all produced excellent results.
EXAMPLE 4
An epoxy acrylate polymeric surfactant dispersion is formed
by reacting an epoxy resin with the acrylic prepolymer of Example I
under tertiary amine esterification catalysis as follows:
Parts bv Weight
~Epon 828"1 ttrademark) 1445,0
Bisphenol A 780.2
2-Butoxyethanol 245.0
Tri-n-butylamine 4.6
Acrylic prepolymer of Example f 2674.0
Deionized Water I38.9
Dimethylaminoethanol 89.0
Dimethylaminoethanol 79.1
Cymel 1156" (trademark) ' 150.2
Deionized Water ' 4944.2
~M 1~550.2
l." Epon 8281l(Shell Chemical Co.) - An 182-l90 epoxy equivalent weight
diglycidyl ether of bisphenol A.
The procedure of the epoxy acrylate preparation and
dispersion of Example I are followed with the exception that a minor
amount of water is added with the acrylic prepolymer to help control
reaction viscosity and temperature. The resulting polymer has an
acid number of 85.7. The dispersion product has a solids content of
29.2~, a pH of ~.8, viscosity of 12,600 centipoise and particle size
0.17 microns.
The above polymeric sur~actant dispersion (4500 parts) is
charged to a 12 l reactor together with 4320 parts of deionized
- . : . .
-
, ~ ' ' ' ~ :
.
,
F-2079(208Q) -15-
water, 27 parts of dimethylaminoethanol and 21 parts of ammonium
bisulflte ~45%). The mixture is heated to 65~ under a nitrogen
blanket. A premix of 657 parts of styrene, 657 parts of butyl
acrylate and 8.73 parts of t-butyl hydroperoxide (90/0) is added over
2 hours at 65C and the mixture then held for an additional 1/2
hour. An additional 0.9~ parts of t-butyl hydroperoxide (70~) is
added. After 5 minutes a mixture of 1.8 parts ammonium bisulfite
and 27 parts of water is added. Temperature (65~C) is held for an
additional 1/2 hr. The resulting emulsion product has a solids
content of 25.5%, a pH of 7.1, an acid number of 51.0 and viscosity
(Brookfield) of 1140 centipoiseO
Test results on aluminum and tin plate panels, as in
Example 2, all produced excellent results.
EXQMPLE 5
The emulsion product of Example 4 (4000 parts) is mixed
with 222 parts of butanol, 882 parts of water and 9.43 parts of
dimethylaminoethanol until uniform. The resulting finish, which is
réady for spray liner application, has a solids content of lg.gYo~ a
pH of 7.4, surface tension of 26.2 dynes/cm and viscosity of ~6 sec
as measured by ~4 Ford Cup.
Test results on spray application using aluminum and
tinplate cans produced blister-~ree interior can coatings with
excellent enamel rater coverage. The sprayed coatings also showed
excellent adhesion, reverse impact resistance and pasteurization
reslstance.
EXAMPLES 6-14
A series of compositions were prepared in the manner
described in Example 4. The amount of dimethylaminoethanol present
during reaction of the epoxy resin and the carboxyl containing
.
,
~2~
F-2079(2080) -16-
acrylic copolymer was varied in increments from 10 percent to 35
percent of the amount necessary to neutralize the carboxyl groups of
the acrylic copolymer. Results of reduced specific viscosity,
viscosity and particle size were measured at various stages of the
process. The results are summarized in Tables I and II. It is
evident that the amount of amine present during the reaction between
epoxy resin and the carboxyl group containing acrylic copolymer has
a profound effect on the viscosity and particle size of the ionic
polymer and that this effect is also evident after the styrene-butyl
acrylate polymer is introduced.
TABLE I
IONIC RESIN SOLUTION IONIC RESIN_DISPERSION
% Cat* Part. Size
EX. _ DMEOA Y NV AN RSV** ~ NV _ _pH Visc. Y Neut Microns
6 i0 57.5- 90.8 0-.39~ 29-.2 6.833,750 38.3 0.23
7 12 57.8 ~0.1 0.36 29.2 6.820.750 37.1 0.21
8 14 58.7 88.8 0.33 29.3 6.810,46û 37.3 0.18
g 16 58.3 89.0 0.32 29.2 6.69,340 38.4 0.17
18 56.8 89.4 0.31 29.3 6.85,800 38.3 0.17
11 20 57.3 8~.4 0.29 29.0 6.83,200 38.5 0.16
~2 25 58.5 90.4 0.26 29.8 6.7590 37.1 0.24
13 30 57.3 88.4 0.25 29.4 6.7366 40.3 0.27
14 35 58.6 87.0 0.25 29.5 6.8280 41.1 0.39
*Percent neutralization of acrylic prepolymer.
**Reduced speoific viscosity - 1~ by weight of dry resin in
dimethylformamide at 25C.
7~;~
F~2079(2080) -17-
TABLE II
DISPERSION OF IONIC RESIN
AND COPOLYMER
IONIC RESIN DISPERSION (24.8 + .2% solids)
% Cat.*
EXAMPLE DMEOA RSV** Visc. Part. Size RSV*** Visc. Part Size
(cp) Microns (cp) _ Microns .
6 10 0.39 33,75~ 0.230.81 1410 0.25
7 12 0.36 20,750 0.210.63 630 0.30
8 14 0.33 10,460 0.180.70 500 ~.28
g 16 0.32 9,340 0.170.65 275 0.27
18 0.31 5,800 0.170.68 200 0.27
11 20 0.29 3,200 0.160.80 110 0.27
12 25 0.26 590 0.240.7g 31 0.31
13 30 0.25 366 0.270.60 2i 0.39
14 35 0.25 280 0.390.61 16 0.57
*Percent neutralization of acrylic polymer.
**Reduced specific viscosity - 1~ by weight of dry resin
in dimethylformamide at 25C.
*~*Reduced Speci~ic viscosity - 1% by weight o~ dry resin
in tetrahydrofuran at 25C.
. . ~ ~ '' ~, -
.
: .
.' . ' . ', : ~' .
, ~
F-2079(2080) -18-
EXAMPLE 15
A. ~
~~- A 12 1 reactor equipped with stirrer, reflux condenser,
thermometer, heating mantle and nitrogen blanket was charged with
3800.7 parts butanol. A premix of 1652.4 parts glacial methacrylic
acid, 824.4 oarts styrene, 275.4 parts ethyl acrylate and 197.1
parts benzoyl peroxide (70~ water wet) was also prepared. Twenty
percent of the premix was added to the reactor wnich was heated to
93C under nitrogen and held at temperature for 15 minutes. The
remaining premix was added over 5 hours at 93C after which this
temperature was held ~or 2 hours. Butanol (225000 parts) was added
to give an acrylic prepolymer solution at 33.5~ NV, acid number of
~92 and viscosity of 9660 centipoise.
In a five liter reactor equipped as ab*ove were charged 65.5
parts of 2-butoxyethanol, 655.9 parts ~oon 828, 364.5 parts
bispnenol A and 2.1 parts tri-n-butylamine. The charge was heated
to 136C and allowed to exotherm to 175C, then held at 150C for
1.5 hours. The upgraded epoxy was defunctionalized 33~ b~ addition
of 27.0 parts stearic acid to an epoxy value of 0.21 meq~g oxirane.
2-Butoxyethanol 164.0 parts, 100 parts butanol and 551.2 parts o~
the above acrylic containing 29.6 parts of a 25% aqueous solution of
trimethylamine esterification catalyst were added. A cloudy~ opaque
mixture was formed which was held at reflux (1~9C) for oonstant
acid number. At the end of 2.5 hours, the mixture had cleared
completely and reached the acid number, 46.7, calculated for
complete oxirane esterification. 2-Hexoxyethanol 18.û parts,
dimethylaminoethanol, 54.4 parts and"Cymel 1156, 61.5 parts were
added and stirred unkil unif~rm. Deionized water (2242 parts) was
added to form a dispersion. After transfer to a 6 1 container, 33
parts butanol and 17 parts 2-butoxyethanol were added and a ~inish
was prepared at 19.5% NV by addition of deionized water.
* l~ad~[ ark
.,~ r
'-
' .: ' ~ : ,'
7~
F-2079t2080) -19-
B. Preparation of St~rene/Butyl Acr~late Modified_Epoxy-Acrylate
Twenty three hundred parts of the above dispersion was
transferred to a 5 1 reactor equipped as before. A premix of 76.9
parts styrene, 76.9 parts butyl acrylate and 0.02 parts t-butyl
hydroperoxide (90~) was prepared and emulsified in the reactor under
a nitrogen blanket where it was heated to 65C. A premix of 1.5
parts of ammonium bisulfite in 15 parts water was added and 70C was
held for 3.0 hours. To remove any butyl acrylate residue, a premix
of 3804 parts styrene and 0.13 parts of t-butylhydroperoxide (9C~)
was then added followed in five minutes by a premix of 3.5 parts
ammonium bisulfite in 5 parts water. The styrene overpolymerization
was complete after holding at 70C for 2 hours. A spray finish at
20% NV was prepared by the addition of deionized water. The finish
gave excellent properties for the coating of can interiors including
resistance to fracturing on a 40F can drop test which is not passed
by epoxy acrylates modified with 30% styrene add-on. The dispersion
had a pleasant odor not objectionable for use as a commercial can
coating.
.
'
