Note: Descriptions are shown in the official language in which they were submitted.
,~I 50120
-- 21~
AQUEOUS COATING COMPOSITION
This invention relates to protective coatings containing
zero or very low levels of volatile organic compounds
(VOC), and more particular' y to aqueous dispersed epoxy-
ester acrylic-graft polymeric binders particularly useful
15 for coating interior substrates of beer and beverage
containers ( cans ) .
Protective surface coatings are organic compositions
applied to substrates to form continuous films w~ich are
20 cured or otherwise hardened to provide protection as well
as a decorative appearance to the substrate. Protective
surface coatings ordinaril~ comprise an organic polymeric
binder, pigments, inert fillers and other additives, where:
the polyl[leric binder acts as a fluid vehicle for the
25 pigments and imparts rheological properties to the f luid
paint coating. Upon curing, the polymeric binder hardens
and functions as a binder for the pigments and provides
adhesion of the dried paint film to the substra e. The
plgments may be organic or inorganic and functionally
30 contribute to opacity and colour in addition to durabiLity
and hardness, although sor~.e paint coatings contain little
or no opacifying pigments and are described as clear
coatings. The manufacture of paint coatings involves
the preparation of a polyrr,eric binder, mixing of component
35= materials, grinding of plgments in the polymeri~ binder,
and thinning to co~[l}[Lercial standards.
~156~68
Epoxy resins are particularly desirable for use in
surface coating materials as a vehicle or polymeric binder
to advantageously provide toughness, flexibility, adhesion,
and chemical resistance to the applied coating film. Hence
5 water-dispersed coating cornpositions containing epoxy
resins are highly desirable for can coating compositions.
Coatings for soft drink and beer cans, for instance, are
critical due to taste sensitivity and must not alter the
taste of canned beverages. Taste problems can occur in a
10 variety of ways such as by leaching of coating components
into the beverage, or by adsorption of flavour by the
coating, or sometimes by chemical reaction, or by some
combination thereof.
lS In our US Patent No. 4 212 781, a process is disclosed
for modifying epoxy resin by reacting the epoxy resin with
addition polymerizable ethylenic monomer in the presence of
at least 3% by weight of benzoyl peroxide (or the free
radical initiating equivalent thereof ) based on monomer at
20 a suitable reaction temperature to produce a reaction
mixture comprising an epoxy-acrylic polymer, and
associatively-formed ungrafted addition polymer. The
in-situ polymerized monomers include acid functional
monomers to provide acid functionality in the reaction
25 mixture sufficiently high to effect stable dispersion of
the resulting reaction product in a basic aqueous medium.
Similarly, our ~S Patent No. 3 552 961 relates to a mixture
of polymers comprising a self-curing emulsion polymer
(latex), an epoxy-acrylic graft copolymer, and preferably a
30 phosphate additive. Related patents are US Patent Nos. 4
2~5 ~47 and 4 399 241, and 5 212 241. Most prior art
water-dispersed epoxy coatings utilise relatively high
levels of organic solvent to assist processing of the epoxy
resin. Although epoxy containing coatings have long been
35 the standard of excellence in the interiors of beverage
cans, such coatings cannot be prepared without significant
21~6~ -
amounts of solvent, where typically 50~ to lOOï volatile
organic solvent is required based on solids (about 2 . 5 to
lbs./gal. or about 0.3 to 5Kg/l) . Recent environmental
concerns and legislative pressure have created the need for
5 a zero or near zero VOC Gan coating.
It now has been found that high quality aqueous
dispersed epoxy coatings can be produced with no organic
solvent by esterifying low molecular weight epoxy resin
10 with low molecular weight carboxyl functional polyester to
produce a carboxyl functional low molecular weight epoxy-
ester, mixing the epoxy-ester with ethylene monomers and
dispersing the mixture into water, and then copolymerizing
the ethylenically unsaturated monomers to produce a
15 crQsslinked emulsion polyc.er useful as a polymeric binder .
In particular, it has bee~l found that aqueous emulsion
dispersions of the crosslinked epoxy-ester copolymer can
be prepared and maintained dispersed in water without
conventional surfactants and by ammonia neutralisation of
20 the epQxy-ester carboxyl groups without the need for any
volatile organic solven~ s. Copolymerization of the
ethylenic monomers produces a stable small particle size
polymeric dispersion.
It has been found that low molecular weight epoxy
resins are eas~ily processable at lower temperatures and
viscosities while low molecular weight oligomeric carboxyl
functional polyesters lower the overall viscosity of the
mixture ar,d provides considerably improved processability.
Temperature control during the formation of the epoxy
ester advantageously avoids unwanted molecular weight
advancement while the liquid ethylenic monomers serve as a
temporary solvent for the epoxy-ester which in turn
facilitates the si~ple dispersion of the organic mixture
into water. Once epoxy resin is reacted with a low
molecular weight, acid ~-unctional polyester oligomer in
4 2156~G8
accordance with the invention, the resultant epoxy-ester
can be dissolved in acrylic monomer and dispersed into
water with very low levels of ammonia. The epoxy-ester is
water dispersed and becomes addition grafted and
5 crosslinked with the copolymerized ethylenic monomers to
form a very small particle microgel stably dispersed in
water. Grafting of the epoxy-ester with ethylenic
monomers in water produces very small size crosslinked
microgel particles, a physical property particularly
10 useful for producing tough but resilient and flexible
coatings .
According to the present invention there is provided
an aqueous dispersed, protective coating composition
15 substantially free of volatile organic compounds and
containing a polymeric binder dispersed into water, the
polymeric binder comprising a crosslinked epoxy-ester
copolymer containing by weight:
a) between 1% and 70~ low molecular weight epoxy
resin having a number average molecular weight between
100 and 1, 000;
b) between 1% and 70~ low molecular weight, carboxyl
functional, unsaturated polyester oligomer having an
acid number between 30 and 500 and a number average
molecular weiqht between 200 and 3, OOOi and
c) between 1% and 90% addition copolymer made of
copolymerized ethylenic monomer;
where the crosslinked epo:~y-ester copolymer is produced by
esterifying the carboxyl functional polyester oligomer with
epoxy resin to produce a carboxyl functional, unsaturated
epoxy-ester having an acid number between 30 and 200 and
then copolymerizing the ethylenic monomers in the presence
5 ~ 46~ :
of the epoxy-ester dispersed in water to produce internally
crosslinked emulsion microgel particles of an epoxy-ester
copolymer crosslinked with ethylenic monomer having an acid
number between 25 and 150, where the crosslinked microgel
5 particles have an average particle size less than 0 . 02
microns, and where said microgel particles are stably
dispersed into water free of surfactant.
This invention incorporates the advantages of epoxy
lO chemistry providing good barrier properties and excellent
resistance to flavour absorption along with a synthesis
technique that eliminates the need for organic solvents,
organic amines and surfactants. Baked paint films
utilising the resulting polymeric binder are clear, glossy,
15 solvent resistant, and water resistant.
Briefly, the zero VOC protective coating composition of
this invention is substantially free of volatile organic
compounds and surfactants and is based on an aqueous
20 dispersed polymeric binder comprising an epoxy-ester
polymer binder grafted with ethylenic monomers to produce a
crosslinked epoxy-ester emulsion copolymer. The copolymer
is produced by copolymerizing an aqueous dispersed mixture
of carboxyl functional epoxy-ester and ethylenically
25 unsaturated monomers to produce very small particle
microgel particles comprising a stable aqueous dispersed
crosslinked epoxy-ester copolymer binder.
The epoxy-ester comprises the esterification reaction
30 product of an epoxy resin esterified with a carboxylic acid
functional, low molecular weight polyester oligomer. A
useful epoxy-ester can be produced, for example, by
reacting a monofunctional or difunctional epoxy resin with
a carboxylic acid functional polyester oligomer to produce
35 a carboxyl functional epoxy-ester copolymer.
,
6 215~6~ ~l
Epoxy resins are characterised by the three-membered ether
group:
resin - CH - CH
O
5 where any one of the hydrogens can be replaced with a lower
alkyl group, where said three-membered ring is commonly
referred to an epoxy or oxirane group and such groups
typically terminate epoxy backbone chain and/or branched
chains. Epoxy-ester groups are formed by esterification of
10 an epoxy group with a carboxyl functional polyester
oligomer to produce a carboxyl functional epoxy ester.
Useful epoxy resin comprise conventional bisphenol epoxy
resins, glycidyl functional resins, epoxy novalac resins,
and alkylene oxide resins. Bisphenol epoxies are
15 preferred and are predominantly linear chain molecules
comprising the coreaction product of polynuclear
dihydroxy phenols or bisphenols with hal ohydrins to
produce epoxy resins containing at least one and preferably
two epoxy groups per molecule. The most common bisphenols
20 are bisphenol-A, bisphenol-F, bisphenol-S, and 4, 4' -
dihydroxy bisphenol, with the most preferred being
bisphenol-A. Halohydrins include epichlorohydrin,
dichlorohydrin, and 1, 2-dichloro-3-hydroxypropane with the
most preferred being epichlorohydrin. Preferred epoxy
25 resins comprise the coreaction product of excess molar
equivalents of epichlorohydrin with bisphenol-A to produce
pr~nmin~ntly an epoxy group terminated linear molecular
chain of repeating units of diglycidyl ether of bisphenol-A
containing between 2 and 25 repeating copolymerized units
30 of diglycidyl ether of bisphenol-A. In practice, an
excess molar equivalent of epichlorohydrin is reacted with
bisphenol-A to produce epoxy resins where up to two moles
of epichlorohydrin coreact with one mole of bisphenol-A,
although less than complete reaction can produce
35 difunctional epoxy resin along with monoepoxide chains
terminated at the other end with a bisphenol-A unit. The
21~6S
most preferred linear epoxy resins are polyglycidyl ethers
of bisphenol-A having terminating 1,2-epoxide groups.
Commercially available Lower molecular weight resins
include Dow Chemical epoxy resins identified by trade
5 number and average molecular weights as follows: DER 333
(380); DER 6~1 (525); while Shell Chemical epoxy resins
are EPON 1007 F (4000); and Ciba-Geigy linear epoxy resins
GT-7013 (1400); GT-7014 (1500); GT 7074 (2000); and GT-
259 (1200)~ Particularly preferred lower molecular
weight epoxy resins include EPON 828, EPON 1001, DER 333,
and DER 661 having a number average molecular weight less
than 1, 000 and preferably between 300 and 500, measured by
gel permeation chromatography (GPC) according to AST~I
methods such as D3536-76, D3593-80, or D3016-78. Preferred
epoxy resins ~ ~ve an equivalent weight between 180 and 500 .
High equivale~t weight epoxy resins form a viscous melt
when combined with acid functional polyester oligomers
causing mixing problems, although epoxy blends containing
minor amounts of high molecular weight epoxy resins are
20 workable.
Epoxy resins further include non-aqueous alkylene oxide
resins which are epoxide functional resins comprising an
alkylene oxide adduct of a bisphenol compound. The
25 alkylene oxide is an aliphatic alkyl derivative having up
to about 26 carbon atoms although preferred oxides are
lower alkyl oxides such as ethylene, propylene, and
butylene oxides. Bisphenol compounds include bisphenol-A,
bisphenol-F and bissulfone or sulfides. Typically two or
30 more moles of alkyl oxide are coreacted with one mole of
bisphenol compound. Preferred compositions are 2 :1 molar
reactions while suitable molecular weight range of alkylene
oxide resins is between 200 and l, 000 as measured by GPC.
35 Useful polyester oligomers comprise the esterification
products of glycols, diols, or polyols with excess
* ~ 46~
equivalents of dicarboxylic acid anhydrides or
polycarboxylic acids, where the polyester ~ligomers are
unsaturated polyesters containing ethylenic unsaturation.
Linear aliphatic glycols are esterified with greater molar
5 amounts of aromatic dicarboxylic acid and/or linear
dicarboxylic acid having between 2 and 36 linear carbon
atoms such as adipic, azelaic, succinic, glutaric, pimelic,
suberic or sebacic acid, as well as unsaturated
dicarboxylic acids such as maleic, fumaric or itaconic acid
10 to produced low molecular weight, unsaturated polyesters.
Although not preferred, minor amounts or monocarboxylic
unsaturated acid such as acrylic, rnethacrylic or ethacrylic
acid can be esterified. Preferred and commercially
available linear saturated dicarboxylic acids are
15 dodecanedioic acid, dimer fatty acids, or azelaic acid,
while preferred unsaturated acid are maleic and fumaric.
Aromatic dicarboxylic acids (anhydrides) include phthalic,
isophthalic, terephthalic, and tetrahydrophthalic. Minor
amounts of polyfunctional acids such as tri~ell~tic acids
20 can be added. Suitable glycols include linear aliphatic
glycols havi~g 2 to 16 carbon atoms such as 1, 3- or 1, 4-
butylene glycol, 1, 6-hexane diol, neopentyl glycol,
propylene gly-col, ethylene glycol and diethylene glycol,
propylene, and dipropylene glycol, and similar linear
25 glycols. Preferred glycols are hydrophobic glycols such as
hydrogenated Bisphenol A, neopentyl glycol and 1, 6-hexane
diol. although not desirable, minor amounts of polyols can
be used such as glycerol, pentaerythritol,
dipentaerythritol, or trimethylol ethane or propane. The
30 molar excess of the dicarboxylic acid over glycol is
between about 1~ and 50~ and preferably between about 20%
and 50%, where at least 1 molar % and preferably between
20% and 100~ molar percent of the carboxylic acid
components comprises ethylenically unsaturated mono or
35 dicarboxylic acid. ~he polyester oligomer contains
considerable excess unreacted carboxylic groups. The
-
9 215~
carboxyl functional polyester oligomer preferably has an
acid number between 100 and 300 rL~illigrams of KOH per gram
epoxy ester. The molecular weight of useful polyester
oligomer is preferably between 300 and 1, 500.
Acid functional polyester oligomers can be prepared by
esterification of the common diacids with dihydroxyl
compounds. Useful glycols include for instance ethylene
glycol, propylene glycol, butanediols, diethylene glycol,
10 dipropylene glycol, triethylene glycol, hexane diol, and
similar glycols. Preferred glycols such as p_opylene,
butylene, diethylene glycol and the like can be reacted
with diacids such as maleic, adipic, isophthalic acid and
the like at an excess of acid to hydroxyl functionality, to
15 produce a carboxylic acid functional polyester having a
preferred molecular weight about 300 to 1, 500 . ~ufficient
acid functionality in the polyester oligomer needs to be
present to allow reaction with the epoxy resin, and then
dispersion into water.
Small quantities of monofunctional acids and alco~.~ls (such
as benzoic acid, 2-ethylhexanoic acid, benzyl a~' cohol and
the like) can be used to modify the polyester str-_~ture, as
can polyfunctional acids and alcohols (such as t-imellitic
25 anhydride, trimethylol propane, and the like).
Polyfunctional alcohols and acids can serve t~ provide
higher acid contents to the polyesters, which can render
the resultant epoxy-esters more water dispersible.
Polyester oligomers containing unsaturated diacids (fumaric
30 and maleic) are preferred, as the unsaturation provides
grafting crosslinking functionality for the acrylic
monomer .
The polyester component can be synthesised by bulk
35 polymerization, where the raw materials are charged in bulk
and esterified at temperatures typically betwee-l 1~0~C -o
lo 21~6~68
240~C, although moderately higher or lower temperatures can
be utilised satisfactorily. An esterification catalyst can
be used, typically an organic tin compound at less than 1%
levels based on weight of the charge.
The acid number of the epoxy-ester resin (the reaction
product of the acid functional polyester oligomer and the
epoxy resin) is preferably between 50 and 150 mg KOH per
gram of epoxy ester. The epoxy-ester preferably has a
number average molecular weight between 500 and 4, 000 and
more preferably between 600 and 2, 000.
Epoxy-esters are formed by the reaction of the epoxy resins
with the preformed acid functional polyester oligomers.
15 Although considerable levels of free diacid may be present
in the polyester oligomers, any unreacted carboxylic
material ordinarily reacts with epoxy groups without
substantially affecting the properties of the epoxy-ester.
Nucleophilic compound such as tertiary amines are excellent
20 catalysts for this epoxy acid reaction, which can be
carried out at about 30 to 1203C, but pre~erably from about
70~ to 110aC. ~emperatures higher than about 120'C should
be avoided, as resin viscosity can rise c~uickly, and
gelation can result. Hence, epoxy polyester mixtures which
25 are fluid, and can be easily mixed at about 100~C are
preferred. ~referred epoxy-esters contain from abut 10% to
90% by weight epoxy resin with the remaining weight being
oligomer polyester and dicarboxylic acid if any. Epoxies
will react with carboxyl polyester oligomers at 100 to
30 140~C without a catalyst, but the reaction proceeds quicker
and at preferred lower temperatures in the presence of a
suitable nucleophile, such as tertiary amine. Good
reaction rates in the presence of about 0.1~ benzyldimethyl
amine occur at about 70~C to 100~C.
11 215~6~
The crosslinked epoxy-ester copolymer can be produced by
first mixing the epoxy-ester with ethylenic monomers to
reduce the resin viscosity to render the epoxy-ester more
easily dispersible in water, and then dispersing the
5 mixture into water and copolymerising the monomerS.
Alternatively, the crosslinked epoxy-ester copolymer can be
produced by dispersing lower viscosity, low molecular
weight epoxy-esters directly into water without the
addition of monomer, and then adding the ethylenic monomers
10 to the epoxy-ester aqueous dispersion. ~he epoxy-ester is
dispersed by neutralising it at least partially with
ammonia and forming a small particle size dispersion in
water. ~he epoxy-ester is then copolymerized in water with
the ethylenic monomers to produce internally crosslinked
15 microdispersions of crosslinked epoxy-ester.
According to the present invention there is also provided a
process for producing an aqueous dispersed, protective
coating composition substantially free of volatile organic
20 compounds and containing a polymeric binder dispersed into
water, the polymeric binder being emulsion polymerised
microgel polymer particles, the process comprising:
esterifying by weight between 1~ and 70% low ~lecular
25 weight epoxy resin having a number average molecul~r weight
between 100 and 1, 000 with between 1~ and 70~ low
molecular weight, carboxyl functional, unsaturated
polyester oligomer having an acid number between 30 and 500
and a number average molecular weight between 200 and 3, 000
30 to form a carboxyl functional unsaturated epoxy-ester
having an acid number between 30 and 200i
dispersing the carboxyl functional epoxy-ester into water
by at least partially neutralising the carboxyl functional
35 epoxy-ester with ammonia;
i2
2~6~
copolymerizing, by emulsion polymerisation at least 1% by
weight ethylenic monomer ln the presence of the epoxy-ester
dispersed into water to produce internally crosslinked
emulsion microgel polymer particles of a copolymer of
5 emulsion polymerised ethylenic monomer crosslinked with the
epoxy-ester by addition copolymerisation crosslinking, the
emulsion microgel polymer particles having an acid number
between 25 and 150, where the emulsion crosslinked microgel
particles have an average particle size less than 0 . 02
10 microns, and where said microgel particles are stably
dispersed into water without surfactant.
Copolymerizable ethylenic monomers useful for reacting with
the epoxy-ester polymer are monomers containing carbon-to-
15 carbon, ethylenic unsaturation and include vinyl monomers,acrylic monomers, allylic monomers, acrylamide monomers,
and mono- and dicarboxylic unsaturated acids. Vinyl esters
include vinyl acetate, vinyl propionate, vinyl butyrates,
vinyl benzoates, vinyl isopropyl acetates and similar
20 vinyl esters. Vinyl halides include vinyl chloride, vinyl
fluoride, and vinylidene chloride. Vinyl aromatic
hydrocarbons include styrene, methyl styrenes and similar
lower alkyl styrenes, chlorostyrene, vinyl toluene, vinyl
naphthalene, divinyl benzoate, and cyclohexene. Vinyl
25 aliphatic hydrocarbon monomers include alpha olefins such
as ethylene, propylene, isobutylene, and cyclohexene as
well as coniugated dienes such as 1, 3 butadiene, methyl-2-
butadiene, 1, 3-piperylene, 2, 3-dimethyl butadiene,
isoprene, cyclopentadiene, and dicyclopentadiene. Vinyl
30 alkyl ether include methyl vinyl ether, isopropyl vinyl
ether, n-butyl vinyl ether, and isobutyl vinyl ether.
Acrylic monomers include monomers such as lower alkyl
esters of acrylic or methacrylic acid having an alkyl ester
portion containing between 1 to 12 carbon atoms as well as
35 aromatic derivatives of ~ acrylic and methacrylic acid.
Useful acrylic monomer include, for example, acrylic and
13 21~6~
methacrylic acid, methyl acrylate and methacrylate, ethyl
acrylate and methacrylate, butyl acrylate and methacrylate,
propyl acrylate and methacrylate, 2-ethyl hexyl acrylate
and methacrylate, cyclohexyl acrylate and methacrylate,
5decyl acrylate and methacrylate, isodecylacrylate and
methacrylate, benzyl acrylate and methacrylate, and
various reaction products such as butyl, phenyl and
cresyl glycidyl ethers reacted with acrylic and methacrylic
acids, hydroxyl alkyl acrylates and methacrylates such
10as hydroxyethyl and hydroxy propyl acrylates and
methacrylates, as well as amino acrylates and
methacrylates. Carboxylic acid functional monomers can be
included if desired. Carboxylic acid monomers include 3
acrylic and methacrylic acids. Acrylic acids include
15acrylic and methacrylic acid, ethacrylic acid, alpha-
chloracrylic acids, alpha-cyanoacrylic acid, crotonic acid,
and beta-acryloxy propionic acid. Ethylenic monomer
mixtures of acrylic and/or methacrylic esters with styrene
are preferred. Styrene copolymerized very efficiently with
20the double bond unsaturation in the epoxy-ester. On a
weight basis of total ethylenic monomers, the ethylenic
monomers preferably comprise between 0~ and 100~ styrene
monomers, and preferably between 20~ and 80~ styrene
monomer, with the balance being other ethylenic monomers.
On a weight basis, the crosslinked epoxy-ester copolymer
contains preferably between 25~ and 70% addition polymer
component of copolymerized ~onomers based on the total
weight of the crosslinked epoxy-ester copolymer with the
30balance being the epoxy-ester polymer component. The
crosslinked epoxy-ester copolymer preferably contains
between 1% and 50% epoxy resin, more preferably 10 to 40~.
The crosslinked epoxy-ester copolymer preferably comprises
between 1% and 50% polyester oligomer, more preferably 10
35to 4Q%. These compositions are preferably free o~ volatile
~ 14 21a~G~
organic compounds in these ranges. The balance of the
copolymer is copolymerized èthylenic monomers.
The number average molecular weight of the crosslinked
5 epoxy-ester copolymer is aoove about 50, 000 and typically
the crosslinked microgel particles of epoxy-ester
mollecular weight readily exceeds and is typically well
over l, OOo, ooo
10 In accordance with this invention, the epoxy-ester solution
in monomer can be easily dispersed into water by simple
mixing with water containing sufficient ammonia to
neutralise a substantial portion of the acid groups
available in the epoxy-ester . About 0 . 5 to 5~ by weight
15 ammonia as NH? on polymeric solids is typical. Aqueous
dispersion pH' s close to 7 are preferred to eliminate the
possibility of polyester hydrolysis. Acrylic monomers can
be polymerized and initiated with any of the common free
radical initiators, such as the peroxides, persulfates,
20 peresters, and the azo initiators. Peroxide and perester
redox initiation is preferred with systems such as Na
formaldehyde sulfoxylate/Fe/persulfale, and ascorbic acid/
Fe/t-butyl perbenzoate.
25 The resulting crosslinked epoxy-ester copolymers comprise
very small micro-dispersion, crosslinked microgel polymer
particles having an average microgel particle si~e belo~
0.2 microns, preferably below 0.02 microns, most preferably
between 0.02 and 0.06 microns. The microgel particles
30 produced by ethylenic monomer crosslinking of the water
dispersed, linear epoxy-ester polymer surprisingly provides
highly crosslinked copolymers in the forrn of a stable
aqueous microdispersion of extraordinarily small internally
crosslinked microgel polymer particles wl~hout the need
35 for, and particularly without, external surfactants.
Excellent protective film formations on substrates are
21-~4~8
achieved without surfactants and even though the microgel
particles are intPrn~l ly highly crosslinked. E~ence, the
quality coatings for the interior of beverage cans can be
produced with crosslinked epoxy-ester copolymer microgel
5 particles. Aqueous dispersions of these blended resins can
be prepared in water with ammonia neutralisation without
the use of a~y volatile solvent. The acid functional
epoxy-esters (dissolved in acrylic monomer) can be easily
dispersed into water with low to moderate shear.
10 Polymerization of the acrylic monomers produces the polymer
blend in the ~orm of ver-t~ small particles size microgel
crosslinked polymer particles in dispersion form. cured
films exhibit excellent water resistance, and good clarity
and gloss.
The merits of this inventi~n are further illustrated upon
referring to the following illustrative examples.
~ 16 21~68
EXAMPLE 1
An acid functional polyester oligomer and epoxy ester was
prepared as follows: :
Grams
180.2 1, 3-butylene glycol
392 maleic anhydride
0 . 5 piperidine (maleic to fumaric isomerization
catalyst)
10 The aboue raw materials were warmed with, good stirring to
about 120~C, held for 2 hou~s, and then cooled. Titration
gave an acid Number of 133 and equivalent weight (143
theoretical). 266 g of the above unsaturated polyester was
combined with 188 grams DER 333 epoxy (epoxy equivalent
15 weight 190 Dow Chemical). The mixture was warmed while
controlling exotherm and limiting the reaction mixture
temperature to 100~C to produce an ep~xy-ester having an
acid number of 120 and a n~ber average molecular weight of
about 1, 0 0 0 .
EXAMPLE 2
An epoxy ester acrylic copolymer resin dispersion was
prepared as follows:
Grams
a) 554 epoxy ester from Example (1)
3 4 0 s tyrene
114 butyl acrylate
b) 900 water
121 ammonia (28~)
c) 1605 water
d) 9 . 0 t-butyl perbenzoate
e) 9 . 0 ascorbic acid
f) 5 ml FeSO~ solution, 1000 ppm
Epoxy ester of Example 1 was mixed in monomers to form
35 liquid mix (a), and then dispersed into (b) which had been
purged with nitrogen at 20~C for two hours. The mixture
17 21~6~
was mixed with a paddle stirrer at about 300 - 500 rpm for
about 2 minutes, and then (c) was added, which has also was
purged with nitrogen at 20 C for 2 hours. Components (d),
~e), and (f) were added se~Llentially to the dispersion, and
5 the reaction mixture was insulated such that the
temperature rose to about 50~C. The mixture was held for 2
hours, and then 1 g additional t-butyl perbenzoate was
added .
EXAMPLE 3
10 A polyester oligomer and an epoxy ester was prepared as in
Example (1), but using 27.5 g maleic anhydride, 155.8 g
diethylene glycol, 1. 0 g piperidine, and 278 . 7 g DER 333 .
Then 0 . 5 g triethylene diamine was added to the epoxy ester
after 2 hours at 95~C, held for 2 ~ore hours prior to
15 cooling. Then 181 grams styrene were added during the cool
down to cut viscosity.
EXAMPLE 4
An epoxy ester acrylic blended resin dispersion was
prepared as follows:
2 0 Grams
a) 125 epoxy ester in styrene from example (3)
styrene (additional)
t-butyl perbenzoate
b) 200 water
12 ammonia, 28
c) 400 water
d) 2.0 ascorbic 2cid (10% in water at pH 6.5)
e) 2 FeSO~ solution, lO00 ppm
30 Solution (a) was poured into (b) with 500 rpm paddle
agitation, and then (c) was added. Ammonia was added
dropwise to give pH 6 . 5 . Then (d) and (e) were added in
sequence. Both (b) and (c) were previously purged for 2
hours with nitrogen. ~xotherm was immediate, rising to
50~C in about 15 minutes. Then 1 g additional t-butyl
perbenzoate was added after 2 hours.
~ 18 215~4G8
EXAMPLE 5
Example (4) was repeated but included 75 g of the epoxy
ester solution in styrene, and the addition of an
5 additional 125 g styrene.
RESULTS
Resin dispersions of Examples 2, 4 and 5 were all free from
10 grit, shear stable, and very small in particle size (<0.1
micron) .
Draw down sa~ples of resins in Examples 2, 4 and 5 on
aluminum sheet with a ~28 wire wound bar were baked at
184-C ~390~F) for 2 minutes to provide the following cured
film properties:
Sample Gloss Cl arity Water Resistance
2 high good no blush noted
4 high good no blush noted
high good no blush noted
Resin Example 2 was exposed to 70~C ~180~F) water for 30
minute~, while samples 4 and 5 were exposed to boiling
25 water for 5 ~inutes.
The foregoing description and representative examples
illustrate the merits of this invention but are not
intended to be limiting except as def ined by the appended
30 claims.
