Note: Descriptions are shown in the official language in which they were submitted.
1~29132
~ he present invention relates to thermosetting aqueous epoxy-
ethylenically unsaturated amine copolymer coating systems which are adapted
to cure on air dryine. Such coating systems are two package systems which
cure upon admixture with one another and are particularly adapted for the
painting of porches and floors, including cementitious substrates.
Aqueous coating compositions of the general type under considera-
tion are in commerce, being produced under the disclosure of United States
Patent 3,719,629 issued March 6, 1973. These known compositions are not only
expensive, but they exhibit poor chalking resistance, and poor tint reten-
tion. They are also marginal from the standpoints of (1) applicability toporches; (2) film hardness; and (3) cracking resistance.
In the aqueous coating compositions of said patent 3,719,629, the
epoxy resin component is combined in an aqueous medium with an aminoethylated
vinyl polymer having pendant aminoethyl groups, these groups having the for-
mula:
0 /H
-C - 0 - cH2- CH2- N~H
and the cure is between the oxirane (epoxy) group in the epoxy resin and the
amino hydrogen atoms in the aminoethyl group pictured. In the present inven-
tion, the amino hydrogen atoms which are essential in the prior art are not
present Moreover, the production of the pendant aminoethyl groups in the
prior art required the use of expensive and hazardous ethylene imine, and
thi~ is avoided in this invention.
From the broader standpoint, and in addition to the aqueous epoxy
~ystem noted previously, other resin systems have been employed to provide
air drying porch and floor paints. Thus, the systems of this invention are
intended to replace two existing aqueous systems, one based on an alkyd resin
" ~
~12913Z
and another based on an aqueous copolymer latex, and also to replace an or-
ganic solvent-based epoxy system. The invention exhibits significant supe-
riority to all three as will be documented hereinafter.
In one aspect, the present invention provides a method of providing
a thermosetting aqueous epoxy resin-ethylenically unsaturated amine copolymer
coating system adapted to cure on air drying comprising providing a mixture
in water consisting essentially of a first component constituted by acid-
neutralized organic solvent soluble tertiary amine copolymer of copolymerized
monomers substantially free of hydroxy functionality and comprising at least
about 60% of nonreactive monoethylenic monomer, and from 15-~0% of mono-
ethylenic tertiary amine monomer selected from the group consisting of ter~
tiary amino esters and tertiary amino amides of monoethylenic carboxylic
acids, said copolymer being in solution in a water miscible inert organic
solvent, and a second component constituted by a resinous polyepoxide in so-
lution in at least partially watermiscible organic solvent.
In another aspect, the invention provides a thermosetting aqueous
epoxy resin-acrylic copolymer coating composition consisting essentially of
water having dissolved therein an acid-neutralized organic solvent soluble
tertiary amine copolymer of copolymerized monomers substantially free of
hydroxy functionality and comprising at least about ~0% of nonreactive mono-
ethylenic monomer, and from 15-40% of monoethylenic tertiary amine monomer
selected from the group consisting of esters and amides of monoethylenic car-
boxylic acias, said water further having emulsified therein with the aid of
a surfactant a resinous polyepoxide.
In yet another aspect, the invention provides a two component pack
for preparing a thermosetting aqueous epoxy resin-ethylenically unsaturated
amine copolymer coating system which pack comprises a first component con-
stituted by acid-neutralized organic solvent soluble tertiary amine copolyer
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of copolymerized monomer substantially free of hydroxy functionality and com-
prising at least about 60% of non-reactive monoethylenic monomer; and from
15 - 40% of monoethylenic tertiary amine monomer selected from the group con-
sisting of tertiary amino esters and tertiary ~mino amides of monoethylenic
acids, said copolymer being in solution in a watermiscible inert organic sol-
vent, and a second component constituted by a resinous polyepoxide in solu-
tion in an at least partially watermiscible solvent, the two components being
present in the pack in such relative proportions that on mixing of the two
components and the addition of water there is obtained a thermosetting aque-
ous epoxy resin-ethylenically unsaturated amine copolymer coating system.
A two package system is employed in the present invention. In one
component is placed an acid-neutralized tertiary amine copolymer in solution
in a watermiscible alcoholic solvent. The other component contains the epoxy
resin, desirably together with a catalyst for the epoxy-tertiary amine reac-
tion, in solution in organic solvent which is at least partially water-
miscible, and which is preferably alcoholic. Before applying the coating,
the two separately stable solution components are mixed together to form an
aqueous mixture of limited pot life, and this aqueous mixture is coated upon
the surface to be painted. ~he water which is present in the aqueous mixture
is normally added to the first compocent prior to admixture of the two com-
ponents, but all or a portion of the water can be added after the mixture is
formed. The first component also desirably includes a surfactant for main-
taining the epoxy resin in relatively stable emulsion in the aqueous mixture
which is provided.
Typical coatings produced by the present invention have a pot life
of at least about ô hours, usually about 12-14 hours, and can be applied by
roller, brush, or air spray. The applied aqueous coatings dry to the touch
in air at room temperature in about 6-7 hours and become water and solvent
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l~Z9132
resistant in about 8-12 days. Recoat propertie~ are comparable to that of
conventional porch and floor paints. Importantly, polymer solubility i8 ob-
tained using acids like lactic or acetic acid which are less toxic than
anionic systems solubilized with a~ines, and generally less than 10% of non-
objectionable alcoholic solvents are needed which is advantageous from sev-
eral well known standpoints, such as cost, hazard, pollution, and the like.
Referring more particularly to the tertiary amine copolymers, these
are organic solvent-soluble copolymers comprising two copolymerized mono-
ethylenically unsaturated components, namely: (1) nonreactive monomeri and
(2) tertiary amine monomer. ~1hile small amounts of other monomers may be
present, such as monoethylenic carboxylic acids, monoethylenic amides or N-
methylol derivatives thereof, or polyethylenic hydroxyfunctional materials
such as polyesters, these are not necessary.
The nonreactive monoethylenically unsaturated (monoethylenic)
monomer should constitute at least about 60% of the copolymer in order to
provide desirably physical characteristics. Styrene is the preferred non-
reactive monoethylenic monomer, but vinyl toluene is also useful. Methyl
methacrylate, acrylonitrile, and vinyl acetate will further illustrate the
nonreactive monomers which are useful. A portion of a flexibilizing non-
reactive monomer is also desirably present, such as ethyl acrylate or meth-
acrylate or butyl acrylate or methacrylate. These flexibilizing monomers can
be more generally defined as C2 - C18 alkanol esters of monoethylenic car-
boxylic acids.
In preferred practice, the nonreactive monomer component will con-
stitute from about 60% to about 85% of the weight of the tertiary amine co-
polymer, typically about 73%.
Our copending application Serial No. 317,715, filed December 11,
1978 is concerned with thermosetting aqueous epoxy resin-acrylic copolymer
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coating compositions consisting essentially of water having dissolved therein
an acid-neutralized organic solvent soluble tertiary amine copolymer of co-
polymerized monomers comprising at least about 40% of nonreactive monoethyl-
enic monomer, and from 5-35% of monoet~ylenic hydroxyfunctional monomer, and
from 5-35% of monoethylenic tertiary amine monomer selected from the group
consisting of esters and amides of monoethylenic carboxylic acids, said water
further having emulsified therein with the aid o~ a surfactant a resinous
polyepoxide.
In that application, monoethylenic hydro~yfunctional monomer was
used in an amount of from 5-35% of the weight of the tertiary amine copolymer
for various reasons. First, the hydroxy functionality assists in achieving
water solubility with the aid of a solubilizing acid, but with an increased
proportion of the amine monomer, this is not essential. Second, the presence
of the primary hydroxy group provided by the hydroxy functional monomer helps
the ultimate cure. It has now been found that with enough amine monomer, the
secondary hydroxyl groups provided by the epoxy component provides a satis-
factory cure. Also, sufficient reaction involving the tertiary amine group
adequately couples the acrylic copolymer and the epoxy resin in the film
which is formed.
The crucial component of the tertiary amine copolymer is t~e mono-
ethylenic tertiary amine monomer. Typical tertiary amine monomers are di-
methyl aminoethyl acrylate or methacrylate, dimethyl aminopropyl acrylate or
methacrylate, diethyl aminomethyl acrylate or methacrylate, and diethyl amino-
ethyl or aminopropyl acrylate or methacrylate. The corresponding crotonates
~nd tertiary amino esters of other monoethylenic carboxylic acids are also
useful. Additionally, the corresponding amides are useful such as dimethyl
aminoethyl methacrylamide.
The proportion of the tertiary amine monomer can vary in the same
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112~13Z
way as the hydroxy monomer, namely, from 15-40% by weight of the copoly~er,
preferably from 20-30% by weight.
Water miscible organic solvents whicb are useful in this invention
are preferably alcoholic and are illustrated by ethanol, propanol, iso-
propanol, n-butanol, isobutanol, 2-ethoxy ethanol and 2~butoxy ethanol.
The specific nature of the solubilizing acid used to disperse the
amine copolymer in water is of secondary significance. Inorganic acids, such
as hydrochloric acid or sulfuric acid, are useful, though not preferred. It
is presently preferred to employ phosphoric acid, glycolic acid (hydroxy
acetic acid), or acetic acid, but other acids can be used, such as formic
acid or carbonic acid. Propionic acid is also useful.
The solubili~ing acid is used in an amount to provide a colloidal
dispersion having a preferred pX in the range of pH 6.o - 7.o, though a pH
in the ran8e of pH3 - 8 is broadly useful.
The epoxy resins which are used in this i-nvention can be broadly
referred to as resinous polyepoxides, and those which possess a 1, 2-epoxy
equivalency in the range of about 1.4 to about 2.0 are preferred. Poly-
epoxides which are diglycidyl ethers of bisphenols are particularly preferred,
especially those having an average molecular weight in the range of about 350
to 4000. A diglycidyl ether of bisphenol A having an average molecular
weight of about 390 will be used to illustrate the invention.
The polyepoxide component i6 itself conventional, as discussed in
patent 3,719,629 referred to previou~ly.
The polyepoxide is desirably used in an amount providing approx-
imate stoichiometry between epoxy groups in the polyepoxide and tertiary
nitroger atoms in the amine copolymer~ + 50%, more preferably + 20%.
The organic solvent component of the package containing the poly-
epoxide is intended to provide desirably liquidity, particularly since the
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polyepoxide is normally a viæcous liquid or a solid at room temperature.Since it i8 clesired that the polyepoxide be stably dispersed in the aqueous
mixture which is ultimately produced, the organic solvent should be at least
partially water miscible, but the partial miscibility which is intended need
merely be that which is consistent wit~ the ultimate stable dispersion which
is contemplated, and it is most accurate to refer to the form of the disper-
sion aæ an emulsion since the presence of the polyepoxide component in the
aqueous mixture which is formed is such as to induce considerably opacity to
the liquid mixture.
A surfactant is normally included in the polyepoxide solution in
order to stabilize the aqueous emulsions which are formed. Appropriate sur-
factants may be nonionic or anionic and the selection of surfactants appro-
priate for the emulsification of epoxy resins in water is well known and is
not a feature of this invention. Surfactants are not needed, however, since
the cationic copolymer itself functions to help to maintain the epoxy resin
in relatively stable emulsion.
It is also permissible to include catalysts for the tertiary amine-
epoxy curing reaction. ~his reaction is itself well known, and thus the se-
lection of catalysts for the reaction is not of primary concern. Appropriate
catalysts are Lewis acids, such as dibutyl tin dilaurate. Indeed, no cat-
alyst is needed, and none is used in the preferred form of the invention.
The systems of this invention can be applied clear or pigmented,
but pigmented systems containing titanium dioxide rutile at a pigment to
binder ratio of 0.3:1.0 are preferred.
The invention is illustrated in the following examples.
EXAMPLE 1
Pre~aration of solvent soluble tertiary amine copol~mer
in solution in water miscible organic solvent.
~50 parts of 2-butoxy ethanol are heated to 120C. in a reactor
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l~Z9~32
equipped with an agitator, a reflux condenser, a thermometer, and a nitrogen
inlet tube for sparging the reaction mixture.
~ onomers and catalysts are premixed in an addition tank. 900 parts
of styrene, 630 parts of butyl acrylate, 560 parts oY dimethyl a~inoethyl
methacrylate and 30 parts of azobisisobutyronitrile are thus premixed and
slowly added to the reactor over a period of 3 hours. The temperature in
the reactor is maintained at 120C. during the period of addition and for
one hour thereafter.
To complete monomer conversion, 2 parts of azobisisobutyronitrile
are added and the reaction continued for one hour at 120 C. and then 2 more
parts of the same catalyst and the reaction continued for 2 additional hours
at the same temperature.
The product is then cooled to about 70 C. and 250 parts of 2-butoxy
ethanol are added together with 700 parts of 2-ethoxy ethanol and the final
copolymer solution is filtered to provide a solution having a Gardner vis-
cosity of Zl~ a Gardner-Holdt color of 1-2 and a nonvolatile solids content
of 58.~%.
EXAMPLE 11
Preparation of pigmented acidified copolymer aqueous solution.
Parts Component
223.6 solution of Example 1
3 surfactant ~note 1)
150 titanium dioxide rutile
amorphous silica
~ Attapulgus clay
-
Note 1 - The surfactant utilized is the American Cyanamide
product Aerosol C-61 which is a cationic surfactant.
Surfactant selection is not critical.
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The above is ground at high speed and then 510wly add, with slow
agitation, 12 parts of acetic acid. After continuing the agitation for 3
minutes, add 558.11 parts of water containing 1 part of 37% aqueous formal-
dehyde and 1.5 parts of a biocide. The formaldehyde and the biocide prevent
the growth of mold and are optional. 1.0 part of defoamer (Drew Chemical
Company L-475) may also be used, but is not necessary.
EXAMPLE III
PreParation of pol.YePoxide curing solution.
Pa Component
3.04 Diglycidyl ether of bisphenol
A having an average molecular
weight of 390.
10.1 2-butoxy ethanol.
EXAMPLE IV
Upon admixture of the solutions of Examples II and III, one obtains
an aqueous emulsion which has a pot life of about ô hours. Coating this emul-
sion by brushing on a concrete surface followed by air drying at room temper-
ature for 8 hours provided a painted surface which was hard enough to be
walked upon without being marred.
The advantages of the invention will be apparent from the tabulated
data presented below in which X indicates a positive feature, O indicates a
negative feature, and 1 indicates neither.
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TABLE
Competitive Materials in Commerce
United States
Example Two-Component Patent 3,719,629
Property I~ Latex Alkyd Epoxy (Dow)
Water Based X X l X
Solvent Based O O
Price X X X O O
One Package X X
Two Package O ~ O O
Ease of Clean X X O O X
Up
Use on Previous
Paints X X X O X
Flammable X X O O X
Use on Interior X X O O X
Hazardous 1 O
Use on Porches X X X O ?
One Coat Hide X O O X X
Alkali Resis- X X O X X
tance
Abrasion
Resistance X 1 1 X X
Chemical
Resistance X 1 O X X
Hardness X O O 1 1
Good Adhesion X X X X X
Tire Track
Adhesion X O 1 X X
Tint Retention 1 X 1 O O
Chalking Resis-
tance 1 X 1 O O
Cracking Resis-
tance 1 1 ?
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