Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1067Z3'~
This invention relates to the formation of water-
based paints. This application is a division of copending
~anadian application Serial No. 228,423 filed May 30, 1975.
Water-based paints of the prior art have included
"solution paints" and "emulsion (or latex) paints" with
distinction being made with reference to the manner in which
the sole or principal binder polymer is dispersed within the
aqueous medium.
In those paints wherein the sole or principal binder
polymer is soluble in the aqueous medium, the polymer is
ordinarily of low molecular weight. These paints can be
formulated to provide coatings of very high gloss. They tend
to be slow drying and prone to sagging during application and
to solvent popping during baking under high humidity conditions.
Application solids are much lower than comparable latex
paints.
The emulsion or latex paints have employed as their
sole or principal binder polymer a polymer of very high
molecular weight, i.e., in the range of about 100,000 to about
1,000,000 or higher. Such paints have been characterized by
rapid drying and comparatively low gloss relative to paints
based on water-soluble polymers.
Water-soluble polymers of high molecular weight
have been added to latex paints as thickeners. Characteris-
tically, such thickener polymers are used in very small
amounts, e.g., of the order of one percent.
It has been discovered that water-based paints having
a superior combination of physical properties and application
characteristics can be obtained by using certain novel
combinations of solution polymers and emulsion polymers.
The coatings obtained from these hybrid compositions exhibit
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- 1~67Z3Z
~ligll gloss and generally excellent appearance.
In accordance with the present invention, there is
provided an improvement in a method for producing an aqueous
dispersion of paint in which a carboxy-functional polymer
is at least partially neutralized with a water-soluble amine
and dispersed with an amino resin cross-linking agent
selected from melamine-formaldehyde resins and urea-formal-
dehyde resins in an aqueous solution of water and water-
soluble amine, wherein the carboxy functional polymer,
amino resln cross-linking agent and water~soluble amine
constitute about 30 to 50% by weight of the continuous
aqueous phase of the paint with the balance of the continu-
ous aqueous phase being water or a mixture of water and an
organic solvent, the water soluble amine is present in an
amount sufficient to provide an aqueous phase pH of about
7.1 to about 8.5, and said water or mixture of water and
organic solvent constitutes about 50 to about 65% by weight
o the paint.
The improvement is that the aqueous dispersion is
produced essentially free of organic solvents by intimately
dispersing with the water, the amino resin cross-linking agent
and the water soluble amine: I. an aqueous emulsion consisting
essentially of water, water-soluble amine, and about 50 to
about 95 parts by weight of an emulsion polymer having
functionality selected from carboxy functionality and hydroxy
functionality and is a copolymer of acrylic monomers that:
(a) is essentially insoluble in the aqueous solution; (b)
has average molecular weight (Mn) in the range of about 3,000
to about 20,000, and (c) has Tg in the range of -15C to
50C and II. about 5 to about 50 parts by weight of a sol-
ution polymer which is a carboxy functional copolymer of
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IJ
1~)67Z32
acrylic monomers th~t: (a) is at ].east partially neutralized
with water-soluble amine. (b) is soluble in the aqueous
solution; (c) has average molecular weight (Mn) in the range
of about 3,000 to about 20,000, (d) has Tg in the range of
-15C to 50C,and (e) has been prepared by emulsion poly-
merization in water of about 5 to about 25 mole percent of
an alpha-beta olefinically unsaturated monocarboxylic acid
selected from acrylic and methacrylic acid and 75 to 95 mole
percent of other monoethylenically unsaturated monomers
consisting of monomers selected from the group consisting
of monoacrylates, monomethacrylates and monovinyl
- 3a -
~3
1(;~67Z32
hydrocarbons at a temperature between about 45~C. and the
reflux temperature of the reaction mixture and subsequently
at least partially neutralized with water-soluble amine in the
water in which it is formed, the amino resin cross-linking
agent being present in an amount in the range of about 15
to about 35 weight percent of the sum of the weights of
the solution polymer and the emulsion polymer.
The term "parts" when used herein without further
designation shall mean "parts by weight".
The term "acrylic monomer" shall mean acrylic
acid, methacrylic acid, esters of acrylic acid and a
Cl - C8 monohydric alcohol, e.g., ethyl acrylate butyl
acrylate, hexyl acrylate and 2-ethylhexyl acrylate, esters
of methacrylic acid and a Cl - C8 monohydric alcohol, e.g.,
methyl methacrylate, butyl methacrylate, hexyl methacrylate
and 2-ethylhexyl methacrylate, hydroxyalkYl acrylates, e.g.,
hydroxyethyl acrylate and hydroxypropyl acrylate,
hydroxyalkyl methacrylates, e.g., hydroxyethyl methacrylate
and hydroxypropyl methacrylate, acrylamide, methacrylamide,
methylolacrylamides, e.g., n-methylolacrylamide, methylol-
methacrylamides, e.g., N-methylDlmethacrylamide, alkyl ethers of
methylolacrylamides, e.g., N-isobutoxymethylolacrylamide, and
alkyl ethers of methylolmethacrylamides, e.g., N-isobutoxy-
methylolmethacrylamide.
The term "copolymer of acrylic monomers" shall
mean a polymer of at least two different monoethylenically
unsaturated monomers of which more than S0 mole percent are
acrylic monomers.
The hybrid, water-based, paint compositions formed in
this invention employ in combination a low molecular weight
emulsion polymer and a low molecular weight solution polymer
)6~232
with the latter being present in an ~mount sufficient to
contribute significantly to the composition of the polymeric
binder, i.e., at least about 5 weight percent of this
polymeric combination. Thus, they differ from the conventional
emulsion type paints employing a water-soluble thickener
polymer in at least three compositional respects irrespective
of chemical functionality, namely (1) the emulsion polymers
of the instant paints have significantly lower molecular
weights, (2) the solution polymers of the instant paints
have significantly lower molecular weights, and (3) the
solution polymers of the instant paints are employed in
significantly higher concentrations than are the water-soluble
thickener polymers.
More specifically, the hybrid paint compositions
formed in this invention, exclusive of optional components
such as pigments, particulate fillers and catalysts, have a
liquid continuous aqueous phase. About 30 to about 50% by
weight of this phase, exclusive of the aforecited optional
components, is made up of a mixture of (a) an amino resin
cross-linking agent; (b) a mixture of at least two copolymers
of acrylic monomers; and (c) an amine. The balance is water
or, in certain embodiments, water and an organic solvent.
The mixture of copolymers preferably comprises about 10 to
about 30 parts by weight of the solution polymer and about 60
to about 90 parts by weight of the emulsion polymer. The
amine is a water-soluble amine and is present in an amount
sufficient to solubilize the solution polymer in the aqueous
phase at a pH range of about 7.1 to about 8.5.
When applied to the substrate to be coated by
spraying, these water-based paints including pigments,
particulate fillers, and catalysts, if any, contain between
about 50 and about 65% by weight water or in those embodiments
wherein such solvents are used, water and organic cosolvents.
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In the present invention both the solution polymer
i and the emulsion polymer are prepared by emulsioll polymerization
in water. The paints thus prepared are prepared without
organic solvents and thus employed free of same. Organic
solvents may be added to the dispersion, if desired, preferably
in the range of about 10 to about 20 volume percent of the
volatile phase. In carrying out one or both, preferably both,
of the emulsion polymerizations the surfactant may be
replaced by a solution polymer, as claimed in our copending
Canadian application Serial No. 251,35~ filed concurrently
herewith.
The solution polymer used to form the paints in
this invention has carboxy functionality and may also have
hydroxy functionality and/or amide functionality. These
polymers usually contain about 5 to about 30 mole percent
-
of acrylic or methacrylic acid and 70 to 95 mole percent of
olefinically unsaturated monomers copolymerizable with such
acid component. Preferably, these other olefinically
unsaturated monomers are monoacrylates or monomethacrylates.
In the embodiment wherein the primary solution polymer has only
carboxy functionality, these are preferably esters of acrylic
acid or methacrylic acid and a Cl - C8 monohydric alcohol.
C8 ~ C12 monovinyl hydrocarbons such as styrene, alpha methyl
styrene, t-butyl styrene, and vinyl toluene may comprise up
to about 30 mole percent of such polymer. Vinyl monomers
such as vinyl chloride, acrylonitrile, methacrylonitrile and
vinyl acetate may be included in the copolymer as modifying
monomers. However, when employed, these modifying monomers
should constitute only between about 0 and about 30,
preferably 0 to 15, mole percent of such polymer. In the
embodiment wherein the solution polymer has both carboxy
functionality and hydroxy functionality, the copolymer
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usually contains about 5 to about 25 mole percent of acrylic
or methacrylic acid, about 5 to about 25 mole percent of a
hydroxyalkylacrylate or methacrylate, e.g., hydroxylethyl
acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate or
hydroxypropyl methacrylate, and a remainder of the same
monofunctional monomers as set forth above for the solely
carboxy-functional polymer. In still another embodiment, the
polymer has amide functionality in addition to carboxy
functionality. Such a polymer usually contains about 5 to
about 25 mole percent acrylic acid or methacrylic acid, about
5 to about 25 mole percent of acrylamide, methacrylamide,
N-methylolacrylamide, N-methylolmethacrylamide, or the alkyl
ether or a methylolacrylamide or a methylolmethacrylamide,
e.g., N-isobutoxymethylolacrylamide, with the remainder of
the same monofunctional monomers as set forth above for the
solely carboxy-functional polymer~ A portion of the amide
functional monomer may be replaced with an equimolar amount of
one of the aforementioned hydroxyacrylates or hydroxymeth-
acrylates.
Other monomers not heretofore mentioned may be used
in these polymers if used in limited concentrations. These
include 2-acrylamido-2-methylpropanesulfonic acid and
methacryloyloxyethylphosphate, which may comprise up to
about 3~ of such polymer.
The emsulsion polymer used to form the paints in
this invention has carboxy functionality, hydroxy functionality
or carboxy and hydroxy functionality. These polymers
contain 0 to 15 mole percent acrylic acid or methacrylic acid,
preferably 0 to 10 mole percent, and 85 to 100 mole percent
of other olefinically unsaturated monomers ~hat are copoly-
merizable with each other and with the acid component when
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the latter is used. Such other olefinically unsaturated
monomers are the same in type and of the same percentage dis-
tribution range as those heretofore disclosed for the solution
polymer with the exception of the acid monomer content above
noted.
In those embodiments, wherein both the solution
polymer and the emulsion polymer have hydroxy functionaltiy
and carboxy functionality, it is preferred to have a greater
concentration of carboxy functionality on the solution
polymer relative to the emulsion polymer and a greater con-
centration of the hydroxy functionality on the emulsion
polymer relative to the solution polymer.
Thus, the combinations involved include (a) a
carboxy-functional solution polymer and a hydroxy-functional
emulsion polymer, (b) a carboxy-functional solution polymer
and a carboxy-functional emulsion polymer, (c) a carboxy-
functional solution polymer and a carboxy-functional, hydroxy-
functional emulsion polymer, (d) a carboxy-functional and
hydroxy-functional solution polymer and a hydroxy-functional
emulsion polymer, (e) a carboxy-functional, hydroxy-functional
solution polymer and a carboxy-functional and hydroxy-
functional emulsion polymer, (f) a carboxy-functional and
amide-functional solution polymer and a hydroxy-functional
emulsion polymer, (g) a carboxy-functional and amide-
functional solution polymer and a carboxy-functional emulsion
polymer, (h) a carboxy-functional and amide-functional
solution polymer and a carboxy-functional and hydroxy-
functional emulsion polymer, (i) a carboxy-functional,
hydroxy-functional, and amide-functional solution polymer and
a hydroxy-functional emulsion polymer, (j) a carboxy-
functional, hydroxy-functional, amide-functional solution
1067Z3;~
polymer and a carboxy-functional emulsion polymer, and (k)
a carboxy-functional, hydroxy-functional, amide-functional
solution polymer and a carboxy-functional, hydroxy-functional
emulsion polymer. Amide functionality may also be incorporated
into the emulsion polymer but this is more difficult to achieve
efficiently than in the solution polymer, particularly in the
case of modified amide functionality, e.g., N-methylol-
acrylamide.
The amino resin cross-link~ng agent, may be and
is hereafter illustrated as a conventional amino resin
cross-linking agent o~ the type long in use as a cross-linking
agent in acrylic enamels, e.g., melamine-formaldehyde resins
and urea-formaldehyde resins.
In the formation of water-based paints, in accor-
dance with this invention, the following procedure may be
adopted.
In the preparation of the solution polymer
emulsion polymerization is used. The functional monomers
are mixed and reacted by conventional free-radical initiated
polymerization in aqueous emulsion to obtain the copolymer
desired. The resulting acid-functional copolymer latex is
converted to a polymer solution by the addition of an
appropriate base, usually ammonia or an organic amine.
Conventional surfactants, chain transfer agents, and
initiators are employed in the emulsion polymerization. The
monomer charge is usually emulsified by one or more micelle-
forming compounds composed of a hydrophobic part, such as a
hydrocarbon group containing six or more carbon atoms, and a
hydrophilic part, such as hydroxyl group, alkali metal or
ammonium carboxylate groups, phosphate or sulfate partial
ester groups, sulfonate groups, or a polyether chain.
_ g _
1~67232
Exemplary emulsifying agents include alkali metal sulfonates
of styrene, naphthalene, decyl benzene and dodecyl benzene;
sodium dodecyl sulfate; sodium stearate; sodium oleate, the
sodium alkyl aryl polyether or sulfates and phosphates; the
ethylene oxide condensates of long chain fatty acids, alcohols,
and mercaptans, and the alkali metal salts of rosin acids.
These materials and the techniques of their employment in
emulsion formation and maintenance are well known in the art.
When emulsion polymerization is used to produce a solution
polymer, there is no need for the resulting latex to be
stable under conditions different from those ensuing at the
end of the polymerization process since the latex no longer
exists as such after the polymer goes into solution upon
neutralization. To facilitate such conversion to solution
polymers, polymers prepared by emulsion polymerization for
use as a solution polymer ordinarily contain a higher concen-
tration of carboxyl groups and a lower concentration of
decidedly hydrophobic monomers, e.g., 2-ethylhexyl acrylate,
relative to the corresponding concentrations in the polymers
prepared for use as emulsion polymers. Further, when
preparing the latter, an alkali metal or ammonium persulfate
is used either as the sole polymerization initiator or as one
constituent of a mixed initiator system to avoid coagulum
formation through time and under a variety of pH conditions,
solvent environment, etc. Such initiators may be used when
preparing the solution polymer by emulsion polymerization but
conventional peroxide initiators are quite suitable for this.
Hence, this method offers an advantage, in this respect, in
that the concentration of ionic inorganic contaminants, e.g.,
s~lfate ions, in the paint formulation is reduced. A chain
trar,sfer agent or mixture of chain transfer agents may be
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1067232
added to the reaction medium to limit the molecular weight
of the polymer, such chain transfer agents are generally
mercaptans such as dodecanethiol, benzenethiol, l-octanethiol,
pentanethiol and butanethiol. These are conventional
materials employed in a conventional manner. The polymeriza-
tion initiator is composed of one or more water-soluble, free-
radical-generating species such as hydrogen peroxide or the
sodium, potassium or ammonium persulfates, perborates,
peracetates, percarbonates and the like. As is well known
in the art, these initiators may be associated with
activating systems such as redox system which may incorporate
mild reducing agents, such as sulfites and thiosulfites and
redox reaction promoters such as transition metal ions.
However, it is desirable to maintain a low concentration of
non-polymeric ionic species in the finished paint formulation
in order that the cured paint film may have optimum resistance
to water. Hence, it is preferred to use a minimum concentra-
tion of such optional inorganic salts as ferrous sulfate,
sodium bisulfite, and the like. Those skilled in the art
will be aware that other emulsifying agents, polymerization
initiators and chain transfer agents may be used which are
compatible with the polymerization system herein required
and with the attainment of acceptable cured paint film
properties.
The polymerization is carried out at a temperature
between about 45C and the reflux temperature of the reaction
mixture.
The resultant acid-functional copolymer latex is
converted to a polymer solution by the addition of an
appropriate base, usually ammonia or an organic amine.
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In preparing ~he emulsion copolymer, the functional
monomers are mixed and reacted by conventional free-radical
initiated polymerization in aqueous emulsion to obtain the
copolymer desired.
Conventional surfactants, chain transfer agents,
and initiators are employed in the emulsion polymerization.
The monomer charge is usually emulsified by one or more
micelle-forming compounds composed of a hydrophobic part,
such as a hydrocarbon group containing six or more carbon
atoms, and a hydrophilic part, such as hydroxyl groups,
alkali metal, ammonium carboxylate groups, sulfonate groupsr
phosphate or sulfate partial ester groups, or a polyether
chain. Exemplary emulsifying agents include alkali metal
sulfonates of styrene, naphthalene, decyl benzene, and dodecyl
benzene; sodium dodecyl sulfate; sodium stearate; sodium
oleate; the sodium alkyl aryl polyether sulfates and phos-
phates; the ethylene oxide condensates of long chain fatty
acids, alcohols, and mercaptans, and the alkali metal salts
of rosin acids. These materials and the techniques of their
employment in emulsion formation and maintenance are well
known in the art. A chain transfer agent or mixture of chain
transfer agents may be added to the reaction medium to limit
the molecular weight of the copolymer; such chain trans~er
agents are generally mercaptans such as dodecanethiol,
benzenethiol, l-octanethiol, pentanethiol, and butanethiol.
These are conventional materials and are employed in a
conventional manner. The polymerization initiator is composed
of one or more water-soluble, free-radical-generating species
such as hydrogen peroxide or the sodium, potassium, or
ammonium persulfates, perborates, peracetates, percarbonates
and the like. The polymerization is carried out at a
1~6723Z
tomperature between about 45C. and the reflux temperature of
the reaction mixture. As is well known in the art, these
initiators may be associated with activating systems such
as redox systems which may incorporate mild reducing agents,
such as sulfites and thiosulfites, and redox reaction
promoters such as transition metal ions, and that these allow
the polymerization to be carried out at a lower temperature,
e.g., 0C or below. As, however, it is desirable to maintain
a low concentration of non-polymeric ionic species in the
finished paint formulation in order that the cured paint film
may have optimum resistance to water, it is preferred to use
a minimum concentration of such optional inorganic salts
as ferrous sulfate, sodium bisulfite, and the like.
Those skilled in the art will be aware that other
emulsifying agents, polymerization initiators and chain
transfer agents may be used which are compatible with the
polymerization system herein required and with the attainment
of acceptable cured paint film properties.
There are different needs involved in the after-
preparation employment of the emulsion polymer that is used as
such in formulation of paint and the solution polymer which
although prepared by emulsion polymerization is subsequently
converted as described above to a solution polymer and used
as such. These needs should be taken into consideration in
the preparation procedure.
In the use of emulsion polymerization to produce
a solution polymer, there is no need for the resulting latex
to be stable under conditions different from those ensuing
at the end of the polymerization process since the latex no
longer exists, as such, after the polymer goes into solution
upon neutralization. To facilitate such conversion to solution
polymers, polymers prepared by emulsion polymerization for
~067Z32
use as solution polymers ordinarily contain a higher
concentration of carboxyl groups and a lower concentration
of decidedly hydrophobic monomers, e.g., 2-ethylhexyl acrylate,
relative to the corresponding concentrations in the polymers
prepared by emulsion polymerization for use as such.
In contrast, latices which are used as such in
the formulation of paint are required to remain essentially
as stable latices throughout the processes of polymerization,
paint formulation, and product distribution and use. This
implies a requirement of stability, i.e., freedom from
coagulum formation through time and under a variety of pH
conditions, solvent environment, etc. These requirements
are best met, and hence it is preferred to use, an alkali
metal or ammonium persulfate either as the sole polymerization
initiator, or as one constituent of a mixed initiator system.
In those embodiments in which conventional surfactants are
used, it is pre~erred to use a plurality of surfactants, more
specifically a combination of anionic and nonionic surfactants,
to obtain a more stable latex. Such surfactant mixtures are
well known in the art.
The polymer solution and the polymer latex
prepared according to the aforedescribed procedures are
subsequently converted into a paint using conventional
paint formulation techniques. Typically, a mill base is
prepared which comprises the bulk of the pigment and/or
particulate filler of the paint formulation. The mill base
is "let down" i.e., blended with the remaining polymeric
and liquid constituents of the final formulation. A mill
base, prepared by conventional sand grinding, ball milling,
3~ or pebble milling generally comprises all or a part of the
water soluble resin, pigments, organic cosolvents, and may
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1067Z32
also comprise a quantity of amine in excess of that required
to solubilize the solution polymer. To complete the paint,
the polymer latex which has been neutralized to a pH range
of 5.0 to 10, preferably 5 to 9, is added with mild agitation
to the balance of the water required in the total formulation.
The balance of the water-soluble resin, cross-linking agent,
and mi11 ~ase are added slowly with agitation. Additional
quantities of pigment may ~e added subsequently as slurries
in organic solvents or as separate mill bases to adjust the
colour as desired. The viscosity of the finished paint is
determined and adjusted as required to obtain desired
application properties.
Alternately, all or a portion of the (preferably
neutralized) polymer latex, water, organic cosolvent, and
amine may be added to the solution polymer and pigments
prior to ball milling, sand grinding, or pebble milling.
This procedure is advantageously employed to reduce the
viscosity of mill bases prepared using the solution polymers
of relatively high molecular weight.
Organic amines are used to neutralize carboxyl
groups on the solution polymer and hence to render it soluble
in the aqueous dispersion. They are also used to maintain
the pH of the finished paint formulation above about 7, e.g.,
in the range of 7 to 10, preferably between 7 and 9.5, and
with certain pigments such as aluminum flakes preferably
between 7 and 9, to prevent premature reaction of the
functional groups on the acrylic copolymer with the amino
resin cross-linking agent. Those skilled in the art will be
aware that in certain embodiments the paint dispersion can
be made up at a pH outside the pH range for application and
later adjusted to the desired p~ shortly before it is applied.
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A portion of the amine, e.g., preferably between about 60 and
100% of the amount chemically equivalent to the carboxyl
functionality of the polymer is added to the solution polymer
directly. Advangageously, a small additional portion of amine
is used to raise the pH of the emulsion polymer to about 5 to
about 10, preferably 5 to 9, prior to finishing the paint
formulation so that tbe mill base is not subjected to the low
pH environment of the polymer latex (pH about 2.5).
Suitable amines are amines (1) which are soluble in
the aqueous medium of the paint, (2) that ionize sufficiently
in such aqueous medium to solubilize the solution polymer,
(3) that ionize sufficiently in such aqueous medium when
employed in suitable amounts to provide the paint dispersion
with a pH of at least about 7, preferably 7.2 or higher, and
thereby keep the rate of reaction between reactive groups of -~
the amino resin (cross-linking agent) negligible prior to
curing, and (4) that allow for rapid curing of the enamel
upon heating. Suitable amines include alkyl, alkanol and aryl
primary, secondary and tertiary amines. Preferred are secon-
dary and tertiaryalkyl and alkanol amines having a boiling
point within the range of 80 to 200C. By way of example,
these include N,N-dimethyl ethanolamine, N,N-diethylethanol-
amine, isopropanolamine, morpholine, N-methylmorpholine,
N-ethylmorpholine, N-methylethanolamine, 2,6-dimethylmorpholine,
methoxypropylamine, and 2-amino-2-methyl-1-propanol.
Catalysts for the curing of resins described herein
are not normally required to obtain satisfactory film
properties. If desired, however, for purposes of lowering
the film baking temperature or of further improving cured
film properties, strong acid catalysts can be employed in an
amount not in excess of 3% by weight of the total finished
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paint formulation. Said strong acid catalysts may be
introduced either as copolymerizable species incorporated
in one or both acrylic copolymers, e.g., 2-acrylamide-2-
methylpropanesulfonic acid, or as a non-polymerizable
additive, e.g., p-toluenesulfonic acid. It is generally
preferred not to add such catalysts, however, as they may
tend to increase the water sensitivity of the cured film and
may deleteriously affect storage stability of the liquid paint.
This invention will be more fully understood from
the following illustrative examples:
EXAMPLE I
Step I P~paration of the Solution Polymer
- An acrylic copolymer soluble in the aaeous phase
of the water-based paint of which it later becomes a
part is prepared from the following materials in the manner
hereinafter described: ~~
Materials Parts by Weight
methyl methacrylate 45.0
methacrylic acid 15.0
butylacrylate 40.0
water go.o
"TRITON" (Trade Mark) X-200(1) 1.15
Triton X-305( ) 3.58
Potassium persulfate 0.4
l-octanethiol 1.5
Reactor Charge
water 60.0
Triton X-200( ) 1.67
potassium persulfate 0.1
(1) an anionic surfactant containing 28% active component
described as the sodium salt of an alkyl aryl polyether
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,ulfonate and solid by Rohm and EIaas Company.
(2) a nonionic surfactant containing 70% active
component described as an alkylaryl polyether alcohol averaging
30 ethylene oxide units per molecule and sold by Rohm and
Hass Company.
The reactor charge is heated quickly to boiling and
cooled to 95C. A monomer emulsion is formed from the above
by mixing and stirring. The monomer emulsion is added to the
hot reactor charge over a two-hour period. The temperature
is maintained at 90 + 5C throughout the monomer addition
period and for two hours after addition is complete. The
2-(dimethylamino)ethanol is added in an amount equivalent to
the acid monomer incorporated in the polymer and the solids
content is reduced with water to 30~ by weight. The polymer
(Mn) is about 5,000 and the Tg is calculated to be 25C.
Step II Pre~aration of the Emulsion Polymer
An emulsion polymer is prepared following the
procedure of Step I from the following reactant monomers,
initiator and chain transfer agent.
Materials Parts by Weight
methyl methacrylate48.0
methacrylic acid 7.0
ethyl acrylate 35.0
butyl acrylate 10.0
l-octanethiol 0.4
t-butylperoctoate 3.5
The average molecular weight of this copolymer is
about 10,000 and it has a Tg of about 40C.
Step III Formulation of Paint (free of organic solvent)
A mill base is prepared by pebble milling together
the following materials:
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~ 106723Z
MaterialsParts by Weight
polymer solution from Step I 18.4
"CYMEL" (Trade ~lark) 300(1) 6.7
titanium dioxide pigment 16.5
water 8.3
(I) a commercial grade of hexamethoxymeth~ylmelamine
- sold by American Cyanamid Company.
An enamel is formulated by blending together the
following materials:
Materials Parts by Weight
latex from Step II 46.0
10~ a~ueous 2-(dimethylamino)ethanol 3.3
10% aqueous p-toluene sulfonic acid 0.8
(neutralized with 2-(dimethylamino)
ethanol
mill base 49.9
The viscosity of the paint is adjusted to 17-20
seconds (No. 4 Ford Cup), and sprayed on primed steel panels.
- The panels are baked 25 minutes. The baking temperature at
the beginning is 80C. This is increased gradually to 180C
and maintained at 180C over a ten-minute period. The resultant
panels have a coating of excellent gloss and organic so]vent
resistance (one minute xylene exposure). Appearance and
hardness do not noticeably change when water soaked at 32C.
EXAMPLE II
The procedures of Example I are repeated with the
following differences: (1) the reactant monomers and the
chain transfer agent used in the monomer emulsion of Step II
are as follows:
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B
~067232
Reactant Monomers and Chain Parts by Weight
Transfer Agent
methyl methacrylate 49.0
methacrylic acid 5.0
butyl acrylate 30.0
ethyl acrylate 16.0
l-octanethiol 0.1
and ~2) the reactor charge is heated up to 55 + 5C with
nitrogen purging. The emulsifie~ monomers are added for a
period of four hours. Reaction is continued for another two
hours with the temperature maintained at 55 + 5C. The
latex thus obtained is cooled, filtered, and used in the
formulation of a water-based enamel as in Example I.
EXAMPLE III
. .
A series of water dilutable polymers are prepared
as in Step I of Example I and employed in place of the
water dilutable polymer of Step I, Example I in the water-
based paint described in Example I. The procedures of prepar-
ation are the same as used in Step I of Example I. The
materials employed in preparing these "solution polymers" and
the molecular weights and glass transition temperatures of
the resultant copolymers are set forth below:
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` lQ67Z32
Materials Polymer Designation
A B C D E
styrene 25
methyl methacrylate 50 45 35 35
methacrylic acid 10 15 15 15 15
butyl acrylate 30 25 40 50 50
ethyl acrylate 10
butyl methacrylate 35
Triton X-200 2.8 2.8
Triton X-305 3.6 3.6 3.6 3.6 . 3.6
Aerosol 22( ) 2.4 2.4 2.4
l-octanethiol 1 1.5 2 1.5
Properties of Polymer
(Mn) 7500 5400 4000 5400 7500 !
Tg, C -8 16 25 8 8
(I) Aerosol 22 is a product of American Cyanamlc
Comp.any.
EXAMPLE IV
A series of emulsion polymers are prepared as in
Step II of Example I and employed in place of the emulsion
polymer of Step II, Example I. The procedures are the
same as used in Step II of Example I. The materials employed
in preparing these "emulsion polymers" and the molecular
weights and glass transition temperatures of the resultant
copolymers are set forth in the following Table:
106723Z
a~ ~D 00
H N ,~ ~ ~ O O
~ ~ In
N ,~ U) ~I N ~ O o U~
a~ ~D 1`
C~ O O O CO N ~ O ~
o~ .
O ' E4 11~ 0 N ~ O O U~
H 0
~D ~
. O t~ O ~ N ~ O O N
P
14 ~ O t~ ~ It~ ~1 ~ O O
. ~
C~ N N N ~r o N
U~
~`7
. ~D 'I
m "~ O u~ o ~) N ~ o ~
I`
N N N N o ~
u
o
U~ o;
o ~ o
~ O O rl
IJ rl 0 ~ ~ O rl N t~)
~ h ~3 1 I N
:E: ~ ~ ~ Q. ~d X X
o ~ o o
h ~ ~ ~ O
-- 22 --
1067232
~XAMPLE V
~ater-based enamel is prepared by mixing the follow-
ing materials:
Mate-ials Parts by Weight
Mill base (prepared by
pebble milling)
polymer (solution polymer)18.8
from Step I, Example I
Cymel 300(I) 4.6
10 . titanium dioxide pigment16.~
water 7~3
(1) defined in Example I.
Other materials (to let down)
... . . ~
polymer (emulsion polymer from 47.0
Example II
i 10% aqueous 2(dimethylamino)ethanol 4.4
- 10% aqueous p-toluene sulfonic acid 1.0
(neutralized with 2-(dimethylamino)
ethanol)
The above enamel is sprayed on primed steel panels
and baked for 25 minutes. The initial temperature of the
bake is 80C and this is raised gradually to 180C where
the latter temperature is maintained for 10 minutes. The
appearance of the baked panel and the properties of the baked
coating are essentially the same as those obtained in
Example I.
EXAMPLE VI
A water-based enamel is prepared by mixing the
following materials:
- 23 -
1067Z32
Mill Base (Prepared bv ball millin~) Parts bY Weight
polymer "D" of Example III (solution 18.5
polymer)
Cymel 301 ) 7.6
titanium dioxide pigment 16.5
water 8.4
Other Materials (to let down)
polymer "G" of Example IV (emulsion 46.1
polymer
10% aqueous 2-(dimethylamino)ethanol 2.9
(1) a product of American Cyanamid Company, and
a commercial grade of hexamethoxymethylmelamine.
This enamel is adjusted to a viscosity of 17-20
seconds (No. 4 Ford Cup), by adding water and sprayed over
primed steel panels. The coated steel panels are baked at
160C for 25 minutes. The baked coatings exhibit good gloss,
good solvent resistance and retained their gloss and hardness
after soaking in water at 32C for 240 hours.
EXAMPLE VII
_ _ _
A water-based enamel is prepared by mixing the
- following materials:
Mill Base (pre~ared by ball milling) Parts by Weight
polymer "A" of Example III (solution 14.8
polymer~
Cymel 300(1) 4.5
titanium dioxide pigment 17.7
water 9
Other Materials (to let down)
polymer "A" of Example IV (emulsion 49.4
polymer)
10% aqueous 2(dimethylamino)ethanol 3.6
10% aqueous p-toluene sulfonic acid 11
(1) defined in Example I
- 24 -
106~232
This enamel is adjusted to a viscosity of 20
seconds (No. 4 Ford Cup) by adding water, and sprayed over
primed steel panels. These coatings are baked for 25 minutes.
The initial baking temperature is 80C and this is gradually
raised to 180C where it is maintained for at least 10
minutes. These coatings exhibit good physical properties.
EXAMPLE VIII
A water-based enamel is prepared by mixing the
following materials:
Mill Base (prepared by ball milling) Parts by Weight
Polymer "B" of Example III (solution 12.4
polymer)
titanium dioxide pigment 16.3
Cymel 301(1) 8.3
water 8.3
(1) defined in Example VI.
Other Materials (to let down)
Polymer "IN of Example IV (emulsion 45.6
polymer)
10% 2-(dimethylamino)ethanol9.1
This enamel is adjusted to a viscosity of 20
seconds (No. 4 Ford Cup) by adding water and sprayed on
primed steel panels. The coated panels are baked at 160C
- for 25 minutes. The coatings thus obtained exhibit excellent
gloss 80 at 20 and good solvent resistance.
- 25 -
