Note: Descriptions are shown in the official language in which they were submitted.
CA 02384180 2002-02-06
,l.'~~
~ A2t~u
Lv~
NONIONIC ASSOCIATIVE THICKENER COMPOSITION WITH IMPROVED
VISCOSITY RETENTION UPON TINTING IN ARCHITECTURAL LATEX COATING
BACKGROUND TO THE INVENTION
1. Technical Field
The present invention relates to a water soluble copolymer composition
containing a
linear aminoplast-ether copolymer possessing a relatively high content of the
hydrophobe
tristyryl phenol. Such a copolymer contains a unit of the formula:
(RO)P (Rp2)q
Amp----Roy
a
wherein the divalent Ro, contains a divalent alkyleneoxy containing moiety,
Amp is the skeletal
residue of an aminoplast, R is hydrogen, alkyl containing 1 to about 4 carbon
atoms, or acyl
containing 1 to about 4 carbon atoms, RO is bonded to alkylene units of Amp,
and a is a number
greater than 1, preferably greater than 2. Amp includes any dimer and oligomer
component of
the aminoplast. Ro2 is tristyryl phenol, that is covalently bonded to Amp
through a heteroatom, p
is number that is equal to the free valence of Amp minus (2 + q), and q is a
positive number
2. Background
Nonionic associative thickeners have been used in latex architectural coatings
for nearly
20 years. They-have replaced the traditional cellulosic thickeners because
coatings that utilize
nonionic associative thickeners exhibit improved application properties such
as brush drag, flow
and leveling, and water sensitivity. The term "associative thickener" is
recognized in the art to
mean a nonionic hydrophobically modified water-soluble polymer capable of
interacting in
aqueous solution with itself and with other species such as latex particles.
Associative thickeners
are widely used to enhance the performance properties of paints and coatings.
The use of
associative thickeners in water based compositions are described in a
1
f~I~~f t~~~y'~ w''~'~~
a
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numberofpatents, including U.S. Patent Nos. 5,574,127, 4,426,485, 4,155,892,
4,079,028; 3,035,004;
2,795,564; 2,875,166 and 3,037,952.
One type of associative thickener is described by the two Emmons et al.
patents, U.S. Pat. No.
4,079,028 and U.S. Pat. No. 4,155,892, patented Mar. 14,1978 and May 22,1979,
respectively. These
patents describe polyurethane associative thickeners that contain hydrophobic
groups interconnected by
hydrophilic polyether groups. The thickeners are nonionic.
Another type of associative thickener is described in US Patent Nos. 5,627,232
and 5,629,373
issued on May 6, 1997 and May 13, 1997 respectively. These patents describe
water-based coating
compositions containing a water soluble linear aminoplast-ether copolymer
containing aminoplast segments
interlinked through ether segments. Aminoplasts are defined in those patents,
and herein, and in the claims,
as an A-stage class of thermosetting resin based on the reaction of an amine
with an aldehyde and the
related acetals containing amines or amides. The structural features and
commercial uses of aminoplasts
are also described in detail in those patents. Figure 1 contains a partial
list of aminoplasts.
Fig 1.
R0' ~OR
\\N N OR O OR
O~\ ~O
N N N N
RO OR RO OR
RO OR
OR
Rod ~ ~ RO~N NOR
n~ x
O
OR OR
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US Patent Nos.5,627,232 and 5,629,373 describes a linear aminoplast-ether
copolymer with
the formula as described in Fig 2.
(RO)p
Fig 2.
gyp- R~ ~
a
where the divalent R~, contains a divalent alkyleneoxy containing moiety, Amp
is the skeletal residue of an
aminoplast, R is hydrogen, alkyl containing 1 to about 4 carbon atoms, or acyl
containing 1 to about 4
carbon atoms, p is a positive number that is equal to the free valence of Amp
minus 2, RO is bonded to
alkylene units of Amp, and a is a number greater than 1.
For the purposes of this invention and the discussion of the prior art, the
skeletal unit of the
aminoplast is the structure of the aminoplast minus the ROleaving groups
bonded to alkylene ofthe
alkylol or alkylol ether or ester of the aminoplast, regardless of whether any
of the ROgroups are
removed from the aminoplast. That skeletal unit is referred to herein and in
the claims as "Amp."
The term "linear," when used herein and in the claims to characterize a
polymer, relates to a
polymer that is devoid of crosslinking or branching that renders the polymer
solid and cured. A "wholly
linear" polymer is apolymer that is devoid of crosslinkinQ and branching. A
linearpolymermay ormaynot
be a wholly linear polymer.
The term "acrylic polymer" means any polymer wherein at least 50% by weight is
an acrylic or
methacrylic acid or ester, including mixtures of such acids and esters
individually and together. The term
"vinyl acetate polymer" means any polymer containing at least 50% by weight of
vinyl acetate.
The symbols and designations used herein are intended to be consistently
applied, especially as
used in formulations and equations, unless specifically stated otherwise.
Typical nonionic associative
thickeners have had only limited success when used in latex coatings for the
mid to neutral base
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formulations based on small particle size acrylics. The problem arises when
colorants are added to said
formulations. The addition of colorant in the amounts of about ~ ounces or
above results in a substantial
reduction in the viscosity of the coating. This reduction in viscosity leads
to undesirable coating properties
and has been addressed by architectural coating manufacturers in a number of
ways.
One method manufacturers have used is to compensate for the viscosity drop
that occurs upon
tinting. The coating is formulated to have a very high viscosity before the
colorant is added. The colorant
is added expecting that the viscosity of the coating drop to an acceptable
level. Another method that
manufacturers have used is to incorporate large amounts of surfactants and
solvents into the coating to
control the viscosity drop upon tinting. Still yet another method used by
manufacturers is to incorporate
other thickening agents such as cellulosics and alkai-swellable thickeners to
compensate for the viscosity
drop. While these methods do address the viscosity problem, each of these
corrective methods has
problems associated with them that make their use less than ideal.
The problem with formulating a pre-tinted coating with a very high viscosity
is that it creates
problems in the manufacturing process. The problem with additives such as
surfactants and solvents, or
cellulosics and alkai-swellable thickeners is that it compromises the
application properties of the resulting
coating. The additives can also cause problems with the physical properties of
the final dried paint filin.
For example, high levels of surfactants or the use of alkai-swellable
thickeners can lead to water sensitivity
or poor scrub resistance
What is needed is a nonionic associative thickener that can be used in latex
coatings for the mid
to neutral base formulations based on small particle size acrylics that
results in minimal reduction in viscosity
when the colorant is added.
What is needed is a nonionic associative thickener that can be used in latex
coatings ofthe mid to
neutral base formulations based on small particle size acrylics that does not
need the addition of surfactants
and solvents, or other thickening agents to achieve a satisfactory viscosity
when the colorant is added.
What is needed is a nonionic associative thickener that can be used in latex
coatings for the mid
to neutral base formulations based on small particle size acrylics that
maintains desirable
4
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A ~ ~'~,U111'
application properties when the colorant is added without compromising the
final film properties.
Summary of the Invention
The present invention relates to a water soluble copolymer composition
containing a linear
aminoplast-ether copolymer possessing a relatively high content of the
hydrophobe tristyryl
phenol. Such a copolymer contains a unit of the formula:
(RD)p (Rp2)q
Amp----Ray
a
I.
wherein
---,,,
the divalent Roy contains a divalent alkyleneoxy containing moiety, Amp is the
skeletal residue of
an aminoplast, R is defined above, RO is bonded to alkylene units of Amp, and
a is a number
greater than 1, preferably greater than 2. Amp includes any dimer and oligomer
component of
the aminoplast. Ro2 is tristyryl phenol, that is covalently bonded to Amp
through a heteroatom, p
is number that is equal to the free valence of Amp minus (2+ q), and q is a
positive number. The
relatively high content of the hydrophobe means a copolymer that contains more
than about 3%
tristyryl phenol based on weight. In the preferred embodiment, the copolymer
contains about
4% tristyryl phenol to about 10% tristyryl phenol based on weight when the
polymer is produced
using polyethylene oxide and a glycoluril compound.
In another embodiment of the invention, the -invention relates to a novel
water-based
4
coating composition that contains a linear aminoplast-ether copolymer
possessing end groups
characterized by a component of the units making up the copolymer, or a
monofunctional group
that effectively end-caps the copolymer, forming the end group. This yields a
copolymer of the
formula:
A~,~~~~~D SHEET
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(RO)p (R°?)q
II.
00 gyp- R°' Roo
a
where each R"" is the same or different terminal group, such as hydrogen,
R~,H, Amp bonded
(OR)p,, -Amp-(OR)p,, tristyryl phenol, or any other monofunctional organic
groups, such as alkyl,
cycloalkyl, aryl, allcaryl, aralkyl, alkyoxyalkyl, aroxyalkyl,
cycloallcoxyalkyl, and the like, and p, is a positive
number that is equal to the free valence of Amp minus 1
A particularly preferred linear aminoplast-ether copolymer comprises units of
the formula:
'Roi
N N
O
N N III.
wherein Ro,,Ro,, and R are described above, n has a value ofat least 2, x is 0
or 1, and s+t equals (i) the
free valence of the
N N
O p IV.
N N
x
6
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moiety and (ii) 4-x: and the average value of t/s+ t is about 0.01 to about
0.5.
In a furrherpreferred embodiment ofthe invention, the linear aminoplast-
ethercopolymeremployed
in the coating composition ofthe invention comprises a copolymer that
possesses end groups as illustrated
by the following structure:
RooyRoy
N N
V.
N N
Roo.
~RO~s
wherein each R°°1 is the same or different terminal group, such
as hydrogen, -R°,-H, -(OR)p,,
Amp°---(OR)p,, tristyryl phenol, or any other monofunctional organic
groups, such as alkyl, cycloalkyl,
aryl, alkaryl, aralkyl, allcyoxyalkyl, aroxyalkyl, cycloalkoxyalkyl, and the
like, and p ~ is a positive number
that is equal to the free valence of Amp° minus 1. Amp° is
depicted in formula V.
The present invention further relates to a latex coating for the mid to
neutral base formulations based
on small particle size acrylics. The present invention improves on this type
of latex coatings by reducing
the drop in viscosity that normally occurs when the colorant is added to latex
coating for the mid to neutral
base formulations based on small particle size acrylics. The present invention
also yields overall improved
color acceptance compared to other compositions and competitive products.
Detailed description of the invention
This invention relates to the use of any aminoplast, including those
specifically recited in FIG. 1
above, to make the copolymer ofthe invention. Ofthese aminoplasts, exceptional
performing associative
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thickeners, for use in latex coatings for the mid to neutral base
forn~ulations based on small particle size
acrylics, are obtained from the reaction of glycolurils with alkylene oxide
glycols to which are incorporated
the tristyryl phenol pendant moieties.
The linear aminoplast-ether copolymers of formula I et seq. are made by the
novel condensation
reaction of a polyfunctional aminoplast with a di-functional polyether (alone
or with another polyol, as
characterized with respect to formulae XII and XIII) in the presence of an
acid catalyst. In the prior art,
as noted above, aminoplasts are condensed with polyfunctional compounds to
produce thermosetting resins
or thermoset products (i.e., C-stage resin). This reaction produces a linear
copolymer. Thus, the
copolymers of formulae I, II, III, IV, and V are either liquid or
thermoplastic solids that are solvent soluble
and water soluble or dispersible.
The linear aminoplast-ether copolymer are made by the copolymerization
reaction of a
polyfunctional aminoplast with an ether containing two active hydrogen
terminal groups, in the presence of
an acid catalyst, especially a Bronsted-Lowery acid provided in catalytically
effective amounts. The
reaction is continued until the desired molecular weight is achieved. The
desired molecular weight of the
copolymer is dependent on the intended use of the copolymer. The molecular
weight of the copolymer may
range from about 12,000 to about 800,000, preferably from about 20,000 to
about 100,000, and most
preferably from about 30,000 to about 80,000. The aminoplast is a
polymerizable resin of the general
formula:
(ROB--Amp VI
wherein z is a positive number having a value of at least 2. The ether
containing two active hydrogen
terminal groups comprises a wide variety of compositions. A preferred class is
nonionic. Illustrative of a
preferred class of such ethers are polyalkylene oxides of the formula:
HAlkylene Oxide -H VII.
8
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where "alkylene oxide" is a divalent moiety containing at least two alkylene
oxide units in which
1. the alkylene oxide units form a linear chain and provide a terminal OH, or
2. the alkylene oxide units are bonded to a starter molecule, such as a
diamine, urea, carbamate,
phenoxy, amide, bis-imide, and the like, and providing a terminal OH, and/or
3. in which alkylene oxide are bonded to a terminal group that possesses a
moiety that provides
the active hydrogen (-H in formula VII).
Further illustrative of such a preferred class are the water soluble or
dispersible polyether compounds of
the formula:
HX~X-(Raa)x4(Ros)Xs(Rob)X6(Roz)Xz(Ros)Xa ~Xz VIII.
wherein
X is an active hydrogen functional moiety such as oxy (--D-), sulfidyl (S-),
amino (N<), carboxy
(-COO), carboxamido, silyl, phosphoryl, ureido, and the like;
Ro4 and Ro8 are alkyl of 2 to about 8 carbon atoms;
RoSand Rfl~are one ormore alkylene oxide units, e.g., such as water soluble or
dispersible ethylene oxide,
propylene oxide, mixed ethylene oxide/1,2-propylene oxide, mixed ethylene
oxide/1,3-propylene oxide,
mixed ethylene oxide/1,2-butylene oxide, mixed ethylene oxide/1,4-butylene
oxide, and the like;
R~is a divalent group such as alkyleneoxy, allcylenepolyamine, cycloallcylene
polyamine, phenoxy, uriedo,
carbamate, amide, and the like;
x 1 and x2 are each equal to the free valence of X;
x3, x4, x5, x6 and x7 are each 0 or 1, and one or more of x4 and x6 is 1.
9
SUBSTITUTE SHEET (R ULE 26)
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Specific illustrations of a limited class of polyethers encompassed by formula
VIII are the
Carbowax~ and Pluracol~ polyether diols sold by Union Carbide Chemicals &
Plastics, Inc. and
BASF Performance Chemicals, respectively. There are a variety of functional
fluids based on
alkylene oxides that are sold by Union Carbide Chemicals & Plastics, Inc. and
BASF
Performance Chemicals that are encompassed by formula VIII. The molecular
weight of the
polyether reagent may range from about 106 and lower, to about 35,000, and
higher.
In the prior art, as noted above, aminoplasts are condensed with
polyfunctional
compounds to produce thermosetting resins or thermoset products (i.e., C-stage
resin). The above
method produces a linear copolymer. Thus, the copolymers of formulae I, II,
III, IV, and V are
either liquid or thermoplastic solids that are solvent soluble and water
soluble or dispersible.
Aminoplast reagents include, but are not restricted to, aldehyde reaction
products of
r melamines, ureas, benzoguanamines, glycolurils, and the like, to produce the
array of
aminoplasts, including but not limited to those described in FIG. 1 above.
While any of these can
be used to make associative thickeners, the glycolurils, such as those of
formula IX
H3co ocH3
N N
N N
HgCO (OCH3)x H~_x
where x is defined above, have shown appropriate hydrolyric stability, when
reacted with the
polyether compounds, such as those encompassed by formula VIII, to meet
commercial criteria
for associative thickener-containing coating compositions. However, the
reaction products of
such aminoplasts with, e.g., thiols and NH groups from amides and carbamates,
encompassed by
formula VIII, are much
AMENDED ~~'~~
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more hydrolytical 1y stable than aminoplast ether linkages. The use of such
reactants allow for the production
of most hydrolytically stable aminoplast-based copolymers.
Suitable polyethers include polyalkylene polyethers. The preferred polyethers
are water soluble.
The most preferred polyethers are the alkylene polyethers where the
predominant alkylene groups are
ethylene. The most desirable polyethers are polyethylene oxide diols that
possess molecularweights from
about 1,000 to about 35,000.
Illustrative of the desirable polyethylene oxide diols are those of the
formula:
HO(-CH,CH,O)x"CH,CH,OH X.
wherein x 11 has a value of about 20 to about 800, preferably from about 50 to
about 500, and most
preferably from about 100 to about 300.
A further desirable embodiment of the invention is the modification of the
linear
aminoplast-ether copolymers used in making the coatings of the invention by
including a minor mole
proportion of the following unit structure in the repeating structure of the
copolymer:
-Amp-RI5- XI.
wherein R, 5 is the residue of a diol possessing greater hydrophobicity than
Ro,, thereby providing for a
linear copolymer containing the structure
Amp--R°'~ ~A'T'p---R~'~ XII
x29 x30
wherein x29 has a value that is greater than x30. Preferably, x30/x29 is less
than about l, preferably less
than about 0.33. Illustrative of such R,5 groups are
11
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O
HO(CHZ)x3iOH
HOH,CH,C~
N (CH=)~3,CH3
CH,CH,OH
H(OCH,CH2)x~y0 O(CH,CH,O)x3jH
wherein x31 has a value of about 8 to about 20, x32 has a value of about 8 to
about 23, x33 and x34 have
values of 0 to about 8. The linear copolymer of formula XII may be modified to
possess the terminal groups
of formulae II and V, discussed above.
The linear aminoplast-ether copolymers of this invention, contains a
hydrophobe pendant
group. Acceptable hydrophobe groups include aliphatic to alkyl phenol to
tristyryl phenol. The most
preferred hydrophobic pendant group is tristyryl phenol. Tristyryl phenol
extends from aminoplast
component of the linear backbone of the aminoplast-ether copolymer. Tristyryl
phenol groups are typically
bonded to the backbone through ether or ester groups, as illustrated in
formula II. The presence of tristyryl
phenol enhances the performance of the resulting aminoplast-ether copolymer as
an associative thickener
in architectural coating compositions for the mid to neutral base formulations
based on small particle size
acrylics where the level of colorant added is in large amounts for about the 5
to 16 oz per gallon range.
This invention relates to the use of any aminoplast, including those
specifically recited in FIG.
1 above, to make the copolymer of the invention. Of these aminoplasts,
exceptional performing associative
thickeners are obtained from the reaction of glycolurils with alkylene oxide
glycols to which are
incorporated tristyryl phenol pendant moieties at a relatively high
concentration. The relatively high
concentration oftristyryl phenol means about 3% or gl-eater based on weight.
In the preferred embodiment
the concentration of tristyrl phenol is at a concentration of about 4% to
about 10% based on weight.
12
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The production of the aminoplast-ether copolymers are made by solvent or melt
polymerization. The typical preparation of an aminoplast-, such as glycoluril-
, based associative thickener
involves dissolving the aminoplast (e.g., glycoluril), apolyether compounds
within the scope of formula IX
(such as a Carbowax « polyether sold by Union Carbide Chemical and Plastics,
Inc., Danbury, Conn.),
with or without the addition of a more hydrophobic polyol within the scope of
formula XI,with the addition
of ethoxylated tristyryl phenol (such as Soprophor BSU), in a stripping
solvent, such as alkylated benzene
(e.g., toluene or xylenes). Prior to the combination of these reagent, each
may be dried by azeotropic
distillation with toluene, xylenes, or a mixture of them, or by any other
drying procedure. Total
concentration ofthe reagents in the solvent may be maintained from about 10 to
about 60 weight %. The
temperature of the mixture may be brought to about 60°-140° C.,
preferably to about 80°-120° C. An acid
catalyst, such as a sulfonic acid catalyst, is then added. The reaction
mixture is placed under reduced
pressure to bring about a steady distillation of the toluene/xylenes which
azeotropes the alcohol byproduct
that must be removed in order for the reaction to proceed. Fresh solvent is
constantly added to maintain
a constant level. The reaction is allowed to proceed until a given high
viscosity is achieved as measured by
Gardner bubble tubes or until viscosity increase ceases. Such viscosity
increase indicates an increase in the
molecular weight of the copolymer.
SPECIFIC ILLUSTRATION OF SOLVENT PROCESS
The following is an illustration of the sequential steps involved in preparing
the aminoplast-
ether copolymer.
1. Polyetherpolyol, ethoxylated tristyryl phenol, and azeotroping solvent
(e.g., toluene) are
added to an appropriately sized container that accommodates a heater,
temperature reading
device, a nitrogen inlet, and a Dean Stark water trap and condenser.
13
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2. The mixture of step 1 is heated to reflux to dry the mixture by azeotropic
distillation. When
water removal ceases, the mixture is cooled to about 100° C., and the
water trap is
removed. A distillation column and receiving vessel are installed in the
container.
3. Glycoluril (e.g., Powderlink 1174) is added and allowed to melt.
4. The catalyst is added and vacuum is applied. The pressure is reduced to a
level that
causes a steady distillation of solvent at about 100° C. The solvent is
continually replenished
from a pressure equalizing add funnel.
5. As the reaction proceeds, samples are removed and cooled to room
temperature, and the
Gardner bubble viscosity is measured.
6. When the proper viscosity is reached, the heat is removed and the mixture
is cooled in a
water bath. When the temperature has been reduced to below 75 ° C., an
amine neutralizing
agent is added. When the temperature is reduced to below 65° C., the
polymer solution is
poured out onto trays to air dry.
7. The dried polymer is cut into strips and redissolved in water or
water/cosolvent mixture.
Polymerization in the melt involves the admixture of the same reagents in the
absence of a
solvent with a heavy duty laboratory mixer (such as an Universal Sigma Blade
Mixer, sold by Baker
Perkins Guittard SA, Paris, France) at a temperature sufficient to generate
leaving groups and remove the
reaction condensation products. The removal of volatile byproducts by vacuum
is necessary in order to shift
the reaction to the right and prevent an equilibrium reaction from occurnng
that impedes the reaction before
the desired degree of polymerization is achieved.
14
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Catalysts useable for effecting the copolymerization reaction includes the
standard
Broonsted-Lowery acid catalysts typically used for the condensation of
aminoplast resins. Such acid
catalysts include mineral acids (e.g., HCI, H,SO,,, H~PO~, and the like), aryl
sulfonic and alkylated aryl
sulfonic acids, such as benzene sulfonic acid, p-toluene sulfonic acid, 1-
naphthalene sulfonic acid,
2-naphthalene sulfonic acid, naphthalene-1,5-disulfonic acid, naphthalene-2,7-
disulfonic acid,
1,3,6-naphthalene trisulfonic acid, naphtholsulfonic acid, dinonylnaphthalene
disulfonic acid,
dodecylbenzene sulfonic acid, oxalic acid, malefic acid, hexamic acid, alkyl
phosphate ester, phthalic acid,
and copolymerized acrylic acid. Of these catalysts, the sulfonic acid
catalysts are the most effective and
efficient for making the copolymers of the invention and dodecylbenzene
sulfonic acid is the most preferred
sulfonic acid catalyst.
Glycolurils are marketed by Cytec Industries as Cymel 1170, 1171,1175 and
Powderlink
1174. The Cymel versions are either mixed methylolated species and typically
contain a relatively high
dimer or oligomer content of up to about 20 weight percent. Powderlink 1174 is
a purer form that is solely
the methyl ester of the formula:
H3C0' /OCH3
°~N~ ~° XIII
N N
H3COJ ~OCH~
with about 3-5 weight percent of a dimer-oligomer of the monomer form. The
purer the monomeric form
of the aminoplast, the better it is in forming the copolymers of the
invention. In about 5-7 weight percent
ofPowderlink 1174, x is 0, and such monomer form is trifunctional. The dimer-
oligomer forms provide
greater amounts ofmethoxy per molecule. For example, the dimer contains 6
methoxy functional groups.
Such tri- and hexa-functionality does not alter this invention. The glycoluril
ether linkage is much more
resistant to hydrolysis than other aminoplast ether bonds. The higher dimer-
oligomer content of the less pure
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glycolurils is not as favored as the lower dimer-oligomer content of Powder
link 1174.' Further reduction
of oligomers can be effected by recrystallization.
' Powderlink 1174 is called a "resin" and "crosslinker" by Cytec, and has been
sold under
the Cymel k0 name (i.e., Cymel 1174). Its empirical structure is C, ~H~,Na06.
Its chemical name is Imidazo
[4,5-D] imidazole-2,5 (1H,3H)-dione, tetrahydro-1,3,4,6-tetrakis
(methoxymethyl)-. CAS 17464-88-9.
It is also known by the following names: (i) Glycoluril, 1,3,4,6 tetrakis
methoxymethyl, (ii) Glycoluril,
tetrakis methoxymethyl, (iii) Glycoluril, N,N,N,N tetrakis methoxymethyl, (iv)
Glyoxal diuriene, tetrakis
methoxymethyl, and (v) Tetramethoxytetramethylol acetylenediurea. The favored
name is (i) and such
skeletal structure is called glycoluril.
The ratio of aminoplast resin to the difunctional polyether is not critical.
Typically, either the
aminoplast resin or the difunctional polyether may be used in molar excess or
stoichiometrically equivalent
amounts in making the linear copolymer of the invention. In characterizing
stoichiometry of the aminoplast
resin, the resin is treated as being difunctional since linearity, according
to the invention, is achieved when
the aminoplast resin functions as a difunctional monomer even though the resin
has the capability ofhigher
functionality, e.g., tri- and tetrafunctionality, as the case may be. Thus,
more than one mole of a polyether
diol to one mole of, e.g., a glycoluril such as Powderlink 1174, represents a
stoichiometric excess ofthe
polyether to the glycoluril. Using this characterization, one may use between
1-2 moles of one of these
reagents to 1 mole of the other. Either the polyether or the aminoplast may be
in excess. However, it is
more typical to use a mole amount of one reagent of about 1-1.75 to 1 of the
other reagent. Typically, one
employs a molar excess ofthe aminoplast resin because one may incorporate more
hydrophobicity into the
copolymer this way. This is especially the case when the copolymer is dimeric
to oligomeric (e.g.,
possessing less than about 15 repeating units). When making higher polymeric
structures, one uses a greater
proportion ofthe polyether reagent, up to a 1:1 mole ratio. In general, it is
desirable to use a molar excess
ofaminoplast ofabout 1.001-2.0 moles to 1 mole ofthe difunctional polyether.
The amount ofethoxylated
tristyryl phenol should not exceed about 2.0 moles, nor be less than about 0.4
mole per mole of reacted
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aminoplast resin in the copolymer of the invention. Usually, the amount of
ethoxylated tristyryl phenol ranges
from about 0.7 mole to about 1.~ mole per mole of reacted aminoplast.
Waterborne coatings may be defined as coatings that contain water as the major
volatile
component and utilize water to dilute the coating to application consistency.
These coatings consist mainly
ofresinous binder, pigments, water, and organic solvent. The type
ofpigmentation and the method of
incorporation of the pigment vary widely.
Waterborne coatings can be made by dispersing, emulsifying or emulsion
polymerizing the
resin binder by use of added surfactants. Tlus technique leads to opaque
liquids. Because some hard resins
are difficult or impossible to disperse directly into water, the resin
sometimes can be dissolved in a water-
immiscible solvent, and the resulting solution dispersed by the use of added
surfactants. In this case, the
solvent aids subsequent film coalescence. Surface activity or water
dispersability also can be introduced
into resin molecules by chemical modification ofthe resin by introducing
fimctional polar groups such as the
carboxyl group.
Some very finely dispersed resins appear as clear or slightly hazy liquids;
they frequently are
described as soluble, solubilized, colloidal dispersions, micro-emulsions,
hydrosols, etc. These resins
contain built-in fimctional groups that confer water "solubility" upon the
resin, and, normally, external added
surfactants are not used.
Waterborne resin binders can be classified as anionic, cationic, or non-ionic.
Anionic
dispersions are characterized by negative charges on the resin or by negative
charges on the surfactant
associated with the resin. Cationic dispersions have a positive charge on the
resin or on the surfactant
associated with the resin. Nonionic dispersions are those that have been
dispersed by addition of nonionic
surfactants or that contain a built-in hydrophilic segment such as
polyethylene oxide which is part ofthe
main chain of a relatively hydrophobic resin molecule.
The coating compositions may be ofthe thermosetting or thermoplastic
varieties. The resin
used in forming the coating may be insoluble in water, and the conversion of
such a resin into a waterborne
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system typically involves converting the resin into air emulsion or
dispersion. hi the context ofthis invention,
the waterborne composition contains the aminoplast-ether copolymer associative
thickener ofthe invention.
The aqueous polymer dispersions may be prepared according to well known
emulsion
polymerization procedures, using one or more emulsifiers of an anionic,
cationic, or nonionic type. Mixtures
of two or more non-neutralizing emulsifiers regardless of type may be used.
The amount of emulsifier may
range from about 0.1 to 10% by weight or sometimes even more, based on the
weight ofthe total monomer
charge. In general, the molecular weight of these emulsion polymers is high,
e.g., from about 100,000 to
10,000,000 number average molecular weight, most commonly above 500,000.
The water insoluble resin may be any ofthose known in the art, and may be a
conventional
natural or synthetic polymer latex emulsified with one of a nonionic, cationic
or anionic surfactant. The
primary resins are based on homopolymerized and copolymerized olefinic
monomers such as vinyl acetate;
vinyl chloride; styrene; butadiene; vinylidene chloride; acrylonitrile;
methacrylonitrile; acrylic acid;
methacrylic acid; alkyl acrylates; alkyl methacrylates; acrylamide;
methacrylamide; hydroxyethyl
methacrylate ("HEMA"); glycidyl methacrylate; dihydroxypropyl methacrylate;
homopolymers of CZ-C~
alpha-olefins such as ethylene, isobutylene, octene, nonene, and styrene, and
the like; copolymers of one
or more of these hydrocarbons with one or more esters, nitriles or amides of
acrylic acid or of methacrylic
acid or with vinyl esters, such as vinyl acetate and vinyl chloride, or with
vinylidene chloride; and dime
polymers, such as copolymers of butadiene with one or more of styrene, vinyl
toluene, acrylonitrile,
methacrylonitrile, and esters of acrylic acid or methacrylic acid, and the
like. It is also quite common to
include a small amount, such as 0.1 to 5% or more, of an acid monomer in the
monomer mixture used for
making the copolymers mentioned above by emulsion polymerization. Acids used
include acrylic,
methacrylic, itaconic, crotonic, malefic, fumaric, and the like.
The vinyl acetate copolymers are well-known and include copolymers such as
vinyl
acetate/butyl acrylate/2-ethylhexyl acrylate, vinyl acetate/butyl maleate,
vinyl acetate/ethylene, vinyl
acetate/vinyl chloride/butyl acrylate and vinyl acetate/vinyl
chloride/ethylene.
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Other waterborne systems involve reactive copolymers that are crosslinked by
the presence
of complementary functional groups in the system. For example, a copolymer of
acrylic
ester/glycidylmethacrylate can be emulsified and crosslinked by the presence
of a melamine-formaldehyde
resin similarly emulsified in the system. In another system, a copolymer of
HEMA and another acrylate,
hydroxyl terminated polyesters, polyethers, or polyurethanes, can be
emulsified and crosslinked by the
presence of either an aminoplast resin, a polyisocyanate or blocked
polyisocyanate.
The term "acrylic polymer" means any polymer wherein at least 50% by weight is
an acrylic
or methacrylic acid or ester, including mixtures of such acids and esters
individually and together. The term
"vinyl acetate polymer" means any polymer containing at least 50% by weight of
vinyl acetate.
Small particle size (about 0. I-0.15 micron) acrylic and other latices are
thickened effectively,
and flow and leveling improved, by thickeners of the invention. The use ofthis
invention forproducing
architectural coatings for the mid to neutral base formulations based on small
particle size acrylics where
the level of colorant added is in large amounts for about the 5 to 16 oz per
gallon range eliminates the need
to incorporate other thickener systems, such as cellulosics and alkai-
swellable thickeners or large amounts
of surfactants.
The amount of the aminoplast-ether copolymer described herein that is employed
in the
coating composition of the invention is not critical. That amount will vary
based on the resin system used,
the water concentration, the amount of fillers and the choice of fillers, the
presence or absence of
thixotropic agents, and the like. In that respect, the amount of the
aminoplast-ether copolymer in the
composition is sufficient to thicken the composition. However, in general, the
amount ofthe copolymerwill
range from about 0.1 weight percent to about 15 weight percent, preferably
from about 0.5 weight percent
to about 10 weight percent, and most preferably from about I weight percent to
about 8 weight percent,
of the weight of the coating composition, exclusive of fillers, pigments and
like additives.
The following is an illustrative formulation for an architectural coating
based on small particle
size acrylic. Optiflo H600 is the aminoplast-ether copolymer described above.
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EXAMPLE
1 ) Water, propylene glycol, Tamol 731, foamaster VL, Kathon LX are added to a
high speed disperser
tank equipped with a cowls high speed agitator blade. Agitation is begun
followed by the addition of the
R-900 dry Ti02 pigment. The mixture is ground at high speed (2,000 rpm) for 20
to 30 minutes or until
the Ti02 is well dispersed (usually determined using a hegman grind gauge of
greater than 6).
2) Once the grind is complete the speed or shear is decreased and the grind
paste is transferred to another
tank equipped with a mixing blade (usually a slow speed paddle blade). The SG-
l OM and OP62 are
added and mixed for approximately 10 minutes. The remaining ingredients can be
added (water, Optiflo
L 100 and Optiflo H600). A defoamer (Foamaster VL) is usually added so as to
remove any entrained air.
3 ) Quality Control checks usually consist of viscosity (Stormer & ICI), pH,
weight per gallon (WPG),
hiding power and color acceptance.
SEMI-GLOSS
SG-1 OM
GRIND POUNDS GALLONS
WATER 11.13 1.34
PROPYLENE GLYCOL 65.00 7.51
TAMOL 731 12.88 1.40
FOAMASTER VL 1.00 0.13
KATHON LX 1.80 0.22
TI-PURE R-900 253.00 7.60
GRIND Ti02 @ 1300 rpm FOR 30 MINUTES
RECORD MAXIMUM GRIND
TEMPERATURE:
LET DOWN 5 GALLON PAIL - 3F
BLADE
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WATER 88 10.56
RHOPLEX SG-10 465.5 52.78
ROPAQUE OP-62 27.96 3.25
TEXANOL 24.32 3.07
SUB TOTAL:
950.62 87.87
MIX AT LOW SPEED 30 MINUTES
RECORD WPG : 10.82
RECORD pH:
PREMIX
WATER 72.20 8.67
L100 28.35 3.28
H600 0.50 0.06
FOAMASTER VL 1.00 0.13
TOTAL:
1,052.67 100.00
PVC%: 27.26
VS%: 34.10
Paint Examples
Evaluation in a Neutral Base Latex Paint Formuation:
The 17.5% solution from example 1 was evaluated in a semi-gloss neutral base
fonnuation which
contained Rhopex SG-1 OM acrylic latex. The paints were tinted with 12 oz of F
Colorant (red iron oxide)
from CreaNova (888).
Loading Initial Stormer Stormer after tinting ~KU
(Dry lbs/100ga1) (KU) (KU)
Example 1 0.525 108 98 10
Acrysol RM825 0.525 102 82 20
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Evaluation in a deep Base Latex Paint Formulation:
The 17.5% solution from example 1 was evaluated in a senu-gloss neutral base
formulation which
contained Rhopex SG-20M acrylic latex. The paints were tinted with 8 oz of F
Colorant (red iron oxide)
from CreaNova (888).
Loading Initial Stormer Stormer after tinting ~KU
(Dry lbs/100ga1) (KU) (KU)
Example 1 0.44 111 91 20
Acrysol RM825 0.44 110 64 246
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