Pigmented air drying latex paints having superior gloss

A high gloss, water base, pigmented latex is provided by grinding a pigment into a water-free solution of a carboxyl-functional addition solution copolymerized copolymer of monoethylenically unsaturated monomers including at least about 10% by weight of monoethylenically unsaturated carboxylic acid in water miscible alcoholic organic solvent, the copolymer being at least partially neutralized at the time of grinding with an hydroxy amine, to render the said copolymer dispersible in water, and thereby form a nonaqueous pigment paste, and then mixing the nonaqueous pigment paste with an air drying aqueous latex of aqueous emulsion copolymerized copolymer particles. The invention includes the latex paint so-produced.

This invention relates to high gloss, water base, pigmented air drying 
latex house paints. 
Conventional air drying latex paints develop little gloss, as is well 
known. These conventional latex paints include pigment which is dispersed 
in the water phase by means of surfactants or wetting agents, and this 
leads to low gloss. The pigment is quite differently dispersed in this 
invention, leading to a very significant increase in gloss, as will be 
illustrated. 
In accordance with this invention, a high gloss, water base, pigmented 
latex is provided by grinding a pigment into a water-free solution of a 
carboxyl-functional solution copolymerized addition copolymer of 
monoethylenically unsaturated monomers including at least about 10% by 
weight of monoethylenically unsaturated carboxylic acid in water miscible 
organic solvent, especially an alcoholic solvent, the copolymer being at 
least partially neutralized with an amine, particularly an hydroxy amine, 
to render the said copolymer dispersible in water, and thereby form a 
nonaqueous pigment paste, and then mixing the nonaqueous pigment paste 
with an aqueous latex, which is adapted to provide good film properties 
upon air drying. The invention includes the latex paint so-produced. 
Referring more particularly to the solution copolymerized copolymer of 
monoethylenically unsaturated monomers containing a high level of carboxyl 
functionality, any addition copolymer of monoethylenically unsaturated 
monomers may be used, the usual monomers being acrylic or vinyl acetate, 
including at least about 10% by weight of monoethylenically unsaturated 
carboxylic acid. However, in this invention, it is preferred that both the 
solution copolymer and also the emulsion copolymerized latex copolymer 
contain a major proportion (more than 50% by weight) of acrylic esters, 
more particularly constituted by a blend of methyl methacrylate with alkyl 
acrylate in which the alkyl group contains from 1-8 carbon atoms. Styrene, 
vinyl toluene, or vinyl acetate may be used in place of the methyl 
methacrylate, but these are less preferred. Acrylonitrile may also be 
present. These are nonreactive monoethylenic monomers. Hydroxy functional 
monomers may also be present, such as 2-hydroxyethyl acrylate, and amide 
groups are also permissible, such as are provided by acrylamide, 
methacrylamide, or other monoethylenic carboxylic acid amide. 
The copolymers of high acidity are solution copolymers which denotes 
copolymerization in organic solvent solution. Water miscible organic 
solvents, and especially alcohols, such as butanol, 2-ethoxy ethanol and 
2-butoxy ethanol, are preferably selected in this invention since the 
copolymer is ultimately dispersed in the aqueous medium provided by the 
latex. 
At least 10%, up to about 40%, of the copolymer is to be constituted by 
monoethylenically unsaturated carboxylic acid. Many acids are appropriate, 
particularly acrylic acid. Other appropriate acids are methacrylic acid, 
crotonic acid, itaconic acid, monobutyl maleate, and the like. Preferred 
proportions are from 15-30% of the copolymer. 
The solution copolymerization which is used is a conventional one which is 
carried out in solvent solution in the presence of a free radical 
polymerization catalyst. Preferred water miscible organic solvents are 
2-ethoxy ethanol and 2-butoxy ethanol, though numerous others are well 
known and useful herein, such as isopropanol, acetone, and the like. 
The copolymer solution is then at least partially neutralized with an 
amine, hydroxy amines giving the best results. Neutralization is carried 
out to the extent needed for subsequent dispersion in water, 
neutralization to at least about 50% of the acidity of the copolymer being 
generally contemplated. 
While amines, such as triethyl amine or ammonium hydroxide (usually 
considered an amine in the art of solubilizing carboxyl copolymers) are 
generally useful, hydroxy amines yield significantly better gloss. Hydroxy 
amines have the formula: 
##STR1## 
in which R is hydrogen, or an alkyl group, preferably an alkyl group 
containing 1-4 carbon atoms, R' is an alkylene group, preferably 
containing 1-4 carbon atoms, and X is either R or R'OH. 
Appropriate hydroxy amines are illustrated by propanol amine, diethanol 
amine, dipropanol amine, dimethyl ethanol amine, dimethyl propanol amine, 
diethyl ethanol amine, methyl diethanol amine, ethyl diethanol amine, and 
the like. Tertiary amines containing at least one hydroxy group are 
particularly contemplated, and the invention will be illustrated using 
dimethyl ethanol amine. 
While any pigment may be included in the paints of this invention, titanium 
dioxide pigment, both rutile and anatase, are particularly contemplated. 
The hydroxy amines are especially significant in achieving the effect of 
dispersion and high gloss containing results contemplated herein when 
titanium dioxide pigment is relied upon to provide the major proportion of 
the pigmentation. The proportion of pigment should be sufficient to 
provide a paste in known fashion. A pigment volume concentration of at 
least 10% is usual. 
After neutralization of at least a portion of the carboxyl functionality 
contained in the copolymer solution, the pigment is added and conventional 
grinding is carried out to produce a pigment paste. In preferred practice, 
from 3-12 parts by weight of pigment are dispered in the copolymer-solvent 
solution per part of copolymer, more preferably from 5-10 parts of pigment 
per part of copolymer. The aqueous latex providing the bulk of the resin 
solids of the paint is then added either directly or after preliminary 
admixture of a small amount of water, into the neutralized solvent 
solution. 
The neutralized solution of carboxyl-functional solution copolymer 
preferably contains from 40% to 70% of solvent, based on the weight of the 
solution copolymer, to provide a viscosity appropriate for grinding in the 
pigment. 
While any conventional air drying emulsion copolymer latex used in the 
paint industry may be employed herein, vinyl acetate-butyl acrylate 
copolymers, vinyl acetate-ethylene copolymers, and methyl 
methacrylate-ethyl acrylate (or butyl acrylate) copolymers illustrate the 
more usual paint latices, and the methyl methacrylate-acrylic ester 
copolymers are preferred. In general, aqueous emulsion copolymers having a 
T.sub.g below 20.degree. C. are useful herein since these provide air dry 
paints. T.sub.g denotes the glass transition temperature and is well 
recognized to define the nature of an emulsion copolymer which is not 
significantly cross-linked in the emulsion. A small amount of coalescing 
solvent, as is well known, may be present to facilitate air drying. 
Reactive monomers cannot be present in the large amounts needed for a 
baking system, for these would have to be reacted in order to provide good 
film properties, and baking is not available in a house paint. Thus, up to 
about 1% of a carboxylic monomer may be included for emulsion stability 
and up to about 2% of amine-functional monomers may be present to maximize 
adhesion and other properties, but larger amounts of reactive materials 
should be avoided since these are inconsistent with an air dry latex. The 
total proportion of reactive monomers should be less than about 4%. The 
amine functional monomers are illustrated in U.S. Pat. Nos. 3,356,653; 
3,356,654; 3,356,655; and 3,509,085. 
It is desired to call particular attention to some of the superior 
attributes which are obtained in pigmented paints formulated in accordance 
with this invention in comparison with other commercially available 
semigloss paints, aside from the significant improvement in gloss which is 
obtained. Thus, better visual hiding is obtained at the same level of 
pigmentation, and the pigment dispersing properties are superior. This 
enables dispersion in the absence of the surfactants normally introduced 
to aid in dispersing the pigment. This characteristic is particularly 
beneficial from the standpoint of processing because in the previous 
technique of grinding the pigment into water containing a surfactant, 
foaming was troublesome. Also, and from the product standpoint, higher 
solids content paints are enabled by this invention. The superior 
dispersion also enables darker colors using smaller amounts of prime 
pigment (the titanium dioxide), and the tendency of the pigment to 
flocculate is avoided. 
From the standpoint of application, it has been found that wetting of the 
substrate is superior and the rheology of the coating is better, causing 
brush marks to flow out and become less discernible. The better wetting 
which is obtained enables the formulation of paints in which the polyester 
component normally introduced to provide the desired chalk penetration can 
be eliminated. As a result, one can wet chalky surfaces without 
introducing any tendency to yellow. 
It is also possible in this invention to reduce the proportion of titanium 
dioxide pigment which is needed for hiding, and this can be done by 
increasing the amount of extender pigment, such as aluminum silicate. This 
is not possible in the corresponding conventional system where aluminum 
silicate introduction reduces gloss. 
Throughout this specification, and particularly in the examples and claims 
which follow, all proportions are by weight unless otherwise specified.

EXAMPLE 1 (FOR COMISON) 
______________________________________ 
Charge Composition (Pounds) 
______________________________________ 
83 Water 
4.5 Anionic Surfactant - sodium salt of polyacrylic acid 
(Rohm and Haas Tamol 731 may be used) 
125 Titanium dioxide rutile 
Disperse the pigment using a high speed mixer 
Add the following in order 
425 Water 
dissolve 
10 Hydroxy ethyl cellulose 
thickener 
8 Butyl Carbitol (coalescing agent) 
319 Acrylic Emulsion Polymer (47% solids) - see note 1 
4 Defoamer (Drew L-475 may be used) 
1 Anionic surfactant (dioctyl sodium sulfosuccinate [60% 
solids in isopropanel]) 
Solids: 28% by weight 
Weight per gallon: 9.4 pounds 
The formulation contains: 
125 pounds of titanium dioxide pigment 
150 pounds of emulsion polymer solids 
______________________________________ 
Note 1 - The acrylic emulsion polymer utilized is made in accordance with 
the teachings of Example 2 of U.S. Pat. No. 3,356,653, and had the 
following monomer composition: 
53% methyl methacrylate 
44% butyl acrylate 
1% methacrylic acid 
2% amino adduct (see Example 1 of U.S. Pat. No. 3,356,653) 
100% 
EXAMPLE 2 
Example 1 was repeated, only the 4.5 pounds of the anionic surfactant 
dispersant and the 83 pounds of water were replaced with 27.2 pounds of 
water soluble acrylic copolymer solution of Example 3 at 55% solids. The 
proportion of acrylic emulsion was reduced to maintain the solids content 
at 150 pounds: 
______________________________________ 
135 pounds 
90% Emulsion polymer solids 
15 pounds 
10% Water soluble acrylic polymer solids 
______________________________________ 
EXAMPLE 3 
Example 3 
______________________________________ 
Charge Composition (grams) 
______________________________________ 
1080 2-Ethoxy ethanol solvent - heat to 120.degree. C. 
360 Methyl methacrylate 
1700 Ethyl acrylate 
520 Acrylic acid 
80 Benzoyl peroxide 
Add the above over a three hour period while 
maintaining temperature at 120.degree. C. Hold one hour 
and add: 
12 Tertiary-butyl perbenzote 
Hold 11/2 hours. Start cooling and add: 
370 2-Ethoxy ethanol solvent 
Cool to 70.degree. C. and add the following over a 
20 minute period: 
650 Dimethyl ethanol amine 
Strain to provide an acrylic copolyer solution: 
Nonvolatile solids: 55% 
Viscosity (Gardner) Z.sub.3 
Acid value (nonvolatiles) 148 
______________________________________ 
Aqueous latex paints prepared in accordance with Examples 1 and 2 were 
compared as follows: 
______________________________________ 
Gloss Example 1 Example 2 
______________________________________ 
60.degree. Gloss meter reading 
Dry 1 week at room temperature 
36 78 
Film Properties 
Scrub resistance Good Good 
Blocking resistance 
Good Good 
Burnishing resistance 
Good Good 
Stain removal Very good Very good 
Hiding Good Very good 
______________________________________ 
As will be seen, the invention has been illustrated by a comparison between 
two similar latex paints, one produced in conventional fashion (Example 
1), and the other produced in accordance with the teachings of this 
invention (Example 2). 
The generally superior properties which are produced have been described 
previously, and the marked increase in gloss (from 36 to 78 measured on a 
60.degree. glossmeter) represents a large increase which stands out under 
the most casual inspection. 
The invention is defined in the claims which follow.