CA1065080A - Latex paint containing plastic pigment - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An opacified latex dispersion paint composition comprises film-forming latex binder having a major weight proportion of polymer particles not smaller than about 1,000 .ANG., non-film-forming plastic polymer particles having a weighted average particle size diameter between about 1,000 .ANG., and 10,000 .ANG., and opacifying pigment. The latex paint is compounded at a pigment-volume-content (PVC) greater than the critical-PVC
as measured by opacity and provides improved opacified paint film having excellent film integrity properties.

Description

lQ6SO~O

This invention relate~ to opacified latex paints.
Conventional latex paints are prepared by dispersing suf-ficient opacifying pigment such as titanium dioxide into film-forming transparent polymeric binders to provide an opacified paint film. More recently, opaque or decorative paint films have been suggested based on the presence of air voids in the paint films such as provided by cellular or vesiculated particles in British Patent No. 1,178,162, Canadian Patent No. 856,863, and Briti~h Patent No. 1,192,492.
Opacification has been further achieved by entrapping air in the film to provide voids in the paint film and general-- ly are referred to as "bubble coatings". Such coatings, however, have limited opacity and function primarily as decorative or semi-opaque coatings rather than opacified paint coatings having adequate hiding. Hence, the best opacified paint films are conventional latex paints com-pounded with titanium dioxide and extender pigments such a~ calcium carbonate.
A conventional parameter for de~cribing prior , 20 art latex paints i~ the pigment-volume content (PVC) which -~ is the per cent by volume of pigment pre~ent in the dried paint film relative to the total volume of the dried paint film. At a certaln PVC, the volume of pigments in the - paint film abruptly causes considerable air voids in the dry paint film due to binder deficiency~ The PVC measure-

-2-, : - -.
, . . .. . :

0~0 ment at this level of pigment content is characterized as critical-PVC wherein a binder deficiency occurs such that insufficient binder is present in the paint film to encapsul-ate the pigment particles and fill any remaining voids in the film. At the onset of such porosity in the paint film due to binder deficiency, the physical durability properties of the dried paint film abruptly diminish with higher PVC's thereby causing a substantial drop or discontinuity of physical properties of conventional paint films due to in-creased pigment loading. In conventional prior art latexpaints, opacity and porosity exhibit approximately the same sensitivity to the onset of air voids in the paint film wherein opacity ordinarily increases with increased film ; porosity but most paint film physical properties (except opacity) such as scrub resistance and enamel holdout abrupt-ly diminish at approximately the same PVC which has become known in prior art paints as a critical-PVC. Conventional prior art paints suffer a drastic loss of enamel holdout properties simultaneous with achieving increased opacity or hiding characteristics of the paint film with the result that the critical-PVC of conventional latex paints is a narrow PVC range (Figure 1) wherein the critical-PVC is generally a compromise at a point of minimum opacity (for given Tio2 level) and maximum paint film physical properties.
It now has been found that latex paints containing ; - solid non-film-forming plastic pigment and opacifying pig--` ments provide hard, dried paint films having substantially increased opacity as well as substantially improved physical properties. Improved opacity is obtained over a wide range of PVC's before the onset of excessive porosity in the paint , . . .

~06S~10 film whereby the preferred useful range of PVC's of the paint of this invention incorporates both maximum opacity and maximum enamel holdout as well as other optimized physical properties. This invention broadly provides for improved latex paints having a PVC above the critical-PVC
and capable of providing good opacified paint films having desirable paint film integrity properties.
Accordingly, primarily, this invention provides an improved latex dispersion paint having a wide range of P~C's above the critical-PVC as measured by opacity for providing substantially improved paint films having high PVC's while retaining good paint film characteristics.
The aqueous latex dispersion paint of this in-vention comprises film-forming latex binder having a pre-ponderance of film-forming polymer particles not smaller than about 1,000 A in diameter, solid non-film-forming poly-mer particles having a weighted average particle size diameter between about 1,000 A and 10,000 A, and at least about 5% opacifying pigment on a dry solids volume basis. -According to the invention, an aqueous latex dispersion paint composition is provided having about 30%
to 70% by weight total solids and comprising on a dry solids volume basis:
25% to 70% of a film-forming latex binder having a major weight portion of polymer particles between about 1,000 A and 10,000 A and having a glass transition tempera-ture at least about 5C. below said coalescing temperature whereby said binder particles will coalesce into a binding matrix, said latex binder being a polymer or a copolymer of ethylenically lmsaturated monomers;
, ~ 0~;5~)~3Q

10% to 60% of solid, non-cellular, non-film-forming polymer particles having a weighted average diameter be-tween about l,000 A and 10,000 A and having a glass transi-tion temperature at least about 30C. above the glass transition temperature of said binder, said non-film-form-ing particles being polymerized ethylenically unsaturated monomers having carbon-to-carbon unsaturation;
5% to 25% opacifying pigment having a refractive in-dex of at least about l.~;
0% to 60% of non-opacifying pigment; and said latex paint having a pigment-volume-content (PVC) between about 30~ to 75% wherein the PVC is greater than the critical-PVC as measured by opacity.
Figure l is a scaled graph indicating a PVC ladder series of a typical prior art latex paint showing physical properties of paint films as a function of pigment-volume-content (PVC);
Figure 2 is a scaled graph indicating a PVC ladder series of a paint of this invention showing physical properties of paint films as a function of pigment-volume-content (PVC);
Figure 3 is a scaled graph comparing opacity of various paint films as a function of pa~nt film porosity;
Figure 4 is a scaled graph similar to Figure 2 ghowing opacity as a function of PVC indicating varying levels of TiO~;
Figure 5 is a scaled graph similar to Figure 2 indicating a PVC ladder series of a latex paint of this invention showing the retention of film integrity properties at high PVC~s beyond the critical surface porosity (CSP) PVC;

~0~080 Figure 6 shows gloss (60) and sheen (85) as a function of PVC for paint films of this invention in com-parison to prior art paint films; and Figure 7 is a scaled graph showing opacity as a function of TiO2 content at constant PVC relative to prior art paints.
A PVC ladder series is a scaled graph relating physical properties of dried paint films as a function of pigment-volume-content (PVC). The PVC is varied by changing the relative volume of the binder by adding or subtracting a given pigment component while maintaining the volume per cent of other pigment components constant. Paint film characteristics shown in the drawings are more particularly defined in the Examples.
Referring first to the drawing, Figure 1 shows a ; PVC ladder series of a typical prior art paint film contain-ing 23% by volume titanium dioxide and variable amounts of calcium carbonate pigment as an extender pigment to provide a variable pigment-volume-content (PVC). Opacity and enamel holdout are plotted as a function of PVC which is a well-known descriptive parameter for characterizing paint films and is defined as the volume per cent of pigment in a unit volume of a dried paint film. A critical-PVC is indi-cated to be a narrow range on the PVC-axis at which just ` 25 sufficient binder is available to encapsulate each pigment particle and fill the residual voids between the pigments.
The critical-PVC is determined in Figure 1 by the break in the opacity curve and the break in the enamel holdout curve wherein the breaks in each curve are approximately at the same PVC. As viewed in Figure 1, the enamel holdout ~, , . , . . ~ ... .. . .. . ... .

~Q~5(~80 property declines drastically as opacity increases wherein neither the enamel holdout nor the opacity is simultaneous-ly at a maximum. Opacity and enamel holdout both exhibit sensitivity to the onset of air voids in the dry paint film as indicated by PVC's proximate and beyond the critical-PVC.
Most other conventional physical properties of paint films such as scrub resistance, tensile strength, and the like diminish ~uite drastically upon reaching the critical-PVC.
Figure 2 shows a scale graph of paint films of this invention and relates enamel holdout and opacity as a function of non-film-forming components or pigment-volume-content (PVC). The paint films comprise binder, 23% (volume) opacifying TiO2, and varying amounts of non-film-forming solid plastic particles to achieve the indicated variable PVC on the X-axis. The critical-PVC as measured by opacity, hereinafter critical-PVC (opacity), is indicated as the break in the opacity curve and determined by a straight line coinciding with the lower horizontally disposed portion of the opacity curve intersecting with a straight line coincid- -ing with the vertically disposed portion of the opacity curve as more particularly described by A. Ramig in Journal of Paint Technology, Vol. 47, pages 60-66 (March 1975), or the Official Digest of the Federation of Societies for Paint Technology (March 1965), the article commencing at page 272 and incorpor-ated herein by reference. Figure 2 readily indicates that paints containing non-film-forming plastic particles in com-bination with a given amount of opacifying TiO2 surprisingly provide paint films having maximum enamel holdout properties well beyond the substantial increase in opacity occurring at the conventional critical-PVC. Accordingly, a major benefit :, : . . -;S~30 achieved by this invention i5 that substantially higher levels of opacity can be obtained by paint films prior to the onset of excessive porosity in the paint film in addi-tion to maintaining good film integrity properties at high PVC's beyond the critical surface porosity-PVC as will be-come more apparent hereinafter. The broad PVC range for obtaining substantially improved paint films in accordance with this invention is between about 30% to 75% PVC. The lowermost PVC level (30%) in the broad range of 30~ to 75%
PVC represents the lowermost critical-PVC for opacity, whereas the uppermost PVC level represents a maximum allow-able PVC for maintaining film integrity properties of the paint film. Preferred paints of this invention provide paint films substantially free of surface porosity and such preferred paints have a PVC above the critical-PVC
(opacity) but less than the critical surface porosity PVC
as measured by enamel holdout. The critical surface porosity PVC as measured by enamel holdout, hereinafter critical surface PVC (enamel holdout), is the PVC at the break in the enamel holdout curve where enamel holdout properties abruptly diminish and such break in the enamel holdout curve can be determined in a manner similar to determining the break in the opac~ity curve at critical-PVC.
The useful PVC range is dependent upon the formulation of the paint. The desirable PVC differential between critical-PVC (opacity3 and critical surface porosity PVC (enamel hold-out) for preferred paints is at least about five PVC units. -~
The preferred PVC range for preferred top quality paints is between about 48% to 64% PVC. At least about 5~ opacifying pigment such as Ti~2 is required to achieve minimum accept-' ~ -~5~80 able opacity for ordinary paint films up to about 8 mils thickness.
Figure 3 compares a typical prior art paint to paint films of this invention by relating opacity to surface porosity of the paint films. Surface porosity was measured by HG intrusion porosimity using American Instrument Co.
Aminco Model 5-7121B. Surface porosity is directly related to PVC but primarily depicts the increase of paint film surface porosity in the paint film as the critical surface porosity is reached and surpassed. Figure 3, like Figure 2, indicates that substantially improved opacity can be achiev-ed by paint films of this invention before the onset of ex-cessive porosity in the paint film at PVC's greater than the critical-PVC of the paint film whereby enamel holdout and other film integrity properties can be maintained while substantially increasing opacity. Although not intended to be bound by theory, it is believed that the increased opacity achieved in region A on the curves in Figure 3 is primarily due to a combination of improved dispersion of opacifying pigment within the paint film caused by efficient inter-spacing of opacifying pigment by the plastic particles and closed cell microvoids in the paint film caused by packing of plastic particles. Opacity achieved at range B in Figure

3 is due primarily to the formation of open cell voids within the paint film by packing plastic particles wherein microvoid frequency increases resulting in light scattering within the microvoid cells which provides increased opacity with minimal surface porosity of the dried paint film. Region C in Figure 3 is beyond the critical surface porosity PVC wherein opacity increases slightly and enamel holdout properties are reduced , ~. . .;

~650f30 but nevertheless surprisingly provide very useful porous paint films having good fllm integrity properties at high PVC's above the critical surface porosity Pvc. Useful PvC's in accordance with this invention are within region A, s and C provided that the film surface porosity is less than about 0.25 cc/yrams, advantageously below 0.15 cc/grams, and preferably less than 0.10 cc/grams as measured by mercury intrusion of pores less than 1.5 microns in diameter. Paint films in accordance with this invention fall broadly within regions A, B and C, preferred paint films within regions A
and B, and most preferred paint films within region A in : Figure 3. Non-film forming polymer particles substantially larger than 10,000 A tend to form large microvoids which in turn increase detrimentally excessive porosity in the paint film and thus the most preferred polymer particles are be-tween about 1,000 ~ and 6,000 ~. Accordingly, the most pre-ferred high quality and high opacity paints of this invention are generally formulated to correspond to range A on the representative curves in Figure 3 and preferred paints within regions B and C. All paints in accordance with this invention exceed the maximum opacity obtained by conventional paints formulated at critical-PVC and at equivalent levels of opacifying pigments.
Figure 4 is a scaled graph similar to Figure 2 ; 25 showing opacity of various inventive paint films as related to Tio2 content. Paint film at a given Tio2 content plus non-film-forming plastic particles are plotted with opacity ; -(contrast ratio) as a function of per cent pigment-volume-content (PVC). Although not shown in Figure 4, opacity of the 0% level of Tio2 is essentially negligible below a PVC

:
.

~06S~)~30 of about 60% whereas above 60% PVC opacity is measurable but results in less than acceptable opacity for conventional opacified paint films. Accordingly, at least about 5% TiO2 is required and preferably at least about 10% on a dry solids volume basis TiO2 is present in the paint films of this in-vention.
Figure 5 illustrates a ladder series of paint films in accordance with a further aspect of this invention in-dicating that improved paint films can be achieved by latex paints at PVC's beyond the critical surface porosity PVC
whereby the dried paint film has low enamel holdout properties but surprisingly retains film integrity properties such as scrub resistance, burnish resistance, mar resistance, stain resistanae, dirt resistance, grime resistance, and abrasion resistance as identified by the film integrity curve in Figure 5. Latex paint compositions in accordance with this aspect of the invention can be compounded at PVC's up to about 75~ PVC wherein non-opacifying extender and filler pigments as described hereinafter can be effectively utilized at high PVC levels in combination with plastic pigment and opacifying pigment.
Figure 6 relates gloss of paint films as a function of PVC. Gloss is measured at 60 and sheen is measured at 85 in accordance with ASTM D523-67. Conventional paints decline drastically in gloss in the vicinity of about 30%
PVC and continue to decline and asymptotically approach zero ' gloss at PVC's above critical-PVC. In contrast, both gloss and sheen recover in paint films of this invention at PVC's above critical-PVC and continue to increase with increasing PVC.

, ~o~so~o Figure 7 shows opacity (oontrast ratio) of a series of paint films of this invention as a function of decreasing amounts of TiO2 and compares this with a prior art paint (dotted line) which contains about 250 pounds of TiO2 per 100 gallons of paint and a volume solid of 33~. The series of paint films shown in Figure 7 contain the indicated amount of TiO2 plus plastic particles to yield constant PVC's.
Referring now to the paint composition of this in-vention, the latex dispersion paint comprises solid non-film-forming polymeric particles (plastic particles), opacifying pigment, and film-forming polymer particles. The total solids by weight is between about 30% and 70%. Various conventional additives can be added to the paint for stability and appli-cation purposes. Paint films are formed by coalescence of the film-forming binder into a binding matrix at the applica-tion temperature to generate a hard, tack-free paint film.
~he non-film-forming particles are solid and non-cellular as well as being non-film-forming under the conditions~of paint application. Non-film-forming polymer particles can be identified generally as having a glass transition temperature of at least about 5C., advantageously about 15C., and preferably about 25C. higher than the ambient coalescing temperature that the paint film coalesces into a hardened dry paint film. Thus, paint films of this invention applied and formed at room temperature of about 25C. will contain non-film-forming polymer particles having a glass transition temperature of at least about 30C., advantageously above 40C., and preferably at least about 50C. Similarly, paint ; films force dried by heating processes contain non-film-- 30 forming polymeri~ particles having a glass transition tempera- -12-... , . ~ . . : . . : . : . . . :. .: .
.. . . . . .. ....

1(~65()80 ture preferably at least about 25~C. greater than the ambient coalescence temperature of the binder. The term "glass transition temperature" is a term well known in the art and generally defines the onset of long range molecular motion wherein the polymer preserves the outward appearance of a solid but becomes rubbery and then tacky with increasing temperature and undergoes plastic flow and elastic deforma-tion. A polymer particle having a glass transition tempera-ture greater than room temperature will be a non-film-former at room temperature. The glass transition temperature can be measured in accordance with 41 Journal of P~int Technology, pages 167-178 (1969). The glass transition temperature (Tg) are best measured when such polymer particles are in the latex paint wherein interacting effects of various paint ingredients are taken into account such as coalescing agents.
The Tg can be calculated in accordance with the Fox equation or estimated by testing for a Vicat softening point as set forth in ASTM-1525. Under force drying conditions of the paint film, ambient coalescence temperatures are higher than ' 20 room temperature, such as 120F. to 200F. or even as high as 400F. In high temperature curing, the glass transition temperature of the non-film-forming polymer particle must be higher than the ultimate temperature of the film being dried.
Referring now to the non-film-forming particles, the glass transition temperature (Tg) for the solid, non-film-forming polymer particles herein are measured when such poly-mer particles are in the a~ueous latex emulsion paint mixture whereby the interacting effects of the various paint in-gredients such as coalescing aids are taken into account.

.
. . .

~6~0~0 The non-film-forming polymer particles have a weighted average particle diameter between about 1,000 A and 10,000 A
(0.1 to 1.0 microns). Ad~antageously, the solid polymer particles are between about 1,000 A to 8,000 A, and preferably between about 1,000 A to 6,000 A. Average particle, dia-meters can be measured in accordance with known electron-microscopy techniques as described by S.H. Maron in Journal of Applied Physics, Vol. 23, page 900 (August 1952) or by disc centrifuge in accordance with Polymer Engineering and Science, Vol. 14, pages 332-337 (May 1974). The refractive index of the non-film-forming particles is between about 1.3 ; and 1.7 as measured by ASTM D-542 whereas the density or specific gravity thereof is between about 0.9 and 1.5. The -non-film-forming polymer particles are solid and non-cellular and preferably are substantially spherical in geometric shape.
The opacified paint contains about 5% to 70% non-film-forming polymer particles, advantageously 10% to 60% and preferably 15% to 50% on a dry solids volume basis. Preferably the latex paint contains at least about 10% non-film-forming particles or alternatively contain such particles in a volumetric proportion greater than the volumetric proportion o opacifying pigment. The non-film-forming particles are preferably polystyrene but can be polymers and copolymers of other ethylenically unsaturated monomers such as disclosed in -U.S. 3,423,351 providéd the Tg of the particles are sufficient-ly high and remain discrete and do not coalesce at the ambient application and curing temperature. The non-film-forming polymer particles can be copolymerized ethylenically unsatu-rated monomers having a carbon-to-carbon ethylenic double bond un~aturation capable of addition polymerization through .

8(~

the ethylenic double ~ond and can include, for example, styrene, substituted styrenes, vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile, esters of acrylic and methacrylic acid and tertiary butyl acrylate wherein the polymers or copolymers thereof having a Tg greater than about 30C. Preferred polymer particles are polystyrene, poly-vinyl chloride, and polymethyl methacrylate, as further illustrated in the Examples.
Opacifying pigments used in combinatiGn with the non-film-forming polymeric particles are generally pigments having a refractive index of at least about 1.8. Typical white opacifying pigments include rutile and anatase titanium dioxide, lithopone, zinc sulfide, lead titanate, antimony oxide, zirconium oxide, titanium calcium, white lead, titanium barium, zinc oxide, leaded zinc oxide, mixtures of the same, and like pigments. The preferred white inorganic opacifying pigment is rutile titanium dioxide having a weight average particle size between about 0.2 to 0.4 microns. Titanium yellow and like pigments having a high refractive index can be utilized as opacifying pigments as well as imparting tints to the paint. Although most opacify-ing pigments are white, all opacifying pigments having a high index of refraction above about 1.8 should be considered an opacifying pigment for the purpose of this invention regard-less of its tinting (tinctorial) effect on the resultingpaint film. Opacifying pigments comprise at least about 5%
and up to 30% on a dry solids volume basis of the latex paint and preferably between about 10% to 25% on a dry solids volume basis.
A film-forming binder is utilized to coalesce at . . ,.~ . . . . . .
.. .
.

~6S080 the temperature of pain~ application and drying of the paint film to form a binding matrix for the opacifying pigments, non-film-~orming polymer particles (plastic particles), and other non-film-forming additives such as extender and filler pigment. The film-forming latex binder has a major weight portion of polymer particles preferably between 1,000 A and 10,000 A. Providing a film-forming binder having a major weight portion of particles not smaller than about 1,000 A
is desirable in order to obtain the desired opacity which appears to be due to the inability of binder particles to penetrate the microvoid structure formed in the film as a result of the packing of the non-film-forming particles.
The film-forming latex polymer particles should have weight average diameter between about 1,000 A to 10,000 A, and preferably 3,000 A to 8,000 A for desirable rheological behavior.
, Aqueous compounded film-forming binder latices can be emulsions or dispersions of a very broad class of synthetic resins suitable for compounding into latex paints.
The suitable latices by themselves or when compounded with plasticizers, solvents and the like contain polymer parti-cles having a glass transition temperature suitable for fusing and coalescing into a film under application condi-tions. Thus, for air-drying latex paints at ordinary temperature, e.g., 2$C., the film-forming binder latex will have polymer particles having a glass transition témperature less than 20C. and at least about 5C. and preferably at least 15C. below the ambient coalescing temperature and therefore will form a film or binding matrix at such prevailing ambient coalescing temperature. Where . :
' '~ :.......

~06~080 the film is to be force dried, as by heating in an oven, the glass transition temperature of the film-forming binder polymer particles can be substantially higher, but still preferably at least about 15C. lower than the drying coalescing temperature so that said binder will form a bind-ing matrix film under the force drying conditions. The glass transition temperature of the film-forming binder must be at least about 10C. lower than the glass transi-tion temperature of the non-film-forming polymer particles which must have a glass transition temperature above the ultimate maximum temperature of the film being dried.
Preferably, the differential between the glass transition temperature of the film-forming and the non-film-forming polymer particles is about 30C. Glass transition tempera-tures can be measured when the film-forming polymer parti-cles are in the latex paint mixture wherein the interacting effects of the various paint ingredients such as coalescing aids are taken into account.
Typical polymeric film-forming binders suitable for the latex dispersion paints of this invention to ~e applied at about room temperature include a wide variety of polymers and copolymers of ethylenically unsaturated mono-mers, such as polymers containing units of vinyl acetate, acrylate, methacrylates, isoprene, butadiene, styrene, alkylated styrene and/or dibutyl maleate, and are often compounded with stabilizers and additives and are for ex-ample, disclosed in the following U.S. Patents:
2,498,712; 2,676,930; 2,700,026; 2,702,284; 2,728,737;
2,731,434; 2,731,435; 2,739,136; 2,773,849; 2,807,597;
2,809,950; 2,833,747; 2,837,444; 2,852,475; 2,852,476;

2,868,752; 2,875,166; 2,881,143; 2,883,355; 2,884,397;
2,886,546; 2,887,460; 2,888,421; 2,888,422; 2,888,505;
2,889,236; 2,889,314; 2,892,802; 2,894,927; 2,895,930;
2,897,100; 2,897,165; 2,899,397; 2,905,649; 2,907,720;
2,902,721; 2,904,523; 2,912,399; 2,913,429; 2,914,497;
2,917,476; 2,921,046; 2,922,781; 2,933,467; 2,933,469;
2,934,529; 2,936,295 and 2,937,156.
Other film-forming binders useful for higher temperature work are polymers which often include vinyl chloride units, tetrafluoroethylene units, ethylene units and acrylonitrile units. Various film-forming acrylic binders are useful for the practice of this invention, and include polymers of methacrylic acid, acrylic acid, and their mixtures, copoly-mers or terpolymers of acrylic and/or methacrylic acid .
15 esters with styrene and/or vinyl acetate and copolymers or :
terpolymers of methacrylic acid esters an~/or acrylic acid .
esters with acrylonitrile, as well as emulsion copolymeriz-ates such as bodied oils and phenolic monomers as shown in U.S. Patent No. 2,962,151. Suitable film-forming late~ ~
binders include: those which are vinyl and vinylidene poly- :
mers and contain units such as vinyl acetate, vinyl chloride, ` vinylidene chloride, and the like; those which are hydro-carbon polymers and copolymers and contain ethylene or propyl-. ene units and oxygenated or halogenated derivatives of either, .-~
butadiene, oxygenated b-~tadiene, isoprene, oxygenated iso-prene, butadiene-styrene, butadiene vinyl toluene, iso-prene-styrene and the like; those which are acrylic and contain units of acrylic acid, methacrylic acid, their e~ters, and acrylonitrile; copolymers containing hydrocarbon . 30 monomers with unsaturated materials such as the reaction .. .
., ,, .. . . . .

~065080 product of maleic acid with styrene; and, broadly, various other resinous and rubber-like elastomerlc latex products which are polymers and copolymers of ethylenically unsaturat-ed monomers and are polymers obtainable in stable aqueous latex form and are capable of coalescing into a pigmented film-forming binder when brushed, sprayed, or rolled onto a surface for curing at room temperature or elevated temp-eratures. Coalescing assistants such as diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, ethylene glycol monophenyl ether, or 2,2,4-tri-methyl-1,3-pentanediol monoisobutyrate, are helpful in modifying the properties of the film-forming latex binders to obtain desired coalescence of the film-forming polymer particles at the ambient coalescing temperature.
Opacifying pigment efficiently interacts with the plastic pigment and becomes uniformly spaced throughout the paint film by the plastic pigment. The increased opacity achieved prior to the onset of high surface porosity is primarily attributed to a combination of increased dispersion and spacing of opacifying pigment caused by the spacing effect of the plastic particles and by the formation of an essentially closed cell microvoid structure within the paint film. Ordinary paint films are usually about 1 to 3 mils thick when applied by brush or roller, and in such instance, between about 5% and about 25% opacifying pigment -such as rutile TiO2 on a dry solids volume basis is required fox the opacified paint of this invention. In general, the thinner the film, the higher the opacifying pigment content required. For best hiding in such films, pigmentary rutile - 30 TiG2 preferably will be used at about a 10% to 25% level : .

:~0~5~80 on a dry solids volume basis.
The paint of this invention can further contain non-opacifying filler or extender pigments often referred to in the art as inerts and include clays, such as kaolinite clays, silica, talc, mica, wollastonite, barytes, slate flour, calcium carbonate and other conventional filler pig-ments. All filler or extender pigments have fairly low Refractive Indices and can be described generally as pig-ment other than opacifying pigment. Filler and extender pigments generally should not be above 44 microns in effec-tive diameter for painting purposes and generally are of particle size not substantially larger than 25 microns for best finishes. Filler and extender pigments can comprise 0% to 60% of the latex paint on a dry solids volume basis and advantageously between about 5% to 50% in accordance with higher pigment loading aspects of this invention. Pre-ferred filler and extender pigments include calcined clay, amorphous silica, crystalline silica, and diatomaceous silica which have been found to not significantly detract from the very desirable and advantageous interaction of the non-film-forming particles and opacifying pigment dis-persed in dried opacified paint films in accordance with this invention. In contrast, conventional latex paints con-taining filler and extender pigments invariably show a sub-stantial reduction in film integrity properties at PVC'sbeyond the critical-PVC.
- The latex paint of this invention can contain tinctorial pigments which are pigmertary materials suitable for imparting a specific hue to the resulting latex emsulsion paint. Tinctorial pigments generally include, for example, . ~ . , .

~Q~5080 ferrite yellow oxide, ferric oxide, "brown" iron oxide (which is a blend of red, yellow, and black iron oxides), tan oxide of iron (which is a similar blend), raw sienna and burnt sienna, raw and burnt umber, chromium oxide green, phthalocyanine green (chlorinated copper phthalonitrile) the green iron salt of nitroso beta naphthol, copper, phthalonitrile blue, ultramarine blue, carbon black, lamp-black, toluidine red, parachlor red, para toner (red, alkali resistant red, BON red, and maroon), cadmium reds and yellows, Watchung red, madder lake (red), Duratone red, carmine red, chrome yellow (lead chromate), chrome orange, Hansa yellows (which are azo couplings of metranitroparatoluidine and acetoacetanilide), and golden nickel azo complexes such as those shown in U.S. Patent No. 2,396,327. Other conventional specialty pigmentary additives such as nacreous graphite, nacreous glass frit, etc., and fluorescent, pearlescent and opalescent materials can be classified broadly as tinctorial pigments since such pigmentary additives give special opti-cal effects such as pearlescent and nacreous effects. Tinc-torial pigments comprise 0% to 20% and advantageously 0% to 10% of the dry solids volume basis of the opacified latex paint of this invention and such tinctorial pigments are generally opacifying but can be either opacifying or non-opacifying depending on the Index of Refraction.
One interesting and valuable characteristic of the latex emulsion paint of this invention is that higher than conventional sheen and gloss can be obtainable at high PVC's which can be achieved particularly with non-film-forming monodisperse polymer particles having approximately the same size. ~seful monodisperse polymer particles can be produced ~, :

~ ' '. :: ' -: ~ , : , .

by careful seeding and emulsion polymerization such 25 sug-gested in Pierce et al., U.S. Patent No. 3,423,351 -In said Pierce patent, water-emulsifiable polymerizable organic liquid having preferably ethylenic carbon-to-carbon unsaturation can be - polymerized in a dispersed state in aqueous medium contain-ing anionic and nonionic surfactants under emulsion polymer-ization conditions wherein the ratio of surfactants is care-fully controlled along with the temperature and the water solubility of polymerizable liquid in the reaction mixture.
The particle diameter of suspension or emulsion can be - readily determined by electron-microscopy techniques. In determining the uniformity or particle diameter, the weight ' average diameter (Dw) is divided by the number average diameter (Dn) to provide a DW/Dn ratio or polydispersity '` index which determines whether a suspension of polymer parti-' cles is monodisperse or polydisperse. When the ratio DW/Dn is l.00, the particles are perfectly monodisperse, and for ; purposes of this invention, all of the polymer particles are considered monodisperse when the DW/Dn ratio is from 1.0 to ' about 1.1 and preferably from 1.00 to 1.05.
A further surprising advantage can be achieved with paint compositions highly loaded with non-film-forming com-~ ponents and having high PVC's beyond the critical surface ', 25 porosity PVC (enamel holdout) whereby the dried paint films ' produced have low enamel holdout but surprisingly maintain substantial film integrity properties such as dirt resistance, grime resistance, mar resistance, stain resistance, abrasion resistance, and scrub resistance and like film integrity properties. The high pigment-binder ratio is beyond the PVC

' '. ' ' ' , ., lO~S080 level where sufficient film-forming binder is available to - totally encapsulate the non-film-forming solid components.
In contrast, conventional latex paints without plastic poly-meric particles lack cohesiveness and film integrity at high S PVC's above the critical-PVC due to a non-continuous paint phase. In accordance with this aspect of the invention, latex paint is preferably based on film-forming binders of acrylic polymers containing at least about 40% by weight co-polymerized acrylic unsaturated monomers such as for example acrylic and methacrylic acid, methyl acrylate and methacryl-ate, ethyl acrylate and methacrylate, butyl acrylate and methacrylate, propyl acrylate and methacrylate, 2-ethyl hexyl acrylate and methacrylate, and various reaction products such : as butyl, phenyl and cresyl glycidyl ethers reacted with acrylic and methacrylic acids, hydroxy alkyl acrylates and methacrylates such as hydroxyethyl and hydroxypropyl acryl-- ates and methacrylates, as well as amino acrylates and meth- ~
acrylates. Other useful binders for paints compounded at ~:
. PVC's beyond the critical surface porosity-PVC include acrylic copolymers containing up to 60~ styrene, styrene-butadiene copolymers containing between about 35% to 65% copolymerized styrene or styrene derivatives and copolymers of acrylo-- nitrile, vinyl chloride, and vinylidene chloride which are often copolymerized with plasticizing monomers such as di-butyl maleate, butadiene or alkyl acrylates.
The film-forming binders utilized to coalesce at ~ ~ :
; the temperature of paint application provide drying of the :~
paint film and form a binding matrix for the opacifying pig-ments, non-film-forming polymer (plastic particles), non-opacifying pigment éxtenders and fillers and other non-film--23- :

: . .

~()65080 forming additives. Coalescing assistants such as diethylene glycol monoethyl ether acetate, 2,2,4-trimethyl-1,3-pentane-diol monoisobutyrate, or dibutyl phthalate are useful co-alescent materials for the latex paints of the invention.
The latex paint composition of this invention has a PVC broadly between about 30% and 75% wherein the PVC of a paint composition is greater than the critical-PVC as measur-ed by opacity. The latex paints can have a PVC up to 75~
and produce dried paint films having excellent film integrity properties such as scrub resistance, burnish resi~tance, mar resistance, stain resistance, dirt resistance, grime resist-ance and abrasion resistance which can be all approximately represented by a scrub resistance curve measured in accord-ance with ASTM Test No. 2486 modified in that a shim is not used. The scrub test is run with a 10% aqueous slurry of Crest soap used as an abrasive scrub medium and reported as the number of scrub cycles to remove 50% of the paint film thickness. Film integrity properties can be expediently measured by scrub resistance wherein the minimum film integrity properties of paint films produced in accordance with this invention withstand at least about lO0 scrub cycles, advantageously above 450 scrub cycles for good paint films and preferably at least about 600 scrub cycles for high quality paint films. The most preferred paints have a PVC
greater than the critical-PVC (opacity) and less than the critical surface porosity PVC tenamel holdout) indicating that the most preferred paint films have very low film surface porosity. Paint films produced in accordance with the broader aspects of this invention at PVC's above the critical surface porosity PVC have lower enamel holdout properties than the ~.06S080 preferred films produced where critical surface porosity PVC
is not exceeded. Surprisingly, though, such higher PVC
films of this invention retain excellent film integrity properties. This is believed to be achieved by close pack-ing of the solid, non-cellular, plastic particles.
The solid, non-film-forming polymer particles appear to effectively resist scrubbing and, even though such particles may become worn down in place, they have the advantage of exhibiting exposed solid polymeric material rather than apertures as would be obtained where such worn polymer particles were hollow, tuberculated, or vesiculated.
Accordingly, the paint of this invention would be expected to present a more resistant surface to dirt and grime even when abraded a bit, and less dry mineral pigment per unit area would be exposed than is the case of a corresponding conventional paint film, whj.ch dry pigment often is fairly receptive to absorbing surface markings. Accordingly, even though the inventive paint film in these upper PVC ranges is clearly '!binder-starved", it can exhibit good film integrity properties up to 75% PVC. Such unexpectedly good performance perhaps is attributable to some sort of interaction between the solid, non-film-forming plastic particles and the latex -~ paint binder, the former possibly even functioning as a binder extender or adjuvant in some fashion.
The inventive latex emulsion paint can be made in a disperser mill such as a Cowles disperser. Preferably the conventional pigment dispersion ingredients except the non-film-forming polymer particles and film-forming binder are first mixed together in the disperser mill, or alternatively, a sand mill, a pebble mill, a roller mill, or a ball mill.

.: . , ;5~)80 Then the n~n-film-forming polymer particles and film-fGrming binder plus conventional letdown ingredients are added to the resulting mixture and blended in, suitably with a conventional tank stirrer. The resulting paint is an intimate dispersion.
5 ~ The following Examples illustrate the merits of this invention and provide methods of practicing the inven-tion but should not be construed as limiting the scope of this invention.
i- EXAMPLE 1 A pigmented latex emulsion paint was prepared as ~ollows:
Pigment Grind PoundsGallons Water 17.5 2.10 Bactericide; 1-(3-chlorallyl)-3,5,7-triazo-l-azoniodomantane chloride.
(Dowicil 100, T.M. of Dow Chemical Co.) 1.0 .12 Thickener (2.5% aq. soln. of hydroxy ethyl cellulose having a solution - 20 viscosity of 15,000 cps). Cellosize100.0 12.12 Defoamer, mineral oil and silica derivatives. Drew L-475* 2.0 .26 Pigment dispersant, sodium salt of poly-acrylic acid. Tamol 731, T.M. of Rohm & Haas, Co. 7.8 Wetting Agent (Triton CF-32, T.M. of Rohm & ~aas Co.) 0.25 .0 Rutile Tio2 175.0 5.23 Letdown Water 118.1 14.17 Coalescing aid (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate)2.4 .30 Coalescing aid (diethylene glycol butyl8 1 20 ether acetate) 9, Film-forming binder latex (vinyl acetate- 22 dibutyl maleate copolymer) 207. .9 * Trade mark , :
~ ., iO~SO~C~

Letdown (cont'd) Pounds Gallons Non-film-forming plastic particle latex (polystyrene 2325 A) 254.5 29.40 *
Defoamer Dow L-475 2.0 .26 Thickener (2.5% aq. soln. of hydroxy ethyl cellulose) 92.4 11 20 TOTALS 1022.75 100.02 The resulting pigment-volume-content (PVC) was 65~, the volume solids content was 33%, and the welght solids con-~, tent was 45.3%.
Paint films were air dried at room temperature (72F.) for at least 16 hours before the following measure-ments were made. Opacity is measured on a 3 mil wet film applied to Lenata Form 3B chart and dried at 72F. for 16 hours wherein reflectance is measured over black and white portions of the chart using a Color Eye spectrophotometer to provide a contrast ratio reported as the ratio of reflec-~ tance over black to reflectance over white. Surface porosity ; is measured by enamel holdout wherein a test paint of 3 mils wet film was applied by a Bird applicator on a Lenata Form 3B opacity chart and dried at 72F. for at least 16 hours.
Thereafter 1.5 mils wet film of alkyd enamel (white alkyd Y-5950 comprising 17.3% Tio2; 14.5~ inerts; 30.7% Tall oil alkyd; 37.5% mineral spirits, a product of Glidden-Durkee - 25 DiVision of SCM Corporation) was applied over the dried paint film and the alkyd enamel was dried at room tempera-ture for 24 hours. The gloss of alkyd over the dried latex paint film was compared to the gloss of the same alkyd - applied to a sealed substrate. Enamel holdout is reported as the ratio of per cent gloss over the test paint when , -27-* Trade mark , . . . .

S()80 compared to the gloss of the alkyd enamel over the sealed substrate. Surface porosity was also measured by K & N Ink holdout wherein a 3 mil wet film of test paint was drawn down on a 2C Lenata opacity chart by a 3 mil Bird applicator and air dried for 16 hours. K & N Ink is then cast at right angles to the test paint over the white portions of the 2C chart and allowed to dry for two minutes. Excess ink is thereafter rubbed off with paper towels. Penetra- ¦
tion of ink into the test film is then measured by reading per cent reflectance on the Y scale of an IDI, Color Eye colorimeter spectrophotometer (Instrument Development Labs, Kollmorgan Corp.) using a white vitrolite standard. Porosity is indicated by per cent reflectance. Similar paint films of 3 mils wet and dried at 72E. for 16 hours were subjected to abrasion resistance (modified ASTM Test No. D-2486), and stain resistance (Test No. D-2198). The results are set forth in Table 1.

Property PVC 65%
Volume solids 33%
TiO2 level (pounds/100 gal.) 175 Opacity (Contrast ratio) .970 Surface porosity (enamel holdout)80%
Surface porosity (K & N Ink holdout) 80%
Abrasion resistance (scrubbability) Excellent Stain resistance Excellent Burnish resistance Excellent Sheen (% reflectance at 85) 60%
Gloss (% reflectance at 60) 8%

; * Trade mark , . :.

10~i5080 A paint similar to Example 1 was compounded at a PVC of 56% and containing non-film-forming polymer particles of 5,200 A. Paint films were tested in the manner of Example 1 and results are listed in Table 2 hereinafter.

A paint similar to Example 1 was compounded at a PVC of 64% and containing non-film-forming polymer particles of 2,310 A. Paint films were tested in the manner of Ex-ample 1 and results are listed in Table 2 hereinafter.

A paint similar to Example 1 was compounded at a PVC of 70%. Paint films therefrom were tested in the manner set forth in Example 1 and reported in Table 2 hereinafter.

A prior art paint was formulated containing film-forming latex binder being a copolymer of 82% vinyl acetate and 18% dibutyl maleate, 255 pounds of TiO2 (23%), and inerts. The paint contained by volume 21% TiO2; 5.3% CaC03;
7.7% silica and silicates; 16.2% said binder; 2~ additives;
2.8~ glycol and glycol ethers; and 45% water whereby the volume solids was 33% and the PVC was 42.6%. The prior art paint was tested as described in Example 1 and the results thereof are reported in Table 2 hereinafter.
.

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~o~saso A pigmented latex emulsion paint was prepared as follows:
A. The following ingredients were dispersed by a Cowles dissolver for about 55 minutes: ~~
255 parts rutile pigmentary TiO2 50 parts calcined clay 60 parts calcium carbonate 3 parts nonionic surfactant of iso-octyl phenoxy ethanol : 10 containing 9-10 ethylene oxide units per mole of 3-phenol (Triton X-100,*
8 parts 15% water solution of ? sodium salt of polymeric- '.
carboxylic acid (Tamol 731) *
1 part anti-foam agent, a blend of mineral oils and silica derivatives (Drew 913SX)~
12 parts ethylene glycol : 2.4 parts water soluble cellulosic thickener of hydroxy-propyl methylcellulose eontaining about 19-24~ meth-oxyl and 4-12% hydroxypropoxyl 1 part anti-mierobial agent, 1-(3-chloallyl)-3,5,7-tri-azo-l-aeonioadomantane chloride 150 parts water.
B. The following was added to Part A:
.` 2.3 parts eellulosie thiekener hydroxypropyl methylcellulose 16 parts diethylene glycol monoethyl ether

4 parts 2,2,4-trimethyl-1,3-pentanediol monoisobutyra~e . .
4 parts nonionic surfactant of ammonium salt of sulfate ester of an octyl phenoxy polyoxyethylene ethanol (Alipal C0-436, T.M. of GAF Co.
4 parts dispersing agent, sodium salt of polymethacyclie - acid as a 30% water solution (Tamol 850)-~
4 parts anti-foam agent, a blend of mineral oils and siliea derivatives (Drew 913SX).
C. A series of latex paints were made by mixing part B
(containing part A) with an aqueous dispersion of polystyrene -partieles and film-forming latex. ~he polystyrene partieles * Trade mark , . . .

0~0 had a weight average particle size of 2450 A, a DW/Dn of 1.1, weight solids of 51.4%, and a density of 8.59 pounds/gallon, and glass transition temperature of about 100C. The film-forming latex binder was an aqueous dispersion of film-form-ing latex binder comprising 82~ vinyl acetate copolymerized with 18% dibutyl maleate, being 54.5% weight solids having a weight average particle size of about 6500 A, and a glass transition temperature (Tg) of 15C. To each paint disparsion was added water so that the volume solids of each indicated formulation was 33.1%. The pigment-volume-content (PVC) of the resulting dry film of each formulation is indicated in Table 3. The percentages indicated for the aqueous dispersion polystyrene and for aqueous dispersion of film-forming latex binder were calculated by dry solids volume basis. The sample indicated as "control" was a conventional latex paint com-prising on a dry solids volume basis 57.5% copolymer of 82%
:~ vinyl acetate and 18% of dibutyl maleate, and on a dry solids volume basis 23% rutile TiO2, 19.5% inerts, as described in Example 5.

. Pigment-Monodisperse Volume-Polystyrene Film-Forming Content Particles Latex Binder (PVC) -25 A-61 3.4% 57.5% 42.5%
B-65 12.4% - 48.5~ 51.5%
C-69 23.5% 37.4% 62.6~
D-70 33.5% 27.4~ 72.6%
Control 0 57.5% 42.5%
Paint films of the foregoing samples were air dried at room temperature (72F.)~ for at least 16 hours. The film-forming ~ , .
.. , .: :
.. . .

~s~o latex coalesced into a matrix wherein the polystyrene remain-ed particles dispersed therein. Other dried paint films were tested for scattering and opacity as noted hereinafter and the results listed in Table 4.

X(0.98)** Dry Film S*, scattering thickness for a con-Sample No. reciprocal mils trast ratio of 0.98 A-61 5.5 mil 1 1.9 mils B-65 5.9 mil~l 1.85 mils C-69 5.4 mil~l 2.0 mils D-70 8.0 mil 1 1.4 mils Control 4.6 mil~l 2.4 mils wherein:

*S = Kubelka-Munk Scattering Coefficient and units are reciprocal mils; and **X(0.98) = dry film thickness of X thickness which gives a contrast ratio over Lenata Form 3B opacity chart of 0.98, and units are mils. Opacity is determine~ with Kubelka-Munk solution for multiple light scattering in accordance with page 106 et. seq. of Reflecta~ce Spectroscopy, Springs-Verlog, N.Y. (1969).
Similar dried paint films were tested for enamel holdout and scrubbability, in a manner hereinafter described and the re-sults thereof are indicated in Table 5.

,. .
Relative Scrub Sample No. Enamel Holdout Scrubbability % of Control _ _ _ A-61 88.4%947 cycles 105%

B-65 83.7%1347 cycles 150%

C-69 89.0%1800 cycles 200~

D-70 3.8%700 cycles 78%

Control 84.9%900 cycles 100%

Enamel holdout is tested by applying 3 mils wet film by Bird , , ~, ', :. . ' ... ' s~'v applicator on a Lenata Form 3B opacity chart and air dried at 72F. for at least 16 hours. Thereafter, 1.5 mils wet film of alkyd enamel (Glidden, white semigloss Y-5g50) is applied over the dry latex paint film and dried at room temperature for 24 hours. The alkyd has very poor holdout properties. The gloss of the alkyd over the latex paint is compared to the gloss of the same alk~d applied to a sealed substrate. Enamel holdout is reported at the ratio or per cent of gloss over latex paint to gloss over sealed sub-strate. Scrubbability was measured by applying 6 mils wet film of latex paint by Bird applicator onto a Lenata Form P-121-ION chart and air drying at 72F. for at least 16 hours. The dried films are subjected to a Gardner scrub machine using a 10% solution of 105 Crest soap in water.
Scrubbability is reported as number of cycles to failure (50~ of paint film removed).
Improved paint film properties can be achieved at a substantially broader range of PVC's wherein excellent paint films result at higher PVC~s. Conventional paints have a narrow critical-PVC wherein opacity and enamel hold-out properties are compromised. Conventional hiqh quality latex paints ordinarily exhibit enamel holdout of about 85%
and scrubbability of less than 1000 cycles to failure.

Paint samples were formulated as indicated in the following Table 6 in a manner similar to Example 6. The pigmentary rutile Tio2 content was reduced in a stepwise manner. Opacity was maintained by increasing the concentra~
tion of plaRtic polymer particles while simultaneously de-creasing the concentration of titanium dioxide. The volume .- ' :.

: ~ ' ' : , . .
: , :
- . : ,, . . ,: . -10650~30 of polystyrene polymer particles was adjusted to maintain the pigment volume concentration (PVC) of the dry film at about 62.6%. The volume fraction of ingredients indicated in Table 6 are volume fractions in the dry film listed as volume solids on a dry solids volume basis.

TiO2 Polystyrene Inert Film-Forming Sample Vol. Vol. Vol. Latex Vol.
No. Fraction Fraction Fraction Fraction 10 E-69 23.0%23.5% 16.1% 37.4%
F-76 21.7%24.8~ 16.1% 37.4%
G-75 19.0%27.5% 16.1% 37.4%
H-74 16.2%30.3% 16.1% 37.4%
I-73 13.5%33.0% 16.1% 37.4%
15Control 23.0%0.0% 18.5% 57.5%
Paint films of the foregoing were tested in a manner indicat-ed in Examples 1 and 6, and the results thereof are indicated in the following Table 7.

.' .
Film Thick-ness for con-Sample Scattering trast ratio Enamel No. S, mil~l of 0.98 Scrubbability Holdout E-69 5.5 mil 1 2.0 mils 1800 cycles 89.0%

F-76 5.2 mil 1 2.2 mils 1200 cycles 86.6%

G-75 5.4 mil 1 2.0 mils 1850 cycles 84.3%

H-74 5.6 mil 1 2~0 mils 2000 cycles 88.4%

I-73 5.4 mil~l 2.0 mils 1400 cycles 78.6% -Control 4.6 mil~l 2.4 mils 900 cycles 84.9%

Paint samples were formulated in a manner similar to Example 6. As indicated in the following Table 8, the con-' :~

. .
.
,- , -~o~o~

centration of pigmentary rutile titanium dioxide was maintain-ed constant and the content of polystyrene particles was varied. Sufficient inert, as indicated, was added to main-tain the pigment-volume-con~entration (PVC) of the dry film at about 63.0%. The volume fraction of pigments and film-forming latex based on the dry film is likewise indicated.

TiO2 Monodisperse Inert Film-Forming Sample Vol. Polystyrene Vol. Latex Vol.
No. Fraction Vol. Fraction Fraction Fraction J-9D 13.5% 8.4% 41.1% 37.0%
K-9C 13.5% 16.8% 32.7% 37.0%
L-9B 13.5% 25.1% 24.4% 37.0%
M-9A 13.5% 33.5% 16.0% 37.0%
N-7B 13.5% 37.5% 12.0% 37.0%
0-7C 13.5% 41.5~ 8.0% 37.0%
P-7D 13.5% 45.5% 4.0% 37.0%
Q-7E 13.5% 49.5% 0 37.0%
Control 13.5% 0 49.5% 37.0%
20 Paint films from the foregoing compositions were tested in - a manner similar to Example 6. Results are indicated in ~- the following Table 9. Gloss was measured at 85 by ASTM
D-523-67.
:- :

- ` -36-- -_.. . ..

so~

TAsLE 9 Film Thickness 85 Gloss Sample Scattering for Contrast Enamel Reading No. S! MilRatio of 0.98Holdout ASTM D-523~67 J-9D 4.0 mil~l 2.6 mils 84% 3.2 K-9C 4.2 mil~l 2.5 mils 90% 4.8 L-9B 4.4 mil 1 2.4 mils 96~ 7.8 M-9A 5.3 mil 1 2.1 mils 94% 20.6 N-7B 5.5 mil 1 2.0 mils 95% 31.8 0-7C 5.6 mil~l 2.0 mils 94% 47.0 P-7D 5.g mil 1 2,0 mils 94% 60.6 Q-7E 5.5 mil~l 2.0 mils 98~ 73 Control 3.8 mil~l 2.7 mils 35% 2.8 The foregoing demonstrates advantages of this invention wherein the paint mixtures produce films having high sheen although the dried films contain 63% volume per cent pigment, whereas conventional latex paint films at 63% produce "flat" films with respect to sheen. Sheen is measured in accordance with ASTM Test No. D-523-67. Further noteworthy advantages of this invention are demonstrated including in-creased opacity as the plastic polymer content increases ~ .
from 5 to 37% while at the same time porosity decreases which is uncharacteristic of conventional paint films having a pigment volume concentration of 63%.

Paint mixtures were formulated in a manner similar to Example 4. In the following Table 10, various indicated -~ film-forming latex binders were utilized in sufficient :
quantities in the paint formulation to maintain pigment-volume-content in the dry film at about 63%. Total volume solids was maintai~ed at about 33%.

1~i50~30 Glass Sample Fi~Forming Wt. % Particle Transition No. Latex Binder Solids SizeTemp. T
O
R-23 Copolymer of 82%54.4% 6500 A21C.
vinyl acetate and 18% dibutyl maleate S-24 Terpolymer of methyl 50.0%4800 A 5C.
methacrylate, butyl acrylate, and acrylic acid T-25 Cbpolymer of vinyl 55.0%1100 A unknown chloride and butyl acrylate U-26 Copolymer of methyl 46.5%1000 A 9C.
methacrylate and butyl acrylate V-27 Copolymer of 83%51.0% 3500 A10C.
vinyl aoetate and 17% of 2-ethyl-hexyl acrylate W-28 T ~ olymer of vinyl 52.0%4800 A 15C.
acetate, vinyl chlor-ide, and ethylene -X-29 Terpolymer of methyl 65.0%30% 850 A 0C.
methacrylate, meth- 70% 6000 acrylic acid, and butyl acrylate The foregoing film-forming latex binders were mixed with .
polystyrene particles, opacifying pigments, and inerts in a manner similar to previous examples. The film-forming latex binders set forth in Table 10 were used in sufficient quantity to maintain the pigment-volume-content in the dry film at approximately 63%. Film-forming binders from Table 10 were utilized at 37%, monodisperse polystyrene particles at 33.0%, and Tio2 at 13.5%, on a dry solids volume basis. By main-taining constant the ratio of ingredients, however, the paints indicated in the following Table 1~ are not neces-sarily optimized since the preferred useful PVC range depends :
,, , 1~08(~

on the average particle size of plastic particles as well as the relative particle size of binder. Paint films there-from were tested in a manner similar to Example 10, and the results are indicated in the following Table 11.
TAsLE 11 Sample Film-Forming Enamel No. Latex Binder Contrast Ratio Holdout !
X 37% of R-23 0.965 99.5 Y 37~ of S-24 0.967 87.6 Z 37% of T-25 0.951 86.5 - AA 37% of U-26 0.949 95.1 AB 37% of V-27 0.965 47.7 AC 37% of W-28 0.961 86.5 AD 37~ of X-29 0.967 86.0 15 Contrast ratio was measured by applying a 3 mil wet film to a Lenata Form 3B opacity chart and air drying to film at 72F. for at least 16 hours. Reflectance measurements are made over both white and black portions of the chart using a Color Eye Spectrophotometer. Contrast ratio is reported 20 as the ratio of reflectance over black to reflectance over - white.
Table 12 indicates binders in Table 10 and Table compounded in optimized formulations at the most preferred PVC .

- Volume Sample Film-Forming Contrast Fraction No. Latex Binder PVC Ratio Holdout TiO
.
AE R-23 65 .979 89.0% 13 AF S-24 52 .973 88.0~ 13~

AG U-26 62 .969 88.5% 13%
AH X-29 60 .976 89.5% 13%
Prior Art Control R-23 42 .970 87.0% 23 ~ .
.

10~ 0 Paint mixtures were prepared in a manner similar to that in Example 1, using a homopolymer methyl methacryl-ate latex as plastic particles. PVC was 44~, TiO2 was 13%
by volume of paint solids, volume solids of paint was 33%, leaving 31% by volume of plastic particles in the dried paint film. The proper PVC was chosen as described herein to be the point of critical surface porosity. Table 13 summarizes the results of opacity and porosity measurements.

Paint mixtures were formulated in a manner similar to Example 1, using homopolymer vinyl chloride as plastic particles. The PVC was 52%, volume solids 33%; the paint film contained 13% by volume of TiO2 and 39% plastic parti-cles. The proper PVC was chosen as the point of criticalsurface porosity as described herein. Table 13 summarizes the results of opacity and porosity measurements.

Plastic - 20 Particle Particle E~mel Contrast ~xposition Size Pol~dispersity PVC Holdout Ratio H~x~olymer vinyl dhloride1,790 A 1.12 52 81% .970 - 25 Ho~olym~er methyl O
methacrylate 2,694 A 1.06 44 80% .966 - The paint sample previously designated in Example 6 a~ C-69 was modified by adding 1% by weight of black colorant which is a 5.1% dispersion of carbon black in ethylene glycol base. A wet paint film of 3 mils was cast upon a Lenata opacity chart form 3B by a Bird applicator and air dried at :

. .

lO~S080 - room temperature for at least 16 hours. The dried film has a reflectance of 78.7 as measured through a Y filter of a Color Eye spectrophotometer. For comparison, a conventional dry latex paint film similarly modified by 1~ black colorant L 5 had a reflectance of 73.6%. Conventional paint films re-quire approximately 50% more Tio2 to match the improved tinting strength of the latex emulsion of this invention as measured by reflectance.
The following Examples 13 to 17 (Tables 14-17) inclusive illustrate latex paints containing non-film-form-ing polymer particles at high PVC's beyond the critical - surface porosity PVC as measured by enamel holdout.

Figure 5 is a ladder series of paint compositions . 15 produced as follows. Two pigmented latex emulsion paints were prepared by dispersing the pigmentation at high speed with an impeller type disperser (e.g., Cowles Dissolver) to ` a Hegman Value of 8, then reduced at low speed with the ~,~ binder latex and non-film-forming plastic pigment latex plus auxiliary ingredients as follows:
PIOE~T ~ND (lbs./100 gal.) (lbs./100 gal.) ; Water 30 10 Preservative: 1-(3-chloroallyl-3, 5, 7-triazo-1-azoiodo[Tantane ~ 25 chloride (Dowicil 100) ; Hydro~ E~yl Cellulose (2.5% ~Fueous - solution Cellulosize QP-15,000) 50 100 Ethylene Glycol 25 25 Defoamer: mineral oil & silica 30 derivatives (Drew-I,475) 2 2 Pigment Dispersant: sodium poly-acrylate 8.3 8.3 , ''~' .
* Trade mark ., ~

1065~80 Pigment Grind (contld) (lbs./100 gal.) (lbs./100 gal.) Wi~tting Agent (Triton CF-32) 0.26 0.26 ~utile TiO2 (Zopaque P~L-7, T.M. of SCM Corporation)250 250

5 IE~N
, Water 100 135 Defoamer 3 2 Binder latex, copolymer of 50%
butyl acrylate + 50% methyl methacrylate, 5000 A, Tg=0~C.
and 50% weight solids 370 123.4 Plastic Pigment, polystyrene Tg=100C. and 55.8% weight solids 90 7 300 Coalescent: 2,2,4-trilrethyl-1,3-pentanediol isobutyrate11 4 Thic~kener, Hydroxyethyl Cellulose (2.5% aqueous solution)101.7 76 Cancentrated Aqueous ~131.5 1.5 Pigment-Volure Content 40% 80%
Volume Solids 33% 33%
Weight Solids 46.5% 46.1%
A series of paints were prepared by blending the 40 PVC and 80 PVC paints at appropriate ratios to yield a ladder series over the PVC range of 40% to 80%. After 24 hours equilibration of the finished paints, films were cast on appropriate substrates with a Bird film applicator to pro-vide a 3 mil wet film for further testing.
Opacity was .ested on films cast on Lenata chart form 3B with a 3 mil Bird applicator and dried for 24 hours.
Reflectance readings over the black and white portions of the chart were made with a Color Eye spectrophotometer and the contrast ratio is defined as the reflectance over black divided by reflectànce over white. Higher ratios indicate --, 106tiQ8~

greater opacit~ or hiding power.
Surface porosity was measured by enamel holdout wherein the film from the opacity test is subsequently coated with a gloss alkyd enamel using a 1.5 mil Bird appli-cator. The gloss of the alkyd over the test paint divided by the gloss of the alkyd over the sealed chart alone is defined as the percentage enamel holdout. Higher numbers , indicate lower surface porosity. The gloss is measured with a Hunter gloss meter with a 60 incident and reading angle.
Surface porosity can be alternatively tested by - applying K & N Testing Ink to a film, as with enamel holdout, for two minutes, then removing with paper towels. The pene-tration of the ink into the paint film causes a darkening in color which is proportional to the porosity of the film ~i which is measured by reading the Y scale reflectance with ,i an IDL Color Eye spectrophotometer using a white vitrolite standard. Higher numbers indicate lower porosity.
Scrub resistance is measured in accordance with ASTM Test D-2486, except that a shim is not used. A 10%
:;
slurry Crest soap is used as the abrasive scrub medium and ., , results are expressed as the number of cycles to remove 50%
of the paint film. Scrub is preferably expressed as a , percentage of an accepted commercial standard latex paint which is simultaneously tested on the same test panel. The standard herein is Spred Satin Y3400*;Glidden-Durkee Div. of ;' SCM) latex paint which contains 21% TiO2; 5.3% CaCO3; 7.7%
; silica and silicates; 16.2% vinyl acetate copolymer; 2.8%
glycol ethers,and glycols; 45% water. Thus a 100% scrub indicates scrub resistance equivalent to the standard.
., .

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106~08~

Higher percentage or scrub values indicate better scrub resistance.
Stain resistance and removal is measured in accordance with ASTM Test D-2198 with the results reported in the manner reported for scrub resistance.
The results of such testing are conveniently viewed as a scaled graph of the respective property versus PVC. At some characteristic PVC, an abrupt change occurs in each property which is defined as the critical-PVC for that physical property.

Several latex paint compositions having variable binder polymers were compounded and comparatively tested for film integrity properties (scrub) as-well as enamel holdout and opacity (contrast ratio). The physical properties of the paint film are reported relative to a standard high quality conventional latex paint Spred Satin (T.M.) as in Example 13. The performance ratings in Table 14 are rela-tive to the 100% rating (standard). All paints in Table 14 were compounded at 60% PVC. The volume solids were main-tained at 32% comprising 19.2% non-film-forming components and 12.8% film-forming binder. The Tg of the binder was calculated in accordance with the Fox equation l/Tg = ~Wi/T
where Tg is in K for the copolymer; Wi is the weight frac-tion of each comonomer; and Ti is the homopolymer Tg for each monomer in K. The test paints were compounded from the -following components wherein the binder composition varied as indicated:
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Paint Components Vol. solids/100 gal.
Tio2 4.48 gallons Calcined clay (Optiwhite)5.46 gallons Silica (Min-U-Sil 10, T.M. of Pennsylvania Glass Company)2.26 gallons Diatomaceous Silica (Celite 499) 1.30 gallons Polystyrene, non-film-forming polymeric particles, 2,800 ~, Tg=lOOJC. 5.70 gallons Latex Film-Forming Binder (Table 14) 12.80 gallons Coalescent 20.0 pounds lOt;S08V

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~06$080 Latex paint compositions were compounded in themanner set forth in Example 14 except that the volumes of both the non-film-forming polymeric particles and the film-forming binder were varied to provide PVC levels from 50%to 75%. The binder was 60% butyl acrylate + 40% methyl methacrylate at 50% weight solids, Tg = -10C., and 2,000 A.
The plastic pigment was 2,800 A polystyrene. The plastic pigment/binder latex is indicated in gallons per 100 gallon 10 of paint and paint films were tested as in Example 14.

Plastic Pigment Enamel Scrub PYCBinder Latex Holdout Resistance Opacity 502.50 80% >400% 78%
' 16.00 ;~ 15 554.10 80% >400% 85%
14.40 .
' 605.70 75% ~40~% 90%
1-2-.-8 657.30 53% 325% 105%

708.90 15% 260% 115%

7510.50 0% 170~ 125%
, ~ -8.00 ' In the same manner of Example 15, the binder was 50% butyl acrylate + 25% methyl methacrylate + 25% isobuty methacrylate at 65~ weight solids, Tg=-4C. and 4,950 A.
The PVC was varied as indicated in Table 16 and tested com-parable to Example 15.

. .
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o Plastic Pigment Enamel Scrub PVCBinder Latex Holdout Resistance Opacity 2.50 90% 270% 86%
16.00 4.10 85% 270% 95%
14.40 5.70 70% 215% 110%
12.80 7.30 35% 160% 120%
lI.20 8.90 5% 120% 130%
9.60 10.50 0% 95% 140%
8.00 lQThe foregoing illustrative examples of this inven-tion demonstrate that latex paint compositions can be pro-duced with non-film-forming polymeric particles in combina-tion with opacifying pigment to provide substantially im-proved opacified paint films at PVC's between 30% and 75%
.. 15wherein the PVC is greater than the critical-PVC as measured by opacity. The foregoing illustrative examples are not ;intended to be limiting except as defined in the appended clJlmJ.

.

:~ -49-

Claims (12)

The embodiments of the invention which an exclusive property or privilege is claimed are defined as follows:

1. An aqueous latex dispersion paint composition which coalesces at an ambient coalescing temperature into a hardened paint film, said latex paint having about 30% to 70% by weight total solids and comprising on a dry solids volume basis:
25% to 70% of a film-forming latex binder having a major weight portion of polymer particles between about 1,000 .ANG. and 10,000 .ANG. and having a glass transition temperature at least about 5°C. below said coalescing temperature whereby said binder particles will coalesce into a binding matrix, said latex binder being a polymer or a copolymer of ethylenically unsaturated monomers;
10% to 60% of solid, non-cellular, non-film-forming polymer particles having a weighted average diameter between about 1,000 .ANG. and 10,000 .ANG. and having a glass transition temperature at least about 30°C. above the glass transition temperature of said binder, said non-film-forming particles being polymerized ethylenically unsaturated monomers having carbon-to-carbon unsaturation;
5% to 25% opacifying pigment having a refractive index of at least about 1.8;
0% to 60% of non-opacifying pigment; and said latex paint having a pigment-volume-content (PVC) between about 30% to 75% wherein the PVC is greater than the critical-PVC as measured by opacity.

2. An aqueous latex paint according to claim 1, wherein said pigment-volume-content (PVC) is between about 48% and 64%.

3. An aqueous latex paint according to either of claims 1 and 2, wherein said solid, non-cellular, non-film-forming particles are between about 1,000 .ANG. and 6,000 .ANG..

4. An aqueous latex paint according to claim 1, containing between about 15% to 50% solid, non-cellular, non-film-forming particles.

5. An aqueous latex paint according to claim 1, wherein the non-film-forming polymer particles comprise polymers selected from the group consisting of styrene, methyl methacrylate, and vinyl chloride.

6. An aqueous latex paint according to claim 1, containing up to about 20% tinctorial pigments on a dry solids volume basis.

7. A latex paint according to claim 1, wherein the paint contains between 5% to 50% of non-opacifying pigment on a dry solids volume basic.

8. A latex paint according to claim 1, wherein the PVC
of the latex paint is greater than the critical-PVC as measured by opacity and less than the critical surface porosity-PVC as measured by enamel holdout.

9. A latex paint according to claim 1, wherein said opacifying pigment is in a volumetric proportion less than the volumetric proportion of said non-film-forming polymer particles.

10. A latex paint according to claim 1, wherein the film-forming binder is selected from acrylic copolymers containing at least 40% by weight copolymerized acrylic unsaturated monomers, styrene copolymers containing between about 35% to 65% copolymerized styrene, acrylonitrile copolymers, vinly chloride copolymers, and vinylidene chloride copolymers.

11. A latex paint according to claim 1, wherein the PVC
is greater than the critical surface porosity-PVC as measured by enamel holdout.

12. A paint composition according to claim 1, wherein the non-opacifying pigments are selected from calcined clay, amorphous silica, diatomaceous silica, and crystalline silica.