Patent Description:
More specifically, this disclosure relates to coating compositions that include emulsion polymers that provide the resulting film or coating layer with resistance to a wide range of hydrophilic and hydrophobic stains.

The statements in this section merely provide background information related to the present invention and may not constitute prior art.

Stain resistance is a desirable property for any coating that is to be applied to the surface of a substrate. However, stain resistance is lacking in most commercial latex paints and particularly hard to attain in "flat" interior wall paints. Adding to this challenge is the wide variations in chemical and physical characteristics of the different household stains encountered.

Polymers that contain strong acid groups are used in a variety of coatings, inks, and adhesives. The strong acid groups provide for improved adhesion of the polymer to substrates, form crosslinks in the presence of divalent metal ions, and promote adsorption of the polymer onto pigment particles, such as titanium dioxide. <CIT> and <CIT> provide waterborne coating compositions that include a vinyl copolymer having phosphorous-containing functional groups. <CIT> discloses an aqueous stain-blocking coating composition that includes an aqueous emulsion copolymer having polymerized units derived from an ethylenically unsaturated nonionic monomer and an ethylenically unsaturated strong acid monomer. <CIT> describes a polymer composition that includes co-polymer particles bearing phosphorus acid groups dispersed in an aqueous medium. <CIT> sets forth a binder composition that comprises an aqueous emulsion copolymer having polymerized units derived from an ethylenically unsaturated monomer and a phosphorous containing monomer. <CIT> discloses an aqueous copolymer dispersion obtained from a mixture of an ethylenically unsaturated nonionic monomer, a phosphorous-containing monomer, an alkoxysilane functional monomer, and a sulfur-based monomer.

The present invention generally provides an emulsion polymer comprising, as polymerized units:.

The relative amounts of the first and second acid monomers are such that the ratio of b/c is from <NUM> ± <NUM> to <NUM> ± <NUM>. The polymer composition exhibits a glass transition temperature (Tg) as calculated using the Fox equation ranging from -<NUM> to <NUM>.

According to one aspect of the present disclosure, the ethylenically unsaturated nonionic monomer may be without limitation any (meth)acrylate, vinyl ester, styrene and substituted styrene, with butyl acrylate, methyl methacrylate, unsubstituted or substituted styrene, acrylic monomer, or a mixture thereof being preferred, while the first acid monomer is phosphate esters of polypropylene glycol mono(meth)acrylate, phosphate esters of polyethylene glycol mono(meth)acrylate, or a mixture thereof and the second acid monomer is methacrylic acid.

According to another aspect of the present disclosure, a coating composition is provided that comprises the emulsion polymer dispersed in an aqueous medium. The emulsion polymer may be present in an amount ranging from <NUM> to <NUM> wt. % based on the entire weight of the coating composition. The coating composition may further comprise an organic pigment, and inorganic pigment, or a mixture thereof. When desirable, the coating composition may also comprise one or more additives, including but not limited to, surfactants, dispersants, extenders, rheology modifiers, defoamers, coalescent agents, and opacifiers.

According to yet another aspect of the present disclosure, a use of the coating composition includes applying the composition to a surface of a substrate to form a film or coating layer on the surface, such that the film or coating layer is resistant to hydrophilic stains and hydrophobic stains. The total ΔE measured for the resistance of the coating composition to the hydrophilic stains and hydrophobic stains is less than <NUM>. In some embodiments, the total ΔE measured for the resistance of the coating composition to hydrophilic stains being less than <NUM>, the total ΔE measured for the resistance of the coating composition to hydrophobic stains being less than <NUM>, and the ΔE measured for the resistance of the coating composition to the consumer union stain being less than <NUM>.

The hydrophilic stains include mustard, ketchup, wine, coffee, and fountain ink, while the hydrophobic stains include ballpoint pen, No. <NUM> pencil, blue crayon, red grease pencil, two red lipsticks (lipstick #<NUM> or CoverGirl Hot Passion, and lipstick #<NUM> or Maybelline Royal Red), and a consumer union black stain.

The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. For example, the emulsion polymers made and used in coating compositions according to the teachings contained herein is described throughout the present disclosure in conjunction with an architectural paint in order to more fully illustrate the composition and the use thereof. The incorporation and use of such emulsion polymers as coating compositions used in other applications as an adhesive, a caulk, a sealant or a mastic are contemplated to be within the scope of the present disclosure. It should be understood that throughout the description, corresponding reference numerals or letters indicate like or corresponding parts and features.

In the context of the present disclosure, washability or stain removal refers to a coating's ability to withstand a scrubbing action that removes the staining material(s) without changing the coating's appearance or protective function. The term "nonionic monomer" as used herein is meant to indicate that the monomer does not bear an ionic charge within the pH range of <NUM> to <NUM>.

The present disclosure generally provides emulsion polymers and coating compositions made therefrom, as well as uses thereof. The emulsion polymers comprise, consist of, or consist essentially of an emulsion polymer having, as polymerized units:.

The relative amounts of the first and second acid monomers in the emulsion polymer is selected such that the ratio of b/c is from <NUM> ± <NUM> to <NUM> ± <NUM>. This emulsion polymer exhibits a glass transition temperature (Tg) that ranges from -<NUM> to <NUM> and is polymerized in a reaction pH range of <NUM> to <NUM>. Alternatively, the glass transition temperature is between - <NUM> to <NUM>. The glass transition temperatures of the polymer phases are calculated using the Fox equation: <MAT> where W(a) and W(b) are the weight fractions of comonomers (a) and (b) and Tg(a) and Tg(b) are the glass transition temperatures for homopolymers (a) and (b), respectively. Glass transition temperatures for various homopolymers are available in many literature sources, including <NPL>).

The ethylenically unsaturated nonionic monomer (a) is not limited to any specific ethylenically unsatured, nonionic monomer. The ethylenically unsaturated nonionic monomers may include, without limitation, (meth)acrylic ester monomers, such as methyl acrylate, ethyl acrylate, butyl acrylate, <NUM>-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, methyl methacrylate, butyl methacrylate, isodecyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate; (meth)acrylonitrile; (meth)acrylamide; diacetone acrylamide, methylol (meth)acrylamide, glycidyl methacrylate, <NUM>-hydroxybutyl acrylate glycidyl ether; amino-functional and ureido-functional monomers (e.g., Norsocryl® <NUM>, Arkema Inc. , King of Prussia, PA); monomers bearing acetoacetoxy-functional, acetoacetamido-functional, and/or cyanoacetamido-functional groups; styrene and substituted styrenes; butadiene; ethylene, propylene, a-olefins such as <NUM>-decene; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl versatate esters (e.g., VeoVa™ <NUM> and VeoVa™ <NUM> from Momentive Performance Materials, CT) and other vinyl esters; and vinyl monomers such as vinyl chloride, vinylidene chloride; monomers containing hydrolysable organo-silane such as trialkoxylsilane. Alternatively, the ethylenically unsaturated nonionic monomer is butyl acrylate, ethyl acrylate, methyl methacrylate, butyl methacrylate, unsubstituted or substituted styrene, or a mixture thereof.

The amount of the ethylenically unsaturated nonionic monomer is between <NUM> and less than <NUM> wt. %, or preferably from <NUM> to <NUM>, based on the entire weight of the emulsion polymer.

Alternatively, the amount of the ethylenically, unsaturated nonionic monomer is within the range of about <NUM> to <NUM> wt. %; alternatively, between about <NUM> to <NUM> wt. %, or preferably greater than <NUM> wt. %, wherein the term "about" refers to ± <NUM>, alternatively, ± <NUM>.

The first acid monomer (b) is a strong acid monomer selected from phosphate esters of polypropylene glycol mono(meth)acrylate, phosphate esters of polyethylene glycol mono(methacrylate), or a mixture thereof. The amount of the first acid monomer in the emulsion polymer is within the range of <NUM> to <NUM> wt. When desirable, the amount of the first acid monomer is about <NUM> wt. %, wherein the term "about" refers to ± <NUM>, alternatively, ± <NUM>.

The first acid monomer is selected from mono(meth)acrylate; phosphate esters of polypropylene glycol mono(meth)acrylate (PAM2); or mixtures thereof. Specific examples of preferred phosphate monomers include, but are not limited to Sipomer® PAM <NUM>, Sipomer® PAM <NUM> and Sipomer® PAM <NUM> (Solvay), respectively.

The second acid monomer (c) includes one or more ethylenically unsaturated monomers that have at least one carboxyl or carboxylic anhydride functional group. The amount of the second acid monomer in the emulsion polymer is within the range of <NUM> and <NUM> wt.

Several examples of this type of monomer include without limitation, ethylenically unsaturated carboxylic or dicarboxylic acids Alternatively, the second acid monomer is (meth)acrylic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid, cinnamic acid, acrylic acid, or itaconic acid, with methacrylic acid being preferred.

In the emulsion polymer of the present disclosure, the ratio (b/c) of the first acid monomer to the second acid monomer is about <NUM> to <NUM>, wherein the term "about" refers to ± <NUM>, alternatively, ± <NUM>.

A non-exhaustive list of possible monomer combinations that may be polymerized or used to form the emulsion polymers according to the teachings of the present disclosure is provided in Table <NUM>. The monomers associated with the abbreviations used in Table <NUM> include: butyl acrylate (BA); methyl methacrylate (MMA); another acrylic monomer (AM); ethylmethacrylate phosphate (PAM <NUM>) - not according to the present invention; phosphate esters of polypropylene glycol monomethacrylate (PAM2); and methacrylic acid (MAA).

PAM1 and polymers comprising it as the only first acid monomer are not according to the present invention.

According to one aspect of the present disclosure, coating compositions comprising the emulsion polymers dispersed in an aqueous medium are formed. The emulsion polymers are incorporated into the coating compositions in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the total weight of the coating composition; alternatively, between <NUM> wt. % and <NUM> wt. %, preferably between <NUM> to <NUM> wt. Alternatively, the amount of the emulsion polymers present in the coating composition is greater than <NUM> wt. %; alternatively, less than or equal to <NUM> wt. %, based on the total weight of the coating composition.

The coating compositions may further comprise a dye, a pigment, or a mixture thereof. These pigments may act as colorants, fillers, or extenders with several specific examples including, but not being limited to, carbon black, colored organic pigments, and metal oxide pigments, such as titanium dioxide, zinc oxide, clay, aluminum silicate, zinc oxide, zinc hydroxide, aluminum silicate, magnesium silicate, calcium silicate, amorphous silica, vapor phase silica, colloidal silica, alumina, aluminum hydroxide, zirconium oxide, and cerium oxide, as well as calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, and zinc carbonate.

When desirable, the coating compositions may also comprise one or more additives, including, but not limited to, surfactants, dispersants, rheology modifiers, defoamers, coalescent agents, or opacifiers. Various surfactants and defoamers may include any organic, organosilicon, and silicone molecules that are well known to one skilled-in-the-art to function in such a capacity. In order to enhance the weatherability of the film or coating formed from the coating composition, the coating composition may include hindered amines or UV absorber molecules. Several specific examples of surfactants or dispersants include without limitation ionic and nonionic compounds, such as alkyl polyglycol ethers, alkyl phenol polyglycol ethers, alkali metal or ammonium salts of alkyl, aryl or alkylaryl sulfonates, sulfates and phosphates.

The coating compositions may be applied to the surface of a substrate by any conventional application method known to one skilled in the art, including but not limited to brushing, draw-down methodology, spin coating, dip coating, flow coating, curtain coating, roller application, and spray methodology, for example, air spray, air-assisted spray, airless spray, high volume low pressure (HVLP) spray, and air-assisted airless spray. Films or coating layers formed using these coating compositions exhibit excellent resistance to a wide range of hydrophilic and hydrophobic stains. Conventional coating formulations are often optimized for hydrophobic stain washability at the expense of hydrophilic stain removal and vice versa. One benefit associated with the emulsion polymers of the present disclosure and the coating formulations formed therefrom is the capability of providing for the efficient or clean removal of both hydrophilic and hydrophobic stains.

The following specific examples are given to further illustrate the preparation and testing of emulsion polymers and coating formulations containing the emulsion polymers according to the teachings of the present disclosure and should not be construed to limit the scope of the disclosure.

A total of <NUM> gram of a seed latex and <NUM> gram water is added into a three-liter, jacketed glass reactor equipped with dual impellers, reflux condensers, and stainless steel feed lines. The reactor is then heated to <NUM>. A monomer mixture containing <NUM> gram butyl acrylate, <NUM> gram methyl methacrylate, <NUM> gram Norsocryl® <NUM> (Arkema Inc. , King of Prussia, PA), and <NUM> gram methacrylic acid are combined with water and then emulsified using equal active amounts of sodium dodecylbenzene sulfonate and alkyldiphenyloxide disulfonate under agitation.

The polymerization is initiated at <NUM> using t-butyl hydroperoxide (t-BHP) solution as an oxidizer and sodium metabisulfite (SMBS) as a reducer. Commencing simultaneously, monomer pre-emulsion, ammonium hydroxide solution, oxidizer and reducer solutions are fed to the reactor over a period of <NUM> minutes and <NUM> minutes, respectively. Then, additional t-BHP and SMBS solutions are fed over <NUM> minutes to lower the amount of residual monomers. The pH of the resulting latex is adjusted to <NUM> - <NUM> with <NUM>% ammonium hydroxide. The solid content of the latex is -<NUM>%. The emulsion polymer may then be collected or stored as an aqueous dispersion or latex.

Polymer dispersions are prepared using the same procedure as described in Example <NUM>, except that phosphate monomer (PAM1 - comparative-or PAM2) is included and the amounts of MAA, PAM1 or PAM2 are varied as shown in Table <NUM>.

The emulsion polymer samples <NUM>-<NUM> prepared in Example <NUM> are used in the preparation of paint samples A-E. Each paint sample, which is comprised of the composition described in Table <NUM>, is prepared using the same procedure as described in Example <NUM>, with the only exception being the composition of the emulsion polymer sample incorporated therein. Each paint sample is prepared by mixing the titanium dioxide slurry with coalescent, dispersant and water using a dispersator at low speed, followed by additions of ammonia, defoamer, and extender pigments. The mixture of above ingredients was then mixed at a higher speed till an acceptable Hegman fineness reading was achieved. The dispersator speed was then reduced and final additions of opaque polymer and thickeners were made to produce the paint base. The paint base was weighed out into pint-sized cans, to which appropriate amounts of latex, coalescent, and water were added. Paints were stirred on a bench top lab mixer for <NUM> minutes before initial KU viscosity and pH were measured.

The Paint Samples A-E as prepared in Example <NUM> are evaluated for resistance to staining. Stain resistance is measured by determining the degree to which a stain can be removed from a film or coating layer according to a modified ASTM D-<NUM> method. More specifically, a <NUM>-mil (<NUM>) wet paint film is cast onto a black Leneta scrub chart and dried for a minimum of three days in a controlled temperature & humidity (CT/CH) chamber. Five hydrophilic stains (mustard, ketchup, hot coffee, red wine, and blue fountain ink) and seven hydrophobic stains (ball point pen, #<NUM> pencil, blue crayon, grease pencil, and two red lipsticks, as well as the Consumers Union black stain), are included in the test. Mustard, ketchup, and Consumer Union (CU) black stains are applied using a <NUM> mil (<NUM>) square draw-down bar. For coffee, red wine, and fountain ink, a strip of a single ply paper towel is used to hold the liquid stains in place. Other hydrophobic stains are directly marked onto the scrub panels.

All stains are allowed to sit on the paint film for two hours while the Consumers Union (CU) stain is held in place for <NUM> hours. The films are washed for <NUM> cycles using ASTM standard sponges and Leneta standardized Non-Abrasive Scrub Media as the cleaning solution. Fantastik® (S. Johnson Company) is the cleanser for the CU stain, which is washed for <NUM> cycles on a Gardner Wear Abrasion machine. The degree of staining is assessed using the ΔE values of unstained versus stained and then washed portions of the paint film, measured by a BYK Gardner spectrophotometer. The measurement is taken in triplicate and then averaged. Small ΔE values are desirable, denoting slight or no residual staining of the paint surface. The measurement of the ΔE associated with each type of stain formed on and removed from the different paint samples is provided in Table <NUM>.

Referring to Table <NUM>, in comparison to paint samples A, B, or C, paint samples D and E consistently provides higher resistance to each hydrophilic stain without significant changes of the hydrophobic stain removal. In other words, the individual ΔE values measured for the removal of the same stains on paint samples A-C are observed to be usually higher than the corresponding values measured for paint samples D and E. The ratio of b/c in paint samples A-C is less than <NUM>, while the ratio of b/c in paint samples D and E is greater than <NUM>.

A summary of the total value of the measured ΔE for paint samples A-E is provided in Table <NUM>. The total ΔE measured for the resistance of the coating composition (e.g., removal of the stain from the coating composition) to a combination of the hydrophilic stains and hydrophobic stains is less than about <NUM> for paint samples D and E; alternatively, less than about <NUM>; alternatively, between about <NUM> and <NUM>, wherein about refers to ±<NUM>; alternatively, ±<NUM>. The total ΔE measured for the resistance of the coating composition in Samples D and E to the hydrophilic stains is less than about <NUM>; alternatively, less than about <NUM>; alternatively, less than about <NUM>. The total ΔE measured for the resistance of the coating composition in Samples D and E to the hydrophobic stains is less than about <NUM>; alternatively, less than about <NUM>. In comparison, the total ΔE values measured for the removal of the same stains on paint samples A-C are observed to be usually higher than the values measured for paint samples D and E.

Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.

Claim 1:
An emulsion polymer comprising, as polymerized units:
a) at least one ethylenically unsaturated nonionic monomer in an amount ranging between <NUM> wt. % to less than <NUM> wt.% based on the overall weight of the polymer composition;
b) a first acid monomer in an amount ranging from <NUM> to <NUM> wt.%, the first monomer being a strong acid monomer selected from phosphate esters of polypropylene glycol mono(meth)acrylate, phosphate esters of polyethylene glycol mono(meth)acrylate, or a mixture thereof, and
c) a second acid monomer in an amount ranging from <NUM> to <NUM> wt.%, the second monomer being one or more ethylenically unsaturated monomers having at least one carboxyl or carboxylic anhydride functional group;
wherein the relative amounts of the first and second acid monomers are such that the ratio of b/c is from <NUM> ± <NUM> to <NUM> ± <NUM>;
wherein the polymer composition has a glass transition temperature (Tg) ranging from -<NUM> to <NUM>, the Tg being calculated using the Fox equation as defined herein.