Improved heat-aged stability when blending acrylic latex and PVDF-acrylic hybrid dispersions

Abstract

A method including measuring the heat stability of a screening blend by a heat-age stability test, wherein the screening blend includes an acrylic latex, a PVDF-acrylic hybrid latex, a surfactant, and a coalescent agent. A composition of an acrylic latex, a PVDF-acrylic hybrid latex, and a surfactant, wherein the surfactant is selected from the group of anionic and nonionic surfactants, wherein composition comprises 0.25 to 10 wt%, such as 0.5 to 5 wt%, such as 1 to 5 wt%, such as 1 to 4 wt% of the surfactant.

Description

IMPROVED HEAT-AGED STABILITY WHEN BLENDING ACRYLIC LATEX AND PVDF-ACRYLIC HYBRID DISPERSIONSTECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to a method of measuring a heat stability of a composition including an acrylic latex, a PVDF-acrylic hybrid latex, a surfactant, and a coalescent agent. Embodiments of the present disclosure relate to a blend of an acrylic latex, a PVDF-acrylic hybrid latex, and a surfactant; more specifically, embodiments relate to a blend that is heat stable when subjected to a heat-age stability test as a screening blend with a coalescent agent.BACKGROUND

[0002] A latex composition may be screened by a formulator for general properties. An exemplary screening test is a heat-age stability test. For a heat-age stability test, a latex composition is usually blended with a coalescent agent to form a screening composition. In the heat-age stability test, the screening composition is placed in an oven, usually at 50 °C, for a time period, usually a month. Viscosity of the screening composition is measured at the beginning and end of the test, and optionally throughout. A screening composition that demonstrates a consistent viscosity, or at least only a small increase in viscosity during the heatage stability test is considered "heat stable." A screening composition that demonstrates a significant increase in viscosity during the heat-age stability test is considered not "heat stable."

[0003] Once a screening composition is considered not "heat stable," the latex composition therein is generally considered to not be commercially viable, and the latex composition is not considered for further development or use.

[0004] If a screening composition is considered "heat stable" by exhibiting an allowable change in viscosity during the testing time, a formulator could then proceed to developing a full waterborne paint formulation. A waterborne paint formulation can include binders like latex, pigments, and additives such as surfactants, dispersants, and wetting agents. Addition of these ingredients can help contribute to the stability of a full formulation.

[0005] A traditional acrylic latex is generally heat stable when subjected to the heat-age stability test as a screening blend with a coalescent agent.

[0006] A PVDF-acrylic hybrid latex is generally heat stable when subjected to the heat-age stability test as a screening blend with a coalescent agent.

[0007] However, known blends of a traditional acrylic latex and a PVDF-acrylic hybrid latex are not considered heat stable when subjected to the heat-age stability test as a screening blend with a coalescent agent.

[0008] This generally prevents known blends of a traditional acrylic latex and a PVDF-acrylic hybrid latex from further development or use.SUMMARY

[0009] It has been surprisingly discovered that adding a surfactant to a blend of an acrylic latex and a PVDF-acrylic hybrid latex may result in a blend that is heat stable when subjected to a heat-age stability test as a screening blend with a coalescent agent. In an embodiment, the surfactant is an anionic or nonionic surfactant and may be present in amount of 0.25 to 10 wt%, such as 1 to 5 wt%. This is significant as the same blend, without the surfactant, or with different amounts of surfactant, may not be considered heat stable when subjected to the heatage stability test as a screening blend with a coalescent agent.

[0010] A method including: measuring the heat stability of a screening blend by a heat-age stability test, wherein the heat-age stability test includes: placing the screening composition in an oven, the oven being at a temperature of 30-100 °C, such as at 40-70 °C, such as about 50 °C; maintaining the screening composition in the oven for a time period, the time period being at least one week, such as 7-100 days, such as 10 to 50 days, such as about 30 days; and measuring the viscosity of the screening composition at the end of the time period, wherein the screening blend includes: an acrylic latex; a PVDF-acrylic hybrid latex; a surfactant; and a coalescent agent.

[0011] A screening blend consisting essentially of, or consisting of: 50 to 95 wt%, such as 60 to 85 wt%, of the acrylic latex; 5 to 50 wt%, such as 15 to 40 wt%, of the PVDF-acrylic hybrid latex; 1 to 5 wt%, such as 1 to 4 wt%, of the surfactant; and 0.5 to 5 wt%, such as 0.5 to 5 wt%, of the coalescent, wherein the surfactant is selected from the group of anionic and nonionic surfactants.

[0012] A composition consisting of: 50 to 95 wt%, such as 60 to 85 wt%, of the acrylic latex; 5 to 50 wt%, such as 15 to 40 wt%, of the PVDF-acrylic hybrid latex; 1 to 5 wt%, such as 1 to 4 wt%, of the surfactant; and wherein the surfactant is selected from the group of anionic and nonionic surfactants.DETAILED DESCRIPTION

[0013] Specific embodiments of the invention will now be described. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description is not intended to be limiting of the invention.

[0014] Embodiments of the present disclosure relate to a method including a step of measuring the heat stability of a screening blend by a heat-age stability test. The screening blend includes an acrylic latex, a PVDF-acrylic hybrid latex, a surfactant, and a coalescent agent. In an embodiment the screening blend may be limited to those four components, or effectively limited to those four components allowing other components in minor amounts, such as less than 0.5 wt%, or less than 0.3 wt%, or less than 0.1 wt%.

[0015] In an embodiment, the method includes forming the screening blend by blending a latex composition with the coalescent agent, the latex composition including the acrylic latex, the PVDF-acrylic hybrid latex, and the surfactant. In an embodiment the latex composition may be limited to an acrylic latex, a PVDF-acrylic hybrid latex, and a surfactant, or effectively limited to those components allowing other components in minor amounts, such as less than 0.5 wt%, or less than 0.3 wt%, or less than 0.1 wt%.

[0016] The latex composition may be provided to a formulator. The formulator may screen the latex composition for general properties. For screening, the formulator may blend the latex composition with a coalescent agent to form a screening composition. A specific screening test is a heat-age stability test. In the heat-age stability test, the screening composition is placed in an oven, usually at 50 °C, for a time period, usually a month. Viscosity of the screening composition may be measured at the beginning and end of the test, and optionally throughout.A screening composition that demonstrates a consistent viscosity, or at least a small increase in viscosity during the heat-age stability test is considered "heat stable." A screening composition that demonstrates a significant increase in viscosity during the heat-age stability test is considered not "heat stable."

[0017] For example, a heat stable latex composition may have a change in viscosity (after 28 days at 50 °C) of less than 140% (measured in KU; [(day 28 KU - day 1 KU) / day 1 KU]), such as less than 100% change, less than 50% change, less than 30% change, less than 20% change, or less than 10% change. For example, a heat stable latex composition may have a viscosity (after 28 days at 50 °C) of 140 KU or less, of 120 KU or less, or 100 KU or less, of 80 KU or less, or of 60 KU or less.

[0018] In an embodiment of the disclosure, the heat-age stability test includes, an optional first step of measuring the viscosity of a screening composition; a step of placing the screening composition in an oven, the oven being at a temperature of 30-100 °C, such as at 40-60 °C, such as about 50 °C; a step of maintaining the screening composition in the oven for a time period, the time period being at least one week, such as 7 to 100 days, such as 10 to 56 days, such as 20 to 40 days, such as about 30 days; and a step of measuring the viscosity of the screening composition at the end of the time period. When measuring the viscosity of the screening composition at the end of the time period, the screening composition is first allowed to cool at room temperature for approximately 2 hours, such the viscosity is measured when the screening composition is in a temperature range of 18-30 degrees, such as 18-25 degrees, such as 20-23 degrees.

[0019] In an embodiment, the disclosure includes a method of measuring the heat stability of a screening blend by a heat-age stability test, wherein the heat-age stability test comprises: placing the screening composition in an oven, the oven being at a temperature of 30-100 °C, such as at 40-70 °C, such as about 50 °C; maintaining the screening composition in the oven for a time period, the time period being at least one week, such as 7-100 days, such as 10 to 50 days, such as about 30 days; and measuring the viscosity of the screening composition at the end of the time period, wherein the screening blend comprises: an acrylic latex; a PVDF-acrylic hybrid latex; a surfactant; and a coalescent agent.

[0020] In an embodiment, the method includes forming the screening blend by blending a latex composition with the coalescent agent, wherein the latex composition includes: the acrylic latex; the PVDF-acrylic hybrid latex; and the surfactant.

[0021] In an embodiment, the disclosure including modifying a latex composition including an acrylic latex and a PVDF-acrylic hybrid latex by adding a surfactant to the latex composition prior to conducting a heat stability test on a screening blend formed from the latex composition.

[0022] In an embodiment, the addition of the surfactant is able to limit the viscosity in a sample, after being in an oven at 50 °C for 28 days, to less than 10,000 cP, less than 4,000 cP, less than 1000 cP, less than 800 cP, less than 200 cP, less than 100 cP, or less than 50 cP.

[0023] Embodiments of the present disclosure relate to a blend of an acrylic latex, a PVDF- acrylic hybrid latex, and a surfactant; more specifically, embodiments relate to a blend that is heat stable when subjected to a heat-age stability test as a screening blend with a coalescent agent.Acrylic Latex

[0024] As used herein, "latex" refers to an aqueous dispersion of polymer particles prepared by emulsion polymerization of one or more monomers.

[0025] The acrylic latex may be any well know acrylic latex. Embodiments of an acrylic latex are described in US Pats. No. 6,930,143, US9777100B2, and US9834698B. The teachings related to acrylic latex in each of these patents is hereby incorporated by reference.

[0026] As described hereinabove, the water-based compositions of the present disclosure may comprise a latex polymer. Latex polymers are generally emulsions of polymer particles in an aqueous solution. Latex polymers may be utilized that have a wide range of glass transition temperatures (Tg) depending on the intended application. In embodiments, the latex polymer may have a Tgof from about -50 °C to about 30 °C.

[0027] The latex polymer may be obtained by emulsion polymerization of a monomeric composition comprising one or more ethylenica I ly unsaturated monomers. In other words, the latex polymer may comprise polymerized units derived from one or more ethylenica I ly unsaturated monomers. In particular, the latex polymer may be obtained by single-stage emulsion polymerization of a monomeric composition comprising one or more ethylenica llyunsaturated monomers or the latex polymer may be obtained by multi-stage emulsion polymerization of a monomeric composition comprising one or more ethyle nical ly unsaturated monomers.

[0028] The acrylic polymer is made by polymerizing a combination of Monomers selected from Monomers (a), (b), (c), (d), (e), (f), (g) and any mixture or combination thereof.

[0029] The monomeric composition may comprise monomer (a). Monomer (a) is an alkyl (meth)acrylate, a vinyl ester, a mixture of vinyl esters, vinyl acetate, a vinyl aromatic, a mixture of vinyl aromatic, an acidic monomer, a mixture of acidic monomers, functionalized monomer.

[0030] Monomer (a) may comprise or consist of one or more alkyl (meth)acrylates selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl, sec-butyl, isobutyl or tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, lauryl (meth)acrylate and mixtures thereof. Preferably Monomer (a) comprises an alkyl (meth)acrylate, preferably a C1-C12 alkyl (meth)acrylate.

[0031] Monomer (b) may comprise or consist of one or more vinyl esters selected from vinyl acetate, vinyl propionate, vinyl hexanoate, vinyl 2-ethylhexanoate, vinyl octanoate, vinyl pelargonate, vinyl laurate, vinyl stearate, a vinyl ester of versatic acid and mixtures thereof.

[0032] Monomer (c) may comprise or consist of one or more vinyl aromatics selected from styrene, alpha-methylstyrene, tert-butylstyrene, ortho-, meta-, and para-methylstyrene, ortho-, meta- and para-ethylstyrene, o-methyl-p-isopropylstyrene, p-chlorostyrene, p-bromostyrene, o,p-dichlorostyrene, o,p-dibromostyrene, ortho-, meta- and para-methoxystyrene, optionally substituted indenes, optionally substituted vinylnaphthalenes, acenaphthylene, diphenylethylene, vinyl anthracene and mixtures thereof. In particular, monomer (c) may comprise or consist of one or more vinyl aromatics selected from styrene, alpha-methylstyrene and mixtures thereof.

[0033] Monomer (d) may comprise or consist of one or more acidic monomers selected from C3-C10 mono- or dicarboxylic acids, cyclic anhydrides, phosphorous-based acidic monomers, sulfur-based acidic monomers, salts thereof and mixtures thereof.

[0034] Monomer (e) may be a mixture of functionalized monomers, ethyle nically unsaturated monomers bearing a silane group, ethylenically unsaturated monomers bearing a hydroxyl group, comprises or consists of one or more crosslinking monomers.

[0035] The functionalized monomer may comprise 2 to 30 carbon atoms and an ethylenically unsaturated group selected from the group consisting of acryloyl (-C(=O)-CH=CH2), methacryloyl (-C(=O)-C(CH3)=CH2), vinyl (-CH=CH2), crotyl (-CH=CH(CH3)) or allyl (-CH2-CH=CH2). The functional group may be selected from the group consisting of hydroxyl, ketone, aldehyde, acetoacetoxy, acetoacetamide, l,l-dimethyl-3-oxobuyl (diacetone), glycidyl ether, amino (— NH2), alkylamino or dialkylamino (-NHR or -NR2with R is alkyl), cyano (-CN) or a heterocycle with one or more nitrogen ring atoms (in particular a ureido group).

[0036] In a preferred embodiment, monomer (e) may comprise or consist of one or more ethylenically unsaturated compounds bearing a hydroxyl functional group, in particular a hydroxylated (meth)acrylate, and / or one or more ethylenically unsaturated compounds bearing a ureido functional group, in particular 2-(2-oxo-l-imidazolidinyl)ethyl (meth)acrylate. In one embodiment, monomer (e) does not contain any (meth)acrylamide.

[0037] In particular, monomer (f) may comprise or consist of one or more monomers selected from 3-methacryloxypropyl tri(alkoxy)silane, methacryloxymethyl tri(alkoxy)silane, 3-methacryloxypropylmethyl di(alkoxy)silane, vinylalkyl di(alkoxy)silane, vinyl tri(alkoxy)silane and mixtures thereof.

[0038] More particularly, monomer (f) may comprise or consist of one or more monomers from vinyl trimethoxysilane, vinyl diimethoxymethylsilane, vinyl triethoxysilane, vinyl tripropoxysilane, vinyl triisopropoxysilane, vinyl tris(methoxyethoxy)silane, vinyl tri butoxysilane, vinyl triacetoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropylmethyl dimethoxysilane, methacryloxymethyl trimethoxysilane, 3-methacryloxypropyl tris(2-methoxyethoxy) silane, vinyl trichlorosilane, vinyl methyldichlorosilane, vinyltris(2-methoxyethoxy)silane and mixtures thereof.

[0039] A crosslinking monomer may be a compound bearing at least two functional groups which are capable of reacting with ethylenically unsaturated monomers. In particular, a crosslinking monomer may comprise at least two polymerizable carbon-carbon double bonds.

[0040] Monomer (g) may comprise or consist of one or more crosslinking monomers. More particularly, monomer (g) may comprise or consist of one or more crosslinking monomers selected from allyl (meth)acrylate, diallyl (meth)acrylate, vinyl acrylate, divinyl benzene, diallyl ether, glycerol diallyl ether, glycerol triallyl ether, trimethylolpropane diallyl ether, trimethylolpropane triallyl ether, pentaerythritol triallyl ether, diallyl phthalate, dicyclopentenyl oxyethyl methacrylate, ethylene glycol di(meth)acrylate, di-, tri- or tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, di-, tri- or tetrapropylene glycol di(meth)acrylate, 1,2-butanediol di(meth)acrylate, 2,3-butanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-methyl-2,4-pentanediol di(meth)acrylate, polybutadiene di(meth)acrylate, cyclohexane-l,4-dimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, di(trimethylolpropane) diacrylate, di(trimethylolpropane) triacrylate, di(trimethylolpropane) tetra(meth)acrylate, sorbitol penta(meth)acrylate; di(pentaerythritol) tetra(meth)acrylate; di(pentaerythritol) penta(meth)acrylate; di(pentaerythritol) hexa(meth)acrylate; tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, as well as the alkoxylated (e.g., ethoxylated and / or propoxylated) derivatives thereof; and mixtures thereof.

[0041] Monomers (a), (b), (c), (d), (e), (f), and (g) are distinct from one another.

[0042] Embodiments of the disclosure include acrylic latexes, such as ENCOR 627, Encor 631,Encor 636.

[0043] Embodiment of the disclosure include acrylic latex with a Tg range of -50 to 50 °C, a particle size of 50nm to 500nm, a total solids range of 40-70%, and a pH range of 4-12.

[0044] The composition may include 50 to 95 wt%, such as 60 to 85 wt% of acrylic latex. A lower limit of the wt % of acrylic latex may be from 50, 60, 70, 75, wt% and an upper limit of the wt% of acrylic latex may be from 95, 90, 85, 80, wt%.PVDF-Acrylic Hybrid Latex

[0045] Embodiments of the disclosure include an acrylic modified fluoropolymer composition.

[0046] By "acrylic modified fluoropolymer composition" means a composition in which an acrylic has been polymerized in the presence of a fluoropolymer seed, thereby producing an acrylic modified fluoropolymer. Such hybrid compositions are described in US patents and applications such as US5349003, US 6680357, and US 2011 / 0118403. The teachings related to acrylic modified fluoropolymer composition in each of these patents is hereby incorporated by reference.

[0047] Acrylic encompasses both acrylic and meth acrylic monomers unless otherwise specified. Acrylic polymer encompasses having acrylic and / or meth acrylic monomer units unless otherwise specified.

[0048] In embodiments, the fluoropolymers used as seed for the acrylic polymerization are formed primarily of fluoromonomers. The term "fluoromonomer" or the expression "fluorinated monomer" means a polymerizable alkene which contains at least one fluorine atom, fluoroalkyl group, or fluoroalkoxy group attached to the double bond of the alkene that undergoes polymerization. The term "fluoropolymer" means a polymer formed by the polymerization of at least one fluoromonomer, and it is inclusive of homopolymers, copolymers, terpolymers. The fluoropolymer preferably contains at least 50 mole percent of one or more fluoromonomers.

[0049] Fluoromonomers useful in the practice of the invention include, for example, vinylidenefluoride (VDF), tetrafluoroethylene (TFE), trifluoroethylene (VF3), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), vinyl fluoride (VF), hexafluoroisobutylene, perfluorobutylethylene (PFBE), pentafluoropropene, 2, 3,3,3- tetrafluoropropene (HFO-1234yf), 2-chloro-l-l-difluoroethylene (R-1122), 3,3,3-trifluoro-l- propene, 2-fluoromethyl-3,3,3-trifluoropropene, a fluorinated vinyl ether, a fluorinated allyl ether, a non-fluorinated allyl ether, a fluorinated dioxole, and combinations thereof.

[0050] Embodiments of the acrylic modified fluoropolymer composition particularly include a PVDF-acrylic hybrid latex. PVDF includes polyvinylidene fluoride (PVDF) homopolymers and copolymers.

[0051] Embodiments of a PVDF-acrylic hybrid latex are described in US 10,920,088 and US 10,533,109 B2. The teachings related to PVDF-acrylic hybrid latex in each of these patents is hereby incorporated by reference.

[0052] The term "polyvinylidene fluoride " (PVDF) used herein includes both normally high molecular weight homopolymers, copolymers, and terpolymers within its meaning. Such copolymers include those containing at least 50 mole percent, preferably at least 75 mole %, more preferably at least 80 mole %, and even more preferably at least 85 mole % of vinylidene fluoride copolymerized with at least one comonomer.

[0053] Embodiments of the disclosure include terpolymers of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene such as the copolymer composition described in U.S. Patent No. 2,968,649 and terpolymers of vinylidene fluoride, trifluoroethylene and tetrafluoroethylene are also representatives of the class of vinylidene fluoride copolymers.

[0054] In one embodiment, the PVDF is a copolymer of VDF and HFP having up to 30%, and preferably up to 15%, by weight of hexafluoropropene (HFP) units and up to 70%, preferably up to 85%, by weight or more of VDF units in the polymer. It is desired that the HFP units be distributed as homogeneously as possible. Preferably, the PVDF copolymer has a melt viscosity of greater than 1.0 kilopoise, preferably greater than 5 kilopoise, more preferably greater than 10 kilopoise and most preferably greater than 20 kilopoise, and even greater than 23 kilopoise, according to ASTM method D-3835 measured at 450 °F and 100 sec1. Preferably, the fluoropolymer is formed by an emulsion process. Preferably, the process is fluoro-surfactant free. The fluoropolymer used in the invention is free of fluorosurfactant.

[0055] The AMF polymer contains an acrylic portion. The acrylic portion is obtained by emulsion-polymerizing 5-100 parts by weight ( per 100 parts by weight of vinylidene fluoride) of a monomer mixture comprising at least one monomer selected from the group consisting of alkyl acrylates whose alkyl groups have 1-18 carbon atoms and alkyl methacrylates whose alkyl groups have 1-18 carbon atoms and an ethylenica lly unsaturated compound copolymerizable with the alkyl acrylates and the alkyl methacrylates, in an aqueous medium in the presence of 100 parts by weight of particles of a vinylidene fluoride polymer. In addition, any of the acrylicmonomers used in the acrylic latex discussed above may be used in the acrylic portion of the AMF polymer.

[0056] Preferably, the acrylic polymer portion in the AMF polymer comprises (methyl)methacrylate monomer units and preferably may contain greater than 50 wt% (methyl)methacrylate monomer units based on the total monomer in the acrylic portion of the AMF polymer.

[0057] The average particle diameter of the AMF polymer in the aqueous dispersion is 0.05-3 pm, preferably 0.05-1 pm, more preferably 0.1-1 pm.

[0058] For example, the acrylic portion includes polymers and copolymers formed from alkyl methacrylate and alkyl acrylate monomers, and mixtures thereof. The alkyl methacrylate monomer is preferably methyl methacrylate, which may make up from 50 to 100 percent of the monomer mixture. 0 to 50 percent of other acrylate and methacrylate monomers or other ethylenica lly unsaturated monomers, including but not limited to, styrene, alpha methyl styrene, acrylonitrile, and crosslinkers may also be present in the monomer mixture. Other methacrylate and acrylate monomers useful in the monomer mixture include, but are not limited to, methyl acrylate, ethyl acrylate and ethyl methacrylate, butyl acrylate and butyl methacrylate, iso-octyl methacrylate and acrylate, lauryl acrylate and lauryl methacrylate, stearyl acrylate and stearyl methacrylate, isobornyl acrylate and methacrylate, methoxy ethyl acrylate and methacrylate, 2-ethoxy ethyl acrylate and methacrylate, hydroxymethyl acrylate and methacrylate, hydroxyethyl acrylate and methacrylate, dimethylamino ethyl acrylate and methacrylate monomers.

[0059] In various embodiment, the acrylic polymer is partially or fully thermodynamically miscible with the fluoropolymer.

[0060] Acrylic polymers suitable for use in the present disclosure can be manufactured by any means known in the art, including emulsion polymerization, solution polymerization, and suspension polymerization.

[0061] Embodiments of the PVDF-acrylic hybrid latex include dispersions that have MFFTs from 10-25 °C, have solids from 40-45% and contain 50-70% fluoropolymer.

[0062] The composition may include 5 to 50 wt%, such as 10 to 40 wt%, such as 15 to 40 wt%, such as 20 to 30 wt% of PVDF-acrylic hybrid latex. A lower limit of the wt% of PVDF-acrylic hybrid latex may be from 5 wt% and an upper limit of the wt% of acrylic latex may be from 50, 45, 40, 35, 30, 25, 20, 15, 10 wt%.

[0063] The weight ratio of acrylic latex to PVDF-acrylic hybrid latex is 95:5 to 50:50, such as 90:10 to 60:10, such as 80:15 to 60:30.Surfactant

[0064] As used herein, a "surfactant" refers to an agent that lowers the surface tension of a liquid and / or lowers the interfacial tension between two liquids.

[0065] A conventional polymerization surfactant may be used in the emulsion polymerization reaction of the present disclosure. Useful surfactants include, but are not limited to, anionic and / or nonionic emulsifiers such as, for example, alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates, sulfonates or phosphates; alkyl sulfonic acids; sulfosuccinate salts; fatty acids; ethylenically unsaturated surfactant monomers; and ethoxylated alcohols or phenols, among others.

[0066] In an embodiment, a surfactant includes a hydrophilic head and hydrophobic tail, typically with a middle portion.

[0067] In an embodiment, the hydrophobic tail is fatty-acid derived and can be categorized by length of C chains, typically without any modifications.

[0068] In an embodiment, the middle portion of surfactants can be modified with ethoxylation (or not). In an embodiment, the degree of ethoxylation may be 10-20, such as 12-18, such as about 16.

[0069] Embodiments of the disclosure include surfactants of the following classes:Anionic surfactants - negative charge on their hydrophilic head;Nonionic surfactants - no charge on their hydrophilic head;Cationic surfactants - positive charge on their hydrophilic head; andAmphoteric surfactants - dual charge (both positive and negative) on their hydrophilic head.

[0070] In an embodiment, the surfactant is an anionic surfactant. An anionic surfactant may have an acid head, which is deprotonated / stabilized with a metal cation. For example, the head may include carboxylic acid, sulfuric acid, etc., with a Na+, K+ cation.

[0071] Embodiments of anionic surfactants include:Fatty acid-based / Fatty acid salt: Oldest class of surfactants / most typical; consist only of salt of carboxylic head group with an aliphatic tailPolyoxyethylene alkyl ether carboxylic acid: Carboxylic acid / sa It head, hydrophilic ethylene oxide middle and aliphatic tail.Polyoxyethylene alkyl ether sulfate: sulfate / salt head, hydrophilic ethylene oxide middle and aliphatic tail.Alkyl polyoxyethylene sulfosuccinate (APS): sulfosuccinate / salt head, ethylene oxide middle, aliphatic tail

[0072] In an embodiment, the surfactant is a nonionic surfactant, such as a tristerylphenol- based surfactant, such as Polystep TSP 16 or Polystep TSP 2528. The nonionic surfactant may include a tail with aryl groups, such a degree of ethoxylation of between 10-30, such as between 12-27, such as about 16 or about 25. In an embodiment, a screening blend may include 1-5 wt%, such as 1-4 wt% of a nonionic surfactant, such as a bulky nonionic surfactant, such as a tristerylphenol-based surfactant, such as Polystep TSP 16 or Polystep TSP 2528 ( Stepan Company).

[0073] In an embodiment, the surfactant may be a fatty-acid, anionic surfactant. An exemplary fatty-acid, anionic surfactant, such as CHsfCI-hJxOSOsM, wherein x is from 7 to 15 and wherein M is Na or K, such as Sodium Dodecyl Sulfate. In an embodiment, a screening blend may include 1- 5 wt%, such as 1-4 wt% of a fatty-acid, anionic surfactant, such as Sodium Dodecyl Sulfate.

[0074] In an embodiment, the surfactant may be a polyoxyethylene alkyl ether sulfate (PAES), anionic surfactant. An exemplary PAES, anionic surfactant is Disponil FES 27A (from BASF) , which has a C12-C14 hydrophobe chain length and a degree of ethoxylation of 2. Embodiments of the disclosure include similar PAES, anionic surfactants, such as where the hydrophobe chain length varies from C8-C18 and the degree of ethoxylation varies from 1 to 6. An exemplary PAES, anionic surfactant is Disponil FES 993, which has a C12-C14 hydrophobe chain length anda degree of ethoxylation of 12. Embodiments of the disclosure include similar PAES, anionic surfactants, such as where the hydrophobe chain length varies from C8-C18 and the degree of ethoxylation varies from 8 to 16.

[0075] In an embodiment, the surfactant may be an alkyl polyoxyethylene sulfosuccinate (APS), anionic surfactant. An exemplary APS, anionic surfactant is Aerosol A-102, which has a C10-C12 hydrophobe chain length and a degree of ethoxylation of 1-4. Embodiments of the disclosure include similar APS, anionic surfactants, such as where the hydrophobe chain length varies from C6-C16 and the degree of ethoxylation varies from 12-20.

[0076] The composition may include 0.25 to 10 wt%, such as 0.5 to 5 wt%, such as 1 to 5 wt%, such as 1 to 4 wt%, such as 0.5 to 3 wt% of surfactant. A lower limit of the wt % of surfactant may be from 0.25wt% and an upper limit of the wt% of surfactant may be from, 2.0, 1.5, 1.0 wt%.Coalescent Agent

[0077] When subjecting the composition to a heat-stability test, the composition will be blended with a coalescent agent to form a screening blend.

[0078] Embodiments of the present disclosure relate to a screening blend of an acrylic latex, a PVDF-acrylic hybrid latex, a surfactant, and a coalescent agent; more specifically, embodiments relate to a blend that is heat stable when subjected to a heat-age stability test.

[0079] The coalescent agent may be an organic solvent or plasticizer that can lower the minimum film forming temperature (MFFT) of a polymer. A coalescent agent may eventually diffuse out of the coating composition and evaporate under normal ambient conditions of temperature, humidity, and atmospheric pressure.

[0080] Coalescent agents are used in coatings to aid in the film formation of the latex or polymer binder. Film formation of a water-based latex paint occurs through four basic steps: after the application of a coating, first water will evaporate, leading to concentration of the latex particles and other components of the coating. The spherical latex particles will then start to pack and deform into honeycomb shaped particles. As water continues to evaporate, the particles will start to "coalesce" allowing for interdiffusion of the polymer material between latex particles. Successful film formation will result in a homogenous and strong film caused byinterdiffusion of these particles. Coalescent agents are typically volatile components that work to help soften the latex particles, promoting interdiffusion of the particles during film formation. Because coalescent agents are volatile, they will contribute to the calculation of Volatile Organic Components (or VOCs). There is much legislation / concern around VOCs in coatings and organizations such as the South Coast Air Quality Management Department (SCAQMD) have set local regulations, restricting the amount of VOCs that can be put into commercial coatings.

[0081] To this end, most commercial coating formulations aim to contain less than 50 g / L VOC. For screening purposes using just latex and coalescent, the present disclosure attributes 50 g / L VOC to 5% coalescent on polymer solids.

[0082] The amount of coalescent needed for desired film formation also depends on the MFFT (Minimum Film Formation Temperature) or Tg (Glass Transition Temperature) of the polymer latex. For screening purposes, the present disclosure targets "good" film formation (not having any cracks, adhesion issues, high gloss) by how well a latex can film form at 40 °F. A higher MFFT (15-25 °C) latex will require more coalescent, whereas a low MFFT latex (<0 °C). Higher MFFT latices are able to supply harder coatings which can be more scratch resistant, more chemically resistant and less susceptible to dirt pick up. Lower MFFT latices produce much softer coatings that can be more susceptible to scratching and dirt pick up.

[0083] Ultimately, coalescents soften the polymer, by lowering the Tg of the polymer. Coalescents act as temporary plasticizers, reducing the MFFT of the latex during film formation and then evaporating from the system.

[0084] Exemplary types of coalescent agents include:Hydrophobic coalescents - these are made up of hydrocarbon solvents. These agents will typically reside inside the polymer latex. Because they reside inside the latex, they tend to result in swelling of the particle, which results in an increase in the viscosity of the overall mixture. These hydrophobic coalescents have been found to be the best agents for film formation of PVDF-acrylic hybrid dispersions. They are able to more efficiently lower the MFFT. Coalescents that are particularly efficient with PVDF-acrylic hybrid dispersions are DPnB, Texanol, DPMM (Dipropylene Glycol Dimethyl ether), DPM, DEB (Diethylene glycol monobutyl ether), and EB (Ethylene glycol monobutyl ether)Examples of hydrophobic coalescents : DOWA OL™ DPnBHydrophilic coalescents: these include water-soluble solvents, such as glycols or water- soluble glycol ethers. Because they are more likely to reside in the aqueous medium of a polymer latex and have less interactions with the polymer latex particle, they have poor efficiency in lowering MEET. Examples of hydrophilic coalescents: DPM, glycol butyl ether (PB), dipropylene glycol butyl ether (DPB).Partially water-soluble coalescents: Depending on their hydrophilicity these particles can either reside fully in the aqueous state or partially dispersed between the aqueous medium and polymer latex particle. They are concentrated on the boundary region. Examples of partially water-soluble coalescents: Texanol® 2,2,4-trimethyl-l,3-pentane diol mono-isobutyrate.

[0085] The composition may include 0.5 to 5 wt%, such as 1 to 5 wt%, such as 1 to 5 wt%, such as 1 to 4 wt%, such as 0.5 to 3 wt% of coalescent agent. A lower limit of the wt % of coalescent may be from 0.5 wt% and an upper limit of the wt% of coalescent may be from 10 wt%.Composition and Screening Blend

[0086] In an embodiment of the disclosure, the composition may include, such as include only:- 50 to 95 wt%, such as 60 to 85 wt% of the acrylic latex;- 5 to 50 wt%, such as 15 to 40 wt% of the PVDF-acrylic hybrid latex; and- 0.25 to 10 wt%, such as 0.5 to 5 wt% of the surfactant; and-0.5 to 10 wt%, such as 0.5 to 8 wt%, of a coalescent agent.

[0087] Such a composition may include by-products and other materials from the production of the acrylic latex, PVDF-acrylic hybrid latex, and surfactant.

[0088] The composition may be the sample that is provided to a formulator, who then adds a coalescent agent for screening purposes.

[0089] A lower limit of the wt% of coalescent agent may be from 0.5, wt% and an upper limit of the wt% of coalescent agent may be from 10, wt%.

[0090] In an embodiment of the disclosure, the screening blend may include, such as include only:- 50 to 95 wt%, such as 60 to 85 wt% of the acrylic latex;- 5 to 50 wt%, such as 15 to 40 wt% of the PVDF-acrylic hybrid latex;- 0.25 to 10 wt%, such as 0.5 to 5 wt% of the surfactant; and- 0.5 to 10 wt%, such as 0.5 to 5 wt% of the coalescent.Examples

[0091] Materials used in the Examples include:Acrylic Latex 1: Encor 631. This is waterborne acrylic latex manufactured by Arkema Coatings Resins. It is 50% solids, has an MFFT of 0 °C and has a particle size of 0.13 micron. It is a high performance 100% acrylic latex for both interior and exterior applications.Acrylic Latex 2: Encor 627. This is waterborne acrylic latex manufactured by Arkema Coatings Resins. It is 43.5% solids, has an MFFT of 9 °C and has a particle size of 0.1 micron. It is a high performance 100% acrylic latex for both interior and exterior applications.Acrylic Latex 3: Encor 636. This is a waterborne latex manufactured by Arkema Coatings Resins. It is 50% solids, has an MFFT of 20 °C and a particle size of 0.2 micron. It is used for both interior and exterior applications.PVDF-Acrylic Hybrid Latex 1: Kynar Aquatec® ARC Latex. This material has an MFFT of ~25 °C, 44% solids and contains 70% fluoropolymer. It is typically used for high performance coating applications where color and gloss retention are important. Surfactant 1: Aerosol A-102. This is an APS, anionic surfactant.Surfactant 2: Polystep TSP 16. This is a nonionic surfactant.Surfactant 3: Disponil FES 27A. This is a polyoxyethylene alkyl ether sulfate (PAES), anionic surfactant.Surfactant 4: Disponil FES 993. This is a polyoxyethylene alkyl ether sulfate (PAES), anionic surfactant.Surfactant 5: Sodium Dodecyl Sulfate. This is a fatty-acid, anionic surfactant.Surfactant 6: Polystep TSP 2528. This is a nonionic surfactant.Coalescent Agent 1: Texanol®. This is 2,2,4-trimethyl-l,3-pentane diol mono-isobutyrate manufactured by Eastman. CAS # 25265-77-4Coalescent Agent 2: Dowanol ™ DPM (dipropylene glycol methyl ether) CAS # 34590-94- 8.

[0092] The Heat Stability Test conducted included measuring the viscosity of a composition at day 0. The composition is then placed in an oven maintained at 50 °C. The viscosity of the composition is then measured at days 1, 7, 14, 21, 28, and 32 (as indicated). The viscosity was measured with a Stormer Viscometer.Counter Example 1

[0093] The Heat Stability Test was conducted on the following samples:

[0094] The results in Table 1 show that when the acrylic latexes are blended with only a coalescent agent, the blends do not increase, or at least meaningfully increase, in viscosity. However, with a blend of an acrylic latex, a PVDF-acrylic hybrid latex, and a coalescent agent, the viscosity increased meaningfully, rising to an "Above limit" level, which indicates that the sample has a viscosity higher than 141 KU. For example, the tested blends of an acrylic latex and a PVDF-acrylic hybrid latex are not considered heat stable. Values in parentheses are converted to centipoise (cP) from Table A-2 in Brookfield Manual M04-242-E1213.Table 1:Counter Example 2

[0095] The Heat Stability Test was conducted on the following samples:

[0096] The results in Table 2 show that that without addition of PVDF-acrylic latex to the 100% acrylic latex, viscosity stays the same. Addition of increasing levels of PVDF-acrylic latex leads to increased viscosity over time. The blend of CE2-C and CE2-D are not considered heat stable.

[0097] Viscosity, recorded in centipoise (cP), was measured on Brookfield Viscometer with Spindle #3 at 60 rpm. If the limit of 2000 cP was surpassed, Spindle #4 was used (limit of 10,000 cP). If the limit of 10,000 cP was surpassed, the speed was lowered to 0.6 rpm to measure higher viscosities (limit of 200,000 cP). Samples were kept in 50 °C over time. This Table shows "Above limit" indicates samples that have viscosities higher than 200,000 cP.Table 2:Counter Example 3

[0098] The Heat Stability Test was conducted on the following samples:

[0099] The results in Table 3 show that without addition of PVDF-acrylic latex to the 100% acrylic latex, viscosity stays the same. Addition of increasing levels of PVDF-acrylic latex leads to increased viscosity over time. Each blend including PVDF- acrylic latex is not considered heat stable.

[0100] Viscosity, recorded in centipoise (cP), was measured on Brookfield Viscometer with Spindle #3 at 60 rpm. If the limit of 2000 cP was surpassed, Spindle #4 was used (limit of 10,000 cP). If the limit of 10,000 cP was surpassed, the speed was lowered to 6 rpm to measure higherviscosities (limit of 20,000 cP). This Table shows "Above limit" indicates samples that have viscosities higher than 20,000 cP.Table 3:Inventive Example 1

[0101] The Heat Stability Test was conducted on the following samples:

[0102] The results in Table 4 show that without addition of surfactant, viscosity increases.Addition of different surfactants (at 0.25 wt%) to the latex blends prohibited a significant increase in viscosity.Table 4:Inventive Example 2

[0103] The results in Table 5 show that without addition of nonionic tristerylphenol-based surfactants, viscosity increases over time. Addition of increasing levels of surfactants reduces viscosity increase over time.

[0104] Viscosity, recorded in centipoise (cP), was measured on Brookfield Viscometer with Spindle #3 at 60 rpm. If the limit of 2000 cP was surpassed, Spindle #4 was used (limit of 10,000 cP). "Above limit" indicates samples that have viscosities higher than 10,000 cP.Table 5:Inventive Example 3

[0105] The Heat Stability Test was conducted on the following samples:

[0106] The results in Table 6 show that without addition of fatty-acid, anionic surfactants, viscosity increases over time. Addition of increasing levels of surfactants reduces viscosity increase over time.

[0107] Viscosity, recorded in centipoise (cP), was measured on Brookfield Viscometer with Spindle #3 at 60 rpm. "Above limit" indicates samples that have viscosities higher than 2,000 cP.Table 6:Aspects1. A method comprising:- measuring the heat stability of a screening blend by a heat-age stability test, wherein the heat-age stability test comprises: placing the screening composition in an oven, the oven being at a temperature of 30-100 °C, such as at 40-70 °C, such as about 50 °C;maintaining the screening composition in the oven for a time period, the time period being at least one week, such as 7-100 days, such as 10 to 50 days, such as about 30 days; and measuring the viscosity of the screening composition at the end of the time period, wherein the screening blend comprises:- an acrylic latex;- a PVDF-acrylic hybrid latex;- a surfactant; and- a coalescent agent.2. The method of aspect 1, wherein the method comprises forming the screening blend by blending a latex composition with the coalescent agent, wherein the latex composition comprises:- the acrylic latex;- the PVDF-acrylic hybrid latex; and- the surfactant.3. The method of any of aspects 1 to 2, wherein the screening blend comprises:- 50 to 95 wt%, such as 60 to 85 wt%, of the acrylic latex;- 5 to 50 wt%, such as 15 to 40 wt%, of the PVDF-acrylic hybrid latex;- 0.25 to 10 wt%, such as 0.5 to 5 wt%, of the surfactant; and- 0.5 to 5 wt%, such as 0.5 to 5 wt%, of the coalescent.4. The method of any of aspects 1 to 3, wherein the weight ratio of acrylic latex to PVDF- acrylic hybrid latex is 95:5 to 50:50, such as 90:10 to 60:10, such as 80:15 to 60:305. The method of any of aspects 1 to 4, wherein the heat-age stability test comprises measuring a viscosity of the screening blend after 24 hours in the oven, wherein a screeningblend is heat stable with change in viscosity (after 28 days at 50 °C) of less than 140% (measured in KU; [(day 28 KU - day 1 KU) / day 1 KU]), such as less than 100% change, less than 50% change, less than 30% change, less than 20% change, or less than 10% change.6. The method of any of aspects 1 to 5, wherein the screening blend is heat stable with a viscosity of the screening blend, after being in an oven at 50 °C for 28 days, of 140 KU or less, of 120 KU or less, or 100 KU or less, of 80 KU or less, or of 60 KU or less.7. The method of any of aspects 1 to 6, wherein the surfactant is selected from the group of anionic and nonionic surfactants.8. The method of any of aspects 1 to 7, wherein the screening blend comprises 0.75-5 wt%, such as 0.75-4 wt%, of a nonionic surfactant, such as a bulky nonionic surfactant, such as a tristerylphenol-based surfactant, such as Polystep TSP 2528.9. The method of any of aspects 1 to 7, wherein the screening blend comprises 0.25-5 wt%, such as 0.25-4 wt%, of a fatty-acid, anionic surfactant, such as CH3(CH2)xOSO3Na, wherein x is from 7 to 15, such as Sodium Dodecyl Sulfate.10. A screening blend consisting essentially of, or consisting of:- 50 to 95 wt%, such as 60 to 85 wt%, of the acrylic latex;- 5 to 50 wt%, such as 15 to 40 wt%, of the PVDF-acrylic hybrid latex;- 1 to 5 wt%, such as 1 to 4 wt%, of the surfactant; and- 0.5 to 5 wt%, such as 0.5 to 5 wt%, of the coalescent, wherein the surfactant is selected from the group of anionic and nonionic surfactants.11. The screening blend of aspect 10, wherein the weight ratio of acrylic latex to PVDF- acrylic hybrid latex is 95:5 to 50:50, such as 90:10 to 60:10, such as 80:15 to 60:30.12. The composition of any of aspects 10 to 11, wherein the surfactant is a nonionic surfactant, such as a tristerylphenol-based surfactant, such as Polystep TSP 2528.13. The composition of any of aspects 10 to 11, wherein the surfactant is a fatty-acid, anionic surfactant, such as CHsfCHzJxOSChNa, wherein x is from 7 to 15, such as Sodium Dodecyl Sulfate.14. The screening blend of any of aspects 10 to 13, wherein screening blend is heat stable by being able to meet the heat-age stability test comprising measuring a viscosity of the screening blend after 24 hours in an oven at 50 °C and measuring a change in viscosity (after 28 days at 50 °C) of less than 140% (measured in KU; [(day 28 KU - day 1 KU) / day 1 KU]), such as less than 100% change, less than 50% change, less than 30% change, less than 20% change, or less than 10% change.15. The screening blend of any of aspects 10 to 14, wherein the screening blend is heat stable with a viscosity of the screening blend, after being in an oven at 50 °C for 28 days, of 140 KU or less, of 120 KU or less, or 100 KU or less, of 80 KU or less, or of 60 KU or less.16. A composition consisting of:- 50 to 95 wt%, such as 60 to 85 wt%, of the acrylic latex;- 5 to 50 wt%, such as 15 to 40 wt%, of the PVDF-acrylic hybrid latex;- 1 to 5 wt%, such as 1 to 4 wt%, of the surfactant; and wherein the surfactant is selected from the group of anionic and nonionic surfactants.17. The composition of aspect 16, wherein the surfactant is a nonionic surfactant, such as a tristerylphenol-based surfactant, such as Polystep TSP 2528.18. The composition of aspect 16, wherein the surfactant is a fatty-acid, anionic surfactant, such as CI- CHzJxOSChNa, wherein x is from 7 to 15, such as Sodium Dodecyl Sulfate.19. The composition of any of aspects 16 to 18, wherein the weight ratio of acrylic latex to PVDF-acrylic hybrid latex is 95:5 to 50:50, such as 90:10 to 60:10, such as 80:15 to 60:30.

[0108] Various examples and embodiments of the inventive subject matter disclosed here are possible and will be apparent to a person of ordinary skill in the art, given the benefit of this disclosure. In this disclosure reference to "embodiments" means that those embodiments are non-limiting examples of the inventive subject matter, and there may be alternative embodiments which are not excluded.

[0109] The articles "a," "an," and "the" are used herein to refer to one or more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0110] As used herein, the term "about" means ±10% of the noted value. By way of example only, a composition comprising "about 30 wt.%" of a compound could include from 27 wt.% of the compound up to and including 33 wt.% of the compound.

[0111] The word "comprising" is used in a manner consistent with its open-ended meaning, that is, to mean that a given product or process can optionally also have additional features or elements beyond those expressly described. It is understood that wherever embodiments are described herein with open-ended meaning, otherwise analogous embodiments described in terms of "consisting of" and / or "consisting essentially of" are also contemplated and within the scope of this disclosure.

[0112] For the purposes of defining the present technology, the transitional phrase "consisting of" may be introduced in the claims as a closed preamble term limiting the scope of the claims to the recited components or steps and any naturally occurring impurities. For the purposes of defining the present technology, the transitional phrase "consisting essentially of" may be introduced in the claims to limit the scope of one or more claims to the recited elements, components, materials, or method steps as well as any non-recited elements, components, materials, or method steps that do not materially affect the novel characteristics of the claimed subject matter.

[0113] The different aspects, alternatives and embodiments of the invention disclosed herein can be combined with one or more of the other aspects, alternatives and embodiments described herein. Two or more aspects can be combined.

[0114] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0115] While the embodiments of the present disclosure have been described with particular reference to certain embodiments thereof, it will be understood that changes and modifications may be made by those of ordinary skill within the scope and spirit of the following claims.

Claims

CLAIMS1. A method comprising:- measuring the heat stability of a screening blend by a heat-age stability test, wherein the heat-age stability test comprises: placing the screening composition in an oven, the oven being at a temperature of 30-100 °C, such as at 40-70 °C, such as about 50 °C; maintaining the screening composition in the oven for a time period, the time period being at least one week, such as 7-100 days, such as 10 to 50 days, such as about 30 days; and measuring the viscosity of the screening composition at the end of the time period, wherein the screening blend comprises:- an acrylic latex;- a PVDF-acrylic hybrid latex;- a surfactant; and- a coalescent agent.

2. The method of claim 1, wherein the method comprises forming the screening blend by blending a latex composition with the coalescent agent, wherein the latex composition comprises:- the acrylic latex;- the PVDF-acrylic hybrid latex; and- the surfactant.

3. The method of any of claims 1, wherein the screening blend comprises:- 50 to 95 wt%, such as 60 to 85 wt%, of the acrylic latex;- 5 to 50 wt%, such as 15 to 40 wt%, of the PVDF-acrylic hybrid latex;- 0.25 to 10 wt%, such as 0.5 to 5 wt%, of the surfactant; and- 0.5 to 5 wt%, such as 0.5 to 5 wt%, of the coalescent.

4. The method of any of claims 1 , wherein the weight ratio of acrylic latex to PVDF-acrylic hybrid latex is 95:5 to 50:50, such as 90:10 to 60:10, such as 80:15 to 60:

305. The method of any of claims 1 to 4, wherein the heat-age stability test comprises measuring a viscosity of the screening blend after 24 hours in the oven, wherein a screening blend is heat stable with change in viscosity (after 28 days at 50 °C) of less than 140% (measured in KU; [(day 28 KU - day 1 KU) / day 1 KU]), such as less than 100% change, less than 50% change, less than 30% change, less than 20% change, or less than 10% change.

6. The method of any of claims 1 to 4, wherein the screening blend is heat stable with a viscosity of the screening blend, after being in an oven at 50°C for 28 days, of 140 KU or less, of 120 KU or less, or 100 KU or less, of 80 KU or less, or of 60 KU or less.

7. The method of any of claims 1 to 4, wherein the surfactant is selected from the group of anionic and nonionic surfactants.

8. The method of any of claims 1 to 4, wherein the screening blend comprises 1-5 wt%, such as 1-4 wt%, of a nonionic surfactant, such as a bulky nonionic surfactant, such as a tristerylphenol-based surfactant, such as Polystep TSP 2528.

9. The method of any of claims 1 to 4, wherein the screening blend comprises 1-5 wt%, such as 1-4 wt%, of a fatty-acid, anionic surfactant, such as CHsfCI-hJxOSOsNa, wherein x is from 7 to 15, such as Sodium Dodecyl Sulfate.

10. A screening blend consisting essentially of, or consisting of:- 50 to 95 wt%, such as 60 to 85 wt%, of the acrylic latex;- 5 to 50 wt%, such as 15 to 40 wt%, of the PVDF-acrylic hybrid latex;- 1 to 5 wt%, such as 1 to 4 wt%, of the surfactant; and- 0.5 to 5 wt%, such as 0.5 to 5 wt%, of the coalescent, wherein the surfactant is selected from the group of anionic and nonionic surfactants.

11. The screening blend of claim 10, wherein the weight ratio of acrylic latex to PVDF-acrylic hybrid latex is 95:5 to 50:50, such as 90:10 to 60:10, such as 80:15 to 60:30.

12. The screening blend of any of claims 10 to 11, wherein the surfactant is a nonionic surfactant, such as a tristerylphenol-based surfactant, such as Polystep TSP 2528.

13. The screening blend of any of claims 10 to 11, wherein the surfactant is a fatty-acid, anionic surfactant, such as CI-hfCI-hJxOSOsNa, wherein x is from 7 to 15, such as Sodium Dodecyl Sulfate.

14. The screening blend of any of claims 10 to 11, wherein screening blend is heat stable by being able to meet the heat-age stability test comprising measuring a viscosity of the screening blend after 24 hours in an oven at 50 °C and measuring a change in viscosity (after 28 days at 50 °C) of less than 140% (measured in KU; [(day 28 KU - day 1 KU) / day 1 KU]), such as less than 100% change, less than 50% change, less than 30% change, less than 20% change, or less than 10% change.

15. The screening blend of any of claims 10 to 11, wherein the screening blend is heat stable with a viscosity of the screening blend, after being in an oven at 50 °C for 28 days, of 140 KU or less, of 120 KU or less, or 100 KU or less, of 80 KU or less, or of 60 KU or less.

16. The screening blend of any of claims 15, wherein the surfactant is a nonionic surfactant, such as a tristerylphenol-based surfactant, such as Polystep TSP 2528.

17. The screening blend of any of claims 15, wherein the surfactant is a fatty-acid, anionic surfactant, such as d- d-bJxOSC Na, wherein x is from 7 to 15, such as Sodium Dodecyl Sulfate.

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