Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/20—Compounding polymers with additives, e.g. colouring
  • C08J3/205—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D17/00—Pigment pastes, e.g. for mixing in paints
  • C09D17/004—Pigment pastes, e.g. for mixing in paints containing an inorganic pigment
  • C09D17/007—Metal oxide
  • C09D17/008—Titanium dioxide
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/02—Emulsion paints including aerosols
  • C09D5/024—Emulsion paints including aerosols characterised by the additives
  • C09D5/027—Dispersing agents
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/45—Anti-settling agents
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/65—Additives macromolecular
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
  • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
  • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C08J2333/08—Homopolymers or copolymers of acrylic acid esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
  • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
  • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C08J2333/10—Homopolymers or copolymers of methacrylic acid esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
  • C08K2003/2237—Oxides; Hydroxides of metals of titanium
  • C08K2003/2241—Titanium dioxide
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/49—Phosphorus-containing compounds
  • C08K5/51—Phosphorus bound to oxygen
  • C08K5/52—Phosphorus bound to oxygen only
  • C08K5/521—Esters of phosphoric acids, e.g. of H3PO4

Definitions

• the invention is further directed generally to a process for preparing aqueous compositions including titanium dioxide pigment, and more particularly to the dispersion and distribution of titanium dioxide particles in products formed by the loss of water from such aqueous compositions, including aqueous coating compositions.
• This invention also features a coating containing opacifying pigment particles and a polymer matrix. More specifically, the invention relates to such a coating wherein the opacifying pigment particles have improved hiding power.
• the invention further relates to a coating vvherem the opacifying pigment particles are composite particles, which are inorganic-organic particles containing an opacifying pigment particle with at least one polymer particle attached thereto.
• This invention still further relates to methods of preparing composite particles, and to a method of preparing coating compositions containing composite particles.
• Aqueous dispersions of polymeric latex are used to prepare a large variety of commercially important products, including coatings, paints, mastics, primers, caulks, binders for non-woven materials, and adhesives.
• the polymeric latex is included to form a continuous phase as the water is lost in order to bind the product together, and to contribute important physical properties.
• Opacifying capacity is a function of the spacing between the particles of opacifying pigment in the dried applied coating. Opacifying capacity of a coating is maximized when the light scattering capability of the opacifying pigment is maximized. Maximum, light scattering efficiency occurs when the opacifying pigment particles have a certain diameter and spacing, so that the light scattering capability of each particle does not interfere with the light scattering capability of its neighboring particles. This condition may occur in coatings containing sufficiently low levels of opacifying pigment such that the individual opacifying pigment particles are isolated from each other. Coatings containing such low levels of opacifying pigment, however, do not provide sufficient whiteness and hiding at typical dried coating thicknesses. Achieving the desired levels of hiding and whiteness typically requires higher levels of opacifying pigment.
• a statistical distribution of opacifying pigment particles occurs, which results in at least some of the opacifying pigment particles being in such close proximity to one another that there is a loss of light scattering efficiency due to crowding of the opa cifying pigment particles.
• opacifying coatings and paints have a high opacifying capacity so as to enable the coating or paint to completely conceal the undersurfa.ee, even if of a sharply contrasting color, while utilizing a minimal application of the coating or paint. It is highl desirable that complete covering of the undersurface is attained with a single application of the coating or paint, having the minimum possible thickness.
• Opacifying coating and paint manufacturers have Song sought to formulate opacifying coatings and paints having the desired opacity by maximizing the level of hiding for a defined level of opacifying pigment, in an attempt to approach the theoretical maximum hiding capability for a specific opacifying pigment, while minimizing the amount of opacifying pigment actually utilized.
• titanium dioxide pigment particles are forced to be nearer to each other than the desired optimum merely by the lack of available space.
• This lack of available space may be caused by the space take up by the other coating fillers and extenders which are of a comparable size to, or which are larger than, the pigment particles.
• the binder polymer particles themselves can crowd pigment particles, especially if they are of comparable or larger in size than the titanium, dioxide particles.
• aqueous dispersion of titanium dioxide pigment with other fillers or extenders.
• This dispersion also known as a "mill base” or “grind,” may contain water-miscibie solvents, such as for example glycols and glycol ethers, and relatively low molecular weight water soluble polyelectrolytes as titanium dioxide pigment grinding aids or dispersants.
• these pigment dispersants are anionic polyelec trolytes. Many different types of such dispersants are kno wn.
• a number of techniques have been proposed to disperse inorganic particles such as titanium dioxide particles in aqueous polymer containing coating compositions.
• inorganic particles such as titanium dioxide particles
• aqueous polymer containing coating compositions there exist methods for encapsulating solid particles by admixing the particles in an aqueous reaction medium with a water-insoluble po!ymerizable monomer in the presence of nonionic surface active stabilizing agent (such as a poiyethoxyiated aikyiphenoi containing at least about 8 carbon atoms in the alkyl group and preferably at least 40-50 ethylene oxide groups per molecule) to form a water-insoluble polymer free of ionic charge.
• nonionic surface active stabilizing agent such as a poiyethoxyiated aikyiphenoi containing at least about 8 carbon atoms in the alkyl group and preferably at least 40-50 ethylene oxide groups per molecule
• a redox polymerization is employed which is free of
• the Derjaguin et al. theory mathematically expresses a balance between attractive forces attributed to van der Waals forces and repulsive forces attributed to like electrical charges on the surfaces of interacting particles.
• Other types of interaction forces for example steric repulsion and attraction due to dissolved polymer, can be incorporated into the basic theory at least semi- quantitatively, investigators have shown the applicability of the theory in very dilute systems.
• Their conclusions are typically expressed in terms of particle collisions and minimum repulsive energy barriers between particles sufficient to overcome the attractive forces. Below this energy- barrier there are too many collisions of particles with energies exceeding this minimum repulsive energy barrier to prevent coagulation.
• colloidal dispersions of particles differing in sign of charge are mixed, the usual result is a gross floeeuiaiion or coagulation.
• This result may be a. desirable consequence in some circumstances, such as, for example, in instances where it is desired to purif water containing suspended matter or to isolate a bulk solid material from its colloidal suspension.
• the dispersions of particles having different sign of charge are mixed together under conditions of low particle concentration, and where one of the particle types is smaller than the other and present in greater number, then gross coagulation may be avoided and the smaller particles may form a monolayer on the larger ones.
• the Derjaguin et al. theory and extensions thereof have been useful as a guide for interpreting and correlating aspects relating to the stability of small particles and dilute colloidal dispersions. These theories has been useful despite their quantitative limitations, and the fact that- all of the necessary parameters for implementation, such as, for example, the material attraction or Hamaker constants, are not always known, or are not known with sufficient accuracy for all the materials of possible interest.
• the primary deficiency of the Derjaguin et ai. theory is that it is limited to the interactions of two isolated particles of the same type with each other in ver - dilute dispersions.
• inorganic particles are commonly incorporated into organic coatings as opacifying pigments to provide whiteness and opacity or "hiding" to opacifying coati gs, such as paints. These pigments are present in all coatings that are designed to provide an opaque coating onto a substrate surface and are absent from those coatings that are designed to be clear or transparent. Opacifying pigments are present in opacifying coatings, especially paints, both white or colored. The opacifying pigment of most paints is distinguished from the color specific pigments, also known as tinting agents or colorants, which are additionally present in colored paints. It is the color specific pigments that provide the specific color or tint to non- white paints.
• opacifying coatings and paints have a high opacifying capacity to enable the coating or paint to completely conceal the iindersurface, even if of a sharply contrasting color, while utilizing a minimal application of the coating or paint. It is highly desirable that complete covering of the iindersurface is obtained with a single application of the coating or paint having the minimum, possible thickness. Opacifying coating and paint manufacturers have long sought to formulate opacifying coatings and paints having the desired opacity by maximizing the level of hiding for a defined level of opacifying pigment, in order to minimize the amount of opacifying pigment utilized.
• the opacifying capacity or hiding power of an opacifying coati g or paint is a measure of the coating's ability to conceal a surface to which the coating is applied.
• Opacifying capacity is a function of the spacing between the particles of opacifying pigment in the dried applied coating.
• Opacifying capacity of a coating is maximized when the light scattering capability of the opacifying pigment is maximized.
• Maximum light scattering efficiency occurs when the opacifying pigment particles have a certain diameter and spacing, so that the light scattering capability of each particle does not interfere with the light scattering capability of its neighboring particles. This condition may occur in coatings containing sufficiently low levels of opacifying pigment such that the individual opacifying pigment particles are isolated from each other.
• Coatings containing such low levels of opacifying pigment do not provide sufficient whiteness and hiding at typical dried coating thicknesses. Achieving the desired levels of hiding and whiteness typically requires higher levels of opacifying pigment. At these higher levels, agglomeration of opacifying pigment particles occurs, which results in a statistical distribution of particle sizes of the opacifying pigment particles.
• Titanium, dioxide (Ti0 2 ) is the most commonly used opacifying pigmen in paints. There is often a shortage of Ti0 2 and prices for this raw material are escalating. There is significant interest in the marketplace to improve the hiding performance of Ti0 2 in paint and other coatings so that less can be used and thus lower the cost of coating formulations containing it.
• TiOa is usually randomly distributed throughout a paint film. This randomness allows for the formation of doublets, triplets etc. of agglomerated pigment particles, reducing their scattering efficiency. Methods to decrease this phenomenon should improve hiding. Ti0 2 products are often treated with silica and alumina for various properties (see Figure 1).
• US patent 7,960,026 B2 discloses a process to make an organic / inorganic composite particle to aid in spacing of the Ti0 2 .
• the process requires a Ti0 2 particle, a plurality of polymer latex particles in contact with the Ti0 2 surface (primary composite particle), and a polymer layer encapsulating the primary composite particle.
• the primary composite particle is prepared by producing latex particles with phosphate groups on their surfaces and contacting with a TiO? particle, preferably one with alumina on its surface.
• the phosphate groups on the latex particle have an attraction for the alumina sites on the Ti0 2 particle surface, resulting in adhesion of the latex particles to the TiOa pigment surface.
• This primary particle is then encapsulated in another latex layer to hold it together.
• the phosphate groups on the surface of the latex particle are derived from the incorporation of phosphate-containing monomers that copolymerize with the other latex particle monomers.
• Figure 1 shows a Ti0 2 particle treated with alumina/silica.
• Figure 2 illustrates the particle size distribution of the R-741 (Ti0 2 ).
• Figure 3 features the particle size distribution of a composite particle (latexl84 having a reactive phosphate surfactant having 202nm + Ti0 2 ).
• Figure 4 shows the particle size distribution of a composite particle (latex 185 sulfate 196nm + Ti0 2 ).
• Figure 5 illustrates the particle size distribution of a composite particle (latex 186 phosphate 130nm + Ti0 2 ).
• Figure 6 features the particle size distribution of a composite particle (latex 187 sulfate 128nm + Ti0 2 ).
• Figure 7A shows a cast film from latexl84 Phosphate surfactant + Ti0 2 .
• Figure 7B illustrates a cast film from latexl85 Sulfate surfactant + Ti0 2 .
• the invention provides a method for improving the opacity or hiding power of an aqueous latex coating which method comprises adding a Ti0 2 dispersion to a latex particle dispersion in which the latex particles are manufactured in the presence of a phosphate- containing ethylenically unsaturated reactive surfactant.
• the invention also relates to a process for preparing an aqueous dispersion of composite particles, the composite particles each comprising a plurality of polymeric latex particles adsorbed onto a titanium dioxide particle, the process comprising: (a) suspending polymeric latex particles in an aqueous medium, the polymeric latex particles having been polymerized in the presence of a phosphate containing ethylenically unsturated reactive surfactant; (b) suspending titanium dioxide particles in the aqueous medium; and (c) mixing the aqueous medium containing the titanium dioxide particles and the polymeric latex particles, the polymeric latex particles adsorbing onto the titanium dioxide particles in a controlled manner to provide the composite particles.
• the present invention further provides a process for preparing an aqueous dispersion of composite particles, the composite particles each including a plurality of polymeric latex particles adsorbed onto a titanium dioxide particle.
• the resulting composite particles can be used in preparing formulated aqueous compositions, such as coating compositions and paints, which in turn give coatings in which the titanium dioxide is more efficaciously dispersed than in prior art coatings.
• the improved dispersion of the titanium dioxide particles provided by the process of the present invention advantageously reduces the amount of titanium dioxide required to provide desired coating properties, such as opacity or hiding, tint strength, mechanical properties, viscosity, gloss, and scub resistance.
• the process also provides coating compositions giving coatings with improved opacity for a given pigment level.
• aqueous composition further includes at least one latex polymer, at least one inorganic pigment and water. It should be noted that the reactive surfactant is preferentilly used during the making of the latex via emulsion polymerization.
• the aqueous coating composition can further include at least one anti-freezing agent and one or more additives selected from the group consisting of plasticizers, drying retarders, dispersants, surfactants or wetting agents, rheology modifiers, defoamers, thickeners, coalescing agents, biocides, mildewcides, colorants, waxes, perfumes and co-solvents.
• additives selected from the group consisting of plasticizers, drying retarders, dispersants, surfactants or wetting agents, rheology modifiers, defoamers, thickeners, coalescing agents, biocides, mildewcides, colorants, waxes, perfumes and co-solvents.
• the aqueous coating composition is an acrylic latex paint composition, comprising at least one phosphate containing ethylenically unsaturated reactive surfactant as described above; at least one acrylic latex polymer derived from at least one acrylic monomer selected from the group consisting of acrylic acid, acrylic acid esters, methacrylic acids, and methacrylic acid esters; titanium dioxide and water.
• the at least one acrylic latex polymer can be selected from the group consisting of pure acrylics, styrene acrylics, vinyl acrylics and acrylated ethylene vinyl acetate copolymers and is more preferably a pure acrylic.
• the present invention further includes a method of preparing an aqueous coating composition. Specifically, at least one phosphate containing ethylenically unsaturated reactive surfactant as described above, at least one latex polymer, and at least one inorganic pigment are mixed to produce the aqueous coating composition.
• the at least one inorganic pigment is in slurry form.
• the at least one inorganic pigment is preferably selected from the group consisting of Ti0 2 and CaC0 3 .
• the at least one latex polymer is preferably selected from the group consisting of pure acrylics, styrene acrylics, vinyl acrylics and acrylated ethylene vinyl acetate copolymers, and more preferably includes a pure acrylic.
• At least one anti-freezing agent and at least one additive selected from the group consisting of plasticizers, drying retarders, dispersants, surfactants or wetting agents, rheology modifiers, defoamers, thickeners, coalescing agents, biocides, mildewcides, colorants, waxes, perfumes and co-solvents, can also be mixed in the composition.
• the method can further include the step of preparing the polymer latex binder using emulsion polymerization by feeding monomers to a reactor in the presence of at least one initiator and the at least one phosphate containing ethylenically unsaturated reactive surfactant described above and polymerizing the monomers to produce the latex binder.
• the resulting latex binder can then be mixed with the at least one inorganic pigment to produce the aqueous coating composition.
• the step of preparing the polymer latex binder can include the steps of preparing an initiator solution comprising the initiator, preparing a monomer pre-emulsion comprising monomers and the surfactant, adding the initiator solution to a reactor and adding the monomer pre-emulsion to the reactor.
• the initiator solution is added to the reactor prior to adding the monomer pre-emulsion.
• a seed latex is preferably added to the reactor prior to adding the initiator and adding the monomer pre-emulsion.
• the latex binder is preferably chemically stripped by adding a peroxide and a reducing agent to the latex binder thereby decreasing the residual monomer content of the latex binder.
• the monomers fed to a reactor to prepare the polymer latex binder preferably include at least one acrylic monomer selected from the group consisting of acrylic acid, acrylic acid esters, methacrylic acids, and methacrylic acid esters.
• the monomers can include one or more monomers selected from the group consisting of styrene, a- methyl styrene, vinyl chloride, acrylonitrile, methacrylonitrile, ureido methacrylate, vinyl acetate, itaconic acid, crotonic acid, maleic acid, fumaric acid, ethylene, and C4-C8 conjugated dienes such as 1,3-butadiene, isoprene or chloroprene.
• the monomers include one or more monomers selected from the group consisting of n-butyl acrylate, methyl methacrylate, styrene and 2-ethylhexyl acrylate.
• the aqueous coating compositions of the invention maintains better dispersion of the Ti0 2 particles or other inorganic pigment particles than conventional compositions that do not use the reactive surfactants of the invention.
• Semi gloss paint formulations prepared in accordance with the invention also have excellent high shear viscosities, low shear viscosities, gloss and hiding power and show improvements in these properties over conventional formulations.
• the phosphate groups are derived from the surfactant used to prepare the latex particle, thus obviating the need for separate phosphate monomers and polymerization surfactants.
• the phosphate groups are part of a surface-active molecule, they partition largely onto the surface of the latex particles rather than being incorporated randomly along the latex particle backbone. Since only the phosphate groups on the latex particle surface can associate with the alumina sites on the TiC)2 particle surface and create adhesion, the instant invention allows for stronger adhesion between latex and TiO particles. This obviates the prior art need to encapsulate the composite particle with another latex coating and can allow less phosphated material to be used.
• the present invention is a aqueous coating composition that provides excellent dispersion of Ti0 2 particles and other inorganic pigment particles.
• the aqueous coating composition of the invention includes at least one phosphate containing ethylenically unsaturated reactive surfactant, at least one latex polymer, at least one inorganic pigment and water.
• the reactive surfactants useful for making the latexes of the invention have the following structures: Ri-O- (CH 2 CHR20) x (CH2CHR 3 0) y -P03H2 or
• Ri phenol, monostyrenated phenol, distyrenated phenol or tristyrenated phenol, Cs-Cisalkyl substituted phenol, arylalkyl
• the mean particle sizes of the inorganic pigments range from about 0.01 to about 50 microns.
• the T1O 2 particles used in the aqueous coating composition e.g. provided by the slurry
• the inorganic pigment e.g. Ti0 2 and/or CaC0 3
• Exemplary Ti0 2 slurries for use in the invention include TI-PURE R TM R-746 and R-942, commercially available from DuPont; TIOXIDE R TM RCS-535, RCS-9 and R-HD6X, commercially available from Huntsman Corp.; and KRONOS R TM 4102, commercially available from Kronos, Inc.
• the inorganic pigment is preferably present in the aqueous coating composition in an amount from about 5 to about 40 percent by weight, more preferably from about 10 to about 30 percent by weight (based on the weight of the inorganic pigment, not the weight of the slurry).
• the at least one latex polymer used in the aqueous coating composition is preferably derived from monomers comprising at least one acrylic monomer selected from the group consisting of acrylic acid, acrylic acid esters, methacrylic acids, and methacrylic acid esters.
• the latex polymer can optionally include one or more monomers selected from the group consisting of styrene, a-methyl styrene, vinyl chloride, acrylonitrile, methacrylonitrile, ureido methacrylate, vinyl acetate, itaconic acid, crotonic acid, maleic acid, fumaric acid, and ethylene.
• the monomers include one or more monomers selected from the group consisting of n-butyl acrylate, methyl methacrylate, styrene and 2-ethylhexyl acrylate.
• the latex polymer is typically selected from the group consisting of pure acrylics (comprising acrylic acid, methacrylic acid, an acrylate ester, and/or a methacrylate ester as the main monomers), styrene acrylics (comprising styrene and acrylic acid, methacrylic acid, an acrylate ester, and/or a methacrylate ester as the main monomers), vinyl acrylics (comprising vinyl acetate and acrylic acid, methacrylic acid, an acrylate ester, and/or a methacrylate ester as the main monomers) and acrylated ethylene vinyl acetate copolymers (comprising ethylene, vinyl acetate and acrylic acid, methacrylic acid, an acrylate ester, and/or a methacrylate ester as the main monomers).
• pure acrylics comprising acrylic acid, methacrylic acid, an acrylate ester, and/or a methacrylate ester as the main monomers
• the monomers can also include other main monomers such as acrylamide and acrylonitrile, and one or more functional monomers such as itaconic acid and ureido methacrylate, as would be readily understood by those skilled in the art.
• the latex polymer is a pure acrylic such as a butyl acrylate/methyl methacrylate copolymer derived from monomers including butyl acrylate and methyl methacrylate.
• the latex polymer dispersion preferably includes from about 30 to about 75% solids and a mean latex particle size of from about 70 to about 650 nm.
• the latex polymer is preferably present in the aqueous coating composition in an amount from about 5 to about 60 percent by weight, and more preferably from about 8 to about 40 percent by weight (based on the weight of the latex polymer and not the latex dispersion).
• the aqueous coating composition can optionally further include at least one anti- freezing agent to improve the freeze-thaw stability of the composition such as propylene glycol, ethylene glycol and diethylene glycol. More preferably, propylene glycol is used.
• the anti-freezing agent is typically present in the aqueous coating composition in an amount of from 0 to about 15% by weight, more preferably from about 1 to about 10% by weight, based on the total weight of the aqueous coating composition.
• the selected polymeric latex particles themselves do provide a binder for the product formed by the fully formulated aqueous composition.
• an average polymeric latex particle diameter of from about 80 nm to 600 nm is preferred, and more preferably an average particle diameter of 80-300 nm.
• the polymeric latex can also be prepared by standard emulsion polymerization techniques. The optimum size of selected polymeric latex particles is believed to depend to some extent on the level of the functionality incorporated in the selected polymeric latex particles, with particle size varying inversely with the level of functionality.
• the concentration of the titanium dioxide particles (and any other pigments which may be present in the composition) in a coating formulation is expressed in terms of the pigment volume concentration of the formulation.
• the pigment volume concentration (hereinafter referred to as the "PVC") of a formulation is defined as the volume amount of inorganic particles, including titanium dioxide and other pigment particles as well as extender particles, present in the formulation, divided by the sum of the volume amount of such inorganic particles plus polymeric latex particle solids in the formulation and expressed herein as a percentage.
• the PVC of compositions prepared according to the present invention is from about 5 to 60 percent, and more preferably from about 10 to 50 percent.
• polymeric latexes used in the practice of the present invention can have monomer compositions and particle sizes closely related to polymeric latex binders prepared by standard emulsion polymerization techniques known in the art.
• the initiator solution is added to the reactor prior to adding the monomer pre-emulsion.
• a seed latex such as a polystyrene seed latex can be added to the reactor.
• water, one or more surfactants, and any monomers not provided in the monomer pre-emulsion can be added to the reactor prior to adding the initiator and adding the monomer pre-emulsion.
• the reactor is operated at an elevated temperature at least until all the monomers are fed to produce the polymer latex binder. Once the polymer latex binder is prepared, it is preferably chemically stripped thereby decreasing its residual monomer content.
• the ethylenically unsaturated monomer can also include at least one multi-ethylenically unsaturated monomer effective to raise the molecular weight and crosslink the polymer.
• acrylic acid methacrylic acid, beta-acryloxypropionic acid and higher monoacidic oligomers of acrylic acid, ethacrylic acid, alpha-chloroacrylic acid, a-vinylacrylic acid, crotonic acid, a-phenylacrylic acid, cinnamic acid, chlorocinnamic acid, ⁇ -styrylacrylic acid, itaconic acid, and maleic acid.
• small molecular species such as silanes or titanates
• examples of such species include N-2-aminoethyl-3 -amino- propyltrimethoxysilane, 3 -aminopropyltrimethoxysilane, 3 -methacryloxypropyltrimethoxysilane, and vinyltriacetoxysilane.
• other species can be simply adsorbed to the surface of the titanium dioxide pigment particles. The most important examples of these are low molecular weight polyelectrolytes such as conventional pigment dispersants.
• the adsorption of polymeric latex particles on titanium dioxide pigment particles is presently believed to be a complex function of the type and level of adsorbing moiety on the titanium dioxide pigment particles surface, the surface treatment on the titanium dioxide pigment particle's surface, the pigment and binder surface area, the level and type of dispersants present in the mixture, the type of thickener used, the ionic strength of the mixture, and the presence or absence of other, competing molecules. Together, these factors are believed to detemiine the adsorption level, thereby affecting viscosity and viscosity stability, hiding, gloss, and block.
• the process of the present invention can significantly increase the hiding of titanium dioxide containing emulsion paint formulations (as deteirriined by measuring the scattering coefficient of the paint) of the same PVC compared with the scattering coefficient of a paint formulation prepared by the use of conventional polymeric latices.
• An alternate way of expressing this improvement is that the process of the invention permits the reduction of the PVC of a 20% PVC titanium dioxide paint formulation by as much as 20 percent or more while achieving the same scattering coefficient or degree of hiding as can be obtained by the use of a conventional polymeric latex.
• DSP Distyrenated phenol
• AGE allyl glycidyl ether
• KOH potassium hydroxide
• DSP Distyrenated phenol
• AGE allyl glycidyl ether
• KOH potassium hydroxide
• Example 1 was sulfated with sulfamic acid in a glass reactor equipped with a stirrer, thermometer, and reflux condenser by heating to 120 C until the %sulfate was > 90%.
• the product, Example 2 was isolated as the ammonium salt.
• the product is also known as ERS 1618.
• Example 1 Three moles of Example 1 was phosphated with one mole of phosphorus pentoxide (P 2 O 5 ) in a glass reactor equipped with a stirrer, thermometer, and reflux condenser by heating to 70 C until the reaction was complete.
• the product was isolated as the ammonium salt in aqueous solution.
• DSP Distyrenated phenol
• AGE allyl glycidyl ether
• KOH potassium hydroxide
• Example 2D The same ethoxylate in Example 1 was converted to the sulfate by reaction with sulfamic acid according to methods known in the art.
• the sulfate in the ammonium ion form is Example 2D.
• R-741 Dispersed Ti0 2 - 64% solids - DuPont.
• R-741 a predispersed TiO? product in water from DuPont was used for simplicity, instead of making a dispersion from dry pigment. This is the same product as R-931, in Table 1 below, but dispersed in water. It has a particle size of 550 nm and has high alumina content. Table 1
• the particle size was adjusted by changing the concentration of the seed latex.
• the seed latex is a preformed latex of very small particle size. This helps ensure the predictability of the final particle size as the number of particles are set at the beginning of the polymerization: (1) For latex samples 184 and 185, 45g of the seed latex was used to obtain a particle size of -200 nm
• the particle sizes of the latexes are shown in Table 3 below.
• the particle size distributions were monomodal.
• Latex / Ti0 2 blend ratios were obtained from a typical satin paint formulation. The particle size of the blends were then measured.
• the particle size distribution data would show data indicative of a simple blend.
• a distribution for the latex particles would be visible around the 100 - 200 nm size range as well as a distribution around 800 nm for the TiO particles together on the same scan (a bimodal distribution).
• the presence of particles larger than the Ti() 2 particles indicates the formation of composite particles formed from both particle types joined by an attractive force.
• the particle size of the latex composites are listed below in Table 5. All of the composites have a larger Mv (volume average) than the R-741 indicating some degree of agglomeration. The exception is the 185 composite.
• the Mn (number average) for the composites is only larger for the 184 composite. This indicates that some significant portion of free latex still exists and is not bound to the surface. It is possible that there is insufficient TiO> surface to accommodate all the particles in the small particle size latexes (186 and 187).
• the particle size distributions of the Ti0 2 and composites are shown below in Figures 2 to 6.
• the X-axis is a log scale centered at 1 ⁇ (1000 nm)
• the left Y axis is the cumulative Mv line while the right Y axis indicates a scale for the histogram.
• the particle size of the R-741 (TiO?) in shown in Figure 2. It appears bimodal. The right mode compares favorably with the literature data of 550 nm obtained from the DuPont literature. The dispersion was not perfect, as there appears to be a significant volume of doublets at 1100 nm.
• the composite particles size distributions (Ti0 2 and latex) are also shown ( Figures 3 to 6).
• Figure 3 demonstrates that the phosphate-modified latex has effectively adsorbed to the surface to the Ti() 2 since there is no peak associated with the particle size of the latex (202 nm).
• Figure 4 demonstrates that the sulfate-modified latex has not adsorbed to the surface to the Ti €1 ⁇ 2 since there is a large peak associated with the particle size of the latex (196nm).
• the phosphate latex does not appear in the distribution, the sulfate particle size is not significantly present either.
• the phosphate composite has a more narrow distribution (aside from some gross coagulation), than the sulfate composite. It is hypothesized that the small particle sized latexes may not be stable in any case in the presence of the Ti0 2 due to a larger surface area that the surfactant must cover, and some coagulation ensued.
• the data indicates that composite particles were formed, at least when the larger particle sized latexes were employed.
• the 184 and 185 Ti0 2 + latex blends were drawn down into films cast on BYK PA-2811 charts (3 mil - wet applied). The opacity was measured on 1 day dried latex + TiO> blend paint films.
• LW is the lightness measured over the white portion of the chart

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