Abstract: Colored lustrous pigments of superior quality are prepared by dry blending a platy substrate such as a metal oxide-coated mica nacreous pigment and a hydrophobic colorant at low shear. The resulting blend exhibits a well dispersed, stable coloration, increased hydrophobicity and is particularly useful in industrial and automotive applications. The technique can also be employed to prepare pigments for cosmetic application.

Abstract: A black composite iron oxide pigment of the present invention comprises composite iron oxide particles having an average particle size of 0.08 to 1.

Abstract: Iron oxide hydroxide composite particles having an average particle diameter of 0.005 to 1.0 &mgr;m, comprises: iron oxide hydroxide particles as core particles, a coating formed on surface of said iron oxide hydroxide particles, comprising at least one organosilicon compound selected from the group consisting of: (1) organosilane compounds obtainable from alkoxysilane compounds, and (2) polysiloxanes or modified polysiloxanes, and an organic pigment coat formed on said coating layer comprising said organosilicon compound, in an amount of from 1 to 30 parts by weight based on 100 parts by weight of said iron oxide hydroxide particles. The iron oxide hydroxide composite particles of the present invention contain no harmful elements and exhibit not only excellent chemical resistances such as acid resistance and alkali resistance, but also excellent heat resistance.

Abstract: The invention relates to a non-dusting, homogeneous pigment preparation which is distinguished by the fact that it comprises at least 40% by weight of one or more effect pigments and 0.5-59.5% by weight of a modified colophony resin, based on the pigment preparation, and the use thereof, in particular for the production of dry preparations. The pigment preparation according to the invention and the dry preparations produced therefrom are particularly suitable for the pigmenting of paints, coatings, powder coatings, printing inks and plastics.

Abstract: The present invention relates to a process for producing briquetted and pressed granular material and the use thereof for coloring building materials, such as concrete and asphalt, and organic media, such as paint systems, plastics and colored pastes.

Abstract: Surface-modified conductive pigment obtainable by partial coating of a conductive pigment with an organic modifying agent. The modifying agent is an organometallic compound of the elements silicon, tin, titanium, zirconium or aluminum. The pigment is prepared by dispersing a conductive pigment, subsequently adding the modifying agent, if appropriate as a mixture with a solvent, to the pigment dispersion, and in particular in an amount such that the powder electrical conductance of the partly coated conductive pigment is in the range between 80% of the starting value and 10−7 S, removing the solvent present, if appropriate, with further agitation and heating of the pigment to 100° C. and finally drying the partly coated pigment.

Abstract: A flake-based pigment is provided having improved specular reflectance characteristics in the visible wavelength range. The flake-based pigment has a plurality of core flake sections each formed of a central reflector layer and dielectric support layers on opposing sides of the reflector layer. The resulting core flake section is a very thin three-layered structure that exhibits a uniaxial compressive strength much greater than a corresponding uniaxial tensile strength. This structure provides the benefits of rigidity and brittle fracture during manufacturing and application processes, which ultimately provides favorable planar and specular reflectance characteristics for the pigment in the visible wavelength range. A variety of outer coating layers can be formed around the core flake sections, such as various dielectric and absorber layers having thicknesses dependent upon the desired optical characteristics of the pigment.

Abstract: A flake-based pigment is provided having improved specular reflectance characteristics in the visible wavelength range. The flake-based pigment has a plurality of core flake sections each formed of a central reflector layer and dielectric support layers on opposing sides of the reflector layer. The resulting core flake section is a very thin three-layered structure that exhibits a uniaxial compressive strength much greater than a corresponding uniaxial tensile strength. This structure provides the benefits of rigidity and brittle fracture during manufacturing and application processes, which ultimately provides favorable planar and specular reflectance characteristics for the pigment in the visible wavelength range. A variety of outer coating layers can be formed around the core flake sections, such as various dielectric and absorber layers having thicknesses dependent upon the desired optical characteristics of the pigment.

Abstract: The present invention relates to a water-thinnable coating composition comprising binders, inorganic pigments, and, if desired, organic pigments and also further customary additives such as solvents, fillers, plasticizers, stabilizers, wetting agents, dispersing auxiliaries, levelling agents, defoamers, catalysts and also further additives, individually or in a mixture with one another, and comprises at least one phosphoric ester and at least one fatty alcohol alkoxylate.

Abstract: A pigment dispersion comprising pigment, an aqueous carrier selected from water and a mixture of water and at least one organic solvent, and a pigment dispersant is described. The pigment dispersant has core and arm star-type architecture, and is prepared by controlled radical polymerization, e.g., atom transfer radical polymerization, using (i) arm-core, (ii) arm-core-arm, (iii) core-arm, or (iv) concurrent core and arm methods. The arms of the pigment dispersant each have hydrophobic and hydrophilic polymeric chain segments.

Abstract: The present invention relates to pigment mixtures containing at least two components component A being Al2O3 flakes coated with one or more metals, metal oxides and/or metal sulfides and component B being acicular or spherical colorants, and to their use in particular in varnishes, paints, printing inks, powder coating materials, plastics and cosmetic formulations.

Abstract: Pigment concentrates comprising a pigment, a liquid carrier medium and a dimerdiolalkoxylate, wherein a dimer portion of the dimerdiolalkoxylate comprises from about 36 to about 44 carbon atoms, and wherein the at least one dimerdiolalkoxylate has from about 1 to about 200 moles of alkylene oxide per mole of dimerdiol, are described in conjunction with methods of preparing the same.

Abstract: Pigment concentrates comprising a pigment, a liquid carrier medium and a diol alkoxylate of the general formulae (I), (II) and/or (III) are described in conjunction with methods of preparing the same.

Abstract: Optical coating compositions containing thin film particulates or pigments that are capable of imparting to the coating preselected optical characteristics or properties, such as selective reflectance, transmission and absorptance of light energy, are comprised of film forming binder and improved high volume pigment particles dispersed in the binder. Each pigment particle is a high volume flake comprised of an inorganic or polymer core having two sides and a thin film optical structure deposited onto each of the two sides of the core. The core occupies a large volume of the coating composition and dramatically reduces the number of flakes and the amount of thin film structures required to produce a coating of given thickness and desired optical properties. The core may also be fabricated to have diffuse and irregular side surfaces in order to render the applied coating visually diffuse and nonspecular. Methods of making the pigment particles are disclosed.

Abstract: The invention provides new stains which fire to a red-brown color for coloring ceramic compositions. The stains comprise Fe2O3 and/or an Fe compound which forms Fe2O3 on firing, in uniform distribution in a pulverulent matrix based on an oxide-like and/or silicate-like material which is amorphous to X-rays to the extent of at least 50% and has a specific surface area (BET) of at least 40 m2/g, and are obtainable by bringing the constituents into intensive contact together. The matrix preferably comprises 80 to 100% amorphous SiO2 or SiO2-rich silicate with a BET surface area of 90 to 300 m2/g and 0 to 20% of an auxiliary substance, such as silicone oil. The stains can be prepared by intensive dry grinding.

Abstract: A process for preparing an agglomerate-free suspension of nanosize iron-containing oxide particles coated in a stable manner comprises preparing an aqueous suspension of nanosize iron-containing oxide particles which are partially or completely in the form of agglomerates; adding a trialkoxysilane and a water-miscible polar organic solvent which has a boiling point at least 10° C. higher than the boiling point of water; treating the resulting suspension with ultrasound until at least 70% of the particles present are in the range of ±20% of the average particle diameter; removing the water by distillation under the action of ultrasound; and separating the non-disintegrated agglomerates.

Abstract: A process of using silicate and alkylphenol to surface-modify black iron oxide. The modified pigment shows superior heat stability. The process may be applied on a native slurry, hence providing a simple, economical and non-invasive method to modify black iron oxide on an industrial scale. The resultant black iron oxide may be used in lieu of mixed metal oxide in the majority of thermal applications.

Abstract: Modified pearl luster pigments for waterborn coating systems, based on a platelet-form substrate coated with metal oxides and, located on the topmost metal oxide layer, a top layer consisting of at least two oxides and/or mixed oxides from the group consisting of silicon dioxide, aluminium oxide, cerium oxide, titanium oxide and zirconium oxide, and on a water-based oligomeric silane system. The oligomeric silane system can be described, for example, by the following approximate structure: [HO[Si(A)(OH)z(CH3)1−zO]a[Si(B)(OH)y(CH3)1−yO]b[Si(E)(OH)w(CH3)1−wO]c[Si(D)(OH)v(CH3)1−vO]dH].

Abstract: A corrosion-inhibiting composition for application to a metal substrate, such as steel, silver, copper or aluminum, includes a film-forming organic polymer component and a dispersed pigment phase of a stable unitary hybrid which contains organic and inorganic solid phase constituents interfaced at a micro-crystalline level, which are inseparable by physical separation procedures and which display uniphase behavior. The inorganic phase includes a cation selected from Zn, Al, Mg, Ca, Sr, Ti, Zr, Ce and Fe and an anion selected from phosphates, polyphosphates, phosphites, molybdates, silicates and cyanamides.

Abstract: The present invention relates to inorganic pigment pellets for coloring building materials, lacquers and plastics and to a process for the production thereof and to the use thereof inter alia for the production of pastes, suspensions and emulsion paints.

Abstract: A colorless or only slightly colored pigment dispersing agent which is feasible as a pigment dispersing agent for pigments having various hues and has the general formula (1), ##STR1## wherein R.sub.1, R.sub.2, X.sub.1, Y.sub.1, Y.sub.2, k and h are as defined in claim 1.

Abstract: A process of producing a non-conductive ink formed from colorant particles and a non-conductive carrier liquid where the colorant particles are inherently of a low electrical resistivity. The process includes the steps of applying to the surface of the colorant particles a material with a high electrical resistivity to give the particle a higher surface resistivity and blending the treated colorant particle with the non-conductive carrier to form the non-conductive ink. The insulative material may be selected from polymers, waxes, organic pigments and dye stuffs and the colorant may be carbon black, magnetic iron oxide or metallic powder.

Abstract: Black ultrafine magnetite particles of this invention have an FeO content of 31 to 35% and a particle size of 0.1 .mu.m or less. A process for producing the black ultrafine magnetite particles comprises dispersing ultrafine magnetite particles with a particle size of 0.1 .mu.m or less in water containing ferrous hydroxide, aging the dispersion of 90 to 200.degree. C. at a free alkali concentration of 1 mol/liter (M/l) or more, then adding 0.2 to 5%, based on the magnetite particles, of sodium oleate or potassium oleate, and adjusting the pH to 5 to 6 to adhere oleic acid to magnetite.

Abstract: Effective anti-corrosive pigments are obtained using basic or neutral to basic polyvalent metal organophosphonates. The anti-corrosive organophosphonate pigments may optionally contain a co-acidic substance such as silica. The organophosphonate pigments provide ant-corrosive protection comparable to traditional pigments while enabling the avoidance of heavy metals.

Abstract: An adhesive-free, dry, free-flowing powder composition suitable for use in surface defect detection, where the powder composition comprises a physical mixture of particles of a colorant and particles of an extender, which mixture includes particles of colorant and particles of extender each having a particle size of less than 100 .mu.m. The powder compositions of the invention provide a simple, effective guide coat which readily highlights surface imperfections, such as scratches, orange peel effect and dry over-spray without the need for solvents. Also, there are disclosed methods of using such a powder composition to detect surface imperfections, an apparatus for applying same, a device for refilling such applying apparatus, and coated surfaces formed thereby.

Abstract: The molding composition contains, in a flowable binder, from 20 to 50% by vol., based on the total volume of the molding composition, of a powder comprising one or more metal oxides and, if desired, metal carbides and/or metal nitrides which cannot be reduced using hydrogen, where at least 65% by vol. of the powder has a maximum particle size of 0.5 .mu.m and the remainder of the powder has a maximum particle size of 1 .mu.m, and at least 90% by vol. of the powder comprises metal oxides which can be reduced using hydrogen. The metal oxides which can be reduced using hydrogen are Fe.sub.2 O.sub.3, FeO, Fe.sub.3 O.sub.4, NiO, CoO, Co.sub.3 O.sub.4, CuO, Cu.sub.2 O, Ag.sub.2 O, Bi.sub.2 O.sub.3, WO.sub.3, MoO.sub.3, SnO, SnO.sub.2, CdO, PbO, Pb.sub.3 O.sub.4, PbO.sub.2 or Cr.sub.2 O.sub.3, or mixtures thereof.

Abstract: A modified particle is disclosed wherein a particle has an attached group having the formula: ##STR1## wherein Ar represents an aromatic group; R.sup.1 represents a bond, an arylene group, an alkylene ##STR2## wherein R.sup.4 is an alkyl or alkylene group or an aryl or arylene group; R.sup.2 and R.sup.3, which can be the same or different, represent hydrogen, an alkyl group, an aryl group, --OR.sup.5, --NHR.sup.5, --NR.sup.5 R.sup.5, or --SR.sup.5, wherein R.sup.5, which is the same or different, represents an alkyl group or an aryl group; and SFR represents a stable free radical. Also disclosed is a modified particle or aggregate having attached a group having the formula: ##STR3## wherein CoupA represents a Si-containing group, a Ti-containing group, or a Zr-containing group; R.sup.8 and R.sup.9, which can be the same or different, represent hydrogen, an alkyl group, an aryl group, --OR.sup.10, --NHR.sup.10, --NR.sup.10 R.sup.10, or --SR.sup.10, wherein R.sup.

Abstract: The present invention relates to a magnetic powder that contains resin-coated magnetic particles. The resin-coated magnetic particles include magnetic particles A and B that are formed in non-spherical shapes, with the magnetic particles A and B coated with a resin C. The resin-coated magnetic particles make it possible to increase the filling quantity of the magnetic particles A and B when the magnetic powder is employed to constitute a magnetic molded article, to ultimately improve the electromagnetic characteristics of the magnetic molded article.

Abstract: Magnetic iron oxide-containing granules for producing toners or inks, the granules comprising 95.0 to 99.8 wt. % of a magnetic iron oxide-containing compound and 0.2 to 5.0 wt. % of a binder, wherein the magnetic iron oxide-containing compound has an iron content of 50 to 73 wt. %, and wherein the granules have the following properties: a lightness under brightening L* of 40 to 79 CIELAB units, a color cast a* of -1.0 to 4.0 CIELAB units, a color cast b* of 0.0 to -7.0 CIELAB units, an average particle size of 30 to 250 .mu.m, and a residue of less than 2 wt. % in a flow properties test having a 1 mm sieve and 400 strokes.

Abstract: A stir-in pigment composition for coloring high-molecular-weight material, particularly coatings and ink systems, comprises 85 to 99.5 parts by weight of a pigment and 0.5 to 15 parts by weight of an additive comprising a vinylpyrrolidone polymer or copolymer. The stir-in pigment composition is in the form of microgranules and is obtainable by spray drying a high solids content aqueous pigment dispersion containing the pigment and the additive. The new pigment composition powders are easily handled, easily wetted and disperse rapidly to form homogeneous aqueous pigment dispersions which are practically free of larger pigment aggregates and can readily be incorporated into aqueous ink and paint systems as stir-in pigments without a dispersion step in a bead mill.

Abstract: A method for making coated pigment particles by forming a suspension of the desired pigment particles in a medium that also comprises a polymer characterized by having hydrophobic moieties on the polymer backbone and ionic moieties that are present on, or can be formed on a polymer side chain or at the polymer terminals; allowing the suspension of pigment particles to contact said polymer at a temperature above the softening point of the polymer, allowing the resultant suspension to cool to a temperature below the solidification temperature for the polymer while maintaining the pigment particles in suspension, and, if required, forming the ionic moieties.

Abstract: Modified iron-containing pigment particles modified with an encapsulant comprising an alkylphenol and lecithin having an HLB value from about 10 to about 15. The modified iron oxide pigments made using the encapsulant exhibit enhanced dispersibility in solvents over a wide range of polarity.

Abstract: Surface-modified, pyrogenically produced mixed oxides which contain two or more components of the series SiO.sub.2, Al.sub.2 O.sub.3, TiO.sub.2, ZrO.sub.2, Fe.sub.2 O.sub.3, Nb.sub.2 O.sub.5, V.sub.2 O.sub.5, WO.sub.3, SnO.sub.2, GeO.sub.2 and have been surface-modified with one to several compounds of the following groups:(a) organosilanes of the type (RO).sub.3 Si(C.sub.n H.sub.2n+1),(b) R'.sub.x (RO).sub.y Si(C.sub.n H.sub.2n+1),(c) X.sub.3 Si(C.sub.n H.sub.2n+1),(d) X.sub.2 (R')Si(C.sub.n H.sub.2n+1),(e) X(R').sub.2 Si(C.sub.n H.sub.2n+1),(f) (RO).sub.3 Si(CH.sub.2).sub.m --R',(g) (R").sub.x (RO).sub.y Si(CH.sub.2).sub.m --R',(h) X.sub.3 Si(CH.sub.2).sub.m --R',(i) (R)X.sub.2 Si(CH.sub.2).sub.m --R',(j) (R).sub.2 X Si(CH.sub.2).sub.m --R',(k) Silazanes of the type ##STR1## (l) Cyclic polysiloxanes, (m) Polysiloxanes or silicone oils.

Abstract: A pigment of the present invention comprises:pigment particle as core particle;a lower coat formed on at least a part of surface of the pigment particle, comprising squaric acid, polyol having an anthraquinone skeleton represented by the general formula (I): ##STR1## wherein m is an integer of 0 to 4, n is an integer of 0 to 4 and m+n is an integer of 2 to 4,or a mixture of the squaric acid and the polyol having an anthraquinone skeleton represented by the general formula (I); andan upper coat formed on at least a part of surface of the obtained particle, comprising at least one alkylene glycol represented by the general formula (II):C.sub.q H.sub.2q (OH).sub.2 (II)wherein q is an integer of 2 to 10.Such pigment has excellent dispersion facility, dispersion homogeneity and dispersion stability, and is suitably used for not only organic solvent-type paints but also water-based paints.

Abstract: Initiator-treated pigment particles for use in making polymer coated pigment particles, are made up of a plurality of pigment particles. Each of the pigment particles has an outer surface that is covered with a coating of initiator material. The initiator material operates as a nucleus for initiating polymerization on the surface of the particle. The initiator-treated pigment particles are made by providing a plurality of pigment particles and applying a coating of initiator material to the outer surface of each pigment particle.

Abstract: The invention relates to granules of inorganic pigments, a process for their production using several auxiliary substances by compacting and their use in many technical fields.

Abstract: A surface derivatizing agent is allowed to contact an aqueous slurry of transition metal-containing pigment particles to increase the hydrophobicity of the surface of such particles. The modified pigment particles disperse easily in a wide variety of organic solvents, and provide stable, dispersions having a small mean pigment particle size and narrow particle size distribution.

Abstract: A process for preparing a low-dusting, free-flowing pigment which has not been subjected to any micronizing treatment comprising the steps of providing an inorganic pigment material; providing a source of water; forming a fine, well dispersed slurry of the pigment and water; milling the slurry; depositing a treating agent having the formula ROOCCHSO.sub.3 MCH.sub.2 COOR' wherein R and R' are monovalent alkyl radicals having from about 2 to about 20 carbon atoms, and M is a metallic monovalent cation on the slurried milled pigment; and drying the pigment material having a treating agent deposited thereon. The invention also provides the free-flowing pigments produced by this process.

Abstract: The present invention relates to a process for producing inorganic granules and to their use for the coloring of building materials, particularly concrete, asphalt, plaster, mortar and cement mortar, and for the production of paints for the protection of buildings.

Abstract: A surface coordinating agent is allowed to contact an aqueous slurry of transition metal-containing pigment particles to increase the hydrophilicity of the surface of such particles. The modified pigment particles disperse easily in a wide variety of solvents, and provide stable, dispersions having a small mean pigment particle size and narrow particle size distribution.

Abstract: Aqueous pigment preparations comprisinga) 10 to 80% by weight, in particular 20 to 60% by weight, of a pigment,b) 0.1 to 20% by weight, in particular 0.1 to 15% by weight, of an oxyalkylation product which is obtained by addition of optionally substituted styrenes onto optionally substituted phenols and reaction with ethylene oxide and/or propylene oxide,c) 2 to 30% by weight of a polyether-polyol having a boiling point under normal pressure of greater than 150.degree. C. andd) if appropriate further additives, and water as the remainder,which are particularly suitable for pigmenting naturally occurring and synthetic materials, such as emulsion paints, emulsion coatings and emulsion printing inks, have been found.

Abstract: A method for coloring cementitious systems using compacted inorganic granules, wherein said compacted inorganic granules comprise an inorganic pigment and a dispersing agent. Particularly, a method for coloring cementitious systems using compacted inorganic granules; wherein said compacted inorganic granules are produced by a process consisting of: (a) mixing an inorganic pigment and a dispersing agent, (b) compacting the mixture, (c) milling the compacted mixture, and (d) classifying the compacted mixture into at least one oversize material stream, at least one undersize material stream and at least one product stream of compacted inorganic granules; and wherein the coloring effect of the compacted inorganic granules in the cementitious system equals or exceeds the powder standard.

Abstract: A method for making magnetic ink compositions is disclosed. The magnetic particles used in the ink are prepared from an aqueous slurry. A surface derivatizing agent is added to the slurry to render the magnetic pigment particles hydrophobic. The particles then sink to the bottom of the slurry, and the bulk water is then removed. After air drying, dry magnetic pigment particles are provided. The particles will be hydrophobic, and thus will have superior resistance to water as compared to previously known magnetic pigment particles. Magnetic ink compositions are formulated from the magnetic particles.

Abstract: Magnetic paint or ink additives are formulated from ferromagnetic particles, preferably iron powder, having a mixed particle range of from about 0.01.mu. to about 297.mu., and preferably to about 250M and more, preferably from about 0.01.mu. to about 37 to 44.mu.; 6 to 20.mu. particles are used in one latex-based embodiment. Preferred additives are formulated by blending the particles with a surfactant, a surfactant mixture, or a surfactant and alcohol mixture in amounts sufficient to suspend the particles; a polyvinyl acetate polyer is used in one embodiment. The additives may be blended with any oil-, latex-, or lacquer-based paint, ink, or coating to form a magnetic paint or coating having a viscosity substantially similar to the paint or ink containing no particles and/or additive. Surfaces such as paper, cloth, wood, wallboard, sheet rock, foam, foam board, plywood, plastic, fiberboard, and the like so coated may be cut with conventional woodworking tools, scissors or knives.

Abstract: A treated inorganic solid comprises particulate inorganic material the particles of which are coated with an alkylphosphonic acid or ester thereof, the alkylphosphonic acid containing 6 to 22 carbon atoms. The particulate material is usually a pigment, extender or filler which is treated by mixing with the alkylphosphonic acid or ester for example in an aqueous dispersion or during a process step such as milling. The treated inorganic solid is particularly useful for preparing polymer compositions such as masterbatches.

Abstract: A surface-modified colored pigment is disclosed which includes a colored pigment having no primary amines and at least one attached hydrophilic organic group, wherein said organic group comprises a) at least one aromatic group, and b) at least one ionic group or ionizable group, or a mixture of an ionic group or an ionizable group. The colored pigment may be blue, brown, cyan, green, violet, magenta, red, orange, yellow, mixtures thereof and the like. The surface-modified colored pigment, due to the hydrophilic groups on its surface, is readily dispersed in a liquid vehicle without the addition of a surfactant or other dispersing aid or additive. The surface-modified color pigment may be used in a variety of aqueous systems including, but not limited to, coatings, paints, papers, adhesives, latexes, inks, toners, textiles and fibers. In addition, an aqueous composition is disclosed including water-based liquid vehicle and the surface-modified colored pigment described above.

Abstract: Ballpoint pen pastes comprising at least one phthalocyanine pigment and customary ballpoint pen paste resin and organic solvent as essential components and also, if desired, further customary additives, and the preparation thereof.

Abstract: A method for producing bulking and opacifying kaolin fillers for filling cellulosic products is disclosed. An aqueous slurry of anionically dispersed kaolin particles is formed at 1 to 30% solids. A low-molecular-weight cationic aggregating agent is then added to the dispersed slurry to selectively aggregate fine and ultra-fine particles. The resultant aggregates are of larger mean particle size than the feed material and contain little or no fine and ultra-fine or colloidal particles. The net charge present on the aggregated particles is lower than that of the feed material. The aggregated structure contains within it a labyrinth of internal voids or pores. These mineral aggregates are then of a suitable size and surface charge to be retained well in a fiber web, and provide added bulk and opacity to the cellulosic products.

Abstract: A method for producing structured calcium carbonate pigments for coating paper is disclosed. An aqueous slurry of anionically dispersed calcium carbonate particles is formed at 1 to 30 percent solids. A low-molecular-weight cationically charged aggregating agent is then added to the slurry to selectively aggregate fine and ultra-fine particles. The resultant aggregates are of larger mean particle size than the mixture of particles in the original slurry and contain little or no fine and colloidal particles. The net charge present on the aggregated particles is lower than that of the original mineral particles. The low solids suspension of the aggregated mineral particles is then dewatered, or increased in solids to form a slurry with a solids content greater than 60 percent by weight.

Abstract: A process is provided for the selective aggregation of the fine and ultrafine particles present in an anionically or cationically dispersed mineral pigment slurry, such that an aggregated structure is formed which contains within it a labyrinth of internal voids or pores, which collectively function as light scattering centers. The aggregates are formed from an assemblage of fine mineral particles, interconnected or bonded together with small quantities of a cationic or anionic polymer or agent of low molecular weight. The resultant aggregates are of larger mean particle size than the feed material and contain little or no fine and colloidal particles. The net charge present on the aggregated particles is lower than that of the feed material. These mineral aggregates are then of a suitable size and surface charge to be retained well in a fiber web by a combination of filtration retention and adsorption retention, and provide added bulk and opacity to the finished sheet of paper.