EP4646464A1 - Poly(alcool vinylique) en tant qu'agent de codispersion pour dispersions minérales - Google Patents

Poly(alcool vinylique) en tant qu'agent de codispersion pour dispersions minérales

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Publication number
EP4646464A1
EP4646464A1 EP24700516.8A EP24700516A EP4646464A1 EP 4646464 A1 EP4646464 A1 EP 4646464A1 EP 24700516 A EP24700516 A EP 24700516A EP 4646464 A1 EP4646464 A1 EP 4646464A1
Authority
EP
European Patent Office
Prior art keywords
dispersing agent
mol
mineral material
aqueous suspension
polyvinyl alcohol
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24700516.8A
Other languages
German (de)
English (en)
Inventor
Louise MCCULLOCH
Fabio Ippolito
Antti FINÉR
Jonas Hannus
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Omya International AG
Original Assignee
Omya International AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Omya International AG filed Critical Omya International AG
Publication of EP4646464A1 publication Critical patent/EP4646464A1/fr
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K23/00—Use of substances as emulsifying, wetting, dispersing, or foam-producing agents
    • C09K23/52—Natural or synthetic resins or their salts
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/02—Compounds of alkaline earth metals or magnesium
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/02—Compounds of alkaline earth metals or magnesium
    • C09C1/021—Calcium carbonates
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/36—Compounds of titanium
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/40—Compounds of aluminium
    • C09C1/42—Clays
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/22—Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability

Definitions

  • the present invention relates to the use of polyvinyl alcohol as a co-dispersing agent for an aqueous suspension comprising a mineral material and dispersing agent, a method for producing such an aqueous suspension in combination with said co-dispersing agent, an aqueous suspension obtainable by said method, use of said aqueous suspension, and a dispersing agent composition comprising a dispersing agent in combination with polyvinyl alcohol as co-dispersing agent.
  • Mineral materials are among the main constituents in paints, plastic, paper or paper coating colours. Mineral materials such as calcium carbonate, may provide improvements, for example, in paper and painting quality and agriculture properties, notably relative to their optical properties.
  • dispersing agents may impair the material properties of the final products, for example, their optical properties may be deteriorated.
  • Dispersing agents such as polyacrylates are also not biodegradable and it is therefore desirable to further reduce their use for environmental reasons.
  • dispersing agents may be a significant cost factor in the production of mineral dispersions.
  • EP0461635 A1 relates to a polyvinyl alcohol resin soluble in high solids aqueous paper coating compositions without external heating. Multifunctional poly(vinyl alcohol) binders for fine particle size calcium carbonate pigments are described in WO0134906 A1 .
  • an object of the present invention to provide an aqueous mineral suspension which has a high solids content at a workable viscosity. Furthermore, it is desirable that the aqueous suspension contains a reduced amount of dispersing agent.
  • the aqueous suspension may also have additional improved properties such as improved long term stability, improved wet-grindability, or improved optical properties.
  • aqueous mineral suspension which is suitable for paper production, especially paper coating applications, and may even improve the optical or mechanical properties of a paper substrate.
  • an additive for an aqueous mineral suspension which can be added during the production of said mineral suspension, for example, before grinding the mineral material or precipitating the mineral material or before or during the up-concentration of the mineral suspension to its final solids content .
  • polyvinyl alcohol as co-dispersing agent for an aqueous suspension comprising a mineral material and a dispersing agent
  • the mineral material is selected from an alkaline earth mineral material, clay, calcined clay, titanium dioxide, and mixtures thereof
  • the dispersing agent is a polyacrylate-containing dispersant
  • a method for producing an aqueous suspension comprising a mineral material and a dispersing agent in combination with a co-dispersing agent comprising the steps of: i) providing a mineral material selected from an alkaline earth mineral material, clay, calcined clay, titanium dioxide, and mixtures thereof, ii) providing a dispersing agent, wherein the dispersing agent is a polyacrylate-containing dispersant, iii) providing a co-dispersing agent, wherein the co-dispersing agent is a polyvinyl alcohol, iv) providing water, and v) contacting the mineral material of step i), the dispersing agent of step ii), the co-dispersing agent of step iii), and the water of step iv).
  • a method for producing an aqueous suspension comprising a mineral material and a dispersing agent in combination with a co-dispersing agent is provided, wherein the mineral material is precipitated calcium carbonate, and the method comprises the following steps:
  • co-dispersing agent is a polyvinyl alcohol
  • step IV preparing a milk of lime by mixing water, the calcium oxide containing material of step I) and the co-dispersing agent of step III),
  • step V) carbonating the milk of lime obtained in step IV) to form an aqueous suspension of precipitated calcium carbonate
  • step VI) mixing the aqueous suspension obtained in step V) with the dispersing agent of step II).
  • a dispersing agent composition comprising a dispersing agent in combination with a co-dispersing agent
  • the dispersing agent is a polyacrylate-containing dispersant
  • the co-dispersing agent is polyvinyl alcohol
  • an aqueous suspension obtainable by a method according to the present invention is provided.
  • an aqueous suspension according to the present invention in paper applications, packaging applications, polymer applications, or water treatment applications is provided.
  • the polyvinyl alcohol has a degree of hydrolysis of at least 75 mol-%, preferably at least 85 mol-%, more preferably at least 90 mol-%, even more preferably at least 95 mol-%, and most preferably at least 98 mol-%, and/or the polyvinyl alcohol has an average molecular weight M w from 10 000 to 150 000 g/mol, preferably from 12 000 to 100 000 g/mol, more preferably from 14 000 to 50 000 g/mol, and most preferably from 16 000 to 30 000 g/mol.
  • the aqueous suspension comprises the polyvinyl alcohol in an amount of 2 wt.-% or less, based on the total weight of the aqueous suspension, preferably in an amount from 0.01 to 1 .8 wt.-%, more preferably in an amount from 0.05 to 1 .5 wt.-%, even more preferably in an amount from 0.08 to 1 wt.-%, and most preferably in amount from 0.1 to 0.6 wt.-%.
  • the dispersing agent is a polyacrylate homopolymer, a polyacrylate copolymer, or a mixture thereof, and preferably the dispersing agent is a polyacrylate homopolymer, preferably at least partially neutralized, preferably with sodium ions, potassium ions, lithium ions, ammonium ions, calcium ions, and mixtures thereof, more preferably with sodium ions, calcium ions, or mixtures thereof, and most preferably with sodium ions.
  • the dispersing agent has a neutralization degree of at least 30 mol-%, preferably at least 40 mol-%, more preferably at least 60 mol-%, and most preferably at least 80 mol-%, and/or the dispersing agent has an average molecular weight M w from 1000 to 15 000 g/mol, preferably from 2000 to 12 000 g/mol, more preferably from 3000 to 11 000 g/mol, and most preferably from 4000 to 10 000 g/mol.
  • the aqueous suspension comprises the dispersing agent in an amount of 3 wt.-% or less, based on the total weight of the aqueous suspension, preferably in an amount from 0.01 to 2 wt.-%, more preferably in an amount from 0.05 to 1 .5 wt.-%, and most preferably in an amount from 0.1 to 0.8 wt.-%.
  • the mineral material is in the form of particles having a weight median particle size dso from 0.05 to 100 pm, preferably from 0.1 to 50 pm, more preferably from 0.15 to 25 pm, even more preferably from 0.25 to 10 pm, and most preferably from 0.5 to 2 pm, and/or having a weight determined top cut particle size dgs from 0.1 to 200 pm, preferably from 0.2 to 100 pm, more preferably from 0.3 to 50 pm, even more preferably from 0.25 to 20 pm, and most preferably from 1 to 4 pm.
  • the aqueous suspension comprises the mineral material in an amount from 10 to 78 wt.-%, preferably from 20 to 75 wt.-%, and most preferably from 50 to 72 wt.-%, based on the total weight of the aqueous suspension.
  • the step v) comprises the steps of: a1) contacting the dispersing agent of step ii), the co-dispersing agent of step iii), and the water of step iv), and a2) adding the mineral material of step i) to the mixture obtained in step a1), or b1) contacting the dispersing agent of step ii), and the co-dispersing agent of step iii), and b2) adding the mineral material of step i) and water of step iv) to the mixture obtained in step b1), wherein the mineral material and the water are added separately or in combination, preferably in combination, or c1) contacting the dispersing agent of step ii), the mineral material of step i), and the water of step iv), and c2) adding the co-dispersing agent of step iii) to the mixture obtained in step c1), or d) contacting the mineral material of step i), the dispersing agent of step
  • a “calcium oxide-containing material” in the meaning of the present invention can be a mineral or a synthetic material having a content of calcium oxide of at least 50 wt.-%, preferably 75 wt.-%, more preferably 90 wt.-%, and most preferably 95 wt.-%, based on the total weight of the calcium oxide containing material.
  • mineral in the meaning of the present application encompasses natural or synthetic minerals, fillers and/or pigments, like calcium carbonate, chalk, dolomite, titanium dioxide, etc.
  • Natural ground calcium carbonate in the meaning of the present invention is a calcium carbonate obtained from natural sources, such as limestone, marble, or chalk, and processed through a wet and/or dry treatment such as grinding, screening and/or fractionating, for example, by a cyclone or classifier.
  • Precipitated calcium carbonate in the meaning of the present invention is a synthesised material, obtained by precipitation following reaction of carbon dioxide and lime in an aqueous, semi-dry or humid environment or by precipitation of a calcium and carbonate ion source in water.
  • PCC may be in the vateritic, calcitic or aragonitic crystal form. PCCs are described, for example, in EP2447213 A1 , EP2524898 A1 , EP2371766 A1 , EP1712597 A1 , EP1712523 A1 , or WO2013142473 A1.
  • the “particle size” of the mineral herein is described by its weight-based distribution of particle sizes d x .
  • the value d x represents the diameter relative to which x % by weight of the particles have diameters less than d x .
  • the d2o value is the particle size at which 20 wt.% of all particles are smaller than that particle size.
  • the dso value is thus the weight median particle size, i.e. 50 wt.-% of all particles are smaller than this particle size.
  • the particle size is specified as weight median particle size dso(wt) unless indicated otherwise.
  • Particle sizes were determined by using a SedigraphTM 5100 instrument or SedigraphTM 5120 instrument of Micromeritics Instrument Corporation. The method and the instrument are known to the skilled person and are commonly used to determine the particle size of fillers and pigments. The measurements were carried out in an aqueous solution of 0.1 wt.-% Na4P2O?.
  • polymer generally includes homopolymers and copolymers such as, for example, block, graft, random and alternating copolymers, as well as blends and modifications thereof.
  • the polymer can be an amorphous polymer, a crystalline polymer, or a semi-crystalline polymer, i.e. a polymer comprising crystalline and amorphous fractions.
  • the degree of crystallinity is specified in percent and can be determined by differential scanning calorimetry (DSC).
  • DSC differential scanning calorimetry
  • An amorphous polymer may be characterized by its glass transition temperature and a crystalline polymer may be characterized by its melting point.
  • a semi-crystalline polymer may be characterized by its glass transition temperature and/or its melting point.
  • copolymer refers to a polymer derived from more than one species of monomer. Copolymers that are obtained by copolymerization of two monomer species may also be termed bipolymers, those obtained from three monomers terpolymers, those obtained from four monomers quaterpolymers, etc. (cf. IUPAC Compendium of Chemical Terminology 2014, “copolymer”). Accordingly, the term “homopolymer” refers to a polymer derived from one species of monomer.
  • the “moisture content” of a material refers to the percentage of moisture (i.e. water) which may be desorbed from a sample upon heating to 220°C.
  • the moisture content may be measured according to the Karl Fischer coulometric titration method, desorbing the moisture in an oven at 220 °C for at least 10 min and passing it continuously into a Karl Fischer coulometer (Mettler Toledo coulometric KF Titrator C30, combined with Mettler Toledo oven DO 0337) using dry nitrogen at 100 ml/min for at least 10 min. A calibration curve using water may be recorded and a blank of 10 min nitrogen flow without a sample taken into account.
  • the “specific surface area” (expressed in m 2 /g) of a material as used throughout the present document can be determined by the Brunauer Emmett Teller (BET) method with nitrogen as adsorbing gas and by use of an ASAP 2460 instrument from Micromeritics. The method is well known to the skilled person and defined in ISO 9277:2010. Samples are conditioned at 100°C under vacuum for a period of 30 min prior to measurement. The total surface area (in m 2 ) of said material can be obtained by multiplication of the specific surface area (in m 2 /g) and the mass (in g) of the material.
  • BET Brunauer Emmett Teller
  • a “solution” as referred to herein is understood to be a single phase mixture of a specific solvent and a specific solute, for example a single phase mixture of a water-soluble salt and water.
  • the term “dissolved” as used herein thus refers to the physical state of a solute in a solution.
  • a “suspension” or “slurry” in the meaning of the present invention comprises undissolved solids and water, and optionally further additives, and usually contains large amounts of solids and, thus, is more viscous and can be of higher density than the liquid from which it is formed.
  • aqueous suspension refers to a system, wherein the liquid phase comprises, preferably consists of, water. However, said term does not exclude that the liquid phase of the aqueous suspension comprises minor amounts of at least one water-miscible organic solvent selected from the group comprising methanol, ethanol, acetone, acetonitrile, tetrahydrofuran and mixtures thereof.
  • the liquid phase of the aqueous suspension comprises the at least one water-miscible organic solvent in an amount of from 0.1 to 40.0 wt.-% preferably from 0.1 to 30.0 wt.-%, more preferably from 0.1 to 20.0 wt.-% and most preferably from 0.1 to 10.0 wt.-%, based on the total weight of the liquid phase of the aqueous suspension.
  • the liquid phase of the aqueous suspension consists of water.
  • viscosity or “Brookfield viscosity” refers to Brookfield viscosity.
  • the Brookfield viscosity is for this purpose measured by a Brookfield DV-II+ Pro viscometer at 25 °C ⁇ 1 °C at 100 rpm using an appropriate spindle of the Brookfield RV-spindle set and is specified in mPa s. Based on his technical knowledge, the skilled person will select a spindle from the Brookfield RV-spindle set which is suitable for the viscosity range to be measured.
  • the spindle number 3 may be used, for a viscosity range between 400 and 1 600 mPa s the spindle number 4 may be used, for a viscosity range between 800 and 3200 mPa s the spindle number 5 may be used, for a viscosity range between 1 000 and 2 000 000 mPa s the spindle number s may be used, and for a viscosity range between 4 000 and 8 000 000 mPa s the spindle number 7 may be used.
  • polyvinyl alcohol as co-dispersing agent for an aqueous suspension comprising a mineral material and a dispersing agent.
  • the mineral material is selected from an alkaline earth metal mineral material, clay, calcined clay, titanium dioxide, and mixtures thereof, and the dispersing agent is a polyacrylate-containing dispersant.
  • the aqueous suspension comprises a mineral material, wherein the mineral material is selected from an alkaline earth metal mineral material, clay, calcined clay, titanium dioxide, and mixtures thereof.
  • the mineral material is in the form of particles having a weight median particle size cko from 0.05 to 100 pm, preferably from 0.1 to 50 pm, more preferably from 0.15 to 25 pm, even more preferably from 0.25 to 10 pm, and most preferably from 0.5 to 2 pm.
  • the weight determined median particle size cko may be evaluated using a SedigraphTM 5100 instrument or SedigraphTM 5120 instrument of Micromeritics Instrument Corporation.
  • the mineral filler is in the form of particles having a weight determined top cut particle size dgs from 0.1 to 200 pm, preferably from 0.2 to 100 pm, more preferably from 0.3 to 50 pm, even more preferably from 0.25 to 20 pm, and most preferably from 1 to 4 pm.
  • the volume determined top cut particle size dgs may be evaluated using a a SedigraphTM 5100 instrument or SedigraphTM 5120 instrument of Micromeritics Instrument Corporation.
  • the mineral filler is in the form of particles having a specific surface area in the range from 1 to 100 m 2 /g, preferably from 5 to 90 m 2 /g, more preferably from 10 to 80 m 2 /g, even more preferably from 15 to 70 m 2 /g, and most preferably from 17 to 60 m 2 /g, measured using nitrogen and the BET method according to ISO 9277:2010.
  • the aqueous suspension comprises the mineral material in an amount from 10 to 78 wt.-%, preferably from 20 to 75 wt.-%, and most preferably from 50 to 72 wt.-%, based on the total weight of the aqueous suspension.
  • the mineral material is selected from an alkaline earth metal mineral material.
  • the alkaline earth metal mineral material may be selected from the group consisting of alkaline earth metal carbonates, alkaline earth metal phosphates, alkaline earth metal sulphates, alkaline earth metal oxides, alkaline earth metal hydroxides, and mixtures thereof.
  • the alkaline earth metal mineral material is an alkaline earth metal carbonate, an alkaline earth metal hydroxide, or a mixture thereof.
  • the alkaline earth metal mineral material is selected from the group consisting of calcium carbonate, magnesium carbonate, calcium magnesium carbonate, calcium hydroxide, magnesium hydroxide, and mixtures thereof, preferably the alkaline earth metal mineral material is selected from the group consisting of ground calcium carbonate, precipitated calcium carbonate, dolomite, hydromagnesite, calcium hydroxide, magnesium hydroxide, and mixtures thereof.
  • Dolomite is a carbonatic calcium-magnesium-mineral having the chemical composition of CaMg(CC>3)2 (“CaCOs ⁇ MgCOs”).
  • Dolomite minerals may contain at least 30.0 wt.-% MgCOs, based on the total weight of dolomite, preferably more than 35.0 wt.-%, more preferably more than 40.0 wt.-% MgCOs.
  • Clay refers to crystalline small particles of mainly hydrous silicates of aluminium, sometimes with magnesium and/or iron substitution for all or a part of the aluminium.
  • the main groups of clay minerals are: kaolinite (the main constituent of kaolin), halloysite, illite, montmorillonite, and vermiculite. Calcined clay may be obtained by a heating a source of kaolin to between 650 and 750°C.
  • Titanium dioxide can have an anatase, rutile, or amorphous structure. Titanium dioxide particles are usually prepared in the chloride process, in which TiCU is oxidized to TiC>2 particles, or in the sulfate process, in which sulfuric acid and ore containing titanium are dissolved, and the resulting solution goes through a series of steps to yield the at least one titanium dioxide-containing particles.
  • the titanium dioxide can be essentially pure titanium dioxide or may contain other metal oxides, such as silica, alumina, zirconia and the like, preferably silica. Such other metal oxides may be incorporated into the titanium dioxide particles by co-oxidizing or co-precipitating titanium compounds with other metal compounds during their preparation in the chloride or sulfate process.
  • the alkaline earth metal mineral material is calcium carbonate, optionally in combination with magnesium carbonate, calcium magnesium carbonate, calcium hydroxide, magnesium hydroxide, or a mixture thereof.
  • the calcium carbonate is selected from the group consisting of ground calcium carbonate, precipitated calcium carbonate, or mixtures thereof. According to a preferred embodiment the calcium carbonate is ground calcium carbonate.
  • Ground (or natural ground) calcium carbonate is understood to be manufactured from a naturally occurring form of calcium carbonate, mined from sedimentary rocks such as limestone or chalk, or from metamorphic marble rocks, eggshells or seashells.
  • Calcium carbonate is known to exist as three types of crystal polymorphs: calcite, aragonite and vaterite. Calcite, the most common crystal polymorph, is considered to be the most stable crystal form of calcium carbonate. Less common is aragonite, which has a discrete or clustered needle orthorhombic crystal structure. Vaterite is the rarest calcium carbonate polymorph and is generally unstable. Ground calcium carbonate is almost exclusively of the calcitic polymorph, which is said to be trigonal-rhombohedral.
  • source of the calcium carbonate in the meaning of the present application refers to the naturally occurring mineral material from which the calcium carbonate is obtained.
  • the ground calcium carbonate is selected from the group consisting of marble, chalk, limestone and mixtures thereof.
  • the source of the calcium carbonate may comprise further naturally occurring components such as magnesium carbonate, alumino silicate etc.
  • the GCC is obtained by dry grinding. According to another embodiment of the present invention the GCC is obtained by wet grinding and optionally subsequent drying.
  • the grinding step can be carried out with any conventional grinding device, for example, under conditions such that comminution predominantly results from impacts with a secondary body, i.e. in one or more of: a ball mill, a rod mill, a vibrating mill, a roll crusher, a centrifugal impact mill, a vertical bead mill, an attrition mill, a pin mill, a hammer mill, a pulveriser, a shredder, a de-clumper, a knife cutter, or other such equipment known to the skilled man.
  • a ball mill i.e. in one or more of: a ball mill, a rod mill, a vibrating mill, a roll crusher, a centrifugal impact mill, a vertical bead mill, an attrition mill, a pin mill, a hammer mill, a pulveriser, a shredder, a de-clumper, a knife cutter, or other such equipment known to the skilled man.
  • the grinding step may be performed under conditions such that autogenous grinding takes place and/or by horizontal ball milling, and/or other such processes known to the skilled man.
  • the wet processed ground calcium carbonate comprising mineral material thus obtained may be washed and dewatered by well-known processes, e.g. by flocculation, centrifugation, filtration or forced evaporation prior to drying.
  • the subsequent step of drying may be carried out in a single step such as spray drying, or in at least two steps. It is also common that such a mineral material undergoes a beneficiation step (such as a flotation, bleaching or magnetic separation step) to remove impurities.
  • a beneficiation step such as a flotation, bleaching or magnetic separation step
  • the calcium carbonate comprises one type of ground calcium carbonate.
  • the calcium carbonate comprises a mixture of two or more types of ground calcium carbonates selected from different sources.
  • Precipitated calcium carbonate in the meaning of the present invention is a synthesized material, generally obtained by precipitation following reaction of carbon dioxide and calcium hydroxide in an aqueous environment or by precipitation of calcium and carbonate ions, for example CaCh and Na2COs, out of solution. Further possible ways of producing PCC are the lime soda process, or the Solvay process in which PCC is a by-product of ammonia production.
  • Calcite has a trigonal structure with typical crystal habits such as scalenohedral (S-PCC), rhombohedral (R- PCC), hexagonal prismatic, pinacoidal, colloidal (C-PCC), cubic, and prismatic (P-PCC).
  • S-PCC scalenohedral
  • R- PCC rhombohedral
  • P-PCC prismatic
  • Aragonite is an orthorhombic structure with typical crystal habits of twinned hexagonal prismatic crystals, as well as a diverse assortment of thin elongated prismatic, curved bladed, steep pyramidal, chisel shaped crystals, branching tree, and coral or worm-like form.
  • Vaterite belongs to the hexagonal crystal system.
  • the obtained PCC slurry can be mechanically dewatered and dried.
  • the precipitated calcium carbonate is precipitated calcium carbonate, preferably comprising aragonitic, vateritic or calcitic mineralogical crystal forms or mixtures thereof.
  • the calcium carbonate comprises one precipitated calcium carbonate.
  • the calcium carbonate comprises a mixture of two or more precipitated calcium carbonates selected from different crystalline forms and different polymorphs of precipitated calcium carbonate.
  • the at least one precipitated calcium carbonate may comprise one PCC selected from S-PCC and one PCC selected from R-PCC.
  • the alkaline earth metal mineral material is hydromagnesite, optionally in combination with calcium carbonate, magnesium carbonate, calcium magnesium carbonate, calcium hydroxide, magnesium hydroxide, or mixtures thereof.
  • Hydromagnesite or basic magnesium carbonate which is the standard industrial name for hydromagnesite, is a naturally occurring mineral which is found in magnesium rich minerals such as serpentine and altered magnesium rich igneous rocks, but also as an alteration product of brucite in periclase marbles. Hydromagnesite is described as having the following formula Mgs(CO3)4(OH)2 ⁇ 4 H 2 O.
  • hydromagnesite is a very specific mineral form of magnesium carbonate and occurs naturally as small needle-like crystals or crusts of acicular or bladed crystals.
  • hydromagnesite is a distinct and unique form of magnesium carbonate and is chemically, physically and structurally different from other forms of magnesium carbonate.
  • Hydromagnesite can readily be distinguished from other magnesium carbonates by x-ray diffraction analysis, thermogravimetric analysis or elemental analysis. Unless specifically described as hydromagnesite, all other forms of magnesium carbonates (e.g.
  • Mg2(CC>3)(OH)2 ⁇ 3 H2O dypingite
  • Mgs(CO3)4(OH)2 ⁇ 5 H2O dypingite
  • giorgiosite Mgs(CO3)4(OH)2 ⁇ 5 H2O
  • pokrovskite Mg2(CC>3)(OH)2 ⁇ 0.5 H2O
  • magnesite MgCOs
  • barringtonite MgCOs ⁇ 2 H2O
  • lansfordite MgCOs ⁇ 5 H2O
  • nesquehonite MgCOs ⁇ 3 H2O
  • precipitated hydromagnesite can be prepared.
  • aqueous solutions of magnesium bicarbonate typically described as “Mg(HCO3)2”
  • Mg(HCO3)2 magnesium bicarbonate
  • a base e.g., magnesium hydroxide
  • compositions containing both, hydromagnesite and magnesium hydroxide wherein magnesium hydroxide is mixed with water to form a suspension which is further contacted with carbon dioxide and an aqueous basic solution to form the corresponding mixture; cf. for example US 5979461 .
  • the hydromagnesite can be one type or a mixture of different types of hydromagnesite.
  • the hydromagnesite comprises, preferably consists of, one type of hydromagnesite.
  • the hydromagnesite comprises, preferably consists of, two or more types of hydromagnesites.
  • the hydromagnesite is precipitated hydromagnesite.
  • the aqueous suspension of the present invention comprises a dispersing agent, wherein the dispersing agent is a polyacrylate-containing dispersant.
  • the polyacrylate-containing dispersant may be a polyacrylate homopolymer, a polyacrylate copolymer, or a mixture thereof.
  • the polyacrylate homopolymer may be prepared from the polymerisation reaction of acrylic acid or methacrylic acid or salts thereof.
  • the polyacrylate copolymer may be prepared from the polymerisation reaction of acrylic acid or methacrylic acid or salts thereof and at least one non-ionic compound selected from hydroxyethylacrylate, hydroxypropylacrylate, hydroxyethylmethacrylate, hydroxypropylmethacrylate, Ci - C5 esters of acrylic acid, C1-C5 esters of methacrylic acid, fumaric acid, itaconic acid, acrylamide, crotonic acid, maleic anhydride acid, isocrotonic acid, aconitic acid (cis or trans), mesaconic acid, sinapinic acid, undecylenic acid, angelic acid, canellic acid, hydroxyacrylic acid, acrolein, acrylonitrile, dimethylaminoethyl methacrylate, vinylpyrrolidone, vinylcaprol
  • the C1-C5 ester of acrylic acid and/or C1-C5 ester of methacrylic acid may be selected from alkyl esters of acrylic acid and/or alkyl esters of methacrylic acid.
  • the alkyl esters may comprise further substituents, such as hydroxy groups and/or sulfonic acid groups.
  • the C1-C5 ester of acrylic acid is selected from alkyl esters of acrylic acid.
  • the C1-C5 ester of acrylic acid is selected from the group consisting of methyl, ethyl, propyl, hydroxypropyl, butyl, and pentyl acrylate, preferably the C1-C5 ester of acrylic acid is selected from the group comprising methyl, ethyl, propyl, and hydroxypropyl acrylate, and most preferably the ester of acrylic acid is hydroxypropyl acrylate.
  • the C1-C5 ester of methacrylic acid may be selected from alkyl esters of methacrylic acid.
  • the C1-C5 ester of methacrylic acid is selected from the group consisting of methyl, ethyl, propyl, hydroxypropyl, butyl, and pentyl methacrylate, preferably the C1-C5 ester of methacrylic acid is selected from the group comprising methyl, ethyl, and hydroxypropyl methacrylate, and most preferably, the ester of methacrylic acid is hydroxypropyl methacrylate.
  • the polyacrylate homopolymer is prepared from the polymerisation reaction of acrylic acid or methacrylic acid or salts thereof
  • the polyacrylate copolymer is prepared from the polymerisation reaction of acrylic acid or methacrylic acid or salts thereof and at least one non-ionic compound selected from the group consisting of hydroxyethylacrylate, hydroxypropylacrylate, hydroxyethylmethacrylate, hydroxypropylmethacrylate, C1-C5 esters of acrylic acid, C1-C5 esters of methacrylic acid, fumaric acid, itaconic acid, acrylamide, crotonic acid, maleic anhydride acid, isocrotonic acid, aconitic acid (cis or trans), mesaconic acid, sinapinic acid, undecylenic acid, angelic acid, canellic acid, hydroxyacrylic acid, acrolein, acrylonitrile, dimethylaminoethyl methacrylate, vinylpyr
  • the polyacrylate homopolymer may be one kind of polyacrylate homopolymer, or a mixture of two or more kinds of polyacrylate homopolymers.
  • the polyacrylate homopolymer may be a mixture of two or three kinds of polyacrylate homopolymers.
  • the polyacrylate homopolymer is one kind of polyacrylate homopolymer.
  • the polyacrylate copolymer may be one kind of polyacrylate copolymer, or a mixture of two or more kinds of polyacrylate copolymers.
  • the polyacrylate copolymer may be a mixture of two or three kinds of polyacrylate copolymers.
  • the polyacrylate copolymer is one kind of polyacrylate copolymer.
  • the polyacrylate-containing polymer comprises, preferably consists of, one kind of polyacrylate homopolymer or one kind of polyacrylate copolymer.
  • the polyacrylate-containing polymer is a mixture comprising, preferably consisting of, one kind of polyacrylate homopolymer and one kind of polyacrylate copolymer.
  • the carboxylic acid functions of the polyacrylate-containing polymer may be at least partially neutralized.
  • the dispersing agent has a neutralization degree of at least 30 mol-%, preferably at least 40 mol-%, more preferably at least 60 mol-%, and most preferably at least 80 mol-%.
  • the carboxylic acid functions of the dispersing agent may be at least partially neutralized by any suitable monovalent cation such as sodium ions, potassium ions, lithium ions, ammonium ions, calcium ions, and mixtures thereof, preferably with sodium ions, calcium ions, or mixtures thereof, and most preferably with sodium ions.
  • the carboxylic acid functions of the polyacrylate-containing polymer are at least partially neutralized sodium ions, potassium ions, lithium ions, ammonium ions, calcium ions, and mixtures thereof, preferably in an amount of at least 30 mol-%, preferably at least 40 mol-%, more preferably at least 60 mol-%, and most preferably at least 80 mol-%.
  • the term “partially neutralized” as used herein indicates that the polyacrylate-containing polymer still contains non-neutralized carboxylic acid functions, i.e. free carboxylic acid functions are present.
  • the term “totally neutralized” indicates that any carboxylic acid function present in the polyacrylate-containing polymer is neutralized, i.e. no free carboxylic acid functions are present.
  • the methods of partially or totally replacing protons of carboxylic acid functions by monovalent cations are well known as well as the methods to determine whether a polymer is partially or totally neutralized.
  • the dispersing agent has an average molecular weight M w from 1000 to 15 000 g/mol, preferably from 2000 to 12 000 g/mol, more preferably from 3000 to 11 000 g/mol, and most preferably from 4000 to 10 000 g/mol.
  • the dispersing agent is a polyacrylate homopolymer being at least partially neutralized with sodium ions.
  • said dispersing agent has a neutralization degree of at least 30 mol-% and an average molecular weight Mwfrom 1000 to 15 000 g/mol.
  • the dispersing agent is a polyacrylate homopolymer being fully neutralized with sodium ions and having an average molecular weight M w from 4000 to 10 000 g/mol.
  • the dispersing agent may be provided in the form of a solution in water or in solid form, and preferably in the form of an aqueous suspension.
  • the aqueous suspension comprises the dispersing agent in an amount of 3 wt.-% or less, based on the total weight of the aqueous suspension, preferably in an amount from 0.01 to 2 wt.-%, more preferably in an amount from 0.05 to 1 .5 wt.-%, and most preferably in an amount from 0.1 to 0.8 wt.-%.
  • polyvinyl alcohol is used as co-dispersing agent for an aqueous suspension comprising a mineral material and dispersing agent as defined above.
  • the polyvinyl alcohol may be prepared by any method known in the art.
  • polyvinyl alcohol may be manufactured by polymerization of vinyl acetate monomers, followed by hydrolysis of the polyvinyl acetate.
  • commercially available polyvinyl alcohols may be used, e.g. BF-05, BF-04, BF-14, BF-17, BP-04, or BP-05 of Chang Chun Petrochemical Co., Ltd.
  • the polyvinyl alcohol may be partially or fully hydrolyzed. According to one embodiment, the polyvinyl alcohol has a degree of hydrolysis of at least 75 mol-%, preferably at least 85 mol-%, more preferably at least 90 mol-%, even more preferably at least 95 mol-%, and most preferably at least
  • the polyvinyl alcohol has a degree of hydrolysis from 80 to 100 mol-%, and more preferably from 85 to 99 mol-%, for example, from 85 to 90 mol-% or 98 to
  • the polyvinyl alcohol has an average molecular weight Mwfrom 10 000 to 150 000 g/mol, preferably from 12 000 to 100 000 g/mol, more preferably from 14 000 to 50 000 g/mol, and most preferably from 16 000 to 30 000 g/mol.
  • the polyvinyl alcohol may be one kind of polyvinyl alcohol, or a mixture of two or more kinds of polyvinyl alcohols.
  • the polyvinyl alcohol may be a mixture of two or three kinds of polyvinyl alcohol.
  • the polyvinyl alcohol is one kind of polyvinyl alcohol.
  • the polyvinyl alcohol may be provided in the form of a solution in water or in solid form. According to one embodiment, the polyvinyl alcohol is provided in solid form.
  • the polyvinyl alcohol may be provided in the form of a powder, or in the form of particles, beads, or granules. According to one embodiment, the polyvinyl alcohol is provided in the form of a powder and/or in the form of granules.
  • the aqueous suspension comprises the polyvinyl alcohol in an amount of 2 wt.-% or less, based on the total weight of the aqueous suspension, preferably in an amount from 0.01 to 1 .8 wt.-%, more preferably in an amount from 0.05 to 1 .5 wt.-%, even more preferably in an amount from 0.08 to 1 wt.-%, and most preferably in amount from 0.1 to 0.6 wt.-%.
  • the aqueous suspension comprises the polyvinyl alcohol in an amount of 2 wt.-% or less, based on the total weight of the aqueous suspension, and the polyvinyl alcohol has a degree of hydrolysis of at least 75 mol-%.
  • the aqueous suspension comprises the polyvinyl alcohol in an amount of 2 wt.-% or less, based on the total weight of the aqueous suspension, and the polyvinyl alcohol has an average molecular weight M w from 10 000 to 150 000 g/mol.
  • the aqueous suspension comprises the polyvinyl alcohol in an amount of 2 wt.-% or less, based on the total weight of the aqueous suspension, the polyvinyl alcohol has a degree of hydrolysis of at least 75 mol-%, and the polyvinyl alcohol has an average molecular weight Mwfrom 10 000 to 150 000 g/mol.
  • the polyvinyl alcohol has a degree of hydrolysis of at least 85 mol-%, more preferably at least 90 mol-%, even more preferably at least 95 mol-%, and most preferably at least 98 mol-%.
  • the aqueous suspension comprises the polyvinyl alcohol in an amount from 0.1 to 0.6 wt.-%, based on the total weight of the aqueous suspension, and the polyvinyl alcohol has a degree of hydrolysis of at least 75 mol-%.
  • the aqueous suspension comprises the polyvinyl alcohol in an amount from 0.1 to 0.6 wt.-%, based on the total weight of the aqueous suspension, and the polyvinyl alcohol has an average molecular weight M w from 12 000 to 100 000 g/mol.
  • the aqueous suspension comprises the polyvinyl alcohol in an amount from 0.1 to 0.6 wt.-%, based on the total weight of the aqueous suspension, the polyvinyl alcohol has a degree of hydrolysis of at least 75 mol-%, and the polyvinyl alcohol has an average molecular weight Mwfrom 12 000 to 100 000 g/mol.
  • the polyvinyl alcohol has a degree of hydrolysis of at least 85 mol-%, more preferably at least 90 mol-%, even more preferably at least 95 mol-%, and most preferably at least 98 mol-%.
  • the inventors of the present invention surprisingly found that using polyvinyl alcohol as a codispersing agent in an aqueous mineral material suspension comprising a dispersing agent can further reduce the viscosity of the mineral material suspension.
  • This provides the possibility to reduce the amount of dispersing agent in the mineral material suspension and/or to provide a mineral suspension having a higher solids content in a workable viscosity range.
  • dispersing agents such as polyacrylates tend to affect the optical properties in a negative way, for example, if they are included in paper coating, the reduction of dispersing agents may also have a positive impact on the optical properties of such products.
  • the addition of polyvinyl alcohol can further improve the optical properties of the mineral material suspension and products containing the same, and may increase e.g. light scattering.
  • a dispersing agent composition comprising a dispersing agent in combination with a co-dispersing agent is provided, wherein the dispersing agent is a polyacrylate-containing dispersant, and the co-dispersing agent is polyvinyl alcohol.
  • the aqueous suspension of the present invention may comprise further additives.
  • the aqueous suspension comprises cationic homopolymers based on monomer units, such as diallyl dialkyl ammonium salts or polyethylene imines, alkali polyphosphates, carboxymethylcellulose, or mixtures thereof.
  • monomer units such as diallyl dialkyl ammonium salts or polyethylene imines, alkali polyphosphates, carboxymethylcellulose, or mixtures thereof.
  • the aqueous suspension may comprise a preservative, a grinding agent, pH stabilizer, a pH adjusting agent, a biocide, or mixtures thereof.
  • Suitable preservatives are quaternary ammonium salts, peroxides, perchlorates, tributyl tin, zinc, biocidal enzymes, biocidal polypeptides, sulphonamides and mixtures thereof.
  • the aqueous suspension only consists of a mineral material selected from an alkaline earth metal mineral material, clay, calcined clay, titanium dioxide, and mixtures thereof, a dispersing agent, wherein the dispersing agent is a polyacrylate-containing dispersant, and co-dispersing agent, wherein the co-dispersing agent is a polyvinyl alcohol.
  • a method for producing an aqueous suspension comprising a mineral material and a dispersing agent in combination with a co-dispersing agent comprises the steps of: i) providing a mineral material selected from an alkaline earth metal mineral material, clay, calcined clay, titanium dioxide, and mixtures thereof, ii) providing a dispersing agent, wherein the dispersing agent is a polyacrylate-containing dispersant, iii) providing a co-dispersing agent, wherein the co-dispersing agent is a polyvinyl alcohol, iv) providing water, and v) contacting the mineral material of step i), the dispersing agent of step ii), the co-dispersing agent of step iii), and the water of step iv).
  • the mineral material may be provided in any suitable liquid or dry form.
  • the mineral material may be in the form of a powder and/or a suspension.
  • the suspension can be obtained by mixing the mineral material with a solvent, preferably water.
  • the mineral material to be mixed with a solvent, and preferably water may be provided in any form, for example, as a suspension, slurry, dispersion, paste, powder, moist filter cake or in pressed or granulated form, and preferably is provided as a powder.
  • the mineral material is provided in the form of an aqueous suspension, preferably having a solids content of at least 20 wt.-%, preferably at least 40 wt.-%, more preferably at least 60 wt.-%, and most preferably at least 68 wt.-%, based on the total weight of the suspension.
  • the mineral material is provided in the form of an aqueous suspension having a solids content from 10 to 78 wt.-%, preferably from 20 to 75 wt.-%, and most preferably from 50 to 72 wt.-%, based on the total weight of the aqueous suspension.
  • the dispersing agent may be provided in the form of an aqueous solution.
  • the co-dispersing agent may be provided in the form of a solution in water or in solid form.
  • the co-dispersing agent is provided in solid form, preferably in the form of a powder, or in the form of particles, beads, or granules, and most preferably in the form of a powder or in the form of granules.
  • any type of water can be provided in method step iv).
  • the water is tap water, deionized water, process water, or mixtures thereof.
  • the water is tap water.
  • the water of step iv) is provided in combination with the mineral material of step i) and/or in combination with the dispersing agent of step ii) and/or in combination with the co-dispersing agent of step iii), preferably the water of step iv) is provided in combination with the mineral material of step i).
  • the contacting step v) may be carried out in any manner known to the skilled person.
  • the contacting of the mineral material of step i), the dispersing agent of step ii), the codispersing agent of step iii), and the water of step iv) may be carried out under mixing and/or homogenizing and/or particle dividing conditions.
  • the skilled person will adapt these mixing and/or homogenizing and/or particle dividing conditions such as the mixing speed, dividing, and temperature according to his process equipment.
  • Suitable mixing methods are known to the skilled person. Examples of suitable mixing methods are shaking, mixing, stirring, agitating, ultrasonication, or inducing a turbulent or laminar flow by means such as baffles or lamellae.
  • Suitable mixing equipment is known to the skilled person, and may be selected, for example, from stirrers, such as rotor stator systems, blade stirrers, propeller stirrers, turbine stirrers, or anchor stirrers, static mixers such as pipes including baffles or lamellae. According to an exemplary embodiment of the present invention, a rotor stator stirrer system is used. The skilled person will adapt the mixing conditions such as the mixing speed and temperature according to his process equipment.
  • Simultaneous mixing and homogenizing may take place by means of a ploughshare mixer.
  • Ploughshare mixers function by the principle of a fluidized bed produced mechanically.
  • Ploughshare blades rotate close to the inside wall of a horizontal cylindrical drum and convey the components of the mixture out of the product bed and into the open mixing space.
  • the fluidized bed produced mechanically ensures intense mixing of even large batches in a very short time.
  • Choppers and/or dispersers are used to disperse lumps in a dry operation.
  • Equipment that may be used in the inventive process is available, for example, from Gebruder Lbdige Maschinenbau GmbH, Germany.
  • method step v) is carried out in a milling device, preferably in a ball mill, preferably in combination with a cyclone device that recirculates agglomerates and/or aggregates formed during method step v) back to the inlet of the milling device.
  • a cyclone device enables the separation of particulate material such as particles, agglomerates or aggregates, into fractions of smaller and larger particulate material based on gravity.
  • the mineral material particles are divided into smaller particles.
  • the term “dividing” as used in the present invention means that particles are split into smaller particles. This may be done by grinding, e.g.
  • any other device that is able to divide the mineral material during method step v) into smaller particles may be used.
  • method step v) is carried out under mixing conditions.
  • the mineral material of step i), the dispersing agent of step ii), the codispersing agent of step iii), and the water of step iv) are mixed.
  • Method step v) may be carried out at room temperature, i.e. at a temperature of 20°C ⁇ 2°C, or at other temperatures. According to one embodiment, method step v) is carried out at about 25°C. According to one embodiment of the present invention, method step v) is carried out for at least 1 s, preferably for at least 1 min, e.g. for at least 15 min, 30 min, 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, or 10 hours.
  • the components of the aqueous suspension may be contacted in any suitable order.
  • step v) comprises the following steps: a1) contacting the dispersing agent of step ii), the co-dispersing agent of step iii), and the water of step iv), and a2) adding the mineral material of step i) to the mixture obtained in step a1).
  • step v) comprises the following steps: b1) contacting the dispersing agent of step ii), and the co-dispersing agent of step iii), and b2) adding the mineral material of step i) and water of step iv) to the mixture obtained in step b1), wherein the mineral material and the water are added separately or in combination, preferably in combination.
  • step v) comprises the following steps: c1) contacting the dispersing agent of step ii), the mineral material of step i), and the water of step iv), and c2) adding the co-dispersing agent of step iii) to the mixture obtained in step c1).
  • the co-dispersing agent is added in the form of a solution in water.
  • step v) comprises the following step: d) contacting the mineral material of step i), the dispersing agent of step ii), the co-dispersing agent of step iii) and the water of step iv) simultaneously.
  • the aqueous suspension formed in step v) has a solids content from 10 to 78 wt.-%, based on the total weight of the aqueous suspension, preferably from 20 to 75 wt.-%, and most preferably from 50 to 72 wt.-%.
  • the Brookfield viscosity of the obtained aqueous suspension may be from 10 to 5 000 mPa s at 25°C, preferably from 50 to 2 000 mPa s at 25°C, more preferably from 100 to 1000 mPa s at 25°C, and most preferably from 150 to 800 mPa s at 25°C.
  • the method further comprises the step of grinding and/or dewatering the aqueous suspension during and/or after step v).
  • the grinding process may be undertaken by all the techniques and grinders well known to the person skilled in the art for wet grinding.
  • the grinding step may be carried out with any conventional grinding device, for example, under conditions such that refinement predominantly results from impacts with a secondary body, i.e. in one or more of: a ball mill, a rod mill, a vibrating mill, a centrifugal impact mill, a vertical bead mill, an attrition mill, or other such equipment known to the skilled person.
  • the grinding may be carried out in batch or continuously, preferably continuously.
  • the grinding is carried out at a temperature from 30 to 110°C, preferably from 40 to 100°C.
  • the grinding can be carried out at room temperature, i.e. at a temperature of 20°C ⁇ 2°C.
  • the mineral material may have a weight median particle size dso from 0.05 to 100 pm, preferably from 0.1 to 50 pm, more preferably from 0.15 to 25 pm, even more preferably from 0.25 to 10 pm, and most preferably from 0.5 to 2 pm.
  • the aqueous suspension may be dewatered during and/or after method step v). Thereby, the solids content of the suspension can be increased.
  • the suspension may be partially or fully dewatered by a filtration, centrifugation or thermal separation process.
  • the suspension may be partially or fully dewatered by a filtration process such as nanofiltration or a thermal separation process such as an evaporation process under ambient, atmospheric pressure or at reduced pressure.
  • step v) comprises the following steps: e1) contacting the dispersing agent of step ii), the mineral material of step i), and the water of step iv), e2) dewatering the aqueous suspension obtained in step e1), and e3) adding the co-dispersing agent of step iii) to the dewatered suspension obtained in step e2), preferably in the form of a solution in water, and e4) optionally dewatering the suspension obtained in step e3).
  • the solids content of the aqueous suspension obtained after dewatering is from 55 to 80 wt.-%, preferably from 60 to 79 wt.-%, and more preferably from 65 to 78 wt.-%, based on the total weight of the aqueous suspension.
  • a method for producing an aqueous suspension comprising a mineral material, and a dispersing agent in combination with a co-dispersing agent is provided, wherein the mineral material is precipitated calcium carbonate and the method comprises the following steps:
  • dispersing agent is a polyacrylate-containing dispersant, or a mixture thereof
  • co-dispersing agent is a polyvinyl alcohol
  • step IV preparing a milk of lime by mixing water, the calcium oxide-containing material of step I) and the co-dispersing agent of step III),
  • step V) carbonating the milk of lime obtained in step IV) to form an aqueous suspension of precipitated calcium carbonate
  • the calcium oxide-containing material of step I) can be obtained by calcining a calcium carbonate-containing material. Calcination is a thermal treatment process applied to calcium carbonate-containing materials in order to bring about a thermal decomposition resulting in the formation of calcium oxide and gaseous carbon dioxide.
  • Calcium carbonate-containing materials which may be used in such a calcination process are those selected from the group comprising precipitated calcium carbonates, natural calcium carbonate containing minerals such as marble, limestone and chalk, and mixed alkaline earth carbonate minerals comprising calcium carbonate such as dolomite, or calcium carbonate rich fractions from other sources. It is also possible to subject a calcium carbonate-containing waste material to a calcination process in order to obtain a calcium oxide-containing material.
  • calcination step may be carried out under conditions and using equipment well-known to the person skilled in the art. Generally, calcination may be carried out in furnaces or reactors (sometimes referred to as kilns) of various designs including shaft furnaces, rotary kilns, multiple hearth furnaces, and fluidized bed reactors.
  • the end of the calcination reaction may be determined, e.g. by monitoring the density change, the residual carbonate content, e.g. by X-ray diffraction, or the slaking reactivity by common methods.
  • the calcium oxide-containing material of step I) is obtained by calcining a calcium carbonate-containing material, preferably selected from the group consisting of precipitated calcium carbonate, natural calcium carbonate minerals such as marble, limestone and chalk, mixed alkaline earth carbonate minerals comprising calcium carbonate such as dolomite, and mixtures thereof.
  • a calcium carbonate-containing material preferably selected from the group consisting of precipitated calcium carbonate, natural calcium carbonate minerals such as marble, limestone and chalk, mixed alkaline earth carbonate minerals comprising calcium carbonate such as dolomite, and mixtures thereof.
  • the calcium oxide- containing material has a minimum calcium oxide content of at least 75 wt.-%, preferably at least 90 wt.-%, and most preferably 95 wt.-%, based on the total weight of the calcium oxide-containing material.
  • the calcium oxide-containing material consists solely of calcium oxide.
  • the calcium oxide-containing material can consist of only one type of calcium oxide-containing material.
  • the calcium oxide-containing material can consist of a mixture of two or more types of calcium oxide-containing materials.
  • the calcium oxide containing material can be used in the inventive process in its original form, i.e. as a raw material, for example, in the form of smaller and bigger chunks.
  • the calcium oxide-containing material can be ground before use.
  • the calcium oxide-containing material is in the form of particles having weight median particle size cko from 0.1 to 1000 pm, and preferably from 1 to 500 pm.
  • a milk of lime is prepared by mixing water, the calcium oxide-containing material of step I), and the co-dispersing agent of step III).
  • the reaction of the calcium oxide-containing material with water results in the formation of a milky calcium hydroxide suspension, better known as milk of lime. Said reaction is highly exothermic and is also designated as “lime slaking” in the art.
  • the temperature of the water, which is used in mixing step IV i.e. the temperature of the water that is used to slake the calcium oxide-containing material, is adjusted to be in the range from more than 0°C and less than 100°C. In other words, the water that is used to slake the calcium oxidecontaining material is adjusted to a temperature range, in which the water is in liquid form.
  • the temperature of the water, which is employed in mixing step IV) is adjusted to be from 1 °C to 70°C, more preferably from 2°C to 50°C, even more preferably from 30°C to 50°C, and most preferably from 35 to 45°C.
  • the initial temperature of the water is not necessarily the same one as the temperature of the mixture prepared in step IV) due to the highly exothermic slaking reaction and/or due to the mixing of substances having different temperatures.
  • step IV) comprises the steps of:
  • step A2) adding the co-dispersing agent of step II) to the mixture of step A1).
  • method step A2) is carried out after the reaction between the calcium oxide- containing material of step I) with water is completed, i.e. after the lime has been completely slaked.
  • step IV) comprises the steps of:
  • step B2) adding the calcium oxide-containing material of step I) to the mixture of step B1).
  • step IV the calcium oxide-containing material of step I), the co-dispersing agent of step III), and water are mixed simultaneously.
  • the co-dispersing agent of step III) may be added in step IV) in one portion or in several portions.
  • the co-dispersing agent is mixed with the water, and the calcium oxide-containing material by adding the co-dispersing agent in one portion or in two, three, four, five, or more portions.
  • Method step IV) may be performed at room temperature, i.e. at a temperature of 20°C ⁇ 2°C, or at an initial temperature of 30 to 50°, preferably 35 to 45°C. Since the reaction is exothermic, the temperature typically raises to a temperature between 70 and 85°C during step IV). According to a preferred embodiment, process step IV) is performed with mixing, agitation, or stirring, for example, mechanical stirring. Suitable process equipment for mixing, agitation or stirring is known to the skilled person. The progress of the slaking reaction may be observed by measuring the temperature and/or conductivity of the reaction mixture. It can also be monitored by turbidity control. Alternatively or additionally, the progress of the slaking reaction can be inspected visually.
  • the calcium oxide-containing material and the water are mixed in a mass ratio from 1 :4 to 1 :15. According to one preferred embodiment, in step IV) the calcium oxide-containing material and the water are mixed in a mass ratio from 1 :5 to 1 :9.
  • the milk of lime of step IV) has a solids content from 5 to 25 wt.-%, based on the total weight of the milk of lime, preferably from 10 to 20 wt.-%, and most preferably from 10 to 15 wt.-%.
  • the milk of lime of step IV) has a Brookfield viscosity from 10 to 1000 mPa s at 25°C, more preferably from 20 to 800 mPa s at 25°C, and most preferably from 50 to 600 mPa s at 25°C. According to one embodiment, the Brookfield viscosity is measured at 100 rpm.
  • Method step IV) can be carried out in the form of a batch process, a semi-continuous or a continuous process.
  • step V) the milk of lime obtained from step IV) is carbonated to form an aqueous suspension of precipitated calcium carbonate.
  • the carbonation is carried out by means and under conditions well-known by the person skilled in the art.
  • the introduction of carbon dioxide into the milk of lime quickly results in the formation of the carbonate ion (CO3 2 ), and thus, the requisite concentration for calcium carbonate to be formed.
  • the carbonation reaction can be readily controlled considering the reactions involved in the carbonation process.
  • Carbon dioxide dissolves according to its partial pressure forming carbonate ions via the formation of carbonic acid (H2CO3), which, in such an alkaline solution, dissociates to its constituent hydrogen and carbonate ions.
  • H2CO3 carbonic acid
  • step V) the carbonation is carried out by feeding pure gaseous carbon dioxide or technical gases containing at least 10 vol.-% of carbon dioxide into the milk of lime.
  • the progress of the carbonation reaction can be readily observed by measuring the conductivity, density, turbidity and/or pH.
  • the pH of the milk of lime before addition of carbon dioxide will be more than 10, usually between 11 and 12.5, and will constantly decrease until a pH of about 7 is reached. At this point the reaction can be stopped.
  • the progress of the carbonation may be monitored by measuring the pH and/or the conductivity of the reaction mixture.
  • the temperature of the milk of lime obtained from step IV), which is used in step V) is adjusted to be in the range from 5°C to 95°C. It will be apparent to the skilled person that the initial temperature of the milk of lime is not necessarily the same one as the temperature of the mixture prepared in step IV) due to the exothermic carbonation reaction and/or due to the mixing of substances having different temperatures. According to one embodiment of the present invention, step V) is carried out at a temperature from 5 to 95°C, preferably from 30 to 70°C, and more preferably from 40 to 60°C.
  • Method step V) can be carried out in form of a batch process, a semi-continuous or a continuous process.
  • the method of the present invention involving the method steps I) to V) is carried out in form of a batch process, a semi-continuous or a continuous process.
  • Method step V) may involve any suitable mixing method known to the skilled person, e.g. any of the mixing methods described above.
  • the method further comprises the step of dewatering the aqueous suspension during and/or after step V), as described in more detail above.
  • the method for producing an aqueous suspension comprising a mineral material and a dispersing agent in combination with a co-dispersing agent according to the present invention may comprise a further step of sieving the aqueous suspension after step v) or step VI.
  • Such sieving can be carried out with any conventional sieving means known to the skilled person.
  • the sieving can be carried out using one or more mesh sizes. Suitable mesh sizes are, for example, 180 pm, 90 pm, 63 pm, or 45 pm.
  • an aqueous suspension obtainable by a method according to the present invention is provided.
  • an aqueous suspension comprising a mineral material and a dispersing agent in combination with a co-dispersing agent
  • the mineral material is selected from an alkaline earth metal mineral material, clay, calcined clay, titanium dioxide, and mixtures thereof
  • the dispersing agent is a polyacrylate-containing dispersant
  • the co-dispersing agent is polyvinyl alcohol
  • the aqueous dispersion comprises the dispersing agent in an amount of 3 wt.-% or less, based on the total amount of the aqueous suspension, the co-dispersing agent in an amount of 2 wt.-% or less, based on the total amount of the aqueous suspension, and the mineral material in an amount from 10 to 78 wt.-%, based on the total weight of the aqueous dispersion.
  • the aqueous suspension obtainable by the methods of the present invention may be used in various materials and applications.
  • the aqueous suspension is used in paper applications, packaging applications, polymer applications, or water treatment applications.
  • the aqueous suspension of the present invention is used in a paper coating composition.
  • a paper coating composition is provided comprising the aqueous suspension according to the present invention.
  • the inventors of the present invention surprisingly found that paper coating compositions comprising the aqueous suspension according to the present invention may improve the optical and/or mechanical properties of the coated paper products such as paper substrates or cardboards. In particular it was found that the water retention of the paper product can be improved as well as its mechanical surface strength.
  • the weight determined median particle size cfeo(wt) was measured by the sedimentation method, which is an analysis of sedimentation behaviour in a gravimetric field.
  • the measurement was made with a SedigraphTM 5120 of Micromeritics Instrument Corporation, USA.
  • the method and the instrument are known to the skilled person and are commonly used to determine particle size distributions of fillers and pigments.
  • the measurement was carried out in an aqueous solution of 0.1 wt% N34P2O7.
  • the samples were dispersed using a high speed stirrer and supersonicated.
  • the processes and instruments are known to the skilled person and are commonly used to determine particle sizes of fillers and pigments.
  • the Brookfield viscosity in Examples 1 to 10 was measured by a Brookfield DV-II+ Pro viscometer at 25°C ⁇ 1 °C at 100 rpm using an appropriate spindle of the Brookfield RV-spindle set and is specified in mPa s. A spindle was selected from the Brookfield RV-spindle set which was suitable for the viscosity range to be measured.
  • the spindle number 2 was used, for a viscosity range between 200 and 800 mPa s the spindle number 3 was used, for a viscosity range between 400 and 1 600 mPa s the spindle number 4 was used, and for a viscosity range between 800 and 3 200 mPa s the spindle number 5 was used.
  • Example 11 The Brookfield viscosity in Example 11 was measured by a Brookfield DV-III Ultra viscometer at 24°C ⁇ 3°C at 100 rpm using an appropriate spindle of the Brookfield RV-spindle set and is specified in mPa s. Once the spindle has been inserted into the sample, the measurement was started with a constant rotating speed of 100 rpm. The reported Brookfield viscosity values are the values displayed 60 seconds after the start of the measurement.
  • the spindle number 3 was used, for a viscosity range between 400 and 1 600 mPa s the spindle number 4 was used, and for a viscosity range between 800 and 3 200 mPa s the spindle number 5 was used.
  • the ACAV viscosity measurement was conducted in an ACAV-2 viscosimeter.1 liter of coating composition was put into the probe chamber of the viscosimeter and the automatic routine was started. At the end of the measurement a graph was obtained that showed the viscosity in dependency of the shear rate.
  • Shear rate is a measure used to describe the flow of liquid through a channel. More specifically, the shear rate is the rate at which the velocity of a fluid under shear changes through its thickness, also known as its velocity gradient. For the present application the ACAV viscosity at a shear rate of 500000 1/s was taken.
  • the water retention was determined using an AA-GWR water retention meter (GRADEKTM, DT Paper Science). It comprised a measurement chamber, into which a piece of test paper (test blotter paper) was placed, covered with a perforated plastic sheet (test filter PCTE), wherein both the paper and the sheet are commercially available from the retention meter manufacturer.
  • GRADEKTM AA-GWR water retention meter
  • the pH of a suspension or solution was measured at 25°C using a Mettler Toledo Seven Easy pH meter and a Mettler Toledo InLab® Expert Pro pH electrode.
  • a three-point calibration (according to the segment method) of the instrument was first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 20°C (Sigma-Aldrich Corp., USA).
  • the reported pH values are the endpoint values detected by the instrument (the endpoint was when the measured signal differed by less than 0.1 mV from the average over the last 6 seconds).
  • Paper gloss was measured using LGDL-05.3-lab instrumentation (Lehmann Messsysteme GmbH, Germany) according to EN ISO 8254-1 :2009, TAPPI 75° (%).
  • the brightness was measured according to standard ISO 2470-2:2008 with an Elrepho 450 spectrometer (light: D65, view: 10°, Datacolor, Germany).
  • Paper surface roughness was measured using the L&W PPS tester (Lorentzen & Wettre, Sweden) according to DIN ISO 8791-4 with a pressure of 1 .0 mPa using soft component, PPS 1.0 (pm).
  • the setoff optical ink density was measured according to the lab standard usuallyWegsch lagtest Offset 11 using the test device “Prufbau Multipurpose Printability Testing Instrument MZ II” (Prufbau, Germany).
  • Printing speed 0.5 m/s Ink quantity: 300 mm 3
  • Counter times 15, 30, 60, and 120 s
  • Printing ink test colour (Prufbau, Germany)
  • the device settings were made on the test device.
  • the timer was set to 5 seconds.
  • the counter paper was clamped on the clamping bolt in such a way that the counter paper could be easily attached to the print sample carrier after proofing.
  • a clean metal printing form was placed on the second printing unit.
  • the print sample carrier with the paper to be tested was positioned in front of the first printing unit.
  • the ink was applied to the first ink sector of the rubber roll and the distribution unit was started.
  • the metal printing form was placed and inked for 30 seconds.
  • the inked form was placed on the first printing unit and started.
  • the stopwatch was switched on during the start release.
  • the print sample carrier was caught by the timer so that the printing process could be stopped immediately.
  • the counter paper was inserted into the gap of the second printing unit together with the print sample carrier and the first counter pressure was applied after 15 seconds using the lubrication lever. This allowed 4 counter times to be reproduced in succession on one print (15, 30, 60, 120 s). To prevent possible picking or sticking, the test strip was separated from the counter printing paper immediately after reverse printing. A strip of the sample was then printed to check the printed image for errors and the required amount of ink. The distribution unit and the print form were recoloured for each subsequent print.
  • the dry pick refers to the extent to which a paper will resist picking in the absence of moisture fountain solution.
  • Pick resistance also called surface strength, refers to the extent to which a paper can withstand a force applied at right angles to its surface (such as that generated by a sticky ink film during printing) without rupturing, or picking.
  • Picking can include either a delamination of the plys of a paper and/or a partial or total removal of a paper coating.
  • the dry pick was measured according to the lab standardumbleTrockenrupfen” using the test device “Prufbau Multipurpose Printability Testing Instrument MZ II” (Prufbau, Germany).
  • Printing ink pick test colour (Prufbau, Germany): No. 1 (low tack), No. 2 (medium tack), and No. 3 (high tack)
  • Counter printing paper Norm Ubuntu horrinsky APCO ll/ll 150 g/m 2
  • the device settings were made on the test device.
  • the ink pipette was filled and the print sample carrier with the paper to be tested was positioned in front of the second printing unit.
  • the ink was applied to the first inking sector of the rubber roll, wherein the distribution time was 30 s.
  • the rubber blanket printing form was placed on said roll, and after a further 30 seconds, the inked rubber blanket printing form was placed on the second printing unit.
  • the sample carrier was guided under the rubber blanket printing form until there was contact between the rubber blanket printing form and the sample at the 0 point of the 200 mm printing path.
  • the rubber blanket printing form was placed on the printing unit in such a way that the gap in the blanket elevator did not lead to any interruption in printing over the 200 mm long printing path. As soon as the rubber blanket printing form was placed on the printing surface, the printing unit drive (speed) was switched on and the plucking test was carried out.
  • picking test colors no. 1 - 3 with the appropriate tack were selected.
  • the distribution sector and rubber blanket printing form were recoloured.
  • the final speed of 3 m/s in the plucking test with increasing speed referred to a pressure distance of 200 mm.
  • the start of picking was the point on the printed paper strip where the first fibers or pigment particles were lifted or torn from the paper surface. This point was marked on the side with a pencil.
  • the distance from the start of printing to the start of picking was measured and entered in the equation given below under the corresponding colour number in mm.
  • the start of picking in m/s was calculated using the following equation: m/s
  • the deltack was measured according to lab standard “Messung der Oberflachenfesttechnik im Offset Druck“ using the test device “Prufbau Deltack” (Prufbau, Germany).
  • the deltack reflects the surface strength of a printing substrate in offset printing and indicates the force at which parts of the substrate (e.g. fibres, pigments, etc.) are torn out of the substrate.
  • a paper sample was attached to a load cell of a rotating cylinder, which passed a printing unit again and again until rupture was visible and force was measured.
  • Pressure sample carrier Adapted to substrate (for paper) or blanket strips with 263 pm (for cardboard)
  • the paper strip to be tested was taped at both ends so that the holes from the subsequent hole process were in the area of the adhesive tape.
  • the cardboard strip to be tested was glued to the metal printing form 63.45 using double-sided adhesive tape. Two measurements were made for each sample. If the results deviated too much from each other, more repetitions were made in order to obtain a more representative result.
  • the paper sample to be tested was placed with the corresponding side facing upwards in the tensile measurement holder and on the compression sample carrier. It was ensured that the sample did not already trigger tensile forces on the measuring unit.
  • a pressure sample carrier was used on the opposite measuring unit to smear the paint. This ensured that the amount of ink was reduced during initial printing and supplemented with continuous printing on the printing roller. This resulted in a more even increase in tack overtime/cycles.
  • the required amount of ink was rubbed into the ink distribution system for 30 seconds.
  • the rubber blanket printing form was then inked for a further 30 seconds. After inking, said printing form was placed on printing unit B. The pressure was applied using the "Start measurement” and "Press 1/2 turn” fields. After clicking on "Start", the test strip ran through the pressure section again and again at the same settings.
  • the rubber blanket strip was placed with the darker side facing upwards in the tensile measurement holder and on the pressure sample carrier. It was ensured that the rubber blanket strip did not already trigger tensile forces on the measuring unit.
  • the prepared metal printing form with the cardboard sample to be tested was placed on printing unit B. The required amount of ink was rubbed into the ink distribution system for 30 seconds. The rubber blanket printing form was then inked for a further 30 seconds. After inking, this printing form was placed on printing unit A. The pressure was applied using the “Start measurement” and “Press 1/2 turn” fields. The pressure was applied using the "Start measurement” and “Press 1/2 turn” fields. After clicking on "Start", the test strip ran through the pressure section again and again at the same settings.
  • the sample came to a standstill for a defined time. During this time, the surface was inspected for damage. The letters A - Z and the numbers 1 - 9 were used to clearly mark any damage detected during the corresponding pass. Once the damage was confirmed, the measurement was stopped.
  • the formula for bulk is thickness (mm) x basis weight (g/m 2 ) x 1000. Using the value for the thickness and the basis weight, the bulk can be calculated. 2. Materials
  • PVOH Polyvinyl alcohol
  • Table 4 Materials for paper coating compositions.
  • Polyvinyl alcohol was used in the examples below in form of pre-made aqueous solutions having a PVOH concentration of 20 wt.-%, based on the total weight of the solution.
  • the 20 wt.-% PVOH pre-made solutions were obtained by dissolving PVOH granules or powder in water (85-90°C) with stirring until no more particles were visible.
  • the pre-made solutions were cooled to room temperature and used within one week of preparation.
  • the mineral material was provided in the form of an aqueous suspension having a solids content of approximately 50 wt.-%. Said suspensions were further diluted until they could be homogeneously mixed with 0.4-0.5 % dispersant. This was typically the case at a solids content of between 30 and 40 wt.-%.
  • Viscosity was measured using the appropriate spindle on a Brookfield viscometer once the suspensions had cooled to room temperature. 3.1. Example 1
  • Table 5 Composition and viscosity of aqueous mineral suspensions prepared according to Example 1 (comp.: comparative).
  • Aqueous mineral material suspensions were prepared by adding 0.5 wt.-% PVA 1 , 0.75 wt.-%
  • the viscosity was reduced from 3036 mPa s for the Pigment B suspension without any PVOH to 105 mPa s for the Pigment B suspension with PVOH (PVA 1) and to 110 mPa s for the Filler B suspension with PVOH (PVA 2).
  • the viscosity of Pigment B suspension with 0.4 wt.-% Dispersant A was so high that it could not be measured without the addition of PVOH.
  • the viscosity of the final suspension (Pigment B suspension + mix of PVA 1 and PVA 2 + Dispersant A) was 156 mPa s.
  • Table 6 Composition and viscosity of suspensions prepared according to Example 2 (comp.: comparative).
  • Aqueous mineral material suspensions were prepared by adding 0.5 wt.-% PVA 3 or PVA 4 to a 68 wt.-% Pigment A suspension with 0.5 wt.-% Dispersant A.
  • comparative suspensions without PVOH were prepared. The compositions of the tested suspensions are listed in Table 5 above.
  • the longer chain length PVOH could be used to reduce the viscosity replacing some of the dispersant. It was shown that a larger filler particle size requires less dispersant to reduce the viscosity. The viscosity was not reduced as much with the coarser particle size of Pigment A, however, the surprising viscosity reduction effect with PVOH was still visible.
  • Table 7 Composition and viscosity of suspensions prepared according to Example 3 (comp.: comparative).
  • An aqueous mineral material suspension was prepared by adding 0.5 wt.-% PVA 4 to a
  • an aqueous mineral material suspension was prepared by premixing a 20 wt.-% PVA 6 solution with Dispersant A in a 1 :1 weight ratio.
  • the PVA 6-dispersant solution was added to a Filler A suspension prior to evaporation to 68 % in such an amount that a concentration of 0.5 wt.-% Dispersant A and 0.5 wt.-% PVA 6 was achieved in the final suspension.
  • the viscosity was reduced from 740 mPa s for the Pigment A suspension without any PVOH to 389 mPa s for the Pigment A suspension with PVOH (PVA 5).
  • the viscosity in the test trial # 3.4 using a PVOH/dispersing agent premix was 207 mPa s.
  • a 1 wt.-% Dispersant A suspension (Pigment A suspension + Dispersant A) without PVOH had a viscosity of 77 mPa s.
  • PVOH partially hydrolysed PVOH
  • the PVOH was added after the dispersant addition, however, as shown in this example with PVA 6, the PVOH can also be added at the same time as the dispersant.
  • PVOH can be used to reduce the dispersant concentration required to reduce the viscosity of a suspension having a solids content of 68 wt.-%. This can be also achieved at higher slurry concentrations as was shown in this example for a solids content of 72 wt.-%.
  • a 65 wt.-% suspension of Pigment C was prepared by adding water to Pigment C powder with stirring. 0.25 wt.-% PVOH (PVA 1) was added for the inventive example (grey line with squares). Dispersant B was added incrementally and the viscosity was measured after each addition. It can be seen from Fig. 5 that the presence of PVOH reduced the amount of dispersant required to reach a specific viscosity compared to the suspension without PVOH. 3.6.
  • Example 6 Calcium hydroxide
  • a pre-made, non-stabilised 30 wt.-% suspension of Pigment D was homogenised with Dispersant C and 0-0.6 wt.-% PVOH.
  • the PVOH used was PVA 1.
  • Dispersant C was also added incrementally with stirring, and the viscosity was measured after each addition. It can be seen from Fig. 6 that the presence of 0.6 wt.-% PVOH (grey line with diamonds) resulted in lower viscosities at lower dispersant concentrations compared to the suspension without PVOH.
  • An aqueous suspension of Pigment A with a solids content of 22.1 wt.-% was used as starting material.
  • 0.4-0.8 wt.-% Dispersant A (and 0.5-0.8 wt.-% PVA 2 if used) were added (according to the amounts outlined in the Table 8 below).
  • the obtained suspension was dewatered first with an Andritz centrifuge to a solids content of 55 wt.-% and then with an Epcon evaporator to a solids content of 72 wt.-% (final slurry).
  • Dispersant D An aqueous suspension containing a mixture of Pigment E and Pigment F (solids content 76 wt.-%) and 0.29 wt.-% of Dispersant D was provided as feed material.
  • the ground suspensions were treated with 250 ppm AMP and sieved at 63 pm.
  • Table 10 Composition of coating compositions prepared and used in Example 9 (pph: parts per hundred, dry weight; wt.-% are based on total weight of dry pigment (except for the solids content, wherein the wt.-% is based on the total weight of the suspension)). Paper coating trials 1 and 2 were run at a pilot coater at the following conditions:
  • Base paper 46 g/m 2 wood-containing commercial LWC base
  • coating composition 10 including the same amount of dispersing agent as comparative coating composition 1 , has higher brightness as well as significantly improved dry pick and Deltack (influences the coating strength, resulting in less “picking” during printing) at good gloss, and good roughness,
  • inventive coating compositions 5 and 6 wherein coating composition 5 contains the same amount of dispersing agent but only half the amount of PVOH, shows that both compositions exhibit very similar paper properties, both optically and in terms of surface strength.
  • Table 13 Composition of coating compositions prepared and used in Example 10 (pph: parts per hundred, dry weight; wt.-% are based on total weight of dry pigment (except for the solids content, wherein the wt.-% is based on the total weight of the suspension)). Board coating trials were run at a pilot coater at the following conditions:
  • Base board 230 g/m 2 commercial folding boxboard (FBB) base
  • Aqueous mineral material suspensions were prepared by adding 0.5 wt.-% PVA to a 68 wt.-% Pigment B suspension with 0.7 wt.-% Dispersant A, wherein the wt.-% are based on the total weight of the mineral suspension.
  • a comparative suspension without PVOH was prepared.
  • the aqueous mineral suspensions listed in Table 15 below were used to prepare the coating compositions compiled in Table 16 below.
  • Table 15 Composition and viscosity of aqueous mineral suspensions prepared according to Example 11 (comp.: comparative).
  • Table 16 Composition of coating compositions prepared and used in Example 11 (pph: parts per hundred, dry weight; wt.-% are based on total weight of suspension). Paper coating trials were run at a pilot coater at the following conditions:

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
  • Emulsifying, Dispersing, Foam-Producing Or Wetting Agents (AREA)

Abstract

La divulgation concerne une utilisation de poly(alcool vinylique) en tant qu'agent de codispersion pour une suspension aqueuse comprenant un matériau minéral et un agent de dispersion, le matériau minéral étant choisi parmi un matériau minéral de métal alcalino-terreux, l'argile, l'argile calcinée, le dioxyde de titane et leurs mélanges et l'agent de dispersion étant un dispersant contenant du polyacrylate. La divulgation concerne en outre des procédés de production d'une suspension aqueuse comprenant un matériau minéral et un agent de dispersion en combinaison avec un agent de codispersion et des suspensions aqueuses pouvant être obtenues par lesdits procédés. La divulgation concerne également une composition d'agent de dispersion comprenant un agent de dispersion en combinaison avec un agent de codispersion, l'agent de dispersion étant un dispersant contenant du polyacrylate et l'agent de co-dispersion étant du poly(alcool vinylique).
EP24700516.8A 2023-01-05 2024-01-02 Poly(alcool vinylique) en tant qu'agent de codispersion pour dispersions minérales Pending EP4646464A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US935418A (en) 1907-10-28 1909-09-28 George Sisson Method of producing magnesium carbonate.
US1361324A (en) 1918-03-18 1920-12-07 Nat Magnesia Mfg Company Process of manufacturing magnesium carbonate
GB548197A (en) 1941-02-24 1942-09-30 Ocean Salts Products Ltd Producing high quality magnesium compounds from magnesium-containing substances
GB544907A (en) 1941-02-24 1942-05-01 Ocean Salts Products Ltd Improvements relating to the production of magnesium basic carbonate, or magnesia
US3477970A (en) * 1962-09-04 1969-11-11 Du Pont Pigmented paper coating and adhesive compositions containing a polyvinyl alcohol binder and a modifier therefor
JPS63233011A (ja) * 1986-11-07 1988-09-28 Nippon Shokubai Kagaku Kogyo Co Ltd 炭酸カルシウム水分散液の製造方法
US5057570A (en) 1990-06-13 1991-10-15 Air Products And Chemicals, Inc. Polyvinyl alcohol resin soluble in high solids aqueous paper coating compositions without exernal heating
US5979461A (en) 1997-03-24 1999-11-09 Philip Morris Inc. Smoking article wrapper having filler of hydromagnesite/magnesium hydroxide and smoking article made with said wrapper
US6414065B1 (en) 1999-11-05 2002-07-02 Celanese International Corporation Multifunctional poly(vinyl alcohol) binder for fine particle size calcium carbonate pigment
EP1712523A1 (fr) 2005-04-11 2006-10-18 Omya Development AG Pigment à base de carbonate de calcium précipité pour le revetement de papier pour impression par jet d'encre
EP1712597A1 (fr) 2005-04-11 2006-10-18 Omya Development AG Procédé de préparation de carbonate de calcium précipité pour le revêtement de papier pour imprimante à jet d'encre et le carbonate de calcium précipité
SI2371766T1 (sl) 2010-04-01 2013-07-31 Omya Development Ag Postopek za pridobivanje oborine kalcijevega karbonata
PT2447213E (pt) 2010-10-26 2015-08-20 Omya Int Ag Produção de carbonato de cálcio de alta pureza
DK2524898T3 (en) 2011-05-16 2015-12-14 Omya Int Ag Process for the preparation of precipitated calcium carbonate from fiber pulp mill waste
CA2865647C (fr) 2012-03-23 2017-04-18 Omya International Ag Procede pour la preparation de carbonate de calcium precipite scalenoedrique
DK2641941T3 (en) * 2012-03-23 2015-08-24 Omya Int Ag Manufacture of pigments

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WO2024146883A1 (fr) 2024-07-11
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