WO2001000712A1 - Dry pigment granulate and a method for the manufacture thereof - Google Patents

Dry pigment granulate and a method for the manufacture thereof Download PDF

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Publication number
WO2001000712A1
WO2001000712A1 PCT/FI2000/000563 FI0000563W WO0100712A1 WO 2001000712 A1 WO2001000712 A1 WO 2001000712A1 FI 0000563 W FI0000563 W FI 0000563W WO 0100712 A1 WO0100712 A1 WO 0100712A1
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WO
WIPO (PCT)
Prior art keywords
pigment
granulate
styrene
dry
pigments
Prior art date
Application number
PCT/FI2000/000563
Other languages
French (fr)
Inventor
Mikael Skrifvars
Toivo Kärnä
Jukka Koskinen
Hanna Laamanen
Nikitas Katsaras
Original Assignee
Dynea Chemicals Oy
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 Dynea Chemicals Oy filed Critical Dynea Chemicals Oy
Priority to EP00940438A priority Critical patent/EP1196479A1/en
Priority to AU55375/00A priority patent/AU5537500A/en
Publication of WO2001000712A1 publication Critical patent/WO2001000712A1/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
    • C09D11/037—Printing inks characterised by features other than the chemical nature of the binder characterised by the pigment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
    • C09D133/04—Homopolymers or copolymers of esters
    • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09D133/062—Copolymers with monomers not covered by C09D133/06
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/65—Additives macromolecular
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/66—Additives characterised by particle size
    • C09D7/69—Particle size larger than 1000 nm
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/36—Coatings with pigments
    • D21H19/38—Coatings with pigments characterised by the pigments
    • D21H19/42—Coatings with pigments characterised by the pigments at least partly organic
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
    • C08J2325/02—Homopolymers or copolymers of hydrocarbons
    • C08J2325/04—Homopolymers or copolymers of styrene
    • C08J2325/06—Polystyrene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
    • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C08J2333/10—Homopolymers or copolymers of methacrylic acid esters
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/24—Acids; Salts thereof
    • C08K3/26—Carbonates; Bicarbonates
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/14—Polymer mixtures characterised by other features containing polymeric additives characterised by shape
    • C08L2205/18—Spheres
    • C08L2205/20—Hollow spheres
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
    • C08L25/02—Homopolymers or copolymers of hydrocarbons
    • C08L25/04—Homopolymers or copolymers of styrene
    • C08L25/06—Polystyrene

Definitions

  • Dry pigment granulate and a method for the manufacture thereof
  • the present invention relates to dry pigment granulates comprising organic hollow and/or solid pigments for paper coating, plastic mixtures, paints, coatings and printing inks, especially for fine paper and to a method for the manufacture thereof.
  • Inorganic pigments such as clay, caolin, calcium carbonate and titanium dioxide are used in paper coatings to provide a surface with a desired appearance and printability.
  • Organic pigments commonly referred to as plastic pigments, are used as partial replacement for inorganic pigments to improve the optical print properties for coated paper and paper board.
  • Two general classes of plastic pigments e.g. solid bead and hollow sphere pigments, are used in the preparation of coatings for paper and paper board.
  • Plastic pigments enhance the performance of pigmented coatings for paper and paper board in a variety of ways. In most cases they are used as additives where they are substituted for mineral pigments in the range of 3-20 % by dry weight of pigments.
  • Plastic pigments enhance the optical performance of coatings by increasing sheet gloss, brightness and opacity.
  • Plastic pigments are generally supplied as polymer particles dispersed in water or as latex where the solid content varies between 25 and 60 wt%.
  • plastic pigments Water dispersions of plastic pigments are shipped and stored in tanks, drums or the like and during longterm storage settling can occur. Additionally, plastic pigments are not normally freeze and thaw stable, therefore freezing must be avoided. Long term storage may also cause microbial growth, such as bacterial and fungicidal growth, which has to be prevented by toxic additives.
  • a further disadvantage of plastic pigment dispersions is the costs related to the transport of large volumes of water. The addition of plastic pigment dispersions with low solid contents will also increase the amount of water in paper coating formulations, which in turn will require a lot of heating energy to evaporate water from the coating and to dry the coated paper.
  • EP-06146766 discloses a coated paper suitable for ink fusion thermal transfer and manufacture thereof.
  • the uppermost layer of the recording layer of the paper comprises at least 100 parts by weight of a pigment and 10-50 parts by weight of a binder, and 30-70 wt% of the pigment consist of
  • Synthetic silica having a specific surface area of 20-600 m /g.
  • Synthetic silica is blended in the coating solution containing pigment.
  • Suitable pigments are inorganic pigments and organic pigments, such as fine particles of styrene resins or acrylic resins, and they may be hollow particles of polystyrene or styrene methyl methacrylate copolymers.
  • the binder may be a resin, emulsion, latex or natural high polymer and suitable binders are polyvinyl alcohol, starches, fibre derivatives such as carboxy methyl cellulose, styrene acrylic resins and the like. Additionally dyes or coloured pigments may be added to adjust the colour of the coating.
  • the coating solution is manufactured by blending the components with each other.
  • FI-970936 discloses a method for the preparation of hollow polymer particle latex useful in coating applications, by emulsion copolymerization.
  • the method comprises the preparation of seed latex with a water-soluble initiator and an anionic surfactant, followed by the preparation of latex of a highly carboxylated copolymer on the seed latex, then further preparing an intermediate shell, then swelling the particles and finally preparing a hard shell on the swollen expanded particles and optionally preparing an external shell on the hard shell.
  • plastic pigments according to prior art become dusty powders with a particle size of 1-50 ⁇ m, which powders are difficult to handle and thus dry plastic pigments are not commonly used. Based on the above it can be seen that there exists a need for plastic pigments which are easy to handle and to blend with other ingredients needed for applications, such as paper coating, and without the need to transport large amounts of water.
  • An object of the invention is to provide dry pigment granulate comprising organic hollow and/or solid pigments for applications, such as paper coating, and especially for fine paper, coated paper board, plastic mixtures, paints, coatings and printing inks and to provide a method for the manufacture thereof.
  • a further object of the invention is to provide dry pigment granulate comprising organic hollow and/or solid pigments, which can be easily handled at a paper mill, and a method for the manufacture thereof.
  • dry pigment granulate comprising organic hollow and/or solid pigments, and by the method for the manufacture thereof according to the invention.
  • dry pigment granulate comprising organic hollow and/or solid pigments for paper coating and especially for fine paper can be manufactured by granulating pigment particles, preferably by spray-drying, with a suitable binder or a mixture of binders, and preferably with binders which also are commonly used in paper coating application.
  • the binder binds the particles in to agglomerates, which are easy to handle in powder form without dusting problems.
  • Suitable organic pigments for granulating are organic hollow or solid polymer pigments i.e. fine particles of styrene based polymers such as polystyrene, fine particles of acrylic resins such as polymethyl methacrylate, polyacrylate, polyacrylonitrile and fine particles of polyvinyl chloride or polycarbonates or copolymers thereof or combinations thereof. Also melamine-formaldehyde and urea- formaldehyde pigment particles may be used.
  • Preferred organic pigments are hollow particles of polystyrene or styrene methyl methacrylate copolymers.
  • organic pigments are polyacrylate, polystyrene and copolymers thereof and melamine-formaldehyde and urea-formaldehyde pigments.
  • the binder may be a resin, an emulsion, a latex or a natural high polymer or a compound which preferably is used in paper coating applications.
  • suitable binders are polyvinyl alcohol, polyvinylacetate, styrene-butadiene latex, polyethylene glycol, polyethylene wax, calcium stearate, cellulose derivatives, such as carboxy methyl cellulose, hydroxy ethyl cellulose and similar compounds.
  • Carboxy methyl cellulose is especially suitable because it is used in paper manufacture as a thickener in sizing pastes, for improving retention and for binding and it is easy to handle.
  • Styrene-butadiene latex, polyvinyl acetate and carboxymethyl cellulose are particularly suitable when inorganic pigments are also used.
  • inorganic pigment is incorporated into the dry pigment granulate.
  • Suitable inorganic pigments are caolin, calcium carbonate, (GCC and PCC), titanium dioxide and other white inorganic pigments. Dry white pigment granulates are specially suitable for paper coating, plastic mixtures, paints and printing inks.
  • the particle size of the organic pigment in the dispersion to be granulated is typically 120-2000 nm.
  • the pigment granulate comprises 5-99.5 wt% of organic polymer pigment, 0-94.5 wt% of inorganic pigment and 0.5-5 wt% of a binder or a mixture of binders. Additionally the granulate may contain other components such as whitening agents, antistatic agents and antibacterial agents.
  • the particle size of the spray-dried granulate is between 4 and 400 ⁇ m, and preferably between 100 and 300 ⁇ m in the case no inorganic pigment is used.
  • the particle size of the dry pigment granulate comprising organic hollow and/or solid particles and inorganic pigment or pigments is typically 4-60 ⁇ m, with an average of approx. 25 ⁇ m.
  • the method for the manufacture of dry pigment granulate comprises spray-drying of a pigment particle dispersion having a dry solid content of 15-75 vol%, preferably 30-65 vol%.
  • a binder as such or as a water solution is blended with the organic pigment particles and water in a high speed mixer and then the mixture is granulated by spraying using any suitable spray-drying apparatus known in the art.
  • the binder or a mixture of binders are preferably dispensed in water to obtain a water solution containing 0.5-20 wt% of the binder, before blending with the pigment particles and spray-drying.
  • Other additives, such as whitening agents, antistatic agents or antimicrobial agents may be incorporated in the water solution.
  • the inorganic pigment is slurried in water (when solid form), the obtained slurry is blended with the organic pigment particle dispersion, desired additives are added and the mixture is spray-dried.
  • desired additives are added and the mixture is spray-dried.
  • the granulate according to the invention can also readily be used in coatings like paints, in thermoplastics, plastic mixtures, printing inks, in decorative paper applications and as fillers in concrete.
  • FIG. 1 An example of an equipment which is suitable for spray-drying of the granulates is provided in Figure 1.
  • Figure 1 is presented a spray-drying apparatus with A product inlet, B gas/steam, C air inlet, D compressed air inlet, E product outlet, F air outlet, G retained particles, and 1 represents feed tank, 2 nozzle atomizer, 3 drying chamber, 4 fluid bed, 5 cyclon separator, 6 filter and 7 secondary product inlet.
  • the product is fed to the atomizer system and sprayed downwards in the drying chamber co-currently with hot drying air.
  • the required moisture is reached in the fluid bed, wherefrom the powder is taken out.
  • Primary drying air is directed into the drying chamber through an air distributor at a top. Secondary air enters through the bed and mixes with a primary air.
  • Fine powder particles in the spent drying air are caught by the wet droplets in the atomization zone and move with these into the fluid bed. Any fine material which is not caught this way is conveyed with the exhaust air to the cyclone collector, where it is separated from the air and returned to the atomization zone or the fluid bed.
  • Spray-drying granulating was performed by using spray-bed with a high pressure nozzle at the top, and a fluid bed at the air bottom. The fines were recirculated.
  • the operating conditions were the following:
  • Spray-drying granulating was performed in a similar way as was described in Example 1.
  • the operating conditions were the following:
  • the total spraying time was 35 min.
  • Granulated hollow polymer particles with the following characteristics were obtained at the product outlet:
  • Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
  • Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
  • Example 5 0.04 wt% of Dispex N40 (0.12 g) with respect to inorganic pigment was added to 1 litre of water, and the pH of the mixture was adjusted to alkaline (8.5) with NaOH. 300 g of calcium carbonate (PCC-10) was added to the mixture with vigorous agitation and a homogeneous slurry was obtained. Then 6 kg of organic polymer pigment and a sufficient amount of water were added to obtain a suitable dispersion for spray-drying.
  • PCC-10 calcium carbonate
  • Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
  • Dry pigment granulate comprising organic polymer pigment according to example
  • Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
  • Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
  • the spray-drying of disperions from Examples 3-8 was performed at drying temperature of approx. 180 °C and at cyclone temperature of approx. 80 °C.
  • the homogeneous granulate particles had a particle size of 4-60 ⁇ m, with an average of approx. 25 ⁇ m.

Abstract

The present invention relates to dry pigment granulates comprising hollow and/or solid pigments for paper coating, especially for fine paper and to a method for the manufacture thereof. The pigment granulate comprises 95-99.5 wt% of organic polymer pigment, 0-94.5 wt% of inorganic pigment and 0.5-5 wt% of a binder or a mixture of binders and the particle size of the granulate is 4-400 νm.

Description

Dry pigment granulate and a method for the manufacture thereof
The present invention relates to dry pigment granulates comprising organic hollow and/or solid pigments for paper coating, plastic mixtures, paints, coatings and printing inks, especially for fine paper and to a method for the manufacture thereof.
Inorganic pigments such as clay, caolin, calcium carbonate and titanium dioxide are used in paper coatings to provide a surface with a desired appearance and printability. Organic pigments, commonly referred to as plastic pigments, are used as partial replacement for inorganic pigments to improve the optical print properties for coated paper and paper board. Two general classes of plastic pigments, e.g. solid bead and hollow sphere pigments, are used in the preparation of coatings for paper and paper board. Plastic pigments enhance the performance of pigmented coatings for paper and paper board in a variety of ways. In most cases they are used as additives where they are substituted for mineral pigments in the range of 3-20 % by dry weight of pigments. Plastic pigments enhance the optical performance of coatings by increasing sheet gloss, brightness and opacity. Plastic pigments are generally supplied as polymer particles dispersed in water or as latex where the solid content varies between 25 and 60 wt%.
Water dispersions of plastic pigments are shipped and stored in tanks, drums or the like and during longterm storage settling can occur. Additionally, plastic pigments are not normally freeze and thaw stable, therefore freezing must be avoided. Long term storage may also cause microbial growth, such as bacterial and fungicidal growth, which has to be prevented by toxic additives. A further disadvantage of plastic pigment dispersions is the costs related to the transport of large volumes of water. The addition of plastic pigment dispersions with low solid contents will also increase the amount of water in paper coating formulations, which in turn will require a lot of heating energy to evaporate water from the coating and to dry the coated paper.
EP-06146766 discloses a coated paper suitable for ink fusion thermal transfer and manufacture thereof. A coated paper giving excellent image reproduction when used in ink fusion transfer type thermal printers and copiers with also high gloss in both the non-image and image parts, is described. The uppermost layer of the recording layer of the paper comprises at least 100 parts by weight of a pigment and 10-50 parts by weight of a binder, and 30-70 wt% of the pigment consist of
2 synthetic silica having a specific surface area of 20-600 m /g. Synthetic silica is blended in the coating solution containing pigment. Suitable pigments are inorganic pigments and organic pigments, such as fine particles of styrene resins or acrylic resins, and they may be hollow particles of polystyrene or styrene methyl methacrylate copolymers. The binder may be a resin, emulsion, latex or natural high polymer and suitable binders are polyvinyl alcohol, starches, fibre derivatives such as carboxy methyl cellulose, styrene acrylic resins and the like. Additionally dyes or coloured pigments may be added to adjust the colour of the coating. The coating solution is manufactured by blending the components with each other.
FI-970936 discloses a method for the preparation of hollow polymer particle latex useful in coating applications, by emulsion copolymerization. The method comprises the preparation of seed latex with a water-soluble initiator and an anionic surfactant, followed by the preparation of latex of a highly carboxylated copolymer on the seed latex, then further preparing an intermediate shell, then swelling the particles and finally preparing a hard shell on the swollen expanded particles and optionally preparing an external shell on the hard shell.
When spray-dried, plastic pigments according to prior art become dusty powders with a particle size of 1-50 μm, which powders are difficult to handle and thus dry plastic pigments are not commonly used. Based on the above it can be seen that there exists a need for plastic pigments which are easy to handle and to blend with other ingredients needed for applications, such as paper coating, and without the need to transport large amounts of water.
An object of the invention is to provide dry pigment granulate comprising organic hollow and/or solid pigments for applications, such as paper coating, and especially for fine paper, coated paper board, plastic mixtures, paints, coatings and printing inks and to provide a method for the manufacture thereof.
A further object of the invention is to provide dry pigment granulate comprising organic hollow and/or solid pigments, which can be easily handled at a paper mill, and a method for the manufacture thereof.
Characteristic features of the dry pigment granulate comprising organic hollow and/or solid pigments, and of the method for the manufacture thereof are stated in the claims.
The disadvantages of the dusty plastic pigments according to the state of the art can be avoided or significantly reduced by the dry pigment granulate comprising organic hollow and/or solid pigments, and by the method for the manufacture thereof according to the invention. It has bees noted that dry pigment granulate comprising organic hollow and/or solid pigments for paper coating and especially for fine paper can be manufactured by granulating pigment particles, preferably by spray-drying, with a suitable binder or a mixture of binders, and preferably with binders which also are commonly used in paper coating application. The binder binds the particles in to agglomerates, which are easy to handle in powder form without dusting problems.
Suitable organic pigments for granulating are organic hollow or solid polymer pigments i.e. fine particles of styrene based polymers such as polystyrene, fine particles of acrylic resins such as polymethyl methacrylate, polyacrylate, polyacrylonitrile and fine particles of polyvinyl chloride or polycarbonates or copolymers thereof or combinations thereof. Also melamine-formaldehyde and urea- formaldehyde pigment particles may be used. Preferred organic pigments are hollow particles of polystyrene or styrene methyl methacrylate copolymers. When inorganic pigments are also incorporated in the pigment granulate, preferable organic pigments are polyacrylate, polystyrene and copolymers thereof and melamine-formaldehyde and urea-formaldehyde pigments.
The binder may be a resin, an emulsion, a latex or a natural high polymer or a compound which preferably is used in paper coating applications. Examples of suitable binders are polyvinyl alcohol, polyvinylacetate, styrene-butadiene latex, polyethylene glycol, polyethylene wax, calcium stearate, cellulose derivatives, such as carboxy methyl cellulose, hydroxy ethyl cellulose and similar compounds. Carboxy methyl cellulose is especially suitable because it is used in paper manufacture as a thickener in sizing pastes, for improving retention and for binding and it is easy to handle. Styrene-butadiene latex, polyvinyl acetate and carboxymethyl cellulose are particularly suitable when inorganic pigments are also used.
When dry white pigment granulate is desired also inorganic pigment is incorporated into the dry pigment granulate. Suitable inorganic pigments are caolin, calcium carbonate, (GCC and PCC), titanium dioxide and other white inorganic pigments. Dry white pigment granulates are specially suitable for paper coating, plastic mixtures, paints and printing inks.
The particle size of the organic pigment in the dispersion to be granulated is typically 120-2000 nm. The pigment granulate comprises 5-99.5 wt% of organic polymer pigment, 0-94.5 wt% of inorganic pigment and 0.5-5 wt% of a binder or a mixture of binders. Additionally the granulate may contain other components such as whitening agents, antistatic agents and antibacterial agents. The particle size of the spray-dried granulate is between 4 and 400 μm, and preferably between 100 and 300 μm in the case no inorganic pigment is used. The particle size of the dry pigment granulate comprising organic hollow and/or solid particles and inorganic pigment or pigments is typically 4-60 μm, with an average of approx. 25 μm.
The method for the manufacture of dry pigment granulate comprises spray-drying of a pigment particle dispersion having a dry solid content of 15-75 vol%, preferably 30-65 vol%. A binder as such or as a water solution is blended with the organic pigment particles and water in a high speed mixer and then the mixture is granulated by spraying using any suitable spray-drying apparatus known in the art. The binder or a mixture of binders are preferably dispensed in water to obtain a water solution containing 0.5-20 wt% of the binder, before blending with the pigment particles and spray-drying. Other additives, such as whitening agents, antistatic agents or antimicrobial agents may be incorporated in the water solution.
In the case inorganic pigments are used the inorganic pigment is slurried in water (when solid form), the obtained slurry is blended with the organic pigment particle dispersion, desired additives are added and the mixture is spray-dried. Preferable inorganic pigments are caolin, calcium carbonate (GCC = ground calcium carbonate or PCC = precipitated calcium carbonate) and titanium dioxide.
One of the most important applications of the invention is the use of the granulated pigment in coating of fine paper, in printing and for coated paper board, but the granulate according to the invention can also readily be used in coatings like paints, in thermoplastics, plastic mixtures, printing inks, in decorative paper applications and as fillers in concrete.
An example of an equipment which is suitable for spray-drying of the granulates is provided in Figure 1. In Figure 1 is presented a spray-drying apparatus with A product inlet, B gas/steam, C air inlet, D compressed air inlet, E product outlet, F air outlet, G retained particles, and 1 represents feed tank, 2 nozzle atomizer, 3 drying chamber, 4 fluid bed, 5 cyclon separator, 6 filter and 7 secondary product inlet. The product is fed to the atomizer system and sprayed downwards in the drying chamber co-currently with hot drying air. The required moisture is reached in the fluid bed, wherefrom the powder is taken out. Primary drying air is directed into the drying chamber through an air distributor at a top. Secondary air enters through the bed and mixes with a primary air. Fine powder particles in the spent drying air are caught by the wet droplets in the atomization zone and move with these into the fluid bed. Any fine material which is not caught this way is conveyed with the exhaust air to the cyclone collector, where it is separated from the air and returned to the atomization zone or the fluid bed.
The invention is illustrated in more detail with the following examples to which the scope of the invention is not limited.
Example 1
Spray-drying granulating was performed by using spray-bed with a high pressure nozzle at the top, and a fluid bed at the air bottom. The fines were recirculated.
37.5 kg of hollow particle polyacrylate-polystyrene based polymer dispersion with a solid content of approx. 30 wt% and 4.2 kg of a 10 % polyvinyl alcohol - water solution were mixed a high speed mixer. The solution was then fed into the cyclon via the nozzle atomizer.
The operating conditions were the following:
Inlet temperature 152°C Outlet temperature 59 C Inlet to fluid bed 70°C Fluid bed 54°C Nozzle pressure 130 bar The total spraying time was 57 min.
Granulated hollow polymer particles with the following characteristics where obtained at the product outlet:
Particle size 240 μm Untapped density: 0.24 g/1,
Tapped density: 0.27 g/1, Water content 0.9 %
Example 2
Spray-drying granulating was performed in a similar way as was described in Example 1.
38.8 kg of hollow particle polyacrylate-polystyrene based polymer disspersion with a solid content of approx. 30 wt% and 1.5 kg of a 10 % carboxy methyl cellulose - water solution were mixed with a high speed mixer. The solution was then fed into the cyclon via the nozzle atomizer.
The operating conditions were the following:
Inlet temperature 165 O C,
Outlet temperature 68 O C,
Inlet to fluid bed 70 O C,
Fluid bed 65°C Nozzle pressure 130 bar
The total spraying time was 35 min. Granulated hollow polymer particles with the following characteristics were obtained at the product outlet:
Particle size 280 μm
Untapped density: 0.24 g/1 Water content 1.0 %
Example 3
Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
0.04 wt% of Dispex N40 (0.4 g) with respect to inorganic pigment was added to 1 litre of water, and the pH of the mixture was adjusted to alkaline (8.5) with
NaOH. 600 g of calcium carbonate (PCC-40) was added to the mixture with vigorous agitation and a homogeneous slurry was obtained. Then 3 kg of organic polymer pigment and a sufficient amount of water were added to obtain a suitable dispersion for spray-drying.
Example 4
Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
0.04 wt% of Dispex N40 (0.12 g) with respect to inorganic pigment was added to 1 litre of water, and the pH of the mixture was adjusted to alkaline (8.5) with NaOH. 300 g of calcium carbonate (PCC-10) was added to the mixture with vigorous agitation and a homogeneous slurry was obtained. Then 6 kg of organic polymer pigment and a sufficient amount of water were added to obtain a suitable dispersion for spray-drying. Example 5
Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
2 wt% of Dispex N40 (12 g) with respect to inorganic pigment was added to 1 litre of water. 600 g of caolin-40 was added to the mixture with agitation and a homogeneous slurry was obtained. Then 3 kg of organic polymer pigment and a sufficient amount of water were added to obtain a suitable dispersion for spray- drying.
Example 6
Dry pigment granulate comprising organic polymer pigment according to example
1 and inorganic pigment.
2 wt% of Dispex N40 (6 g) with respect to inorganic pigment was added to 1 litre of water. 300 g of caolin- 10 was added to the mixture with agitation and a homogeneous slurry was obtained. Then 6 kg of organic polymer pigment and a sufficient amount of water were added to obtain a suitable dispersion for spray- drying.
Example 7
Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
600 g of titanium-dioxide -40 was added to 1 litre of water with agitation and a homogeneous slurry was obtained. Then 3 kg of organic polymer pigment was added and a dispersion was obtained for spray-drying. Example 8
Dry pigment granulate comprising organic polymer pigment according to example 1 and inorganic pigment.
300 g of titanium-dioxide -10 was added to 1 litre of water with agitation and a homogeneous slurry was obtained. Then 6 kg of orgamc polymer pigment was added and a dispersion for spray-drying was obtained
The spray-drying of disperions from Examples 3-8 was performed at drying temperature of approx. 180 °C and at cyclone temperature of approx. 80 °C. The homogeneous granulate particles had a particle size of 4-60 μm, with an average of approx. 25 μm.

Claims

Claims
1. Dry pigment granulate, characterized in that it comprises 5-99.5 wt% of an organic polymer pigment, 0-94.5 wt% of an inorganic pigment and 0.5-5 wt% of a binder or a mixture of binders and the particle size of the granulate is 4-400 μm.
2. Dry pigment granulate according to claim 1, characterized in that the organic polymer is styrene based polymer, acrylic resin, polyvinyl alcohol, polyacrylonitrile, melamine-formaldehyde, urea- formaldehyde, polyacrylate, polycarbonate or a copolymer thereof and preferably a hollow particle polymer of styrene, styrene metyl methacrylate or polyacrylate.
3. Dry pigment granulate according to claim 1 or 2, characterized in that the inorganic pigment is caolin, calcium carbonate or titanium dioxide.
4. Dry pigment granulate according to any one of claims 1-3, characterized in that the binder is polyvinyl alcohol, polyethylene glycol, polyethylene wax, polyvinylasetate, styrene-butadiene latex or a cellulose derivative, preferably carboxy methyl cellulose, styrene-butadiene latex or polyvinylacetate.
5. Dry pigment granulate according to any one of claims 1-4, characterized in that the granulate comprises additives, preferably whitening agents, antistatic agents and antimicrobial agents.
6. Method for the manufacture of pigment granulate, characterized in that the method comprises followings steps: a) mixing pigment(s), binder(s), water and optionally additives into a dispersion, b) spray-drying the dispersion obtained from a).
7. Method for the manufacture of organic pigment granulate according to claim 6, characterized in that the solid content in the dispersion is 5-75 wt-%, preferably 30-65 wt%.
8. Use of a pigment granulate according to any one of claims 1-5 or obtained according to claim 6 or 7 in paper coating, in thermoplastics in printing inks, in decorative papers, in coatings, in paints in plastic mixtures, in coated paper boards and in concrete fillers.
PCT/FI2000/000563 1999-06-24 2000-06-22 Dry pigment granulate and a method for the manufacture thereof WO2001000712A1 (en)

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WO2001060510A1 (en) * 2000-02-18 2001-08-23 Dynea Chemicals Oy Process for making cationic hollow particle latex and a composition obtainable therefrom useful for coating and/or impregnating
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WO2013060657A1 (en) * 2011-10-26 2013-05-02 Akzo Nobel Coatings International B.V. Improved solvent-free low energy coatings
WO2015051364A1 (en) * 2013-10-05 2015-04-09 Omnova Solutions Inc Supraparticles including hollow polymeric particles
WO2017062538A1 (en) * 2015-10-09 2017-04-13 Rohm And Haas Company Hollow polymer composition
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AU5537500A (en) 2001-01-31
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FI991438A (en) 2000-12-25

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