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Paper Coating Formulas. Currently dominated by aqueous, pigmented systems. Pigment - 96 to 50% of total weight Calcium Carbonate and Kaolin dominate synthetic (poly-styrene) pigments Talc / Satinwhite / Aluminum Tri-hydrate etc…. Binder - 4 to 50% of total weight

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paper coating formulas
Paper Coating Formulas
  • Currently dominated by aqueous, pigmented systems.
    • Pigment - 96 to 50% of total weight
      • Calcium Carbonate and Kaolin dominate
        • synthetic (poly-styrene) pigments
        • Talc / Satinwhite / Aluminum Tri-hydrate etc….
    • Binder - 4 to 50% of total weight
      • Emulsion (Latex) polymers dominate
        • starches (corn, potato, tapioca)
        • milk (casein) and soy protein (isolate)
coating application metering
Coating Application / Metering
  • Most common metering processes
    • roll coating
    • blade coating
    • air knife coating
  • low impact coating
    • spray coating
      • wet / dry
    • curtain / slide / slot
coating application metering3
Coating Application / Metering
  • Current technology emphasizes random, uniform dispersion of all coating components prior to application
    • “condenses” as water removed
      • drainage to basestock
      • evaporation (active drying)
    • rheology optimized for metering processes
      • minimize particle - particle interactions
    • how to induce order (decrease entropy)
binder as a necessary evil here s the necessary part
Binder as a “necessary evil”(Here’s the necessary part)
  • Cohesion of coating is primary function
      • resist disruption by mechanical / physical (solvation) processes
  • Binder content contributes to properties
      • opacity / brightness (scattering)
      • permeability (air and liquid)
      • calender response
      • ink setting / print quality
binder as a necessary evil
Binder as a “necessary evil”
  • Expense
        • can be 10X versus mineral pigments
        • represent as much as 50% of total formula cost
  • handling / storage / preservation
        • “natural binders”
          • starches
          • proteins
  • environmental impact
        • latexes
          • non-renewable
          • slower to degrade
ain t nature grand
“Ain’t Nature Grand”
  • XXXXX rigid, cohesive structures in which adhesive materials are present at very low levels (< 2% by weight)
    • self-assembly
    • spatially specific deposition of adhesives
      • only where needed to reinforce structure
binder demand
“Binder Demand”
  • expression of adhesive required to hold structure together
      • often considered a function of (proportional to) pigment surface area
      • influenced by processes of migration and depletion
        • non-uniformity in coating composition
          • spatially / temporally
binder demand8
“Binder Demand”
  • expression of adhesive required to hold structure together
    • Latexes
      • physical entrainment within matrix
        • average diameter of discrete particles sets limit to pore size accessible to binder
        • coalescence during consolidation / drying
          • increases strength
      • at high binder levels, behavior like continuous film
binder demand9
“Binder Demand”
  • expression of adhesive required to hold structure together
    • solution polymers (starches, PvOH)
      • deposition results from “precipitation” out of continuous phase (water) as menisci recede through pore throats1
      • at high binder levels, behavior like continuous film
binder demand10
“Binder Demand”
  • expression of adhesive required to hold structure together
    • colloidal polymers (soy protein / casein)
      • cationic regions form strong electrostatic bonds to pigments
      • effective hydrated volume is large
        • image: Umaine photo?
where can nano help
Where can Nano help?
  • induction of selective deposition through mechanical / thermodynamic processes
    • binders deposited at points of contact between pigment particles
      • pigment surfaces modified to heighten attraction
      • binders placed on pigment surface prior to coating preparation / dispersion