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CaCO 3 Coating Immobilization Technical Concepts and Importance to Quality

This presentation outlines the critical concepts and laboratory techniques for coating immobilization, focusing on soy protein polymers. Factors affecting coating immobilization, process conditions, and critical concentrations are discussed. The discussion also covers the comparison of faster and slower coating immobilization methods and strategies for improving immobilization. The role of soy protein polymers in coating properties and their interactions with pigment are highlighted. The mechanism of coating immobilization with soy protein polymers is explained, emphasizing the importance of good immobilization control for enhancing quality.

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CaCO 3 Coating Immobilization Technical Concepts and Importance to Quality

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  1. CaCO3 Coating ImmobilizationTechnical Concepts and Importance to Quality Team Management Meeting, 8 March 2001 Donald Hiscock DuPont Soy Polymers St. Louis, Missouri, USA

  2. Presentation Outline • Introduction -- Importance of Immobilization • Theoretical Concepts • Laboratory Techniques • Immobilization Mechanism of Soy Protein Polymers • Machine Trial Results • Summary

  3. Factors Affecting Coating Immobilization • Base Sheet • structure, porosity • Pigment • particle size, packing characteristics • Cobinders • Aqueous phase coating viscosity, interaction between components • Process Conditions on Coater

  4. Impacts of Coating Immobilization • Coating Uniformity • print mottle, binder migration • Coating Holdout • fiber coverage • Coating Microporosity • glueability, ink receptivity

  5. Coating Process • Application (roll, fountain, etc) • Metering (blade, bar, air knife, etc) • Drying • Dewatering into base sheet • Evaporation Immobilization of Coating

  6. Immobilization ConceptsCritical Concentrations • Initially: Wet Coating, Gloss ­ Water Phase Dispersed (Solid) Phase

  7. Immobilization ConceptsCritical Concentrations • First Critical Concentration: Gloss ¯

  8. Immobilization ConceptsCritical Concentrations • Second Critical Concentration: Opacity ­

  9. } Maximum Coating Volume Immediately After Metering · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · • Faster Coating Immobilization: • Better Coating Holdout • Greater Void Volume and Structure • More Uniform Distribution of Binder } · · · · · · · · · · · · · · · · · · · · · • Slower Coating Immobilization: • Less Coating Holdout • Less Void Volume Due to More Pigment Packing • Less Uniform Distribution of Binder } · · · · · · · · · · · · · · · · · · · · · Rapid Immobilization Improves Quality • Comparison of two coatings: Time

  10. After Blade (or Rod, or AK) Faster Water Release During Application and Metering Good Water Holding Needed Water Holding / Water Release • Controlled Water Holding is NeededNeeded for Runnability in Application, MeteringNot needed for Immobilization after Metering

  11. Viscosity Immobilization Point • Water Loss from Coating Leads to Higher Viscosity • Viscosity Immobilization Solids similar to FCC, but lower.

  12. Viscosity Immobilization Solids (VIMS) • Solids Content where no further redistribution of coating components can occur. • Viscosity too high for components to change distribution, although shrinkage can still occur. • For laboratory convenience, use 20000 mPa·s, Brookfield 10 min-1.

  13. Laboratory Measurement of VIMS • Prepare coating at high solids content. • Measure viscosity using Brookfield 10 min-1 to simulate static conditions after metering. • Dilute coating, re-measure to obtain 3-5 data points. • Graph using semi-log axes to make extrapolation to VIMS point easier. • Compare difference from running solids to VIMS.

  14. Slower to Immobilize Faster to Immobilize Typical VIMS Graph -- Linear

  15. Strategies for Improving Immobilization • Operating ConditionsRunning Solids as high as possibleWatch for problems with coat weight control, cross-machine profile, blade runnability. • Formulation DesignImmobilization control agent to lower difference from running solids to immobilization.

  16. Properties of Soy Protein Polymers • Water-soluble polymers from soybean protein. • Amphoteric, (positive and negative charges). • Chemically-Modified for viscosity and charge control. • Dry powders, dissolved in water under alkaline conditions. • Range of viscosity and pigment-reactivity levels to suit different applications.

  17. Functions of Soy Protein Polymers • Pigment-interactive; product charge. • Water Holding; hydrated polymer. • Viscosity modifying: long-chain dissolved molecule and pigment interaction. • Good running; protective colloid action. • Binder

  18. Effects on Coating Propertiesfrom Soy Protein Polymers • Microporosity + Bulkhigher coating void volume from pigment interaction. • Ink Hold Out + Fountain Solution Acceptance controlled pore size distribution; good ink gloss and minimizes water interference on the press. • Binder Migration + Mottle Controlrapid immobilization; uniform distribution of components. • Stiffness + Non-Thermoplasticityfrom polymer properties

  19. Interaction of Soy Protein Polymers with Pigment • Amphoteric Protein adsorbs to dispersed pigment • Part on pigment surface, part in water phase In Water Phase Adsorbed on Pigment

  20. { } Mechanism of Coating Immobilization withSoy Protein Polymers • Increase in effective volume of pigment due to adsorbed protein. Coatings without Structuring Agent have More Dense Pigment Packing Coatings with Adsorbed Protein have More Open Packing, More Void Volume in Dried Coating

  21. Conclusions • Good immobilization control is important to quality. • Immobilization determined by base sheet, operating conditions, coating formulation. • Soy protein polymers interact with pigments, and help coating immobilize quickly.

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