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Stickies:

Stickies:. Richard A. Venditti(1), Mahendra Doshi(2) (1)North Carolina State University Dept. of Wood and Paper Science (2) Progress in Paper Recycling. Stickies. A sticky particle: is typically hydrophobic is tacky and depositable often DEPOSITS ON EQUIPMENT

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Stickies:

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  1. Stickies: Richard A. Venditti(1), Mahendra Doshi(2) (1)North Carolina State University Dept. of Wood and Paper Science (2) Progress in Paper Recycling

  2. Stickies A sticky particle: • is typically hydrophobic • is tacky and depositable • often DEPOSITS ON EQUIPMENT • Often adsorbs particulates/dissolved species • Examples of adsorbed species might include talc, Calcium Carbonate, Inks, Toners, polymers …

  3. What are stickies? Stickies in paper recycling are believed to be a mixture of ----Hot melts adhesives ----Pressure-sensitive adhesives (PSA’s) ----Wax ----Inks, Paper additives, Coating ----Wood derived extractives…

  4. *The actual surface behavior of stickies depends on the adsorbed species. PSA Surface PSA Surface with CaCO3

  5. Composition of Hot Melts • Vinyl Acetate Polymers and Copolymers • Tackifiers • Wax

  6. Properties of Hot Melts • 100 Percent Solid Formulations • Softens at 150OF to 250OF • Insoluble in Aqueous Media • Soluble in Many Organic Solvents • Density 0.9 to 1.0 g/cc

  7. Composition of PSA • Rubber Elastomer (e.g. Styrene-butadiene or poly acrylate) • Tackifier • Fillers (MgO. ZnO, etc.)

  8. Properties of PSA • Insoluble in Aqueous Media • Soluble in Many Organic Solvents • Density 0.9 to 1.1 g/cc

  9. CLASSIFICATION OF STICKIES SECONDARY PRIMARY (Formed in pulper) (Change in environment, pH, temp., etc.)

  10. MACRO VS MICRO STICKIES Macrostickies Retained on 6-cut (0.15 mm) slotted screen* Microstickies Accepted by 6-cut (0.15 mm) slotted screen* * Trend is towards 0.10 mm or 0.075 mm slotted screen

  11. Stickies-Related Problems • Product quality • Dirty spots in paper • Holes • Converting issues • Operational problem • Deposition on machine • Breaking web • Down time for cleaning

  12. Control and Removal Methods for Stickies • Use of environmentally benign adhesive (recyclable adhesive) • Avoidance: Control of recovered paper quality • Mechanical removal: screening and water clarification • Chemical control: polymers surfactants, others • Passivation with inorganics • Enzyme hydrolysis • Physical adsorption to paper fibers: retention • Dispersion • Protection: treatment of equipment to limit deposits • Mill shut down for clean-up

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