Behavior of Adhesives During Behavior of Adhesives During Paper - - PowerPoint PPT Presentation

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Behavior of Adhesives During Behavior of Adhesives During Paper - - PowerPoint PPT Presentation

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Behavior of Adhesives During Behavior of Adhesives During Paper Recycling Paper Recycling Steve Severtson, Jihui Guo, Haiyan Li, Helen Xu, Matt Dubay and Mark Calhoun University of Minnesota Carl Houtman USDA Forest Service, Forest Products

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SLIDE 1

Behavior of Adhesives During Behavior of Adhesives During Paper Recycling Paper Recycling

Steve Severtson, Jihui Guo, Haiyan Li, Helen Xu, Matt Dubay and Mark Calhoun University of Minnesota Carl Houtman USDA Forest Service, Forest Products Laboratory

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SLIDE 2

Water Based 59% Hot Melt 20% Solvent Based 9% Reactive 10% Other 2%

Polymer Wetting Agent Defoamer Tackifer Rheology Modifier

Water Based PSA

Emulsifier Tackifier Plasticizer Polymer Antioxidant

Hot Melt PSA

PSA Market Share and Composition PSA Market Share and Composition for Label Products for Label Products

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SLIDE 3

Project Objective Project Objective

Development of new pressure sensitive adhesive (PSA) products th Development of new pressure sensitive adhesive (PSA) products that are at are engineered for enhanced PSA removal during the screening of recy engineered for enhanced PSA removal during the screening of recycled fiber cled fiber

The impact on paper recycling operations should be a design parameter in the development of all PSA systems formulated for label applications

development of wet-end recipes for facestock that promotes PSA removal characterization of PSA- substrate adhesion and development of techniques for manipulating adhesion to enhance removal identification of properties that govern PSA removal and development of techniques for formulating benign PSAs

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SLIDE 4

Testing the Removal Efficiency of PSAs Testing the Removal Efficiency of PSAs

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Adirondack Formax Temperature Control Pulpers

  • consistency = 10%
  • 60 Hz (≈ 690 rpm)
  • typical time = 30 min.

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TAPPI Method T-205 om-88 Accepts Rejects

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Valley Flat Screen 15-cut screen (0.38 mm slots) Paper Shredder 1/4″ strips

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laminates are attached to sheets in a sample of copy paper PSA content = 0.5% PSA film is pressed onto facestock

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removal efficiency is quantified gravimetrically Removal Efficiency IA Area Fraction ∝ Cellulose Dissolution & Resin Oxidation (when required)

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SLIDE 5

Identification of Key Characteristics for Benign Materials Synthesis and Formulation

  • f Model and Commercial

Systems Laboratory and Pilot Testing of Screening Removal Efficiencies

Database Generation & Analysis

Output Commercially Feasible Benign Products Characterization of Bulk Mechanical and Surface Properties Input Access to Existing Product Lines Input Commercial Assessment

  • f New Product

Approaches

Research Strategy Research Strategy

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SLIDE 6

Easily Shaped for Characterization Melt Processing G′, G″, Tan δ 20-50 wt. % Base Polymer 30-60 wt. % Tackifier 0-25 wt. % Plasticizer

Hot Hot-

  • melt

melt PSA PSA’ ’s s

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SLIDE 7

Predicting Hot Predicting Hot-

  • melt PSA Recycling Performance

melt PSA Recycling Performance

0.5 1 1.5 2 2.5 3

  • 40 -20

20 40 60 80 100 120 140

Temperature (°C)

Commercial PSA 2

SAFT = 80 °C ΔT = 70 °C

ΔT

SAFT

3.5 2 4 6 8 10 12 14 16 18

Tan δ

Commercial PSA 1

SAFT = 57 °C ΔT = 59 °C

ΔT

SAFT

Commercial PSA 2

T50 = 80 °C α = 7.3 °C

20 40 60 80 100 20 40 60 80 100 120 Temperature (°C) Removal Efficiency (%)

Commercial PSA 1

T50 = 57 °C α = 6.2 °C Predicted Removal

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Emulsifier(s) Initiator(s) Buffer(s) Tackifying Dispersion(s) Monomers Adhesive Emulsion Crosslinking Agents Biocide(s) Formulated PSA Processing requires coating of low energy substrate and drying Wetting Agent(s) Rheology Modifiers Defoamer(s) Characterization samples restricted to thin films with properties dependent on formulation

Polymerization Formulation

G′, G″, Tan δ ?

Water Water-

  • based

based PSA PSA’ ’s s

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SLIDE 9

COO-

  • SO4

COO-

  • SO4
  • +-
  • +

+ + + + + + + + + + + + + +

COO-

carboxylate anions

  • n latex surface

positive counterions (Na+, K+, or NH4+) persulfate residues from initiator anionic and/or nonionic surfactants coiled, HMW polymer chains

+ + +

  • 1μm

Colloidal Dispersion of Spherical Polymer Particles in Water

PSA Latex PSA Latex

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SLIDE 10

Estim ated com positions of w ater Estim ated com positions of w ater-

  • based PSA latex

based PSA latex and film and film

0.05-0.68 0.08-0.93 Reducer & oxidizer 0.065-0.54 0.04-0.25 Biocide(s) 0.32-1.03 0.08-0.59 Buffer 0.12-0.55 0.08-0.31 Initiator(s) 2.13-9.86 1.21-6.58 Emulsifier(s) 88.93-97.79 50.21-61.46 Monomers 33.06-48.45 Water

Dried PSA film(Mass%) Coating ready emulsion dispersion (Mass%) Components

Note: The components of PSA latex film listed above refer to those in adhesive

  • emulsion. Formulated PSAs also contain coating package comprised of tackifying

dispersion(s), rheology modifier(s), wetting agent(s) and defoamer(s).

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Release Liner Release Liner Release Liner Facestock Release Liner Release Liner Facestock

TRANSFER COATING “cold flow” in addition to additive migration

Temperature/Relative Humidity

HIGH LOW

Time

Fate of Latex Additives Fate of Latex Additives

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Removal Efficiency NOT Controlled by Removal Efficiency NOT Controlled by Performance Properties Performance Properties

5 10 15 20 25 Peel Strength (N/25mm) 10 20 30 40 50 60 70 80 90 100 Removal Efficiency (%) 2 4 6 8 10 12 14 16 18 20 Loop Tack (N/25mm) 10 20 30 40 50 60 70 80 90 100 Removal Efficiency (%) 5 10 15 20 25 30 35 40 Shear (hr.) 10 20 30 40 50 60 70 80 90 100 Removal Efficiency (%) Commercial Water-based PSA 5 10 15 20 25 30 35 40 Surface Energy (mJ/m 2) 10 20 30 40 50 60 70 80 90 100 Removal Efficiency (%) Commercial Water-based PSA

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Composition of Model Systems Composition of Model Systems

Model System RE (%) Soft Monomer Hard Monomer Functional Monomer n-BA EHA MMA VA Styrene MAA AA M1 70.8 10.0 16.0 3.2 2 M2 70.8 10.0 16.0 3.2 57 M3 70.8 10.0 16.0 3.2 79 M4 70.8 10.0 16.0 3.2 10 M5 70.8 10.0 16.0 3.2 77 M6 70.8 10.0 16.0 3.2 70 M7 70.8 10.0 16.0 3.2 75 M8 80.8 16.0 3.2 90 M9 80.8 8.0 8.0 84 M10 80.8 16.0 3.2 90 M11 80.8 16.0 3.2 81

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Tensile Strength vs. Removal Tensile Strength vs. Removal

0.2 0.4 0.6 0.8 1 1.2 1.4

M1 M4 M 2 M 6 M 7 M 5 M 3 M 9 M 8

Model Water-based PSA Maximum Tensile Force (N) 10 20 30 40 50 60 70 80 90 100 Removal Efficiency (%)

Dry Tensile Force at 22°C

Maximum Tensile Force (N) 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45

M 4 M 1 M 2 M 6 M 7 M 5 M 3 M 9 M 8

Model Water-based PSA 10 20 30 40 50 60 70 80 90 100 Removal Efficiency (%)

50°C 22°C

Wet Tensile Force at 22 and 50°C

Jihui Guo, Steven J. Severtson and Larry G. Gwin INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 49(9), 2753-2759, 2007

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SLIDE 15

Microstructure Characterization of Microstructure Characterization of PSA film PSA film

AFM image Cryo SEM image

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SLIDE 16

Sample Piezoelectric (z) Stage (x,y)

z x y

Cantilever Tip

AFM of Adhesive Films AFM of Adhesive Films

Contact Mode Tapping Mode

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SLIDE 17

Surface morphologies of water Surface morphologies of water-

  • based

based PSA films PSA films

AFM image of PSA film Particle size distribution

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SLIDE 18

Surfactant Removal Surfactant Removal

Top surface of PSA latex film Solvent Soaking for 1 minute Solvent soaking for 5 minutes

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SLIDE 19

Effect of Moisture Cycles Effect of Moisture Cycles

Initial cycle 3% RH Increase moisture to 90% RH End cycle 3% RH

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SLIDE 20

Results Results

  • Water uptake of PSA films likely controls

behavior during paper recycling

  • Surfactants used to synthesize the original

polymers can migrate during processing

  • Physical properties of wet films can be used to

predict removal efficiency during screening

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SLIDE 21

Recycling Recycling-

  • compatible Adhesives

compatible Adhesives (RCA) (RCA)

  • A committee associated with the Tag and Label

Manufacturers Institute (TLMI) have developed test methods and specification for certifying an adhesive is RCA

  • Several label suppliers are now marketing labels with

RCA’s

  • State of Wisconsin is using this specification for

Governmental purchases

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SLIDE 22

Recycling Recycling-

  • compatible Adhesive Testing

compatible Adhesive Testing

Adirondack Pulper Temperature = 46º C Consistency = 15% 40 Hz (≈ 500 rpm) Time = 8 min. Accepts Rejects Valley Flat Screen 6-cut screen (0.15 mm slots) Paper Shredder 1/4″ strips PSA label is pressed onto envelope paper at 5% label stock by weight

Full description found at http://www.tlmi.com/recycling-standards.php

Denver Flotation Cell Accepts Handsheets Handsheets Handsheets

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SLIDE 23

Summary Summary

  • Removal efficiency of hot-melt PSAs can be predicted from its

dynamic mechanical and performance properties.

  • Water-based PSAs involve more complex formulations and
  • processing. Removal efficiency is determined by its strength when

saturated with water.

  • The removal efficiency of a PSA is strongly influenced by the overall

laminate design and its processing, e. g., the wet-strength of facestock properties can vary the removal efficiency of an attached PSA film by as much as 60%.

  • Test methods have been developed to certify Recycling-compatible

adhesives, and RCAs are now commercially available.

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SLIDE 24

Acknowledgements Acknowledgements

  • Department of Energy
  • United States Postal Service
  • Mark Kroll (H.B. Fuller)
  • Larry Gwin (Franklin International)
  • Jennifer Lien (Boise Solution)
  • Karen Scallon (FPL)
  • Mike Nowak (H.B. Fuller)