Adhesives Mag logo
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
Adhesives Mag logo
  • NEW PRODUCTS
  • NEWS
    • Adhesives & Sealants Headlines
    • Mergers/Acquisitions
    • Events Calendar
    • Market Trends
  • TOPICS
    • Finished Adhesives and Sealants
    • Pressure-Sensitive Adhesives (PSAs)
    • Coatings
    • Raw Materials and Chemicals
    • Materials Handling/Processing
    • Meter/Mix/Dispense
    • Curing
    • Testing/Quality Control
    • Packaging of Adhesives & Sealants
    • Converting/Packaging
    • Composites
    • Sustainability
  • COLUMNS
    • European Perspectives
    • Strategic Solutions
    • Supply Chain Strategies
    • Tape Talk
  • TOP 20
  • MULTIMEDIA
    • Videos
    • Podcasts
    • Webinars
    • eBooks
  • EXPLORE
    • Adhesives in Action
    • Blog
    • ASI Store
    • Industry Links
    • Market Research
    • Classifieds
  • DIRECTORIES
    • Buyers' Guide
    • Global Adhesives & Sealants Directory
    • Raw Materials, Chemicals, Polymers and Additives Handbook
    • Equipment Handbook
    • Distributor Directory
  • EMAGAZINE
    • EMAGAZINE
    • ARCHIVE ISSUES
    • ADVERTISE
      • Custom Content & Marketing Services
    • CONTACT
  • SIGN UP!
SustainabilityPressure-Sensitive Adhesives (PSAs)FormulatorsManufacturers

Recycling Pressure-Sensitive Products

By Jihui Guo, Larry Gwin, Carl Houtman, Mark Kroll, Steven J. Severtson
asi0412-UnivMinn-equation-slide.jpg
asi0412-UnivMinn-img-slide.jpg
asi0412-UnivMinn-Slide1-slide.jpg
asi0412-UnivMinn-Slide2-slide.jpg
asi0412-UnivMinn-Slide3-slide.jpg
asi0412-UnivMinn-Slide4-slide.jpg
asi0412-UnivMinn-Slide5-slide.jpg
asi0412-UnivMinn-table-slide.jpg
asi0412-UnivMinn-equation-slide.jpg
asi0412-UnivMinn-img-slide.jpg
asi0412-UnivMinn-Slide1-slide.jpg
asi0412-UnivMinn-Slide2-slide.jpg
asi0412-UnivMinn-Slide3-slide.jpg
asi0412-UnivMinn-Slide4-slide.jpg
asi0412-UnivMinn-Slide5-slide.jpg
asi0412-UnivMinn-table-slide.jpg
March 19, 2012


The efficient control of contaminants such as metals, plastics, inks and adhesives during the processing of recovered paper products determines the profitability of recycling mills. In fact, it is arguably the most important technical obstacle in expanding the use of recycled paper.1-4 An especially challenging category of contaminants to manage is pressure-sensitive adhesive (PSA). PSAs are soft elastomer-based materials that are highly viscous and sticky to the touch. In recovered paper, they are usually found as part of pressure-sensitive (PS) label systems, consisting of facestock coated with a 0.7-1.0 mil layer of PSA.

During the initial stages of the paper recycling process, the bonds between fibers are broken using water and mechanical energy. This operation, known as repulping, also fragments adhesive films. Much of the removal of these fragments in the recycling process occurs at the pressure screens and is governed mainly by the size and shape of the residual adhesive. The PSA that is not removed by screening is introduced into the remaining fiber recovery operations and the papermaking process, where it can significantly diminish production efficiency and product quality.5-7

A widely acknowledged approach to reduce the negative impact of PSA on paper recycling is to design adhesives for enhanced removal early in the recycling process. Given the high efficiency of particle removal demonstrated by screening operations, the most promising PSAs are those designed to generate larger residual particles.

Our recent research efforts have focused on developing guidelines for producing these types of PS products. This article includes the rationale for our test methods to gauge screening removal efficiencies, the identification of properties controlling the fragmentation of both hot-melt and water-based PSAs, and a discussion of the role additives and laminate design play in determining the fragmentation behavior of adhesive films.


MEASUREMENT OF PSA REMOVAL EFFICIENCIES
While mill trials would be the best way to determine which PSAs are problematic, they are expensive and the results are often difficult to interpret. Fortunately, the U.S. Postal Service (USPS) provided the resources required to test the same set of adhesives on a lab, pilot and mill scale.5 Based on the work sponsored by the USPS, a laboratory-scale test method has been developed by a subcommittee of the Tag and Label Manufacturers Institute (TLMI).8 These specification and test methods have been shown to correlate with other tests and are gaining wider acceptance.9

For this work, we have focused on Adirondack Plastic and Paper Recycling’s high-consistency laboratory repulper, and a gravity-flow flat screen from Valley Plastics and Paper Recycling. The repulper is equipped with a heating/cooling jacket and connected to a recirculating water bath to maintain temperatures during testing within ± 2°C of targets. The test requires only about 1.5 g of PSA film and an additional 300 g of conditioned paper, which includes the label facestock (~ 5 g), envelope-grade substrate (~ 8 g), and copy paper (287 g). Laminates and the copy paper are repulped for 30 minutes in 3 L of tap water, and the resulting fiber slurry is passed through the flat screen, which is equipped with a 0.015-in. slotted screen, wider than the 0.006-0.008-in. slots found in fine screens in typical fine paper recycling operations.

For this test, the amount of PSA rejected at the screen is measured gravimetrically. Screening rejects are composed of PSA particles, as well as cellulose fiber. The fiber is dissolved in copper (II)-ethylenediamine (CED), and the adhesive particles are isolated via filtration and dried at 105°C to a constant weight. Rejected PSA mass is reported as a removal efficiency, which is the percentage of PSA mass added to the repulper that is rejected at the screen. Tested PSA films are soaked in CED aqueous solutions and dried at 105°C for extended periods to determine the mass loss of PSA additives (e.g., emulsifiers and tackifiers) during the analysis. Losses are usually found to be negligible. The details of this procedure are available elsewhere.10,11 Reproducibility of removal efficiency measurements was determined to be ± 3-4%.
 

OPTIMIZING THE REMOVAL OF PSA FILMS
Water-based acrylic PSA dominates the PS label market and, along with hot-melt PSAs, composes most of the PSA used to produce labels.12 By providing guidelines for making these two types of PSAs more recycling compatible, the majority of adhesives presented to recycling mills could be reformulated.

Hot-melt adhesives have phase transitions near typical recycling temperatures. If the repulping temperature is high relative to these transitions, the adhesive is soft, allowing it to break down more easily and form smaller fragments. The fragmentation of a water-based PSA is controlled by its strength in aqueous environments. This is determined in large part by its water resistance, which is reduced by the presence of surfactants, which are needed for synthesis and formulation, and the greater polarity of the adhesive polymer. In general terms, the fragmentation of hot-melt PSA films is controlled by temperature, while the residual strength under high moisture conditions controls the fragmentation of water-based adhesive films.

The goal is to limit the extent of PSA fragmentation during repulping operations. The focus is on the films themselves, so additives and laminate designs are held constant for most of the tests reviewed here to provide for direct comparisons. As will be shown, relatively minor modifications (that do not compromise performance or costs) can be used to substantially increase the screening removal efficiencies of PSA films. 

KEYWORDS: films hot melts labels recycling/recyclability

Share This Story

Looking for a reprint of this article?
From high-res PDFs to custom plaques, order your copy today!

Jihui Guo is an Associate Scientist with The Dow Chemical Co.
Larry Gwin Serves as Senior Research Associate with Franklin International.
Carl Houtman is a Research Chemical Engineer with the U.S. Department of Agriculture's Forest Products Laboratory.
Mark Kroll serves as a Research Chemist/Senior Section Leader for H.B. Fuller Co.
Steven J. Severtson is a professor in the Department of Bioproducts and Biosystems Engineering at the University of Minnesota.

Recommended Content

JOIN TODAY
to unlock your recommendations.

Already have an account? Sign In

  • mouse in hole

    Using Foam Sealants for Pest Prevention

    According to the National Pest Management Association,...
    Adhesives and Sealants Topics
    By: Kevin Corcoran
  • linked network nodes

    Using the Power of AI for Adhesive and Sealant Formulation

    With the help of software solutions, adhesive formulators...
    Adhesives and Sealants Topics
    By: Karen Parker
  • top20-hero.jpg

    2024 ASI Top 20: Leading Global Manufacturers of Adhesives and Sealants

    ASI's annual ranking of the top 20 global adhesive and...
    Pressure-Sensitive Adhesives (PSAs)
Previous 1 2 3 4 Next
Manage My Account
  • eMagazine Issues
  • eNewsletter
  • Online Registration
  • Manage My Preferences
  • Subscription Customer Service

More Videos

Popular Stories

Picture of a tub and a tube of an epoxy

CREATIVE MATERIALS INC.: Conductive Epoxies

cardboard packaging

Utilizing Biobased Materials to Enable Sustainability in Hot-Melt Pressure-Sensitive Adhesives

rolls of tape

What’s Next in Tapes: A Look at Industry Trends

ASI Top 20 website

Events

January 1, 2030

Webinar Sponsorship Information

For webinar sponsorship information, visit www.bnpevents.com/webinars or email webinars@bnpmedia.com.

View All Submit An Event

Products

Structural Adhesives: Properties, Characterization and Applications

Structural Adhesives: Properties, Characterization and Applications

See More Products

ASI CASE EBOOK

Related Articles

  • Chemsultants figure 1

    Manufacturing Pressure-Sensitive Adhesive Products: A Coating and Laminating Process

    See More
  • 2002-2003 Tape Products Directoryby The Pressure Sensitive Tape Council

    See More
  • Development of Environmentally Benign Pressure Sensitive Adhesives

    See More

Related Products

See More Products
  • technology-of-pressure-sens.gif

    Technology of Pressure-Sensitive Adhesives and Products

  • pressure-sensitive-advesive.gif

    Pressure-Sensitive Adhesives and Applications

See More Products

Related Directories

  • Pressure Sensitive Tape Council

    The Pressure Sensitive Tape Council (PSTC) is a nonprofit North American trade association dedicated to helping the industry produce quality pressure sensitive adhesive tape products in the global marketplace. PSTC members range in size from privately owned companies with less than 50 employees to multi-national, fortune 100 companies.
×

Keep the info flowing with our eNewsletters!

Get the latest industry updates tailored your way.

JOIN TODAY!
  • RESOURCES
    • Advertise
    • Contact Us
    • Directories
    • Store
    • Want More
  • SIGN UP TODAY
    • Create Account
    • eMagazine
    • eNewsletters
    • Customer Service
    • Manage Preferences
  • SERVICES
    • Marketing Services
    • Reprints
    • Market Research
    • List Rental
    • Survey & Sample
  • STAY CONNECTED
    • LinkedIn
    • Facebook
    • Youtube
    • X (Twitter)
  • PRIVACY
    • PRIVACY POLICY
    • TERMS & CONDITIONS
    • DO NOT SELL MY PERSONAL INFORMATION
    • PRIVACY REQUEST
    • ACCESSIBILITY

Copyright ©2025. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing