Packaging Tapes: To Recycle Or Not, And If So, How?

Timothy B. Jensen, Ph.D.
3M

Abstract

Packaging tapes are the most widely used pressure sensitive adhesive tapes with global production in excess of 10 billion sq. meters per year. Their primary application is corrugated carton closure. Since carton recycling is a well established practice, two questions arise; first, does the tape interfere with the recycling of the cartons; second, should or can the tape be recycled? Comprehensive studies have shown that polypropylene box sealing tapes do not appreciably interfere with the carton recycling process and that tape residue from the process may be recycled by means of incineration with energy recovery.

Introduction

Environmental issues have become increasingly important in much of the industrialized world over the last third of the 20th Century. These concerns are now new: citizens of classical Greece worried about deforestation well before the birth of Christ. Yet the immediacy of modern times with high energy consumption, increased emissions from manufacturing and agriculture, and an expanding human population seems to intrude across most aspects of society and has weighed heavily in major political campaigns. In fact, contrary to commonly held views that environmental issues are technical or scientific in nature, they are primarily political with a strong economic flavor. While science can provide regulatory guidance and solutions, at least partial, to some problems, the issues are ultimately resolved in the arena of the political economy.

That is why words, with their power to define and deceive, become very important. What is meant by environmentally friendly, environmentally benign? What is recycling? What is the public interest?

The world of packaging with concomitant food safety and municipal solid waste issues is even more subject to an Orwellian future since almost every9one has experience with packaged goods and has an opinion. Terms like degradable, biodegradable, recyclable, recycled, natural, safe, reusable, etc. are often found on packaging without clear definition. Europe, particularly Germany, has focused on packaging waste with a wide range of regulations and directives.

For the scientist or engineer working in the area of environmental issues, a balanced perspective is invaluable, one that recognizes that some concerns are well placed and that some practices are clearly inimical to health and safety and that others are less so and some even may result from the elevation of environmentalism to a modern secular religion where belief  replaces dispassionate factual analysis.

Conceptual Framework

A number of reputable organizations and individual writers have attempted to provide conceptual frameworks for analysis and resolution of environmental concerns. These usually involve the doctrine of life cycle assessment (LCA) to provide guidance LCA accounts for total emission and total energy consumption over the lifetime of a product. A good early example was that of Hocking (1) which compared polystyrene with paper beverage containers for single use. Contrary to the perception that paper drink containers are environmentally "friendly", it was found that the production, use, and disposal/recycling of the paper container required more energy and produced two-and-one half times more emissions than the plastic container’s life cycle. This principle has been embodied in life cycle management (LCM) as described by DeSimone and Popoff (2). Another framework is that of the ISO14000 Environmental Management System which is the environmental analog of ISO 9000 for quality. More specific to packaging products are the guidelines provided by the Institute of Packaging Professionals (IOPP), the Coalition of Northeastern Governors (CONEG), and the US Environmental Protection Agency (EPA). To sum up briefly they suggest the following in order of preference:

  • No packaging;
  • Minimal packaging;
  • Consumable, returnable, or resealable packaging; and
  • Recyclable packaging or recycled material packaging.

Another framework, or actually practice is provided in ASTM D-1974-94a, "Standard Practice for Methods of Closing, Sealing, and Reinforcing Fiberboard Boxes," Section 5.6, Environmental Considerations. Since most packaging tapes are used for these applications it forms an appropriate framework to address the issue of: "Packaging Tapes: To Recycle Or Not, And If So, How?"

ASTM D1974-94a

The section relevant to this paper is 5.6 which reads as follows:

5.6 Environmental Considerations:

5.6.1 General - Although the environmental impact of a package is a component of the package design and evaluation process, the integrity of the product should not be compromised. Product damage or disposal resulting from package failure, or both, may well cause greater environmental impact that the package. Product containment, protection, and preservation, along with consumer safety, remain the primary functions of the package.

5.6.2 Toxic Content - The use of potentially toxic materials in packaging components is a concern for their presence in emissions when packaging is incinerated, or in leachate when packaging is landfilled. Materials used for the closure, sealing, or reinforcement of boxes shall not have any lead, cadmium, mercury, barium, silver, arsenic, selenium, or hexavalent chromium which has been intentionally introduced as a component during manufacturing or distribution as opposed to the incidental presence of any of these elements. Box closure, sealing, and reinforcing materials presented in this standard typically meet this requirement.

5.6.3 Solid Waste - Considerations of packaging solid waste involve the total mass and volume of all package components. The closure, sealing, and reinforcing components are usually less than 1% of this total. While these materials are still part of solid waste considerations, emphasis should be on the total.

5.6.3.1 Source Reduction - Reductions in closure, sealing, and reinforcing materials should be consistent with performance and material requirements specified in contracts and regulations and with good engineering practice.

5.6.3.2 Reuse - Closure, sealing, and reinforcing materials which allow the reuse of fiberboard boxes are encouraged.

5.6.3.3 Recycling - Efforts should be focused on maximizing the reuse and fiber recovery of fiberboard boxes. One consideration in the choice of a closure, sealing, or reinforcing material should be compatibility with the recycling of old fiberboard containers. Materials should be chosen which can be removed from a box prior to recycling, removed from the pulper (vessel for dispersing old fiberboard into pulp slurry), or otherwise removed in the recycling process. The materials  should then be suitable for appropriate recycling, incineration, or landfill in accordance with applicable regulations. If the materials are not removable in the recycling process, they should not cause significant reductions in the properties of the recycled paper or paperboard.

These latter considerations build on the framework provided by CONEG and especially on implementation of the German "Verpackungsverordnung" (packaging ordinance) of June 12, 1991 through the German recycling organization RESY which in January 1992 promulgated the following policy: "In Explanation of the Recyclability of Packaging made of Paper or Cardboard," section 4: "Adhesive tape and stick-on labels are packaging aids which are not  supposed to hinder the recycling process. This requirement is met when they disintegrate as little as possible in the slushing phase and can already be completely - which means both the adhesive material as well as the bearing material (plastic or paper) - separated in the pulper or in the following sorting phase. In the case of thermal recycling, the adhesive tape which as been sorted out must not cause any harmful emissions."

Closure Methods for Cartons

The most common means of closing transport cartons are pressure sensitive tapes; gluing systems including hot melt adhesives, water activated tape, staples, and non-metallic strapping.

The user/purchaser of transport cartons may wish to evaluate the closure method for conformance to ASTM D1974-94a. Performance varies amongst these closure methods and must be evaluated for the intended purpose. Only the two tape products provide sealing as well as closure. Toxic content is not an issue unless the closure has been printed or coated with an ink or coating containing heavy metals though most of these have been phased out. On the matter of source reduction, Table I is most illustrative with the polypropylene PSA box sealing tape providing the best source reduction among common closure methods. (3) One disadvantage with staples and gluing systems is that the box flaps are often damaged during unloading rendering the container unusable.

The issue of recycling is more complex. It has been well stated, and this fits nicely with LCA, that: "Recycling in the material sense is only environmentally sound if there is a net gain in resources. In the case of plastic-based materials there is usually a larger net gain in resources if waste materials are burned with energy recovery and then fresh oil used to make fresh plastics, rather than using fresh oil for energy and re-using the plastic. Overall, 2% of mineral oil is used to make plastic packaging of all types, and this plastic packaging still contains typically 95% of the original oil energy." (4) The first sentence and the words "net gain" are most important. In the instance of carton closure, ASTM rightly points out that recycling of the carton is to be emphasized. Recycling of the closure is secondary and the primary requirement is that the closure not interfere with the carton recycling process or product derived therefrom.

Carton Recycling

In the U.S., approximately 50% of corrugated cartons are recycled. In Europe it can run as high as 80%. The recycled product is usually fiberboard, media, or linerboard and may comprise up to 100% recycle fiber content. Depending on end use, quality criteria vary but, in any case, input material including contaminants, tramp material, and other packaging components will affect output quality. Paper recycling processes are designed to handle some level and types of foreign material. One of the most troubling of these is materials which produce "stickies." Stickies may be defined as small insoluble suspended particles that arise in the repulping stage. They vary in composition but are typically thermoplastic polymeric materials. Since removal of stickies is a challenge, paper recyclers prefer feed stock low in potential stickies content.

The total global market of PSA box sealing tape is in excess of 10 billion square meters. As a major manufacturer of plastic film box sealing tape with a significant share of this market, 3M wanted to be certain that its products did not pose a problem to carton recyclers. While unpublished studies conducted in the 1970s indicated that although, the carton recycling process shredded the tape, the adhesive stayed with the film and the tape pieces were easily removed from the repulping stage by conventional techniques employed by the mills, additional studies were undertaken in recent years to test the validity of that earlier work.

The first tests were laboratory scale using TAPPI UM213 for repulpability. The hand sheets were comparable to controls.

Next, tests were conducted on pilot scale equipment at the University of Western Michigan and at Forest Product Laboratory, Madison, Wisconsin with similar results. The report from FLP concluded "The fact that the adhesive stays with the backing in your tape product, and that the backing remains largely intact, means that the tapes do not appreciably interfere with recycling, either process or product." (3, 5, 6)

As another approach to understanding, a large OCC (Old Corrugated Container) recycler provided samples of "stickies" from their repulper. They were analyzed using optical light microscopy and infrared microspectroscopy. The results are shown in Table II.

None of the samples were consistent with the composition of 3M’s box sealing tapes.

A survey of eight other OCC recycle plants was conducted. All eight reported that hot melt adhesives were the major contaminant. One reported plastic tape particles getting through the screening process and into the final product. Other problems included staples that occasionally would affect valves, shredded glass fiber from reinforced gum tape ending up in paper fibers, and asphaltic tape, though not encountered frequently, are a problem.

The survey also asked about the advisability of a water soluble or dispersible adhesive. Three plants disliked the idea because of potential build-up in the system or affect on output quality. Three more thought the approach questionable and two supported the idea.

In order to satisfy the German requirements, tests were also undertaken at Papier Technische Siftung (Paper Technical Institute) in Munich. These were reported by Grossman (7) who concluded "Plastic adhesive tapes or tapes of wet strength paper with a firmly anchored adhesive and a high comminution resistance are as a rule "recycling oriented" if the pressure sensitive adhesive coating remains firmly connected with the substrate material. Tapes of this type do not impair cardboard recycling, since they can be removed from the fiber suspension by screening at an early stage."

Thus, film backed packaging tapes are deemed suitable for use in Germany, a nation regarded as having some of the most demanding environmental regulations.

What about other closure methods and their affect on OCC recycling? Table III taken from Sheehan and Gruenwald (8) summarizes the destiny of various closure materials in OCC recycling. Note that materials listed as removable may be recyclable by themselves (e.g. blend staples into feedstreams for steel mills). From an environmentalist's position, one concluded that there is no perfect closure material in that all are of finite mass and end up someplace. However, a thorough understanding of the alternatives can help in making choices. A lack of apparent understanding on the part of the Gummed Industries Association that had advertised, among other things, that plastic tape must be manually stripped from corrugated containers before recycling the container, led to a lawsuit. A Final Consent on Judgement was issued by the Federal District Court for the Eastern District of New York (9). The decree "permanently enjoined (GIA) from directly or indirectly making, issuing, circulating, or disseminating any advertising promotion, representations or other marketing claims which include in words or in substance any of the following: …" Among the "following" were the above stated claims and other claims about gummed tape’s supposed environmental superiority.

Recycling of Post Consumer Tape

Recycling of corrugated containers is a process with sound economics. It provides a net gain. The next question concerns recycling of the closure materials - can they be recycled with a net gain? Looking to the German experience the answer is "yes", at least in the case of plastic film box sealing tape.

OCC recycling plants produce as a byproduct shredded plastic box sealing tape and other shreds of plastic which are removed from the repulper. According to our survey, which was confined to the U.S., five of eight plants landfilled plastic scrap and three incinerated it. Strict material recycling would require a complex process to separate, clean, and redensify such material - hardly a sound economic idea with plastic resin prices as low as they are. Yet the opportunity for recycling via thermal recycling, i.e. incineration with electrical energy generated, looks appealing. This is a high-energy content material and thermal recycling is increasingly attractive. Originally, the German law required that packaging must in future be recyclable and that the only form of recycling was to be material recycling (10). This has changed.

First, a 1994 German law permitted energy recovery from waste at a 75 percent recovery level. Since steam-powered generating plants operate at no more than 35 to 40 percent efficiency, waste-to-energy was restricted to gasification, heating of cement films, and for fuel in steel factories (11).

More recently, German law has encouraged thermal recycling, called "Verwatung" (recovery), by reducing the efficiency requirements to that of coal, gas, or oil. Accordingly, electrical energy is now generated at several power plants that utilize fuel pellets made from tape and plastic scrap as part of the total fuel consumed (12).

Thus, one may think of using crude oil to produce energy but using it first as packaging materials and aids, and then as fuel. One restriction imposed on such scrap is that total chlorine content fall below 1%. This is not a serious problem since the use of PVC in tape products is declining. Might this use of energy recovery indicate some larger force at work in society to alter commonly held views about recycling? Perhaps.

An article in the influential New York Times Magazine in 1996 had the title, "Recycling Is Garbage" (13). The lead-in states, "Rinsing out tuna cans and tying up newspapers may make you feel virtuous, but recycling could be America’s most wasteful activity." This represents quite a change from the idea that recycling is some sort of magic bullet that will solve all environment problems. Another article in The Economist further supports Tierney’s view (14). A BASF facility is experimenting with energy recovery from waste plastics in place of gas or oil as a supplemental fuel with sewage sludge (15). Modern combustion technology with good temperature control drastically reduces objectionable emissions thus making thermal reycling more viable (16).

The Future

With environmental issues a part of our political economy, what is the future and how best can scientists and engineers affect it?

By working with governmental organizations and standards organizations.

By providing factual information to governmental bodies and countering irresponsible proposals and arguments.

By considering business activities within the framework of ISO 14000.

By designing processes and products to minimize negative environmental effects as understood through Life Cycle Management. Examples include modified hot melt adhesives and new products such as stretchable tape which provides approximately 75% material reduction over stretch film.

By communicating your thoughts to the press and civic groups.

Conclusion

Environmental considerations for products and processes often go beyond mere technical concerns. Conceptual frameworks such as ISO 14000 provide overall guidance on such considerations. Recycling of corrugated containers, clearly an environmentally beneficial activity, is not adversely affected by plastic film pressure sensitive adhesive tapes used for transport packaging. The tape scraps resulting from container recycling may best be disposed of through thermal recycling, an improved technology which is gaining acceptance.

 

Table I

Approximate Mass of Box Closure Materials

Box Closure Material

Mass

   

Polypropylene PSA Box-Sealing Tape

3 Grams

   

Staples

9 Grams

   

Hot-Melt Adhesive

6 Grams

   

Non-Metallic Strapping

9 Grams

   

Reinforced Gummed Tape

12 Grams

   

Table II

Description of Particles from OCC Plant

Colorless film fragments

1.        polyethylene

2.        polyethylene

3.        polyethylene

4.        polyethylene

5.        Daran film—90:10 vinylidene choride:methyl acrylate

6.        polyethylene

7.        polyethylene

8.        polyethylene

9.        polyethylene

Colorless chunks

1.        EVA and rosin ester

2.        EVA and coumarone indene

3.        polyethylene

4.        polyethylene

5.        EVA

6.        EVA

7.        EVA and rosin ester

8.        EVA

Colored materials

1.        Blue sticky material­: isoprene/styrene, ethylene, rosin ester, hydrocarbon resin

2.        Green sticky material: polyethylene, vinyl acetate/methyl acrylate or methacrylate/styrene similar to Flexcryl 1625

3.        Yellow sticky material: isoprene/styrene, clay, rosin ester

4.        Light green solid: EVA, rosin ester

5.        Dark blue solid: EVA, rosin ester

6.        Dark green solid: cellulose, amide

7.        Brown solid: long chain ester, possibly degradation products

8.        Amber solid: cellulose, amide, phenolic

9.        Green foam: polyether urethane

10.     Colorless foam: polyether urethane

11.     Polka dot film: clay, styrene, vinyl acetate/acrylate

12.     Yellow film: polyethylene, polypropylene, carbonate

13.     Blue film shred: Polyethylene, talc

14.     Red film shred: polyethylene, polypropylene

15.     White film: polyethylene

16.     Light blue film: polystyrene

17.     Brown fibers: paper (wood pulp)

Table III

Fate of Closure Materials

Closure Type

Recyclable

Removable

Possible Paper Contaminant

Possible Water Contaminant

Staples

 

X

   

Pressure Sensitive Tape

 

X

   

Reinforced Gummed Tape:
-paper
-fiberglass
-laminating adhesive
-gummed adhesive

X

X

X

X

Strapping

 

X

   

Hot-Melt Adhesive

   

X

 

Water-Borne Adhesive

     

X

         

References

1.        M.B. Hocking, Science Magazine, Feb. 1991

2.        L.D. Desimone, F. Popoff, Eco Efficiency, MIT Press, Cambridge MA, 1997

3.        T.B. Jensen, Adhesives Age, Sept. 1992

4.        Johnson, AFERA Congress Proceedings, Amsterdam, 1991

5.        J.H. Klungness, Private Correspondence, Aug. 1992

6.        J.H. Klungness, L. Gruenewald, M.S. Wu, D. Bormett, TAPPI Pulping Conference Proceedings, 1992

7.        H. Grossmann, European Tape and Label Conference, Brussels, 1993

8.        R.L. Sheehan, L.E. Gruenewald, J. of Applied Mfg. Systems, Spring/Summer, 1997

9.        Minnesota Mining & Manufacturing Co. v. The Gummed Industries Association Inc., U.S. District Court, Easter District of New York, Civil Action No. 92 Civ 5555 (ADS), Jan. 27, 1993

10.     T. Rummler, W. Schott, The German Packaging Ordinance: A Practical Guide with Commentary, Perchard Assoc., St. Albans, UK, 1992

11.     T.B. Jensen, Packaging Technology and Engineering, Oct. 1995

12.     H. Korfmacher, Private Communication, Sept. 1997

13.     J. Tierney, The New York Times Magazine, June 30, 1996

14.     The Economist, p. 63, Oct. 18, 1997

15.     J. Brandrup, M. Bittner, W. Michaeli, G. Menges, Recycling and Recovery of Plastics, 8.14, Hansen, New York, 1996

16.     T.B. Jensen, AFERA Congress Proceedings, Florence, 1990