Green Packaging Assembly Solutions

Joining profiles for bio-based plastic ensure commercial-grade performance for the millions of bags, pouches, clamshells, cartons, coffee canisters, caps, filters and seals that are produced annually.

Ultrasonic Welding Advances Bio-based Packaging Applications

By Andres Abreu, Business Development Manager, Packaging, Branson Welding and Assembly at Emerson

Manufacturers of products that use plastic, especially packaging manufacturers, have committed to a global effort to reduce the use of single-use packaging and boost use of plastics that are recyclable or bio-based. There is also an effort within the plastics manufacturing industry to create a framework that improves public understanding of how to use and recycle bio-based plastics (BBP) and biodegradable and compostable plastics (BDCP).

The topic can be complexecause bio-based and biodegradable plastics have a variety of differences. Currently, plastic packaging only requires 20% or more of biological feedstock content to be considered BBP; the other content may or may not be biodegradable. In addition, while BDCP are biodegradable, there is no guidance about whether they should require industrial composting, should they break down in soil or water, or how long they should take for complete biodegradation. The industry is working to establish policies that will address issues such as these.

Extended Producer Responsibility (EPR)

Some U.S. states are pursuing an initiative called Extended Producer Responsibility (EPR) to mandate that manufacturers take more responsibility for the life cycle of their products and packaging to ensure they can be reused, recycled, composted or biodegraded. Several goals of these states’ EPR bills include:

  • Maximizing recycling and collection potential
  • Minimizing the use of single-use packaging and plastics
  • Expanding manufacturer participation in “producer responsibility organizations”
  • Increasing beverage bottle recycling and recycled content in plastic products

Some of the world’s leading consumer product manufacturers have joined the effort and made an impressive commitment that 100% of their packaging will be reusable, recyclable or compostable by 2025. Corporate giants such as Johnson & Johnson, Colgate-Palmolive, Unilever, SC Johnson, Mars, Apple, Nestle, Walmart, Coca-Cola, and PepsiCo are among the more than 250 manufacturers responsible for producing around 20% of the world’s plastic packaging.

Traditional heat sealing methods

Consumer product manufacturers are not the only participants in the effort to transition to more BBP and BDCP. Resin producers, package and film producers, brand manufacturers, and technology suppliers — everyone in the plastics value chain — are working to develop more sustainable package solutions using BBP and BDCP.

We are joining this global effort, working with resin makers and other plastics innovators to create new and effective joining profiles for bio-based plastic that ensure commercial-grade performance for the millions of bags, pouches, clamshells, cartons, coffee canisters, caps, filters and seals that are produced annually.

Producing commercial-grade packaging and sealing with BBP and BDCP requires much stricter temperature and process control as compared to traditional plastics, as the temperature range at which bio-based materials melt and seal effectively before they degrade is much more narrow.

When traditional heat-sealing methods compress two layers of plastic together between heated bars, the process must be controlled for temperature, pressure and dwell time. Because BBP has such a narrow processing window and sensitivity to heat, it is nearly impossible for thermal welders to hit this “sweet spot” every time — a necessity for repeatedly producing packaging with the strength and performance needed. This is causing manufacturers to question whether traditional thermal-sealing equipment can provide the control and consistent, repeatable quality they need for their BBP products.

Ultrasonic sealing technology

Unlike traditional heat-sealing equipment, ultrasonic welders employ high-frequency vibration to create frictional heat within the plastic layers’ interface only during the brief (less than 1 second) weld cycles. Manufacturers using ultrasonic welders can monitor process parameters in real time, since ultrasonic welders provide multiple modes of digital, closed-loop control.

Every weld input and quality parameter can be precisely controlled and monitored. Energy input can be controlled within a joule, and downforce can be controlled within a Newton. The exact resonating frequency of ultrasonic tooling allows microscale adjustments in amplitude to fine-tune the heat generated at the weld interface.

Ultrasonics allow users to set high/low limits on weld results and configure alarms to automatically identify out-of-spec weld cycles, and enable automated bad-part processing. Precise weld control is just one of many advantages offered by ultrasonic welders when processing bio-based plastics.

Additional benefits

In addition to more precise weld control, manufacturers of flexible packaging are also looking for ways to make their products “greener.” Fortunately, ultrasonic sealing technology offers additional sustainability benefits.

For example, by consuming energy only during its millisecond weld cycles, ultrasonics delivers energy savings of 25% to 75% relative to thermal-sealing equipment, which consumes energy continuously to maintain the surface temperature of the heated bars whether they are actively sealing or not. In addition, ultrasonic welding requires less plastic to create a seal. Conventional thermal sealing needs about 0.5 inch of material, whereas a comparable ultrasonic seal needs just 0.125 inch. So, a package requiring two seals — top and bottom — uses 0.75 inch less material. This savings adds up fast when considering material costs and shipping weight for hundreds of millions of packages a year.

Enabling BBP in familiar applications

As governments struggle to sort out the complexities of reducing waste streams and boosting circular plastics use, the market for bio-based and recycled plastic packages is growing rapidly worldwide. Many of these applications focus on replacing petroleum-based plastics in popular, single-use products.

In most cases, retrofitting a packaging line with modern ultrasonic-sealing equipment is not difficult, and the increased control can open new opportunities for sustainability. From compostable coffee pods and standup pouches to food packaging that uses ever-increasing amounts of compostable content, manufacturers worldwide can now produce packaging using bio-based plastics, thanks to the process control available through ultrasonic welding technology.

About the Author

Andres Abreu is the business development manager, Packaging, Branson Welding and Assembly at Emerson. Abreu is a trends expert in manufacturing processes, government regulations and plastics materials. Learn more at www.emerson.com.

Comparison of package-sealing process controls

Thermal sealing controls Ultrasonic welding controls
  • Temperature setting
  • Pressure setting
  • Dwell (time) setting
  • Operating frequency
  • Tool amplitude
  • Welding modes — time, energy, depth, peak power
  • Pressure (downforce), velocity, hold time
  • Real time data acquisition for QA, setting reject limits, product traceability

New, single-use teabag designs place leaf tea between two discs of porous, nonwoven PLA (polylactic acid) mesh that are ultrasonically plunge-welded together. PLA is an industrially compostable BDCP. Image courtesy of Branson Welding and Assembly at Emerson.

Resealable or squeezable food pouches can now be built with BDCP such as PLA or PHA (polyhydroxyalkanoates). Equipped with resealable plastic zippers or screw-on caps, they are ideal for packaging food products like cheese, sliced or dried meats, tuna, and nut butter. Single-use packages like these are a focal point for package redesigns that use BDCP. Image courtesy of Branson Welding and Assembly at Emerson.

This coffee capsule incorporates a compostable, two-piece bio-based PP ring frame sealed into an air-laid, nonwoven paper filter basket. While heat-sealing tooling caused material degradation and seal inconsistency between the ring and basket, Branson ultrasonic welding technology from Emerson solved the problem, meeting seal integrity and cycle-time requirements. Image courtesy of Branson Welding and Assembly at Emerson.

Sustainable, circular packaging also emphasizes recycled materials. This example shows how Kwik, an outdoor products producer, switched from PVC (polyvinyl chloride) to recycled PET (polyethylene terephthalate), or RPET, for its clamshell packages, while continuing to use its installed base of ultrasonic welding equipment. The recycled-content package used ultrasonic “stitch welds” that produced weld seams stronger than the parent RPET material. All that was needed was a new ultrasonic horn-anvil combination and an update to the package welding program. Image courtesy of Branson Welding and Assembly at Emerson.

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