Browse Prior Art Database

ROBUST PACKAGING WINDOWS THROUGH ULTRASONIC SEALING IN HFFS PACKAGING EQUIPMENT

IP.com Disclosure Number: IPCOM000236625D
Publication Date: 2014-May-06

Publishing Venue

The IP.com Prior Art Database

Abstract

Compared to conventional heat sealing, utilization of ultrasonic sealing in flexible packaging, offers performance advantages such as the ability: (i) to seal through contamination, (ii) to form narrower seal zones, and (iii) to form seals at higher line speeds and at lower temperature environment. However, due to the contact geometry between the horn and the anvil and the oscillatory deformation, ultrasonic sealing often leads to significant material outflow and squeeze-out of polymer away from the seal area. This “squeeze-out” phenomenon of ultrasonic sealing can cause damage, and eventual destruction of the laminate structure in the formed ultrasonic seal. Further work has been conducted on optimizing the laminate structures for ultrasonic sealing in Horizontal-Form-Fill-Seal (HFFS) flow wrap applications. It has been found that: • The type of polymer used as sealant material will determine the onset of sealing at particular sealing conditions of sealing force and packaging line speed. • Damage to the laminate substrate can be delayed by selecting polyolefin materials, which will start to melt at higher temperature for the core and outside layer in the polyolefin coextrusion film • Damage to the laminate substrate can be delayed by selecting a lamination substrate with a higher stiffness • The thickness ratio of sealing agent to total thickness should be less than 1:3

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 22% of the total text.

Page 01 of 11

Robust Packaging Windows Through Ultrasonic Sealing in

HFFS Packaging Equipment

Jef Van Dun, R&D Fellow, Packaging and Specialty Packaging TS&D, Dow Europe GmbH, Bachtobelstrasse 3, CH-8810 Horgen

Norbert Hoechst, Senior Consultant Packaging, Bosch Packaging Systems AG, Industriestrasse 8, CH-8222 Beringen

Paul Kaftan, Mechanical Development Engineer, Bosch Packaging Systems AG, Industriestrasse 8, CH-8222 Beringen


2.Introduction

Ultrasonic sealing and welding was developed in the middle of the last century and has been widely used for welding molded plastic parts. During ultrasonic welding, the polymer parts or films get compressed and oscillated by longitudinal vibrations of the sealing tool. The deformation causes viscoelastic dissipation in the material, leading to rising temperature, eventually melting semi-crystalline polymers. Once molten, both joining partners can connect with each other and will be welded. Typical frequencies for ultrasonic welding are 20 to 40 kHz.

Compared to conventional heat sealing, utilization of ultrasonic sealing in flexible packaging, offers performance advantages such as the ability: (i) to seal through contamination, (ii) to form narrower seal zones, and (iii) to form seals at higher line speeds and at lower temperature environment. Packaging systems suitable for ultrasonic welding include vertical- or horizontal-form-fill-sealing. Despite these benefits, ultrasonic sealing has a significant drawback. Due to the contact geometry between the horn and the anvil and oscillatory deformation, ultrasonic sealing often leads to significant material outflow and squeeze-out of polymer away from the seal area. This "squeeze-out" phenomenon of ultrasonic sealing can cause damage, and eventual destruction of the laminate structure in the formed ultrasonic seal. Layer steps, i.e., step changes in the thickness of the material between the horn and anvil (such as in gussets and folds, and cross-section fin seals) are particularly susceptible to damage when ultrasonically sealed. Faulty sealing in these areas reduces seal strength (as measured by peeling tests), may destroy the laminate in the seal zone, and create channel leakers resulting in loss of barrier properties in packaging laminates with thin layers of aluminum or barrier polymers, such as ethylene vinyl alcohol copolymers (EvOH).

Page 1 of 11


1.Authors



Page 02 of 11

Approaches proposed to mitigate the aforementioned problems include (i) optimization of the contact geometry, especially the energy director and (ii) control of horn displacement during sealing both of which are subject to limitations.

Careful selection of polymers and optimization of the multilayer structures offers an alternate route to mitigate the problems above. In "Polyolefins for ultrasonic sealing", PackagingFilms 4-2013, p8-10, Van Dun et al. address the fundamentals of ultrasonic sealing, Several polyolefin materials with excellent ultrasonic sealing behaviour are presented...