Technology behind the patents
In heavy duty sack packaging, the surface of the packages is often too slippery, which leads to deformed unit loads, damaged goods and frustrated customers. Load shifting costs money. The purpose of the patented technology is to roughen the surface of the packaging film (or woven fabric) in order to increase its effective package-on-package (i.e., selective) coefficient of friction. This roughening happens in a dedicated converting machine as an additional converting step, during a reel-to-reel rewind of the (printed) film or woven fabric. Solid plastic anti-slip micro-protrusions are formed on the surface of the film (or woven fabric). This is an additive technology for which the micro-protrusions’ plastic raw material is provided in powder form, and the process is based on melt-forming the micro-protrusions and heat-bonding them to the carrier film (or woven fabric). This does not essentially affect the recyclability of the film (or woven fabric). Depending on configuration setup and material selection, the patented process can be implemented in three different approaches, as follows.
GripTop® configuration:
In the GripTop® configuration the surface of the film (or woven fabric) is roughened with flat elastomeric micro-protrusions. The three-dimensional micro-pattern in combination with the protrusions’ elastomeric softness results in an increased coefficient of friction between roughened and unroughened surface parts. Therefore, packages need to be roughened either on their top surfaces only, or on their bottom surfaces only (up to the manufacturer’s choice). Increased coefficient of friction may be provided even in a wet or moderately dusty environment. The soft touch of the almost unnoticeable micro-protrusions may make this concept useful both for industrial and consumer packaging sacks. With this innovative GripTop® concept, Flexinnova won Silver Award in Dow’s 2020 Packaging Innovation Awards.
GripTop® presentation
GripTop® performace test, wet condition
GripTop® performace test, clean and dry condition
GripTop® performace test, wet condition
GripTop® performace test, dusty condition
Self-grip configuration:
In the self-grip configuration both of the opposed abutting film (or woven fabric) surfaces are to be roughened. In this case the anti-slip micro-protrusions are to be made of a stiffer polymer. The roughened surface of the film may be slid on metal or other hard surfaces (e.g., of V-FFS collars, chutes, sliding plates, conveyor belts etc.) in the usual way, essentially without any increased friction. However, thanks to their special undercut shape, the opposing individual micro-protrusions of the opposing film surfaces engage, “hook” with each other, providing a surprising level of mechanical interlock between the abutting surfaces of the adjacent packages, effectively decreasing their slipperiness on each other. Self-grip-style anti-slip film- and woven fabric pairs may have a considerable effective mutual coefficient of friction even under expressly dusty circumstances, as for example, with a severe cement dust surficial contamination. Further, films or woven fabrics roughened in the self-grip style (i.e., with stiff, undercut micro-protrusions) can be used as walking surface in a lumber wrap or roof underlayment or protective builders’ film, providing highly enhanced walking safety possibly even under dusty, wet or freezing conditions.
Self-grip style roughening on film
Self-grip style roughening on woven fabric
Self-grip performance compared, in a test, with ordinary plastic sacks.
COF values read from the slide angles: Ordinary sack: COF = 0.44 Self-grip sack: COF > 0.85
With the permission of Starlinger.
Fleece-grip configuration:
The fleece-grip configuration we consider as the masterpiece of the patented technology. In this configuration, one of the abutting films (or woven fabrics) is roughened in the self-grip roughening style (i.e., with stiff, undercut micro-protrusions) while the surface of the opposing film (or woven fabric) is laminated with a thin nonwoven (i.e., fleece). While both of them, in themselves, can be slid on normal surfaces in the normal way, they together provide a velcro-like interlock, or hooking, between the roughened surface (as male component) and the fleece-laminated surface (as female component). This grip provides a surprising level of effective static coefficient of friction (typically far greater than 1.0) between the two components and, more over, it may effectively resist such surficial contaminations as moisture, dust, grease, oil, ice and white frost. The grip is repeatable multiple times and does not generate any resistance against a vertical or peeling separation. The sacks are considered to be recyclable.
Fleece-grip configuration
Fleece-grip demo
Fleece-grip sacks in practice
