Multilayer Barrier Film for Low-Static, Non-Blocking Unwinding
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Solution Overview
Problem
Commercially available multilayer films for labels and packaging suffer from severe static discharge when unwound at high speeds due to a triboelectric mismatch between polyurethane and polyamide surfaces, which traditional static dissipation techniques cannot effectively address, and the use of antistatic coatings often results in film blocking or inconsistent transfer.
Innovation Solution
A multilayer film structure comprising a soft polyurethane coating layer, a core layer, a polyamide barrier layer, and a hard polyurethane adhesive receptive layer, with specific minimum film forming temperatures and compositions to reduce static discharge and prevent blocking, including tie layers for enhanced adhesion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a blend of hard and soft polyurethanes is used on the external print surface with polyamide on the opposing surface, then printability and adhesion are improved, but severe static discharge occurs when unwound at high speed
Solution Approach 1:
The patent introduces an intermediary antistatic coating layer between the polyurethane print surface and the polyamide barrier surface. This intermediary layer reduces the triboelectric mismatch and prevents severe static discharge while maintaining the printability and adhesion properties of the underlying layers.
Solution Approach 2:
The patent modifies the triboelectric properties of the film by introducing a specific antistatic coating with controlled composition and thickness. This changes the electrical parameters of the interface between the polyurethane and polyamide layers, reducing static discharge without compromising other properties.
2Object-generated harmful factors
If antistatic coatings such as polysorbate 20 are applied to reduce static discharge, then static discharge intensity is reduced, but film blocking or undesirable inconsistent transfer occurs
Solution Approach 1:
The patent optimizes the parameters of the antistatic coating, including its composition, concentration, and thickness, to achieve the right balance. The coating contains specific additives and has a controlled thickness that reduces static discharge while preventing film blocking and ensuring consistent transfer to the opposing surface.
Solution Approach 2:
The antistatic coating is formulated as a composite material containing multiple components including polysorbate 20, along with other additives and polymers. This composite formulation provides both antistatic properties and prevents blocking, overcoming the limitations of single-component antistatic coatings.
3Object-generated harmful factors
If traditional static dissipation techniques such as static bar, tinsel, or ionized air are used, then static discharge is managed, but they cannot resolve the triboelectric mismatch that occurs immediately upon separation of layers
Solution Approach 1:
The patent applies a preliminary antistatic coating to the film surfaces before the separation and unwinding process. This preliminary action prevents the triboelectric mismatch from generating severe static discharge in the first place, rather than attempting to manage it after it occurs. The coating is applied during film manufacturing and remains effective throughout storage and unwinding.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The film achieves minimal static discharge (less than 2000 V) and prevents blocking when unwound at high speeds, ensuring safety and operational efficiency in commercial applications.
Implementation Method 1
This extreme difference in position on the triboelectric scale results in severe and dangerous electrical discharge when a roll of material is unwound a high speed
Implementation Method 2
the soft polyurethane has a minimum film forming temperature (MFFT) less than 0° C.; the MFFT of the hard polyurethane is greater than 0° C.
Data Source
AI summary
A multilayer film is disclosed, including a printable coating layer including a soft polyurethane, and defining a first surface of the multilayer film; a core layer under the printable coating layer; a barrier layer under the core layer and including a polyamide; and an adhesive receptive layer under the barrier layer, defining a second surface of the multilayer film opposite the first surface, and including a hard polyurethane, wherein: the soft polyurethane has a minimum film forming temperature (MFFT) <0° C.; the MFFT of the hard polyurethane is >0° C.; the hard polyurethane is effective to reduce static discharge from a roll of the multilayer film unwound at a rate of at least 600 m/min; and the multilayer film is biaxially oriented and exhibits a blocking force <1000 g. Also disclosed is a label including the multilayer film of the invention and ink bonded to the printable coating layer.