Oriented Polypropylene Film Blocking Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cold seal release films face issues with blocking and scuff resistance due to unwanted adhesion between the cold seal adhesive layer and the release layer, particularly under pressure and aging conditions, despite existing solutions that often rely on migratory additives and soft release materials.
Innovation Solution
The use of high crystalline polypropylene and low ethylene containing polybutene-1 polymers in combination with partially crosslinked polydialkylsiloxane in the outer release layer, which reduces the coefficient of friction and prevents silicone oil transfer, thereby enhancing blocking resistance and scuff resistance without relying on migratory additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If migratory additives and soft release materials are used in the outer release layer, then blocking resistance is improved, but silicone oil transfer and contamination occur
Solution Approach 1:
The patent extracts and eliminates migratory silicone oil additives from the release layer formulation. Instead of using traditional silicone oil-based release agents that migrate and cause contamination, the invention uses a non-migratory polymer matrix (polypropylene and polyethylene blend) that provides release functionality without oil transfer to the adhesive layer.
Solution Approach 2:
The patent changes the chemical composition parameters of the release layer by specifying a polypropylene-polyethylene blend with particular weight ratios (30-70 wt% polyethylene, 70-30 wt% polypropylene) and controlled molecular weights. This parameter optimization achieves low blocking force without relying on migratory silicone oil additives.
2Strength
If high crystalline polypropylene is used in the outer release layer, then scuff resistance is improved, but blocking resistance deteriorates
Solution Approach 1:
The patent merges two polymers with complementary properties: high crystalline polypropylene (providing scuff resistance, stiffness, and low blocking force) and polyethylene (providing flexibility and processability). The synergistic blend achieves both scuff resistance and acceptable blocking resistance, which neither polymer could achieve alone in the required performance range.
Solution Approach 2:
The release layer is formulated as a composite material system consisting of polypropylene and polyethylene in specific proportions, along with anti-blocking agents (1-5 wt%) and slip agents (0.1-1 wt%). This composite formulation balances the high scuff resistance of polypropylene with the blocking resistance requirements through controlled composition and additive packages.
3Reliability
If low ethylene containing polybutene-1 is used in the outer release layer, then blocking resistance is improved, but the film becomes too soft
Solution Approach 1:
The patent applies low ethylene containing polybutene-1 (with ethylene content <5 mol%) as a minor component (1-10 wt%) specifically at the release layer surface to reduce blocking force, while the bulk matrix remains dominated by stiff polypropylene (70-90 wt%) to maintain overall film rigidity. This localized application of soft polymer achieves blocking resistance without compromising film stiffness.
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
This solution effectively prevents blocking and scuffing by maintaining low friction and preventing silicone oil transfer, ensuring reliable performance of cold seal release films under various conditions, including ambient and heat-aged scenarios.
Implementation Method 1
partially crosslinked polydialkylsiloxane can efficiently lower and stabilize the coefficient of friction ("COF") of the outer release layer
Implementation Method 2
high crystalline polypropylene and low ethylene containing polybutene-1 polymers in combination with partially crosslinked polydialkylsiloxane in the outer release layer
Data Source
AI summary
The present disclosure is directed to a film formulation that resulted in a substantially non-migratory cold seal release film with improved blocking resistance. Specifically, the multilayered biaxially oriented polypropylene film can include a core layer of polypropylene homopolymer; a first outer layer on one side of the core layer that can be suitable for sealing, printing, or coating; and a second outer layer on the opposite side of the core layer that is a blocking resistant layer comprising thermoplastic polymers which reduce blocking tendency.