Biaxially Oriented HDPE Film Sealant Layer
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Solution Overview
Problem
Biaxially oriented high density polyethylene (OHDPE) films face challenges in achieving improved heat sealing properties, such as higher seal strength and a wider temperature range, while maintaining optical properties like transparency and clarity, without adding complexity or cost to the manufacturing process.
Innovation Solution
A multi-layer OHDPE film formulation incorporating a blend of high density polyethylene (HDPE) resins with a nucleating agent in the core layer and a blend of linear low density polyethylene with a polyolefin co-monomer elastomer in the sealant layer, which reduces the seal initiation temperature and enhances heat seal strength, achieved through coextrusion and discharge treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid coating or extrusion coating is used to add a heat sealable skin on top of the OHDPE film core layer, then heat seal ability is achieved, but manufacturing complexity and cost increase due to special treatments and tie layers
Solution Approach 1:
The patent combines the heat sealable layer and core layer into a single co-extruded multilayer structure, eliminating the need for separate coating processes and tie layers. The heat sealable layer (5-20 microns) is directly co-extruded onto the core layer during film formation, integrating multiple functions into one manufacturing step.
Solution Approach 2:
The heat sealable layer serves multiple functions simultaneously: it provides heat sealability, acts as the sealing surface, and eliminates the need for separate primer or tie layers. This multi-functional layer reduces the number of process steps and materials required.
2Reliability
If co-extrusion of heat sealable skin is used on top of OHDPE core layer, then heat sealability is obtained, but heat seal strength is low and limited to narrow temperature range
Solution Approach 1:
The patent modifies the chemical composition of the heat sealable layer by incorporating specific polyolefin copolymers with controlled comonomer content (5-20 wt%). This compositional parameter change enables the layer to achieve both high heat seal strength (exceeding 1000 grams per inch) and a broad sealing temperature range (at least 50°F or 28°C).
Solution Approach 2:
The heat sealable layer is formulated as a composite material blending polyolefin homopolymer with polyolefin copolymer containing 5-20 wt% comonomer. This composite structure combines the structural integrity of the homopolymer with the enhanced sealability and temperature range of the copolymer.
3Illumination intensity
If conventional OHDPE film formulation is used, then optical properties are maintained, but heat seal properties are insufficient with high seal initiation temperature and limited seal range
Solution Approach 1:
The patent applies local quality by creating a distinct heat sealable layer with specific compositional characteristics (5-20 micron thickness, specific polyolefin copolymer blend) only where heat sealing is required, while the core layer maintains the optical properties. This localized functional differentiation allows the core to provide optical clarity while the surface layer provides enhanced sealability.
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 solution provides a lower seal initiation temperature, broader heat seal range, and improved mechanical properties, enabling faster production speeds and lower energy usage while maintaining film clarity and mechanical strength, thus addressing the limitations of prior art OHDPE films.
Implementation Method 1
adding an amount from 1-9 wt % of a nucleating agent to the core layer of the film
Implementation Method 2
achieved through coextrusion and discharge treatment processes
Data Source
AI summary
A multi-layer biaxially oriented high density polyethylene (OHDPE) film with a novel formulation which exhibits superior heat seal properties is disclosed. This improved formulation comprises a blend of a single grade of high density polyethylene (HDPE) or several grades of high density polyethylene (HDPE) with a nucleating agent (NA) used in the core layer to achieve a lower sealing initiation temperature, higher heat seal strength and broader sealing temperature range HDPE-based film that still exhibits typical properties of OHDPE films and a lower haze than conventional OHDPE films. The multi-layer BOPP film has additional layers such as a third polyolefin resin-containing layer, a metal layer, or combinations thereof.