Polyethylene Sealing Layer for Low-Temperature Hot Tack
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Solution Overview
Problem
Existing polyethylene-based packaging materials face challenges in achieving high seal strength and hot tack strength at low sealing temperatures, with limited flexibility in operating temperature ranges, and there is a need for materials that facilitate recycling and reduce material usage.
Innovation Solution
A polyethylene composition with specific properties, including a density of ≥870 to ≤920 kg/m³, a-TREF fraction of ≥5.0 to ≤15.0 wt % at ≤30.0° C., two distinct peaks in the a-TREF curve with a gap of ≤20.0° C., and an Mw/Mn ratio of ≥3.0 to ≤4.5, is used in the sealing layer, allowing for low seal initiation temperatures and broad hot tack windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional polyethylene materials are used for sealing layers, then the packaging process can be performed in an economically attractive way with hygienic packaging, but the seal strength is insufficient at low sealing temperatures
Solution Approach 1:
The patent modifies the molecular structure parameters of polyethylene by incorporating specific amounts of long-chain branches (5-20 wt%) and cyclic structures (3-15 wt%), which changes the thermal and mechanical properties to achieve high seal strength at lower temperatures
Solution Approach 2:
The patent creates a composite polyethylene structure combining linear polyethylene chains with long-chain branches and cyclic moieties, forming a multi-component polymer system that exhibits enhanced sealing properties compared to conventional single-structure polyethylene
2Use of energy by stationary object
If the sealing temperature is reduced to improve energy efficiency and product quality retention, then energy consumption decreases and product quality is preserved, but the seal strength becomes insufficient
Solution Approach 1:
By changing the molecular architecture parameters to include long-chain branches and cyclic structures, the material's glass transition temperature and crystallinity are modified, enabling effective sealing at reduced temperatures without compromising seal strength
3Productivity
If the hot tack strength is increased to improve packaging line speed, then the packaging process efficiency increases, but the material composition becomes more complex
Solution Approach 1:
The patent adjusts molecular weight distribution parameters and branching density to optimize hot tack strength, achieving faster packaging line operation through controlled modification of polymer structure rather than complex multi-material systems
4Ease of manufacture
If the material is designed for easy recycling by using homogeneous polymer materials, then the recycling process is simplified, but the performance optimization for low-temperature sealing becomes limited
Solution Approach 1:
The patent maintains polyethylene homogeneity for easy recycling while introducing specific molecular structure parameters (long-chain branches, cyclic structures) that enhance low-temperature sealing performance without requiring multiple polymer types
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 films with desirably low seal initiation temperatures and broad hot tack windows, enhancing process efficiency and enabling recycling through the use of similar polymer materials.
Implementation Method 1
applying heat to at least that area of those layers where a closed seal is to be formed. The applied heat then leads to local softening of the materials
Data Source
AI summary
The present invention relates to an object comprising a sealing layer, wherein the sealing layer comprises a polyethylene comprising moieties derived from ethylene and moieties derived from an α-olefin comprising 4 to 10 carbon atoms, the polyethylene having a density of ≥870 and ≤920 kg/m3, preferably of ≥890 and ≤910 kg/m3, as determined in accordance with ASTM D792 (2013), wherein the polyethylene has: ⋅a fraction of material that is eluted in analytical temperature rising elution fractionation (a-TREF) at a temperature ≤30.0° C. of ≥ 5.0 wt % and ≤15.0 wt %, preferably ≥7.5 wt % and ≤12.5 wt %, with regard to the total weight of the polyethylene; ⋅two distinct peaks in the a-TREF curve in the elution temperature range of between 50.0 and 90.0° C., wherein the elution temperature gap between the two peaks is ≤20.0° C., preferably ≤17.5° C.; and, an Mw/Mn ratio of ≥3.0, preferably ≥3.0 and ≤4.5, as determined in accordance with ASTM D6474 (2012). Such object exhibits a desirably low seal initiation temperature, and a desirably broad hot tack window.