CBC Tie Layers With Functionalized Polyethylene for Heat-Resistant Bonding
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Solution Overview
Problem
Conventional tie layers fail to maintain adhesion between polypropylene and polar layers at high temperatures, leading to delamination, especially in applications requiring high line speeds and limited polymer travel time in the air gap.
Innovation Solution
Utilizing a tie layer comprising a crystalline block composite (CBC) component and functionalized polyethylene, which includes an ethylene polymer, an alpha-olefin-based crystalline polymer, and a block copolymer, along with a polyolefin elastomer modifier, to enhance adhesion and heat resistance up to 120°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional tie layers are used, then adhesion between polypropylene and polar layers is achieved at normal temperatures, but adhesion fails and delamination occurs at high temperatures (greater than 100°C)
Solution Approach 1:
The patent modifies the chemical composition parameters of the tie layer by incorporating functionalized polyethylene with specific graft content (0.1-5 wt% carboxylic acid groups) and controlled molecular weight (MFR 0.1-100 dg/min). These parameter changes enable the tie layer to maintain adhesion stability at elevated temperatures up to 120°C, resolving the contradiction between normal temperature adhesion and high temperature resistance.
Solution Approach 2:
The patent creates a composite tie layer system combining functionalized polyethylene with specific polyolefin resins (polyethylene, polypropylene, or their copolymers) in defined ratios (1-10 phr functionalized polyethylene per 100 phr polyolefin resin). This composite material approach provides both adhesion capability and thermal stability, simultaneously achieving reliable adhesion at normal temperatures and resistance to delamination at high temperatures.
2Productivity
If high line speed (greater than or equal to 300 mpm) is used during extrusion coating, then productivity is improved, but polymer travel time in the air gap is limited preventing stress relaxation and generating high residual stress that challenges bonding to substrates
Solution Approach 1:
The patent adjusts the rheological parameters of the tie layer material by selecting polyethylene with specific melt flow rates (MFR 0.1-100 dg/min at 190°C/2.16 kg) and controlling the graft content of functionalized polyethylene (0.1-5 wt%). These parameter changes enable the material to achieve proper adhesion quality even with limited stress relaxation time at high line speeds of 300 mpm or greater, resolving the contradiction between productivity and adhesion quality.
Solution Approach 2:
The functionalized polyethylene acts as an intermediary substance between the polypropylene layer and the polar substrate (aluminum foil or metalized film). The carboxylic acid groups on the functionalized polyethylene provide chemical interaction with the polar substrate, enabling effective bonding even when the polymer residence time in the air gap is limited due to high production speeds.
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 CBC component and functionalized polyethylene provide superior adhesion and improved heat resistance, maintaining bond integrity at high temperatures, suitable for applications like retort packaging and battery packaging.
Implementation Method 1
a tie layer that adheres the polypropylene layer to the polar layer
Implementation Method 2
provide improved heat resistance for high-temperature applications such as retort packaging or battery packaging
Data Source
AI summary
A coated substrate includes a polar layer, at least one polypropylene layer, and at least one tie layer that adheres the polypropylene layer to the polar layer, wherein the tie layer includes a crystalline block composite (CBC) component including an ethylene polymer (EP) comprising at least 90 mol % polymerized ethylene by weight of the ethylene polymer, an alpha-olefin-based crystalline polymer (CAOP), and a block copolymer including an ethylene polymer block comprising at least 90 mol % polymerized ethylene by weight of the ethylene polymer block and a crystalline alpha-olefin block (CAOB), functionalized polyethylene having a melt flow rate MFR (190 °C/ 2.16 kg) of 1.0 to 10.0 dg/min as determined according to ASTM D1238, wherein the functionalized polyethylene comprises polyethylene grafted with ethylenically unsubstituted dicarboxylic acid or derivative thereof, and a modifier comprising a polyolefin elastomer.