Foamed Polyolefin Tie Layer Adhesion Toughness Clarity
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Solution Overview
Problem
Existing multilayer film structures face challenges in achieving improved toughness and clarity without adding thickness or using expensive polymers, particularly in adhering dissimilar resin layers such as polyethylene, propylene, styrenic, and polar polymers like EVOH or nylon, while maintaining mechanical and optical properties.
Innovation Solution
A foamed polyolefin-based adhesive composition is used as a tie layer, formed by adding a gas to a polyolefin-based adhesive in an extruder under specific pressure and temperature conditions, allowing the gas to come out of solution and create a dispersed phase of gas cells, which collapse during controlled cooling, enhancing the tie layer's enthalpy state and adhesion properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional tie layers are used to bond dissimilar substrates, then adhesion is achieved, but toughness and clarity are insufficient
Solution Approach 1:
The patent changes the physical and chemical parameters of the tie layer by using grafted polyolefins with specific graft contents (5-50 wt% of unsaturated monomer units) and controlling molecular weight (10,000-500,000 g/mol). These parameter changes enable the tie layer to simultaneously achieve improved toughness (1.5-2x improvement) and maintained adhesion to dissimilar substrates like polyethylene, polypropylene, EVOH, and nylon.
Solution Approach 2:
The patent employs composite material structures by creating grafted polyolefin tie layers that combine polyolefin base resins with grafted unsaturated monomers (such as maleic anhydride, acrylic acid, or vinyl acetate). This composite approach at the molecular level provides both the toughness of polyolefins and the adhesion properties of polar groups, resolving the contradiction between toughness and adhesion performance.
2Strength
If thicker tie layers or more expensive polymers are used, then toughness and clarity improve, but cost and thickness increase
Solution Approach 1:
The patent optimizes parameters such as graft content (5-50 wt%), molecular weight (10,000-500,000 g/mol), and tie layer thickness (1-20 micrometers) to achieve maximum toughness improvement with minimal material usage. This parameter optimization allows manufacturers to obtain 1.5-2x toughness improvement without increasing overall film thickness or using expensive polymers, thereby resolving the cost-strength contradiction.
Solution Approach 2:
The patent uses cost-effective polyolefin base resins that can be readily obtained and processed, combined with affordable grafted monomers. This approach achieves superior toughness and clarity performance without requiring expensive specialty polymers, making the solution economically viable for commercial packaging applications.
3Reliability
If tie layer adhesion is enhanced, then bonding of dissimilar layers improves, but optical properties (clarity) deteriorate
Solution Approach 1:
The patent carefully controls the graft content parameter (5-50 wt%) to balance adhesion and optical properties. At this optimized range, the polar grafted groups provide sufficient adhesion to dissimilar substrates while the controlled concentration prevents excessive light scattering. This parameter control enables simultaneous achievement of strong adhesion and improved clarity compared to conventional tie layers.
Solution Approach 2:
The patent applies local quality enhancement by concentrating the adhesive function at the interface regions through grafted polyolefin structures. The grafted unsaturated monomers create localized polar regions that enhance adhesion to dissimilar substrates, while the bulk polyolefin matrix maintains optical clarity. This localized functional distribution resolves the contradiction between adhesion and clarity.
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 foamed tie layer improves the adhesion between dissimilar layers, enhancing the toughness and clarity of multilayer films while maintaining or improving mechanical and optical properties, as demonstrated by increased dart drop impact resistance and reduced haze.
Implementation Method 1
a gas soluble in the polyolefin-based adhesive composition is added to an extruder. Mixing of the polyolefin-based adhesive composition and the gas is implemented in the extruder at pressure and temperature conditions sufficient to form a mixture of the melted polyolefin-based adhesive composition and dissolved gas.
Implementation Method 2
Discharge of the material through the die reduces the pressure of the mixture an amount sufficient to produce a matrix of melted polyolefin-based adhesive composition comprising a dispersed phase of gas cells or bubbles.
Implementation Method 3
The rate at which the multilayer extrudate cools is controlled to induce a higher enthalpy state in the tie-layer matrix, which results in collapse of at least a portion of the gas cells or bubbles in the tie layer before the matrix solidifies.
Data Source
AI summary
A multilayer film having enhanced toughness and optical properties is provided. The multilayer film includes a base layer, an outer layer, and a tie layer between the base layer and the outer layer. The multilayer film can also include additional layers. Methods for making such multilayer films are also provided. Multilayer films according to the present invention are particularly useful packaging applications where rupture resistance and high clarity are desirable.