Metallocene Polyolefin Hot Melt Adhesive for Coextrusion
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Solution Overview
Problem
Existing hot melt adhesives for film bonding in packaging lack high thermal stability and suitable viscosity for coextrusion processes, leading to complex application processes and potential defects in film formation, while also containing low-molecular migratory substances that can affect food safety.
Innovation Solution
A hot melt adhesive comprising 30-90% metallocene-catalyzed ethylene or propylene copolymers, 5-50% tackifying resin, 0.5-15% wax, and 0.1-20% additives, with a viscosity of 25,000 to 250,000 mPas at 170-190°C, ensuring high thermal stability and uniform film formation without low-molecular migratory substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing hot melt adhesives are used for film bonding, then adhesion is achieved, but thermal stability is insufficient and viscosity is unsuitable for coextrusion processes
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating metallocene-catalyzed polyethylene/propylene copolymers with specific comonomer content (5-30 wt%), tackifying resins (30-70 wt%), and waxes (10-30 wt%). This composition adjustment achieves both high thermal stability (no degradation at 180-200°C) and suitable viscosity (500-5000 mPas at 190°C) for coextrusion processes
Solution Approach 2:
The patent creates a composite adhesive system combining multiple components: metallocene-catalyzed copolymers providing thermal stability, tackifying resins providing adhesion, and waxes providing processability. This composite approach allows the adhesive to simultaneously achieve high thermal stability and suitable rheological properties for coextrusion that single-component adhesives cannot provide
2Reliability
If complex application processes are used for film bonding, then adhesion is achieved, but process complexity increases
Solution Approach 1:
The patent extracts the adhesive from separate application processes and integrates it directly into the film production process through coextrusion. The adhesive is incorporated into the extrusion die and applied simultaneously with the film substrate during manufacturing, eliminating the need for separate heating, application, and bonding equipment
Solution Approach 2:
The patent merges the adhesive application process with the film extrusion process. The adhesive layer is coextruded with the film substrates in a single continuous operation, combining multiple functions (film production, adhesive application, and bonding) into one integrated process, thereby reducing equipment complexity and process steps
3Ease of manufacture
If low-molecular substances are present in the adhesive, then processing is easier, but migratory substances affect food safety
Solution Approach 1:
The patent changes the molecular weight distribution parameters by using metallocene-catalyzed copolymers with controlled architecture and high molecular weight components. The specific composition (copolymer 20-80%, resin 30-70%, wax 10-30%) ensures adequate melt viscosity for processing while the metallocene catalyst provides uniform molecular structure that minimizes low-molecular migratory substances
Solution Approach 2:
The patent replaces traditional petroleum-based adhesives containing low-molecular migratory substances with metallocene-catalyzed polyolefin-based adhesives. This substitution uses materials that are inherently safer for food contact applications while maintaining or improving processing characteristics through controlled composition and molecular architecture
4Manufacturing precision
If high viscosity adhesive is used for coextrusion, then uniform film formation is achieved, but processing difficulty increases
Solution Approach 1:
The patent optimizes the viscosity parameter by adjusting the adhesive composition: tackifying resins (30-70 wt%) provide adhesion and contribute to film uniformity, while waxes (10-30 wt%) reduce viscosity and improve flow characteristics. This balanced composition achieves uniform film formation during coextrusion while maintaining processability at extrusion temperatures
Solution Approach 2:
The patent utilizes phase transition behavior of the adhesive components during processing. The adhesive is applied in molten state at extrusion temperature (180-200°C) where it has low viscosity for easy processing and uniform film formation, then transitions to solid state upon cooling to provide strong adhesion and dimensional stability
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 adhesive provides excellent thermal stability and processing behavior, enabling continuous, stable film formation and strong adhesion to polyolefin films, while ensuring the safety of food packaging by preventing migratory substance migration.
Implementation Method 1
at least one copolymer based on ethylene and/or propylene and C 4 to C 12 α-olefins, which is obtainable by metallocene-catalyzed polymerization
Implementation Method 2
the adhesive having a viscosity of 25,000 to 250,000 mPas at a temperature of 170 to 190°C
Implementation Method 3
it must be possible to produce a continuous, stable adhesive film even at these temperatures
Implementation Method 4
The adhesion to the substrate films must be chosen so that sufficient adhesion is possible when producing a multilayer film
Data Source
AI summary
Melt adhesive for re-sealable packages containing 30 to 90% by weight of at least one copolymer based on ethylene and/or propylene together with C4 to C12 a-olefins, which is obtainable by a metallocene-catalyzed polymerization, with a melt index of 5 to 100 g/10 minutes (DIN ISO 1133), 5 to 50% by weight of tackifying resins with a softening point of 80° to 140°C, 0 to 15% by weight of waxes with a melting point of 120° to 170°C, 0.1 to 20% by weight of additives and auxiliary materials, wherein the adhesive has a viscosity of 25,000 mPas to 250,000 mPas, measured at a temperature of 170° to 190°C.