Biodegradable Polylactide Coating Adhesion via Acrylic Copolymer
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Solution Overview
Problem
Biodegradable packaging materials face challenges with non-biodegradable polymer coatings, polylactide's brittleness, high extrusion temperature requirements, and poor heat sealing abilities, which lead to adhesion issues and tearing during extrusion.
Innovation Solution
A biodegradable packaging material with a polymeric coating layer comprising not less than 90 weight-% polylactide and not more than 10 weight-% non-biodegradable acrylic copolymer, which improves adhesion and heat sealing abilities by coextrusion with a biodegradable adhesive layer, such as polybutylene adipate terephthalate, and uses ethylene butyl acrylate glycidyl methacrylate terpolymer as an additive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polylactide is used as the coating polymer for biodegradable packaging material, then biodegradability is achieved, but adhesion to fiber substrate and heat sealing ability deteriorate due to brittleness and high melting temperature
Solution Approach 1:
The patent uses a composite coating structure with an inner adhesion layer (polyester amide or polyolefin) and an outer polylactide layer. The inner layer provides strong adhesion to the fiber substrate, while the outer layer provides biodegradability and moisture barrier properties. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent modifies the extrusion parameters and layer thickness to optimize the performance. By controlling the thickness of the polylactide layer and the adhesion layer, and adjusting extrusion temperature and speed, the patent achieves both good adhesion and heat sealing ability while maintaining biodegradability.
2Strength
If polylactide is extruded at high temperature to manage adherence, then adhesion improves, but degradation and structural defects (tearing, pin holes) increase
Solution Approach 1:
The patent introduces an inner adhesion layer as an intermediary between the fiber substrate and the polylactide layer. This intermediate layer facilitates adhesion at lower temperatures, preventing degradation and structural defects in the polylactide while maintaining strong bonding to the substrate.
Solution Approach 2:
The patent optimizes extrusion parameters including temperature, speed, and pressure to achieve proper adhesion without excessive heat that would cause degradation. The controlled parameter changes allow the polylactide to adhere properly while maintaining its structural integrity.
3Reliability
If polylactide is used in outermost coating layer, then biodegradability is maintained, but heat sealing ability deteriorates due to high melting temperature
Solution Approach 1:
The patent creates a composite coating with an inner adhesion layer and an outer polylactide layer. The inner layer is designed with appropriate melting characteristics for heat sealing, while the outer polylactide layer maintains biodegradability. This composite structure enables heat sealing functionality without compromising biodegradability.
Solution Approach 2:
The patent applies different properties to different layers: the inner layer provides adhesion and heat sealing functionality, while the outer layer provides biodegradability and moisture barrier properties. This local differentiation of material properties resolves the contradiction between heat sealing ability and biodegradability.
4Strength
If multiphase film lamination is used to improve adhesion, then adhesion improves, but manufacturing complexity increases
Solution Approach 1:
The patent combines the adhesion layer and polylactide layer into a single coextruded coating structure, eliminating the need for separate lamination steps. This merging of functions into a unified extrusion process reduces manufacturing complexity while maintaining strong adhesion through the optimized inner layer composition.
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 enhances the heat sealing ability and adhesion of polylactide to the fiber substrate, reducing the need for multiphase film lamination and allowing for effective heat sealing at lower temperatures, while maintaining biodegradability and safety for food contact.
Implementation Method 1
not more than 10 weight-% non-biodegradable of acrylic copolymer blended therein for improving the adhesion of said coating layer to the fiber substrate
Implementation Method 2
allowing for effective heat sealing at lower temperatures
Implementation Method 3
provides the material with an effective barrier to water vapor and oxygen
Data Source
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AI summary
The invention relates to a heat-sealable biodegradable packaging material, which comprises a fiber substrate 1 as well as one or more polymeric coating layers extruded thereon. According to the invention, the material includes a polymeric coating layer 2, which contains not less than 90 weight-% of polylactide and, as an additive, not more than 10 weight-% of acrylic copolymer blended therein for improving the adhesion and/or heat sealing ability of the layer. The invention encompasses also a method for manufacturing packaging material, as well as a product package obtained from the material.