Biodegradable PLA-PBS Coating for Liquid Container Integrity
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Solution Overview
Problem
Biodegradable packaging materials face challenges with polylactide's stiffness, high extrusion temperature requirements, and poor heat-sealability, leading to issues like raw-edge penetration in liquid containers, which affects the integrity and appearance of disposable cups.
Innovation Solution
A biodegradable polymer blend comprising at least 70 weight-% polylactide and 5 weight-% polybutylene succinate or its derivatives, with an optional acrylate copolymer, is extruded directly onto a fibrous substrate to enhance adhesion and reduce raw-edge penetration, improving heat-sealability and preventing liquid penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polylactide is used as the coating polymer to achieve biodegradability, then environmental friendliness is improved, but extrusion temperature increases and material becomes stiff and fragile
Solution Approach 1:
The patent uses a composite material system consisting of polylactide coating layer combined with specific fibrous substrates (paper,纸板, or non-woven fabrics) to achieve biodegradability while managing the stiffness and fragility issues through material composition rather than modifying the polylactide itself
2Reliability
If polylactide coating layer is applied to achieve biodegradability, then environmental compatibility is improved, but heat-sealability deteriorates due to high melting point
Solution Approach 1:
The patent modifies the thermal parameters of the polylactide coating by controlling its thickness (5-20 μm) and combining it with substrates having specific thermal properties, enabling heat-sealing at temperatures below the polylactide melting point through thermal conduction from the substrate
3Strength
If polylactide is extruded at high temperature to improve adhesion, then bonding strength is improved, but material deterioration increases and pin holes form
Solution Approach 1:
The patent optimizes the extrusion temperature parameter to a specific range that provides sufficient adhesion without causing polylactide deterioration, and controls the coating thickness parameter (5-20 μm) to prevent pin hole formation while maintaining bonding strength
4Reliability
If coating layer thickness is increased to improve adhesion and reduce pin holes, then coating integrity is improved, but extrusion temperature requirement increases
Solution Approach 1:
The patent identifies an optimal coating thickness range (5-20 μm) that provides sufficient adhesion and integrity without requiring excessive extrusion temperature, balancing coating quality with process feasibility
5Reliability
If polylactide coating is applied to replace non-biodegradable materials, then environmental sustainability is improved, but raw-edge penetration occurs in liquid containers
Solution Approach 1:
The patent controls the coating thickness parameter (5-20 μm) to provide sufficient barrier properties that prevent raw-edge penetration of liquids while maintaining the biodegradable nature of the polylactide coating
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 significantly reduces raw-edge penetration and improves heat-sealability, preventing liquid from reaching the fibrous substrate and maintaining the integrity and appearance of disposable cups, especially those containing hot beverages.
Implementation Method 1
a biodegradable polymer blend comprising at least 70 weight-% polylactide and 5 weight-% polybutylene succinate or its derivatives, with an optional acrylate copolymer, is extruded directly onto a fibrous substrate
Implementation Method 2
improving heat-sealability and preventing liquid penetration
Data Source
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AI summary
The invention concerns a heat-sealable biodegradable packaging material, which comprises a fibrous substrate (1) and one or more polymer coating layers (2) extruded onto said substrate. According to the invention the packaging material includes at least one polymer coating layer (2) containing at least 70 weight-% of polylactide (PLA) and at least 5 weight-% of polybutylene succinate (PBS) or its derivate blended therewith. Optionally an acryl copolymer such as ethylene butyl acrylate glycidyl methacrylate terpolymer (EBAGMA) may be included in the polymer blend. The invention further concerns a heat-sealed container, such as a disposable drinking cup, and a heat-sealed product package made from the packaging material, as well as uses of PBS or its derivates as blends with PLA in extrusion coating, for improving adhesivity of the coating to the fibrous substrate and reduced raw edge penetration to the packaging material, especially penetration of hot coffee held in the drinking cup.