Biodegradable Three-Layer Film for Food Packaging
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Solution Overview
Problem
Conventional biodegradable packaging films for perishable foods, such as polypropylene and polyethylene, lack transparency and high oxygen and water vapor permeability, leading to reduced shelf life due to inadequate packaging properties.
Innovation Solution
A 8 to 20 μm thick three-layer polyester film with specific layer structures and compositions, including outer layers made of polybutylene sebacate-co-terephthalate and a middle layer containing starch, providing high transparency, tear propagation resistance, and optimized oxygen and water vapor permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional biodegradable plastic films (polypropylene, polyethylene) are used, then biodegradability is achieved, but transparency and oxygen/water vapor permeability are insufficient
Solution Approach 1:
The patent uses a three-layer composite film structure where the outer layers consist of polybutylene sebacate-co-terephthalate (a biodegradable polyester) and the middle layer consists of starch blend. This composite structure combines the biodegradability of polyester with the transparency and barrier properties of starch, achieving both biodegradability and high transparency while maintaining appropriate oxygen and water vapor permeability.
2Strength
If starch-containing biodegradable films are used, then tear propagation resistance is improved, but transparency deteriorates
Solution Approach 1:
The patent divides the film into three functional layers: outer layers made of polybutylene sebacate-co-terephthalate provide transparency and appropriate gas permeability, while the middle starch-containing layer provides tear propagation resistance. This segmentation allows each layer to optimize its specific function without compromising the others, solving the contradiction between tear strength and transparency.
3Duration of action of stationary object
If oxygen permeability is increased to extend shelf life, then ripening is accelerated, but if decreased, condensation and mold growth are promoted
Solution Approach 1:
The patent optimizes the oxygen permeability parameter to a specific range (5500-18000 ml/m²/day) that balances two opposing requirements: allowing sufficient oxygen transmission to prevent anaerobic conditions and condensation that promote mold growth, while limiting oxygen intake to slow down ripening processes. The starch content (25-70% in middle layer) and film thickness (8-20 μm) are adjusted to achieve this optimal permeability parameter.
4Reliability
If film thickness is reduced to 8-20 μm for environmental reasons, then biodegradability is improved, but mechanical strength decreases
Solution Approach 1:
The patent creates a composite three-layer film with outer layers of biodegradable polyester (8-20 μm total thickness) and a middle layer of starch blend. This composite structure maintains mechanical strength through the reinforcing effect of the starch layer while keeping the overall thickness minimal (8-20 μm) to ensure rapid biodegradation. The synergistic combination allows thin-film applications with adequate mechanical properties.
Data Source
AI summary
The invention relates to a biodegradable, 8- to 20-μm-thick three-layer polyester film having a layer structure A/B/C or preferably A/B/A, wherein the two outer layers (A) or (A, C) are composed of: Ai) 55 to 99.99 wt.%, relative to the polyester mixture of the outer layers, of a polyester selected from the group consisting of: polybutylensebacat-co-terephthalate, polybutylensebacat-co-adipat-co-terephthalats, polybutylensebacat-co- succinat-co-terephthalats or mixtures thereof or a mixture of Polybutylensebacat-co-terephthalate and Polybutylenadipat-co-terephthalate; Aii) 0.01 to 5 wt.%, relative to the polyester mixture of the outer layers, at least one additive selected from the group consisting of: a wax, a softener, a nucleating agent, an anti-fog agent, a filler and an antiblocking agent; and Aiii) 0 to 44.99 wt.%, relative to the polyester mixture of the outer layers, of an additional biodegradable polymer selected from the group consisting of: polyactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate, polypropylene carbonate (PPC) or polyester, produced from aliphatic dicarboxylic acids and an aliphatic didydroxy compound; and the center layer B composed of: Bai) 40 to 75 wt.%, relative to the mixture of the center layer, of a biodegradable, alphatic-aromatic polyester; Baii) 25 to 40 wt.%, relative to the mixture of the center layer, starch having a softener content of 0 to 5 wt.%, relative to the total weight of the component Baii); and Baiii) 0 to 20 wt.%, relative to the mixture of the center layer, of an additional biodegradable polymer selected from the group consisting of: polyactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate, polypropylene carbonate (PPC) or polyester, produced from aliphatic dicarboxylic acids and an aliphatic dihydroxy compound; or Bbi) 25 to 70 wt.% relative to the mixture of the center layer, of a biodegradable, aliphatic-aromatic polyester Bbii) 30 to 55 wt.%, relative to the mixture of the center layer, starch having a softener proportion of 5 to 35 wt.%, relative to the total weight of the component Bbii); and Bbiii) 0 to 20 wt.%, relative to the mixture of the center layer, of an additional biodegradable polymer, selected from the group consisting of: polyactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate, polypropylene carbonate (PPC) or polyester, produced from aliphatic dicarboxylic acids and an aliphatic dihydroxy compound.