Lactide Copolymer Film for Flexible Food Packaging
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Solution Overview
Problem
Polylactide resins used in packaging films face challenges with weak impact resistance and flexibility due to hydrolysis by catalysts and moisture, limiting their application in semipermanent uses and requiring costly processing methods.
Innovation Solution
A packaging film incorporating a lactide copolymer with block copolymerized repeating units linked by urethane connecting groups derived from a polyvalent isocyanate compound, providing enhanced mechanical properties and flexibility while minimizing toxicity and pollution risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polylactide resin is used for packaging film, then mechanical strength is achieved, but flexibility and impact resistance deteriorate
Solution Approach 1:
The invention uses a block copolymer structure combining polylactide hard segments with polyether polyol soft segments. This creates a composite material at the molecular level where the hard segments provide mechanical strength while the soft segments provide flexibility and impact resistance, resolving the contradiction between strength and flexibility.
Solution Approach 2:
The copolymer is segmented into distinct hard segments (polylactide) and soft segments (polyether polyol) that are block copolymerized together. This segmentation allows each segment to contribute its specific properties - the hard segments for strength and the soft segments for flexibility - without compromising the other.
2Quantity of substance
If ring opening polymerization method is used, then high molecular weight is obtained, but preparation complexity and cost increase
Solution Approach 1:
The invention merges the advantages of both polycondensation and ring opening polymerization methods. It uses ring opening polymerization to achieve high molecular weight but simplifies the process by directly copolymerizing lactide with polyether polyol in one step, eliminating the need for separate lactide monomer preparation and reducing overall process complexity.
3Adaptability or versatility
If polylactide resin is processed into film, then packaging application is enabled, but hydrolysis resistance deteriorates
Solution Approach 1:
The block copolymer structure creates a composite where the polylactide hard segments provide packaging functionality while the polyether polyol soft segments provide resistance to hydrolysis. The urethane connecting groups further stabilize the structure against moisture-induced degradation.
Solution Approach 2:
The polyether polyol segments act as intermediaries that protect the polylactide segments from hydrolysis by moisture. These soft segments are more resistant to hydrolytic degradation and shield the ester bonds in the polylactide from water attack, thereby improving overall hydrolysis resistance.
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 lactide copolymer film exhibits superior mechanical properties, flexibility, and processability, making it suitable for food packaging with reduced concerns about residual catalysts and monomers, and maintains biodegradability.
Implementation Method 1
block copolymerized repeating units of Chemical Formula 1 in which the hard segments of polylactide repeating units are linked to both ends of the soft segments of polyether polyol repeating units, wherein the block copolymerized repeating units are connected to each other through the intermediation of urethane connecting groups derived from a polyvalent isocyanate compound
Data Source
Figure 1
AI summary
[SUMMARY] The present invention relates to a packaging film including a lactide copolymer having no problem of pollution or toxicity while having good flexibility in addition to excellent properties such as mechanical properties, transparency, and processability, and preferably being applicable to food packaging. The packaging film includes a lactide copolymer including two or more specific block copolymerized repeating units that the hard segments of polylactide repeating units are connected to both ends of the soft segments of polyether polyol repeating unit, wherein the block copolymerized repeating units are connected to each other through the intermediation of urethane connecting groups derived from polyvalent isocyanate compound of which the average equivalent of isocyanate group per a molecule is more than 2 and less than 3.