Polylactic Acid Resin Composition for Flexible Packaging Films
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Solution Overview
Problem
Conventional polylactic acid resins used for packaging materials lack sufficient flexibility and exhibit poor mechanical properties, transparency, and stability due to the use of low-molecular weight flexibilizers, which lead to issues like yellowing and decreased heat resistance.
Innovation Solution
A polylactic acid resin composition incorporating a hard segment with polylactic acid repeating units and a soft segment of polyurethane polyol repeating units linked via a urethane bond, along with an optimized antioxidant content, to enhance flexibility, transparency, and mechanical properties while preventing yellowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low-molecular weight flexibilizers or plasticizers are added to polylactic acid resins, then flexibility is improved, but mechanical properties deteriorate and yellowing occurs
Solution Approach 1:
The invention changes the molecular weight parameter of the flexibilizer from low-molecular weight to high-molecular weight (number average molecular weight of 10,000 to 1,000,000). This parameter change resolves the contradiction by providing sufficient flexibility improvement while maintaining mechanical properties and preventing yellowing, as the high molecular weight prevents degradation and maintains structural integrity.
Solution Approach 2:
The invention creates a composite material system by combining polylactic acid resin with high-molecular weight flexibilizers and specific antioxidants. This composite approach allows the system to achieve flexibility enhancement while the antioxidant component prevents yellowing and the high molecular weight flexibilizer maintains mechanical properties, resolving the multiple contradictions simultaneously.
2Ease of operation
If plasticizers are added to polylactic acid resins, then flexibility is improved, but transparency decreases due to increased haze
Solution Approach 1:
The invention changes the molecular weight parameter of the flexibilizer to high-molecular weight (10,000 to 1,000,000), which prevents phase separation and maintains optical uniformity. This resolves the transparency issue while still providing flexibility improvement, as the high molecular weight flexibilizer integrates better with the polymer matrix without creating light-scattering interfaces.
3Strength
If conventional polylactic acid resins are used for packaging films, then mechanical properties are maintained, but flexibility is insufficient
Solution Approach 1:
The invention introduces a new parameter - high-molecular weight flexibilizers with number average molecular weight of 10,000 to 1,000,000 - which provides flexibility enhancement without compromising mechanical properties. This resolves the contradiction by finding a molecular weight range that balances both flexibility and strength requirements.
4Ease of operation
If plasticizers are added to polylactic acid resins, then flexibility is improved, but stability decreases due to plasticizer bleed-out over time
Solution Approach 1:
The invention changes the molecular weight parameter of the flexibilizer from low to high (10,000 to 1,000,000), which dramatically improves stability by preventing bleed-out. The high molecular weight creates a more stable interaction with the polylactic acid matrix through increased entanglement and reduced mobility, while still maintaining flexibility improvement.
Data Source
AI summary
The present invention relates to a polylactic acid resin composition useful as a packaging material which has not only improved flexibility but also superior external appearance and superior properties such as mechanical property, transparency, heat resistance, anti-blocking property, workability of a film, and the like, and a packaging film including the same.The polylactic acid resin composition comprises a polylactic acid resin including a hard segment comprising a polylactic acid repeating unit and a soft segment comprising a polyurethane polyol repeating unit in which polyether polyol repeating units are linearly linked via a urethane bond; and a specific content of antioxidant.