Polylactic Acid Film Transparency via Polyolefin Crystallinity Control
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Solution Overview
Problem
Polylactic acid-based resin compositions with polyolefin-based resins face challenges in achieving a balance between flexibility and transparency due to differences in refractive index and crystallinity, making it difficult to produce transparent and impact-resistant materials.
Innovation Solution
A polylactic acid-based resin composition comprising 50-90% polylactic acid and 10-50% polyolefin-based resin, where the polyolefin-based resin is a copolymer with a heat quantity of crystallization of 40 J/g or less, measured by differential scanning calorimetry, to enhance compatibility and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polylactic acid is mixed with polyolefin to impart flexibility and impact-resistance, then flexibility and strength are improved, but transparency deteriorates due to significant refractive index difference and internal separation
Solution Approach 1:
The patent changes the crystallinity parameter of the polyolefin component by selecting specific types (linear low-density polyethylene with crystallinity of 30-50% or polypropylene with crystallinity of 40-60%) and controlling their molecular weight and distribution. This parameter optimization reduces the refractive index difference between polylactic acid and polyolefin, thereby maintaining transparency while preserving flexibility and impact-resistance.
Solution Approach 2:
The patent creates a composite resin composition by carefully selecting and combining polylactic acid with specific polyolefin types (linear low-density polyethylene or polypropylene) in controlled ratios. This composite approach leverages the complementary properties of each material: the biodegradability and strength of polylactic acid combined with the flexibility and impact-resistance of the selected polyolefin, while managing compatibility issues through proper material selection.
2Strength
If conventional polyolefin is used to improve flexibility, then impact-resistance is enhanced, but compatibility with polylactic acid deteriorates leading to internal separation and poor transparency
Solution Approach 1:
The patent optimizes the crystallinity parameter of the polyolefin component, selecting linear low-density polyethylene with crystallinity of 30-50% or polypropylene with crystallinity of 40-60%. This specific crystallinity range improves compatibility with polylactic acid by reducing refractive index differences, thereby enhancing both transparency and impact-resistance simultaneously.
Solution Approach 2:
The patent applies different material characteristics to different aspects of the final product: it selects polyolefin with specific crystallinity and molecular weight properties to locally optimize compatibility and transparency in the resin composition, while maintaining the overall flexibility and impact-resistance needed for the application.
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 provides a polylactic acid-based resin composition with excellent flexibility and transparency, suitable for applications such as elongated films, heat-shrinkable labels, and containers, maintaining strength and thermal resistance while improving printability and solvent seal properties.
Implementation Method 1
the heat quantity of crystallization of the polyolefin-based resin (B) is 40 J/g or less as measured by differential scanning calorimetry in a thermal process comprising the steps of: heating up to 200 °C at a heating rate of 10 °C/min; keeping the temperature at 200 °C for 5 minutes; and cooling down to the room temperature at a cooling rate of 10 °C/min
Data Source
AI summary
The present invention provides a polylactic acid-based resin composition comprising: 50-90 mass % of a polylactic acid-based resin (A) ; and 10-50 mass % of a polyolefin-based resin (B), wherein the heat quantity of crystallization of the polyolefin-based resin (B) is 40 J/g or less as measured by using differential scanning calorimetry as measured in a thermal process comprising the steps of: heating up to 200 °C at a heating rate of 10 °C/min; keeping the temperature at 200 °C for 5 minutes; and cooling down to the room temperature at a cooling rate of 10 °C/min. The invention also provides: a polylactic acid-based film, a molded product using the film, an elongated film, a heat-shrinkable label, and a container having the label thereon.