Polylactic Acid Block Copolymer Stereo-Complex Production
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Solution Overview
Problem
Current methods for producing polylactic acid block copolymers with high molecular weight and low cost face challenges in achieving 100% stereo-complex crystal content without homo-PLA formation, and are hindered by the high market price of D-lactide, limited supply, and unsuitable industrial scalability.
Innovation Solution
A method involving ring-opening polymerization of D-lactide or L-lactide in the presence of poly-L-lactic acid or poly-D-lactic acid, with a biased mass ratio of 60/40 to 91/9, allowing for the production of polylactic acid block copolymers with weight average molecular weights from 80,000 to 500,000, and achieving a high rate of stereo-complex crystal content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If poly-L-lactic acid and poly-D-lactic acid are mixed in a mass ratio of 1:1 to form stereo-complex polylactic acid, then heat resistance is improved, but homo-PLA crystals appear simultaneously and production cost increases due to limited supply of D-lactide
Solution Approach 1:
The patent changes the compositional parameter from equal mixing (1:1 mass ratio) to biased mixing (L-component/D-component mass ratio of 60:40 to 91:9), which fundamentally alters the crystallization behavior to suppress homo-PLA formation while maintaining stereo-complex crystal structure and heat resistance properties
Solution Approach 2:
The patent applies local quality by creating specific local structures through biased compositional mixing, where the L-component and D-component are distributed in a non-uniform ratio to favor the formation of stereo-complex crystals while preventing the formation of homo-PLA crystals in certain regions
2Temperature
If poly-L-lactic acid and poly-D-lactic acid are mixed in a mass ratio of 1:1 to form stereo-complex polylactic acid, then heat resistance is improved, but homo-PLA crystals appear simultaneously reducing the effectiveness of scPLA
Solution Approach 1:
The patent changes the compositional parameter from equal mixing (1:1 mass ratio) to biased mixing (L-component/D-component mass ratio of 60:40 to 91:9), which fundamentally alters the crystallization behavior to suppress homo-PLA formation while maintaining stereo-complex crystal structure and heat resistance properties
Solution Approach 2:
The patent applies preliminary anti-action by preemptively suppressing the formation of homo-PLA crystals through biased compositional mixing before the crystallization process begins, preventing the harmful effect of homo-PLA contamination rather than addressing it after formation
3Reliability
If D-lactide is used in equal amounts to produce polylactic acid block copolymer, then stereo-complex crystal content reaches 100%, but production cost increases due to limited supply and high market price
Solution Approach 1:
The patent uses the principle of substituting expensive D-lactide with cheaper L-lactide by utilizing the inherent chirality difference between L and D forms, achieving the desired stereo-complex crystal structure with reduced dependence on the more expensive and limited-supply D-lactide
Solution Approach 2:
The patent changes the compositional parameter from equal mixing (1:1 mass ratio) to biased mixing (L-component/D-component mass ratio of 60:40 to 91:9), which fundamentally alters the crystallization behavior to suppress homo-PLA formation while maintaining stereo-complex crystal structure and heat resistance properties
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
This approach enables the stable production of polylactic acid block copolymers with high heat resistance and biodegradability, suitable for various applications, including fibers that can withstand ironing at high temperatures, while reducing production costs by utilizing a cheaper raw material in larger quantities.
Implementation Method 1
ring-opening polymerization of D-lactide (D component) is carried out in the presence of poly-L-lactic acid (L component), or ring-opening polymerization of L-lactide (L component) is carried out in the presence of poly-D-lactic acid (D component)
Implementation Method 2
it is difficult to stably form scPLA having 100% rate of content of a stereo-complex crystal by heat melting process
Data Source
AI summary
It is an object of the present invention to provide a method for producing a polylactic acid block copolymer having high molecular weight, and in lower cost, wherein only a stereo-complex crystal is capable of growing, even when heat melting process is repeated. The present invention relates to a method for producing a polylactic acid block copolymer characterized in that (i) ring-opening polymerization of D-lactide (D component) is carried out in the presence of poly-L-lactic acid (L component), or (ii) ring-opening polymerization of L-lactide (L component) is carried out in the presence of poly-D-lactic acid (D component), and mass ratio of the D component and the L component is the D component/the L component=60/40 to 91/9, or the L component/the D component=60/40 to 91/9.