Lactide-Caprolactone Adhesive Carbodiimide Stabilization
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Solution Overview
Problem
Non-reactive hot melt adhesives based on poly(L-lactide) and poly(ε-caprolactone) copolymers with a molar ratio of 81/19 exhibit poor long-term thermal stability, leading to degradation of adhesion strength when exposed to elevated temperatures, making them unsuitable for storing and using in packaging applications, especially with materials like cardboard and wood.
Innovation Solution
Incorporating a small amount (0.05-2.5% by weight) of a carbodiimide compound, such as dicyclohexyl carbodiimide or bis-3-isocyanoato-4-methylphenyl carbodiimide, into the copolymer of lactide and caprolactone with a molar ratio of at least 1.5, which stabilizes the adhesion properties and prevents unwanted degradation, while maintaining the adhesive's biodegradability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a copolymer of lactide and caprolactone with molar ratio 81/19 is used as hot melt adhesive, then biodegradability is improved, but long-term thermal stability deteriorates
Solution Approach 1:
The patent combines lactide-copolymer with carbodiimide compounds to create a composite adhesive system. The carbodiimide acts as a stabilizing component that prevents thermal degradation of the biodegradable copolymer, resolving the contradiction between biodegradability and thermal stability by creating a synergistic material composition where each component compensates for the other's weaknesses
Solution Approach 2:
The carbodiimide compound serves as a chemical intermediary that reacts with carboxylic acid groups formed during thermal degradation of the lactide-copolymer. This intermediary mechanism prevents the accumulation of degradation products that would otherwise cause adhesion loss, thereby maintaining reliability while preserving biodegradability
2Ease of operation
If adhesive is stored at elevated temperatures for long periods, then packaging application convenience is improved, but adhesion strength deteriorates
Solution Approach 1:
The carbodiimide compound is incorporated into the adhesive formulation in advance to preemptively prevent thermal degradation. This preliminary protective action allows the adhesive to be stored at elevated temperatures without subsequent loss of adhesion strength, enabling convenient storage while maintaining performance
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 addition of carbodiimide significantly enhances the thermal stability of the adhesive, maintaining adhesion strength over time even at elevated temperatures, preventing brittleness at optimal concentrations (0.1-2.0% by weight), thus ensuring reliable sealing of packages made from various materials.
Implementation Method 1
the adhesive further comprises a carbodiimide compound... stabilizes the adhesion properties and prevents unwanted degradation
Data Source
Figure 1
AI summary
The invention relates to a non-reactive hot melt adhesive containing a copolymer being substantially composed of a reaction product of lactide (L) and caprolactone (C) in a molar ratio (L/C) of at least 1.5. According to the invention, the adhesive further comprises a carbodiimide compound. The presence of a small but effective amount of carbodiimide causes a stabilizing effect on the sealing properties of the adhesive, especially if it is exposed to higher temperatures. The invention further relates to a method for manufacturing such adhesive as well as to a method for sealing a package by means of such adhesive.