Dyed substrate comprising poly(lactic acid) fibres
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Solution Overview
Problem
The widespread application of poly(lactic acid) fibers in the textile industry is hindered by hydrolytic degradation under conventional aqueous dyeing conditions, leading to loss of strength and tenacity, and the challenge of achieving deep shades of dark colors such as navy blue or black remains unsolved in existing dyeing methods.
Innovation Solution
Dyeing poly(lactic acid) fibers using a dyeing medium comprising at least 80 wt.% supercritical carbon dioxide and less than 3 wt.% water, with disperse dyes at a pressure of 12-50 MPa and a temperature of 70-100°C, ensuring a dye-to-substrate ratio of 100 kg/g or higher, to achieve deep shades of black or navy blue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional aqueous dyeing conditions are used to dye PLA fibers, then the fibers can be dyed with disperse dyes, but hydrolytic degradation occurs leading to loss of strength and tenacity
Solution Approach 1:
The patent changes the fundamental parameter of the dyeing medium from aqueous to supercritical carbon dioxide. This parameter change eliminates water from the system, preventing hydrolytic degradation of PLA fibers while maintaining effective dyeing capability through disperse dyes in the supercritical CO2 environment.
Solution Approach 2:
The patent employs supercritical carbon dioxide as an inert dyeing medium that does not cause hydrolysis of PLA fibers. The inert nature of CO2 creates a protective environment that preserves fiber strength and tenacity during the dyeing process, unlike water which causes harmful hydrolytic degradation.
2Ease of manufacture
If conventional aqueous dyeing is used, then dyeing can be performed, but deep shades of dark colors such as navy blue or black cannot be achieved
Solution Approach 1:
The patent changes the physical state and chemical properties of the dyeing medium to supercritical carbon dioxide. This parameter change enables deep shade achievement by improving dye penetration and distribution in PLA fibers, allowing production of deep navy blue and black colors that are unattainable with conventional aqueous dyeing.
3Difficulty of detecting and measuring
If high temperature aqueous dyeing is used to achieve deep shades, then color depth improves, but PLA fibers show high shrinkage in water at temperatures in excess of 90°C
Solution Approach 1:
The patent uses supercritical carbon dioxide as an inert dyeing medium that eliminates water contact with PLA fibers. This prevents water-induced shrinkage at elevated temperatures while still enabling deep shade achievement through the supercritical fluid's enhanced penetration and dye carrying capacity.
Solution Approach 2:
The patent utilizes the phase transition properties of carbon dioxide to achieve deep shades without water. By operating in the supercritical phase of CO2, the system achieves enhanced dye penetration and color depth while avoiding the shrinkage problems associated with aqueous dyeing at high temperatures.
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 method results in PLA fibers with excellent rub and wash fastness, minimal hydrolysis, and no adverse effect on substrate properties, enabling the use of PLA fibers in demanding textile applications.
Implementation Method 1
passing a stream of dyeing medium through the dyeing chamber containing the substrate, said dyeing medium comprising at least 80 wt.% of supercritical carbon dioxide
Implementation Method 2
The method results in PLA fibers with excellent rub and wash fastness, minimal hydrolysis
Data Source
Figure 1~2
AI summary
The present invention provides a dyed substrate comprising at least 70 wt.% of dyed PLA- fibres having a poly(lactic acid) content of at least 70 wt.%, the dyed substrate having a total poly(lactic acid)) content of at least 70 wt.%, wherein the dyed PLA-fibres are dyed with one or more disperse dyes and wherein the dyed substrate has the following ClELAB colour: • 0 ≤ L* ≤ 25; • -5 ≤ a* ≤ 5; -5 ≤ b* ≤ 5. The invention also provides method of preparing a dyed substrate comprising at least 70 wt.% of dyed PLA-fibres having a poly(lactic) acid content of at least 70 wt.%, the dyed substrate having a total poly(lactic) acid content of at least 70 wt.%, wherein the dyed PLA- fibres are dyed with one or more disperse dyes and wherein the dyed substrate has the following ClELAB colour: • 0 ≤ L* ≤ 25; • -128 ≤ a* ≤ 10; -128 ≤ b* ≤ 128.