Deinking Plastic Material Using Oxidizing Inorganic Acid
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Solution Overview
Problem
Current methods for deinking and delaminating plastic materials, particularly plastic waste, are inefficient in removing a wide variety of inks, including solvent-based, water-based, and UV-based inks, especially when these inks are protected by multiple layers or cause degradation of the plastic material, limiting their reuse in high-value applications.
Innovation Solution
A method involving the use of an oxidizing inorganic acid, such as sulfuric acid, to deink plastic materials without the need for organic solvents or surfactants, which oxidizes or hydrolyzes various types of inks, including cross-linked structures, while applying shear to enhance deinking efficiency, and optionally combining with fatty acids for delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If water-based liquid solutions comprising surfactants are used to deink plastics, then the treatment is easy to handle from safety perspective, but it is not able to deink all types of inks and/or all types of plastic films
Solution Approach 1:
The patent changes the chemical parameters of the deinking solution by using oxidizing acids (nitric acid, sulfuric acid, or a combination) instead of conventional water-based surfactant solutions. This parameter change enables the solution to effectively deink diverse ink types including solvent-based, water-based, and UV-based inks that were previously resistant to conventional methods.
Solution Approach 2:
The patent employs strong oxidizing acids (nitric acid with oxidation potential +0.96V, sulfuric acid with oxidation potential +0.17V) to chemically oxidize and remove inks from plastic surfaces. This accelerated oxidation mechanism provides superior deinking capability compared to conventional surfactant-based methods, effectively breaking down various ink compositions.
2Productivity
If ethyl acetate is used as extractant to deink plastic material, then it can remove some inks, but it does not work for ink covered by polymer layers or UV-based inks
Solution Approach 1:
The patent uses strong oxidizing acids to chemically attack and remove inks that are either covered by polymer layers or are UV-based. The oxidation mechanism penetrates and breaks down the ink structures that conventional extractants like ethyl acetate cannot access or dissolve, significantly expanding the range of deinkable materials.
Solution Approach 2:
The patent replaces the mechanical extraction mechanism of ethyl acetate with a chemical oxidation mechanism using strong acids. This substitution allows the deinking process to effectively remove inks that are protected by polymer layers or have cross-linked structures that resist conventional extraction methods.
3Ease of manufacture
If mechanical recycling processes are used to recycle plastics, then the process is simple and widely applicable, but contaminations from inks and additives adversely affect the quality of recycled plastics
Solution Approach 1:
The patent applies preliminary deinking treatment using oxidizing acids before the mechanical recycling process. This preliminary action removes ink and additive contaminants from the plastic material, preventing them from adversely affecting the quality of the final recycled plastic products while maintaining the simplicity of the overall recycling workflow.
Solution Approach 2:
The patent extracts and removes harmful contaminants (inks and additives) from the plastic material using oxidizing acids before recycling. This extraction step separates the contaminants from the base plastic material, allowing the recycled plastic to achieve higher quality suitable for high-value applications.
4Stability of the object's composition
If compatibilizers are used to enhance blending of different polymers during mechanical recycling, then the compatibility of multilayer plastic packaging is improved, but the use of compatibilizers is still limited and requires more research
Solution Approach 1:
The patent applies preliminary deinking and cleaning treatment using oxidizing acids before the mechanical recycling and blending processes. This preliminary action removes contaminants that would interfere with polymer compatibility, allowing different polymers to blend more effectively without requiring complex compatibilizer systems.
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 method effectively deinks and delaminates plastic materials with different types of inks, improving deinking rates and degrees without degrading the main plastic components, making recycled plastics suitable for higher-value applications and enhancing recycling efficiency.
Implementation Method 1
contacting the plastic material with an oxidizing inorganic acid having a standard electrode potential of at least 0 V, wherein the oxidizing inorganic acid oxidizes or hydrolyzes the inks
Implementation Method 2
contacting the plastic material with an oxidizing inorganic acid having a standard electrode potential of at least 0 V, wherein the oxidizing inorganic acid oxidizes or hydrolyzes the inks
Data Source
AI summary
This disclosure relates to a method to deink plastic material comprising or provided with ink. The method comprises the step of contacting the plastic material with an oxidizing inorganic acid having a standard electrode potential of at least 0 V. The disclosure also relates to a method to delaminate and deink plastic material by contacting the plastic material with an oxidizing inorganic acid and with a short chain or medium chain fatty acid. Furthermore, the disclosure relates to an installation to deink or to delaminate and deink plastic material.