Release Layer for Alkaline Ink Removal
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Solution Overview
Problem
Existing methods for removing printed ink from plastic products during recycling are inefficient, particularly due to the need for high-temperature alkaline treatments, use of organic solvents, and insufficient water resistance of the release layer, which also pose environmental concerns.
Innovation Solution
A layered product with a release layer formed from an aqueous dispersion of granular carboxylic anhydride-modified olefin resin and an acid group-free thermoplastic resin, which is quickly released during alkaline treatment and exhibits excellent water resistance, using an aqueous coating liquid that maintains environmental friendliness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional release layers are used that require high-temperature alkaline treatment (90°C or more) for ink removal, then ink removal is achieved, but work efficiency during recycling is low and energy consumption increases
Solution Approach 1:
The patent changes the chemical parameters of the release layer by incorporating carboxylic anhydride-modified olefin resin with specific acid value (400-800 mg KOH/g) and controlling the ratio of carboxylic anhydride groups to olefin units (0.5-2.0 mol/mol). This parameter optimization enables the release layer to be effectively removed at lower temperatures (50-70°C) while maintaining ink removal capability, thus improving work efficiency and reducing energy consumption
2Reliability
If polyurethane resin with neutralized carboxyl groups is used in aqueous coating liquid, then water solubility is improved, but the formed primer layer has insufficient water resistance
Solution Approach 1:
The patent extracts the carboxyl groups from the polymer structure by using carboxylic anhydride-modified olefin resin instead of polyurethane resin with neutralized carboxyl groups. The carboxylic anhydride groups provide water solubility through their chemical reactivity with water, while the olefin backbone maintains water resistance. This extraction of the problematic neutralized carboxyl structure resolves the contradiction between water solubility and water resistance
3Ease of manufacture
If organic solvents are used for forming the release layer, then coating performance is achieved, but environmental issues arise and wastewater treatment is required
Solution Approach 1:
The patent changes the physical state of the coating liquid from organic solvent-based to aqueous-based by utilizing the water reactivity of carboxylic anhydride groups. The carboxylic anhydride-modified olefin resin dissolves or disperses in water to form a stable coating liquid that maintains good coating performance. Upon drying, the residual carboxylic anhydride groups react with moisture in the air or substrate to form carboxyl groups, ensuring adequate adhesion without requiring organic solvents, thus eliminating environmental harm and wastewater treatment requirements
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 enables efficient removal of printed layers from plastic products during recycling with improved water resistance and environmental conservation, enhancing the recyclability of plastic materials.
Implementation Method 1
the acid value when the carboxylic anhydride-modified olefin resin is ring-opened by hydrolysis is 400 mg KOH/g or more
Implementation Method 2
an aqueous coating liquid as the coating liquid for the release layer
Data Source
AI summary
The present invention provides a layered product comprising a release layer that can be formed from an aqueous coating liquid, that is quickly released from the substrate when alkaline treatment is performed, and that has excellent water resistance. The layered product of the present invention is a layered product comprising a release layer on a substrate, the release layer comprising a granular carboxylic anhydride-modified olefin resin and a binding part containing an acid group-free thermoplastic resin, the carboxylic anhydride-modified olefin resin having an average particle size of 0.5 to 20 μm, the binding part having a thickness of 0.25 to 20 μm, and the release layer having an actual acid value of 100 mg KOH/m2 or more.