Deinking Coated Paper Using Calcium-Exchanged Clay
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Solution Overview
Problem
Current deinking processes for coated paper face challenges such as inefficient ink release, especially with pigment inks, and the use of reagents like sodium hydroxide that can deactivate pH-sensitive collector agents, complicating further purification steps.
Innovation Solution
A process involving a coated paper or paperboard with a calcium- or magnesium-exchanged clay and a water-soluble carboxymethylcellulose binder, activated with monovalent ions like sodium, which facilitates the detachment of ink layers through water treatment and subsequent flotation, using collector agents like modified polyethyleneimines to separate ink from pulp.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional deinking processes use strong bases like sodium hydroxide to remove ink, then ink release is improved, but pH-sensitive collector agents are deactivated
Solution Approach 1:
The invention changes the pH parameter from strongly alkaline (conventional) to mildly alkaline (pH 8-10), allowing effective deinking while preserving collector agent activity. This is achieved by using calcium- or magnesium-exchanged clay that releases these cations during treatment, creating a gentle alkaline environment sufficient for ink removal without deactivating pH-sensitive reagents.
Solution Approach 2:
The calcium- or magnesium-exchanged clay acts as an intermediary substance that mediates between the need for alkaline conditions (for ink removal) and the need to maintain mild pH (for collector agent stability). The clay exchanges its cations with water, providing gentle alkalinity without the harsh effects of strong bases like sodium hydroxide.
2Manufacturing precision
If pigment inks are used on coated paper, then printing quality is improved, but deinking efficiency deteriorates
Solution Approach 1:
The invention changes the chemical environment parameters (pH and cation composition) to mildly alkaline conditions with calcium or magnesium ions, which effectively loosen pigment ink bonds on coated paper without requiring harsh chemicals. This enables efficient removal of pigment inks that are otherwise difficult to remove.
Solution Approach 2:
The process uses a composite approach combining calcium- or magnesium-exchanged clay with water-soluble binders (carboxymethylcellulose) to create a coating that facilitates ink removal. The clay binder system works synergistically to enable effective deinking of pigment-based inks while maintaining printing quality.
3Productivity
If water-soluble binders with excess monovalent ions are used in the coating, then ink detachment is improved, but binder cost increases
Solution Approach 1:
The invention uses water-soluble binders that can be easily removed during the deinking process, effectively making them disposable. These binders (carboxymethylcellulose) perform their function during printing and ink detachment, then are washed away with water during deinking, eliminating the need for expensive permanent or reusable binder systems.
Solution Approach 2:
The invention changes the binder composition parameters to include water-soluble polymers with specific ion content (excess monovalent ions like sodium). This compositional change enables the binder to facilitate ink detachment through ion exchange mechanisms while being easily removable during deinking, providing cost-effective 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
This process effectively removes ink from paper pulp under moderate conditions, allowing for high flexibility in ink types and reagents, improving the efficiency of the deinking process while preserving the activity of pH-sensitive agents.
Implementation Method 1
activating the calcium- or magnesium-exchanged clay before or during step (iii) by, providing in step (i) the binder (a2), wherein the binder (a2) is soluble in water and comprises monovalent ions selected from the group consisting of sodium, lithium, potassium, ammonium and mixtures thereof
Implementation Method 2
treating the coated paper or paperboard as provided in step (i) with water to obtain an aqueous suspension comprising at least ink, clay particles and a paper pulp or paper residue
Implementation Method 3
subjecting the aqueous suspension to flotation, using collector agents like modified polyethyleneimines to separate ink from pulp
Data Source
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AI summary
A process for the deinking of a coated paper or paperboard is disclosed, the process comprises a step of providing a coating layer comprising a calcium- or magnesium-exchanged clay which is deposited on the paper or paperboard before the ink layer. In a further step said calcium- or magnesium-exchanged clay is activated and the paper is subsequently treated with water.