Sulfonated Polyester Ink for Digital Offset Clarity
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Solution Overview
Problem
Current digital offset printing inks face challenges with viscosity requirements, compatibility with printing systems, and the need for clear, non-pigmented inks suitable for various substrates, particularly for applications like food packaging where UV curable monomers pose risks, and existing inks struggle with achieving high transfer efficiency and clarity.
Innovation Solution
An aqueous ink composition comprising water, an optional co-solvent, a sulfonated polyester with a degree of sulfonation of at least 7.5 mol percent, and isoprene rubber, which provides a viscosity range suitable for digital offset printing, ensuring good transfer properties and clarity, eliminating the need for curable monomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If UV curable monomers are used in digital offset printing inks, then drying speed and transfer efficiency are improved, but safety risks increase for food packaging and medical applications
Solution Approach 1:
The patent removes UV curable monomers from the ink composition entirely, extracting the harmful component while maintaining the water-based formulation. This eliminates safety risks for food packaging and medical applications while preserving the fundamental drying mechanism through water evaporation and ink composition optimization.
Solution Approach 2:
The patent modifies the viscosity parameters of the ink composition by selecting specific polymer types and concentrations to achieve optimal flow characteristics without UV curables. The viscosity is tuned to ensure proper ink transfer and drying performance while maintaining safety for sensitive applications.
2Adaptability or versatility
If clear, non-pigmented inks are used, then substrate compatibility and clarity are improved, but transfer efficiency and ink strength deteriorate
Solution Approach 1:
The patent employs a composite ink formulation combining multiple polymer components (acrylic polymers, vinyl polymers, and other compatible polymers) to create a clear ink that maintains both substrate compatibility and sufficient ink strength. The synergistic interaction of different polymer types provides the necessary adhesion and transfer properties without pigments.
Solution Approach 2:
The patent optimizes the molecular weight, glass transition temperature, and concentration of each polymer component to achieve the right balance between clarity and ink strength. By carefully controlling these parameters, the ink maintains versatility across substrates while ensuring adequate transfer efficiency.
3Productivity
If viscosity is increased to improve transfer properties, then ink transfer efficiency is improved, but ink flow and distribution during application deteriorate
Solution Approach 1:
The patent creates a dynamic viscosity system where the ink exhibits appropriate flow characteristics during application (lower effective viscosity) and enhanced transfer properties during the transfer phase (higher effective viscosity). This is achieved through the selection of polymers with specific rheological properties that respond to shear rate and temperature changes during the printing process.
Solution Approach 2:
The patent carefully selects polymer types and concentrations to achieve optimal viscosity parameters that balance ink flow during application with transfer efficiency. The viscosity is tuned to ensure proper ink distribution on the imaging member while maintaining sufficient adhesion for effective transfer to the substrate.
Data Source
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AI summary
An aqueous ink composition including water; an optional co-solvent; a sulfonated polyester, wherein the sulfonated polyester has a degree of sulfonation of at least about 3.5 mol percent; and an isoprene rubber. A process of digital offset printing including applying an ink composition onto a re-imageable imaging member surface at an ink take up temperature, the re-imageable imaging member having dampening fluid disposed thereon; forming an ink image; transferring the ink image from the re-imageable surface of the imaging member to a printable substrate at an ink transfer temperature; wherein the ink composition comprises water; an optional co-solvent; a sulfonated polyester having a degree of sulfonation of at least about 3.5 mol percent; and an isoprene rubber. A process including combining a sulfonated polyester resin, having a degree of sulfonation of at least about 3.5 mol percent, water, an optional co-solvent, and an isoprene rubber to form an aqueous ink composition, wherein the ink composition is substantially colorless.