Polyurethane Primer for High-Speed Liquid Toner Adhesion
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Solution Overview
Problem
High-speed digital printing presses present challenges for existing primers in achieving effective liquid toner transfer and adhesion to substrates due to shorter toner-to-substrate transfer times and higher speeds, leading to poor performance with newer generation printing systems.
Innovation Solution
A water-based primer coating comprising an aliphatic polyurethane dispersion and an anionic wax emulsion, with optional additives like surfactants and biocides, applied to substrates to enhance adhesion, particularly suitable for high-speed electrophotographic printing systems, and can be applied in-line or off-line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing primers based on ethylene-acrylic acid copolymers are used, then adhesion enhancement is achieved for conventional printing presses, but toner transfer and adhesion performance deteriorates in high-speed digital presses due to shorter transfer times and higher speeds
Solution Approach 1:
The patent changes the chemical composition parameters of the primer by replacing ethylene-acrylic acid copolymers with a new formulation comprising polyurethane dispersion (30-70 wt%), acrylic polymer emulsion (10-40 wt%), and anionic wax emulsion (5-20 wt%). This parameter change enables the primer to provide adequate adhesion enhancement even under the shorter transfer times and higher speeds of high-speed digital presses, while maintaining compatibility with electrophotographic printing systems.
2Productivity
If higher printing speeds are implemented, then productivity increases, but toner transfer time decreases leading to poor adhesion and transfer performance
Solution Approach 1:
The patent applies a specially formulated primer coating to the substrate before printing, which creates a surface layer that facilitates rapid toner adhesion. This preliminary action prepares the substrate surface in advance to accommodate the reduced transfer time at high printing speeds, ensuring that toner can still adhere effectively even when the substrate moves quickly through the printing system.
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 primer coating provides enhanced adhesion and transfer of liquid toner on various substrates, including polymers and paper, ensuring non-blocking surfaces and compatibility with high-speed digital presses like the HP Indigo WS 6000 series, without requiring additional coatings, and is environmentally friendly.
Implementation Method 1
a primer for use on a variety of substrates including polymers and paper... provides enhanced liquid toner or ink transfer and adhesion to substrates
Implementation Method 2
The primer preferably further includes a wetting agent. The wetting agent is preferably selected from the group consisting of alcohols and surfactants
Data Source
AI summary
A water-based primer coating for use on paper and polymeric substrates is provided for enhancing the adhesion of liquid toner to the substrates, which are designed to be printed using an electrophotographic printing device. The primer coating includes an aliphatic polyurethane dispersion and an anionic wax emulsion, and is substantially free of copolymers of ethylene and acrylic acid.