Cast Polyurethane Printing Blanket Coating Method
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Solution Overview
Problem
Current methods for applying cast polyurethane layers in printing blankets face issues such as uneven thickness, build-up on coating equipment, and impractical cure times, making them inefficient and difficult to manage.
Innovation Solution
A method involving slot die coating, electrostatic or non-electrostatic spraying, or knife coating is used to apply UV or radiation curable polyurethane layers in a single pass, with curing initiated by UV light, electron beam, or heat, isolated from the coating process to prevent premature curing and build-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If two-part polyurethane systems are used with extended pot life, then processing difficulty is reduced, but cure time becomes excessively long and impractical
Solution Approach 1:
The polyurethane components are pre-mixed and prepared in advance with extended pot life formulation, allowing the coating operation to proceed without time pressure while maintaining workable viscosity throughout the coating and initial processing stages
Solution Approach 2:
The chemical composition of the polyurethane system is modified to extend pot life by adjusting the ratio of isocyanate to hydroxyl groups and selecting specific polyol and diisocyanate components that react more slowly, thereby providing a longer working window without sacrificing final cure properties
2Manufacturing precision
If slot die coating is used to eliminate the rolling bank of material, then gauge control is improved, but cured polyurethane still builds up and occludes the die opening
Solution Approach 1:
The slot die coating process operates continuously with constant material flow and consistent gap spacing, eliminating the rolling bank that causes intermittent build-up and allowing uniform coating application without periodic shutdowns for cleaning
Solution Approach 2:
The viscosity and flow characteristics of the polyurethane mixture are optimized to ensure complete refreshment along the inner walls of the slot die blade, preventing cured material from adhering and occluding the die opening while maintaining precise gauge control
3Object-generated harmful factors
If moisture curable polyurethanes are used to prevent premature curing, then equipment build-up is reduced, but extreme care is required in handling and equipment design
Solution Approach 1:
The polyurethane components are protected from moisture exposure by maintaining an inert or controlled atmosphere in the coating equipment and handling system, preventing premature curing until the material exits the slot die and contacts the atmosphere
Solution Approach 2:
Moisture acts as an intermediary that triggers curing only at the desired location and time (after exiting the slot die), allowing the polyurethane to remain uncured and pumpable through the equipment without build-up issues
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 allows for consistent, single-pass application of polyurethane layers on printing blankets or sleeves, reducing equipment build-up and enabling efficient production with various polyurethane types, including two-part and moisture curable systems, while maintaining control over layer thickness and curing.
Implementation Method 1
The substrate or sleeve with the polyurethane layer thereon is then transported downstream from the slot die where the polyurethane layer is cured
Implementation Method 2
curing initiated by UV light, electron beam, or heat
Implementation Method 3
curing initiated by UV light, electron beam, or heat
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A method of making a printing blanket or printing sleeve which includes one or more cast polyurethane layers is provided. Each cast polyurethane layer may be applied in a single pass to a moving substrate web or a rotating sleeve by slot die coating, electrostatic or non-electrostatic spraying, or knife coating. The method may utilize UV or radiation curable polyurethanes, two-part polyurethanes, moisture curable polyurethanes, or cure-blocked or delayed-cure polyurethanes.