PPDI Polyurethane Press Jacket Casting Without Clogging Defects
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Solution Overview
Problem
The mixing and casting process of polyurethane-based press jackets for shoe presses is prone to complications such as clogging and defect formation due to the use of phenylene diisocyanate (PPDI), leading to issues like dripping and the formation of gaps, bubbles, or holes.
Innovation Solution
A press jacket with a polyurethane layer formed by reacting a prepolymer containing phenylene diisocyanate (PPDI) with a crosslinking component comprising bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 4,4'-methylenebis(2-ethylaniline) (MBOEA), which allows for easy casting and curing without complications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phenylene diisocyanate (PPDI) is used as the isocyanate component in the polyurethane prepolymer, then the polyurethane layer achieves enhanced properties such as high wear resistance and good abrasion resistance, but the mixing and casting process becomes prone to complications including clogging of the mixer and casting device, formation of polyurethane particles, and defects like dripping, gaps, bubbles, or holes
Solution Approach 1:
The patent applies preliminary action by pre-mixing the polyol component and catalyst before adding the PPDI isocyanate component. This sequence prevents premature reaction and clogging in the mixing head, as the isocyanate is introduced last to avoid early polyurethane formation. The preliminary preparation of the polyol-catalyst mixture ensures smooth casting without defects.
Solution Approach 2:
The patent employs parameter changes by optimizing the catalyst concentration (0.1-5 wt% based on polyol weight) and the mixing sequence. These parameter adjustments control the reaction kinetics to prevent premature crosslinking during mixing and casting, enabling smooth processing while maintaining the enhanced properties provided by PPDI.
2Productivity
If the polyurethane prepolymer is mixed with the crosslinking component and cast immediately, then the casting process can be completed efficiently, but premature crosslinking occurs leading to clogging of the casting nozzle and formation of defects
Solution Approach 1:
The patent applies preliminary action by preparing the polyol and catalyst mixture in advance before introducing the isocyanate component. This ensures the mixture is ready for immediate casting without premature crosslinking, maintaining both casting efficiency and preventing defects. The preliminary mixing of polyol and catalyst creates a stable base that reacts controllably when isocyanate is added.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring the mixing and casting process proceeds without interruption once initiated. The optimized formulation with catalyst and controlled isocyanate addition allows the reaction to proceed continuously through casting without stopping to address clogging or defects, achieving both efficiency and precision.
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 the formation of a polyurethane layer that can be reliably cast and cured without mixer or casting device clogging, resulting in defect-free press jackets with enhanced properties.
Implementation Method 1
the prepolymer is a reaction product of an isocyanate component and a polyol component
Implementation Method 2
the polyurethane is formed by reacting a prepolymer and a crosslinking component
Data Source
Figure 1~2
AI summary
The present invention relates to a press jacket for a press roller, in particular for a press roller of a shoe press for dewatering a fibrous web, in particular a paper, cardboard, tissue or pulp web, or a conveyor belt, in particular for a machine for producing or treating a fibrous web, in particular a paper, cardboard or tissue machine, wherein the press jacket or the conveyor belt comprises at least one polyurethane-containing layer, wherein the polyurethane is formed by reacting a prepolymer and a crosslinking component, wherein the prepolymer is a reaction product of an isocyanate component and a polyol component, wherein the isocyanate component contains phenylene diisocyanate (PPDI), and wherein the crosslinking component contains bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 4,4'-methylenebis(2-ethylaniline) (MBOEA).