NDI Polyurethane Press Jacket for Chemical Resistance
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Solution Overview
Problem
Press jackets in shoe presses face challenges with chemical resistance, abrasion resistance, crack formation, crack growth, and swelling behavior, particularly when exposed to water and oil, which affects their stability and performance during the dewatering process.
Innovation Solution
The use of naphthalene-1,5-diisocyanate (NDI) as an isocyanate combined with polyols such as polycarbonate polyol or polyether-polycarbonate polyol in the polymer layers of the press jacket enhances flexibility, rigidity, and chemical resistance, while also improving abrasion resistance and reducing deformation under mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional press sleeves are used, then flexibility and basic rigidity are achieved, but chemical resistance, abrasion resistance, and crack formation resistance are insufficient
Solution Approach 1:
The press sleeve uses a composite material system consisting of polyurethane polymer combined with NDI or PPDI isocyanate and specific polyols (polycarbonate polyol, polyether-polycarbonate polyol). This composite formulation creates a material that simultaneously achieves high chemical resistance to water and oil, while maintaining dimensional stability and resistance to swelling, directly resolving the contradiction between chemical resistance and swelling behavior.
2Reliability
If press sleeve material is optimized for chemical resistance, then stability improves, but abrasion resistance and crack growth resistance need improvement
Solution Approach 1:
The invention optimizes the chemical composition parameters of the polyurethane polymer by specifically selecting NDI or PPDI isocyanates combined with polycarbonate polyols or polyether-polycarbonate polyols in controlled ratios. This parameter optimization simultaneously enhances abrasion resistance and crack growth resistance by creating a molecular structure that is both surface-durable and structurally resilient.
3Strength
If press sleeve is made more rigid to resist press load, then rigidity improves, but flexibility and deformation under alternating nip decrease
Solution Approach 1:
The polyurethane polymer composite with NDI/PPDI and specific polyols creates a material with balanced viscoelastic properties. The molecular structure provides sufficient rigidity to resist press loads while maintaining the flexibility needed to accommodate alternating nip deformation during operation, resolving the contradiction between rigidity and flexibility.
4Strength
If press sleeve material is optimized for rigidity, then press load resistance improves, but chemical resistance to water and oil needs improvement
Solution Approach 1:
The invention changes the chemical composition parameters by selecting specific isocyanate-polyol combinations (NDI with polycarbonate polyol, or PPDI with polyether-polycarbonate polyol) that create a polymer matrix with both high mechanical strength for press load resistance and high chemical resistance to water and oil through controlled crosslinking and molecular structure.
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 configuration results in a press jacket with increased stability, consistent drainage performance, and extended service life by maintaining constant dewatering volume and resistance to changing nip conditions.
Implementation Method 1
their chemical resistance, particularly to water and oil, their abrasion resistance, their resistance to crack formation and crack growth and their swelling behavior are in need of improvement
Implementation Method 2
The press sleeve is also exposed to severe alternating bending loads during operation... the tendency of the press sleeve to break, especially at this point, is very high due to the high mechanical stress
Implementation Method 3
The webs of the polymer layer that define the grooves and into which the grooves are incorporated then withstand the changing nip particularly well. They deform less than those of conventional press sleeves. As a result, the dewatering volume of the press sleeve, which the grooves and the counterroll define together in the nip, remains constant.
Data Source
Figure 1~2a
Figure 2b~3
AI summary
The present invention relates to a press jacket, comprising at least a first polymer layer, the polymer layer containing a polyurethane or being produced from a polyurethane, wherein the polyurethane is formed from a prepolymer and a cross-linking agent, and the prepolymer is a reaction product of naphthalene-1,5-diisocyanate (NDI) or 1,4-phenylene diisocyanate (PPDI) and at least one polyol, which is selected from a polycarbonate polyol, a polytetramethylene ether glycol (PTMEG), polyether polycarbonate polyol or mixtures thereof.