PPDI Polyurethane Press Cover for Shoe Press Wear Resistance
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Solution Overview
Problem
Press covers for shoe presses used in dewatering fibrous material webs, such as paper or cardboard, face challenges in achieving optimal mechanical properties like hardness, modulus of elasticity, wear resistance, abrasion resistance, and water swelling, which are not adequately addressed by existing polyurethane-based solutions.
Innovation Solution
A press cover or conveyor belt with a polyurethane layer formed by reacting a prepolymer of phenylene 1,4-diisocyanate (PPDI) with a polyol component containing polyether or polycarbonate polyols, and a crosslinker component that includes a C6-14 diol, such as hexane-1,6-diol, to enhance mechanical properties and chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional polyurethane formulations are used for press covers, then flexibility and basic functionality are achieved, but mechanical properties such as hardness, modulus of elasticity, wear resistance, and water swelling resistance are insufficient
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyurethane by selecting specific polyols (polyester, polyether, polycarbonate) with defined molecular weights and hydroxyl values, and reacting them with phenylene diisocyanate under controlled conditions to achieve optimal mechanical and chemical resistance properties
Solution Approach 2:
The press cover is constructed as a composite material system combining fiber reinforcement (scrim or weave) with the polyurethane matrix, where the fiber orientation and density are specifically designed to enhance mechanical strength while the polyurethane composition provides chemical resistance and flexibility
2Strength
If the press cover is made hard and stiff to resist deformation under pressing load, then structural stability is improved, but flexibility to pass around the shoe is reduced
Solution Approach 1:
The press cover exhibits different mechanical properties in different directions: high stiffness in the radial direction (perpendicular to the shoe surface) to resist pressing loads, while maintaining flexibility in the circumferential direction to allow wrapping around the shoe, achieved through anisotropic fiber reinforcement and polyurethane formulation
3Reliability
If fiber reinforcement is embedded in polyurethane matrix to enhance mechanical properties, then wear resistance and abrasion resistance are improved, but manufacturing complexity increases
Solution Approach 1:
The fiber scrim or weave is pre-formed and positioned within the polyurethane matrix before the curing process, allowing the reinforcement structure to be prepared in advance and then integrated into the press cover through a standardized molding process, reducing overall manufacturing complexity
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 provides improved hardness, modulus of elasticity, wear resistance, and reduced water swelling, while maintaining excellent cracking resistance and chemical resistance, surpassing the performance of conventional polyurethane formulations.
Implementation Method 1
a polyol component and phenylene diisocyanate, in a ratio of isocyanate groups to hydroxyl groups of between 0.95:1 and 1.05:1, in each case based on the total amount of isocyanate groups and hydroxyl groups
Implementation Method 2
with a crosslinker component, in particular with a polyamine crosslinker, in a ratio of isocyanate groups to hydroxyl groups of between 0.95:1 and 1.05:1
Data Source
AI summary
A press cover is provided for a press roll, in particular for a press roll of a shoe press for dewatering a web of fibrous material, in particular a paper, cardboard, tissue or pulp web, or for a conveyor belt, in particular for a machine for producing or treating a web of fibrous material, in particular a paper, cardboard or tissue producing machine. The press cover or conveyor belt includes at least one polyurethane-containing layer. The polyurethane is formed by reacting a prepolymer and a crosslinker component. The prepolymer is a reaction product of phenylene 1,4-diisocyanate (PPDI) and of a polyol component containing at least one polyether polyol and/or at least one polycarbonate polyol. The crosslinker component contains a C6-14 diol. A shoe press for dewatering of a fibrous material web and a machine for production or treatment of a fibrous material web, are also provided.