Crosslinked Polyurethane Press Sleeve Wear Resistance
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Solution Overview
Problem
Press covers and conveyor belts for fibrous web processing machines, such as shoe presses and paper machines, face challenges in achieving high wear resistance, abrasion resistance, crack resistance, and chemical resistance while maintaining flexibility and rigidity.
Innovation Solution
A method involving a press cover or conveyor belt with at least one layer of crosslinked polyurethane, where the crosslinked polyurethane is produced by reacting an isocyanate component containing methylenediphenyl diisocyanate with a polyol component and a crosslinker component featuring a polyol with a weight-average molecular weight greater than 1000 g/mol, enhancing mechanical and chemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fiber-reinforced polyurethane is used to meet wear and chemical resistance requirements, then wear resistance and chemical resistance are improved, but flexibility and rigidity balance becomes difficult to achieve
Solution Approach 1:
The patent applies parameter changes by systematically adjusting the molecular weight of polyol components (using both low molecular weight polyols for rigidity and high molecular weight polyols with Mw > 1000 g/mol for flexibility), the ratio of isocyanate to polyol, and the crosslinking density. These parameter adjustments enable the press cover to simultaneously achieve high wear resistance and the required flexibility-rigidity balance for shoe press application
Solution Approach 2:
The patent employs composite materials by combining fiber reinforcement (such as glass fibers or aramid fibers) with a specially formulated polyurethane matrix that contains both low and high molecular weight polyols. This composite structure provides enhanced wear resistance from the fibers while the dual polyol system maintains the necessary flexibility and rigidity properties
2Strength
If crosslinked polyurethane is used to improve mechanical strength and chemical resistance, then strength and chemical resistance are improved, but the complexity of the manufacturing process increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the polyurethane composition with the specific combination of low molecular weight polyol, high molecular weight polyol (Mw > 1000 g/mol), and isocyanate before applying it to the shoe press. The crosslinking process is then initiated under controlled conditions, allowing the complex chemical reactions to proceed systematically and reducing manufacturing complexity compared to attempting to achieve the same properties through post-processing or multiple sequential steps
3Reliability
If high crosslinking density is used to improve crack resistance and wear resistance, then crack resistance and wear resistance are improved, but flexibility decreases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by using high molecular weight polyols (Mw > 1000 g/mol) as crosslinking agents. These long-chain polyols provide sufficient flexibility even at high crosslinking densities because their extended molecular structures maintain chain mobility. Simultaneously, the high crosslinking density achieved through these polyols provides excellent crack resistance and wear resistance, thus resolving the contradiction between flexibility and durability
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 a press cover or conveyor belt with improved wear resistance, abrasion resistance, crack resistance, and chemical resistance, particularly to water, oil, acids, and solvents, while maintaining sufficient flexibility and rigidity, suitable for use in shoe presses and paper machines.
Implementation Method 1
the crosslinked polyurethane being obtained by the step in which a prepolymer which is the reaction product of an isocyanate component containing methylenediphenyl diisocyanate (MDI) and a polyol component containing a polycarbonate polyol, is reacted with a crosslinker component
Data Source
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AI summary
A press sleeve for a pressing roller, in particular for a pressing roller of a shoe press for dewatering a web of fibrous material, in particular a web of paper, card, tissue or wood pulp, or a conveyor belt, in particular for a machine for producing or treating a web of fibrous material, in particular a paper-, card- or tissue-making machine, comprises at least one layer containing crosslinked polyurethane, wherein the crosslinked polyurethane is obtainable by a process in which a prepolymer which is the reaction product of an isocyanate component containing methylene diphenyl diisocyanate and a polyol component containing a polycarbonate polyol is reacted with a crosslinking agent component, which contains at least one polyol with a weight-average molecular weight of over 1000 g/mol.