Polyurethane Press Cover Resisting Water and Oil Swelling
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Solution Overview
Problem
Press covers for shoe presses face challenges with chemical resistance, particularly to water and oil, abrasion resistance, crack resistance, and swelling behavior, which affect their durability and safety in fibrous web dewatering processes.
Innovation Solution
A polyurethane matrix is developed using a specific mixture of prepolymers, including polyether polyol and polycarbonate polyol, with a 50/50 mixing ratio and a crosslinker composition that enhances mechanical and chemical resistance, reducing swelling and maintaining good dynamic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a press cover is made from conventional polyurethane materials, then it achieves basic flexibility and rigidity, but its chemical resistance, abrasion resistance, and swelling behavior are insufficient
Solution Approach 1:
The patent employs composite materials by combining polyether polyol and polycarbonate polyol in a specific ratio (0.3-0.7 weight ratio) within the polyurethane matrix. This composite approach creates a material that simultaneously achieves superior chemical resistance (particularly to water and oil), enhanced abrasion resistance, and reduced swelling behavior, while maintaining the necessary mechanical strength and flexibility for press cover application.
Solution Approach 2:
The invention applies parameter changes by precisely controlling the molecular weight ranges of the polyols used (polyether polyol: 1,000-5,000 g/mol; polycarbonate polyol: 1,000-3,000 g/mol) and their mixing ratio. By optimizing these parameters, the patent achieves a polyurethane matrix with improved chemical resistance, reduced swelling, and enhanced durability, resolving the contradiction between chemical resistance and material strength.
2Reliability
If the press cover material is made more resistant to chemicals and swelling, then its durability improves, but its flexibility and dynamic properties may deteriorate
Solution Approach 1:
The patent uses composite materials combining polyether polyol and polycarbonate polyol in a balanced ratio (0.3-0.7 weight ratio). This composite structure provides enhanced abrasion resistance and chemical resistance while the specific composition maintains the flexibility and dynamic properties required for the press cover to conform to the shoe and backing roll. The composite approach ensures that durability improvements do not compromise operational flexibility.
Solution Approach 2:
The invention optimizes parameter changes by controlling the molecular weights (polyether polyol: 1,000-5,000 g/mol; polycarbonate polyol: 1,000-3,000 g/mol) and the crosslinker content (5-20 weight percent). These parameter optimizations achieve high abrasion resistance and chemical resistance while preserving the material's flexibility and dynamic characteristics, resolving the contradiction between durability and ease of operation.
3Productivity
If the press cover is designed to store more water during nip passage, then dewatering efficiency improves, but the material's swelling behavior and structural integrity are compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the polyol composition and ratios to control the material's swelling behavior. By using polyether polyol (molecular weight 1,000-5,000 g/mol) and polycarbonate polyol (molecular weight 1,000-3,000 g/mol) in a controlled weight ratio (0.3-0.7), the material achieves low swelling behavior while maintaining the capacity to store pressed-out water during nip passage, thus preserving structural integrity while supporting dewatering efficiency.
Solution Approach 2:
The invention employs composite materials with polyether polyol and polycarbonate polyol that provide a balanced structure. This composite material can temporarily store water during nip passage (supporting dewatering efficiency) while exhibiting low swelling behavior and maintaining structural integrity. The specific composite composition ensures that water storage capability does not compromise material stability.
4Ease of manufacture
If conventional polyurethane formulations are used, then manufacturing is simple, but the press cover exhibits high sensitivity to water, oil, and solvents
Solution Approach 1:
The patent uses composite materials combining polyether polyol and polycarbonate polyol in a specific weight ratio (0.3-0.7). This composite formulation maintains manufacturing simplicity (using standard polyurethane synthesis processes) while dramatically improving chemical resistance to water, oil, and solvents. The composite structure provides the necessary resistance to harmful chemical factors without complicating the manufacturing process.
Solution Approach 2:
The invention applies parameter changes by selecting specific molecular weight ranges for the polyols (polyether polyol: 1,000-5,000 g/mol; polycarbonate polyol: 1,000-3,000 g/mol) and optimizing their mixing ratio. These parameter changes reduce sensitivity to water, oil, and solvents while keeping the manufacturing process straightforward and compatible with existing polyurethane production methods, thus resolving the contradiction between ease of manufacture and chemical resistance.
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 press covers with high abrasion resistance, low crack formation tendency, and reduced sensitivity to water, oil, acids, and solvents, ensuring improved durability and safety in harsh environments.
Implementation Method 1
a) by means of a polyaddition reaction between a diisocyanate and a mixture of at least one polyether polyol and at least one polycarbonate polyol
Implementation Method 2
b) by means of a crosslinking reaction in the polyurethane formed in step a) with a crosslinker
Data Source
AI summary
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 conveyor belt, in particular for a machine for producing or treating a fibrous web, in particular a paper, cardboard or tissue machine, comprises at least one polyurethane-containing layer, wherein the at least one layer has a polyurethane matrix with a prepolymer, which is a reaction product of a polyisocyanate with a mixture of at least two different polyols, and at least one crosslinker, characterized in that it contains prepolymers, each of which is a reaction product of 3.3'-Dimethyl-4,4'-biphenylene diisocyanate (TODI), 1,4-phenylene diisocyanate (PPDI), naphthylene-1,5-diisocyanate (NDI) with the mixture of at least two different polyols with a polyisocyanate polyether polyol, such as polytetramethylene ether glycol (PTMEG), polycarbonate polyol or polyether carbonate polyol.