Polyurethane Press Jacket Hard Segment Optimization
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Solution Overview
Problem
Press sleeves in paper machines face high mechanical stress and instability, leading to a high tendency to break, despite the use of modern polymers like polyurethanes, which do not achieve satisfactory stability and service life in existing applications.
Innovation Solution
The solution involves optimizing the molecular arrangement of polyurethane by increasing the 1,4-BDO content through the use of aliphatic amines and replacing some aromatic amines with alkanolamines, such as monoethanolamines, to enhance the mechanical properties by improving the arrangement of hard segments, allowing for thicker, monolithic polymer layers with improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If modern polymers like polyurethanes are used for press jackets, then flexibility is improved, but stability and service life remain insufficient
Solution Approach 1:
The patent employs composite material strategy by combining polyurethane base material with specifically formulated crosslinking agents (aromatic polyamines and aliphatic amines in defined ratios). This composite approach creates a multi-phase structure where the polyurethane provides flexibility while the crosslinked network delivers enhanced stability and resistance to hydrolysis, pressure, and temperature, thereby resolving the contradiction between flexibility and reliability.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the crosslinking density and molecular structure of the polyurethane through specific compositional ratios of 1,4-BDO (10-30 wt%), aromatic polyamines (70-85 wt%), and aliphatic amines (5-20 wt%). These parameter adjustments optimize the balance between chain flexibility (from polyol content) and crosslinked network stability (from amine content and ratio), enabling simultaneous achievement of flexibility and long-term stability under harsh paper machine conditions.
2Shape
If the press sleeve is subjected to alternating bending loads during operation, then the press sleeve undergoes deformation, but this makes it particularly prone to breakage
Solution Approach 1:
The patent implements beforehand cushioning by incorporating a pre-formed crosslinked network structure within the polyurethane matrix before the press sleeve encounters alternating bending loads. The crosslinks act as preemptive reinforcement points that distribute and absorb stress during entry and exit deformation, preventing crack initiation and propagation that would otherwise lead to breakage under cyclic mechanical stress.
Solution Approach 2:
The patent addresses the bending stress issue by optimizing the molecular architecture to include curved or cyclic structural elements within the crosslinked network (such as cyclic carbonates or aromatic rings in the polyamine structure). These curved molecular geometries provide inherent flexibility and stress distribution capabilities, allowing the material to accommodate alternating bending loads more effectively and resist fracture compared to rigid linear structures.
3Strength
If polyurethanes are used with higher 1,4-BDO content to improve hard segment arrangement, then mechanical properties are enhanced, but the crosslinking agent composition must be optimized
Solution Approach 1:
The patent systematically adjusts compositional parameters to resolve the contradiction: 1,4-BDO content is optimized to 10-30 wt% of total polyol to ensure adequate hard segment formation for mechanical strength, while the crosslinking agent composition is simultaneously tuned with aromatic polyamines at 70-85 wt% and aliphatic amines at 5-20 wt%. This coordinated parameter optimization achieves superior mechanical properties without excessive compositional complexity, as the specific ratio range provides a balanced crosslinking density that simplifies processing while maximizing performance.
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 approach results in a press sleeve with increased stability and extended service life, capable of withstanding the mechanical stresses and deformation in paper machine operations.
Implementation Method 1
the inventors considered the relationships at the molecular level. Their approach was based on the understanding that polyurethane, at least in its elastomeric form, comprises hard segments that form crystalline structures and disordered soft segments. The hard segments prevent the soft segments from sliding past each other when the material is stretched. The degree to which the hard segments are arranged relative to one another has a decisive influence on the mechanical properties of the polyurethane.
Implementation Method 2
The polyurethane is formed from a prepolymer and a crosslinking agent. The crosslinking agent comprises at least a first component K1 comprising 1,4-butanediol or 1,4-hydroquinone bis(2-hydroxyethyl) ether, at least a second component K2 comprising at least one aliphatic diamine, and at least a third component K3 comprising at least one alkanolamine.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a press jacket comprising at least one 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 1,4-phenylene diisocyanate and a polyol, the cross-linking agent containing the following components: a first component comprising 1,4-butanediol or 1,4-hydroquinone bis(2-hydroxyethyl)ether (HQEE); a second component comprising at least one aliphatic diamine; and a third component comprising at least one alkanolamine.