Polyurethane Calender Roll Cover Toughness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Calender rolls in papermaking machines require materials with high modulus of elasticity, abrasion resistance, toughness, and resistance to elevated temperatures, but existing epoxy compounds often lack toughness and have processing challenges.
Innovation Solution
A calender roll design featuring a polyurethane topstock layer with a glass transition temperature of 120-150°C, strain at failure of 7-12%, and hardness of 70-90 ShD, reinforced with fibers, formed from a mixture of isocyanate, catalyst, and hardener, applied over a base layer, providing enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy compounds are used for calender roll covers, then high modulus of elasticity and resistance to elevated temperatures are achieved, but toughness is insufficient
Solution Approach 1:
The patent uses polyurethane as a composite material that combines high modulus of elasticity with improved toughness. The polyurethane cover layer is applied over the metallic roll core, creating a composite structure that provides both rigidity and impact resistance, resolving the contradiction between modulus and toughness that plagues epoxy-based solutions.
Solution Approach 2:
The patent changes the material parameter from epoxy to polyurethane, which has different mechanical properties. Specifically, polyurethane provides a glass transition temperature of 120-150°C and strain at failure of 7-12%, giving it both the required rigidity and the toughness that epoxy lacks.
2Strength
If epoxy compounds are used for calender roll covers, then high modulus of elasticity is achieved, but processing becomes difficult
Solution Approach 1:
The patent changes the material from epoxy to polyurethane, which has more favorable processing characteristics. The polyurethane formulation with specific glass transition temperature (120-150°C) and strain at failure (7-12%) allows for easier application and curing processes while maintaining the required mechanical properties.
3Strength
If conventional materials are used for calender roll covers, then abrasion resistance is achieved, but toughness is insufficient
Solution Approach 1:
The patent employs polyurethane as a composite material that inherently combines abrasion resistance with toughness. The polyurethane cover layer provides both wear resistance and impact resistance, eliminating the need to trade off abrasion resistance for toughness that plagues conventional material selections.
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 polyurethane topstock layer offers improved toughness and processing efficiency compared to epoxy compounds, with reduced curing time and increased filler loading, enhancing the calender roll's performance in demanding papermaking environments.
Implementation Method 1
the polyurethane having a glass transition temperature of between about 120 and 150° C.
Implementation Method 2
the topstock layer being fiber-reinforced
Data Source
AI summary
A calender roll for a papermaking machine includes: a substantially cylindrical core; and a cover circumferentially surrounding the core. The cover comprises a base layer circumferentially overlying the core; and a topstock layer comprising polyurethane circumferentially overlying the base layer, the topstock layer being fiber reinforced, the polyurethane having a glass transition temperature of between about 120 and 150° C., the topstock layer having a hardness of 70 to 90 ShD.